Materials Literature
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStable heptamethine pyrylium dyes that absorb in the infraredG. A. Reynolds and K. H. DrexhageCite this: J. Org. Chem. 1977, 42, 5, 885–888Publication Date (Print):March 1, 1977Publication History Published online1 May 2002Published inissue 1 March 1977https://pubs.acs.org/d…
Abstract The properties of mixtures of poly(2, 6‐dimethyl p‐phenylene oxide) and poly(styrene) have been measured by DSC, density gradient, dynamic mechanical response, and tensile testing. The mixtures are found to have single glass trasitions that vary continuously with the composition. They also have small negative…
Abstract Nylon 6 can exist in either of two stable crystal structures, the α crystal with hydrogen bonds between antiparallel chains or the γ crystal with hydrogen bonds between parallel chains. Both structures have been observed in the same highly annealed fiber, suggesting that the polymer should not be regarded as…
The effects of Dy doping and sintering parameters on the properties of BaTiO 3 ceramics were studied. The average grain size decreases with increasing Dy content and is controlled at ∼1.5 μ m by 0.8 at.% Dy. The Curie temperature change, associated with ≤1.2 at.% Dy, is <3°C. The dielectric constant is ∼2600 for sp…
Abstract The photodegradation of cellulose acetate fibers by ultraviolet light in vacuo at 77°K and at ambient temperature was studied. Three kinds of light sources with different wavelengths between 2353 and 6000 Å were employed. ESR studies at 77°K show that several kinds of free radicals are produced from cellulose…
Fluorite, halite, periclase, and sylvite have been abraded in a wind tunnel by windblown dust from the "normal" air of the intake room plus or minus introduced silt-sized particles of calcite, barite, or snow. The results indicate that the effective kinetic energy of a projectile and the bond strength of the target-ra…
The evolution of enthalpy of As 2 Se 3 glass during structural relaxation in the glass transition region was measured via differential scanning calorimetry for two types of time‐temperature programs: rate‐heating at 10 K/min following a cool at a constant rate (‐20 to ‐0.31 K/min) and isothermal annealing following a…
The first order Raman spectrum of the layer type semiconducting compound, WSe 2 , has been investigated. The frequencies of the Raman active A 1g , E 2g 1 E 1g , and E 2g 2 modes have been determined to be 253,250, 178, and 25 cm −1 respectively. Using a scaling relation the results have been compared to the values ob…
Abstract The effects of hydrostatic pressure on the shear, compressive, and tensile stress‐strain behavior of both amorphous and crystalline polymers are reviewed and illustrated. For polymers with T g near to but below ambient temperature, there is a steep increase of modulus with pressure and, above some critical pr…
In the transition between the CsCl-type and NaCl-type structures, caesium chloride retains a definite orientation relation of [110] (CsC1) || [100] (NaC1) and [001] (CsC1) || [011] (NaCl). The closest-packing planes of both structures are retained in the transition and have an approximately equal density of ions at th…
Adsorption of N 2 and water vapor was studied in completely hydrated tricalcium silicate and in fully hydrated tricalcium silicate from which Ca(OH) 2 had been extracted. Compared with results obtained using N 2 , water vapor adsorption led to increased values for small‐pore volume, peak shifts to smaller sizes, and d…
Abstract Nylon 46 was synthesized from the salt of 1,4‐diaminobutane and adipic acid. High molecular weight polymers could be obtained by reaction for 1 hr at 215°C in a closed system and at least for 1 hr in vacuo at a temperature in the range 290–305°C. The reactions at 290°C were found to have taken place in the so…
The solubilities of apatites of varying compositions were measured as a function of pH in seawater at 10° and 25°C. Wide ranges of solubilities were observed; at pH = 7.4 they ranged from 0.4 to 11 µ M PO 4 ‐P liter −1 , depending on the nature of the samples. Results are interpreted in terms of complex coatings forme…
A three-dimensional analysis is presented for high velocity impact problems. A Lagrangian finite-element technique is formulated for tetrahedron elements subjected to large strains and displacements. The effects of material strength and compressibility are included to account for elastic-plastic flow and wave propagat…
Abstract Massachusetts Institute of Technology Cambridge, Massachusetts 02.139 The phenomenology of plastic deformation in glassy polymers is described, and a theory based on a molecular model for such deformation is presented and contrasted with other published theories. A phenomenological yield criterion is presente…
Abstract The dependence of stress‐strain curves on temperature and extension rate is first discussed qualitatively along with aspects of the fracture process. Considered thereafter are the strength and extensibility, measured over broad ranges of temperature and extension rate, of elastomers in several classes: (a) si…
Abstract Under uniaxial tensile load, the plastic deformation of unoriented crystalline polymers first transforms the lamellae into a fibrous structure. Usually the drawing is inhomogeneous with a neck propagating through the sample. The higher the draw ratio, the higher the axial elastic modulus as a consequence of t…
Abstract A method is presented for anticipating condition under which anomalous diffusion effects can be expected for amorphous polymer–solvent systems. The diffusion process is characterized by a dimensionless group called the diffusion Deborah number, and a method for calculating this dimensionless number is present…
The microstructure of (Co,Cu,Fe)7Sm magnets has been characterized at various states of aging by transmission electron microscopy. At peak magnet properties, the magnet consists of cells of 17 : 2 phase about 500 Å in diameter, separated by a thin continuous fully coherent 5 : 1 boundary phase. This structure evolved…
Abstract Using radioactive tracer Fe‐59 and measuring rest activities after sectioning, the tracer diffusivities of Fe in almost single crystalline magnetite Fe 3‐Δ O 4 have been measured as a function of temperature and oxygen partial pressure. The measured curves log D Fe * /log p O2 all exhibit a minimum in the tem…