JP2005255503A - Low thermal expansion composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new composite material having a low thermal expansion coefficient and a thermal conductivity. <P>SOLUTION: The composite material having a low thermal expansion coefficient and an improved thermal conductivity is formed by mixing at least a tungstic acid compound or a molybdic acid compound having a negative thermal expansion coefficient with a carbon material having a high thermal conductivity and firing the resultant mixture. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low thermal expansion composite having low thermal expansion and excellent heat conductivity.

  In a material used in an environment that requires heat resistance, mechanical stress is generally generated by thermal stress. For example, in an application used in a high temperature region such as an electronic device or a catalyst carrier, a dimensional accuracy shift, mechanical deterioration or destruction becomes a problem.

  As a method of reducing mechanical stress depending on the material, it is considered to apply a ceramic material having a low thermal expansion coefficient. For example, development of a structure using a cordierite-based low thermal expansion ceramic or the like is underway (for example, Patent Documents 1 and 2). In addition, materials themselves having a small thermal expansion coefficient have been developed, and materials such as low thermal expansion glass and composite oxides improved from cordierite are being developed (for example, Patent Document 3).

  In addition, the possibility of new materials has been suggested. Generally, common materials such as glass, oxide, metal, and resin have a positive coefficient of thermal expansion. On the other hand, in recent years, complex oxides exhibiting various negative thermal expansion coefficients have begun to be reported. For example, Patent Documents 4 to 8 disclose oxides (hereinafter sometimes referred to as “tungstic acid compounds”) such as tungstic acid compounds and molybdic acid compounds having a negative thermal expansion coefficient. Using these materials having a negative thermal expansion coefficient (hereinafter sometimes referred to as “negative thermal expansion materials”) in combination with other materials suggests the possibility of obtaining new low thermal expansion materials. ing. For example, a metal oxide is added to a negative thermal expansion material made of a tungstic acid compound or the like to improve the firing state and adjust the thermal expansion coefficient (for example, Patent Documents 9 and 10).

Further, the applicant of the present application described in Patent Document 11 is a material having a coefficient of thermal expansion almost zero over a wide temperature range by mixing a positive thermal expansion oxide and a negative thermal expansion oxide of the same oxide system. Is disclosed.
JP-A-7-157377 Special table 2003-502261 gazette JP 2000-290064 A US Pat. No. 5,322,559 US Pat. No. 5,433,778 US Pat. No. 5,514,360 US Pat. No. 5,919,720 US Pat. No. 6,183,716 Japanese Patent Laid-Open No. 10-96827 JP-T-2002-517377 JP 2003-89572 A JP 2001-79977 A (particularly paragraph number 0002) JP-A-3-146472

  However, as described above, the development of a new low thermal expansion material has just started, and sufficient characteristics have not yet been obtained for various applications. In applications that require heat dissipation, heat transfer, etc., such as in the vicinity of a heating element, a low thermal expansion material of a composite oxide such as a tungstic acid compound has a problem that it is difficult to use because of its low thermal conductivity.

  In order to solve this problem, it is necessary to improve the heat conduction characteristics. As a material development, it is technically conceivable to prepare a composite by adding and mixing a metal such as aluminum or copper or an oxide having thermal conductivity such as magnesium oxide to a tungstic acid-based low thermal expansion compound. However, since tungstic acid compounds easily react with metals and oxides, compounds of other compositions are formed by the reaction, and it is difficult to obtain a mixed sintered body having good characteristics.

  The present invention has been made in view of the above points, and a main object thereof is to provide a novel composite material having a low thermal expansion coefficient and thermal conductivity.

In order to solve the conventional problems, the low thermal expansion composite of the present invention has at least a composition formula I: A ^{l +} _n (M ⁶⁺ O ₄ ) _m (A is a metal element having a valence of 1 or an average valence of a plurality of metal elements to be l, M is a metal element having a valence of 6 or a plurality of metal elements having an average valence of 6, m and n representing the composition are integers of 1 or more, and l × n = 2 × m is satisfied)) and the carbon material (2).

