Materials Literature
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Abstract The kinetics of polyesterification of the glycolyzed PET waste with adipic acid is reported. Glycolysis of PET waste was carried out with ethylene glycol at three different ratios of PET waste to glycol. The glycolyzed products could be readily polyesterified by reacting with adipic acid, to give polyester po…
A ferroelectric polarization P (permanent, spontaneous electric dipole moment) is predicted for certain non-racemic liquid crystals based upon simple symmetry arguments. The magnitude of this polarization is a major factor in determining the eletro-optic response times achievable in ferroelectric liquid crystal (FLC)…
Infrared spectra demonstrate that at pressures above 20 gigapascals and room temperature the regular tetrahedral coordination of oxygen around both silicon and aluminum ions is severely disrupted in SiO(2), CaMgSi(2)O(6), and CaAlSi(2)O(8) composition glasses. The spectra are consistent with gradual, pressure-induced…
The specific heats of the β1(DO3) and β′1(18R) phases in a Cu + 16.1 wt% Zn + 8.0 wt% Al alloy are measured at temperatures close to its martensitic transformation temperature by two different calorimetric techniques. In the measured temperature range no appreciable difference in the specific heat values of the phases…
It is shown that a three-mirror device with ideal mirror reflectivities may be used in place of a halfwave plate to rotate the plane of polarization of a plane polarized beam by any angle with no loss of polarization purity. For coated mirrors, with more general reflectivities, specifications are set on the allowed re…
KMO 2 P 3 O 12 cristallise dans le systeme orthorhombique, groupe d'espace Pbnm et sa structure est affinee jusqu'a R=0,028. RbMo 2 P 3 O 12 cristallise dans Pbcm avec R=0,044
A novel technique, which employs \ensuremath{\omega}\ensuremath{\chi}'/\ensuremath{\chi}'' of the longitudinal susceptibility in place of the shape function \ensuremath{\chi}''/\ensuremath{\omega}\ensuremath{\chi}(0), reveals a coupling of the heavily overdamped soft mode to a relaxation mode in the transverse Ising f…
High-resolution Fourier spectroscopy has been used to study bound-to-bound transitions at the deep platinum acceptor in silicon. Phonon replicas have been observed for both the ${P}_{3/2}$ and the ${P}_{1/2}$ Rydberg series; the energy of the pseudolocalized phonon causing the replicas is 7.2 meV. In addition, Fano re…
Scanning-tunneling-microscope images of layer structure dichalcogenides exhibiting charge-density-waves (CDW's) have been studied at 4.2 K. CDW amplitudes in the 2H, 1T, and 4Hb phases of ${\mathrm{TaSe}}_{2}$ have been measured with the strongest CDW phase showing only the superlattice modulation while the weaker CDW…
The photoemission spectra of NiS in both antiferromagnetic and Pauli paramagnetic phases show similar characteristic features of localized d electrons. This finding is in contrast with the results of band-structure calculations which predict drastic spectral changes between the two phases. It is suggested that fluctua…
An extended Thomas--Fermi--von Weizsacker theory is used to investigate the properties of simple metal surfaces. Fundamental surface quantities such as the work function and surface energy are found to compare quite favorably with the corresponding results obtained through the use of density-functional theory. Applica…
We use a perturbative density matrix treatment to investigate the behavior of the static polarizabilities α of linear conjugated chains CNHN+2, with respect to the chain length and to the presence of neutral and charged conjugation defects of soliton and polaron type. The molecules are described by the Pariser–Parr–Po…
The static structure factor g(k) of the concentrated solution of stiff polymers is calculated based on the generalized random phase approximation (RPA) which accounts for the nematic interaction (i.e., the interaction causing the nematic phase of stiff polymers) between the segments. The structure factor is obtained i…
We report observation of microcrystalline interface phases at the ${\mathrm{SiO}}_{2}$-Si(001) interface. The crystallites have varying degrees of orientational order with respect to the substrate depending on preparation techniques. Most of the diffraction peaks from these phases can be indexed as due to the \ensurem…
We use a perturbative density matrix treatment to investigate the behavior of the first and second static hyperpolarizabilities of linear conjugated chains CNHN+2 described by a Pariser–Parr–Pople Hamiltonian. We examine the evolution of the hyperpolarizabilities with increasing chain lengths, and the effect of differ…
The absorption spectrum of Dy3+:LaCl3 at 4 K has been photographed and measured from 20 000 to 38 000 cm−1. Based on this and previous data, an empirical energy level scheme consisting of 151 observed crystal levels from 0 to 34 130 cm−1 has been determined for the 4f9 ground configuration of trivalent dysprosium in L…
GaSe β 2H cristallise dans le systeme hexagonal avec le groupe d'espace P6 3 /mmc. Affinement de la structure jusqu'a 0,054. La structure est isotypique avec celle de GaS β
The crystal structure of β-CuI at 400°C has been refined from powder crystal X-ray diffraction data. The crystal belongs to the trigonal system with the space group C 1 3v -P3m1, and has lattice constants of a =4.279±0.002 A, c =7.168±0.007 A. The low temperature phase of solid electrolytes is often of tetrahedral str…
Neutron irradiation of ${\mathrm{MgAl}}_{2}$${\mathrm{O}}_{4}$ spinel crystals produces an F-center absorption band in the uv accompanied by a broad absorption band in the visible region. Excitation and emission experiments identify the observed structure in the visible absorption band as optical transitions of transi…
A molecular-dynamics study of the structure and dynamics of monatomic liquids and glasses is presented. The local atomic structure and its development during the quenching process are analyzed in terms of fluctuations of atomic-level stresses and their correlations. This approach extends the basis for the description…