Yu. V. Naidich

• National Academy of Sciences of Ukraine

The dispersion kinetics of molybdenum nanofilms of 100 nm thickness deposited on the leucosapphire, alumina ceramics or quartz glass substrates and annealed in vacuum at 1200–1600°C for different exposure times at each temperature in the interval of 2–20 min. As determined, the molybdenum film deposited on alumina ceramic is the most stable during...

A new design of electron beam gun for welding in open space has been developed. The gun design is based on the application of triode emission system with improved quality of electron beam formation. This provides increased specific power of the beam and, as a result, the high capability to increase the penetration depth of welded joints. To reduce...

The results are presented of the study of kinetics of fragmentation of titanium and zirconium nanofilms 100 nm thick deposited onto the surface of samples made from single crystals of Al2O3 (leucosapphire) and ZrO2 ceramics and annealed in vacuum at temperatures 1300 ÷ 1600 °C with different exposition times at each temperature within 2–20 min rang...

The dispersion process kinetics of palladium and platinum nanofilms 100 nm in thickness was deposited onto oxide substrate (quartz glass, leucosapphire, ceramics based on ZrO2) and annealed in vacuum at 1000 ÷ 1600 °C for different exposure times at each temperature. Built kinetic curves dispersion process these films and made recommendations for p...

The dependence of contact angles on gravity in conditions simulating reduced gravitational force is studied. The contact angles for various solid–liquid systems are measured using both lowtemperature liquids (water, glycerin, hyposulfite, phosphoric acid) and metal melts (tin, silver). It is found that gravity has no effect on the contact angle whe...

As a transition metal compound, zirconia can lose oxygen with the formation of nonstoichiometric phases. The stoichiometry affects the properties of material, therefore, the wetting of nonstoichiometric zirconia with inert metals (Cu, Ni, Sn, Ge, Ag, Pt) and alloys (Cu–Ga, Cu–Ge, Cu–Ni) is studied under conditions when the high oxygen deficit in zi...

Optimized processes for obtaining the braze-welded joints of oxide ceramics based on Al2O3 and ZrO2 by pressure welding of ceramics with ceramics and ceramics with metals are developed. It is established that these braze-welded joints are prepared in the 1300–1600°C temperature range with pressure holding for 30–120 min under 15–25 MPa. The samples...

The wetting of some nonmetals coated with nickel and deposited in vacuum at 700°C using molten aluminum is studied. The sessile drop method and capillary purification are used. The threshold thickness of wetting is 150 nm for most materials and 400 nm for basalt. The high degree of wetting is observed because the metal melt wets better metal coatin...

The authors present the results of an investigation into the dispersion kinetics of niobium and hafnium nanofilms with a thickness of 100 nm, deposited on the surface of specimens of aluminium oxide ceramics, sapphire and ceramics based on ZrO2 as a result of vacuum annealing at a temperature of 1300–1600°C with different holding times in the range...

Wettability and interface microstructure were studied for Nb-containing melts in the contact with ceramic oxide materials of Al 2 O 3 -SiO 2 system. Ni-40.5 at.%Nb and Au-(0-20) at.%Nb alloys were investigated as prospective alloys for high temperature brazes. Ceramic samples ranged in composition from pure Al 2 O 3 to pure SiO 2 . The wettability...

Изучены смачивание материалов на основе Al2O3, ZrO2, HfO2, TiO2, CaF2, BaTiO3, AlPO4 расплавами Ag—5Cu и Ag—39Cu в воздушной среде и контактное взаимодействие в этих системах. Wetting of materials based on Al2O3, ZrO2, HfO2, TiO2, CaF2, BaTiO3, AlPO4 by Ag—5Cu and Ag—39Cu alloys on the air and contact interaction in these systems where inwestigate...

The thermodynamic theories for surface tension of solutions, Gibbs adsorption equation, surface stability condition, experimental data (composition dependences of surface tension and molar volumes of alloys), and thermodynamic activities of components by volume are used to determine the composition, integral and excess Gibbs energies of formation,...

