Pub Date : 2026-01-14DOI: 10.1016/j.vacuum.2026.115096
Rui Liu , Yang Li , Dongbin Jiang , Yuliang Bai , Xu Luo , Yanhui Sun
Surface peeling defects caused by inclusions are commonly observed in pickling coils of commercially pure titanium (CP-Ti) ingots, which deteriorate the surface quality of the rolled products. In this work, inclusions in the CP-Ti ingots melted by Electron Beam Cold Hearth Melting (EBCHM) and Vacuum Arc Remelting (VAR) are extracted by the electrolytic extraction, and their three-dimensional morphology, type, and size distribution are analyzed by using SEM. Moreover, the origins of the various inclusion types were also investigated. Besides, a dissolution model for titanium oxides is developed to simulate the dissolution of TiO2. The results show that most of inclusions are titanium oxides, accounting for 89 % of the total. The rest is a small amount of Al2O3, composite inclusions, and high-density inclusions containing W. Their sizes predominantly range from 80 to 300 μm. The total inclusion content measured in the VAR ingot is 51 % higher than that in the EBCHM ingot. During the dissolution of titanium oxides, the phase transformation occurs on the surface, leading to the formation of a thin layer of Ti3O5. In the EBCHM process, it takes 466s for the 500 μm TiO2 particle to be completely dissolved at 1720oC. The dissolution rate of inclusions is enhanced with the high temperature, but it remains almost constant with the size and time. Therefore, a low melting speed and high temperature process can promote the inclusion dissolution.
{"title":"Investigation of inclusions in CP-Ti ingots melted by electron beam cold hearth melting and Vacuum Arc remelting with electrolytic extraction method","authors":"Rui Liu , Yang Li , Dongbin Jiang , Yuliang Bai , Xu Luo , Yanhui Sun","doi":"10.1016/j.vacuum.2026.115096","DOIUrl":"10.1016/j.vacuum.2026.115096","url":null,"abstract":"<div><div>Surface peeling defects caused by inclusions are commonly observed in pickling coils of commercially pure titanium (CP-Ti) ingots, which deteriorate the surface quality of the rolled products. In this work, inclusions in the CP-Ti ingots melted by Electron Beam Cold Hearth Melting (EBCHM) and Vacuum Arc Remelting (VAR) are extracted by the electrolytic extraction, and their three-dimensional morphology, type, and size distribution are analyzed by using SEM. Moreover, the origins of the various inclusion types were also investigated. Besides, a dissolution model for titanium oxides is developed to simulate the dissolution of TiO<sub>2</sub>. The results show that most of inclusions are titanium oxides, accounting for 89 % of the total. The rest is a small amount of Al<sub>2</sub>O<sub>3</sub>, composite inclusions, and high-density inclusions containing W. Their sizes predominantly range from 80 to 300 μm. The total inclusion content measured in the VAR ingot is 51 % higher than that in the EBCHM ingot. During the dissolution of titanium oxides, the phase transformation occurs on the surface, leading to the formation of a thin layer of Ti<sub>3</sub>O<sub>5</sub>. In the EBCHM process, it takes 466s for the 500 μm TiO<sub>2</sub> particle to be completely dissolved at 1720<sup>o</sup>C. The dissolution rate of inclusions is enhanced with the high temperature, but it remains almost constant with the size and time. Therefore, a low melting speed and high temperature process can promote the inclusion dissolution.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115096"},"PeriodicalIF":3.9,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 10.1016/j.vacuum.2026.115091
Kusuma Putri Suwondo , Muhammad Kozin , Rima Angellina , Yulia Elfena , Diah Ayu Fitriani , Agus Nugroho , Adita Wardani Rahmania , Erie Martides , Muhammad Prisla Kamil , Prabowo Puranto
Hydroxyapatite (HA) coatings enhance the biological integration and corrosion performance of titanium implants; however, conventional direct-current (DC) electrochemical deposition (ECD) often yields porous, weakly adherent layers. This study introduces a DC-biased alternating current (AC) ECD, by superimposing a 10 V sinusoidal waveform onto DC biases of 2.5, 5.0, and 7.5 V, to regulate HA growth on Ti-6Al-4V. Increasing the DC bias shifted the deposition regime, leading to a morphological evolution from short crystallites to elongated, interconnected needle-like networks. X-ray diffraction revealed sharpened HA reflections, indicating enhanced crystallinity, while surface roughness and hydrophilicity also increased. Potentiodynamic polarization demonstrated improved corrosion resistance, with 2.5 VDC exhibit lowest jcorr of (3.17 ± 0.05) × 10−8 A cm−2 and protection efficiencies of (91 ± 4) %. All coatings promoted secondary apatite formation in simulated body fluid. This approach provides a tunable, low-temperature pathway for engineering compact, corrosion-resistant HA layers.
