A sawtooth-shaped nano-zinc oxide strip and a preparation method thereof

Abstract

This invention discloses a method for preparing serrated nano-zinc oxide strip materials, relating to the field of nano-zinc oxide preparation. The method uses brass as the raw material, and employs Joule heating in an atmospheric or low-vacuum environment, with an energizing time of less than 1 ms and an average current not exceeding 1.58 × 10⁻⁶. 5 A. After the sample cooling rate exceeds 940℃ / s, serrated nano-zinc oxide strips are obtained on the brass surface. The resulting zinc oxide product is strip-shaped, with a serrated structure on one side. The zinc oxide strips can reach a length of 1-70μm, a width of 200-800nm, a serration height of 200nm, and a serration width of 30-40nm. The main raw materials for this preparation method are inexpensive and readily available, the operation is convenient, the process is simple, and the preparation cycle is short. The serrated zinc oxide strip product prepared by this invention has potential application value in the fields of gas sensing, ultraviolet light shielding materials, antibacterial agents, fluorescent materials, and photocatalytic materials.

Description

Technical Field

[0001] This invention relates to the field of preparation of nano zinc oxide, specifically a method for preparing serrated three-dimensional nano zinc oxide strips using Joule heating. Background Technology

[0002] The properties of nano-zinc oxide are closely related to its structure, so controlling and preparing the structural morphology of nano-zinc oxide materials has always been a key focus in the field of nanomaterials research. Currently, zinc oxide preparation techniques can be divided into physical and chemical methods based on whether a chemical reaction occurs. Physical methods include mechanical crushing and deep plastic deformation. Chemical methods can obtain fine ZnO nanostructures. Based on the differences in zinc oxide growth methods, chemical methods can be simply divided into chemical deposition, sol-gel, microemulsion, spray pyrolysis, hydrothermal synthesis, solid-state reaction, and laser-induced chemical methods. In published literature, serrated nano-zinc oxide strips are obtained by pushing zinc vapor to the vicinity of the deposition substrate in a tube furnace to combine with oxygen. This method requires initial heating to obtain gaseous zinc vapor; traditional processes involve long heating times, and tube furnaces have low heating efficiency, typically requiring several hours to reach the target temperature. Furthermore, the synthesis conditions are very demanding. It is necessary to find a way to rapidly cool and deposit zinc vapor near the deposition substrate while simultaneously reacting with oxygen to generate zinc oxide. Summary of the Invention

[0003] To address the problem of preparing serrated zinc oxide nanoribbons, this invention aims to provide a method for preparing serrated three-dimensional zinc oxide nanoribbon materials using Joule heating. Under atmospheric or low-vacuum conditions, a substrate is instantaneously heated by Joule heating and then rapidly cooled to obtain serrated zinc oxide nanoribbon deposits on the surface of the substrate or deposition substrate.

[0004] This invention provides a method for preparing serrated nano-zinc oxide strips, comprising the following steps:

[0005] Step 1:

[0006] Calculate the amount of heat required to heat the base material to be processed;

[0007] The base material is a conductive zinc-containing alloy with the chemical formula A. x Zn (1-x) Where A represents the elements other than zinc in the zinc alloy, and x represents the atomic percentage of the other elements, where x is greater than or equal to 35%.

[0008] The required heat includes: the heat required to heat the base material and the energy required for zinc sublimation;

[0009] Configure a power supply that meets the requirements for instantaneous discharge:

[0010] The instantaneous discharge power supply, when the electrical charge output within 1ms is converted into heat energy in the form of Joule heat, can achieve the required heat.

[0011] Install an electrically powered heating device:

[0012] The electrically heated device includes: an instantaneous discharge power supply and positive and negative electrodes;

[0013] The positive and negative electrodes are respectively connected to both ends of the base material; the positive and negative electrodes are respectively connected to the output electrodes of the instantaneous discharge power supply; the contact resistance between the base material and the positive and negative electrodes is less than the internal resistance of the base material;

[0014] The parent material is placed in either an open environment or a sealed container environment;

[0015] Step Two:

[0016] The substrate to be processed is brought into contact with the positive and negative electrodes, and the power is turned on to heat the substrate through Joule heating. Heat is dissipated through the substrate and the positive and negative electrodes. The heat dissipation rate of the substrate surface area between the positive and negative electrode contacts is greater than 907℃ / s, and serrated nano zinc oxide strips are obtained in the substrate surface area between the positive and negative electrode contacts.

