超细镧-钴混合氧化物的制备与表征

以La2O3和Co(NO3)2.6H2O为主要原料,用"超临界流体干燥"技术结合"溶胶-凝胶"法制备超细镧-钴混合氧化物。采用TG-DTA、XRD、FT-IR、TEM等手段进行表征;考察了超临界流体干燥技术对混合氧化物晶态和形貌的影响;并通过"2NO+2CO=N2+2CO2"的反应测试混合氧化物的催化活性。结果显示,260℃时,经超临界流体干燥得到的镧-钴混合氧化物为疏松、絮状且有较好分散性的棕色粉末,由大量直径小于10nm的球形小颗粒组成;850℃热处理后,镧-钴混合氧化物主要由晶态的LaCoO3、La2O3和非晶态的Co2O3组成;球形颗粒出现一定程度的团聚,粒径介于15～35nm;稀土镧影响了镧-钴混合氧化物中钴氧化物的晶化。     

Nitrous Oxide Reduction with Ammonia and Methane Over Mesoporous Silica Materials Modified with Transition Metal Oxides

Transition metal oxides (Cu, Cr and Fe) were deposited on various mesoporous silicas (MCM-48, SBA-15, MCF and x-MSU) by an impregnation method. Electron microprobe analysis, BET, UV-VIS-DRS and temperature programmed desorption of NH₃ were used for the characterization of the samples. The modified mesoporous silicas were tested as catalysts of the N₂O decomposition and the N₂O reduction using ammonia and methane. The Cu-containing samples presented the highest catalytic activity in the N₂O decomposition, while the Cr- and Fe-modified materials were more active in the reduction of nitrous oxide with NH₃ and CH₄. The type of the silica support strongly influenced the catalytic performance of the studied materials.     

晶态介孔金属氧化物的合成研究进展

晶态介孔金属氧化物与相应的无定形材料相比具有更加优异的催化、光学、电学、磁学和力学等性能,具有较宽的应用范围,是近年来介孔材料合成的热点。本文主要对晶态介孔金属氧化物的制备方法,包括非晶晶化法、蒸发诱导自组装法和硬模板法进行了介绍,并对这些方法的优缺点进行了比较。     

纳米复合金属氧化物/聚酰胺6复合纤维的制备及性能

用共沉淀法制备了锌铝、锌镁铝及镁铝层状双氢氧化物(LDHs),将LDHs经过500℃煅烧后,得到相应的纳米复合金属氧化物(MMO)。MMO经偶联剂表面改性后,与聚酰胺6(PA6)切片共混造粒、熔融纺丝制备MMO/PA6复合纤维,并织造了MMO/PA6织物。用差示扫描量热仪(DSC)、扫描电子显微镜(SEM)以及红外成像仪等研究了MMO/PA6复合纤维的热性能、横截面形貌及MMO/PA6织物的红外辐射性能。结果表明:MMO/PA6复合纤维的可纺性好;加入MMO后,PA6复合纤维的强度下降约10%,但对PA6纤维的熔融温度没有影响;MMO的加入显著提高了PA6纤维的红外辐射性能,60℃保温的MMO/PA6织物,当MMO的质量分数为2.0%时,其温度高于空白PA6织物约2.0℃,具有优异的远红外辐射性能。     

Defect Equilibria in Transition Metal Oxides

This paper assesses the importance of vacancy aggregates in transition metal oxides. It presents the predictions of quantitative atomistic calculations and discusses them in relation to observed structural, diffusion, thermodynamic, and other data. The results indicate that vacancy complexes constitute the major defect species at high nonstoichiometry. The commonly discussed vacancy-hole complexes appear to be unimportant except, perhaps, over a very limited composition range.     

Oxygen in Catalysis on Transition Metal Oxides

Reactions of catalytic oxidation over oxide catalysts have been extensively studied in recent years following expansion of their applications in petrochemistry as well as their wide theoretical interest. Studies in this field have also contributed greatly to our understanding of the general mechanisms of catalyst action.     

介孔半导体化氧化物和硫化物的研究进展

非硅组成的介孔金属氧化物和硫化物半导体材料在光、电、催化和传感等诸多领域展示了独特的应用前景.介绍了最近几年来国内外有关半导体介孔材料合成和应用的研究动向及最新研究成果,内容包括半导体金属氧化物和硫化物等.     

铁氧化物的合成及其表征

合成了两种铁氧化物--针铁矿、赤铁矿,用红外光谱、X-晶体衍射及BET等手段对铁氧化物进行了表征,并研究了铁氧化物吸附苄嘧磺隆的特性.研究结果表明,针铁矿和赤铁矿是纯度较高的氧化物,针铁矿吸附苄嘧磺隆的量大于赤铁矿.     

