Nitride Powders Research Articles

Eco-Friendly Reinforcement: Enhancing Wear and Corrosion Resistance of Al7079 with Boron Nitride and Aloe Vera Powder

Eco-Friendly Reinforcement: Enhancing Wear and Corrosion Resistance of Al7079 with Boron Nitride and Aloe Vera Powder

Raman signatures of type A and B influenza viruses: molecular origin of the "catch and kill" inactivation mechanism mediated by micrometric silicon nitride powder.

A multiomic study of the structural characteristics of type A and B influenza viruses by means of highly spectrally resolved Raman spectroscopy is presented. Three virus strains, A H1N1, A H3N2, and B98, were selected because of their known structural variety and because they have co-circulated with variable relative prevalence within the human population since the re-emergence of the H1N1 subtype in 1977. Raman signatures of protein side chains tyrosine, tryptophan, and histidine revealed unequivocal and consistent differences for pH characteristics at the virion surface, while different conformations of two C-S bond configurations in gauche and trans methionine rotamers provided distinct low-wavenumber fingerprints for different virus lineages/subtypes. Short-term exposure to a few percent fraction of silicon nitride (Si3N4) micrometric powder in an aqueous environment completely inactivated the influenza virions, independent of lineage/subtype dependent characteristics. The molecular-scale details of the inactivation process were studied by Raman spectroscopy and interpreted in terms of a "catch and kill" mechanism, in which the hydrolyzing ceramic surface first attracts virions with high efficiency through electrochemical interactions (mimicking cellular sialic acid) and then "poisons" the viruses by local hydrolytic elution of ammonia and nitrogen radicals. The latter event causes severe damage to the virions' structures, including structural degradation of RNA purines, rotameric scrambling of methionine residues, formation of sulfhydryl and ionized carboxyl groups, and deprotonation/torsional deformation of tyrosine, tryptophan, and histidine residues. This study confirmed the antiviral effectiveness of Si3N4 powder, which is safe to the human body and simply activated by water molecules. Raman spectroscopy was confirmed as a powerful tool in molecular virology, complementary to genomics and unique in providing direct information on virus structures at the molecular scale.

Oxygen content of α-silicon nitride powder depending on the synthesis method

Oxygen content of α-silicon nitride powder depending on the synthesis method

Optimization of microstructure to improve Si3N4 ceramics with thermal conductivity and mechanical properties: effect of Si and α-Si3N4 powder composition

The heat dissipation capacity and mechanical reliability of silicon nitride (Si3N4) ceramic substrates determine the service life of power devices. In this work, a two-step sintering method was designed to produce Si3N4 ceramics with excellent performance using Si and α-Si3N4 powders with different ratios as raw materials. The nitridation mechanism and the microstructural evolution mechanism were clarified. The in-situ-generated β-Si3N4 seeds regulated the microstructure of the post-sintered Si3N4 ceramics. The introduction of Si powder reduced the content of oxygen impurities and regulated the microstructure of Si3N4 ceramics, thereby improving thermal conductivity while maintaining excellent mechanical properties. When the mass ratio of Si powder nitridation to α-Si3N4 was 0.75, its thermal conductivity was 120W·m-1·K-1, fracture toughness was 11.92±0.36MPa·m1/2, and bending strength was 712±20.6MPa. This study provides a strategy to reduce the introduction of oxygen impurities while optimizing the microstructure to prepare Si3N4 ceramics with excellent performance.

Nickel-Free Austenitic Stainless Steel Manufactured by Laser Powder-Bed Fusion from Martensitic Powder Mixed with Interstitial Compounds

Abstract Using laser powder bed fusion (L-PBF), nickel-free austenitic stainless steel was manufactured from mixing AISI 420S martensitic stainless-steel powder with austenite-stabilizing components. Chromium nitride (Cr2N), chromium carbide (Cr3C2), chromium (Cr) and graphite (C) powder were admixed in different quantities. The resulting microstructures were investigated using light- and electron microscopy, X-ray diffraction, and hardness indentations. Nitrogen, carbon, and chromium from the admixed powders were dissolved in solid solution; no remnants of nitrides/carbides were identified. The as-built specimens had a lower nitrogen content than the mixed powders. Insufficient additions of austenite-stabilizing elements resulted in a dual-phase microstructure of austenite and martensite, which experienced in-situ tempering of martensite during fusion of consecutive layer(s) in the L-PBF process. Relatively high contents of austenite-stabilizing elements resulted in a fully austenitic microstructure with a hardness of 380–500 HV5, depending on Cr and interstitial content. The tendency for forming hot cracks was found to correlate with the solidification interval as calculated using a modified version of the Scheil-Gulliver model.

