Technical new feature

A continuous process for the commercial production of isopropenyl stearate (IPS) from triple pressed stearic acid and a stabilized form of propyne has been developed. Cost estimates, including capital costs, operating costs, and profitability, for commercial scale plant production which show the process to be economically feasible are presented. This potentially profitable process offers the advantages of reliable raw material sources, minimal external thermal requirements, and usable process waste streams. For a plant producing 5 million pounds of IPS per year, the selling price range is 80 to 107 cents/lb IPS, corresponding to a raw material cost range of 27 to 54 cents/lb of IPS. For a 20 million pound per year plant, the selling price range is 58 to 85 cents/lb IPS. The selling prices include a 20% annual return on fixed capital investment. Fixed capital requirement ranges from 2.7 to 10.9 million dollars (3rd quarter, 1975) for plants ranging in size from 5 to 50 million pounds of IPS per year, respectively.     

Poeosity as a factor in the elastic modulus of zirconium and niobium monocarbides

Conclusions The influence of the porosity on the elastic properties of niobium and zirconium monocarbides can be described satisfactorily by exponential type equations in which the parameter P/(1–P) (P is the porosity) is the argument. It was established that Young's modulus for the nonporous carbides is 47,900 kg/mm² for NbC_0.98, 40,000 kg/mm² for ZrC^0.95, and 38,900 kg/mm² for ZrC^0.91.The shape and relative orientation of the pores do not influence the value of the exponents to a significant extent.Translated from Ogneupory, No. 2, pp. 47–49, February, 1976.     

Pneumatic spinning of chemical fibres (review)

Scientific-Research Center for Problems of Resource and Waste Management, Mytishchi, Translated from Khimicheskie Volokna, No. 4, pp. 27–29, July–August, 1995.     

Technological features of casting zirconia parts

Conclusions Alkaline slips made of zirconium dioxide stabilized with calcium oxide, which have been obtained by grinding the materials in a rubber-lined zirconium-ball mill, exhibit poor casting properties and a tendency to stratification. The green ware obtained shows a low bulk density of the order of 2.5 g/cm³. The inadvisability of preparing material for casting in this way is further confirmed by the need to restore a large number of the grinding balls which quickly wear out during operation. In order to obtain a uniform degree of fineness of the material, the grinding time for zirconium balls, as opposed to the process in metal mills, should be increased.A sharp improvement in the casting properties of slip, an increase in the porosity of the green ware and a reduction in shrinkage during firing can be obtained by casting acidic slips treated with hydrochloric acid. This determines the technological advisability of washing the stabilized ZrO₂ with acid after grinding, and the possibility, therefore, of grinding for a shorter period in steel metal-ball mills.The most favorable conditions for casting slip made of stabilized ZrO₂ treated with hydrochloric acid are a moisture content of about 30% and a pH value of 1.5–2. Here the densityof the casting is 2.8 g/cm³ and the density of the fired part 5.45 g/cm³. The casting properties of slip are improved and the density of the green ware is raised by 0. 2 g/cm³ if the materials are left to stand for 2 to 4 days after treatment.     

New method of determining the slag-resistance of refractories

Conclusions A new method is proposed for determining the slag resistance of refractories with lever apparatus which is qualitative.The new technique permits the specific features of the destruction of refractories by slags to be determined, and explains the mechanism of this process by mineralogical analysis and by describing the external appearance of the changed specimens.Data on the changes in the specimens during tests and the compositions of the zones will be given in the next article.Data obtained by the new method show that the slag destruction of refractories accelerates with time.     

Early soot formation stages in low-pressure diffusional counterflow hydrocarbon flames

Early soot formation stages were investigated in low-pressure counterflow hydrocarbon flames. A mechanism is proposed for the formation of aggregates and discrete spherical soot particles. It is proposed that the formation of the physical surface is preceded by the emergence of a skeleton structure consisting of carbon molecule chains as a result of their polarizing and dipole interaction with the charged soot nuclei.Kiev. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 97–100, May–June, 1993.     

Environment-Sensitive Hardness and Machinability of Al2O3

The influences of water, toluene, and n -alcohols on the pendulum hardness of Al₂O₃ monocrystals and on the ease of drilling of mono- and polycrystalline Al₂O₃ were studied. Adsorption-induced increases in pendulum hardness were produced by certain alcohol environments; these increases resulted in rates of drilling with diamond-studded core bits of up to 10 times those measured under water. A correlation between pendulum hardness, machinability, and surface charge (as indicated by ζ-potential measurements) was established and revealed that Al₂O₃ is hardest and most effectively drilled with a diamond core bit at its zero point of charge. The possible use of this correlation in developing more cost-effective and ecologically viable cutting fluids for the machining of Al₂O₃ is discussed.     

Mechanosynthesis of complex oxides and preparation of mixed conducting nanocomposites for catalytic membrane reactors

Nanopowders of LaGaO₃- and LaMnO₃-based complex perovskites (P) and ceria-based fluorites (F) were prepared by mechanosynthesis. Compatible nanocomposites F + P and P + P with mixed ion and electron conducting (MIEC) properties were prepared and sintered at moderate temperatures up to dense ceramics. The obtained materials were studied by means of XRD, SEM, TEM, electrical conductivity measurements, temperature programmed (TP) reduction/oxidation and preliminary estimations of permeability were obtained. A new strategy based on the advantages of the mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one-step sintering were used for the production of thin film membranes with MIEC properties on porous substrates. The coarse fraction of as-milled powders from agglomerates with density 70% was used for the porous substrate, and fine fractions of aggregates with sizes <1 μm were used in preparation of composites for thin dense films. Ceria-based composites prepared by the Pechini route and/or mechanochemical method are proposed as materials for protecting thin films.