Technology Overview

Nanocarbons offer some distinct advantages in comparison to activated carbon and other type of carbon materials such carbon gels and aerogels, or different nanostructured catalytic materials such as mixed oxides. There is still need to improve these catalytic materials, particularly in terms of control of the characteristics at nanoscale level. Nevertheless, nanocarbons for the nanosize-related functional performances provide rather interesting opportunities for the design of advanced catalytic materials, from the possibility to provide better mass and heat transfer, to the possibility of synergistic interactions with other nanocarbons and/or metal particles or mixed oxides (realizing advanced hybrid materials). CNTs offer advantages over activated carbon for the following properties:

  • Surface area / pore structure
  • Uniformity
  • Number of defects (impurities)
  • Oxidative resistance
  • Electron-heat transfer

All these characteristics indicate that nanocarbons are the best catalytic materials to realize the nanoengineering of the catalytic sites. It is necessary to improve the capabilities to realize tailored syntheses at the nanoscale level driven from the understanding of the relationships between nano-structure and functional/catalytic behavior, e.g. realize the nanoengineering of the catalytic sites. This requires combining advances in the synthesis and manipulation of nanocarbon objects to an improved characterization of nanocarbons, particularly of defects and surface species (including their localization), as well as their relationship with the catalytic and functional performance. By replacing some of the carbon atoms with heteroatoms, such as boron, nitrogen, sulfur or phosphorus, it is possible to tailor the structure, electronic, mechanical and chemical reactivity properties of the nanotubes for specific applications.

Redox and doped atoms are catalytic sites present in 3D CBx-CNTs nanosponge materials. Redox sites are actives for various liquid and gas–phase oxidation reactions and ODH of alkanes, while edge sites and doped atoms centers are active for oxidative- reduction reaction (ORR) that occurs in the anode of proton-electrolyte-membrane fuel cells. The exotic combination of multifunctional properties of the 3D CBx-CNTs nanosponge make these material effective for recovering and stabilizing emulsions and for catalyzing reactions at the oil/water interphase. This has potential applications in many field of the chemical and fuel industry.

Carbon nanotubes (CNTs) are “nano” (1×10 – 9 meters, ~ 1/100,000 the width of a human hair) size tubes of carbon (tubular graphene) with extraordinary properties:

  • Tunable optical and electronic properties
  • Conduct electricity and heat better than copper at nanoscale
  • Are the strongest strength-to-weight materials in the world
  • Thermal conductivity better than diamond
  • Better semiconductor than silicon at nanoscale
  • Chemically inert and can tolerate even the most demanding environments (temperature, radiation, moisture, etc.)
  • Can be dispersed in a wide range of materials
  • Can absorb radiation very efficiently to generate rapid and extreme heating

Single-wall (SW) CNTs are comprised of single tubes (only one wall) vs. multi-wall (MW) CNTs being comprised of concentric tubes having several walls (typically 10 walls). Few-wall (FW) CNTs are comprised of concentric tubes with a few walls (typically 2 walls).

These individual nanoscale CNT elements can manifest themselves in the macroscale in the following common macro-forms:
(a) powder
(b) paper
(c) thin web-like films
(d) Aligned Forrest
(e) spun into fibers

CNTs in all of their forms are considered “gamechanger” materials that will revolutionize the modern world through many diverse applications. Over 20 years of research has gone into CNT materials, yet we still see their limited use in many real-world applications. Part of the reason is because it has remained a challenge to engineer these extraordinary nano-scale building blocks into covalently interconnected three-dimensional (3-D) macro-forms, and to realize macro-scaled sizes via an economical commercial synthesis process.

Our novel “NanoSponge” product meets this need and provides MWCNTs in a novel macro-form having a 3D CNT solid network that extends the extraordinary 1D nanoscale properties into 3D space on a macro-scale. This is the competitive advantage that will allow us to pioneer new markets for CNT materials.

