Structural transformations of bioactive glass 45S5next term with thermal treatments

International audienceWe report on the structural transformations of Bioglass® during thermal treatments. Just after the glassy transition, at 550 °C, a glassy phase separation occurs at 580 °C, with the appearance of one silicate- and one phosphate-rich phase. It is followed by the crystallization of the major phase Na2CaSi2O6, from 610 to 700 °C and of the secondary phase, silico-rhenanite, at 800 °C. The latter evolves from the phosphate-rich glassy phase, which is still present after the first crystallization. In order to control the processing of glass-ceramic products from Bioglass®, crystallization kinetics were studied via differential scanning calorimetry measurements in the range of 620–700 °C and temperature–time–transformation curves were established

Optimization of chromium oxide nanopowders dispersion for spray-drying

Abstract The aim of this work is to produce spherical micron-sized granules by spray-drying. This technique requires stable and well-dispersed suspensions. The targeted application for such granules is the development of wear resistant Cr 2 O 3 nanostructured coatings by plasma projection. The work reported in this paper was performed to develop and to optimize Cr 2 O 3 nanopowders dispersion by a ball milling method for producing granules. Physical, structural and microstructural properties of Cr 2 O 3 nanopowders were followed by XRD analysis, helium pycnometer density, gas adsorption (BET), SEM and TEM observations. The choice of suitable dispersant was determined by zeta potential measurements. The dispersant amount has been optimized from the rheological behavior of slurries containing 30 wt.% nanopowders. Slip stabilization was investigated by sedimentation tests and zeta potential measurements. The influences of milling time, milling balls diameter and milling balls to powder ratio were studied by granulometric measurements. A welldispersed and stable aqueous Cr 2 O 3 slip, suitable for spray-drying, was achieved

Processing, microstructure, mechanical properties of Si3N4 obtained by slip casting and pressureless sintering

International audienc

Sintering behaviour of 45S5 bioactive glass

International audienceIn this study, we report on the effect of Bioglass® structural transformations on its sintering behaviour. While heating up to 1000 °C, five successive transformations occur: glass transition, glass-in-glass phase separation, two crystallization processes and a second glass transition. The sintering of the material exhibits two main shrinkage stages associated with the two glass transitions at 550 and 850 °C. At 580 °C, the glass-in-glass phase separation induces a decrease in the sintering rate immediately followed by the major crystalline phase crystallization (Na2CaSi2O6) between 600 and 700 °C, from the surface to the bulk of the particles. A complete inhibition of sintering takes place followed by a minor shrinkage effect due to crystallization. A plateau is then observed until the second glass transition temperature is reached. A modification of Frenkel's model allows the determination of the glass-in-glass phase separation kinetics and the identification of the structural transformations effects on sintering behaviour

Optimization of chromium oxide nanopowders dispersion for spray-drying

International audienceThe aim of this work is to produce spherical micron-sized granules by spray-drying. This technique requires stable and well-dispersed suspensions. The targeted application for such granules is the development of wear resistant Cr2O3 nanostructured coatings by plasma projection. The work reported in this paper was performed to develop and to optimize Cr2O3 nanopowders dispersion by a ball milling method for producing granules. Physical, structural and microstructural properties of Cr2O3 nanopowders were followed by XRD analysis, helium pycnometer density, gas adsorption (BET), SEM and TEM observations. The choice of suitable dispersant was determined by zeta potential measurements. The dispersant amount has been optimized from the rheological behavior of slurries containing 30 wt.% nanopowders. Slip stabilization was investigated by sedimentation tests and zeta potential measurements. The influences of milling time, milling balls diameter and milling balls to powder ratio were studied by granulometric measurements. A well-dispersed and stable aqueous Cr2O3 slip, suitable for spray-drying, was achieved

