Structure And Properties Of Activated Carbon Fibers From Liquefied Wood By Disodium Hydrogen Phosphate Activation Treatment

In order to to make clear the variation of microstructure and properties of liquefied wood carbon fibers by chemical activation, based on orthogonal experimental design, the activated carbon fibers were prepared from liquefied wood by disodium hydrogen phosphate activation. The influences of different impregnation ratio, different activation temperature and different activation time of activated carbon fibers including crystal structure, surface chemical structure, pore structure, surface morphological structure, as well as the adsorption properties and mechanical properties were investigated.The main conclusions are as follows:1. The yield value of activated carbon fibers from liquefied wood first decreased and then increased with increasing impregnation ratio under activation temperature and time certain conditions. The activation temperature was increased from 600℃ to 900℃, the yield was decreased 23.30%; The activation time was increased from 60 min to 150 min, the yield was increased 14.27%.2. The crystal structure of activated carbon fibers from liquefied wood belonged to graphite-like structure. With the increased of impregnation ratio or time, the value of d002 gradually increased, whereas that of Lc and Lc/doo2 decreased. With the increases of activation temperature, the value of doo2 gradually decreased, whereas that of Lc and Lc/doo2 gradually increased.3. The micropore ratio increased to above 70% at the impregnation ratio was 1:5 and 1:6. The specific surface area was found to be the maximum of 1284 m2/g at impregnation ratio 1:5. The micropore ratio increased to above 60% at the activation temperature 800℃ and 900℃. With increasing activation temperature, the BET specific surface area and pore volume of activated carbon fibers gradually increased and reached maximum specific surface area of 1306 m2/g and pore volume of 0.670 cm3/g at 900℃. With increasing activation time, the BET specific surface area and pore volume of activated carbon fibers gradually decreased. The micropore size was mainly in the range 0.5～2 nm, small amount mesopore size in the range 2～3 nm and micropore ratio was 76% when the activation time of 60 min. The micropore size was mainly in the range 0.7～1.8 nm, the numerous mesopore size was in the range 2～4 nm and the micropore ratio in the range 49～68% with increasing activation time.4. The numerous graphite carbon and a small amount of C-OH, C=O and -COOH were distributed on the surface of activated carbon fibers. The relative content of the graphitic carbon decreased, the relative content of C-OH increased, the relative content of C=O,-COOH change was not obvious with increasing activation temperature.5. The surface of activated carbon fibers from liquefied wood was almost smooth. At the same time, the surface was a few impurities. The activated carbon fibers had ellipse cross-section, but the activated carbon fibers had circular cross-section at low activation temperature. The cross-section of activated carbon fibers have air hole at the activation temperature of 600℃.6. The iodine adsorption value of activated carbon fibers from liquefied wood first increased and then decreased with increasing impregnation ratio. The iodine adsorption value of activated carbon fibers from liquefied wood gradually increased with increasing activation temperature. The iodine adsorption value of activated carbon fibers was 1189.39 mm/g at 900℃. With increasing activation time, the iodine value of activated carbon fibers from liquefied wood gradually decreased, decreased 12.42%.7. With increasing impregnation ratio, the tensile strength and elastic modulus of activated carbon fibers first decreased and then increased. With increasing activation time, the tensile strength and elastic modulus of activated carbon fibers gradually decreased. With increasing impregnant ratio to 1:5, the tensile strength and elastic modulus were decreased by 42.82% and 21.28%, respectively, whereas the tensile strength and elastic modulus of activated carbon fibers were increased by 67.07% and 31.53%, respectively when concentration of impregnation used was over certain value. The activation temperature was increased from 600℃ to 900℃, the tensile strength and elastic modulus of activated carbon fibers were decreased by 12.65% and 55.59%, respectively. With increasing activation time, the tensile strength and elastic modulus gradually increased. The activation time was increased from 60min to 150 min, the tensile strength and elastic modulus was increased by 57.67% and 44.12%, respectively.