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

Vacuum

Pub Date : 2024-11-27 DOI: 10.1016/j.vacuum.2024.113894

Linlin Liu , Guoqun Zhao , Xingting Zhao , Yexu Li , Zhengfeng Lv

Al-Zn-Mg-Cu alloy profiles are widely used as aircraft components because of lightweight and high strength. The section of thin-walled profile is easy to have unavoidable heterogeneous strain. However, the influence mechanism of different cumulative plastic strains (CPS) on the material properties at different cross-section locations needs to be further clarified. This study carried out an extrusion experiment to study the influence of CPS on the microstructure, properties, and strengthening mechanisms by TEM, SEM and XRD. Results show that the strength and micro-hardness are positively correlated with CPS, while the elongation exhibits an inverse correlation. The orientation relationships between different micro- and nano-scale precipitates and the matrix were characterized. The strengthening mechanisms under different CPS were clarified. It was found that the contribution of solid solution strengthening is 22.6 % under the maximum cumulative strain, while Orowan strengthening accounts for 20.3 %. In contrast, these contributions are 30.2 % and 11.9 % under lower cumulative strain, respectively. Specimens at low CPS have the precipitated phase bands parallel to the extrusion direction, while the high CPS induces smaller and dense precipitated phases in the matrix and grain boundaries, resulting in precipitate-free zones with a width of 200–500 nm at the sub-grain boundary, which reduces the strengthening effect at the grain boundary. The research findings can guide for optimizing the heat treatment processes of thin-walled profiles.

Al-Zn-Mg-Cu合金型材因其重量轻、强度高而广泛应用于飞机零部件。薄壁型材截面容易产生不可避免的非均质应变。但不同累积塑性应变（CPS）对不同截面位置材料性能的影响机理有待进一步研究。通过挤压实验，通过TEM、SEM、XRD等手段研究了CPS对复合材料显微组织、性能的影响及强化机理。结果表明，强度和显微硬度与CPS呈正相关，延伸率呈负相关。表征了不同微纳析出物与基体的取向关系。阐明了不同CPS下的强化机制。结果表明，在最大累积应变下，固溶强化的贡献为22.6%，而Orowan强化的贡献为20.3%。相比之下，在较低的累积应变下，这些贡献分别为30.2%和11.9%。低CPS时，析出相带平行于挤压方向，而高CPS时，在基体和晶界处析出相较小且密集，在亚晶界处形成宽度为200 ~ 500 nm的无析出带，降低了晶界处的强化效果。研究结果对薄壁型材热处理工艺的优化具有指导意义。

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引用次数: 0

Effects of magnetic conduction sleeve on the performance of a multi-cusped field thruster 磁导套对多尖头场推力器性能的影响

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113880

Peng Hu , Wei Mao , Hui Liu , Daren Yu

The multi-cusped field thruster is a type of plasma electric propulsion device. Several alternating polarity permanent magnets are employed to form a unique cusped magnetic field. The thruster exhibits many performance advantages such as long lifetime, extremely large range thrust throttle ability, and high thrust density. In this paper, a magnetic conduction sleeve has been designed in a multi-cusped field thruster. The experimental results show that the additional magnetic conduction sleeve can significantly reduce the plume divergence angle, shifting the peak of the ion current density towards the axis from 24.5° to 15.1°. The main reason for this is that in the exit acceleration region, the magnetic field lines near the axis bend upwards, causing the electric field to be deflected towards the axis. As a result, the ions are accelerated by this focused electric field to form a collimated plume. In addition, the magnetic conduction sleeve can also reduce the radial gradient of the magnetic field in the main ionization region, and the ionization rate is enhanced. All these effects resulting in a significant increase in both thrust and efficiency. This work presents a new solution for optimizing the performance of a multi-cusped field thruster.

多尖头场推力器是一种等离子体电推进装置。几个交变极性永磁体被用来形成一个独特的尖头磁场。该推进器具有寿命长、推力节流能力大、推力密度高等性能优势。本文设计了多尖头场推力器的导磁套。实验结果表明，增加导磁套可以显著减小羽流发散角，使离子电流密度峰值向轴方向由24.5°移动到15.1°。其主要原因是在出口加速区，靠近轴的磁力线向上弯曲，导致电场向轴方向偏转。结果，离子被这个聚焦的电场加速，形成一个准直的羽流。此外，导磁套还可以降低主电离区磁场的径向梯度，提高电离速率。所有这些影响导致推力和效率的显著增加。本文提出了一种优化多尖头场推力器性能的新方法。

