Isotropic and anisotropic prepregs

The manufacture and use of carbon materials in prepregs is one of the most required areas in the industry. The prepregs are a woven material impregnated with a polymeric binder.

The “classic” version of the prepreg is a carbon fiber (CF) fabric impregnated with epoxy resin. Carbon plastics for the aircraft and aerospace construction, automotive, shipbuilding, and other industries are obtained of these prepregs.

Replacement of carbon fiber fabric with carbon nanotubes or adding it to carbon fiber can increase the strength of the final product, reduce its fragility, and allow for successful use in aircraft, aerospace, shipbuilding, and automotive industries, electronics and electrical appliances, household appliances.

Nanomodification of prepregs allows improving material properties by 30-50%: weight optimization, product productivity, to obtain a composite material with good mechanical properties — fatigue load, tensile strength, stiffness, good aging, etc.

By changing the orientation (laying) of the prepreg — isotropic or unidirectional, it is possible to influence the specific mechanical characteristics of the composite. Anisotropic (unidirectional) composites have predominant mechanical properties in one direction. Isotropic materials have the same properties in all directions. Unlike isotropic polymer nanocomposites, anisotropic nanocomposites possess a set of special properties: its mechanical characteristics along the anisotropy axes are higher than in isotropic materials and it has the property of damping loads; the electrical and thermal conductivity along the anisotropy axes is much higher.

For example, prepregs with CNTs can be successfully used to manufacture parts that are used in airplanes, helicopters and other aerospace vehicles, as well as in shipbuilding. It significantly lightens the weight of the structure but at the same time increases stiffness and strength.

Roving and twisted thread

Carbon nanotubes tend to stick together firmly in bundles, forming roving, rope or thread, which is a durable, flexible and wear-resistant material capable of withstanding multiple cyclic loads.

Individual bundles of nanotubes woven into strands will be slightly thicker, but much longer and stronger than the original material. The strength of such threads depends significantly on the diameter and angle of twisting; the maximum is achieved with a thread thickness of about 10 microns. Due to their high conductivity and low weight, these strong and flexible threads can act as an alternative to even heavy metal wires, become the basis for the manufacture of heavy-duty materials and their use in the production of prepregs, fabrics, and cables, including conductive and Production of high-pressure composite cylinders.

Carbon nanotubes that conduct current can withstand the current density 102-103 times higher than conventional metals.

Thus, the current density in nanotubes can exceed 1000 times the maximum permissible density for a copper wire (above which a copper wire explodes).

Carbon nanotubes of a semiconductor type allow creating field-effect transistors.

Flexible carbon paper

Flexible carbon paper of carbon nanotubes are strong, flexible, light and thin sheets of absolutely black color, which consist of only carbon nanotubes compressed without the use of additional binders. Due to the correlation of such characteristics as flexibility, strength and light weight, flexible carbon paper can be used as electrical energy storage devices for the automotive and aviation industries, household electrical appliances. Also promising is the use of such materials as mechanically strong coatings, heat-removing, moisture-resistant coatings, as well as coatings resistant to chemically aggressive media.

Nanotube ink and filled polymers

Nanotube ink and filled polymers are nanocomposites consisting of chaotically distributed carbon filler particles in a polymer matrix. Nano-carbon plastics are able to take a complex and unusual shape while maintaining rigidity, strength and lightweight. Carbon plastics with carbon nanotubes have higher strength, lower weight, higher thermal conductivity than conventional CFRPs, which opens prospects for the use of these materials in shipbuilding, automotive, household appliances, construction parts and other components with complex geometric shapes.

Fabrics

Fabrics based on carbon fiber and nanotubes are high-tech textiles with excellent performance. It has higher tensile strengths than carbon fabrics — about 4-5 GPa^*, are resistant to the action of most chemically aggressive reagents, allow achieving high mechanical properties in plastic and create products with complex geometry. The use of fabric based on carbon nanotubes allows increasing the strength of products.

^* Мультиаксиальная углеродная ткань 12К-1270-610 (0/+45/-45)°.

Composite carbon-plastic thread

Composite carbon-plastic yarn based on carbon nanotubes is a light, high-strength yarn with a lower degree of wear and high thermal conductivity (about 15 W/m×K)^*. The use of such carbon-plastic threads can be used for production of prepregs, fabrics, and cables (including fireproof and electrically conductive), and production of high-pressure composite cylinders.

For example, for storage and transportation of compressed gases of air, oxygen, nitrogen, acetylene and other gases, cylinders are used at a pressure of 16-20 MPa, which are made of seamless tubes. Modern high-pressure composite cylinders have an external power shell made of carbon fiber that is wound on the surface of the shell and impregnated with a binder material. External power shell of high-pressure composite cylinders can be reinforced with carbon nanotubes, which will make the cylinder walls extremely elastic and more durable.

^* S.V. Reznik, P.V. Prosuntsov, V.S. Railyan, A.V. Shulyakovsky, Method and results of investigations of thermophysical properties of carbonpolymer composites with full-scale samples of beam space structures // Proc. 2nd Int. Symp. on Inverse Problems, Design and Optimization (April 16–18, 2007, Miami, Florida, U.S.A.). – P. 657 – 660. 4.

