Abstract: The plasma spraying Al2O3-13%TiO2 (abbreviated as AT-13) ceramic coatings on Q235B steel surface were dealed with laser remelting technique. The microstructure and properties before and after laser remelting were studied. Experiment results shown that the microstructure of laser remelted ceramic coatings was dense, no porosity appeared. The main compositions of laser remelted ceramic coatings were α-Al2O3 and a small amount of TiO2 and TiAl2O5. Microhardness of AT-13 plasma spraying coatings and laser remelting coatings were measured with vickers, and the maximum microhardness value of the former was 1000 HV0.2 , while that of the latter was 1700 HV0.2; The average bonding strength value of AT-13 plasma spraying coating was 24.36 Mpa, while the average bonding strength value of laser remelting coating was more than 67.02 Mpa. The wear resistance of laser remelting coatings was higher than that of AT-13 plasma spraying coatings through the pin-dish particle wear test.
Abstract: Ga-doped ZnO (GZO) films were prepared on glass substrates at 523K temperature by non-reactive DC magnetron sputtering. The effects of sputtering power on microstructure and properties of the GZO films were investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), Hall effect measurements and UV-Vis-NIR spectrometer. The results show that GZO thin films exhibit high c-axis-orientation, and the intensity of peak increase as the enhanced of sputtering power; the increase of power will reduce the film’s visible-light transmittance, but for all of the GZO thin films the average transmittance of the visible-light is above 80%. The sheet resistance of GZO films decreases when the sputtering power gradually heightened from 80W to 200W. The lowest resistivity of 6.559×10-4Ω•cm can be obtained in the condition of the sputtering power is 100W, and the lowest square resistance is 7.9Ω/□.
Abstract: The abrasion of piston rings/tribomate pairs of cylinder jacket has great damage to engine, which can shorten the life of piston rings and cylinder bore, decrease the power of engine, enlarge the amount of oil, and release more pollution. Take a research of abrasive wear of piston ring and cylinder jacket made by different materials, will create a positive influence on extending the life of engine. This paper takes the SRV friction and wear tester, conducts the research on the abrasive ability of the three tribomate pairs (Cr plated piston ring and P-B, Cu-Cr-Ni-Mo and bainite cylinder bores) under the condition that there lies a certain amount of quartz sand in the lubricant and find that the hardness, intensity and tenacity of tribomate materials can have influence on its capability of resisting abrasion.
Abstract: The red phosphor Gd2(MoO4)3:Eu3+,Sm3+ was prepared by sol-gel method. The morphology and luminescence characteristics of the phosphor particles were characterized by scanning electron microscopy (SEM) and fluorophotometer. The results showed that the phosphor had the advantages of small particle size and the uniform particle size distribution. The luminescence properties of Eu3+ ions in Gd1.37Eu0.6Sm0.03(MoO4)3 could be evidently improved by co-doping of Sm3+ ions, which was due to the efficient energy transfer process from Sm3+ to Eu3+ ions. The chromaticity coordinates for Eu3+ doped Gd1.4Eu0.6(MoO4)3 and Eu3+ and Sm3+ codoped Gd1.37Eu0.6Sm0.03(MoO4)3, are(0.662, 0.329) and (0.668, 0.331), respectively. Because of the introduction of Sm3+ into the red-emitting phosphors, the chromaticity coordinates of Gd1.37Eu0.6Sm0.03(MoO4)3 phosphor is closer to the standard values of International chromaticity coordinates(0.67, 0.33). So Gd1.37Eu0.6Sm0.03(MoO4)3 shows good prospect for red phosphors of white LED.
Abstract: The calculation of elastic modulus of carbon nanotubes is an essential prerequisite for future Micro-nano devices fabrication that based on carbon nanotubes. The interaction potential of C-C covalent bond in single-walled carbon nanotubes (SWCNTs) is described by Terrsoff-Brenner potential in this paper. The elastic modulus of SWCNTs is ranged from 1.1078TPa to 1.23789TPa with the diameter increases from 0.3176nm to 2.0626nm by molecular dynamics (MD) simulation. The critical diameters of armchair and zigzag nanotubes are 1nm and 0.6nm.The elastic modulus changes with the diameter of nanotubes increasing clearly when the diameter smaller than the critical diameter, but the value of elastic modules tends to convergence when the diameter of nanotubes larger than the critical diameter.
