Mineral-based form-stable phase change materials for thermal energy storage: A review on encapsulation techniques, performance enhancements and practical applications

Interface manipulation and its effects on the resultant thermal conductivity of hot-forged copper/Ti-coated diamond composites

Copper/diamond composites are regarded as the next-generation heat sink materials and have great potential to be used for future high-power electronic devices. The interphase layer characteristics between the copper matrix and the diamond have a significant influence on the composite’s thermophysical properties. In this work, a cost-effective hot forging process is used to fabricate diamond particles (about 70 μm diameter) reinforced Cu-xB matrix (x = 0.3, 0.5 and 1.0 wt.%) composites. The results show that B4C particles are easier to nucleate on the diamond (100) facet than on diamond (111) facet during the hot forging. The morphology of the newly formed B4C interphase layer on the diamond (100) facet evolved from a fine dispersed particle (Cu-0.3B/diamond) to a continuous dense structure (Cu-1B/diamond). On the diamond (111) facet, the B4C nucleation is difficult due to relative stronger carbon bonds formed on the diamond (111) facet (three bonds) than on the diamond (100) facet (two bonds), the growth of previously nucleated B4C become predominated, resulting in forming a B4C interphase layer with large particle size and low density on the diamond (111) facet. The Cu-0.5B/diamond has the highest thermal conductivity among the three fabricated composites (440 W/mK), and a low coefficient of thermal expansion (6.57 × 10–6 /K) at 313 K is obtained. With increasing the diamond particle size to 200 μm, the hot-forged Cu-0.5B/diamond had an increased thermal conductivity (495 W/mK). It demonstrates that hot forging is a feasible method to fabricate Cu/diamond composites with acceptable thermal conductivity from powder mixture.

Interphase layer characteristics and thermal conductivity of hot-forged Cu-B/diamond composites

Unveiling interfacial structure and improving thermal conductivity of Cu/diamond composites reinforced with Zr-coated diamond particles

Manipulating the interfacial structure is vital to enhancing the interfacial thermal conductance (G) in Cu/diamond composites for promising thermal management applications. An interconnected interlayer is frequently observed in Cu/diamond composites; however, the G between Cu and diamond with an interconnected interlayer has not been addressed so far and thus is attracting extensive attention in the field. In this study, we designed three kinds of interlayers between a Cu film and a diamond substrate by magnetron sputtering coupled with heat treatment, including a W interlayer, an interconnected W-W2C interlayer, and a W2C interlayer, to comparatively elucidate the relationship between the interfacial structure and the interfacial thermal conductance. For the first time, we experimentally measured the G between Cu and diamond with an interconnected interlayer by a time-domain thermoreflectance technique. The Cu/W-W2C/diamond structure exhibits an intermediate G value of 25.8 MW/m2 K, higher than the 19.9 MW/m2 K value for the Cu/W2C/diamond structure and lower than the 29.4 MW/m2 K value for the Cu/W/diamond structure. The molecular dynamics simulations show that the G of the individual W2C/diamond interface is much higher than those of the individual Cu/diamond and W/diamond interfaces and W2C could reduce the vibrational mismatch between Cu and diamond; however, the G of the Cu/W2C/diamond structure is reduced by the lower thermal conductivity of W2C. This study provides insights into the relationship between the interconnected interfacial structure and the G between Cu and diamond and offers guidance for interface design to improve the thermal conductivity in Cu/diamond composites.

Interfacial Thermal Conductance between Cu and Diamond with Interconnected W-W2C Interlayer.

Copper/diamond composites have drawn lots of attention in the last few decades, due to its potential high thermal conductivity and promising applications in high-power electronic devices. However, the bottlenecks for their practical application are high manufacturing/machining cost and uncontrollable thermal performance affected by the interface characteristics, and the interface thermal conductance mechanisms are still unclear. In this paper, we reviewed the recent research works carried out on this topic, and this primarily includes (1) evaluating the commonly acknowledged principles for acquiring high thermal conductivity of copper/diamond composites that are produced by different processing methods; (2) addressing the factors that influence the thermal conductivity of copper/diamond composites; and (3) elaborating the interface thermal conductance problem to increase the understanding of thermal transferring mechanisms in the boundary area and provide necessary guidance for future designing the composite interface structure. The links between the composite’s interface thermal conductance and thermal conductivity, which are built quantitatively via the developed models, were also reviewed in the last part.

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S. Q. Jia

Papers

High thermal conductive copper/diamond composites: state of the art