Ta与Ta-2.5W在硫酸溶液中的电化学性能比较

利用电化学测试仪Model273A测试了Ta和Ta-2.5W在温度为60℃,浓度为30%,60%和80%的硫酸溶液中的Tafel曲线和动电位扫描阳极极化曲线.结果表明,在3种浓度的硫酸溶液中,Ta-2.5W的腐蚀倾向小于Ta的腐蚀倾向,腐蚀电流密度比Ta的小,钝化性能比Ta的优越.     

Ta-12W合金氩弧焊工艺研究

采用Ta-12W合金板材进行对接自熔和加钛焊料氩弧焊实验,观察了焊缝区的金相组织,并用能谱分析了加钛焊料氩弧焊焊缝区的成分;试样加工成拉伸样,一组为焊接态,另一组进行1200℃/1h真空退火处理,所有样品测量了焊接强度.实验结果表明:1)Ta-12W合金氩弧焊接组织很不均匀;2)Ta-12W合金采用氩弧焊焊缝强度不高,拉伸断裂均发生在热影响区;3)Ta-12W合金采用对接自熔氩弧焊方式优于加钛焊料氩弧焊方式.     

Ta-10W/Ti的高温界面反应研究

采用多弧离子镀技术在金属钛表面成功制备出连续致密且厚度均匀的α-Ta相Ta-10W涂层。在900℃下分别对涂层进行高温氧化和真空扩散处理,通过XRD、SEM、EDS等分析测试手段对涂层的抗氧化性能及元素扩散行为进行研究。结果表明:在高温氧化过程中,存在氧化和扩散双重作用,涂层与基体间发生相互扩散且涂层表面形成氧化膜,致使涂层脆化,但涂层/基体界面处氧化不明显,说明Ta-10W涂层对基体起到了有效的抗氧化作用;在真空扩散过程中,Ta向基体中扩散较为剧烈且沿着逐渐趋直的α-Ti晶界进行扩散。     

电镀非晶态镍钨合金工艺研究

研究了电镀非晶态镍钨合金工艺,采用EDS、XRD等手段检测了镍钨合金镀层,并将工艺条件如电流密度Jc、镀液pH值、镀液温度等对镀层的影响进行了比较,得出非晶态镍钨合金电镀的最佳工艺:[W]/([W] [Ni])为0.6～0.8,Jc=6.0～12.0 A/dm2,温度55～65℃,pH=6.5～7.5.结果表明,W含量质量分数高于44%的镍钨合金镀层结构为非晶态;且在此工艺下易得到钨含量在44%以上的非晶态钨合金镀层.     

Al2O3含量对Al2O3/W复合材料合成的影响

以铝热法为基础制备了A12O3/W复合材料，探讨了A12O3含量对复合材料合成的影响。研究表明：主要物相为α-A12O3、金属W。刚玉含量小于0．3时，温度影响不显著，大于0．3时，温度影响显著，有大量碳化物生成，且WC/W2C相对含量随A12O3含量增加及煅烧温度的提高而增加。当刚玉含量为0．5mol时，有正交晶钨酸铝生成。随刚玉含量变化，金属钨分布从连续分布向弥散分布变化。连续分布的金属钨因被氧化铝包裹因此难以碳化，而弥散分布的金属钨则易于被碳化。     

W与CuCrZr焊接应力的有限元分析及剪切强度的研究

为了研究应用于聚变试验堆的面向等离子体部件中W与CuCrZr的焊接,选用有限元软件ABAQUS对未用无氧铜箔、或使用不同厚度的无氧铜箔,及在不同温度、压力时的焊接应力进行了有限元分析。实验中使用、或未用无氧铜中间层均成功实现了W与CuCrZr的焊接。测定了焊接试样的剪切强度,并通过SEM观察了其断口形貌。实验结果表明,无氧铜箔的使用大大地提高了焊接强度,最高剪切强度高于198MPa,其剪切断口均位于距离焊缝1mm左右的钨块中,且在钨块中均出现了撕裂现象。ABAQUS有限元数值分析的结果表明,无氧铜箔很好地降低了W与CuCrZr之间的焊接应力,较低的焊接温度、较高的焊接压力、增加无氧铜箔的厚度均有助于减小W与CuCrZr之间的焊接应力。     

