Abstract:
A heat transfer fluid with heteroatom-containing carbon nanocapsules. The heat transfer fluid comprises a fluid and a plurality of heteroatom-containing carbon nanocapsules, uniformly dispersed in the fluid, in an amount of 0.01 to 10 parts by weight, based on 100 parts by weight of the heat transfer fluid. Since the heteroatom-containing carbon nanocapsules are apt to disperse in fluid and have superior thermal conductivity, the heat conduction capability of the heat transfer fluid therewith is enhanced.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a heat transfer fluids, and in particular relates to a heat transfer fluids with heteroatom-containing carbon nanocapsules.  
         [0003]     2. Description of the Related Art  
         [0004]     The electric power consumption results in generation of heat during the operation of devices such as computers, electronic equipments, or communication apparatuses. Since the rate of device aging is in direct ratio to the operating temperature thereof, the operating temperature must to be maintained within a specific range in order to prevent the device from being affected by the generated heat. Therefore, it is important to design a device with superior heat dissipation capability.  
         [0005]     With the development and advancement of technology, efficiency and convenience are important orientations in the use of electronic products that are desirably made with low profile, multiple functions and highly efficient operation. With respect to semiconductor industry and integrated circuit (IC) design, although it has successfully attained to important improvements such as profile miniaturization, high integration and multi-functions for electronic elements, reliability issue is generated due to heat production during operation of the electronic elements.  
         [0006]     A conventional cooling device having a heat sink and a small fan mounted in association with the electric device, however, cannot meet the demand for efficient dissipation of the electronic device. Moreover, noise is generated during the operation of the fan.  
         [0007]     Recently, with the development and wide application of electronic products, such as mobile phones, PDA, and notebook computers, there has been an increasing demand for electriconec devices which have longer run-time and occupy less space. Accordingly, the heat in the device excessively accumulates and is concentrated, thus creating a challenge for heat dissipating technology.  
         [0008]     Higher efficiency heat dissipating technology such as fluid cooling is often required. In a conventional fluid cooling system for a notebook computer, pure water serves as a heat transfer fluid in general. However, for many applications, the thermal conductivity of pure water is too low. The rate of heat transmission is too slow, and the operating efficiency of the heat pipe is unsatisfactory.  
         [0009]     Therefore, it is necessary to develop a novel heat transfer fluid with high thermal conductivity and suitable mobility for electronic devices such as notebook computers.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     The invention provides a heat transfer fluid with carbon nanocapsules serving as cooling liquid for a heat dissipation system such as a Micro-Fluid Heat Exchanger. The heat transfer fluid comprises a fluid and a plurality of heteroatom-containing carbon nanocapsules, uniformly dispersed in the fluid, in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 4 parts by weight, based on 100 parts by weight of the heat transfer fluid.  
         [0011]     The heteroatom-containing carbon nanocapsule is a carbon nanocapule containing heteroatoms, comprising a closed graphite layer represented by a chemical formula C(D)x, wherein C is a carbon exhibiting sp2 hybrid orbital, D is a atom of Group III or V of the periodic table bonded to the carbon, and X is a molar equivalent from 0.0001 to 0.1, based on the molar equivalent of carbon as 1. Since the heteroatom-containing carbon nanocapsules are apt to disperal in fluid and have superior thermal-conductivity, the heat conduction capability of the heat transfer fluid is enhanced.  
         [0012]     Particularly, the D comprises N, B, P, or S atoms and can further bond with hydrogen, alkyl group, alkoxy group, halogen, hydroxyl group, amino group, metal, or metal complex are modified to form covalent or coordination bonds.  
         [0013]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0015]      FIG. 1  is a close-up schematic drawing of carbon nanocapsules containing heteroatoms according to the invention;  
         [0016]      FIG. 2  is an electron paramagnetic resonance spectrum of doped-B carbon nanocapsules of the invention;  
         [0017]      FIG. 3  is a high resolution SEM (scanning electron microscope) photograph of doped-N carbon nanocapsules in one example of the invention; and  
         [0018]      FIG. 4  shows the positive charge migrating to the nitrogen atom when nitrogen atom bonds with a hydrogen ion (H + ). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.  
         [0020]     The heat transfer fluid comprises a fluid and a plurality of heteroatom-containing carbon nanocapsules disperse uniformly in the, fluid. The fluid can be water or organic solvent (such as alcohol or engine oil). In some embodiments of the invention, the fluid is water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, t-pentanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, styrene, ethyl acetate, toluene, xylene, methyl ethyl ketone, acetone, engine oil, or combinations thereof.  
