Materials Literature
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Results obtained on the polymerisation, copolymerisation, and graft copolymerisation of vinyl fluoride, various properties of the polymers thus produced, and also possible fields of application are discussed on the basis of 435 references published up to the beginning of 1976.
CONTENTS 1. Introduction 432 2. The Electronic State of Adsorbed Atoms 432 3. Interaction of Adsorbed Particles. Dependence of Heat of Adsorption and Work Function on Concentration of Adatoms 437 4. Atomic Structure of Submonolayer Films and Phase Transitions in Them 441 5. Conclusion 448 References 449
We report the structure and electronic properties of ${(\mathrm{SN}{\mathrm{Br}}_{0.4})}_{x}$ and the first chemical modification of the polymeric superconductor ${(\mathrm{SN})}_{x}$. Its dc conductivity at 300 K is ten times greater than that for ${(\mathrm{SN})}_{x}$ and the thermoelectric power is positive rather…
Abstract Systematic measurements of the core-electron binding energies of the rare-earth metals terbium to lutetium, and their surface and bulk oxides, have been made with a VG-ESCA3 X-ray photoelectron spectrometer coupled with a PDP/8E computer. Comparison of the measured binding energies for the core levels with ac…
The linear thermal expansion of a polycrystalline sample has been measured in the ranges 1.5<T<34K, 55<T<90K, and at room temperature; and its heat capacity in the range 1.3<T<16K. Expansion is strongly negative at low temperatures, with Gruneisen parameters gamma 0 th =-2.4+or-0.4 and gamma min th =…
Abstract When a high molecular weight polymer, in a solution of concentration above the critical concentration for entanglement, is lightly crosslinked to effect only a few bonds per macromolecule, its solution viscosity is significantly affected. The random coil model predicts a monotonous increase in viscosity as a…
Ternary chalcopyrite crystals are well studied and some of the promising crystals are finding useful applications in nonlinear optical devices. Two other groups of diamond-like crystals are considered: stannite and famatinite which are derived from chalcopyrite. Nonlinearity and average refractive index are calculated…
It is shown that the strong far-infrared absorption in small Al particles, recently observed by Granqvist et al., may be explained as arising from the dielectric losses in the amorphous oxide layers covering the particles. Aggregation of particles into clusters is found essential in order to produce the observed depen…
The low-frequency (0 to 500 cm−1) Raman spectra are recorded at different temperatures between 40 and 413 K through the different structural modifications: P21/c ↔ P42/ncm ↔ Cmca ↔ ↔↔ I4/mmm. The results agree with previous NMR data and show that the three higher-temperature tetragonal and orthorhombic phases exhibit…
The growth of LiYO2 and its structure are discussed. The absorption and luminescence spectra of Nd3+ in LiYO2 monocrystals are recorded at 4.2, 50, 77, and 300 K in the region from 250 to 2500 nm. The Nd3+ ion energy level diagram is constructed on the basis of the spectral data. Theoretical calculations of the intrin…
The isotope effect for diffusion of $^{113}\mathrm{Sn}$ and $^{121}\mathrm{Sn}^{m}$ in Ti has been measured at five temperatures in the bcc $\ensuremath{\beta}$ phase. Separation of the Sn isotopes was effected by $\ensuremath{\beta}$ spectroscopy on electroplated sources. The effect is small and highly temperature de…
Measurements of the $^{77}\mathrm{Se}$ nuclear magnetic resonance as a function of temperature are reported for the $2H$ polytypes of Nb${\mathrm{Se}}_{2}$ and Ta${\mathrm{Se}}_{2}$. Below the critical temperatures, the charge-density waves (CDW) produce a distribution of Knight shifts resulting in an asymmetrical bro…
The torsion-effusion method, with simultaneous torque angle and weight loss measurements, was used to study the thermal decomposition of MgSO4 and CaSO4. The initial step in the decomposition/vaporization process appears to be the evolution of an SO3 molecule from the lattice, followed by conversion to SO2 and O2 on t…
The structures of [Ln(H20)9I(BrO3) 3 and ILn(H20)gI(CzHsSO4)3, Ln = Pr and Yb, have been determined by X-ray diffraction. The structures were refined to R = 0.025--0.040. Accurate cell dimensions for the bromates and ethyl sulphates of all the trivalent Ln ions except Pm were determined at 23°C with Guinier-H~igg powd…
In order to gain some insight into the nature of the interactions in TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane), we compare the magnitude of the observed magnetic susceptibility $\ensuremath{\chi}$ with the predictions of two simple models. First we consider a tight-binding band of noninteracting electrons…
An alternative formulation of the generalized van der Waals theory of nematic liquid crystals is presented and discussed briefly. The derivation is considerably more straightforward than that of Gelbart and Baron and is closely analogous to the usual derivation of the van der Waals equation of state.
The glass transition temperatures (Tg) of binary mixtures of the lower normal alkanols with several aprotic Lewis bases have been measured as a function of composition. The initial molar slope (IMS) at the pure alcohol end of the curve of Tg against mole fraction of base was accurately determined for each base. A rela…
Relationships between the molecular dimensions of polymers adsorbed on solid surfaces and the ’’hydrodynamic thickness’’ obtained by viscosimetry or flow rates through capillaries are derived by solving the corresponding Navier–Stokes equation. An exponential density distribution of polymer segments in the vicinity of…
Bound and excited negative ion states of gaseous 7,7,8,8-tetracyanoquinodimethan (TCNQ) are studied from experiments involving collisions of electrons and fast cesium beams with TCNQ. The electron affinity of TCNQ is measured to be 2.8+0.05−0.3 eV by the collisional ionization technique. TCNQ attaches electrons with e…
In this paper, a theoretical analysis of secondary electron emission in the nearly-free-electron (NFE) metals is presented. Restricting ourselves to excitation of secondary electrons (SE's) from the valence (or conduction) band only, we investigate the roles played by screened electron-electron scattering and by volum…