Carbon nanotubes (CNTs) are low density, flexible, electrically conductive materials, with individual tubes having relatively high tensile strength. Nanocomp Technologies, Inc. produces carbon nanotubes in the form of sheets, tapes, powders, dispersions, and yarns. Nanocomp's products are used for aerospace, aviation, armor, and flame-resistant applications.
Carbon nanotubes are hollow, tubular cylinders of aromatic carbon atoms that exhibit distinct mechanical, electrical, thermal, and chemical properties. Individual tube diameters are ~10 nm with lengths of ~1 mm. Nanocomp’s CNTs have tremendous aspect ratios; thousands of times greater than other commercially available carbon nanotubes.
Part of producing the carbon nanotube powders and slurries involves a proprietary, surfactant-free dispersion process. The result of this process is bundles of CNTs that are ~100 um in width and ~1000 um in length. That’s where Joe Johnson, Ph.D., the Principal Scientist at Nanocomp comes in. He oversees the dispersion and particle labs, as well as related applications like paints, composites and polymers. He’s been with the company for three years, but his background includes over 20 years of experience working with anything involving particles including synthesis, modification, product development, applications, and characterization.
Dr. Johnson wanted an instrument that would help with determining the grinding quantification of carbon nanotubes. Nanocomp’s CNT production procedure results in non-woven sheets being made, with the CNTs held together mainly by van der Waal’s forces. An analogy, although using vastly different forces and scale, would be having many Velcro® tapes being pushed together forming a sheet. A grinding device was previously identified to “rip” the nanotubes from each other resulting in fibers, or bundles of CNTs. Previous experiments identified process conditions (e.g., CNT concentration and instrument conditions). The time of grind to achieve small, uniform fibers was unknown, so a study was planned that would measure particle size vs. grind time. Dr. Johnson needed a quantifying instrument that could accurately measure the width, length, aspect ratio, ESD (equivalent size diameter), and their distributions for dispersed carbon nanotubes.