AlN 粉末制备的热力学分析和实验研究

对制备 AlN 的体系 AlCl_3-NH_3-N_2进行了热力学分析,确立了 AlN 粉末合成所需要的热力学条件.在700～1000℃下,利用无水 AlCl_3和 NH_3的化学气相淀积反应合成得到了高纯 AlN 超细粒子粉末,研究了反应温度、AlCl_3浓度和总流量等对 AlN 粉末理化性质的影响.实验确立了产物低温和高温热处理条件.     

SiC粒子增强铸造Al基复合材料的研制

本文用真空烘烤封罐法对 SiC 粒子进行预处理,在固液两相区内搅拌添加,制造了铸造 Al 基复合材料。测试表明,该复合材料具有铸造性能好,力学性能高的优点,适用于采用压铸、石膏型精密铸造、金属型铸造等工艺方法成型的活塞、连杆等要求苛刻的零件。     

颗粒增强TiAl基复合材料及其Si的韧化作用研究EI

运用ＸＤ工艺制备了颗粒增强ＴｉＡｌ基复合材料。增强颗粒均匀分布于ＴｉＡｌ基体中并细化ＴｉＡｌ合金。通过在ＴｉＢ_２／ＴｉＡｌ、ＴｉＣ／ＴｉＡｌ复合材料中加入适量的Ｓｉ，颗粒增强ＴｉＡｌ基复合材料的室温延性得到了改善。     

Handling of fine-particles by time-averaged particle driving method in plasmas

We developed a noble technique for the fine-particle handling in plasmas. In this method a pair of point electrodes are introduced in the plasma, to which positive pulses are applied alternatively. When the pulse repetition period is shorter than the particle response time, the particles feel only time-averaged force because of their large mass. Spatial profile of the equivalent potential of the time-averaged force varies from a circle to an ellipse with an increase in the local discharge at the electrodes. The particles are eventually transported toward a middle point between two point-electrodes, being almost independent of their initial positions. This method is quite effective for converging fine particles in the plasma.     

PREPARATION OF TiN FILMS BY N_2 ASSISTED Xe~+ ION BEAM ENHANCED DEPOSITION AND THEIR MECHANICAL PROPERTIES

A new method for preparation of hard TiN films has been developed by using electronbeam evaporation-deposition of Ti and bombardment with 40 keV Xe~+ ion beam ina N_2 gas environment.The synthesized TiN films were superior to PVD and CVDones in respects of improved adhesion to substrate and low preparing temperature.Theyexhibited good wear resistance and high hardness up to 2200 kg/mm~2.Some industrialapplications have been reported.     

Micron-Scale Soft Actuators Fabricated from Multi-Shell Polystyrene Particle-Gold Nanoparticle Nanohybrids

Actuators made of soft matter are needed for a variety of fields ranging from biomedical devices to soft robotics to microelectromechanical systems. While there are a variety of excellent methods of soft actuation known, the field is still an area of intense research activity as new niches and needs emerge with new technology development. Here, a soft actuation system is described, based on a core-multi-shell particle, which moves via photothermal expansion. The system consists of a novel polystyrene-based thermally expandable microsphere, with a secondary shell of a silicate-silane graft copolymer, to which gold nanoparticles are covalently linked. The gold nanoparticles act as photothermal nano-transducers, converting light energy into the thermal energy necessary for microsphere expansion, which in turn results in material movement. Actuation is shown in isolated particles in thermal and photothermal regimes using metal ceramic heaters or 520 nm laser illumination, respectively. Macroscale actuation is demonstrated by making a composite material of particles suspended in the transparent elastomer polydimethylsiloxane. The sample demonstrates an inchworm-like movement by starting from an arched geometry. Overall, this work describes a new particle-based actuation method for soft materials, and demonstrates its utility in driving the movement of a composite elastomer.     

