Pub Date : 2025-04-23DOI: 10.1016/j.vacuum.2025.114365
Haolan Zhang , Zhongwei Chen , Weijiang Song , Yijun Wu , Bo An
The precipitation behavior of the secondary L12-Al3(Sc, Zr) precipitates in the selective laser melting (SLM) fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloy is investigated. And the distribution of Sc and Zr atoms in the secondary Al3(Sc, Zr) precipitates at different aging temperatures was studied by HAADF-STEM. The secondary L12-Al3(Sc, Zr) precipitates are predominantly comprise Al and Sc atoms after direct aging at 225 °C for 2.5 h, and this indicating that Sc elements primarily control the nucleation and the growth of the L12-Al3(Sc, Zr) phase at 225 °C. The distinct Al3Sc-rich core and Al3Zr-rich shell structure were observed when the aging temperature increases to 440 °C, and both Sc atoms and Zr atoms actively participate in the nucleation and growth of Al3(Sc, Zr) particles at 440 °C. Furthermore, Cu element enriched at the interface between Al3(Sc, Zr) precipitate and Al matrix following direct aging treatment at 440 °C for 0.5 h. And during non-isothermal aging process, the oxidation was observed occurs at the grain boundary mainly when the aging temperatures were higher than 440 °C.
{"title":"Precipitation behavior of the secondary L12-Al3(Sc, Zr) phase in the SLM fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloy during aging process","authors":"Haolan Zhang , Zhongwei Chen , Weijiang Song , Yijun Wu , Bo An","doi":"10.1016/j.vacuum.2025.114365","DOIUrl":"10.1016/j.vacuum.2025.114365","url":null,"abstract":"<div><div>The precipitation behavior of the secondary L1<sub>2</sub>-Al<sub>3</sub>(Sc, Zr) precipitates in the selective laser melting (SLM) fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloy is investigated. And the distribution of Sc and Zr atoms in the secondary Al<sub>3</sub>(Sc, Zr) precipitates at different aging temperatures was studied by HAADF-STEM. The secondary L1<sub>2</sub>-Al<sub>3</sub>(Sc, Zr) precipitates are predominantly comprise Al and Sc atoms after direct aging at 225 °C for 2.5 h, and this indicating that Sc elements primarily control the nucleation and the growth of the L1<sub>2</sub>-Al<sub>3</sub>(Sc, Zr) phase at 225 °C. The distinct Al<sub>3</sub>Sc-rich core and Al<sub>3</sub>Zr-rich shell structure were observed when the aging temperature increases to 440 °C, and both Sc atoms and Zr atoms actively participate in the nucleation and growth of Al<sub>3</sub>(Sc, Zr) particles at 440 °C. Furthermore, Cu element enriched at the interface between Al<sub>3</sub>(Sc, Zr) precipitate and Al matrix following direct aging treatment at 440 °C for 0.5 h. And during non-isothermal aging process, the oxidation was observed occurs at the grain boundary mainly when the aging temperatures were higher than 440 °C.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114365"},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874022","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}
—Despite the decline in their use after the advent of semiconductor devices, hot cathodes still find applications in specialized detectors and high-power systems. This paper focuses on the simulation of the thermal behavior of an oxide cathode (Y2O3), considering the variation in emissivity as a function of both material and temperature. Most previous studies on hot cathodes have overlooked the importance of radiative emissivity, a parameter that significantly affects thermal exchange, electronic emission and hence the measurement of the work function with a Richardson plot. Our results emphasize the need for a precise measurement of material emissivity to accurately assess cathode performance and enable fair comparisons between different cathode types.
