球形Ta2O5/Nb2O5制备方法的研究

研究了用氨沉淀氟钽（或铌）酸溶液制备球形Ta2O5／Na2O5工艺。通过实验探讨了沉淀条件、溶液浓度、沉淀时间、焙烧温度等工艺参数的最佳组合。结果表明，用氨沉淀氟钽（或铌）酸溶液制备球形的Ta2O5／Nb2O5，必须首先得到不规则的Ta（OH）5/Nb（OH）5。要得到不规则Ta（OH）5/Nb（OH）5，反应时搅拌强度要大，搅拌速率应控制在800～1200r／min，反应结束后继续搅拌10～20min，终点pH值控制为8．5；氟钽（或铌）酸溶液浓度为60～80g，L沉淀10min，浓度为120～140g，L沉淀15min，之后可得到不规则Ta（OH）5/Nb（OH）5。再在800～850℃，焙烧6h可得到球形Ta2O5／Nb2O5。     

去除Ta2O5/Nb2O5中杂质S的工艺研究

从理论和实际应用方面,研究了去除Ta2O5/Nb2O5中杂质S的方法.通过对制取高纯Ta2O5和Nb2O5的中间产品高纯Ta（OH）5/Nb（OH）3进行过氧化处理,改变Ta,Nb,S等元素在物料中的存在方式,增大了含S杂质的溶解性,降低了物料对含S离子的吸附能力及硫酸盐的分解温度,通过洗涤、焙烧达到有效去除产品中杂质元素S的目的.该方法可在不影响Ta2O5/Nb2O5产品质量的情况下,使杂质S降低到0.0001%以下.     

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Highly reflective dielectric mirror coatings are critical components in a range of precision optics applications including frequency combs, optical atomic clocks, precision interferometry and ring laser gyroscopes. A key limitation to the performance in these applications is thermal noise, arising from the mechanical loss of the coatings. The origins of the mechanical loss from these coatings is not well understood.Recent work suggests that the mechanical loss of amorphous Ta₂O₅ coatings can drop by as much as 40% when it is doped with TiO₂. We use a combination of electron diffraction data and atomic modelling using molecular dynamics to probe the atomic structure of these coatings, and examine the correlations between changes in the atomic structure and changes in the mechanical loss of these coatings. Our results show the first correlation between changes in the mechanical loss and experimentally measured changes in the atomic structure resulting from variations in the level of TiO₂ doping in TiO₂-doped Ta₂O₅ coatings, in that increased homogeneity at the nearest-neighbour level appears to correlate with reduced mechanical loss. It is demonstrated that subtle but measurable changes in the nearest-neighbour homogeneity in an amorphous material can correlate with significant changes in macroscopic properties.     

乙醇钽化学气相沉积制备Ta2O5薄膜研究进展

Ta2O5薄膜层具有较高的介电常数、折射率以及和ULSI加工过程中的相容性，因而将在硅芯片栅层材料、动态随机存储器、减反膜、气敏传感器、太阳能光伏电池面板介电层等方面得到应用。对以Ta（OC2H5）5为原料，通过常规金属有机化合物气相沉积、光致化学气相沉积、等离子增强化学气相沉积、原子层化学气相沉积和脉冲化学气相沉积法制备Ta2O5薄膜进行了评述，并对这些方法存在的问题进行了分析。     

Dissolution behaviors of Ta2O5, Nb2O5 and their mixture in KOH and H2O system

The dissolution behaviors of Ta2O5,Nb2O5 and their mixture in KOH and H2O system were investigated.A L9(34) orthogonal design was used to study the effects of reaction temperature,mass ratio of KOH to Ta2O5,and reaction time on the dissolution rate of tantalum.It was found that the effect of reaction temperature on the dissolution rate of tantalum was much greater than that of the other factors.The results of factorial experiments showed that Ta2O5 was mainly transformed into insoluble potassium tantalate at low temperature(350 ℃) and transformed into soluble potassium tantalate at high temperature(450 ℃).The insoluble potassium tantalate was analyzed by XRD,which was proved to be KTaO3.Differently,almost all Nb2O5 was transformed into soluble potassium niobate at 350-450℃.As for the mixture of Ta2O5 and Nb2O5,the dissolution rate of tantalum increased and the dissolution rate of niobium decreased as an interaction existed between niobium and tantalum.And increasing the mole ratio of Nb2O5 to Ta2O5 in the mixture was beneficial to the dissolution of both Ta2O5 and Nb2O5.In addition,the mechanism of the interaction between niobium and tantalum was also investigated through phase and chemical analysis.     

