METHOD FOR PRODUCING NANO-CARBON COMPOSITE

Abstract

A method for producing a nano-carbon composite is provided. The method includes mixing nano-carbon powder and matrix alloy powder by milling, to provide a mixed powder and substantially evenly penetrating the nano-carbon powder inside of the matrix alloy by milling the mixed powder. In addition, the method includes clustering the mixed powder by milling the mixed powder slower than in the penetrating process.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent Application Number 10-2013-0158796 filed Dec. 18, 2013, the entire contents of which application is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present invention relates to a method for producing a nano-carbon composite, which secures easy oxidation and dispersion thereof and minimizes damage and oxidation in molten metal of carbon nano tube (CNT) or carbon nano fiber (CNF) by artificially enlarging particle size of the nano composite powder through milling condition change, in particular, by conducting ball milling.

BACKGROUND

A typical aluminum composite in which CNT or CNF is dispersed has been generally produced by sintering and extruding processes through powder molding. Moreover, some composite for casting has been produced by preparing composite powder to prevent powder oxidation and floating; conducting intermediate process to form the pellet; and charging the pellet in molten metal.

In particular, a typical method using the composite powder generally produces a nano-carbon dispersed composite by preparing composite powder of nano-carbon and matrix alloy through high energy ball milling; preparing intermediate material in the form of pellet (green compact) through sintering or press; and charging the pellet in molten metal. However, the above-mentioned method may raise problems, such as inefficiency and high production cost, since the intermediate process for pellet preparation costs additional time and efforts.

The description provided above as a related art of the present invention is merely for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.

SUMMARY

The present invention provides a technical solution to the above-described problems associated with conventional methods.

In one exemplary embodiment, the present invention provides a method for producing a nano-carbon composite, which may include: mixing nano-carbon powder and matrix alloy powder by milling, to provide a mixed powder; substantially evenly penetrating the nano-carbon powder inside of the matrix alloy by milling the mixed powder; and clustering the mixed powder by milling the mixed powder slower than in the penetrating step.

The nano-carbon powder may contain at least one of CNT and CNF. The milling condition in the mixing step may be about 40 to 60 RPM for about 8 to 11 hours. The milling condition in the penetrating step may be about 500 to 700 RPM for about 2 to 3 hours. The milling RPM in the coarsening step may be about 75 to 85% of the milling RPM in the penetrating step. The milling condition in the coarsening step may be about 450 to 500 RPM for 40 to 70 min. The matrix alloy powder may be an aluminum alloy powder.

In another exemplary embodiment, the nano-carbon composite produced by the method of the present invention may include particles in the size of about 400 μm or greater.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is an exemplary microscopic view showing the nano-carbon composite particles in the size of about 400 μm or less according to one exemplary embodiment of the present invention;

FIG. 2 is an exemplary microscopic view showing the nano-carbon composite particles in the size of about 400 μm or greater according to another exemplary embodiment of the present invention;

FIG. 3 is an exemplary microscopic view showing CNT penetrates inside of the matrix powder of the nano-carbon composite according to one exemplary embodiment of the present invention; and

FIG. 4 is an exemplary graph showing a correlation between the hardness of particles and the particle size of the nano-carbon composite according to one exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various exemplary features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.

Hereinafter, the exemplary embodiments of the present invention now will be described in detail with reference to the accompanying drawings.

FIG. 1 is an exemplary microscopic view showing the nano-carbon composite particles in the size of about 400 μm or less in one exemplary embodiment of the present invention; FIG. 2 is an exemplary microscopic view showing the nano-carbon composite particles in the size of about 400 μm or greater according to another exemplary embodiment of the present invention; and FIG. 4 is an exemplary graph showing a correlation between the hardness of particles and the particle size of the nano-carbon composite according to one exemplary embodiment of the present invention.

In one exemplary embodiment of the present invention, the method for producing the nano-carbon composite may include: a mixing step for mixing nano-carbon powder and matrix alloy powder by milling, to provide a mixed powder; a penetrating step for substantial evenly penetrating of the nano-carbon powder inside of the matrix alloy by milling the mixed powder; and a coarsening step for clustering the mixed powder by milling the mixed powder slower than in the penetrating step. In certain exemplary embodiments, the nano-carbon powder may contain at least one of CNT and CNF.

In addition, the milling condition in the mixing step may be about 40 to 60 RPM for 8 to 11 hours; and the milling condition in the penetrating step may be about 500 to 700 RPM for about 2 to 3 hours. The milling RPM in the coarsening step may be about 75 to 85% of the milling RPM in the penetrating step. In addition, the milling condition in the coarsening step may be about 450 to 500 RPM for about 40 to 70 min. The matrix alloy powder may be an aluminum alloy powder and the nano-carbon composite produced by the method of the present invention may include particles in the size of about 400 μm or greater.

