Microstructure and Mechanical Properties of Cu Matrix Composites Reinforced byTiB2/TiN Ceramic Reinforcements

Cu matrix composites reinforced by TiB₂/TiN ceramic reinforcements (Cu/TBN composites) were prepared by hot pressing method. Prior to the hot pressing, Cu/TiB₂/TiN composite powders (CTBN powders), which were used as the starting materials of Cu/TBN composites, were fabricated by self-propagating high-temperature synthesis method. The CTBN particles were found to be in a special core-shell structure with a Cu-Ti alloy core and a TiB₂/TiN ceramic shell. The test results presented obvious improvements in mechanical properties. The highest ultimate tensile strength reached up to 297 MPa, 77 MPa higher than that of Cu. And the highest hardness reached up to 70.7 HRF, 15.7 HRF higher than that of Cu. A comparative study indicated that the core-shell structured particles could bring about more obvious strengthening effect than the traditional irregularly shaped particles, which was due to the improved Cu/ceramics interfacial bonding, the linkage strengthening effect of both TiB₂ and TiN, and higher load bearing ability of the core-shell structured reinforcements.     

Ultra-thin Laminated Metal Composites with Ultra-high Strength and Excellent Soft Magnetic Properties

Structural metallic materials with excellent functional performance and lightweight features have always been the goal of material scientists' pursuit.In this work,laminated metal composites of different thicknesses(less than 0.4 mm) composed of structural materials with great differences in deformation ability were successfully fabricated via a novel processing procedure.Ultra-high strength and excellent soft magnetic properties were combined perfectly in the ultra-thin and super-light laminated metal composite strips due to unique structural design and essential attributes of the initial materials.These results emphasize the significant potential application value of the ultra-thin laminated metal composites in the field of structural and functional integration.     

脉冲偏压对TiAlCN薄膜结构与力学性能的影响

利用多弧离子镀-磁控溅射复合技术通过改变脉冲偏压在Si片与SS304基体表面制备了TiAlCN薄膜,研究了不同脉冲偏压对薄膜结构和力学性能的影响。薄膜成分、表面形貌、相结构及力学性能分别利用能量弥散X射线谱(EDS)、扫描电镜(SEM)、X射线衍射(XRD)和纳米压痕仪等设备进行表征。结果表明,随着脉冲负偏压的增加,薄膜中Ti元素的含量先减小后增大,而Al元素有相反的变化趋势。适当增大脉冲偏压,薄膜表面颗粒、凹坑等缺陷得到明显改善。物相分析表明TiAlCN薄膜主要由(Ti,Al)(C,N)相,Ti4N3-x相和Ti3Al相组成。薄膜平均硬度与弹性模量随脉冲负偏压的增加先增大后减小,在负偏压-200 V时达到最大值分别为36.8 GPa和410 GPa。     

反应磁控溅射(CrMoTaNbVTi)N多主元薄膜的微观组织与机械性能研究

本文采用直流反应磁控溅射方法，通过溅射（CrMoTaNbV）镶嵌靶和纯Ti靶制备了(CrMoTaNbVTi)N多主元氮化物薄膜。研究了不同氮气流量比RN对(CrMoTaNbVTi)N薄膜的微观结构、力学性能和摩擦学性能的影响。结果表明，当RN=0% 和10%时薄膜为简单的体心立方结构，当RN=20%、30% 和40%时为简单的面心立方结构。随着氮气流量比RN的增大，表面颗粒逐渐减小，断面柱状晶更为致密，同时(CrMoTaNbVTi)N薄膜的残余应力、膜基结合力、硬度和弹性模量逐渐增大，且当RN=40%时达到最大值，分别为-3.3 GPa, 352 mN, 25.6±1.2 GPa 和 278.8±11.2 GP。RN =40%制备的氮化物薄膜具有最小的比磨损率，相较合金薄膜降低了约1个数量级，表现出优异的耐磨损性能。     

固溶时效处理对QCr1铸件性能的影响

研究了固溶及时效处理对铬青铜QCr1铸件力学性能及电导率的影响。研究结果表明,固溶温度不应超过1 030℃,时效处理后强度随时间先升后降,时效温度越高,可达到的强度峰值的时间越短,峰值强度越低。优化后的规范使QCr1铸件的强度及电导率均满足DIN系列相关标准要求。     

纳米纤维素的疏水改性及应用研究进展

纳米纤维素作为一种性能优越的可再生纳米材料，应用前景极为广阔。然而，由于纳米纤维素结构上富含羟基，使其具有极强的亲水性，严重影响了纳米纤维素的疏水性能，并且在一定程度上限制了其在复合材料领域的应用。综述了纳米纤维素疏水改性的研究进展，从物理吸附、表面化学修饰（甲硅烷化、烷酰化、酯化等）、聚合物接枝共聚3个方面简述了目前应用较为广泛的疏水化改性方法，并对疏水纳米纤维素在包装材料、造纸、水净化等方面的应用现状进行了总结。最后对疏水改性纳米纤维素的未来发展进行了展望，旨在为疏水纳米纤维素的研究和应用提供参考。     