聚变装置钨涂层面对等离子体材料的性能

对铜基体上真空等离子体喷涂1 mm的钨涂层进行了分析研究,主要包括微观结构、热力学属性以及成分分析.结果显示,钨涂层气孔率仅为7.6%,室温热导率达到79.7 W/(m·K),W/Cu结构界面结合强度高达45 MPa,这些结果对钨作为聚变装置面对等离子体材料的应用是令人鼓舞的.涂层材料的出气性能也是面对等离子材料的一个重要指标,钨涂层出气气体种类主要是氢气和水蒸气.而且在300℃经过4 h高温烘烤后出气率大幅度降低,更长时间的烘烤则对出气率影响不是太明显.因此可以看出钨涂层作为聚变装置面对等离子体材料的应用是可行的.     

钨精矿中砷的测定

本文论述钨精矿中砷含量的测定方法,对试样分解、还原、滴定、共存元素影响、方法的准确度和精密度的考察作了详细研究。方法的相对标准偏差为0.515%-1.164%,样品加标回收率为99.80-102.00%,适用于钨精矿中0.5%以上砷的测定。     

Ta-10W合金高温抗氧化涂层的制备

主要讲述Ta10W合金高温抗氧化涂层的制备方法、性能检测方法及显微组织分析以及合金和涂层的性能及应用领域。     

低压等离子喷涂厚钨涂层的组织与性能

为获得高致密度、高热导率及低氧含量的钨喷涂层,采用低压等离子喷涂(LPPS)技术,以4种不同工艺参数在铬锆铜基体上制备了0.9～1.2 mm钨喷涂层。用扫描电镜、氧氮分析仪及闪光导热仪研究了4种钨喷涂层的显微结构、氧含量及热导率,揭示了优化工艺制备的钨喷涂层的孔径分布,分析了喷涂功率和真空室压力对涂层的影响。结果表明,4种钨喷涂层均呈层状结构,优化工艺制备的钨喷涂层的致密度为98.4%,氧含量为0.2%(质量分数),热导率为110.76 W/(m.K),孔隙的主要孔径分布范围为0.2～4.0μm,以1.0μm左右的孔隙为主。     

双波长K系数分光光度法测定镍钨合金镀液中的钨含量

以NH4SCN方法测定镍钨合金镀液中的钨含量,镀液中的Ni2+会对其产生干扰。应用双波长K系数分光光度法有效消除了共存Ni2+的影响。测定镍钨合金镀液中的钨时以420 nm为测量波长、370 nm为参比波长,钨的线性回归方程为y=0.426 0x+0.982 3,相对标准偏差为1.2%,加标回收率为96.89%～106.10%。此法用于镍钨合金镀液中钨含量的测定,结果准确。     

TiCp/W复合材料热冲击损伤行为的数值模拟

为了揭示TiC颗粒增强的钨基复合材料（TiCp/W)高温下的失效规律,采用有限元方法从宏观和微观两个方面对该复合材料在氧乙炔冲击中的损伤行为进行了数值模拟,模拟结果表明,复合材料试样宏观损伤行为是裂纹在试样周边萌生,沿径向向心部扩展,微结构损伤行为是微裂纹在TiCp/W界面附近产生,而生在基体中扩展,TiC颗粒含量越高,复合材料超易损伤。TiC颗粒没有阻止裂纹扩展的作用,在基体中增加TiC反而会降低材料的抗热冲击性能。复合材料非稳态温度场的模拟结果,材料的宏观与微观损伤行为的模拟结果都与实验结果吻合。     

