阅读说明：本技术 一种网式二氧化钛纳米管阵列的制备方法 (Preparation method of net type titanium dioxide nanotube array ) 是由 何运兵 王晗 梁机 谭振荣 陈子豪 于 2019-10-08 设计创作，主要内容包括：本发明公开了一种网式二氧化钛纳米管阵列的制备方法,属于光催化材料制备技术领域。该制备方法是通过将钛网打磨抛光后作为阳极置入恒温电解液中,调节阴阳两电极的间距,在30～80V下阳极氧化3-12h,取出、清洗、烘干,置于高温炉中,在300-700℃下于空气中保温3-5h,自然冷却至室温后制得的。本发明的制备方法操作简单易行,易于实现工业化生产,所制得的纳米管能够很好地附着于钛网上而形成整体网式纳米管阵列,很好地避免了纳米管的大量脱落,有效解决了催化剂床层阻力的问题,便于应用。(The invention discloses a preparation method of a net type titanium dioxide nanotube array, belonging to the technical field of preparation of photocatalytic materials. The preparation method comprises the steps of polishing a titanium mesh, placing the polished titanium mesh serving as an anode into constant-temperature electrolyte, adjusting the distance between a positive electrode and a negative electrode, oxidizing the anode for 3-12 hours at 30-80V, taking out, cleaning, drying, placing in a high-temperature furnace, preserving heat for 3-5 hours in the air at the temperature of 300-700 ℃, and naturally cooling to room temperature. The preparation method provided by the invention is simple and easy to operate, and easy to realize industrial production, the prepared nanotubes can be well attached to the titanium mesh to form an integral mesh type nanotube array, so that the nanotubes are well prevented from falling off in large quantity, the problem of catalyst bed resistance is effectively solved, and the preparation method is convenient to apply.)

1. A preparation method of a net type titanium dioxide nanotube array is characterized by comprising the following steps: the method comprises the following steps:

s1, polishing the titanium mesh, cleaning, polishing in polishing solution, cleaning with deionized water and drying;

s2, preparing electrolyte, placing the titanium mesh obtained in the step S1 as an anode in the electrolyte with constant temperature, adjusting the distance between a positive electrode and a negative electrode to be 2-7 cm, anodizing for 3-12 hours under the voltage of 30-80V, taking out, cleaning and drying;

and S3, placing the titanium mesh obtained in the step S2 in a high-temperature furnace, preserving the heat in the air for 3-5 hours at the temperature of 300-700 ℃, and naturally cooling to room temperature to obtain the mesh type titanium dioxide nanotube array.

2. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: the titanium content of the titanium net is 50-99.9 wt%.

3. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: and the titanium mesh polished in the step S1 is subjected to ultrasonic cleaning by using ethanol, acetone and distilled water in sequence.

4. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 3, wherein: the ultrasonic cleaning frequency is 30-50 KHZ, the power is 350-450W, and the cleaning time is 5-30 min.

5. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: the polishing solution comprises the following components in percentage by volume: NH (NH)₄F:HNO₃:H₂O＝(1～3):(2～5):(4～7)。

6. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: the electrolyte in the step S2 comprises 0.05-2 wt% of fluorine-containing ions and 1-5 wt% of H₂O, 93-98.95 wt% of alcohol organic solvent.

7. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 6, wherein: the fluorine-containing ion is NH₄F. At least one of NaF, KF and HF.

8. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 6, wherein: the alcohol organic solvent is ethylene glycol or glycerol or the mixture of the ethylene glycol and the glycerol.

9. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: the temperature of the constant-temperature electrolyte in the step S2 is 25-50 ℃.

10. The method for preparing a mesh-type titanium dioxide nanotube array according to claim 1, wherein: the distance between the anode and the cathode in the step S2 is 2-4 cm, the oxidation voltage is 50-70V, and the anodic oxidation time is 7-10 h.

Technical Field

The invention relates to the technical field of preparation of photocatalytic materials, in particular to a preparation method of a net type titanium dioxide nanotube array.

