Crystal-like Growth of a Metal Oxide/CNT Composite Fiber with Electroplated “Seed” from a CNT-Dispersed Nonaqueous Electrolyte

Abstract

A fabrication technique is developed for the preparation of metal oxide/CNT composites. An essential feature of the technique lies in the use of nonaqueous electrolyte in place of the usual aqueous electrolyte, which ensures well-dispersed CNTs without surfactants. After a "seed" is formed by electroplating on the anode, the seed is simply pulled up at a certain speed to grow a 1D CNT composite structure. The technique leads to a uniform distribution of metal oxide and a high weight fraction of CNT in the composite structure. Moreover, the conductivity of the composite is much higher than that of the CNT fibers fabricated with polymer.

High performance CNT point emitter with graphene interfacial layer

“…Upon applying the bias between the copper tip and counter electrode, the CNTs that are negatively charged through the purification process and the 2 changes into WO 3 during the plating process, encouraging tight contact between the adjacent CNTs as well as the CNT and the graphene surface. An electron probe microanalysis (EPMA) technique reveals that the tungsten and carbon are uniformly distributed throughout the composite structure in which the WO 3 was electroplated on the SWNT wall [11]. After the electroplating process, the copper tip is withdrawn with a droplet; the CNT and WO 3 composite are included.…”

“…The composite structure is finally detached from the Teflon surface, as shown in figure 1(d); then, the resulting emitter has a cylindrical geometry with a diameter of ∼30 μm, of which the length can be controlled by adjusting the plating time [11]. The 'nail head' geometry (see the tip of the CNT emitter in figure 1(d)) is formed due to the contact-drying process that is necessary to make the structure straight.…”

“…As shown in the inset of figure 1(d), the CNTs are well aligned along the emitter axis. The CNTs, which are randomly dispersed in the solution, are aligned in the direction of the emitter during the crystal-like growth process [11]. Since the alignment is made in the direction of the electron path during the field emission, the self-alignment helps to enhance the performances of the emitter.…”

“…The adhesion method of CNTs at a metal tip is appropriate for the fabrication of the point emitter when considering the quality issues of CNTs in the growth method [8,9]. The CNT point emitters, based on the adhesion method, were fabricated either by the wet-spinning of CNT fibers [10], the crystal-like growth method [11] or by attaching CNTs using dielectrophoresis [12], utilizing well-dispersed CNT colloidal solutions. However, these methods usually result in emitters with high thermal and electrical contact resistances between the metal and CNT, which seriously degrade the field emission performances of the emitters [13][14][15].…”

Better than 10 mA Field Emission from an Isolated Structure Emitter of a Metal Oxide/CNT Composite

“…The fabrication involves two distinct steps of growing a macroscopic CNT composite emitter followed by electrical discharge machining (EDM) treatment of the grown emitter. For the growth, a crystal-like growth technique is utilized. The EDM treatment is used to control the emitter length and endow the treated emitter with highly desirable properties for the field emission.…”