半导体纳米复合材料的制备及其光电催化CO2还原

本实验通过模拟植物光合作用,设计制备了新颖的光电联合催化池3D-ZnO/Ni BiVO4/FTO,用电化学沉积法制备了泡沫镍负载的ZnO纳米棒光电阴极和BiVO4光电阳极,以0.1 mol·L^−1 KHCO3水溶液作为电解质,1 mmol·L^−1曙红Y为光敏剂,在−0.6 V硅太阳电池的电压下光电催化还原CO2得到了乙醇、乙酸和甲醇,总产率22.5μmol·L^−1·h^−1·cm^−2。实现了将太阳能贮存为化学能并减少了空气中的CO2,加深了学生对绿色化学和植物Calvin循环机理的理解。     

Improving breakdown strength and energy storage efficiency of poly(vinylidene fluoride-co-chlorotrifluoroethylene) and polyurea blend films by double layer structure design

All-organic composites are widely used in energy storage application due to the high breakdown strength performance, but the improvement of energy storage was limited by the relatively low dielectric constant. Therefore, to satisfy the high demands of dielectric materials, energy storage properties of polymer composites should be further enhanced. In this article, poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) and polyurea (PUA), which are known as high dielectric ferroelectric material and linearly high energy storage efficiency material respectively, are composited through double layer (DL) casting method for the first time. The properties of DL structured composite film is contrasted with solution blending structure especially in energy storage efficiency, and the results demonstrate that DL structure design can make great use of advantages of two materials and also can avoid the influence of phase separation between P(VDF-CTFE) and PUA efficiently. Moreover, high breakdown strength (6180 kV/cm) and high energy storage efficiency (77%) of DL composites can be realized simultaneously by incorporating PUA as an insulating layer, and the mechanism is discussed in detail. This work provides an effective route to improve the energy storage properties of polymer dielectric materials and shows great application potential.     

Mechanical characterization of a new Kevlar/Flax/epoxy hybrid composite in a sandwich structure

Natural fibers are inexpensive, biodegradable, and have similar specific properties to some synthetic fibers. Hardly any previous investigations exist of a composite made of multiple layers of pure Kevlar fiber fabric and pure Flax fiber fabric in a “sandwich structure”, but it only measured impact properties. The composite was made of 12 Flax/epoxy layers at the core in 3 possible configurations (i.e. [0]_12F, [0/90]_6F, or [±45]_6F) that were sandwiched by 2 Kevlar/epoxy layers (i.e. plain weave) on each side. This study showed maximum change in the mechanical properties with respect to Flax/Epoxy for tension (+137.85% in E_T, and +171.22% in σ_UT), compression (+171.22% in E_c, and −10.6% in σ_UC), 3-point bending (−11.54% in E_B, and +2.19 in σ_UB), torsion (−5.31% in G, and 395.82% in τ), and water absorption (60.04%). This novel hybrid composite may be useful for research and industry applications.     

Experimental and molecular simulating study on promoting electrolyte-immersed mechanical properties of cellulose/lignin separator for lithium-ion battery

Lithium-ion batteries have been developing intensively and earn an unprecedented reputation, yet advanced performance and safety issue still require considerable investigation. Separator is vital to comprehensive properties of batteries, where the mechanical properties are key to breaking through of new-type separator. Unfortunately, electrolyte submersion has caused damage to strength of cellulose separator. Whereupon, in this work, cellulose separator is optimized by introducing lignin particles to promote electrolyte-immersed mechanical strength. Experiments are conducted concerning surface morphology, contact angle, porosity, electrolyte uptake, mechanical properties and electrochemical performance. Molecular simulation is implemented to explore the mechanism of tensile behavior of cellulose and lignin subjected to electrolyte solvents. Experimental results confirm positive effect of lignin addition in improving mechanical properties and simultaneously maintaining impressive electrochemical performance of the cellulose/lignin composites separators. Besides, lignin addition amount of 2.5% and 5% is recommended to achieve promising overall properties. Molecular simulation has successfully unveiled that weakening of cellulose separator submerged in electrolyte is resulted by the deformed cellulose amorphous region and the promoting effect of adding lignin is contributed from the new hydrogen bonds generated between cellulose and lignin molecules. Hopefully, this work provides novel insight on preparing remarkable separator and mechanism of materials behavior.     

