Materials Literature
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Abstract The oxygen index test is a fundamental tool in basic research on polymer combustion and on mechanisms of fire retardance. Although the oxygen index should provide an evaluation of intrinsic flammability of polymeric materials, its response may depend on geometry of the specimen. This is shown by comparing the…
The temperature dependence of the yield-stress of mono- and poly-crystalline α-brasses containing 5 to 35 at% zinc in the range 4 to 300 K is analysed in terms of the kink-pair model of solid-solution hardening. The parameter W0 in the theoretical relation τ = τo exp (–mkT/W0), where m is a constant equal to about 25,…
The scattering of conduction electrons at grain boundaries in polycrystalline copper, molybdenum, and iron is studied. Linear functions of the specific electrical resistance versus concentration of grain boundaries are determined. Coefficients of conduction electron scattering kGB at grain boundaries as well as the sp…
The effect of crystallite sizes L smaller than 100 nm on the integrated Raman cross section Σc of the transverse optical (TO) mode of fcc silicon was studied experimentally in fully nanocrystallized thin films. The Σc/Σa (amorphous) ratio of this mode is shown to be 1 up to L=30 Å, and to decay exponentially down to 0…
Sr 2 Sb 2 O 7 cristallise dans Imma avec a=7,4557, b=10,3708 et c=7,6860 A, Z=4; affinement jusqu'a R=3,48%
We measured, via LIF, time-dependent concentrations of OH resulting from the reaction of O(3 P) with B2H6 and C2H6. The oxygen atoms were generated by titrating microwave discharged N2 /He with NO to the chemiluminescent end point. The operating pressures in the flow reactor ranged from 5 to 15 Torr; the mixtures cons…
In WO3 thin films the optical dispersion parameters (single-oscillator energy E0 and dispersion energy Ed developed by Wemple and DiDomenico [Phys. Rev. B 3, 1338 (1971)]) have been analyzed in the sample thickness range 100–1000 nm using the experimental results by Davazoglou and Donnadieu [Thin Solid Films 147, 131…
We have measured the reflectivity of ${\mathrm{Bi}}_{4}$${\mathrm{Ge}}_{3}$${\mathrm{O}}_{12}$ single crystals at 300 and 80 K from 4 to 40 eV. Beyond the first sharp peak at 4.57 eV, assigned to an excitonic transition, several other structures have been found between 5 and 10 eV, followed by a broad reflectivity ban…
Gelatin films glued to an O-ring are proposed as a new procedure to record interference patterns when a CO(2) laser is used as an infrared light source. With this method the unwanted effects given by asubstrate, on which the thin recording film is laid, are avoided. To characterize the medium, interferometric studies…
The ferromagnetic Ising model on the dual Penrose lattice is simulated by the Monte Carlo method. Using a phenomenological Monte Carlo renormalization group based on finite-size scaling, the critical temperature and the magnetic critical exponent are estimated as T c / J =2.150±0.006 and y H =1.88±0.02. It is shown th…
We present results of absorbance measurements in the range of 300--900 nm on submicrometer-size solid silver needles with aspect ratios near 7:1. The needles have parallel major axes and are formed on a transparent substrate. The needles are modeled as prolate spheroids with shapes determined from electron micrographs…
M\"ossbauer spectroscopy (MS) in $^{119}\mathrm{Sn}$ and $^{129}\mathrm{I}$ was employed to investigate the evolution and properties of the high-pressure amorphous-metallic phase of ${\mathrm{SnI}}_{4}$. Measurements were carried out at pressures up to 27 GPa using diamond-anvil cells. Both MS probes detect the onset…
In optical coating calculations, a 2 x 2 matrix formalism is generally used to describe the effect of each layer on the electromagnetic field. In current applications, the layers are considered homogeneous, and, therefore, the matrix used is restricted to this particular case. In this paper, a 2 x 2 matrix describing…
A time-domain light scattering study of acoustic and Mountain modes in glycerol is reported. By using light-scattering angles between 0.89° and 88.9°, a wide range of acoustic frequencies is sampled. The data also yield information about time-dependent density responses to stress and to heat (the latter is the time-de…
We have measured the low-temperature thermal conductivity and specific heat of ${\mathrm{CdGeAs}}_{2}$ to investigate the influence of coordination number on the thermal properties of amorphous solids. ${\mathrm{CdGeAs}}_{2}$ is tetrahedrally bonded in the crystalline state and strong evidence exists that this local o…
Detailed studies have been made of the luminescence properties of ${\mathrm{Eu}}^{3+}$ ions in Ca(${\mathrm{PO}}_{3}$${)}_{2}$ glass excited into the $^{5}\mathrm{D}_{1}$ manifold by a tunable dye laser at 77 K. The observed excitation-wavelength dependence of the intensities and energies of the fluorescence lines is…
Macroscopic magnetic measurements, Mössbauer, and neutron diffraction studies have been carried out on BaCoxZn2−xFe16O27 [(Zn−Co)2-W] single-crystal hexaferrites. The extrapolated saturation magnetization values σs(0) are slightly lower than those found in the literature. Such differences have been justified as due to…
Absorption spectra measured between 0.3 and 6.7 \ensuremath{\mu}m are reported for ${\mathrm{Gd}}^{3+}$, ${\mathrm{Nd}}^{3+}$, and ${\mathrm{Cr}}^{3+}$ in single-crystal gadolinium scandium gallium garnet, ${\mathrm{Gd}}_{3}$${\mathrm{Sc}}_{2}$${\mathrm{Ga}}_{3}$${\mathrm{O}}_{12}$, at various temperatures. Energy lev…
A light scattering study is presented on static and dynamic interactions between monodisperse, charged silica spheres suspended in an optically matching, salt free mixture of ethanol and toluene up to volume fractions of 10%. The static structure factor S(K), well described by calculations in the RMSA approximation, i…
Fracture testing of silicon cantilever beams (thicknesses 10–20 μm) was performed in situ in a scanning electron microscope by means of an equipment specially designed for this purpose. Beams of various sizes and orientations (〈011〉 and 〈001〉) were manufactured in Si (100) wafers by two different micromachining proced…