均匀沉淀法制备纳米TiO2/膨胀珍珠岩复合材料

以膨胀珍珠岩为载体,TiOSO4为钛源,采用均匀沉淀法制备了纳米TiO2/膨胀珍珠岩复合材料,通过SEM、TEM、XRD和BET比表面积法进行了分析表征,并以罗丹明B溶液为降解对象研究其光催化性能.结果表明随着TiOSO4加入量的增加,复合材料的TiO2负载量和比表面积越来越大,而光催化性能先升高后降低.当TiO2负载量为15.27;时光催化性能最好,此时纳米TiO2颗粒在膨胀珍珠岩表面均匀致密分布成一层薄膜,TiO2晶粒尺寸为11.93nm,经300 W高压汞灯照射60 min时对罗丹明B溶液的降解率超过95;,达到了与P25相同的降解效果.     

H2O/HAc对纳米TiO2/硅藻土复合材料TiO2晶相和性能的影响

以硅藻土为载体,钛酸四丁酯为前驱体,采用溶胶-凝胶法制备了纳米TiO2/硅藻土复合材料.在750下对复合材料煅烧晶化,以罗丹明B为降解对象检测了材料的光催化性能.并结合XRD、BET、SEM等表征手段,探究了H2O/HAc比例对复合材料晶型、比表面积和光催化性能的影响.结果表明,H2O/HAc比例对TiO2/硅藻土复合材料中TiO2的晶相组成和光催化性能有很大影响.当H2O/HAc=6时,二氧化钛颗粒均匀地负载在硅藻土表面,样品具有较大的比表面积和较好的光催化效果,同时锐钛矿晶型比例为80.2;.     

TiO2/石墨烯纳米复合材料制备及其光催化性能研究

以TiCl3和氧化石墨(GO)为原料,采用简便的原位液相法制备了TiO2/石墨烯(RGO)纳米复合材料.利用XRD、SEM、XPS和UV-Vis光谱表征了其微观结构及性能,实验考察了复合材料光催化还原CO2性能,探究了其光催化反应机理.研究表明,TiO2/石墨烯纳米复合材料具有显著的光催化还原活性,光催化反应产物选择性高,反应6.0h甲醇的累积产量为3.43 mmol/L,石墨烯的协同效应提高了TiO2半导体的光催化活性和反应效率.     

炭黑吸附水热法制备纳米TiO2粉体及其光催化降解甲基橙

利用炭黑吸附钛酸异丙酯水热法制得锐钛矿型TiO2纳米粉体.采用热重/差热分析(TG-DTA)、X-射线衍射(XRD)、扫描电镜(SEM)、比表面积吸附(BET)和紫外-可见光谱(Uv-vIS)等分析方法对不同煅烧机制下所得粉体的物相、颗粒度、分散性和光吸收性能进行表征.同时利用纳米TiO2粉体对甲基橙进行了光催化降解,研究了其光催化性能.结果表明,炭黑的吸附阻止了纳米TiO2超细颗粒的团聚和烧结,制得的颗粒分散均匀、具有单一锐钛矿晶型结构的TiO2纳米粉体.经500℃煅烧获得的TiO2粉体粒径约为15 nm,比表面积为76.31 g/m2.在紫外灯照射下,由于炭黑的吸附和纳米TiO2的光催化形成协同效应,甲基橙的光催化降解率在6min达到99;.     

La掺杂TiO2/电气石的制备及光催化性能研究

以电气石为载体,TiCl4为前驱体,采用水解沉淀法负载La掺杂纳米TiO2薄膜,制备La掺杂TiO2/电气石复合材料.结合XRD、FESEM、UV-vis等现代测试手段对所制备样品的结构和性能进行了表征.以甲醛为目标降解物,考察了样品的光催化活性.结果表明:La掺杂TiO2晶粒细小,均匀分布于电气石表面.经550℃煅烧,La掺杂后锐钛矿型TiO2粒径由13.5 nm降为8.73 nm.La掺杂后,TiO2光催化剂的吸收光谱向可见光区发生红移.1m3环境舱内,日光灯下照射360 min,La掺杂TiO2前后复合材料对甲醛的去除率分别达到66.4;和82.2;.     

