Development of rugged and crack-resistant structures in ceramics (review)

The paper considers methods for increasing crack resistance in ceramics, including microcracking in local stress areas, reorientation of crack movement, polymorphous martensite transition in partly stabilized zirconium dioxide, and bridging of cracks with a plastic phase or crystals with highly nonisometric shape (plates, needles, fibers) in the context of the irreversibility and nonequilibrium, producing self-organization, and a synergetic approach. The possibility of increasing crack resistance due to diffuse polymorphous transitions, twinning, and mechanochemical reactions is discussed.     

Design of polymeric dispersants for waterborne coatings

Block and random copolymers of ammonium methacrylate and dimeth-ylaminoethyl methacrylate have been synthesized and tested as dispersants of various organic and inorganic pigments in formulations for waterborne paints. Blockiness of the co-monomer distribution is a prerequisite for good color characteristics in the final paint. It is however noteworthy that a tapered diblock (one-step anionic synthesis), a diblock copolymer with a regular change in composition from one block to the other one, has an interfacial activity quite comparable to the parent “pure” diblock copolymer (two-step anionic synthesis). The most interesting observation is that the poly(dimethylaminoethyl methacrylate) anchoring block can impart stability to dispersions of pigments as different as iron oxide, a blue Cu-phthalocyanine pigment, and a red organic pigment based on pyrrole in representative aqueous paint formulations. This type of diblock copolymer is promising for the design of universal dispersants. Center for Education and Research on Macromolecules (CERM), Sart-Tilman, B6, 4000 Liège, Belgium. Rijksstraatweg 31, P.O.Box 3, 2170 BA Sassenheim, The Netherlands.     

Adsorption processes in the technology of polymer composite materials with magnetic properties

The selection of a model of an adsorption solution was substantiated. Satisfaction of the Larionov criterion [3] indicates that the selected parameters of the adsorption phase do not contradict the physical picture of adsorption. The basic thermodynamic characteristics of adsorption of phenol-formaldehyde oligomer on the solid surface of ferromagnetic disperse fillers were calculated. The correlation of the limiting adsorption value, adsorption layer thickness, and adhesive strength in polymeric magnetic materials was demonstrated. Translated from Khimicheskie Volokna, No. 3, pp. 50–52, May–June, 1998.     

Characteristics of phase transitions in poly[bis(trifluoroethoxy)phosphazene]

The data on phase transitions in bis(trifluoroethoxy)phosphazene were examined and generalized. Their nature was determined and the mechanism of the transitions was described. Schemes were proposed for the phase transitions that take into account the conditions of fabrication and thermal history of the samples. Translated from Khimicheskie Volokna, No. 5, pp. 24–27, September–October, 1998.     

Efficiency of using ion-exchange fibre materials for removal of surfactants from wastewaters

A comparative analysis of the efficiency of removing surfactants from wastewaters by different fibre chemisorbents was conducted. In studying the chemical stability of the chemisorption materials with respect to aggressive media, their good resistance to weakly basic and acid media was determined. Translated from Khimicheskie Volokna, No. 4, pp. 48–50, July–August, 1998.     

Development of a novel metal hydride–air secondary battery

A laboratory metal hydride/air cell was evaluated. Charging was via a bifunctional air gas-diffusion electrode. Mixed nickel and cobalt oxides, supported on carbon black and activated carbon, were used as catalysts in this electrode. At 30mAcm–2 in 6m KOH, the air electrode potentials were –0.2V (oxygen reduction) and +0.65V (oxygen evolution) vs Hg/HgO. The laboratory cell was cycled for 50 cycles at the C/2 rate (10mAcm–2). The average discharge/charge voltages of the cell were 0.65 and 1.6V, respectively. The initial capacity of the metal hydride electrode decreased by about 15% after 50 cycles.     

Charge–discharge characteristics of polythiopheneas a cathode active material in a rechargeable battery

Polythiophene films were electrochemically deposited on glassy carbon substrates under potentiostatic control and used as cathode active material together with a Zn anode in a rechargeable battery with propylene carbonate, Zn(ClO4)2, LiClO4 electrolyte. Charge–discharge characteristics were studied. The average discharge voltage of the polythiophene/Zn cell was 1.25V. In the low current density region (i.e. 10–50μAcm?2) the cycling coulombic efficiency was above 95%, but in the fast charge–discharge region, where current densities were 0.1–0.5mAcm?2, the coulombic efficiency decreased to 55% with increasing discharge rate. Additionally, it was found that the cyclic coulombic efficiency was a function of the charging depth.     

AN EMPIRICAL APPROACH TO THE PREDICTION OF ELUTRIATION OF FINES FROM FLUIDIZED BEDS AT DIFFERENT FREEBOARD LEVELS

An empirical approach has been developed to predict the total entrainment flux at different levels of freeboard height. The approach is based on the results of experimental investigations carried out in a 152 mm diameter column, with FCC as the feed powder. The powder was fluidized at superficial gas velocities of 0.2 m/s and 0.7 m/s.     

Absolute determination of reaction mechanisms by in situ measurements of reaction intermediates

This paper presents a general methodology to determine reaction mechanisms using in situ measurement of concentration and reaction rate of intermediates. The criteria for testing the validity of a reaction sequence are discussed. An example is given for a heterogeneous catalytic reaction, the decomposition of ozone on manganese oxide. This revised version was published online in August 2006 with corrections to the Cover Date.