Preparation method of magnetic composite nano-zirconia

Abstract

The invention discloses a preparation method of magnetic composite nano-zirconia, which comprises the following steps: dissolving terephthalic acid in DMF (dimethyl formamide), adding into a reaction kettle, adding modified composite silicon dioxide, stirring and mixing, adding glacial acetic acid and zirconium chloride, heating and stirring, cooling, centrifugally filtering to obtain a precipitate, and drying in vacuum to obtain the magnetic composite nano-zirconia. MOF / composite silicon dioxide powder is obtained; then roasting the MOF / composite silicon dioxide powder in a muffle furnace to obtain magnetic composite nano zirconium oxide; a silicon dioxide protective layer is formed on the surface of the nano Fe3O4 particles, amino in 3-aminopropyltriethoxysilane reacts with hydroxyl on the surface of silicon dioxide, acetic acid is used as a catalyst, zirconium chloride is used as a metal catalyst, and a layer of zirconium oxide is formed outside the silicon dioxide in a coating mode, so that the oxidation phenomenon of the Fe3O4 particles is reduced, and the service life of the nano Fe3O4 particles is prolonged. The wave-absorbing performance, the corrosion resistance and the high-temperature performance of the magnetic composite nano zirconium oxide material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a preparation method of magnetic composite nano-zirconia. Background Art

[0002] Due to its excellent thermal, electrical, mechanical, chemical and processing properties, nano-zirconia materials have been widely used in many fields, such as electronic information technology, catalysts and thermal barrier coatings, etc. Especially in the context of the continuous development of electronic information technology, the demand for magnetic composite nano-zirconia materials shows an increasing trend. Magnetic composite nano-zirconia not only has excellent stability and high-temperature resistance, but also has excellent wave absorption performance, making its application in the fields of optoelectronics and wave-absorbing coatings more and more extensive.

[0003] Wave-absorbing coatings are increasingly widely used in military and civilian fields. According to different wave absorption principles, wave-absorbing materials can be divided into magnetic loss type and electrical loss type. Among them, ferrite is one of the common wave-absorbing agents. Due to its high magnetic permeability and excellent wave absorption effect, it is widely used in wave-absorbing materials at home and abroad. Since iron is a metal with strong reactivity and is easy to react with air and moisture, resulting in problems such as corrosion and oxidation, thus affecting its wave absorption performance. In high-temperature and humid environments, these problems are particularly serious, which also limits the use of ferrite in these special environments.

[0004] Chinese Patent with Publication No. CN103351611 B discloses a nylon capable of shielding electromagnetic waves. By mixing polyamide fiber, coupling agent, toughening agent, dispersing lubricant, silica and zirconia, drying, heating and cooling, and then drawing into strips, and finally air-drying and pelletizing, a nylon material with electromagnetic wave shielding function is prepared. In this process, the combination between the polyamide fiber with electromagnetic wave shielding function and silica and zirconia only relies on the coupling agent, and a simple mechanical mixing method is adopted. This combination method leads to low compounding degree and bonding strength, thus easily causing agglomeration phenomenon, and further affecting the wave absorption performance of the material. Summary of the Invention

[0005] The purpose of the present invention is to solve how to reduce the corrosion and oxidation phenomena of ferrite in water or air, and improve the wave absorption and corrosion resistance of magnetic composite nano-zirconia, and provide a preparation method of magnetic composite nano-zirconia.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of magnetic composite nano-zirconia, comprising the following steps:

[0008] Step 1: Dissolve terephthalic acid in DMF and add it to a reaction kettle. Then add modified composite silica, stir for 1 - 2 h, add glacial acetic acid and zirconium chloride, continue stirring for 5 - 10 min, heat up to 120 - 130 °C and stir for reaction for 2 - 3 h. Cool to room temperature, centrifuge and filter to obtain a precipitate. Wash the precipitate and dry it under vacuum to obtain MOF / composite silica powder;

[0009] Step 2: Calcinate the MOF / composite silica powder in a muffle furnace at 400 - 450 °C for 4 - 5 h to obtain magnetic composite nanozirconia.

