Patent Application
20250215603
The present invention relates to a method for simultaneously achieving a superhydrophobic and superoleophobic surface on a 5000 series aluminum alloy in an anodic oxidation process without a pre-patterning step and anodic oxidation process condition data obtained from the present invention may be utilized for machine learning.
Generally, hydrophobicity and oleophobicity refer to properties of being difficult to get wet by water and oil, respectively, and superhydrophobicity/superoleophobicity are generally defined in the field that a contact angle of water which is in contact with a surface of a solid is 150° or larger and a contact angle of oil is 150° or larger.
Recently, the superhydrophobic surface having a water contact angle of 150° or larger has attracted considerable interest with its importance in both fundamental studies and practical applications. The superhydrophobicity and superoleophobicity refer to a physical property of a surface of an object which is extremely difficult to be wet with water and oil. For example, leaves of plants, wings of insects, or wings of birds possess the ability to naturally remove any external contaminants without a special removal process or prevent contamination in the first place. This is because the leaves of plants, the wings of insects, and the wings of birds have superhydrophobicity.
The wettability is a main surface characteristic of a solid material and is mainly controlled by both a chemical composition and geometric micro/nanostructure. Wettable surfaces have attracted much attention due to their potential applications in various fields such as oil-water separation, antireflection, anti-bioadhesion, anti-sticking, anti-contamination, self-cleaning, and fluid turbulence suppression.
In the meantime, although there have been several reports on the manufacturing of superhydrophobic aluminum, superhydrophobicity/superoleophobicity on a metal base have received relatively little attention.
As air pollution has become more serious due to recent environmental pollution and the occurrence of yellow dust and fine dust has increased, it is common to operate a ventilation system to purify the indoor air rather than opening windows to ventilate. Further, in order to remove living dust, food odors, or cigarette odors generated in residential, business, and commercial facilities such as homes, workplaces, industrial sites, restaurants, offices, restrooms or bathrooms, various harmful odors generated during work, harmful air such as carbon monoxide, fine dust, and oil vapor, ventilation devices are operated on a regular basis.
Such ventilation devices are usually implemented by complex facilities such as ventilation systems that are systematized and installed in specific locations to automatically operate depending on the level of indoor pollution or by window-type ventilation fans that are installed on walls adjacent to the outside and simply circulate the air inside and outside.
However, these ventilators have the problem that dust is inevitably accumulated on the inside and outside of the ventilator when used for a certain period of time, which is unsanitary and requires the troublesome task of disassembling and cleaning the ventilator to remove the dust.
Particularly, ventilators installed in restaurants or places where oil vapor is generated do not have any filtering devices to primarily absorb oil or fine dust. Therefore, when used for a long period of time, oil and fine dust are combined to flow downward, which may cause serious hygiene concerns and may also be exposed to the risk of fire.
An object of the present invention is to provide a manufacturing method of an oleophobic and hydrophobic film on a 5000 series aluminum alloy without pre-patterning process.
Another object of the present invention is to provide a 5000 series aluminum alloy on which an oleophobic and hydrophobic film manufactured by the above-described manufacturing method is formed.
In order to achieve the above-described objects, the present invention provides a manufacturing method of an oleophobic and hydrophobic film on a 5000 series aluminum alloy, including: a step of performing primary anodic oxidation on a 5000 series aluminum alloy for 1 to 10 minutes at 35 to 45 V (step 1); a step of performing pore widening by immersing the alloy in 0.05 to 1.0 M phosphoric acid (H3PO4) solution for 10 to 60 minutes (step 2); a step of performing secondary anodic oxidation for 1 to 10 minutes at 35 to 45 V (step 3); and a step of coating with a coating composition including a cross-linked polydimethylsiloxane (PDMS) derivative represented by Chemical Formula 1 and an organic solvent (step 4), and prior to step 1, a pre-patterning process is omitted.
(In Chemical Formula 1, x and y are each an integer of 1 to 30).
Further, the present invention provides a 5000 series aluminum alloy on which an oleophobic and hydrophobic film manufactured by the above-described manufacturing method is formed.
