Thermal conductivity of silicon carbide ceramics doped with beryllium oxide

The thermal conductivity of silicon carbide ceramics containing up to 3 wt % BeO was measured in the temperature range 300–1300 K. The effective thermal conductivity was found to rise notably with increasing BeO content in the range 1.3–1.5 wt % BeO and to decrease exponentially with increasing porosity.     

Nitriding of High-Alloy Steel During Plasma Arc Remelting

Metallurgist - An experimental unit is described for effective alloying of steel with nitrogen by plasma arc remelting. Production regimes are developed for unit operation making it possible to...     

Comprehensive Study of the Effect of Plasma Stream on Heat-Resistant Materials

An experimental set-up with a unified system of synchronized control signals was constructed to study the interaction of high-enthalpy plasma jet with the surface of heat-resistant materials. The analysis of air–plasma stream interaction with technical (isotropic) graphite is performed. The air–plasma jet has a temperature of 7000–8000 K in the interaction zone, this interaction is accompanied by destruction of the graphite material and lasts for 100–200 s. Using methods like two-positioning visualization, micropyrometry and spectroscopy the following data are obtained: temperature fields on the graphite sample’s surface and their temporal and spatial changes, dynamics of the sample’s mass loss rate, changes in the parameters (temperature and concentration of electrons, heavy particles temperature) of the incoming plasma stream.     

Room temperature passive mode-locked laser based on InAs/GaAs quantum-dot superlattice

Passive mode-locking is achieved in two sectional lasers with an active layer based on superlattice formed by ten layers of quantum dots. Tunnel coupling of ten layers changes the structural polarization properties: the ratio between the transverse electric and transverse magnetic polarization absorption coefficients is less by a factor of 1.8 in the entire electroluminescence spectrum range for the superlattice.     

The Thermal and Elastic Properties of Zinc Oxide-Based Ceramics at High Temperatures

The thermal conductivity, thermal expansion coefficient (TEC), and the propagation velocity of longitudinal and transverse ultrasonic waves in ZnO-based ceramics are investigated in the temperature range from 300 to 1200 K with a porosity from 1.5 to 21%. The Young, shear, and bulk moduli and the Poisson ratio are calculated from the data on the propagation velocities of ultrasonic waves. Formulas are suggested to calculate the investigated parameters as a function of temperature and porosity.     

Electrical breakdown voltage of transformer oil with gas bubbles

Electrical breakdown strength of liquid-gas micro bubble mixtures of transformer oil with sulfur hexafluoride and air for the case of quasi homogeneous gas inclusions distribution and 10% volumetric gas content was experimentally investigated. DC voltage up to 140 kV was applied to a 8 mm gap between hemispherical electrodes. It is shown that transformer oil bubbled with air leads to threshold breakdown voltage decrease by 34% and 19% when bubbled with sulfur hexafluoride. The stabilization effect of sulfur hexafluoride micro bubbles on the value of threshold breakdown voltage is observed.     

Picosecond semiconductor lasers with a multisection saturable absorber, fabricated by heavy ion implantation

A method of implanting high-energy heavy ions across the emitter layer of a semiconductor laser has been developed to create distributed regions of ultrafast saturable absorber integrated into the cavity of a quantum-well laser. This method was used to fabricate picosecond laser diodes having high average powers and to demonstrate colliding-pulse mode-locking of a diode laser with a multisection saturable absorber. Pis’ma Zh. Tekh. Fiz. 25, 4–9 (July 12, 1999)