Background

Along with the increasing severity of indoor formaldehyde pollution, higher requirements are put forward on the treatment of formaldehyde pollution. There are various techniques for treating formaldehyde pollution, and catalytic oxidation is known as an effective technique for removing indoor formaldehyde and the like. The nanometer titanium dioxide is one of catalytic materials widely applied to the air purification industry in recent years, has large specific surface area and good oxidation activity, and is especially the nanometer TiO with a tubular array structure₂(titanium nanotube arrays, TNAs). Grimes et al (Gong D, et al, j. mater.res, 2001,16,3331) in 2001 produced highly ordered TNAs on titanium substrates for the first time by electrochemical anodization, which attracted considerable attention. The anodic oxidation method is simple to operate, the prepared TNAs have a structure with controllable size and ordered height, a large specific surface area and strong adsorption capacity, and simultaneously, photo-generated carriers are quickly conducted along the length direction of the nano tube, so that the recombination probability of electrons is reduced, the capture efficiency of photons is enhanced, and the TNAs have more excellent catalytic performance and application prospect than powder titanium dioxide.

At present, research aiming at TNAs mainly focuses on the aspects of the formation mechanism, the appearance and size regulation, the catalytic performance regulation of nanotubes, the application of nanotube catalysts in different fields and the like. However, the TNAs prepared by the anodic oxidation method is a separate film (i.e. the TNAs film is separated from the Ti substrate), and is inconvenient to apply. In practical application, the TNAs film needs to be immobilized on a carrier, and the TNAs film is brittle and can be easily broken in the subsequent treatment process, so that partial advantages of the TNAs film in structure are lost. Attempts have been made to obtain monolithic nanotubes for ease of application, such as Wong et al, by double-sided anodization of titanium sheet-based TNAs (Wong R.J., et al. AICHE J.,2016,62, 415). The applicant also prepares the TNAs embedded in the Ti sheet substrate by designing a specific anodic oxidation device in the earlier stage, and the result shows that the probability of the prepared integral nanotube breaking in use is greatly reduced, but the resistance of mixed gas flowing through the nanotube array is large, the adsorption and the reaction of gas molecules are not facilitated, and the preparation process is complex. The dropping of TNAs is mainly caused by the difference of thermal expansion coefficients of titanium dioxide and metallic titanium and the difference of thermal expansion and contraction degrees of the two materials in the subsequent heat treatment process. In addition, the tube length of TNAs is also an important factor affecting their shedding. The longer the nanotube, the more easily the nanotube is dropped, and the shorter the nanotube, the less easily the nanotube is dropped.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a preparation method of a net type titanium dioxide nanotube array.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a preparation method of a net type titanium dioxide nanotube array comprises the following steps:

s1, polishing the titanium mesh, cleaning, polishing in polishing solution, cleaning with deionized water and drying;

s2, preparing electrolyte, placing the titanium mesh obtained in the step S1 as an anode in the electrolyte with constant temperature, adjusting the distance between a positive electrode and a negative electrode to be 2-7 cm, anodizing for 3-12 hours under the voltage of 30-80V, taking out, cleaning and drying;

and S3, placing the titanium mesh obtained in the step S2 in a high-temperature furnace, preserving the heat in the air for 3-5 hours at the temperature of 300-700 ℃, and naturally cooling to room temperature to obtain the mesh type titanium dioxide nanotube array.

In a preferred embodiment of the present invention, the titanium content of the titanium mesh is 50 to 99.9 wt%.

In a preferred embodiment of the present invention, the polished titanium mesh in step S1 is sequentially ultrasonically cleaned with ethanol, acetone, and distilled water.

In a preferred embodiment of the present invention, the ultrasonic cleaning frequency is 30 to 50KHZ, the power is 350 to 450W, and the cleaning time is 5 to 30 min.

As a preferred embodiment of the present invention, the polishing liquid is prepared by mixing the following components by volumeThe components in percentage by weight are as follows: NH (NH)₄F:HNO₃:H₂O＝(1～3):(2～5):(4～7)。

In a preferred embodiment of the present invention, the electrolyte in step S2 comprises 0.05-2 wt% of fluoride ion and 1-5 wt% of H₂O, 93-98.95 wt% of alcohol organic solvent.

