Heterostructure-engineered diamond-graphene composites for high-performance and stable electromagnetic wave absorption

Domain: biology
Published: 2026-04-02
Editorial outcome: major_revision

Abstract
Designing electromagnetic wave absorbing (EWA) materials that simultaneously deliver strong attenuation and withstand harsh environments remains a major challenge due to long-standing trade-offs between dielectric performance and structural robustness. Here, we report a heterostructured diamond-graphene composite synthesized under moderate high-pressure and high-temperature conditions, in which multilayer graphene is embedded within a nanodiamond framework through covalently bonded interfaces. This architecture enables modulation of the sp3/sp2 hybridization ratios, yielding tunable dielectric responses, improved impedance matching, and multiple, synergistic energy-dissipation pathways. The optimized composite achieves a minimum reflection loss of -60 dB and an effective absorption bandwidth of 4.0 GHz. Simultaneously, the material exhibits exceptional environmental tolerance, including high thermal stability, reliable absorption at high temperatures, large fracture toughness, and enhanced corrosion resistance, which originates from the mechanically interlocked diamond/graphene networks and chemically stable carbon interfaces. Our results establish a scalable heterointerface-engineering strategy for constructing multifunctional carbon architectures that unify strong microwave attenuation with outstanding thermal, mechanical, and chemical durability, offering a promising platform for next-generation EWA materials suitable for harsh or demanding environments.

Introduction
The rapid advancement of wireless communication technology has led to a substantial increase in electromagnetic radiation in the environment1–3. This growing pollution poses potential human health risks from prolonged exposure and causing serious electromagnetic interference due to strong induction effects4,5. To mitigate these issues, ideal electromagnetic wave absorbing (EWA) materials should be lightweight, highly efficient, thin, and capable of operating across a broad frequency range6. Conventional EWA materials, such as ferrites, metals, conductive polymers, and dielectrics materials, have been used to reduce reflection and radiation7,8. However, their practical applications are limited by issues like impedance mismatch, narrow bandwidth, single loss mechanism, and poor resistance to corrosion or oxidation9. These limitations reduce their effectiveness and durability, particularly under demanding environmental conditions6. Therefore, there is an urgent need to develop advanced EWA materials that offer both high absorption efficiency and strong environmental stability.

Carbon materials—including graphene, carbon nanotubes, and carbon dots—have garnered considerable attention for electromagnetic wave absorption because of their low density, tunable electrical properties, and cost-effective synthesis10,11. Unfortunately, single-component carbon nanomaterials often exhibit poor impedance matching and insufficient energy attenuation, primarily attributed to their excessively high electrical conductivity and the absence of diverse loss mechanisms12-14. To overcome these shortcomings, various strategies such as multicomponent design or element doping have been explored to optimize electromagnetic parameters and enhance energy dissipation by regulating composition, interface architecture, and defect density14–17. Despite notable progress, existing carbon-based composites still face persistent challenges, including weak filler-matrix interactions, non-uniform dispersion, and limited resistance to oxidation and corrosion under extreme environmental conditions6,18. To address these limitations, the integration of diamond and graphene via covalent bonding presents a promising avenue19–24. Diamond contributes exceptional chemical and thermal stability25, while graphene imparts high electrical conductivity and facilitates efficient charge transport23,24. The formation of robust covalent interfaces between these two components maybe improve impedance matching, introduce multiple energy dissipation pathways26, and enhance mechanical robustness. This synergistic design strategy offers a pathway toward high-performance EWA materials capable of withstanding harsh operating environments.

Here we report an efficient strategy for the fabrication of heterostructured diamond composites engineered within a diamond matrix for designing high-performance EWA materials under moderate pressure and temperature conditions27. The material consists of multilayer graphene domains embedded in nanodiamond (ND) matrices, with covalently bonded interfaces. The optimized material shows a maximum effective absorption bandwidth (EAB) of 4.0 GHz at 2.7 mm and a minimum reflection loss (RL) of -60 dB at 3.0 mm, while maintaining stable performance across a broad temperature range (300–973 K). The composite also exhibits a fracture toughness of 16.8 MPa·m1/2, a Vickers hardness of 41.9 GPa, an oxidation onset temperature of 1145 K, a corrosion potential of -0.210 V, and a low corrosion current density of 10-6 A/cm2. These findings provide a promising strategy for designing multifunctional EWA materials, offering new possibilities for advanced applications in harsh environments such as aerospace, military systems, and advanced electronics.

Results
Design and preparation of diamond composites

Figure 1a illustrates the synthesis route for the diamond composites (DC). ND particles with an average diameter of ~5 nm were first annealed at 1200 oC, inducing partial graphitization and forming fullerene-wrapped diamond nanostructures. These pre-graphitized NDs were then used as precursors for high-pressure and high-temperature (HPHT) treatment. Under conditions of 7.0 GPa and 1100-1300 oC, three composite samples were obtained, each exhibiting a distinctive hybrid microstructure in which multilayer graphene fragments are coherently embedded with a diamond matrix (Fig. 1b). For clarity, the products synthesized at 1100 oC, 1200 oC, and 1300 oC are denoted DC-1, DC-2, DC-3, respectively. A key distinction of the present diamond–graphene composites is the substantially reduced synthesis pressure enabled by the pre-graphitization strategy. Unlike Diaphene, which requires ~12 GPa, the composites form at 7 GPa while retaining comparable mechanical properties. This reduction arises from an interface-mediated phase transformation pathway introduced by the pre-formed sp² carbon shell. During HPHT treatment, the graphitic layers accommodate compressive strain through bond rehybridization and interlayer sliding, redistributing local stress and lowering the effective barrier for sp²→sp³ reconstruction at the diamond surface47–49. In addition, the intimate contact between graphene and nanodiamond provides coherent interfacial templates that facilitate localized nucleation of sp³ bonds, bypassing bulk diffusion-controlled transformation50. These cooperative effects, such as stress accommodation, reduced nucleation barriers, and constrained carbon migration, shift the transformation from a pressure-dominated bulk process to an interface-controlled reconstruction mechanism, enabling hybrid diamond–graphene architectures to form under milder conditions. Structurally, both materials feature interconnected ND grains bridged by few-to multi-layer graphene domains, forming continuous sp²-sp³ covalent interfaces that promote efficient load transfer and improve toughness. Consistently, the DC composites exhibit Vickers hardness values ranging from 41.9 to 51.7 GPa and fracture toughness spanning 10.5 to 16.8 MPa·m1/2, closely matching those of Diaphene.

Beyond mechanical robustness, the covalently bonded diamond/graphene interface imparts a suite of advantageous properties, summarized in Fig. 1c. Notably, DC-3 exhibits an oxidation onset temperature of 1145 K, exceeding those of natural diamond, nanopolycrystalline diamond (NPD), and Diaphene. The thermal conductivity of 3.5 W·m-1·K-1 highlights the strong phonon scattering inherent to the nanostructured architecture, while the corrosion potential of -0.210 V. reflects enhanced electrochemical stability. Most importantly, the optimized composite delivers excellent electromagnetic wave absorption, with a RL of -60 dB and an EAB of 4.0 GHz, positioning it among the leading carbon-based absorbers capable of operating under extreme environmental conditions.

Microstructure and dielectric properties

To examine the microstructure of the diamond composites, we performed scanning transmission electron microscopy (STEM). High-resolution high-angle annular dark field-STEM (HAADF-STEM) images (Figs. 2a-b) reveal a ND matrix embedded with multilayer graphene domains. Magnified images reveal an atomic-scale continuity between graphene and diamond (Figs. 2c-d), providing direct evidence of covalently bonded sp2-sp3 interfaces21 rather than simple van der Waals contact. Carbon K-edge electron energy loss spectroscopy (EELS) mapping acquired across the interfacial region (Fig. 2e) further confirms mixed bonding character: graphene domains exhibit a prominent π* at 284 eV, whereas diamond grains show the σ* feature at 292 eV19. These observations demonstrate the formation of covalently bridged diamond/graphene heterointerfaces throughout the composite. X-ray diffraction patterns (Fig. 2f and Supplementary Fig. 1a) display the coexistence of broad graphitic (002) peak and characteristic diamond reflections at (111), (220) and (311). Rietveld refinement yields diamond phase fractions of 78.3%, 74.1%, and 63.9% for DC-1, DC-2, and DC-3, respectively (Supplementary Fig. 2), consistent with progressive graphitization at higher synthesis temperatures. Despite the HAADF-STEM observation of multilayer graphene, no discernible 2D band is detected in Raman spectra (Supplementary Fig. 1b), likely due to interfacial bonding, local lattice distortions, and defect formation that disrupt the double-resonance process28,29. The decreasing ID/IG ratios and enhanced sp2 signal in XPS (Supplementary Fig. 1c) corroborate the formation of interconnected diamond/graphene networks.

Electromagnetic parameters (Fig. 2g and Supplementary Fig. 3) indicate that dielectric loss in the DC composites originates from the combined contributions of conduction loss and multiscale polarization mechanisms. Abundance sp³/sp² heterojunctions introduces strong interfacial polarization due to the conductivity contrast, while defect-rich graphene layers support dipolar relaxation30. Graphitic networks further facilitate electron hopping and conduction loss17, increasing the magnitude of ε′′ while maintaining the frequency-dependent trends observed in ND. The prominent loss peaks near 6-8 GHz and 11-15 GHz are attributed primarily to interfacial and defect-mediated relaxation associated with the diamond-rich matrix, explaining why graphene incorporation enhances the overall dielectric loss but does not shift the relaxation frequencies31. Cole-Cole plots demonstrate multiple relaxation semicircles for all DC samples (Supplementary Fig. 4), in contrast to the simpler profile of graphene powder, reflecting a more heterogeneous distribution of dipolar species and interfacial polarization sites. DC-2 and DC-3 show broader and more numerous semicircles than either ND or CVD diamond, consistent with their richer population of sp2-sp3 interfaces. Quantitative analysis of conductive (εc″) and polarization (εp″) components (Fig. 2h) further reveals that conduction loss dominates below 4 GHz, whereas polarization loss becomes the principal attenuation mechanism at 4–18 GHz. For DC-3, εc″ accounts for ~77% of total ε″ at 3 GHz, but decreases to 24% at 11 GHz and 15% at 14 GHz, accompanied by a corresponding increase in polarization contributions (Fig. 2j and Supplementary Fig. 5). Magnetic loss is negligible for all sample, as evidenced by the nearly uniform complex permeability (Supplementary Fig. 3), confirming the nonmagnetic nature of carbon-based materials. Instead, impedance matching is strongly modulated by the sp³/sp² ratio. As the diamond fraction decreases with increasing synthesis temperature, impedance matching improves. For DC-3 (63.9% sp3), the majority of impedance values fall within the optimal 0.8-1.2 window (Fig. 2i), enabling efficient microwave coupling and broadband attenuation.

Impact of heterostructure engineering on dielectric properties

The advantages of heterostructure engineering are further demonstrated by the enhanced EWA performance. The calculated RL and EAB of all DC composites and the ND precursor were calculated from transmission line theory6:

Zin =Z’−jZ’’=Z0 √μr/εr tanh[j(2πfd/c)√μr εr] (1)

RL (dB)=20•log |(Zin -Z0)/(Zin +Z0)| (2)

where Zin is the input impedance, d is the absorber thickness, c is the speed of light, f is the microwave frequency, and Z0 is the characteristic impedance of free space. To elucidate how interfacial defect sites and diamond grain size modulate the dielectric response, we carried out first-principles calculations. Two representative diamond/graphene interface models were constructed: one defect-free and one containing vacancy defects (Figs. 3a-b). Their calculated dielectric constants and impedance matching coefficients are presented in Fig. 3c. Due to the intrinsic non-magnetic nature of carbon-based materials, the complex magnetic permeability was set to 1.0, and the impedance matching coefficient Z was evaluated accordingly32:

Z =|Zin/Z0| =|√μr/εr tanh(j(2πfd/c)√μr εr)| (3)

Incorporation of the calculated dielectric parameters into the impedance model shows that the defective interface yields a matching coefficient closer to unity at a thickness of 1.0 mm, indicating that vacancy defects at the heterointerfaces promote improved impedance matching and thereby enhance EWA performance. Defective sites at the diamond-graphene interface serve as pivotal centers for energy dissipation, as the local chemical heterogeneity induces both permanent dipoles and charge‐trapping states that amplify dielectric loss. The presence of dangling bonds and sp³–sp² transitions creates a distribution of dipole moments and relaxation times, which manifest as broadened and overlapping semicircles in the Cole–Cole representation (Supplementary Fig. 4), thereby elevating ε″. To further assess the role of structural length scale, we constructed additional interface models with systematically varied diamond grain sizes, labeled size-1, size-2, and size-3 (Figs. 3d-f). The resulting complex dielectric constants are presented in Fig. 3g. Below 12 GHz, the largest-grain model (size-3) exhibits the highest real permittivity, reflecting enhanced charge-storage capability. However, above 12 GHz, its permittivity decreases sharply and becomes lower than that of the smaller-grain models. The imaginary permittivity (Fig. 3h) increases monotonically with grain size, indicating progressively stronger dielectric loss. Despite this trend, the impedance matching coefficients (Fig. 3i) reveal that the smallest-grain model achieves the most favorable matching at 1.0 mm thickness. This suggests that reduced grain size facilitates better wave penetration and balanced energy dissipation. The first-principles results demonstrate that both interfacial defect chemistry and grain-size modulation play decisive roles in optimizing EWA behavior. These insights highlight the critical importance of microstructural design in enabling next-generation diamond/graphene absorbers with tunable and superior electromagnetic attenuation performance.

EWA performance

In the ND precursor, the high content of sp3-hybridized carbon limits electron transport and suppresses polarization-relaxation processes, resulting in poor microwave absorption (Figs. 4a-c). As the synthesis temperature increases, the sp2 carbon content rises, thereby modifying the dielectric properties and electrical conductivity of the composites (Supplementary Fig. 6). These structural and compositional transitions directly influence EWA performance, as reflected by the evolution of RLmin, EABmax, and optimal thickness (Figs. 4d-f). Specifically, DC-1 exhibits an RLmin of -12.5 dB with an EABmax of 2.6 GHz at 6.0 mm (Supplementary Figs. 7g-i). DC-2 shows a marked improvement with an RLmin of -30.0 dB and an EABmax of 3.6 GHz at 2.8 mm (Supplementary Figs. 7m-o). Notably, DC-3 delivers the strongest performance, enabled by its optimized graphene content. It achieves an EABmax of 4.0 GHz and an RLmin of -42.3 dB at 2.7 mm, and further reaches an ultradeep RLmin of -60 dB at only 3.0 mm (Fig. 4f).

