JPH08208323A - Productionn of nonmagnetic ceramic for magnetic head - Google Patents

Abstract

PURPOSE: To obtain such a nonmagnetic ceramic material for a magnetic head that has an almost equal coefft. of thermal expansion to that of a head material, high hardness and excellent sliding characteristics, hardly causes chipping during mechanical processing, and is suitable for an inexpensive slider. CONSTITUTION: A soln. containing complex of amino acids and nitrates of Fe and Zn comprising >=60mol% Fe2 O3 in terms of oxide and the balance ZnO is heated to obtain a powder. The obtd. powder is compacted and the compacted body is sintered to obtain a sintered compact comprising a Fe2 O3 phase and a ZnFe2 O4 phase and having <=5μm average grain diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-magnetic ceramic for a magnetic head, and more particularly to a method for manufacturing a non-magnetic ceramic suitable for a slider used in a part of a magnetic head.

[0002]

2. Description of the Related Art The characteristics of a non-magnetic ceramic for a magnetic head are that the coefficient of thermal expansion is equivalent to that of the head material, that it is hard, and that the sliding characteristics between the non-magnetic ceramic and the magnetic film structure are excellent. It is required that chipping chipping does not occur during machining.

That is, when the coefficient of thermal expansion is greatly different from that of the magnetic film structure, the vapor-deposited magnetic film structure is easily peeled off, and stress is generated due to the difference in the coefficient of thermal expansion to cause cracks.

If the hardness is low, the hardness and wear resistance are different from those of the magnetic film structure, and the friction generated by sliding on the magnetic tape causes uneven wear and the like, and the magnetic head characteristics change.

Further, when the hardness is low, not only the life of the magnetic head is shortened, but also defects such as chipping during machining may occur depending on the manufacturing conditions.

Generally, barium titanate, calcium titanate, non-magnetic ferrite and the like are used as non-magnetic ceramics for magnetic heads.

[0007]

However, when barium titanate or calcium titanate is used, the friction coefficient increases after a long time sliding with a magnetic tape, a disk, etc., and the sliding characteristics deteriorate. There was a problem.

On the other hand, non-magnetic ferrite is superior in sliding characteristics to the above materials, but has a small coefficient of thermal expansion such as ZnFe ₂ O ₄ having a coefficient of thermal expansion of 87 × 10 ^−7. It is difficult to put into practical use due to high cost, difficult process control, and so on.

The reason why the cost is high is that the manufacturing process of the material is largely due to complicated steps of powder metallurgy such as mixing of raw materials, calcination, fine pulverization and firing.

In addition, it is generally said that the finest grain size of the material is the best method for improving the chipping characteristics. For that purpose, fine pulverization after calcination is performed. Since fine pulverization must be performed for a long time in the process, not only the cost becomes high, but also process control becomes difficult.

The present invention solves the above-mentioned drawbacks.
An object of the present invention is to provide a slider material manufacturing method which has a coefficient of thermal expansion equivalent to that of a head material, has high hardness, is excellent in sliding characteristics, does not cause chipping during machining, and is inexpensive.

[0012]

Means for Solving the Problems As a result of various studies, the present inventor has found that Fe ₂ O ₃ in an oxide conversion composition is 60 mol.
%, The balance is ZnO, the solution containing Fe, a nitrate of Zn and a complex of an amino acid is heated to obtain a compact, and a compact is obtained, and the compact is a Fe ₂ O ₃ phase. And ZnFe ₂ O ₄ phase with an average crystal grain size of 5 μm
By the following, it was found that a non-magnetic ceramic for a magnetic head having a coefficient of thermal expansion equivalent to that of the head material, excellent sliding characteristics, and free from chipping during machining can be obtained at a low cost.

That is, according to the present invention, a solution containing Fe ₂ O ₃ of 60 mol% or more in terms of oxide and the balance ZnO and a complex of nitrate of Fe and Zn and an amino acid is heated, and the obtained powder is fired, A method for producing a non-magnetic ceramic for a magnetic head, characterized in that a fired body comprising a mixed phase of Fe ₂ O ₃ phase and ZnFe ₂ O ₄ phase and having an average crystal grain size of 5 μm or less is obtained.

Here, Fe ₂ O ₃ is 60 in terms of oxide conversion composition.
ZnO is 40 m because the balance ZnO is more than mol%
This is because if it is ol% or more, the coefficient of thermal expansion becomes small, which causes cracks during glass bonding.

[0015]

The thermal expansion coefficient can be improved by mixing the Fe ₂ O ₃ phase having a high thermal expansion coefficient with the ZnFe ₂ O ₃ phase.

It is generally known that the smaller the crystal grain size, the better the chipping characteristics such as the amount of chipping and the size of chipping. According to the present invention,
The powder obtained by heating the solution containing the complex of nitrate of Fe and Zn and the amino acid is fine, and the particle size distribution of the powder is sharp, so it is possible to obtain a fully densified fired product even at low temperature firing. Therefore, since the crystal grain size can be controlled to 5 μm or less, the chipping characteristics can be improved.

Further, various investigations have been made on the cause of the improvement of the sliding characteristics, but at present, it is unclear in detail. However, it is considered that the use of the powder having a fine and sharp particle size distribution as described above allows sufficient densification and drastically reduces pores in the firing step.

Further, in the powder manufacturing method of the present invention, since the steps such as calcination and crushing which have been generally performed conventionally are not required, the manufacturing process can be shortened and the manufacturing cost can be reduced. It is possible to reduce the cost and provide an inexpensive product.

