形貌可控的TiO2纳米晶的溶胶凝胶-水热法组合制备

以四烷基氢氧化铵为结构导向剂,正丁醇为结构导向助剂,采用溶胶凝胶-水热法组合制备了不同形貌的二氧化钛纳米晶.通过TG/DTA、TEM、XRD、DLS等手段对产物进行了结构和形貌表征.研究表明,通过选择结构导向剂的烷基种类可分别得到四方型和纺锤型纳米晶,在一定范围内改变其浓度则可以控制晶体的晶化度、分散性和颗粒尺寸.     

二氧化锡纳米中空球制备研究进展

综述了近年来纳米二氧化锡中空球的制备方法,包括硬模板法、软模板法、溶胶-凝胶法、水热法、奥斯特瓦尔德熟化法、一步烧结法、超声喷雾热解法等。对纳米二氧化锡中空球材料的发展前景和制备方法进行了展望。     

微波干燥法制备纳米TiO2光催化剂及其催化性能研究

以钛酸丁酯为前驱物,离子液体1-丁基-3-甲基咪唑四氟硼酸盐为模板剂,采用溶胶-凝胶法及微波干燥法制备了纳米TiO2光催化剂。通过XRD、SEM及BET对光催化剂进行结构表征,以甲基橙溶液为模拟污染物,太阳光为光源,评价了其光催化活性,考察了模板剂及微波干燥条件对纳米TiO2光催化剂活性的影响。结果表明,采用离子液体作为模板剂,微波干燥条件下制备的TiO2光催化剂活性明显高于普通溶胶-凝胶法制备的TiO2光催化剂,光照3h甲基橙溶液降解率可达到95%。     

C-TiO2/CdS复合纤维膜的制备及光催化产氢性能研究

采用溶胶-凝胶法和水热法合成C-TiO2/CdS复合催化剂,并使用静电纺丝法以聚乙烯醇(PVA)为模板剂制备纳米纤维膜载体,通过浸渍法负载催化剂制成壳-核状的C-TiO2/CdS复合纤维膜.通过X射线衍射、X射线光电子能谱技术、漫反射光谱和扫描电镜对催化剂结构组成和形貌进行分析.以乙醇为牺牲试剂,测试了C-TiO2/C...     

多孔氧化钛薄膜的制备及结构的探讨

介绍了模板剂法制备多孔氧化钛薄膜的机理、工艺及影响薄膜结构的因素.实验采用溶胶-凝胶工艺,以钛酸丁酯为前驱体,二乙醇胺为络合剂,分别选用聚乙二醇和十六烷基三甲基溴化铵为模板剂配制溶胶,制备多孔薄膜,通过SEM观察薄膜的表面结构.实验表明:随着模板剂分子量、用量,镀膜焙烧工艺的改变,薄膜表面孔的数量、分布、及孔径大小也随之改变.     

非水解溶胶-凝胶法制备氧化钇稳定氧化锆粉体

非水解溶胶-凝胶法(Non-hydrolytic sol-gel,NHSG)作为一种新的合成方法,融合了溶胶-凝胶法和溶剂热两者的优势。本文分别采用回流和容弹两种NHSG工艺制备了纯ZrO2和氧化钇稳定的氧化锆(YSZ)粉体。DTA和XRD分析结果表明:容弹工艺制备的纯ZrO2和YSZ粉体在凝胶阶段就已具有较高的结晶度,且YSZ粉体经330℃热处理后具有较完整的四方晶相结构;回流工艺制备的产物在凝胶阶段其无定形程度较高,经500℃左右热处理析出晶体。两种NHSG工艺制备粉体中单个颗粒尺寸绝大部分都在100nm以下。     

以嵌段共聚物调控中间层的SiO_2复合膜的制备和表征

采用溶胶-凝胶模板法,以三嵌段共聚物PEO20PPO70PEO20(P123)为模板剂,制备SiO2中间层膜以改善SiO2复合膜的渗透和分离性能。比较了模板剂含量对溶胶粒径和膜孔径的影响。研究表明:随着模板剂含量的增加,溶胶粒子的尺寸和所制备的中间层的孔径随之增加;中间层的加入利于制备出孔径分布窄,孔隙率高的SiO2复合膜。相对于无中间层膜,复合膜具有较高的渗透量和分离性能。在跨膜压差0.04MPa时,复合膜对氮气的渗透系数可达5×10-8mol/m2s Pa,正己烷/氮气的分离因子为2.6。     

纳米花结构制备方法及应用研究进展

从制备工艺条件的角度,着重介绍了氧化物及贵金属纳米花结构的主要制备方法,包括电化学沉积法、化学电镀法、水热法、模板法、多元醇法、热蒸发法、低温溶液合成法、溶胶-凝胶法等几种新型方法。同时,简要地综述了纳米花结构在各领域的应用现状。     

溶胶-水热法制备亚微米4A分子筛

以硅胶湿样和铝矾土为原料,利用溶胶-水热法合成了亚微米4A分子筛,并采用XRD、SEM和FT-IR等分析手段与常规水热法合成的4A分子筛进行了对比.结果表明,采用溶胶-水热法制备的产品,结晶度为96%,形状规则、大小均匀、呈正态分布且分布范围较窄;粒度小于等于1μm的可达到100%;钙离子交换容量为335mg Ca-CO3/g(干基)4A分子筛,白度为97%,完全满足洗涤助剂的要求.     

