Pub Date : 2026-01-29DOI: 10.1016/j.vacuum.2026.115144
Xinru Lin, Zheming Feng, Peng Song
One-dimensional (1D) MoO3 nanobelts and MoO3 nanobelts/Ti3C2Tx MXene composites were successfully fabricated using hydrothermal and electrostatic self-assembly technology. Characterization indicates that the composites have more unique microstructure and a higher surface adsorbed oxygen content. The gas sensitivity performance results indicate that the optimal operating temperature (180 °C) of MoO3 nanobelts/Ti3C2Tx MXene composites gas sensor is significantly reduced, and the response value to 50 ppm MEA rose from 298.3 % to 470.1 %. The response/recovery times are only 5 s and 9 s respectively, and it has stability and good selectivity for MEA gas. In addition, this study elaborated on its sensing mechanism in depth by constructing a mechanism model. This study proposes a technical solution to enhancing the gas-sensitive performance of MoO3 through efficient compounding with other functional materials, and also lays a foundation for the research and development and practical application of high-performance MEA gas sensors.
{"title":"Synthesis of 1D/2D MoO3 nanobelts/Ti3C2Tx MXene composites for selective detection of ethanolamine","authors":"Xinru Lin, Zheming Feng, Peng Song","doi":"10.1016/j.vacuum.2026.115144","DOIUrl":"10.1016/j.vacuum.2026.115144","url":null,"abstract":"<div><div>One-dimensional (1D) MoO<sub>3</sub> nanobelts and MoO<sub>3</sub> nanobelts/Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> MXene composites were successfully fabricated using hydrothermal and electrostatic self-assembly technology. Characterization indicates that the composites have more unique microstructure and a higher surface adsorbed oxygen content. The gas sensitivity performance results indicate that the optimal operating temperature (180 °C) of MoO<sub>3</sub> nanobelts/Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> MXene composites gas sensor is significantly reduced, and the response value to 50 ppm MEA rose from 298.3 % to 470.1 %. The response/recovery times are only 5 s and 9 s respectively, and it has stability and good selectivity for MEA gas. In addition, this study elaborated on its sensing mechanism in depth by constructing a mechanism model. This study proposes a technical solution to enhancing the gas-sensitive performance of MoO<sub>3</sub> through efficient compounding with other functional materials, and also lays a foundation for the research and development and practical application of high-performance MEA gas sensors.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115144"},"PeriodicalIF":3.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.vacuum.2026.115138
Ahmad Shoja-sani , Ehsan Roohi , Maryam Javani , Hassan Akhlaghi , Stefan Stefanov
The collision process is essential to the Direct Simulation Monte Carlo (DSMC) method, as it incorporates the fundamental principles of the Boltzmann and Kac stochastic equations. The primary impetus of this paper is to rectify a long-standing theoretical flaw in the widely used no-time-counter (NTC) collision algorithm. We demonstrate that the standard NTC scheme is fundamentally non-Markovian, relying on a fixed majorant product that introduces a system ‘memory’ and leads to inaccuracies at low particle counts. We propose a new algorithm, NTC-Pre-Scan, which transforms the scheme into a fully Markovian process. When repeated collisions are not crucial, our new NTC scheme, called NTC-Pre-Scan, can operate accurately with a very low number of particles per cell (PPC), with average PPC < 1 (e.g., PPC = 0.01), resulting in several empty cells in simulations. This contrasts with the standard NTC schemes, which typically require a PPC greater than 1. Then, a systematic evaluation of different Bernoulli-Trial (BT)-based collision partner selection schemes, including the simplified Bernoulli trials (SBT), generalized Bernoulli trials (GBT), symmetrized and simplified Bernoulli trials (SSBT), and the newly proposed symmetrized and generalized Bernoulli trials (SGBT), is conducted to treat some benchmark rarefied gas dynamics problems. The results show that the BT-based collision algorithms and NTC-Pre-scan successfully maintain the collision frequency as the number of particles per cell decreases. Simulation of the Bobylev-Krook-Wu (BKW) problem, for which an exact solution of the Boltzmann equation is available, indicates that, like the GBT, the SGBT algorithm yields the same results as theory for the average of the fourth moment of the velocity distribution function (VDF). The simulation on the three-dimensional computational grid for the GBT and SGBT schemes matches the fourth moment of the velocity component of the VDF exactly with the analytical solution. Performance analysis in a micro cavity reveals that the GBT, SSBT, and SGBT decrease the computational cost of simulation. Specifically, the computational cost of the SGBT scheme has been reduced by around 40 % when an appropriate selection number (Nsel) is chosen, and this scheme requires a sample size of 0.62 of the NTC scheme. Finally, we demonstrate that all algorithms successfully capture complex flow phenomena, such as shock waves, in the case of hypersonic flow over a cylinder. Moreover, in the cylinder problem, the SGBT scheme can achieve the same level of accuracy with 28 % less computational cost and an outstanding sample size of 0.319 of the nearest neighbor (NN) scheme, which is the modern invariant of the NTC scheme. These advancements enable accurate simulation of rarefied gases with fewer particles (NTC-Pre-Scan) and lower computational cost (SGBT), which is directly beneficial for the design of complex vacuum systems.
