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纳米晶ZrO2:Sm3+的制备与发光性质研究 总被引:11,自引:1,他引:11
用化学共沉淀法制备了Sm3 掺杂浓度不同、煅烧温度不同的纳米晶ZrO2:Sm3 系列发光粉体,所制备的粉体均具有Sm3 离子特征强室温荧光发射.通过XRD分析发现:经600℃煅烧2 h后制备的纳米晶ZrO2:Sm3 是四方相结构;经800℃煅烧2 h得到的样品,以四方相为主,有少量单斜相;经950℃煅烧2 h后得到的样品,以单斜相为主,四方相的比例较小.不同煅烧温度下样品发光性质研究表明:因经不同温度煅烧制备的样品所处晶体场环境不同,发光中心也不同,经800和950℃煅烧的样品中稀土离子占据两种不同的格位,其一为四方相格位,其二是单斜相格位;ZrO2基质与Sm3 之间有能量传递,单斜相结构更有利于能量传递.荧光强度与掺Sm3 浓度关系研究表明:荧光强度先随Sm3 浓度提高而增强,在浓度达0.7%(摩尔分数)时达到最大,然后又随之降低. 相似文献
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采用复合模板表面活性剂辅助水热法一步合成WO3/ZrO2体系多级孔固体酸催化剂,探讨了煅烧温度对所合成催化剂试样酸强度及酸量的影响,并考察了催化剂针对苯和十二烯的烷基化反应中的催化性能.结果表明,WO3/ZrO2体系催化剂具有较强的酸强度,并且与催化剂的比表面积和晶化程度有密切关系,比表面积的增大和四方相ZrO2的生成能有效地提高催化剂的酸强度.该催化剂具有优良的烷基化反应催化活性和选择性,其中450℃,5h煅烧的WO3/ZrO2催化剂样品酸性最强,其烷基化催化活性和选择性最优. 相似文献
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Y2O3和CeO2复合掺杂ZrO2纳米晶的制备与表征 总被引:2,自引:0,他引:2
以ZrOCl2.8H2O,Y2O3,Ce(NO3)3.5.5H2O为原料,NH3.H2O作沉淀剂,少量表面活性剂PE作分散剂,采用反向共沉淀-喷雾干燥法,结合物理、化学分散技术,成功地制备了Y2O3,CeO2复合掺杂ZrO2纳米粉末。通过DSC-TG,XRD,XPS,BET和SEM等方法对所制得粉末进行了表征。结果表明:以Ce0.1Y0.1Zr0.8O1.95化学计量比制备的多元氢氧化物胶体经过喷雾干燥处理后,在500℃基本完成水合氧化物的分解,577℃附近完成由非晶相向立方相的转变;经过580-1000℃煅烧后,CeO2和Y2O3已经完全固溶到ZrO2中,形成类质同相体,该粉末系列均属于立方相萤石结构;掺杂进入ZrO2晶格中的Ce呈+4价形式存在;比表面积由22.0 m^2.g^-1(580℃煅烧)减至4.97 m^2.g^-1(1000℃煅烧);SEM结果显示800℃煅烧的该粉末颗粒尺寸分布均匀,多呈类球状,且粒径在50-80 nm。 相似文献
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以油菜花粉为生物模板,通过温和易控的水浴-陈化法制备了纳/微米结构ZrO2中空微球.利用扫描电子显微镜(SEM)、红外光谱(FTIR)、X射线能谱(EDS)、X射线衍射(XRD)、比表面孔隙度分析、热分析等对所制备的产物和前驱体进行了表征,并对产物的吸附性能进行了初步的研究.结果表明,ZrO2中空微球的球壳由纳米粒子构筑并形成介孔结构.花粉模板前处理方式不同,其模板作用不同,可以获得两种不同球壳厚度、表面形貌和比表面积的ZrO2中空微球.其中"镂空"结构的ZrO2微球对铬黑T有良好的吸附性能.对ZrO2中空结构形成的机理进行了分析和讨论. 相似文献
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采用聚苯乙烯(PS)微球作为模板剂,经溶胶-凝胶及煅烧后处理的方法制备了三维有序大孔(3DOM)复合材料Ag/ZrO2-TiO2。通过FTIR、XRD、XPS、N2吸附-脱附和SEM-EDS等对其进行了表征。结果显示,经PS微球作用后的复合材料Ag/ZrO2-TiO2具有锐钛矿晶型结构,其Ag以单质形式存在。该复合材料的孔结构高度有序,属三维有序大孔,平均孔直径为120 nm,孔壁由紧密堆积的Ag/ZrO2-TiO2纳米晶粒组成,孔收缩率约为40%。该复合材料表现出较好的紫外光催化降解水杨酸和甲基橙等染料性能,其活性明显高于商用光催化剂(Degussa P-25)、Ag/ZrO2-TiO2和3DOM ZrO2-TiO2,在90 min内对甲基橙的降解率达80.1%。 相似文献
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硫酸化剂和制备方法对锆基固体酸催化剂的结构和性能的影响 总被引:3,自引:0,他引:3
采用沉淀法制备ZrO2氧化物,用氯磺酸和硫酸对其进行改性制备了Zr基固体酸催化剂,以XRD、BET和NH3-FTIR等手段考察了制备条件对催化剂晶相结构和表面性质的影响,研究了催化剂结构与其对棕榈油酯化反应的催化活性之间的关系.NH3-FTIR表明催化剂表面有B酸和L酸中心的生成.硫酸化剂的种类及其引入顺序都将影响催化剂的晶相结构和孔结构.酸的引入将阻止ZrO2·nH2O在焙烧时直接向单斜相ZrO2转变,氯磺酸将使ZrO2·nH2O转变为四方相ZrO2,而硫酸将导致四方相ZrO2和Zr(SO4)2·5H2O的生成.以氯磺酸改性的四方相和单斜相ZrO2基催化剂均具有很高的催化酯化活性,比硫酸改性的S-Z固体酸催化活性高.CS-ZrO2固体酸催化活性最高,在醇油比6:1、催化剂用量7 wt%、温度338 K和常压下反应2 h,棕榈油的酯化率可达98.9%. 相似文献
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A. Braileanu M. Zaharescu D. CriŞan D. FĂtu E. Segal C. Danciulescu 《Journal of Thermal Analysis and Calorimetry》1996,47(2):569-575
Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3.The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3. 相似文献
