Pub Date : 2026-01-31DOI: 10.1016/j.vacuum.2026.115150
Bohang Yang , Jie Yu , Chenxiang Jin , Ling Zhang , Huihui Wang , Shengzhi Hao
A novel preparation technique of block cathode used for high current pulsed electron beam (HCPEB) emission was essayed. Through the sedimentation of short carbon fibers (SCF) of length 6 mm and adhesion of phenol formaldehyde resin (PFR) of concentration from 6 to 24 wt%, the discrete SCF could be integrated randomly and constituted a desirable structure. The microstructure of cathode was investigated by using X-ray microscopy (XRM) and scanning electron microscopy (SEM). The results showed that a stacked network of SCF was formed homogenously without the bundling phenomena. The carbonized PFR was found at the intersections of SCF. With the PFR of 24 wt%, the severe agglomeration was noticed with an appearance of spheres. The density of cathode increased with the content of SCF and PFR, as well as its capacity of structure maintenance. Contrarily, the resistance rate and evacuation speed were ruined by the density of block cathode. Considering the working requirements, the optimized parameter was selected as the SCF of 6 g and PFR of 12 wt%. The cathode was tested by the HCPEB emission experiment and exhibited satisfactory performance, including the spot size, energy uniformity, emission stability and long-term durability performance.
{"title":"Preparation of block cathode through sedimentation process for high current pulsed electron beam emission","authors":"Bohang Yang , Jie Yu , Chenxiang Jin , Ling Zhang , Huihui Wang , Shengzhi Hao","doi":"10.1016/j.vacuum.2026.115150","DOIUrl":"10.1016/j.vacuum.2026.115150","url":null,"abstract":"<div><div>A novel preparation technique of block cathode used for high current pulsed electron beam (HCPEB) emission was essayed. Through the sedimentation of short carbon fibers (SCF) of length 6 mm and adhesion of phenol formaldehyde resin (PFR) of concentration from 6 to 24 wt%, the discrete SCF could be integrated randomly and constituted a desirable structure. The microstructure of cathode was investigated by using X-ray microscopy (XRM) and scanning electron microscopy (SEM). The results showed that a stacked network of SCF was formed homogenously without the bundling phenomena. The carbonized PFR was found at the intersections of SCF. With the PFR of 24 wt%, the severe agglomeration was noticed with an appearance of spheres. The density of cathode increased with the content of SCF and PFR, as well as its capacity of structure maintenance. Contrarily, the resistance rate and evacuation speed were ruined by the density of block cathode. Considering the working requirements, the optimized parameter was selected as the SCF of 6 g and PFR of 12 wt%. The cathode was tested by the HCPEB emission experiment and exhibited satisfactory performance, including the spot size, energy uniformity, emission stability and long-term durability performance.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115150"},"PeriodicalIF":3.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174071","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}
Two-dimensional (2D) transition metal dichalcogenides (TMDs) are of great interest for next-generation electronic and optoelectronic devices due to their unique band structures. Here, we report the synthesis of high-quality few-layer MoS2 films using the sodium chloride (NaCl)-assisted chemical vapor deposition (CVD) method. This approach enables growth at a reduced temperature of 650֯C, significantly lower than the conventional 850֯C. Structural and morphological characterizations performed using optical microscopy, SEM, TEM, synchrotron-based XRD, Raman spectroscopy, UV–Vis spectroscopy, and Rutherford backscattering spectrometry (RBS) confirm crystalline, uniform, and nearly defect-free films. The Raman A1g-E2g1 mode separation of ≈24.5 cm−1 and RBS measurements indicate ≤6 layers of MoS2. XRD and SAED analyses further confirm the predominantly single-crystalline nature with an interplanar spacing of 0.27 nm. To examine ion-beam induced structural and electronic properties modification in post-synthesis MoS2, the films were irradiated with 100 MeV Ni ions at fluences between 1 × 1011 and 1 × 1013 ions/cm2. UV–Vis spectra reveal systematic blue shifts in excitonic absorption peaks, corresponding to a ∼24 meV band gap increase. RBS analysis attributes these changes to sulfur deficiency induced by preferential sputtering, which generate compressive strain. This study demonstrates ion irradiation as an effective route for tailoring the optoelectronic properties of 2D MoS2.
