JP5448673B2 - Method for producing composite oxide nanoparticles - Google Patents

Description

  The present invention relates to a method for producing novel composite oxide nanoparticles.

  Complex oxide particles represented by perovskite type compounds have many material properties such as ferroelectricity, thermoelectric conversion, superconductivity, electron / ion conductivity, catalytic functionality, etc., as functional inorganic materials and their raw materials. Widely used.

  In recent years, various ultrafine particles (nanoparticles) having a particle diameter of 100 nanometers or less have been studied for the purpose of further enhancing the functions of these composite oxide particles. Examples of the method for producing nanoparticles include a spray pyrolysis method, a coprecipitation method, a reverse micelle method, a hot soap method, a sol-gel method, a solvothermal method, and a hydrothermal method.

  Among them, the spray pyrolysis method, coprecipitation method, and reverse micelle method can control the particle size according to the synthesis conditions, and although highly crystallized particles can be obtained, the particles are agglomerated under high temperature conditions. Since crystallization is performed, only aggregated particles can be obtained, and only those having a large particle size can be obtained.

  The hot soap method is a method of controlling the growth of metal oxide crystals using adsorption and decomposition of a surfactant on the surface of a metal oxide precursor in a high boiling point surfactant. In the hot soap method, although nanoparticles having good crystallinity and dispersibility can be obtained, a high temperature of about 300 ° C. is usually required for synthesis, and the solvent itself is a surfactant. There was a problem that impurities such as decomposition products of surfactants were easily taken up.

  Furthermore, the sol-gel method is one of the most commonly used metal oxide synthesis methods, and there are many research examples. Specifically, it is a method of obtaining metal oxide nanoparticles by hydrolyzing a metal alkoxide that is a metal oxide precursor in the presence of a catalyst, and nano-sized particles that are relatively close to monodispersion are obtained. However, the sol-gel method has problems in that the crystallinity is insufficient because it is synthesized at a low temperature, and a large amount of unreacted components remain.

  Solvothermal methods (Patent Documents 1 to 3) and hydrothermal methods (Non-Patent Documents 1 and 2) have been proposed as methods for solving the above-described problems and having relatively high crystallinity and capable of controlling the particle shape to some extent. Has been. In any of these, a solvent and a composite oxide raw material are sealed in a pressure vessel called an autoclave and placed at a high temperature of 50 to 500 ° C. to perform a reaction under high temperature and high pressure. However, in the solvothermal method, although the particle shape can be controlled to a substantially cubic shape, it is essential to include an organic solvent in the reaction system, and the load on the environment is large, and the particle shape is still not sufficiently controlled. It was hard to say. On the other hand, in the hydrothermal method, a reaction that preferentially dissolves from the corner portion having a large interface energy occurs simultaneously with the growth along the cubic shape, which is the original shape of the crystal, due to the presence of water. It was difficult to get.

JP 2007-269601 A JP 2008-030966 A JP 2008-230872 A

“Journal of Crystal Growth”, 281 pages, 669 pages, 2005 “Journal of the Ceramic Society of Japan”, Volume 103, p. 1220, 1995

  As described above, attempts have been made to produce composite oxide nanoparticles by various methods, but particles that do not use an organic solvent with a large environmental burden and obtain a cubic shape that is the original shape of the particles with higher crystallinity. It was difficult to say that there was a manufacturing method that realized shape control.

As a result of intensive studies to solve the above problems, the present inventors have made a hydrothermal reaction between a strontium compound and a water-soluble group 4 metal compound in the presence of an amphiphilic compound and a metal element-free basic compound. As a result, it was found that the particle size and shape are highly controlled, and that it is possible to produce extremely high quality composite oxide nanoparticles that are less likely to cause aggregation of the particles, and the present invention has been completed.

That is, the present invention provides a composite oxide nanoparticle produced by hydrothermal reaction of a strontium compound and a water-soluble group 4 metal compound in the presence of an amphiphilic compound and a metal element-free basic compound. Is the method.

  According to the present invention, it is possible to obtain composite oxide nanoparticles with highly controlled crystallization and particle shape (particularly cubic shape) using water with a small environmental load as a solvent.

