Nb2O5掺杂对BaTiO3陶瓷介电常数的影响

BaTiO3陶瓷以其优异的铁电、压电和绝缘性能广泛应用于体积小、容量大的电子器件材料,但其在一定的工作温度区间介电常数却呈现不稳定变化。对其常用的改性方法进行了分类和阐述,同时对Nb2O5掺杂改性对BaTiO3陶瓷介电性能的影响作了简单介绍,最后讨论了Nb2O5在多层陶瓷电容器制备领域的应用和重要性。     

五价钽、锂掺杂对Y-TZP微观结构和性能的影响

在前人工作的基础上,本文作者进一步深入细致地分析了总结了Ｎｂ２Ｏ５和Ｔａ２Ｏ５对Ｙ－ＴＺＰ微观结构和宏观性能的影响并提出了自己的见解,研究发现Ｎｂ２Ｏ５和Ｔａ２Ｏ５的添加使得Ｙ－ＴＺＰ轴比及热膨胀各向异性增大,马氏体相变起努温度升高,可相变,ｔ－ＺｒＯ２含量上升有利于材料机械性能的提高。     

Activity and acidity of Nb2O5-MoO3 and Nb2O5-WO3 in the Friedel-Crafts alkylation

Nb₂O₅ loaded on the supports and mixed with oxides was studied to investigate the activity and acidity for Friedel-Crafts benzylation of anisole. From the study on the loaded catalysts, a preliminary conclusion for the selection of metal oxide was obtained; namely, such an acidic oxide as silica was suitable for the support of Nb₂O₅. Then, MoO₃ and WO₃ were mixed with Nb₂O₅, and prominent high catalytic activity and acidities were observed. Both oxides of Nb₂O₅-MoO₃ and Nb₂O₅-WO₃ showed almost similar behavior with respect to characterization and catalytic activity. Surface area increased, X-ray diffraction (XRD) and Raman bands were lost, acid sites, both Brønsted and Lewis characters generated, and surface acid site density was as high as 2–4 nm⁻². The acid sites were generated on the amorphous metal oxides consisting of Nb and Mo or W oxides, different in nature from those of Nb₂O₅ calcined and un-calcined, and active for Friedel-Crafts benzylation.     

In-Nb复合半导体氧化物Cl2敏感特性的研究

以检测Cl2为目标,采用恒温化学共沉积法合成了In-Nb复合半导体氧化物,并研究了其气体传感器的制作方法,分析了In-Nb气敏材料的微观特性和敏感特性,探讨了气敏机理。实验证明,In-Nb材料具有良好的Cl2敏感特性。     

铬和钼掺杂对HCa2Nb3O10／Pt光催化性能的影响

通过高温固相反应合成了铌酸盐KCa2Nb3O10及Cr^3＋和Mo^6＋掺杂（摩尔分数5％）的KCa2Nh3O10，并通过离子交换反应制备出HCa2Nb3O10及Cr^3＋和Mo^6＋掺杂的HCa2Nb3O10采用X射线衍射、原子吸收光谱、扫描电镜等对所制得的样品进行了表征．在甲醇为电子给体、Pt为助催化剂的情况下，研究了催化剂HCa2Nb3O10及Cr^3＋和Mo^6＋掺杂的HCa2Nb3O10在紫外光辐射下分解水产氢的光催化活性，并讨论了引起催化剂活性差异的原因，     

The nickel–niobia–silica interactions at low nickel contents

Nickel was impregnated in two Nb₂O₅/SiO₂ samples. The first one contained small crystallites of niobia dispersed over silica and the second one a niobia monolayer distributed quite uniformly over the silica substrate. These systems were submitted to different treatments (calcination and water vapor) in order to obtain different interactions between the nickel and niobia. A preferential interaction of the nickel with niobia was observed in both niobia–silica samples. The hydrogenation of benzene and dehydrogenation of cyclohexane were used to characterize the reduced surface nickel. Suppression in the catalytic activity was observed due to a strong metal-support interaction (SMSI) and nickel niobate formation. The extension of SMSI and nickel niobate formation depend on the niobia–silica interactions, which are a function of sample preparation and treatment.     

