Synthesis of an ultradispersed diamond phase during detonation of composites

Conclusion We have attempted to analyze the synthesis of the diamond phase during, the detonation of secondary explosives by comparing the results of an explosion experiment with data obtained by studying preserved UDD powders.These data show that during detonation the growth in the UDD particles is a strongly limited process that is essentially independent of the size of the explosive charge or the external cooling conditions. The size distributions of diamond particles formed during direct synthesis from the carbon contained in the molecular structure of the explosive and during dissociation of inert organic substances are in satisfactory agreement with a lognormal distribution. The thermodynamic conditions during synthesis determine the dispersivity of the product UDD particles and this must be taken into account in thermodynamic detonation calculations. The effect of the different constituents of the, explosive on UDD synthesis (heat and mass transfer) is strongly limited.These data may support the concept of detonation in secondary explosives as a set of relatively fast and much slower reactions [25, 26] where, in the case of composites, the coagulation of carbon released during decomposition of each component separately and diffusion processes among the components may both act as slow exothermic reactions.Novosibirsk. Translated from Fizika Goreniya i. Vzryva, Vol. 29, No. 1, pp. 120–128, January–February, 1993.     

Neutron Damage in Single Crystal Aluminum Oxide

Synthetic aluminum oxide crystals were irradiated with fast neutrons to a dose of 1.8 × 10²⁰ nvt and examined by. transmission electron microscopy. As-irradiated crystals contained damage on a fine scale, revealed by diffraction contrast, and showed a 28% increase in Knoop diamond hardness compared with unirradiated material. Annealing above 600° C decreased the hardness and caused the small defect clusters to grow, forming dislocation loops on [10     0] planes with 1/3(10     1) Burgers vectors. High temperature annealing caused the loops to interact to give dislocation segments. These tended to align with the (10     0) and (1120) directions, and some of them had 1/3(10     1) Burgers vectors. Grown-in dislocations also began to climb but showed evidence of impurity pinning. Isolated platelike precipitates on [10     1] planes were observed in samples annealed at high temperatures. Possible effects of the observed damage on physical properties are considered; there is qualitative agreement between predictions and existing data.     

Evaluation of Polyester Resin as a New Compatibilizer for SBR/PVC Blends

A polyester (PE) based on the glycolyzed products of PET was prepared and added in different concentrations to a series of SBR/PVC blends. The addition of the polyester showed that all properties of SBR/PVC blends were improved by incorporation of PE. Highest mechanical strength values were obtained at a polyester concentration of 7.5 phr. Thermal analysis as well as dynamic mechanical properties of SBR/PVC blends after the addition of 7.5 and 10 phr polyester indicated one single glass transition temperature. The dielectric losses (?") were analyzed in the frequency domains in the two terms of Fröhlich related to the Maxwell Wagner effect and the orientation of the aggregates caused by the movement of the main chain. The permittivity (?') values were found to increase by increasing the polyester content. This increase was followed by a decrease in the ?" up to a 7.5 phr polyester content after which no pronounced change was noticed.     

Influence of amorphous silica on the hydration of tricalcium aluminate

Amorphous silica influences tricalcium aluminate (C₃A) hydration both in pastes and in suspensions. Two heat peaks are found by isothermal calorimetry during the paste hydration of C₃A. The addition of amorphous silica causes the second heat peak to shift towards shorter reaction times and become more pronounced. In suspensions, the change in ion concentration in the water phase is not influenced by the presence of amorphous silica except that the change in concentration occurs more quickly. Quantitative X-ray analysis shows that more 3CaO.Al₂O₃.6H₂O is present in suspensions containing amorphous silica than in silica-free suspensions at equal hydration times.     

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.