Vacuum最新文献

英文中文

Self-forming LaF3-Ti-MoS2/Ti-DLC nanomultilayer films for excellent atmospheric-vacuum alternating tribological performance

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-02-01 DOI: 10.1016/j.vacuum.2025.114099

Yaxin Zhang , Yongqi Zhu , Shifan Ju , Hongxuan Li , Pengfei Ju , Jingzhou Liu , Wenge Fan , Chufeng Sun , Xiaohong Liu , Xingping Luo , Jia Li , Li Ji

Spacecraft components need to fulfill requirements for low friction and long service life in alternating atmospheric-vacuum environments. In this study, based on the lubricating characters of LaF₃-Ti-MoS₂ in vacuum and Ti-DLC in the atmospheric environment, LaF₃-Ti-MoS₂/Ti-DLC(MTLC) multilayer films are designed and self-formed by controlling the residence time of the sample at the target position in magnetron sputtering process. The effect of rotational speed on the microstructure, mechanical properties, and tribological performance of the MTLC films are systematically investigated. The multilayer structure exhibits excellent mechanical properties at the rotational speed of 0.5 rpm, which allows the MTLC films to achieve a lifespan exceeding 2 × 10⁵ laps in alternating atmospheric-vacuum environments. Transmission electron microscope(TEM) results suggest the environmentally adaptive mechanism is that the LaF₃-Ti-MoS₂ layer acts effective in vacuum and the Ti-DLC layer acts effective in atmosphere. This dynamic interplay between the layers contributes to the prolonged lifespan of the films in these alternating environments, highlighting their potential for various space applications.

{"title":"Self-forming LaF3-Ti-MoS2/Ti-DLC nanomultilayer films for excellent atmospheric-vacuum alternating tribological performance","authors":"Yaxin Zhang , Yongqi Zhu , Shifan Ju , Hongxuan Li , Pengfei Ju , Jingzhou Liu , Wenge Fan , Chufeng Sun , Xiaohong Liu , Xingping Luo , Jia Li , Li Ji","doi":"10.1016/j.vacuum.2025.114099","DOIUrl":"10.1016/j.vacuum.2025.114099","url":null,"abstract":"<div><div>Spacecraft components need to fulfill requirements for low friction and long service life in alternating atmospheric-vacuum environments. In this study, based on the lubricating characters of LaF<sub>3</sub>-Ti-MoS<sub>2</sub> in vacuum and Ti-DLC in the atmospheric environment, LaF<sub>3</sub>-Ti-MoS<sub>2</sub>/Ti-DLC(MTLC) multilayer films are designed and self-formed by controlling the residence time of the sample at the target position in magnetron sputtering process. The effect of rotational speed on the microstructure, mechanical properties, and tribological performance of the MTLC films are systematically investigated. The multilayer structure exhibits excellent mechanical properties at the rotational speed of 0.5 rpm, which allows the MTLC films to achieve a lifespan exceeding 2 × 10<sup>5</sup> laps in alternating atmospheric-vacuum environments. Transmission electron microscope(TEM) results suggest the environmentally adaptive mechanism is that the LaF<sub>3</sub>-Ti-MoS<sub>2</sub> layer acts effective in vacuum and the Ti-DLC layer acts effective in atmosphere. This dynamic interplay between the layers contributes to the prolonged lifespan of the films in these alternating environments, highlighting their potential for various space applications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114099"},"PeriodicalIF":3.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143265951","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

Design status of the vacuum system of IFMIF-DONES particle accelerator

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-31 DOI: 10.1016/j.vacuum.2025.114091

César Caballero Pérez , Marcelo Juni Ferreira , Volker Hauer , Iván Podadera , Anderson Sabogal , Daniel Sánchez Herranz , Claudio Torregrosa