Use of Nb2O5 as nickel passivating agent: characterisation of the Ni/Nb2O5/SiO2 system

Niobia-modified silica was used as support for nickel-based catalysts. Catalysts with different nickel loading were prepared by successive incipient-wetness impregnation of toluenic nickel octanoate solutions. The samples were characterised after both calcination and reduction by TEM-EDX techniques and tested in the ethane hydrogenolysis. Their catalytic behaviour was compared to that of related silica-supported nickel catalysts. A high suppression of hydrogenolysis activity (93–99%) was determined for the niobia-modified silica-supported nickel catalysts which do not show nickel particles on silica.     

油菜花粉诱导合成多孔中空催化剂Nb2O5/TiO2及其在醇氧化反应中的应用

采用油菜花粉为模板制备了一种具有多孔中空结构的催化剂——五氧化二铌/二氧化钛(Nb2O5/Ti O2),它在光照下的醇氧化反应中表现出良好的活性。反应可以在无溶剂下进行,以O2作为氧化剂,2,2,6,6-四甲基哌啶-N-氧自由基(TEMPO)作为助催化剂,反应过程绿色环保,对环境友好。该体系下,10 m L苯甲醇可以得到31mmol苯甲醛,收率为33%,选择性达98%。与单纯用Ti O2作催化剂相比,该文所制催化剂具有多孔结构及Nb2O5,反应的选择性提高。     

Colloidal Sol–Gel Synthesis and Photocatalytic Activity of Nanoparticulate Nb2O5 Sols

A detailed study of a novel synthesis via colloidal sol–gel route for obtaining nanoparticulate Nb₂O₅ was performed. Parameters such as temperature and H⁺:Nb⁵⁺ and Nb⁵⁺:H₂O molar ratios were controlled in order to determine the best conditions of synthesis. Moreover, particle size distribution, zeta potential, structure by X‐ray diffraction, and the photocatalytic activity of the particulate sols were also evaluated. The obtained results indicate that the colloidal sol–gel synthesis is a good alternative for obtaining Nb₂O₅ either as stable nanoparticulate sol or as a nanosized powder. Nb₂O₅ amorphous nanoparticles with an average size of 20 nm were obtained by controlling the synthesis variables. The heat‐treatment process allowed the formation of Nb₂O₅ with orthorhombic structure that transforms at higher temperatures to monoclinic phase. The highest photocatalytic activity was observed under λ = 365 nm, the smallest UV energy used in the experimental tests.     

Nb2O5纳米材料在催化氢化肉桂醛中的影响

使用Nb2O5纳米线（W-Nb2O5）和介孔Nb2O5（S-Nb2O5）两种载体负载金属Pd,制备了Pd/W-Nb2O5和Pd/S-Nb2O5两种催化剂对肉桂醛(CMA)进行催化还原,考察了催化剂的活性和选择性。以乙醇为反应溶剂,催化剂用量0.10 g,80 oC,2MPa H2压力下反应6 h,Pd/W-Nb2O5对CMA的转化率为99%,HCMA的选择性为65%。Pd/S-Nb2O5在相同条件下反应, CMA转化率为98%,HCMA选择性为84%。W-Nb2O5表面酸性过强,导致HCMA选择性变低。继续考察Pd/S-Nb2O5在不同条件下对CMA加氢反应的影响。结果显示温度,H2压力,催化剂载体Nb2O5的晶化温度对反应均有影响。     

共沉淀法合成一种新型的水合镍锰复合氧化物NiMnO3·H2O

通过共沉淀NaOH溶液和含等浓度的Ni2+、Mn2+的NH3·H2O-NH4NO3缓冲溶液的方法,在加热、搅拌的条件下,合成了一种新型的水合镍锰复合氧化物NiMnO3·H2O.采用TG-DTA、XRD、SEM、EDAX、XPS、IR、重量分析以及化学滴定等方法对合成产物的形貌和化学组成进行了表征,可以确定产物的化学组成为NiMnO3·H2O.XRD分析表明合成产物为一种文献上没有报道过的新物质,SEM图片显示合成产物的颗粒是由大量形貌不规则的纳米粒子组成的.     

