Topic
Calcium aluminates
About: Calcium aluminates is a research topic. Over the lifetime, 490 publications have been published within this topic receiving 9200 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, a thermodynamic model has been calculated using Factsage to predict the type of calcium aluminates and sulfides present in the steel, and the results showed that alumina generated from deoxidation had transformed to MgOAl2O3 spinel with a small amount of CaO by using high basicity and high Al 2O3 slag during ladle furnace (LF) refining.
Abstract: The objective of this study was to investigate the evolution of inclusions during secondary refining in aluminum killed steels. As calcium treatment is also used to modify solid alumina inclusions to liquid or partially liquid calcium aluminates for keeping free from nozzle clogging, a thermodynamic model has been calculated using Factsage to predict the type of calcium aluminates and sulfides present in the steel. The results showed that alumina generated from deoxidation had transformed to MgOAl2O3 spinel with a small amount of CaO by using high basicity and high Al2O3 slag during ladle furnace (LF) refining. Though soft blowing after LF refining is benefit for the removal of inclusions by floatation, vigorous stirring which may make slag layer exposing an “eye” to air reoxidation should be avoided. After calcium treatment, the inclusions were restricted mainly to globular calcium aluminates and the sulfur in the steel was associated with these inclusions as calcium sulfide. The ND (number density) of inclusions seems to appear a similar tendency to the size distribution of smaller inclusions, and the similar change between the AF (area fraction) of inclusions and the total oxygen content of the steel can be also found by careful comparison. Predicted inclusion type in the steel were validated with measurement based on samples collected from industrial heats and a reasonable range of Ca content was also given for the experimental steel.
16 citations
TL;DR: In this paper, dilatometric studies performed on compacts made of the as-prepared powder, just after pre-heating at 450°C, has shown a superposition between sintering shrinkage and expansion related to CA2 formation, an intermediate phase formed during calcination and phase evolution to CA6.
Abstract: By using a wet chemical route, pure calcium hexaluminate (CA6) was yielded, significantly lowering the reaction temperature and shortening the synthesis time if compared to usual industrial procedures. owever, dilatometric studies performed on compacts made of the as-prepared powder, just after pre-heating at 450°C, has shown a superposition between sintering shrinkage and expansion related to CA2 formation, an intermediate phase formed during calcination and phase evolution to CA6. oupling of such opposite phenomena led to microcracking of the material, mainly if the heating rates (10°C min-1) were high. However, lower heating rates (1-5°C min-1) could quite avoid microcracking but also limit densification.
16 citations
TL;DR: The preferential uptake of aluminium ions by lactone and carboxylic acid groups in glucuronic-6,3-lactone and gluconic acid suggested that these organic admixtures have a high potential as set-retarding admixtures of high-temperature calcium aluminate cement slurry as discussed by the authors.
Abstract: The preferential uptake of aluminium ions by lactone and carboxylic acid groups in glucuronic-6,3-lactone and gluconic acid suggested that these organic admixtures have a high potential as set-retarding admixtures of high-temperature calcium aluminate cement slurry. However, the liberation of abundant free calcium ions caused by the adsorption of aluminium ions by the admixtures, increased the carbonation rate of hydrated cement pastes after exposure to Na2CO3-laden water at 300 ‡C. Using inorganic acid admixtures, such as boric acid and sodium tetraborate decahydrate, the retarding ability of colloidal Ca(BO2)2 ·nH2O and aluminium hydroxide yielded by the reaction between admixture and cement was less than that of the reaction products derived from organic acid admixtures. Although Ca(BO2)2 ·nH2O in hot Na2CO3 solution was converted into CaCO3, the rate of alkali carbonation was almost the same as that of admixture-free calcium aluminate cement pastes.
16 citations
Patent•
27 Sep 2012
TL;DR: In this paper, systems, methods, and compositions related to mixtures of calcium aluminate cements with compositions comprising carbonate are described, where carbonates may be formed by sequestering carbon dioxide.
Abstract: Provided herein are systems, methods, and compositions related to mixtures of calcium aluminate cements with compositions comprising carbonate. The compositions comprising carbonates may be formed by sequestering carbon dioxide.
16 citations
TL;DR: In this article, the enthalpy and entropy values for solid calcium aluminates have been compared with activity measurements and the known phase diagram to obtain improved revised values and an accurate calculated phase diagram for this binary system.
Abstract: Enthalpy and entropy values for solid calcium aluminates have been compared with activity measurements and the known phase diagram to obtain improved revised values and an accurate calculated phase diagram for this binary system. The revised entropies (J mol/sup -1/ K/sup -1/) at 298/sup 0/K are 205.05 +- 0.8 for Ca/sub 3/Al/sub 2/O/sub 6/, 114.22 +- 0.8 for CaAl/sub 2/O/sub 4/, and 188.73 +- 0.8 for CaAl/sub 4/O/sub 7/. The excess enthalpy of mixing of CaO and AlO/sub 1/ /sub 5/ liquids has been calculated and plotted. Heats of fusion can be calculated from these values, but all the pure calcium aluminates melt incongruently.
16 citations