凝胶-溶胶法制备纳米二氧化锆

以廉价无机盐八水氧氯化锆为原料,用氨水作沉淀剂,采用溶胶—凝胶法制备纳米级二氧化锆。讨论了不同干燥方法、焙烧温度、凝聚方式等对二氯化锆粒径、比表面积的影响。     

掺钇纳米二氧化钛光催化降解甲基橙的研究

采用金属钇掺杂改性,以钛酸四丁酯为主要原料,在室温下,利用溶胶-凝胶法制备了Y3+掺杂纳米TiO2光催化剂,通过X射线衍射分析(XRD)方法分析其改性机制;掺钇纳米TiO2光催化剂经太阳光照射后,用分光光度计测量光催化降解反应后甲基橙溶液浓度的变化,考察其光催化活性;研究了掺杂量和焙烧温度对光催化活性的影响。结果表明,Y3+掺杂能有效地抑制锐钛矿型TiO2向金红石型TiO2的转化,可使纳米TiO2的衍射峰宽化,粒径从80.5 nm降低到42.15 nm,掺杂量为1.2%,焙烧温度在400℃左右时,能够有效地提高TiO2光催化剂光催化活性。     

溶胶-凝胶法制备钇掺杂的纳米氧化锆粉体

以廉价的无机盐氯氧化锆、硝酸钇、草酸为原料，在不同的溶剂体系条件下，采用溶胶—凝胶法进行钇掺杂的ZrO2（YSZ）纳米粉体的制备研究，并通过扫描电子显微镜（SEM）、热重—差热（TG／DTA）分析、X射线粉末衍射（XRD）等手段对该粉体进行表征。结果表明：两种溶剂体系下制得的干凝胶在650℃，3h热处理，都得到了Y完全固溶、球形、立方相、分散性好的纳米YSZ粉体。     

溶胶-凝胶法制备纳米二氧化锆

以锆的无机盐 (ZrOCl2 ·8H2 O)为前体 ,采用溶胶—凝胶法制备 ,常压下流动氮气气氛干燥获得了纳米二氧化锆。采用MicromeriticsASAP - 2 0 2 0C型吸附仪、XRD和TEM对其进行了表征。结果表明该方法制备的纳米二氧化锆具有粒径小、比表面大和热稳定性好的特点     

纳米二氧化硅制备工艺的研究

以TEOS(正硅酸乙酯)为前驱体、氨水为催化剂和无水乙醇为溶剂,采用溶胶-凝胶法制备了纳米二氧化硅。利用傅里叶变换红外光谱(FT-IR)仪和纳米激光粒度分布仪对纳米二氧化硅的结构、粒径及其分布进行了表征,并着重探讨了反应温度、催化剂浓度和反应时间等对纳米二氧化硅粒径的影响。研究结果表明:当反应温度为60℃、催化剂浓度为0.82 mol/L和反应时间为3~4 h时,制得的纳米二氧化硅平均粒径为300 nm左右。     

纳米ZrO2的制备

本实验研究了利用ZrOCl2·8H2O为原料,根据不同的醇水配比及氨水配比,采用溶胶-凝胶法,并以超临界干燥法（SCFD）制备纳米ZrO2。得出在一个大气压,温度在15～25℃,采用溶胶-凝胶法,在不同的醇水配比及氨水配比下,对ZrO2颗粒将有一定的影响。     

纳米二氧化硅制备工艺的研究

以正硅酸乙酯(TEOS)为前驱液、氨水为催化剂和去离子水、无水乙醇为溶剂,采用溶胶-凝胶法制备出了纳米二氧化硅。利用傅里叶变换红外光谱仪(FT-IR)、动态激光散射粒度分析仪(DLS)、透射电子显微镜(TEM)对纳米二氧化硅的元素组成结构、粒径范围及分布、颗粒形状结构等一系列的性能进行了表征。实验结果表明:产品微观形貌为规整的圆球状;当催化剂氨水浓度为0.4 mol/L,TEOS浓度为0.17 mol/L时,纳米二氧化硅颗粒的峰平均值为215.4 nm,平均粒径为299.6 nm。     

溶胶-凝胶法制备多晶钇铝石榴石纤维

以廉价的铝粉、工业盐酸和醋酸钇为主要原料,通过溶胶-凝胶法制各了高性能的多晶钇铝石榴石纤维.采用X射线衍射、Fourier变换红外光谱、扫描电镜和热重-差示扫描热分析等表征了不同温度下焙烧所得纤维的物相组成、纤维形貌以及前驱体纤维的热分解特性.结果表明:纤维经热处理到900℃时可获得纯相的钇铝石榴石晶体.经1550℃热处理后,所得到的多晶钇铝石榴石纤维的平均晶粒尺寸在200 nm左右,拉伸强度在485MPa.     

