CN108220737B - Metal ceramic with negative dielectric constant and preparation method thereof - Google Patents

Metal ceramic with negative dielectric constant and preparation method thereof Download PDF

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CN108220737B
CN108220737B CN201810027514.4A CN201810027514A CN108220737B CN 108220737 B CN108220737 B CN 108220737B CN 201810027514 A CN201810027514 A CN 201810027514A CN 108220737 B CN108220737 B CN 108220737B
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dielectric constant
ball milling
cermet
negative dielectric
powder
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CN108220737A (en
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江勇
罗思杰
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Central South University
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/12—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on oxides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/005—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides comprising a particular metallic binder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Abstract

The invention discloses a cermet with negative dielectric constant and a preparation method thereof, wherein the cermet comprises the following components of Y2Ti2O7As the ceramic phase, Fe asA metallic phase. The volume fraction of Fe in the metal ceramic is 20-40%. The preparation method comprises the following steps: by Y2O3And TiO2Solid phase reaction of powder to produce Y2Ti2O7Powder; preparation of Y2Ti2O7Mixing the powder with Fe, pressing and sintering in vacuum to finally obtain the metal ceramic. The invention utilizes Y2Ti2O7The elastic modulus is very close to that of Fe, the chemical compatibility is good, and the characteristics of no solid phase reaction exist between the elastic modulus and the Fe, so that the metal ceramic with the negative dielectric constant is obtained, the obtained metal ceramic has the negative dielectric constant between 10MHz and 1GHz, and has the negative magnetic susceptibility between 60MHz and 1 GHz.

Description

Metal ceramic with negative dielectric constant and preparation method thereof
Technical Field
The invention belongs to the technical field of functional materials, and particularly relates to a metal ceramic with a negative dielectric constant and a preparation method thereof.
Background
The negative dielectric material is a material with a negative dielectric constant measured in a certain frequency band, and the negative dielectric constant is finally caused by changing the structure of the material to convert the conductance from the tunnel conduction to the variable-range transition. The negative dielectric material has wide application in many fields, especially has huge application prospect in the fields of super capacitor, electromagnetic shielding and wave-absorbing material, and is also a research hotspot at present.
Negative dielectric materials are not found in nature at present, and mainly rely on artificial synthesis, which is usually composed of an insulator and a highly conductive material. At present, a negative dielectric constant material is mainly composed of a polymer and a conductive material, for example, in patent 201610303343.4, a composite material having a negative dielectric constant at 10MHz-1GHz is prepared by compounding a carbon nanotube and polypyrrole; as another example, patent 20161033502.4 discloses a negative dielectric material composed of graphene, carbon nanotubes and phenolic resin to limit the leakage current; however, the above patents all adopt polymers as matrix materials, and the prepared negative dielectric materials have the defects of poor thermal conductivity and poor high temperature resistance, so that the application of the negative dielectric materials under the high-power condition is limited.
Disclosure of Invention
The invention aims to provide the metal ceramic with the negative dielectric constant and the preparation method thereof, and overcomes the defects of poor thermal conductivity and no high temperature resistance of a negative dielectric material.
The invention provides the negative mediumCermet of electric constant comprising a ceramic phase Y2Ti2O7And a metal phase Fe, wherein the volume percentage of the metal phase Fe is 20-40 vol%.
The metal ceramic has negative dielectric constant in a frequency range of 10MHz to 1GHz and negative magnetic susceptibility in a frequency range of 60MHz to 1 GHz.
