JPS6361362B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides magnetic particle powder for high-density recording, especially
The particle size, which is optimal for short wavelength recording, is uniform, there are no dendritic particles mixed in, and the axial ratio (long axis: short axis) is small, 3:1 or less, especially 2:1 or less. The present invention relates to a spindle-shaped metal magnetic particle powder whose main component is iron and has a coercive force of 500 to 1000 Oe, and a method for producing the same. In recent years, as magnetic recording and reproducing equipment has become longer recording time and has become smaller and lighter, both magnetic recording and reproducing equipment and magnetic recording media such as magnetic tapes and magnetic disks have been required to achieve higher performance and higher density recording. Demand is increasing. In order to improve the performance and high density recording of magnetic recording media, dispersibility, filling properties, residual magnetic flux density Br, and coercive force are required.
It is necessary to improve Hc and saturation magnetization σs, improve the smoothness of the tape surface, and make the coating film thinner. This fact can be seen, for example, on page 140 of ``Development of Magnetic Materials and Technology to Highly Disperse Magnetic Particles (1982)'' published by the Sogo Technological Center. It is necessary to increase Br.In order to increase Br, not only the magnetic field orientation but also the filling rate of magnetic powder must be increased.''
On page 15, ``An important index expressing performance in magnetic recording is...recording density. Until now, its increase has been achieved mainly by improving magnetic heads and recording media. To summarize the direction of improvement so far,...Recording media: Emphasis has been placed on realizing a thin magnetic layer with high coercive force (Hc)...'', page 141 of the same document. ``For high-density recording, the thinning of the coating film is an important factor.'' On page 312 of the same document, ``The conditions for high-density recording with coated tape are short wavelength signals.'' It is possible to maintain high output characteristics with low noise, but in order to do so, it is necessary that the coercive force Hc and residual magnetization Br are both large in a balanced manner, and that the coating film is thinner. ”, and in the case of floating heads such as rigid disks, on page 143 of the same document, “The flying height of the head is the controlling factor for high-density recording.
By reducing this, higher density becomes possible. ...When the flying height is lowered, if the surface of the disk is poor, the reproduction output decreases due to chipping of the head, and stable flying is disturbed, resulting in head crash. Therefore, high-precision finishing of the coating film surface is important. It is clear from the statement ``. These properties of magnetic recording media are closely related to the magnetic particles used in magnetic recording media, and there is a strong desire to improve the properties of magnetic particles. The relationship between the various characteristics of the magnetic recording medium and the characteristics of the magnetic particles used will now be detailed as follows. First, the residual magnetic flux density Br of a magnetic recording medium depends on the dispersibility of the magnetic particles in the vehicle, the orientation and filling properties in the coating film. In order to improve the dispersibility in the vehicle, the orientation and filling properties in the coating film, the particle size of the magnetic particles dispersed in the vehicle must be uniform and dendritic particles should not be mixed. As a result, a high bulk density is required. Next, in order to improve the surface properties of magnetic recording media,
A magnetic particle powder with good dispersibility, good orientation, and small particle size is preferable.Such a magnetic particle powder has a uniform particle size, does not contain dendritic particles, and has a low bulk density. Large is required. Furthermore, in order to thin the coating film of magnetic recording media,
On page 141 of the aforementioned document, ``To make the coating film thinner, it is necessary to reduce the size of the magnetic powder and improve its orientation in the thickness direction of the coating film.In the end, forming a thin coating film means 2.3. As mentioned above, using magnetic powder with low oil absorption leads to the creation of magnetic paint with good coating properties.''As is clear from the statement,
Magnetic particle powders with good dispersibility and orientation are preferred, and examples of such magnetic particle powders include, as mentioned above,
It is required that the particle size is uniform and that dendritic particles are not mixed. As mentioned above, the coercive force Hc of the magnetic recording medium is
For high-density recording, it is necessary that the coercive force Hc of the magnetic particles dispersed in the vehicle be as high as possible. Currently, acicular magnetite particles or acicular maghemite particles are mainly used as magnetic particles for magnetic recording. These generally have a coercive force Hc of about 250 to 350 Oe. It is known that the coercive force can be improved by adding cobalt to the above-mentioned acicular magnetite particles or acicular maghemite particles, and these have a coercive force of about Hc 400 to 800 Oe. , saturation magnetization σs is 70~85emu/
g, so when applied as a magnetic recording medium
Only a Bm of about 2000 Gauss can be obtained. In order to increase the density of magnetic recording media, it is necessary for magnetic particles to have a high coercive force Hc and a large saturation magnetization σs. Metallic magnetic particles containing as a main component are attracting attention and are being put into practical use. The saturation magnetization σs of currently available iron magnetic particles or metal magnetic particles whose main component is iron is 110.
