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.
Magnetic liquid metal is regarded as a promising material due to its integration of fluidic, metallic, and magnetic properties simultaneously. Previously, few methods of fabricating magnetic liquid metal have been proposed. However, either the alloying reaction inside the matrix or the poor performance in electrical and thermal conduction is troublesome in practical applications. Here, inspired by the mussel in nature, polydopamine is introduced to in situ reduce and immobilize silver shells on the surface of iron particles, and then the modified particles mix with liquid metal to prepare liquid metal-based magnetic suspensions (LMMSs). The silver shells can prevent iron particles from alloying with liquid metal and enhance the electrical and thermal conductivities of the LMMS concurrently. Besides, the LMMS thus obtained can keep its magnetism intact for a long period, at least during the 60 days of the test. Compared to directly mixing bare iron particles with liquid metal, the maximum electrical conductivities increase by at least 13.69% and the thermal conductivities increase by almost 4 times in the LMMS. The LMMS also exhibits potential applications in patterning and magnetic manipulation. This work puts forward a new strategy for preparing a LMMS with appealing properties and its broad applications are expected in the future.
Multilayer structure is one of the research focuses of thermoelectric (TE) material in recent years. In this work, n-type 800 nm Bi2Te3/(Pt, Au) multilayers are designed with p-type Sb2Te3 legs to fabricate ultrathin microelectromechanical systems (MEMS) TE devices. The power factor of the annealed Bi2Te3/Pt multilayer reaches 46.5 µW cm-1 K-2 at 303 K, which corresponds to more than a 350% enhancement when compared to pristine Bi2Te3. The annealed Bi2Te3/Au multilayers have a lower power factor than pristine Bi2Te3. The power of the device with Sb2Te3 and Bi2Te3/Pt multilayers measures 20.9 nW at 463 K and the calculated maximum output power reaches 10.5 nW, which is 39.5% higher than the device based on Sb2Te3 and Bi2Te3, and 96.7% higher than the Sb2Te3 and Bi2Te3/Au multilayers one. This work can provide an opportunity to improve TE properties by using multilayer structures and novel ultrathin MEMS TE devices in a wide variety of applications.
The metal/diamond interface consisting of two highly dissimilar materials is widely present in high-power microelectronic devices using a diamond film as a heat spreader or using a metal matrix/diamond filler composite as a heat sink for thermal management applications. To improve the interfacial thermal conductance (G), a common method is to add an appropriate interlayer in between the two materials; however, the effect of the interlayer on G is still not clear. In this work, we prepare a Cu/TiC/diamond structure by magnetron sputtering to detect how the crystallinity, grain size, and thickness of the TiC interlayer influence G between Cu and diamond. We characterize in detail the interface by transmission electron microscopy and X-ray photoelectron spectroscopy and measure experimentally G by the time-domain thermoreflectance technique. The results indicate that the higher crystallinity and thinner interlayer are both beneficial to the improvement of G between Cu and diamond, but the G is insensitive to the grain size of TiC. An increase of G between Cu and diamond as much as 48% can be reached by a highly crystallized 10 nm thick TiC interlayer. The microscopic characteristics of the TiC interlayer have played a decisive role for G between Cu and diamond. While an inserted interlayer in principle has a potential to enhance G between two dissimilar materials, the low crystallinity and large thickness of the interlayer will weaken the enhancement or even reverse this positive effect. The G of a sandwiched structure can be regulated in a wide range by the microscopic characteristics of the interlayer, which provides guidelines for preparation of metal/nonmetal interfaces with high interfacial thermal conductance for thermal management applications.
