Jan Majling

Fluoroapatite - material for medicine, Growth, morphology and thermoanalytical properties

Fluoroapatite containing glass-ceramics were prepared from Li2O-CaO-CaF2-P2O5-SiO2 system. The glass was melted at 1480°C for 1 h. The object of observation was the preparing crystal phase of fluoroapatite in amorphous glass matrix. The morphology of lithium disilicate glass-ceramics was studied by SEM. The crystal growth and thermal properties of fluoroapatite were studied by X-ray diffraction and DTA. The more the content of P2O5, the more the presence of fluoroapatite particles. SEM investigation clearly indicated the phase separation and formation of a primary crystalline phase of fluoroapatite in the studied glass-ceramics. DTA curves of the fluoroapatite samples exhibit exothermic effects in the temperature range 337-694°C depending on the composition of the materials. The position of exothermic peak for lithium disilicate on DTA curves moves with increasing specific surfacetowards lower temperatures which points on its preferential surface crystallization. As far as physical qualities are concerned, mainly color and gloss, the best qualities of all observed materials belong to glass-ceramics with 10% P2O5.

Polyvinylpyrrolidone thin film pyrolysis as accessed by the real-time optical transmission measurements

Present results reveal basic features of the optical transmission thermo-analytical method in its employment to investigate the oxidative pyrolysis of supported thin polyvinylpyrrolidone films. The OT curves naturally vary in shapes and positions on the time/temperature scales, respective to the examined rate of sample heating, to the wavelengths of radiation as well as to the film thickness. Recorded OT curves exhibit characteristic shapes with well-expressed OT minima. The temperatures at which the OT minima appear are in a linear relationship with heating rates of samples, at a frequency of radiation as well as a film thickness kept constant. Similarly, the OT values at which the OT minima appear are in a linear relationship with film thickness, at a frequency of the radiation and sample heating rate unchanged.

Theoretical thermo-optical patterns relevant to glass crystallisation

Mie computations are performed to evaluate light scattering on the virtual microstructures relevant to lithium disilicate glass internal crystallisation. The computations are expressed in the form of optical transmission (OT) patterns evolved on a scale of growing lithium disilicate crystals. Input data include the crystals number density, their size, the wavelength of the incident electromagnetic radiation, the indices of refraction of the lithium disilicate glassy and crystalline phases and the thickness of the virtual glass slab. In the computations, the spherical shape of crystals and their random distribution are assumed. The results reveal the quantitative effects of individual input data constants on the overall course of the computed OT patterns. They also relate the computed OT data magnitudes to the corresponding glass crystallinity (α). In addition, they point to singular combinations of the input data constants defining the conditions under which the OT data could potentially stand for the kinetically important α data. Finally, the results aid better recognition of some fundamental as well as practical properties of the optical thermal methods based on the optical transmission measurements.

Recognition of the carbon thin films sub-structures: thermo-optical measurements

Carbon thin films oxidation was investigated on-line by high-sensitivity optical transmission (OT) method. The films have been prepared by common vacuum arc discharge and subsequently air oxidized at linear heating rates until temperatures of their complete gasification. The shape of the optical curves acquired was interpreted in light of deduced partial optical changes, each of them being ascribed by simple sigmoidal dependence. The dependencies converted to their derivative form ordered respective to the temperature scale conveniently represent an inter-relationship among the sequentially evolved films’ optical events, considered as being closely related to the individual carbon-replenishing steps. The dependencies correspond well to the ones obtained on thicker films by means of the thermogravimetry (TG) measurements.