Fe(Ⅲ)掺杂Nb2O5微纳球的水热合成及其电化学性能

采用一步水热法合成Nb₂O₅和Fe（Ⅲ）掺杂的五氧化二铌微纳米球（Fe-Nb₂O₅）,并利用X射线衍射（XRD）、扫描电子显微镜（SEM）及透射电子显微镜（TEM）等测试手段分别对其结构和形貌进行了表征。结果发现,所合成的Fe-Nb₂O₅和Nb₂O₅均为正交晶相,Nb₂O₅为尺寸分布在50~300 nm之间的形貌不规则颗粒,而Fe-Nb₂O₅是由约50 nm的一次颗粒自组装而成的直径约为1 μm的均匀微纳米球,即具有多级结构,其有利于增大电极材料与电解液的接触界面。电化学测试结果表明,Fe-Nb₂O₅的循环稳定性和倍率性能得到明显改善,在50 mA·g^-1电流密度下,100次循环后放电容量仍保持在193.2 mAh·g^-1,即使在5 A·g^-1的电流密度下,容量仍可达到108.4 mAh·g^-1。并分析了其性能改善的原因。     

新铌酸盐Ba5NdTi3Nb7O30的合成与介电性能

The New Niobate Ba₅NdTi₃Nb₇O₃₀ was synthesized by solid state reaction at 1250℃ for 48h. The crystal structure and dielectric properties of Ba₅NdTi₃Nb₇O₃₀ were determined by X-ray powder diffraction and dielectric measurements. The results show that Ba₅NdTi₃Nb₇O₃₀ belongs to ferroelectric phase of tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.24424(4)nm, c=0.39476(2)nm, calculated density 5.719g·cm^-3. Ba₅NdTi₃Nb₇O₃₀ belongs to relaxor ferroelectrics. The phase transition temperature (T_c) of Ba₅NdTi₃Nb₇O₃₀ from ferroelectric to paraelectric is found to shift toward higher temperature side at higher fre-quency, and T_c is 90℃ at 1kHz. At room temperature, the dielectric constant (ε_r) and dielectric loss of Ba₅NdTi₃Nb₇O₃₀ decrease with the increase of frequency, and Ba₅NdTi₃Nb₇O₃₀ ceramic have high dielectric constant 489 at 1kHz.     

胍盐化合物[C(NH2)3]6.3K[Nb1.3W10.7O40H2]·H2O的合成及性质

通过粉状白钨酸和可溶性铌酸钾水溶液的反应,合成了十二聚系列的钨铌杂多阴离子胍盐化合物[C(NH₂)₃]_6.3K[Nb_1.3W_10.7O₄₀H₂]·H₂O,研究了其水溶液的酸碱稳定性。根据红外、拉曼和紫外光谱、化学性质,认为该化合物可能具有十二聚偏钨酸根阴离子的结构骨架。     

层状类钙钛矿结构新铌酸盐KSr2Nb3O10

A new niobate compound KSr₂Nb₃O₁₀ was synthesized for the first time. The chemical compositions, crystal structure, optical property, density and melting point of the new compound were characterized by EPMA, TEM, XRD, DTA and so on. KSr₂Nb₃O₁₀ crystallizes the orthorhombic system with unit cell parameters a=0.7816(1) nm, b=0.7764(2) nm, c=2.9995(2) nm, V=1.8114(4) nm³, and space group P2₁2₁2₁, Z=8. The structure may be described as treble perovskite sheets ［Sr₂Nb₃O₁₀］^- interleaved with K⁺. Further, it was found that KSr₂Nb₃O₁₀ has intercalation phenomenon. Na⁺, Li⁺, H⁺, NH⁺₄ could exchange the interlayer cations K⁺ of KSr₂Nb₃O₁₀, and n-hexylamine also could intercalate into the place between the layers of ［Sr₂Nb₃O₁₀］^-.     

类钙钛矿新铌酸盐Ba6LaTi3Nb3O21的合成、结构与介电特性

A New Niobate Ba₆LaTi₃Nb₃O₂₁ was synthesized by high temperature solid state reaction in the BaO-La₂O₃-TiO₂-Nb₂O₅ system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, DTA and so on. Ba₆LaTi₃Nb₃O₂₁ crystallizes the rhombohedral system with unit cell parameters a=0.57388(2) nm, c=4.928 3(3) nm, and space group R3m, Z=3. The structure may be described as six (Nb,Ti)O₆ octahedra corner-sharing along c-axis to form perovskite layer connected by Ba atoms. The Ba₆LaTi₃Nb₃O₂₁ ceramics exhibits high dielectric of 74.1, low dielectric loss of 4.7×10^-4 and small temperature coefficient of dielectric constant of -69 ppm·K^-1 at 1 MHz due to its close structure and relative high dielectric polarizabilities of Ba²⁺, La³⁺, Ti⁴⁺ and Nb⁴⁺. Ba₆LaTi₃Nb₃O₂₁ might be a suitable candidate of high ε_r microwave dielectric ceramics.     