~170emu/g, and the coercive force Hc is
It is approximately 1000 to 1500 Oe, and efforts are being made to further improve the coercive force. These iron magnetic particles or metal magnetic particles whose main component is iron are generally made from acicular hydrated ferric oxide particles, acicular ferric oxide particles, or a different metal other than iron as a starting material. It is obtained by heating and reducing the substance contained in a reducing gas. On the other hand, there is a close relationship between the coercive force Hc of the magnetic recording medium and the performance of the magnetic head, and if the coercive force Hc of the magnetic recording medium is too high, the write current will become high. It is known that in a head, due to an insufficient saturation magnetic flux density Bm in the head core, the core becomes magnetically saturated, making it impossible to sufficiently magnetize the magnetic recording medium. This fact is reflected in, for example, the Institute of Electronics and Communication Engineers Technical Report MR82-19 (1982), page 19: ``...in order to record on these high Hc tapes (Hc 1000 to 1500 Oe), a high saturation magnetic flux density Bm core is required. This is clear from the statement, "There is a concern that in conventional MnZn ferrite-based video heads, magnetic saturation of the head core occurs due to lack of Bm, and high Hc tapes may not be sufficiently magnetized." As mentioned above, there is a close relationship between the coercive force Hc of the magnetic recording medium and the performance of the magnetic head, and for this reason, acicular magnetite particles, acicular maghemite particles, and their surface layers are modified with Co. Coercive force Hc of acicular iron oxide particles is 1000Oe
Ferrite heads are used in magnetic recording and reproducing equipment for magnetic recording media manufactured using magnetic particles having the following: On the other hand, Sendust is used for magnetic recording and reproducing equipment compatible with magnetic recording media manufactured using magnetic particles having a coercive force Hc of 1000 Oe or more, such as iron magnetic particles or metal magnetic particles containing iron as a main component. Heads, amorphous heads, thin film heads, etc. are made of materials with a high saturation magnetic flux density for the head core. However, heads made of these materials have new problems that have not been a problem with ferrite heads, such as head wear due to contact between the magnetic recording medium and the recording and reproducing heads. Therefore, iron magnetic particles or metal magnetic particles mainly composed of iron are required, which have a large saturation magnetization σs and an appropriate coercive force Hc for use in magnetic recording and reproducing equipment using ferrite heads. ing. As mentioned above, the coercive force Hc of the magnetic recording medium is
It is necessary to strike a balance in terms of both high-density recording and the material of the magnetic head. High-density recording is possible as a magnetic recording medium used in magnetic recording and reproducing equipment incorporating ferrite heads, which are currently the most widely used.
In addition, it is required to have an appropriate coercive force Hc, that is, about 500 to 1000 Oe, to avoid magnetic saturation of the ferrite head. The coercive force Hc is
In order to obtain a magnetic recording medium having a coercive force of about 500 to 1000 Oe, it is necessary that the magnetic particles dispersed in the vehicle have a coercive force of 500 to 1000 Oe. In view of the above, the present inventor has determined that the particle size is uniform, dendritic particles are not mixed, and the coercive force is uniform.
The present invention was achieved as a result of various studies aimed at obtaining magnetic particles with a large saturation magnetization σs of about 500 to 1000 Oe. That is, the present invention has an axial ratio (long axis: short axis) of 3:1.
Consisting of iron-based metal magnetic particles having a spindle shape and containing 0.1 to 10 atomic percent of Si relative to Fe and having a coercive force of 500 to 1000 Oe. Goethite, which has a spindle shape, is produced by passing an oxygen-containing gas through an aqueous solution containing FeCO <sub>3</sub> obtained by reacting an aqueous solution of iron-based metal magnetic particles and a ferrous salt aqueous solution with an alkali carbonate to oxidize it. In producing particles, the ferrous salt aqueous solution, the alkali carbonate, and the oxygen-containing gas are passed through the oxidation reaction.
