JPS5993806A - Production of needle fe-co alloy - Google Patents

Abstract

PURPOSE:To obtain a titled alloy having high satd. magnetization and high coercive force by flowing a gaseous mixture composed or iron chloride, cobalt chloride gasified under the reduced pressure and hydrogen over a substrate and depositing a needle Fe-Co alloy. CONSTITUTION:Iron chloride and cobalt chloride are put in a boat 5 in a furnace core tube 2 for reaction, etc. and the boat is put in the position of a heater 3. A substrate 6 for deposition made of Mo or the like placed in the position of a heater 4, and the air in the tube 2 is evacuated by using a rotary pump 7. The heater 3 is heated to 250-450 deg.C and the heater 4 to 550-1,150 deg.C, whereafter hydrogen is flowed at about 100-1,000cc/min rate from a hydrogen supply bomb 1 so that the reaction for decomposition and deposition of the needle Fe- Co is induced on the substrate 6. The inside of the tube is maintained in the reduced pressure condition of about 10-200 Torr during the reaction. The heaters 3, 4 are switched off upon ending of the reaction, then the substrate 6 is removed and the deposited needle Fe-Co is recovered from the substrate 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing an acicular Fe--Co alloy capable of high-density recording.

Conventional Structures and Problems Most magnetic powders for magnetic tapes and magnetic disks currently in practical use use acicular particles of γ-Fe2O3 (maghemite). However, in recent years, as magnetic recording and reproducing equipment has become smaller and lighter, demands for higher performance recording media have been increasing. In other words, high-density recording,
Improvements in high output characteristics and frequency characteristics are required.

In order to satisfy the above-mentioned requirements in a magnetic recording medium, the characteristics necessary for magnetic UII are to have large saturation magnetization and cylindrical coercive force. By the way, in addition to the above-mentioned γ-Fe2O3 (maghemite), magnetic materials conventionally used in magnetic recording media include magnetic powders such as magnetite (Fe304) and chromium dioxide (CrO+). Magnetization (σ8) is at most 9Qemu/y.

The coercive force (Hc)' is at most 5000e (Oersted), which limits the reproduction output and recording density of magnetic recording media using these magnetic powders.

Furthermore, in Cod-Fe2Q3 magnetic powder containing Co, the coercive force ClTc) is 8000e, but the saturation
, a s becomes as low as 60 to 80 emu/y, which also limits the reproduction output and recording density. Recently, there has been active development of magnetic particles having characteristics suitable for high output and high density recording, that is, magnetic powders having large saturation magnetization and high coercive force.

As a material having such characteristics, there is an acicular magnetic powder mainly composed of Fe--Co. Fe-Co ρ1-like magnetic f/
For l powder, C8 is 180 emu/, Hc is 1200
It is possible to create a medium with high playback output and high recording density. As for the method.

(2) Iron oxide reduction method, that is, a method in which sword-shaped Co-containing iron oxide powder is reduced in an elemental gas to form Fe--Co alloy powder.

(2) Borohydride method, that is, a method in which salts of Fe and Co (eg, ferrous sulfate, cobalt sulfate) are reduced in an aqueous solution using sodium borohydride as a reducing agent.

etc. The magnetic powder obtained by these conventional methods has the following drawbacks. All Fe--Co particles obtained by these methods are oxidized.

In particular, if the powder after the reaction is suddenly taken out into the air, it may react with oxygen in the air and cause a fire. Therefore, after reduction or precipitation, immediately put it in an organic solvent such as acetone and take it out into the air. It is necessary to disperse σ19 with Xun-I fat, regular 11th class fatty acids, etc. without getting too excited. In addition, the Fe-Co particles obtained by this method have various defects introduced during the reduction of the oxide and the precipitation process in an aqueous solution, resulting in a 1 lower than the theoretical saturation magnetization of Fe-Co, C8-4285 emtl/cc.
It's only about 80emu/cc.

Hc is also low at around 12,000e, and weather resistance is not good (reduction in C5 due to moisture resistance test, mainly due to parts/chemicals).
It has the disadvantage of

Purpose of the Invention The present invention solves ten disadvantages of the conventional technology.The present invention has a needle-like shape, has high saturation magnetization and high coercive force, has few defects, is highly weather resistant, and can be easily used in the air. The purpose of the present invention is to provide a method for producing magnetic powder that can be used in different ways.

Composition of the invention In order to achieve the above object, one aspect of the present invention is acicular Fe-C.

