Sergey Onufriev

• Russian Academy of Sciences

Представлены результаты измерения свойств диборида циркония ZrB2 в интервале температур 2500–5000 К: энтальпии, теплоты плавления, теплоемкости, удельного электросопротивления. Данные для жидкой фазы получены впервые. Исследование выполнено методом нагрева импульсом тока микросекундной длительности - методом ¾взрыва проводников¿ Лебедева на пластин...

Investigation of the tantalum carbide physical properties at temperatures ranging from 2000 to 5500 K during rapid current pulse heating were carried out. The experimental results were obtained on the 150 μm thick lamellas cut from the Spark Plasma Sintered bulk samples with a TaC0,9 composition. The conducted experiments showed that carbide of thi...

A fast method for studying the physical properties of substances is considered, -heating by a single current pulse for 5-8 µs. Its advantages over the stationary methods is in obtaining bulk thermophysical properties of carbides at high temperatures (2500-5000 K). The temperature was measured by an optical method using high-speed photo-detectors PD...

The study was performed to establish a graphite melting line. Bundy’s phase diagrams are presented, in which the melting point of graphite (Tm) does not exceed 5500 K for all the considered pressures, up to (at least) 1 Mbar. The results of several studies on pulsed current heating related to measuring the melting temperature of graphite and obtain...

Hafnium carbide HfC (at%: 42%C; 49%Hf; 7%O) was investigated under rapid heating by a current pulse, in a time of 5–8 μs. The temperature was measured by radiance of a flat surface of a carbide plate (thickness 130 microns) at a given emissivity. This carbide plate was clamped between two K-8 plates, to prevent evaporation of the carbide and to pre...

The results of the study of zirconium nitride ceramics (0.9ZrN + 0.1ZrO2) in solid and liquid phases are presented: temperature dependences of the specific input energy (enthalpy), specific heat, heat of fusion, electrical resistivity at temperatures of 2000–4500 K. To measure these properties the method of microsecond electrical current pulse heat...

Key experimental studies (mainly pulse heating) aimed at obtaining the physical properties of the most refractory substance — graphite — in the temperature range of 2000–8000 K are discussed. The properties considered are enthalpy, input (Joule) energy, thermal expansion, specific heat, and electrical resistance, as well as their dependence on the...

Carbide Ta0.8Hf0.2C in the form of a thin magnetron sputtering layer (~1 μm) was studied under rapid heating (5 μs) by an electric current pulse. The resistivity of this carbide (referred to initial dimensions) and temperature coefficient of resistance were obtained up to 5000 K for the first time. The temperature was measured by surface radiation...

We studied the carbide Ta0.81Hf0.19C0.94 in the form of a thin deposited layer (1 μm) under rapid heating (5 μs) by electric current pulse. We obtain the properties of this carbide: melting heat; specific heat, and enthalpy in the solid phase from 2000 K up to Tmelt = 4300 K, and for the first time in the liquid state up to 5000 K. We measured the...

The results of an experiment with pulse current heating of high purity iron are presented: temperature dependences of the specific energy input and specific heat up to 4000 K. The specific heat of the liquid iron is shown to be constant Cp ≈ 0.9 J/(g K) at both normal and high (up to 10 kbar) pressure.

A technique for measuring the specific heat of conducting substances (metals, zirconium carbide and nitride, and graphite) in conditions of pulsed heating with a microsecond current pulse at a constant and increasing pressure is considered. The reliability of the detection of a steep increase in specific heat before melting, which is presumably ass...

Past studies have led to the conclusion that graphite melting point is a point of change from solid metallic graphite to liquid nonmetallic. Here, new experimental values have been obtained for the carbon resistance, temperature coefficient of resistance and specific heat (near to CV) under fast electrical heating. The emergence of a specific heat...

Experimental studies of carbides are briefly reviewed. The high-temperature properties of carbides used in nuclear power and aerospace engineering are considered. Temperature is measured from either plane surface emittance or the emittance of thin samples prepared in the form of a melting blackbody model. The following quantities are measured: Joul...

