A pure titanium composite coating sensor and its preparation method and application

Abstract

The present invention relates to the field of coating materials, and discloses a pure titanium material composite coating sensor, its preparation method and application. The sensor of the present invention comprises a pure titanium material, a micro-arc oxidation coating, an electrode and a metal oxide coating; the micro-arc oxidation coating is arranged on the surface of the pure titanium material through micro-arc oxidation using sodium silicate and sodium stannate electrolytes, the electrode is arranged on the micro-arc oxidation coating, and the metal oxide coating is arranged on the micro-arc oxidation coating with the electrode, and the metal oxide comprises CuO and ZnO. The present invention utilizes the advantage of the high porosity of the micro-arc oxidation film layer itself to perform surface modification on the micro-arc oxidation film layer to form a composite coating. By taking advantage of the advantages of low cost, high stability and simple working principle of metal oxide semiconductor materials, it can effectively, quickly and accurately detect formaldehyde gas, and can realize the detection of formaldehyde gas with a safety threshold (80ppb).

Description

Technical Field

[0001] The present invention relates to the field of coating materials, and in particular to a pure titanium composite coating sensor and a preparation method and application thereof. Background Art

[0002] Formaldehyde is a very dangerous indoor volatile organic compound. Inhalation of formaldehyde may induce bronchial asthma, respiratory irritation and headaches. In 2004, it was classified as a Group 1 human carcinogen by the International Agency for Research on Cancer. The World Health Organization has set the safe threshold for exposure to formaldehyde at 0.1 mg / m 3 Therefore, in order to protect the human body from the harm of formaldehyde, it is particularly important to monitor low concentrations of formaldehyde.

[0003] Currently, conventional methods for detecting formaldehyde gas include electrochemistry, high-performance liquid chromatography, gas chromatography, spectrophotometry, polarography, and fluorescence. Although these methods have certain applications in formaldehyde detection, their high cost, complex operation, and difficulty in achieving real-time monitoring hinder their large-scale application.

[0004] The applicant's previous research results provide a pure zinc material with a coating on the surface of the pure zinc material formed by micro-arc oxidation with sodium phosphate and sodium stannate electrolytes. At the same time, an interdigitated electrode with a connecting wire is provided on the coating, which is used as the positive electrode to detect formaldehyde. It has high sensitivity and selectivity. However, after further research by the applicant, it was found that there is still room for improvement in formaldehyde detection.

[0005] Therefore, it is very necessary to study portable instruments to detect formaldehyde concentration in the environment and achieve low concentration, high sensitivity and rapid detection. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a pure titanium material composite coating sensor, which can be used for formaldehyde detection and significantly improves the sensitivity and selectivity to formaldehyde;

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned sensor and its application in detecting formaldehyde and preparing formaldehyde detection products.

[0008] In order to solve the above technical problems or at least partially solve the above technical problems, the present invention provides a method for solving the above technical problems or at least partially solving the above technical problems. As a first aspect of the present invention, a pure titanium material composite coating sensor is provided, comprising a pure titanium material, a micro-arc oxidation coating, an electrode and a metal oxide coating; the micro-arc oxidation coating is arranged on the surface of the pure titanium material through micro-arc oxidation with a sodium silicate and sodium stannate electrolyte, the electrode is arranged on the micro-arc oxidation coating, and the metal oxide coating is arranged on the micro-arc oxidation coating with the electrode, and the metal oxide comprises CuO and ZnO.

[0009] Optionally, the pure titanium material includes TA1 pure titanium material.

[0010] Optionally, the electrodes are interdigitated electrodes.

[0011] Optionally, the concentrations of sodium silicate and sodium stannate in the electrolyte are independently selected from 0.01 to 25 g / L.

[0012] Optionally, the mass ratio of CuO to ZnO in the metal oxide is (0.1-50): (0.1-50).

