A method for preparing ultrafine iron powder

Abstract

A method for preparing ultrafine iron powder, belonging to the field of iron powder preparation, includes the following steps: S1: High-purity iron oxide red is ball-milled to obtain iron oxide red powder; S2: Iron oxide red powder is added to pure water, then Schiff base-hydroxymethyl cellulose modifier is added, pH is adjusted with citric acid-sodium citrate buffer solution, and vacuum freeze-drying is performed to obtain a mixed powder; S3: The mixed powder is heated, hydrogen gas is added, the temperature is increased to carry out the reaction, and the temperature is decreased to obtain reduced iron powder coated with a passivation layer; S4: The reduced iron powder coated with the passivation layer is added to deoxygenated water, bubbled with N2, 3-methylacrylamide and methoxy polyethylene glycol amine are added, pH is adjusted with NaOH, stirred at room temperature, magnetically separated, dispersed in trehalose aqueous solution and stirred evenly, and freeze-dried to obtain ultrafine reduced iron powder.

Description

Technical Field

[0001] This invention belongs to the field of iron powder preparation technology, specifically relating to a method for preparing ultrafine iron powder. Background Technology

[0002] With the development and progress of industries such as electronics, power, computers, communications, national defense, new energy, and artificial intelligence, the requirements for the purity of iron powder are becoming increasingly stringent. In the process of preparing iron powder by reducing iron oxide, iron-containing raw materials and reducing agents need to be mixed together for batching, processing, and pressing into balls for subsequent work. During the batching and mixing process, if the iron oxide does not agglomerate well and is easily dispersed, it may lead to incomplete reduction of some particles, leaving residual FeO or Fe3O4, resulting in excessive impurities in the iron powder and thus affecting the purity of the prepared iron powder. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing ultrafine iron powder.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing ultrafine iron powder includes the following steps:

[0008] S1: Take high-purity iron red and ball-mill it to 20-80μm to obtain iron red powder;

[0009] S2: Add iron oxide red powder to pure water at 15-17% of the iron oxide red mass, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 5-6 with citrate-sodium citrate buffer, use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm, and freeze dry under vacuum to obtain mixed powder;

[0010] S3: Heat the mixed powder to 280-320℃ and keep it at that temperature for 2-5 hours. Add hydrogen and heat it to 600-700℃ for 60-80 minutes. Then, cool it down to 120-130℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 20-40 minutes to obtain reduced iron powder coated with a passivation layer.

[0011] S4: By weight, take 10 parts of reduced iron powder coated with passivation layer and add it to deoxygenated water. Bubble with N2 for 5-10 min, add 0.1-0.15 parts of 3-methylacrylamide and 0.15-0.2 parts of methoxy polyethylene glycolamine, adjust the pH to 8-9 with NaOH, stir at room temperature for 30-40 min, magnetically separate for 3-4 min, disperse in trehalose aqueous solution and stir evenly, freeze dry at -40-45℃ for 22-24 h to obtain ultrafine reduced iron powder.

[0012] Furthermore, the amount of the Schiff base-hydroxymethyl cellulose modifier used is 2.5-3.5% of the mass of iron oxide red.

[0013] Furthermore, the amount of deoxygenated water used is 1g of reduced iron powder coated with a passivation layer and 4-5ml of deoxygenated water.

[0014] Furthermore, the amount of trehalose aqueous solution used is 1g of reduced iron powder coated with a passivation layer and 1-1.5ml of trehalose aqueous solution.

[0015] Furthermore, the trehalose aqueous solution has a mass fraction of 3-3.5%.

[0016] Furthermore, the preparation method of the Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0017] A1: By weight, disperse 10 parts of hydroxymethyl cellulose in ice water, purge with N2 for 30 min, swell at 0-5℃ for 1 h, add 1.5-2 parts of oxidized polyvinyl alcohol, adjust pH to 9.0 with Na2CO3, stir slowly at 25℃ for 20 min, raise the temperature to 45℃, add 1.2-1.3 g of 6-(allyloxycarbonylamino)-1-hexanol dropwise, continue the reaction for 45 min, and obtain Schiff base crosslinked product;

[0018] A2: Add 0.03-0.04 parts of potassium persulfate to the Schiff base crosslinker at 60-65℃ and react for 20 min. Then add 0.1-0.15 parts of sodium cyanoborohydride and react at 45℃ for 30-35 min to obtain the hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge, and vacuum dry at 70-75℃ to obtain the Schiff base-hydroxymethyl cellulose modified product.