The decrease in geological surveys in Ukraine complicates field tests of experimental batches of diamond bits produced using advanced scientific developments. The strength of samples that model an impregnated layer of diamond bits both in terms of their composition and production method has been tested in laboratory. The process for producing the s...

The thermodynamic theories for surface tension of solutions, Gibbs adsorption equation, surface stability condition, experimental data (composition dependences of surface tension and molar volumes of alloys), and thermodynamic activities of components by volume are used to determine the composition, integral and excess Gibbs energies of formation,...

The paper examines the tribotechnical characteristics of samples produced from superhard boron nitride materials in friction contact with hard alloys of VK and TK grade without lubrication. All friction pairs possess high wear resistance. The hard alloys show three to six times higher wear than that of boron nitride materials in all friction pairs...

Data are presented as to results on wettability and joining of ceramic materials performed during last years at the Frantsevich Institute for Problems of Materials Science of National Academy of Sciences of Ukraine. Wettability of ceramics by advanced filler alloys is considered to be a background for brazing alloy design. Joining techniques (brazi...

A new diamond-hard alloy macrocomposite material consisting of diamond grits (0.5–0.8 mm or more in size) and a WC-Co matrix has been developed. The material is characterized by high mechanical properties of the matrix (the same as for WC-Co monolithic hard alloys) while diamonds remain completely intact (no graphitization or dissolution in cobalt...

The sessile droplet method is used to study the wettability of aluminum oxide (single-crystal Al2O3, i.e. sapphire) by melts of Au-Si, Cu-Si, Ni-Si, Pd-Si, and Ge-Si in relation to silicon concentration, temperature and exposure time. Addition of silicon to melt leads to a fall in the wetting angle from 120–140° for Au, Cu, Ni, Pd and Ge to 70–90°...

The surface tension and density of copper-zirconium alloys were measured over a wide range of zirconium concentration (from 7.182 to 74.0 at.%) at temperatures between 1000 and 1250 degrees C by the "large drop" method in cups made on calcium fluoride. The surface tension and density polytherms are straight lines with negative temperature coefficie...

The wetting of zirconia by a number of pure metals was studied. The wetting of zirconia by Cu-Ga-Ti, Cu-Ga-Zr, Cu-Ge-Ti and Cu-Ge-Zr alloys was studied. For Cu-Ga-Ti the minimal contact angle was near 60∘, for Cu-Ga-Zr it was near 30∘. Cu-Ge based alloys wet the zirconia worse because of the low solubility of titanium and zirconium in germanium. Th...

Alumina and zirconia ceramics joints were made by diffusion bonding through platinum and palladium gaskets in air at temperatures between 1300 and 1550°C. The instrumentation and the procedure for these joints manufacturing are described. The effects of temperature, pressure and exposition time on 3-pt bending strength of resulting joints were esta...

Some capillary phenomena, shapes of surfaces and menisci of liquids, wetting processes under lowered or zero value of Earth gravitation acceleration (weightlessness) are studied. Theoretically, on the basis of computer integration of classic capillarity equations using previously created programs and varying acceleration g values, and experimentall...

Experimental isotherms are presented for (1) wettability of AlN ceramics by Ge–Al and Sn–Al alloys, (2) surface tension and density of Ge–Al and Sn–Al alloys in the whole concentration range. Complex consideration of capillary characteristics of the melts under study is performed taking into account data available on thermodynamic activities of the...

The wetting of calcium fluoride by liquid metal alloys containing 10-50 mass% of chemically active metals (vanadium, niobium, and chromium) was studied by the sessile drop method in vacuum at 700-1350C. At temperatures above 900C these alloys did not wet calcium fluoride. The wetting angle was above 90deg;. This is explained by the formation of vol...

The method of brazing by capillary impregnation of Cu–Ga melt through a titanium powder layer situated between brazed details is elaborated. Samples of ZrO2 ceramic/metal brazed joints using Cu–Ga–Ti filler and Cu–Sn–Pb–Ti filler were fabricated. The joints’ shear strength was 277±37 MPa for the Cu–Ga–Ti and 156±25 MPa for the Cu–Sn–Pb–Ti.

