Al/Ni/Fe界面扩散反应的实验研究

采用"铆钉法"制备了含有Al/Ni、Al/Fe和Ni/Fe两相界面的扩散偶,以及Al/Ni/Fe多相扩散偶,利用光学显微镜、电子探针分别对每组扩散偶的界面区域进行了观察分析.实验结果显示,固态扩散促使两相界面处生成扩散层,Al/Ni/Fe多层扩散偶中,由于混相层中不同产物的生长速率不同,促使界面不稳定生长,形成束集型的扩散层结构.     

Al2O3界面钝化与热处理对Gd2O3-HfO2高κ薄膜电性能影响

采用磁控溅射技术在p-Si(100)衬底上生长了Gd2O3掺杂HfO2( GDH)高κ薄膜,制备了GDH/Si和GDH/Al2O3/Si两种堆栈层.结果表明Al2O3界面钝化使漏电流密度降低了两个数量级,并改善了回滞窗口和平带电压的偏移.高温N2退火对堆栈层电学性能影响明显:随着温度的增加,界面性能逐步改善,退火温度为900℃时,回滞窗口小于20 mV,积累区趋势平缓并且单位面积电容值增大,薄膜介电常数为20.     

工艺参数对Fe3Al/Al2O3复合材料力学性能的影响研究

以自制的亚微米Fe3Al为增强相、Al2O3为基体相,通过常压烧结制备出Fe3Al/Al2O3复合材料,研究了Fe3Al含量、烧结温度及保温时间对复合材料力学性能的影响.结果表明:增加Fe3Al含量、提高烧结温度及延长保温时间都可以不同程度的提高复合材料力学性能.最佳工艺参数为:Fe3Al含量(质量分数)为15%,成形压力为2488MPa,烧结温度为1380℃.此条件下制备的复合材料的各项力学性能较好:相对密度为93%,维氏硬度为9.3GPa,断裂韧度为7.51MPa·m1/2.烧结温度对提高复合材料力学性能的影响较大.     

钢基Fe/Al2O3复合材料的界面特征

用喷涂法和溶胶-凝胶法相结合的工艺制备钢基Fe／Al2O3,梯度复合材料,并对其性能进行分析。采用电子万能材料试验机进行结合测试,利用金相显微镜分析复合材料断面组织,用X射线衍射仪分析陶瓷涂层成分。结果表明,Fe／Al2O3,梯度涂层与钢基体界面结合强度较高,平均达到17.62MPa;涂层与基体以及涂层与涂层之间相互融合,并未出现明显的界面联接层,实现了涂层与钢基体在同一区域共存,有助于提高涂层与基体的结合强度;Fe／Al2O3,梯度涂层主要由α-Al2O3、AlFeO3、AlFe3和Al86Fe14等物相组成,对材料的结构和性能都非常有利。     

Au/Ni/Al/Ti/AlxGa1-xN/GaN和Au/Pt/Al/Ti/AlxGa1-xN/GaN欧姆接触研究

研究并对比了Ti/Al/Ni/Au和Ti/Al/Pt/Au多层金属膜与未掺杂的Al0 .2 2 Ga0 .78N/GaN(i AlGaN/GaN)异质结构之间的欧姆接触性质。在退火温度低于 70 0℃时 ,两种接触样品上都不能得到欧姆接触。随着退火温度的升高 ,85 0℃快速退火后 ,在Ti/Al/Ni/Au接触上获得了 1.2 6×10 - 6 Ω·cm2 的比接触电阻率 ,在Ti/Al/Pt/Au接触上获得了 1.97× 10 - 5Ω·cm2 的比接触电阻率。研究结果表明 ,金属与半导体接触界面和Al0 .2 2 Ga0 .78N异质结构界面载流子沟道之间适当的势垒的存在对高质量欧姆接触的形成起重要作用 ,势垒的宽度取决于退火温度以及退火的具体进程。对Ti/Al/Ni/Au和Ti/Al/Pt/Au欧姆接触比接触电阻率的差异进行了解释。     

纳米NiAl2O4圈层包覆Al2O3复合粉末的制备

采用高温氧化的方法制备出纳米NiAl2O4圈层包覆Al2O3粉体.在纳米Al2O3粉体表面包覆一层金属Ni,在1 350℃高温下焙烧Ni/Al2O3复合粉体得到纳米NiAl2O4圈层包覆Al2O3粉体.利用TEM对Ni/Al2O3复合粉体进行观察,发现Ni/Al2O3复合粉体颗粒呈球形,大小为50～60 nm;Ni/Al2O3复合粉体的DTA分析结果表明,Ni/Al2O3复合粉体在900和1 300℃时有新相生成,经XRD检测,新相分别为NiO和NiAl2O4.     