[0019] Furthermore, the volume of the ethanol is 3-4 times that of the hydrophobically modified Schiff base crosslinker.

[0020] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0021] 1. The Schiff base-hydroxymethyl cellulose modifier contains oxidized polyvinyl alcohol, which provides crosslinking points for crosslinking between hydroxymethyl cellulose and 6-(allyloxycarbonylamino)-1-hexanol. Sodium cyanoborohydride can enhance the thermal stability of the crosslinking network formed between hydroxymethyl cellulose and 6-(allyloxycarbonylamino)-1-hexanol. Potassium persulfate initiates allyl free radicals, which are covalently grafted with the remaining hydroxyl / carboxymethyl groups of hydroxymethyl cellulose, so that the 6-carbon alkyl chains are permanently "stitched" on the surface of the three-dimensional network, forming a hydrophobic barrier, inhibiting the swelling of water vapor in the reducing gas, and improving the wetting and anchoring force on iron oxide red particles.

[0022] 2. In the technical solution of the present invention, the thermal stability provided by the cross-linking network formed between hydroxymethyl cellulose and 6-(allyloxycarbonylamino)-1-hexanol, and the hydrophobic barrier provided by the addition of potassium persulfate, synergistically enhance the aggregation ability of iron red, thereby improving the purity of the prepared iron powder. Detailed Implementation

[0023] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] Example 1:

[0025] This embodiment prepares an ultrafine iron powder.

[0026] A method for preparing a Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0027] A1: By weight, 10 parts of hydroxymethyl cellulose were dispersed in ice water, N2 was introduced for 30 min, and the mixture was allowed to swell at 0-5℃ for 1 h. 1.75 parts of oxidized polyvinyl alcohol were added, and the pH was adjusted to 9.0 with Na2CO3. The mixture was stirred slowly at 25℃ for 20 min, and the temperature was raised to 45℃. 1.25 g of 6-(allyloxycarbonylamino)-1-hexanol was added dropwise, and the reaction was continued for 45 min to obtain the Schiff base crosslinking product.

[0028] A2: By weight, add 0.035 parts of potassium persulfate to the Schiff base crosslinker at 65°C and react for 20 min. Then add 0.13 parts of sodium cyanoborohydride and react at 45°C for 35 min to obtain a hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge, and vacuum dry at 70°C to obtain a Schiff base-hydroxymethyl cellulose modified product. The volume of the ethanol is 3.5 times that of the hydrophobically modified Schiff base crosslinker.

[0029] A method for preparing ultrafine iron powder includes the following steps:

[0030] S1: Take high-purity iron red and ball-mill it to 50μm to obtain iron red powder;

[0031] S2: Add iron oxide red powder to 16% pure water by weight of iron oxide red, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 6 with citrate-sodium citrate buffer, and use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm. Vacuum freeze-dry to obtain mixed powder. The amount of Schiff base-hydroxymethyl cellulose modifier is 3% of the iron oxide red mass.

[0032] S3: Heat the mixed powder to 300℃, keep it at that temperature for 3.5h, add hydrogen, raise the temperature to 650℃ and react for 70min, cool it down to 125℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 30min to obtain reduced iron powder coated with a passivation layer.

[0033] S4: By weight, take 10 parts of reduced iron powder coated with a passivation layer and add it to deoxygenated water. Bubble with N2 for 10 min, add 0.125 parts of 3-methacrylamide and 0.17 parts of methoxy polyethylene glycolamine, adjust the pH to 9 with NaOH, stir at room temperature for 35 min, magnetically separate for 4 min, disperse in a 3.25% (w / w) trehalose aqueous solution and stir evenly. Freeze dry at -45℃ for 23 h to obtain ultrafine reduced iron powder. The amount of deoxygenated water used is 4.5 ml of deoxygenated water for 1 g of reduced iron powder coated with a passivation layer, and the amount of trehalose aqueous solution used is 1.25 ml of trehalose aqueous solution for 1 g of reduced iron powder coated with a passivation layer.

