Vacuum最新文献_第3页

Molecular flow model of gas transmission rate test device with auxiliary chamber for high barrier film

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

Vacuum

Pub Date : 2024-11-23 DOI: 10.1016/j.vacuum.2024.113861

Liu Xiaofeng, Hu Baofa, Zhuang Jiafu, Chu Ruobo, Su Zhicong, Xie Qinglai

The oxygen barrier test of plastic film is an important step in the sealing and preservation process of food and drugs, and the system leakage is pivotal factor of the test device that affecting the efficiency and accuracy. In order to reduce the impact of system leakage on the oxygen barrier detection of plastic film, a test device with an auxiliary seal on the outer layer is designed by using series dual sealing structure technology. Based on the molecular flow states hypothesis, according to the conservation of gas throughput and the invariance of flow resistance, a mathematical model and simulation platform for permeability test of flexible packaging materials with high barrier with outer auxiliary sealing chamber and forward leakage are established. By using Laplace transform method, the analytical solutions and corresponding characteristics of the pressure and leakage rate changes in the inner and outer sealing chamber are discussed, and the equivalent test time expression of the forward leakage test device is derived. The simulation and measured results show that the equivalent test time of the test device with the outer auxiliary sealing chamber is much longer than 24 h, and the test results of the pressure change of the inner sealing chamber are the same as the ideal leak-free system. Compared with the single sealing structure test device, the test error of the same high barrier film permeability test is negligible. By using the test device with an auxiliary sealing chamber, the oxygen barrier property can be accurately measured without any leak measurement and correction.

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引用次数: 0

Assessing the assumption of non-Reliance of concentration-dependent interdiffusion coefficient on maximum component concentration

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

Vacuum

Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113860

Soheil Shaker, Samuel Afolabi, Olanrewaju Ojo

It is generally assumed that the concentration dependence of the interdiffusion coefficient is a constant material parameter under isothermal conditions, unaffected by the maximum component concentration. Consequently, it is expected that the interdiffusion coefficient obtained from pure-metal/pure-metal diffusion couples can be used to predict diffusion effects, such as concentration profiles in alloy/pure-metal or alloy/alloy diffusion couples within the same binary alloy system, regardless of the maximum component concentration and vice versa. However, this non-trivial assumption neglects the potential influence of diffusion-induced stress on the concentration-dependent interdiffusion coefficient, D(C). This study assesses this assumption, and the results show that predicted concentration profiles based on this common assumption grossly fail to match experimental data. The findings demonstrate that using a constant D(C), irrespective of the maximum component concentration, in the prediction and analysis of diffusion effects can lead to significant errors.

引用次数: 0

Dielectric high gradient insulator – Progress towards multilayer insulating structures 高梯度介质绝缘体 - 多层绝缘结构的进展

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

Vacuum

Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113858

Anat Karlin , Michal Sakajio , Meirav Mann-Lahav , Gennady E. Shter , Shai Zamir , Gideon S. Grader

High gradient insulators (HGI) consisting of ceramic and metallic alternating layer structure, have been shown to reduce surface breakdown occurrence in high voltage devices. Recently, the HGI's metal layers were replaced with high dielectric constant ceramics, creating dielectric high gradient insulators (DHGI) that were shown to outperform pure alumina analog. A 2-layer DHGI prototype manufactured by spark plasma sintering (SPS) demonstrated an increased surface breakdown field and fewer surface breakdowns during conditioning, compared to plain alumina. However, weak breakdowns at the opposite polarity were observed in the 2-layer structure. This study focuses on overcoming this issue by introducing a 3-layer design, with two high dielectric layers capping a plain alumina layer. Breakdown tests confirmed the elimination of weak breakdowns and improved dielectric strength, consistent with simulations predictions. Additionally, post-SPS air annealing was shown to be essential for removing adsorbed gases and recovering the high dielectric layers composition that changed during SPS. The annealed DHGIs were shown to reduce significantly the breakdown pulses during high-voltage conditioning. The 3-layer DHGI exhibited a 33.5 % higher breakdown field than plain alumina and a 13.5 % improvement over the 2-layer DHGI reported earlier.

