CN106278281A - A kind of boronation titanio composite cathode material and preparation method thereof - Google Patents

Abstract

A kind of boronation titanio composite cathode material and preparation method thereof, belongs to technical field of ceramic material.Boronation titanio composite cathode material, by TiB₂Powder, metal Mo powder and Si are composited；Its phase composition is TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅.Its preparation method, including: (1) prepares TiB₂Mo mixed powder；(2) by TiB₂Mo mixed powder is mixed homogeneously with binding agent, and preparation molds material；(3) material compression molding will be molded, it is thus achieved that TiB₂Mo biscuit；(4) by TiB₂Mo biscuit is as skeleton, and Si, as infiltrant, carries out infiltration in vacuum, it is thus achieved that boronation titanio composite cathode material.The method is passed through first by raw material compression molding, then carries out, without pressure vacuum siliconising, preparing the boronation titanio composite cathode material that consistency is high, may be used in aluminium cell；The method step is simple, sintering temperature is low, and sintering process is undeformed, preparation cost is relatively low, and can produce variously-shaped product complicated, large-sized.

Description

Titanium boride-based composite cathode material and preparation method thereof

Technical Field

The invention belongs to the technical field of ceramic materials, and particularly relates to a titanium boride-based composite cathode material and a preparation method thereof.

Background

Titanium boride (TiB)₂) The ceramic has the advantages of high melting point, high hardness, wear resistance, corrosion resistance, oxidation resistance, good electrical conductivity and thermal conductivity and the like, and is widely applied to industries such as metallurgy, military, machinery, chemical engineering, electronics and the like. Especially due to TiB₂Has the characteristics of excellent conductivity and no reaction with aluminum (Al) liquid and cryolite, and can be used as a cathode material of an aluminum electrolysis cell. By using TiB₂The cathode can increase the yield of aluminum, improve the current efficiency (1000-2000 kWh electricity can be saved per ton of aluminum produced), and reduce the pollution caused by manufacturing carbon electrodes and the fluoride pollution caused by the sealing problem of an electrolytic cell.

The prior titanium boride product is mainly prepared by a pressureless sintering method and a hot-pressing sintering method, the pressureless sintering step comprises material mixing, molding and sintering, the sintering temperature is about 2000 ℃, the compactness of the titanium boride product prepared by pressureless sintering is low, so that electrolyte and aluminum liquid are easy to corrode materials during electrolysis, the service life of the materials is reduced, and the technical performance index of the titanium boride product cannot meet the requirements of the electrolytic aluminum industry; in addition, the hot-pressing sintering method is a main method for manufacturing the high-density titanium boride product, and comprises the steps of mixing materials and hot-pressing sintering; the sintering temperature is generally over 1800 ℃, the cost of the hot pressing method is higher, and products with large size and complex shape are difficult to process by adopting the hot pressing method; the problems lead the popularization and the application of the titanium boride ceramic material in the electrolytic aluminum industry to be greatly limited.

Disclosure of Invention

The invention aims to provide a titanium boride-based composite cathode material and a preparation method thereof, aiming at the problems in the existing preparation method of the titanium boride-based composite cathode material for an aluminum electrolytic cell. The method prepares the titanium boride-based composite cathode material with high density by compression molding the raw materials and then carrying out pressureless vacuum siliconizing, and can be used in an aluminum electrolytic cell; the method has the advantages of simple steps, low sintering temperature, no deformation in the sintering process, low preparation cost and capability of producing various products with complex shapes and large sizes.

