Vacuum最新文献

{"title":"Insight into the keyhole behaviour and its role on residual stress formation in vacuum electron beam welding of TC4 titanium alloy","authors":"Yu Wan,&nbsp;Laimin Song,&nbsp;Xuyang Zhang,&nbsp;Wenchun Jiang,&nbsp;Xuefang Xie,&nbsp;Xinyue Qi","doi":"10.1016/j.vacuum.2024.113835","DOIUrl":"10.1016/j.vacuum.2024.113835","url":null,"abstract":"<div><div>Electron beam welding (EBW) is the preferred technique for joining TC4 titanium alloy. Accurately characterizing the welding keyhole and residual stress distribution, along with analyzing their formation mechanisms, is of paramount importance for ensuring high reliability of the TC4 EBW structures. In this regard, a “thermal-fluid-metallurgical-mechanical” multi-field coupling numerical method was developed, which was then validated by the vital experiments. The evolution of the keyhole, molten pool temperature, phase volume fraction and residual stresses was then revealed. The influencing mechanism of keyhole on residual stress was explored comprehensively. The results show that metal vapor recoil pressure serves as the primary factor in keyhole formation, while the surface tension promotes keyhole closure. The β-phase in the weld zone undergoes a complete transformation into α′ acicular martensite. Moreover, the maximum longitudinal stress occurs at the weld center, while the transverse stress exhibits a substantial stress gradient along the thickness direction. Increasing the welding power raises the temperature of molten pool. The keyhole depth and width are also enlarged, accompanying by the increase of residual stress, which is expected to offer a theoretical foundation for managing the keyhole and residual stress generated during the EBW of TC4 titanium alloy.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113835"},"PeriodicalIF":3.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703167","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}

{"title":"IPFOA-MKSVM and BA-MLP models for predicting closed busbar temperatures in high voltage nuclear power plants in different vacuum environments","authors":"Zuoxun Wang,&nbsp;Guojian Zhao,&nbsp;Jinxue Sui,&nbsp;Wangyao Wu,&nbsp;Chuanzhe Pang,&nbsp;Liteng Xu","doi":"10.1016/j.vacuum.2024.113825","DOIUrl":"10.1016/j.vacuum.2024.113825","url":null,"abstract":"<div><div>The nuclear power closed busbar is a key power transmission component in the power system, and its high temperature may cause equipment failure. In this paper, for the temperature prediction of nuclear power closed busbar under vacuum environment, a multi-core support vector machine model optimized by the improved falcon predation algorithm and a multi-layer perceptron model enhanced by the back propagation algorithm are proposed. The vacuum pump is used to reduce the air pressure in the closed space to achieve a vacuum state. The collected data are preprocessed to improve the accuracy and stability of the model. In addition, the PSO and SVM models are used to compare and verify the superiority of the proposed model. The data set is divided into a training set and a test set. The results show that under different vacuum degrees, the prediction accuracy and stability of the IPFOA-MKSVM model are better than those of other models, but its error is slightly higher than the physical calculation result. Finally, the performance of the model in wind speed prediction is verified, and compared with several models to verify the accuracy of IPFOA-MKSVM under different vacuum and wind speed conditions.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113825"},"PeriodicalIF":3.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Martensite instability induced surface hardening on gradient nano-structured 316L stainless steel","authors":"Y.B. Lei ,&nbsp;Z.M. Niu ,&nbsp;B. Gao ,&nbsp;Y.T. Sun","doi":"10.1016/j.vacuum.2024.113831","DOIUrl":"10.1016/j.vacuum.2024.113831","url":null,"abstract":"<div><div>Gradient nanostructured (GNS) 316L stainless steel manufactured by surface mechanical rolling treatment (SMRT) with a full martensitic phase on the surface exhibits an extraordinary annealed hardening. The surface hardness increases by 44 % from 4.1 GPa of the SMRTed 316L stainless steel up to 5.9 GPa after annealed at 400 °C for 120 min. Surface hardening is primarily attributed to the formation of low angle grain boundaries (LAGBs) within the original nano-grains. LAGBs function as substructures that effectively divide the grains into smaller units. These LAGBs originate from lattice distortions caused by Ni segregation during the annealing process. Furthermore, the redistribution of Ni can be regarded as a nucleation step leading to phase reversion from martensite to austenite. Additionally, the presence of Ni-enriched zones distributed within the martensite matrix serves to hinder dislocation movement, thus contributing to the observed surface hardening.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113831"},"PeriodicalIF":3.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657455","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}

