Materials Literature
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The effect of electron traps on the current-voltage (J-V) relationship and the charge distribution in insulators, under conditions of space-charge-limited current flow, is well understood. This paper extends the consideration of trapping effects into the region of emission-limited current flow. Trapped space charge di…
The theory of the Portevin—Le Chatelier effect is extended to include the effect of dislocation multiplication. The dislocation density ρ in Cu-3.2 at. % Sn is measured as a function of true plastic strain ε by the transmission electron microscopy of thin films, and the relation ρ= 4.73 × 1011 ε1.17 established. The e…
The steady-state flow stress, σ, of commercial purity aluminium was determined by extrusion over a range of temperatures, T, from 255–616 °C, and strain rates, [Formula: see text], between 0.1–10 sec −1 . The data are shown to fit the relationship[Formula: see text]where A, α, and n′ are constants. The activation ener…
1. The diatom, Hantzschia virgata, appears on the surface sands of Barnstable Harbor, Mass., during daytime low tides. Surface accumulations of this organism reach such concentrations that the sand takes on a golden-brown color. As the tide returns the cells re-burrow into the sand. 2. The cells can be prevented from…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCrystal structures of the red, yellow, and orange forms of mercuric iodideGeorge A. Jeffrey and Marcus VlasseCite this: Inorg. Chem. 1967, 6, 2, 396–399Publication Date (Print):February 1, 1967Publication History Published online1 May 2002Published inissue 1 February 1967htt…
Current theories of work hardening in stage II of stress–strain curves of f.c.c. crystals are reviewed critically. A detailed account is given of a theory described previously in outline by Hirsch (1964).
Abstract In the part installment of the present paper, the authors formulated the dynamics of melt spinning by introducing a set of fundamental equations that consist of the equations of heat, force, and material balances. Some steady‐state solutions were also given. Additional steady‐state solutions corresponding to…
Chloramphenicol-resistant strains of Escherichia coli which carry the episomal resistance transfer factor R inactivate the antibiotic by enzymatic acetylation. In the presence of chloramphenicol and acetyl coenzyme A, cell extracts catalyze the formation of both a monoacetyl and a diacetyl derivative of chloramphenico…
Polycrystalline specimens of α-phase copper–aluminium alloys of varying composition, amalgamated with mercury, have been deformed in tension in a soft tensile machine. In all cases, brittle intergranular failure occurred at stresses and strains below those required for fracture in air, the degree of embrittlement incr…
When excited by the proper wavelength, Tb+3 in Y2O3 transfers some of that energy to Eu+3 centers which subsequently emit 6125-Å light. The actual mechanism involves an initial high-energy excitation state (a broad band, indicating a perturbed activator state) which relaxes to one of the 5DJ states, from which emissio…
The approximate corona-starting relation for concentric cylinders Ec/δ = A + B/√rδ, long established at lower gas densities, has been checked in air to δ = 35 over the respective ranges of inner and outer cylinder diameters of 0.0178 to 0.635 cm and 4.72 to 15.40 cm (Ec = corona-starting field at surface of inner elec…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of Metal Hydrides. II. Spectroscopic Studies of Fluorovinylplatinum(II) DerivativesH. C. Clark and W. S. TsangCite this: J. Am. Chem. Soc. 1967, 89, 3, 533–539Publication Date (Print):February 1, 1967Publication History Published online1 May 2002Published inissue 1…
The thermal expansions of TiB 2 , ZrB 2 , HfB 2 , NbB 2 , and TaB 2 were measured to temperatures above 1600°C by an X‐ray method. Lattice constants were measured for each compound; each had the AlB 2 ‐type hexagonal structure. The mean linear thermal expansion coefficients were calculated from the data and are compar…
Solid solution formation in the system BaTiO 3 —KnbO 3 was established by X‐ray diffraction and dielectric measurements. Solid solutions with cubic symmetry were observed in the composition range from 4 to 90 mole % KnbO 3 at room temperature. The lattice parameter for the BaTiO 3 solid solutions increased with increa…
The processes leading to a spark breakdown or corona discharge are discussed very briefly. A quantitative breakdown criterion for use in high-voltage design is derived by which spark breakdown or corona starting voltages in nonuniform fields can be calculated. The criterion is applied to the sphere gap, and it is show…
The effects of temperature, strain rate, and purity on the yield and flow stresses of α titanium at low temperatures (T < 0.4 T M ) are examined to ascertain the rate controlling dislocation mechanism. The effect of impurity content on the thermal component of the yield and flow stresses increases with the decrease in…
Magnetic properties in VO 2 have been studied in the temperature range from 100 to 380°K with the Mössbauer effect measurement of Fe 57 doped in VO 2 . Above and below the transition temperature, no internal field is observed. The observation indicates that VO 2 is paramagnetic even below the transition temperature an…
The elastic properties of molybdenum single crystals have been measured using thin-rod resonance techniques as a function of temperature from −198° to over +650°C. Molybdenum behaves in a normal manner over this temperature range. Its elastic stiffness coefficients, with the exception of C12 which increased 3%, decrea…
The nucleation and crystallization of Li 2 O‐Al 2 O 3 ‐SiO 2 glasses containing TiO 2 were investigated using transmission electron microscopy of thin sections produced from bulk samples. Phase separation occurs during cooling from the melt, and on heating, a large number of titanium‐aluminum crystals approximately 50…
The stress–strain behavior of single crystals of tantalum, niobium, and molybdenum has been studied in both tension and compression in the temperature range 4.2–400 °K. The crystals were stressed in both the [Formula: see text] and the [Formula: see text] directions.At high temperatures, the yield stress of all three…