热处理温度对Fe掺杂纳米ZnO/SnO2催化剂粉体的光催化性能的影响

以SnCl4.5H2O、ZnNO3.6H2O、HCl、NaOH、FeCl3.6H2O为原料,采用共沉淀法制备Fe掺杂纳米ZnO/SnO2复合催化剂粉体,以溶液降解甲基橙反应为模型,借助透射电镜(TEM)、X射线衍射(XRD)测试仪等研究了热处理温度对0.2wt%Fe-Zn4Sn1(ZnO/SnO2=4/1(物质的量比))复合催化剂(简为:FZS)粉体催化活性和结构的影响。结果表明:随着热处理温度的升高,光催化活性先升高后降低,热处理温度为650℃时所得的FZS粉体的光催化活性达到最高,对甲基橙的降解率为89.63%(紫外光照50 min)。随着热处理温度升高,FZS粉体的粒径逐渐增大,分散性仍然较好。当热处理温度达到750℃时,随着热处理温度的升高,FZS粉体团聚现象明显,比表面积急剧减小,使得光催化活性降低。在热处理温度高于850℃时,样品中出现Zn2SnO4晶体,也使得光催化活性降低。     

铋基碘氧化物/煤矸石复合粉体的制备及光催化性能

以表面改性的煤矸石粉、硝酸铋和碘化钾为原料,采用超声法制备了BiOI/煤矸石复合粉体和Bi5 O7I/Bi4O5I2/煤矸石复合粉体,利用XRD、SEM、EDS对所制得的样品进行了表征,并以模拟太阳光为光源,罗丹明B为目标降解物,对其光催化活性进行了研究.结果表明:BiOI/煤矸石复合粉体和Bi5O7I/Bi4O5I2/煤矸石复合粉体均表现出较高的可见光光催化降解能力,并且Bi5O7I/Bi4O5I2/煤矸石复合粉体的光催化活性要大于BiOI/煤矸石复合粉体的光催化活性.Bi5O7I/Bi4O5I2/煤矸石复合粉体三次循环利用后光催化2h对罗丹明B的降解率仍可达到88.9;,可重复使用.     

金属离子掺杂ZnO晶体的制备及其光催化性能的研究

本文采用水热合成法,以3 mol/L KOH为矿化剂,填充度为35;,分别在ZnO中添加SnCl4·5H2O、CoCl2·6H2O、NiCl2 ·6H2O作为前驱物,温度430℃,反应24h,合成几种金属离子掺杂的ZnO晶体.采用扫描电镜(SEM)和X射线衍射(XRD)对其形貌进行了表征.并与用同种方法合成的纯ZnO的光催化效率进行了对比.结果表明:金属离子掺杂的ZnO晶体和用同种方法合成的纯ZnO晶体对亚甲基蓝均具有光催化活性,其中Sn掺杂的ZnO晶体的光催化性能较好,并且经过10次循环实验后仍保持较高的催化效率.     

Ce掺杂ZnO纳米晶的光催化性能研究

以Zn( NO3)3·6H2O、Ce( NO3)3·6H2O为原料,明胶为模板分散剂,采用凝胶模板燃烧法制备纯ZnO和Ce/ZnO纳米晶,利用XRD、TEM、BET、UV-Vis漫反射进行表征.以染料罗丹明B为目标降解物考察了样品的光催化活性.结果表明:产物粒子形状基本为球形,结晶良好,属六方晶系结构.相比纯ZnO,Ce/ZnO对光具有更高的吸收利用率,在紫外和可见光下对罗丹明B的降解能力均有明显提高;随Ce掺杂量的增加,样品的粒径减小,比表面积增大,罗丹明B的降解率相应增大,在紫外和可见光下降解率分别可达98.6;、78.3;,其原因在于Ce掺杂有利于在ZnO纳米粒子中心和表面之间产生电势差,实现光生电子-空穴对的有效分离.     

α-Fe2O3/TiO2光催化剂的制备及可见光催化降解罗丹明B的研究

采用浸渍法制备不同掺杂量的负载型光催化剂 α-Fe2O3/TiO2,通过XRD、SEM-EDX、XPS和N2-sorption等手段对其进行表征,并研究其在可见光照射下对罗丹明B的降解性能.考察了不同掺杂量的复合纳米粒子、不同浓度的H2O2溶液、不同pH等条件对可见光降解罗丹明B的影响.结果表明,复合α-Fe2O3/TiO2催化剂的光催化活性均高于单一的α-Fe2O3或TiO2,其中α-Fe2O3掺杂量为6.0wt;的α-Fe2O3/TiO2的光催化活性和光降解稳定性最好.     

镧掺杂混晶结构TiO2纳米粉体的制备及其光催化性能

以钛酸四丁酯为Ti源,采用溶胶-凝胶自蔓燃法制备了镧掺杂的La-TiO2(简写为LT)纳米粉体.利用X射线粉末衍射(XRD)、红外光谱(FIIR)、透射电子显微镜(TEM)等对掺杂型TiO2粉体的晶型结构与颗粒尺寸等进行表征.利用紫外-可见光吸收光谱(UV-vis)研究了H2O2改性、镧掺杂量以及混晶结构对TiO2纳米粉体降解甲基橙的影响.结果表明:镧掺杂混晶TiO2粉体的光催化活性明显优于未掺杂的锐钛矿TiO2粉体.当La3+掺杂量为0.5;,合成温度为475℃(金红石相含量为26.0;)时,得到的TiO2粉体光催化活性最好.H2O2的加入有助于TiO2光催化剂表面的电子-空穴对生成,提高光催化剂对甲基橙的降解率,当H2O2浓度为6;时,光照3h后,降解率达到了91.97;.     