羟基磷灰石（HA）涂层增强了钛种植体的生物整合和腐蚀性能；然而，传统的直流（DC）电化学沉积（ECD）通常会产生多孔的、粘附较弱的层。本研究引入了直流偏置交流（AC） ECD，通过将10 V正弦波形叠加到2.5、5.0和7.5 V直流偏置上，来调节Ti-6Al-4V上HA的生长。增加直流偏压改变了沉积模式，导致从短晶到细长的、相互连接的针状网络的形态演变。x射线衍射显示HA反射增强，表明结晶度增强，表面粗糙度和亲水性也增加。动电位极化具有较好的耐蚀性，在2.5 VDC下，其腐蚀系数最低，为（3.17±0.05）× 10−8 A cm−2，保护效率为（91±4）%。所有涂层都促进了模拟体液中磷灰石的次生形成。这种方法为设计致密、耐腐蚀的HA层提供了可调的低温途径。
{"title":"Dynamic polarity switching under DC-biased AC waveforms: Mechanistic insights into hydroxyapatite coating via electrochemical deposition","authors":"Kusuma Putri Suwondo , Muhammad Kozin , Rima Angellina , Yulia Elfena , Diah Ayu Fitriani , Agus Nugroho , Adita Wardani Rahmania , Erie Martides , Muhammad Prisla Kamil , Prabowo Puranto","doi":"10.1016/j.vacuum.2026.115091","DOIUrl":"10.1016/j.vacuum.2026.115091","url":null,"abstract":"<div><div>Hydroxyapatite (HA) coatings enhance the biological integration and corrosion performance of titanium implants; however, conventional direct-current (DC) electrochemical deposition (ECD) often yields porous, weakly adherent layers. This study introduces a DC-biased alternating current (AC) ECD, by superimposing a 10 V sinusoidal waveform onto DC biases of 2.5, 5.0, and 7.5 V, to regulate HA growth on Ti-6Al-4V. Increasing the DC bias shifted the deposition regime, leading to a morphological evolution from short crystallites to elongated, interconnected needle-like networks. X-ray diffraction revealed sharpened HA reflections, indicating enhanced crystallinity, while surface roughness and hydrophilicity also increased. Potentiodynamic polarization demonstrated improved corrosion resistance, with 2.5 V<sub>DC</sub> exhibit lowest <em>j</em><sub>corr</sub> of (3.17 ± 0.05) × 10<sup>−8</sup> A cm<sup>−2</sup> and protection efficiencies of (91 ± 4) %. All coatings promoted secondary apatite formation in simulated body fluid. This approach provides a tunable, low-temperature pathway for engineering compact, corrosion-resistant HA layers.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115091"},"PeriodicalIF":3.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 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":"2026-01-13","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}
Pub Date : 2026-01-13DOI: 10.1016/j.vacuum.2026.115092
Ning Wang , Huiru Wang , Yuxin Liu , Weijun Liu , Zhenyu Liu , Hongyou Bian , Kai Zhang
An innovative triply periodic minimal surface (TPMS)-enhanced Voronoi structure was successfully designed and fabricated from Ti6Al4V alloy using selective laser melting (SLM) technology. The introduction of the TPMS topology significantly enhanced compressive performance of Voronoi structure. Specifically, the elastic modulus, yield strength, and ultimate strength were enhanced by over 35 % compared to the pure Voronoi structure. The G-Voronoi structure exhibited superior compressive performance and exceptional structural stability compared to the D-Voronoi and IWP-Voronoi structures, with the underlying enhancement mechanisms further elucidated through finite element analysis. Furthermore, analysis based on the Gibson–Ashby model revealed that this significant enhancement in compressive performance primarily stemmed from a fundamental transition in the structural deformation mechanism, shifting from a bending-dominated to a more efficient stretching-dominated mode. This TPMS topological enhancement strategy successfully achieved a simultaneous and substantial improvement in mechanical performance, offering a promising solution for the development of the next generation of high-performance bone implants.
