Materials Literature
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Abstract Continuous silicon carbide fiber of high-tensile strength (about 350 Kg/mm2) was synthesized by means of the heat-treatment of organosilicon polymer obtained from dodecamethylcyclohexasilane. X-ray analysis and high voltage electron microscopic observations revealed that the obtained continuous fiber is an ul…
We consider phenomena which are frequently designated jointly as the Jahn-Teller effect and result from dynamic electron-vibrational (vibronic) coupling in polyatomic systems with degenerate and pseudodegenerate terms. Principal attention is paid to the case of strong coupling, when the adiabatic potential in the spac…
Stimulated emission due to the 4 I 11/2 – 4 I 13/2 transition (λ = 2.936 μ) in yttrium aluminum garnet (Y 3 Al 5 O 12 ) doped with Er 3+ ions (30 wt%) was observed for the first time at 300°K. The output energy from crystals of 50 × 3 mm dimensions was 0.3 J under free-oscillation conditions and 0.05 J in the case of…
Relative energies and relative intensities of the K alpha satellites and the K beta bands of Mg and Al metals and anodized Al have been measured. Spectra were obtained with a PAX spectrometer which provided high resolution and accurate intensity data (PAX identical to photoelectron spectrometry for the analysis of X-r…
A new method is presented for the evaluation of the edge-capacitance correction for electrodes of finite thickness. The corrections are divided into three separate components: electrode thickness, the lower edge of the electrodes, and the back of the electrodes. Simple correction formulae are derived for the first two…
Abstract A method is described whereby absolute values for the Seebeck coefficient, the thermal conductance and the thermal capacity of thermoelectric devices may be obtained without the need to measure temperature differences or heat flows. The only requirement in addition to the device to be calibrated and its usual…
X-ray-diffuse-scattering measurements of tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) show structural evidence of a phase transition. The low-temperature three dimensional superlattice ($2a\ifmmode\times\else\texttimes\fi{}3.7b\ifmmode\times\else\texttimes\fi{}\mathrm{Xc}$) is found to be preceded above 40 K…
The effect of strain rate changes on the flow stress of Au–Cu alloys in the region of strain prior to the start of serrated yielding has been investigated. The measurements of Δσ/Δ Δσ/Δ were found to depend on strain, strain rate, temperature, and composition. Negative values of Δσ/Δ ln ϵ were observed prior to the on…
New oscillation phenomena in VO2 crystals were observed. The oscillation is generated in the temperature region of the crystal transition, and its voltage and frequency depend upon the ambient temperature. The waveform of the oscillation is a rectangular pulse.
The I3 C chemical shifts and 13 C– 31 P spin–spin couplings (where applicable) are reported for pyridoxine, pyridoxamine, pyridoxal, pyridoxamine phosphate, and pyridoxal phosphate. Resonance assignments are made by consideration of substituent chemical shift effects, as tested on an analogous series of pyridine deriv…
A time-dependent Landau theory is proposed for the transition-metal dichalcogenides coupling the motion of the charge-density waves to the electron liquid. The dissipative terms are related to the metallic resistance. The "phason" or "phonon" excitations of the charge-density wave are found to be overdamped. Resistive…
Transport measurements were performed on thin films of Si3N4 deposited on Si using carrier injection from low-energy corona ions and a shallow junction detector. Large hole conduction is found for both corona polarities. Examination of the electronic structure of Si3N4 by x-ray photoemission spectroscopy (XPS or ESCA)…
NMR spectra at temperatures down to 1.8 K are given for the 19F resonance of SF6 and CF4 in H2O and D2O clathrates and for the 1H resonance in CH4–D2O and CH4–tetrahydrofuran-d8–D2O clathrates. The second moments correspond effectively to isotropic reorientation of encaged SF6, CF4, and CH4 molecules at temperatures a…
High-numerical-aperature lead silicate and barium crown glass uncald fibers have been doped with cerium to decrease their radiation sensitivity. The radiation-induced optical loss in both the visible and near-infrared in these core materials has been studied as a function of time (10−3–104 sec) after pulsed irradiatio…
The amino acid salt glycine hydrochloride, H3N+⋅CH2⋅COOH⋅Cl−, crystallizes in the space group P21/c, a=7.117(2) Å, b=5.234(2) Å, c=13.745(3) Å, β=97.25(1) °. The crystal structure has been refined from three-dimensional neutron diffraction data to a final R value based on F2 of 0.058. Estimated standard deviations in…
There have been several studies of the charge transfer photochemistry of aqueous Fe 3+ but the complexity of hydrolytic equilibria and the requirement for scavengers to render the primary photochemical processes observable has left several issues moot as recent reports show. Using tert-butyl alcohol as a scavenger, it…
The thermal conductivity of a harmonic Bravais crystal containing randomly distributed substitutional defects due to impurity-phonon scattering is theoretically investigated using the methods of double-time thermal Green's functions and Kubo formalism considering nondiagonal terms in the heat-current operator as propo…
The density of valence states (DOVS) of amorphous and crystalline ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ and ${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$ and of amorphous ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ have been investigated with monochromatized x-ray photoemission spectroscopy (XPS). All three compounds exhibit sim…
The optical properties of W are presented between 0.15 and 33 eV. The optical absorptivity or reflectivity was measured at near-normal incidence, and the data were Kramers-Kronig analyzed to determine the dielectric functions. Drude parameters were determined at low energy and were used to separate interband and intra…
The theory for the spin Hamiltonian parameters of low spin cobalt(II), d 7 , complexes has been developed to third order in perturbation theory for all reasonable ground states. Two extensions beyond previous treatments have been made: (1) the spin–orbit mixing of excited quartet states into the doublet ground state h…