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Patent Issued for Porous Substrates Filled with Nanomaterials

September 3, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventors Worsley, Marcus A. (Hayward, CA); Baumann, Theodore F. (Discovery Bay, CA); Satcher, Jr., Joe H. (Patterson, CA); Stadermann, Michael (Pleasanton, CA), filed on August 1, 2011, was published online on August 19, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8809230 is assigned to Lawrence Livermore National Security, LLC (Livermore, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "A need exists to prepare better composite materials including nanostructured composite materials. For example, many energy applications such as capacitors and batteries require better performance of materials. Nanostructured materials provide the ability to engineer important properties such as surface area and electrical charge transport.

"An important class of material is highly porous material which provides high surface area. For example, carbon aerogels (CAs) are a unique class of porous materials that are being commercialized and hold technological promise for a variety of applications, including catalysis, adsorption and energy storage..sup.[1] The utility of these materials is derived, at least in part, from their high surface areas, electrically conductive frameworks, and tunable porosities. To expand the applications for these materials, efforts have focused on the incorporation of modifiers, such as carbon nanotubes (CNTs) or metal nanoparticles, into the carbon framework that can potentially enhance the thermal, electrical, mechanical, or catalytic properties of the aerogel..sup.[2] For example, a new class of ultra low-density CNT-CA composites was recently reported that exhibit both high electrical conductivity and robust mechanical properties..sup.[3] These CA composites are believed to be among the stiffest low-density solids reported and exhibit elastic behavior to compressive strains as large as about 80%. In these materials, however, the CNTs are embedded within the skeletal network of the CA and, as a result, the accessible surface area associated with the nanotubes is minimal. While this structural motif does serve to enhance the bulk electrical and mechanical properties of these low-density materials, a need exists for many applications to design CA composites that provide functional access to the surfaces of the CNTs. Other types of composite materials comprising nanomaterials such as nanowires and nanotubes are needed, particularly materials having macroscopic dimensions but nanostructured elements."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "At least some embodiments described herein provide a straightforward method for the fabrication of novel monolithic composites, including composites carbon nanotubes and carbon aerogel. These and other embodiments are described herein. Embodiments provided herein include compositions, devices, and articles, as well as methods of making and methods of using the compositions, devices, and articles.

"For example, one aspect provides a composition comprising: at least one porous carbon monolith comprising internal pores, and at least one nanomaterial disposed throughout the internal pores.

"In one embodiment, the nanomaterial is disposed uniformly throughout the internal pores.

"In one embodiment, the porous carbon monolith comprises two external surfaces which define a width and a width middle for the monolith, and the nanomaterial is disposed uniformly at the width middle.

"In one embodiment, the nanomaterial increases a volumetric surface area of the composition relative to a volumetric surface area of the porous carbon monolith considered independently of the nanomaterial.

"In one embodiment, the nanomaterial has a weight, and the porous carbon monolith has a weight, and the weight of the nanomaterial is greater than the weight of the porous carbon monolith.

"In one embodiment, the amount of the porous carbon monolith is less than about 75% by weight of the composition.

"In one embodiment, the amount of the porous carbon monolith is less than about 50% by weight of the composition.

"In one embodiment, the porous carbon monolith is an aerogel, a xerogel, or an open-cell foam.

"In one embodiment, the porous carbon monolith is an aerogel.

"In one embodiment, the porous carbon monolith is an activated carbon aerogel.

"In one embodiment, the internal pores comprise a bimodal pore size distribution.

"In one embodiment, the internal pores comprise pores which have an average diameter of 100 nm or more.

"In one embodiment, the internal pores comprise one set of pores which have an average diameter of 1 micron or more and another set of pores which have an average diameter of 10 nm or less.

"In one embodiment, the porous carbon monolith has a BET surface area of at least 2,000 m.sup.2/g, independently of the nanomaterial disposed in the internal pores.

"In one embodiment, the nanomaterial is a nanotube or a nanowire.

"In one embodiment, the nanomaterial is a carbon nanotube.

"In one embodiment, the nanomaterial is a multi-walled carbon nanotube.

"In one embodiment, the composition further comprises catalyst adapted for nanomaterial growth.

"In one embodiment, the composition comprising the porous carbon monolith and the nanomaterial has a BET surface area of at least 1,000 m.sup.2/g.

"In one embodiment, the composition has a bulk electric conductivity of at least 1 S/cm.

"Another aspect comprises a composition comprising: at least one carbon aerogel comprising internal pores and at least one dimension which is at least 100 microns, wherein carbon nanotubes are disposed in the internal pores, wherein the amount of the carbon aerogel is less than about 75% by weight of the composition.

"In one embodiment, the amount of the carbon aerogel is less than about 50% by weight of the composition.

"In one embodiment, the carbon aerogel is a monolith.

"In one embodiment, the carbon nanotubes are disposed uniformly in the internal pores.

"In one embodiment, the composition further comprises catalyst for growth of the carbon nanotubes.

"In one embodiment, the carbon nanotubes increase the volumetric surface area of the composition compared to the carbon aerogel.