{"title":"Efficient collision algorithms in DSMC for rarefied gas dynamics: Markovian NTC-pre-scan and Bernoulli-trial schemes","authors":"Ahmad Shoja-sani , Ehsan Roohi , Maryam Javani , Hassan Akhlaghi , Stefan Stefanov","doi":"10.1016/j.vacuum.2026.115138","DOIUrl":"10.1016/j.vacuum.2026.115138","url":null,"abstract":"<div><div>The collision process is essential to the Direct Simulation Monte Carlo (DSMC) method, as it incorporates the fundamental principles of the Boltzmann and Kac stochastic equations. The primary impetus of this paper is to rectify a long-standing theoretical flaw in the widely used no-time-counter (NTC) collision algorithm. We demonstrate that the standard NTC scheme is fundamentally non-Markovian, relying on a fixed majorant product that introduces a system ‘memory’ and leads to inaccuracies at low particle counts. We propose a new algorithm, NTC-Pre-Scan, which transforms the scheme into a fully Markovian process. When repeated collisions are not crucial, our new NTC scheme, called NTC-Pre-Scan, can operate accurately with a very low number of particles per cell (PPC), with average PPC < 1 (e.g., PPC = 0.01), resulting in several empty cells in simulations. This contrasts with the standard NTC schemes, which typically require a PPC greater than 1. Then, a systematic evaluation of different Bernoulli-Trial (BT)-based collision partner selection schemes, including the simplified Bernoulli trials (SBT), generalized Bernoulli trials (GBT), symmetrized and simplified Bernoulli trials (SSBT), and the newly proposed symmetrized and generalized Bernoulli trials (SGBT), is conducted to treat some benchmark rarefied gas dynamics problems. The results show that the BT-based collision algorithms and NTC-Pre-scan successfully maintain the collision frequency as the number of particles per cell decreases. Simulation of the Bobylev-Krook-Wu (BKW) problem, for which an exact solution of the Boltzmann equation is available, indicates that, like the GBT, the SGBT algorithm yields the same results as theory for the average of the fourth moment of the velocity distribution function (VDF). The simulation on the three-dimensional computational grid for the GBT and SGBT schemes matches the fourth moment of the velocity component of the VDF exactly with the analytical solution. Performance analysis in a micro cavity reveals that the GBT, SSBT, and SGBT decrease the computational cost of simulation. Specifically, the computational cost of the SGBT scheme has been reduced by around 40 % when an appropriate selection number (<em>N</em><sub><em>sel</em></sub>) is chosen, and this scheme requires a sample size of 0.62 of the NTC scheme. Finally, we demonstrate that all algorithms successfully capture complex flow phenomena, such as shock waves, in the case of hypersonic flow over a cylinder. Moreover, in the cylinder problem, the SGBT scheme can achieve the same level of accuracy with 28 % less computational cost and an outstanding sample size of 0.319 of the nearest neighbor (NN) scheme, which is the modern invariant of the NTC scheme. These advancements enable accurate simulation of rarefied gases with fewer particles (NTC-Pre-Scan) and lower computational cost (SGBT), which is directly beneficial for the design of complex vacuum systems.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115138"},"PeriodicalIF":3.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.vacuum.2026.115146
Zhexuan Huang , Chao Tan , Shechun Wei , Han Wang , Jinjun Wang , Jingyuan Li
