O Bretcanu | PubMed Health

PubMed2005

The influence of crystallised Fe3O4 on the magnetic properties of coprecipitation-derived ferrimagnetic glass-ceramics.

Ferrimagnetic glass-ceramics are potential candidates for magnetic induction hyperthermia, which is one form of inducing deep-regional hyperthermia, by using a magnetic field. The aim of this work was to analyse the influence of the amount of crystallised magnetite on the magnetic properties of glass-ceramic samples. Thus, two different ferrimagnetic glass-ceramics with the composition of the system Na(2)O-CaO-SiO(2)-P(2)O(5)-FeO-Fe(2)O(3) were prepared by melting at 1500 degrees C for 30 min of the coprecipitation-derived starting products. The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The estimated amount of crystallised magnetite varies between 20 and 45 wt.%, as a function of the chemical composition. The morphology of the crystals was studied by scanning electron micrography and transmission electron micrography. Glass transition temperature and thermal stability were investigated by differential thermal analysis. Magnetic hysteresis cycles were analysed using a vibrating sample magnetometer with a maximum applied field of 17 kOe, at room temperature, in quasi-static conditions. Calorimetric measurements were carried out using a magnetic induction furnace. The power losses estimated from calorimetric measurements under a magnetic field of 40 kA/m and 440 kHz are 65 W/g for the glass-ceramic with lower iron oxides content and 25 W/g for the glass-ceramic with higher iron oxide content.

Biocompatible Materials↗

PubMed2004

Macroporous glass-ceramic materials with bioactive properties.

In the present research work, glass powders and three different organic starches were used to realize macroporous glass-ceramic scaffolds for bone substitutions. For this purpose, bioactive glass powders belonging to the system SiO2-CaO-Na2O-MgO were mixed in a liquid medium with the desired amount of the selected organic phase. Afterwards, by progressively raising the temperature, the water uptake of starches occurred and led to the gelling of the whole system. The resultant gel underwent two thermal treatments in order to eliminate the organic phase and to allow the sintering of the glassy phase. In this way, macroporous glass-ceramic scaffolds were successfully prepared. The samples were characterized by means of optical and scanning electron microscopy with compositional analysis. The volume and mean size of the obtained porosity were investigated by means of mercury intrusion porosimetry, whereas its morphology was assessed by means of microscopic observations. The structure of the original and the resultant materials were investigated by X-ray diffraction. In order to study the reactivity of the scaffolds towards physiological media, the samples were soaked in a simulated body fluid for various times. On their soaked surfaces, scanning electron microscopy and compositional analysis were carried out in order to assess their bioactivity.

Body Fluids↗