U.S. patent application number 14/532848 was filed with the patent office on 2015-12-17 for method of surface-treating aluminum material for dissipating heat.
The applicant listed for this patent is HYUNDAI MOTOR COMPANY, PUSAN NATIONAL UNIVERSITY INDUSTRY-UNIVERSITY COOPERATION FOUNDATION. Invention is credited to Won Sub CHUNG, Tae Ho JEONG, Dong Hyun KIM, Cheol Ung LEE, Ji Yong LEE, Jung Hoon LEE, Kwang Min YOON.
Application Number | 20150361575 14/532848 |
Document ID | / |
Family ID | 54706768 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150361575 |
Kind Code |
A1 |
LEE; Ji Yong ; et
al. |
December 17, 2015 |
METHOD OF SURFACE-TREATING ALUMINUM MATERIAL FOR DISSIPATING
HEAT
Abstract
The present application relates to a method of surface-treating
an aluminum material for dissipating heat, which is capable of
increasing the radiation heat flux to thus enhance heat dissipation
performance, and includes anodizing an aluminum material using an
electrolyte composed of oxalic acid, and forming cobalt sulfide
(CoS) in surface pores of the aluminum material thus sealing the
surface of the aluminum material.
Inventors: |
LEE; Ji Yong; (Seoul,
KR) ; LEE; Cheol Ung; (Busan, KR) ; YOON;
Kwang Min; (Suwon-Si, KR) ; JEONG; Tae Ho;
(Yongin-si, KR) ; KIM; Dong Hyun; (Busan, KR)
; LEE; Jung Hoon; (Busan, KR) ; CHUNG; Won
Sub; (Busan, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HYUNDAI MOTOR COMPANY
PUSAN NATIONAL UNIVERSITY INDUSTRY-UNIVERSITY COOPERATION
FOUNDATION |
Seoul
Pusan |
|
KR
KR |
|
|
Family ID: |
54706768 |
Appl. No.: |
14/532848 |
Filed: |
November 4, 2014 |
Current U.S.
Class: |
205/203 |
Current CPC
Class: |
C25D 11/10 20130101;
C25D 11/08 20130101; C25D 11/246 20130101 |
International
Class: |
C25D 11/10 20060101
C25D011/10; C25D 11/24 20060101 C25D011/24; C25D 11/14 20060101
C25D011/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 2014 |
KR |
10-2014-0073159 |
Claims
1. A method of surface-treating an aluminum material for
dissipating heat, the method comprising steps of: anodizing an
aluminum material with an electrolyte comprising oxalic acid; and
sealing a surface of the aluminum material by formation of cobalt
sulfide (CoS) in surface pores of the aluminum material.
2. The method of claim 1, wherein the oxalic acid of the
electrolyte upon anodizing has a concentration of 0.2.about.0.8
M.
3. The method of claim 1, wherein the electrolyte upon anodizing
has a temperature of 10.about.40.degree. C.
4. The method of claim 1, wherein anodizing is performed for at
least 30 min.
5. The method of claim 1, wherein the sealing step comprises:
primarily immersing the anodized aluminum material in a cobalt
acetate solution; and secondarily immersing the aluminum material
in an ammonium sulfide solution.
6. The method of claim 5, wherein upon the primary immersion,
cobalt acetate (Co(CH.sub.3COO).sub.2) of the cobalt acetate
solution has a concentration of 100.about.250 g/L.
7. The method of claim 5, wherein upon the secondary immersion,
ammonium sulfide ((NH.sub.4).sub.2S) of the ammonium sulfide
solution has a concentration of 10.about.50 g/L.
8. A method of surface-treating an aluminum material for
dissipating heat, the method comprising steps of: anodizing an
aluminum material with an electrolyte comprising oxalic acid and a
second acid selected from sulfuric acid, phosphoric acid or chromic
acid, wherein a concentration of the second acid is between 0.1 to
1 M; and sealing a surface of the aluminum material by formation of
cobalt sulfide (CoS) in surface pores of the aluminum material.
9. The method of claim 8, wherein the oxalic acid of the
electrolyte upon anodizing has a concentration of 0.2.about.0.8
M.
