CN1631949A - Method for preparing hollow magnetic composite particles for magnetorheological fluid by using polystyrene microspheres - Google Patents

Abstract

The invention belongs to the technical field of composite materials and functional materials, in particular to a hollow magnetic composite particle used for magnetorheological fluid and a preparation method thereof. The magnetic composite microsphere is formed by covering a layer _{of Fe3O4} on the surface of the hollow polystyrene microsphere. The raw materials are hollow polystyrene microspheres, third-order iron salts, second-order iron salts, dispersants, and alkalis, and are prepared through steps such as ultrasonic dispersion, microparticle coating, and post-treatment according to a suitable weight ratio. The hollow composite microparticles prepared by the invention have low density, good magnetic properties, high shear stress and excellent sedimentation stability.

Description

Method for preparing hollow magnetic composite particles for magnetorheological fluid by using polystyrene microspheres

technical field

The invention belongs to the technical field of composite materials and functional materials, and in particular relates to a hollow magnetic particle for magnetorheological fluid and a preparation method thereof.

Background technique

Hollow microspheres are a new type of particulate material developed in the 1950s and 1960s. Its most notable features are low density, high mechanical strength and good stability. Magnetic oxide Fe ₃ O ₄ can be prepared into particles with a particle size of tens of nanometers, which has a good application prospect as a magnetorheological fluid material. However, the density of magnetic particles in traditional magnetorheological fluids is much higher than that of the medium, so they are easy to agglomerate and settle, which seriously affects the performance and application of magnetorheological fluids. _Fe3O4 particles are no exception, too dense and easy to settle, _which limits its application in this field.

Contents of the invention

The object of the present invention is to propose a magnetic particle that can be used in magnetorheological fluid and its preparation method, which has low density, good magnetic properties, excellent sedimentation stability and high shear yield stress.

The magnetic particle used for magnetorheological fluid proposed by the present invention is a hollow composite magnetic particle formed by coating a layer of _Fe3O4 on the surface of hollow PS microspheres. _The ratio of its raw material components by weight is as follows:

                                                                               

dispersant 0-50 parts

                                                                                                  

                                                                             

Alkali 20-200 parts

Wherein, the hollow PS microsphere is a hollow polystyrene microsphere with a particle diameter of 20nm-20μm.

The dispersant refers to various organic, inorganic and composite surfactants.

The ferric salt refers to a salt containing ferric ions, such as FeCl ₃ , Fe(NO ₃ ) ₃ , Fe ₂ (SO ₄ ) _{3 ,} etc., but not limited thereto.

The ferrous salt refers to a salt containing ferric ions, such as FeCl ₂ , FeSO ₄ , Fe(NO ₃ ) _{2 ,} etc., but not limited thereto.

The alkali refers to an alkaline substance whose solution pH value can be greater than 9, such as NaOH, NH ₃ ·H ₂ O, etc., but not limited thereto.

The preparation method of the present invention is as follows:

(1) Dispersion of hollow PS microspheres

The hollow PS microspheres were ultrasonically dispersed in the dispersion medium to obtain sample a.

(2) Fe ₃ O ₄ coated hollow PS microspheres

Put the ferric salt solution and the ferrous salt solution in a reaction container, add sample a and alkali, heat and stir to react, then add dispersant, cool to room temperature while stirring.

(3) Post-processing:

Sample washing, magnetic separation.

In the above preparation method, the heating and stirring reaction can generally be carried out in stages, that is, after adding sample a, heat for 0.5-1.5 hours, and raise the temperature to 50-65°C; add alkali solution, continue heating and raise the temperature to 90-100°C; then add the dispersant , cooled to room temperature with stirring.

At present, there have been reports on the surface of hollow glass microspheres coated with barium ferrite coating (Wang Caifang, Xiong Weihao, Preparation and Research of Ferrite Composite Materials Based on Hollow Microspheres, Functional Materials, 2004, 35: 536- 538), but there is no report on coating Fe ₃ O ₄ on the surface of hollow PS microspheres as magnetorheological materials similar to the present invention.

The hollow magnetic composite particles prepared by the invention have low density, good magnetic properties, high shear stress and excellent sedimentation stability.

Description of drawings

Figure 1 is a comparison of the sedimentation stability of Fe ₃ O ₄ particles and PS hollow microspheres coated with Fe ₃ O ₄ composite particles in water.

Fig. 2 is based on Fe ₃ O ₄ particles (content 8wt%) and PS hollow microspheres coated Fe ₃ O ₄ magnetic composite particles (composite particle content 8wt%) apparent viscosity of the magnetorheological fluid (water is the medium) Variation with magnetic field strength.

Detailed ways

The following examples are only to further illustrate the present invention in detail, and the present invention should not be limited to the specific and express contents of the following experimental examples without violating the gist of the present invention.

Example 1

The ratio of raw materials used is as follows:

    Hollow PS microspheres (average particle size 2.5 μm) 100 parts (weight)

Sodium Lauryl Sulfate 5 parts by weight

100 copies of iron chloride (weight)

                                                                                                 

Sodium hydroxide 50 parts (weight)

  Preparation of Magnetic Composite Particles:

According to the proportion of the above components, the hollow PS microspheres were ultrasonically dispersed in deionized water for 3 hours to obtain sample a. Make a solution of ferric chloride and ferrous sulfate heptahydrate into the reaction vessel, add sample a, stir and heat for 0.5-1 hour, and raise the temperature to 60°C; dissolve NaOH in deionized water to form a solution, and add it to the reaction vessel After stirring for 1 hour, continue to heat up to 90°C, stop heating, add sodium lauryl sulfate, and cool under stirring. Wash with deionized water until neutral, and magnetically separate.

