Development of a glass-ceramic for biomedical applications

Park, Jongee
The glass-ceramics containing apatite [Ca10(PO4)6(O,F2)] and wollastonite [CaOSiO2] crystals as the predominant crystalline phases, (A-W glass-ceramics) were produced through controlled crystallization of the glasses in the MgO-CaO-SiO2-P2O5-F system. Phases formed in the crystallized counterpart of the glasses were identified by powder X-ray diffraction (XRD) analysis. The crystal morphology of the resultant glass-ceramics was examined using a scanning electron microscope (SEM). The crystallization kinetic parameters consisting of the activation energy for crystallization, (E), the Avrami parameter, (n), and frequency factor of the glass were determined with regard to small amount of TiO2 additions using non-isothermal differential thermal analysis (DTA). The values for E and n for apatite and wollastonite were 460 kJ/mol and 433 kJ/mol, and 3.1±0.1 and 1.5±0.1, respectively. When 4 wt% TiO2 was incorporated into the base glass, the values for E decreased to 408 and 320 kJ/mol for apatite and wollastonite, respectively; but the values for n increased from 3.1±0.1 to 3.3±0.1, and from 1.5±0.1 to 1.9±0.1 for apatite and wollastonite, respectively. TiO2 is an effective nucleating agent in this glass system for promoting the precipitation of both apatite and wollastonite crystals. Structure oriented changes in the indentation microhardness and tribological properties of the A-W glass-ceramics were evidenced. The microhardness at the free surface was 650±12 HV, but decreased with increasing depth distance from the free surface and attained 520±8 HV at a distance 0.5 mm below the free surface. The wear rate at the free surface was 0.7±0.05 ×10-4 mm3/Nm, but increased as the distance from the free surface increased and became 2.9±0.15 ×10-4 mm3/Nm at a distance 0.5 mm below the free surface. Tribological properties of the A-W glass-ceramics were compared with those of commercially available dental ceramics including IPS Empress 2®, Cergo Pressable Ceramic®, Cerco Ceram®, Super porcelain EX-3®, and bovine enamel. The wear rate, friction coefficient, and wear mechanisms of the A-W glass-ceramics were similar to currently used artificial dental materials.


Development of lead alloys for valve-regulated lead-acid (VRLA) batteries
Halıcı, Şafak; Aydınol, Mehmet Kadri; Department of Metallurgical and Materials Engineering (2010)
In this study, Mg, Sn, Cd, Bi and Sb containing, five binary, three ternary and two quaternary different alloys to be used in a Valve-Regulated Lead-Acid (VRLA) batteries have been studied in terms of their mechanical and electrochemical properties. The investigated properties are hardness, passivity, corrosion rate, hydrogen gassing and the conductivity of the passive film. All electrochemical tests were carried out in 3.75 M H2SO4 solution by using open-circuit potential, anodic polarization, polarization...
An investigation of the microstructural and mechanical properties of tri-calcium phosphates doped with aluminum and fluoride ions
Tahmasebifar, Aydin; Evis, Zafer; Department of Engineering Sciences (2011)
The aim of this study was to investigate the microstructure and mechanical properties of pure tricalcium phosphate (TCP) and tricalcium phosphates doped with aluminum (Al3+) and fluoride (F-) ions at different compositions. TCP was synthesized via precipitation method and sintered at 1100C for 1 and 5 h. It was observed that density and relative density of the sintered materials were decreased by extending the sintering time. Increased densities were achieved upon Al3+ and/or F- doping. For structural anal...
Influence of B2O3 additions on the microstructure of mica based glass-ceramics
Aykut, Hakan; Öztürk, Abdullah; Department of Metallurgical and Materials Engineering (2005)
Mica based glass - ceramics have been produced by subjecting the glasses in the SiO2 , Al2O3 , CaO , MgO, K2O , and F system to a controlled heat treatment called crystallization. TiO2 was added into the batch in the amount of 1 wt% of the glass as nucleating agent. B2O3 additions in the amounts of 1, 2, 4 and 8 wt% of the glass have been made in the batch to see and evaluate the effects of B2O3 additions on the texture of the mica glass ceramics. Crystallization was accomplished in two steps, nucleation an...
Assessment and modelling of particle clustering in cast aluminum matrix composites
Çetin, Arda; Kalkanlı, Ali; Department of Metallurgical and Materials Engineering (2008)
The damage and deformation behaviour of particle reinforced aluminum matrix composites can be highly sensitive to local variations in spatial distribution of reinforcement particles, which markedly depend on melt processing and solidification stages during production. The present study is aimed at understanding the mechanisms responsible for clustering of SiC particles in an Al-Si-Mg (A356) alloy composite during solidification process and establishing a model to predict the risk of cluster formation as a f...
Synthesis and characterization of nickel based bulk amkorphous alloys
Arslan, Hülya; Mekhrabov, Amdulla O.; Department of Metallurgical and Materials Engineering (2004)
The aim of this study is to synthesize and characterize new bulk amorphous alloys in the Ni- based systems. Theoretical studies on the basis of semi-empirical rules and the electronic theory of alloys in pseudopotential approximation has been provided in order to predict the impurity elements that will lead to an increase in the glass forming ability of Ni-based alloy systems. Glass forming ability of ten different compositions of alloys of Ni-Nb, Ni-Fe, Ni-B, Ni-Hf and Ni-Cr was simulated by using FORTRAN ...
Citation Formats
J. Park, “Development of a glass-ceramic for biomedical applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2008.