This study numerically investigates a 915 MHz iplas-type MPCVD reactor. Electromagnetic analysis identified the TE10 mode in the annular waveguide and the TM012 mode in the resonant cavity, clarifying the slot antenna's magnetic coupling mechanism. Subsequently, multi-dimensional simulations were conducted on the iplas cavity. Firstly, a plasma simulation was carried out based on the phenomenological method, and it was found that there were limitations in characterizing the spatial variations. To more accurately simulate plasma spatial distribution, an innovative approach was adopted, which reasonably simplified the non-axisymmetric three-dimensional (3D) cavity into a two-dimensional (2D) axisymmetric structure, and a self-consistent pure hydrogen plasma simulation was then carried out. The results showed that, at a fixed power, an increase in pressure led to plasma contraction and an increase in electron number density; at a fixed pressure, an increase in power caused plasma expansion, and when exceeding the critical value, the central electron number density decreased. Three sets of process parameters were selected for simulation and experiment validation, verifying the accuracy of the simulation prediction results using this simplified structure. Under the simulated process conditions (30 kW-10.5 kPa), high-quality 6-inch polycrystalline diamond films were successfully deposited.
{"title":"Numerical simulation of plasma in a 915 MHz MPCVD reactor using a simplified 2D structure","authors":"Xue Liu, Cuiting Zhang, Xianyi Lv, Qiliang Wang, Liuan Li, Guangtian Zou","doi":"10.1016/j.vacuum.2026.115159","DOIUrl":"10.1016/j.vacuum.2026.115159","url":null,"abstract":"<div><div>This study numerically investigates a 915 MHz iplas-type MPCVD reactor. Electromagnetic analysis identified the TE<sub>10</sub> mode in the annular waveguide and the TM<sub>012</sub> mode in the resonant cavity, clarifying the slot antenna's magnetic coupling mechanism. Subsequently, multi-dimensional simulations were conducted on the iplas cavity. Firstly, a plasma simulation was carried out based on the phenomenological method, and it was found that there were limitations in characterizing the spatial variations. To more accurately simulate plasma spatial distribution, an innovative approach was adopted, which reasonably simplified the non-axisymmetric three-dimensional (3D) cavity into a two-dimensional (2D) axisymmetric structure, and a self-consistent pure hydrogen plasma simulation was then carried out. The results showed that, at a fixed power, an increase in pressure led to plasma contraction and an increase in electron number density; at a fixed pressure, an increase in power caused plasma expansion, and when exceeding the critical value, the central electron number density decreased. Three sets of process parameters were selected for simulation and experiment validation, verifying the accuracy of the simulation prediction results using this simplified structure. Under the simulated process conditions (30 kW-10.5 kPa), high-quality 6-inch polycrystalline diamond films were successfully deposited.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115159"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174108","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 : 2026-04-01Epub Date: 2026-02-04DOI: 10.1016/j.vacuum.2026.115161
Bilal Ahmed , Muhammad Bilal Tahir , Arafa A. Yagob , Mohja Jaouadi , Solima I. Yagoob
Acquiring hydride materials that are structurally stable, have good hydrogen absorption thermodynamics, and have several useful physical properties is still a major challenge for next-generation hydrogen storage methods. This study presents the inaugural full first-principles analysis of hitherto unexamined cubic CaX3H9 (X = Cr, Mn, Fe) hydrides, employing density functional theory inside the CASTEP framework. Structural optimization, negative formation enthalpies (−0.081 to −0.078 eV/atom), phonon dispersion without imaginary modes, and ab initio molecular dynamics simulations up to 800 K all show that they are thermodynamically, dynamically, and thermally stable. Calculations of the electronic structure show that substantial transition-metal 3d–H-1s hybridization causes inherent metallic behavior. This is also related to how hydrogen moves and how it can be reversed. Spin-polarized computations reveal unique magnetic ground states: CaCr3H9 and CaFe3H9 display ferromagnetism, but CaMn3H9 stabilizes in an antiferromagnetic arrangement. The elastic constant analysis shows that all of the compounds are mechanically stable. However, CaMn3H9 and CaFe3H9 are ductile (B/G > 2.2), whereas CaCr3H9 is brittle. Optical spectra show that the material absorbs a lot of light in the visible to UV range, mostly because of interband transitions between transition-metal d-states. This shows that the material has more optoelectronic functions. Most crucially, CaX3H9 hydrides store hydrogen well, with gravimetric capacities of 4.35, 4.24, and 4.19 wt% and volumetric capacities of 176.8–183.0 gH2 L−1 for CaX3H9 (X = Cr, Mn, Fe), respectively. They also have moderate desorption temperatures (521–538 K). These findings identify CaX3H9 as an innovative and adjustable category of perovskite-like hydrides that integrate structural stability, metallic conductivity, magnetic ordering, and effective hydrogen storage capabilities, presenting a viable foundation for enhanced solid-state hydrogen energy systems.
