RF-PCVD法制备纳米Al2O3粉体动力学模型

本文采用RF-PCVD法，分析了富氧高频等离子反应器内反应物AlCl3的高温氧化反应、产物Al2O3气相成核及晶粒长大过程，认为晶粒的长大过程为制备过程的主要步骤。采用Browmtian碰撞理论，经合理简化，建立了晶粒长大的动力学模型。模型分析表明：在富氧高频等离子反应器内，传递因素决定Al2O3纳米晶粒的最终粒径大小及其分布。在实验操作条件下，模型数值解与实验结果相接近，并对模型计算结果的偏大进行了初步分析。     

Ti_2AlNb基合金表面磁控溅射Al/Al_2O_3薄膜及扩散处理对其抗高温氧化性能的影响

为提高Ti2Al Nb合金的抗高温氧化性能,在Ti2AlNb合金表面磁控溅射Al/Al2O3薄膜,于真空退火炉内对其进行600℃,1 h扩散处理后,分别在650,750,850℃下氧化100 h。利用XRD,SEM,EDS技术对基体和扩散试样的相组成、微观形貌进行了分析;研究了Al/Al2O3薄膜扩散层的抗高温氧化性能及扩散处理对Al/Al2O3薄膜氧化动力学曲线的影响。结果表明:Al/Al2O3薄膜扩散层的氧化行为受氧离子渗入薄膜运动过程的控制,在高温条件下表层形成连续致密的Al2O3膜,使薄膜扩散层的氧化系数远低于基体,并且次表层的富铝相能有效阻止氧离子扩散通道的形成,减少基体与氧化性气体接触,从而显著提高Ti2Al Nb基合金的抗高温氧化性能。     

Al-TiO2—C体系MC法合成Al2O3-TiCP／Al基复合材料的动力学分析

利用Al-TiO2-C体系熔铸法制备原位自生Al2O3-TiCP／Al基复合材料。采用Kissinger法测定该体系的激活能。该材料反应的动力学机制由熔化、扩散、反应和冷却四个阶段组成。该体系的主体反应为Al与TiO2之间发生的、伴随着强烈放热的置换反应,以及石墨粒子与其周围富钛层的反应。前者导致了Al2O3粒子生成;后者则生成了TiC粒子。基于理论计算和实验研究,建立了Al-TiO2-C体系MC合成工艺制备原位自生Al2O3-TiCP／Al基复合材料的动力学模型。动力学分析表明,石墨和TiO2颗粒愈细,混粉效果愈好,增强相的体积分数愈高,反应速率就愈大,反应完成所需时间也愈短。     

原位Al/_2O_(3P)/7075复合材料微观组织与磨损行为

采用原位反应近液相线铸造法制备具有不同质量分数的Al2O3P/7075复合材料,并对其进行干滑动磨损实验研究,通过OM,SEM,TEM等材料分析方法测试了材料的微观组织和磨损表面形貌。结果表明,原位Al2O3颗粒对7075铝合金的晶粒组织有明显细化效果,Al2O3P/7075复合材料的耐磨性比基体7075铝合金有明显的提高。原因是原位合成的复合材料界面结合良好,原位Al2O3颗粒在摩擦过程中起着抑制金属流动和支撑的双重作用。磨损表面形貌显示,原位Al2O3颗粒的加入,使磨损机制由黏着磨损变为磨粒磨损,从而改善了材料的耐磨性。     

射频反应溅射AL2O3薄膜组分研究

通过射频反应溅射的方法制备Al2O3薄膜,并研究其中AL和O的化学配比,并取得初步结果。实验以高纯Al作为靶材,高纯度O2为反应气体,在单晶(100)Si片上镀制Al2O3薄膜。用XPS能谱分析仪测试,不同氩氧比的情况下,氧化铝薄膜的化学配比,并与反应速率曲线进行对比确定氩氧比工艺。结果表明,应用此工艺制备的Al2O3薄膜具有良好的化学配比,得出了用试验方法确定反应溅射Al2O3薄膜氧氩比工艺的方法,此方法简单有效。     

