Preparation And Research On Decorative Glass-ceramics Of Red Mud

Decorative glass-ceramics with high-performance, low-cost and high value-added were made from a kind of solid waste red mud in this paper. The research not only has environmental, ecological effects, important economic and social significance, but also in line with the strategic objective of sustainable development of our country.The composition of sintered red mud from Shandong Aluminium Industry Co.Ltd were analyzed at first.The main chemical compostion of red mud were CaO, SiO₂,Fe₂O₃,Al₂O₃ and TiO₂, the rest parts were R2O. Based of theory using red mud in CaO(MgO)-Al₂O₃-SiO₂ glass-ceramics system meets the composition requirement. Preliminary studies indicated that the addition of red mud was limited. The optimum addition of red mud was discussed when designing batch compostions of red mud glass-ceramics. A series of research showed that sintered method and melting process were suitable to red mud glass-ceramics, the appropriate melting temperature for the first method was 1400℃, 2h;while 1350-1360℃,2h, for the other. The properties indicated that the sintered and melting samples had good performance with higher bulk density, microhardness, bending strength and outstanding alkali-resistant.A lot of experiments showed that decorative glass-ceramics with smooth surface, beautiful crystalline pattern, dense structure and low-porosity could be prepared by sintered method when adding 30-42.5wt% red mud. The results proved that sample S-1 was better than the others, and its optimal heating treatment was nucleation at 860℃ for lh;crystallization at 1065℃ for 2h, while by melting method, the glass-ceramics with high-performance could be prepared when adding about 60wt% red mud, and its optimal heating treatment was nucleation at 720℃ for lh;crystallization at 920℃ for 2h.XRD and EPMA showed that β-wollastonite (β-CaSiO₃), hardystonite (Ca₂ZnSi₂O₇), akermanite (Ca₂MgSi₂O₇), ferrogehlenite (Ca₂FeSi₂O₇), hyalophane [(K,Ba)(Si,Al)₄O₈] were found in sintered glass-ceramics of red mud. In the same time, akermanite , kalsilite(KAlSiO₄) , ferrogehlenite and p-wollastonite were found in melting glass-ceramics of red mud. SEM results showed that crystalline grains of the two kinds of glass-ceramics were very small between 0.1-0.5μm;and they mostlylooked like rice grains that were piled up, distributed uniformly, some were accompanied by some flake grains.IR and EPMA indicated that the sintered sample mostly had structural units of [SiO4 ], [BO4 ], [AIO4 ] and [Fe3+ O4 ] tetrahedron in silicate net, Na\ K\ Ca2\ Fe2+ and some Fe3+ were in the places of maintaining charges balance;in the same time, [SiO^ [AIO4] and [Fe3+O4] tetrahedron units existed in the melting sample and Na+> K\ Ca2+, Mg2\ Fe2+and some Fe3+existed in the positons of maintaining charges balance. The heating treatment processing, the effects on crystallization and structure of samples with different kinds of fluoride and different content of fluorite were studied using XRD, SEM and other testing means.A deep discussion on colours of glass-ceramics of red mud was presented in this paper, it can be concluded that Fe2C>3 and TiC>2 in red mud were the main factors, especially Fe2O3. The phenomenon of pores in the simples were analyzed in detail, it showed that the generation of pores be related with not only the recipe, the melting system, but also the heating treatment. The nucleation and crystallization mechanism with Fe2C^ T1O2 and fluorite as nucleation agent were also discussed.The crystallization kinetics of both sintered and melting basic glass of red mud were respectively studied by DTA, crystallization activiation (E)n frequency factor (A)% reaction rate parameter (k) and crystal growth index (n) were calculated, and also analyzed and discussed in this paper.It was proved that getting rid of iron from red mud by regular physical and chemical methods was ineffective, and needs more further research.