{"title":"Superior compressive performance of TPMS-enhanced Voronoi Ti6Al4V alloy fabricated by selective laser melting","authors":"Ning Wang , Huiru Wang , Yuxin Liu , Weijun Liu , Zhenyu Liu , Hongyou Bian , Kai Zhang","doi":"10.1016/j.vacuum.2026.115092","DOIUrl":"10.1016/j.vacuum.2026.115092","url":null,"abstract":"<div><div>An innovative triply periodic minimal surface (TPMS)-enhanced Voronoi structure was successfully designed and fabricated from Ti6Al4V alloy using selective laser melting (SLM) technology. The introduction of the TPMS topology significantly enhanced compressive performance of Voronoi structure. Specifically, the elastic modulus, yield strength, and ultimate strength were enhanced by over 35 % compared to the pure Voronoi structure. The G-Voronoi structure exhibited superior compressive performance and exceptional structural stability compared to the D-Voronoi and IWP-Voronoi structures, with the underlying enhancement mechanisms further elucidated through finite element analysis. Furthermore, analysis based on the Gibson–Ashby model revealed that this significant enhancement in compressive performance primarily stemmed from a fundamental transition in the structural deformation mechanism, shifting from a bending-dominated to a more efficient stretching-dominated mode. This TPMS topological enhancement strategy successfully achieved a simultaneous and substantial improvement in mechanical performance, offering a promising solution for the development of the next generation of high-performance bone implants.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115092"},"PeriodicalIF":3.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 10.1016/j.vacuum.2026.115093
Qingyun Li , Haibo Sun , Guoyong Zhao , Yanjie Li , Shuo Yu , Jingyao Bian
The internal flow characteristics and hydraulic performance of water ring vacuum pumps are significantly affected by the impeller and casing profiles. To reduce energy losses and improve suction performance and efficiency, a multi-objective co-optimization of the impeller and casing profiles of a water ring vacuum pump is conducted by integrating experimental measurements with numerical simulations. First, a theoretical model of hydraulic losses in water ring vacuum pumps is established based on entropy production theory, revealing the underlying mechanisms of these losses. Subsequently, the flow fields and overall performance before and after optimization are compared through integrated suction-performance analysis. The effects of profile parameters on suction capacity and hydraulic losses are thereby revealed, providing a theoretical basis for the structural optimization of water ring vacuum pumps. Results indicate that, in the optimization model targeting minimal wall effect entropy production, the wall effect entropy production decreases by 15.14 %, accompanied by a 0.47 % improvement in isothermal compression efficiency. In the optimization model targeting maximum suction capacity, the suction capacity increases by 17.83 %, and the isothermal compression efficiency improves by 4.16 %.
