Titanium dioxide coated by atomic layer deposition and preparation method and application thereof

Abstract

The invention relates to the field of chemical engineering, in particular to titanium dioxide coated by atomic layer deposition and a preparation method and application thereof. The preparation method comprises the following steps: 1) placing titanium dioxide in a rotary reaction cavity, and then rotating under protective gas; 2) introducing a precursor 1 into the reaction cavity in a pulse manner, wherein the introduced precursor 1 is adsorbed on the surface of titanium dioxide; (3) after adsorption equilibrium, introducing a precursor 2 into the reaction cavity in a pulse manner, and reacting and adsorbing the introduced precursor 2 and the precursor 1 on the surface of the titanium dioxide; (4) repeating the step (2) and the step (3) until a thin film with the required thickness is deposited on the surface of the titanium dioxide; wherein the precursor 1 is a silicon-containing precursor or an aluminum-containing precursor, and the precursor 2 is an oxygen-containing precursor. According to the prepared multilayer coated titanium dioxide, the photocatalytic activity of titanium dioxide is remarkably reduced, and the titanium dioxide has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to a titanium dioxide powder coated with multiple layers by atomic layer deposition, a preparation method thereof and uses thereof. Background Art

[0002] Ultrafine titanium dioxide (TiO2) powder is the most commonly used white pigment, with global consumption exceeding 7 million tons per year. When used as a pigment, it is often combined with organic matter. Ultrafine titanium dioxide powder has high photocatalytic activity, which can cause organic matter to turn yellow or degrade when exposed to light, changing the hue or performance of the object. Physical isolation methods such as inorganic insulating oxide coating of ultrafine titanium dioxide powder are important methods for maintaining its white pigment properties while reducing its photocatalytic activity. In applications such as coatings and plastics, TiO2 coating can improve the material's anti-aging, weather resistance, and hydrophilicity, extending the product's service life. In addition, in the medical and energy fields, TiO2 coating can help improve the biocompatibility of implants and the stability of battery materials. Currently, the main methods for titanium dioxide coating include: sol-gel method, chemical vapor deposition method, mechanical grinding method, etc.

[0003] CN103897437A discloses a method for coating titanium dioxide with alumina using a sol-gel method, using an organoaluminum compound as a precursor to obtain an alumina sol, and then subjecting titanium dioxide to the electrostatic interaction and condensation reaction of the alumina sol to achieve the alumina coating. This method requires multiple washings to remove organic matter or inorganic ions, thus generating a large amount of wastewater; the coating layer is not dense enough or cannot be conformally coated, causing the pigment particle size to become larger and the particle distribution to become wider. CN105668622A discloses a method for coating titanium dioxide with silicon dioxide using a low-pressure chemical vapor deposition method, the technical feature of which is to spread the heat-treated titanium dioxide powder in a culture dish, place it in a vacuum dryer, and use silicon tetrachloride as a precursor to perform silicon oxide coating. On the one hand, this method cannot accurately control the amount of silicon tetrachloride precursor introduced, and its hydrolysis will produce HCl gas, the exhaust gas corrodes the equipment, and excessive silicon tetrachloride causes the film layer to be uneven; on the other hand, the titanium dioxide powder is in a static state, the titanium dioxide on the surface is in full contact with the silicon tetrachloride gas, and the coating will be relatively uniform, while the powder on the bottom layer has less and uneven coating.

[0004] Therefore, it is of great significance to develop uniform and conformal titanium dioxide coating methods at the nanoscale. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a titanium dioxide powder coated with multiple layers by atomic layer deposition, and a preparation method and use thereof, so as to solve the problems in the prior art.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a method for coating titanium dioxide using atomic layer deposition, the method comprising the following steps:

[0007] 1) Placing titanium dioxide in a rotary reaction chamber and then rotating it under protective gas;

[0008] 2) introducing a pulse of precursor 1 into the reaction chamber, and the introduced precursor 1 is adsorbed on the surface of titanium dioxide;

[0009] 3) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber, and the introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide to form a silicon dioxide film and / or an aluminum oxide film;

[0010] 4) Repeating steps 2) and 3) until a film of desired thickness is deposited on the surface of the titanium dioxide;

[0011] The precursor 1 is a silicon-containing precursor or an aluminum-containing precursor, and the precursor 2 is an oxygen-containing precursor.

