JPH03237100A - Metal titanate fiber and production thereof - Google Patents

Abstract

PURPOSE:To obtain fibers of a perovskite type metal titanate having superior strength, dielectric characteristics and a prescribed shape by allowing titanium dioxide fibers to react with a compd. of an alkaline earth metal in an aq. soln. of a strong alkali. CONSTITUTION:Fibers of potassium titanate or titanium dioxide derived from the titanate are allowed to react with a compd. of Ca, Sr, Ba or Mg in an aq. soln. of a strong alkali such as KOH to obtain fibers of a perovskite type metal titanate represented by a formula ATiO3 (where A is Ca, Sr, Ba or Mg). The diameter of the fibers is 0.2-3mum and the length is >=10 times as large as the diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a metal titanate compound fiber used, for example, as a dielectric material, and a method for producing the same.

<Prior Art> Metal titanate compounds such as barium titanate and strontium titanate are widely used as materials for dielectrics, semiconductors, and piezoelectrics, and are also industrially produced in large quantities. On the other hand, several studies have been conducted to utilize methods for producing barium titanate in the form of fibers for particle-oriented ceramics and ivy.

For example, in the specification of Japanese Patent Publication No. 62-7160 and Japanese Patent Application No. 1-204273 (unpublished) previously filed by the present applicant, potassium titanate and titanium oxide fibers are prepared in a barium hydroxide solution. A manufacturing method is described in which fibrous barium titanate is obtained by hydrothermal treatment. However, the barium titanate fibers obtained by these methods are often aggregates of fine particles, and have the disadvantage that the fiber shape is easily destroyed. Therefore, as an example of actively utilizing this disadvantage in producing fibers, Japanese Patent Application No. 1-72145 describes a method for obtaining fine particles of barium titanate by reacting only crystal water of barium hydroxide. Disclosed.

<Problems to be Solved by the Invention> In recent years, whiskers and short fibers of silicon carbide, silicon nitride, aluminum, potassium titanate, and the like have come to be used for composite materials. However, all of these fibers are used solely for the purpose of improving heat resistance and mechanical strength. In order to create composite materials that combine the purpose of reinforcement and the properties of dielectrics, semiconductors, and piezoelectrics, whiskers of metal titanate compounds such as barium titanate, or short fibers with tensile strength comparable to whiskers, are required. ing.

Therefore, an object of the present invention is to provide a novel titanate metal salt compound fiber and a method for manufacturing the same that satisfy such requirements.

<Means for solving the problem> The barium titanate fiber of the present invention has a fiber diameter of 0.2 to 3
μm, the length is at least 10 times the fiber diameter, and the center is potassium titanate (K20. n -2 to 8, not necessarily an integer) or titanium dioxide hydrate (Ti
Oz, nHz 0.0<n<5), is composed of derivatives from potassium titanate such as anatase titanium dioxide, and rutile titanium dioxide, and is characterized in that the surface layer is mainly made of barium titanate.

Further, the method for producing the titanate metal salt compound fiber of the present invention includes:
A metal titanate compound fiber is obtained by reacting one or more alkaline earth metal compounds such as Sr and Ba in an aqueous potassium hydroxide solution.

Potassium titanate fiber, which is the TiO2 source for barium titanate AO/TiO2 (where A is the above-mentioned group A element), is used to produce B'A 4-form titanium dioxide permanent, anatase-type titanium dioxide, and rutile-type titanium oxide fiber. Any type of Kasuri is good, and potassium hydroxide, which is a strong alkali, can be replaced with sodium hydroxide, lithium hydroxide, etc.

Moreover, as for the alkaline earth metal compounds of Ca, Sr, Ba, and Mg, hydroxides are preferable, but chlorides, oxides, carbonates, etc. can be substituted. That is, a compound that dissolves in an alkaline solution at room temperature is desirable, but any compound that dissolves under the hydrothermal conditions of the alkaline solution may be used.

The potassium titanate fiber used in the present invention has a flux property (Japanese Unexamined Patent Publication No. 56-22632) and a firing method (Japanese Patent Publication No. 59-1989).
Many manufacturing methods are known, such as 434.40), and titanium dioxide permanent fibers are produced by acid-treating potassium titanate fibers, and Ari-Taze type titanium dioxide is produced by processing titanium dioxide permanent fibers into 800% titanium dioxide fibers. Rutile type titanium dioxide fibers can be obtained by heat treatment at 1100°C.

The fibers such as potassium titanate, an alkaline earth metal salt compound, and an aqueous solution of potassium hydroxide, which is a strong alkali, are placed in a reaction vessel and reacted at a predetermined temperature and time. The reaction temperature is 60°C or higher, preferably 100°C or higher, and reaction under hydrothermal conditions is effective because the reaction time can be shortened. Reactions at 100°C or higher naturally require a pressure vessel. The time required for 100% reaction to complete is approximately 20 hours or more at 60°C, approximately 5 hours at 200°C,
At 500°C, it takes less than 1 hour. Therefore, although a high temperature can shorten the reaction time, it becomes difficult to select the material and structure of the reaction vessel, and from an economical standpoint, a temperature of 500° C. or lower is desirable.

