Materials Literature
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The conformational behaviour of 1,1′-disubstituted tetra benzopentafulvalene is strongly substituent-dependent; in the 2,2′-difluoro-derivative, the energy barriers associated with the cis–trans-isomerization did not prove to be low.
Abstract The optical rotatory dispersion of solutions of cellulose acetates with different degrees of acetylation in a series of solvents is studied. Increasing the degree of esterification of the cellulose acetate results in a shift of the optical rotation to more negative values. These changes have been explained on…
The transformation between a long‐period antiferro‐magnetic and a triangular‐type weak ferromagnetic phase was investigated by magnetic, x‐ray and neutron diffraction methods on polycrystalline and single‐crystal samples of non‐stoichiometric Mn3Sn with hexagonal DO19 structure. The transition is of first‐order, being…
Abstract : The TPRC Data Series published in 13 volumes plus a Master Index volume constitutes a permanent and valuable contribution to science and technology. This 17,000 page Data Series should form a necessary acquisition to all scientific and technological libraries and laboratories. These volumes contain an enorm…
Abstract After some introductory remarks a survey is given (in part 2) of the basic notions of OD‐theory, including the concept of the OD‐groupoid family. In part 3 a new procedure is presented for the determination of the OD‐groupoid family of an OD‐crystal from general features of its X‐ray diagrams and applied to t…
Passivation phenomena have been observed upon cathodic and anodic polarization of the Al electrode in AlCl 3 ‐ KCl ‐ NaCl melts between 100° and 160 °C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents incre…
Ion-exchange isotherms have been measured at 25°C for the high framework charge chabazite-type zeolite, K-G1, and involving the cation pairs: K+⇌ Na+, Na+⇌ Li+, Na+⇌ Cs+, Na+⇌ Ca2+, Na+⇌ Sr2+, and Na+⇌ Ba2+. The results have been compared with those for an isostructural natural chabazite of lower charge density. The v…
Dans les composés considérés, isomorphes de Zn2Mo3O8, les cations divalents Fe2+ et M2+ se répartissent dans des sites octaédriques ou tétraédriques de symétrie trigonale. L'occupation des différents sites, ainsi que les propriétés électroniques et magnétiques des ions Fe 2+ dans chacun des sites ont été déduites de l…
The equilibrium phase diagram of the lithium‐sulfur system has been investigated. A miscibility gap extends from 0.2 to 37.0 atom per cent (a/o) lithium above a monotectic temperature of 364.8°C; the critical temperature is greater than 600°C. The only intermediate phase found is , which melts at 1372°C.
The preparation of 21,24-dioxacorroles by condensation of dipyrromethane-5,5′-dicarboxylic acids with 5,5′-diformyl-2,2′-bifuryl or bis-(5-formyl-2-furyl) sulphide is described. It is suggested that the latter reaction involves a non-aromatic meso-thia-macrocyclic intermediate which loses sulphur by a disrotatory cycl…
The values of mechanical quality factor Q m are determined for lead zirconate titanate ceramics containing various oxides as impurities in various amounts. Impurities are found to be classified into two groups with respect to the change of Q m values, viz. , (1) Q m decreases in the presence of impurities ( e. g. Nb 2…
The reduction of zinc (II) tetraphenylporphin (ZnTPP) in dimethylformamide (DMF) was investigated. The products of electron transfer and associated chemical reactions were studied by polarography, cyclic voltammetry, thin‐layer controlled potential coulometry and spectroscopy, and epr. Reduction proceeds initially as…
Abstract The surface tension of a polymer liquid is a property of considerable practical importance. Within the past decade the experimental difficulties in accurately measuring the surface tension of viscous polymer melts have been overcome, and a considerable body of data is now available. This review discusses the…
Description The Second Conference on Composite Materials: Testing and Design was held 20-22 April 1971 in Anaheim, Calif. Committee D30 on High Modulus Fibers and Their Composites of the American Society for Testing and Materials sponsored the conference, in conjunction with the American Institute of Mining, Metallurg…
N THE ferroelectric and piezoelectric applications of BaTiOa I and Pb(Zr,Ti)O,, dependence on time of many of their
The magnetic properties during tempering of Fe‐ 30∼50wt% Cr‐ 10 ∼30wt% Co alloys, which consist of bcc high‐temperature phase (α) obtained by quenching from 1300°C, have been measured. Alloys in a certain range of composition showed desirable permanent‐magnetic properties by a step‐tempering following a thermomagnetic…
Hexagonal NaLnF 4 : Yb 3 + , Er 3 + ( Ln : Y , Gd , La ) was found to be an efficient green‐emitting phosphor with infrared excitation. It was prepared by firing a mixture of Na 2 SiF 6 and coprecipitated Ln 1 − y − z Yb y Er z F 3 at 630°C in an argon atmosphere. The optimum firing condition of NaYF 4 : Yb 3 + , Er 3…
Abstract Fibers and solvent‐cast films of polyacrylonitrile have been investigated by x‐ray small‐angle and wide‐angle measurements and dynamic‐mechanical analysis. It has been found that the structure of this polymer is better described by a two‐phase model consisting of more and less ordered regions. By the aid of x…
The morphological properties as derived from wide- and small-angle x-ray scattering, IR dichroism, electron spin resonance, and electron microscopy, and the anisotropy of mechanical properties of the fiber structure can be well explained by the microfibrillar concept developed on the basis of a detailed study of plast…
The evolution of thought during the last 25 years on the mechanism of pitting corrosion of copper in supply waters is traced and the significance of early observations reconsldered m the light of recent knowledge. A simplified approach to the Membrane Cell Theory, the role of surface films in the initiation mechanism…