Headwaters Technology Innovation, LLC (Lawrenceville, NJ) inventors Cheng Zhang and Bing Zhou found a way to produce and reduce the size of agglomerates of carbon nanospheres according to U.S. Patent 7,666,915.
The particle sizes of agglomerates of carbon nanospheres are reduced by dispersing the carbon nanospheres in a polar solvent. The carbon nanospheres are multi-walled, hollow, graphitic structures with an average diameter in a range from about 10 nm to about 200 nm, more preferably about 20 nm to about 100 nm. Spectral data shows that prior to being dispersed, the carbon nanospheres are agglomerated into clusters that range in size from 500 nm to 5 microns. The clusters of nanospheres are reduced in size by dispersing the carbon nanospheres in the polar solvent (e.g., water) using a surface modifying agent (e.g., glucose) and ultrasonication. The combination of polar solvent, surface modifying agent, and ultrasonication breaks up and disperses agglomerates of carbon nanospheres.
The combination of the polar solvent, surface modifying agent, and ultrasonication can yield a very stable dispersion of carbon nanospheres within the polar solvent. Carbon nanospheres dispersed using the Headwaters method can be stable in the polar solvent for hours, days, months, or even longer. Surprisingly, the particle size distribution can be very narrow.
In contrast to just sonicating in water, the combination of ultrasonicating the carbon nanospheres in a polar solvent in the presence of the surface modifying agent can yield a carbon nanomaterial with a surprisingly narrow particle size distribution as measured using dynamic light scattering. In one embodiment, at least 80% of the carbon nanomaterial has an average particle size of less than 500 nm, more preferably less than 300 nm, and most less than 200 nm.
FIG. 2A is a high resolution SEM image of carbon nanospheres agglomerated into a plurality of nanosphere clusters;
FIG. 2B is a high resolution SEM image showing a closer image of individual clusters of carbon nanospheres of FIG. 2A and showing one cluster that has been broken open to reveal the plurality of carbon nanospheres that make up the cluster;
FIG. 2C is a high resolution TEM image of the carbon nanomaterial of FIG. 2A showing a plurality of carbon nanospheres agglomerated together and revealing the multi-walled and hollow nature of the carbon nanospheres that form the cluster;
FIG. 4A is an SEM image of the carbon nanospheres of FIG. 2A after being dispersed in a polar solvent;
FIG. 4B is a TEM image of the carbon nanospheres of FIG. 4A
The carbon nanospheres are manufactured using all or a portion of the following steps: (i) forming a precursor mixture that includes a carbon precursor and a plurality of templating nanoparticles, (ii) allowing or causing the carbon precursor to polymerize around the catalytic templating nanoparticles, (iii) carbonizing the precursor mixture to form an intermediate carbon material that includes a plurality of nanostructures (e.g., carbon nanospheres), amorphous carbon, and catalytic metal, and (iv) purifying the intermediate carbon material by removing at least a portion of the amorphous carbon and optionally a portion of the catalytic metal. The purification step can also include removing oxygen containing functional groups generated during the removal of amorphous carbon or adding additional oxygen-containing functional groups to impart greater hydrophilicity to the carbon nanospheres.