According to the exemplary embodiment of the present invention, the nano-carbon composite may be produced by a casting process for mass production. In such a method, high energy ball milling may be conducted using a mechanical mixing method to remove an intermediate pellet process. Thus, oxidation and dispersion of the nano composite may be more easily secured by artificially enlarging particle size of the nano composite powder with changes in milling condition. The present invention further provides such a process which may minimize damage and oxidation in molten metal of CNT or CNF.

In one exemplary embodiment of the present invention, the method for producing coarse powder of the aluminum nano-carbon composite in which a nano-carbon such as CNT or CNF is dispersed may include: mixing CNT of about 10 to 15 wt % or CNF of about 10 to 15 wt % and aluminum alloy powder by a first slow milling at about 50 RPM for 10 hour; milling of high energy ball milling (HEM) at about 600 RPM for 2 to 3 hours; and milling at about 480 RPM, which may be reduced for about 20% from the RPM of the second milling, for 1 hour for powder coarsening. In particular, the first slow milling may improve the clustered state of the CNT or CNF, and the second high energy milling may penetrate the CNT/CNF inside the aluminum powder using cold welding using high energy. The third powder coarsening milling may obtain powder in the particle size of about 400 μm or greater by clustering aluminum powder.

Further, the nano composite powder may be charged while stirring with molten metal, to produce aluminum composite for casing in which the CNT/CNF may be dispersed. Therefore, intermediate process for pellet processing may be removed by the powder coarsening process. Accordingly, by the methods of the exemplary embodiment of the present invention, mass production of the nano-carbon composite may be simplified, the cost for production thereof may be reduced, and a melting time may be reduced by charging the powder itself in the molten metal.

FIG. 1 shows an exemplary microscopic view of particles in the size of 400 μm or less, and FIG. 2 shows exemplary composite particles in the size of 400 μm or greater according to the exemplary embodiment of the present invention. Furthermore, according to the exemplary embodiment of the present invention, CNT may penetrate the matrix powder material as shown in FIG. 3.

Additionally, FIG. 4 is an exemplary graph showing a correlation between the hardness of particles and the particle size of the nano-carbon composite. As shown in FIG. 4, from the hardness test results among a specimen produced by using pure aluminum, a specimen produced using powder in the size of about 400 μm or less and a specimen produced by using powder in the size of about 400 μm or greater, the hardness of the specimen produced using powder in the size of about 400 μm or greater is increased for about 150% against the specimen of pure aluminum matrix, and is equal to or greater than the hardness of the specimen produced using powder in the size of about 400 tm or less.

According to the method for producing the nano-carbon composite having the characters described above, in particular, when conducting ball milling, oxidation and dispersion may be more easily maintained by artificially enlarging particle sizes of the nano composite powder through milling condition change, and damage and oxidation in molten metal of CNT or CNF may be minimized. In particular, since the intermediate pellet producing process may be removed, the process efficiency may be improved, and time and cost for producing the composite may be reduced.

The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes or modifications may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for producing a nano-carbon composite, comprising:

mixing nano-carbon powder and matrix alloy powder by milling, to provide a mixed powder;

substantially evenly penetrating the nano-carbon powder inside of the matrix alloy powder by milling the mixed powder; and

clustering the mixed powder by milling the mixed powder slower than in the penetrating process.

2. The method for producing the nano-carbon composite of claim 1, wherein the nano-carbon powder includes at least one of a group selected of: carbon nano tube (CNT) and carbon nano fiber (CNF).

3. The method for producing the nano-carbon composite of claim 1, wherein the milling condition in the mixing step is about 40 to 60 RPM for about 8 to 11 hours.

4. The method for producing the nano-carbon composite of claim 1, wherein the milling condition in the penetrating step is about 500 to 700 RPM for about 2 to 3 hours.

5. The method for producing the nano-carbon composite of claim 1, wherein the milling RPM in the clustering step is about 75 to 85% of the milling RPM in the penetrating step.

6. The method for producing the nano-carbon composite of claim 1, wherein the milling condition in the clustering step is about 450 to 500 RPM for about 40 to 70 min.

7. The method for producing the nano-carbon composite of claim 1, wherein the matrix alloy powder is aluminum alloy powder.

8. The method for producing the nano-carbon composite of claim 1, wherein the nano-carbon composite includes particles in a size of about 400 μm or greater.