Method of fabricating hydrophilic-hydrophobic transformable composite film

Abstract

A method of fabricating a hydrophilic-hydrophobic transformable composite film is provided. The method includes forming a silicon-containing layer on an iron-containing substrate; coating a titanium-containing sol-gel film on the said silicon-containing layer; and heating the iron-containing substrate with the silicon-containing layer and the titanium-containing sol-gel film thereon.

Claims

1. A method of fabricating a hydrophilic-hydrophobic transformable composite film, comprising: (A) forming a silicon layer, by a sputtering process, on an iron-containing substrate; (B) spin-coating a titanium-containing sol-gel film on the said silicon layer for twice or more; and (C) heating the iron-containing substrate with the silicon containing layer and the titanium-containing sol-gel film thereon after the step (B) such that the titanium-containing sol-gel film is formed into a porous film, wherein the iron-containing substrate is made of interstitials free (IF) steel, and the porous film is formed of anatase titanium oxide; and wherein sputtering conditions of the sputtering process are as follows: the distance between a target and the iron-containing substrate is 5 cm, the processing time is 20 minutes, the chamber bottom pressure is 3.5×10.sup.−5 torr, the working pressure is 8.5×10.sup.−3 torr, the argon flow rate is 30 sccm, and the operating power is 125 W.

2. The method as claimed in claim 1, wherein the heating temperature of step (C) is 350° C.˜450° C.

3. The method as claimed in claim 2, wherein the heating temperature of step (C) is 400° C.

4. The method as claimed in claim 1, wherein a titanium-containing sol-gel of the titanium-containing sol-gel film is titanium isopropoxide sol-gel, or titanium tetraisopropoxide sol-gel.

5. The method as claimed in claim 1, wherein the step (C) is heating the iron-containing substrate with the silicon layer and the titanium-containing sol-gel film thereon by a furnace.

6. The method as claimed in claim 5, wherein a pre-heating rate of the step (C) is 5° C./min, and the heating temperature of the step (C) is 400° C.

7. The method as claimed in claim 6, wherein the heating time of the step (C) is 1 hour.

8. The method as claimed in claim 1, further comprising: (D) cooling the iron-containing substrate with the silicon containing layer and the porous film thereon.

9. The method as claimed in claim 1, wherein a titanium-containing sol-gel of the titanium-containing sol-gel film contains titanium isopropoxide, isopropyl alcohol, 2-ethylcaproic acid, and polyethylene glycol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed Description of the Preferred Embodiment

Example 1

(1) Preparation of Titanium-Containing Sol-Gel

(2) 0.025 mol of titanium isopropoxide (TIP) is added to 30 ml of isopropyl alcohol (IPA), 0.01 mol of 2-ethylcaproic acid (EA) and 0.6 g of polyethylene glycol (PEG) is then added thereto. Isopropyl alcohol is added to dilute the above mixture volume to 50 ml followed with 2 hrs of ultrasonic mixing, thus the titanium-containing sol-gel is prepared.

(3) Preparation of Hydrophilic-Hydrophobic Transformable Composite Film

(4) A silicon layer is formed on a pre-cleaning substrate by using a sputtering process, in which the sputtering conditions are as following.

(5) Distance between the target and the substrate: 5 cm

(6) Processing time: 20 min

(7) Chamber bottom pressure: 3.5×10−5 torr

(8) Working pressure: 8.5×10−3 torr

(9) Argon flow rate: 30 sccm

(10) Operating power: 125 W

(11) The silicon layer made by sputtering may have a preferred heat resistance, but the method of making the silicon layer is not limited thereto. Subsequently, the prepared titanium-containing sol-gel is coated twice at 1500 rpm on the above substrate having the silicon layer formed thereon. Further, the substrate is heated at 400° C. (the pre-heating rate is 5° C./min) for 1 hour of calcination followed with furnace cooling to the room temperature. Therefore, the hydrophilic-hydrophobic transformable composite film of the present example is fabricated.

(12) The hydrophilic and hydrophobic properties of the present composite film are switched by UV light illumination. In detail, the composite film is hydrophobic before being exposed to UV light, but changes to hydrophilic after being exposed to UV light, and changes back to hydrophobic after releasing without further exposure to UV light in a period of time, for example, about 24 hours.

(13) The substrate used in the present example should be an iron-containing substrate, which can be made of stainless steel or interstitials free (IF) steel etc. Because interstitials free (IF) steel is a commercially reachable material with low price, an iron-containing substrate made of interstitials free (IF) steel is used in the present example.

(14) The coating times of the titanium-containing sol-gel film on the silicon layer, which is formed on the iron-containing substrate, are not limited. The titanium-containing sol-gel film can be coated on the silicon layer for once, twice, three times, or more in order to adjust the thickness of the titanium-containing sol-gel film to enable the forming of porous film (anatase titanium oxide) that further becomes an excellent catalyst. The porous film is advanced in many advantages comprising (1) good solidifying ability; (2) well-controlled particle size of TiO.sub.2 particles wherein the minimum particle size is 100 nm or less, which may result in excellent quantum effect; and (3) high uniformity of TiO.sub.2 particle distribution that means the aggregation phenomenon is reduced, which results in the increasing of the contact area with UV light.