{"title":"Research on energy loss mechanism and optimization method of liquid ring vacuum pump based on entropy production theory","authors":"Huayi Liu ,&nbsp;Guoyong Zhao ,&nbsp;Shuo Yu ,&nbsp;Qingyun Li ,&nbsp;Yanjie Li ,&nbsp;Fanrui Meng","doi":"10.1016/j.vacuum.2024.113833","DOIUrl":"10.1016/j.vacuum.2024.113833","url":null,"abstract":"<div><div>To solve the problem of high energy consumption of liquid ring vacuum pumps and serious hydraulic losses that make it difficult to improve the efficiency of the pumps. Firstly, the mechanism of the influence of radical clearance on the energy loss of liquid ring vacuum pumps is investigated, and a directional and quantitative analysis of the energy loss in the flow field within a liquid ring vacuum is made based on the entropy production theory. Then the structural parameter control model oriented to the maximum suction capacity and minimum wall effect entropy production of the liquid ring vacuum pump is established. The results indicate that turbulent entropy production and wall entropy production dominate the energy losses of liquid ring vacuum pumps with radial clearance of 24 mm, 28 mm, 32 mm, and 36 mm. The entropy production caused by the wall effect mainly occurs at the shell of the gas compression region. The optimized liquid ring vacuum pump model achieves an increase in suction capacity of 8.74 %, an increase in isothermal compression efficiency of 3.75 %, and a reduction in wall effect entropy production of 19.7 %.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113833"},"PeriodicalIF":3.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703171","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}

{"title":"Self-catalyzed growth of sub-25-nm-diameter InAs nanowire arrays on Si patterned substrate","authors":"Xiaoye Wang ,&nbsp;Xiaoguang Yang ,&nbsp;Tao Yang","doi":"10.1016/j.vacuum.2024.113832","DOIUrl":"10.1016/j.vacuum.2024.113832","url":null,"abstract":"<div><div>The feature size of advanced Si-based chips is approaching its physical limit, and it is difficult to continue Moore's Law by simply pursuing the technical route of miniaturizing device size to increase the integrated density. III-V nanowire devices represented by InAs material have much higher mobility than Si based devices, but they have not been successfully applied to CMOS nanowire devices and have not shown excellent performance. The reason is that the hole mobility of III-V materials is much lower than their electron mobility. If the nanowire diameter becomes ultrafine, the quantum confinement effect becomes more prominent, the light hole band will reverse above the heavy hole band, and the hole mobility will be greatly increased. Aiming at the integrability of III-V high mobility CMOS devices on Si, how to prepare ultrafine InAs nanowire arrays on Si/SiO₂ patterned substrates has been studied in this work. New method in this work has solved the problem that the nanohole will enlarge due to etching side wall of nanohole by HF process before growth. A technology and mechanism of ultrafine InAs nanowire arrays grown by this method was developed, and the smallest diameter of nanowire in array has reached only 25 nm.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113832"},"PeriodicalIF":3.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703277","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}

{"title":"Molecular dynamics study on the mechanical behavior and deformation mechanism of gradient oxygen content nano-polycrystalline α-T","authors":"Junqiang Ren ,&nbsp;Xinyue Zhang ,&nbsp;Qing Gao ,&nbsp;Qi Wang ,&nbsp;Junchen Li ,&nbsp;Hongtao Xue ,&nbsp;Xuefeng Lu ,&nbsp;Fuling Tang","doi":"10.1016/j.vacuum.2024.113830","DOIUrl":"10.1016/j.vacuum.2024.113830","url":null,"abstract":"<div><div>Interstitial oxygen significantly affects the mechanical properties of <em>α</em>-Titanium (<em>α</em>-Ti) by modifying dislocation slip and deformation twinning mechanisms. This study utilizes molecular dynamics simulations to investigate the influence of interstitial oxygen atoms on the tensile mechanical properties and deformation mechanisms of nano polycrystalline <em>α</em>-Ti, taking into account two distinct average grain sizes and varying gradients of oxygen content. The pinning effect of interstitial oxygen atoms on grain boundary relaxation dislocations is critical for stabilizing the nano-polycrystalline grain boundaries (GBs), with this effect becoming increasingly pronounced as the oxygen content rises. Additionally, the simulation results indicate that oxygen atoms at the twin boundary enhance the stability of the {10 <span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 2} twin boundary while exerting minimal influence on the migration of the {10<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 1} twin boundary. The deformation associated with {10<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 1} twinning leads to a crystallographic orientation transformation of the entire grain, which contrasts with the conventional grain rotation mechanism typically observed in nanocrystals. During plastic deformation, the primary dislocation slip mechanism is identified as the Shockley partial dislocation <span><math><mrow><mfrac><mn>1</mn><mn>3</mn></mfrac></mrow></math></span> &lt;<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 100&gt;, whereas the basal plane perfect dislocation <span><math><mrow><mfrac><mn>1</mn><mn>3</mn></mfrac></mrow></math></span> &lt;11<span><math><mrow><mover><mn>2</mn><mo>‾</mo></mover></mrow></math></span> 0&gt; easily dissociates into two Shockley partial dislocations due to the pinning effect of oxygen atoms. As a result, the dislocation density of the Shockley partial dislocation <span><math><mrow><mfrac><mn>1</mn><mn>3</mn></mfrac></mrow></math></span> &lt;<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 100&gt; is the highest.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113830"},"PeriodicalIF":3.8,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657369","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}