{"title":"Tailoring band gap, structural, and optical properties of CVD-grown few-layer MoS2 via swift heavy-ion irradiation","authors":"Mayur Khan , Lara Gigli , Jasper Rikkert Plaisier , Romana Mikšová , Anna Macková , Devesh Kumar Avasthi , Ambuj Tripathi","doi":"10.1016/j.vacuum.2026.115151","DOIUrl":"10.1016/j.vacuum.2026.115151","url":null,"abstract":"<div><div>Two-dimensional (2D) transition metal dichalcogenides (TMDs) are of great interest for next-generation electronic and optoelectronic devices due to their unique band structures. Here, we report the synthesis of high-quality few-layer MoS<sub>2</sub> films using the sodium chloride (NaCl)-assisted chemical vapor deposition (CVD) method. This approach enables growth at a reduced temperature of 650֯C, significantly lower than the conventional 850֯C. Structural and morphological characterizations performed using optical microscopy, SEM, TEM, synchrotron-based XRD, Raman spectroscopy, UV–Vis spectroscopy, and Rutherford backscattering spectrometry (RBS) confirm crystalline, uniform, and nearly defect-free films. The Raman A<sub>1g</sub>-E<sub>2g</sub><sup>1</sup> mode separation of ≈24.5 cm<sup>−1</sup> and RBS measurements indicate ≤6 layers of MoS<sub>2</sub>. XRD and SAED analyses further confirm the predominantly single-crystalline nature with an interplanar spacing of 0.27 nm. To examine ion-beam induced structural and electronic properties modification in post-synthesis MoS<sub>2</sub>, the films were irradiated with 100 MeV Ni ions at fluences between 1 × 10<sup>11</sup> and 1 × 10<sup>13</sup> ions/cm<sup>2</sup>. UV–Vis spectra reveal systematic blue shifts in excitonic absorption peaks, corresponding to a ∼24 meV band gap increase. RBS analysis attributes these changes to sulfur deficiency induced by preferential sputtering, which generate compressive strain. This study demonstrates ion irradiation as an effective route for tailoring the optoelectronic properties of 2D MoS<sub>2</sub>.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115151"},"PeriodicalIF":3.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174099","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 : 2026-01-31DOI: 10.1016/j.vacuum.2026.115140
Yongning Ma , Yesong Liang , Mingyuan Guo , Enzhou Liu , Xiaolong Li
Photocatalytic cathodic protection (PCP) offers a sustainable alternative to sacrificial anodes by eliminating anode consumption. In this work, Ag nanoparticle-loaded nitrogen-defective (CNv) and carbon-defective (CvN) g-C3N4 were synthesized for steel protection. Characterization confirmed the uniform loading of Ag nanoparticles on the defective structures. Notably, the 0.5%AgCvN composite exhibited superior anti-corrosion performance, evidenced by the lowest surface roughness and corrosion rate (4.7 g m−2·year−1), which is only 17.3% of that of bare steel (27.2 g m−2·year−1). EPR and PL analyses reveal that carbon vacancies serve as effective hole traps to suppress the recombination rate of charge carriers, and Ag nanoparticles facilitate electron migration via the Schottky barrier. Furthermore, Mott-Schottky analysis demonstrates that the 0.5%AgCvN possesses the most negative conduction band potential (−1.25 eV), endowing it with a stronger reducing power. The efficient migration of photoexcited electrons to the steel surface effectively suppresses anodic corrosion processes by providing cathodic protection. This study thus offers a promising strategy for the development of high-performance photocatalytic anti-corrosion materials.
