scholarly journals ТЕПЛОФИЗИЧЕСКИЕ ХАРАКТЕРИСТИКИ И ТЕРМОЭРОЗИОННАЯ СТОЙКОСТЬ КЕРАМИЧЕСКОГО МАТЕРИАЛА НА ОСНОВЕ КАРБИДА БОРА

2020 ◽  
pp. 136-145
Author(s):  
Юрий Игоревич Евдокименко ◽  
Ирина Александровна Гусарова ◽  
Геннадий Александрович Фролов ◽  
Вячеслав Михайлович Кисель ◽  
Сергей Васильевич Бучаков
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Heat Resistance ◽  
Specific Heat ◽  
Thermal Conductivity Coefficient ◽  
Erosion Resistance ◽  
Combustion Products ◽  
Structural Ceramics ◽  
Radiation Coefficient ◽  
Temperature Dependences

A study of the thermophysical characteristics, heat resistance, and thermal erosion resistance of high-temperature structural ceramics (SC), which was developed at NTUU "I. Sikorsky Kyiv Polytechnic Institute" under the supervision of Corresponding Member of the National Academy of Sciences of Ukraine, Professor P. I. Loboda was made. This high-temperature structural ceramics is intended for use in aerospace engineering, in particular - for the manufacture of aerodynamic surfaces of reusable hypersonic aircraft and heat-stressed elements of the gas-dynamic paths of their engines. The samples of B4C-SiC-B6Si ceramics of two compositions (No. 1 and No. 2) were studied, which differ in the mass content of the initial components. Temperature dependences of the specific heat and thermal conductivity of the spacecraft, radiation coefficient, heat resistance in an oxidizing environment, and the thermal erosion resistance in supersonic flow of combustion products of an air-kerosene fuel mixture were determined. The temperature dependence of the specific heat was determined using an IT-c-400 instrument (in the range of 40 °C - 440 °C) and by the calculation of the temperature dependences of the specific heat capacity of the system components following the Reno rule (up to 2100 °C). The temperature dependence of the thermal conductivity coefficient of the SC of composition No. 1 was determined by solving the inverse heat conduction problem on a computer model based on experimental data. Temperature fields and heat fluxes were obtained under conditions of one-sided heat-ing with a reducing flame of a propane-oxygen welding burner. The thermal conductivity coefficient of SC composition No. 1 increases from 11 W/(m×K) at 20 °С to 25 W/(m×K) at 1400 °С. Its radiation coefficient in the temperature range 1000 °С - 1400 °С is ε = 0.96 ± 0.02. Heat resistance of SC of both compositions in the oxidizing flame of an oxygen welding burner at a surface temperature of 1400 °C has demonstrated that after two hours of heating, the average values of mass ablation for the two tested samples of compositions №1 and № 2 respectively 2.1% and 1.4% (a sample thickness of 4 mm). Tests in the supersonic flow of combustion products at the same surface temperature confirm the high resistance of the material to thermoerosion in the oxidizing medium. The change in the morphology of the heated surface of the sample after six five-minute heating cycles was manifested only by an increase in its roughness without visible oxidation. High thermal conductivity, heat and thermoerosion resistance, radiation coefficient of the studied SC at a temperature of 1400 °C in combination with low density (2.7 g / cm3) make this high-temperature structural material of aerospace technology promising for use.

Transport and Thermodynamic Properties of CeRu2Al10 Controlled by Pressure at around Critical Pressure

2018 ◽  
Vol 941 ◽  
pp. 1378-1383 ◽  
Author(s):  
Yukihiro Kawamura ◽  
Chihiro Sekine ◽  
Kazuyuki Matsubayashi ◽  
Yoshiya Uwatoko ◽  
Takashi Nishioka
Keyword(s):  
Electrical Resistivity ◽  
High Temperature ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Joule Heating ◽  
Ground State ◽  
Critical Pressure ◽  
Antiferromagnetic Ordering ◽  
Temperature Dependences

