溶胶-凝胶法合成高纯锆英石粉

研究了添加锆英石晶种在溶胶－凝胶法合成高纯锆英石粉过程中的作用，在此基础上探讨了添加氧化钇对合成过程的影响。研究表明，添加适量的氧化钇可显著降低锆英石的合成温度，并且不会引入其他多余相。     

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。     

氧化钇掺杂对Al2O3块状气凝胶结构与性能的影响

以AlCl3·6H2O为原料,YCl3·6H2O为添加剂,采用溶胶-凝胶法和超临界干燥工艺制备得到氧化钇掺杂氧化铝块状气凝胶.其中掺杂含量控制在2.5wt%～30wt%Y2O3范围内.利用扫描电镜(SEM)、X射线衍射(XRD)、BET比表面积测定等测试手段对样品进行表征.结果表明:氧化钇的掺杂可以使氧化铝气凝胶在高温下维持高比表面积以及提高其在高温的热稳定性.经1000 ℃热处理后5.0wt%Y2O3-Al2O3气凝胶仍然处于无定形态,未发生相转变,比表面积仍达380～400 m2/g,比纯Al2O3气凝胶(174 m2/g)高出许多.     

纳米氧化钇的制备及形貌调控研究进展

由于不同形貌结构的纳米氧化钇对其性能有重要影响,因此,探究不同制备条件下如何调控纳米氧化钇形貌结构显得尤为重要。阐述近年来纳米氧化钇的主要制备方法,包括水热-溶剂热法、共沉淀法、电沉积法等。着重从形成原理、形成条件控制及形成机理等方面分析氧化钇制备过程与其尺寸控制关系,并在此基础上对纳米氧化钇形貌调控进行阐述。     

氧化钇稳定二氧化锆的制备及表征

以氯氧化锆为前躯体,尿素为沉淀剂,采用溶胶-凝胶法结合超临界CO2干燥进行了氧化钇稳定二氧化锫的制备。并通过XRD、TG—DTA、BET、FT—IR等方式对所制备的样品进行表征。结果显示,经过不同温度煅烧的样品都呈现出四方相氧化锆特性。400℃煅烧样品的比表面积高达120．25m^2／g。     

超声波-淬冷-均匀沉淀法制备超细氧化钇

以硝酸钇和尿素为原料通过超声波-淬冷-均匀沉淀法制备超细氧化钇，对氧化钇的前驱物——Y（OH）CO，的合成及煅烧工艺进行了详细研究。讨论了制备、干燥和煅烧前驱物时的团聚对氧化钇粒径的影响，通过超声波-淬冷技术的联用抑制了制备氧化钇前驱物时的团聚，用添加溴化十六烷基三甲基铵（CTMAB）和硫酸铵的方法成功地解决了干燥和煅烧前驱物时的硬团聚问题。用XRD，SEM和DTA—TG等手段对产物进行表征。结果表明，在一定的条件下，可获得粒径约7～15nm的超细氧化钇，XRD分析表明，合成的氧化钇为体心立方型。     

氧化钇基高熵固溶体陶瓷的SPS烧结与性能研究

研究了以蔗糖为燃料剂,通过溶胶-凝胶燃烧反应制备以氧化钇为主要成分的固溶体氧化物粉末,并且以SPS烧结技术制备氧化钇基高熵陶瓷。研究了球磨对粉末以及SPS烧结工艺对陶瓷性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)和显微硬度分析对陶瓷组织与性能进行了表征。结果表明:粉体制备过程中球磨有助于消除杂相,提高粉体分散度和均匀性;SPS烧结高熵陶瓷硬度最高达到8.683GPa,在红外波段透过率也接近40%。     

氧化钇对氧化镁陶瓷烧结和抗热震性能的影响

为提高氧化镁陶瓷抗热震性和烧结性能,以高纯纳米氧化镁为主要原料,高纯纳米氧化钇粉为添加剂,聚乙烯醇为结合剂,制备了氧化镁陶瓷试样,研究了氧化钇添加量(外加,质量分数分别为0、1%、2%、3%和4%)和煅烧温度(1 350、1 450和1 550℃)对氧化镁陶瓷性能的影响。结果表明:氧化钇与方镁石形成有限置换型固溶体,提高了烧结试样致密度;氧化钇抑制了烧结试样中方镁石晶粒生长;氧化钇通过第二相增韧和微裂纹增韧提高了氧化镁陶瓷的抗热震性。     

硬脂酸修饰纳米氧化钇的制备及其亲油特性

引 言 氧化钇独特的4f电子层结构[1-2],使其具有了诸多的优良性能.在催化、陶瓷、光学玻璃、荧光、涂料等领域得到了广泛的应用[3-4].作为润滑油添加剂,其抗磨减摩效果明显,抗磨润滑性能卓越,潜在发展空间较大[5].纳米化后的氧化钇具有更多的新性能,然而,纳米氧化钇颗粒的粒径小、比表面积大、表面活性高、容易团聚使得纳米氧化钇的应用受到一定的局限[6].     