{"title":"Probing the structural, electronic, optical, magnetic and mechanical properties of CaX3H9 (X = Cr, Mn, Fe) hydrides towards next-generation hydrogen storage applications","authors":"Bilal Ahmed , Muhammad Bilal Tahir , Arafa A. Yagob , Mohja Jaouadi , Solima I. Yagoob","doi":"10.1016/j.vacuum.2026.115161","DOIUrl":"10.1016/j.vacuum.2026.115161","url":null,"abstract":"<div><div>Acquiring hydride materials that are structurally stable, have good hydrogen absorption thermodynamics, and have several useful physical properties is still a major challenge for next-generation hydrogen storage methods. This study presents the inaugural full first-principles analysis of hitherto unexamined cubic CaX<sub>3</sub>H<sub>9</sub> (X = Cr, Mn, Fe) hydrides, employing density functional theory inside the CASTEP framework. Structural optimization, negative formation enthalpies (−0.081 to −0.078 eV/atom), phonon dispersion without imaginary modes, and ab initio molecular dynamics simulations up to 800 K all show that they are thermodynamically, dynamically, and thermally stable. Calculations of the electronic structure show that substantial transition-metal 3d–H-1s hybridization causes inherent metallic behavior. This is also related to how hydrogen moves and how it can be reversed. Spin-polarized computations reveal unique magnetic ground states: CaCr<sub>3</sub>H<sub>9</sub> and CaFe<sub>3</sub>H<sub>9</sub> display ferromagnetism, but CaMn<sub>3</sub>H<sub>9</sub> stabilizes in an antiferromagnetic arrangement. The elastic constant analysis shows that all of the compounds are mechanically stable. However, CaMn<sub>3</sub>H<sub>9</sub> and CaFe<sub>3</sub>H<sub>9</sub> are ductile (B/G > 2.2), whereas CaCr<sub>3</sub>H<sub>9</sub> is brittle. Optical spectra show that the material absorbs a lot of light in the visible to UV range, mostly because of interband transitions between transition-metal d-states. This shows that the material has more optoelectronic functions. Most crucially, CaX<sub>3</sub>H<sub>9</sub> hydrides store hydrogen well, with gravimetric capacities of 4.35, 4.24, and 4.19 wt% and volumetric capacities of 176.8–183.0 gH<sub>2</sub> L<sup>−1</sup> for CaX<sub>3</sub>H<sub>9</sub> (X = Cr, Mn, Fe), respectively. They also have moderate desorption temperatures (521–538 K). These findings identify CaX<sub>3</sub>H<sub>9</sub> as an innovative and adjustable category of perovskite-like hydrides that integrate structural stability, metallic conductivity, magnetic ordering, and effective hydrogen storage capabilities, presenting a viable foundation for enhanced solid-state hydrogen energy systems.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115161"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174097","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 : 2026-04-01Epub Date: 2026-02-07DOI: 10.1016/j.vacuum.2026.115167
Maghfirah Jayalaksamana , Nanang Masruchin , Makhmudun Ainuri , Herman Marius Zendrato
Global environmental awareness has driven strategies to convert waste into high-value products in an eco-friendly manner. One approach involves utilizing sago pith waste (SPW), a by-product of sago starch extraction, to produce nanomaterials: microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). This study evaluates the efficiency of transforming SPW pretreated with alkaline hydrogen peroxide (AHP) using peracetic acid (PAA) and percitric acid (PCA) under autoclave and water bath heating. AHP pretreatment increases fiber accessibility by reacting SPW with a mixture of 5 wt% NaOH and 5 vol% H2O2 (1:1 v/v). PAA treatment reacts AHP-pretreated SPW with H2O2, CH3COOH, and H2O (50:30:20 v/v) at 121 °C and 0.1 MPa in an autoclave or 95 °C in a water bath for 60 min. PCA treatment follows the same temperature sequence using H2O2 and citric acid (1:1 v/v). It is found that PCA effectively oxidizes lignin and hydrolyzes cellulose, while the water bath prevents rapid H2O2 decomposition, allowing longer reaction time for acid ions with SPW fibers. PCA treatment under water