Structure properties and sintering densification of Gd2Zr2O7 nanoparticles prepared via different acid combustion methods

Gadolinium zirconate(Gd2Zr2O7) nanocrystals were prepared via two different combustion methods: citric acid combustion(CAC) and stearic acid combustion(SAC). The effects of the different preparation methods on the phase composition, microtopography, and sintering densification of the resulting Gd2Zr2O7 nanopowders were investigated by thermal-gravimetric and differential thermal analysis(TG-DTA), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), and transmission electron microscopy(TEM) techniques. The results indicated that both methods could produce Gd2Zr2O7 nanopowders with an excellent defective fluorite structure. The reaction time was reduced by the SAC method, compared with the CAC method. The nanopowders synthesized by the two methods were different in grain size distribution. The resulting nanoparticle diameter was about 50 nm for CAC and 10 nm for SAC. After vacuum sintering, the sintered bodies also had a different relative density of about 93% and 98%, respectively. Thus the preparation of Gd2Zr2O7 nanopowders by SAC was the first choice to achieve the desired sintering densification.     

Gd_2Ti_2O_7:Ce粒子的表观活化能及发光性能

采用共沉淀法在不同母盐溶液浓度条件下合成出Gd_2Ti_2O_7:Ce纳米粒子;用XRD、SEM、TG-DTA等测试手段分析了样品的物相、形貌及发光性能;用热分析动力学计算不同升温速率下样品的活化能。结果表明:前驱体在升温过程的物相变化分3个阶段,用Doyle-Ozawa和Kissinger法分别对初始浓度为0.08和0.04 mol/L条件下各阶段表观活化能进行计算,其平均值为42.43、145.58、381.98 k J·mol~(-1)和51.28、161.51、446.30 k J·mol~(-1),晶粒生长活化能分别为12.58和19.54 k J·mol~(-1)。浓度为0.08 mol/L时,1173 K煅烧2 h制备出的纳米粒子表面活性较高,铈离子掺杂0.7%(摩尔分数)时发光强度最大。     

Al_2O_3-TiCN/Co-Ni复合材料制备及力学性能

用真空热压烧结法制备了Al2O3-Ti C0.5N0.5/Co-Ni复合材料,用扫描电子显微镜、能谱仪、电子万能试验机和Vickers硬度仪等测试分析了不同烧结参数对样品显微组织及力学性能的影响。结果表明:当烧结温度1 650℃,压力25 MPa,保温时间30 min时,样品的相对密度、抗弯强度(σmax)、断裂韧性(KICmax)和Vickers硬度(HV)的最大值分别达到99.6%,σmax=1 100 MPa,KICmax=10.5 MPa·m1/2和HV=23.7 GPa,样品断口形貌存在混晶断裂特征。