Effect of Carbon as Foaming Agent on Pore Structure of Foam Glass

Abstract

Insulation effect and mechanical performance of foam glass depend, to a large extent, on foam structure. Hence understanding foam formation is not only a problem of significant fundamental interest but also of tremendous practical impact. In this paper, foam growth was modeled comparing to grain growth theory in sintering. TG-DTG analysis of carbon black indicated that pre-oxidation took place prior to foaming temperature. Furthermore effects of heating rate and particle size of carbon black on foam structure have been taken into account. Several borosilicate foam glasses were fabricated by powder sintering process at different heating rates using carbon black of different particle sizes as foaming agent, respectively. It was found that increasing the heating rate tended to decrease the pre-oxidation of carbon black resulting in inhomogeneous foam distribution. Foam structure of sample heated at a rate of 8°C/min using carbon black with particle size of 0.15mm was optimal.

Fabrication of highly insulating foam glass made from CRT panel glass

“…All the foams prepared with carbon had a homogeneous pore structure, in accordance with the results reported in [6,17,19]. The appearance of a representative foam sample prepared with carbon is shown in the inset of Fig.…”

“…Carbon black and glycerol are known for their use in the production of foam-glass boards [14,15], while SiC is used in the production of foam-glass aggregate [16]. The foaming process using SiC has been frequently reported, while foaming with pure carbon compounds (e.g., charcoal, graphite, and soot) or carbohydrates has been relatively less well investigated [13,[17][18][19]. The reaction of SiC with a glass matrix has been shown to be very complex, leading to the release of CO as well as H 2 , if water is present, and to the formation of SiO 2 , which acts as a nucleation and crystallization agent [7,8].…”

“…However, foaming with calcium carbonate proved to be extremely sensitive to the preparation conditions for the mixture of glass powder and foaming agent, and it was difficult to obtain a foam product with a homogeneous porosity. On the other hand, the foam products obtained from the oxidation of carbon compounds are usually fine-pored and homogeneous [6,17,19]. Because of the advantages of pure carbon compounds, charcoal was chosen as the source of carbon in this study.…”

Effects of graphite additive on dielectric properties and microwave absorption properties of zinc-containing foam glass

“…2-12.4 GHz and additional zinc filler could adjust porous structure of foam glass and zinc content of glass matrix, which was the main mechanism of microwave absorption [4]. Foaming agent, like graphite, carbon black, sulfate, organic compounds and carbonates, had important effects on creating pore and controlling the pore structure of foam glass [5][6][7]. Therefore, for the purpose of designing foam glass-matrix composites as low cost microwave absorbing materials, it is interesting to explore effects of foaming agent additives on microwave absorption properties of foam glass.…”

Closed porosity ceramics and glasses

“…The wet‐mixed mixtures of SiO 2 , Al 2 O 3 , B 2 O 3 , Sb 2 O 3 , other oxides and carbon black were heat‐treated at 1400ºC/30 min. As known carbon black has oxidation temperature below 900ºC meaning that pre‐oxidized carbon black was not the only pore former but probably also other high‐temperature oxygen releasing additives such as Sb 2 O 3 , MnO 2 , etc Sodium silicate can also be used as a blowing agent. Na 2 O·2.3SiO 2 , Na 2 HPO 4 (stabilizer), Na 2 B 4 O 7 (flux), and fly ash were mixed, pressed into disk‐shaped tablets, followed by sintering at 800°C/1h/air.…”