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。     

海面油膜的偏振反射特性仿真实验

为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。     

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.     

Microwave dielectric ceramics in (Mg1/3Sb2/3)O2-ZrO2-TiO2 system with near zero τf and low loss in a very wide range

A series of (ZrTi)_1-x(Mg_1/3Sb_2/3)_2xO₄ (0.04?≤?x?≤?0.36) ceramics were successfully synthesized through the conventional solid-state processing. Appropriate content of CuO was added as sintering aids to promote the density of ceramics. The XRD analysis revealed that the main crystalline phase of ceramics sintered at optimal temperature belonged to α-PbO₂-type structure. Raman spectroscopy and far infrared reflectivity (FIR) spectra were employed to study the phonon modes of ceramics, which explained the relationship between microwave dielectric properties and structure. It is interesting that the τ_f are near-zero (+6.6 ~ ?4.6?ppm/°C) and meanwhile the Q×f are relatively high (29,000–41,800?GHz) for samples with x in a very wide range of 0.10–0.36. In this range, their dielectric constants (ε_r) can be adjustable from 35.4 to 24.4. The results demonstrated this ceramic system is a potential candidate for microwave dielectric applications requiring an adjustable dielectric constants and near zero τ_f.     

Growth,microstructure, energy–storage and dielectric performances of chemical–solution NBT–based thin films: Effect of sodium nonstoichimometry

Na_0.5+δBi_0.5(Ti_0.96W_0.01Ni_0.03)O₃ thin films with various Na contents (abbreviated as Na_.5+δBTWN, δ?=?? 3.0, ??1.5, 0, 1.5%) were fabricated on ITO/glass substrates using a chemical–solution process. The effects of Na nonstoichiometry on the microstructure, insulating, ferroelectric and dielectric performances are investigated. The pure perovskite phase can be obtained in Na_0.5BTWN and Na_0.515BTWN, while for Na_0.470BTWN or Na_0.485BTWN, the main composition contains secondary phase of TiO₂. The grain size increases from 30?nm at δ?=?? 3.0% to 55?nm at δ?=?0%, then decreases to 52?nm with δ?=?1.5%. The leakage current of Na_0.485BTWN sample is reduced dramatically in comparison with Na_0.5+δBTWN (δ?=?? 3.0, 0, 1.5%). The big recoverable energy–storage density of 63.1?J/cm² and high energy–storage efficiency of 55.0% can be obtained for Na_0.485BTWN due to the improved electric break–down strength and large difference value between the remanent polarization and maximum polarization. Enhanced dielectricity is achieved in Na_0.485BTWN with a high tunability of 36.0% and a figure of merit of 4.0 at 450?kV/cm and 500?kHz. These results demonstrated that the crystallization, micrographs and energy storage and dielectric properties of Na_0.5Bi_0.5TiO₃ are highly sensitive to low levels of Na–site nonstoichiometry.