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Phosphate Glasses (phosphate + glasses)
Selected AbstractsAn Ab Initio Molecular Dynamics Study of Bioactive Phosphate Glasses,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Emilia Tang First principles molecular dynamics simulations of ternary phosphate-based glasses P2O5CaONa2O (PBGs) have been carried out in order to provide an accurate description of the local structure and properties of these important materials for biomedical applications. The structures of PBGs with compositions (P2O5)0.45(CaO)x(Na2O)0.55,,,x (x,=,0.30, 0.35, and 0.40) were generated using a full ab initio molecular dynamics melt-and-quench procedure. The analysis of the structure of the glasses at 300,K shows the prevalence of the metaphosphate Q2 and pyrophosphate Q1 species, whereas the number of Q3 units, which constitute the three-dimensional phosphate network, significantly decreases with the increase in calcium content in the glass. Calculation of the pair and angular distribution functions suggests that the rigidity of the phosphate tetrahedral glass network increases with the concentration of calcium, an observation which is interpreted in terms of the tendency of Ca2+ to be a stronger coordinator than sodium. [source] Effect of B2O3 Addition on the Thermal Stability of Barium Phosphate Glasses for Optical Fiber DevicesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2004Takashi Harada The effect of B2O3 addition on the thermal stability of BaO,P2O5 glasses is studied by differential thermal analysis (DTA), X-ray diffraction (XRD) analysis, scanning electron microscopy, and micro-Raman spectroscopy. The difference between glass-transition and onset-crystallization temperatures increases monotonically with increasing B2O3 concentration. The DTA result reveals that no exothermic peak due to surface crystallization exists in the BaO,P2O5 glass doped with 3 mol% B2O3. A single-mode BaO,P2O5 -B2O3 glass fiber could be fabricated by a rod-in-tube technique. The modification of glass structure due to B2O3 addition is qualitatively discussed. [source] Fluorescence Spectroscopy of Color Centers Generated in Phosphate Glasses after Exposure to Femtosecond Laser PulsesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2002James W. Chan A confocal fluorescence microscopy setup was used to observe, in situ, spectral changes in phosphate glasses which were modified using 0.3 ,J of tightly focused 800 nm, 130 fs laser pulses. On 488 nm excitation, the modified glass shows a broad fluorescence centered at roughly 600 nm, which decays with prolonged exposure to the 488 nm light. The decay behavior is dependent on the 488 nm power, with a faster decay rate for higher powers. A mechanism whereby color centers, formed by the femtosecond pulses, fluoresce when excited by the 488 nm light and are simultaneously photobleached is proposed to explain the observed behavior. [source] Control of surface free energy in titanium doped phosphate based glasses by co-doping with zincJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Ensanya Ali Abou Neel Abstract To significantly improve the biocompatibility of titanium doped phosphate based glasses, codoping with zinc has been attempted. This study investigated the effect of doping a quaternary 15Na2O:30CaO:5TiO2:50P2O5 glass with zinc oxide (1, 3, and 5 mol %) on bulk, structural, surface, and biological properties; the results were compared with glasses free from ZnO and/or TiO2. ZnO as adjunct to TiO2 was effective in changing density, interchain bond forces, degradation behavior, and ions released from the degrading glasses. Incorporation of both TiO2 and ZnO in T5Z1, T5Z3, and T5Z5 glasses reduced the level of Zn2+ release by two to three orders of magnitude compared with glasses containing ZnO only (Z5). 31P NMR results for T5Z1, T5Z3, and T5Z5 glasses showed the presence of Q3 species suggesting that the TiO2 is acting as a network former, and the phosphate network becomes slightly more connected with increasing ZnO incorporation. Regardless of their relative lower hydrophilicity and surface reactivity compared with the control glass free from TiO2 and ZnO (T0Z0), these glasses have significantly higher surface reactivity compared with Thermanox®. This has been also reflected in the maintenance of >98% viable Osteoblasts, proliferation rate, and expression level of osteoblastic marker genes in a comparable manner to Thermanox® and T5 glasses, particularly T5Z1 and T5Z3 glasses. However, T0Z0 and Z5 glasses showed significantly reduced viability compared to Thermanox®. Therefore, it can be concluded that ZnO doped titanium phosphate glasses, T5Z1 and T5Z3 in particular, can be promising substrates for bone tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Fluorescence Spectroscopy of Color Centers Generated in Phosphate Glasses after Exposure to Femtosecond Laser PulsesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2002James W. Chan A confocal fluorescence microscopy setup was used to observe, in situ, spectral changes in phosphate glasses which were modified using 0.3 ,J of tightly focused 800 nm, 130 fs laser pulses. On 488 nm excitation, the modified glass shows a broad fluorescence centered at roughly 600 nm, which decays with prolonged exposure to the 488 nm light. The decay behavior is dependent on the 488 nm power, with a faster decay rate for higher powers. A mechanism whereby color centers, formed by the femtosecond pulses, fluoresce when excited by the 488 nm light and are simultaneously photobleached is proposed to explain the observed behavior. [source] | ||||||||||