scholarly journals Thermophysical properties of BiFeO3/REE multiferroics in a wide temperature range

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060019
Author(s):  
Sidek Khasbulatov ◽  
Suleiman Kallaev ◽  
Haji Gadjiev ◽  
Zairbek Omarov ◽  
Abumuslim Bakmaev ◽  
...  

The paper presents the results of a comprehensive study of the thermophysical properties (thermal conductivity, thermal diffusivity, heat capacity) of high-temperature multiferroic BiFeO3 modified with rare-earth elements (REEs) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu). The regularities of the formation of the mentioned characteristics were established. The assumptions about the nature of the observed phenomena were suggested.

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Ľuboš Krišťák ◽  
Rastislav Igaz ◽  
Ivan Ružiak

The results of using the EDPS (extended dynamic plane source) method to determine thermophysical properties of solid wood of coniferous trees growing in Slovakia with 0% and 12% equilibrium moisture content are presented in the paper. Solid wood of two different tree species: Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.) was used in the research. The research was carried out independently in three anatomical planes. Coefficients of thermal conductivity, thermal diffusivity, and specific heat capacity were determined following the research. Comparing the research results to the values determined by other authors and already published models to calculate individual parameters, the fact that the data gathered using the EDPS method can be accepted in case of all studied thermophysical properties can be stated.


1978 ◽  
Vol 100 (2) ◽  
pp. 330-333 ◽  
Author(s):  
R. E. Taylor

Samples of sintered and arc-cast tungsten are available from NBS as thermal conductivity (SRM 730) and electrical resistivity (SRM 799) standards for the temperature range from 4 to 3000K. NBS recommended values for these properties above room temperature are based on results of various researchers during a previous international program which included arc-cast and sintered tungsten. The sintered tungsten used in this program was found to be unsuited for use as a standard material due to inhomogeneity and high temperature instability. The present paper gives results at high temperatures for thermal conductivity, electrical resistivity, specific heat, thermal diffusivity and Wiedemann-Franz-Lorenz ratio for a sample of the NBS sintered tungsten using the Properties Research Laboratory’s multiproperty apparatus. These results are compared to values recommended by the Thermophysical Properties Research Center, NBS, and an international program.


2021 ◽  
Vol 2119 (1) ◽  
pp. 012135
Author(s):  
D A Samoshkin ◽  
A Sh Agazhanov ◽  
S V Stankus

Abstract The heat capacity and the thermal diffusivity of NP2 brand nickel were investigated in the temperature interval 296–1000…1375 K of the solid-state, including the region of the magnetic phase transformation. Measurements were carried out on samples from one initial ingot by laser flash technique and method of differential scanning calorimetry using LFA-427 and DSC 404 F1 setups, respectively. The thermal conductivity was calculated based on the measured thermophysical properties. The estimated errors of the obtained results were 2–4%, 3–5%, and 2–3% for thermal diffusivity, thermal conductivity, and heat capacity, respectively. For investigated thermophysical properties the fitting equations and the reference table have been received.


Author(s):  
B. W. Zhao ◽  
Y. Zhao ◽  
H. Liu ◽  
Y. Q. Li ◽  
K. X. Duan ◽  
...  

Soil thermophysical properties are the key factors affecting the internal heat balance of soil. In this paper, biochars (BC300, BC500 and BC700) were produced with wheat straw at the temperatures of 300, 500 and 700°, respectively. The effects of biochar amendment at the rates of 0%, 1%, 3%, and 5% on the thermophysical properties (thermal conductivity, heat capacity, and thermal diffusivity) of a loessial soil were investigated with and without water content respectively. Although the bulk density of soil significantly decreased with biochar amendment, due to enhancing soil porosity and organic matter content, the thermophysical properties of soil did not change largely with biochar amendment rate and pyrolysis temperature. Water content exhibited significant effects on the thermophysical properties of soils added with biochars, where the thermal conductivity and heat capacity of soil were linearly proportional to water content, the thermal diffusivity initially increased and then decreased with the increase of water content. In the meanwhile, there was no significant correlation between the biochar amendment rate or pyrolysis temperature and thermophysical properties. The results show that water content should be mainly concerned as a factor when the internal heat balance of loess soil is evaluated, even though the soil is amended with biochar.


2020 ◽  
Vol 62 (7) ◽  
pp. 1137
Author(s):  
Р.Г. Митаров ◽  
С.Н. Каллаев ◽  
А.М. Бакмаев ◽  
С.А. Резниченко ◽  
А.Т. Темиров

The temperature dependence of the thermal diffusivity and thermal conductivity of the multiferroics BiFeO3, Bi0.90Sm0.10FeO3 and Bi0.90Еu0.10FeO3 is studied. It was found that the substitution of bismuth ions by the rare-earth europium and samarium ions in bismuth ferrite leads to a decrease in phonon thermal conductivity in a wide temperature range. It was established that the decrease in the thermal conductivity of bismuth ferrite is due to resonance scattering of phonons at paramagnetic levels of europium and samarium ions.


