JPS6139509A - Material containing ultrafine grain ferrous oxide and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the material containing stabilized ultrafine grain ferrous oxide with which the particle growth of the material containing ferrous oxide of magnetic ultrafine grains and ferrous oxide can be obstructed by a method wherein ultrafine grain ferrous oxide is dispersed in the matrix containing one or more kinds of silicon oxide, aluminum oxide and titanium oxide. CONSTITUTION:Ultrafine grain ferrous oxide of 100Angstrom or less in grain diameter having the magnetic properties is dispersed in the matrix containing one or more kinds of silicon oxide, aluminum oxide and titanium oxide. Also a mixed solution, consisting of the alkoxide compound solution containing one or more kinds of silicon, aluminum and titanium, and the reactive solution consisting of an iron compound and a polyhydric alcohol compound, is formed. Deposit is grown by hydrolyzing said mixed solution, the deposit is sintered, and the material containing ultrafine grain ferrous oxide as above-mentioned can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic ultrafine iron oxide-containing material and a method for producing the same.

Conventional technology In recent years, in search of new materials, the development of ultra-fine particle technology for inorganic materials such as metals and metal oxides has been considered. Research is also continuing into the production of ultra-thin films, typified by the production of zero artificial lattices. This is two-dimensional ultrafine particle formation, and three-dimensional ultrafine particle formation is not easy.

Conventionally, methods for producing fine metal particles include evaporating the metal at high temperatures and collecting the soot to produce fine particles on gold (evaporation method), and using an aqueous solution of metal components or their salts as a carrier (matrix). A method in which a mixture of component metals is heated and melted to form an alloy and one component of the resulting alloy is precipitated (kneading method) law)
etc. have been proposed.

Problems to be Solved by the Invention With the evaporation method described above, it is impossible to selectively produce ultrafine particles with a particle size of 100 Å or less.

It is said that the diameter of metal particles produced by this evaporation method is about 500, and even if ultrafine particles of 100 Å or less are temporarily produced, they are unstable and quickly aggregate into larger particles. This is because it will grow.

In addition, metal particles produced by dipping and kneading methods also have a particle size of 10
It is a non-uniform metal particle with a particle size of 0 Å or more and a very wide particle size distribution ranging from 100 to several thousand particles.

Therefore, these methods cannot provide a technique for controlling the particle size of ultrafine particles stably.

On the other hand, magnetic ultrafine particles of iron oxide are sought after as new materials due to their characteristics, but conventional evaporation, immersion, and kneading methods can stably produce magnetic ultrafine particles of 100 Å or less. I was unable to do so.

The present invention has been made against the background of such problems in the prior art, and its purpose is to obtain ultrafine iron oxide-containing particles having magnetic properties that have not been previously available, and to inhibit the particle growth of the iron oxide. The object of the present invention is to provide a method for producing a stable ultrafine iron oxide-containing material.

A means for solving the B illumination point, that is, the present invention, includes magnetic ultrafine iron oxide particles with a particle size of 100 Å or less in a matrix of at least one selected from the group of silicon oxide, aluminum oxide, and titanium oxide. The present invention provides an ultrafine iron oxide-containing material characterized by being dispersed, and a method for producing the same.

In the present invention, in order to inhibit the particle growth of the generated ultrafine particles, the presence of a matrix that captures and stabilizes the ultrafine particles is essential. It has the characteristic of using a metal oxide as a matrix.

In the present invention, the superfine wax of the ultrafine iron oxide-containing material (hereinafter sometimes simply referred to as "contained material") containing magnetic ultrafine iron oxide includes silicon oxide and aluminum oxide. or a metal oxide consisting of titanium oxide or a combination thereof.

These metal oxides are extremely chemically stable and do not cause any chemical reaction with iron oxide even at high temperatures, and can inhibit the grain size growth of iron oxide even during high temperature treatment of inclusions and over time.

That is, the metal oxide can uniformly disperse and support iron oxide in the containing material as a matrix, and can also inhibit the grain size growth of the iron oxide.

The metal oxide is used as a matrix for 1i in the inclusion material.
The iron oxide that can be oxidized is iron tetroxide (magnetite).
, γ sesquioxide (T hematite), etc., and the particle size of these iron oxides is 100 Å or less, preferably 50 to 10
It's a person.

Iron oxide particles with a particle size of more than about 100 particles are known in the art, and when the resulting inclusions are used, for example, as a catalyst, the surface area of the iron oxide is not large enough and the catalytic activity tends to be poor. .

