Effect of prolonged high-temperature loading on the structure of the KhN65VMTYu alloy

A complex analysis of changes in the structure and in the phase composition arising as a result of both a prolonged operation of articles made of the alloy KhN65VMTYu (EI893) and after conducting imitation tests of model samples. The tests for long-term strength using samples cut out from the body of a large-dimension turbine blade which was exploited for 63 622 h showed that the blade preserved a significant residual reserve of service life (at 750°C and 250 MPa, the time to failure is 4243.5 h).     

Investigation of strained InxGa1−x As/InP quantum wells fabricated by metalorganic compound hydride epitaxy

An investigation was made of the possibility of using reduced-pressure MOC hydride epitaxy to fabricate highly strained (compressive stress) In_xGa_1−x As/In_0.53Ga_0.47As quantum wells on indium phosphide (100) substrates. The photoluminescence properties of these heterostructures were investigated. It was shown that these heterostructures are potentially useful for laser diodes emitting in the 1.5–2 μm range, which is important for environmental monitoring. Pis’ma Zh. Tekh. Fiz. 24, 46–51 (November 26, 1998)     

Phase Composition,Structure, and Hydrolytic Durability of a Uranium-Containing Magnesium Potassium Phosphate Compound

Uranium-containing samples of magnesium potassium phosphate (MPP) compound were synthesized using a nitric acid uranium solution. Uranium is incorporated in the MPP compound in the form of potassium uranyl phosphate with the structure of metaankoleite natural mineral, K(UO₂)PO₄·3H₂O. The differential and integral uranium leach rates, determined in accordance with GOST (State Standard) R 52 126–2003 on the 28th day of contact of the compound with water, are 1.7 × 10^–6 and 2.7 × 10^–6 g cm^–2 day^–1, respectively, and the degree of leaching is 0.014%. High hydrolytic durability of the compound with respect to uranium leaching reduces the risk of release of uranium isotopes from radioactive waste into the environment.     

Studying the characteristics of pulse-pumped semiconductor 1060-nm lasers based on asymmetric heterostructures with ultrathick waveguides

High-power semiconductor lasers based on asymmetric quantum-dimensional separate confinement InGaAs/GaAs heterostructures with ultrathick waveguides were fabricated by means of metalorganic hydride vapor phase epitaxy technology. The laser characteristics were studied in a pulsed pumping regime, in which the emission was excited by current pulses of 100 ns duration at a repetition frequency of 10 kHz and an amplitude of up to 200 A. The passage to a pulsed lasing regime allowed the active region heating to be reduced and the output power to be increased to 145 W for a laser diode with a 100-μm exit aperture. The results obtained for the pulsed lasing regime show that saturation of the output power-current characteristic observed in the continuous-wave regime is fully determined by overheating of the active region of a semiconductor laser.     

Effect of the active region thickness on characteristics of semiconductor lasers based on asymmetric AlGaAs/GaAs/InGaAs heterostructures with broadened waveguide

The effect of the active region thickness on the basic characteristics of high-power semiconductor lasers based on AlGaAs/GaAs/InGaAs asymmetric separate-confinement heterostructures grown by MOCVD epitaxy has been studied. It is shown that the threshold current, temperature sensitivity of the threshold current density, internal quantum efficiency of stimulated emission, and differential quantum efficiency are improved as the active region thickness increases. It is demonstrated that the maximum attainable optical emission power of a semiconductor laser and the internal quantum efficiency of photoluminescence are the most sensitive to defect formation in the heterostructure and become lower as the critical thickness of the strained In_xGa_1–x As layer in the active region is exceeded.     

Hydrolytic durability of uranium-containing sodium aluminum (iron) phosphate glasses

Normalized mass loss and leach rates of elements from the synthesized sodium aluminum phosphate and sodium aluminum iron phosphate glasses in relation to the content of uranium introduced into the glass-forming charge in the form of uranium dioxide or uranyl nitrate were determined by the РСТ procedure (variant А). The relationship between the element leaching parameters and the structure of the anionic motif of the glass network, up to the formation of a polyanionic structure from aluminum (iron)–phosphorus–oxygen network and uranium–oxygen polyanions, was determined. The resistance of the glasses to leaching of elements is on the same level as that of reference iron phosphate glasses.     

Carbon nanotube-doped composite sol–gel coatings for float glass

We have demonstrated the feasibility of synthesizing sol–gel composite coatings consisting of SiO₂ and multiwalled carbon nanotubes (MWCNTs) on float glass, and investigated the effect of the nature of surfactants, which ensure stability of MWCNT suspensions in water and SiO₂ sol and wetting of the glass by the suspensions. We have found conditions that enable uniform MWCNT dispersion and stabilization during the growth of composite coatings. Different, technologically viable approaches to producing composite coatings have been examined. Using laser Raman spectroscopy, we have assessed the MWCNT distribution over the composite coatings. The electrical conductivity, microhardness, and optical transmission of the coatings have been measured. It has been shown that the MWCNT-containing composite coatings possess enhanced microhardness and high electrical conductivity compared to the uncoated glass.