Microstructure and Processing of 3D Printed Tungsten Microlattices and Infiltrated W–Cu Composites

Tungsten is of industrial relevance due its outstanding intrinsic properties (e.g., highest melting‐point of all elements) and therefore difficult to 3D‐print by conventional methods. Here, tungsten micro‐lattices are produced by room‐temperature extrusion‐based 3D‐printing of an ink comprising WO₃–0.5%NiO submicron powders, followed by H₂‐reduction and Ni‐activated sintering. The green bodies underwent isotropic linear shrinkage of ≈50% during the thermal treatment resulting in micro‐lattices, with overall 35–60% open‐porosity, consisting of 95–100% dense W–0.5%Ni struts having ≈80–300 μm diameter. Ball‐milling the powders and inks reduced the sintering temperature needed to achieve full densification from 1400 to 1200 °C and enabled the ink to be extruded through finer nozzles (200 μm). Partial sintering of the struts is achieved when NiO is omitted from the ink, with submicron interconnected‐porosity of ≈34%. Several tungsten micro‐lattices are infiltrated with molten copper at 1300 °C under vacuum, resulting in dense, anisotropic W–Cu composites with 40–65% tungsten volume fraction. Partially sintered struts (containing nickel) with submicron open porosity are also infiltrated with Cu, resulting in co‐continuous W–Cu composites with wide W struts/Cu channels at the lattice scale (hundreds of micrometers), and fine W–Cu interpenetrating network at the strut scale (hundreds of nanometers) allowing for the design of anisotropic mechanical and electrical properties.

     

Photoelectrochemical response studies of W deposited TiO2 nanotubes via thermal evaporation technique

Titania (TiO₂) nanotube arrays were successfully formed by anodising titanium (Ti) foil in a standard two-electrode bath in 1?M of glycerol (HOCH₂CH(OH)CH₂OH) containing 0.5?wt% ammonium fluoride (NH₄F). It was observed that such anodisation condition resulted in self-organised of TiO₂ nanotubes with the average pore sizes of approximately 90?nm and the length was approximately 1?µm. In this study, various thicknesses of tungsten (W) were deposited on TiO₂ nanotubes via thermal evaporation technique to investigate the photoelectrochemical (PEC) response and hydrogen generation rate. The improvement in PEC response was found by using a photoanode of 2.5?nm W deposited TiO₂ nanotubes as compared to the pure TiO₂ nanotubes. It was believed that a shallow trap was provided for charge carrier to inhibit the recombination and eventually extend the lifetime of charge carrier. In contrast, the higher deposition of W on TiO₂ nanotubes resulted in lower PEC response because it acts as charge carrier recombination center. The experiment results show that the maximum photocurrent density of 0.9?mA/cm² and maximum hydrogen production rate of 12?µL/cm²/min was achieved using 2.5?nm W deposited TiO₂ nanotubes.     

9Cr3W3Co钢高温时效脆化现象与改进方法

采用SEM进行显微组织观察,研究导致9Cr3W3Co钢时效脆化的主要因素。采用Thermo-Calc软件,计算平衡态下不同W含量(2.36%,2.63%,2.96%,3.11%,质量分数)的9Cr3W3Co钢中析出相的含量。利用TEM,SAXS和相分析等实验手段研究时效过程中的组织演变。结果表明:9Cr3W3Co钢的冲击韧度在100h时效后的迅速降低是时效过程中大量析出的富W Laves相所造成的。平衡态的Laves相含量主要由钢中的W含量决定。时效8000h后,W含量最低的钢冲击韧度最好,同时其Laves相的尺寸最小,粗化速率最低。通过降低W含量能够抑制9Cr3W3Co钢的时效脆化。     