The International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES) will be an installation capable of qualifying materials for use in future fusion power reactors. To do so, a linear accelerator will deliver high-intensity deuteron beam to a liquid Li loop, creating a flow of neutrons that will produce material damage equivalent to that expected in a fusion reactor. The vacuum system must maintain high vacuum conditions during operation with high reliability. For this reason, a careful study of the vacuum has been assessed and implemented in the accelerator project. Vacuum simulations have been performed in order to have a first estimation of the expected pressure profile, and documentation is being produced to standardize the subsystem. Additionally, valuable knowledge from the prototype installation, IFMIF/Engineering Design and Engineering Validation Activities (EVEDA), is being taking into account in engineering design activities. Moreover, two vacuum related prototypes are being manufactured; the Multipurpose Vacuum Accident Scenarios (MuVacAS) prototype will enable experimental studies of air inrush in the last section of the accelerator; and the Quick Disconnecting System (QDS) prototype is being developed to study the feasibility of the remote handling of the interface located between the accelerator beam line and the target chamber. The paper presents the status of the design of the vacuum subsystem of the accelerator and discusses the future challenges.

{"title":"Design status of the vacuum system of IFMIF-DONES particle accelerator","authors":"César Caballero Pérez , Marcelo Juni Ferreira , Volker Hauer , Iván Podadera , Anderson Sabogal , Daniel Sánchez Herranz , Claudio Torregrosa","doi":"10.1016/j.vacuum.2025.114091","DOIUrl":"10.1016/j.vacuum.2025.114091","url":null,"abstract":"<div><div>The International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES) will be an installation capable of qualifying materials for use in future fusion power reactors. To do so, a linear accelerator will deliver high-intensity deuteron beam to a liquid Li loop, creating a flow of neutrons that will produce material damage equivalent to that expected in a fusion reactor. The vacuum system must maintain high vacuum conditions during operation with high reliability. For this reason, a careful study of the vacuum has been assessed and implemented in the accelerator project. Vacuum simulations have been performed in order to have a first estimation of the expected pressure profile, and documentation is being produced to standardize the subsystem. Additionally, valuable knowledge from the prototype installation, IFMIF/Engineering Design and Engineering Validation Activities (EVEDA), is being taking into account in engineering design activities. Moreover, two vacuum related prototypes are being manufactured; the Multipurpose Vacuum Accident Scenarios (MuVacAS) prototype will enable experimental studies of air inrush in the last section of the accelerator; and the Quick Disconnecting System (QDS) prototype is being developed to study the feasibility of the remote handling of the interface located between the accelerator beam line and the target chamber. The paper presents the status of the design of the vacuum subsystem of the accelerator and discusses the future challenges.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114091"},"PeriodicalIF":3.8,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143265945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of annealing temperature on microstructure, optical, and optoelectronic properties of Ga2O3:F-Nb films

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-31 DOI: 10.1016/j.vacuum.2025.114097

Xue Meng , Jinxiang Deng , Qing Zhang , Rui Wu , Kun Tian , Jiawei Xu , Weiman Liu , Xiaolei Yang , Ruidong Li

This study successfully prepared Ga₂O₃:F-Nb films using the dual-target radio frequency co-sputtering technique and systematically investigated the effects of annealing temperature on the microstructure, optical, and optoelectronic properties of the Ga₂O₃:F-Nb films. The optimal annealing temperature for the Ga₂O₃:F-Nb films was found to be 400 °C, at which their MSM devices exhibited better performance. Additionally, when the annealing temperature was ≥600 °C, substrate mismatch and significant F loss led to film cracking or degraded device performance. Introducing a Ga₂O₃ transition layer partially addressed the substrate mismatch issue and restored the photoelectric response of the device. As the annealing temperature increased, the films' optical band gap widened and their crystalline quality improved. This enhancement in crystallinity was attributed to the reduction of oxygen vacancies during annealing. This study provides data and new insights for the research of multi-element doped Ga₂O₃ materials.