The titanium boride-based composite cathode material consists of TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is (1: 2) - (1: 19); the mass M of Si is:

$M=\[\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+{\mathrm{\ρ}}_{Si}\left(V-\frac{M_1\×W_2}{{\mathrm{\ρ}}_{{\mathrm{TiB}}_2}}-\frac{\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+M_1\×W_1}{{\mathrm{\ρ}}_{{\mathrm{MoSi}}_2}}\right)\]---\left(1\right)$

wherein M is the mass of Si in the titanium boride-based composite cathode material; m₁Is TiB₂-the mass of the Mo biscuit; w₁Is TiB₂-Mo in the Mo mixed powder accounts for mass percent; ar (Ar)_MoIs the relative atomic mass of Mo; ar (Ar)_SiIs the relative atomic mass of Si; rho_SiIs the density of Si; v is TiB₂-volume of Mo biscuit; w₂Is TiB₂TiB in-Mo Mixed powder₂The mass percentage of the components is calculated;is TiB₂(ii) a density of (d);is MoSi₂The density of (c).

The phase composition of the titanium boride-based composite cathode material is TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅。

The titanium boride-based composite cathode material has the Vickers hardness of 14-21 GPa, the bending strength of 195-265 MPa and the fracture toughness of 4.0-4.6 MPa.m^1/2An open porosity of 0.1 to 0.4% and a bulk density of 3.6 to 4.1g/cm³The relative density is 97.02% -98.65%, the resistivity is 1.12 × 10^-7～9.67×10^-7Ω·m。

TiB as described above₂The purity of the powder is more than 98 percent, and the granularity is less than or equal to 0.5 mm.

The purity of the metal Mo powder is more than 99 percent, and the granularity is less than or equal to 50 mu m.

The above Si has a particle size of 0.1 to 10 mm.

The above-mentioned Si mass was calculated based on the Mo content and the pore volume.

The mass M of Si mentioned above is the theoretical mass.

The invention relates to a preparation method of a titanium boride-based composite cathode material, which comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder;

(2) according to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂5-10% of the total mass of the-Mo mixed powder;

(3) compression molding is carried out on the molded material under the pressure of 100-350 MPa, and drying is carried out for 10-20 h at the temperature of 80-350 ℃ after compression molding, so as to obtain TiB₂-a Mo biscuit;

(4) mixing TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameter is that the temperature is increased to 1450-1650 ℃ at the speed of 3-10 ℃/min, then the temperature is kept for 10-70 min, and the actual consumption of Si is 100-200% of the theoretical mass.

Wherein,

the method for calculating the mass of the required infiltration agent Si in the process of preparing the titanium boride-based composite cathode material comprises the following steps:

(a) measurement of TiB₂Mass M of the Mo biscuit₁According to TiB₂W in mass percentage of Mo in-Mo mixed powder₁Calculating TiB₂-mass of Mo in the Mo biscuit;

(b) according to TiB₂Mass and reaction equation of Mo in Mo biscuit, calculating and reacting with TiB₂Mass m of silicon required for Mo reaction in Mo biscuit₁With MoSi₂Mass m of₂；

Mo+2Si→MoSi₂

(c) Calculating the volume of the air hole:

(I) measurement of TiB₂Mass M of the Mo biscuit₁According to TiB₂TiB in-Mo Mixed powder₂Mass percentage of W₂Calculating TiB₂TiB in-Mo biscuit₂Calculating the mass of TiB₂Volume V of₁；

(II) according to MoSi₂Mass m of₂Calculating MoSi₂Volume V of₂；

(III) measurement of TiB₂Volume V of the Mo green body, volume V of the pores₃＝V-V₁-V₂；

Volume of air hole V₃I.e. filling TiB₂-the volume of silicon required for the pores in the Mo biscuit;

(d) according to the filling of TiB₂-the volume of silicon required for pores in the Mo biscuit, calculating the TiB fill₂Mass m of silicon required for pores in the Mo biscuit₃；

(e) Amount of actual silicon M_{Oozing out}Is 100-200% of theoretical mass M, because in the vacuum infiltration process, the temperature is higher, and the melted Si is partially evaporated;

namely M_{Oozing out}＝M×(100％～200％)＝(m₁+m₃)×(100％～200％)。

The specific calculation formula is as follows:

