Ternary eutectic metal ceramic material and application thereof

Abstract

The invention provides a ternary eutectic metal ceramic material and application thereof. In the melting process of a nickel oxide ceramic phase and a nickel ferrite ceramic phase, at least one of Cu and Ni metal particles is subjected to in-situ precipitation in a ceramic phase melt, so that the metal particles are uniformly dispersed and distributed between the nickel oxide ceramic eutectic phase and the nickel ferrite ceramic eutectic phase, and finally the ternary eutectic composite material of the metal phase, the nickel oxide phase and the nickel ferrite phase is formed. According to the invention, the balance of corrosion resistance and conductivity of the material can be realized by changing the ratio of the raw materials and adjusting the proportion of phases of the ternary eutectic, so that the basic requirements of the molten salt electrolysis industrial field on the performance of the inert anode material can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to a cermet material, in particular to a ternary eutectic cermet material and its application as an inert anode for molten salt electrolysis. BACKGROUND

[0002] In order to overcome the poor conductivity of ceramic materials, metal powder is often added during the sintering process of the ceramic to form a cermet to meet the electrical conductivity requirements of the ceramic material. However, in the actual sintering process, if the sintering temperature is low, the material will not be sintered densely, the porosity of the material will be high, and the corrosion resistance will be reduced; if the sintering temperature is high, the metal will overflow from the ceramic body, thereby failing to achieve the purpose of improving the conductivity. A more stable method is to increase the metal content so that the metal completely fills the ceramic voids after melting, thereby improving the overall density of the material. For example, in order to achieve a balance between density, mechanical properties, electrical and thermal conductivity, and high-temperature molten salt corrosion resistance, the Cu(Ni) metal content in the NiFe2O4-NiO cermet inert anode is often increased, which will cause the Cu(Ni) metal in the cermet inert anode to corrode preferentially during electrolysis, thereby causing the appearance of through micro-pores on the surface of the cermet inert anode, providing a penetration channel for the high-temperature molten salt electrolyte, and causing the cermet to corrode more severely as an inert anode. SUMMARY

[0003] In view of the defects or deficiencies of the prior art, the present application provides a ternary eutectic cermet material.

[0004] Therefore, the preparation method of the ternary eutectic cermet material provided by the present application comprises the following steps:

[0005] Step 1: Ball-milling iron oxide, nickel oxide, copper oxide, lithium oxide, magnesium oxide, nickel ferrite, aluminum oxide, and ytterbium oxide according to the formula ratio to obtain a ceramic matrix raw material, drying, cold pressing, and then pre-sintering under an inert atmosphere and at a temperature of 1300-1500℃ to obtain a ceramic sintered body; the mass percentage of the iron oxide is 0-10%, the mass percentage of the nickel oxide is 32%-64%, the mass percentage of the copper oxide is 6%-22%, the mass percentage of the lithium oxide is 0-2%, the mass percentage of the magnesium oxide is 0-4%, the mass percentage of the nickel ferrite is 30%-50%, the mass percentage of the aluminum oxide is 0-15%, and the mass percentage of the ytterbium oxide is 0-15%.

[0006] Step 2: heating and melting the ceramic sintered body under an inert atmosphere or an oxidizing atmosphere, then holding the temperature, and then cooling and solidifying to obtain the ternary eutectic cermet material.

[0007] Optionally, the cold pressing temperature in step 1 is normal temperature, the pressure is 20-200 Mpa, and the pressure maintaining time is 1-10 min.

[0008] Optionally, the melting temperature in step 2 is 1700-1900 ℃, and the cooling speed is 5-10 ℃ / min.

[0009] Optionally, the material of the application is composed of a metal phase and two ceramic phases, the metal phase includes one or both of Ni and Cu metal elements, and the two ceramic phases are a nickel oxide phase and a nickel ferrite phase respectively. Further, the nickel oxide phase contains lithium oxide, magnesium oxide, copper oxide or / and iron oxide; the nickel ferrite phase contains aluminum oxide or / and ytterbium oxide. Further, the metal phase particle size in the material is 0.1-20 microns, the nickel oxide phase crystal size is 50-500 microns, and the nickel ferrite phase crystal size is 10-300 microns.

