Macro- and Micro-Scale Thermal Conductivities of SiC Single Crystal and Ceramic

2008 ◽  
Vol 403 ◽  
pp. 179-183 ◽  
Author(s):  
Ikuko Yamada ◽  
Shoichi Kume ◽  
Hiromi Nakano ◽  
Koji Watari
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Laser Flash ◽  
Periodic Heating ◽  
Average Value ◽  
Macro Scale ◽  
Laser Flash Technique ◽  
Micrometer Scale ◽  
Good Agreement ◽  
Thermal Conductivities

Thermal properties of SiC at the micrometer-scale were measured quantitatively with a thermal microscope using thermo-reflectance and periodic heating techniques. In this study, SiC single crystal and polycrystal were investigated. The small values of standard deviation suggest that the SiC single crystal had constant thermal conductivities. For the single crystal, the average value of the thermal conductivity at the micrometer-scale was in good agreement with the macro-scale thermal conductivity value obtained by the laser flash technique. On the other hand, thermal conductivity of the polycrystal was heterogeneous at the micrometer-scale. An average thermal conductivity value of 257 Wm-1K-1 was obtained within an area of 50 m ×100 µm. The highest and lowest values of the thermal conductivity from the polycrystal were 300 and 220 Wm-1K-1, respectively.

Thermal Conductivity Measurement of the AlN Ceramics at the Grain Scale Using Thermoreflectance Technique

2008 ◽  
Vol 403 ◽  
pp. 65-67
Author(s):  
Sang Kee Lee ◽  
Ikuko Yamada ◽  
Shoichi Kume ◽  
Hiromi Nakano ◽  
Koji Watari
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Conductivity Measurement ◽  
Boundary Phase ◽  
Average Value ◽  
Grain Boundary Characteristics ◽  
The Individual ◽  
Boundary Characteristics ◽  
Micrometer Scale ◽  
Thermal Conductivities

The thermal conductivity at the micrometer-scale of AlN ceramics with eliminated grain boundary phase was measured by the thermoreflectance technique with periodic heating. Thermal conductivities were ranged from 160 to 260 W/m•K and an average value of 201 W/m•K was obtained from a 22 m2 area. The variation in the thermal conductivities was related to the individual AlN grains and grain boundary characteristics.

Determination of thermal conductivity of silica dioxide Tarkosil T-50 nanopowder by laser flash technique

2016 ◽  
Vol 25 (2) ◽  
pp. 174-181 ◽  
Author(s):  
A. V. Nomoev ◽  
S. P. Bardakhanov ◽  
V. V. Syzrantsev ◽  
V. Ts. Lygdenov
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Laser Flash Technique ◽  
Flash Technique ◽  
Silica Dioxide

Studying the Progress of Sintering in Ferrous Powder Compacts by In-Situ Measuring the Thermal Conductivity

2018 ◽  
Vol 18 (2) ◽  
pp. 80-95
Author(s):  
H. Danninger ◽  
G. Leitner ◽  
Ch. Gierl-Mayer
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Sintering Process ◽  
In Situ Characterization ◽  
Dimensional Changes ◽  
Flow Through ◽  
Powder Compacts ◽  
Good Agreement

Abstract In situ characterization of the sintering process is a difficult task, in particular for systems without pronounced dimensional changes. Dilatometry is not too helpful in those cases, and therefore other properties have to be recorded. In the present study, sintering of ferrous powder compacts was studied in situ by measuring the thermal diffusivity a using a laser flash apparatus. This property is a measure to characterise the heat flow through a material; it depends on the contact area between the particles and thus reveals their change during sintering. It is shown that the change of a during sintering of ferrous compacts is much less pronounced than in the case of cemented carbides which is not surprising when regarding the widely differing porosity changes. The results are however in good agreement with expectations when considering some experimental limitations. The trend for the thermal conductivity λ. which can be calculated from a, the specific heat and the density, is in good agreement with that found for the electrical conductivity, both properties being linked through Wiedemann-Franz’ law.

Thermal-Wave Probing at Various Spatial Scales

MRS Bulletin ◽  
2001 ◽  
Vol 26 (6) ◽  
pp. 465-470 ◽  
Author(s):  
Danièle Fournier
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Thermal Wave ◽  
Spatial Scales ◽  
High Thermal Conductivity ◽  
Heterogeneous Microstructures ◽  
Thermal Conductivities

In recent years, high thermal conductivity has been found in materials with heterogeneous microstructures, that is, ceramics and films with granular microstructures having different phases. Understanding the thermal conductivities and microstructures of these materials is more difficult, however, than in the case of single-crystal materials because they consist of grains and grain boundaries.

