Anisotropic thermal conductivity of three-layer laminated carbon-graphite composites from carbonized wood

Composites with characteristics of anisotropic thermal conductivity for thermal management in Solar Power Satellite (SPS), to discharge the heat that was generated when solar energy was not converted to electricity, were developed by alternating layers of laminated graphite and carbonized wood. The effects of the weight fraction of carbonized wood, particle size, interlayer interfaces, and environment temperature on the thermal conductivity and the ratio of thermal conductivity between horizontal and vertical directions (H/V ratio) to the plain surface of samples were discussed. The thermal conductivities of carbon–graphite (C/G) composites were measured using the laser flash method. Laminated C/G composites improved the anisotropic thermal conductivity. The highest H/V ratio of 10.17 was obtained at 10 wt% of carbonized wood. Particle size and interlayer interfaces were found to affect the anisotropic thermal conductivity. The thermal conductivity of C/G composites increased with increasing temperature from 25 °C to 150 °C.     

Effect of disulfide bonds in human hair fibers on the melting behavior of their crystalline structure

In order to reveal the role of disulfide (S‐S) bonds in the fine structure of human hair fibers, especially in the complex between intermediate filaments (IFs) and intermediate filament‐associated proteins (IFAP), we investigated the relationship between melting behavior of (‐crystallites on thermal analysis and structural orientation of the fibers when S‐S bonds were oxidized using 1.5 wt% peracetic acid (PAA) solution. It was revealed that oxidative treatment of human hair fibers immersed in PAA solution made cystine residues dissociate to cysteic acids and that the (‐crystalline structure of the oxidized hair fibers was maintained despite the fission of S‐S bonds. Their thermographs in water on high pressure differential scanning calorimetry (HPD‐SC) showed that the endothermic peak assigned as the melting of (‐crystallites became separated into two endothermic peaks with progression of the treatment time, and the one started melting at a lower temperature while the other had a higher melting temperature than the melting temperature of untreated hair. Furthermore, the sum of the two endothermic peak areas decreased. Polarized light microscopic observation indicated that the orientation of IFAP still existed at the temperature at which the orientation of IFs disappeared. Therefore, these results suggested that some S‐S linkages at the interface between IFs and IFAP dissociated with the PAA treatment and that there was not only some region of IFs stabilized by S‐S bonds but also another region of IFs stabilized by hydrophobic interaction for their thermostability. Keywords: human hair fiber, peracetic acid, disulfide bonds, intermediate filament, (‐crystallites, thermostability, high pressure differential scanning calorimetry, polarized light microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy