Method for improving coercivity of neodymium-iron-boron magnetic material by using waste fluorescent powder

Abstract

This invention discloses a method for improving the coercivity of NdFeB magnetic materials using phosphor waste, belonging to the field of phosphor waste recycling technology. The invention uses recycled phosphor waste from tri-color fluorescent lamps as raw material. The raw material is first calcined at 300-500℃ to remove colloids, then calcium powder is added and subjected to a second reduction calcination at 500-700℃ in an inert gas atmosphere. After crushing, grinding, acid washing, water washing, drying, and sieving, recycled phosphor material is prepared. Finally, the recycled phosphor material is mixed into NdFeB alloy powder, and following conventional magnetic material production processes, NdFeB blanks are produced through hydrogen crushing, powdering, molding, and sintering, significantly improving the coercivity of NdFeB magnetic materials. This invention features a short process flow, simple equipment requirements, easily achievable experimental conditions, and a short production cycle. It not only improves the coercivity of NdFeB magnetic materials but also recycles phosphor waste from tri-color fluorescent lamps, reducing environmental pollution, and can be used for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of phosphor waste recycling technology, specifically relating to a method for improving the coercivity of neodymium iron boron magnetic materials using phosphor waste. Background Technology

[0002] In recent years, rare-earth tri-color fluorescent lamps have been gradually replaced by LED lighting projects, resulting in a large number of fluorescent lamps being discarded directly due to their obsolescence, causing significant waste of global resources. The main components of discarded tri-color fluorescent lamps are glass, nickel-copper wire, aluminum, and tri-color phosphors, which can be recycled separately based on their individual composition. Rare earth elements in tri-color phosphors are scarce resources; effective processing could not only solve the environmental pollution problem caused by discarded phosphors but also facilitate recycling, effectively alleviating some of the rare earth resource shortages. Current phosphor waste recycling methods use the liquid-phase method, but this method requires alkali and acid dissolution, which is cumbersome and the resulting alkaline or acidic solutions can easily pollute the environment. Furthermore, recycling these alkaline or acidic solutions would undoubtedly increase recycling costs. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a method for improving the coercivity of NdFeB magnetic materials using phosphor waste. The method involves secondary roasting of phosphor waste to obtain phosphor recycled material, which is then mixed into NdFeB alloy powder. After hydrogen pulverization, powdering, molding, and sintering, NdFeB blanks are produced. This method can not only improve the coercivity of NdFeB magnetic materials but also recycle phosphor waste from tri-color fluorescent lamps, reducing environmental pollution.

[0004] To achieve its purpose, the present invention adopts the following technical solution: This invention provides a method for improving the coercivity of neodymium iron boron magnetic materials using recycled phosphor materials, specifically including the following steps: S1. Using recycled phosphor waste from tri-color fluorescent lamps as raw material, the process involves crushing and grinding. The powder is sieved into fine powder, placed in a crucible, and placed in a muffle furnace. It is first calcined in air, then naturally cooled to room temperature, ground, and sieved to obtain the first-calcined powder. The temperature of the first calcination is 300-500℃. S2. Add 1-10 wt% calcium powder to the powder calcined in S1, mix evenly, put it into a crucible, place it in a pressure furnace, and calcine it a second time under a protective atmosphere. After naturally cooling to room temperature, crush, grind, acid wash, water wash, dry and sieve to obtain fluorescent powder recovery material; the secondary calcination temperature is 500-700℃. S3. 1-10wt% of recycled phosphor material is added to NdFeB alloy powder, and after hydrogen crushing, powdering, molding and sintering processes, NdFeB blanks are obtained.

[0005] As a further preferred embodiment of the technical solution of the present invention, in step S1, the primary roasting temperature of the phosphor waste is 350-450℃, and the roasting time is 3-5 hours. It should be noted that if the roasting time is less than 3 hours, the solidified adhesive cannot be completely removed; if the time exceeds 5 hours, the adhesive vapors will be completely removed, resulting in energy waste.

[0006] Furthermore, in step S2, the amount of calcium powder added during the secondary roasting is 5-7 wt% of the powder from the primary roasting.

[0007] Furthermore, in step S2, the secondary calcination temperature is 550-650℃, and the calcination time is 6-8 hours. If the calcination time is less than 6 hours, the reaction is not completely completed; if it is more than 8 hours, the reaction is completed, resulting in energy waste.

[0008] Furthermore, in step S2, the protective atmosphere for the secondary roasting is an inert atmosphere, preferably argon or nitrogen.

