Application of foaming agent–oxidizing agent couples to foamed-glass formation

We report on the use of foaming agent couples to foam cathode-ray-tube panel glass and uncover the influence of the carbon type, Mn_xO_y and furnace atmosphere on the foaming effect and physical properties of the foams. In oxidizing atmosphere, carbon burns out before the foaming starts and the best foaming effect is achieved with MnO₂. The samples are open porous and thermal conductivity is 47 mW m^–1 K^–1 at 161 kg m^–3. In oxygen-free atmosphere, oxidation of carbon is facilitated by Mn₃O₄ as an oxidizing agent. Activated carbon with a high reactivity leads to the formation of CO and open porosity. Thermal conductivity of the closed-porous sample with CO₂ in the pores, produced with carbon black and Mn₃O₄, reaches 50 mW m^–1 K^–1 at 204 kg m^–3 and exhibits the highest potential for improving the thermal insulation further by decreasing the density.