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• Foaming couples for foaming CRT panel glass in air and argon atmosphere. • Best foaming effect in air achieved with MnO 2 , open-porous foam. • Beneficiary role of oxidizing agent on foaming in oxygen-free atmosphere revealed. • Best foaming effect in argon with carbon black and Mn 3 O 4 , closed-porous foam. • Pore-gas analyzed as in major part CO 2. 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 x O 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 MnO 2. 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 Mn 3 O 4 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 CO 2 in the pores, produced with carbon black and Mn 3 O 4 , 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. [ABSTRACT FROM AUTHOR]

• Development of low-density open- and closed-porous foamed glasses. • Homogeneous pore structure with >90% of open or closed pores. • Open porosity achieved by partial crystallization of the glass. • Low thermal conductivity (37.5–65.6 mW m−1 K−1) measured using heat-flow meter. • Analysis of the difference in the thermal conductivity. Future developments in foamed glass should focus on improving the thermal insulation properties, controlling the foamed structure and the type of porosity. In this study, we report on the synthesis and properties of foamed glasses with open-porous and closed-porous structures prepared from waste cathode-ray-tube (CRT) panel and soda-lime-silica glasses with the addition of carbon black, and manganese or iron oxides. The samples exhibit a homogeneous structure with an average pore size in the range 0.5–1.35 mm and open porosity above 91% or closed porosity above 92%. The open porosity was obtained by partial crystallization of the glass during the foaming process. The thermal conductivity, measured using a heat flow meter at 10 °C, is 57.2–65.6 mW m−1 K−1 at 116–143 kg m−3 for the open-porous samples and 37.5–56.2 mW m−1 K−1 at 107–245 kg m−3 for the closed-porous samples. The conduction in the solid phase contributes the major part to the effective thermal conductivity (52–72%). The conduction in the gaseous and solid phases, respectively, is higher in the open-porous foamed glass due to the different gas composition (air) and the different solid composition (glass composition and crystalline content). The developed foamed glasses also have high mechanical strength, making them suitable for load-bearing applications. [ABSTRACT FROM AUTHOR]