JP2002226926A - Composite functional material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite catalytic material in which fine particles having various functions according to the combination of a metal X and a metal Y are dispersedly precipitated. SOLUTION: A mixture in which the metallic element X having a strong affinity for a vapor-phase element Z is mixed with the metallic element Y having a weak affinity is heated and melted at a temperature not lower than the melting points of the metallic element X and metallic element Y, and the resultant melt is cooled at >=103 deg.C/s cooling rate or at zero gravity, by which a solid solution of the metallic element Y and the metallic element Y is prepared. Subsequently, the solid solution is heated in the atmosphere of the vapor- phase element Z having potential high enough to form a compound of the metallic element X and the vapor-phase element Z but not high enough to form a compound of the metallic element Y and the vapor-phase element Z, and the fine particles of the compound of the metallic element X and the vapor- phase element Z are dispersedly precipitated in the inner part of the metallic element Y or at its surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite functional material having various functions by dispersing and depositing compound particles of different metals in a metal serving as a matrix.

[0002]

2. Description of the Related Art Fine-particle-dispersed composite functional materials are produced by blending fine particles having a predetermined function with a metal or alloy powder constituting a matrix, molding the resulting mixture into a predetermined shape, and then firing. I have. However, according to this production method, it is difficult to uniformly disperse the functional fine particles in the matrix. Incidentally, in the case of a composite functional material in which catalyst particles requiring a large specific surface area are dispersed, the smaller the particle size of the functional fine particles, the more effectively it contributes to the catalytic reaction, but the fine particles having an extremely fine particle size tend to aggregate. Therefore, the functional fine particles are distributed as large-diameter aggregated particles in a state of being mixed with the metal or alloy powder constituting the matrix, and it is not possible to expect an improvement in the reaction activity due to ultrafine granulation.

In order to avoid aggregation of functional fine particles in the powder mixing and sintering method, there is a method of internally oxidizing an alloy containing a metal element to be an oxide (functional fine particles). The present inventors have also introduced that functional materials such as conductive materials, contact materials, and high-strength materials can be obtained by dispersing and depositing oxide particles in a matrix by internal oxidation under specific conditions (JEMS NEWS. 28 (1986) pp. 1-5).

[0004]

According to the internal oxidation method, a functional oxide can be dispersed in a matrix. However, the application of the internal oxidation method is limited to a solid solution alloy in which a metal element to be a functional oxide is uniformly dissolved. Also,
In many cases, the concentration of the additional element exceeds the solid solubility limit in the equilibrium diagram, and the additional element exceeding the solid solubility limit is distributed as a mass in the matrix. Therefore, a compound is generated at the interface between the bulk additive element and the matrix, and the functional oxide cannot be uniformly dispersed, and the additive element inside the bulk tends to remain unreacted. Moreover, the generated functional oxide tends to grow to a large particle size by heating during oxidation. As a result, the effective specific surface area of the functional oxide does not become as large as expected,
The functionality is limited, and there is a limit to the improvement in functionality due to the functional oxide having an extremely fine particle size.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem, and is a solid solution obtained by uniformly dissolving a metal element which becomes functional fine particles by rapid solidification or solidification in a zero-gravity field. Is reacted in a gas atmosphere of a specific potential to provide a composite functional material in which functional fine particles are uniformly dispersed without being restricted by a solid solubility limit.

In order to achieve the object, the production method of the present invention mixes a metal element X having a large affinity with an element Z in a normal gas phase and a metal element Y having a small affinity to form a metal element X.
A mixture having a concentration of 0.0001 to 70 atomic% is prepared, and the mixture is heated and melted at a temperature equal to or higher than the melting points of the metal element X and the metal element Y to form a melt in which the metal element X is completely dissolved in the metal element Y, By cooling the melt at a cooling rate of 10 ³ ° C / sec or more or in a zero gravity state, a solid solution of the metal element X and the metal element Y is produced, and a compound of the metal element X and the gas phase element Z is generated. Is heated in an atmosphere of a gaseous phase element Z having a potential that is insufficient for the formation of a compound of a metal element Y and a gaseous phase element Z. Alternatively, it is characterized by being dispersed and deposited on the surface.

