Sensitivity of Thermal Conductivity of Carbon Nanotubes to Defect Concentrations and Heat-Treatment

2012 ◽  
Author(s):  
Michael F. P. Bifano ◽  
Jungkyu Park ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Interatomic Potential ◽  
Side Wall ◽  
Chemical Vapor ◽  
Md Simulations ◽  
Heat Treated ◽  
Side Walls ◽  
Non Equilibrium Molecular Dynamics ◽  
Vacancy Concentrations

In the present study, classical MD simulations using reverse non-equilibrium molecular dynamics with the AIREBO interatomic potential are used to investigate the sensitivity of thermal conductivity in SWCNTs to side-wall defect concentration and heat-treatment. Two types of defects are investigated. First, the thermal conductivity of (6,6) SWCNTs is obtained as a function of concentration of chemisorbed hydrogen adatoms. Secondly, the thermal conductivity is obtained as a function of point-vacancy concentrations. The results of the studies show that 2 atom% of hydrogenation and 1.5–2% vacancy concentrations have very similar detrimental effects on the thermal conductivity of SWCNT. Vacancy repair is evident with heat treatment, and heat-treatments at 3000°C for up to 22 ns are found to transform point vacancies into various types of non-hexagonal side-wall defects; this vacancy repair is accompanied by a ca. 10% increase in thermal conductivity. Thermal conductivity measurements in both heat-treated and non-heat treated chemical vapor deposition grown MWCNTs are also reviewed. The results suggest that CNT thermal conductivity can be drastically increased if measures are taken to remove common defects from the SWCNT side-walls.

Effects of Postdeposition in situ Heat Treatment on the Properties of Low Dielectric Constant Plasma Polymer Films Deposited Using Decahydronaphthalene and Tetraethyl Orthosilicate as the Precursors

2002 ◽  
Vol 17 (6) ◽  
pp. 1371-1375 ◽  
Author(s):  
Jaeyoung Yang ◽  
Cheonman Shim ◽  
Donggeun Jung
Keyword(s):  
Heat Treatment ◽  
Dielectric Constant ◽  
Polymer Films ◽  
Chemical Vapor ◽  
Relative Dielectric Constant ◽  
Tetraethyl Orthosilicate ◽  
Plasma Polymer ◽  
Low Dielectric ◽  
Heat Treated

We investigated effects of postdeposition heat treatment (HT) on the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decahydronaphthalene and tetraethyl orthosilicate as the precursors, which were referred to as plasma-polymerized decahydronaphthalene:tetraethyl orthosilicate (PPDHN:TEOS) films. HTs at 350, 450, and 500 °C decreased the relative dielectric constant k of the PPDHN:TEOS films from 3.16, the k value of the as-deposited film, to 2.82, 2.72, and 3.02, respectively. The change of k value as a function of HT temperature was correlated with the change of Fourier transform infrared absorption peaks of O–H, C = O, and Si-related groups. As the HT temperature increased, the thermal stability of the PPDHN:TEOS film increased. PPDHN:TEOS films, as-deposited or heat treated, showed leakage current density in the order of 10−7 A/cm2 at 1 MV/cm.

Thermal Conductivity of Heat Treated and Non-Heat Treated Individual Multiwalled Carbon Nanotubes

2011 ◽  
Author(s):  
Michael F. P. Bifano ◽  
Pankaj B. Kaul ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Multiwalled Carbon ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
Annealing Heat Treatment

Thermal conductivity measurements of commercially available CVD grown individual multiwalled carbon nanotubes (MWCNTs) are reported. The measurements are performed using the three-omega-based Wollaston T-Type probe method inside a scanning electron microscope (SEM). An average 385% increase in thermal conductivity is measured for those MWCNTs samples which undergo a 20 hour 3000°C post annealing heat treatment. However, in most samples qualitatively characterized defects are found to negate any advantage of the heat treatment process. The highest thermal conductivity measured is 893.0 W/mK and is of a heat-treated sample. These results will help to improve the quality of MWCNT production and aid in the development of highly efficient CNT-structured thermal management devices and engineering materials.

scholarly journals The effect of heat treatment on thermal conductivity of paulownia wood

2019 ◽  
Vol 78 (1) ◽  
pp. 205-207
Author(s):  
Z. Pásztory ◽  
S. Fehér ◽  
Z. Börcsök
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Treatment ◽  
Thermal Insulation ◽  
Insulation Materials ◽  
Heat Treated ◽  
Paulownia Wood

AbstractThe thermal conductivity properties of wood of Paulownia Clones in Vitro 112 were investigated after heat treatment at temperatures of 180 °C, 200 °C and 220 °C. After the treatment, the density decreased by 5.6, 8.9, and 14.1% for the samples heat-treated at 180 °C, 200 °C and 220 °C, respectively. The decrease in the thermal conductivity was 0, 2.6 and 15.7%, respectively. The thermal conductivity of kiri wood after thermal treatment at 220 °C was 0.064 W/mK, which is almost the same as that of thermal insulation materials.

