时效处理对Mg-2.0Zn-0.5Zr-3.0Gd生物降解镁合金组织、力学性能及耐腐蚀性能的影响

通过金相显微分析(OM)、扫描电镜观察(SEM)、透射电镜观察(TEM)和拉伸性能测试研究不同时效时间对Mg-2.0Zn-0.5Zr-3.0Gd生物镁合金显微组织及力学性能的影响,通过质量损失和电化学方法研究合金在模拟体液(SBF)中的耐腐蚀性能。结果表明:时效时间为4~20 h时,合金中析出相的尺寸及数量随时效时间的延长而增加,析出相主要以纳米级棒状和颗粒状的(Mg,Zn)3Gd相形式存在,部分棒状析出相与α-Mg基体具有共格界面关系。合金的强度及伸长率随时效时间的延长先升高后降低。在120 h的浸泡实验中,合金的平均腐蚀速率、点蚀孔洞的数量及孔洞尺寸随时效时间的延长而逐渐增大,腐蚀速率随浸泡时间延长呈现出先减小、后增大、再缓慢减小以及最后趋于稳定的过程。     

石墨烯基自支撑夹层材料在锂硫电池中的研究进展

近年来，高比能锂-硫电池作为最具前景的新能源储存装置之一引起了人们的广泛关注。然而，在该电池体系中，中间产物聚硫化物的溶解造成的穿梭效应会明显降低电池的循环性能和硫利用率，严重阻碍锂-硫电池的推广应用。综述了近年来石墨烯和石墨烯基复合自支撑中间层材料在锂-硫电池中的应用，例如，通过物理或化学限域的方法减缓多硫化物的穿梭并改善锂-硫电池电化学性能等，并对石墨烯基复合自支撑中间层材料未来在锂硫电池中的实际应用进行了展望。     

稀土元素Dy对Mg-2Zn-0.5Zr生物镁合金组织与性能的影响

通过拉伸试验、浸泡实验、电化学测试、扫描电镜(SEM)以及光学显微镜(OM)等方法研究了Dy含量对Mg-2Zn-0.5Zr-xDy生物镁合金微观组织、耐腐蚀性能和力学性能的影响。结果表明:随Dy含量的增加,合金的晶粒尺寸逐渐变小,第二相逐渐增多且主要沿晶界分布,合金的平均腐蚀速率先降低后升高,合金的力学性能先升高后降低;当Dy含量为1.5 mass%时,合金的耐蚀性能和综合力学性能均最好,平均腐蚀速率从未添加稀土元素时的1.28 mm/a降为0.92 mm/a,抗拉强度和伸长率分别为154 MPa和8.6%。     

Structure and properties of TiC/Ti coatings fabricated on NiTi by plasma immersion ion implantation and deposition

A titanium carbide (TiC) nanostructured coating and Ti intermediate layer are fabricated on NiTi by plasma immersion ion implantation and deposition (PIII&D) to improve the surface properties. The chemical composition and structure are determined by X-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Nano-indentation is used to evaluate the mechanical properties of the thin film and the biological characteristics are assessed by electrochemical measurement and soaking tests in simulated body fluids. Based on the potentiodynamic polarization and Ni release data after the polarization test, the Ti/TiC nanostructure coating has better corrosion resistance compared to the NiTi substrate and there is significantly less Ni ion release from the NiTi substrate into the simulated body fluids than the uncoated NiTi alloy.     

Predictive model of superplastic properties of aluminum bronze and of the superplastic extrusion test

The superplastic properties of aluminum bronze were studied by way of artificial neural network. The model was established using Levenberg–Marquardt algorithm. It was improved by studying superplastic tension test data of aluminum bronze such that the superplastic forming parameters were optimized. According to the parameters, the experiment of superplastic extrusion of a solid bearing was performed. It is shown that the model reflected well the relationship between superplastic properties of aluminum bronze and superplastic tension conditions. The relative error between the test values and the predicted values of the network is less than 8.5%, which meets perfectly the demands of superplastic deformation of aluminum bronze. Moreover, the superplastic forming of solid cage of aluminum bronze show that it is feasible to produce solid cage using superplastic extrusion process. This extrusion process has remarkable economic benefits as well.     