According to the present disclosure, the method for manufacturing a superhydrophilic anodic oxide film on a 5000 series aluminum alloy can manufacture a uniform anodic oxide film even without a pre-patterning step, thereby reducing manufacturing costs, can impart superhydrophobicity and superoleophobicity to the anodic oxide film according to a coating composition using a cross-linked PDMS derivative represented by Chemical Formula 1 and an organic solvent in a specific mixing ratio and the coating composition has an inexpensive manufacturing cost and adjusts a coating film thickness to several to several tens of nm to be applied to the coating of a microstructured oxide film.
The present invention provides a manufacturing method of an oleophobic and hydrophobic film on a 5000 series aluminum alloy, including: a step of performing primary anodic oxidation on a 5000 series aluminum alloy for 1 to 10 minutes at 35 to 45 V (step 1); a step of performing pore widening by immersing the alloy in 0.05 to 1.0 M phosphoric acid (H3PO4) solution for 10 to 60 minutes (step 2); a step of performing secondary anodic oxidation for 1 to 10 minutes at 35 to 45 V (step 3); and a step of coating with a coating composition including a cross-linked polydimethylsiloxane (PDMS) derivative represented by Chemical Formula 1 and an organic solvent (step 4), and prior to the step 1, a pre-patterning process is omitted.
In the manufacturing method according to the present invention, the steps 1 to 3 are manufacturing steps for forming an anodic oxide film with a pillar-on-pore (POP) structure on a 5000 series aluminum alloy surface by anodic oxidation and pore widening. Here, the anodic oxide film exhibits hydrophilicity and the anodic oxide film with POP structure according to the present invention exhibits superhydrophilicity. Here, the coating composition according to step 4 is intended to impart oleophobicity and hydrophobicity and its technical feature is that the coating composition is coated on a micronano surface with POP structure as thin as a thickness of a monomolecular layer to maintain a micronano surface structure of the anodic oxide film, thereby maximizing the oleophobic and hydrophobic effects.
As the 5000 series aluminum alloy, Al 5005, Al 5052, Al 5023, Al 5042, Al 5054, Al 5056, Al 5082, Al 5083, Al 5084, Al 5086, Al 5154, Al 5182, Al 5252, Al 5352, Al 5383, Al 5454, Al 5456, Al 5457, Al 5657, or Al 5754 may be used.
The anodic oxide film exhibits hydrophilicity and the anodic oxide film with a pillar-on-pore micro structure according to steps 1 to 3 of an exemplary embodiment of the present disclosure in which pillars are formed on a pore structure may exhibit superhydrophilicity of a contact angle of 100 or smaller.
The pre-patterning process is a process of performing anodic oxidation on the 5000 series aluminum alloy and then etching the 5000 series aluminum alloy to remove the anodic oxide film, thereby remaining a microstructure pattern on a surface of the 5000 series aluminum alloy.
According to a method for forming an anodic oxide film on a surface of a metal base by the anodic oxidation of the related art, it is common to perform the pre-patterning process to form a microstructure pattern on a surface of a metal base and then perform anodic oxidation. This is intended to uniformly form the anodic oxide film which is formed by the anodic oxidation which is a post-process along a microstructure pattern of the surface of the metal base which is performed by the pre-patterning process.
An object of the present invention is to provide a method for uniformly forming an anodic oxide film even without the pre-patterning process and the pre-patterning process is omitted to achieve a significant advantage in reducing manufacturing costs.
Desirably, the method may include a step of performing primary anodic oxidation on a 5000 series aluminum alloy for 3 to 7 minutes at 38 to 42 V (step 1); a step of performing pore widening by immersing the alloy in 0.05 to 0.15 M phosphoric acid (H3PO4) solution for 30 to 45 minutes (step 2); and a step of performing secondary anodic oxidation for 3 to 7 minutes at 38 to 42 V (step 3).
More desirably, the method may include a step of performing primary anodic oxidation on a 5000 series aluminum alloy for 4 to 6 minutes at 39 to 41 V (step 1); a step of performing pore widening by immersing the alloy in 0.06 to 0.14 M phosphoric acid (H3PO4) solution for 33 to 42 minutes (step 2); and a step (Step 3) of performing secondary anodic oxidation for 4 to 6 minutes at 39 to 41 V.
