超疏水光催化协同自清洁表面研究进展

超疏水光催化自清洁表面同时具有物理自清洁和化学自清洁性能,近年来已成为研究热点.主要介绍了超疏水表面、光催化表面的自清洁原理和制备方法,阐述了超疏水光催化协同自清洁表面的制备原理及其在纺织品基材和其他基材上的研究现状,并展望了超疏水光催化协同自清洁表面的发展前景和趋势.     

氯氧化铋晶体的制备及其表征研究

采用铋盐转化水解法制备了四方相氯氧化铋晶体,研究反应温度、水解反应用水量以及反应液滴加顺序对产物粒径、产率及表面形貌的影响.结果表明,最佳反应条件为Bi(NO3)3·5H2O与HCl摩尔比为1∶5,反应温度为25～30℃,反应液滴加顺序为A→B,用水量为35 mL.该条件下制备出片状氯氧化铋晶体颗粒粒径0.5～2 μm,产物分散性良好.利用马尔文激光粒径分析仪、X射线衍射仪(XRD)、热场发射扫描电子显微镜(SEM)对氯氧化铋的粒度分布、晶面结构和微观形貌分析可知,所制备的氯氧化铋粒径分布符合正态分布曲线,且纯度高无任何杂质,反应液滴加顺序对产物形貌影响较大.     

分相铁红釉的研制及微观结构分析

采用钾长石、石英、苏州土、滑石、牛骨灰、氧化铁等原料制备出分相铁红釉,研究了釉料配方以及釉层厚度对分相铁红釉的影响,利用X射线衍射仪(XRD)、扫描电镜(SEM)和能谱分析仪(EDS)等手段,对铁红釉的微观结构进行了表征.结果表明:牛骨灰、氧化铁、滑石的添加量对铁红釉有显著的影响;釉表面红色区域Fe元素含量远远大于棕褐色区域,并富聚有大量的α-Fe2O3晶体;同时,在釉的断面也发现有大量晶体析出,呈上密下稀的分布规律;铁红釉最佳的釉层厚度应控制在0.8 ～1.0 mm范围之内.     

钨基陶瓷结晶釉的快速结晶制备及其光催化性能探索

本文通过对钨基陶瓷结晶釉材料进行了快速结晶制备,所得釉层晶相为WOP2O7结构.通过扫描电镜分析发现其表面具有显著地结晶化特征形貌,进一步结合EDS能谱分析发现其表面形貌有钨基结晶釉相和底釉相两种结构构成.在光催化性能探索中发现该釉层材料在紫外可见光照射下展现出一定的催化降解罗丹明B溶液的能力,为陶瓷结晶釉材料的功能化价值提升提供了参考.     

Al液滴在GaAs表面的熟化行为研究

为探究Al液滴在GaAs表面的熟化行为,利用液滴外延法在GaAs衬底表面制备Al液滴.在零As压环境下,通过控制退火时间有效控制Al液滴的生长、成核.结合热力学原理和晶体生长理论对样品形貌变化现象进行物理解释,构建出液滴形貌变化过程中熟化、刻蚀和扩散行为的基本模型.理论计算表明,液滴在熟化行为达到退火239 s的平衡点后,被向下刻蚀和向外扩散两个行为同时消耗.     

银色金属光泽釉的研制及微观结构分析

通过在基础釉中添加金属氧化物MnO2 、CuO和V2O5,在随炉冷却的烧成制度下,成功制备了银色金属光泽釉.采用L9 (33)正交实验的方法研究了MnO2、CuO、V2O5加入量对釉面效果的影响.利用X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)对釉层的微观结构进行了表征.研究表明:(1)CuO加入量对釉面金属光泽的产生显著影响,V2O5的影响不明显,当CuO加入量小于3;时,釉层为透明状.随着MnO2和CuO加入量的增大,釉面逐渐呈现无光及变色的趋势,MnO2、CuO、V2O5的推荐加入量分别为4;、3;和2;.(2)釉层中存在大量亚微米级甚至纳米级片状晶体.晶体尺寸均匀,表面平整光滑,并形成大面积平面网状排布.(3)釉层中大量沿坯体表面平行生长的片状晶体容易对光线造成强烈的镜面反射,是造成釉面出现高亮度银色金属光泽的重要原因之一.     