Titanium Compound Coating on SUS Separator for PEFC By Screen Printing

Currently, the metal separators of polymer electrolyte fuel cells (PEFCs) are mainly made of Ti alloys with press working. According to the report by Strategic Analysis Inc1), Ti separator accounts for a large ratio of the PEFC stack cost. To reduce this cost, it is effective to use inexpensive stainless steel and to apply the coating by screen printing, which is relatively easy to form patterns and less expensive than evaporation or sputtering. However, stainless steel has lower corrosion resistance than that of titanium, and its conductivity decreases in aqueous solution due to the formation of passive film. The purposes of this study are to develop a coating with excellent corrosion resistance and conductivity, as well as adhesion and durability, and to apply the coating on stainless steel by screen-printing. Titanium nitride and titanium carbide were employed as tillers among titanium compounds that have high corrosion resistance and sufficiently low electrical resistivity comparable to that of titanium. As a result of the research, a coating thickness of several hundred micro-m became possible, and it was decided that the gas flow path fabrication would also be done by screen printing.In this experiment, we used titanium nitride powder with different particle sizes, Olycox KC-1300 as binder, and 2-(2-butoxyethoxy) ethyl acetate as solvent to prepare printing pastes. 4 g of binder and 10 mL of solvent were weighed and stirred at 80°C for 12 hours using a magnetic stirrer. 4 g of the stirred solution was mixed with 4 g of titanium nitride powder to form a paste. The paste was screen-printed on SUS304 using a plate simulating a gas flow channel, and then dried at 250°C for 6 hours. The resistance of the coatings prepared by the above method was evaluated after pressure treatment. In addition, anodic polarization was measured in a three-electrode system. The contact resistance was targeted to be less than 10 mΩcm2 , the target value for the contact resistance of PEFC separators, as specified by the U.S. DOE.2) References 1) Mass Production Cost Estimation of Direct H2 PEM Fuel Cell Systems for Transportation Applications: 2017 Update, Brian D. James, Jennie M. Huya-Kouadio, Cassidy Houchins, Daniel A. DeSantis, Strategic Analysis Inc., December 2017.2) Fuel Cell Technologies Multi-Year Research, Development, and Demonstration Plan, U.S. DOE, 2017

A new process route for the additive manufacturing of a high nitrogen containing martensitic stainless steel - A feasibility study

High-nitrogen martensitic stainless steels, such as X30CrMoN15 (0.3 to 0.5 mass% nitrogen), exhibit an excellent combination of strength and corrosion resistance, making them well-suited for applications in the medical technology and aerospace industry. The qualification of these steels for additive manufacturing (AM) could generate new application areas where AM, due to its process-specific advantages, could offer added value compared to conventional manufacturing methods. However, the laser powder bed fusion (PBF-LB/M) of high-nitrogen alloyed steels is challenging due to the high tendency for gas pore formation, resulting from the limited nitrogen solubility in the steel melt. In this work, a new process route for AM of a high nitrogen containing X50CrMoV15 martensitic stainless steel is presented, which consists of a process combination of powder nitriding, PBF-LB/M and subsequent hot isostatic pressing (HIP) with integrated quenching. Gas nitriding is used to achieve a nitrogen content in the starting powder that exceeds the maximum solubility in the melt. Although the nitrogen content decreases during the PBF-LB/M process, the high solidification and cooling rates prevent the melt from reaching equilibrium nitrogen levels, resulting in a nitrogen content above the solubility limit in the final PBF-LB/M state. The pores formed during the process are closed through HIP, which also allows hardening via integrated gas quenching. With an additional cryogenic treatment, the process produces a fully dense steel with 75% martensitic structure and 0.246 mass% nitrogen. Further optimization opportunities have been identified and are discussed.

Synthesis, Structural, and Raman Investigation of Lanthanide Nitride Powders (Ln = La, Ce, Nd, Sm, Gd, Tb, Dy, Er, Lu).

