阅读说明：本技术 一种一步法制备耐腐蚀磁性金属粉体的方法 (Method for preparing corrosion-resistant magnetic metal powder by one-step method ) 是由 张林博 万为鸿 汪博 梁迪飞 邓龙江 于 2021-09-16 设计创作，主要内容包括：本发明属于金属抗腐蚀领域,涉及金属粉体,具体为一种一步法制备耐腐蚀磁性金属粉体的方法,为金属粉体的应用提供基础。在本发明中通过硅酸锂水解产生金属表面亲和力强的硅溶胶保证和金属粉体的良好接触,通过硅烷偶联剂KH560形成有机基体-硅烷偶联剂-无机基体的结合,利用溶胶-凝胶法,以交联网络结构包覆金属粉体,同时低表面能的PDMS使金属粉体的疏水性、耐热性和抗腐蚀能得到提升。经本发明技术方案改性后的金属粉体抗氧化性大幅度上升,具有优良的耐腐蚀性能,优良的化学稳定性,且工艺简单、成本低廉、实施周期较短,为高性能金属粉体的制备提供一种新的工艺方案。(The invention belongs to the field of metal corrosion resistance, relates to metal powder, and particularly relates to a method for preparing corrosion-resistant magnetic metal powder by a one-step method, which provides a foundation for application of the metal powder. In the invention, the lithium silicate is hydrolyzed to generate the silica sol with strong affinity on the metal surface to ensure good contact with the metal powder, the silane coupling agent KH560 is used to form the combination of an organic matrix, the silane coupling agent and an inorganic matrix, the metal powder is coated by a cross-linked network structure by using a sol-gel method, and meanwhile, the hydrophobicity, the heat resistance and the corrosion resistance of the metal powder are improved by the PDMS with low surface energy. The metal powder modified by the technical scheme of the invention has greatly improved oxidation resistance, excellent corrosion resistance, excellent chemical stability, simple process, low cost and shorter implementation period, and provides a new process scheme for preparing high-performance metal powder.)

1. The method for preparing the corrosion-resistant magnetic metal powder by the one-step method is characterized by comprising the following steps of:

step 1, preparing materials: preparing a solution B and a dispersion system C;

solution B: taking 60-80 parts of gamma-glycidoxypropyltrimethoxysilane (KH560) and 10 parts of deionized water by mass fraction, placing the gamma-glycidoxypropyltrimethoxysilane and the KH560 into a reaction vessel, and uniformly mixing the gamma-glycidoxypropyltrimethoxysilane and the deionized water at room temperature to obtain a solution A; then adding 10 parts of hydroxyl-terminated Polydimethylsiloxane (PMDS) into the solution A, and fully dissolving at room temperature to obtain a solution B;

dispersion system C: placing 5 parts of metal powder and 7-9 parts of lithium silicate in a reaction vessel by mass fraction, and ultrasonically mixing uniformly to obtain a dispersion system C;

step 2, uniformly mixing the solution B prepared in the step 1 with the dispersion system C, heating to 60-80 ℃, and stirring to completely perform a crosslinking reaction to obtain a suspension;

and 3, filtering the suspension obtained in the step 2, washing with absolute ethyl alcohol until the system is clear, performing suction filtration, and completely drying in vacuum at 50-70 ℃ to obtain the corrosion-resistant magnetic metal powder coated with the cross-linked network structure.

2. The one-step method for preparing corrosion-resistant magnetic metal powder according to claim 1, wherein: the metal powder is flaky carbonyl iron powder with the length and width of 4-7um and 2-3um respectively and the thickness of 0.3-0.5 um.

3. The one-step method for preparing corrosion-resistant magnetic metal powder according to claim 1, wherein: the reaction rate is controlled by controlling the concentration of the reaction system and the reaction temperature, so as to adjust the thickness of the coating layer of the metal powder.

Technical Field

The invention belongs to the field of metal corrosion resistance, relates to metal powder, and particularly relates to a method for preparing corrosion-resistant magnetic metal powder by a one-step method, which provides a foundation for application of metal powder (such as carbonyl iron powder).

Background

Carbonyl iron powder is a typical representation of a magnetic metal micro powder wave-absorbing material, has high magnetic conductivity in a microwave frequency band and good frequency dispersion characteristics of a real part and an imaginary part of the magnetic conductivity, and has strong absorption efficiency on radar waves under the condition of low matching thickness. Has wide application prospect and potential in the field of wave-absorbing materials.