This study investigates an Mg-Gd-Y-Zn-Zr alloy containing long-period stacking ordered (LPSO) phases to clarify how lamellar morphology and multidirectional forging (MDF, 480 °C, 18 passes) influence its microstructure and mechanical response. After homogenization, the furnace-cooled sample (F) retained dense lamellar LPSO structures, while the water-quenched sample (Q) exhibited sparse lamellae and partially block-shaped phases. EBSD results revealed that Q possessed a higher recrystallized fraction (22.9 %) and finer grains (33.3 μm), whereas F showed inhibited recrystallization (13.2 %, 51.4 μm). TEM bright-field images demonstrated dislocation accumulation and strain localization adjacent to dense lamellae, in contrast to the relatively uniform matrix around sparse lamellae. Mechanical testing indicated that both alloys exhibited substantial strengthening after MDF; the F alloy achieved higher strength (TYS = 233 MPa, UTS = 294 MPa), while the Q alloy displayed improved ductility (EL = 4.5 %). These results suggest that densely arranged LPSO lamellae enhance load-bearing capacity but constrain dislocation motion and grain-boundary migration, whereas sparse lamellae facilitate more homogeneous deformation.
{"title":"Effect of LPSO phase morphology on the microstructure evolution and mechanical performance of Mg–Gd–Y–Zn–Zr alloys processed by multidirectional forging","authors":"Zhexuan Huang , Chao Tan , Shechun Wei , Han Wang , Jinjun Wang , Jingyuan Li","doi":"10.1016/j.vacuum.2026.115146","DOIUrl":"10.1016/j.vacuum.2026.115146","url":null,"abstract":"<div><div>This study investigates an Mg-Gd-Y-Zn-Zr alloy containing long-period stacking ordered (LPSO) phases to clarify how lamellar morphology and multidirectional forging (MDF, 480 °C, 18 passes) influence its microstructure and mechanical response. After homogenization, the furnace-cooled sample (F) retained dense lamellar LPSO structures, while the water-quenched sample (Q) exhibited sparse lamellae and partially block-shaped phases. EBSD results revealed that Q possessed a higher recrystallized fraction (22.9 %) and finer grains (33.3 μm), whereas F showed inhibited recrystallization (13.2 %, 51.4 μm). TEM bright-field images demonstrated dislocation accumulation and strain localization adjacent to dense lamellae, in contrast to the relatively uniform matrix around sparse lamellae. Mechanical testing indicated that both alloys exhibited substantial strengthening after MDF; the F alloy achieved higher strength (TYS = 233 MPa, UTS = 294 MPa), while the Q alloy displayed improved ductility (EL = 4.5 %). These results suggest that densely arranged LPSO lamellae enhance load-bearing capacity but constrain dislocation motion and grain-boundary migration, whereas sparse lamellae facilitate more homogeneous deformation.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115146"},"PeriodicalIF":3.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nanocrystalline powders with an average particle size from 25 to 50 nm were obtained by milling of microcrystalline NbCy powder. The crystal structure, phase and chemical composition, morphology and particle size of the NbCy powders, their specific surface area and density were studied using XRD, SEM, BET, gas pycnometry, and chemical analysis for carbon and oxygen content. It was established that the NbCy powders contain a large amount of impurity oxygen, the amount of which is proportional to their specific surface area, and part of it is present in the form of amorphous Nb2O5. The effect of the average particle size of the NbCy powder, the impurities present in it, especially oxygen, and the temperature of vacuum annealing up to 1400 °C on its chemical and phase composition, average particle size and morphology, as well as density was studied. It was found that most of the oxygen contained in the powders reacts with NbCy upon heating in vacuum, forming niobium oxides. At higher temperatures, these oxides are reduced by carbon from NbCy. This process alters both the stoichiometry y and the phase composition of the powder. Heating of the nanocrystalline powders in vacuum to 1200 °C and above turns them into microcrystalline powders.