By adding water-soluble silicate in an aqueous solution containing FeCO <sub>3</sub> in an amount of 0.1 to 10 atomic % (calculated as Si) to Fe, spindle-shaped goethite particles containing Si are generated, and the Si The spindle-shaped goethite particles containing Si, the spindle-shaped hematite particles containing Si obtained by heating and dehydrating the goethite particles, or the spindle-shaped goethite particles containing Si in a non-reducing atmosphere. Spindle-shaped iron produced by heat-reducing spindle-shaped hematite particles containing substantially high-density Si obtained by heat treatment at 400°C to 600°C in a reducing gas. This is a method for producing metal magnetic particle powder whose main component is iron, which is composed of metal magnetic particles whose main component is iron. Next, the configuration of the present invention will be described. The present inventor has found that magnetic particle powder that enables high-density recording and avoids magnetic saturation of the ferrite head has uniform particle size;
No dendritic particles mixed in and coercive force 500
We learned that it is necessary to use metal magnetic particles whose main component is iron, which has a large saturation magnetization of about 1000 Oe. In order to obtain a magnetic particle powder with a uniform particle size and no dendritic particles mixed in, it is necessary that the starting material goethite particles have a uniform particle size and no dendritic particles mixed therein. . Conventionally, the most typical known method for producing goethite particles is to add a solution containing ferrous hydroxide particles to a ferrous salt solution by adding an equivalent amount or more of an alkaline solution, and then boiling the solution containing ferrous hydroxide particles at a pH of 11 or above and below 80°C. Goethite particles are obtained by carrying out an oxidation reaction at a temperature of . The goethite particles obtained by this method are particles with an acicular shape with an axial ratio (long axis: short axis) of 10:1 or more, with dendritic particles mixed, and in terms of particle size. , it is difficult to say that the particles have a uniform particle size. Therefore, the present inventor developed a method for producing goethite particles by passing an oxygen-containing gas through an aqueous solution containing FeCO <sub>3</sub> obtained by reacting an aqueous solution of ferrous salt with an alkali carbonate to oxidize it (Japanese Patent Laid-Open No. −80999
We focused on the following. When using this method, the particle size is uniform,
A powder consisting of spindle-shaped goethite particles without dendritic particles mixed therein is obtained. Metal magnetic particles whose main component is iron obtained by heat reduction using spindle-shaped goethite particles with no dendritic particles as a starting material are also uniform in particle size and have dendritic particles. Even though there are no mixed particles, the coercive force Hc becomes more than 1000 Oe. This fact can be seen, for example, in JP-A-53-
This is clear from the description in "Example 3" of Publication No. 10100. That is, the method described in "Example 3" of JP-A-53-10100 involves passing an oxygen-containing gas through an aqueous solution containing FeCO <sub>3</sub> obtained by reacting an aqueous ferrous salt solution with an alkali carbonate. Metal magnetic particles containing iron as a main component are obtained by thermally reducing goethite particles exhibiting a spindle shape obtained by oxidation.The coercivity of the metal magnetic particles containing iron as a main component is It is 1020~1165Oe. Therefore, the present inventor has determined that the particle size is uniform,
As a result of various studies on how to control the coercive force of iron-based metal magnetic particles containing no dendritic particles to about 500 to 1000 Oe, we found that a method of controlling the coercive force of metal magnetic particles containing no dendritic particles to around 500 to 1000 Oe resulted in a method of reacting an aqueous ferrous salt solution with an alkali carbonate. obtained
In producing spindle-shaped goethite particles by passing an oxygen-containing gas through an aqueous solution containing FeCO <sub>3</sub> for oxidation, the ferrous salt aqueous solution, the alkali carbonate, and the oxygen-containing gas are passed through to carry out the oxidation reaction. Add water-soluble silicate to any of the FeCO <sub>3</sub> -containing aqueous solutions before applying 0.1 to Fe in terms of Si.
By adding 10 atom%, spindle-shaped goethite particles containing Si are generated, and the Si
The spindle-shaped goethite particles containing Si, the spindle-shaped hematite particles containing Si obtained by heating and dehydrating the goethite particles, or the spindle-shaped goethite particles containing Si in a non-reducing atmosphere. When spindle-shaped hematite particles containing substantially high-density Si obtained by heat treatment at 400°C to 600°C are thermally reduced in a reducing gas, the particle size is uniform and dendritic. There are no mixed particles,
We have found that it is possible to obtain iron-based metal magnetic particles having a coercive force of 500 to 1000 Oe. Why is the coercive force of metal magnetic particles whose main component is iron?
