# Elaboration of complex aluminum nitride parts by binder jetting: Optimization of printing parameters and powder characteristics

Fanny Pruvost, Sophie Guillemet-Fritsch, Alexia Mortagne-Coderch, Yohann

Thimont, Régis Delsol, Xavier Clausse, Lionel Presmanes

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Fanny Pruvost, Sophie Guillemet-Fritsch, Alexia Mortagne-Coderch, Yohann Thimont, Régis Delsol, et al. Elaboration of complex aluminum nitride parts by binder jetting: Optimization of printing parameters and powder characteristics. Materials Science in Additive Manufacturing, 2025, 4 (4), pp.025090008. 10.36922/MSAM025090008. hal-05329040

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Distributed under a Creative Commons Attribution 4.0 International License
ORIGINAL RESEARCH ARTICLE

Elaboration of complex aluminum nitride parts
by binder jetting: Optimization of printing
parameters and powder characteristics

Fanny Pruvost<fnref n="1" />†, Sophie Guillemet-Fritsch<fnref n="1" />*‡, Alexia Mortagne-Coderch<fnref n="1" />, Yohann Thimont<fnref n="1" />, Régis Delsol<fnref n="2" />, Xavier Clausse<fnref n="3" />, and Lionel Presmanes<fnref n="1" />,‡

Abstract

Aluminum nitride (AlN) is a promising material for heat sinks and power electronics substrates due to its high thermal conductivity, electrical insulation, high mechanical strength, and low thermal expansion. At present, there is a significant demand for the development of ceramics with complex geometries that can achieve previously unmatched properties, and additive manufacturing (AM) techniques are well-suited to meet these challenges. In this study, we chose the binder jetting (BJ) technology and investigated the influence of printing parameters and powder characteristics on AlN part quality and densification. Different strategies were used to enhance densification: employing multimodal powders and adding Yttrium oxide (Y₂O₃) to improve the shrinkage, and optimizing the printing parameters. Multimodal powder was prepared using two AlN powders (D50 ~14.7 µm and 2.2 µm) at varying fine powder ratios. After sintering at 1900°C, monoclinic yttrium aluminum monoclinic and perovskite yttrium aluminum perovskite phases formed alongside AlN and Y₂O₃. The highest achieved densification, 64.2%, set a new record for BJ-printed AlN. This study demonstrates the feasibility of BJ for AlN ceramics and underscores the crucial role of powder selection and AM process parameters optimization.

**Keywords:** Ceramics; Additive manufacturing; Aluminum nitride; Binder jetting; Multimodal mixture

1. Introduction

Aluminum nitride (AlN) ceramic is a promising candidate for power electronics substrates<fnref n="1" />⁻<fnref n="3" /> by virtue of its high thermal conductivity (up to 250 W·m⁻<fnref n="1" />·K⁻<fnref n="1" /> at room temperature),⁴⁻⁶ low thermal expansion, suitable dielectric properties, and bending strength of more than 300 MPa, making them ideal for thermal management applications.⁷⁻¹⁰ Traditionally, dense AlN ceramics are obtained after sintering in an inert atmosphere at temperatures exceeding 2000°C.¹¹ At present, there is a significant demand for the creation of ceramics featuring intricate geometries that can achieve exceptional properties, which can be effectively addressed through additive manufacturing (AM)

<footnote n="1">¹CIRIMAT, Université Toulouse, Toulouse INP, CNRS, 118 Route de Narbonne, CEDEX 9, 31062 Toulouse, France</footnote>

<footnote n="2">²CEA Tech Occitanie, 51 Rue Innovat, Labege, France</footnote>

<footnote n="3">³Toyal Europe, Route de Lescun, Accous, France</footnote>

<footnote>†These authors contributed equally to this work.</footnote>

<footnote>*Corresponding author: Sophie.Guillemet-Fritsch (sophie.guillemet@univ-tlse3.fr)</footnote>

<footnote>**Citation:** Pruvost F, Guillemet-Fritsch S, Mortagne-Coderch A, et al. Elaboration of complex aluminum nitride parts by binder jetting: Optimization of printing parameters and powder characteristics. *Mater Sci Add Manuf.* 2025;4(4):025090008. doi: 10.36922/MSAM025090008</footnote>

<footnote>**Received:** February 25, 2025</footnote>

<footnote>**Revised:** March 20, 2025</footnote>

<footnote>**Accepted:** March 26, 2025</footnote>

<footnote>**Published online:** September 9, 2025</footnote>

<footnote>**Copyright:** © 2025 Author(s). This is an Open-Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution, and reproduction in any medium, provided the original work is properly cited.</footnote>

<footnote>**Publisher's Note:** AccScience Publishing remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.</footnote>
techniques. The fabrication of ceramics with complex shapes is challenging due to their hardness and brittleness.<sup>12,13</sup> Various AM techniques<sup>14</sup> such as binder jetting (BJ),<sup>11</sup> digital light processing (DLP),<sup>15</sup> stereolithography (SLA),<sup>16</sup> robocasting<sup>17</sup> and direct ink writing<sup>18</sup> have been explored for AlN fabrication. The values of densities and thermal conductivities obtained are reported in Table 1. High densities, up to 99.4%, have been obtained with SLA and DLP. However, the challenge is to elaborate AlN ceramic complex parts with the highest possible density using BJ.<sup>19-21</sup> Thus, BJ was chosen in this work as it enables printing at ambient atmosphere and temperature without requiring a heat source. Moreover, it is a method with low manufacturing cost and no upstream preparation is necessary.<sup>22</sup> In addition, no support structures are needed, as the powder bed itself acts as a support during printing.<sup>23</sup> However, an essential characteristic is the flowability of the powder. Thus, using non-spherical particles may lead to a trade-off between improved packing density and reduced flowability if there are too many fine particles.

One of the main challenges in BJ printing is overcoming high porosity to achieve high density in both printed and sintered parts.<sup>22</sup> Several strategies have been proposed to enhance densification, including the post-infiltration process, the use of multimodal powder mixtures, and

binder-incorporated nanopowders.<sup>24-29</sup> Starting with using multimodal powders in AM, particularly in the BJ process, is a strategy aimed at improving the packing density of powders, the density of printed parts, and their mechanical properties. Multimodal mixtures combine particles of different sizes, typically coarse and fine particles, to optimize compaction and reduce porosity. Multimodal powders have been used in various AM processes to improve packaging density and part properties (Table 2). Hence, adding fine particles to coarse powder can improve the packing density printed part density and their mechanical properties.<sup>30</sup>