[0013] As a second aspect of the present invention, based on the excellent performance of high sensitivity and selectivity of the sensor of the present invention in detecting formaldehyde, the present invention provides the use of the sensor in detecting formaldehyde or in preparing formaldehyde detection products.

[0014] As a third aspect of the present invention, a method for preparing the sensor is provided, comprising:

[0015] Step 1: Pre-treatment of pure titanium material by grinding, degreasing and cleaning;

[0016] Step 2: The pretreated pure titanium material is subjected to micro-arc oxidation in a sodium silicate and sodium stannate electrolyte to form a micro-arc oxidation coating;

[0017] Step 3, arranging an electrode on the micro-arc oxidation coating;

[0018] Step 4: dissolving CuO and ZnO in a solvent to form a slurry, drop-coating the slurry on the micro-arc oxidation coating with the electrode, and obtaining the sensor after drying.

[0019] As a fourth aspect of the present invention, a product for detecting formaldehyde is provided, comprising a device for recording changes in resistance values and the sensor of the present invention, wherein electrodes on the device and the sensor are connected via wires.

[0020] Optionally, the device for recording resistance value changes includes a multimeter and a data processor.

[0021] As a fifth aspect of the present invention, a method for detecting formaldehyde is provided, wherein the sensor of the present invention is placed in formaldehyde standard samples of different concentrations, and a standard curve of resistance change data and formaldehyde concentration is established by a device that records resistance value changes; then, the sensor is placed in a test environment, resistance value change data is obtained, and the formaldehyde concentration in the test environment is obtained through the standard curve.

[0022] The present invention uses a composite electrolyte of sodium silicate and sodium stannate to perform micro-arc oxidation to form a TiO2 coating that can be used for formaldehyde detection on the surface of a pure titanium material. The surface of the micro-arc oxidation film is then modified by coating CuO / ZnO. Electrodes are set and detection is performed using the oxygen adsorption-desorption principle. Compared with conventional gases, the method exhibits extremely excellent sensitivity and extremely high selectivity to formaldehyde, and thus can effectively, real-timely, and simply detect formaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is the physical appearance of the sensor of the present invention;

[0024] Figure 2 Shown are the SEM and EDS images of the sensor composite coating of the present invention;

[0025] Figure 3 Shown is a process flow chart of the sensor of the present invention;

[0026] Figure 4 The figure shows the composition diagram of the detection system for gas selectivity test;

[0027] Figure 5 Shown is the response of the uncoated metal oxide group to 20 ppm formaldehyde at the optimal working temperature (200°C);

[0028] Figure 6 Shown is the response graph to 20 ppm formaldehyde at the optimal working temperature (240°C) after coating the CuO / ZnO group;

[0029] Figure 7 Shown is the response graph to 20 ppm formaldehyde at the optimal working temperature (260°C) after coating the SnO2 group;

[0030] Figure 8 The figure shows the Ra / Rg value line graph of the sensor of the present invention for formaldehyde under different heating temperature conditions;

[0031] Figure 9 The figure shows the Ra / Rg value broken line graph of the sensor of the present invention for formaldehyde at the safety threshold (80 ppb) under the optimal working temperature condition;

[0032] Figure 10 Shown is a bar graph of Ra / Rg values of different gases detected by the sensor of the present invention;

[0033] Figure 11 Shown is the fitting curve of the sensor of the present invention for detecting formaldehyde at different concentrations. DETAILED DESCRIPTION

[0034] The present invention discloses a pure titanium composite coating sensor, its preparation method, and its application. Those skilled in the art can refer to the contents of this document and appropriately improve the process parameters to achieve the desired effect. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The sensor, its preparation method, and its application of the present invention have been described through preferred embodiments. It is obvious that relevant personnel can modify or appropriately change and combine the pure zinc material, its preparation method, and its application described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0035] In the first aspect of the present invention, a pure titanium composite coating sensor is provided, comprising a pure titanium material, a micro-arc oxidation coating, an electrode, and a metal oxide coating; the micro-arc oxidation coating is disposed on the surface of the pure titanium material by micro-arc oxidation with a sodium silicate and sodium stannate electrolyte, the electrode is disposed on the micro-arc oxidation coating, and the metal oxide coating is disposed on the micro-arc oxidation coating with the electrode, wherein the metal oxide comprises CuO and ZnO. Figure 1 , the SEM and EDS images of the sensor composite coating are shown in Figure 2 .