{"title":"Simulation of yttria hot cathode and radiative emissivity impact on its performances and the work function measurement","authors":"Audrey Mayrat , Quentin Rafhay , Claire Verrier , Jean-Luc Deschanvres","doi":"10.1016/j.vacuum.2025.114363","DOIUrl":"10.1016/j.vacuum.2025.114363","url":null,"abstract":"<div><div>—Despite the decline in their use after the advent of semiconductor devices, hot cathodes still find applications in specialized detectors and high-power systems. This paper focuses on the simulation of the thermal behavior of an oxide cathode (Y<sub>2</sub>O<sub>3</sub>), considering the variation in emissivity as a function of both material and temperature. Most previous studies on hot cathodes have overlooked the importance of radiative emissivity, a parameter that significantly affects thermal exchange, electronic emission and hence the measurement of the work function with a Richardson plot. Our results emphasize the need for a precise measurement of material emissivity to accurately assess cathode performance and enable fair comparisons between different cathode types.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114363"},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874023","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 : 2025-04-23DOI: 10.1016/j.vacuum.2025.114359
Mingjin Wu
The oxidation behavior of Al-Mg-Sc-Zr alloy at 300 °C for different oxidation times was systematically studied, the influence of oxidation time on the composition of the oxide scale and the microstructure of the substrate was revealed, and the relationship between oxidation time, microstructure of substrate and oxide scale composition and structure was established. The results showed that with the increase of oxidation time, the morphology of the oxide scale changed from irregular and thin film to a loose structure oxide scale with MgO particle aggregates, and finally formed a thick and dense oxide scale. Initially, Al2O3 dominated the oxide scale composition, but with increasing oxidation time, the MgO content gradually increased. At 1.5h, the MgO content in the oxide scale exceeded that of Al2O3, eventually becoming the predominant component. And at 2.0 h, the composition of the oxide scale changed to MgO, MgAl2O4, and a few Al2O3, and MgAl2O4 was present largely in the deep part of the oxide scale, gradually replacing MgO in the thickness direction as the oxidation time prolonged. At the same time, the orientation of the matrix grains changed, and the proportion of HAGBs increased dramatically, which increased the diffusion rate of Mg atoms. As the oxidation time increased, changes in dislocation density and precipitation of nanoparticles also affected the path and speed of atomic migration, thereby determining the phase composition and structural stability of the oxide scale on Al-Mg-Sc-Zr alloy.
{"title":"Effect of oxidation time on the composition and structure evolution of the oxide film on Al-Mg-Sc-Zr alloy","authors":"Mingjin Wu","doi":"10.1016/j.vacuum.2025.114359","DOIUrl":"10.1016/j.vacuum.2025.114359","url":null,"abstract":"<div><div>The oxidation behavior of Al-Mg-Sc-Zr alloy at 300 °C for different oxidation times was systematically studied, the influence of oxidation time on the composition of the oxide scale and the microstructure of the substrate was revealed, and the relationship between oxidation time, microstructure of substrate and oxide scale composition and structure was established. The results showed that with the increase of oxidation time, the morphology of the oxide scale changed from irregular and thin film to a loose structure oxide scale with MgO particle aggregates, and finally formed a thick and dense oxide scale. Initially, Al<sub>2</sub>O<sub>3</sub> dominated the oxide scale composition, but with increasing oxidation time, the MgO content gradually increased. At 1.5h, the MgO content in the oxide scale exceeded that of Al<sub>2</sub>O<sub>3</sub>, eventually becoming the predominant component. And at 2.0 h, the composition of the oxide scale changed to MgO, MgAl<sub>2</sub>O<sub>4</sub>, and a few Al<sub>2</sub>O<sub>3</sub>, and MgAl<sub>2</sub>O<sub>4</sub> was present largely in the deep part of the oxide scale, gradually replacing MgO in the thickness direction as the oxidation time prolonged. At the same time, the orientation of the matrix grains changed, and the proportion of HAGBs increased dramatically, which increased the diffusion rate of Mg atoms. As the oxidation time increased, changes in dislocation density and precipitation of nanoparticles also affected the path and speed of atomic migration, thereby determining the phase composition and structural stability of the oxide scale on Al-Mg-Sc-Zr alloy.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114359"},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868310","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}
Ti, Zr, V, Zr-Ti, Zr-V, Ti-V and Ti-Zr-V alloy thin films were co-evaporated under UHV. Their composition was characterized by Rutherford Backscattering Spectrometry while their microstructure was characterized directly by X-ray diffraction and scanning electronic microscopy, and indirectly by electrical measurements. Depending on their composition, films are polycrystalline or amorphous and have a resistivity ranging from 60 to 160 μΩ cm. Amorphous films exhibit resistivities higher than 150 μΩ cm and negative TCRs, in accordance with Mooij rule. No bulk oxidation in ambient air was detected by electrical measurements over a period as long as 2 years. After deposition, films were activated during a thermal annealing at 5 °C/min up to 400 °C under 10−7 mbar vacuum or 10−3 mbar of H2. An in situ sheet resistance monitoring of the films during annealing allowed to detect their hydrogenation and thus to compare their activation temperatures. Films with amorphous microstructure (ZrV, TiZrV) have lower activation temperatures than single element films and nanocrystalline ZrTi and TiV films. TiZrV has the lowest activation temperature, while single metal films have the highest activation temperatures.
