Holey Carbon Allotropes
materials and coatings
Holey Carbon Allotropes (LAR-TOPS-165)
Innovative manufacturing methods for bulk preparation of holey graphene and holey carbon nanotubes
Overview
Researchers at NASA have developed new methods to manufacture carbon materials (e.g., nanotubes, graphene) with holes through the graphitic surface of the particles. The methods generate materials with increased accessible surface area, increased functional groups at damage sites, and improved through-surface molecular transport properties. The materials generated using these techniques are anticipated to be applicable to a variety of industries, especially energy storage (e.g. super-capacitors and batteries) and separation membranes (e.g. for gas, ions, organics, proteins, etc.).
The Technology
This invention is for scalable methods that allows preparation of bulk quantities of holey nanocarbons with holes ranging from a few to over 100 nm in diameter. The first method uses metal particles as a catalyst (silver, copper, e.g.) and offers a wider range of hole diameter. The second method is free of catalysts altogether and offers more rapid processing in a single step with minimal product work-up requirements and does not require solvents, catalysts, flammable gases, additional chemical agents, or electrolysis. The process requires only commercially available materials and standard laboratory equipment; and, it is scalable. Properties that can be controlled include: surface area, pore volume, mechanical properties, electrical conductivity, and thermal conductivity.

Benefits
- Produces carbon nanomaterials with increased surface area, improved electrochemical performance, and through-surface molecular transport properties
- Eliminates need for catalysts, solvents, and flammable gases for processing
- Consistently produces holes with a narrow size distribution, especially in the sub 10-nm ranges
- Allows for control of material properties such as surface area, modulus, thermal conductivity, and thermopower
- Is readily scalable and can be used to generate bulk quantities (only dependent on the availability/cost of pristine materials)
Applications
- Energy storage (supercapacitors, batteries)
- Membranes for gas separation, water desalination, biomolecular separation
- Gas and drug delivery
- Chemical and biological sensors
- Thermoelectrics
- Coatings
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Similar Results

Carbon Bipolar Membranes for Solid-State Batteries
In traditional batteries with liquid electrolytes, e.g., lithium-ion, each battery cell must be individually sealed, packaged, and electrically connected to other cells in the pack. The cells in solid-state batteries on the other hand may be stacked on top of one another with only a separation layer in between, called a bipolar plate. These bipolar plates or membranes if thin enough must be electrochemically inert to the electrode and electrolyte materials while providing electrical connectivity between the individual cells.
Here, NASA has combined advances in the preparation of carbon nanomaterials and solid-state batteries to create extremely lightweight bipolar plates and membranes. These bipolar membranes will enable high energy density solid-state batteries unachievable with typical bipolar plate materials like stainless steel, aluminum, aluminum-copper, or conductive ceramics. The carbon bipolar membranes may be fabricated in multiple ways including but not limited to directly compressing carbon powders onto an electrode-electrolyte stack or separately making a film of the carbon material and dry pressing the film between other battery layers. The new bipolar membranes have been demonstrated in high energy density solid-state batteries in coin and pouch cells.
The carbon bipolar membranes are at technology readiness level TRL-4 (Component and or breadboard validation in laboratory environment)and are available for patent licensing.

Holey Graphene Mesh from Solvent-Free Manufacturing and Composites Thereof
The HGM or composite HGM developed is a novel nanocarbon-based architecture that (1) is prepared from dry processing from commercially available starting materials or readily prepared composites thereof; (2) exhibits micropores and mesopores due to the holey graphene sheets and their stacking; (3) exhibits micron- and macro-sized pores in the article. The method can produce a range of high-fidelity hole size, shape, and distribution on the graphene or composite articles. The disclosed laser-based method is easily scaled-up and automatable. The result is a novel ultra-lightweight graphene-based mesh structure with high electrical conductivity, thermal conductivity, high surface area, high through-thickness unimpeded ion transport, mechanical robustness. The HGM-based composites utilize HGM as a novel framework, matrix, or substrate for secondary components that are active for energy storage, catalysis, sensing, optical, filtration, and biological applications.