棒状PANI/TiO2纳米复合材料的制备及光催化性能研究

通过共混法和原位氧化聚合法成功制备了棒状聚苯胺/TiO2纳米复合材料,通过SEM、XRD、FT-IR、TGA、TEM、紫外-可见漫反射光谱等测试对其进行表征.并以罗丹明B溶液为模拟污染物,在可见光条件下,棒状PANI/TiO2纳米复合材料的催化降解效率与纯PANI和TiO2相比明显提高.另外,对两种不同方法合成的PANI/TiO2纳米复合材料的光催化性能进行对比,结果表明原位氧化聚合法制得的复合材料,由于TiO2在复合材料中的均匀分布及其与PANI的协同效应,光催化降解率可达91.11;.     

纳米TiO2/蛋白土复合材料的制备与表征

为了解决纳米TiO2在使用过程中分散性差、难以回收等缺点,将纳米TiO2负载在酸浸蛋白土表面,提高光催化效率.以酸浸蛋白土为载体,TiCl4为前驱体,采用水解沉淀法制备了纳米TiO2/蛋白土复合材料.采用XRD、TEM等方法对复合材料性能进行了表征,并进行了复合材料的光催化降解甲醛实验研究.结果表明负载在蛋白土表面的Ti02晶型为锐钛型,晶粒粒度为5～20 nm.对甲醛降解实验研究结果表明,所制备的蛋白土负载纳米TiO2复合材料具有良好的光催化降解性能,其24h对甲醛的降解去除率可以达到90;以上.     

三维有序大孔TiO2/CeO2光催化剂的制备及性能研究

以自组装SiO2纳米球为模板,通过煅烧和模板刻蚀制备具有三维有序大孔结构的TiO2/CeO2复合光催化剂(3DOM TiO2/CeO2).用XRD、SEM、FT-IR、DRS、PC等手段对所制备的光催化剂进行表征,在模拟太阳光下,以罗丹明B为模型降解物,对样品的光催化活性进行测试.结果表明,3DOM TiO2/CeO2的光催化降解活性与TiO2/CeO2相比得到进一步提高,其原因可能是由于3DOM结构可以产生慢光子效应,提高了TiO2/CeO2复合光催化剂的光吸收能力,进而提高了TiO2/CeO2的光催化性能.     

硅藻土/TiO2/氧化石墨烯复合材料的制备及其光催化性能研究

本文以硅藻土为载体,硫酸氧钛为前驱体,在硅藻土表面原位水解形成二氧化钛纳米颗粒,后经氧化石墨烯修饰改性,得到硅藻土/TiO2/氧化石墨烯三元复合光催化材料.通过SEM、XRD、XPS、IR对样品的晶体结构、形貌及元素形态等进行了表征,研究了复合催化剂对罗丹明B溶液的光催化降解性能.结果表明,硅藻土/TiO2/氧化石墨烯三元复合材料在2 h的光降解率高达99;,比同时间的硅藻土/TiO2二元复合材料高出10;,比硅藻土高出73;,硅藻土作为载体有效的避免了二氧化钛颗粒的团聚,同时氧化石墨烯的高导电性能有效分离光生载流子,从而提高TiO2的光催化活性和反应效率.     

钒掺杂纳米二氧化钛的制备及光催化活性研究

以钛酸四丁酯为钛前驱体,偏钒酸铵为掺杂离子给体.采用溶胶-凝胶法制备了V掺杂纳米二氧化钛粉体;并使用TGA-DSC、XRD、BET、SEM对其晶化温度与结构进行了表征.结果表明:V掺入促进锐钛矿相向金红石相转变、抑制晶粒长大、增大比表面积,纳米粉体颗粒呈分布较均匀的类球形晶粒.以亚甲基蓝为模型反应,考察了V掺杂量、煅烧温度对催化剂光催化性能的影响,结果表明:V掺杂的TiO2 粉体降解亚甲基蓝符合一级反应动力学规律;晶格中V4+能够作为电荷转移物种,有效的抑制光生电子与空穴的复合,增加了表面空穴浓度,提高TiO2 纳米粉体的光催化活性,当掺杂量为1.5 mol;,煅烧温度为450 ℃时,TiO2 具有最佳的光催化性能.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.