mohammad javad torkamani

Synthesis of a hard layer on the surface of mild steel is a proper way to rise its performance. Titanium carbide is among the preferred wear-resistant materials. In this research, the carbothermal synthesis of TiC via pulsed laser is studied. Ilmenite is used, as an economic raw material, for in-situ synthesis of TiC. However, the conversion of FeTiO3 to TiC in the short period of laser processing is challenging. Therefore two solutions were accompanied: the applied carbon content was more than the stoichiometry of reduction, while the blended ilmenite and graphite powders were mechanically activated. The increase of activation time to 200 hours was investigated via X-ray diffraction analysis. Afterward, a layer of the powder was preplaced on the substrate and the laser cladding was conducted. The effect of mechanical activation on the formation of the dispersed particles is studied, especially considering the transformation of oxides to TiC. SEM with EDS analyzer and XRD analysis were applied for this aim. The morphology of TiC particles and the microstructure of the matrix were also deliberated. The characteristic microstructure of directional solidification with equiaxed, cellular, dendritic and eutectic regions was observed. Otherwise, the Vickers microhardness measurements represented a gradual increase from the substrate toward the surface, which has reached to 1600 HV. It is confirmed that the synthesis of a composite layer with gradual dispersion of TiC particles via laser reduction of ilmenite is a feasible process.

Methicillin-resistant Staphylococcus Aureus (MRSA) is an important infection source in dentistry for different disinfectants to be used to prevent its transmission. Furthermore, a variety of chemical disinfectants are developed to remove bacterial infections from the dental care workers' hands and claims are made regarding their superiority in infection control, although all requires scientific investigations. The aim of present study was to compare the effects of chemical hand-disinfectants Micro Zed HD, Aseptoman and Decosept on MRSA (methicillin resistant staphylococcus aureus) in different periods of time. In this experimental study, the antibacterial efficacy of three hand-disinfectants on standard strain of MRSA (USA300: ATCC® BAA-1717™) was evaluated according to European standard of evaluating antiseptics (EN 1040:2005 CSN EN). First we prepared a 0.5 Mc Farland (108 CFU/ml) suspension of MRSA, and exposed to three disinfectants for 15, 30, 60 and 90 seconds. Then, they were transferred to separate plates of Mueller-Hinton medium and incubated in 37◦C for 24 hours. The plates were compared then with control plate to evaluate the efficacy of materials on bacteria by calculating the CFU/ml of plates. Three hand-disinfectants evaluated in this study had the maximum anticabterial effect on MRSA in the minimum time of exposure (15 seconds), and we found no trace of growth in any plates. The three hand-disinfectans (MicroZed HD, Aseptoman and Decosept) in the concentration suggested by their companies, showed no difference in efficacy to remove MRSA from hands.

Digital shearography is widely used as a nondestructive inspection method in detection of subsurface defects and strain measurement in experimental mechanics. In addition, full field measurement and low vibration isolation requirements cause to higher application of this method in quality control applications. In this paper, the application of digital shearography in inspection of metallic samples has been studied. The subsurface defects of aluminum samples have been investigated by using a proper setup of digital shearography. The thickness of samples is 3mm and 5mm and the shear size in experiments is equal to 4mm. The samples are irradiated by a 660nm diode laser and recorded shearograms before and after thermal load have been analyzed by means of appropriate software. The results showed that, the diameter to depth ratio of defects employs important role in detectability of subsurface defects. By using this method, the minimum detectable diameter of defect is 2.5 times of its depth.