Corrosion behavior of tantalum and its nitride in alkali solution

The corrosion behavior of tantalum and its nitrides in stirring NaOHsolutions was researched by potentiostatic method, cyclic voltammetry and XPS. The results showedthat the corrosion products were composed of Ta_2O_5 and NaTaO_3. The corrosion reaction formula oftantalum and its nitrides was written according to cyclic volt-ampere curves. The electric chargetransfer coefficient and the electric charge transfer number were calculated

Phase evolution of tantalum nitride and tantalum carbide films with PBII parameters

Tantalum nitride and tantalum carbide films were fabricated using magnetron sputtering of tantalum followed by nitrogen and carbon plasma-based ion implantation （N-PBII and C-PBII）. The phase evolution and morphology of the films were studied using glancing angle X-ray diffraction （GXRD） and transmission electron microscopy （TEM）. It was found that the main phase in the tantalum nitride films was crystalline TaNo.1 whose grain size increases with increasing implantation voltage and phase content increases with increasing implantation dose. In the tantalum carbide film, the main phase was Ta2C. TaC phase also appeared as the implantation dose increased. XRD results from various glancing angles show that the phases with high nitrogen or carbon content, Ta4N5 and TaC, are present in the surface of the films. X-ray photoelectron spectra （XPS） from the tantalum carbide film reveal that the surface carbon content is higher than that of the inner film.

Premature failure induced by non-equilibrium grain-boundary tantalum segregation in air-plasma sprayed ZrO_(2)-YO_(1.5)-TaO_(2.5)thermal barrier coatings

ZrO_(2)-YO_(1.5)-TaO_(2.5)(ZYTO)is a promising top-coat material for thermal barrier coatings(TBCs).The bulk properties of ZYTO have been reported by several studies,but its performances as TBCs are less-well understood.In this work,ZYTO TBCs were prepared by air plasma spraying(APS)and their thermal cycling performances were investigated at 1150℃.Despite of the good bulk properties,APS ZYTO TBCs present an extremely short thermal fatigue life.This is attributed to the non-equilibrium grain-boundary segregation of TaO_(2.5) induced by limited solubility and rapid quenching during APS process,resulting in a tetragonal(t)to cubic(c)and metastable-tetragonal(tm)phase transformation in ZYTO TBCs.The volume shrinkage(~0.74vol%)of phase transformation leads to many cracks at the c/tm phase boundaries after deposition.On the other hand,the formation of cubic phase with massive grain-boundary Ta segregation induces a large intergranular embrittlement and a weak bonding strength(~5.3 MPa),resulting in the premature failure of the ZYTO TBCs.

Engineering tantalum nitride for efficient photoelectrochemical water splitting

Photoelectrochemical(PEC)water splitting is a promising energy conversion strategy for directly converting solar energy into green hydrogen fuel.Constructing an efficient PEC device,finding an efficient photoanode material with a suitable band gap and favorable band-edge positions is essential.Tantalum nitride(Ta_(3)N_(5))meets these fundamental requirements,and its theoretical maximum solar-to-hydrogen(STH)conversion efficiency can reach 15.9%.Consequently,it has been widely applied as a photoanode material for the PEC oxygen evolution reaction(OER).However,severe bulk and interface charge recombination,along with sluggish water oxygen kinetics,seriously limits its STH conversion efficiency for PEC water splitting.Herein,this feature article briefly reviews recent advances by our research group in improving the STH conversion efficiency of the Ta_(3)N_(5)photoanode using various strategies,including defect engineering,construction of a gradient band structure,interface engineering,and surface modification of self-healing OER cocatalyst.Up to now,the obtained half-cell STH efficiency has exceeded 4%,providing a solid foundation for the development of tandem PEC devices for unbiased solar-driven overall water splitting toward practical application.

Plasma-nitriding of tantalum at relatively low temperature

The combined quadratic orthogonal regression method of experiment design wasemployed to explore the effects of process parameters of plasma nitriding of tantalum such as totalpressure, temperature and original hydrogen molar fraction on the hardness, roughness and structureof nitriding surfaces. The regression equations of hardness, roughness and structure were givenaccording to the results of regression and statistic analysis. And the diffusion activation energyof nitrogen in tantalum on plasma nitriding conditions was calculated according to the experimentaldata of hardness of plasma-nitriding of tantalum vs time and temperature. The diffusion activationenergy calculated belongs to (155.49 +- 10.51) kJ/mol (783-983 K).

