ABSTRACT
The main aim of this work was to synthesize calcium phosphate silicate bioceramics by a low energy-consuming sol-gel method applying various phosphorous precursors (triethyl phosphate, phosphoric acid, and ammonium hydrogen phosphate). The investigations concentrated on the influence of phosphorous initial compounds on the bond and crystalline structures and the material quality. The application of the alkoxide and inorganic P-precursors results in considerably different textures. The inorganic PO4-containing precursors lead to sol formations. The sol systems can be characterized by a randomly bonded aggregate structure. Monolith gel systems can only be prepared by using TEP. The alkoxide P-precursor more effectively furthers the connection between the phosphorous and silicon tetrahedra than the inorganic phosphate compounds. Over the P-precursors, the catalyst also affects the structure and properties. In the present work, a special attention was paid to identify the POSi bonds in the FTIR and 31P NMR spectra. The bond systems were investigated by FTIR, 31P and 29Si MAS NMR spectroscopies, the morphology by SEM, WAXS, and XRD measurements, and the water solubility of the ceramic systems also was tested.
Subject(s)
Biocompatible Materials/chemistry , Calcium Phosphates/chemistry , Phosphorus/chemistry , Silicates/chemistry , Crystallization , Magnetic Resonance Spectroscopy , Solubility , Spectroscopy, Fourier Transform Infrared , Temperature , Time Factors , Vibration , Water/chemistry , X-Ray DiffractionABSTRACT
Calcium silicate ceramics are intended for application as long-term implant materials. In the present work, attention was paid to understand the correlations between the nanostructure (aggregate size, crystallinity, porosity) and the macroscopic properties (solubility in water and simulated body fluids, SBF; hardness) varying the chemical composition. Varying the catalyst (from a base to various acids) during the chemical synthesis was shown to significantly impact on the pore size, crystallinity and mechanical properties. The basic catalyst yields the ceramics with the highest mechanical strength. Ammonia used in 1.0 or 10.0 molar ratio results in bulk ceramics with parameters required for a biomedical application, good hardness (180-200 HV) and low solubility (1-3%) in water and in SBF. The fine porosity (~50 nm) and homogeneous amorphous structure induce good mechanical character.
Subject(s)
Biocompatible Materials/chemistry , Calcium/chemistry , Ceramics/chemistry , Nanostructures/chemistry , Ammonia/analysis , Calcium Compounds/chemistry , Catalysis , Crystallization , Hardness , Materials Testing , Nanostructures/ultrastructure , Phosphoric Acids/chemistry , Silicates/chemistry , Solubility , Spectrometry, X-Ray Emission , Spectroscopy, Fourier Transform Infrared , Temperature , Time Factors , X-Ray DiffractionABSTRACT
The main aim of this study is to synthesize calcium silicate ceramics that exhibit suitable properties to be used for biomedical applications. In the present work, attention was paid to the understanding of processing-structure relationships. A particular effort was made to clarify the identification of Ca-O-Si bonds by means of spectroscopy. The calcium silicate systems were prepared via a sol-gel route, varying the chemical compositions, the catalyst concentration, and the temperature and time of aging and heat treatment. The processes and the phases evolved during the sol-gel procedure were determined. The bond systems were investigated by Fourier transform infrared (FTIR) and (29)Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and the aggregate structures by scanning electron microscopy (SEM), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and X-ray diffraction (XRD) measurements.