Effects of Current Annealing on Thermal Conductivity of Carbon Nanotubes

This work documents the annealing effect on the thermal conductivity of nanotube film (CNTB) and carbon nanotube fiber (CNTF). The thermal properties of carbon nanotube samples are measured by using the transient electro-thermal (TET) technique, and the experimental phenomena are analyzed based on numerical simulation. During the current annealing treatment, CNTB1 always maintains the negative temperature coefficient of resistance (TCR), and its thermal diffusivity increases gradually. When the annealing current is 200 mA, it increases by 33.62%. However, with the increase of annealing current, the TCR of CNTB2 changes from positive to negative. The disparity between CNTB2 and CNTB1 suggests that they have different physical properties and even structures along their lengths. The high-level thermal diffusivity of CNTB2 and CNTF are 2.28–2.46 times and 1.65–3.85 times higher than the lower one. The results show that the decrease of the thermal diffusivity for CNTB2 and CNTF is mainly caused by enhanced Umklapp scattering, the high thermal resistance and torsional sliding during high temperature heating.

Download Full-text

Thermal Transport Properties of Multi-Walled Carbon Nanotube Arrays

First International Conference on Integration and Commercialization of Micro and Nanosystems, Parts A and B ◽

10.1115/mnc2007-21033 ◽

2007 ◽

Author(s):

Huaqing Xie ◽

An Cai ◽

Xinwei Wang

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotube ◽

Thermal Diffusivity ◽

Room Temperature ◽

Infrared Detector ◽

Laser Flash ◽

Temperature Range ◽

Nanosecond Pulsed Laser ◽

Multi Walled Carbon Nanotube ◽

Individual Cnts

A laser flash technique was applied to measure the thermal diffusivity along a multi-walled carbon nanotube (CNT) array in temperature range of −55∼200 °C. In the measurements, a nanosecond pulsed laser was used to realize noncontact heating and the temperature variations were recorded by an infrared detector. The experimental results show that the thermal diffusivity of the CNT array increases slightly with temperature in the −55∼70 °C temperature range and exhibits no obvious change in the −75∼200 °C temperature range. The CNT array has much larger thermal diffusivity than several known excellent thermal conductors, reaching about 4.6 cm2s−1 at room temperature. The mean thermal conductivity (λ) of individual CNTs was further estimated from the thermal diffusivity, specific heat (Cp), and density (ρ) by using the correlation of λ = αρCp. The thermal conductivity of individual CNTs increases smoothly with the temperature increase, reaching about 750 Wm−1K−1 at room temperature.

Download Full-text

Role of rheology in tunning thermal conductivity of polyamide 12/polyamide 6 composites with a segregated multiwalled carbon nanotube network

Journal of Composite Materials ◽

10.1177/0021998317749715 ◽

2017 ◽

Vol 52 (18) ◽

pp. 2549-2557 ◽

Cited By ~ 2

Author(s):

Laura Arboleda-Clemente ◽

Xoán García-Fonte ◽

María-José Abad ◽

Ana Ares-Pernas

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotubes ◽

Carbon Nanotube ◽

Thermal Diffusivity ◽

Multiwalled Carbon Nanotubes ◽

Polyamide 6 ◽

Multiwalled Carbon ◽

Polyamide 12 ◽

Nanotube Composites ◽

Carbon Nanotube Network

Effect of multiwalled carbon nanotubes in thermal conductivity of an immiscible blend of polyamides, 50/50 (wt%/wt%) polyamide 12/polyamide 6, was analyzed as function of nanofiller amount and temperature. Effect of the molding temperature in the structure of conductive network was investigated by rheology. Data show that 5 vol% multiwalled carbon nanotubes caused an increase of 41% in thermal diffusivity and 78% in thermal conductivity respect to polyamide blend values. Thermal conductivity improvement could be described by percolation theory, with a low threshold composition (φc = 0.09 vol% carbon nanotube). Fitting parameters obtained from Agari’s adjustment model show that polyamides structure is not affected by carbon nanotubes and the nanofillers can easily form conductive paths in the polyamide 12/polyamide 6 matrix. The temperature increase facilitates nanofiller dispersion causing the formation of a denser carbon nanotube network and rising the thermal diffusivity of carbon nanotube composites with low percolation level, as was proved on annealed samples at 255℃.

Download Full-text

Development of a Backfill for Containment of High-Level Nuclear Waste

MRS Proceedings ◽

10.1557/proc-11-641 ◽

1981 ◽

Vol 11 ◽

Cited By ~ 2

Author(s):

Floyd N. Hodges ◽

Joseph H. Westsik ◽

Lane A. Bray

Keyword(s):

Thermal Conductivity ◽

Thermal Diffusivity ◽

Nuclear Waste ◽

Release Rate ◽

Sodium Bentonite ◽

Waste Package ◽

Diffusivity Measurements ◽

High Level Nuclear Waste ◽

High Level ◽

Host Rocks

ABSTRACTSodium and calcium bentonites, pressed to densities between 1.9 and 2.2 g/cm3, have hydraulic conductivities in the range of 10−11 to 10−13 cm/s. Batch sorption distribution ratios (Rd) indicate that Sr, Cs, and Am are strongly sorbed on bentonites and zeolites, that Np and U are moderately sorbed on bentonites and zeolites, and that Am, Np, U, I, and Tc are strongly sorbed on charcoal. Sorption results with basalt and tuff ground waters are similar; however, iodine in tuff ground water sorbs more strongly on bentonites Thermal diffusivity measurements for dry, compacted (p ∼ 2.1 g/cm3) sodium bentonite indicate that the thermal conductivity of a high density bentonite backfill should be roughly similar to that of silicate host rocks (basalt, granite, tuff). These results indicate that a bentonite backfill can significantly delay the first release of many radionuclides into the host rock and that by forming a diffusion barrier a bentonite backfill can significantly decrease the longterm release rate of radionuclides from the waste package.

Download Full-text

Thermal Transport in MWNT Sheet: Extremely High Radiation From The Carbon Nanotube Surface

MRS Proceedings ◽

10.1557/proc-0963-q16-02 ◽

2006 ◽

Vol 963 ◽

Author(s):

Ali E. Aliev ◽

C. Guthy ◽

M. Zhang ◽

A. A. Zakhidov ◽

J. E. Fischer ◽

...

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotube ◽

Thermal Diffusivity ◽

Chemical Vapor ◽

Laser Flash ◽

Heat Radiation ◽

Free Standing ◽

Multiwalled Carbon ◽

Excessive Heat ◽

Anisotropic Thermal Conductivity

ABSTRACTLaser flash and self-heating 3ω techniques were employed to determine the anisotropic thermal conductivity and thermal diffusivity of highly oriented free standing multiwalled carbon nanotube (MWNT) sheet drawn from a sidewall of a MWNT forest that was grown by chemical-vapor deposition. The thermal conductivity and the thermal diffusivity along the alignment are 50±5 W/m·K and 45±5 mm2/s, respectively, and are mostly limited by intrinsic defects of individual nanotubes and phonon-phonon interaction within bundles which form the supporting matrix of the MWNT sheet. The long tube-tube overlapping substantially decreases the electrical and thermal interconnection resistances which are usually dominate in randomly deposited mat-like nanotube assemblies. The extremely large surface area of the MWNT sheet leads to excessive heat radiation that dose not allow to transfer the heat energy by means of phonons to distances > 2 mm.

Download Full-text