bath heating produces cellulose with white color, high crystallinity (79%), uniform morphology (diameter 25.73 μm, length 86.47 μm), intact functional groups, estimated degree of polymerization (541.2), thermal stability (Tmax 361 °C), and oil- (2.32 g/g) and water-holding capacity (4.10 g/g) comparable to commercial MCC. The same treatment yields NCC with average diameter 16.33 nm and length 276.01 nm, stably dispersed in solution. These results demonstrate that water bath heat source can effectively serve as a sustainable source of simultaneous MCC and NCC production from SPW through to support eco-friendly manner compared to autoclave heat source.
{"title":"Comparative effects of peracetic and percitric acid treatments under autoclave and water bath heating on the structural transformation of cellulose sago pith waste","authors":"Maghfirah Jayalaksamana , Nanang Masruchin , Makhmudun Ainuri , Herman Marius Zendrato","doi":"10.1016/j.vacuum.2026.115167","DOIUrl":"10.1016/j.vacuum.2026.115167","url":null,"abstract":"<div><div>Global environmental awareness has driven strategies to convert waste into high-value products in an eco-friendly manner. One approach involves utilizing sago pith waste (SPW), a by-product of sago starch extraction, to produce nanomaterials: microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). This study evaluates the efficiency of transforming SPW pretreated with alkaline hydrogen peroxide (AHP) using peracetic acid (PAA) and percitric acid (PCA) under autoclave and water bath heating. AHP pretreatment increases fiber accessibility by reacting SPW with a mixture of 5 wt% NaOH and 5 vol% H<sub>2</sub>O<sub>2</sub> (1:1 v/v). PAA treatment reacts AHP-pretreated SPW with H<sub>2</sub>O<sub>2</sub>, CH<sub>3</sub>COOH, and H<sub>2</sub>O (50:30:20 v/v) at 121 °C and 0.1 MPa in an autoclave or 95 °C in a water bath for 60 min. PCA treatment follows the same temperature sequence using H<sub>2</sub>O<sub>2</sub> and citric acid (1:1 v/v). It is found that PCA effectively oxidizes lignin and hydrolyzes cellulose, while the water bath prevents rapid H<sub>2</sub>O<sub>2</sub> decomposition, allowing longer reaction time for acid ions with SPW fibers. PCA treatment under water bath heating produces cellulose with white color, high crystallinity (79%), uniform morphology (diameter 25.73 μm, length 86.47 μm), intact functional groups, estimated degree of polymerization (541.2), thermal stability (T<sub>max</sub> 361 °C), and oil- (2.32 g/g) and water-holding capacity (4.10 g/g) comparable to commercial MCC. The same treatment yields NCC with average diameter 16.33 nm and length 276.01 nm, stably dispersed in solution. These results demonstrate that water bath heat source can effectively serve as a sustainable source of simultaneous MCC and NCC production from SPW through to support eco-friendly manner compared to autoclave heat source.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115167"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174077","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 : 2026-04-01Epub Date: 2026-01-23DOI: 10.1016/j.vacuum.2026.115128
Xiaokang Yang , Hongze Fang , Lingyan Zhou , Xianfei Ding , Fuxin Wang , Bobo Li , Baohui Zhu , Ruirun Chen
The influence of temperature gradient on the microstructure and high-temperature mechanical behavior of directionally solidified Ti-47Al-6Nb-0.1C-1.6Ta-0.8Hf alloys was systematically investigated. Columnar grain alignment and lamellar orientation improve with increasing power up to 45 kW, beyond which orientation dispersion and equiaxed grains emerge, driven by the stability of the solidification front and competitive β-dendrite growth. High temperature gradients enhance peritectic reaction kinetics, promoting α-variant selection, lamellar convergence, and suppression of residual β, whereas low gradients lead to dispersed lamellar structures. Elemental analysis reveals uniform hydrogen and oxygen distribution with minimal segregation, attributed to high-vacuum melting and rapid peritectic consumption of β. High-temperature tensile testing at 900 °C shows peak strength and ductility at 45 kW, correlated with effective dislocation blockage at B2/γ and γ/α2 interfaces, where high slip-energy barriers and controlled dislocation transmission mitigate local stress concentrations. These findings demonstrate that precise control of heating power and temperature gradient enables the optimization of microstructure, phase transformation, and high-temperature mechanical performance in TiAl alloys.