Experiments on the wetting of zirconia ceramics by CuGaTi alloys have been carried out. A method was developed for brazing by capillary infiltration of a layer of titanium powder with CuGa alloy. Specimens of brazed joints were prepared and their shear strength was measured. That strength reached 620 MPa, the average hardness being about 380 MPa.

Contact interaction and wetting have been examined for graphite and diamond acted on by melts of the system Cu−Sn−Ni−Ti, the independent variables being the nickel and titanium contents. There is an optimal composition for the alloy that provides good wetting. It has been used in a technique for metallizing and brazing diamond powders and crystals.

The wettability of aluminium nitride by Sn–Al melts was studied by the sessile drop method in a vaccum of 2 10–3 Pa at 1100 C over the whole concentration region. The minimum interval on the contact-angle concentration dependence curve was observed at intermediate composition. For comparison, experiments were also performed on porous AlN. Wetting o...

The wettability of SiC-monocrystals by Au–Si melts (covering the full concentration range) was studied at high temperature (1500°C). The concentration dependence of the contact angle passes through a broad minimum near 25 at.% Si. This is explained by intrinsic properties of Au–Si alloys and their interaction with SiC surface.

Widespread use of modern ceramic materials with good hardness, wear resistance, mechanical strength is limited by their great brittleness. To improve the resistance of ceramics to impact loads and to stop crack propagation is possible, in particular, by reinforcing materials with a metallic component that has good fracture toughness. Metal-ceramic...

New Cu-Ga-Ti active filler for brazing of silicon nitride ceramic are processed. High-strength Si3N4/Si3N4 joints by using of the Cu-Ga-Ti filler at the optimal brazing conditions are obtained. The room temperature 3-point bending average strength of the brazing joints for Cu-Ga-Ti alloys reaches 711 MPa (max 957 MPa) that is 82% of monolithic cera...

The process of contact melting in iron-carbon systems was investigated using a dilatometric method. Specimens of iron, and diamond or graphite of various structures were studied at different temperatures and pressures. The thickness of the layer of eutectic melt formed and removed from the interface of contact was measured. The experimental data we...

The linear thermal expansion coefficient (LTEC) of multilayer brazed cermet composites made of alternating plates of Si3N4 and Cu (ZrO2 and Cu) has been studied. The coefficient was observed to be anisotropic parallel and perpendicular to the plane of brazing. In the first case the coefficient of the composite was practically equal to that of silic...

The sessile drop method has been used with a vacuum of 2.10-3 Pa to examine the wettability of aluminum nitride by fourteen molten pure metals as well as the effects of adding chromium, vanadium, niobium, tantalum, and titanium to the liquids on the wetting angle in systems containing aluminum nitride and liquid tin, copper, and germanium. Aluminum...

relative to various solid bodies is due to the formation at the interface of bonds, the energy of which is comparable with the liquid phase surface energy and which can only be achieved via interatomic chemical forces during the chemical reaction. When a solid nonmetallic substance (e.g., diamond) or a compound (material based on cubic boron nitrid...

The wettability of two-phase composite materials whose components have different surface energy have been studied under conditions of advancing and receding of metal melts. Experimental results are compared with those calculated by the Horsthenke model. It is established that this model does not consider all factors affecting wetting of inhomogeneo...

An automated TV system with a computer for measuring the capillary constant, surface tension, density, and wetting angles of melts by the sessile-drop method is described. Hardware and software support issues have been treated. Surface tension and density of a number of high temperature melts, including copper, CaF2, and alloys Pb+0.34 at %S, 5Cu+0...

According to the current views, wetting of the solids by metallic melts is determined by the intensity of the chemical reaction which takes place at the contact boundaries [3]. in this work, we examined wetting of lanthanum hexaboride by metals of the iron group, platinum and palladium, as well as copper, gold, germanium, and tin. ~ The selected me...

