This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 200910110311.2, filed on Oct. 22, 2009 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Technical Field
The present disclosure relates to methods for bonding members together, and more particularly, to a method for bonding members together utilizing a carbon nanotube structure.
2. Description of Related Art
In a case where two members are bonded together, an adhesive has often been used. However, the bonding strength is relatively low and takes a long time for the adhesive to harden.
Alternative stronger bonding methods are available; one such method involves using a high level of heat to bond members. This high temperature heat treatment bonding method can overheat some areas of the members and cause deformation or unwanted distortion to the members being bonded together. Therefore, improvement in the art is highly desired.
Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.
One embodiment of a method for bonding members is illustrated in
(a) providing a first member 100, a second member 200 and a carbon nanotube structure 120;
(b) placing the carbon nanotube structure 120 between the first member 100 and the second member 200; and
(c) energizing the carbon nanotube structure 120.
In step (a), the first member 100 has a first surface 102, which is needed to be bonded to a second surface 202 of the second member 200.
The shape of the first member 100 is not limited. The first member 100 can be made of insulative materials, such as ceramic, glass, or polymeric materials. Examples of the polymeric materials comprise epoxide resin, bismaleimide resin, cyanate resin, polypropylene, polyethylene, polyvinyl alcohol, polystyrene enol, polycarbonate, and polymethylmethacrylate. In some embodiments, the first member 100 or the second member 200 can be parts of an apparatus or device, and the parts may be coated or may be encapsulated by insulative materials. Examples of a constituent material of the parts include polymeric materials, metals, and ceramic.
The shape and materials of the second member 200 can be the same as or different from those of the first member 100 so long as the second surface 202 can mate with the first surface 102. Examples of the shape of the second member 200 comprise a plate shape, a block shape, or a stick shape. Examples of a constituent material of the second member 200 include insulative materials, such as ceramic, glass, or polymeric materials. Examples of the polymeric materials comprise epoxide resin, bismaleimide resin, cyanate resin, polypropylene, polyethylene, polyvinyl alcohol, polystyrene enol, polycarbonate, or polymethylmethacrylate.
In one embodiment, the first member 100 and the second member 200 are made of materials that have a low melting point, such as lower than 600 centidegree. Then the first member 100 and the second member 200 may be bonded together at a low temperature, and it is possible to further reduce thermal stress, which would be generated on the bonding interface. In one embodiment, the first member 100, and the second member 200 each have a plate shape, and are made of same materials, such as polycarbonate.
The carbon nanotube structure 120 is disposed between and contacts with the first surface 102 and the second surface 202. The carbon nanotube structure 120 can be a free-standing structure, that is, the carbon nanotube structure 120 can be supported by itself and does not require a substrate to lay on and supported thereby.
The carbon nanotube structure 120 includes a plurality of carbon nanotubes combined by van der Waals attractive force therebetween. The carbon nanotube structure 120 can be a substantially pure structure of the carbon nanotubes, with few impurities. The carbon nanotubes can be used to form many different structures and provide a large specific surface area. The heat capacity per unit area of the carbon nanotube structure 120 can be less than 2×10−4 J/m2*K. In one embodiment, the heat capacity per unit area of the carbon nanotube structure 120 is less than or equal to 1.7×10−6 J/m2*K. As the heat capacity of the carbon nanotube structure 120 is very low, this makes the carbon nanotube structure 120 have a high heating efficiency, a high response heating speed, and accuracy. Further, the carbon nanotubes have a low density, about 1.35 g/cm3, so the carbon nanotube structure 120 is light. As the carbon nanotube has large specific surface area, the carbon nanotube structure 120 with a plurality of carbon nanotubes has large specific surface area. When the specific surface of the carbon nanotube structure 120 is large enough, the carbon nanotube structure 120 is adhesive and can be directly applied to a surface.
The carbon nanotubes in the carbon nanotube structure 120 can be orderly or disorderly arranged. The term ‘disordered carbon nanotube structure’ refers to a structure where the carbon nanotubes are arranged along different directions, and the aligning directions of the carbon nanotubes are random. The number of the carbon nanotubes arranged along each different direction can be almost the same (e.g. uniformly disordered). The disordered carbon nanotube structure can be isotropic, namely the carbon nanotube film has properties identical in all directions of the carbon nanotube film. The carbon nanotubes in the disordered carbon nanotube structure can be entangled with each other.
The carbon nanotube structure 120 including ordered carbon nanotubes can be an ordered carbon nanotube structure. The term ‘ordered carbon nanotube structure’ refers to a structure where the carbon nanotubes are arranged in a consistently systematic manner, e.g., the carbon nanotubes are arranged approximately along a same direction and/or have two or more sections within each of which the carbon nanotubes are arranged approximately along a same direction (different sections can have different directions). The carbon nanotubes in the carbon nanotube structure 120 can be selected from single-walled, double-walled, and/or multi-walled carbon nanotubes.
