JP2008063191A - Manufacturing method of metal boride fine powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable manufacturing method of a metal boride fine powder molding a thin film or a molded body having high transparency and also excellent conductivity and heat ray shielding property. <P>SOLUTION: The manufacturing method of the fine powder of the metal boride is composed of a first heat treating step wherein boron oxide and carbon are added to an oxide of at least one kind of metal selected from among a rare earth metal, a group IVa transition metal, a group Va transition metal and a group VIa transition metal, and wherein the carbon is added in an atomic ratio of ≥1.3 to the sum of the oxygen originated from the metal oxide and the boron oxide, and the mixture is fired in an inert gas atmosphere, a second heat treating step wherein a residual carbon is oxidized and decomposed at a temperature T<SB>2</SB>lower than a temperature T<SB>1</SB>in the first heat treating step and a third heat treating step wherein the treated matter is fired at a temperature lower than T<SB>1</SB>and higher than T<SB>2</SB>in the inert gas atmosphere. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a metal boride fine powder capable of forming a thin film or a molded article having transparency and excellent conductivity and heat ray shielding properties.

  Conventionally, conductive materials have been used as materials for forming transparent electrodes such as solar cells and liquid crystal displays, transparent conductive films such as electroluminescence displays and touch panels, or transparent heat-shielding films such as vehicle window glass and architectural glass. Widely used. As a technique for forming a transparent conductive film and a transparent heat ray shielding film, sputtering, vacuum deposition, CVD, etc. are generally used. However, these means are expensive in film formation apparatus, yield is poor, and productivity is low. There were also many problems. With the recent development of fine particle production technology, instead of these technologies, a method of forming a film by dispersing it in an organic resin by coating it with fine powder or forming it into a molded body has been developed. Alternatively, antimony-containing tin oxide (ATO) fine powder or tin-containing indium oxide (ITO) fine powder is known as a material suitable for the resin dispersion method. However, ATO cannot be used as an electrode material in terms of electrical conductivity, and remains in an antistatic application, and also has insufficient shielding ability in the near infrared region as a heat ray shielding material. Although both the function and the heat ray shielding function are excellent, the heat ray shielding function still has a problem with respect to the shielding ability in a wavelength region closer to visible light, and further has a problem of depletion of indium as a raw material. In view of such a situation, the present inventors have focused on metal borides as materials having advantages in both functions and costs over ATO or ITO, and as a result of intensive studies, they have reached the production method of the present invention. is there.

  Regarding the method for producing metal boride fine particles, for example, a method in which a metal boride powder prepared in advance in Patent Document 1 is made into ultrafine particles using an arc heat source in an inert atmosphere. And / or hydrates, or metal oxides obtained by heat treatment thereof, boron compounds and carbon are mixed, and then a manufacturing method is proposed in which heat treatment is performed at less than 1,500 ° C. in a vacuum or inert atmosphere. ing.

However, in the method described in Patent Document 1, the metal boride which is a raw material is disposed obliquely as both electrodes, an arc is generated between both electrodes, and metal boride vapor is generated from the raw material by this arc heat. This is a method for obtaining ultrafine particles, which is very complicated and is disadvantageous in terms of cost in terms of yield. Moreover, in the method described in Patent Document 2, a metal hydroxide and / or hydrate as a precursor, or a metal boride in which the particle size of the metal oxide obtained by heat-treating it is the final product It is necessary to optimize the conditions in the neutralization reaction at the time of preparing the precursor, and the final heat treatment temperature is set to less than 1,500 ° C. to prevent particle coarsening. In particular, the appropriate range is limited, and stable production has problems.
JP-A-2-59418 Japanese Patent Laid-Open No. 2005-1918

  The object of the present invention is to solve the above-mentioned problems and provide a method capable of stably producing a metal boride fine powder capable of forming a thin film or a molded article having transparency and excellent conductivity and heat ray shielding properties. There is to do.

