高能球磨制备纳米掺La硬质合金粉末

用XRD、SEM和DTA等分析检测手段，研究了高能球磨过程中，掺La硬质合金粉末的结构、形貌和相的变化。结果表明：微量La的加入，有利于硬质合金粉末晶粒的细化；高能球磨10h，即可获得晶粒度为30nm的掺La硬质合金粉末；高能球磨20h,Co相的X－ray衍射峰消失，说明Co相已完全固溶或亚固溶于WC相中。高能球磨30h，可获得晶粒度约10nm的掺La硬质合金粉末。DTA分析表明，与高能球磨前的粉末相比，在300－600℃温度范围内加热时，高能球磨掺La硬质合金粉末出现了明显的结构弛豫，说明粉末晶粒内部产生了许多缺陷，如：内应力、位错、晶格畸变等。     

稀土复合氧化物陶瓷热导率理论及其热物性能

综述了稀土复合氧化物陶瓷热导率理论的发展情况和热物性能方面的研究现状,介绍了材料热导率的影响因素,分析了材料微结构对热导率的影响,总结了具有A2B2O7通式的烧绿石型和萤石型稀土复合氧化物的热物性能,以及掺杂对其热导率和热膨胀系数的影响.     

Effect of rare earth doping on thermo-physical properties of lanthanum zirconate ceramic for thermal barrier coatings

The effect of rare earth doping on thermo-physical properties of lanthanum zirconate was investigated. Oxide powders of various compositions La2Zr2O7 were synthesized by coprecipitation-calcination method. High-temperature dilatometer, DSC, and laser thermal diffusivity methods were used to analyze thermal expansion coefficient （TEC）, specific heat, and thermal diffusivity. The results showed that CeO2 doped pyrochlores La2（Zr1.8Ce0.2）2O7 and La1.7（DyNd）0.15（Zr0.8Ce0.2）2O7 had higher TEC than La2Zr2O7 and La1.7Dy0.3Zr2O7. La2（Zr1.8Ce0.2）2O7, La1.7Dy0.3Zr2O7, and La1.7（DyNd）0.15（Zr0.8Ce0.2）2O7 had lower thermal conductivity than undoped La2Zr2O7. The Dy2O3, Nd2O3, and CeO2 codoped composition showed the lowest thermal conductivity and the highest TEC. Thermo-physical results also indicated that TEC of rare earth oxide doped La2Zr2O7 ceramic was slightly higher than that of conventional ZrO2-8Wt.% Y2O3 （8YSZ）, and its thermal conductivity was lower than that of 8YSZ.     

Effects of yttrium on recrystallization and grain growth of Mg-4.9Zn-0.7Zr alloy

Recrystallization and grain growth in Mg-4.9Zn-0.7Zr and Mg-4.9Zn-0.9Y-0.7Zr alloys as a function of temperature on deformation were investigated with regards to hot rolling and annealing. The influence of yttrium addition on the microstructure was examined by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicated that yttrium addition promoted nucleation of recrystallization during hot rolling process. The grain size of Mg-4.9Zn-0.7Zr alloy samples grew significantly with annealing temperature （300-400 ℃） and holding time （0-120 min）, while the microstructure of the alloy with yttrium addition remained unchanged and fine. The activation energy of grain boundary migration for Mg-4.9Zn-0.9Y-0.7Zr alloy samples （56.34 kJ/mol） was higher than that for Mg-4.9Zn-0.7Zr （42.66 kJ/mol） owing to the pinning effect of Y-containing particles. The proposed growth models of recrysta/lized grains for the two studied alloys conformed well to E. Robert＇s grain-growth equation. Besides, the ultimate strength and yield strength of the alloys with yttrium addition were improved with good plasticity.     