Strength adhesion of the material to the diamond is the condition for providing for abrasive and monocrystalline tools qualities with use of metallic bonds or the matrix. This is reached by applying coatings on the diamond those chemically interact with its surface and the metal or by applying alloys adhesionally-active to diamond as solders and bo...

The wettability of (111) and (100) diamond grains by melts of the Ni-Mn-B system is studied. The (111) diamond face is wetted by melts containing up to 10 at.% boron to a lesser extent than the (100) face. Further increase in boron concentration in the melt results in inversion of the contact wetting angles. In accordance with the wettability inver...

perature of the onset of interaction in oxide-metal systems, and analyze the effect of the substance of the oxide cation on the process of interaction. The investigations were carried out by the mass spectrometric method on a series produced instrument MI-1305 adapted for high-temperature measurements. The sensitivity of the instrument to pressure...

Oxygen-free ceramics based on SisN~ are promising and are used as electroinsulating and strong structural materials. It is often required to produce reliable joints between ceramic components and between these components and metal structures. The adhesion and wetting of the ceramic materials by metallic melts represent the most important characteri...

The effect of the adhesionally active component Cr and the time of holding the melt on the diamond surface on the adhesion of molten and solidified Cu-Ga-Cr alloys to diamond is studied. It is shown that with increase in Cr content and increase in holding time the work of adhesion gradually increases, and the limiting wetting angle is decreased. Mo...

During the wetting of rare-earth oxides (REO) by liquid metals the energy of the bond (work of adhesion) of the metal with the surface of the oxide is determined by two processes: reaction of the metal of the liquid phase with the anionic sublattice of the solid phase (oxygen of the oxide), and the reaction of the metal of the melt with the cation...

Knowledge of the capillary properties (wettability, work of adhesion) of the contacting phases during the solid--liquid phase transformation of the surface being wetted is necessary, for example, for revealing features of the interphase interaction and solution of a number of technical problems, in particular in powder metallurgy in production of c...

The wetting angles of rare-earth metal oxides of the yttrium group with copper and copper-titanium alloys are higher than for Al2O3, which qualitatively agrees with the greater changes (in absolute values) in the free Gibbs energies for the formation of rare-earth oxides in comparison with Al2O3. The nonstoichiometric nature of the rare-earth oxide...

The wettability of diamond (111) and (100) crystallographic faces by metals chemically inert to carbon (Cu, Ag, Au, Ge and Sn), was studied in comparison with graphite MPG-6. It is shown that the diamond (100) face possesses a higher wettability by these metals than does the (111) face.

Systematic studies of the mechanical (rupture) strength of the bond formed between Ti, Cr, Mo and W coatings, and also Cu-Ga plus Ti, Cr alloys and diamond surfaces, are reported. It is shown that the bond strength is influenced by the deposition temperature, deposition time, and Ti, Cr content in the alloy. The effects of diffusion processes that...

At the boundary with diamond there forms a carbide interlayer consisting mainly of Mn7C3, which ensures a strong bond between the coating and diamond. In the case of a titanium-containing coating, titanium carbide and oxycarbides forming as a result of the dissolution of oxygen adsorbed on the surfaces of metal powder particles do not occur at the...

The strength of adhesion of diamonds to coatings of carbide-forming metals (Ti, Cr, Mo, and W) and alloys with additives consisting of active elements (Ti, Cr) is studied. It is shown that the strength of adhesion of the diamond to the metal as a function of the temperature-time and concentration-time conditions of formation of the contact is extre...

The following materials were employed: technical leucosapphire with 99. 97% Al//2O//3; KV quartz glass with 99. 95% SiO//2; fluorite (CaF//2); MPG-6 single-crystal graphite SU-2000 vitreous carbon and pyrographite. Wetting improved with rise in temperature. Thermodynamic data and results of profilometer measurements indicated that the intensities o...

The wettability of different faces of a number of single crystals (thymol, diphenylamine, dibenzyl, salol, benxophenone, sodium thiosulphate, germanium) by their own melt in the course of their growth was studied using various methods (bubble method, sessile drop method, by the melt meniscus shape). The wettability of the crystals by the own melt i...

