US20140083843A1

US20140083843A1 - Preparation apparatus for porous alumina template

Info

Publication number: US20140083843A1
Application number: US14/035,122
Authority: US
Inventors: Cheng-Hsin Chuang; Yu-Min Shen; Sheng-Chang WANG; Sung-Wen TSAI
Original assignee: Southern Taiwan University of Science and Technology
Current assignee: Southern Taiwan University of Science and Technology
Priority date: 2012-09-25
Filing date: 2013-09-24
Publication date: 2014-03-27
Also published as: TWI465301B; TW201412432A

Abstract

Disclosing is a preparation apparatus of a porous alumina plate, including an electrolytic tank, an aluminum substrate, a negative electrode, a thermostatic apparatus, a circulation apparatus, and a power supply. The electrolytic tank includes an accommodating space and connects to a first opening and a second opening of the accommodating space, respectively, and a slot wall of the electrolytic tank is installed with an input tube and an output tube. The accommodating space is used to accommodate an electrolyte. The aluminum substrate and the negative electrode are installed on the first opening and the second opening, respectively, to contact the electrolyte. The thermostatic apparatus is used to maintain a temperature of the electrolyte, and the circulation apparatus is connected to the thermostatic apparatus and the electrolytic tank to circularly transport the electrolyte in the thermostatic apparatus and the electrolytic tank.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Taiwan Patent Application No. 101135155, filed on Sep. 25, 2012 in Taiwan Intellectual Property Office, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention is related to a preparation apparatus for a porous alumina plate, and particularly related to a preparation apparatus for a large area porous alumina plate.
2. Description of the Related Art
Porous material has long been used in industry and academic researches, and nano-scale porous material is gradually developed to meet the demand of advanced technologies in different areas. Furthermore, an anode oxidation reaction employing anodic oxidation of electrochemistry has been well noticed in recent years, the operation procedures are basically to put an acid solution into an electrolytic tank as an electrolyte, to use an aluminum substrate as an anode and a metal or carbon material as a cathode, to exert a current or a voltage to form a current circuit such that the surface of the aluminum substrate is oxidized to form an anodic oxidation aluminum (AAO) having nano array pores of fixed regularity.
The present nano-scale porous material possesses not only large surface area, but also various merits, for example, the excellent performances in antioxidation, anticorrosion, and anti-abrasion. Therefore, the present nano-scale porous material can not only withstand high temperature processes, but also possesses unique optical, electrical, magnetic, and mechanical properties. The present nano-scale porous material has been widely applied to the manufacturing of display panels, solar panels, a light-emitting layer of a light-emitting diode, and nano wires.
With the vigorous developments of nano structures, industry and academic research organizations are actively preparing to manufacture large area porous alumina plates. Due to the fact that the temperature of the electrolyte and the current density are not uniformly distributed in the oxidation process, however, porous alumina plates manufactured by using the current anodic oxidation reaction tend to have current density concentrated on specific areas and crack up, thus unable to produce large area porous alumina plates with ease.

SUMMARY OF THE MENTION

According to the problem of prior arts, one of the purpose of the present invention is to provide a preparation apparatus for a porous alumina plate to solve the easy cracking problem of porous alumina plates during the manufacturing process.
Based on the other purpose of the present invention, a preparation apparatus for a porous alumina plate is proposed to uniformly distribute the current density over a aluminum substrate.
Based on another purpose of the present invention, a preparation apparatus for a porous alumina plate is proposed to solve the problem of uneven temperature distribution of a electrolyte.
To achieve the aforementioned purposes, a preparation apparatus for a porous alumina plate is proposed, including an electrolytic tank, an aluminum substrate, a negative electrode, a thermostatic apparatus, a circulation apparatus, a power supply. The electrolytic tank includes an accommodating space and is connected to a first opening and a second opening of the accommodating space, respectively, a slot wall of the electrolytic tank is installed with an input tube and an output tube, the accommodating space is used to accommodate an electrolyte, the input tube is close to the first opening, and the output tube is away from the first opening. The aluminum substrate is installed on the first opening of the electrolytic tank to contact the electrolyte within the accommodating space, and the negative electrode Contacts the electrolyte within the accommodating space through the second opening of the electrolytic tank. The thermostatic apparatus is to maintain a temperature of the electrolyte, and the circulation apparatus is connected to the thermostatic apparatus and the input tube or the output tube of the electrolytic tank to circularly transport the electrolyte within the thermostatic apparatus and the electrolytic tank. The power supply is to provide a positive electric potential and a negative electric potential to the aluminum substrate and the negative electrode, respectively, to produce a voltage difference between the aluminum substrate and the negative electrode, such that the aluminum substrate is oxidized to obtain the porous alumina plate. Furthermore, the electrolytic tank is a acid and alkali resistant tank made of Teflon material, the electrolyte is sulfuric acid, oxalic acid, or phosphorus acid, and material of the negative electrode is platinum or stainless steel. Besides, the circulation apparatus is a peristaltic pump, the flow rate of the circulation apparatus is between 1 ml/s and 11000 ml/s, the temperature of the electrolyte is maintained at 4° C., and the voltage difference aluminum substrate and negative electrode is within 15 V to 300 V.
Furthermore, the preparation apparatus for the porous alumina plate of the present invention further comprises a waterproof gasket and a seal valve. The waterproof gasket is installed between the aluminum substrate and the electrolyte within the electrolytic tank to prevent the electrolyte from leaking out of the first opening. The seal valve installed at the second opening is to fix the negative electrode, such that the aluminum substrate and the negative electrode is separated from 3 to 10 centimeters.
As mentioned above, the preparation apparatus of the porous alumina plate of the present invention may have one or more characteristics and advantages as described below:
(1) The preparation apparatus for the porous alumina plate of the present invention is able to solve the problem of uneven temperature distribution of the electrolyte by means of the thermostatic apparatus to maintain the temperature of the electrolyte.
(2) The preparation apparatus for the porous alumina plate of the present invention is able to uniformly distribute the current density over the aluminum substrate by means of the circulation apparatus to circularly transport the electrolyte within the thermostatic apparatus and the electrolytic tank.
(3) The preparation apparatus for the porous alumina plate of the present invention is able to separate the electrode connected to the aluminum substrate from the electrolyte to exclude the problems of electricity leakage and electricity wire erosion. Besides, the backside erosion problem can be avoided because the backside of the aluminum substrate does not contact the electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a preparation apparatus for a porous alumina plate according to a preferred embodiment of the present invention.