Features of measuring the temperature of conducting materials (metals, carbide, graphite) with a brightness pyrometer upon heating with a microsecond pulse of electric current are considered. Problems of pyrometer calibration and developing a blackbody model for measuring true temperatures in solid and liquid phases are examined. Estimates of tempe...

Experiments with HOPG graphite grade showed that the melting temperature of graphite equals 4800-4900 K and that the melting of graphite is possible only at elevated pressures. The data were obtained for resistivity, specific heat and input (Joule) energy up to 5000 K. HAPG (Highly Annealing Pyrolytic Graphite) is a form of highly oriented pyrolyti...

The temperature dependences of the thermal and electro physical properties of the zirconium carbide ZrC + C and ZrCa0.95 were studied in the temperature range 2000-5000 K. The Zr+C specimens were in the form of thin layers sputtered on quarts substrate and ZrC0.95 specimens were in the form of plates cut off from the sintered block. The properties...

The study of the high-temperature properties of a complex composition (Ni–Cr–Al–Re–Hf–Y) alloy was performed under the rapid heating of the foil by a single pulse current during a few microseconds. The alloy melted in the temperature range of 1670 to 2050 K and heated in a liquid state up to 4000 K. There were measured thermal properties (energy Jo...

Sintered zirconium carbide (C/Zr ≈ 0.95) was studied by pulsed electrical heating method with microsecond duration. Thermophysical properties such as Joule energy, heat of melting, the specific heat, and electrical resistance were measured in the temperature range of 2500–5000 K by this method for the first time. The steep increase of the specific...

Physical processes during a rapid (microsecond) heating of metals, carbon, and their compounds by a single pulse of electric current are discussed. Effects arising in such short-term heating near the melting point are noted: the electron emission and heat capacity anomalies and the possible occurrence of Frenkel pair (interstitial atom and vacancy)...

By means of pulse current heating (3–5 μs), specimens of a new highly oriented pyrolytic graphite (the highly annealing pyrolytic graphite, HAPG) within the temperature range 2500–5000 K were investigated. The temperature, electrical resistance (compared to the initial sizes), and Joule energy of heating were measured. The beginning of graphite mel...

To study the properties of graphite at high temperatures and elevated pressures a method of fast heating by current pulse is presented. The experiment to obtain the dependencies of electrical resistance, input energy and specific heat versus temperature up to 5000 K for highly annealed pyrolytic graphite is shown. Specific heat up to 4600 K is near...

The zirconium nitride specimens were obtained as a thin (2.5 μm) layer deposited on the insulating K-8 glass substrates by the magnetron sputtering technique. The impulse current heating permitted reaching the nitride melting region in 5 μs. The current, the voltage, and the radiation at the wavelength of 856 nm were registered. The energy input (t...

The microsecond technique of electrical pulse heating which gives rather uniform energy input into a film specimen is considered. ZrC + C specimens in the form of a thin layer (4.9 μm) sputtered on isolating substrates by magnetron sputtering technique were used. Specimens contained (in at.%): Zr – 17.88; C – 67.69; N – 8.13; O – 5.98. It was measu...

The main task of this paper to show experimental evidence that there is no any overheating above the steady state melting temperature of a metal under fast heating. Polycrystalline refractory metal (Ta with 2 at % Nb) was investigated in the present study. Melting temperature of Ta was measured using the technique of electrical pulse heating during...

On the basis of measurements of radiation intensity and pressure [1] in the cone vertex during explosion of a hydrogen-air mixture, an estimate is presented of the explosion product temperature. The estimation is obtained by a simple graphical method. Under the pressures of 472 atm and 684 atm at the moment of explosion, the explosion product tempe...

Equipment and results of an investigation of the resistivity of zirconium and tantalum carbides in the solid and liquid states as a function of the specific energy employed are described. Estimates of the heat of fusion of the carbides are given. The investigation is carried out using pulsed electric heating of samples cut out of massive blocks, an...

On the basis of similarity of thermal expansion of liquid metals and data on the temperature dependence of density of zirconium, hafnium, and tungsten, estimates of the critical parameters of these metals are obtained.