         [0021]     In the invention, the heteroatom-containing carbon nanocapsules are carbon nanocapsules containing heteroatoms and can be polyhedral carbon clusters with completed and closed polyhedral graphite layers. In carbon nanocapsule containing heteroatoms of the invention, some carbon atoms are replaced with atoms of Group III or V of the periodic table, such as nitrogen, boron, phosphorous or sulfur atoms, as shown in  FIG. 1 . Due to the doped heteroatom, the nanocapsule exhibits specific properties of atoms of Group III or V, such as hole-rich or electron-rich ferromagnetism. The graphite layer with heteroatoms replacing the carbon atom is made up of pentagonal and hexagonal rings, atoms thereof exhibiting sp2 hybrid orbital. The carbon nanocapsule containing heteroatoms exhibits unsaturated double bonds while retaining the specific properties of graphite.  
         [0022]     Referring to  FIG. 2 , the doped-B carbon nanocapsules are characterized by electron paramagnetic resonance spectroscopy. Accordingly, the heteroatoms (D) of the carbon nanocapsules exhibit lone pair electrons.  
         [0023]     Since the heteroatoms, such as N, favor exhibition of Sp3 hybrid orbital and prefer to locate on the corners of the polyhedral graphite layer, namely on the pentagonal rings, the carbon nanocapsules containing heteroatoms exhibit superior electric and thermal conductivity in comparison with undoped carbon nanocapsules. Theoretically, nitrogen atoms located at the corners of the polyhedral graphite layer exhibits a different configuration from those on the hexagonal rings. The polyhedral graphite layer of the carbon nanocapsule containing heteroatoms can have, but is not limited to, 12 corners.  FIG. 3  is a high resolution SEM (scanning electron microscope) photograph of the heteroatom-containing carbon nanocapsule in an embodiment of the invention  
         [0024]     Due to the electron-rich or electron-poor characters of the heteroatoms (such as N, B. P, or S atoms), the heteroatom-containing carbon nanocapsules are apt to disperse into water or high polarity solvent. Further, the heteroatoms of the carbon nanocapsules can bond with hydrogen, alkyl group, alkoxy group, halogen group, hydroxyl group, amino group, metal, or metal complex and be charged, improving the solubility of the carbon nanocapsules in fluid.  
         [0025]     In some embodiments of the invention, the carbon nanocapsule is a Doped-N carbon nanocapsule. Referring to  FIG. 4 , when nitrogen atom bonds with a hydrogen ion (H + ), the positive charge migrates to the nitrogen atom, resulting in the Doped-N carbon nanocapsule charged with positive electricity. Due to the electricity, the carbon nanocapsules can uniformly disperse into the fluid without addition of surfactant.  
         [0026]     The carbon nanocapsule can be hollow and comprise a graphite layer. Furthermore, the carbon nanocapsule can comprise two graphite layers and be filled with 0.1˜80 wt % fillers, such as metal, metal oxide, metal carbides, metal sulfide, metal nitride, metal borate, or alloy, based on the weight of the nanocapsule. Suitable metals or metallines can comprise, without being limited to, Sc, V, Cr, Fe, Co, Ni, Cu, Y, Zr, Mo, Ru, Rh, Pd, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, Ta, Os, Ir, Pt, Au, Th, U, or combinations thereof. The heat transfer fluid with carbon nanocapsule filled with magnetic filters exhibits magnetic activity and can be used in Micro-Fluid Heat Exchanger with applied magnetic or electric field.  
         [0027]     Since the heteroatom-containing carbon nanocapsules have superior thermal conductivity (more than 1800 W/mK), large surface area, and lightweight characteristics, the heat transfer fluid is more apt to more efficiently remove the heat. Further, since the carbon nanocapsules have diameters of less than 100 nm (most of them between 30 to 40 nm) and superior thermal stability, the heat transfer fluid is suitable for heat dissipation system employing a Micro-Fluid Heat Exchanger with a diameter less than 10 μm.  
         [0000]     Preparation of Heat Transfer Fluid with Heteroatom-Containing Carbon Nanocapsules  
         [0028]     100 mg of doped-N nanocapsules was added into 100 g of pure water, and 0.1 wt % heat transfer fluid with heteroatom-containing carbon nanocapsules was obtained.  
         [0000]     Properties of Heat Transfer Fluid with Water-Soluble Carbon Nanocapsules  
         [0029]     The measured results of properties for the 0.1 wt % heat transfer fluid with heteroatom-containing carbon nanocapsules is shown in Table 1.  
                                             TABLE 1                                       0.1 wt % doped-N               nanocapsules in           Pure-water   water                                        Thermal   0.64   0.92           conductivity           (W/mk)                      
 
         [0030]     As described in Table 1, since the thermal conductivity of the heat transfer fluid is larger than that of pure water, the addition of heteroatom-containing carbon nanocapsules enhances the heat dissipation capability of water.  
         [0031]     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.