1 is an electron micrograph showing the particle shape of the composite oxide nanoparticles obtained in Example 1. FIG.

The strontium compound used in the present invention is not particularly limited as long as it is a compound containing strontium, and known compounds can be used .

Specific examples of such compounds include strontium hydroxide, strontium nitrate, strontium chloride, strontium bromide, strontium acetate, strontium di (methoxyethoxide), strontium dipivaloylmethanonote, strontium formate, Examples include strontium acid and strontium sulfate .

Among them, strontium hydroxide is useful in that it does not contain an acidic group that may be an obstacle when producing the composite oxide nanoparticles of the present invention, and is particularly preferably used.

As the water-soluble group 4 metal compound used in the present invention, a water-soluble compound containing a group 4 metal can be used without any particular limitation. In view of the remarkable effects of the present invention, water-soluble group 4 metal compounds such as titanium, zirconium and hafnium are more preferable.

Examples of water-soluble Group 4 metal compounds that can be used in the present invention include Group 4 metal chlorides such as titanium trichloride and titanium tetrachloride, Group 4 metal sulfates such as titanyl sulfate, and water-soluble compounds such as titanium peroxocitrate complexes. Although a group 4 metal complex etc. are mentioned, A water-soluble group 4 metal complex is more preferable from the viewpoint of stability and the like.

Such water-soluble group 4 metal complexes include chelating agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), 2,2′-bipyridyl (bpy), diethylenetriaminetetraacetic acid (DTPA); citric acid, Hydroxycarboxylic acids such as lactic acid, tartaric acid, malic acid, hydroacrylic acid, glyceric acid; and carboxylic acids such as succinic acid, oxalic acid, maleic acid, malonic acid, acrylic acid, propionic acid, acetic acid; glycine, alanine, serine In addition, a complex in which a Group 4 metal is stabilized with amino acids such as glutamic acid, aspartic acid, and cysteic acid can be exemplified.

Specifically, ammonium peroxocitrate ammonium, titanium peroxomalate ammonium, titanium peroxotartrate ammonium, titanium peroxoglycolate ammonium, titanium peroxoglycolate ammonium, titanium peroxoEDTA ammonium, tantalum peroxocitrate ammonium, tantalum peroxomalate ammonium, tantalum Ammonium peroxotartrate, ammonium tantalum peroxo lactate, ammonium tantalum peroxoEDTA, ammonium niobium peroxocitrate, ammonium niobium peroxomalate, ammonium niobium peroxotartrate, ammonium niobium peroxolactate, niobium peroxoEDTA ammonium, titanium peroxoserine ammonium, titanium peroxo Carboxylic acids such as ammonium stain acids, amino acids, water-soluble Group 4 metal complexes and their ammonium complexes such as complexes obtained by coordinating a chelating agent, and the like.

When the amount of the strontium compound and the water-soluble group 4 metal compound is too small, the amount of the obtained composite oxide nanoparticles decreases, and when the amount is too large, the generation of impurities increases. / Liter) to 5000 mM (mmol / liter), preferably 1 mM (mmol / liter) to 2000 mM (mmol / liter).

Further, the amount (molar ratio) of the strontium compound and the water-soluble group 4 metal compound is not particularly limited, but is generally in the range of 1: 100 to 100: 1, preferably 1:10 to 10: 1. The molar ratio of elements in the target compound is most preferable.

  The amphiphilic compound used in the present invention is not particularly limited as long as the compound has a hydrophilic group and a hydrophobic group, and a known compound can be used without limitation. For example, compounds that become anions when dissociated in water, such as alkyl carboxylic acids, alkyl sulfonic acids, and alkyl phosphate compounds, compounds that become cations when dissociated in water, such as alkyl ammonium compounds, polyethylene glycol and polyvinyl alcohol And polymer compounds that do not dissociate in water. Among them, from the viewpoint of safety to the environment and easy availability, compounds that become anions when separated in water, such as alkyl carboxylic acids, alkyl sulfonic acids, and alkyl phosphate compounds, can be preferably used. Alkylcarboxylic acids that do not contain undesirable sulfur and phosphorus as impurities when using composite oxide nanoparticles are more preferred.

