Preparation method of high-sensitivity nano magnetic material magnetic sensor

Abstract

The invention provides a preparation method of a high-sensitivity nano magnetic material magnetic sensor, and relates to the technical field of magnetic sensor preparation, and the preparation method comprises the four steps of preparation and treatment of a substrate material, preparation of a nano magnetic material, preparation of an outer protection layer and post-treatment of the magnetic sensor. According to the preparation method, the silicon wafer is adopted as the substrate and is oxidized, so that the silicon dioxide layer is formed as the insulating layer, and then the nano composite magnetic material is prepared by adopting the ferromagnetic material as the basis and combining the rare earth element material, so that the rare earth material is combined with the nano material; the material can generate obvious magnetization change under small magnetic field change, so that the sensitivity of the sensor is improved, then talcum powder, calcium carbonate and a heat-resistant modifier are added on the basis of polystyrene to prepare a composite protective layer material, and the composite protective layer material can adapt to some application scenes with higher temperature.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic sensor preparation, and in particular to a method for preparing a high-sensitivity nanomagnetic material magnetic sensor. Background Art

[0002] Magnetic sensors are devices that convert changes in the magnetic properties of sensitive components caused by external factors such as magnetic field, current, stress strain, temperature, light, etc. into electrical signals, and detect corresponding physical quantities in this way. Magnetic sensors are widely used in modern industry and electronic products to measure physical parameters such as current, position, and direction by sensing magnetic field strength. In the prior art, there are many different types of sensors used to measure magnetic fields and other parameters.

[0003] However, the sensitivity of magnetic sensors may be affected by many factors, resulting in low sensitivity. For example, anisotropic magnetoresistive (AMR) sensors are sensors that detect magnetic fields by using the property that the resistance of ferromagnetic materials changes with the magnetization direction. In the AMR effect, when the current flows along the easy magnetization axis of the ferromagnetic material, the resistance is the lowest; and when the current flows perpendicular to the easy magnetization axis, the resistance is the highest. This change in resistance is related to the direction of the magnetic field, so it can be used to measure the direction and strength of the magnetic field. AMR sensors usually have a low resistance change rate. Therefore, the present invention proposes a method for preparing a high-sensitivity nanomagnetic material magnetic sensor to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for preparing a high-sensitivity nanomagnetic material magnetic sensor, which has the advantage of improving sensitivity and can solve the problems existing in the prior art.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a terbutaline sulfate atomized inhalation solution, comprising the following steps:

[0006] Step 1: Preparation and processing of substrate materials

[0007] A silicon wafer is prepared as a substrate of a magnetic sensor, and is pretreated, and then oxidized under high temperature to obtain a treated substrate for standby use;

[0008] Step 2: Preparation of nanomagnetic materials

[0009] Based on ferromagnetic material, combined with rare earth element material, a nanocomposite magnetic material is prepared, and then the nanocomposite magnetic material is dispersed in a first solvent to obtain a magnetic material suspension, and then the magnetic material suspension is deposited on a treated substrate by spin coating to form a nanocomposite magnetic material layer;

[0010] Step 3: Preparation of outer protective layer

[0011] Taking polystyrene as the basis, talcum powder, calcium carbonate and a heat-resistant modifier are added to prepare a composite protective layer material, which is then dispersed in a second solvent to obtain a protective layer solution, and then the protective layer solution is deposited on the nanocomposite magnetic material layer by spin coating to form an outer protective layer, thereby obtaining a magnetic sensor;

[0012] Step 4: Post-processing of magnetic sensors

[0013] After the outer protective layer is formed, it is placed in a drying device for drying, and after drying, it is annealed and magnetized to complete the preparation.

[0014] A further improvement is that in step 1, the specific method of pretreatment is: first polishing the surface of the silicon wafer, and then ultrasonically cleaning the silicon wafer with deionized water, the cleaning times being 1 to 3 times.

[0015] A further improvement is that in step 1, the specific method of oxidation treatment is: placing the pretreated silicon wafer in an oxidation furnace, heating it to 950-1050° C. in an oxygen environment, and the duration is 50-70 minutes.