Lanthanide nitride (LnN) materials have garnered significant interest in recent years due to their promising potential as heterogeneous catalysts for green ammonia synthesis under low temperature and pressure reaction conditions. Here, we report on the synthesis of an extended series of lanthanide (Ln) nitride powders (Ln = lanthanum, cerium, neodymium, samarium, gadolinium, terbium, dysprosium, erbium, lutetium) and their structural and vibrational properties. Polycrystalline powders were fabricated using a ball milling mechanochemical process, and their structural properties were assessed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experimental lattice constants deduced from XRD and TEM were compared with density functional theory-based calculated lattice constants using the Perdew-Burke-Ernzerhof exchange-correlation functional. We show that the calculated lattice constants are within 1-1.5% of the experimental values for the majority of the LnN species-a notable increase in accuracy over prior computational approaches. The frequencies of Raman scattering from the LO(Γ) phonon are reported across the series and compare well with published thin-film data on a smaller selection of the series. As expected, there is a linear relationship between the LO(Γ) phonon frequency and atomic number. Finally, we demonstrate that Raman spectroscopy can be used to detect the presence of a nanoscale oxide layer on the surface of ErN powders.

SORPTION OF Fe(III) IONS ON CARBON NITRIDES SYNTHESIED FROM VARIOUS PRECURSORS

In the present work, graphitic carbon nitride powders synthesized from urea, melamine and dicyandiamide were ultrasonic exfoliated and used to evaluate their adsorption efficiency for iron ions –Fe(III) from aqueous solution. It has been established that the efficiency of sorption is significantly influenced by the pH of the medium, contact time, weight of the sorbent and the initial concentration of Fe(III). High adsorption of the iron ion (97–99%) occurs at pH4. It is shown that the Fe(III) sorption isotherm on the studied carbon nitride samples can be modeled by both Langmuir and Freundlich adsorption isotherms based on correlation coefficients

Thermal interface materials of PDMS with h-BN fillers synthesized from ferroboron via SHS

Thermal interface materials (TIMs) are widely used to enhance heat transfer between heat-generating components of electronic devices and cooling radiators. The rapid miniaturization of electronic devices and the increase in their specific capacity have led to excessive heat loads, necessitating the development of TIMs based on dielectric powder fillers with high thermal conductivity. This paper presents an energy-efficient approach for synthesizing hexagonal boron nitride (h-BN) powder, used as a filler for thermal interface pads with a polydimethylsiloxane polymer matrix. The h-BN filler was produced through a two-step process: (1) self-propagating high-temperature synthesis of Fe-BN powder through the self-sustaining exothermic reaction of an affordable ferroboron powder with gaseous nitrogen, followed by (2) acid leaching of the synthesized powders to remove iron. The BN phase content in the resulting powder filler is 99.6 wt%. The pads demonstrated a thermal conductivity of up to 1.95 W m⁻1K⁻1 with a 40 wt% filler content and an average particle size of 40 μm, all while retaining adequate flexibility and elasticity.

On the analysis of physical properties of thermal interfaces based on hexagonal boron nitride and copper

The physical properties (thermal and thermal diffusivity) of thermal interfaces based on powdered boron nitride with a hexagonal crystal lattice (h-BN) and copper with a cubic crystal lattice (Cu) for cooling the electronic component base of micro- and nanoelectronics are studied. The physical properties are determined by the flash method. The prospects of using pressed hexagonal boron nitride powder as a thermal interface without using a binder are described. A comparison with the physical properties of other thermal interfaces that are widely used at present is made.

Numerical Studies of Influencing Factors on the Homogeneity of the Powder Mixture during the Powder Spreading Process of Powder Bed Fusion–Laser Beam/Metal

Recent studies have focused on the alloying of nitrogen (N) in high‐alloy stainless steels by powder bed fusion–laser beam/metal (PBF‐LB/M). However, N‐induced pore formation remains a challenge. To overcome this, a combined PBF‐LB/M and hot isostatic pressing (HIP) process is developed. AISI 304L stainless steel powder was mixed with silicon nitride (Si3N4) powder and processed by PBF‐LB/M, allowing partial retention of Si3N4. This helps to maintain sufficient N content while reducing pore formation. The microstructure is then homogenised by HIP. A major challenge of this process is to maintain the homogeneity of the deposited powder mixture on the powder bed to ensure a consistent N content in the final products. This study combines experimental and numerical methods to address this issue: scanning electron microscopy is used to characterize the microstructure and map the local N content, while various numerical studies based on the discrete element method are carried out to investigate the effects of layer thickness, substrate surface roughness, and powder properties on the intermediate product. The numerical approach effectively predicts the N content distribution and homogeneity on the powder bed. The models are validated with experimental data and optimal process conditions for PBF‐LB/M are identified.

