JP2006096651A - Method for manufacturing inorganic oxide material, inorganic oxide material, and carbon-metal compound oxide material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a silica nanotube or an inorganic oxide nano material other than silica in a diversity of shapes, and to provide a new composite material using it. <P>SOLUTION: In the method for manufacturing the inorganic oxide material, a substrate structure obtained by comprising a step of depositing an inorganic oxide precursor on a substrate, a step of making the inorganic oxide precursor into the inorganic oxide, and a step of oxidation removal of the substrate is used as a template. The inorganic oxide material can have a hexagonal cross-sectional shape, and can carry a metal selected from among Cu, Ni, Ag, Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, Ca, or mixtures of them. Furthermore, a carbon-inorganic oxide composite material containing carbon nanofiber attached to at least the inside wall or the outside wall of the inorganic oxide material can be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel method for producing a nano-sized inorganic oxide material, an inorganic oxide material having a novel form produced by the method, and a carbon-inorganic oxide composite material.

  Since the discovery of carbon nanotubes, synthesis and application of various materials having a nanotube structure have been studied. Among them, the template method is a typical method for synthesizing silica nanotubes. In general, this method uses an organic substance such as a quaternary ammonium surfactant as a template material, and alkoxysilane or the like as a raw material sol and is synthesized by a sol-gel method (Patent Document 1) or on a template such as a carbon nanotube or anodized alumina. Has been synthesized by hydrolyzing tetraethoxysilane or the like (Non-patent Document 1).

  However, these templates have problems such as (1) since the shape of the template is uniform, there is no diversity in the shape of the generated silica nanotubes, and (2) the cost of the template is high. Although there have been many reports on the synthesis of silica nanotubes, there are very few examples of their application, and the application of inorganic nanotubes other than silica nanotubes and silica with nanoscale hollow structures is expected. In addition, a novel material system in which metal particles are supported only on the outer wall or inner wall of an inorganic oxide nanomaterial other than silica nanotube or silica is not known.

  Further, if it becomes possible to produce branched carbon nanofibers attached only to the outer wall or inner wall of silica nanotubes or inorganic oxide nanomaterials other than silica using these new material systems, a novel catalyst material Application to environmental purification materials, electron emission materials, electromagnetic wave absorbers, etc. is expected, but no such composite materials have been proposed to date. On the other hand, the present inventors have conventionally studied synthesis of carbon nanofibers (hereinafter referred to as CNF) having a nano-sized diameter by hydrocarbon decomposition on a metal catalyst (Non-patent Document 2). These CNFs are characterized by being obtained at a low temperature of about 500 ° C. using an inexpensive metal Ni catalyst, methane or the like. Furthermore, it has been found that CNFs having various shapes can be synthesized by controlling reaction conditions and the like. In addition, until now, a method for highly controlling the loading on the nano-sized inorganic oxide material has not been developed, and a specific reaction can be caused by controlling the loading of the metal. Application as a novel nano-sized catalyst is expected.

JP 2000-256007 A Mitchell et al., J. Am. Chem. Soc. 2002, 124, 11864. S. Takenaka, S. Kobayashi, H.H. Ogihara, and K. Otsuka J. Catal. 217 (2003) 79.

  The present invention has been made in view of the above-described prior art, and more generally, an object thereof is to provide an inorganic oxide material having a novel morphology.

  Another object of the present invention is to produce an inorganic oxide having a hollow structure such as a silica nanotube by using CNF generated from hydrocarbon decomposition as a template, and thus the problems (1) shown in the prior art. The object is to solve (2).

  Further, another object of the present invention is to provide a novel inorganic oxide in which metal particles are supported on the inner wall or the outer wall of an inorganic oxide material on silica nanotubes prepared using the CNF as a template material or an inorganic oxide material other than silica. It is to provide material.