草酸铵沉淀法制备纳米氧化钇研究

以氧化钇、浓硝酸为原料,草酸铵为沉淀剂,十六烷基三甲基溴化铵为分散剂,采用草酸铵沉淀法制备纳米氧化钇前驱体,将前驱体在空气中焙烧制备纳米氧化钇粉体。用差热-热重分析确定了前驱体分解温度,用 X射线衍射和扫描电镜对样品进行表征,用激光粒度仪测量不同反应物物质的量比所得产品的粒度分布,得到制备纳米氧化钇最佳条件。实验表明,在最佳条件下可以制得平均粒径为40 nm的氧化钇粉体,其形貌为椭球形。     

Effect of yttria on crystallization and microstructure of an alumina–YAG fiber prepared by aqueous sol–gel process

Continuous fiber development is needed for high performance and high temperature composites. Various methods have been used to make ceramic fibers. In this research, composite fibers (yttrium aluminum garnet (YAG)/Al₂O₃) were prepared by a sol–gel method using aqueous solution. They were synthesized from aluminum salt, aluminum metal, yttrium oxide and water used as solvent. Transparent gel fibers were obtained by immersing a thin wire into the viscous sol, then pulling it out by hand. The obtained fibers contained very fine grains with diameter ranging from 10 to 80 μm after heat treatment. When yttria content was increased, the crystallization of YAG shifted to a lower temperature, whereas the transformation temperature to α-Al₂O₃ shifted to a higher temperature. Nevertheless, the fibers with different amounts of yttria contained alumina and YAG after heat treatment at 1400 °C. The composite fibers had vermicular structure and were denser than alumina fibers. The yttria percent concerning the limits of this study (≤10 wt%) effected on fiber diameter. As the yttria content was increased, the fiber diameter increased, whereas grain size and densification of the composite fibers decreased.     

镧、钇共掺杂纳米ZnO的制备及处理染料废水研究

以醋酸锌、硝酸镧和硝酸钇为原料,丙烯酰胺为单体,N,N’-亚甲基双丙烯酰胺为网络剂,过硫酸铵为引发剂,采用高分子网络凝胶法制备得到镧、钇共掺杂的Zn O纳米粉体。用紫外灯作为光源,以15 mg/L甲基橙溶液为光催化反应模型污染物,研究了不同掺杂量的纳米Zn O的光催化性能,并用XRD、TEM、XPS、BET等对其进行表征。试验结果表明:当镧、钇的掺杂比分别为0.12%、0.23%时,光催化降解效果最好,反应1 h对甲基橙溶液的色度和COD去除率分别达到95.7%和87.8%。     

Yttrium Silicate Powders Produced by the Sol–Gel Method, Structural and Thermal Characterization

Yttrium silicate (Y₂SiO₅) powders of high purity have been synthesized using the sol–gel method. Alkoxide precursors were used with commercial tetraethyl orthosilicate as the silica source and yttrium propoxide synthesized from YCl₃. Powders calcined from the xerogel showed submicrometer crystal sizes. These powders were sintered at temperatures <1300°C and are suitable for coating applications such as a thermal barrier system for SiC/SiC composites.     

The effects of chelating agent type on the morphology and phase evolutions of alumina nanostructures

In this work, pure aluminum oxide nanoparticle was obtained by the chemical method at low temperature. In this approach, alpha-alumina nanoparticle was prepared by aluminum nitrate nonahydrate and triethanolamine (TEA) as the Al³⁺ and both gel agent, respectively. FESEM images show that TEA has better efficiency in controlling particle size and agglomeration as compared with citric acid as a chelating agent. Then, yttrium aluminum garnet (YAG) powder was prepared by yttrium nitrate, urea, and tetraethyl orthosilicate (TEOS) as a Y³⁺, precipitation agent, and flux agent, respectively. Furthermore, results show that by using TEOS, the YAG particles were obtained, while in the absence of this agent, the impurely YAG phase was achieved at the simillar annealing temperature.     

