CN101312088B - Composite magnetism super fine powder and method for making same - Google Patents

Composite magnetism super fine powder and method for making same Download PDF

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CN101312088B
CN101312088B CN2007100995594A CN200710099559A CN101312088B CN 101312088 B CN101312088 B CN 101312088B CN 2007100995594 A CN2007100995594 A CN 2007100995594A CN 200710099559 A CN200710099559 A CN 200710099559A CN 101312088 B CN101312088 B CN 101312088B
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powder
kernel
fine powder
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CN101312088A (en
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彭颖
宗保宁
孟祥堃
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Abstract

The invention provides a composite magnetic superfine powder and a process for preparation thereof, the particle diameter of the superfine powder is 10-80mm, after roasting 4 hours with the temperature of 600 DEG C, the specific saturation magnetization is more than 20emu/g, the particle of the superfine powder is formed by a magnetic inner core and a SiO2 coating layer, the magnetic inner core is formed from Fe3O4 and/or gamma-Fe2O3, and the weight percentage of the magnetic inner core is ranged between 40% and 95%. The superfine powder is obtained by sequentially twice-SiO2-coating the magnetic inner core with superparamagnetism sequentially in organic phase and water phase. The composite magnetic superfine powder of the invention has superparamagnetism and strong specific saturation magnetization with stable physicochemical property, and is particularly suitable for preparing magnetic catalysts.

Description

A kind of composite magnetism super fine powder and preparation method thereof
Technical field
The present invention relates to a kind of composite magnetism super fine powder and preparation method thereof.
Background technology
Superfine powder has the unique effect that is different from bulk material, and as small-size effect, skin effect, quantum size effect and macro quanta tunnel effect etc., these effects are given character such as the magnetic, light, electricity, heat, catalysis, mechanics of superfine powder excellence.
When the particle diameter of magnetic powder is little to a certain degree the time, because magnetic anisotropy can reduce, under the effect of heat energy, particle moment will make it to show superparamagnetism at each direction of easy axis random orientation, and promptly remanent magnetism and coercive force are zero.This characteristic of magnetism super fine powder makes it at aspects such as catalysis, biology, medicine wide application prospect be arranged.But because the particle diameter of magnetism super fine powder is little, surface energy and surface activity height are easily reunited between particle, and easily oxidation is not corrosion-resistant, makes its application be subjected to certain limitation.
" Langmuir.1994,10 (1), P92-99 " reported a kind ofly have the nanometer Fe of superparamagnetism 3O 4Surface coated Si O 2Method.This method step is as follows: preparation has the nanometer Fe of superparamagnetism 3O 4Particle, and it is carried out peptization with Tetramethylammonium hydroxide handle, then with this magnetic nanoparticle at Na 2SiO 3Carry out the SiO first time in the solution 2Coat, more above-mentioned magnetic particle is carried out the SiO second time in teos solution 2Coat, final formation has the magnetic Fe of nucleocapsid structure 3O 4/ SiO 2Particle.The Fe of this method preparation 3O 4/ SiO 2The magnetic kernel that coats in the particle is few, the magnetic of composite magnetic particle a little less than, a little less than the external magnetic field responding ability, need apply the enrichment that the high strength external magnetic field could realize this particle.
Among the Chinese patent CN1224590C, provide a kind of with magnetic Fe 3O 4Particle is a kernel, successively at Na 2SiO 3In solution and the teos solution, twice coated Si O 2Method.Owing to adopt tetraethoxysilane at the outer SiO that coats of magnetic particle 2Not fine and close, so the Fe of its preparation 3O 4/ SiO 2Magnetic particle is in the instructions for use that can not satisfy on the chemical stability under high temperature or the corrosive atmosphere.
In above-mentioned two kinds of methods, all need use Tetramethylammonium hydroxide to prepare Fe 3O 4Colloidal sol, the concentration of the magnetic-particle in its organic facies coating process is very low.