TEM and DFT investigation of CVD TiN/κ-Al2O3 multilayer coatings

This paper investigates the interfacial structure in hot-wall CVD TiN/κ-Al₂O₃ multilayer coatings using both HREM and DFT modeling. Two multilayers with different thicknesses of the TiN layers (50 and 600 nm) separating the κ-Al₂O₃ layers are analyzed. The general microstructure of the two multilayers is relatively similar. The TiN layer in the thicker TiN/κ-Al₂O₃ coating is thick enough to be several TiN grains high. This means that epitaxial columns, which are often found in the thinner TiN/κ-Al₂O₃ coatings, are not present. However, the orientation relationships at the TiN/κ-Al₂O₃ interfaces are the same in both multilayers. The HREM investigations show that κ-Al₂O₃ (001) planes can grow directly on flat (111) TiN faces, without any other phases or detectable amounts of impurities, such as sulphur, present. Where the TiN layers are more curved, γ-Al₂O₃ can be grown, at least partly stabilized by the cube-on-cube orientation relationship between γ-Al₂O₃ and the underlying TiN. The DFT calculations show very similar adsorption strengths for an O monolayer positioned on Ti-terminated TiC(111) and TiN(111) surfaces, with preferred adsorption in the fcc site. O adsorption on N-terminated TiN(111) is much weaker, with preferred adsorption in the top site. Calculated elastic-energy contributions yield a higher stability for κ-Al₂O₃ on TiN(111) than on TiC(111) and a higher stability for κ-Al₂O₃ than for α-Al₂O₃ on both TiC and TiN. This indicates that the observed higher stability of κ-Al₂O₃ on TiC(111) than on TiN(111) is not due to the lattice mismatch, while the preferred epitaxial growth of κ-Al₂O₃ over α-Al₂O₃ can be partly attributed to the mismatch.     

GCr15SiMn轴承钢中大尺寸TiN生成与控制

 以西宁特钢EAF→LF→VD→IC工艺路线生产GCr15SiMn轴承钢为研究背景,采用矿物解离分析仪、夹杂物自动分析系统、化学分析及X射线荧光光谱仪等检测手段与热力学计算相结合的方法,研究了铸锭中大尺寸TiN夹杂物的析出机理,分析了冶炼阶段钢液中钛含量增加的原因,并提出了相应的改进工艺。通过对轴承钢中残余钛、氮含量的热力学计算,发现大尺寸TiN主要是在凝固过程中析出和长大,降低冶炼过程中钛含量是控制TiN生成的主要途径。对原工艺冶炼过程钛含量变化进行分析,钢液中钛增量主要发生在EAF出钢→LF结束阶段,其中52%钛增量来自于炉渣。为了避免炉渣中钛进入钢液,借助于七元炉渣CaO-SiO₂-MgO-FeO-Al₂O₃-MnO-TiO₂与钢液之间平衡的钛分配比(LTi)模型,计算了铝含量和炉渣中CaO含量对LTi 的影响,预测了最佳的平衡炉渣成分。结果表明,适当降低铝含量和炉渣中CaO含量可以提高渣-钢之间的钛分配比,降低钢液的钛含量;当铝质量分数为0.015%～0.025%、CaO质量分数为50%～55%时,其他炉渣组元的最佳成分(质量分数)为18%～24% Al₂O₃和12%～17% SiO₂。此外,定量描述了不同LTi条件下EAF下渣量与LF终点钛含量的关系。最后,采用“低炉渣碱度、低铝含量以及严格控制电炉下渣量”的改进措施进行了优化试验,优化后冶炼终点钛质量分数可控制在小于0.002 0%,铸锭TiN平均数密度可由原工艺的2.09个/mm2降低至0.73个/mm2,且TiN尺寸几乎都小于10 μm。     

SiC含量对SiCp/Al复合材料摩擦性能的影响

采用粉末冶金技术制备了SiC_p/Al复合材料,探讨了SiC颗粒质量分数对SiC_p/Al复合材料密度、布氏硬度、微观形貌以及摩擦磨损性能的影响。结果表明,SiC颗粒表面形成了少量可提高界面结合性的Al₄C₃化合物。随着SiC质量分数增加,SiC_p/Al复合材料的密度没有明显的变化,当SiC质量分数增加至25%时,密度明显下降。SiC_p/Al复合材料的布氏硬度随着SiC质量分数的增加呈先增长后减小的变化趋势。当SiC质量分数为20%时,材料的硬度最优（HBW 114）,平均摩擦系数达到最大值（0.3425）,摩擦后试样表面形貌平整且犁沟较浅,SiC颗粒未出现明显剥落。     

钽粉颗粒强度的研究

研究了采用激光粒度分布仪测试电容器级团化钽粉粒度分布及强度的方法。其中心内容是:先采用3种不同比表面积、松装密度和费氏平均粒径的钠还原原粉,按3种烧结工艺制得团化钽粉。然后把烧结得到的6种试样加入纯水中,以200～300r/min进行高速搅拌并以40W,42kHz超声波振动。将激光衍射分析仪的激光束穿过经不同搅拌时间的悬浊钽粉,测得不同时间的钽粉粒径分布曲线。分析分布曲线可以获得团化钽粉的一系列信息,包括:①几种团化钽粉颗粒的相对强度;②影响团化钽粉颗粒强度的因素;③钽粉强度和其他性能如介电损耗、流动性,平均粒径及密度的关系等。