To further interpret the absorption behavior, impedance matching was analyzed using the impedance-matching coefficient Z33:

Z =|Zin/Z0| =|√μr/εr tanh(j(2πfd/c)√μr εr)| (4)

when Z = 1.0, incident microwaves enter the absorber with minimal reflection. Achieving Z values close to 1.0 over a broad frequency range is critical to ensure maximum electromagnetic wave entry into the absorber. Although graphene is highly conductive and ND is insulating—conditions that usually lead to poor impedance matching—the formation of covalently bonded sp²-sp³ interfaces introduces heterogeneous microstructures containing defects and interfaces of varying dimensions19. These features suppress the overall conductivity and significantly improve impedance matching. As shown in Figs. 3g-i, DC-1 and DC-2 maintain Z values mostly above 1.2, whereas DC-3 exhibits a broad optimal matching region (Z = 0.8-1.2), consistent with its superior EWA performance. To elucidate the role of interfacial structures, ND and nanographene (NG) were mechanically mixed at ratios of 8:2, 7:3, and 6:4 and treated under the same HPHT conditions as DC-3 (Supplementary Fig. 8). The resulting composites (DG-1, DG-2, DG-3) showed progressively improved EWA performance with increasing NG content; however, all remained inferior to DC-3. For example, DG-3 achieves an RLmin of −55.7 dB at 4.5 mm and an EABmax of 3.3 GHz at 2.0 mm, whereas DC-3 reaches −60 dB at a smaller thickness of 3.0 mm and a broader EABmax of 4.0 GHz at 2.7 mm (~3.8 GHz at 2.0 mm). This disparity highlights that physical mixing produces heterogeneous, weakly bonded interfaces and discontinuous sp² domains, which hinder charge transport and degrade impedance matching26. In contrast, the pre-graphitization strategy of the DC composites yields continuous covalent sp²-sp³ networks, enabling efficient conduction and polarization losses that result in superior EWA capability. Importantly, impedance matching alone is insufficient. The absorber must also possess strong energy-attenuation capability to dissipate incident microwaves; otherwise, reflected energy from the backing layer may reemit into free space. As shown in Supplementary Fig. 9, DC-3 exhibits the highest attenuation coefficient, consistent with its elevated imaginary permittivity and enhanced dielectric loss behavior. Compared with state-of-the-art carbon-based and magnetic absorbers32-38 (Fig. 4j and Supplementary Table1), DC-3 achieves both an ultrahigh RLmin (-60 dB) and a broad EABmax of 4.0 GHz, placing it among the leading carbon-based EWA materials. Importantly, this degree of attenuation at such a small thickness surpasses many high-performance absorbers, which typically require 4-5 mm to achieve comparable suppression. The optimized sp²/sp³ hybrid architecture in DC-3 therefore provides an advantageous balance between minimal thickness, strong attenuation, and broadband absorption, underscoring its potential for lightweight and miniaturized electromagnetic shielding and stealth applications.

To elucidate the underlying mechanisms, we analyzed both conduction and polarization contributions to dielectric loss (Fig. 4k). The highly conductive sp2-rich networks enhance conduction loss via efficient charge transport. Meanwhile, the numerous heterointerfaces create local electric-field gradients where electrons preferentially accumulate on the graphene side, intensifying interfacial polarization. Dielectric loss arises from two primary contributions—conduction loss and polarization loss. The internal architecture of the composites contains numerous heterogeneous diamond–graphene interfaces, at which electrons preferentially accumulate on the graphene side, thereby strengthening interfacial polarization and contributing to enhanced energy dissipation2. Defective and edge carbon atoms introduce permanent dipoles, supporting dipolar relaxation and further boosting dielectric loss. Overall, the integrated diamond-graphene structure enables strong conduction and interfacial polarization losses while maintaining favorable impedance matching, collectively yielding efficient and broadband microwave attenuation.

Serviceability in extreme environments

To assess the suitability of the DC composites for use under extreme environments, we examined their mechanical, thermal and chemical stability. Thermal transport measurements reveal that DC-3 exhibits a remarkably low thermal conductivity of 3.5 W·m-1·K-1 at room temperature (Fig. 5a and Supplementary Fig. 10). This strong insulating behavior arises from its nanostructured architecture, with diamond nanograins surrounded by abundant interfaces and defect-rich boundaries that strongly scatter phonons and charge carriers. The composite also displays excellent oxidation resistance, with an onset temperature of 1145 K, surpassing natural diamond, NPD, and Diaphene (Supplementary Fig. 11). This enhancement may originate from the sp³-sp² covalent interfaces19,20,24, where graphene layers act as an oxygen-blocking barrier and the diamond nanograins become energetically stable25. Moreover, interfacial stress and charge redistribution further reduce surface energy and suppress oxidative reactions21. The cooperative effect of these factors leads to the delayed onset of oxidation, demonstrating that interface engineering is an efficient strategy to improve the environmental tolerance of diamond-based composites. Fracture toughness and Vickers hardness were measured under a 9.8 N load (Fig. 5b and Supplementary Fig. 12). The DC samples show fracture toughness values of 10.5-16.8 MPa·m1/2, with Vickers hardness values of 51.7 ± 2.4 GPa (DC-1), 44.5 ± 3.1 GPa (DC-2), and 41.9 ± 1.5 GPa (DC-3). Flexural strength is critical for maintaining structural stability under mechanical loading, ensuring that EWA components preserve their geometry and performance during service. Although the flexural strength of DC-3 (20~60 MPa, as shown Supplementary Figs. 12-13) is lower than that of CVD diamond (350.7 MPa, as shown Supplementary Fig. 12e), it remains high for carbon-based composites39. However, the stress–strain curves exhibit pronounced non-brittle behavior (Supplementary Fig. 13), attributable to the diamond–multilayer graphene architecture. The graphene layers hinder crack propagation through crack bridging, interfacial sliding, and deflection, thereby suppressing catastrophic brittle fracture typical of monolithic diamond and ensuring adequate mechanical integrity for load-bearing or vibration-intensive electromagnetic applications.

Electrochemical corrosion resistance was evaluated in NaCl solution (Fig. 5c). DC-3 show a corrosion potential (Ecorr = -0.21 V) and a corrosion current density (Icorr < 10-6 A/cm2), indicating strong electrochemical passivation. The positive shift in Ecorr suggests that the composite acts as an anodic barrier, suppressing electron release and minimizing corrosion18. Bode impedance spectra (Fig. 5d) further demonstrate high |Z| values at low frequencies, confirming robust protection. This behavior correlates directly with the sp³/sp² ratio: the diamond matrix supplies chemical inertness, while sp2 domains promote charge delocalization and minimize local potential gradients. Excessive sp², however, increases surface reactivity, underscoring the need for an optimized hybrid ratio (Fig. 5e). Thus, an optimal balance between the two ensures both structural stability and electronic equilibrium at the interface22, effectively improving corrosion resistance through synergistic chemical passivation and charge delocalization. Finite element simulations of power-loss density (PLD) distribution (Fig. 5f) consistently show that DC-3 exhibits the most intense and spatially extensive PLD at 7 GHz (C-band), 11 GHz (X-band), and 15 GHz (Ku-band)11, directly reflecting its superior microwave attenuation capacity. High-temperature absorption measurements (Fig. 5g and Supplementary Fig. 14) demonstrate that DC-3 maintain stable microwave attenuation between 773-973 K. With increasing temperature, the permittivity decreases (Supplementary Fig. 15) and the optimal absorption thickness shifts toward larger thickness; at a fixed 3.2 mm thickness, the bandwidth gradually narrows35.

Although HPHT synthesis reliably produces covalently bonded sp³-sp² interfaces and high-performance composites, scale-up remains limited by the requirements of ultra-high pressure, high temperature, and high energy consumption. Strategies to reduce cost and improve throughput include tailoring precursor chemistry to lower transformation thresholds, adopting spark plasma sintering (SPS)40 or hot-pressing, and exploring hybrid HPHT-SPS approaches. In addition, emerging metal-catalyzed pathways, such as liquid Ga-, Ni-, or Cu-mediated formation of sp³-sp² interfaces41-46 offer promising alternative routes to large-scale production of covalently integrated carbon heterostructures. Overall, DC-3 combines high mechanical strength, low thermal conductivity, excellent oxidation and corrosion resistance, and stable high-temperature microwave absorption, making it a promising candidate for demanding aerospace, aviation, and high-performance engineering applications.

In summary, we have developed a diamond composite that combines efficient electromagnetic wave absorption with exceptional environmental tolerance by integrating multilayer graphene within a nanodiamond matrix through sp2-sp3 heterointerfaces. This engineered architecture enhances mechanical robustness, enables favorable impedance matching, and activates multiple energy-dissipation pathways, allowing the material to retain strong absorption performance even under extreme operating conditions. The optimized composite achieves a minimum reflection loss of −60 dB together with an effective absorption bandwidth of 4.0 GHz, outperforming many previously reported carbon-based absorbers. This heterointerface design strategy, combined with scalable fabrication route, provides a versatile framework for creating multifunctional and highly stable carbon-based EWA materials through controlled tuning of diamond and graphene domains. The demonstrated thermal, mechanical, and chemical durability further positions the composite as a compelling candidate for aerospace, marine, and advanced electronics applications, where reliable operation in harsh environments is essential.

Methods
Sample preparation

Nanodiamond powers (99%) were purchased from Shanghai Aladdin Biochemical technology Co., Ltd. The initial nanodiamonds were first annealed in air at 450 oC for 60 minutes to remove amorphous carbon and sp2-bonded carbons. Subsequently, the samples were dried under vacuum in a tube furnace at 1200 oC for 10 minutes to induce structural transformation. High-pressure high-temperature synthesis was conducted using a China-type cubic large-volume press system equipped with a custom-designed sample assembly. Temperature was monitored with type-C thermocouples, and pressure was estimated based on established calibration curves. The recovered samples were 13.5-14.0 mm in diameter and 1.5-2.0 mm in height.

Structural characterization

X-ray diffraction (XRD) measurements were performed using a Rigaku SmartLab diffractometer with Cu Kα radiation source (λ = 1.5406 Å). Phase composition and volume fractions were determined through Rietveld refinement analysis. Raman spectra were recorded at room temperature using a Horiba LabRAM HR Evolution system with a 532 nm excitation laser. X-ray photoelectron spectroscopy (XPS) spectra were conducted on an ESCALAB 250 Xi system (Thermo Fisher Scientific) to analyze elemental chemical states. Thin lamellae for transmission electron microscopy (TEM) were prepared via focused ion beam using a Helios G4 system. High-resolution TEM and scanning transmission electron microscopy (STEM) images were acquired using a FEI Themis Z spherical aberration-corrected microscope operating at 300 kV. Electron energy loss spectroscopy (EELS) was acquired to determine the bonding sates of the composites.

Electromagnet parameter measurement

The electromagnetic parameters of the composites were measured using a vector network analyzer (Agilent E5071C) in the frequency range of 1–18 GHz. For testing, the samples were fabricated into toroidal shapes with outer and inner diameters of 7.00 mm and 3.04 mm, respectively. The reflection loss (RL), effective absorption bandwidth (EAB), attenuation coefficient, and impedance matching coefficient were calculated using custom Python scripts and CST Microwave Studio software. Electrical resistivity (ρ) as a function of temperature was measured in the range of 2-300 K using the standard four-probe method with a Physical Property Measurement System (PPMS, Quantum Design Inc.). Platinum wires were affixed to the polished sample surface using silver paste to ensure good electrical contact. The electrical conductivity (σ) was calculated from the measured resistivity values according to the relation σ =1/ρ.

Corrosion resistance measurement

The electrochemical measurements were conducted to further evaluate the stability of DC samples. Bulk specimens were tested using Princeton VersaSTAT 4 electrochemical workstation, employing a of 3.5 % NaCl solution as the electrolyte and Ta saturated calomel electrode as the reference electrode. Electrochemical impedance (EIS) measurements were performed within the frequency range of 0.1–105 Hz with an amplitude of 10 mV. Tafel polarization curves were recorded over a potential range of -1 V to 1 V at a scan rate of 1 mV/s to determine the corrosion potential and the corrosion resistance of the samples.

High temperature microwave absorption testing

Microwave absorption performance at elevated temperatures was assessed using the waveguide method with a vector network analyzer (Ceyear 3672B) in the X-band frequency range. Samples were machined into rectangular parallelepipeds with dimensions of 22.86 mm × 10.16 mm × 1 mm to ensure compatibility with the waveguide system. The multiple synthesized samples were ground and consolidated using high-purity silica gel (SiO2·nH2O) to form specimens suitable. A controlled heating rate of 5 °C/min was applied, followed by a 10-minute isothermal holding period at each target temperature (773 K, 873 K, and 973 K) to ensure achieve thermal equilibrium prior to measurement. In addition, to exclude any potential influence of the high-purity silicone (a high transparency adhesive used for high-temperature microwave absorption measurement51) on the measurements, a control experiment was performed at 873 K, and its effect was found to be negligible (Supplementary Fig. 16).

Mechanical and thermal measurements

The standard Vickers hardness of samples was measured using a microhardness tester (KB5-BVZ) on polished surfaces. An applied load was maintained for a dwell time of 10 s. The Vickers hardness (Hv) was calculated using the equation: Hv = 1854.4F/L2, where F (N) is the applied load and L (μm) is the average diagonal length of the Vickers indentation. Five indentations were obtained at each to calculate an average hardness value. Fracture toughness (KIC) was determined from KIC = 0.016(E/Hv)0.5F/C1.5, where F (N) is the applied load, C (μm) is the average length of the radial cracks measured from the indent center, and E (1140 GPa) is Young’s modulus of diamond. The flexural strength of the synthesized samples was evaluated using a three-point bending test. The thermal stability of the samples was tested using a NETZSCH STA 449F3 system, with a heating rate of 5 K/min across a temperature range from 300 to 1473 K. The thermal diffusivity was determined using an LFA467HT HyperFlash system, with measurements conducted at intervals of 50 K from 300 to 800 K, and at least three data points collected at each temperature to ensure accuracy.

Numerical simulation

Power loss density (PLD) distributions were simulated using COMSOL Multiphysics®. To optimize computational efficiency, a simplified cubic model with dimensions of 6 mm × 6 mm × 4 mm was employed. Microwave excitation at frequencies of 7, 11, and 15 GHz was introduced along the z-axis from the top surface. Periodic boundary conditions were applied in both the x and y directions to emulate infinite lateral extension and reduce edge effects.