Finally, sintering AlN without sintering aids remains a significant challenge. Yttrium oxide ($Y_2O_3$) is commonly used to enhance densification while also improving thermal conductivity.<sup>37</sup> $Y_2O_3$ reacts with the naturally occurring $Al_2O_3$ layer on the surface of AlN particles, forming a liquid phase that promotes sintering. In addition, the removal of $Al_2O_3$ impurities contributes to higher thermal conductivity. According to phase diagram,<sup>38</sup> the interaction between $Y_2O_3$ and $Al_2O_3$ leads to the formation of three possible phases, depending on their ratio: The monoclinic yttrium-rich phase Yttrium aluminum monoclinic (YAM) ($Y_4Al_2O_9$), the garnet phase yttrium aluminum garnet (YAG) ($Y_3Al_2O_{12}$), and the perovskite phase yttrium aluminum perovskite (YAP) ($YAlO_3$).<sup>6</sup>

<table><caption>Table 1. Density and thermal conductivity of different AlN structures obtained with different AM process</caption><thead><tr><th>Reference</th><th>AM process</th><th>Final relative density (%)</th><th>Thermal conductivity (W.m<sup>-1</sup>.K<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Rauchenecker et al.<sup>15</sup></td><td>DLP</td><td>96.6</td><td>166 (®RT)</td></tr><tr><td>Lin et al.<sup>16</sup></td><td>SLA</td><td>99.4</td><td>N/A</td></tr><tr><td>Qin et al.<sup>17</sup></td><td>Injection molding</td><td>99.9</td><td>248 (®RT)</td></tr><tr><td>Belmonte et al.<sup>18</sup></td><td>Direct ink writing</td><td>54.3</td><td>9.5 (®RT)</td></tr><tr><td>Diaz-Moreno et al.<sup>11</sup></td><td>Binder jetting and HIP</td><td>60.1</td><td>4.82 (®RT)</td></tr></tbody></table>

Abbreviations: ®RT: At room temperature; AlN: Aluminum nitride; AM: Additive manufacturing; DLP: Digital light processing; HIP: Hot isostatic pressing; SLA: Stereolithography, N/A: Not available.

<table><caption>Table 2. Use of multimodal powders for different AM methods</caption><thead><tr><th>Reference</th><th>AM process</th><th>Composition</th><th>Coarse particle size (μm)</th><th>Fines particle size (μm)</th><th>Fines particle percentage (%)</th><th>Powder density (g/cm<sup>3</sup>)</th><th>Green density (%)</th><th>Sintered density (%)</th></tr></thead><tbody><tr><td>Liu<sup>31</sup></td><td>Sintering</td><td>Stainless steel</td><td>50 – 100</td><td>5 – 20</td><td>20 – 40</td><td>-</td><td>-</td><td>~95</td></tr><tr><td>Haferkamp et al.<sup>32</sup></td><td>Laser powder bed fusion</td><td>316L steel</td><td>40 – 80</td><td>10 – 30</td><td>35</td><td>-</td><td>52</td><td>95</td></tr><tr><td>Yun Bai and Williams.<sup>33</sup></td><td>Binder Jetting</td><td>316L steel</td><td>45 – 75</td><td>5 – 15</td><td>30</td><td>4.8</td><td>~50</td><td>92.6</td></tr><tr><td>Clares et al.<sup>34</sup></td><td>Binder Jetting</td><td>316L steel</td><td>50 – 100</td><td>5 – 20</td><td>30</td><td>4.6</td><td>~55</td><td>93</td></tr><tr><td>Ye et al.<sup>35</sup></td><td>Hot Pressing</td><td>Superalloy</td><td>50 – 100</td><td>10 – 20</td><td>25</td><td>4.5</td><td>~52</td><td>94</td></tr><tr><td>Du et al.<sup>36</sup></td><td>Binder Jetting</td><td>SiC</td><td>30 – 60</td><td>2 – 8</td><td>30</td><td>2.3</td><td>50.7</td><td>96</td></tr><tr><td>Ziaee<sup>13</sup></td><td>Binder Jetting</td><td>$Al_2O_3$</td><td>60 – 100</td><td>20 – 50</td><td>40</td><td>3.7</td><td>65.7</td><td>98</td></tr><tr><td>Du et al.<sup>28</sup></td><td>Binder Jetting</td><td>SiC</td><td>70</td><td>2 – 10</td><td>24.1</td><td>2.3</td><td>50.7</td><td>66.1</td></tr></tbody></table>

Abbreviation: AM: Additive manufacturing.
In this work, we employed the BJ method to elaborate complex 3D-shaped AlN components using optimized powders. The mixture consists of two powders of various particle size distributions (PSDs) with irregular shapes, both containing an additional fraction of $Y_2O_3$. The impact of this multimodal mixture on the structure, microstructure, and density of the powder bed, as well as green and sintered parts, was carefully analyzed and compared to the unimodal powder. After the powders were characterized, multimodal mixtures tailored to the manufacturing process were prepared. In the second step, printing parameters, such as deposition rate, saturation, and layer thickness (LT), were optimized, with a particular focus on the compaction pass (CP) parameter used to maximize green density. Finally, the manufactured parts were subjected to structural and microstructural characterization after heat treatments, including debinding and sintering.

# 2. Materials and methods

## 2.1. Materials

### 2.1.1. Powders

The AlN powders were supplied by Total Europe (Japan). The fine powder (JCGA-BLY5) containing 5 wt% of $Y_2O_3$ will hereafter be referred to as AlN JCGA. The coarse AlN powder (TFZ-N15P) with a purity of ≥96 wt% and no additives, will be designated as AlN TFZ. In addition, the $Y_2O_3$ powder (Grade C, purity >99.95%) was procured from Höganäs, Germany.

### 2.1.2. Powders mixture preparation

The TFZ powder of AlN was mixed with two different fractions of $Y_2O_3$ powder (3 and 5 wt%) using a 3D Turbula mixer with alumina balls (diameter = 10.5 mm) for 2 h. An initial test with 5 wt% of $Y_2O_3$ resulted in an inhomogeneous distribution of yttrium phases along the AlN grain boundaries. Consequently, 3 wt% $Y_2O_3$ was selected. This formulation, referred to as AlN-3Y, was used as the initial coarse powder for subsequent multimodal mixtures.

Two multimodal powders were prepared with varying fine powder (JCGA) contents of 10 wt% and 15 wt%, designated as AlN-3Y-10% and AlN-3Y-15%, respectively. The mixing process consisted in two steps. The first step was performed using a KakuHunter planetary mixer (Shashin Kagaku, Japan) in 100 g batches (2 cycles × 2 min at 800 rpm in mixing mode, followed by 4 min at 1000 rpm in mixing and oscillation mode). This step was optimized by testing different durations and speeds. The second step involved batches homogenization for 2 h in the Turbula mixer.

