A method for chemically synthesizing fine M-type barium ferrite nanomaterials

Abstract

This invention belongs to the field of magnetic nanomaterials technology, specifically relating to a method for chemically synthesizing fine M-type barium ferrite nanomaterials. This method involves co-precipitation of Fe and Ba salt solutions in a magnetic field to prepare small and uniform M-type barium ferrite nanomaterials. Applying a magnetic field increases the nucleation rate and refines the particles; adjusting the magnetic field strength controls the length of the M-type barium ferrite nanowires. Changing the type and amount of co-precipitating dispersant, the type of flux, and the mixing ratio of flux to precursor further controls the size of the nanomaterials and the length of the nanowires. Adjusting the sintering temperature and time controls the morphology and size of the product.

Description

Technical Field

[0001] This invention belongs to the field of magnetic nanomaterials technology, specifically relating to a method for chemically synthesizing fine M-type barium ferrite nanomaterials. Background Technology

[0002] M-type barium ferrite (BaFe) 12 O 19 Barium ferrite nanomaterials possess excellent antioxidant properties, high coercivity, magnetic energy product, and uniaxial magnetocrystalline anisotropy, making them widely used as permanent magnet materials, high-density perpendicular magnetic recording media, microwave absorbing materials, and microwave / millimeter-wave device materials. The application performance of M-type barium ferrite nanomaterials is closely related to their morphology, size uniformity, and phase structure. In particular, M-type barium ferrite nanomaterials with anisotropic shapes exhibit superior magnetic properties and rectangularity ratios, showing broad application prospects in high-density magnetic storage and magnetic transport devices. Currently, the main methods for synthesizing M-type barium ferrites include: high-temperature solid-state method, hydrothermal synthesis method, self-propagating combustion method, sol-gel method, and microemulsion method. The high-temperature solid-state method has high cost, large particle size, high energy consumption, and is prone to introducing impurities; the hydrothermal synthesis method has high equipment investment, high operating costs, and a long production cycle; the self-propagating combustion method is difficult to form multi-component nanopowders; the sol-gel method has high synthesis cost, a slow gelation process, and a long synthesis cycle; and the microemulsion method has large intermolecular gaps. Therefore, how to obtain high-performance, small and uniform M-type barium ferrite nanomaterials using the best synthesis process is a bottleneck problem in this field.

[0003] The coprecipitation method has advantages such as simple process, easy control of composition, low preparation cost, dense product particles, suitability for large-scale mass production, and high maturity. However, this method also has disadvantages such as easy particle agglomeration, wide particle size distribution, and difficulty in preparing one-dimensional M-type barium ferrite nanowires. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in existing coprecipitation techniques by providing a chemical method for synthesizing fine M-type barium ferrite nanomaterials. This method involves coprecipitating Fe and Ba salt solutions under a magnetic field to prepare small and uniform M-type barium ferrite nanomaterials. Experiments have shown that applying a specific magnetic field can increase the nucleation rate, thereby refining the grains. Increasing the magnetic field strength can magnetize the particles and link them into wires, preparing M-type barium ferrite nanowires. The nanowire length increases with increasing magnetic field strength. The size of the nanomaterials and the length of the nanowires can be controlled by changing the type and amount of the coprecipitation dispersant, the type of flux, and the mixing ratio of the flux to the precursor. The morphology and size of the product are controlled by adjusting the sintering temperature and time.

[0005] The technical solution of this invention is:

[0006] A method for chemically synthesizing fine M-type barium ferrite nanomaterials includes the following steps:

[0007] Step 1: Preparation of Fe salt 1 solution or Fe salt 2 solution:

[0008] Step 1.1 Preparation of Fe Salt 1 Solution: Grind 10-50g of iron concentrate using a ball mill at 100-600r / min for 1-8h to obtain iron concentrate powder with a particle size of 0.1-50μm, and set aside. Mix the ball-milled iron concentrate thoroughly with an alkaline solution of 10-50wt.% concentration, and keep it at 160-200℃ for 2-4h to remove impurities. Filter and wash the alkaline-washed iron concentrate thoroughly with deionized water to remove soluble silicates, and obtain purified iron concentrate, set aside. Transfer the purified iron concentrate to a glass dish, add an acidic solution with a concentration of 3-8mol / L, the ratio of iron concentrate to acidic solution is 1:(10-50), unit is g:ml, and stir at a constant temperature of 50-80℃ for 1-3h in air atmosphere to form Fe Salt 1 solution.

[0009] Step 1.2, Preparation of Fe salt 2 solution: Transfer 1.0-5.0g of Fe precursor to a glass dish, add 10-30ml of deionized water, and stir at a constant temperature of 50-80℃ for 1-3h under air atmosphere to form Fe salt 2 solution;

[0010] Step 2, coprecipitation reaction:

[0011] Step 2.1, according to the ratio n(Ba) 2+ ):n(Fe 3+ = 1:(6~12), weigh the Ba precursor and add it to the Fe salt 1 or Fe salt 2 solution, and continuously stir magnetically for 5~20 min to disperse the solution, to obtain Ba 2+ / Fe 3+ Mixed solutions;

[0012] Step 2.2, under magnetic field condition 1, towards Ba 2+ / Fe 3+ Slowly add 10-50 wt.% of either saturated sodium hydroxide (NaOH) or sodium sulfite (Na2SO3) solution to the mixed solution to generate Fe intermediate precipitate, while controlling the solution pH to 7-13 during the process. The magnetic field strength of magnetic field condition 1 is 0-2.0 T.

[0013] Step 2.3: Add a dispersant, which is polyethylene glycol HO(CH2CH2O). n H, Polyacrylic acid (C3H4O2) n Triethylamine C6H 15One of N, added in an amount of (Fe precursor + Ba precursor): dispersant = 1:(0.1~0.5), in g:ml, modifies the surface of precipitate particles and refines particle size during the precipitation process by dispersant;

[0014] Step 2.4, according to n(Ba) 2+ ):n(CO3 2 SO4 2- PO4 3- Weigh out one of the following: sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), or trisodium phosphate (Na3PO4) in a ratio of 1:(1-2), and prepare a 0.1-1.0 mol / L Na2CO3, Na2SO4, or Na3PO4 solution. Then, slowly add Ba under magnetic field condition 2. 2+ / Fe 3+ In the mixed solution, to generate Fe-Ba intermediate mixed precipitate, the magnetic field strength of the magnetic field condition 2 is 0 to 2.2 T.

