Viscosity and Thermal Expansion of Sodium and Potassium Galliosilicate Glasses

The transformation-range viscosity and thermal expansion behavior of several series of sodium and potassium galliosilicate glasses were studied. The trends observed in the results are similar to those found for alkali aluminosilicate glasses. This result suggests a similarity in the structural roles of aluminum and gallium ions. The present data are discussed in terms of this structural role. In addition, the influence of silica content, alkali content, and alkali identity on the thermal properties of these glasses is discussed.     

Thermal Expansion Anisotropy of Oxides and Oxide Solid Solutions

The thermal expansion properties of the oxides stishovite (the rutile form of SiO₂), tetragonal vanadium dioxide, and zincite (ZnO) were measured. Solid solutions of rutile-, corundum-, and zincite-structure oxides were prepared, and the thermal expansion properties were measured in an effort to find compositions with more isotropic thermal expansion coefficients. The changes in the observed lattice constants and the changes expected on the basis of the cation radii were compared for both pure oxides and the oxide solid solutions. The difference in these changes indicates the variations to be expected in the thermal expansion anisotropy. A composition range containing the thermally isotropic composition in the system A1₂O₂,-Cr₂O₃ was determined, and the isotropic composition was estimated to be 75% Al₂O₃-25% Cr₂O₃.     

Synthesis and Thermal Stability of Aluminum Titanate Solid Solutions

Aluminum titanate solid solutions with empirical formulas of Al₂Ti_1-xZr_xO₅, Al_6(2-x)(6+x)Si_6x/(6+x)□_6x/(6+x)TiO₅, and Al_2(1-x)Mg_xTi_1+xO₅ were synthesized by reaction sintering and annealed at 900° to 1300°C in air to evaluate the thermal stability. Substitution of Al in Al₂TiO₅ by Si and 2Al by Mg and Ti ions to form solid solutions such as AI_{6(2-x)/(6+x)l-Si}6x/(6+x)□_6x/(6+x)TiO₅, and Al_2(1-x)Mg_xTi_1+xO₅ was effective in controlling the thermal decomposition, but substitution of Ti by Zr had little effect.     

Crystal Structures and Mechanism of Thermal Expansion of High Cordierite and Its Solid Solutions

The crystal structure of high cordierite and that of high cordierite solid solutions containing either Mn or Ga or Ge were refined. The structural changes caused by substitutions and the characteristic features of deformations of each T1O₄, T2O₄ tetrahedron and MO₆ octahedron were clarified. Thorough crystal chemical considerations led to a conclusion that the structure of Mn-bearing solid solution at room temperature may be regarded as a model structure of high cordierite at an elevated temperature. On the basis of the thermal expansion mechanism derived from this consideration, the thermal expansion behavior of the solid solutions is presented.     

Thermal Expansion of Synthetic β-Spodumene and β-Spodumene—Silica Solid Solutions

Synthetic β-Spodumene and several β-Spodumene-silica solid solutions were prepared, and their thermal expansion behavior was studied using high-temperature X-ray diffraction techniques. Data indicate that all β-Spodumenes are characterized by a pronounced anisotropy of thermal expansion much the same as that of the silica polymorph keatite. Anisotropy increases slightly and the volume expansion decreases as the compositions become richer in SiO₂. Specimens with more than 80.8 wt% SiO₂ at 130O°C and 1 atm contain P-cristobalite along with β-Spodumene. The lattice parameters of β-Spodumene compositions throughout the solid solution range were determined. The structural aspects of the anisotropy of thermal expansion are discussed.     

Dielectric Properties of Solid Solutions of Sodium Niobate-Lead Zirconate and Sodium Niobate-Lead Titanate

Solid solutions based on sodium niobate with limited amounts of lead and zirconium or lead and titanium solute ions have been investigated with respect to their dielectric constant versus temperature at 1 kc. per second from −175° to 300°C. Lead zirconate additions to sodium niobate up to 15 mole % cause an increase in dielectric constant, with a value of 1345 at 6°C. being the maximum recorded. Lead titanate additions to sodium niobate cause a general increase in dielectric constant up to 25 mole %, with 675 at 30°C. and 4670 at 154°C. being the maximum values recorded. Polarization versus applied field measurements up to 30,000 volts per cm. show nonreversible polarity for the lead zirconate compositions, whereas the compositions containing from 10 to 50 mole lead titanate are ferroelectric. An induced ferroelectricity phenomenon occurs for the composition containing 5 mole % lead titanate. A remanent polarization of 15 microcoulombs per sq. cm. at a coercive force of 7800 volts per cm. was obtained at room temperature for the composition 0.85 NaNbO₃–0.15 PbTiO₃.     