光催化阴极保护（PCP）通过消除阳极消耗，为牺牲阳极提供了一种可持续的替代方案。本文合成了载氮缺陷（CNv）和载碳缺陷（CvN）的Ag纳米粒子g-C3N4。表征证实了银纳米粒子在缺陷结构上的均匀加载。值得注意的是，0.5%AgCvN复合材料表现出优异的抗腐蚀性能，表面粗糙度和腐蚀速率最低（4.7 g m−2·year−1），仅为裸钢（27.2 g m−2·year−1）的17.3%。EPR和PL分析表明，碳空位是有效的空穴陷阱，可以抑制载流子的重组速率，银纳米粒子促进电子通过肖特基势垒迁移。此外，Mott-Schottky分析表明，0.5%AgCvN具有最负的导带电位（- 1.25 eV），使其具有更强的还原能力。光激发电子向钢表面的有效迁移通过提供阴极保护有效地抑制了阳极腐蚀过程。因此，本研究为开发高性能光催化防腐材料提供了一个有希望的策略。
{"title":"Photocatalytic anti-corrosion performance and mechanism investigation over Ag nanoparticles loaded defective g-C3N4","authors":"Yongning Ma , Yesong Liang , Mingyuan Guo , Enzhou Liu , Xiaolong Li","doi":"10.1016/j.vacuum.2026.115140","DOIUrl":"10.1016/j.vacuum.2026.115140","url":null,"abstract":"<div><div>Photocatalytic cathodic protection (PCP) offers a sustainable alternative to sacrificial anodes by eliminating anode consumption. In this work, Ag nanoparticle-loaded nitrogen-defective (CNv) and carbon-defective (CvN) g-C<sub>3</sub>N<sub>4</sub> were synthesized for steel protection. Characterization confirmed the uniform loading of Ag nanoparticles on the defective structures. Notably, the 0.5%AgCvN composite exhibited superior anti-corrosion performance, evidenced by the lowest surface roughness and corrosion rate (4.7 g m<sup>−2</sup>·year<sup>−1</sup>), which is only 17.3% of that of bare steel (27.2 g m<sup>−2</sup>·year<sup>−1</sup>). EPR and PL analyses reveal that carbon vacancies serve as effective hole traps to suppress the recombination rate of charge carriers, and Ag nanoparticles facilitate electron migration via the Schottky barrier. Furthermore, Mott-Schottky analysis demonstrates that the 0.5%AgCvN possesses the most negative conduction band potential (−1.25 eV), endowing it with a stronger reducing power. The efficient migration of photoexcited electrons to the steel surface effectively suppresses anodic corrosion processes by providing cathodic protection. This study thus offers a promising strategy for the development of high-performance photocatalytic anti-corrosion materials.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115140"},"PeriodicalIF":3.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174074","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 : 2026-01-31DOI: 10.1016/j.vacuum.2026.115152
Dianguo Ma , Xiaojun Zhang , Meng Wang , Wei Zhang , Yingmin Wang , Zhenya Song , Xiaogang You , Zhiqiang Song , Zhongkai Guo , Mingji Zong , Yanli Zhu , Lincai Zhang
A hard magnetic high-entropy alloy (HEA) Fe35Co20Ni5Pt15B25 was designed and prepared by a two-step process of melt-spinning and subsequent annealing in high vacuum conditions. A nanocomposite structure consisting of amorphous and fcc-(Fe, Co, Ni)Pt phases was obtained in as-quenched alloy, while a composite structure composing of nanoscaled L10-(Fe, Co, Ni)Pt and (Fe, Co, Ni)2B phases was created after an appropriate vacuum annealing. The annealed HEA exhibited hard magnetic properties. The coercivity (iHc), saturation magnetizations (Bs), remanence ratio (Mr/Ms), and the maximum energy product ((BH)max) of the annealed Fe35Co20Ni5Pt15B25 high-entropy alloy were in the ranges of 207.7–996.6 kA/m, 0.50–0.77 T, 0.64–0.70, and 18.3–21.7 kJ/m3, respectively. When the annealing temperature was increased, iHc firstly increased to a maximum value of 996.6 kA/m, and then decrease. The good hard magnetic property is due to the formation of homogeneous nanocomposite structure in the annealed HEA, leading to exchange couplings among the nano-sized hard L10-(Fe, Co, Ni)Pt and soft (Fe, Co, Ni)2B magnetic phases.