[0036] In certain embodiments of the present invention, the pure titanium material contains Ti ≥ 99.99%; in other embodiments of the present invention, the pure titanium material includes TA1 pure titanium material. More specifically, the elemental composition (mass fraction) of the TA1 pure titanium material is: N ≤ 0.03%, C ≤ 0.08%, H ≤ 0.013%, Fe ≤ 0.20%, O ≤ 0.15%, and Ti as the remainder.

[0037] In certain embodiments of the present invention, the electrodes are interdigitated electrodes.

[0038] In certain embodiments of the present invention, the concentrations of sodium silicate and sodium stannate in the electrolyte are independently selected from 0.01 to 25 g / L; in other embodiments of the present invention, the concentrations of sodium silicate and sodium stannate in the electrolyte are independently selected from 1 to 10 g / L, for example, 6 g / L or 8 g / L; more specifically, the concentrations of sodium silicate and sodium stannate in the electrolyte are 8 g / L and 6 g / L, respectively.

[0039] In certain embodiments of the invention, the mass ratio of CuO and ZnO in the metal oxide is (0.1-50):(0.1-50); in other embodiments of the invention, the mass ratio of CuO and ZnO is (0.5-10):(0.5-10), more specifically, the mass ratio of CuO and ZnO is 0.5:1.

[0040] The sensor described in this invention detects formaldehyde gas based on the resistance change of the metal oxide formed by micro-arc oxidation and coating when exposed to air and formaldehyde gas. This is based on the "oxygen adsorption-desorption" principle of metal oxides. When the composite coating material is exposed to air, oxygen captures free electrons in the composite coating material's surface, forming adsorbed oxygen, which increases the resistance. When formaldehyde is exposed to the composite coating material's surface, the formaldehyde and adsorbed oxygen undergo a redox reaction, releasing the captured electrons and reducing the resistance. The equation is as follows:

[0041] HCHO ads +2O - ads →CO2+H2O gas +2e -

[0042] The sensor described in the present invention is made of a composite of CuO / ZnO and micro-arc oxidation. By coating the surface of the micro-arc oxidation film with CuO / ZnO slurry, the gas-sensing performance can be improved. Specifically, by coating the surface of the micro-arc oxidation film with CuO / ZnO slurry, the electrical properties of the film surface can be changed, and more reaction sites can be provided to enhance the reaction to formaldehyde. Specifically, by coating the surface of the micro-arc oxidation film with CuO / ZnO slurry, the adsorption of oxygen is facilitated, which decomposes into chemically adsorbed monatomic oxygen and "overflows" to the surface of the micro-arc oxidation film. The oxygen concentration on the micro-arc oxidation surface increases, which facilitates interaction with the gas to be detected, thereby increasing reactivity.

[0043] In view of the beneficial effects of the sensor of the present invention and its excellent performance in the actual detection process, in a second aspect of the present invention, the application of the sensor in detecting formaldehyde or in preparing a formaldehyde detection product is provided.

[0044] In a third aspect of the present invention, a method for preparing the sensor is further provided, comprising:

[0045] Step 1: Pre-treatment of pure titanium material by grinding, degreasing and cleaning;

[0046] Step 2: The pretreated pure titanium material is subjected to micro-arc oxidation in a sodium silicate and sodium stannate electrolyte to form a micro-arc oxidation coating;

[0047] Step 3, arranging an electrode on the micro-arc oxidation coating;

[0048] Step 4: dissolving CuO and ZnO in a solvent to form a slurry, drop-coating the slurry on the micro-arc oxidation coating with the electrode, and obtaining the sensor after drying.