[0034] Example 2:

[0035] This embodiment prepares an ultrafine iron powder.

[0036] A method for preparing a Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0037] A1: By weight, 10 parts of hydroxymethyl cellulose were dispersed in ice water, N2 was introduced for 30 min, and the mixture swelled at 0℃ for 1 h. 1.5 parts of oxidized polyvinyl alcohol were added, the pH was adjusted to 9.0 with Na2CO3, and the mixture was slowly stirred at 25℃ for 20 min. The temperature was raised to 45℃, and 1.2 g of 6-(allyloxycarbonylamino)-1-hexanol was added dropwise. The reaction was continued for 45 min to obtain the Schiff base crosslinking product.

[0038] A2: By weight, add 0.03 parts of potassium persulfate to the Schiff base crosslinker at 60°C and react for 20 min. Then add 0.1 parts of sodium cyanoborohydride and react at 45°C for 30 min to obtain a hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge, and vacuum dry at 70°C to obtain a Schiff base-hydroxymethyl cellulose modified product. The volume of the ethanol is 3 times that of the hydrophobically modified Schiff base crosslinker.

[0039] A method for preparing ultrafine iron powder includes the following steps:

[0040] S1: Take high-purity iron red and ball-mill it to 20μm to obtain iron red powder;

[0041] S2: Add iron oxide red powder to 15% pure water by weight of iron oxide red, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 5 with citrate-sodium citrate buffer, and use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm. Vacuum freeze-dry to obtain mixed powder. The amount of Schiff base-hydroxymethyl cellulose modifier is 2.5% of the iron oxide red mass.

[0042] S3: Heat the mixed powder to 280℃, keep it at that temperature for 2 hours, add hydrogen, raise the temperature to 600℃ and react for 60 minutes, cool it down to 120℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 20 minutes to obtain reduced iron powder coated with a passivation layer.

[0043] S4: By weight, take 10 parts of reduced iron powder coated with a passivation layer and add it to deoxygenated water. Bubble with N2 for 5 minutes, add 0.1 parts of 3-methacrylamide and 0.15 parts of methoxy polyethylene glycolamine, adjust the pH to 8 with NaOH, stir at room temperature for 30 minutes, magnetically separate for 3 minutes, disperse in a 3% (w / w) trehalose aqueous solution and stir evenly. Freeze dry at -40℃ for 22 hours to obtain ultrafine reduced iron powder. The amount of deoxygenated water used is 1g of reduced iron powder coated with a passivation layer to 4ml of deoxygenated water, and the amount of trehalose aqueous solution used is 1g of reduced iron powder coated with a passivation layer to 1ml of trehalose aqueous solution.

[0044] Example 3:

[0045] This embodiment prepares an ultrafine iron powder.

[0046] A method for preparing a Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0047] A1: By weight, 10 parts of hydroxymethyl cellulose were dispersed in ice water, N2 was introduced for 30 min, and the mixture swelled at 5°C for 1 h. 2 parts of oxidized polyvinyl alcohol were added, and the pH was adjusted to 9.0 with Na2CO3. The mixture was stirred slowly at 25°C for 20 min, and the temperature was raised to 45°C. 1.3 g of 6-(allyloxycarbonylamino)-1-hexanol was added dropwise, and the reaction was continued for 45 min to obtain the Schiff base crosslinking product.

[0048] A2: By weight, add 0.04 parts of potassium persulfate to the Schiff base crosslinker at 65°C and react for 20 min. Then add 0.15 parts of sodium cyanoborohydride and react at 45°C for 35 min to obtain a hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge and vacuum dry at 75°C to obtain a Schiff base-hydroxymethyl cellulose modified product. The volume of the ethanol is 4 times that of the hydrophobically modified Schiff base crosslinker.

