Toward High Strength and High Electrical Conductivity in Super‐Aligned Carbon Nanotubes Reinforced Copper

The miniaturization of electronic products is drawing higher demand in the strength and conductivity of conductors. This work demonstrates the possibility of substantially increasing the dislocation density in copper to enhance the strength of super‐aligned carbon nanotubes (SACNTs) reinforced copper matrix composites (SACNT/Cu) without compromising the electrical conductivity. High strain is introduced into pure copper and SACNT/Cu by accumulative roll‐bonding (ARB) process up to 16 cycles at ambient temperature. SACNTs with initial laminated distribution turn out to be dispersed uniformly with maintained directional arrangement inside the copper matrix after ARB, which can then effectively block the motion of dislocations. Therefore, large number of dislocations propagated by large strains can be accumulated without subdivision. The accumulated dislocations will result into strain hardening, which is the major strengthening mechanism in SACNT/Cu after ARB. Furthermore, the contribution of dislocations to resistivity increase is little, thus maintaining high electrical conductivity. As a result, a high tensile strength (505 MPa) combined with a high electrical conductivity (90% IACS) is achieved in large‐sized composite sheet.

     

中间相沥青纤维制备高导热炭材料的研究

利用中间相沥青纤维中沥青分子的高度择优取向和适度的热塑性热压制备高导热块体炭材料. 对比研究了经不同氧化处理的带形及圆形中间相沥青纤维热压所得炭材料的传导性及力学性能. 结果表明: 相对圆形纤维来说, 由于带形中间相纤维具有更高的纤维轴向取向度和纤维之间更高的接触面积, 故其热压所得材料具有更高的密度和传导性. 经260℃氧化的带形纤维热压所得炭材料的密度、抗弯强度、电阻率及热导率分别达到了2.18g·cm^-3、118.4MPa、1.13μΩm和717W/m·K.     

聚丙烯腈基高模量碳纤维导热性能的影响因素

采用激光闪射法测试了6种不同强度和模量的聚丙烯腈(PAN)基碳纤维(CF)的热导率,探讨了不同温度下CF轴向热导率的变化及样品厚度对热导率测试结果的影响。采用X射线衍射(XRD)、拉曼等技术检测了CF的微晶尺寸、取向及有序度,考察了CF热导率与其微观结构的相关性。结果显示,实验范围内PAN基CF样品厚度对热导率测试结果略有影响,热导率随测试温度升高而降低,PAN基CF的致密性、晶体尺寸及结构有序度对其热导率有较大影响。     

Self‐Organized Epitaxial Vertically Aligned Nanocomposites with Long‐Range Ordering Enabled by Substrate Nanotemplating

Vertically aligned nanocomposites (VAN) thin films present as an intriguing material family for achieving novel functionalities. However, most of the VAN structures tend to grow in a random fashion, hindering the future integration in nanoscale devices. Previous efforts for achieving ordered nanopillar structures have been focused on specific systems, and rely on sophisticated lithography and seeding techniques, making large area ordering quite difficult. In this work, a new technique is presented to produce self‐assembled nanocomposites with long‐range ordering through selective nucleation of nanocomposites on termination patterned substrates. Specifically, SrTiO₃ (001) substrates have been annealed to achieve alternating chemical terminations and thus enable selective epitaxy during the VAN growth. La_0.7Sr_0.3MnO₃:CeO₂ (LSMO):CeO₂ nanocomposites, as a prototype, are demonstrated to form well‐ordered rows in matrix structure, with CeO₂ (011) domains selectively grown on SrO terminated area, showing enhanced functionality. This approach provides a large degree of long‐range ordering for nanocomposite growth that could lead to unique functionalities and takes the nanocomposites one step closer toward future nanoscale device integration.     

In‐Plane Anisotropic Thermal Conductivity of Few‐Layered Transition Metal Dichalcogenide Td‐WTe2

2D Td‐WTe₂ has attracted increasing attention due to its promising applications in spintronic, field‐effect chiral, and high‐efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in‐plane anisotropic thermal conductivities in suspended Td‐WTe₂ samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides. The results reveal an obvious anisotropy in the thermal conductivities between the zigzag and armchair axes. The theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in stronger anisotropy. The findings here are crucial for developing efficient thermal management schemes when engineering thermal‐related applications of a 2D system.     

Boosting the Heat Dissipation Performance of Graphene/Polyimide Flexible Carbon Film via Enhanced Through‐Plane Conductivity of 3D Hybridized Structure

The development of materials with efficient heat dissipation capability has become essential for next‐generation integrated electronics and flexible smart devices. Here, a 3D hybridized carbon film with graphene nanowrinkles and microhinge structures by a simple solution dip‐coating technique using graphene oxide (GO) on polyimide (PI) skeletons, followed by high‐temperature annealing, is constructed. Such a design provides this graphitized GO/PI (g‐GO/PI) film with superflexibility and ultrahigh thermal conductivity in the through‐plane (150 ± 7 W m^‐1 K^‐1) and in‐plane (1428 ± 64 W m^‐1 K^‐1) directions. Its superior thermal management capability compared with aluminum foil is also revealed by proving its benefit as a thermal interface material. More importantly, by coupling the hypermetallic thermal conductivity in two directions, a novel type of carbon film origami heat sink is proposed and demonstrated, outperforming copper foil in terms of heat extraction and heat transfer for high‐power devices. The hypermetallic heat dissipation performance of g‐GO/PI carbon film not only shows its promising application as an emerging thermal management material, but also provides a facile and feasible route for the design of next‐generation heat dissipation components for high‐power flexible smart devices.