Electric insulating properties of refractory coatings obtained by flame spraying

Conclusions Coatings of alumina, aluminomagnesia spinel and zirconia have a sufficiently high electrical insulating capacity at 20–700°C.The purity of the material is important for the electrical resistance and dielectric loss of the coatings.Ceramic materials as a rule have a low thermal conductivity. Laminated cermet coatings made from alumina and nickel have a low thermal conductivity; they are electrically insulating in the direction perpendicular to the layers of metal and good current conductors and heat conductors over these layers. They can be used for removing heat from local overheated sites (hot spots) in special units.Coatings of titania with low coefficients of thermal conductivity [8] may be used for heat insulation and also as excellent current conductors in nonoxidizing conditions and at temperatures up to 100°C in oxidizing conditions.The investigation was carried out at the ceramics faculty of the University of Illinois under the direction of A. L. Friedberg.Translated from Ogneupory, No. 6, pp. 52–56, June, 1967.     

Anorthite insulating refractory

Conclusions A technology was developed for manufacturing heat-insulating refractories with an anorthite composition and an apparent density of 0.3–0.4 g/cm³ or more using kaolin, semihydrated gypsum and stabilized foam. The proposed method guarantees a reduction in the production cycle, yielding cheap insulating brick, and the possibility of mechanizing the production processes.Anorthite ultralightweight refractories in terms of their basic factors correspond to insulating products made by foreign concerns for service at 1100–1260°C.Translated from Ogneupory, No.5, pp. 36–40, May, 1970.     

Velocity of flame propagation upon development of hydrodynamic instability

On the basis of a theoretical analysis and numerical calculations, it has been shown that the dynamics of a flame surface under conditions of hydrodynamic instability can be represented as the interaction of a finite number of nonlinear configurations of the flame front. Their number is defined by the physical size of the system in which the flame propagates. It has been shown that the development of an initial plane front leads to a stationary regime at which the propagation velocity of the curved flame tends asymptotically to its limiting value independent of the size of the system in which burning takes place. This conclusion is based on the exact solution of the nonlinear equation describing hydrodynamic instability of flame. Institute of Thermophysics, Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 19–25, November–December, 1993.     

Statistical analysis of the scale factor in the strength of high-modulus fibres

Conclusions Distribution curves for the probability density of the strength values of complex SVM and Terlon yarns have been investigated with variation in the clamped length of specimens from 5 to 500 mm.The best conformity between the empirical distribution of yarn strength figures was observed for a distribution law for extreme values of the third kind, which conforms to the weak-unit theory.With increase in clamped length, disappearance of both very large and also of very small values of yarn strength takes place and because of this a shift in the modal value of strength takes place in the direction of low values. The latter circumstance is explained by the special features in the technology of making ultrahigh-modulus yarns.VNIIPV, Kiev Branch. Translated from Khimicheskie Volokna, No. 2, pp. 32–34, March–April, 1992.     

Strength level of high-strength complex fibre from stiff-chain polymers

The discrete strength levels for ultrahigh-modulus Terlon, Armos, and SVM fibre were found. Small-angle x-ray scattering and the calculation procedure known as the method of tangents were used to estimate the radii of submicrocracks. The limiting and actual values of the average strength levels of these types of fibre were calculated for two characteristic radii of inertia R₁ and R₂. The agreement of the results with the published data confirms the accuracy of the method of tangents.Ukrainian Scientific-Research Institute of Fibre, Kiev. Translated from Khimicheskie Volokna, No. 6, pp. 33–35, November–December, 1992.     

Improving thermal insulation for graphitization furnaces

Alternative materials are proposed for the lateral thermal insulation in graphitization furnaces. It is possible to reduce the loss of heat and the consumption of electricity by using carbon dust for insulation, and it is also possible to use plates of thermally and electrically insulating carbon material to hold it in the furnace. Translated from Novye Ogneupory, No. 12, pp. 3–5, December, 2008.