Ar Gas Flow Research Articles

Dibutyl phthalate degradation and toxicity assessment based on hydroxyl radicals generated by plasma jet

Phthalate esters such as dibutyl phthalate (DBP) are widely used as plasticizers in various industries and are known to cause water pollution reaching 15.7 mgL-1 in freshwater and 0.01 mgL-1 in seawater. This study investigated the effectiveness of DBP degradation using an atmospheric-pressure plasma jet (APPJ). Variation in the argon (Ar) gas flow rate influenced the spatial distribution of the hydroxyl radicals (∙OH) as it altered the laminar-to-turbulent flow transition. The highest density of ∙OH was recorded to be 3.1 × 1016 cm−3 when the Ar flow rate was maintained at 2 standard liters per minute. Additionally, the ∙OH concentration in plasma-activated water substantially increased to 35.5 μM with prolonged treatment. Similarly, the concentrations of H2O2, which is formed as a result of the recombination of the ∙OH, gradually increased to 34.4 μM over 8 min of treatment time, and subsequently reduced to 32.6 μM after an additional 2 min of treatment. A degradation rate of 96.6 % was achieved within 10 min of treatment, as confirmed by a gas chromatography (GC)-flame ionization detector. GC-mass spectrometry was used to identify the intermediate products, and propose possible degradation pathways. However, a decline in the energy efficiency was observed because of reduced initial concentration over the extended treatment time. Furthermore, a 40 % increase in cell viability and a 45 % decrease in the percentage of the dead cell population were observed during the exposure of MRC5, astrocytes, and PC-3 cell lines to APPJ-treated DBP solution, indicating reduced toxicity of the contaminant. Thus, the proposed approach can effectively reduce the contamination of water resources by DBP.

Oxygen Evolution Behavior of Ni-Containing Alloy Electrodes in NaOH–KOH Hydrate Melt

Hydrogen is expected to be the next-generation energy carrier with zero CO2 emissions. Alkaline water electrolysis (AWE) is one of the methods for hydrogen production; however, improving its energy efficiency is a challenge. We are currently developing a highly efficient water electrolysis using hydroxide hydrate melts at 150–200°C [1,2]. Recently, we reported that the overpotential for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a Ni electrode in a NaOH–KOH hydrate melt at 200°C under atmospheric pressure was significantly reduced compared to a 30 wt% KOH aqueous solution at 80°C, which is a typical electrolyte for conventional commercial AWE [2]. In addition, the OER overpotential was found to be larger than the HER overpotential at the Ni electrode in the NaOH–KOH hydrate melt [2]. In the present study, we investigated the OER behavior of Ni-containing alloys in the NaOH–KOH hydrate melt.Linear sweep voltammetry was performed in the NaOH–KOH hydrate melt (NaOH:KOH:H2O = 9:61:30 mol%) at 150 and 200°C using a three-electrode cell. Several types of commercially available Ni-containing alloy plates with a flag-shaped and 3 mm diameter were used as the working electrode. A Ni rod was used as the counter electrode. A palladium hydride (Pd–H) electrode was used as the reference electrode and the potential was calibrated with respect to the reversible hydrogen electrode (RHE). All measured potentials were IR compensated. All measurements were performed in stationary electrolytes under Ar gas flow at atmospheric pressure.Figure 1 shows anodic polarization curves at Ni–Fe and Ni–Cu alloy electrodes in the NaOH–KOH hydrate melt at 150°C. The polarization of Ni–Fe and Ni–Cu alloy electrodes is lower than that of the Ni electrode. In this paper, we will also present the results for other Ni-containing alloys.A part of this study was supported by Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) from Japan Science and Technology Agency (JST) Grant Number JPMJTR23TB.[1] K. Kawaguchi, K. Goto, A. Konno, and T. Nohira, J. Electrochem. Soc., 170, 084507 (2023).[2] K. Goto, K. Kawaguchi, and T. Nohira, Electrochemistry, 92, 043021 (2024). Figure 1

Traveling Solvent Floating Zone Growth and Ionic Conductivity of Li0.1La0.3Nb0.8Ta0.2O3 Single Crystals