[0010] The application forms a ternary eutectic composite material of a metal phase, a nickel oxide phase and a nickel ferrite phase by making at least one of Cu and Ni metal particles precipitate in situ in the ceramic phase melt during the melting of the nickel oxide ceramic phase and the nickel ferrite ceramic phase, and dispersing the metal particles uniformly between the nickel oxide and the nickel ferrite ceramic eutectic phase. In a specific scheme, the balance between the corrosion resistance and the electrical conductivity of the material is achieved by changing the raw material ratio and adjusting the proportion of the three phases in the ternary eutectic, so as to meet the basic requirements of the inert anode material performance in the molten salt electrolysis industry.

[0011] The material is prepared by the method of high-temperature melting and cooling solidification, and the three component phases in the material are precipitated from the melt, so the material is dense, the phases are tightly combined, the ceramic phase crystal size is large, the crystal boundary content is low, the molten salt cannot corrode into the material through the crystal boundary, and the corrosion resistance of the material is greatly improved.

[0012] The metal particles in the material of the application are dispersed in the nickel ferrite ceramic phase, which greatly improves the electrical conductivity of the nickel ferrite ceramic phase and the electrical conductivity of the material. The high content of the nickel oxide phase improves the overall corrosion resistance of the material. The metal particles do not directly contact the molten salt medium and do not form preferential corrosion or corrosion channels.

[0013] The content of the nickel ferrite ceramic phase in the material system of the application is low (about 30%-50%), which reduces the molten salt corrosion probability of the nickel ferrite phase, reduces the iron content in the anode corrosion elements and the cathode product, and overcomes the long-standing problem of high iron content in the inert anode electrolysis product.

[0014] The material of the present application can improve the conductivity and corrosion resistance of the metal ceramic inert anode for molten salt electrolysis, and improve the purity of electrolytic products. For example, it can be used as an anode material for molten salt electrolysis of aluminum and molten salt electrolysis of carbon. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Micrograph of Cu-NiO-NiFe2O4 ternary eutectic metal ceramic material prepared in Example 1.

[0016] Figure 2 Micrograph of phase distribution of Cu-NiO-NiFe2O4 ternary eutectic metal ceramic material prepared in Example 1.

[0017] Figure 3 XRD curve of Cu-NiO-NiFe2O4 ternary eutectic metal ceramic material prepared in Example 1.

[0018] Figure 4 Microstructure energy spectrum of Ni-NiO-Ni2FeO4 ternary eutectic material prepared in Example 1; from left to right, the first frame is the SEM photo of the microstructure of the Ni-NiO-Ni2FeO4 ternary eutectic material, and the second, third and fourth frames are the energy spectrum diagrams of iron, nickel and oxygen elements respectively.

[0019] Figure 5 SEM and energy spectrum of electrolytic carbon prepared by using the material of Example 1 as an anode for molten salt electrolysis of carbon dioxide. DETAILED DESCRIPTION

[0020] Unless otherwise specified, the scientific and technical terms used herein are understood according to the knowledge of the ordinary skilled in the art.

[0021] The content of the present application is further described below in conjunction with examples, which are not intended to limit the scope of protection of the claims of the present application. The materials prepared in the following examples were subjected to molten salt electrolysis of aluminum and molten salt electrolysis of carbon dioxide, respectively, wherein:

[0022] Molten salt electrolysis of aluminum: the electrolyte composition was a mixture of 70% Na3AlF6, 17% AlF3, 5% CaF2, and 8% Al2O3 by mass percentage, and the electrolysis temperature was 920℃; the cathode was aluminum, and the anode was the material prepared in the examples; the corrosion rate was calculated using formula (1).

[0023] Molten salt electrolysis of carbon dioxide: the electrolyte composition was a mixture of 90% CaCl2 and 10% CaCO3 by mass percentage, and the electrolysis temperature was 850℃; the cathode was aluminum, and the anode was the material prepared in the examples; the corrosion rate was calculated using formula (1).

[0024] (Wloss = W b × C b + W a × C a ) x 106 x 365 x 24 / (S x p x t) (1)

[0025] In formula (1):

[0026] W loss is the annual corrosion rate of the anode (cm / year);

[0027] W b is the total amount of electrolyte (g), C b is the impurity concentration entering the electrolyte (ppm), W a is the total amount of cathode aluminum (g), C a is the impurity concentration entering the cathode aluminum (ppm), S is the surface area of the anode immersed during electrolysis (cm 2 ), p is the bulk density of the anode (g / cm 3 ), and t is the electrolysis time (h).

[0028] Example 1:

[0029] The mass fraction of the raw material powder used in this example is as follows: NiFe2O4 is 45%, NiO is 45%, and CuO is 10%.