[0012] The present invention also provides a multi-layer coated titanium dioxide, which is prepared by the above method.

[0013] As described above, the titanium dioxide powder coated with multiple layers by atomic layer deposition and its preparation method and use of the present invention have the following beneficial effects:

[0014] 1) Using a rotary atomic layer deposition system (RP-ALD) to achieve a conformal, dense, adjustable Si / Al ratio Si-Al oxide coating on the surface of titanium dioxide with controllable nanoscale dimensions;

[0015] 2) By coating with silica and alumina, the photocatalytic activity of titanium dioxide is reduced on the one hand, and its compatibility with nylon, resin, etc. is improved on the other hand, thereby improving the weather resistance of the polymer material and extending its service life;

[0016] 3) During the coating process, silicon and aluminum precursors need to be introduced separately, and then water vapor, ozone and other reactants are introduced. The coating thickness is increased through multiple cycles, and the coating is continuous without wastewater discharge.

[0017] 4) Compared with sol-gel and other coating methods, this method has the advantages of simple operation, basically no change in the size of the pigment titanium dioxide, atomic-level film precision, dense and uniform, and no waste liquid. It is a more energy-saving, environmentally friendly, efficient and intelligent manufacturing coating method.

[0018] 5) Titanium dioxide coated with a composite material prepared by coating with silicon dioxide (SiO2) film and aluminum oxide (Al2O3) film utilizes the synergistic effect of the inert isolation of the inner layer (SiO2) and the stable protection of the outer layer (Al2O3), which not only effectively solves the contradiction between the photocatalytic activity and weather resistance of titanium dioxide, but also further inhibits the photocatalytic activity of titanium dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a transmission electron microscope photograph of titanium dioxide coated with 40 circles of SiO2 in Example 3 of the present invention.

[0020] Figure 2 Shown is a high-resolution transmission electron microscope photograph of titanium dioxide coated with 80 circles of SiO2 in Example 5 of the present invention.

[0021] Figure 3 Shown are the transmission electron microscope energy spectrum element distribution diagrams of titanium dioxide coated with 10 circles of Al2O3 in Example 6; (a) dark field image; (b) O element distribution diagram; (c) Al element distribution diagram.

[0022] Figure 4 Shown are the transmission electron microscope energy spectrum element distribution diagrams of titanium dioxide coated with 80 circles of SiO2 and 10 circles of Al2O3 in Example 7; (a) dark field image; (b) Ti element distribution diagram; (c) O element distribution diagram; (d) Si element distribution diagram; (e) Al element distribution diagram; (f) overall distribution diagram.

[0023] Figure 5 Schematic diagram of the photocatalytic performance of titanium dioxide coated in Examples 2, 3, 4, 5, and 7. DETAILED DESCRIPTION

[0024] The present invention uses silicon-containing precursors and aluminum-containing precursors as precursors and introduces them into the reaction chamber through a carrier gas. They are fixed on the surface of titanium dioxide powder through monolayer chemical adsorption, and excess precursors are removed by vacuum. The adsorption rate and uniformity of the powder are improved by a rotating device, and the saturated adsorption state is detected by mass spectrometry. Then, an oxidant hydrolyzing agent such as ozone or water is introduced through a carrier gas to convert the chemically adsorbed monolayer into oxides, basic oxides or hydroxides.