Li x La(1-x)/3Nb1-y Ta y O3 (LLNT) is a solid electrolyte with a double perovskite-type structure. It was reported that the highest ion conductivity of LLNT was 7.78 × 10-5 S/cm at x = 0.1, y = 0.2 [1,2]. Therefore, in this study, we investigated the preparation conditions of the feed and the growth conditions of Li0.1La0.3Nb0.8Ta0.2O3 single crystals by the traveling solvent floating zone (TSFZ) method.Li2CO3, La2O3, Nb2O5, and Ta2O5 were used as starting materials, weighed at Li x La(1-x)/3Nb1-y Ta y O3 (x = 0.1, y = 0.2) stoichiometric composition, and mixed with ethanol. The mixed powder was calcined at 800 °C for 2 hours in air. The calcined powder was grounded and calcined again at 1200°C for 12 hours in air. The calcined powder was then shaped into a cylindrical shape by rubber pressing and sintered at 1350°C for 5 hours in air. Solvent of 5 mol% of La(Nb,Ta)3O9-poor, La(Nb0.5Ta0.5)O4-poor or La(Nb0.8Ta0.2)O4-poor composition relative to the stoichiometric composition of LLNT feeds was prepared using the same procedure as the feed rod preparation. The optical floating zone machine was used for crystal growth. The growth conditions were the growth rate of 2 or 5 mm/h, the growth atmosphere of Ar or N2. The grown crystals were characterized using X-ray diffraction, electron probe micro-analyzer (EPMA), and impedance measurements.As a result of crystal growth of LLNT by the floating zone (FZ) method, the La(Nb,Ta)3O9 phase was deposited as an inclusion in the initial growth region, even though Li evaporation from the molten zone was not observed. This result indicates that LLNT is an incongruently melting compound. Next, the TSFZ method, FZ method using solvents, was applied to the growth of LLNT crystals. La(Nb,Ta)O4 inclusion phase deposited in the initial growth part of the grown crystal when using solvent of 5 mol% La(Nb,Ta)3O9-poor composition relative to the stoichiometric LLNT. In the case of using a 5 mol% La(Nb0.8Ta0.2)O4-poor solvent composition, crystals with a length of 12 mm and a diameter of 5 mm were obtained as shown in Fig. 1(a). La(Nb,Ta)O4 inclusion phase was not detected in the grown crystal. The chemical composition of the LLNT phase was determined to be y = 0.14-0.25 by quantitative analysis using EPMA as shown in Fig. 1(b). Therefore, inclusion-free LLNT crystals were obtained using a solvent with 5 mol% La(Nb0.8Ta0.2)O4-poor composition relative to the stoichiometric LLNT composition. Moreover, the molten zone was stable in Ar gas or N2 gas flow at growth rate of 5 mm/h. The ionic conductivity of the grown crystal was σ= 2.0 ×10-5 S/cm . The low conductivity is due to cracks, and inhomogeneous in the grown LLNT crystal. Optimization of the solvent composition is required for LLNT crystals with homogeneous and high ionic conductivity.References.[1]Y. Maruyama, et. al., J. Ceram. Soc. Jpn. 128, 761-765 (2020). [2]Y. Maruyama, et. al., J. Ceram. Soc. Jpn. 129, 535-539 (2021). Figure 1

INFLUENCE OF THE RATIO OF GASE CONSUMPTION N<sub>2</sub>/Ar AND MAGNETRON POWER ON THE DENSITY AND STOICHIOMETRIC COMPOSITION OF TIN<sub>X</sub> FILMS SYNTHESIZED BY MAGNETRON SPUTTERING METHOD

The films of titanium nitride were deposited by direct current magnetron sputtering on the surface of singlecrystalline silicon samples in an Ar-N2 atmosphere for use as a diffusion barrier. The thickness and density of films were measured by X-ray reflectometry. The design of the MAGNA TM-200-01 installation has been changed to increase the supply of nitrogen into the chamber. The influences of sputtering conditions, including the flow rate of nitrogen and argon gases and their N2 /Ar ratios in the range of 1–60 in the chamber, magnetron power of 690–1400 W on the formation of TiNx films, their density and stoichiometric composition, were studied. It is shown that the value of x is affected not only by the N2 /Ar gas flow rate ratio, but also by the magnetron power. At the sputtering parameters 1200 W, N2 /Ar = 30, 0.8 Pa, 320 s and 100°C, a maximum density of 5.247 g/cm3 of a film was achieved, which corresponds to the composition TiN0.786 = Ti56N44. The presence of nanocrystalline film of titanium nitride and the absence of a nanocrystalline titanium phase were confirmed by photographic X-ray diffraction. It was found that for the synthesis of titanium nitride as close as possible to the stoichiometric composition TiN0.770 - TiN0.786, it is necessary to use magnetron power in the range of 900–1200 W, nitrogen rate of 30 cm3 /min with low argon flows of 1–5 cm3 /min.