[0017] Preferably, the heat required for heating the base material includes the product of the specific heat capacity of the base material, the volume of the base material, and the difference between the target temperature and the initial temperature. The energy required for zinc sublimation includes the latent heat of zinc vaporization and the latent heat of zinc fusion.

[0018] The target temperature is higher than the sublimation point of zinc under the current working environment pressure, but lower than the melting point of the base material.

[0019] Preferably, in step two, the open environment is at one atmosphere of pressure and is in direct contact with air; the sealed container is an airtight container, which provides the parent material with an air pressure of not less than 1 kPa during the heating process, and the airtight container contains oxygen required for the generation of zinc oxide.

[0020] Preferably, in step two, the serrated nano-zinc oxide strips obtained are deposited in situ on the surface of the substrate by vapor deposition.

[0021] The present invention also provides a serrated nano zinc oxide strip material.

[0022] Furthermore, the serrated nano zinc oxide strip material is strip-shaped, with a length of 10-70 μm and a width of 200-800 nm, exhibiting a single-sided serrated structure, with a serration height of 200 nm and a serration width of 30-40 nm.

[0023] This invention proposes a novel method for preparing serrated zinc oxide nanoribbon materials, which has advantages such as simple operation, energy saving and environmental protection, extremely short reaction time, easy control, and low requirements for the parent material and substrate. This method is beneficial for the rapid preparation of serrated zinc oxide ribbons for industrial applications. The serrated zinc oxide ribbon products prepared by this invention have potential applications in gas sensing, ultraviolet light shielding materials, antibacterial agents, fluorescent materials, and photocatalytic materials. Attached Figure Description

[0024] To more clearly illustrate the specific technical solutions in the embodiments of this invention, the following will briefly introduce the specific implementation examples and the drawings required in the description of the prior art. Of course, the drawings described below are only examples involved in this invention; those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings:

[0025] Figure 1 This is a schematic diagram of the positive and negative electrode contacts, core working area, secondary working area and heat-affected zone during the Joule heating process of the present invention.

[0026] Figure 2 The diagram shows the connection of the capacitor Joule heating device used in embodiments 1-7 of this invention. In the diagram, 1 is the positive electrode copper block pressure plate, 2 is the copper block, 3 is the base material, 4 is the negative electrode copper block, 5 is the negative block plate, 6 is the capacitor array, and 7 is the switch.

[0027] Figure 3 This is a SEM image of the nano zinc oxide strip product obtained in Embodiment 1 of the present invention.

[0028] Figure 4 The XRD pattern of the nano zinc oxide strip product obtained in Embodiment 1 of this invention.

[0029] Figure 5 This is a SEM image of the nano zinc oxide strip product obtained in Embodiment 2 of the present invention.

[0030] Figure 6 This is a SEM image of the nano zinc oxide strip product obtained in Embodiment 3 of the present invention.

[0031] Figure 7 This is a SEM image of the product obtained in Embodiment 4 of the present invention.

[0032] Figure 8 This is a SEM image of the product obtained in Embodiment 5 of the present invention.

[0033] Figure 9 This is a photograph of the product obtained in Embodiment 6 of the present invention.

[0034] Figure 10 This is a SEM image of the product obtained in Embodiment 7 of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] This invention is achieved through the following technical solution: a method for preparing a serrated three-dimensional nano-zinc oxide strip material, which is accomplished through the following steps:

[0037] Step 1: Calculate the heat required for heating based on the volume of the material to be processed (base material).

[0038] Step 2: Set up a power supply that meets the requirements for instantaneous discharge.

[0039] Step 3: Set up the power-on heating device, ensuring good contact between the base material and the positive and negative contacts of the power supply, and that the contact resistance is less than the internal resistance of the base material. If necessary, place the base material in an open environment or a low-pressure environment, and provide cooling conditions for the base material.