First-principles calculations

All calculations were performed using the Vienna ab initio simulation package (VASP) within the GGA-PBE framework and projector augmented wave (PAW) pseudopotentials. The 500 eV cutoff energy was used. Structural relaxation was conducted with a 10×3×1 k-point mesh until forces were below 0.02 eV/Å and energy convergence reached 10-6 eV. We constructed diamond/graphite heterostructures, then created a carbon vacancy model and 3, 6, 9-layer variants. Dielectric constants were computed after full optimization of all five systems.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "General Comment\nThe authors report on a composite composed entirely of carbon allotropes for EM wave absorption. The EWA performance\nitself seems solid, with calculations done using trivially utilized methods. However, extensive improvements must be made\nin revealing the role of the interfaces and individual materials inside the composite on the EWA properties, especially in\nnanocomposites like this case where the combined materials are composed of the same element. (It is much easier to split\nthe role in a more ‘heterogeneous’ structure such as a graphene-polymer composite).\nComments\n- Is the term ‘graphene’ fully appropriate in this study? It feels like terms such as ‘graphitic carbon’ would better suit in this\ncase.\n- In the Raman data, show the full-range data to include the 2D peak regions. Also, add additional interpretations on the\ngraphitic structure based on the 2D peak region.\n- In Figure 2h, the authors must discuss in detail the correlation between material chemistry and dielectric loss parameters,\nand what types of vibrations at which dimensions (atomic? Molecular? Dipolar?) result in the dielectric properties observed\nin the composite.\n- For the imaginary permittivity (e’’) in Figure 2h, the pattern of nanodiamond (black lines) is similar to those of DC-1, DC-2,\nand DC-3 (Especially for the peaks near 6-8 GHz and 11-15 GHz). It is understandable that the conductive graphitic sheets\ncontribute to the increased real permittivity (e’), but why does e’’ show a similar pattern bettwen DC-1, 2, 3 and nd? If the\ngraphene with sp2 carbon should contribute, it should add a different dielectric loss pattern compared to the sp3\nnanodiamond.\n- Add analyses based on Cole-Cole plots on the EWA performance and properties.\n- I do not see any clear proof on the covalent bonding between and diamond. It is very important to reveal this, as the edge\nbonding structure of diamond and graphene will highly differ depending on whether they are physically adjoined or\ncovalently bound together, which eventually influences the dielectric properties.\n- Discuss the influence of defective sites at the interface between graphene and diamond, and how their chemical structure\nand dipoles influence the EWA performance.\n- In Figure 3j, authors must add comparison with state-of-the-art composites based on magnetic materials as well. Although\nthis paper is based on dielectric materials (carbons), the overall comparison still needs to include magnetic materials, as\nthey are the dominant EWA materials in the studies frequency range.\n- I think that this composite could also be made and controlled by initially adding nanodiamonds and nanographenes\ntogether and apply the HTHP process, which would create different interfaces. Discuss on this method in creating\ncomposites and their EWA properties.", "reviewer_2": "Carbon has many allotropes, and each one has greatly boosted technological progress and social development. This\ndiversity comes from carbon's ability to form sp, sp2, and sp3 hybridizations. Different hybridizations lead to stark differences\nin physical and chemical properties. Recently, hybrid structures and composites combining diamond with graphite/graphene\nhave been developed. These materials integrate diamond's superhardness and the high electrical conductivity of\ngraphite/graphene, achieving unique property combinations that single allotropes cannot match, which is of great\nsignificance for expanding the application scope of carbon materials. This type of novel carbon material is typically obtained\nby using high pressure to induce phase transitions from sp2-hybridized carbon precursors to the sp3-hybridized diamond\nphase. In this work, the authors reversed this process by inducing an sp³ to sp² transition under moderate high-pressure and\nhigh-temperature conditions, resulting in the production of large-size diamond/graphene composites. These composites not\nonly exhibit superhardness and electrical conductivity but also show potential for electromagnetic wave-absorbing\napplications. This study, demonstrating both timeliness and importance, is recommended for publication in Nature\nCommunications. Nevertheless, there are several issues that need to be addressed.\n1. The authors are advised to supplement the structural characterization with detailed TEM observations focusing on the\ninterface between diamond and graphene. The authors should provide direct evidence to clarify the nature of the bonding at\nthe interface, determining the type of interaction—whether it is van der Waals or covalent. This clarification is crucial for\noffering a structural explanation for the superior mechanical and microwave absorption performance.\n2. Given the authors' recent report on synthesizing similar composite Diaphene [PNAS, 2024, 121.9: e2316580121], the\nauthors are expected to conduct a thorough comparison between this work and the Diaphene in three aspects: differences in\npreparation methods, microstructural characteristics, and mechanical properties.\n3. Regarding the microwave absorption performance of the samples, the optimal sample achieves a minimum reflection loss\nof -61.47dB at a thickness of 5.5mm, which is relatively thick. Generally, studies typically report data up to a thickness of\n5mm. The material shows nearly -60dB performance at 3.5mm, which is comparable to previously reported carbon-based\nmicrowave absorption materials and offers a certain thickness advantage. It is suggested that the authors select this data\npoint as the optimal RL value for specific analysis.\n4. In the discussion of serviceability in extreme environments, hardness may not be the most critical mechanical property for\nelectromagnetic wave absorption materials. It is recommended that the authors provide additional mechanical property\nindicators such as fracture toughness, and bending strength.\nAdditionally, the DC-3 sample's initial oxidation temperature of 1145 K surpasses that of natural diamond and NPD, and\neven exceeds the previously reported Diaphene. Further comparative analysis and discussion are needed to elaborate on\nthis aspect.\n5. There are several minor issues in the paper that need to be addressed:\nThere is a discrepancy between the sample dimensions mentioned in the synthesis method and those used in the high-\ntemperature microwave absorption tests. The recovered samples are described as having a diameter of 13.5-14.0mm and a\nheight of 1.5-2.0mm, whereas the samples for microwave absorption testing are rectangular parallelepipeds with dimensions\nof 22.86mm × 10.16mm × 1mm.\nThe Raman fitting results in Fig. 2f and Fig. S1b are inconsistent.\nThere is a spelling error in the word \"hardness\" at line 210.\nThe horizontal axis label in Fig. S1c contains a spelling error.", "reviewer_3": "The manuscript titled \"Heterostructure-Engineered Diamond-Graphene Composites for High-Performance and Stable\nElectromagnetic Wave Absorption\" presents a systematic study on the synthesis, characterization, and electromagnetic\nwave absorption (EWA) performance of heterostructured diamond-graphene composites. This work addresses critical\nlimitations of conventional carbon-based EWA materials, such as poor impedance matching and insufficient environmental\nresilience, but several core academic questions require further clarification. Here are some specific comments for the\nauthors:\n1. The optimized composite (DC-3) achieves a minimum reflection loss of -61.47 dB, yet the supplementary Table 1\ncompares the material with other carbon-based absorbers but does not include data on the thickness corresponding to the\nminimum reflection loss of these reference materials. How does the thickness of DC-3 (5.5 mm for -61.47 dB) compare to\nthat of the referenced materials when achieving their respective minimum reflection loss values, and what impact does this\nthickness difference have on practical application potential?\n2. The authors mention that the incoherent interface between diamond and graphene enhances impedance matching, but\nthey do not elaborate on the specific mechanism by which the incoherent interface regulates the impedance matching\ncoefficient. What is the relationship between the structural features of the incoherent interface (e.g., grain size of the ND,\ninterface defect density, lattice mismatch) and the impedance matching performance, and is there experimental or simulation\nevidence to support this relationship? A theoretical simulation would be helpful to elucidate the underline mechanism.\n3. The electrical conductivity of the DC samples increases with decreasing sp³ content, as shown in Fig. 2i, but the\nmanuscript does not discuss how the change in electrical conductivity specifically affects the conduction loss mechanism of\nelectromagnetic waves. How to quantitatively distinguish the contribution of conduction loss from other loss mechanisms\n(e.g., interfacial polarization loss, dipole polarization loss) in the total dielectric loss of the composites?\n4. The corrosion potential of DC-3 is -0.210 V, and the corrosion current density is less than 10⁻⁶ A/cm², indicating good\ncorrosion resistance. But the manuscript does not explain why the corrosion resistance of DC-1 (with higher sp³ content) is\nslightly better than that of DC-2 and DC-3, as suggested by the Nyquist plots. What is the intrinsic relationship between\nsp³/sp² content and the corrosion resistance mechanism of the composites?\n5. The high-temperature electromagnetic wave absorption performance of DC-3 is stable between 773 K and 973 K, but the\nabsorption bandwidth decreases slightly with increasing temperature. The manuscript attributes this to temperature-\ndependent hopping conductivity and dipole polarization, but there is no experimental data on the change of dielectric\nparameters (ε', ε'') with temperature. What are the variations of complex permittivity and permeability of DC-3 at different high\ntemperatures (773 K, 873 K, 973 K), and how do these variations explain the change in absorption bandwidth?\n6. The manuscript proposes that the heterostructure design of diamond-graphene composites provides a new strategy for\nmultifunctional electromagnetic wave absorbing materials, but it does not discuss the scalability and cost of the moderate\nhigh-pressure and high-temperature (HPHT) synthesis method. What challenges exist in scaling up the HPHT preparation\nprocess for industrial production, and are there potential improvements to reduce the synthesis cost while maintaining\nmaterial performance?\n7. The author should provide a more updated review of literatures with covalent bonded sp3-sp2 carbon interfaces, which\ncould be catalyzed by metal such as liquid gallium, nickel or copper."}, "author_response": "Point-by-Point Response to the Reviewers’ Comments\nWe sincerely thank the reviewers for their careful reviews and constructive\nsuggestions, which have significantly improved the clarity and quality of our work. We\nbelieve that the revised manuscript and this response letter fully address the reviewers’\ncomments. Below, we provide detailed point-by-point responses. For clarity, the\nreviewers’ comments are shown in black, our replies in blue, and the corresponding\nmanuscript revisions are marked in red.\nReviewer #1 (Remarks to the Author):\nGeneral Comment: The authors report on a composite composed entirely of carbon\nallotropes for EM wave absorption. The EWA performance itself seems solid, with\ncalculations done using trivially utilized methods. However, extensive improvements\nmust be made in revealing the role of the interfaces and individual materials inside the\ncomposite on the EWA properties, especially in nanocomposites like this case where\nthe combined materials are composed of the same element. (It is much easier to split\nthe role in a more ‘heterogeneous’ structure such as a graphene-polymer composite).\nReply: We sincerely thank you for your detailed comments and valuable\nsuggestions, which have been very helpful in improving the quality of our manuscript.\nIn response to the comments regarding the role of interfacial structures and the\nindividual components within the composite in determining the EWA properties, we\nhave incorporated additional experimental results and theoretical analyses to establish\na clearer correlation between the structural characteristics and the EWA properties.\nPlease refer to our detailed point-by-point responses below for further clarification.\n1. Is the term ‘graphene’ fully appropriate in this study? It feels like terms such as\n‘graphitic carbon’ would better suit in this case.\nReply: We appreciate the reviewer’s insightful comment. In our study, the term\n“graphene” was used to describe multilayer, sp²-bonded carbon structures that formed\nwithin the diamond matrix during high-pressure, high-temperature processing. As\nshown in Fig. R1, these layers exhibit (002) diffraction peak and Raman features (G\nand D bands) of graphitic carbons, as confirmed by XRD, XPS and Raman analyses.\nTo further clearly characterize the microstructure, we have conducted high-angle\nannular dark-field scanning transmission electron microscopy (HAADF-STEM)\nmeasurements. Fig. R2 shows the HAADF-STEM images of the DC-3 sample, in which\ndiamond (D) and graphene (G) nanodomains are clearly distinguished. However, we\nagree that these carbon layers are not ideal monolayer graphene but rather graphitic\ndomains with multilayer structures. To ensure accuracy and consistency, we have\nrevised the manuscript to refer to them as “multilayer graphene” where appropriate.\nThis clarification more accurately reflects their structural characteristics.\n(a) X-ray diffraction (XRD) pattern. (b) Raman spectra (532 nm excitation). (c) X-ray\nphotoelectron spectroscopy (XPS) pattern.\nFig. R2. Microstructures of the DC-3 sample. (a) High-resolution HAADF-STEM\nimage, where a diamond (D) matrix embedded with multilayer graphene (G) sheets. (b)\nMagnified HAADF-STEM image of the white-boxed region in a, revealing an\natomically covalent interface between graphene and diamond. (c, d) Additional high-\nmagnification HAADF-STEM images exhibiting multilayer graphene. (e) HAADF-\nSTEM image showing multiple diamond/graphene interfaces. (f) Carbon K-edge EELS\nspectra extracted from the surface-scan region marked by white dashed box in e.\n2. In the Raman data, show the full-range data to include the 2D peak regions. Also,\n2\nadd additional interpretations on the graphitic structure based on the 2D peak region.\nReply: Thank you very much for your valuable comments. Following your\nsuggestion, we show the full-range Raman spectra, including the 2D peak region, as\nshown in Fig. R3. Although the HAADF-STEM images confirm the presence of\nmultilayer graphene (see Fig. R2), the 2D peak is not evident in the Raman spectra of\nour samples, unlike the case of graphene sample. This absence can be attributed to\nseveral factors. First, the strong interaction and bonding between graphene and diamond\nat the incoherent interfaces may distort the π–π* electronic structure of graphene,\nthereby suppressing the resonance conditions required for the 2D band. Second,\nstructural defects, lattice distortions, and partial sp³ hybridization introduced during\nhigh-pressure, high-temperature synthesis can significantly reduce the intensity or even\neliminate the 2D peak. These combined effects result in an undetectable 2D peak,\ndespite the confirmed presence of multilayer graphene in the composite.\nWe have updated Fig. R3 into the revised manuscript as Supplementary Fig. 1b,\nand have revised accordingly in the revised manuscript: “Despite the HAADF-STEM\nobservation of multilayer graphene, no discernible 2D band is detected in Raman\nspectra (Supplementary Fig. 1b), likely due to interfacial bonding, local lattice\ndistortions, and defect formation that disrupt the double-resonance process28,29.” (Page\n7, Lines 14–17)\nFig. R3. Raman spectra of the DC composites and ND precursors. The Raman\nspectrum of graphene powder is shown for comparison.\n3. In Figure 2h, the authors must discuss in detail the correlation between material\nchemistry and dielectric loss parameters, and what types of vibrations at which\ndimensions (atomic? Molecular? Dipolar?) result in the dielectric properties observed\nin the composite.