Bi4Ti3O12/BiOBr复合材料的溶剂热合成及可见光催化性能

采用一步溶剂热法合成了Bi4Ti3O12/BiOBr复合光催化剂,采用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积及孔径测定仪(BET)以及紫外可见漫反射光谱仪(DRS)等对样品的组成、形貌及可见光催化性能等进行了表征,讨论了合成条件对样品光催化活性的影响,探究了光催化反应过程中的活性物种及反应机理.研究结果表明,Bi、Ti、Br的投料比为10∶7∶5、乙二醇为溶剂、聚乙烯吡咯烷酮为表面活性剂且加入量为0.2g时,合成样品具有较高的光催化活性和较好的循环稳定性.在7 W LED灯照射140 min后,光催化剂对罗丹明B(RhB)的降解率达到85.1;.·O2-与h+在降解过程中起主要作用.     

不同酸性助剂水热合成钨酸铋的制备及光催化性能研究

以Bi(NO3)3·5H2O、Na2WO4·2H2O为原料,NaOH为矿化剂,采用水热法合成Bi2WO6纳米晶体,并使用XRD、SEM、TEM、DRS和低温氮吸附等手段对样品进行表征,考察了其可见光降解RhB的催化性能,分析了不同酸性助剂CH3 COOH和HNO3对水热法合成Bi2WO6光催化剂的影响.实验结果表明,不同酸性助剂对Bi2WO6样品的形貌和可见光催化活性均有较大影响.HNO3的添加抑制了花状微球的形成,使Bi2WO6样品的紫外-可见光吸收边发生红移,比表面积增大.光催化测试结果表明,以HNO3为酸性助剂时所制备样品的光催化活性最高,添加CH3COOH则相对降低.     

微波合成Bi2S3/g-C3N4复合光催化剂及其光催化性能研究

采用微波合成法制备了Bi2 S3/g-C3 N4复合光催化剂,利用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)、紫外可见-漫反射吸收光谱(Uv-vis)、物理吸附仪(BET)等对其进行了表征,以罗丹明B(RhB)为目标化合物对其光催化性能进行了评价.结果表明,与纯Bi2 S3和g-C3 N4相比,复合样品的禁带宽度变小,比表面积增大,光生载流子的复合效率降低,显著提高了其光催化降解RhB的效率.复合样品5-CNBS对RhB的降解率达99;以上,分别是纯g-C3 N4和Bi2 S3单体对RhB降解效率的1.59倍和4.95倍.     

Bi3Ti4O12/α-Bi2O3/TiO2复合光催化剂的制备及其可见光催化活性研究

以工业二氧化钛(TiO2)、五水合硝酸铋(Bi(NO3)3·5H2O)为原料制备了Bi3Ti4O12/α-Bi2O3/TiO2复合光催化剂.采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、紫外-可见吸收光谱(UV-Vis)、荧光光谱(PL)等表征方法对光催化剂结构进行分析,表明复合样品中形成了Bi3 Ti4 O12/α-Bi2 O3/TiO2异质结结构,其禁带宽度减小、吸收带边红移,光催化效率有明显提高.以亚甲基蓝为目标污染物评价其光催化活性,TiO2与Bi(NO3)3·5H2O质量比为1:2.5,煅烧温度为600℃,煅烧时间为5 h时,复合样品光催化活性最佳,在12 W LED灯下,180 min后对浓度为10 mg/L的亚甲基蓝溶液的去除率达96.8;.     

不同形貌的钨酸铋纳米材料的制备及其光催化性能

利用水热法通过调节溶液pH值和表面活性剂CTAB浓度制备了不同结构与形貌的钨酸铋纳米材料,用X射线衍射(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)等测试方法对产物进行了结构与形貌的表征,并研究了不同结构与形貌的钨酸铋样品对甲基橙的可见光催化降解性能.结果表明,在低pH值时样品为Bi2WO6相纳米片,随着pH值的增加,样品中出现了Bi3.84W0.16O6.24相八面体纳米颗粒,高pH值时,样品则为纯Bi3.84W0.16O6.24相八面体颗粒.随着表面活性剂浓度的增加,Bi2WO6纳米片有自组装的趋势,最终形成花瓣状结构.光催化甲基橙实验结果表明不同形貌的钨酸铋样品对甲基橙有不同的催化降解活性,片状Bi2WO6相纳米片高于Bi3.84W0.16O6.24相八面体颗粒.     

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.     

