Na_2HPO_4活化木材液化物碳纤维孔隙结构与表面化学结构

为了探究Na2HPO4活化处理引起的木材苯酚液化物碳纤维微细结构的变化,以Na2HPO4溶液为活化剂对杉木苯酚液化物碳纤维原丝进行了浸渍、干燥和不同温度的活化处理,对活性碳纤维的晶体结构、孔隙结构和表面化学结构进行了表征。结果表明:随着活化温度的上升,活性碳纤维的得率逐渐减小。活性碳纤维的晶体结构属于类石墨结构;随着活化温度上升,微晶层间距d002减小,而石墨片层平面尺寸Lc和Lc/d002增加。活化温度在600℃或700℃时,微孔率小于48vol%;当活化温度为800℃或900℃时,微孔率大于60vol%。活性碳纤维的微孔孔径主要集中在0.5~1.6nm范围内,中孔孔径主要分布在2.0~4.0nm范围内。随着活化温度的上升,纤维的比表面积和孔容积均逐渐增加,900℃时二者均达到最大值,此时的比表面积为1 306m2/g。C和O是活性碳纤维的基本元素,纤维表面大部分的含碳基团为石墨碳,含有少量的C—OH、CO和—COOH。研究为制备新型活性碳纤维和进一步探明活化剂同碳纤维分子之间相互作用提供参考。

Pore structure and surface chemical structure of Na2HPO4 activated liquefied wood carbon fibers

In order to investigate the microstructure variation of phenol liquefied wood carbon fibers caused by activating treatment by Na₂HPO₄, by using Na₂HPO₄ solution as the activator, the phenol liquefied cunninghamia lanceolata carbon fiber precusors were impregnated, dried and activating treated at different temperatures. The crystal structure, pore structure and surface chemical structure of activated carbon fibers were characterized. The results show that the yield of activated carbon fibers decreases gradually with the increasing of activating temperature. The crystal structure of activated carbon fibers belongs to graphite-like structure. With the increasing of activation temperature, the microcrystalline layer spacing d₀₀₂ decreases, while plan size of graphene sheets L_c and L_c/d₀₀₂ increase. When the activation temperature is 600 ℃ or 700 ℃, the micropore ratio is below 48vol%; when the activation temperature is 800 ℃ or 900 ℃, the micropore ratio is above 60vol%. The microporous pore size of activated carbon fibers mainly concentrates in the range of 0.5-1.6 nm, and the mesoporous pore size mainly distributes in the range of 2.0-4.0 nm. With the increasing of activation temperature, the specific surface area and pore volume of fibers gradually increase, and both reache the maximum at 900 ℃, the specific surface area is 1 306 m²/g in this case. C and O are the basic elements of activated carbon fibers. On the surfaces of fiber, a large proportion of carbon-containing groups are graphite carbon, and containing a small proportion of C-OH, C=O and -COOH. The investigation provides references for preparing new type activated carbon fibers and further ascertaining the interaction between activator and molecules of carbon fibers.