{"title":"Effects of annealing temperature on microstructure, optical, and optoelectronic properties of Ga2O3:F-Nb films","authors":"Xue Meng , Jinxiang Deng , Qing Zhang , Rui Wu , Kun Tian , Jiawei Xu , Weiman Liu , Xiaolei Yang , Ruidong Li","doi":"10.1016/j.vacuum.2025.114097","DOIUrl":"10.1016/j.vacuum.2025.114097","url":null,"abstract":"<div><div>This study successfully prepared Ga<sub>2</sub>O<sub>3</sub>:F-Nb films using the dual-target radio frequency co-sputtering technique and systematically investigated the effects of annealing temperature on the microstructure, optical, and optoelectronic properties of the Ga<sub>2</sub>O<sub>3</sub>:F-Nb films. The optimal annealing temperature for the Ga<sub>2</sub>O<sub>3</sub>:F-Nb films was found to be 400 °C, at which their MSM devices exhibited better performance. Additionally, when the annealing temperature was ≥600 °C, substrate mismatch and significant F loss led to film cracking or degraded device performance. Introducing a Ga<sub>2</sub>O<sub>3</sub> transition layer partially addressed the substrate mismatch issue and restored the photoelectric response of the device. As the annealing temperature increased, the films' optical band gap widened and their crystalline quality improved. This enhancement in crystallinity was attributed to the reduction of oxygen vacancies during annealing. This study provides data and new insights for the research of multi-element doped Ga<sub>2</sub>O<sub>3</sub> materials.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114097"},"PeriodicalIF":3.8,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143265950","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 insights into the stability and mechanical properties of four typical tantalum carbides

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-31 DOI: 10.1016/j.vacuum.2025.114093

Guang Yang , WenYu Zhang , ShangYi Ma , YunFei Li , Tao Jiang , Yang Qi

From a first-principles perspective, the four typical tantalum carbides, TaC, Ta₂C, Ta₃C₂, and Ta₄C₃ are comprehensively investigated by calculating their formation energies, phase diagrams, Ta-C bonding strength, and mechanical properties, such as elastic modulus, ductile, and Vickers hardness. The Vickers hardnesses at finite temperatures were also predicted. Our calculations clearly show that the stabilities of the four tantalum carbides are highly temperature-dependent. Although Ta₃C₂ is slightly metastable at lower temperatures, it becomes stable above 1200 °C and lies ∼0.003 kJ/mol below convex hull. This may explain why it has been hardly reported in experiments. The calculations further indicate that the relative stability ranking of the four tantalum carbides significantly changes across four distinct temperature regions defined by three temperatures of ∼415 K, ∼855 K, and ∼1165 K. Below ∼1165 K, Ta₄C₃ is the most stable phase. Although TaC is least stable below ∼415 K, its stability step-wisely increases in the four temperature regions and becomes the most stable phase above ∼1165 K. The Ta₂C, which seems to be ductile in our calculations, is least stable above ∼415 K due to its weaker Ta-C bonding. Our calculations provide comprehensive insights into the stability and mechanical properties of the four tantalum carbides.

{"title":"First-principles insights into the stability and mechanical properties of four typical tantalum carbides","authors":"Guang Yang , WenYu Zhang , ShangYi Ma , YunFei Li , Tao Jiang , Yang Qi","doi":"10.1016/j.vacuum.2025.114093","DOIUrl":"10.1016/j.vacuum.2025.114093","url":null,"abstract":"<div><div>From a first-principles perspective, the four typical tantalum carbides, TaC, Ta<sub>2</sub>C, Ta<sub>3</sub>C<sub>2</sub>, and Ta<sub>4</sub>C<sub>3</sub> are comprehensively investigated by calculating their formation energies, phase diagrams, Ta-C bonding strength, and mechanical properties, such as elastic modulus, ductile, and Vickers hardness. The Vickers hardnesses at finite temperatures were also predicted. Our calculations clearly show that the stabilities of the four tantalum carbides are highly temperature-dependent. Although Ta<sub>3</sub>C<sub>2</sub> is slightly metastable at lower temperatures, it becomes stable above 1200 °C and lies ∼0.003 kJ/mol below convex hull. This may explain why it has been hardly reported in experiments. The calculations further indicate that the relative stability ranking of the four tantalum carbides significantly changes across four distinct temperature regions defined by three temperatures of ∼415 K, ∼855 K, and ∼1165 K. Below ∼1165 K, Ta<sub>4</sub>C<sub>3</sub> is the most stable phase. Although TaC is least stable below ∼415 K, its stability step-wisely increases in the four temperature regions and becomes the most stable phase above ∼1165 K. The Ta<sub>2</sub>C, which seems to be ductile in our calculations, is least stable above ∼415 K due to its weaker Ta-C bonding. Our calculations provide comprehensive insights into the stability and mechanical properties of the four tantalum carbides.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114093"},"PeriodicalIF":3.8,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143265956","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

