Papers by Keyword: Solidification Kinetics

Abstract: Geopolymers are formed from silica and alumina oxides mixed with alkali hydroxide or alkali silicate. This paper presents the findings on the study of the solidification of fly ash geopolymer through setting time by varying alkaline activators, their concentrations and geopolymer curing temperature. This work focuses on the transformation of geopolymer from liquid paste to solid through Avrami’s Kinetic Theory. From the experimental results, alkaline activation with sodium silicate produced shortest time for geopolymer solidification as compared to KOH and NaOH. The increase in concentrations of alkaline solution and curing temperatures were found to reduce setting time for geopolymer’s solidification. From Avrami theory perspective, the growth forms of geopolymer in the geopolymerization process exhibit two and three dimensional structure with the presence of secondary nucleation.

Abstract: The effect of the latent heat related to the rate of the solidification kinetics during solidification was investigated by using the heat transfer simulation. The latent heat was generated proportional to the amount of the fraction of transformed solid phase and directly affected the temperature compensation during solidification. The importance of the solidification kinetics was discussed by comparing cooling curves calculated using different solidification kinetics with experimentally measured cooling curve of A356 alloy.

Abstract: Both thermal analysis (TA) and differential thermal analysis (DTA) have been used since long to evaluate latent heat release and solid fraction evolution during solidification of metallic alloys. TA makes use of cooling curves recorded under "natural" cooling while DTA consists in recording the temperature difference between the sample temperature and an inert reference during a controlled cooling, i.e. at imposed constant cooling rate. In both cases, the solid fraction evolution is deduced from a calculation of the latent heat release as estimated by means of a heat transfer model. This paper provides a comparison of such evaluations performed on one Al-Si alloy.