Abstract
Invoking Effective Media Percolation theory (EMPT), Hasselaman-Johnson effective media theory (EMT), and Nan and Birringer EMT, the effect of addition of SiC and Al2O3 nanoparticles on Kapitza resistance (RBd) of Ni0.05Mo3Sb5.4Te1.6 was investigated. Pore size and their volume distribution, and surface area were characterized using BET technique to correlate pore effect and surface area on RBd. Bounds for effective thermal conductivity were determined using Lipton–Vernescu model. Variation of thermal conductance with respect to temperature was studied and compared with the results of other materials. According to EMPT, RBd in Ni0.05Mo3Sb5.4Te1.6/SiC composites ranged from 3.84 × 10-7 to 5.42 × 10-7 m2KW–1 and 3.36 × 10-7 to 3.86 × 10-7 m2KW–1 for Ni0.05Mo3Sb5.4Te1.6/Al2O3 composites. Kapitza radius (aK) for SiC samples was ranged between 2.01 – 2.84 μm; for Al2O3 samples it was 1.86 μm. Hasselman-Johnson model gave RBd values 55%, 51%, and 8% more than what EMPT is predicting, but of the same order and aK values 3.5 μm, 4 μm, 3 μm for SiC samples and 1.2 μm, 0.6 μm, 0.55 μm for Al2O3 samples. Nan-Birringer model yielded large aK of 7.25 μm and RBd ∼ 1.4 × 10–6 m2KW–1 for Ni0.05Mo3Sb5.4Te1.6/SiC. So obtained parameters are reasonable estimates. Variation of effective thermal conductivity in Al2O3 samples is more sensitive to particle size compared to SiC samples. Mechanical properties were studied using micro–indentation technique and their effect on effective thermal properties was ascertained. Addition of Al2O3 nanoparticles have aided in enhancing mechanical properties of bulk material.
Highlights
A preponderance of experimental and theoretical studies on the thermal conductivity of composite materials are heavily emphasized on one major category of materials
According to effective medium percolation theory (EMPT), RBd for SiC samples is increasing with SiC content (3.84 × 10-7– 5.42 × 10-7 m2KW–1) and for Al2O3 samples RBd is 3.86 × 10-7 m2KW–1
Macropore volume for SiC samples is larger than Al2O3 samples
Summary
A preponderance of experimental and theoretical studies on the thermal conductivity of composite materials are heavily emphasized on one major category of materials. Κbulk, κcomp (κeff , effective thermal conductivity in some literature), and f are κ of bulk, composite, and vol fraction of embedded particles respectively. It has been reported that when a highly conducting particles are embedded in a relatively low conducting matrix, the thermal conductivity of matrix increase or decreases depending on the size of embedded particle.[11] When the size of the embedded particles decreases, the effective thermal conductivity of matrix/nanoparticle decreases as the interface per unit vol generated by the particles increases phonon scattering with interfaces.[16,20,35] In such cases, interfacial thermal boundary resistance begins to play considerable role in heat transfer.[23,27,36] Polycrystals are known to exhibit low thermal conductivity and they are technologically very important. The effect of SiC and Al2O3 nanoparticles on the thermal boundary resistance of Ni0.05Mo3Sb5.4Te1.6 is scrutinized Effective media theories such as EMPT, Hasselman-Johnson model, and Nan-Birringer model were applied to estimate the approximate values of RBd, ak, and hc. Both composites in this article are assumed to have imperfect interfaces
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