JPH02215105A - Manufacture of magnetic fluid - Google Patents

Abstract

PURPOSE:To make it possible to manufacture the title magnetic fluid easily at low cost by a method wherein an interface activator treatment and a dispersion treatment are conducted on the ferromagnetic powder which is obtained using a glass crystallizing method. CONSTITUTION:After the mixed ingredients of the basic component of an oxide magnetic material and a glass forming ingredient (ZnO, MnO, Fe2O3 and H3BO3 for example) have been heated up and fused, a flake-like amorphous material is formed by rolling and quenching. Then, the above-mentioned material is heat-treated at the temperature not exceeding the crystallization temperature of the oxide magnetic material plus 80 deg.C, which is 750 deg.C, and the crystal of oxide magnetic material (ferrite) is deposited. The sintered body is pulverized, treated by a dilute acid (acetic acid), (B2O3) is melted, the crystal of the oxide (Mn-Zn) magnetic material is washed out, said slurry is adsorbed by adding an interface activator (oleic acid soda), and after the material has been dehydrated and dried up, it is stirred up by adding an organic solvent medium, and a magnetic fluid is obtained.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an improvement in a method for producing magnetic fluid.

(Prior art) A magnetic fluid made by stably dispersing colloid-sized ferromagnetic fine powder (fine particles) in a liquid phase can be used, for example, as a magnetic seal,
It has been put to practical use in applications such as improving the damping characteristics of speakers and sorting out differences in specific gravity to recover useful resources. In other words, magnetic seals using magnetic fluids have zero leakage, do not cause wear because there is no friction between solid objects, have sufficient shaft surface finish and dimensional tolerances, and do not generate heat, making them suitable for semiconductors. Used in manufacturing vapor deposition equipment, etc. Furthermore, when a magnetic field is applied to a magnetic fluid, a magnetic gradient is generated therein, producing the same effect as creating a density distribution. Therefore, it is known that when a non-magnetic material is placed in this density distribution, buoyancy is generated in the direction of a lower magnetic field, which is used to select useful resources based on their specific gravity.

The magnetic fluid is usually manufactured in the following manner. First, the ferromagnetic fine powder (fine particles) required for the ball mill, such as Pe304.

(Mn-Zn) Po204, (Nl-Zn)
Ferromagnetic oxide powder such as Fe204, ferromagnetic metal or alloy powder, dispersion solvent such as ester hydrocarbon, fluorinated hydrocarbon oil or water, polarity such as carboxyl group, sulfone group, amino group, sulfosuccinic acid group at the end A magnetic fluid having a group-containing surfactant such as sodium oleate is charged and mixed and pulverized for a long period of time to form a stable dispersion system.

(Problems to be Solved by the Invention) However, the above method for producing magnetic fluid has the following disadvantages. That is, the production of ferromagnetic powder or fine particles that form the main part of the magnetic fluid, and the preparation (manufacturing) of the magnetic fluid.
and are done as separate processes. In other words, the ferromagnetic oxide powder must be manufactured in advance, and the ferromagnetic oxide powder must be manufactured and prepared (
In order to disperse the stored ferromagnetic oxide powder in the required solvent, a discontinuous two-step method is adopted in which the required surfactant is added and the mixture is stirred and mixed for a long time using a ball mill or the like. For this reason, there is a consensus that not only is the manufacturing equipment and manufacturing operations complicated, but the manufacturing costs are also relatively high. That is, since the ferromagnetic oxide powder and the like tend to aggregate, they have poor dispersibility even when treated with a surfactant, and a relatively long period of stirring and mixing is required to form a stable dispersion system.

The present invention has been made in response to these conventional circumstances, and it is an object of the present invention to provide a method of manufacturing a required magnetic fluid easily and at relatively low cost.

[Structure of the Invention] (Means for Solving the Problems) The method for producing a magnetic fluid of the present invention involves heating and melting a raw material mixture containing a basic component of an oxide magnetic material and a glass-forming component, and then rapidly cooling it to make it non-stick. a step of forming a crystalline body; a step of precipitating crystals of the oxide magnetic substance by heat-treating the amorphous body at a temperature not exceeding 80° C. higher than the crystallization temperature of the oxide magnetic substance to be formed; The heat-treated sintered body is finely pulverized, the glass-forming components are dissolved and removed with dilute acid, and the crystals of the oxide magnetic material are washed out. After drying, the washed out crystals are adsorbed with a surfactant. It is characterized by comprising a step of stirring and mixing with oil.