星用微波集成电路TaN薄膜电阻的功率耐受值研究

氮化钽(tantalum nitride,TaN)薄膜电阻电路是星载放大器、功分器等典型产品中必不可少的组成部分。在较大功率信号施加的条件下,TaN埋嵌电阻部位热效应较强,出现电路失效或烧毁的可能性也较其他部位大。星载微波单机应用环境条件恶劣,对于薄膜电阻的应用可靠性要求极高,常规侧重高温工况,热处理等条件下的氮化钽电阻功率耐受性研究无法得到实际星载应用工况中氮化钽电阻的功率特性,势必需要通过模拟实际应用工况和边界条件,通过设计制作氧化铝基板上不同尺寸TaN薄膜电阻样件,测量在施加不同电流的工况下电阻表面和电阻电极的温度,并根据电阻表面最大允许温升对应的电流,计算出可耐受的最大功率,完成了TaN薄膜电阻的功率耐受性研究。研究结果表明,在基板厚度一定时,随着电阻面积增大,薄膜电阻耐受功率呈增大趋势;较大尺寸薄膜电阻的功率耐受随着基板厚度的增加而降低。此研究结果对后续优化星用微波电路设计,提高宇航微波产品应用可靠性,减少不必要的设计冗余,有重要意义。

Valence electronic structure of tantalum carbide and nitride

The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.

Prediction of stable high-pressure structures of tantalum nitride TaN2

Structure searches based on a combination of first-principles calculations and a particle swarm optimization technique unravel two new stable high-pressure structures(C2/m and Cmce) for Ta N2. The structural features, mechanical properties, formation enthalpies, electronic structure, and phase diagram of Ta N2 are fully investigated. Being mechanically and dynamically stable, the two phases could be made metastable experimentally at ambient conditions.

提高高压MnO_(2)钽电容器漏电流稳定性的试验研究

高压MnO_(2)钽电容器漏电流在高温和高压应用环境中的稳定性对电路的安全性和可靠性有重要影响。通过正反向偏置V-I特性测试可知,高压MnO_(2)钽电容器漏电流主要为氧空位缺陷和介质表面的微晶诱发的Poole-Frenkel电流和隧穿电流。在Ta2O5介质表面通过浸渍的方法涂覆一层绝缘树脂阻挡层,以提高界面的势垒和Poole-Frenkel电阻,屏蔽介质表面的晶化点,且抑制氧空位缺陷和晶化点在高温和高场环境应用过程中的互作用。浪涌电流/电压冲击、高低温稳定性、加速121℃-85%RH-63 h和125℃-2000 h寿命测试表明,漏电流在高温和高压环境中的稳定性明显改善,电容器的可靠性和稳定性显著提高。该研究对电子装备系统在严酷环境中的安全可靠运行具有重要的支撑作用。

真空热处理炉绝缘陶瓷对钽粉杂质的影响

主要研究了真空热处理炉绝缘陶瓷在投入使用前的一种适用性检测方法,并通过对比95氧化铝陶瓷、99氧化铝陶瓷、氮化硼陶瓷和氮化铝陶瓷杂质结果,分析了真空热处理炉绝缘陶瓷对钽粉杂质的影响。结果表明:95氧化铝陶瓷会造成钽粉Fe、Si杂质增加,氮化硼陶瓷会造成钽粉B、N杂质增加,而氮化铝陶瓷会造成钽粉Al、N、C杂质增加。99氧化铝陶瓷对钽粉杂质的影响最小,但在1100~1380℃温度范围内会导致钽粉Al杂质增加,可以通过减少炉内绝缘陶瓷的面积来降低Al杂质。

钽等离子体渗氮的表面过程分析

对钽表面渗氮的固 气界面反应过程进行了热力学和动力学分析 ,从理论上预测了各种参数 (压力、气体组成、温度、电参数等 )对表面过程的影响 ,并借助于等离子体 ,在较低温度下获得了由表面层与N在Ta中的固溶体组成的表面硬化层。表面层为六方晶系的Ta6N2 ,57和 /或非晶态。通过调整工艺参数有效地抑制了钽表面氧的渗入和Ta2 O5 的形成 ,使得离子渗氮后 。

非平衡磁控溅射沉积Ta-N薄膜的结构与电学性能研究

采用直流反应非平衡磁控溅射技术在单晶Si（100）和玻璃表面沉积氮化钽（Ta-N）薄膜。分别测试了薄膜的结构、成分、电阻率和吸收光谱，研究了氯氩流量比（N2：Ar）变化对Ta—N薄膜的结构和电学性能的影响。研究结果表明随N2：Ar增加，依次生成六方结构的γ-Ta2N、面心立方结构（fcc）的δ-TaNx体心四方结构（bct）的TaNx；N2：Ar在0．2～0．8的范围内，Ta—N薄膜中只存在着fcc δ-TaNx；当N2：Ar〉1之后，Ta—N薄膜中fCC δ-TaN，和bct TaNx共存。Ta—N薄膜电阻率随N2：Ar流量比增加持续增加，当N2：Ar为1．2时，薄膜变为绝缘体，光学禁带宽度为1．51eV。