The proportion of iron oxide dispersed in the content of the present invention is
The amount is 1 to 80'm'Wk parts, preferably 5 to 30 parts by weight, per 100 parts by weight of the matrix made of the metal oxide.

If iron oxide is less than about 1 part by weight based on 100 parts by weight of the matrix, the resulting inclusion will not have the characteristics of ultrafine iron oxide (e.g., high catalytic activity), whereas if it exceeds about 80 parts by weight, iron oxide will be present. If the ratio is too high, the effect of uniformly dispersing and supporting iron oxide in the matrix decreases, and the ratio of non-magnetic γ sesquioxide increases, making it impossible to obtain the inclusions aimed at in the present invention.

Furthermore, although the inclusions of the present invention essentially consist of the magnetic iron oxide and matrix described above, other metals may be included as long as they do not impede the object of the present invention.

Further, the shape of the content of the present invention varies depending on its use, and may be powder, pellet, or fibrous.

Such ultrafine iron oxide-containing material of the present invention has the following (a) to
It can be obtained by a manufacturing method including the step (c).

(B) A solution of at least one alkoxide compound selected from the group of silicon, aluminum and titanium (A) and a reaction solution of an iron compound and a polyhydric alcohol compound (B)
) The first step is to create a mixed solution consisting of

(b) A second step of hydrolyzing the mixed solution obtained in (a) to form a precipitate.

(c) Third step of firing the precipitate.

The method for producing the ultrafine iron oxide-containing material of the present invention will be explained in detail below, divided into steps.

(B) First step The first step consists of a reaction solution (B) of an iron compound and a polyhydric alcohol compound, which are raw materials for magnetic iron oxide, and a metal oxide (silicon oxide, aluminum oxide, titanium oxide) that is a matrix. Alkoxide compound (A) that is the raw material for
This is the process of preparing a mixed solution with

Here, the iron compound is, for example, iron nitrate, iron chloride, iron sulfate, etc., and any iron compound may be used as long as it dissolves in a polyhydric alcohol compound described later, preferably alkylene glycol, to produce an iron alkoxide compound. .

Examples of alkylene glycols include ethylene glycol and propylene glycol.

Examples of the alkoxide compound (A) include tetraethoxysilane, tetramethylsilane, tetrapropoxylane,
Examples include aluminum triisopropoxide, titanium tetraisopropoxide, titanium tetramethoxide, titanium tetraethoxide, aluminum trimethoxide, and aluminum triethoxide.

In the first step, an alkylene glycol solution of a monoferrous compound (
Adding the alkoxide compound (A) to B) includes, but is not limited to, mixing an alkylene glycol solution of an iron compound and an alkylene glycol solution of the alkoxide compound (A), or adding an iron compound and an alkoxide compound to an alkylene glycol. (A) may be mixed.

Note that the obtained mixed solution is usually stirred at 10 to 50°C for 2 to 10 hours.

The proportions of the iron compound, alkylene glycol, and alkoxide compound (A) vary depending on the hydrolysis conditions and calcination conditions described below, as well as the composition of the residual material obtained, but usually 1 to 1 to 100 parts by weight of the iron compound to 100 parts by weight of the alkylene glycol are used. It is preferable that the content is 10 parts by weight, iron compound/(alkoxide compound (A) ten iron compound) -1 to 80% by weight.

(b) Second step The second step is a step in which water is added to the mixed solution obtained in (a) and hydrolyzed to generate a precipitate.

The amount of water used for hydrolysis is usually 2 to 101 parts by weight, preferably 4 parts by weight, per 1 part by weight of the alkoxide compound.
~6 parts by weight.

Preferred hydrolysis conditions are a temperature of 20-80°C and a time of 1-80°C.
It is carried out for 4 hours under agitation such as stirring.

Since the precipitate is a gel mainly composed of silanol or the like, it is usually left to stand for 3 to 24 hours after the precipitate is formed, washed with water if necessary, dried at 80 to 100° C., and crushed to form a powder if necessary.

(c) Third step The precipitate obtained in the second step is denatured into a magnetic metal oxide by firing to obtain the ultrafine iron oxide-containing material of the present invention.

Prior to calcination, the precipitate is washed with water and dried if necessary as described above, but is usually ground into powder or the resulting powder is formed into pellets.

The firing conditions cannot be uniformly defined because they affect the particle size of the iron oxide dispersed in the resulting inclusions, but the firing temperature is usually 400-1500°C, preferably 400-100°C.
The firing is carried out at 00° C. for 2 to 4 hours under air.