不锈钢基体上制备Al2O3涂层的研究

在核反应堆液态Li-Pb包层中,涂层的研究和发展是重要的内容.由于Al2O3涂层高电阻率的特性及与液态Li-Pb有良好的兼容性,所以成为陶瓷涂层中的最佳候选材料之一.采用射频磁控溅射法,在奥氏体不锈钢基体上制备了Al2O3涂层,并且研究了分别于800和1000℃进行热处理时温度对涂层的相组成、表面形貌、界面组织及绝缘电阻率的影响.结果表明,Al2O3涂层组织致密、均匀.经1000℃热处理后主要组成相为具有高温热稳定性能的α-Al2O3和少量的γ-Al2O3.不锈钢基体与Al2O3涂层层间界面结合良好可能是由于经退火处理后出现新生FeAl相,提高了涂层与基体的结合强度;涂层电阻率在1×1012～1×1014Ω·cm,绝缘性能良好.     

纳米NiAl2O4/Al2O3复合粉末的制备新工艺

本研究采用高温氧化的方法制备出纳米NiAl2O4／Al2O3粉体。在纳米Al2O3粉体表面包覆一层金属Ni，在1350℃高温下焙烧Ni／Al2O3复合粉体得到纳米NiAl204／Al2O3粉体。利用TEM对Ni／Al2O3复合粉体进行观察，发现Ni／Al2O3复合粉体颗粒成球形，大小为50～60nm；通过对Ni／Al2O3复合粉体的DTA析，显示Ni／Al2O3复合粉体在900℃和1300℃下有新相生成，经XRD检测，新相分别为NiO和NiAl2O4。     

退火对MgO/NiFe/MgO多层膜平面霍尔效应的影响

采用磁控溅射的方法制备了结构为Ta(5 nm)/Mg O(6 nm)/Ni Fe(t_(NiFe))/Mg O(4 nm)/Ta(3 nm)的磁性多层膜,Ni Fe的厚度t_(NiFe)从5 nm增加到100 nm,之后在真空退火炉中经过400℃,1 h的退火处理并且进行随炉冷却,整个过程中沿着薄膜易轴方向施加大约4378 A·m-1的磁场。采用四探针的方法来测量平面霍尔电压(PHE)和相对电阻变化率,通过X射线衍射(XRD)和高分辨透射电子显微镜(HRTEM)来分析多层膜退火前后的微结构变化。研究结果表明:对于制备态和退火态的Ta/Mg O/Ni Fe/Mg O/Ta纳米磁性多层膜结构,当t_(NiFe)40 nm时,霍尔输出电压骤减,随着t_(NiFe)的继续增加,霍尔电压基本保持不变。然而,所有的制备态同一厚度的样品经过退火处理之后,霍尔电压都有一定程度的提高,当t_(NiFe)=5 nm时,平面霍尔输出电压增加最大。随着Ni Fe厚度的继续增加,退火处理所导致的输出电压的提高幅度逐渐减小,当t_(NiFe)=100 nm时,霍尔电压退火之后几乎保持不变。不同Ni Fe厚度的样品,霍尔电压经退火处理后之所以提高幅度不同,主要与两个因素有关,一是Mg O/Ni Fe异质界面会增强电子自旋相关散射提高PHE输出电压,二是Ni Fe层因分流也会导致PHE输出电压下降。     

Ni/Al_2O_3及La改性Ni/Al_2O_3催化CO浆态床甲烷化性能

采用等体积浸渍法制备了Ni/Al2O3及La改性的Ni-La/Al2O3催化剂,并考察了其浆态床CO甲烷化反应性能。借助XRD、H2-TPR、CO-TPD、H2-TPD等对催化剂进行了表征。结果表明,La助剂改性制备的Ni-La/Al2O3催化剂较Ni/Al2O3催化剂具有更高的CO甲烷化活性,La助剂的添加促进了Ni物种在载体表面的分散,降低了还原温度,增强了催化剂对CO和H2的吸附能力。La助剂的添加次序对甲烷化活性影响较大,采用共浸渍法制备的催化剂具有最佳的甲烷化活性,CO转化率达到96.3%,CH4选择性和时空收率分别达到87.1%和179.6 m L·kg-1·h-1,优于先浸渍Ni后浸渍La或先浸渍La后浸渍Ni制备的催化剂。     

Microstructural observations of pressure cast Ni3Al/Al2O3 and Ni/Al2O3 composites