{"title":"Thermal activation of co-evaporated Ti, Zr and V-based binary and ternary getter alloy thin films: characterization by electrical measurements during hydrogenation","authors":"Sylvain Lemettre , Charlotte Kutyla , Clément Bessouet , Laetitia Leroy , Alain Bosseboeuf , Thierry Sauvage , Olivier Wendling , Aurélien Bellamy , Stéphanie Escoubas , Christophe Guichet , Olivier Thomas , Johan Moulin","doi":"10.1016/j.vacuum.2025.114354","DOIUrl":"10.1016/j.vacuum.2025.114354","url":null,"abstract":"<div><div>Ti, Zr, V, Zr-Ti, Zr-V, Ti-V and Ti-Zr-V alloy thin films were co-evaporated under UHV. Their composition was characterized by Rutherford Backscattering Spectrometry while their microstructure was characterized directly by X-ray diffraction and scanning electronic microscopy, and indirectly by electrical measurements. Depending on their composition, films are polycrystalline or amorphous and have a resistivity ranging from 60 to 160 μΩ cm. Amorphous films exhibit resistivities higher than 150 μΩ cm and negative TCRs, in accordance with Mooij rule. No bulk oxidation in ambient air was detected by electrical measurements over a period as long as 2 years. After deposition, films were activated during a thermal annealing at 5 °C/min up to 400 °C under 10<sup>−7</sup> mbar vacuum or 10<sup>−3</sup> mbar of H<sub>2</sub>. An in situ sheet resistance monitoring of the films during annealing allowed to detect their hydrogenation and thus to compare their activation temperatures. Films with amorphous microstructure (ZrV, TiZrV) have lower activation temperatures than single element films and nanocrystalline ZrTi and TiV films. TiZrV has the lowest activation temperature, while single metal films have the highest activation temperatures.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114354"},"PeriodicalIF":3.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873894","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 : 2025-04-22DOI: 10.1016/j.vacuum.2025.114364
Xiangna Cong , Muhammad Najeeb Ullah Shah , Wenlong He
van der Waals (vdW) two-dimensional (2D) materials have the capability to fabricate heterostructures with a diverse range of adjustable bandgaps, which has created a multitude of possibilities in the field of optoelectronics applications. This study comprehensively analyses the SnS2/SnSe2 heterostructure, uncovering a type-I band alignment that considerably enhances electron-hole recombination and energy transfer. First-principles density functional theory (DFT) analysis shows that the conduction band minimum (CBM) and valence band maximum (VBM) of SnSe2 fall within the CBM and VBM of SnS2, thereby confirming the existence of type I band alignment. Photoluminescence (PL) spectroscopy reveals efficient energy transfer from SnS2 to SnSe2, leading to enhanced PL intensity in SnSe2. These results propose that combining SnSe2 and SnS2 creates a heterostructure that facilitates stable and efficient energy transfer, placing it as a promising candidate for next-generation optoelectronics.