FIG. 2 is a decomposed diagram showing an electrolytic tank, an aluminum substrate, and a negative electrode before assembling according to the preferred embodiment of the present invention.

FIG. 3 is a diagram showing the preparation apparatus for the porous alumina plate according to the preferred embodiment of the present invention.

FIG. 4 is a current vs. time diagram showing manufacturing of the porous alumina plate according to the preferred embodiment of the present invention.

FIG. 5 is a scanning electron microscope top view diagram showing the porous alumina plate manufactured by the preparation apparatus according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, FIG. 1 is a block diagram showing a preparation apparatus for a porous alumina plate according to a preferred embodiment of the present invention. As shown in FIG. 1, a preparation apparatus for a porous alumina plate of the present invention includes an electrolytic tank 10, an aluminum substrate 20, a negative electrode 30, a thermostatic apparatus 40, a circulation apparatus 50, and a power supply 60. The aluminum substrate 20 and the negative electrode 30 are installed within the electrolytic tank 10, and the power supply 60 is electrically connected to the aluminum substrate 20 and the negative electrode 30. The thermostatic apparatus 40 is used to maintain a temperature of the electrolyte, and the circulation apparatus 50, the thermostatic apparatus 40, and the electrolytic tank 10 constitute an inter-connected channel, such that the circulation apparatus 50 is able to circularly transport the temperature-stabilized electrolyte to the electrolytic tank 10. FIG. 1 is used to explain the apparatus structure of the preparation apparatus for the porous alumina plate of the present invention, the connection manner of the electrolytic tank 10, the aluminum substrate 20, the negative electrode 30, the thermostatic apparatus 40, the circulation apparatus 50, and the power supply 60 shown in FIG. 1 is not limited thereof.
Referring to FIG. 2, FIG. 2 is a decomposed diagram showing an electrolytic tank, an aluminum substrate, and a negative electrode before assembling according to the preferred embodiment of the present invention. The electrolytic tank 10 includes an accommodating space 12 and is connected to a first opening 13 and a second opening 15 of the accommodating space 12, respectively, and a slot wall of the electrolytic tank 10 is installed with an input tube 17 and an output tube 19. The accommodating space 12 is used to accommodate an electrolyte, the input tube 17 is close to the first opening 13, and the output tube 19 is away from the first opening 13. The aluminum substrate 20 is installed on the first opening 13 of the electrolytic tank 10 to contact the electrolyte within the accommodating space 10, and the negative electrode 30 contacts the electrolyte within the accommodating space 12 through the second opening 15 of the electrolytic tank 10. Furthermore, the electrolytic tank 10 is a acid and alkali resistant tank made of Teflon material, the electrolyte is sulfuric acid, oxalic acid, or phosphorus acid, and material of the negative electrode 30 is platinum or stainless steel. The type of the electrolyte and the material of the electrolytic tank 10 and the negative electrode 30 are not limited thereof.
Referring to FIG. 3, FIG. 3 is a diagram showing the preparation apparatus for the porous alumina plate according to the preferred embodiment of the present invention. As shown in FIG. 3, the electrolytic tank 10, the aluminum substrate 20, and the negative electrode 30 in FIG. 2 are assembled first, and then a tube 52 is connected to the thermostatic apparatus 40 and the circulation apparatus 50, such that the circulation apparatus 50 is connected to the thermostatic apparatus 40 and the input tube 17 of the electrolytic tank 10 to achieve the purpose of circularly transporting the electrolyte within the thermostatic apparatus 40 and the electrolytic tank 10. Besides, the connection manner of the tube 52 to the thermostatic apparatus 40 and the circulation apparatus 50 is not limit thereof. A user can further connect the circulation apparatus 50 to the thermostatic apparatus 40 and the output tube 19 of the electrolytic tank 10 to achieve the same purpose of circularly transporting the electrolyte within the thermostatic apparatus 40 and the electrolytic tank 10. By means of the circulation apparatus 50 to circularly transport temperature-stabilized electrolyte, the preparation apparatus for the porous alumina plate of the present invention is able to solve the uneven distribution problem of the electrolyte temperature within the electrolytic tank 10 and uniformly distribute the current density over the aluminum substrate 20, so as to achieve the goal of manufacturing large area porous alumina plates.
As shown in FIG. 3, the power supply 60 is to provide a positive electric potential and a negative electric potential to the aluminum substrate 20 and the negative electrode 30, respectively, to produce a voltage difference between the aluminum substrate 20 and the negative electrode 30, such that the aluminum substrate 20 is oxidized to obtain the porous alumina plate. Furthermore, the circulation apparatus is, for example, a peristaltic pump, and flow rate of the circulation apparatus is, for example, 1 ml/s to 11000 ml/s, preferred to be 2000 ml/s to 3000 ml/s_;and even better to be 2800 ml/s. The stationary temperature of the electrolyte is, for example, −4□ to 4□, preferred to be 0□ to 4□, and even better to be 4□. The voltage difference between the aluminum substrate and the negative electrode is, for example, 15 V to 300 V, preferred to be 40 V to 80 V, and even better to be 40V.