由陶瓷和金属交替层结构组成的高梯度绝缘体（HGI）已被证明可以减少高压设备中的表面击穿现象。最近，HGI 的金属层被高介电常数陶瓷取代，从而产生了介电高梯度绝缘体 (DHGI)，其性能超过了纯氧化铝类似物。与普通氧化铝相比，通过火花等离子烧结（SPS）制造的双层 DHGI 原型在调节过程中显示出更高的表面击穿场和更少的表面击穿。然而，在 2 层结构中观察到了极性相反的微弱击穿。本研究主要通过引入 3 层设计来克服这一问题，即在普通氧化铝层上覆盖两层高介电层。击穿测试证实消除了弱击穿现象，提高了介电强度，这与模拟预测一致。此外，SPS 后的空气退火对于去除吸附气体和恢复在 SPS 期间发生变化的高介电层成分至关重要。退火后的 DHGI 在高压调节过程中可显著降低击穿脉冲。三层 DHGI 的击穿场强比普通氧化铝高出 33.5%，比之前报告的两层 DHGI 高出 13.5%。

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引用次数: 0

A new understanding of phase transformation in vacuum electron beam welding of NS163 Co-based superalloy and AISI 410L stainless steel: Based on in situ observation and variant selection 对 NS163 Co 基超合金和 AISI 410L 不锈钢真空电子束焊接中相变的新认识：基于现场观察和变体选择

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

Vacuum

Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113862

Xin Wen , Xinyu Gao , Shichang Qiao , Fengzhen Wang , Na Li , Shuai Liu , Chao Yuan

This study establishes a link between crystallographic variants and mechanical properties at both the edge and center regions of NS163 Co-based superalloy wires and AISI 410L stainless steel plates welded joints. The thermal cycle of vacuum electron beam welding was simulated using in situ laser confocal microscopy to clarify the martensitic transformation process. Results indicate that martensite preferentially nucleates at grain boundaries, maintaining the Kurdjumov-Sachs orientation relationship with the parent austenite. Most variant boundaries in these regions correspond to variants within the same crystal packet, with V1/V3&V5 emerging as dominant pairs. At the edge, the increased cooling rate and temperature gradient amplify the driving force for martensitic transformation, fostering the generation of diverse variants. Conversely, lower cooling rate at the center raises the martensitic transformation temperature and expands variant selection. The study notes significant dislocation slip during micropillar compression, with the edge of weld exhibiting finer martensite laths and dense dislocations, which enhances strength (∼1279 MPa) compared to the center (∼1040 MPa), aligning with the results obtained via nanoindentation. The observed "size effect" results in a twice strength as measured by micropillar compression compared to nanoindentation. Additionally, staggered Bain groups at the edge include a greater number of high angle grain boundaries, indirectly improving toughness. This research aligns with recent literature and aids in the development of compositional design and machining techniques for heterogeneous welds.

本研究确定了 NS163 Co 基超合金焊丝和 AISI 410L 不锈钢板焊接接头边缘和中心区域的结晶变体与机械性能之间的联系。研究利用原位激光共聚焦显微镜模拟了真空电子束焊接的热循环，以阐明马氏体转变过程。结果表明，马氏体优先在晶界处成核，与母体奥氏体保持库尔德朱莫夫-萨克斯取向关系。这些区域的大多数变体边界对应于同一晶包内的变体，其中 V1/V3&V5 是主要的变体对。在边缘，冷却速率和温度梯度的增加会放大马氏体转变的驱动力，促进各种变体的产生。相反，中心冷却速率降低，马氏体转变温度升高，变体选择范围扩大。研究注意到在微柱压缩过程中存在明显的位错滑移，焊缝边缘表现出更细的马氏体板条和密集的位错，与中心（∼1040 兆帕）相比，增强了强度（∼1279 兆帕），这与纳米压痕获得的结果一致。观察到的 "尺寸效应 "导致微柱压缩测量的强度是纳米压痕测量的两倍。此外，边缘交错的贝恩组包括更多的高角度晶界，间接提高了韧性。这项研究与最近的文献一致，有助于开发异质焊接的成分设计和加工技术。