[0010] Furthermore, the dosage ratio of terephthalic acid, DMF, modified composite silica, glacial acetic acid and zirconium chloride is 0.2 - 0.4 g : 80 - 100 mL : 3 - 5 g : 10 - 12 mL : 0.4 - 0.6 g.

[0011] Furthermore, the modified composite silica is prepared by the following steps:

[0012] Add 3 - aminopropyltriethoxysilane and ammonia water to the composite silica colloidal solution in a reaction kettle, stir for reaction for 1 - 2 h, then centrifuge, and dry the precipitate to obtain modified composite silica.

[0013] Furthermore, the dosage ratio of the composite silica colloidal solution, 3 - aminopropyltriethoxysilane and ammonia water is 100 - 120 mL : 0.2 - 0.3 g : 5 - 8 mL.

[0014] Furthermore, the composite silica colloidal solution is prepared by the following steps:

[0015] Mix nano - Fe3O4 particles and an ethanol - aqueous solution in a reaction kettle, drop in ammonia water, ultrasonically disperse for 1 - 2 h, drop tetraethyl orthosilicate into the reaction kettle, stir for reaction at 500 - 600 rpm for 3 - 4 h, centrifuge and filter to obtain a precipitate. Wash the precipitate with ethanol and deionized water 2 - 3 times respectively, dry for 1 - 2 h, and then redisperse the precipitate in absolute ethanol and stir until a colloidal solution is formed to obtain the composite silica colloidal solution.

[0016] Furthermore, the dosage ratio of the nano - Fe3O4 particles, ethanol - aqueous solution, ammonia water, tetraethyl orthosilicate and absolute ethanol is 2 - 5 g : 300 - 400 mL : 6 - 8 mL : 4 - 8 mL : 100 - 120 mL.

[0017] The beneficial effects of the present invention:

[0018] The present invention hydrolyzes and undergoes a condensation reaction of tetraethyl orthosilicate to form silica, forming a silica protection layer on the surface of nano-Fe3O4 particles; reducing the contact between nano-Fe3O4 particles and air and moisture, improving the corrosion resistance and reducing the oxidation phenomenon of nano-Fe3O4 particles.

[0019] Then, through a hydrolysis reaction, the amino group and silane group in 3-aminopropyltriethoxysilane react with the hydroxyl groups on the surface of silica, grafting the amino functional group onto the surface of silica; using terephthalic acid as the ligand for MOF synthesis, the carboxyl group in terephthalic acid reacts with the amino group on the surface of the modified composite silica, and an amidation reaction occurs between the amino group and the carboxyl group to form an amide bond; acetic acid is used as a catalyst and zirconium chloride is used as a metal catalyst to promote the reaction, forming a layer of zirconia coated on the silica.

[0020] Finally, by high-temperature sintering of the MOF / composite silica powder, a zirconia shell layer with good crystallinity is obtained; zirconia plays a role in protecting nano-Fe3O4 particles in the structure; reducing the oxidation phenomenon of Fe3O4 particles, and at the same time, silica forms a protection layer on the surface of nano-Fe3O4 particles, improving the dispersibility of nano-Fe3O4 particles, and enhancing the wave absorption performance, corrosion resistance and high-temperature performance of the magnetic composite nano-zirconia material. Specific Embodiments

[0021] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] Example 1:

[0023] A preparation method of magnetic composite nano-zirconia, comprising the following steps:

[0024] S1. In a reaction kettle, 2 g of nano-Fe3O4 particles and 300 mL of 65 wt% ethanol aqueous solution are mixed, 6 mL of 1 M ammonia water is dropped in, ultrasonically dispersed for 1 h, 4 mL of tetraethyl orthosilicate is dropped into the reaction kettle, stirred and reacted at 500 rpm for 3 h, centrifuged and filtered to obtain a precipitate, the precipitate is washed twice with ethanol and deionized water respectively, dried for 1 h, and then the precipitate is dispersed again in 100 mL of anhydrous ethanol and stirred until a colloidal solution is formed to obtain a composite silica colloidal solution.

