bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Analysis of Low Defect Ammonothermally Grown GaN Wafers by Borrmann Effect X-ray Topography
Authors: Kirste Lutz , Grabianska Karolina , Kucharski Robert , Sochacki Tomasz , Lucznik Boleslaw , Bockowski Michal
Published: September 2021

X-ray topography defect analysis of entire 1.8-inch GaN substrates, using the Borrmann effect, is presented in this paper. The GaN wafers were grown by the ammonothermal method. Borrmann effect topography of anomalous transmission could be applied due to the low defect density of the substrates. It was possible to trace the process and growth history of the GaN crystals in detail from their defect pattern imaged. Microscopic defects such as threading dislocations, but also macroscopic defects, for example dislocation clusters due to preparation insufficiency, traces of facet formation, growth bands, dislocation walls and dislocation bundles, were detected. Influences of seed crystal preparation and process parameters of crystal growth on the formation of the defects are discussed.
Estimation of Machining Sustainability Using Fuzzy Rule-Based System
Authors: Iqbal Asif , Zhao Guolong , Cheok Quentin , He Ning
Published: September 2021

Quantification of a highly qualitative term ‘sustainability’, especially from the perspective of manufacturing, is a contemporary issue. An inference mechanism, based on approximate reasoning, is required to tackle the complexities and uncertainties of the manufacturing domain. The work presents development of a fuzzy rule-based system to quantify sustainability of the most widely utilized manufacturing process: machining. The system incorporates the effects of key control parameters of machining on several sustainability measures, as reported in the literature. The measures are categorized under the three dimensions of sustainability and contribute to the sustainability scores of the respective dimensions with different weightages. The dimensions’ scores are added up in different proportions to obtain the holistic sustainability score of the process. The categories of the control parameters incorporated into the system include type of the process, work material, material hardness, tool substrate and coating, tool geometry, cutting fluids, and cutting parameters. The proposed method yields sustainability scores, ranging between 0 and 100 of machining processes against the given values of their prominent control parameters. Finally, the rule-based system is applied to three different machining processes to obtain the measures of their accomplishment levels regarding economic, environmental, and societal dimensions of sustainability. The sustainability score of each process is then obtained by summing up the three accomplishment levels under the respective weightages of the dimensions. The presented approach holds immense potentials of industrial application as it can conveniently indicate the current sustainability level of a manufacturing process, leading the practitioners to decide on its continuation or improvement.
Mechanical Properties and Microstructural Characterization of Laser Welded S32520 Duplex Stainless Steel
Authors: Abdo Hany S. , Seikh Asiful H.
Published: September 2021

This paper investigates an experimental design of laser butt welding of S32520 duplex stainless steel, which has been passed out with the help of a pulsed Nd: YAG laser supply. The intention of the present research is to learn the impact of beam diameter, welding speed, and laser power on the superiority of the butt weld. The individuality of butt joints has been characterized in terms of tensile properties, fractography, and hardness. It was noticed that unbalanced particle orientations indirectly produce a comparatively fragile quality in the laser welded joint. The outcome of varying process parameters and interaction effect of process parameters on ultimate tensile strength and micro hardness were studied through analysis of experimental data. With different process parameters, the heat energy delivered to the material was changed, which was reflected in tensile strength measurement for different welded samples. From this present research, it was shown that, up to a certain level, an increase in process parameters amplified the tensile strength, but after that, certain level tensile strength decreased with the increase in process parameters. When process parameters exceeded that certain level, the required amount of heat energy was not delivered to the material, resulting in low bead width and less penetration, thus producing less strength in the welded joint. Less strength leads to more ductile weld joints. Microhardness was higher in the weld zone than in the base region of welded samples. However, the heat affected zone had a high microhardness range.
Numerical Simulation of the Whole Thermal Lensing Process with Z-Scan-Based Methods Using Gaussian Beams
Authors: Boudebs Georges
Published: September 2021

A general study of the diffracted far field due to thermal lens heating using Gaussian beams is presented. The numerical simulation considers the whole system, including both the optical and the thermal parameters. It is shown that the existing simplified relations found in the literature and used up to now only give the order of magnitude of the thermo-optical coefficients. More accurate, simplified formulas are derived to measure the induced thermal phase shift when working with Z-scan-based methods. Temperature estimation in absorbing media turn out to be more reliable whether using time-resolved or steady-state techniques. The extension of the calculation to the image formation in a 4f system is also addressed.
Thermal Stability and Dynamic Mechanical Properties of Poly(ε-caprolactone)/Chitosan Composite Membranes
Authors: Zhang Yanbo , Wu Yaqi , Yang Ming , Zhang Gang , Ju Haiyan
Published: September 2021

