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1.
《材料科学技术学报》2019,35(8):1767-1778
The mechanical, tribological and corrosion protection offered to Mg-9Li-7Al-1Sn and Mg-9Li-5Al-3Sn-1Zn alloys by the epoxy coating containing polyaniline/graphene (PANI/Gr) pigments is undertaken in the current work. PANI/Gr containing coatings were observed to be strongly adherent with a higher scratch hardness (Hs) and plowing hardness (Hp), i.e. Hs of 0.43 GPa, and Hp of 0.61 GPa, respectively when compared to that of neat epoxy coating (Hs of 0.17 GPa, and Hp of 0.40 GPa, respectively). Due to their higher Hs and Hp values, PANI/Gr based coatings displayed an enhanced wear resistance (Wear volume, Wv = 4.53 × 10-3 m3) than that of neat epoxy coating (Wv = 5.15 × 10−3 m3). The corrosion protection efficiency in corrosive environment of 3.5 wt% NaCl solution was obtained to be >99% for PANI/Gr containing coatings when compared to that of neat epoxy coating. The charge-transfer resistance (Rct) of the PANI/Gr containing coatings were estimated to be >106 Ω cm2, which indicates their highly protective nature when compared to that of neat epoxy coating (Rct ˜105 Ω cm2). Hence, PANI/Gr containing coatings can be potentially used for wear resistance and corrosion protection applications in marine environments. 相似文献
2.
针对四旋翼无人机在实际应用过程中出现质量变化的情况,基于自适应控制理论设计质量观测器,用于实时观测无人机的质量并修正其质量参数.在经典反步控制器(CBC)基础上,结合质量观测器和第一类控制误差积分,提出反步积分自适应控制器(BIAC),用于无人机的轨迹跟踪控制.该控制器的设计过程基于Lyapunov稳定性理论,能够保证... 相似文献
3.
The design of an ultraprecision displacement sensor with sub-nanometre resolution is proposed for the use of ultraprecision technologies. The sensor is based on the highly sensitive detection of power change at a specific point in light reflected from an object surface when the surface is subject to a small displacement. The sensor consists of a single light source, the reflective object and reference surfaces, optical fibre bundles for tranmission of the illuminating and the reflected light, and the photodiode set-up. In operation, the object and the reference surfaces are illuminated by light transmitted through the optical fibre bundle from the single light source. The reflected light from both surfaces is then transmitted through the optical fibre bundle to two individual but equivalent photodiodes. By using a differential amplifier, the diodes give a highly sensitive displacement signal which is included in the total signal of the reflected light. The sensor proposed has some distinctive features in its performance, such as non-contact measurement, a high resolution of 0.5 nm, a wide working range of about 30 μm within 5% linearity, and the sufficient stability of 1 nm in 20 s for specific research purposes. 相似文献
4.
Silicon carbide (SiC) interphase was introduced by chemical vapor deposition (CVD) process to prevent carbon fiber degradation and improve fiber–matrix interface bonding of C/ZrC composite prepared via precursor infiltration and pyrolysis (PIP) process. Moderate thickness of SiC interphase in fiber bundles could increase the density of the composite, but when the thickness of SiC interphase was over 0.5 μm, more close pores formed and the density of the composite decreased. The SiC interphase could protect carbon fiber effectively from carbo-thermal reduction, but could not enhance the mechanical properties of C/ZrC composite. The flexural strength and fracture toughness of C/ZrC composites with 0.05 μm thickness SiC layer were 252 MPa and 13.6 MPa m1/2, and for those with 0.5 μm thickness SiC layer 240 MPa and 12.8 MPa m1/2, both close to the value of the composite without SiC interphase (254 MPa and 14.5 MPa m1/2), while those with 0.7 μm thickness SiC layer were only 191 MPa and 10.8 MPa m1/2, respectively. Moderate content of SiC interphase could improve the ablation property of C/ZrC composites; however excessive content of SiC interphase would decrease the ablation property. 相似文献
5.
The interaction between microstructure, mechanical, and frictional properties of a commercial brake lining material (BLM) was investigated in order to correlate them to braking performance. For this purpose, a Scanning Electron Microscope (SEM) with energy dispersive X-ray (EDX) mapping and spectrum were used to identify and analyze different constituents. The mechanical properties were determined using compression test. Relevant physical properties (density and porosity) were determined using standard test methods. The friction coefficient and wear behavior of the friction material on contact with the grey cast iron disc were established using a pad-on disc tribometer. The results have shown that the brake lining material contains phenol resin such as the matrix and other various ingredients, including silica, rock and mineral filler reinforcement, barium sulfate and carbon-rich particles as filler and brass particles as friction modifier. It had a varied amount and size up to 1 mm for brass particles. The density and porosity were 1.8 g cm−3 and 7%, respectively. The investigated material exhibited excellent mechanical properties in the normal solicitation direction. The average friction coefficient was about 0.65, whereas the friction coefficient was stable. The different actions of various ingredients in terms of their effects on the friction and wear behavior of the BLM could be related to their different bonding strengths with the resin matrix and their different abilities to form friction films (third-body layer) on the surfaces of the material and transfer films on the counterpart cast iron surface in relation to the surface temperature evolution and mechanical properties. 相似文献
6.
