Passivated magnesium powder and preparation method thereof

Abstract

The invention belongs to the technical field of ferrous metallurgical industry, and particularly relates to passivated magnesium powder and a preparation method thereof. According to the preparation method of the passivated magnesium powder provided by the invention, a layer of uniformly distributed passivation film is formed on the surface of the magnesium powder by adopting a chemical passivation and physical passivation mode, so that the loss of the magnesium powder is reduced, and the magnesium powder has good oxidation resistance and has good reaction activity when being applied to molten iron desulfurization. The salt solution, the oxidizing agent, the surface active agent and the complexing agent are adopted to jointly form a chemical passivating agent, magnesium powder is subjected to chemical passivation, and the thickness of a passivation film on the surface of the passivated magnesium powder is controlled by controlling the concentration of the passivating agent, the particle size of inorganic mineral powder and the dosage of the inorganic mineral powder, nano silicon dioxide and other substances; and the phenomena of magnesium powder combustion caused by a too thin passive film layer or magnesium powder activity reduction caused by a too thick passive film layer and the like are effectively avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of steel metallurgy industry, and particularly relates to passivated magnesium powder and a preparation method thereof. Background Art

[0002] Sulfur, a harmful element in steel, can cause various damages, including hot brittleness. Especially in steel companies using continuous casting technology, the segregation of sulfides in steel is a major cause of cracking in continuous-cast billets and a key factor affecting the yield rate of continuous-cast billets. In recent decades, offshore oil production, the development of the automotive industry, and large-scale construction projects have placed increasingly stringent demands on steel quality, requiring steel to possess high strength, low-temperature toughness, and excellent cold-forming and weldability. To meet these market demands, steel industries worldwide are striving to improve steel quality by reducing impurities, particularly sulfur content.

[0003] Magnesium-based composite powder spray desulfurization technology is the mainstream process for hot metal desulfurization, and magnesium powder is a key factor in determining desulfurization effectiveness. Magnesium metal is highly reactive and therefore requires passivation treatment for safe transportation, storage, and use. Numerous methods exist for passivating the surface of magnesium metal, such as organic film protection, electroplating, and chromate passivation. However, these methods are generally applicable to the surface treatment of magnesium ingots and not to the surface passivation of magnesium granules used as desulfurizers. Currently, two methods are used to treat the surface of magnesium granules: a chemical reaction method, in which the magnesium on the surface of the granules reacts with a passivating agent to form a dense thin film of reaction products; and a surface coating method, in which the surface of the granules is coated with a non-reactive substance. Method one produces a uniform passivation layer and good passivation, but results in some loss of magnesium metal. Method two, while preventing magnesium metal loss, can lead to uneven and poor passivation. In addition, the existing dry process for producing magnesium powder and aluminum-magnesium alloy powder requires inert gas protection during the production process, and has high requirements for the airtightness of the equipment. Otherwise, it is easy to cause dust leakage and even cause safety accidents.

[0004] Chinese patent application publication number CN107088655A discloses a passivated magnesium powder, a passivated aluminum-magnesium alloy powder, and a wet production process thereof. Specifically, magnesium particles, aluminum-magnesium alloy particles, and an antioxidant aqueous solution are added to a wet pulverization apparatus for wet pulverization. The solid-liquid mixture is then wet-screened or hydraulically classified to achieve solid-liquid separation. After drying, the passivated magnesium powder or passivated aluminum-magnesium alloy powder is obtained. The antioxidants used in this method are one or more of phytic acid, boric acid, and potassium dichromate. However, these antioxidants only form a thin oxide film on the surface of the magnesium powder, which does not meet the requirements of steelmaking. The magnesium powder rapidly oxidizes and burns before being added to the molten steel, significantly reducing its desulfurization efficiency in the molten steel. Therefore, this method is not optimal in terms of safety and desulfurization efficiency. Summary of the Invention

[0005] In order to solve the technical problems existing in the related art such as uneven passivation film layer, poor passivation effect, and magnesium powder combustion, the present invention provides a passivation magnesium powder and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for preparing passivated magnesium powder comprises the following steps: S1: Under inert gas protection, magnesium particles, magnesium oxide powder, and erbium oxide powder are uniformly mixed, a passivating agent is added, the temperature is raised to 85-90°C, stirred and ground, cooled, and filtered to obtain powder I; S2: Evenly mix the powder I obtained in step S1 with the inorganic mineral powder to obtain powder II; S3: adding the powder II obtained in step S2 to the polyvinyl pyrrolidone aqueous solution, stirring, filtering, drying, and grinding to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, and grinding at high speed to obtain passivated magnesium powder; The passivating agent in step S1 includes a salt solution and an oxidant; the salt solution is a carbonate solution and / or a phosphate solution; and the oxidant is hydrogen peroxide.