  With this configuration, a novel composite material having a low thermal expansion coefficient and thermal conductivity can be provided.

  M contained in the oxide (1) in the present invention is preferably either tungsten or molybdenum. Furthermore, it is preferable that the oxide (1) in the present invention has a negative coefficient of thermal expansion. Moreover, it is preferable that A which the oxide (1) in this invention has contains a positive bivalent metal element and a positive tetravalent metal element.

  In an embodiment, the carbon material (2) in the present invention is graphite.

In order to solve the above-mentioned conventional problems, the method for producing a low thermal expansion composite according to the present invention includes at least a composition formula I: A ^{l +} _n (M ⁶⁺ O ₄ ) _m (A is a metal element having an valence of 1 or an average A plurality of metal elements having a valence of l, M is a metal element having a valence of 6 or a plurality of metal elements having an average valence of 6, m and n representing the composition are integers of 1 or more, 1 × n = 2 × m is satisfied)) and the carbon material (2) are mixed and fired.

  According to the low thermal expansion composite of the present invention, a composite having low thermal expansion and thermal conductivity can be provided. The present invention can be suitably used in an environment where heat resistance, thermal shock resistance, etc. are required, and can also dissipate and transfer heat even in an environment where heat is generated.

  According to the low thermal expansion composite of the present invention, since the oxide (1) represented by the composition formula I and the carbon material (2) are mixed, the thermal expansion coefficient is adjusted and controlled by the combination thereof. This makes it easy to design a material that adjusts thermal stress due to thermal expansion. In particular, the combination of oxide (1), which is a negative thermal expansion material, and carbon material (2), which has high thermal conductivity, has the effect of providing a material having extremely low thermal expansion and thermal conductivity. ing.

  Conventionally, when trying to develop such a material using a metal such as copper or aluminum or a thermally conductive oxide such as magnesium oxide, the composite is combined with the oxide (1) made of a tungstic acid compound. When trying to make it, since the tungstic acid compound easily reacts with a metal or another oxide to form another compound, the material design could not be performed well. On the other hand, since the carbon material (2) hardly reacts with the oxide (1), it has an effect that a composite can be manufactured satisfactorily.

  Embodiments according to the present invention will be described below with reference to the drawings.

The low thermal expansion in the present invention means a coefficient of thermal expansion, which is a change in dimension due to a change in heat, on the order of 10 ⁻⁶ / ° C., and its absolute value is defined as approximately 5 × 10 ⁻⁶ / ° C. or less. To do. As the low thermal expansion composite of the present invention, a composite having an absolute value of a thermal expansion coefficient of approximately 1 × 10 ⁻⁶ / ° C. or less can be prepared and used with thermal expansion close to zero.

(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing a configuration of a low thermal expansion composite 10 of Embodiment 1 according to the present invention.

The low thermal expansion composite 10 includes at least a composition formula I: A ^{l +} _n (M ⁶⁺ O ₄ ) _m (A is a metal element having a valence of 1 or a plurality of metal elements having an average valence of 1; A metal element having a valence of 6 or a plurality of metal elements having an average valence of 6, m and n representing the composition are integers of 1 or more, and satisfy the relational expression of l × n = 2 × m. An oxide (1) 101 represented and a carbon material (2) 102 are included. According to this configuration, it has a low thermal expansion coefficient and can have thermal conductivity.

  At this time, when an oxide having high thermal conductivity such as magnesium oxide or aluminum oxide is used without using the carbon material (2) 102, it is combined with the oxide (1) 201 as shown in FIG. The oxide 202 reacts during the sintering to form another oxide 203. Mainly, it becomes a tungstic acid compound in which a plurality of metal elements in the composition formula I are mixed, and the ratio of the oxide 202 having a high thermal conductivity is reduced, so that the effect is not obtained. The greatest effect of the present invention is that such problems can be solved.

  First, as the oxide (1) 101 represented by the composition formula I in the present invention, there are a positive thermal expansion material of a tungstic acid compound and a negative thermal expansion material, which are combined with the carbon material (2) 102. By design, the coefficient of thermal expansion is selected.

