Growth and Characterization of Uniform Carbon Nanotube Arrays on Active Substrates

Abstract

Carbon nanotubes (CNTs) have unique thermal/electrical/mechanical properties and high aspect ratios. Growth of CNTs directly onto reactive material substrates (such as metals and carbon based foam structures, etc.) to create a micro-carbon composite layer on the surface has many advantages: possible elimination of processing steps and resistive junctions, provision of a thermally conductive transition layer between materials of varying thermal expansion coefficients, etc. Compared to growing CNTs on conventional inert substrates such as SiO2, direct growth of CNTs onto reactive substrates is significantly more challenging. Namely, control of CNT growth, structure, and morphology has proven difficult due to the diffusion of metallic catalysts into the substrate during CNT synthesis conditions. In this study, using a chemical vapor deposition method, uniform CNT layers were successfully grown on copper foil and carbon foam substrates that were pre-coated with an appropriate buffer layer such as Al2O3 or Al. SEM images indicated that growth conditions and, most notably, substrate surface pre-treatment all influence CNT growth and layer structure/morphology. The SEM images and pull-off testing results revealed that relatively strong bonding existed between the CNT layer and substrate material, and that normal interfacial adhesion (0.2‒0.5 MPa) was affected by the buffer layer thickness. Additionally, the thermal properties of the CNT/substrate structure were evaluated using a laser flash technique, which showed that the CNT layer can reduce thermal resistance when used as a thermal interface material between bonded layers.

Thermal Properties Enhancement of Vertically Aligned Carbon Nanotubes-Based Metal Nanocomposites as Thermal Interface Materials

“…Before the CNT growth process was initiated, an optimized 10-15 nm aluminum (Al) buffer layer was applied to the precleaned Cu substrate surface using a sputter coating technique. The growth process/conditions of CNTs by FCCVD is the same as previously reported (Zhang et al, 2004). The density and length of VACNT layer on Cu foil was controlled by growth time under the same growth conditions (Zhang et al, 2004).…”

“…The growth process/conditions of CNTs by FCCVD is the same as previously reported (Zhang et al, 2004). The density and length of VACNT layer on Cu foil was controlled by growth time under the same growth conditions (Zhang et al, 2004). In this study, VACNT/Cu samples, with a VACNT layer thickness between 80 and 100 µm, were selected to prepare a series of three-layer (sandwich) samples.…”

“…The VACNT layer were synthesized directly on a 10 mm × 10 mm × 2.35 mm copper (Cu) substrate (purchased from Online metals) via a FCCVD (Floating Catalyst CVD) method (Zhang et al, 2004). Before the CNT growth process was initiated, an optimized 10-15 nm aluminum (Al) buffer layer was applied to the precleaned Cu substrate surface using a sputter coating technique.…”

“…Previous work by this group demonstrated that a uniform VACNT layer can be grown directly on a conductive substrate (Cu, Carbon, etc.) when a suitable thin buffer layer was coated on the surface (Zhang et al, 2004). In order to improve the interface connection between the CNTs and the matching substrate, this study focused on the surface modification of the VACNT array grown on the Cu foil substrate (as CNT/Cu), followed by optimum CNT-surface solder filtration processing to form a VACNT-based metal nanocomposite (MNC) structure.…”

Conducting Interface for Efficient Growth of Vertically Aligned Carbon Nanotubes: Towards Nano-Engineered Carbon Composite

“…Substrates of different nature and morphology are evidenced as suitable for the growth of VACNT due to easy-to-analyze or easy-to-industrialize properties. Various substrates have been used for the growth of VACNT, such as silicon wafers [9,24,31,34,35], quartz [36], aluminium foil [13,37,38], piezoelectric aluminium nitride film [39], stainless steel [40], titanium wire [41], magnesia and magnesium aluminate [42], as well as carbon fiber cloth [36,[43][44][45] or paper [46,47], graphite [5,48], graphene paper [49] or oxide [50], reticulated carbon foam [51], and many others [21,52]. Among all, commercial fibrous carbon 3D substrates (CF tow, cloth, felt, paper, or other woven or non-woven fabrics) are advantageous since they possess exceptionally high mechanical strength and well-defined anisotropic thermal and electrical properties [53].…”