[0015] Step 2.5: Stir the obtained Fe-Ba intermediate mixed precipitate at a constant temperature of 40-100℃ for 0.5-5.0h; connect the vacuum filtration device, wash the Fe-Ba intermediate mixed precipitate with deionized water, dry it in a constant temperature drying oven at 40-80℃ for 6-12h, and then grind the agglomerated dried sample thoroughly with a mortar to obtain Fe-Ba mixture powder sample.

[0016] Step 3, Sintering of the precursor:

[0017] Step 3.1: Add a co-solvent to the Fe-Ba mixture powder sample, with a mass ratio of co-solvent:(Fe precursor + Ba precursor) = 1:(5~15);

[0018] Step 3.2: Place the sample in a crucible and place the crucible in the center of a vacuum heat treatment furnace. Heat the sample to 500-800℃ at a rate of 1-10℃ / min and hold it in air for 0.5-10.0h to obtain barium ferrite powder. After cooling to room temperature, remove the barium ferrite powder sample and collect it for storage.

[0019] Step 4: Removal of NaCl / KCl / LiCl:

[0020] Step 4.1: Cool the sintered mixed powder to room temperature. Take a mixture of deionized water and anhydrous ethanol and dissolve and disperse the sintered mixed powder. Then centrifuge at a speed of 4000-10000 rpm for 3-10 min to remove NaCl / KCl / LiCl and discard the upper layer of centrifuged liquid.

[0021] Step 4.2: Add anhydrous ethanol to dissolve and disperse the powder. The ratio of anhydrous ethanol added is 1:(10-40) for the sintered mixed powder:anhydrous ethanol, in g:ml.

[0022] Step 4.3: Add deionized water in the same proportion as the anhydrous ethanol in step 4.2, centrifuge again, and discard the supernatant; the centrifugation speed is 4000-8000 rpm, and the centrifugation time is 3-10 min.

[0023] Step 4.4: Repeat steps 4.2 to 4.3 3 to 5 times to obtain M-type barium ferrite nanomaterials;

[0024] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, in step 1.1, the iron concentrate contains 60% to 71% iron; the alkaline solution is one of sodium hydroxide (NaOH), sodium bicarbonate (NaHCO3), or sodium ammonium hydrogen phosphate (NH4NaHPO4); the ratio of iron concentrate to alkaline solvent is 1:(1 to 10), in g:m; and the acidic solution is one of hydrochloric acid (HCl), sulfuric acid (H2SO4), or nitric acid (HNO3).

[0025] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the Fe precursor in step 1.2 is one of ferric chloride hexahydrate FeCl3·6H2O, ferric sulfate pentahydrate Fe2(SO4)3·5H2O, or ferric nitrate nonahydrate Fe(NO3)3·9H2O.

[0026] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, one of the Fe salt 1 and Fe salt 2 solutions in step 1 can be selected as the Fe source.

[0027] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the Ba precursor in step 2.1 is one of barium chloride dihydrate BaCl2·2H2O, barium sulfate BaSO4, or barium carbonate BaCO3.

[0028] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the co-solvent in step 3.1 is one of sodium chloride (NaCl), potassium chloride (KCl), and lithium chloride (LiCl).

[0029] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, in step 4.1, the deionized water and anhydrous ethanol are mixed in equal volumes.

[0030] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the M-type barium ferrite nanomaterials obtained in step 4.4 are dispersed in anhydrous ethanol for preservation.

[0031] Furthermore, in step 4.4 of the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the magnetic properties of the nanomaterials are measured by a vibrating sample magnetometer (VSM), the morphology and distribution of the nanomaterials are observed by field emission scanning electron microscopy (SEM), and the phase composition of the nanomaterials is analyzed by X-ray diffraction (XRD), confirming that M-type barium ferrite nanomaterials have been obtained.

[0032] Furthermore, in the above-mentioned chemical method for synthesizing fine M-type barium ferrite nanomaterials, the M-type barium ferrite nanomaterials obtained in step 4.4 have an average particle size of 20-200 nm, an average one-dimensional length of 100-2000 nm, a saturation magnetization of 30-100 emu / g, and a coercivity of 4000-6000 Oe.

[0033] This invention employs a co-precipitation method to directly synthesize small and uniform M-type barium ferrite nanomaterials. Commercial iron concentrate, after alkali washing and acid dissolution, is then used to prepare M-type barium ferrites via co-precipitation under magnetic field conditions. The co-precipitation process is controlled by adjusting the magnetic field strength, reaction conditions of the colloidal precipitate, and Ba... 2+ / Fe 3+ The molar ratio and dispersant addition conditions were determined, and the effects on BaFe were controlled by adjusting the sintering process, including the drying precipitate sintering conditions and flux addition conditions. 12 O 19 The influence of particle size and morphology on performance.

[0034] Advantages and beneficial effects of the present invention:

[0035] (1) Two types of iron sources were used to prepare M-type barium ferrite nanomaterials. The two types of iron sources included commercially available Fe precursor and commercial iron concentrate. The pure chemical reagent Fe precursor can achieve the preparation of high-purity barium ferrite. The commercial iron concentrate is inexpensive, with a market price of 650 to 900 yuan / ton. Using commercial iron concentrate as the Fe source can achieve the preparation of low-cost barium ferrite.

[0036] (2) Ba under magnetic field conditions 2+ / Fe 3+ Co-precipitation allows for the formation of a one-dimensional structure between the precipitated particles, resulting in M-type barium ferrite nanomaterials with anisotropic shape, superior magnetic properties, and a better rectangularity. Adding a dispersant during co-precipitation ensures uniform particle distribution.

[0037] (3) Adding flux during sintering can not only isolate the material but also prevent it from agglomerating and growing abnormally at high temperatures, thus producing fine-particle-size M-type barium ferrite nanomaterials.

[0038] (4) Since M-type barium ferrite has important applications in permanent magnet materials, high-density perpendicular magnetic recording media, microwave absorbing materials and microwave millimeter-wave device materials, this invention will promote the practical application of one-step synthesis technology of M-type barium ferrite, simplify the existing process, further save costs, and have good dispersion effect. The fine-particle-size M-type barium ferrite nanomaterials prepared by sintering have excellent magnetic properties, providing a research basis for promoting its application. Attached Figure Description

[0039] Figure 1 The hysteresis loop of the M-type barium ferrite nanomaterial prepared in Example 1 of the present invention;

[0040] Figure 2 The XRD pattern of the M-type barium ferrite nanomaterial prepared in Example 1 of the present invention;

[0041] Figure 3 This is a SEM image of the M-type barium ferrite nanomaterial prepared in Example 1 of the method of the present invention;

[0042] Figure 4 The hysteresis loop of the M-type barium ferrite nanomaterial prepared in Example 2 of the present invention;

[0043] Figure 5 The XRD pattern of the M-type barium ferrite nanomaterial prepared in Example 2 of the present invention;

[0044] Figure 6 This is a SEM image of the M-type barium ferrite nanomaterial prepared in Example 2 of the method of the present invention;

[0045] Figure 7 The hysteresis loop of the M-type barium ferrite nanomaterial prepared in Example 3 of the present invention;

[0046] Figure 8 The XRD pattern of the M-type barium ferrite nanomaterial prepared in Example 3 of the present invention;

[0047] Figure 9 This is a SEM image of the M-type barium ferrite nanomaterial prepared in Example 3 of the present invention. Detailed Implementation

[0048] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be used to limit the scope of the present invention.

