Synthesis of polystyrene/poly(butyl acrylate) core–shell latex and its surface morphology

A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The T_g's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003     

Nanocomposite piezoelectric films of P(VDF‐TrFE)/LiNbO3

Piezoelectric films were prepared by incorporation of lithium niobate (LiNbO₃) nanoparticles into copolymer of vinylidene difluoride and trifluoroethylene. Nanoparticles of LiNbO₃ with ferroelectric phase were successfully synthesized and dispersed homogenously by ultrasonication in the copolymer matrix without any surfactant or surface functionalization. The nanocomposites were fully characterized by electronic microscopy, X‐ray diffraction, differential scanning calorimetry, dynamical mechanical analysis, and piezometer. Surprisingly, the copolymer matrix crystallinity and morphology were not affected by the incorporation of nanoparticles. Therefore the nanocomposites remained good mechanicals properties and high ferroelectricity coupled to nonlinear optical activity thanks to the noncentro symmetric space group of lithium niobate. This could be a novel approach to develop new multifunctional materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhancement of fibroblastic proliferation from photoreactive starch with immobilized epidermal growth factor

Carboxymethyl starch was modified by the incorporation of an azidophenyl group to prepare photoreactive starch, and characterized by Fourier transform infrared reflectance (FT‐IR), proton nuclear magnetic resonance (¹H‐NMR), and ultraviolet (UV) spectroscopy. Photo‐irradiation immobilized the Az‐starch on a polystyrene plate and it was stably retained on the surface. The protein containing immobilized Az‐starch was also immobilized on a stripe micropatterned plate. UV irradiation time and Az‐starch concentration were used to alter the physical properties of Az‐starch and consequently control the rate of epidermal growth factor (EGF) release. The Az‐starch that released growth factor was not cytotoxic to 3T3‐L1 fibroblast cells, and the immobilized EGF maintained its activity and induced cellular proliferation in vitro. These results suggest that Az‐starch could be useful as a clinical synthetic material for medical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of a Shroud Tube on Flow Field and Particle Behavior Inside a Bag-Filter Vessel

A shroud tube was used to decrease the amount of particles toward the bag filters from whole particles entering a filter vessel. The effects of the shroud tube on the flow field and particle behavior inside the vessel were studied. The air mixed with dust particles enters the vessel through a tangential inlet duct. Some of the particles are deposited on the inside wall of the vessel and the surface of the shroud tube. The other ones are collected on the filter surface or passed through it. The particles deposited on the wall surfaces fall into a hopper by gravity, and those collected on filters are removed by back pulse-jet flow. Computational simulation was performed to know the prereduction rate of particles by deposition on the wall surfaces for the different shroud tubes. The experiment was accomplished with some shroud tubes suggested by the results of computational simulation, and the experimental results were compared qualitatively with the computational results. The shroud tube blocked the direct transport of particles toward the bag filters and reduced the particle loading onto the filters. The particle loading was reduced when the upper region of the vessel was not blocked by the shroud tube more than when the vessel was blocked wholly with the filters from the upper end wall. However, the re-entrainment of the particles removed from the filters by the back pulse cleaning increased when the upper region of the vessel was not blocked by the shroud tube more than when the vessel was blocked wholly with the filters from the upper end wall.     

Polypyrrole composite membrane with high permeability prepared by interfacial polymerization

Novel polypyrrole (PPy)/polydimethylsiloxane (PDMS) composite membrane was prepared by interfacial polymerization to make a very effective gas separation membrane. We found that Polymerized PPy films as thin as ～200 nm could be chemically synthesized as freestanding membranes by using the interfacial polymerization technique. Additionally, we show that difference morphology of PPys films was obtained by controlling polymerization rate and more dense films were formed at low polymerization rate. Wide X-ray diffraction study showed the d spacing value of the PPy film decreased from 4.89 å to 3.67 å by the rate of polymerization decreases. According to d spacing value decrease, selectivity of a PPy composite membrane was increased dramatically and permeability was reduced gradually. This high selectivity was derived from d spacing closed to the kinetic diameter of nitrogen. These results indicated that the permeability is controlled by the diffusion coefficient, reflecting the packed structure of the PPy film. The highest selectivity value of composite membrane that was prepared by interfacial polymerization was O₂/N₂=17.2 and permeability for O₂ was 40.2 barrer.     

Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization

In this research, p‐type Bi₂Te₃–75% Sb₂Te₃ thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK² was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values.     

关于Filon算法的一点注记

本文对谐波分析中数值积分的Filon公式提出了一点改进,改进后的算法在微机上得到实现,经实算表明,计算结果满足工程精度要求。     

Site-selective substitution and resulting magnetism in arc-melted perovskite ATiO3-δ (A = Ca,Sr, Ba)

Magnetic properties in perovskite titanates ATiO_3-δ (A = Ca, Sr, Ba) were investigated before and after arc melting. Crystal structure analysis was conducted by powder synchrotron X-ray diffraction with Rietveld refinements. Quantitative chemical element analysis was carried out by X-ray photoelectron spectroscopy. Magnetic measurements were conducted by vibrating sample magnetometer and X-ray magnetic circular dichroism (XMCD). The magnetic properties are found to be affected by impurities of 3d elements such as Fe, Co, and Ni. Depending on the composition and crystal structure, the occupation of the magnetic ions in perovskite titanates is selectively varied, which is interpreted to be the origin of the different magnetic behaviors in arc-melted perovskite titanates ATiO_3-δ (A = Ca, Sr, Ba). In addition, both formation of oxygen vacancies and the reduction of Ti⁴⁺ to Ti³⁺ during arc-melting also play a role as proven by XMCD. Nevertheless, preferential site occupation of magnetic impurities is dominant in the magnetic properties of arc-melted perovskite ATiO_3-δ (A = Ca, Sr, Ba).     

Interfacial tension measurement between immiscible polymers: improved deformed drop retraction method

This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size.     

Synthesis and optimization of NASICON-type Li3V2(PO4)3 by adipic acid-mediated solid-state approach

We report the synthesis and optimization of NASICON-type carbon-coated Li₃V₂(PO₄)₃ by solid-state approach. Adipic acid (AA) is used as the source material for the carbon. Initially, the synthesis of monoclinic Li₃V₂(PO₄)₃ is optimized at a precalcination temperature of 300 °C for 4 h and 900 °C for 8 h under Ar flow to yield a single phase. Powder characterizations such as thermogravimetric–differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and particle size distribution are conducted, and the results are presented. The AA concentration is varied according to the total metal ion composition in the compound (0.05, 0.1, and 0.15 M). Electrochemical Li-insertion properties are evaluated in half-cell configurations between 3 and 4.8 V vs. Li at a current density of 0.1 mA cm^?2 at room temperature. Compared with the lower AA concentrations, Li/Li₃V₂(PO₄)₃ (0.15 M AA) cell exhibited discharge capacities of 178 and 147 mAh g^?1 for the 1st and 50th cycles, respectively, and a capacity retention of 83 % after 50 cycles, which is 11 % higher than that of the native compound. Li/Li₃V₂(PO₄)₃ (0.15 M AA) showed better rate performances and delivered discharge capacities of 173, 165, 150, 132, 105, and 76 mAh g^?1 at rates of 0.1, 0.2, 0.5, 1, 5, and 12 C, respectively. Electrochemical impedance spectroscopy reveals the enhancement in electronic conductivity profile after carbon coating.