JP3164986B2 - Method for producing potassium titanate sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method for producing a potassium titanate sintered body useful as a friction material or the like.

[0002]

_2. Description of the Related Art Potassium hexatitanate (K ₂ Ti ₆ O ₁₃ )
Is a synthetic inorganic compound with heat resistance, heat insulation, abrasion resistance, mechanical strength, chemical stability, etc. Applications as structural materials and functional materials have been attempted for various applications. For a sintered body made of potassium titanate, for example, potassium hexatitanate crystal powder is used as a sintering raw material, an appropriate amount of an organic binder (forming aid) is added thereto, and the kneaded product is formed into a powder compact and then sintered. It is manufactured by processing (for example, Japanese Patent Publication No. 2-10793).

[0003]

In the conventional method of manufacturing a potassium titanate sintered body, it is necessary to synthesize potassium hexatitanate crystal powder in advance as a sintering raw material, which requires a large number of processing operations. Costs are high. There is also room for improvement in the denseness and mechanical strength of the resulting sintered product. In view of the above, the present invention provides a method for efficiently producing a potassium titanate sintered body having high density, excellent mechanical strength and simple steps.

[0004]

According to the present invention, there is provided a method for producing a potassium titanate sintered body, comprising: mixing a fine powder mixture comprising an amorphous powder having a chemical composition equivalent to potassium dititanate and a titanium oxide powder; After pressure molding, temperature 1100
The sintering process is performed at 1400 ° C.

[0005]

The present invention provides a powder compact comprising an amorphous powder having a chemical composition equivalent to potassium dititanate (K ₂ Ti ₂ O ₅ ) (hereinafter, “amorphous potassium dititanate powder”) and a titanium oxide powder. In the sintering process, the reaction between the amorphous potassium dititanate particles and the titanium oxide particles generates fine fibrous crystals of potassium titanate, and the fibrous crystals are entangled with each other and bonded together. A high sintered body is formed. Amorphous potassium dititanate powder used as a sintering raw material can be obtained at low cost as an intermediate product in the production process of potassium hexatitanate crystals and the like, and titanium oxide powder is added to the amorphous powder. Powder mixture (sintering raw material)
Is more likely to cause a sintering reaction than a case where a crystalline powder such as potassium hexatitanate is used as a sintering raw material (the sintering process of potassium hexatitanate crystals requires heating of about 1100 ° C. or more. On the other hand, a reaction occurs from a low temperature range of about 800 to 900 ° C.), so that it is easy to ensure homogeneity and denseness of the sintered body.

Hereinafter, the present invention will be described in detail. [Production of Amorphous Potassium Dititanate Powder] Amorphous potassium dititanate powder is, for example, titanium oxide (TiO ₂ ).
And heat mixed powder of potassium oxide (K ₂ O)
An amorphous material obtained by rapidly solidifying a molten product can be used. The amorphous material includes titanium oxide or a titanium compound that produces titanium oxide by heating, and potassium oxide or a potassium compound that produces potassium oxide by heating, wherein TiO ₂ / K ₂ O (molar ratio) is 1.5 to 2; .
It is manufactured by heating and melting a mixed powder mixed at a ratio of 5 and then rapidly solidifying the molten product.

The mixing ratio (molar ratio of TiO ₂ / K ₂ O) of titanium oxide and potassium oxide as the raw material for heating and melting is 1.5 to 2.5.
In this range, the heating and melting treatment can be achieved in a relatively low temperature range (temperature of about 950 to 1150 ° C.), and the amorphous potassium dititanate can be efficiently obtained by rapid solidification of the molten product. Because. The rapid solidification treatment of the heated molten product, for example, applying a metal twin roll method,
This is performed by flowing the melt down into the gap between the metal rolls rotating at high speed. The amorphous coagulated material in this case is obtained as flakes (flakes). .