[0049] A method for preparing ultrafine iron powder includes the following steps:

[0050] S1: Take high-purity iron red and ball-mill it to 80μm to obtain iron red powder;

[0051] S2: Add iron oxide red powder to 17% pure water by weight of iron oxide red, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 6 with citrate-sodium citrate buffer, and use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm. Vacuum freeze-dry to obtain mixed powder. The amount of Schiff base-hydroxymethyl cellulose modifier is 3.5% of the iron oxide red mass.

[0052] S3: Heat the mixed powder to 320℃ and keep it at that temperature for 5 hours. Add hydrogen and heat to 700℃ for 80 minutes. Then cool down to 130℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 40 minutes to obtain reduced iron powder coated with a passivation layer.

[0053] S4: By weight, take 10 parts of reduced iron powder coated with a passivation layer and add it to deoxygenated water. Bubble with N2 for 10 min, add 0.15 parts of 3-methacrylamide and 0.2 parts of methoxy polyethylene glycolamine, adjust the pH to 9 with NaOH, stir at room temperature for 40 min, magnetically separate for 4 min, disperse in a 3.5% (w / w) trehalose aqueous solution and stir evenly. Freeze dry at -45℃ for 24 h to obtain ultrafine reduced iron powder. The amount of deoxygenated water used is 1g of reduced iron powder coated with a passivation layer in 5ml of deoxygenated water, and the amount of trehalose aqueous solution used is 1g of reduced iron powder coated with a passivation layer in 1.5ml of trehalose aqueous solution.

[0054] Example 4:

[0055] This embodiment prepares an ultrafine iron powder.

[0056] A method for preparing a Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0057] A1: By weight, 10 parts of hydroxymethyl cellulose were dispersed in ice water, N2 was introduced for 30 min, and the mixture was allowed to swell at 0-5℃ for 1 h. 1.56 parts of oxidized polyvinyl alcohol were added, the pH was adjusted to 9.0 with Na2CO3, and the mixture was stirred slowly at 25℃ for 20 min. The temperature was raised to 45℃, and 1.23 g of 6-(allyloxycarbonylamino)-1-hexanol was added dropwise. The reaction was continued for 45 min to obtain the Schiff base crosslinking product.

[0058] A2: By weight, 0.032 parts of potassium persulfate were added to the Schiff base crosslinker at 62°C and reacted for 20 min. Then, 0.12 parts of sodium cyanoborohydride were added and reacted at 45°C for 32 min to obtain a hydrophobically modified Schiff base crosslinker. The hydrophobically modified Schiff base crosslinker was precipitated with ethanol, centrifuged, and vacuum dried at 71°C to obtain a Schiff base-hydroxymethyl cellulose modified product. The volume of the ethanol was 3.2 times that of the hydrophobically modified Schiff base crosslinker.

[0059] A method for preparing ultrafine iron powder includes the following steps:

[0060] S1: Take high-purity iron red and ball-mill it to 30μm to obtain iron red powder;

[0061] S2: Add iron oxide red powder to 15.5% pure water by weight of iron oxide red, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 5 with citrate-sodium citrate buffer, and use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm. Vacuum freeze-dry to obtain mixed powder. The amount of Schiff base-hydroxymethyl cellulose modifier is 2.8% of the iron oxide red mass.

[0062] S3: Heat the mixed powder to 290℃, keep it at that temperature for 2.5h, add hydrogen, raise the temperature to 620℃ and react for 65min, cool it down to 123℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 25min to obtain reduced iron powder coated with a passivation layer.

[0063] S4: By weight, take 10 parts of reduced iron powder coated with a passivation layer and add it to deoxygenated water. Bubble with N2 for 6 min, add 0.12 parts of 3-methacrylamide and 0.16 parts of methoxy polyethylene glycolamine, adjust the pH to 8 with NaOH, stir at room temperature for 32 min, magnetically separate for 3.4 min, disperse in a 3.2% trehalose aqueous solution and stir evenly. Freeze dry at -44℃ for 22.5 h to obtain ultrafine reduced iron powder. The amount of deoxygenated water used is 4.3 ml of deoxygenated water for 1 g of reduced iron powder coated with a passivation layer, and the amount of trehalose aqueous solution used is 1.2 ml of trehalose aqueous solution for 1 g of reduced iron powder coated with a passivation layer.