Spatial distribution of thermal conductivity of diamond wafers as measured by laser flash technique

1998 ◽  
Author(s):  
Victor G. Ralchenko ◽  
A. Vlasov ◽  
Igor I. Vlasov ◽  
Boris V. Zubov ◽  
Alexander P. Nikitin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Spatial Distribution ◽  
Laser Flash ◽  
Laser Flash Technique ◽  
Flash Technique

scholarly journals Thermophysical properties of NP2 brand nickel

2021 ◽  
Vol 2119 (1) ◽  
pp. 012135
Author(s):  
D A Samoshkin ◽  
A Sh Agazhanov ◽  
S V Stankus
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Thermophysical Properties ◽  
Magnetic Phase ◽  
Laser Flash ◽  
Scanning Calorimetry ◽  
Reference Table ◽  
Laser Flash Technique ◽  
Flash Technique

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.

REVIEW AND APPLICATIONS OF THERMAL CONDUCTIVITY MODELS TO ALUMINUM CELL SIDEWALL REFRACTORIES

2009 ◽  
Vol 23 (06n07) ◽  
pp. 790-795 ◽  
Author(s):  
YUHUA PAN ◽  
STEVEN WRIGHT ◽  
SHOUYI SUN
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Aluminum Electrolysis ◽  
Laser Flash ◽  
Modeling Methods ◽  
Electrolysis Cells ◽  
Model Predictions ◽  
One Step ◽  
Laser Flash Technique ◽  
Multi Phase

Silicon nitride bonded silicon carbide ( Si 3 N 4- SiC ) refractories are commonly used as the sidewall of aluminum electrolysis cells. They have to withstand an extremely corrosive molten electrolyte bath for long periods. The sidewall is normally protected with a layer of solidified electrolyte (called frozen ledge), which is sensitive to the thermal conductivity of the sidewall. In this work, through review of the literature on modeling methods for predicting the effective thermal conductivity of dense composites and porous materials, some selected methods were applied to calculate the effective thermal conductivity of Si 3 N 4- SiC refractories. The model predictions were compared with the thermal conductivity of a commercial Si 3 N 4- SiC refractory measured by using laser flash technique. The present study showed that, due to multi-phase nature and complex microstructure of Si 3 N 4- SiC refractories, most of the selected modeling methods individually do not give satisfactory predictions in one step. Recursive applications of one method or combinations of different methods are capable of giving satisfactory predictions.

scholarly journals Thermal Conductivities of Unidirectional Materials

1967 ◽  
Vol 1 (2) ◽  
pp. 166-173 ◽  
Author(s):  
George S. Springer ◽  
Stephen W. Tsai
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Model ◽  
Longitudinal Shear ◽  
Unidirectional Composite ◽  
Shear Loading ◽  
Square Packing ◽  
Good Agreement ◽  
Thermal Conductivities

In this paper the composite thermal conductivities of unidirec tional composites are studied and expressions are obtained for pre dicting these conductivities in the directions along and normal to the filaments. In the direction along the filament an expression is presented based on the assumption that the filaments and matrix are connected in parallel. In the direction normal to the filaments composite thermal conductivity values are obtained first by utiliz ing the analogy between the response of a unidirectional composite to longitudinal shear loading and to transverse heat transfer; second by replacing the filament-matrix composite with an idealized ther mal model. The results of the shear loading analogy agree reason ably well with the results of the thermal model particularly at filament contents below about 60%. These results were also com pared to experimental data reported in the literature and good agreement was found between the data and those theoretical re sults that were derived for circular filaments arranged in a square packing array.

Prediction of Thermal Conductivity of Two-Dimensional Superlattices of Graphene and Boron Nitride by Equilibrium Molecular Dynamics

2015 ◽  
Author(s):  
Fernan Saiz ◽  
Carlos da Silva ◽  
Cristina H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Boron Nitride ◽  
Heat Capacities ◽  
Two Dimensional ◽  
Electronic Band ◽  
Electronic Band Gap ◽  
Interface Orientation ◽  
Good Agreement ◽  
Thermal Conductivities

Graphene is a promising material to design faster microprocessors given its exceptionally high thermal conductivity. However, due to its null electronic band gap, graphene must be combined with high-electric conductivity materials such as boron nitride to manufacture competitive alternatives to traditional semiconductors. Thus, the goal of this study is to determine the thermal conductivities and heat capacities of two-dimensional superlattices of graphene and boron nitride as a function of the secondary periodicity and interface orientation. We apply the Green-Kubo method to atomic trajectories calculated with Molecular Dynamics to determine the thermal conductivities of superlattices with periodicities between one and five in the armchair and zigzag orientations at 300 K. Results show that conductivities increase with decreasing periodicity, in good agreement with predictions made with Harmonic Lattice Dynamics. Thermal conductivities parallel to the interface are significantly higher than those perpendicular to the interface in the armchair configuration and vice versa in the zigzag orientation. Moreover, the heat capacities are practically independent of the periodicity and interface orientation up to 1500 K.

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