[Preparation of Sintering Raw Material] A sintering raw material is prepared by mixing a titanium oxide powder with an amorphous potassium dititanate powder. The powder particle size is preferably a fine powder having a particle size of about 10 μm or less in order to enhance the homogeneity and denseness of the final product sintered body. When using the flake-like amorphous coagulated product,
It is advisable to mix the powder with a titanium oxide powder, knead and pulverize it with a ball mill or the like. The flake-like solidified pieces are easily pulverized by a ball mill or the like, unlike granular or fibrous powders. During the kneading and pulverizing treatment, an appropriate amount of a deflocculant (for example, a polycarboxylate) and a molding aid (an organic binder such as a methylcellulose solution) are appropriately added. Further, after the pulverization treatment, it is preferable to granulate (for example, a particle size of about 10 to 100 μm) using a spray dryer or the like before use.

The mixing ratio of the amorphous potassium dititanate powder and the titanium oxide powder is adjusted according to the kind of potassium titanate crystals of the target sintered body. When producing a sintered body composed of potassium hexatitanate crystals (K ₂ Ti ₆ O ₁₃ ), TiO ₂ / K ₂ O (molar ratio) is about 5.8 to 6.2 in accordance with the composition. It is good to mix so that it becomes. If the ratio is out of this range, the efficiency of the sintering reaction is deteriorated, and the formation of a different phase (such as a TiO ₂ crystal phase) other than the potassium hexatitanate crystal is accompanied.

[Press molding and sintering process of sintering raw material powder] The sintering raw material powder mixture is press-formed into an appropriately shaped powder compact and subjected to a sintering process. For the compacting of the powder compact, for example, cold isostatic pressing (rubber press) is applied, and a suitable pressing force (for example, 10 to 100 MPa) is applied for a proper time (for example, 0.5 to 3 minutes). It is performed by The sintering process is performed at a temperature of about 1100 to 1400 ° C.
For a suitable time (eg, 1 to 3 hours) to form fine fibrous crystals of potassium titanate by the reaction between the amorphous potassium dititanate particles and the titanium oxide particles, and to bond the crystals together. Is generated. Although this sintering reaction occurs even in a relatively low temperature range (approximately 800 to 900 ° C.), the treatment temperature of 1100 ° C. or more is effective in efficiently forming a high-density sintered body by the sintering reaction. To do that. On the other hand, the reason why the upper limit of the treatment temperature is 1400 ° C. is that if the temperature exceeds that, a part of the potassium titanate crystal generated is melted, and the molten phase forms an amorphous phase, and the toughness and strength of the sintered body are increased. This is because it causes the quality of the product to deteriorate.

[0011]

EXAMPLES (1) Production of amorphous potassium dititanate (1.1) Heat-melting raw material and heat-melting: Purified titanium oxide powder (purity 99.8%) and industrial potassium carbonate powder (purity 99.5%)
%). TiO ₂ / K ₂ O (molar ratio): 1.8. The powder mixture is put into a platinum crucible and melted by heating (1100 ° C. × 40
min). (1.2) Rapid solidification of a melt: The melt is rapidly solidified by a metal twin roll method to obtain a flake solid. The solidified product is a completely amorphous material (X-ray diffraction).

(2) Preparation of sintering raw material: the above-mentioned amorphous solidified product
230 g of purified titanium oxide powder (purity 99.8%) is mixed with 170 g (TiO ₂ / K ₂ O = 6). To this, 400 ml of a molding aid (2% solution of methylcellulose) and 4 g of a deflocculant (40% solution of polycarboxylate) are added to form a slurry. The slurry is kneaded (24Hr) with a ball mill and pulverized (particle size 10μm or less)
After that, it is dried by a spray dryer and granulated (particle size: about 50 μm). (3) Press molding The granulated powder is subjected to cold isostatic pressing (rubber press) to obtain a powder compact (pressing force: 150 MPa, pressurizing time: 30 seconds).