### 2.1.3. Powder characterizations

The particles size distribution of each preparation was analyzed using a Mastersizer 3000 particle size analyzer (Malvern Panalytical, USA) in dry mode. The apparent and tapped densities of the unimodal and multimodal powders were measured using a density meter. PSDs were evaluated before and after mixing. Tapped density measurements were performed using an LSCI IVOL-03 tap density meter (LCSI, France). A 70 g powder sample was compacted through 3000 taps in cycles of 300 taps. The apparent density was determined using an ELECTOLAB EV-02 density meter (India) with a 25.03 cm³ container. All the measurements were conducted in triplicate. Powder flowability was estimated³⁹ based on the Hausner index (H) and Compaction index (C) calculated using formulas stated in the following:

$$H = \frac{\text{Tap density}}{\text{Apparent density}} \qquad (I)$$

$$C = \frac{\text{Tap density} - \text{Apparent density}}{\text{Tap density}} \times 100 \qquad (II)$$

The flowability of a powder, as well as the H and C index, are associated with its flow behaviors based on the values obtained for each index.³⁹ A powder is considered to have good flowability if its H index ranges between 1 and 1.25 and its C index between 1% and 25%. The lowest possible value for both indices is 1. However, these reference values are specifically valid for spherical powders (e.g., atomized or granulated). While they may not directly apply to nonspherical particles, they serve as useful guidelines, as lower index values generally indicate improved flowability.

### 2.1.4. BJ parameters and components design

The BJ process was carried out using the ExOne Innovent+ system (ExOne, Germany). This AM technique builds 3D parts layer by layer by selectively depositing a binder onto a powder bed, allowing 2D layers to be stacked. In this system, a hopper distributes the powder onto the job box surface (160 × 65 × 65 mm) using ultrasonic vibrations. Two rollers then level and smooth the powder bed. Finally, the print head selectively deposits the binder onto the designated areas of the powder bed. The binder used in this work is ExOne's AquaFuse, composed of water, ethanediol, and 2-butoxyethanol.

The printing parameters selected for this study are presented in Table 3. The CP⁴⁰,⁴¹ is a parameter used to enhance the density of both the powder bed and the green parts. In the first step, the print bed is lowered by one LT and one compaction thickness (CT). In the second stage, after
<table><caption>Table 3. Selected printing parameters</caption><thead><tr><td>Parameters</td><td>Values</td></tr></thead><tbody><tr><td>Layer thickness</td><td>70 µm</td></tr><tr><td>Desired saturation</td><td>70%</td></tr><tr><td>Ultrasound intensity</td><td>75%</td></tr><tr><td>Powder packing rate</td><td>45 – 50%</td></tr><tr><td>Powder bed temperature</td><td>60°C</td></tr><tr><td>Powder bed drying time</td><td>20 s</td></tr><tr><td>Compaction thickness</td><td>50 µm</td></tr><tr><td>Compaction pass</td><td>2</td></tr></tbody></table>

irradiation with the infrared lamp, the hopper deposits the powder, and the rollers remove the excess material while smoothing the bed. The third step involves raising the plate by a CT height and passing the rollers again to compact the newly deposited powder to LT. Finally, the print head moves over the powder bed to deposit the binder. For example, Moghadasi et al.²⁷ obtained a sintered density of 72.0% using alumina nanopowder and applying the CP parameter while they obtained a maximum final density of 67% without using this parameter.

The powder packing rate (PR) is a parameter that represents the powder bed density. Its value lies between the apparent and the tapped density value. A crucible, used as a reference to calculate the density of the unbound powder, was also prepared by BJ. The resulting value represents the powder PR, which is used to determine the amount of binder required. The saturation refers to the percentage of porosity filled with binder. For example, a 70% saturation theoretically means that 70% of the pores are filled with binder.

Several geometries were selected and fabricated to test print resolution and calculate the densities of both green and sintered parts. These included pellets (20 × 4 mm), crucibles (external dimensions 20 × 6 mm, internal dimensions 16 × 4.5 mm) and stems (20 × 2 × 2 mm). In addition, more complex parts were fabricated to assess feasibility, resolution, and the strength of thin walls (honeycomb laces, large and fin meshes). Reference pellets with a diameter of 20 mm were created by pressing 2.5 g of powders using a hydraulic press at 10 tons of pressure for 1'30".

## 2.2. Post-processing

### 2.2.1. Curing

After the printing process, the job box containing the AlN parts was thermally treated at 200°C for 3 h to polymerize the binder (curing step). The green parts were then cleaned of excess powder using brushes and vacuuming, and their

apparent densities were measured. Using a digital caliper (ABS digimatic, Mitutoyo, Japan), the dimensions and the density values of AlN parts were calculated. Each measurement was repeated 5 times. The density (g/cm³) of the pellets was determined using Equation III:

$$ \rho_{\text{pellet}} = \frac{m}{\pi \times r^2 \times t} \qquad (\text{III}) $$

Where ρ = Density (g/cm³), m = Mass (g), r = Radius (cm), and t = Thickness (cm). The mass of the green part is corrected by subtracting the mass of the binder. The theoretical value of AlN density is $\rho_{\text{AlN}} = 3.3 \text{ g/cm}^3$

Thermogravimetric analyses (TGA) were performed using a TGA-92 (SETARAM, France). The analysis was conducted from 20°C to 600°C with a temperature ramp of 3°C/min in an alumina crucible under air, and used to determine the binder content in the green parts and the binder degradation temperature.

### 2.2.2. Debinding and sintering

First, the parts were heated in an air atmosphere until 600°C for 30 min with a ramp of 4°C/min to evaporate the binder. At this temperature, the atmosphere was switched to an inert environment using dinitrogen ($N_2$) to prevent oxidation of AlN. The temperature was then increased to 1000°C at 4°C/min, followed by a ramp to the maximum temperature of 1900°C at 2°C/min. The parts were held at 1900°C for 6 h before cooling.

## 2.3. Structural and microstructural characterizations

X-ray diffraction (XRD) analysis was performed using a D8 Endeavor X-ray diffractometer (Bruker) with a slit size of 0.5 mm and sample holder rotation. The scans were conducted in the 2θ range from 20° to 80°, with an increment of 0.016° and a scanning speed of 0.04°/min. Powders and pellets were analyzed, and pellets with a diameter of 2 cm were manufactured with BJ and hydraulic press (thickness between 2 mm and 6 mm). These pellets were placed in sample holders of varying heights, which are suitable for analyzing parts. The samples were positioned horizontally at the height of the holder for analysis. The indexation of the AlN and $Y_2O_3$ diffractograms was carried out using the hexagonal (#00-025-1133) and cubic (#00-043-1036) crystallographic systems, respectively. The morphology of the powder particles was examined using a VEGA3 scanning electron microscope (SEM; Tescan, Japan). An integrated EDS spectrometer (X-Max, Oxford Instrument, United Kingdom) was employed to determine the chemical composition of the parts and to create elemental maps for both the green and sintered components.
# 3. Results and discussion

## 3.1. Powder characterization

SEM observations of the powders, the fine AlN JCGA (containing 5 wt% of Y₂O₃), and the coarse powder obtained by mixing AlN TFZ with Y₂O₃, are presented in Figure 1. It can be seen that the fine AlN JCGA particles (Figure 1A) and the coarse AlN TFZ particles (Figure 1B) have angular shapes. The Y₂O₃ particles (Figure 1C) exhibit an elongated shape, with a size smaller than 1 µm, and form numerous agglomerates several micrometers in size. Figure 1D shows the microstructure of the coarse AlN powder containing 3 wt% of Y₂O₃ (AlN-3Y). Fine particles, which are not visible in Figure 1B, are observed on the large particles, likely due to the presence of yttria in the mixture, as confirmed by energy-dispersive X-ray spectroscopy (EDS) analyses.