Although it is not yet clear whether it can be controlled to about 500 to 1000 Oe, the present inventor believes that this is due to the fact that the shape anisotropy of metal magnetic particles containing iron as a main component has become smaller. That is, in producing spindle-shaped goethite particles as a starting material, either an aqueous ferrous salt solution, an alkali carbonate, and an oxygen-containing gas are passed through the aqueous solution containing FeCO <sub>3</sub> before the oxidation reaction is carried out. When water-soluble silicate is added, it is possible to reduce the axis ratio (long axis: short axis) of the spindle-shaped goethite particles that are produced, and the axial ratio (long axis: short axis) is small. Iron-based metal magnetic particles obtained by heating and reducing spindle-shaped goethite particles as a starting material also have a small axial ratio (long axis: short axis), and as a result, the shape anisotropy is small. I think it will be. This phenomenon will be explained as follows by extracting some of the many experimental examples conducted by the present inventor. FIG. 1 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped goethite particles containing Si. That is, 3.0 mol of ferrous sulfate aqueous solution containing 1.0 mol of Fe <sup>2+</sup> was mixed with sodium silicate prepared in advance in a reactor in an amount of 0 to 10 atomic % in terms of Si relative to Fe.
A suspension containing FeCO <sub>3</sub> was obtained at a pH of approximately 10, and an oxidation reaction was carried out by bubbling 15 air per minute through the suspension at a temperature of 50°C. This figure shows the relationship between the axial ratio (major axis: short axis) of spindle-shaped goethite particles containing Si obtained by this process and the amount of water-soluble silicate added. As is clear from FIG. 1, the axial ratio (long axis:short axis) tends to decrease as the amount of water-soluble silicate added increases. FIG. 2 shows the relationship between the amount of water-soluble silicate added and the bulk density of spindle-shaped goethite particles containing Si obtained in the same manner as in FIG. 1. As is clear from FIG. 2, the bulk density tends to increase as the amount of water-soluble silicate added increases. Figure 3 shows the amount of water-soluble silicate added and the spindle-shaped iron-based metal magnetic particles containing Si obtained by thermal reduction of spindle-shaped goethite particles containing Si. It is a relationship diagram with the axis ratio (long axis: short axis). That is, 5.0 atomic% Co <sup>2+</sup> in terms of Co relative to Fe <sup>2+</sup>
Cobalt sulfate containing cobalt sulfate and ferrous sulfate aqueous solution containing 1.0 mol of Fe <sup>2+</sup> were obtained by adding sodium silicate prepared in advance in a reactor in an amount of 0 to 10 atomic % in terms of Si relative to Fe. In addition to the sodium carbonate aqueous solution 2.0, a suspension containing FeCO <sub>3</sub> at a pH of about 10 was obtained, and the suspension was heated at a temperature of 50°C at a rate of 15 min.
Substantial high-density Si, obtained by heating spindle-shaped goethite particles containing Si and Co at 500°C in air, which were obtained by aeration of air to perform an oxidation reaction. Axial ratio (long axis: short axis) of iron-based metal magnetic particles obtained by heating and reducing Co-containing spindle-shaped hematite particles at 300°C for 8 hours and water-soluble silicic acid This shows the relationship with the amount of salt added. As is clear from FIG. 3, as the amount of water-soluble silicate added increases, the axial ratio (long axis:short axis) of the metal magnetic particles containing iron as a main component tends to decrease. Axial ratio (long axis:
If the short axis) is 3:1 or less, increase the coercive force Hc from 500 to
It can be controlled to 1000Oe, and when the axial ratio (major axis: short axis) is 2:1 or less, the coercive force Hc can be controlled to 500~
Can be controlled to 850Oe. The invention described in "Example 3" of the above-mentioned Japanese Patent Application Publication No. 53-10100 uses spindle-shaped goethite particles with an axial ratio (long axis: short axis) of 5:1 as a starting material. As is clear from Figure 3B of the same publication, the axial ratio (long axis: short axis) of the metal magnetic particles containing iron as a main component obtained by thermal reduction of the particles is 5:1, which is the same as that of the goethite particles that are the starting material. As a result,
It is thought that only those with a coercive force of 1000 Oe or more could be obtained. Next, various conditions for implementing the present invention will be described. Examples of the ferrous salt aqueous solution used in the present invention include a ferrous sulfate aqueous solution and a ferrous chloride aqueous solution. As the alkali carbonate used in the present invention, sodium carbonate, potassium carbonate, and ammonium carbonate are used alone or in combination with an alkali hydrogen carbonate such as sodium hydrogen carbonate, potassium hydrogen carbonate, and ammonium hydrogen carbonate. be able to. The reaction temperature in the present invention is 40 to 80°C.