$m_1=\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si};$

$m_2=\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+M_1\×W_1;$

$V_3=V-\frac{M_1\×W_2}{{\mathrm{\ρ}}_{{\mathrm{TiB}}_2}}-\frac{m_2}{{\mathrm{\ρ}}_{{\mathrm{MoSi}}_2}};$

m₃＝ρ_si×V₃；

the theoretical mass M general formula of the infiltration agent Si required in the process of preparing the titanium boride-based composite cathode material is as follows:

$M=\[\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+{\mathrm{\ρ}}_{Si}\left(V-\frac{M_1\×W_2}{{\mathrm{\ρ}}_{{\mathrm{TiB}}_2}}-\frac{\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+M_1\×W_1}{{\mathrm{\ρ}}_{{\mathrm{MoSi}}_2}}\right)\]$

practical dosage M of infiltration agent Si required in the process of preparing titanium boride-based composite cathode material_{Oozing out}The general formula is:

wherein M is_{Oozing out}Process for preparing titanium boride-based composite cathode materialThe actual dosage of the required infiltration agent Si; m is the theoretical mass of a required infiltration agent Si in the process of preparing the titanium boride-based composite cathode material; m₁Is TiB₂-the mass of the Mo biscuit; w₁Is TiB₂-Mo in the Mo mixed powder accounts for mass percent; ar (Ar)_MoIs the relative atomic mass of Mo; ar (Ar)_siIs the relative atomic mass of Si; rho_siIs the density of Si; v is TiB₂-volume of Mo biscuit; w₂Is TiB₂TiB in-Mo Mixed powder₂The mass percentage of the components is calculated;is TiB₂(ii) a density of (d);is MoSi₂The density of (c).

In the above (1), TiB₂The preparation method of the-Mo mixed powder comprises the following steps: mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder (1: 2) to (1: 19), metal Mo powder and absolute ethyl alcohol (1: 3) to (1: 20).

The step of drying to remove the absolute ethyl alcohol is drying for 4-10 hours at the temperature of 100-300 ℃.

The described TiB₂The powder, the metal Mo powder and the absolute ethyl alcohol are uniformly mixed by adopting a mechanical mixing mode.

In the step (2), the binder is polyvinyl alcohol aqueous solution, polyvinyl pyrrolidone aqueous solution or carboxymethyl cellulose aqueous solution, and the mass percentage concentration of the binder is 3-8%.

In the above (2), the TiB₂the-Mo mixed powder and the adhesive are mixed by a manual mixing or mechanical mixing mode, and during the mixing process, the adhesive material naturally forms granular adhesive material.

And (3) carrying out compression molding on the molding material, wherein the compression molding temperature is normal temperature, and the pressure is maintained for 5-15 s.

In the step (4), the vacuum infiltration adopts pressureless vacuum infiltration.

In the step (4), the vacuum infiltration equipment is a graphite vacuum heating furnace.

In the step (4), the vacuum degree of the vacuum infiltration is less than or equal to 200 Pa.

In the step (4), the amount of Si is determined according to the actual amount M_{Oozing out}Is determined by the formula (c).

The principle of the invention is as follows: adopts liquid silicon with reaction activity as an impregnant and infiltrates porous TiB containing Mo under the action of capillary force₂-Mo ceramic biscuit and reaction with Mo therein to MoSi₂And the impregnant fills the original air holes in the biscuit to finish the densification process.

Compared with the prior art, the invention has the advantages that:

1. the method has simple steps and low temperature requirement, can obtain the titanium boride-based composite cathode material with high density under the condition of lower preparation cost, has sample size change of less than 0.5 percent in the preparation process, and belongs to net size sintering.

2. The method can produce various products with complex shapes and large sizes, and is easy to popularize and apply in the field of manufacturing titanium boride-based composite cathode materials for aluminum electrolysis cells.