[0049] In the following embodiments:

[0050] All the equipment used in the preparation is commercial and can be purchased on the market. The equipment includes: planetary ball mill, vacuum drying oven, circulating water multi-purpose vacuum pump, magnetic stirrer, magnetic field device, vacuum heat treatment furnace, electronic balance, pen-type pH meter, centrifuge, wide-mouth flask and quartz mortar, etc.

[0051] The vacuum drying oven is model DZ-2BCIV; the magnetic field device is model JMTD-12T; the vacuum heat treatment furnace is model T1255A; the centrifuge is model HC-2066; the planetary ball mill is model YXQM-0.4L; the circulating water multi-purpose vacuum pump is model SHB-3; the magnetic stirrer is model ZNCL-TS; the electronic balance is model ME104 / 02; the pen-type pH meter is model PH-20; the wide-mouth flask and quartz mortar are commercially available products.

[0052] The components used in this invention embodiment are: iron concentrate, sodium hydroxide (NaOH), sodium bicarbonate (NaHCO3), sodium ammonium hydrogen phosphate (NH4NaHPO4), hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), ferric chloride hexahydrate (FeCl3·6H2O), ferric sulfate pentahydrate (Fe2(SO4)3·5H2O), ferric nitrate nonahydrate (Fe(NO3)3·9H2O), barium chloride dihydrate (BaCl2·2H2O), barium sulfate (BaSO4), barium carbonate (BaCO3), deionized water, sodium hydroxide (NaOH), sodium sulfite (Na2SO3), and polyethylene glycol (HO(CH2CH2O)). n H, Polyacrylic acid (C3H4O2) n Triethylamine C6H 15 N, sodium carbonate Na2CO3, sodium sulfate Na2SO4, trisodium phosphate Na3PO4, sodium chloride NaCl, potassium chloride KCl, and lithium chloride LiCl were all commercially available products purchased from the market.

[0053] Example 1:

[0054] 5.0 g of ferric chloride hexahydrate FeCl3·6H2O was transferred to a glass dish, 30 ml of deionized water was added, and the mixture was stirred at 50 °C for 1 h under air atmosphere to form a Fe salt solution.

[0055] According to the proportion n(Ba 2+ ):n(Fe 3+ A ratio of 1:12 was used to weigh barium chloride dihydrate BaCl2·2H2O and add it to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaCl2·2H2O. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.0T, Ba... 2 + / Fe 3+ A 30 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 10. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.1, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(CO3 2- Sodium carbonate (Na₂CO₃) was weighed in a ratio of 1:1.5 and prepared into a 1.0 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.0 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 65℃ for 5 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 60℃ constant temperature drying oven for 8 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0056] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:5. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 600℃ at a rate of 5℃ / min and held at that temperature for 2 hours in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 4000 rpm for 3 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a sintered mixture:anhydrous ethanol ratio of 1:10. Then, deionized water in an equal proportion to anhydrous ethanol was added, and the mixture was centrifuged again, discarding the supernatant. This process was repeated three times.

[0057] The magnetic properties of the nanomaterial were measured using a vibrating sample magnetometer (VSM). Its coercivity was 4310 Oe, and its saturation magnetization reached 52.8 emu / g. (See attached image.) Figure 1 As shown. The phase structure of the sample was measured using X-ray diffraction. The relative intensity and position of the diffraction peaks containing the product at 2θ angles of 30.14°, 32.20°, 34.11°, 37.08°, 40.32°, 42.42°, 55.06°, 56.60°, and 63.06°, and the BaFe... 12 O 19 The phase standard spectrum (JCPDS#43-0002) is consistent, as shown in the attached figure. Figure 2 As shown in the attached figure. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 37 nm, and an average one-dimensional length of 176 nm. Figure 3 As shown.

[0058] Example 2:

[0059] First, 10g of iron concentrate with an iron content of 71% was ground using a ball mill at 500 rpm for 5 hours to obtain iron concentrate powder with a particle size of 8.0 μm. The ball-milled iron concentrate was then thoroughly mixed with a 10 wt.% sodium hydroxide (NaOH) solution, with an iron concentrate to alkaline solvent ratio of 1:1. The mixture was kept at 180℃ for 3 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. A 3 mol / L hydrochloric acid (HCl) solution was added to the purified iron concentrate, with an iron concentrate to acidic solvent ratio of 1:10. The mixture was stirred at 80℃ for 3 hours under air atmosphere to form an Fe salt solution.

[0060] According to the proportion n(Ba 2+ ):n(Fe 3+ A ratio of 1:9 was used to weigh barium chloride dihydrate BaCl2·2H2O and add it to the Fe salt solution. The solution was then continuously stirred magnetically for 20 minutes to disperse the solution, yielding BaCl2·2H2O. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 0.7T, [the solution is applied to] Ba[a / B]. 2 + / Fe 3+ A 30 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 13. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.2, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(CO3 2- Sodium carbonate (Na₂CO₃) was weighed in a 1:1 ratio and prepared into a 0.8 mol / L solution. Ba was then slowly added under a magnetic field strength of 0.7 T. 2+ / Fe 3+ Ba intermediate precipitate was formed in the mixed solution. The obtained Fe-Ba intermediate mixed precipitate was stirred at 80℃ for 1.5h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 70℃ constant temperature drying oven for 6h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0061] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:10. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 700℃ at a rate of 5℃ / min and held at that temperature for 3 hours in air to obtain barium ferrite powder. The sintered powder mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered powder mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added to dissolve and disperse the powder mixture, resulting in a powder-to-ethanol ratio of 1:30. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again, discarding the supernatant. The centrifugation speed was 5000 rpm for 3 minutes, and this process was repeated 5 times.