Local atomic disorder and temperature dependence of saturation magnetization in yttrium iron garnet

In the present work experimental data for saturation magnetization at low temperatures, of yttrium iron garnet nanoparticles are different from that expected by the T^3/2 Bloch's Law. This result is mainly conditioned by the local atomic disorder induced during the nanoparticles preparation by using the sol gel method. To correctly describe the experimental curves, a fitting using Cojocaru's theory was performed because the model uses geometric and other conditions in agreement with our experimental results. The magnetic ions localized at the nanoparticles surface, outside the crystalline periodicity, are the responsible by the saturation magnetization behavior presented here.     

Prospects for creating new optically transparent materials with yttrium oxide and yttrium aluminum garnet (review)

The properties of optically transparent ceramic materials made of yttrium oxide and yttrium — aluminum garnet were analyzed. The promise of preparing a transparent ceramic that combines both of these compounds was demonstrated. Methods of synthesizing yttrium oxide and yttrium — aluminum garnet were examined. Selection of the method of synthesis was substantiated. The possibility of creating such materials without modifying additives was confirmed.     

Atomic Resolution Transmission Electron Microscopy of the Intergranular Structure of a Y2O3-Containing Silicon Nitride Ceramic

High-resolution transmission electron microscopy (HRTEM) employing focus-variation phase-reconstruction methods is used to image the atomic structure of grain boundaries in a silicon nitride ceramic at subangstrom resolution. Complementary energy-dispersive X-ray emission spectroscopy experiments revealed the presence of yttrium ions segregated to the 0.5–0.7-nm thin amorphous boundary layers that separate individual grains. Our objective here is probing if yttrium ions attach to the prismatic planes of the Si₃N₄ at the interface toward the amorphous layer, using Scherzer and phase-reconstruction imaging, as well as image simulation. Crystal structure images of grain boundaries in thin sample (<100 Å) areas do not reveal the attachment of yttrium at these positions, although lattice images from thicker areas do suggest the presence of yttrium at these sites. It is concluded that most of the yttrium atoms are located in the amorphous phase and only a few atoms may attach to the terminating prism plane. In this case, the line concentrations of such yttrium in the latter location are estimated to be at most one yttrium atom every 17 Å.     

Gold Nanoparticles on Yttrium Modified Titania: Support Properties and Catalytic Activity

A series of titanium oxide catalysts modified with yttrium has been prepared by sol–gel method and their structural properties have been studied. The incorporation of yttrium in the titania lattice favors the formation of oxygen vacancies while at low Y loadings the anatase structure is preserved. The catalytic activity of these solids for CO oxidation is found to be significantly dependent on their physical properties. In particular the amount of dopant controls the number of surface oxygen vacancies created as well as the gold particle size, which directly affects the catalytic activity. Also, a linear relationship between the catalytic activity and the band gap values, which depend on the Y loading, is observed. Density functional theory based calculations show that Y atoms are incorporated at the TiO₂ surface at substitutional positions only, while the preferred oxygen vacancies arise by removing the bridge surface oxygen atoms. These O-vacancies are the preferential adsorption sites for Au atoms and nanoparticles, acting as nucleation centers that favor the dispersion of the catalyst active phase over the support surface. In agreement with experiment, Y doping is found to decrease the band gap of the support due to a destabilization of the valence band of the oxide.     

三氯化钇-异丙醇加合物合成异丙醇钇的研究

采用Y2 O3 为原料先制得无水YCl3 然后与异丙醇反应生成YCl3·3C3H7OH加合物 ,并采用自制异丙醇钠与之反应制备得到异丙醇钇 ,反应的最佳条件为 80℃回流 3～ 4小时 ,然后静置 12h以便NaCl的分离。在YCl3·6H2 O脱水制备YCl3 的过程中 ,采用醋酸酐脱水法 ,具有方法简单 ,污染小 ,且易于操作等特点     

Y2O3陶瓷粉末及Y对玻璃态Zr55Al15Ni10Cu20材料相析出的影响

在Zr55Al15Ni10Cu20(Zr55)材料中分别添加0.4 at%,1 at%的Y及1 at%,5 at%的Y2O3陶瓷粉末,再通过铜模吸铸得到棒状样品。通过透射电镜(TEM),X射线衍射(XRD),高能X射线和扫描电镜(SEM)观察Y2O3的添加对Zr55Al15Ni10Cu20材料析出相的影响,并进一步研究了随着Y及Y2O3的添加,试样组织形貌的演变过程。研究发现,通过少量Y2O3的添加对Zr55Al15Ni10Cu20试样的玻璃形成能力影响不大。而直接添加Y对Zr55析出相的影响却尤为明显,Y的氧化物更是导致了Zr3Al5相的析出。这对于提高材料的玻璃形成能力起到了一定的限制。透射电镜(TEM)实验直接给出了Y2O3相作为形核核心导致Zr3Al5相析出的证据。