IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-16 DOI: 10.1016/j.vacuum.2025.114754

Justin Hijam , Alok Kumar , Madhu Vadali , Pradipta Ghosh , Raghavan Ranganathan

{"title":"Robust method for surface modulation in Cu-Zn alloys via pulsed laser surface melting","authors":"Justin Hijam , Alok Kumar , Madhu Vadali , Pradipta Ghosh , Raghavan Ranganathan","doi":"10.1016/j.vacuum.2025.114754","DOIUrl":"10.1016/j.vacuum.2025.114754","url":null,"abstract":"<div><div>This study investigates the segregation behaviour of Zn in Cu-Zn brass during pulsed laser surface melting (pLSM), through a combination of experiments and molecular dynamics (MD) simulations. Understanding the segregation phenomena is critical for tailoring surface properties in alloys, which has significant implications for improving material performance in demanding applications. Starting from a Cu<sub>90</sub>Zn<sub>10</sub> random solid solution brass alloy, well-defined, Zn-rich annular regions that contain about 35 % Zn arise due to segregation during pLSM and subsequent solidification. MD simulations reveal that Zn atoms possess significantly higher mobility than Cu during both the melting and solidification stages, leading to pronounced surface segregation, corroborating experiments. This selective surface enrichment of Zn holds promise for enhancing corrosion resistance and surface hardness in brass alloys, paving way for further optimization of alloy compositions and laser processing parameters to achieve tailored surface properties in brasses and other alloy systems.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114754"},"PeriodicalIF":3.9,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145105847","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}

引用次数: 0

Wall morphology dependence of rare gas Knudsen diffusion in silica and graphite slit nanopore: A molecular dynamics study 稀有气体在二氧化硅和石墨狭缝纳米孔中Knudsen扩散的分子动力学研究

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-16 DOI: 10.1016/j.vacuum.2025.114756

Pierre Magnico

{"title":"Wall morphology dependence of rare gas Knudsen diffusion in silica and graphite slit nanopore: A molecular dynamics study","authors":"Pierre Magnico","doi":"10.1016/j.vacuum.2025.114756","DOIUrl":"10.1016/j.vacuum.2025.114756","url":null,"abstract":"<div><div>Gas/wall collision mechanisms play a key role in Knudsen diffusion process. In particular, the channel wall structure has a major influence in mass transfer. So, we investigate the influence of the wall roughness, anisotropy and porosity on the self-diffusion of helium and neon in nanochannels. Three materials are proposed: graphite and β-cristobalite and amorphous silica. The study makes it possible to analyze, in function of temperature, the correlation between 1/the ballistic/diffusion transition regime of the surface gas transfer, 2/the transition of the bouncing process to a linear increase of the bounce number with time and 3/the shape of the surface residence time distribution characterized by a Fréchet like distribution at short time and an exponential decay at long time. As concerns the amorphous SiO<sub>2</sub>, the bounce must be redefined owing to the transfer inside the material which is dominated by a cage effect. The anisotropy effect on collision process and Knudsen diffusion is analyzed by means of a tensorial computation of the tangential momentum accommodation coefficient and of the mean square displacement. Using the Langevin at the channel scale and the Arya model, the ballistic/diffusion transition time of the mean square displacement is related to the collision frequency and the collision number required for the velocity to be uncorrelated. A stochastic model confirms the molecular dynamics results with β-SiO<sub>2</sub> channel: The behavior of the Knudsen diffusion coefficient according to the Arrhenius law and the influence of collision frequency on transition time.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114756"},"PeriodicalIF":3.9,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106294","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}

引用次数: 0

Evaluation of the stability of ultra-thin TiN films for the suppression of surface flashover events in vacuum 超薄TiN薄膜在真空中抑制表面闪络事件的稳定性评价

