- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
Nano-CuO was prepared by methods of liquid-phase precipitation and solid state reaction. The structure of nano-CuO was analyzed by XRD, XPS, TEM and BET techniques, and the effect of the structure of nano-CuO on the removing performance of H2S was also studied. The results indicate that various crystal size nano-CuO can be prepared by changing preparation process parameters. The desulfurization performance of nano-CuO decreases significantly with the increases of crystal size. The nano-CuO with the crystal size of 9.3 nm exhibits the best desulfurization performance, and the breakthrough time of H2S can reach 270 min. A small amount cluster caused by small crystal size has a little impact on the desulfurization activity of nano-CuO. However, the appearance of oxygen vacancies on the copper oxide surface and the decrease of electron cloud density around the copper are beneficial to the improving of desulfurization performance of nano-CuO. When the specific surface area is a little different,the effect on the desulfurization activity of nano-CuO is not obvious. But the removal of H2S can be improved when the irregular pore formed by grain accumulation distribution is narrow, and the open and contraction pore structures exist at the same time.
Several heterogeneous Ziegler-Natta catalysts were prepared by loading TiCl4 using mixture of modified montmorillonite (MMT) and functionalized muti-walled carbon nanotubes (MWCNTs) as effective composite nanofillers. The polyethylene nanocomposites were produced by in-situ polymerization with these catalysts. The effect of composition of MMT and MWCNTs on the mechanical properties of polyethylene nanocomposite was investigated. The results show that highly active polymerization catalyst with the nanofillers containing MMT and modified MWCNTs can be obtained. The composition of nanofiller has a remarkable influence on mechanical properties of polyethylene nanocomposite. The maximum tensile strength of polyethylene nanocomposite is 38.7MPa using the mass ratio of MMT to MWCNTs of 1:1.
The effect of different curing temperatures on the mechanical properties of flax fiber and their reinforced composites was studied during hot pressing forming process. The results show that the tensile strength of single flax fiber declines in varying degrees when flax fibers are treated for 2h at 120, 140℃ and 180℃, respectively, the tensile strength of epoxy resin E-51 has a little change after treated at the same conditions. Tensile and impact strength change slightly, when unidirectional flax yarn reinforced epoxy resin composites is cured under 120℃ and 140℃. However, when the curing temperature increases to 180℃, owing to the serious damage of flax fiber at high temperature, the tensile and impact strength of the flax fiber reinforced composites then decrease obviously. Meanwhile, as the curing temperature increases, the tensile modulus of composites improves in some degree.
Pre-alloyed NbSS solid-solution fine powder with a D50 size of 3.3μm, pre-alloyed Nb5Si3 and Cr2Nb compound powders with D50 size respectively of 22.1μm and 23.5μm were used as raw materials, and two-phase NbSS/Nb5Si3 alloy and three-phase NbSS/Nb5Si3/Cr2Nb alloy were fabricated by Spark Plasma Sintering (SPS). The microstructure, mechanical properties and oxidation behavior at room and/or high temperatures were investigated. The results show that the microstructure of the NbSS/Nb5Si3 alloy consists of the NbSS matrix and the uniformly distributed Nb5Si3 islands. As for the NbSS/Nb5Si3/Cr2Nb alloy, the NbSS phase tends to connect to be the matrix, while the Nb5Si3 and Cr2Nb blocks scatter in the NbSS phase. Fracture toughness KQ at room temperature of the two-phase and three-phase alloys are 15.0MPa·m1/2and 11.3 MPa·m1/2, respectively. The NbSS phase is found to fail in a dimple mode under bending, which is greatly beneficial to KQ of the bulk Nb-Si based alloys; while the Nb5Si3 and Cr2Nb phases fracture in a brittle mode. At 1250℃, the compressive strength of the NbSS/Nb5Si3/Cr2Nb alloy is higher than that of the NbSS/Nb5Si3 alloy, whereas it is contrary at 1350℃. The Cr2Nb phase plays a positive role in oxidation resistance at high temperature. Air exposed at 1250℃ for 100h, the oxidation mass gain of NbSS/Nb5Si3 alloy is 233mg/cm2, greater than 175mg/cm2 of the NbSS/Nb5Si3/Cr2Nb alloy.
The hot deformation process of GCr15 bearing steel was simulated by the MMS300 thermal mechanical simulator. The effect of final deformation temperature on microstructure was investigated. The results show that, within the range of 770-870℃,the microstructure of GCr15 bearing steel consists of lamellar pearlite plus proeutectoid carbide which is distributed along the grain boundary and surrounded by ferrite thin film. With the increase of the final deformation temperature,the grain size and pearlite colony size both increase,the mean interlamellar spacing of pearlite decreases slightly and the hardness increases. By means of regression analysis,the fitted curve of Vickers hardness vs the reciprocal of mean interlamellar spacing is given by HV=38.3S-1+92.7. The degree of carbide network increases when the final deformation temperature increases within the range of 810-870℃. Compared with 810℃,the degree of carbide network is more serious at the final deformation temperature of 770℃ and 790℃.
