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.

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.

Preparation and Properties of Rigid Carbon Felt Thermal Insulation

2015 ◽  
Vol 833 ◽  
pp. 48-51 ◽  
Author(s):  
Wei Shi ◽  
Jia Yan Li ◽  
Qi Fan You ◽  
Tong Lu ◽  
Yi Tan
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Insulation ◽  
Bending Strength ◽  
High Thermal Conductivity ◽  
Carbon Felt ◽  
Matrix Concentration ◽  
Thermal Conductivities

Matrix derived from resin after carbonization in rigid carbon felt thermal insulation has many advantages. The microstructures and properties of these materials were investigated in this paper. Results showed that matrix tend to accumulate at the intersections of fibers. This can improve mechanical properties and have a little influence on thermal conductivities of the composites. The excellent bending strength of 2.66MPa, compressive strength of 0.91MPa and a high thermal conductivity of 0.81W/(m·K) (at 1500°C) with a matrix concentration of 32.7% is achieved. However, high thermal conductivity is harmful for those materials which are used as thermal insulators.

Lattice Thermal Conductivity of Fe-Cr Alloys With 〈001〉 Tilt Boundaries: An Atomistic Study

2014 ◽  
Author(s):  
Ishraq Shabib ◽  
Mohammad Abu-Shams ◽  
Mujibur R. Khan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Lattice Thermal Conductivity ◽  
The Other ◽  
Tilt Boundaries ◽  
Cr Concentration ◽  
Non Equilibrium Molecular Dynamics ◽  
Atomistic Study

The objective of this study is to examine lattice thermal conductivity (κ) of Fe-Cr alloys containing different 〈001〉 tilt grain boundaries (GBs). The effects of Cr concentration (2 and 10%) and three different 〈001〉 tilt boundaries (Σ5{310}, Σ13{510}, and Σ17{530}) have been examined at 70K using the reverse non-equilibrium molecular dynamics (rNEMD) simulation technique. The results exhibit higher κ for Fe or Fe-Cr models with Σ5[310] GB. The values are 2–4% and 12–16% more than those of models with Σ13[510] and Σ17[530] GBs, respectively. Pure Fe single crystal models exhibit higher conductivities than Fe/Fe-Cr models with various Σ tilt boundaries. κ decreases 7–9% as GBs are introduced into the pure Fe single crystal models. On the other hand, the conductivities of Fe-Cr models are affected more by the Cr concentration than the presence of a particular GB. As 10% Cr is added into the system the conductivity decreases by 7.6–9.4% compared to the pure Fe models.

scholarly journals Flux growth and characterization of an FeSi4P4 single crystal

RSC Advances ◽  
2017 ◽  
Vol 7 (76) ◽  
pp. 47938-47944
Author(s):  
Tongtong Yu ◽  
Shanpeng Wang ◽  
Huapeng Ruan ◽  
Chunlong Li ◽  
Xixia Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Semiconductor Material ◽  
High Thermal Conductivity ◽  
Flux Growth ◽  
P Flux

Flux growth of the bulk FeSi4P4 single crystal, a paramagnetic semiconductor material with high thermal conductivity.

An electron microscopy study of high-thermal-conductivity ribbon-shape carbon fibers

1993 ◽  
Vol 51 ◽  
pp. 618-619
Author(s):  
Kerry E. Robinson
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Liquid Crystalline ◽  
Structural Information ◽  
Low Cost ◽  
Microscopy Study ◽  
High Thermal Conductivity ◽  
Mesophase Pitch ◽  
Thermal Conductivities ◽  
Shaped Fibers

In an effort to develop a low-cost high thermal conductivity carbon fiber, ribbon-shaped fibers were meltspun from a liquid crystalline, mesophase pitch precursor. Initial tests indicated that the ribbon-shaped fibers could be processed more easily and exhibited improved thermal conductivities when compared to commercial round fibers. Evidently, it is the more linear, polycrystalline structure within these fibers that accounts for their improved thermal conductivities. Thus, studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to fully analyze the transverse and longitudinal structure of these high thermal conductivity fibers.Ribbon-shaped fibers, melt-spun from a synthetic mesophase pitch and then heat treated, were tested to determine their tensile strengths, tensile moduli and thermal conductivities. A Jeol JSM-I C848 SEM at an accelerating voltage of 20 kV was used to obtain general structural information, such as extent and texture of lamellar organization of the graphitic layers within the fibers, and the microstructure of the fibers was studied by TEM.