[0025] The present invention first provides a method for coating titanium dioxide using atomic layer deposition, the method comprising the following steps:

[0026] 1) Placing titanium dioxide in a rotary reaction chamber and then rotating it under protective gas;

[0027] 2) introducing a pulse of precursor 1 into the reaction chamber, and the introduced precursor 1 is adsorbed on the surface of titanium dioxide;

[0028] 3) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber, and the introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide to form a silicon dioxide film and / or an aluminum oxide film;

[0029] 4) Repeating steps 2) and 3) until a film of desired thickness is deposited on the surface of the titanium dioxide;

[0030] Wherein, the precursor 1 is a silicon-containing precursor or an aluminum-containing precursor, and the precursor 2 is an oxygen-containing precursor.

[0031] In certain embodiments of the present invention, in step 1), the titanium dioxide is ultrafine TiO2 powder. Typically, the particle size of the ultrafine TiO2 powder is in the nanometer to micrometer range, specifically, the particle size of the ultrafine TiO2 powder is 10 to 100 nm.

[0032] In certain embodiments of the present invention, in step 1), the titanium dioxide is anatase phase or rutile phase titanium dioxide.

[0033] In the present invention, the titanium dioxide is pigment-grade titanium dioxide powder, which can be primary titanium dioxide produced by the sulfuric acid process or the chlorination process, and can be particles without any surface treatment or after coating treatment.

[0034] In certain embodiments of the present invention, in step 1), the rotation speed of the reaction chamber is 40-90 rpm. The rotation speed of the reaction chamber is selected from any of the following ranges: 40-50 rpm, 50-60 rpm, 60-70 rpm, 70-80 rpm, and 80-90 rpm. Preferably, the rotation speed of the reaction chamber is 40-50 rpm.

[0035] In certain embodiments of the present invention, in step 1), the protective gas is nitrogen.

[0036] In certain embodiments of the present invention, in step 1), the flow rate of the shielding gas is 200-400 sccm. The flow rate of the shielding gas is selected from any of the following ranges: 200-240 sccm, 240-280 sccm, 280-320 sccm, 320-360 sccm, and 360-400 sccm. Preferably, the flow rate of the shielding gas is 200-240 sccm.

[0037] In certain embodiments of the present invention, in step 1), the titanium dioxide is placed in front of the rotary reaction chamber, and the titanium dioxide is also dried.

[0038] In certain embodiments of the present invention, in step 1), after placing the titanium dioxide in the rotary reaction chamber, the step further includes heating and vacuuming the reaction chamber.

[0039] Furthermore, the temperature of the reaction chamber is raised to 150-250° C. The reaction chamber temperature is selected from any of the following ranges: 150-170° C., 170-190° C., 190-210° C., 210-230° C., 230-250° C. Preferably, the reaction chamber temperature is 190-210° C.

[0040] Furthermore, the reaction chamber is evacuated to a pressure of 0.01 torr to 0.05 torr. The reaction chamber pressure is selected from any of the following ranges: 0.01 torr to 0.02 torr, 0.02 torr to 0.03 torr, 0.03 torr to 0.04 torr, and 0.04 torr to 0.05 torr. Preferably, the reaction chamber is evacuated to a pressure of 0.03 torr to 0.04 torr.

[0041] In certain embodiments of the present invention, in step 2), the silicon-containing precursor is selected from one or more of tris(dimethylamino)silane, hexachlorodisilane, or tetrachlorosilane.

[0042] In certain embodiments of the present invention, in step 2), the aluminum-containing precursor is selected from one or more of trimethylaluminum, aluminum trichloride, or aluminum ethoxide.

[0043] In certain embodiments of the present invention, in step 2), before the precursor 1 is pulse-introduced into the reaction chamber, the step further includes heating the precursor 1.

[0044] Furthermore, if the precursor 1 is a silicon-containing precursor, the heating temperature is 30-60° C. The heating temperature is selected from any of the following ranges: 30-35° C., 35-40° C., 40-45° C., 45-50° C., 50-55° C., 55-60° C.