If the temperature is below 40°C, goethite particles exhibiting a spindle shape cannot be obtained. If the temperature is 80°C or higher, particulate Fe <sub>3</sub> O <sub>4</sub> will be mixed. The PH in the present invention is 7-11. 7 or less,
Or, if it is 11 or more, goethite particles exhibiting a spindle shape cannot be obtained. The oxidation means in the present invention is carried out by passing an oxygen-containing gas (for example, air) into the liquid. The water-soluble silicates used in the present invention include sodium and potassium silicates. The water-soluble silicate in the present invention is involved in the axis ratio (major axis: short axis) of spindle-shaped goethite particles to be produced, and therefore, the production reaction of spindle-shaped goethite particles is It is necessary to be present before the oxidation reaction is started and added to either the ferrous salt aqueous solution, the aqueous solution containing FeCO <sub>3</sub> before bubbling the alkali carbonate and oxygen-containing gas to carry out the oxidation reaction. I can do it. The amount of water-soluble silicate added in the present invention is
It is 0.1 to 10 atomic % based on Fe in terms of Si. If it is 0.1 atomic % or less, the effect of reducing the axis ratio (long axis: short axis) of spindle-shaped metal magnetic particles mainly composed of iron, which is the objective of the present invention, cannot be sufficiently achieved. Can not. If the content is 10 atomic % or more, it is not preferable because the saturation magnetization of metal magnetic particles containing iron as a main component, which is obtained by heating and reducing the resulting powder consisting of spindle-shaped goethite particles, decreases. When considering the axial ratio (long axis: short axis) and saturation magnetization of the spindle-shaped metal magnetic particles mainly composed of iron, 0.3 to 8 atomic % is preferable. Almost the entire amount of the added water-soluble silicate is contained in the produced goethite particles, and as shown in Table 1 below, the obtained goethite particles have a Si equivalent amount of approximately the same amount of Fe as the added amount. 0.10~
As shown in Table 3 below, metal magnetic particles containing 10.02 at. Contains 0.100 to 10.00 at% in terms of Si. Next, regarding the thermal reduction process, spindle-shaped metal magnetic particles mainly composed of iron are produced by thermally reducing spindle-shaped goethite particles with uniform particle size and no dendritic particles. When obtaining iron, the higher the ring temperature, the more spindle-shaped metal magnetic particles mainly composed of iron with larger saturation magnetization can be obtained. However, as the reduction temperature becomes higher,
The deformation of the spindle-shaped metal magnetic particles mainly composed of iron and the sintering between the particles and the particles become significant. The causes of deformation of particles and sintering between particles and particles in the thermal reduction process will be explained below. Generally, 300 spindle-shaped goethite particles are
The spindle-shaped hematite particles obtained by heat dehydration at temperatures around ℃ retain the particle shape of goethite particles, but on the other hand, there are many particles generated by dehydration on the particle surface and inside the particle. Voids are present, grain growth of single grains is insufficient, and therefore the degree of crystallinity is very small. When heat reduction is performed using hematite particles exhibiting such a spindle shape, uniform particle growth of a single particle is difficult to occur because the particle growth of a single particle, that is, the physical change is rapid. It is thought that in areas where the grain growth of a single grain has rapidly occurred, sintering of grains and grains occurs, making the grain shape more likely to collapse. Furthermore, during the thermal reduction process, rapid volumetric contraction from the oxide to the metal occurs, making the particle shape more likely to collapse. Therefore, in order to prevent particle shape deformation and sintering between particles and particles in the thermal reduction process, it is necessary to prepare sufficient single particles of hematite particles that have a spindle shape and , spindle-shaped hematite particles that have a substantially high density with an increased degree of crystallinity by achieving uniform particle growth, and that retain and inherit the particle shape of spindle-shaped goethite particles. It is necessary to keep it as As a method for obtaining substantially high-density spindle-shaped hematite particles with an increased degree of crystallinity, spindle-shaped goethite particles are heat-treated at 400°C to 600°C in a non-reducing atmosphere. method is known. If the temperature is below 400°C, it is difficult to say that the particles have a substantially high density with an increased degree of crystallinity, and if the temperature is above 600°C, it may cause deformation of the particles and sintering between particles. It ends up. In the present invention, when reducing Si-containing spindle-shaped goethite particles or Si-containing spindle-shaped hematite particles obtained by heating and dehydrating the same, the reduction temperature is preferably 300°C to 450°C. . If the temperature is below 300℃, the reduction reaction progresses slowly.
