A Comparison of Catalytic Properties of Cs x H3−x PW12O40 Salts of Various Cesium Contents in Gas Phase and Liquid Phase Reactions

The cesium salts Cs _x H_3?x PW₁₂O₄₀ of Cs content x = 2 up to x = 3 were tested as the catalysts in the gas and liquid phase reactions. Dehydration of ethanol and transesterification of triglycerides with methanol were selected as the catalytic reactions. Apart from the standard preparation, the catalysts were prepared by two-stage procedure with methanol or water as a solvent. The Cs-salts were characterized by FT-IR, XRD, scanning electron microscopy and energy dispersive X-ray techniques. In turn, the influence of Cs-salts composition on the pH and conductivity of their aqueous colloidal solutions was investigated. The results obtained by the latter techniques were also characteristic for acidity of surface layer of colloidal particles because of surface layer-solution equilibrium. It has been shown that the secondary structure of acidic cesium salts existing in crystalline samples (solid solution of H₃PW₁₂O₄₀ in Cs₃PW₁₂O₄₀) changes after contacting with polar medium to the system consisting most probably of Cs₃PW₁₂O₄₀ core with epitaxial layer of heteropolyacid. This is result of the protons migration from bulk to surface layer of primary particles enhanced by polar medium. It strongly influences the surface acidity of primary particles as well as the activity of Cs-salts in transesterification of triglycerides with methanol. In such polar medium, Cs₂HPW₁₂O₄₀ salt becomes the most active catalyst, more active than Cs_2.5H_0.5PW₁₂O₄₀. An accumulation of partial glycerides and in particular glycerol on the surface of primary particles of Cs-salts resulted in relatively low maximum conversion of triglycerides, most probably due to partial blockage of the catalytic centers. This effect and the almost constant activity of Cs-salts under recycling use in the transesterification experiments are considered to be experimental evidences that methanolysis over Cs-salts was accomplished with the participation of surface protons.     

Soft chemistry preparation of layered Al0.3V2O5·5H2O

A novel layered compound Al_0.3V₂O₅·5H₂O was successfully prepared and characterized using powder X-ray diffraction, Thermal analysis, scanning and transmission electron microscopes. The new layered Al_0.3V₂O₅·5H₂O has like-nanowires shape and the layered structure was stable until 400 °C. At higher temperature (500 °C), it decomposes to orthorhombic Al_xV₂O₅ and triclinic AlVO₄.     

Dielectric properties of porous Ba0·997La0·003Ti1·0045O3 ceramics

An oxalate method was used in this work to produce La–BaTiO₃ materials. The obtained powders had small particle size and were disaggregated. However, the sintering process is difficult due to the presence of large pores uniformly distributed in the matrix. Grain size is not uniform, and the type of microstructure obtained suggests that clusters of particles readily sinter and densify, while leaving between them large pores. Impedance spectroscopy was done up 230°C. The variation of the permittivity with temperature showed that lanthanum changes the transition temperature of BaTiO₃, to T_o ∼115°C. One of the resistances of the proposed equivalent circuit was related to grain boundary conductance, since its associated activation energy, 0·72 eV, is too high to be assigned to a donor species. It is proposed that La substituting Ba is compensated by Ba vacancies, which turns the material highly resistive, not showing the PTC effect.     

Effects of humidity on the electrical behaviour of Sr0·97Ti0·97Fe0·03O3-δ

It is widely recognised that the electrical behaviour of acceptor-doped strontium titanate ceramics is often controlled by resistive grain boundaries. This work shows that the electrical behaviour of Sr_0·97Ti_1-xFe_xO_3−δ materials may also be affected by other factors such as the humidity in the atmosphere, especially for materials with open porosity. For example, the impedance of dense samples with large grain size may exceed the impedance of samples with residual porosity. The bulk and grain boundary resistivities both increase with the humidity in the atmosphere.     

