单分散钛酸锶纳米晶体的形成机理

采用水热法,利用乙醇和水的混合溶剂合成了单分散钛酸锶纳米晶体。X射线衍射(XRD)结果显示该晶体为立方相,延长反应时间其结晶性增强。扫描电子显微镜(SEM)、透射电子显微镜(TEM)结果显示样品为70nm左右的均匀立方块晶体。利用SEM、TEM、高分辨透射电子显微镜(HRTEM)和电子衍射(ED)谱研究了该纳米晶体的生长过程,结果表明:前驱体经过扩散反应生成钛酸锶晶核,晶核之间由于定向生长作用而团聚连接形成颗粒球,最后颗粒球在缓慢的奥斯特瓦尔德熟化作用下转化为钛酸锶晶体。这一“扩散反应、定向生长、奥斯特瓦尔德熟化”的生长过程揭示了钛酸锶纳米晶体的生长机理。利用Johnson-Mehl-Avrami(JMA)方程模拟证实了其初始阶段的扩散反应机理,并得出反应活化能为15.79kJ·mol^-1。     

单分散钛酸锶纳米晶体的形成机理

采用水热法,利用乙醇和水的混合溶剂合成了单分散钛酸锶纳米晶体.X射线衍射(XRD)结果显示该晶体为立方相,延长反应时间其结晶性增强.扫描电子显微镜(SEM)、透射电子显微镜(TEM)结果显示样品为70 nm左右的均匀立方块晶体.利用SEM、TEM、高分辨透射电子显微镜(HRTEM)和电子衍射(ED)谱研究了该纳米晶体的生长过程,结果表明：前驱体经过扩散反应生成钛酸锶晶核,晶核之间由于定向生长作用而团聚连接形成颗粒球,最后颗粒球在缓慢的奥斯特瓦尔德熟化作用下转化为钛酸锶晶体.这一“扩散反应定向生长奥斯特瓦尔德熟化”的生长过程揭示了钛酸锶纳米晶体的生长机理.利用Johnson-Mehl-Avrami(JMA)方程模拟证实了其初始阶段的扩散反应机理,并得出反应活化能为15.79 kJ·mol^-1.     

四方相钛酸钡纳米枝晶阵列的水热合成

采用水热法,在表面活性剂十六烷基三甲基溴化铵(CTAB)和合适的矿化剂NaOH的作用下,得到具有新颖结构的钛酸钡纳米枝晶阵列。X射线衍射(XRD)和拉曼光谱(Raman)结果分析显示该枝晶为四方相,随着时间的延长其结晶性增强、四方相更加明显。利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)和电子衍射(ED)研究了该枝晶的生长特点和生长机理,结果表明该枝晶其各枝均沿着[111]方向生长,并且同级枝相互平行形成阵列;在枝晶阵列的外侧部分会有2级子枝长出,中间部位由于空间阻碍没有子枝形成。同时探讨了CTAB和NaOH在枝晶形成过程中的作用机理,以及枝晶产品的介电性能。     

纳米钛酸钡生成的热分解机理

钛酸钡作为重要的铁电材料 ,多年来一直被研究者们所关注．传统方法制备钛酸钡大多采用固相法或草酸盐法得到微米级基料．随着纳米材料研究与应用的发展 ,溶胶 凝胶技术成为制备各种金属氧化物纳米材料的较普遍方法．溶胶 凝胶法制备纳米钛酸钡就是其中之一．该法一般采用钛的有机醇盐与钡盐反应生成溶胶 ,然后形成凝胶 ,再以凝胶为先体进行热处理制得纳米钛酸钡．虽然已有人对溶胶 凝胶技术制备纳米钛酸钡进行了研究 ,并对所得产物进行了表征［１,２］,但尚无人对该方法中凝胶的热分解过程作详细的研究．因凝胶的热分解过程对钛酸钡纳…     

表面修饰的钛酸钡纳米粉体的制备

采用水热法制备出表面包裹有硬脂酸的钛酸钡纳米粉体,并运用一系列手段对其微结构进行了表征.结果表明:产物粒径较小,粒度分布较窄,单分散性较好,其表面为非极性,同时表现出良好的流动性能.认为钛酸钡纳米粉体表面极性的改变是由于其表面包裹了一层硬脂酸,并且包裹层降低了粉体间的相互作用力,从而提高了粉体的流动性.     

