Processes of the Collision Interaction between Ceramic Particles Being Crushed in a Circulation Pneumatic Crusher

A new circulation pneumatic crusher capable of producing submicron powders of refractory materials is presented. A mathematical model is constructed for the dynamic breaking of ceramic macroparticles. This model allows the basic laws of shock-wave crushing in the circulation pneumatic apparatus to be analyzed.__________Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 3, 2005, pp. 327–333.Original Russian Text Copyright © 2005 by Belov, Biryukov, Roslyak, Yugov, Afanas’ev.     

Concurrent effect of microporosity and chemical structure on the equilibrium sorption properties of cellulose-based hydrogels

Polyelectrolite hydrogels are crosslinked polymers which display high sorption capacity in water and water solutions. They are widely used in the marked of personal hygiene products, as well as in other biomedical and industrial applications. In the most industrial application they are not biodegradable and prepared starting from acrylamide.In this work, the chemical-physical analysis of a novel class of natural polymers-based microporous superabsorbent hydrogels has been presented. The main focus is the definition of the relationship between material's chemical-physical structure and its equilibrium sorption properties.The effect of the variation of the degree of crosslinking, the polyelectrolyte nature of the backbone and the hydrogel microporosity on its swelling properties has been analysed, and a good agreement with the theoretical statements has been displayed.The effect of the ionic strength and the pH of the external solution in contact with the hydrogel on its equilibrium sorption properties has also been assessed, and an high sensitivity to these variations was detected for all the tested chemical compositions and physical structures.This work have to be considered part of the efforts towards the reduction of the environmental impact of the large scale consumption industrial polymer based products.     

Interfacial strength and chemistry of additive-free silicon nitride ceramics brazed with aluminium

Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints. The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints.     

Transparent monolithic zirconia gels: effects of acetylacetone content on gelation

Transparent yttria-stabilized zirconia monolithic gels were synthesized under controlled conditions for hydrolysis and chemical polymerization. The influence of acetylacetone on the previous chemical reactions was explored, and a plausible explanation was proposed concerning the outstanding role of this additive during the gelation process. Small-angle X-ray scattering was used to estimate the size of the polymeric species and to investigate the influence of acetylacetone on the structure of the gels prepared.     

Calibrating high-vacuum gauges

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 19–20, June, 1989.     

Study of dielectric properties of RbNO3 single crystals

Dielectric properties, dielectric constant (k), dielectric loss (tan δ) and a.c. conductivity (σ) in the solution-grown single crystals of RbNO₃ are presented from room temperature to about 200°C covering the frequency range 10² to 10⁵ Hz. A broad peak observed in tan δ-frequency data between 10³ and 10⁵Hz is thought to be due to impurity-vacancy dipoles. The sudden rise of three parameters near 160°C is attributed to the known phase transition from trigonal to CsCl structure.