Vacuum最新文献

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Temperature-dependent dynamics and dislocation behavior in nanoscale machining of FeCoNiCrAl high-entropy alloys: Molecular dynamics simulation 铁钴镍铬铝高熵合金纳米级加工过程中与温度有关的动力学和位错行为：分子动力学模拟

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

Vacuum

Pub Date : 2024-10-04 DOI: 10.1016/j.vacuum.2024.113701

This study investigates the impact of machining parameters on forces, thermal dynamics, dislocation behavior, and crystalline structure changes in FeCoNiCrAl high-entropy alloys during nanoscale material removal using molecular dynamics (MD) simulations. Utilizing Embedded Atom Method (EAM) and Tersoff interaction potentials, simulations were performed at cryogenic (73 K) and room (293 K) temperatures. Novel findings reveal that at 73 K, cutting velocities below 200 m/s produced the highest forces along the [001] direction, whereas at 200 m/s, the peak force shifted to [100]. Increasing velocity decreased the force along [001], while [100] exhibited an inverse relationship. At 293 K, the force remained highest along [001] across all velocities. Notably, forces at 73 K were 1.82, 1.79, and 1.58 times higher than at 293 K for velocities of 100, 200, and 300 m/s, respectively. Dislocation density, particularly 1/6<112> (Shockley) dislocations, peaked under all machining conditions, with a slight initial decrease at 293 K before a significant drop with higher cutting speeds. At 293 K and a cutting speed of 100 m/s, dislocation densities for depths of 5, 10, 15, and 20 Å were approximately 1.04, 1.54, 1.17, and 1.14 times greater than those at 73 K, respectively.

本研究利用分子动力学（MD）模拟研究了加工参数对纳米级材料去除过程中 FeCoNiCrAl 高熵合金中的力、热动力学、位错行为和晶体结构变化的影响。利用嵌入式原子法（EAM）和特尔索夫相互作用势，在低温（73 K）和室温（293 K）下进行了模拟。新发现表明，在 73 K 时，切割速度低于 200 m/s 时，沿 [001] 方向产生的力最大，而在 200 m/s 时，峰值力转移到 [100]。速度越快，沿[001]方向的力越小，而[100]方向则呈现反比关系。在 293 K 时，沿 [001] 方向的力在所有速度下都保持最高。值得注意的是，当速度为 100、200 和 300 m/s 时，73 K 时的力分别是 293 K 时的 1.82、1.79 和 1.58 倍。位错密度，尤其是 1/6<112>（肖克利）位错密度，在所有加工条件下均达到峰值，在 293 K 时最初略有下降，然后随着切削速度的提高而显著下降。在 293 K 和 100 m/s 的切削速度下，深度为 5、10、15 和 20 Å 的位错密度分别是 73 K 时的约 1.04、1.54、1.17 和 1.14 倍。

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引用次数: 0

Interfacial binding and heterogeneous nucleation mechanisms of HfC/HfO2 in HfO2/DZ125 composites: Insights from first-principles calculations and experiments HfO2/DZ125 复合材料中 HfC/HfO2 的界面结合和异质成核机制：第一原理计算和实验的启示

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

Vacuum

Pub Date : 2024-10-03 DOI: 10.1016/j.vacuum.2024.113710

In this paper, the interfacial bonding strengths of the precipitated phase (carbides) and addition phase (HfO₂) in the DZ125 nickel-based superalloy, as well as the nucleation potential of carbides with HfO₂ as a heterogeneous substrate, were calculated by first-principles calculations. Results show that the mismatches of HfC(011)/HfO₂(011) and HfC(111)/HfO₂(011) satisfy the semi-coherent relationship.

Adhesion work (W_ad) and interfacial energy were computed for six interfacial structures with varying terminations and stacking sequences. Model 3 in HfC(111)/HfO₂(011) exhibited the highest W_ad (6.67 J/m²), with an interfacial spacing of 0.95 Å and interfacial energy ranging from −3.2–1.81 J/m², indicating the strongest interfacial bonding strength. Electronic structure analysis confirmed that the strong bonding in Model 3 is due to the formation of a robust Hf-C covalent bond at the interface. Uniaxial tensile tests revealed that Model 3 has a broad strain range and high tensile strength, with the Hf-C bond maintaining its integrity without fracture. Model 3, the most stable structure, supports the adhesion and growth of HfC on HfO₂. The experiment confirms that HfO₂ can serve as a heterogeneous nucleation site for HfC and contribute to the refinement of HfC grains.