Optimizing plasma-activated water for enhanced microbial control in agricultural produce processing

The study utilized a pinhole plasma jet discharge system to generate plasma-activated water (PAW) for the removal of microbes on bird's eye chili. Optimal conditions for PAW generation were determined using response surface methodology, achieving maximum microbial inactivation. The novelty of this study lies in designing a PAW system model for agricultural cooperatives using the Quality Function Deployment (QFD) methodology, which integrates customer and engineer/designer perspectives. The results demonstrate a maximum 82.54% microbial removal rate on bird's eye chili under optimal conditions (e.g., exposure time = 20 min, Ar gas flow rate = 5 L/min, and O2 mixture = 2% Ar gas), indicating effective antimicrobial activity of plasma-activated water. Furthermore, a model of the PAW system for agricultural cooperatives, including cost and electrical power usage estimates, is proposed based on the correlation matrix of QFD. This conceptual PAW model for agricultural cooperatives warrants further investigation to assess its consistency in sterilization efficiency and long-term effects on treated agricultural products.

Synthesis of nano-silicon carbide by SiO–C reaction

Carbon black has been successfully converted into silicon carbide by reacting it with SiO vapor at 1500 °C under Ar gas environment. The influence of reaction temperature, duration and Ar gas flow rate on the final product was examined. The structural and microstructural property of synthesized SiC was characterized using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Micrographs of synthesized SiC showed that the final product was an agglomeration of SiC nano-powder of 50–500 nm size and nano-whiskers/fibres having a diameter of 50–500 nm and lengths in 0.1–10 μm depending on Ar gas flow rate. The higher conversion of C into SiC was observed at 1500 °C with Ar gas flow rate ∼250 ml/min.

One-step formation of ZrON thin film on surface of carbon fine particles for membrane electrode assembly

Zirconium nitride and oxynitride films were deposited on alumina or carbon particles by reactive sputtering using a magnetron sputtering apparatus with a Zr hollow cylindrical target and a vibrating equipment with heating capability. The vibrating equipment developed in this study was effective if the particles are spherical and highly monodisperse. Uniform film deposition was achieved over the entire surface of highly monodisperse spherical alumina particles using the vibrating equipment during deposition. Pure ZrN crystalline layers was deposited under Ar and N2 gas flows with heating on XC-72 carbon powder particles removed adsorbed oxygen. Energy dispersive x-ray spectroscopy mapping analysis for deposited XC-72 carbon particles showed ubiquitous film deposition on agglomerated particles regardless of vibration during sputtering. Uniform film deposition with vibrating equipment was achieved on the entire surface of CGB-10 particles with more spherical and monodisperse than XC-72 but precipitated crystalline phase depended on unintentional oxygen chemisorbed on the particles. Addition and increase in flow rate of oxygen to the sputtering gas resulted in the formation of desired crystalline phase, Zr2ON2, Zr7O8N4, and monoclinic ZrO2, precipitated in the film using CGB-10 particles with chemisorbed oxygen removed. Current density for oxygen reduction reaction measured for MEA made from CGB-10 particles with ZrON-based crystals deposited was larger than that for thin film deposited on a carbon plate substrate.

