Sharif Digital Repository

In the present study, bioceramic composites based hydroxyapatite (HAp) reinforced with carbon nanotubes (CNTs) was synthesized via sol-gel technique. The dried gels were individually heated at a rate of 5°C/min up to 600°C for 2 h in a muffle furnace in order to obtain HAp-MWCNTs mixed powder. Composites were characterized by XRD, FT-IR, SEM, TEM/SAED/EDX and Raman spectroscopy techniques. Results showed the synthesis of HAp particles in the MWCNTs sol which was prepared in advance, leads to an excellent dispersion of MWCNTs in HAp matrix. Apparent average size of crystallites increased by increasing the percentage of MWCNTs. The average crystallite size of samples (at 600°C), estimated by... 

Addition of spinel (MgAl2O4) to Al2O3-ZrO2 composite inhibits alumina grain growth and produces phase boundaries that leads to formation of a ceramic matrix composite with special mechanical properties such as high temperature superplastic deformation. However, the room temperature mechanical properties of Alumina-zirconia-magnesia spinel composite (AZM) such as fracture toughness were rarely investigated by researchers. In this research the AZM nanocomposite powders were synthesized via the solution combustion method. The dense AZM composite samples were fabricated through gelcasting process. Phase analysis studies were performed on both powder and sintered samples and the effects of spinel... 

Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods... 

Ni-Co/SiC composite coatings with various contents of SiC particles were electrodeposited in a modified Watt's type of Ni-Co bath containing suspended 20 nm SiC particles. Deposition parameters including current density, bath SiC concentration and magnetic stirring rate were optimized for the highest amount of the SiC codeposition: the current density of 4 A/dm2, 40 g/dm 3 SiC concentration and 480 rpm stirring rate. In order to study the SiC particles codeposition, the Guglielmi's model of codeposition was modified for high volume percentages of the second phase and the modified model was employed to explain the effects of deposition parameters on the kinetics of the particles codeposition.... 

Modern techniques for expanding stem cells play a substantial role in tissue engineering: the raw material that facilitates regeneration of damaged tissues and treats diseases. The environmental conditions and bioprocessing methods are the primary determinants of the rate of cultured stem cell proliferation. Bioceramic scaffolds made of calcium phosphate are effective substrates for optimal cell proliferation. The present study investigates the effects of two bioceramic scaffolds on proliferating cells in culture media. One scaffold was made of hydroxyapatite and the other was a mixture of hydroxyapatite and ferromagnetic material (Fe3O4 nanoparticles). Disk-shaped (10 mm × 2 mm) samples of... 

Glass-ceramic composites in the SiO2-CaO-MgO-(Na2O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass-ceramic. Mechanical properties of glass-ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10...