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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.

本工作旨在发展新形态稀土氧化物的制备方法，并阐明其性质随形态变化的规律。重点研究了表面改性氧化铈-氧化锆复合氧化物的氧化还原性能和表面包覆氧化铈微粒的光学性能。这些材料分别用作汽车尾气三效催化剂和紫外线防晒剂中的助剂。用氯气、氯化铵和碱金属氯化物对铈锆固溶体进行了表面改性。氧化铈-氧化锆固溶体表面的挥发性物质通过化学气相传输被剥离。这一过程被称为“化学锉削”。“化学填充过程后样品的还原温度低于新鲜样品。此外，即使在高温下老化后，氧化还原性能也得以保持，这表明与通过常规程序制备的固溶体相比，其耐久性。通过拉曼散射、X射线光电子能谱和高分辨透射电子显微镜的测量，确定了氧化铈和乱层氮化硼（t-BN）的结构、组成和形态的变化是导致这些性能的原因。通过高分辨透射电子显微镜估计的t-BN层的厚度为约100 μ m。10纳米。BN涂层在降低氧化铈的催化活性方面非常有效，并且所得材料显示出良好的光散射和UV光吸收。有机薄膜中包含的BN涂覆的二氧化铈颗粒比传统的微粉化二氧化钛和氧化锌颗粒（化妆品中常用的两种无机材料以及许多其他应用中作为紫外线阻挡材料）显示出更高的透明度并更有效地阻挡紫外线。