简捷水热前驱物技术制备钛酸钡纳米棒与纳米球

A facile synthesis route has been developed to prepare barium titanate nanoparitcles via a low temperature (120 ℃) hydrothermal decomposition of single-source metal-organic precursor. A mixture of tetramethylammonium hydroxide (TMAH) and distilled water was used as reaction media, and Barium titanium ethyl-hexano- isoproxide [BaTi(O₂CC₇H₁₅)(OC₃H₇)₅] was used as precursor. The architecture of products can be selectively controlled from nanorods to nanospheres by adjusting the precursor′s concentration in the reaction system. Powder X-ray diffraction (XRD) analysis indicated that the products were in cubic phase. Transmission electronic microscopy (TEM) observation showed that the nanospheres were 30～50 nm in diameter, and the nanorods were 5～10 nm in diameter and 100～600 nm in length, respectively. Phase transformation behavior of the as-prepared products was also investigated.     

反相微乳液法合成纳米钛酸钡球形颗粒

0引言BaTiO3陶瓷是一种具有高介电常数及优良的铁电、压电和绝缘性能的电子陶瓷材料。不仅是重要的电子陶瓷、PTC陶瓷原料[1],而且也是制备多层陶瓷电容器(M LC C)的必要组分[2,3]。随着现代科学技术的发展,人们更注重材料颗粒的大小和形貌,当材料的粒径达到纳米级时,材料的性能将发生很大的变化。另外,这种具有纳米尺度、球形颗粒的电子陶瓷材料,可能还具有一些新的物理作用,具有潜在的应用价值。B aTiO3粉体的制备方法有:固相煅烧法、化学共沉淀法、溶胶-凝胶法、水热法[4￣11]等。固相法反应温度高(一般1000￣1200℃)、反应活性差…     

CdSe微米球的水热合成及表征

用合成的硒代硫酸钠作为硒源,Cd(NO3)2·4H2O作为Cd源,通过控制配位剂与反应物的比例及表面活性剂的加入,在水溶液中合成了球状的CdSe微米晶.产物用X射线衍射仪,扫描电子显微镜、透射电子显微镜进行表征.结果表明:此法合成了结晶性良好的六方相的CdSe微米晶.并探讨了可能的生长机理.     

纳米晶钛酸钡的介电性能

采用硬脂酸凝胶法制备了纳米晶BaTiO3,用差热热重分析、红外光谱分析、X射线衍射分析等手段对产物的形成过程、晶型、粒径进行了分析.通过对材料介电性能的研究发现,纳米材料的静态介电常数远大于常规材料的介电常数,随着粒径的减小,纳米材料的介电常数先增大而后有所降低.随着环境湿度的升高,纳米晶材料的介电常数逐渐增大,在高湿度条件下,其介电常数与湿度成线性关系.     

纳米钛酸钡及其烧结物的制备

溶胶 凝胶技术已为制备各种金属氧化物纳米材料的较普遍方法[1],其优点是产物具有超细颗粒尺寸 ,高纯度和化学均匀性 .溶胶 凝胶法制备纳米钛酸钡时一般将钛的有机醇盐与钡盐反应生成溶胶 ,然后形成凝胶 ,再进行热处理制得纳米钛酸钡[2 ,3].本文以钛酸丁酯和氢氧化钡为原料 ,采用溶胶 凝胶工艺制备出纳米钛酸钡晶体粉末 .用ＴＧ ＤＴＡ和ＦＴＩＲ技术考查了纳米晶钛酸钡凝胶先体热分解反应过程 ,用ＳＥＭ和ＸＲＤ对粉体形貌和晶型进行分析 ;并用上述粉体制成了微观组织结构仍保持纳米尺寸的陶瓷材料 .粉体制备 :称 15 7ｇ氢氧化钡 (Ｂａ(…     

单分散钛酸钡纳米晶的制备

采用溶剂热法制备出表面包裹油酸的单分散立方相钛酸钡纳米晶, 晶粒平均尺寸为6.0 nm, 采用TEM和XRD对其微结构进行了表征; 研究了醇的链长度、油酸用量和热处理温度等对钛酸钡的相组成和形貌的影响规律. 研究结果表明, 产物粒径较小, 粒度分布较窄, 单分散性较好, 其表面为非极性, 可溶于非极性试剂; 由于纳米晶表面由亲油性的长链烷基所覆盖, 与周围的水性环境不相容, 产生一定的斥力; 在重力和该斥力的共同作用下, 纳米晶可以有效地从液相环境中分离出来.     