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114751

Akio Ogura, Ryotaro Kakutani, Hiromitsu Nogi, Souichi Katagiri

{"title":"Evaluation of the stability of ultra-thin TiN films for the suppression of surface flashover events in vacuum","authors":"Akio Ogura, Ryotaro Kakutani, Hiromitsu Nogi, Souichi Katagiri","doi":"10.1016/j.vacuum.2025.114751","DOIUrl":"10.1016/j.vacuum.2025.114751","url":null,"abstract":"<div><div>The possibility of the occurrence of a discharge along the surface of an electrical insulator in a vacuum system limits the applicable maximum voltage and the degree of miniaturization. It has been shown that ultra-thin TiN coatings can suppress at least two factors in typical surface flashover events, but the stability of the slight conductivity of such films has not yet been investigated in detail. Therefore, we deposited ultra-thin TiN films on insulating alumina substrates and investigated the electric-field-, light-, and adsorption-induced changes in the conductivity. We found that TiN films with a thickness ≥1.2 nm lead to a significant reduction in the secondary electron emission yield, and that the surface conductivity is sufficiently low for a film thickness in the range 1.5–2.0 nm: here, a surface resistivity in the range 10<sup>9</sup>–10<sup>15</sup> Ω/sq. is obtained. We show that this type of coating is sensitive to exposure to light and ambient air, and that the conductivity has a square-root dependence on time. Such ultra-thin TiN films with a moderate suppression of the surface current may be used in accelerator tubes that rely on alumina insulators to support the high-voltage terminal.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114751"},"PeriodicalIF":3.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145105853","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}

引用次数: 0

Investigation of the impact of BN/graphite composite nozzles on arcjet thruster performance BN/石墨复合喷管对电弧推力器性能影响的研究

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114745

Yong Wang , Yangkai Zhu , Yongjie Ding , Jifei Ye

{"title":"Investigation of the impact of BN/graphite composite nozzles on arcjet thruster performance","authors":"Yong Wang , Yangkai Zhu , Yongjie Ding , Jifei Ye","doi":"10.1016/j.vacuum.2025.114745","DOIUrl":"10.1016/j.vacuum.2025.114745","url":null,"abstract":"<div><div>The use of the hot-start ignition method addresses the cathode erosion issue caused by traditional high-voltage ignition. However, the specific impulse of the thruster using krypton remains relatively low. To further enhance the specific impulse and thrust efficiency, this study proposes the boron nitride (BN)/graphite composite nozzle, which features different nozzle area ratios and groove structures. Research indicates that nozzles with a smaller area are preferable. A groove-free design offers better performance, while a groove design helps delay throat insulation failure, providing a longer service life. The optimal nozzle configuration F (area ratio: 81, with annular groove), demonstrated the best performance, with a maximum specific impulse of 78 ± 1.5 s, generating 43.4 ± 0.29 mN of thrust and 11.2 ± 0.14 % thrust efficiency at 101 W of power. Considering the trade-off between performance and lifespan, nozzle C (area ratio: 81, without annular groove) is also an optimal choice. Compared to the initial configuration (nozzle A), the optimal nozzles C and F achieved an increase in specific impulse by 11.5 %–27.9 % and thrust efficiency by 7.7 %–13.5 %.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114745"},"PeriodicalIF":3.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106235","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}

引用次数: 0

Redeposition-free dry etching of copper thin films using organic gas mixtures 使用有机气体混合物的铜薄膜无复位干蚀刻

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114743

Yoon Jae Cho, Ha Rin Song, Hong Ju Yang, Dae Han Won, Chee Won Chung

引用次数: 0

Optimized oxygen flux in sputtering amorphous Ga2O3 thin films enables high-performance solar-blind UV photodetectors 优化溅射非晶Ga2O3薄膜中的氧通量，实现高性能的太阳盲紫外光电探测器

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114748

Zihan Zhang , Anzhen Zhang , Qiyi Wan , Rui Qin , Xinyue Zhang , Weiwei Cao , Jiuhong Wang