The carbon nanotube structure 120 can be a carbon nanotube film structure with a thickness ranging from about 0.5 nanometers (nm) to about 1 mm when the first member 100 and the second member 200 each have a plate shape. The carbon nanotube structure 120 can include at least one carbon nanotube film. The carbon nanotube structure 120 can also be at least one linear carbon nanotube structure with a diameter ranging from about 0.5 nm to about 1 mm, when the first member 100 and the second member 200 each have a stick shape or linear shape. The carbon nanotube structure 120 can also be a combination of carbon nanotube film structures and/or linear carbon nanotube structures. In other words, the carbon nanotube structure 120 can be variety of shapes.
In one embodiment, the carbon nanotube film structure includes at least one drawn carbon nanotube film. A film can be drawn from a carbon nanotube array, to obtain a drawn carbon nanotube film. Examples of drawn carbon nanotube film are taught by U.S. Pat. No. 7,045,108 to Jiang et al., and WO 2007015710 to Zhang et al. The drawn carbon nanotube film includes a plurality of successive and oriented carbon nanotubes, as part of segments, joined end-to-end by van der Waals attractive force therebetween. The drawn carbon nanotube film is a free-standing film. Referring to
The carbon nanotube film structure can include at least two stacked carbon nanotube films. In other embodiments, the carbon nanotube structure can include two or more coplanar carbon nanotube films, and can include layers of coplanar carbon nanotube films. Additionally, when the carbon nanotubes in the carbon nanotube film are aligned along one preferred orientation (e.g., the drawn carbon nanotube film), an angle can exist between the orientations of carbon nanotubes in adjacent films, whether stacked or adjacent. Adjacent carbon nanotube films can be combined by only the van der Waals attractive force therebetween. An angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films can range from about 0 degrees to about 90 degrees. When the angle between the aligned directions of the carbon nanotubes in adjacent carbon nanotube films is larger than 0 degrees, a microporous structure is defined by the carbon nanotubes. The carbon nanotube structure in an embodiment employing these films will have a plurality of micropores. Stacking the carbon nanotube films will also add to the structural integrity of the carbon nanotube structure.
In other embodiments, the carbon nanotube film structure includes a flocculated carbon nanotube film. Referring to
In other embodiments, the carbon nanotube film structure can include at least a pressed carbon nanotube film. Referring to
In other embodiments, the linear carbon nanotube structure includes carbon nanotube wires and/or linear carbon nanotube structures.
The carbon nanotube wire can be untwisted or twisted. Treating the drawn carbon nanotube film with a volatile organic solvent can obtain the untwisted carbon nanotube wire. In one embodiment, the organic solvent is applied to soak the entire surface of the drawn carbon nanotube film. During the soaking, adjacent parallel carbon nanotubes in the drawn carbon nanotube film will bundle together, due to the surface tension of the organic solvent as it volatilizes, and thus, the drawn carbon nanotube film will be shrunk into an untwisted carbon nanotube wire. Referring to
The twisted carbon nanotube wire can be obtained by twisting a drawn carbon nanotube film using a mechanical force to turn the two ends of the drawn carbon nanotube film in opposite directions. Referring to
The linear carbon nanotube structure can include one or more carbon nanotube wires. The carbon nanotube wires in the linear carbon nanotube structure can be, twisted and/or untwisted. Referring to
In one embodiment, the carbon nanotube structure 120 comprises a plurality of stacked drawn carbon nanotube films. A method for fabricating the carbon nanotube structure 120 includes the steps of: (a) providing an array of carbon nanotubes; (b) pulling out one carbon nanotube film from the array of carbon nanotubes; (c) providing a frame and adhering the carbon nanotube film to the frame; (d) repeating steps (b) and (c), depositing each successive film on a preceding film, thereby achieving at least a two-layer carbon nanotube film; and (e) peeling the carbon nanotube film off the frame to achieve the carbon nanotube structure 120.
In step (b), the carbon nanotube structure 120 is placed between the first surface 102 and the second surface 202. In order to make the first member 100 and the second member 200 be uniformly heat-treated, the carbon nanotube structure 120 is evenly disposed between the first surface 102 and the second surface 202. The first surface 102 and the second surface 202 are attached to opposite surfaces of the carbon nanotube structure 120. As mentioned above, in some embodiments, the carbon nanotube structure 120 is adhesive and can be directly applied to a surface. Thus, when the carbon nanotube structure 120 having adhesiveness is disposed between the first surface 102 and the second surface 202, the first surface 102 and the second surface 202 can be provisionally bonded together by the carbon nanotube structure 120.