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引用次数: 0

Diatomic nitrogen-fixation electrocatalysts supported on graphitic carbon nitride achieve significantly low over potentials 石墨氮化碳负载的双原子固氮电催化剂具有明显的低过电位

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113888

Zheng-Yun Xiong , Wen-qing Hong , WangDong Zeng , Zhi-Min Ao , Ying Xu

The construction and screening of diatomic catalysts (DAC), as well as the exploration of intrinsic descriptors, are attracting increasing attention. In this work, using graphitic carbon nitride (g-CN) as the substrate, we assembled W, Mo, Cr, Mn, Fe, Co, and Ni atoms into DAC and conducted a systematic exploration of the catalytic capabilities of these systems for nitrogen reduction reaction (NRR) using first-principles calculations. Our research demonstrates that MoMn@g-CN exhibits outstanding catalytic activity and selectivity among the investigated 28 catalysts. The overpotential for NRR on MoMn@g-CN along the enzymatic pathway is merely 0.10 V, which is lower than most of the reported catalysts. By conducting in-depth electronic structure calculations, the catalytic mechanism of the DAC is investigated. N₂ adsorption and activation are influenced by the σ-acceptor-π∗-donor mechanism. The enhanced activation of nitrogen molecules is attributed to the synergistic effect of two hetero-diatomic species. Moreover, we have identified an new intrinsic descriptor for NRR related to the electronegativity of the two transition metal atoms. This descriptor correlates with the volcano plot of NRR's limiting potential. Our findings can provide valuable insights for the design and high-throughput screening of DAC.

双原子催化剂（DAC）的构建、筛选以及本征描述子的探索日益受到人们的关注。在这项工作中，我们使用石墨化碳氮（g-CN）作为衬底，将W， Mo, Cr, Mn, Fe， Co和Ni原子组装到DAC中，并使用第一性原理计算对这些体系对氮还原反应（NRR）的催化能力进行了系统的探索。我们的研究表明MoMn@g-CN在28种催化剂中表现出优异的催化活性和选择性。NRR在MoMn@g-CN上的过电位仅为0.10 V，低于大多数已报道的催化剂。通过深入的电子结构计算，研究了DAC的催化机理。N2的吸附和活化受σ-受体-π * -供体机制的影响。氮分子活化的增强归因于两种异双原子物质的协同作用。此外，我们还确定了与两个过渡金属原子的电负性有关的NRR的一个新的本征描述符。这个描述符与NRR极限潜力的火山图相关。我们的研究结果可以为DAC的设计和高通量筛选提供有价值的见解。

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引用次数: 0

Internal cylindrical cathode arc deposited Cr coatings on the interior of slender tube: The influence of arc currents 细长管内圆柱形阴极弧沉积Cr涂层：电弧电流的影响

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113883

Benfu Wang, Xiubo Tian, Chunzhi Gong, Huiyuan Geng, Tianshi Hu

In this study, a novel internal cylindrical cathode arc device with electric-field assistance is proposed to address the issue of uniform coating on the interior of a slender tube. The relative average deviation of Cr coating thickness has been reduced to as low as 0.53 %, indicating high uniformity in axial thickness of the coatings. The effect of different arc currents (25–55 A) on the structure and surface properties of the coatings is investigated. The thickness, micro-structure, surface roughness, nano-hardness, friction and wear, adhesion between the coating and substrate as well as corrosion resistance of the deposited coatings are measured by a scanning electron microscopy, atom force microscopy, X-ray diffraction spectrometer, nano indenter, friction and wear instrument, scratch and indentation apparatus and electrochemical instrument, respectively. The results suggest that the proportion of macroparticles increases with arc current. Additionally, the macroparticles exhibit an atypical oblate pattern. This may lead to weaker, more fragile regions that are prone to flaking. Consequently, larger arc current gives rise to the deterioration in the tribological properties, adhesion between the coating and substrate, and electrochemical properties of the coatings. This study provides a feasible solution to obtain extremely uniform Cr coatings on the interior of slender tube by using the axially cylindrical cathode arc ion plating. At the same time, minimizing the arc current is beneficial to improve the performance of the coatings.