{"title":"Tailoring peritectic solidification and lamellar orientation in TiAl alloys through controlled heating power","authors":"Xiaokang Yang , Hongze Fang , Lingyan Zhou , Xianfei Ding , Fuxin Wang , Bobo Li , Baohui Zhu , Ruirun Chen","doi":"10.1016/j.vacuum.2026.115128","DOIUrl":"10.1016/j.vacuum.2026.115128","url":null,"abstract":"<div><div>The influence of temperature gradient on the microstructure and high-temperature mechanical behavior of directionally solidified Ti-47Al-6Nb-0.1C-1.6Ta-0.8Hf alloys was systematically investigated. Columnar grain alignment and lamellar orientation improve with increasing power up to 45 kW, beyond which orientation dispersion and equiaxed grains emerge, driven by the stability of the solidification front and competitive β-dendrite growth. High temperature gradients enhance peritectic reaction kinetics, promoting α-variant selection, lamellar convergence, and suppression of residual β, whereas low gradients lead to dispersed lamellar structures. Elemental analysis reveals uniform hydrogen and oxygen distribution with minimal segregation, attributed to high-vacuum melting and rapid peritectic consumption of β. High-temperature tensile testing at 900 °C shows peak strength and ductility at 45 kW, correlated with effective dislocation blockage at B2/γ and γ/α2 interfaces, where high slip-energy barriers and controlled dislocation transmission mitigate local stress concentrations. These findings demonstrate that precise control of heating power and temperature gradient enables the optimization of microstructure, phase transformation, and high-temperature mechanical performance in TiAl alloys.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115128"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-13DOI: 10.1016/j.vacuum.2026.115089
Mahach N. Magomedov
The properties of rhodium (Rh) have been calculated analytically, both without and taking into account the electronic subsystem (ELS). The ELS effect on the baric (P) and temperature (T) dependences of Rh properties has been studied. It was shown that when ELS is taken into account, both the isotherms of the equation of state and the P-T dependences of the following properties change negligibly: the Debye temperature, the Grüneisen parameter, the elastic modulus (BT), the specific surface energy (σ), the isochoric derivative of the σ function with respect to temperature and the isothermal derivative of the σ function with respect to pressure. When ELS is taken into account at high temperatures and low pressures, the following properties change noticeably: the thermal expansion coefficient (αp), isochoric and isobaric (cp) heat capacity, the product αp·BT, and the isobaric derivative of the σ function with respect to temperature. When ELS is taken into account, the agreement of calculated dependencies with experimental data improves. For example, at P = 0 and T = 2000 K, for αp, consent improves by 11 %, for cp, consent improves by 23.5 %. With increasing pressure, the ELS contribution to the properties decreases. It was shown that at a certain temperature (TB), the product αp·BT does not change with an isothermal increase in pressure. At T < TB, the αp·BT function decreases, and at T > TB, the αp·BT function increases with isothermal pressure increase. For fcc-Rh was obtained TB = 188.5 K and it does not depend on the ELS accounting. Calculations of the baric dependence of the melting point, Tm(P), have shown that the ELS influence on the Tm(P) dependence for fcc-Rh is very small even at low pressures.