As the positive thermal expansion material, as the metal element M in the composition formula I, a metal element having a valence of 6 selected from tungsten W and molybdenum Mo, or a plurality of elements having an average valence of 6 selected from an arbitrary composition from W and Mo. Those which are metal elements are preferred. Further, as the metal element A, a metal element having a valence of 2 selected from magnesium Mg, calcium Ca, strontium Sr, and barium Ba, or an average valence of 2 selected from any composition from Mg, Ca, Sr, and Ba And a plurality of metal elements having an average valence of 3 selected by combining Al and Sc, Y, and Lu. For example, exemplified _{MgWO 4, CaWO 4, SrWO 4} , Al 2 (WO 4) 3, AlSc (WO 4) 3, AlY (WO 4) 3, MgMoO 4, Al 2 composite oxide such as (MoO _{4) 3} can do. The thermal expansion coefficient of these compounds is a positive thermal expansion coefficient, and the linear thermal expansion coefficient is approximately 0 to + 10 × 10 ⁻ in a temperature range from room temperature (about 25 ° C.) to 500 ° C. or higher, preferably 800 ° C. or higher. Has a small value in the range of ⁶ / ° C.

As the negative thermal expansion material, as the metal element M in the composition formula I, a metal element having a valence of 6 selected from tungsten W and molybdenum Mo, or a plurality of elements having an average valence of 6 selected from an arbitrary composition from W and Mo Those which are metal elements are preferred. The metal element A is a metal element having a valence of 4 selected from zirconium Zr and hafnium Hf, or a plurality of metal elements having an average valence of 4 selected from Zr and Hf in an arbitrary composition. , Yttrium Y, lutetium Lu, or a metal element having a valence of 3 selected from Sc, Y, Lu, or a plurality of metal elements having an average valence of 4, selected from any composition, magnesium Mg, calcium Ca, strontium A plurality of metal elements having a valence of 3 formed by arbitrarily combining a metal element having a valence of 2 selected from Sr and barium Ba and a metal element having a valence of 4 selected from Zr and Hf. For example, in addition to the negative thermal expansion oxide described above, HfMg (WO ₄ ) ₃ , ZrMg (WO ₄ ) ₃ , HfCa (WO ₄ ) ₃ , ZrCa (WO ₄ ) ₃ , HfMg (MoO ₄ ) ₃ , ZrMg ( MoO ₄ ) ₃ , ScY (WO ₄ ) ₃ , ScLu (WO ₄ ) ₃ , Zr _x Hf _1-x Mg (WO ₄ ) ₃ (0 <x <1), ZrMg _x Ca _1-x (WO ₄ ) ₃ (0 <x <1), HfMg x Ca 1-x (WO 4) 3 (0 <x <1), ZrMg (W y Mo 1-y O 4) 3 (0 <y <1), HfMg (W _y Mo _1-y O ₄ ) ₃ (0 <y <1), Sc ₂ (W _y Mo _1-y O ₄ ) ₃ (0 <y <1), Y ₂ (W _y Mo _1-y O ₄ ) _{3 (0 <y <1)} , Zr (W y Mo 1-y O 4) 2 (0 <y <1), Hf (W y Mo 1-y O 4) 2 (0 <y <1) , etc. is there. Further, among these, since the coefficient of thermal expansion can be controlled by a combination of metal elements, the metal element A includes a positive divalent metal element (preferably Mg) and a positive tetravalent metal. And an element (preferably Zr, Hf or a mixture thereof). The thermal expansion coefficient of these compounds is a negative thermal expansion coefficient, and the linear thermal expansion coefficient is approximately 0 to −10 × 10 in the temperature range from room temperature (about 25 ° C.) to 500 ° C. or higher, preferably 800 ° C. or higher. It has a small value in the range of ^-6 / ° C. Note that these oxides having a negative coefficient of thermal expansion have a spatial distance (for example, a crystal) in which a metal element in the compound is arranged by increasing the rotational movement of the bond with an increase in temperature in the metal-oxygen-metal bond. If so, it is thought that the overall thermal expansion becomes negative due to shrinkage of the crystal lattice constant).