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引用次数: 0

Insight into the evaporation characteristics of vacuum environment describing the different zones 深入了解描述不同区域的真空环境蒸发特性

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

Vacuum

Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113837

Sarvjeet Singh , Pankaj K. Arya , Prodyut R. Chakraborty , Hardik B. Kothadia

The integrity of the nuclear reactor coolant system and the pressure within the pipes are of utmost concern during the practical operation. Any leakage in the pipes due to fracture/thermal stratification can cause the leakage of high-pressure fluid into the low-pressure environment. This results in a high-pressure drop and phase change from liquid to vapour, which causes accidental mishaps. In depth knowledge of the physics that regulates phase change is needed to forecast the consequences of phase change and guarantee the safety of nuclear activities. The present work aims to augment the understanding of low pressure vaporization through experimental observations. A new experimental setup has been set up to study low pressure vaporization. Experiments are conducted with different initial temperatures ranging from 65 °C to 80 °C, initial water heights between 100 mm to 140 mm, and high vacuum tank pressure varying from 11.32 to 31.32 kPa. Based on the pressure difference, The process is characterized into two different zones and their respective stages. The concept of static superheat and instant superheat is described in the work. The results show that the temperature drop during the first zone is much less than the flashing zone. Flashing time can be increased by increasing the pool height and initial temperature. Instant superheat has a direct relationship to the initial temperature but has an inverse relation to the initial height of the pool. These outcomes will be advantageous in enhancing the design of nuclear coolant systems and addressing safety concerns.

在实际操作过程中，核反应堆冷却剂系统的完整性和管道内的压力是最值得关注的问题。管道内因断裂/热分层造成的任何泄漏都可能导致高压流体泄漏到低压环境中。这将导致高压下降和从液体到蒸汽的相变，从而造成意外事故。要预测相变的后果并保证核活动的安全，就需要深入了解调节相变的物理学知识。目前的工作旨在通过实验观察加深对低压汽化的理解。为了研究低压汽化，我们建立了一个新的实验装置。实验的初始温度从 65 °C 到 80 °C，初始水高从 100 mm 到 140 mm，高真空罐压力从 11.32 kPa 到 31.32 kPa。根据压力差，该过程分为两个不同的区域和各自的阶段。工作中描述了静态过热和瞬时过热的概念。结果表明，第一区的温降远小于闪蒸区。闪蒸时间可以通过增加水池高度和初始温度来延长。瞬时过热度与初始温度有直接关系，但与水池的初始高度成反比。这些结果将有利于改进核冷却剂系统的设计和解决安全问题。

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引用次数: 0

Effects of water-guided laser surface strengthening on surface properties and fatigue life of TC4 titanium alloy in tension-tension fatigue tests 水引导激光表面强化对 TC4 钛合金拉伸疲劳试验中表面性能和疲劳寿命的影响