Nano-structuring of all-d-metal NiCoMnTi-based Heusler compounds

The emerging all-d-metal Ni(Co)MnTi-based Heusler compounds attract extensive attention because it can potentially be employed for solid-state refrigeration. However, in comparison to the abundant physical functionalities in bulk conditions, the hidden properties related to the NiCoMnTi-based Heusler nanoparticles (NPs) have not yet been investigated experimentally. Here, we present NiCoMnTi Heusler NPs that have been manufactured by spark ablation under Ar gas flow, and the related magnetic and microstructural properties have been studied. Compared with the bulk sample, it is found that the magneto-structurally coupled transition in the bulk sample has collapsed into a magnetic transition for the NPs sample. Superparamagnetic NPs with widely distributed dislocations have directly been observed by high-resolution transmission electron microscopy. For the NPs, the magnetocrystalline anisotropy constant is 3.54 × 104 J/m3, while the saturation magnetization after post-treatment has been estimated to be around 26 Am2 kg−1. Our current research reveals that Ni-Co-Mn-Ti-based quaternary NPs could show interesting properties for future nano-application, and the produced NPs will further expand the functionalities of this material family.

Tunnel-Structured Phosphate Exhibiting High Proton Conductivity and Thermal Stability over a Wide Intermediate Temperature Range.

For the practical application of fuel cells in vehicles, it is a challenge to develop a proton solid electrolyte that coexhibits thermal stability and high proton conductivity at wide intermediate temperatures. Here, we report on the tunnel structured phosphate KNi1-xH2x(PO3)3·yH2O, which exhibits high proton conductivity at room temperature up to 500 °C, with the conductivity value reaching 1.7 × 10-2 S cm-1 at 275 °C for x = 0.18. This material, composed of the smallest cations that form the tunnel framework with face-shared (KO6) and (NiO6) chains and PO4 tetrahedral chains, retained the rigid framework up to 600 °C. Two oxygen sites of water molecules located adjacent to each other along the PO4 tetrahedral chains in the tunnel provided the proton conduction pathway. The sample maintained a conductivity of 5.0 × 10-3 S cm-1 for 10 h at 150 °C while changing the measurement atmosphere to a N2 gas flow, a 4% H2-96% Ar gas flow, and an O2 gas flow. The conductivity value at x = 0.18 obtained from the DC measurement was in the order of 10-6 S cm-1, close to the instrument's measurement limit. These results demonstrate that tunnel phosphate has potential as a proton solid electrolyte for next-generation fuel cells.

Numerical Modelling and Simulation for Sliding Wear Effect with Microstructural Evolution of Sputtered Titanium Carbide Thin Film on Metallic Materials

Titanium carbide materials are introduced into manufacturing industries for the reinforcement and surface protection of base materials due to their substantial ability to withstand severe environments, which include sliding wear, corrosion, and mechanical failures. A thin film of titanium carbide (TiC) is coated onto brass and copper substrates using the radio frequency magnetron sputtering (RFMS) deposition method. The coating process is carried out at constant processing parameters, which include a sputtering power of 200 W, a temperature of 80 °C, a deposition time of 180 min, and an argon (Ar) gas flow rate at 10 standard cubic centimetres per minute (SCCM). The coating, together with the base materials, is modelled and its behaviours are simulated using ANSYS Workbench R19.2 Academic, supported by Mechanical APDL solver for nonlinear finite element analysis (FEA). The deformation, equivalent stress–strain characteristics, and elastic–plastic properties of the coating are determined at applied loads of 60 N and 25 N and coefficients of friction (CoF) of 0.25 and 0.38 for the thin film deposition on brass and copper substrates. The sliding distance and the speed of the alloy steel ball used during the sliding wear operation are found to be 3 mm and 4 mm/s, respectively. The sliding wear modelling and simulation process are, however, designed for the ball-on-flat (BoF) wear technique with a dry sliding approach. Therefore, BoF wear simulations are also performed on titanium carbide–brass (TiC-Br) and titanium carbide–copper (TiC-Cu) conjugates for the evaluation of surface engineering applications such as cutting tools and in automotive, aerospace, thermomechanical, and biomedical fields. The ball used for the FEA wear simulation is made from alloy steel material (AISI 52100) with a radius of 3.175 mm.