In the composition formula I, the metal element A may be a composite oxide including a plurality of metal elements including a valence element, a valence element, and a valence element. For example, it is a compound represented by (HfMg) _1-x Al _2x (WO ₄ ) ₃ (0 <x <1), and this oxide varies from a negative thermal expansion coefficient to a positive thermal expansion coefficient depending on the value of x. Since it has the feature that it can be taken, it can be preferably used. Although this compound has a different thermal expansion coefficient depending on its composition, it can be controlled in the range of + 2 × 10 ⁻⁶ / ° C. to −2 × 10 ⁻⁶ / ° C. depending on the composition. In particular, in the temperature range from room temperature to about 800 ° C. when the composition x = 0.2 to 0.3, a linear thermal expansion coefficient whose absolute value is within 0.5 × 10 ⁻⁶ / ° C. can be obtained. .

Furthermore, as the oxide (1), a quasi-multicomponent mixed oxide can also be used. Here, the quasi-multielement mixed oxide is a mixed oxide formed by mixing a plurality of oxides. A plurality of oxides constituting the quasi-multielement mixed oxide may be particularly referred to as “unit oxides”. The plurality of unit oxides preferably include a unit oxide composed of a negative thermal expansion oxide and a unit oxide composed of a positive thermal expansion oxide. As specific compounds, it is preferable to use the above-described positive thermal expansion material and negative thermal expansion material as unit oxides. This is because the unit oxides made of negative thermal expansion oxide and the unit oxides made of positive thermal expansion oxide have similar chemical structures, so the affinity of each unit oxide at the time of production is low. This is because the tendency to improve and the tendency to become mechanically stable is obtained. A porous structure containing such a quasi-multicomponent mixed oxide can also obtain a linear thermal expansion coefficient having an absolute value within 1 × 10 ⁻⁶ / ° C. in the temperature range from room temperature to about 800 ° C. . Furthermore, the combination of the positive and negative unit oxides of the quasi-multi-system mixed oxide, the difference in linear thermal expansion coefficient due to the material combined with the control of the thermal expansion coefficient is approximately + 10 × 10 ⁻⁶ / ° C. to −10 × 10 ^-6 / ° C can be controlled.

Next, as the carbon material (2) 102 in the present invention, a compound having high thermal conductivity and hardly reacting with the oxide (1) represented by the composition formula I is selected. In addition, a material having a thermal expansion coefficient as small as possible is selected. Since the carbon material does not easily react with the tungstic acid compound, it is preferable to select a compound having high thermal conductivity and a relatively low coefficient of thermal expansion. Examples of the carbon material include graphitized carbon such as graphite, carbon fiber, diamond, diamond-like carbon, fullerene, carbon tubes such as carbon nanotubes and carbon nanohorns, and highly conductive activated carbon. For example, graphite (thermal conductivity approximately several hundred W / mK, linear thermal expansion coefficient approximately 10 × 10 ⁻⁶ / ° C.), diamond (thermal conductivity approximately 1000 to 2000 W / mK, linear thermal expansion coefficient approximately 4.2 × 10 ^{− 6} / ° C.), carbon nanotube (thermal conductivity of about several thousand W / mK, linear thermal expansion coefficient of about 3 × 10 ⁻⁶ / ° C.), carbon fiber (thermal conductivity of about several tens of W / mK, linear thermal expansion coefficient of about −0 .5 × 10 ⁻⁶ / ° C.) or the like can be used. In particular, graphitized carbon such as graphite is preferably used because it has a high thermal conductivity and high effect, and is available at a relatively low cost.

  As the form of the carbon material (2) 102, various shapes can be used, but in order to improve dispersibility with the oxide (1) or its raw material, powder form and granular form are preferable. Further, the mixing amount of the two can be appropriately set from the viewpoints of thermal conductivity and thermal expansion coefficient obtained as a composite, and moldability. As the mixing amount, the carbon material (2) at the time of forming the composite can be produced in a volume ratio of approximately 0.3 to 0.8. Preferably, it is effective that the volume ratio of the carbon material (2) is approximately in the range of 0.4 to 0.7.