(Function) The method for producing a magnetic fluid of the present invention involves the following steps: 1) treating the obtained ferromagnetic powder with a surfactant; 1) stirring in a dispersing solvent; will be held. In other words, the production of the required ferromagnetic powder and the preparation (manufacturing) of the magnetic fluid are performed as a series of operations, and the ferromagnetic powder is produced in an aggregated form by treating each individual powder or particle with a surfactant. Therefore, it is possible to easily form a stable dispersion system, thereby easily reducing manufacturing complexity and cost.

(Example) The present invention will be described in detail below. First, in terms of oxide, Z
nO: 15so1%, MnO: 22*o1%, Fe2O
3: 3g 101%, B 203: 1 oz. ZnO so that the ratio is 25101%.

MnO, Fez O! , )l s Bo3 were each weighed in predetermined amounts and mixed to prepare raw material components.

Next, this mixture was placed in a platinum crucible, heated and melted at a temperature of 1400°C using a high-frequency induction heater, and this melt was rapidly cooled by rolling on water-cooled high-speed twin rolls to a temperature of 40 to 50°C.
A flaky amorphous material with a thickness of 0 μm was prepared. Subsequently, the temperature of the amorphous body was raised at a constant rate, and then heated at 750°C for 5 hours.
Heat treatment was performed to precipitate ferrite crystals. Thereafter, this heat-treated product was pulverized using a brown crusher or the like, and further subjected to wet pulverization using a ball mill. next,
While heating the obtained fine powder, applying ultrasonic waves and treating it with an acetic acid solution to dissolve and remove the B2O3 phase of the glass-forming substance, and after this acid treatment, the powder was repeatedly washed with hot water,
A slurry of Mn-Zn based fine particles (fine powder) was obtained. An aqueous solution of sodium oleate was added to the Mn--Zn-based fine particle slurry obtained above, and ultrasonic waves were applied to cause the sodium oleate to be adsorbed onto the Mn--Zn-based fine particle slurry. After that, it is dehydrated by centrifugation, dried, and then added to kerosene (organic solvent) and Daysilver (stirrer).
A magnetic fluid in which Mn--Zn-based fine particles were stably dispersed was obtained by stirring. In the above, Mn-Zn ferrite was used as the ferromagnetic oxide powder or fine particles, but it is not limited to this, and for example -1Ni-Zn
It may be a Ba-based ferrite, a Ba-based ferrite, Pe203, or the like. Furthermore, the surfactant to be adsorbed to the ferromagnetic oxide powder or fine particles precipitated by the glass crystallization method is not limited to sodium oleate, but any surfactant used in the production of magnetic fluids may be used. obtain. Furthermore, the solvent in which the ferromagnetic oxide powder or fine particles are dispersed is not limited to the above-mentioned kerosene, but may be other organic solvents, water, or the like.

In other words, the ferromagnetic powder, surfactant 8 dispersion solvent, etc. can be appropriately selected depending on the intended use of the prepared magnetic fluid.

In the method of the present invention, the heat treatment of the amorphous material obtained by rapid cooling is performed within a temperature range that does not exceed 80°C than the crystallization temperature of the resulting ferromagnetic oxide powder or fine particles. This is because crystallization progresses, making it difficult to obtain the required ferromagnetic oxide powder or fine particles.

[Effects of the Invention] According to the method of the present invention, in the process of producing ferromagnetic oxide powder by the glass crystallization method, that is, after crushing the amorphous material, acid treatment, and washing the obtained ferromagnetic powder with water, Then, a surfactant treatment is performed. Since the surfactant is adsorbed and retained on the surface of the ferromagnetic oxide powder, aggregation between the ferromagnetic oxide powders (particles) is completely suppressed or prevented. Therefore, even in the process of preparing a desired magnetic fluid by dispersing this ferromagnetic oxide powder (particles) in a dispersion solvent, a uniform dispersion system can be easily formed. That is, a magnetic fluid forming a stable dispersion system can be easily obtained by a relatively short mixing and stirring operation. Thus, the present invention can be said to be a practical manufacturing method because the manufacturing operations are simple, the mixing and stirring operations can be performed in a short time, and the manufacturing process can be performed at relatively low cost.

Applicant: Toshiba Glass Corporation Agent Patent Attorney Suyama Sa (1 idiot)

Claims (1)

[Claims] A step of heating and melting a raw material mixture containing a basic component of an oxide magnetic material and a glass-forming component and then rapidly cooling it to form an amorphous body; A step of precipitating crystals of the oxide magnetic material by heat treatment at a temperature not exceeding 80°C higher than the crystallization temperature of the oxide magnetic material, and a step of finely pulverizing the heat-treated sintered body and pulverizing it with dilute acid. A magnetic material characterized by comprising a step of dissolving and removing glass-forming components and washing out crystals of the oxide magnetic material, and a step of adsorbing a surfactant to the washed out crystals, drying them, and then stirring and mixing them with a dispersion solvent. Fluid manufacturing method.