Abstract: In order to explore whether the step gating system played a role in lost foam casting (LFC) process, this paper simulated the mold filling process of a step gating system with an auxiliary sprue and three side ingates by using the gravity LFC model of the code FLOW-3D, and analyzed its mold filling characteristics in LFC. It is found the mass flux ratio through the bottom-side ingate exceed 82% the total mass flux, much more than through the others. And it is also found the metal temperature of the middle region in the height direction is lower than the upper region or bottom region. The results show that the step gating system is not able to achieve its main roles in LFC. Our results can be used to design gating system in LFC.
Abstract: When fire breaks out, the gas composition and concentration as well as smoke concentration of burning part vary from those in normal environment. The gas and smoke absorbed during solidification of short circuited melted mark occurred in such environment will certainly have an effect on grain shape, grain size, holes distribution and impurity element distribution of organization of melted mark. The gas in the environment has a certain influence on the organization of short circuited melted mark, but the influence is smaller than that of smoke. The reason may be that the gas is mingled with certain amount of tiny smoke particles inevitably which play a role in the solidification of melted mark. Compared with short-circuit samples in normal atmosphere, carbon content of short-circuit samples increases and oxygen content decreases in the environment of smoke.
Abstract: Uniaxial tensile tests were performed on a Ti-6Al-4V alloy sheet over the temperature range of 923K-1023K with the strain rates of 5×10-4s-1-5×10-2s-1 up to a 25% length elongation of the specimen. The true stress-strain curves reveal that the flow stress decreases with the increase of the temperature and the decrease of the strain rate. In the same process, the accompanying softening role increases. It is found that the Ti-6Al-4V shows the features of non-linearity, temperature sensitivity and strain rate dependence in hot environment. Finally, an Arrhenius-type law has been established to predict the experimental data and the prediction precision was verified by the plotting of parameter and flow stress, which revealed that the error of stress exponent was only 4.99%. This indicates the flow stress model has high precision and can be used for the process design and the finite element simulation of hot forming thin-wall Ti-6Al-4V alloy components.
Abstract: According to actual axle load data and the measured mechanical parameters of cement stabilized macadam material with different cement dosages, the bottom tensile stresses of different subbase structures are calculated and the results show that: to graded gravel subbase, the weight of construction vehicle is inadvisable to be more than 35t and the cement dosage of base course shall be more than 3.0%; and, the maximum bottom tensile stress of graded gravel subbase shall be much more than that of lime-flyash soil subbase. According to the measured dry shrinkage strain and dry shrinkage coefficient, the dry shrinkage crack space of base course is analyzed and the results show that: under the same cement dosage, the crack space of the base course with graded gravel subbase is smaller than that of lime-flyash soil subbase; with the increase of cement dosage, the crack space of base course increase first and then decrease, and when the cement dosage is 3.5%, the dry shrinkage strain and dry shrinkage coefficient is minimum and the crack space of base course is maximum.
Abstract: Friction factor and flow behavior of melt glass lubricants A5 and up68/2886 during hot plastic deformation of Ni-based alloys Incoloy800H and Inconel 690 were studied by using ring compression tests. The results indicated that glass up68/2886 had higher mobility than glass A5. Friction factor between interfaces went up with temperature in sufficient lubrication, but the opposite in inadequate lubrication, and the friction factor went down with strain rate under both conditions. Besides, yield strength of specimen material also slightly influenced lubrication performance of glass lubricants in inadequate lubrication. Low friction factor about 0.1 was still obtained in inadequate lubrication by using glass up68/2866, therefore excellent performance could be expected when glass up68/2886 was used properly such as at higher strain rate.