It takes a long time. Furthermore, if the temperature is 450° C. or higher, the reduction reaction rapidly progresses, causing deformation of the particle morphology and sintering of the particles and each other. In the present invention, when reducing spindle-shaped goethite particles containing substantially high-density Si, the reduction temperature is preferably 300°C to 500°C. The reason for this is the same as in the case of thermally reducing Si-containing spindle-shaped goethite particles or Si-containing spindle-shaped hematite particles obtained by heating and dehydrating the goethite particles. The present invention configured as described above has the following effects. That is, according to the present invention, the particle size is uniform, dendritic particles are not mixed, and the coercive force is 500~
Since it is possible to obtain a spindle-shaped metal magnetic particle powder containing iron as a main component and having a strength of about 1000 Oe, it is suitable as a magnetic particle powder for high recording density, which is currently most required. In addition, the spindle-shaped iron-based metal magnetic particles containing Si obtained by the present invention have a small axial ratio (long axis: short axis) of 3:1 or less, especially 2:1 or less. Therefore, it is suitable as a magnetic particle powder for short wavelength recording. The fact that magnetic particles with a small axial ratio (long axis: short axis) is suitable as magnetic particle powder for short wavelength recording is as follows.
For example, ``The present invention...
Instead of the usual acicular particles with a long diameter of 0.4 to 2μ or 0.3 to 1μ and an aspect ratio (axial ratio) of 5 to 20, which are used in the above-mentioned prior art, the particle size is as small as 0.3μ or less... By making the shape short with an aspect ratio of more than 1 and less than 3, the noise level due to discontinuity of magnetization caused by the particle size is lowered, and by reducing the aspect ratio... suppressing the tendency to lie down and orient;
Moreover, if necessary, it is characterized in that it has a tendency to be easily oriented perpendicular to the plane, so that a large residual magnetization perpendicular to the plane can be obtained. ” and “The magnetic recording medium thus obtained has a short recording wavelength range,
For example, at 1μ, the output is high and the noise is low, so as a result, an excellent S/N ratio can be obtained. It is clear from the statement ``. Furthermore, when the spindle-shaped iron-based metal magnetic particle powder containing Si obtained according to the present invention is used in the production of magnetic paint, it is well dispersed in the vehicle, and it is easy to fill. It is possible to obtain a preferable magnetic recording medium with extremely excellent properties. The effects of the present invention described above are due to the addition of Co, Mg, Al, Cr, Zn, Ni, which has been added during the production of goethite particles as a starting material in order to improve various properties of metal magnetic particles whose main component is iron. , Ti, Mn, Sn,
It also works effectively when a different metal other than Fe, such as Pb, is added. In addition, the axial ratio (long axis: short axis) and long axis of the particles in the above experimental examples, the following examples, and comparative examples are as follows:
All values are shown as the average value of values measured for more than 100 particles from electron micrographs of two or more fields of view magnified more than 100,000 times, and the bulk density is
Measured according to JIS K 5101 "Pigment test method". The amount of Si, Co, Zn and Ni in the particles is determined by
The measurement was carried out by performing fluorescence X-ray analysis using a ray analyzer 3063 M type (manufactured by Rigaku Denki Kogyo) in accordance with JIS K 0119 "General Rules for Fluorescence X-ray Analysis."<Production of spindle-shaped goethite particles> Examples 1 to 12, Comparative Example 1; Example 1 Ferrous sulfate aqueous solution containing 1.0 mol/Fe ²⁺ 30
3.53 mol of sodium silicate (No. 3) (SiO ₂ 28.55 wt%) was added to the Fe prepared in advance in the reactor to contain 0.20 atomic % in terms of Si. In addition to Na ₂ CO ₃ aqueous solution 20, PH9.9,
FeCO ₃ containing Si was produced at a temperature of 50°C. Temperature 50 to the aqueous solution containing _FeCO3 containing Si above.
at 130 °C for 6.5 hours at 130 air per minute.