[0045] Furthermore, if the precursor 1 is an aluminum-containing precursor, the heating temperature is 20-40° C. The heating temperature is selected from any of the following ranges: 20-25° C., 25-30° C., 30-35° C., and 35-40° C.

[0046] In certain embodiments of the present invention, in step 2), if precursor 1 is a silicon-containing precursor, it is pulsed into the reaction chamber until the chamber pressure reaches 1 to 5 torr. The silicon-containing precursor is pulsed into the reaction chamber, and the chamber pressure is selected from any of the following ranges: 1 to 2 torr, 2 to 3 torr, 3 to 4 torr, and 4 to 5 torr. Preferably, it is pulsed into the reaction chamber until the chamber pressure reaches 0.5 to 2 torr.

[0047] In certain embodiments of the present invention, in step 2), if precursor 1 is a silicon-containing precursor, the pulse introduction hold time is 1 to 10 minutes. The hold time is selected from any of the following ranges: 1 to 3 minutes, 3 to 5 minutes, 5 to 7 minutes, and 7 to 10 minutes. Preferably, the hold time is 3 to 6 minutes.

[0048] In certain embodiments of the present invention, in step 2), if precursor 1 is an aluminum-containing precursor, it is pulsed into the reaction chamber until the chamber pressure reaches 0.1 to 4 torr. The aluminum-containing precursor is pulsed into the reaction chamber, and the chamber pressure is selected from any of the following ranges: 0.1 torr, 1 torr, 2 torr, 3 torr, or 4 torr. Preferably, it is pulsed into the reaction chamber until the chamber pressure reaches 0.5 torr.

[0049] In certain embodiments of the present invention, in step 2), if precursor 1 is an aluminum-containing precursor, the pulse introduction hold time is 1 to 10 minutes. The hold time is selected from any of the following ranges: 1 to 3 minutes, 3 to 5 minutes, 5 to 7 minutes, and 7 to 10 minutes. Preferably, the hold time is 2 to 4 minutes.

[0050] In certain embodiments of the present invention, in step 3), the adsorption state is detected using conventional mass spectrometry detection means in the prior art.

[0051] In certain embodiments of the present invention, in step 3), nitrogen is introduced for purging after adsorption equilibrium.

[0052] Furthermore, the purging time is 1 to 3 minutes.

[0053] In certain embodiments of the present invention, in step 3), the oxygen-containing precursor is selected from one or more of H2O, O2, H2O2 or O3.

[0054] In certain embodiments of the present invention, in step 3), if precursor 1 is a silicon-containing precursor, precursor 2 is pulsed into the reaction chamber until the chamber pressure reaches 1 to 6 torr. Precursor 2 is pulsed into the reaction chamber, and the chamber pressure is selected from any of the following ranges: 1 to 2 torr, 2 to 3 torr, 3 to 4 torr, 4 to 5 torr, and 5 to 6 torr. Preferably, the precursor 2 is pulsed into the reaction chamber until the chamber pressure reaches 2 to 4 torr.

[0055] In certain embodiments of the present invention, in step 3), if precursor 1 is a silicon-containing precursor, the duration of the pulse introduction of precursor 2 is 1 to 10 minutes. The duration is selected from any of the following ranges: 1 to 3 minutes, 3 to 5 minutes, 5 to 7 minutes, and 7 to 10 minutes. Preferably, the duration is 2 to 5 minutes.

[0056] In certain embodiments of the present invention, in step 3), if precursor 1 is an aluminum-containing precursor, precursor 2 is pulsed into the reaction chamber until the chamber pressure reaches 1 to 4 torr. Precursor 2 is pulsed into the reaction chamber, and the chamber pressure is selected from any of the following ranges: 1 to 2 torr, 2 to 3 torr, and 3 to 4 torr. Preferably, the precursor 2 is pulsed into the reaction chamber until the chamber pressure reaches 1.5 to 2.5 torr.