[0016] A further improvement is that in step 2, the specific steps of preparing the nanocomposite magnetic material are:

[0017] S1: preparing neodymium nitrate, samarium nitrate and ferric nitrate, and dissolving them in deionized water using ultrasonic dispersion technology to obtain a mixed solution;

[0018] S2: adjusting the pH value of the mixed solution, and then adding a precipitant for mixing;

[0019] S3: Under the condition of water bath heating, the mixed solution is continuously stirred to promote the co-precipitation of neodymium, samarium and iron ions to form a precursor powder;

[0020] S4: Separate the precipitated precursor powder by filtering, wash the precursor powder with deionized water, and then dry it to obtain a nanocomposite magnetic material.

[0021] A further improvement is that in S1, the ratio of neodymium nitrate, samarium nitrate and ferric nitrate is 1:1:3, and the precipitant is ammonium carbonate.

[0022] A further improvement is that the first solvent is water.

[0023] A further improvement is that in step three, the composite protective layer material includes the following materials in parts by weight: 70 to 90 parts of polystyrene, 10 to 20 parts of talcum powder, 8 to 18 parts of calcium carbonate, and 1 to 3 parts of a heat-resistant modifier.

[0024] A further improvement is that in step three, the second solvent is ethanol.

[0025] A further improvement is that in step 4, the specific method of annealing is: placing the magnetic sensor in an annealing device, heating it to 380-450° C., maintaining it for 1-3 hours, and then naturally cooling it to room temperature.

[0026] A further improvement is that in step 4, the specific method of magnetization treatment is: placing the annealed magnetic sensor into a magnetic field generator, the magnetic field generator generates a strong magnetic field, and magnetizing the annealed magnetic sensor, wherein the magnetic field intensity is 600-1000A / m, and the time is 30-40min.

[0027] The beneficial effects of the present invention are as follows: the preparation method of a high-sensitivity nanomagnetic material magnetic sensor provided by the present invention uses a silicon wafer as a substrate and performs an oxidation treatment on it to form a silicon dioxide layer as an insulating layer, and then uses a ferromagnetic material as a basis and combines it with a rare earth element material to prepare a nanocomposite magnetic material, thereby utilizing the combination of rare earth materials and nanomaterials so that the material can produce a significant magnetization change under a small magnetic field change, thereby improving the sensitivity of the sensor. Afterwards, polystyrene is used as a basis, talcum powder, calcium carbonate and a heat-resistant modifier are added to prepare a composite protective layer material, so that the present invention can adapt to some application scenarios with higher temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0029] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0030] In the following examples, all materials were purchased from the market, and unless otherwise specified, room temperature refers to 25±2°C.

[0031] Embodiment 1

[0032] according to Figure 1 As shown, this embodiment proposes a method for preparing a high-sensitivity nanomagnetic material magnetic sensor, comprising the following steps:

[0033] Step 1: Preparation and processing of substrate materials

[0034] Silicon wafer is the most commonly used type of wafer, so in this embodiment, silicon wafer is used as the substrate of the magnetic sensor, and it is pre-processed in the following way: first, the surface of the silicon wafer is polished, that is, the surface of the silicon wafer is preliminarily polished with a coarser abrasive, and then finely polished with a finer abrasive, and finally placed on a polishing machine, and finally polished by chemical mechanical polishing, so as to remove the microscopic unevenness and defects on the surface of the silicon wafer and improve the surface flatness, and then the silicon wafer is ultrasonically cleaned with deionized water for one cleaning to remove the abrasive particles and chemical residues generated during the polishing process, and then the silicon wafer is cleaned at high temperature. The silicon wafer is subjected to oxidation treatment in a high temperature environment. Specifically, the pretreated silicon wafer is placed in an oxidation furnace, and the atmosphere in the furnace is adjusted, that is, the temperature is raised to 950° C. in an oxygen environment for 50 minutes. During this process, the silicon wafer undergoes an oxidation reaction in a high temperature and oxygen environment, and a high-quality silicon dioxide layer is formed on the surface of the silicon wafer, which is used as an insulating layer. The insulating layer can prevent direct contact between the nano-magnetic material and the substrate, thereby avoiding current leakage or short circuit. At the same time, it can protect the nano-magnetic material from being affected by the chemical composition of the substrate material, prevent the occurrence of chemical reactions, and maintain the stability and performance of the nano-magnetic material.