We present transport and thermodynamic properties of CeRu2Al10 controlled by pressure in a vicinity of a critical pressure PC ~ 4GPa, where antiferromagnetic ordering disappears. The resistivity under pressure was measured with DC four terminal method and the AC specific heat under pressure was measured by Joule heating type technique. The pressure was applied by cubic-anvil-apparatus and palm-cubic-anvil-apparatus. The results of AC specific heat indicate TN holds at high temperature up to 3.9 GPa but suddenly disappears above this pressure. We confirmed TN from thermodynamic properties. Although CeRu2Al10 is in a Kondo semiconducting ground state at 4 GPa, temperature dependences of electrical resistivity at 4.6 GPa and 5.9 GPa indicate metallic ground state in these pressures. CeRu2Al10 does not show superconductivity down to 0.7 K at 4.6 GPa and 5.9 GPa.

Automated Determination of Protein-Nitrogen in Cereals and Grains

1977 ◽  
Vol 60 (6) ◽  
pp. 1238-1242
Author(s):  
Robert N Revesz ◽  
Norman Aker
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Organic Material ◽  
Combustion Products ◽  
Direct Reading ◽  
Protein Nitrogen ◽  
Operational Characteristics ◽  
Temperature Sample ◽  
Automated Determination

Abstract This paper presents the design, performance, and operational characteristics of a new direct reading instrument for determining nitrogen in cereal and grain. Precision, accuracy, range, speed, ease of operation, sensitivity, sample size, and flexibility of the instrument are presented. Results on various cereals and grains are presented and compared with those obtained by the Kjeldahl technique. The apparatus is the result of research for a rapid method for determining nitrogen in organic material. The instrument uses a combination of a unique high temperature sample oxidation, a sampling valve for separating combustion products, and thermal conductivity detection for the liberated nitrogen in a helium carrier gas.

Measurement of Refractive Index, Specific Heat Capacity, and Thermal Conductivity for Ag6.0In4.5Sb60.8Te28.7at High Temperature

2009 ◽  
Vol 48 (5) ◽  
pp. 05EC02 ◽  
Author(s):  
Masashi Kuwahara ◽  
Osamu Suzuki ◽  
Kouichi Tsutsumi ◽  
Takashi Yagi ◽  
Naoyuki Taketoshi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Refractive Index ◽  
High Temperature ◽  
Specific Heat ◽  
Specific Heat Capacity

scholarly journals TECHNOLOGY IMPROVEMENT OF PLAIN BEARINGS’ TECHNICAL CONTROL IN CONSTRUCTION MACHINERY AND EQUIPMENT

2019 ◽  
Vol 15 (6) ◽  
pp. 854-865 ◽  
Author(s):  
R. F. Salikhov ◽  
V. V. Akimov ◽  
A. F. Mishurov ◽  
G. N. Musagitova
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Internal Combustion Engines ◽  
Thermal Conductivity Coefficient ◽  
Thermal Method ◽  
Test Duration ◽  
Thickness Change ◽  
Construction Machinery ◽  
Technical Control ◽  
Technology Improvement

Introduction. The creation of new machinery and development of modern technologies of its repair in many respects with generation of materials with required properties are defined. Special attention is paid to the economy and widespread introduction of resource-saving and environmentally friendly technologies and to the problems of obtaining and exploitation of new materials, improvement of the goods’ quality.The quality control of materials, which have been used for plain bearings manufacture, during repair action of construction machinery and equipment, as well as reduction of cost and duration of technical control operations implementation are among the issues for repair service organizations. Their solution would enable to increase post-repair resource, cut down failures number, and reduce costs of faults removal in warranty period.Materials and methods. The authors suggest a thermal method of plain bearings materials quality assessment in internal combustion engines. This method is remarkable for its comparative simplicity; it does not require destruction of the material and application of expensive equipment.Results. The dependences of “Cummins” and “Mahle” bushings thickness change on the heating temperature as well as samples warming temperature dependence on test duration have been obtained. According to the derived results such parameters as specific heat and thermal conductivity coefficient are defined. The results of carried out tests show that thermal physic parameters of unoriginal bushings differ from original ones by 11% in thermal conductivity coefficient and by 1.56 times in specific heat.Discussion and conclusions. The calculation of specific heat, thermal conductivity of plain bearings allows to determine the probability of their failure at the stage of entrance control and therefore, to make a more correct decision when choosing parts for execution high-quality repair. As  a consequence of temperature change comparison, when bushings samples of “Cummins” and “Mahle” companies are heated, it could be concluded that heating intensity of an original bushing is 17% higher and the reciprocal of bushing temperature gradient under warming is 1.27 times lower in comparison with an unoriginal plain bearing.

