Browsing by Author "Bradley, Robert K."

Now showing 1 - 4 of 4
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    Gas-phase nucleation and growth of single-wall carbon nanotubes from high pressure CO
    (2004-07-13) Smalley, Richard E.; Smith, Kenneth A.; Colbert, Daniel T.; Nikolaev, Pavel; Bronikowski, Michael J.; Bradley, Robert K.; Rohmund, Frank; Rice University; United States Patent and Trademark Office
    The present invention discloses the process of supplying high pressure (e.g., 30 atmospheres) CO that has been preheated (e.g., to about 1000° C.) and a catalyst precursor gas (e.g., Fe(CO)5) in CO that is kept below the catalyst precursor decomposition temperature to a mixing zone. In this mixing zone, the catalyst precursor is rapidly heated to a temperature that results in (1) precursor decomposition, (2) formation of active catalyst metal atom clusters of the appropriate size, and (3) favorable growth of SWNTs on the catalyst clusters. Preferably a catalyst cluster nucleation agency is employed to enable rapid reaction of the catalyst precursor gas to form many small, active catalyst particles instead of a few large, inactive ones. Such nucleation agencies can include auxiliary metal precursors that cluster more rapidly than the primary catalyst, or through provision of additional energy inputs (e.g., from a pulsed or CW laser) directed precisely at the region where cluster formation is desired. Under these conditions SWNTs nucleate and grow according to the Boudouard reaction. The SWNTs thus formed may be recovered directly or passed through a growth and annealing zone maintained at an elevated temperature (e.g., 1000° C.) in which tubes may continue to grow and coalesce into ropes.
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    Method for scalable production of nanoshells using salt assisted purification of intermediate colloid-seeded nanoparticles
    (2005-06-21) Halas, Nancy J.; Bradley, Robert K.; Rice University; United States Patent and Trademark Office
    A method for purifying a suspension containing colloid-seeded nanoparticles and excess colloids is provided that includes adding to the suspension a filter aid comprising a salt. The method further includes filtering the suspension with a filter of a pore size intermediate between the average colloid-seeded nanoparticle size and the average excess colloid size, so as to form a retentate that includes the majority of the colloid-seeded nanoparticles and a filtrate that includes the majority of the excess colloids. Still further, the method includes collecting the retentate. The method may be incorporated into a method of making metallized nanoparticles, such as nanoshells, by reduction of metal ions onto the purified colloid-seed nanoparticles so as to form the metallized nanoparticles.
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    Partial coverage metal nanoshells and method of making same
    (2003-12-09) Halas, Nancy J.; Bradley, Robert K.; Rice University; United States Patent and Trademark Office
    Metal Nanoshells having partial coverage of a substrate or core particle and methods of making them are provided. A method of making a partial metal nanoshell preferably includes asymmetrically confining a substrate particle and selectively layering a metallic material over the substrate particle according to the asymmetry. Confining the substrate particle may include attaching it to a support defining an exposed portion and a contact portion. The method may include either chemically modifying the substrate particle. The solid angle of coverage of the partial metal nanoshell may be influenced by the nature of the chemical modification, such as alternatives of activating and passivating the exposed portion.
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    Single-wall carbon nanotubes from high pressure CO
    (2007-04-17) Smalley, Richard E.; Smith, Kenneth A.; Colbert, Daniel T.; Nikolaev, Pavel; Bronikowski, Michael J.; Bradley, Robert K.; Rohmund, Frank; Rice University; United States Patent and Trademark Office
    The present invention discloses the process of supplying high pressure (e.g., 30 atmospheres) CO that has been preheated (e.g., to about 1000° C.) and a catalyst precursor gas (e.g., Fe(CO)5) in CO that is kept below the catalyst precursor decomposition temperature to a mixing zone. In this mixing zone, the catalyst precursor is rapidly heated to a temperature that results in (1) precursor decomposition, (2) formation of active catalyst metal atom clusters of the appropriate size, and (3) favorable growth of SWNTs on the catalyst clusters. Preferably a catalyst cluster nucleation agency is employed to enable rapid reaction of the catalyst precursor gas to form many small, active catalyst particles instead of a few large, inactive ones. Such nucleation agencies can include auxiliary metal precursors that cluster more rapidly than the primary catalyst, or through provision of additional energy inputs (e.g., from a pulsed or CW laser) directed precisely at the region where cluster formation is desired. Under these conditions SWNTs nucleate and grow according to the Boudouard reaction. The SWNTs thus formed may be recovered directly or passed through a growth and annealing zone maintained at an elevated temperature (e.g., 1000° C.) in which tubes may continue to grow and coalesce into ropes.