\nexpanded the discussion to clarify the correlation between material chemistry and the\nobserved dielectric loss parameters, as well as the nature and scale of the associated\npolarization and vibration mechanisms.\nIn our diamond composites, the dielectric loss primarily originates from\nconduction loss and polarization loss, both of which are strongly influenced by the\nmaterial’s chemical composition and heterostructure. The incorporation of sp²-bonded\nmulti-layer graphene within the sp³-bonded diamond matrix creates numerous\nheterointerfaces, defects, and localized charge accumulation sites. These structural and\nchemical features lead to several distinct polarization mechanisms operating at different\nlength scales:\nMolecular or dipolar polarization: The presence of defects, vacancies, and\nfunctional groups within the graphitic domains introduces dipoles that align with the\napplied electromagnetic field, generating relaxation-type dielectric losses.\nInterfacial polarization: At the nanoscale, the large number of diamond/graphitic\ninterfaces leads to charge accumulation due to conductivity contrast, resulting in\nsignificant interfacial polarization and energy dissipation.\nConduction loss: The graphitic networks facilitate electron hopping and migration\nunder the alternating field, further enhancing dielectric loss.\nThe degree of graphitization directly affects the electrical conductivity and\ninterfacial density, which in turn modulate both ε′ (energy storage) and ε″ (energy\ndissipation). As shown in Fig. R4, increasing sp² content enhances dielectric loss\nthrough improved charge transport and intensified interfacial polarization.\nWe have added Fig. R4 into the revised manuscript as Fig. 2g, and added detailed\ndiscussions in the manuscript: “Electromagnetic parameters (Fig. 2g and\nSupplementary Fig. 3) indicate that dielectric loss in the DC composites originates from\nthe combined contributions of conduction loss and multiscale polarization mechanisms.\nAbundance sp³/sp² heterojunctions introduces strong interfacial polarization due to the\nconductivity contrast, while defect-rich graphene layers support dipolar relaxation30.”\n(Page 7, Lines 19–22; Page 8, Line 1)\nFig. R4. The complex permittivity of DC, graphene, and diamond. (a) The real part\nof the complex permittivity. (b) The imaginary part of the complex permittivity. (c) The\ntangent value of complex permittivity.\n4\n4. For the imaginary permittivity (ε’’) in Figure 2h, the pattern of nanodiamond (black\nlines) is similar to those of DC-1, DC-2, and DC-3 (Especially for the peaks near 6-8\nGHz and 11-15 GHz). It is understandable that the conductive graphitic sheets\ncontribute to the increased real permittivity (ε’), but why does ε’’ show a similar pattern\nbetween DC-1, 2, 3 and nd? If the graphene with sp2 carbon should contribute, it should\nadd a different dielectric loss pattern compared to the sp3 nanodiamond.\nReply: We thank the referee for the excellent question. To address this issue, we\nperformed additional experiments and compared the complex permittivity of the DC\ncomposites, graphene, ND precursors and CVD diamond in the 2-18 GHz range (See\nFig. R4). For sp2 graphene, conduction loss is the dominant dielectric loss mechanism\ndue to its delocalized π-electron system, complemented by defect/dipolar polarization\n(defects or functional groups) and interfacial polarization (stacked or agglomerated\ngraphene layers). Thus, the incorporation of graphene increases the overall ε′ and ε″\nintensity (ε″ ∝ σ/ω) through improved electrical conductivity, but without shifting the\ncharacteristic relaxation frequencies because GHz frequencies are far below graphene’s\nintrinsic plasmonic range (THz).\nFor ND precursors synthesized via the detonation method, their surfaces inevitably\ncontain a certain amount of sp2 carbon, as evidenced by the Raman spectrum (Fig. R1b).\nThese surface-rich structure leads to interfacial polarization between sp3 core and\ndisordered sp2 shell and dipolar relaxation from surface functional groups. In contrast,\nCVD diamond exhibits extremely low dielectric loss across 2-18 GHz due to its\nelectrically insulating nature, where ε″ primarily arises from dipolar relaxation related\nto intrinsic defects, impurity-induced dipoles, and grain boundary polarization.\nTherefore, in the 2–18 GHz range, the main dielectric loss mechanism is not\nintrinsic plasmon resonance of sp2 graphene, but rather interfacial polarization and\ndipolar relaxation caused by lattice defects, surface functional groups, and\ndiamond/graphene interfaces. These relaxation processes occur at similar time scales in\nboth ND, graphene and DC composites, leading to comparable ε″ peak patterns. The\npresence of graphene increases ε″ intensity but does not shift the peak positions.\nWe have updated Fig. R4 into the revised manuscript as Fig. 2g, and have revised\naccordingly in the revised manuscript: “Graphitic networks further facilitate electron\nhopping and conduction loss17, increasing the magnitude of ε′′ while maintaining the\nfrequency-dependent trends observed in ND. The prominent loss peaks near 6-8 GHz\nand 11-15 GHz are attributed primarily to interfacial and defect-mediated relaxation\nassociated with the diamond-rich matrix, explaining why graphene incorporation\nenhances the overall dielectric loss but does not shift the relaxation frequencies31.”\n(Page 8, Lines 1-5)\n5. Add analyses based on Cole-Cole plots on the EWA performance and properties.\nReply: Thank you very much for your valuable suggestions. We sincerely\napologize for the oversight in our previous work, as Cole-Cole plots were inadvertently\nomitted and has now been added in Fig. R5. The Cole–Cole plots of the DC samples,\nnanodiamond (ND), and CVD diamond reveal multiple relaxation semicircles,\nsuggesting the presence of several distinct relaxation processes. In contrast, graphene\npowder exhibits fewer semicircular features, indicating a reduced number of relaxation\n5\nmechanisms, thereby confirming that polarization losses are primarily associated with\nthe DC and diamond-based samples. Moreover, the Cole–Cole profiles of DC samples,\nND, and CVD diamond display markedly different relaxation characteristics, reflecting\nvariations in their dielectric loss behavior. The DC-3 sample exhibits a series of\noverlapping semicircles with larger diameters and broader dispersion, indicative of\nmultiple relaxation processes and pronounced interfacial or dipolar polarization effects.\nBy comparison, the ND and CVD diamond samples show fewer and smaller semicircles,\nimplying a limited number of active relaxation pathways and weaker polarization\nstrength. The enlarged and more numerous relaxation semicircles observed in DC-2 and\nDC-3 correspond to higher ε″ values over a broader frequency range, signifying\nenhanced energy dissipation and greater dielectric loss. These findings suggest that DC-\n3 possesses a more heterogeneous polarization environment, likely arising from\ncomplex defect states and interfacial polarization, which collectively contribute to its\nsuperior dielectric loss performance relative to ND.\nWe have added Fig. R5 into the revised manuscript as Supplementary Fig. 4, and\nadded detailed discussions in the revised manuscript: “Cole-Cole plots demonstrate\nmultiple relaxation semicircles for all DC samples (Supplementary Fig. 4), in contrast\nto the simpler profile of graphene powder, reflecting a more heterogeneous distribution\nof dipolar species and interfacial polarization sites. DC-2 and DC-3 show broader and\nmore numerous semicircles than either ND or CVD diamond, consistent with their\nricher population of sp2-sp3 interfaces.” (Page 8, Lines 6-10)\nplots of ND, Diamond, and Graphene. (d) Cole-Cole plots of DC-1. (e) Cole-Cole plots\nof DC-2. (f) Cole-Cole plots of DC-3.\n6. I do not see any clear proof on the covalent bonding between and diamond. It is very\nimportant to reveal this, as the edge bonding structure of diamond and graphene will\nhighly differ depending on whether they are physically adjoined or covalently bound\ntogether, which eventually influences the dielectric properties.\nReply: We sincerely appreciate your valuable suggestion. We have conducted the\natomic-resolution high-angle annular dark-field (HAADF-STEM) measurement to\nobserve the coherent interfaces between diamond and graphene domains. Fig. R6 shows\nthe HAADF-STEM images of the DC-3 sample, in which the red box highlights the\n7\nmultilayer graphene region, while the remaining areas are predominantly diamond\nnanograins. Magnified HAADF-STEM image in Fig. R6a clearly reveals a well-defined\ncovalent interface between diamond and graphene domains, with red and blue regions\ncorresponding to graphene and diamond, respectively (Fig. R6b).\nWe have added Fig. R6 into the revised manuscript as Figs. 2b-c, and added some\ndescriptions in the revised manuscript: “To examine the microstructure of the diamond\ncomposites, we performed scanning transmission electron microscopy (STEM). High-\nresolution high-angle annular dark field-STEM (HAADF-STEM) images (Figs. 2a-b)\nreveal a ND matrix embedded with multilayer graphene domains. Magnified images\nreveal an atomic-scale continuity between graphene and diamond (Figs. 2c-d),\nproviding direct evidence of covalently bonded sp2-sp3 interfaces21 rather than simple\nvan der Waals contact.” (Page 7, Lines 1-6)\nFig. R6. Microstructures of the DC-3 sample. (a) High-resolution HAADF-STEM\nimage of the DC-3 sample, where a diamond (D) matrix embedded with multilayer\ngraphene (G) sheets. (b) Magnified HAADF-STEM image of the white-boxed region\nin a, showing an atomically covalent interface between graphene and diamond.\n7. Discuss the influence of defective sites at the interface between graphene and\ndiamond, and how their chemical structure and dipoles influence the EWA performance.\nReply: We are grateful for your kind comments. The defective sites at the\ngraphene–diamond interface significantly influence the EWA performance. We\nperformed first-principles calculations to compare the impedance matching coefficients\nof interface structures between diamond and graphene with and without vacancy defects\n(Fig. R7a and b). Calculations of their dielectric constants and impedance matching\ncoefficient for both models are presented in Fig. R7c. The interface with defects yielded\na matching coefficient closer to unity at a thickness of 1.0 mm. These results suggest\nthat the presence of vacancy defects at the diamond–graphene interface enhances EWA\nby improving impedance matching. Defective sites at the graphene–diamond interface\nserve as pivotal centers for energy dissipation, as the local chemical heterogeneity\ninduces both permanent dipoles and charge‐trapping states that amplify dielectric loss.\nThe presence of dangling bonds and sp³–sp² transitions creates a distribution of dipole\n8\nmoments and relaxation times, which manifest as broadened and overlapping\nsemicircles in the Cole–Cole representation, thereby elevating ε″. At the same time, the\nconductivity contrast inherent to the graphene/diamond junction enables Maxwell–\nWagner interfacial polarization and microscopic current loops, further increasing loss\nwithout compromising impedance matching. By tuning the density, chemistry and\nspatial arrangement of these defects, the absorber material achieves both higher\nmagnitude and broader bandwidth of microwave attenuation. Thus, the defect-rich\ngraphene–diamond interface establishes multiple polarization and conduction pathways,\nimproving impedance matching and enhancing electromagnetic energy attenuation.\nWe have added Fig. R7 into the revised manuscript as Figs. 3a-c, and added a\ndetailed discussion into the revised manuscript: “To elucidate how interfacial defect\nsites and diamond grain size modulate the dielectric response, we carried out first-\nprinciples calculations. Two representative diamond/graphene interface models were\nconstructed: one defect-free and one containing vacancy defects (Figs. 3a-b). Their\ncalculated dielectric constants and impedance matching coefficients are presented in\nFig. 3c. Due to the intrinsic non-magnetic nature of carbon-based materials, the\ncomplex magnetic permeability was set to 1.0, and the impedance matching coefficient\nZ was evaluated accordingly32:\n𝑍 1 2𝜋𝑓𝑑\nin\n𝑍 = | | = √ 𝑡𝑎𝑛ℎ(𝑗 √𝜀 )\n𝑍 𝜀 𝑐 𝑟\n0 𝑟\nIncorporation of the calculated dielectric parameters into the impedance model\nshows that the defective interface yields a matching coefficient closer to unity at a\nthickness of 1.0 mm, indicating that vacancy defects at the heterointerfaces promote\nimproved impedance matching and thereby enhance EWA performance. Defective sites\nat the diamond-graphene interface serve as pivotal centers for energy dissipation, as the\nlocal chemical heterogeneity induces both permanent dipoles and charge‐trapping states\nthat amplify dielectric loss. The presence of dangling bonds and sp³–sp² transitions\ncreates a distribution of dipole moments and relaxation times, which manifest as\nbroadened and overlapping semicircles in the Cole–Cole representation\n(Supplementary Fig. 4), thereby elevating ε″.” (Page 10, Lines 10-22; Page 11, Lines\n1-4)\ninterfaces. (a) Diamond/graphene interface without vacancy defects. (b)\nDiamond/graphene interface incorporating vacancy defects at the boundary. (c)\nCalculated real and imaginary parts of permittivity and impedance matching coefficient\nfor the defect-free (a) and defective (b) interface models.\n8. In Figure 3j, authors must add comparison with state-of-the-art composites based on\nmagnetic materials as well. Although this paper is based on dielectric materials\n(carbons), the overall comparison still needs to include magnetic materials, as they are\nthe dominant EWA materials in the studies frequency range.\nReply: We sincerely appreciate your valuable suggestion. Comparative plots with\nstate-of-the-art composites based on dielectric and magnetic materials have been\nincluded in Fig. R8. The EWA performance of reported pure carbon absorbers, carbon-\nbased composites, and magnetic materials is demonstrated in Supplementary Table 1.\nWe have added Fig. R8 into the revised manuscript as Fig. 4j, and added\ncorresponding discussions in the revised manuscript: “Compared with state-of-the-art\ncarbon-based and magnetic absorbers32-38 (Fig. 4j and Supplementary Table1), DC-3\nachieves both an ultrahigh RL (-60 dB) and a broad EAB of 4.0 GHz, placing it\nmin\namong the leading carbon-based EWA materials. Importantly, this degree of attenuation\nat such a small thickness surpasses many high-performance absorbers, which typically\nrequire 4-5 mm to achieve comparable suppression. The optimized sp²/sp³ hybrid\narchitecture in DC-3 therefore provides an advantageous balance between minimal\nthickness, strong attenuation, and broadband absorption, underscoring its potential for\nlightweight and miniaturized electromagnetic shielding and stealth applications.” (Page\n14, Lines 16-22; Page 15, Line 1)\nFig. R8. Comparison of L and EAB of the DC-3 with reported pure carbon\nmin max\nmaterials, carbon-based composites, and magnetic composites.\nTable R1. The EWA performance of pure carbon materials, carbon-based composites,\nand magnetic composites.\nmax\nSamples RL (dB) d (mm) d (mm)\nmin\n(GHz)\nrGO -6.9 2.0 0 2.0\nTi C T -46.0 4.9 2.3 1.3\n3 2 x\nTi C T /nano-carbon\n3 2 x\n-54.67 4.8 1.1 4.8\nsphere\nC/PANI -50.96 3.09 4.0 3.09\nTiC/SiBCN -45.44 2.3 4.0 2.3\nrGO and CNTs -44.6 3.0 3.3 3.0\nrGO and BN -40.5 1.6 5.0 1.6\nHollow carbon sphere -50.8 4.5 4.8 1.9\nrGO/Cu O/Cu -51.8 / 4.0 /\nCNTs/ceramic -51.9 2.65 4.4 2.65\nrGO/Ag -26.8 / 3.7 /\nGraphene Foam -53.9 / 4.56 3.2\nTi C /ZnO -26.3 2.8 1.4 2.8\n3 2\nTiC/Al O -37.6 / 2.1 2.16\n2 3\nWC/Al O -25.0 / 2.2 2.54\n2 3\nPolyaniline/carbon black -40.0 / 2.5 2.6\nZnO@MWCNTs -47.4 / 3.7 /\nBowl-like carbon\n-45.3 3.1 4.2 3.1\nnanoparticles\nFlake graphite -19.4 / 3.6 /\nCarbon black -37.0 3.0 2.4 2.55\nCarbon nanofibers -22.0 / 2.0 3.0\nTi C T /PPy -68.0 3.0 6.65 2.26\n3 2 x\nMG-3 -47.98 2.7 4.08 2.7\nMGL-3 -58.9 2.68 3.44 2.68\nTi C Tx -34.4 1.7 4.7 1.7\n3 2\nP-MXene/NiCo O -64.0 4.47 2.0 4.4\n2 4\nMCFC-69-8 -20.0 4.3 4.9 1.48\nMXene@Co -57.32 2.5 5.2 2.5\nMXene/NiCo S -52.0 1.82 5.6 1.53\n2 4\nMXene@TMOs -50.3 1.8 5.12 1.7\nSi N @WS ceramics -65.0 4.35 4.2 3.92\n3 4 2\nSiC/ Si N aerogels -25.0 3.97 4.3 3.97\n3 4\nSiOC/SiO -28.1 1.9 6.38 2.3\nBN@NC-900 -42.2 2.2 4.48 1.8\nSiCN(Ni)/BN -53.4 4.2 2.32 3.48\nGraphene/BN/Fe/BN -44.53 1.4 4.4 1.5\ncarbon/SiCN -45.37 2.5 5.95 2.5\nSiCN-1200 -21.12 3.22 4.2 32.2\nporous SiOC -67.98 3.19 4.45 3.19\nSiOC@C-3 -51.4 2.42 6.7 2.42\nDSHS -75.1 2.21 6.08 2.21\nCuCo S @EG -72.28 1.4 4.14 1.4\n2 4\nCNs (NS, P, B) -60.0 2.6 7.05 2.6\nTi AlC N -83.4 1.9 3.4 1.9\n2 0.5 0.5\nNFAG-900 -68.87 2.5 5.25 2.5\nFe C -52.09 2.9 2.55 2.9\n2 2 7 2 2 7\n9. I think that this composite could also be made and controlled by initially adding\nnanodiamonds and nanographenes together and apply the HTHP process, which would\ncreate different interfaces. Discuss on this method in creating composites and their\nEWA properties.