Gluing of sintered parts made of silicon nitride

Problems of gluing parts made of silicon nitride are considered. The quality of glued joints is estimated. The effects of the composition (the types of binder and filler), the technological parameters (thickness of the joint, roughness of the glued surfaces, porosity of the parts), and the test conditions are considered. The technology for gluing parts made of RBSN and HP parts made of Si₃N₄ and results of tests of glued joints are described.Translated from Ogneupory, No. 4, pp. 18 – 20, April, 1996.     

On Pontryagin’s example with many evadors

The problem of pursuit of a single evador or several evadors by a group of pursuers with equal capabilities of all players is considered in Pontryagin’s example under the condition that the characterstic equation has at least one positive root. Some sufficient conditions of the solvability of the pursuit problems are obtained.     

Corundum-zircon crucibles for induction melting of nickel alloys

Refractories and Industrial Ceramics -     

Electro-oxidation of two reactive azo dyes on boron-doped diamond electrode

Electrochemical oxidation (decolorization/degradation) of blue and red commercial reactive azo dyes was carried out on boron-doped diamond (BDD) electrode. The effect of various quantities of FeSO(4) was investigated in the electro-Fenton reaction on BDD. Progress of dyes degradation during the electrolysis and electro-Fenton reaction was monitored by UV-visible absorption and by estimation of the chemical oxygen demand (COD). Direct electrolysis showed a limiting capacity for red and blue dye removal even at high current densities, e.g. maximum red color and COD removal were 70 and 20%, respectively at 30 mA cm(-2) after 300 min. Higher red and blue color removal efficiencies were achieved by electro-Fenton oxidation. Current density of 30 mA cm(-2) in the presence of 0.05 mmol/L of FeSO(4) resulted in the red color and COD removal of 98 and 96%, respectively. The optimum FeSO(4) concentration for the electro-Fenton reaction was determined to be 0.05 mmol/L. Instantaneous current efficiency (ICE) in the presence of FeSO(4) was almost three times higher than for experiments carried out without FeSO(4).     

Laminar Flow Past a Circular Cylinder under the Effect of Nonstationary Jet Efflux to the Near‐Wake Region

Changes in a laminar flow past a circular cylinder under the effect of jets blowing out to its rare region have been studied numerically. Jet efflux was caused by a return flow of a part of the incoming flow in the inner channels of the cylinder due to the pressure difference between its front and end stagnation points. The channels connected the inlet window formed in the zone of the front stagnation point with two outlet windows on the backside surface of the cylinder. The influence of the coordinates of the jets issuing through the outlet windows and dimensions of the inlet and outlet windows on variation of the drag and lift coefficient and distribution of the coefficients of pressure and friction on the cylinder surface has been considered. It is shown that under the effect of blowing out the cylinder drag decreased by 4% and the amplitude of buoyancy force oscillations decreased by 40%.     

The microstructure and physicotechnical characteristics of fused and cast corundum

Conclusions Certain physicotechnical properties of Cor-93 material and their interrelationship with microstructure were investigated. Base plates of Cor-93 material, which are being used successfully on a unit for isothermal deformation of high-temperature strength alloys, were produced. The use of Cor-93 as a constructional material for large ceramic parts for a service temperature up to 1200°C and absorbing a unit load up to 150 MPa is recommended.Translated from Ogneupory, No. 3, pp. 50–52, March, 1982.