[0007] In the above technical solution, magnesium oxide powder can form an antioxidant layer on the surface of the magnesium powder after being mixed with magnesium powder. After reacting with the passivator, a more uniform and stronger passivation layer can be generated, effectively preventing further oxidation of the magnesium powder and improving the thermal stability of the passivation layer. Erbium oxide has a high melting point and good thermal stability. During the stirring and grinding process, it can form a solid solution and a dense and stable oxide film on the surface of the magnesium powder. This film layer can effectively block oxygen and moisture from contacting the magnesium powder, thereby preventing the magnesium powder from undergoing oxidation reactions. After the initial oxidation, the magnesium powder is added to a mixed solution of salt solution and oxidant to further form a composite salt film with anti-corrosion properties on the surface of the magnesium powder, effectively increasing the ignition point of the magnesium powder, reducing the gasification rate, and thereby improving the desulfurization efficiency.

[0008] In the present invention, adding inorganic mineral powder to magnesium powder can destroy the continuity of magnesium powder, thereby delaying the speed of magnesium gasification under molten iron desulfurization temperature conditions, reducing the vapor pressure of magnesium, improving the desulfurization efficiency of magnesium, and avoiding clogging of the spray gun during the spraying process, and finally entering the slag without participating in the desulfurization reaction. The magnesium powder mixed with inorganic mineral powder is added to a polyvinylpyrrolidone aqueous solution, stirred, and dried. A layer of polyvinylpyrrolidone film is coated on the surface of the mixture of magnesium powder and inorganic mineral powder, further improving the oxidation resistance and water resistance of the magnesium powder. Finally, it is mixed with nano-silica. After high-speed grinding, nano-silica is coated on the surface of powder III. Under the high temperature of molten iron, nano-silica forms a thin ceramic film, effectively preventing the gasification of magnesium powder and improving desulfurization efficiency.

[0009] Furthermore, the mixing mass ratio of the magnesium particles, magnesium oxide powder, and erbium oxide powder in step S1 is 17-20:5-9:2-4.

[0010] In the above technical solution, the amount of magnesium oxide powder and erbium oxide powder used will affect the flame retardant properties of the passivated magnesium powder. Excessive use of magnesium oxide powder and erbium oxide powder will not only fail to increase the flame retardant time of the magnesium powder, but will also reduce the reactivity of the passivated magnesium powder. This is because excessive use of magnesium oxide powder and erbium oxide powder will lead to poor uniformity of the passivation film layer.

[0011] Furthermore, the carbonate solution in the passivator is an ammonium bicarbonate solution and / or a sodium bicarbonate solution, and the concentration of the carbonate in the passivator is 1.5-2.2 mol / L; the phosphate solution is one of a sodium dihydrogen phosphate solution, a disodium hydrogen phosphate solution and a diammonium hydrogen phosphate solution, and the concentration of the phosphate in the passivator is 1.7-2.4 mol / L; the mass concentration of hydrogen peroxide in the passivator is 20%-30%.

[0012] Furthermore, the carbonate solution is an ammonium bicarbonate solution with a concentration of 1.8 mol / L; and the phosphate solution is a diammonium hydrogen phosphate solution with a concentration of 2.1 mol / L.

[0013] In the above technical solution, the carbonate solution can react with the magnesium powder to form basic magnesium carbonate, and the phosphate solution can react with the magnesium powder to form magnesium phosphate. The basic magnesium carbonate and magnesium phosphate can effectively isolate the magnesium powder from the external environment, prevent oxygen in the external atmosphere from penetrating into the magnesium liquid, prevent the magnesium liquid from volatilizing, and increase the ignition point of the magnesium powder.