[0040] Step 4: Connect the power supply to obtain serrated nano zinc oxide strips on the surface of the base material within the working area between the positive and negative contacts of the power supply.

[0041] The base material mentioned in step one is a zinc-containing alloy. Its alloy composition is A. x Zn (1-x) Where A represents other elements, and x represents the atomic proportion of other elements, x should be greater than or equal to 35%.

[0042] The heat required in step one includes: the heat required to heat the base material (the product of the material's heat capacity, volume, and heating temperature) and the energy required for zinc sublimation (the latent heat of sublimation is approximately equal to the sum of the latent heat of fusion and the latent heat of vaporization). That is:

[0043] Required heat = [Material heat capacity × Material volume × (Target temperature - Initial temperature)] + (Latent heat of vaporization of zinc + Latent heat of fusion of zinc)

[0044] The target temperature mentioned above needs to be higher than the sublimation point of zinc under the current working pressure, and strictly lower than the melting point of the base material. The sublimation point of zinc under the current working pressure can be estimated using the Antonie equation.

[0045]

[0046] Where P is the current atmospheric pressure, B and C are the coefficients of Antonie's empirical equation, which are 133 and 9.92 respectively, and T 锌升华 This is the sublimation temperature of zinc at the current atmospheric pressure.

[0047] The instantaneous discharge power supply mentioned in step two needs to meet the following condition: the average output current is not less than 1.56*10 6 A. The electrical energy output within 1ms is converted into heat energy in the form of Joule heat to achieve the required heat in step one, and the input heat error is approximately 5%.

[0048] The electric heating device mentioned in step three should ensure good contact with the power source mentioned in step two, and its internal resistance should be less than the internal resistance of the base material mentioned in step one.

[0049] The electrically powered heating device described in step three should provide heat dissipation and cooling for the base material described in step one during and after the heating process, ensuring that the overall cooling rate of the system is greater than 907℃ / s. There are many ways to achieve strong cooling, such as forced heat exchange or heat diffusion. As long as the cooling rate requirement is met, it can be achieved.

[0050] In step three, the open environment refers to the parent material and the system being directly exposed to the air, while the vacuum environment refers to placing the parent material in a sealed container and evacuating it; the vacuum pressure is not less than 1 kPa and contains sufficient oxygen to participate in the reaction.

[0051] The working area mentioned in step four is the area between the positive and negative contacts of the power supply, such as... Figure 1 As shown. The base material within the working zone is heated by Joule heating. However, only the zinc component of the base material within the core working zone will volatilize. The base material outside the working zone is in the heat-affected zone, which is not directly heated by Joule heating, but its temperature will rise, providing a small amount of cooling intensity to the working zone. The secondary working zone on the base material is in close contact with the positive and negative electrodes to reduce resistance and increase heat dissipation; the heat-affected zone on the base material also serves to dissipate heat to the core working zone. The base material cools down through its own heat dissipation and the heat dissipation of the positive and negative electrode areas. To ensure that the cooling rate meets the requirements, positive and negative electrodes and the base material with good thermal conductivity are preferred.

[0052] When calculating the required heat in step one, all the base materials within the working area described in step four need to be included in the calculation.

[0053] The serrated nano zinc oxide strip product obtained in step four is as follows: strip-shaped, with a length of 10-70μm and a strip width of 200-800nm, exhibiting a single-sided serrated structure, with a serration height of 200nm and a serration width of about 30-40nm.

[0054] The serrated nano-zinc oxide strips obtained in step four can be obtained under atmospheric pressure or low vacuum. As the working environment pressure decreases, the heat required in step one should be reduced accordingly, and the number and length of the obtained nano-zinc oxide strips will decrease.

[0055] Implementation Case 1:

[0056] A method for preparing a serrated three-dimensional nano-zinc oxide strip material is achieved through the following steps:

[0057] (1) Use 25μm thick commercial brass H65 as the base material. After cleaning the surface, cut it into rectangular foil sheets of 25mm×31mm×25μm. H65 has a melting point of about 947℃. The target temperature should be greater than 907℃ and less than 947℃.