Besides, the preparation apparatus for the porous alumina plate of the present invention further includes, for example, a waterproof gasket 70 and a seal valve 80, as shown in FIG. 3. The waterproof gasket 70 is installed between the aluminum substrate 20 and the electrolyte within the electrolytic tank 10 to prevent the electrolyte from leaking out of the first opening. Since the contact surface of the aluminum substrate 20 with the electrolyte within the electrolytic tank 10 is the reaction surface of the anodic oxidation reaction, installing the waterproof gasket 70 between the aluminum substrate 20 and the electrolyte within the electrolytic tank 10 can not only prevent the electrolyte from leaking out, but also further define the area of the porous alumina plate generated by the anodic oxidation reaction. The seal valve 80 is installed at the second opening 15 to fix the negative electrode 30, such that the aluminum substrate 20 and the negative electrode 30 are separated from 3 to 10 centimeters. The distance between the aluminum substrate 20 and the negative electrode 30 can be adjusted according to practical demands. Besides, installing the seal valve 80 at the second opening 15 can effectively prevent the electrolyte from leaking out of the second opening 15.
For example, the manufacturing flow of porous alumina plates by applying the preparation apparatus for the porous alumina plate of the present invention is as following. First, an aluminum substrate 20 of purity 99.9 to above 99.999% is put into acetone and alcohol and supersonic waves is used to oscillate for 10 to 30 minutes to remove the filth on the surface of the aluminum substrate 20. Afterward, the aluminum substrate 20 is acid-washed by using deionized water and acid solutions such as hydrogen fluorine acid, hydrochloric acid, or nitric acid, etc. Finally, perchloric acid and alcohol are used to perform electrochemical polishing, thus conclude the pre-processing of the aluminum substrate 20.
Next, the aluminum substrate 20 and the negative electrode 30 after the pre-processing are packaged in the manner shown in FIG. 3. During the packing process, the electrolytic tank 10, the waterproof gasket 70, and the aluminum substrate 20 can be tightly jointed by further applying methods such as screw packing, etc., to prevent the electrolyte from leaking to the back side of the aluminum substrate 20 which is for performing the anodic oxidation reaction. After finishing packaging the testpiece of the aluminum substrate 20, the input tube 17 and the output tube 19 are connected to the circulation apparatus 50 and the thermostatic apparatus 40, respectively, to circularly transport the temperature-stabilized electrolyte. Afterward, a positive potential end and a negative potential end of the power supply 60 are electrically connected to the aluminum substrate 20 and the negative electrode 30, respectively, thus finish the overall apparatus of the preparation apparatus for the porous alumina plate of the present invention. Based on practical demands, a user can adjust the temperature of the electrolyte, the circulation flow rate or flow speed of the electrolyte, and the voltage difference between the aluminum substrate 20 and the negative electrode 30 to produce the desired porous alumina plate.
Referring to FIG. 4, FIG. 4 is a current vs. time diagram showing manufacturing of the porous alumina plate according to the preferred embodiment of the present invention. Furthermore, the X axis represents the duration of the anodic oxidation reaction, the Y axis represents the current of the anodic oxidation reaction, and the voltage difference between the aluminum substrate and the negative electrode is 40 V. As shown in FIG. 4( a) to (b), a uniform alumina layer is formed on the surface of the aluminum substrate in the early stage of the anodic oxidation reaction and causes the resistance to rise sharply and the current to drop evidently; as shown in FIG. 4( c) to (d), the growing of the alumina pores causes part of the alumina to gradually dissolve, such that the resistance is gradually dropping and the current is gradually rising; as shown in FIG. 4( d) to (e), the generation and dissolution of the alumina reaches dynamic equilibrium and the current also remains in an equilibrium state, such that the porous alumina is able to stably grow downward. Due to the generation and dissolution of the alumina reaches dynamic equilibrium, it can be verified that the preparation apparatus for the porous alumina plate of the present invention can be actually use to prepare large area porous alumina plates. Furthermore, the areas of the porous alumina plates, which are manufactured by using the preparation apparatus for the porous alumina plate of the present invention, are up to 51 cm².
Referring to FIG. 5, FIG. 5 is a scanning electron microscope top view diagram showing the porous alumina plate manufactured by the preparation apparatus according to the preferred embodiment of the present invention, Furthermore, the magnifying power in FIG. 5( a) is 30000, and that of FIG. 5( b) is 100000. As shown in FIG. 5( a) and (b), nano-scale porous alumina plates having uniform sizes in appearance and complete structures can be produced by using the preparation apparatus for the porous alumina plate of the present invention, and the porous alumina plate has the hexagonal close packing structure.
The aforementioned preferred embodiment is to explain the technical ideas and features of the present invention. The purpose is to enable those who skilled in this technical area to understand the content of the present invention and realize it. It will be understood that the present invention is not limited to the details thereof Various equivalent. variations and modifications may still occur to those skilled in this art in view of the teachings of the present invention. Thus, all such variations and equivalent Modifications are also embraced within the scope of the present invention as defined in the appended claims.

