In Sub Han

Mechanical properties of C–SiC composite materials fabricated by the Si–Cr alloy melt-infiltration method:

Although carbon fiber-reinforced silicon carbide matrix composites fabricated using the liquid silicon infiltration method exhibit high thermal and oxidation resistances, their physical characteristics are limited because of the presence of unreacted, free Si within the materials. To resolve this problem, ingots prepared by alloying Cr with Si in ratios of 0, 5, 10, 25, and 50 at% were melted and made to infiltrate the composite, resulting in the formation of CrSi2 in the unreacted, free Si region without degrading the composite’s properties. The CrSi2 in the composite material reduced the amount of free Si and caused minimal variation in the flexural strength while significantly improving the fracture toughness of the composite. The results of scanning electron microscopy and transmission electron microscopy analyses indicated that the improvement in the fracture toughness was due to the presence of an amorphous interlayer between the Si and CrSi2 phases, as well as because of a stress field surrounding the CrSi2 phase.

Electrical properties of cellulose-based carbon fibers investigated using atomic force microscopy

Natural fibers have been actively investigated for the reinforcement of biocomposite, absorbent, and functional fibers, because of their environmentally friendly properties. We manufactured carbon materials based on two different natural fibers by heat treatment at 700, 900, and 1100 °C, respectively. The thermal behavior, surface morphology, and electrical properties of these carbon materials were investigated by thermogravimetric analysis (TGA) and atomic force microscopy (AFM); specifically, the electrical properties were studied through three-dimensional current images, and the current-voltage curve (I–V) characteristics using current-atomic force microscopy (c-AFM) on a nano-ampere scale. The thermal stability, roughness, and local current of the carbon materials were improved by increasing the carbonization temperature, and carbonized filter paper (FP) showed higher values in all characterization analyses than carbonized henequen (HQ) due to the higher content of cellulose in FP. Moreover, the currentvoltage characteristics of carbonized FP at 1100 °C and commercial carbon fiber were similar at high voltages (−5 or 5 V). Therefore, we expected that carbon materials from FP would be more suitable than HQ for use as environmentally friendly electrode materials.