Production of few-layer graphene and boron nitride nano onions via lamp ablation

Abstract Few-layer graphene, and separately, boron nitride nano onions have been synthesised by a novel lamp ablation method which is a one-step, high-yield process that is catalyst-free, devoid of toxic reagents, with short reaction times, and potentially scalable. The precursor for the few-layer graphene is graphite flake, while that of boron nitride nano onions is hexagonal boron nitride powder. Product nanostructures are characterised by high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS). We also report on our commercialisation trajectory to translate promising research findings in the laboratory to the market. For the few-layer graphene product, it is presently on a pre-commercial pilot plant phase.

Synthesis of near‐spherical BN powders by templated carbothermal reduction and nitridation

AbstractBoron nitride (BN) powders with near‐spherical particles of more than 10 µm were synthesized by templated carbothermal reduction and nitridation. The effects of processing factors, such as raw material mixing methods, C/B2O3 molar ratios, and carbon templates, were systematically studied, and the reaction mechanism was discussed. The experimental results showed that the integrity and morphology of the carbon templates was usually destroyed during ball milling or grinding, but preserved during magnetic stirring. The morphology of synthesized BN particles depended on the C/B2O3 molar ratio in starting reactant mixtures and gradually changed from sheet‐like to near‐spherical shape with decreasing C/B2O3 molar ratio. The morphology and size of synthesized BN particles agreed with that of the carbon templates, which means that the morphology and size of synthesized BN particles can be tailored by controlling that of the carbon template. The BN near‐spherical particles synthesized in this work may be used as thermally conductive fillers for electronic packaging.

Preparation and optimization of silicon nitride slurries for digital light processing

AbstractDigital light processing (DLP) three‐dimensional printing has the advantages of both high printing resolution and efficiency and has been used to manufacture high‐precision, small, and complex shaped ceramic parts. One of the challenges of DLP is to develop photosensitive ceramic slurries with high solid content and low viscosity, especially for non‐oxide ceramics such as silicon nitride due to the dispersion and light absorption problem. This study mainly explores the dispersibility of silicon nitride in ultraviolet (UV)‐cured resins and the photocured properties of the slurry. Rheological measurements were utilized to characterize and screen different dispersants in the resin. It was found that DISPERMP is an effective dispersant. In order to improve the curing depth of Si3N4 photosensitive paste, the surface of silicon nitride powder was treated by oxidation, and organic compounds with different refractive indices were also introduced to increase the light penetration depth. It was found that glycerol with a refractive index of 1.474 resulted in the greatest improvement in the curing depth of Si3N4 photosensitive paste. Finally, a proposed slurry composition was developed to successfully print silicon nitride ceramics through UV‐curing molding technology.

Few-layered-graphene - Si3N4 composite powders prepared by decomposition of methane onto a Si3N4 powder bed: Control of the average number of layers in the graphene stack

The chemical vapor deposition of carbon is performed onto a commercial silicon nitride powder bed. This produces few-layered-graphene (FLG) films or islands on the Si3N4 particles. The samples are characterized by several techniques including Raman spectroscopy, scanning and transmission electron microscopy. The experimental parameters of the methane (CH4) decomposition (temperature, CH4 concentration, dwell time) are correlated to the average number of graphene layers (N). Complete coverage of the Si3N4 particles is achieved for FLG with N controlled in the range 5–12, corresponding to 4–12 wt%. of carbon. Below that, for stacks with N = 3–4, the coverage of the surface by FLG islands is not total. The value found for the activation energy of CH4 conversion into carbon shows that island-growth is favored over layer-growth. A macroscopical method based on a carbon proportion evaluation gives an approximation of both the coverage ratio and the average number of layers in the stack.

Physical and mechanical properties of ceramics based on ZrN-ZrO2 obtained by spark plasma sintering method