[0062] The magnetic properties of the nanomaterial were measured using a vibrating sample magnetometer (VSM). The coercivity was 5698 Oe, and the saturation magnetization was 58.2 emu / g. (See attached image.) Figure 4 As shown. The phase structure of the sample was measured using X-ray diffraction. The relative intensity and position of the diffraction peaks containing the product at 2θ angles of 30.14°, 32.20°, 34.11°, 37.08°, 40.32°, 42.42°, 55.06°, 56.60°, and 63.06°, and the BaFe... 12 O 19 The phase standard spectrum (JCPDS#43-0002) is consistent, as shown in the attached figure. Figure 5 As shown in the attached figure. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 48 nm, and an average one-dimensional length of 234 nm. Figure 6 As shown.

[0063] Example 3:

[0064] 1.0 g of ferric sulfate pentahydrate Fe2(SO4)3·5H2O was transferred to a glass dish, 10 ml of deionized water was added, and the mixture was stirred at 80 °C for 3 h under air atmosphere to form a Fe salt solution.

[0065] According to the proportion n(Ba 2+ ):n(Fe 3+ A ratio of 1:9 was used to weigh barium chloride dihydrate BaCl2·2H2O and add it to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaCl2·2H2O. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.5T, Ba... 2 + / Fe3+ A 50 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 12. Subsequently, polyacrylic acid (C3H4O2) was added as a dispersant. n The addition ratio is (Fe precursor + Ba precursor): dispersant = 1:0.5. During the precipitation process, the dispersant modifies the surface of the precipitate particles and refines the particle size. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a ratio of 1:2 and prepared into a 0.8 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.5 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 100℃ for 1 h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a constant temperature drying oven at 80℃ for 6 h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0066] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:15. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 800℃ at a rate of 5℃ / min and held at that temperature for 3 hours in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 10000 rpm for 10 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a powder-to-ethanol ratio of 1:40. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 8000 rpm for 10 minutes, discarding the supernatant. This process was repeated four times.

[0067] The magnetic properties of the nanomaterial were measured using a vibrating sample magnetometer (VSM). The coercivity was 50 × 10 Oe, and the saturation magnetization was 40.1 emu / g. (See attached image.) Figure 7 As shown. The phase structure of the sample was measured using X-ray diffraction. The relative intensity and position of the diffraction peaks containing the product at 2θ angles of 30.14°, 32.20°, 34.11°, 37.08°, 40.32°, 42.42°, 55.06°, 56.60°, and 63.06°, and the BaFe... 12 O 19 The phase standard spectrum (JCPDS#43-0002) is consistent, as shown in the attached figure. Figure 8As shown in the attached figure. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 71 nm, and an average one-dimensional length of 354 nm. Figure 9 As shown.

[0068] Example 4:

[0069] First, 50g of iron concentrate with an iron content of 60% was ground using a ball mill at 600 rpm for 8 hours to obtain iron concentrate powder with a particle size of 0.1μm. The ball-milled iron concentrate was then thoroughly mixed with a 36wt.% NaOH solution at a ratio of 1:10. The mixture was kept at 200℃ for 2 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 5mol / L dilute hydrochloric acid was added at a ratio of 1:50. The mixture was stirred at 50℃ for 3 hours under air atmosphere to form an Fe salt solution.

[0070] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium sulfate (BaSO4) was weighed out at a ratio of 1:6 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 15 minutes to disperse the solution, yielding BaSO4. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 0T, Ba... 2+ / Fe 3+ A 35 wt.% saturated sodium sulfite (Na₂SO₃) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 7. Subsequently, polyacrylic acid (C₃H₄O₂) was added as a dispersant. n The addition ratio is (Fe precursor + Ba precursor): dispersant = 1:0.3. During the precipitation process, the dispersant modifies the surface of the precipitate particles, refining the particle size. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a ratio of 1:1.5 and prepared into a 0.6 mol / L solution. Ba was then slowly added under a magnetic field strength of 0T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 40℃ for 3 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 40℃ constant temperature drying oven for 10 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0071] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:5. The crucible was placed in the center of a vacuum heat treatment furnace, which was heated to 500℃ at a rate of 6℃ / min and held at that temperature for 7 hours in air to obtain barium ferrite powder. The sintered powder mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered powder mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the powder mixture, resulting in a powder-to-anhydrous ethanol ratio of 1:40. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 4000 rpm for 5 minutes, discarding the supernatant. This process was repeated four times.

[0072] The coercivity of the nanomaterials, measured using a vibrating sample magnetometer (VSM), was 6000 Oe, and the saturation magnetization reached 30.0 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterials were nanospheres with good dispersion and an average particle size of 200 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0073] Example 5:

[0074] 2.0 g of ferric chloride hexahydrate FeCl3·6H2O was transferred to a glass dish, 20 ml of deionized water was added, and the mixture was stirred at 60 °C for 2 h under air atmosphere to form a Fe salt solution.

[0075] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium sulfate (BaSO4) was weighed at a ratio of 1:9 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaSO4. 2+ / Fe 3+ Mixed solution.

[0076] Under a magnetic field strength of 0.5T, to Ba 2+ / Fe 3+ A 10 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 8. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.2, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(PO4 3-Weigh out trisodium phosphate (Na3PO4) in a 1:1 ratio and prepare a 0.1 mol / L solution. Slowly add Ba under a magnetic field strength of 0.5 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 100℃ for 0.5h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a constant temperature drying oven at 40℃ for 12h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0077] Potassium chloride (KCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:10 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 700℃ at a rate of 3℃ / min and held at that temperature for 1 hour in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove KCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a powder-to-ethanol ratio of 1:20. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again, discarding the supernatant. The centrifugation was repeated four times at 6000 rpm for 5 minutes.

[0078] The coercivity of the nanomaterial was determined to be 4000 Oe and the saturation magnetization to be 67.8 emu / g using a vibrating sample magnetometer (VSM). Field emission scanning electron microscopy (SEM) revealed that the nanomaterial consisted of nanospheres with good dispersion and an average particle size of 20 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0079] Example 6:

[0080] First, 35g of iron concentrate with an iron content of 66% was ground using a ball mill at 200 rpm for 1 hour to obtain iron concentrate powder with a particle size of 50μm. The ball-milled iron concentrate was then thoroughly mixed with a 39wt.% NaOH solution, with an iron concentrate to alkaline solvent ratio of 1:5. The mixture was kept at 180℃ for 3 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 8mol / L dilute hydrochloric acid was added, with an iron concentrate to acidic solvent ratio of 1:20. The mixture was stirred at 60℃ for 2 hours under air atmosphere to form an Fe salt solution.