Among the Chinese patent CN1217352C, provide a kind of through acidization in nanometer Fe 3O 4The surface coats multilayer SiO 2Method.In these class methods, if SiO 2Covering amount is less, then can be at Fe 3O 4The surface forms continuous fine and close coating layer, causes its non-oxidizability and corrosion resistance to reduce; If coat multilayer SiO 2, then the magnetic of particle can decline to a great extent.
Above-mentioned preparation method all is directed to biomedical sector, and its prepared composite magnetic particle can not satisfy the requirement of magnetic catalyst in the petrochemical industry.
Summary of the invention
The problem to be solved in the present invention provides a kind ofly has superparamagnetism and specific saturation magnetization is big, physico-chemical property is stable composite magnetism super fine powder, and a kind of composite magnetism super fine powder that is applicable to magnetic catalyst particularly is provided.The present invention also provides the preparation method of above-mentioned composite magnetism super fine powder.
Composite magnetism super fine powder provided by the present invention, its average grain diameter is 10-80nm, is preferably 20-60nm.Its particle is by magnetic kernel and SiO 2Coating layer constitutes, and magnetic kernel is by Fe 3O 4And/or γ-Fe 2O 3Form, the percentage by weight of magnetic kernel is preferably 65%-90% between 40%-95%.Behind 600 ℃ of roasting 4h of composite magnetism super fine powder of the present invention, specific saturation magnetization〉20emu/g; Under the preferred situation, specific saturation magnetization〉50emu/g.
The preparation method of composite magnetism super fine powder provided by the present invention may further comprise the steps:
(1), in the water-soluble iron salting liquid, add aqueous slkali, until pH value=8-12, crystallization, separation, washing, drying obtain having the magnetic kernel of superparamagnetism;
(2), gained magnetic kernel in (1) is disperseed with low-carbon alcohols, add alkoxy silane, its addition is the 0.001-0.02mol/g magnetic kernel, add aqueous slkali then, the mol ratio of alkali and alkoxy silane is 10-30, stirring reaction, and separation, washing, drying obtain coated Si O for the first time 2Magnetic powder;
(3), with gained magnetic powder aqueous dispersion in (2), with aqueous slkali regulation system PH=8-10, under 50-100 ℃, add silicate solutions and inorganic acid solution, the addition of silicate is the 0.001-0.01mol/g magnetic powder, stirring reaction, separation, washing, drying obtain coated Si O for the second time 2Magnetic powder.
Among the above-mentioned preparation method:
In the water-soluble iron salting liquid of step (1), cation is Fe 3+Or/and Fe 2+, anion is Cl, SO 4 2-, NO 3 -Isoionic one or more.Every kind of cationic molar concentration is 0.05-3mol/L, is preferably 0.1-1.5mol/L.
In the step (1), when pH value is 8-12, stop to add aqueous slkali, preferably when 10＜pH value＜12, stop to add aqueous slkali.
In the crystallization process of step (1), crystallization temperature is 20-90 ℃, is preferably 30-70 ℃; Crystallization time is 0.1-10h, is preferably 0.5-5h.
After the magnetic kernel elder generation calcination process of step (1) gained, be used further to step (2).Roasting condition is 100-350 ℃ of roasting 0.5-5h, preferred 150-300 ℃ of following roasting 1-2h.
Low-carbon alcohols in the step (2) is the fatty alcohol of C1-C8, is preferably in methyl alcohol, ethanol, propyl alcohol, isopropyl alcohol, the butanols one or more.
The content of magnetic kernel in low-carbon alcohols in the step (2) is 1-200g/L, is preferably 10-50g/L.
In the step (2), alkoxy silane is Si (OR) nH 1-nRepresented compound (R is the alkyl of C1-C4, and n is 3 or 4) is preferably tetramethoxy-silicane, tetraethoxysilane or triethoxysilane.
In the step (2), the consumption of alkoxy silane is the 0.001-0.02mol/g magnetic kernel, is preferably the 0.002-0.005mol/g magnetic kernel.