Concentration of strong alkaline aqueous solutions such as potassium hydroxide! 4.1
It is effective up to a concentration of mol % or more that can be dissolved under the reaction conditions, and if it is less than 1 mol %, it is not possible to sufficiently suppress the formation of spherical particles of the metal titanate compound, so the concentration is preferably 3 mol % or more. The obtained metal titanate compound fiber retains the shape of the raw material fiber (including the fiber surface) without precipitation of spherical particles, unlike when the reaction is carried out without adding a strong alkali. This is the same when different types of alkaline earth metals or two or more types are mixed. By mixing more than one type of element, it is possible to adjust the dielectric constant at room temperature and improve the temperature characteristics of the dielectric constant. This makes it possible to use a variety of electrical characteristics.

The blending amount of raw material fiber such as potassium titanate and alkaline earth metal compound is such that the molar ratio as TiO7/Ao is 1.
If it is 0 or more, compounds such as 2A○ and Ti○2 are not produced, and 100% perovskie 1-type titanate metal salt compound fiber is produced, and its usefulness is needless to say. Even when the mixing molar ratio is less than 1.0, compounds such as Ao·4T i O2 are not generated, and the surface layer is a perovskite metal titanate compound and the core has a double structure in which the raw material fibers remain.

This double-layered structure of metal titanate compounds and raw fibers has the electrical properties of each metal titanate compound, as well as the tensile strength of the whisker raw fibers. Conceivable. For example, this can improve the bending strength of a composite material made by mixing barium titanate fibers created at a mixing molar ratio of 0.75 with plastic (polybutylene terephthalate) at 5 Qwt%, and the dielectric constant of the plastic is also high. This is clear from the fact that it was possible to do so (Table 1). Therefore, Ti
Single-layer fibers made with an O2/BaO mixing ratio of 1.0 or less are also industrially useful.

<Example> Potassium tetratitanate represented by 20.4 T i O2 was placed in a pottery pond 1-1 by a flux method. That is, predetermined amounts of titanium dioxide, barium carbonate, and potassium molybdate were prepared, heated to 1100 C in a platinum crucible, and heated to 5.
The crucible was cooled to 850.degree. C. at a rate of .degree. C/hour, after which the crucible was removed from the furnace and cooled to room temperature in air. Subsequently, the product was washed with water to separate the flux, and potassium tetratitanate was obtained.

Thus obtained potassium tetratitanate], Og, 30.5 g of barium hydroxide octahydrate (BaO/Ti0z=1.
．． 0), a 3 mol % aqueous solution prepared by dissolving 1.11.8 g of potassium hydroxide in 7 Qcc of pure water in a nitrogen stream was placed in a reaction vessel and sealed. The filling rate at this time was about 80%.

Next, this reaction vessel was placed in an electric furnace, and a reaction was carried out at 200° C. for 5 hours.

After the reaction, the contents were washed with water, filtered, and dried at 80°C for 24 hours. The product obtained was about 23 g.

Powder X-ray diffraction measurement of the product showed a diffraction peak of only barium titanate, and electron microscopy observation showed that
As shown in FIG. 1, the shape of the raw material fibers remained unchanged.

4 titanium oxide prepared in the same manner as in Example 1)
0g1 barium hydroxide octahydrate 22.9g (BaO/T
i0z=1.75>, 10 mol% C of potassium hydroxide
70 cc of the aqueous solution was put into a reaction container and the container was sealed. Next, the reaction vessel was placed in an electric furnace, and a reaction was carried out at 100°C for 10 hours. After the reaction, the contents were washed with water, filtered, and heated at 80°
It was dried at C for 24 hours. The product obtained was approximately 19 g.

The obtained product showed peaks of barium titanate and potassium titanate when measured by powder X-ray diffraction, and 2
Next, ion mass spectrometry revealed that barium atoms were distributed on the surface of the fiber, and potassium atoms were distributed in the center. Moreover, as shown in FIG. 1, observation using an electron microscope revealed that the shape of the raw material fibers remained unchanged.

Potassium titanate 11 prepared by the same method as Example 1)
g, 45.8 g of barium hydroxide octahydrate (Bad/Ti○2=1.5), 200 CC of a 3 mol% sodium hydroxide aqueous solution was placed in a glass container equipped with a reflux condenser, and heated to 60 g in a nitrogen stream. - Reaction was carried out for C125 hours. After the reaction was completed, the contents were washed with water, filtered, and dried at 80° C. for 24 hours to obtain about 20 g of product.

The obtained product showed a peak of only barium titanate when measured by powder X-ray diffraction, and when observed using an electron microscope, the shape of the raw material fiber remained intact as shown in FIG.

4) Potassium titanate prepared in the same manner as in Example 1) was
Acid treatment with specified hydrochloric acid for 24 hours, 4TiO□, 2H20
A titanium dioxide permanent fiber was created.

10g of this titanium dioxide hydrate fiber, 23g of barium chloride
．． 4g (BaO/Ti0z = 1.0), 3 mol%
Put 70 cc of potassium hydroxide aqueous solution into a reaction container,
The reaction was carried out at 00-C for 1 hour.