Most desirably, the method may include a step of performing primary anodic oxidation on a 5000 series aluminum alloy for 4.75 to 5.25 minutes at 39.5 to 40.5 V (step 1); a step of performing pore widening by immersing the alloy in 0.095 to 0.105 M phosphoric acid (H3PO4) solution for 34 to 36 minutes (step 2); and a step of performing secondary anodic oxidation for 4.75 to 5.25 minutes at 39.5 to 40.5 V (step 3).
Problems in that uniform anodic oxide film is not formed or the superhydrophilicity is not achieved may occur out of the treatment conditions of steps 1 to 3 described above.
The anodic oxidation process is performed by applying an anode electrode with the 5000 series aluminum alloy to be anodic oxidized as a working electrode and then applying a cathode electrode with a platinum (Pt) or carbon electrode as a counter electrode, in an oxidation reaction tank containing an electrolyte at −5 to 30° C., to oxidize it. The distance between the working electrode and the counter electrode may be 1 to 15 cm, desirably 3 to 12 cm, more desirably 4 to 10 cm, more desirably 4.5 to 8 cm, and the most desirably 4.75 to 5.25 cm.
As electrolytes for the primary anodic oxidation and the secondary anodic oxidation, sulfuric acid (H2SO4), phosphoric acid (H3PO4), oxalic acid (C2H2O4), chromic acid, hydrofluoric acid, or dipotassium phosphate (K2HPO4) may be used either alone or in combination of two or more.
The electrolyte may use desirably 0.1 to 0.5 M oxalic acid of −5 to 25° C., more desirably 0.27 to 0.33 M oxalic acid of 15 to 25° C., and most desirably 0.285 to 0.315 M oxalic acid of 19 to 21° C.
In the coating composition used in the step 4, the organic solvent may be pentane, hexane, heptane, or octane, used alone or in a combination of two or more and in the present invention, hexane is used as an example.
Desirably, the coating composition used in the step 4 may contain 0.01 to 10 parts by weight of a cross-linked PDMS (polydimethylsiloxane) derivative represented by Chemical Formula 1, based on 10 parts by weight of the organic solvent.
More desirably, the coating composition used in the step 4 may contain 0.04 to 5 parts by weight of a cross-linked PDMS (polydimethylsiloxane) derivative represented by Chemical Formula 1, based on 10 parts by weight of the organic solvent.
Still more desirably, the coating composition used in the step 5 may contain 0.04 to 2 parts by weight of a cross-linked PDMS (polydimethylsiloxane) derivative represented by Chemical Formula 1, based on 10 parts by weight of the organic solvent.
More desirably, the coating composition used in the step 4 may contain 0.04 to 1 parts by weight of a cross-linked PDMS (polydimethylsiloxane) derivative represented by Chemical Formula 1, based on 10 parts by weight of the organic solvent.
The most desirably, the coating composition used in the step 4 may contain 0.05 to 0.17 parts by weight of a cross-linked PDMS (polydimethylsiloxane) derivative represented by Chemical Formula 1, based on 10 parts by weight of the organic solvent.
If the content of the cross-linked PDMS derivative represented by Chemical Formula 1 is out of the above-mentioned range, there may be problems in that the oleophobicity and the hydrophobicity are degraded or the coating uniformity is insufficient.
The coating composition according to the present invention does not contain the PMDS (polydimethylsiloxane) derivative represented by the following Chemical Formula 2.
(In Chemical Formula 2, m is an integer of 1 to 100, desirably an integer of 1 to 80, and more desirably an integer of 1 to 60).
The coating composition may be used for drop coating, deep coating, and spin coating, but is not limited thereto.
Further, the present invention provides a 5000 series aluminum alloy on which an oleophobic and hydrophobic film manufactured by the above-described manufacturing method is formed.
Hereinafter, the present invention will be described in more detail with reference to following Examples. However, the following Examples are set forth to illustrate the present invention but are not to be construed to limit the present invention.
