Theoretical estimation of dielectric loss of oxide glasses using nonequilibrium molecular dynamics simulations

To theoretically explore amorphous materials with a sufficiently low dielectric loss, which are essential for next-generation communication devices, the applicability of a nonequilibrium molecular dynamics simulation employing an external alternating electric field was examined using alkaline silicate glass models. In this method, the dielectric loss is directly evaluated as the phase shift of the dipole moment from the applied electric field. This method enabled us to evaluate the dielectric loss in a wide frequency range from 1 GHz to 10 THz. It was observed that the dielectric loss reaches its maximum at a few THz. The simulation method was found to qualitatively reproduce the effects of alkaline content and alkaline type on the dielectric loss. Furthermore, it reasonably reproduced the effect of mixed alkalines on the dielectric loss, which was observed in our experiments on sodium and/or potassium silicate glasses. Alkaline mixing was thus found to reduce the dielectric loss.     

Comb-shaped diblock copolystyrene for anion exchange membranes

To improve the properties of diblock copolystyrene-based anion exchange membranes (AEMs), a series of AEMs with comb-shaped quaternary ammonium (QA) architecture (QA-PS_m-b-PDVPPA_n-xC where x denotes the number of carbon atoms in different alkyl tail chains and has values of 1, 4, 8, and 10 and C denotes carbon) were designed and synthesized via subsequent quaternization reactions with three different alkyl halogens (methyl iodide and N-alkane bromines (CH₃[CH₂] _x-1Br where x = 4, 8, and 10). Compared with triblock analogues quaternized with methyl iodide in our previous research, QA-PS_m-b-PDVPPA_n-xC (x = 4, 8, and 10) AEMs are more flexible with the introduction of a long alkyl tail chain; this probably impedes crystallization of the rigid polystyrene-based main chain and induces sterically adjustable ionic association. An increase in the pendant alkyl tail chain length generally led to enhanced microphase separation of the obtained AEMs, and this was confirmed using small-angle X-ray scattering and atomic force microscopy. The highest conductivity (25.5 mS cm⁻¹) was observed for QA-PS₁₂₀-b-PDVPPA₈₀-10C (IEC = 1.94 meq g^–1) at 20 °C. Furthermore, the water uptake (<30%) and swelling ratio (<13.1%) of QA-PS_m-b-PDVPPA_n-xC AEMs are less than half of these corresponding values for their triblock counterparts. The QA-PS₁₂₀-b-PDVPPA₈₀-10C membrane retained a maximum stability that was as high as 86.8% of its initial conductivity after a 40-day test (10 M NaOH, 80 °C), and this was probably because of the steric shielding of the cationic domains that were surrounded by the longest alkyl tail chains. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47370.     

有色冶炼二次含砷物料碱法脱砷工艺现状

分析了典型二次含砷物料化学成分特点,概括了当前有色冶炼工业中产生的二次含砷物料碱法脱砷工艺及原理,主要包括湿法脱砷工艺和火法—湿法联合脱砷工艺。其中,碱法脱砷工艺常用NaOH单碱浸出、NaOH-Na_2S混合碱浸出和NaOH+Na_2S混合碱两段浸出三种体系,并采用双氧水、加压、曝气、微波、球磨等氧化手段强化砷的浸出;火法—湿法联合脱砷工艺主要有低温碱性熔炼—水浸、焙烧预氧化—碱性浸出以及低温碱性焙烧—热水浸出工艺,低温碱性焙烧—热水浸出工艺选择性脱砷效果好,物料普适性广。最后,结合现有研究指出了碱法脱砷工艺存在的问题及二次含砷物料无害化、资源化研究方向。     

Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications

In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. ¹H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm^?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 10⁷ Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry     

小麦麸皮淀粉的提取及其结构分析

以小麦麸皮为原料，分别采用碱性蛋白酶法和超声波辅助碱性蛋白酶法提取麸皮淀粉，优化两种方法的提取条件，并对麸皮淀粉的颗粒结构及分子结构进行了初步测定分析。结果表明，碱性蛋白酶法最优提取条件为固液比1∶10（g∶mL），酶用量529.92 U/mL，酶作用时间50 min，反应温度45 ℃，pH 12，麸皮淀粉得率为30.40%，淀粉含量59.24%，小麦麸皮淀粉呈淡褐色粉末状。超声波辅助碱性蛋白酶法的最优条件：固液比为1∶15（g/mL），超声功率为200 W，超声时间为15 min，麸皮淀粉得率为21.06%，淀粉含量为90.64%，麸皮淀粉呈白色粉末。超声波辅助碱性蛋白酶法提取麸皮淀粉的纯度及提取率均优于碱性蛋白酶法。经测定分析小麦麸皮淀粉中支/直比为4.69，破损淀粉含量1.78%。淀粉麸皮颗粒呈椭球型，平均粒径为15.86 μm，具有径向结晶结构，为A型结晶。     

京尼平交联制备枯草杆菌碱性蛋白酶聚集体

本研究利用新型交联剂京尼平制备了枯草杆菌碱性蛋白酶交联聚集体(BAP-CLEAs)。以酶活回收率为指标,确定了BAP-CLEAs制备的最佳条件为:交联剂质量浓度0.50%,交联温度35℃,交联时间12 h,此时BAP-CLEAs的酶活回收率为55.04%。采用扫描电镜及红外光谱对BAP-CLEAs进行表征,结果证明枯草杆菌碱性蛋白酶在京尼平的作用下成功交联。与游离酶相比,BAP-CLEAs的最适p H值向碱性方向偏移,由9.4变为10.3,在较宽的p H范围和温度范围内保持较高的酶活。另外,在2%浓度的酪蛋白底物中重复使用5次后,BAP-CLEAs还能保持86.42%的酶活性。以上催化特性的结果表明,枯草杆菌碱性蛋白酶在京尼平的作用下可成功交联形成酶聚集体,且该交联酶聚集体具有比游离酶更优越的p H稳定性、温度稳定性和重复使用稳定性,有良好的工业应用前景。     

煤/石油焦共气化过程中AAEM的催化转化行为

以富含碱金属及碱土金属的准东煤和石油焦为原料,在热重反应器上分别进行了水蒸气及CO2条件下的共气化实验,探究了AAEM的赋存形态对其转化行为及燃料气化特性的影响规律.研究表明,准东煤与石油焦在水蒸气条件下的共气化反应速率明显快于CO2条件,来自煤中的AAEM促进了石油焦的气化.在CO2气氛中,不同赋存形态矿物的催化作用存在较大差异,盐酸溶态的Ca起主要催化作用,并在气化过程中生成CaS.而在水蒸气气氛中,不同赋存形态矿物的催化作用差异较小,气化过程中含Ca组分主要生成CaO.     

Grape stalk fibers as reinforcing filler for polymer composites with a polystyrene matrix

Lignocellulosic fibers have been one of the most used reinforcements for different types of composites. In this context, grape stalks—often discarded in landfills—can be a potential reinforcement for composites. The present study aimed to incorporate in natura and alkali treated grape stalks into the polystyrene (PS) matrix. Initially, the grape stalks were treated with NaOH and 10, 20, and 30 wt % of stalks were added into the PS matrix. The alkaline treatment of the grape stalk fibers promoted the removal of hemicellulose and the partial removal of lignin, thus increasing the surface roughness and crystallinity index of the fibers. An improvement in the mechanical and dynamic-mechanical properties and an increase in the maximum degradation temperature of the composites were observed. In conclusion, the use of grape stalks is a promising alternative for reinforcing composites, and, in addition, a more proper destination can be given to this type of residue. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47427.