Mechanical behavior of cold-water fish gelatin gels crosslinked with 1,4-butanediol diglycidyl ether

In this work, chemical crosslinking with 1,4-butanediol diglycidyl ether (BDDGE) is used as strategy to enhance mechanical performance of fish gelatin (FG) gels in order to meet the properties' range of mammalian gelatin physical gels. Joint analysis of free amino groups, swelling ratio, and total soluble material indicates that crosslinking degree increases with increasing FG concentration and it is favored by a 0.2 BDDGE/FG ratio. Increasing crosslinking degree enhances gel indentation strength and shear modulus (μ) while decreases fracture toughness (G_IC). Measured μ and G_IC values lies within the range exhibited by mammalian gelatin physical gels, but the relationship between these parameters is opposite. This is due to the different fracture mechanisms occurring in chemically crosslinked and physical gels.     

Evaluation of polyphosphoric acid on the performance of polymer modified asphalt binders

The aim of this research is to evaluate the effect of polyphosphoric acid (PPA) on the mechanical performance of styrene–butadiene–styrene (SBS) and styrene–butadiene–rubber (SBR) modified asphalt. Conventional properties, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS) tests were conducted to evaluate the performance characteristics of asphalt at different PPA inclusions. Gel-permeation chromatography (GPC), saturates, aromatics, resins, and asphaltenes (SARA), and Fourier transform infrared (FTIR) were carried to reveal the molecular weight, component and infrared spectra of asphalt. Results showed that PPA hardened the asphalt, improved the rutting and fatigue performances of polymer modified asphalt (PMA) binder, but weakened the anti-cracking performances. Besides, storage stability had a significant improvement as the addition of PPA. The addition of PPA brought more macromolecules into asphalt and led to more high-average molecular weight compounds. Furthermore, PPA changed four component ratios of asphalt. Both PMA with or without PPA have similar absorption peaks. This may be due to absorption peak of PMA covered the changes in PPA modification process as the low content of PPA. 0.8% dosage of PPA may be considered optimum for composite modified binder combining the above experimental results for this binder source.     

Waterborne star-shaped styrene-alkyd resins

Waterborne star-shaped styrene-alkyd resins (SSARs) were synthesized from a branched alkyd resin (AR) and styrene (St) by miniemulsion polymerization. SSARs are an environmentally friendly material. The ratio of AR to St for obtaining SSARs was as follows: 50:50 (SSAR1), 60:40 (SSAR2), 70:30 (SSAR3), and 80:20 (SSAR4). The conversion percentage was directly proportional to St used, and was higher than 94.0 %. Infrared analysis and protonic nuclear magnetic resonance revealed the reaction between AR and St. The synthesis process also leads to the formation of polystyrene and its concentration increases with the concentration of St. The values of the reacted double-bond fractions were higher than 17.80%. The SSARs drop size was bigger than the particle size. The miniemulsion colloidal stability was good at room temperature. The SSARs zeta potential was between −55 and −90 mV. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48386.     

Reversible Na+-extraction/insertion in nitrogen-doped graphene-encapsulated Na3V2(PO4)2F3@C electrode for advanced Na-ion battery

NASICON-structured sodium vanadium fluorophosphate has caused widespread concern for sodium energy conversion and storage because of its high voltage platform and high theoretical energy density. However, the inferior electrical conductivity is still a big problem, which greatly prevent the applications of Na₃V₂(PO₄)₂F₃ material. Herein, the nitrogen-doped graphene-encapsulated Na₃V₂(PO₄)₂F₃@C (NG-NVPF@C) has been prepared using the sol-gel approach. The physical and electrochemical performances for the resulted NG-NVPF@C composite have been systematically characterized and compared with that of Na₃V₂(PO₄)₂F₃@C (NVPF@C) in this study. The electrochemical tests demonstrate that the as-fabricated NG-NVPF@C displays higher capacity, superior rate property and better cyclic life than NVPF@C. It displays the discharge capacity of 108.6 mAh g⁻¹ at 5C. Moreover, it also possesses the high capacity of 101.6 mAh g⁻¹ at 10C over 300 cycles with the capacity retention of about 96.5%. The improved properties of NG-NVPF@C electrode are assigned to the constructed conductive network by nitrogen-doped graphene, which can modify the conductivity of Na₃V₂(PO₄)₂F₃.