溶胶-凝胶法制备纳米二氧化硅

本文通过溶胶一凝胶法制备纳米SiO2。考察了不同温度、pH值、催化剂对制备纳米SiO2的影响。并运用了TEN表征了纳米SiO2的粒径大小、分散度以及粒子性状，得出了制备纳米SiO2较好的工艺条件。     

钇铝石榴石长纤维制备研究

本文以氯化铝、金属铝粉、氧化钇、冰醋酸为原料,采用溶胶-凝胶法制备了钇铝石榴石纤维。研究了纺丝助剂的不同种类对前驱体凝胶纤维长度的影响。结果表明,以聚乙烯吡咯烷酮为纺丝助剂,得到的凝胶纤维长度最长,达25cm。凝胶纤维在1000℃煅烧2小时,全部结晶为钇铝石榴石,纤维的直径为15～18μm,表面光滑。     

醇-水盐溶液加热法制备纳米氧化锆工艺研究

以氧氯化锆为原料,通过醇水环境下的水解反应制得溶胶状锆盐,经过超声波分散和氨水沉淀等过程制得氧化锆前躯体,再经干燥和焙烧制备出纳米氧化锆。采用红外光谱（IR）、X射线衍射（XRD）及扫描电镜（SEM）等对合成过程和最终产品的性能进行了测试和表征。结果表明,在醇水体积比为5∶1、锆盐浓度为0.1 mol/L、聚乙二醇用量为10%（物质的量分数）、焙烧温度为650 ℃条件下,可制备出纳米氧化锆粉体,其分散性好且颗粒细小均匀。     

High-pressure sintered yttria stabilized zirconia ceramics

Fast densification of 8YSZ ceramics under a high pressure of 4.5 GPa was carried out at different temperatures (800, 1000, 1450 °C), by which a high relative density above 92% could be obtained. FT-Raman spectra indicate that the 8YSZ underwent a phase transition from partially tetragonal to partially cubic phase as temperatures increase from 1000 to 1450 °C when sintering under high pressure. The electrical properties of the samples under different high-pressure sintering conditions were measured by complex impedance method. The total conductivity of 0.92 × 10⁻² S cm⁻¹ at 800 °C has been obtained for 8YSZ under high pressure at 1450 °C, which is about 200 °C lower than that of the samples prepared by conventional pressureless sintering.     

常压水热合成纳米氧化锆工艺研究

以ZrOCl2.8H2O和氨水为主要原料,利用常压水热工艺制备出纳米氧化锆粉体,系统研究了氧氯化锆浓度、pH、反应温度及时间对产物晶型、粒度的影响,得出制备氧化锆纳米粉体的最佳工艺条件。并结合X射线衍射分析、透射电镜等方法对样品进行表征。结果表明,所制得的氧化锆样品为纳米氧化锆粉体,且粒度较均匀、分散性好,平均粒径约为7 nm。     

Transparent high-strength nanosized yttria stabilized zirconia obtained by pressure-less sintering

This work describes the development of transparent high-strength Yttria-Stabilized Zirconia (YSZ) ceramics with ultra-fine grain size utilizing conventional pressure-less densification. Starting with nanoparticles with diameter < 10 nm, it was possible to achieve full densification (>99.5% of theoretical density) at a sintering temperature of 1100–1200 °C. The average grain size of the resulting dense ceramics was 75 nm in 3 mol. % YSZ and 85 nm in 8 mol. % YSZ, showing in-line light transmission of 38% and 51% at a wavelength of 800 nm and average biaxial strength (piston on three balls test on samples of diameter 12 mm and thickness 1 mm) of 1980 MPa and 680 MPa, respectively. The nano-grained structure, absence of color centers, and miniaturization of residual pores enable the excellent light transmission. The high biaxial strength is attributed to the refined microstructure, but also to the martensitic tetragonal-to-monoclinic phase transformation that remains active even in nano-sized zirconia grains.     

High temperature mechanical properties of zirconia metastable t'-Phase degraded yttria stabilized zirconia

Air plasma sprayed (APS) 8 wt%-yttria stabilized zirconia (8YSZ) with metastable tetragonal prime phase (t′) has been widely applied as thermal barrier coatings (TBCs) for gas turbine blades because of its outstanding mechanical properties at high temperatures. In the present research, a carefully designed process was used to prepare 8YSZ samples with different phase composition (t′, t and c) simulating the phase degradation of the material during operation conditions. High temperature (1000–1200 °C) bending strength, elastic modulus, and thermal expansion coefficient were measured, which exhibit strong dependence on the phase degradation during heat treatment. Effect of the phase composition on high temperature thermo-mechanical properties and the enhancement of the bending strength have been discussed, providing a new perspective for further improvements.     