Electrically conductive and heat sinks

The high electrical conductivity of carbon nanotubes opens wide prospects for their use in electroconductive elements: the electrical conductivity of CNTs is within the electrical conductivity of metallic conductors, but due to their low density (<2 g/cm³) their conductivity corresponds to or exceeds the conductivity of many metals (aluminum, copper and etc). Also weight is a significant cost driver for the aerospace industry, which will benefit from lightweight wires and cable CNTs even by increasing the resistance. Wires. Wires used in shipbuilding are exposed to direct action of seawater, which makes chemical inertness a critical parameter for long-term use.

The thermal conductivity of carbon nanotubes can reach 759 W/m×K, which is much higher than the thermal conductivity of copper-385 W/m×K and aluminum-247 W/m×K^*. This makes it possible to provide much more efficient heat removal in comparison with the materials currently used in electronics, engine building, etc. Radiators made of nanotubes can provide much more efficient heat removal from powerful chips.

^* Dawid Janasa, Krzysztof K. Koziol, Carbon nanotube fibers and films: synthesis, applications and perspectives of the direct-spinning method/ Nanoscale, p 25 DOI: 10.1039/C6NR07549E.

Carbon-carbon composites

Carbon-carbon composites are materials based on the carbon matrix and carbon fillers. Commonly used as a carbon matrix are pyrolytic carbon, coke residues of thermosetting resins or petroleum pitch. Used as carbon reinforcing element are: discrete fibers, continuous threads or strands, felts, ribbons, fabrics with a flat and three-dimensional netting, volumetric frame structures. Carbon-carbon composites have low density (1.3-2.1 g/cm³)^*; high heat capacity, resistance to thermal shock, erosion and irradiation; low friction coefficients and linear expansion; high corrosion resistance; wide range of electrical properties (from conductors to semiconductors); high strength and rigidity. Such a wide range of properties of carbon-carbon composites makes it possible to use them in radio-space and aviation engineering: in brake discs, rocket engine nozzles, protective linings of wings, high pressure pipes, for plain bearings, seals, etc.

High strength (up to 5.5 GPa^**) and resistance to high temperatures, as well as resistance to vibrational loads and a low specific gravity of carbon nanotubes allow them to be used in composite carbon-carbon materials. Composite carbon-carbon materials with nanotubes can be widely used in radio-space and aviation engineering. They will improve the functional characteristics of aircraft, will reduce the weight of the final product and thereby reduce operating costs and fuel consumption.

^* LALIT M MANOCHA (24 April 2003), High performance carbon—carbon composites, Sadhana. 28: 349–358.; Carbon-Carbon Composite — Material Information.

^** Dawid Janasa, Krzysztof K. Koziol, Carbon nanotube fibers and films: synthesis, applications and perspectives of the direct-spinning method/ Nanoscale, p 25 DOI: 10.1039/C6NR07549E.

Electrodes

Carbon nanotubes have a high specific surface area (50-1300 m²/g)^*, electrical conductivity (1.06-2.24×10⁴ S/cm)^**, chemical stability, and an ideal ratio of the characteristics of nanotubes — flexibility / strength / mass, allows for them Create ultra-strong flexible and light organic films.

The combination of these properties of carbon nanotubes makes them attractive for use in electrodes of electrochemical capacitors as electrical energy storage devices for the automotive and aircraft industries, household electrical appliances.

The traditional electrode material of the supercapacitor is activated carbon; its electrochemical capacity is ~30 F/g. The specific electrochemical capacitance of supercapacitors from arrays of oriented carbon nanotubes in aqueous electrolytes is 100-120 F/g^***, whereas the capacity of composites based on carbon nanotubes can reach 500-700 F/g, they also withstand a large number of recharge cycles.

^* Cor Koning, Marie-Claire Hermant, Nadia Grossiord, «Polymer Carbon Nanotube Composites: The Polymer Latex Concept», p. 80

^** Dawid Janasa, Krzysztof K. Koziol, Carbon nanotube fibers and films: synthesis, applications and perspectives of the direct-spinning method/ Nanoscale, p 25 DOI: 10.1039/C6NR07549E

^*** А. В. Окотруб, П. С. Галкин «СДЕЛАНО В СО РАН» Институт неорганической химии СО РАН, Новости науки.

Electrically conductive and heat sinks

The high electrical conductivity of carbon nanotubes opens wide prospects for their use in electroconductive elements: the electrical conductivity of CNTs is within the electrical conductivity of metallic conductors, but due to their low density (<2 g / cm³) their conductivity corresponds to or exceeds the conductivity of many metals (aluminum, copper and etc). Also weight is a significant cost driver for the aerospace industry, which will benefit from lightweight wires and cable CNTs even by increasing the resistance. Wires. Wires used in shipbuilding are exposed to direct action of seawater, which makes chemical inertness a critical parameter for long-term use.

The thermal conductivity of carbon nanotubes can reach 759 W/m×K, which is much higher than the thermal conductivity of copper-385 W/m×K and aluminum-247 W/m×K^*. This makes it possible to provide much more efficient heat removal in comparison with the materials currently used in electronics, engine building, etc. Radiators made of nanotubes much more efficient heat removal from powerful chips.

^* Dawid Janasa, Krzysztof K. Koziol, Carbon nanotube fibers and films: synthesis, applications and perspectives of the direct-spinning method/ Nanoscale, p 25 DOI: 10.1039/C6NR07549E.