[0035] Step 2: Preparation of nanomagnetic materials

[0036] After the substrate is prepared, it is necessary to coat a layer of nanomagnetic material. In this embodiment, a nanocomposite magnetic material is prepared based on a ferromagnetic material and combined with a rare earth element material, that is, a rare earth element is combined on the basis of a magnetic material, and the addition of rare earth elements can increase the magnetic moment of the material, thereby improving its magnetic response. At the same time, the addition of rare earth elements can optimize the hysteresis loop of the magnetic material, so that the material can produce obvious magnetization changes under a small magnetic field change, thereby improving the sensitivity of the sensor. Specifically, the specific steps for preparing the nanocomposite magnetic material are:

[0037] S1: preparing neodymium nitrate, samarium nitrate and ferric nitrate in a ratio of 1:1:3, dissolving them in deionized water using ultrasonic dispersion technology, and the weight ratio between deionized water and the materials (neodymium nitrate, samarium nitrate and ferric nitrate) is 1:5 to obtain a mixed solution;

[0038] S2: The pH value is then adjusted to be between 7 and 8, and a precipitant is added for mixing, wherein the precipitant is ammonium carbonate;

[0039] S3: Further, the mixed solution is continuously stirred under a water bath heating condition (70° C.) for 40 min to promote the co-precipitation of neodymium, samarium and iron ions to form a precursor powder;

[0040] S4: Separate the precipitated precursor powder by filtering, wash it with deionized water, and dry it with a drying device to obtain a nanocomposite magnetic material.

[0041] The nanocomposite magnetic material is then dispersed in a solvent. In this embodiment, the solvent is water, and a suspension is obtained (the concentration of the nanocomposite magnetic material in the suspension is 20wt.%). The suspension is then deposited onto a treated substrate using a spin coating method with a rotation speed of 2500r / min and a spin coating time of 20s. After drying, a nanocomposite magnetic material layer is formed.

[0042] Therefore, in this embodiment, rare earth element doping is used to improve the sensitivity of the nanocomposite magnetic material layer.

[0043] Step 3: Preparation of outer protective layer

[0044] Weigh the raw materials according to the following weight proportions: 70 parts of polystyrene, 20 parts of talcum powder, 18 parts of calcium carbonate, and 3 parts of heat-resistant modifier, wherein the heat-resistant modifier is SAM-Ⅰ heat-resistant modifier. Disperse the above raw materials in ethanol at a mass ratio of 1:4 to obtain a protective layer solution, and then use a spin coating method to deposit the protective layer solution on the nanocomposite magnetic material layer, and form an outer protective layer after drying. The spin coating parameters are the same as step 2;

[0045] The outer protective layer is used to protect the nanomagnetic material from the influence of the external environment and improve the stability and durability of the sensor. Therefore, in this embodiment, polystyrene is used as the basis. Polystyrene has the advantages of easy processing and low cost. At the same time, talcum powder, calcium carbonate and heat-resistant modifiers are added to increase its heat deformation temperature and dimensional stability, so that the outer protective layer has certain heat resistance.

[0046] Step 4: Post-processing of magnetic sensors

[0047] After the outer protective layer is formed, it is placed in a drying device for drying, and then annealed and magnetized to complete the preparation. The specific method of annealing is: the magnetic sensor is placed in an annealing device, heated to 450°C, maintained for 1 hour, and then naturally cooled to room temperature.

[0048] The specific method of the magnetization treatment is: put the annealed magnetic sensor into a magnetic field generator, generate a strong magnetic field by the magnetic field generator, and magnetize the annealed magnetic sensor, wherein the magnetic field intensity is 1000A / m and the time is 30min.

[0049] Embodiment 2

[0050] according to Figure 1 As shown, this embodiment proposes a method for preparing a high-sensitivity nanomagnetic material magnetic sensor, comprising the following steps:

[0051] Step 1: Preparation and processing of substrate materials

[0052] Silicon wafer is the most commonly used type of wafer, so in this embodiment, silicon wafer is used as the substrate of the magnetic sensor, and it is pre-processed in the following way: first, the surface of the silicon wafer is polished, that is, the surface of the silicon wafer is preliminarily polished with a coarser abrasive, and then finely polished with a finer abrasive, and finally placed on a polishing machine, and finally polished by chemical mechanical polishing, so as to remove the microscopic unevenness and defects on the surface of the silicon wafer and improve the surface flatness, and then the silicon wafer is ultrasonically cleaned with deionized water for 3 times to remove the abrasive particles and chemical residues generated during the polishing process, and then at high temperature. Specifically, the pretreated silicon wafer is placed in an oxidation furnace, and the atmosphere in the furnace is adjusted, that is, the temperature is raised to 1050° C. in an oxygen environment for 70 minutes. During this process, the silicon wafer undergoes an oxidation reaction in a high temperature and oxygen environment, and a high-quality silicon dioxide layer is formed on the surface of the silicon wafer, which is used as an insulating layer. The insulating layer can prevent direct contact between the nano-magnetic material and the substrate, thereby avoiding current leakage or short circuit. At the same time, it can protect the nano-magnetic material from being affected by the chemical composition of the substrate material, prevent the occurrence of chemical reactions, and maintain the stability and performance of the nano-magnetic material.