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

Vacuum

Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113863

Ping Zhang , Yeran Gao , Yan Yu , Yajie Sun , Hanping Zhou , Jinlong Zhang

In this study, we introduce a novel surface strengthening technique known as Water-Jet Guided Laser (WJGL) strengthening. This method is investigated for its impact on the surface properties of TC4 titanium alloy, highlighting its effectiveness in enhancing material performance and extending service life. WJGL strengthening influences material characteristics by adjusting jet velocity and laser overlap ratio.Surface roughness increases with higher jet velocities, and residual stress distribution is similarly affected. Specifically, at a 30 % overlap ratio, surface roughness values rise by 0.0562, 0.2551, and 0.6634 μm as jet velocity increases from 300 to 400 mm/s. Residual compressive stress initially increases with jet velocity, reaching peaks of 827.5, 1018.8, and 1003.3 MPa, before declining.The technique shows consistent effects on maximum residual compressive stress across various overlap ratios, with jet velocity being the primary factor affecting residual stress distribution. WJGL strengthening significantly improves high-cycle fatigue life and thermo-mechanical fatigue performance under tensile-tensile loading conditions. Higher jet velocities correlate with an increased number of cycles to failure in high-cycle fatigue testing. The fracture-prone area initially contracts and then expands, likely due to changes in residual stress.In thermo-mechanical fatigue tests, the central region exhibits a reduced lifespan, indicating a concentrated stress distribution. Fatigue cycle counts show a consistent pattern across different overlap ratios and jet velocities, with higher overlap ratios contributing to longer fatigue life.Compared to traditional techniques such as Water-Jet (WJ) and Laser Shock Peening (LSP), WJGL strengthening demonstrates superior performance and presents a promising approach for material enhancement.

在本研究中，我们介绍了一种新型表面强化技术，即喷水导引激光（WJGL）强化技术。研究了这种方法对 TC4 钛合金表面特性的影响，突出了它在提高材料性能和延长使用寿命方面的有效性。WJGL 强化通过调整喷射速度和激光重叠率来影响材料特性。具体来说，在重叠率为 30% 时，随着喷射速度从 300 mm/s 增加到 400 mm/s，表面粗糙度值分别增加了 0.0562、0.2551 和 0.6634 μm。残余压应力最初随喷射速度的增加而增加，在达到 827.5、1018.8 和 1003.3 兆帕的峰值后开始下降。该技术对不同重叠率的最大残余压应力具有一致的影响，而喷射速度是影响残余应力分布的主要因素。在拉伸-拉伸加载条件下，WJGL 强化技术显著提高了高循环疲劳寿命和热机械疲劳性能。在高循环疲劳测试中，喷射速度越高，失效循环次数越多。在热机械疲劳测试中，中心区域的寿命缩短，表明应力分布集中。在不同的重叠率和喷射速度下，疲劳循环次数显示出一致的模式，重叠率越高，疲劳寿命越长。与水喷射（WJ）和激光冲击强化（LSP）等传统技术相比，WJGL 强化技术性能优越，是一种很有前途的材料强化方法。

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引用次数: 0

Study on surface integrity and crack propagation mechanism of Ti/Al composite plates enhanced based on water jet peening 基于喷水强化的钛铝复合板表面完整性和裂纹扩展机理研究

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

Vacuum

Pub Date : 2024-11-21 DOI: 10.1016/j.vacuum.2024.113818

Ping Zhang , Yeran Gao , Xiaomin Jiang , Yan Yu , Youqiang Wang

This study investigates the mechanisms through which water jet (WJ) enhancement affects surface integrity and crack propagation in Ti/Al composite plates. Finite element models for both WJ enhancement and crack propagation were developed using ABAQUS, complemented by experiments analyzing the influence of different jet velocities on surface integrity parameters, such as residual stress and surface roughness. These parameters were then examined for their effects on the stress intensity factor (SIF), fatigue crack propagation rate (FCP), and crack propagation path.The results demonstrated a positive relationship between jet velocity and both surface roughness and maximum residual compressive stress in specimens treated with WJ enhancement. Specifically, as jet velocity increased from 300 mm/s to 350 mm/s, surface roughness rose approximately 4.2-fold to around 0.95813 μm, while maximum residual compressive stress increased from 1109.9 MPa to 1472.5 MPa. The uniform distribution of residual compressive stress contributed significantly to the reduction in the stress intensity factor.Additionally, the crack propagation rate was inversely correlated with jet velocity. The residual compressive stress induced by higher jet velocities effectively slowed crack propagation. The theoretical interpretation of residual compressive stress as an equivalent damping layer further validated the effectiveness of WJ enhancement in reducing crack propagation in Ti/Al composites.