本文通过第一性原理计算了DZ125镍基超级合金中析出相（碳化物）和添加相（HfO2）的界面结合强度，以及以HfO2为异质基底的碳化物成核势。结果表明，HfC(011)/HfO2(011)和 HfC(111)/HfO2(011) 的错配满足半相干关系。计算了六种具有不同端点和堆积序列的界面结构的粘附功（Wad）和界面能。HfC(111)/HfO2(011)中的模型 3 显示出最高的 Wad (6.67 J/m2)，界面间距为 0.95 Å，界面能范围为 -3.2-1.81 J/m2，表明界面结合强度最强。电子结构分析证实，模型 3 中的强键合是由于在界面上形成了牢固的 Hf-C 共价键。单轴拉伸试验表明，模型 3 具有较宽的应变范围和较高的拉伸强度，Hf-C 键能保持其完整性而不会断裂。模型 3 是最稳定的结构，支持 HfC 在 HfO2 上的粘附和生长。实验证实，HfO2 可作为 HfC 的异质成核场所，有助于 HfC 晶粒的细化。

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引用次数: 0

Enhanced wear resistance of in-situ nanoscale TiC reinforced Ti composites fabricated by additive manufacturing 通过增材制造提高原位纳米级 TiC 增强钛复合材料的耐磨性

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

Vacuum

Pub Date : 2024-10-02 DOI: 10.1016/j.vacuum.2024.113704

The poor wear resistance of Ti alloys limits its application in the orthopedic and dental surgery field. TiC as an ideal reinforcement phase can improve wear resistance due to its high hardness, low coefficient of friction, and good bio-compatibility. However, the wettability of the interface between the TiC and Ti matrix is poor, which leads to low mechanical properties and wear resistance. In situ TiC formed through the addition of a C source can enhance interfacial bonding. In this work, the Ti-graphite composites are prepared by Laser powder bed fusion (LPBF). On the one hand, the LPBF can prepare various complex porous shapes according to the personalized customized demand. On the other hand, the LPBF can provide a high cooling rate, suppressing grain growth and refining grains, and also can obtain equally distributed nanoscale TiC particles. The results show that the composites are mainly composed of Ti, TiC, and residual graphite. With the increase of graphite content, the amount of TiC increases and the grain becomes smaller, and the microhardness increases from 317 HV_0.2 to 408 HV_0.2. Meanwhile, the Ti-1.5 wt%Gr composite has a low friction coefficient, volume of wear, and wear rate, which is attributed to the high hardness of TiC particles and lubrication of graphite. The oxide on the surface of the wear mark is mainly composed of TiO₂ and TiO. The main wear mechanisms of the composites are oxidation wear and adhesive wear.

钛合金的耐磨性较差，限制了其在整形外科和牙科手术领域的应用。TiC 作为一种理想的增强相，具有硬度高、摩擦系数低和生物相容性好的特点，可以提高耐磨性。然而，TiC 与钛基体之间的界面润湿性较差，导致机械性能和耐磨性较低。通过添加 C 源在原位形成的 TiC 可以增强界面结合力。在这项工作中，钛-石墨复合材料是通过激光粉末床熔融（LPBF）制备的。一方面，LPBF 可根据个性化定制需求制备各种复杂的多孔形状。另一方面，LPBF 可以提供较高的冷却速率，抑制晶粒生长并细化晶粒，还能获得均匀分布的纳米级 TiC 颗粒。结果表明，复合材料主要由 Ti、TiC 和残余石墨组成。随着石墨含量的增加，TiC 的含量增加，晶粒变小，显微硬度从 317 HV0.2 增加到 408 HV0.2。同时，Ti-1.5 wt%Gr 复合材料的摩擦系数、磨损体积和磨损率都很低，这归因于 TiC 颗粒的高硬度和石墨的润滑作用。磨损痕迹表面的氧化物主要由 TiO2 和 TiO 组成。复合材料的主要磨损机理是氧化磨损和粘着磨损。

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引用次数: 0

Multi-stage hierarchical self-assembled ZnIn2S4/ZnO flexible room temperature sensor for DMF sensing 用于传感 DMF 的多级分层自组装 ZnIn2S4/ZnO 柔性室温传感器

