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NIRE Annual Report
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 1999

Mesoporous Carbons with Metal Fine Particles

Carbon Materials Division
Energy Resources Department
Objectives
Recently, carbons complexed with diverse atoms are actively studied with a wide variety of interests concerning catalytic activity, magnetism, oxidation resistivity, etc. We have already reported that mesoporous (2<D<50nm) carbons are prepared by the impregnation of some kind of metal compounds on coal and following activation. As a result of our recent study, we have found that mesoporous structure is also formed in polyimide derived carbon samples by the effect of nickel metal particles without activation procedure. The mesopore formation in the Ni-carbon complex was correlated with the growth of metal particle and the change of carbon microtexture.
Results
Fine particles of Ni metal (cubic) with a diameter of ca. 10nm were dispersed in Ni containing polyimide treated at 600°C in flowing argon. The size of Ni particles became larger up to 100nm by heat-treatment at 800°C. The development of turbostratic carbons, clearly shown in X-ray diffraction profiles in Fig. 1, occurs at 800°C. It can be observed by TEM that the carbon layers windingly develop in the whole of 800°C samples. Pore size distribution curves determined by the nitrogen adsorption measurement are shown in Fig. 2. Mesopore formation is clearly found in Ni containing samples treated above 700°C. On the other hand, neither mesopores and turbostratic carbons are not generated in Cu containing samples at 800°C.
Fig. 1. X-ray diffraction profiles of Ni containing samples treated at 600°C and 800°C ;
: turbostratic carbon, : Ni(cubic)

Fig. 2. Pore size distribution of carbon of carbonized samples

It is obvious from the present result that the formation of mesopores is related to the growth of metal particles and the change of carbon microtexture. In case of activation with metal catalysts, mesoporous structure is formed by the oxidation on the metal oxide surface and no turbostratic carbon layers is observed. Mesopores in the Ni-carbon complexes treated at 800°C is considered to be formed by the turbostratic carbon layers windingly developed from some planes of Ni crystal.

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