[0014] Furthermore, the passivating agent in step S1 also includes a surfactant and a complexing agent; the surfactant is one or more of stearic acid, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium dioctyl sulfosuccinate; the complexing agent is one or more of tartaric acid, ethylenediaminetetraacetic acid, citric acid, and pyridinedicarboxylic acid; the mass concentration of the surfactant in the passivating agent is 4%-9%, and the mass concentration of the complexing agent is 11%-15%.

[0015] The surfactant in the passivation solution can reduce the surface tension of the passivation solution, making it easier for the passivation solution to spread on the magnesium powder, forming a uniform passivation solution water film, which is conducive to the formation of a uniform passivation film on the metal surface. At the same time, it can also evenly distribute the metal powder in the passivation solution, avoiding the agglomeration of the metal powder and the uneven formation of the passivation film. The magnesium ion can form a stable complex with the complexing agent, thereby controlling the concentration of free magnesium ions in the passivation solution and preventing uneven precipitation or excessive deposition of the passivation film caused by uneven distribution of magnesium ions, which affects the performance of the passivation film.

[0016] Furthermore, the particle size of the inorganic mineral powder in step S2 is 3-7 μm, the inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of the calcite powder to the magnesite powder is 3-5:7-11.

[0017] The study found that the type, particle size and distribution uniformity of inorganic mineral powder will affect the antioxidant effect of inorganic mineral powder. Fine inorganic mineral powder can be evenly dispersed on the surface of magnesium powder. Calcite powder decomposes at high temperature to generate calcium oxide, which will adhere to the surface of magnesium powder. Magnesite powder decomposes at high temperature to generate magnesium oxide, forming a mixed oxide film with CaO and MgO on the upper layer and MgO and Er2O3 on the lower layer. This oxide film can effectively prevent oxygen in the external atmosphere from penetrating into the magnesium liquid, while preventing the volatilization of the magnesium liquid and reducing the gasification rate of magnesium, thereby improving the ignition point and desulfurization efficiency of the magnesium powder.

[0018] Furthermore, the amount of inorganic mineral powder added in step S2 is 5%-9% of the mass of powder I.

[0019] Adding an appropriate amount of inorganic mineral powder can effectively improve the antioxidant and corrosion resistance of magnesium powder. However, excessive addition of inorganic mineral powder may lead to uneven coating or reduced activity of magnesium powder, more porosity in the coating, etc., reducing the effectiveness of the inorganic mineral powder.

[0020] Furthermore, the mass fraction of the polyvinyl pyrrolidone aqueous solution in step S3 is 25%-30%.

[0021] Furthermore, in step S4, the mixing mass ratio of the powder III and the nano-silicon dioxide is 16-20:7-9.

[0022] The present invention also provides passivated magnesium powder prepared by the preparation method of the passivated magnesium powder.

[0023] Compared with the prior art, the passivated magnesium powder and the preparation method thereof provided by the present invention have the following technical advantages: (1) The preparation method of the passivated magnesium powder provided by the present invention adopts a chemical passivation + physical passivation method to form a uniformly distributed passivation film on the surface of the magnesium powder, which not only reduces the loss of magnesium powder, but also makes the magnesium powder have good antioxidant properties, so that it has good reaction activity when used in molten iron desulfurization; (2) The present invention controls the thickness of the passivation film on the surface of the passivated magnesium powder by controlling the concentration of the passivating agent, the particle size of the inorganic mineral powder, the amount of the inorganic mineral powder and the nano-silicon dioxide, thereby effectively avoiding the phenomenon of magnesium powder burning due to the passivation film being too thin or the reduction of magnesium powder activity due to the passivation film being too thick; (3) The passivation magnesium powder provided in the present invention has a high active magnesium content. When the molten iron is desulfurized, the use of the passivation magnesium will not affect the quality of the molten iron or make the molten iron composition abnormal. In addition, the passivation solution provided by the present invention has low environmental pollution and low processing cost, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 1; Figure 2 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 2; Figure 3 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 3; Figure 4 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 4; Figure 5 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 5; Figure 6 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Example 6; Figure 7 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Comparative Example 1; Figure 8 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Comparative Example 2; Figure 9 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Comparative Example 3; Figure 10 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Comparative Example 4; Figure 11 This is the oxidation kinetics curve of the passivated magnesium powder prepared in Comparative Example 5; Figure 12This is the SEM image of the passivated magnesium powder prepared in Example 4; Figure 13 This is the SEM image of the passivated magnesium powder prepared in Example 5; Figure 14 This is the SEM image of the passivated magnesium powder prepared in Example 6. DETAILED DESCRIPTION

[0025] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art may make various modifications based on the basic concept of the present invention, but as long as they do not depart from the basic concept of the present invention, they are all within the scope of the present invention.

