Materials Science Forum Vol. 750

Abstract: In the present work, Ni/MgO powder was prepared by co-precipitation in which CO restore NiO to elemental subtance Ni due to C2O42- was decompose to CO and CO2 at 700°C. As the process of the second sintering, H3BO3 was added into the sintered powder of 700°C and was grinded. Then the powder of H3BO3 added was sintered at 800°C，so that the powder was refined, obviously. Thermogravimetric analysis (TGA) and differential thermal analysis(DTA) was carried out in CO2 flow at 10°C/min. X-ray diffraction (XRD) was carried out on a X-ray diffractometer operated at 20KV and 40mA. The microstructures and morphologies were studied by EPMA and XPS.

Abstract: Screw-thread steel, which is produced using the quenching process through wear water controlled rolling system, would prone to generate red rust on its surface. For this reason a combustion apparatus with a smoke backflow area containing partly unburnt combustible fuel is designed to study the rusted 20MnSi wear water screw-thread steel under high temperature flame hot melting. With SEM/EDS and XRD analysis we could affirm that the main composition of the red rust is Fe₂O₃ It assumes loose, porous branches and leaves, therefore makes the absorption of water and gas easier and intensified the sprawling of corrosion. While the steel surface after hot melting treatment form a tight passivation layer made of Fe₃O₄ and FeO, which would isolate outer circumstance thereby protects the metal body. In the article we analyzed two main reasons that cause the red rust and point out contents that requires further studies. Compared with using chemical addition agent, this high temperature flame hot melting reaction technique is beneficial to the environment while of lower cost.

Abstract: In order to study the details of deformation and microstructures evolution during rolling and annealing process, magnesium alloy AZ31 blank, cast by unidirectional solidification and then sliced, has been rolled at high temperature with one pass deduction of 50% in a 2-high mill. During the rolling process, the mill was stopped, and the rolled sheet was rapidly cooled by the cold rolls. Samples with full length of rolling bite zone were cut form the semi-rolled sheet. Because twinning deformation can be reserved even the sample was polished and etched. The continuous changes of microstructure, from entrance to exit of roll bite, both rolled and annealed samples, were evaluated by Optical Microscope (OM), Scanning Electron Microscope (SEM). The results revealed that grain refinement mechanism was twinning intersection which segmented large grains into small pieces. The average grain size is 7µm after one pass 50% reduction hot rolling and 350°C, 15min annealing.

Abstract: It is well known that the advances in the biomedicinal applications of magnetite nanoparticles were studied recently. As a drug delivery tools, it only affects on the target region of illness. We investigated the application of magnetic nanoparticles as drug delivery tools by the mice model of atopic dermatitis. The results involve that after magnetic nanoparticles are applied to the skin, the condition of atopic dermatitis becomes much better than the former one of atopic mice model. It only affects on the illness region and healthy regions almost have no influence. It is suitable for the medical treatment technique usage on the atopic dermatitis.

Abstract: A pseudo-binary phase diagram of the (Bi,Pb)-Sr-Ca-Cu-O system along the Bi1.6Pb0.4Sr2Can-1CunOx line is constructed. This resulting phase diagram shows three kinds of peritectic reactions, one eutectic reaction and one peritectoid reaction. The equilibrium solid phases in this diagram are the 2201 (n=1), 2212 (n=2), 2223 (n=3) and (Sr,Ca)CuO2 (n→∝) phases. The 2201 phase is solid solution which is stable at 1≤n≤1.2. The eutectic composition point is close to the maximum solid solution composition of the 2201 phase. The temperature interval between the peritectic reaction of L + (Sr,Ca)2CuO3 + (Sr,Ca)CuO2 → 2212 and the eutectic reaction of L → 2201 + 2212 is only about 3°C. For the composition of n=3, CaO and the liquid phase are stable at temperatures above 940°C. During the cooling, these two phases react peritectically to (Sr,Ca)2CuO3. At around 890°C, (Sr,Ca)2CuO3 reacts with the liquid to produce (Sr,Ca)CuO2. At around 865°C, (Sr,Ca)2CuO3 and (Sr,Ca)CuO2 react with the liquid to produce the 2212. The 2223 phase is transformed by a peritectoid reaction of the 2212 phase and residual (Sr,Ca)2CuO3, (Sr,Ca)CuO2.