Calculation of the spray supply system characteristics for obtaining film material by spray-pyrolysis

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-30 DOI: 10.1016/j.vacuum.2025.114100

E.A. Pecherskaya, A.D. Semenov, T.O. Zinchenko, S.A. Gurin, S.V. Konovalov, M.D. Novichkov, A.E. Shepeleva, D.E. Tuzova

Mathematical models of the main characteristics of a spray atomizer have been developed, namely: dispersion characteristics that define the torch (the spray flow from the nozzle) as a certain set of particles of different sizes; distribution characteristics that reflect the profile of specific liquid flows across the torch cross-section; shape characteristics that allow determining the dimensions of the torch at a given distance from the sprayer. These characteristics have been calculated for a pneumatic nozzle and the calculation results have been compared with experimental data, which confirmed the adequacy of the developed models. Based on calculations, it was found that the spray droplet diameter distribution curve obeys the log-normal distribution, the median spray droplet diameter is 754 μm, the most common diameter is 249 μm. The average droplet evaporation time is about several minutes. A system of nonlinear differential equations for the motion of aerosol particles in a spray torch was obtained, which made it possible to determine its parameters. When deriving the equations, the following assumptions were made: aerosol particles have a spherical shape, the particles move at low Reynolds numbers, and the drag force is determined by the Stokes formula. As a result of the numerical solution of the nonlinear equations system, an equation for calculating the distance of a spray droplet movement in the direction perpendicular to the torch axis, which made it possible to estimate the law of the torch spray density distribution was found. The effect of the spray torch parameters (torch height and spray angle) on the type of irrigation curves was revealed. The obtained results are in good agreement with the experimental data obtained by the authors of the article, as well as with the results given in scientific sources. A technological and functional scheme for obtaining transparent conductive thin films is proposed.

{"title":"Calculation of the spray supply system characteristics for obtaining film material by spray-pyrolysis","authors":"E.A. Pecherskaya, A.D. Semenov, T.O. Zinchenko, S.A. Gurin, S.V. Konovalov, M.D. Novichkov, A.E. Shepeleva, D.E. Tuzova","doi":"10.1016/j.vacuum.2025.114100","DOIUrl":"10.1016/j.vacuum.2025.114100","url":null,"abstract":"<div><div>Mathematical models of the main characteristics of a spray atomizer have been developed, namely: dispersion characteristics that define the torch (the spray flow from the nozzle) as a certain set of particles of different sizes; distribution characteristics that reflect the profile of specific liquid flows across the torch cross-section; shape characteristics that allow determining the dimensions of the torch at a given distance from the sprayer. These characteristics have been calculated for a pneumatic nozzle and the calculation results have been compared with experimental data, which confirmed the adequacy of the developed models. Based on calculations, it was found that the spray droplet diameter distribution curve obeys the log-normal distribution, the median spray droplet diameter is 754 μm, the most common diameter is 249 μm. The average droplet evaporation time is about several minutes. A system of nonlinear differential equations for the motion of aerosol particles in a spray torch was obtained, which made it possible to determine its parameters. When deriving the equations, the following assumptions were made: aerosol particles have a spherical shape, the particles move at low Reynolds numbers, and the drag force is determined by the Stokes formula. As a result of the numerical solution of the nonlinear equations system, an equation for calculating the distance of a spray droplet movement in the direction perpendicular to the torch axis, which made it possible to estimate the law of the torch spray density distribution was found. The effect of the spray torch parameters (torch height and spray angle) on the type of irrigation curves was revealed. The obtained results are in good agreement with the experimental data obtained by the authors of the article, as well as with the results given in scientific sources. A technological and functional scheme for obtaining transparent conductive thin films is proposed.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114100"},"PeriodicalIF":3.8,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143265623","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 discontinuous change in the anode potential drop in a helium glow discharge with a cylindrical hollow cathode

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-29 DOI: 10.1016/j.vacuum.2025.114095