Effect of Calcium Salts of Glutaric Acid and Pimelic Acid on the Formation of β Crystalline Form in Isotactic Polypropylene

The effect of calcium glutarate (Cagt) and calcium pimelate (Capt) on the formation of β crystalline form in isotactic polypropylene (iPP) after isothermal crystallization at 130°C for 30 min has been investigated. The maximum K_WAXD and K_DSC values were 31.97% and 38.06%, respectively, for iPP doped with 0.2 wt.% Cagt. The maximum values of K_WAXD and K_DSC were 73.60% and 68.44% for iPP doped with 0.3 wt.% and 0.15 wt.% Capt, respectively. The crystal size of iPP doped with Capt is finer than that of iPP doped with Cagt. It is shown that the β nucleation ability of Capt is superior to that of Cagt. The difference in the β nucleation ability between Cagt and Capt is explained by the structural difference of the nucleators with β-iPP.     

Improvement in the non-linear electrical characteristics of the SnO2·Co2O3·Ta2O5 varistor material with Pr6O11 additive

The electrical and microstructural properties of SnO2-based varistor ceramic sample were improved by addition of Pr6O11. It was found that the introduction of Pr6O11 can lead to a great improvement in the threshold voltage and the non-linear electrical properties of SnO2-based varistors. As the amount of Pr6O11 increased from 0.00 to 0.5 mol%, the mean grain size decreases from 16.64 to 7.58 μm, the relative dielectric constant (at 1 kHz) increases from 1243.2 to 4534.6, the non-linear coefficient increases from 15.44 to 18.25 and the break down electrical field increases from 275.3 to 880.5 V/mm. The structure-property relationship is discussed systematically.     

Comparative Studies of Some Physico‐mechanical Properties of Alkali and Diazonium Salts‐Treated Jute Fiber

Abstract

The effect of diazonium salts and alkali on some physico‐mechanical properties, viz, tensile strength, tenacity, elongation at break, moisture regain, shrinkage, loss in weight, etc. of jute fiber has been studied. The tensile strength, tenacity, elongation at break, and moisture regain properties of the treated (dyed) fiber are found lower in comparison with those of raw (control) fiber. However, higher tensile strength and tenacity of the diazonium salts‐treated jute fiber are observed in comparison with those of the alkali‐treated fiber. The nature of the shades developed on jute fiber is also reported.     

Phase equilibria in the CaO·SiO2Na2O·SiO2Na2O·Al2O3·6SiO2 system

Equilibrium phase relations in the system CaO·SiO₂Na₂O·SiO₂Na₂O·Al₂O₃·6SiO₂ at 40–80 wt% Na₂O·Al₂O₃·6SiO₂ composition range have been experimentally studied at temperatures between 800 °C and 1200 °C. The liquidus temperature was determined with differential scanning calorimetry. The equilibrated samples were quenched with pressurized nitrogen, and examined with electron probe X-ray microanalysis and X-ray diffraction for identification of microstructure and phase relations. Five primary phase fields, CaO·SiO₂, Na₂O·SiO₂, Na₂O·2CaO·3SiO₂, 2Na₂O·CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ were established. The ternary eutectic point of CaO·SiO₂, Na₂O·2CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ was determined to be at 1030 °C with the composition of 29.0 wt% CaO·SiO₂, 12.0 wt% Na₂O·SiO₂ and 59.0 wt% Na₂O·Al₂O₃·6SiO₂. Peritectic reaction of Na₂O·2CaO·3SiO₂, 2Na₂O·CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ occurred at 930 °C with the composition of 13.0 wt% CaO·SiO₂, 29.0 wt% Na₂O·SiO₂ and 58.0 wt% Na₂O·Al₂O₃·6SiO₂. The liquidus surface projection of the ternary system has been constructed in the composition region important for the bottom ash application.     

Antibacterial Properties of Ester—Cross-Linked Cellulose–Containing Fabrics Post-Treated with Metal Salts

To improve the performance properties of cellulose-containing fabric, ester was cross-linked with polycarboxylic acid in the presence of specific catalysts. Its pendant carboxyl groups were exploited in binding some heavy metals (by reacting with some salts, such as zinc acetate, zinc chloride, zinc sulfate, cupric acetate, cupric chloride, cupric sulfate, and nickel sulfate) capable of imparting their antibacterial activity toward some gram-positive bacteria (viz., B. subtilis, B. mycoides, Sta. aureus) and a gram-negative bacteria (E. coli). Zinc salts impart to the fabric the highest antibacterial activity, followed by cupric acetate. Zinc chloride proved to be the metal salt that yielded the maximum antibacterial activity.     