模板法制备介微双孔HKUST-1材料

以三嵌段共聚物P123作为模板剂,以正癸烷与TMB(1,3,5-三甲苯)作为扩孔剂,采用水热法,成功合成出了具有良好微孔与介孔结构的介微双孔HKUST-1材料,并用XRD、N2吸附-脱附实验、SEM、TEM进行表征。同时考察模板剂含量,以及不同类型的扩孔剂对于介微双孔HKUST-1材料孔结构及晶体形貌的影响。结果表明,加入模板剂P123可成功合成介微双孔HKUST-1,TMB(1,3,5-三甲苯)扩孔剂起到较好扩孔效果,有助于合成具有大介孔孔容的介微双孔HKUST-1。同时模板剂P123及扩孔剂的加入可调节HKUST-1的晶体形貌,在适当条件下可能出现片状堆叠晶体。     

A new soft template-oriented method for the preparation of hollow analcime microspheres with nanosheets-assembled shells

This paper highlights a controlled synthesis of two-dimensional analcime nanosheets templated by organic additives and an impressive strategy that hollow hierarchical analcime microspheres with layered shells can be assembled by taking advantage of the intrinsic growth law of material. Specifically, ultrathin analcime nanosheets were initially obtained by precisely manipulating the amounts of cetyltrimethylammonium cation (CTA⁺) and ethylenediaminetetraacetate (EDTA^4?) in the synthesis system. As building blocks, these nanosheets then self-assembled layer by layer from outside to inside driven by the reversed crystal growth mechanism of analcime, resulting in a hollow structure with lamellar shells and enhanced specific surface area of 722.3 m² g^?1. Series of experiments were carried out in order to explore the influence of CTA⁺ and EDTA^4? on the formation of analcime nanosheets. The results indicated that CTA⁺ was the micro-mesoporogen of hierarchical analcime and synergistically collaborated with EDTA^4? in directing analcime nanosheets. The effect of hydrothermal temperature was discussed and a surfactant packing parameter (g = V/a ₀ l) was cited to explain the behavior of organics. In addition, the investigation of hydrothermal process clearly revealed the crystallization and self-assembly process of hollow structure. And the UV Raman results unraveled that four-membered rings (4MRs) as the active building units for analcime framework were firstly formed in the synthesis gel, followed by reconstruction and self-assembly which lead to the formation of 6MRs and 8MRs.     

The informal discreditation of “doranite” as the magnesium analog of analcime

Zeolites that fill vugs in basalt from the type locality of “doranite” near Carrickfergus, UK, were reexamined with the hope of establishing the magnesium analog of analcime as a valid species. However, contents of Mg in the zeolites as measured by electron microprobe analysis were not above the limits of detection (0.01 wt% MgO). X-ray powder diffraction and optical microscopy show a vug assemblage of thomsonite + natrolite + analcime + Mg-rich clay minerals.     

Synthesis of zeolites NaA and analcime using rice husk ash as silica source without using organic template

Silica was extracted from Fajr rice husk ash (RHA) with approximately 97% purity, converted to sodium and potassium silicate solutions and used as silica source for the synthesis of NaA and analcime zeolites. NaOH and KOH without organic templates were used in the synthesis of NaA and analcime zeolite, respectively. Conventional heating and microwave-assisted hydrothermal were used in zeolite synthesis. Zeolites were characterized with XRD, SEM and IR spectroscopy. Heating time and Si/Al ratio were optimized for the synthesis of zeolites.     

Hydrothermal processing on potassic syenite powder: Zeolite synthesis and potassium release kinetics

To make potassium accessible to agricultural application from K-silicates, processing on potassic syenite powder under mild alkaline hydrothermal conditions was conducted, as a result of which, potassium became accessible into solution, and to two zeolite powders (analcime and hydroxycancrinite) were successfully obtained. A scale-up operation in 25L-hydrothermal reactor supported the feasibility of further industrial implementation. The kinetic model derived from geochemical study was adopted to describe K⁺ release behavior, and two kinetic factors, reaction order and apparent activation energy, over temperature range of 477–531 K were 2.61 and 46.61 kJ/mol. The concentrated alkaline solution giving rise to higher reaction order and lower apparent activation energy was a dominated factor accelerating K-feldspar dissolution accomplished within hours. The hydrothermal approach proposed in this work is a simplified and green chemical way for the comprehensive utilization of K-silicates.     

