Effect of SiC Whiskers on the Microstructure and Thermal Conductivity of Carbon Foam

2018 ◽  
Vol 917 ◽  
pp. 106-111 ◽  
Author(s):  
Sheng Jie Yu ◽  
Zhao Feng Chen ◽  
Yang Wang
Keyword(s):  
Thermal Conductivity ◽  
Random Distribution ◽  
Chemical Vapor ◽  
Carbon Foam ◽  
Laser Flash ◽  
Homogeneous Distribution ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Flash Diffusivity ◽  
Insulation Performance

This paper describes the modification of ultralight flexible carbon foam by chemical vapor deposition (CVD) of silicon carbide whiskers (SiCw). The effect of SiC whiskers on the microstructure and the thermal conductivity of carbon foam were investigated by scanning electron microscopy (SEM) and laser flash diffusivity method in a Netzsch LFA427. The results show that the macro-pores (~30 μm) of the carbon foam were divided by the random distribution of SiC whiskers. The diameter of SiC whiskers decreased with decreasing catalyst concentration which resulted in the improved microstructure with a smaller pore diameter (4~6 μm) and a more homogeneous distribution of the pores. The carbon foam reinforced by SiCw exhibits better insulation performance than the pristine carbon foam when the temperature exceeds 200°C.

Temperature Dependence of Thermal Conductivity of Electronic Ceramics by an Improved Flash Diffusivity Technique

1989 ◽  
Vol 167 ◽  
Author(s):  
R. C. Enck ◽  
R. D. Harris
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Ceramic Materials ◽  
Laser Flash ◽  
Flow Measurements ◽  
Electronic Ceramics ◽  
Temperature Dependences ◽  
Commercial Sources ◽  
Materials Used ◽  
Flash Diffusivity

AbstractThe thermal conductivity of ceramic materials used for IC substrates and packages has increased in importance as chip sizes have decreased and heat loads have risen. AIN which has a room temperature (RT) thermal conductivity (λ) greater than 200 W/m·K and BeO with λ(RT) ∼260 W/m·K are the major candidates for applications demanding high conductivity. Conflicting reports of the temperature dependences of λ for these materials over the range of interest for packaging use (≤200°C) have been published, with some reports suggesting a crossover in λ. These reported differences may be due to the reported problems in measuring λ in AIN using the flash diffusivity method. For the present experiments, we have used a new long wavelength laser flash diffusivity system which has been shown to determine thermal diffusivity to better than ± 3% for AIN with sample thicknesses ranging from 0.3 mm to 5 mm. No absorbinq coatings are required and no correction factors are needed to fit the data to theory. We report λ from room temperature to 400°C for AIN from a number of commercial sources, and for BeO and SiC. At room temperature, BeO has the highest thermal conductivity, but as the temperature is raised, the values for BeO and AIN approach one another, with crossover observed at about 350°C for the highest conductivity AIN sample studied. Recent steady state heat flow measurements agree with our thermal conductivity values rather than with previous literature values.

Assessment of Homogeneity of Extruded Alumina-SiC Composite Rods Used in Microwave Heating Applications by Impedance Spectroscopy

2013 ◽  
Vol 1538 ◽  
pp. 323-328
Author(s):  
Justin R. Brandt ◽  
Rosario A. Gerhardt
Keyword(s):  
Electrical Conductivity ◽  
Electrical Response ◽  
Percolation Model ◽  
Homogeneous Distribution ◽  
Impedance Response ◽  
Silicon Carbide Whiskers ◽  
Percolation Behavior ◽  
Sic Whiskers ◽  
The Individual

ABSTRACTComposite rods consisting of Alumina (Al2O3) and Silicon Carbide whiskers (SiCw) are used to fabricate microwave cooking racks because they effectively act as a microwave intensification system that allows cooking at much faster rates than conventional microwave ovens. The percolation behavior, electrical conductivity and dielectric properties of these materials have been reported previously. However, it has been observed that the electrical response of the extruded bars is a function of the rod length and that long rods show substantially different behavior than thinner disks cut from them. A percolation model has been proposed that describes the effect of the alignment of the semiconducting SiC whiskers and the quality of the interfaces present in the composite rods: SiC-SiC and SiC-Al2O3-SiC for example. This study was undertaken with the goal of testing out whether the response of the individual sections could be used to generate the response of the full length rods and to assess the importance of the homogeneous distribution of the SiC fillers on the resultant impedance response.