In原子在GaAs(001)表面的成核与扩散研究

近年来,半导体量子点特别是InAs量子点的基本物理性质和潜在应用得到了广泛研究。许多研究者利用InAs量子点结构的改变以调制其光电特性。本文采用液滴外延法在GaAs(001)表面沉积了不同沉积量的In(3 ML、4 ML、5 ML),以研究In的成核机制和表面扩散。实验发现,随着In沉积量的增加,液滴尺寸(包括直径、高度)明显增大。不仅如此,在相同的衬底温度下,沉积量越大,液滴密度越大。利用经典成核理论,计算了GaAs(001)表面In液滴形成的临界厚度为0.57 ML,计算的结果与已报道的实验一致。从In原子在表面的迁移和扩散,以及衬底中Ga和液滴中的In之间的原子互混原理解释了In液滴形成和形貌演化的机理。实验中得到的In液滴临界厚度以及In液滴在GaAs(001)上成核机理,可以为制备InAs量子点提供实验指导。     

分子束外延生长过程中GaAs(001)表面铝液滴的扩散成核过程

量子点的性质主要由其密度及尺寸参数控制,而原子在衬底上的成核运动又决定了量子点的密度、直径、高度等参数,因此研究原子的扩散成核过程对自组装制备量子点具有重要意义。本文通过分子束外延生长技术研究了GaAs(001)表面金属铝液滴的成核过程,发现衬底温度和金属铝沉积速率的变化直接影响了液滴的尺寸、密度以及形状等特征。根据经典成核理论分析GaAs(001)表面金属铝液滴空间分布与几何结构的演化规律,推导得出表面金属铝液滴密度与衬底温度、金属铝沉积速率的关系方程。在此基础上,进一步计算得出液滴形成过程中未成核态、临界成核态、成核态三种亚稳态所包含的最小原子数分别为1个、2个、5个。     

烧成制度对R2O-CaO-Al2O3-B2O3-SiO2分相乳浊釉的影响研究

用DSC、色度仪、XRD、SEM等仪器对R2O-CaO-Al2O3-B2O3-SiO2分相乳浊釉样品进行检测分析,探究烧成制度对釉面性状及显微结构的影响.结果表明,升温速率快慢影响釉中组分扩散和迁移的时间,致使釉中分相液滴的尺寸分布、平均粒径、体积分数产生变化,釉面呈现乳蓝、乳白等效果;提高烧成温度可促进釉层中组分的相互扩散,在1160～1220℃范围内可得到白度大于70;的光亮乳浊釉面,温度过高容易导致釉面出现针孔缺陷;降温冷却过程中釉熔体在热力学和动力学相互作用下发生分相现象,分相液滴的组分、形貌和尺寸是此过程中某一瞬时的平衡态,因此降温冷却过程对分相乳浊釉有重要影响.     

分形理论在硅酸锌系结晶釉研究中的应用

本实验对采用不同工艺条件(析晶温度、析晶保温时间、釉层厚度)制备出具有晶花形貌的硅酸锌系结晶釉,应用分形理论对其晶花形貌进行了研究.结果发现该结晶釉的晶花形貌具有良好的分形特征,并且分形与制备工艺存在一定关系:随着析晶温度的增加,分形维数值与析晶温度除了在1140 ℃时稍有波动,基本上是成反比例关系,结晶形貌的变化趋势由针状或棒状转化为叶片状或圆盘状;随着析晶保温时间的增加,分形维数值逐渐增大,结晶形貌由针微晶逐渐转化成放射状晶体,尺寸也有明显增大的趋势;随着釉层厚度的增加,结晶产物的分形维数明显减小.     

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.     

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 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.     

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.     

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.     

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.     

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.     

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.     

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...