A Study of Ionic Conductivity of Glasses in the PbCl2–PbO · B2O3 and PbCl2–2PbO · B2O3 Systems

The steady-state electrical conductivity of oxychloride glasses in the PbCl₂–PbO · B₂O₃ and PbCl₂–2PbO · B₂O₃ systems is investigated. In the temperature range from 190 to 380°C, the dependence of log on the reciprocal of the temperature exhibits a linear behavior. The nature of charge carriers is studied using the Hittorf technique. It is demonstrated that protons and chlorine ions are charge carriers in solid glasses. The concentration dependence of the transport numbers of chlorine ions is examined by the Tubandt method. The contribution of the electronic component to the total electrical conductivity is estimated with the use of the Liang–Wagner technique. The concentration dependences of the electrical conductivity and the transport numbers of chlorine ions are interpreted in terms of the microinhomogeneous glass structure associated with the selective interaction of components during synthesis of glasses.     

AC behaviour and conductive mechanisms of 2·5 mol% La2O3 doped PbZr0·53Ti0·47O3 ferroelectric ceramics

Impedance spectroscopy (IS) is an effective characterization method for the investigation of many ceramic systems including the ferroelectric systems. It is employed to analyze the properties of the intragranular and interfacial regions, their interrelations, their temperature and frequency dependences and the DC and AC phenomena in order to separate the individual contributions from the total cell impedance. Using this technique and thermally stimulated current measurements we have studied the ac behavior and the conductive mechanisms in lanthanum-doped lead zirconate titanate, a donor-doped ferroelectric ceramic system. AC and DC conductivity components were found; a Jonscher power-law behavior was obtained and a strong low frequency dispersion was observed in a wide frequency range. A mixture of ionic–electronic conductive behavior was analyzed from the experimental results and the energy activation values obtained. ©     

Influences of 4ZnO·B2O3·H2O whisker based intumescent flame retardant on the mechanical,flame retardant and smoke suppression properties of polypropylene composites

In this work, the influences of 4ZnO·B₂O₃·H₂O zinc borate (ZB) whisker based intumescent flame retardant (IFR) containing ammonium polyphosphate and dipentaerythritol on the mechanical, flame retardant and smoke suppression properties of polypropylene (PP) composites were characterized by the universal testing machine, UL-94, limiting oxygen index (LOI), and cone calorimeter tests, respectively. The results indicate that only 1 phr of ZB could effectively improve the LOI value and slow down the burning rate of PP composite. The peak heat release rate, average of HRR, total heat release, peak smoke production rate, and total smoke production values are all decreased from 413.8 kW/m², 166.3 kW/m², 82.3 MJ/m², 0.0995 m²/s, and 17.9 m² for PPc/20IFR composite to 267.8 kW/m², 128.3 kW/m², 66.8 MJ/m², 0.0478 m²/s, and 12.6 m² for PPc/20IFR/1ZB composite, respectively. The scanning electron microscopy images, energy dispersive spectrometry, and Raman spectra of char residue reveal that ZB is helpful to form a compact and graphitized intumescent char residue so that the heat diffusion and oxygen transmission are greatly hindered. The thermogravimetry analysis-fourier transform infrared spectroscopy (TGA-FTIR) results show that less combustible volatiles and more H₂O vapor are generated with the appearance of ZB. Hence, the combustion mechanism in gas phase is suppressed.     

Hydrothermal synthesis and characterization of nanorods “LixV2−δO4−δ·H2O”

Nanorods “Li_xV_2−δO_4−δ·H₂O” were hydrothermally synthesized with starting agents LiOH·H₂O and V₂O₅, and reducing agent hydrazine monohydrate (NH₂NH₂·H₂O) under alkaline condition at 160 °C. The samples were characterizated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nanorods obtained have diameters from 80 to 100 nm with length up to several micrometers. Molecular coordination and assembly mechanism can be assumed to explain the formation of one-dimensional nanorods.     

