Materials Literature
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The structural relaxation rates, which are crucial in understanding the liquid \ensuremath{\leftrightarrow} glass transition, are investigated within the free-volume theory. We discuss the origin of the observed dispersion of relaxation times and show that it is simply related to the dispersion of the total surface-to…
We persent tempeature measurements of the importnt parameter defming the properties of the semctic C* Phase in a series of schiff bases. The pitch of the helica texture is measured optically. The molecular tilt is deduced from optical observations and from X-ray measurements of the smectic layer thickness. The critica…
The solid state reactions that take place between many ceramics and metals can be utilised to produce strong vacuum-tight joints that maintain their strength and durability even at elevated temperatures. In this context platinum can play an especially important role because of its high melting point and resistance to…
The results are presented and discussed of previous and recent experiments concerning the mechanism of the anti ferroelectric phase transition in squaric acid. Special emphasis is laid upon an extended discussion of the static equation of state of the order parameter because of its importance for establishing microsco…
Cerium dioxide doped with Y3+ ions, which is of interest for its ionic conductivity, is here studied by anelastic methods. The internal friction peaks observed are analyzed into peaks A, B, C (with Hr = 0.64, 0.71 and 0.78 eV, respectively). Peak A, present at low Y3+ concentrations is established to be due to a YV Pa…
The reduction in the dielectric anomaly near Tc in improper ferroelectrics suggests that this behavior may be exploited to significantly enhance the figure-of-merit for pyroelectric infrared detection. This “reduction” is associated with a decoupling of the thermal and dielectric responses which, in turn, reflects the…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStrategy for the synthesis of cylindrical macropolycyclic hosts with hydrophilic interior surfaces: crown ether rings fused by the tetrahydroxymethylethylene (THYME) unitDavid M. Walba, Rodney M. Richards, Steven P. Sherwood, and R. Curtis HaltiwangerCite this: J. Am. Chem.…
Abstract Poly(methyl methacrylate) (PMMA) microspheres were swollen in methanol vapor, the swelling penetrant was quickly evacuated, and the subsequent relaxation of the polymer under vacuum was monitored by determination of the rate of settling of rapidly measured low pressure pseudoequilibrium CO 2 sorption isotherm…
Poly(vinyl chloride) resins are produced by four basic processes: suspension, emulsion, bulk and solution polymerization. PVC suspensions resins are usually relatively dust-free and granular with varying degrees of particle porosity. PVC emulsion resins are small particle powders containing very little free monomer. B…
Abstract Perfluoroalkyltin(IV) halides (RfSnX2I) were prepared in situ by the oxidative addition of perfluoroalkyl iodides to tin(II) halide in N,N-dimethylformamide. Aldehydes and ketones readily reacted with RfSnCl2I giving perfluoroalkylcarbinols in the N,N-dimethylformamide-pyridine system. RfSnF2I, however, did n…
Abstract Thermal polymerization of acrylamide was studied by differential scanning calorimetry. Latent heat of fusion Δ H f and enthalpy of polymerization Δ H p values were found to be 36 and −18.0 kcal mol −1 , respectively. The overall activation energy E for the polymerization was calculated to be 19 k cal mol −1 u…
Experimental and theoretical work on the transverse ballistic impact of Kevlar and nylon fabrics is presented in two parts. Part I is an experimental investigation into (a) the relation between the multi-layer and single layer impact; (b) the effect of fabric finishes; and (c) the effect of weave. A simple model of im…
Abstract 13C NMR spectra of chitin oligomers in aqueous solution were analyzed for a reference of assignment of solid state 13C NMR spectra of chitin and N-acyl chitosans, and also of 13C chemical shift data in aqueous solution.
The Manual presents a methodology for integrating projectile impact damage tolerance into aircraft structural design. The information is presented in three sections: (1) Description of Projectile Threats; (2) Analysis Methods for Predicting Structural Response to Projectile Impact; and (3) Design Guidelines for Impact…
A spherical Fabry Perot interferometer is used to determine the refractive index of argon to a few hundred bars, with a better accuracy than those obtained in preceding experiments.The first and second refractivity virial coefficients have been determined. Measurements have been made for eight wavelengths in the visib…
Alumina and silica powders were sintered at 1250° to 1460°C in the presence of liquid phases containing CaO, A1 2 O 3 , and SiO 2 . The data were analyzed using the equation D = K log t +C and the Arrhenius equation. The activation energy for sintering decreases with increasing amounts of liquid phase.
Abstract Preparations have been made of acid‐soluble collagens whose telopeptides have suffered different levels of proteolytic attack. The collagens with more intact telopeptides form fibrils more rapidly than those with degraded telopeptides. In addition, we have shown that a high molecular weight aggregate rich in…
A method has been developed that can be used to describe the volume of space occupied by a given molecule with a known conformational structure as it rotates about a defined axis. The packing requirements of these volumes of revolution have been utilized in the prediction of phase formation, particularly of the B and…
Pyroelectric-piezoelecric glass ceramics of polar materials like Li2Si2O5, Ba2TiGe2O8, Ba2TiSi2O8, and Various compositions in the systems Li2O-B2O3, Li2O-SiO2-ZnO, Li2O-SiO2-B2O3 have been prepared by oriented recrystallization of the glasses under a strong temperature gradient, providing a simple inexpensive process…
Abstract The materials problems of capacitor ceramics are discussed with emphasis on recent advances in scientific understanding of means of achieving higher dielectric constants, better voltage stability, use of cheaper electrode materials (Ag or Ag-rich Ag-Pd alloys) and lower sintering temperatures(for energy savin…