Design of a graphene oxide@melamine foam/polyaniline@erythritol composite phase change material for thermal energy storage

At present,only a single modification method is adopted to improve the shortcomings of erythritol(ET)as a phase change material(PCM).Compared with a single modification method,the synergistic effect of multiple modification methods can endow ET with comprehensive performance to meet the purpose of package,supercooling reduction,and enhancement of thermal conductivity.In this work,we innovatively combine graphene oxide(GO)nanosheet modified melamine foam(MF)and polyaniline(PANI)to construct a novel ET-based PCM by blending and porous material adsorption modification.PANI as the nucleation center can enhance the crystallization rate,thereby reducing the supercooling of ET.Meanwhile,GO@MF foam can not only be used as a porous support material to encapsulate ET but also as a heat conduction reinforcement to improve heat storage and release rate.As a result,the supercooling of GO@MF/PANI@ET(GMPET)composite PCM decreases from 91.2℃ of pure ET to 57.9℃ and its thermal conductivity(1.58 W·m^(-1)·K^(-1))is about three times higher than that of pure ET(0.57 W·m^(-1)·K^(-1)).Moreover,after being placed at 140℃ for 2 h,there is almost no ET leakage in the GMPET composite PCM,and the mass loss ratio is less than 0.75%.In addition,the GMPET composite PCM displays a high melting enthalpy of about 259 J·g^(-1) and a high initial mass loss temperature of about 198℃.Even after the 200th cycling test,the phase transition temperature and the latent heat storage capacity of the GMPET PCM all remain stable.This work offers an effective and promising strategy to design ET-based composite PCM for the field of energy storage.

The establishment of Boron nitride@sodium alginate foam/polyethyleneglycol composite phase change materials with high thermal conductivity, shape stability, and reusability

Adopting organic phase change materials(PCMs) for the management of electronic devices is restricted by low thermal conductivity. In this paper, the composite PCMs are established by freeze-drying and vacuum impregnation. Herein, polyethylene glycol(PEG) is induced as heat storage materials, boron nitride(BN) is embedded as filler stacking in an orderly fashion on the foam walls to improve thermal conductivity and sodium alginate(SA) is formed as supporting material to keep the shape of the composite stable. X-ray diffractometry, scanning electron microscopy-energy dispersive spectrometer, thermal gravimetric analysis, thermal conductivity meter, differential scanning calorimeter, and Fourier transform infrared were used to characterize the samples and thermal cycles were employed to measure the shape stability. The results exhibit the BN@SA/PEG composite PCMs have good chemical compatibility, stable morphology, and thermal stability. Due to the high porosity of foam, PEG endows the composite PCMs with high latent heat(149.11 and 141.59 J·g^(-1)). Simultaneously, BN@SA/PEG shows an excellent heat performance with high thermal conductivity(0.99 W·m^(-1)·K^(-1)), reusability, and shape stability, contributing the composite PCMs to application in the energy storage field. This study provides a strategy to manufacture flexible, long-serving, and shape-stable PCMs via introducing BN@SA foam as a storage framework, and these PCMs have great potential in thermal management in the electronic field.

The study on the mechanical properties of PU/MF double shell self-healing microcapsules

The self-healing microcapsules can be buried in the coating to improve the anticorrosive ability.In this paper,self-healing microcapsules of polyurea(PU)/melamine resin(MF)double shell were prepared by in-situ polymerization and interfacial polymerization with isocyanate as the core material.Scanning electron microscope was used to observe the microcapsule morphology.The structures of microcapsules prepared with different chain extenders were characterized by Fourier transform infrared spectroscopy.The micromanipulation system was used to loading–holding,loading–unloading and loading to rupture individual microcapsules,so as to explore the mechanical properties of microcapsules.The Young’s modulus corresponding to microcapsules was calculated by mathematical model fitting.The self-healing properties of microcapsule coating were characterized by optical microscope.The experimental results showed that the microcapsule shell prepared under optimized conditions had a complete morphology and good mechanical properties.The microcapsule was in the elastic deformation stage under small deformation,and the plastic deformation stage under large deformation.The Young’s modulus range of microcapsules was 9.29–14.51 MPa,and the corresponding Young’s modulus could be prepared by adjusting the process.The surface crack of the coating containing microcapsule could heal itself after48 h in a humid environment.

On Accelerated Singular Value Thresholding Algorithm for Matrix Completion

An accelerated singular value thresholding (SVT) algorithm was introduced for matrix completion in a recent paper [1], which applies an adaptive line search scheme and improves the convergence rate from O(1/N) for SVT to O(1/N2), where N is the number of iterations. In this paper, we show that it is the same as the Nemirovski’s approach, and then modify it to obtain an accelerate Nemirovski’s technique and prove the convergence. Our preliminary computational results are very favorable.