The rolling wear and damage characteristics of wheel and rail materials under different axle-loads were investigated using a WR-1 wheel/rail rolling wear testing apparatus. The results show that both of the wear rates of wheel and rail materials rise linearly with the increase of axle-load, and the wear rate of rail specimen is larger than wheel. The hardening rates of wheel and rail specimens firstly increase obviously and then keep stable along with the test time. With the increase of axle-load, the depth of plastic deformation layer and the hardness rate of wheel and rail specimens increase. The hardness rate of wheel is larger than rail. The surface damage morphology of wheel specimen is different from rail. For the surface damage morphology of wheel specimen consists of fatigue cracks perpendicular to rolling direction, however, the rail surface damage morphology is dominated by cracks and spalls. The surface damage of the wheel and rail specimens gets increasingly severe along with the in crease of axle-load. Debris, which comes from fatigue cracks fracture of wheel specimen and spalling of rail, is composed of Fe2O3 and martensite. With the increase of axle-load, the size of debris increases, the components and their content, however, have no obvious change.
Single and hybrid Al matrix composites with 2%Mg2B2O5w/6061Al,2%Gr/6061Al,2%SiCp/6061Al,2%Mg2B2O5w+2%Gr/6061Al, 2%Mg2B2O5w+2%SiCp/6061Al, 2%Mg2B2O5w+2%Gr+2%SiCp/6061Al reinforcements were prepared by powder hot extrusion process, and the wear resistance and the friction behaviour of the single and hybrid Al matrix composites were studied. The results show that the wear rates of all kinds of the composites increase with the load increasing, the wear rate of Al matrix composites increase with the addition of graphite, the friction coefficients of all kinds of the composites decrease with the load increasing and then become stabilized, the friction coefficient is between 0.22 to 0.32. Abrasive wear and slight adhesive wear dominate the wear mechanism of Al matrix composites without graphite, after the addition of graphite, the wear mechanism of Al matrix composites converts into serious adhesive wear.
Intercalated kaolin was prepared with two dimethyl sulfoxide (DMSO) as precursor, polyacrylonitrile(PAN)/K-DMSO nanocomposites was prepared by in situ polymerization with PAN and intercalated kaolin, and the fiber membranes of PAN/K-DMSO composite were prepared through electrostatic spinning technology. The microstructure and thermal properties of intercalation composites PAN/K-DMSO were studied by using XRD, FTIR, TEM and TGA. The micro-morphology and tensile strength of fiber membranes were characterized by SEM, POM and tensile testing machine. The results show that PAN/K-DMSO containing hydroxyl group peak which belong to the kaolin. The d001 layer spacing value of kaolinite increases with PAN into interlayer, and part of kaolinite is peeled and forms lamellar structure with thickness of 2~5nm dispersed in a polymer matrix. The heat resistance of PAN/K-DMSO composite is increased with the addition of K-DMSO. The diameter of PAN fiber membranes decreases and the tensile strength increases with the increase of K-DMSO.When the mass ratio of the PAN and K-DMSO is 8:1,the tensile strength is increased by 0.92,1.73MPa and 1.96MPa in untreated, cold pressing and heat treatment conditions, respectively,when compared with PAN.
Micro-arc oxidation (MAO) process on ZM6 Mg alloy was carried out in a dual electrolyte system of sodium silicate and sodium hydroxide alkalescent solution. The microstructure characteristics of coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The performance of adhesion, corrosion resistance and fatigue was evaluated by dynamic stretch training, neutral salt spray test and axial loading fatigue test. The results show that MAO coating consists of three layers, outer layer, medial layer and inner layer. The outer layer is porous and loose, however the inner layer has good bond strength with substrate, which is above 50MPa. The MAO coating can improve corrosion resistance of substrate significantly. The neutral salt spray test is above 336 h. Compared with the sample without MAO coating, the reduction of fatigue is about 18%.
Ni/MoS2 based composite coatings containing nano-SiC particles was prepared by doublepulse electrodepositing in Watts nickel plating solution. The effect of content of nano-SiC in the solution on the micro morphology, microstructure, hardness and friction properties of coating was investigated. The results show that the micro morphology of Ni/MoS2 composite coating changes obviously after adding nano-SiC particles in electrolyte, the density of the coating surface increases with the increasing of the concentration of nano-SiC particles in electrolyte,the microstructure of coatings is mainly composed of nickel,MoS2 and SiC,when the content of nano-SiC ranging from 1.0-1.5g/L, the hardness of composite coatings increased with increasing the content of nano-SiC in electrolyte, when nano-SiC is 1.5g/L in electrolyte, the microhardness of coating reaches the maximum value of 505 HV and the friction coefficient of coating is 0.28,which is about 1.6 times and 1/2 of pure Ni/MoS2 composite coating respectively;and the wear mechanism of coatings is mainly abrasive wear .
