Thermal conductivity of Al2O3-SiC nanocomposites prepared by the electroconsolidation method (original) (raw)
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Functional properties (e.g. thermal and electrical conductivity) of polycrystalline alumina ceramics can be modified by the addition of second phases, such as silicon carbide nanoparticles, carbon nanotubes or nanofibers, or graphene sheets. In this work we studied the influence of SiC particles addition on the DC electrical and thermal conductivity of the Al 2 O 3 /SiC micro/nanocomposites both at room and elevated temperatures. The composites with high relative density and with various volume fractions of SiC ranging from 3 vol% to 20 vol% were prepared by hot pressing at 1740 1C and at 30 MPa pressure in the atmosphere of argon. The influence of the volume fraction and the size of SiC particles (two different powders with the mean size of SiC particles 40 and 200 nm were used), and final microstructure of the composites on thermal and electrical conductivity were evaluated. The properties of the composites were compared to the monolithic Al 2 O 3 reference. The microstructure of the composites was significantly affected by the volume fraction of SiC, with the mean size of alumina matrix grains decreasing with increasing content of SiC particles. The maximum of room temperature thermal conductivity was measured in the composites with 20 vol% of SiC (38 W/ m K), irrespective of the granulometry of the used SiC powder. The DC electrical conductivity increased with increasing volume fraction of SiC. The highest electrical conductivity 4.05 Â 10 À 2 S/m was measured in the composites containing 20 vol% of SiC, in comparison to the electrical conductivity of the monolithic alumina reference, which was by four orders of magnitude lower. No statistically significant difference in thermal or electrical conductivity was found between the composited with different granulometry, but identical content of SiC.
Journal of Materials Science, 2009
Al/SiC composites with volume fractions of SiC between 0.55 and 0.71 were made from identical tapped and vibrated powder preforms by squeeze casting (SC) and by two different setups for gas pressure infiltration (GPI), one that allows short (1-2 min) liquid metal/ ceramic contact time (fast GPI) and the other that operates with rather long contact time, i.e., 10-15 min, (slow GPI). Increased liquid metal-ceramic contact time is shown to be the key parameter for the resulting thermal and electrical conductivity in the Al/SiC composites for a given preform. While for the squeeze cast samples neither dissolution of the SiC nor formation of Al 4 C 3 was observed, the gas pressure assisted infiltration led inevitably to a reduced electrical and thermal conductivity of the matrix due to partial decomposition of SiC leading to Si in the matrix. Concomitantly, formation of Al 4 C 3 at the interface was observed in both sets of gas pressure infiltrated samples. Longer contact times lead to much higher levels of Si in the matrix and to more Al 4 C 3 formation at the interface. The difference in thermal conductivity between the SC samples and the fast GPI samples could be rationalized by the reduced matrix thermal conductivity only. On the other hand, in order to rationalize the thermal conductivity of the slow GPI a reduction in the metal/ceramic interface thermal conductance due to excessive Al 4 C 3-formation had to be invoked. The CTE of the composites generally tended to decrease with increasing volume fraction of SiC except for the samples in which a large expansive drift was observed during the CTE measurement by thermal cycles. Such drift was essentially observed in the SC samples with high volume fraction of SiC while it was much smaller for the GPI samples. G. Sinicco-formerly an undergraduate student of É cole Polytechnique Fédérale de Lausanne, EPFL.
Thermal conductivity of Al–SiC composites with monomodal and bimodal particle size distribution
Materials Science and Engineering: A, 2008
The thermal conductivity of aluminum matrix composites having a high volume fraction of SiC particles is investigated by comparing data for composites fabricated by infiltrating liquid aluminum into preforms made either from a single particle size, or by mixing and packing SiC particles of two largely different average sizes (170 and 16 m). For composites based on powders with a monomodal size distribution, the thermal conductivity increases steadily from 151 W/m K for particles of average diameter 8 m to 216 W/m K for 170 m particles. For the bimodal particle mixtures the thermal conductivity increases with increasing volume fraction of coarse particles and reaches a roughly constant value of 220 W/m K for mixtures with 40 or more vol.% of coarse particles. It is shown that all present data can be accounted for by the differential effective medium (DEM) scheme taking into account a finite interfacial thermal resistance.
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/the-influence-of-sic-particle-size-on-the-thermal-and-electrical-conductivities-of-cusic-composites https://www.ijert.org/research/the-influence-of-sic-particle-size-on-the-thermal-and-electrical-conductivities-of-cusic-composites-IJERTV2IS100665.pdf The Potential demands for reliable materials in electronic industries are ever increasing. The main pronounced failure that occurs during microelectronic circuits' application involves thermal fatigue. Heat generated in electronic packages can be dissipated by developing suitable materials as heat sinks. Copper metal matrix composites reinforced with silicon carbide (SiC) proffer possibility of meeting these demands. Thus, the interest for appropriate coefficient of thermal expansion (CTE) of packaging materials in combination with a high thermal and electrical conductivity is inevitable in the design and selections of heat sink material. This research work entails producing copper matrix using silicon carbides (SiC) as reinforcement. This is aimed at getting a material with high thermal and electrical conductivities by non convectional liquid metallurgy. Copper silicon carbide composites were produced in 80%Cu-20%SiC, 70%Cu-30%SiC, 60% Cu-40% SiC, 50% Cu-50%SiC, 40%Cu-60%SiC ratios with an average grain size of 212µm, 425µm and 710µm respectively via liquid metallurgy m e t h o d. T he result revealed that increasing volume fraction and p a r t i c l e s i z e s of t h e particulate h a d significant effect o n the thermal and electrical conductivity of the composites.