10. The method of claim 8, wherein the electrolyte upon anodizing
has a temperature of 10.about.40.degree. C.
11. The method of claim 8, wherein anodizing is performed for at
least 30 min.
12. The method of claim 8, wherein the sealing step comprises:
primarily immersing the anodized aluminum material in a cobalt
acetate solution; and secondarily immersing the aluminum material
in an ammonium sulfide solution.
13. The method of claim 12, wherein upon the primary immersion,
cobalt acetate (Co(CH.sub.3COO).sub.2) of the cobalt acetate
solution has a concentration of 100.about.250 g/L.
14. The method of claim 12, wherein upon the secondary immersion,
ammonium sulfide ((NH.sub.4).sub.2S) of the ammonium sulfide
solution has a concentration of 10.about.50 g/L.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority of Korean Patent
Application Number 10-2014-0073159 filed on Jun. 16, 2014, the
entire contents of which application are incorporated herein for
all purposes by this reference.
TECHNICAL FIELD
[0002] The present application relates to a method of
surface-treating an aluminum material for dissipating heat, and
more particularly, to a method of surface-treating an aluminum
material for dissipating heat, which is capable of increasing the
radiation heat flux to thus enhance heat dissipation
performance.
BACKGROUND
[0003] An aluminum material is light and has high thermal
conductivity and electrical conductivity. Further, when an aluminum
material is subjected to surface treatment, it may be enhanced in
corrosion resistance and mechanical performance and is thus widely
utilized in various fields. In particular, an aluminum material has
been mainly utilized in vehicle parts because of its
properties.
[0004] Use of an aluminum material for vehicle parts f is primarily
intended to achieve lightness and to enhance heat dissipation
performance. Conventionally, aluminum has been selectively used for
parts requiring lightness or heat dissipation performance.
[0005] However, with an increase in vehicle technology, performance
required of parts for vehicles has increased, and thus thorough
research into ensuring lightness and high heat dissipation
performance of an aluminum material is ongoing.
[0006] To achieve lightness, techniques for improving properties of
an aluminum material by adjusting the composition of an aluminum
alloy have been variously proposed.
[0007] However, it is difficult to enhance heat dissipation
performance by adjusting the composition of an aluminum alloy.
Accordingly, there is a need for a technique for increasing heat
dissipation performance of an aluminum material through surface
treatment.
[0008] Typically useful is an aluminum material having enhanced
corrosion resistance and wear resistance through surface treatment
such as anodization. Also, a film resulting from anodization has
many pores and thus may exhibit a variety of colors through
coloring using a dye or the surface thereof may be sealed through
impregnation with a functional material.
[0009] Anodization for surface treatment of an aluminum material is
generally performed by virtue of a sulfuric acid process using as
an electrolyte a 10.about.18 wt % sulfuric acid aqueous solution.
The reason why such a sulfuric acid process is employed is that the
electrolyte is the cheapest and power consumption is low, thus
generating economic benefits. The anodization technique using a
sulfuric acid process is aimed to enhance wear resistance and
corrosion resistance of an aluminum material, but does not take
into consideration heat dissipation performance of the aluminum
material.
[0010] Recently, there are devised techniques for performing
anodization treatment in a manner that enhances performance and
properties of the aluminum material with the use of electrolytes
having various compositions.
[0011] For example, when an electrolyte composed mainly of citric
acid instead of sulfuric acid is added with oxalic acid, the
resulting oxide film layer may have a porous structure which is
formed regularly and stably, which is disclosed in "Method of
forming anodizing electrolyte of aluminum alloy material and
composition therefor" (Patent Document 1).
[0012] In Patent Document 1, as the porous structure of the oxide
film is regularly and stably formed, the electrolyte may be
prevented from remaining to thereby obviate the post treatment
process. Furthermore, the aluminum material is enhanced in terms of
not only chemical and mechanical properties including surface
strength, corrosion resistance, wear resistance, insulating
properties and heat resistance, but also electrical properties
including voltage resistance. However, no consideration is given of
heat dissipation performance of the aluminum material.
[0013] Typical examples of sealing treatment for finishing the
surface of the anodized aluminum material include a boiling water
sealing process, a low-temperature sealing process (NiF.sub.2),
etc. This sealing treatment process takes account of only the
protection of the oxide film on the aluminum material, without the
consideration of heat dissipation performance of the aluminum
material.