  Still another object of the present invention is to support the inorganic oxide material supporting the metal particles by supporting the metal particles, and branching CNF from the outer wall or inner wall of the silica nanotube or the like supporting the metal particles. It is providing the carbon-inorganic oxide composite material containing this.

  The present invention relates to a material having oxidation resistance by using carbon nanofibers that can be removed by oxidation as a substrate, and a material having novel morphological characteristics, preferably by growing an inorganic oxide material. It was made based on the idea that it can be provided.

  The inorganic oxide material produced according to the present invention has a high aspect ratio and has a hollow structure. For this reason, it is possible to carry metal particles on either or both of the inner wall and the outer wall, and it is possible to control the metal adhesion to the inner wall or the outer wall according to the present invention.

  In addition, a fine structure such as a carbon nanofiber having a higher aspect ratio can be grown on the inorganic oxide material, and higher-order form control becomes possible.

  In the present invention, for example, silica nanotubes are prepared by using carbon nanofibers (CNF) of 1 to 100 nm generated by catalytic decomposition of carbon hydrogen as templates, and mixing these CNFs and organosilicon compounds such as tetraethoxysilane (TEOS). This is achieved by obtaining silica nanotubes having a wavelength of 1 to 600 nm by removing CNF by air baking after heating under a flow of argon or the like.

  In addition, as a hollow inorganic oxide material other than silica, for example, CNF is immersed and mixed in a sol solution obtained by hydrolysis of titanium alkoxide or zirconium alkoxide, and after filtration and washing, air firing is performed in the same manner as described above. By removing CNF by this, a hollow titanium oxide material or zirconium oxide material can be obtained.

  In the present invention, for example, an inorganic oxide material in which metal particles selected from iron, cobalt, nickel, platinum, palladium, platinum, and the like are included in the inner wall of a silica nanotube is an inorganic oxide material manufactured according to the present invention. Is immersed in an aqueous metal salt solution. Subsequently, when the sample is subjected to suction filtration, the sample is subjected to a washing treatment, and the dried sample is reduced with hydrogen or the like and then air baked.

  In order to support the metal on the outer wall of the inorganic oxide material, CNF coated with the inorganic oxide material is placed in the aqueous metal salt solution, heated and stirred, and the dried sample is reduced with hydrogen or the like. It is manufactured by performing air firing, removing CNF, and supporting the metal only on the outer wall.

  Furthermore, according to the present invention, an inorganic oxide material carrying a metal on the inner wall or the outer wall is installed in a fixed bed flow type reactor, and hydrocarbons such as methane are allowed to flow for a predetermined time at a high temperature to catalytically decompose the hydrocarbons. By doing so, a carbon-inorganic oxide composite material in which CNF is grown from the outer wall or the inner wall is provided.

That is, according to the present invention,
Attaching an inorganic oxide precursor to a solid substrate;
Converting the inorganic oxide precursor to an inorganic oxide;
And a step of oxidizing and removing the substrate. A method for producing a hollow inorganic oxide material using the structure of the substrate as a template can be provided.

  In the present invention, the substrate may be a carbonaceous material. The carbonaceous material of the present invention can be a material having a high aspect ratio of 1 to 600 nm. The substrate is preferably a carbon nanofiber. Further, the step of attaching the inorganic oxide precursor to the substrate may include the step of supporting the inorganic oxide precursor on the substrate. Further, the inorganic oxide material is selected from Cu, Ni, Ag, Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, Ca, or a mixture thereof. Metal can be supported.

  According to the second configuration of the present invention, a hollow structure inorganic oxide material having a size of 1 to 600 nm and a high aspect ratio is provided. In the present invention, the inorganic oxide material may have a hexagonal cross section. In the present invention, a metal selected from the group consisting of Cu, Ni, Ag, Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, and Ca, or a mixture thereof. The selected metal can be supported.

  In the third configuration of the present invention, a carbon-inorganic oxide composite material including carbon nanofibers attached to at least an inner wall or an outer wall of the inorganic oxide material described above can be provided.