Domain-based local pair natural orbital methods within the correlation consistent composite approach

Ab initio composite approaches have been utilized to model and predict main group thermochemistry within 1 kcal mol⁻¹, on average, from well-established reliable experiments, primarily for molecules with less than 30 atoms. For molecules of increasing size and complexity, such as biomolecular complexes, composite methodologies have been limited in their application. Therefore, the domain-based local pair natural orbital (DLPNO) methods have been implemented within the correlation consistent composite approach (ccCA) framework, namely DLPNO-ccCA, to reduce the computational cost (disk space, CPU (central processing unit) time, memory) and predict energetic properties such as enthalpies of formation, noncovalent interactions, and conformation energies for organic biomolecular complexes including one of the largest molecules examined via composite strategies, within 1 kcal mol⁻¹, after calibration with 119 molecules and a set of linear alkanes. © 2019 Wiley Periodicals, Inc.     

波形钢板-UHPC组合桥面板结构截面优化

对实腹式波形顶板-UHPC(超高性能混凝土)组合桥面板进行了改进, 采用空腹式结构建立波形钢板-UHPC组合桥面板有限元模型, 研究UHPC层厚度、波形钢板厚度、波形长度、下缘板宽度和波形高度等截面参数变化对组合桥面板受力特性的影响, 并确定其合理取值范围. 在此基础上, 通过理想点法对参数组合进行优化, 得到合理的参数匹配. 研究结果表明 相较于实腹式组合桥面板, 优化后的组合桥面板自重减小35%, 钢板弯折处应力减小16%; 相较于正交异性钢桥面板, 桥面板用钢量减小7%, 顶板与U肋连接位置应力减小47%.     

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self‐assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant‐free emulsion polymerization to form hybrid polyurea‐acrylic particles despite the absence of a measureable water‐soluble fraction. The T_g of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 °C and >175 °C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea‐acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373–1388     

4D Printing based piezoelectric composite for medical applications

Additive manufacturing (AM), otherwise known as three‐dimensional (3D) printing, is driving major innovations in many areas, such as engineering, manufacturing, art, education, and medicine. Although a considerable amount of progress has been made in this field, additional research work is required to overcome various remaining challenges. Recently, one of the actively researched areas lies in the AM of smart materials and structures. Electroactive materials incorporated in 3D printing have given birth to 4D printing, where 3D printed structures can perform as actuating and/or sensing systems, making it possible to deliver electrical signals under external mechanical stimuli and vice versa. In this paper, we present a lightweight, low cost piezoelectric material based on the dispersion of inorganic ferroelectric submicron particles in a polymer matrix. We report on how the proposed material is compatible with the AM process. Finally, we discuss its potential applications for healthcare, especially in smart implants prostheses. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 109–115     

Facile preparation and synergy study of DMC/ZnGA composite catalyst for the synthesis of oligo (propylene‐carbonate) diols

To overcome the weak carbon dioxide (CO₂) conversion ability of Zn‐Co double metal cyanide (DMC) catalyst, zinc glutarate (ZnGA) catalyst was introduced into the DMC catalytic system and applied for the synthesis of oligo (propylene‐carbonate) diols. The DMC/ZnGA composite catalyst (mass ratio = 10:1) exhibited an excellent synergistic effect which had enhanced CO₂ activation ability, high yield and good selectivity. In copolymerization process, ZnGA catalyst not only provided activated CO₂ for DMC catalyst, but also transferred the propagating chain with more alternating structures to DMC catalyst. Both of the two effects increased the carbonate content in the final products. Overall, DMC catalyst dedicated to the polymer chain growth, while the increased CO₂ conversion mainly attributed to ZnGA catalyst. Oligo (propylene‐carbonate) diols with carbonate unit content of 45.1 mol%, Mn of 1228 g/mol, W_PC of 4.3 wt% and high yield of 1689 g/g _cat was obtained.