[0057] In certain embodiments of the present invention, in step 3), if precursor 1 is an aluminum-containing precursor, the duration of the pulse introduction of precursor 2 is 1 to 10 minutes. The duration is selected from any of the following ranges: 1 to 3 minutes, 3 to 5 minutes, 5 to 7 minutes, and 7 to 10 minutes. Preferably, the duration is 3 to 8 minutes.

[0058] In certain embodiments of the present invention, in step 3), after the reaction adsorption is completed, nitrogen is introduced for purging.

[0059] Furthermore, the purging time is 1 to 3 minutes.

[0060] In certain embodiments of the present invention, in step 4), the number of repetitions is 10 to 80 times.

[0061] In certain embodiments of the present invention, when steps 2) and 3) are cycled in step 4), the same precursor 1 may be used in step 2) in different numbers of cycles to prepare titanium dioxide coated with a silicon thin film or an aluminum thin film. Specifically, in different numbers of cycles, the precursor 1 used in step 2) is a silicon-containing precursor, i.e., titanium dioxide coated with multiple layers of silicon dioxide thin films is obtained; alternatively, in different numbers of cycles, the precursor 1 used in step 2) is an aluminum-containing precursor, i.e., titanium dioxide coated with multiple layers of aluminum oxide thin films is obtained.

[0062] In certain embodiments of the present invention, when step 2) and step 3) are cycled in step 4), different precursors 1 may be used in step 2) in different numbers of cycles to prepare titanium dioxide containing both silicon and aluminum thin films. Specifically, the method comprises the following steps:

[0063] 1) Placing titanium dioxide in a rotary reaction chamber and then rotating it under protective gas;

[0064] 2) introducing a pulse of precursor 1 into the reaction chamber, where the introduced precursor 1 is adsorbed on the surface of the titanium dioxide, wherein the precursor 1 is a silicon-containing precursor;

[0065] 3) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber. The introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide, thereby coating the surface of the titanium dioxide with a silicon dioxide film;

[0066] 4) introducing a pulse of precursor 1 into the reaction chamber, where the introduced precursor 1 is adsorbed on the surface of the silicon film, wherein the precursor 1 is an aluminum-containing precursor;

[0067] 5) After adsorption equilibrium, the precursor 2 is pulsed into the reaction chamber. The introduced precursor 2 and the precursor 1 on the surface of the silicon film are

[0068] Reactive adsorption to coat the aluminum oxide film;

[0069] 6) Repeat steps 2) and 5) until a film of desired thickness is deposited on the surface of the titanium dioxide, thereby obtaining titanium dioxide alternately coated with silicon and aluminum films.

[0070] Similarly, the precursor 1 described in step 2) of the above method can also be an aluminum-containing precursor, and the precursor 1 described in step 4) can also be a silicon-containing precursor, so as to prepare titanium dioxide alternately coated with silicon and aluminum thin films.

[0071] Specifically, the method may further include the following steps:

[0072] 1) Placing titanium dioxide in a rotary reaction chamber and then rotating it under protective gas;

[0073] 2) introducing a precursor 1 into the reaction chamber in a pulsed manner, wherein the introduced precursor 1 is adsorbed on the surface of the titanium dioxide, wherein the precursor 1 is a silicon-containing precursor;

[0074] 3) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber. The introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide, thereby coating the surface of the titanium dioxide with a silicon dioxide film;

[0075] 4) Repeating steps 2) and 3) until a silicon dioxide film of desired thickness is deposited on the surface of the titanium dioxide;

[0076] 5) The precursor 1 is pulsed into the reaction chamber, and the introduced precursor 1 is adsorbed on the surface of the silicon dioxide film.

[0077] It is an aluminum-containing precursor;

[0078] 6) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber. The introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide to coat the aluminum oxide film;

[0079] Repeat steps 5) and 6) until an aluminum oxide film of a desired thickness is deposited on the surface of the titanium dioxide powder, thereby obtaining titanium dioxide powder coated with a silicon film inside and an aluminum film outside.