微量稀土Nd对AZ91微观组织及腐蚀性能的影响

采用X-射线衍射(XRD)、扫描电镜(sEM)、能谱分析(EDS)、集气法、动电位极化及浸泡实验等手段和方法研究了添加微量稀土元素钕(Nd)对AZ91镁合金微观组织及耐蚀性的影响,并从热力学角度分析了Nd对提高合金耐蚀性的影响机制.结果表明.少量稀土Nd细化了合金的微观组织,使β-Mg17Al12相变得断续、弥散,生成了Al3Nd相及Mg-Al-Mn-Nd-Fe金属问化合物;稀土Nd使合金在3.5%NaCl溶液中的自腐蚀电位升高,且与Al、O生成了不连续的致密的氧化膜,提高了合金的耐腐蚀性能;添加1.0wt%Nd时合金的耐蚀性最佳,腐蚀速率为0.28 mg·cm-2·d-1,比AZ91合金下降了一个数量级.     

热障涂层的研究现状与发展方向

热障涂层(TBCs)是目前最先进的高温防护涂层之一,具有良好的隔热效果和抗高温氧化性能.综述了热障涂层的陶瓷材料、粘结层材料、涂层结构、制备工艺及涂层失效机理等5个方面的研究现状,在此基础上提出了热障涂层的发展方向.     

Nb-Ti-Al高温Nb合金氧化行为的研究

 用真空电弧熔炼制备了β(Nb-35Ti-6A1)和β+δ(Nb-30Ti-15A1、Nb-15Ti-11Al)Nb台金,研究了3种Nb合金1000℃静止空气中的连续氧化行为,采用金相显微镜、XRD和SEM分析了氧化膜的结构和组成.研究表明,由Nb2O5,金红石TiO2和-A12O3组成的混合氧化膜具有一定的保护作用,3种Nb-Ti-Al合金氧化动力学曲线均遵循抛物线规律;Nb-35Ti-6Al中的富Ti偏析区发生内氧化,而Nb-30Ti-15Al和Nb-15Ti-11Al中δ相的存在有利于降低氧在基体中的溶解和扩散,使β+δ两相合金的氧化性能优于β单相合金.     

聚合物电致发光器件中用类金刚石碳膜增强电子注入

用正丁胺作碳源,采用射频辉光等离子系统制备类金刚石碳膜(DLC),沉积在聚合物发光器件中的发光层(MEH-PPV)和铝(Al)阴极间作电子注入层.制备了结构为ITO/MEH-PPV/DLC/Al的不同DLC厚度的器件,测量了器件的I-V特性、亮度及效率,研究了DLC层对器件电子注入性能影响的机制.结果表明:当DLC厚度小于1.0nm时,其器件有较ITO/MEH-PPV/Al高的启动电压和低的发光效率;当DLC厚度在1.0～5.0nm之间时,器件的性能随着DLC厚度增加而变好;当DLC厚度为5.0nm时,器件具有最低的启动电压与最高的发光效率;当DLC厚度继续增加时,器件的性能随着DLC厚度增加而变差.并对ITO/MEH-PPV/DLC/Al和ITO/MEH-PPV/LiF/Al的器件性能进行了比较研究.     

Zr和Ce对Ti-11Si亚共晶合金组织及压缩性能的影响

采用显微组织观察(OM)、X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)以及压缩性能测试等手段,研究了元素Zr和Ce对Ti-11 at%Si铸态亚共晶合金组织和室温压缩性能的影响。结果表明,在Ti-Si亚共晶合金中添加8.0 at%的Zr可降低Si在α-Ti中的固溶度,促进硅化物细小、弥散析出,可改善合金的压缩强度和塑性。而添加0.5 at%的Ce可以明显细化α-Ti枝晶和共晶团组织,也可提高合金的压缩强度和塑性。且Ce对Ti-Si亚共晶合金的细晶强化效果比Zr要好。物相分析和EDS结果表明,Zr和Ce都主要存在于Ti5Si3相中,Zr则取代了部分Ti原子,形成了(Ti,Zr)5Si3相,Ce取代了部分Si原子,形成了三元硅化物Ti5(Si,Ce)3相。