The Nature of Nanoparticles of Crystalline Phases in Cenospheres and Morphology of Their Shells

Cenospheres prepared using fly ashes from combustion of Kuznetskii coals are investigated by Mossbauer spectroscopy, scanning electron microscopy (SEM), and thermodynamic analysis. It is shown that, in the composition range with an iron content of lower than 3.3 wt %, cenospheres involve nanosized crystalline phases, such as feldspars, ferrispinels, and pyroxenes. It is revealed that the outer and inner surfaces of the cenospheres are covered with 30- to 50-nm-thick nanofilms enriched in nanosized crystalline phases. The sizes of crystalline inclusions are estimated by etching the surface film in mineral acids with the formation of a nanosized porosity.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, N. Anshits, Vereshchagina, Bayukov, Salanov, A. Anshits.     

Structure and Catalytic Properties of Iron-Containing Bimetallic Catalysts

The world's largest industrial process, ammonia synthesis, uses promoted iron catalysts. Fifty years ago fused and promoted iron catalysts were first utilized in the Fischer-Tropsch synthesis. The importance of this latter process has increased during the last few years because of the current energy crisis. Iron sulfide catalysts were also used by Varga [1] for the high pressure hydrogenation of coal. This procese, however, has been substituted by other methods.     

Mullitization of Andalusite and Influence of Aggregates on Properties of Aluminosilicate Refractories Based on Andalusite Matrix

The mullitization of andalusite from Xinjiang,China and influence of aggregates on properties of aluminosilicate refractories were studied by XRD,SEM,EDS,DSC.It was found that mullitization was obvious at 1 400 ℃,but considerable at 1 500 ℃.The refractories with corundum aggregates had the highest RUL and the lowest creep rate,but refractories with bauxite aggregates had the lowest RUL and the highest creep rate.     

高分散性纳米铁的制备及其表征

以可生物降解的聚苯乙烯磺酸钠(PSS)为分散剂,制备了能稳定分散于水中的零价纳米铁(nZⅥ).未改性的零价纳米铁呈规则的球形或椭球形,平均粒径为60～80 nm,经PPS分散后的纳米铁nZVI/PSS则呈现微小的粒状分散在PSS中.pH=8时,与nZVI相比,nZVI/PSS的ζ电位由+9.4 mV降至-36.7 mV,同时等电点也由8.7变为小于5.XPS分析结果显示,nZVI和nZVI/PSS表面元素构成相同,但nZVI/PSS表面有零价铁存在,而nZVI表面则主要由铁的氧化物组成.实验结果表明,两种纳米铁对Cr(VI)的去除率非常接近,在纳米铁投加量为1.0g·L-1,Cr(VI)初始浓度为100 mg·L-1的条件下,Cr(VI)的去除率在10 min内均能达到95％,在30 min内能达99％,表明nZVI/PSS具有较高活性.     

Study of Crystallization and Spectral Properties of Zinc Sulfide Nanoparticles in Mesoporous Matrix

The aim of this work is to report the optical and structural properties of ZnS nanoparticles in mesoporous matrix. The samples were obtained by sulfidation of the Zn²⁺ ion-exchange mesopore in a Na₂S solution at room temperature. The final product (ZnS/MCM-41) was characterized by X-ray diffraction (XRD) pattern, transmission electron microscopy, scanning electron microscopy (SEM), infrared spectrometry and UV–Vis spectroscopy. Its crystalline structure and morphology was studied by XRD and SEM. Exciton absorption peaks at higher energy than the fundamental absorption edge of bulk ZnS indicates quantum confinement effects in nanoparticles as a consequence of their small size.     

Formation and Properties of Calcium Aluminosilicate Glasses

The glass-forming region for calcium aluminosilicate glasses has been determined. A number of properties of these glasses (thermal expansion coefficient, glass transformation and dilatometric softening temperature, and refractive index) have been studied. The results of these measurements suggeq that the structures of these glasses may not as closely resemble those of alkali aluminosilicate glasses as is commonly assumed. Evidence is presented which suggests that the binary calcium aluminate glasses may be phase separated.     