Cryogenic Flux Capacitor
Storage and transfer of fluid commodities such as oxygen, hydrogen, natural gas, nitrogen, argon, etc. is an absolute necessity in virtually every industry on Earth. These fluids are typically contained in one of two ways; as low pressure, cryogenic liquids, or as a high pressure gases. Energy storage is not useful unless the energy can be practically obtained ("un-stored") as needed. Here the goal is to store as many fluid molecules as possible in the smallest, lightest weight volume possible; and to supply ("un-store") those molecules on demand as needed in the end-use application. The CFC concept addresses this dual storage/usage problem with an elegant charging/discharging design approach.
The CFC's packaging is ingeniously designed, tightly packing aerogel composite materials within a container allows for a greater amount of storage media to be packed densely and strategically. An integrated conductive membrane also acts as a highly effective heat exchanger that easily distributes heat through the entire container to discharge the CFC quickly, it can also be interfaced to a cooling source for convenient system charging; this feature also allows the fluid to easily saturate the container for fast charging. Additionally, the unit can be charged either with cryogenic liquid or from an ambient temperature gas supply, depending on the desired manner of refrigeration. Finally, the heater integration system offers two promising methods, both of which have been fabricated and tested, to evenly distribute heat throughout the entire core, both axially and radially.
NASA engineers also applied the CFC to a Cryogenic Oxygen Storage Module to store oxygen in solid-state form and deliver it as a gas to an end-use environmental control and/or life support system. The Module can scrub out nuisance or containment gases such as carbon dioxide and/or water vapor in conjunction with supplying oxygen, forming a synergistic system when used in a closed-loop application. The combination of these capabilities to work simultaneously may allow for reduced system volume, mass, complexity, and cost of a breathing device.

Dispersion of Carbon Nanotubes in Polymers
The technology portfolio spans several methods for dispersion and processing of CNTs in polymer resins and composites. CNT/resin systems with high dispersion and long-term stability are provided by three general approaches. One method relies on mechanical dispersion by sonication simultaneous with partial polymerization to increase the resin viscosity to maintain dispersion and enable further polymer processing of the CNT blend into films and other articles. Another approach relies on what is termed donor acceptor bonding, which essentially is a dipole bond created on the CNT/resin interface to maintain dispersion and stability of the CNT/resin blend. This dispersion method also provides advantages in mechanical properties of processed composites due to the interface characteristics. A range of polymer types can be used, including polymethyl methacrylate, polyimide, polyethylene, and others.
An additional dry blending approach provides advantages for a variety of
thermoplastic and thermoset systems. Use of ball mill mixing achieves effective
blending and dispersion of the CNT, even at high loadings. Further processing steps
using injection molding or similar melt processing methods have yielded CNT/
polymer composites with a range of useful electronic, optical, and mechanical
properties.

Conductive Carbon Fiber Polymer Composite
The new composite developed by NASA incorporates PGS and CNTs to enhance its thermal conductivity while preserving the mechanical properties of the underlying carbon fiber polymer composite. NASA has also improved the composite manufacturing process to ensure better thermal conductivity not only on the surface, but also through the thickness of the material. This was achieved by adding perforations that enable the additives to spread through the composite.
The process for developing this innovative, highly thermally conductive hybrid carbon fiber polymer composite involves several steps. Firstly, a CNT-doped polymer resin is prepared to improve the matrix's thermal conductivity, which is then infused into a carbon fiber fabric. Secondly, PGS is treated to enhance its mechanical interface with the composite. Thirdly, perforation is done on the pyrolytic graphite sheet to improve the thermal conductivity through the thickness of the material by allowing CNT-doped resin to flow and better interlaminar mechanical strength. Finally, the layup of PGS and CNT-CF polymer is optimized.
Initial testing of the composite has shown significant increases in thermal conductivity compared to typical carbon fiber composites, with a more than tenfold increase. The composite also has higher thermal conductivity than aluminum alloys, with more than twice the thermal conductivity of the Aluminum 6061 typically used in the aerospace industry. For this new material, NASA has completed a proof-of-concept demonstration and work continues to use the material in a heat exchanger system and further characterize the properties including longevity and radiation impact analysis.