  According to the present invention, shape control can be achieved on a nano scale, metal loading control can be performed, and a method for producing an inorganic oxide material having a novel morphology with carbon nanofibers attached to the outer wall or inner wall Inorganic oxide materials and carbon-inorganic oxide composite materials can be provided.

Hereinafter, embodiments of the present invention will be described.
[Create template]
[Carbon nanofiber production catalyst]
In the present invention, a carbonaceous substrate that is solid and can be removed by oxidation can be used as the template (substrate). Examples of such a substrate include carbon black, carbon fiber, or carbon nanofiber. From the viewpoint of effectively producing a specific morphology and an inner wall or an outer wall, carbon nanofiber (hereinafter referred to as CNF). It is preferable to use as The CNF used can be produced using production methods known so far. More specifically, as the carrier for the catalyst for producing CNF, carbon fiber produced by hydrocarbon decomposition (Japanese Patent Application Laid-Open No. 2004-074060), silica, titania, Y-type zeolite, zirconia, magnesia, alumina, diamond oxide Conventionally known carriers such as JP-A-2003-112050 can be used.

  Moreover, as a catalyst for carbon nanofibers produced by the hydrocarbon decomposition method, iron group metals such as iron, cobalt, and nickel described in JP-A-2004-074060 and JP-A-2003-111050 are preferable. Nickel exhibiting high activity is particularly preferred.

  The amount of the iron group metal supported is preferably 5 to 90% by mass with respect to the entire catalyst from the viewpoint that the amount of carbon atom deposition per active component atom until the catalyst is completely deactivated in the decomposition of hydrocarbons is high. 10-70 mass% is more preferable, and 20-50 mass% is further more preferable.

  In the production of the catalyst supporting the iron group metal of the present invention, the above-described support is immersed in a solution of an iron group metal salt of nickel, cobalt, or iron. As the solution, an aqueous solution or a solution using an organic solvent can be used. As the aqueous solution, for example, a nickel nitrate aqueous solution, a cobalt nitrate aqueous solution, an iron nitrate aqueous solution, or the like can be used. As the organic solvent, for example, acetone, ketone solvents such as methyl ethyl ketone and diethyl ketone can be used. When silica or the like having high surface hydrophilicity is used as the carrier, an aqueous solution is preferable. However, when carbon fiber or the like having high surface hydrophobicity is used, hydrated iron group metal ions are dispersed and adsorbed on the carbon carrier. Since it is difficult to do so, it is more preferable to use an acetone solvent or the like because the surface of the carbon fiber is well wetted with acetone when acetone with weak polarity is used as the solvent.

The catalyst is impregnated with a solution of an iron group metal salt, and then dried by evaporating the solvent while stirring the mixed solution (heating as necessary). When an aqueous solution is used as the solution, it can be evaporated by heating to about 80 ° C. to about 100 ° C. Hydrogen is passed through the prepared sample at about 300 ° C. to 500 ° C., and the metal salt on the support is reduced to metal. By the above-described treatment, a catalyst carrier for producing CNF in which iron group metal particles are present can be prepared. Among these, a Ni / SiO ₂ catalyst is more preferable because it has high activity and the catalyst can be easily regenerated.

  The particle size of the supported iron group metal is preferably in the range of 10 to 100 nm, particularly 20 to 80 nm, from the viewpoint that the life of the catalyst until the activity is completely deactivated is long. When hydrocarbons are decomposed on the catalyst for producing CNF of the present invention, CNF having a diameter corresponding to the particle diameter of the metal can be grown, and the metal particles of 20 to 80 nm can grow carbon nanofibers most efficiently. It is. The metal particles outside this range are deactivated relatively quickly although CNF is grown to some extent.

