SYNTHESIS OF RARE EARTH OXIDES HAVING NEW FORMS

新形态稀土氧化物的合成

基本信息

批准号：
11450335
负责人：
ADACHI Gin-ya
金额：
$ 8.77万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450335/
关键词：
Rare earths Automotive exhaust catalysts Oxygen storage capacity Cerium oxide Sunscreen Boron nitride Surface coating Cosmetics 希土類酸化物自動車排ガス浄化触媒ジルコニア

项目摘要

In this work we aimed development of preparation methods of rare earths oxides having new forms, and clarified the properties with the change of the forms. Especially we focused on the redox properties of the surface-modified ceria-zirconia mixed oxides and optical properties of the surface coated cerium oxide fine particles. These materials are applied as promoters in the automotive exhaust three-way catalysts and sunscreens against UV light, respectively.Surface modification of the ceria-zirconia solid solutions has been carried out using chlorine gas, ammonium chloride, or alkali-metal chlorides. The formed volatile species were stripped off the surface of the ceria-zirconia solid solutions by the chemical vapor transportation. This process was named as "chemical filing." Reduction temperature of the samples after the chemical filing process were lower than those of the fresh samples. In addition, the redox properties were maintained even after the aging at high temperatures, indicating its durability compared to the solid solution prepared by the conventional procedures. Using Raman scattering, X-ray photoelectron spectroscopy, and high-resolution TEM measurements, it was identified that the change of structures, compositions, and forms is responsible for these properties.Also, a new UV-blocking material consisting of ceria and turbostratic boron nitride (t-BN) has been synthesized. The thickness of the t-BN layer estimated by high resolution transmission electron microscopy was ca. 10 nm. The BN-coating was very effective in reducing the catalytic activity of the ceria and the resulting material showed good light scattering and absorption of UV light. BN-coated ceria particles included in an organic thin film showed higher transparency and blocked UV light more effectively than conventional micronized titanium dioxide and zinc oxide particles, two inorganic materials in common use in cosmetics and in many other applications as UV blocking materials.

在这项工作中，我们的目标是开发具有新形态的稀土氧化物的制备方法，并随着形态的变化阐明其性质。我们特别关注表面改性的氧化铈-氧化锆混合氧化物的氧化还原性能和表面涂覆的氧化铈细颗粒的光学性能。这些材料分别用作汽车尾气三效催化剂和防紫外线防晒霜的促进剂。使用氯气、氯化铵或碱金属氯化物对氧化铈-氧化锆固溶体进行了表面改性。通过化学气相传输将形成的挥发性物质从二氧化铈-氧化锆固溶体的表面剥离。这个过程被命名为“化学归档”。化学填充处理后样品的还原温度低于新鲜样品的还原温度。此外，即使在高温老化后，其氧化还原性能仍保持不变，这表明其与传统程序制备的固溶体相比具有耐久性。利用拉曼散射、X 射线光电子能谱和高分辨率 TEM 测量，发现结构、成分和形式的变化是造成这些特性的原因。此外，一种由二氧化铈和乱层硼组成的新型紫外线阻挡材料已合成氮化物（t-BN）。通过高分辨率透射电子显微镜估计t-BN层的厚度约为。 10纳米。 BN涂层对于降低二氧化铈的催化活性非常有效，并且所得材料表现出良好的光散射和紫外光吸收。与传统的微粉化二氧化钛和氧化锌颗粒（化妆品和许多其他应用中常用的紫外线阻挡材料）这两种无机材料相比，有机薄膜中包含的氮化硼涂覆的二氧化铈颗粒显示出更高的透明度，并且更有效地阻挡紫外线。