[0081] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium carbonate (BaCO3) was weighed out at a ratio of 1:12 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 5 minutes to disperse the solution, yielding BaCO3. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.8T, [the solution is applied to] Ba[a]. 2+ / Fe 3+ A 20 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 12. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.5, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(PO4 3- Weigh out trisodium phosphate (Na3PO4) in a ratio of 1:2 and prepare a 0.2 mol / L solution. Slowly add Ba under a magnetic field strength of 1.8 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 80℃ for 1.5h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 40℃ constant temperature drying oven for 12h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0082] Potassium chloride (KCl) was added to the Fe-Ba mixture powder sample as a fluxing agent at a mass ratio of (Fe precursor + Ba precursor) = 1:15. The crucible was placed in the center of a vacuum heat treatment furnace, which was heated to 600℃ at a rate of 1℃ / min and held at that temperature in air for 8 hours to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove KCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a powder-to-ethanol ratio of 1:30. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 8000 rpm for 5 minutes, discarding the supernatant. This process was repeated three times.

[0083] The coercivity of the nanomaterial, measured by a vibrating sample magnetometer (VSM), was 5600 Oe, and the saturation magnetization reached 53.4 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 67 nm, and an average one-dimensional length of 650 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0084] Example 7:

[0085] 4.0 g of ferric sulfate pentahydrate Fe2(SO4)3·5H2O was transferred to a glass dish, 25 ml of deionized water was added, and the mixture was stirred at a constant temperature of 70 °C for 1.5 h under air atmosphere to form a Fe salt solution.

[0086] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium sulfate (BaSO4) was weighed out at a ratio of 1:6 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaSO4. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 2.0T, Ba... 2+ / Fe 3+ A 15 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 9. Subsequently, polyacrylic acid (C3H4O2) was added as a dispersant. n The addition ratio is (Fe precursor + Ba precursor): dispersant = 1:0.2. During the precipitation process, the dispersant modifies the surface of the precipitate particles, refining the particle size. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a ratio of 1:1.5 and prepared into a 0.5 mol / L solution. Ba was then slowly added under a magnetic field strength of 2.0 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 40℃ for 5 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 70℃ constant temperature drying oven for 10 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0087] Potassium chloride (KCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:5 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was raised to 750℃ at a rate of 10℃ / min and held at that temperature for 3 hours in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature, and a mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture. The mixture was then centrifuged at 7000 rpm for 6 minutes to remove KCl, and the supernatant was discarded. Anhydrous ethanol was added to dissolve and disperse the mixture, and the ratio of sintered mixture to anhydrous ethanol was 1:20. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again, with the supernatant discarded. The centrifugation speed was 5000 rpm for 5 minutes, and this process was repeated 4 times.

[0088] The coercivity of the nanomaterial was determined to be 5500 Oe using a vibrating sample magnetometer (VSM), and the saturation magnetization reached 50.3 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 42 nm, and an average one-dimensional length of 1800 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0089] Example 8:

[0090] First, 30g of iron concentrate with an iron content of 65% was ground using a ball mill at 300 rpm for 5 hours to obtain iron concentrate powder with a particle size of 20μm. The ball-milled iron concentrate was then thoroughly mixed with a 39wt.% NaOH solution, with an iron concentrate to alkaline solvent ratio of 1:3. The mixture was kept at 160℃ for 4 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 3mol / L dilute hydrochloric acid was added, with an iron concentrate to acidic solvent ratio of 1:20. The mixture was stirred at 50℃ for 3 hours under air atmosphere to form an Fe salt solution.

[0091] According to the proportion n(Ba 2+ ):n(Fe 3+ Weigh out BaCl2·2H2O at a ratio of 1:10 and add it to the Fe salt solution. Stir magnetically for 8 minutes to dissolve the BaCl2·2H2O, obtaining Ba... 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.0T, Ba... 2+ / Fe 3+A 10 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to form a Fe intermediate precipitate, while maintaining the solution pH at 11. Subsequently, triethylamine (C6H2O) was added as a dispersant. 15 N, added at a ratio of (Fe precursor + Ba precursor): dispersant = 1:0.2, modifies the surface of precipitate particles and refines particle size during precipitation by using the dispersant. According to n(Ba 2+ ):n(CO3 2- Sodium carbonate (Na₂CO₃) was weighed in a 1:1 ratio and prepared into a 0.3 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.0 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 70℃ for 3 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 50℃ constant temperature drying oven for 10 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0092] Potassium chloride (KCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:10 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 500℃ at a rate of 6℃ / min and held at that temperature for 10 hours in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove KCl and discard the supernatant. Anhydrous ethanol was added to dissolve and disperse the mixture, resulting in a powder-to-ethanol ratio of 1:20. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again, discarding the supernatant. The centrifugation was repeated four times at 6000 rpm for 10 minutes.

[0093] The coercivity of the nanomaterial was determined to be 5800 Oe using a vibrating sample magnetometer (VSM), and the saturation magnetization reached 30.8 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 54 nm, and an average one-dimensional length of 260 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0094] Example 9:

[0095] 3.0 g of ferric chloride hexahydrate FeCl3·6H2O was transferred to a glass dish, 20 ml of deionized water was added, and the mixture was stirred at 60 °C for 3 h under air atmosphere to form a Fe salt solution.

[0096] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium sulfate (BaSO4) was weighed at a ratio of 1:9 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaSO4. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 2.0T, Ba... 2+ / Fe 3+ A 20 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 12. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.5, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(CO3 2- Sodium carbonate (Na₂CO₃) was weighed in a ratio of 1:2 and prepared into a 0.6 mol / L solution. Ba was then slowly added under a magnetic field strength of 2.2 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 65℃ for 2 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 60℃ constant temperature drying oven for 6 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0097] Lithium chloride (LiCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:15 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was raised to 800℃ at 8℃ / min and held at that temperature for 0.5h in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature, and a mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture. The mixture was then centrifuged at 7000 rpm for 6 min to remove LiCl, and the supernatant was discarded. Anhydrous ethanol was added to dissolve and disperse the mixture, and the ratio of sintered mixture to anhydrous ethanol was 1:30. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 8000 rpm for 5 min, and the supernatant was discarded. This process was repeated 4 times.