In the step (2), the reaction time is 0.5-30h, preferred 2-24h.
In the step (3), the content of magnetic powder in water is 1-200g/L, is preferably 10-50g/L.
In the step (3), said silicate solutions is sodium metasilicate or potassium silicate solution.Be preferably sodium silicate solution.
In the step (3), the modulus of said silicate is 1-3.4.
In the step (3), the concentration of said silicate solutions is 0.005-1mol/L, preferred 0.01-0.3mol/L.
In the step (3), the consumption of said silicate is the 0.001-0.01mol/g magnetic powder, is preferably the 0.001-0.004mol/g magnetic powder.
In the step (3), said inorganic acid is sulfuric acid, hydrochloric acid, nitric acid or phosphoric acid, and its effect in course of reaction is that the pH value=8-10 that keeps suspension gets final product.
In the step (3), the concentration of said inorganic acid is 0.01-1mol/L, preferred 0.05-0.3mol/L.
In the step (3), silicate solutions and inorganic acid solution both can add the mode that also can and flow respectively and add, and preferably joined in the solution in the mode that also flows, and so both can prevent SiO 2Non-homogeneous coating on the magnetic particle surface can prevent SiO again 2Spontaneous nucleation in the aqueous solution.
In the step (3), reaction temperature is 50-100 ℃, is preferably 70-95 ℃, and temperature is too low, is unfavorable for coating; Temperature is too high, there is no need.
The reaction speed of step (3) is very fast, can separate after adding silicate solutions and inorganic acid solution, the preferred reaction 5-120min that continues.
In step (1), (2) and (3), said aqueous slkali is alkali metal hydroxide aqueous solution, aqueous alkali carbonate solution, the alkali metal hydrogencarbonate aqueous solution or ammoniacal liquor.Wherein in the step (1), be preferably the NaOH aqueous solution or the KOH aqueous solution; In the step (2), be preferably ammoniacal liquor; In the step (3), be preferably the NaOH aqueous solution, the KOH aqueous solution or ammoniacal liquor.
In the step (1), the molar concentration of the NaOH aqueous solution or the KOH aqueous solution is 0.05-3mol/L, is preferably 0.1-1.5mol/L.
The mass percentage concentration of the ammoniacal liquor in the step (2) is 5%-35%, is preferably 20%-30%, and its addition (in amino molecule) is 10-30 with the mol ratio of alkoxy silane, is preferably 15-25.
The dispersing mode that step (2) and step (3) are adopted is ultrasonic dispersion or regulates the suspension pH value and disperse, preferred ultrasonic dispersion, and jitter time is 5-90min, is preferably 5-60min.
In step (1), (2) and the step (3), separate mode adopts magnetic to separate; Washing is first water with solution washing to neutral, and then with solvent such as absolute ethanol washing; Drying is dry 0.5-5h under 25-150 ℃, preferred 60-100 ℃ of dry 1-3h.
The present invention is that the magnetic kernel that will have superparamagnetism carries out earlier coating the first time in the alkoxy silane alcoholic solution, is transferred to SiO then 2Carry out in the aqueous solution coating the second time, filling and further coating by to the coating layer hole first time finally form evenly and the SiO of densification on the magnetic kernel surface 2Shell.
Composite magnetism super fine powder provided by the present invention has the following advantages:
(1), composite magnetism super fine powder of the present invention has good thermal stability and chemical stability.It still keeps former crystal phase structure behind 800 ℃ of following roasting 1h, magnetic does not reduce, and soaks 24h and do not dissolve in the hydrochloric acid solution of 0.1mol/L.
(2), the specific saturation magnetization of the composite magnetism super fine powder of the present invention's preparation is big.Behind 600 ℃ of roasting 4h, its specific saturation magnetization is all greater than 20emu/g.