{"title":"Co-optimization and performance investigation of water ring vacuum pump impeller and casing profiles based on entropy production theory","authors":"Qingyun Li , Haibo Sun , Guoyong Zhao , Yanjie Li , Shuo Yu , Jingyao Bian","doi":"10.1016/j.vacuum.2026.115093","DOIUrl":"10.1016/j.vacuum.2026.115093","url":null,"abstract":"<div><div>The internal flow characteristics and hydraulic performance of water ring vacuum pumps are significantly affected by the impeller and casing profiles. To reduce energy losses and improve suction performance and efficiency, a multi-objective co-optimization of the impeller and casing profiles of a water ring vacuum pump is conducted by integrating experimental measurements with numerical simulations. First, a theoretical model of hydraulic losses in water ring vacuum pumps is established based on entropy production theory, revealing the underlying mechanisms of these losses. Subsequently, the flow fields and overall performance before and after optimization are compared through integrated suction-performance analysis. The effects of profile parameters on suction capacity and hydraulic losses are thereby revealed, providing a theoretical basis for the structural optimization of water ring vacuum pumps. Results indicate that, in the optimization model targeting minimal wall effect entropy production, the wall effect entropy production decreases by 15.14 %, accompanied by a 0.47 % improvement in isothermal compression efficiency. In the optimization model targeting maximum suction capacity, the suction capacity increases by 17.83 %, and the isothermal compression efficiency improves by 4.16 %.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"247 ","pages":"Article 115093"},"PeriodicalIF":3.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145993596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 10.1016/j.vacuum.2026.115086
Sizhuo Bao , Yi Cui , Qianglong He , Aiyang Wang , Weimin Wang
A high-performance WC–0.5 wt% Co hard alloy with uniform and fine grains are successfully prepared in a vacuum pressureless sintering furnace. The effects of Cr3C2–VC content on the microstructural evolution and mechanical properties of WC hard materials are examined. The results show that the VC–Cr3C2 considerably inhibits the abnormal growth of WC grains, and they exhibit pronounced refinement. Moreover, VC–Cr3C2 influences the WC grain morphology. With the addition of VC–Cr3C2, sharp triangular WC grains with multisteps and partly rounded WC grains form, resulting in incomplete WC intergranular contact and reduced interfacial energy. The sample with 0.35 wt% Cr3C2–0.15 wt% VC has optimal comprehensive mechanical properties. Its average grain size, relative density, Vickers hardness, transverse rupture strength, and fracture toughness are 363 nm, 99.28 %, 28.7 GPa, 1350 MPa, and 7.36 MPa‧m1/2, respectively. The strengthening and toughening mechanisms of low–Co content WC hard materials are attributed to the formation of dense, homogeneous WC nanograins. This study provides a new strategy for fabricating high-performance low–Co content WC cemented carbide.
{"title":"Effects of Cr3C2–VC on the microstructure and mechanical properties of low–Co WC hard alloy by vacuum pressureless sintering","authors":"Sizhuo Bao , Yi Cui , Qianglong He , Aiyang Wang , Weimin Wang","doi":"10.1016/j.vacuum.2026.115086","DOIUrl":"10.1016/j.vacuum.2026.115086","url":null,"abstract":"<div><div>A high-performance WC–0.5 wt% Co hard alloy with uniform and fine grains are successfully prepared in a vacuum pressureless sintering furnace. The effects of Cr<sub>3</sub>C<sub>2</sub>–VC content on the microstructural evolution and mechanical properties of WC hard materials are examined. The results show that the VC–Cr<sub>3</sub>C<sub>2</sub> considerably inhibits the abnormal growth of WC grains, and they exhibit pronounced refinement. Moreover, VC–Cr<sub>3</sub>C<sub>2</sub> influences the WC grain morphology. With the addition of VC–Cr<sub>3</sub>C<sub>2</sub>, sharp triangular WC grains with multisteps and partly rounded WC grains form, resulting in incomplete WC intergranular contact and reduced interfacial energy. The sample with 0.35 wt% Cr<sub>3</sub>C<sub>2</sub>–0.15 wt% VC has optimal comprehensive mechanical properties. Its average grain size, relative density, Vickers hardness, transverse rupture strength, and fracture toughness are 363 nm, 99.28 %, 28.7 GPa, 1350 MPa, and 7.36 MPa‧m<sup>1/2</sup>, respectively. The strengthening and toughening mechanisms of low–Co content WC hard materials are attributed to the formation of dense, homogeneous WC nanograins. This study provides a new strategy for fabricating high-performance low–Co content WC cemented carbide.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115086"},"PeriodicalIF":3.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-12DOI: 10.1016/j.vacuum.2026.115078
Jayanta Das
Epitaxial NiO films of varying thickness were grown on Ag(001) substrate by molecular beam epitaxy under optimized growth condition and characterized in situ using low-energy electron diffraction (LEED) and photoemission spectroscopy. LEED patterns confirm high crystalline order and reveal coexisting (1 × 2) and (2 × 1) antiferromagnetically reconstructed surface domains in ultrathin films. Angle-resolved ultraviolet photoemission (ARPES) measurements show weakly dispersive Ni -O hybridized bands along - and - directions. Core-level characteristic Ni 2p multiplet features, whose intensity and satellite structure evolve with film thickness and oxygen stoichiometry, were probed by x-ray photoemission. Enhanced nonlocal screening is evident in the ultrathin limit. Comparison of ARPES data with reported theoretical calculations and experimental results facilitates a deeper interpretation of the observed features and validate the reliability and consistency of current findings. Annealing in ultrahigh vacuum creates oxygen vacancies that introduce a non-dispersive defect state near 0.7 eV binding energy (BE). The results establish a comprehensive picture of growth, structure, and electronic evolution in NiO/Ag(001) ultrathin films.