{"title":"Optimized oxygen flux in sputtering amorphous Ga2O3 thin films enables high-performance solar-blind UV photodetectors","authors":"Zihan Zhang , Anzhen Zhang , Qiyi Wan , Rui Qin , Xinyue Zhang , Weiwei Cao , Jiuhong Wang","doi":"10.1016/j.vacuum.2025.114748","DOIUrl":"10.1016/j.vacuum.2025.114748","url":null,"abstract":"<div><div>This study systematically investigates the effect of oxygen flux on the optical properties of amorphous gallium oxide (a-Ga<sub>2</sub>O<sub>3</sub>) thin films deposited on SiO<sub>2</sub>/Si substrates via RF magnetron sputtering. Through comprehensive material characterization and device performance analysis, we elucidate the correlation between defect evolution (including oxygen vacancies and other intrinsic defects) and the resulting optoelectronic responses. Our findings reveal that oxygen vacancy concentration mainly influences the optical band gap. Although increasing oxygen flux significantly reduces the oxygen vacancy concentration, the overall defect density exhibits a nonlinear trend because additional defect states are concurrently introduced. Consequently, the device performance exhibits a nonlinear dependence on oxygen flux. The detector prepared under moderate oxygen flux conditions exhibits an ultra-high light-dark current ratio of up to 4 × 10<sup>5</sup> and a low dark current at the pA level. Furthermore, these devices demonstrate rapid response kinetics, with a rise time of 28.9 ms and a fall time of 0.9 ms. These changes are attributed to the interplay between defects and material properties. This study provides critical insights into the process development of high-performance a-Ga<sub>2</sub>O<sub>3</sub> solar-blind UV photodetectors.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114748"},"PeriodicalIF":3.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106234","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}

引用次数: 0

First-principles investigations of structural, electronic and optical properties of cubic and tetragonal IrO2 立方和四方IrO2结构、电子和光学性质的第一性原理研究

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114747

Nan Wang , Yonghua Duan , Lin Su , Lishi Ma , Ancang Yang , Linhui Su , Bo Huang , Mengnie Li

{"title":"First-principles investigations of structural, electronic and optical properties of cubic and tetragonal IrO2","authors":"Nan Wang , Yonghua Duan , Lin Su , Lishi Ma , Ancang Yang , Linhui Su , Bo Huang , Mengnie Li","doi":"10.1016/j.vacuum.2025.114747","DOIUrl":"10.1016/j.vacuum.2025.114747","url":null,"abstract":"<div><div>Owing to its unique electronic structure and outstanding catalytic performance, IrO<sub>2</sub> holds great potential for applications in energy conversion and storage technologies. In this work, first-principles calculations were employed to comprehensively investigate the electronic structures, phase stability and optical properties of both cubic and tetragonal IrO<sub>2</sub>, with the aim of uncovering their fundamental physical characteristics. The electronic structure analysis, including band structure, density of states, differential charge density, and Mulliken population, reveals that the O–Ir bonds in both cubic (C) and tetragonal (T) IrO<sub>2</sub> exhibit pronounced covalent characteristics, with stronger bonding observed in the tetragonal phase. Optical properties such as dielectric constant, reflectivity, and absorption coefficient were also analyzed. The dielectric constants <em>ε</em><sub>1</sub> (0) of cubic and tetragonal IrO<sub>2</sub> were found to be 29.500 and 36.212, respectively. Additionally, IrO<sub>2</sub> exhibits significant absorption in the ultraviolet (UR) region, and its absorption coefficient gradually decreases with increasing laser wavelength. These findings underscore the strong potential of IrO<sub>2</sub>, particularly its tetragonal phase-as a material for saturable absorbers in laser devices and as a cocatalyst for UR-driven photocatalysis applications, including water splitting and organic pollutant degradation.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114747"},"PeriodicalIF":3.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145105851","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}

引用次数: 0

Radiation tolerance of additively manufactured Ti6Al4V: Swelling resistance versus dislocation-mediated hardening under Au2+ ion irradiation 增材制造Ti6Al4V的辐射耐受性：Au2+离子辐照下的抗溶胀与位错介导硬化

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-15 DOI: 10.1016/j.vacuum.2025.114755

Chuan Lv , Luhang Yan , Ping Xu , Linfeng Ye , An Li , Lvjun Zhou

引用次数: 0

Surface characteristics and biological evaluation of TiO2 nanotubes fabricated on Ti6Al4V implant surface Ti6Al4V植入表面制备TiO2纳米管的表面特性及生物学评价

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-13 DOI: 10.1016/j.vacuum.2025.114742