Table 4 presents the values of grain size (obtained with granulometry analysis; see below), tapped density, and apparent densities for the different AlN powders, and the calculated values of the H and C indices. It can be observed that both densities of AlN TFZ (coarse particles) are approximately twice of AlN JCGA (fine particle). Based on the Hausner ratio, both powders exhibit poor flowability. However, the particles are not spherical, so the H value only serves as an indicator of the flowability of these powders.

In the first experiment, 5 wt% of yttria was mixed with the AlN TFZ powder for comparison with the commercial AlN JCGA powder, which also contains 5 wt% of yttria. Figure 2B provides an SEM observation of a sintered

pressed pellet made with this powder mixture, highlighting the heterogeneity of the powder. In some areas, a high concentration of yttrium can be observed at the AlN grain boundaries, as shown by EDS analysis (Figure 2D). The excess yttria powder in the preparation resulted in the formation of localized agglomerates during the mixing process, leading to a non-uniform distribution of the final mixture.

To achieve a better distribution of fine particles, the yttria content was lowered to 3 wt% for a more homogeneous distribution of the particles as shown by SEM and EDS analysis in Figure 2A and C. The densities and PSD of this mixture are presented in Table 4. A significant decrease in D50, compared with the TFZ powder, is observed due to the addition of fine yttria particles. On the other hand, the tapped and apparent densities of AlN-3Y are similar to those of the raw AlN TFZ powder, indicating that the addition of yttria has a minimal impact on the rearrangement of the particles and consequently on the flowability of the powder.

The AlN mixtures with different ratios of fine powder (JCGA) were prepared, and their microstructures are shown in Figure 3. In Figure 3A, a wide distribution of large particles is observed. As expected, the proportion of large particles visible in the SEM micrographs decreases as the percentage of fine particles increases (Figure 3B). The presence of yttria is observed on large AlN TFZ grains, regardless of the fine powder content in the mixture. Apparent and tapped densities determined

<figure><img src="image_2.png" /><figcaption>**Figure 1.** SEM images of the (A) fine AlN (JCGA), (B) coarse pure AlN (TFZ), (C) Y₂O₃ powder, and (D) coarse AlN with 3 wt% of Y₂O₃ (AlN-3Y) Abbreviations: AlN: Aluminum nitride; SEM: Scanning electron microscopy; Y₂O₃: Yttrium oxide</figcaption></figure>

<table><caption>**Table 4.** Particle size, density, Hausner index, and compaction index of AlN powders (average of three analyses)</caption><thead><tr><th>Powder</th><th>AlN (JCGA)</th><th>AlN (TFZ)</th><th>AlN-3Y</th><th>AlN-3Y-10%</th><th>AlN-3Y-15%</th></tr></thead><tbody><tr><td>Y<sub>2</sub>O<sub>3</sub> percentage</td><td>5.0</td><td>0.0</td><td>3.0</td><td>3.2</td><td>3.3</td></tr><tr><td>Median particle size (µm)</td><td>2.2</td><td>14.7</td><td>5.8</td><td>5.5</td><td>3.9</td></tr><tr><td>Apparent density (%)</td><td>16.6</td><td>31.4</td><td>28.6</td><td>27.1</td><td>26.1</td></tr><tr><td>Tap density (%)</td><td>32.4</td><td>63.0</td><td>56.7</td><td>58.8</td><td>57.9</td></tr><tr><td>Hausner index</td><td>1.9</td><td>2.0</td><td>2.0</td><td>2.2</td><td>2.2</td></tr><tr><td>Compaction index (%)</td><td>48.7</td><td>50.1</td><td>49.6</td><td>54.0</td><td>54.9</td></tr></tbody></table>

Abbreviation: AlN: Aluminum nitride.
for each multimodal mixture, are reported in Table 4, along with the calculated values of H and C index for the different multimodal mixtures. The density of the mixtures decreases as the fine particles are added. The values of H and C indices increase proportionally with the amount of JCGA powder. The tapped density of the mixtures with 10% and 15% of fine particles is higher than that of the raw TFZ powder with 3 wt% of Y₂O₃ (AlN-3Y).

**Figure 4A** shows the volume PSD of the unimodal powders. It is observed that the fine JCGA powder has a wider distribution than the TFZ powder, with an average D50 value of approximately 2 µm, consistent with the value

<figure><img src="image_3.png" /><figcaption>**Figure 2.** SEM and EDS images of sintered pellets of AlN TFZ with 3 wt% (A and C) and 5 wt% (B and D) of Y₂O₃. (A and B) SEM images of pressed sintered pellets of AlN TFZ with 3 wt% (a) and 5 wt% (b) of Y₂O₃. (C and D) EDS images (yttrium maps) of the same pellets with 3 wt% (c) and 5 wt% (d) of Y₂O₃.</figcaption></figure>

Abbreviations: AlN: Aluminum nitride; EDS: Energy-dispersive X-ray spectroscopy; SEM: Scanning electron microscopy; Y₂O₃: Yttrium oxide

<figure><img src="image_4.png" /><figcaption>**Figure 3.** SEM images of the multimodal AlN coarse powder (TFZ) with 10% (A) and 15% (B) of fine powder</figcaption></figure>

Abbreviations: AlN: Aluminum nitride; SEM: Scanning electron microscopy

given by the supplier (Table 4). Similarly, the distributions of the TFZ and AlN-3Y powders have average values close to those measured, approximately 15 – 20 µm for AlN TFZ and 5 µm for AlN-3Y. As expected, the addition of yttria to the AlN TFZ powder reduces the average PSD. **Figure 4B** shows the PSD of multimodal and AlN-3Y powders. Notably, the PSD of the 10% mixture is very similar to that of AlN-3Y (D50 ~ 5 µm). In contrast, for the mixture with 15% of fine particles, two distinct peaks, centered on 2.5 µm and 10 µm, are observed.

Through these characterizations and a simple test using the BJ dispenser (ultrasonic vibration of the hopper without printing process), we determined that AlN TFZ exhibited sufficient flowability for printing, unlike AlN JCGA, which did not flow through the hopper. Therefore, it is essential to select a mixture that has H and C indices, as well as densities, similar to those of AlN TFZ, while also containing enough fine particles to facilitate the rearrangement of particles on the powder bed and thus in the green parts. Three powder mixtures were successfully printed: AlN-3Y, AlN-3Y-10%, and AlN-3Y-15%.

