1. Field of the Invention
The invention relates to thermally conductive pads and, particularly, to a thermally conductive pad with an array of carbon nanotubes and a method for making the same.
2. Description of Related Art
Since the report of their discovery in 1991 by Iijima, carbon nanotubes (CNTs) have been extensively studied for their structural, physio-chemical, mechanical, electrical, and electromechanical properties. Many potential technological applications have been proposed including hydrogen storage, nanoelectronic devices, field emission displays (FED), field emission microscopy (FEM), chemical sensors, and so on. Carbon nanotubes are desirable, at least in part, due to their unique electrical and mechanical properties. Currently, the study of carbon nanotube/polymer composite materials is gaining significant attention. Such nanotube-reinforced composite materials have broad applications because of their good antistatic performance, microwave absorbing capability, electromagnetic shielding ability, and so on.
Generally speaking, composite materials with carbon nanotubes have been prepared via an in-situ polymerization process, a solution compounding process, and/or a melt compounding process.
Carbon nanotubes arrays have excellent mechanical strength and good heat conductivity and/or heat diffusivity, as such they have been used to produce heat conductive materials and reinforced composite materials. However, the density of the carbon nanotubes in the composite material effects the mechanical strength and the heat conductivity of the composite material.
Currently, the technology for chemical vapor deposition (CVD) method for producing/making carbon nanotube arrays has reached a mature state. However, the carbon nanotube arrays directly produced or grown by the CVD method have a density of less than 0.01 grams per cubic centimeter (g/cm3). Thus, the carbon nanotube arrays are not tightly bounded to each other, and the spacings between the carbon nanotubes are in the order of several times the diameter of the carbon nanotubes. Furthermore, the density of the carbon nanotube arrays directly grown by the CVD method is difficult to change and/or control. As such, composite materials containing low-density carbon nanotube arrays have poor thermal conductivity. Thereby, the composite materials may not achieve the desirable effects required of thermally conductive composite materials.
Further, a thermally conductive pad can be obtained by cutting the above-described thermal conductive composite material. However, the thermally conductive pad has a low coefficient of thermal conductivity. Thus, the thermally conductive pad is restricted in its use in the thermal conductive field.
What is needed, therefore, is to provide a thermally conductive pad with a high-density array of carbon nanotubes, and a method for producing the same that is very simple and efficient and the density of carbon nanotubes therein is easily controlled during the production process.