The preparation method of the cermet with the negative dielectric constant, provided by the invention, comprises the following steps:
(a) weighing powdery Y according to the molar ratio of 1:22O3And TiO2Ball milling is carried out after mixing, drying is carried out at set temperature after ball milling is finished, and then solid phase reaction sintering is carried out to obtain Y2Ti2O7A porous sintered body;
(b) subjecting Y in step (a)2Ti2O7Ball milling the porous sintered body, and drying at a set temperature after ball milling to obtain Y2Ti2O7Powder;
(c) mixing Fe powder with Y in the step (b)2Ti2O7The powder is prepared, then ball milling and mixing are carried out, and drying is carried out at a set temperature after ball milling is finished, so as to obtain mixed powder;
(d) adding a binder into the mixed powder in the step (c), grinding and uniformly mixing, then carrying out compression molding, then placing in a vacuum furnace for vacuum sintering, and obtaining Y after sintering2Ti2O7-cermet of Fe.
In the step (a), the ball milling medium is absolute ethyl alcohol, the ball-material ratio is (6-8):1, the ball milling rotation speed is 250-; the solid phase sintering temperature is 1200-1300 ℃, and the sintering time is 5-8 h.
In the step (b), the ball milling medium is absolute ethyl alcohol, the ball-material ratio is (6-8):1, the ball milling rotation speed is 250-.
In said step (c), Y2Ti2O7The volume fraction ratio of the powder to the Fe powder is (80-60) to (20-40).
In the step (c), the ball milling and mixing time is 6-8h, the ball milling medium is absolute ethyl alcohol, the ball milling rotation speed is 250-300r/min, and the drying temperature is 70-90 ℃.
In the step (d), the binder is 5% polyvinyl alcohol aqueous solution, and the mass ratio of the binder to the mixed powder is (1-3): 20.
In the step (d), the compression molding pressure is 200-220MPa, and the pressure holding time is 2-3 min.
In the step (d), the vacuum sintering process comprises the following steps: heating to 600-650 ℃ at the speed of 10-12 ℃/min, preserving heat for 1-1.5h, heating to 1400-1450 ℃ at the speed of 5-8 ℃/min, preserving heat for 2-4h, and cooling along with the furnace after sintering.
The cermet is a heterogeneous composite material consisting of metal or alloy and at least one ceramic, the material has the advantages of good metal heat conductivity and high-temperature resistance of the ceramic, and the microstructure and the performance of the material can be regulated and controlled by changing the proportion of metal/ceramic components. The invention adopts a microwave medium (dielectric constant is 40-80) Y with middle dielectric constant2Ti2O7As a ceramic phase, Fe is adopted as a metal phase, and the content of the Fe in the metal phase is adjusted to enable the metal ceramic to exceed the percolation threshold of the metal ceramic, so that the dielectric constant of the metal ceramic becomes a negative value, and the metal ceramic with the negative dielectric constant is obtained. In addition, Fe adopted by the metal ceramic prepared by the invention is a metal phase which has certain magnetism, and the metal phase can form a large number of annular microstructures, so that when an external magnetic field changes or magnetic resonance effect occurs, a magnetic field is generated inside the material by induction to resist the change, and the magnetic conductivity of the metal ceramic is reduced, so that the magnetic conductivity of the metal ceramic prepared by the invention is below 1, and the metal ceramic has negative magnetic susceptibility.
The invention has the beneficial effects that:
the invention utilizes Y2Ti2O7Has good chemical compatibility and associativity with Fe and similar elastic modulus, does not generate chemical reaction, and prepares Y2Ti2O7-a cermet of Fe; the metal ceramic has good thermal conductivity,The advantage of high temperature resistance; when the volume fraction of the metal phase of the metal ceramic is between 20 and 40 percent, the dielectric constant of the metal ceramic is a negative value in a frequency band between 10MHz and 1 GHz; and the magnetic material has negative magnetic susceptibility between 60MHz and 1GHz frequency bands, so that the direct current bias capability can be further improved, the loss value is reduced, and the application range of the magnetic material in the field of electronic engineering is wider; the invention has simple preparation process, low cost, easy realization of large-scale production and no pollution in the production process.
Drawings
FIG. 1 is a microscopic topography of a cermet having a negative dielectric constant prepared in example 1;
FIG. 2 is a dielectric spectrum of a cermet having a negative dielectric constant prepared in example 1;
FIG. 3 is a magnetic spectrum of the cermet having a negative dielectric constant prepared in example 1.