SUMMARY
[0014] Accordingly, the present application has been developed
keeping in mind the above problems encountered in the existing art.
An object of the present application is to provide a method of
surface-treating an aluminum material for dissipating heat, which
may enhance heat dissipation performance using a surface treatment
process and a sealing treatment process of an aluminum
material.
[0015] In order to accomplish the above objective, an embodiment of
the present application provides a method of surface-treating an
aluminum material for dissipating heat. The method includes
anodizing an aluminum material with an electrolyte comprising
oxalic acid. The surface of the aluminum material is sealed by
formation of cobalt sulfide (CoS) in surface pores of the aluminum
material.
[0016] The oxalic acid of the electrolyte upon anodizing may have a
concentration of 0.2.about.0.8 M.
[0017] The electrolyte upon anodizing may have a temperature of
10.about.40.degree. C.
[0018] The anodizing may be performed for at least 30 min.
[0019] The sealing may primarily include immersing the anodized
aluminum material in a cobalt acetate solution; and secondarily
immersing the aluminum material in an ammonium sulfide
solution.
[0020] Upon primary immersion, cobalt acetate
(Co(CH.sub.3COO).sub.2) of the cobalt acetate solution may have a
concentration of 100.about.250 g/L.
[0021] Upon secondary immersion, ammonium sulfide
((NH.sub.4).sub.2S) of the ammonium sulfide solution may have a
concentration of 10.about.50 g/L.
[0022] According to embodiments of the present application, an
electrolyte for use in anodization includes only oxalic acid, so
that the color of the resulting oxide film is closer to black, thus
enhancing the heat dissipation performance of the aluminum
material.
[0023] Also, according to the present application, CoS is formed in
the pores of the anodized surface, so that the surface color of the
aluminum material is much closer to black, thus enhancing the heat
dissipation performance of the aluminum material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and other objects, features and advantages of the
present application will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0025] FIG. 1A illustrates the surfaces of oxide films depending on
the temperature and time period when conventional anodization using
a sulfuric acid electrolyte was performed;
[0026] FIG. 1B illustrates the surfaces of oxide films depending on
the temperature and time period when anodization using an oxalic
acid electrolyte according to the present invention was
performed;
[0027] FIG. 2A illustrates the relative radiation results of the
oxide films depending on the temperature and time period when
conventional anodization using a sulfuric acid electrolyte was
performed;
[0028] FIG. 2B illustrates the relative radiation results of the
oxide films depending on the temperature and time period when
anodization using an oxalic acid electrolyte according to the
present application was performed;
[0029] FIG. 3 illustrates the surface photographs and the relative
radiation results of the aluminum materials after conventional
sealing treatment and the sealing treatment according to the
present application;
[0030] FIG. 4A illustrates changes in the radiation heat flux
depending on the concentration of cobalt acetate in the course of
primary immersion for sealing treatment using a black sealing
process according to the present application; and
[0031] FIG. 4B illustrates changes in the radiation heat flux
depending on the concentration of ammonium sulfide in the course of
secondary immersion for sealing treatment using a black sealing
process according to the present application.
DETAILED DESCRIPTION
[0032] Hereinafter, a detailed description will be given of
embodiments of the present application with reference to the
appended drawings. The present application is not limited to the
following embodiments and may be variously modified, and the
present embodiments are merely intended to complete the disclosure
of the present application and are apparent to those having
ordinary knowledge in the art within the scope of the present
application.
[0033] It is typically known in the art that an aluminum material
increases in radiation heat flux as the color of an oxide film
formed thereon by surface treatment is closer to black, thus
enhancing heat dissipation performance.
[0034] Accordingly, the present application addresses a method of
surface-treating an aluminum material for dissipating heat, wherein
conditions for anodization and sealing treatment that are applied
to an aluminum material are improved, so that the surface color of
the aluminum material is closer to black.
[0035] Particularly, the method of surface-treating the aluminum
material for dissipating heat according to the present application
includes anodizing an aluminum material with an electrolyte
comprising oxalic acid, and sealing the surface of the aluminum
material by formation of cobalt sulfide (CoS) in surface pores of
the aluminum material.