[0098] The coercivity of the nanomaterial was determined to be 4800 Oe using a vibrating sample magnetometer (VSM), and the saturation magnetization reached 30.0 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 47 nm, and an average one-dimensional length of 2000 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0099] Example 10:

[0100] First, 40g of iron concentrate with an iron content of 68% was ground using a ball mill at 100 rpm for 8 hours to obtain iron concentrate powder with a particle size of 30μm. The ball-milled iron concentrate was then thoroughly mixed with a 39wt.% NaOH solution at a ratio of 1:8. The mixture was kept at 200℃ for 2 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 6mol / L dilute hydrochloric acid was added at a ratio of 1:50. The mixture was stirred at 60℃ for 1 hour under air atmosphere to form an Fe salt solution.

[0101] According to the proportion n(Ba 2+ ):n(Fe 3+ Weigh out BaCl2·2H2O at a ratio of 1:10 and add it to the Fe salt solution. Stir magnetically for 10 minutes to dissolve the BaCl2·2H2O, obtaining Ba... 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.2T, [the solution is applied to] Ba[a / B]. 2+ / Fe 3+ A 20 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 12. Subsequently, polyacrylic acid (C3H4O2) was added as a dispersant. n The addition ratio is (Fe precursor + Ba precursor): dispersant = 1:0.2. During the precipitation process, the dispersant modifies the surface of the precipitate particles, refining the particle size. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a ratio of 1:1.5 and prepared into a 0.6 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.2 T. 2+ / Fe 3+In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 80℃ for 1.5h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 40℃ constant temperature drying oven for 12h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0102] Lithium chloride (LiCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:5 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 700℃ at a rate of 3℃ / min and held at that temperature in air for 2 hours to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove LiCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a sintered mixture:anhydrous ethanol ratio of 1:30. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 8000 rpm for 6 minutes, discarding the supernatant. This process was repeated 5 times.

[0103] The coercivity of the nanomaterials, measured by a vibrating sample magnetometer (VSM), was 6000 Oe, and the saturation magnetization reached 62.7 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterials exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 75 nm, and an average one-dimensional length of 356 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0104] Example 11:

[0105] 2.0 g of ferric nitrate nonhydrate Fe(NO3)3·9H2O was transferred to a glass dish, 20 ml of deionized water was added, and the mixture was stirred at 80 °C for 1 h under air atmosphere to form a Fe salt solution.

[0106] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium carbonate (BaCO3) was weighed at a ratio of 1:12 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaCO3. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.2T, [the solution is applied to] Ba[a / B]. 2+ / Fe 3+A 30 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 10. Subsequently, polyacrylic acid (C3H4O2) was added as a dispersant. n The addition ratio is (Fe precursor + Ba precursor): dispersant = 1:0.1. During the precipitation process, the dispersant modifies the surface of the precipitate particles, refining the particle size. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a 1:1 ratio and prepared into a 0.8 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.2 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 100℃ for 1 h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a constant temperature drying oven at 80℃ for 12 h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0107] Lithium chloride (LiCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:10 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was increased to 600℃ at a rate of 3℃ / min and held at that temperature in air for 10 hours to obtain barium ferrite powder. The sintered mixture was cooled to room temperature, and a mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture. The mixture was then centrifuged at 7000 rpm for 6 minutes to remove LiCl, and the supernatant was discarded. Anhydrous ethanol was added to dissolve and disperse the mixture, and the ratio of sintered mixture to anhydrous ethanol was 1:20. Then, deionized water in an equal proportion to anhydrous ethanol was added, and the mixture was centrifuged again, with the supernatant discarded. The centrifugation speed was 7000 rpm for 10 minutes, and this process was repeated 3 times.

[0108] The coercivity of the nanomaterial was determined to be 5500 Oe and the saturation magnetization to be 72.4 emu / g using a vibrating sample magnetometer (VSM). Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 62 nm, and an average one-dimensional length of 328 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0109] Example 12:

[0110] First, 35g of iron concentrate with an iron content of 66% was ground using a ball mill at 500 rpm for 6 hours to obtain iron concentrate powder with a particle size of 10μm. The ball-milled iron concentrate was then thoroughly mixed with a 39wt.% NaOH solution, with an iron concentrate to alkaline solvent ratio of 1:5. The mixture was kept at 200℃ for 4 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 8mol / L dilute hydrochloric acid was added, with an iron concentrate to acidic solvent ratio of 1:20. The mixture was stirred at 80℃ for 3 hours under air atmosphere to form an Fe salt solution.

[0111] According to the proportion n(Ba 2+ ):n(Fe 3+ Weigh BaCl2·2H2O at a ratio of 1:9 and add it to the Fe salt solution. Stir magnetically for 15 minutes to disperse the solution, obtaining BaCl2·2H2O. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.5T, Ba... 2+ / Fe 3+ A 20 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to generate a Fe intermediate precipitate, while maintaining the solution pH at 7. Subsequently, polyethylene glycol (HO(CH2CH2O)) was added as a dispersant. n H, with an addition ratio of (Fe precursor + Ba precursor): dispersant = 1:0.2, modifies the surface of precipitate particles and refines particle size during precipitation. According to n(Ba 2+ ):n(PO4 3- Weigh out trisodium phosphate (Na3PO4) in a ratio of 1:2 and prepare a 0.4 mol / L solution. Slowly add Ba under a magnetic field strength of 1.5 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 60℃ for 3 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a constant temperature drying oven at 80℃ for 8 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0112] Lithium chloride (LiCl) was added to the Fe-Ba mixture powder sample as a flux:(Fe precursor + Ba precursor) = 1:15 by mass. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was raised to 800℃ at 7℃ / min and held at that temperature for 0.5h in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature, and a mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture. The mixture was then centrifuged at 7000 rpm for 6 min to remove LiCl, and the supernatant was discarded. Anhydrous ethanol was added to dissolve and disperse the mixture, and the ratio of sintered mixture to anhydrous ethanol was 1:40. Deionized water in an equal proportion to anhydrous ethanol was then added, and the mixture was centrifuged again at 7000 rpm for 5 min, and the supernatant was discarded. This process was repeated 3 times.

[0113] The coercivity of the nanomaterial was determined to be 4900 Oe and the saturation magnetization to be 58.7 emu / g using a vibrating sample magnetometer (VSM). Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 43 nm, and an average one-dimensional length of 394 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0114] Example 13:

[0115] 3.0 g of ferric sulfate pentahydrate Fe2(SO4)3·5H2O was transferred to a glass dish, 25 ml of deionized water was added, and the mixture was stirred at 70 °C for 2 h under air atmosphere to form a Fe salt solution.