  Examples of alkyl carboxylic acids preferably used as amphiphilic compounds in the present invention include propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, Saturated fatty acids such as arachidic acid, behenic acid, lignoceric acid, α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, oleic acid, And unsaturated fatty acids such as elaidic acid, erucic acid, and nervonic acid. Among these, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, which is a saturated fatty acid having a hydrocarbon chain having 6 to 20 carbon atoms, and a hydrocarbon chain having 6 to 20 carbon atoms. Saturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid and the like are preferably used. Furthermore, oleic acid can be most preferably used because it has a particularly high effect on the present invention and has little biological harm.

The compounding amount of the amphiphilic compound is not particularly limited and may be appropriately set according to the target compound. However, when the compounding amount is small, the effect of the present invention is not exhibited, and the obtained composite oxide nanoparticles If the particle size becomes large and, on the contrary, too large, the target substance may not be obtained. Therefore, in general, it is 0 with respect to the total molar amount of the strontium compound and water-soluble group 4 metal compound as raw materials. The amount is preferably 0.01 to 100 times the molar amount, more preferably 0.1 to 10 times the molar amount.

  The metal element-free basic compound used in the present invention is not particularly limited as long as it shows basicity in an aqueous solution, and any known compound can be used without limitation. For example, basic organic compounds having no metal elements such as quaternary ammonium compounds, amine compounds, ammonia, pyridine and derivatives thereof, and hydrazine and derivatives thereof can be used. Among these, hydrazine and its derivatives or amine compounds are preferably used because they do not contain metal impurities that adversely affect the performance of the composite oxide particles of the present invention and are relatively easy to handle.

  Specific examples of the metal element-free basic compound preferably used in the present invention include hydrazine derivatives such as hydrazine, 1-monomethylhydrazine, 1,1-dimethylhydrazine and 1-ethyl-2-methylhydrazine; methylamine Primary amines such as ethylamine, n-propylamine and ethanolamine; secondary amines such as dimethylamine and diethylamine; tertiary amines such as trimethylamine and triethylamine. Among these, a hydrazine derivative is more preferable, and hydrazine is most preferable because the effect on the shape control of the composite oxide particles of the present invention is more remarkable.

  Two or more of these metal element-free basic compounds can be used in combination, but the use of hydrazine or a derivative thereof as one of them can control the shape of the resulting composite oxide nanoparticles into a cube. Is preferable.

The compounding amount of the non-metal element-containing basic compound is not particularly limited, and may be set as appropriate according to the target compound. However, when the compounding amount is small, the effect of the present invention is not exhibited, and the obtained composite oxide Since the target particle may not be obtained if the particle size of the nanoparticle is too large and too large, it is generally based on the total molar amount of the strontium compound and water-soluble group 4 metal compound that are the raw materials. It is 0.0001-10000 times mole amount, and it is preferable that it is 1-1000 times mole amount.

  Although there is no restriction | limiting in particular in the water used for the hydrothermal reaction of this invention, Usually, water which does not contain impurities, such as ion-exchange water, demineralized water, distilled water, tap water, can be used conveniently, for example.

  Moreover, another solvent can be added to the water used by this invention in the range which does not impair an effect. As the solvent, a known solvent can be used without particular limitation, and an organic solvent of 10% by volume or less, preferably 3% by volume or less can be used with respect to water. Such solvents include hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, acetals, ketones, esters, etc., among which methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone. A water-soluble organic solvent such as is preferably used.

The method for producing composite oxide nanoparticles of the present invention comprises a strontium compound and a water-soluble group 4 metal compound as raw materials for composite oxide nanoparticles, together with an amphiphilic compound, a metal element-free basic compound, and water. It is possible to employ a method of sealing in a heat-resistant and pressure-resistant container called an autoclave, and generally holding it at 50 to 300 ° C. for 0.5 to 72 hours.

