Abstract
Various types of coiled carbon filaments have been synthesized using chemical vapor deposition and other methods. These carbon filaments exhibit unique electrical and mechanical properties due to their versatile shapes and structures. To form coiled shapes, different types of catalyst compositions and reactive gases have been explored. Generally, coiled carbon filaments are classified by coil diameter and shape (e.g., microcoil and nanocoil). In this review, coiled carbon filaments are classified into three growth mechanism categories: (1) bidirectional double helical growth; (2) bidirectional twisted growth; and (3) tip single helical or twisted growth. Next, their synthesis methods and hypothetical growth mechanisms are discussed. Then, their electrical and mechanical properties are listed. Finally, potential applications and uses of coiled carbon filament are mentioned.
Highlights
Carbon is one of the most versatile chemical elements of the periodic table and exists in various allotropic forms including diamond, graphite, and amorphous carbon
It was suggested that helical shape of carbon filaments is formed by the rotation of catalyst and the different shapes between bidirectionally grown double helical carbon filaments (b-DHCFs) and bidirectionally grown twisted carbon filaments (b-TCFs) are attributed to rotation direction of catalysts (Figure 12) [27]
Coiled carbon filaments have been classified by external coil diameters
Summary
Carbon is one of the most versatile chemical elements of the periodic table and exists in various allotropic forms including diamond, graphite, and amorphous carbon. In particular, Crystals 2014, 4 have been found to possess attractive morphologies, as well as excellent mechanical and electrical properties including superelasticity, low Young’s modulus, relatively high electrical conductivity, and good electromagnetic (EM) wave absorption [7,8,9,10]. These properties have led to the evaluation of helically shaped filaments with nano and micrometer coil diameters for use as tactile sensors, electromagnetic interference (EMI) shielding, and field emission devices [7,10,11]. All of these growth modes strongly depend on catalyst and reactive gas compositions
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