[0030] The preparation method is as follows: the above-mentioned raw material powder is uniformly mixed in a ball mill for 4 h; the dried powder is cold-pressed into an anode green body at room temperature under a pressure of 200 MPa for 6 min, and then the anode green body is pre-sintered at 1400°C in an argon inert atmosphere for 4 h to obtain a ternary eutectic metal ceramic sintered body;

[0031] Then the sintered body is melted at 1800°C in an argon atmosphere and kept for 1 h, and the material is cooled to room temperature at a cooling rate of 8°C / min to obtain a Cu-NiO-NiFe2O4 ternary eutectic metal ceramic.

[0032] The macro optical micrograph of the material prepared in this example is shown in Figure 1 The material is dense in texture and the copper particles are uniformly distributed in the ceramic phase according to the optical microscopic analysis. The micrograph of the phase distribution of the material at a further magnification is shown in 2, the nickel oxide phase A accounts for about 52%, the nickel ferrite phase B accounts for about 45%, and the copper particle C accounts for about 3%. The XRD curve analysis of the material is shown in Figure 3 The graph shows that the material contains three crystal phases, which are determined as the nickel oxide phase, the nickel ferrite phase, and the copper phase. The microstructure of the ternary eutectic metal ceramic material prepared in this example is shown in Figure 4As shown in the figure, the distribution of iron, nickel and oxygen elements indicates that the metal nickel is distributed between the ceramic phases.

[0033] The molten salt electrolysis of aluminum was measured at 920℃ with a conductivity of 30S / cm, the anode in the electrolyte of aluminum with a current density of 0.8A / cm 2 , the electrolysis time was 24h, the annual corrosion rate of the anode electrode was 0.58cm; the prepared aluminum purity was 99.5%.

[0034] The molten salt electrolysis of carbon dioxide was measured with the anode in the electrolyte of carbon dioxide with a current density of 0.8A / cm 2 , the electrolysis time was 3h, the annual corrosion rate of the anode electrode was <2mm.

[0035] The SEM and energy spectrum of the electrolytic carbon prepared by the molten salt electrolysis of carbon dioxide are shown in Figure 5 , the EDS analysis results of the electrolytic carbon material are shown in Table 1, and the main component of the electrolytic carbon material is elemental carbon with a carbon content of more than 90%.

[0036] Table 1

[0037]

[0038] Example 2:

[0039] The mass fraction composition of the raw material powder used in this example is as follows: NiFe2O4 is 35%, Yb2O3 is 10%, NiO is 40%, and CuO is 15%.

[0040] The preparation method is: the above raw material powder is uniformly mixed in a ball mill, the ball milling time is 4h, the dried powder is cold-pressed into an anode green body at room temperature under a pressure of 100MPa for 1min, then the anode green body is pre-sintered at 1300℃ in an inert atmosphere for 5h, and a ternary eutectic metal ceramic sintered body is obtained;

[0041] Then the sintered body is melted at 1700℃ in an air environment and kept for 2h, and cooled to room temperature at a cooling rate of 5℃ / min, and a Cu-NiO-NiFe2O4 ternary eutectic metal ceramic is obtained.

[0042] The molten salt electrolysis of aluminum was measured at 920℃ with a conductivity of 40S / cm, the anode in the electrolyte with a current density of 0.8A / cm 2 , the electrolysis time was 24h, the annual corrosion rate of the anode electrode was 0.70cm, and the prepared aluminum purity was 99.7%.

[0043] The molten salt electrolysis of carbon dioxide was measured with the anode in the electrolyte of carbon dioxide with a current density of 0.8A / cm 2 , at a temperature of 850℃, the electrolysis time was 3h, and the annual corrosion rate of the anode electrode was <3mm.

[0044] Example 3

[0045] The raw material powder used in this example has the following composition by mass fraction: NiFe2O4 35%, Yb2O3 7%, Al2O3 8%, NiO 40%, CuO 10%.

[0046] The preparation method is as follows: the above raw material powder is uniformly mixed in a ball mill for 5 h, and the dried powder is cold-pressed into an anode green body at room temperature under a pressure of 150 MPa for 10 min, and then the anode green body is pre-sintered in an inert atmosphere at 1500°C for 3.5 h to obtain a ternary eutectic cermet sintered body;

[0047] Then the sintered body is melted at 1780°C in an argon atmosphere and kept for 1 h, and cooled to room temperature at a cooling rate of 10°C / min to obtain a Cu-NiO-NiFe2O4 ternary eutectic cermet.

