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

Effect of CaF2 addition on the densification and the foaming

• f sintered glass‐ceramics by metallurgical slag

1Esmat M. A. Hamzawy, 2Alexander Karamanov, 1Hussein Darwish, 2Emilia

Karamanova

1Glass Research Department, National Research Centre, Cairo, Egypt 2Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria

https://lab.akaramanov.com 6th International Conference on Sustainable Solid Waste Management Naxos Island, Greece, 13–16 June 2018

Aims of the work

70 wt % metallurgical slag 30 wt % industrial sand + addition of CaF2 glass melting 1 h at 1350‐1400 oC water quenching sintering foaming

Samples

2

SiO

3

O

2

Al

3

O

2

Fe CaO MgO MnO BaO TiO2 O

2

Cr O

2

K O

2

Na

3

SO

5

O

2

P

2

CaF 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

chemical compositions of used raw materials and resulting glasses (wt %)

heating microscope tests example with H‐5

sintering non‐isothermal curves fractions < 125 μm at 20oC/min

high magnification low magnification

sintered glass‐ ceramics foams self‐glazed glass‐ ceramics

sintering non‐isothermal curves fractions < 53 μm at 5 and 30 oC/min compositions H‐0 and H‐7.5

Density Porosity Hardness g/cm3 vol % kg/mm2 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

self‐glazed glass‐ceramics fractions < 38 μm, 10oC/min, 3 min at 1000 oC H‐0 ‐ SEM of fracture

isothermal heat‐treatment of H‐5 at 1120 oC

Sample Density )

3

(g/cm Porosity (vol. %) H‐0 1.29 52.2 H‐2.5 0.89 64.3 H‐5.0 0.54 82.0

glass‐ceramic foams fractions < 38 μm, 20oC/min, 10 min at 1110 oC

SEM fracture H‐0 H‐5

1000 oC

XRD results

1110 oC

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 % CaF2 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 CaF2 addition (5 %) using higher heating rates and holding temperatures of 1100‐1130 oC.

• 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 CaF2 and holding temperatures of 950‐1000 oC.