Phase relations in the Ta2O5-WO3-SiO2 system

Subsolidus relations and liquidus boundaries in the Ta₂O₃-WO₃-SiO₂ system at temperatures ranging from 1200 °C to 1500 °C were investigated. Phase diagrams were constructed. Compounds with stoichiometries of Ta₂₂W₄O₆₇, Ta₂WO₈ and Ta₁₆W₁₈O₉₄ formed in the Ta₂O₅-WO₃ subsystem at 1200 °C. SiO₂ was compatible with each of the compounds. A solid solution with a formula of (1 − x) Ta₂O₅·xWO₃ formed on the Ta₂O₅-WO₃ line in the compositional range of Ta₂O₅:WO₃ > 11:4. SiO₂ had a maximum solubility of 25% SiO₂ in the solid solution. Liquid phase first appeared in the WO₃-rich corner at 1300 °C. As the temperature was increased up to 1500 °C, the liquidus area boundary gradually expanded towards the SiO₂- and the Ta₂O₅-rich corners.     

IrO2＋Ta2O5系钛基改性涂层阳极和失效特点

研究了Ti／（IrO2＋Ta2O5）涂层阳极钛基表面不同改性条件下的表面形貌，截面扫描和界面元素分布，电解强化寿命和失效机理。结果表明，钛基体表面改性对涂层表面形貌没有根本性影响，表面改性的涂层阳极在槽电压-电解时间曲线上具有很长的平台期，显示出很好的强化寿命，平台期的主要失效特点在于涂层的电化学溶解，溶解从“龟裂”处始发，并且逐层进行。     

还原氧化钽和氧化铌制备电容器用粉末的方法评述

评述了氧化铌、氧化钽的两步镁还原、镁蒸气还原、在CaCl2-NaCl熔融盐里钙还原和在CaCl2-NaCl熔融盐里钠还原的方法。两步镁还原氧化铌、氧化钽的工艺路线长。采用镁蒸气还原能够得到性能好的钽粉,但是还原时间长,还原装置复杂,希望能找到一种有效的设备。用CaCl2-NaCl熔融盐里钙还原氧化铌、氧化钽,还原温度高,得到的金属粉末比表面积小,工艺不够成熟。在CaCl2-KCl-NaCl熔盐里金属Na还原Ta2O5、Nb2O5,反应时间短,还原温度范围广,能够得到高纯度高比表面积的钽、铌粉末。     

固体透氧膜法制备金属Ta

利用固体透氧膜（SOM）法进行了从Ta2O5中提取金属Ta的实验．在1150℃,外加直流电解电压3．2V下,以55．5％MgF2-44．5％CaF2的熔盐体系为介质,阴极为经过预烧成型的Ta2O5,阳极为氧化锆管内的碳饱和铜液．测试结果显示：Ta2O5阴极中氧含量大大降低甚至消失,Ta2O5还原为金属Ta．     

Interfacial Interaction and Wetting in the Ta2O5/Cu-Al System

Wettability and interfacial interaction of the Ta₂O₅/Cu-Al system were studied. Pure Cu does not wet the Ta₂O₅ substrate, and improved spreading is achieved when relatively a high fraction of the active element (~40 at.% Al) was added. The Al₂O₃ and AlTaO₄ phases were observed at the Ta₂O₅/Cu-Al interface. A thermodynamic evaluation allowed us to suggest that the lack of wetting bellow 40 at.% Al is due to the presence of a native oxide, which covers the drop. The conditions of the native oxide decomposition and the formation of the volatile Al₂O suboxide strongly depend on the vacuum level during sessile drop experiments and the composition of the Cu-Al alloy. In our case, Al contents greater than 40% provides thermodynamic conditions for the formation of Al₂O (as a result of Al reaction with Al₂O₃) and the drop spreading. It was suggested that the final contact angle in the Ta₂O₅/Cu-Al system (50°) is determined by Ta adsorption on the newly formed alumina interlayer.     

阴极结构对SOM法制备金属钽的影响

在CaCl2熔盐中,利用固体氧离子膜(SOM)法电解还原Ta2O5直接制备金属钽。研究了成形压力与烧结温度对阴极形貌及孔隙率的影响,进而获得阴极微结构对产物形貌及氧含量的影响规律。结果表明:阴极片的颗粒尺寸和孔隙率大小是影响电解还原的重要因素;Ta2O5片的孔隙率随着成形压力的增大、烧结温度的升高明显降低;孔隙率大,有利于电解还原的进行,产物颗粒尺寸大;孔隙率小,会导致阴极产物形成致密的金属外层;在成形压力为4MPa经1150℃烧结2h或6MPa经1100℃烧结2h条件下,阴极反应活性良好,电解产物氧含量低。     

TiN基IrO2＋Ta2O5涂层电催化性能研究

采用热分解法制备了一种以离子镀TiN膜为基体的IrO2＋Ta2O5涂层电极，通过极化曲线、循环伏安、电化学阻抗谱等电化学方法并结合扫描电镜、X射线能谱和X射线衍射研究了涂层的析氧电催化活性，并对460℃制备的涂层进行强化寿命实验。结果表明：涂层呈多孔、多裂纹的显微结构和多层电化学结构；制备温度对涂层表面形貌和电催化活性影响很大；该涂层阳极在保持了高电催化活性的同时，其使用寿命高于传统Ti基阳极，说明TiN作为此类催化电极的载体是可行的。     

Development of γ phase stacking faults during high temperature creep of Ru-containing single crystal superalloys

An unusual deformation mode involving the formation of intrinsic stacking faults in the γ matrix of experimental Ru-containing γ–γ′ superalloys with high Co and Re contents during high temperature creep at 950 °C/290 MPa has been observed. The morphology, distribution and dependence of these stacking faults on alloy chemistry has been investigated along with their formation mechanism. Additions of Re and Co substantially decrease the stacking fault energy of the γ matrix. The observed stacking faults in the γ matrix form by the dissociation of a/2〈1 1 0〉 matrix dislocations with Burgers vectors perpendicular to the loading direction in the early stages of creep. The dependence of creep properties on elemental additions that influence stacking fault energy is discussed.     