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

Vacuum

Pub Date : 2024-10-02 DOI: 10.1016/j.vacuum.2024.113709

It's demanding to exploit flexible room temperature (FRT) sensors due to the hazardous effects of N, N-dimethylformamide (DMF) on human tissues. In this paper, ZnIn₂S₄ (ZIS) is synthesised by solvothermal method, followed by the construction of ZIS/ZnO nanocomposites. The XRD and SEM confirm nanoflower-like ZIS is self-assembled from highly chemically active (110) nanosheets. The gas-sensing measurements indicate that the ZIS/ZnO FRT sensor exhibits excellent selectivity (100 ppm DMF, 78.35 %) and cycling stability, which is approximately a 39-fold improvement over ZnO sensor. In addition, the response decreases by only 5.43 % after 360 bends at 45°, and the response value of the sensor after 15 days is 72.02 %. The improved sensing characteristics can be attributed to the synergistic effect of increased specific surface area (61.09 g/cm²), linear ohmic contact and hetero-nanojunctions. The innovative material design provides a reference for improving the DMF detection efficiency of ZnO-based FRT sensor.

由于 N, N-二甲基甲酰胺（DMF）对人体组织有害，因此开发柔性室温（FRT）传感器的要求很高。本文采用溶热法合成了 ZnIn2S4 (ZIS)，然后构建了 ZIS/ZnO 纳米复合材料。XRD 和 SEM 证实纳米花状 ZIS 是由高化学活性 (110) 纳米片自组装而成。气体感应测量结果表明，ZIS/ZnO FRT 传感器具有出色的选择性（100 ppm DMF，78.35%）和循环稳定性，比 ZnO 传感器提高了约 39 倍。此外，在以 45°弯曲 360 次后，响应仅降低 5.43%，15 天后传感器的响应值为 72.02%。传感特性的改善可归因于比表面积的增加（61.09 克/平方厘米）、线性欧姆接触和异质纳米结的协同效应。创新的材料设计为提高氧化锌基 FRT 传感器的 DMF 检测效率提供了参考。

引用次数: 0

Accelerated elimination of residual B2 phase in TiAl-based alloys by low-temperature annealing plus stretching 通过低温退火加拉伸加速消除 TiAl 基合金中的残余 B2 相

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

Vacuum

Pub Date : 2024-10-02 DOI: 10.1016/j.vacuum.2024.113706

Low-temperature annealing plus stretching is an efficient method to accelerate the elimination of B2 phase in TiAl-based alloys. The stretching stress can produce radial compressive stress on atom and promote the formation of atomic vacancies, both of which promote the atom diffusion, thus accelerating the elimination of B2 phase.

低温退火加拉伸是加速消除 TiAl 基合金中 B2 相的有效方法。拉伸应力能对原子产生径向压应力，并促进原子空位的形成，这两种应力都能促进原子扩散，从而加速 B2 相的消除。

引用次数: 0

Optimized substrate temperature for high-quality CdZnTe epitaxial film in X-ray flat panel detectors 优化 X 射线平板探测器中高质量碲锌镉外延薄膜的基片温度

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

Vacuum

Pub Date : 2024-10-02 DOI: 10.1016/j.vacuum.2024.113705

Cadmium zinc telluride (CdZnTe or CZT) materials, favored for their physical superiority in optoelectronic applications, can be efficiently produced as large-area epitaxial film via close space sublimation (CSS), enhancing potential in flat-panel detector imaging. However, the application of CdZnTe epitaxial film in medical imaging equipment is limited by their lower resistivity, prolonged response times, and diminished sensitivity. By elevating the substrate temperature, we enhanced the number and depth of reverse sublimation pits on the surface of the CdZnTe epitaxial film, established an approximately 100 nm Zn-rich layer, broadened the bandwidth, and minimized electrode injection. Additionally, we observed an aggregation of dislocations at the edges of the reverse sublimation pits, which promoted surface recombination and reduced leakage current. These modifications significantly increased the film's resistivity to 10¹¹ Ω cm. Further, they notably decreased the rise and drop times to 2 m s and 4 m s, respectively. Integrated with thin-film transistors (TFTs), the optimized CdZnTe epitaxial film now distinctly differentiate between air, plastics, and metals under X-ray examination. This improved performance of X-ray flat panel detectors (FPDs) based on CdZnTe epitaxial film is promising for the development of next-generation X-ray detection systems.

