Papers by Keyword: Interfacial Thermal Resistance

Abstract: Interfacial thermal resistances of Al-Si alloys were evaluated by comparing the measured thermal conductivities and the simulated thermal conductivities. Al-7%Si, Al-18%Si and Al-18%Si held in the solid-liquid coexistence temperature for 90 minutes were fabricated by gravity casting. Thermal conductivities were measured with the steady state thermal conductivity measuring device. Thermal conductivities were also simulated by using optical microscope images. Comparing the measured thermal conductivities and the simulated thermal conductivities, interfacial thermal resistances in Al-Si interfaces were evaluated as about 2.5-4.8×10^-9 m²K/W.

Abstract: Interfacial thermal resistance of Al-AlN composites was evaluated by comparing the measured thermal conductivity and the simulated thermal conductivity. Al-10vol.%AlN and Al-20vol.%AlN composites were fabricated by spark plasma sintering. Effective thermal conductivity was measured with the steady state thermal conductivity measuring device. Effective thermal conductivity was also simulated by using FE-SEM image and the measured relative density. Comparing the measured thermal conductivity and the simulated thermal conductivity, interfacial thermal resistance in Al-AlN composites was evaluated as about 1.27-6.2510^-9 m²K/W.

Abstract: Short carbon fibers reinforced ZrB₂-SiC ceramics were prepared by hot pressing sintering process. The short carbon fibers with different volume fractions (0.2.4.6.8.10.20) were added for improving the thermal insulation properties of ZrB₂-SiC ceramics. The experimental results showed that as the content of short carbon fiber increased, the thermal diffusivity decreased from 43.9m²/s to 32.9m²/s, the thermal conductivity decreased from 104.3 W/(m·K) to 72.9 W/(m·K) and thermal insulation performance reduced by 43.1%, respectively. The enhancement of the thermal insulation properties is mainly due to high interfacial thermal resistance of short carbon fiber and matrix.

Abstract: Steady state thermal conductivity measuring device was designed to measure the effective thermal conductivity of composites. Computer simulations of thermal conduction revealed that the designed device over estimates the effective thermal conductivity, and the correction coefficient was suggested. With this designed device, the effective thermal conductivities of Al/SiC particle-dispersed composites were measured by changing the size of SiC particles from 0.3 μm to 3 μm. The critical element size which could determine the optimal size of reinforcements have been suggested, and validity of the critical element size for Al/SiC composites was confirmed. The thermal conductivity of the composites including small SiC particles was degraded by the interfacial thermal resistance between the matrix and the reinforcement. On the other hand, the thermal conductivity of the composites including large SiC particles was not affected by the interfacial thermal resistance. These results suggest that consideration of the critical element size is valid.

Abstract: Using classical non-equilibrium molecular dynamics simulations (NEMD), the interfacial thermal resistance and thermal rectification of nitrogen-doped zigzag graphene (NDZG) are investigated. Two different structural models about nitrogen-doped graphene are constructed. It is found that the interfacial thermal resistance at the location of nitrogen-doping causes severe reduction in thermal conductivity of the NDZG. Thermal rectification of the triangular single-nitrogen-doped graphene (SNDG) decreases with increasing temperature. However, thermal rectification is not detected in the parallel various–nitrogen-doped graphene (VNDG). These results suggest that SNDG might be a promising structure for thermal device.

Abstract: Diamond/Copper composite (Diamond/Cu) is a kind of ideal thermal management material, with high thermal conductivity and low thermal expansion. While the interface control is the center of the Diamond/Cu composites design. This paper summarizes the relevant studies on Diamond/Cu composite interface, including the researches of author’s group and other researchers. In addition, the prospect of research is mainly elaborated from following three parts: using carbide elements to control and improve the diamond/Cu composite interface bonding; the introduction of the research on Diamond/Cu composite interface with technologies of powder metallurgy, high temperature and high pressure process, spark plasma sintering and pressure infiltration; studying the thermal conductivity of Diamond/Cu composite by SThM analysis and testing technology and the Hasselman-Johnson model. The results show that controlling and improving the quality of Diamond/Cu composite interface bonding can improve the performance and stability of the composite.

Abstract: In this paper the spline subdomain approach is applied to the 2D simulations of the temperature distributions for composites containing a single rectangular particle with an interfacial thermal resistance at the interface between the particle and matrix. The bicubic B-splines are used to construct the trial functions for the approximations of the potential fields of composites. Applying the weighted residual point collocation method inside each subdomain and also on the boundaries between different subdomains, a system of linear algebraic equations is set up to determine the unknowns of the trial functions. The temperature distributions both inside the rectangular particle and along the interfaces under different interfacial contact conditions can be simulated approximately. Numerical results which are compared with the available solutions obtained by FEM method illustrate the accuracy and suitability of the present approach for steady-state conduction. Even in the adjacent areas of corners in the rectangular particle, the simulation results are also satisfactory.

Abstract: A new micromechanical method, the weighted residual self-consistent method (WRSCM) is developed to study the effective thermal conductivity of two-phase composites with different particle geometries in the presence of a thermal barrier resistance at the interface between constituents. The imperfect interface involves the continuity of the normal flux but allow for a finite temperature differences across the interface. Within the framework of self-consistent scheme, the effective thermal conductivity of two-phase composite is obtained using numerical iterative method on the basis of a surface integral of temperature over the imperfect interfaces. Numerical results show that for the given composite system, due to the existence of an interfacial thermal resistance, the particle geometries have significant impact on the effective thermal conductivity of composites.

Abstract: In this paper we report on the effects of variables in thermal resistance measurement of high power GaN-based light-emitting diodes (LEDs). The investigated variables include ambient temperature, thermal interface material (TIMs) at different pressure. The combination of transient thermal measurement method and optical measurement was employed for the study. The measured thermal resistance of LED packages was found to increase with the ambient temperature. The temperature dependence of optical efficiency, forward voltage, and thermal properties of packaging materials are thought to be responsible for the increase of thermal resistance with the ambient temperature. The interface effect on the thermal resistance was studied by applying different external pressure on the interface with different TIMs. And the measured thermal resistances were found to reach stabilization at certain pressure level after initial decrease with the external applied pressure.

Abstract: Thermal conductivity of as-prepared MoSi2/SiC composites has been determined by Laser Flash method. Interfacial thermal conductance for composites with 100nm SiC and with 0.5µm has been determined by using effective medium theory. The results of interfacial thermal conductance exhibit that both the inclusion size and the clustering of the inclusions play an important role in determining composite thermal conductivity.