scholarly journals Development and experimental studies of heat insulating coatings of basalt and glass-fiber tubing

2019 ◽  
Author(s):  
M.A. Komkov ◽  
Yu.Z. Bolotin ◽  
T.V. Vasiljeva ◽  
O.V. Zarubina
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Thermal Conductivity Coefficient ◽  
Heat Insulation ◽  
Unit Length ◽  
Experimental Studies ◽  
Low Density ◽  
Basalt Fibers ◽  
Insulating Materials ◽  
Insulation Wall

The study shows that in order to significantly reduce the thermal conductivity coefficient of heat insulating materials made of staple basalt raw fibers, it is necessary to grind and clean them from impurities by liquid method. Within the research, we found that tubing heat insulating coating has the insulation wall thickness and mass per unit length limitations. In this paper we give the results of studying high-temperature and low-density heat insulation of short basalt fibers and alumina bundles.

scholarly journals Characterization of AlN-based Ceramic Composites for Use as Millimeter Wave Susceptor Materials at High Temperature: High Temperature Thermal Properties of AlN:Mo with 0.25% to 4.0% Mo by Volume

MRS Advances ◽  
2019 ◽  
Vol 4 (27) ◽  
pp. 1531-1542 ◽  
Author(s):  
Brad W. Hoff ◽  
Frederick W. Dynys ◽  
Steven C. Hayden ◽  
Rachael O. Grudt ◽  
Martin S. Hilario ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Elevated Temperatures ◽  
Ceramic Composites ◽  
Dsc Measurements ◽  
Mo Content

ABSTRACTIn order to begin to evaluate and model the suitability of high temperature ceramic composites, such as AlN:Mo, as susceptor materials for power beaming applications, the electromagnetic, thermal, and mechanical properties of the material must be known at elevated temperatures. Work reported here focuses on the development of thermal property datasets for AlN:Mo composites ranging from 0.25% to 4.0% Mo by volume. To calculate thermal conductivity of the AlN:Mo composite series, specific heat capacity, thermal diffusivity, and density data were acquired. The calculated specific heat capacity, Cp, of the set of AlN:Mo composites was, on average, found to be approximately 803 J/kgK at 100 °C and to increase to approximately 1133 J/kgK at 1000 °C, with all values to be within +/- 32 J/kgK of the average at a given temperature. These calculated specific heat capacity values matched values derived from DSC measurements to within the expected error of the measurements. Measured thermal diffusivity, α, of the set of AlN:Mo composites was, on average, found to be approximately 3.93 x 10-1 cm2/s at 100 °C and to increase to approximately 9.80 x 10-2 cm2/s at 1000 °C, with all values within +/- 1.84 x 10-2 cm2/s of the average at a given temperature. Thermal conductivity, k, for the set of AlN:Mo composites was found to be approximately 108 W/mK at 100 °C and to decrease to approximately 38 W/mK at 1000 °C, with all values within +/- 5.3 W/mK of the average at a given temperature. Data trends show that increasing Mo content correlates to lower values of of Cp, α, and k at a given temperature.

Sign in / Sign up

Export Citation Format

Share Document