[0080] Similarly, the precursor 1 in the above step 2) can be an aluminum-containing precursor, and the precursor 1 in step 5) can be a silicon-containing precursor, so as to prepare titanium dioxide coated with an aluminum film inside and a silicon film outside.

[0081] The present invention also provides a multi-layer coated titanium dioxide, which is prepared by the above method.

[0082] In certain embodiments of the present invention, the multi-layer coated titanium dioxide includes titanium dioxide and a silicon dioxide film coated on the surface of the titanium dioxide; or, the multi-layer coated titanium dioxide includes titanium dioxide and an aluminum oxide film coated on the surface of the titanium dioxide.

[0083] In certain embodiments of the present invention, the multi-layer coated titanium dioxide includes titanium dioxide, a silicon dioxide film coated on the surface of the titanium dioxide, and an aluminum oxide film coated on the surface of the silicon dioxide film; or, the multi-layer coated titanium dioxide includes titanium dioxide, an aluminum oxide film coated on the surface of the titanium dioxide, and a silicon dioxide film coated on the surface of the aluminum oxide film.

[0084] In certain embodiments of the present invention, the thickness of the multi-layer coated titanium dioxide film is 1 to 50 nm.

[0085] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0086] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are for describing specific specific embodiments rather than for limiting the scope of protection of the present invention; in the present specification and claims, unless otherwise expressly stated herein, the singular forms "a", "an" and "the" include plural forms.

[0087] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0088] Example 1

[0089] (1) Industrially produced anatase titanium dioxide was dried in an oven at 60°C for 24 hours. 10 g of the treated titanium dioxide was placed in a rotary chamber and heated under nitrogen protection. After the chamber temperature and pressure reached the set values, the deposition step was performed. The chamber temperature was set to 200°C and the chamber pressure was 0.04 torr. The carrier gas was high-purity nitrogen with a flow rate of 200 sccm. The chamber rotation speed was 40 rpm.

[0090] (2) SiO2 coating: Tris(dimethylamino)silane (precursor cylinder temperature set at 40-60°C) is pulsed into a rotary chamber to achieve atomic-level SiO2 coating by deposition; the chamber pressure is 1 torr, the holding time is 3 minutes, and after adsorption is complete, high-purity nitrogen is introduced for 3 minutes; O3 gas is pulsed into the chamber, the chamber pressure is 2 torr, the holding time is 5 minutes, and high-purity nitrogen is introduced for 3 minutes. The above steps are repeated 40 times to obtain 40 circles of SiO2-coated titanium dioxide, i.e., SiO2 / titanium dioxide.

[0091] (3) Al2O3 coating: 10g of SiO2 / titanium dioxide was placed in the chamber, and the deposition chamber temperature was set to 170℃. Trimethylaluminum (the temperature of the precursor cylinder was set to 30-40℃) was pulsed into the rotary chamber, the chamber pressure was 3 torr, and the holding time was 4 minutes. After the adsorption was completed, high-purity nitrogen was purged for 3 minutes; O3 gas pulsed into the chamber, the chamber pressure was 2 torr, and the holding time was 5 minutes. The above steps were repeated 10 times to finally obtain titanium dioxide coated with 40 circles of SiO2 and 10 circles of Al2O3.

[0092] Example 2

[0093] The same mass of titanium dioxide as that in Example 1 was placed in the chamber of the atomic layer deposition system, and only 20 cycles of SiO2 deposition were performed according to the implementation method in Example 1.

[0094] Example 3

[0095] Titanium dioxide of the same mass as that in Example 1 was placed in the chamber of the atomic layer deposition system, and only 40 cycles of SiO2 deposition were performed according to the implementation method in Example 1.

[0096] Depend on Figure 1 As shown in the transmission electron microscope photo of titanium dioxide coated with 40 circles of SiO2, the light gray layer on the surface is silicon dioxide, and each particle is coated uniformly and densely.

