Reaction of Iradium with Metal Carbides in the Temperature Range of 1923 to 2400 K

The reactions of titanium carbide and hafnium carbide with iridium have been studied in thin film couples fabricated by vapor deposition processes. The reaction product layers after exposure in the temperature range of 1923 to 2400 K are dependent on the stoichiometry of the metal carbide layers and range from simple solid solutions to MIr_x compounds. The observed microstructures are predictable from available thermochemical data. The morphology of residual carbon in the reacted metal carbide-iridium product layer varies from interfacial deposits to uniform carbon dispersion and depends upon exposure temperature and metal carbide stoichiometry.     

EDTA络合滴定法快速测定碳酸锆中锆铪含量

锆铪氧化物含量的测定通常采用苦杏仁酸[C6H5CH（OH）COOH]重量法。该法经典、准确,但操作烦琐,分析时间长,对日常生产、入库或销售不利。乙二胺四乙酸二钠（EDTA）络合滴定法（容量法）操作简便、快速、准确,适合日常检验。但用基准氧化锌、高纯二氧化锆或氯氧化锆来标定EDTA时,测定结果偏低。采用重量法和容量法相结合,先用重量法测定锆铪氧化物含量,以已知锆铪氧化物含量的碳酸锆作标定物,再标定EDTA标准溶液的滴定度,用此EDTA标准溶液测定相同原料生产的碳酸锆。该法简便、快速、准确,试剂安全性好。     

Thermal Expansion of Solid Solutions in the ZrTiO4—In2O3—M2O5 (M = Sb, Ta) System

Axial and dilatometric thermal expansions and phase transformations were studied for solid solutions having the α-PbO₂ structure in the ZrTiO₄—In₂O₃—M₂O₅ (M = Sb, Ta) system with nominal formulas of Zr _x Ti _y In _z Sb _z O₄ and Zr _x Ti _y In _z Ta _z O₄ where x + y + 2 z = 2. With increased substitution of z , the cell volume increased, the difference in the b parameters at room temperature between those quenched from 1400° and 1000°C decreased, and the thermal expansion decreased. The axial thermal expansion of ZrTi _y In _z · Ta _z O₄ with z = 0.3 was almost identical with that of HfTiO₄, and those with z = 0.4 and z = 0.45 were smaller than that of HfTiO₄. Unit-cell volumes of these compound were compared with those of single oxides to make it clear that the unit-cell volume of ZrTiO₄ was small anomalously and to distinguish the normal and abnormal substitution systems. These results were explained by the working hypothesis proposed for these compounds.     

Application of a counter-current gaseous diffusion model to the oxidation of hafnium carbide at 1200 to 1530°C

A counter-current gaseous diffusion model is presented to describe the oxidation of hafnium carbide between 1200 and 1530°C. The model separates the porous hafnia scale into two gas diffusion regions separated by a flame front, where O ₂ and CO react to form CO ₂.In the outer region, O ₂ and CO ₂ counter-diffuse; in the inner region, CO ₂ and CO counter-diffuse. The concentration gradients of each gaseous specie in the pores of the hafnia are determined and the rate of oxidation is calculated. A porosity of 2% and a pore radius of 0.01 m are representative of the values observed in hafnia during the early stages of HfC oxidation. These values lead to predictions of parabolic rate constants that are close to those measured by thermogravimetric analysis. In addition, the predicted and measured parabolic rate constants are shown to have the same dependence upon temperature and oxygen partial pressure.     

粉末高温合金FGH97疲劳裂纹扩展行为

测定不同晶粒尺寸、γ'相以及不同Hf含量的粉末高温合金FGH97在650℃高温条件下的疲劳裂纹扩展速率,并将其与FGH95和FGH96两代粉末合金的疲劳裂纹扩展速率进行对比.用定量分析的方法对FGH97合金在疲劳断裂各个阶段的行为特征进行分析.较大晶粒尺寸的FGH97合金具有较低的裂纹扩展速率,合理的二次和三次γ'相匹配析出,可以获得较高的疲劳寿命;Hf元素的添加使合金的整体疲劳寿命增大;FGH97合金与FGH95和FGH96相比,具有较高的疲劳裂纹萌生抗力,更低的高温疲劳裂纹扩展速率.     

Hf-Si-La-O-N体系中HfN的形成及相关系

本研究探讨了一步法制备HfN复合硅酸镧盐陶瓷材料的可行性和配方设计问题,并对HfO2-Si3N4-La2O3三元系统反应合成HfN进行了实验验证.因为在HfO2-Si3N4-La2O3三元系统的反应过程中涉及到硅酸镧盐Si3N4-SiO2-La2O3系统,所以将其延伸为HfO2-Si3N4-La2O3-SiO2-HfN...     

HfO2 Gate Dielectrics for Future Generation of CMOS Device Application

Introduction High- k gate dielectrics have been extensivelystudied as alternates to conventional gate oxide( Si O2 ) due to the aggressive downscaling of Si O2thickness in CMOS devices,and hence the exces-sive gate leakage.Hf O2 has emerged as one...     

Dynamics of phase formation during combustion of Zr and Hf in air

The processes of phase formation taking place during combustion of Zr and Hf in air have been explored by time-resolved XRD (TRXRD) at a time resolution of 0.1 s. In case of Zr combustion, the final product was found to form in two stages: first the tetragonal high-temperature modification of ZrO₂ is formed (in the combustion wave) and then the latter undergoes polymorphic transition (behind the combustion wave) into its monoclinic modification. In combustion of Hf, product formation proceeds in three stages: the low-temperature monoclinic modification of α-HfO₂ is formed in the combustion wave, which is followed by its transformation into the tetragonal β-HfO₂ and backward conversion of the latter into α-HfO₂ behind the combustion wave. The obtained data were comparatively analyzed with those reported for combustion of Ti in air.      

Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature

Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO₂ under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO₂, above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials.     

Hf含量对FGH97合金γ/γ′晶格错配度的影响

采用X射线衍射(XRD)方法测算镍基粉末冶金高温合金FGH97中γ和γ′相的晶格常数,计算出γ/γ′晶格错配度。结果表明:γ′相的晶格常数比γ相的小,错配度为负值。Hf 主要存在于γ′相中,随着合金中 Hf 加入量的增加,进入γ′相中 Hf 的数量增加,使γ′相的晶格常数逐渐增大,错配度的绝对值逐渐减小。