Study on cobweb‐like carbon nanotubes/calcium aluminate cement and its effect on the properties of Al₂O₃–SiC–C castables

Abstract

Cobweb‐like carbon nanotubes/calcium aluminate cement (CNTs/CAC) were synthesized through catalytic sintering with citric acid, calcium carbonate, and alumina as raw materials and ferric chloride as catalyst precursor. The products were characterized by X‐ray diffractometry, scanning electron microscopy, Raman spectroscopy, and high‐resolution transmission electron microscopy. The in situ cobweb‐like carbon firmly bonded between calcium aluminate grains, which endows the better oxidation resistance and water dispersion of carbon. The research had also shown that the bamboo‐like multiwalled carbon nanotubes with high aspect ratio were formed in cement by catalysis, which were entangled and aggregated to form cobweb‐like carbon. CNTs/CAC was applied in the Al2O3–SiC–C castables as a binder. Compared with the castables with spherical asphalt and in situ high‐content carbon‐containing calcium aluminate cement (HCCAC) as carbon source, the oxidation resistance index ratio of the castables bonded with CNTs/CAC increased by 45% and 22%, and the residual strength ratio increased by 25% and 20%, respectively. The results indicated that the oxidation resistance and thermal shock of the Al2O3–SiC–C castables bonded with CNTs/CAC were significantly improved.

Enhanced performance of Al2O3–SiC–C castables via in-situ formation of multi-reinforced phases by introducing surface treated composite metal powders

“…Nevertheless,the high temperature oxidation of carbon (C) reduces the service life of ASC castables and limits their application [4][5][6]. As a result, to solve the issues, various methods and techniques have been developed, including changing the morphology of the introduced C such as graphitic carbon sphere [7],cobweblike carbon nanotubes [8] and modified coal tar pitch [9],adding antioxidants such as andalusite [10,11], Si2BC3N [12]and Al [13], and formation in-situ whiskers reinforcement [14][15][16].Among them, the most popular is adding metal and its alloy powders to ASC castables, which can not only improve its oxidation resistance, but also improve its toughness due to the reinforcing phases that were formed in-situ in ASC castables. For example, Sun et al [17] found that the addition of 4 wt.…”