Thermal hysteresis in ferrite memory cores

The effects of different writing and reading temperatures on the switching voltage waveform, permeability, and flux state of standard nickel-copper-manganese and copper-manganese ferrite memory cores have been investigated over a temperature range of 0 to 70°C. These temperatures are well below the Curie temperatures of the materials being tested. It has been found that writing at a higher temperature than the read temperature leads to increased low temperature voltage switching thresholds, higher low frequency (<40 MHz) permeabilities, lower high frequency (>40 MHz) permeabilities, and flux states almost equal to the equilibrium value for the lower temperature. Read current pulse rise time and duration have been found to have no effect on the increase in threshold with temperature. Externally produced stresses have been used to simulate the effects of temperature changes on the core.     

Sonic quality control for SP-11-type mullite-corundum stoppers

Refractories and Industrial Ceramics -     

Waves in soft soil as a viscoelastic medium

Combustion, Explosion, and Shock Waves -     

Analytical melting model for extrusion: Stress of fully compacted solid polymers

Our laboratory recently published several analytical equations that can be used to predict the melting rate of fully compacted solid polymers sliding on a heated metal surface, modeling the melting mechanism inside an extruder. These equations were obtained by seeking asymptotic solutions to the differential equations describing the melting mechanism, temperature, and shear-dependent viscosity of polymer melts. Following the same asymptotic approach, we successfully developed accompanying analytical equations for predicting the stress required to slide fully compacted solid polymers on a heated metal surface. The accuracy of these analytical stress equations was found to be reasonable, although not fully satisfactory, by comparing their predictions to the experimentally measured values. The accuracy of the stress calculation is directly related to the accuracy of the viscosity values at high shear rates. The consideration of the temperature and shear dependencies of melt viscosity is most important for accurate prediction of the stress, just as it is for the melting rate. The stress not only depends on the melt rheological properties of the polymer but also on the thermodynamic properties.     

Industrial uses of high erucic oils

Vegetable oils rich in erucic acid have desirable properties for a variety of applications. At present, only a fraction of the potential that exists for commercial exploitation of high erucic oils in the United States is fulfilled with 10 million pounds of rapeseed oil imported annually. Though rape is not a crop in the United States, another member of the mustard family, crambe, has been recommended by the USDA as a practical crop for domestic cultivation. Compared to rapessed oil, crambe oil is more suitable for industrial use because it consistently contains a higher percentage of erucic acid. High erucic oils, as examplified by crambe, can be employed as lubricants in continuous steel casting, in formulated lubricants and in the manufacture of rubber additives. Both the hydrogenated oil and derived wax esters have properties comparable to commercial waxes. Useful nitrogen derivatives can be prepared from either the erucic acid or mixed acids from the oil; behenyl amine is used in a corrosion inhibitor, disubstituted amides are effective plasticizers and erucamide is an excellent slip and antiblocking agent for plastic films. Oxidative ozonolysis of erucic acid produces the dibasic acid, brassylic, and the monoacid, pelargonic. Mixed diacids, mainly brassylic and azelaic, can be obtained by ozonolysis of fatty acids from the oil. Alkyl diesters of brassylic, or of the mixed diacids, are excellent low temperature plasticizers. Two new nylons (13 and 1313), which are derived from C-13 difunctional products of erucic acid ozonolysis, contain repeating units that have longer uninterrupted polymethylene chains than other nylons. Moderate melting points and exceptionally low water absorption are a consequence of this structure. The low-melting characteristic is an advantage in adhesive uses and facilitates fluidized-bed coating, molding and extrusion; low moisture affinity contributes to excellent electrical properties and dimensional stability. One of 9 papers presented at the Symposium, “Cruciferous Oil-seeds”. ISF-AOCS World Congress. Chicago, September 1970. No. and Eastern Utilliz. Rev. Div., ARS, USDA.     

High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs

High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors.     

Protective coatings as a means of improving heat resistance of the refractory lining for extra-furnace steelmaking facilities

Protective coatings based on metallic aluminum are developed that can be used to improve the resistance of the refractory lining for extra-furnace steelmaking facilities. By sintering a slurry sprayed on the refractory surface, a heat-resistant gas-impermeable coating containing -corundum is formed.__________Translated from Novye Ogneupory, No. 10, pp. 61 – 63, October, 2004.