Poly (ε-caprolactone) (PCL) and chitosan (CS) are widely used as biodegradable and biocompatible polymers with desirable properties for tissue engineering applications. Composite membranes (CS–PCL) with various blend ratios (CS:PCL, w/w) of 0:100, 5:95, 10:90, 15:85, 20:80, and 100:0 were successfully prepared by lyophilization. The thermal stabilities of the CS–PCL membranes were systematically characterized by thermogravimetric analysis (TG), dynamic thermogravimetry (DTG), and differential scanning calorimetry (DSC). It was shown that the blend ratio of PCL and CS had a significant effect on the thermal stability, hydrophilicity, and dynamic mechanical viscoelasticity of the CS–PCL membranes. All the samples in the experimental range exhibited high elasticity at low temperature and high viscosity at high temperatures by dynamic mechanical thermal analysis (DMTA). The performances of the CS–PCL membranes were at optimum levels when the blend ratio (w/w) was 10:90. The glass transition temperature of the CS–PCL membranes increased from 64.8 °C to 76.6 °C compared to that of the pure PCL, and the initial thermal decomposition temperature reached 86.7 °C. The crystallinity and porosity went up to 29.97% and 85.61%, respectively, while the tensile strength and elongation at the breakage were 20.036 MPa and 198.72%, respectively. Therefore, the 10:90 (w/w) blend ratio of CS/PCL is recommended to prepare CS–PCL membranes for tissue engineering applications.
Analysis of Fire Resistance of Square-Cased Square Steel Tube Reinforced Concrete (ST-RC) Columns
Authors: Wang Gaoxiong , Bao Yanhong , Yang Li , Yu Yang
Published: September 2021

Based on the finite element (FE) analysis software Abaqus, an FE model of square-cased square steel tube reinforced concrete (ST-RC) columns under the hybridized action of high-temperature and load is established. The accuracy of the FE model is verified using experimental data from existing studies. This model is used to analyze the temperature change, internal force distribution, and failure characteristics of the square-cased square ST-RC columns under the action of fire, as well as the factors affecting the fire resistance limit of the column. The results of FE analysis show that under the action of fire, the maximum internal temperature of the square-cased square ST-RC columns occurs in the corner of the section. Moreover, the stress and strain reach their maximum values at the concrete corner outside the tube. During the heating process, an internal force redistribution occurs in the square-cased square ST-RC column. At the same time, the proportion of the axial force and the bending moment of the reinforced concrete outside the pipe decreases gradually, while the proportion of the internal force of the core concrete-filled steel tube (CFST) increases gradually. In essence, it is a process of load transfer from the high-temperature to the low-temperature zone. In addition, the section size, load ratio, slenderness ratio, cross-sectional core area ratio, steel content, and external concrete strength are the main parameters affecting the fire resistance limit of the square-cased square ST-RC columns. Among them, the cross-sectional core area ratio, section size, steel ratio, and external concrete strength are positively correlated with the fire resistance limit of the composite column. On the contrary, with the increase in the load ratio and the slenderness ratio, the fire resistance limit of the square-cased square ST-RC columns decreases. On this basis, a simplified formula to calculate the fire resistance limit of square-cased square ST-RC columns is proposed. The research results can be used as a theoretical reference for the fire protection design of this kind of structure in practical engineering.
Carbon Fiber Reinforced Polymers
Authors: Lionetto Francesca
Published: September 2021

The current demand for lightweight and high-performance structures leads to increasing applications of carbon fiber reinforced polymers, which is also made possible by novel production methods, automation with repeatable quality, the reduced cost of carbon fibers, out of autoclave processes such as resin transfer molding and resin infusion technologies, the re-use of waste fibers, development in preform technology, high-performance, fast-curing resins, etc [...]
Recent Advances on Development of Hydroxyapatite Coating on Biodegradable Magnesium Alloys: A Review
Authors: Chen Junxiu , Yang Yang , Etim Iniobong P. , Tan Lili , Yang Ke , Misra R. D. K. , Wang Jianhua , Su Xuping
Published: September 2021

The wide application of magnesium alloys as biodegradable implant materials is limited because of their fast degradation rate. Hydroxyapatite (HA) coating can reduce the degradation rate of Mg alloys and improve the biological activity of Mg alloys, and has the ability of bone induction and bone conduction. The preparation of HA coating on the surface of degradable Mg alloys can improve the existing problems, to a certain extent. This paper reviewed different preparation methods of HA coatings on biodegradable Mg alloys, and their effects on magnesium alloys’ degradation, biocompatibility, and osteogenic properties. However, no coating prepared can meet the above requirements. There was a lack of systematic research on the degradation of coating samples in vivo, and the osteogenic performance. Therefore, future research can focus on combining existing coating preparation technology and complementary advantages to develop new coating preparation techniques, to obtain more balanced coatings. Second, further study on the metabolic mechanism of HA-coated Mg alloys in vivo can help to predict its degradation behavior, and finally achieve controllable degradation, and further promote the study of the osteogenic effect of HA-coated Mg alloys in vivo.
Exergy Analysis of Phase-Change Heat-Storage Coupled Solar Heat Pump Heating System
Authors: Zhu Chuanhui , Yan Shubin , Dong Xiaodong , Zhang Wei , Huang Biyi , Cui Yang
Published: September 2021