In a preferred embodiment of the present invention, the fluorine-containing ion is NH₄F. At least one of NaF, KF and HF.

In a preferred embodiment of the present invention, the alcohol organic solvent is ethylene glycol or glycerol or a mixture of both.

In a preferred embodiment of the present invention, the temperature of the constant-temperature electrolyte in step S2 is 25 to 50 ℃.

In a preferred embodiment of the present invention, the distance between the positive electrode and the negative electrode in step S2 is preferably 2 to 4cm, the oxidation voltage is preferably 50 to 70V, and the anodic oxidation time is preferably 7 to 10h, which is beneficial to ensure the product yield and reduce the shedding rate.

As a preferred embodiment of the invention, the purity of the titanium mesh is preferably equal to or more than 99.7 percent, so that the quality of the product is ensured; the water in the electrolyte and the water for cleaning each time are deionized water, so that impurities are prevented from being introduced; drying in a forced air drying oven at 40-80 deg.C.

Compared with the prior art, the invention has the beneficial effects that:

1. the net type titanium dioxide nanotube array prepared by the preparation method is characterized by using a scanning electron microscope and an X-ray diffractometer respectively, and the results show that the outer diameter of the tube of the titanium dioxide nanotube array structure is 150-200nm, the wall thickness is 20-40nm, the titanium dioxide nanotube array structure can be well adhered to a titanium net substrate to form an integral net type structure, the nanotubes are prevented from falling off in a large amount, the actual application is facilitated, and the problem of catalyst bed resistance is relieved.

2. The preparation method of the invention adopts the titanium mesh to replace a titanium sheet in the conventional method as an anode of the anodic oxidation reaction, prepares the TNAs on the longitude and latitude lines of the titanium mesh, controls the tube length of the TNAs by adjusting the anodic oxidation reaction conditions, coordinates the relation between the tube length of the TNAs and the falling thereof, enables the prepared TNAs to be fixed on the titanium mesh to form the integral net type TNAs, and simultaneously ensures enough tube length.

3. The preparation method disclosed by the invention is simple and easy to operate, low in equipment requirement, low in cost, energy-saving, efficient, high in safety and easy to realize industrial production.

Drawings

FIG. 1 is a graph comparing the effect of the distance between two electrodes on the shedding rate according to the present invention;

FIG. 2 is a graph comparing the effect of anodization time on exfoliation rate in accordance with the present invention;

FIG. 3 is a graph comparing the effect of anodization voltage on exfoliation rate in accordance with the present invention;

FIG. 4 is a scanning electron microscope image of the titanium dioxide nanotube array prepared by the present invention;

FIG. 5 is an enlarged view of a scanning electron microscope of the titanium dioxide nanotube array prepared by the present invention;

FIG. 6 is an X-ray diffraction pattern of the titanium dioxide nanotube array prepared by the present invention;

FIG. 7 is a diagram showing the effect of the titanium dioxide nanotube array prepared in comparative example 1 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The experimental procedures used in the following examples are, unless otherwise specified, conventional: the raw materials, auxiliary agents and the like used are all commercial raw materials and auxiliary agents which can be purchased from conventional markets unless otherwise specified.

1.1 Experimental materials

Titanium mesh (purity 99.7%, available from Shaanxi Baoji titanium industries, Ltd.), ammonium fluoride (analytically pure, available from Guangdong Guanghua chemical works, Ltd.), ethylene glycol (chemically pure, available from Tianjin Mao chemical reagent works), and deionized water.