When the firing temperature is less than about 400°C, the magnetic force is weak;
When the temperature exceeds 500°C, the particle size of the iron oxide in the obtained content exceeds 100, and some of the particles may become non-magnetic T iron sesquioxide.

EXAMPLES The present invention will be explained in more detail with reference to Examples below. still,
Parts and % refer to parts by weight and % by weight.

Examples 1 to 4 After 2 parts of ferric nitrate was dissolved in 50 parts of ethylene glycol, 10 parts of ethyl silicate was added thereto, and the mixture was stirred at 80°C for 4 hours. 50 parts of distilled water was further added to this and stirred for 5 hours. After stopping stirring, the gel product was allowed to stand for 12 hours at room temperature to precipitate, and a solid was obtained by suction filtration. The obtained solid was dried in a dryer kept at 80° C. for 24 hours to obtain a reddish brown powder. After thoroughly pulverizing this powder, it was fired for 3 hours under the following conditions to obtain silica powder containing 10% iron.

Examples 5 to 7 All preparations were made in the same manner as in Example 1 except that 4 parts of ferric nitrate were used, and fired for 3 hours under the following conditions to reduce the iron content to 2.
0% silica powder was obtained.

Comparative Examples 1-2 3 parts of ferrous nitrate was dissolved in 50 parts of distilled water, and 4.6 g of synthetic Aerosil silicate (manufactured by Nippon Aerosil ■) was added thereto.
Stir at 80°C for 4 hours, then heat the container with a gas burner, keep the obtained solid at 80°C, do not evaporate to dryness, and dry in a dryer for 24 hours, then under the following conditions: After firing for 3 hours, silica powder with an iron content of 20% was obtained.

Comparative Example 3 Comparative Example 1 was prepared in the same manner as in Comparative Example 1 except that 1.5 parts of ferrous nitrate was used, and silica powder with an iron content of 10% was obtained by firing at 400° C. for 3 hours.

Example 8 Figures 1 (a) and (b) show the samples obtained in Examples 6 and 7 fired at 1000°C and 1300°C, respectively, using an X-ray diffractometer (manufactured by Rigaku Nan, C-2'zzBy5).
! 6y,) is shown.

In the sample fired at a temperature below 1000°C, no cavities were observed in the diffraction pattern, but in the sample fired at 1300°C, three broad and minute peaks were observed.

From the positions of these diffraction peaks, it was estimated that the iron oxide contained in the silica powder was magnetite. By analyzing this diffraction peak using the X-ray diffraction line broadening method 4, it was estimated that the size of the magnetite particles in the silica powder fired at 1300° C. was about 40 particles.

In general, when the particle size of the object to be measured becomes smaller than about 40 to 50 times, no diffraction pattern is observed (therefore, the particle size of magnetite in silica powder calcined at a temperature lower than 1000°C) It is thought that the number is even smaller than 40 people.

For comparison, FIG. 2 shows the X-ray diffraction patterns of samples obtained in Comparative Examples 1 and 2, in which silica powder containing 20% iron was also produced by a conventional dipping method. FIGS. 2(a) and (b) show samples fired at 400°C and 600°C, respectively.

In all cases, the diffraction pattern of α-hematite (α-iron sesquioxide) was clearly observed.

Therefore, it is concluded that the iron oxide in the iron oxide-containing silica powder produced by the usual dipping method is α hematite (α sesquioxide) and its particle size is quite large.

*The peak position of the X-ray diffraction line Broadnisong normal diffraction line indicates the regularity of the arrangement of atoms or molecules, and the half-width of the X-ray diffraction line (half w
idth) and the linear shape (line 5shape), it is possible to know the disorder of regularity and the size of the structural unit. Among these methods, this is a method for estimating the size of a structural unit from the degree of broadening of the half-width of the XvA diffraction line (line broadening).

Example 9 EXAFS (Extended Area X-ray Absorption Fine Structure) spectroscopy is one of the methods for investigating the structure of particles smaller than 40 to 50 particles, which cannot be observed by X-ray diffraction.

EXAFS spectroscopy provides information on the type and number of adjacent atoms, the interatomic distance, and the degree of fluctuation from parallel positions from the fine structure that appears in the high-energy region of several tens to 4 eV of the intrinsic absorption edge of atoms in the X-ray region. can be obtained.

