不同形貌纳米CeO2的制备最新研究进展

CeO2是一种用途极广的稀土材料,可广泛应用于多种研究领域。纳米CeO2具有特殊的性质及应用。因此,纳米CeO2的制备、功能特性和应用研究成为研究的热点之一。综述了不同形貌纳米CeO2制备方法的最新研究进展,着重介绍了CeO2纳米颗粒、纳米棒、纳米管、纳米纤维以及一些特殊形貌纳米CeO2的制备方法和应用前景,并对今后纳米CeO2的研究方向进行了展望。     

超声雾化反应法制备CeO2纳米粉体

以硝酸铈和碳酸氢铵为原料,采用超声雾化反应法制备了纳米CeO2粉. 用红外光谱(IR)、 X射线衍射分析(XRD)和透射电子显微镜(TEM)技术,对制得的纳米CeO2纳米粒子的物相结构、形貌特征、成分等进行了表征. 结果表明,双液超声雾化法能制备出颗粒分散性好,粒度分布均匀的纳米CeO2粒子,所得CeO2粒子为萤石型结构,粒径约为3～5 nm左右. 初步探讨了用超声雾化反应法制备纳米粉的机制,认为CeO2纳米粒子的成核和长大受到液滴大小的限制,是一个液相的微区反应过程,正是液滴的微小体积保证了更小纳米粒子的形成.     

纳米CeO2/聚苯乙烯杂化材料的制备及表征

用反相胶束微乳液法制备了纳米CeO2/聚苯乙烯杂化材料 .XRD分析表明,纳米CeO2/聚苯乙烯杂化材料中,CeO2是无定形粒子.XPS分析表明,杂化材料并非简单的物理混合,CeO2纳米粒子与有机物之间存在着一定强度的化学键.FTIR分析表明,CeO2粒子的吸收存在蓝移现象.     

均匀沉淀和碳吸附耦合法制备CeO2纳米粒子及表征

均匀沉淀和碳吸附耦合法制备CeO2纳米粒子及表征;均匀沉淀;碳吸附;纳米;CeO2     

CO在纳米CeO2负载的Pd-Cu催化剂上的低温催化氧化

用溶胶一凝胶法制得了平均晶粒度为15nm的CeO2粉体,并用浸渍法制备了Pd-Cu/纳米CeO2催化剂;通过XRD、SEM和HRTEM等表征手段研究了纳米CeO：粉体和Pd-Cu/纳米CeO2催化剂的性能;考察了催化剂对CO的低温催化氧化活性。结果表明：纳米CeO2粉体负载的Pd-Cu催化剂对CO的低温催化氧化活性明显优于一般CeO2颗粒负载的Pd-Cu催化剂,其CO完全氧化的最低温度比Pd-Cu,热分解法CeO2催化剂低约70℃,比Pd-Cu,工业CeO：催化剂低约130℃。因此,纳米CeO2粉体作载体可极大地提高Pd-Cu催化剂的CO氧化性能。     

CO在纳米CeO2负载的Pd-Cu催化剂上的低温催化氧化

用溶胶-凝胶法制得了平均晶粒度为15nm的CeO2粉体,并用浸渍法制备了Pd-Cu/纳米CeO2催化剂;通过XRD、SEM和HRTEM等表征手段研究了纳米CeO2粉体和Pd-Cu/纳米CeO2催化剂的性能;考察了催化剂对CO的低温催化氧化活性.结果表明纳米CeO2粉体负载的Pd-Cu催化剂对CO的低温催化氧化活性明显优于一般CeO2颗粒负载的Pd-Cu催化剂,其CO完全氧化的最低温度比Pd-Cu/热分解法CeO2催化剂低约70℃,比Pd-Cu/工业CeO2催化剂低约130℃.因此,纳米CeO2粉体作载体可极大地提高Pd-Cu催化剂的CO氧化性能.     

CeO2—TiO2复合纳米晶多孔膜的光电化学行为

用溶胶凝胶法制备了CeO2－TiO2复合纳米晶多孔膜电极，并用XRD及原子力显微镜（AFM）进行表征．通过光电化学研究，发现了CeO2-TiO2复合纳米晶电极光响应的p型和n型转换现象．结果表明，随着CeO2含量的不同及外电场的变化，CeO2－TiO2复合纳米晶电极可以呈现不同的光响应．     

掺杂纳米CeO2的纳米玻璃的微观结构研究

采用溶胶-凝胶技术制备了掺杂纳米CeO2的纳米玻璃. XRD分析表明, 掺杂CeO2纳米玻璃为无定形. SEM分析表明, 掺杂纳米CeO2的纳米玻璃中掺杂的纳米粒子分布均匀, 无团聚现象; 玻璃各成分之间混合均匀; 采用不同溶剂所制备的纳米玻璃的致密程度不同. 热分析表明, 掺杂纳米CeO2的纳米玻璃在68 ℃附近有1个吸热峰, 故在该温度时, 应长期保温, 使样品中溶剂充分挥发, 当温度达到500 ℃附近时, 样品几乎不再失重, 仅发生致密化.     

V^5＋离子掺杂纳米氧化铈的合成与表征

以硝酸铈、柠檬酸和偏钒酸铵为原料,采用溶胶-凝胶(sol-Gel)法制备了V5+离子掺杂纳米CeO2粉体.利用X射线粉晶衍射(XRD)和 扫描电镜(SEM)等方法研究了合成反应条件(焙烧温度、V5+掺入量等)对合成物的微观结构、物相组成以及性能的影响.XRD分析表明所合成的CeO2纳米晶粒具有空间群符号为Fm3m的立方晶体结构.随焙烧温度的升高,合成的CeO2晶粒结晶度增高.对甲基蓝的光催化降解试验表明,纳米CeO2对甲基蓝具有较好的光催化降解效果,焙烧温度对纳米CeO2的光催化活性有较大影响,适量V5+的掺入有利于提高纳米 CeO2的光催化降解效果,掺1%V5+离子的CeO2光催化降解甲基蓝6 h,其降解率可达89%以上.     

0,1,3维CeO2的可控制备及CuO/CeO2催化剂上CO氧化反应

以水、乙醇和乙二醇为溶剂,采用溶剂热法可控制备了0,1,3维CeO2.结果表明,0维CeO2由0.2～0.5 μm纳米粒子组成;1维CeO2是直径为25～30 μm,长约500 μm的六方棒;松针型的3维CeO2是由以纳米粒子为单元构成的直径为1～5 μm,长约50 μm的光滑棒组成,其比表面积高达234 m2/g.将...     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Effect of the Method of Modification of Zeolite X on Selectivity of Catalytic Methylation of Toluene

Theoretical and Experimental Chemistry - The effect of the method of modification of catalysts based on zeolite X by cesium and magnesium cations (ion exchange and impregnation) on the selectivity...     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Synthesis of tetrabenzoporphins of the basis of isoindoline

Chemistry of Heterocyclic Compounds -