Claims

What is claimed is:

1. A preparation apparatus for a porous alumina plate, comprising:

an electrolytic tank, comprising an accommodating space and connected to a first opening and a second opening of the accommodating space, respectively, a slot wall of the electrolytic tank being installed with an input tube and an output tube, the accommodating space being used to accommodate an electrolyte, the input tube being close to the first opening, and the output tube being away from the first opening;

an aluminum substrate, being installed on the first opening of the electrolytic tank to contact the electrolyte within the accommodating space;

a negative electrode, contacting the electrolyte within the accommodating space through second opening of the electrolytic tank;

a thermostatic apparatus, to maintain a temperature of the electrolyte;

a circulation apparatus, connected to the thermostatic apparatus and the input tube or the output tube of the electrolytic tank to transport the electrolyte within the thermostatic apparatus and the electrolytic tank; and

a power supply, to provide a positive electric potential and a negative electric potential to the aluminum substrate and the negative electrode, respectively, to produce a voltage difference between the aluminum substrate and the negative electrode, such that the aluminum substrate being oxidized to obtain the porous alumina plate.

2. The preparation apparatus for a porous alumina plate of claim 1, wherein a waterproof gasket is further installed between the aluminum substrate and the electrolyte within the electrolytic tank to prevent the electrolyte from leaking out of the first opening.

3. The preparation apparatus for a porous alumina plate of claim 1, further comprising a seal valve installed at the second opening to fix the negative electrode, such that the aluminum substrate and the negative electrode is separated from 3 to 10 centimeters.

4. The preparation apparatus for a porous alumina plate of claim 1, wherein the electrolytic tank is a acid and alkali resistant tank made of Teflon material.

5. The preparation apparatus for a porous alumina plate of claim 1, wherein the electrolytic is sulfuric acid, oxalic acid, or phosphorus acid.

6. The preparation apparatus for a porous alumina plate of claim 1, wherein the temperature of the electrolyte is maintained at 4° C.

7. The preparation apparatus for a porous alumina plate of claim 1, Wherein the circulation apparatus is a peristaltic pump.

8. The preparation apparatus for a porous alumina plate of claim 1, wherein the flow rate of the circulation apparatus is between 1 ml/s and 11000 ml/s.

9. The preparation apparatus for a porous alumina plate of claim 1, wherein material of the negative electrode is platinum or stainless steel.

10. The preparation apparatus for a porous alumina plate of claim 1, wherein the voltage difference is between 15 V and 300 V.