With the rapid development of industrialization, the excessive use of fossil fuels has caused problems such as increased greenhouse gas emissions and energy shortages. The development and use of renewable energy has attracted increased attention. In recent years, solar heat pump heating technology that uses clean solar energy combined with high-efficiency heat pump units is the development direction of clean heating in winter in northern regions. However, the use of solar energy is intermittent and unstable. The low-valley electricity policy is a night-time electricity price policy. Heat pump heating has problems such as frosting and low efficiencies in cold northern regions. To solve these problems, an exergy analysis model of each component of a phase-change heat-storage coupled solar heat pump heating system was established. Exergy analysis was performed on each component of the system to determine the direction of optimization and improvement of the phase-change heat-storage coupled solar heat pump heating system. The results showed that optimizing the heating-end heat exchanger of the system can reduce the exergy loss of the system. When the phase-change heat-storage tank meets the heating demand, its volume should be reduced to lower the exergy loss of the tank heat dissipation. Air-type solar collectors can increase the income exergies of solar collectors.
Face Damage Growth of Sandwich Composites under Compressive Loading: Experiments, Analytical and Finite Element Modeling
Authors: Kinawy Moustafa , Rubino Felice , Canale Giacomo , Citarella Roberto , Butler Richard
Published: September 2021

Sandwich panels with composite laminate skins having [(±45C)2,(0C,0G)4,(±45C)2] stacking sequence (subscript C for carbon fibers, G for glass) and containing barely visible impact damage (BVID) induced on the whole sandwich structure impacted at low energy, were tested in edge after-impact-compression with load direction parallel and transversal to the fibers direction (0-dir.). The morphology of impact damage on the sandwich structure was determined by using ultrasonic C-Scan and visual observation of laminate cross section. A Digital Image Correlation (DIC) system was used to measure the delamination evolution during the test. Two different failure behaviors were observed in two different impacted panels. Panel with fibers oriented transversally to the compressive load showed an opening (Mode-I) propagation of a delamination, while the panel with fibers parallel to the load showed shear (Mode-II) propagation. The static load such to determine local buckling of the composite face and failure was experimentally measured. An analytical model was implemented to predict the static strength of laminate with Mode-I opening. An FE model was instead built to predict the local buckling failure mode of the laminate with BVID, which is the first phenomenon to appear. The results of the analytical model and the numerical simulation correlate well with the test.
Annealing-Induced Off-Stoichiometric and Structural Alterations in Ca2+- and Y3+-Stabilized Zirconia Ceramics
Authors: Zhu Wenliang , Nakashima Shizuka , Marin Elia , Gu Hui , Pezzotti Giuseppe
Published: September 2021

In the current study, high-temperature stability was investigated in two types of zirconia ceramics stabilized with two different additives, namely, calcia and yttria. The evolutions of structure and oxygen-vacancy-related defects upon annealing in air were investigated as a function of temperature by combining X-ray diffractometry with Raman, X-ray photoelectron and cathodoluminescence spectroscopies. We systematically characterized variations in the concentration of oxygen vacancies and hydroxyl groups during thermal treatments and linked them to structural alterations and polymorphic transformation. With this approach, we clarified how the combined effects of different dopants and temperature impacted on structural development and on the thermal stability of the oxygen-vacancy-related defect complex.
Exploration of the Temperature Sensing Ability of La2MgTiO6:Er3+ Double Perovskites Using Thermally Coupled and Uncoupled Energy Levels
Authors: Vu Thi Hong Quan , Bondzior Bartosz , Stefańska Dagmara , Dereń Przemysław J.
Published: September 2021

This work aimed to explore the temperature-sensing performance of La2MgTiO6:Er3+ double perovskites based on thermally coupled and uncoupled energy levels. Furthermore, the crystal structure, chemical composition, and morphology of the samples were investigated by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy, respectively. The most intense luminescence was observed for the sample doped with 5% Er3+. The temperature-dependent emission spectra of La2MgTiO6:5% Er3+ were investigated in the wide range of 77–398 K. The highest sensitivity of the sample was equal to 2.98%/K corresponding to the thermally coupled energy level 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 as compared to 1.9%/K, obtained for the uncoupled energy level 2H11/2 → 4I15/2 and 2H9/2 → 4I15/2. Furthermore, the 300 K luminescent decay profiles were analyzed using the Inokuti–Hirayama model. The energy transfer among Er3+ ions was mainly regulated by the dipole–dipole mechanism. The critical transfer distance R0, critical concentration C0, energy transfer parameter Cda, and energy transfer probability Wda were 9.81 Å, 2.53×1020 ions·cm−3, 5.38×10−39 cm6·s−1, and 6020 s−1, respectively.
Interactions of Aminopropyl–Azithromycin Derivatives, Precursors in the Synthesis of Bioactive Macrozones, with E. coli Ribosome: NMR and Docking Studies
Authors: Mikulandra Ivana , Jednačak Tomislav , Bertoša Branimir , Parlov Vuković Jelena , Kušec Iva , Novak Predrag
Published: September 2021