[Manufacturing CNF]
The CNF used in the present invention can be produced by decomposing a hydrocarbon by heating the hydrocarbon to about 400 ° C. to about 600 ° C. in the presence of the CNF production catalyst obtained as described above. . In this case, hydrogen gas is generated with the production of CNF. Although it does not specifically limit as hydrocarbon which can be used in order to manufacture CNF by this invention, C1-C10 linear or branched aliphatic hydrocarbons, such as methane, hexane, and octane, are preferable. Moreover, a C1-C10 alicyclic hydrocarbon and aromatic hydrocarbon can also be used suitably. The produced CNF can be immersed in, for example, a concentrated nitric acid aqueous solution, heated and stirred, and after filtering and washing CNF, a template for silica nanotube synthesis can be obtained.

[Production of inorganic oxide material having hollow structure: Silica nanotube]
CNF obtained by hydrocarbon decomposition generally has a strong surface hydrophobicity and cannot be used as a template for synthesizing silica nanotubes as it is. Therefore, CNF having a hydrophilic surface can be produced by functionalizing the CNF surface with a hydroxyl group (OH), carboxyl group (COOH) or the like, and this can be used as a template for silica nanotube synthesis. In order to functionalize the CNF surface, a method using a conventionally known oxidizing agent, alkoxide silane, or the like is possible. Separately from this, the produced CNF can be heated / stirred in a concentrated nitric acid aqueous solution, washed and dried to generate a site for adsorbing the inorganic oxide precursor described later.

  CNF with functionalized CNF surface and organosilicon compounds including alkoxysilanes such as tetraethoxysilane mentioned above are stirred in a saturated water vapor atmosphere and the alkoxysilanes and metal alkoxy compounds are stirred to hydrolyze the alkoxy compounds. Silica nanotubes can be obtained by heat treating the filtered and dried sample in an inert atmosphere such as Ar and then removing CNF by firing with air. The air baking temperature is preferably in the range of 400 ° C to 1000 ° C.

  In addition, the hollow inorganic oxide material that can be produced in the present invention has a length of several hundred to several thousand nm, an outer diameter in a range of about 1 to 600 nm, and an aspect ratio of about 10 It can be made into the range of-several hundred.

[Production of inorganic oxide materials having hollow structure: titanium oxide nanotubes and zirconium oxide nanotubes]
By using an organic metal compound such as another metal alkoxide or metal soap as the inorganic oxide precursor, an inorganic oxide material containing the target element can be produced in the present invention. For example, in the present invention, a sol solution of titanium oxide or zirconium oxide can be obtained by hydrolyzing titanium alkoxide or zirconium alkoxide. CNF was immersed in this oxide sol solution, and the oxide sol was adsorbed by CNF. Titanium oxide nanotubes or zirconium oxide nanotubes can be obtained by air baking after filtration and drying to remove CNF.

In the present invention, an organosilicon compound can be used as the organosilicon compound used for producing the silica nanotube, and the organosilicon compound that can be used in the present invention is represented by the general formula R _a Si (OR ′ ) The organosilicon compound represented by _4-a can be raised. In the above general formula, R is a vinyl group, an aryl group, an acrylic group, an alkyl group having 1 to 8 carbon atoms, a hydrogen atom or a halogen atom, and R ′ is a vinyl group, an aryl group, an acrylic group, or a carbon number of 1 to 8. An alkyl group, —C ₂ H ₄ OC _n H _{2n + 1} (n = 1 to 4) or a hydrogen atom, and a is an integer of 0 to 3. ) Is preferred.

  Examples of the organosilicon compounds described above include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, and methyltriisopropoxy. Conventionally known compounds such as silane, vinyltrimethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane can be used.

