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51.
The history and present state of the art in the chemistry of mesophase pitch, which is an important precursor for carbon fiber and other high-performance industrial carbons, are reviewed relative to their structural properties. The structural concepts in both microscopic and macroscopic views are summarized in terms of the sp(2) carbon hexagonal plane as a basic unit common to graphitic materials, its planar stacking in clusters, and cluster assembly into microdomains and domains, the latter of which reflect the isochromatic unit of optical anisotropy. Such a series of structural units is described in a semiquantitative manner corresponding to the same units of graphitic materials, although the size and stacking height of the hexagonal planes (graphitic sheets) are very different. Mesophase pitch is a liquid crystal material whose basic structural concepts are maintained in the temperature range of 250 to 350 degrees C. The melt flow and thermal properties are related to its micro- and mesoscopic structure. The structure of mesophase-pitch-based carbon fiber of high tensile strength, modulus, and thermal conductivity has been formed through spinning, and has inherited the same structural concepts of mesophase pitch. Stabilization settles the structure in successive heat treatments up to 3000 degrees C. Carbonization and graphitization enable growth of the hexagonal planes and their stacking into units of graphite. Such growth is governed and controlled by the alignment of micro- and mesoscopic structures in the mesophase pitch, which define the derived carbon materials as nanostructural materials. Their properties are controlled by the nanoscopic units that are expected to behave as nanomaterials when appropriately isolated or handled. 相似文献
52.
Kikuo Miyokawa Masayuki Itoh Takummi Etoh Setsuko Kinoshita Isao Masuda 《Thermochimica Acta》1985,96(1):227-234
Kinetic and thermodynamic aspects of the axial base dissociation of solid Co(salen) (X-py) complexes, X = H (1), 3-Me (2), 4-Me (3), 3,4-Me2 (4), 3,5-Me2 (5), 3-NH2 (6), 3-Cl (7), 3-CN (8), 4-CN (9), have been investigated by means of TG-DSC and isothermal weight-loss measurements. These adducts endothermically dissociate the axial base giving rise to the oxygen-active Co(salen) complex. The axial base dissociation reactions fit the contracting disc equation and the kinetic compensation effect is observed for all the adducts excepting Adducts 4–6. For the remaining adducts the kinetic and thermodynamic stabilities of the Co-(X-py) bond are found to increase linearly with increasing Hammett's substitution constants of X except for Adducts 3 and 9. These results are discussed in terms of the σ and π interactions between cobalt(II) and substituted pyridine. Factors dominating the kinetic bond stability are briefly discussed. 相似文献
53.
Kapurimycin A3 (kap A3, 1 ), an antitumour antibiotic, alkylates N7 of guanine2 (G2) and G4 of d(C1G2C3G4)2 to produce their covalent adducts 2 (64 %) and 3 (7.0 %), respectively. Heating at 90 °C for 5 min degraded both adducts to kap A3 - G adduct (5) with the concurrent release of their respective abasic-site containing oligomers 4 and 6. 相似文献
54.
A novel lignan: sphaerophyside SC was isolated from ethanolic extract of the seeds of Sphaerophysa salsula (Pall.) DC. The structure of the compound was elucidated mainly on the basis of the 1D NMR and 2D NMR data. 相似文献
55.
A catalytic immuno-reactor for the determination of human serum albumin (HSA) was constructed by using immobilized antibody and an amperometric detector. A sandwich assay with hemin-labeled antibody to catalyze the decomposition of hydrogen peroxide was used, the catalytic activity of the hemin-antibody conjugate being determined by measuring the decrease in hydrogen peroxide concentration. The reaction of hemin-labeled antibody with antigen was complete within 30 min and the current decrease was correlated with the HSA concentration. The relative standard deviation was about 9% at an HSA concentration of 1 mg ml?1. 相似文献
56.
Koichi Kikuta Koji Noda Shin Okumura Toshiaki Yamaguchi Shin-ichi Hirano 《Journal of Sol-Gel Science and Technology》2007,42(3):381-387
Orientation control of perovskite compounds was investigated by the application of a seed layer prepared from oxide nanosheets.
An aqueous suspension of oxide nanosheets was prepared by the exfoliation of a layered compound of KCa2Nb3O10 oxide grains. A seed layer composed of (TBA)Ca2Nb3O10 nanosheets (TBA = tetrabutylammonium) was formed on a glass substrate by simply dip coating it in the suspension. Two kinds
of perovskite compounds, LaNiO3 (LNO) and Pb(Zr,Ti)O3 (PZT) with a preferred orientation of (00l) were successfully grown on this seeded glass substrate. In this study, the relation between lattice mismatch and electrical
properties is investigated. A large, oriented PZT film with a size of 5 ×4 cm shows an improved P-E hysteresis behavior by
use of this orientation control. 相似文献
57.
Isao Watanabe Kusuo Nishiyama Kanetada Nagamine Kenji Kawano Ken-ichi Kumagai 《Hyperfine Interactions》1994,86(1):603-608
Zero field positive muon spin rotation method (
+SR) is applied on La2–x
Sr
x
CuO4 around forx=0.12 at which the high-T
c
superconductivity (SC) is suppressed. The magnetically ordered state of Cu-moments, which is not a spin glass state but an antiferromagnetic like state, appears below 15 K for 0.105x0.120. The magnetic phase boundary is very similar to the one of the La2–x
Ba
x
CuO4 in which the structural transition from the low temperature orthorhombic (LTO) phase to the low temperature tetragonal (LTT) phase is observed aroundx=0.12. The present study suggests that there is no big difference of the electronic state of the CuO2 plane between the La-Ba system and the La-Sr system and that the magnetic ordering of Cu-moments plays an important role for the suppression of the high-T
c
SC aroundx=0.12 in both of the systems, although the LTO-LTT structural transition has not been observed yet in the La-Sr system. 相似文献
58.
Yoshitsugu Hasegawa Suguru Kontani Isao Tomita 《Journal of inclusion phenomena and macrocyclic chemistry》1993,16(4):329-337
Intercalation of alkylalcohols into -zirconium phosphate was investigated at 25°C and/or under reflux.n-Alcohols having two to five carbons and 2-propanol were taken up at 25°C. These alcohols, andn-hexanol and heptanol, also intercalated under reflux.n-Alcohols having eight to eighteen carbon atoms intercalated when a stepwise method was employed. 2-Butanol and tertiary amylalcohols intercalated under reflux using a butanol intercalate as a starting material. Ethanol-to-butanol intercalates were unstable at room temperature, losing alcohols and changing to -zirconium phosphate. The particle size of the -zirconium phosphate did not affect the intercalation of alcohols. 相似文献
59.