However, in practical applications, the metal powder (such as carbonyl iron powder) is exposed to a complex application environment (high temperature, acidity, salt spray, etc.) for a long time, and is exposed to problems such as high temperature oxidation and electrochemical corrosion. The components of the carbonyl iron powder can be changed no matter high-temperature oxidation or electrochemical corrosion, the effective magnetic absorption volume in the material is reduced, the absorption capacity of the absorption material is deteriorated, and the application of the carbonyl iron powder is limited. Therefore, the preparation of carbonyl iron powder with excellent chemical stability is a very important and promising hot topic.

In the current research, researchers generally coat a continuous, uniform, compact, and difficult-to-oxidize organic or inorganic protective layer on the surface of carbonyl iron powder to isolate the invasion of external oxygen or other corrosive ions, thereby achieving the purpose of protecting the powder. SiO 2₂Is a key material widely used for corrosion prevention in modern industry, and the patent CN105798291A uses alkoxide compounds such as Tetraethoxysilane (TEOS) and Tetramethoxysilane (TMOS) as silicon source to coat SiO on the surfaces of carbonyl iron powder particles₂Improving the oxidation resistance and the corrosion resistance of the alloy, but the single SiO₂The hydrophobic property of the coating is poor, and the long-term application of the powder in a salt spray environment is difficult to meet. Patent CN112563010A uses various organosilanes to form uniform silicon-containing coating layers on the surface of iron powder, the obtained coated iron powder has no rusty spot after 1000h salt spray experiment, but the fluorine-containing organic matter used by the coated iron powder has high cost and is easy to cause pollution, meanwhile, the process steps are complex, the metal powder needs to be treated for many times, the reaction period is long, and the application of the metal powder is limited.

Disclosure of Invention

Aiming at the problems and the defects, the problems that the cost of using fluorine-containing organic matters is high, pollution is easy to cause, the process steps are complex and the reaction period is long in the existing metal powder protection measures are solved; the invention provides a method for preparing corrosion-resistant magnetic metal powder by a one-step method, which considers the selection of materials and improves the preparation of solution to prepare the metal powder with excellent corrosion resistance and chemical stability.

In order to realize the aim, the invention adopts the technical scheme that:

a method for preparing corrosion-resistant magnetic metal powder by a one-step method comprises the following steps:

step 1, preparing materials: preparing a solution B and a dispersion system C.

Solution B: taking 60-80 parts of gamma-glycidoxypropyltrimethoxysilane (KH560) and 10 parts of deionized water by mass fraction, placing the gamma-glycidoxypropyltrimethoxysilane and the KH560 into a reaction vessel, and uniformly mixing the materials at room temperature to obtain a solution A. Then, 10 parts of hydroxyl terminated Polydimethylsiloxane (PMDS) was added to the solution A and sufficiently dissolved at room temperature to obtain a solution B.

Dispersion system C: and (3) placing 5 parts of metal powder and 7-9 parts of lithium silicate in a reaction vessel by mass fraction, and ultrasonically mixing uniformly to obtain a dispersion system C.

And 2, uniformly mixing the solution B prepared in the step 1 with the dispersion system C, heating to 60-80 ℃, and stirring to completely perform a crosslinking reaction to obtain a suspension.

And 3, filtering the suspension obtained in the step 2, washing with absolute ethyl alcohol until the system is clear, performing suction filtration, and completely drying in vacuum at 50-70 ℃ to obtain the corrosion-resistant magnetic metal powder coated with the cross-linked network structure.

Furthermore, the metal powder is sheet carbonyl iron powder with length and width of 4-7um and 2-3um respectively and thickness of 0.3-0.5 um.

Furthermore, the reaction rate is controlled by controlling the concentration of the reaction system and the reaction temperature so as to adjust the thickness of the coating layer of the metal powder and realize the improvement of the chemical stability of the magnetic metal powder.

The invention utilizes a sol-gel method to coat metal powder with a cross-linked network structure, and the composite coating shell layer is formed by the synergistic hydrolytic condensation of gamma-glycidoxypropyltrimethoxysilane (KH560), hydroxyl Polydimethylsiloxane (PMDS) and lithium silicate. Lithium silicate is mainly applied to glass systems, molten salt systems and high-temperature ceramic glazes, and is also used as surface coatings of steel and the like and as an adhesive for inorganic zinc-rich coatings and advanced welding rods. In the invention, the lithium silicate is hydrolyzed to generate the silica sol with strong affinity on the metal surface, so that the silica sol is ensured to be in good contact with the metal powder, the combination of an organic matrix, a silane coupling agent and an inorganic matrix is formed through the silane coupling agent KH560, and meanwhile, the hydrophobicity, the heat resistance and the corrosion resistance of the metal powder are improved through the PDMS with low surface energy.