[0053] Step 2: Preparation of nanomagnetic materials

[0054] After the substrate is prepared, it is necessary to coat a layer of nanomagnetic material. In this embodiment, a nanocomposite magnetic material is prepared based on a ferromagnetic material and combined with a rare earth element material, that is, a rare earth element is combined on the basis of a magnetic material, and the addition of rare earth elements can increase the magnetic moment of the material, thereby improving its magnetic response. At the same time, the addition of rare earth elements can optimize the hysteresis loop of the magnetic material, so that the material can produce obvious magnetization changes under a small magnetic field change, thereby improving the sensitivity of the sensor. Specifically, the specific steps for preparing the nanocomposite magnetic material are:

[0055] S1: preparing neodymium nitrate, samarium nitrate and ferric nitrate in a ratio of 1:1:3, and dissolving them in deionized water, wherein the weight ratio of deionized water to the materials (neodymium nitrate, samarium nitrate and ferric nitrate) is 1:5, to obtain a mixed solution;

[0056] S2: The pH value is then adjusted to be between 7 and 8, and a precipitant is added for mixing, wherein the precipitant is ammonium carbonate;

[0057] S3: Further, under a water bath heating condition (60° C.), the reaction time is 50 min, and the mixed solution is continuously stirred to promote the coprecipitation of neodymium, samarium and iron ions to form a precursor powder;

[0058] S4: Separate the precipitated precursor powder by filtering, wash it with deionized water, and dry it with a drying device to obtain a nanocomposite magnetic material.

[0059] The nanocomposite magnetic material is then dispersed in a solvent. In this embodiment, the solvent is water, and a suspension is obtained (the concentration of the nanocomposite magnetic material in the suspension is 20wt.%). The suspension is then deposited onto a treated substrate using a spin coating method with a rotation speed of 1500r / min and a spin coating time of 55s. After drying, a nanocomposite magnetic material layer is formed.

[0060] Therefore, in this embodiment, rare earth element doping is used to improve the sensitivity of the nanocomposite magnetic material layer.

[0061] Step 3: Preparation of outer protective layer

[0062] Weigh the raw materials according to the following weight proportions: 90 parts of polystyrene, 10 parts of talcum powder, 8 parts of calcium carbonate, and 1 part of heat-resistant modifier, wherein the heat-resistant modifier is SAM-Ⅰ heat-resistant modifier. Disperse the above raw materials in ethanol at a mass ratio of 1:4 to obtain a protective layer solution, and then use a spin coating method to deposit the protective layer solution on the nanocomposite magnetic material layer, and form an outer protective layer after drying. The spin coating parameters are the same as step 2;

[0063] The outer protective layer is used to protect the nano-magnetic material from the influence of the external environment and improve the stability and durability of the sensor. Therefore, in this embodiment, polystyrene is used as the basis. Polystyrene has the advantages of easy processing and low cost. At the same time, talcum powder, calcium carbonate and heat-resistant modifier are added to improve its heat deformation temperature and dimensional stability, so that the outer protective layer has certain heat resistance.

[0064] Step 4: Post-processing of magnetic sensors

[0065] After the outer protective layer is formed, it is placed in a drying device for drying, and then annealed and magnetized to complete the preparation. The specific method of annealing is: the magnetic sensor is placed in an annealing device, heated to 380°C, maintained for 3 hours, and then naturally cooled to room temperature.

[0066] The specific method of the magnetization treatment is: putting the annealed magnetic sensor into a magnetic field generator, which generates a strong magnetic field to magnetize the annealed magnetic sensor, wherein the magnetic field intensity is 600 A / m and the time is 40 minutes.

