Influence of Sodium Microalloying on Rolling Contact Endurance and Mechanical Properties of Hot-Deformed Powder Steels

Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of...     

Energy release behind the Jouguet point during detonation of plasticized PETN from the results of experiments by the T-20 method

The trajectory of motion of a copper shell, the velocity of its flight, and the pressure of the explosion products on the inside of the copper shell were simulated. It was found that there is a significant difference in pressure behavior between experiments and calculations performed using the standard equations of state of explosives and explosion products. Most likely, there is a significant contribution of kinetic processes to the energy release behind the Jouguet point. In this case, the conversion of explosives to explosion products apparently include not only exothermic reactions but also endothermic processes.     

Hydroxyapatite-calcium carbonate ceramic composite materials

Hydroxyapatite/calcium carbonate (CC) composite powders containing up to 50 wt % CO₃²⁻, have been prepared via precipitation from aqueous solutions. According to chemical analysis data, the CO₃²⁻ content of the powders coincides with the intended one over the entire composition range studied. With increasing CO₃²⁻ content, the specific surface area of the powders decreases because of the formation and growth of large needlelike CC crystals up to 1.5 μm in size. The addition of low-melting-point alkali carbonates to the starting powder mixture reduces the sintering temperature of the powders to below 720°C, thereby preventing the thermal decomposition of CC. The highest bending strength, up to 76 MPa, is offered by the materials with the lowest CC content, about 20 wt %, and an average crystal size of 100 nm. The solubility of the composites gradually increases with CC content. In vitro experiments with a human fibroblast model (MTT test) demonstrate that the composites have zero cytotoxicity.     

Effects of infant formula feeding on the distribution of copper in the body of 8-day-old rats

The oxidase activity of ceruloplasmin (Cp, EC 1.16.3.1), the content of immunoreactive Cp and copper ion concentration were measured in the serum of eight day-old rats receiving either breast feeding (control group) or commercial nutritive mixture which has been recommended for the newborn children beginning from zero age (experimental group). It was shown that the artificial feeding caused almost 3-fold increase of Cp oxidase activity and copper content in the serum when compared to age-matched controls. No changes in the copper content per Cp molecule were observed. Dot-hybridization of the total liver polyribosomal RNA with Cp [32P]cDNA showed that the increased Cp level in the blood of the rats of experimental group correlated well with the level of expression of Cp gene. The copper content in the liver of experimental rats was two times lower that in control animals while no differences was found in the brain copper content between two groups of rats. The role of the regulation of Cp gene expression in the lactating mammary gland and of milk Cp in the copper homeostasis in the newborn body is discussed.     

The use of electrically heated melt-spinning heads having forced polymer feed on spinning machines for synthetic fibres

Conclusions The operation of electrically heated melt-spinning heads with forced polymer feed has been investigated on machines for spinning low thread-number Capron fibre.All-Union Research Institute for Synthetic Fibre Plant (VNIIMSV), Chernigov. Chernigov Factory. Translated from Khimicheskie Volokna, No. 6, pp. 50–52, November–December, 1969.     

Formation processes,structure, and properties of spark coatings of armco iron obtained with the use of nanostructured and microstructured WC-Co electrodes

Nanostructured and microstructured electrode materials of the composition 92%WC-8%Co were used for deposition of spark coatings on Armco iron upon variation in the energy of pulsed discharges in the range from 0.01 to 1.2 J. Physicochemical processes on contact surfaces are considered during operation by both types of electrode pairs, namely, in the forming coating of the cathode substrate and in the secondary structure of the anode electrode. It is found that the main phases in coatings are the amorphous phase and tungsten semicarbide W₂C. In the case of a nanostructured electrode, an increase in the energy mode above a certain threshold value leads to an increase in the fraction of crystalline phases and to the formation of a structure consisting of submicron W₂C/WC grains surrounded by an amorphous binder. With the use of a microstructured electrode, the fraction of the amorphous phase in coatings prevails in all energy modes. The use of nanostructured electrodes in the technology of spark treatment of substrates made from Armco iron is expedient only at a pulse energy of <0.23 J.     

A new technology for coprocessing man-made wastes

The possibility of the selective separation of components of starting materials with concentrations of Fe, P, and Ga in cast iron and Al₂O₃, TiO₂, and Sc₂O₃ in slag suitable for cement production is established based on the results of reduction smeltings of cakes after leaching the mixtures of greasy mill scale (GMS) with 75 and 100% red mud (RM) and fired pellets made of these cakes. It is shown that, depending on how long the melts were held (20–60 min at 1620°C), the components are transferred into cast iron: 98 Fe, 22–66 Si, 1 S, 99 P, 11–20 Ti, and 98–99% Ga. Components that are concentrated in slag are 95–99 Al₂O₃, 55–65 SiO₂, 88–90 TiO₂, and 98–99% Sc₂O₃. A flowchart of the joint utilization of GMS and RM is developed.