{"title":"Study of the electronic subsystem influence on the rhodium thermodynamic properties","authors":"Mahach N. Magomedov","doi":"10.1016/j.vacuum.2026.115089","DOIUrl":"10.1016/j.vacuum.2026.115089","url":null,"abstract":"<div><div>The properties of rhodium (Rh) have been calculated analytically, both without and taking into account the electronic subsystem (ELS). The ELS effect on the baric (<em>P</em>) and temperature (<em>T</em>) dependences of Rh properties has been studied. It was shown that when ELS is taken into account, both the isotherms of the equation of state and the <em>P-T</em> dependences of the following properties change negligibly: the Debye temperature, the Grüneisen parameter, the elastic modulus (<em>B</em><sub><em>T</em></sub>), the specific surface energy (σ), the isochoric derivative of the σ function with respect to temperature and the isothermal derivative of the σ function with respect to pressure. When ELS is taken into account at high temperatures and low pressures, the following properties change noticeably: the thermal expansion coefficient (α<sub><em>p</em></sub>), isochoric and isobaric (<em>c</em><sub><em>p</em></sub>) heat capacity, the product α<sub><em>p</em></sub>·<em>B</em><sub><em>T</em></sub>, and the isobaric derivative of the σ function with respect to temperature. When ELS is taken into account, the agreement of calculated dependencies with experimental data improves. For example, at <em>P</em> = 0 and <em>T</em> = 2000 K, for α<sub><em>p</em></sub>, consent improves by 11 %, for <em>c</em><sub><em>p</em></sub>, consent improves by 23.5 %. With increasing pressure, the ELS contribution to the properties decreases. It was shown that at a certain temperature (<em>T</em><sub><em>B</em></sub>), the product α<sub><em>p</em></sub>·<em>B</em><sub><em>T</em></sub> does not change with an isothermal increase in pressure. At <em>T</em> < <em>T</em><sub><em>B</em></sub>, the α<sub><em>p</em></sub>·<em>B</em><sub><em>T</em></sub> function decreases, and at <em>T</em> > <em>T</em><sub><em>B</em></sub>, the α<sub><em>p</em></sub>·<em>B</em><sub><em>T</em></sub> function increases with isothermal pressure increase. For fcc-Rh was obtained <em>T</em><sub><em>B</em></sub> = 188.5 K and it does not depend on the ELS accounting. Calculations of the baric dependence of the melting point, <em>T</em><sub><em>m</em></sub>(<em>P</em>), have shown that the ELS influence on the <em>T</em><sub><em>m</em></sub>(<em>P</em>) dependence for fcc-Rh is very small even at low pressures.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115089"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080120","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}
Herein, an interface-engineered strategy was developed to enhance the structural and electrical properties of tin monoxide (SnO) thin films by using tellurium (Te) as a surface capping layer and controlling the annealing atmosphere via rapid thermal annealing (RTA). The Te layer effectively stabilized the SnO surface and suppressed Sn valence drift. X-ray photoelectron spectroscopy depth profiling revealed that RTA under the N2 atmosphere significantly promoted Te0 diffusion into SnO. X-ray diffraction confirmed improved crystallinity and grain coarsening in the N2-annealed sample, attributed to interfacial atomic rearrangement. These findings highlight the synergistic role of Te coating and inert-atmosphere annealing in tuning interfacial defect chemistry and enhancing the physical properties of p-type oxide semiconductors.