(4) Sintering process The powder compact is sintered in an electric furnace (temperature: 1250 ° C.,
(Time: 2 hours, atmosphere: air). After the treatment, cool in a furnace. This sintered body is referred to as a test material A. The sintered body is composed of potassium hexatitanate crystals (X-ray diffraction) and has a structure in which fine fibrous crystals are entangled (scanning electron microscope).

[Comparative Example] To 400 g of potassium hexatitanate crystal powder (according to the following Reference Example), 100 g of a molding aid (5% polyvinyl alcohol solution) was added and mixed well, followed by cold isostatic pressing. (Pressure: 150MPa, pressurization time: 30 seconds) to obtain a powder compact, and then sintering temperature in an electric furnace:
(1250 ° C., time: 2 hr, atmosphere: air) to obtain a sintered body. This sintered body is referred to as a test material B. Like the test material A, it is composed of potassium hexatitanate crystals (X-ray diffraction) and has a structure in which fine fibrous crystals are entangled (scanning electron microscope).

For each of the test materials A and B, the relative density (%) and the three-point bending strength (span distance 30 mm) according to JIS B1601 (Testing method for bending strength of fine ceramics) were measured. The result was obtained. The sintered body A of the invention example obtained using the mixed powder of the amorphous potassium dititanate powder and the titanium oxide powder has a higher density than the sintered body B using the potassium titanate crystal powder. High and excellent in mechanical strength.

[0016]

[Table 1]

Reference Example: Production of potassium hexatitanate crystal powder (1) Melting and coagulation treatment A mixture of purified titanium oxide (purity 99.8%) and industrial potassium carbonate (purity 99.5%) (TiO ₂ / K ₂ O = 6) is placed in an alumina crucible, and is heated and melted at 1300 ° C. for 2 hours, and then the melt is naturally cooled to room temperature. (2) Coagulation washing process The obtained coagulation is washed with pure, the soluble substance is separated and the powdered material is collected and dried at 1500 ° C. (3) Pulverization and classification , Sieve and classify to 50 μm or less. The obtained powder is a potassium hexatitanate crystal (X-ray diffraction) and has a particle size of 5 to 40 μm.

[0018]

According to the present invention, it is not necessary to synthesize potassium titanate crystal powder in advance, and it is possible to use amorphous potassium dititanate (an intermediate product of the potassium titanate crystal powder production process). Thus, a potassium titanate sintered body can be obtained, and the effects of simplification of the manufacturing process and cost reduction can be obtained. In addition, the resulting sintered body is highly dense and has excellent mechanical strength, so it is used as a refractory material, a heat insulating material, a heat resistant material, a friction material, or a component requiring mechanical strength in the electric and electronic industries. It is useful as such.

Continuation of the front page (56) References JP-A-6-329467 (JP, A) JP-A-63-282160 (JP, A) JP-A-58-199774 (JP, A) JP-A-60-231464 (JP, A) JP-A-1-246139 (JP, A) JP-A-63-260821 (JP, A) JP-A-63-256526 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C04B 35/42-35/49 C04B 35/00-35/22 CA (STN) JICST file (JOIS) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A fine powder mixture comprising an amorphous powder having a chemical composition equivalent to potassium dititanate and a titanium oxide powder, is subjected to pressure molding, and then subjected to a temperature of 1100 to 1400.
A method for producing a potassium titanate sintered body, characterized by performing sintering at a temperature of ° C. 2. A method according to claim 1, wherein titanium oxide or a titanium compound which forms titanium oxide by heating, and potassium oxide or a potassium compound which forms potassium oxide by heating are mixed with TiO 2
Heat-melt a powder mixture blended at a molar ratio of ₂ / K ₂ O of 1.5 to 2.5, and quench the heated melt to form an amorphous solidification with a chemical composition equivalent to potassium dititanate A titanium oxide is added to the amorphous coagulated product to form a fine powder mixture, and the mixture is pressed and then sintered at a temperature of 1100 to 1400 ° C. Production method.