\nReply: We really appreciate the reviewer’s insightful suggestion. Accordingly, we\nconducted additional experiments in which nanodiamonds (ND) and nanographene\n(NG) were mechanically mixed at ratios of 8:2, 7:3, and 6:4 and then subjected to the\nsame HPHT process as DC-3. These samples, referred to as DG-1, DG-2, and DG-3,\nwere selected to approximate the sp³/sp² ratios of DC-1, DC-2, and DC-3, respectively.\nAs shown in Fig. R9, increasing the NG content enhances the EWA performance of the\nDG series. However, their overall performance remains inferior to DC-3. DG-1 shows\nonly weak absorption (RL = −10.8 dB, EAB < 1 GHz at 3 mm). DG-2 achieves an\nmin\nEAB of 2.9 GHz at 2.1 mm and RL of −46.1 dB at 5.5 mm, while DG-3 exhibits an\nmin\nEAB of 3.3 GHz at 2.0 mm and RL = −55.7 dB at 4.5 mm. By comparison, DC-3\nmin\nachieves a deeper RL of −60 dB at a smaller thickness of 3.0 mm and an EAB of\nmin max\n4.0 GHz at 2.7 mm, while still maintaining ~3.8 GHz at 2.0 mm. This performance\ndifference arises from the fundamentally different interfacial structures of the two\nsystems. In the DG composites, physically mixing ND and NG results in heterogeneous\ninterfaces and weak interfacial bonding, which hinder charge transport and\nelectromagnetic coupling. The externally introduced NG also disrupts the formation of\ncontinuous sp²–sp³ transition regions, leading to poor impedance matching and lower\ndielectric loss efficiency. In contrast, the DC composites synthesized by in situ pre-\ngraphitization develop coherent, covalently bonded sp2-sp3 interfaces, where graphene\nlayers evolve directly from the diamond surface. This produces a structurally\ncontinuous conductive network, enabling efficient electron transport, optimized\nimpedance matching, and synergistic conduction and polarization losses. Thus, the\nsuperior EWA performance of DC composites originates not only from the sp²/sp³ ratio\nbut from the quality and continuity of the sp²–sp³ interfacial architecture.\nWe have added Fig. R9 into the revised manuscript as Supplementary Fig. 8, and\nadded corresponding discussion in the revised manuscript: “To elucidate the role of\ninterfacial structures, ND and nanographene (NG) were mechanically mixed at ratios\n12\nof 8:2, 7:3, and 6:4 and treated under the same HPHT conditions as DC-3\n(Supplementary Fig. 8). The resulting composites (DG-1, DG-2, DG-3) showed\nprogressively improved EWA performance with increasing NG content; however, all\nremained inferior to DC-3. For example, DG-3 achieves an RL of −55.7 dB at 4.5\nmin\nmm and an EAB of 3.3 GHz at 2.0 mm, whereas DC-3 reaches −60 dB at a smaller\nthickness of 3.0 mm and a broader EAB of 4.0 GHz at 2.7 mm (~3.8 GHz at 2.0 mm).\nThis disparity highlights that physical mixing produces heterogeneous, weakly bonded\ninterfaces and discontinuous sp² domains, which hinder charge transport and degrade\nimpedance matching26. In contrast, the pre-graphitization strategy of the DC composites\nyields continuous covalent sp²-sp³ networks, enabling efficient conduction and\npolarization losses that result in superior EWA capability.” (Page 13, Line 22; Page 14,\nLines 1-11)\nFig. R9. EWA performance of the DC-3 and DG samples obtained by directly\nmixing ND and nanographene (NG) at ratios of 6:4, 7:3, and 8:2 under the same\nvarious thicknesses for DG samples. (d-f) 2D diagrams of RL values versus frequency\nand thickness for DG samples. (g-i) 2D contour plots of the impedance matching\ncoefficient as a function of frequency and sample thickness for DG samples. (j) 3D\nEWA performance plots of DC-3. (k) 2D EWA performance diagrams of DC-3. (l) 2D\ncontour plots of the impedance matching coefficient of DC-3.\nCarbon has many allotropes, and each one has greatly boosted technological\nprogress and social development. This diversity comes from carbon's ability to form sp,\nsp2, and sp3 hybridizations. Different hybridizations lead to stark differences in physical\nand chemical properties. Recently, hybrid structures and composites combining\ndiamond with graphite/graphene have been developed. These materials integrate\ndiamond's superhardness and the high electrical conductivity of graphite/graphene,\nachieving unique property combinations that single allotropes cannot match, which is\nof great significance for expanding the application scope of carbon materials. This type\nof novel carbon material is typically obtained by using high pressure to induce phase\ntransitions from sp2-hybridized carbon precursors to the sp3-hybridized diamond phase.\nIn this work, the authors reversed this process by inducing an sp³ to sp² transition under\nmoderate high-pressure and high-temperature conditions, resulting in the production of\nlarge-size diamond/graphene composites. These composites not only exhibit\nsuperhardness and electrical conductivity but also show potential for electromagnetic\nwave-absorbing applications. This study, demonstrating both timeliness and importance,\nis recommended for publication in Nature Communications. Nevertheless, there are\nseveral issues that need to be addressed.\nReply: We are profoundly grateful to the reviewer for the positive evaluation:\n“These composites not only exhibit superhardness and electrical conductivity but also\nshow potential for electromagnetic wave-absorbing applications”, and\nrecommendation for publication in Nature Communications. We greatly appreciate\nthese suggestions, which have been invaluable in improving the quality and clarity of\nour work. We have carefully addressed all of your comments in a point-by-point manner\nand revised the manuscript accordingly, as detailed below.\n1. The authors are advised to supplement the structural characterization with\ndetailed TEM observations focusing on the interface between diamond and graphene.\nThe authors should provide direct evidence to clarify the nature of the bonding at the\ninterface, determining the type of interaction—whether it is Van der Waals or covalent.\nThis clarification is crucial for offering a structural explanation for the superior\nmechanical and microwave absorption performance.\nReply: Thank you for this constructive suggestion. We fully agree that clarifying\nthe interfacial bonding between diamond and graphene is critical to understanding the\norigin of the superior mechanical and microwave absorption performance. To address\nthis issue, we have added additional high-angle annular dark field scanning\ntransmission electron microscopy (HAADF-STEM) characterizations focusing on the\ndiamond-graphene interface (Fig. R1). Fig. R1a presents the HAADF-STEM image of\nthe sample synthesized at 7.0 GPa and 1300 °C, where diamond (D) and graphene (G)\nnanodomains can be clearly distinguished. The magnified STEM images further reveal\nan atomically coherent alignment at the interface—showing a correspondence between\nthe graphene and diamond layers. This observation provides direct structural evidence\nthat the composite is composed of nanoscale diamond and graphitic domains that are\ninterconnected via coherently bonded interfaces rather than simple Van der Waals\ncontact. Such atomic-level continuity suggests partial sp²-sp³ hybrid bonding across the\n15\ninterface, which plays a critical role in ensuring mechanical integrity and facilitating\ninterfacial polarization and electron transport, thereby enhancing electromagnetic wave\nabsorption performance.\nWe have added Fig. R1 into the revised manuscript as Figs. 2b-c, and added some\ndescriptions in the revised manuscript: “To examine the microstructure of the diamond\ncomposites, we performed scanning transmission electron microscopy (STEM). High-\nresolution high-angle annular dark field-STEM (HAADF-STEM) images (Figs. 2a-b)\nreveal a ND matrix embedded with multilayer graphene domains. Magnified images\nreveal an atomic-scale continuity between graphene and diamond planes (Figs. 2c-d),\nproviding direct evidence of covalently bonded sp2-sp3 interfaces21 rather than simple\nvan der Waals contact.” (Page 7, Lines 1-6)\nFig. R1. Microstructures of the DC-3 sample. (a) High-resolution HAADF-STEM\nimage of the DC-3 sample, where diamond (D) and graphene (G) nanodomains can be\nclearly distinguished. (b) Magnified HAADF-STEM image corresponding to the white-\nboxed region in a, showing the covalent interface between graphene and diamond.\n2. Given the authors' recent report on synthesizing similar composite Diaphene [PNAS,\n2024, 121.9: e2316580121], the authors are expected to conduct a thorough comparison\nbetween this work and the Diaphene in three aspects: differences in preparation\nmethods, microstructural characteristics, and mechanical properties.\nReply: We thank the reviewer for raising this important point regarding the\ncomparison with the Diaphene composite (PNAS, 2024, 121(9), e2316580121). We\nhave conducted a detailed comparison between the present DC composite and the\nDiaphene material in terms of preparation methods, microstructural characteristics, and\nmechanical properties, as summarized below.\nPreparation methods: Unlike conventional high-pressure and high-temperature\n(HPHT) conversions of sp² carbon to diamond, Diaphene was synthesized through the\npartial graphitization of nanodiamond precursors under moderate HPHT conditions\n(~12 GPa and 1300-1500 °C), enabling centimetre-scale synthesis in a large-volume\npress. In contrast, our DC composites were prepared using a pre-graphitization strategy,\nin which nanodiamond precursors were first annealed at 1200 °C in a vacuum to induce\n16\ncontrolled surface graphitization while preserving the sp3 diamond cores, followed by\nHPHT treatment at ~7 GPa and 1100-1300 °C. This approach effectively reduces the\nsynthesis pressure and temperature while still enabling centimetre-scale fabrication in\na large-volume press.\nMicrostructural characteristics (Fig. R2): The Diaphene material exhibits a\nbicontinuous nanoscale architecture consisting of 5-10 nm diamond grains\ninterpenetrated by curved few-layer graphene domains (typically ~5 layers),\ninterconnected through covalent sp²-sp³ interfaces that ensure mechanical and electrical\ncoupling. Similarly, the DC composites comprise multi-layer (~20 layers) graphene\ndomains uniformly embedded within nanodiamond matrices, with strong covalently\nbonded interfaces that form a robust hybrid framework.\nMechanical properties (Fig. R3): The Diaphene exhibits a Vickers hardness of\n42.5-55.8 GPa, and a fracture toughness of 10.8-19.8 MPa·m1/2, whereas our DC\ncomposites show comparable values, with hardnesses of 41.9-51.7 GPa and fracture\ntoughnesses of 10.5-16.8 MPa·m1/2. The mechanical performance parity between DC\nand Diaphene can be attributed to their similar microstructural compositions—\nspecifically, the coexistence of diamond and graphene components connected through\ncovalent sp²-sp³ bonding networks.\nWe have added corresponding discussions in the revised manuscript: “Under\nconditions of 7.0 GPa and 1100-1300 oC, three composite samples were obtained, each\nexhibiting a distinctive hybrid microstructure in which multilayer graphene fragments\nare coherently embedded with a diamond matrix (Fig. 1b). For clarity, the products\nsynthesized at 1100 oC, 1200 oC, and 1300 oC are denoted DC-1, DC-2, DC-3,\nrespectively. This pre-graphitization route contrasts with the synthesis of Diaphene24,\nwhich requires substantially higher pressures and temperatures (~12 GPa, 1300-1500\noC) to induce partial graphitization within ND precursors. By introducing sp² layers into\nthe precursor prior to compression, the present strategy reduces the HPHT threshold\nwhile still enabling centimeter-scale fabrication of diamond-based composites.\nStructurally, both materials feature interconnected ND grains bridged by few- to multi-\nlayer graphene domains, forming continuous sp²-sp³ covalent interfaces that promote\nefficient load transfer and improve toughness. Consistently, the DC composites exhibit\nVickers hardness values ranging from 41.9 to 51.7 GPa and fracture toughness spanning\n10.5 to 16.8 MPa·m1/2, closely matching those of Diaphene.” (Page 5, Lines 4–16)\ndifferential phase contrast scanning transmission electron microscopy (iDPC-STEM)\nimage of Diaphene sample, where the contrast of diamond (D) nanograins and few-\nlayered graphene sheets (G) can be observed. (b) High-magnification HAADF-STEM\nimage exhibiting multilayer graphene, where diamond (D) units and multilayer\ngraphene (G) nanodomains can be clearly distinguished.\nFig. R3. Vickers hardness and fracture toughness of the Diaphene and DC samples.\n3. Regarding the microwave absorption performance of the samples, the optimal sample\nachieves a minimum reflection loss of -61.47 dB at a thickness of 5.5 mm, which is\nrelatively thick. Generally, studies typically report data up to a thickness of 5 mm. The\nmaterial shows nearly -60 dB performance at 3.5 mm, which is comparable to\npreviously reported carbon-based microwave absorption materials and offers a certain\nthickness advantage. It is suggested that the authors select this data point as the optimal\nRL value for specific analysis.\nReply: We really appreciate the reviewer for providing the insightful comment.\nIndeed, as the reviewer indicated, the DC-3 achieves a RL value of -60 dB at a\nmin\nthickness of 3.0 mm, which is comparable to previously reported carbon-based\nmicrowave absorption materials and offers a certain thickness advantage. We have\n18\nselected this data point as the optimal RL value for specific analysis in the revised\nmanuscript.\nWe have updated Fig. R4 into the revised manuscript as Fig. 4f, and make\nmodifications to the manuscript content: “Notably, DC-3 delivers the strongest\nperformance, enabled by its optimized graphene content. It achieves an EAB of 4.0\nmax\nGHz and an RL of -42.3 dB at 2.7 mm, and further reaches an ultradeep RL of -\nmin min\n60 dB at only 3.0 mm (Fig. 4f).” (Page 13, Lines 8-11)\n“Compared with state-of-the-art carbon-based and magnetic absorbers32-38 (Fig. 4j\nand Supplementary Table1), DC-3 achieves both an ultrahigh RL (-60 dB) and a\nmin\nbroad EAB of 4.0 GHz, placing it among the leading carbon-based EWA materials.\nImportantly, this degree of attenuation at such a small thickness surpasses many high-\nperformance absorbers, which typically require 4-5 mm to achieve comparable\nsuppression. The optimized sp²/sp³ hybrid architecture in DC-3 therefore provides an\nadvantageous balance between minimal thickness, strong attenuation, and broadband\nabsorption, underscoring its potential for lightweight and miniaturized electromagnetic\nshielding and stealth applications.” (Page 14, Lines 16-22)\nFig. R4. The RL of DC-3 sample at various thicknesses.\nmin\n4. In the discussion of serviceability in extreme environments, hardness may not be the\nmost critical mechanical property for electromagnetic wave absorption materials. It is\nrecommended that the authors provide additional mechanical property indicators such\nas fracture toughness, and bending strength.\nAdditionally, the DC-3 sample's initial oxidation temperature of 1145 K surpasses that\nof natural diamond and NPD, and even exceeds the previously reported Diaphene.\nFurther comparative analysis and discussion are needed to elaborate on this aspect.\nReply: We are grateful for your kind comment. In the revised version, we have\nadditionally included the fracture toughness and bending strength of the sample, as\nshown in the Fig. R5. As the synthesis temperature increases, the sp3 bond content\ndecreases, leading to an improvement in fracture toughness and a decline in Vickers\nhardness (Fig. R5a). The bending strength of the DC-3 and CVD-diamond samples was\n19\nevaluated using a three-point bending test. The DC-3 exhibited a bending strength of\n10.04 GPa (Fig. R5c), while that of the CVD diamond reached 33.23 GPa (Fig. R5d),\nindicating its higher mechanical robustness. Nevertheless, the bending strength of 10.04\nGPa achieved by DC-3 remains relatively high among carbon-based composites,\ndemonstrating its potential for applications under extreme conditions.\nThe superior oxidation resistance of DC-3 (1145 K) compared with natural\ndiamond, NPD, and Diaphene arises from both thermodynamic and kinetic stabilization\neffects introduced by the diamond/graphene heterostructure. The interfacial sp³-sp²\ncovalent bonds reduce surface dangling bonds and lower the system’s Gibbs free energy,\nthereby suppressing oxygen adsorption and increasing the oxidation activation energy.