"In one embodiment, the carbon nanotubes increase the electrical conductivity of the composition compared to the carbon aerogel.

"In one embodiment, the carbon aerogel comprise pores having an average pore diameter of at least 100 nm.

"In one embodiment, the carbon aerogel comprises a bimodal pore size distribution.

"In one embodiment, the composition comprising the carbon aerogel and the carbon nanotubes has a BET surface area of at least 1,000 m.sup.2/g.

"Another aspect provides a method comprising: providing a porous substrate having a thickness of 100 microns or more, wherein the porous substrate comprises a plurality of macropores throughout the thickness of the porous substrate; disposing a catalyst inside the porous substrate; and forming a nanomaterial in the macropores by vapor deposition, wherein the catalyst catalyzes the growth of the nanomaterial, and wherein the nanomaterial is deposited throughout a thickness of porous substrate.

"In one embodiment, the forming step comprises allowing a precursor to the nanomaterial to fill up the macropores and then react the precursor in presence of catalyst to form the nanomaterial in the macropores.

"In one embodiment, the substrate is an aerogel, a xerogel, or an open-cell foam.

"In one embodiment, the catalyst comprises at least one metal.

"In one embodiment, the average diameter of the macropores is 100 nm or more.

"In one embodiment, the nanomaterial is a carbon nanotube.

"In one embodiment, the deposition of the nanomaterial increases the bulk electric conductivity of the porous substrate by 50% or more.

"In one embodiment, the deposition of the nanomaterial increases the mass of the porous substrate by 50% or more.

"In one embodiment, the deposition of the nanomaterial increases the volumetric surface area of the porous substrate by 10% or more.

"In one embodiment, the method further comprises the step of removing the porous substrate from the nanomaterial.

"Another aspect provides a method comprising: providing a carbon aerogel having a thickness of 100 microns or more, wherein the carbon aerogel comprises a plurality of macropores throughout the thickness of the carbon aerogel; disposing a catalyst inside the carbon aerogel; and growing carbon nanotubes in the macropores by vapor deposition, wherein the catalyst catalyzes the growth of the carbon nanotubes, and wherein the carbon nanotubes are deposited throughout the thickness of porous substrate.

"In one embodiment, the carbon nanotubes are formed from a carbon-containing precursor gas, and the carbon aerogel is first filled with the carbon-containing precursor gas before heating to grow the carbon nanotubes.

"In one embodiment, the carbon aerogel comprises a bimodal pore size distribution.

"In one embodiment, the carbon nanotubes are multi-walled carbon nanotubes.

"Another aspect comprises making a carbon-nanotube-filled activated carbon aerogel, comprising the steps of: preparing an activated carbon aerogel substrate, and carbonizing the activated carbon aerogel substrate to produce the carbon nanotube-filled activated carbon aerogel.

"Another aspect are articles comprising the composition described herein. For example, an article can comprise the compositions as described herein, wherein the article is a capacitor, a battery, an electrode, sensor, a membrane, a catalyst support, or hydrogen storage device.

"In at least some embodiments, the approach involves the catalyzed CVD growth of multi-walled CNTs on the inner surfaces of activated CA substrates. In these embodiments, the bimodal pore structure of the substrate allows for efficient diffusion of the CVD gases through the aerogel during the growth process and provides substantial surface area for the growth of CNTs. Microstructural analysis of the composites indicates substantially uniform CNT yield throughout the free internal pore volume of CA monoliths with macroscopic dimensions. The resulting composite structures exhibit large surface areas and high electrical conductivity and, as such, provide a robust platform for the design of materials for a variety of applications, including, for example, battery electrodes, capacitors, membranes and/or catalyst supports. In addition, the flexibility associated with this approach provides ability to adapt material properties for specific applications. For example, the use of alternative graphitization catalysts can be used either to change characteristics (i.e. diameter, number of walls) of the CNTs or to grow other types of carbon nanostructures, such carbon nanobelts or nanocoils, within the activated CA substrate.

"SUMMARY: FIG. 1 shows an SEM image of an activated carbon aerogel (ACA) substrate prior to CVD treatment. The inset show the size of the ACA monolith used for the CVD experiments.

"FIG. 2 shows an SEM image of the multi-walled CNT network grown within the Ni-loaded ACA substrate.

"FIG. 3 shows an SEM images of a fracture surface of the ACA-CNT composite showing uniform CNT yield from (a) the surface to (b) the center (about 365 .mu.m from surface) of the monolith.

"FIG. 4 shows a TEM image of multi-walled CNTs grown within the Ni-loaded ACA substrate."

URL and more information on this patent, see: Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael. Porous Substrates Filled with Nanomaterials. U.S. Patent Number 8809230, filed August 1, 2011, and published online on August 19, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8809230.PN.&OS=PN/8809230RS=PN/8809230

Keywords for this news article include: Fullerenes, Nanotechnology, Carbon Aerogels, Carbon Nanotubes, Emerging Technologies, Lawrence Livermore National Security LLC.

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Source: Journal of Engineering


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