Polycarbosilane particles were dispersed in a novolac-phenolic resin matrix, and the resulting polymer blend was meltspun, stabilized and heat-treated at 1000°C or 1200°C for 1 h in an inert atmosphere. The heat-treated blend fibers were oxidized in nitric acid solution to remove the carbon matrix and the nanofibers thus released were collected by filtration. The nanofibers obtained from the 1000°C-blend fibers were oxidized more severely by nitric acid, resulting in a rougher nanofiber surface compared with that of nanofibers from the 1200°C-blend fibers. The former nanofibers also showed a larger specific surface area (288 m²/g) than did the latter (44m²/g). Analysis of a filament from the 1200°C-nanofibers showed carbon present at about 30 atom %, whereas just a few atom % of carbon was found in the 1000°C-nanofiber. It was concluded that more intact nanofibers with stronger oxidation resistance were derived from the polymer blend fibers heated at a higher temperature.

View full abstract

Catalytic removal of NO₂ by the reduction with activated carbon (AC) loaded with Pt, Cu and Ni with regard to weight loss of AC have been studied in an air atmosphere. ACs from coconut shells (YAC) and coal (MAC) adsorbing metal ion complex were heated at 700°C in N₂ atmosphere befor use. A mixture of 3 mmol NO and air was circulated over 0.5 g of metals loaded AC for 90 minutes and residual NO₂ and weight loss of AC were measured. Both removal of NO₂ and weight loss of AC increased with increasing temperature and the amounts of Pt and Cu on AC. A complete removal of NO₂ and about 35 % weight loss of AC were observed at 0.66 % of Pt loaded ACs (300 t) and 1.1 % of Cu loaded MAC (400°C). When Ni was loaded on ACs, NO₂ removal increased with increasing the temperature between 200-450°C. Ni content more than 0.76 % did not show any increase of NO2 conversion and hence it was difficult to remove 100 % of NO₂ within 90 minutes although Ni loaded on ACs reduced the residual quantity of NO₂ and the weight loss of AC at lower temperatures (200-300°C).

View full abstract

The absorption factor for carbon materials, one of very weakly absorbing materials, was investigated with a simple assumption that the cross section of the incident X-ray beam with a rectangle of a height (h) and breadth (b_r) to the flat sample was kept for the scattered X-ray beam. For calculation, in both of the reflection and transmission methods of diffraction measurements, the divergence angles of the divergence slit β and scatter slit γ were considered in two cases with β<<γ and β= γ. For the case β<<γ, all of the scattered beam could be determined with the detector. The following results were obtained.
a) Reflection method
b) Transmission method
where A (θ) is the absorption factor at glancing angle θ, b_r=Rsinβ, R is the radius of the goniometer, , μ' is the apparent absorption coefficient of the sampleand t is the thickness of the sample. Influence of the absorption factor on intensity recording of the 002 diffraction was examined for the powder samples contained in a glass holder of 0.2 mm depth, assuming the intensity could be expressed by Gaussian functions. The influence could be significant for the intensity recording when the full width at the half maximum for the intensity plotted against 2θ exceeds 3°.

View full abstract

Nine commercially available activated carbons (ACs) made by different manufacturers were used to evaluate their physical properties such as pore size distribution (PSD) with various numerical analysis based on nitrogen adsorption/ desorption isotherms at 77 K. Though similar results were exhibited among the numerical analysis methods, different PSD related the characteristics of ACs was obtained between micropore analysis method (MP method) and Dubinin-Stoeckli (DS) method on the analysis. Amount of methylene blue uptake in aqueous phase adsorption were well correlated with the surface area of more than 0.50 nm pore width calculated by MP method.

View full abstract

Carbonaceous materials containing boron and nitrogen (B/C/N materials) have been reviewed. The material with a composition BC₆N made by CVD method had the graphite-like layered structure whose X-ray (100) and (101) diffraction lines were separately observed. The materials with compositions BC_xN (x=1-4, 6) showed semi-conducting properties that could be explained by nanostructures in their layers. The materials BC₂N and BC₆N were chemically and electrochemically intercalated by alkali metals and could be used as new host materials. Applications of the materials to anode matrix of secondary Li ion batteries, luminescent materials, etc. have been also summarized.

View full abstract