JPS6011228A - Heat-resistant heat-insulating material of octotitanate - Google Patents

Abstract

PURPOSE:To provide a heat-resistant heat-insulating material proof against high temp., having a significant heat insulating effect, and made of a specified octotitanate having a high m.p., low heat conductivity and a hollandite type structure. CONSTITUTION:An octotitanate represented by formula I (where A is an alkali metal, Ba, Cu or Ni; B is Mg, a bivalent transition metal, Al, Fe, Cr or Ga; each of (x) and (y) is 0.5-3; and (z) is 5-8) is used as a heat insulating material. The octotitanate has a high m.p., low heat conductivity and a hollandite type structure. Titanium oxide is mixed wih the oxide of the metal (A) and the oxide of the metal (B) to prepare a solid soln., and this solid soln. is mixed with a metallic molybdate represented by formula II (where (n) is 0-3). The mixture is melted, and crystals are grown from the melt to obtain the octotitanate represented by the formula I as fibrous crystals.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a novel heat-resistant thermal insulation material. More specifically, the present invention relates to a heat-resistant heat insulating material made of octotitanate having a hollandite structure.

BACKGROUND OF THE INVENTION Conventionally, asbestos has been the most widely used heat-resistant heat insulating material. However, asbestos has the disadvantage that it easily shrinks and causes pollution, and there is a demand for the development of alternative materials.

As an alternative material, one of the inventors of the present invention previously developed a fiber made of potassium titanate (Japanese Patent Publication No. 55-25
(See Publication No. 157). However, although the potassium titanate fiber has excellent heat insulation properties among ceramics, it has a drawback that its melting point is 1370°C, so it can only be used at a temperature of up to about 1200°C.

The object of the present invention is to overcome these drawbacks and to provide an excellent heat insulating material that is resistant to temperatures above 1500°C and has a lower thermal conductivity.

Structure of the Invention As a result of many years of research into potassium titanate, the present inventors have revealed that the cause of its heat insulating properties is related to its one-dimensional tunnel structure.

Furthermore, as a result of intensive research to obtain a substance with a larger tunnel structure and higher melting point than potassium titanate, we found that a specific octotitanate crystal has a higher melting point and thermal conductivity than potassium titanate. was also found to have small characteristics. The present invention was completed based on this knowledge.

The gist of the present invention is the general formula Ax(ByTiz) 801
6 (However, the person in the formula is an alkali metal, Ba, Ou
and Ni; B is Mg, a divalent transition metal;

1, metal selected from Fe, Or and Ga,
6 in a heat-resistant heat insulating material made of an octotitanate crystal having a hollandite structure, where X is 0.5 to 3 and y is 0.5 to 3.2 is 5 to 8 This is component A shown in the general formula in the invention.

Alkali metals such as Li, Na, K, Rb, and Os, as well as Ba, Ou, and Ni are all metals that can be coordinated in the tunnel structure. In particular, K and Ba are preferred because they are easy to coordinate, easy to prepare samples, and have low thermal conductivity. In addition, component A may be a solid solution component containing two or more of the above-mentioned elements.

In addition, Mg1Gu which is the B component shown in the above general formula
, Zn, Ni, Go divalent transition metals, A7.
Fe%0'rXGa is T that forms the framework of the tunnel.
It is a metal that can replace and occupy the Ti seat in the ie6aj octahedron. In particular, Mg and Al are preferable because they can easily replace Ti, make samples easy to prepare, and have a high melting point. Moreover, the B component may be a solid solution component of two or more of the above-mentioned elements.

All xly shown in the above general formula needs to be in the range of 0.5 to 3, preferably 1.0 to 2.
The range is 4. Outside this range, phases other than the target octotitanate are formed and a mixed phase is formed, resulting in an increase in thermal conductivity and a decrease in mechanical strength.

Moreover, 2 needs to be 5-8. Outside this range, it becomes difficult to obtain a TiO6 octahedron with a tunnel structure.

Methods for producing the heat-resistant heat insulating material made of crystalline octotitanate of the present invention include a firing method and a melting method.

It can be produced by either the hydrothermal method or the flux method, but powder is preferable for making paints and sintered products, so the firing method is suitable.For making fibrous products,
It is preferable to manufacture by flux method using 7 kg of molybdate or tungstate. This is because the equipment can be large-sized, continuous production is easy, crystals can be grown at relatively low temperatures, and high pressure is not required, so there is no danger, and the flux has low volatility, so it does not cause pollution due to volatilization. This is because the fibers produced are easy to separate and recover because they are easily soluble in water.

The method for producing octotitanate having a hollandite structure according to the present invention by the flux method is as follows.

