P. Souza Santos

Standard transition aluminas. Electron microscopy studies

The aim of this paper is to present the results of characterization of the particle shapes of six standard transition aluminas samples using transmission and scanning electron microscopies; selected area electron diffraction, in parallel with X-ray powder diffraction were used for confirmation of the different transition aluminas types. The transition aluminas - chi; kappa; gamma; theta; delta; and eta were supplied by ALCOA Central Laboratory. The chi-; kappa-;gamma- and delta-Al203 microcrystals are pseudomorphs from their respective precursors gibbsite and boehmite. However, theta-Al203 microcrystals are not pseudomorphs after the standard delta-Al203 sample. Also, eta-Al203 are not pseudomorphs after bayerite somatoids.

Aluminas by Thermal Activation of Fibrillar Pseudoboehmite Powders

The aluminum monohydroxide pseudoboehmite is a common precursor for catalysts and ad/absorbents. Fibrillar pseudoboehmite powders were synthesized by the same preparation method from aqueous sols but aged in different times: 24, 48 and 168 hours. The sol particles were from fibrillar pseudoboehmite; the average length of the microfibrils changed sample to sample, the sizes increasing with the thermal aging time. The sols were dried by different methods: at room temperatures, forming a solid membrane; spray dried; dried at 60°C and 110°C from a gel from the sol aged 168 hours; all were fired between 200°C and 1000°C in oxidative atmosphere to produce activated transition aluminas. The phases formed was identified by XRD. The aim of the present paper is to present data showing that method of drying the sol has an effect on the temperature of formation of alpha-alumina due to the anisodiametric shape of the pseudoboehmite crystals.

Study Aiming the Use of Powder Waste Reject from the Sanitary Ware Production in Mass for Red Ceramics

A procedure that comes being studied for the exploitation of powder waste rejected from the sanitary ware production is the incorporation in mass for red ceramics. Objective of this work is to present the results gotten in the incorporation of this rejects. The used clay was from ceramics industries of the Jundiai region, SP. Spherical bodies test samples had been conformed incorporating 1%, 5%, 10%, 20% and 30% of the powder waste in mass. These bodies had been evaluated on compression resistance after dried to 110°C and to color after burns to 950°C. The composition that presented better results had been conformed by extrusion in prismatic bodies test samples. Again, the dried to 110°C and burnt to 950°C bodies test samples had been evaluated on flexion resistance but to linear retraction too. It was measured the ceramic properties of the burnt bodies test samples. Results indicate that there is a great potential in the formula with 30% incorporation of powder waste in mass. Comparative assays were made being used a mixture without incorporation of the denominated white reject.

Complex Carbon-Mineral Sorbents from Common Clay

Carbon/mineral complexes are materials with surfaces covered partially or totally by carbon materials contains. They have high industrial potential uses as material adsorbents and ceramic filters. The objective of this work is to evaluate the corrosion strength in acid and alkaline solutions, and the adsorption capacity of methylene blue of some materials prepared in the LMPSol. The compositions were prepared with an industrial common clay named “taguá” and organic and inorganic additives from industrial residues up to 50%. The corrosion test was performed in water at 60°C and in aqueous solutions of HCl and NaOH at room temperature, with mass losses measured after 15 days. The samples were pressed manually and heated at different temperatures: 110°C, 350°C and 500°C. The performed tests were transverse flexural strength, porosity and water absorption.