## 3.2. Green printed parts

Powder printing was carried out using the compaction parameter. The rollers passed the 1st time to smooth the bed, then the job box plate rose by a pre-defined thickness, and

<figure><img src="image_5.png" /><figcaption>**Figure 4.** Measured particle size distributions of unimodal AlN powders (A) and multimodal AlN powders (B)</figcaption></figure>

Abbreviation: AlN: Aluminum nitride
the rollers passed over the surface a 2nd time to compact and press the powder. Without pass compaction, the powder bed exhibited an irregular and distorted appearance with visible voids (Figure 5A), particularly when printing multimodal powders. However, after applying the CP to each multimodal powder bed, a significant improvement in powder bed roughness was observed (Figure 5B). This effect was particularly noticeable when the plate was raised by 50 µm and a slower second pass of the rollers was applied.

Initially, pellets and crucibles were manufactured, as shown in Figure 6A-C. To assess the feasibility of producing narrow-walled structures, elongated parts

with dimensions of 15 × 2 × 2 mm and 20 × 2 × 2 mm were fabricated (Figure 6D and E). Finally, more complex geometries featuring thin walls and honeycomb alcoves were produced (Figure 6F-H) to demonstrate the feasibility of manufacturing complex structures and evaluate the resolution of the printed parts. Parts f and g have external dimensions of 20 × 20 mm. Part f has an internal wall thickness of 1 mm whereas those of part g are 0.5 mm thick. Finally, part h has dimensions twice as large as part g.

After curing in an oven for 3 h at 200°C to polymerize the binder, a step was required to remove the residual free powder surrounding the manufactured parts. TGA analyses (Figure S1 in Supplementary File) were performed on an AlN-3Y green part. The results showed a mass loss of 3%, corresponding to the decomposition of the AquaFuse binder upong heating. Consequently, the densities of each part were recalculated, accounting for the binder mass and subtracting it from the total mass of the parts. TGA analyses also showed that oxidation of AlN started at 800°C in the air atmosphere.

Table 5 presents the raw densities of the printed green parts alongside those of the pressed pellets. Applying the CP to the multimodal powder resulted in an increase in green material density. The addition of 10 wt% of fine powder led to a 7.7% increase in raw density, while 15 wt% resulted in an 8.6% increase when CP was used. A similar trend, though less pronounced, was observed for the AlN-3Y-15% mixture, where the pressed pellets achieved the highest density of 69.2% (compared to the printed pellets of 51.9%). Our printed parts have relative densities of approximately 50%, which are comparable to the values obtained by Du *et al.*²⁸ for SiC multimodal mixtures and higher than the density data reported for AlN green parts.¹¹

Figure 7 presents SEM observations of the core of the green parts obtained from different AlN mixtures. Figure 7A corresponds to parts produced from the AlN-3Y mixtures with CP, where large AlN-TFZ particles (~15 – 20 µm) are visible, along with finer Y₂O₃ particles (<1 µm). In Figure 7D and G, AlN JCGA particles (~1 – 2 µm) can also be observed. The particles appear well compacted, with visible porosity. At low magnification (Figure 7B, E and H), the porosity of the parts is highly visible. In addition, the distribution of large

<figure><img src="image_6.png" /><figcaption>**Figure 5.** Improved powder bed appearance with the use of CP: (A) Powder bed without the CP, and (B) powder bed with a CT of 50 µm for AlN-3Y-15%</figcaption></figure>

Abbreviations: AlN: Aluminum nitride; CP: Compaction pass; CT: Compaction thickness

<figure><img src="image_7.png" /><figcaption>**Figure 6.** Green parts of AlN-3Y: (A and B) Pellets for measuring the green parts density, (C) crucible for calculating the powder bed density, (D and E) fine stems, and (F-H) lace-shaped honeycombs</figcaption></figure>

<table><caption>**Table 5.** Green density of printed and pressed parts of AlN unimodal and multimodal powders</caption><thead><tr><th rowspan="2">Powder</th><th rowspan="2">AlN-3Y</th><th rowspan="2">AlN-3Y-10%</th><th rowspan="2">AlN-3Y-15%</th><th colspan="2">References</th></tr><tr><th>AlN</th><th>SiC</th></tr></thead><tbody><tr><td>Green density – pressed pellet (%)</td><td>66.6</td><td>68.2</td><td>69.2</td><td>N/A</td><td>N/A</td></tr><tr><td>Green density – printed pellet (%)</td><td>43.3</td><td>51.0</td><td>51.9</td><td>32<sup>11</sup></td><td>50.7<sup>28</sup></td></tr></tbody></table>

Abbreviation: AlN: Aluminum nitride, N/A: Not available.
<figure><img src="image_8.png" /><figcaption>**Figure 7.** SEM images of green part of AlN-3Y (A-C), AlN-3Y-10% (D-F), and AlN-3Y-15% (G-I)</figcaption></figure>

Abbreviations: AlN: Aluminum nitride; SEM: Scanning electron microscope

and fine particles appears homogeneous. However, parts manufactured with AlN multimodal powders exhibit smaller and less pores. The printed layers (~70 µm thick) can be distinguished (highlighted by red lines), as shown in Figure 7C, F and I, which reveal porosity between each layer.

The EDS mapping of the different printed parts is shown in Figure 8. The large particles mainly consisted of AlN, and the smaller particles attached on their surface consisted of yttria (Figure 8A). In Figure 8B and C, the higher concentration of yttria is evident.

### 3.3. Sintered parts

The density of the green and sintered parts is reported in Figure 9. The sintered pressed pellet of AlN-3Y-10% exhibits the highest increase in density by 14.4%. In comparison, the highest increase in density for the printed pellet is observed for AlN-3Y-15%, by 12.3%.

The shrinkage after sintering was measured along two directions: x (diameter) and z (thickness, layer stacking orientation) (Table 6). The AlN-3Y pellet processed with CP exhibits the lowest shrinkage, with a reduction of 5.2% along the x-direction and 5.1% along the z-direction. In contrast, the multimodal powder-based pellets showed more significant shrinkage, particularly in the z-direction, with values of 7.1% for AlN-3Y-10% and 10.3% for AlN-3Y-15%. The shrinkage in the x-direction was slightly higher for AlN-3Y-15% (8.0%) compared to that for AlN-3Y-10% (7.7%).

The AlN-3Y powder achieves a higher final sintered density when printed with multimodal powder. Although the multimodal powder mixtures provide higher initial green density, their density behavior differs, as evidenced by the variation in shrinkage rates in the z-direction. Notably, AlN-3Y-15% exhibits the highest density increase, which can be attributed to its greater shrinkage in both
<figure><img src="image_9.png" /><figcaption>**Figure 8.** Mapping EDS distribution of green parts with AlN-3Y (A), AlN-3Y-10% (B), and AlN-3Y-15% (C)
Abbreviations: AlN: Aluminum nitride; EDS: Energy-dispersive X-ray spectroscopy</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>**Figure 9.** Relative density (geometrical) of AlN of pressed and printed parts before and after sintering. The orange-colored error bars denote standard deviations from Student's *t*-test
Abbreviation: AlN: Aluminum nitride</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>**Figure 10.** Green and sintered printed parts of AlN-3Y-15%
Abbreviation: AlN: Aluminum nitride</figcaption></figure>

x- and z-directions. **Figure 10** shows green and sintered parts, where a slight shrinkage in the overall size of the

<table><caption>**Table 6.** Shrinkage of printed and sintered AlN parts in the x- and z-directions</caption><thead><tr><th rowspan="2">Sintered parts</th><th colspan="2">Relative shrinkage (%)</th></tr><tr><th>(x)</th><th>z</th></tr></thead><tbody><tr><td>AlN-3Y</td><td>5.2</td><td>5.1</td></tr><tr><td>AlN-3Y-10%</td><td>7.7</td><td>7.1</td></tr><tr><td>AlN-3Y-15%</td><td>8.0</td><td>10.3</td></tr></tbody></table>

Abbreviation: AlN: Aluminum nitride.