Fracture Behavior of SiC-Whisker-Reinforced Barium Aluminosilicate Glass-Ceramic Matrix Composites

Barium aluminosilicate (BAS) glass-ceramic composites reinforced with various volume percents (0, 10, 20, 30, 40 vol%) of SiC whiskers were fabricated by hot pressing. The microstructure, the whisker/matrix interface structure, the phase constitution, and the mechanical properties of the composites were systematically studied by means of SEM, TEM, and XRD techniques as well as by indentation crack microfracture and single-edge-notched-beam bend testing. It was demonstrated that the incorporation of SiC whiskers could significantly increase the flexural strength and fracture toughness of BAS glass-ceramic matrices. The addition of active Al₂O₃ to the BAS matrix reduced the amount of SiO₂ in the matrix, forming needlelike mullite, which further improved the mechanical properties.     

Effect of Adding Cenospheres on Heat-Resistant Lightweight Concrete Properties

Refractories and Industrial Ceramics - Results are provided for a study of the effect of adding cenospheres (coal combustion waste) on hydration of alumina cement and exothermic reaction...     

Fracture of an Aluminosilicate Fiberboard

Mode-I fracture of aluminosilicate fiberboard that is used in large mirror casting molds was studied. The material was idealized as a transversely isotropic, layered composite that was composed of planar sheets of crosslinked fibers. Elastic constants, the toughness ( K_R ) curve, and the fracture work were measured at room temperature. The observed rising K_R behavior was attributed to crack bridging. Experimental measurements of the bridging stress were made using a specimen-renotching technique. Relationships between the bridging stress, K _R , and fracture work were explored and shown to be consistent.     

Elastic Properties and Molar Volume of Rare-Earth Aluminosilicate Glasses

The elastic properties, molar volume, and glass transition temperature ( T _g) of rare-earth-containing aluminosilicate glasses were investigated in the compositions of SiO₂–LnAlO₃ and SiO₂–Ln_3/4Al_5/4O₃, where Ln is Y, La, Nd, Eu, or Yb. The molar volume decreased with decreased ionic size of the Ln³⁺ ion, and T _g and elastic moduli increased in the same order. The Yb-containing glasses showed the highest Young's modulus among all the oxide glasses, even higher than the highest value ever known for glass containing Y₂O₃, as expected from the smaller ionic radius of Yb³⁺ than that of Y³⁺. The bulk modulus was found to be almost proportional to the inverse four-thirds power of the molar volume of glasses in each composition, indicating that Ln³⁺ ions can substitute for each other without changing the glass structure except for the size of the local structure around themselves. From the comparison of these properties, the structural role of rare-earth ions in these glasses is discussed.     

Microscopic Origins of Compositional Trends in Aluminosilicate Glass Properties

Revealing and understanding the microscopic origins of the macroscopic properties of aluminosilicate glasses is important for the design of new glasses with optimized properties. In this work, we study the composition‐structure‐property relationships in 20 MgO/CaO sodium aluminosilicate glasses upon Al₂O₃‐for‐SiO₂ and MgO‐for‐CaO substitutions. We find that some properties (density, molar volume, Young's modulus, and shear modulus) are linear through the investigated range of Al₂O₃ compositions, while others (refractive index, coefficient of thermal expansion, Vickers hardness, isokom temperatures, and liquid fragility index) exhibit a change in the slope around the composition with [Al₂O₃] = [Na₂O], which is especially pronounced for the glasses containing MgO. We discuss these phenomena based on structural information obtained by NMR spectroscopy and topological considerations.     

天然产物绿色合成小尺寸纳米银及抗菌性

利用液相化学还原法,以硝酸银作前驱体,采用天然产物壳聚糖和葡萄糖分别作稳定剂和还原剂制备了小尺寸的球形纳米银(AgNPs)。运用紫外-可见分光光度计(UV-vis)、透射电子显微镜(TEM)和X射线衍射(XRD)技术对一系列AgNPs样品进行了表征,并考察了稳定剂、前驱体和还原剂的浓度、pH、反应温度和时间等制备条件对AgNPs成核或生长过程的影响。通过调节制备条件可调控AgNPs的尺寸分布,得到粒径分别为(3±1)nm、(6±2)nm和(9±3)nm分散均匀且稳定的AgNPs。采用OD600法对AgNPs的抗菌性进行了测试,结果表明,AgNPs对大肠杆菌(E.coil)和金黄色葡萄糖球菌(S.aureus)都有很好的抑制作用。     

Transverse Fracture of an Aluminosilicate Fiberboard

Mode I transverse fracture of an aluminosilicate fiberboard was studied under ambient conditions. The material showed tension softening behavior when loaded perpendicular to the isotropic plane. The measured softening curve was treated as the cohesive bridging stress function in a fictitious crack model. The observed peak loads, fracture energy, apparent fracture toughness, and load–displacement curves of various double cantilever beam specimens were shown to be consistent with model predictions.     