[0007]

According to the present invention, a solid solution of the metal element X and the metal element Y is prepared by rapid solidification or weightless solidification. Due to rapid solidification or weightless solidification, the metal element X exists as a solid solution in the matrix even in a supersaturated state without being restricted by the XY alloy equilibrium state. When the obtained solid solution is heated in the atmosphere of the gaseous phase element Z, the reaction of the metal element X / the gaseous phase element Z proceeds, but the vapor phase of the atmosphere reaches a potential where the reaction of the metal element Y / the gaseous phase element Z does not proceed. Maintain the partial pressure of element Z. By controlling the partial pressure of the gas phase element Z, the metal element X selectively reacts to form compounds such as oxides, nitrides, fluorides, chlorides, and hydrides.
At this time, in a solid solution containing the metal element X in a non-equilibrium supersaturated state, the non-equilibrium state is collapsed, so that the compound generation reaction proceeds rapidly.

The compound is distributed on the surface or inside of the matrix in a dispersed form such as fine particles or tabular form. Therefore, a composite functional material that exhibits the functions of the compound and the matrix can be obtained. The function of the formed compound becomes remarkable when the addition amount of the metal element X is 0.0001 atomic% or more based on the solid solution. However, when the addition amount of the metal element X exceeds 70 atomic%, it becomes difficult to disperse the functional compound particles in the matrix.

As the metal element X, Si, Mn, P, A
1, Zn, Ti, Ni, Cr, Co, Fe, Be, M
g, K, Na, Cd, In, Zr, Sn, Ce, Ga,
La, Tl, B, Sb, Tb, Pb, Nb, Ta, B
One or more selected from i, Li, Mo, W, V, Hf, Y, U and the like are used. As the metal element Y,
As long as the standard free energy of formation of the compound is smaller than that of the metal element X, Ag, Cu, Ni, Fe, Pd, Co,
Au, Pt, Cr, Mo, W, Ti, Zr, Hf, V,
One or more selected from Nb, Ta, Ge, Sn, Pb, and Mg are used. Examples of the gas phase element Z that forms a compound with the metal element X include O, N, F, Cl, and H.

For example, a composite functional material in which oxide fine particles such as TiO ₂ and WO ₃ are dispersed in a matrix such as Ag and Ni has both a photocatalytic action derived from the oxide fine particles and a chemical catalytic action derived from the matrix metal. . A
In a composite material in which nitride fine particles such as 1N and Si ₃ N ₄ are dispersed in a matrix such as Cu and Ag, high thermal conductivity and dispersion strengthening derived from the nitride fine particles are exhibited, and Cu, Ag
The thermal conductivity and catalytic activity derived from the matrix such as are emphasized. In this way, a composite material having various functions provided in a complex manner is obtained by the combination of the metal element X, the metal element Y, and the gas phase element Z.

When O is selected as the gas phase element Z, Si, Mn, P, Al, Z
n, Ti, Ni, Cr, Co, Fe, Be, Mg, C
d, In, Zr, Sn, Ce, Ga, Tl, B, Sb,
Pb, Nb, Ta, Bi, Li, Mo, W, V, Hf,
One or more of Y and the like, and as the metal element Y constituting the matrix, Ag, Cu, Ni, Fe, Pd, C having a smaller standard free energy of formation of an oxide than the metal element X are used.
o, Au, Pt, Cr, Mo, W, Ti, Zr, Hf,
One or more of V, Nb, Ta, Ge, Sn, Pb and the like are used.

When N is selected as the gas phase element Z, Ti, Zr, Al, Fe,
One or more of Cr, Ti, Mo, V, Si, etc., and the metal element Y constituting the matrix is Ag, C, which has a smaller standard free energy of formation of nitride than the metal element X.
u, Ni, Fe, Pd, Co, Au, Pt, Cr, M
One or more of o, W, Ti, Zr and the like are used. In this case, ammonia HN ₃ which decomposes to N at a high temperature can be used as a source of the gas phase element Z.

When F or Cl is selected as the gaseous phase element Z, the metal element X to be fluoride or chloride is B
e, one or more of Mg, Ca, Al, Ti, Si, Cr, etc., and the metal element Y constituting the matrix is Ag, which has a smaller standard free energy of formation of fluoride or chloride than the metal element X, Cu, Ni, Fe, Pd, Co, A
one or two of u, Pt, Cr, Mo, W, Ti, Zr, etc.
More than seeds are used.

