Enhanced Power Density of Alcohol Biofuel Cell by Polymer-assisted Crosslinks of 3D Graphene on Carbon Paper as the Bioanode

Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.     

Direct visualization of the nanoscopic three‐phase structure and stiffness of NBR/PVC blends by AFM nanomechanical mapping

The PeakForce Quantitative Nanomechanical Mapping based on atomic force microscope (AFM) is employed to first visualize and then quantify the elastic properties of a model nitrile rubber/poly(vinyl chloride) (NBR/PVC) blend at the nanoscale. This method allows us to consistently observe the changes in mechanical properties of each phase in polymer blends. Beyond measuring and discriminating elastic modulus and adhesion forces of each phase, we tune the AFM tips and the peak force parameters in order to reliably image samples. In view of viscoelastic difference in each phase, a three‐phase coexistence of an unmixed NBR phase, the mixed phase, and PVC microcrystallites is directly visualized in NBR/PVC blends. The nanomechanical investigation is also capable of recognizing the crosslinked rubber phase in cured rubber. The contribution of the mixed phase was quantified and it was found that the mechanical properties of blends are mainly determined by the homogeneity and stiffness of the mixed phase. This study furthers our understanding the structure–mechanical property relationship of thermoplastic elastomers, which is important for their potential design and applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 662–669     

Scaling properties of fracture surfaces on glass strengthened by ionic exchange

In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K⁺-Na⁺. atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent (ζ) and the correlation length (ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange.     

离心力场作用下多孔介质中强制对流换热的研究

对离心流化床中空气通过多孔物料层的强制对流换热进行了理论和实验研究。获得了气流和物料间强制对流换热的准则关联式。研究结果表明,在气流速度和温度梯度方向一致的条件下,强制对流换热比通常的边界层强制对流换热有所强化,其换热的准则关联式具有 Nu=CRePr的线性形式。从而验证了改变气流方向和热流密度矢量之间夹角可以强化换热的这一强化传热新原理。     

On a stochastic nonlinear equation in one-dimensional viscoelasticity

In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.

     

原子力显微镜在生物物理领域的新应用

介绍了原子力显微镜在生物物理领域的最新应用:蛋白质去折叠、DNA拉伸、生物膜受力,通过分析实验得到的力谱,可以获取关于蛋白质、DNA、生物膜结构信息.原子力显微镜不仅能反映测量体系的力学性质,由于其具有独特的时间、空间分辨及实时成像,因而能提供更多信息.     

中心势场中粒子运动轨道的研究

在中心势场中粒子运动轨道方程的基础上,进一步讨论粒子轨道的闭合性、稳定性.     

堆焊切粒刀技术初探

介绍堆焊切粒刀的优点 ,着重探讨了采用靠模法加工堆焊切粒刀螺旋槽的原理 ,论证了所介绍加工工艺的合理性 .事实证明 ,采用介绍的加工工艺生产的堆焊切粒刀 ,可满足设计的技术性能 ,质量可达到国外同类产品的水平     

Fine Dry Grinding of Zeolite in a Laboratory Ball Mill

This paper presents the importance and usage of natural zeolites, which was recently recognized in the industry. Therefore, the grinding properties of natural zeolite were studied with the emphasis on a kinetic study in a ball mill. The experimental mill employed was laboratory sized, 200 mm diameter, 191 mm length, providing a total mill volume of 6000 cm³, with a total mass of 5.62 kg of steel balls of 25 mm diameter with a charge of 20% of the mill volume and with a rotation speed of 76 rpm. The breakage parameters were determined by using single sized feed fractions of ?850+600 μm, ?600+425 μm, and ?425+300 μm for the zeolite samples. The S_i (specific rate of breakage) and B_{i, j} (primary breakage distribution) values were obtained for those feed size fractions in order to predict the product size distributions by simulation for comparison to the experimental data. From the experimental results, S_i values increased as the feed sizes became coarser, i.e., the highest S_i value was 0.85 min^?1 for ?850+600 μm, while the lowest S_i value was 0.65 min^?1 for ?425+300 μm feed ground in the mill. The B_{i, j} values obtained for the zeolite sample were γ=0.84, ?=0.61, and β=4.25. The breakage parameters obtained showed that the zeolite is broken faster than quartz and slower than calcite and barite in terms of the a_T values reported previously at the same experimental conditions. The simulations of the product size distributions of zeolite were in good agreement with the experimental data using a standard ball mill simulation program. The slowing‐down effect was also seen in the mill after 4 min. of grinding.