Reuse of sugarcane bagasse ash (SCBA) to produce ceramic materials.

A low cost macroporous support for ceramic membranes was prepared by in situ reaction sintering from local natural mineral kaolin with dolomite as sintering inhibitor. The characterization focused on the phase evolution, microstructure, pore structure, mechanical strength and water permeability at various compositions and sintering temperatures. The sintering of kaolin was improved with 5 wt% dolomite, but clearly inhibited with ≥10 wt% dolomite. For the 20 wt% dolomite samples, the crystalline phases were mainly composed of mullite, cordierite and anorthite after sintering between 1,150 and 1,300 °C. Moreover, both mean pore size and mechanical strength increased with increasing sintering temperature from 1,100 to 1,300 °C, but the water permeability and porosity decreased. The 1,250 °C sintered macroporous support with 20 wt% dolomite exhibited good performances such as porosity 44.6%, mean pore size 4.7 μm, bending strength 47.6 MPa, water permeability 10.76 m3 m−2 h−1 bar−1, as well as good chemical resistance. This work provides opportunities to develop cost-effective ceramic supports with controllable pore size, porosity, and high strength for high performance membranes.

Elaboration and characterization of tubular macroporous ceramic support for membranes from kaolin and dolomite

A new processing route for manufacturing partially interconnected open-cell, microcellular mullite ceramics has been developed. The strategy adopted for making microcellular mullite ceramics entailed the following steps: (i) fabricating a formed body from combining polysiloxane, Al 2 O 3 (a reactive filler), polymer microbeads (used as sacrificial templates), and Y 2 O 3 (a sintering additive); (ii) cross-linking the polysiloxane in the formed body; (iii) transforming the polysiloxane by pyrolysis into SiO 2 ; and (iv) synthesizing mullite by reacting SiO 2 and Al 2 O 3 . By controlling the sintering temperature and the micro-bead and additive contents, it was possible to adjust the porosity so that it ranged from 38% to 85%. The compressive strengths of the microcellular ceramics with ∼40% and ∼70% porosities were ∼90 and ∼10 MPa, respectively. The superior compressive strengths were attributed to the homogeneous distribution of small (≤ 20 μm), spherical cells with dense struts in the microcellular ceramics.

Processing of Microcellular Mullite

Diopside–albite glass–ceramics were fabricated by sintering the powder mixtures of crystallization promoters and waste glass. Two kinds of promoters were synthesized using kaolin clay, talc and chemical reagents. The crystalline phases were formed by a reactive crystallization between promoters and glass during sintering. The effect of promoter components, additions and sintering temperatures on the crystallizing and densifying behavior, microstructures and mechanical properties of glass–ceramics was investigated. The results showed that the higher densities and better mechanical properties were obtained for the glass–ceramics with 12–15% crystallization promoters sintered at 950 °C for 2 h.

Sintering and reactive crystal growth of diopside–albite glass–ceramics from waste glass

https://repositorio.ufrn.br/bitstream/123456789/30484/1/PreparationOfMulliteBasedCeramics_Silva_2016.pdf

Preparation of mullite based ceramics from clay–kaolin waste mixtures

Sintering of kaolinite in the presence of certain carbonate mineralizers, viz., CaCO 3 , Na 2 CO 3 , and K 2 CO 3 , has been conducted at 950°-1350°C. The influence of these mineralizers at the above temperatures is evaluated using XRD and SEM techniques. A comparative study of phase formation of the above compositions shows that the sodium- and calcium-fluxed samples give rise to multiphase systems, while K 2 CO 3 -incorporated samples give phase-pure mullite. The observation that kaolinite in the presence of K 2 CO 3 can act as a precursor material for phase-pure mullite is of great industrial significance.

Sankaranarayana Devanarayanan

Papers

Phase‐Pure Mullite from Kaolinite