Optical properties of gadolinia-doped cubic yttria stabilized zirconia single crystals

Cubic zirconia single crystals stabilized with yttria and doped with Gd₂O₃ (0.10–5.00 mol%) were prepared by the optical floating zone method, and characterized by a combination of X-ray diffraction (XRD), and Raman, electron paramagnetic resonance (EPR), ultraviolet–visible (UV–Vis), photoluminescence excitation (PLE) and photoluminescence (PL) spectroscopic techniques. XRD and Raman spectroscopy showed that the crystal samples were all in the cubic phase, whereas the ceramic sample consisted of a mixture of monoclinic and cubic phases. The absorption spectrum showed four peaks at 245, 273, 308, and 314 nm in the ultraviolet region, and the optical band gap differed between samples with ≤3.00 mol% and those with >3.00 mol% Gd₂O₃. The emission spectrum showed a weak peak at 308 nm and a strong peak at 314 nm, which are attributed to the ⁶P_5/2 → ⁸S_7/2 and ⁶P_7/2 → ⁸S_7/2 transitions of Gd³⁺, respectively. The intensities of the peaks in the excitation and emission spectra increased with Gd³⁺ concentration, reached a maximum at 2.00 mol%, then decreased with higher concentrations. This quenching is considered to be the result of the electric dipole-dipole interactions, and this interpretation is supported by the Gd³⁺ EPR spectra, which showed progressive broadening with increasing Gd³⁺ concentration throughout the concentration range investigated.     

四氯化硅水解制纳米二氧化硅粉体工艺研究

多晶硅合成过程中副产大量四氯化硅。以四氯化硅为硅源,通过水解反应成功合成了二氧化硅粉体。探讨了反应温度、四氯化硅的加料速度、四氯化硅和水的加料比、循环比等条件对二氧化硅比表面积的影响,并利用X射线粉末衍射仪、傅里叶红外光谱仪、比表面测定仪和粒度分析仪等测试工具对所制备的二氧化硅的结构、粒径等参数进行了表征。实验结果表明：在温度为50 ℃,四氯化硅的加料速度为2.0 L/min,加料比［m（四氯化硅）∶m（水）］为0.10~0.15,循环比为10 h-1的条件下,可制得满足橡胶补强剂要求的二氧化硅粉体。     

氯氧化锆前驱体制备纳米氧化锆的机理探讨

介绍了以无机盐氯氧化锆为前驱体，以氢氧化铵为水解促进剂，通过溶胶-凝胶法制备纳米二氧化锆的工艺条件。结合XRD和TG—DSC等测试手段，研究了溶胶-凝胶法制备纳米二氧化锆的机理。结果表明，锆原子在胶体中是以氢氧化锆四聚物的形式存在的，纳米氧化锆是四聚物脱去质子进一步缩聚的结果。     

Influence of flash sintering on the ionic conductivity of 8 mol% yttria stabilized zirconia

The ionic conductivity of flash-sintered, polycrystalline 8 mol% yttria stabilized zirconia (8YSZ) was enhanced compared with that of conventionally-sintered specimens. Flash sintering was carried out at a furnace temperature of 850 °C with an electric field of 100 V cm^–1 to initiate flash. The current density limit was varied between 60 and 100 mA mm^–2. Post-flash impedance measurements over the range 215–900 °C showed that both bulk and grain boundary conductivities had increased with the increased current density limit which was set prior to flash. The conductivity increases post-flash were ionic, not electronic, although electronic conductivity probably occurred, in addition to ionic conductivity, during flash. The conductivity increases were not attributable to sample densification or microstructural changes. The higher ionic conductivities are attributed to a change in YSZ defect structure that led to an increased concentration of mobile charge carriers; possible explanations for this are discussed.     

Thermophysical behavior of thermal sprayed yttria stabilized zirconia based composite coatings

The effective thermal conductivity of a composite coating depends on intrinsic thermal conductivity of the constituent phases, its characteristics (size, shape) and volume fraction of porosities. The present study concerns studying the effect of CoNiCrAlY and Al₂O₃ content on the coefficient of thermal expansion and thermal conductivity of the YSZ (YSZ-CoNiCrAlY and YSZ-Al₂O₃) based composite coatings developed by thermal spray deposition technique. The coefficient of thermal expansion and thermal conductivity of the composite coatings were measured by push rod dilatometer and laser flash techniques, respectively, from room temperature to 1000 °C. Variation in density, porosity, coefficient of thermal expansion, and thermal conductivity was observed in the composite coatings with the addition of different volume fraction of CoNiCrAlY and Al₂O₃ powders in YSZ-CoNiCrAlY and YSZ-Al₂O₃ composites, respectively. Comparison between the theoretical and experimental thermal conductivities showed a mismatch varying from 4% to 58% for YSZ-CoNiCrAlY composite coatings and from 58% to 80% for YSZ-Al₂O₃ composite coatings. Model based analyses were used to understand the mechanism of thermal conductivity reduction in the composite coatings. It was concluded that the morphology of porosities varied with composition.