Formation of carbon nanofibers via carbon monoxide disproportionation

Experimental results suggesting that carbon nanofibers are formed from amorphous carbon released at several compact active sites are reported. It was shown that the sites in question are catalyst crystal lattice defects formed at the crystallite contact boundaries.     

An algorithm for deducing an effective sieve residue from the rate of powder passage through a sieve

The effect of non-ideal aperture distribution of a sieving surface on the sieve residue has been the object of many experimental studies. Unfortunately, the sieving kinetics of many sieving techniques do not result in a simple probability relationship between the size distribution function of the powder and the sieve aperture distribution function. If one specifies a certain type of sieving kinetics, then one can apply probability theory to the rate of movement of powder through the sieve and the size aperture distribution function of the sieve. Under such specified sieving conditions it can be shown that it is possible to deduce a size characteristic parameter of the powder being sieved, which in this publication is described as the kinetic residue of the sieve. An algorithm for the automatic computation of the kinetic residue from the rate of powder sieving is described. The possible implementation of this algorithm to automate sieve analysis is explored.     

Strength properties of chamotte concretes based on phosphate binders

Conclusions The authors have investigated the strength properties of chamotte concretes based on phosphate binders over a wide range.They have shown the dependence of the compressive strength of the concretes on the type of phosphate binder used, the heat treatment temperature of the concrete, and its test temperature. Maximal compressive strength is exhibited by concretes roasted at 1450°C.They have established a relation between the physicochemical transitions taking place in a phosphate binder during heating and the strength characteristics of the concrete.Simultaneous introduction of phosphate binder and clay to the extent of 10–20% into chamotte concretes increases their strength at 20°C and during heating.Translated from Ogneupory, No. 6, pp. 32–36, June, 1979.     

Mechanical properties and transition temperatures of copolymers of N-n-alkylacrylamides and vinylidene chloride

Mechanical and solution properties, melting transitions, torsional stiffness temperatures, T_f, and selected modulus-temperature curves are presented for copolymers of the N-n-alkylacrylamides with vinylidene chloride. Copolymers were prepared at 60°C across the range of compositions, using as comonomers N-n-butyl-, octyl-, dodecyl- and oleyl-acrylamide, which have amorphous side-chains, and N-n-octadecyl acrylamide and n-octadecyl acrylate whose side-chains are crystalline. The mechanical properties reflected the effect of the decline in backbone crystallinity and the simultaneous development of strong intermolecular interactions in the amorphous stage. Copolymers were stiff or showed brittle failure across the compositional range except when intermolecular forces were reduced (with n-octadrcyl acrylate) and side-chain crystallization eliminated (with N-oleylacrylamide). These systems and the n-dodecylacrylamide copolymers had yield strengths less than brittle strengths and substantial elongations. Backbone crystallinity was eliminated at about 15 mole % amide and side-chain crystallinity vanished at less than 10 mole % of the amide in the N-n-octadecylacrylamide series. No depression in side-chain melting point occurred with dilution by segments of vinylidene chloride. Over-all decline in the flex-temperature was the normal monotonic function of composition except that values increased in magnitude at high vinylidene chloride contents, the effect presumably being caused by the presence of crystallinity. An empirical equation was developed which permitted the calculation of T_f for any N-n-alkylacrylamide composition with any number of carbon atoms in the side-chain, above 3.     

Flash pyrolysis of coal: effect of nitrogen,argon and other atmospheres in increasing olefin concentration and its significance on the mechanism of coal pyrolysis

Samples of three Indian coals, of widely differing origin and rank, were subjected to flash pyrolysis at a temperature of about 1150 °C for 30 s in vacuo, and under atmospheres of nitrogen, argon, ammonia, and perdeuterobenzene. The gaseous products of the pyrolyses were analysed by infra-red and mass spectroscopy and by gas chromatography. Observed variations in gas compositions are discussed relative to the possible mode of influence by the pyrolytic atmospheres. It would appear that the pyrolytic atmosphere is an important factor in determining the composition of the pyrolysis products; the influence of nitrogen, argon and perdeuterobenzene is a physical one, leading especially to higher yields of olefins.     

