Cf/C复合材料与纯铜的胶接辅助钎焊连接

采用胶接辅助钎焊方法,以TiH_2粉为活性元素源,环氧树脂为粘性载体,Ag-Cu共晶合金为钎料,Cu箔为应力缓冲层材料,实现了C_f/C复合材料与纯铜的钎焊连接,结果表明,接头界面处产生TiC,TiCu,Ag(s,s),Cu(s,s)等反应产物,其结构可表示为(C_f/C)/TiC+Ag(s,s)+Cu(s,s)+TiCu/Cu。通过钎焊工艺试验得出,在930℃保温25 min钎焊条件下接头的抗剪强度达到最大值30 MPa。     

Fabrication of Cu/graphite film/Cu sandwich composites with ultrahigh thermal conductivity for thermal management applications

Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m⁻¹·K⁻¹, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film.     

Unusual Two-Step Assembly of a Minimalistic Dipeptide-Based Functional Hypergelator

Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.     

固溶处理对TiB2/6061复合材料硬度及耐磨性的影响

采用氟盐法制备了TiB₂质量分数为3%的原位合成TiB₂/6061复合材料,研究了固溶温度和固溶时间对复合材料硬度和耐磨性能的影响。结果表明:TiB₂颗粒弥散分布在6061铝合金基体中,明显细化6061铝合金基体晶粒。当固溶温度一定时,随固溶时间延长,复合材料的硬度和耐磨性可获得明显提高,但固溶时间在6~10 h时,复合材料的性能变化不显著。当固溶时间一定时,随固溶温度升高,复合材料硬度和耐磨性呈现先上升后下降的趋势。3wt%TiB₂/6061复合材料经530 ℃×10 h固溶处理后,硬度和耐磨性能最佳,相较于铸态硬度值提高了79.5％,磨损量减少了59.1%。固溶处理后复合材料的磨损表面犁沟变细变浅,材料脱落现象减少。     

木粉疏水改性对HDPE基木塑复合材料性能的影响

采用一种操作简便且易于工业推广的方法对木粉进行疏水改性，具体过程为：将3种可热聚合的单体，即甲基丙烯酸甲酯（MMA）、甲基丙烯酸丁酯（BMA）和苯乙烯（St）均匀喷洒在木粉上，经过预热处理后，与配方中其他组分，如高密度聚乙烯（HDPE）和马来酸酐接枝聚乙烯（MAPE）等通过高速混合机混合均匀，采用双螺杆挤出机造粒后，注射制备木塑复合材料（WPC）样条，测试其力学性能。另外，考察了疏水改性对WPC接触角、维卡软化温度、洛氏硬度、吸水性能、热性能的影响规律。结果表明：疏水改性后WPC的接触角增大，木粉和HDPE的界面相容性改善，力学性能得到明显提高。其中，当MMA、BMA和St的添加量为3%时，WPC的力学性能最好，与疏水改性前相比，弯曲强度分别提高了17.3%、26.3%和27.5%，弯曲模量分别提高了24.4%、24.4%和26.0%，冲击强度分别提高了54.7%、57.7%和60.5%。 此外，疏水改性后WPC的维卡软化温度、洛氏硬度、耐水性和耐热性也得到改善。     

Fabrication of dense Ce0.9Mg0.1P2O7-PmOn composites by microwave heating for application as electrolyte in intermediate-temperature fuel cells

In the present work, we report a method of fabrication of dense 10 mol% Mg²⁺-doped cerium pyrophosphate-phosphate (Ce_0.9Mg_0.1P₂O₇-P_mO_n; CMP-P) composites by microwave heat-treatment of the preformed Ce_0.9Mg_0.1P₂O₇ substrates in the presence of phosphoric acid. The composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The microwave heating at 375 °C for 5 min resulted in the formation of dense CMP-P composites which retained most of the pyrophosphate phase. The electrical conductivity was extracted from the EIS data and for the CMP-P composite prepared by H₃PO₄ loading for 10 h and microwave heat-treatment for 5 min it was found to be >10^?2 S m^?1 in 100–250 °C range with a maximum of 0.062 S cm^?1 at 190 °C, which was significant for its application as electrolyte in intermediate temperature fuel cells.     

On the thermal conductivity of bimodal SiC/A356 composites fabricated via powder metallurgy route

The present study investigates the thermal conductivity of bimodal SiC particulate distribution in aluminum matrix composites fabricated via powder metallurgy route. The effects of the SiC_p reinforcement size distribution and processing parameters such as sintering time and temperature on the thermal conductivity have been examined. The Box–Behnken experimental array was employed to identify the effects of selected variables on the thermal conductivity of the composite. A reasonable augmentation in the thermal conductivity was observed with an increase in sintering time and %volume fraction of fine SiC particulates. It has been demonstrated that the matrix doped with fine SiC particulates (37?µm) occupied interstitial positions and formed continuous SiC–matrix network resulting in minimizing the micropores that contributed for good thermal conductivity, that is, 235?W/mK. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were conducted to evaluate the microstructure architecture and interfacial phase formation.     

Poly(L-lysine)-poly(ethylene glycol) layers with different structure and their influence on silica suspension stability

The effects of the structure of di- and triblock copolymers of poly(L-lysine) – LYS with poly(ethylene glycol) – PEG as well as the length of nonionic fragment in the LYS-PEG macromolecule on the copolymer chains conformation in the adsorption layer formed on the colloidal silica (SiO2) surface were examined. Spectrophotometry and turbidimetry were applied for the determination of copolymer adsorbed amounts and stability coefficients of silica aqueous suspensions. The electrokinetic parameters such as solid surface charge density and zeta potential were also estimated. The adsorption of LYS-PEG was proved to be the highest at pH 10 whereas the lowest adsorption on the solid surface was found for the triblock copolymer with long fragments of LYS at the same pH value.     

In‐plane shear damage behaviours of 2D needled C/SiC composites

Understanding the in‐plane shear behaviour of composites is essential to establish the design basis for practical applications. This study aims to investigate the shear damage behaviours of 2D needled C/SiC composites by various characterization techniques. The effect of layer arrangement on shear modulus and strength was discussed via shear stress‐strain responses. The shear strain field evolution and uniformity variation were studied by digital image correlation. It shows that the uniformity of shear strain field changes with the shear load, and the shear strain field evolution consist of 5 stages. The electrical resistivity measurement results indicate that structural deformation and damage evolution caused the electrical resistivity change. Furthermore, the damage evolution has a double effect on the electrical resistivity variation. The acoustic emission monitoring shows that the shear damage evolution is a 3‐stage nonlinear process before failure. The shear damages were categorized via acoustic characteristics. Besides, the postfailure behaviours were also discussed in this study.