{"title":"Efficient carrier transfer in the van der Waals straddling heterostructure","authors":"Xiangna Cong , Muhammad Najeeb Ullah Shah , Wenlong He","doi":"10.1016/j.vacuum.2025.114364","DOIUrl":"10.1016/j.vacuum.2025.114364","url":null,"abstract":"<div><div>van der Waals (vdW) two-dimensional (2D) materials have the capability to fabricate heterostructures with a diverse range of adjustable bandgaps, which has created a multitude of possibilities in the field of optoelectronics applications. This study comprehensively analyses the SnS<sub>2</sub>/SnSe<sub>2</sub> heterostructure, uncovering a type-I band alignment that considerably enhances electron-hole recombination and energy transfer. First-principles density functional theory (DFT) analysis shows that the conduction band minimum (CBM) and valence band maximum (VBM) of SnSe<sub>2</sub> fall within the CBM and VBM of SnS<sub>2</sub>, thereby confirming the existence of type I band alignment. Photoluminescence (PL) spectroscopy reveals efficient energy transfer from SnS<sub>2</sub> to SnSe<sub>2</sub>, leading to enhanced PL intensity in SnSe<sub>2</sub>. These results propose that combining SnSe<sub>2</sub> and SnS<sub>2</sub> creates a heterostructure that facilitates stable and efficient energy transfer, placing it as a promising candidate for next-generation optoelectronics.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114364"},"PeriodicalIF":3.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874021","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}
A nonlinear in-vacuum kicker (NIK) was developed to facilitate beam injection into the Taiwan Photon Source (TPS) storage ring. The system consists of a titanium vacuum chamber that encloses a ceramic support structure, precisely aligning eight copper kicker coils to generate the desired nonlinear magnetic field profile. Experimental measurements show that the profile of the first magnetic integral closely aligns with simulation result. To reduce heating from image currents and minimize magnetic field attenuation, a 5 μm-thick titanium coating was applied to the ceramic surface. Outgassing rate measurements and pressure readings after bake-out and pump activation confirm that the nonlinear in-vacuum kicker meets the ultra-high vacuum (UHV) requirements for TPS storage ring operation.
{"title":"Development of the nonlinear in-vacuum kicker at Taiwan photon source","authors":"Chin-Chun Chang, Che-Kai Chan, Bo-Ying Chen, Chun-Shien Huang, Chin-Kang Yang, Fu-Yuan Lin, Chyi-Shyan Fang, Ke-Kang Lin, Jing-Hao Kang","doi":"10.1016/j.vacuum.2025.114356","DOIUrl":"10.1016/j.vacuum.2025.114356","url":null,"abstract":"<div><div>A nonlinear in-vacuum kicker (NIK) was developed to facilitate beam injection into the Taiwan Photon Source (TPS) storage ring. The system consists of a titanium vacuum chamber that encloses a ceramic support structure, precisely aligning eight copper kicker coils to generate the desired nonlinear magnetic field profile. Experimental measurements show that the profile of the first magnetic integral closely aligns with simulation result. To reduce heating from image currents and minimize magnetic field attenuation, a 5 μm-thick titanium coating was applied to the ceramic surface. Outgassing rate measurements and pressure readings after bake-out and pump activation confirm that the nonlinear in-vacuum kicker meets the ultra-high vacuum (UHV) requirements for TPS storage ring operation.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114356"},"PeriodicalIF":3.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868311","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 : 2025-04-22DOI: 10.1016/j.vacuum.2025.114361
Abdelhak Missaoui , Oussama Jdaini , Mohamed El Bojaddaini , Morad El Kaouini , Hassan Chatei
This paper investigates the formation and structure of the sheath in a magnetized, collisionless, non-extensive plasma under the influence of electron impact ionization. A modified -dependent electron-neutral ionization frequency is derived for the ionization process in the sheath region, revealing a strong dependence of the ionization frequency on the non-extensive parameter . The results show that the ionization frequency significantly increases for lower values of (super-extensive electrons), leading to more energetic electrons and enhanced ionization effects. Additionally, a modified q-dependent Bohm criterion is derived, showing that the Bohm velocity limit for approaches the zero-source term limit. The impact of the -dependent source term on sheath characteristics such as charged particle densities, space charge density, electric field, ion flux, and ion velocities is thoroughly examined. It is found that the source term affects the sheath characteristics, especially in the case of a super-extensive electron distribution () case. Furthermore, the analysis reveals that increasing the magnetic field angle leads to a stronger electric field within the sheath, and that the sheath length is significantly influenced by both the non-extensive parameter and the magnetic field angle.