The present invention relates to the following inventions.
1. Boron oxide and carbon are added to an oxide of at least one metal selected from a rare earth metal, a group IVa transition metal, a group Va transition metal, and a group VIa transition metal, and the carbon is derived from the metal oxide and boron oxide. Added at a ratio of atomic ratio of 1.3 or more with respect to the total amount of oxygen to be performed, and remains at a temperature T ₂ lower than the temperature T ₁ in the first heat treatment step and firing in an inert gas atmosphere. second heat treatment step of decomposing oxidation of carbon to further third manufacturing method of fine metal boride fines consisting of a heat treatment step of firing in an inert gas atmosphere at a temperature range exceeding T ₂ less than T _1.
2. 2. The method for producing fine metal boride powder according to 1 above, wherein the metal oxide is obtained by heat-treating a metal hydroxide which is a precursor thereof.
3. 2. The method for producing fine metal boride powder according to 1 above, wherein boric acid is used in place of boron oxide.

  According to the present invention, metal boride fine powder can be produced with simple operation, high yield, and stable production conditions.

The metal used for the metal oxide as a starting material in the present invention can be arbitrarily selected from metal elements selected from rare earth metals, IVa group transition metals, Va group transition metals and VIa group transition metals. Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, etc. as metals, Ti, Zr, Hf, etc. as group IVa transition metals, Va group transition metals V, Nb, Ta and the like, and VIa group transition metals include Cr, Mo, W and the like. Moreover, in this invention, what is obtained by heat-processing the metal hydroxide which is the precursor can also be used as said metal oxide.
These metal hydroxides and oxides may be commercially available, or by dissolving water-soluble compounds such as nitrates, sulfates, and chlorides in water and reacting them with an alkaline solution. The obtained hydroxide or the oxide obtained by further heat-treating the hydroxide may be used.

  In the present invention, boron oxide is used as the boron compound, but boric acid may be used. This is because, as will be described later, the first heat treatment step in which the boring reaction occurs is a treatment in a high temperature range exceeding at least 1,000 ° C. Even if boric acid is used as the boron compound, the boric acid is not treated with boron. This is because it is decomposed into boron oxide before the chemical reaction. The boron oxide added at this time is equivalent to the stoichiometric amount of the metal boride composition to be obtained with respect to the metal element, but may be added in a slight excess to improve the reactivity, and is usually 1.02 to 1.05 equivalents. It is preferable to set the degree.

In the present invention, carbon is used as a reducing agent, but the addition amount is important, and an atomic ratio of 1.3 or more is added to the sum of oxygen derived from the metal oxide and boron oxide. For example, when LaB ₆ is synthesized using La as a metal, the reaction formula is as follows. If 1 mol of LaB ₆ is to be obtained, the theoretical amount of carbon required is 10.5 mol. In the present invention, 1.3 times or more, that is, 13.65 mol or more is added.
0.5La ₂ O ₃ + 3B ₂ O ₃ + 10.5C → LaB ₆ + 10.5CO

  By adding carbon in an atomic ratio of 1.3 or more, a metal boride having a fine particle size capable of exhibiting desired transparency in the visible light wavelength region can be generated. Although the reason for achieving atomization by adding excess carbon is not clear, the boring reaction is a treatment in a high temperature region exceeding 1,000 ° C., and inevitably the coarsening of particles due to grain growth is promoted. It is thought that one factor is that excess carbon that does not contribute to reduction enters between the metal boride particles generated and acts as a buffer for grain growth. Therefore, if the amount of carbon added as the reducing agent is less than 1.3 in atomic ratio, the desired particle size cannot be obtained due to the remarkable particle coarsening due to grain growth. Further, if the atomic ratio is 1.3 or more, the upper limit is not particularly required, but it is preferably 3.0 or less, more preferably 1.5 or more and 2.5 or less in consideration of cost and removal of excess after boring. Is preferred. As the carbon source, carbon black such as lamp black, channel black, furnace black, etc., carbon produced by burning pitch coke, monosaccharides or polysaccharides can be used.

