2007, Vol.8, No.2

Carbon Letters 2023 KCI Impact Factor : 1.35 KCI-WoS Impact Factor : 6.04

pISSN : 1976-4251 / eISSN : 2233-4998
https://journal.kci.go.kr/carbon

The application of Carbon and graphite based materials in unprotected environment is limited to a temperature of 450oC orso because of their susceptibility to oxidation at this temperature and higher. To over come these obstacles a low cost chemicalvapour reaction process (CVR) was developed to give crystalline and high purity SiC coating on graphite and isotropic C/Ccomposite. CVR is most effective carboththe CVR method, a sic conversation layer is formed by reaction between carbon and gaseous reagent silicon monoxide at hightemperature. Characterization of SiC coating was carried out using SEM. The other properties studied were hardness densityand conversion efficiency.

A series of activated carbons (ACs) were derived from sugarcane bagasse under two activation schemes: steam-pyrolysis at600-800C and chemical activation with H3PO4 at 500C. Some carbons were treated at 400, 60C, or for 1-3 h, and/or inflowing air during pyrolysis of acid-impregnated mass. XRD profiles displayed two broad difuse bands centered around2θ= 23 and 43, currently associated with diffraction from the 002 and 100/101 set of planes in graphite, respectively. Thesed microcrystallite lateral dimensions, La, of the turbostratic (fully disordered)graphene layers. Steam pyrolysis-activated carbons exhibit only the two mentioned broad bands with enhancement in numberof layers, with temperature, and small decrease in microcrystallite diameter, La. XRD patterns of H3PO4-ACs display moredeveloped and separated peaks in the early region with maxima at 2θ= 23, 26 and 29, possibly ascribed to fragmentedmicrocrystallites (or partially organized structures). Diffraction within the 2θ= 43 is still broad although depressed anddiffuse, suggesting that the intragraphiti conditions of chemical activation inflictsinsignificant structural alterations. Circulating air during pyrolysis leads to enhancement of the basic graphitic structure withdestruction and degradation in the lateral dimensions.

In this work, activated carbon (AC) after HNO3 modification was used as the support during the production of supportedTiO2 to increase the high deposition efficiency and the photocatalytic activity. The results of N2 adsorption showed that theBET surface area of samples decreased with an increasing of the concentration of HNO3 due to the penetration of TiO2. FromXRD data, a single crystal structure of anatase peak was observed in diffraction patterns for the AC coated with titaniumcomplexes. From the SEM results, almost all particles were aggregated with each other at the carbon surface and AC wascovered with TiO2 particles in all of the samples. The EDX spectra show the presence of C, O, Ti and other elements. It wasalso observed a decreasing of amount of C content with increasing Ti and O content from the EDX. The results of FT-IRrevealed that the modified AC contained more surface oxygen bearing groups than that of the original AC. The effect ofsurface acidity and basity calculated from Boehm titration method was also evaluated from correlations as a function ofNaOH, NaHCO3, and Na2CO3 uptake. The surface modification of AC by HNO3 leads to an increase in the catalyticefficiency of AC/TiO2 catalysts, and the catalytic efficiency increases with increasing of HNO3 concentration.