\nMeanwhile, the dense graphene domains act as diffusion barriers that hinder oxygen\ntransport and delay carbon–oxygen bond formation. Additionally, charge redistribution\nat the interface generates localized dipoles that stabilize surface electrons and suppress\ndefect-driven oxidation. These combined effects effectively inhibit lattice disorder and\ncarbon oxide formation, resulting in the remarkably high oxidation onset temperature\nobserved in DC-3.\nWe have added Fig. R5 into the revised manuscript as Supplementary Fig. 12, and\nadded the corresponding discussion in the revised manuscript: “Fracture toughness and\nVickers hardness were measured under a 9.8 N load (Fig. 5b and Supplementary Fig.\n12). The DC samples show fracture toughness values of 10.5-16.8 MPa·m1/2, with\nVickers hardness values of 51.7 ± 2.4 GPa (DC-1), 44.5 ± 3.1 GPa (DC-2), and 41.9 ±\n1.5 GPa (DC-3). Flexural strength is critical for maintaining structural stability under\nmechanical loading, ensuring that EWA components preserve their geometry and\nperformance during service. Although the flexural strength of DC-3 (10.0 GPa) is lower\nthan that of CVD diamond (33.2 GPa), it remains high for carbon-based composites39,\nensuring adequate mechanical integrity for load-bearing or vibration-intensive\nelectromagnetic applications.” (Page 17, lines 14–22)\n“The composite also displays excellent oxidation resistance, with an onset\ntemperature of 1145 K, surpassing natural diamond, NPD, and Diaphene\n(Supplementary Fig. 11). This enhancement may originate from the sp³-sp² covalent\ninterfaces19,20,24, where graphene layers act as an oxygen-blocking barrier and the\ndiamond nanograins become energetically stable25. Moreover, interfacial stress and\ncharge redistribution further reduce surface energy and suppress oxidative reactions21.\nThe cooperative effect of these factors leads to the delayed onset of oxidation,\ndemonstrating that interface engineering is an efficient strategy to improve the\nenvironmental tolerance of diamond-based composites.” (Page 17, lines 7–14)\ndiamond-based materials. (a) Vickers hardness and fracture toughness of the DC and\nDiaphene samples. (b) Thermostability comparison of the DC-3 with other known\ndiamond-based materials, such as ND, diamond-like carbon film (DLC), CVD diamond,\nnano-polycrystalline diamond (NPD), paracrystalline diamond (p-D) and Diaphene. (c)\nFlexural strength of DC-3 sample. (d) Flexural strength of CVD diamond sample.\n5. There are several minor issues in the paper that need to be addressed:\nThere is a discrepancy between the sample dimensions mentioned in the synthesis\nmethod and those used in the high-temperature microwave absorption tests. The\nrecovered samples are described as having a diameter of 13.5-14.0mm and a height of\n1.5-2.0mm, whereas the samples for microwave absorption testing are rectangular\nparallelepipeds with dimensions of 22.86mm × 10.16mm × 1mm.\nThe Raman fitting results in Fig. 2f and Fig. S1b are inconsistent.\nThere is a spelling error in the word \"hardness\" at line 210.\nThe horizontal axis label in Fig. S1c contains a spelling error.\nReply: Thank you very much for your constructive suggestions and corrections.\nThe recovered bulk samples were approximately 13.5-14.0 mm in diameter and 1.5-2.0\nmm in height. For high-temperature microwave absorption measurements, the DC\nsamples were ground into fine powders and subsequently bonded using high-purity\nsilica sol to prepare rectangular specimens with dimensions of 22.86 mm × 10.16 mm\n× 1 mm, in accordance with the measurement requirements.\nAdditionally, we sincerely thank you for the careful and constructive evaluation of\nour manuscript and for highlighting several linguistic inaccuracies in our Raman data\nand some spelling errors. We have carefully corrected spelling errors and revised\ngrammatical issues throughout the manuscript to further improve clarity and readability.\nThe manuscript titled \"Heterostructure-Engineered Diamond-Graphene\nComposites for High-Performance and Stable Electromagnetic Wave Absorption\"\npresents a systematic study on the synthesis, characterization, and electromagnetic\nwave absorption (EWA) performance of heterostructured diamond-graphene\ncomposites. This work addresses critical limitations of conventional carbon-based EWA\nmaterials, such as poor impedance matching and insufficient environmental resilience,\nbut several core academic questions require further clarification.\nReply: We are profoundly grateful to the reviewer for the very positive evaluation\nof our manuscript “This work addresses critical limitations of conventional carbon-\nbased EWA materials, such as poor impedance matching and insufficient environmental\nresilience”. We sincerely thank the reviewer for the careful evaluation of our manuscript\nand for providing constructive and insightful comments. In response to the points raised,\nwe have undertaken additional experiments, theoretical calculations and detailed\nanalyses to address each comment thoroughly. Our detailed responses are provided\nbelow.\nHere are some specific comments for the authors:\n1. The optimized composite (DC-3) achieves a minimum reflection loss of -61.47 dB,\nyet the supplementary Table 1 compares the material with other carbon-based absorbers\nbut does not include data on the thickness corresponding to the minimum reflection loss\nof these reference materials. How does the thickness of DC-3 (5.5 mm for -61.47 dB)\ncompare to that of the referenced materials when achieving their respective minimum\nreflection loss values, and what impact does this thickness difference have on practical\napplication potential?\nReply: Thank you for your insightful comment. To assess the practical potential\nof DC-3, its minimum reflection loss (RL ) and matching thickness were compared\nmin\nwith those of representative carbon-based and hybrid microwave absorbers. As shown\nin Fig. R1, DC-3 achieves an exceptionally deep RL of −60 dB at a thickness of 3.0\nmin\nmm, which is notably thinner than many reported high-performance absorbers that\ntypically require 4-5 mm or thicker layers to reach comparable attenuation levels (Table\n1). The relatively small thickness indicates effective impedance matching and high\nintrinsic dielectric loss efficiency.\nIn practical terms, the reduction in absorber thickness translates to lower weight\nand improved conformability, which are advantageous for aerospace, flexible, and\ncompact electronic applications. However, it should be noted that the enhanced\nabsorption at reduced thickness is often accompanied by a slightly narrower effective\nabsorption bandwidth, reflecting the balance between resonance depth and frequency\nrange. The optimized sp²/sp³ hybrid architecture in DC-3 enables a favorable\ncompromise between minimal thickness, strong absorption intensity, and broadband\nperformance, underscoring its promise for lightweight and miniaturized\nelectromagnetic shielding or stealth applications.\nIn summary, the 3 mm matching thickness required for DC-3 to achieve a −60 dB\nreflection loss demonstrates its superior intrinsic attenuation efficiency compared with\n22\nmost reported absorbers, establishing it as a promising candidate for lightweight, high-\nperformance electromagnetic wave absorption in next-generation stealth and electronic\nprotection systems.\nWe have added Table 1 into the revised Supplementary Information as\nSupplementary Table 1, and added above discussions in the revised manuscript:\n“Notably, DC-3 delivers the strongest performance, enabled by its optimized graphene\ncontent. It achieves an EAB of 4.0 GHz and an RL of -42.3 dB at 2.7 mm, and\nmax min\nfurther reaches an ultradeep RL of -60 dB at only 3.0 mm (Fig. 4f).” (Page 13, Lines\nmin\n8-11)\n“Compared with state-of-the-art carbon-based and magnetic absorbers32-38 (Fig. 4j\nand Supplementary Table1), DC-3 achieves both an ultrahigh RL (-60 dB) and a\nmin\nbroad EAB of 4.0 GHz, placing it among the leading carbon-based EWA materials.\nImportantly, this degree of attenuation at such a small thickness surpasses many high-\nperformance absorbers, which typically require 4-5 mm to achieve comparable\nsuppression. The optimized sp²/sp³ hybrid architecture in DC-3 therefore provides an\nadvantageous balance between minimal thickness, strong attenuation, and broadband\nabsorption, underscoring its potential for lightweight and miniaturized electromagnetic\nshielding and stealth applications.” (Page 14, Lines 16-22; Page 15, Line 1)\nFig. R1. The EWA performance of the DC-3 and its comparison with other\nrepresentative materials. (a) The minimum reflection loss (RL ) and effective\nmin\nabsorption bandwidth (EAB) at various sample thicknesses. (b) Comparison of the\nminimum reflection loss values and corresponding optimal thicknesses among different\nabsorbing materials.\nTable 1 | Comparison of minimum reflection loss and matching thickness for the\nDC-3 and representative absorbers.\nEAB\nmax\nSamples RL (dB) d (mm) d (mm)\nmin\n(GHz)\nrGO -6.9 2.0 0 2.0\nTi C T -46.0 4.9 2.3 1.3\n3 2 x\nTi C T /nano-carbon -54.67 4.8 1.1 4.8\n3 2 x\n23\nsphere\nC/PANI -50.96 3.09 4.0 3.09\nTiC/SiBCN -45.44 2.3 4.0 2.3\nrGO and CNTs -44.6 3.0 3.3 3.0\nrGO and BN -40.5 1.6 5.0 1.6\nHollow carbon sphere -50.8 4.5 4.8 1.9\nrGO/Cu O/Cu -51.8 / 4.0 /\nCNTs/ceramic -51.9 2.65 4.4 2.65\nrGO/Ag -26.8 / 3.7 /\nGraphene Foam -53.9 / 4.56 3.2\nTi C /ZnO -26.3 2.8 1.4 2.8\n3 2\nTiC/Al O -37.6 / 2.1 2.16\n2 3\nWC/Al O -25.0 / 2.2 2.54\n2 3\nPolyaniline/carbon black -40.0 / 2.5 2.6\nZnO@MWCNTs -47.4 / 3.7 /\nBowl-like carbon\n-45.3 3.1 4.2 3.1\nnanoparticles\nFlake graphite -19.4 / 3.6 /\nCarbon black -37.0 3.0 2.4 2.55\nCarbon nanofibers -22.0 / 2.0 3.0\nTi C T /PPy -68.0 3.0 6.65 2.26\n3 2 x\nMG-3 -47.98 2.7 4.08 2.7\nMGL-3 -58.9 2.68 3.44 2.68\nTi C Tx -34.4 1.7 4.7 1.7\n3 2\nP-MXene/NiCo O -64.0 4.47 2.0 4.4\n2 4\nMCFC-69-8 -20.0 4.3 4.9 1.48\nMXene@Co -57.32 2.5 5.2 2.5\nMXene/NiCo S -52.0 1.82 5.6 1.53\n2 4\nMXene@TMOs -50.3 1.8 5.12 1.7\nSi N @WS ceramics -65.0 4.35 4.2 3.92\n3 4 2\nSiC/Si N aerogels -25.0 3.97 4.3 3.97\n3 4\nSiOC/SiO -28.1 1.9 6.38 2.3\nBN@NC-900 -42.2 2.2 4.48 1.8\nSiCN (Ni)/BN -53.4 4.2 2.32 3.48\nGraphene/BN/Fe/BN -44.53 1.4 4.4 1.5\ncarbon/SiCN -45.37 2.5 5.95 2.5\nHollow SiC@MnO -30.0 1.8 5.71 1.8\nSiCN-1200 -21.12 3.22 4.2 32.2\nporous SiOC -67.98 3.19 4.45 3.19\nSiOC@C-3 -51.4 2.42 6.7 2.42\nDSHS -75.1 2.21 6.08 2.21\n2 4\nCNs (NS, P, B) -60.0 2.6 7.05 2.6\nTi AlC N -83.4 1.9 3.4 1.9\n2 0.5 0.5\nNFAG-900 -68.87 2.5 5.25 2.5\nFe C -52.09 2.9 2.55 2.9\n2 2 7 2 2 7\n2. The authors mention that the incoherent interface between diamond and\ngraphene enhances impedance matching, but they do not elaborate on the specific\nmechanism by which the incoherent interface regulates the impedance matching\ncoefficient. What is the relationship between the structural features of the incoherent\ninterface (e.g., grain size of the ND, interface defect density, lattice mismatch) and the\nimpedance matching performance, and is there experimental or simulation\nevidence to support this relationship? A theoretical simulation would be helpful to\nelucidate the underline mechanism.\nReply: Thank you very much for your kind suggestions and corrections. To\naddress these issues, we have performed first principles calculations to elucidate their\ninfluence and provide a more comprehensive understanding of the observed behavior.\nTo elucidate the role of interfacial defects, we constructed two types of interface\nmodels between diamond and graphene—one incorporating vacancy defects and the\nother defect-free. Calculations of their dielectric constants and impedance matching\ncoefficient for both models are presented in Figs. R2a-c. When the calculated dielectric\nparameters were introduced into the impedance matching model, the interface with\ndefects yielded a matching coefficient closer to unity at a thickness of 1.0 mm. These\nresults suggest that the presence of vacancy defects at the diamond–graphene interface\nenhances EWA by improving impedance matching.\nTo elucidate the effect of grain size on the impedance matching behavior, we\nconstructed interfacial models with varying grain sizes. The models were systematically\nlabeled size-1, size-2, and size-3 to denote a progressive increase in grain size. The\ntheoretically derived complex dielectric constants are presented in Figs. R2d-i.\nBelow 12 GHz, size-3 exhibits a superior dielectric constant (real part), indicating strong\ncharge storage capability. But beyond 12 GHz, its permittivity drops sharply, falling\nbelow that of both size-1 and size-2. Fig. R2h presents the imaginary component of the\ndielectric constant for three models with varying sizes at 1.0 mm, showing a gradual\nincrease in dielectric loss with increasing size. However, comparison of their\nimpedance matching coefficients (Fig. R2i) reveals that smaller-sized models exhibit\nsuperior impedance matching, indicating that reduced grain size facilitates more\nefficient penetration and attenuation of electromagnetic waves within the material.\nWe have added Fig. R2 into revised manuscript as Fig. 3, and added detailed\ndiscussions in the revised manuscript: “To elucidate how interfacial defect sites and\ndiamond grain size modulate the dielectric response, we carried out first-principles\ncalculations. Two representative diamond/graphene interface models were constructed:\none defect-free and one containing vacancy defects (Figs. 3a-b). Their calculated\ndielectric constants and impedance matching coefficients are presented in Fig. 3c. Due\n25\nto the intrinsic non-magnetic nature of carbon-based materials, the complex magnetic\npermeability was set to 1.0, and the impedance matching coefficient Z was evaluated\naccordingly32:\n𝑍 1 2𝜋𝑓𝑑\nin\n𝑍 = | | = √ 𝑡𝑎𝑛ℎ(𝑗 √𝜀 )\n𝑍 𝜀 𝑐 𝑟\n0 𝑟\nIncorporation of the calculated dielectric parameters into the impedance model\nshows that the defective interface yields a matching coefficient closer to unity at a\nthickness of 1.0 mm, indicating that vacancy defects at the heterointerfaces promote\nimproved impedance matching and thereby enhance EWA performance. Defective sites\nat the diamond-graphene interface serve as pivotal centers for energy dissipation, as the\nlocal chemical heterogeneity induces both permanent dipoles and charge‐trapping states\nthat amplify dielectric loss. The presence of dangling bonds and sp³–sp² transitions\ncreates a distribution of dipole moments and relaxation times, which manifest as\nbroadened and overlapping semicircles in the Cole–Cole representation\n(Supplementary Fig. 4), thereby elevating ε″. To further assess the role of structural\nlength scale, we constructed additional interface models with systematically varied\ndiamond grain sizes, labeled size-1, size-2, and size-3. The resulting complex dielectric\nconstants are presented in Fig. 3g. Below 12 GHz, the largest-grain model (size-3)\nexhibits the highest real permittivity, reflecting enhanced charge-storage capability.\nHowever, above 12 GHz, its permittivity decreases sharply and becomes lower than\nthat of the smaller-grain models. The imaginary permittivity (Fig. 3h) increases\nmonotonically with grain size, indicating progressively stronger dielectric loss.\nDespite this trend, the impedance matching coefficients (Fig. 3i) reveal that the\nsmallest-grain model achieves the most favorable matching at 1.0 mm thickness. This\nsuggests that reduced grain size facilitates better wave penetration and balanced energy\ndissipation.\nThe first-principles results demonstrate that both interfacial defect chemistry and grain-\nsize modulation play decisive roles in optimizing EWA behavior. These insights\nhighlight the critical importance of microstructural design in enabling next-generation\ndiamond/graphene absorbers with tunable and superior electromagnetic attenuation\nperformance.” (Page 10, Lines 10-22; Page 11, Lines 1-16)\ninterfaces. a, Diamond/graphene interface without vacancy defects. b,\nDiamond/graphene interface incorporating vacancy defects at the boundary. c,\nCalculated real and imaginary parts of permittivity and impedance matching coefficient\nfor the defect-free (a) and defective (b) interface models. d-f, Diamond/graphene\ninterfacial structures with varying grain sizes. g-i, Corresponding real (g) and imaginary\n(h) permittivity components, and impedance matching coefficient (i) for the grain-size-\ndependent interface models shown in d-f.\n3. The electrical conductivity of the DC samples increases with decreasing sp³\ncontent, as shown in Fig. 2i, but the manuscript does not discuss how the change in\nelectrical conductivity specifically affects the conduction loss mechanism of\nelectromagnetic waves. How to quantitatively distinguish the contribution of\nconduction loss from other loss mechanisms (e.g., interfacial polarization loss, dipole\n27\npolarization loss) in the total dielectric loss of the composites?