本文提出了一种新型的电场辅助内圆柱形阴极电弧装置，以解决细长管内部涂膜均匀的问题。Cr涂层厚度的相对平均偏差降低到0.53%，表明涂层轴向厚度的均匀性较高。研究了不同电弧电流（25 ~ 55 A）对镀层结构和表面性能的影响。分别用扫描电镜、原子力显微镜、x射线衍射光谱仪、纳米压头、摩擦磨损仪、划痕压痕仪和电化学仪测量镀层的厚度、显微组织、表面粗糙度、纳米硬度、摩擦磨损、涂层与基体的附着力以及耐蚀性。结果表明，随着电弧电流的增大，微粒的比例增大。此外，大颗粒呈非典型扁圆形。这可能会导致更弱、更脆弱的区域容易剥落。因此，较大的电弧电流会导致涂层的摩擦学性能、涂层与基体之间的附着力和电化学性能的恶化。本研究为利用轴向圆柱形阴极电弧离子镀在细长管内部获得极均匀的Cr涂层提供了可行的解决方案。同时，减小电弧电流有利于提高涂层的性能。

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引用次数: 0

Kinetic study of a-Si crystallization induced by an intermetallic compound 金属间化合物诱导a-Si结晶动力学研究

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113877

Evgeny T. Moiseenko , Vladimir V. Yumashev , Roman R. Altunin , Leonid A. Solovyov , Sergey M. Zharkov

The problem under study is concerned with amorphous silicon (a-Si) crystallization which is induced by an intermetallic compound, with this compound chosen to be Al₂Cu, formed by a solid-state reaction between nanolayers of aluminum and copper in a Cu/Al/a-Si multilayer system. In the case of crystallization initiated by the intermetallic compound Al₂Cu, the crystallization temperature of amorphous silicon was found to be ≈ 300°С (upon heating at a rate of 5–10 °C/min), which was significantly higher than in the case of pure Al (≈170°С), but lower as compared to using pure Cu (≈485°С). The higher crystallization temperatures in comparison with aluminium-induced crystallization are assumed to be caused by a decrease in the number of free electrons due to the presence of copper and formation of the Al₂Cu phase. By kinetic modeling, it was revealed that the mechanism of a-Si crystallization induced by the intermetallic compound Al₂Cu was similar to the mechanism of Al-induced crystallization of a-Si in multilayer (Al/a-Si)_n films, i.e the process of a-Si crystallization occurred in two subsequent stages: Cn-X→Fn. Kinetic parameters of silicon crystallization for each reaction step were obtained. The enthalpy of a-Si crystallization initiated by Al₂Cu was estimated to be ΔH = 12.3 ± 0.5 kJ/mol.

本文研究的是非晶硅（a- si）结晶是由一种金属间化合物引起的，该化合物选择为Al2Cu，由Cu/Al/a- si多层体系中的纳米铝层和铜层之间的固相反应形成。在金属间化合物Al2Cu引发结晶的情况下，发现非晶硅的结晶温度为≈300°С（以5-10°C/min的速率加热时），明显高于纯Al（≈170°С），但低于纯Cu（≈485°С）。与铝诱导结晶相比，较高的结晶温度被认为是由于铜的存在和Al2Cu相的形成导致自由电子数量的减少。通过动力学模拟发现，金属间化合物Al2Cu诱导a-Si结晶的机理与Al诱导多层（Al/a-Si）n薄膜中a-Si的结晶机理相似，即a-Si的结晶过程发生在Cn-X→Fn两个后续阶段。得到了硅结晶各反应步骤的动力学参数。Al2Cu引发的a-Si结晶焓为ΔH = 12.3±0.5 kJ/mol。

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引用次数: 0

Labyrinth seal design for space applications 空间应用的迷宫密封设计

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113882

Josef Pouzar , David Kostal , Lars-Göran Westerberg , Erik Nyberg , Ivan Krupka

Labyrinth seals, extensively used in space applications, serve to prevent the loss of liquid lubricants and shield satellite subsystems from contamination. These seals are essential for the reliable functioning of bearings and for protecting satellite subsystems from contamination. This study compares analytical predictions of lubricant loss against experimental measurements and computer simulations to optimize labyrinth seal configurations. Analytical models tend to overestimate mass loss by 5–8 times compared to experimental data, indicating limited reliability for complex seal geometries. Simulations using MolFlow+ and COMSOL Multiphysics align closely with experimental results, providing accurate mass loss predictions. Key findings highlight that labyrinth length, width, and surface roughness are critical factors in minimizing evaporative mass loss. Notably, stepped labyrinth seals with relief grooves and optimized step positioning effectively reduce molecular beaming effects and improve sealing performance compared to straight geometries. Effective sealing not only reduces mission failures but also helps to minimize space debris, thereby promoting safer satellite missions.