Influence of the Gas Flow Rate on the Crack Formation of AlCoCrNi High-Entropy Metallic Film Fabricated Using Magnetron Sputtering

In the present study, the AlCoCrNi high-entropy metallic film was deposited on a Si wafer using a magnetron sputtering system. To capture the effects of the sputtering parameters on the microstructure and mechanical properties of the film, the flow rate of Ar gas injected into the chamber (5, 7, and 8 sccm) was controlled. All films were identified as being of BCC phase with compositions of near equiatomic proportions, regardless of the gas flow rates. Nano-scale clusters were observed on the surfaces of all films, and nano-cracks were found in the film deposited at the Ar gas flow rate of 8 sccm, unlike the films deposited at the gas flow rates of 5 and 7 sccm. Detailed microstructural analysis of film deposition at an Ar gas flow rate of 8 sccm indicated that the void boundaries contribute to the formation of nano-cracks. The nano-indentation results indicated that the Ar gas flow rate 5 sccm specimen, with the smallest cluster size at the topmost surface, showed the highest hardness (12.21 ± 1.05 GPa) and Young’s modulus (188.1 ± 11 GPa) values.

Correlation analysis between microstructure and mechanical properties of spark-plasma-sintered Ti(C, N)–W cermets according to changes in titanium, carbon and nitrogen contents

In this study, TiC–50 wt% W, TiN–50 wt% W, TiC0.7N0.3–50 wt% W, Ti0.55C0.13N0.32–50 wt% W, TiC0.5N0.5–50 wt% W and TiC0.5N0.5–70 wt% W cermet specimens with grain sizes smaller than 1 μm were prepared by blending TiC, TiN, TiC0.5N0.5, W and Ti powders followed by the spark plasma sintering of the blended powders. Under Ar gas flow conditions at 1973 K, the TiC0.5N0.5–50 wt% W and TiC-50 wt% W cermet specimens exhibited the first and second highest strengths, respectively, whereas the TiN–50 wt% W and Ti0.55C0.13N0.32–50 wt% W cermet specimens exhibited the lowest strength among all the cermet specimens prepared in this study. In contrast, the Ti0.55C0.13N0.32–50 wt% W and TiC0.5N0.5–50 wt% W cermet specimens exhibited the first and second highest strengths, respectively, at room temperature in laboratory air. Coherent interfaces, whose type differed from those of the TiC0.5N0.5–50 wt% W and TiC0.5N0.5–70 wt% W cermet specimens, were found in (Ti, W)C grains in the TiC–50 wt% W cermet specimen. The coherent interfaces in the TiC–50 wt% W cermet specimen were considered to suppress the grain growth because these interfaces normally suppress the interdiffusion of Ti, W and C atoms. Moreover, the grain growth seemed to be suppressed in the TiC0.7N0.3–50 wt% W, Ti0.55C0.13N0.32–50 wt% W, TiC0.5N0.5–50 wt% W and TiC0.5N0.5–70 wt% W cermet specimens owing to the core–rim structures with coherent interfaces in the cermet specimens. The coherent interfaces and core–rim structures are thus considered to contribute to improving the high-temperature strength of all the cermet specimens except for the TiN–50 wt% W cermet specimen, which contained neither core–rim structures nor coherent interfaces.

Growth and characterization of germanium telluride nanowires via vapor–liquid–solid mechanism

Phase-change materials (PCMs), which can transition reversibly between crystalline and amorphous phases, have shown great promise for next-generation memory devices due to their nonvolatility, rapid switching periods, and random-access capability. Several groups have investigated phase-change nanowires for memory applications in recent years. The ability to regulate the scale of nanostructures remains one of the most significant obstacles in nanoscience. Herein, we describe the growth and characterization of germanium telluride (GeTe) nanowires, which are essential for phase-change memory devices. GeTe nanowires were produced by combining thermal evaporation and vapor–liquid–solid (VLS) techniques, using 8 nm Au nanoparticles as the metal catalyst. The influence of various growth parameters, including inert gas flow rate, working pressure, growth temperature, growth duration, and growth substrate, was examined. Ar gas flow rate of 30 sccm and working pressure of 75 Torr produced the narrowest GeTe nanowires horizontally grown on a Si substrate. Using scanning electron microscopy, the dimensions, and morphology of GeTe nanowires were analyzed. Transmission electron microscopy and energy-dispersive x-ray spectroscopy were utilized to conduct structural and chemical analyses. Using a SiO2/Si substrate produced GeTe nanowires that were thicker and lengthier. The current–voltage characteristics of GeTe nanowires were investigated, confirming the amorphous nature of GeTe nanowires using conductive atomic force microscopy. In addition, the effects of the VLS mechanism and the Gibbs–Thomson effect were analyzed, which enables the optimization of nanowires for numerous applications, such as memory and reservoir computing.

