Nedjeljka Petric

Effect of TiO2, SiO2 and Al2O3 on properties of sintered magnesium oxide from sea water

Abstract The process of isothermal sintering of magnesium oxide obtained from sea water (by precipitation with 80% and 120% of the stoichiometric quantity of the calcined dolomite and magnesium oxide p.a. (pro analysi purity grade) ) was examined with the addition of SiO2, Al2O3 and TiO2, at temperatures in the range 1300–1800 °C. The process was followed by determining the product density, as well as densification of the compacts. With compacts containing SiO2 or Al2O3 densification was examined in relation to the sintering temperature and quantity of the sintering aid; with compacts containing TiO2 densification was examined in relation to the sintering temperature and pressing pressure. Sample densification and pore removal during isothermal sintering have been shown to be a function of the exponent α in the expression (Δ V/V0) − m = τα. The specific surfaces, chemical compositions and particle size distribution were determined for the magnesium oxide samples examined.

Sintering of magnesium oxide obtained from sea water

U svrhu izucavanja procesa sinteriranja magnezij-okisda, ispitivanja su vrsena uz razne kolicine dodatka TiO2 magnezij-oksidu koji je dobiven nestehiometrijskim i prestehiometrijskim nacinom taloženja magnezij-hidroksida u morskoj vodi, dolomitnim vapnom. Ispitivan je sadržaj B2O3 u sinteriranim uzorcima u ovisnosti o temperaturi izotermnog sinteriranja, kolicini dodanog TiO2 i nacinu dobivanja magnezij-oksida. Izvrsena je termodinamicka obrada rezultata.

Isothermal and activated sintering of magnesium oxide from sea water

Abstract The influence of TiO 2 addition in sintering magnesium oxide was investigated as a function of the time and temperature of isothermal sintering and of the quantity of the addition. The magnesium oxide used was obtained from sea water by precipitation of magnesium hydroxide with 80% of the stoichiometrical quantity of dolomite lime. It has been noted that the content of B 2 O 3 in sintered magnesium oxide samples is significantly reduced by the addition of TiO 2 . The results were analysed thermodynamically, according to expressions used in open system thermodynamics.

Effect of TiO2 on properties of magnesium oxide obtained from seawater

The effect has been examined of TiO2 on B2O3 content in sintered magnesium oxide samples obtained by precipitation of magnesium hydroxide in seawater with 80 or 120% of the stoichiometrical quantity of the precipitation agent, i.e. the effect of TiO2 on product properties has been examined. Coefficients were calculated for dependent reactions of Ca2B2O5 and CaTiO3 formation.

Activated sintering of magnesium oxide from sea water

The process of activated sintering of magnesium oxide obtained from sea water (by precipitation with 80 percentage and 120percentage of the stoichiometric quantity of the dolomite lime) was examined with addition of 1, 2 and 5 wt percentage TiO_2, at temperatures of 1600°C and 1700°C with soaking at the maximum temperature of 1, 3 and 5 hours respectively. The product density and porosity were examined and the dependences obtained were described by appropriate analytical expressions. The compatibility relationships between addition of TiO_2 and the B_2O_3 content in the sintered magnesium oxide samples were determined, based on an important theorem due to Onsanger. The phenomenological coefficients were calculated for two irreversible processes, namely those of formation of Ca_2B_2O_5 and CaTiO_3 respectively.