{"title":"Impact of q-dependent ionization frequency on sheath formation and behavior in magnetized collisionless plasma with non-extensive electron distribution","authors":"Abdelhak Missaoui , Oussama Jdaini , Mohamed El Bojaddaini , Morad El Kaouini , Hassan Chatei","doi":"10.1016/j.vacuum.2025.114361","DOIUrl":"10.1016/j.vacuum.2025.114361","url":null,"abstract":"<div><div>This paper investigates the formation and structure of the sheath in a magnetized, collisionless, non-extensive plasma under the influence of electron impact ionization. A modified <span><math><mrow><mi>q</mi></mrow></math></span>-dependent electron-neutral ionization frequency is derived for the ionization process in the sheath region, revealing a strong dependence of the ionization frequency on the non-extensive parameter <span><math><mrow><mi>q</mi></mrow></math></span>. The results show that the ionization frequency significantly increases for lower values of <span><math><mrow><mi>q</mi></mrow></math></span> (super-extensive electrons), leading to more energetic electrons and enhanced ionization effects. Additionally, a modified q-dependent Bohm criterion is derived, showing that the Bohm velocity limit for <span><math><mrow><mi>q</mi><mspace></mspace><mo>></mo><mspace></mspace><mn>1</mn></mrow></math></span> approaches the zero-source term limit. The impact of the <span><math><mrow><mi>q</mi></mrow></math></span>-dependent source term on sheath characteristics such as charged particle densities, space charge density, electric field, ion flux, and ion velocities is thoroughly examined. It is found that the source term affects the sheath characteristics, especially in the case of a super-extensive electron distribution (<span><math><mrow><mi>q</mi><mspace></mspace><mo><</mo><mspace></mspace><mn>1</mn></mrow></math></span>) case. Furthermore, the analysis reveals that increasing the magnetic field angle leads to a stronger electric field within the sheath, and that the sheath length is significantly influenced by both the non-extensive parameter <span><math><mrow><mi>q</mi></mrow></math></span> and the magnetic field angle.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114361"},"PeriodicalIF":3.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863790","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 : 2025-04-21DOI: 10.1016/j.vacuum.2025.114353
Meng Han , Lansong Deng , Zhichao Wang , Xingyu Zhang , Chuwei Zhou , Vadim V. Silberschmidt , Qinsheng Bi
Oxidation behavior significantly influences the mechanical properties of carbon/carbon (C/C) composites operating in high-temperature service environments. A thermal-mechanical-chemical coupling constitutive model is developed using a kinetic method for the gas-solid oxidation reaction. This model incorporates a four-phase representation of the carbon/carbon composite and derives the mass transfer rate for a first-order irreversible reaction. Component conversions and their nondimensional reaction times are predicted. By coupling the constitutive relations for oxidation and the mechanical behavior, transient mechanical properties are theoretically determined. This multi-scale model is integrated into Abaqus finite-element software to numerically simulate and the progressive oxidation and damage processes in needle-punched carbon/carbon composites that are experimentally validated. The obtained results showed that modulus and strength decreased by 15 % and 17.6 % due to oxidation, respectively. The matrix phase between punched bundles oxidized and damaged first, with the subsequent crack propagation accelerating the oxidation process by providing oxygen diffusion channels. This research contributes to a potential reuse of thermal protection structures in aerospace engineering.
{"title":"Thermal-mechanical-chemical coupling behaviors of carbon/carbon composites","authors":"Meng Han , Lansong Deng , Zhichao Wang , Xingyu Zhang , Chuwei Zhou , Vadim V. Silberschmidt , Qinsheng Bi","doi":"10.1016/j.vacuum.2025.114353","DOIUrl":"10.1016/j.vacuum.2025.114353","url":null,"abstract":"<div><div>Oxidation behavior significantly influences the mechanical properties of carbon/carbon (C/C) composites operating in high-temperature service environments. A thermal-mechanical-chemical coupling constitutive model is developed using a kinetic method for the gas-solid oxidation reaction. This model incorporates a four-phase representation of the carbon/carbon composite and derives the mass transfer rate for a first-order irreversible reaction. Component conversions and their nondimensional reaction times are predicted. By coupling the constitutive relations for oxidation and the mechanical behavior, transient mechanical properties are theoretically determined. This multi-scale model is integrated into Abaqus finite-element software to numerically simulate and the progressive oxidation and damage processes in needle-punched carbon/carbon composites that are experimentally validated. The obtained results showed that modulus and strength decreased by 15 % and 17.6 % due to oxidation, respectively. The matrix phase between punched bundles oxidized and damaged first, with the subsequent crack propagation accelerating the oxidation process by providing oxygen diffusion channels. This research contributes to a potential reuse of thermal protection structures in aerospace engineering.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114353"},"PeriodicalIF":3.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859535","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 : 2025-04-21DOI: 10.1016/j.vacuum.2025.114355
Jinyu Shi , Lina Chen , Yiming Lei , Chenxu Wang , Jie Zhang , Jingyang Wang
Zirconium carbide (ZrC) has emerged as attractive candidate material for next-generation fission and fusion energy system that are inevitably exposed to extreme irradiation environment. In this work, irradiation induced damage evolution in ZrCx (x = 0.55, 0.78, 0.86) induced by 3 MeV Au2+ irradiation at the fluences ranging from 1 × 1014 cm−2 to 2 × 1016 cm−2 at room temperature (RT) was systematically investigated. The observations revealed that the radiation tolerance, especially its resistance to amorphization, was sensitive to the stoichiometry. Additionally, local accumulation of carbon vacancies both in the ordered phases and twin interfaces promotes the recombination of irradiation point defects, thereby enhancing the irradiation tolerance of substoichiometric ZrCx. This work provides a fundamental understanding of correlation between the stoichiometry and irradiation damage in zirconium carbide.