Self-made EXAFS spectrometer [Deji, for Uda, spectroscopic research
11.255 (1983)), the EXAFS results (radial distribution function obtained by Fourier transforming the EXAFS spectrum) of the samples calcined at 400 °C or 800 °C obtained in Examples 1 and 3 were obtained. This is shown in FIG. 3 (b) and (C). Further, the results of the sample obtained in Comparative Example 3 are summarized in (a). For comparison, the E of commercially available α hematite (α sesquioxide, Tokyo Kasei side type), magnetite (triferric tetroxide, manufactured by Wako Pure Chemical Industries, Ltd.) and -iron oxide (manufactured by Tokyo Kasei ■)
The XAFS results are shown in Figure 4 (a), (b) and (C).
It was shown to.

By comparing and examining Figures 3 and 4, it was reconfirmed that the iron oxide in the silica powder produced by the usual dipping method or kneading method was α-hematite.

Moreover, EXAF of the sample manufactured according to the manufacturing method of the present invention
The S pattern is different from the EXAFS pattern of commercially available magnetite, but this is because the magnetite in the sample is ultrafine.

Generally, in an EXAFS pattern, when the object to be measured becomes an ultrafine particle, the peak intensity tends to decrease as the distance from the central metal atom (in the horizontal axis direction) increases. Lyt
CJ, Catalysisz 63.4 established a method for calculating the particle size of the target object by comparing the peak intensity of the standard substance and the peak intensity of the target object.
76 (1980)).

By applying Lytle et al.'s method to the results obtained from this measurement, the particle size of magnetite in silica powder fired at 400°C is approximately 10 particles, and when fired at E100°C, it is approximately 20 particles. It was speculated that.

FIG. 5 shows the relationship between the firing temperature of the silica powders produced in Examples 1 to 4 and the particle size of magnetite in the silica powders.

Furthermore, the particle size of the sample obtained in Comparative Example 3 was 3000 Å or more, which is the same as that of commercially available α-hematite.

The particle diameter of commercially available α-hematite was measured using a scanning electron microscope (manufactured by Hitachi, Ltd. 9), and was confirmed to be 3,000.

Example 10 Magnetite-containing silica powder produced according to the production method of the present invention adheres when a commercially available simple magnet is brought close to it.
α-hematite-containing silica powder produced by ordinary dipping or kneading methods does not stick even when a magnet is brought close to it. That is, the magnetite in the magnetite-containing silica powder according to the present invention maintains the properties of a ferromagnetic material even though it is in the state of ultrafine particles.

Therefore, the magnetic susceptibility of the sample obtained in Example 2 (calcined at 600°C) containing the iron component of IC9A was measured using a vibrating sample magnetometer model VSM-3 (manufactured by Toei Kogyo 91).

The results are shown in FIG. The magnetization curve shows an S-shape,
Although it exhibits the characteristics of a ferromagnetic material, its coercive force is extremely small at around 100e, indicating superparamagnetism. This means that the particle size of the magnetite in the sample powder is small, and each particle directly becomes a magnetic domain.

The magnitude of the coercive force varies depending on the concentration of iron components in the silica powder and the firing temperature, but even in the sample containing 20% iron components obtained in Example 5 (calcined at 800°C), it was about 200e at most. .

Example 11 The silica powder obtained in Example 1 was measured using a Mössbauer spectrometer (
The spectra were measured using a prototype device in Sano Laboratory, Tokyo Metropolitan University, and the electronic state of iron ions in silica powder was investigated.

Mössbauer spectroscopy uses 5tC as a source of 57CO.
0-11S7F The T-ray emitted at 6 o'clock is irradiated onto a moving iron-containing object to be measured, and the amount of resonance due to the Doppler effect is measured. The type of nucleus and the charge (electronic state) of the iron atom can be determined from the asymmetry of the charge distribution and the isomer shift from the internal magnetic field splitting.

The measurement results are shown in FIG. The measurements were performed at liquid nitrogen temperature so that the internal magnetic field splitting of iron ions could be observed.

However, as can be seen from Figure 7, internal magnetic field splitting cannot be observed even at such low temperatures.

This means that the magnetite particles are in an ultrafine state,
This shows that thermal motion occurs even in the liquid nitrogen temperature range.

Also, from the same figure, the value of isomer shift (1, S,) is 0
．． 46"2/sec, which means that the iron ions in the sample are mainly trivalent. However, the symmetry of the peak is considerably broken, which means that divalent iron ions are also present. It shows that there are quite a lot of them.

Example 12 As the particles become smaller, the proportion of atoms that are exposed on the surface of the particles increases among the atoms that make up the particles.

For example, when the particle size is about 20, about 80% of the atoms making up the particle are exposed on the surface.