According to a method for forming an anodic oxide film on a surface of a metal base by the anodic oxidation of the related art, it is common to perform the pre-patterning process to form a microstructure pattern on a surface of a metal base and then perform anodic oxidation. The pre-pattering process is a process of performing anodic oxidation on the metal base to form an anodic oxide film and then etching the anodic oxide film to remove the formed oxide film, thereby remaining a microstructure pattern on a surface of a base material. The pre-pattering process is intended to uniformly form the anodic oxide film which is formed by the anodic oxidation which is a post-process, along a microstructure pattern of the surface of the base material formed by the pre-patterning process.
An object of the present invention is to provide a method for uniformly forming an anodic oxide film even without the pre-patterning process and the pre-patterning process is omitted to achieve a significant advantage in reducing manufacturing costs.
Specifically, according to the present invention, in order to form the anodic oxide film using an aluminum 5052 alloy as a base material by omitting the pre-patterning process and find out an anodic oxidation treatment condition to form the anodic oxide film with a pillar-on-pore (POP) structure in which a bundle of pillars is formed on a pore structure of the anodic oxide film, the followings are carried out.
Composition information of the aluminum 5052 alloy (Al 5052, size 20×30 mm, manufactured by Alcoa INC, USA) is as follows:
Mg 2.2 to 2.8%, Si 0.25%, Fe 0.40%, Cu 0.10%, Mn 0.10%, Zn 1.0%, Cr 0.15 to 0.35%, and Al balance
In order to remove impurities on a surface of the aluminum 5052 alloy, the alloy was washed by ultrasonic treatment in acetone at 20° C. for 10 minutes and in ethanol for 10 minutes.
In order to achieve a surface roughness, the ultrasonically washed aluminum 5052 alloy was placed in a mixed solution of ethanol and perchloric acid (Junsei, HClO4:C2H5OH=4:1 (v/v)) and electrochemically polished for 1 minute at room temperature (20° C.) by applying a voltage of 20 V. The aluminum alloy surface on which the electrochemical polishing was finished was confirmed to be flat with good reflection.
The electrochemically polished aluminum 5052 alloy (a thickness of 1 mm and a size of 20×30 mm) was used as a working electrode and a platinum (Pt) electrode was used as a cathode electrode and a distance between two electrodes was constantly maintained to be 5 cm to carry out the primary anodic oxidation. The primary anodic oxidation was performed using 0.3 M oxalic acid as the electrolyte while maintaining a temperature of the electrolyte constant at 20° C. using a double beaker. In order to suppress the disruption of stable oxide growth due to local temperature increase, stirring was performed at a constant speed, and the primary anodic oxidation process was performed by applying a voltage of 40 V for 1 to 10 minutes using a constant voltage method to grow an alumina layer.
The alumina layer which was grown by the primary anodic oxidation was subject to the pore widening (PW) process to immerse the alumina layer in 0.1 M phosphoric acid solution at 30° C. for 10 to 60 minutes before performing the secondary anodic oxidation.
The same process as the primary anodic oxidation was performed, but the secondary oxidation process was performed by fixing a voltage applying time to 5 minutes to further grow the alumina layer.
The primary anodic oxidation (step 1), the pore widening (step 2), and the secondary anodic oxidation (step 3) processes were performed under the condition of the following Table 1 to manufacture an anodic oxide film with a microstructure on a surface of the aluminum 5052 alloy.
Fabricate Examples 1-1 to 1-10 of Table 1 were specimens which have undergone only up to the primary anodic oxidation (step 1) and a surface (top view) and a cross-sectional surface (cross-view) thereof were observed using the field-emission scanning electronic microscope (FE-SEM) system (AURIGA®, small dual-bean FIB-SEM, Zeiss).
Specifically, each aluminum alloy anodic oxide film specimen was cut into small pieces and then fixed onto a stage with a carbon tape, and then coated with gold (Au) for 15 seconds by sputtering, and then imaged using the field-emission scanning electron microscope (SEM). At this time, a surface and a cross-sectional structure of the aluminum alloy anodic oxide film were observed by bending the film specimen at 90° to create parallel cracks.
