Invented by Tetsuya Inoue, Hiroyuki Maruyama, Yoko Kawakami, Hitachi Zosen Corp

The market for carbon nanotube composite materials has been steadily growing over the past decade. These materials, which combine the unique properties of carbon nanotubes with other materials, have found applications in various industries such as aerospace, automotive, electronics, and energy. Carbon nanotubes (CNTs) are cylindrical structures made up of carbon atoms arranged in a hexagonal lattice. They possess exceptional mechanical, thermal, and electrical properties, making them highly desirable for enhancing the performance of other materials. When incorporated into a composite material, CNTs can significantly improve its strength, stiffness, conductivity, and thermal stability. One of the key methods for producing carbon nanotube composite materials is the dispersion of CNTs in a matrix material. Achieving a uniform dispersion of CNTs is crucial to fully exploit their properties. However, due to the strong van der Waals forces between CNTs, they tend to agglomerate, making dispersion a challenging task. Various techniques have been developed to overcome this challenge, including sonication, functionalization, and the use of surfactants. Sonication involves the application of high-frequency sound waves to break up CNT agglomerates and disperse them in a liquid medium. This method is effective in achieving a homogeneous dispersion, but it can also damage the CNTs if not carefully controlled. Functionalization, on the other hand, involves modifying the surface of CNTs with chemical groups that increase their compatibility with the matrix material. This approach improves the dispersion and bonding between CNTs and the matrix, leading to enhanced mechanical properties. Surfactants are another commonly used method for dispersing CNTs. These are molecules that have both hydrophilic and hydrophobic regions, allowing them to stabilize the dispersion of CNTs in a liquid medium. Surfactants reduce the surface tension between CNTs and the liquid, preventing agglomeration and promoting a uniform dispersion. Once the CNTs are dispersed, they can be mixed with the matrix material using various techniques such as melt mixing, solution casting, or electrospinning. Melt mixing involves blending the CNTs with a molten polymer, followed by cooling and solidification to form the composite material. Solution casting involves dissolving the matrix material in a solvent, dispersing the CNTs in the solution, and then evaporating the solvent to obtain the composite. Electrospinning is a technique where a high voltage is applied to a polymer solution containing dispersed CNTs, resulting in the formation of nanofibers that can be collected to create a composite material. The market for carbon nanotube composite materials is driven by the increasing demand for lightweight, high-performance materials in various industries. In the aerospace sector, CNT composites are used to reduce the weight of aircraft components while maintaining their strength and stiffness. In the automotive industry, CNT composites are employed to enhance fuel efficiency and reduce emissions by replacing heavier materials. In electronics, CNT composites are utilized to improve the conductivity and thermal management of electronic devices. Furthermore, in the energy sector, CNT composites are being explored for applications in energy storage and conversion. Despite the numerous advantages of carbon nanotube composite materials, their widespread adoption is still limited by factors such as high production costs, scalability issues, and safety concerns associated with the handling of CNTs. However, ongoing research and development efforts are focused on addressing these challenges and exploring new methods for producing cost-effective and scalable carbon nanotube composite materials. In conclusion, the market for carbon nanotube composite materials is expanding rapidly, driven by the need for advanced materials with superior properties. Various methods for producing these composites, including dispersion techniques and mixing processes, have been developed to ensure a uniform distribution of CNTs in the matrix material. Although challenges remain, the potential applications and benefits of carbon nanotube composites make them a promising area of research and development for the future.

The Hitachi Zosen Corp invention works as follows

A carbon nanotube composite material consists of a fixture sheet with a front and a rear side and a carbon array sheet that is embedded or bonded on both the front and the back sides.

Background for Carbon nanotube composite materials and methods for producing carbon nanotube Composite Materials

Thermoconductive materials (Thermal Interface Materials: hereinafter called TIM) are placed between an electronic component, and a heat sink in order to reduce the distance between them and to effectively conduct the heat generated by the electronic component towards the heat sink. A polymer sheet made of a silicone-based grease and a polymer has been used as a TIM.

The polymer sheet is not able to conform to the surface roughness of the heat sink and electronic component. These bumps or dents can cause gaps to form between the heat sink and electronic component. There are also limitations in terms of thermal conductivity.

The silicone grease conforms to the bumps and dents of the heat sink and electronic component, but repeated temperature changes can cause pumping (a discharge from the heat sink and electronic component) and it’s difficult to maintain the thermal conductivity for a prolonged period of time.

The use of CNT (carbon nanotube) as TIM was examined because it is able to conform to the bumps and dent on the surface of the heat sink or electronic component.

Patent Document 1 proposes, for example, a thermal pad with CNTs arranged in an array on both surfaces of the substrate. (See Patent Document 1 as an example).

This thermal interface pad can be produced by allowing CNTs to grow on the two surfaces of the substrate using chemical vapor deposition. CNT is placed on both surfaces of the substrate in such a thermal pad. The CNT can then be allowed to conform with the bumps and dentations on the surface.


Patent Document

Patent document 1: WO2015-526904

Problem that the invention will solve

The thermal interface pad described by patent document 1 was produced by allowing CNTs to grow on both surfaces of the substrate using chemical vapor deposition. As a result, the adhesive strength between CNT and substrate cannot be sufficiently secured. When the thermal interface pads are used as TIMs, CNT can be dropped from the substrate. It is not possible to ensure thermal conductivity in this case. The dropped CNT can cause electronic components to short circuit.

The present invention aims to develop a carbon-nanotube composite material that can conform to minor dents and bumps in the surface of an item, while preventing the carbon nanotube from falling out. It also aims to develop a method of producing the carbon nanotube material.

Means of Solving the Problems

The present invention [1] consists of a carbon-nanotube composite material that includes a fixture sheet with a front and a rear side, as well as a carbon-nanotube array sheet embedded or bonded on both the front and back surfaces of the fixture sheet.

The carbon nanotube sheet is included in this configuration. When the carbon composite material contacts an object, a number of CNTs are allowed to conform the surface of the object.

Furthermore the carbon nanotube sheet is embedded or bonded on both the front and the back side of the fixture sheets, and thus the CNT can be suppressed to drop out from the fixture sheets.

The carbon nanotube composite sheet of [1] is included in [2] and has a bulk density of at least 50 mg/cm3.

The carbon nanotube composite can also be made to conduct heat better with this configuration.

It is difficult, however, to achieve the lower limit of bulk density for the carbon nanotubes array when they are allowed to grow both on the substrate and the other side by using chemical vapor deposition.

The carbon nanotube sheet that has been removed from the substrate can then be densified by embedding it in the fixture sheet or bonding it to the sheet. The average bulk density can therefore be set at the lower limit described above or higher.

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