Hyperbaric oxygenation and current methods of detoxication in multimodal intensive therapy of diffuse peritonitis

The course of diffuse peritonitis has been followed up in 219 patients, 20 of these with the reactive, 165 with toxic, and 34 with the terminal stages of the condition. Multiple-modality intensive care included, besides routine therapy, local abdominal hypothermia, UV irradiation of autoblood (UVIAB), and, if indicated, hyperbaric oxygenation (HBO) and hemoperfusion. In addition to clinical tests, immunobiochemical monitoring of medium-molecular peptide fractions MM1 and MM2 and index of their distribution, as well as of circulating immune complexes CIC1 and CIC2 and the levels of immunoglobulins IgA, IgM, and IgG were the criteria for assessing the severity of intoxication and efficacy of intensive care and for predicting the course and outcome of the disease. The results indicate that HBO in combination with hemoperfusion, local abdominal hypothermia, and UVIAB have a positive impact on the clinical picture of the disease and on the time course of markers of endogenous intoxication and humoral immunity in patients with the terminal and toxic phases of diffuse peritonitis.     

Thermophysical properties of composite materials in the Si<Subscript>3</Subscript>N<Subscript>4</Subscript> - BN system

The results of a study of the thermophysical properties (thermal diffusivity, heat capacity, heat conductivity, and coefficient of linear thermal expansion) of Si₃N₄ - BN hot-pressed composite (with BN concentration varying from 10 to 60 wt.%) in the temperature range of 20 – 900°C are reported.__________Translated from Novye Ogneupory, No. 10, pp. 47 – 49, October, 2004.     

BEHAVIOR OF DISCRETE AND CONTINUOUS Sic AND C FIBERS IN a SILICON NITRIDE MATRIX UNDER CONDITIONS OF HOT PRESSING

Aspects of the problem of creating ceramic-matrix composites (CMC) in Si₃N₄ – SiCf and Si₃N₄ – Cf systems with high strength and crack resistance under the conditions of hot pressing are considered. Results of an evaluation of physicomechanical properties and a detailed study of the microstructure of CMC by electron and optical microscopy and fractographic analysis are presented. A complex analysis of the microstructure has shown the general rules of its formation in CMC and the behavior of SiC and C fibers of various types under the conditions of the developed technology. The level of the properties of CMC in the studied systems seems to be improvable by the creation of an interphase layer that controls the cohesion between the fibers and the matrix and by optimization of its composition.     

Study of the microstructure of ceramic matrix composites in the SiC - C<Subscript>f</Subscript> system

Results of a study of the microstructure of ceramic matrix composites (CMC) in the SiC - C_f system with high crack resistance and strength tested under conditions of unidirectional infiltration of molten high-purity silicon by methods of electron and optical microscopy and fractography are reported.__________Translated from Novye Ogneupory, No. 10, pp. 41 – 46, October, 2004.     

Tribological properties and testing of bearings fabricated from hot-pressed silicon nitride-based ceramics

Results of studies of tribological properties of hot-pressed silicon nitride-based ceramics for fabrication of rolling bearings are reported.__________Translated from Novye Ogneupory, No. 10, pp. 50 – 56, October, 2004.     

Efficiency of the use of silicon nitride ceramics as an armor material

The efficiency of the use of materials based on Si₃N₄ for armor is estimated experimentally in comparison with conventional alumina ceramics. It is shown that the studied compositions of monolithic and composite ceramics based on Si₃N₄ are 12–30% more efficient in ballistic applications than alumina ceramics. Monolithic high-density OTM-917 ceramics based on Si₃N₄ (PCS) is shown to have the highest physicomechanical properties among the studied materials. The choice of the composition depends on the requirements on the mass, size, and cost of the armor. The experimental results have been confirmed by tests for bullet and splinter strength. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 9–12, June, 1997.     

Postindentation slow growth of cracks in structural ceramics

Different forms of representing data on subcritical crack growth are discussed, which makes it possible to compare materials and (or) interpret the physical meaning of the parameters of slow crack growth (SCG). The SCG parameters are determined for hot-pressed OTM-914 materials and an Si₃N₄ — SiC (NK) composite. The scattering of the results can be explained by errors of the method, variation of the properties over the bulk of the material, surface oxidation, and other causes.     

Resistance of Ceramics in the Si3N4 – BN System to Long-Term Oxidation,Thermal Cycling,and High-Temperature Gas Stream

Composite ceramics in the Si₃N₄ – BN system (BN = 0 – 50%) are tested for resistance to long-term oxidation, thermal cycling, and high-temperature gas stream. The results of high-temperature tests suggest a potential of the developed material for application as the rotary seal in gas-turbine engines at 1000 – 1300°C. The composite material owing to its hardness and resistance to oxidation at lower temperatures can be used for fabrication of bearing cages.     

Hot-pressed ceramics based on SHS silicon nitride

The creation of new effective technologies and materials with an optimum ratio of quality and price is a significant achievement. The high cost of ceramics made of silicon nitride is a result of the expensiveness of the initial powder. The present study of the applicability of -Si₃N₄ powder prepared by the method of self-developing high-temperature synthesis (SHS) in hot-pressing technology has shown that although materials based on SHS -Si₃N₄ powders are inferior to materials based on plasmachemical compositions, their high strength, crack resistance, and hardness at a moderate density in combination with the lower cost of the initial raw material make them suitable for operation in aggressive media under moderate temperatures and loads. The materials developed have also shown high armoring properties.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 9, pp. 20 – 24, September, 1996.