{"title":"Effect of vacuum annealing temperature and oxygen impurity content on microstructure and composition of NbCy nanocrystalline powders","authors":"Alexey Kurlov , Anna Postovalova , Larisa Buldakova , Danil Danilov","doi":"10.1016/j.vacuum.2026.115147","DOIUrl":"10.1016/j.vacuum.2026.115147","url":null,"abstract":"<div><div>Nanocrystalline powders with an average particle size from 25 to 50 nm were obtained by milling of microcrystalline NbC<sub><em>y</em></sub> powder. The crystal structure, phase and chemical composition, morphology and particle size of the NbC<sub><em>y</em></sub> powders, their specific surface area and density were studied using XRD, SEM, BET, gas pycnometry, and chemical analysis for carbon and oxygen content. It was established that the NbC<sub><em>y</em></sub> powders contain a large amount of impurity oxygen, the amount of which is proportional to their specific surface area, and part of it is present in the form of amorphous Nb<sub>2</sub>O<sub>5</sub>. The effect of the average particle size of the NbC<sub><em>y</em></sub> powder, the impurities present in it, especially oxygen, and the temperature of vacuum annealing up to 1400 °C on its chemical and phase composition, average particle size and morphology, as well as density was studied. It was found that most of the oxygen contained in the powders reacts with NbC<sub><em>y</em></sub> upon heating in vacuum, forming niobium oxides. At higher temperatures, these oxides are reduced by carbon from NbC<sub><em>y</em></sub>. This process alters both the stoichiometry <em>y</em> and the phase composition of the powder. Heating of the nanocrystalline powders in vacuum to 1200 °C and above turns them into microcrystalline powders.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115147"},"PeriodicalIF":3.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study reveals the synergistic degradation mechanism between surface oxide layer and interface diffusion barrier in CrSi (7.7 at.% Si) coatings during 1–8 h oxidation in 1200 °C steam. Initially (0–1 h), a dense Cr2O3/SiO2 duplex layer develops on the surface, while a stoichiometric Zr2Si diffusion barrier develops at the interface, providing optimal protection. During 2–6 h, Si depletion causes the transformation of subsurface SiO2 from continuous to discrete particles and triggers Zr-rich phase precipitation within the Zr2Si layer, leading to progressive performance degradation. At the failure stage (7–8 h), following the breakdown of the Zr2Si diffusion barrier, ZrO2 networks form and serve as short-circuit paths, which significantly accelerate oxygen transport to the substrate.
{"title":"Oxidation behavior and synergistic surface-interface degradation mechanism of CrSi coatings in 1200 °C steam","authors":"Song Zeng, Chang Jiang, Youxing He, Yiyou Wu, Xuebing Yang, Jiuming Yu, Linwei Zhang, Wenfu Chen","doi":"10.1016/j.vacuum.2026.115143","DOIUrl":"10.1016/j.vacuum.2026.115143","url":null,"abstract":"<div><div>This study reveals the synergistic degradation mechanism between surface oxide layer and interface diffusion barrier in CrSi (7.7 at.% Si) coatings during 1–8 h oxidation in 1200 °C steam. Initially (0–1 h), a dense Cr<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> duplex layer develops on the surface, while a stoichiometric Zr<sub>2</sub>Si diffusion barrier develops at the interface, providing optimal protection. During 2–6 h, Si depletion causes the transformation of subsurface SiO<sub>2</sub> from continuous to discrete particles and triggers Zr-rich phase precipitation within the Zr<sub>2</sub>Si layer, leading to progressive performance degradation. At the failure stage (7–8 h), following the breakdown of the Zr<sub>2</sub>Si diffusion barrier, ZrO<sub>2</sub> networks form and serve as short-circuit paths, which significantly accelerate oxygen transport to the substrate.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115143"},"PeriodicalIF":3.9,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1016/j.vacuum.2026.115141
Yue Wang , Chaofeng Sang , Jintao Wu , Nami Li , Yu Bian , Changjiang Sun , Mingzhou Zhang , Chen Zhang , Yao Peng , Chongyang Jin , Yue Tian , Dezhen Wang
