The usefulness of image analysis for images observed by microscopy is explained by presenting experimental results on several carbon materials with a discussion on what we can and cannot understand as a result of these analyses. Much useful information is contained in the images. Quantitative information can be obtained from the micrographs by image analysis and the data obtained can be used to compare one sample with another. Transmission electron microscopy (TEM) and image processing were used for the structural analysis of the side walls of carbon nanotubes. They were also used for the TEM examination of disordered carbon. The textures of the cross-section of pitch-based carbon fibers were analyzed by scanning electron microscopy and image processing. They were also used to analyze the pore shapes of isotropic graphite from optical micrographs. The same image analysis techniques can be used to analyze images obtained by all microscopy methods but the quality of the data obtained depends on the original definition of the image. However, image analysis does not provide a complete picture of the same characteristics and it is most important that it is used together with other analysis methods.
There are various kinds of porous materials as industrial products, which are widely used in consumer and industrial applications. However, the range of applications of porous carbon is limited, because many products have small pore sizes. If there were carbon products with mesopores, the range of applications that make use of the properties of carbon would be greatly increased. In this review, the author describes an industrial process for the manufacture of mesoporous carbon using the template method and the characteristics of the product obtained. Mesoporous carbon using magnesium oxide as a template has excellent pore size controllability and interconnected pores. The material enables the adsorption separation of macromolecules that are difficult to separate using conventional activated carbon. The method of manufacturing porous carbon using templates has been found to be effective for the development of new carbon applications.
Mechanical tests of a single carbon fiber are difficult because of its small size. The diameter or the shape of the cross section is very important for a precise evaluation of the properties. However, most size evaluations use a measurement of fiber diameter in only one direction and its effect on the results has not been studied sufficiently. In order to investigate the apparent diameter variation of carbon fibers, we have developed a new apparatus with two functions. One is that we can accurately control the measurement position along the fiber axis and the other is that we can rotate a single fiber around its axis. Measurements were carried out for two types of carbon fibers. Though the cross section of one of them was far from circular, its shape was almost the same along the fiber axis and its orientation was rotating randomly. For both fibers, an assumption of an elliptical cross section gave a smaller coefficient of variation for torsional modulus and tensile properties.
Composting is used as a method of recycling spent coffee grounds (SCG). Chemical analysis revealed that coffee grounds compost (CGC) has a lower content of crude fat, and higher contents of crude protein and ash, than those of SCG. Activated carbons were prepared from CGC and SCG, and their chemical compositions and pore structures were compared. The N/C ratios of activated CGC (CGCAC) and activated SGC (SCGAC) were 2.1 and 1.9 wt%, respectively, being similar, although the raw CGC originally had a N/C ratio twice (10 wt%) that of the raw SCG (4.5 wt%). The BJH method with nitrogen adsorption revealed that CGCAC had a larger mesopore diameter (10.6 nm) than SCGAC (4.8 nm), while the micropore diameters were almost the same (about 0.4 nm). It is suggested that changing the ratio of the components by composting, especially ash as the activation catalyst, affects the mesopore structure of the activated carbon.
A highly-oriented continuous carbon tape was prepared from a coal tar-based mesophase pitch by melt-blowing using a slit type nozzle. The molten precursor pitch was continuously extruded through the slit nozzle to produce a pitch tape along the drawing direction. The tape was oxidized, carbonized and graphitized. Examination of the crystallite orientation distribution function (CODF) for the (002) plane by X-ray diffraction revealed that the carbon layer planes were oriented parallel to the tape surface indicating a strong anisotropy. The degree of CODF largely depended on the oxidation time and carbonization temperature. The orientation was greater in the tape drawing direction than in the tape width direction. The mechanical properties largely depended on the oxidation temperature and reached maximum values at around the softening point.