Step (b) further comprises a sub-step of placing two electrodes 126 on the carbon nanotube structure 120 before or after the first member 100 and the second member 200 are provisionally held together. The carbon nanotubes of the carbon nanotube structure 120 form at least one electrically conductive path between the two electrodes 126. As shown in
The two electrodes 126 are made of electrical conductive materials. The shape of the two electrodes 126 is not limited. Each of the two electrodes 126 can be an electrical conductive film, sheet metal, or wire. In one embodiment, the two electrodes 126 can be electrical conductive films each having a thickness ranging from 0.5 nm to about 100 nm. The electrical conductive film can be made of a plurality of conductive materials such as, metal, alloy, ITO, antimony tin oxide (ATO), conductive silver glue, electro-conductive polymer, or electrical conductive carbon nanotubes. The metal or alloy can be aluminum, copper, tungsten, molybdenum, gold, titanium, neodymium, palladium, cesium, or any combination thereof. The two electrodes 126 can be disposed on the surface of the carbon nanotube structure 120 by sputtering deposition, electrochemical process, direct writing method, or screen printing method.
Further, some of the carbon nanotube structures have large specific surface area and are adhesive in nature, in some embodiments, the two electrodes 126 can be adhered directly to the carbon nanotube structure 120. The two electrodes 126 can also be adhered onto the carbon nanotube structure 120 via conductive adhesives such as conductive silver glues. The conductive adhesive can firmly secure the two electrodes 126 to the carbon nanotube structure 120.
In one embodiment shown in
In step (c), the carbon nanotube structure 120 is energized to generate heat, which causes the first surface 102 and the second surface 202 to melt or soften. In one embodiment, a voltage is applied to the two electrodes 126 and an electrical current flowing through the carbon nanotube structure 120, making the carbon nanotube structure 120 generate heat between the first surface 102 and the second surface 202, allowing the first surface 102 and the second surface 202 to be uniformly heated since the carbon nanotube structure 120 is evenly disposed between the first surface 102 and the second surface 202.
When the temperatures of the first surface 102 and the second surface 202 reach to their melting points, the first surface 102 and the second surface 202 become soft or molten. During this process, the melting materials of the first surface 102 and the second surface 202 tend to permeate into and through micropores of the carbon nanotube structure 120 to opposite surfaces. As a result, the first surface 102 and the second surface 202 are bonded together.
For example, when the first member 100 and the second member 200 are made of polycarbonate, which has a melting point of about 220 to 230 centidegrees, a voltage can be applied to the carbon nanotube structure 120 until the temperatures of the first surface 102 and the second surface 202 reach or get a little beyond the melting point of about 220 to 230 centidegrees. Then, the first surface 102 and the second surface 202 can be bond together.
It is noteworthy that the voltage needed to be applied to the carbon nanotube structure 120 depends on the materials of the first and second members 100 and 200 and the resistance of the carbon nanotube structure 120. The higher the melting points of the materials of the first and second members 100 and 200, the higher the voltage applied to the carbon nanotube structure 120. The smaller the resistance of the carbon nanotube structure 120, the lower the voltage applied to the carbon nanotube structure 120. The resistance of the carbon nanotube structure 120 is associated with the thickness of the carbon nanotube structure 120. The thickness of the carbon nanotube structure 120 is associated with the number of the layers of the carbon nanotube films. The voltage can be in a range from about 1 volt to 10 volts when the melting points of the materials are not high.
It is noteworthy that step (c) can be carried out in vacuum environment of about 10−2 Pascals to about 10−6 Pascals, or in a specific atmosphere of protective gases including nitrogen gas and inert gases. The carbon nanotube structure 120 can generate a lot a heat and reach the temperature of about 2000° C. to bond members which have high melting points when the carbon nanotube structure 120 works in vacuum environment or in a specific atmosphere.
The method further comprises another step (d) of applying pressure to the first member 100 and/or the second member 200 when the first surface 102 and the second surface 202 are in melting or softening state. In this process, the melting materials of the first surface 102 and the second surface 202 are pressed and accelerated to permeate into and go through micropores of the carbon nanotube structure 120 to opposite surfaces. As a result, the first surface 102 and the second surface 202 can be tightly and quickly bond together.
It is noteworthy that the electrodes 126 can be removed by directly removing the electrodes 126 or by cutting the resulting assembly of the first member 100 and the second member 200, after the first member 100 and the second member 200 are bond together.
An example of a bonding interface 320 of the first member 100 and the second member 200 is shown in
It is also clear from
Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the present disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. Elements associated with any of the above embodiments are envisioned to be associated with any other embodiments. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.
Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. It is also to be understood that the description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.
Number | Date | Country | Kind |
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200910110311.2 | Oct 2009 | CN | national |