{"title":"Design a self-reinforcement buffer layer to assist braze SiC and Nb with Cu-xTiH2 filler alloy","authors":"Qiang Ma ,&nbsp;Zhekai Zhu ,&nbsp;Peng He ,&nbsp;Yongwei Chen ,&nbsp;Shujin Chen ,&nbsp;Jun Wang","doi":"10.1016/j.vacuum.2024.113829","DOIUrl":"10.1016/j.vacuum.2024.113829","url":null,"abstract":"<div><div>A buffer layer was designed to assist to braze SiC and Nb. The effect of brazing temperature and holding time on the microstructure and the shear strength of the joint was analyzed. The strengthening mechanism of the joint was evaluated. The results found that the SiC-Nb joint was brazed with Cu-5TiH₂, because of its good wettability on the surface of SiC. The typical microstructure of SiC-Nb joint brazed at 1060 °C for 5 min was SiC/C particles + TiC + Cu(s,s)/α-Ti + Nb(s,s)/Cu(s,s)+(Ti,Nb)₅Si₃+Ti₅Si₃/α-Ti/(Ti,Nb)Si/Nb. In addition, a buffer layer formed, which was consisted of two parts: reaction layer (α-Ti + Nb(s,s)) and infiltration layer (much C particles, little TiC and Cu(s,s)). With brazing temperature and holding time increasing, element Nb continuously diffused into brazing seam and solidified into α-Ti. With Nb content increasing, the α-Ti existed in the form of discontinuous to continuous layer, and then to particles. When Nb solidified into α-Ti continuous layer, the strength of the layer was improved and effective joining between SiC and Nb formed. In addition, the buffer layer was contributed to forming a good gradient transition of coefficient of thermal expansion (CTE), and released residual stress. So, the shear strength of the joint was increased to 52.6 MPa.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113829"},"PeriodicalIF":3.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659328","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}

{"title":"Thermodynamic modelling of a twin-stage claw vacuum pump and its gas pressurization analysis","authors":"Yuanjie Xin ,&nbsp;Chunji Ren ,&nbsp;Jun Wang ,&nbsp;Shiyang Pan ,&nbsp;Tao Nie ,&nbsp;Zengli Wang ,&nbsp;Dong Cui","doi":"10.1016/j.vacuum.2024.113821","DOIUrl":"10.1016/j.vacuum.2024.113821","url":null,"abstract":"<div><div>Multi-stage claw vacuum pumps are crucial in various industrial applications for efficiently achieving high vacuum levels compared to other positive displacement vacuum pumps. In order to elucidate the gas pressurization process of the multi-stage claw vacuum pump and clarify its structural design principles, the authors investigated a twin-stage claw vacuum pump as the main research subject, and analyzed its working characteristic. A thermodynamic model of the twin-stage claw vacuum pump describing the pressurization process was established, and the results were verified by means of experiments. Moreover, effects of the phase difference <em>φ</em>_Ⅰ-Ⅱ, the first-stage discharge port angle <em>θ</em>_d,Ⅰ and the thickness ratio <em>B</em>₁:<em>B</em>₂ on pump performance were discussed. Results show that as <em>φ</em>_Ⅰ-Ⅱ increases, the pump power of the first stage gradually increases, while the power of the second stage decreases and then increases. With the increase of <em>θ</em>_d,Ⅰ, the pump power decreases and then increases. When the suction pressure is 10 kPa, the specific power reaches its minimum value under <em>B</em>₁: <em>B</em>₂ = 2:1. As the suction pressure increases, the pump power gradually increases, and its specific power fells substantially and then levels out. These contents are of great significance for the design and optimization of multi-stage claw vacuum pumps.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113821"},"PeriodicalIF":3.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703172","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}