The structure and interactions of several aminopropyl–azithromycin derivatives (1a–c) have been studied by using NMR spectroscopy and docking calculations. Compounds 1a–c are precursors in the synthesis of macrozones, novel bioactive azithromycin–thiosemicarbazone conjugates active against some resistant bacterial strains. Today, bacterial resistance is considered as one of the major threats to human health. Knowledge on drug binding mode and conformations is one of the key factors in the process of designing molecules to fight resistance. In solution state, compounds 1a and 1c exist in the 3-endo-folded-out conformation, while 1b adopts a classical folded-out conformation. 13C and 15N CPMAS NMR spectra pointed towards similar structures in the solid state. The transferred NOESY NMR spectra confirmed binding to the E. coli ribosome and suggest that dominant conformations in the bound state resemble those in the free one. STD experiments identified reactive groups of 1a–c in close contact with the ribosome resembling binding epitopes observed for the related 15-membered macrolides. Docking studies revealed that the studied compounds bind to the same ribosome binding pocket similarly to erythromycin in the crystal state, and that the binding is achieved through H-bonds and van der Waals interactions. The bound conformation is the same as determined by NMR. STD enhancements observed for methylene protons in the aminopropyl side chain indicate additional interactions which contribute to the overall binding energy.
Synthesis and Thermal, Photophysical, Electrochemical Properties of 3,3-di[3-Arylcarbazol-9-ylmethyl]oxetane Derivatives
Authors: Korzec Mateusz , Tavgeniene Daiva , Samuel Nizy Sara , Beresneviciute Raminta , Krucaite Gintare , Pająk Agnieszka Katarzyna , Kotowicz Sonia , Vasylieva Marharyta , Gnida Paweł , Malecki Jan Grzegorz , Grigalevicius Saulius , Schab-Balcerzak Ewa
Published: September 2021

Novel oxetane-functionalized derivatives were synthesized to find the impact of carbazole substituents, such as 1-naphtyl, 9-ethylcarbazole and 4-(diphenylamino)phenyl, on their thermal, photophysical and electrochemical properties. Additionally, to obtain the optimized ground-state geometry and distribution of the frontier molecular orbital energy levels, density functional theory (DFT) calculations were used. Thermal investigations showed that the obtained compounds are highly thermally stable up to 360 °C, as molecular glasses with glass transition temperatures in the range of 142–165 °C. UV–Vis and photoluminescence studies were performed in solvents of differing in polarity, in the solid state as a thin film on glass substrate, and in powders, and were supported by DFT calculations. They emitted radiation both in solution and in film with photoluminescence quantum yield from 4% to 87%. Cyclic voltammetry measurements revealed that the materials undergo an oxidation process. Next, the synthesized molecules were tested as hole transporting materials (HTM) in perovskite solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au, and photovoltaic parameters were compared with the reference device without the oxetane derivatives.
High-Resolution Mapping of Local Photoluminescence Properties in CuO/Cu2O Semiconductor Bi-Layers by Using Synchrotron Radiation
Authors: Kobayashi Masakazu , Izaki Masanobu , Khoo Pei Loon , Shinagawa Tsutomu , Takeuchi Akihisa , Uesugi Kentaro
Published: September 2021

The quality of a semiconductor, which strongly affects its performance, can be estimated by its photoluminescence, which closely relates to the defect and impurity energy levels. In light of this, it is necessary to have a measurement method for photoluminescence properties with spatial resolution at the sub-micron or nanoscale. In this study, a mapping method for local photoluminescence properties was developed using a focused synchrotron radiation X-ray beam to evaluate localized photoluminescence in bi-layered semiconductors. CuO/Cu2O/ZnO semiconductors were prepared on F:SnO2/soda-lime glass substrates by means of electrodeposition. The synchrotron radiation experiment was conducted at the beamline 20XU in the Japanese synchrotron radiation facility, SPring-8. By mounting the high-sensitivity spectrum analyzer near the edge of the CuO/Cu2O/ZnO devices, luminescence maps of the semiconductor were obtained with unit sizes of 0.3 μm × 0.3 μm. The devices were scanned in 2D. Light emission 2D maps were created by classifying the obtained spectra based on emission energy already reported by M. Izaki, et al. Band-like structures corresponding to the stacking layers of CuO/Cu2O/ZnO were visualized. The intensities of emissions at different energies at each position can be associated with localized photovoltaic properties. This result suggests the validity of the method for investigation of localized photoluminescence related to the semiconductor quality.
Mechanical Behavior and Healing Efficiency of Microcapsule-Based Cemented Coral Sand under Various Water Environments
Authors: Qin Yue , Wang Qiankun , Xu Dongsheng , Chen Wei
Published: September 2021

The cracks in the cemented coral sand (CCS) would result in significant damage for the marine structures. In this study, the effective and efficiency of microcapsules in self-healing CCS under various water environments were investigated with a series of experimental tests. Firstly, a new preparation method was proposed to fabricate the microcapsules with a wide particle size distribution, which was adapted to the high porosity, large difference in pore size, and uneven distribution of CCS. Secondly, the mechanical properties of microcapsule-based CCS were examined by the uniaxial compressive tests and split Hopkinson pressure bar (SHPB) tests. The results indicated that the microcapsule could improve the initial strength of CCS. The CCS mixed with 3% of the microcapsule that synthesized under a rotating speed of 450 rmp had the highest compressive strength at the initial strain state. Finally, the healing efficiency of microcapsule for CCS was investigated in various environmental conditions, which were freshwater, seawater, and water of various pH values. The non-destructive experiment approach of the piezoelectric transducer (PZT) test was adopted to evaluate the healing efficiency of microcapsules. Experimental results indicated that the healing efficiency of microcapsules in freshwater and seawater were 75% and 59.56%, respectively. In contrast, the acid and alkali water environment would greatly reduce the healing efficiency of microcapsules in CCS.
Use of Design of Experiments (DoE) to Model the Sulphate Agent Amount of (Ultra)Finely Ground and Fast Hardening Portland Cement Clinker
Authors: Schade Tim , Middendorf Bernhard
Published: September 2021

