Hielscher - Ultrasound Technology

Carbonnanotubes are strong and flexible but very cohesive. This makes it difficult to disperse them into liquids, such as water, ethanol, oil, polymer or epoxy resin. Ultrasound is an effective method to obtain discrete - single-dispersed - carbonnanotubes.

Carbonnanotubes (CNT) are macromolecules in the shape of a long thin cylinder. Only a nanometer in diameter, but molecules that can be manipulated chemically and physically. Carbon-nanotubes are interesting for many industries because of their electrical and thermal conductivity, strength, stiffness and toughness. They open incredible applications in materials, electronics, chemical processing and energy management. There are two categories of carbon nanotubes: Single-wall nanotubes (SWNT) and multi-wall nanotubes (MWNT).

Carbonnanotubes are used in adhesives coatings and polymers and as electrically conductive fillers in plastics to dissipate static charges in electrical equipment and in electrostatically paintable automobile body panels. By the use of nanotubes, polymers can be made more resistant against temperatures, harsh chemicals, corrosive environments, extreme pressures and abrasion.

As carbonnanotubes are commonly available as bulk material, e.g. from companies, such as SES Research or CNT Co., Ltd., a simple, reliable and scaleable process to deagglomerate (untangle) them is required, in order to utilize the nanotubes to their maximum potential. For liquids of up to 100,000cP (approx.) ultrasound is a very effective technology to be used for this application. This allow the use of ultrasound for the dispersing of nanotubes in water, oil or polymers at low or high concentrations. The liquid jet streams resulting from ultrasonic cavitation, overcome the bonding forces, e.g. van der Waals' forces, between the nanotubes, and separate the tubes. Because of the ultrasonically generated shear forces and micro turbulences ultrasound can assist in the surface coating and chemical reaction of nanotubes with other materials, too.

Generally, a coarse nanotube-dispersion is first premixed by a standard stirrer and then homogenized in the ultrasonic flow cell. The videos to the right show a lab trial (batch trial using a UP400S) dispersing multiwall carbonnanotubes in water at low and high concentration, respectively. Because of the chemical nature of carbon the dispersing behavior of nanotubes in water is rather difficult. As show in the video, it can be easily demonstrated that ultrasonic processing is capable to disperse nanotubes effectively.

Hielscher offers a broad range of ultrasonic devices and accessories for the efficient dispersing of nanotubes.

• Compact laboratory devices of up to 400 watts power
  These devices are mainly used for sample preparation or initial feasibility studies and are available for rental.
• 500 and 1,000 and 2,000 watts ultrasonic processors like the UIP1000 set with flow cell and various booster horns and sonotrodes can process larger volume streams.
  Devices like this are used in the optimization of the parameters (like: amplitude, operational pressure, flow rate etc.) in bench-top or pilot plant scale.
• Ultrasonic processors of 2, 4, 8 and 16kW and larger clusters of several such units can process production volume streams at almost any level.

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