TECHNICAL FIELD

The Present invention relates to a negative thermal expansion material which contracts with increase in temperature, a manufacturing method thereof and a composite material comprising the negative thermal expansion material.

BACKGROUND ART

In most of materials, the length and the volume increase by thermal expansion as the temperature increases. On the other hand, a material exhibiting negative thermal expansion (hereinafter, may be also referred to as “negative thermal expansion material”) is also known the volume of which contrarily reduces when it is heated. It is known that a material exhibiting negative thermal expansion can be used with other materials to suppress changes of the material due to thermal expansion caused by temperature change.

As materials exhibiting negative thermal expansion, for example, β-eucryptite, zirconium tungstate (ZrW2O8), zirconium phosphate tungstate (Zr2WO4(PO4)2), ZnxCd1-x(CN)2, manganese nitride, bismuth-nickel-iron oxide etc. are known.

Zirconium phosphate tungstate, which has high negative thermal expansion property, has a linear expansion coefficient of −3.4 to −3.0 ppm/K at a temperature within the range of 0 to 400° C., and can be used in combination with a material exhibiting positive thermal expansion (hereinafter, may be also referred to as “positive thermal expansion material”) to manufacture a material having low thermal expansion property (for example, see Patent Literatures 1 and 2, and Non Patent Literature 1).

The present inventors also previously proposed a zirconium phosphate tungstate useful as a negative thermal expansion material (Patent Literatures 3 and 4).

CITATION LIST

Patent Literature

Patent Literature 1

Japanese Patent Laid-Open No. 2005-35840
Patent Literature 2Japanese Patent Laid-Open No. 2015-10006
Patent Literature 3Japanese Patent Laid-Open No. 2015-199000
Patent Literature 4Japanese Patent No. 6190023
Patent Literature 5Japanese Patent No. 6105140

Non Patent Literature

Non Patent Literature 1

Materials Research Bulletin, 44(2009), 2045-2049.

SUMMARY OF INVENTION

Technical Problem

A negative thermal expansion material is used in combination with a positive thermal expansion material, and in view of compatibility with a positive thermal expansion material used in combination and in view of application etc., development of negative thermal expansion materials having various thermal expansion coefficients is desired.

Therefore, the object of the present invention is to provide a negative thermal expansion material made of zirconium phosphate tungstate having various thermal expansion coefficients, an industrially advantageous manufacturing method thereof and a composite material comprising the negative thermal expansion material.

Solution to Problem

In view of the above situation, the present inventors engaged in diligent study, and consequently completed the present invention by discovering that when accessory component elements such as a Mg atom, for example, are added to zirconium phosphate tungstate, the thermal expansion coefficient described below tends to be lower in comparison with the case without addition of any accessory component elements, but when an Al atom is added to zirconium phosphate tungstate, unlike the accessory component elements such as Mg atom, the thermal expansion coefficient described below tends to be higher in comparison with the case without addition of any accessory component elements, and that the thermal expansion coefficient can be varied within a specific range by varying the content of Al.

Specifically, (1) the present invention provides a negative thermal expansion material made of zirconium phosphate tungstate containing an Al atom, and having a thermal expansion coefficient of −2.0×10−6to −3.3×10−6/K.

(2) The present invention provides the negative thermal expansion material according to (1), wherein the content of Al atom in the negative thermal expansion material is 100 to 6000 ppm by mass.

(3) The present invention provides the negative thermal expansion material according to (1) or (2), comprising one or more accessory component elements selected from the group consisting of Mg, Zn, Cu, Fe, Cr, Mn, Ni, V, Li, B, Na, K, F, Cl, Br, I, Ca, Sr, Ba, Ti, Hf, Nb, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy and Ho.

(4) The present invention provides the negative thermal expansion material according to any of (1) to (3), having a BET specific surface area of 0.1 to 30 m2/g.

(5) The present invention provides the negative thermal expansion material according to any of (1) to (4), having an average particle size of 0.1 to 50 μm.

(6) The present invention provides a method for manufacturing a negative thermal expansion material, comprising a first step of mixing a W source, a Zr source, a P source and an Al source to prepare a slurry containing the W source, the Zr source, the P source and the Al source, a second step of spray drying the slurry to obtain a reaction precursor, and a third step of baking the reaction precursor to obtain Al-containing zirconium phosphate tungstate, wherein

in the first step, the Al source is mixed into the slurry so that the content of Al atom is 100 to 6000 ppm by mass relative to the Al-containing zirconium phosphate tungstate obtained by conducting the third step.

(7) The present invention provides the method for manufacturing a negative thermal expansion material according to (6), wherein in the first step, one or more of compounds having one or more accessory component elements selected from the group consisting of Mg, Zn, Cu, Fe, Cr, Mn, Ni, V, Li, B, Na, K, F, Cl, Br, I, Ca, Sr, Ba, Ti, Hf, Nb, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy and Ho is further mixed into the slurry.

(8) The present invention provides the method for manufacturing a negative thermal expansion material according to any of (6) or (7), wherein the Al source is aluminum nitrate.

(9) The present invention provides a composite material comprising the negative thermal expansion material according to any of (1) to (5) and a positive thermal expansion material.

(10) The present invention provides the composite material according to (9), wherein the positive thermal expansion material is at least one selected from metal, alloy, glass, a ceramic, rubber and resin.

Advantageous Effects of Invention

According to the present invention, a negative thermal expansion material made of zirconium phosphate tungstate having various thermal expansion coefficients of −2.0×10−6to −3.3×10−6/K can be provided. Furthermore, according to the method for manufacturing the present invention, the negative thermal expansion material can be provided by an industrially advantageous method.