本研究探讨了水射流（WJ）增强对钛/铝复合板表面完整性和裂纹扩展的影响机制。研究人员使用 ABAQUS 建立了水射流增强和裂纹扩展的有限元模型，并通过实验分析了不同射流速度对残余应力和表面粗糙度等表面完整性参数的影响。结果表明，在经过 WJ 增强处理的试样中，射流速度与表面粗糙度和最大残余压应力之间存在正相关关系。具体来说，当喷射速度从 300 mm/s 增加到 350 mm/s，表面粗糙度增加了约 4.2 倍，达到约 0.95813 μm，而最大残余压应力则从 1109.9 MPa 增加到 1472.5 MPa。残余压应力的均匀分布在很大程度上降低了应力强度因子。较高的喷射速度引起的残余压应力有效地减缓了裂纹的扩展。残余压应力作为等效阻尼层的理论解释进一步验证了 WJ 增强在减少钛/铝复合材料裂纹扩展方面的有效性。

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引用次数: 0

Phase evolution and mechanical properties of AlxCrTaTi refractory medium entropy alloys AlxCrTaTi 难熔中熵合金的相变和机械性能

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

Vacuum

Pub Date : 2024-11-20 DOI: 10.1016/j.vacuum.2024.113847

Xiangxing Xiao , Jiadong Wen , Kechuan Wei , Xian Wang , Xingdong Zhao , Xingqiang Wang , Guixue Zhang , Ying Xu , Yan Wei , Hualong Ge , Hongzhong Cai , Xuehang Wang , Li Chen , Junmei Guo , Kunhua Zhang , Changyi Hu

In multi-principal refractory alloys (high-entropy alloys, medium-entropy alloys), the presence of the second phase has an important influence on the mechanical properties of the alloys. In this paper, AlxCrTaTi (x = 0, 0.25, 0.5, 1.0) refractory medium-entropy alloys were prepared by vacuum arc melting method, and the microstructure, density, and mechanical properties were investigated. The CrTaTi alloy consists of BCC dendritic and C15 Laves phases, whereas the Al_xCrTaTi alloys consist of a two-phase eutectic organization (BCC phase and C14 Laves phase). With the increase of Al content, the content of the second phase increases from 15.97 % to 42.19 %, resulting in an increase in the yield strength of the alloy from 1491 MPa to 2354 MPa at 25 °C, and from 253 MPa to 426 MPa at 1000 °C. The addition of Al element changes the enthalpy, elemental distribution, and solidification process of the alloy, resulting in the formation of Cr-rich and Ti-rich two-phase eutectic organizations in the alloy. With the increase of Al, the second phase strengthening is the main reason for the enhancement of alloy properties.

在多本征难熔合金（高熵合金、中熵合金）中，第二相的存在对合金的力学性能有重要影响。本文采用真空电弧熔炼法制备了 AlxCrTaTi（x = 0、0.25、0.5、1.0）难熔中熵合金，并对其显微组织、密度和力学性能进行了研究。CrTaTi 合金由 BCC 树枝状相和 C15 Laves 相组成，而 AlxCrTaTi 合金则由两相共晶组织（BCC 相和 C14 Laves 相）组成。随着铝含量的增加，第二相的含量从 15.97 % 增加到 42.19 %，从而使合金在 25 °C 时的屈服强度从 1491 兆帕增加到 2354 兆帕，在 1000 °C 时的屈服强度从 253 兆帕增加到 426 兆帕。铝元素的加入改变了合金的焓、元素分布和凝固过程，使合金中形成了富铬和富钛的两相共晶组织。随着铝元素的增加，第二相强化是合金性能增强的主要原因。