Detailed Description
The following description of the embodiments of the present invention is provided, but the scope of the present invention should not be limited by the embodiments.
Example 1
This example prepares a cermet having a negative dielectric constant, ceramic phase Y2Ti2O7Is 60% by volume and the volume fraction of the metallic phase Fe is 40% by volume.
The preparation method comprises the following steps:
1)Y2Ti2O7preparation of
Weighing Y according to the molar ratio of 1:22O3With TiO2Wet grinding and mixing the powder in a planetary ball mill according to the weight ratio of the absolute ethyl alcohol to the powder of 1:1, wherein the ball material ratio is 8:1, the rotation speed of the ball mill is 300r/min, the ball milling time is 24 hours, after the ball milling is finished, the obtained mixed powder is placed in a drying oven at 80 ℃ for drying, then solid-phase reaction sintering is carried out at 1200 ℃ for 5 hours to obtain Y2Ti2O7A porous sintered body.
Will Y2Ti2O7Wet grinding the porous sintered body in a planetary ball mill according to the weight ratio of absolute ethyl alcohol to powder of 1:1, wherein the ball material ratio is 8:1, the rotating speed of the ball mill is 300r/min, and the ballsGrinding for 24h, drying in a drying oven at 80 ℃ after ball milling is finished to obtain Y2Ti2O7And (3) powder.
2)Y2Ti2O7Preparation of Fe cermet
Mixing Fe powder and prepared Y2Ti2O7And (3) preparing the powder according to the volume fraction of Fe of 40%, carrying out wet milling and mixing on the mixed powder in a planetary ball mill according to the weight ratio of absolute ethyl alcohol to the powder of 1:1, wherein the ball-material ratio is 4:1, and the rotating speed of the ball mill is 250 r/min.
And (3) drying the ball-milled mixed material in a vacuum drying oven at 70 ℃, grinding the mixed material and a 5% PVA aqueous solution according to the mass ratio of 1:20 after drying, and then carrying out compression molding for 3min under the pressure of 200MPa to obtain a sample.
Placing the sample in a vacuum furnace for vacuum sintering, heating to 600 ℃ at the speed of 10 ℃/min, preserving heat for 1h, heating to 1400 ℃ at the speed of 5 ℃/min, preserving heat for 2h, and cooling along with the furnace after sintering is finished to finally obtain Y2Ti2O7-Fe cermet.
Prepared Y2Ti2O7-Fe cermet with microstructure as shown in figure 1: FIG. 1 is Y2Ti2O7SEM photograph of/Fe cermet microstructure. In the figure, the bright contrast phase is Fe and the dark contrast phase is Y2Ti2O7A substrate. The adjacent Fe particles are communicated and combined, the distribution divergence of the particle sizes is large, the appearance is quite irregular, and even the adjacent Fe particles are fused together to form a metal ring or an open ring.
Prepared Y2Ti2O7The Fe cermet dielectric spectrum is shown in FIG. 2: since the Fe content exceeds the percolation threshold, free electrons in the metal can move freely in the material, and thus the dielectric behavior of the entire cermet becomes similar to that of a metal, exhibiting a negative dielectric characteristic.
Prepared Y2Ti2O7The magnetic spectrum of Fe cermet is shown in FIG. 3: the magnetic spectrum of the sample is typically of the relaxation type, with permeability throughout the test bandAlways below 1, a negative magnetic susceptibility is exhibited, and its permeability decreases with increasing frequency, already very close to 0 at 1GHz, and the tendency to decrease does not diminish. It can be presumed that if the magnetic field frequency is larger than a certain value of 1GHz, Y is prepared in this example2Ti2O7The permeability of Fe cermet may become negative, thus achieving double negativity.
Example 2
Cermet of negative dielectric constant, ceramic phase Y prepared in this example2Ti2O7Is 80% by volume, the volume fraction of the metallic phase Fe is 20%.
