Materials Literature
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Thermal conductivity measurements on high-purity SiC and impure Si and SiC have been made over the temperature range from 3° to 300°K. These results show that the thermal conductivity K, of the highest purity SiC is intermediate between those of pure Si and pure diamond, and at 300°K is greater than that of copper. Th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and Fluorescence of Some Trivalent Lanthanide ComplexesL. R. Melby, N. J. Rose, E. Abramson, and J. C. CarisCite this: J. Am. Chem. Soc. 1964, 86, 23, 5117–5125Publication Date (Print):December 1, 1964Publication History Published online1 May 2002Published inissue…
Measurements have been made of the crystal-field splitting of the $^{7}F_{J}$ energy levels of the $4{f}^{6}$ configuration of the ${\mathrm{Sm}}^{2+}$ ion which is dissolved in a number of alkali-halide lattices. Crystal-field term assignments were made from the results of polarized-emission measurements. Observed cr…
Luminescence observed upon low-temperature x-ray excitation of alkali-halide crystals has been identified as due to radiative electron-hole recombination in the perfect lattice. In KCl the emission spectrum is a single band, while in KBr, KI, and NaCl there are two bands. In crystals containing self-trapped holes, opt…
The use of the Kramers-Kronig relation in the analysis of reflectance data is discussed briefly. The recent results of Walker and Osantowski for diamond are reanalyzed and found to be in some error. New data are presented which appear more consistent with the expected optical behavior of diamond.
New high pressure forms of the sesquioxides of holminum, erbium, thulium, ytterbium, lutetium, and yttrium have been obtained by exposure of the C-type sesquioxides to pressures between 25 and 40 kilobars and temperatures between 900 degrees and 1020 degrees C. X-ray diffraction analysis shows that these new high-pres…
Abstract The type of stress pulse produced when a liquid mass strikes a solid at high velocity is first examined. Compressible behaviour, giving rise to a sharp peak of pressure, is found to occur in the initial stages of the impact. The duration of this peak depends on the dimensions and impact velocity of the liquid…
Moths, by virtue of the loose scales that cover their wings and bodies, are admirably adapted to elude capture by orb-weaving spiders. Rather than sticking to the web, they may simply lose some of their scales to the viscid threads, and then fly on. Other insects, covered with detachable hairs or waxy powder, are simi…
The theory developed by Ziman for the scattering of phonons by electrons is extended to high temperatures using the formalism of Klemens and Callaway. The theory is applied to the experimental results recently published by Dismukes et al. on the effect of doping on the thermal conductivity of Ge-Si alloys. After subtr…
Experimental photoemission data from copper and silver are presented and interpreted in detail in terms of the calculated band structures over a photon energy range from 1.5 to 11.5 eV. It is shown that nondirect optical transitions are stronger than direct ones in both metals. In fact, the only direct optical transit…
The electron paramagnetic resonance of Re4+ in single cubic crystals of K2PtCl6 at wavelengths of 3 cm, 1 cm, and 8 mm is reported. The experimental results were analyzed assuming the Re4+ ground state is a spin quartet with S=32 and I=52. The cubic spin Hamiltonian is given by H=gβH·S+AI·S+uβ{HxSx3+HySy3+HzSz3−15(H·S…
Absorption, fluorescence, and excitation spectra of aqueous solutions of europium(III) perchlorate, chloride, nitrate, ethylenediaminetetra-acetate, and diethylenetriaminepenta-acetate were investigated. The latter three anions readily form complexes and were examined over a range of concentrations. The organic anions…
The interpretation of the energies of excimer luminescence of some polyacenes is considered and it is shown that neither simple molecular exciton attitudes nor charge resonance attitudes can provide satisfactory agreement with experiment. The D2k excimer formed from D2h aromatics is investigated and it is shown that t…
The problem of surface diffusion-controlled whisker growth is considered in a moving frame of reference. In addition, diffusive exchange with the substrate, a problem not treated heretofore, is considered. The results are compared with experiment and with prior treatments of whisker growth. The possibility of occurren…
The absorption and fluorescence spectra of Eu3+ in single crystals of Y2O3 have been observed and analyzed. The intermediate-coupling free-ion energy levels for Eu3+, including the effects of the 46 singlet states of the 4f6 configuration, are presented for all levels appearing below 41 000 cm—1. The results obtained…
I have touched upon the great variety of crystal forms and dendritic forms in nature, have discussed the essential physics involved in the generation of these forms during either constrained or unconstrained crystal growth, and have shown how this knowledge helps in the classification of this seemingly infinite variet…
Abstract : Evidence is presented that the atomic arrangement of high-pressure FeVO4 is similar to that of ambientpressure FeNbO4. Evidence is presented in the form of comparing the indexing of high-pressure FeVO4 and the disordered wolframite FeNbO4, which indicates that FeVO4 crystallizes in the disordered wolframite…
In contrast to the extensive studies performed on AgBr and AgC1 l i t t le effort has been made to unders tand the nature of s t ructural disorder in AgI, CuC], CuBr and CuI. This is p r imar i ly a consequence of the comparat ive s t ructural s impl ic i ty of AgC1 and AgBr, as Table 1 i l lustrates. In t r ins ic th…
The structure of a synthetic iron mica, KFe~+(Fea+Sia)O10(OH)~, determined from visually estimated intensities, shows very slight departure from Pabst's idealized biotite structure. The sextuple cell formerly used to describe micas accounts for the observed twinning.
The lactic dehydrogenase of a strain of Streptococcus bovis specifically requires fructose-1,6-diphosphate for activity. Phosphate or fructose-1-6-diphosphate prevents inactivation of the dehydrogenase, but phosphate and other compounds cannot be substituted for the fructose-1,6-diphosphate required for activity. Lact…