[0116] According to the proportion n(Ba 2+ ):n(Fe 3+ Barium carbonate (BaCO3) was weighed at a ratio of 1:12 and added to the Fe salt solution. The solution was then continuously stirred magnetically for 10 minutes to disperse the solution, yielding BaCO3. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 0.8T, Ba... 2+ / Fe 3+ A 10 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to form a Fe intermediate precipitate, while maintaining the solution pH at 8. Subsequently, triethylamine (C6H2O) was added as a dispersant. 15 N, added at a ratio of (Fe precursor + Ba precursor): dispersant = 1:0.5, modifies the surface of precipitate particles and refines particle size during precipitation by using the dispersant. According to n(Ba 2+ ):n(PO4 3-Weigh out trisodium phosphate (Na3PO4) in a ratio of 1:1.5 and prepare a 1.0 mol / L solution. Slowly add Ba under a magnetic field strength of 0.8 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 70℃ for 2 hours; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 70℃ constant temperature drying oven for 10 hours, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0117] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:5. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was raised to 500℃ at 8℃ / min and held at that temperature for 5 hours in air to obtain barium ferrite powder. The sintered powder mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered powder mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the powder mixture, resulting in a sintered powder:anhydrous ethanol ratio of 1:10. Then, deionized water in an equal proportion to anhydrous ethanol was added, and the mixture was centrifuged again, discarding the supernatant. This process was repeated three times.

[0118] The coercivity of the nanomaterial was determined to be 5200 Oe using a vibrating sample magnetometer (VSM), and the saturation magnetization reached 85.6 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 33 nm, and an average one-dimensional length of 153 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0119] Example 14:

[0120] First, 45g of iron concentrate with an iron content of 70% was ground using a ball mill at 600 rpm for 8 hours to obtain iron concentrate powder with a particle size of 0.1μm. The ball-milled iron concentrate was then thoroughly mixed with a 39wt.% NaOH solution, with an iron concentrate to alkaline solvent ratio of 1:5. The mixture was kept at 180℃ for 3 hours for alkaline washing to remove impurities. The alkaline-washed iron concentrate was then thoroughly filtered and washed with deionized water to remove soluble silicates, yielding purified iron concentrate. The purified iron concentrate was weighed and transferred to a glass dish, and 6mol / L dilute hydrochloric acid was added, with an iron concentrate to acidic solvent ratio of 1:30. The mixture was stirred at 70℃ for 3 hours under air atmosphere to form an Fe salt solution.

[0121] According to the proportion n(Ba 2+ ):n(Fe 3+ Weigh BaCl2·2H2O at a ratio of 1:6 and add it to the Fe salt solution. Stir magnetically for 20 minutes to disperse the solution, obtaining BaCl2·2H2O. 2+ / Fe 3+ Mixed solution. Under a magnetic field strength of 1.5T, Ba... 2+ / Fe 3+ A 15 wt.% saturated sodium hydroxide (NaOH) solution was slowly added to the mixed solution to form a Fe intermediate precipitate, while maintaining the solution pH at 12. Subsequently, triethylamine (C6H2O) was added as a dispersant. 15 N, added at a ratio of (Fe precursor + Ba precursor): dispersant = 1:0.5, modifies the surface of precipitate particles and refines particle size during precipitation by using the dispersant. According to n(Ba 2+ ):n(SO4 2- Sodium sulfate (Na₂SO₄) was weighed in a ratio of 1:2 and prepared into a 0.6 mol / L solution. Ba was then slowly added under a magnetic field strength of 1.5 T. 2+ / Fe 3+ In the mixed solution, Ba intermediate precipitate was formed. The obtained Fe-Ba intermediate mixed precipitate was stirred at 80℃ for 1.5h; a vacuum filtration device was connected, and the mixed precipitate was washed with deionized water. After drying in a 50℃ constant temperature drying oven for 6h, the agglomerated dried sample was thoroughly ground with a mortar and pestle to obtain Fe-Ba mixed powder sample.

[0122] A Fe-Ba mixture powder sample was added to a fluxing agent, sodium chloride (NaCl), at a mass ratio of flux:(Fe precursor + Ba precursor) = 1:10. The crucible was placed in the center of a vacuum heat treatment furnace, and the temperature was raised to 600℃ at 8℃ / min and held at that temperature for 8 hours in air to obtain barium ferrite powder. The sintered mixture was cooled to room temperature. A mixture of deionized water and anhydrous ethanol was used to dissolve and disperse the sintered mixture, followed by centrifugation at 7000 rpm for 6 minutes to remove NaCl and discard the supernatant. Anhydrous ethanol was added again to dissolve and disperse the mixture, resulting in a sintered mixture:anhydrous ethanol ratio of 1:20. Then, deionized water in an equal proportion to anhydrous ethanol was added, and the mixture was centrifuged again at 8000 rpm for 3 minutes, discarding the supernatant. This process was repeated 5 times.

[0123] The coercivity of the nanomaterial was determined to be 5800 Oe using a vibrating sample magnetometer (VSM), and the saturation magnetization reached 100.0 emu / g. Field emission scanning electron microscopy (SEM) revealed that the nanomaterial exhibited a one-dimensional nanosphere morphology with good dispersion, an average particle size of 46 nm, and an average one-dimensional length of 260 nm. X-ray diffraction analysis confirmed the phase structure of the sample to be BaFe. 12 O 19 Mutually.

[0124] As can be seen from the above embodiments, the M-type barium ferrite nanomaterials with fine grains synthesized by the chemical method of the present invention have excellent magnetic properties, and the nanomaterials exhibit a one-dimensional nanosphere interconnection morphology with good dispersibility.