In the present invention, boron oxide and carbon as a reducing agent are added to the metal oxide in an atomic ratio of 1.3 or more with respect to the total oxygen derived from the metal oxide and boron oxide, and then a three-step heat treatment process is performed. That is, a first heat treatment step for firing in an inert gas atmosphere, a second heat treatment step for oxidizing and decomposing carbon remaining at a temperature T ₂ lower than the temperature T _{1 in the first} heat treatment step, and T ₁ It is a third heat treatment step for firing in an inert gas atmosphere at a temperature range lower than T ₂ and less than T ₂ , and through this three-step heat treatment step, a metal boride containing no fine particles and no unreacted components is obtained. Can do.

The first heat treatment step for firing in an inert gas atmosphere is a reaction step for boring metal hydroxide and / or metal oxide, and examples of the inert gas include rare gas, nitrogen, etc. Nitrogen is preferably a rare gas because it may react with a metal hydroxide or metal oxide, or boron to form a nitride. The heat treatment temperature T ₁ at this time is 1,000 ° C. or more and 1,600 ° C. or less, and if it is less than 1,000 ° C., the boride reaction is insufficient, and the metal hydroxide and / or metal oxide as an unborated product or Metal borate remains as an intermediate product, and in the temperature range exceeding 1,600 ° C., the effect of suppressing grain growth by excessively added carbon is impaired, resulting in generation of coarse particles, and high temperature. Heat treatment equipment is required, which is disadvantageous in terms of cost, including running costs. Although processing time is not specifically limited, 1 to 6 hours are preferable.

The particle size of the metal boride as a final product in the first heat treatment step is determined, also, although the particle size varies depending on the heat treatment temperature T _1, 1 primary particle Considering the transparency of case of the film The diameter is preferably adjusted to 20 to 100 nm, but a fine powder having a diameter of 20 to 40 nm is particularly useful. Since the particle size of the metal hydroxide and / or metal oxide as the starting material hardly reflects the particle size of the metal boride as the final product, the degree of freedom with respect to the starting material is extremely high, and the metal is stable under stable production conditions. A fine boride powder can be produced.

The subsequent second heat treatment step is a step for oxidatively decomposing carbon remaining at a temperature T ₂ lower than the temperature T ₁ in the first heat treatment step. The temperature T2 is preferably 400 ° C. or more and 900 ° C. or less. If the temperature T ₂ is less than 400 ° C., the remaining carbon is not sufficiently oxidized and decomposed, and if it exceeds 900 ° C., the generated metal boride is oxidized. Although processing time is not specifically limited, 1 to 6 hours are preferable. The atmosphere during the treatment may be atmospheric, but oxygen may be positively introduced.

The present invention further to conduct the calcination under inert gas atmosphere at a temperature range between the temperature T ₁ of the third temperature T ₂ in the second heat treatment step as a heat treatment step of the first heat treatment step. Those partially oxidized in the second heat treatment step by the treatment (for example, LaBO ₃ when La is used as the metal) and remaining unborides (for example, La ₂ O when La is used as the metal) ₃ ) can likewise be completely borated by reaction with the remaining boron oxide and carbon. As the inert gas, a rare gas and nitrogen can be exemplified, but a rare gas is preferable because nitrogen may react with a product to produce a nitride. Moreover, although processing time is not specifically limited, 1 to 6 hours are preferable.
Examples of the metal boride obtained in the present invention include ScB ₆ , YB ₆ , LaB ₆ , CeB ₆ , PrB ₆ , NdB ₆ , TiB ₂ , ZrB ₂ , VB ₂ , NbB ₂ , and WB. .
In the present invention, the target metal boride can be obtained with high purity. For example, the purity of the target product can be 96.0% by weight or more, particularly 98.0% by weight or more.