Relevance. Increasing the service life of mining tools is an important task in the development of geology associated with the investigation of new ceramic materials for functional purposes. The ability to reduce wear and thermal and chemical effects of rocks on the working elements of mining equipment determines the vector of development of the use of super-hard, high-strength and refractory ceramics. At the same time, the task is set to increase the fracture toughness of the materials used to solve the problem of maintaining the operability of equipment under conditions of critical deformations. To accomplish this task, it is necessary to study the patterns of consolidation of ceramic materials and search for the optimal combination of consolidation parameters to achieve improved physical and mechanical properties. Aim. To develop a method for producing high-density durable ceramics based on commercially available zirconium nitride powders using spark plasma sintering under vacuum conditions, to study the phase composition and physical and mechanical properties of the resulting samples. Methods. X-ray phase analysis of the studied samples, nanoindentation, microscopic analysis. Results and conclusion. The authors have studied the physical and mechanical properties of zirconium nitride consolidated by spark plasma sintering at 2000℃, a pressure of 30–60 MPa and a holding time at a given temperature of 5–10 minutes. Qualitative and quantitative X-ray phase analysis was carried out, within which the content of the main phase of zirconium nitride and zirconium dioxide phase was determined. It was found that an increase in the pressure applied during consolidation and holding time contributes to better compaction and a decrease in the porosity of the samples from 8.52 to 2.72%. It was found that with a decrease in porosity, the elastic modulus increased in the range from 320 to 378 GPa, and the hardness from 7.3 to 10.4 GPa. At the same time, by extrapolating the data, it was established that non-porous zirconium nitride samples will have an elastic modulus of 394 GPa and a Martens hardness of 11.56 GPa. For the samples under study, critical stress intensity factors were determined. It was established that at a porosity of less than 5%, the critical stress intensity factor of zirconium nitride consolidated by spark plasma sintering has values of at least 4 MPa m1/2.

Preparation of dispersible carbon nitride powder and fabrication of its thin films by wet-process

To establish a low-cost and environment-friendly method for producing blue fluorescent materials and their thin films, we investigated the conditions for synthesizing graphitic carbon nitride (g-C3N4) powder from urea and melamine. We found that urea can be used to synthesize g-C3N4 at lower annealing temperatures than melamine. The synthesized g-C3N4 powder showed good dispersibility in deionized water and methanol, and it was found that relatively uniform g-C3N4 thin films could be obtained by low-speed spin-coating, especially with highly volatile methanol dispersions. These results indicate that blue fluorescent thin films can be fabricated using a wet process at room temperature.

Effects of Hexagonal Boron Nitride and Mesoporous Silica Nanoparticles on the Morphology, Mechanical Properties and Antimicrobial Activity of Dental Composites

Hexagonal boron nitride (HBN), an artificial material with unique properties, is used in many industries. This article focuses on the extent to which hexagonal boron nitride and silica nanoparticles (MSN) affect the physicochemical and mechanical properties and antimicrobial activity of prepared dental composites. In this study, HBN, and MSN were used as additives in dental composites. 5% and 10% by weight of HBN are added to the structure of the composite materials. FTIR analysis were performed to determine the components of the produced boron nitride powders, hexagonal boron nitride-containing composites, and filling material applications. The structural and microstructural properties of dental composites have been extensively characterized using X-ray diffractometry (XRD). Surface morphology and distributions of nano boron nitride were determined by scanning electron microscopy (SEM)-EDS. In addition, the solubility of dental composites in water and their stability in water and chemical solution (Fenton) were determined by three repetitive experiments. Finally, the antimicrobial activity of dental composites was detected by using Minimum Inhibitory Concentration (MIC) measurement, as well as Minimum Fungicidal Concentration (MFC) method against yeast strain Saccharomyces cerevisiae, and Minimum Bactericidal Concentration (MBC) method against bacteria strains, Staphylococcus aureus and Escherichia coli. Since the HMP series have better antimicrobial activity than the HP series, they are more suitable for preventing dental caries and for long-term use of dental composites. In addition, when HMP and HP series added to the composite are compared, HMP-containing dental composites have better physicochemical and mechanical properties and therefore have a high potential for commercialization.

Effect of nitrogen addition on sintering behavior of high-entropy alloy CrMnFeCoNi powder

The effect of nitrogen addition on sintering behavior of high-entropy alloy CrMnFeCoNi powder has been investigated. CrMnFeCoNi alloy powders were nitrided to add nitrogen and then consolidated at three different temperatures. The microstructure of the nitrided CrMnFeCoNi alloy powders and sintered compacts was characterized using electron probe microanalysis (EPMA) system. In the compact sintered at 800 °C, a high-nitrogen-content region formed a continuous network structure around the low-nitrogen-content substrate. The hardness of the sintered compacts with nitrogen was higher than that of the compacts without nitrogen. The high-nitrogen-content region expanded into the substrate region. The Vickers hardness of the sintered compacts increased with an increase of sintering temperature up to 950 °C. Sintering at 1100 °C did not completely finish; the vacuum pressure in the sintering chamber rapidly increased because chromium nitride (CrN) decomposed. The results indicate that high-temperature sintering is ineffective for nitrogen-added CrMnFeCoNi alloy powder.