Nonlinear Optic Nanocomposites Based on Oxide Glasses

The first nonlinear optic nanocomposite based on a low-melting vitreous matrix and a ferrielectric crystal has been obtained. The matrix consists of lead-borate glass and the filler is single-phase powder of ferrielectric KNbSi₂O₇. The quadratic optical nonlinearity of composites was studied depending on temperature and time of dissolution of crystals in the glass matrix. Conditions for producing transparent nanocomposites that generate the second optic harmonic are identified.     

Product composition of the dynamic conversion of brown coal in supercritical water

The product composition of the dynamic conversion of brown coal, which was continuously supplied as a water-coal slurry to a flow reactor at 30 MPa, was studied. The temperature of water and coal particles was increased from room temperature to 400°C (top part of the reactor). The conversion of the organic matter of coal was ～48%, and the products collected at the reactor outlet consisted of solid tar components, substances dissolved and emulsified in water, and volatile substances, whose major constituent was CO₂. The composition of solid tar components and oils was determined.     

Acid- and alkali-catalyzed tannin-based rigid foams

Acid- and alkali-catalyzed polyflavonoid tannin-based rigid foams were prepared. These foams have comparable physical and mechanical properties to the synthetic phenolic rigid foam used as a comparative standard. The fluid polymer phase was based on a mimosa tannin-formaldehyde resin with a minor addition of a fortifier resin. Expansion of the fluid phase was brought about by a physical blowing agent, whereas dimensional stabilization was achieved through cross-linking at the desired density. In the case of the acid-catalyzed foam, a heat-generating agent in the form of furfuryl alcohol was employed. The polymer composition of tannin–formaldehyde/urea–formaldehyde systems as a function of pH was predicted from the respective gel times and rate constants, i.e., above pH 7, the copolymer proportion will tend to 100% and, that at pH 3.4, the polymer blend proportion will tend to a maximum. © 1994 John Wiley & Sons, Inc.     

Unfired dolomite refractories with increased hydration resistance

Conclusions The use of dolomite burnt in grain form for the manufacture of unfired goods with a tar bond makes it possible to obtain refractories with a high hydration resistance and with high physicomechanicai properties. Coal tar with a 65–70% pitch content should be used as a bonding agent.Sintered grain dolomite should be added to the batch without being ground, preferably in combination with finely ground metallurgical magnesite or magnesite-dolomite clinker.     

Comparison between some empirical equations of state for polymers

Some commonly used empirical equations of state for polymers are considered: the Spencer-Gilmore equation with two and three adjustable parameters, the Whitaker-Griskey equation, and the Rehage-Breuer equation. Also, a new equation is proposed: the Inverse Volume equation. These equations are evaluated with regard to fitting experimental P-V-T data and agreement with experimental data on isothermal compressibility and thermal expansion coefficient. The adjustable parameters for each equation are determined with the help of Rosenbrock's optimum-seeking technique. Analysis of the residuals on specific volume for a variety of materials suggests that the Spencer-Gilmore equation with three adjustable parameters, the Rehage-Breuer and the Inverse Volume equations yield the smallest and most random residuals and thus the least systematic error. The same three equations mentioned above yield results in good agreement with experimental isothermal compressibility data. However, among all the equations considered in this study, the Inverse Volume equation yields the best agreement with experimental thermal expansion coefficient data. Furthermore, it is the only equation to correctly predict the rise in thermal expansion coefficient with increasing temperature.     

EMI shielding of intinsically conductive polymers

Results of this study, in which shielding efficiencies are measured for a number of blends containing various conductive fillers including intrinsically conductive polymers, are reported. It is shown that a very high level of shielding performance can be achieved by use of intrinsically conductive polymers in thermoplastic blends and that the most reliable measure of this performance is obtained from far-field shielding measurements. However, near-field measurements provide a useful method for comparing the relative shielding effectiveness of different samples. A PVC blend containing nearly uniformly dispersed intrinsically conductive polymer proved to be the best performing sample.     

Kinetics of the decomposition of total aliphatic waxes in olive oil during deodorization

Changes in the content of aliphatic waxes during industrial deodorization and/or physical refining of bleached olive oil were studied in an experimental discontinuous pilot plant of 250 kg deodorizer using nitrogen as stripping gas in place of steam. The kinetic constants for the decomposition of waxes during the deodorization process were determined. The reaction orders studied are zero (or can be considered zero) within the working interval. The values of rate constants, activation energy, frequency factor, increment of activation Gibbs free energy, activation enthalpy, and activation entropy are established.     

The electrochemistry of nitrate-amide melts: Reactions of nickel and copper in nitrate-amide melts

Copper and nickel may be electrodeposited from their ions in solution in nitrate-amide melts at room temperature. In the ammonium nitrate-acetamide-urea melt at 23°C, the reduction to the metal competes with the corrosion reaction at low rates and with the reduction of the ammonium and nitrate ions of the melt at high current densities. Two distinct types of nickel complexes are found in solution. The nickel complex formed by the corrosion reaction is bound by at least one ammonia ligand. Nickel complexes formed by dissolving the halide in the melt show evidence of coordination by less strongly bounding ligands, probably by amides. Similarly, the visible spectra of copper chloride in solution suggest that the cupric ions are coordinated primarily by amides. The copper corrosion reaction produces a complex with a spectra distinctly different from that of cupric chloride in solution. The shift in absorption maxima suggests that the copper complex formed by the corrosion reaction has at least one ammonia ligand in the coordination sphere.