After the reaction was completed, the product was washed with water, filtered, and dried at 80° C. for 24 hours to obtain about 26 g of product.

The obtained product showed a peak of only barium titanate when measured by powder XVA diffraction, and when observed using an electron microscope, the shape of the raw fiber remained as it was, as shown in FIG.

Loss of fertility group 11 Titanium dioxide permanent fibers prepared in the same manner as in Example 4 were heat treated at 1000°C for 2 hours to produce a mixture of anatase type and rutile type titanium dioxide fibers.

10g of this mixed fiber, 39°5g of barium hydroxide (
BaO/"I"10z=1.0) and 70 cc of a 3 mol% potassium hydroxide aqueous solution were placed in a reaction vessel, and 200.
The reaction was carried out at C for 10 hours. After the reaction, the contents were washed with water, filtered, and dried at 80° C. for 24 hours to obtain about 25 g of product.

The obtained product showed a difference in titanium titanate and some titanium dioxide when measured by powder X-ray diffraction.
Observation using an electron microscope revealed that the shape of the raw material fibers remained unchanged, as shown in FIG.

1 side port 1L 4 titanium oxide Lo produced in the same manner as in Example 1
g, barium hydroxide octahydrate 17.1 g, strontium hydroxide octahydrate 4.82 g (B a O-3r○
/Ti○2=0.75) and 7 Qcc of a 5 mol % potassium hydroxide aqueous solution were placed in a reaction vessel and sealed. Next, the reaction container was placed in an electric furnace, and a reaction was carried out at 200° C. for 5 hours.

After the reaction, the contents were washed with water, filtered, and dried at 80'C for 24 hours. The product obtained was approximately 18 g.

Powder X-ray diffraction measurements of the product showed a perovskite structure diffraction peak similar to that of barium titanate, and elemental analysis using fluorescent X-rays detected Ba, Sr, and Ti. Furthermore, as shown in FIG. 1, observation using an electron microscope revealed that the shape of the raw material fibers remained unchanged.

<Comparative Example> In order to prove the characteristics of the present invention, an experiment was conducted in which potassium titanate and barium hydroxide were reacted in an aqueous solution other than a strong alkaline aqueous solution.

That is, 10 g of hydrium tetratitanate and 30.5 g of barium hydroxide (BaO/
Ti0z = 1.0) and 80 cc (7) of pure water were placed in a reaction vessel, and a reaction was carried out at 200°C for 5 hours. Next, the contents after the reaction was washed with water, filtered, and dried at 80° C. for 24 hours to obtain about 23 g of product.

The obtained product showed only a barium titanate peak when measured by powder X-ray diffraction, and when observed using an electron microscope, it had a shape of spherical particles strung together in a fibrous shape, as shown in Figure 2. Ta.

<Effects of the Invention> The barium titanate fiber according to the present invention exhibited significantly superior strength and dielectric properties compared to conventional products.

Table 1 shows a comparison of test data of the conventional example and the product of the present invention regarding tensile strength, bending strength, and dielectric constant. In carrying out this test, since it is not possible to conduct a practical test with 34 barium titanate fiber alone, we used PBT (polybutylene terephthalate) resin and 5 barium titanate fiber.
This was done for composites mixed at 0% by weight.

Furthermore, by adding Sr, the dielectric constant could be increased.

Table 1 FIG. 2 shows an electron micrograph of a conventional example.

According to this test data, it will be understood that the tensile strength, bending strength, and dielectric constant of the product of the present invention are approximately twice as high as those of the conventional product.

[Brief explanation of drawings]

FIG. 1 shows an electron micrograph of a product according to Example 2 of the present invention. 5

Claims (3)

[Claims] (1) ATiO_3(
However, A is a perovskite-type metal titanate compound represented by the above-mentioned group A element), and the fiber diameter is 0.2 to 3μ.
m, a titanate metal salt compound fiber whose length is 10 times or more the fiber diameter. (2) In a perovskite metal titanate compound represented by ATiO_3, which is composed of one or more group A elements of alkaline earth elements such as Ca, Sr, Ba, and Mg, the fiber diameter is 0.2 to 3 μm. , the length is 1 relative to the fiber diameter
0 times or more, and the center is mainly potassium titanate (K_
2O・nTiO_2, n=2 to 8 and may not be an integer), or titanium dioxide hydrate (TiO_2・nH_
2O, (0<n<5), composite type titanate metal salt compound fiber composed of derivatives from potassium titanate such as anatase type titanium dioxide, rutin type titanium dioxide, etc., and whose surface layer mainly consists of a titanate metal salt compound. . (3) A perovskite-type metal titanate compound represented by ATiO_3 consisting of one or more group A elements of alkaline earth elements such as Ca, Sr, Ba, and Mg, from potassium titanate or potassium titanate. Induced titanium dioxide fibers and Ca, Sr, Ba, Mg
The titanate metal salt fiber according to claim 1, or the composite titanium composite according to claim 2, characterized in that an alkaline earth metal compound is reacted in a strong alkaline aqueous solution such as potassium hydroxide. Method for producing acid metal salt fiber.