This paper presents a model to calculate the sulphate agent amount and sulphate agent ratio for fine grounded and fast hardening Portland cement clinker. Despite sufficient knowledge about the influence of calcium sulphate on the hydration process of cement, the sulphate agent amount is mostly adjusted empirically. As a result, often a wide and unfeasible experimental matrix has to be tested. In this work, Design of Experiments (DoE) was used in combination with in-situ X-ray diffraction (XRD) tests to accurately adjust the sulphate agent of different finely ground cement by calculation. With only 42 tests, it was possible to analyse in total the influence of the sulphate agent, the grinding fineness and the use of C-S-H-seeds for the use in fast-hardening Portland cement-based systems. In addition, it was found that a hemihydrate to anhydrite content of 25/75 leads to a stabilisation of the hydrated system in the first 24 h of hydration. A model for the optimisation of the sulphate agent composition in dependency of the cement fineness could be determined. Furthermore, it was shown that the DoE also provides optimal results in material sciences in a resource-saving way.
Effect of Service Environmental Parameters on Electrochemical Corrosion Behavior of L80 Casing Steel
Authors: Sun Xiaoguang , Cui Huaiyun , Li Zhong , He Renyang , Liu Zhiyong , Lu Lin
Published: September 2021

The corrosion behavior of L80 casing steel was studied in a simulating annulus environment using the electrochemical measurement method, immersion test, and tensile test under a high-temperature and high-pressure H2S/CO2 environment. The partial pressure of CO2 (PCO2), the partial pressure of H2S (PH2S), water content, and preloading stress remarkably affected the corrosion behavior of L80 steel. The influence of PCO2 on stress corrosion cracking (SCC) susceptibility has an inflection point of approximately 1.1 MPa. The SCC susceptibility reaches the maximum when the PCO2 is about 1.1 MPa. The SCC susceptibility has a positive correlation to PH2S and water content. The higher water content of the corrosion medium can increase the electrical conductivity of the corrosion medium and promote the corrosion of L80 steel, which can improve the diffusion of hydrogen into steel and promote the SCC of L80 steel. Preloading stress can promote local corrosion, thereby promoting SCC of steel under stress. The dislocation emergence point caused by preloading stress can accelerate the diffusion of hydrogen into steel and increase SCC susceptibility.
Exploration of the Cs Trapping Phenomenon by Combining Graphene Oxide with α-K6P2W18O62 as Nanocomposite
Authors: Nugroho Bangun Satrio , Kato Akane , Kowa Chie , Nakashima Tomoya , Wada Atsushi , Wihadi Muh. Nur Khoiru , Nakashima Satoru
Published: September 2021

A graphene oxide-based α-K6P2W18O62 (Dawson-type polyoxometalate) nanocomposite was formed by using two types of graphene oxide (GO) samples with different C/O compositions. Herein, based on the interaction of GO, polyoxometalates (POMs), and their nanocomposites with the Cs cation, quantitative data have been provided to explicate the morphology and Cs adsorption character. The morphology of the GO-POM nanocomposites was characterized by using TEM and SEM imaging. These results show that the POM particle successfully interacted above the surface of GO. The imaging also captured many small black spots on the surface of the nanocomposite after Cs adsorption. Furthermore, ICP-AES, the PXRD pattern, IR spectra, and Raman spectra all emphasized that the Cs adsorption occurred. The adsorption occurred by an aggregation process. Furthermore, the difference in the C/O ratio in each GO sample indicated that the ratio has significantly influenced the character of the GO-POM nanocomposite for the Cs adsorption. It was shown that the oxidized zone (sp2/sp3 hybrid carbon) of each nanocomposite sample was enlarged by forming the nanocomposite compared to the corresponding original GO sample. The Cs adsorption performance was also influenced after forming a composite. The present study also exhibited the fact that the sharp and intense diffractions in the PXRD were significantly reduced after the Cs adsorption. The result highlights that the interlayer distance was changed after Cs adsorption in all nanocomposite samples. This has a good correlation with the Raman spectra in which the second-order peaks changed after Cs adsorption.
Spin Polarization and Magnetic Moment in Silicon Carbide Grown by the Method of Coordinated Substitution of Atoms
Authors: Kukushkin Sergey A. , Osipov Andrey V.
Published: September 2021