[0049] In certain embodiments of the present invention, step 1 is:

[0050] The pure titanium material is polished in stages, ultrasonically cleaned with anhydrous ethanol and water, and then degreased and cleaned with an alkaline degreasing solution. The polishing is performed using silicon carbide sandpaper of increasing grades until the surface is shiny, scratch-free, and has a consistent grain. The alkaline degreasing solution is sodium hydroxide, preferably a 10% sodium hydroxide solution.

[0051] Considering that the energy attenuation in the constant pressure mode in the later stage is not conducive to the generation of a high-porosity membrane surface, which will reduce the surface quality of the coating, in certain embodiments of the present invention, the micro-arc oxidation is carried out in an AC constant current mode, and the prepared coating has high porosity and a large specific surface area, which is conducive to formaldehyde detection.

[0052] In some other embodiments of the present invention, in the AC constant current mode, the forward current is +2A to +10A, which can be selected as +4V; the negative voltage is -1A to -10A, which can be selected as -2A; the pulse frequency is fixed at 0.1 to 0.3Hz, which can be selected as 0.2Hz; the duty cycle is set to 70% to 90%, which can be selected as 80%. In some other embodiments of the present invention, in the AC constant current mode, the current directly uses the preset value, and the positive and negative currents are synchronized.

[0053] In certain embodiments of the present invention, micro-arc oxidation uses pure titanium material as the positive electrode and other suitable metals such as stainless steel as the negative electrode. The distance between the positive and negative electrodes can be controlled to be about 10 cm; the temperature of the sodium silicate and sodium stannate electrolytes is controlled by an internal and external circulation refrigeration device to maintain at 20-25°C.

[0054] In certain embodiments of the present invention, the micro-arc oxidation time is 2-8 minutes, while in other embodiments, the micro-arc oxidation time is 3 minutes.

[0055] In certain embodiments of the present invention, the electrodes are formed into interdigitated electrodes by using a mask to cover the surface coating of the pure titanium material, and an ion sputtering process is used. In other embodiments of the present invention, the ion sputtering process uses a cyclic sputtering method, and the sputtering time and number of cycles are adjusted according to the desired interdigitated electrode shape; in other embodiments of the present invention, the sputtering time is 90 seconds and the number of cycles is 6 cycles.

[0056] In certain embodiments of the present invention, the CuO and ZnO are independently selected from 0.1 to 50 mg / mL and dissolved in an organic solvent, such as ethylene glycol solvent; in other embodiments, the concentrations of CuO and ZnO are independently selected from 0.5 to 10 mg / mL; specifically, CuO and ZnO are 0.5 mg / mL and 1 mg / mL, respectively.

[0057] In certain embodiments of the present invention, CuO and ZnO are dissolved in ethylene glycol at 0.5 mg / mL and 1 mg / mL, respectively, and then ultrasonically vibrated to form a uniform solution. The solution is then evenly drop-coated on the surface of a micro-arc oxidation film having interdigitated electrodes, and the film is then dried to form a composite coating to obtain the sensor.

[0058] In a fourth aspect of the present invention, it comprises a device for recording changes in resistance value and the sensor of the present invention, wherein the electrodes on the device and the sensor are connected via wires.

[0059] In some embodiments of the present invention, the conductive wire is a conductive metal wire, such as a copper wire; in other embodiments of the present invention, the conductive wire is adhered to the electrode through conductive silver paste or other conductive materials to form a connection.

[0060] In certain embodiments of the present invention, the device for recording the change in resistance value includes a multimeter and a data processor, wherein the multimeter can be a digital multimeter and the data processor can be a computer device.