Properties of Magnetic Composite Particles:

(1) The apparent density of the hollow composite particles measured by the density gradient tube method is 1.3 g/cm ³ , which is about a quarter of the density of the Fe ₃ O ₄ particles.

(2) The hollow magnetic particles prepared by the present invention have excellent sedimentation stability. In the case of not adding any additives and using water as the carrier liquid, when the content of the magnetic composite particle is greater than 8 wt%, it will not settle for a long time. Fig. 1 is the settling performance curve of Fe ₃ O ₄ particles with a particle size of about 50 nm when the content of the composite particles prepared by the present invention is 3 wt%, and the content is 8 wt%. The sedimentation performance of the magnetic particles is expressed by the sedimentation rate V, where V=a/(a+b)×100%, a is the volume of the supernatant liquid, and b is the volume of the turbid liquid in the lower layer. The sedimentation stability of the hollow magnetic particles prepared by the invention is greatly improved.

(3) Fe ₃ O ₄ coated PS hollow microsphere magnetic composite particles and Fe ₃ O ₄ particles were used to make magnetorheological fluid with water as the medium, and the modified NDJ-79 rotary viscometer (Tongji University machine power plant) to study its magnetorheological properties. As shown in Figure 2, the magnetorheological properties of the two magnetorheological fluids are relatively close, and the zero-field viscosity is lower. With the increase of the magnetic field intensity, the magnetorheological fluid The apparent viscosity also increases sharply.

Example 2

The proportioning of used raw materials by weight share is as follows:

    Hollow PS microspheres (average particle size 50nm) 100 parts

Sodium Lauryl Sulfate 0 Parts

Fe(NO ₃ ) ₃ 50 parts

FeSO ₄ 20 parts

Sodium Hydroxide 20 parts

  Preparation of Magnetic Composite Particles:

According to the proportion of the above components, the hollow PS microspheres were ultrasonically dispersed in deionized water for 2 hours to obtain sample a. Make a solution of Fe(NO ₃ ) ₃ and FeSO ₄ into the reaction vessel, add sample a, stir and heat for about 1 hour, and raise the temperature to 65°C; dissolve NaOH in deionized water to form a solution, add it into the reaction vessel and stir After reacting for 1.5 hours, continue to heat up to 95°C, stop heating, and cool under stirring. Wash with deionized water until neutral, and magnetically separate. The properties of the obtained magnetic particles are similar as shown in Fig. 1 and Fig. 2 .

Example 3

The proportioning of used raw materials by weight share is as follows:

    Hollow PS microspheres (average particle size 20 μm) 100 parts (weight)

Sodium lauryl sulfate 50 parts (weight)

Fe ₂ (SO ₄ ) ₃ 400 parts (weight)

FeCl ₂ 200 parts (weight)

NH ₃ H ₂ O 200 parts (weight)

Preparation of magnetic composite particles:

The hollow PS microspheres were ultrasonically dispersed in deionized water for 5 hours to obtain sample a. Make a solution of Fe ₂ (SO ₄ ) ₃ and FeCl ₂ into the reaction vessel, add sample a, stir and heat for 1-1.5 hours, and raise the temperature to 55°C; dissolve NH ₃ H ₂ O in deionized water to make a solution, After adding to the reaction vessel and stirring for 1 hour, continue to heat up to 100°C, stop heating, add sodium lauryl sulfate, and cool under stirring. Wash with deionized water until neutral, and magnetically separate. The properties of the obtained magnetic particles are similar as shown in Fig. 1 and Fig. 2 .

In the above-mentioned embodiments, the raw materials and amounts of each component and the parameters of the preparation process are only selected representatives for describing the present invention. In fact, a large number of experiments have shown that within the scope defined in the summary of the invention, magnetic composite particles with properties similar to those of the above examples can be obtained.

Claims (7)

1, a kind of hollow magnetic composite particle that is used for magnetic flow liquid is characterized in that coating one deck Fe by hollow PS microsphere surface ₃O ₄And the Hollow Compound magnetic particle of forming, its material component proportioning by weight is as follows:

100 parts of hollow PS microballoons

Dispersion agent 0-50 part

Trivalent iron salt 50-400 part

Divalent iron salt 20-200 part

Alkali 20-200 part

Wherein, hollow PS microballoon is that particle diameter is the hollow polystyrene microsphere of 20nm-20 μ m.

2. magnetic composite particle according to claim 1 is characterized in that described dispersion agent is organic and inorganic or compound tensio-active agent.

3. magnetic composite particle according to claim 1 is characterized in that described trivalent iron salt is FeCl ₃, Fe (NO ₃) ₃Or Fe ₂(SO ₄) ₃

4. magnetic composite particle according to claim 1 is characterized in that described divalent iron salt is FeCl ₂, FeSO ₄Or Fe (NO ₃) ₂

5. magnetic composite particle according to claim 1, the alkali described in it is characterized in that for the pH value of its solution greater than 9 alkaline matter.

6. the preparation method of a magnetic composite microsphere as claimed in claim 1 is characterized in that step is:

(1) hollow PS particulate disperses: with hollow PS microballoon ultra-sonic dispersion in dispersion medium, get sample a;

(2) Fe ₃O ₄Coat hollow PS microballoon: ferric salt solution and divalent iron salt solution are added in the reaction vessel, add sample a, and add alkaline solution, the heated and stirred reaction adds dispersion agent, is cooled to room temperature under stirring;

(3) aftertreatment: washing, magnetic separates.

7, preparation method according to claim 6 is characterized in that the heated and stirred reaction segmentation in the step (2) is carried out: after adding sample a, heat 0.5-1.5 hour, be warming up to 50-65 ℃ add alkaline solution after the continuation heat temperature raising to 90-100 ℃; Add dispersion agent again, be cooled to room temperature under stirring.

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