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The paper deals with the influence of the deviation of the true heating rate with respect to the programmed one on the values of non-isothermal kinetic parameters for the solid-gas thermal decompositions of CaC2O4.H2O and [Ni(NH3)6]Br2. An original method, based on integration over small ranges of the variables and making use of local heating rates, was applied in order to determine the non-isothermal kinetic parameter values. The results show significant differences between values of non-isothermal kinetic parameters obtained by using true local heating rates and those obtained by using the programmed heating rate. 相似文献
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Optimization of the Sintering Process by DSC for the Preparation of High-Temperature Superconductors
M. Ochsenkühn-Petropulu P. Tarantilis R. Argyropulu G. Parissakis 《Journal of Thermal Analysis and Calorimetry》1998,52(3):903-914
The optimum calcination and sintering conditions for the preparation of the desired phases with the proper stoichiometry of
the bulk high-temperature superconductors YBa2Cu3O7-x (YBCO) and Bi2Sr2CaCu2Oy> (BSCCO) were investigated by differential scanning calorimetry. DSC analysis on the corresponding superconducting coatings,
electrophoretically deposited, indicated that the sintering and annealing procedure was suitable for the production of stable,
strong and adherent coatings. X-ray diffraction analysis, Raman spectroscopy and magnetic measurements confirmed the improved
properties of the superconducting powders and coatings obtained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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The thermal decomposition of [CO(NH2)2H]CrF6·H2O, (C3N6H8)CrF5·H2O and the solid state reaction of CrF3 and melamine are investigated under non-reciprocal quasi-static conditions and compared with the thermal behaviour of other fluorochromates(III) ([Cr(NH3)6]CrF6, (NH4)3CrF and [C(NH2)3]3CrF6). The comparison of the results shows that the amount of chromium(II) in the final product is determined by the thermal stability and consequently by the decomposition temperature of the intermediates. Neither bonding properties in the starting materials nor the absolute amount of generated NH3 influence the composition of the final product. 相似文献
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Yu. A. Titov N. S. Slobodyanik V. V. Chumak 《Theoretical and Experimental Chemistry》2006,42(2):102-105
The calculated (models of the ideal layered perovskite-like structures (LPS)) and experimental values of the unit cell parameters
of compounds of the AnBnO3n+2 type were analyzed. The interconnection between the peculiarities of the distortion of the LPS in these compounds, the number
of layers of BO6 octahedra in the perovskite-like blocks, and the limits of the morphotropic transitions were established.