  The thermal expansion coefficient of the low thermal expansion composite is measured as follows. The linear thermal expansion coefficient can be measured by measuring a change in geometric dimension with respect to a temperature change by thermomechanical analysis (hereinafter abbreviated as TMA) or laser interferometry. The thermal conductivity can be measured by a laser flash method.

(Embodiment 2)
Next, the manufacturing method of the low thermal expansion composite in this invention is demonstrated.

  For the production of the low thermal expansion composite according to the present invention, a general production method of ceramic or glass can be applied. Examples thereof include (a) and (b).

  (A) Powder / granule of oxide (1) represented by composition formula I or its raw material and powder / granule of carbon material (2) are molded, and then solid phase reaction of oxide (1) A method of firing at a temperature.

  (B) Powders / grains of oxide (1) represented by composition formula I, powders / grains of carbon material (2), and a small amount of binder material are molded and then bonded to the binder. A method of firing in

As a raw material of the oxide (1) represented by the composition formula I, oxides, hydroxides, carbonates, and the like of each constituent metal element can be used. For example, tungsten oxide, molybdenum oxide, magnesium oxide, zirconium oxide, hafnium oxide, calcium oxide, strontium oxide, aluminum oxide, scandium oxide, yttrium oxide, lutetium oxide, vanadium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, Magnesium carbonate, calcium carbonate, and phosphates of each metal. Also, organometallic compounds of each constituent metal element, such as metal alkoxide, metal acetylacetonate, metal acetate, metal methacrylate, metal acrylate, aluminum isopropoxide, aluminum-sec-butoxide, hafnium -T-butoxide, hafnium ethoxide, hafnium-2,4-pentadionate, lutetium-2,4-pentadionate, magnesium ethoxide, magnesium methoxide, magnesium n-propoxide, magnesium methyl carbonate, magnesium-2 , 4-Pentadionate, Magnesium acetate, Magnesium methacrylate, Calcium acetate, Molybdenum oxide bis (2,4-pentadionate), Tungsten hexaethoxide, Zirconium isopropo Side, zirconium butoxide, yttrium isopropoxide, magnesium aluminum alkoxide is magnesium zirconium alkoxide. Furthermore, as raw materials, trivalent tungsten oxides such as MgWO ₄ , CaWO ₄ , and SrWO _{4 that} are divalent tungsten oxides, such as HfW ₂ O ₈ and ZrW ₂ O _{8 that} are tetravalent tungsten oxides. ₂ W ₃ O ₁₂ , Sc ₂ W ₃ O ₁₂ or the like may be used.

  In general, a composite oxide can be produced in the order of preliminary firing, coarse pulverization, molding, and main firing after mixing and kneading or kneading a raw material metal oxide using a method such as a ball mill. The material of the present invention can also be produced by these general production methods. In addition, if the fine pulverization is sufficiently performed in the mixing and pulverizing step, it is possible to produce an equivalent sample without pre-baking. As a method of mixing and coarse pulverization according to the present embodiment, not only a likai machine and a wet ball mill, but also a wet pulverization method can be used as long as it is a mixed pulverization method such as a planetary mill or a medium mill (for example, an attritor or a vibration mill). Therefore, uniform mixing and pulverization is possible, and the effects of the present invention can be obtained.

  In addition, the molding is performed to adjust the form of the complex oxide, and the same effect is obtained regardless of the molding method, such as molding using a green sheet using various sheet coating apparatuses as well as pressure molding. It goes without saying that it can be obtained.

