A technique of ultrasonic testing of articles with curvilinear surfaces

The results of development of a technique, specimens, and special transducers for ultrasonic testing of valves (taps) for high-pressure pipelines and for the compressed part of pipeline taps (elbows) are discussed. Specific features of adjustment of the scan duration, a depth gauge, and the sensitivity of a flaw detector are considered.     

A linear accelerator-injector for the SIBERIA and TNK complexes of special synchrotron radiation sources

An 80-MeV electron linear accelerator-injector operates in a pulsed standing-wave mode. A 2.8-GHz disk-and-washer accelerating structure is composed of six 1-m-long regular sections with power input in the middle. The electron beam with parameters of 4 A/40 kV/18 ns/1 Hz from the diode gun enters the accelerating structure without prebunching. During acceleration, the beam is divided into bunches with a repetition frequency of 2.8 GHz and transported over the electron-optic channel to the booster ring. Today, the electron beam has an energy of 80 MeV, a current of 80 mA, and an energy spread of 1% and maintains continuous operation of the SIBERIA facility.     

The extrinsic photoconductivity of chalcogens in Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript>x</Subscript> solid solutions

The effect of ～3% of silicon additive on the energy spectra of selenium and tellurium impurities in germanium is studied. The photoconductivity spectra are measured at 80 K in a spectral range from 2.5 to 5 μm. Narrow lines corresponding to the excited states of chalcogen ions are observed against the background of the extrinsic-photoconductivity band. It is found that the spectrum of excited states is not affected by silicon at the concentration used. An increase in the energy gaps between the conduction band and impurity states of the chalcogens is detected.     

Structural changes in a nickel-copper catalyst during growth of nitrogen-containing carbon nanofibers by ethylene/ammonia decomposition

Structural changes in a 65Ni-25Cu-Al₂O₃ catalyst during the decomposition of a C₂H₄/NH₃ mixture at different stages of nitrogen-containing carbon nanofiber (N-CNF) synthesis were studied by X-ray diffraction (XRD) analysis, X-ray diffraction using anomalous scattering effect and extended X-ray absorption fine structure (EXAFS) spectroscopy. The N-CNF growth over a catalyst particle was supposed to proceed via the formation of an oversaturated solid solution of carbon and nitrogen in a nickel-enriched alloy “NiCu_xC_yN_z”. The latter resulted in an increase of the alloy lattice parameter to abnormally large values а = 3.616-3.706 Å without destruction of its cubic structure. The formation of the “NiCu_xC_yN_z” phase and its presence in the system coincide with the optimum time for the synthesis of N-CNFs with the highest nitrogen concentration and maximum values of specific surface area and total pore volume.     

Antireflective coatings based on SiO<Subscript>2</Subscript> nanoparticles

Single-layer antireflective coatings, produced by sol-gel method on soda-lime glass substrates, were studied. Optimal parameters of the silica sols synthesis and coating procedure of the antireflective coatings based on SiO₂ nanoparticles on soda-lime glasses for producing composite glasses with high optical transmittance within the visible range of wavelengths were obtained.     

Improving the safety of aluminum press molds by protecting them from wear and corrosion by the microarc oxidation method

The results of an increase of wear and corrosion resistance of the working surfaces of transfer press molds by means of the development and use of the microarc oxidation method are given. The protective coatings obtained enabled an increase their service life mainly within the most stressed area of the junction (closing area) and its sharp edges. Taking into account the processes occurring in the transfer press molds, the best properties of the coating and their operation modes are specified. The laboratory tests of coatings for bending, compression with shear, wear and thermal resistance, as well as tests on the structure of the transfer press mold in full-scale production proved their safe operation over 10⁵ cycles without any damage.     

Growth and Luminescent Properties of NaGd(WO4)2:Yb3+ Crystals

Data are presented on the spectroscopic properties of Yb³⁺-activated NaGd(WO₄)₂, a disordered scheelite-like tungstate potentially attractive as a gain medium. NaGd(WO₄)₂:Yb³⁺ crystals are grown by the Czochralski technique. The polarized absorption and luminescence spectra and the luminescence decay kinetics of oriented samples with different Yb³⁺ concentrations are studied at 300 K. The gain coefficients are calculated for different populations of the upper lasing level 2F _5/2 of the Yb³⁺ ion.