  Under the above conditions, a metal boride fine powder having transparency and capable of forming a thin film or molded article having excellent conductivity and heat ray shielding properties can be stably obtained.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1
200 g of 7% ammonia water was added over 20 minutes to 109.6 g of La (NO ₃ ) ₃ 6H ₂ O dissolved in water to form a precipitate, followed by aging for another 20 minutes. During this time, the liquid temperature was maintained at room temperature. What was dried at 150 ° C. after washing the obtained precipitate was a mixture of needle-like crystals and columnar crystals as shown in the electron micrograph of FIG. 1. From the X-ray diffraction pattern, La (OH) ₃ and Identified. Next, 54.5 g of B ₂ O ₃ and 49.0 g of carbon black (corresponding to the amount of oxygen atoms derived from La ₂ O ₃ and B ₂ O ₃ × 1.5) were added to the dried product and mixed in a ball mill. Heat treatment was performed at 1,400 ° C. for 3 hours in an atmosphere. Then, after air baking at 500 ° C. for 2 hours, heat treatment was further performed at 1,200 ° C. for 2 hours in an Ar gas atmosphere. The obtained processed product was a fine particle of 30 to 50 nm as shown in the electron micrograph of FIG. 2, and was identified as LaB ₆ from the X-ray diffraction pattern shown in FIG.

Example 2
To a solution obtained by dissolving 109.6 g of La (NO ₃ ) ₃ 6H ₂ O in water, 500 g of 2.8% aqueous ammonia was added over 3 hours to form a precipitate, and then the mixture was further aged for 30 minutes. During this time, the liquid temperature was maintained at 5 ° C. The obtained precipitate was washed, dried at 150 ° C., and then calcined at 500 ° C., as shown in the electron micrograph of FIG. 4, which is a mixture of needle-like crystals and columnar crystals, and an X-ray diffraction pattern Was identified as La ₂ O ₃ . Next, 55.5 g of B ₂ O _{3 and} 83.1 g of carbon black (corresponding to the amount of oxygen atoms derived from La ₂ O ₃ and B ₂ O ₃ × 2.5) were added to the fired product and mixed in a ball mill. Heat treatment was performed at 1,450 ° C. for 3 hours in an atmosphere. Then, after air baking at 600 ° C. for 3 hours, heat treatment was further performed at 1,100 ° C. for 2 hours in Ar gas atmosphere. The obtained processed product was 20 to 40 nm fine particles as shown in the electron micrograph of FIG. 5, and was identified as LaB ₆ from the X-ray diffraction pattern as in Example 1.

Example 3
Kishida Chemical Ltd. _La 2 _{O 3} (first grade reagent) 41.2 g boric acid _{(H 3} BO _{3) 96.7g} and oxygen atomic weight × 1 derived from carbon black 42.5g _(La 2 _{O 3} and _B 2 _{O 3} .3 equivalent) and mixing in a ball mill, the same three-stage heat treatment as in Example 1 was performed. The finally obtained processed material was fine particles of 20 to 50 nm, and was identified as LaB ₆ from the X-ray diffraction pattern.

Example 4
The same treatment as in Example 1 was carried out except that 96.9 g of Y (NO ₃ ) ₃ 6H ₂ O was used as the metal compound. The finally obtained processed product was a fine particle of 30 to 50 nm, and was identified as YB ₆ from the X-ray diffraction pattern.

Example 5
The same treatment as in Example 1 was carried out except that 65.6 g of ScCl ₃ .6H ₂ O was used as the metal compound. The finally obtained processed product was 40-70 nm fine particles, and was identified as ScB ₆ from the X-ray diffraction pattern.

Example 6
The same treatment as in Example 3 was carried out except that 42.6 g of Nd ₂ O ₃ (reagent grade 1) manufactured by Kishida Chemical was used as the metal compound. Finally obtained treated product is fine particles of 20 to 40 nm, were identified as NdB ₆ from X-ray diffraction pattern.

Example 7
250 g of 7% aqueous ammonia was added to 240 g of a 20% strength TiCl ₄ aqueous solution over 20 minutes to form a precipitate, followed by aging for another 20 minutes. During this time, the liquid temperature was maintained at room temperature. The obtained precipitate was washed and dried at 150 ° C. to obtain Ti (OH) ₄ . To this, 18.0 g of B ₂ O ₃ and 23.0 g of carbon black (corresponding to the amount of oxygen atoms derived from TiO ₂ and B ₂ O ₃ × 1.5) were added and mixed by a ball mill. Thereafter, the same three-stage heat treatment as in Example 1 was performed. The finally obtained treated product was fine particles of 60 to 100 nm, and was identified as TiB ₂ from the X-ray diffraction pattern.