{"title":"Preparation of Au@AuAg yolk-shell nanoparticles with porous surface and their catalytic reduction of 4-nitrophenol","authors":"Meng Yao,&nbsp;Sitong Zhao,&nbsp;Xiankui Lv,&nbsp;Junqi Tang","doi":"10.1016/j.vacuum.2024.113828","DOIUrl":"10.1016/j.vacuum.2024.113828","url":null,"abstract":"<div><div>Yolk-shell structure nanoparticles, consisting of outer shell, inner core and cavity, are a combination of core-shell structure and hollow structure. Due to the existence of their internal gaps, yolk-shell nanostructures have more excellent optoelectronic properties than hollow nanostructures and core-shell nanostructures, and have promising applications in catalysis, energy storage, drug delivery, lithium batteries, biosensors and nanoreactors. In this paper, gold-silver bimetallic yolk-shell nanoparticles (Au@AuAg Y-SNPs) with porous surface structure were synthesized. The morphology and structure of Au@AuAg Y-SNPs were characterized by UV–vis, XRD, SEM, TEM, HRTEM, SAED, and HAADF-STEM, the results demonstrated that the nanostructures are composed of gold and silver bimetals with various shell thickness, and tunable internal voids. In addition, the catalytic activity of the Au@AuAg yolk-shell nanoparticles were investigated based on the model catalytic reaction of hydrogenation reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with superfluous sodium borohydride. The yolk-shell nanostructure had the best catalytic activity when the ratio of Ag to Au was 1:4. The kinetic constant of the reaction, apparent rate constants (K_app) was 0.0072 s⁻¹ when 100 μL of this nanocatalyst was added. This suggests that Au@AuAg Y-SNPs have a promising application in the removal of pollutants from water bodies and environmental remediation.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113828"},"PeriodicalIF":3.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659327","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}

{"title":"Defect engineering of anchored on F-doped BNNR surface to enhance low-frequency microwave absorption and achieve exceptional thermal conductivity properties","authors":"Zhen Lv ,&nbsp;Zhongyang Duan ,&nbsp;Ning Jiang ,&nbsp;Ruoxuan Zheng ,&nbsp;Di Yin ,&nbsp;Yufeng Bai ,&nbsp;Tingting Yang ,&nbsp;Tai Peng","doi":"10.1016/j.vacuum.2024.113826","DOIUrl":"10.1016/j.vacuum.2024.113826","url":null,"abstract":"<div><div>The growing demand for AI and smart computing drives the development of compact, lightweight electronic products to mitigate electromagnetic wave (EMW) pollution and thermal management issues. This necessitates materials with enhanced microwave absorption (MA) and optimal thermal conductivity (TC). Herein, we designed and synthesized fluorinated boron nitride nanorods (F-BNNRs) in a single step via plasma ball milling. Ammonium fluoride (NH₄F) served as the fluorinating agent for hexagonal boron nitride nanorods (h-BNNRs). F-BNNR3, with a NH₄F to h-BNNR ratio of 10:1 and 5.84 % fluorine (F) content, exhibits excellent MA, achieving a minimum reflection loss (RLmin) of −68.56 dB at 5.14 GHz with a thickness of 4.32 mm. It also displays a broad MA frequency range (4.6–6.1 GHz, 15.4–17.2 GHz) with significant RL &lt; −10 dB. Additionally, a 0.09 wt% F-BNNR3 solution achieves a thermal conductivity (TC) of 0.95 W m⁻¹K⁻¹, 134 % higher than that of a 0.09 wt% h-BNNR dispersion fluid. Following a post-static treatment, F-BNNR3 attains a TC of 0.86 W m⁻¹K⁻¹, 118 % higher than that of h-BNNR. The incorporation of F into h-BNNRs significantly enhances MA and TC performance, addressing EMW pollution and thermal management challenges in advanced communication technologies utilizing nanofluids.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113826"},"PeriodicalIF":3.8,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657338","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}