[0048] The molten salt electrolysis aluminum experiment measures an electrical conductivity of 27 S / cm at 940°C, and the anode has a current density of 0.8 A / cm 2 in the electrolyte, an electrolysis time of 24 h, and an anode electrode annual corrosion rate of 0.51 cm, and the prepared aluminum has a purity of 99.4%.

[0049] The molten salt electrolysis carbon dioxide experiment measures an anode current density of 0.8 A / cm 2 in the carbon dioxide electrolyte, an electrolysis time of 3 h at a temperature of 850°C, and an anode electrode annual corrosion rate of <2 mm.

[0050] Example 4

[0051] The raw material powder used in this example has the following composition by mass fraction: NiFe2O4 35%, Yb2O3 5%, Al2O3 5%, NiO 32%, Fe2O3 5%, CuO 18%.

[0052] The preparation method is as follows: the above raw material powder is uniformly mixed in a ball mill for 6 h, and the dried powder is cold-pressed into an anode green body at room temperature under a pressure of 200 MPa for 8 min, and then the anode green body is pre-sintered in an inert atmosphere at 1400°C for 4.5 h to obtain a ternary eutectic cermet sintered body;

[0053] Then the sintered body is melted at 1900°C in an argon atmosphere and kept for 2 h, and cooled to room temperature at a cooling rate of 7°C / min to obtain a Cu-NiO-NiFe2O4 ternary eutectic cermet.

[0054] The molten salt electrolysis of aluminum was tested at 940°C with a conductivity of 34 S / cm, an anode current density of 0.8 A / cm 2 , an electrolysis time of 24 h, and an anode electrode annual corrosion rate of 0.68 cm, with the aluminum purity of 99.6%.

[0055] The molten salt electrolysis of carbon dioxide was tested at 850°C with an anode current density of 0.8 A / cm 2 , an electrolysis time of 3 h, and an anode electrode annual corrosion rate of <2 mm.

Claims

1. A ternary eutectic metal ceramic material, characterized in that: The preparation method of the material comprises the following steps: Step 1: ball-milling and mixing iron oxide, nickel oxide, copper oxide, lithium oxide, magnesium oxide, nickel ferrite, aluminum oxide, and ytterbium oxide according to a formula ratio to obtain a ceramic matrix raw material, drying, cold-pressing, and pre-sintering in an inert atmosphere at 1300-1500° C. to obtain a ceramic sintered body; wherein the mass percentage of the iron oxide is 0-10%, the mass percentage of the nickel oxide is 32%-64%, the mass percentage of the copper oxide is 6%-22%, the mass percentage of the lithium oxide is 0-2%, the mass percentage of the magnesium oxide is 0-4%, the mass percentage of the nickel ferrite is 30%-50%, the mass percentage of the aluminum oxide is 0-15%, and the mass percentage of the ytterbium oxide is 0-15%; Step 2: heating and melting the ceramic sintered body in an inert atmosphere or an oxidizing atmosphere, keeping the temperature, and then cooling and solidifying it to obtain a ternary eutectic metal ceramic material.

2. The ternary eutectic metal ceramic material according to claim 1, characterized in that: In step 1, the cold pressing temperature is room temperature, the pressure is 20-200 MPa, and the holding time is 1-10 minutes.

3. The ternary eutectic metal ceramic material according to claim 1, characterized in that: In step 2, the melting temperature is 1700-1900° C., and the cooling rate is 5-10° C. / min.

4. The ternary eutectic metal ceramic material according to claim 1, characterized in that: The material consists of a metal phase and two ceramic phases. The metal phase includes one or both of Ni and Cu metal elements. The two ceramic phases are respectively a nickel oxide phase and a nickel ferrite phase.

5. The ternary eutectic metal ceramic material according to claim 4, characterized in that: The nickel oxide phase contains lithium oxide, magnesium oxide, copper oxide and / or iron oxide; the nickel ferrite phase contains aluminum oxide and / or ytterbium oxide.

6. The ternary eutectic metal ceramic material according to claim 1, characterized in that: The particle size of the metal phase in the material is 0.1-20 microns, the crystal cluster size of the nickel oxide phase is 50-500 microns, and the crystal cluster size of the nickel ferrite phase is 10-300 microns.

7. Use of the material according to claim 1 as an anode material for molten salt electrolysis.

8. Use of the material according to claim 1 as an anode material for molten salt electrolysis of aluminum.

9. Use of the material according to claim 1 as an anode material for molten salt electrolysis of carbon dioxide.

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