20% nano ZrO2 (3Y) powders were added to high purity submicron Al2O3 powders,then composite ceramics were prepared by high-pressure dry pressing and constant heating, multi-stage, short insulation sintering method at different temperatures. The effect of sintering temperature on mechanical properties of composite ceramics was investigated, the phase composition and microstructure of composite ceramics were analyzed by XRD, EDS and SEM. The results show that the sintering temperature affects the mechanical properties and microstructure of composite ceramics greatly. The relative density, vickers hardness and fracture toughness reach the maximum value, respectively 98.6%, 18.54GPa and 9.3MPa·m1/2 under atmospheric sintering at 1600℃ and insulation 8h. While the grain size of the matrix is about 1.4-8.1μm and ZrO2 phase transition is 34.6%. Composite ceramics have excellent microstructure sintered at 1600℃. The fracture mode of the composite ceramics is intergranular-transgranular mixed fracture mode. The fracture toughness of the composite ceramics is improved by phase transition toughening, intragranular particles toughening, crack deflection and other aspects when adding nano-sized ZrO2 (3Y) powder.
The MH/Fe3O4/SR magnetic rubber composites were prepared with SR, nano-Fe3O4 and nano-MH as raw materials. The friction, heat-resistant, physical and mechanical properties of the MH/Fe3O4/SR composites were studied using different proportions of nano-Fe3O4 and nano-MH. The results show that nano particles are well distributed in the silicone rubber matrix. The physical and mechanical properties of silicone rubber are effectively improved by different ratios of Fe3O4/MH. When the ratio is 20phrMH/10phrFe3O4, the tensile strength and elongation of the composites are somewhat improved, increase by 5%, compared with common silicone rubber.With the increase of the addition of nano MH and Fe3O4, the heat-resistant and friction properties of composites are continuously improved, the friction coefficient is effectively demoted. When the ratio is 30phrMH/10phrFe3O4, the decomposition temperature of the composites increases to 450℃. When the ratio is 20phrMH/20phrFe3O4, the friction coefficient of the composites is demoted to 0.52.
The friction and wear characteristics of acrylonitrile-butadiene rubber/316L stainless steel tribo-pairs were investigated using a sphere-on-disc test device. The influence of Al2O3 hard particles and the particle size on the tribological behavior of the tribo-pairs was discussed. The morphology of worn surface was analyzed via scanning electron microscope (SEM) and by using a surface profilometer. The results show that the particles wear can reduce the friction coefficient of the contact pairs; Large particles can accelerate the wear of rubber and large particles can be embedded into the rubber matrix,resulting in micro cutting effect, however, as particle size decreases to about dozens of microns, the existence of particles can mitigate the wear of rubber; All the particles embedded in the rubber matrix can aggravate the wear of metal counterpart and lots of furrows can be observed on metal worn surface caused by the ploughing effect of hard particles; In addition, the NBR/stainless steel tribo-pairs exhibit different damage mechanism under conditions of no particles and particles with different size.
The friction and wear characteristics of Fe-0.03Te-0.3Pb-0.9Mn free-cutting stainless steel were investigated using a lubricated rolling wear testing apparatus. The wear morphology, hardness, friction coefficient and wear volume of alloy surface were compared in different wear time, its mechanism of lubricated rolling wear was studied further. The results show that, at the beginning of wear, the performance of alloy surface wear is relatively stable, under the interaction of free-cutting phase, such as MnS and Pb, that cracks occur at the alloy surface plough bottom; When the wear is stable, the performance of alloy surface changed gradually, the cracks of plough bottom continue growing, interweaved cracks begin to generate flake or block convex parts; When the wear is over, the alloy surface lubrication film and exfoliation numerous are flaking off, exfoliation formed abrasive wear, plough disappeared step by step, the alloy surface system is collapsed rapidly.
Carbon nanotube reinforced metal matrix composites (CNT/MMCs) owing to high specific strength and specific elastic modulus as well as exceptional thermal and electrical properties, possess great potential in aerospace applications. Based on the analysis on the published literatures, the processing techniques and the CNT/metal interface research advances was evaluated,and some typical properties were summarized. It is pointed out that, the dispersion of carbon nanotubes, and interfacial characteristics between CNT and metal matrix would be mainly important research areas in future.
The chemical reaction mechanism of preparing typical ceramics (C,SiC and BxC) was studied,using C3H6(propylene)+H2, MTS+H2+Ar, CH4+BCl3+H2, and C3H6(propylene)+BCl3+H2 as precursors,and based on the quantum mechanics combined with statistical thermodynamics, variational transition state theory and chemical reaction kinetics. The thermochemistry data are predicted in a prescript high accuracy. The process is to determine as many as possible the reaction intermediates and transition states, to develop their thermochemistry data, to examine the reaction thermodynamics properties of the reaction system, to identify the possible reaction pathways, to evaluate the rate constants of the most favorable paths, and to explore the reaction rates. These researches are scientifically instructive to the composition control and processing optimization for layered carbon, anti-oxidation SiC and self-healing BxC. Problems concerning the theoretical methods are also proposed to be further studied.
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