To sum up, the metal powder modified by the technical scheme of the invention comprises the following components: 1. the defects of poor water resistance and the like of the metal powder coated by a single silicon oxide layer are overcome, and the oxidation resistance, electrochemical corrosion resistance and acid resistance of the coated metal powder are obviously improved; 2. the method has the advantages of simple implementation process, short reaction period, mild reaction conditions and easy control; 3. the raw materials adopted in the implementation process of the invention are easy to obtain, have low cost (no high-cost fluorine-containing organic matter), are environment-friendly and are beneficial to large-scale industrial production. Provides a new process scheme for the preparation of high-performance metal powder.

Drawings

Fig. 1 is SEM images of uncoated and examples one to three and HRTEM pictures of example one.

FIG. 2 is a TG-DSC curve of uncoated and one to three powders of examples.

FIG. 3 is a polarization curve for the test of uncoated and example one to two powders in 3.5% NaCl solution.

FIG. 4 is the contact angle of uncoated and example one to three powders.

Fig. 5 is an SEM picture of uncoated and example one to three powders after neutral salt spray environment.

Fig. 6 shows the results of the acid resistance test of the uncoated powder and the powder of examples one to three.

FIG. 7 is a schematic flow diagram of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples and the accompanying drawings.

The first embodiment is as follows:

1) 60 parts of gamma-glycidoxypropyltrimethoxysilane (KH560) and 10 parts of deionized water are placed in a reaction vessel by mass fraction, and the solution A is obtained by magnetic stirring for 10min at room temperature and at the stirring speed of 400 rpm.

2) And adding 10 parts by mass of hydroxyl-terminated Polydimethylsiloxane (PMDS) into the solution A, and magnetically stirring for 2 hours at room temperature at the stirring speed of 400rpm to fully dissolve the PDMS to obtain a solution B.

3) And placing 5 parts of carbonyl iron powder and 7 parts of lithium silicate in a reaction container by mass fraction, and ultrasonically mixing uniformly to obtain a dispersion system C, wherein the carbonyl iron powder is flaky carbonyl iron powder with the length and width of 4-7um, 2-3um and the thickness of 0.3-0.5um respectively.

4) Uniformly mixing the solution B prepared in the step 2) with the dispersion system C obtained in the step 3), heating to 60 ℃, mechanically stirring at the stirring speed of 420rpm, and carrying out crosslinking reaction for 1h, wherein the total reaction period is about 3 h.

5) Filtering the suspension obtained in the step 4), washing the suspension by using absolute ethyl alcohol until the system is clear, performing suction filtration, and performing vacuum drying at the temperature of 60 ℃ for 12 hours; thus obtaining the corrosion-resistant magnetic metal powder.

Fig. 1(b) and (c) are SEM and HRTEM pictures of the first example, respectively, and it is confirmed that a dense coating layer with a thickness of about 20.6nm is formed on the surface of the flaky carbonyl iron powder. Meanwhile, the obtained powder is subjected to a salt spray experiment, and as shown in fig. 5(b), the shape of the powder is not obviously changed after 2000 hours.

Example two:

1) 70 parts of gamma-glycidoxypropyltrimethoxysilane (KH560) and 10 parts of deionized water are placed in a reaction vessel by mass fraction, and the solution A is obtained by magnetic stirring for 10min at room temperature and at the stirring speed of 400 rpm.

2) And adding 10 parts by mass of hydroxyl-terminated Polydimethylsiloxane (PMDS) into the solution A, and magnetically stirring for 2 hours at room temperature at the stirring speed of 400rpm to fully dissolve the PDMS to obtain a solution B.

3) And placing 5 parts of carbonyl iron powder and 8 parts of lithium silicate in a reaction container by mass fraction, and ultrasonically mixing uniformly to obtain a dispersion system C, wherein the carbonyl iron powder is flaky carbonyl iron powder with the length and width of 4-7um, 2-3um and the thickness of 0.3-0.5um respectively.

4) Uniformly mixing the solution B prepared in the step 2) with the dispersion system C obtained in the step 3), heating to 70 ℃, mechanically stirring at the stirring speed of 420rpm, and carrying out crosslinking reaction for 2 hours, wherein the total reaction period is about 4 hours.

5) Filtering the suspension obtained in the step 4), washing the suspension by using absolute ethyl alcohol until the system is clear, performing suction filtration, and performing vacuum drying at the temperature of 60 ℃ for 12 hours; thus obtaining the corrosion-resistant magnetic metal powder.

