Humic acid was extracted and employed as a dispersant in an alumina suspension. The higher zeta potential for HA (-42 mV) was measured at pH 11 showing that an electrostatic repulsion might occur in the alumina/HA suspension. As a consequence of the long chain molecules of HA it was also expected a steric effect on deflocculation. The best dispersion conditions for the alumina suspension (28 vol%) were found with 0.016 wt% HA, close to the viscosity achieved with a commercial sodium polyacrylate. The rheological characterisation showed results beneficial for the slip casting process, such as slightly thixotropy and pseudoplastic behaviour. The excellent colloidal stability at pH 11 as evidenced through rheological and sedimentation tests was attributed to the polyelectrolyte nature of the HA. From deflocculated suspensions it was possible to obtain high density pieces by slip casting method.

The secondary steel refining process uses filler sand as a thermal insulating barrier that separates the liquid metal from direct contact with slide-gate system of the steel ladle. The effective use of this practice must provide a high free opening rate, impacting on increased productivity and quality of steel, reducing the number of stops, thermal loss and even the steel re-oxidation. Both operational parameters and material properties have influence on the free opening rate. In the present work, two chromite-silica sands were analyzed, and some composition changes were proposed. The properties of these materials and the relevant process parameters were evaluated according to the free opening rate under normal operational conditions. The increases in carbon content and in particle size were considered the main factors relating to the filler sand. The percentage of free opening is also strongly influenced by time and temperature of the steel contact.

In this work, the feldspar used as a flux in typical porcelain was replaced by waste glass, and the resulting batch composition contained 50% kaolin, 25% quartz and 25% waste glass. The properties of this porcelain with glass powder (GP) were compared to traditional porcelain (TP), which utilizes feldspar. The samples were fired at different temperatures, ranging from 1200 °C to 1400 °C. Technical parameters, such as water absorption, modulus of rupture and K IC, phase analysis by XRD, and microstructure by SEM were analysed. The results indicated that the lower fracture toughness and MOR of GP is a consequence of the peculiar microstructure of this porcelain. The reduction in firing temperature and the use of a cheaper substitute for feldspar makes GP also an attractive economical alternative.