Linear plasma devices (LPDs) are important experimental platforms for investigating plasma–material interactions (PMI). In PMI experiments, it has been found that applying a target bias not only effectively modifies the incident ion energy, but also induces significant changes in the electron density and electron temperature, whereby the evolution of these plasma parameters is primarily governed by plasma transport processes. However, at present, the physical process and mechanism underlying such bias-induced variations remain unclear. In this work, biasing experiments under argon plasma discharge conditions were first carried out on the MPS-LD device. For the corresponding experiments, an electric potential model was newly developed based on the BOUT++ LPD module, enabling self-consistent simulations of plasma transport under biased conditions. Numerical simulations were then performed to reproduce the experimental results and to validate the accuracy of the proposed model. Finally, by combining experimental measurements with numerical simulations, a bias-voltage scan was performed to investigate how the electron density and electron temperature vary with the bias voltage (Ubias). The results show that applying negative bias decreases the target electron density (ne,T) while increasing the target electron temperature (Te,T). In contrast, positive bias increases both ne,T and Te,T; however, at high positive bias, ne,T first reaches a maximum and subsequently decreases with further increases in Ubias. The underlying physical mechanisms are analyzed using particle flux, momentum, and energy conservation. It indicates that the applied bias regulates the parallel electric field, thereby changing ion and electron velocities, and consequently affecting the electron density. At high positive bias, the ion velocity is further influenced by ion viscosity, leading to the reversal in ne,T. Meanwhile, the enhanced parallel electric field drives stronger currents, significantly increasing ion–electron frictional work and converting the input bias power into electron energy, which raises the electron temperature. These results contribute to a deeper understanding of the effects and mechanisms of biasing on plasma transport in the MPS-LD device.
{"title":"Experimental and simulation study of target biasing effects on plasma transport in linear plasma device MPS-LD","authors":"Yue Wang , Chaofeng Sang , Jintao Wu , Nami Li , Yu Bian , Changjiang Sun , Mingzhou Zhang , Chen Zhang , Yao Peng , Chongyang Jin , Yue Tian , Dezhen Wang","doi":"10.1016/j.vacuum.2026.115141","DOIUrl":"10.1016/j.vacuum.2026.115141","url":null,"abstract":"<div><div>Linear plasma devices (LPDs) are important experimental platforms for investigating plasma–material interactions (PMI). In PMI experiments, it has been found that applying a target bias not only effectively modifies the incident ion energy, but also induces significant changes in the electron density and electron temperature, whereby the evolution of these plasma parameters is primarily governed by plasma transport processes. However, at present, the physical process and mechanism underlying such bias-induced variations remain unclear. In this work, biasing experiments under argon plasma discharge conditions were first carried out on the MPS-LD device. For the corresponding experiments, an electric potential model was newly developed based on the BOUT++ LPD module, enabling self-consistent simulations of plasma transport under biased conditions. Numerical simulations were then performed to reproduce the experimental results and to validate the accuracy of the proposed model. Finally, by combining experimental measurements with numerical simulations, a bias-voltage scan was performed to investigate how the electron density and electron temperature vary with the bias voltage (<em>U</em><sub><em>bias</em></sub>). The results show that applying negative bias decreases the target electron density (<em>n</em><sub><em>e,T</em></sub>) while increasing the target electron temperature (<em>T</em><sub><em>e,T</em></sub>). In contrast, positive bias increases both <em>n</em><sub><em>e,T</em></sub> and <em>T</em><sub><em>e,T</em></sub>; however, at high positive bias, <em>n</em><sub><em>e,T</em></sub> first reaches a maximum and subsequently decreases with further increases in <em>U</em><sub><em>bias</em></sub>. The underlying physical mechanisms are analyzed using particle flux, momentum, and energy conservation. It indicates that the applied bias regulates the parallel electric field, thereby changing ion and electron velocities, and consequently affecting the electron density. At high positive bias, the ion velocity is further influenced by ion viscosity, leading to the reversal in <em>n</em><sub><em>e,T</em></sub>. Meanwhile, the enhanced parallel electric field drives stronger currents, significantly increasing ion–electron frictional work and converting the input bias power into electron energy, which raises the electron temperature. These results contribute to a deeper understanding of the effects and mechanisms of biasing on plasma transport in the MPS-LD device.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115141"},"PeriodicalIF":3.9,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1016/j.vacuum.2026.115135
Jinyin Fu , Libo Zhou , Zhou Li , Cong Li , Minbo Wang , Jian Chen