[0061] In a fifth aspect of the present invention, a method for detecting formaldehyde is provided, wherein the sensor of the present invention is placed in formaldehyde standard samples of different concentrations, and a standard curve of resistance change data and formaldehyde concentration is established by a device that records resistance value changes; then, the sensor is placed in a test environment, resistance value change data is obtained, and the formaldehyde concentration in the test environment is obtained through the standard curve.

[0062] During the test, the sensor is tested using a static measurement method. A certain volume of formaldehyde liquid is injected onto the hot plate to generate the analyte concentration to be measured. The volume of liquid (V) required for a given gas concentration (C) is calculated using the following equation:

[0063]

[0064] Wherein, P is standard atmospheric pressure, V0 is the volume of the test box (in the specific embodiment of the present invention, it is 288cm 3 ), M is the molar mass of the target gas, R is the gas constant, T is the working environment temperature, and ρ is the density of the target gas.

[0065] In a comparison of common volatile gases that need to be detected urgently, such as formaldehyde, ethanol, acetone, ammonia and triethylamine, the sensor of the present invention was used to detect the responsivity of each gas. The results showed that the sensitivity (K=Ra / Rg) to 10ppm formaldehyde at the optimal operating temperature was as high as over 20, while the sensitivity values of several other test substances were less than 3. In addition, the composite coating had a response of 1.119 to 80ppb formaldehyde, indicating that the sensor of the present invention not only has high sensitivity to low-concentration formaldehyde gas, but also has good selectivity and high practicality.

[0066] Unless otherwise specified, the experimental environment and parameter conditions of each group in the specific embodiment tests remain consistent except for the differences explicitly stated.

[0067] The following further describes a pure titanium composite coating sensor provided by the present invention, and its preparation method and application.

[0068] Example 1: Preparation of a sensor for formaldehyde detection according to the present invention

[0069] 1. Preparation method

[0070] 1. TA1 substrate pretreatment

[0071] The pure titanium substrate is TA1 titanium, and its elemental composition (mass fraction) is: N ≤ 0.03%, C ≤ 0.08%, H ≤ 0.013%, Fe ≤ 0.20%, O ≤ 0.15%, and Ti is the remainder. The TA1 substrate is cut into 25mm × 25mm × 2mm pieces using wire cutting, and then polished with 400# → 800# → 1000# → 2000# silicon carbide sandpaper to achieve a bright surface with no obvious scratches and consistent texture. It is then ultrasonically cleaned in anhydrous ethanol and deionized water for 5 minutes respectively, and air-dried with a hair dryer to obtain the pre-treated TA1 substrate.

[0072] Immerse the bright and clean TA1 substrate in a degreasing solution of 10% sodium hydroxide solution at 60°C, and then perform ultrasonic cleaning for 5 minutes. Take out the TA1 substrate, rinse it with clean water three times, and then use a hair dryer to dry it to obtain the ultrasonically treated TA1 substrate.

[0073] 2. Prepare micro-arc oxidation electrolyte

[0074] The formula of the micro-arc oxidation electrolyte is 6g / L sodium stannate and 8g / L sodium silicate. When preparing, first add 3L of deionized water to the electrolytic cell, then add 6g of sodium stannate and 8g of sodium phosphate and dissolve them fully. The micro-arc oxidation electrolyte needs to be replaced every time a micro-arc oxidation operation is performed, and each prepared micro-arc oxidation electrolyte must be used within 24 hours to prevent the micro-arc oxidation electrolyte from deteriorating;

[0075] 3. Micro-arc oxidation

[0076] The TA1 substrate after surface pretreatment was placed in a micro-arc oxidation electrolyte, wherein the TA1 substrate was connected to the positive electrode of the power supply as the positive electrode, and the stainless steel electrolytic cell was connected to the negative electrode of the power supply as the cathode, and the distance between the positive and negative electrodes was controlled at 10 cm; the circulating cooling device was turned on and the temperature was controlled at 20°C; the micro-arc oxidation AC pulse power supply was used to start power supply, and in constant current mode, the voltages were +3A and -2A, respectively, in the positive and negative directions simultaneously, the pulse frequency was fixed at 0.2Hz, the duty cycle was set to 80%, and the micro-arc oxidation time was 5 minutes, after which the TA1 substrate with a micro-arc oxidation coating on the surface was obtained;