[0064] Example 5:

[0065] This embodiment prepares an ultrafine iron powder.

[0066] A method for preparing a Schiff base-hydroxymethyl cellulose modified material includes the following steps:

[0067] A1: By weight, 10 parts of hydroxymethyl cellulose were dispersed in ice water, N2 was introduced for 30 min, and the mixture swelled at 4℃ for 1 h. 1.8 parts of oxidized polyvinyl alcohol were added, the pH was adjusted to 9.0 with Na2CO3, and the mixture was slowly stirred at 25℃ for 20 min. The temperature was raised to 45℃, and 1.28 g of 6-(allyloxycarbonylamino)-1-hexanol was added dropwise. The reaction was continued for 45 min to obtain the Schiff base crosslinking product.

[0068] A2: By weight, add 0.038 parts of potassium persulfate to the Schiff base crosslinker at 64°C and react for 20 min. Then add 0.1-0.15 parts of sodium cyanoborohydride and react at 45°C for 34 min to obtain a hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge, and vacuum dry at 74°C to obtain a Schiff base-hydroxymethyl cellulose modified product. The volume of the ethanol is 3.8 times that of the hydrophobically modified Schiff base crosslinker.

[0069] A method for preparing ultrafine iron powder includes the following steps:

[0070] S1: Take high-purity iron red and ball-mill it to 70μm to obtain iron red powder;

[0071] S2: Add iron oxide red powder to 16.5% pure water by weight of iron oxide red, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 6 with citrate-sodium citrate buffer, and use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm. Vacuum freeze-dry to obtain mixed powder. The amount of Schiff base-hydroxymethyl cellulose modifier is 3.2% of the iron oxide red mass.

[0072] S3: Heat the mixed powder to 310℃, keep it at that temperature for 4.5h, add hydrogen, raise the temperature to 690℃ and react for 75min, cool it down to 129℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 35min to obtain reduced iron powder coated with a passivation layer.

[0073] S4: By weight, take 10 parts of reduced iron powder coated with a passivation layer and add it to deoxygenated water. Bubble with N2 for 8 min, add 0.4 parts of 3-methacrylamide and 0.18 parts of methoxy polyethylene glycolamine, adjust the pH to 9 with NaOH, stir at room temperature for 38 min, magnetically separate for 3.8 min, disperse in a 3.4% trehalose aqueous solution and stir evenly. Freeze dry at -41℃ for 23.5 h to obtain ultrafine reduced iron powder. The amount of deoxygenated water used is 4.8 ml of deoxygenated water for 1 g of reduced iron powder coated with a passivation layer, and the amount of trehalose aqueous solution used is 1.4 ml of trehalose aqueous solution for 1 g of reduced iron powder coated with a passivation layer.

[0074] The difference between Comparative Example 1 and Example 1 is that 6-(allyloxycarbonylamino)-1-hexanol was not added during the preparation of the Schiff base-hydroxymethyl cellulose modified product in Comparative Example 1.

[0075] The difference between Comparative Example 2 and Example 1 is that potassium persulfate was not added in the preparation of the Schiff base-hydroxymethyl cellulose modified product in Comparative Example 2.

[0076] The difference between Comparative Example 3 and Example 1 is that 6-(allyloxycarbonylamino)-1-hexanol was not added during the preparation of the Schiff base-hydroxymethyl cellulose modified product in Comparative Example 3, and potassium persulfate was not added either.

[0077] The purity calculation results of the iron powders prepared in Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0078] Table 1:

[0079]

[0080] In conjunction with Examples 1-5 and Table 1, the ultrafine iron powder prepared by the technical solution of the present invention has high purity.