\nReply: We thank the reviewer for this perceptive question. To quantify the\nseparate contributions of conduction loss and polarization-related loss (interfacial and\ndipole polarization loss) we analysed the complex permittivity and conductivity over a\nbroad frequency and temperature range (Fig. R3). In brief, the total imaginary\npermittivity (ε ʺ) can be expressed as the sum of a conduction term (ε ʺ) and\ntotal c\npolarization (ε ʺ) terms:\np\n𝜀′′ (𝜔,𝑇) = 𝜀′′(𝜔,𝑇)+𝜀′′(𝜔,𝑇)\ntotal c p\nThe conduction contribution is given by the classical relation:\n𝜎 (𝑇)\n𝜀′′(𝜔,𝑇) = dc\nc 𝜀 𝜔\n0\nwhere 𝜎 (𝑇) is the DC conductivity measured independently, 𝜀 is the vacuum\ndc 0\npermittivity and 𝜔 = 2𝜋𝑓. According to the Debye’s theory, we have quantitatively\ndistinguished the separate contributions of conduction loss (ε ʺ) from polarization-\nc\nrelated loss (ε ʺ) in the total dielectric loss of the composites.\np\n𝜀 −𝜀 𝜎\n𝜀′′ = 𝑠 ∞ 𝜔𝜏+ 𝑑𝑐 = 𝜀′′ +𝜀′′\n1+𝜔2𝜏2 𝜔𝜀 p c\n0\nwhere ε , ε , and τ represent the relative dielectric permittivity at the high\n∞ s\nfrequency limit, static permittivity, relaxation time, respectively. The conductivity loss\ncan be directly derived from the measured electrical conductivity, and by subtracting\nthis value from the total dielectric loss, the corresponding polarization loss can be\nobtained. As shown in Fig. R3, as the sp³ fraction decreases and conductivity increases,\nthe conduction loss becomes dominant at low frequencies (below 4 GHz), whereas\npolarization loss (interfacial and dipole) is responsible for loss peaks at 4-18 GHz.\nThese combined effects indicate that the dielectric loss mechanism of the DC\ncomposites arises from a synergistic interplay between conduction and interfacial\npolarization, both of which are strongly modulated by the sp²/sp³ ratio and interfacial\nmicrostructure.\nWe have added Fig. R3 into the revised manuscript as Fig. 2g, i and Supplementary\nFig. 5, and added corresponding discussions in the revised manuscript: “Quantitative\nanalysis of conductive (ε ″) and polarization (ε ″) components (Fig. 2h) further reveals\nc p\nthat conduction loss dominates below 4 GHz, whereas polarization loss becomes the\nprincipal attenuation mechanism at 4–18 GHz. For DC-3, ε ʺ accounts for ~77% of total\nc\nε″ at 3 GHz, but decreases to 24% at 11 GHz and 15% at 14 GHz, accompanied by a\ncorresponding increase in polarization contributions (Fig. 2j and Supplementary Fig.\n5).” (Page 8, Lines 10-14)\nc p\n(a-c) Contribution of conduction loss and polarization loss of DC-1, DC-2, and DC-3,\nrespectively. (d) Contribution of conductive and polarization components. (e) Relative\ncontributions of conduction loss and polarization loss to total dielectric loss at\nrepresentative frequencies in the C-band (3 GHz), X-band (11 GHz), and Ku-band (14\nGHz).\n4. The corrosion potential of DC-3 is -0.210 V, and the corrosion current density is less\nthan 10⁻⁶ A/cm², indicating good corrosion resistance. But the manuscript does not\nexplain why the corrosion resistance of DC-1 (with higher sp³ content) is slightly better\nthan that of DC-2 and DC-3, as suggested by the Nyquist plots. What is the intrinsic\nrelationship between sp³/sp² content and the corrosion resistance mechanism of the\ncomposites?\nReply: Thank you for your insightful comment. The corrosion resistance of the\nDC composites is intrinsically governed by the ratio and distribution of sp³ and sp²\ncarbon domains, which jointly determine the chemical stability and electrochemical\nactivity of the material. The sp³-bonded diamond phase provides a chemically inert\nframework with high bond energy and low surface reactivity, acting as a barrier against\noxidative and electrochemical attack. In contrast, sp²-bonded graphene domains possess\nhigher electrical conductivity and facilitate charge transfer at the solid–liquid interface,\nbut their π-bonded structure is more susceptible to oxidation and electron-induced\ncorrosion. Therefore, the corrosion behavior arises from a delicate balance: a higher sp³\nfraction enhances chemical inertness and passivation stability, while moderate sp²\nincorporation improves charge dissipation and reduces local potential gradients that can\ninitiate pitting. Moreover, the covalently bonded sp²-sp³ interfaces suppress defect\nformation and inhibit electrolyte penetration, providing synergistic protection.\nConsequently, the optimized sp³-sp² hybrid architecture yields superior corrosion\nresistance by combining the chemical stability of diamond with the electronic buffering\ncapability of graphene.\nWe have added the corresponding discussions in the revised manuscript: “This\nbehavior correlates directly with the sp³/sp² ratio: the diamond matrix supplies chemical\ninertness, while sp2 domains promote charge delocalization and minimize local\npotential gradients. Excessive sp², however, increases surface reactivity, underscoring\nthe need for an optimized hybrid ratio. Thus, an optimal balance between the two\nensures both structural stability and electronic equilibrium at the interface22, effectively\nimproving corrosion resistance through synergistic chemical passivation and charge\ndelocalization.” (Page 18, Lines 5-10)\n5. The high-temperature electromagnetic wave absorption performance of DC-3 is\nstable between 773 K and 973 K, but the absorption bandwidth decreases slightly with\nincreasing temperature. The manuscript attributes this to temperature-dependent\nhopping conductivity and dipole polarization, but there is no experimental data on the\nchange of dielectric parameters (ε', ε'') with temperature. What are the variations of\ncomplex permittivity and permeability of DC-3 at different high temperatures (773 K,\nReply: Thank you for your insightful comment. We apologize for the earlier\nomission of the dielectric parameters (ε', ε'') corresponding to high-temperature\nmicrowave absorption measurements. The evolution of the complex permittivity and\npermeability at different high temperatures are shown in Fig. R4. Both ε' and ε'' decrease\nwith increasing temperature, particularly a substantial decrease in ε′. In contrast, the\nmagnetic permeability, owing to its intrinsically low magnitude, shows only a minor\nthermal dependence.\nThe reflection loss values at different thicknesses and frequencies were calculated\nto get the reflection loss plot of 2D based on the measured electromagnetic parameters\n(Fig. R5). As the temperature increases, the optimal absorption performance gradually\nshifts toward larger thicknesses, indicating that the thickness of the absorber plays a\ncrucial role in determining electromagnetic wave attenuation. To enable a consistent\ncomparison, we analyzed the absorption bandwidths at different temperatures at a fixed\nthickness of 3.2 mm. Under this condition, the absorption bandwidth was found to\ndecrease progressively with increasing temperature.\nWe have added Fig. R4 and Fig. R5 into the revised manuscript as Supplementary\nFig. 13 and Fig. 14, and added some relevant discussions in the revised manuscript:\n“High-temperature absorption measurements (Fig. 5g and Supplementary Fig. 13)\ndemonstrate that DC-3 maintain stable microwave attenuation between 773-973 K.\nWith increasing temperature, the permittivity decreases (Supplementary Fig. 14) and\nthe optimal absorption thickness shifts toward larger thickness; at a fixed 3.2 mm\nthickness, the bandwidth gradually narrows35.” (Page 18, Lines 13-17)\nRL and EAB of DC-3 at 773 K. (b) RL and EAB of DC-3 at 873 K. (c) RL and EAB of\nDC-3 at 973 K.\nFig. R5. (a) The frequency dependent curve of the complex permittivity of DC-3 at\ndifferent temperatures. (b) The variation curve of complex magnetic permeability of\nDC-3 with frequency at different temperatures.\n6. The manuscript proposes that the heterostructure design of diamond-graphene\ncomposites provides a new strategy for multifunctional electromagnetic wave\nabsorbing materials, but it does not discuss the scalability and cost of the moderate\nhigh-pressure and high-temperature (HPHT) synthesis method. What challenges exist\nin scaling up the HPHT preparation process for industrial production, and are there\npotential improvements to reduce the synthesis cost while maintaining material\nperformance?\nReply: Thank you for this valuable comment. We agree that the scalability and\ncost of the HPHT method are important considerations for practical application. While\nour study focuses primarily on revealing the structure-property relationship in diamond-\ngraphene heterostructures, we acknowledge that several challenges remain in scaling\nup the HPHT process for industrial production.\nHPHT synthesis requires ultra-high pressure and high temperature. These systems\nare expensive, energy intensive, and currently limited to small batch sizes. In addition,\nhigh-strength anvils, heating elements, and pressure medium materials degrade under\nextreme conditions and require frequent replacement, increasing production costs.\nSeveral potential strategies may help improve scalability and reduce cost.\nOptimizing catalysts or introducing pre-bonded nanodiamond-graphene intermediates\n31\nmay reduce the required P-T conditions while still forming stable heterostructures. Also,\ncombining HPHT with techniques such as spark plasma sintering (SPS) or hot pressing\nunder moderate pressure may lower energy consumption and enable near-net-shape\nfabrication.\nWe have added this discussion into the revised manuscript: “Although HPHT\nsynthesis reliably produces covalently bonded sp³-sp² interfaces and high-performance\ncomposites, scale-up remains limited by the requirements of ultra-high pressure, high\ntemperature, and high energy consumption. Strategies to reduce cost and improve\nthroughput include tailoring precursor chemistry to lower transformation thresholds,\nadopting spark plasma sintering (SPS)40 or hot-pressing, and exploring hybrid HPHT-\nSPS approaches. In addition, emerging metal-catalyzed pathways, such as liquid Ga-,\nNi-, or Cu-mediated formation of sp³-sp² interfaces41-46 offer promising alternative\nroutes to large-scale production of covalently integrated carbon heterostructures.”\n(Page 18, Lines 18-22; Page 19, Lines 1-3)\n7. The author should provide a more updated review of literatures with covalent bonded\nsp3-sp2 carbon interfaces, which could be catalyzed by metal such as liquid gallium,\nnickel or copper.\nReply: Thank you for your insightful comment. We have updated the relevant\nliteratures with covalent bonded sp3-sp2 carbon interfaces in the revised manuscript,\nand discussed this point in the revised manuscript: “In addition, emerging metal-\ncatalyzed pathways, such as liquid Ga-, Ni-, or Cu-mediated formation of sp³-sp²\ninterfaces41-46 offer promising alternative routes to large-scale production of covalently\nintegrated carbon heterostructures.” (Page 18, Line 22; Page 19, Lines 1-3)\nCited References:\n1. Berman, D. et al. Metal-induced rapid transformation of diamond into single and\nmultilayer graphene on wafer scale. Nat. Commun. 7, 12099 (2016).\n2. Tulić, S. et al. Covalent diamond–graphite bonding: mechanism of catalytic\ntransformation. ACS Nano 13, 4621–4630 (2019).\n3. Ding, G. et al. Chemical vapor deposition of graphene on liquid metal catalysts.\nCarbon 53, 321–326 (2013).\n4. Vejpravová, J. Mixed sp2–sp3 nanocarbon materials: a status quo review.\nNanomaterials 11, 2469 (2021).\n5. Yuan, Q., Lin, C.-T. & Chee, K. W. A. All-carbon devices based on sp2-on-sp3\nconfiguration. APL Mater. 7, 030901 (2019).\n6. Rein, V. et al. In situ characterisation of graphene growth on liquid copper-gallium\nalloys: Paving the path for cost-effective synthesis. Appl. Surf. Sci. 657, 159723\n(2024).\nWe sincerely thank the referees for their careful reviews and constructive\nsuggestions, which have significantly improved the clarify and quality of our work. We\nbelieve that the revised manuscript and this response letter fully address the referees’\ncomments. Below, we provide detailed point-by-point response. For clarify, the referees’\ncomments are shown in black, our replies in blue, and the corresponding manuscript\nrevisions are marked in red. We would also like to take this opportunity to wish you a\njoyful Christmas.\nReviewer #1 (Remarks to the Author):\nThe authors seem to have sufficiently addressed the comments raised by all of the\nreviewers, and I think the current revised version is suitable for publication.\nReply: We really appreciate the referee for the thoughtful comments and excellent\nsuggestions in the previous rounds of review and thank you for recommending our\npaper for publication in Nature Communication.\nI appreciate the detailed revisions and additional data provided, which have\naddressed several key concerns. However, a few critical points raised in the previous\nround require further attention to fully satisfy the standards of Nature Communications.\nReply: We sincerely thank you for the positive evaluation on our revised\nmanuscript: “I appreciate the detailed revisions and additional data provided, which\nhave addressed several key concerns”. We greatly appreciate these suggestions, which\nhave been very helpful in improving the quality of our manuscript. In response to the\npoints raised, we have undertaken corresponding discussions and explanations to\naddress each comment thoroughly. We have carefully addressed all of your comments\nin a point-by-point manner and revised the manuscript accordingly, as detailed below.\nThe following issues should be clarified or corrected in the next revision:\n1.Your pre-graphitization strategy successfully enables the synthesis of diamond-\ngraphene composites at a significantly lower pressure (7 GPa) than your previously\nreported Diaphene (12 GPa), while preserving comparable mechanical properties. This\nis a notable achievement. However, the manuscript currently lacks a mechanistic\nexplanation for why the presence of pre-formed sp² carbon layers facilitates this process\nunder milder conditions. Does the graphitic shell alter the phase transformation pathway,\nact as a stress modifier, or lower the nucleation barrier for the sp³ phase? A brief\ndiscussion of the underlying principle is needed to elevate the work from an empirical\nobservation to a conceptual advance.\nReply: We thank the reviewer for this insightful comment. The reduced synthesis\npressure enabled by the pre-graphitization strategy arises from an interface-mediated\ntransformation pathway. The graphitic shell modifies the local stress environment under\nHPHT conditions, accommodating strain through layered sp² carbon and promoting\nstress concentration at the nanodiamond interface. This facilitates sp²–sp³ bond\nrearrangement and lowers the effective pressure required for diamond stabilization.\nIn addition, the intimate contact between the sp² shell and the nanodiamond core\nprovides a structurally coherent interface that reduces the nucleation barrier for covalent\nsp²–sp³ bonding. This favors interfacial reconstruction over bulk phase transformation,\nenabling hybrid diamond–graphene architectures to form under milder conditions. The\ngraphitic shell also constrains long-range carbon diffusion, suppressing excessive\ngraphitization and stabilizing nanoscale sp²/sp³ networks.\nIn all, these effects shift the phase evolution from a pressure-driven bulk\ntransformation, as in Diaphene, to an interface-governed reconstruction pathway. This\nmechanistic understanding elevates pre-graphitization from an empirical processing\nstep to a general strategy for lowering synthesis thresholds in covalently bonded carbon\nheterostructures.\nWe have added a brief discussion into the revised manuscript: “A key distinction\nof the present diamond–graphene composites is the substantially reduced synthesis\npressure enabled by the pre-graphitization strategy. Unlike Diaphene, which requires\n~12 GPa, the composites form at 7 GPa while retaining comparable mechanical\nproperties. This reduction arises from an interface-mediated phase transformation\n2\npathway introduced by the pre-formed sp² carbon shell. During HPHT treatment, the\ngraphitic layers accommodate compressive strain through bond rehybridization and\ninterlayer sliding, redistributing local stress and lowering the effective barrier for\nsp²→sp³ reconstruction at the diamond surface25,47–49. In addition, the intimate contact\nbetween graphene and nanodiamond provides coherent interfacial templates that\nfacilitate localized nucleation of sp³ bonds, bypassing bulk diffusion-controlled\ntransformation50. These cooperative effects, such as stress accommodation, reduced\nnucleation barriers, and constrained carbon migration, shift the transformation from a\npressure-dominated bulk process to an interface-controlled reconstruction mechanism,\nenabling hybrid diamond–graphene architectures to form under milder conditions.”