Preparation of calcium aluminate cement by combustion synthesis and application for corundum‐based castables

Abstract

Calcium aluminate cement was prepared by combustion synthesis with CaO2, Al, and Al2O3 as raw materials. The effects of CaO/Al2O3 (C/A) molar ratios in raw materials on the phase compositions and morphologies of calcium aluminate were investigated in detail. It was found that when the C/A reduced from 1.1 to 0.74, the content of CaO·2Al2O3 (CA2) in products increased, whereas contents of CaO·Al2O3 (CA) and 12CaO·7Al2O3 (C12A7) decreased; when the C/A was 0.8, the phase composition of product (CS71) was equal to that of Secar71. Additionally, the crystallines of CA and CA2 in the product were reduced when the C/A molar ratio was decreased. And then, the bulk density, apparent porosity, permanent linear change, cold crushing strength (CCS), and cold modulus of rupture (CMOR) of the corundum‐based castables bonded with CS71, Secar7 were compared. The castables bonded with CS71 demonstrate obviously improved CCS, CMOR, and volume stability.

Characterization and separation resistance of an in-situ 2D nanocarbon/calcium aluminate composite synthesized via a combustion method

“…As raw materials, calcium peroxide powder (CaO 2 , particle size <25 µm), calcium carbonate powder (CaCO 3 , particle size <25 µm), aluminum powder (Al, particle size 2~3 µm) and alumina powder (Al 2 O 3 , particle size <74 µm) of analytical purity were purchased from Sinopharm Chemical Reagent (Shanghai) Co. Ltd. A previous study reported that the phase compositions of the combusted product were equal to those of commercial Secar71 when the molar ratio of CaO/Al 2 O 3 (C/A) in the ratio of raw materials CaO 2 , Al and Al 2 O 3 was 0.8 [30]. Therefore, aiming at the combustion synthesis of in-situ nanocarbon/aluminate composites with similar phase compositions to commercial Secar71, the C/A molar ratio was fixed at 0.8 in the present study, and CaCO 3 was used as a carbon and calcium source to partially replace CaO 2 .…”

“…In contrast to the CVD process, which consumes flammable and explosive gases directly, CO 2 gas that originates from the decomposition of carbonate during the process of combustion synthesis acts as a carbon source for the formation of in-situ nanocarbons. The combustion method has been applied to the synthesis of aluminate cement [26][27][28][29][30][31] and nanocarbon materials [32,33]. Therefore, the synthesis of in-situ nanocarbon/aluminate composites via the combustion method is feasible.…”