  Moreover, as firing conditions, it can produce on general conditions. As firing conditions, although the firing temperature varies depending on the type of composite oxide to be generated or the type of binder material, it is about 300 ° C. or higher, preferably in the range up to 1600 ° C. The firing atmosphere is performed in air or in an atmosphere containing oxygen, and may be performed in an inert gas atmosphere or under reduced pressure as the case may be. When the tungstic acid compound is formed by solid phase reaction, the firing temperature is preferably 900 ° C. to 1200 ° C. for the tungsten composite oxide, and 700 ° C. to 1000 ° C. for the molybdenum oxide. If the calcination temperature is lower than this, the reaction of the oxide is not sufficient and the desired compound cannot be obtained. On the other hand, when the temperature is higher than this, the compound tends to melt or the tungsten oxide or molybdenum oxide in the compound tends to sublimate. These conditions may be determined by selection of raw materials. In the present invention, since the carbon material (2) is used, air may be used in the case of firing at less than about 500 ° C. However, since it burns at 500 ° C. or higher in the air, it is preferable to carry out in a low-concentration oxygen atmosphere when setting the temperature so high. The low oxygen concentration atmosphere in the present invention means that the oxygen concentration of the atmosphere is 0 to 10%. Firing at this time can be performed by a dry distillation method, heating in an inert gas atmosphere such as nitrogen or argon, or heating in a vacuum.

  Furthermore, additives can be used for the purpose of improving the density and improving the reproducibility of material properties. Additives include alkaline earth metals, Al, Y, Sc, Lu, Zr, Hf, W, Mo, Fe, Mn, Ni, Si oxides or compounds, such as magnesium oxide, calcium oxide, Aluminum oxide, yttrium oxide, scandium oxide, iron oxide, manganese dioxide, silicon dioxide, nickel oxide, zirconium oxide, hafnium oxide, tungsten oxide and other oxides, magnesium hydroxide, calcium hydroxide, aluminum hydroxide and other hydroxides Further, carbonates such as magnesium carbonate, calcium carbonate, and barium carbonate can be used. These additives are effective at an addition amount of 5% by weight or less based on the main raw material, and an addition amount of 0.1 to 2% by weight is particularly preferable. If the addition amount is small, the effect cannot be sufficiently obtained, and if the addition amount is 5% or more, it melts due to a melting point drop or reacts with a part of the main raw material or the main raw material itself to generate a byproduct. This is not preferable because it affects the original characteristics of the main raw material. These additives may be used in combination.

  Furthermore, the above-mentioned additive may act as a binder material for binding the powder / particles of the oxide (1) represented by the composition formula I and the powder / particles of the carbon material (2). Furthermore, low melting glass, water glass such as sodium silicate, and inorganic binder such as silicone compound can be preferably used. The amount used is preferably the same amount as the additive. These binder materials may be used in combination.

  Specific examples of the low thermal expansion composite according to the present invention are shown below, but the present invention is not limited thereto.

(Example 1)
First, HfMg (WO ₄ ) ₃ was produced as follows. As starting materials, HfO ₂ , MgO and WO ₃ were weighed at a molar ratio of 1: 1: 3, and mixed and ground for 144 hours by a wet ball mill using pure water as a solvent. After drying for a whole day and night to remove moisture, the obtained raw material powder was temporarily fired at a temperature of 1000 ° C. to obtain a fired powder of HfMg (WO ₄ ) ₃ .

Next, the calcined powder of HfMg (WO ₄ ) ₃ and graphite powder (particle size of about 18 μm) obtained by this preliminary calcination are 2.5: 0.8 by weight ratio (approximately 0.5: volume ratio). 0.5), and then coarsely pulverized with a lyric machine, followed by pressure molding, followed by firing at 1100 ° C. for 4 hours under nitrogen flow to obtain a low thermal expansion composite. For comparison, the main firing was performed by firing a fired powder of HfMg (WO ₄ ) ₃ at 1100 ° C. for 4 hours in the air. Note that the average particle size when pulverized by the Reika machine was about 0.8 μm.

As a result of measuring the linear thermal expansion coefficient by TMA and measuring the thermal conductivity by the laser flash method for the produced low thermal expansion composite, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. is about 4 × 10 ^−6. The thermal conductivity was about 5 W / mK. HfMg (WO ₄ ) ₃ produced as a comparison had a linear thermal expansion coefficient of about −3 × 10 ⁻⁶ / ° C. and a thermal conductivity of about 0.8 W / mK. This indicates that the absolute value of the linear thermal expansion coefficient is reduced and the thermal conductivity can be improved.

