Carbon Nanospheres Superior to Carbon Nanotubes and Are Cheaper to Manufacture Say Headwater Technology Scientists

Headwaters Technology Innovation, LLC (Lawrenceville, NJ) earned U.S. Patents 7,718,155 and  7,718,156 for a method for manufacturing carbon nanostructures by catalytic templating nanoparticles. The carbon nanostructures have minimal surface functional groups that have superior qualities compared to carbon nanotubes.  The carbon nanostructures are particularly advantageous for some applications where high porosity, high surface area, and/or a high degree of graphitization are desired. Carbon nanostructures manufactured can be substituted for carbon nanotubes, which are typically more expensive to manufacture.

 The carbon nanostructures within the carbon nanomaterial have useful properties such as unique shape, size, and/or electrical properties. The absence of some or substantially all the functional groups on the surface of the carbon nanomaterial is believed to be responsible for at least some of the beneficial and novel properties of the carbon nanomaterials of the invention. For example, carbon nanomaterials having reduced functional groups have shown improved dispersibility in many organic polymers. 

FIG. 1A is a high resolution SEM image of a carbon nanomaterial formed which includes a plurality of nanosphere clusters. 

FIG. 1B is a high resolution, SEM image showing a closer image of individual clusters of carbon nanostructures and showing one cluster that has been broken open to reveal the plurality of carbon nanostructures that make up the cluster.

According to inventors Cheng Zhang, Martin Fransson and  Bing Zhou, carbon nanostructures are formed from a carbon precursor and catalytic templating nanoparticles. Methods for manufacturing carbon nanostructures generally include (1) forming a precursor mixture that includes a carbon precursor and a plurality of catalytic templating particles, (2) carbonizing the precursor mixture to form an intermediate carbon material including carbon nanostructures, amorphous carbon, and catalytic metal, (3) purifying the intermediate carbon material by removing at least a portion of the amorphous carbon and optionally at least a portion of the catalytic metal, and (4) heat treating the purified intermediate carbon material and/or treating the purified intermediate carbon material with a base to remove functional groups on the surface thereof. The removal of functional groups increases the graphitic content of the carbon nanomaterial and decreases its hydrophilicity.

During the manufacturing process, the carbon nanostructures are produced as part of an intermediate carbon material that includes the carbon nanostructures and amorphous carbon. The intermediate carbon material is purified to remove amorphous carbon. It has been found that the purified intermediate material often have surface functional groups such as, but not limited to, carboxylic acids, hydroxyl groups, hydronium groups, or the like.

In the Headwaters method, at least a portion of the functional groups are removed to give the nanomaterial desired properties. In one embodiment, the functional groups are removed by heating the purified intermediate carbon material. Alternatively or in addition to heating, the purified intermediate carbon material can be treated with a base to neutralize acidic groups. Removing all or a portion of the functional groups from the surface of the carbon nanomaterial can give the carbon nanomaterial beneficial properties including, but not limited to, improved dispersibility in hydrophobic materials and improved electrical conductivity. 

In one embodiment, all or a portion of the nanostructures formed in the manufacturing process are nanospheres. The nanospheres are typically multi-walled hollow carbon nanostructures. The nanospheres can have a spheroidal shape and typically agglomerate to form a cluster that is also spheroidal or grape-like.

The carbon material manufactured can be nearly pure nanospheres and/or nanosphere clusters. Alternatively a portion of the carbon material can, be graphite sheets or other graphitic materials. The carbon nanomaterials can include non-graphitic amorphous carbon. However, it is typically advantageous to minimize the percentage of non-graphitic amorphous carbon by removing it during purification and/or by converting non-graphitic amorphous carbon to graphite during additional heat treatment steps.

The carbon nanostructures have superior electrical and material properties compared to carbon nanotubes. For example, when mixed with a polymer, nanostructures including carbon nanospheres have significantly reduced electrical resistance compared to polymers that include the same weight percent of carbon nanotubes. 

FIG. 6 is a high resolution TEM of a purified intermediate carbon material manufactured according to Headwaters invention, but that has not been treated to remove functional groups; 

FIG. 7 is a high resolution TEM of the carbon nanomaterial of FIG. 6 that has been treated with a base to remove functional groups