[0025] Ammonia water is added dropwise to the solution, which will increase the pH of the solution. For nano-Fe3O4 particles, ammonia water promotes the formation of amino functional groups on their surface. Under alkaline conditions, tetraethyl orthosilicate (TEOS) will hydrolyze and undergo a condensation reaction to form silica, forming a silica protection layer on the surface of the nano-Fe3O4 particles.

[0026] S2. Add 0.2 g of 3-aminopropyltriethoxysilane and 5 mL of 1 M ammonia water to 100 mL of the composite silica colloidal solution in a reaction kettle, stir and react for 1 h, then centrifuge, and dry the precipitate to obtain modified composite silica.

[0027] Since 3-aminopropyltriethoxysilane is a chemical reagent containing amino and silyl groups, it reacts with the hydroxyl groups on the surface of silica through a hydrolysis reaction to form a silicon-oxygen bond connection, thereby grafting the amino functional group onto the surface of silica.

[0028] S3. Dissolve 0.2 g of terephthalic acid in 80 mL of DMF and add it to the reaction kettle, then add 3 g of modified composite silica, stir for 1 h, add 10 mL of glacial acetic acid and 0.4 g of zirconium chloride, continue to stir for 5 min, heat up to 120 °C and stir and react for 2 h, naturally cool to room temperature, centrifuge and filter, wash the precipitate with DMF, ethanol and deionized water once respectively, and dry it in vacuum at 60 °C for 10 h to obtain MOF / composite silica powder.

[0029] By using terephthalic acid as the ligand for MOF synthesis, the carboxyl group in terephthalic acid reacts with the amino group on the surface of the modified composite silica, and an amidation reaction occurs between the amino group and the carboxyl group to form an amide bond; acetic acid is used as a catalyst, and zirconium chloride is used as a metal catalyst to promote the reaction, and finally MOF / composite silica powder is formed.

[0030] S4. Bake the MOF / composite silica powder in a muffle furnace at 400 °C for 4 h to obtain magnetic composite nano-zirconia.

[0031] Example 2:

[0032] A preparation method of magnetic composite nano-zirconia, comprising the following steps:

[0033] S1. Mix 3 g of nano-Fe3O4 particles and 350 mL of 65 wt% ethanol aqueous solution in a reaction kettle, drop in 7 mL of 1 M ammonia water, ultrasonically disperse for 1.5 h, drop 6 mL of tetraethyl orthosilicate into the reaction kettle, stir and react at 550 rpm for 3.5 h, centrifuge and filter to obtain a precipitate, wash the precipitate with ethanol and deionized water twice respectively, dry for 1.5 h, and then redisperse the precipitate in 1100 mL of absolute ethanol and stir until a colloidal solution is formed to obtain a composite silica colloidal solution.

[0034] S2. Add 0.25 g of 3-aminopropyltriethoxysilane and 6 mL of 1 M ammonia water to 110 mL of the composite silica colloidal solution in a reaction kettle. After stirring and reacting for 1.5 h, centrifuge and dry the precipitate to obtain modified composite silica.

[0035] S3. Dissolve 0.3 g of terephthalic acid in 90 mL of DMF and add it to the reaction kettle. Then add 4 g of the modified composite silica, stir for 1.5 h, add 11 mL of glacial acetic acid and 0.5 g of zirconium chloride, continue stirring for 8 min, heat up to 125 °C and stir and react for 2 h. Naturally cool to room temperature, centrifuge and filter. Wash the precipitate with DMF, ethanol and deionized water once respectively, and dry it in vacuum at 65 °C for 11 h to obtain MOF / composite silica powder.

[0036] S4. Calcinate the MOF / composite silica powder in a muffle furnace at 420 °C for 4.5 h to obtain magnetic composite nanozirconia.