{"title":"Investigating the impact of rapid thermal annealing atmosphere on the properties of sputtered SnO thin films with a tellurium capping layer","authors":"Bojun Zhang , Kai-Jhih Gan , Zefu Zhao , Jialong Xiang , Zhibo Zeng , Kuei-Shu Chang-Liao , Chao-Yi Fang , Dun-Bao Ruan","doi":"10.1016/j.vacuum.2026.115148","DOIUrl":"10.1016/j.vacuum.2026.115148","url":null,"abstract":"<div><div>Herein, an interface-engineered strategy was developed to enhance the structural and electrical properties of tin monoxide (SnO) thin films by using tellurium (Te) as a surface capping layer and controlling the annealing atmosphere via rapid thermal annealing (RTA). The Te layer effectively stabilized the SnO surface and suppressed Sn valence drift. X-ray photoelectron spectroscopy depth profiling revealed that RTA under the N<sub>2</sub> atmosphere significantly promoted Te<sup>0</sup> diffusion into SnO. X-ray diffraction confirmed improved crystallinity and grain coarsening in the N<sub>2</sub>-annealed sample, attributed to interfacial atomic rearrangement. These findings highlight the synergistic role of Te coating and inert-atmosphere annealing in tuning interfacial defect chemistry and enhancing the physical properties of p-type oxide semiconductors.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115148"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174096","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 : 2026-04-01Epub 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":"2026-04-01","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 : 2026-04-01Epub Date: 2026-01-27DOI: 10.1016/j.vacuum.2026.115142
Angel Regalado-Contreras , Jonathan Rosas-Alcántara , Karla Paola Valdez-Núñez , Mayra Cecilia Ramírez-Camacho , Wencel de la Cruz
p-type TiOx thin films have been fabricated using vacuum-based techniques at different deposition pressures, but no reproducible processing window has been established. Herein, TiOx thin films were deposited by laser ablation of a Ti target under O2 atmospheres at pressures ranging from 1.2 × 10−5 to 0.1 Torr. In vacuo X-ray Photoelectron Spectroscopy (XPS) revealed Ti4+/Ti3+ mixed valence below 10−2 Torr and exclusively Ti4+ above this threshold. Quantification based on Gaussian peak deconvolution revealed Ti4+ ranging from 20 to 30.6 at.%, Ti3+ from 10.1 to 1.5 at.%, and oxygen approximately constant at ∼69 at.%, with an uncertainty of ±5 %. The electrical properties were carrier concentrations from 2 × 1020 cm−3 (electrons) to 2 × 1016 cm−3 (holes), resistivity from 0.4 to 460 Ω cm, and mobility from 0.5 to 6 cm2 V−1 s−1. The films with mixed Ti valence were n-type and those with Ti4+ alone were p-type. Cathodoluminescence, in combination with XPS, revealed shallow acceptor levels mediating p-type conductivity, located at 0.32–0.36 eV above the VBM. Optically, average transmittance as high as 66 % on the visible spectrum (350–750 nm) was achieved. Surface morphology analyzed through atomic force microscopy revealed RMS roughness as low as 0.77 nm. Thin-Film-Transistors (TFT) were fabricated by photolithography. The output/transfer characteristics evolve from non-saturated/weak gate modulation to fully saturated/gate-controlled, consistent with TiOx channels exhibiting carrier concentrations on the order of 1019 to 1017 cm−3, respectively. This study advances the body of knowledge on semiconducting TiOx thin films and their reproducible integration into TFT with tunable performance.