碲化镉锌（CdZnTe 或 CZT）材料因其在光电应用中的物理优越性而备受青睐，可通过近空间升华（CSS）技术高效生产大面积外延薄膜，从而提高平板探测器成像的潜力。然而，由于 CdZnTe 外延薄膜电阻率较低、响应时间较长、灵敏度较低，其在医疗成像设备中的应用受到了限制。通过提高衬底温度，我们增加了 CdZnTe 外延薄膜表面反向升华凹坑的数量和深度，形成了约 100 nm 的富锌层，拓宽了带宽，并最大限度地减少了电极注入。此外，我们还观察到反向升华凹坑边缘的位错聚集，这促进了表面重组并降低了漏电流。这些改性使薄膜的电阻率大幅提高到 1011 Ω cm。此外，它们还将上升和下降时间分别显著缩短至 2 m s 和 4 m s。与薄膜晶体管（TFT）集成后，经过优化的碲化镉外延薄膜现在可以在 X 射线检测下明显区分空气、塑料和金属。基于 CdZnTe 外延薄膜的 X 射线平板探测器（FPD）性能的提高为下一代 X 射线探测系统的开发带来了希望。

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引用次数: 0

Study on thermoelectric properties and atomic-scale mechanism of B-site molybdenum-modified La0.1Sr0.9TiO3 B 位钼改性 La0.1Sr0.9TiO3 的热电性能和原子尺度机理研究

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

Vacuum

Pub Date : 2024-10-02 DOI: 10.1016/j.vacuum.2024.113703

Extensive studies on strontium titanate thermoelectric materials have shown that their poor conductivity results in a low ZT value. However, elemental doping can effectively improve the thermoelectric properties of these materials. In this study, a two-step sintering process was applied, using physical mixing to introduce 1 % molybdenum powder as a modification to the lanthanum-doped strontium titanate solid powder (La_0.1Sr_0.9TiO₃). The obtained sample exhibited a maximum conductivity of 7830 S/m, with a maximum ZT of 0.12. Furthermore, this study combined experimental data with first-principles simulation calculations to elucidate the mechanism at the atomic scale. The incorporation of Mo⁶⁺ in place of Ti⁴⁺ at the B-site by molybdenum (Mo) adds two free electrons, leading to an elevated carrier concentration. This change concurrently reduces the Fermi level of the material and improves mobility, collectively resulting in a substantial increase in electrical conductivity. Phonon simulation indicated that Mo doping increased structural defects, thereby reducing lattice thermal conductivity. This significant enhancement in electrical conductivity and decrease in lattice thermal conductivity collectively increased the ZT value of the material.

对钛酸锶热电材料的广泛研究表明，其导电性差导致 ZT 值较低。然而，元素掺杂可以有效改善这些材料的热电特性。本研究采用两步烧结工艺，通过物理混合将 1% 的钼粉引入掺杂镧的钛酸锶固体粉末（La0.1Sr0.9TiO3）中作为改性剂。所得样品的最大电导率为 7830 S/m，最大 ZT 为 0.12。此外，该研究还将实验数据与第一原理模拟计算相结合，以阐明原子尺度上的机理。钼（Mo）在 B 位加入 Mo6+ 取代 Ti4+，增加了两个自由电子，导致载流子浓度升高。这一变化同时降低了材料的费米级，提高了迁移率，从而大大提高了导电性。声子模拟表明，掺杂钼增加了结构缺陷，从而降低了晶格热导率。电导率的显著提高和晶格热导率的降低共同提高了材料的 ZT 值。

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引用次数: 0

A novel triethylamine gas sensor based on PrVO4 material by hydrothermal synthesis 基于水热合成 PrVO4 材料的新型三乙胺气体传感器

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

Vacuum

Pub Date : 2024-10-01 DOI: 10.1016/j.vacuum.2024.113700

Triethylamine (TEA) is a colorless, oily organic compound that can cause serious harm to humans and the environment. Therefore, it is crucial to develop a gas sensor that can rapidly detect TEA. Rare earth vanadate has attracted much attention in the field of sensors due to their strong catalytic effect, good crystallization and chemical stability. In this work, PrVO₄ nanorods were synthesized by hydrothermal method. The crystal structure and morphology of PrVO₄ were characterized by XRD, SEM, TEM and SAED. The novel PrVO₄ gas sensor exhibits excellent gas sensitivity to TEA at 230 °C, including low concentration detection capability, fast adsorption/desorption times (19 s/14 s), good repeatability and long-term stability. In addition, the gas-sensitive mechanism of PrVO₄ is briefly discussed. Therefore, PrVO₄ can be used as a novel gas-sensitizing material.