Example 2

(15) The same method as described in Example 1 is used to fabricate the hydrophilic-hydrophobic transformable composite film of the present example, except that the coating of the titanium-containing sol-gel film is performed three times instead of twice and the silicon layer is replaced by a silicon oxide layer.

(16) According to the three-times-coated titanium-containing sol-gel film, the distribution depth of the Ti element is 1.3 μm and the concentration in the depth of 1.0 μm is about 10 at. % after being calcined.

Example 3

(17) Preparation of Titanium-Containing Sol-Gel

(18) 0.025 mol of titanium isopropoxide (TIP) is added to 30 ml of isopropyl alcohol (IPA), 0.01 mol of 2-ethylcaproic acid (EA) and 0.6 g of polyethylene glycol (PEG) is then added thereto. Isopropyl alcohol is added to dilute the above mixture volume to 50 ml followed with 2 hrs of ultrasonic mixing, thus the titanium-containing sol-gel is obtained.

(19) Preparation of Silicon Oxide Sol-Gel

(20) 5 ml of 0.1N acetic acid and 0.025 mol of tetraethoxysilane (TEOS) is added to 30 ml of isopropyl alcohol. After mixing, more isopropyl alcohol is added to dilute the above mixture volume to 50 ml to form the silicon sol-gel.

(21) Preparation of Hydrophilic-Hydrophobic Transformable Composite Film

(22) The above-prepared silicon sol-gel is coated on a pre-cleaned interstitials free (IF) steel substrate followed with drying. Then, a titanium-containing sol-gel film is formed by coating the titanium-containing sol-gel for three times on the dried silicon sol-gel layer following with heating at 400° C. (the pre-heating rate is 5° C./min) for 1 hour of calcination. Finally, the substrate is subjected to furnace cooling to the room temperature, thus the hydrophilic-hydrophobic transformable composite film of the present example is obtained.

Comparative Example 1

(23) A pre-cleaned interstitials free (IF) steel substrate is heated at 400° C. (the pre-heating rate is 5° C./min) for 1 hour followed with furnace cooling to the room temperature. Accordingly, the sample of the present comparative example is prepared.

Comparative Example 2

(24) Use the same method as described in Example 1 to prepare titanium-containing sol-gel, then coat the prepared titanium-containing sol-gel on a pre-cleaning interstitials free (IF) steel substrate. The coated IF steel substrate is then heated at 400° C. (the pre-heating rate is 5° C./min) for 1 hour of calcination followed with furnace cooling to the room temperature. Accordingly, the sample of the present comparative example is prepared.

Experiment Example 1

(25) Take the hydrophilic-hydrophobic transformable composite films of Examples 1 and 3, and the samples of Comparative Examples 1 and 2 for water-contacting angle test to compare the contact angles of those films and samples before and after exposing to UV light. The results are listed in Table 1.

(26) TABLE-US-00001 TABLE 1 Contact angle before Contact angle after UV light exposing UV light exposing Example 1  93.10° 0°  Example 3  99.36°  25.85° Comparative 117.08° 110.00° Example 1 Comparative 133.99° 107.65° Example 2

(27) According to the results of Examples 1 and 3 shown in Table 1, a great difference between contact angles of the films before and after exposing to UV light is shown, in which the contact angle of the film made from Example 1 after exposing to UV light is 0°, which means the hydrophilic-hydrophobic transformable composite film of Example 1 is completely changed to hydrophilic after exposing to UV light. Namely, from the testing results, it is shown that the composite film of the present invention has excellent hydrophilic-hydrophobic transforming ability.

(28) Comparing the testing results of composite films of Examples 1 and 3, it can be seen that the composite film in which the silicon-containing layer is formed by sputtering (Example 1) shows a better hydrophilic-hydrophobic transforming ability compared to the composite film in which the silicon-containing layer is formed by sol-gel process (Example 3).

(29) However, there is no apparent hydrophilic-hydrophobic transforming shown from testing results of Comparative Examples 1 and 2 before and after UV light illuminating, which means substrates having titanium-containing sol-gel films but no silicon-containing layer formed thereon can not obtain the expected hydrophilic-hydrophobic transforming ability.

(30) As mentioned above, the hydrophilic-hydrophobic transformable composite film of the present invention has excellent hydrophilic-hydrophobic transforming efficiency wherein the hydrophilic-hydrophobic transforming is switched by UV light exposing. The composite film of the present invention is hydrophobic before being exposed to UV light, but changes to hydrophilic after being exposed to UV light, and changes back to hydrophobic after releasing without further exposure to UV light in a period of time. Moreover, the contact angle of the composite film of the present invention after exposing to UV light is 0°, which means the composite film is completely changed to hydrophilic after exposing to UV light and such phenomenon cannot be reached by the prior arts.

(31) The hydrophilic-hydrophobic transformable composite film of the present invention can be extensively applied into the fabrication of various apparatus such as sanitary equipment, vehicle outer shells, exterior wall tiles, etc., and therefore can improve the self-cleaning property of these apparatus when being applied. Accordingly, the hydrophilic-hydrophobic transformable composite film and the method fabricating thereof are indeed more practical than the material of merely hydrophilic properties of the prior arts.

(32) Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.