فصلنامه نانو مواد
پیاپی 6 (زمستان 1389)

In this present research, manganese oxide thin films were deposited by sol-gel method and using dip coating process and the effect of concentration of solution on the optical and structural properties of manganese oxide thin films draying by IR were studied. These films prepared by acidic and basic sols and with manganese acetyl acetonate and manganese (П) acetat tetrahydrat as precursors. The films prepared by high viscous basic sol were thicker than other samples. The structural and morphologic properties of the films were examined by XRD and AFM measurements respectively. The optical properties of the films were determined by using transmittance spectra. Optical constants and energy band gap of manganese oxide thin films were calculated by minimizing of generated transmission with respect to experimental data.

In this work, B4C-TiB2 nanocomposite powders were synthesized by mechanochemical method of B, C and Ti elements. Mixed powders with a theoretical composition were milled for 6, 1 , 14, 20, 26, 32, 50 and 70 h. In order to complete the reactions, milled powders were heat treated at 800o, 1000o and 1200 oC for 1 h. The morphology of powders was studied by SEM. Phase characterization, crystalline sizes were determined by XRD. Results showed that titanium diboride forms during the early stage of milling and after 70 h of milling, the crystallite sizes become 7.5 nm. No boron carbide was detected in powders milled for 70 h and after heating at 800 oC and higher this phase appeared.

In this research, HA-TiO2 and HA-TiO2-CNT nanocomposite coated on 316L stainless steel substrates by electrophoretic method. In order to making a stable suspension, isopropanol was used as solvent and tri-ethanol amine as dispersant. Microstructure and particle distribution of nanoparticles were characterized by scanning electron microscopy (SEM) and elemental sputtering, respectively. Effect of carbon nanotube and titanium oxide nanoparticles on hardness and elastic modulus of nanocomposite coatings were compared by nanohardness curves of coatings. Morphology, topography and surface roughness of coatings were observed by Field Emission Scanning Electron Microscopy (FESEM) and Atomic force microscopy (AFM).

In this paper, the effect of nano-magnesia particles on the self-flow characteristics of high-alumina low-cement self-flowing refractory castables has investigated. For this reason, reactive alumina is substituted by nano-magnesia particles in 0-2 wt.% range and the flow and setting behavior of these castables have tested. Also, major physical (B.D and A.P), mechanical properties (C.C.S and M.O.R), phase analysis (XRD) and microstructure (SEM) of these castables have evaluated. The results showed that with increase of nano-magnesia particles with high surface area, the self-flow value and working time tend to decrease. Also, the mechanical strength of these castables after drying is enhanced with increase of these particles in castable composition by pores filling between coarse particles. As a result of using nanometer-sized magnesia particles with high surface area, the higher amount of spinel phase can be formed at lower temperatures 1250 °C). Increasing of porosity and then, decreasing of strength can occur with formation of expanding spinel phase.

There is much more attention to the synthetic biomaterials for bone and teeth reconstruction in the recent years. Hydroxyapatite and its derivatives like fluorohydroxyapatite are categorized in this group. In this research, hydroxyapatite and fluorohydroxyapatite powder were synthesized by hydrothermal method. The biological response of the human osteoblast and mesenchymal stem cells in contact with these materials were evaluated. Cell proliferation assay (MTT), alkaline phosphatase secretion and the also expression of collagen type I and alkaline phosphatase as the biological activity criterion of these materials were assessed. The results showed that fluoride can increase the rate of osteoblast proliferation and gene expression. However there was no significant observation in the cell proliferation rate and gene expression between two differentsamples of hydroxyapatite and fluorohydroxyapatite. In addition, it has been shown that the amount of alkaline phosphatase and gene expression in osteoblast cells were higher than mesenchymal stem cells.

In this research, the results obtained from studying the phase transition of γ-alumina (γ-A 2O3) to α-Alumina (α-Al2O3) during intense mechanical activation in high-energy ball milling are presented. The powder samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal and thermogravimetric analyses (TG-DTA). With respect to the results achieved from above analyses, depending on experimental conditions, the γ→α- alumina transition through δ- and θ-phases, can be initiated. Also it was detected that the pure γ- alumina phase showed great stability and no transformation to any other phase after a long milling time (30 hours). On the other hand, γ-alumina, which contained a small amount of the α Alumina phase, showed a gradual phase transition from γ-alumina to α-alumina in milling. The phase transition mechanism during milling is nucleation and growth which is promoted by the α alumina seed.

TiB2-TiC nanocomposites have been considered as one of the main materials in produce of cutting tools and wear-resistant covers recently.SHS method as one of the most common and commercial techniques for manufacture of composites that can be a pre-stage operation along with ball milling. In the present study, two different chemical formulations (Tiހ) and (TiO2 H3BO3 Mg C) were used to achieve the mentioned compound. Mixing of the starting materials was done according to the stoichiometric ratio for 1 to 6 hours by planetary ball mill. Milled powders were pressed in a steel die to form a compact tablet with 55% -65% relative Density and then were sent to combustion reactor for synthesis. Samples were synthesized through SHS process under the same temperature condition in 1100 oC. Investigation of The XRD results showed that, increasing of the raw materials milling time led to increasing of combination tendency. This phenomenon led to reduction of particle size and increasing of the surface contact on the other hand, activation of particle products caused facilitates the process of SHS and increasing of products purity. In this research, the Influence time of the milling process in the first formulation (TB) is equal 6 h and in the second formulation (HT) is equal 3 h.