Идентификация NV-центров в синтетических флуоресцентных наноалмазах и контроль дефектности кристаллитов методом электронного парамагнитного резонанса

A 100 nm synthetic diamond particle with a large (> 4 ppm) amount of nitrogen vacancy (NV) centers has been studied. The latter exhibit lines associated with forbidden Delta m_s = 2 and allowed Delta m_s = 1 transitions in the electron paramagnetic resonance (EPR) spectra of the ground state of the NV(-) center. The luminescence intensity of particles in the range 550-800 nm increases with an increase in the irradiation dose of 5 MeV electrons and correlates with the integrated intensity of the EPR line with a g-factor g = 4.27.This value is used to estimate the concentration of NV(-) centers and to select diamond powders with the highest fluorescence intensity. The dependence of the EPR signal intensity of the Delta m_s = 2 transition of the NV(-) center on the microwave power has the form of a curve with saturation and subsequent decay, and rather well characterizes the crystal quality of the local environment of the centers under study in these particles. The intensity of the x,y Delta m_s = 1 transition (at ~281.2 mT, 9.444 GHz) turns out to be more sensitive to changes in particle size in the submicron range and the appearance of near-surface defects obtained during mechanical processing.

MODIFICATION OF HEAT-RESISTANT OXIDES AND CHLORIDES OF GRAIN SURFACES OF SYNTHETIC DIAMOND GRINDING POWDERS FOR APPLICATION IN GRINDING TOOLS

Further development of modern technologies of diamond processing is connected with application in the diamond tool of powders with new unique properties, special morphology of grains, with the increased chemical and thermal stability. To increase the heat resistance of diamonds, they are covered with a metal (metallization) or glass-ceramic layer, or introduced into the reaction mixture used in the synthesis of diamonds, alloying additives of certain elements. Recently, other methods of coating to increase the heat resistance of diamonds have been developed, such as: vacuum ion-plasma sputtering, epitaxial synthesis, magnetron sputtering, the method of liquid-phase deposition. The latter method is promising for modifying the grain surface of grinding powders of superhard materials by heat-resistant inorganic non-metallic coatings, as it is the most economically advantageous. Determining the features of the technology of modification by the method of liquid-phase application of heat-resistant inorganic coatings (oxides and chlorides of metals and nonmetals) on the surface of grains of grinding powders of synthetic diamond brand AC6, used for grinding tools in mechanical engineering. Modification was performed by the isothermal method of liquid-phase application of saturated solutions of both heat-resistant oxides (В2О3, Al2O3), chlorides (СаСl2, NaCl, MgCl2, FeCl3), and their mixtures (В2О3+СаСl2, В2О3+NaCl). Based on the analysis of the results of the research, it can be stated that the application of coatings of inorganic substances (some oxides and chlorides) increases the heat resistance of synthetic diamond grinding powders. Modification allows to reduce expenses of diamonds in wheels at grinding. Conditions for modification of heat-resistant oxides and chlorides, as well as their mixtures, grain surface of synthetic diamond grinding powders are determined. Modification of the surface of diamond grains with a combination of B2O3+Al2O3 is guaranteed to double the wear resistance of diamond wheels. It is established that in all cases of modification the roughness of the parameter Ra decreases. It is determined that by changing the surface modifier of diamond grains it is possible to affect the bearing capacity of the rough surface obtained by grinding. The development of effective ways to increase the heat resistance of grinding powders made of superhard materials, primarily abrasive grinding powders made of synthetic diamond powders, helps to improve the quality of the grinding tool.

Team durability test of a 1.3 MW locomotive diesel engine with prototype piston rings

Objective of this work was to realize a test of durability of railway engine EMD645 with power about 1300 kW. Within the framework of this test were investigated a prototyped piston’s rings with diamond embankment. Piston rings are made of chromium layer with including of diamond powders technology with a porous chromium coating, where in pores is deposited on said diamond powder with a grain size about 1 micron. The work will be carried out of an analysis of collaboration piston – piston rings – cylinder unit in internal combustion engine and an analysis of the use of hard materials (diamond powder) in friction pairs. During work of this unit we can observe wear of piston rings, precisely - of coating which is deposited on ring to prolong service life. After testing of the locomotive engine EMD645 on the basis of the collected results are developed conclusions of the wearing intensity on piston ring and relating them to the requirements for coatings. The work aims to show the possibilities and benefits of the application of new protective coatings on structural elements of the internal combustion engine in order to reduce their wearing, which is consistent with the observed trend of technology development.