Properties of Soda Aluminosilicate Glasses IV, Relative Acidities and Some Thermodynamic Properties

Electrochemical cells using the oxygen electrode reactions of Förland and Tashiro were constructed from soda aluminosilicate glasses (containing up to 34.8 wt% alumina) and sodium silicate glasses. The emf developed by these cells was measured as a function of temperature. The relative acidities of the glasses, as indicated by the activities of the soda, increased with increasing alumina content, the rate of change increasing when the Al/Na ratio reached 1. The entropy change for the cell reaction went through a maximum. These properties are correlated with the measurements of, and the structural model used in, the previous three parts of this series. Measurements were made to show that the emf values obey an additive relation.     

Synthesis and Characterization of Highly Dispersed Antimony-Doped Stannic Hydroxide Nanoparticles: Effects of the Azeotropic Solvents to Remove Water on the Properties and Microstructures of the Nanoparticles

Highly dispersed antimony (Sb)-doped stannic hydroxide nanoparticles have been successfully prepared using the solution chemistry method. The properties and microstructures of the nanoparticles are investigated in detail by means of infrared, transmission electron microscope, X-ray diffractometer, and Brunauer-Emmett-Teller nitrogen surface area measurements. The results indicate that the properties and microstructures of the nanoparticles strongly depend on the azeotropic solvents used to remove water at the drying stage. Various azeotropic solvents are screened to investigate their effects on the size and dispersivity of dried Sb-doped stannic hydroxide. Three empirical rules are drawn for selecting an effective azeotropic solvent: (1) the solvent molecule should contain at least one atom such as oxygen as the hydrogen (H)-bond acceptor to form H bonds with the surface –OH (acting as an H-bond donor) of polymer particle; (2) the H-bond acceptor should locate in the middle of the alkane chain rather than on the terminal so that the alkane chain can stretch out and cover more surface area, improving the dispersivity of the dried product; and (3) the solvent should have a higher boiling point (∼140°C) to reduce the time of azeotropic distillation for removing water and maintain a lower residual amount of azeotropic agent. Based on the empirical rules, it is discovered that iso-amyl acetate is the most effective azeotropic solvent.     

Dielectric and Thermal Properties of Tetragonal PbTiO3 Nanoparticles/Clusters Embedded in Lithium Tetraborate Glass Matrix

Silicon - PbTiO3 nanoparticles/clusters embedded in lithium tetraborate glass matrix (glass nanocomposite (GNCs)) of composition (100-x) Li2B4O7-xPbTiO3 (where x = 5, 10, 15 and 20 in...     

无机纳米微粒在聚合物中的复合与组装

介绍了将纳米微粒引入聚合物光学材料制备高功能性的复合光学树脂,以及通过在有序膜中的界面组装制备功能化复合膜材料的工作,并研究了复合材料中纳米微粒的性质.     

BaO/ZnO对无碱铝硅酸盐玻璃体系物理性能的影响

以SiO2-Al2O3-RO系统为基础玻璃组成,掺杂BaO和ZnO,采用传统熔体冷却法制备了高温玻璃釉,借助于膨胀系数测试仪、烧结影像仪和Keythley 2410型高压源表测试分析方法,重点探讨了BaO和ZnO对高温玻璃釉的膨胀系数、烧成温度和电阻率的影响。结果表明:随着BaO质量分数的增加,玻璃釉的熔融温度呈下降趋势,但是玻璃釉的膨胀系数和电阻率不断增大;随着ZnO质量分数的增加,玻璃的膨胀系数呈增大趋势,但是玻璃釉的熔融温度和电阻率不断的降低。