Role of Ar dilution of SiH4/PH3 gas mixture on PECVD based film growth process, hydrogen bonding configuration, and optical properties of n-type a-Si:H thin films

Amorphous silicon is considered as one of the most promising materials for solar cell applications due to its enhanced optical absorption, high temperature coefficient of resistance, controllable forbidden-band gap, and to reduce the costs of solar panels. In this study, we took notice of the film growth, hydrogen bonding configuration, and optical properties of the phosphorus doped a-Si:H films by varying the dilution of silane using argon gas. Argon gas is a chemically non-reactive gas, but it affects the percentage of silicon atoms during processing. A change in growth process and microstructure factor with varying Ar gas flow is observed, which causes changes in the optical properties of P-doped a-Si:H films. The proportion of SiH bonding rises with increasing argon flow rate, as seen by the infrared-absorption spectra. According to optical tests of the films, the refractive index of the films rises with the Ar flow rate, whereas the band gap Eg decreases. Dilution of SiH4 results in a good-quality film with increased optical conductivity. We established experimental proof of a correlation between band gap and refractive index and compared it with previously reported theoretical models. An investigation into the band gap's dependency on Urbach energy revealed its linearity.

The Effects of Thermal Annealing and Postirradiation on Silver Nanoparticle Films Fabricated by Pulsed Laser Deposition in the Flowless Open Air

Herein, Ag nanoparticle (NP) films are fabricated by pulsed laser deposition technique in the flowless atmospheric air. A Q‐switched Nd:YAG pulsed laser beam is used for the ablation process. The fabricated NP films are postirradiated by the pulsed laser beam. In addition, as‐deposited NP films are annealed in argon gas flow ambient for 45 min at different temperatures (250, 350, and 450 °C), and also annealed at 450 °C for 15, 30, and 45 min. The characteristics of fabricated NP films are investigated after postirradiating by pulsed laser beam, and thermal annealing in Ar gas flow. UV–vis absorption spectroscopy is utilized to provide surface plasmon resonance (SPR) characteristics of films. The results show that thermal annealing can lead to strong enhancement, and also narrowing of the SPR spectrum. The results of field emission scanning electron microscopy and atomic force microscopy show that the annealing and postirradiation processes can influence the NPs size and film structure. As an application, the fabricated film is utilized for surface‐enhanced Raman spectroscopy (SERS) using a 10−6 molar aqueous solution of Rhodamine 6G. The SERS results indicate that the annealed NP films become more sensitive than the as‐deposited films.

Enhancing the efficiency and short-circuit current of silicon solar cells using MoO3 as emitter layers

Molybdenum trioxide (MoO3) is an interesting material for optoelectronic applications due to their low-cost, simple processing and thickness-dependent band gap tunability. So far, however, few have been reported to date the impact of post-synthesis annealing on the electrical characteristics of the MoO3 in silicon heterojunctions solar cells. Here, we show that Ar annealing treatment can promote the crystallization of MoO3 nano structures (NSs) and enlarge the MoO3 NSs crystalline size. In this work, thermal evaporation technique is used to prepare MoO3 NSs to be used as emitter layers in silicon heterojunctions solar cell. Then, the as-synthesized sample is annealed under Ar gas flow at 600 °C to improve structural and optical properties of the sample. It is noted that by Ar treatment at 600 °C, we found its quantum efficiency (QE) enhances from 8.41 % to 10.74 %, showing a 27.70 % increase due to a significant enhancement of short circuit-current (ISC). Furthermore, EQE of Ag/Ar treatment MoO3/n-type Si/Ag showed significant enhancement entire spectra range especially in visible region respect to the bare cell.