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引用次数: 0

Synthesis and characterization of ammonia strengthened and ambient dried N-doped hydrophilic graphene aerogel with good electrical conductivity 具有良好导电性的氨强化和常温干燥 N 掺杂亲水石墨烯气凝胶的合成与表征

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

Vacuum

Pub Date : 2024-11-20 DOI: 10.1016/j.vacuum.2024.113846

Feng Xiong , Jiabin Wang , Neville Dickman , Yujing Liu , Michael R.C. Hunt , Lidija Šiller

We present a novel ‘one-pot’ approach for strengthening reduced graphene oxide (rGO) hydrogels by nitrogen doping. Ammonia is directly added to the precursor reaction mixture prior to hydrothermal gel formation, as opposed to treating as-synthesised rGO hydrogel by ammonia in a second hydrothermal process. This process ensures that the resulting hydrogels are sufficiently robust that aerogels may then be produced by natural drying under ambient temperture and pressure. The as-formed rGO aerogel possesses a Young's modulus as high as 28 kPa and exhibits superelasticity, withstanding strains of up to 95 %. Moreover, the strengthed graphene aerogel possesses an electrical conductivity of up to 1.5 S cm⁻¹ and a specific surface area of 280.0 m² g⁻¹. Although the rGO aerogel was sufficiently reduced to provide good electrical conductivity, it retains a water contact angle of 47 ± 1°, indicating hydrophilic behaviour.

我们提出了一种通过氮掺杂强化还原氧化石墨烯（rGO）水凝胶的新型 "一步法"。在水热凝胶形成之前，氨被直接添加到前驱体反应混合物中，而不是在第二个水热过程中用氨处理合成的 rGO 水凝胶。这种工艺可确保生成的水凝胶足够坚固，从而可以在环境温度和压力下通过自然干燥生产气凝胶。成型的 rGO 气凝胶具有高达 28 kPa 的杨氏模量和超弹性，可承受高达 95% 的应变。此外，强化石墨烯气凝胶的导电率高达 1.5 S cm-1，比表面积为 280.0 m2 g-1。虽然 rGO 气凝胶已被充分还原以提供良好的导电性，但它的水接触角仍保持在 47 ± 1°，这表明它具有亲水性。

引用次数: 0

Influence of oxygen on metastable pitting behavior of super 13Cr stainless steel in CO2-saturated environment 氧气对二氧化碳饱和环境中超 13Cr 不锈钢瞬态点蚀行为的影响

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

Vacuum

Pub Date : 2024-11-19 DOI: 10.1016/j.vacuum.2024.113845

Lv Naixin , Fu Anqing , Chen Chao , Bai Haitao , Zhao Zaipeng , Li Xuanpeng , Xu Zhengyi , Guozhe Meng

This study investigates the effect of oxygen on the metastable pitting corrosion behavior of Super 13Cr martensitic stainless steel in a CO₂-saturated environment, which is pertinent to challenging extraction conditions of oil and gas industry. Potentiostatic polarization and comprehensive statistical analysis to assess the corrosion dynamics. The results indicate that the presence of oxygen significantly influences the initiation and progression of metastable pitting. In the 50 % O₂ + 50 % CO₂ environment, a decrease in the frequency and size of metastable pitting events was observed, along with a reduction in the peak current, pit radius, and stable product, suggesting that oxygen inhibits the transition from metastable to stable pitting.

本研究探讨了氧气对超级 13Cr 马氏体不锈钢在二氧化碳饱和环境中的转移点腐蚀行为的影响，这与石油和天然气工业的挑战性开采条件有关。通过恒电位极化和综合统计分析来评估腐蚀动态。结果表明，氧气的存在极大地影响了易生点蚀的发生和发展。在 50%O2 + 50% CO2 的环境中，观察到可迁移点蚀事件的频率和大小有所下降，峰值电流、点蚀半径和稳定产物也有所减少，这表明氧气抑制了从可迁移点蚀到稳定点蚀的转变。

引用次数: 0