Journal of Advanced Materials in Engineering (Esteghlal)

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This new method which is worked out in Isfahan University of Technology, makes it possible to analyze the phases quantitatively in minerals and powdered materials by X Ray Diffraction and without any reference material. To identify n unknown phases, n different combinations of phases, from fine and coarse fractions, or etc., must be obtained. Amorphous phases should not exist. Intensity ratios of selected peaks of different phases to the suitable peak of added substances are plotted against the weight ratio of unknown material to substances. The phase is used to eliminate the effect of absorption in measurements. After detecting the slopes of linear plots which pass through the origin, n equations are obtained which are solved for n unknown coefficients. The quantitative phase analysis is subsequently performed in all n samples. If reference materials are available for some phases, n is reduced. The method is to analyze three phases MgO, CaO, Ca(OH)2 with substance CaF2, in magnesite – dolomite, partially hydrated refractories.

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One of the main reasons for the blocking and sticking of the expendable layer in tundish plaster to the permanent layer and the subsequent increase in refractory consumption and associated costs is the use of low-melting phosphate binders. At high temperatures in continuous casting of steel, phosphate binders provide low-melting point melts which cause reactions between the two consuming and permanent layers, so that deskulling becomes difficult and the permanent layer is damaged. In this work, the using sulphate binders such as sulphamic acid and sulphates of aluminum, magnesium, ammonium, sodium, potassium, and calcium are studied as substitute binders. Some of the plaster properties manipulated by these different binders, namely cold crushing strength(CCS), Bulk Density (B.D), and Apparent Porosity (AP%), were measured according to ASTM. Studies by SEM and XRD showed that magnesium sulphate would be the best selection as a binder in tundish plaster. This binder provides strength at low temperatures, but dissociates to MgO and SO3 at high temperatures. SO3 evaporates and MgO is an oxide with a high melting point that does not react with the host oxide, usually MgO. No melting or reaction occurred and deskulling was easy without any damage to the permanent layer.

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In the present study phase transformation of silicon and silica during milling in different atmospheres was investigated. The silicon powder was subjected to high energy ball milling in ammonia (25%) atmosphere. The milled powder was subsequently annealed at 1200 ◦C for 1 hour. In another test a mixture of AlN and amorphous silica (micro silica) was subjected to high energy ball milling. The milled powder mixture was subsequently annealed at 1200 ◦C for 2 hours. Phase analysis of the as milled and annealed powders was performed by X-ray diffractometery (XRD). Powder morphology was also examined using a scanning electron microscope (SEM). Results showed that ball milling of silicon in ammonia formed an amorphous phase which transformed to quartz on further milling. After annealing quartz, cristobalite and another oxide phase called O phases were developed on XRD patterns. Ball milling of AlN and amorphous silica led to the transformation of amorphous silica to stishovite phase. This process was completed after annealing..

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In the last decade, Calcium Titanate has been introduced as a bioceramic with acceptable mechanical and biological properties for orthopaedic implant applications. In this study, CaTiO3 nano-structure coating was produced by sol-gel dip-coating route for biomedical applications. Calcium nitrate and titanium isopropoxide were used as a precursor. After coating process, the specimen was subjected to rapid thermal annealing (RTA) at 800°C. The phase structure, functional groups and surface morphology of coating were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Uniform crack-free nano-structured coatings were obtained with perovskite crystal structure.