The founder of CSSN created and patent protected a 3D CNT “NanoSponge” foam-like material by catalytic chemical vapor deposition (CCVD) using boron impurities in the precursor during the growth process (please see Hashim et al. [1] and paper published in the “Peer-Reviewed Scientific Publication” section of the Appendix). It is this breakthrough in CNT technology that will open up a myriad of applications for CNTs into new industrial markets.

The boron impurity process converts the individual one-dimenisional CNTs into a three dimensional macrostructure foam or “NanoSponge” material.

The as-produced CNT nanosponge has a randomly intertwined 3D structure and displays high porosity and very low density. The CNT nanosponge can float on oil contaminated water and remove oil with a large adsorption capacity (80 to 120 times their own weight for a wide range of solvents and oils). The sponge had a tendency to move to the oil film area due to its highly oleophilic yet superhydrophobic properties, leading to the unique “floating-and-cleaning” capability that is very useful for spill cleanup. The oil-saturated CNT sponge can be easily regenerated through gentle heating/evaporation (or refining the oil out), or mechanical compression to recover the valuable resources, or directly burning the oil out leaving the sponge structure intact and not destroyed.

The superhydrophobic NanoSponge being used on the surface of water to soak up various organics and oil at the surface to demonstrate an oil-spill-cleanup application. NanoSponge can be manipulated with magnets and can be burned or squeezed out to salvage oil. The CNT “NanoSponge” materials possess a variety of extraordinary multifunctional properties, all of which make them advantageous over common CNT materials being used in the market today. These multifunctional properties are listed in the Figure below and allow CNTs to be used in niche markets that common CNTs may not be able to reach.

Overview of the multifunctional properties of CNT NanoSponge made by CSSN.

Please see the video demonstration of the various multifunctional properties of our advanced CNT “NanoSponge” material:

A three-dimensional foam structure is particularly advantageous for filtration membrane materials requiring a porous structure for filtrations with minimum pressure drop across the membrane. In addition to serving as direct adsorbents, CNTs can also be utilized as excellent scaffolds for macromolecules or metal oxides with intrinsic adsorption ability.

The tunable surface chemistry and controllable pore size make CNTs good support for composite adsorbents. Examples of CNTs as scaffolds for pollutant removal include CNT decoration with iron oxide for europium adsorption, chitosan for methyl orange adsorption and ceria nanoparticles for chromium adsorption. Moreover, the unique electrical properties of CNTs could be utilized for enhanced adsorption with electrochemical assist which is important as electrodes in energy storage devices such as supercapacitors, batteries, and fuel cells.

The mechanical flexibility and robustness, thermal stability and resistance to harsh environment endow CNTs with excellent application potential in water treatment. CNTs have the potential to serve as superior adsorbents for removal of both organic and inorganic contaminants from water systems.

Other potential identified industrial applications 3D CBx-CNTs nanosponge are:

  • Metal-catalyst supports or as metal-free carbon-based catalysts for environmental control and chemical processes
  • Functionalized membranes for water treatment including desalination
  • Rubber composites alternative substitute for carbon black and activated carbons
  • Gas adsorption/storage and separation
  • Air purification/sanitation
  • Porous electrodes for supercapacitors, batteries, and fuel cells

One of the most interesting features of our NanoSponge materials is their remarkable ability to absorb microwave radiation very readily. This is a very unique property being that not many materials, outside from water, will absorb microwaves so efficiently to generate extreme rapid heating. By exploiting this property of our NanoSponge materials, in combination with the unique form factor of 3D porosity, we can pave the way for innovative, cutting edge, non-existent, and otherwise non-obtainable market segments by the aforementioned “common” CNT macro-forms. Volumetric microwave heating (VMH) will be feasible to heating many types of fluids and gases as novel heat exchanger units for many industrial processes or chemical pyrolysis processing. In particular, the petrochemical industry can benefit from improved refining and thermal “cracking” methods used to produce valuable chemical products such as olefins (e.g. ethylene, propylene) production. This gives us a strong competitive advantage in the overall CNT market.