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61.
Libo Mei Chunming Wang Yuhang Wei Sufen Xiao Yungui Chen 《International Journal of Hydrogen Energy》2018,43(14):7102-7107
The titanium dihydride (TiH2) powder metallurgy has been attracted a lot of attention, but TiH2 powder is difficult to press moulding. In this paper, the titanium hydride powder metallurgy including TiH2 and unsaturated titanium hydrides (TiH1.5) was investigated simultaneously compared with pure titanium metal powder metallurgy. The results indicates that the titanium hydride powder metallurgy is accompanied by the deoxidation self-purification effect during dehydrogenation process for both of TiH2 and TiH1.5, which have higher sintering density than pure titanium. There are the three stages relative to densification rate, namely the slow, rapid and full densification stages for all of three materials. The compressive yield strengths increase rapidly in the rapid densification stage and are unchangeable almost in the full densification stage after holding 2 h at 1300 °C. The titanium hydride powder metallurgy is helpful to obtain much better mechanical properties than the pure titanium metal powder metallurgy. Here the compressive yield strength of the as-sintered TiH2 compact with the maximum hydrogen content is the best but has very small difference compared with that of the as-sintered TiH1.5 compact after full sintering densification. 相似文献
62.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system. 相似文献
63.
采用水热反应制备出β-Ni(OH)2,然后通过水热还原得到Ni/β-Ni(OH)2纳米复合粉体材料,采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对复合材料的相结构、成分及形貌进行表征分析。采用四球摩擦磨损试验机评价制备的Ni/β-Ni(OH)2作为润滑油添加剂的摩擦学性能,基础油为PAO6。摩擦试验后,采用SEM分析典型试验钢球磨斑的表面形貌,利用能谱仪(EDS)研究磨斑表面化学元素的组成,探讨Ni/β-Ni(OH)2纳米复合润滑添加剂的减摩抗磨机制。结果表明:Ni/β-Ni(OH)2纳米复合材料作为润滑添加剂具有极好的减摩抗磨性能,显著优于基础油PAO6和未负载纳米Ni的二维β-Ni(OH)2层状材料;与基础油相比,添加0.1%质量分数Ni/β-Ni(OH)2添加剂的油样的摩擦因数和磨斑直径分别降低了17.6%和41.5%;Ni/β-Ni(OH)2纳米复合粉体综合了纳米Ni及层状β-Ni(OH)2两部分结构特性,在摩擦过程中,复合材料中的纳米金属粒子Ni与层状结构材料β-Ni(OH)2能够相互增强起到协同润滑作用。 相似文献
64.
Improving the performance of heat transfer fluids is altogether significant. The best approach for improving the thermal conductivity is the addition of nanoparticles to the base fluid. In the present study, specific heat, dynamic viscosity, and thermal conductivity of water-based Indian coal fly ash stable nanofluid for 0.1% to 0.5% volume concentration in the temperature range of 30 to 60°C has been investigated. To evaluate an average particle diameter of 11.5 nm, the fly ash nanoparticles were characterized with scanning electron microscopy and dynamic light scattering. Using zeta potential, the stability of nanofluid in the presence of surfactant Triton X-100 was tested. Thermal conductivity and viscosity of fly ash nanofluid increased, while specific heat decreased as volume concentration increased. The effect of temperature on the fly ash nanofluid was directly proportional to its thermal conductivity and specific heat and inversely proportional to viscosity. 相似文献
65.
66.
67.
A series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid-phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction-reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10−4 mm3/Nm for the platelet-filled composite coatings and 1.15 × 10−4 mm3/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10−5 mm3/Nm for the platelet-filled composite coatings and 0.84 × 10−5 mm3/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 106 Ω·cm2, approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48936. 相似文献
68.
采用共沉淀法和沉淀浸渍法制备了纳米氧化铈-二氧化硅(CeO2-SiO2)介孔材料吸附剂,主要考察了其对水中铜离子(Cu2+)的吸附行为。通过X射线衍射(XRD)、扫描电镜(SEM)和氮吸附(BET)等手段对合成的介孔材料进行了性能表征,并通过静态吸附实验分析了溶液pH、溶液初始金属离子质量浓度、吸附剂用量、吸附时间等条件对介孔材料吸附Cu2+性能的影响。结果表明:共沉淀法制备的纳米CeO2-SiO2介孔材料对Cu2+的去除效果较沉淀浸渍法要好;当溶液pH=7.0时CeO2-SiO2介孔材料对Cu2+的吸附效果最好,20 min时基本达到吸附平衡;溶液初始Cu2+浓度增大Cu2+去除率降低,Cu2+累计吸附量增大;随着吸附剂用量增加Cu2+去除率增大,当CeO2-SiO2吸附剂用量为0.15 g/L时对Cu2+的去除率趋于稳定;CeO2-SiO2吸附剂对不同金属离子吸附性能由大到小的顺序为Cu2+、Fe2+、Mn2+,该吸附过程均符合准二级动力学模型。 相似文献
69.
《Ceramics International》2020,46(1):381-390
Ce-doped TiO2 thin films were synthesized by sol-gel dip coating route to evaluate the effect of Ce doping percentage on properties of TiO2. X-ray diffraction spectra revealed both anatase and brookite phases, and Ce doping favours the anatase–brookite transformation of TiO2 films. The optical constants of the thin films were achieved by evaluating spectroscopic UV-VIS-NIR spectrophotometry data. The band gap of the Ce doped TiO2 was reduced from ~3.93 eV to ~3.79 eV with an increase in Ce doping percentage. All films have shown ferromagnetic behaviors which increase with the increase in Ce content due to enhancement in the bound magnetic polaron. Higher Ce doping increases the oxygen vacancies and saturation magnetization. Boost magnetic properties stem from the generation of the interaction between the Ce ion and an oxygen vacancy. The study showed that the antimicrobial activity of Ce doped TiO2 is ineffective. Hence doping of Ce can modify the properties of TiO2 and are used in LEDs, magneto-optical devices and solar cells. 相似文献
70.
采用微动摩擦磨损试验机在干摩擦条件下对新型高速重载传动轴用25CrNi2MoV钢进行微动磨损试验,研究了不同载荷(50~200N)和频率(15~30Hz)下该钢的微动磨损性能。结果表明:在频率为20Hz条件下,当载荷由50N增至200N时,25CrNi2MoV钢的平均摩擦因数由0.766减至0.661,磨损体积由19.65×10^-3 mm^3增至75.83×10^-3 mm^3;在载荷为30N条件下,当频率由15Hz增至30Hz时,平均摩擦因数由0.790增至0.905,磨损体积由11.43×10^-3 mm^3增至23.88×10^-3 mm^3;在不同试验参数下,25CrNi2MoV钢磨损表面均出现了氧化和犁沟现象,磨损机制包含氧化磨损和磨粒磨损;在频率为20Hz条件下,载荷为50,100N时,25CrNi2MoV钢的磨损机制以黏着磨损为主,载荷为150,200N时,主要磨损机制为疲劳磨损;在载荷为30N条件下,频率为15~25Hz时,磨损机制以磨粒磨损为主,当频率增至30Hz时,磨损机制以疲劳磨损为主。 相似文献