Moreover, as an organic titanium compound such as titanium alkoxide, which is a material for producing a titanium oxide nanotube, a compound represented by the general formula R _a Ti (OR ′) _3-a can be used. In the above general formula, R is a vinyl group, an aryl group, an acrylic group, an alkyl group having 1 to 8 carbon atoms, a hydrogen atom or a halogen atom, and R 'is a vinyl group, an aryl group, an acrylic group, or a carbon number of 1 to 8 An alkyl group, —C ₂ H ₄ OC _n H _{2n + 1} (n = 1 to 4) or a hydrogen atom, and a is an integer of 0 to 2. ) Is preferred. Specific examples of the organic titanium compound include titanium trimethoxide, titanium triethoxide, titanium tri-n-propoxide, titanium tri-i-propoxide, titanium tri-n-butoxide, titanium tri-sec-butoxide. , Titanium tri-tert-butoxide, isopropoxybis (ethyl acetoacetate) titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium, tetrakis (2-ethylhexyloxy) titanium, tetrastearyloxy titanium, tetrastearyloxy titanium, tetramethoxy A known titanium alkoxide compound such as a tetraalkoxide titanium compound such as titanium can be used.

  Furthermore, materials such as zirconium alkoxide and aluminum alkoxide can also be used. Specific examples of organometallic compounds that can be used for this purpose include, for example, aluminum isopropylate, aluminum trisecondary butoxide, mono- Examples include trialkoxyaluminum compounds such as butoxyaluminum diisopropylate, and tetraalkoxyzirconium compounds such as diacetylacetone tributoxyzirconium and tetra-n-butoxyzirconium.

  In addition to the above compounds, examples of the metal compound that can be used in the present invention include aluminum ethyl acetoacetate diisopropylate, aluminum tris (ethyl acetoacetate), aluminum tris (acetylacetate), aluminum bisethylacetate. Acetate monoacetylacetonate, titanium chelate compound, titanium acylate compound and the like can be mentioned, and these compounds are suitably used alone or as a mixture for producing the inorganic oxide material of the present invention having a desired composition. can do.

Furthermore, in the present invention, as the metal oxide, tin oxide (SnO ₂ ), titanium oxide (TiO ₂ ), cobalt trioxide (CoO ₃ ), cobalt oxide (CoO), tungsten oxide (WO ₃ ), molybdenum oxide (MoO) ₃ ), aluminum oxide (Al ₂ O ₃ ), indium tin oxide (ITO), indium oxide (In ₂ O ₃ ), lead oxide (PbO ₂ ), PZT, SrCe _0.95 Yb _0.05 O _{3 −δ} , niobium oxide (Nb ₂ O ₅ ), thorium oxide (ThO ₂ ), tantalum oxide (Ta ₂ O ₅ ), calcium titanate (CaTiO ₃ ), lanthanum cobaltate (LaCoO ₃ ), rhenium trioxide (ReO ₃₎ ), chromium oxide _{(Cr 2 O} 3), iron oxide _{(Fe 2 O} 3), lanthanum chromate (LaCrO _3), Ji Barium phosphate _(BaTiO 3), or the like may be used _ZnO-Bi 2 _{O 3.}

  Furthermore, as a precursor material for giving an inorganic oxide that can be used in the present invention, more specifically, Sn, W, Mo, Co, In, Sb, As, Ti, Co, Al, Zr , Yb, Sr, Th, Ta and the like, alkoxides containing the above-mentioned metals, acetates, metal organic acid salts, metal salts, metal soaps, halides, etc. Can be used alone or in any mixture to suit the properties to be achieved.

[Metal loading on the inner or outer wall]
The metal particles used for the production of a new material carrying metal particles only on the outer wall of the inorganic oxide material produced according to the present invention include nickel, iron, cobalt, platinum, palladium, etc., Cu, Ni, Ag, Metal particles selected from Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, Ca, or mixtures thereof can be used. In general, the supported amount of these metals is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and particularly preferably 20 to 50% by mass with respect to the entire catalyst. The same applies to the production of titanium oxide nanotubes, zirconia nanotubes, alumina nanotubes and the like.

