Cold sintering of bioglass and bioglass/polymer composites

2009

The sintering process of 45S5 Bioglass ® powder (mean particle size < 5 m) was investigated by using different thermal analysis methods. Heating microscopy and conventional dilatometry techniques showed that bioactive glass sinters in two major steps: a short stage in the temperature range 500-600 • C and a longer stage in the range 850-1100 • C. The optimal sintering temperature and time were found to be 1050 • C and 140 min, respectively. Differential thermal analysis (DTA) showed that Bioglass ® crystallises at temperatures between 600 and 750 • C. The characteristic crystalline phases were identified by Fourier Transformed Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The crystallisation kinetics was studied by DTA, using a non-isothermal method. The Kissinger plot for Bioglass ® powder heated at different heating rates between 5 and 30 • C/min yielded an activation energy of 316 kJ/mol. The average value of Avrami parameter determined using the Augis-Bennett method was 0.95 ± 0.10, confirming a surface crystallisation mechanism. After sintering at 1050 • C for 140 min, the main crystalline phase was found to be Na 2 Ca 2 Si 3 O 9 . The results of this work are useful for the design of the sintering/crystallisation heat treatment of Bioglass ® powder which is used for fabricating tissue engineering scaffolds with varying degree of bioactivity.

Materials & Design

Eight novel silicate, phosphate and borate glass compositions (coded as NCLx, where x = 1 to 8), containing different oxides (i.

Sintering and crystallisation phenomena in powders of a typical bioactive glass composition (45S5 Bioglass s) have been investigated in order to gain further understanding of the processes involved in the fabrication of Bioglass s based glass–ceramic scaffolds for tissue engineering applications. In situ experiments in an environmental scanning electron microscope with a heating stage were carried out to follow the morphology of Bioglass s particles during sintering and crystallisation. Optimal processing parameters for the manufacture of Bioglass s based glass–ceramic scaffolds by the foam-replica technique were determined. To assess the in vitro performance and bioreactivity of Bioglass s-derived glass–ceramic scaffolds, the biodegradation of samples in simulated body fluid (SBF) was investigated using various techniques, including SEM, TEM, XRD and EDX. The mechanism of interaction of the glass–ceramic surface with SBF was determined, which involves (i) preferential dissolution at glass/crystal interfaces, (ii) breakdown of crystalline particles into very fine grains through preferential dissolution at crystal structural defects, and (iii) amorphisation of the crystalline structure by introduction of point defects produced during ion exchange. The present report thus offers for the first time a complete assessment of the processing parameters, microstructure, and in vitro performance of Bioglass s derived glass–ceramic scaffolds intended for bone tissue engineering.

2006

Bioactive glasses and glass-ceramics were made from the system Na2O-CaO-SiO2-P2O5 by the melt quench method. The optimal conditions for heat and chemical treatments were determined. The effects of the heat and chemical treatments on the structure of the glasses and glass-ceramics were investigated using optical microscopy. Heat treatments of nine hours produced a higher degree of crystallization and larger crystals than heat treatments of three and six hours. The samples from batch 45S exhibited greater crystallization than the other samples tested. 1.0M HCl for the chemical treatment was found to be superior to 0.3M and 3.0M HCl because the 1.0M acid produced the highest pore density and the most uniform structure. One hour and 85°C were determined to be the best time and temperature, respectively, for the chemical treatment because they resulted in the highest porosity and most even structure compared to temperatures of 70°C and times of two hours. Overall, the six hour heat treat...

Biomaterials, 2006

Three-dimensional (3D), highly porous, mechanically competent, bioactive and biodegradable scaffolds have been fabricated for the first time by the replication technique using 45S5 Bioglass s powder. Under an optimum sintering condition (1000 1C/1 h), nearly full densification of the foam struts occurred and fine crystals of Na 2 Ca 2 Si 3 O 9 formed, which conferred the scaffolds the highest possible compressive and flexural strength for this foam structure. Important findings are that the mechanically strong crystalline phase Na 2 Ca 2 Si 3 O 9 can transform into an amorphous calcium phosphate phase after immersion in simulated body fluid for 28 days, and that the transformation kinetics can be tailored through controlling the crystallinity of the sintered 45S5 Bioglass s . Therefore, the goal of an ideal scaffold that provides good mechanical support temporarily while maintaining bioactivity, and that can biodegrade at later stages at a tailorable rate is achievable with the developed Bioglass s -based scaffolds. r