Effect of surfactant on zeta potential and rheology behavior of methylene bis (thiocyanate) suspension concentrate

Methylene bis(thiocyanate)(MBT) is insoluble in water, so suspension concentrate(SC) of MBT is extremely relied on surfactants. In this paper, SC of MBT was prepared with wet-grinding technology, and the effect of surfactants,such as Morwet D425(D425) and Morwet EFW(EFW)(two kinds of dispersant), on the Zeta potential and rheology behavior of MBT SC were investigated. The results showed that the Zeta potential absolute value of MBT SC increased with the increasing content of D425, and it decreased with the increasing content of EFW at acidic solution(pH = 4.5). In the combination system of D425 and EFW, Zeta potential of MBT SC decreased first and then increased with the increasing content of EFW. The relationship between shear rate(γ) and viscosity(η) was studied according to Herschel–Bulkley model: η = η0+ k/γ, and the relationship between shear rate(γ) and shear force(τ) was investigated according to:τ = τ0+Kγ~n. It was revealed that the mixed fluid belonged to Yield Pseudoplastic Fluid.

LCPs勇闯5G人才招聘会

随着5G时代的来临,各国在高新技术领域你追我赶,功能高分子材料的发展也是日新月异。在这样的背景下,液晶聚合物(LCP)在5G材料领域大显身手,成为站在时代风口浪尖的“超级明星”。本文通过一场特殊的人才招聘大会,简述了液晶科学的历史以及液晶高分子的性质与应用。

Preparation and characterization of a novel antibacterial acrylate polymer composite modified with capsaicin

A novel antibacterial acrylate polymer composite modified with capsaicin was successfully synthesized by a two-step reaction.Capsaicin and acryloyl chloride were firstly esterified,and then applied to solution polymerization with acrylate monomers and styrene.The yield of the esterified products was about 85.3%.The polymer was characterized by Fourier transform infrared spectroscopy(FTIR),gel permeation chromatography(GPC),thermogravimetric analysis(TGA),contact angle(CA)and antibacterial ring tests.The number-average molecular weight(M_n)of the polymer was 27214,based on the capsaicin-acrylate dosage of 6.5 wt%.The TGA revealed a stable thermal property.The contact angles of the polymers films on tinplate increased from 77.5°to 86.2°with the increasing amount of capsaicin-acrylate.The antibacterial tests demonstrated excellent antimicrobial capability of the polymers.

新冠疫情对中小微企业的冲击与纾困策略

一方面中小微企业自身应当通过适应线上经济新趋势、稳定供应链、提升价值链地位、加强技术创新等措施积极自救;另一方面,政府应当通过提振消费、畅通国内国际产业链、推动新基建、提高政策效能等措施帮助中小微企业纾困。

A general mechanism of grain growth-Ⅱ: Experimental

The formed microstructure inside polycrystalline materials strongly influences their practical performances,which process is mostly dominated by grain growth behaviors.However,the general evolution of grain growth behaviors,especial for the occurrence of abnormal grain growth and stagnant growth,remains ambiguous despite decades of efforts.Here,we investigate systematically the general evolution of grain growth behaviors by combining a new grain growth theory with grain growth experiments in SrTiO_(3) polycrystalline materials.The results demonstrate that the observed evolution of grain growth behaviors is in accord with the theoretical predictions,which reveals that the abnormal and stagnant behaviors of grain growth may intrinsically occur in polycrystalline systems due to the existence of nonzero step free energy for grain growth.Furthermore,the general growth theory reveals that normal grain growth results from the roughening transition of grain boundaries which corresponding to step free energy equal to zero.Besides the lower GB energy as commonly believed,the narrower grain size distribution is revealed to play an important role on the thermal stability of grains,which may lead to the counter-intuitive phenomenon of smaller nano-sized grains with higher thermal stability as recently reported in the literature.The general,quantitative growth theory may offer an accurate guidance for the microstructural design with optimal physical properties in polycrystalline materials.

A general mechanism of grain growth-Ⅰ.Theory

The behaviors of grain growth dominate the formation of the microstructure inside polycrystalline materials and thus strongly influence their practical performances.However,grain growth behaviors still remain ambiguous and thus lack a mathematical formula to describe the general evolution despite decades of efforts.Here,we propose a new migration model of grain boundary(GB)and further derive a mathematical expression to depict the general evolution of grain growth in the cellular structures.The expression incorporates the variables influencing growth rate(e.g.GB features,grain size and local grain size distribution)and thus reveals how the normal,abnormal and stagnant behaviors of grain growth occur in polycrystalline systems.In addition,our model correlates quantitatively GB roughening transition with grain growth behavior.The general growth theory may provide new insights into the GB thermodynamics and kinetics during the cellular structure evolution.