[0077] 4. Ion sputtering

[0078] The mask was covered on the surface of the micro-arc oxidation coating and fixed in a vacuum ion sputtering instrument. The sputtering current was controlled constant and the interdigitated electrodes were prepared by a cyclic sputtering method. Each sputtering lasted 90 seconds, and a total of 6 cycles were sputtered.

[0079] 5. Surface coating

[0080] CuO and ZnO were dissolved in ethylene glycol at 0.5 mg / mL and 1 mg / mL, respectively, and then ultrasonically vibrated to form a uniform solution. The solution was then evenly drop-coated on the surface of the micro-arc oxidation film with interdigitated electrodes. The film was then placed in a constant temperature oven at 100°C and dried for 5 hours to form a composite coating.

[0081] 6. Copper wire adhesion

[0082] After sputtering, a multimeter was used to test the conductivity and the processing quality of the interdigital electrodes. Then, copper wires were bonded to the interdigital electrodes using conductive silver paste and dried at 80°C for 2 hours to ensure good contact between the sensor circuits.

[0083] The flow chart of preparing the sensor in the present invention is shown in Figure 3 . Figure 2 The SEM and surface scanning EDS test results of the sensor composite coating are shown in Figure 2. Figure 2 SEM images show that the coating surface is uniformly distributed with micron-sized pores, with no visible defects, high porosity, and a large specific surface area, which facilitates formaldehyde detection. EDS images show that Sn, Zn, and Cu elements have been successfully incorporated into the surface of the micro-arc TiO2 film.

[0084] Example 2: Gas selectivity test and fitting curve

[0085] 1. Formaldehyde gas sensitivity test method

[0086] Reference Figure 4The detection system shown in the figure is tested. A heating platform is set in a confined space, and the sensor prepared by the present invention is placed on it. Copper wires are adhered to the interdigital electrodes through conductive silver paste and connected to a multimeter. The multimeter establishes data transmission with a computer.

[0087] A fixed amount of solution of each volatile gas is injected into the confined space, and the solution is quickly evaporated into gas by the heating platform. The gas comes into contact with the sensor to react and generate a signal. The thermometer is used to indicate the temperature of the confined space, and the fan is used to quickly exhaust the measured volatile gas after the test is completed.

[0088] 2. Impact of different coatings on formaldehyde detection

[0089] The following table shows the results of the experiment: Group 1: uncoated metal oxide group; Group 2: CuO / ZnO coated group of the present invention; Group 3: SnO2 coated group; other parts of the three groups are consistent with those of Example 1, so that they can be compared; the results are shown in Figure 5-7 :

[0090] Figure 5 The results showed that the response of the uncoated metal oxide group to 20 ppm formaldehyde at the optimal working temperature of 200°C was 2.04; Figure 6 The results showed that the response of the CuO / ZnO coated group to 20 ppm formaldehyde at the optimal working temperature of 240 °C was 40.613; Figure 7 The results show that the response of the SnO2-coated group to 20 ppm formaldehyde at the optimal operating temperature of 260°C is 13.611. Compared with the uncoated and SnO2-coated treatment groups, it can be seen that the CuO / ZnO-coated material of the present invention has a higher response to formaldehyde and a lower operating temperature, as shown in Table 1.