迷宫密封广泛用于空间应用，用于防止液体润滑剂的损失和保护卫星子系统免受污染。这些密封件对于轴承的可靠运行和保护卫星子系统免受污染至关重要。本研究将润滑油损失的分析预测与实验测量和计算机模拟进行比较，以优化迷宫密封配置。与实验数据相比，分析模型往往高估了5-8倍的质量损失，这表明对于复杂密封几何形状的可靠性有限。使用MolFlow+和COMSOL Multiphysics进行的模拟与实验结果非常吻合，提供了准确的质量损失预测。主要研究结果强调，迷宫的长度、宽度和表面粗糙度是减少蒸发质量损失的关键因素。值得注意的是，与直线几何形状相比，带卸压槽的阶梯迷宫密封和优化的阶梯定位有效地减少了分子光束效应，提高了密封性能。有效的密封不仅可以减少任务失败，还有助于减少空间碎片，从而促进更安全的卫星任务。

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引用次数: 0

Microstructure and temperature-dependent fretting wear behaviour of AA7075/MoS2/Red-Mud Hybrid composites via vacuum-assisted stir casting route 真空辅助搅拌铸造AA7075/MoS2/赤泥复合材料显微组织及温度相关微动磨损行为

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113884

Priyeshiv Kumar Gurmaita , Virendra Pratap Singh , Rosang Pongen

The present research explores the fabrication and characterization of AA7075/MoS₂/Red-mud hybrid composites (HC) through vacuum-assisted stir casting, varying both reinforcement contents from 5 to 15 wt%. Various tests were conducted, including microstructural evolution, XRD, hardness, and impact strength. The fretting wear test was performed at various temperatures (i.e., room temperature, 50 °C, and 100 °C). The coefficient of friction first increased and then decreased with temperature for higher MoS₂ content composite, whereas hardness increased and impact strength reduced. Various second-phase particles, including SiO₂, Fe₂O₃, Al₂O₃, MoS₂, MgO, and MgZn, were detected in the developed HCs, directly influencing the mechanical and tribological properties.

本研究探索了通过真空辅助搅拌铸造制备AA7075/MoS2/赤泥混杂复合材料（HC）并对其进行表征。进行了显微组织演化、XRD、硬度和冲击强度等测试。微动磨损试验在不同温度下进行（即室温、50℃和100℃）。MoS2含量高的复合材料，摩擦系数随温度的升高先增大后减小，硬度升高，冲击强度降低。在开发的hc中检测到各种第二相颗粒，包括SiO2， Fe2O3, Al2O3, MoS2， MgO和MgZn，直接影响机械和摩擦学性能。

引用次数: 0

Effects of pressure on the electronic and optical properties of defect-free and defect-containing fused silica: A first-principles study 压力对无缺陷和含缺陷熔融石英的电子和光学特性的影响：第一原理研究

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113881

Rongqi Shen , Yi Lu , Zhongxi Zhang

Fused silica is a widely used optical material in high-power solid-state laser systems. The electronic and optical properties of fused silica are affected by point defects and stress in the material. In this paper, the electronic and optical properties of fused silica are calculated using the first-principles method. The study found that the band gap of defect-free fused silica material gradually decreases as the pressure increases. When the fused silica material contains oxygen vacancy or silicon vacancy defects, the band gap size is not proportional to pressure. During the elastic deformation stage, low strain and high strain cause a sudden change in the band gap size of defect-containing fused silica. This paper reveals the mechanism of the influence of pressure on the band gap and optical properties of defect-free and defect-containing fused silica materials from the perspective of micro-stress.

熔融石英是一种广泛应用于高功率固体激光系统的光学材料。熔融石英的电子和光学特性受到材料中的点缺陷和应力的影响。本文采用第一原理方法计算了熔融石英的电子和光学特性。研究发现，无缺陷熔融石英材料的带隙随着压力的增加而逐渐减小。当熔融石英材料含有氧空位或硅空位缺陷时，带隙大小与压力不成正比。在弹性变形阶段，低应变和高应变会引起含缺陷熔融石英带隙大小的突然变化。本文从微应力的角度揭示了压力对无缺陷和含缺陷熔融石英材料带隙和光学特性的影响机理。

引用次数: 0

Micro milling mechanism and tool wear of Unidirectional HfZrTiTaNbCu0.2 fiber reinforced aluminum matrix composites 单向HfZrTiTaNbCu0.2纤维增强铝基复合材料微铣削机理及刀具磨损