1.2 Experimental methods

Cutting the titanium net into small pieces with certain size, polishing, cleaning and the likeAnd drying for later use after pretreatment. 0.34g of NH are weighed₄F was dissolved in 1.8ml of deionized water, and 58.2ml of ethylene glycol was added after dissolution. Pouring the uniformly stirred electrolyte into an anodic oxidation reaction tank, inserting a pretreated titanium net serving as a cathode and an anode, switching on a direct current power supply, adjusting voltage to react, and placing the whole electrolytic tank into a 25 ℃ constant-temperature water bath. And washing the reacted titanium mesh with deionized water, drying, and calcining in a muffle furnace at 450 ℃ for 2 h. The falling condition of the TNAs is inspected by falling the TNAs from the ground of an 80cm experiment table, and the mass m of the whole titanium net before and after the TNAs fall is measured₁、m₂The TNAs shedding rate was calculated by the formula (1).

2.1 Effect of anodic Oxidation Voltage on exfoliation Rate

Pouring the uniformly stirred electrolyte (the composition of the electrolyte is shown in an experimental method 1.2, the same below) into an anodic oxidation reaction tank, inserting a pretreated titanium mesh to serve as a cathode and an anode, adjusting the distance between the two electrodes to be 4cm, carrying out anodic oxidation reaction for 8 hours, and controlling the temperature of the electrolyte to be 25 ℃ through a constant temperature circulator. Washing the reacted titanium net with deionized water, drying, calcining for 2h at 450 ℃ in a muffle furnace, naturally cooling to normal temperature, inspecting the falling condition of the titanium net by dropping TNAs from a 80cm experiment table to the ground, and measuring the mass m of the whole titanium net before and after the TNAs fall₁、m₂The TNAs shedding rate was calculated. The above experiment was repeated while maintaining the other conditions and adjusting the anodization time to 10V, 20V, 30V, 40V, 50V, 60V, 70V, and 80V, respectively, and the results are shown in table 1 and fig. 1.

TABLE 1 Effect of anodizing Voltage on the exfoliation Rate of TNAs

As can be seen from table 1 and fig. 1, the dropping rate of TNAs generally increases as the anodization voltage increases. The reason for this is that as the anodic oxidation voltage increases, the reaction rate of TNAs formation increases, the tube length thereof continues to increase, and the adhesion thereof to the substrate surface decreases. According to the experimental result, 50-70V is selected as a relatively suitable anodic oxidation voltage.

2.2 Effect of anodic Oxidation time on exfoliation Rate

Pouring the uniformly stirred electrolyte into an anodic oxidation reaction tank, inserting a pretreated titanium mesh as a cathode and an anode, adjusting the distance between the two electrodes to be 4cm, reacting under the voltage of 60V, and controlling the temperature of the electrolyte to be 25 ℃ through a constant temperature circulator. Washing the reacted titanium net with deionized water, drying, calcining for 2h at 450 ℃ in a muffle furnace, naturally cooling to normal temperature, inspecting the falling condition of the titanium net by dropping TNAs from a 80cm experiment table to the ground, and measuring the mass m of the whole titanium net before and after the TNAs fall₁、m₂The TNAs shedding rate was calculated. The above experiment was repeated while maintaining the other conditions and adjusting the anodization time to 1h, 3h, 6h, 7h, 8h, 9h, 10h, and 12h, respectively, and the results are shown in table 2 and fig. 2.

TABLE 2 Effect of anodizing time on the TNAs exfoliation Rate

Time/h	1	3	6	7	8	9	10	12
									Rate of fall/%)	0.119	0.414	1.4	0.29	0.187	0.239	0.34	0.918

As can be seen from table 2 and fig. 2, the exfoliation rate first increased with the increase of the anodization time, and was maximized at 6 hours, and then decreased again as the anodization time continued to increase, and was minimized at 8 hours, and the exfoliation rate increased by further extending the reaction time. The TNAs prepared by the anodic oxidation method mainly comprises an anodic oxidation process of field titanium sheet and a dissolution process of field titanium oxide, and the electric field intensity at the bottom end of a hole is far higher than that of a pipe wall, so that the consumption rate of titanium metal is higher than that of titanium oxide at the bottom end, and the TNAs are continuously increased; when the electrolessly oxidized titanium sheet anodic oxidation rate and the electrolessly oxidized titanium dissolution rate are equal, the length of TNAs is not increased. Therefore, the preferred anodic oxidation reaction time is 7-8 hours.