Structural Mechanisms of Anomalous Thermal Expansion of Cordierite-Beryl and Other Framework Silicates

The structural mechanisms controlling the anomalous thermal expansion behavior of the cordierite-beryl type structure and other framework silicates are discussed. The expansion of a particular silicate framework depends on the temperature response of the framework itself involving T–O–T and O–T–O angular changes, the expansion coefficient(s) of the nontetrahedral bonds, if present, and the interplay between these two factors. For cordierite, beryl, and β -eucryptite, expanding nontetrahedral bonds play a critical role in driving the anomalous thermal expansion observed. For β -spodumene and the feldspars, the thermal response of the framework dominates the expansion mechanism. The effects of channel constituents on the thermal expansion of the cordierite-beryl framework are also discussed.     

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

Ferrierite type zeolite can be synthesized without using any organic structure-directing agent from Na- or (Na, K)- or K-aluminosilicate system. (Na, K)-ferrierite is synthesized from wide range of OH/SiO₂ region of the reactant mixture compared with Na- and K-ferrierite. The crystallization process of ferrierite in each system is investigated in detail by X-ray diffraction and Raman spectroscopy. The role of potassium and sodium cations and cooperative effect of two cations in the formation of the framework of ferrierite are elucidated.     

Thermodynamic and Structural Properties of Sodium Lithium Niobate Solid Solutions

Thermodynamics of the Na_1−xLi _x NbO₃ system is investigated by high-temperature drop-solution calorimetry in molten 3Na₂O–4MoO₃ solvent at 973 K. Standard molar enthalpies of formation are derived. The estimated heats of transition between hypothetical and stable structures, lithium niobate and perovskite for NaNbO₃ and vice versa for LiNbO₃ are −6 kJ/mol and −10 kJ/mol, respectively. X-ray diffraction studies at room temperature showed for 0 ≤ x ≤ 0.14 there are three phases based on different ordering of the perovskite type lattice: orthorhombic with a quadrupled reduced perovskite cell at 0 ≤ x ≤ 0.02, orthorhombic with a doubled reduced perovskite cell at 0.015 ≤ x ≤ 0.14, and rhombohedral at 0.08 ≤ x ≤ 0.13. There are two two-phase (morphotropic) regions with coexistence of the two orthorhombic phases at 0.015 ≤ x ≤ 0.02 and with the second orthorhombic phase coexisting with the rhombohedral phase at 0.08 ≤ x ≤ 0.13. A reproducible anomaly in specific heat at ∼600 K, not reported previously, has been observed in pure NaNbO₃. Heat-capacity measurements confirm a phase transition at 553 K for 0.07 ≤ x ≤ 0.09. With increasing lithium concentration, a gradual disappearance of high-temperature phase transitions associated with tilting of oxygen octahedra has been observed.     

Synthesis and Thermal Expansion of Polycrystalline Cesium Minerals

CsAlSi₂O₆, CsAlGe₂O₆, CsFeSi₂O₆, CsFeGe₂O₆, and CsBSi₂O₆ were prepared by reaction of Cs₂CO₃ and oxides and by a base-exchange method. The compounds were characterized by optical examination and X-ray diffraction. Dilatometric measurements of the linear thermal expansions of the cubic silicate pollucites gave relatively low coefficients, but the expansion of the germanate analogs is considerably higher. Attempts at synthesis of CsCrSi₂O₆ and CsCrGe₂O₆ and the special nature of CsBSi₂O₆ are briefly described.     

负热膨胀材料钨酸锆研究进展

ZrW2O8是由0.3K至分解温度1050K都具有各向同性的负热膨胀化合物,但由于其窄的热稳定范围反应合成相当困难。本文综述了该材料的各种合成技术以及该材料的负热膨胀的机理,讨论了ZrW2O8的特性,介绍了其潜在的应用。     

Gelation in Multicomponent Colloidal Solutions Based on Potassium Liquid Glass

The influence of the pH, concentration, and temperature of a solution on the gelation period of the solutions containing colloidal phosphate ions is studied. The role played by the solution composition in the range of pH < 6 is revealed. The temperature dependence of the gelation period is determined.     

Thermogravimetric Analysis and Chemical Kinetics for Regeneration of Sodium and Potassium Carbonate Solid Sorbents

In this study, nonisothermal kinetic methods for the decomposition of potassium hydrogen carbonate (KHCO₃) and sodium hydrogen carbonate (NaHCO₃) were investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). Four different heating rates were measured to calculate the order of reaction (n), preexponential factor (A), and activation energy (E_a) using four different models: Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Kim–Park, and analytical methods. The results showed that the analytical method provided highly accurate results compared with the experimental data, whereas KAS, FWO, and Kim–Park methods gave less accurate results due to the approximation of employed equations. The order of the decomposition reaction of KHCO₃ and NaHCO₃ was approximately 2. The preexponential factor of KHCO₃ was slightly higher than NaHCO₃. The obtained kinetic parameters from those four methods then were used to calculate the chemical reaction conversion for further applications.     