Abstract: Spherical carbon nanoparticles were prepared by the polycondensation of resorcinol and formaldehyde using sol-gel method in the presence of cetyltrimethylammonium bromide (CTAB) and subsequent carbonization. Addition of carbon nanotubes (CNTs) in the precursor solution resulted in CNT/carbon porous composites. The effect of carbon nanotubes (CNTs) on the microstructure, pore structure and electrical double layer capacitance of CNT/porous carbon composites was examined based on the field emission scanning electron microscope, transmission electron microscope observation, N2 isothermal adsorption, cyclic voltammetry and charge/discharge tests. The results showed that 20% CNT addition had little effect, but 50% CNT addition significantly changed the microstructure and pore distribution, and charge/discharge properties.

Abstract: Mechanical properties, especially fatigue strength, of ferritic spheroidal graphite cast iron might depend not only on the graphite size but also on the ferrite grain size, little systematic research has been made on these factors. To clarify the influences of these structural factors as well as loading condition, fatigue tests have been carried out on ferritic spheroidal graphite cast iron with different sizes of graphite nodules and ferrite grains, under the axial loading with mean stress from -70MPa to 240MPa. The results obtained in this study are summarized as follows: (1) The fatigue limits are decreased with increasing graphite nodule and matrix grain sizes. (2) The fatigue limit decreases with increasing tensile mean stress. The fatigue limit at an arbitrary mean stress has been estimated by the modified Goodman diagram as well. (3) The parameter α is evaluated from the experimental results relating to the stress ratio R, for the mean stress acting on the tensile side and on the compressive side separately. For the case of R0, the value of α is 0.324. The result has been applied to the fatigue limit evaluation equation of Y.Murakami et al, the fatigue limit ratio falls within the range of about ±10%.

Abstract: In this study, a biaxial tensile test of cruciform specimens containing centre notch was conducted in order to clarify the deformation behavior near the crack tip at the early stages of crack initiation when objected to a biaxial stress state. Results show that the hardness and stress value within the deformed zone increased with increase in the loading ratio. Observation of the microstructure reveals that the deformation is dominated by basal slip under equal biaxial tensile loading. The asymmetrical biaxial tensile loading generates deformation twins near the crack tip. These results indicate that existing deformation twins contribute to higher hardness, and there is obvious anisotropism in the vicinity of crack tip under asymmetrical biaxial tensile loading.

Abstract: Using the microwave atomic force microscope (M-AFM) measuring system, the sample of Au nanowires arranged on glass wafer was sensed with three kinds of scanning speed. As the results shown, the spatial resolution of topographies is increased with the decrease of scanning speed. However, the precision of microwave images is not changed much with decreasing the scanning speed. Since M-AFM with the compact microwave instrument can always implement the real time measurement, the variation of scanning speed will not affect the microwave measurement.

Abstract: This paper focus on the investigation of tensile strength and thermal residual stress in UACS/Al laminates. The UACS (unidirectionally arrayed chopped strands) is made by cutting parallel slits on unidirectional carbon fiber prepreg. Thus all of the carbon fibers in the cut prepreg are 25 mm in length. Six cases of UACS prepregs are prepared with different slit angle θ, which is the angle between slit and fiber direction, including 5.7o, 11.3o, 16.7o, 31o, 45o and 90o. A UACS/Al laminate consists of one UACS layer with four UACS plies and two aluminum layers, such as [Al/UACS4/Al]. Four pieces of UACS prepreg with alternate slit angle [θ/-θ/θ/-θ] are stacked together in the same fiber direction. Then stacked UACS/Al laminate are cured using an autoclave. Tensile tests are performed to investigate the thermal residuals stress using the yielding-point-shift method. Experiment results show that thermal residual stress is reduced in the case of UACS/Al compared with conventional CFRP/Al. Among all the cases, specimen with slit angle of 11.3o is the most impressive one with 37.7% reduction of thermal residual stress.