Papers by Keyword: Glas Ceramics

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Authors: A.G. Dias, M.A. Lopes, Kanji Tsuru, Satoshi Hayakawa, José D. Santos, Akiyoshi Osaka
Abstract: This work reports the structure of two glass ceramics prepared in the calcium phosphate system, MK5B and MT13B, using 31P MAS-NMR technique. The results obtained showed that the network of MK5B consisted mainly of Q1 and Q2 groups. Besides these two groups, MT13B material also present Q3 units. The Qn groups detected in both glass ceramics seem to be correlated to the crystalline phases present in their microstructure.
Authors: R.A. Pires, I. Abrahams, Teresa G. Nunes, G.E. Hawkes
Authors: Artemis Stamboulis, Robert G. Hill, Robert V. Law, Shigeki Matsuya
Authors: Xiang Tian Chen, Ye Han, Shu Yu Yao, Wei Wei Zhang, Yun Sui Yao, Zong Feng Wang
Abstract: A new glass-ceramic coating material on nickel based super alloy substrate had been found, the glass¬-ceramic coating material was developed from a glass based on MgO–Al2O3–TiO2 system. The coating material was characterized through X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), hardness, thermal expansion coefficient testing. XRD analysis of the coating materials and the resultant coatings showed presence of a number of microcrystalline phases. SEM micrographs indicated microstructure of the material. Optical micrographs showed smooth glossy impervious free surface with defects. Hardness analysis showed the glass-ceramic coating material had higher microhardness. The thermal expansion coefficient of the nimonic alloy was much higher compared to the coating material at specific temperature.
Authors: Ye Han, Shu Yu Yao, Wei Wei Zhang, Ming Gu, Yu Sui Yao
Abstract: A novel wear resistant glass-ceramic coating system (based on SiO2-B2O3-Al2O3 glass system) on iron based substrate was developed. Friction coefficient, wear rate and coefficient of thermal expansion of coating material were evaluated using suitable methods. The coating materials and the resultant coatings were characterized using differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and Scanning Electron Microscope (SEM). XRD analysis of the coating materials showed presence of a number of microcrystal. SEM micrographs indicate strong chemical bonding at the iron-ceramic interface. The coating material showed perfect properties for protection the iron substrate from abrasion.
Authors: W.T. Young, L.K.L. Falk, H. Lemercier, Stuart Hampshire
Authors: Xanthippi Chatzistavrou, Konstantinos M. Paraskevopoulos, Vehid Salih, Aldo Roberto Boccaccini, Toshihiro Kasuga
Abstract: The aim of this work was to improve a newly developed family of glass-ceramic composite materials by incorporating silver ions in the ceramic structure, thus developing new Ag-doped materials with the ability of showing antibacterial activity for dental applications. Two different sol-gel methodologies were applied for the fabrication of colorless, homogenous and chemically durable materials which can slowly release silver ion for relatively long periods. Both methods led to the successful development of Ag-doped glass-ceramics with silver ions incorporated in the structure that can slowly release in buffer solution, during a period of 45 days. The potential, application of these materials involve the development of bioactive surfaces on dental substrates which can seal the marginal gap creating a bacterial free environment finally supporting the success of dental restorations.
Authors: M.S. Jogad, V.K. Shrikhande, A.H. Dyama, L.A. Udachan, Govind P. Kothiyal
Abstract: AC and DC conductivities have been measured by using the real (e¢) and imaginary (e¢¢) parts of the dielectric constant data of glass and glass-ceramics (GC) at different temperatures in the rage 297-642K and in the frequency range 100 Hz to 10 MHz. Using Anderson –Stuart model, we have calculated the activation energy, which is observed to be lower than that of the DC conductivity. The analysis for glass/glass-ceramics indicates that the conductivity variation with frequency exhibits an initial linear region followed by nonlinear region with a maximum in the high-frequency region. The observed frequency dependence of ionic conductivity has been analyzed within the extended Anderson–Stuart model considering both the electrostatic and elastic strain terms. In glass/glassceramic the calculations based on the Anderson-Stuart model agree with the experimental observations in the low frequency region but at higher frequencies there is departure from measured data.
Authors: Michael Shepilov, Olga Dymshits, Valerii V. Golubkov, Alexander A. Zhilin
Abstract: An evolution of the structure of three glasses of Na2O-Nb2O5-SiO2 system in the course of isothermal heat treatments at 660–700°C and the extinction coefficient of the material were studied. Spinodal phase separation was found to be a primary process followed by precipitation of nano-sized NaNbO3 crystalline phase. It was found that the spectral dependence of the extinction coefficient in the wavelength range λ= 400–800 nm corresponds to light scattering by spinodal structure at the phase separation stage and by independent Rayleigh scatterers (NaNbO3 nanocrystals) at the early stage of crystallization. The extinction coefficient increases at the first half of the crystallization stage and then decreases. At the late stage of crystallization and for the final glass-ceramics, the extinction coefficient α is 10–20 times smaller than that calculated for independently scattering nanocrystals and is characterized by anomalous wavelength dependence (α ∝ λ−6). The model for calculation of extinction coefficient is proposed, in which the interference effects in light scattering by nanocrystals are taken into account. On this basis, the variation of extinction coefficient in the course of crystallization and its wavelength dependence are explained.
Authors: Enrica Verné, Marta Miola, Sara Ferraris
Abstract: A glass (G) and a glass-ceramic (GC) of different composition were selected and studied to realize a biocompatible e/o bioactive material with antibacterial properties through the introduction of silver ions. The glass was produced in bulk form, instead glass-ceramic powders were sintered to abtain massive samples, which are characterized in terms of biocompatibility and subjected to ion- exchange technique [1] to allow the silver ions introduction and modify only the external surface layer of the materials, thus maintaining unchanged the bulk characteristics. The obtained samples were completely characterized to verify if the silver introduction leads to structural, morphological or in vitro behaviour change; silver release test was also carried out as well as antibacterial test with Staphylococcus Aureus and cytotoxicity test on human cells.
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