Ionic conductivity of synthetic analcime,sodalite and offretite

The ionic conductivity of pressed pellets of dehydrated synthetic analcime, sodalite and offretite was determined by a.c. measurements within the range 10 Hz to 10 MHz. The ionic conductivity values of those zeolites exchanged with various monovalent cations were determined by the complex impedance plane method. The conduction activation energies range between 63 and 101 kJ mol^–1. Sodium analcime shows the best ionic conductivity, namely 1.8×10^–4–1 cm^–1 at 400° C. A comparison with the conductivity of other ion-conducting solids was made.     

Hydrothermal transformation of clinoptilolite

Procedure for hydrothermal transformation of natural clinoptilolite at 160°C is described. The synthesis is carried out in the system Na₂O-Al₂O₃-SiO₂-H₂O. Products of 24–168 hr runs are characterized by x-ray diffraction,ir spectroscopy, energy dispersive analysis of x-rays (edax), and electron microscopy. Presence of analcime-type and faujasite-type zeolites in the final products is established. Si/Al ratio of the final mixed phase is estimated as 2·91. Spheroid crystals of analcime, fibrous crystals of mordenite (on analcime), and well developed polyhedral crystals of analcime-faujasite mixed phase are illustrated and described. It is shown that crystals grow by two-dimensional nucleation mechanism.     

Effect of temperature on hydrothermal synthesis of analcime and viséite

The zeolite minerals analcime (Na₁₆(Al₁₆Si₃₂O₉₆) · 16H₂O) and viséite (Na₂Ca₁₀(Al₂₀Si₆P₁₀O₆₀(OH)₃₆) · 16H₂O) were synthesized by hydrothermal treatment of artificial glasses of the respective same composition in a temperature range between 80 and 630°C at 100 MPa H₂O pressure. The crystal symmetry of both zeolites varied systematically with temperature under the given experimental conditions, starting from orthorhombic symmetry at low synthesis temperatures, tetragonal at medium leading to cubic symmetry at highest zeolite synthesis temperatures. The crystal sizes varied between 500 nm and 100 μm. In case of analcime water free tectosilicates instead of zeolites were formed at T≥500°C while viséite was formed up to 630°C. The investigations showed the direct correlation between chemical composition of the starting materials and the formed zeolite phase under the given p–T conditions.     

Reversed Crystal Growth: Implications for Crystal Engineering

The discovery of reversed crystal growth routes in zeolite analcime and zeolite A implies that crystal growth does not always follow the classic theory established 100 years ago. Aggregation of nanoparticles may dominate in the early stages of crystal growth, followed by surface crystallization, and then extension from surface to core of the disordered aggregates. A perfect polyhedral morphology can be developed in a thin surface crystalline layer of a particle with a disordered core. Evidence of such a novel crystal growth phenomenon can be also found in many other materials. This article highlights the recent achievements in this topic, which might have a significant impact on crystal engineering, materials science, and mineralogy.     

An integrated microfluidic device for rapid cell lysis and DNA purification of epithelial cell samples

In this paper, we describe the design and fabrication of a microfluidic device for cell lysis and DNA purification, and the results of device tests using a real sample of buccal cells. Cell lysis was thermally executed for two minutes at 80 degrees C in a serpentine type microreactor (20 microL) using an Au microheater with a microsensor. The DNA was then mixed with other residual products and purified by a new filtration process involving micropillars and 50-80 microm microbeads. The entire process of sample loading, cell lysis, DNA purification, and sample extraction was successfully completed in the microchip within five minutes. Sample preparation within the microchip was verified by performing a SY158 gene PCR analysis and gel electrophoresis on the products obtained from the chip. The new purification method enhanced DNA purity from 0.93 to 1.62 after purification.     

Hydrothermal decomposition of K-feldspar with Cs enrichment into pollucite in Cs-included alkaline solution

Hydrothermal decomposition of K-feldspar in Cs-included NaOH (2.2 mol/kg) and KOH (3.0 mol/kg) solutions with initial Cs/(Cs + Na) and Cs/(Cs + K) ratios varying from 0 to 1 was investigated. Results showed that the solid products exhibited high selectivity for Cs with respect to Na and K, where pollucite crystals instead of analcime and kalsilite in cubic and trioctahedra morphologies with less than 5 mol% Na or K replacement were obtained from Na-Cs (220 °C) and K-Cs (240 °C) solutions respectively. The distribution of Cs between the final solid and solution exhibited as liner relations in similar slops (about 0.06) for the two mixed mediums, and an extremum Cs/(Cs + Na + K) value of about 0.95 in solid phase was derived. Present work indicated that Cs was enriched during the hydrothermal processing on K-feldspar, almost pure pollucite was synthesized even in mixed ion systems, and radioactive Cs could be immobilized from vast polluted silicates including feldspar minerals.