Zijia Chu , Kurban M. Rabadanov , Aleksandr M. Astafiev , Anatoly A. Kudryavtsev , Jingfeng Yao , Chengxun Yuan , Xiangbao Lyu , Zhongxiang Zhou

Experimental and numerical investigations of a DC glow discharge in helium, operating between a cylindrical hollow cathode and a flat anode, were conducted in a 25 mm diameter tube with a 25 mm interelectrode gap. Experimentally, it was found that at a gas pressure of 2.6 Torr, an intense glow appears near the anode surface, which intensifies with increasing pressure. Probe measurements of the potential between the anode and the probe revealed a sharp potential drop when the pressure increased from 2.4 Torr to 2.6 Torr. Numerical calculations showed that as the gas pressure rises, the excitation reaction rate of the helium resonant level decreases in the interelectrode space, but increases near the anode. At a pressure of 4 Torr, the excitation reaction rate at the anode surface becomes an order of magnitude higher than in the region between the cathode and anode. Additionally, the numerical calculations indicated that under the conditions considered, the electric field near the anode is always positive, leading to a positive anode potential drop.

{"title":"Investigation of the discontinuous change in the anode potential drop in a helium glow discharge with a cylindrical hollow cathode","authors":"Zijia Chu , Kurban M. Rabadanov , Aleksandr M. Astafiev , Anatoly A. Kudryavtsev , Jingfeng Yao , Chengxun Yuan , Xiangbao Lyu , Zhongxiang Zhou","doi":"10.1016/j.vacuum.2025.114095","DOIUrl":"10.1016/j.vacuum.2025.114095","url":null,"abstract":"<div><div>Experimental and numerical investigations of a DC glow discharge in helium, operating between a cylindrical hollow cathode and a flat anode, were conducted in a 25 mm diameter tube with a 25 mm interelectrode gap. Experimentally, it was found that at a gas pressure of 2.6 Torr, an intense glow appears near the anode surface, which intensifies with increasing pressure. Probe measurements of the potential between the anode and the probe revealed a sharp potential drop when the pressure increased from 2.4 Torr to 2.6 Torr. Numerical calculations showed that as the gas pressure rises, the excitation reaction rate of the helium resonant level decreases in the interelectrode space, but increases near the anode. At a pressure of 4 Torr, the excitation reaction rate at the anode surface becomes an order of magnitude higher than in the region between the cathode and anode. Additionally, the numerical calculations indicated that under the conditions considered, the electric field near the anode is always positive, leading to a positive anode potential drop.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114095"},"PeriodicalIF":3.8,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143205567","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

(HfNbZrTaW)C5 high entropy carbide ceramics by spark plasma sintering for shielding materials of spent fuels

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-29 DOI: 10.1016/j.vacuum.2025.114096

Penghui Lei , Xiaoyu Ji , Jiahao Chen , Yonghong Lu , Jie Qiu , Di Yun

For the transportation and storage of spent fuels, where significant levels of neutron and gamma radiation are encountered, shielding materials are essential. In this paper, a new type of (HfNbZrTaW)C₅ high-entropy carbide ceramics with face-centered cubic rock-salt structure was designed and prepared as an integrated shielding material for both neutron and gamma ray protection, intended to replace the existing lead and epoxy resin. A single-phase (HfNbZrTaW)C₅ pellet with the best oxidation resistance was synthesized at 1700 °C by spark plasma sintering (SPS), achieving a theoretical density of 98.51 % and a hardness value of 25.28 GPa. Incorporating 10 wt % ZrB₂ into (HfNbZrTaW)C₅ ceramic sintered at 1700 °C can significantly enhance its the neutron absorption capacity, thermal conductivity, and oxidation resistance, positioning it as a potential integrated shielding material for spent nuclear fuels.