Acid–Base Reactions of Transition Metal Oxides in the Solid State

Subsolidus compatibility data exist for a number of ternary oxide systems containing a transition metal oxide. Ternary diagrams, suitable for the present purpose, are limited mainly to those that include FeO, Fe₂O₃, ZnO, or Cr₂O₃, and these are examined in the context of Lewis acid–base interaction by considering the electron densities borne by the oxygen atoms or ions. These electron densities can be expressed on the optical basicity scale, and a significant acid–base difference exists between the reactants when they differ markedly in optical basicity. For many reactions the optical basicity difference between the products is much less, suggesting that acid–base neutralization is a major driving force. This principle has been found previously for nontransition metal oxide ternary systems. However, there are notable exceptions, especially in reactions where FeO or ZnO is the end product. This exceptional behavior is examined.     

TiO2-ZrO2复合氧化物的制备与表征

采用共沉淀法制备了TiO2-ZrO2复合氧化物和单一的TiO2、ZrO2粉体,不同温度下煅烧后得到样品.用N2吸附、X-射线衍射仪、热重-差示扫描量热法对样品进行了表征.考察了单一组分与复合氧化物结构性能的差别以及煅烧温度对复合氧化物性能的影响.结果表明:550 ℃煅烧2 h后,单一TiO2、ZrO2分别是结晶良好的锐钛矿和单斜相(含少量四方相),而TiO2-ZrO2复合氧化物依然是无定型结构且具有较大的比表面积(190.15 m2/g).600 ℃煅烧后TiO2-ZrO2复合氧化物中出现了ZrTiO4晶型.随煅烧温度的升高,复合氧化物的比表面积出现了明显的下降(190.15～19.16 m2/g).DSC-TG曲线给出了TiO2、ZrO2以及TiO2-ZrO2的相转变温度,分别为440.2 ℃、445.7 ℃、713.5 ℃.     

Pathways for Carboxylic Acid Decomposition on Transition Metal Oxides

The concept of structure sensitivity is well established for reactions catalyzed by metals as it has been generally demonstrated by the use of supported metal catalysts exhibiting different particle size [l-71. The con-cept of structure sensitivity in catalysis by metal oxides is considerably less well developed than in catalysis by metals, in spite of the growing number of examples of such reactions. Characterization of oxide catalyst is generally more problematical than that of metal; it is difficult, for example, to titrate the active surface areas of supported oxides by chemisorption techniques. Carboxylic acid decomposition could be used as a probe to establish struc-tural dependence and selectivity on metal oxides. For example, in the case of formic acid decomposition, bimolecular decomposition of two adsorbed formates occurs on a surface with Ti4+ cation of fourfold oxygen coordi-znation while unimolecular decomposition occurs in the case of formates adsorbed on Ti4+ fivefold coordinated cations [8]. Similarly, acetic acid adsorbed on Ti02 with Ti0,(011) leads to the production of ketene by unimolecular dehydration whereas on the Ti02(l 14) faceted surface, bi-molecular reaction of surface acetate takes place to form acetone [9, 101. Thus understanding the pathway of decomposition of carboxylic acid is likely not only to throw light on the new catalyst search for ketene formation but also to establish the use of this molecular decomposition model as a probe for the study of the structural property of metal oxide catalysts.     

Pathways for Carboxylic Acid Decomposition on Transition Metal Oxides

The concept of structure sensitivity is well established for reactions catalyzed by metals as it has been generally demonstrated by the use of supported metal catalysts exhibiting different particle size [l-71. The con-cept of structure sensitivity in catalysis by metal oxides is considerably less well developed than in catalysis by metals, in spite of the growing number of examples of such reactions. Characterization of oxide catalyst is generally more problematical than that of metal; it is difficult, for example, to titrate the active surface areas of supported oxides by chemisorption techniques. Carboxylic acid decomposition could be used as a probe to establish struc-tural dependence and selectivity on metal oxides. For example, in the case of formic acid decomposition, bimolecular decomposition of two adsorbed formates occurs on a surface with Ti4+ cation of fourfold oxygen coordi-znation while unimolecular decomposition occurs in the case of formates adsorbed on Ti4+ fivefold coordinated cations [8]. Similarly, acetic acid adsorbed on Ti02 with Ti0,(011) leads to the production of ketene by unimolecular dehydration whereas on the Ti02(l 14) faceted surface, bi-molecular reaction of surface acetate takes place to form acetone [9, 101. Thus understanding the pathway of decomposition of carboxylic acid is likely not only to throw light on the new catalyst search for ketene formation but also to establish the use of this molecular decomposition model as a probe for the study of the structural property of metal oxide catalysts.     