(Example 2)
First, Hf (WO ₄ ) ₂ calcined powder, MgO and WO ₃ are weighed at a molar ratio of 3: 1: 1, and further, graphite powder (particle size of about 18 μm) with respect to the total raw material weight of the tungstic acid compound. Is mixed at a weight ratio of tungstic acid-based compound raw material: graphite powder = 3.0: 0.6 (volume ratio at the time of forming the composite is approximately 0.6: 0.4), and then coarsely pulverized by a likai machine. After the pressure molding, the main calcination was performed at 1150 ° C. for 4 hours under reduced pressure to obtain a low thermal expansion composite. As a comparison, a calcined tungstic acid compound was obtained by weighing Hf (WO ₄ ) ₂ fired powder, MgO and WO ₃ at a molar ratio of 3: 1: 1.

The obtained low thermal expansion composite was a composite of Hf (WO ₄ ) ₂ , HfMg (WO ₄ ) ₃ and graphite. As a result of measuring the linear thermal expansion coefficient by TMA and the thermal conductivity by the laser flash method, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. is about 1.5 × 10. ⁻⁶ / ° C., and the thermal conductivity was about 8 W / mK. The tungstic acid compound prepared as a comparison is a mixture of Hf (WO ₄ ) ₂ and HfMg (WO ₄ ) ₃ , the linear thermal expansion coefficient is about −5 × 10 ⁻⁶ / ° C., and the thermal conductivity is about 1 W. / MK. From this, it was found that by forming the low thermal expansion composite of the present invention, the coefficient of linear thermal expansion is small and high thermal conductivity can be obtained.

(Example 3)
First, ZrO ₂ and MoO ₃ are weighed at a molar ratio of 1: 2, and the diamond powder (particle diameter of several μm or less) is 2.0: 2.2 (roughly volume ratio) with respect to the total raw material weight. 0.4: 0.6), and then coarsely pulverized by a lyric machine, followed by pressure molding, followed by firing at 1000 ° C. for 4 hours to obtain a low thermal expansion composite. For comparison, ZrO ₂ and MoO ₃ were weighed in a molar ratio of 1: 2 and fired to obtain a molybdate compound.

The obtained low thermal expansion composite was a composite of Zr (MoO ₄ ) ₂ and diamond. As a result of measuring the linear thermal expansion coefficient by TMA and the thermal conductivity by the laser flash method, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. is approximately −0.5 ×. The temperature was 10 ⁻⁶ / ° C., almost zero thermal expansion, and the thermal conductivity was about 10 W / mK. The molybdate compound produced as a comparison was Zr (MoO ₄ ) ₂ , the linear thermal expansion coefficient was about −7 × 10 ⁻⁶ / ° C., and the thermal conductivity was about 1 W / mK.

Example 4
First, ((HfMg) _0.5 Al) (WO ₄ ) ₃ was prepared as follows. As a starting material, HfMg (WO ₄ ) ₃ and Al ₂ (WO ₄ ) ₃ prepared in Example 1 were weighed at a molar ratio of 1: 1, and mixed and ground for 144 hours by a wet ball mill using pure water as a solvent. went. After drying for a whole day and night to remove moisture, the obtained raw material powder was calcined at a temperature of 1000 ° C. to obtain a calcined powder of ((HfMg) _0.5 Al) (WO ₄ ) ₃ .

Next, the calcined powder of ((HfMg) _0.5 Al) (WO ₄ ) ₃ and the pulverized carbon fiber powder obtained by this preliminary calcination were 3.8: 0.5 by weight ratio (approximately 0 by volume ratio). 7: 0.3), and then coarsely pulverized by a reika machine, followed by pressure molding, followed by firing at 1100 ° C. for 4 hours under an argon stream to obtain a low thermal expansion composite. For comparison, the main firing was performed by firing a fired powder of ((HfMg) _0.5 Al) (WO ₄ ) ₃ in air at 1100 ° C. for 4 hours.