In this study, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloy was fabricated using laser powder bed fusion. By analyzing the printing quality and mechanical properties of TC11 alloy printed under different process parameters, an optimum processing window (laser power of 200 W, laser scanning speed of 1100 mm/s) was identified. Under the optimal process parameters, the sample achieved a relative density of 99.6 % and excellent mechanical properties (Ultimate Tensile Strength of 1331 ± 11 MPa, Yield Strength of 1004 ± 13 MPa and Elongation of 12.1 ± 1.2 %). After heat-treated at 900 °C, the sample exhibited an equiaxed α phase and thin film β phase with the elongation increasing by approximately 39.3 % (from 12.1 ± 1.2 % to 16.8 ± 0.6 %), while the yield strength (996 ± 1 MPa) remained at the as-built level. The enhanced ductility of the heat-treated sample is attributed to three key factors: the decreased low-angle grain boundaries which minimizes stress concentration during deformation, the reduced α′ martensite with thin-film β-phase formation (coordinating plastic flow via a ductile phase), and the improved α-β crystallographic coincidence with reduced lattice distortion, lowering interfacial stress and promoting slip transmission.
{"title":"Microstructure and mechanical properties of titanium alloy via laser powder bed fusion and heat treatment","authors":"Jinyin Fu , Libo Zhou , Zhou Li , Cong Li , Minbo Wang , Jian Chen","doi":"10.1016/j.vacuum.2026.115135","DOIUrl":"10.1016/j.vacuum.2026.115135","url":null,"abstract":"<div><div>In this study, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloy was fabricated using laser powder bed fusion. By analyzing the printing quality and mechanical properties of TC11 alloy printed under different process parameters, an optimum processing window (laser power of 200 W, laser scanning speed of 1100 mm/s) was identified. Under the optimal process parameters, the sample achieved a relative density of 99.6 % and excellent mechanical properties (Ultimate Tensile Strength of 1331 ± 11 MPa, Yield Strength of 1004 ± 13 MPa and Elongation of 12.1 ± 1.2 %). After heat-treated at 900 °C, the sample exhibited an equiaxed α phase and thin film β phase with the elongation increasing by approximately 39.3 % (from 12.1 ± 1.2 % to 16.8 ± 0.6 %), while the yield strength (996 ± 1 MPa) remained at the as-built level. The enhanced ductility of the heat-treated sample is attributed to three key factors: the decreased low-angle grain boundaries which minimizes stress concentration during deformation, the reduced α′ martensite with thin-film β-phase formation (coordinating plastic flow via a ductile phase), and the improved α-β crystallographic coincidence with reduced lattice distortion, lowering interfacial stress and promoting slip transmission.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115135"},"PeriodicalIF":3.9,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-27DOI: 10.1016/j.vacuum.2026.115142
Angel Regalado-Contreras , Jonathan Rosas-Alcántara , Karla Paola Valdez-Núñez , Mayra Cecilia Ramírez-Camacho , Wencel de la Cruz
p-type TiOx thin films have been fabricated using vacuum-based techniques at different deposition pressures, but no reproducible processing window has been established. Herein, TiOx thin films were deposited by laser ablation of a Ti target under O2 atmospheres at pressures ranging from 1.2 × 10−5 to 0.1 Torr. In vacuo X-ray Photoelectron Spectroscopy (XPS) revealed Ti4+/Ti3+ mixed valence below 10−2 Torr and exclusively Ti4+ above this threshold. Quantification based on Gaussian peak deconvolution revealed Ti4+ ranging from 20 to 30.6 at.%, Ti3+ from 10.1 to 1.5 at.%, and oxygen approximately constant at ∼69 at.%, with an uncertainty of ±5 %. The electrical properties were carrier concentrations from 2 × 1020 cm−3 (electrons) to 2 × 1016 cm−3 (holes), resistivity from 0.4 to 460 Ω cm, and mobility from 0.5 to 6 cm2 V−1 s−1. The films with mixed Ti valence were n-type and those with Ti4+ alone were p-type. Cathodoluminescence, in combination with XPS, revealed shallow acceptor levels mediating p-type conductivity, located at 0.32–0.36 eV above the VBM. Optically, average transmittance as high as 66 % on the visible spectrum (350–750 nm) was achieved. Surface morphology analyzed through atomic force microscopy revealed RMS roughness as low as 0.77 nm. Thin-Film-Transistors (TFT) were fabricated by photolithography. The output/transfer characteristics evolve from non-saturated/weak gate modulation to fully saturated/gate-controlled, consistent with TiOx channels exhibiting carrier concentrations on the order of 1019 to 1017 cm−3, respectively. This study advances the body of knowledge on semiconducting TiOx thin films and their reproducible integration into TFT with tunable performance.