原位合成含有Al2O3晶须Al2O3/Ti-Al复合材料机理的研究

利用氧对金属Ti,Al粉的部分氧化,原位合成含Al2O3晶须的Al2O3/Ti-Al复合材料,利用XRD,EDAX和NO-RAN能谱仪对材料的晶相组成和元素成分进行分析,利用SEM观察材料显微组织和断口形貌。结果表明,反应步骤为:Ti,Al金属粉表面氧化→铝的熔化→TiAl3的生成→Ti2Al,TiAl,Ti3Al等多种化合物生成和Al对TiO2的还原反应;铝含量决定了材料的晶相组成,铝不足时,生成Ti2Al,TiAl,Ti3Al等多种金属间化合物和氧化铝,铝含量足够时,最终的产物为TiAl3,金属铝以及氧化铝等相;氧化铝晶须是通过VLS机理生成的,产物中晶须的数量和发达程度随铝含量的增加而递增,晶须的直径随热处理温度升高而增加。     

Al_2O_3-H_2O纳米流体相变蓄冷特性研究

在水介质中悬浮少量的纳米氧化铝颗粒(粒径20nm),通过添加分散剂和超声波振荡,制备成均匀分散的Al2O3-H2O纳米流体。对水和Al2O3-H2O纳米流体的相变蓄冷特性进行了实验比较。结果表明,加入纳米Al2O3可降低水的过冷度,缩短结冰时间;在相同的时间内,纳米流体的蓄冷量要大于纯水。     

原位Al_2O_3颗粒增强铝基复合材料的高能超声制备及性能研究

采用反应烧结和熔体超声分散法,以SiO2为原料成功制备了Al2O3颗粒增强铝基复合材料。利用X射线衍射仪、差热分析仪、扫描电镜、能谱仪等分析了复合材料的显微组织、生成的颗粒以及颗粒的形貌、尺寸和颗粒的分布。利用电子式万能试验机进行室温拉伸实验。结果表明,在800℃下,经过8h烧结后的坯块中SiO2完全反应生成了团聚的Al2O3颗粒,Al2O3颗粒粒度约为1μm。在熔体中施加1.0kW/cm2的高能超声使坯块熔化,获得的复合材料中Al2O3颗粒分布均匀,颗粒尺寸基本没有变化;复合材料的抗拉强度110.6 MPa,较纯铝基体的92.0MPa,提高了20.2%。     

Al_2O_3颗粒镀铜对铜基粉末冶金摩擦材料Al_2O_3-Fe-Sn-C/Cu摩擦磨损性能的影响

通过对陶瓷摩擦组元的表面进行化学镀铜来改善铜基粉末冶金摩擦材料中陶瓷相与基体间的结合效果,从而提高材料摩擦磨损性能。分别采用镀铜Al2O3颗粒和未镀铜Al2O3颗粒与铜粉和铁粉等经混合、压制、加压烧结制备Al2O3-Fe-Sn-C/Cu摩擦磨损试样。测试并分析了摩擦材料的微观结构、力学性能及摩擦磨损性能。结果表明:摩擦组元镀铜可使硬质颗粒与铜基体结合紧密;摩擦材料的布氏硬度增加了12%,弹性模量提高了约7%,摩擦系数提高了5%~10%,线磨损量降低了20%~50%;表面镀铜后的Al2O3颗粒不易脱落,摩擦系数稳定性提高了13%~23%。研究结果表明,摩擦组元表面镀铜可提高材料的综合性能。     

Al2O3表面弥散铜基导电材料的制备

用渗铝－内氧化技术制备了Al2O3表面的弥散铜基导电材料，研究了渗铝层的铝浓度分布和表面弥散层的显微组织及有关性能。结果表明，渗层的铝浓度接近渗剂中铝粉的含量，渗层深度可达100μm，内氧化后，能在渗铝层形成Al2O3弥散硬化层，Al2O3含量也影响了铜的表面硬度、电阻率和磨损抗力。     