钽表面离子渗氮工艺研究

采用组合的二次回归正交设计方法 ,针对表面硬度、表面粗糙度 ,对钽表面离子渗氮工艺参数 (气体压力、温度、氢气摩尔分数 )进行了优化。

TiN基IrO_2-Ta_2O_5涂层析氢电极的催化性能

采用热分解法制备了以离子镀TiN膜为基体的IrO2-Ta2O5涂层电极,通过循环极化曲线并结合扫描电镜、X射线能谱和X射线衍射研究了涂层的析氢电催化性能.结果表明,涂层呈多孔多裂纹的结构,焙烧温度对涂层的表面形貌和电催化活性影响很大.420℃下焙烧的涂层具有最优的电催化活性.涂层电极的析氢反应电极电位为-0·26V(vsSCE),低析氢过电位下的Tafel斜率为-0·04V,而在高析氢过电位下,电极表面吸附的大量氢原子改变了氧化物电极的结构,从而抑制了氧的阴极还原反应.

铜布线工艺中阻挡层钽膜的研究

从钽膜质量的角度研究了用溅射方法在硅衬底上得到的 60 nm钽膜对铜硅互扩散的阻挡效果 ,钽膜的质量通过对硅衬底的表面处理以及钽膜的淀积速率来控制。研究发现 ,适当的硅衬底表面处理对钽膜是否能产生良好的防扩散能力起着关键的作用。本研究还得到了能有效阻挡铜硅接触的钽膜的淀积速率。

钽表面渗氮层的氧化行为

进行了钽表面预先离子渗氮 对其后续表面高温熔盐阳极化过程及性能影响的试验研究。发现钽表面预先离子渗氮并不改变其后表面阳极化处理的动力学过程控制步骤，但表面膜层生长速度减慢。膜层物相由钽的氧化物变为氮化物。膜层静态电阻率增大；致密性更好。表面粗糙度降低，耐碱腐蚀性能提高。

氮化钽薄膜的制备及其血液相容性研究

本文利用磁控反应溅射技术制备氮化钽薄膜，对磁控反应溅射制备氮化钽薄膜的工艺参数（包括氮分压比、加热温度、溅射压力、溅射电流）用正交设计进行优化。研究表明，影响氮化钽薄膜结合力的主要因素为溅射压力和加热温度，氮分压比、溅射电流为次要因素；氮分压对氮化钽薄膜的硬度影响较大。动态凝血及血小板粘附实验研究表明，氮化钽薄膜的血液相容性性能优于热解碳（LTIC）。

热处理时间和压制密度对氮化钽粉电性能的影响

用均相钠还原得到的纳米氮化钽粉在1 350℃进行不同时间的热处理,热处理后的粉末制成烧结体并进行阳极氧化过程。通过XRD和场发射扫描电镜分析了粉末的物相结构和形貌,研究了热处理时间和压制密度对氮化钽粉末电性能的影响。结果表明:热处理温度为1 350℃、热处理时间40min、压制密度约4g/cm时氮化钽阳极块体有较高的比容和较低的漏电流常数。

Ta等离子体渗氮的非平衡热力学

讨论了Ｔａ表面等离子体渗氮的热力学问题，将超平衡氢和非平衡热力学的反应耦合理论引入离子渗氮反应的计算，从理论上解释了等离子体和氢在 Ｔａ表面渗氮过程中的作用 ，给出了渗氮条件下的 Ｔａ—Ｎ—Ｏ非平衡定态相图，与实验验结果符合得较好．实验表明，氢和等离子体的存在，有利于提高氮原子的活度，促进热力学上不稳定的Ｔａ的氮化物的形成，抑制粗糙的Ｔａ的氧化物的形成．

阳极氧化工艺条件对氮化钽烧结体电性能的影响

用纳米氮化钽粉末烧结制备了氮化钽烧结体,分析了烧结体的物相结构,研究了形成液种类、形成液浓度、温度、电流密度以及赋能电压等条件对氮化钽阳极氧化膜电性能的影响。结果表明,该烧结体是由纯氮化钽组成的,氮化钽阳极块体阳极氧化过程的最佳赋能工艺:磷酸溶液浓度0.01%,形成液温度55℃,电流密度40mA/g,形成电压小于16V。