[0026] Example 1 A method for preparing passivated magnesium powder comprises the following steps: S1: Under nitrogen flow, 17 g of magnesium granules, 5 g of magnesium oxide powder, and 2 g of erbium oxide powder were thoroughly mixed. 30 g of a passivating agent was added, and the mixture was heated to 85°C and ground with stirring until the average particle size of the magnesium powder reached 80 μm. After cooling, the mixture was filtered and the filter cake was dried at 70°C. The powder I was obtained by grinding. The passivating agent is a mixture of ammonium bicarbonate solution, sodium dihydrogen phosphate solution, hydrogen peroxide, sodium dodecylbenzenesulfonate and tartaric acid, wherein the concentration of ammonium bicarbonate is 1.5 mol / L, the concentration of sodium dihydrogen phosphate is 2.4 mol / L, the mass concentration of hydrogen peroxide is 20%, the mass concentration of sodium dodecylbenzenesulfonate is 4%, and the mass concentration of tartaric acid is 11%.

[0027] S2: The powder I prepared in step S1 is mixed evenly with an inorganic mineral powder having a particle size of 3 μm, wherein the amount of the inorganic mineral powder added is 5% of the mass of the powder I, to obtain powder II; The inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of calcite powder to magnesite powder is 3:7; S3: Powder II prepared in step S2 was added to 50 g of a 25% by mass polyvinyl pyrrolidone aqueous solution, stirred for 1.2 h, filtered, and the obtained filter cake was dried at 60° C. and ground to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, wherein the mixing mass ratio of the powder III to the nano-silicon dioxide is 16:7, and performing high-speed grinding at a rotation speed of 1200 rpm to obtain passivated magnesium powder.

[0028] Example 2 A method for preparing passivated magnesium powder comprises the following steps: S1: Under nitrogen flow, thoroughly mix 20 g of magnesium granules, 9 g of magnesium oxide powder, and 4 g of erbium oxide powder. Add 30 g of a passivating agent, heat to 90°C, and grind while stirring until the average particle size of the magnesium powder is 120 μm. After cooling, filter with suction, and dry the filter cake at 80°C. Grind to obtain powder I. The passivating agent is a mixture of sodium bicarbonate solution, disodium hydrogen phosphate solution, hydrogen peroxide, stearic acid and ethylenediaminetetraacetic acid, wherein the concentration of sodium bicarbonate is 2.2 mol / L, the concentration of disodium hydrogen phosphate is 1.7 mol / L, the mass concentration of hydrogen peroxide is 30%, the mass concentration of stearic acid is 9%, and the mass concentration of ethylenediaminetetraacetic acid is 15%.

[0029] S2: The powder I prepared in step S1 is mixed evenly with an inorganic mineral powder having a particle size of 7 μm, wherein the amount of the inorganic mineral powder added is 9% of the mass of the powder I, to obtain powder II; The inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of calcite powder to magnesite powder is 5:11; S3: Powder II prepared in step S2 was added to 50 g of a 30% by mass aqueous solution of polyvinyl pyrrolidone, stirred for 1.5 h, filtered, and the obtained filter cake was dried at 70° C. and ground to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, wherein the mixing mass ratio of the powder III to the nano-silicon dioxide is 20:9, and performing high-speed grinding at a rotation speed of 1400 rpm to obtain passivated magnesium powder.