[0037] Example 3:

[0038] A preparation method of magnetic composite nanozirconia, comprising the following steps:

[0039] S1. Mix 5 g of nano-Fe3O4 particles and 400 mL of 65 wt% ethanol aqueous solution in a reaction kettle, drop in 8 mL of 1 M ammonia water, ultrasonically disperse for 2 h, drop 8 mL of tetraethyl orthosilicate into the reaction kettle, stir and react at 600 rpm for 4 h, centrifuge and filter to obtain a precipitate. Wash the precipitate with ethanol and deionized water 3 times respectively, dry for 2 h, and then redisperse the precipitate in 120 mL of absolute ethanol and stir until a colloidal solution is formed to obtain a composite silica colloidal solution.

[0040] S2. Add 0.3 g of 3-aminopropyltriethoxysilane and 8 mL of 1 M ammonia water to 120 mL of the composite silica colloidal solution in a reaction kettle. After stirring and reacting for 2 h, centrifuge and dry the precipitate to obtain modified composite silica.

[0041] S3. Dissolve 0.4 g of terephthalic acid in 100 mL of DMF and add it to the reaction kettle. Then add 5 g of the modified composite silica, stir for 2 h, add 12 mL of glacial acetic acid and 0.6 g of zirconium chloride, continue stirring for 10 min, heat up to 130 °C and stir and react for 3 h. Naturally cool to room temperature, centrifuge and filter. Wash the precipitate with DMF, ethanol and deionized water 2 times respectively, and dry it in vacuum at 70 °C for 12 h to obtain MOF / composite silica powder.

[0042] S4. Calcinate the MOF / composite silica powder in a muffle furnace at 450 °C for 5 h to obtain magnetic composite nanozirconia.

[0043] Comparative Example 1: The difference from Example 1 is that tetraethyl orthosilicate is not added in S1 to obtain a composite solution, and this composite solution is used to replace the composite silica colloidal solution; zirconia-coated iron oxide powder is obtained.

[0044] Comparative Example 2: The difference from Example 1 is that the nano-ferroferric oxide particles are replaced with the same mass of nano-ferric oxide particles in S1, and the remaining steps remain unchanged to prepare composite nano-zirconia.

[0045] The sources of some reagents in the examples and comparative examples are as follows:

[0046] Nano-Fe3O4 particles, ferric oxide, and tetraethyl orthosilicate are purchased from Shanghai Guoyao Chemical Reagent Co., Ltd.; 3-aminopropyltriethoxysilane is purchased from Nanjing Herun Coupling Agent Co., Ltd.; DMF is purchased from Tianjin Fuchen Chemical Reagent Factory; glacial acetic acid is purchased from Xilong Chemical Co., Ltd.; terephthalic acid is purchased from Tianjin Guangfu Fine Chemical Research Institute; zirconium chloride and zirconium salt aqueous solution are purchased from Aladdin Reagent Co., Ltd.

[0047] The microwave absorbing coatings prepared from the magnetic composite nano-zirconia powders prepared in Examples 1 - 3 and Comparative Examples 1 - 2 were subjected to performance tests. The standard sample for measuring the microwave absorbing performance of the coating was prepared by mixing commercially available polyurethane and magnetic composite nano-zirconia in a mass ratio of 4:1, stirring until homogeneous, and then spraying it onto an aluminum plate of 180 mm × 180 mm by electrostatic spraying to form a 1-mm-thick microwave absorbing coating, which was cured at room temperature for 12 hours to obtain the standard sample; the effective absorption bandwidth in the range of 2 - 18 GHz and the lowest reflectivity in the range of 0.5 - 18 GHz were measured using an HP8722ES microwave vector network analyzer measurement system; the impact resistance of the standard sample was tested according to the standard GB / T1732—1993, and the salt spray resistance of the standard sample was tested according to the standard GB / T1771—2007; the results are shown in Table 1:

[0048] Table 1

[0049]

[0050] As can be seen from Table 1, when the magnetic composite nano-zirconia powder prepared by the present invention is used as a filler for coatings, it exhibits excellent broadband absorption characteristics, low reflectivity, strong salt spray resistance, and good impact resistance.