{"title":"Irradiation damage of zirconium carbide with different stoichiometry","authors":"Jinyu Shi , Lina Chen , Yiming Lei , Chenxu Wang , Jie Zhang , Jingyang Wang","doi":"10.1016/j.vacuum.2025.114355","DOIUrl":"10.1016/j.vacuum.2025.114355","url":null,"abstract":"<div><div>Zirconium carbide (ZrC) has emerged as attractive candidate material for next-generation fission and fusion energy system that are inevitably exposed to extreme irradiation environment. In this work, irradiation induced damage evolution in ZrC<sub>x</sub> (x = 0.55, 0.78, 0.86) induced by 3 MeV Au<sup>2+</sup> irradiation at the fluences ranging from 1 × 10<sup>14</sup> cm<sup>−2</sup> to 2 × 10<sup>16</sup> cm<sup>−2</sup> at room temperature (RT) was systematically investigated. The observations revealed that the radiation tolerance, especially its resistance to amorphization, was sensitive to the stoichiometry. Additionally, local accumulation of carbon vacancies both in the ordered phases and twin interfaces promotes the recombination of irradiation point defects, thereby enhancing the irradiation tolerance of substoichiometric ZrC<sub>x</sub>. This work provides a fundamental understanding of correlation between the stoichiometry and irradiation damage in zirconium carbide.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"239 ","pages":"Article 114355"},"PeriodicalIF":3.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863789","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 : 2025-04-19DOI: 10.1016/j.vacuum.2025.114345
Zhengyu Hou , Miaosen Yu , Zhe Zhang , Xuhui Liu , Hao Yan , Xiangyang Liu
Micro-cathode arc thruster (μCAT) has the advantages of super lightweight, high specific impulse and modularity, which has a broad application prospect in micro satellites and nanosats. However, from the engineering aspect, the lifetime is the key issue that determines the space flight applications for μCAT. The arc rotating characteristics of the μCAT play an important role in influencing the lifetime and ablation of the conductive film. In this paper, we propose a magnetic probe array to measure the azimuthal varying magnetic field components from the discharge arc, and thus to evaluate the arc rotating characteristics of the thruster. The design of the magnetic probe is carried out based on Faraday's law of electromagnetic induction and the exit dimensions of the thruster. A capacitive discharge in the energised straight conductor is used as a standard magnetic field for the magnetic probe calibration. The average calibration coefficient is calculated to be 0.311 T/V, with the maximum repeatability error of 8.9 %. Through multi-points magnetic field measurements, the arc rotation speed, angle, duration, and the change rate of the arc rotation speed can be investigated experimentally. By changing the discharge energy levels, it is measured that the tendency of arc rotation slowing down during the discharge process become smoother from 17.65 % to 13.91 % with the decrease of the μCAT discharge energy. With the increase of the applied magnetic field, it is found that the rotation angle of the μCAT discharge arc is significantly increased around 300°, while the discharge time is reduced to a limited extent by 14.11 μs. Furthermore, the new insights into arc behavior can provide valuable perspectives on issues related to overall performance of the thruster.
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