[0030] Example 3 A method for preparing passivated magnesium powder comprises the following steps: S1: Under nitrogen flow, 18 g of magnesium granules, 8 g of magnesium oxide powder, and 3 g of erbium oxide powder were thoroughly mixed. 30 g of a passivating agent was added. The mixture was heated to 90°C and ground with stirring until the average particle size of the magnesium powder reached 100 μm. After cooling, the mixture was filtered and the filter cake was dried at 75°C. The powder I was obtained by grinding. The passivating agent is a mixture of ammonium bicarbonate solution, diammonium hydrogen phosphate solution, hydrogen peroxide, sodium lauryl sulfate and citric acid, wherein the concentration of ammonium bicarbonate is 2.1 mol / L, the concentration of diammonium hydrogen phosphate is 2.0 mol / L, the mass concentration of hydrogen peroxide is 25%, the mass concentration of sodium lauryl sulfate is 6%, and the mass concentration of citric acid is 13%.

[0031] S2: The powder I prepared in step S1 is mixed evenly with an inorganic mineral powder having a particle size of 5 μm, wherein the amount of the inorganic mineral powder added is 7% of the mass of the powder I, to obtain powder II; The inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of calcite powder to magnesite powder is 4:9; S3: Powder II prepared in step S2 was added to 50 g of a 28% by mass polyvinyl pyrrolidone aqueous solution, stirred for 1.4 h, filtered, and the obtained filter cake was dried at 65° C. and ground to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, wherein the mixing mass ratio of the powder III to the nano-silicon dioxide is 17:8, and performing high-speed grinding at a rotation speed of 1300 rpm to obtain passivated magnesium powder.

[0032] Example 4 A method for preparing passivated magnesium powder comprises the following steps: S1: Under nitrogen flow, 19 g of magnesium granules, 7 g of magnesium oxide powder, and 3 g of erbium oxide powder were thoroughly mixed. 30 g of a passivating agent was added, and the mixture was heated to 90°C and ground with stirring until the average particle size of the magnesium powder reached 100 μm. After cooling, the mixture was filtered and the filter cake was dried at 75°C. The powder I was obtained by grinding. The passivating agent is a mixture of ammonium bicarbonate solution, diammonium hydrogen phosphate solution, hydrogen peroxide, sodium fatty alcohol polyoxyethylene ether sulfate and picolinic acid, wherein the concentration of ammonium bicarbonate is 1.8 mol / L, the concentration of diammonium hydrogen phosphate is 2.1 mol / L, the mass concentration of hydrogen peroxide is 26%, the mass concentration of sodium fatty alcohol polyoxyethylene ether sulfate is 8%, and the mass concentration of picolinic acid is 14%; S2: The powder I prepared in step S1 is mixed evenly with an inorganic mineral powder having a particle size of 5 μm, wherein the amount of the inorganic mineral powder added is 7% of the mass of the powder I, to obtain powder II; The inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of calcite powder to magnesite powder is 4:9; S3: Powder II prepared in step S2 was added to 50 g of a 28% by mass polyvinyl pyrrolidone aqueous solution, stirred for 1.4 h, filtered, and the obtained filter cake was dried at 65° C. and ground to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, wherein the mixing mass ratio of the powder III to the nano-silicon dioxide is 17:8, and performing high-speed grinding at a rotation speed of 1300 rpm to obtain passivated magnesium powder.

[0033] Example 5 The preparation method of the passivated magnesium powder in this embodiment is similar to that in Example 4. The difference between this embodiment and Example 4 is that step S1 in this embodiment is specifically as follows: Under nitrogen flow, 19 g of magnesium granules, 6 g of magnesium oxide powder, and 4 g of erbium oxide powder were thoroughly mixed, 30 g of a passivating agent was added, and the mixture was heated to 90°C and ground with stirring until the average particle size of the magnesium powder reached 100 μm. After cooling, the mixture was filtered and the filter cake was dried at 75°C. The powder I was then ground. The passivating agent is a mixture of ammonium bicarbonate solution, sodium dihydrogen phosphate solution, hydrogen peroxide, sodium fatty alcohol polyoxyethylene ether sulfate and picolinic acid. The concentration of ammonium bicarbonate is 1.7 mol / L, the concentration of sodium dihydrogen phosphate is 1.9 mol / L, the mass concentration of hydrogen peroxide is 25%, the mass concentration of sodium fatty alcohol polyoxyethylene ether sulfate is 7%, and the mass concentration of picolinic acid is 13%.