Thermal Conductivity of Biomorphic Porous SiC Based Ceramics

2010 ◽  
Author(s):  
Nadejda Popovska ◽  
Emad Alkhateeb ◽  
Tanja Kugler ◽  
Andreas P. Fro¨ba ◽  
Alfred Leipertz
Keyword(s):  
Thermal Conductivity ◽  
Single Phase ◽  
Porous Ceramic ◽  
Chemical Vapor ◽  
Composite Ceramic ◽  
Laser Flash ◽  
Ceramic Composites ◽  
Chemical Vapor Infiltration ◽  
Composite Ceramics ◽  
Porous Sic

Biomorphic porous SiC composite ceramics were produced by chemical vapor infiltration and reaction (CVI-R) technique using paper preforms as template. The thermal conductivity of four samples with different composition and microstructure was investigated: a) C-template b) C-SiC, c) C-SiC-Si3N4 and d) SiC coated with a thin layer of TiO2. The SiC-Si3N4 composite ceramic showed enhanced oxidation resistance compared to single phase SiC. However; a key property for the application of these materials at high temperatures is their thermal conductivity. The later was determined experimentally at defined temperatures in the range 298–373K with a laser flash apparatus. It was found that the thermal conductivity of the porous ceramic composites increases in the following order: C-template < C-SiC < C-SiC-Si3N4 < SiC-TiO2. The results were interpreted in regard to the porosity and the microstructure of the ceramics.

Fabrication and properties of carbon/carbon-carbon foam composites

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4452-4460
Author(s):  
Bin Wang ◽  
Bugao Xu ◽  
Hejun Li
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Bonding Strength ◽  
Carbon Foam ◽  
Shear Load ◽  
Foam Composite ◽  
Final Failure ◽  
Carbon Foams ◽  
Insulation Performance

This paper was focused on the development of a new composite for high thermal insulation applications with carbon/carbon (C/C) composites, carbon foams and an interlayer of phenolic-based carbon. The microstructure, mechanical properties, fracture mechanism and thermal insulation performance of the composite was investigated. The experiment results showed that the bonding strength of the C/C-carbon foam composite was 4.31 MPa, and that the fracture occurred and propagated near the interface of the carbon foam and the phenolic-based carbon interlayer due to the relatively weak bonding. The shear load-displacement curves were characterized by alternated linear slopes and serrated plateaus before a final failure. he experiment revealed that the thermal conductivity of the C/C-carbon foam composite was 1.55 W·m−1ċK−1 in 800℃, which was 95.8% lower than that of C/C composites, proving that the thermal insulation of the new foam composite was greatly enhanced by the carbon foam with its porous hollow microstructure.

Experimental Study of VACNT Arrays as Thermal Interface Material

2013 ◽  
Author(s):  
Yulong Ji ◽  
Gen Li ◽  
Hongbin Ma ◽  
Yuqing Sun
Keyword(s):  
Thermal Conductivity ◽  
Chemical Vapor ◽  
Laser Flash ◽  
Thermal Interface Material ◽  
Chemical Vapor Deposition Method ◽  
Free Standing ◽  
Thermal Interface ◽  
Thermal Paste ◽  
Laser Flash Analysis ◽  
Contact Thermal Conductivity

In order to improve thermal interface material (TIM), vertically aligned carbon nanotube (VACNT) arrays were synthesized by the chemical vapor deposition method, and then transferred by dipping in hydrofluoric acid (HF acid) solution to get a free standing VACNT array. Different TIM samples with sandwiched structures were fabricated by inserting the free standing VACNT arrays between two copper plates with and without bonding materials. The laser flash analysis method was applied to measure the overall thermal conductivity of these samples. Results show that: compared with two copper plates in direct contact, thermal conductivity of samples only with VACNT arrays as TIM can be enhanced about 142%–460% depending on the thickness of VACNT arrays. Conventional TIM made up of thermal paste (TG-550 with thermal conductivity of 5 W/mK) and a thermal pad (TP-260 US with thermal conductivity of 6 W/mK) was used as a bonding material between copper plates and VACNT arrays, thermal conductivity has been shown to further improve with the highest values at 8.904 W/mK and 10.17 W/mK corresponding to the different bonding materials and different thicknesses of VACNT arrays used. Results also show that the thicker the VACNT array is when used as a TIM, the lower the overall thermal conductivity of the corresponding samples. This lower thermal conductivity caused by more defects in amorphous carbon of thicker VACNT arrays and lower density of the corresponding sandwiched samples.