  The silica nanotubes in which the metal particles are supported only on the outer wall of the silica nanotubes of the present invention are obtained by placing CNF coated with silica in an aqueous solution such as nickel salt, iron salt, cobalt salt, platinum salt, palladium salt or water-alcohol solution. As a reduction method of heating and stirring, drying and solidifying a sample with a reducing agent to form metal particles, a method of circulating hydrogen at about 300 ° C. to 500 ° C. is preferable. Thereafter, air calcination at 400 ° C. to 600 ° C. is performed to remove CNF, and silica nanotubes in which a metal is supported only on the outer wall can be obtained. Similarly, titanium oxide nanotubes, zirconia nanotubes, alumina nanotubes or the like in which metal particles are supported only on the outer wall can be produced.

  Silica nanotubes carrying metal particles on the inner wall of the silica nanotube of the present invention, after leaving the silica nanotubes in an aqueous solution or water-alcohol solution such as nickel salt, iron salt, cobalt salt, platinum salt, palladium salt, etc. While performing the washing treatment, the sample is suction filtered and then dried, and hydrogen is passed through the prepared sample at about 300 ° C. to 500 ° C. to reduce the metal salt on the support to metal. It can manufacture by performing air baking and enclosing a metal particle.

[Making composite materials of inorganic oxide nanotubes and carbon]
In the present invention, the CNF growth from the outer wall / inner wall of the inorganic oxide nanotube is carried out in the presence of a catalyst for producing carbon nanofibers in the presence of a catalyst for producing carbon nanofibers on the metal particles described above, in particular, the inorganic oxide nanotubes supporting an iron group element. Compounding can be performed by heating the hydrogen to about 400 ° C. to about 600 ° C. to decompose the hydrocarbon. In accordance with the present invention, CNF grows in a branch shape from the outer wall / inner wall from the site where the metal particles of the inorganic oxide nanotube are supported to form an inorganic oxide nanotube-CNF composite material. Although it does not specifically limit as hydrocarbon, A C1-C10 linear or branched aliphatic hydrocarbon, such as methane, hexane, and octane, is preferable. Moreover, C1-C10 alicyclic hydrocarbon and aromatic hydrocarbon can also be used. The same applies when CNF is grown from the outer wall of the inorganic oxide nanomaterial.

Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the examples described below as long as the configuration of the present invention is provided and the effects are exhibited.
(Example 1)

A silica supported Ni catalyst was prepared by impregnation method for CNF synthesis. Specifically, silica was impregnated in a 15 g / L nickel nitrate aqueous solution, and the solution was heated and stirred. Hydrogen was passed through the sample prepared after drying at about 400 ° C. to reduce the metal salt on the support to metal. The dried sample was air calcined at 600 ° C. to obtain a silica-supported Ni catalyst (Ni / SiO ₂ ). The obtained silica support (Ni / SiO ₂ ) was placed in a fixed bed flow reactor, and pure hydrogen was allowed to flow at about 500 ° C. for 1 hour, and then pure methane was brought into contact with Ni / SiO ₂ at about 550 ° C. It was. The gas produced during the reaction was analyzed by gas chromatography, and methane was circulated until no more hydrogen was generated. The produced CNF was immersed in a concentrated aqueous nitric acid solution and stirred at about 80 ° C. for 4 hours. CNF was filtered and washed, and then used as a template for silica nanotube synthesis.

  Next, as a synthesis of silica nanotubes, 50 mg of CNF and 5 ml of tetraethylsilane (TEOS) were placed in a glass container and stirred for a predetermined time (4 to 48 hours) in the presence of water vapor saturated at 40 ° C. The sample was suction filtered, dried at 80 ° C., and then heated at about 500 ° C. under an argon stream to calcine the inorganic oxide precursor. Silica-coated CNF was air-fired at about 600 ° C. to oxidize and remove only CNF, thereby obtaining silica nanotubes.

  In FIG. 1, the TEM image of CNF produced by methane decomposition | disassembly and the produced | generated silica nanotube is shown. The shapes of silica nanotubes and CNF are similar, indicating that CNF functions as a template for producing silica nanotubes. The length of the silica nanotube was several hundred to several μm, and the diameter was about 50 nm. In addition, silica nanotubes having a curved structure were obtained as compared with the conventional method of producing silica nanotubes using anodized alumina as a template.