[0067] In this embodiment, after step four, the magnetic sensor has been prepared, but in subsequent use, it is necessary to open the part that needs to be connected to the electrode layer through photolithography and etching processes, then deposit a conductive layer, and finally deposit the electrode layer on the conductive layer, and then perform subsequent cutting, packaging and other operations.

[0068] In combination with Example 1 and Example 2, the sensitivity of the magnetic sensor is compared by the change in resistance change rate (dR / R), which is a measure of the magnetoresistance effect, where dR is the change in resistance and R is the original resistance. In a magnetic sensor, this effect can be used to detect changes in the magnetic field. The higher the resistance change rate (dR / R), the higher the sensitivity of the magnetoresistance sensor. A commercially available anisotropic magnetoresistance (AMR) sensor is used as a control group, as shown in the following table:

[0069] Resistance change rate Embodiment 1 Embodiment 2 Control group Unit (dR / R) ≈4.1％ ≈4.2％ ≈2.5％

[0070] As shown in the above table, compared with the control group, the resistance change rate of the magnetic sensors prepared in Example 1 and Example 2 is improved by more than 30%.

[0071] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the framework and scope of application of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a high-sensitivity nanomagnetic material magnetic sensor, characterized in that: The following steps are involved: Step 1: Preparation and processing of substrate materials A silicon wafer is prepared as a substrate of a magnetic sensor, and is pretreated, and then oxidized under high temperature to obtain a treated substrate for standby use; Step 2: Preparation of nanomagnetic materials Based on ferromagnetic material, combined with rare earth element material, a nanocomposite magnetic material is prepared, and then the nanocomposite magnetic material is dispersed in a first solvent to obtain a magnetic material suspension, and then the magnetic material suspension is deposited on a treated substrate by spin coating to form a nanocomposite magnetic material layer; Step 3: Preparation of outer protective layer Taking polystyrene as the basis, talcum powder, calcium carbonate and a heat-resistant modifier are added to prepare a composite protective layer material, which is then dispersed in a second solvent to obtain a protective layer solution, and then the protective layer solution is deposited on the nanocomposite magnetic material layer by spin coating to form an outer protective layer, thereby obtaining a magnetic sensor; Step 4: Post-processing of magnetic sensors After the outer protective layer is formed, it is placed in a drying device for drying, and after drying, it is annealed and magnetized to complete the preparation.

2. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 1, the specific method of pretreatment is: firstly polishing the surface of the silicon wafer, and then using deionized water to ultrasonically clean the silicon wafer for 1 to 3 times.

3. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 1, the specific method of oxidation treatment is: placing the pretreated silicon wafer in an oxidation furnace, heating it to 950-1050° C. in an oxygen environment, and the duration is 50-70 minutes.

4. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 2, the specific steps of preparing the nanocomposite magnetic material are: S1: preparing neodymium nitrate, samarium nitrate and ferric nitrate, and dissolving them in deionized water using ultrasonic dispersion technology to obtain a mixed solution; S2: adjusting the pH value of the mixed solution, and then adding a precipitant for mixing; S3: Under the condition of water bath heating, the mixed solution is continuously stirred to promote the co-precipitation of neodymium, samarium and iron ions to form a precursor powder; S4: Separate the precipitated precursor powder by filtering, wash the precursor powder with deionized water, and then dry it to obtain a nanocomposite magnetic material.

5. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 4, characterized in that: In the S1, the ratio of neodymium nitrate, samarium nitrate and ferric nitrate is 1:1:3, and the precipitant is ammonium carbonate.

6. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: The first solvent is water.

7. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step three, the composite protective layer material includes the following materials in parts by weight: 70 to 90 parts of polystyrene, 10 to 20 parts of talcum powder, 8 to 18 parts of calcium carbonate, and 1 to 3 parts of a heat-resistant modifier.

8. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 3, the second solvent is ethanol.

9. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 4, the specific method of annealing is: placing the magnetic sensor in an annealing device, heating it to 380-450° C., maintaining it for 1-3 hours, and then naturally cooling it to room temperature.

10. The method for preparing a high-sensitivity nanomagnetic material magnetic sensor according to claim 1, characterized in that: In the step 4, the specific method of the magnetization treatment is: placing the annealed magnetic sensor into a magnetic field generator, generating a strong magnetic field by the magnetic field generator, and magnetizing the annealed magnetic sensor, wherein the magnetic field intensity is 600-1000A / m and the time is 30-40min.

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