In the present work, a new method for obtaining silicon carbide of the cubic polytype 3C-SiC with silicon vacancies in a stable state is proposed theoretically and implemented experimentally. The idea of the method is that the silicon vacancies are first created by high-temperature annealing in a silicon substrate Si(111) doped with boron B, and only then is this silicon converted into 3C-SiC(111), due to a chemical reaction with carbon monoxide CO. A part of the silicon vacancies that have bypassed “chemical selection” during this transformation get into the SiC. As the process of SiC synthesis proceeds at temperatures of ~1350 °C, thermal fluctuations in the SiC force the carbon atom C adjacent to the vacancy to jump to its place. In this case, an almost flat cluster of four C atoms and an additional void right under it are formed. This stable state of the vacancy, by analogy with NV centers in diamond, is designated as a C4V center. The C4V centers in the grown 3C-SiC were detected experimentally by Raman spectroscopy and spectroscopic ellipsometry. Calculations performed by methods of density-functional theory have revealed that the C4V centers have a magnetic moment equal to the Bohr magneton μB and lead to spin polarization in the SiC if the concentration of C4V centers is sufficiently high.
Deformation Prediction and Experimental Study of 316L Stainless Steel Thin-Walled Parts Processed by Additive-Subtractive Hybrid Manufacturing
Authors: Wu Xuefeng , Zhu Wenbo , He Yu
Published: September 2021

The hybrid process integrates two or more different processes, such as additive and subtractive manufacturing, which have gained appreciable consideration in recent years. The deformation of hybrid manufacturing is an essential factor affecting machining quality. The purpose of this paper is to study the effect of milling on stress release and surface deformation of additive manufacturing (AM) specimens in the process of additive and subtractive hybrid manufacturing (ASHM) of 316L stainless steel thin-walled parts, so as to effectively improve the forming quality of thin-walled parts manufactured by the combined processing of ASHM. To this end, a series of experiments were carried out to study the relationship between stress distribution and thermal stress deformation of 316L stainless steel thin-walled parts prepared by LMD, and the changes of stress and deformation of these thin-walled parts after subsequent milling. An infrared camera and laser distance sensor were used to record the temperature field data and deformation data to analyze the influence factors of temperature and stress on the machining results. Then, the finite element software was used to simulate the stress and deformation of the thin-walled parts in the additive manufacturing process and the subsequent milling process. Meanwhile, the model was verified through the experiments. In addition, the relationship between the milling force and the milling parameters of the AM parts was studied by orthogonal test and regression analysis.
Influence of the Laser Cladding Parameters on the Morphology, Wear and Corrosion Resistance of WC-Co/NiCrBSi Composite Coatings
Authors: Hulka Iosif , Uțu Ion D. , Avram Diana , Dan Mircea L. , Pascu Alexandru , Stanciu Elena M. , Roată Ionuț C.
Published: September 2021

To enhance the sliding wear and corrosion behavior of steels with low carbon content, cermet composite coatings are usually deposited on their surface by various deposition processes. Laser cladding, compared to other deposition techniques such as electroplating, arc welding, and thermal spraying, has numerous advantages to produce such protective coatings. The paper presents the optimization of laser cladding deposition speed versus energy density in order to obtain WC-Co/NiCrBSi coatings with Ni-Al addition free of defects and reduced porosity deposited on low carbon steel substrate. The microstructure and chemical composition were investigated by SEM combined with EDX analysis while XRD was performed in order to examinate the phases within the coatings. In order to investigate the cladding speed influence on the coatings, hardness measurements, POD (pin on disk) wear tests and corrosion tests in 3.5% NaCl solution were carried out. The results showed that an optimal cladding speed has a crucial impact on the microstructure, composition, and hardness. It was found out that optimizing the cladding deposition speed proved to be effective in enhancing the sliding wear resistance and corrosion behavior by controlling the iron content within the coatings.
Hydrothermal Co-Processing of Coal Fly Ash Cenospheres and Soluble Sr(II) as Environmentally Sustainable Approach to Sr-90 Immobilization in a Mineral-like Form
Authors: Vereshchagina Tatiana , Kutikhina Ekaterina , Solovyov Leonid , Vereshchagin Sergei , Mazurova Elena , Anshits Alexander
Published: September 2021

Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a resource-saving approach for efficient stabilization/solidification of radioactive components of wastewater. In this context, the paper is focused on the hydrothermal synthesis of Sr2+-bearing aluminosilicate/silicate phases as analogs of a mineral-like 90Sr waste form using hollow glass-crystalline aluminosilicate microspheres from coal fly ash (cenospheres) as a glassy source of Si and Al (SiO2-Al2O3)glass) and Sr(NO3)2 solutions as 90Sr simulant wastewater. The direct conversion of cenosphere glass in the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system as well as Sr2+ sorption on cenosphere-derived analcime (ANA) in the Sr(NO3)2-H2O-ANA system were studied at 150–200 °C and autogenous pressure. The solid and liquid reaction products were characterized by SEM-EDS, PXRD, AAS and STA. In the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system, the hydrothermal processing at 150–200 °C removes 99.99% of the added Sr2+ from the solution by forming Sr-tobermorite and Sr-plagioclase phases. In the Sr(NO3)2-H2O-ANA system, Sr2+ sorption on analcime results in the formation of solid solutions (Na1−nSrn/2)AlSi2O6·H2O of the Na-analcime–Sr-wairakite series. The results can be considered as a basis for the development of environmentally sustainable technology for 90Sr removal from wastewater and immobilization in a mineral-like form by co-processing waste from coal-fired and nuclear power plants.
An Experimental and Theoretical Study of Dye Properties of Thiophenyl Derivatives of 2-Hydroxy-1,4-naphthoquinone (Lawsone)
Authors: Monroy-Cárdenas Matías , Forero-Doria Oscar , Araya-Maturana Ramiro , Martínez-Cifuentes Maximiliano
Published: September 2021