As a result of measuring the linear thermal expansion coefficient by TMA and the thermal conductivity by the laser flash method for the produced low thermal expansion composite, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. is about 0.5 × 10. ⁻⁶ / ° C., and the thermal conductivity was about 5 W / mK. The ((HfMg) _0.5 Al) (WO ₄ ) ₃ produced as a comparison had a linear thermal expansion coefficient of about 1 × 10 ⁻⁶ / ° C. and a thermal conductivity of about 0.8 W / mK.

(Example 5)
First, Zr (WO ₄ ) ₂ and graphite powder produced in the same manner as in Example 3 were 2.8: 0.7 (roughly 0.5: 0.5 by volume) by weight, and further 1% by weight or less. An inorganic binder material mainly composed of water glass (sodium silicate) was mixed, and mixed and ground for 144 hours by a wet ball mill using pure water as a solvent. After drying, pressure molding was performed, and then main firing was performed in the atmosphere at 400 ° C. for 4 hours to obtain a low thermal expansion composite.

As a result of measuring the linear thermal expansion coefficient by TMA and the thermal conductivity by the laser flash method for the produced low thermal expansion composite, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. is about 0.5 × 10. ⁻⁶ / ° C., and the thermal conductivity was about 8 W / mK.

(Example 6)
First, the calcined powder of HfMg (WO ₄ ) ₃ produced in Example 1 and the pulverized carbon nanotubes are 1.7: 1.0 by weight (approximately 0.3: 0.7 by volume). Then, an inorganic binder material mainly composed of 1% by weight or less of water glass (sodium silicate) was mixed, and mixed and ground for 144 hours by a wet ball mill using pure water as a solvent. After drying, pressure molding was performed, and then main firing was performed in the atmosphere at 400 ° C. for 4 hours to obtain a low thermal expansion composite.

As a result of measuring the linear thermal expansion coefficient by TMA and the thermal conductivity by the laser flash method, the linear thermal expansion coefficient in the temperature range from room temperature to 500 ° C. was about 1 × 10 ^−6. The thermal conductivity was about 15 W / mK.

  The low thermal expansion composite according to the present invention has low thermal expansion and high thermal conductivity, and is useful as a heat generating member, a heat transfer / heat dissipation member, a drive mechanism member around the engine, and the like. In particular, in an environment where the temperature is high, or in an environment where the temperature changes greatly, such as a low temperature or a high temperature, heat storage or the like becomes a problem, and a favorable effect can be obtained when applied to a portion that requires heat dissipation.

  It can also be applied to applications such as semiconductor components, their packages, and substrate materials.

Schematic sectional view as an example of the composite 10 of the embodiment according to the present invention Typical sectional drawing as an example of the conventional composite 20

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Low thermal expansion composite 101 Oxide (1) represented by composition formula I
102 Carbon material (2)
20 Conventional Composite 201 Oxide (1) Represented by Composition Formula I
202 Metal or metal oxide 203 Composition obtained by reacting oxide (1) with metal or metal oxide

Claims (6)

At least composition formula I: A ^{l +} _n (M ⁶⁺ O ₄ ) _m (A is a metal element having a valence of 1 or a plurality of metal elements having an average valence of 1 and M is a metal element having a valence of 6 or A plurality of metal elements having an average valence of 6, m and n representing the composition are integers of 1 or more, and satisfy the relational expression of l × n = 2 × m (1) And a carbon material (2). The low thermal expansion composite according to claim 1, wherein M of said oxide (1) is either tungsten or molybdenum. The low thermal expansion composite according to claim 1 or 2, wherein the oxide (1) has a negative coefficient of thermal expansion. The porous structure according to any one of claims 1 to 3, wherein A of the oxide (1) includes a positive divalent metal element and a positive tetravalent metal element. The low thermal expansion composite according to claim 1, wherein the carbon material (2) is graphite. At least the composition formula: A ^{l +} _n (M ⁶⁺ O ₄ ) _m (A is a metal element having a valence of 1 or a plurality of metal elements having an average valence of 1 and M is a metal element having a valence of 6 or an average A plurality of metal elements having a valence of 6, m and n representing the composition are integers of 1 or more, and satisfy the relational expression of l × n = 2 × m) (1) And a carbon material (2) are mixed and fired, and a method for producing a low thermal expansion composite.

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