The alloy is manufactured by flowing a mixed gas of iron chloride, cobalt chloride, and hydrogen, which has been heated and vaporized at 250°C to 450°C under reduced pressure, onto a substrate heated to 550°C to 1150°C to form acicular Fe- After depositing the Co alloy, Fe-C is deposited from the substrate.
o alloy and yields 1 yield.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on two drawings. The present invention aims to obtain acicular Fe--Co powder by a gas phase method. That is, needle-like crystals (whiskers) of Fe--Co are precipitated on a substrate by the chemical reaction described below, and then the needle-like crystals of Fe--Co are collected to form magnetic powder.

FeCes 4- CoCe3 +”/2 Hz →F
e-Co +8HCg -■Here, Fe CC3 is iron chloride, and CoCe3 is cobalt chloride.

Hz is hydrogen and llCe is hydrogen chloride. t Kodashi iron chloride.

Cobalt chloride is FeCe2. It may also be in the form of CoC (12). This reaction usually occurs at normal pressure and at temperatures above 500°C.

Depending on the flow rate of FeCe3, CoCe5 and Hz, or the atmospheric pressure in the reactor and the humidity of the substrate, various crystal forms and alloy ratios can be obtained, but the reaction represented by equation 0 is generally a chloride reduction-precipitation reaction. Yes.

In principle, crystals with high purity and few defects can be obtained.

It is said that whiskers can be obtained with almost no defects. An example of the basic structure of an apparatus for producing acicular powder of Fe-Co will be explained with reference to the drawings. In the figure, (1) is the hydrogen supply cylinder, (2) is the reaction furnace core tube (quartz H7), (31 is FeC11!3°C
oCe3 evaporation heater, (4) is a heater for Fe-Co needle crystal precipitation reaction, (5) is FeCe3. CoC
A port (made of Fe) for putting e3 in (61 is a needle-shaped base for Fe-Co precipitation.

(7) is a rotary pump for exhaust and pressure adjustment, (8
) is a valve. First, FeCe3 and CoCf/3 are put into the boat (5) in the reactor core tube (2), and placed at the heater (3). Next, place the molybdenum deposition substrate (6) on the heater (4) and the rotary pump (7).
) to exhaust the air in the reaction furnace core tube (2), heat the heater (3) to 250°C to 450°C, and set the heater (4) to 500°C.
Heat the hydrogen supply cylinders (
Open the valve (8) of 1) and supply hydrogen at 100CC/min to 1e.
/min to cause a precipitation and decomposition reaction of acicular Fe-Co on the substrate (6). During the reaction.

Adjust the valve (8) of the rotary pump (7),
Keep it at 10 Torr to 200'rorr. After the reaction was completed, the heater (31 (4)) was turned off and the substrate (6) was taken out after the temperature of the furnace had decreased.

The precipitated acicular Fe--Co is recovered from the substrate (6) and its magnetic properties are measured. Here, heat the heater (temperature of 3 to 250
℃ to 450℃ because below 250℃ FeCe3
．． The vapor pressure of CoCe3 is low, so FeCe3.
CoCe3 has a small amount of t, and Fe-C on the substrate (6)
This is because o is difficult to precipitate. The temperature was set at 450°C or lower because at temperatures above 450°C, the amount of evaporation of CoC (I3) becomes too large, resulting in needle-shaped
This is because e-Co alloy crystals become difficult to q. That is, this is because it is difficult to control the composition of the Fe--Co alloy and composition deviations occur. The liquid amount of hydrogen is 100CC
This is because the precipitation rate of Fe-Co slows down below 1000 OCC/min when the flow rate is set to 100 OCC/min.
This is because it is difficult to obtain high-quality needle-shaped crystals at a speed of more than cc./min (it is easy to obtain powdered Fe--Co).

The temperature of the heater (4) was set at 550°C to 1150°C.

At temperatures below 550°C, precipitation of acicular Fe-Co does not occur.

At temperatures above 1150°C, a reaction occurs between the substrate and the precipitated Fe-Co.

This is because a product with good magnetic properties cannot be obtained.

Furthermore, the pressure during the reaction was adjusted to 10 Torr~200 Torr.
r is less than 10To r r (10 m
This is because at mI (2 or less), the number of gas molecules is small and the precipitation rate is slow, and at mI (200 Torr or higher), the degree of supersaturation is thermodynamically lower, resulting in granular or powdery Fe-C rather than acicular.
This is because o tends to precipitate (at normal pressure, the degree of supersaturation is low and it becomes sword-shaped).

