JPH1160329A - Highly hydrophilic, low friction ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic material excellent in mechanical strength, durability and friction characteristics in the presence of water by uniformly dispersing acicular and/or platy multiple oxide grains (A) essentially contg. Zn and Al and multiple oxide grains (B) having a spinel type crystal structure of ZnAl2 O4 in a matrix phase of α-alumina. SOLUTION: The average ratio of ZnO:Al2 O3 in the grains A is 1: >=3 when Zn and Al are expressed in terms of oxides and the aspect ratio of the acicular grains is >=3. The amt. of the grains B in the ceramic material is 30 wt.%. The objective ceramic material is obtd. by forming a compact of a prescribed shape from a mixture of α-alumina powder as principal starting material, acicular multiple oxide powder of ZnO.nAl2 O3 and a small amt. of a powdery sintering aid and firing the compact in the air. The ceramic material contains acicular multiple oxide grains B21 uniformly dispersed in the matrix phase 20 of α-alumina.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly hydrophilic and low friction ceramic material used for an on-off valve of a water tap or the like.

[0002]

2. Description of the Related Art Conventionally, JP-A-6-93277 and JP-A-7-93277
As disclosed in Japanese Patent Publication No. 108774, etc., as a sliding friction material for reducing the friction coefficient in water, diamond-like carbon coated on the surface of alumina material, a mixture of silicon carbide and carbon on the surface of alumina material Are known, ceramics in which a large number of pores serving as a water reservoir are uniformly dispersed, ceramics in which a solid lubricant is dispersed, and ceramics impregnated with oil.
However, conventional sliding friction materials have disadvantages in that the strength of the material is insufficient, the coating serving as lubrication is easily peeled off, and the manufacturing unit price is high.

[0003] Further, in an alumina material to which zinc oxide (ZnO) is added in order to solve the above-mentioned problems, ZnAl ₂ O ₄ composite oxide particles having hydrophilicity fall off due to sliding friction for a long period of time, and the frictional characteristics are reduced. There is a problem that is damaged.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a highly hydrophilic and low friction ceramic material having excellent mechanical strength, durability and friction characteristics in the presence of water. It is in.

[0005]

Means for Solving the Problems In order to solve the above problems, the constitution of the present invention comprises zinc (Zn) and aluminum (Al) as main components in a matrix of α-alumina (α-Al ₂ O ₃ ). And / or plate-like composite oxide particles are uniformly dispersed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in order to satisfy the hydrophilicity, strength, toughness and friction coefficient of a material, α-alumina (α-A
l ₂ O ₃ ) in the matrix, acicular composite oxide particles of ZnO.nAl ₂ O ₃
ZnAl ₂ O _{4 and} the composite oxide particles are uniformly dispersed.

The composite oxide particles of ZnAl ₂ O ₄ having a spinel-type crystal structure having a property of strongly absorbing water increase the hydrophilicity of the material. Acicular complex oxide particles of ZnOnAl ₂ O ₃ are
Ensure the strength and toughness of the material.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A highly hydrophilic and low friction ceramic material according to the present invention comprises zinc (Zn) in an α-alumina (α-Al ₂ O ₃ ) matrix.
And acicular or plate-like composite oxide particles containing aluminum (Al) as a main component are uniformly dispersed. The acicular or plate-like composite oxide particles have a composition ratio of ZnO: Al ₂ O ₃ when zinc (Zn) and aluminum (Al) as main components are converted to oxides.
Is 1: 3 or more. The aspect ratio (elongation ratio) of the acicular composite oxide particles is 3 or more.

Further, highly hydrophilic, low-friction ceramics material according to the invention, alpha-Al ₂ O in the matrix phase of the _3, ZnO · nAl ₂ O ₃ as a main component and zinc (Zn) and aluminum (Al) Or plate-like composite oxide particles, and composite oxide particles having a spinel-type crystal structure of ZnAl ₂ O ₄ are uniformly dispersed. The content of the composite oxide particles having a spinel type crystal structure of ZnAl ₂ O ₄ contained in the highly hydrophilic and low friction ceramic material according to the present invention is 30 wt% or less. The highly hydrophilic and low friction ceramic material according to the present invention exhibits excellent durability and low friction in the presence of water.

[Example 1] α-alumina (α
-Al ₂ O ₃ ) powder is prepared by adding acicular composite oxide powder of ZnO · nAl ₂ O ₃ containing zinc (Zn) and aluminum (Al) and a small amount of sintering aid powder. From the mixture, a molded article of a predetermined shape was produced. The molded body was fired in the air to obtain a ceramic material (sample) A as a sintered body. FIG.
FIG. 2 is an organization diagram schematically showing an organization of the obtained ceramic material A. The ceramic material A of the present invention comprises a matrix 20 of α-alumina (α-Al ₂ O ₃ ) and a needle-like and / or plate of ZnO · nAl ₂ O ₃ containing zinc (Zn) and aluminum (Al) as main components. Composite oxide particles 21 are uniformly dispersed. 35 mm in diameter and 5 mm in thickness from the ceramic material A of the present invention
Of a disk-shaped test piece of
It was smoothed to a max of 0.4 or less by lapping.
The obtained two test pieces were superimposed and subjected to a sliding friction test in water at a temperature of 25 ° C. to measure a friction coefficient.