The wettability of graphite by liquid iron, rhodium, palladium, platinum, and alloys of these metals with carbon is studied. Under nonequilibrium contact conditions (pure metal-graphite) the wettability is considerably higher than under equilibrium conditions when a carbon-saturated iron is in contact with the surface of graphite. The specific free...

1. It has been established that shrinkage and densification during liquid phase sintering under pressure in the W-Cu-Ni system, like those in the system W-Cu, are only slightly affected by changes in the particle size of the solid phase above 100 . A marked effect of the particle size on densification is observed only with micropowders. 2. The pres...

Drops of Au-Si and Au-Ge melts were formed in A1203 dishes with sharp, ground annular edges, which ensured a symmetrical drop shape. The dish volume was calibrated with mercury. Experiments were carried out under a vacuum of 2 �9 10 -5 mm Hg in the apparatus described in [3]. Values of density p and surface tension Crlv were determined during cooli...

1. In systems composed of gallium and an oxide material, oxygen constitutes an adhesion-active substance, which substantially increases the strength with which the metal adheres to the substrate wetted by it. 2. Spontaneous spreading of gallium over oxide materials in the presence of oxygen is prevented by the presence of a strong oxide film on the...

1. Titanium added to a nickel or nickel-molybdenum melt improves the adhesion of the melt to alumina and the wetting of alumina by the melt. The presence of molybdenum intensifies this effect. 2. At nickel-titanium/alumina and nickel-molybdenum-titanium/alumina interfaces (where the alumina is in the form of sapphire or ceramic A-995) an intermedia...

It is shown that the application of pressure intensifies particle regrouping processes and enables nonporous materials to be produced in cases where this cannot be achieved by free sintering.The effects have been determined of the volume content of the liquid phase and the particle size of the refractory component on the degree of densification att...

1. A study was made of the effects of applied pressure, liquid phase content, sintering temperature, the degree of wetting of the solid phase by the liquid, and solid phase particle size on densification in the system W-Cu. 2. Better wetting of the solid by the liquid phase helps the liquid penetrate into the interparticle contact zones, thereby in...

S>The compaction process in liquid-phase sintering under pressure was ; studied in the system tungsten-copper. The effect of the applied pressure on the ; compaction is studied as dependent on the liquid phase content, sintering ; temperature, degree of solid phase wenting with liguid, and size of solid-phase ; particles. It is shown that a rise in...

Metal deposition on abrasive powders such as those of diamond or Borazon (cubic boron nitride) is widely used today as a method of improving the strength characteristics of these powders and ensuring that their particles are held securely in abrasive tools with organic, ceramic, and metallic binders. The operation is usually performed by the techni...

reaction of thin Mo films applied to various nonmetallic materials, namely, A1203 (sapphire), SiO 2 (vitreous quartz), and graphite, and also on the wetting of these metal-coated materials by a molten metal (copper). The subject selected is of considerable practical importance from the point of view of determination of the optimum coating thickness...

1. A study was made of the wetting of Al2O3 by molten Cu-Ti and Au-Ti alloys. It is shown that the system Cu-Ti/Al2O3 is characterized by better wetting and stronger adhesion compared with the system Au-Ti/Al2O3. 2. To determine the effect of crystallographic orientation in the support plate, a special technique was developed, with the aid of which...

1. A study was made of the densification produced by free sintering in the presence of a liquid phase in diamond — metal systems (diamond — Cu — Ag — Ti and diamond — Cu — Sn — Ti). 2. The effect was examined of diamond particle size on the extent of densification observed. It was established that, in those systems in which particle regrouping is t...

1. A study was made, using the high-speed motion picture filming technique (at up to 3000 frames/ sec), of the kinetics of spreading of molten metals on solid surfaces. The systems Si-graphite, Ni-graphite, Ni(C)-graphite, Sn-Ge, and Sn(Ge)-Ge were investigated. 2. The data obtained enabled a number of conclusions to be drawn as regards the possibi...