Since the magnetite in the silica powder according to the present invention is 81 fine particles with a particle size of 100 Å or less, preferably 50 Å or less, the proportion of iron atoms exposed on the surface of the magnetite particles is high.

It is thought that these iron atoms form "iron-oxygen-silicon bonds" with the silica matrix, promoting stabilization of the magnetite particles within the matrix.

Therefore, the existence of this "iron-oxygen-silicon bond" was observed using infrared spectroscopy.

That is, FIG. 8 shows the results of measuring the sample obtained in Example 2 with an infrared spectrophotometer (manufactured by JASCO fII, model A2).

The spectrum in FIG. 8 shows three absorption bands in the region of 700-130-Ocm-'. Of these, 800C
The absorption bands I11-' and 107107O' are characteristic of silica powder. Also, “metal-oxygen-silicon bond”
The absorption band due to
9.127 (1983)), it is concluded that the absorption band at 980 cta-' observed in FIG. 8 is due to the "iron-oxygen-silicon bond."

Thus, the observation of "iron-oxygen-silicon bond" indicates the state of stabilization of the magnetite particles in the silica powder, and also means that the magnetite particles are ultrafine particles.

Example 13 Aluminum oxide powder with an iron content of 10% was obtained in the same manner as in Example 2 except that a solution of 10 parts of aluminum isopropoxide dissolved in 30 parts of butanol was used instead of ethyl silicate in Example 2. Ta.

The saturation magnetization of this sample is 8-5 Cm'l-/'6,
The coercive force was 80e, and the iron oxide particle size was about 20mm.

Example 14 Titanium oxide powder having an iron content of 20% was obtained in the same manner as in Example 3 except that a solution dissolved in 20 parts of titanium isopropoxide was used instead of ethyl silicate in Example 3.

The saturation magnetization of this sample is L4.5emu/g, and the coercive force is 1
80e, the particle size of iron oxide was about 30.

Effects of the Invention The thus obtained inclusion of the present invention has ultrafine magnetic iron oxide particles with a particle size of 100 Å or less stably dispersed in a matrix made of silicon oxide, aluminum oxide, or titanium oxide. .

The content of the present invention is such that the iron oxide contained in the content is (
i) It has full property, (ii) The particle size is 10
Because they are ultrafine particles with a size of less than 0 Å, they have a large surface area and excellent chemical activity.Using these characteristics, they can be used to produce electronic materials such as magnetic recording media, conductive materials, electromagnetic shielding materials, and chemical materials. It can be effectively used as a reaction catalyst.

[Brief explanation of the drawing]

Figures 1 and 2 are X-ray diffraction patterns of iron oxide-containing silica powder, Figures 3 and 4 are EXAFS charts, Figure 5 is a relationship between the firing temperature of silica powder and the particle size of magnetite particles, and Figure 6 is The magnetization curve, FIG. 7 is the Mössbauer spectrum, and FIG. 8 is the infrared spectrum. Figure 1 X-rut UXJi pattern of powder (el) 1000°C calcining (1)) 1300°C melting ) EXAFS of iron oxide-containing silica powder
(b) 1 Saijo Invention According to the Invention
(EXAFS of 400'C sintering Figure 4) EAF of hematite (X iron sesquioxide)
EXAF of S(b) fa sales magnetite (ferric tetroxide)
S (C) Commercially available - EX XAFS of iron 610 Blood Tatami Nog - Iron tip, magnetization curve when fired at 600'C with a silica old bundle containing component water - 4-3-2-10+ 2 3 4 Vel
ocity (mm/5ec) ω Mossbauer spectrum, according to the iron-butyric acid-containing flattened silica (400°C sobbing, 101% amount) J [Imotozuit element mie 8 Figure Kazuo IM-Jt- element 18 go)'s infrared cycle 6 view 1''J'J

Claims (1)

[Scope of Claims] 1. Magnetic ultrafine iron oxide particles with a particle size of 100 Å or less are dispersed in at least one matrix selected from the group of silicon oxide, aluminum oxide, and titanium oxide. A substance containing ultrafine iron oxide. 2. A method for producing an ultrafine iron oxide-containing material, which comprises the following steps (a) to (c). (A) A solution of at least one alkoxide compound selected from the group of silicon, aluminum and titanium (A) and a reaction solution of an iron compound and a polyhydric alcohol compound (B)
The first step is to create a mixed solution consisting of. (b) A second step of hydrolyzing the mixed solution to form a precipitate. (c) Third step of firing the precipitate. 3. The method for producing an ultrafine iron oxide-containing material according to claim 2, wherein the polyhydric alcohol compound is an alkylene glycol.