Non crystalline solids

Bioactive glasses have attracted considerable interest in recent years, due to their technological application, especially in biomaterials research. Differential scanning calorimetry (DSC) has been used in the study of the crystallization mechanism in the SiO2–Na2O–CaO–P2O5 glass system, as a function of particle size. The curve of the bulk glass presents a slightly asymmetric crystallization peak that could be deconvoluted into two separate peaks, their separation being followed in the form of powder glasses. Also, a shift of the crystallization peaks to lower temperatures was observed with the decrease of the particle size. FTIR studies – that are confirmed by XRD measurements – proved that the different peaks could be attributed to different crystallization mechanisms. Moreover, it is presented the bioactive behavior of the specific glass as a function of particle size. The study of bioactivity is performed through the process of its immersion in simulated human blood plasma (simulated body fluid, SBF) and the subsequent examination of the development of carbonate-containing hydroxyapatite layer on the surface of the particles. The bioactive response is improved with the increase of the particle size of powders up to 80 μm and remains almost unchanged for further increase, following the specific surface to volume ratio decrease.

The energy resolution of the Laplace transformation method for measuring localized-state distributions, based on the analysis of transient photoconductivity (TPC) in amorphous semiconductors, has been improved analytically. The improvement of the energy resolution of the Laplace transformation method is shown for representative localized-state distributions often found in amorphous semiconductors using computer-generated photocurrent transients. The most important finding is that the improved Laplace transformation (LT) method can map a localized-tail-state distribution whose width is smaller than kT.