Polymer derived silicon carbide (SiC) interphase was introduced by precursor infiltration and pyrolysis (PIP) to prevent carbon fiber erosion and to improve the fiber–matrix interface bonding of C/ZrC composites prepared by PIP. Introducing SiC interphase increased the density of the composites. The SiC interphase not only protected carbon fibers effectively from erosion by carbo-thermal reduction, but also enhanced the mechanical properties of C/ZrC composites by strengthening the interface bond. The flexural strength and fracture toughness of C/ZrC composites with SiC interphase prepared by two PIP cycles were 319 MPa and 18.8 MPa m1/2 respectively. The ablation properties of C/ZrC composites were with rising content of SiC interphase but then decreased when excessive. The mass loss rate and the linear recession rate of the C/ZrC composites with SiC interphase prepared by one PIP cycle were 0.0079 g/s and 0.0084 mm/s, respectively. 相似文献
7.
The purpose of the present work was to investigate and compare the mechanical and tribological behaviors of ceramic-matrix friction material (CMFM) with steel fiber (SF), mullite fiber (MF), and mixing SF and MF. The CMFM was prepared by hot-pressing sintering, and the tribological behaviors were determined using a constant speed friction tester. The worn surfaces and wear debris were observed by a scanning electron microscopy (SEM). Experiment results show that the combination of SF and MF can improve the mechanical properties that each single fiber does not have. The sever fade for the specimen reinforced by single MF during the whole friction testing can be attributed to the poor interface cohesive strength between MF and matrix. Mixing the SF and MF can improve the friction stability, and the friction coefficients for friction material with a mixture of the SF and MF increases with increasing MF content. For all specimens, increasing in the friction temperatures result in the increase of wear rates. 相似文献
8.
L. Zhang Y.B. Liu Z.Y. Cao Y.F. Zhang Q.Q. Zhang 《Journal of Materials Processing Technology》2009,209(2):792-797
The effects of isothermal process parameters on the microstructure evolution of semisolid AZ91D alloy produced by strain-induced melt activation (SIMA) were investigated using the self-programmed analysis software based on quantitative metallography. The results showed that long isothermal time could make the semisolid particles more globular, but the size of the particles would grow larger; high semisolid isothermal temperature would reduce the solid volume fraction and accelerate the spherical evolution of the solid particles. It was found that the optimal process parameters should be 570 °C and 10–20 min of isothermal temperature and time respectively based on the conditions of this paper. The mechanism of the particles’ formation was also discussed during the isothermal treatment. 相似文献
9.
为研究边界润滑条件下表面固体润滑涂层对活塞裙摩擦磨损性能的影响,从而为高强化内燃机活塞裙涂层的设计提供支撑,采用自制往复式摩擦磨损试验机,设计活塞裙–气缸套试样级试验,开展38CrMoAl镜面氮化气缸套分别与石墨、二硫化钨涂层活塞裙（铝硅合金基体）的摩擦磨损试验,获得了不同工况条件下两种活塞裙–气缸套配副的摩擦系数和磨损量结果,并分析了磨损表面情况。结果表明：在所有试验工况下,二硫化钨涂层活塞裙磨损量、摩擦系数均小于石墨涂层活塞裙。在15、25、35 MPa三种强化负荷试验条件下,随着负荷升高,摩擦系数和磨损量整体呈现上升趋势;试验温度由120 ℃升高到150 ℃时会促进润滑油中二烷基二硫代磷酸锌（zinc dialkyl dithiophosphate, ZDDP）添加剂的分解,摩擦系数和磨损量总体呈下降趋势;在35 MPa条件下,试验温度由150 ℃升高到180 ℃时,摩擦系数和磨损量会再次升高,在高温高载作用下,活塞裙基体硅颗粒露出引起的磨粒磨损程度增加。 相似文献
10.
《Ceramics International》2020,46(6):7687-7693
In order to improve the corrosion resistance and bioactivity of biodegradable Mg alloy substrate, novel Zn-HA/Zn double-layer coatings with different HA/Zn ratios in weight were deposited on AZ91D substrates by cold spraying. Phase compositions and microstructures of as-sprayed coatings and coatings after corrosion tests were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Electrochemical corrosion behaviors of both Zn-HA/Zn double-layer coatings were investigated in Hanks’ simulated body fluid using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results showed that both the pure Zn coating and HA/Zn composite coatings presented the similar phase compositions with their primary powders in addition to Zn oxidizations. Zn powders were plastically deformed and partially oxidized due to its low melting point, while HA powders were mainly crashed into fragments and hill-like splats. Both Zn under layer and HA/Zn upper layer were well bonded and presented dense structures, differences in HA/Zn upper layers were related to the HA/Zn ratios. Potentiodynamic polarization and EIS measurements illustrated that the cold-sprayed Zn-HA/Zn double-layer coatings not only improve the corrosion resistance of Mg alloy substrates, but also enhance its bioactivity due to the HA existed in composite upper layer. 相似文献