A metal oxide of component A or a compound that generates the metal oxide when heated, represented by the general formula, a metal oxide of component B or the metal oxide that generates the metal oxide when heated, and titanium oxide or a compound that generates the metal oxide when heated. A titanium compound is used as a raw material.

Examples of compounds that generate #)AO upon heating include Mu(OH)21 AGO3, ACNo3)21 AF21
Examples include AO121AB O, ASO4, and the like. In addition, as a compound that generates BO upon heating, MgOO3 has a valence of -
:=Carbonide of carbonate metal, Mg(OH)2. Hydroxide of divalent transition metal, MgH2(Co, ), 2 deuterium carbonate of divalent transition metal, 1(OH), , Fe(
OH), , 0r(OH), , Ga(OH), lA4
2(003)5. Fe2(Co, ), , 0r2(
Co3), Ga2(Co,).

Examples include.

Compounds that generate TiO2 upon heating include the same Ti compounds as mentioned above.

Among these raw materials, component B is expressed by the general formula BI[0 (however,
BII represents Mg or a divalent transition metal) and general formula B
IIIO (however, BII[represents Az, Fet or Ga), and the molar ratio of each raw material is AO:BI[0:Tie2=2:1:3
~5:2:3 or AO:BI[0:Tie2=2:1:3
-Create a mixture or solid solution in the ratio of 4:3:3.

A molybdate represented by the general formula A2M004.nMOo5 (where A represents the metal and n represents O-3) is mixed therein.

This mixing ratio is preferably 10:90 to 50:50 in mol%. A mixture of these, for example 80
It can be obtained by melting at 0 to 1500°C to form a melt, and pre-crystals are formed from the melt. Specific examples thereof are shown in Examples.

Example 1. Production of crystalline powder of K) ((AlyTiz) 6016 (where x = y = 2.0 to 2.4, z = 8 - y) 2003: Al2O3:Ti02=
1.0:1・I'o: 6~1.2: 1.2:
5.6°, mixing port at the ratio! This mixture was further thoroughly ground and mixed to obtain a starting material. Approximately 3O of this starting material
f was filled in a 50-degree platinum crucible, calcined at 1200°C for 3 hours in a silicon carbide heating element electric furnace, taken out, ground and mixed, and fired again at 1200°C for about 20 hours.

The obtained powdery crystalline material was identified by X-ray powder diffraction.

Its composition is 2. . A.I. Ti6016 ~ 2.4
A'2.4"5.60.6.

In this case, when X and y are smaller than 2.0 and 2 is larger than 6.0, a rutile phase is formed in addition to potassium-aluminum-octatitanate, and At molar ratios greater than 2.4 and 2 less than 5.6, unknown phases were formed.

Also, instead of Al2O3, Fe2O3, Cr2O3, T
When a2o3 was used, octotitanate crystalline powder was similarly obtained.

Example 2. K) ((MgyTiz) ao+6 (however, X=2.0~2.4,'/=''/2,z
= 8''/'2) (Production of D crystalline powder, -).

Potassium carbonate, magnesium carbonate, and oxidized powder were added to K2O03: Kg (io, : 'I'10
2 = 1,0: ・Fuwa also 8□. ~1.2: 1.2
: 6.8°, Ya ratio. This mixture was further thoroughly ground and mixed to obtain a starting material. This starting material is about 307
was filled into a 50-platinum crucible and fired in the same manner as in Example 1. The obtained crystalline material was identified by X-ray powder diffraction. Its composition is 2. . MgTi, 0.6~2.4Mg1.2T
It was i6.80.6.

In this case, when X is smaller than 2, y is smaller than 1, and z is larger than 7, a rutile phase is formed in addition to octotitanate, and X is larger than 2.4 and y is 1. An unknown phase was formed in a molar ratio mixture where 2 was greater than 2 and 2 was less than 6.8.

Example 3. 8ax (AlyTi2) 80.6 (x = 1.0 to 1.4, y = 2x, z = 8-y) Production of crystalline powder Each powder of barium carbonate, aluminum oxide, and titanium oxide was mixed with Ba0O ,: k120. : Tie□=
1.0: 2.0: 6-1.4: 2.8:
It was a mixture of 1', Ba'ma, a''2,8 Tis, 20115 with a molar ratio of 5.2.

,・1, di)-:,)-3, Fe2O3+ instead of Al2O3
0r20. , Ta20x was used to similarly obtain octotitanate crystalline powder.

Example 4 - Bax (MgyTiz) 6016 (where x = 1.0-1.4, V = 1.0-1.4
, z=s-y) Production of crystalline powder Barium carbonate, magnesium carbonate and chip oxide p7 powders were converted into BaGO,: Mg(EO,: Tie2=
1.0: 1.0: 7.0~1.4: 1.4
: A mixture having a molar ratio of 6.6 was used as a starting material and calcined in the same manner as in Example 1. The composition of the obtained crystal is BaMgTi70,6~Ba1.4 Mg1.4''6
．． It was 6016.