Tritium release behavior from neutron-irradiated FLiNaK mixed with Ti powder

• FLiNaK mixed with Ti powder was irradiated by mainly thermal neutrons. • Amounts of TF, T2 and T2O released from the FLiNaK by heating were investigated. • Chemical form ratio of released tritium was approximately TF:T2:T2O = 5:70:25. • Approximately 70% of tritium was released as T2O from the FLiNaK exposed to air. • Ti powder mixed to the FLiNaK contributed to the suppression of tritium release. FLiNaK is used as a simulant of FLiBe and FLiNaBe which are promising candidates of liquid blanket material in fusion reactors. In this study, to obtain useful knowledge for tritium release behavior from molten salts such as FLiBe and FLiNaBe, tritium release experiments were carried out for neutron-irradiated FLiNaK containing Ti powder. The solid-state samples were irradiated by mainly thermal neutrons at Kyoto University Research Reactor, and tritium release behavior as TF and T 2 by heating in Ar gas flow was observed and additionally total amount of released T 2 O was obtained. Most of the tritium generated inside the FLiNaK was released to the gas phase even when the FLiNaK was in a solid state at a temperature below its melting point. From the molten FLiNaK unintentionally exposed to air, approximately 70% of tritium was released as tritiated water vapor. The amount of TF released from the molten FLiNaK was considerably less than that of T 2 . This result is consistent with the tendency of tritium release from neutron-irradiated FLiNaBe in our previous study. The ratio of chemical form was approximately TF:T 2 :T 2 O = 5:70:25. It was experimentally confirmed that the Ti powder added to the salt contributes to the suppression of tritium release from the molten salt.

High-temperature compression tests of Ti(C, N)–70 wt% W cermet and isothermal forging of Inconel 718 alloys using cermet molds

In this study, TiC0·5N0.5–70 wt% W cermet specimens consisting of a core–rim grain structure with coherent interfaces and the binder phase were prepared by blending TiC0·5N0.5 and W powders with particle sizes of less than 1 μm and then spark plasma sintering the blended powders. The compression tests of the cermet specimens were conducted in the temperature range of 1873 K–2073 K in a vacuum and under Ar gas flow conditions. At all testing temperatures, this cermet exhibited much higher yield stress than MoSiBTiC and MoNbTaVW high-entropy alloys, which are some of the structural materials showing the highest strength at temperatures exceeding 1873 K. After isothermal upset forging of commercially available solid-solution heat-treated Inconel 718 alloy specimens with a diameter of 5 mm and a height of 5 mm using cermet molds at loads of 40 kN and 10 kN at 1273 K and 1373 K in a vacuum, respectively, their average grain size (2 μm) was found to be much smaller than that before forging. Such fine microstructures were assumed to be formed by dynamic recrystallization during forging.

Optimized APCVD method for synthesis of monolayer H-Phase VS2 crystals

Abstract Monolayer transition metal dichalcogenides, specifically H-phase vanadium disulfide (VS2), hold great significance as fundamental components for next-generation low-dimensional spintronic, optoelectronic, and future electronic devices. They also offer an opportunity to explore the intrinsic magnetic properties associated with monolayer H-phase VS2 crystals at room temperature. However, there have been limited experimental studies on synthesizing pure monolayer H-phase VS2 crystals using sodium metavanadate (NaVO3) and sulfur (S) as precursors for vanadium (V) and S, respectively. In this study, we present a facile atmospheric pressure chemical vapor deposition (APCVD) approach for the synthesizing monolayer H-phase VS2 crystals with a thickness of ∼0.7 nm. The lateral dimensions of monolayer VS2 crystals extends up to ∼26 µm. Additionally, we have modulated the growth parameters, such as the temperature of NaVO3 and the Ar gas flow rate, to obtain VS2 flakes with different sizes and morphologies. This significant advancement paves the way for the synthesis of monolayer H-phase VS2 crystals on SiO2/Si substrates using the APCVD technique.

Growth of 2-inch diameter Mg<sub>2</sub>Si crystal by the VGF method under Ar normal pressure

A 2-inch diameter Mg2Si crystal was synthesized via the vertical gradient freeze (VGF) method in an open-tube system using pyrolytic boron nitride crucibles coated with boron nitride. Using this open-tube system, Mg evaporation was significantly prevented under Ar gas flow. Many grain boundaries were observed at the crystal cross section. A 5-mm square wafer without grain boundaries was cut out from the crystal and characterized by X-ray rocking curve (XRC) analysis, exhibiting a sharp single peak with a full width at half maximum (FWHM) of 50.4 arcsec. This indicates good crystallinity of the single crystalline area of the synthesized crystal.