فصلنامه علم مواد
سال یکم شماره 1 (زمستان 1388)

Nano-sized carbon materials were synthesized by using accelerated metal dusting process. Surface morphology of the samples was examined by stereoscopy and SEM with EDS attachment. The carbonaceous depositions on sample surface were analyzed using SEM, TEM and Raman spectroscopy. In this paper, we demonstrate that nano-sized carbon materials can be prepared by exploiting the metal dusting process. It has been confirmed herein that the amount of the nano-sized carbon materials remarkably increases when the reaction time is extended up to 300 hours, indicating a possibility of the mass production.

In this paper, synthesis and characterization of nanostructured fluorapatite via mechanochemical process was investigated. For this aim, the initial powders with given stoichiometric proportionality were mixed in polymeric vial using a high energy planetary ball mill. The characterizations and structural features of synthesized powders were evaluated by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive Xray spectroscopy (EDX), and transmission electron microscopy (TEM). Results revealed that the thermal treatment led to the improvement of crystallinity degree. Also, heat treatment at 600° C did not affect on phase transitions and the crystallite size and the lattice strain of product reached to the 36 ± 3 nm and 0.291 %, respectively.

Electroless Ni composite coatings, containing dry lubricant particles, due to the formation of surfaces with low friction coefficient and high wear resistance for unsing in specific applications arewidely considered by researchers. one of the most important nanocomposite coatings is Ni-P-nano particle TiO2 coatings. In this research this type of coatings was applied on steel and were heat treated at 400 ̊C. Surface morphology of coatings were examined by Scanning Electron Microscopy and X-Ray Diffraction and Wear resistance of nanocompopsite coatings were studied by wearing test. It was found that heat treated composite coatings have a higher wear resistance and lower friction cofficient in comparison with unheated coatings.

In the current research, we have utilized the electron diffraction patterns to investigate the crystallization of the PZT perovskite phase in the alumina template pores, and modify the firing process. Lead zirconate titanate nanotubes were grown through the template-based electrophoretic deposition process using porous anodic alumina templates. The alumina templates were initially prepared through a two-step anodizing of the aluminum foils in a cooled anodizing cell at 1ºC. Phosphoric acid (10 wt%) solution was employed as the electrolyte. Stabilized PZT sol was prepared using lead acetate and organo-metallic precursors of zirconium, and titanium. Glacial acetic acid was also used as the modifier. A DC electric field was then applied to drive the precursor solution into the template channels and form the nanotubes. The filled membranes were dried at 100ºC overnight, and then fired at 700ºC for 1h in air to develop the desired perovskite structure.

In the present work, the effects of alloying elements such as Mn and Mg on the potential and current capacity of Al-Zn- In anodes have been investigated. In order to prepare the samples, appropriate amounts of Mn (0.01, 0.05, 0.1, 0.15, 0.2, 0.3 wt.%) and Mg (0.5, 1, 1.5, 2, 2.5, 3 wt.%) was used. The alloying process was performed at 750 oC. Electrochemical polarization and NACE standard methods were used to evaluate the anodic behavior, potential and current capacity of the anodes. It was found that addition of the 0.15 wt.% Mn and 2 wt.% Mg to the base alloy cause increasing efficiency up to 83 %. Under these conditions, corrosion and consumption of anode is homogeneous.

In this research the ZnO nanowire were gown on the copper, tungsten and graphite substrate with the double-tube CVTC system. The effect of chemical vapor density on the probability of growth and morphology of the nanowires were investigates by the means of SEM. It is observed that the increasing of the chemical vapor density raise the probability of growth and in the grown sample in addition to nanowire, nanobelt also appeared.

In the present research the effect of addition of Mg (0 and 20wt%) on the crystallite size, morphology and particles size of Al-5wt%Al2O3 composite during mechanical milling in a high energy planetary ball mill for different milling times up to 20 h were investigated. The phase evolution and crystallite size of milled powders were studied by XRD analysis. The morphology and particles shapes of powders were investigated with SEM. Average particle size of powders was determined by tangential method using SEM micrographs. Results of XRD analysis showed that crystallite size decreases to rang of nanometer with increasing milling time and Mg content. Results of SEM showed that particle size in the samples whit 20 wt% Mg reached to steady state value after about 20 h of milling operation. Addition of Mg to Al matrix leads to reduction of particle size of milled powders at different milling times and accelerates the mechanical milling stages.

Corrosion tests on 1015 low-carbon steel and 316 stainless steel were conducted in two molten zinc baths in order tostudy the reaction mechanisms that occur during the degradation of submerged hardware at industrial hot dip galvanizing baths. It was found that, in general, 1015 carbon steel has a better dissolution resistance than 316 stainless steel, despite of the fact that there are high percentage of Cr and Ni in 316 stainless steel, and that the 316 stainless steel have a face-centered-cubic (FCC) structure which is more compact than 1015 carbon steel with a body-centered-cubic (BCC). Microscopic studies showed that a reason for the difference of corrosion behavior of these two steels, is that the thickness of inter-metallic layer is thinner on the stainless steel than 1015 carbon steel. The presented lead in the bath had no penetration into the formed coating on 1015 carbon steel while it affected 316 steel coating. The presence of lead in the bath results in the dendritic structure of coating and growth of surface grains which causes more penetration of zinc into coating.