Claims

1. A method for synthesizing fine M-type barium ferrite nanomaterials by chemical method, characterized in that, The method comprises the following steps: Step 1, preparation of Fe salt 1 solution or Fe salt 2 solution: Step 1.1, preparation of Fe salt 1 solution: 10-50 g of iron concentrate powder is ground by using a ball mill, and the ball milling is carried out at a rotating speed of 100-600 r / min for 1-8 h to obtain iron concentrate powder with a particle size of 0.1-50 μm, which is used for standby; the iron concentrate powder after ball milling is mixed with an alkaline solution with a concentration of 10-50 wt.% and is treated by alkali washing at 160-200 °C for 2-4 h to remove impurities, and then the iron concentrate powder after alkali washing is washed with deionized water to remove soluble silicates, thereby obtaining the iron concentrate powder after impurity removal, which is used for standby; the iron concentrate powder after impurity removal is transferred into a glass dish, an acidic solution with a concentration of 3-8 mol / L is added, the addition amount of the iron concentrate powder and the acidic solution is 1:(10-50) g:ml, and the mixture is stirred at 50-80 °C under an air atmosphere to form the Fe salt 1 solution; Step 1.2, preparation of Fe salt 2 solution: 1.0-5.0 g of Fe precursor is transferred into a glass dish, 10-30 ml of deionized water is added, and the mixture is stirred at 50-80 °C under an air atmosphere to form the Fe salt 2 solution; Step 2, coprecipitation reaction: Step 2.1, according to the ratio n(Ba 2+ ) : n(Fe 3+ )=1:(6~12), take the Ba precursor and add it into the Fe salt 1 or Fe salt 2 solution, and continuously stir for 5~20 min to disperse the solution, to obtain a Ba 2+ / Fe 3+ mixed solution; Step 2.2, under magnetic field condition 1, Ba 2+ / Fe 3+ Slowly add 10~50 wt.% of saturated sodium hydroxide NaOH or sodium sulfite Na2SO3 solution in the mixed solution to generate Fe intermediate precipitate, control the solution pH to 7~13 during the process, and the magnetic field strength of the magnetic field condition 1 is 0.5~2.0 T; Step 2.3, adding dispersant, dispersant is polyethylene glycol HO(CH2CH2O) n H, polyacrylic acid (C3H4O2) n , triethylamine C6H 15 One of N, the amount of addition is (Fe precursor + Ba precursor): dispersant = 1: (0.1~0.5), unit is g:ml, the surface of the precipitate particles is modified by the dispersant during the precipitation process, and the particle size is refined; Step 2.4, according to n(Ba) 2+ ): n(CO3) 2 SO4 2- PO4 3- Weigh out one of the following: sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), or trisodium phosphate (Na3PO4) in a ratio of 1:(1~2), and prepare a 0.1~1.0 mol / L Na2CO3, Na2SO4, or Na3PO4 solution. Then, slowly add Ba under magnetic field condition 2. 2+ / Fe 3+ In the mixed solution, to generate a Fe-Ba intermediate mixed precipitate, the magnetic field strength of the magnetic field condition 2 is 0.5~2.2T; Step 2.5, the obtained Fe-Ba intermediate mixed precipitate is stirred at 40-100 °C for 0.5-5.0 h; a suction filtration device is connected, the Fe-Ba intermediate mixed precipitate is washed with deionized water, and the mixture is dried in a constant temperature drying box at 40-80 °C for 6-12 h; then the caked dry sample is ground with a mortar to obtain a Fe-Ba mixture powder sample; Step 3, sintering of the precursor: Step 3.1, the Fe-Ba mixture powder sample is added into a cosolvent, and the mass ratio of the cosolvent to the Fe precursor and the Ba precursor is 1:5 or 1:15; Step 3.2, the sample is placed in a crucible, the crucible is placed in the center of a vacuum heat treatment furnace, and the temperature is raised to 500-800 °C at a rate of 1-10 °C / min and is kept at this temperature for 0.5-10.0 h under an air atmosphere, thereby obtaining a barium ferrite powder; after cooling to room temperature, the barium ferrite powder sample is taken out and collected and stored; Step 4, removal of NaCl / KCl / LiCl: Step 4.1, the sintered mixed powder is cooled to room temperature, a mixture of deionized water and anhydrous ethanol is taken, the sintered mixed powder is dissolved and dispersed, and then centrifugation is carried out at a speed of 4000-10000 rpm for 3-10 min to remove NaCl / KCl / LiCl, and the upper centrifugal liquid is discarded; Step 4.2, anhydrous ethanol is added again, and the sintered mixed powder is dissolved and dispersed, wherein the addition amount of the anhydrous ethanol is in a ratio of 1:(10-40) g:ml of the sintered mixed powder to the anhydrous ethanol; Step 4.3, deionized water is added in an equal ratio to the anhydrous ethanol in step 4.2, and centrifugal separation is carried out again, and the upper centrifugal liquid is discarded; wherein the centrifugal speed is 4000-8000 rpm, and the centrifugal time is 3-10 min. Step 4.4, repeating step 4.2~step 4.3 for 3~5 times to obtain M-type barium ferrite nanomaterials; The iron concentrate in step 1.1 contains 60%~71% of iron; the alkaline solution is one of sodium hydroxide NaOH, sodium bicarbonate NaHCO3, ammonium sodium hydrogen phosphate NH4NaHPO4; the addition amount of the iron concentrate and the alkaline solution is 1:(1~10) g:m; the acid solution is one of hydrochloric acid HCl, sulfuric acid H2SO4, nitric acid HNO3; The Fe precursor in step 1.2 is one of ferric chloride hexahydrate FeCl3·6H2O, iron sulfate pentahydrate Fe2(SO4)3·5H2O, and ferric nitrate nonahydrate Fe(NO3)3·9H2O; In step 4.4, the magnetic properties of the nanomaterials are determined by a vibrating sample magnetometer (VSM), the morphology and distribution of the nanomaterials are observed by a field emission scanning electron microscope (SEM), and the phase of the nanomaterials is analyzed by X-ray diffraction (XRD) to confirm that the M-type barium ferrite nanomaterials are obtained; The method co-precipitates Fe salt and Ba salt solution in a magnetic field to prepare M-type barium ferrite nanomaterials with small and uniform size, and the obtained M-type barium ferrite nanomaterials have an average particle size of 20~200 nm, an average one-dimensional length of 100~2000 nm, a saturation magnetization of 30~100 emu / g, and a coercive force of 4000~6000 Oe.

2. The method for synthesizing fine M-type barium ferrite nanomaterials by chemical method according to claim 1, characterized in that, Optionally, one of the Fe salt 1 and Fe salt 2 solutions in step 1 is used as the Fe source.

3. The method for synthesizing fine M-type barium ferrite nanomaterials by chemical method according to claim 1, characterized in that, The Ba precursor in step 2.1 is one of barium chloride dihydrate BaCl2·2H2O, barium sulfate BaSO4, and barium carbonate BaCO3.

4. The method for synthesizing fine M-type barium ferrite nanomaterials by chemical method according to claim 1, characterized in that, The cosolvent in step 3.1 is one of sodium chloride NaCl, potassium chloride KCl, and lithium chloride LiCl.

5. The method for synthesizing fine M-type barium ferrite nanomaterials by chemical method according to claim 1, characterized in that, In step 4.1, the mixture of deionized water and anhydrous ethanol is prepared by mixing equal volumes of deionized water and anhydrous ethanol.

6. The method for synthesizing fine M-type barium ferrite nanomaterials by chemical method according to claim 1, characterized in that, The M-type barium ferrite nanomaterials obtained in step 4.4 are dispersed in anhydrous ethanol for storage.

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