Method of the present invention is not only applicable to Fe 3O 4Or γ-Fe 2O 3Coat any surface and SiO 2Nano particle such as TiO that affinity is arranged 2And Al 2O 3All available method of the present invention is carried out SiO to it 2Coat.The composite magnetism super fine powder of gained of the present invention is specially adapted to the magnetic catalyst in the magnetic stablizing bed technology, but it should be interpreted as and be only applicable to petrochemical industry, and it also can be used for biomedical sector.
Embodiment
Embodiment 1
FeCl with 0.5mol/L 2The FeCl of solution 60ml and 0.5mol/L 310ml solution mixes, and adds the NaOH solution of 0.1mol/L under strong agitation, until 10＜pH value＜12, behind the crystallization 2h, promptly gets the Fe with superparamagnetism through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h in 50 ℃ of water-baths 3O 4Nano particle.
With above-mentioned Fe 3O 4Be diluted to 40g/L with absolute ethyl alcohol, after the ultrasonic dispersion, add tetraethoxysilane (0.002mol/gFe 3O 4), under stirring condition to the NH that wherein adds 25% 3.H 2O (mol ratio of ammonia and tetraethoxysilane is 20), stir 6h after, the product of promptly winning and time coating through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h.
With the product that coats for the first time with distilled water diluting to 20g/L, after the ultrasonic dispersion, regulating PH with the NaOH solution of 0.1mol/L is 8-10, and this suspension is warming up to 80 ℃, then to the slow SiO of adding 0.15mol/L simultaneously wherein 2(the sodium metasilicate modulus is 1 to solution, and addition is 0.001molSiO 2/ g magnetic powder) and the H of 0.05mol/L 2SO 4Solution, and under this temperature, react 1h, naturally cool to room temperature after, can obtain coated prod for the second time through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h.Product is behind 600 ℃ of roasting 4h, and recording specific saturation magnetization through vibrating specimen magnetometer is 63.3emu/g, floods 24h in the HCl of 0.1mol/L solution, after high speed centrifugation separates, does not detect iron ion in the surplus liquid.Fe in the product 3O 4Content be 85%, and its average grain diameter is 25nm.
Embodiment 2
Keep embodiment 1 other conditions constant, that different is preparation Fe 3O 4Used NaOH concentration is 0.5mol/L in the process, and in coating for the first time, the tetraethoxysilane addition is 0.003mol/gFe 3O 4, ammoniacal liquor addition (in ammonia) is 20 with the mol ratio of tetraethoxysilane, and in coating for the second time, the sodium metasilicate modulus is 1, and addition is 0.004mol SiO 2/ g magnetic powder, product are behind 600 ℃ of roasting 4h, and recording specific saturation magnetization through vibrating specimen magnetometer is 49.3emu/g.Fe in the product 3O 4Content be 65%, and its average grain diameter is 40nm.
Embodiment 3
FeSO with 0.5mol/L 4The FeCl of solution 25ml and 1.5mol/L 317ml mixes, and adds the NaOH solution of 1mol/L under strong agitation, until 10＜pH value＜12, behind the crystallization 1h, promptly gets Fe behind magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h in 30 ℃ of water-baths 3O 4
With above-mentioned Fe 3O 4Be diluted to 10g/L with methyl alcohol, after the ultrasonic dispersion, add methyl silicate (0.002mol/gFe 3O 4), under stirring condition to the NH that wherein adds 25% 3.H 2O solution (mol ratio of ammonia and tetraethoxysilane is 20), stir 24h after, through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h time coated prod of promptly winning.
For the first time coated prod with distilled water diluting to 50g/L, ultrasonic dispersion 5min, regulating suspension PH with the KOH solution of 0.1mol/L is 8-10, and this suspension is warming up to 95 ℃, then to the slow SiO of adding 0.05mol/L simultaneously wherein 2(the sodium metasilicate modulus is 1 to solution, and addition is 0.004molSiO 2/ g magnetic powder) and the HCl solution of 0.1mol/L, and under this temperature, react 2h, naturally cool to room temperature after, can obtain coated prod for the second time through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h.Product is behind 600 ℃ of roasting 4h, and recording specific saturation magnetization through vibrating specimen magnetometer is 50.2emu/g.Fe in the product 3O 4Content be 70%, and its average grain diameter is 36nm.
