مجله مواد نوین
سال چهارم شماره 2 (پیاپی 14، زمستان 1392)

The purpose of this research is evaluation of the effects of chemical compositions on the fluidity of steel continuous casting high speed mold powders in laboratory. Thermal microscope analysis was used to compare the fluidity of generated powders with that of the industrial mold powder. A sample purpose with low fluorine and other samples purposed from mixture of iron oxide، zinc oxide، sodium carbonate and titanium oxide showed similar fluidity to the industrial mold powder. These powders can be substituted for high speed casting powder in steel continuous casting processes.

Because of one phase polymers and ceramics due to their properties can not be used in bone defect repairs، attention has been focused to the development of double phase polymer and ceramics and their properties and ability to make bones. Mechanical stability and dynamical properties have been investigated. The nano bioglass which contains magnesium in sol-gel methods has been synthesized in this work. The magnesium oxide dose not have any destructive effects on preparation and specification and thermal processing but it preserves osteoporosis. FT-IR، XRD، TEM tests are under taken to observe the characteristics of synthesized Nano powder. FTIR tests were carried to evaluate the chemical links in scaffold composition. Also to observe bio-compatibility of nano-bioglass scaffold viability cell test was modeled. The results of FTIR test confirmed the chemical links in synthesized nano powders. XRD test indicated nano-bioglass powder is amorphous. TEM and SEM images showed the powder particles are 20-70 nm. The results show biodegradable and biocompatible nano–glass could be chosen as suitable substitute in bone implantation.

In this work، phase evolution of CoFe2O4 nanoparticles prepared by limited mechanical activation and heat treatment in comparison to conventional powder metallurgy route is reported (mixed oxides method). The starting raw materials for both methods were hematite and cobalt which were mixed together with the molar ratio of 1:1، (Co: Fe2O3=1:1). The mechanical activation was performed in a Spex 8000 high–energy vibratory mill for 1h. Various characterization techniques such as XRD and VSM were utilized to study the prepared samples. The study of phase evolution in samples produced by the mixed oxides method in comparison with those prepared by the mechanical alloying method، with heat treatment at the same temperature، suggests that formation of CoFe2O4 in samples produced by the latter method was started at a lower temperature and revealed stronger characteristic peaks of CoFe2O4. Furthermore، increased formation of CoFe2O4 phase was observed by increasing the heat treatment temperature. The study of magnetic properties of samples produced by the mentioned methods which were heat treated at 850 °C، suggests that samples produced by the mechanical activation method show considerably higher magnetic properties with respect to the samples made by the conventional method.

Recently، due microelectronic technology developments، it is important to improve the electronic properties ceramic dielectrics، for some applications e. g. capacitors. Accordingly، one of these advanced materials that has attracted much attention in recent research is NiO-based ceramics which shows an extraordinarily a range of high dielectric constant. In the present work، for the first time Li0. 05Ni0. 95O ceramic dielectrics were prepared by mechanical alloying. The structure and microstructure of the milled powders were characterized by X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) at different milling times. The quantitative analyses of the XRD results were done by the Rietveld refinement. According to the results، by milling operation، nanocrystallization and particles refinement were developed in which the crystallite and particles size of the powders reached to values of about 20 nm to 200 nm، after 24h of milling. In order to improve the dielectric properties، the 24h milled Li0. 05Ni0. 95O powders were mixed with iron oxide (Fe2O3) and after sintering process، the morphology of the Li0. 05Fe0. 02Ni0. 93O sample studied by SEM. It revealed that the grains sizes remained in the submicron range. By measuring the dielectric properties of the Li0. 05Fe0. 02Ni0. 93O sample using LCR meter at 120 Hz-200 kHz frequency range، high dielectric constant (about 5000) and relatively low loss (about 0. 9) were obtained at 20 kHz which remained constant up to 200 kHz.

The research has been focused on the effects of adding tin oxide nanoparticles (SnO2) into poly (3، 4-ethylene-dioxythiophene) poly (styrenesulfonate) (PEDOT: PSS) to produce a nanocomposite thin film of PEDOT: PSS/SnO2 as a carbon monoxide (CO) gas sensor. The composite thin film was produced by a spin coater. The produced nanocomposites were studied by analytical techniques، such as FTIR، AFM، and XPS. In order to determine the appropriate operating temperature، the sensitivity of the sensor was studied at different temperatures. The optimized weight percent of the SnO2 nanoparticles was determined to the highest sensitivity and selectivity of CO gas sensors. Also، the effect of humidity on the sensor response to CO gas was studied. The advantage of this sensor is short response time، easy fabrication، and operation at room temperature.

The effects of the heat treatment parameters on the microstructure of dual matrix structure (DMS) Aluminium Ductile Irons has been investigated in this research. The samples were cast and full annealing heat treatment was carried out in order to produce ferritic structure. The samples preheated at 600 °C for 10 minutes، followed by austenitising at 2 temperatures (920 °C، 950 °C) in motlen aluminium for various times (1 minutes to 15 minutes)، followed by oil-quenching. Scaning Electron Microscopy (SEM) and Optical Microscopy (OM) were used to evaluate the distribution of martensite in matrix. The results revealed that martensite is created in the intercellular regions at shorter partial austenitizing times، nevertheless، it is also formed around spherical graphites by increasing the partial austenitizing time. Moreover، it is seen that raising the temperature at a constant partial austenitizing time will increase the volume fraction of the martensite and totally، the rate of creating of the martensite in 950 °C is more than that in 920 °C. In addition، the volume fraction of the martensite at 950 °C and 4 minutes was obtained to maximum of 90. 7%.

In this study، scratch test was performed at different conditions to examine the effects of calcium carbonate on scratch resistance of polyethylene (PE). To do this، PE reinforced with different content of nano-sized calcium carbonate (0، 5، 7. 5 and 10 wt. %) were produced. The samples of PE and PE-10%CaCO3 recrystallized in toluene solvent to study their microstructures using potassium permanganate solution as etchant. Nanocomposite samples were scratched by a conical indenter at the normal loads of 5، 15، and 25 N and scratch speed of 1 mm/s. In order to represent the materials resistance to scratch deformation، the scratch hardness of each sample was calculated. The scratch groove of some samples was examined by scanning electron microscopy (SEM). The microstructures illustrate that the reinforcement of polyethylene with calcium carbonate causes the decrease the average diameter of spherulites. The results of scratch test indicate that the scratch hardness is increased by increasing CaCO3% for all normal loads; although for small normal loads، this positive effect is much higher than that of big loads. The deformation mechanism of PE and PE-CaCO3% is ductile ploughing and this is similar at the loads which are smaller than 25N. However، it is fish-scale for PE and plastic drawing for PE-10%CaCO3 at the load of 25N.

In this study، cadmium selenide nanostructures were synthesized using solvothermal process. To Study the effects of solvent type on the morphology and crystal structure of cadmium selenide nanostructures obtained by hydrothermal process is the purpose of this work. Morphology was studies by FE-SEM images. Various morphologies include: Petal-like morphology in the presence of ethanolamine، a mixture of nanoparticles and nano-rods in the presence of three ethylene tetra-amine and nano-rods with average length of one micrometer in the presence of ethylene-diamine were obtained. The crystal structure of cadmium selenide is not effected by solvent type and in all cases was wurtzite. The FTIR spectrum showed cadmium selenide nanostructures formed in all solvents at the site of the peak about 1380 cm-1.