Vladimir Stepanovich Urbanovich

National Academy of Sciences of Belarus | NAS B · Laboratory of refractory ceramics and nanomaterials

Additive-free boron carbide (B4C) powders were densified at 4 GPa using the high-pressure “anvil-type with hollows” apparatus in the temperature range of 1500-1900 °C. The boron carbide ceramics prepared by this method showed a hardness of 37 GPa, which is very close to the hardness of mono-crystal boron carbide. The study showed that the boron car...

Additive-free boron carbide (B4C) – silicon carbide (SiC) ceramic composites with different B4C and β-SiC powders ratio were densified using the high-pressure “anvil-type with hollows” apparatus at 1500 °C under a pressure of 4 GPa for 60 s in air. The effect of starting powders ratio on the composites sintering behavior, relative density, microstr...

Additive-free boron carbide (B4C) – silicon carbide (SiC) ceramic composites with different B4C and β-SiC powders ratio were densified using the high-pressure “anvil-type with hollows” apparatus at 1500 °C under a pressure of 4 GPa for 60 seconds in air. The effect of starting powders ratio on the composites sintering behavior, relative density, mi...

The effect of electroerosive treatment of the surface of carbide plates from superhard nitride ceramics on their phase composition and vacuum soldering of cutting elements is studied. Studies of the surface quality and elemental composition have been carried out. The surface of the plates for soldering is processed by the method of electroerosive c...

The investigation of nano-mechanical properties of sphene sintered under ultra-high pressures in the order of 4GPa is done using indentation techniques. An indentation hardness of 6.6GPa and reduced elastic modulus of 112.3GPa is reported at maximum load of 7mN. The material exhibits a high elastic recovery (∼59.1%) and the nature of deformation me...

Investigations of the high-pressure sintered nanocrystalline mullite powder are presented. The synthesized mullite powder with crystallite size of 51 nm was densified by using high-pressure “anvil-type with hollows” apparatus at 4 GPa over the temperature range of 1100–1500 °C in 100 °C steps. The phase composition and structural parameters of the...

Additive-free β-SiC nanopowders were densified by using high-pressure “anvil-type with hollows” apparatus at the pressure of 4 GPa in the range of 1500–1900 °C. The starting powder with average particle size of 10 nm was synthesized by a sol–gel process. Crystallite size and lattice parameters of the samples have been studied at room temperature by...

Amorphous-nanocrystalline composite based on nanocarbon, obtained by sintering under high pressure.

Sphene (CaTiSiO5), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO3, TiO2 and SiO2 using vibro-milling for homogenization and activation of precursors. During the high-pressure and high-temperature synthesis (HPS) process at 4 GPa and 1,200 °C, sphene undergoes into phase transition, from room-temperature phase P21...

By using a cheap fullerenes-free high-pressure method of sintering extracted fullerene soot (EFS) with addition of 10% Fe, a superhard amorphous-nanocrystalline composite has been obtained on the basis of carbon with the dispersity of nanocrystallites 2.5–14.5 nm in an amorphous matrix with the microhardness of the superhard phase inclusions of up...

Different 30 Si3N4/70vol.%SiC composites, without and with additions of titanium (Ti), titanium diboride (TiB2) and cubic boron nitride (cBN), were obtained by High Pressure - High Temperature (HPHT) sintering. Density, Young's modulus, hardness, fracture toughness and coefficient of friction were measured. Microstructural (SEM) investigations were...

Purpose: The purpose of the presented work is to study the influence of different Si3N4 and SiC powders on mechanical properties of Si3N4–SiC composites, to obtain a hard and tough engineering material, especially for cutting applications.Design/methodology/approach: Three kinds of Si3N4 – SiC composite, with initial powders of different grain size...

The effects of compacting pressure, powder degassing and high pressure sintering temperature and time on the densification and properties of nanocrystalline titanium nitride have been investigated. For this reason, TiN powder with a mean particle size of 55 nm was pressed in the range of compacting pressure from 0.2 to 1.0 GPa and sintered under st...

Calculation of stress-deformed states of high pressure apparatus (HPA) of "anvils with recesses" type for sintering of nanomaterials is realized by finite element analysis (FEA). At first three general regimes of HPA: "assembly", "loading" and "unloading" are considered together. It is shown, that in certain zones of HPA hard alloy anvils arisen st...

A two-step process has been proposed for the preparation of refractory rare-earth diborides: high-temperature high-pressure elemental synthesis followed by argon annealing. Using this process, we have synthesized terbium, erbium, thulium, and lutetium diborides containing no more than 3 wt % impurity phases.

The paper examines the high-pressure sintering of nanograined ceramic polycrystals based on TiN-TiB2 and TiC0.5N0.5 refractory compounds. Using the optimum pressure (up to 4 GPa) allows keeping the initial nanostate (TiN-TiB2 and TiC0.5N0.5) and obtaining high-density ceramics with enhanced mechanical properties. An x-ray structural analysis is use...

In this paper the effect of high-pressure sintering (HPS) temperature on the microstructure, physical and mechanical properties of TiB2 ceramics has been investigated. Initial TiB2 powder with the average particle size of 5 μm was sintered in a modified high-pressure anvil-type apparatus under static pressure of 4 GPa in the temperature range of 14...

