**2.2 Glass of Ca0 – Si02 – P205 – Na20 system**

Glass calcium – silicate – phosphate from the system Ca0 – Si02 – P205 – Na20 was obtained at 13500C by fritting method. Initial materials were:

Calcium carbonate – analytically pure Sodium phosphate – analytically pure Silicon dioxide – pure sodium carbonate – analytically pure.

Three frits were obtained from completely transparent with bluish aquamarine to milky opaque amber colour. Frits were milled in the planetary mill Pulverisette 6 type (Fritsch Company), in the agate chamber with agate balls by 5, 10, 15 and 20 hours with the addition of distilled water. Samples were removed after a certain time subjecting them to further test procedure. A similar procedure was used as in the case of submicrocrystalline sintered corundum grains.

The resulting glass was subjected to chemical analysis on the spectrometer ARL Advant'XP by X – ray fluorescence spectral method. The results of oxide glass compositions were very closed to the calculated theoretically composition, taking into account 10% of the volatility of phosphorus.

Observations of the glassy frits using the scanning electron microscope revealed the presence of elongated grains, irregularly shaped with sharply outlined edges. After prolonged milling a few large grains and clusters of small grains were visible.

Fig. 5. Glass FB3 system after fritting process.

Biocompatible Ceramic – Glass Composite –

Fig. 7. DTA and DTG of glass FB2 system.

Fig. 8. DTA and DTG of glass FB3 system.

of 400 oC for CO2 particles.

Manufacturing and Selected Physical – Mechanical Properties 235

DTA and DTG studies allowed us to determine the glass temperature of vitrification (FB1 – 538 0C, FB2 – 535 0C, FB3 – 525 0C) and temperature of dilatometric softening point (FB1 697 oC, FB2 700,9 oC, FB3 711,9 0C). DTG curve for the glass FB3 system indicated a normal weight loss about 1 wt.% for temperature of 600 0C. In case of glass FB2 system the mass loss, about 5wt% was far too large. This suggested the presence of internal defects, consisting in incorporating the occluded water and CO2 particle in the glass structure. This was confirmed by the investigation using the DTA apparatus containing the gas analyzer, indicating volatilization of particles at a temperature of 150 °C, for H20 and at a temperature

Fig. 6. SEM images of glass FB3 system milled for 5 and 20 hours.

Prolonged milling did not significantly influence the growth of specific surface area of glass system. Only after 20 hours of milling glass system specific surface area was doubled. The reasons for this phenomena might be explained by the acting of large cohesive forces of glass particles.

The densities of glasses were determined by helium method using the pycnometer AccuPyc 330. Analysis of results showed that these glasses belong to a light group of glass (density of 2.65 – 2.70 g/cm3). Knowing the density and specific surface area and using the formula:

$$2r = \frac{6}{\mathcal{S}\_{BET} \cdot d} \tag{1}$$

diameters of the grains were calculated. Only after 20 hours of milling the grain sizes were nearly two times decreased from 2.47 µm to 1.17 µm diameter.


Table 3. Average grains sizes of glass FB3 system after milling by 5, 10, 15, 20 hours and related them specific surface areas.

Prolonged milling did not significantly influence the growth of specific surface area of glass system. Only after 20 hours of milling glass system specific surface area was doubled. The reasons for this phenomena might be explained by the acting of large cohesive forces of

The densities of glasses were determined by helium method using the pycnometer AccuPyc 330. Analysis of results showed that these glasses belong to a light group of glass (density of 2.65 – 2.70 g/cm3). Knowing the density and specific surface area and using the formula:

diameters of the grains were calculated. Only after 20 hours of milling the grain sizes were

Time milling Value of specific surface area m2/g Average size of grains µm

5 hours 0,9159 2,47 10 hours 0,9553 2,36 15 hours 1,1964 1,89 20 hours 1,9241 1,17 Table 3. Average grains sizes of glass FB3 system after milling by 5, 10, 15, 20 hours and

(1)

Fig. 6. SEM images of glass FB3 system milled for 5 and 20 hours.

nearly two times decreased from 2.47 µm to 1.17 µm diameter.

related them specific surface areas.

glass particles.

DTA and DTG studies allowed us to determine the glass temperature of vitrification (FB1 – 538 0C, FB2 – 535 0C, FB3 – 525 0C) and temperature of dilatometric softening point (FB1 697 oC, FB2 700,9 oC, FB3 711,9 0C). DTG curve for the glass FB3 system indicated a normal weight loss about 1 wt.% for temperature of 600 0C. In case of glass FB2 system the mass loss, about 5wt% was far too large. This suggested the presence of internal defects, consisting in incorporating the occluded water and CO2 particle in the glass structure. This was confirmed by the investigation using the DTA apparatus containing the gas analyzer, indicating volatilization of particles at a temperature of 150 °C, for H20 and at a temperature of 400 oC for CO2 particles.

Fig. 7. DTA and DTG of glass FB2 system.

Fig. 8. DTA and DTG of glass FB3 system.

Biocompatible Ceramic – Glass Composite –

1350 oC using an electric furnace.

• cold pressing and sintering

The composites were obtained with two techniques:

• cold pressing, isostatic densification and sintering.

soak, at maximum temperature at the time of 2 hours.

(Si04)2, sodium aluminum silicate NaAlSi04 and quartz Si02.

**3. Biocomposites** 

densification.

Manufacturing and Selected Physical – Mechanical Properties 237

The composites containing a matrix from submicrocrystalline sintered corundum and bioglass of Ca0 – Si02 – P205 – Na20 system (FB3) in 10, 20 and 30 wt.%, obtained by powder metallurgy technique, in the process of free sintering in air atmosphere, in the electric furnace. Bioglass of the Ca0 – Si02 – P205 – Na20 system was obtained by fritting process at

Samples of small (Ø10x2) and large (Ø16x5) size were pressed on the screw press, and after they were isostatically densified or not. The heat treatment was performed without the mould in an electric furnace in air, according to the established characteristics of isothermal

Phase composition of biocomposite samples was identified using X – ray diffractometer August Siemens Type D 500 Cristal Reflex with copper lamp with monochromatic radiation. The phases composition were determined for the samples doped with 10 wt.% bioglass admixture isostatic densification or without densification (w1ssc), the identity of the spectra was found in both cases, suggesting the identity of the phase composition of the samples, regardless of the method of obtaining. In samples following phases were identified : alpha and kappa – Al203 (kappa in the trace amounts), anortit – aluminum calcium silicate – CaAl2

Fig. 11. The XRD spectra for w1ssc samples a) with isostatic densification, b) without

Fig. 9. DTG of glass FB2 system with gas analysis.

Microhardness measurements were carried out using the micro tester FM7 with 100g load. The results show that these are hard glass systems within 5.5 – 6.0 GPa hardness.

Wettability research test of glass system to plate substrates from submicrocrystalline sintered corundum carried out at high temperature microscope MH02 by sessile – drop method showed that the glass FB3 was not gasified, there was no significant change in the dimensions of the swelling and contact angle theta was about 450.

Fig. 10. Wettability of glass FB3 system on the substrate from submicrocrystalline sintered corundum, a) 110°C, b) 904°C, c) 1010°C.

For further research the submicrocrystalline sintered corundum milled for 20 hours and the glass FB3 system were chosen because of the obtained value of specific surface area of corundum and the properties stability of glass.