  If the reaction temperature is too low, the crystal quality will be low, and if the reaction temperature is too high, the resulting particles will be large and the particle shape may not be controllable, so the reaction temperature is generally 50 to 300 ° C. It is preferably 80 to 250 ° C. In addition, if the reaction time is too short, the target crystal cannot be obtained, and if the reaction time is too long, the production efficiency is lowered and the resulting particles may be increased. Preferably, it is from 72 hours.

  In the present invention, it is not always clear what role each component plays, but when the basic compound containing no metal element controls the crystal shape generated by controlling the pH in the reaction system Conceivable. In addition, the amphiphilic compound contributes to obtaining the nanoparticles of the present invention by suppressing crystal growth by adsorbing to the surface of the generated crystal in the middle of the reaction. It is thought that it has the effect which prevents aggregation of particle | grains by staying.

  In the present invention, the pH of water as a reaction field is preferably adjusted to 7.5 to 14 in terms of controlling the crystal shape of the composite oxide nanoparticles. For this purpose, the amount of the basic compound not containing a metal element may be appropriately set according to the basic strength of the compound, but is generally 1 μM to 12M. As a specific method for adjusting the pH, a method of checking the pH at any time while adding a metal element-free basic compound is simple.

  The composite oxide nanoparticles produced by the production method of the present invention have an average particle diameter of 1 to 60 nm, preferably 1 to 30 nm, more preferably 8 to 20 nm, are in a cubic shape, and are generally composite. It consists of a single phase of oxide. In addition, since the surface is modified with an amphiphilic compound, the particles are less likely to aggregate.

  The composite oxide nanoparticles produced by the production method of the present invention are not particularly limited and can be used for known applications. For example, thermoelectric conversion materials, photocatalysts, ion conductive materials, ferroelectric materials, magnetic materials, It can be used for applications such as a catalyst material, an oxygen electrode material, a piezoelectric material, a pyroelectric material, a nonlinear optical material, and a filler.

  EXAMPLES Hereinafter, although an Example shows this invention concretely, this invention is not limited at all by these Examples.

Abbreviations of the compounds used in the examples are shown below.
(1) Strontium compound Sr-H: Strontium hydroxide Sr-N: Strontium nitrate
Sr-A: Strontium acetate (2) Water-soluble group 4 metal compound TALH: Titanium peroxoammonium lactate TACH: Titanium peroxoammonium citrate TAGH: Titanium peroxoglycolate (3) Amphiphilic compound OA: Oleic acid LA: Linoleic acid SA: Stearic acid (4) Metal element-free basic compound TMA: Tetramethylammonium HYD: Hydrazine MHYD: 1-Monomethylhydrazine MA: Methylamine Example 1
In a 50 mL (milliliter) Teflon container, 25 mL of water and 25 mM (mmol / liter) titanium peroxoammonium lactate (TALH), 25 mM (mmol / liter) strontium hydroxide (Sr -H) was added, and the pH was adjusted to 13.5 using tetramethylammonium (TMA) 1.8 M (mol / liter). Further, 100 mM (mmol / liter) oleic acid (OA) and 4 mM (mmol / liter) hydrazine (HYD) were added, and heat treatment was performed in a thermostatic bath at 200 ° C. for 24 hours.

The obtained powder was collected and observed with a transmission electron microscope (“H-800” manufactured by Hitachi High-Technologies Corporation) at an observation magnification of 300,000 times. As a result, cubic particles with an average particle diameter of 9 nm were generated. It was confirmed that there was no aggregation between the particles. A transmission electron micrograph (magnification: 300,000 times) of the obtained particles is shown in FIG. Moreover, it was confirmed that the crystal | crystallization of the obtained powder was strontium titanate by the powder X-ray-diffraction apparatus (RINT2100 by Rigaku Corporation).
Example 2-12, Comparative Example 1 and 2
A composite oxide was obtained by performing a hydrothermal reaction in the same manner as in Example 1 except that the raw materials and reaction conditions shown in Tables 1 and 2 were used. The results are shown in Tables 1 and 2.

Claims (1)

A method for producing composite oxide nanoparticles, comprising hydrothermally reacting a strontium compound and a water-soluble group 4 metal compound in the presence of an amphiphilic compound and a metal element-free basic compound.