Preparation of Barium Titanate Nanopowder through Thermal Decomposition of Peroxide Precursor and Its Formation Mechanism

H₂TiO₃ was dissolved in the mixture of hydrogen formed peroxide and ammonia under the pH range of 8–10 with a transparent yellow solution formed. When an equivalent mole of Ba²⁺ solution was added into the yellow solution, the precipitate produced was the peroxide precursor of barium titanate. The cubic nanopowder of barium titanate was obtained when the precipitate was washed, stoved, and then calcined at 600°C for 1 h. The peroxide precursor of barium titanate and barium titanate nanopowder prepared were characterized to be BaTi(H₂O₂)₂O₃ by TGA‐DTA, XRD, TEM, SEM, and XREDS. The peroxide precursor of barium titanate was determined to be BaTi(H₂O₂)₂O₃. The particle size of the barium titanate nanopowder, the calcined product of BaTi(H₂O₂)₂O₃, was in the range of 20–40 nm. A formation mechanism of the barium titanate nanopowder through thermal decomposition of its peroxide precursor was proposed and then validated.     

聚苯胺/钛酸钡纳米复合粒子的制备与表征

采用原位复合法制备出聚苯胺/钛酸钡复合粒子,借助TEM、XRD、FT-IR、 XPS、TG等分析手段研究了复合粒子的形貌、结构及其热性能.结果表明,复合粒子的粒径为1 μm左右,BaTiO3以40 nm左右的晶粒分散于聚苯胺基体之中,聚苯胺与钛酸钡之间存在化学键合作用,同时在一定程度上减少了纳米粒子的团聚.     

形貌可控钛酸锶钡的制备及其电场响应性能

采用低温共沉淀法, 借助调控合成反应体系的pH值, 制备了星形、花形和柱形3种不同形貌的钛酸锶钡(Ba_0.85Sr_0.15TiO₃)粒子. 通过XRD, ICP, SEM及CA分别对粒子的内部结构和表面进行了表征. 结果表明, 3种钛酸锶钡粒子均具有钙钛矿立方相结构, 其粒径约为5~15 μm. 研究了3种形貌的钛酸锶钡粒子在含水复合弹性体介质中对电场作用的响应性能, 发现粒子形貌对其在电场中的响应能力有很大影响.     

Multiparameter Sensor Chip with Barium Strontium Titanate as Multipurpose Material

It is well known that biochemical and biotechnological processes are strongly dependent and affected by a variety of physico‐chemical parameters such as pH value, temperature, pressure and electrolyte conductivity. Therefore, these quantities have to be monitored or controlled in order to guarantee a stable process operation, optimization and high yield. In this work, a sensor chip for the multiparameter detection of three physico‐chemical parameters such as electrolyte conductivity, pH and temperature is realized using barium strontium titanate (BST) as multipurpose material. The chip integrates a capacitively coupled four‐electrode electrolyte‐conductivity sensor, a capacitive field‐effect pH sensor and a thin‐film Pt‐temperature sensor. Due to the multifunctional properties of BST, it is utilized as final outermost coating layer of the processed sensor chip and serves as passivation and protection layer as well as pH‐sensitive transducer material at the same time. The results of testing of the individual sensors of the developed multiparameter sensor chip are presented. In addition, a quasi‐simultaneous multiparameter characterization of the sensor chip in buffer solutions with different pH value and electrolyte conductivity is performed. To study the sensor behavior and the suitability of BST as multifunctional material under harsh environmental conditions, the sensor chip was exemplarily tested in a biogas digestate.     

Preparation of Barium Titanate and Related Materials by the Alkoxide-Hydroxide Route

Formation of perovskites MTiO₃ (M = Ba, Sr) at low temperature (< 100°C) by heterogeneous reactions of M(OH)₂ aqueous solutions with hydrolysis products of Ti(OBu)₄ is discussed. Reaction products are characterized by means of chemical and X-ray analysis, and electron microscopy. Reaction rate is enhanced by hydroxide concentration and reaction temperature, and increases drastically when Sr(OH)₂ is used instead of Ba(OH)₂. Particles shape and size of the perovskites formed is independent of morphology of Ti(OBu)₄ hydrolysis product. The main factor of perovskites morphology regulation lies in the rate of M(OH)₂ absorption. Lowering the absorption rate allows us to prepare uniform perovskite powders which can be readily sintered to ceramic bodies with high dielectric permittivity.     

超细钛酸钡粉体的水热合成

以偏钛酸和氢氧化钡为原料,用水热反应制备了超细钛酸钡粉体,其结构经XRD和-IEM表征。粒径60nm-100nm。较佳的反应条件为：偏钛酸20mmol,n(Ba)：n(Ti)=1．2,于240℃反应8h,加入少量异丙醇可明显改善粉体的分散性能。