Study On Foaming Agents And Additives Of Borosilicate Foam Glass

In this study, Borosilicate foam glasses were prepared by sintering powder. The effects of foaming agents and additives on borosilicate foam glasses have been investigated.By changing the types and content of foaming agents, the pore structure and the crystallization of the samples were inspected. The thermal expansion coefficient, acid corrosion resistance, bulk density and water absorption property of the samples were tested. The results showed that: to the borosilicate foam glass containing 78wt % silica with C as a foaming agent and Sb2O3 as a supplying oxygen agent, when added 0.9wt% C and 8.1wt% Sb₂O₃, the sample has the largest number of porosity, uniform size and distribution, mostly circular pores and closed pores. This sample is characterized by low bulk density of 0.5g/cm3, low water absorption of 0.4%. The average thermal expansion coefficient of the sample is 9.22×10-6/℃. Acidproof experiment was done by immersing samples in 0.1mol/L H2SO4. The quality of the samples first increased and then remained unchanged, showing a better acid corrosion resistance. With C and CaCO3 as foaming agents, pore structure of the samples changed little with the content of foaming agents. The samples possess many circular and closed pores, but lower porosity and thicker pore wall. The average thermal expansion coefficient of this kind of foam glasses is 8.79×10-6/℃, bulk density is 0.8g/cm3, and water absorption is 0.5%. Moreover, the samples showed a good acid corrosion resistance.The relative content of boric acid to sodium carbonate and potassium carbonate has been adjusted. The effects of the ratioФ= (M₂O-Al₂O₃) /B₂O₃ (M = Na, K) on the structure and properties of borosilicate glass bubble have been researched. The results showed that: with this ratio changed, the pore structure of borosilicate foam glasses changed largely. WhenФ=1, the best structure appeared with uniform and circular pores distributing throughout the sample, very thin pore wall and almost no open pores. WhenФis near 1, the pore structure is not very different from that ofФ=1, only with a small number of connecting holes. WhenФis largely deviated from 1, pore structure of the samples becomes disorganized and with open pores controlling. This borosilicate foam glasses withФ=1 has the smallest thermal expansion coefficient of 2.69×10-6/℃, its bulk density is 0.3g/cm3, and water absorption is 0.01%. What is more, they showed the best acid corrosion resistance: when immersed in the acid, without any changes in their quality. The NMR results show that: [SiO4], [AlO4] and [BO4] formed a compact network, which improved the structure and property of the borosilicate foam glass.This study also attempted to use TiO2 and ZnO as additives to prepare borosilicate foam glasses. The results were as follows: with 8wt% TiO2 added, the pore structure of the samples was better and their crystallization increased. With ZnO added, the pore structure of the samples became disordered with many big connecting holes.