Nanopowder dispersion and spray-drying process: The case of Cr 2O3

International audienceThe work reported in this paper was performed in order to develop and to optimize the dispersion of Cr2O3 nanopowders by a ball-milling method and to produce spherical micrometer-sized granules by spray-drying. The targeted application for such granules is the development of wear resistant nanostructured Cr2O3 coatings by plasma spraying. Cr2O3 nanopowders were dispersed in deionized water. The suitable dispersant (DarvanC) was determined by zeta potential measurements and the dispersant quantity was optimized by rheological tests. The influence of milling time, diameter of milling balls and weight ratio of milling balls to powder was studied by granulometric measurements. A well-dispersed and stable suspension was then obtained and spray-dried. Dense and spherical micrometer-sized granules, with a monodispersed distribution centered about 50 µm, have been achieved and Cr2O3 plasma-sprayed coatings have been realized

Slow crack growth in zirconia ceramics : from the single crystal to the composites

International audienc

Sintering behaviour of 45S5 bioactive glass

In this study, we report on the effect of Bioglass® structural transformations on its sintering behaviour. In a previous paper, we showed that while heating up to 1000°C, five successive transformations occur: glassy transition, phase separation, two crystallization processes and a second glassy transition. The sintering of the material exhibits two main shrinkage stages associated to the two glassy transitions at 550°C and 850°C. At 580°C, the glass-in-glass phase separation induces a decrease of the sintering rate immediately followed by the crystallisation of the major phase Na2CaSi2O6 between 600 and 700°C, from the surface to the bulk of the particles. A completed inhibition of sintering takes place followed by a minor shrinkage due to volume crystallization. A plateau is observed until the second glassy transition

Sintering behavior of 45S5 bioactive glass

In this study, we report on the effect of Bioglass (R) structural transformations on its sintering behaviour. While heating up to 1000 degrees C, five successive transformations occur: glass transition, glass-in-glass phase separation, two crystallization processes and a second glass transition. The sintering of the material exhibits two main shrinkage stages associated with the two glass transitions at 550 and 850 C. At 580 degrees C, the glass-in-glass phase separation induces a decrease in the sintering rate immediately followed by the major crystalline phase crystallization (Na2CaSi2O6) between 600 and 700 degrees C, from the surface to the bulk of the particles. A complete inhibition of sintering takes place followed by a minor shrinkage effect due to crystallization. A plateau is then observed until the second glass transition temperature is reached. A modification of Frenkel's model allows the determination of the glass-in-glass phase separation kinetics and the identification of the structural transformations effects on sintering behaviour

EVALUATION OF A PDLLA/45S5 BIOGLASS COMPOSITE: MECHANICAL AND BIOLOGICAL PROPERTIES

33rd International Conference on Advanced Ceramics and Composites, Daytona Beach, FL, JAN 18-23, 2009International audienceThe present study aims to characterize a composite made of poly-L,DL-lactic acid (P(L,DL)LA, Mv: 120 KDa) containing 30 wt% of 45S5 bioactive glass particles. Glass transition (around 52 degrees C) of the polymer was assessed by differential scanning calorimetry (DSC). The mechanical properties of the neat polymer and the composite were evaluated by tensile and compressive tests. From these tests, it was confirmed that the addition of bioglass into the polymer matrix leads to a slight decrease in tensile strength and an increase in elastic modulus. In vitro bioactivity of this composite was evaluated by immersion in a simulated body fluid (SBF) at 37 degrees C for different durations. Formation of hydroxyapatite crystals on the surface of the composite was recorded by scanning electron microscopy and confirmed by X-ray diffraction. Many hydroxyapatite crystals covered the surface of the composite after 14 days of immersion in simulated body fluid. Osteoblast cells MG-63 (human osteosarcoma cell line) were cultured in direct contact with the polymer and the composite. Cells morphology and attachment were analysed using SEM and MTT viability test. Scanning electron microscopy analysis showed the presence of cells at the surface of the composite. These results confirmed the biocompatibility of the composite and the positive effect of the bioglass on the osteoblast cells adhesion and proliferation on the composite