2019 ◽  
Vol 30 (1) ◽  
pp. 33-38
Author(s):  
V. A. Gorban

As a result of a study of the effect of artificial forest plantations formed by Robinia pseudoacacia L. and Quercus robur L., on the thermophysical features of the chernozems of the Komissarovsky reserve (Pyatykhatsky district, Dnepropetrovsk region, Ukraine), it was found that the stand of robinia reduced air temperature by 4, 5 °С, oak – by 9.4 °С in comparison with the open area. The maximum temperature of the soil surface is found in ordinary chernozem. The effect of robinia plantation manifested itself in the form of a decrease in the temperature of the soil surface by 5.4 °C, and the oak surface by 8.0 °C. The maximum soil temperature at a depth of 50 cm is also found in ordinary chernozem. At the same depth, the soil under robinia plantation turned out to be 7.6 °C, under oak – 6.9 °C colder. According to the average temperature of the 50-centimeter layer of all the studied soils, ordinary chernozem is distinguished, the soils under the plantations almost do not differ according to this indicator. The smallest difference between the air temperature and the average temperature of the soil layer 0–50 cm was in the soil under oak plantation, the largest – in the soil under robinia plantation. The smallest difference between the temperature of the soil surface and at a depth of 50 cm was found in the soil under oak plantation, and the greatest difference in the soil under robinia plantations. Based on the analysis of the results obtained, an assumption was made about the thermal features of the upper horizons, which fall within the interval of 0–50 cm, of each of the three studied soils. The soil under robinia plantation is characterized by maximum values of thermal diffusivity, and ordinary chernozem – minimal. The soil under the oak plantation occupies an intermediate value for this indicator. Ordinary chernozem is characterized by maximum values of heat capacity, slightly smaller values are characteristic of soil for robinia plantations. The minimum values of heat capacity are characteristic of oak plantation soil. The soil under robinia plantation is sharply distinguished by the maximum values of thermal conductivity compared to ordinary chernozem and the soil under oak planting. The actual study of thermophysical properties confirmed the correctness of the assumption in only one of the three indicators for each of the studied soils. This indicates a significant limitation of predicting the thermophysical indicators of soils, based only on measuring their temperature. The influence of robinia plantation on the thermal physical properties of ordinary chernozems is manifested in an increase in their thermal diffusivity and thermal conductivity, as well as in a certain decrease in heat capacity. The influence of oak stands is characterized by an increase in thermal diffusivity and heat capacity, as well as a decrease in thermal conductivity of ordinary chernozem.


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 ◽  
...  

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.


2010 ◽  
Vol 649 ◽  
pp. 487-491 ◽  
Author(s):  
Witold K. Krajewski ◽  
Józef Szczepan Suchy

The presented work is aimed at determining thermal diffusivity, thermal conductivity and heat capacity of insulating sleeves used in Polish metallurgical/foundry practice. On basis of the theory elaborated in [1] the mean values of thermophysical properties for temperatures range of about 150-1000 oC were obtained. The results obtained during the examinations presented in the paper can be helpful when formulating boundary conditions during the computer aided simulation of the processes of heat and mass transfer in the system: casting (ingot) – mould riser (ingot head) – ambient, which uses the investigated insulating sleeves [2, 3]. The method of determining thermal properties can be also used for other foundry materials, e.g. sands or cores.


2019 ◽  
Vol 142 (4) ◽  
Author(s):  
Zhengbin Wu ◽  
Shu Jiang ◽  
Lei Wang ◽  
Yiguo Zhang

Abstract Air-assisted steam injection is a new technique for heavy oil reservoir exploitation. This paper focused on the thermophysical properties of the air/steam system, such as density, viscosity, specific heat capacity, enthalpy, and thermal conductivity coefficient, and these have been calculated using the Redlich–Kwong equation of state (RK EOS). The viscosity of the air/steam system under high temperature and high pressure was calculated with the corresponding state principle and rectified with the Dean–Stiel residual viscosity method. The results showed that compared with the saturated steam of the same mass, the viscosity, specific heat capacity, thermal conductivity, and enthalpy of the air/steam mixture decreased, while the specific volume increased, which indicated that the addition of air to steam weakened the thermal effect of the steam and makes use of the heat insulation and thermal expansion of air. This study can provide guidance for parameter design of air-assisted steam injection for heavy oil recovery.


2020 ◽  
Vol 31 (2) ◽  
pp. 82-86
Author(s):  
V. A. Gorban

Thermophysical properties are an important characteristic of the general condition of soils, which determine the peculiarities of the distribution of heat flow in them. Today studies of thermophysical properties of soils, including the steppe zone of Ukraine, are practically not performed. This determines the relevance of the work, which is devoted to establishing the characteristics of the thermal properties of various soils. As a result of the study of thermal diffusivity, heat capacity and thermal conductivity of soils of northern and southern exposures, as well as the thalweg of the Voyskovoy Bayrak (located near the village of Voyskovoe Solonyansky district of Dnipropetrovsk region), it was found that the most important soil factors particles of physical clay and organic matter content. It was found that the eluvial horizons of the chernozem of the forest of the northern exposure differ in the reduced values ​​of heat capacity and thermal conductivity in comparison with the illuvial horizons. Eluvial horizons of forest-meadow soil of thalweg are characterized by increased values ​​of thermal diffusivity and thermal conductivity, as well as reduced values ​​of heat capacity compared to illuvial horizons. Eluvial horizons of forest chernozem of southern exposure are characterized by lower values ​​of thermal diffusivity, heat capacity and thermal conductivity compared to illuvial horizons. The most significant boundary between eluvial and illuvial horizons in terms of thermophysical properties is characteristic of the chernozem of forest southern exposure, which is manifested in a sharp increase in the values ​​of thermophysical properties in the first illuvial horizon. Cluster analysis revealed that the most similar in terms of thermal diffusivity are forest chernozems of southern and northern exposures, and in terms of heat capacity and thermal conductivity – forest chernozems of northern exposure and forest-meadow soil of thalweg ravine.


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