[0081] Based on the data from Example 1, Comparative Example 1, and Table 1, it can be seen that the addition of 6-(allyloxycarbonylamino)-1-hexanol to the Schiff base-hydroxymethyl cellulose modified product can improve the purity of iron powder prepared by iron red reduction.

[0082] Based on the data from Example 1, Comparative Example 1, Comparative Example 3, and Comparative Example 4, and Table 1, it can be seen that the addition of potassium persulfate to Schiff base-hydroxymethyl cellulose can synergistically enhance the agglomeration ability of the modified Schiff base-hydroxymethyl cellulose on iron red, thereby improving the purity of iron powder in the iron powder prepared by iron red reduction.

[0083] 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 preparing ultrafine iron powder, characterized in that, Includes the following steps: S1: Take high-purity iron red and ball-mill it to 20-80μm to obtain iron red powder; S2: Add iron oxide red powder to pure water at 15-17% of the iron oxide red mass, then add Schiff base-hydroxymethyl cellulose modifier, adjust the pH to 5-6 with citrate-sodium citrate buffer, use zirconium oxide microsphere planetary milling to D50 radius ≤1-5μm, and freeze dry under vacuum to obtain mixed powder; S3: Heat the mixed powder to 280-320℃ and keep it at that temperature for 2-5 hours. Add hydrogen and heat it to 600-700℃ for 60-80 minutes. Then, cool it down to 120-130℃ and keep it in an O2 / N2 mixed atmosphere with O2≤100ppm for 20-40 minutes to obtain reduced iron powder coated with a passivation layer. S4: By weight, take 10 parts of reduced iron powder coated with passivation layer and add it to deoxygenated water. Bubble with N2 for 5-10 min, add 0.1-0.15 parts of 3-methacrylamide and 0.15-0.2 parts of methoxy polyethylene glycolamine, adjust the pH to 8-9 with NaOH, stir at room temperature for 30-40 min, magnetically separate for 3-4 min, disperse in trehalose aqueous solution and stir evenly, freeze dry at -40-45℃ for 22-24 h to obtain ultrafine reduced iron powder; The preparation method of the Schiff base-hydroxymethyl cellulose modified material includes the following steps: A1: By weight, disperse 10 parts of hydroxymethyl cellulose in ice water, purge with N2 for 30 min, swell at 0-5℃ for 1 h, add 1.5-2 parts of oxidized polyvinyl alcohol, adjust pH to 9.0 with Na2CO3, stir slowly at 25℃ for 20 min, raise the temperature to 45℃, add 1.2-1.3 g of 6-(allyloxycarbonylamino)-1-hexanol dropwise, continue the reaction for 45 min, and obtain Schiff base crosslinked product; A2: Add 0.03-0.04 parts of potassium persulfate to the Schiff base crosslinker at 60-65℃ and react for 20 min. Then add 0.1-0.15 parts of sodium cyanoborohydride and react at 45℃ for 30-35 min to obtain the hydrophobically modified Schiff base crosslinker. Precipitate the hydrophobically modified Schiff base crosslinker with ethanol, centrifuge, and vacuum dry at 70-75℃ to obtain the Schiff base-hydroxymethyl cellulose modified product.

2. The method for preparing ultrafine iron powder according to claim 1, characterized in that, The amount of the Schiff base-hydroxymethyl cellulose modifier used is 2.5–3.5% of the mass of iron oxide red.

3. The method for preparing ultrafine iron powder according to claim 1, characterized in that, The amount of deoxygenated water used is 1g of reduced iron powder coated with a passivation layer and 4-5ml of deoxygenated water.

4. The method for preparing ultrafine iron powder according to claim 1, characterized in that, The amount of trehalose aqueous solution used is 1g of reduced iron powder coated with a passivation layer and 1-1.5ml of trehalose aqueous solution.

5. The method for preparing ultrafine iron powder according to claim 1, characterized in that, The trehalose aqueous solution has a mass fraction of 3-3.5%.

6. The method for preparing ultrafine iron powder according to claim 5, characterized in that, The volume of the ethanol is 3-4 times that of the hydrophobically modified Schiff base crosslinker.

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