Effect of Initial Alpha-SiC Content on Thermal Conductivity of Silicon Carbide Ceramics
Key Engineering Materials, 2014
By using α-and/or β-SiC powders, the effects of initial α-phase content on the microstructure and thermal properties of the SiC ceramics sintered with Y2O3 and Sc2O3 were investigated. When α-SiC powder was used, the microstructure consisted of large equiaxed grains and small equiaxed grains. The average grain size decreased with increasing α-SiC content in the starting composition. The thermal conductivity decreased with increasing α-SiC content in the starting composition. Such results suggest that the grain growth of SiC ceramics is beneficial in increasing the thermal conductivity of liquid-phase sintered SiC ceramics. The thermal conductivity of SiC ceramics processed from a 90% β-SiC-10% α-SiC powder mixture was 159 W/m∙K at room temperature.
SiC/SiC composites used in fusion reactor applications are subjected to high heat fluxes and require knowledge and tailoring of their in-service thermal conductivity. Accurately predicting the thermal conductivity of SiC/SiC composites as a function of temperature will guide the design of these materials for their intended use, which will eventually include the effects of 14-MeV neutron irradiations. This paper applies an Eshelby–Mori–Tanaka approach (EMTA) to compute the thermal conductivity of unirradiated SiC/SiC composites. The homogenization procedure includes three steps. In the first step EMTA computes the homogenized thermal conductivity of the unidirectional (UD) SiC fiber embraced by its coating layer. The second step computes the thermal conductivity of the UD composite formed by the equivalent SiC fibers embedded in a SiC matrix, and finally the thermal conductivity of the as-formed SiC/SiC composite is obtained by averaging the solution for the UD composite over all possible fiber orientations using the second-order fiber orientation tensor. The EMTA predictions for the transverse thermal conductivity of several types of SiC/SiC composites with different fiber types and interfaces are compared to the predicted and experimental results by Youngblood et al.
International Journal of Pediatric Otorhinolaryngology, 2011
The present work investigates the feasibility of microwave sintering to produce bulk metal-based nanocomposites having blend composition of Cu99Cr1, Cu94Cr6, Cu99Cr1–4 wt.% SiC and Cu94Cr6–4 wt.% SiC (average particle size ∼30 nm). The 50 h ball-milled samples were uniaxially pressed, and then pellets were sintered at 800 °C, 900 °C and 1000 °C for a constant soaking period of 30 min by microwave sintering technique. Microstructural characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Sintered compacts resulted a highly densified compacts (∼95% relative density) while retaining ultra-fine grains (100–200 nm) in the matrix. The mechanical properties, namely, hardness and wear resistance, and electrical conductivity of the sintered specimens were also evaluated. The best combination of mechanical properties (e.g. hardness ∼2.4 GPa) and electrical conductivity (60.3% of IACS) were obtained for Cu94Cr6–4 wt.% SiC sintered at 900 °C. This is possibly due to presence of ultra-fine grains in the bulk samples, good densification and proper bonding between particles. The results were analyzed in the light of interactions of microwaves between metallic matrix and microwave susceptive SiC particulates.► Ball-milled Cu–Cr and Cu–Cr–SiC nanopowders successfully consolidated by microwave sintering. ► Addition of nanosize SiC in Cu–Cr leads to enhanced sintered density, wear and hardness. ► A good combination of wear resistance, hardness and electrical conductivity resulted in Cu94Cr6–4% SiC. ► Microwave suscepting SiC particles played a pivotal role in good densification retaining matrix grains <200 nm.
2016
Metal matrix composites have been regarded to be one of the most principal classifications in composite materials. Microstructural analysis and metallography is one of the predominant terms commonly used in the research of materials. The thermal characterization of composite materials has received broad deliberation and has become governing in materials science and engineering. In this paper, the microstructural investigation of Al 6061, silicon carbide (SiC) and graphite (Gr) hybrid metal matrix composites with varying percentage reinforcements 2.5%, 5%, 7.5% and 10% have been carried out. The analysis of these hybrid compositions have been accomplished by using optical microscope, scanning electron microscope and energy dispersive spectroscopy that benefits to accomplish thermal characterization and analysis of composite material. Aluminium based composites reinforced with silicon carbide and graphite particles have been prepared by stir casting technique. It has been observed tha...
Chapter 3 Thermal Conductivity of Particulate Nanocomposites
2013
The modeling of the thermal conductivity of composites made up of metallic and non-metallic micro/nanoparticles embedded in a solid matrix is discussed in detail, at both the dilute and non-dilute limits of particle concentrations. By modifying both the thermal conductivity of the matrix and particles, to take into account the strong scattering of the energy carriers with the surface of the nanoparticles, it is shown that the particle size effect shows up on the thermal conductivity of nanocomposites through: (1) the collision cross-section per unit volume of the particles and, (2) the mean distance that the energy carriers can travel inside the particles. The effect of the electron–phonon interactions within metallic particles shows up through the reduction of the thermal conductivity of these particles with respect to its values obtained under the Fourier law approach. The thermal conductivity of composites with metallic particles depend strongly on (1) the relative size of the pa...