A prospective study of the dye properties of non-toxic lawsone thiophenyl derivatives, obtained using a green synthetic methodology allowed for the description of their bathochromic shifts in comparison to those of lawsone, a well-known natural pigment used as a colorant that recently also has aroused interest in dye-sensitized solar cells (DSSCs). These compounds exhibited colors close to red, with absorption bands in visible and UV wavelength range. The colorimetric study showed that these compounds exhibited a darker color than that of lawsone within a range of colors depending on the substituent in the phenyl ring. Computational calculations employing Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT), showed that the derivatives have lower excitation energies than lawsone, while the alignment of their frontier orbitals regarding the conduction bands of TiO2 and ZnO and the redox potential of the electrolyte I−/I3− suggests that they could be employed as sensitizers. The study of the interactions of the lawsone and a derivative with a TiO2 surface model by different anchoring modes, showed that the adsorption is thermodynamically favored. Natural bond orbital (NBO) analysis indicates a two-center bonding (BD) O-Ti as the main interaction of the dyes with TiO2.
First Principles Calculations of Atomic and Electronic Structure of TiAl3+- and TiAl2+-Doped YAlO3
Authors: Piskunov Sergei , Gopejenko Aleksejs , Pankratov Vladimir , Isakoviča Inta , Ma Chong-Geng , Brik Mikhail G. , Piasecki Michal , Popov Anatoli I.
Published: September 2021

In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti3+ and Ti2+ ions substituted for the host Al atom in orthorhombic Pbnm bulk YAlO3 crystals. The disordered crystalline structure of YAlO3 was modelled in a large supercell containing 160 atoms, allowing simulation of a substitutional dopant with a concentration of about 3%. In the case of the Ti2+-doped YAlO3, compensated F-center (oxygen vacancy with two trapped electrons) is inserted close to the Ti to make the unit cell neutral. Changes of the interatomic distances and angles between the chemical bonds in the defect-containing lattices were analyzed and quantified. The positions of various defect levels in the host band gap were determined.
A Comparison of Amplitude-and Time-Dependent Cyclic Deformation Behavior for Fully-Austenite Stainless Steel 316L and Duplex Stainless Steel 2205
Authors: Li Shaohua , Jiang Wenchun , Xie Xuefang , Dong Zhilong
Published: September 2021

Austenite and duplex stainless steels are widely used in engineering, and the latter exhibits a more excellent combination of mechanical properties and corrosion resistance due to the coexistence of austenite and ferrite and higher nitrogen. However, fatigue failure still threatens their structural integrity. A comprehensive comparison of their cyclic deformation behavior is a major foundation to understand the role of duplex-phase microstructure and nitrogen in the safety assessment of engineering components. Thus, in this paper, the cyclic deformation behavior of fully-austenitic stainless steel 316L and duplex stainless steel 2205 was studied by a series of low cycle fatigue tests with various strain amplitudes, loading rates and tensile holding. A theoretical mechanism diagram of the interaction between nitrogen and dislocation movements during cyclic loads was proposed. Results show that the cyclic stress response of 2205 was the primary cyclic hardening, followed by a long-term cyclic softening regardless of strain amplitudes and rates, while an additional secondary hardening was observed for 316L at greater strain amplitudes. Cyclic softening of 2205 was restrained under slower strain rates or tensile holding due to the interaction between nitrogen and dislocations. The cyclic plasticity of 2205 started within the austenite, and gradually translated into the ferrite with the elevation of the cyclic amplitude, which lead to a decreased hardening ratio with the increase in amplitude and a shorter fatigue life for a given smaller plastic strain amplitude.
Investigation on Fatigue Performance of Asphalt Mixture Reinforced by Basalt Fiber
Authors: Lou Keke , Wu Xing , Xiao Peng , Zhang Cong
Published: September 2021

Basalt fiber has been widely used in asphalt mixture due to its excellent mechanical properties and good combination with asphalt. In order to systematically evaluate the enhancement effect of basalt fiber on the fatigue performance of the mixtures, gradations of Stone Mastic Asphalt and Superpave with different nominal maximum aggregate sizes, namely SMA-13, SUP-20 and SUP-25, were prepared, and a four-point bending beam fatigue test was adopted under the strain control mode. The fatigue damage mode was assessed based on the phenomenology theory, energy dissipation theory and change rate of dissipated energy. The results showed that basalt fiber could well increase the fatigue life of the mixtures. Basalt fiber could also increase the cumulative dissipated energy of the mixtures, and it was linearly correlated with the fatigue life in double logarithmic coordinates. In the meantime, adding basalt fiber could increase the change rate of dissipated energy of the mixtures. Furthermore, it is not appropriate to take the stiffness modulus declined to 50% of the original as the fatigue failure criterion of the mixture; this paper suggested that it is reasonable when the stiffness modulus was 15–25% that of the initial. These findings provide a theoretical basis for exploring the fatigue failure of asphalt pavements.
Lignocellulosic Bioethanol and Biobutanol as a Biocomponent for Diesel Fuel
Authors: Obergruber Michal , Hönig Vladimír , Jenčík Jan , Hájek Jiří , Schlehöfer Dominik , Herink Tomáš
Published: September 2021

