A low carbon footprint material is used to decrease the carbon dioxide emission for production of a high carbon footprint substance. A method of forming composite materials comprises providing a first high carbon footprint substance; providing a carbon nanomaterial produced with a carbon-footprint of less than 10 unit weight of carbon dioxide (CO.sub.2) emission during production of 1 unit weight of the carbon nanomaterial; and forming a composite comprising the high carbon footprint substance and from 0.001 wt % to 25 wt % of the carbon nanomaterial, wherein the carbon nanomaterial is homogeneously dispersed in the composite to reduce the carbon dioxide emission for producing the composite material relative to the high carbon footprint substance.

In one aspect, the disclosure relates to CO.sub.2-free and/or low-CO.sub.2 methods of co-producing hydrogen and solid forms of carbon via natural gas decomposition using microwave radiation. The methods are efficient, self-sustaining, and environmentally benign. In a further aspect, the disclosure relates to recyclable and recoverable catalysts useful for enhancing the disclosed methods, wherein the catalysts are supported by solid forms of carbon. Methods for recycling the catalysts are also disclosed. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.

In one aspect, the disclosure relates to CO.sub.2-free and/or low-CO.sub.2 methods of co-producing hydrogen and solid forms of carbon via natural gas decomposition using microwave radiation. The methods are efficient, self-sustaining, and environmentally benign. In a further aspect, the disclosure relates to recyclable and recoverable catalysts useful for enhancing the disclosed methods, wherein the catalysts are supported by solid forms of carbon. Methods for recycling the catalysts are also disclosed. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.

The present invention relates to a carbon nanotube preparation method and system, which may improve the overall efficiency and economic feasibility of a reaction by collecting fine particles including carbon nanotube particles that have not grown enough and an unreacted catalyst produced during and after the reaction by using a separator at the exterior of a fluidized bed reactor, and then, injecting the fine particles as a bed prior to a subsequent cycle.

The present invention relates to a carbon nanotube preparation method and system, which may improve the overall efficiency and economic feasibility of a reaction by collecting fine particles including carbon nanotube particles that have not grown enough and an unreacted catalyst produced during and after the reaction by using a separator at the exterior of a fluidized bed reactor, and then, injecting the fine particles as a bed prior to a subsequent cycle.

A density of a nanofiber sheet can be changed using an edged surface, and in particular an arcuate edged surface. As described herein, a nanofiber sheet is drawn over (and in contact with) an arcuate edged surface. Depending on whether the arcuate surface facing a direction opposite the direction in which the nanofiber sheet is being drawn is convex or concave determines whether the nanofiber sheet density is increased relative to the as-drawn sheet or decreased relative to the as-drawn sheet.

A density of a nanofiber sheet can be changed using an edged surface, and in particular an arcuate edged surface. As described herein, a nanofiber sheet is drawn over (and in contact with) an arcuate edged surface. Depending on whether the arcuate surface facing a direction opposite the direction in which the nanofiber sheet is being drawn is convex or concave determines whether the nanofiber sheet density is increased relative to the as-drawn sheet or decreased relative to the as-drawn sheet.

A supported catalyst comprises: a support that is particulate; and a composite layer laminate formed outside the support and including two or more composite layers, wherein each of the composite layers includes a catalyst portion containing a catalyst and a metal compound portion containing a metal compound, the support contains 10 mass % or more of each of Al and Si, and a volume-average particle diameter of the support is 50 μm or more and 400 μm or less.

A supported catalyst comprises: a support that is particulate; and a composite layer laminate formed outside the support and including two or more composite layers, wherein each of the composite layers includes a catalyst portion containing a catalyst and a metal compound portion containing a metal compound, the support contains 10 mass % or more of each of Al and Si, and a volume-average particle diameter of the support is 50 μm or more and 400 μm or less.

Provided herein are graphene nanoribbons with high structural uniformity and low levels of impurities and methods of synthesis thereof. Also provided herein are graphene nanoplatelets of superior structural uniformity and low levels of impurities and methods of synthesis thereof. Further provided herein are mixtures of graphene nanoribbons and graphene nanoplatelets of good structural uniformity and low levels of impurities and methods of synthesis thereof. The method includes, for example, the steps of depositing catalyst on a constantly moving substrate, forming carbon nanotubes on the substrate, separating carbon nanotubes from the substrate, collecting the carbon nanotubes from the surface where the substrate moves continuously and sequentially through the depositing, forming, separating and collecting steps. Further processing steps convert the synthesized carbon nanotubes to graphene nanoribbons, graphene nanoplatelets and mixtures thereof.