[0034] Example 6 The preparation method of the passivated magnesium powder in this embodiment is similar to that in Example 4. The difference between this embodiment and Example 4 is that step S1 in this embodiment is specifically as follows: S1: Under nitrogen flow, 19 g of magnesium granules, 7 g of magnesium oxide powder, and 3 g of erbium oxide powder were thoroughly mixed. 30 g of a passivating agent was added, and the mixture was heated to 90°C and ground with stirring until the average particle size of the magnesium powder reached 100 μm. After cooling, the mixture was filtered and the filter cake was dried at 75°C. The powder I was obtained by grinding. The passivating agent is a mixture of ammonium bicarbonate solution, sodium dihydrogen phosphate solution, hydrogen peroxide, sodium dioctyl sulfosuccinate and citric acid, wherein the concentration of ammonium bicarbonate is 1.9 mol / L, the concentration of sodium dihydrogen phosphate is 2.2 mol / L, the mass concentration of hydrogen peroxide is 27%, the mass concentration of sodium dioctyl sulfosuccinate is 6%, and the mass concentration of citric acid is 15%.

[0035] Comparative Example 1 The preparation method of the passivated magnesium powder in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that the amounts of magnesium particles, magnesium oxide powder, and erbium oxide used in step S1 in this comparative example are 19 g, 15 g, and 8 g, respectively.

[0036] Comparative Example 2 The preparation method of the passivated magnesium powder in this comparative example is similar to that in Example 5. The difference between this comparative example and Example 5 is that the concentration of ammonium bicarbonate in the passivating agent used in step S1 in this comparative example is 3.0 mol / L, the concentration of sodium dihydrogen phosphate is 1.0 mol / L, and the mass concentration of hydrogen peroxide is 40%.

[0037] Comparative Example 3 The preparation method of the passivated magnesium powder in this comparative example is similar to that in Example 5. The difference between this comparative example and Example 5 is that the inorganic mineral powder in step S2 of this comparative example is dolomite powder.

[0038] Comparative Example 4 The preparation method of the passivated magnesium powder in this comparative example is similar to that in Example 5. The difference between this comparative example and Example 5 is that the amount of inorganic mineral powder added in step S2 of this comparative example is 15% of the mass of powder I.

[0039] Comparative Example 5 The preparation method of the passivated magnesium powder in this comparative example is similar to that in Example 6. The difference between this comparative example and Example 6 is that the mixing mass ratio of the powder III and the nano-silicon dioxide in step S4 in this comparative example is 8:17.

[0040] Test Example 1: Thermal Performance Test Test samples: passivated magnesium powders prepared in Examples 1 to 6 and Comparative Examples 1 to 5; Flame retardant time test: Place a 0.4g sample on a thin quartz plate. Raise the furnace temperature to 1273K and move the plate to the constant temperature zone within the furnace. Measure the time from the time the sample is placed until it begins to burn. Measure multiple times for each sample and take the average value. See Table 1 for test results.

[0041] Flash point test: The flash point of the sample was tested using a TGA2050 thermogravimetric analyzer from TA, USA, with the temperature rising from room temperature to 900°C at a rate of 20°C / min under air conditions. Figures 1-11 .

[0042] Table 1 Flame retardant time test results

[0043] From Table 1, Figures 1-11 It can be seen that the flame retardant time of the passivated magnesium powder provided by the present invention is more than 17s, up to 20.3s, and the ignition point is above 620°C, up to 660°C, and has a good flame retardant effect. This shows that the passivated magnesium powder provided by the present invention has a uniform passivation film, which can effectively reduce the gasification and combustion of magnesium powder.

[0044] Compared with Example 4, Comparative Example 1 changed the amount of magnesium powder, magnesium oxide powder, and erbium oxide powder, but the flame retardant time and ignition point were both reduced, which indicates that the amount of magnesium oxide powder and erbium oxide powder will affect the flame retardant time of the passivated magnesium powder; Compared with Example 5, Comparative Example 2 changed the concentrations of the salt solution and hydrogen peroxide in the passivator, but the flame retardant time and ignition point were reduced, which indicates that the concentrations of the salt solution and hydrogen peroxide in the passivator are the key to affecting the thickness and uniformity of the passivation film layer; Comparative Example 3 changed the type of inorganic mineral powder, and Comparative Example 4 changed the amount of inorganic mineral powder added, but the flame retardant time and ignition point were slightly reduced, which indicates that the type and amount of inorganic mineral powder will affect the thickness and uniformity of the passivation film layer; Compared with Example 6, the mixing mass ratio of powder III to nano-silicon dioxide in Comparative Example 5 was increased, but the flame retardant time and ignition point were reduced. This is because the excessive amount of nano-silicon dioxide causes it to agglomerate on the surface of the magnesium powder, reducing the uniformity of the passivation film.