The preparation method comprises the following steps:
1)Y2Ti2O7preparation of
Weighing Y according to the molar ratio of 1:22O3With TiO2Wet grinding and mixing the powder in a planetary ball mill according to the weight ratio of the absolute ethyl alcohol to the powder of 1:1, wherein the ball material ratio is 6:1, the rotation speed of the ball mill is 250r/min, the ball milling time is 24 hours, after the ball milling is finished, the obtained mixed powder is placed in a drying oven at 90 ℃ for drying, then solid-phase reaction sintering is carried out at 1300 ℃ for 7 hours to obtain Y2Ti2O7A porous sintered body.
Will Y2Ti2O7Wet grinding the porous sintered body in a planetary ball mill according to the weight ratio of absolute ethyl alcohol to powder of 1:1, wherein the ball material ratio is 7:1, the rotating speed of the ball mill is 275r/min, the ball milling time is 22h, and after the ball milling is finished, drying the porous sintered body in a drying oven at 90 ℃ to obtain Y2Ti2O7And (3) powder.
2)Y2Ti2O7Preparation of Fe cermet
Mixing Fe powder and prepared Y2Ti2O7And (3) preparing the powder according to the volume fraction of 20% of Fe, and carrying out wet grinding and mixing on the mixed powder in a planetary ball mill according to the weight ratio of the absolute ethyl alcohol to the powder of 1:1, wherein the ball-material ratio is 3:1, and the rotating speed of the ball mill is 300 r/min.
And (3) drying the ball-milled mixed material in a vacuum drying oven at 90 ℃, grinding the mixed material and a 5% PVA aqueous solution according to the mass ratio of 2:20 after drying, and then carrying out compression molding for 3min under the pressure of 220MPa to obtain a sample.
Placing the sample in a vacuum furnace for vacuum sintering, heating to 630 ℃ at the speed of 11 ℃/min, preserving heat for 1h, heating to 1430 ℃ at the speed of 7 ℃/min, preserving heat for 1.5h, and cooling along with the furnace after sintering to finally obtain Y2Ti2O7-Fe cermet.
Y prepared in this example2Ti2O7The Fe metal ceramic has negative dielectric constant in a frequency band of 10MHz to 1GHz and negative magnetic susceptibility in a frequency band of 40MHz to 1 GHz.
Example 3
The cermet having a negative dielectric constant prepared in this example, in which the ceramic phase Y2Ti2O7Is 70% by volume and the volume fraction of the metallic phase Fe is 30% by volume.
The preparation method comprises the following steps:
1)Y2Ti2O7preparation of
Weighing Y according to the molar ratio of 1:22O3With TiO2Wet grinding and mixing the powder in a planetary ball mill according to the weight ratio of the absolute ethyl alcohol to the powder of 1:1, wherein the ball material ratio is 7:1, the rotating speed of the ball mill is 275r/min, the ball milling time is 24 hours, after the ball milling is finished, the obtained mixed powder is placed in a drying oven at 100 ℃ for drying, then solid-phase reaction sintering is carried out at 1250 ℃ for 8 hours to obtain Y2Ti2O7A porous sintered body.
Will Y2Ti2O7Wet grinding the porous sintered body in a planetary ball mill according to the weight ratio of absolute ethyl alcohol to powder of 1:1, wherein the ball material ratio is 6:1, the rotating speed of the ball mill is 250r/min, the ball milling time is 24 hours, and after the ball milling is finished, drying the porous sintered body in a drying oven at 100 ℃ to obtain Y2Ti2O7And (3) powder.
2)Y2Ti2O7Preparation of Fe cermet
Mixing Fe powder and prepared Y2Ti2O7And (3) preparing the powder according to the volume fraction of Fe of 30%, carrying out wet milling and mixing on the mixed powder in a planetary ball mill according to the weight ratio of absolute ethyl alcohol to the powder of 1:1, wherein the ball-material ratio is 2:1, and the rotating speed of the ball mill is 275 r/min.