High Thermal Conductivity Graphite Copper Composites with Diamond Coatings for Thermal Management Packaging Applications

1995 ◽  
Vol 390 ◽  
Author(s):  
Chris H. Stoessel ◽  
C. Pan ◽  
J. C. Withers ◽  
D. Wallace ◽  
R. O. Loutfy
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Management ◽  
Heat Sinks ◽  
High Thermal Conductivity ◽  
Graphite Fiber ◽  
Fiber Reinforced ◽  
Cathode Sputtering ◽  
Large Expansion ◽  
Thermal Conductivities

ABSTRACTHigh thermal conductivity heat sinks for thermal management in electronic packaging is enabling to a variety of advanced electronic applications. Heat sinks in industrial semiconductor application have thermal conductivities generally less than 180 W/mK, and frequently have large expansion mismatch with chips such as silicon and gallium arsenide. A unique technology of producing graphite fiber reinforced copper (Cf/Cu) composite has been developed that produced thermal conductivities up to 454 W/mK utilizing a K=640 W/mK fiber reinforcement (with a potential for 800 W/mK when utilizing a K = 1100 W/mK P130 fiber) and thermal expansion that can be matched to chip materials. The process consists of utilizing a hollow cathode sputtering process to deposit a bonding layer followed by copper on spread graphite fibers, which are then consolidated into composites with architectures to achieve desired thermal conductivity and thermal expansion. The copper thickness determines graphite fiber loading up to 80 %. In heat sink applications, where the electrical conductivity of the graphite fiber reinforced copper composite is a problem, processing has been developed for applying electrically insulating diamond film, which has high thermal conductivity and acts as a heat spreader.

Thermal Conductivity of Waste Forms and Geologic Media

1982 ◽  
Vol 15 ◽  
Author(s):  
R. O. Pohl ◽  
J. W. Vandersande
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundaries ◽  
High Temperatures ◽  
Low Temperatures ◽  
Phonon Scattering ◽  
Lamellar Structures ◽  
Waste Forms ◽  
Thermal Conductivities ◽  
Geologic Media

ABSTRACTIn order to predict the range of thermal conductivities to be expected in waste forms and in geologic media, an understanding of the pertinent phonon scattering processes is required. It has been shown that grain boundaries in polycrystalline media are unimportant at low temperatures relative to lamellae which arise from twinning, exsolution, or foreign inclusions within the grains. The possible role of lamellar structures on the conductivity at high temperatures will be discussed.

Numerical Study on the Interaction of Transverse and Longitudinal Roughness on Elastohydrodynamic Lubrication Contact Surfaces With Different Thermal Conductivities and Elastic Moduli

2020 ◽  
Vol 143 (9) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Jinlei Cui ◽  
Peiran Yang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Finite Length ◽  
Elastic Moduli ◽  
Elastohydrodynamic Lubrication ◽  
High Thermal Conductivity ◽  
Low Thermal Conductivity ◽  
Longitudinal Roughness ◽  
Transverse Roughness ◽  
Contact Surfaces ◽  
Thermal Conductivities

Abstract The interaction and surface features between point contact surfaces composed of longitudinal roughness with infinite or finite length and transverse roughness were discussed based on a transient non-Newtonian thermal elastohydrodynamic lubrication (EHL) model. Each surface shape is greatly affected by the difference in elastic moduli, thermal conductivities, and velocities of both contact surfaces. There is a large difference in pressure behavior when the transverse roughness is in contact with the longitudinal roughness with finite length and when it is in contact with the longitudinal roughness with infinite length. In the contact between surfaces with infinitely long longitudinal and transverse roughness, the friction coefficient is lower when the surface with longitudinal roughness has a low thermal conductivity than when it has a high thermal conductivity. Furthermore, the pressure fluctuation is larger when the transverse roughness surface has a high thermal conductivity than when it has a low thermal conductivity.

scholarly journals Thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics

Cerâmica ◽  
2004 ◽  
Vol 50 (315) ◽  
pp. 247-253 ◽  
Author(s):  
A. Franco Júnior ◽  
D. J Shanafield
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Nitride ◽  
Single Crystal ◽  
Single Crystals ◽  
Conduction Mechanism ◽  
Sintering Process ◽  
Polycrystalline Aluminum ◽  
Polycrystalline Ceramics ◽  
Thermal Conductivities

In general, polycrystalline ceramics exhibit lower thermal conductivities than their associated single crystals. For instance, at 300K, the theoretical thermal conductivity of single crystal aluminum nitride (AlN) is 319 W/m-K, whereas, the values measured for polycrystalline AlN ceramics range from 17 W/m-K to 285 W/m-K. This variation is not unusual for polycrystalline ceramics. The variability is strongly dependent upon the purity of the starting materials and the details of sintering process. The process is important since it influences the microstructure and thus influences the conduction mechanism. In this paper we present the causes of this variation and how it can be controlled.

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