[0058] (2) Using a self-made 0.176F cylindrical capacitor array as the power source, the fusion method was used to test that approximately 85% of the energy was converted into heat within the working area of ​​the sample (Note 1). (Note 2). After substituting the parameters of H65 (Note 3) into the calculation, the calculated voltage range is between 31 and 33V. 32V is selected as the charging voltage for the capacitor array.

[0059] Note 1: Fusion method: Because the capacitor discharge rate is not constant and the system resistance is very small, 3 to 5 samples of the same size are used for fusing test to estimate the heat distribution ratio between the sample and the circuit system, which is approximately equal to the ratio of the material internal resistance to the wire resistance.

[0060] Note 2: It is assumed that the capacitor can only discharge up to 99.5%.

[0061] Note 3: The parameters for H65 are shown in Table 1. The latent heat of sublimation of zinc is the sum of the latent heat of melting and the latent heat of vaporization.

[0062] Table 1. Basic Parameters of H65

[0063]

[0064] (3) Connect the base material described in (1) to the capacitor power supply described in (2), as follows: Figure 2 As shown, a 40mm×45mm×25mm copper block is used as the positive and negative contacts. The base material is placed between two copper blocks and in contact with the upper surface of the copper blocks. Then, two 40mm×35mm×10mm copper pressure plates are used to clamp the base material and tighten it with screws to ensure that the contact resistance is strictly less than the internal resistance of the base material (Note 4). The cooling rate required under the conditions of this embodiment can be achieved through the copper pressure plates, copper blocks, and the base material itself (Note 5).

[0065] Note 4: Reducing contact resistance mainly relies on increasing the contact area, including but not limited to clamping and increasing the size of material contact points.

[0066] Note 5: This implementation case uses an OPTCT 3M infrared thermometer to monitor the sample temperature.

[0067] (4) Close the power switch described in (2) to allow the capacitor array to discharge instantaneously. After the discharge is complete, Figure 1 The base material surface of the alloy working area shown has serrated nano zinc oxide strips.

[0068] Implementation Case 2:

[0069] The experimental methods used in this implementation case are basically the same as those in implementation case 1. The differences are: in this implementation case, (1) the size of the base material is 25mm×40mm×10μm; (2) the capacitor array is increased to 0.22F and the charging voltage is adjusted to 40V; (4) the contact copper block and the base material are placed under 1kPa air pressure.

[0070] Implementation Case 3:

[0071] The experimental methods used in this implementation case are basically the same as those in implementation case 1. The differences are: in this implementation case, (1) the size of the base material is 25mm×17mm×20μm; (2) the capacitor array is increased to 0.22F and the charging voltage is adjusted to 31V; (4) the contact copper block and the base material are placed under 10kPa air pressure.

[0072] Implementation Case 4:

[0073] The experimental methods used in this implementation case are basically the same as those in implementation case 1. The difference is that in this implementation case, (1) the size of the base material is 25mm×15mm×20μm; (2) the charging voltage is adjusted to 27.5V.

[0074] Implementation Case 5:

[0075] The experimental methods used in this implementation case are basically the same as those in implementation case 2. The difference is that in this implementation case (2), the capacitor array is increased to 0.44F and the charging voltage is adjusted to 27V; (4) the contact copper block and the base material are placed under 20Pa air pressure.

[0076] Implementation Case 6:

[0077] The experimental method used in this implementation case is basically the same as that in implementation case 2. The difference is that the capacitor array in (2) of this implementation case is increased to 0.352F and the charging voltage is adjusted to 38V.

[0078] Implementation Case 7:

[0079] The experimental method used in this implementation case is basically the same as that in implementation case 4. The difference is that the capacitor array in (2) of this implementation case is changed to a supercapacitor array, the capacity is increased to 50F, and the charging voltage is adjusted to 6.5V.

[0080] Implementation Case 8:

[0081] The experimental method used in this implementation case is basically the same as that in implementation case 5. The difference is that the capacitor array in (2) of this implementation case is changed to a DC power supply with an output voltage of 5V and a current of 200A.

