阳极氧化法制备TiO2有序多孔薄膜

采用二次阳极氧化工艺,以含有氟化铵和水的乙二醇体系作为电解液,在纯钛表面制备有序的TiO2多孔薄膜.通过改变预处理方式、电压、氧化时间和搅拌速度等实验参数来探究其对TiO2多孔薄膜形貌的影响.结果表明,抛光后Ti基片制得的TiO2多孔薄膜表面更加平整;TiO2纳米孔的孔径和孔间距随着阳极氧化电压升高在一定范围内线性增大;TiO2纳米孔的孔径随着阳极氧化时间延长增大,孔壁随时间延长减薄,通过控制氧化时间可以实现纳米孔薄膜向纳米管阵列的转变;搅拌速度在400 r/min时,能够获得有序的自组织TiO2多孔薄膜.     

纳米TiO2/硼泥脱镁硅渣复合材料的制备与光催化性能

硼泥脱镁硅渣是硼泥酸浸脱镁后制取的一种多孔硅质矿物材料.以TiCl4为前驱体,硼泥脱镁硅渣为载体,采用水解沉淀法制备了一种纳米TiO2/硼泥脱镁硅渣复合材料,并采用XRD、SEM、EDS、TEM和FT-IR等手段对复合材料形貌与结构进行了表征.结果表明,复合材料中纳米TiO2以锐钛矿的晶型负载于硼泥脱镁硅渣表面,通过谢乐公式计算纳米TiO2平均晶粒尺寸为11.37 nm,透射电镜测量纳米TiO2粒径在10 ～ 30 nm之间.对水中Cr(Ⅵ)降解实验研究结果表明,光照240 min复合材料对Cr(Ⅵ)降解率可达到93.76;.     

微乳液法制备TiO2纳米粉体及其光催化性能研究

本文以TiCl4为原料,采用阴离子表面活性剂十六烷基三甲基溴化铵为主的微乳体系制备了TiO2的前驱物,并在500℃合成了平均粒径为10nm的纳米锐钛型TiO2微粉,同时利用纳米TiO2粉体对染料罗丹明B进行了光催化降解,研究了其光催化性能,表明在1 h内对罗丹明B的光催化降解率可达98;以上.     

液相沉积法处理TiO2纳米晶膜对其光电性能的影响

将涂有TiO2纳米晶膜的导电玻璃浸渍于氟钛酸铵、硼酸和水的液相沉积(Liquid Phase Deposition,简称LPD)反应溶液中,利用反应液中氟的金属配位离子和金属氟化物之间的化学平衡反应,在TiO2纳米晶多孔膜(简称nc-TiO2膜)上沉积一层TiO2纳米粒子,从而实现对TiO2纳米晶膜进行化学处理。以经过LPD处理的TiO2纳米晶膜作为光阳极组装染料敏化太阳能电池(DSSC)并测试其伏安特性曲线,研究了不同反应时间条件下LPD处理nc-TiO2膜对DSSC光电性能的影响。结果表明:在一定条件下用LPD处理TiO2纳米晶膜可显著提高其DSSC光电性能,短路电流密度最高提高13.13%,能量转化效率最高提高13.95%。论文对LPD处理TiO2纳米晶膜提高DSSC光电转化性能的原因进行了分析。     

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;.     

电气石表面TiO2微孔空心球簇的制备及光催化活性研究

用溶胶-凝胶技术在紫铜表面制备含电气石矿物粉末的TiO2复合薄膜,研究薄膜的制备方法、显微结构及其光催化活性.用SEM技术研究电气石-TiO2复合薄膜的微观结构和电气石表面TiO2的显微结构,测量了TiO2空心球直径、TiO2空心球簇大小,同时用电子探针对电气石-TiO2复合薄膜中的TiO2空心球簇表面及球簇周围TiO2膜进行了成分分析;并用电气石/TiO2复合薄膜光催化降解甲基橙水溶液,研究电气石对TiO2薄膜光催化活性的影响.结果发现,紫铜表面上电气石微粒均匀分布在TiO2薄膜中,且在电气石微粒表面可形成TiO2微孔空心球和微孔空心半球构成的微孔空心球簇,空心球和空心半球的平均粒径为2μm;经紫外线照射180min后,与不含电气石的TiO2薄膜相比,含电气石0.5;的TiO2复合薄膜对甲基橙的光催化降解率可提高31.9;,电气石可以明显提高TiO2薄膜的光催化活性.     

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.     

可磁分离TiO2/BiOI复合纤维的制备及光催化性能

本工作合成了一种可磁分离TiO2/BiOI复合纳米纤维(TiO2/Fe3O4/BiOI),并研究了其可见光催化性能.通过静电纺丝技术获得TiO2纳米纤维,采用溶剂热法在TiO2纳米纤维表面生长Fe3 O4纳米颗粒,最后,在磁场辅助下,通过连续离子吸附反应(SILAR)法在TiO2/Fe3O4表面生长了BiOI纳米片.结果表明,Fe3O4纳米颗粒直径均一,均匀分布在TiO2纳米纤维表面.BiOI纳米片呈交错状垂直沉积在TiO2纳米纤维表面,BiOI纳米片的负载量可以通过SILAR的循环次数控制.光催化测试表明,由于BiOI对可见光吸收的增加,以及与TiO2间形成的半导体异质结,TiO2/Fe3 O4/BiOI复合纳米纤维的光催化效率均高于TiO2/Fe3 O4纳米纤维.此外,TiO2/Fe3 O4/BiOI对外磁场有强的响应,易于进行磁分离回收.     

胶溶法制备具有自清洁与抗菌性能的TiO2薄膜

采用胶溶法合成了纳米晶锐钛矿溶胶,在玻璃基底上用提拉法制备出TiO2纳米薄膜。使用XRD、TEM、SEM和AFM和接触角等方法对TiO2溶胶和薄膜的结构进行了表征。结果表明,胶溶法合成的TiO2溶胶为锐钛矿型且结晶度较高,TiO2晶粒为针状,平均粒径约为8 nm;TiO2薄膜表面光滑,颗粒平均粒径约为86 nm。3层薄膜的厚度约为150 nm,涂膜层数对膜表面结构形貌影响有限。常温制备出的薄膜经紫外光照80 min,对亚甲基蓝的降解率达到93.6%,其活性随着热处理温度升高而提高。薄膜具备超亲水性,自清洁和抗菌性能。     

乙酰丙酮对PMMA负载锐钛矿型TiO2薄膜及其光催化性能影响

以钛酸丁酯作为钛源,水为溶剂,乙酰丙酮(AcAcH)为表面修饰剂,采用微波水热辅助溶胶-凝胶法制备了纳米晶二氧化钛水溶液,利用提拉镀膜法在聚合物聚甲基丙烯酸甲酯(PMMA)基板上沉积得到了透明TiO2纳米晶薄膜.通过X射线衍射(XRD)、红外光谱(FTIR)、透射电子显微镜(TEM)、原子力显微镜(AFM)和紫外-可见光吸收光谱(UV-Vis)等对TiO2纳米颗粒和薄膜的晶相组成、表面形貌及光学性能进行表征.同时通过紫外光光催化降解罗丹明B研究了TiO2薄膜的光催化性能.结果表明:通过引入乙酰丙酮,可以得到高度分散、晶相为锐钛矿型的TiO2水溶胶,在PMMA基板上沉积得到的薄膜表面平整、致密,具有良好的透光率,经过180 min紫外光照射,对罗丹明B的降解率达到90;以上.     

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.     

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.     

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.     

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.