{"title":"Composition design and hard magnetic properties of high-entropy alloys","authors":"Dianguo Ma , Xiaojun Zhang , Meng Wang , Wei Zhang , Yingmin Wang , Zhenya Song , Xiaogang You , Zhiqiang Song , Zhongkai Guo , Mingji Zong , Yanli Zhu , Lincai Zhang","doi":"10.1016/j.vacuum.2026.115152","DOIUrl":"10.1016/j.vacuum.2026.115152","url":null,"abstract":"<div><div>A hard magnetic high-entropy alloy (HEA) Fe<sub>35</sub>Co<sub>20</sub>Ni<sub>5</sub>Pt<sub>15</sub>B<sub>25</sub> was designed and prepared by a two-step process of melt-spinning and subsequent annealing in high vacuum conditions. A nanocomposite structure consisting of amorphous and fcc-(Fe, Co, Ni)Pt phases was obtained in as-quenched alloy, while a composite structure composing of nanoscaled <em>L</em>1<sub>0</sub>-(Fe, Co, Ni)Pt and (Fe, Co, Ni)<sub>2</sub>B phases was created after an appropriate vacuum annealing. The annealed HEA exhibited hard magnetic properties. The coercivity (<sub>i</sub><em>H</em><sub>c</sub>), saturation magnetizations (<em>B</em><sub>s</sub>), remanence ratio (<em>M</em><sub>r</sub><em>/M</em><sub>s</sub>), and the maximum energy product ((<em>BH</em>)<sub>max</sub>) of the annealed Fe<sub>35</sub>Co<sub>20</sub>Ni<sub>5</sub>Pt<sub>15</sub>B<sub>25</sub> high-entropy alloy were in the ranges of 207.7–996.6 kA/m, 0.50–0.77 T, 0.64–0.70, and 18.3–21.7 kJ/m<sup>3</sup>, respectively. When the annealing temperature was increased, <sub>i</sub><em>H</em><sub>c</sub> firstly increased to a maximum value of 996.6 kA/m, and then decrease. The good hard magnetic property is due to the formation of homogeneous nanocomposite structure in the annealed HEA, leading to exchange couplings among the nano-sized hard <em>L</em>1<sub>0</sub>-(Fe, Co, Ni)Pt and soft (Fe, Co, Ni)<sub>2</sub>B magnetic phases.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115152"},"PeriodicalIF":3.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174101","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 : 2026-01-30DOI: 10.1016/j.vacuum.2026.115145
Rei Miyata , Naoto Oishi , Noriko Nitta
Porous structures develop on Ge surfaces under ion beam irradiation, owing to the self-organization of point defects. Porous structures have been explored for applications in electronic devices as electrode materials in lithium-ion batteries and as functional components in gas sensors. For these applications, precise control of the porous morphology is crucial to maximize the desired functionality and device performance. The size and morphology of such structures are influenced by various factors, including irradiation fluence, ion energy, and irradiation angle. We investigated the formation of porous structures on Ge surfaces under step irradiation conditions by systematically varying the irradiation parameters. Two-step irradiation is a process in which the irradiation conditions are modified between step 1 and step 2. At 0° angle of incidence, the number of step irradiations only had a minimal effect on the structure formation. However, at varying irradiation angles, the resulting structures were influenced by the step irradiation angle. Under angle-step irradiation with an increased fluence, structures with a combination of the effects of both irradiations were formed. These results demonstrate that step irradiation offers a practical route to finely tailor porous Ge morphologies, thereby enabling performance optimization for applications.