<table><caption>**Table 7.** Density of sintered printed and pressed parts</caption><thead><tr><th>Blend</th><th>AlN-3Y</th><th>AlN-3Y-10%</th><th>AlN-3Y-15%</th></tr></thead><tbody><tr><td>Printed reference pellet</td><td></td><td></td><td></td></tr><tr><td>Sintered density (%)</td><td>76.2±1.1</td><td>82.6±0.3</td><td>80.1±0.3</td></tr><tr><td>Increase of density (%)</td><td>9.6±0.6</td><td>14.4±0.4</td><td>10.8±0.1</td></tr><tr><td>Printed pellet</td><td></td><td></td><td></td></tr><tr><td>Sintered density (%)</td><td>50.3±0.8</td><td>62.2±0.5</td><td>64.2±0.3</td></tr><tr><td>Increase of density (%)</td><td>5.7±1.3</td><td>11.2±0.5</td><td>12.3±0.1</td></tr></tbody></table>

Abbreviation: AlN: Aluminum nitride.

parts can be seen. Moreover, whitening of the parts due to the removal of the binder during debinding is also observed on the sintered parts.

The density values of each sintered part are detailed in **Table 7**. The AlN-3Y-15% mixture, which exhibited the highest raw density, demonstrated superior dimensional shrinkage and increase in density compared to the AlN-3Y-10% pellet. Notably, the printed AlN-3Y-15% sample yielded the best results, as its initially higher raw density enabled it to reach a final sintered density of 64.2%, compared to 62.2% for the AlN-3Y-10% parts. However, the latter achieved the highest final density among the sintered pressed parts.
The powder AlN-3Y-15% is the optimum choice for printing because of its higher green and final density. BJ-fabricated AlN has only been reported once in literature, by Diaz-Moreno *et al.*¹¹ who used unimodal AlN (~ 45 µm) and achieved a relative density of 60.1% after hot isostatic pressing (HIP) sintering. The density of our sintered print part of AlN-3Y-10% and AlN-3Y-15% surpassed this previously reported value, likely due to the use of multimodal powders and finer particles.

XRD analyses were conducted on the sintered parts and compared with the structure of the initial raw powders to evaluate structural evolution during the sintering treatment (Figure 11). The dominant phase in both the powder and the sintered parts is the hexagonal AlN (#00-025-1133) with a minority cubic Y₂O₃ phase (#00-043-1036). The transformation of Y₂O₃ into the orthorhombic YAP phase (YAlO₃, #01-089-7947) occurs, with only a trace of residual of Y₂O₃ detected in the printed sintered parts.

The difference in the quantities of YAP and YAM (Y₄Al₂O₉) phases can be attributed to the overall difference in raw densities of the pressed and printed pellets. The pressure applied to the reference pellets likely enhances the diffusion of yttria during sintering, and facilitates the formation of the YAP phase, despite identical sintering conditions for all the printed and pressed parts. The nature of the phases is primarily determined by the amount of additive present in the AlN particles.³⁷ From the most concentrated to the least concentrated, the phases observed are: YAM, YAP, and YAG. The formation of the YAP phase is significantly favored compared to the YAM phase. No YAG phase (Y₃Al₅O₁₂), also known as the aluminum-rich phase, was observed. The higher density of the sintered pressed parts, compared to the printed parts, along with the absence of the YAM phase, indicates that the applied pressure increased the concentration of Y₂O₃ on the surface of the AlN particles, thereby favoring the formation of the YAP phase.

<figure><img src="image_12.png" /><figcaption>**Figure 11.** XDR patterns of AlN printed and pressed pellets after sintering at 1900°C during 6h under N₂ (A) and AlN powders (B)
Abbreviations: AlN: Aluminum nitride; XRD: X-ray diffraction; YAM: Yttrium aluminum monoclinic; YAP: Yttrium aluminum perovskite</figcaption></figure>
Figure 12 presents the SEM observations of the sintered parts, focusing on the inner regions of the printed samples produced with different AlN mixtures. A noticeable increase in grain size can be observed in Figure 12A-C. This growth appears to be similar across all printed mixtures, with the fine particles exhibiting a higher growth rate compared to coarse particles. The original coarse green particles, initially 14.7 µm in size, display a final particles size of 20 – 30 µm after sintering. Meanwhile, the fine particles lead to a moderate size increase, growing from approximately 1 µm up to 3 – 6 µm final particles size. The morphology of the

coarse particles remains largely unchanged. However, the fine particles tend to spread and partially fill the existing pores. Yttria particles are found melted and diffused at the grain boundaries (highlighted by black circles). These particles are visible in all sintered parts but appear to be more homogeneously distributed in the samples printed with multimodal powders (Figure 12B and C).

Heterogeneous distribution of pores is evident in Figure 12D-F, along with variations in the growth of different AlN particles. This non-uniform distribution is particularly pronounced in the AlN-3Y parts. In contrast,

<figure><img src="image_13.png" /><figcaption>**Figure 12.** SEM images of sintered part of AlN-3Y (A and B), AlN-3Y-10% (C and D), and AlN-3Y-15% (E and F)
Abbreviations: AlN: Aluminum nitride; SEM: Scanning electron microscopy</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>**Figure 13.** EDS distribution maps of sintered printed parts with AlN-3Y (A), AlN-3Y-10% (B), and AlN-3Y-15% (C)
Abbreviations: AlN: Aluminum nitride; EDS: Energy-dispersive X-ray spectroscopy</figcaption></figure>
the parts printed with multimodal mixtures exhibit smaller pores, which can be attributed to the fine particles filling the initial voids during the sintering process. The incorporation of AlN JCGA particles effectively reduces porosity, contributing to an increase in the final density of the printed parts. However, the densification process remains incomplete, indicating that further optimization of sintering conditions is necessary to achieve full densification.

