Ishu Kansal

Structure, surface reactivity and physico-chemical degradation of fluoride containing phospho-silicate glasses

We report on the structure, apatite-forming ability and physicochemical degradation of glasses along the fluorapatite [FA; Ca5(PO4)3F]–diopside (Di; CaMgSi2O6) join. A series of glasses with varying FA/Di ratio have been synthesised by melt-quenching technique. The amorphous glasses could be obtained only for compositions up to 40 wt.% of FA. The detailed structural analysis of the glasses has been made by infrared spectroscopy (FTIR), Raman spectroscopy and magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). Silicon was predominantly present as Q2 (Si) species while phosphorus was found in an orthophosphate type environment in all the investigated glasses. The apatite forming ability of glasses was investigated by immersion of the glass powders in simulated body fluid (SBF) for times varying between 1 h–28 days. An extensive precipitation of calcite (CaCO3) after immersion in SBF was found in all the glasses, which considerably masked the formation of hydroxyapatite [HA; Ca5(PO4)3OH]. The possible mechanism favouring the formation of calcite instead of HA has been explained on the basis of experimental results obtained for the structure of the glasses, leaching profile of glass powders in SBF solution and pH variation in SBF solution. Furthermore, the physico-chemical degradation of the glasses has been studied in accordance with ISO 10993-14 “Biological evaluation of medical devices – Part 14: Identification and quantification of degradation products from ceramics” in Tris HCl and citric acid buffer. All the FA containing glasses exhibited a weight gain (instead of weight loss) after immersion in citric acid buffer due to the formation of different crystalline products.

Diopside (CaO·MgO·2SiO2)–fluorapatite (9CaO·3P2O5·CaF2) glass-ceramics: potential materials for bone tissue engineering

Glass-ceramics in the diopside (CaMgSi2O6)–fluorapatite [Ca5(PO4)3F] system are potential candidates for restorative dental and bone implant materials. In the present study, a series of glasses along the diopside–fluorapatite binary system have been prepared with varying diopside/fluorapatite ratios for their potential applications in bone tissue engineering. The glasses were obtained from compositions with fluorapatite contents varying between 0 and 40 wt%. The sintering ability and crystallization kinetics of as obtained amorphous glasses have been studied through hot-stage microscopy (HSM) and differential thermal analysis (DTA), respectively, while crystalline phase evolution in sintered GCs has been followed by X-ray diffraction (XRD) adjoined with the Rietveld-R.I.R. technique and scanning electron microscopy (SEM). Further, biodegradation and apatite forming ability of glass-ceramics were investigated by immersion of glass-ceramic discs in simulated body fluid (SBF) solution while chemical degradation and weight loss of glass-ceramics were studied by immersion in Tris–HCl in accordance with the ISO 10993-14 standard. The addition of fluorapatite (10–25 wt%) in the diopside glass system significantly enhanced the sintering ability of glass-ceramics and improved their apatite forming ability along with their biodegradation behaviour. Moreover, the in vitro cellular responses to glass-ceramics showed good cell viability and significant stimulation of osteoblastic differentiation, suggesting the possible use of the glass-ceramics for bone regeneration.

Structure, biodegradation behavior and cytotoxicity of alkali-containing alkaline-earth phosphosilicate glasses.

We report on the effect of sodium on the structure, chemical degradation and bioactivity of glasses in the CaO-MgO-SiO2-P2O5-CaF2 system. The (29)Si and (31)P magic angle spinning-nuclear magnetic resonance spectroscopy of melt-quenched glasses with varying Na2O/MgO ratios exhibit a silicate glass network with the dominance of Q(2)(Si) units and phosphorus mainly forming orthophosphate species. Sodium incorporation in the glasses did not induce a significant structural change in the silicate network, while it did influence the phosphate environment due to its lower ionic field strength in comparison with that of magnesium. The apatite forming ability of glasses has been investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1h and 7 days while their chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Increasing Na(+)/Mg(2+) ratio caused a decrease in the chemical durability of glasses and in the apatite forming ability especially during initial steps of interaction between glass and SBF solution. The cellular responses were observed in vitro on bulk glass samples using mouse-derived pre-osteoblastic MC3T3-E1 cell line. The preliminary study suggested that the increasing alkali-concentration in glasses led to cytotoxicity in the cell culture medium.

Sintering and crystallization behavior of CaMgSi2O6–NaFeSi2O6 based glass-ceramics

We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi2O6−10 mol % NaFeSi2O6. The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850–950 °C in both air and N2 atmosphere. X-ray diffraction studies adjoined with the Rietveld–reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with ...

Crystallisation kinetics of diopside-Ca-Tschermak based glasses nucleated with Cr2O3 and Fe2O3

We report on the crystallisation behaviour and non-isothermal crystallisation kinetic studies of two diopside (CaMgSi2O6)-Ca-Tschermak (CaAl2SiO6) based glasses nucleated with Fe2O3 and Cr2O3. The two glasses with compositions corresponding to CaMg0.75Al0.5Si1.75O6 and Ca0.9Mg0.65Li0.1Al0.5La0.1Si1.75O6 were prepared by the melt-quenching technique. Structural investigations on the glasses have been made by density measurements, molar volume and infrared spectroscopy (FTIR). Non-isothermal crystallisation kinetic studies have been employed to study the mechanism of crystallisation in all the four glasses. Bulk crystallisation was obtained and augite crystallised out being the primary crystalline phase in both the glasses. Crystallisation sequence in the glasses has been followed by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and FTIR.