{"title":"Morphological changes in Ge surfaces induced by step ion beam irradiation","authors":"Rei Miyata , Naoto Oishi , Noriko Nitta","doi":"10.1016/j.vacuum.2026.115145","DOIUrl":"10.1016/j.vacuum.2026.115145","url":null,"abstract":"<div><div>Porous structures develop on Ge surfaces under ion beam irradiation, owing to the self-organization of point defects. Porous structures have been explored for applications in electronic devices as electrode materials in lithium-ion batteries and as functional components in gas sensors. For these applications, precise control of the porous morphology is crucial to maximize the desired functionality and device performance. The size and morphology of such structures are influenced by various factors, including irradiation fluence, ion energy, and irradiation angle. We investigated the formation of porous structures on Ge surfaces under step irradiation conditions by systematically varying the irradiation parameters. Two-step irradiation is a process in which the irradiation conditions are modified between step 1 and step 2. At 0° angle of incidence, the number of step irradiations only had a minimal effect on the structure formation. However, at varying irradiation angles, the resulting structures were influenced by the step irradiation angle. Under angle-step irradiation with an increased fluence, structures with a combination of the effects of both irradiations were formed. These results demonstrate that step irradiation offers a practical route to finely tailor porous Ge morphologies, thereby enabling performance optimization for applications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115145"},"PeriodicalIF":3.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174076","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 : 2026-01-30DOI: 10.1016/j.vacuum.2026.115149
Yulong Yang , Decheng An , Zhiyong Si , Wutao Yang , Wang Yue , Linlin Shi , Xian-Ming Zhang
Bi2Se3 topological insulator is a promising layer-structured thermoelectric compound, whose cleavage fracture behavior in in-plane direction restricts the assembly and reliability of power generation devices. Here we propose a universal bottom-up approach for designing and fabricating reliable Bi2Se3 thermoelectric power generator. The iodine-doped Bi2Se3 polycrystalline sample was synthesized via solvothermal and chemical-etching processes. The anion etching induced defect chemistry in Bi2Se3 was dominated via charged selenium vacancies, which results in the improved carrier concentration (∼1019 cm−3). Similar to “sister material” Bi2Te3, in-plane figure of merit zT value is higher than out-of-plane zT for the same composition Bi2Se3I0.01. We further employ the high-throughput screening and physical vapor deposition techniques to develop aluminum as an effective metallization layer for direct bonding to in-plane Bi2Se3I0.01. This thermally/mechanically stable and ohmic contact interface ensure the n-type Bi2Se3 single-leg to realize a conversion efficiency of 2.5 % under a temperature difference of 250 K. The present work points to a general paradigm for advancing anisotropic thermoelectric semiconductor devices.
{"title":"Bottom-up design and efficient synthesis of layer-structured thermoelectric materials for power generation: the case of Bi2Se3","authors":"Yulong Yang , Decheng An , Zhiyong Si , Wutao Yang , Wang Yue , Linlin Shi , Xian-Ming Zhang","doi":"10.1016/j.vacuum.2026.115149","DOIUrl":"10.1016/j.vacuum.2026.115149","url":null,"abstract":"<div><div>Bi<sub>2</sub>Se<sub>3</sub> topological insulator is a promising layer-structured thermoelectric compound, whose cleavage fracture behavior in in-plane direction restricts the assembly and reliability of power generation devices. Here we propose a universal bottom-up approach for designing and fabricating reliable Bi<sub>2</sub>Se<sub>3</sub> thermoelectric power generator. The iodine-doped Bi<sub>2</sub>Se<sub>3</sub> polycrystalline sample was synthesized via solvothermal and chemical-etching processes. The anion etching induced defect chemistry in Bi<sub>2</sub>Se<sub>3</sub> was dominated via charged selenium vacancies, which results in the improved carrier concentration (∼10<sup>19</sup> cm<sup>−3</sup>). Similar to “sister material” Bi<sub>2</sub>Te<sub>3</sub>, in-plane figure of merit <em>zT</em> value is higher than out-of-plane <em>zT</em> for the same composition Bi<sub>2</sub>Se<sub>3</sub>I<sub>0.01</sub>. We further employ the high-throughput screening and physical vapor deposition techniques to develop aluminum as an effective metallization layer for direct bonding to in-plane Bi<sub>2</sub>Se<sub>3</sub>I<sub>0.01</sub>. This thermally/mechanically stable and ohmic contact interface ensure the n-type Bi<sub>2</sub>Se<sub>3</sub> single-leg to realize a conversion efficiency of 2.5 % under a temperature difference of 250 K. The present work points to a general paradigm for advancing anisotropic thermoelectric semiconductor devices.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115149"},"PeriodicalIF":3.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174075","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.2026.115144
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}
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