H2SO4处理的Nb2O5/γ -Al2O3催化剂表面酸性与催化性能研究

用Hammett指示剂法、红外光谱（IR）、示差扫描量热-热重法（DSC-TG）和微型催化反应装置等研究了H₂SO₄处理的负载型Nb₂O₅/γ-Al₂O₃催化剂表面酸性和催化异丁烯（IB）与异丁醛（IBA）反应生成2，5-二甲基-2，4-己二烯（DMHD）的催化性能。结果表明随所用H₂SO₄浓度增加，Nb₂O₅/γ-Al₂O₃催化剂表面酸性增强，B酸量增加，L酸量先增加后下降。经H₂SO₄处理的Nb₂O₅/γ-Al₂O₃催化剂的催化活性明显增加，但当H₂SO₄浓度超过0.05 mol·L^-1时催化活性又急剧下降，这可能是因为在H₂SO₄处理的催化剂表面形成的强酸中心上，产物分子进一步转化为积炭且封闭催化剂活性表面，导致催化活性下降。     

Mn2O3纳米结构的简易合成与电化学性质

用简易的室温或水热方法制备出不同形貌的MnCO₃微结构。经600 ℃热处理后,室温制备MnCO₃转变成Mn₂O₃胶体片,而水热制备MnCO₃样品则形成多孔Mn₂O₃纳米结构。然而,室温制备MnCO₃经120 ℃热处理后形成Mn₂O₃晶相。制备样品经过XRD和SEM表征表明,热处理MnCO₃前驱物形成Mn₂O₃过程导致产物形貌与结构变化。其形成机理又通过TEM和FTIR进一步研究。Mn₂O₃纳米结构的电容性质通过循环伏安法表征,结果表明Mn₂O₃形貌与结构对其电容有重要影响。     

球形TiO2-Al2O3的制备、结构和理化性能研究

将Ti(SO₄)₂溶于稀盐酸合成酸性钛溶胶，再将其与铝溶胶和六次甲基四胺溶液混合后采用油柱成型法制备了球形TiO₂-Al₂O₃复合氧化物。通过XRD、低温氮吸附-脱附与NH₃-TPD等手段对样品进行表征，结果表明600 ℃焙烧得到的球形TiO₂-Al₂O₃中TiO₂以无定型形式存在;随TiO₂含量的增加，球形TiO₂-Al₂O₃的比表面积、孔容和平均孔径呈增加趋势;TiO₂的引入没有对球形TiO₂-Al₂O₃的强酸和弱酸中心的强度产生影响，弱酸中心数量显著增加，强酸中心数量稍有增加;球形TiO₂-Al₂O₃的堆密度和压碎强度随TiO₂含量的增加而减小，颗粒直径基本保持不变。     

P2O5对Li2O-SiO2-Al2O3-K2O-ZnO体系微晶玻璃析晶性能的影响

采用差热分析、X射线衍射及扫描电镜分析手段研究了P₂O₅对Li₂O-SiO₂-Al₂O₃-K₂O-ZnO体系牙科微晶玻璃析晶性能的影响, 并确定了P₂O₅的最适含量. 结果发现P₂O₅是该玻璃体系的有效成核剂, 未添加P₂O₅的玻璃体系成核密度低, 热处理后不能形成微晶体, 且主晶相为硅酸锂; 添加P₂O₅使玻璃在热处理后形成以二硅酸锂为主晶相的微晶玻璃. 该玻璃体系中添加4.5 wt%的P₂O₅可以得到较高体积含量和理想显微结构的牙科二硅酸锂微晶玻璃. P₂O₅含量为6 wt%的基质玻璃发生乳浊, 呈不透明的乳白色.     

高密度非球形和球形LiNi1/3Mn1/3Co1/3O2的合成和性能比较

利用二次干燥法和共沉淀法分别制备出了非球形的Ni_1/3Co_1/3Mn_1/3OOH前驱体和球形Ni_1/3Co_1/3Mn_1/3(OH)₂前驱体, 并分别和LiNO₃混合烧结合成高密度非球形和球形的锂离子正极材料Li(Ni_1/3Co_1/3Mn_1/3)O₂. XPS分析表明, 二次干燥法制备的非球形Ni_1/3Co_1/3Mn_1/3OOH前驱体其过渡金属Ni, Co和Mn的价态分别是＋2, ＋3和＋4, 而共沉淀法制备的球形Ni_1/3Co_1/3Mn_1/3(OH)₂前驱体其各金属价态为＋2; X射线衍射分析表明, 非球形的Ni_1/3Co_1/3Mn_1/3OOH前驱体比球形的前驱体具有较高的活性, 能够在低温下合成出Li(Ni_1/3Co_1/3Mn_1/3)O₂, 而且制备的产物结晶度高, 具有规整的层状α-NaFeO₂结构, 扫描电镜显示制备的非球形产物颗粒均匀, 颗粒间隙小, 振实密度高达2.95 g•cm^－3, 远高于球形的振实密度2.35 g•cm^－3; 充放电实验表明, 由非球形前驱体制备的Li(Ni_1/3Co_1/3Mn_1/3)O₂其充放电性能和循环性能以及体积比容量均高于球形正极材料.