多孔金属氧化物半导体薄膜的制备及光催化性能

以垂直蒸发沉积法制备的聚苯乙烯(PS)胶态晶体为模板,采用溶胶–凝胶法制备多孔ZnO和TiO_2薄膜,分别考察其对罗丹明B(Rh B)溶液的光催化降解效果。使用扫描电子显微镜观察PS胶态晶体以及多孔ZnO和TiO_2薄膜的形貌,以紫外–可见吸收光谱仪表征光催化降解效果。结果表明:PS微球分散液浓度为0.025%时,胶态晶体为单层和多层结构,随着浓度增加至0.100%,胶态晶体呈现完善的多层结构;PS微球分散液浓度为0.100%、ZnO溶胶浓度为0.3 mol/L制备的多孔ZnO薄膜对Rh B降解效果较好;PS微球分散液浓度为0.025%、TiO_2溶胶浓度为0.1 mol/L获得的多孔TiO_2薄膜对Rh B降解效果较好。多孔ZnO薄膜对Rh B的降解效果优于多孔TiO_2薄膜。     

钙钛矿型金属氧化物粉体的制备与光催化性能

综述了ABO3钙钛矿型金属氧化物光催化性能的研究进展。主要介绍了化学共沉淀法、超声波共沉淀法、溶胶-凝胶法、水热法、固相研磨法、凝胶浇注法、甘氨酸燃烧法等制备方法及其优缺点。讨论了光催化降解有机污染物、光催化还原CO2制备有机物和光催化分解H2O的反应机理。分析了电荷转移能、B-O的结合能、B原子电负性、A、B原子价态、电子构型、掺杂等因素对催化剂光催化效率的影响。     

明胶复合-铁氧化物纳米微粒的制备和表征

用凝胶 -微乳液化学剪裁技术制备了明胶复合的氧化铁纳米量级超细微粒。XRD TEM、和IR测试表明 :微粒为明胶包裹型球形超细微粒 ;微料的粒径为 2 0～ 40nm。     

乙烷桥联型介孔二氧化硅纳米球的制备与表征

本文采用表面活性剂导向溶胶-凝胶法,在碱性条件下,通过两种硅源成功制备了乙烷桥联型介孔纳米粒子(MSN)。在合成MSN的基础上,以γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(MPS)为改性剂对MSN表面进行了修饰。结果表明:合成的MSN呈规整的纳米级球体,界面高度交联,具有直径分布均匀(260nm)的无机-有机杂化骨架,其比表面积、介孔尺寸和孔容分别为540m~2/g、3.7nm和0.52cm~3/g。     

透明介孔氧化锆涂层的制备与表征

以ZrCl4为锆源,以三嵌段聚合物P123（EO20PO70EO20,EO为乙氧基,PO为丙氧基）为模板剂,采用原位水解法制备了透明介孔氧化锆涂层。透射电镜表征结果显示,ZrO2涂层中的介孔孔道呈阵列状排布,孔道垂直于载体。这种特殊的结构是导致涂层透明的主要原因,其形成受溶剂挥发速率、模板剂浓度及空气湿度的影响。从形成...     

Preparation and Thermal Analysis of Mixed Magnesium-Manganese-Iron Oxalates and Hydrated Oxides

A square-loop ferrite composition, Mg_0.675Mn_0.535–Fe_1.8000O₄, having high purity and fine particle size was prepared by pyrolysis of coprecipitated oxalates or hydrated oxides. The control of pH had a marked effect on the stoichiometry of the coprecipitated divalent oxalates, and ap optimum pH of 2.5 to 3.0 was observed. Thermal analysis was performed on the coprecipitated materials and on individual components; it revealed that the coprecipitated oxalates formed a solid solution whereas the hydrated oxides did not.     

尖晶石型复合金属氧化物制备与光催化性能

综述了近年来尖晶石型金属氧化物超微粉体光催化性能的一些最新研究进展.主要介绍了能够得到较小纳米粒子的合成方法,如:微乳-沉淀法、研磨固相反应法和微波辐射技术、水热法、硬脂酸法、共沉淀法、铝单醇盐溶胶凝胶法、聚合物配位法等制备方法.重点讨论了其在降解甲基蓝、甲基橙染料,苯、甲醛有机污染物及分解水等方面的光催化性能.从不同角度对尖晶石型氧化物光催化机理进行解释,并介绍了目前被广泛认可的几种光催化机理.