RuO2、IrO2和Ta2O5多元氧化物涂层阳极的研究

采用H2IrCl6·H2O、RuCl3·3H2O、TaCl5及添加剂组成的复合溶液，利用溶胶-凝胶法工艺在钛基体和预镀钽的钛钽表面氧化烧结形成活性RuO2、IrO2和Ta2O5组成的多元金属氧化物涂层阳极.制备了混合金属氧化物涂层并对制备工艺及其对氧化物涂层结构和化学成分的影响进行了研究.结果表明，H2IrCl6·H2O的含量对氧化物涂层和涂层结合力有直接影响，在IrO2(H2IrCl6·H2O当量换算)含量达到7%～8%(mass)时，涂层的孔隙率出现了最低值；当热氧化烧结温度在400 ℃～500 ℃时，涂层的孔隙率出现了最低值；在钛基体预镀钽后再热分解形成RuO2、IrO2和Ta2O5涂层的表面裂纹较直接形成混合金属氧化物涂层的少.     

氯盐制备IrO2＋Ta2O5混合氧化物阳极的热解形成过程

通过热重分析和差热分析并结合Ｘ射线衍射技术对ＩｒＯ２＋Ｔａ２Ｏ５混合氧化物的热形成进行了研究。结果表明：摩尔分数ｘ〈２５％时,在混合氢盐体系ｘＨ２ＩｒＣｌ６＋（１－ｘ）ＴａＣｌ５中,热解产物中的固溶体为β相（β－Ｔａ２Ｏ５中固溶了Ｉｒ组元）;ｘ≥２５％时,生成的固溶体为固深了Ｔａ组元的ＩｒＯ２组元的ＩｒＯ２金红石相,而且数量在两个以上;只有当ｘ≥４２．８６％时,其中的金红石相固溶体才是稳定的。Ｉｒ     

Ta对Ti_2AlNb基合金微观组织和高温性能的影响

对Ti Al Nb Ta系列合金的组织结构、高温拉伸力学性能进行了研究。结果表明 ,合金中Ta替代部分Nb ,提高了合金的 β/B2转变点温度 ,有利于细化合金的微观组织结构 ;随着Ta含量增加 ,Ti2 AlNb基合金在650℃的屈服强度增加。     

La2O3-Mo5Si3/MoSi2复合材料的力学性能和高温氧化行为

通过自蔓延高温合成了稀土协同Mo5Si3复合强韧化MoSi2的复合粉末,研究了La2O3-Mo5Si3/MoSi2复合材料的室温力学性能和高温氧化特性。结果表明:与纯MoSi2相比,稀土和Mo5Si3细化了材料的晶粒,提高材料的室温弯曲强度和断裂韧性,其强化机制为细晶强化,韧化机制为细晶韧化、裂纹偏转、裂纹分支和微桥接;当Mo5Si3含量不超过30%(摩尔分数)时,随着Mo5Si3含量的增加,材料的抗氧化性能降低,而RE-40%Mo5Si3/MoSi2(摩尔分数)复合材料出现粉化现象;RE-Mo5Si3/MoSi2复合材料抗氧化性的降低,主要是由于Mo5Si3较差的抗氧化性、材料致密度的降低以及晶粒细化的结果;0.8%稀土(质量分数)协同5%Mo5Si3(摩尔分数)的RE-Mo5Si3/MoSi2复合材料具有较好的综合力学性能和高温抗氧化特性。     

涂层IrO2+Ta2O5钛阳极在析氧过程中的形貌和成分变化

作者用热分解法制备钛基IrO2+Ta2O5涂层阳极,涂层制备态在373 K马弗炉中长时间时效处理,然后在0.5mol/L H2SO4介质中、4A·cm-2电流密度下进行强化寿命试验.用自带能谱仪(EDS)的场发射高分辩电子扫描显微镜(SE-SEM)和X射线衍射仪(XRD)进行电解前后的表面形貌和成分分析.研究结果显示涂层制备态在373K马弗炉中长时间时效处理时,金红石IrO2织构优先生长且晶面间距随时效时间延长而增加;电解过程中涂层的失效过程为气体氧对涂层界面的冲刷造成涂层逐层腐蚀消耗,接着涂层产生裂纹和扩展,导致涂层剥落;化学成分方面,涂层氧化铱优先消耗和氧化钛逐步积累.