Example 5. Kx (AlyTi2) 80,6 (however, x
=y=1.5-2.0, z=8-'/) Production of fibrous crystals Potassium carbonate, aluminum oxide, and titanium oxide powders were added to 2C03:Al2O3:Ti02=2:2
To a mixture with a molar ratio of: 3:3, 170% of each powder of potassium molybdate and molybdenum oxide was added as a flux.
A mixture with a molar percentage of 20F80-30Nia0 was mixed with a molar percentage of 20F80-30Nia0. The resulting mixed special contract゛□'12or
was filled in a 100-Platinum crucible, heated to 1300° C. in a silicon carbide heating element electric furnace, and held for about 1 to 20 hours. Thereafter, it was slowly cooled to around 950°C at a rate of 4 to 8°C.

After slow cooling, the mixture was taken out of the furnace, allowed to cool to room temperature, and the crystals were separated by dissolving the flux with hot water. The obtained crystals have a fibrous shape extending in the axial direction and have a length of 1.0 to 10.0111 mm.
It was 111. Its crystal composition is 1.6 A'1.6
Ti was 6.4016.

Example 6 - Kx (MgyTiz) ao+6 (but
x=1.5~2.0, y=gong, z=8-V/2
) Production of fibrous crystals Potassium carbonate, magnesium carbonate and oxide chip p7 (7
) Each powder was converted into K2O05: Mg00. : Tie2
A fibrous crystalline material was produced in the same manner as in Example 5 using a mixture having a molar ratio of 3:1:3 as a starting material. The obtained crystal has a fiber length of 1.0 to 1o extending in the C-axis direction,
It was from omm. Its composition is 1.6 Mgo, 8
It was Ti7, 2016.

, ::°″＼ Each powder of barium carbonate, aluminum oxide and chip p7 was mixed with BaCO3:A12o, :Ti02=2:2
A mixture having a molar ratio of :3 was used as the starting material.

As a flux, a mixture of potassium molybdate powder and molybdenum oxide powder was used in a molar ratio of 1=0.5. Starting material near lux=20:80~30:7
Crystals were obtained in the same manner as in Example 1. The obtained crystals were fibrous substances extending in the C-axis direction, the length was 1.0~J1i), □mm, and the composition was Ba(,8A/1.6Ti6.40.6). Furthermore, when MgOO3 was used instead of Al2O3, fibrous crystals of octotitanate were similarly obtained.

Example 8゜Ba1.4A'2,8 Ti5.
Fibrous crystalline material having a composition of 2016 (hereinafter referred to as the crystalline material of the present invention) 1 (hereinafter referred to as the crystalline material of the present invention).

K= ρ・C・α Here, ρ is calculated based on the external dimensions and weight of the sample, and
C and α were measured by the racer flash method.

The crystal of the present invention is a disc-shaped object with a thickness of 1.964 mm, an outer diameter of 8.10 mm, and a density of 42! For comparison, 2. oA12. . A disk-shaped material made of Ti6o, 6 with a thickness of 1.921mm, an outer diameter of 7.8011111mm, and a density of 3.429mm was used. A Chromel-Conskun thermocouple was adhered to one side of these disk-shaped samples, and graphite fine particles were applied to the other laser-irradiated surface.

When measuring the specific heat capacity, an alumina single crystal was used as a reference sample.

The specific heat capacity C1 thermal diffusivity α and thermal conductivity K of each sample at room temperature and 1000 K were measured, and the results were as follows.

From these results, it is clear that the crystalline material of the present invention exhibits a thermal conductivity lower than that of large potassium titanate, and has a value lower by about 30% or more. Furthermore, 100OK exhibits lower thermal conductivity than room temperature, and exhibits excellent heat insulation properties at high temperatures.

Effects of the Invention The melting point of the heat insulating material made of the octotitanate of the present invention is lower than that of 1:1 potassium phosphate, which has the best heat insulating properties among ceramics, and has extremely excellent heat insulating properties.

Claims (1)

[Claims] 1. General formula AX(ByTi2)80,6, (however,
In the formula, A is a metal selected from alkali metals I Ba IGu and Ni, and B is a metal selected from the group consisting of alkali metals I Ba IGu and Ni; Divalent transition metal + A' r Fer A metal selected from CF and Ga, X is 0. -5 to 3, y is 0.5 to 3.
2 represents 5 to 8) A heat-resistant heat insulating material made of an octotitanate having a hollandite structure.