Morphology of Carbon Micro-Coils

2004 ◽  
Vol 449-452 ◽  
pp. 205-208
Author(s):  
M. Fujii ◽  
S. Motojima
Keyword(s):  
Heat Treatment ◽  
Lattice Structure ◽  
Diffraction Method ◽  
Chemical Vapor ◽  
Amorphous Structure ◽  
Treatment Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Higher Temperature

The double helical carbon micro-coils were obtained by chemical vapor deposition. As-grown carbon micro-coils with amorphous structure were heat-treated at various temperatures up to 3000°C . By heat treatment, the shape of the coils was not changed. The morphology of these coils was observed in detail using electron microscope. The lattice structure was analyzed by X-ray diffraction method. Heat treatment temperature dependence of the magnetoresistance and the measurement of Raman spectra suggest that the coils heattreated at higher temperature are more highly graphitized.

scholarly journals Haptic and Aesthetic Properties of Heat-Treated Modified Birch Wood

Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1081
Author(s):  
Vlastimil Borůvka ◽  
Přemysl Šedivka ◽  
David Novák ◽  
Tomáš Holeček ◽  
Jiří Turek
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Heat Capacity ◽  
Moisture Content ◽  
Thermal Characteristics ◽  
Treated Wood ◽  
Treatment Temperature ◽  
Birch Wood ◽  
Positive Perception ◽  
Heat Treated

This paper deals with the effect of heat treatment on the selected physical properties of birch wood. Five stages of heat treatment were used, ranging from 160 °C to 200 °C, in 10 °C increments, having a peak treatment duration of 3 h for each level. Primarily, changes in thermal characteristics, namely conductivity, diffusivity, effusivity, volume heat capacity, changes in colour and gloss parameters, mass loss due to modification and different moisture content in wood under given equilibrium climatic conditions, were monitored. The ISOMET 2114 analyser was used to measure the thermal characteristics. The measurement principle of this analyser is based on the analysis of the thermal response of the analysed material to pulses of heat flow. Measurements of colour, gloss, density and moisture content were carried out according to harmonised EN standards. The aim was to experimentally verify the more or less generally known more positive perception of heat-treated wood, both by touch and sight, i.e., the warmer perception of darker brown shades of wood. In terms of thermal characteristics, the most interesting result is that they gradually decrease with increasing treatment temperature. For example, at the highest treatment temperature of 200 °C, there is a decrease in thermal conductivity by 20.2%, a decrease in volume heat capacity by 15.0%, and a decrease in effusivity by 17.7%. The decrease in thermal conductivity is nearly constant at all treatment levels, specifically at this treatment temperature, by 6.0%. The fact mentioned above is positive in terms of the tactile perception of such treated wood, which can have a positive effect, for example, in furniture with surface application of heat-treated veneers, which are perceived positively by the majority of the human population visually or as a cladding material in saunas. In this context, it has been found that the thermal modification at the above-mentioned treatment temperature of 200 °C results in a decrease in brightness by 44.0%, a decrease in total colour difference by 38.4%, and a decrease in gloss (at an angle of 60°) by 18.2%. The decrease in gloss is only one essential negative aspect that can be addressed by subsequent surface treatment. During the heat treatment, there is also a loss of mass in volume, e.g., at a treatment temperature of 200 °C and subsequent conditioning to an equilibrium moisture content in a conditioning chamber with an air temperature of 20 ± 2 °C and relative humidity of 65 % ± 5%, there was a decrease by 7.9%. In conclusion, the experiments clearly confirmed the hypothesis of a positive perception of heat-treated wood in terms of haptics and aesthetics.

The Effect of Heat-Treatment on Thermal Conductivity of Silicon Nitride Ceramics

2011 ◽  
Vol 484 ◽  
pp. 52-56
Author(s):  
Katsumi Yoshida ◽  
Yuki Sekimoto ◽  
Keiichi Katayama ◽  
Thanakorn Wasanapiarnpong ◽  
Masamitsu Imai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Glassy Phase ◽  
Boundary Phase ◽  
Sintering Additives ◽  
Heat Treated ◽  
Si3n4 Ceramics

Alpha- or beta-Si3N4 powder with larger grain size was uses as starting material, and the effect of heat-treatment on thermal conductivity of Si3N4 ceramics using MgO, Y2O3 and SiO2 as sintering additives was investigated in terms of their microstructure and the amount of grain boundary phase. Most of the components derived from sintering additives existed as glassy phase in sintered Si3N4. After heat-treatment at 1950oC for 8 h, the amount of glassy phase significantly decreased, and then small amount of glassy phase existed in Si3N4 ceramics was crystallized as Y2O3 and Y2Si3N4O3. In the case of Si3N4 ceramics using SN-7 powder, thermal conductivity of heat-treated Si3N4 was around twice of the value of sintered Si3N4, and the thermal conductivity was increased from 41.4 to 87.2 W/m•K due to not only the reduction of grain boundary phase but also the grain growth. In the case of Si3N4 using SN-F1 powder, thermal conductivity of Si3N4 ceramics was also significantly increased from 36.0 to 73.2 W/m•K after heat-treatment. In this case, the reduction of grain boundary phase mainly affected the thermal conductivity of Si3N4 ceramics because the grain size of heat-treated Si3N4 was nearly the same as that of sintered Si3N4. The reduction of grain boundary phase from Si3N4 was effective for the improvement of their thermal conductivity in addition to grain growth of Si3N4.