{"title":"Thickness and stoichiometry dependence of the electronic structure of NiO/Ag(001) ultrathin films","authors":"Jayanta Das","doi":"10.1016/j.vacuum.2026.115078","DOIUrl":"10.1016/j.vacuum.2026.115078","url":null,"abstract":"<div><div>Epitaxial NiO films of varying thickness were grown on Ag(001) substrate by molecular beam epitaxy under optimized growth condition and characterized <em>in situ</em> using low-energy electron diffraction (LEED) and photoemission spectroscopy. LEED patterns confirm high crystalline order and reveal coexisting (1 × 2) and (2 × 1) antiferromagnetically reconstructed surface domains in ultrathin films. Angle-resolved ultraviolet photoemission (ARPES) measurements show weakly dispersive Ni <span><math><mrow><mn>3</mn><mi>d</mi></mrow></math></span>-O <span><math><mrow><mn>2</mn><mi>p</mi></mrow></math></span> hybridized bands along <span><math><mover><mrow><mi>Γ</mi></mrow><mo>¯</mo></mover></math></span>-<span><math><mover><mrow><mi>X</mi></mrow><mo>¯</mo></mover></math></span> and <span><math><mover><mrow><mi>Γ</mi></mrow><mo>¯</mo></mover></math></span>-<span><math><mover><mrow><mi>M</mi></mrow><mo>¯</mo></mover></math></span> directions. Core-level characteristic Ni 2p multiplet features, whose intensity and satellite structure evolve with film thickness and oxygen stoichiometry, were probed by x-ray photoemission. Enhanced nonlocal screening is evident in the ultrathin limit. Comparison of ARPES data with reported theoretical calculations and experimental results facilitates a deeper interpretation of the observed features and validate the reliability and consistency of current findings. Annealing in ultrahigh vacuum creates oxygen vacancies that introduce a non-dispersive defect state near 0.7 eV binding energy (BE). The results establish a comprehensive picture of growth, structure, and electronic evolution in NiO/Ag(001) ultrathin films.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115078"},"PeriodicalIF":3.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-12DOI: 10.1016/j.vacuum.2026.115090
Shao-Ruei Yang , Chun-Yen Yang , En-Ting He , Chia-Feng Lin , Jing- Jenn Lin , Hsiang Chen , Yung-Hui Li
This study systematically investigates the degradation behavior of vertical Gallium Nitride (GaN) Light-Emitting Diodes (LEDs) under salt spray corrosion in high-humidity and high-salinity environments.
Combining electrical measurements with advanced material analysis techniques—specifically Optical Microscopy (OM), Scanning Electron Microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS), Transmission Electron Microscopy(TEM), and X-ray Diffraction(XRD), the research found that corrosive ions penetrate the GaN layer, causing electrochemical etching and defect formation. This damage critically compromises the P-type electrode interface.
This structural breakdown leads to hindered carrier injection and interrupted conductive paths, resulting in degraded device performance characterized by increased leakage current, reduced forward current, exacerbated current crowding, and decreased emission uniformity.
The findings highlight the critical role of the P-type bottom electrode's structural stability for vertical GaN LED reliability, providing crucial data support for future packaging design, material selection, and the development of smart protection circuits to enhance the long-term stability of LEDs in harsh conditions.
