Materials Literature
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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…
Abstract The collagen‐like peptides ( L ‐Pro‐ L ‐Pro‐Gly) n and ( L ‐Pro‐ L ‐Hyp‐Gly) n with n = 5 and 10, were examined in terms of their triple helix ⇌ coil transitions in aqueous and nonaqueous solvents. The peptides were soluble in 1,2‐propanediol containing 3% acetic acid and they were found to form triple‐helica…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElastic Moduli and Molecular Structures of Several Crystalline Polymers, Including Aromatic PolyamidesKohji Tashiro, Masamichi Kobayashi, and Hiroyuki TadokoroCite this: Macromolecules 1977, 10, 2, 413–420Publication Date (Print):March 1, 1977Publication History Published on…
Abstract Based on the X-ray diffraction analyses of 150 bottom samples from the area of the Atlantic Ocean influenced by the Amazon River, trends in the clay mineral composition were observed. For the < 2 micron size fraction of samples from the mouth of the Amazon River for a distance of 1,400 kilometers along…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagic-Angle 13C NMR Analysis of Motion in Solid Glassy PolymersJacob Schaefer, E. O. Stejskal, and R. BuchdahlCite this: Macromolecules 1977, 10, 2, 384–405Publication Date (Print):March 1, 1977Publication History Published online1 May 2002Published inissue 1 March 1977https…
En el presente trabajo, se investiga en micro-hormigones frescos preparados con esqueletos granulares compactos y agregados normales, la influencia de la finura de molido del cemento portland en la consistencia del cuerpo compuesto fresco, de distintas relaciones agua/cemento. La relación agua/cemento de la pasta cong…
En trabajos anteriores (1), (2), (3) y (4) se estudiaron por espectroscopia infrarroja las fases sintetizadas del clínker, el propio clínker, el cemento hidratado hasta una edad de 4 años y con distintas proporciones de yeso y CaCl2, hasta una edad de 28 días. En el presente trabajo, con el fin de poner de manifiesto,…