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

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.

Silicon Carbide Composites Deposited in Silicon Carbide Whiskers by CVI Process

2012 ◽  
Vol 512-515 ◽  
pp. 789-792
Author(s):  
Fan Tao Meng ◽  
Shan Yi Du ◽  
Yu Min Zhang
Keyword(s):  
Silicon Carbide ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Dilute Gas ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Sic Composites ◽  
Vapor Infiltration

Chemical vapor deposition (CVD) is an effective method of preparing silicon carbide whiskers or films and chemical vapor infiltration (CVI) can be successfully used as the preparation of SiC composites. In this paper, silicon carbides whiskers were firstly deposited on substrates of RB-SiC by CVD process and then silicon carbide composites were prepared by chemical vapor infiltration in the SiC whiskers in an upright chemical vapor deposition furnace of Φ150mm×450mm with methyltrichloride silicane (MTS) as precursor gas, H2 as carrier gas and Ar as dilute gas. The morphologies of the SiC whiskers grown on RB-SiC substrate and SiC composites infiltrated in SiC whiskers were determined by scanning electron microscope (SEM), and the crystalline phase of the final deposits were confirmed with X-ray diffractometry (XRD) As a result, the curly defects of whiskers decrease with the addition of dilute gas. And by chemical vapor infiltration in SiC whiskers the, SiC composites were successfully prepared. Finally the deposits were determined as β-SiC.

Measurement of Thermal Conductivity of Carbon Foams

2003 ◽  
Author(s):  
M. K. Alam ◽  
A. M. Druma
Keyword(s):  
Thermal Conductivity ◽  
Carbon Foam ◽  
Lower Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Heat Spreaders ◽  
Carbon Foams ◽  
Interface Contact ◽  
Flash Diffusivity ◽  
Graphitic Foam

A number of carbon foam products are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. The application of carbon foams in aerospace applications is advantageous due to the high thermal conductivity and low density of the graphitic foam. However, the measurement of thermal conductivity has been difficult due the problems of interface contact and lower strength of the foam. The flash diffusivity method has been used to find thermal conductivity of a wide range of materials. Because of the porous nature of the foam, errors may be introduced with the flash diffusivity method. An analytical and experimental study has been carried out to determine the validity of the flash diffusivity method for foam specimen.

Highly thermally conductive UHMWPE/NG composites with the segregated structure and their application for heat spreader

2020 ◽  
pp. 089270572096564
Author(s):  
Xiao Wang ◽  
Hui Lu ◽  
Jun Chen
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Heating Process ◽  
X Ray Diffraction ◽  
Heat Spreader ◽  
Conductive Composites ◽  
Compression Direction ◽  
Thermal Analyzer ◽  
Thermally Conductive ◽  
Plane Direction

In this work, ultra-high molecular weight polyethylene (UHMWPE)/natural flake graphite (NG) polymer composites with the extraordinary high thermal conductivity were prepared by a facile mixed-heating powder method. Morphology observation and X-ray diffraction (XRD) tests revealed that the NG flakes could be more tightly coated on the surface of UHMWPE granules by mixed-heating process and align horizontally (perpendicular to the hot compression direction of composites). Laser flash thermal analyzer (LFA) demonstrated that the thermal conductivity (TC) of composites with 21.6 vol% of NG reached 19.87 W/(m·K) and 10.67 W/(m·K) in the in-plane and through-plane direction, respectively. Application experiment further demonstrated that UHMWPE/NG composites had strong capability to dissipate the heat as heat spreader. The obtained results provided a valuable basis for fabricating high thermal conductive composites which can act as advanced thermal management materials.

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