And (3) drying the ball-milled mixed material in a vacuum drying oven at 80 ℃, grinding the mixed material and a 5% PVA aqueous solution according to the mass ratio of 3:20 after drying is finished, and then carrying out compression molding for 2min under the pressure of 210MPa to obtain a sample.
Placing the sample in a vacuum furnace for vacuum sintering, heating to 650 ℃ at the speed of 12 ℃/min, preserving heat for 1.5h, heating to 1450 ℃ at the speed of 8 ℃/min, preserving heat for 4h, and cooling along with the furnace after sintering to finally obtain Y2Ti2O7-Fe cermet.
Y prepared in this example2Ti2O7The Fe metal ceramic has negative dielectric constant in a frequency range of 10MHz to 1GHz and negative magnetic susceptibility in a frequency range of 50MHz to 1 GHz.

Claims (8)

1. A cermet having a negative dielectric constant, comprising a ceramic phase Y2Ti2O7And a metal phase Fe, wherein the volume percentage content of the metal phase Fe is 20 ~ 40 vol%;
the preparation method comprises the following steps:
(a) weighing powdery Y according to the molar ratio of 1:22O3And TiO2Ball milling is carried out after mixing, drying is carried out at set temperature after ball milling is finished, and then solid phase reaction sintering is carried out to obtain Y2Ti2O7A porous sintered body;
(b) subjecting Y in step (a)2Ti2O7Ball milling the porous sintered body, and drying at a set temperature after ball milling to obtain Y2Ti2O7Powder;
(c) mixing Fe powder with Y in the step (b)2Ti2O7The powder is prepared, then ball milling and mixing are carried out, and drying is carried out at a set temperature after ball milling is finished, so as to obtain mixed powder;
(d) adding a binder into the mixed powder in the step (c), grinding and uniformly mixing, then carrying out compression molding, then placing in a vacuum furnace for vacuum sintering, and obtaining Y after sintering2Ti2O7-a cermet of Fe;
wherein: the vacuum sintering process comprises the following specific steps: heating to 600-650 ℃ at the speed of 10-12 ℃ per min, preserving heat for 1-1.5h, heating to 1400-1450 ℃ at the speed of 5-8 ℃ per min, preserving heat for 2-4h, and cooling along with the furnace after sintering.
2. The cermet having a negative dielectric constant of claim 1, in which Y is2Ti2O7Fe cermet has a negative dielectric constant in the frequency band 10MHz ~ 1GHz and a negative magnetic susceptibility in the frequency band 60MHz ~ 1 GHz.
3. The cermet with negative dielectric constant of claim 1, wherein in step (a), the ball milling medium is absolute ethyl alcohol, the ball-to-material ratio is (6-8):1, the ball milling rotation speed is 250-; the solid phase sintering temperature is 1200-1300 ℃, and the sintering time is 5-8 h.
4. The cermet with negative dielectric constant of claim 1, wherein in step (b), the ball milling medium is absolute ethanol, the ball-to-material ratio is (6-8):1, the ball milling rotation speed is 250-.
5. The cermet having a negative dielectric constant of claim 1, characterised in that in step (c), Y2Ti2O7The volume fraction ratio of the powder to the Fe powder is (80-60): 20 ~ 40.
6. The cermet with negative dielectric constant of claim 1 or 5, characterized in that, in the step (C), the ball milling and mixing time is 6-8h, the ball milling medium is absolute ethyl alcohol, the ball milling rotation speed is 300r/min and the drying temperature is 70-90 ℃.
7. The cermet having a negative dielectric constant of claim 3, characterized in that in step (d), the binder is a 5% aqueous solution of polyvinyl alcohol, and the mass ratio of the binder to the mixed powder is (1-3): 20.
8. The cermet having a negative dielectric constant of claim 1 or 7, wherein in step (d), the compression molding pressure is 200-220MPa, and the pressure holding time is 2-3 min.
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