Research On Preparation Technics For Mesoporous Glass Of Na₂O-B₂O₃-SiO₂ System

The mesoporous glass of Na₂O-B₂O₃-SiO₂ system is prepared by three steps of melting,phase separation with SiO₂, Na₂CO₃ and B₂O₃ as raw materials in the dissertation. The porousstructure of mesoporou glass is estimated from the total absorbed volume of liquid nitrogen;theoptimization condition of the preparation technics is confirmed. The main features and results ofthis thesis are as below.The optimization condition of the melting glass of Na₂O-B₂O₃-SiO₂ system is SiO₂61.36%, B₂O₃ 27.03%, and Na₂CO₃ 11.34%, melting temperature 1500℃ with 60 min by themelting experiment. The transparent and colorless glass without crystal is made.The optimization condition of the phase separation experiment of Na₂O-B₂O₃-SiO₂ systemis the temperature of phase separation 520℃ and the time of phase separation 12h.The influences of HCl and H₂SO₄ on acid losing of phase separation glass are studied, andthe influences of concentration of dissolvent acid and dissolved time are analyzed. The resultshows that the influence of HCl and H₂SO₄ on acid losing of phase separation glass isindistinctive;the influences of the concentration of dissolvent acid and dissolved time areobvious: the concentration is heightened or dissolvent time is increased, while the acid losing isfalled obviously. The optimization condition of acid dissolution is concentration of HCl orconcentration of H₂SO₄ 0.2 mol/L and dissolved time 2h.The features of the mesoporous glass are water absorption 15.54%, BET surface area140.8m²/g, average pore diameters 3.77nm and pore volume 0.133mL/g.BET surface areas and porous structure parameters of the six samples are menstruated fromthe total absorbed volume of liquid nitrogen. The results are that BET surface area is 82.57～140.8m²/g,Average pore diameters is 3.39～4.99nm, and pore volume is 0.091～0.137mL/g. Theadsorption-desorption isotherms of the six sample are similar, and the characteristic is thatadsorption-desorption isotherms fall suddenly, while relative pressure (p/p0) is in the range of0.4～0.6. The experiment result shows that porous conformation is scrambling(perhaps parallelporou, cuniform porou). The result indicates that the surface areas of the samples are contributedto the inner surface areas.This paper provides importance foundation of the prepared mesoporous glass by three stepsof melting, phase separation and dissolve.