Effect of CaF 2 addition on the densification and the foaming of - PowerPoint PPT Presentation

6th International Conference on Sustainable Solid Waste Management Naxos Island, Greece, 13–16 June 2018 Effect of CaF 2 addition on the densification and the foaming of sintered glass ‐ ceramics by metallurgical slag 1 Esmat M. A. Hamzawy, 2 Alexander Karamanov, 1 Hussein Darwish, 2 Emilia Karamanova 1 Glass Research Department, National Research Centre, Cairo, Egypt 2 Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria https://lab.akaramanov.com

Aims of the work glass melting 1 h at 1350 ‐ 1400 o C 70 wt % metallurgical slag water quenching 30 wt % industrial sand + addition of CaF 2 sintering foaming

chemical compositions of used raw materials and resulting glasses (wt %) Samples SiO Al O Fe O CaO MgO MnO BaO TiO2 Cr O K O Na O SO P O CaF 2 2 3 2 3 2 2 2 3 2 5 2 HHS 28.7 7.0 7.6 25.9 1.5 8.1 15.2 1.0 0.06 0.9 0.5 2.7 0.07 S 99.4 0.3 0.1 H ‐ 0 49.2 5.1 5.5 18.6 1.1 5.8 10.9 0.7 0.04 0.7 0.4 1.9 0.05 ‐‐ H ‐ 2.5 46.7 4.9 5.2 17.7 1.1 5.5 10.3 0.7 0.04 0.6 0.4 1.8 0.05 1.7 H ‐ 5.0 45.9 4.8 5.1 17.4 1.0 5.4 10.2 0.7 0.04 0.6 0.4 1.8 0.05 3.4 H ‐ 7.5 45.7 4.7 5.0 17.3 1.0 5.3 10.1 0.0 0.04 0.6 0.4 1.8 0.05 7.0

heating microscope tests example with H ‐ 5

sintering non ‐ isothermal curves fractions < 125 μ m at 20 o C/min high magnification low magnification

sintering non ‐ isothermal curves fractions < 53 μ m at 5 and 30 o C/min compositions H ‐ 0 and H ‐ 7.5 sintered glass ‐ ceramics foams self ‐ glazed glass ‐ ceramics

self ‐ glazed glass ‐ ceramics Density Porosity Hardness fractions < 38 μ m, 10 o C/min, 3 min at 1000 o C g/cm 3 kg/mm 2 vol % H ‐ 0 ‐ SEM of fracture H ‐ 0 2.22 15 490 H ‐ 2.5 2.47 8 503 H ‐ 5.0 2.54 6 510 H ‐ 7.5 2.57 5 521

isothermal heat ‐ treatment of H ‐ 5 at 1120 o C

glass ‐ ceramic foams fractions < 38 μ m, 20 o C/min, 10 min at 1110 o C Sample Density Porosity 3 (g/cm ) (vol. %) H ‐ 0 1.29 52.2 H ‐ 2.5 0.89 64.3 H ‐ 5.0 0.54 82.0

SEM fracture H ‐ 0 H ‐ 5

1000 o C XRD results 1110 o C

Conclusions • The possibilities to obtain low cost self ‐ glazed sintered glass ‐ ceramics and/or glass ‐ ceramic foams by metallurgical slag and industrial sand is highlighted. • The effect of 2.5, 5 and 7.5 wt % CaF 2 addition on glass melting, densification, crystallization and bloating is established. • The increase of CaF2 amount leads to a notable decrease of melting and sintering temperatures. • Glass ‐ ceramic foams with huge porosity of about 80 vol % and improved crystallinity can be synthesized by using compositions with modest CaF 2 addition (5 %) using higher heating rates and holding temperatures of 1100 ‐ 1130 o C. • When finer glass powder and moderate heating rates are used self ‐ glazed sintered glass ‐ ceramic with improved micro ‐ hardness and crystallinity can be obtained at higher percentage of CaF 2 and holding temperatures of 950 ‐ 1000 o C.