As is apparent from FIG. 2, the ceramic material A of the present invention is composed of a matrix 20 made of α-alumina (α-Al ₂ O ₃ ).
It was confirmed that the formation of the acicular composite oxide 21 of O.nAl ₂ O ₃ reduced the friction coefficient, exhibited high water adsorption, and exhibited low friction in water.

The reason why the ceramic material A of the present invention exhibits low friction in water is that the acicular composite oxide 21 of ZnO.nAl ₂ O ₃ has a crystal structure similar to a spinel type, and the spinel type crystal structure This is due to the fact that water is strongly adsorbed because of the presence of vacancies and polarity as in the above.

Next, α-alumina (α-Al
₂ O ₃₎ variously changed were nine the amount of the composite oxide powder of ZnO · 4Al ₂ O ₃ relative to the powder of ceramics material (Sample) A
Was prepared by the same method as described above, and the strength and fracture toughness of the ceramic material were measured by the same method as described above. As shown in FIG. 3, the strength of the ceramic material A of the present invention is ZnO.
Even if the addition amount of the complex oxide powder of nAl ₂ O ₃ is changed, as shown in FIG. 4, the fracture toughness value of the ceramics material A of the present invention is a needle-like shape made of ZnO.4Al ₂ O _3. by composite oxide particles 21 are present in the material, which is the main raw material alpha-alumina (α-Al ₂ O ₃₎ significantly higher than that ceramics material without the addition of composite oxide powders of ZnO · 4Al ₂ O ₃ powder Become.

In Example 1, the main raw material α
From a mixture of alumina (α-Al ₂ O ₃ ) powder and a needle-like composite oxide powder of ZnAl ₂ O _{4 having} a spinel type crystal structure and a small amount of sintering aid powder, It was confirmed that a ceramic material obtained by preparing a molded body and firing the molded body in the same manner as described above can obtain similar characteristics.

Example 2 α-alumina (α
A molded body having a predetermined shape was produced from a mixture of -Al ₂ O ₃ ) powder, zinc oxide (ZnO) powder and a small amount of a sintering aid powder. The molded body was fired in the atmosphere at a temperature of 1500 ° C. for 3 hours to obtain a ceramic material (sample) B as a sintered body. FIG. 5 is a structure diagram schematically showing the structure of the obtained ceramic material B. In the ceramic material B of the present invention, ZnO.nAl ₂ O ₃ containing zinc (Zn) and aluminum (Al) as main components is used as a matrix 20 of α-alumina (α-Al ₂ O ₃ ).
And the composite oxide particles 21 having a spinel type crystal structure of ZnAl ₂ O ₄ are uniformly dispersed. A disc-shaped test piece having a diameter of 35 mm and a thickness of 5 mm was prepared from the ceramic material B of the present invention, and the flat surface of the test piece was smoothed by lapping to a flatness of Rmax 0.4 or less. The obtained two test pieces were superimposed and subjected to a sliding friction test in water at a temperature of 25 ° C. to measure a friction coefficient.

As is apparent from FIG. 6, the ceramic material B is composed of α-alumina (α-Al ₂ O ₃ ) as a matrix 20 and ZnAl
By uniformly dispersing the composite oxide particles 22 of ₂ O ₄ and the acicular composite oxide particles 21 of ZnO · nAl ₂ O ₃ , the coefficient of friction is further reduced, the water absorption is high, and the water absorption is low. It was confirmed that it exhibited frictional properties.

The reason that the ceramic material B of the present invention exhibits high hydrophilicity and low frictional property is that the ZnAl ₂ O ₄ composite oxide particles 22 have a spinel type crystal structure, have vacancies and are polar. Therefore, acicular composite oxide particles 21 of ZnO.nAl ₂ O ₃
By adsorbing water more strongly.

Next, in the above-mentioned ceramics material B, a ceramics material (sample) in which the addition amount of ZnAl ₂ O ₄ composite oxide powder to α-alumina (α-Al ₂ O ₃ ) powder was changed to 0 to 50 wt%. B was prepared by the same method as described above, and the friction coefficient of the ceramic material B was measured by the same method as described above. As shown in FIG. 7, it was found that the friction coefficient of the ceramics material B decreased as the amount of the ZnAl ₂ O ₄ composite oxide increased. However, it was found that when the added amount of the ZnAl ₂ O ₄ composite oxide powder exceeded 30 wt%, the friction coefficient sharply increased. This is because the amount of the brittle ZnAl ₂ O ₄ composite oxide particles 22 falling off the surface of the ceramic material B increases.