[0036] In the method according to the present application,
anodizing is a step of subjecting the surface of the aluminum
material to anodization to form an oxide film closer to black
thereon. The electrolyte used for anodization may contain only
oxalic acid.
[0037] As such, the concentration of oxalic acid is set to
0.2.about.0.8 M, and preferably 0.3 M. Since the saturated
concentration of oxalic acid at 0.degree. C. is 0.3 M, when the
concentration of oxalic acid is less than 0.2 M considering the
electrolyte temperature, the power necessary for performing
anodization may increase, and the density of surface pores of the
oxide film may decrease. In contrast, when the concentration of
oxalic acid is higher than 0.8 M, oxalic acid is not further
dissolved. Hence, the concentration of oxalic acid is preferably
set to 0.2.about.0.8 M.
[0038] The electrolyte used for the present embodiment preferably
contains only oxalic acid. Alternatively, the electrolyte may
further include an acid typically useful for anodization while
mainly containing oxalic acid. For example, the electrolyte may
include sulfuric acid, phosphoric acid or chromic acid, in addition
to oxalic acid. As such, the concentration of sulfuric acid,
phosphoric acid or chromic acid is preferably set to 0.1.about.1
M.
[0039] When the concentration of oxalic acid in the electrolyte
falls in the range of 0.2.about.0.8 M, a current of 1.about.5 ASD
and a voltage of 50.about.150 V may be employed upon
anodization.
[0040] The temperature of the electrolyte upon anodization may be
set to 10.about.40.degree. C. The optimum temperature of the
electrolyte is preferably 15.about.30.degree. C. When anodization
is carried out using the electrolyte composed of oxalic acid, the
color of the resulting oxide film may be further darkened in
proportion to an increase in the electrolyte temperature. Even when
the electrolyte temperature is higher than 30.degree. C., the
extent of darkening the color of the oxide film may decrease.
Taking into account the maximal darkening of the oxide film,
increasing the electrolyte temperature in excess of 40.degree. C.
is unnecessary.
[0041] The anodization processing time is preferably 30 min or
longer. As the anodization processing time increases, the resulting
oxide film may become thick and thus the radiation heat flux may
increase. In particular, an anodization processing time exceeding
30 min may result in maximized radiation heat flux.
[0042] The reason why the electrolyte temperature and the
processing time upon anodizaiton are limited as above is described
later through the following experiments.
[0043] Also in the method, sealing is a step of sealing the oxide
film formed by anodization, so that the surface color of the
aluminum material is closer to black. This sealing step may include
primarily immersing the anodized aluminum material in a cobalt
acetate solution and secondarily immersing the primarily immersed
aluminum material in an ammonium sulfide solution.
[0044] For primary immersion, the concentration of cobalt acetate
(Co(CH.sub.3COO).sub.2) of the cobalt acetate solution is
100.about.250 g/L, and the temperature of the cobalt acetate
solution is 20.about.50.degree. C., and the immersion time is
preferably set to 10.about.30 min.
[0045] For secondary immersion, the concentration of ammonium
sulfide ((NH.sub.4).sub.2S) of the ammonium sulfide solution is
10.about.50 g/L, and the temperature of the ammonium sulfide
solution is 20.about.50.degree. C. The immersion time is
10.about.30 min.
[0046] The effects depending on the concentration of the immersion
solution, the temperature and the immersion time in the primary and
the secondary immersion procedure are proven through the following
experiments.
[0047] Below is a description of the effects of the invention.
Experimental Example 1
[0048] Comparative examples for anodizing an aluminum material
using as a conventional electrolyte a sulfuric acid aqueous
solution, and examples for anodizing an aluminum material using an
electrolyte composed exclusively of oxalic acid according to the
present application, were performed at different electrolyte
temperatures for different processing times. Then, the surfaces of
the oxide films formed on the aluminum materials were compared.
[0049] In the comparative examples, sulfuric acid had a
concentration of 15 wt %, and in the examples, oxalic acid had a
concentration of 0.3 M. In all the comparative examples and the
examples, the temperature of the electrolyte was changed to
0.degree. C., 15.degree. C. and 30.degree. C., and the processing
time was changed to 10 min, 20 min, 30 min and 40 min.