Embodiment 4
Keep other conditions of embodiment 3 constant, just the sodium metasilicate that uses in the second step coating process is 3 replacement by modulus, and product is behind 600 ℃ of roasting 4h, and it is 53.6emu/g that vibrating specimen magnetometer records specific saturation magnetization.Fe in the product 3O 4Content be 70%, and its average grain diameter is 32nm.
Embodiment 5
Under the vigorous stirring, be the Fe (NO of 0.5mol/L to 60ml concentration 3) 3Add the NaOH solution of 0.5mol/L in the solution,, in 70 ℃ of water-baths, behind the crystallization 5h, behind magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h, 300 ℃ of roasting 2h, promptly get γ-Fe until 10＜pH value＜12 2O 3
With above-mentioned γ-Fe 2O 3Be diluted to 50g/L with absolute ethyl alcohol, after the ultrasonic dispersion, add tetraethoxysilane (0.002mol/g γ-Fe 2O 3), under stirring condition to the NH that wherein adds 25% 3.H 2O solution (mol ratio of ammonia and tetraethoxysilane is 20), stir 12h after, through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h time coated prod of promptly winning.
For the first time coated prod with distilled water diluting to 30g/L, ultrasonic dispersion 5min, regulating suspension PH with the KOH solution of 0.1mol/L is 8-10, and this suspension is warming up to 95 ℃, then to the slow SiO of adding 0.05mol/L simultaneously wherein 2(the sodium metasilicate modulus is 1 to solution, 0.001molSiO 2/ g magnetic powder) and the H of 0.05M 2SO 4Solution, and under this temperature, react 1h, naturally cool to room temperature after, can obtain coated prod for the second time through magnetic separation, distilled water and absolute ethanol washing, 80 ℃ of dry 2h.Product is behind 600 ℃ of roasting 4h, and recording specific saturation magnetization through vibrating specimen magnetometer is 52.1emu/g.γ-Fe in the product 2O 3Content be 85%, and its average grain diameter is 28nm.
Embodiment 6
Keep other conditions of embodiment 5 constant, different is that the addition of tetraethoxysilane is 0.007mol/g γ-Fe in coating for the first time 2O 3, ammoniacal liquor addition (in ammonia) is 20 with the mol ratio of tetraethoxysilane, in coating for the second time, adds 0.004molSiO 2/ g magnetic powder, product are behind 600 ℃ of roasting 4h, and recording specific saturation magnetization through vibrating specimen magnetometer is 29.8emu/g.γ-Fe in the product 2O 3Content be 50%, and its average grain diameter is 56nm.

Claims (21)

1. composite magnetism super fine powder, its particle is by magnetic kernel and SiO 2Coating layer is formed, and the particle diameter that it is characterized in that this superfine powder is 10-80nm, its behind 600 ℃ of roasting 4h, specific saturation magnetization＞20emu/g, the magnetic kernel in its particle is by Fe 3O 4And/or γ-Fe 2O 3Form, the percentage by weight of magnetic kernel is between 40%-95%.
2. according to the described composite magnetism super fine powder of claim 1, the percentage by weight that it is characterized in that magnetic kernel is 65%-90%.
3. according to the described composite magnetism super fine powder of claim 1, it is characterized in that this superfine powder behind 600 ℃ of roasting 4h, specific saturation magnetization＞50emu/g.