In this paper, the fuel properties of mixtures of diesel fuel and ethanol and diesel fuel and butanol in the ratio of 2.5% to 30% were investigated. The physicochemical properties of the blends such as the cetane number, cetane index, density, flash point, kinematic viscosity, lubricity, CFPP, and distillation characteristics were measured, and the effect on fuel properties was evaluated. These properties were compared with the current EN 590+A1 standard to evaluate the suitability of the blends for use in unmodified engines. The alcohols were found to be a suitable bio-component diesel fuel additive. For most physicochemical properties, butanol was found to have more suitable properties than ethanol when used in diesel engines. The results show that for some properties, a butanol–diesel fuel mixture can be mixed up to a ratio of 15%. Other properties would meet the standard by a suitable choice of base diesel.
Phonon Transport and Thermoelectric Properties of Imidazole-Graphyne
Authors: Chen Yanyan , Sun Jie , Kang Wei , Wang Qian
Published: September 2021

The pentagon has been proven to be an important structural unit for carbon materials, leading to different physical and chemical properties from those of hexagon-based allotropes. Following the development from graphene to penta-graphene, a breakthrough has very recently been made for graphyne—for example, imidazole-graphyne (ID-GY) was formed by assembling experimentally synthesized pentagonal imidazole molecules and acetylenic linkers. In this work, we study the thermal properties and thermoelectric performance of ID-GY by combining first principle calculations with the Boltzmann transport theory. The calculated lattice thermal conductivity of ID-GY is 10.76 W/mK at 300 K, which is only one tenth of that of γ-graphyne (106.24 W/mK). A detailed analysis of the harmonic and anharmonic properties, including the phonon group velocity, phonon lifetime, atomic displacement parameter, and bond energy curves, reveals that the low lattice thermal conductivity can be attributed to the low Young’s modulus, low Debye temperature, and high Grüneisen parameter. Furthermore, at room temperature, ID-GY can reach a high ZT value of 0.46 with a 5.8 × 1012 cm−2 hole concentration, which is much higher than the value for many other carbon-based materials. This work demonstrates that changing structural units from hexagonal to pentagonal can significantly reduce the lattice thermal conductivity and enhance the thermoelectric performance of carbon-based materials.
Effect of Cathode Microstructure on Electrochemical Properties of Sodium Nickel-Iron Chloride Batteries
Authors: Ahn Byeong-Min , Ahn Cheol-Woo , Hahn Byung-Dong , Choi Jong-Jin , Kim Yang-Do , Lim Sung-Ki , Choi Joon-Hwan
Published: September 2021

Sodium metal chloride batteries have become a substantial focus area in the research on prospective alternatives for battery energy storage systems (BESSs) since they are more stable than lithium ion batteries. This study demonstrates the effects of the cathode microstructure on the electrochemical properties of sodium metal chloride cells. The cathode powder is manufactured in the form of granules composed of a metal active material and NaCl, and the ionic conductivity is attained by filling the interiors of the granules with a second electrolyte (NaAlCl4). Thus, the microstructure of the cathode powder had to be optimized to ensure that the second electrolyte effectively penetrated the cathode granules. The microstructure was modified by selecting the NaCl size and density of the cathode granules, and the resulting Na/(Ni,Fe)Cl2 cell showed a high capacity of 224 mAh g−1 at the 100th cycle owing to microstructural improvements. These findings demonstrate that control of the cathode microstructure is essential when cathode powders are used to manufacture sodium metal chloride batteries.
Cavitation Effect in Ultrasonic-Assisted Electrolytic In-Process Dressing Grinding of Nanocomposite Ceramics
Authors: Li Guangxi , Chen Fan , Bie Wenbo , Zhao Bo , Fu Zongxia , Wang Xiaobo
Published: September 2021

Ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding is a promising technology that uses a metal-bonded diamond grinding wheel to achieve a mirror surface finish on hard and brittle materials. In this paper, the UA-ELID grinding was applied to nanocomposite ceramic for investigating the cavitation effect on the processing performance. Firstly, the ultrasonic cavitation theory was utilized to define the cavitation threshold, collapse of cavitation bubbles, and variation of their radii. Next, the online monitoring system was designed to observe the ultrasonic cavitation under different ultrasonic amplitude for the actual UA-ELID grinding test. A strong effect of ultrasonic cavitation on the grinding wheel surface and the formed oxide film was experimentally proved. Besides, under the action of ultrasonic vibration, the dressing effect of the grinding wheel was improved, and the sharpness of grain increased by 43.2%, and the grain distribution was dramatically changed with the increase of ultrasonic amplitude. Compared with the conventional ELID (C-ELID) grinding, the average protrusion height increased by 14.2%, while the average grain spacing dropped by 21.2%. The UA-ELID grinding reduced the workpiece surface roughness Rz and Ra by 54.2% and 46.5%, respectively, and increased the surface residual compressive stress by 44.5%. The surface morphology observation revealed a change in the material removal mechanism and improvement of the surface quality by ultrasonic cavitation effect. These findings are considered instrumental in theoretical and experimental substantiation of the optimal UA-ELID grinding parameters for the processing of nanocomposite ceramics.