Electrically treated composite FILMS based on chitosan and methylcellulose blends

Films obtained from chitosan (CH) and methylcellulose (MC) can reduce environmental problems associated with synthetic packaging. The objective of the present work was to analyze the effect of an electrical field applied during drying on microstructure and macroscopic properties of films obtained with different mixtures of CH and MC.     

蛋壳膜对功能性物质的吸附与运载特性

蛋壳膜具有高透水透气性、良好的稳定性及生物相容性等特点,是一种可以以直接作用和交联作用2种方式与功能性物质相结合,能用于吸附、运载包括贵重金属及酶蛋白等功能性物质的天然载体,是一种在日用化工、医药等领域具有明显研究和应用价值的天然产物。     

Effective elastic properties of randomly distributed void models for porous materials

Many 2D analytical models are available for estimating the effective elastic properties of porous materials. Most of these models adopt circular voids of a uniform diameter in superlattice arrays, such as unit void or periodically positioned models. There are two principal issues in a realistic representation of porous materials: the random distribution of a statistically sufficiently large number of voids in the model, and the random distribution of the size and position of the voids. Numerical schemes such as the FEM or the BEM have also been presented to cater for regular patterned circular voids. However, due to the large number of elements needed to produce sufficient accuracy for the curved boundary of circular voids or modelling a statistically sufficient number of voids with a random distribution in both the void size and the position, no such model has yet been produced.Modelling based on an FEM approach using a simplified approximation for void geometry is proposed here for the calculation of the effective elastic properties of porous solids. A plane strain model of a square geometry is adopted for a 2D array of voids. This simplified square shape allows a large number of voids to be simulated with a random distribution for both void sizes and their locations. The problem of anisotropy, which arises from the square shape, is discussed. It is verified that along the two principal directions (parallel to the sides of the square voids), the elastic properties remain the same as those predicted by using a circular void geometry. This square-shaped approximation, with its reduced requirement for FE analysis, has the potential to be extended to 3-dimensional modelling for a realistic simulation of engineering materials.     

Synthesis,structural and luminescence properties of near white light emitting Dy-doped Y2CaZnO5 nanophosphor for solid state lighting

Novel near white light emitting Y₂CaZnO₅ (YCZ) nanocrystalline powders doped with Dy³⁺ ions were synthesized via the citrate gel combustion method. The structure of the compound is found to be triclinic with a particle size in the range of 20–30 nm. Luminescence properties have been characterized using photoluminescence (PL), excitation spectra and decay time measurements. The PL spectra have shown a broad blue band due to ⁴F_9/2→⁶H_15/2 transition and sharp yellow band corresponding to ⁴F_9/2→⁶H_13/2 transition of Dy³⁺ ions. From the concentration dependent PL studies, the optimum concentration of Dy³⁺ ions in YCZ is found to be 1.0 mol%, where intense near white light emission was observed. The Dy³⁺:YCZ nanophosphor has shown relatively better white color properties than the reported Dy³⁺:Y₂O₃ nanophosphor. The yellow to blue intensity ratios, CIE chromaticity coordinates and correlated color temperature studies have shown the possibility of using this compound for white light emission.     

两亲聚氨酯弹性体(APU)的研究Ⅱ.IPN型APU制备及力学性能

以聚酯型聚氨酯为疏水组分,光固化聚乙二醇为亲水组分,通过溶液聚合制备了具有互穿聚合物网络（ＩＰＮ）结构的ＡＰＵ。研究了亲疏水组分比例、光固化条件等因素对ＩＰＮ型ＡＰＵ力学性能的影响。试验结果表明,当ＡＰＵ中光敏剂质量分数为００１０,光照前停放２０ｈ,光照时间为６ｍｉｎ时,ＩＰＮ型ＡＰＵ的力学性能最佳。     

PAN基活性炭纤维研究及展望

综述聚丙烯腈（ＰＡＮ）基活性炭纤维（ＡＣＦ）的基本性能、应用及未来展望。     

Characteristics of wet‐spun and thermally treated poly acrylonitrile fibers

The performance of carbon fibers depends on the quality of the precursor and the conditions of the thermal treatment. In detail, for a PAN precursor fiber the viscosity of a spinning dope and the draw ratio during the spinning process needs to be considered. Through wet spinning, different types of PAN precursor fibers with defined spinning parameters, including solid content, solvent content in a bath, and especially draw ratio resulting in defined cross section diameters, were fabricated and analyzed with tensile tests, density investigations, SEM, TGA‐MS, FTIR, and XRD. The results show that the mechanical properties of the fibers correlate to crystallinity. The cross section diameter is strongly related to the morphology of the fibers after thermal treatment. By extending the postdrawing of PAN fibers high tenacities were obtained at the cost of the cross section shape. In addition, TGA measurements reveal trapped residues of the wet spinning process as well as show several chemical reactions takes place at the same time at different temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43698.     

Light scattering materials with tunable optical properties by controlling refractive index of the dispersed phase

Traditionally, the morphologies of the dispersed phase in Polycarbonate (PC)/poly(styrene‐co‐acrylonitrile) (SAN) blends were strongly influenced if AN content in SAN changed significantly even under constant processing conditions. This would hinder the pure research intended to study the effect of the refractive index difference between the polymer host and the polymeric dispersed particles on the optical properties tough. Therefore, we respectively prepared different PC/SAN light diffusion sheets with four types of SAN containing different AN content ranging just from 20 to 25 wt %, a narrow range that sufficiently ensures the relatively stable morphology of different SAN in PC matrix. The results suggest that the refractive index of SAN increases with an decreasing AN content, thus narrowing the refractive index difference between PC and SAN and producing PC/SAN(70/30) light diffusion sheets with an increasing transmittance and decreasing haze. The interesting phenomenon is further analyzed using Mie scattering theory. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44156.     

Low‐Temperature Synthesis of CoNb2O6 Microwave Dielectric Ceramics

Low‐fired cobalt niobate (CoNb₂O₆) microwave dielectric ceramics were prepared through a developed sol–gel process using Nb₂O₅·nH₂O as starting source. A metal‐dioxo‐bridged complex precursor was described on the basis of FT‐IR spectrum. The crystalline phases of calcined powders were characterized by X‐ray diffraction. Nanosized CoNb₂O₆ particles with orthorhombic α‐PbO₂‐type structure were obtained above 750°C. There was no subsequent phase change upon sintering, and all compounds sintered to at least 94% of theoretical density. At 1000°C/4 h, CoNb₂O₆ ceramics exhibited ε_r ~ 21.9, Q × f ~ 66 140 GHz (at 8.9 GHz) and τ_f ~ ?39.7 ppm/°C, having a good potential for low‐temperature cofired ceramic applications.     

水分对PET聚酯切片流变性能测试的影响

利用毛细管流变仪对不同水分聚酯熔体的流变性能进行了对比研究,讨论储料装置对干燥后聚酯切片吸水性的影响,以及水分对表观粘度、非牛顿指数及粘流活化能的影响。结果表明:由于发生了水解反应,在相同温度下,聚酯熔体的表观粘度随着水分的增加而降低,非牛顿指数随着水分的增加而增大,粘流活化能随着水分的增加而增大。