三乙胺（TEA）是一种无色油状有机化合物，可对人类和环境造成严重危害。因此，开发一种能够快速检测三乙胺的气体传感器至关重要。稀土钒酸盐因其强大的催化作用、良好的结晶性和化学稳定性，在传感器领域备受关注。本研究采用水热法合成了 PrVO4 纳米棒。通过 XRD、SEM、TEM 和 SAED 对 PrVO4 的晶体结构和形貌进行了表征。新型 PrVO4 气体传感器在 230 ℃ 下对三乙醇胺具有优异的气体灵敏度，包括低浓度检测能力、快速吸附/解吸时间（19 s/14 s）、良好的重复性和长期稳定性。此外，还简要讨论了 PrVO4 的气敏机理。因此，PrVO4 可用作一种新型气敏材料。

引用次数: 0

Magnetic properties of bamboo-like Ni-Zn-in nanowires using 3D-AAO templates 使用 3D-AAO 模板的竹节状 Ni-Zn-in 纳米线的磁性能

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

Vacuum

Pub Date : 2024-10-01 DOI: 10.1016/j.vacuum.2024.113694

In this paper, using three-dimensional porous alumina (3D-AAO) as a template, Ni-Zn-In nanowires array with periodically changing diameters was successfully prepared by direct current electrodeposition method. The effect of deposition voltage on the morphology, crystal structure and magnetic properties of Ni-Zn-In ternary alloy nanowires was studied. The experimental results show that the diameters of the nanowires are 212 nm and 151 nm, and the periodic length is 800 nm, which matches the pore size of the phosphoric acid-etched 3D-AAO template. XRD results indicate that the crystal structure of Ni-Zn-In nanowires can be adjusted by the deposition voltage. The VSM results reveal that the Ni-Zn-In nanowires possess soft magnetic properties and significant magnetic anisotropy, with the easy magnetization direction parallel to the film. The nanowires deposited at −1.5 V exhibit the highest coercivity of 161 Oe and squareness of 0.045. Micromagnetic simulations show that the magnetization reversal mechanism of the Ni-Zn-In nanowires is localized nucleation mode.

本文以三维多孔氧化铝（3D-AAO）为模板，采用直流电沉积法成功制备了直径周期性变化的镍锌铟纳米线阵列。研究了沉积电压对 Ni-Zn-In 三元合金纳米线形貌、晶体结构和磁性能的影响。实验结果表明，纳米线的直径分别为 212 nm 和 151 nm，周期长度为 800 nm，与磷酸蚀刻三维-AAO 模板的孔径相匹配。XRD 结果表明，镍锌铟纳米线的晶体结构可以通过沉积电压进行调整。VSM 结果表明，Ni-Zn-In 纳米线具有软磁特性和显著的磁各向异性，易磁化方向与薄膜平行。在 -1.5 V 下沉积的纳米线具有最高的矫顽力（161 Oe）和方正度（0.045）。微磁模拟表明，Ni-Zn-In 纳米线的磁化反转机制是局部成核模式。

引用次数: 0

Synthesis and phase composition of Cd3As2 Dirac semimetal crystals doped with Cr 掺杂铬的 Cd3As2 Dirac 半金属晶体的合成与相组成

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

Vacuum

Pub Date : 2024-10-01 DOI: 10.1016/j.vacuum.2024.113692

In this work we studied variation of structural and microstructural features of Cd

_{3}

_{2}

compound upon introducing the Cr component. Obtained X-ray diffraction data suggest that parent Cd

_{3}

_{2}

phase in studied polycrystals conserve both symmetry and volume of the unit crystal cell, implying low solubility limit of Cr (well below 1 at.

%

). Instead, addition of Cr results in the appearance of CrAs and pure Cd phases. The latter is detected in the form of inclusions of Cd–Cd

_{3}

_{2}

eutectic. Obtained data reveal that CrAs phase formation have rather specific mechanism related to As diffusion, as for large Cr-containing regions we observed clear gradient of As and Cr concentration with radial symmetry. Therefore, varying synthesis parameters one may obtain core–shell inclusions containing different Cr–As phases. Combination of results of thermal and microstructural analysis suggests that Cd

_{3}

_{2}

and CrAs phases are immiscible.

在这项工作中，我们研究了引入铬成分后 Cd3As2 化合物结构和微观结构特征的变化。获得的 X 射线衍射数据表明，所研究多晶体中的母 Cd3As2 相保持了单位晶胞的对称性和体积，这意味着铬的溶解度很低（远低于 1%）。相反，铬的加入会导致 CrAs 和纯镉相的出现。后者以 Cd-Cd3As2 共晶夹杂物的形式存在。获得的数据表明，砷化镉相的形成与砷的扩散有相当特殊的机制，因为在大面积的含铬区域，我们观察到砷和铬的浓度具有明显的梯度，且呈径向对称。因此，改变合成参数可以获得含有不同铬-砷相的核壳夹杂物。热分析和微观结构分析的结果表明，Cd3As2 和 CrAs 相是不相溶的。

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引用次数: 0

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