SAXS AND TEM STUDIES OF PHASE SEPARATION IN BaO-SiO2 GLASSES

La séparation de phases amorphes des verres de BaO-SiO2 a été étudiée par diffusion de rayons X aux petits angles et microscopie électronique de transmission, dans la région de germination et croissance de la lacune de miscibilité. Les diamètres des particules sphéroïdales précipitées, déterminés avec la loi de Guinier et par microscopie électronique, sont en accord. La cinétique de croissance des particules est bien décrite par la théorie classique de "coarsening". Les intégrales des courbes de diffusion de rayons X ont permis de déterminer la frontière de la lacune de miscibilité et le temps nécessaire pour que la matrice atteigne sa composition d'équilibre. La germination se produit pendant le refroidissement du liquide ou dans les tous premiers stades du traitement thermique. La processus de "coarsening" commence avant que la matrice atteigne la composition d'équilibre.Amorphous phase separation was studied in the nucleation and growth region of the BaO-SiO2 miscibility gap. Nearly spherical droplets were precipitated, the diameters obtained from SAXS and TEM being in reasonable agreement. The growth kinetics of the droplets were well described by the classical theory of coarsening. From the integrated SAXS intensities the times to reach the equilibrium matrix compositions at 743 and 760°C were determined, and the binodal boundary located. Nucleation occurred during quenching from the melt or within a very short time of heat treatment. Coarsening began well before the attainment of the equilibrium matrix composition

Crystallization pathways and some properties of lithium disilicate oxynitride glasses

International audienc

Structure and ionic conductivity of nitrated lithium disilicate (LiSiON) glasses

International audienc

Putty-like bone fillers based on CaP ceramics or Biosilicate(R) combined with carboxymethylcellulose: Characterization, optimization, and evaluation

Item does not contain fulltextCalcium phosphates and bioactive glass ceramics have been considered promising biomaterials for use in surgeries. However, their moldability should be further enhanced. We here thereby report the handling, physicochemical features, and morphological characteristics of formulations consisting of carboxymethylcellulose-glycerol and hydroxyapatite-tricalcium phosphate or Biosilicate(R) particles. We hypothesized that combining either material with carboxymethylcellulose-glycerol would improve handling properties, retaining their bioactivity. In addition to scanning electron microscopy, cohesion, mineralization, pH, and viscoelastic properties of the novel formulations, cell culture experiments were performed to evaluate the cytotoxicity and cell proliferation. Putty-like formulations were obtained with improved cohesion and moldability. Remarkably, mineralization in simulated body fluid of hydroxyapatite-tricalcium phosphate/carboxymethylcellulose-glycerol formulations was enhanced compared to pure hydroxyapatite-tricalcium phosphate. Cell experiments showed that all formulations were noncytotoxic and that HA-TCP60 and BGC50 extracts led to an increased cell proliferation. We conclude that combining carboxymethylcellulose-glycerol with either hydroxyapatite-tricalcium phosphate or Biosilicate(R) allows for the generation of moldable putties, improves handling properties, and retains the ceramic bioactivity

Incorporation of bioactive glass in calcium phosphate cement: Material characterization and in vitro degradation

Item does not contain fulltextCalcium phosphate cements (CPCs) have been widely used as an alternative to biological grafts due to their excellent osteoconductive properties. Although degradation has been improved by using poly(D,L-lactic-co-glycolic) acid (PLGA) microspheres as porogens, the biological performance of CPC/PLGA composites is insufficient to stimulate bone healing in large bone defects. In this context, the aim of this study was to investigate the effect of incorporating osteopromotive bioactive glass (BG; up to 50 wt %) on setting properties, in vitro degradation behavior and morphological characteristics of CPC/BG and CPC/PLGA/BG. The results revealed that the initial and final setting time of the composites increased with increasing amounts of incorporated BG. The degradation test showed a BG-dependent increasing effect on pH of CPC/BG and CPC/PLGA/BG pre-set scaffolds immersed in PBS compared to CPC and CPC/PLGA equivalents. Whereas no effects on mass loss were observed for CPC and CPC/BG pre-set scaffolds, CPC/PLGA/BG pre-set scaffolds showed an accelerated mass loss compared with CPC/PLGA equivalents. Morphologically, no changes were observed for CPC and CPC/BG pre-set scaffolds. In contrast, CPC/PLGA and CPC/PLGA/BG showed apparent degradation of PLGA microspheres and faster loss of integrity for CPC/PLGA/BG pre-set scaffolds compared with CPC/PLGA equivalents. Based on the present in vitro results, it can be concluded that BG can be successfully introduced into CPC and CPC/PLGA without exceeding the setting time beyond clinically acceptable values. All injectable composites containing BG had suitable handling properties and specifically CPC/PLGA/BG showed an increased rate of mass loss. Future investigations should focus on translating these findings to in vivo applications. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013