Thermal stability of the engineered interfaces in Wf/W composites

Application of tungsten as a structural material is severely restricted due to its inherent brittleness. Recently, a novel toughening method for tungsten was proposed by the authors using tungsten wires as reinforcement. The idea is analogous to the fiber-reinforced ceramic–matrix composites theory which utilizes the internal energy dissipation caused by the debonding and frictional sliding at the fiber/matrix interfaces to absorb strain energy and to redistribute stress concentrations over an extended volume. To maximize the energy dissipation, the interfaces need to be engineered by coating which can withstand thermal exposure during service. In this work, we studied the thermal stability of various interfacial coatings after heat treatment. Microstructural change and the effect on mechanical properties were investigated by means of electron microscopy and fiber push-out tests. The results show that the microstructural phases of the analyzed interfaces remained relatively stable under thermal exposure of 800 °C for 10 h. Under such thermal exposure, the fracture energy of the Er/W multilayer and the ZrO _x /Zr multilayer were affected by less than 10%, while it was increased by 40% for the ZrO _x /W bilayer. The fracture energy of the C/W dual layer was decreased by a factor of 4, whereas for the Cu/W multilayer case it was increased by a factor of 2.     

Fabrication of W target on carbon backing

¹⁸⁴W enriched isotopic target of 210 μg/cm² thickness on carbon backing of 100 μg/cm² thickness has been made in ultra-high vacuum environment by evaporation method using 6 kW electron beam at Inter University Accelerator Centre (IUAC). Hundred and thirty milligrams of enriched ¹⁸⁴W powder was used in this target preparation process. This target has been successfully used in two nuclear reaction experiments performed at IUAC. Methods adopted to convert the tungsten powder to a special pellet form in order to minimize the consumption of the expensive material, preparation of stress relieved carbon-backing foil, steps taken to make the carbon withstand the heat generated during the tungsten evaporation, the method of tungsten fabrication and details of ultra-high vacuum evaporator facility of IUAC are discussed.     

Fibroblast Adhesion and Proliferation on a New β Type Ti-39Nb-13Ta-4.6Zr Alloy for Biomedical Application

Cell attachment and spreading on Ti-based alloy surfaces is a major parameter in implant technology. Ti-39Nb-13Ta-4.6Zr alloy is a new β type Ti alloy developed for biomedical application. This alloy has low modulus and high strength, which indicates that it can be used for medical purposes such as surgical implants. To evaluate the biocompatibility and effects of the surface morphology of Ti-39Nb-13Ta-4.6Zr on the cellular behaviour, the adhesion and proliferation of rat gingival fibroblasts were studied with substrates having different surface roughness and the results were also compared with commercial pure titanium and Ti-6Al-4V. The results indicate that fibroblast shows similar adhesion and proliferation on the smooth surfaces of commercial pure titanium （Cp Ti）, Ti-39Nb-13Ta-4.6Zr, and Ti-6Al-4V, suggesting that Ti-39Nb-13Ta-4.6Zr has similar biocompatibility to Cp Ti and Ti-6Al-4V. The fibroblast adhesion and spreading was lower on rough surfaces of Cp Ti, Ti-39Nb-13Ta-4.6Zr and Ti-6Al-4V than on smooth ones. Surface roughness appeared to be a dominant factor that determines the fibroblast adhesion and proliferation.     

氦离子辐照下钨纳米丝的自保护行为

采用低能量(200 eV)大流强的He⁺辐照多晶钨材料,辐照温度为1023 K和1373 K,辐照剂量为1.0×10²⁵~1.0×10²⁶ ions/m²。用称重、扫描电子显微镜、导电原子力显微镜等手段分析辐照后钨材料的质量损失、表面形貌和内表面缺陷分布,研究了刻蚀速率与表面形貌的关系。结果表明,具有粗糙钨纳米丝表面的钨样品刻蚀速率只有平滑表面的30%。其原因是,在大流强He⁺辐照下钨表面纳米丝的形成阻碍钨原子的溅射。这也意味着,钨纳米丝表面的形成可作为钨材料的自保护结构层,抑制ITER相关辐照下的强刻蚀。