[0050] The results are shown in FIGS. 1A and 1B.
[0051] FIG. 1A illustrates the surfaces of oxide films depending on
the temperature and time period when conventional anodization using
a sulfuric acid electrolyte was performed, and FIG. 1B illustrates
the surfaces of oxide films depending on the temperature and time
period when anodization using an oxalic acid electrolyte according
to the present invention was performed.
[0052] As illustrated in FIG. 1A, in the comparative examples using
sulfuric acid as the electrolyte, the surface colors of the oxide
films were gradually darkened in proportion to a decrease in the
electrolyte temperature.
[0053] Further, in the comparative examples, the longer the
processing time, the darker the surface colors of the oxide
films.
[0054] Whereas, as illustrated in FIG. 1B, in the examples using
oxalic acid as the electrolyte, the surface colors of the oxide
films were gradually darkened with an increase in the electrolyte
temperature.
[0055] Also in the examples, as the processing time was increased,
the surface colors of the oxide films were gradually darkened as in
the comparative examples. Further, when a processing time of 30 min
and a processing time of 40 min were applied, there was little
difference between the surface colors of the aluminum
materials.
[0056] Hence, in the present application using oxalic acid as the
electrolyte, it can be confirmed that the electrolyte temperature
of 10.about.40.degree. C. and preferably at 15.about.30.degree. C.
and also the processing time of 30 min or longer are preferable,
taking into consideration heat dissipation performance.
Experimental Example 2
[0057] The relative radiation values of the oxide films formed on
the aluminum materials of the comparative examples and the examples
in Experimental Example 1 were measured. The results are shown in
Table 1 below and FIGS. 2A and 2B.
[0058] FIG. 2A illustrates the relative radiation results of the
oxide films depending on the temperature and time period when
conventional anodization using a sulfuric acid electrolyte was
performed, and FIG. 2B illustrates the relative radiation results
of the oxide films depending on the temperature and time period
when anodization using an oxalic acid electrolyte according to the
present invention was performed.
TABLE-US-00001 TABLE 1 Examples Comp. Examples Radiation (0.3M
Oxalic acid) (15 wt % sulfuric acid) (W/m.sup.2) 0.degree. C.
15.degree. C. 30.degree. C. 0.degree. C. 15.degree. C. 30.degree.
C. 10 min 317.52 330.75 330.75 255.78 255.78 269.01 20 min 352.8
330.75 366.03 255.78 269.01 171.99 30 min 282.24 379.26 379.26
269.01 282.24 171.99 40 min 330.75 379.26 379.26 317.52 282.24
233.73
[0059] As is apparent from Table 1 and FIGS. 2A and 2B, the
radiation heat flux was relatively higher in the examples than in
the comparative examples when the same electrolyte temperature and
the same processing time were employed.
[0060] In the examples, as the processing time was longer at high
electrolyte temperature, the radiation heat flux was increased. As
such, when the electrolyte temperatures were 15.degree. C. and
30.degree. C. and the processing times were 30 min and 40 min, the
radiation heat flux values were the same within a measurement error
range. Considering the profitability of the process, when
anodization is performed using the electrolyte composed of 0.3 M
oxalic acid, the electrolyte temperature of 15.degree. C. and the
processing time of 30 min are regarded as the most appropriate.
Experimental Example 3
[0061] To evaluate, depending on the sealing treatment, a
difference in the surface colors of the aluminum materials
subjected to anodization for 60 min using the electrolyte composed
of 0.3 M oxalic acid at 15.degree. C. according to the present
application, the as-anodized aluminum material using the oxalic
acid electrolyte before sealing treatment, the sealed aluminum
material resulting from a boiling water sealing process, the sealed
aluminum material resulting from a low-temperature sealing process
(NiF.sub.2) and the sealed aluminum material according to the
present invention (a black sealing process) were prepared, and the
surface colors thereof were observed and the radiation heat flux
values were measured. The results are shown in FIG. 3.
[0062] For a boiling water sealing process, the anodized aluminum
material was immersed for 30 min in deionized water at 95.degree.
C.