As illustrated in
As illustrated in
When the anodic oxidation is performed, the thickness of the anodic oxide film is increased and when the pore widening is performed, a diameter of pore is increased and a part of an upper portion of the film is cut out to reduce a thickness somewhat. In the present invention, from the viewpoint that the thickness of the anodic oxide film in the final specimen through the primary anodic oxidation-pore widening-secondary anodic oxidation must be at least 1 m to secure durability and superhydrophilicity due to the microstructure, it was determined that it was the most appropriate to ensure the thickness of 700 to 800 nm by setting the primary anodic oxidation to 5 minutes.
(2) Analysis of Microstructure and Thickness of Anodic Oxide Film According to Pore Widening Time Examples 1-1 to 1-8 of Table 1 were specimens which have undergone only up to the pore widening (step 2) and a surface (top view) and a cross-sectional surface (cross-view) thereof were observed using the field-emission scanning electronic microscope (FE-SEM) system (AURIGA®, small dual-bean FIB-SEM, Zeiss).
As illustrated in
As illustrated in
In
Examples 1-1 to 1-8 of Table 1 were specimens which have undergone all to the secondary anodic oxidation (step 3) and a surface (top view) and a cross-sectional surface (cross-view) thereof were observed using the field-emission scanning electronic microscope (FE-SEM) system (AURIGA®, small dual-bean FIB-SEM, Zeiss).
As illustrated in
As illustrated in
In
From the result of Experimental Example 1, it is determined that desirably, the primary anodic oxidation is performed for 5 minutes at an application voltage of 40 V, the pore widening is performed for 35 to 40 minutes, and the primary anodic oxidation is performed for 5 minutes at an application voltage of 40 V.
Contact angles of specimens of Examples 1-1 to 18 with water (purified water) and oil (cooking oil) were measured and a result thereof was represented in the following Table 2 and
As represented in Table 2 and
A coating composition used to impart superhydrophobic and superoleophobic functionality to specimens of Examples 1-1 to 1-8 was evaluated.
Specifically, an aluminum 5052 alloy which had undergone only up to the electrochemical polishing process described in Examples was prepared as a metal base. That is, the anodic oxidation was not performed.
As coating agents, 60 L of SYLGARD 184 Silicon Elastomer Curing Agent (manufactured by Dow chemical company) which was a cross-linked PDMS derivative represented by Chemical Formula 1 and SYLGARD 184 Silicon Elastomer base (manufactured by Dow chemical company) which was a PDMS derivative represented by Chemical Formula 2 and/or hexane was dropped on the electrochemically polished aluminum 5052 alloy for every base material size of 2.5 cm×3 cm, and then the aluminum 5052 alloy was coated by spin coating method (corresponding to Examples 2, 4, 6, and 7). The spin coating was performed at 1000 rpm for 30 seconds. Further, as another coating method, drop coating was performed (corresponding to Examples 1, 3, 5, and 8 to 10). For the drop coating, after dropping an appropriate amount of coating agent, the base material was tilted to the left and right several times to be coated.
In Fabricate Examples 2-1 to 2-4, as a coating agent, a mixture of hexane, a main agent (base) (Chemical Formula 2), and a curing agent (Chemical Formula 1) was used and in Fabricate Examples 2-5 to 2-10, as a coating agent, a mixture of hexane and a curing agent (Chemical Formula 1) was used.
Next, the coated base material was thermally treated for 30 minutes in an oven of 300° C. to complete the curing.
For reference, the following coating composition of Fabricate Examples 2-1 to 2-10 was a composition used in prior application (Application No. 10-2021-0085454) of the inventor of this invention.
(In Chemical Formula 1, x and y are each an integer of 1 to 30).
In Chemical Formula 2, m is an integer of 1 to 100.
Water (purified water) and oil (cooking oil) were dropped on the specimens of Fabricate Examples 2-1 to 2-10 to evaluate a contact angle and a contact hysteresis angle and results were represented in the following Table 4.
Here, the ‘contact angle hysteresis’ was obtained by measuring an inclination angle at which a sample was placed on a stage of a device whose inclination may be finely adjusted, water or oil was dropped on the sample, and then the stage was gradually tilted so that water or oil began to flow down. That is, it may be said that the smaller the contact hysteresis angle, the better the hydrophobicity/oleophobicity. For example, when the contact hysteresis angle is 1°, water or oil flows down even if the sample is tilted by only 1°, and when the contact hysteresis angle is 90°, water or oil does not flow down even if the sample is erected at 90°.