Example 8
A solution of 68.4 g of NbCl ₅ dissolved in 1 L of 5% HCl aqueous solution was added with 650 g of 7% aqueous ammonia over 20 minutes to form a precipitate, followed by further aging for 20 minutes. During this time, the liquid temperature was maintained at room temperature. The obtained precipitate was washed and then dried at 150 ° C., and then B ₂ O ₃ 18.1 g and carbon black 25.5 g (the amount of oxygen atoms derived from Nb ₂ O ₅ and B ₂ O ₃ × 1.5 Equivalent) and mixed with a ball mill. Thereafter, the same three-stage heat treatment as in Example 1 was performed. The finally obtained processed product was a fine particle of 70 to 100 nm, and was identified as NbB ₂ from the X-ray diffraction pattern.

Example 9
Add 29.2 g of B ₂ O ₃ and 18.1 g of carbon black (corresponding to the amount of oxygen atoms derived from WO ₃ and B ₂ O ₃ × 1.3) to 58.7 g of WO ₃ (Reagent grade 1) manufactured by Kishida Chemical Then, the same three-stage heat treatment as in Example 1 was performed. The finally obtained processed product was fine particles of 50 to 70 nm, and was identified as WB from the X-ray diffraction pattern.

Comparative Example 1
The experiment was carried out in the same manner as in Example 1 except that the amount of carbon black used was 39.2 g (corresponding to the amount of oxygen atoms derived from La ₂ O ₃ and B ₂ O ₃ × 1.2). The finally obtained processed product was identified as LaB ₆ from the X-ray diffraction pattern in the same manner as in Example 1. However, as shown in the electron micrograph of FIG.

Comparative Example 2
The experiment was performed in the same manner as in Example 1 except that the third heat treatment step was omitted. The final product obtained had the same particle size as that of Example 1 in terms of particle size, but contained about 10% by weight of LaBO ₃ in addition to LaB _{6 as} indicated by the X-ray diffraction pattern of FIG. It was a thing.

  Table 1 summarizes the physical properties of the products obtained in the above Examples and Comparative Examples.

The product according to _{La (NO 3) 3 6H 2} O and aqueous ammonia Example 1, an electron microscope photograph of dried at 0.99 ° C.. The electron micrograph of the final product obtained by Example 1. The X-ray diffraction pattern of the final product obtained by Example 1. An electron micrograph of the product of La (NO ₃ ) ₃ 6H ₂ O and aqueous ammonia of Example 2 dried at 150 ° C. and then calcined at 500 ° C. in the atmosphere. The electron micrograph of the final product obtained by Example 2. The electron micrograph of the final product obtained by the comparative example 1. The X-ray diffraction pattern of the final product obtained by Comparative Example 2.

Claims (3)

Boron oxide and carbon are added to an oxide of at least one metal selected from a rare earth metal, a group IVa transition metal, a group Va transition metal, and a group VIa transition metal, and the carbon is derived from the metal oxide and boron oxide. Added at a ratio of atomic ratio of 1.3 or more with respect to the total amount of oxygen to be performed, and remains at a temperature T ₂ lower than the temperature T ₁ in the first heat treatment step and firing in an inert gas atmosphere. second heat treatment step of decomposing oxidation of carbon to further third manufacturing method of fine metal boride fines consisting of a heat treatment step of firing in an inert gas atmosphere at a temperature range exceeding T ₂ less than T _1. 2. The method for producing a metal boride fine powder according to claim 1, wherein the metal oxide is obtained by heat-treating a metal hydroxide which is a precursor thereof. 2. The method for producing fine metal boride powder according to claim 1, wherein boric acid is used in place of the boron oxide.

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