This work aims to find an efficient sintering technique and optimal sintering conditions of a novel sol-gel derived Bioglass®-ceramic powder so as to achieve much improved mechanical properties compared to conventional Bioglass®. To this end, the spark plasma sintering (SPS) technique was for the first time used to densify the sol-gel derived Bioglass®-ceramic powder. It was found that the sol-gel derived Bio-glass®-ceramics sintered with the SPS technique at 950°C for 15 min had a high Young's modulus value of~110 GPa, which was comparable to that of compact bone and significantly higher than the maximal value achieved by the conventional heat treatment. Moreover, the Bioglass®-ceramic compacts sintered with SPS released alkaline ions slowly and as a result, these highly densified Bioglass®-ceramics exhibited better cytocompatibility at the early stage of cell culture testing, compared to the conventional Bioglass®. Hence, the SPS technique is recommended to be used in the process of sol-gel derived Bioglass®-ceramics and its tissue engineering scaffolds.

Three-dimensional (3D), highly porous, mechanically competent, bioactive and biodegradable scaffolds have been fabricated for the first time by the replication technique using 45S5 Bioglass s powder. Under an optimum sintering condition (1000 1C/1 h), nearly full densification of the foam struts occurred and fine crystals of Na 2 Ca 2 Si 3 O 9 formed, which conferred the scaffolds the highest possible compressive and flexural strength for this foam structure. Important findings are that the mechanically strong crystalline phase Na 2 Ca 2 Si 3 O 9 can transform into an amorphous calcium phosphate phase after immersion in simulated body fluid for 28 days, and that the transformation kinetics can be tailored through controlling the crystallinity of the sintered 45S5 Bioglass s. Therefore, the goal of an ideal scaffold that provides good mechanical support temporarily while maintaining bioactivity, and that can biodegrade at later stages at a tailorable rate is achievable with the developed Bioglass s-based scaffolds.

Ceramics International, 2017

Consolidation processes aimed at manufacturing cellular solids from bioglasses often result in a glass-ceramic microstructure, whose response to aqueous environment affects their performance. In this study, we evaluated the microstructure and the effect of crystallization on the dissolution mechanism of a Bioglass®-based glassceramic scaffold, produced with a powder metallurgy inspired technology. All the experiments are conducted in a controlled aqueous environment in order to avoid nucleation of different species or unknown chemical interactions between simulated body fluids and bioglass-ceramic material. The presence of a residual silica glass embedding different phases of not fully crystallized particles is highlighted, showing a complex multiscale structure elucidated via Focused Ion Beam (FIB) preparation and Scanning Transmission Electron Microscopy (STEM) observation. Crystalline and amorphous phases dissolved both in water, with different kinetics. The dissolution appears to be a surface phenomenon, which reduces the section of the foam struts without instability of the glass-ceramic material. Amorphization of crystalline phase is observed during immersion of the glass-ceramic material in stirring conditions at room temperature from the ions dissolved in water.

Applied Sciences

The intrinsic brittleness of bioactive glasses (BGs) is one of the main barriers to the widespread use of three-dimensional porous BG-derived bone grafts (scaffolds) in clinical practice. Among all the available strategies for improving the mechanical properties of BG-based scaffolds, strut densification upon sintering treatments at high temperatures represents a relatively easy approach, but its implementation might lead to undesired and poorly predictable decrease in porosity, mass transport properties and bioactivity resulting from densification and devitrification phenomena occurring in the material upon heating. The aim of the present work was to investigate the sinter-crystallization of a highly bioactive SiO2-P2O5-CaO–MgO–Na2O–K2O glass (47.5B composition) in reference to its suitability for the fabrication of bonelike foams. The thermal behavior of 47.5B glass particles was investigated upon sintering at different temperatures in the range of 600–850 °C by means of combined ...

Journal of Biomedical Engineering, 1993

This paper presents details of the fabrication of a glass ceramic, and its application as an artificial bone prosthetic material. Th,is mw biogkzs ceramic, with composition of iVa# 8.4%, CaO 40.60/o, Pz05 12% and $0, 39%, had 7 60-79OWa and 8&I-98OMPa of three-point bending strength and compressive strength respectively. i'%e ceramic bar a (Na, Ca) (P, Si) 0, crystalline phase with a unijkrn crystal sip of about 10~ m, which was attributed to the high nucleationfiequemy. The rabbit condyle test showed that the materialformed a tight chemical bond with biological texture and had good biocompatibility.