Konduru Ashok Kumar Raju, Amit Biswas

{"title":"Surface characteristics and biological evaluation of TiO2 nanotubes fabricated on Ti6Al4V implant surface","authors":"Konduru Ashok Kumar Raju, Amit Biswas","doi":"10.1016/j.vacuum.2025.114742","DOIUrl":"10.1016/j.vacuum.2025.114742","url":null,"abstract":"<div><div>The significant focus of this research was to create the TiO<sub>2</sub> (Titanium dioxide) highly ordered nanotube arrays on a Ti6Al4V surface to improve surface roughness, antibacterial activity and biocompatibility for its use in biomedical applications. In this approach, the anodic oxidation process was carried out in the organic bath solution, which is composed of ethylene glycol, NH<sub>4</sub>F, and ultrapure water. The process was carried out at a constant voltage of 30 V under different anodic oxidation time durations of 3 h, 4 h, and 5 h. The surface roughness of the polished Ti6Al4V, TiO<sub>2</sub> 30 V 3 h, TiO<sub>2</sub> 30 V 4 h, and TiO<sub>2</sub> 30 V 5 h are 2.77 nm, 16.92 nm, 19.75 nm, and 22.01 nm respectively. The early-stage assessment of the antimicrobial efficacy of oxidized specimens was conducted quantitatively against Bacillus subtilis and Escherichia coli after a 24 h period of growth. The cell viability on different surfaces was investigated by MTT and adhesion assays, which revealed improved in vitro response to the crystalline nanotubes. Overall, this work demonstrates the importance of using multifunctional TiO<sub>2</sub> nanotubes to provide a synergistic impact on antibiofilm, antibacterial, and enhanced osseointegration.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114742"},"PeriodicalIF":3.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061059","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}

引用次数: 0

Oscillations of iodine LaB6 hollow cathode 碘LaB6空心阴极的振荡

IF 3.9 2区材料科学

Vacuum Pub Date : 2025-09-13 DOI: 10.1016/j.vacuum.2025.114744

Xin Li , Tianhang Meng , Zhongxi Ning , Hui Liu , Chao Sun , Yang Liu , Stepan I. Eliseev , Daren Yu

{"title":"Oscillations of iodine LaB6 hollow cathode","authors":"Xin Li , Tianhang Meng , Zhongxi Ning , Hui Liu , Chao Sun , Yang Liu , Stepan I. Eliseev , Daren Yu","doi":"10.1016/j.vacuum.2025.114744","DOIUrl":"10.1016/j.vacuum.2025.114744","url":null,"abstract":"<div><div>Iodine-fed electric propulsion systems have achieved significant technological progress in recent years, the operating range of these systems remains fundamentally limited by ampere level iodine compatible hollow cathode technology. Preliminary studies on discharge characteristics have found that LaB<sub>6</sub> hollow cathode is a potential strategy. In this study, a conventional LaB<sub>6</sub> hollow cathode made with iodine-resistant materials was designed and tested in an iodine-compatible vacuum facility. The waveform, bispectral characteristics, and dispersion relation of the iodine hollow cathode were obtained and compared with the estimated collision reaction frequency. We analyzed the potential reaction processes both inside and outside the cathode and assessed how oscillation affects the lifetime of the iodine hollow cathode. The results indicate that the chaotic low-frequency oscillations were the main oscillation mode affecting the performance of the iodine cathode, involving multiple reaction processes that interfere with each other. The oscillation inside the cathode was mainly affected by vibrational excitation and iodine molecular ionization, while the oscillation outside the cathode was affected primarily by processes such as neutral gas flow, excitation, ionization, dissociation, and ion transit-time instability. The overall oscillation of iodine cathode is a non-dominant unstable mode with uniform energy distribution. A single 27-h self-sustaining experiment found that low-frequency oscillation has a significant impact on the emitter and the orifice, thereby reducing the cathode lifetime. The main reaction process inside and outside the iodine cathode and the influence relationship between the reactions were understood by the oscillation characteristics. It provides a theoretical basis to improve the performance of the iodine hollow cathode in the future.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"242 ","pages":"Article 114744"},"PeriodicalIF":3.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057381","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}

引用次数: 0

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