Efficient and Mild Synthesis of Novel Diazo Dyes through Coupling Reaction of Schiff Base Diazonium Salts with β-naphthol

In this study, efficient and mild method for synthesis of some novel diazo dyes containing Schiff bases has been reported. All of the intermediates and final products were obtained in good to high yields and appropriate reaction times. The structures of desired products were determined using physical and spectroscopy data such as; IR, ¹H NMR, ¹³C NMR, mass spectra, and C.H.N. analyses. The worldwide availability, larger scale synthesis, high yields, and short reaction times are the advantages of the present method.     

水到渠成——KLCT西格玛（∑）方程式战略下的K·I．T·L·O·O·G·N车队销售模式

从1931年在吉隆坡芭都律399号建立起第一家轮胎店开始,吉隆轮胎集团始终重视投资先进的轮胎设备和科技,集中精力在轮胎业开拓进取。     

Optimizing the piezoelectric properties of Ba0·85Ca0·15Zr0·10Ti0·90O3·lead-free ceramics via two-step sintering

The two-step sintering of lead-free Ba₀·₈₅Ca₀·₁₅Zr₀·₁Ti_0·9O₃·(BCZT) ceramics was investigated as a way to enhance its piezoelectric properties. The variations in grain size as a function of the calcination and sintering conditions and its effect on performance is discussed. Results indicate that as the calcination and first-step sintering temperatures increased, grain size became large and was independent of the second sintering step. Large grains were responsible for the enhanced piezoelectric properties by causing lattice distortion, larger domains, and easy motion of domain walls. The BCZT ceramic calcined at 1200 °C and sintered at 1540 °C without holding and then cooled to 1400 °C and held at 1400 °C for 4 h exhibited optimal performance with the highest remnant polarization P_r ∼13.5 μC/cm², the largest piezoelectric constant d₃₃ ∼ 529 pC/N at room temperature, and the highest Curie temperature T_c ∼125 °C. Two-step sintering has been turned out to be an effective method to realize high-performance BCZT ceramics by microstructure optimization.     

Crystallization behavior of iron- and boron-containing nepheline (Na2O·Al2O3·2SiO2) based model high-level nuclear waste glasses

This study focuses on understanding the relationship between iron redox, composition, and heat-treatment atmosphere in nepheline-based model high-level nuclear waste glasses. Glasses in the Na₂O–Al₂O₃–B₂O₃–Fe₂O₃–SiO₂ system with varying Al₂O₃/Fe₂O₃ and Na₂O/Fe₂O₃ ratios have been synthesized by melt-quench technique and studied for their crystallization behavior in different heating atmospheres—air, inert (N₂), and reducing (96%N₂–4%H₂). The compositional dependence of iron redox chemistry in glasses and the impact of heating environment and crystallization on iron coordination in glass-ceramics have been investigated by Mössbauer spectroscopy and vibrating sample magnetometry. While iron coordination in glasses and glass-ceramics changed as a function of glass chemistry, the heating atmosphere during crystallization exhibited minimal effect on iron redox. The change in heating atmosphere did not affect the phase assemblage but did affect the microstructural evolution. While glass-ceramics produced as a result of heat treatment in air and N₂ atmospheres developed a golden/brown colored iron-rich layer on their surface, those produced in a reducing atmosphere did not exhibit any such phenomenon. Furthermore, while this iron-rich layer was observed in glass-ceramics with varying Al₂O₃/Fe₂O₃ ratio, it was absent from glass-ceramics with varying Na₂O/Fe₂O₃ ratio. An explanation of these results has been provided on the basis of kinetics of diffusion of oxygen and network modifiers in the glasses under different thermodynamic conditions. The plausible implications of the formation of iron-rich layer on the surface of glass-ceramics on the chemical durability of high-level nuclear waste glasses have been discussed.     

Na~+···苯氰···H_2O复合物分子间协同效应的理论研究

借助B3LYP和MP2(full)方法,在6-311++G(2d,p)基组水平上分别优化出了六种苯氰…H2O二聚体、两种Na+…苯氰二聚体、Na+…H2O和九种Na+…苯氰…H2O三聚体复合物的最优几何构型,并分别计算了Na+…苯氰…H2O复合物中Na+…π及Na+…σ相互作用的协同效应。该结果表明,Na+…σ相互作用的复合物具有协同效应而Na+…π复合物发生了反协同效应。H2O存在的情况下,Na+更易与苯氰结合。