[0091] Table 1

[0092] Working temperature / ℃ Uncoated response CuO / ZnO coating response <![CDATA[SnO2 coating response]]> 160 1.390 1.394 3.031 180 1.711 3.925 3.809 200 2.04 5.069 5.474 220 1.818 13.256 5.722 240 1.291 40.613 8.537 260 -- 18.286 13.611 280 -- 12.929 10.256

[0093] 3. The influence of different heating temperatures on sensor detection of formaldehyde

[0094] Figure 8 The results show that under different heating temperature conditions, the Ra / Rg value of the sensor of the present invention for 20 ppm formaldehyde gradually increases and reaches the highest at 240°C; Figure 9 The results show that the sensor of the present invention can detect formaldehyde gas at a safety threshold (80 ppb) at the optimal working temperature (240°C), which enables the sensor to effectively achieve safe monitoring of formaldehyde.

[0095] 4. Gas selectivity test

[0096] Referring to the detection system described above in this embodiment, after the sensor stabilized at the preset temperature, a solution of a preset gas (10 ppm formaldehyde / ethanol / acetone / ammonia / triethylamine) was added dropwise. The response to formaldehyde was approximately 25.368, the response to ethanol was approximately 2.502, the response to acetone was approximately 1.559, the response to triethylamine was approximately 2.225, and the response to triethylamine was approximately 1.268. Figure 10 The results show that at 240°C and a concentration of 10 ppm, among all volatile gases, the sensor's Ra / Rg value for formaldehyde is significantly higher than that for several other volatile gases, indicating that it has extremely high sensitivity and strong selectivity for formaldehyde.

[0097] 5. Fitting curve test at different concentrations

[0098] Refer to the above detection system of this embodiment, and start adding formaldehyde solutions of different concentrations (80ppb\1ppm\5ppm\10ppm\20ppm) after the sensor stabilizes at the preset temperature. Figure 11 The results show that the sensor of the present invention has a good linear relationship (R 2 =0.975), which has great potential in quantitative gas analysis.

[0099] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A pure titanium composite coating sensor, characterized in that: The invention comprises a pure titanium material, a micro-arc oxidation coating, an interdigitated electrode and a metal oxide coating; the micro-arc oxidation coating is arranged on the surface of the pure titanium material through micro-arc oxidation in a sodium silicate and sodium stannate electrolyte, the interdigitated electrode is arranged on the micro-arc oxidation coating, and the metal oxide coating is arranged on the micro-arc oxidation coating with the interdigitated electrode, the metal oxide comprises CuO and ZnO, and the mass ratio of CuO to ZnO in the metal oxide is (0.1-50):(0.1-50); the concentrations of sodium silicate and sodium stannate in the electrolyte are independently selected from 0.01-25 g / L.

2. The sensor according to claim 1, characterized in that The pure titanium material includes TA1 pure titanium material.

3. Use of the sensor according to any one of claims 1 to 2 in detecting formaldehyde or in preparing a formaldehyde detection product.

4. The method for preparing the sensor according to claim 1, characterized in that: include: Step 1: Pre-treatment of pure titanium material by grinding, degreasing and cleaning; Step 2: The pretreated pure titanium material is subjected to micro-arc oxidation in a sodium silicate and sodium stannate electrolyte to form a micro-arc oxidation coating; Step 3, arranging an electrode on the micro-arc oxidation coating; Step 4: dissolving CuO and ZnO in a solvent to form a slurry, drop-coating the slurry on the micro-arc oxidation coating with the electrode, and obtaining the sensor after drying.

5. A product for detecting formaldehyde, characterized in that: The invention comprises a device for recording resistance value changes and a sensor according to any one of claims 1 to 2, wherein the electrodes on the device and the sensor are connected via a wire.

6. The product according to claim 5, characterized in that: The device for recording the change of resistance value includes a multimeter and a data processor.

7. A method for detecting formaldehyde, characterized in that: The sensor according to any one of claims 1 to 2 is placed in a formaldehyde standard sample of different concentrations, and a standard curve of resistance change data and formaldehyde concentration is established by a device that records resistance value changes; then the sensor is placed in a test environment, resistance value change data is obtained, and the formaldehyde concentration in the test environment is obtained through the standard curve.

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