The microwave dielectric properties of ZrO2-SnO2-TiO2 （ZST） system ceramics were stu- died as a function of the amount of Sb2O5 dopant. With the addition of 0—0.50/0 Sb2O5 （molar ratio）, the substitution of Ti 4+...The microwave dielectric properties of ZrO2-SnO2-TiO2 （ZST） system ceramics were stu- died as a function of the amount of Sb2O5 dopant. With the addition of 0—0.50/0 Sb2O5 （molar ratio）, the substitution of Ti 4+ ions with Sb 5+ ions decreased the sintering temperature and increased the quality factor Q due to the reduction of oxygen vacancies. When the amount of Sb 5+ increased further （above 0.50/0）, Q was decreased by increasing the electron concentration. When the system doped with 0.50/0 Sb2O5 was sintered at 1 150 ℃ for 6 h, the relative dielectric constant ε, Qf0, and the temperature coefficient of resonant frequency （TCF） were 38.46, 44 500 GHz,20.0×10 -6 /℃, respectively, at 6 GHz.展开更多
A S 2O 2- 8/ZrO 2 Al 2O 3 type solid superacid catalyst was prepared from ZrOCl 2·8H 2O, AlCl 3· 6H 2O and (NH 4) 2S 2O 8 by coprecipitation, maceration and calcination processes. Their crystal structures an...A S 2O 2- 8/ZrO 2 Al 2O 3 type solid superacid catalyst was prepared from ZrOCl 2·8H 2O, AlCl 3· 6H 2O and (NH 4) 2S 2O 8 by coprecipitation, maceration and calcination processes. Their crystal structures and acidities were determined by XRD and Hammett method, respectively. The activity of the catalyst was studied as function of Al 2O 3 content, calcination temperature and time in the esterification of acetic acid with butanol, and a conversion of 96 5% was obtained. The catalyst gave also higher yields in syntheses of ketals and acetals: cyclohexanone ethylene ketal(86 2%), acetophenone ethylene ketal(78 5%), acetylacetic ester ketal(88 5%), benzaldehyde glycol acetal(76 3%). The chemical structures of the products were confirmed by IR spectra.展开更多
以纳米ZrO 、微米Al O 为原料,采用无压烧结方式制备了ZTA 复相陶瓷。结果表明:nano-ZrO 的 2 2 3 2加入有利于制备细晶ZTA 复相陶瓷。此外,nano-ZrO 的加入对 Al O 陶瓷的显微结构也产生影响,ZrO ...以纳米ZrO 、微米Al O 为原料,采用无压烧结方式制备了ZTA 复相陶瓷。结果表明:nano-ZrO 的 2 2 3 2加入有利于制备细晶ZTA 复相陶瓷。此外,nano-ZrO 的加入对 Al O 陶瓷的显微结构也产生影响,ZrO 颗粒以 2 2 3 2“晶内型”和晶界型两种形式存在。合理的配方组成及制备工艺有利于 Z r O 以四方亚稳相存在。Z r O 含量为 2 23 0 w t % 时,其四方相含量可达 6 9 %,有利于应力诱导相变增韧,该 Z T A 复相陶瓷的抗弯强度、断裂韧性分别达到 604MPa、6.87MPa·m1/2。展开更多
基金Supported by Natural Science Foundation of Tianjin (No.06YFJMJC01000) the High Technique Research and Development Pro-gram of China (No.2001AA325110).
文摘The microwave dielectric properties of ZrO2-SnO2-TiO2 （ZST） system ceramics were stu- died as a function of the amount of Sb2O5 dopant. With the addition of 0—0.50/0 Sb2O5 （molar ratio）, the substitution of Ti 4+ ions with Sb 5+ ions decreased the sintering temperature and increased the quality factor Q due to the reduction of oxygen vacancies. When the amount of Sb 5+ increased further （above 0.50/0）, Q was decreased by increasing the electron concentration. When the system doped with 0.50/0 Sb2O5 was sintered at 1 150 ℃ for 6 h, the relative dielectric constant ε, Qf0, and the temperature coefficient of resonant frequency （TCF） were 38.46, 44 500 GHz,20.0×10 -6 /℃, respectively, at 6 GHz.
文摘A S 2O 2- 8/ZrO 2 Al 2O 3 type solid superacid catalyst was prepared from ZrOCl 2·8H 2O, AlCl 3· 6H 2O and (NH 4) 2S 2O 8 by coprecipitation, maceration and calcination processes. Their crystal structures and acidities were determined by XRD and Hammett method, respectively. The activity of the catalyst was studied as function of Al 2O 3 content, calcination temperature and time in the esterification of acetic acid with butanol, and a conversion of 96 5% was obtained. The catalyst gave also higher yields in syntheses of ketals and acetals: cyclohexanone ethylene ketal(86 2%), acetophenone ethylene ketal(78 5%), acetylacetic ester ketal(88 5%), benzaldehyde glycol acetal(76 3%). The chemical structures of the products were confirmed by IR spectra.
文摘以纳米ZrO 、微米Al O 为原料,采用无压烧结方式制备了ZTA 复相陶瓷。结果表明:nano-ZrO 的 2 2 3 2加入有利于制备细晶ZTA 复相陶瓷。此外,nano-ZrO 的加入对 Al O 陶瓷的显微结构也产生影响,ZrO 颗粒以 2 2 3 2“晶内型”和晶界型两种形式存在。合理的配方组成及制备工艺有利于 Z r O 以四方亚稳相存在。Z r O 含量为 2 23 0 w t % 时,其四方相含量可达 6 9 %,有利于应力诱导相变增韧,该 Z T A 复相陶瓷的抗弯强度、断裂韧性分别达到 604MPa、6.87MPa·m1/2。