Pressure castings of Ni₃Al(IC218)/Al₂O₃ and Ni/Al₂O₃ composites, made with continuous DuPont FP α-Al₂O₃ and DuPont PRD166 α-Al₂O₃+20 wt pct partially stabilized ZrO₂ 20 μm diameter fibers, were examined by optical, scanning electron microscope (SEM), and transmission electron microscope (TEM) techniques. According to optical magnifications, excellent infiltration took place. However, in SEM and TEM magnifications, small gaps were found adjacent to regions where bonding had taken place between fibers. On the basis of available evidence, the gap formation was attributed to trapped gases and microshrinkage. Titanium was added to the metal to promote infiltration. Diffusion of Ti into the fibers of the Ni/Al₂O₃ composites occurred, but similar diffusion into the fibers of the IC218/Al₂O₃ composites did not take place. The qualitatively higher bond strength of the interfaces of the Ni/Al₂O₃ composites was ascribed to the diffusion of Ti into Al₂O₃. No interface reaction layer was found in any of the composites. Very little grain growth was found to take place in either the FP or PRD 166 fibers after casting and after a subsequent ten day anneal at 1150 °C.     

Thermodynamic analysis of aluminate formation at Fe/Al2O3 and Cu/Al2O3 interfaces

Subsolidus ternary phase relationships in the systems FeAlO and CuAlO are reviewed in order to provide a basis for thermodynamic analysis of aluminate formation at Fe/α-Al₂O₃ and Cu/α-Al₂O₃ interfaces. Expressions for the critical oxygen activity in the Fe-rich and Cu-rich solid solutions necessary to stabilize the equilibrium aluminate phases (FeAl₂O₄ and CuAlO₂, respectively) in the presence of α-Al₂O₃ are derived using data available in the literature. As in previous work in the NiαAl₂O₃ system, aluminate formation by solid state reaction of Fe and Cu with α-Al₂O₃ was calculated to require a threshold concentration of oxygen in the metal, which is of the order of 1/5 the solubility limit. The sults are presented in stability diagrams and compared with previous results on the Ni/α-Al₂O₃ system in terms of the free energies of formation of the aluminates and the relative free energes of solution of oxygen in the metals. The results are also compared with available experimental observations on Fe/α-Al₂O₃ and Cu/α-Al₂O₃ interfaces.     

Al/Fe2O3反应合成材料热力学

运用CALPHAD技术，基于多组元多相复杂平衡体系的吉布斯自由能最小化原理，用大型集成数据库F^*A^*C^*T系统，考察了铝和氧化铁经典反应体系的热力学规律。针对材料的反应合成技术，计算了化学计量铝和氧化铁体系以及各种产物中物种的相变情况；分析了原料初始温度、配料比和SiO2含量对绝热温度和平衡组成的影响。     

Crystallization of the amorphous alloys Fe50Ni30B20and Fe80oB20

Metallurgical and Materials Transactions A - The structure and growth characteristics of crystals growing in the amorphous alloys Fe50Ni30B20 and Fe8oB20 were studied by transmission electron...     

Superplasticity in fine-grained 20% Al2O3/YTZ composite

The microstructure and superplastic deformation of fine-grained, 20% Al₂O₃-reinforced, yttria-stabilized, tetragonal zirconia (Al₂O₃/YTZ) has been investigated. Hot identation and tensile tests were carried out at temperatures between 1000° and 1650°C. The material exhibited extensive plasticity at temperatures higher than 1200°C, and a maximum tensile elongation of over 625% was recorded. The microstructure of the Al₂O₃/YTZ was thermally unstable, and concurrent grain growth, and in particular dynamic grain growth, was observed at temperatures higher than 1450°C. Although the apparent strain rate sensitivity exponent was determined to be approximately 0.5, the true strain rate sensitivity, after compensation for grain growth, is about 0.67. The activation energy for superplasticity in Al₂O₃/YTZ was determined to be 257 kJ/mol which is much lower than the activation energy for superplastic Y-TZP. Of particular interest were the grain-boundary structures and the chemical compositions of the grain boundaries. Microstructures were studies using transmission electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. No glassy phase was detected at grain boundaries.     

Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics. This work involved a study of the wetting of SiC ceramics by two oxide systems, Al₂O₃ /Dy₂O₃ and Al₂O₃ /Yb₂O₃, which have so far not been studied for application in the sintering of SiC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. Samples of the mixtures were pressed into cylindrical specimens, which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere. The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX). The DRX analysis showed that Al₂O₃ and RE₂O₃ reacted and formed the Dy₃Al₅O₁₂ (DyAg) and Yb₃Al₅O₁₂ (YbAg) phases. The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。