Lateral/vertical Homoepitaxial Growth on 4H-SiC Surfaces Controlled by Dislocations

2008 ◽  
Vol 1069 ◽  
Author(s):  
Yoosuf N. Picard ◽  
Andrew J. Trunek ◽  
Philip G. Neudeck ◽  
Mark E. Twigg
Keyword(s):  
Film Growth ◽  
Electron Backscatter Diffraction ◽  
Side Wall ◽  
Chemical Vapor ◽  
Film Structure ◽  
Atomic Step ◽  
Contrast Imaging ◽  
Screw Dislocations ◽  
Side Walls ◽  
Backscatter Diffraction

ABSTRACTThis paper reports the influence of screw dislocations on the lateral/vertical growth behavior of chemical vapor deposited (CVD) on-axis homoepitaxial 4H-SiC films grown on patterned mesas. Electron channeling contrast imaging (ECCI) was utilized to image both atomic steps and dislocations while the film structure/orientation was determined using electron backscatter diffraction (EBSD). The presence and position of screw dislocations within the mesa impacted the resultant film thickness, lateral shape, and atomic step morphology. Mesa side walls that incline inwards due to faceting during screw-dislocation driven vertical film growth can intersect with the dislocation step sources near the side walls. If this occurs for all screw dislocations on a mesa, we observe a transition towards laterally dominated growth that produces webbed structures and films surfaces exhibiting significantly lower step densities. Transition from vertical to lateral dominated growth is consistent with ECCI imaged dislocation very near a mesa side wall.

Molecular Dynamics Simulations of Diffusive-Ballistic Heat Conduction in Carbon Nanotubes

2007 ◽  
Vol 1022 ◽  
Author(s):  
Junichiro Shiomi ◽  
Shigeo Maruyama
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Heat Conduction ◽  
Md Simulations ◽  
Gradual Transition ◽  
Length Dependence ◽  
Conductivity Profile ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

AbstractHeat conduction of finite-length single-walled carbon nanotubes (SWNTs) has been studied by means of non-equilibrium molecular dynamics (MD) simulations. The length-dependence of the thermal conductivity was quantified for a range of nanotube-lengths at room temperature. The length dependence of thermal conductivity exhibits a gradual transition from nearly pure ballistic heat conduction to diffusive-ballistic heat conduction. The results show that the thermal conductivity profile does not converge even beyond a micrometer nanotube-length. Furthermore, the diameter dependence suggests that the phonon diffusion is reduced with the diameter.

Study on Thermal Conductivity of SPS-Sintered Si3N4 Ceramics after Heat-Treatment

2005 ◽  
Vol 475-479 ◽  
pp. 1279-1282 ◽  
Author(s):  
Xin Lu ◽  
Xiao Shan Ning ◽  
Wei Xu ◽  
He Ping Zhou ◽  
Ke Xin Chen
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Heating Rate ◽  
Great Influence ◽  
Heating Rates ◽  
Plasma Sintering ◽  
Heat Treated ◽  
Different Temperatures ◽  
Spark Plasma ◽  
Si3n4 Ceramics

α-Si3N4 ceramics were sintered at a low temperature of 1773K by using a spark-plasma-sintering (SPS) method with different heating rates, and then they were further heat-treated at different temperatures from 1773K to 2273K, to study the effect of the heating rate of SPS on the microstructure and the thermal conductivity of Si3N4 ceramics after the heat-treatment. Results show that the heating rate of SPS has great influence on the phase transformation and the microstructure of the β-Si3N4, but it has little influence on the thermal conductivity of the ceramics. This proves that the thermal conductivity of the ceramics does not have an obvious relationship with the ratio and the size of the columnar β-Si3N4 grain.

BERYLCO 10

Alloy Digest ◽  
1953 ◽  
Vol 2 (4) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Impact Strength ◽  
Physical Properties ◽  
Copper Alloy ◽  
Heat Treating ◽  
High Ductility ◽  
Endurance Strength ◽  
Heat Treated

Abstract BERYLCO 10 is a heat treatable, wrought, beryllium-copper alloy having high elastic and endurance strength, high ductility and impact strength, and high electrical and thermal conductivity. Since this material has good formability and machinability when heat treated, it is generally supplied in this condition, requiring no heat treatment by the fabricator. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fatigue. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Cu-6. Producer or source: Beryllium Corporation.

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