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标题:Microstructure, dangling bonds and impurities in activated carbons
时间:2019-12-03 09:10:02
DOI:10.1016/S0008-6223(99)00052-4
作者:A. Manivannan; M. Chirila; N.C. Giles
关键词:Experimental/ carbon; crystal microstructure; crystallites; dangling bonds; impurities; magnetic impurities; magnetisation; paramagnetic resonance; Raman spectra; X-ray diffraction/ activated C; magnetization studies; microstructure; dangling bonds; wide-angle X-ray diffraction; WAXD; magnetometry; electron spin resonance; Raman spectroscopy; magnetic field variations; magnetic impurities; Curie-law variations; room temperature ESR studies; C/ A6480G Microstructure A7830G Infrared and Raman spectra in inorganic crystals A6170R Crystal impurities: general A7530H Magnetic impurity interactions A7560E Magnetization curves, hysteresis, Barkhausen and related effects A7630 Electron paramagnetic resonance and relaxation (condensed matter)/ C/el
出版源: 《Carbon》 ,37 (11) :1741-1747
摘要:Wide-angle X-ray diffraction (WAXD), magnetometry, electron spin resonance (ESR) and Raman spectroscopy are used to investigate three activated PICA carbons (viz. GX203, P1400, Med 50) with surface areas of 1000, 1150 and 2000 m 2/g, respectively. Although WAXD showed the absence of any minerals in these carbons, temperature and magnetic field variations of the magnetization shows significant magnetic impurities with concentrations in the order GX203>Med 50>P1400. Analysis of WAXD and Raman spectra shows these carbons to consist of graphitic crystallites with L asimesime30 Aring and L csime10 Aring. All three carbons give an ESR line due to dangling bonds with g=2.0028(3) but the linewidth DeltaH and the spin concentration N s are strongly affected by air/oxygen. The linewidths are reduced from DeltaH~4 Oe for the as-received samples to DeltaH~1.2 Oe for the evacuated samples. The N s values are enhanced upon evacuation, with the enhancement factors of about 40, 130 and 670 for GX203, P1400 and Med 50 respectively, correlating well with the increase in the relative surface areas of these carbons. Magnetization studies using a SQUID magnetometer show that below about 30 K, all three carbons yield Curie-law variations with N s~10 19/gram, in good agreement with the N s values obtained from the room temperature ESR studies on evacuated samples
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