[0009] Furthermore, in step S3, the amount of phosphor recycled material incorporated into the NdFeB magnetic material raw material is 5-7 wt%.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention develops a secondary roasting solid-phase recycling process for fluorescent powder waste, which does not require alkali dissolution or acid dissolution, has less environmental pollution, is easy to operate, has simple equipment requirements, and is easy to achieve experimental conditions.

[0011] 2. By mixing recycled phosphor powder into NdFeB alloy powder and producing NdFeB blanks through hydrogen pulverization, powdering, molding, and sintering according to conventional magnetic material production processes, the coercivity of NdFeB magnetic materials can be significantly improved. Detailed Implementation

[0012] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but the following embodiments should not be construed as limiting the scope of protection of the present invention.

[0013] Example 1 Using waste phosphor powder from recycled tri-color fluorescent lamps as raw material, 100g of waste phosphor powder sample was accurately weighed, crushed, ground, and passed through a 30-mesh sieve. The sample was then placed in a 300mL high-alumina crucible and placed in a muffle furnace for constant calcination at 350℃ for 5 hours. After natural cooling to room temperature, the sample was ground and passed through a 30-mesh sieve. This was recorded as the first calcination powder.

[0014] Calcium powder was added to the calcined powder at a rate of 5 wt%, and the mixture was stirred evenly. The mixture was then placed in a 300 mL high-alumina crucible and placed in a pressure furnace. The crucible was kept at 550 °C for 8 hours under a nitrogen protective atmosphere and allowed to cool naturally to room temperature. The resulting material was then crushed, ground, acid-washed, washed with water, dried, and passed through a 30-mesh sieve. This material was then recorded as fluorescent powder recovery material.

[0015] Recycled phosphor material is incorporated into NdFeB alloy powder. The amount of recycled phosphor material in the NdFeB magnetic material raw material is 5wt%. After uniform mixing, NdFeB blanks are produced by hydrogen crushing, powdering, molding, and sintering, in accordance with the conventional production process of magnetic materials.

[0016] Example 2 Using recycled phosphor waste from tri-color fluorescent lamps as raw material, 100g of phosphor waste sample was accurately weighed, crushed, ground, and passed through a 60-mesh sieve. The sample was then placed in a 300mL high-alumina crucible and placed in a muffle furnace at a constant temperature of 450℃ for 4 hours. After naturally cooling to room temperature, the sample was ground and passed through a 60-mesh sieve. This was recorded as the first-calcined powder.

[0017] Add metallic calcium powder to the primary calcined powder, the amount of calcium powder added is 7wt% of the primary calcined powder, mix evenly, put into a 300mL high-alumina crucible, put the crucible into a pressure furnace, and keep it at 600℃ for 7 hours under a nitrogen protective atmosphere. After naturally cooling to room temperature, crush, grind, acid wash, water wash, dry, and pass through a 60-mesh sieve, it is recorded as fluorescent powder recovery material.

[0018] The recycled phosphor material is mixed into the NdFeB alloy powder. The amount of the recycled phosphor material in the NdFeB magnetic material raw material is 7wt%. The mixture is uniform and carried out in accordance with the normal operation process of magnetic materials. After hydrogen crushing, powdering, molding and sintering, NdFeB blanks are made.

[0019] Example 3 Using recycled phosphor waste from tri-color fluorescent lamps as raw material, 100g of phosphor waste sample was accurately weighed, crushed, ground, and passed through a 100-mesh sieve. The sample was then placed in a 300mL high-alumina crucible and placed in a muffle furnace at 400℃ for 3 hours. After naturally cooling to room temperature, the sample was ground and passed through a 100-mesh sieve. This was recorded as the first-calcined powder.

[0020] Add metallic calcium powder to the primary calcined powder, with the amount of calcium powder added being 6 wt% of the primary calcined powder. Mix evenly and place in a 300 mL high-alumina crucible. Place the crucible in a pressure furnace and maintain the temperature at 650℃ for 6 hours under a nitrogen protective atmosphere. Allow it to cool naturally to room temperature. After crushing, grinding, acid washing, water washing, drying, and passing through a 100-mesh sieve, it is recorded as fluorescent powder recovery material.

[0021] The recycled phosphor material is mixed into the NdFeB alloy powder. The amount of the recycled phosphor material in the NdFeB magnetic material raw material is 6wt%. The mixture is uniform and carried out in accordance with the conventional operation process of magnetic materials. After hydrogen crushing, powdering, molding and sintering, NdFeB blanks are made.