[0063] For a low-temperature sealing process, the anodized aluminum
material was immersed for 30 min in an immersion solution
comprising 3 g/L nickel fluoride (NiF.sub.2) at 25.degree. C.
[0064] For a black sealing process according to the present
application, the anodized aluminum material was immersed for 20 min
in an immersion solution comprising 200 g/L cobalt acetate
(Co(CH.sub.3COO).sub.2) at 45.degree. C., and then immersed for 15
min in an immersion solution comprising 30 g/L ammonium sulfide
((NH.sub.4).sub.2S) at 25.degree. C.
[0065] FIG. 3 illustrates the surface photographs and the relative
radiation results of the aluminum materials after conventional
sealing treatment and the sealing treatment according to the
present application. As illustrated in FIG. 3, the aluminum
materials sealed by the boiling water sealing process and the
low-temperature sealing process had a darker surface color than the
non-sealed aluminum material, but the surface color of the aluminum
material subjected to black sealing was the closest to black.
[0066] Based on the results of measurement of the radiation heat
flux, the aluminum material sealed by the boiling water sealing
process had the same radiation heat flux as the pre-sealing result.
The aluminum material sealed by the low-temperature sealing process
had improved radiation heat flux compared to the pre-sealing
treatment, but the radiation heat flux of the aluminum material
sealed by the black sealing process was most improved. Hence, when
the surface of the aluminum material is sealed using a black
sealing process, the radiation heat flux can be confirmed to be
quite high, compared to the other sealing processes.
Experimental Example 4
[0067] Upon primary immersion for sealing treatment using a black
sealing process, changes in the radiation heat flux depending on
the concentration of cobalt acetate (Co(CH.sub.3COO).sub.2) of a
cobalt acetate solution were evaluated. Specifically, during a
primary immersion process in the course of sealing the aluminum
material subjected to anodization using the oxalic acid
electrolyte, the amount of cobalt acetate (Co(CH.sub.3COO).sub.2)
in cobalt acetate solutions was changed. As such, the temperature
of all the cobalt acetate solutions was set to 45.degree. C., and
the immersion time was set to 20 min. During the next secondary
immersion process, the aluminum material was immersed for 15 min in
an immersion solution comprising 30 g/L ammonium sulfide
((NH.sub.4).sub.2S) at 25.degree. C. The results are shown in FIG.
4A.
[0068] As illustrated in FIG. 4A, when cobalt acetate was used in
amounts of 100, 200 and 250 g/L, the radiation heat flux was 400
W/m.sup.2 or greater. Hence, the concentration of cobalt acetate
(Co(CH.sub.3COO).sub.2) of the cobalt acetate solution in the
primary immersion process can be confirmed to be 100.about.250
g/L.
Experimental Example 5
[0069] Upon secondary immersion for sealing treatment using a black
sealing process, changes in the radiation heat flux depending on
the concentration of ammonium sulfide ((NH.sub.4).sub.2S) of an
ammonium sulfide solution were evaluated. The aluminum materials
subjected to anodization using the oxalic acid electrolyte
underwent black sealing. Specifically, after primary immersion for
20 min in the immersion solution comprising 200 g/L cobalt acetate
(Co(CH.sub.3COO).sub.2) at 45.degree. C., the aluminum materials
were secondarily immersed under the conditions that the temperature
of all ammonium sulfide solutions was set to 25.degree. C. and the
immersion time was 15 min while changing the amount of ammonium
sulfide ((NH.sub.4).sub.2S) in the ammonium sulfide solutions. The
results are shown in FIG. 4B.
[0070] As illustrated in FIG. 4B, when ammonium sulfide was used in
amounts of 10, 30 and 50 g/L, the radiation heat flux was 400
W/m.sup.2 or greater. Thus, in the secondary immersion process, the
concentration of ammonium sulfide ((NH.sub.4).sub.2S) of the
ammonium sulfide solution can be confirmed to be 10.about.50
g/L.
[0071] Although the preferred embodiments of the present
application depicted in the drawing have been disclosed for
illustrative purposes, those skilled in the art will appreciate
that various modifications, additions and substitutions are
possible, without departing from the scope and spirit of the
subject matter as disclosed in the accompanying claims.
* * * * *