{"title":"Carrier tuning in room temperature laser-ablated TiOx thin films: In vacuo X-ray photoelectron spectroscopy insights","authors":"Angel Regalado-Contreras , Jonathan Rosas-Alcántara , Karla Paola Valdez-Núñez , Mayra Cecilia Ramírez-Camacho , Wencel de la Cruz","doi":"10.1016/j.vacuum.2026.115142","DOIUrl":"10.1016/j.vacuum.2026.115142","url":null,"abstract":"<div><div>p-type TiO<sub>x</sub> thin films have been fabricated using vacuum-based techniques at different deposition pressures, but no reproducible processing window has been established. Herein, TiO<sub>x</sub> thin films were deposited by laser ablation of a Ti target under O<sub>2</sub> atmospheres at pressures ranging from 1.2 × 10<sup>−5</sup> to 0.1 Torr. <em>In vacuo</em> X-ray Photoelectron Spectroscopy (XPS) revealed Ti<sup>4+</sup>/Ti<sup>3+</sup> mixed valence below 10<sup>−2</sup> Torr and exclusively Ti<sup>4+</sup> above this threshold. Quantification based on Gaussian peak deconvolution revealed Ti<sup>4+</sup> ranging from 20 to 30.6 at.%, Ti<sup>3+</sup> from 10.1 to 1.5 at.%, and oxygen approximately constant at ∼69 at.%, with an uncertainty of ±5 %. The electrical properties were carrier concentrations from 2 × 10<sup>20</sup> cm<sup>−3</sup> (electrons) to 2 × 10<sup>16</sup> cm<sup>−3</sup> (holes), resistivity from 0.4 to 460 Ω cm, and mobility from 0.5 to 6 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>. The films with mixed Ti valence were n-type and those with Ti<sup>4+</sup> alone were p-type. Cathodoluminescence, in combination with XPS, revealed shallow acceptor levels mediating p-type conductivity, located at 0.32–0.36 eV above the VBM. Optically, average transmittance as high as 66 % on the visible spectrum (350–750 nm) was achieved. Surface morphology analyzed through atomic force microscopy revealed RMS roughness as low as 0.77 nm. Thin-Film-Transistors (TFT) were fabricated by photolithography. The output/transfer characteristics evolve from non-saturated/weak gate modulation to fully saturated/gate-controlled, consistent with TiO<sub>x</sub> channels exhibiting carrier concentrations on the order of 10<sup>19</sup> to 10<sup>17</sup> cm<sup>−3</sup>, respectively. This study advances the body of knowledge on semiconducting TiO<sub>x</sub> thin films and their reproducible integration into TFT with tunable performance.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115142"},"PeriodicalIF":3.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents a water vapor-assisted solid-state sintering strategy to fabricate CsPbI3@SiO2 perovskite composites. Through high humidity and temperature, CsPbI3 nanocrystals are efficiently encapsulated within a SiO2 matrix, resulting in dramatically enhanced stability. The composite retains over 85 % of its initial luminescence after 360 days in ambient conditions and demonstrates excellent resistance to polar solvents and acids. Due to its high stability, the composite exhibits promising performance in white light-emitting diodes (WLEDs) and information encryption applications, providing a viable pathway toward practical perovskite-based devices.
