Abstract-Tadpole-shaped (Ni, Al)/AlN nanoparticles were synthesized via evaporating Ni-Al alloy in a mixed atmosphere of N 2 and H 2 . As a counterpart, the spherical-shaped (Ni, Al)/Al 2 O 3 nanoparticles were also prepared from the same target alloy while in a mixture of Ar and H 2 . The electromagnetic parameters of as-made nanoparticles/paraffin composites were then investigated in the frequency range of 2-18 GHz. Excellent microwave absorption can be obtained for the tadpole-shaped (Ni, Al)/AlN-paraffin composite at high frequencies and in a thin layer, which is thought to be the result of the enhanced polarization in the anisotropic tadpole-shaped nanoparticles. With the increasing of the composite thickness, the frequency of effective reflection loss shifts towards lower frequencies due to an improved impedance match and absorption.
This study evaluated fatigue crack growth characteristics, Besides consider compressive
residual stress effect and verified the most suitable shot peening velocity. Fatigue crack growth
delay effect was compressive residual stress, but over peening did action projecting velocity that
accelerate fatigue crack growth rate. X-ray diffraction technique according to crack length
direction was applied to fatigue fractured surface. Fracture mechanics parameters could be
estimated by the measurement of X-ray parameters, and the fractography observation was
performed using a scanning electron microscope (SEM) for fatigue fracture surface. As the shot
peening velocity increases, striation width increased. The changes in X-ray material parameters
described above are directly related to the process of fatigue until the initiation of fatigue crack
and X-ray diffraction pattern is thought that failure prediction with stress distribution is possible.
At present many researches are about low density and high strength material, Metal Matrix Composite (MMC) is one kind of high performance material which is very popular and can fit that condition very well. In this study, matrix material is Al alloy and Al2O3 short fiber is reinforcement, volume fractions of Al2O3 short fiber is 10, 15 and 20 %. Manufacture by a low-pressure infiltration method. And the performance is evaluated by microstructure observation, porosity ratio and relative density. It is found that the porosity ratio can be effectively adjusted by the infiltration temperatures and the loads of Al2O3 short-fibres, exhibiting a minimum of 2 for 10% loading at 700°C. Meanwhile, the relative density of composites reached to be a maximum of 98% for 15% loading at 700°C. The low porosity ratio and high density of composites are reasonably attributed to the proper processing techniques.
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