m. bozorgmehr

In the present study, friction stir process (FSP) was used to produce AL/ZrO2/ZrSiO4 surface hybrid composite at a fixed rotation speed of 1400 rpm and traverse speeds of 20, 25, 31.5 and 40 mm/min. Therefore, the purpose of the mentioned study is to investigate the effect of tool traverse speed on the microstructure, hardness and wear behavior of the above-mentioned surface hybrid composite and compare it with base material aluminum 5052. Investigations showed that as a result of FSP operation, a fine-grained structure is created, which improves the hardness and wear resistance of the samples compared to the base sample with the presence of ZrO2 and ZrSiO4 particles. Also, the results showed that among the FSP samples, the sample with a speed of 20 mm/min has the highest hardness and wear resistance. The reason for this is that in this sample, due to the lower traverse speed compared to other samples, more heat has been generated, which has led to more suitable particle distribution and more fine particles. Therefore, in the sample with the traverse speed of 20 mm/min, the hardness and wear resistance increases by 27.3% and 68.9% respectively compared to the base material sample. Also, the examination of the wear surfaces of the samples showed that the wear mechanism in the base sample is strong adhesive wear, and as a result of the FSP operation and surface compositing due to the fineness of the grains and the increase in hardness, the wear mechanism has become weak adhesive, so the wear resistance of the sample is FSPs have been improved.

Dealing with the destructive effects of electromagnetic waves requires materials with the ability to lose magnetic and electrical energies. These materials are mainly composed of a magnetic material and an electrically conductive material. In the present research, at first, strontium ferrite nanoparticles doped with manganese and calcium with the formula of SrCo2-X(Mn Ca)X/2Fe16O27 (x=0.0-0.5) were synthesized by co-precipitation method. Then these nanoparticles were composited together with functionalized carbon nanotubes (with a volume ratio of 1 to 5%). X-ray diffraction analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and vector network analyzer were used to investigate the structural, magnetic, and microwave properties of the samples. The X-ray diffraction pattern results showed that the strontium ferrite phase was formed in all compounds, and there was no evidence of any impurities in the samples. FE-SEM results indicated that the particles completely covered the outer walls of the carbon nanotubes. Magnetometer test results also showed that with an increase in the amount of manganese and calcium cations in strontium ferrite, the saturation magnetization decreased and the coercive force increased. Reflection losses were also at least 30% higher in composite samples than those of in ferrite samples. The highest reflection loss (7.42 dB at a frequency of 1.12 GHz) was observed in the nanocomposite sample containing 5% by volume of carbon nanotubes. However, based on the results, the sample containing 4% by volume of carbon nanotubes had a wider absorption bandwidth compared to other samples.