Study On Preparation Of In-situ Carbon Nano Tubes By The Catalytic Pyrolysis Method In The Carbonization Process Of Phenolic Resin And Application

Carbon nano tubes were synthesized in-situ in phenolic resin by catalytic pyrolysis method using phenolic resin powders as a carbon source and substrate, nano metal powders(Co, Ni, Fe) and metal salts(Co(NO₃)₂·6H₂O, Ni(NO₃)₂·6H₂O, Fe(NO₃)₃·9H₂O) as the catalyst. And the influences of the addition of the catalyst powder on properties of the MgO-C brick sample were studied.The effects of the type and quantity of catalysts, the atmosphere and the carbonization temperature on morphology of carbon nano tubes in resin carbon were studied. The results are as follows.As for the type and quantity of catalysts, the catalytic effect of Ni in nano metal powders is the greatest under two different atmospheres studied. And the appropriate amount of Ni added is 0.75wt% in the mass of resin powders in the presence of argon, while it is 0.5wt% in the presence of N₂ and CO. When using metal salt as the catalyst, the catalytic effect of Ni(NO₃)₂·6H₂O is the greatest under two different atmospheres, and the suitable quantity that needs to be added is 1wt%. But nano metal powder has a better catalytic effect than the corresponding equivalent metal salt. When the amount of metal salt added is more than 1%, the effect of the test is not significant. But if metal salt is pre-retreated and converted to the corresponding metal oxide before using, the effect will improve.When the effect of atmosphere is concerned, the morphology of carbon nano tubes under argon atmosphere is better than in coke bed condition. 1100℃is the appropriate temperature for carbonization.In-situ carbon nano tubes were characterized by FESEM, TEM, XRD. The results show that in-situ carbon nano tubes are multi-walled carbon nano tubes with a diameter of 30-40nm.The influence of in-situ carbon nano tubes on the thermal property of resin was studied. The results show that the addition of catalyst increases carbon yield of resin due to formation of in-situ carbon nano tubes in modified resin. However, the oxidation resistance of resin carbon remains almost unchanged.The mechanism for the formation of in-situ carbon nano tubes was discussed initially. It was observed that large quantity of pores formed in the carbonization process of resin, and carbon nano tubes mainly grew in these pores via top growth mode, which is in accordence with the particle-wire-tube mechanism.The influences of nano metal powders catalysts added on the apparent porosity,the bulk density,the crushing strength and the bending strength of the MgO-C brick samples treated in coke bed condition at 1100℃for 3h are not significant. Possibly carbon nano tubes didn't form in the samples due to bad coke bed condition and more complicated MgO-C system than phenolic resin system.Compared with the MgO-C brick sample with no catalysts, the high temperature bending strength (1400℃×0.5h)of the sample with Fe catalyst improves by 20% ,up to 10.71MPa, while the sample with Co catalyst and the sample with Ni catalyst change less when adding nano metal powder into the sample.It was observed that a large quantity of SiC whisker and Mg₂SiO₄ whisker formed in samples with the addition of Fe catalyst, which played a main role in reinforcing the toughness of the sample. But carbon nano tubes were not observed in the samples。...