{"title":"Vapor-assisted solid-state sintering of CsPbI3@SiO2 core-shell nanocrystals for enhanced environmental stability","authors":"Longxun Teng, Xin Li, Yuanxin Chunyu, Jiaxiang Liang, Xinyue Shao, Haiqing Sun, Xiaoyuan Zhan, Weiwei Zhang, Rui Liu, Jianxu Ding, Huiling Zhu","doi":"10.1016/j.vacuum.2026.115139","DOIUrl":"10.1016/j.vacuum.2026.115139","url":null,"abstract":"<div><div>This study presents a water vapor-assisted solid-state sintering strategy to fabricate CsPbI<sub>3</sub>@SiO<sub>2</sub> perovskite composites. Through high humidity and temperature, CsPbI<sub>3</sub> nanocrystals are efficiently encapsulated within a SiO<sub>2</sub> matrix, resulting in dramatically enhanced stability. The composite retains over 85 % of its initial luminescence after 360 days in ambient conditions and demonstrates excellent resistance to polar solvents and acids. Due to its high stability, the composite exhibits promising performance in white light-emitting diodes (WLEDs) and information encryption applications, providing a viable pathway toward practical perovskite-based devices.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115139"},"PeriodicalIF":3.9,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-23DOI: 10.1016/j.vacuum.2026.115128
Xiaokang Yang , Hongze Fang , Lingyan Zhou , Xianfei Ding , Fuxin Wang , Bobo Li , Baohui Zhu , Ruirun Chen
The influence of temperature gradient on the microstructure and high-temperature mechanical behavior of directionally solidified Ti-47Al-6Nb-0.1C-1.6Ta-0.8Hf alloys was systematically investigated. Columnar grain alignment and lamellar orientation improve with increasing power up to 45 kW, beyond which orientation dispersion and equiaxed grains emerge, driven by the stability of the solidification front and competitive β-dendrite growth. High temperature gradients enhance peritectic reaction kinetics, promoting α-variant selection, lamellar convergence, and suppression of residual β, whereas low gradients lead to dispersed lamellar structures. Elemental analysis reveals uniform hydrogen and oxygen distribution with minimal segregation, attributed to high-vacuum melting and rapid peritectic consumption of β. High-temperature tensile testing at 900 °C shows peak strength and ductility at 45 kW, correlated with effective dislocation blockage at B2/γ and γ/α2 interfaces, where high slip-energy barriers and controlled dislocation transmission mitigate local stress concentrations. These findings demonstrate that precise control of heating power and temperature gradient enables the optimization of microstructure, phase transformation, and high-temperature mechanical performance in TiAl alloys.
{"title":"Tailoring peritectic solidification and lamellar orientation in TiAl alloys through controlled heating power","authors":"Xiaokang Yang , Hongze Fang , Lingyan Zhou , Xianfei Ding , Fuxin Wang , Bobo Li , Baohui Zhu , Ruirun Chen","doi":"10.1016/j.vacuum.2026.115128","DOIUrl":"10.1016/j.vacuum.2026.115128","url":null,"abstract":"<div><div>The influence of temperature gradient on the microstructure and high-temperature mechanical behavior of directionally solidified Ti-47Al-6Nb-0.1C-1.6Ta-0.8Hf alloys was systematically investigated. Columnar grain alignment and lamellar orientation improve with increasing power up to 45 kW, beyond which orientation dispersion and equiaxed grains emerge, driven by the stability of the solidification front and competitive β-dendrite growth. High temperature gradients enhance peritectic reaction kinetics, promoting α-variant selection, lamellar convergence, and suppression of residual β, whereas low gradients lead to dispersed lamellar structures. Elemental analysis reveals uniform hydrogen and oxygen distribution with minimal segregation, attributed to high-vacuum melting and rapid peritectic consumption of β. High-temperature tensile testing at 900 °C shows peak strength and ductility at 45 kW, correlated with effective dislocation blockage at B2/γ and γ/α2 interfaces, where high slip-energy barriers and controlled dislocation transmission mitigate local stress concentrations. These findings demonstrate that precise control of heating power and temperature gradient enables the optimization of microstructure, phase transformation, and high-temperature mechanical performance in TiAl alloys.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115128"},"PeriodicalIF":3.9,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号