A study of high pressure sintering of partially stabilized zirconia nanopowder at pressure of 4 GPa depending on sintering temperature in the range from 800 to 1700 degrees C is presented. With an increase of the sintering temperature a monotonous variation of phase composition takes place. The reduction of monoclinic phase content is accompanied b...

High-temperature oxidation behavior, microstructural evolution, and oxidation kinetics of additive-free α-, β-, and mixed silicon nitride ceramics is investigated. The oxidation rate of the ceramics depends on the allotropic ratio; best oxidation resistance is achieved for ceramics rich in α-phase. Variations in the oxidation kinetics are directly...

Theoretical and experimental studies of cubic BN mixed with Ti and TiN in the molar ratio 1:1 are reported and compared with the properties of Ti and TiN films grown by the arc plasma deposition method on cBN substrate. Theoretical calculations show that Ti and TiN react with cubic BN forming new phases at 1000 and 1400 °C. The cBN composites were...

Without Abstract

A computerized system of apparatuses for the sintering at high pressure of nanoceramics based on refractory compounds was developed. It allows for carrying out the sintering process according to a given program with rapid and accurate regulation of the P-T parameters. Information on the sintering process is stored in an internal data base with the...

High-pressure sintering is one of the effective methods for obtaining high-density nanoceramics based on high-melting-point compounds [1–4]. for example, TiN ceramics with nearly full density and increased microhardness have been obtained by this method [5, 6]. It is evident that the structure and properties of nanomaterials sintered at high pressu...

High-temperature oxidation behavior, microstructural evolution, and oxidation kinetics of additive-free alpha-, beta-, and mixed silicon nitride ceramics is investigated. The oxidation rate of the ceramics depends on the allotropic ratio; best oxidation resistance is achieved for ceramics rich in a-phase. Variations in the oxidation kinetics are di...

Recently, the interest in nanocrystalline materials based on high-melting point compounds has increased. It is hoped that new superhard materials can be obtained. The main problem in the consolidation of particulate nanostructured materials is to combine full density with conservation of the nanostructure, that is keeping the grain size of the init...

The dependences of density, thermal conductivity and electric resistance of the ceramic composites from mixtures of different compositions (95% diamond - 4.6%AlN - 0.4%Y2O3, 90% diamond - 9.2%AlN - 0.8%Y2O3 and 89% diamond - 8.3%AlN - 0.7%Y2O3 - 2%B) on sintering temperature have been studied at the pressure 7 GPa. It is shown that the material sin...

The main problem of consolidation of particulate nanostructured materials is to provide a complete compaction with retention of the nanocrystalline structure, i.e. maintaining the grain size characteristic of the initial ultrafine powder (UFP). Conventional sintering and hot pressing methods are not acceptable due to intensive recrystallization pro...

A possibility to produce high density ceramics from metal-like high-melting compounds - IVa, Va Group transition metal carbides, nitrides, borides, - as well as from non-metal high-melting compounds of B4C, SiC, Si3N4, AlN without use of activating additions has been investigated. Ceramics have been sintered at pressures up to 7.5 GPa and temperatu...

Composite diamond-containing materials posses certain properties that enable them to combine high abrasive durability of diamond with its unique stress-proof qualities. As a rule they represent composition of diamond particles evenly dispersed within a ceramic matrix, generally based upon tungsten carbide [1–3]. The most well-known representatives...

Nanocomposite materials of TiN/TiB2 system are prepared both by high pressure sintering of ultrafine powders and the films deposition using magnetron sputtering. Properties and structure of obtained paniculate and film materials derived from hardness measurements as well as TEM and SEM analyses are discussed and compared in detail.

The consolidation of TiN ultrafine powders by application of high pressures and high temperatures is described. The evolution of structure and properties is discussed. Results are reported of a hardness test, involving high loads, for characterization of boride PVD films.

Two-phase Si3N4-TiB2 composites were prepared by high pressure (P=4 GPa) at 1800 degrees C. One type of TiB2 powder (S=1.1 m(2)/g) and two types of Si3N4 powders (S=1.7 m(2)/g- composites I, and S=23.5 m(2)/g - composites II) have been used for preparation of Si3N4-TiB2 composites (25, 50, and 75 vol%). Compression tests were conducted at 1500 degr...

The kinetics of the sintering of titanium diboride at pressures of 2.5 and 4 GPa and temperatures up to 2000°C are studied. The activation energy of the different sintering stages are determined, and the TiB2 mass transfer mechanisms characteristic of these stages are considered. The activation energy for the self-diffusion of titanium is 201 kJ/mo...

The authors assess the properties of brittleness, microhardness, porosity, microstructure, crystal structure, ductility, and grain size of the diborides of titanium, zirconium, hafnium, niobium, and tantalum under the effects of pressure. Results show that the micromechanical properties of the diborides are determined not only by the magnitude of t...

The effect of the conditions of thermobaric treatment on the fine crystalline structure parameters of niobium and tantalum diboride along various crystallographic directions is studied. It is shown that for the left bracket 001 right bracket direction the dimensions of the coherent scattering region and the mean square microdeformations are greater...

The effect of grinding titanium diboride powder in air, in ethanol, and under vacuum on its sinterability at high pressures and on its microhardness is studied. It is established that grinding of the powder under vacuum activates the sintering process in sintering this powder at high pressure and ensures that fine grained specimens of high density...