The Influence of Diamond Addition to Ni-Al Powder on Oxidation Behavior of Ni-Al During Plasma Spraying for High Performance Oxide-Free Ni-Al Intermetallic Coating

Ni-Al intermetallics have excellent corrosion and oxidation resistance, but their use in thermal spraying has been limited due to issues with in-flight oxidation. In this study, a novel approach is proposed to remove oxide from Ni-Al droplets in-flight by adding a deoxidizer (diamond) to the feedstock powder. A mixture of nickel, aluminum, and diamond powders was mechanically alloyed using a combination of cryogenic and planetary ball milling. The resulting Ni/Al/diamond composite powder was then plasma sprayed via the APS process, forming Ni-Al coatings on Inconel 738 substrates. Phase composition, microstructure, porosity, and microhardness of the coatings were characterized by X-ray diffraction, scanning electron microscopy, image analysis, and hardness testing, respectively. Oxygen content measurements showed that the coatings contained significantly less oxygen than coatings made from ordinary Ni/Al powders. In-flight particle temperatures were also measured and found to be higher than 2300 °C. The low oxygen content in the coatings is attributed to the in-situ deoxidizing effect of ultrahigh temperature droplets which are also oxide-free.

INVESTIGATING THE PROCESS OF STRUCTURE FORMATION AND WEAR RESISTANCE OF ABRASIVE TOOLS ON THE METAL BOND OF COMPOSITION 51%Fe+9%Ni 32%Cu+8%Sn MADE OF METALLIZED BY TITANIUM DIAMOND POWDERS

The process of of structure formation and wear resistance of abrasive tools on the metal bond of composition 51%Fe+9%Ni+32%Cu+8%Sn made from metallized by titanium diamond powders is investigated. The metallographical substantiation is introduced, as well as the wear-resistance and the working capability of abrasive tools are studied. It is shown that the structure is heterophase and consists of five phases, the first of which is a solid solution based on nickel, the second is a solid solution of tin, nickel, and iron in copper, the third is a solid solution of nickel, copper and tin in iron, the fourth and the fifth are intermetallic compounds with a defective structure. It is revealed that in the developed composite material, the volume content of heavy components is approximately 63%, the plastic component occupies approximately 25% of the sample volume, and the intermetallic phases - approximately 12% of the total volume, which are distributed over the entire sample surface. Based on the results of the complex investigation of the operability and wear resistance of diamond tools manufactured according to the developed technology carried out in the laboratory and production conditions for processing non-metallic materials, the optimal modes of manufacturing highly productive and wear-resistant diamond-metal abrasive tools were selected and substantiated: cold pressing pressure P = 600 MPa, free sintering temperature: T = 850°C, holding at this temperature: τ = 45 min. Applying the developed technology as a method for producing a diamond tool ensures the high efficiency of production.

Hybrid carbon-hydrocarbon structure

A new hybrid carbon-hydrocarbon structure was discovered after pumping a gas mixture of methane and hydrogen through 314 – 400 µm synthetic diamond powder. The experiment was carried out on the microwave plasmachemical installation designed for deposition of polycrystalline diamond films. The main parameters during the experiment were the following: the power of the microwave generator 3,5 kW, the flow rate of hydrogen 400 ml/min, methane 20 ml/min, the pressure in the reactor chamber 63 torr. The gas mixture was pumped at pressure drop of 13 torr. The diamond powders were placed in molybdenum cups inserted into a copper pedestal. In the gaps between the diamond particles of the surface layer unidirectional thread-like structures (length 100 – 500 μm, diameter 2 μm) were found, some of which ended in spherical formations (average diameter 18 μm). Such a composition of thread-like structures and spherical formations was called “dandelion” one. Raman spectroscopy was performed to examine the nature of these formations. The thread-like structure was determined as monocrystalline graphite. The surface of the spherical formation was represented by spindle-shaped structures of nanocrystalline graphite (length 2 μm, thickness 200 nm) and nanodiamond grains with trans-polyacetylene chains [C2H2]n.