Goethite particles containing Si were produced. At the end point of the oxidation reaction, a part of the reaction solution is extracted, adjusted to acidic with hydrochloric acid, and then treated with Fe ²⁺ using red blood salt solution.
Judgment was made based on the presence or absence of a blue color reaction. The generated particles are separated by filtration, washed with water, dried, and
Shattered. As a result of electron microscopy observation, this Si-containing goethite powder consists of spindle-shaped particles with an average long axis of 0.38 μm and an axial ratio (long axis: short axis) of 2.5:1, and the particle size is uniform. It did not contain any dendritic particles. In addition, as a result of fluorescent X-ray analysis, this spindle-shaped goethite particle powder contained 0.19 atomic percent of Si relative to Fe, and its bulk density was 0.41 g/
It was cc. Examples 2 to 12 Examples except that the type of Fe ²⁺ aqueous solution, the type and concentration of alkali carbonate, the type, amount and timing of addition of water-soluble silicate, the type, amount and temperature of metal ions were varied. Goethite particles exhibiting a spindle shape were produced in the same manner as in Example 1. Table 1 shows the main manufacturing conditions and characteristics of the produced goethite particles. Comparative Example 1 Goethite particles were produced in the same manner as in Example 1 except that sodium silicate was not added. As a result of electron microscopy observation, the obtained goethite particles had an average value of 0.55 μm on the long axis and an axial ratio (long axis:
(minor axis) 7:1, and the bulk density was 0.33 g/cc. <Production of substantially high-density spindle-shaped hematite particles> Examples 13 to 20, Comparative Example 2; Example 13 700 g of spindle-shaped goethite particles containing Si obtained in Example 1 was heat-treated in air at 500°C to obtain spindle-shaped hematite particles containing substantially high-density Si. As a result of electron microscopic observation, the average value of these particles was 0.38 μm on the long axis, and the axial ratio (long axis: short axis) was 2.5:1.
The particle size was uniform and dendritic particles were not mixed. Examples 14 to 20, Comparative Example 2 Containing substantially high-density Si in the same manner as in Example 13, except that the type of goethite particles to be treated, the heat treatment temperature, and the type of non-reducing atmosphere were variously changed. A hematite particle powder exhibiting a spindle shape was obtained. Table 2 shows the main manufacturing conditions and various characteristics at this time. As a result of electron microscopy, the obtained spindle-shaped hematite particles containing substantially high-density Si were found to have uniform particle sizes and no dendritic particles. <Production of spindle-shaped hematite particles> Example 21 700 g of spindle-shaped goethite particles containing Si obtained in Example 8 were heated and dehydrated in air at 300°C to produce spindle-shaped particles containing Si. A hematite particle powder exhibiting the following properties was obtained. As a result of electron microscopic observation, the average value of these particles was 0.23 μm on the long axis, and the axial ratio (long axis: short axis) was 2:1.
The grain size was uniform and dendritic particles were not mixed. In addition, as a result of fluorescent X-ray analysis, Si was found to be 1.49% of Fe.
It contains atomic% and its bulk density is 0.50
g/cc. <Production of spindle-shaped metallic magnetic particles mainly composed of iron> Examples 22 to 23, Comparative Example 3; Example 22 Goethite particles containing Si obtained in Example 13 and exhibiting a spindle shape 150 g of the powder was put into a retort reduction container (No. 3), and H ₂ gas was passed through the container at a rate of 35 per minute while the container was driven and rotated, and reduction was carried out at a reduction temperature of 300°C. The spindle-shaped iron-based metal magnetic particle powder containing Si obtained by reduction is heated to prevent rapid oxidation when taken out into the air.
A safe oxide film was formed on the particle surface by immersing it in a toluene solution and evaporating it. The Si-containing spindle-shaped metal magnetic particles mainly composed of iron are treated with fluorescent X.