Next, in order to evaluate the abrasion resistance of the ceramic materials (samples) A and B according to the first and second embodiments of the present invention and the conventional alumina material (sample), reciprocating sliding in water was performed. A dynamic friction test was performed. As shown in FIG.
It has been found that each of the ceramic materials A and B of the present invention can reduce the abrasion amount by about 20% as compared with the conventional alumina material. Further, each of the ceramic materials A and B of the present invention has a higher fracture toughness value than the conventional alumina material, so that the wear resistance is improved.

In order to evaluate the abrasion resistance of the above-mentioned ceramic materials A and B of the present invention and the conventional alumina material, iron oxide powder was applied to the sliding surface of each material.
A reciprocating sliding friction test in water was performed. As shown in FIG. 9, it was found that each of the ceramic materials A and B of the present invention can reduce the abrasion amount by about 30% as compared with the conventional alumina material. The form of wear in the reciprocating sliding friction test described above is
It belongs to aggressive wear, and the wear amount Ws of each of the materials A and B is inversely proportional to the fracture toughness value and the hardness as represented by the following equation.

Ws = E ^4/5 × KIc ^-1/2 × HV ^-57/40 where E: Young's modulus KIc: Fracture toughness HV: Hardness Thus, the ceramic material A according to Example 1 of the present invention is As compared with the conventional alumina material, it has a higher fracture toughness value, and thus has improved wear resistance. Further, the ceramic material A of the present invention is
Since the composite oxide particles 22 of ZnAl ₂ O ₄ which are slightly inferior in wear resistance were not generated and the fracture toughness value was high, the wear resistance was further improved.

[0022]

According to the present invention, as described above, α
Highly dispersed needle-like and / or plate-like composite oxide particles containing zinc (Zn) and aluminum (Al) as main components in the matrix of alumina (α-Al ₂ O ₃ ) An alumina-based ceramic material having hydrophilicity and low friction and low wear in the presence of water can be obtained.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a highly hydrophilic and low friction ceramic material according to the present invention.

FIG. 2 is a diagram showing friction characteristics between the ceramic material and a conventional alumina material.

FIG. 3 is a diagram showing the relationship between the amount of ZnO.nAl ₂ O ₃ added and the strength in the ceramic material.

FIG. 4 is a diagram showing the relationship between the aspect ratio and the strength of ZnO.nAl ₂ O ₃ particles in the ceramic material.

FIG. 5 is a structural diagram of a high hydrophilicity / low friction ceramic material according to a second embodiment of the present invention.

FIG. 6 is a diagram showing friction characteristics between the ceramic material and a conventional alumina material.

FIG. 7 is a graph showing the addition amount of ZnAl ₂ O ₄ and friction characteristics in the ceramic material.

FIG. 8 is a diagram showing the wear resistance of the ceramic material of the present invention and a conventional alumina material.

FIG. 9 is a diagram showing wear resistance of the ceramic material of the present invention and a conventional alumina material.

[Explanation of symbols]

20: mother phase 21: needle-like (plate-like) composite oxide particles 2
2: Composite oxide particles with spinel crystal structure

Claims (6)

[Claims] An acicular and / or plate-like composite oxide particle containing zinc (Zn) and aluminum (Al) as main components is uniformly dispersed in a matrix of α-alumina (α-Al ₂ O ₃ ). Highly hydrophilic, low friction ceramic material characterized by being dispersed. 2. The needle-shaped and plate-shaped composite oxide particles,
Main component of zinc (Zn), the composition ratio of ZnO when the aluminum (Al) were converted to oxide: Average of Al ₂ O ₃ is 1: 3 or more, high hydrophilicity and low friction of claim 1 Ceramics material. 3. The high hydrophilicity and low friction ceramic material according to claim 1, wherein the acicular composite oxide particles have an aspect ratio of 3 or more. 4. A matrix of α-alumina (α-Al ₂ O ₃ ) comprising acicular and / or plate-like composite oxide particles containing zinc (Zn) and aluminum (Al) as main components; _A highly hydrophilic and low friction ceramic material, characterized by uniformly dispersing composite oxide particles having a spinel-type crystal structure of ₂ O ₄ . 5. The highly hydrophilic and low friction ceramic material according to claim 4, wherein the content of the composite oxide particles having a spinel type crystal structure of ZnAl ₂ O ₄ is 30 wt% or less. 6. The highly hydrophilic and low friction ceramic material according to claim 1, wherein said ceramic material is used in the presence of water.