Corrosion durabilty of CaO-Al2O3-SiO2 (CAS) based glass-ceramics produced from natural and waste raw materials

The aim of this study is to produce CAS based glass ceramic as using the natural raw and waste materials and investigate the corrosion behavior of manufactured CAS based glass-ceramics. In accordance with this purpose, powder of pumice that obtain from Nevşehir state, the waste of marble powder consist of marble machining process and pure alumina was used as starting materials. The CAS composition is prepared according to the stoichiometric anorthite composition region (57.5 wt. % SiO2, 27.5 wt. % CaO, 15 wt. % Al2O3). Furthermore, CAS-F composition was prepared as addition 99% purity CaF2 nucleation agent powder as 9 g to CAS composition due to promote crystallization of CAS based glass. Homogenization process applied at 1 hour as dry milled with 250 rpm. Subsequently, the CAS and CAS-F composition powder was melted at 1450 oC for 3 hours and following melting process glass was formed as pouring into graphite mold. Afterwards, in order to crystallization glass materials, heat treatment was applied at the temperature range between 1100–1200 oC and 1 hour up to 5 hours as a single state heat treatment method for each sample in an electric furnace. Thermal properties was determined with DTA methods. The crystallization and viscous flow activation energies of CAS glasses was calculated as 389.12 kJ.mol-1 and 429.80 kJ.mol-1 respectively. As for CAS-F glasses was determined 318.74 kJ.mol-1 and 330.37 kJ.mol-1.XRD result showed that CAS and CAS-F glass ceramics occur anorthite, wollastonite and gehlenite. The microstructure was displayed with aid of SEM as a conclusion laminal and needle-like shape was detected. Chemical durability of CAS and CAS-F glass-ceramic specimens was analyzed as measuring weight loss after chemical attacked at 2h later in 10 vol.% HNO3 and 10 vol. %10 NaOH solution at 100 oC. Corrosion test in HNO3 results showed that weight loss changed between 0.01- 8.62 wt.% for CAS, 0.11-12.82 wt. % for CAS-F glass ceramics. Both of glass-ceramics weight loss after chemical durability test in NaOH solution anchored that smaller than 0.1 wt.%. Later corrosion test in HNO3 solution silica was verified by XRD analysis for glass-ceramics. Microhardness and density of glass-ceramics was increased with CaF2 additive.