{"title":"Degradation behavior of vertical gallium nitride light-emitting diodes in salt spray environments: A study based on electrical and material analysis techniques, integrated with a smart protection circuit application perspective","authors":"Shao-Ruei Yang , Chun-Yen Yang , En-Ting He , Chia-Feng Lin , Jing- Jenn Lin , Hsiang Chen , Yung-Hui Li","doi":"10.1016/j.vacuum.2026.115090","DOIUrl":"10.1016/j.vacuum.2026.115090","url":null,"abstract":"<div><div>This study systematically investigates the degradation behavior of vertical Gallium Nitride (GaN) Light-Emitting Diodes (LEDs) under salt spray corrosion in high-humidity and high-salinity environments.</div><div>Combining electrical measurements with advanced material analysis techniques—specifically Optical Microscopy (OM), Scanning Electron Microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS), Transmission Electron Microscopy(TEM), and X-ray Diffraction(XRD), the research found that corrosive ions penetrate the GaN layer, causing electrochemical etching and defect formation. This damage critically compromises the P-type electrode interface.</div><div>This structural breakdown leads to hindered carrier injection and interrupted conductive paths, resulting in degraded device performance characterized by increased leakage current, reduced forward current, exacerbated current crowding, and decreased emission uniformity.</div><div>The findings highlight the critical role of the P-type bottom electrode's structural stability for vertical GaN LED reliability, providing crucial data support for future packaging design, material selection, and the development of smart protection circuits to enhance the long-term stability of LEDs in harsh conditions.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115090"},"PeriodicalIF":3.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-11DOI: 10.1016/j.vacuum.2026.115087
N. Haberkorn , Jeehoon Kim
Disordered Mo2N thin films exhibit a superconducting transition up to 7.7 K, together with a weak metal–insulator crossover and positive magnetoresistance emerging already near 30 K, well above the critical temperature (Tc). This ≈ 30 K signature persists in both thick and ultrathin films, and even becomes more pronounced in the ultrathin limit, indicating an atomic-scale origin largely insensitive to thickness. The magnetoresistance is nearly isotropic with respect to field orientation and persists up to 16 T, pointing to unexpectedly robust superconducting fluctuations extending far above Tc. For a film with Tc = 7.7 K, by fitting the field-dependent conductance within the weak-localization plus Maki–Thompson framework for T > 8 K, we extract the inelastic scattering time (τi), which is ≈ 5 ps near Tc and decreases systematically with temperature. A decomposition of the inelastic rate reveals electron–electron and electron–phonon channels corresponding to characteristic times of ≈ 10 ps and ≈ 50 ps, respectively. These values agree with previous estimates from vortex critical-velocity measurements and underscore molybdenum nitride as a promising platform for fast radiation detectors.
{"title":"Superconducting fluctuations and quasiparticle recombination times in disordered Mo2N thin films","authors":"N. Haberkorn , Jeehoon Kim","doi":"10.1016/j.vacuum.2026.115087","DOIUrl":"10.1016/j.vacuum.2026.115087","url":null,"abstract":"<div><div>Disordered Mo<sub>2</sub>N thin films exhibit a superconducting transition up to 7.7 K, together with a weak metal–insulator crossover and positive magnetoresistance emerging already near 30 K, well above the critical temperature (<em>T</em><sub><em>c</em></sub>). This ≈ 30 K signature persists in both thick and ultrathin films, and even becomes more pronounced in the ultrathin limit, indicating an atomic-scale origin largely insensitive to thickness. The magnetoresistance is nearly isotropic with respect to field orientation and persists up to 16 T, pointing to unexpectedly robust superconducting fluctuations extending far above <em>T</em><sub><em>c</em></sub>. For a film with <em>T</em><sub><em>c</em></sub> = 7.7 K, by fitting the field-dependent conductance within the weak-localization plus Maki–Thompson framework for <em>T</em> > 8 K, we extract the inelastic scattering time (τ<sub>i</sub>), which is ≈ 5 ps near <em>T</em><sub><em>c</em></sub> and decreases systematically with temperature. A decomposition of the inelastic rate reveals electron–electron and electron–phonon channels corresponding to characteristic times of ≈ 10 ps and ≈ 50 ps, respectively. These values agree with previous estimates from vortex critical-velocity measurements and underscore molybdenum nitride as a promising platform for fast radiation detectors.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115087"},"PeriodicalIF":3.9,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-10DOI: 10.1016/j.vacuum.2026.115075