Bi2O3/g-C3N4/TiO2三元复合物的制备及其可见光催化活性研究

以工业纳米TiO2,三聚氰胺(C3H6 N6)和硝酸铋(Bi(NO3)3·5H2O)为原料,通过高温煅烧制备Bi2O3/g-C3 N4/TiO2三元复合物,采用XRD、XPS、FT-IR、UV-vis、PL光谱等对其结构进行了表征.结果表明g-C3 N4和Bi2O3分散覆盖在TiO2表面,形成具有异质结结构的Bi2O3/g-C3N4/TiO2三元复合物,其带隙降低,对可见光的吸收增强,电子和空穴通过在Bi2O3、g-C3N4和TiO2三者界面间的转移有效延长了光生载流子的寿命,从而提高光催化效率.以亚甲基蓝为目标污染物评价其光催化活性.结果表明,当TiO2与C3H6N6质量比为1∶2.5,Bi(NO3)3·5H2O含量为0.35;,煅烧温度为520℃,煅烧时间为5h时制得的Bi2O3/g-C3 N4/TiO2三元复合物(即0.35Bi/C/T)活性最高,LED灯(12 W)光照180 min后对10mg/L亚甲基蓝溶液降解率达98.1;.     

Ag3 PO4量子点修饰Ag3 PO4/Bi2 WO6异质光催化剂的构筑及其可见响应活性增强机制

采用水热法制备了三维分级球形结构的Bi2 WO6,在此基础上采用沉淀-沉积法将Ag3 PO4量子点(QDs)沉积在Bi2 WO6的表面,成功获得Ag3 PO4/Bi2 WO6异质复合材料光催化剂.借助XRD、FE-SEM、TEM、UV-Vis-DRS等技术对所得Ag3 PO4/Bi2 WO6异质复合材料光吸收性能、形貌和组成进行了系统表征,并以次甲基蓝(MB)和苯酚(Ph)的光催化降解为探针反应,探讨了Ag3 PO4 QDs表面沉积对Bi2 WO6光催化性能的影响.结果表明,尺寸约为10 nm左右的Ag3 PO4 QDs均匀的沉积在Bi2 WO6的表面,二者形成新颖的Ag3 PO4/Bi2 WO6异质结构.活性实验结果表明,与纯Bi2 WO6相比异质催化剂的活性显著增强,当Ag3 PO4与Bi2 WO6复合比为1:1时催化活性最高,其降解Ph的表观速率常数(kapp/min-1)约为纯Bi2 WO6的7倍.     

可见光响应型ZnO/Bi2O3复相光催化剂的制备及其性能研究

以Zn(Ac) 2·2H2O和Bi( NO3)3·5H2O为主要原料,采用溶胶-凝胶法成功制备了可见光响应型的高效复相ZnO/Bi2O3催化剂.利用X射线衍射(XRD)、扫描电镜(SEM)对样品进行了表征,并以甲基橙为目标污染物,测试样品的光催化性能,研究了初始合成条件、光源等对样品光催化性能的影响.实验结果表明:在nZn∶nBi为1∶1,浓度为0.05 mol/L条件下制得的凝胶,经600℃煅烧2h后,样品呈现六方纤锌矿结构的氧化锌晶相并伴有单斜α-Bi2O3、三斜ω-Bi2O3晶相.在16 W紫外灯、500W卤素灯照射下,2.5h后,甲基橙的脱色率为95.73;,68.36;,而经太阳光照射2.5h,甲基橙的脱色率分别为53.8;,但将其继续置于阳台上24h,脱色率可达97.6;.在16 W紫外灯的辐照下,样品重复使用6次,甲基橙的脱色率仍在90;以上,表明催化剂具有较高的重复使用率.     

不同形貌Bi2WO6的可控合成及光催化机理研究

采用水热、溶剂热的合成方法制备了Bi2WO6纳米材料,利用X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)和紫外–可见漫反射光谱(UV-Vis DRS)研究了水热、表面活性剂、溶剂热制备方法及制备条件对Bi2WO6材料的形貌、结晶性、粒径等性质及Bi2WO6可见光催化性能的影响.结果表明:与水热法合成的圆片型和花瓣状Bi2WO6相比,醇热法合成的空心球形貌的Bi2WO6具有最高的光催化效果.随着焙烧温度升高,空心球逐渐塌陷,样品的光催化活性也大幅度下降.捕获剂活性实验表明,空心球Bi2WO6在光催化降解罗丹明B反应中的主要活性物种为空穴(h+)和超氧自由基(·O2-).     

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...     

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.     

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.     

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...     

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.     

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.     

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.     

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.