4. the preparation method of a composite magnetism super fine powder is characterized in that may further comprise the steps:
(1), in the water-soluble iron salting liquid, add aqueous slkali, until pH value=8-12, crystallization, separation, washing, drying obtain having the magnetic kernel of superparamagnetism;
(2), gained magnetic kernel in (1) is disperseed with low-carbon alcohols, add alkoxy silane, its addition is the 0.001-0.02mol/g magnetic kernel, add aqueous slkali then, the mol ratio of alkali and alkoxy silane is 10-30, stirring reaction, and separation, washing, drying obtain coated Si O for the first time 2Magnetic powder;
(3), with gained magnetic powder aqueous dispersion in (2), with aqueous slkali regulation system PH=8-10, under 50-100 ℃, add silicate solutions and inorganic acid solution, the addition of silicate is the 0.001-0.01mol/g magnetic powder, stirring reaction, separation, washing, drying obtain coated Si O for the second time 2Magnetic powder.
5. according to the method for claim 4, it is characterized in that in the water-soluble iron salting liquid of step (1), cation is Fe 3+Or/and Fe 2+, every kind of cationic molar concentration is 0.05-3mol/L.
6. according to the method for claim 4, the crystallization temperature that it is characterized in that step (1) is 20-90 ℃, and the time is 0.1-10h.
7. according to the method for claim 4, it is characterized in that the magnetic kernel elder generation calcination process of step (1) gained after, be used further to step (2).
8. according to the method for claim 4, it is characterized in that the low-carbon alcohols in the step (2) is the fatty alcohol of C1-C8.
9. according to the method for claim 4, it is characterized in that in the step (2), the content of magnetic kernel in low-carbon alcohols is 1-200g/L.
10. according to the method for claim 9, it is characterized in that in the step (2), the content of magnetic kernel in low-carbon alcohols is 10-50g/L.
11., it is characterized in that in the step (2) that alkoxy silane is Si (OR) according to the method for claim 4 nH 4-nRepresented compound, wherein R is the alkyl of C1-C4, n is 3 or 4.
12., it is characterized in that the alkoxy silane in the step (2) is tetramethoxy-silicane, tetraethoxysilane or triethoxysilane according to the method for claim 11.
13., it is characterized in that in the step (2), the reaction time is 0.5-30 hour according to the method for claim 4.
14., it is characterized in that in the step (3), said silicate solutions is sodium metasilicate or potassium silicate solution according to the method for claim 4.
15. according to the method for claim 14, the modulus that it is characterized in that silicate is 1-3.4.
16., it is characterized in that in the step (3), said inorganic acid is sulfuric acid, hydrochloric acid, nitric acid or phosphoric acid according to the method for claim 4.
17., it is characterized in that in the step (3) that silicate solutions and inorganic acid solution join in the solution in the mode that also flows according to the method for claim 4.
18., it is characterized in that in step (1), (2) and (3), said aqueous slkali is alkali metal hydroxide aqueous solution, aqueous alkali carbonate solution, the alkali metal hydrogencarbonate aqueous solution or ammoniacal liquor according to the method for claim 4.
19. according to the method for claim 18, the aqueous slkali that it is characterized in that step (1) is the NaOH aqueous solution or the KOH aqueous solution, the aqueous slkali of step (2) is an ammoniacal liquor, and the aqueous slkali of step (3) is the NaOH aqueous solution, the KOH aqueous solution or ammoniacal liquor.
20. according to the method for claim 4, it is characterized in that the dispersing mode that step (2) and step (3) are adopted is ultrasonic dispersion, jitter time is 5-90min.
21. according to the method for claim 4, it is characterized in that said baking temperature is 25-150 ℃ in step (1), (2) and (3), be 0.5-5h drying time.
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CN101789299B (en) * 2010-01-13 2012-05-23 西安恒旭科技发展有限公司 Method for preparing nanometer SiO2-coated micrometer Fe3O4 compound particles
CN106311246B (en) * 2015-07-08 2019-06-18 神华集团有限责任公司 A kind of support type magnetism precipitated iron fischer-tropsch synthetic catalyst and preparation method thereof
CN105600834A (en) * 2015-12-29 2016-05-25 同济大学 Low-cost large-scale preparation method of ferroferric oxide micron magnetic particles
CN107022290B (en) * 2017-04-10 2019-08-09 滁州卷烟材料厂 A kind of magnetic anti-counterfeit aluminium-foil paper
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