[0082] The samples from implementation cases 1-5 were subjected to SEM testing and XRD analysis to obtain... Figures 3-8 ;

[0083] It is evident that the obtained nano-zinc oxide product is strip-shaped, with a serrated structure on one side. The zinc oxide strips can reach tens of micrometers in length, with a width of approximately 200–800 nm. The serration height is 200 nm, and the serration width is approximately 40 nm. Figure 3 As shown. For samples of different thicknesses, inputting appropriate energy can also yield similar or identical serrated zinc oxide nanoribbon products; their XRD analysis spectra show the formation of zinc oxide components, such as... Figure 4 As shown, with the decrease in ambient air pressure, the amount of zinc oxide deposited on the surface of the base material decreases significantly, resulting in a significant decline in quality. Figure 5 , Figure 6 As shown. When the input heat is below the sublimation point of zinc, the copper matrix separates from the zinc component. The zinc component floats to the surface of the matrix and reacts with oxygen in the air, leaving a wrinkled surface, such as... Figure 7 As shown. Below 1 kPa, it is almost impossible to obtain nano-zinc oxide products, such as... Figure 8 As shown.

[0084] The sample described in Case 6, due to increased capacitance leading to prolonged discharge time, resulted in insufficient heat dissipation to maintain a high cooling rate, causing the sample to overheat and melt. Figure 9 As shown in Case 7, the sample exhibited a relatively slower discharge rate compared to the electrolytic capacitor. Its surface morphology underwent melting and resolidation at high temperatures, resulting in no obvious deposits. Its surface morphology is as follows: Figure 10 As shown. In Case 8, a DC power source was used instead of a capacitor array for discharge. Due to the low heating rate, the experimental system stopped due to overheating after 3 minutes of power-on, and the sample showed no significant change.

[0085] The above description is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing serrated nano-zinc oxide strips, characterized in that: Includes the following steps: Step 1: Calculate the amount of heat required to heat the base material to be processed; The base material is H65 brass; The required heat includes: the heat required to heat the base material and the energy required for zinc sublimation; Configure a power supply that meets the requirements for instantaneous discharge: The instantaneous discharge power supply, when the electrical charge output within 1ms is converted into heat energy in the form of Joule heat, can achieve the required heat. Install an electrically powered heating device: The electrically heated device includes: an instantaneous discharge power supply and positive and negative electrodes; The positive and negative electrodes are respectively connected to both ends of the base material; the positive and negative electrodes are respectively connected to the output electrodes of the instantaneous discharge power supply; the contact resistance between the base material and the positive and negative electrodes is less than the internal resistance of the base material; The parent material is placed in either an open environment or a sealed container environment; Step 2: The base material to be processed is brought into contact with the positive and negative electrodes, and the power is turned on to heat the base material through Joule heating; heat is dissipated through the base material and the positive and negative electrodes, and the heat dissipation rate of the base material surface area between the positive and negative electrode contacts is greater than 907℃ / s, resulting in serrated nano zinc oxide strips on the base material surface area between the positive and negative electrode contacts. The heat required to raise the temperature of the base material includes the product of the specific heat capacity of the base material, the volume of the base material, and the difference between the target temperature and the initial temperature. The energy required for zinc sublimation includes the latent heat of zinc vaporization and the latent heat of zinc fusion. The target temperature is higher than the sublimation point of zinc under the current working environment pressure and lower than the melting point of the base material. The sealed container is an airtight container, which provides the parent material with an air pressure of not less than 1 kPa during the heating process, and contains oxygen required for the generation of zinc oxide.

2. The method for preparing a serrated nano-zinc oxide strip according to claim 1, characterized in that: In step one, the open environment is at one atmosphere of pressure, in direct contact with air.

3. The method for preparing a serrated nano-zinc oxide strip according to claim 1, characterized in that: In step two, the serrated nano zinc oxide strips obtained are deposited in situ on the surface of the substrate by vapor deposition.

4. The method for preparing a serrated nano-zinc oxide strip according to claim 1, characterized in that: The serrated nano zinc oxide strip material is strip-shaped, with a length of 10-70 μm and a width of 200-800 nm, exhibiting a single-sided serrated structure, with a serration height of 200 nm and a serration width of 30-40 nm.

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