In FIG. 2, the SEM photograph of the manufactured silica nanotube is shown. As shown in FIG. 2, the wall of the produced silica nanotube had a hexagonal structure that the carbon nanofiber used as a template had, and the diameter thereof was about 600 nm. The silica nanotube shown in FIG. 2 clearly shows that the carbon nanofiber functions as a template than that shown in FIG.
(Example 2)

  As Example 2, control of the wall thickness of a hollow inorganic oxide material was examined as the form controllability of the inorganic oxide material of the present invention. The wall thickness was controlled by using the same composition and materials as in Example 1 and changing the hydrolysis time of TEOS to 4h, 12h, and 36h.

FIG. 3 shows a TEM image of silica nanotubes produced by changing the hydrolysis time of TEOS. FIG. 3 (A) shows the results obtained for a hydrolysis time of 4h, FIG. 3 (B) for a hydrolysis time of 12h, and FIG. 3 (C) for a hydrolysis time of 36h. From the TEM image of the silica nanotube, in FIG. 3A, the wall thickness of the hydrolysis time of 4 h is 10 nm or less, whereas the wall thickness of the silica nanotube of the hydrolysis time of 36 h shown in FIG. Was found to be 30 nm. That is, in the present invention, it was shown that the thickness of the silica nanotube can be controlled by the hydrolysis time of TEOS. These were not possible with the conventional method of producing silica nanotubes using anodized alumina as a template.
Example 3

As Example 3, a silica nanotube having a metal supported on the inner wall was synthesized. The silica nanotube produced in Example 1 is placed in an aqueous solution (concentration of about 1 to 10% by weight) of nickel nitrate, iron nitrate, cobalt nitrate, chloroplatinic acid, or palladium chloride, and the metal salt is added to the silica nanotube. Attached. Subsequently, when the sample was subjected to suction filtration, washing was performed in a Buchner funnel. After drying, hydrogen was passed through the prepared sample at about 400 ° C. to reduce the metal salt on the silica nanotube to a metal. Thereafter, air firing was performed to obtain silica nanotubes encapsulating metal particles. The type and amount of metal particles present in silica nanotubes were estimated by X-ray fluorescence analysis (XRF) of silica nanotubes encapsulating metal particles and energy dispersive X-ray spectroscopy (EDS) performed simultaneously with TEM observation. .
Example 4

As Example 4, a silica nanotube having a metal supported on the outer wall was produced. CNF coated with a silicon dioxide precursor sol produced in the same manner as in Example 1 was added to an aqueous solution (concentration of about 1 to 10% by weight) of nickel nitrate, iron nitrate, cobalt nitrate, chloroplatinic acid, or palladium chloride. Then, the metal salt was supported by heating and stirring. After drying, hydrogen was passed through the prepared sample at about 400 ° C. to produce silica nanotubes, and at the same time, the metal salt on the silica nanotubes was reduced to metal. Thereafter, air calcination was performed at 600 ° C. to remove CNF, and a silica nanotube having a metal supported only on the outer wall was obtained.
(Example 5)

  As Example 5, titanium oxide nanofibers were produced using tetraisopropoxy titanium instead of TEOS. Titanium oxide nanofibers were synthesized by immersing CNF at room temperature in an ethanol solution containing a titanium oxide sol produced by hydrolysis of titanium tetraisopropoxide. Thereafter, the CNF to which the titanium oxide sol adhered was washed with ethanol to remove the titanium oxide sol that was not adsorbed on the CNF, then dried and air-fired at 600 ° C. to oxidize and remove the carbon nanofibers used as the template.