EDS analyses of the printed and sintered pellets are presented in Figure 13. The EDS mapping along the z-direction clearly highlights the presence of the yttria phase at the grain boundaries. In Figure 13A, black areas are visible on the aluminum (Al) mapping corresponding in size and shape to the regions identified on the yttrium (Y) mapping. In contrast, no such black areas appear on the Al maps of the multimodal mixture parts (Figure 13B and C). These observations corroborate the formation of the YAM and YAP phases identified by the XRD analysis. The EDS mapping further indicates that the grain boundaries of the AlN-3Y parts exhibit a high concentration of Y, whereas the grain boundaries in the multimodal powder parts contain a more balanced proportion of Y and Al elements. In addition, the distribution grain boundaries appear more homogeneous in the pellets produced with multimodal powders compared to those made with unimodal powders. This enhanced homogeneity could contribute to improved mechanical properties in the sintered parts.

## 4. Conclusion

We successfully used BJ to fabricate complex AlN ceramic parts. The use of multimodal powders significantly contributes to improving both the green and sintered densities of the printed parts. In addition, the implementation of a CP resulted in a green density reaching 51.9% and a maximum sintered density of 64.2%. After sintering, a predominant YAP phase (YAlO₃) and a minor YAM phase (Al₂Y₄O₉) were formed, in addition to the AlN and Y₂O₃ phases. Grain growth was observed, and the coarse particles, originally around 15 µm, exhibited a final particle size of 20 – 30 µm, while the fine particles, initially at ~1 µm, expanded up to 3 – 6 µm. The reported densities are the highest recorded in the literature for AlN components produced through BJ, highlighting the effectiveness of our approach. However, further improvements are still being explored to enhance the density and overall properties of the printed and sintered parts. Indeed, despite an improvement in final density, it remains relatively low for use in power electronics. Strategies under consideration include alternative sintering techniques such as HIP or spark plasma sintering as a thermal post-treatment approach, as well as the infiltration

of green parts with an AlN nanoparticle slurry to reduce porosities. Looking ahead, further optimization in powders and printing parameters represent potential avenues of research. The BJ AM process presents a viable alternative to conventional manufacturing methods, opening new possibilities for AlN applications in aerospace, electronics, medical, and biomedical industries.

## Acknowledgments

The authors would like to thank the 3D CAMP platform of CIRIMAT, where the binder jetting printing was carried out.

## Funding

The PhD scholarship was used for the work of this research and the author who received it was Fanny Pruvost. This research was funded by the “Plateformes Régionales de Recherche et d’Innovation (PRRI)” program of the Occitanie Region under the project “3D Camp—3D Ceramic Additive Manufacturing & Multimaterials Platform.”

## Conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.

## Author contributions

**Conceptualization:** Sophie Guillemet-Fritsch and Lionel Presmanes

**Funding acquisition:** Sophie Guillemet-Fritsch and Lionel Presmanes

**Investigation:** Fanny Pruvost

**Methodology:** Fanny Pruvost and Régis Delsol

**Project administration:** Sophie Guillemet-Fritsch and Lionel Presmanes

**Resources:** Xavier Clausse, Régis Delsol

**Visualization:** Alexia Mortagne-Coderch, Yohann Thimont, and Xavier Clausse

**Writing – original draft:** Fanny Pruvost

**Writing – review and editing:** Fanny Pruvost, Sophie Guillemet-Fritsch, Lionel Presmanes, and Yohann Thimont

## Ethics approval and consent to participate

Not applicable.

## Consent for publication

Not applicable.

## Availability of data

Data are available from the corresponding author upon reasonable request.
References

1. Klocke F. Modern approaches for the production of ceramics components. *J Eur Ceram Soc.* 1997;17:457-465.

doi: 10.1016/S0955-2219(96)00163-X

2. Kenfaui D, Valdez-Nava Z, Laudebat L, et al. Innovative ceramic-matrix composite substrates with tunable electrical conductivity for high-power applications. *Sci Technol Adv Mater.* 2022;23:735-751.

doi: 10.1080/14686996.2022.2137695

3. Kenfaui D, Guillemet-Fritsch S, Valdez-Nava Z, et al. Tuning electrical conductivity in AlN-based ceramics by incorporating graphene. *J Eur Ceram Soc.* 2023;43(5):1887-1896.

doi: 10.1016/j.jeurceramsoc.2022.12.039

4. Dinwiddie RB, Whittaker AJ, Onn GG. Thermal conductivity, heat capacity, and thermal diffusivity of selected commercial AlN substrates. *Int J Thermophys.* 1989;10:1075-1084.

doi: 10.1007/BF00503175

5. Nakano H, Watari K, Hayashi H, Urabe K. Microstructural characterization of high-thermal-conductivity aluminum nitride ceramic. *J Am Ceram Soc.* 2002;85(12):3093-3095.

doi: 10.1111/j.1151-2916.2002.tb00587.x

6. Du X, Qin M, Sun Y, Yuan Z, Yang B, Qu X. Structure and thermal conductivity of powder injection molded AlN ceramic. *Adv Powder Technol.* 2010;21:431-434.

doi: 10.1016/j.apt.2010.01.001

7. Sheppard LM. Aluminum nitride: A versatile but challenging material. *J Am Ceram Soc Bull.* 1990;69:1801-1812.

8. Baik Y, Drew RA. Aluminum Nitride: Processing and Applications. *Key Eng Mater.* 1996;122-124:553.

doi: 10.4028/www.scientific.net/KEM.122-124.553s

9. Kume S, Yasuoka M, Lee SK, Kan A, Ogawa H, Watari K. Dielectric and thermal properties of AlN ceramics. *J Eur Ceram Soc.* 2007;27:2967-2971.

doi: 10.1016/j.jeurceramsoc.2006.11.023

10. Watari K, Ishizaki K, Tsuchiya F. Phonon scattering and thermal conduction mechanisms of sintered aluminium nitride ceramics. *J Mater Sci.* 1993;28:3709-3714.

doi: 10.1007/BF00353168

11. Diaz-Moreno CA, Lin Y, Hurtado-Macias A, et al. Binder jetting additive manufacturing of aluminum nitride components. *Ceram Int.* 2019;45:13620-13627.

doi: 10.1016/j.ceramint.2019.03.187

12. Deckers J, Vleugels J, Kruth JP. Additive manufacturing of ceramics: A review. *J Ceram Sci Tech.* 2014;5:245-260.

doi: 10.4416/JCST2014-00032

13. Ziaee M, Crane NB. Binder jetting: A review of process, materials, and methods. *Addit Manuf.* 2019;28:781-801.

doi: 10.1016/j.addma.2019.05.031

14. Liang D, Rujie H, Fang D. Development of additive manufacturing of ceramics. *J Adv Ceram.* 2017;38:231-247.

15. Rauchenecker J, Rabitsch J, Schwentenwein M, Konegger T. Additive manufacturing of aluminum nitride ceramics with high thermal conductivity via digital light processing. *Open Ceram.* 2022;9:100215.

doi: 10.1016/j.o ceram.2021.100215

16. Lin L, Wu H, Xu Y, Lin K, Zou W, Wu S. Fabrication of dense aluminum nitride ceramics via digital light processing-based stereolithography. *Mater Chem Phys.* 2020;249:122969.