[0022] Comparative Example 1 No recycled phosphor material is added to the NdFeB alloy powder. Following the conventional production process of magnetic materials, NdFeB blanks are produced through hydrogen crushing, powdering, molding, and sintering.

[0023] The remanence and coercivity of the neodymium iron boron blanks in the embodiments and comparative examples of the present invention were tested.

[0024] The magnetic properties of NdFeB blanks were tested using an automatic permanent magnet characteristic measuring instrument. The results are shown in Table 1.

[0025] Table 1 Remanence and coercivity of NdFeB blanks As can be seen from the results in Table 1, when 5-7 wt% of recycled phosphor material is added to NdFeB alloy powder, and NdFeB blanks are produced by hydrogen pulverization, powdering, molding, and sintering according to the conventional production process of magnetic materials, the magnetic properties of the NdFeB blanks are tested using an automatic permanent magnet characteristic measuring instrument. The remanence does not change much, but the coercivity can be increased by 5-9 KOe.

[0026] Specifically, when the coercivity of NdFeB magnets increases by 5-9 KOe, their temperature resistance can be improved by 30-50℃, and their service life (anti-demagnetization ability and time) can typically be extended by 2-5 times. The specific values ​​are affected by the process of increasing the coercivity and the application environment. The following is a detailed analysis: 1. Temperature Resistance: The service temperature of ordinary NdFeB magnets is mostly around 80℃. The temperature resistance will be significantly improved after the coercivity is increased. For example, after the coercivity of N50 substrate is improved by grain boundary diffusion technology, it can be transformed into H (100℃) or SH (150℃) grade magnets. The original NdFeB with a coercivity of 12kOe can have its coercivity temperature coefficient reduced from -0.4% - 0.7% / ℃ to below -0.2% - 0.6% / ℃ after being increased by 5-9kOe. It can also reduce irreversible demagnetization at high temperatures of 150-200℃. Some modified magnets can control the magnetic performance decay to within 5% after 500 hours of continuous operation at 200℃.

[0027] 2. Service Life: In high-temperature environments exceeding 150℃, such as those used in new energy vehicle motors and wind turbines, traditional NdFeB magnets are prone to demagnetization due to insufficient coercivity, resulting in a short service life. Increasing the coercivity by 5-9 Koe can slow down microstructural degradation such as grain boundary phase softening and oxidation, significantly reducing irreversible magnetic flux loss. Based on industry application examples, its service life can typically be extended by 2-5 times; with the addition of protective coatings and other processes, performance degradation caused by corrosion can be further reduced, extending service life even further.

[0028] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for enhancing the coercivity of neodymium iron boron magnetic materials using phosphor waste, characterized in that, Includes the following steps: S1. Using waste phosphor powder from the recycling of tri-color fluorescent lamps as raw material, the powder is crushed, ground and sieved into fine powder, placed in a crucible, placed in a muffle furnace, and first calcined in air. After natural cooling to room temperature, it is ground and sieved to obtain calcined powder. The temperature of the first calcination is 300-500℃. S2. Add 1-10 wt% calcium powder to the powder calcined in S1, mix evenly, put it into a crucible, place it in a pressure furnace, and calcine it a second time under a protective atmosphere. After naturally cooling to room temperature, crush, grind, acid wash, water wash, dry and sieve to obtain fluorescent powder recovery material; the secondary calcination temperature is 500-700℃. S3. 1-10 wt% of recycled phosphor material is added to NdFeB alloy powder, and after hydrogen crushing, powdering, molding and sintering processes, NdFeB blanks are obtained.

2. The method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 1, characterized in that: In step S1, the primary roasting temperature of the phosphor waste is 350-450℃.

3. The method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 2, characterized in that: In step S1, the phosphor waste is roasted for 3-5 hours at a time.

4. The method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 1, characterized in that, In step S2, the amount of calcium powder added during the second calcination is 5-7 wt% of the powder from the first calcination.

5. The method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 4, characterized in that, In step S2, the secondary roasting temperature is 550-650℃.

6. The method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 4, characterized in that, In step S2, the secondary roasting time is 6-8 hours.

7. A method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 6, characterized in that, In step S2, the protective atmosphere for the secondary roasting is an inert atmosphere.

8. A method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to claim 7, characterized in that, The inert atmosphere is argon or nitrogen.

9. A method for improving the coercivity of NdFeB magnetic materials using phosphor waste according to any one of claims 1-8, characterized in that, In step S3, the amount of phosphor recycled material added to the NdFeB magnetic material raw material is 5-7 wt%.

Images