[0097] Example 4

[0098] Titanium dioxide of the same mass as that in Example 1 was placed in the chamber of the atomic layer deposition system, and only 60 cycles of SiO2 deposition were performed according to the implementation method in Example 1.

[0099] Example 5

[0100] The same mass of titanium dioxide as that in Example 1 was placed in the chamber of the atomic layer deposition system, and only 80 cycles of SiO2 deposition were performed according to the implementation method in Example 1.

[0101] Depend on Figure 2 As shown in the high-resolution transmission electron microscope photo of titanium dioxide coated with 80 circles of SiO2, the silicon dioxide has an amorphous structure and the film layer is dense with a thickness of 5.2nm.

[0102] Example 6

[0103] The same mass of titanium dioxide as that in Example 1 was placed in the chamber of the atomic layer deposition system, and only 10 cycles of Al2O3 deposition were performed according to the implementation method in Example 1.

[0104] Depend on Figure 3 As shown in the transmission electron microscope energy spectrum element distribution diagram of titanium dioxide coated with 10 circles of Al2O3, the Al element is evenly distributed on the surface of the particles, indicating that the coating is uniform, there are no free alumina particles, and the coating is conformal, which is better than sol-gel and other methods.

[0105] Example 7

[0106] The same mass of titanium dioxide as that in Example 1 was placed in the chamber of the atomic layer deposition system, and 80 cycles of SiO2 deposition were performed. After completion, 10 cycles of Al2O3 deposition were performed.

[0107] Depend on Figure 4 As shown in the transmission electron microscope energy spectrum element distribution diagram of titanium dioxide coated with 80 circles of SiO2 and 10 circles of Al2O3, Si and Al elements are evenly distributed on the surface of the particles, which is better than sol-gel and other coating methods.

[0108] Experimental Example 1 Photocatalytic Activity Test

[0109] The photocatalytic activity of titanium dioxide powders coated with different silicon-aluminum ratios was tested. 5 mg of rhodamine B was weighed and dissolved in 500 mL of deionized water to prepare a 0.01 mg / mL rhodamine B solution, and 280 mL of this solution was taken.

[0110] Weigh 0.1 g of oxide-coated titanium dioxide and add it to the Rhodamine B solution. Stir for 30 minutes in a dark environment. Then, take 40 mL of this solution and irradiate it with UV light. Samples are taken every 6 minutes. After each sampling, the solution is immediately centrifuged (10,000 rpm, 10 minutes) and the supernatant is collected for later use.

[0111] The supernatant after centrifugation was injected into a quartz cuvette with a pathlength of 1 cm and the absorbance at a wavelength of 554 nm was measured. The degradation rate was calculated using the following formula:

[0112] Degradation rate = A / A0×100%

[0113] Where A0 is the initial absorbance of the Rhodamine B solution before illumination, and A is the absorbance of the supernatant sampled after illumination for a certain period of time.

[0114] Depend on Figure 5 The photocatalytic activity diagram of titanium dioxide with different silicon-aluminum ratios shown in the figure shows that after silica coating, especially after 60 layers of coating, the photocatalytic activity of titanium dioxide was significantly inhibited. After 80 layers of SiO2 and then 20 layers of Al2O3 coating, titanium dioxide had almost no photocatalytic activity.

[0115] The above examples are intended to illustrate the embodiments disclosed herein and are not to be construed as limiting the present invention. In addition, the various modifications listed herein and variations of the methods in the invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in conjunction with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, various modifications apparent to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A method for coating titanium dioxide using atomic layer deposition, characterized in that: The method comprises the following steps: 1) Placing titanium dioxide in a rotary reaction chamber and then rotating it under protective gas; 2) introducing a pulse of precursor 1 into the reaction chamber, and the introduced precursor 1 is adsorbed on the surface of titanium dioxide; 3) After adsorption equilibrium is reached, a pulse of precursor 2 is introduced into the reaction chamber, and the introduced precursor 2 reacts and adsorbs with the precursor 1 on the surface of the titanium dioxide to form a silicon dioxide film and / or an aluminum oxide film; 4) Repeating steps 2) and 3) until a film of desired thickness is deposited on the surface of the titanium dioxide; Wherein, the precursor 1 is a silicon-containing precursor or an aluminum-containing precursor, and the precursor 2 is an oxygen-containing precursor.