doi: 10.1016/j.o ceram.2021.100215

17. Qin M, Lu H, Wu H, et al. Powder injection molding of complex-shaped aluminium nitride ceramic with high thermal conductivity. *J Eur Ceram Soc.* 2019;39:952-956.

doi: 10.1016/j.jeurceramsoc.2018.11.037

18. Belmonte M, Lopez-Navarrete G, Osendi MI, Miranzo P. Heat dissipation in 3D printed cellular aluminum nitride structures. *J Eur Ceram Soc.* 2021;41(4):2407-2414.

doi: 10.1016/j.jeurceramsoc.2020.12.005

19. Cima MJ, Sachs EM. *Three-Dimensional Printing: Forms, Materials and Performance. Texas: SFF Symposium*; 1991. Available from: https://hdl.handle.net/2152/64335 [Last accessed on 2025 Apr 15].

doi: 10.15781/T2DB7W70S

20. Sachs E, Cima M, Cornie J. Three-dimensional printing: Rapid tooling and prototypes directly from a CAD model. *Ann CIRP.* 1990;39:201-204.

doi: 10.1016/S0007-8506(07)61035-X

21. Sachs EM, Haggerty JS, Cima MJ, Williams PA. *United States Patent 5.204.055: Three-Dimensional Printing Techniques*; 1993. Available from: https://patents.google.com/patent/US5204055A/en [Last accessed on 2025 Apr 15].

22. Du W, Ren X, Ma C, Pei Z. Binder jetting additive manufacturing of ceramics: A literature review. *ASME 2017 International Mechanical Engineering Congress and Exposition*; 2017. p. 1-12.

doi: 10.1115/IMECE2017-70344

23. Zocca A, Colombo P, Gomes CM, Günster J. Additive manufacturing of ceramics: Issues, potentialities, and opportunities. *J Am Ceram Soc.* 2015;98:1983-2001.

doi: 10.1111/jace.13700

24. Chen Q, Juste E, Lasgorceix M, et al. Post-infiltration to improve the density of binder jetting ceramic parts. *J Eur Ceram Soc.* 2022;42:7134-7148.

doi: 10.1016/j.jeurceramsoc.2022.08.005
25. Baux A, Goillot A, Jacques S, et al. Synthesis and properties of macroporous SiC ceramics synthesized by 3D printing and chemical vapor infiltration/deposition. *J Eur Ceram Soc.* 2020;40:2834-2854.

doi: 10.1016/j.jeurceramsoc.2020.03.001

26. Zhang W, Melcher R, Travitzky N, Bordia RK, Greil P. Three-dimensional printing of complex-shaped alumina/glass composites. *Adv Eng Mater.* 2009;11:1039-1043.

doi: 10.1002/adem.200900213

27. Moghadasi M, Miao G, Li M, Pei Z, Ma C. Combining powder bed compaction and nanopowders to improve density in ceramic binder jetting additive manufacturing. *Ceram Int.* 2021;47:35348-35355.

doi: 10.1016/j.ceramint.2021.09.077

28. Du W, Singh M, Singh D. Binder jetting additive manufacturing of silicon carbide ceramics: Development of bimodal powder feedstocks by modeling and experimental methods. *Ceram Int.* 2020;46:19701-19707.

doi: 10.1016/j.ceramint.2020.04.098

29. Gonzalez JA, Mireles J, Lin Y, Wicker RB. Characterization of ceramic components fabricated using binder jetting additive manufacturing technology. *Ceram Int.* 2016;42:10559-10564.

doi: 10.1016/j.ceramint.2016.03.079

30. Mohammad Akib Y, Marzbanrad E, Ahmed F. Molecular dynamics-based two-dimensional simulation of powder bed additive manufacturing process for unimodal and bimodal systems. *J Manuf Mater Process.* 2025;9(1):1-12.

doi: 10.3390/jmmp9010009

31. Liu, J. *United States Patent 7.070.734: Blended Powder Solid-Supersolidus Liquid Phase Sintering*; 2004. Available from: https://patents.google.com/patent/US7070734B2/en [Last accessed on 2025 Apr 15].

32. Haferkamp L, Liechti S, Spierings A, Wegener K. Effect of bimodal powder blends on part density and melt pool fluctuation in laser powder bed fusion. *Prog Add Manuf.* 2021;6:407-416.

doi: 10.1007/s40964-021-00179-1

33. Yun Bai GW, Williams CB. Effect of Bimodal Powder Mixture On Powder Packing Density and Sintered Density in Binder Jetting of Metals. In: *Annual International Solid Freeform Fabrication Symposium*; 2015. Available from:

https://hdl.handle.net/2152/89376 [Last accessed on 2025 Apr 15].

34. Clares AP, Gao Y, Stebbins R, Van Suin AC, Manogharan G. Increasing density and mechanical performance of binder jetting processing through bimodal particle size distribution. *Mater Sci Add Manuf.* 2022;1(3):20.

doi: 10.18063/msam.v1i3.20

35. Ye X, Li Y, Ai Y, Nie Y. Novel powder packing theory with bimodal particle size distribution-application in superalloy. *Adv Powder Technol.* 2018;29:2280-2287.

doi: 10.1016/j.apt.2018.06.012

36. Du W, Ren X, Chen Y, Ma C, Radovic M, Pei Z. Model Guided Mixing of Ceramic Powders with Graded Particle Sizes in Binder Jetting Additive Manufacturing. *ASME 2018 13th International Manufacturing Science and Engineering Conference*. College Station, TX: American Society of Mechanical Engineers; 2018. p. 1-9.

doi: 10.1115/MSEC2018-6651

37. Chasserio N, Guillemet-Fritsch S, Lebey T, Dagdag S. Ceramic substrates for high-temperature electronic integration. *J Electron Mater.* 2008;38:164-174.

doi: 10.1007/s11664-008-0571-8

38. Mrdak M, Lacnjevac C, Rakin M, Janckovic D, Veljic D, Bajic D. Characterization of deposited plasma spray NiCrAlCoY₂O₃ coating layers on AlMg1 alloy substrates. *Zast Mater.* 2021;62:34-41.

doi: 10.5937/zasmat2101034M

39. European Pharmacopoeia. 8th ed. Strasbourg: Council of Europe; 2014. Available from: https://books.google.fr/books?id=ze7DngEACAAJ or https://fr.scribd.com/document/520931326/European-Pharmacopoeia-8th-Edition [Last accessed on 2025 Apr 15].

40. Moghadasi M, Miao G, Li M, Pei Z, Ma C. Combining powder bed compaction and nanopowders to improve density in ceramic binder jetting additive manufacturing. *Ceram Int.* 2021;47:35348-35355.

doi: 10.1016/j.ceramint.2021.09.077

41. Li M, Wei X, Pei Z, Ma C. Binder jetting additive manufacturing: Observations of compaction-induced powder bed surface defects. *Manuf Lett.* 2021;28:50-53.

doi: 10.1016/j.mfglet.2021.04.003