When H is selected as the gaseous phase element Z, La, Ca, Li, T
i, Na, U, Mg, Ni, Co, V, Fe, Mn, C
One or more of e, Al, Y, Zr, etc., and as the metal element Y constituting the matrix, Ag, Cu, Ni, Fe, Pd, which have a small standard free energy of formation of hydride,
Co, Au, Pt, Cr, Mo, W, Ti, Zr, Mg
One or more of these are used.

The standard free energy of formation of a compound is determined for each of the metal elements X and Y according to the gas phase element Z. For example, it is known that the standard free energy of formation of an oxide differs for each metal element as shown in FIG. 1 (JFElliot, M. Gleiser, Thermochemistry f.
or Steelmaking, vol. 1 (1960), Addison-Wesley), so that the metal element X and the metal element Y are selected in consideration of the standard free energy of formation. When nitrides are formed, the standard free energy of formation (JFElliot, M.
Gleiser, Thermochemistry for Steelmaking, vol. 1 (19
60), Addison-Wesley), and select the metal element X and the metal element Y.

[0016]

Example 1 A mixture of Ni and 30.0 atomic% of Ti was heated and melted at 1500 ° C. in an Ar gas stream, and then rapidly solidified by a twin roll method at a cooling rate of 10 ⁴ ° C./sec.
A solid solution of Ni-Ti was prepared. As a result of X-ray diffraction of the obtained solid solution, a peak of Ni was detected, but no peak of Ti was detected, indicating that the solid solution was a solid solution in which Ti was forcibly dissolved.

The forced solid solution is buried in a powder mixture in which equal amounts of nickel oxide powder, nickel powder and alumina powder are mixed, kept at 1050 ° C. for an hour in an Ar gas stream, and further heated to 550 ° C. for 1 hour.
Hold for 0 hours. Observation of the cross section of the heat-treated sample with a scanning electron microscope revealed a structure in which fine particles were uniformly dispersed inside the sample. In the result of X-ray diffraction, peaks of anatase type and rutile type TiO ₂ were detected in addition to the Ni peak, and the anatase type TiO _{2 having} strong photocatalytic action was detected.
Was dispersed in the Ni matrix.

TiO_TwoSalad on the sample surface where
0.1mg / cm of oil^TwoDripping, 1mW / cm^Two6 o'clock ultraviolet light
Irradiation. Measure the weight of the plate sample before and after irradiation,
The amount of salad oil reduction was determined from the difference. For comparison, T
iO_TwoA similar test was performed for the comparative sample where
The amount of reduction in salad oil was determined by an experiment. As a result, TiO
_TwoThe sample in which is dispersed is more salad oil than the comparative sample.
The amount of reduction is more than 62 times, derived from photocatalysis
It has an antifouling effect. Moreover, chemical catalytic
The matrix is composed of Ni
Iodination, dehydrogenation, reductive desulfurization, reductive alkylation,
Excellent complex with functions such as amino and redox reactions
It could be used as a catalyst material.

[0019]

Example 2 A mixture of Au and 45 atomic% of Ti was added to A
After heating and melting at 1800 ° C. in an air stream, the melt was allowed to fall freely by 500 m using a pit dug underground to produce a plate-like solid solution in which Ti was forcibly dissolved in Au. When the obtained solid solution was subjected to X-ray diffraction, an Au peak was detected, but a Ti peak was not detected. From this result, it can be seen that Ti is forcibly dissolved in Au.

The plate-like solid solution sample was heated at 850 ° C. for 12 hours in a pure oxygen atmosphere at 300 atm, and further maintained at 550 ° C. for 10 hours. The heat-treated plate-like sample was cut with a cutter, and the cut surface was observed with a scanning electron microscope. As a result, particles uniformly dispersed in the matrix were detected. As a result of X-ray diffraction, peaks of anatase type and rutile type TiO _{2 having} photocatalysis were detected in addition to the Au peak.

Salad oil was dropped on the surface of the plate-like sample in which TiO ₂ was dispersed in the same manner as in Example 1, and the amount of salad oil reduced by photocatalysis was determined. For comparison, Ti
For a comparative sample in which O ₂ was not dispersed, the amount of reduction in salad oil was determined in a similar test. As a result, TiO ₂
The plate-like sample in which is dispersed has a salad oil reduction of 72 times or more as compared with the comparative sample, and it has been found that the plate-like sample has an antifouling action derived from the photocatalytic action. Moreover, since the matrix was composed of Au as a chemical catalyst, it functioned as an excellent composite catalyst material.

