Advanced Materials Research Vols. 233-235

Abstract: WO₃-based capacitor-varistor ceramics doped with Er₂O₃ were prepared and the microstructures and nonlinear electrical properties were investigated. The results show that there exist second phase Er₁₀W₂O₂₁ on the surface of WO₃ grains. Doping Er₂O₃ in WO₃ ceramic can inhibit the grain growth. A small quantity of Er₂O₃ can significantly improve nonlinear properties of the samples. The permittivity of doped samples was higher than that of the undoped, and the high permittivity makes Er₂O₃-doped WO₃ ceramics be applicable as a kind of capacitor-varistor materials.

Abstract: The modified Landau-Devonshire thermodynamic theory has been used to investigate the ferroelectricity of Pb(Zr_0.7, Ti_0.3)O₃ film grown on MgO substrate. A set of gradient thermal stresses is imposed on the films. The stress-temperature diagram, the spontaneous polarization and the dielectric susceptibility at 25°C on the stress were computed. Structure transitions of first order can be driven by the stress. The mean of out-plane spontaneous polarization and dielectric susceptibility on the temperature were also predicted.

Abstract: An Environmental friendly sand-fixing agent of water-borne polymer(graft copolymer of starch with acrylic acid and acrylamide)was synthesized. The influences of monomer dosage ratio, initiator dosage , the temperature and reaction time on the properties were discussed. The structure, thermal stability and morphology was characterized by IR spectra, TG-DTA and SEM, respectively. With the sand soil as research object, the tolerance of high temperature and compressive strength of the sand-fixing agent were studied preliminarily. The results show that when the mass ratio of acrylic acid to acrylamide is 15:10, the mass content of initiator is 4%, the reaction temperature is 50°C and time is 6h, the product has a good sand fixation performance for practical application.

Abstract: Rapid low-temperature pack aluminizing was achieved on pipeline steel X80 through combined effect of surface refinement treatment and modification of pack powder. Self-nanocrystallization surface of pipeline steel X80 was obtained by surface mechanical attrition treatment (SMAT). In addition, zinc (Zn), which has lower melting point than that of Al, was added in the pack powder, to enhance the concentration of active aluminum (Al) atom. The mechanism of the low- temperature pack aluminizing was analyzed by examining the distribution of atoms and coating thickness using EDS and SEM. The study shows that aluminizing rate of as-SMATed pipeline steel with self-nanocrystallization surface is higher than that of non-SMATed pipeline steel under the same pack condition. The addition of Zn can increase the activity of diffusion atoms and accelerate the aluminizing by changing the state of pack powder from a single solid phase to a mixture of solid phase and liquid phase. The diffusion of atoms in this low-temperature pack aluminizing is considered as bulk diffusion which is driven by the activity of diffusion atoms in an unstable state following Fick law.

Abstract: For further research on durability of concrete material under salt frozen conditions in cold area, the non air-entraining concrete with water-binder ratio of 0.4 and 0.28, air-entraining concrete with water-binder ratio 0.28 and the air content 7.0% are studied respectively. The fractal dimension of three kinds of concrete pore at different pore diameter range were determined by MIP(mereury intrusion porosimetry) before and after salt freezing and were studied in a comparative way. The research shows that the fractal dimension of pore diameter at range of 50nm ~ 550nm after salt freezing changed remarkably, namely salt frozen process has greater influence on pore within this range. Objectively the pore within this range in concrete suffered supercooled water osmotic pressure is the greatest. In addition, the total porosity reduced after salt freezing injury while fractal dimension changed more obviously. The fractal dimension of concrete pore could be a good reflection of concrete structure after salt freezing injury, showing that the diameter at 50nm ~ 550nm after salt frozen injury coarsening is obvious. Thus the fractal dimension of diameter within this range can be used as a key parameters after salt freezing injury.

Abstract: Sub-ground erosion often resulted in severe problems in various engineering constructions, most of which is due to the sub-erosion in loess. In this paper, the critical condition of “soil bursting” was analyzed and the formula describing the critical condition of soil bursting was derivated by the analytical method. Furthermore, the velocity of tunnel-erosion in loess and its influential factors were studied. A set of tests are designed to study the relationship between the tunnel-erosion velocity and the key influential factors. The key factors considered in the test include soil density as well as the initial water content. The other purpose is to reveal the characteristics of the tunnel-erosion process. Phenomena observed during the tests together with the data from field survey revealed the mechanism of tunneling in loess very well, and the work in this paper formed a theoretical basis for further study about sub-ground erosion in loess.

Abstract: Casein grafted acrylonitrile fibers were treated by different concentration alkali solutions. The fibers component were investigated using chemical analysis before and after alkali treatment. The effects of alkali pH value on homopolymer PAN, free casein, grafted casein and grafting degree of the fibers were discussed individually. At the same time, the mechanical properties of the fibers treated by alkali at various pH values were tested, and the intrinsic and extrinsic factors affecting fibers mechanical properties were analyzed. The results can play a certain reference role to the early manufacture and finishing process of casein grafted acrylonitrile fibers.

Abstract: A new molecular quantum topological index QT was constructed by molecular topological methods and quantum mechanics (QM), which together with Gibbs free energy(G), Constant volume mole hot melting(CV) that were calculated by density functional theory (DFT) at the B3LYP/6-31G(d) level of theory for mercaptans. Index QT can not only efficiently distinguish molecular structures of mercaptans, but also possess good applications of QSPR/QSAR (quantitative structure-property/activity relationships). And most of the correlation coefficients of the models were over 0.99. The LOO CV (leave-one-out cross-validation) method was used to testify the stability and predictive ability of the models. The validation results verified the good stability and predictive ability of the models employing the cross-validation parameters: R_CV, S_CV and F_CV, which demonstrated the wide potential of the index QT for applications to QSPR/ QSAR.

Abstract: Dialdehyde starch has been used to improve comprehensive properties of thermoplastic starch (TPS) in this study. Dialdehyde sweet potato starch (DASS) with various carbonyl contents has been prepared using sodium periodate to oxidize sweet potato starch in the neutral condition. The structure properties of DASS were analyzed by SEM and XRD. The results demonstrate that DASS with the higher carbonyl content comprise lower crystallization. The thermal, mechanical and biodegradable properties of TPDASS were investigated, and the results illustrate that the moisture adsorption and biodegradable ratio decreases with the Tg of TPDASS with higher carbonyl content. This phenomenon could be attributed to the partial cross-linking of DASS which is due to semi-acetal formation by itself. Meanwhile, the mechanical properties of TPDASS95 were less sensitive to the content of plasticizer. The tensile strength could reach even 12.9 MPa while the water content was higher than 13.5% and the biodegradable ratio was 28%.

Abstract: Magnesium hydroxide sulfate hydrate (MHSH) whiskers were prepared using brine, sodium hydroxide and sodium sulfate as raw materials by one-step hydrothermal process. X-ray powder diffraction (XRD), thermal analysis (TG-DTG) and scanning electron microscope (SEM) were employed to characterize the MHSH whiskers. It was shown that the MHSH whiskers were MgSO₄•5Mg(OH)₂ •2H₂O with a diameter of 0.2–0.3 μm and a length of 20–30 μm . The thermal decomposition of MHSH whisker was demonstrated a three-step scheme based on the TG-DTG data. The utilization ratio of magnesium in brine was above 80%.