高压LiNi0.5Mn1.5O4正极材料掺杂Nb离子改性研究

采用固相烧结法合成了Nb掺杂的LiNi0.5Mn1.5O4正极材料.通过XRD测试和充放电测试表征了材料的晶体结构和电化学性能.结果表明Nb掺杂容易产生LiNbO3杂质,并影响其放电能力,少量Nb掺杂获得的LiNi0.425Nb0.03Mn1.5O4展示出良好的大电流放电性能.     

用于燃烧前CO2捕集的微孔Nb2O5膜的制备及其水热稳定性能

以五正丁氧基铌为前驱体,通过溶胶-凝胶法制备出稳定的Nb₂O₅聚合溶胶,详细考察了溶胶制备过程参数(体系酸度、水解比、反应温度、反应时间和螯合剂用量)对溶胶尺寸、稳定性以及制备重复性的影响。采用平均粒径为4.8 nm的Nb₂O₅溶胶,通过浸浆法在平均孔径为3 nm的γ-Al₂O₃中孔膜上制备出Nb₂O₅微孔膜。利用TG、XRD、NH₃吸附-脱附、CO₂吸附、吡啶吸附傅里叶变换红外光谱(Py-IR)和单组分气体渗透实验等手段对Nb₂O₅粉体及微孔膜的性能进行了表征,结果表明:在200℃、0.3 MPa条件下,350℃烧成的微孔Nb₂O₅膜对H₂的渗透率和H₂/CO₂的理想分离因子分别为3.1×10^-9 mol·m^-2·s^-1·Pa^-1和21。此外,微孔Nb₂O₅膜经150 kPa的水蒸气处理8 h后,膜的渗透性能以及H₂/CO₂理想选择性基本保持不变。     

Dielectric behaviors of (Nb2O5)(1-x)xTiO2 ceramics

The dielectric constants (K) of ceramics composition (Nb₂O₅)(_1-x): xTiO₂, (x = 0.05, 0.08, 0.11) have been measured over the temperature range from -180 °C to 180 °C in the frequency range 100 Hz-IMHz. For all three samples, the temperature dependence of the dielectric constants at various frequencies shows the dielectric dispersion and the frequency dependent dielectric losses are observed, suggesting the several relaxation phenomena. Dielectric loss data are analyzed by Arrhenius formalism indicating the presence of relaxation type dielectric mechanisms in (Nb₂O₅)(_1-x): xTiO₂ ceramics.     

Nb2O5/坡缕石固体酸催化合成偏苯三酸三辛酯

利用离子交换法将Nb~(5+)引入坡缕石(Nb~(5+)/PG),经300℃培烧后得坡缕石负载Nb_2O_5的固体酸(300-Nb_2O_5/PG),运用X射线衍射、X射线光电子能谱、紫外漫反射、N_2吸附-脱附(BET)、ICP、NH_3-TPD对其结构、金属含量、酸强度进行表征。在催化合成偏苯三酸三辛酯(TOTM)中,当偏苯三酸酐与异辛醇的摩尔比为1∶4,300-Nb_2O_5/PG用量为酸酐质量的5%,210℃,反应5 h后,偏苯三酸三辛酯酯化率可达到95.3%,催化剂重复使用10次后,酯化率89.2%。     

掺Mn的[YGdCa]3[FeVInMn]5O12复合石榴石

报道了含稀土量少的掺锰复合钇铁石榴石的制备。探讨了替代材料中铁位上锰的掺入对材料特性的影响。结果表明：锰掺入后的材料具有ＹＩＧ相同的结构，并具有良好的施磁性质。该材料适用于制备磁隔离器。