On Application of Carbon-Containing Electrode Materials in Technology of Electrospark Alloying: Part 1. Peculiarities of Coating Formation Using Electrospark Treatment of Titanium Alloy OT4-1

Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings.     

Self-propagating high-temperature synthesis of advanced ceramics MoSi2–HfB2–MoB

This study focuses on the investigation of the macrokinetic features of SHS (combustion synthesis) of elemental mixtures Mo–Hf–Si–B, in particular the mechanisms of structure and phase formation in the combustion front as well as the structure and properties of consolidated ceramics. Two routes for the fabrication of the composite SHS powder in system MoSi₂–HfB₂–MoB were used: (1) synthesis using Mo–Si–B and Hf–B mixtures followed by mixing of the combustion products and (2) synthesis using the four-component Mo–Hf–Si–B mixture. Dense ceramic samples with a homogeneous structure and low residual porosity (0.8–3.6%) were prepared by hot pressing of SHS powders. Although the particles size distribution and phase composition of SHS powders are similar for both synthesis routes, the structure and properties of both the composite SHS powders and hot-pressed ceramics differ considerably. Synthesis using the four-component Mo–Hf–Si–B mixture allows one to produce hierarchically ordered nanocomposite material with improved mechanical properties: hardness up to 17.6?GPa and fracture toughness up to 7.16?MPa?m^1/2.     

Special characteristics of the filtration combustion of the system Ti?C?N in an audio-frequency sound field

The influence of sound fields on the filtration combustion of mixtures of titanium and carbon in nitrogen on the kinetics of self-propagating high-temperature synthesis and on the chemical and phase composition of the synthesis products is investigated. It is shown that filtration hindrances in a wide layer of the sample vanish if the charge material has an initial relative density of 0.2. The carbonitride component is formed most completely when the atomic fraction of carbon in the initial charge has values of 0.3 and 0.5. The optimum acoustic frequency stimulating the filtration of nitrogen deep within the briquette and yielding the most complete nitriding process is the resonance frequency of the acoustic system. Fast-framing photography exhibits the transient nature of the filtration combustion of titanium—carbon mixtures in nitrogen. Institute of Steel and Alloys, Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 44–51, September–October, 1995.     

Combustion and structure formation in the Ti-Ta-C-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> system

Biocompatible composites (Ti, Ta)C _x + Ca₃(PO₄)₂ for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca₃(PO₄)₂ mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have little or no influence on the burning velocity U and combustion temperature T _c. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.      

Aspects of making a superconducting yttrium ceramic by self-propagating high-temperature synthesis

Macrokinjetic features are considered for the combustion in oxygen of BaO₂–Cu–Y₂O₃ mixtures, which produces the high-temperature superconductor yttrium barium cuprate YBa₂Cu₃O_7–x. Studies have been made on how the initial temperature affects the combustion temperature and rate, and the critical temperature for self-ignition has been determined. Ultrasonic activation of the initial powders has an advantageous effect on the product quality. Thermal analysis has been applied to the activated mixtures, which indicates the reason for the rise in burning wave propagation rate and increase in conversion to the superconducting phase.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 62–67, March–April, 1993.     

Engineering of functional supramacromolecular complexes of proteins (enzymes) using reversed micelles as matrix microreactors

The size of the inner water cavity of reversed micelles formedin a triple system ‘water-surfactant-organic solvent’can be widely varied by changing the degree of surfactant hydration.This gives grounds to use reversed micelles as matrix microreactorsfor the design of supramolecular complexes of proteins. Usingultracentrifugation analysis, it has been demonstrated thatthe oligomeric composition of various enzymes (ketoglutaratedehydrogenase, alkaline phosphatase, lactic dehydrogenase, glyceraldehyde-3-phosphatedehydrogenase) solubilized in reversed micelles of Aerosol OT[sodium bis(2-ethylehexyl)sulfosuccinate] in octane changesupon variation of the degree of hydration. An oligomeric complexforms under conditions when the radius of the micelle innercavity is big enough to incorporate this complex as a whole.At lower degrees of hydration the micelles ‘uncouple’such complexes to their components. The catalytic propertiesof various oligomeric complexes have been studied. Possibilitiesof using reversed micelles for the separation of subunits ofoligomeric enzymes under non-denaturating conditions have beendemonstrated. In particular, the isolated subunits of alkalinephosphatase, lactic dehydrogenase and glyceralde-hyde-3-phosphatedehydrogenase have been found to be active in Aerosol OT reversedmicelles. The dependences of the catalytic activity of oligomericenzymes represent saw-like curves. The maxima of the catalyticactivity observed at these curves relate to the functioningof various oligomeric forms of an enzyme. The radii of the micelleinner cavity under conditions when these maxima are observedcorrelate with the linear dimensions of the enzyme oligomericforms. Correlation of the position of a maximum with the shapeof an oligomeric complex is discussed.     

An algorithm for recognizing linear objects in aerial photos automatically

A new algorithm for detecting linear infrastructural objects in aerial photos is presented. It is assumed that these objects pass through the whole image: beginning at one side and finishing at the opposite one. It is also assumed that the altitude of shooting and the image scale are invariable. The presented algorithm synthesizes the operation of an edge detector, a ridge detector, and the Hough accumulator into an object-of-interest mask excluding lots of spurious responses, and it completes missing information missed by detectors. First of all the image is preprocessed and anisotropically and repeatedly shrunk along the direction of the linear object and synthesis is performed by finding the shortest paths in a graph. The graph is presented in the form of a mesh, where each mesh node corresponds to a pixel of the shrunk image. At each node on the edges and in ridge lines, its energy is calculated, which is the reliability of this pixel. Then, the path that maximizes the sum of energies at the nodes is determined by considering its curvature. The obtained paths form a mask of linear objects. The algorithm is verified by using aerial photos for different seasons, and it demonstrates proper results (accuracy is ~80%).     

Investigation of Si–B–C–N coatings produced by ion sputtering of SiBC target

Using the method of ion sputtering of sintered Si–B–C targets, amorphous Si–B–C–N thin-film coatings with different nitrogen contents have been prepared. The structures of coatings are studied by the methods of X-ray phase analysis, scanning electron microscopy, glow-discharge optical-emission spectroscopy, infrared spectroscopy, and Raman spectroscopy. The mechanical properties of the obtained coatings are determined using the nanoindentation method. To evaluate the oxidation resistance of the coatings, they are annealed in air at temperatures of 1000, 1100, and 1200°C. It is established that coatings of the optimal composition show a hardness of 26 GPa, an elastic modulus of 221 GPa, and an elastic recovery of 65%. The coatings obtained in the medium consisting of Ar and 15% N₂ are oxidation-resistant at temperatures of up to 1200°C owing to the formation of a SiO₂-based protective film on their surface.