نشریه علم و مهندسی سرامیک
سال یکم شماره 2 (پاییز 1391)

In this study, the preparation of transparent glass-ceramics with lithium-mica nanocrystals by melt-quenching method was investigated. The influence of Y3+-doping on the luminescence properties of the parent glass and the glass-ceramics was studied. Transparent glass-ceramics, in which a large quantity of lithium-mica with particle size of <50 nm was separated, could be prepared by a suitable heat treatment. The observed emission spectra showed that Y3+ ions in glass and glass-ceramic were emitted blue light. Theses transparent glass-ceramics are promising materials for white LED and laser materials

The investigation of glass membrane nowadays is very important branch in scientific researches, has a differences sides. One of them is the change in composition of glass membrane for control the phase separation and pore size. The important group of usage composition in glass membrane is the borosilicate glass former. The effect of additives such as CaO and BaO on the these systems has been investigated in some scientist`s researches. In this research, the effect of MgO and temperature variation on these compositions and the phase separation quality and their pore size was investigated. Addition of 0, 2, 4 and 6 percent of MgO with change in heat treatment temperature in four temperatures 670oC, 690oC, 710oC, 730oC was investigated. For preparation the glass membranes, after melting the primary composition, the molten glass was cooled and then annealed. Productions heat treated in four temperatures and then etched. After analyzed the samples with SEM, leaching the samples and then samples analyze with porous analysis such as BET and BJH. At the end receiving to mean pore size about 12 nm and although pore size distribution from 5 to 100 nm was the important results of this research.

Calcium phosphate based glasses in the system of with high (≥ 1) were prepared by fritting through. The glass sintering and crystallization performed at 600-1200 temperature interval. Crystalline phases were examined by differential thermal analysis (DTA) and x-ray diffraction (XRD), respectively. The glass-ceramics consisted of crystalline phases such as and with variable amount of glassy phase. Microstructures of glass-ceramics were investigated by scanning electron microscopy (SEM). Mechanical strength of specimens confirmed that the resulted glass-ceramics have high potential to use as biomaterials for bone regeneration in non-load bearing conditions.

Two- step sintering (TSS) has been applied, in the present work, to suppress the accelerated grain growth of Hydroxyapatite Zirconia Alumina nanocomposites in the last sintering stage. The average grain size of near full dense specimens made via conventional sintering (CS) was around 400nm. By using novel tow- step sintering, however, the final grain size (200nm) dropped 2 times less than that for specimens produced by the CS method. After densification, the mechanical properties, the relative proportion of TCP formed and the microstructures of the composite were observed. By used of two step sintering, highest hardness and fracture toughness, lowest relative proportion of TCP and nanostructure were achieved.

In this research barium hexaferrite was partially reduced with graphite or carbon black in the mechanical milling medium, to form BaFe12O19/Fe3O4 nano-composites. The resulted nano-composites were heat treated in air at 300, 350, 400 and 500 °C. The milled and heat treated samples were characterized by XRD, VSM and FE-SEM. The peaks of Fe3O4 were appeared in XRD patterns of barium hexaferrite and graphite mixture with molar ratio of C:O=0.9 after 40 hrs milling and for molar ratio of C:O=1.1 after 20 hrs milling. For barium hexaferrite and carbon black mixtures, Fe3O4 peaks were appeared after 20 hrs for molar ratios of C:O=0.9 and 1.1. This was attributed to the more activity of carbon black compared to graphite. FE-SEM images showed that 20 hrs milled samples were consisted of aggregates with mean particle size of 30 nm. Heat treatment of milled mixtures resulted in an increase in coercivity and saturation magnetization due to the elimination of carbon and reducing of residual stresses. The saturation magnetization was 50.1 emu/g for barium hexaferrite and graphite mixture after 20 hrs milling and heat treating at 400 °C and this value was 55.3 emu/g for barium hexaferrite and carbon black mixture for the same conditions. The difference in the saturation magnetization was attributed to the amount of magnetite phase in the composites.

Razak and Mishan Formations(early to middle Miocene) in Polkavar and Zanjiran areas located in south and southwest of Fars province and Zagros foldbelt. Major minerals are Illite/Muscovite,Chlorite,Calcite,Quartz and minor minerals are Albite, Palygorskite. Analysis of whole rock show high amounts of CaO,MgO and low SiO2, Al2O3, Fe2O3, K2O, Na2O. Low amount of CEC is due to presence of Illite, chlorite, palygorskite and or absences of vermiculite and montmorilonite. Atterberg limits indicates a rang between 10 to16. Final conclusion of these investigations indicate the potential usage of these sediments for brick,tile ceramic and earthenwares. Tile specimens were evaluated by XRD,Liner shrinkage drying and firing,LOI,Flexural strength drying and firing,water absorption. These are clear evidences between flexural strength,water absorption(WA), Liner shrinkage and the type of percentage of size grain

Homogeneous nano-composite calcium phosphate glass-ceramic/yttri-stablized zirconia by the sol-gel method was prepared and the effect of various amounts of zirconia on microstructure of nano-composite was investigated. After heat treatment at 700 C, the glass which is produced by the sol-gel method crystallized partially and hydroxyapatite in the range of nanometer formed. Due to ion exchange of calcium and zirconium between hydroxyapatite and zirconia, hydroxyapatite unit cell volume increased. Also, by increasing zirconium, the degree of crystalinity in the glass-ceramic increased.