The crystal lattice moduli of cellulose I and II were measured by X-ray diffraction using ramie and mercerized ramie. The measured crystal lattice moduli were in the range from 120 to 135 GPa and from 106 to 112 GPa for cellulose I and II, respectively. These values were different from recent theoretical estimates of 167 and 163 GPa for cellulose I and II, respectively, reported by Tashiro and Kobayashi. To study the origin of this difference, a numerical calculation of the crystal lattice modulus, as measured by X-ray diffraction, was carried out by considering effects of the orientation factors of crystal and amorphous chains and crystallinity. In this calculation, a previously introduced model was employed, in which oriented crystalline layers are surrounded by oriented amorphous phases and the strains of the two phases at the boundary are identical. The theoretical results indicate that the crystal lattice modulus measured by X-ray diffraction is different from the intrinsic lattice modulus when a parallel coupling between amorphous and crystalline phases is predominant, while the values of both moduli are almost equal when a series coupling is predominant. Thus, the crystal lattice moduli of cellulose I and II measured by X-ray diffraction are predicted to be dependent upon the morphological properties of the bulk specimens. The numerical calculations, however, indicate that the morphological dependence is less pronounced with increasing degree of molecular orientation and crystallinity. Thus, it is concluded that fibers and films with a high degree of molecular orientation and a high crystallinity should be used as test specimens for measuring crystal lattice moduli by X-ray diffraction.

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For the realization of a next‐generation energy society, further improvement in the activity of water‐splitting photocatalysts is essential. Platinum (Pt) is predicted to be the most effective cocatalyst for hydrogen evolution from water. However, when the number of active sites is increased by decreasing the particle size, the Pt cocatalyst is easily oxidized and thereby loses its activity. In this study, a method to load ultrafine, monodisperse, metallic Pt nanoclusters (NCs) on graphitic carbon nitride is developed, which is a promising visible‐light‐driven photocatalyst. In this photocatalyst, a part of the surface of the Pt NCs is protected by sulfur atoms, preventing oxidation. Consequently, the hydrogen‐evolution activity per loading weight of Pt cocatalyst is significantly improved, 53 times, compared with that of a Pt‐cocatalyst loaded photocatalyst by the conventional method. The developed method is also effective to enhance the overall water‐splitting activity of other advanced photocatalysts such as SrTiO3 and BaLa4Ti4O15.

The relationship between current density and applied DC electric field was measured for carbon black-polyethylene composite films which contain large amounts of carbon black by volume fraction (vr =c 0.16-0.28). The curves relating the current density to the applied DC electric field for the samples show clearly that, at first, the current densities increase in proportion to the applied DC electric fields and then, after the greatest values, they decrease and show negative resistance at high applied DC electric fields. The shapes of the curves are very sensitive to the volume fraction of the carbon black, to a previously applied DC voltage during the sample film molding, and to the density of the matrix polyethylene; yet there is almost no influence due to the particle size of the carbon black or to the melt index of the matrix polyethylene. This finding can be explained well by the tunneling of carriers across the barriers and the generation of Coulomb forces among the carbon black particles.

in all organisms. The similar X-ray diffraction diagrams of ramie and other fibrous celluloses support this. The subtle differences in the structures of different celluloses may, however, never be fully characterized. The only hope lies in the refinement with electron diffraction data, provided that a significant increase in the amount of data can be realized.Acknowledgment. This work has been supported by the National Science Foundation (Grant No. CHE7727749).Supplementary Material Available: Tables II (most probable models after initial cycles of refinement for space group P2i), IV (Cartesian atomic coordinates of the parallel structure), and V (comparison of observed and calculated structure factors for the parallel structure) (10 pages). Ordering information is given on any current masthead page.