The following Table 4 is a result obtained by evaluating the hydrophobicity and oleophobicity after coating a coating liquid according to Fabricate Examples 2-1 to 2-10 on a base material on which a micro-structured oxide film was not formed on a surface as a sample of the aluminum 5052 alloy base material on which the anodic oxidization was not performed.
As represented in Table 4, the contact hysteresis angle of Fabricate Example 2-10 was the smallest so that it was confirmed that the hydrophobicity/oleophobicity was excellent. Based on this result, in Experimental Example 4 to be described below, a coating composition according to Fabricate Example 2-10 was used.
The coating composition according to Fabricate Example 2-10 was coated on aluminum 5052 alloy with microstructure anodic oxide film obtained in Examples 1-1 to 1-8 as a base material. The detailed coating process was the same as in Experimental Example 3.
Water (purified water) and oil (cooking oil) were dropped on the coated specimens (Examples 2-1 to 2-8) to evaluate a contact angle and a contact hysteresis angle and results were represented in the following Table 5 and
Here, if the metal base is subject to anodic oxidation to form the POP microstructure on a surface, a superhydrophilic oxide film is formed. This is an effect caused by oxygen atoms included in the oxide film and the microstructure so that if the microstructure oxide film is coated with a hydrophobicity with a thickness as thin as a monomolecular film and the microstructure is maintained, superhydrophobicity may be realized.
As represented in Table 5 above, it was confirmed that the contact hysteresis angle of Examples 2-4 and 2-5 exhibited superhydrophobicity and superoleophobicity and specifically, Example 2-4 showed excellent effect.
From the results of Experimental Examples 3 and 4 above, it was confirmed that the sample of Fabricate Example 2-10 had excellent hydrophobicity and oleophobicity as well as excellent coatability and also formed a coating film thickness to be thin sufficient to maintain the microstructure.
Accordingly, in Experimental Example 5, in order to derive an optimal mixing ratio of a cross-linked PDMS derivative of Chemical Formula 1 and hexane suitable to be coated on a base material with a microstructure oxide film formed thereon, a contact hysteresis angle experiment was performed in the same manner as Experimental Example 3 and the result was represented in Table 6.
In the following Table 6, a curing agent and hexane of the coating agent were measured and indicated by weight ratio, and the base material was aluminum 5052 alloy formed with a POP microstructured oxide film obtained in Example 1-4 and similar to Fabricate Example 2-10, plasma treatment was not conducted, but drop coating was conducted to prepare a sample. [Table 6]
As represented in Table 6 above, it was confirmed that in Examples 3-3 to 3-8, a coating film thickness was formed to be thin sufficient to maintain the microstructure and the coating film was uniformly formed on the entire base material so that the hydrophobicity and the oleophobicity were significantly excellent. In the meantime, in Examples 3-1 and 3-2, it is expected that the content of the curing agent is too low so that the coating film is not formed in a part of the base material and in Example 3-9, it is expected that the content of the curing agent is too high so that the coating film is too thick to maintain the microstructure.
For now, the present disclosure has been described with reference to the exemplary embodiments. It is understood to those skilled in the art that the present disclosure may be implemented as a modified form without departing from an essential characteristic of the present disclosure. Therefore, the disclosed exemplary embodiments may be considered by way of illustration rather than limitation. The scope of the present invention is presented not in the above description but in the claims and it may be interpreted that all differences within an equivalent range thereto may be included in the present invention.
According to the present disclosure, the method for manufacturing a superhydrophilic anodic oxide film on a 5000 series aluminum alloy may manufacture a uniform anodic oxide film even without a pre-patterning step, thereby reducing manufacturing costs, may impart superhydrophobicity and superoleophobicity to the anodic oxide film according to a coating composition using a cross-linked PDMS derivative represented by Chemical Formula 1 and an organic solvent in a specific mixing ratio and the coating composition has an inexpensive manufacturing cost and adjusts a coating film thickness to several to several tens of nm to be applied to the coating of a microstructured oxide film.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0025826 | Feb 2022 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/017971 | 11/15/2022 | WO |