Mingze Ran , Faming Shen , Xin Zheng , Zenghui Cai , Yi Zheng , Boyu Zhang , Wei Ke , Jia Xie , Deshui Yu , Bo Zhang , Qing Chang , Zhan Sun , Lixia Zhang
In order to address the issues of low seam strength in nickel-based TLP joints, a new Fe-Co-Ni-Al-B multi-component alloy filler was designed. The microstructure of the filler and the microstructure and mechanical properties of TLP joints of GH4648 and K416B using Fe7(CoNi)63Al14B16 filler were investigated. Furthermore the effects of joining parameters on the microstructure and mechanical properties of the joint were discussed. The results show that the Fe7(CoNi)63Al14B16 multi-component alloy filler exhibits a dual-phase microstructure consisting of FCC and BCC phases. Precipitated phases within the seam primarily consisted of the matrix FCC phase, BCC phase, M23B6, Cr-Mo-W boride, and γ′-(Ni, Co)3Al precipitates on the matrix FCC phase. At a holding temperature of 1160 °C for 120 min, the maximum shear strength of the joint at room temperature and 900 °C is 705 MPa and 380 MPa, respectively. The joints exhibit mixed-mode fracture behavior, characterized by both transcrystalline and intergranular features. The maximum differences in hardness and elastic modulus between the bonding seam and the DAZ are 28.77 GPa and 0.37 GPa, respectively. The microhardness and elastic modulus values of the joint were evenly distributed. This work provides a new idea for the TLP bonding of dissimilar superalloys utilized in the manufacturing of aero-engine turbine guide.
{"title":"Effect of joining parameters on mechanical properties of TLP bonded K416B/GH4648 joint reinforced by BCC and γ′ phases","authors":"Mingze Ran , Faming Shen , Xin Zheng , Zenghui Cai , Yi Zheng , Boyu Zhang , Wei Ke , Jia Xie , Deshui Yu , Bo Zhang , Qing Chang , Zhan Sun , Lixia Zhang","doi":"10.1016/j.vacuum.2026.115075","DOIUrl":"10.1016/j.vacuum.2026.115075","url":null,"abstract":"<div><div>In order to address the issues of low seam strength in nickel-based TLP joints, a new Fe-Co-Ni-Al-B multi-component alloy filler was designed. The microstructure of the filler and the microstructure and mechanical properties of TLP joints of GH4648 and K416B using Fe<sub>7</sub>(CoNi)<sub>63</sub>Al<sub>14</sub>B<sub>16</sub> filler were investigated. Furthermore the effects of joining parameters on the microstructure and mechanical properties of the joint were discussed. The results show that the Fe<sub>7</sub>(CoNi)<sub>63</sub>Al<sub>14</sub>B<sub>16</sub> multi-component alloy filler exhibits a dual-phase microstructure consisting of FCC and BCC phases. Precipitated phases within the seam primarily consisted of the matrix FCC phase, BCC phase, M<sub>23</sub>B<sub>6</sub>, Cr-Mo-W boride, and γ′-(Ni, Co)<sub>3</sub>Al precipitates on the matrix FCC phase. At a holding temperature of 1160 °C for 120 min, the maximum shear strength of the joint at room temperature and 900 °C is 705 MPa and 380 MPa, respectively. The joints exhibit mixed-mode fracture behavior, characterized by both transcrystalline and intergranular features. The maximum differences in hardness and elastic modulus between the bonding seam and the DAZ are 28.77 GPa and 0.37 GPa, respectively. The microhardness and elastic modulus values of the joint were evenly distributed. This work provides a new idea for the TLP bonding of dissimilar superalloys utilized in the manufacturing of aero-engine turbine guide.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115075"},"PeriodicalIF":3.9,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977652","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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