[0051] In the magnetic composite nano-zirconia coating of the present invention, nano-zirconia and silica belong to inert materials and, in combination with the synergistic effects of other substances, are not prone to react with acids, alkalis or other corrosive substances in the coating, thereby improving the salt spray resistance of the coating; due to the hydrogen bonding formed between the hydroxyl groups on the surface of silica and water, the dispersibility of silica in the coating is improved, and the binding force with nano-zirconia particles is enhanced, enabling silica to be more firmly filled between nano-zirconia particles and improving the impact resistance of the coating.

[0052] In Comparative Example 1, since the zirconium salt aqueous solution and iron oxide particles were directly mixed, and only the interaction generated by zirconium ions and hydroxyl groups was involved, the bonding strength was relatively low, so the performance was slightly worse than that of Examples 1 - 3.

[0053] In Comparative Example 2, nano-ferroferric oxide particles were used to replace ferric oxide particles. The chemical affinity between ferric oxide particles and zirconia was weak and it was not easy to combine. Moreover, the magnetic property of ferric oxide was inferior to that of ferroferric oxide. Therefore, the performance improvement of the obtained magnetic composite nano-zirconia coating was small.

[0054] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0055] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of magnetic composite nano-zirconia, characterized in that, It includes the following steps: Step 1: Dissolve terephthalic acid in DMF and add it to a reaction kettle. Then add modified composite silica, stir for 1 - 2 h, add glacial acetic acid and zirconium chloride, continue to stir for 5 - 10 min, heat up to 120 - 130 °C and stir for reaction for 2 - 3 h. Cool to room temperature, centrifuge and filter to obtain a precipitate, wash the precipitate, and dry it under vacuum to obtain MOF / composite silica powder; Step 2: Calcinate the MOF / composite silica powder in a muffle furnace at 400 - 450 °C for 4 - 5 h to obtain magnetic composite nano - zirconia.

2. The preparation method of a magnetic composite nano-zirconia according to claim 1, characterized in that, The dosage ratio of terephthalic acid, DMF, modified composite silica, glacial acetic acid and zirconium chloride is 0.2 - 0.4 g : 80 - 100 mL : 3 - 5 g : 10 - 12 mL : 0.4 - 0.6 g.

3. The preparation method of a magnetic composite nano zirconia according to claim 2, characterized in that, The modified composite silica is prepared by the following steps: Add 3 - aminopropyltriethoxysilane and ammonia water to the composite silica colloidal solution in a reaction kettle, stir for reaction for 1 - 2 h, then centrifuge, and dry the precipitate to obtain modified composite silica.

4. The preparation method of a magnetic composite nano zirconia according to claim 3, characterized in that, The dosage ratio of the composite silica colloidal solution, 3 - aminopropyltriethoxysilane and ammonia water is 100 - 120 mL : 0.2 - 0.3 g : 5 - 8 mL.

5. The preparation method of a magnetic composite nano zirconia according to claim 4, characterized in that, The composite silica colloidal solution is prepared by the following steps: Mix nano - Fe3O4 particles and an ethanol - aqueous solution in a reaction kettle, drop in concentrated ammonia water, ultrasonically disperse for 1 - 2 h, drop tetraethyl orthosilicate into the reaction kettle, stir for reaction at 500 - 600 rpm for 3 - 4 h, centrifuge and filter to obtain a precipitate. Wash the precipitate 2 - 3 times with ethanol and deionized water respectively, dry for 1 - 2 h, and then redisperse the precipitate in anhydrous ethanol and stir until a colloidal solution is formed to obtain the composite silica colloidal solution.

6. The preparation method of a magnetic composite nano zirconia according to claim 5, characterized in that, The dosage ratio of nano - Fe3O4 particles, ethanol - aqueous solution, ammonia water, tetraethyl orthosilicate and anhydrous ethanol is 2 - 5 g : 300 - 400 mL : 6 - 8 mL : 4 - 8 mL : 100 - 120 mL.

Images