The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance

The application of magneto-dielectric composite mixture for alternative technology of winding impregnation in electrical and radio engineering products

The relevance of the discussed issue is caused by the need to improve the technology of winding impregnation to increase its quality and reliability. The main aim of the study: to justify the choice of magneto-dielectric impregnating compound and perspective of its use for alternative technology of winding impregnation in electrical and radio engineering products. The methods used in the study: the electro-thermal - to estimate heat conductivity and heat capacity; the electro-magnetic - to define the function of mixture magnetic conductivity from concentration of ferrite; the viscometers - to determine impregnating compound viscosity; capacitive - to control the saturation degree of interturn winding hole by impregnating compound; high-voltage - to investigate the electric strength of composition. The results. The authors found out that application of magneto-dielectric compound for impregnating the electrotechnical windings and radio technical coil products in the first place allows to eliminate all power-consuming, noisy electromechanical devices. Secondly, permits to provide the equal glazing of face parts. Thirdly, the using of magneto-dielectric compound allows to improve the saturation degree of interturn winding hole by impregnating compound. This is achieved through heating current supply to coil after the impregnation, magnetic force of which serves as a gate, whereby the impregnating composition stops to flow out of the cavities during their drying. The high thermal conductivity of the proposed mixture and high rates of impregnation can reduce overheating of the windings, which in several times increases their reliability and durability. It was shown, that the nickel-zinc soft magnetic particles can improve the conductivity of the impregnating mixture more than one and a half times. Thus, magneto-dielectric technological properties of the mixture (viscosity, dielectric strength, etc.) remain within acceptable limits. Higher thermal conductivity of the considered magneto-dielectric mixture, in comparison with the thermal conductivity of the compound KP-34, traditionally used for inkjet-drip impregnation of stator windings, as well as high rates of impregnation when using magneto-dielectric composition, make it possible to reduce overheating of the stator windings not less than 30 %

The application of magneto-dielectric composite mixture for alternative technology of winding impregnation in electrical and radio engineering products

The relevance of the discussed issue is caused by the need to improve the technology of winding impregnation to increase its quality and reliability. The main aim of the study: to justify the choice of magneto-dielectric impregnating compound and perspective of its use for alternative technology of winding impregnation in electrical and radio engineering products. The methods used in the study: the electro-thermal - to estimate heat conductivity and heat capacity; the electro-magnetic - to define the function of mixture magnetic conductivity from concentration of ferrite; the viscometers - to determine impregnating compound viscosity; capacitive - to control the saturation degree of interturn winding hole by impregnating compound; high-voltage - to investigate the electric strength of composition. The results. The authors found out that application of magneto-dielectric compound for impregnating the electrotechnical windings and radio technical coil products in the first place allows to eliminate all power-consuming, noisy electromechanical devices. Secondly, permits to provide the equal glazing of face parts. Thirdly, the using of magneto-dielectric compound allows to improve the saturation degree of interturn winding hole by impregnating compound. This is achieved through heating current supply to coil after the impregnation, magnetic force of which serves as a gate, whereby the impregnating composition stops to flow out of the cavities during their drying. The high thermal conductivity of the proposed mixture and high rates of impregnation can reduce overheating of the windings, which in several times increases their reliability and durability. It was shown, that the nickel-zinc soft magnetic particles can improve the conductivity of the impregnating mixture more than one and a half times. Thus, magneto-dielectric technological properties of the mixture (viscosity, dielectric strength, etc.) remain within acceptable limits. Higher thermal conductivity of the considered magneto-dielectric mixture, in comparison with the thermal conductivity of the compound KP-34, traditionally used for inkjet-drip impregnation of stator windings, as well as high rates of impregnation when using magneto-dielectric composition, make it possible to reduce overheating of the stator windings not less than 30 %

The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance

The application of magneto-dielectric composite mixture for alternative technology of winding impregnation in electrical and radio engineering products