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Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 92–95, March–April, 2006. 相似文献
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Jean -Michel Savariault Alain Serafini Michel Pelissier Patrick Cassoux 《Theoretical chemistry accounts》1976,42(2):155-161
A previously described extended CNDO/2 method is used for investigating the energy level distribution and electronic structure of trifluorophosphine metal complexes: Cr(PF3)6, Fe(PF3)5, Ni(PF3)4. The results are compared with the few experimental data which are known for these complexes. The metal-phosphorus bonds show large (P M) and (M P) charge transfers but small total charge transfers (M P) which induce on the metal in any case a small positive charge.Such ( + ) coordination bonds seem to be generally characterized by small bond overlap populations (or small Wiberg indices). 相似文献
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K Dyrek A Adamski Z Sojka 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1998,54(14):2337-2348
The temperature dependence of EPR spectra provides information on the mobility of paramagnetic species at the gas (liquid)/solid interface and in the bulk of solids. Changes in the environment of molecules on solid surfaces caused by their motion occurring upon thermal treatment at various temperatures are observed. Superoxide radical can migrate from Co(III) to Mg(II) surface sites of the CoO–MgO solid solutions. In aqueous solutions transition metal ions coordinate water molecules, forming aquacomplexes which are usually free to tumble within the liquid medium. Their mobility is, however, strongly modified in the vicinity of the solid surface or inside the narrow pores. In solids the migration of paramagnetic species from the surface into the bulk is controlled by the temperature of thermal treatment. In the case of V2O5–ZrO2 catalyst this process is strongly influenced by the phase transitions occurring in the solid matrix and by the presence of alkali metals. 相似文献
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Anatoly V. Kondratenko Lev N. Mazalov Konstantin M. Neyman 《Theoretical chemistry accounts》1979,54(3):179-185
Restricted Hartree-Fock calculations of the Cl2 molecule have been carried out to investigate the X-ray excited states below Cl 2p-electron ionization potential. Some inner shell excited states are shown to have a valence or a valence-Rydberg nature that results in a considerable intensity of the appropriate transitions in the X-ray absorption spectrum. A significant interaction among some electron configurations with a 2p vacancy is predicted. 相似文献
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Effect of epitaxial growth on the formation of the cobalt catalysts of the Fischer-Tropsch synthesis
Ya. V. Mikhailova S. A. Sviderskii M. N. Mikhailov I. V. Mishin V. Z. Mordkovich 《Russian Chemical Bulletin》2007,56(9):1922-1926
Mixed oxides CoxAlyO4 with different Al/Co ratios applied as supports for the catalysts of the Fischer-Tropsch synthesis were prepared using the
solid-state chemical reaction. The CoxAlyO4 supports were prepared by modifying gibbsite with various cobalt salts (acetate, nitrate, and basic carbonate). The use of
basic cobalt carbonate gives the Co(20%)/CoxAlyO4 catalyst, which provides an increased yield of hydrocarbons C5+ and a decreased methane content compared to the impregnation catalyst Co(30%)/Al2O3. The introduction of small amounts of rhenium additives makes it possible to enhance the yield of hydrocarbons C5+ (179 g m−3) and also to increase the selectivity with respect to the C5–C18 fraction. The introduction of basic cobalt carbonate into the support, most likely, creates favorable conditions for the
epitaxial growth of the precursor of the active phase.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1856–1860, September, 2007. 相似文献
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The reactivity of Zn3 V2 O8 towards ZnMoO4 was investigated by using DTA and XRD methods. A new compound of the formula Zn2.5 VMoO8 was found. It crystallises in an orthorhombic system. The melting temperature was determinated to be 845±5°C.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献