As a result of line analysis, it contained 0.194 atomic% of Si relative to Fe, and as a result of electron microscopy, the long axis was 0.35 μm,
The axial ratio (long axis: short axis) was 2.5:1, the particle size was uniform, and dendritic particles were not mixed. Also, specific surface area 30.5m ² /g, bulk density 0.64g /
cc, and the magnetism was a coercive force of 8700e and a saturation magnetization of 150.2emu/g. Examples 23 to 33, Comparative Example 3 Spindle-shaped metal magnetic particles containing iron as a main component were obtained in the same manner as in Example 22, except that the type of starting material and the reduction temperature were varied. Table 3 shows the main manufacturing conditions and characteristics at this time. As a result of electron microscopy observation, the Si-containing spindle-shaped metal magnetic particle powders mainly composed of iron obtained in Examples 23 to 33 were found to have uniform particle size and a mixture of dendritic particles. It was something I wouldn't do. Figure 4 shows electron micrographs (×20,000) of spindle-shaped metallic magnetic particles containing Si obtained in Example 23 and Example 27, each consisting of iron as a main component.
and shown in FIG. Further, an electron micrograph (×20,000) of the spindle-shaped metal magnetic particle powder mainly composed of iron obtained in Comparative Example 3 is shown in FIG.

【table】

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped goethite particles containing Si. FIG. 2 shows the relationship between the amount of water-soluble silicate added and the bulk density of spindle-shaped goethite particles containing Si.
FIG. 3 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped metal magnetic particles containing Si and mainly consisting of iron. 4 to 6 are
Both are electron micrographs (×20000), and FIGS. 4 and 5 are Example 23 and Example 27, respectively.
Figure 6 shows the spindle-shaped iron-based metal magnetic particles containing Si obtained in Comparative Example 3. It is a particulate powder.

Claims (1)

[Claims] 1. The axial ratio (major axis: minor axis) is 3:1 or less,
Contains 0.1 to 10 at% of Si relative to Fe, and
An iron-based metal magnetic particle powder comprising spindle-shaped iron-based metal magnetic particles having a coercive force of 500 to 1000 Oe. 2 The axial ratio (major axis: minor axis) is 2:1 or less,
Contains 0.3 to 8 at% of Si relative to Fe, and
Claim 1 having a coercive force of 500 to 850 Oe
An iron-based metal magnetic particle powder comprising iron-based metal magnetic particles exhibiting a spindle shape as described in 1. 3. In producing spindle-shaped goethite particles by passing an oxygen-containing gas through an aqueous solution containing FeCO ₃ obtained by reacting a ferrous salt aqueous solution with an alkali carbonate to oxidize it, the ferrous iron Add a water-soluble silicate to Fe to either the aqueous salt solution, the alkali carbonate and the _FeCO3 -containing aqueous solution before performing the oxidation reaction by passing the alkali carbonate and oxygen-containing gas through the aqueous solution.
By adding 0.1 to 10 atomic% in terms of
Generate Si-containing spindle-shaped goethite particles, and reduce the Si-containing spindle-shaped goethite particles or the Si-containing spindle-shaped hematite particles obtained by heating and dehydrating the goethite particles. A method for producing iron-based metal magnetic particle powder consisting of iron-based metal magnetic particles exhibiting a spindle shape characterized by thermal reduction in an aqueous gas. 4 Addition amount of water-soluble silicate is 0.3 to 8 at%
A method for producing iron-based metal magnetic particle powder comprising spindle-shaped iron-based metal magnetic particles according to claim 3. 5 In producing spindle-shaped goethite particles by passing an oxygen-containing gas through an aqueous solution containing FeCO ₃ obtained by reacting a ferrous salt aqueous solution with an alkali carbonate to oxidize the ferrous salt aqueous solution and an alkali carbonate, Add a water-soluble silicate to Fe to either the aqueous salt solution, the alkali carbonate and the _FeCO3 -containing aqueous solution before performing the oxidation reaction by passing the alkali carbonate and oxygen-containing gas through the aqueous solution.
By adding 0.1 to 10 atomic% in terms of
Goethite particles containing Si and having a spindle shape are produced, and the spindle-shaped goethite particles containing Si are heat-treated at 400°C to 600°C in a non-reducing atmosphere. An iron-based metal consisting of spindle-shaped iron-based metal magnetic particles characterized by heating and reducing spindle-shaped hematite particles containing dense Si in a reducing gas. Method for producing magnetic particle powder. 6 Addition amount of water-soluble silicate is 0.3 to 8 at%
A method for producing iron-based metal magnetic particle powder comprising spindle-shaped iron-based metal magnetic particles according to claim 5.