碳纤维化学镀镍表面改性研究题

目的在碳纤维表面进行化学镀镍,对碳纤维化学镀镍的表面改性进行研究。方法通过X射线衍射仪、扫描电子显微镜等测试手段研究pH值、热处理温度及超声波对镀层的形貌、组织结构及镀速的影响。结果 pH值在8.0~10.0时,随pH值增大,沉积速率逐渐变大,镀层表面均匀致密,与基体结合良好,厚度约为0.5μm;pH值在10.0~11.0时,碳纤维发生团聚。热处理温度为400℃时,保温10min,镀层重结晶析出Ni3P相;随温度升高,镀层发生开裂,且开裂部位间隔变小。结论 pH值对镀层沉积影响较大,超过极限值会导致碳纤维团聚。热处理温度过高会导致镀层重结晶,且发生开裂。     

Sliding wear behavior of copper alloy contact wire against copper-based strip for high-speed electrified railways

This paper reports the study of the sliding wear behavior of the Cu–Ag–Cr wire. Cu–Ag–Cr alloy is a promising contact wire material for high-speed electrified railways, which has an excellent combination of mechanical strength and electrical conductivity. Wear tests were conducted under laboratory with a special sliding wear apparatus, which simulated the tribological conditions of sliding current collectors on overhead wires in the railway system. The Cu–Ag–Cr alloy wire was slid against a copper-based powder metallurgy strip under unlubricated conditions. The same strip as those in the train systems were used. Worn surfaces of the Cu–Ag–Cr alloy wire were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). Within the studied range of electrical current, normal pressure and sliding speed, the wear rate increased with the increasing electrical current and the sliding distance. Compared with a Cu–Ag contact wire under the same conditions, the Cu–Ag–Cr alloy wire had much better wear resistance. Adhesive wear, abrasive wear and arc erosion were the dominant mechanisms during the electrical sliding processes.     

Hot deformation behavior and processing map of Mg-2Zn-1Al-0.2RE alloy

In this study,uniaxial hot compression tests were carried out between 200 and 400℃ over strain rates of0.001-1 s~(-1) to investigate the hot deformation behavior of Mg-2 Zn-1 Al-0.2 RE alloy with coarse grains.The average activation energy was measured to be 174.51 kJ/mol.In addition,a constitutive relation based on the Arrhenius equation was established.Dynamic recrystallization(DRX) kinetics were studied by Avrami equation to characterize the evolution of DRX volume fraction.DRX was favored at high temperatures of 300-400℃ and low strain rates of 0.001-0.01 s~(-1).According to dynamic material model and Prasad's instability criterion,a maximum power dissipation of 38% and 32% occurs at 400℃/0.001 s~(-1) and 400℃/0.01 s~(-1),respectively.According to the proce ssing map,330-400℃/0.001-0.01 s~(-1)was determined as the optimum deformation parameter range.     

Effect of BaCu(B2O5) on the sintering and microwave dielectric properties of Ca0.4Li0.3Sm0.05Nd0.25TiO3 ceramics

The sintering behaviors and microwave dielectric properties of the Ca_0.4Li_0.3Sm_0.05Nd_0.25TiO₃ (abbreviated CLSNT) ceramics with different amounts of BaCu(B₂O₅) addition were investigated in this paper. Adding BaCu(B₂O₅) to CLSNT lowered its sintering temperature from 1300 °C to 925 °C. No secondary phase was observed in the CLSNT ceramics and complete solid solution of the complex perovskite phase was confirmed. The CLSNT ceramics with small amounts of BaCu(B₂O₅) addition could be well sintered at 925 °C without much degradation in the microwave dielectric properties. Especially, the 1.75 wt.% BaCu(B₂O₅)-doped CLSNT ceramic sample sintered at 925 °C for 3 h had optimum microwave dielectric properties of ε_r = 93.5 ± 3.2, Q × f = 6486 ± 434 GHz, and τ_f = 5 ± 1.5 ppm/°C (at 3–4 GHz), enabling it a promising candidate material for LTCC applications. Obviously, BaCu(B₂O₅) could be a suitable sintering aid to facilitate the densification and microwave dielectric properties of the CLSNT ceramics.     

Sintering behavior and microwave dielectric properties of 0.67CaTiO3–0.33LaAlO3 ceramics modified by B2O3–Li2O–Al2O3 and CeO2

A low temperature sintering method was used to avoid the relatively high sintering temperatures typically required to prepare 0.67CaTiO₃–0.33LaAlO₃ (CTLA) ceramics. Additionally, CeO₂ was introduced into the CTLA ceramics as an oxygen-storage material to improve their microwave dielectric properties. 0.67CaTiO₃–0.33LaAlO₃ ceramics co-doped with B₂O₃–Li₂O–Al₂O₃ and CeO₂ were prepared by a conventional two-step solid-state reaction process. The sintering behavior, crystal structure, surface morphology, and microwave dielectric proprieties of the prepared ceramic samples were studied, and the reaction mechanism of CeO₂ was elucidated. CTLA+0.05 wt% BLA+3 wt% CeO₂ ceramics sintered at 1360 °C for 4 h exhibited the optimal microwave dielectric properties: dielectric constant (ε_r)=45.02, quality factor (Q×f)=43102 GHz, and temperature coefficient of resonant frequency (τ_f)=2.1 ppm/°C. The successful preparation of high-performance microwave dielectric ceramics provides a direction for the future development and commercialization of CTLA ceramics.