引用次数: 0

DFT study on phase stability of CrB, MoB, and WB in α, β phases, and CrB2, MoB2, and WB2 in hP6 phase

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-29 DOI: 10.1016/j.vacuum.2025.114094

B.O. Mnisi

Transition metal borides are promising materials commonly used in high-temperature structural applications. This study examines the structural, mechanical, vibrational, and electronic properties of MB (M represents Cr, Mo, or W and B is Boron) in both α and β phases, as well as MB₂ compounds in the hP6 phase. These analyses were conducted using first-principles density functional theory calculations to evaluate their suitability for high-temperature structural applications. It was determined that the CrB, MoB, and WB compounds in α and β phases, as well as CrB₂, MoB₂, and WB₂ in the hP6 phase, exhibit thermodynamic stability due to their negative heat of formation. The elastic constants of all the phases demonstrate mechanical stability. The Vickers hardness results indicate that all compounds are hard, with WB₂ (40.16 GPa) classified as superhard. Phonon dispersion curves confirm the dynamic stability of all compounds. Additionally, all compounds exhibit metallic characteristics due to the overlap between the valence and conduction bands at the Fermi energy level. These materials demonstrate thermodynamic, mechanical, and dynamic stability, making them suitable for high-temperature structural applications such as gas turbine engines and aerospace. In addition, WB₂ can be used in machining industries such as grinding or cutting soft materials.

{"title":"DFT study on phase stability of CrB, MoB, and WB in α, β phases, and CrB2, MoB2, and WB2 in hP6 phase","authors":"B.O. Mnisi","doi":"10.1016/j.vacuum.2025.114094","DOIUrl":"10.1016/j.vacuum.2025.114094","url":null,"abstract":"<div><div>Transition metal borides are promising materials commonly used in high-temperature structural applications. This study examines the structural, mechanical, vibrational, and electronic properties of MB (M represents Cr, Mo, or W and B is Boron) in both α and β phases, as well as MB<sub>2</sub> compounds in the hP6 phase. These analyses were conducted using first-principles density functional theory calculations to evaluate their suitability for high-temperature structural applications. It was determined that the CrB, MoB, and WB compounds in α and β phases, as well as CrB<sub>2</sub>, MoB<sub>2</sub>, and WB<sub>2</sub> in the hP6 phase, exhibit thermodynamic stability due to their negative heat of formation. The elastic constants of all the phases demonstrate mechanical stability. The Vickers hardness results indicate that all compounds are hard, with WB<sub>2</sub> (40.16 GPa) classified as superhard. Phonon dispersion curves confirm the dynamic stability of all compounds. Additionally, all compounds exhibit metallic characteristics due to the overlap between the valence and conduction bands at the Fermi energy level. These materials demonstrate thermodynamic, mechanical, and dynamic stability, making them suitable for high-temperature structural applications such as gas turbine engines and aerospace. In addition, WB<sub>2</sub> can be used in machining industries such as grinding or cutting soft materials.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"234 ","pages":"Article 114094"},"PeriodicalIF":3.8,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143205565","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

In situ XPS analysis of surface transformations in activated Ti-Zr-V thin films by nitrogen venting

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-29 DOI: 10.1016/j.vacuum.2025.114089

Xiaopeng Xu, Tao Guo, Xinyu Jin, Wenjing Ma, Heting Li, Le Fan, Yuanzhi Hong, Sihui Wang

Non-evaporable getter (NEG) films have become critical for fourth-generation diffraction-limited storage ring vacuum systems. Repeated venting-activation cycles lead to reduced pumping performance and saturation of the film's absorptive capacity; therefore, it is necessary to minimize the number of activations by protecting or storing the film. In this study, NEG films were deposited on oxygen-free copper substrates using pulsed magnetron sputtering. The microstructure, surface morphology, and phase composition were analyzed. The X-ray photoelectron spectroscopy was employed to investigate the activation characteristics and the evolution of the chemical valence states of the NEG film's surface before and after nitrogen venting. The results indicate that the activated films form oxides and nitrides following initial nitrogen venting at room temperature. Compared to oxygen molecules, the reaction of the film with nitrogen molecules is insufficient, resulting in the formation of only a small quantity of nitrides. After nitrogen venting, the surface of the activated films retains a high proportion of zero-valent metals, exhibiting numerous active surface sites. An extended nitrogen venting period did not lead to a significant increase in oxide and nitride content, indicating that the film had not deteriorated further. These findings suggest the potential use of nitrogen for film protection and storage.

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Editorial Board and Vacuum units

IF 3.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Vacuum

Pub Date : 2025-01-28 DOI: 10.1016/S0042-207X(25)00059-4

引用次数: 0

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