{"title":"Carrier tuning in room temperature laser-ablated TiOx thin films: In vacuo X-ray photoelectron spectroscopy insights","authors":"Angel Regalado-Contreras , Jonathan Rosas-Alcántara , Karla Paola Valdez-Núñez , Mayra Cecilia Ramírez-Camacho , Wencel de la Cruz","doi":"10.1016/j.vacuum.2026.115142","DOIUrl":"10.1016/j.vacuum.2026.115142","url":null,"abstract":"<div><div>p-type TiO<sub>x</sub> thin films have been fabricated using vacuum-based techniques at different deposition pressures, but no reproducible processing window has been established. Herein, TiO<sub>x</sub> thin films were deposited by laser ablation of a Ti target under O<sub>2</sub> atmospheres at pressures ranging from 1.2 × 10<sup>−5</sup> to 0.1 Torr. <em>In vacuo</em> X-ray Photoelectron Spectroscopy (XPS) revealed Ti<sup>4+</sup>/Ti<sup>3+</sup> mixed valence below 10<sup>−2</sup> Torr and exclusively Ti<sup>4+</sup> above this threshold. Quantification based on Gaussian peak deconvolution revealed Ti<sup>4+</sup> ranging from 20 to 30.6 at.%, Ti<sup>3+</sup> from 10.1 to 1.5 at.%, and oxygen approximately constant at ∼69 at.%, with an uncertainty of ±5 %. The electrical properties were carrier concentrations from 2 × 10<sup>20</sup> cm<sup>−3</sup> (electrons) to 2 × 10<sup>16</sup> cm<sup>−3</sup> (holes), resistivity from 0.4 to 460 Ω cm, and mobility from 0.5 to 6 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>. The films with mixed Ti valence were n-type and those with Ti<sup>4+</sup> alone were p-type. Cathodoluminescence, in combination with XPS, revealed shallow acceptor levels mediating p-type conductivity, located at 0.32–0.36 eV above the VBM. Optically, average transmittance as high as 66 % on the visible spectrum (350–750 nm) was achieved. Surface morphology analyzed through atomic force microscopy revealed RMS roughness as low as 0.77 nm. Thin-Film-Transistors (TFT) were fabricated by photolithography. The output/transfer characteristics evolve from non-saturated/weak gate modulation to fully saturated/gate-controlled, consistent with TiO<sub>x</sub> channels exhibiting carrier concentrations on the order of 10<sup>19</sup> to 10<sup>17</sup> cm<sup>−3</sup>, respectively. This study advances the body of knowledge on semiconducting TiO<sub>x</sub> thin films and their reproducible integration into TFT with tunable performance.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115142"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2026-01-22DOI: 10.1016/j.vacuum.2026.115132
G. Yu Yushkov, V.D. Gridilev, A.G. Nikolaev, E.M. Oks
We present the results of our experiments of specific erosion of 13 different cathode materials in a microsecond pulsed vacuum arc with current 200 A. The specific erosion of materials with relatively high melting points, greater than Тmelt = 650 °C for magnesium, was found to lie within the range from 30 to 100 μg/C, which is typical of erosion in vacuum arc cathode spots. For materials with low melting points, below Тmelt = 328 °C for lead, anomalously high specific erosion in the range from 500 to 1000 μg/C was observed. We find that this high erosion is due to the contribution of a microdroplet component to the erosion products from vacuum arc cathode spots, when the cathode surface melts to the depth of tens of micrometers during the arc pulse and splashing of the melt due to electro explosive processes in the cathode spots.
{"title":"Erosion of cathode materials with different melting points in a pulsed vacuum arc","authors":"G. Yu Yushkov, V.D. Gridilev, A.G. Nikolaev, E.M. Oks","doi":"10.1016/j.vacuum.2026.115132","DOIUrl":"10.1016/j.vacuum.2026.115132","url":null,"abstract":"<div><div>We present the results of our experiments of specific erosion of 13 different cathode materials in a microsecond pulsed vacuum arc with current 200 A. The specific erosion of materials with relatively high melting points, greater than <em>Т</em><sub>melt</sub> = 650 °C for magnesium, was found to lie within the range from 30 to 100 μg/C, which is typical of erosion in vacuum arc cathode spots. For materials with low melting points, below <em>Т</em><sub>melt</sub> = 328 °C for lead, anomalously high specific erosion in the range from 500 to 1000 μg/C was observed. We find that this high erosion is due to the contribution of a microdroplet component to the erosion products from vacuum arc cathode spots, when the cathode surface melts to the depth of tens of micrometers during the arc pulse and splashing of the melt due to electro explosive processes in the cathode spots.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115132"},"PeriodicalIF":3.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080215","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 : 2026-04-01Epub 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":"2026-04-01","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}
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