铝掺杂超细氧化锌粉体的制备与性能研究

本文以Zn(NO3)2·6H2O和Al(NO3)3·9H2O为原料采用均匀沉淀法制备了Al掺杂ZnO(ZAO)超细粉体,用XRD、SEM、纳米粒度分析仪及四探针电阻仪等对ZAO超细粉体进行了测试表征.研究了反应温度、煅烧温度、反应物浓度、Al掺杂量及分散剂添加量对ZAO超细粉体形貌、尺寸及电阻率的影响.研究结果表明:制备的ZAO粉体为纤锌矿结构;煅烧温度为550℃时,ZAO晶相形成很好;随着Al掺杂量的增加,ZAO粉体电阻率降低,晶格常数减小,但当Al掺杂量大于2.0 mol;时,生成尖晶石相,其电阻率反而上升.     

稀土金属Ce3+掺杂ZnO材料的光催化机理

通过溶胶凝胶法制备了光催化活性更高的Ce∶ZnO复合粉体光催化材料,并采用X射线衍射(XRD)、电子顺磁共振(EPR)、紫外可见光谱(UV-Vis)技术对所制备的粉体样品的晶体种类及结构、自由基种类及含量、光催化效率进行表征分析。复合样品的X射线衍射测试结果显示,随着掺杂浓度的增加,先后检测到CeO₂的(111)和(200)晶面特征峰,且衍射峰强度逐渐增强。此外,适量的掺杂(c(Ce³⁺)=2%)可减小ZnO晶体的晶粒尺寸。电子顺磁共振测试结果显示,Ce∶ZnO复合光催化材料中存在三类自由基,分别是Zn-H络合物、正一价氧空位、CeO₂表面吸附的超氧根离子。紫外可见光谱测试表明,适量的掺杂可有效提高ZnO催化剂的光催化活性,综合分析显示,ZnO光催化活性提高的主要原因是Ce³⁺的掺入使得材料中电子数量增多,进而提高了活性自由基·O^-₂的数量。本文通过EPR技术和XRD衍射技术,成功表征了Ce³⁺掺杂对ZnO材料中自由基种类合成的影响过程,并结合UV-Vis技术,对Ce∶ZnO复合材料光催化降解甲基橙的过程中的电子转移过程作出了合理的解释。     

ZnO/Fe2O3复合结构的制备及光电化学性能研究

采用水热法在FTO导电玻璃上制备出大面积高能面裸露的ZnO纳米片阵列.采用旋涂法在纳米片表面制备Fe2O3纳米颗粒形成ZnO/Fe2O3复合结构.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见光吸收光谱和三电极光电测试系统对复合薄膜的结构组成、形貌、光学性能和光电化学性质进行了表征和分析.研究结果表明,随着Fe2O3复合次数的增加薄膜的光吸收范围逐步拓宽到可见光区,ZnO/Fe2O3复合结构光电极的光电流明显高于单纯的ZnO纳米片阵列光电极.     

石墨烯/Fe3O4/ZnO磁性纳米催化材料的制备及其性能研究

以石墨烯为助催化剂,借助水热法合成石墨烯/Fe3O4/ZnO磁性纳米复合光催化材料对ZnO改性.光催化降解测试显示复合材料对对硝基苯酚和罗丹明B降解率可分别达到95.7;和94.2;,重复试验3次后,降解率仍超过90;.对复合材料在光催化体系中磁性回收利用进行了研究,其饱和磁化强度为23.05 emu·g-1,并讨论了其光催化反应机理.     

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...     

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.     

A SAXS study of kinetics of aggregation of silica sols

SAXS in situ experiments on the evolution of TMOS solutions during hydrolysis and polycondensation lead to power laws with scaling exponents ≈ 2. It is suggested that this could be the result of the polydispersity of the samples and that only an apparent fractal dimension can be obtained in this way. Kinetic studies tend to indicate that agglomeration in the sol is the result of a diffusion-controlled process.     

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.     

Investigation of the Mechanism of Influence of Stress Corrosion on the Development of Macroplastic Instabilities of Aluminum–Magnesium Alloy

Crystallography Reports - Macroscopic jumps of plastic deformation (few percent in amplitude) on creep curves of aluminum–magnesium alloy, caused by a local effect of concentrated solution of...     

Study of the possibility of interactive control of the surface profile of X-ray optical elements

We investigate the possibility of controlling the curvature parameters of parabolic mirrors that are modular elements of two types consisting of a base and thin inserts placed at the opposite side of the work surface. In the first type of modular elements, bending is controlled by the difference in the coefficients of the thermal expansion of the base and inserts. In the second type of elements, the profile is changed by the piezoelectric straining of the inserts under an electric field. A correlation is established between the parameters of modular elements and their surface curvature profile.     

Mechanism of thermal expansion of structural modifications of zinc pyrovanadate

Crystal chemical characteristics of the α and β modifications of Zn₂V₂O₇ are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn₂V₂O₇ unit cell in the temperature range of 300–600°С, α _V =–17.94 × 10^–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn₂V₂O₇ is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices.     

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.