The temperature dependences are given of enthalpy, heat capacity, mean temperature coefficient of linear expansion, density, thermal conductivity, thermal diffusivity, and emissive properties of hafnium in the temperature range from 293 to 2000 K, which are obtained as a result of analysis and simultaneous processing of literature data.

Results for ZrO2-based refractory materials tested for contact with molten iron, thermal cycling, and single-time thermal impact in an electric furnace are presented. The test results are compared with calculated thermal stresses for the protective layer of an EPR (European Pressurized Reactor) core melt catcher simulating the spill of the molten c...

The results of an investigation of the interaction of metal melt of reactor materials with zirconium dioxide refractories (ceramic, concrete) in an atmosphere with various oxygen contents at temperatures up to 2600 K are presented. The experiments showed that the melt Zr + 2.5% Nb at 2273 K does not give rise to erosion of the ceramic; at 2500–2600...

The results of an investigation of the interaction of zirconium dioxide refractories – ceramic and concrete with iron oxides – are presented. The investigations showed that starting at 1600 K in an argon atmosphere contact of a mixture of iron oxides with refractories gives rise to erosion of the latter. Under isothermal conditions (2270 K), cerami...

Interaction of reactor MM with ZR (ceramics and concrete) in the atmosphere with different oxygen content at the temperatures to 2600 K is investigated. It is shown that Zr+2.5%Nb melt at 2273 K does not lead to erosion of ZR ceramics and at 2500-2600 K impregnates and dissolves them. The obtained results are used for analysis of operation of the r...

Without Abstract

Experimental data on the interaction of ceramics and concrete, based on zirconium dioxide, with metal oxide melts are analysed. The temperature of the liquid phase appearance for the ceramics and concrete is determined. It is shown that the ceramics are characterized by the greater corrosion resistance to melts of metals and their oxides than concr...

The possibility of molten iron interaction with zirconia concrete of hydration solidification and the concrete components (barium and strontium monoaluminates) is investigated. The study was aimed at the evaluation of the concrete resistance to the melt formed in the active zone at the accident of nuclear power station. The data of X ray phase anal...

The interaction of molten iron with hydration-hardened zirconia concrete (TsGB) and its components (barium and strontium monoaluminates) is considered. The results of an x-ray phase and spectral analysis of the materials of ingots and crucible walls show the absence of such an interaction.

The results permit drawing the following conclusions: the penetration depth of the melt into the ceramic during the experiment was equal to approximately 0.12–0.2 mm in the case of a mixed melt of the steel and zirconium and approximately 0.35–0.4 mm in the case of the pure-zirconium melt; the crucible ceramic does not undergo erosion under the act...

Results are presented of investigations of thermochemical processes of interaction of reactor materials melt with refractories on the base of zirconium dioxide. The aim of the investigations is studying the erosion resistance of the zirconium-dioxide ceramics to action of the melt of carbon and stainless steels with zirconium. The conclusion is mad...

The interaction of a concrete (TsGB) with metallic melts that include Fe, Zr, Cr, Ni and with their individual components is investigated. It is shown that this concrete behaves like a beat-resistant material. In contact with metallic melts its properties depend on attainment of the melting temperature of the material of the crucible wall in the ho...

Zirconia concrete is suggested to build traps for hot self-warmed melt of nuclear fuels in nuclear power stations. Reaction of zirconia concrete with the melt of zirconium, iron, chromium, and nickel was studied. The data showed that zirconia concrete of hydratation hardening had high thermal stability. The crucible wall destroyed when the temperat...

Optical properties (the indexes of refraction and absorption) of molybdenum in the wavelength range 0. 4-24 mu m and temperature range 1400-2000 K have been determined by the radiation indicatrix method in the visible region and a high-temperature version of the Kramers-Kronig method in the infrared region. There is good agreement between the resul...

In a hlgh-temperature dilatometer [i], the expansion in the range 293-T~ is measured from the shadow image from the specimen at room temperature and the image of the self-luminous marks with the specimen hot. One therefore has to consider the possible errors arising in the transfer between the two, as well as the effects of mark shape on this error...