[0045] Test Example 2: Characterization of Passivation Film In this test example, the passivated magnesium powders obtained in Examples 4 to 6 were tested by scanning electron microscopy (SEM). The test results are shown in Figure 12-14.

[0046] Depend on Figure 12-14 It can be seen that the surface of the passivated magnesium powder provided by the present invention is evenly coated without obvious protrusions, holes or cracks, and has good density, which shows that the passivation layer can effectively block the contact between oxygen and the internal magnesium metal and prevent the magnesium liquid from vaporizing and volatilizing.

[0047] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A method for preparing passivated magnesium powder, characterized in that: The following steps are involved: S1: Under inert gas protection, magnesium particles, magnesium oxide powder, and erbium oxide powder are uniformly mixed, a passivating agent is added, the temperature is raised to 85-90°C, stirred and ground, cooled, and filtered to obtain powder I; S2: Evenly mix the powder I obtained in step S1 with the inorganic mineral powder to obtain powder II; S3: adding the powder II obtained in step S2 to the polyvinyl pyrrolidone aqueous solution, stirring, filtering, drying, and grinding to obtain powder III; S4: mixing the powder III obtained in step S3 with nano-silicon dioxide, and grinding at high speed to obtain passivated magnesium powder; The passivating agent in step S1 includes a salt solution and an oxidant; the salt solution is a carbonate solution and / or a phosphate solution; and the oxidant is hydrogen peroxide.

2. The preparation method of passivated magnesium powder according to claim 1, wherein The mixing mass ratio of the magnesium particles, magnesium oxide powder, and erbium oxide powder in step S1 is 17-20:5-9:2-4.

3. The preparation method of passivated magnesium powder according to claim 1, wherein The carbonate solution in the passivator is an ammonium bicarbonate solution and / or a sodium bicarbonate solution, and the concentration of the carbonate in the passivator is 1.5-2.2 mol / L; the phosphate solution is one of a sodium dihydrogen phosphate solution, a disodium hydrogen phosphate solution and a diammonium hydrogen phosphate solution, and the concentration of the phosphate in the passivator is 1.7-2.4 mol / L; the mass concentration of hydrogen peroxide in the passivator is 20%-30%.

4. The preparation method of passivated magnesium powder according to claim 3, wherein The carbonate solution is an ammonium bicarbonate solution with a concentration of 1.8 mol / L; the phosphate solution is a diammonium hydrogen phosphate solution with a concentration of 2.1 mol / L.

5. The preparation method of passivated magnesium powder according to claim 1, wherein The passivating agent in step S1 further includes a surfactant and a complexing agent; the surfactant is one or more of stearic acid, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium dioctyl sulfosuccinate; the complexing agent is one or more of tartaric acid, ethylenediaminetetraacetic acid, citric acid, and pyridinedicarboxylic acid; the mass concentration of the surfactant in the passivating agent is 4%-9%, and the mass concentration of the complexing agent is 11%-15%.

6. The preparation method of passivated magnesium powder according to claim 1, wherein The particle size of the inorganic mineral powder in step S2 is 3-7 μm, and the inorganic mineral powder is calcite powder and magnesite powder, and the mass ratio of the calcite powder to the magnesite powder is 3-5:7-11.

7. The method for preparing passivated magnesium powder according to claim 1, wherein The amount of inorganic mineral powder added in step S2 is 5%-9% of the mass of powder I.

8. The method for preparing passivated magnesium powder according to claim 1, wherein The mass fraction of the polyvinyl pyrrolidone aqueous solution in step S3 is 25%-30%.

9. The method for preparing passivated magnesium powder according to claim 1, wherein The mixing mass ratio of the powder III and the nano-silicon dioxide in step S4 is 16-20:7-9.

10. Passivated magnesium powder obtained according to the preparation method of passivated magnesium powder according to any one of claims 1 to 9.

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