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113886

Ping Zhang , Shunxiang Wang , Xiaomin Jiang , Yan Yu

This study delves into the micro milling and tool wear mechanisms of 2A97 aluminum matrix composites reinforced with HfZrTiTaNbCu_0.2 fibers. Finite element analysis models the fibers as uniformly distributed cylindrical entities within the matrix, applying various material constitutive laws, failure, and evolution criteria to simulate milling at three specific angles (45°, 90°, 135°). The research examines the effects of milling parameters, fiber orientations, and tool coating thickness on cutting forces, temperatures, surface roughness, and tool wear. Key findings include: These forces escalate with both cutting speed and depth of cut. Notably, at a feed rate of 68 μm/z, the cutting force is 1.5 times higher compared to 58 μm/z.An increase in milling parameters leads to higher cutting temperatures. Differences of 12 °C and 10 °C were noted at varying depths of cut (10–25 μm) and cutting speeds (1000–1200 mm/s), respectively. As the fiber angle increases, cutting forces first decrease and then rise, with fibers oriented at 90° experiencing only 53 % of the force compared to those at 135°. Similarly, cutting temperatures follow this trend, with a 26 °C difference between 45° and 90° fibers. This factor is positively correlated with depth of cut and fiber angle. Surface roughness at a 55 μm depth is 4.3 times that at 10 μm, and 135° fibers show 2.7 times the roughness of 45° fibers. However, within feed rates of 48–58 μm/z and cutting speeds of 800–1200 mm/s, there is a notable decrease in surface roughness. Variations in cutting parameters, fiber orientations, and tool coating thickness significantly influence peak tool stress. Stress concentration at the central groove tends to reduce tool wear, whereas stress concentration at the peripheral edge or strain concentration at the bottom edge exacerbates it.

研究了HfZrTiTaNbCu0.2纤维增强2A97铝基复合材料的微铣削和刀具磨损机理。有限元分析将纤维建模为均匀分布在基体中的圆柱形实体，应用各种材料本构定律，失效和演化标准来模拟三种特定角度（45°，90°，135°）的铣削。该研究考察了铣削参数、纤维取向和刀具涂层厚度对切削力、温度、表面粗糙度和刀具磨损的影响。这些力随着切削速度和切削深度的增加而增加。值得注意的是，当进给速度为68 μm/z时，切削力是58 μm/z时的1.5倍。铣削参数的增加导致更高的切削温度。在不同的切割深度（10 ~ 25 μm）和切割速度（1000 ~ 1200 mm/s）下，12°C和10°C的温度差异显著。随着纤维角度的增加，切割力先减小后增大，与135°的纤维相比，90°的纤维只承受53%的力。同样，切割温度也遵循这一趋势，在45°和90°纤维之间相差26°C。该因子与切割深度和纤维角度呈正相关。55 μm深度的表面粗糙度是10 μm深度的4.3倍，135°光纤的表面粗糙度是45°光纤的2.7倍。然而，当进给速度为48 ~ 58 μm/z，切削速度为800 ~ 1200 mm/s时，表面粗糙度显著降低。切削参数、纤维取向和刀具涂层厚度的变化显著影响峰值刀具应力。中心槽的应力集中倾向于减少刀具磨损，而外围边缘的应力集中或底部边缘的应变集中则加剧了刀具磨损。

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引用次数: 0

Fast prediction of the melting of FeHx in planetary interiors 快速预测FeHx在行星内部的熔化

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

Vacuum

Pub Date : 2024-11-26 DOI: 10.1016/j.vacuum.2024.113857

Tran Dinh Cuong , Anh D. Phan

FeH

_{x}

is a crucial mineral in geophysics, but its melting properties remain poorly understood at high pressures. In this Short Communication, we introduce a simple analytical model to access the solid–liquid boundary of FeH

_{x}

with minimal time and cost. Inspired by the work-heat equivalence principle, our model allows geophysicists to effectively exploit available ab initio resources to directly deduce the melting temperature of FeH

_{x}

from its equation of state. The obtained results agree quantitatively with cutting-edge atomistic simulations throughout a wide range of hydrogen content and hydrostatic pressure. Therefore, our analyses would have implications for elucidating the internal dynamics of rocky worlds within and beyond our Solar System.

FeHx在地球物理学中是一种至关重要的矿物，但它在高压下的熔融特性仍然鲜为人知。在这篇简短的通讯中，我们介绍了一个简单的分析模型，以最小的时间和成本获得FeHx的固液边界。受工热等效原理的启发，我们的模型使地球物理学家能够有效地利用现有的从头算资源，直接从FeHx的状态方程推断出其熔化温度。所得结果在定量上与广泛的氢含量和静水压力范围内的尖端原子模拟一致。因此，我们的分析将有助于阐明太阳系内外岩石世界的内部动力学。

引用次数: 0

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