[0022]

Example 3 A mixture of Pt and 30 atomic% of Ti was mixed with A
The melt was melted at 1900 ° C. in an r stream, and the obtained melt was quenched by an atomizing method to produce solid solution particles in which Ti was dissolved in Pt. When the solid solution particles were subjected to X-ray diffraction, a Pt peak was mainly detected, and it was found that Ti was in a forced solid solution state.

The solid solution particles are placed in a pure oxygen atmosphere at 300 atm.
After heating to 00 ° C for 12 hours, it was kept at 550 ° C for 10 hours. When the solid solution particles subjected to the heat treatment were subjected to X-ray diffraction, peaks of anatase type and rutile type TiO ₂ were detected in addition to the Pt peak, and it was found that anatase type TiO ₂ fine particles having a strong photocatalytic action were dispersed. When the particles in which the TiO ₂ fine particles are dispersed were used for an electrode of a fuel cell using hydrogen as fuel and oxygen as an oxidant, the cell output was improved by 67% as compared with a conventional electrode comprising Pt particles.

[0024]

Example 4 A mixture of Fe and 5.0 atomic% of Ti was melted by heating to a temperature of 1500 ° C. or higher than the melting points of Fe and Ti in an Ar gas stream, and the resulting melt was melted by a twin-roll method to 10 ^4. A solid solution of Fe-Ti was prepared by rapid solidification at a cooling rate of ° C / sec. When the produced solid solution was subjected to X-ray diffraction, only the peak of Fe was detected, and it was found that Ti was in a forced solid solution state.

The solid solution sample was placed in a pure oxygen 100 atm atmosphere at 550
By holding at 2 ° C. for 2 hours, oxygen diffusion from the sample surface toward the inside was promoted, and the Ti diffusion from the sample inside to the surface direction was balanced. When the sample after the heat treatment was subjected to X-ray diffraction, peaks of anatase type and rutile type TiO ₂ were detected, and it was confirmed that anatase type TiO ₂ fine particles having a strong photocatalytic action were generated on the sample surface.

The heat-treated sample was irradiated with 1 mW / cm ² of ultraviolet light for 6 minutes.
While irradiating for 5 hours, the salt spray test using a 5% aqueous NaCl solution was continued for 48 hours. For comparison, the same sample was placed in a dark place without UV irradiation and subjected to a similar salt spray test. When the sample surface was observed after the salt spray test, corrosion products of Fe were detected on the surface of the sample placed in a dark place, but no corrosion was detected on the sample irradiated with ultraviolet light. From this, it is inferred that the electrons in TiO ₂ were excited by the ultraviolet irradiation, and the electrons were transferred into the Fe matrix, thereby suppressing the progress of corrosion.

[0027]

Example 5 Cu-Al in which Al was forcibly solidified by heating and dissolving a mixture of Cu and 30.0 atomic% of Al in an Ar gas stream at 1300 ° C. and solidifying the melt in a zero-gravity state.
A solid solution was prepared. When the obtained solid solution was subjected to X-ray diffraction, only a peak of Cu was detected, and it was found that Al was in a forced solid solution state.

The Cu—Al forced solid solution was kept at 800 ° C. in a 1 atm NH ₃ atmosphere for 2 hours. Observation of the cross section of the heat-treated sample with a scanning electron microscope revealed a structure in which fine particles were uniformly dispersed inside the sample. In the result of X-ray diffraction, a peak of AlN was detected, and AlN having high thermal conductivity was detected.
It was found that N was dispersed in the Cu matrix. Then, when the thermal conductivity of the sample was measured, it was 0.91 cal / cm
A very high value of ° C. was obtained, which was a material suitable for heat exchangers in combination with the strength improvement effect of AlN precipitation.

[0029]

Example 6 A mixture of Ag and 30.0 atomic% of Mg was melted in an Ar gas stream at 1100 ° C., and the resulting melt was solidified in a zero-gravity state to form an Ag-solid solution.
An Mg solid solution was prepared. When this solid solution was subjected to X-ray diffraction, only the Ag peak was detected, indicating that Mg was in a forced solid solution state.