Plasma spraying of Al2O3 and Al2O3Y2O3

A microstructural study has been carried out of plasma-sprayed Al₂O₃ and mixed and sintered Al₂O₃Y₂O₃. In order to ascertain the degree of metastability achieved by plasma spraying, these results are compared with a similar experiment utilizing a CO₂ laser for melting and the hammer-and-anvil technique for quenching of the same materials. X-ray diffraction methods were used to determine the obtained phases and crystal structures. In addition, transmission electron microscopy was used to confirm the phases present and to study their morpology. The porosity was studied with both mercury intrusion porosimetry and small angle neutron scattering. The addition of Y₂O₃ is shown to decrease the porosity from 15% to 7.5%. Adhesion is likewise related to the addition of Y₂O₃ and it is seen that adhesion of the mixture is measurably improved over that of pure Al₂O₃. The implication of these results is discussed.     

Microstructure and Strength of Al2O3/Al2O3 Joints Bonded with ZnO-Al2O3-B2O3-SiO2 Glass-Ceramic

ZnO-Al2O3-B2O3-SiO2 （ZABS） glass powder was used as interlayer to join alumina ceramics. The effect of joining temperature on the microstructure and strength of joints was investigated. The results showed that the ZABS glass can react with alumina substrate to form a layer of ZnAl2O4 at Al2O3/glass interface. Bending test exhibited that low joining temperature （1150℃） led to low joint strength due to the formation of pores in the interlayer, originated by high viscosity of the glass. High joining temperature （1250 ℃） also resulted in low joint strength, because of large CTE （coefficient of thermal expansion） mismatch between amorphous interlayer and alumina substrate. Therefore, only when the joining temperature was appropriate （1200℃）, defect-free interface and high joint strength can be obtained. The optimum joint strength reached 285 MPa, which was the same as the base material strength.     

Surface tension of PbO-B2O3 and Bi2O3-B2O3 glass melts

The surface tensions of xPbO-(100?x) B₂O₃ (x = 30–80 mol%) and xBi₂O₃-(100?x) B₂O₃ (x = 0–100 mol%) melts were measured using the ring method over the temperature range 973 to 1373 K. The compositional and temperature dependences of surface tension were investigated. Addition of PbO and Bi₂O₃ to B₂O₃ increased the surface tensions of their respective PbO-B₂O₃ and Bi₂O₃-B₂O₃ melts. The surface tension showed a maximum at 60 mol% PbO in the PbO-B₂O₃ melts and at 70–80 mol% Bi₂O₃ in the Bi₂O₃-B₂O₃ melts. The temperature coefficient of surface tension was examined on the basis of its relationship to the structure, and it was suggested that the temperature coefficient of surface tension decreases with an increasing content of four-coordinated boron.     

Preparation of pressureless-sintered SiC-Y2O3-Al2O3

Sintering additives were prepared from aluminium hydroxide and yttrium hydroxide. These additives were soluble in water and resulted in a binder. A -SiC powder was mixed with the additive solution and sintered at 2150° C without pressure. The oxides formed from the additive promoted sintering. The sintered body contained no pores. Aluminium, silicon, and yttrium oxide were precipitated in the sintered body.     

Some physical properties of V2O5-Fe2O3 and V2O5-Fe2O3-Li2O systems

Various methods have been used to study the physical properties of the V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems, including X-ray, electron microscope, Mössbauer effect, NMR and thermogravimetric measurements. The iron ions are approximately equally distributed in substitutional and interstitial sites in the V₂O₅ lattice. The maximum number of iron ions dissolved in the V₂O₅ matrix corresponds to 4 mol % Fe₂O₃. In all the samples a quantity of Fe₂O₃ which has not been included in lattice is observed. The V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems are formed from solid solutions mixed with very small Fe₂O₃ particles. The analysis of the charge compensation of iron ions suggests that V₂O₅ is a quasi-amorphous semiconductor. Irradiation of V₂O₅-based samples with an electron beam induces the V₂O₅ platelets to convert to the VO _x phase.