Also, the mixed weight ratio of FeC63 and CoC113 (7) is 1:
The ratio is 0.01 to 1:0.7, and this reasoning is 1':
When the ratio is lower than 0.01, there is no effect of adding CO;
Therefore, high C5 cannot be obtained. Moreover, if the ratio is 1:0.7 or more, the amount of Co will increase to 3116 and C8 will be lower than in the case of Fe alone.

Specific examples will be described below. First, width 8cm, length 20cm, J! JJ size 8mm molybdenum plate (thread body 2
was placed in the reaction zone in the furnace core tube and the primary FeCe310
It was placed on a boat made of 0Ir, CoCe31fr 8Fe, and placed in the evaporation zone. Next, the air was pumped out using a rotary pump, and the evaporation zone (where FeC11s was placed) was
50℃, reaction zone (place where molybdenum plate was placed)
At 0°C, hydrogen (H2) was flowed at a rate of 100 CC/e.

The valve was adjusted so that the pressure in the furnace was 10 Torr, and the reaction was carried out for about 80 minutes. Next, turn off the heaters in each zone and continue to flow hydrogen until the temperature drops below 100°C.

When the temperature drops below 100° C., air is introduced into the molybdenum substrate, the molybdenum substrate is taken out, and the acicular Fe—Co crystals deposited thereon are brushed off and recovered. When this powder was observed with an electronic mirror, the axial ratio (major axis/minor axis) was about 45 and the length of the major axis was 1.0 μm. Next, the saturation magnetization σ of this acicular powder is
As a result of measuring 8 and coercive force Hc, C5-5-190e/
(I
<H) After being left for 7 days, C5 was measured and the change was 124% decrease. The results are shown in sample number 1 in the following table.

Thereafter, Fe--Co was deposited on the molybdenum substrate in the same manner as in the above specific example. Temperature of the evaporation zone at that time 1 Temperature of the reaction zone, weight ratio of FeCl13 and CoCe3, flow rate of hydrogen, form of precipitated crystals, σ3 + Hc + moisture resistance properties (rate of change in σS after standing for 7 days at 60°C and 90% RH) Shown in sample numbers 2-12. Above temperature conditions.

Comparative examples (sample numbers 28 to 24) with sample numbers 13 to 22 and other acicular Fe-Co powder production methods in which the pressure conditions and the weight ratio of FeCe3 and CoCe3 conditions were outside the scope of the present invention were also included. It shows.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained. As can be seen by comparing the examples (sample numbers 1 to 12) and comparative examples (sample numbers 18 to 24) in the table above, needle-like F
The acicular Fe--Co powder created using a gas phase reaction in the process of creating e--Co has a low saturation magnetization of a% and a high coercive force, and has excellent weather resistance (sustainability). In particular, the evaporation temperature of FeCe3 and CoCe3 is 250℃~4
50℃, the temperature of the fractional precipitation reaction is 550℃~1150℃, and the weight ratio of FeCe3 and CoCe5 is 17o01~1.
10.7, the hydrogen flow rate is between 100cc/min and 1000cc/min.
It is between cc/min and the furnace pressure is 10-200T.
Better characteristics can be obtained if there is a range of orr.

[Brief explanation of the drawing]

The inner surface is an explanatory diagram showing the basic structure of an apparatus for producing needle iron. (1) °°・Hydrogen supply cylinder, (2 doors°・Reaction furnace core, (31...evaporation heater, (4)...precipitation reaction heater, (5)...bo) , (61... Substrate for precipitation, (7)... Rotary pump, (8)... Valve agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. A mixed gas of iron chloride, cobalt chloride, and hydrogen heated and vaporized at 250°C to 450°C under reduced pressure at 550°C to 1
The needle-shaped Fe −
A method for producing an acicular Fe-Co alloy, in which the Fe-Co alloy is recovered from a substrate after the Co alloy is precipitated. 2. The acicular Fe-Co according to claim 1, wherein the hydrogen flow rate is 100 CC/min to 100 OCC/min.
Alloy manufacturing method. 3. The method for producing an acicular Fe-Co alloy according to claim 1, wherein the reduced pressure is 10 Torr to 200 Torr. 4. The method for producing an acicular Fe-Co alloy according to claim 1, wherein the mixing weight ratio of FeC (I3 and CoCea) is 1:0.01 to 1:0.7.