Effects of soy proteins containing trypsin inhibitors in long term feeding studies in rats

Pancreatic hypertrophy that occurs in rats fed raw soy flour containing about 1200 mg tripsin inhibitor (TI)/100 g diet was reversed by switching the rats to control diets or to diets containing 30% toasted defatted soy flour. No pancreatic hypertrophy occurs in rats fed commercial, edible grade soy flours, concentrate or isolate from time of weaning to adulthood (ca. 300 days). TI content of the soy diets ranged from 178–420 mg/100 g. Except for pancreas enlargement in rats fed raw soy flour, gross and microscopic examination of pancreata revealed no abnormalities. The gross appearance of heart, kidney, spleen, and liver was normal. Soy flour, protein concentrate, and protein isolate in a formulated corn-soy diet provided optimum growth and maintained body weight only if supplemented with vitamin B-12 in long term feeding studies with rats. In the absence of such supplementation, rats fed soy diets initially grew at a rate equal to or greater than those fed a comparable corn-casein control diet; but, with continued feeding for ca. 300 days, body weight of rats fed the casein control was significantly greater than that of the soy flour-fed rats. Those fed soy isolate ceased to grow; and rats fed soy concentrate lost weight. No significant differences were found in organ weights between groups fed soy products and casein, except for increased kidney, liver, and testes weights relative to body weight with the group fed soy concentrate. Supplementation of the soy diets with vitamin B₁₂ stimulated growth to the greatest extent, calcium pantothenate or riboflavin had an intermediate effect, other vitamins had little or no effect; whereas a complete mineral mix was detrimental. Supplementation of the soy diets with vitamin B₁₂ stimulated growth to the greatest extent, calcium pantothenate or roboflavin had an intermediate effect, other vitamins had little or no effect; whereas a complete mineral mix was detrimental. Supplementation of the control diet was without effect. The dietary protein level in these diets was 20%, with casein or soy protein representing 75% of total protein. When fed continuously to rats from weaning to adulthood, properly processed soy protein products, when balanced with essential nutrients, can provide growth comparable to corn-casein diets.     

Hertzian Stress Cracks in Beryllia and Glass

The effect of Hertzian stresses resulting from loads acting at the points of contact of beryllia spheres was determined. As-drawn glass and glass ground with various grades of silicon carbide were indented with beryllia spheres, 1 in. in diameter. Also, pairs of these beryllia spheres were pressed together. Circular cracks due to Hertzian stresses were produced; an optical technique was developed for detecting them in a beryllia surface. The outer crack radius was proportional to the cube root of the maximum applied load. Average values obtained for the respective inner crack radii were used to determine average values of the minimum load to fracture these materials. The average minimum load to fracture 1 in. diameter beryllia spheres in air at room temperature under dynamic loading was 235 1b. The crack radius in glass and beryllia was about 20% greater than the radius of the contact surface. This was not significantly affected (in glass) by flaw density. It is considered that the Hertz analysis does not give the correct location and value of the maximum tensile stress when finite displacements of material occur.     

Bestimmung von cyclischen Fettsäuren über eine Harnstoffsäule

Determination of Cyclic Fatty Acids on Urea Column Cyclic monomeric fatty acids (CFA) in the mixture of straight chain saturated and unsaturated fatty acids were determined after methylation (CFA-Me) as non-adducts on an urea column. The method gives quantitative results with mixtures containing 5% or more of cyclic fatty acids. The determination is easy and rapid.     

Refractories with a Boron nitride base

Conclusions A technique for the reaction sintering of a new refractory made of 82–83% boron nitride and 17–18% graphite has been developed.The refractory possesses high specific resistance up to 1500–1800°, a low coefficient of thermal expansion, a moderative evaporation rate in a vacuum, satisfactory strength and machinability, as well as high resistance to cryolite-aluminum melts, borate, chloride and also silicide and boron-silicon alloy melts (at between 900 and 2000°).     

Fast Simulation of the Functional Failure of an s – t-Network with Repair

An s – t-network with highly reliable edges with repair and variable external load is considered. A fast simulation method is proposed to evaluate the probability of functional failure when the real capacity of the network is less than the required capacity. It is proved that under some conditions the estimate has a bounded relative error as edges reliability increases. The numerical example illustrates the efficiency of the method.