Peter Ay

Stabilization of Aqueous Silicon Nitride Suspension with Dolapix A88

The dispersing phenomenon of silicon nitride suspension has been investigated systematically by measuring surface charge density, sediment volume, and turbidity of the suspension. Dolapix A88 has been used as dispersant to improve the stability of the suspension, and assessed through measurement of the specific surface charge of the Si3N4 system. The isoelectric point (IEP) of Si3N4 powder has been found to be at pHiep=6.91, and there was no shift in IEP due to the presence of dispersant, indicating that the interaction between the powder and the dispersant Dolapix A88 is purely physisorbing in nature. Good agreement has been observed among dispersion characteristics, surface charge, and streaming potential inflection. The article also describes the selection and optimization of the dispersant in controlling the stability of an aqueous suspension of Si3N4. It can be concluded from this investigation that the PCD technique for measurement of specific surface charge can be conveniently used for the assessment of dispersibility of ceramic suspensions in dilute as well as in concentrated suspensions.

Evaluation of Dispersant Efficiency for Aqueous Alumina Slurries by Concurrent Techniques

This article reports on results from a comparative study assessing a suitable method for dispersant efficiency evaluation in the case of water‐based suspensions of ultrafine alumina stabilized by a commonly used dispersant, Dolapix CE64. The following measurements were evaluated: zeta potential, specific surface charge, sedimentation behavior, and capillary suction time. The suitability of each of the tested techniques is discussed. A good agreement between the zeta potential and the specific surface charge as a way to determine the optimal dose of dispersant is documented.

Comparative Analysis of Brazilian Residual Biomass for Pellet Production

Brazil is an important producer and the largest exporter of sugar, ethanol, coffee, orange juice, and tobacco. The countrys availability of land, water and labour has allowed for increased production and exports. Continuing the trade expansion and diversification of markets and products remain at the core of Brazil’s agricultural growth strategy (Valdez et al. 2006). The increase in crops generates a biomass residue surplus. It is known that approximately 30% of the sugar cane production is bagasse (Rosillo-Calle et al. 2007) and 22% of rice is constituted of husks (Eriksson and Prior 1990). This residual biomass can be transformed into a valuable fuel, becoming an important local energy source. There are several conversion technologies for biomass, based on the type, available residues and the market demand. Pressing of residues increases storage and transport efficiency. Pellets, briquettes, or any other pressed form can be used as a fuel. Recent research shows different combustion technologies for biomass: gasification, pyrolysis and combined heat and power (Rosillo-Calle et al. 2007).