\n(Page 5, Lines 8-20)\n2.Please correct the presentation of the flexural strength data. The reported strain for\nthe CVD diamond reference (≈400%) in the stress-strain curve is physically implausible\nand indicates a likely error in data processing or axis scaling. The provided flexural\nstress-strain curve for the DC-3 sample indicates a mechanical behavior that appears\ndistinct from that of a typical brittle diamond material. This warrants a direct discussion.\nReply: We appreciate the reviewer’s insightful comment. The stress–strain curves\nin Fig. R1 have now been corrected accordingly. The synthesized DC-3 sample was\nlaser-cut into rectangular beams, and its flexural strength, evaluated by three-point\nbending, was in the range of 20~60 MPa (Fig. R2). The resulting stress–strain curves\ndisplay pronounced non-brittle behavior prior to failure. This response arises from the\ncomposite architecture consisting of a diamond matrix integrated with multilayer\ngraphene. The graphene layers act as effective toughening elements by impeding crack\npropagation through mechanisms such as crack bridging, interfacial sliding, and crack\ndeflection, thereby preventing the catastrophic brittle fracture characteristic of\nmonolithic diamond.\nWe have added Fig. R1 and Fig. R2 into the revised manuscript as Supplementary\nFig. 12 and Supplementary Fig. 13, and added relevant discussions in the manuscript:\n“Although the flexural strength of DC-3 (20~60 MPa, Supplementary Figs. 12-13) is\nlower than that of CVD diamond (350.7 MPa, Supplementary Fig. 12e), it remains high\nfor carbon-based composites39. However, the stress–strain curves exhibit pronounced\nnon-brittle behavior (Supplementary Fig. 13), attributable to the diamond–multilayer\ngraphene architecture. The graphene layers hinder crack propagation through crack\nbridging, interfacial sliding, and deflection, thereby suppressing catastrophic brittle\nfracture typical of monolithic diamond and ensuring adequate mechanical integrity for\nload-bearing or vibration-intensive electromagnetic applications.” (Page 18, Lines 19-\n22; Page 19, Lines 1-4)\nDC-3. (b) Stress-strain curve of CVD diamond.\nFig. R2. Stress-strain curves of DC-3 sample.\n3.For the high-temperature microwave absorption measurements, the composite\npowder was mixed with a silica sol binder to form the test specimen. How was the\npotential influence of this dielectric binder on the measured complex permittivity,\nespecially across the evaluated temperature range, accounted for or determined to be\nnegligible?\nReply: We are grateful for your kind comment. In high-temperature EWA\nmeasurements, powder samples must be stabilized using heat-resistant, optically\ntransparent matrices, typically combined with inorganic binders to maintain structural\nintegrity under elevated temperatures. High-purity silica gel (SiO ·nH O) is widely\n2 2\nadopted for this purpose, as it enables powders to be formed into robust, fixed\ngeometries while offering high transparency and minimal interference with the intrinsic\nelectromagnetic-absorption response. We evaluated the high temperature EWA\ncharacteristics of the high-purity silica gel itself and found its reflection loss values to\nbe negligible in Fig. R3 (the minimum reflection loss value is only between -2.0 dB ~\n-3.0 dB), exerting no measurable influence relative to the absorption performance of\nour composites.\nadded some explanation in the manuscript: “In addition, to exclude any potential\ninfluence of the high-purity silicone (A high transparency adhesive used for high-\ntemperature microwave absorption51) on the measurements, a control experiment was\nperformed at 873 K, and its effect was found to be negligible (Supplementary Fig. 16).”\n(Page 25, Lines 5-8)\nFig. R3. Two-dimensional electromagnetic wave absorption performance plot of\nhigh-purity silica gel.\nThe authors have addressed my questions properly. I hereby recommend its\npublication in NCOMMS.\nReply: We sincerely thank the referee for the thoughtful comments and\nconstructive suggestions provided throughout the review process, and we greatly\nappreciate the recommendation of our manuscript for publication in Nature\nCommunications.\nReviewer #2 (Remarks to the Author):\nThe authors have sufficiently addressed the comments, and I think the current\nrevised version is suitable for publication.\nReply: We really appreciate the referee for the thoughtful comments and excellent\nsuggestions in the previous rounds of review and thank you for recommending our\npaper for publication in Nature Communication."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors seem to have sufficiently addressed the comments raised by all of the\nreviewers, and I think the current revised version is suitable for publication.", "reviewer_2": "I appreciate the detailed revisions and additional data provided, which have addressed several key concerns. However, a few critical points raised in the previous round require further attention to fully satisfy the standards of Nature Communications.\nThe following issues should be clarified or corrected in the next revision:\n1.Your pre-graphitization strategy successfully enables the synthesis of diamond-graphene composites at a significantly\nlower pressure (7 GPa) than your previously reported Diaphene (12 GPa), while preserving comparable mechanical\nproperties. This is a notable achievement. However, the manuscript currently lacks a mechanistic explanation for why the\npresence of pre-formed sp² carbon layers facilitates this process under milder conditions. Does the graphitic shell alter the\nphase transformation pathway, act as a stress modifier, or lower the nucleation barrier for the sp³ phase? A brief\ndiscussion of the underlying principle is needed to elevate the work from an empirical\nobservation to a conceptual advance.\n2.Please correct the presentation of the flexural strength data. The reported strain for the CVD diamond reference (≈400%) in\nthe stress-strain curve is physically implausible and indicates a likely error in data processing or axis scaling.The provided\nflexural stress-strain curve for the DC-3 sample indicates a mechanical behavior that appears distinct from that of a typical\nbrittle diamond material. This warrants a direct discussion.\n3.For the high-temperature microwave absorption measurements, the composite powder was mixed with a silica sol binder\nto form the test specimen. How was the potential influence of this dielectric binder on the measured complex permittivity,\nespecially across the evaluated temperature range, accounted for or determined to be negligible?", "reviewer_3": "The authors have addressed my questions properly. I hereby recommend its publication in NCOMMS."}, "author_response": "Point-by-Point Response to the Reviewers’ comments\nWe sincerely thank the referees for their careful reviews and constructive\nsuggestions, which have significantly improved the clarify and quality of our work. We\nbelieve that the revised manuscript and this response letter fully address the referees’\ncomments. Below, we provide detailed point-by-point response. For clarify, the referees’\ncomments are shown in black, our replies in blue, and the corresponding manuscript\nrevisions are marked in red. We would also like to take this opportunity to wish you a\njoyful Christmas.\nReviewer #1 (Remarks to the Author):\nThe authors seem to have sufficiently addressed the comments raised by all of the\nreviewers, and I think the current revised version is suitable for publication.\nReply: We really appreciate the referee for the thoughtful comments and excellent\nsuggestions in the previous rounds of review and thank you for recommending our\npaper for publication in Nature Communication.\nI appreciate the detailed revisions and additional data provided, which have\naddressed several key concerns. However, a few critical points raised in the previous\nround require further attention to fully satisfy the standards of Nature Communications.\nReply: We sincerely thank you for the positive evaluation on our revised\nmanuscript: “I appreciate the detailed revisions and additional data provided, which\nhave addressed several key concerns”. We greatly appreciate these suggestions, which\nhave been very helpful in improving the quality of our manuscript. In response to the\npoints raised, we have undertaken corresponding discussions and explanations to\naddress each comment thoroughly. We have carefully addressed all of your comments\nin a point-by-point manner and revised the manuscript accordingly, as detailed below.\nThe following issues should be clarified or corrected in the next revision:\n1.Your pre-graphitization strategy successfully enables the synthesis of diamond-\ngraphene composites at a significantly lower pressure (7 GPa) than your previously\nreported Diaphene (12 GPa), while preserving comparable mechanical properties. This\nis a notable achievement. However, the manuscript currently lacks a mechanistic\nexplanation for why the presence of pre-formed sp² carbon layers facilitates this process\nunder milder conditions. Does the graphitic shell alter the phase transformation pathway,\nact as a stress modifier, or lower the nucleation barrier for the sp³ phase? A brief\ndiscussion of the underlying principle is needed to elevate the work from an empirical\nobservation to a conceptual advance.\nReply: We thank the reviewer for this insightful comment. The reduced synthesis\npressure enabled by the pre-graphitization strategy arises from an interface-mediated\ntransformation pathway. The graphitic shell modifies the local stress environment under\nHPHT conditions, accommodating strain through layered sp² carbon and promoting\nstress concentration at the nanodiamond interface. This facilitates sp²–sp³ bond\nrearrangement and lowers the effective pressure required for diamond stabilization.\nIn addition, the intimate contact between the sp² shell and the nanodiamond core\nprovides a structurally coherent interface that reduces the nucleation barrier for covalent\nsp²–sp³ bonding. This favors interfacial reconstruction over bulk phase transformation,\nenabling hybrid diamond–graphene architectures to form under milder conditions. The\ngraphitic shell also constrains long-range carbon diffusion, suppressing excessive\ngraphitization and stabilizing nanoscale sp²/sp³ networks.\nIn all, these effects shift the phase evolution from a pressure-driven bulk\ntransformation, as in Diaphene, to an interface-governed reconstruction pathway. This\nmechanistic understanding elevates pre-graphitization from an empirical processing\nstep to a general strategy for lowering synthesis thresholds in covalently bonded carbon\nheterostructures.\nWe have added a brief discussion into the revised manuscript: “A key distinction\nof the present diamond–graphene composites is the substantially reduced synthesis\npressure enabled by the pre-graphitization strategy. Unlike Diaphene, which requires\n~12 GPa, the composites form at 7 GPa while retaining comparable mechanical\nproperties. This reduction arises from an interface-mediated phase transformation\n2\npathway introduced by the pre-formed sp² carbon shell. During HPHT treatment, the\ngraphitic layers accommodate compressive strain through bond rehybridization and\ninterlayer sliding, redistributing local stress and lowering the effective barrier for\nsp²→sp³ reconstruction at the diamond surface25,47–49. In addition, the intimate contact\nbetween graphene and nanodiamond provides coherent interfacial templates that\nfacilitate localized nucleation of sp³ bonds, bypassing bulk diffusion-controlled\ntransformation50. These cooperative effects, such as stress accommodation, reduced\nnucleation barriers, and constrained carbon migration, shift the transformation from a\npressure-dominated bulk process to an interface-controlled reconstruction mechanism,\nenabling hybrid diamond–graphene architectures to form under milder conditions.”\n(Page 5, Lines 8-20)\n2.Please correct the presentation of the flexural strength data. The reported strain for\nthe CVD diamond reference (≈400%) in the stress-strain curve is physically implausible\nand indicates a likely error in data processing or axis scaling. The provided flexural\nstress-strain curve for the DC-3 sample indicates a mechanical behavior that appears\ndistinct from that of a typical brittle diamond material. This warrants a direct discussion.\nReply: We appreciate the reviewer’s insightful comment. The stress–strain curves\nin Fig. R1 have now been corrected accordingly. The synthesized DC-3 sample was\nlaser-cut into rectangular beams, and its flexural strength, evaluated by three-point\nbending, was in the range of 20~60 MPa (Fig. R2). The resulting stress–strain curves\ndisplay pronounced non-brittle behavior prior to failure. This response arises from the\ncomposite architecture consisting of a diamond matrix integrated with multilayer\ngraphene. The graphene layers act as effective toughening elements by impeding crack\npropagation through mechanisms such as crack bridging, interfacial sliding, and crack\ndeflection, thereby preventing the catastrophic brittle fracture characteristic of\nmonolithic diamond.\nWe have added Fig. R1 and Fig. R2 into the revised manuscript as Supplementary\nFig. 12 and Supplementary Fig. 13, and added relevant discussions in the manuscript:\n“Although the flexural strength of DC-3 (20~60 MPa, Supplementary Figs. 12-13) is\nlower than that of CVD diamond (350.7 MPa, Supplementary Fig. 12e), it remains high\nfor carbon-based composites39. However, the stress–strain curves exhibit pronounced\nnon-brittle behavior (Supplementary Fig. 13), attributable to the diamond–multilayer\ngraphene architecture. The graphene layers hinder crack propagation through crack\nbridging, interfacial sliding, and deflection, thereby suppressing catastrophic brittle\nfracture typical of monolithic diamond and ensuring adequate mechanical integrity for\nload-bearing or vibration-intensive electromagnetic applications.” (Page 18, Lines 19-\n22; Page 19, Lines 1-4)\nDC-3. (b) Stress-strain curve of CVD diamond.\nFig. R2. Stress-strain curves of DC-3 sample.\n3.For the high-temperature microwave absorption measurements, the composite\npowder was mixed with a silica sol binder to form the test specimen. How was the\npotential influence of this dielectric binder on the measured complex permittivity,\nespecially across the evaluated temperature range, accounted for or determined to be\nnegligible?\nReply: We are grateful for your kind comment. In high-temperature EWA\nmeasurements, powder samples must be stabilized using heat-resistant, optically\ntransparent matrices, typically combined with inorganic binders to maintain structural\nintegrity under elevated temperatures. High-purity silica gel (SiO ·nH O) is widely\n2 2\nadopted for this purpose, as it enables powders to be formed into robust, fixed\ngeometries while offering high transparency and minimal interference with the intrinsic\nelectromagnetic-absorption response. We evaluated the high temperature EWA\ncharacteristics of the high-purity silica gel itself and found its reflection loss values to\nbe negligible in Fig. R3 (the minimum reflection loss value is only between -2.0 dB ~\n-3.0 dB), exerting no measurable influence relative to the absorption performance of\nour composites.\nadded some explanation in the manuscript: “In addition, to exclude any potential\ninfluence of the high-purity silicone (A high transparency adhesive used for high-\ntemperature microwave absorption51) on the measurements, a control experiment was\nperformed at 873 K, and its effect was found to be negligible (Supplementary Fig. 16).”\n(Page 25, Lines 5-8)\nFig. R3. Two-dimensional electromagnetic wave absorption performance plot of\nhigh-purity silica gel.\nThe authors have addressed my questions properly. I hereby recommend its\npublication in NCOMMS.\nReply: We sincerely thank the referee for the thoughtful comments and\nconstructive suggestions provided throughout the review process, and we greatly\nappreciate the recommendation of our manuscript for publication in Nature\nCommunications.\nReviewer #2 (Remarks to the Author):\nThe authors have sufficiently addressed the comments, and I think the current\nrevised version is suitable for publication.\nReply: We really appreciate the referee for the thoughtful comments and excellent\nsuggestions in the previous rounds of review and thank you for recommending our\npaper for publication in Nature Communication."}, {"round": 3, "reviewer_comments": {"reviewer_2": "The authors have sufficiently addressed the comments, and I think the current revised version is suitable for publication."}, "author_response": "Reply: We really appreciate the referee for the thoughtful comments and excellent suggestions in the previous rounds of review and thank you for recommending our paper for publication in Nature Communication."}]

Decision letter