FIG. 4 shows a scanning electron micrograph of a titanium oxide nanotube produced using CNF as a template. As shown in FIG. 4, the titanium oxide is formed as a fiber corresponding to a template, and the central carbon nanofiber is removed by air oxidation, so that a high aspect ratio hollow inorganic oxide material Was shown to be obtained.
Example 6

As Example 6, zirconium oxide nanofibers were produced. Zirconium oxide nanofibers were synthesized by using zirconium butoxide as a metal oxide precursor, and immersing CNF in 1-butanol solution containing zirconium oxide sol produced by hydrolysis of zirconium tetra-n-butoxide at room temperature. . Thereafter, the CNF was washed with ethanol to remove the zirconium oxide sol that was not adsorbed on the CNF, dried, and then fired at 600 ° C. to produce a good zirconium oxide nanofiber.
(Example 7)

  As Example 7, a silica nanotube in which carbon nanofibers were grown from the inner wall was produced. Silica nanotubes carrying Ni particles as iron metal particles were produced in the same manner as in Example 3. Methane was passed through the produced silica nanotubes at about 550 ° C. in the presence of the same catalyst for producing carbon nanofibers as in Example 1, and CNF produced by the decomposition of methane was grown from the inner walls of the silica nanotubes. The result is shown in FIG. As shown in FIG. 5, CNF grew from the inner wall of the silica nanotube produced by the present invention, and it was confirmed that a carbon-inorganic oxide composite material having novel morphological characteristics can be produced by the present invention.

  According to the present invention, a hollow inorganic oxide material and a carbon-inorganic oxide composite material having a novel morphology can be provided. The novel material provided by the present invention includes a novel catalyst material, an environmental purification material, It can be applied to electron emission materials, electromagnetic wave absorbers, and the like.

Ni / SiO ₂ TEM image of the carbon nanofiber obtained by performing methane decomposition on the catalyst (a), and TEM images of silica nanotubes were synthesized using carbon nanofibers a template (b). The SEM image which showed the outer wall structure of the inorganic oxide material of this invention. A TEM image of silica nanotubes produced by changing the hydrolysis time of TEOS. The hydrolysis time is 4 hours (a), 12 hours (b), and 36 hours (c). The SEM image of the titanium oxide nanomaterial synthesize | combined using CNF as a template. The TEM image of the carbon-inorganic oxide composite material containing the carbon nanofiber extended from the inner wall of the silica nanotube which decomposed | disassembled methane using the metal Ni particle | grains carry | supported inside the silica nanotube as a catalyst.

Claims (10)

Attaching an inorganic oxide precursor to a solid substrate;
Converting the inorganic oxide precursor to an inorganic oxide;
A process for producing a hollow inorganic oxide material using the structure of the substrate as a template.   The manufacturing method according to claim 1, wherein the substrate is a carbonaceous material.   The manufacturing method according to claim 2, wherein the carbonaceous material is a material having a high aspect ratio of 1 to 600 nm.   The manufacturing method according to claim 1, wherein the substrate is a carbon nanofiber.   5. The manufacturing method according to claim 1, wherein the step of attaching the inorganic oxide precursor to the base includes the step of supporting the inorganic oxide precursor on the base.   Further, the inorganic oxide material is selected from Cu, Ni, Ag, Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, Ca, or a mixture thereof. The manufacturing method of any one of Claims 1-5 which carry | supports the metal.   A hollow structure inorganic oxide material having a size of 1 to 600 nm and a high aspect ratio.   The inorganic oxide material according to claim 7, wherein the inorganic oxide material has a hexagonal cross-sectional shape.   Metal selected from the group consisting of Cu, Ni, Ag, Au, Pt, Rh, Ru, Pd, V, Sn, Ti, Fe, Co, Cr, Nb, Mo, Ca, or a mixture thereof The inorganic oxide material according to claim 7 or 8, which carries   A carbon-inorganic oxide composite material comprising carbon nanofibers attached to at least an inner wall or an outer wall of the inorganic oxide material according to any one of claims 7 to 9.

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