Evaluation of Refractory Performance of Basic Castables Containing Magnesium-Aluminate Sol-Gel Coatings on Graphite

Effect of surface‐treated graphites on the properties of carbon‐containing monolithic refractory materials—A comprehensive comparison

“…These phases appeared during uncontrolled magnesia hydration after casting and aging which impaired the refractory after firing. The evolution of brucite phases in basic castable matrix has also been confirmed too in our previous publication . But the XRD pattern of C 1 + matrix (Figure B) shows hydrated cementitious phases for obvious reason along with hydrated alumina, corundum, graphite, spinel, and some feeble amount of unreacted cement fines.…”

“…The polymeric calal‐sol (CA′) had also been synthesized similarly by hybrid precursors, taking calcium nitrate and Al‐ sec ‐butoxide. A certain amount of supplied graphite was crucially mixed to the precursor sol and the detailed procedure for preparation of the coated graphite has been discussed in our previous studies . In brief, ultrasonication, aging, washing, drying, and calcination (600°C) had been sequentially performed to obtain the surface‐modified graphites.…”

“…Both spinel‐coated (code: G′C and SC) and calal‐coated (code: CA′‐C 1 and CA′‐C 2 ) graphites had been introduced separately in this work in place of respective uncoated graphites. The castable batch composition and fabrication of samples were the same as reported in our introductory work . Sodium hexa meta phosphate (0.05%) was added as a deflocculant of the castable batches.…”

“…The MgO‐based castable containing C 1 and CA′‐C 1 graphites were coded as m− and m+ samples; the high alumina‐based formulations with these two were named, respectively, as C 1 − and C 1 + samples. The apparent porosity (AP), bulk density (BD), and cold crushing strength (CCS) of all these castables at different temperatures were estimated according to our previous laboratory‐scale experiments reported before . These tests were similar to ASTM specifications (i.e., C 20‐00, C 133‐94, and C 133‐97), but performed with 25.4 mm 3 samples.…”

“…To cope up with these practical problems, the graphite surface has been modified by various methods such as solgel, pelletization, molten salt synthesis, etc. [4][5][6] The present author opted for cost-competent thin sol-gel coating on graphite [7][8][9][10][11][12][13][14][15][16][17][18][19] and obtained a threefold benefit from this novel material. Firstly, the hydrophilic nanostructured coating demanded much less water; secondly, the coating improved the service life of individual graphite flakes in the high temperature of the furnace.…”