The Ag-Mg solid solution was placed in an atmosphere of F ₂ at 1 atm.
Hold at 0 ° C. for 2 hours. Observation of the cross section of the sample after the heat treatment with a scanning electron microscope revealed a structure in which fine particles were uniformly dispersed inside the sample. As a result of X-ray diffraction, a peak of MgF ₂ was detected. Since MgF ₂ is excellent in chemical resistance and uses Ag having a chemical catalytic action as a matrix, it is expected to be used as a catalyst having good chemical resistance.

[0031]

Example 7 A mixture of Mg and 30.0 atomic% of Zr was melted in an Ar gas stream at 1800 ° C. and solidified in a zero-gravity state to produce a Mg-Zr solid solution in which Mg was forcibly dissolved. When the obtained solid solution was subjected to X-ray diffraction, only the peak of Mg was detected, and it was found that Zr was in a forced solid solution state.

Next, the solid solution sample was kept at 530 ° C. for 1 hour in an atmosphere of H ₂ at 1 atm. Observation of the cross section of the heat-treated sample with a scanning electron microscope revealed a structure in which fine particles were uniformly dispersed. Xr diffraction results show that ZrH
_Two peaks were detected. ZrH ₂ fine particles are a substance having excellent chemical resistance and are dispersed in a Mg matrix capable of absorbing and releasing hydrogen, so that development as a hydrogen storage material can be expected. In fact, when the release pressure of hydrogen was measured, it was 1 atm at 290 ° C.

[0033]

As described above, in the present invention, the metal element X and the metal element Y having a difference in the standard free energy of formation of the compound generated by the reaction with the gas phase element Z are dissolved and quenched or weightless. After preparing a solid solution solidified in the state, the metal element X is selectively reacted with the gas phase element Z to disperse and precipitate compound fine particles in the matrix. According to this method, regardless of the solubility limit of the metal X with respect to the metal Y, a solid solution in which the metal X is uniformly dissolved in a non-equilibrium state is obtained,
By the heat treatment of the solid solution, compound fine particles such as oxides, nitrides, fluorides, chlorides and hydrides exhibiting various catalytic activities are produced. Therefore, the electrical, magnetic, mechanical, chemical, and catalytic functions derived from the compound fine particles are imparted, and antifouling materials, antibacterial materials, corrosion resistant materials, high heat conductive materials,
A composite functional material having various functions such as a chemical resistant material and a hydrogen storage material is provided.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature-oxygen potential at which a metal element undergoes an oxidation reaction.

FIG. 2 is a graph showing a temperature-nitrogen potential at which a metal element undergoes a nitriding reaction.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C22C 5/06 C22C 5/06 Z 9/01 9/01 23/00 23/00 F-term (reference) 4G069 AA03 AA08 BA04A BA04B BA48A BB02A BB04A BB08B BB11A BC10B BC16A BC31A BC32A BC32B BC33B BC60A BC66B BC68A BC68B BC75B BD05A BD15B CB02 CC32 CD10 DA05 EC22Y EC27 ED04 FA01 FB08 ACB FCA FC21 FC21

Claims (2)

[Claims] 1. A mixture in which a metal element X having a high affinity for an element Z in a gaseous state and a metal element Y having a small affinity is prepared by mixing a metal element X having a concentration of 0.0001 to 70 atomic%.
The mixture is heated and melted at a temperature equal to or higher than the melting points of the metal element X and the metal element Y to form a molten material in which the metal element X is completely dissolved in the metal element Y, at a cooling rate of 10 ³ ° C / sec or more or in a zero gravity state. By cooling the melt, a solid solution of the metal element X and the metal element Y is prepared, and a compound of the metal element X and the gas phase element Z is formed.
The solid solution is heated in an atmosphere of a gaseous phase element Z having a potential that is insufficient for the formation of a compound with the metal element X and the compound fine particles of the metal element X and the gaseous phase element Z are dispersed and deposited inside or on the surface of the matrix. Method for manufacturing a composite functional material. 2. The method according to claim 1, wherein the fine particles of the compound generated by the selective reaction of the metal element X contained in the solid solution are uniformly dispersed inside or on the surface of the matrix. Composite functional materials.