Materials Literature
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The thermoelectric properties of N-type and P-type Si-Ge alloys have been reviewed and detailed calculations for the efficiency of a thermoelectric generator made from a 70% Si-30% Ge alloy have been made over the temperature range from 300 to 1300 K. A model employing one valence band and two conduction bands has bee…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolyimide derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. 1. Synthesis and characterization of polyimides prepared with 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride or pyromellitic dianhydrideTohru Matsuura, Yoshinori Hasuda, Shiro Nishi, and Noriy…
A review is given of the formation, the crystal structure and the magnetic properties of several classes of rare earth based intermetallic compounds that lend themselves as starting materials of permanent magnets. These compounds include R 2 Fe 14 B, R 2 Fe 14 C and R 2 Co 14 B and the large class of ternary rare eart…
One of the (Bi 1/2 Na 1/2 )TiO 3 (BNT)-based solid solutions, Ba-modified bismuth sodium titanate, (Bi 1/2 Na 1/2 ) 1- x Ba x TiO 3 (BNBT), is studied for its dielectric and piezoelectric properties as a new group of lead-free piezoelectric ceramics. A rhombohedral (F α )-tetragonal (F β ) morphotropic phase boundary…
X-ray phase analysis was used for studying the reduction reaction of some metals by mechanicals alloying (MA) and solid state reaction. It is shown that it is possible to obtain both amorphous (Mo, W) and crystalline (Pb) metals as a result of such processes. An assumption is set forth that the amorphous state of meta…
The structure of a non-stoichiometric copper compound Cu 1.8 S (digenite) has been studied by X-ray diffraction. Although digenite has a cubic anti-fluorite structure, satellite reflections were seen along the (111) c axis. Single-crystal X-ray diffraction data, including first- and second-order satellites, were colle…
Thin films ranging from 400 nm to 4 μm thickness of poly( p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by the optical waveguide spectroscopy. These polyimide films, most prominent for potential applications as t…
Detailed information on the electronic structure of the neutral substitutional gold center in silicon (${\mathrm{Au}}^{0}$) has been revealed from Zeeman studies of the donor and acceptor excitation spectra at 793 and 611 meV, respectively. The center is paramagnetic, S=1/2, with ${\mathit{g}}_{\mathrm{\ensuremath{\pa…
The potential at which conducting polymers can be electrochemically doped to the conducting state shifts slowly then the material is maintained in the insulating state. A logarithmic law for the shift as a function of the wait time in the insulating state has been observed over the range ${10}^{\mathrm{\ensuremath{-}}…
We have developed a novel computational scheme that allows direct numerical simulation of polymer-colloid mixtures at constant osmotic pressure. Using this technique, we have studied the entropic attraction that is caused by ideal polymers dissolved in a simple (hard-sphere) colloidal dispersion. In particular, we stu…
Abstract Weather‐induced degradation of polymer properties is caused by all the factors of weather, which include solar radiation, temperature, humidity, wind, rain, environmental pollutants, thermal cycling (cold night and hot days), and sand abrasion. Linear low‐density polyethylene (LLDPE) is exposed to natural wea…
Abstract The ambient temperature structure–property orientation behavior in two different polyureaurethane polymers (one cross‐linked and one linear) was measured by using infrared dichroism along with mechanical response. Thin films (plaques) thermally compression‐molded from TDI‐polypropylene (PO) flexible water‐blo…
Abstract The Avrami equation has been widely used to describe polymer crystallization kinetics. However, the equation accurately fits experimental data only during the early stages of the crystallization process, and is unsuccessful in describing the entire process because it does not take into account secondary cryst…
Abstract Epoxy–imide resins have been obtained through the reaction of Araldite GY 250 (diglycidylether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac‐epoxy resin; polyfunctional) with bis(carboxyphthalimide)s derived from 4,4′‐diaminodiphenylsulfone, 3,3′‐diaminodiphenylsulfone, 4,4′…
Abstract Structural characteristics of the silk fibroin fiber‐modified with epoxide treatment were elucidated by refractive index measurement, differential scanning calorimetry, and thermomechanical analysis and on the basis of strength–elongation measurements. The four epoxides used were glycidol (G), ethylene glycol…
By computer simulation of the electron spin resonance spectra of even and odd isotopes of Mo 5+ in WO 3 -BaO-P 2 O 5 glasses of various compositions, the characteristics of the distributions of g values and hyperfine structure parameters have been deduced. Using these data, the characteristics of the distributions of…
By measuring the complex dielectric susceptibility over 15 decades in frequency we compare the \ensuremath{\alpha} relaxation in low-molecular-weight glass-forming liquids and polymers. To describe the scaling behavior of the \ensuremath{\alpha} relaxation, a minimal set of four parameters is necessary, the mean relax…
Two modified forms of carbon were quenched by a rapid-cooling technique from graphite sheets shock-compressed to 65 gigapascals and 3700 K. One form, ;;n-diamond," which was obtained from the most rapidly cooled part, has a crystal structure close to that of cubic diamond. The other form, found in the relatively slow-…
Absorption and luminescence spectra of phenanthrene have been investigated under pressures up to 2.4 GPa, using a diamond anvil cell. Free-exciton luminescence which is observable at ambient pressure is replaced by self-trapped-exciton luminescence at pressures higher than 1.8 GPa. From this fact it is suggested that…
[CoNd 2 (μ-C 2 H 3 O 2 ) 8 (H 2 O) 10 ] cristallise dans P1 avec a=8,243, b=10,368, c=11,497 A, α=111,64, β=107,94, γ=93,45 o , Z=1; affinement jusqu'a R=0,024. Les chaines sont construites de prismes rhomboedriques deformes [NdO 7 (OH 2 ) 2 ], chapeautes sur 3 faces, et d'octaedres CoO 6 presque reguliers