固相反应合成磷酸锌钾多元微肥及其表征

以聚乙二醇-400为模板,K3PO4·3H2O与ZnSO4·7H2O为原料,经固相反应合成得到缓溶多元微肥磷酸锌钾.用X射线粉末衍射(XRD)、热重-差热分析(TG-DTA)、红外光谱(IR)以及扫描电镜(SEM)对产物进行了分析表征,结果表明产物为KZnPO4.该合成方法除了得到微溶的磷酸锌钾外,同时得到可溶的硫酸钾,合成的工艺简洁,生产过程无废水产生,无论是从工艺上,还是环保上均比液相法更具有优势,是一种颇具工业应用前景的合成法.     

用于RTM工艺的软模材料的热膨胀性能

建立了用于RTM工艺的软模材料的热膨胀—温度特性的测试方法,得到了软模材料的热膨胀参数。研究结果表明,和聚氨酯泡沫及R311硅橡胶相比,COCA31-11硅橡胶随温度上升能产生较大的膨胀力,因此初步确定COCA31-11为本文研究工作的软模材料,其在室温至180℃范围内线胀系数为2.65×10-4/℃、体积膨胀系数为8.26×10-4/℃,在室温至80℃范围内两个方向受约束时第三个方向上的表观线膨胀系数为6.78×10-4/℃、体积弹性模量为510MPa。     

Factors Determining Grain Orientation in Bismuth Sodium Potassium Titanate–Lead Zirconate Titanate Solid Solutions Made by the Reactive Templated Grain Growth Method

Grain-oriented Bi_0.5(Na_0.85K_0.15)_0.5TiO₃-Pb(Zr_{1− x} Ti _x )O₃ (BNKT-PZT) ceramics were prepared via the reactive templated grain growth method, using platelike Bi₄Ti₃O₁₂ particles. Factors that determine the degree of orientation were examined. Prereacted PZT gave a larger degree of orientation than PZT raw materials (PbO, ZrO₂, and TiO₂) in the 75BNKT-25PZT ( x = 0.5) system. Increases in the titanium concentration in the PZT of the 75BNKT-25PZT system and in the BNKT concentration in the y BNKT-(100 − y )PZT ( x = 0.5) system increased the degree of orientation. The direction of material transport between BNKT and PZT was important to obtain ceramics with a large degree of orientation.     

Electrophysical Properties of Oxide Interlanthanides and Solid Solutions Based on Them

The electrophysical properties and nature of oxide interlanthanides LaYO₃, LaYbO₃, LaErO₃, NdLuO₃, LaGdO₃, and GdLuO₃, pure and doped by calcium and hafnium oxides with close ionic radii, are investigated within a temperature interval from 900 to 1600°C and oxygen partial pressure from 2×10⁴ to 1×10^–10 Pa. It is demonstrated that the electric conductivity of the materials considered is determined by nonstoichiometric disordering. The results obtained can be used for synthesis of new types of thermoresistors, oxygen sensors, and other ceramic sensors, as well as various dielectric materials.     

Solid Solubilities of Sulfonamides and Use of Rapid Expansion of Supercritical Solutions for Microparticle Production

The solubility of solid active pharmaceutical ingredients in supercritical fluids is a major thermodynamic criterion for selection and screening of microparticle generation processes. To develop an efficient method for solubility prediction, a solution model was adopted to establish the correlations of the solid solubilities of six sulfonamides in supercritical CO₂. The model was capable of determining solubility correlations. Accordingly, it was attempted to simplify and generalize the model, yielding a predictive solution model, which provided order-consistent solubility predictions. A case study for model extrapolation was conducted. After understanding the mechanisms underlying the solubility of sulfonamides, the rapid expansion of supercritical solutions (RESS) process was applied to produce microparticles of p-toluenesulfonamide, an anticancer drug. The effects of RESS process parameters were investigated.     

低热膨胀原料对滑板的显微结构及抗剥落性的影响

功能滑板必须具备较高的抗剥落性、耐侵蚀性、高温强度等,其中提高抗剥落性的有效方法之一就是在滑板材料中添加铝锆及锆莫来石等含ZrO2的低热膨胀原料。滑板中添加ZrO2可利用ZrO2系原料在1000℃左右发生相变产生的体积变化,使组织中生成微裂纹,依靠低弹性率来提高抗剥落性。本文就ZrO2系原料及其特性对滑板的显微结构、抗剥落性的影响进行了阐述。