Fig. 1(d) is an SEM picture of example two, demonstrating that a dense coating layer is formed on the surface of the flaky carbonyl iron powder. Meanwhile, the obtained powder is subjected to a salt spray experiment, and as shown in fig. 5(c), the shape of the powder is not obviously changed after 1600 hours.

Example three:

1) and putting 80 parts of gamma-glycidoxypropyltrimethoxysilane (KH560) and 10 parts of deionized water in a reaction container by mass fraction, and magnetically stirring for 10min at room temperature and the stirring speed of 400rpm to obtain a solution A.

2) And adding 10 parts by mass of hydroxyl-terminated Polydimethylsiloxane (PMDS) into the solution A, and magnetically stirring for 2 hours at room temperature at the stirring speed of 400rpm to fully dissolve the PDMS to obtain a solution B.

3) And placing 5 parts of carbonyl iron powder and 9 parts of lithium silicate in a reaction container by mass fraction, and ultrasonically mixing uniformly to obtain a dispersion system C, wherein the carbonyl iron powder is flaky carbonyl iron powder with the length and width of 4-7um, 2-3um and the thickness of 0.3-0.5um respectively.

4) Uniformly mixing the solution B prepared in the step 2) with the dispersion system C obtained in the step 3), heating to 80 ℃, mechanically stirring at the stirring speed of 420rpm, and carrying out crosslinking reaction for 3 hours, wherein the total reaction period is about 5 hours.

5) Filtering the suspension obtained in the step 4), washing the suspension by using absolute ethyl alcohol until the system is clear, performing suction filtration, and performing vacuum drying at the temperature of 60 ℃ for 12 hours; thus obtaining the corrosion-resistant magnetic metal powder.

Fig. 1(e) is an SEM picture of example three, demonstrating that a coating layer is formed on the surface of the flaky carbonyl iron powder. Meanwhile, the obtained powder is subjected to a salt spray experiment, and as shown in fig. 5(d), the morphology of the powder is not obviously changed after 1500 hours.

FIG. 2 is a TG curve of uncoated powder and powder of examples one to three, which shows that the heat resistance is significantly improved after powder modification.

FIG. 3 is a polarization curve of uncoated and test examples one to two powders in 3.5% NaCl solution, with reduced corrosion current and increased corrosion potential after powder modification.

FIG. 4 shows the contact angles of the uncoated powder and the powder of examples one to three, and the hydrophobic property of the modified powder is greatly improved.

FIG. 6 shows the results of acid resistance test evaluation of uncoated and one to three powders in examples, which shows that the acid resistance of the modified powder is improved.

In the field of metal powder modification, the improvement of the affinity with the surface of metal powder through a silica network generated by silica sol is a common means, the main way for obtaining the silica sol is to hydrolyze through metal alkoxides such as TEOS and TMOS, but the process of the method has some defects, such as the need of ethanol as a solvent, the need of acid or alkali as a catalyst in the reaction process, and the like; and the whole modification period is long, and the time of the step of pretreatment alone needs more than 12 hours. The lithium silicate used in the invention can directly use water as a solvent, has high activity, is beneficial to industrial production, and greatly shortens the time period of the modification period not exceeding 6 hours.

In this example, carbonyl iron powder is taken as an example, and the corrosion resistance of the prepared corrosion-resistant magnetic carbonyl iron powder is characterized by 3 ways: firstly, testing the electrochemical corrosion resistance of the corrosion-resistant magnetic metal powder in a 3.5% NaCl solution by adopting an electrochemical workstation; secondly, placing the corrosion-resistant magnetic metal powder in a 3.5% neutral salt spray test box to test the salt spray resistance of the powder; thirdly, the corrosion-resistant magnetic metal powder is placed in hydrochloric acid solution with PH 1, and the acid resistance of the powder is represented under the condition of continuously stirring for 1 hour.

In conclusion, in the invention, the lithium silicate is hydrolyzed to generate the silica sol with strong affinity on the metal surface, so that the silica sol can be ensured to be in good contact with the metal powder, the silane coupling agent KH560 is used for forming the combination of an organic matrix, the silane coupling agent and an inorganic matrix, the metal powder is coated by a cross-linked network structure by using a sol-gel method, and meanwhile, the hydrophobicity, the heat resistance and the corrosion resistance of the metal powder are improved by using the PDMS with low surface energy. The metal powder modified by the technical scheme of the invention has greatly improved oxidation resistance, excellent corrosion resistance, excellent chemical stability, simple process, low cost and shorter implementation period, and provides a new process scheme for preparing high-performance metal powder.