2.3 Effect of Bipolar distance on shedding Rate

Pouring the uniformly stirred electrolyte into an anodic oxidation reaction tank, inserting a pretreated titanium mesh as a cathode and an anode, adjusting the distance between the two electrodes, reacting for 6 hours under the voltage of 60V, and controlling the temperature of the electrolyte to be 25 ℃ through a constant temperature circulator. Washing the reacted titanium net with deionized water, drying, calcining in a muffle furnace at 450 ℃ for 2h, and naturally coolingWhen the temperature is normal, the TNAs falls off the ground from a test table of 80cm to examine the falling condition of the TNAs, and the mass m of the whole titanium net before and after the TNAs fall off is measured₁、m₂The TNAs shedding rate was calculated. The above experiment was repeated while keeping the other conditions constant, adjusting the distance between the two electrodes to 2cm, 3cm, 4cm, 5cm, and 6cm, respectively, and the results are shown in Table 3 and FIG. 3.

TABLE 3 Effect of Bipolar spacing on TNAs shedding Rate

Distance/cm	2	3	4	5	6	7
							Rate of fall/%)	0.544	0.529	1.4	0.0662	0.0519	0

As can be seen from table 3 and fig. 3, the dropping rate of TNAs generally tends to decrease with the increase of the distance between the two poles, because the distance between the cathode and the anode affects the resistance between the two poles, and the current in the circuit inevitably changes under the condition of maintaining the voltage between the two poles, thereby affecting the generation of TNAs. In the experiment, the larger the distance between the two electrodes is, the more the generation amount of TNAs on the titanium mesh is reduced gradually, and the falling rate is reduced. Therefore, the falling-off rate is low when the pitch is 5cm, 6cm or 7cm, but the amount of the product is small, which is not preferable. When the distance is 2cm or 3cm, the falling rate is small, the yield is large, and the method has more practical value, so that the distance of selecting the electrode of 2-3cm is more appropriate.

2.4 optimization of anodic Oxidation Process conditions

In order to comprehensively examine the influence of the anodic oxidation time, the anodic oxidation voltage and the titanium mesh spacing on the generation and falling of TNAs, on the basis of a single-factor test, the applicant designs a three-factor three-level orthogonal test to optimize the process conditions of the anodic oxidation reaction, wherein specific parameter values are shown in Table 4, and L9 (3)³) The results of the orthogonality test are shown in table 5.

TABLE 4 orthogonal test factors and levels

TABLE 5 orthogonal test L9 (3)³) Results

The anodic oxidation test was performed according to the test parameters of table 4, and calcined under the same temperature condition, and the detachment rate of each set of test was measured, and the test results were analyzed by a very poor analysis method (as shown in table 5).

According to the principle of an orthogonal test range analysis method, the primary and secondary sequences of factors are discharged according to the range, so that the influence of three factors influencing the TNAs falling in the experiment is as follows: c (distance) > B (voltage) > a (time). The shedding rate is taken as an index, and the optimal conditions are A1B1C3, namely the distance between two electrodes is 4cm, the anodic oxidation voltage is 50V, and the anodic oxidation reaction time is 7 h.

2.5 repeat experiments under optimized conditions

The results of the repetitive experiments were shown in Table 6, based on the optimal conditions obtained from the orthogonal experiments.

TABLE 6 results of repeated experiments

Note: basic no shedding detected in the shedding experiments

From the results of the repeated experiments, the three groups of the compound have small shedding rates, which shows that the experiment has good repeatability, and further proves that the process conditions are the optimal conditions.

The present invention will be described in further detail with reference to specific examples. In the following examples, the polishing was carried out by ultrasonic cleaning the titanium mesh after sanding with ethanol, acetone and distilled water, and then NH₄F:HNO₃:H₂Carrying out chemical polishing in a solution with the volume ratio of O being (1-3) to (2-5) to (4-7), then cleaning with deionized water, and drying at 40-80 ℃, which is not described in the embodiment.