[0019]

Embodiments of the present invention will be described below.

(Example 1) High-purity iron nitrate and zinc nitrate in terms of oxide conversion were 90 to 60 mol% and 10 respectively.
It was weighed to be about 40 mol% and dissolved in pure water.
20 wt% of α-aminoacetic acid was added to this solution and mixed well.

Next, this solution was heated at 200 ° C. to evaporate the water content. After evaporation of water, the residue self-ignited and a powder was obtained. When the generated phase of this powder was confirmed by an X-ray diffractometer, it was confirmed that all the samples were a composite phase of Fe ₂ O ₃ phase and ZnFe ₂ O ₄ phase.

1% of PVA binder was added to the obtained powder.
It was added and granulated with a spray dryer.

The granulated powder was molded at a pressure of 1 ton / cm ² and heated in the air at 1100 ° C. for 3 hours for firing.

After firing, while hot at 1050 ° C. in an Ar gas atmosphere, hot isostatic pressing was carried out at a pressure of 1000 kg / cm ² for 2 hours.

As described above, samples 1 to 5 of non-magnetic ceramics for magnetic heads according to this example were obtained.

As comparative products, Fe ₂ O ₃ and ZnO were weighed to be 50 mol% and 50 mol%, respectively, and mixed in a ball mill for 20 hours.

After mixing, 1% of PVA was added, the mixture was granulated with a spray dryer, and calcined at 900 ° C. for 2 hours.

The calcined powder was finely pulverized by a ball mill for 60 hours, 1% of PVA type binder was added to the slurry, and granulated by a spray dryer.

After the granulation, the granulated powder was molded under a pressure of 1 ton / cm ² and heated in the air at 1250 ° C. for 3 hours for firing.

When the produced phase of this fired product was confirmed with an X-ray diffractometer, it was confirmed to be a ZnFe ₂ O ₄ single phase.

After firing, while hot at 1050 ° C. in an Ar gas atmosphere, hot isostatic pressing was performed for 2 hours at a pressure of 1000 kg / cm ² .

Table 1 shows the thermal expansion coefficients of the product of the present invention and the comparative product,
The Vickers hardness, transverse rupture strength, crystal grain size, maximum chipping diameter, and relative sliding coefficient are shown. The relative sliding coefficient is set to 10 after the start of sliding, assuming that the friction coefficient of the comparative product immediately after sliding is 1.
^It is shown as the ratio of the friction coefficient after ⁵ seconds.

[0033]

[Table 1]

From Table 1, it can be seen that the product of the present invention has a higher coefficient of thermal expansion, a smaller chipping diameter, and a lower coefficient of relative sliding than the comparative product. Further, it can be seen that the Vickers hardness and the bending strength have almost the same characteristics as the comparative product.

(Example 2) High-purity iron nitrate and zinc nitrate in terms of oxides were 70 mol% and 30 mol%, respectively.
Was weighed so that it was dissolved in pure water. Α-
20 wt% of aminoacetic acid was added and mixed well.

Next, this solution was heated at 200 ° C. to evaporate the water content. After evaporation of water, the residue self-ignited and a powder was obtained.

When the produced phase of this powder was confirmed by an X-ray diffractometer, it was found that the Fe ₂ O ₃ phase and Z
It was confirmed to be a composite phase of the nFe ₂ O ₄ phase.

1% of PVA-based binder was added to the obtained powder.
It was added and granulated with a spray dryer.

The granulated powder was molded at a pressure of 1 ton / cm ² and heated in the air at 1000 ° C. to 1200 ° C. for 3 hours to be fired.

After firing, while hot at 1050 ° C. in an Ar gas atmosphere, hot isostatic pressing was performed for 2 hours at a pressure of 1000 kg / cm ² .

As described above, samples 1A to 3A of the non-magnetic ceramics for magnetic head according to this example were obtained.

Table 2 shows the thermal expansion coefficients of the product of the present invention and the comparative product.
Vickers hardness, transverse rupture strength, crystal grain size, maximum chipping diameter, and relative sliding coefficient are shown.

[0043]

[Table 2]

It can be seen from Table 2 that the product of the present invention has a higher coefficient of thermal expansion, a smaller chipping diameter, and a lower coefficient of relative sliding than the comparative product. Further, it can be seen that the Vickers hardness and the bending strength have almost the same characteristics as the comparative product.

[0045]

As described in the above examples, according to the manufacturing method of the present invention, Fe ₂ O ₃ is 60 m in terms of oxide conversion composition.
A solution containing Fe, Zn nitrate and a complex of an amino acid, which is ol% or more and the balance is ZnO, is heated, the obtained powder is compression-molded to obtain a molded body, and the sintered body obtained by firing the molded body is Fe.
_It consists of ₂ O ₃ phase and ZnFe ₂ O ₄ phase, and its average crystal grain size is 5 μm or less, so it has the same coefficient of thermal expansion as the head material, excellent sliding characteristics, and chipping during machining. Non-magnetic ceramics for non-magnetic heads can now be supplied at low cost.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 5/60 CB 21/21 101 KL

Claims (1)

[Claims] 1. A solution obtained by heating a solution containing Fe ₂ O _{3 in an amount} of 60 mol% or more in terms of an oxide and the balance ZnO and a complex of a nitrate of Zn and an amino acid, and calcining the powder to obtain Fe.
_A method for producing a non-magnetic ceramic for a magnetic head, comprising obtaining a fired body which is composed of a mixed phase of ₂ O ₃ phase and ZnFe ₂ O ₄ phase and has an average crystal grain size of 5 μm or less.