Актуальность работы обусловлена необходимостью улучшения технологии пропитки электрических обмоток, повышения их качества и надежности. Цель работы. Обоснование выбора магнитодиэлектрического пропиточного состава и перспективности его применения для ресурсосберегающей технологии пропитки обмоток электротехнических и радиотехнических изделий. Методы исследования. Электротепловые - для определения теплопроводности и теплоёмкости; электромагнитные - для определения зависимости магнитной проницаемости состава от концентрации феррита; вискозиметры - для определения вязкости композиций пропиточных составов; ёмкостные - для контроля степени насыщенности межвитковых полостей обмотки пропиточным составом; высоковольтные - для исследования электрической прочности магнитодиэлектрических композиционных составов. Результаты. Установлено, что применение магнитодиэлектрического состава для пропитки обмоток электротехнических и радиотехнических намоточных изделий способствует: во-первых, устранению всех энергоёмких, шумящих электромеханических устройств; во-вторых, обеспечению более равномерного полива лобовых частей; в-третьих, существенному повышению коэффициента пропитки обмоток, характеризующего степень насыщенности межвитковых полостей пропиточным составом. Это достигается за счет того, что по завершении пропитки в обмотку подается греющий ток, магнитное поле которого служит своеобразным затвором, с его помощью пропиточный состав прекращает вытекать из полостей обмотки при их сушке. Высокая теплопроводность предлагаемой смеси и высокие коэффициенты пропитки позволяют снизить перегрев обмоток при их эксплуатации, что в несколько раз повышает их эксплуатационную надежность и долговечность. Показано, что введение в компаунд КП-34 никель-цинковых магнитомягких частиц позволяет повысить теплопроводность пропиточной смеси более чем в полтора раза. При этом технологические свойства магнитодиэлектрической смеси (вязкость, электрическая прочность и др.) остаются в допустимых пределах. Более высокая теплопроводность рассматриваемой магнитодиэлектрической смеси, по сравнению с теплопроводностью компаунда КП-34, традиционно используемого для струйно-капельной пропитки статорных обмоток, а также высокие коэффициенты пропитки при использовании магнитодиэлектрического состава дают возможность снизить перегрев обмоток статоров не мене чем на 30 %.The relevance of the discussed issue is caused by the need to improve the technology of winding impregnation to increase its quality and reliability. The main aim of the study: to justify the choice of magneto-dielectric impregnating compound and perspective of its use for alternative technology of winding impregnation in electrical and radio engineering products. The methods used in the study: the electro-thermal - to estimate heat conductivity and heat capacity; the electro-magnetic - to define the function of mixture magnetic conductivity from concentration of ferrite; the viscometers - to determine impregnating compound viscosity; capacitive - to control the saturation degree of interturn winding hole by impregnating compound; high-voltage - to investigate the electric strength of composition. The results. The authors found out that application of magneto-dielectric compound for impregnating the electrotechnical windings and radio technical coil products in the first place allows to eliminate all power-consuming, noisy electromechanical devices. Secondly, permits to provide the equal glazing of face parts. Thirdly, the using of magneto-dielectric compound allows to improve the saturation degree of interturn winding hole by impregnating compound. This is achieved through heating current supply to coil after the impregnation, magnetic force of which serves as a gate, whereby the impregnating composition stops to flow out of the cavities during their drying. The high thermal conductivity of the proposed mixture and high rates of impregnation can reduce overheating of the windings, which in several times increases their reliability and durability. It was shown, that the nickel-zinc soft magnetic particles can improve the conductivity of the impregnating mixture more than one and a half times. Thus, magneto-dielectric technological properties of the mixture (viscosity, dielectric strength, etc.) remain within acceptable limits. Higher thermal conductivity of the considered magneto-dielectric mixture, in comparison with the thermal conductivity of the compound KP-34, traditionally used for inkjet-drip impregnation of stator windings, as well as high rates of impregnation when using magneto-dielectric composition, make it possible to reduce overheating of the stator windings not less than 30 %