2. The method according to claim 1, characterized in that In step 1), any one or more of the following features are included: 11) The titanium dioxide is anatase or rutile phase titanium dioxide; 12) The rotation speed of the reaction chamber is 40 to 90 rpm; 13) The protective gas is nitrogen; 14) The flow rate of the protective gas is 200 to 400 sccm; 15) Place titanium dioxide in front of a rotary reaction chamber and dry it.

3. The method according to claim 1, characterized in that In step 1), after placing titanium dioxide in a rotary reaction chamber, the reaction chamber is heated and vacuumed; preferably, the temperature of the reaction chamber is raised to 150-250° C.; preferably, the pressure of the reaction chamber is evacuated to 0.01 torr-0.05 torr.

4. The method according to claim 1, wherein In step 2), any one or more of the following features are included: 21) The silicon-containing precursor is selected from one or more of tris(dimethylamino)silane, hexachlorodisilane or tetrachlorosilane; 22) The aluminum-containing precursor is selected from one or more of trimethylaluminum, aluminum trichloride or aluminum ethoxide; 23) Before the precursor 1 is pulsed into the reaction chamber, the precursor 1 is heated; preferably, if the precursor 1 is a silicon-containing precursor, the heating temperature is 30-60° C.; preferably, if the precursor 1 is an aluminum-containing precursor, the heating temperature is 20-40° C.; 24) If the precursor 1 is a silicon-containing precursor, it is pulsed into the reaction chamber until the chamber pressure reaches 1 to 5 torr; 25) If the precursor 1 is an aluminum-containing precursor, it is pulsed into the reaction chamber until the chamber pressure reaches 0.1 to 4 torr; 26) The pulse introduction and holding time of precursor 1 is 1 to 10 minutes.

5. The method according to claim 1, wherein In step 3), any one or more of the following features are included: 31) After adsorption equilibrium, nitrogen is introduced for purging; preferably, the purging time is 1 to 3 minutes; 32) The oxygen-containing precursor is selected from one or more of H2O, O2, H2O2 or O3; 33) After the reaction adsorption is completed, nitrogen is introduced for purging; preferably, the purging time is 1 to 3 minutes; 34) The pulse introduction and holding time of precursor 2 is 1 to 10 minutes.

6. The method according to claim 1, characterized in that In step 3), if precursor 1 is a silicon-containing precursor, precursor 2 is pulsed into the reaction chamber until the chamber pressure is 1 to 6 torr; And / or, if the precursor 1 is an aluminum-containing precursor, the precursor 2 is pulsed into the reaction chamber until the chamber pressure is 1 to 4 torr.

7. The method according to claim 1, characterized in that In step 4), the number of repetitions is 10 to 80 times.

8. A multi-layer coated titanium dioxide, characterized in that: The titanium dioxide is prepared by the method according to any one of claims 1 to 7.

9. The multi-layer coated titanium dioxide according to claim 8, characterized in that: The multi-layer coated titanium dioxide includes titanium dioxide, a silicon dioxide film coated on the surface of the titanium dioxide, and an aluminum oxide film coated on the surface of the silicon dioxide film; or, the multi-layer coated titanium dioxide includes titanium dioxide, an aluminum oxide film coated on the surface of the titanium dioxide, and a silicon dioxide film coated on the surface of the aluminum oxide film.

10. The multi-layer coated titanium dioxide according to claim 8, characterized in that: The thickness of the multi-layer coated titanium dioxide film is 1 nm to 50 nm.

Images