3. The product prepared by the invention has excellent properties, the Vickers hardness of the product is 14-21 GPa, the bending strength of the product is 195-265 MPa, and the fracture toughness of the product is 4.0-4.6 MPa^1/2An open porosity of 0.1 to 0.4% and a bulk density of 3.6 to 4.1g/cm³The relative density is 97.02% -98.65%, the resistivity is 1.12 × 10^-7～9.67×10^-7Ω·m。

Drawings

FIG. 1 is an X-ray diffraction pattern of a titanium boride-based composite cathode material prepared in an example of the present invention, wherein (a) is the product of example 5 and (b) is the product of example 6;

FIG. 2 is a scanning electron micrograph of a titanium boride-based composite cathode material and an EDS analysis chart of each region in example 5 of the present invention, in which (c) is a scanning electron micrograph of the titanium boride-based composite cathode material, and (d) is TiB₂EDS composition analysis chart of the region, (e) MoSi₂An EDS component analysis map of the region, (f) an EDS component analysis map of the Si region;

FIG. 3 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 1 of the present invention;

FIG. 4 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 2 of the present invention;

FIG. 5 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 3 of the present invention;

FIG. 6 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 4 of the present invention;

FIG. 7 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 5 of the present invention;

FIG. 8 is a scanning electron micrograph of a titanium boride-based composite cathode material according to example 6 of the present invention;

in FIGS. 3 to 8, the light gray area is TiB₂Region, white region is MoSi₂The region, dark gray area is the Si region.

Detailed Description

The present invention will be described in further detail with reference to examples.

TiB used in the embodiment of the invention₂The powder has a purity of more than 98% and a particle size of less than 0.5 mm.

The metal Mo powder adopted in the embodiment of the invention has the purity of more than 99 percent and the particle size of less than 50 mu m.

The granularity of Si adopted in the embodiment of the invention is 0.1-10 mm.

TiB in the examples of the present invention₂The powder, the metal Mo powder and the absolute ethyl alcohol are mixed in a mechanical mixing mode.

TiB in the examples of the invention₂the-Mo mixed powder and the binder are mixed by a manual mixing or mechanical mixing mode, and granular materials are naturally formed in the mixing process.

The equipment adopted by the compression molding in the embodiment of the invention is a WE-10A type hydraulic universal testing machine.

The equipment adopted by infiltration in the embodiment of the invention is a graphite vacuum heating furnace.

The Vickers indentation hardness test method in the embodiment of the invention is a Vickers indentation hardness method, and a 450SVD Vickers hardness tester is adopted.

The bending strength test method in the embodiment of the invention is a three-point bending strength method and adopts an electronic universal stretcher.

The method for testing the fracture toughness in the embodiment of the invention is an SENB method, and an electronic universal stretcher is adopted.

The method for testing the open porosity in the embodiment of the invention adopts an Archimedes drainage method.

In the embodiment of the invention, a double-electric-measurement four-probe tester is adopted for testing the resistivity.

The method for drying and removing the absolute ethyl alcohol in the embodiment of the invention is drying for 4-10 hours at the temperature of 100-300 ℃.

Example 1

A titanium boride-based composite cathode material is prepared from TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 19; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 19, metal Mo powder and absolute ethyl alcohol are 1: 20.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂10% of the total mass of the Mo mixed powder, and the binder is a polyvinyl alcohol aqueous solution with the mass percentage concentration of 3%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at 100MPa and the temperature at normal temperature for 15s, drying at 350 ℃ for 10h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1450 ℃ at the speed of 10 ℃/min, and then the temperature is kept for 70 min.

Wherein,

the method for calculating the mass of the required infiltration agent Si in the process of preparing the titanium boride-based composite cathode material comprises the following steps:

(a) measurement of TiB₂Mass M of the Mo biscuit₁According to TiB₂W in mass percentage of Mo in-Mo mixed powder₁Calculating TiB₂-mass of Mo in the Mo biscuit;

(b) according to TiB₂The mass of Mo in the Mo biscuit and the formula (1.1), the calculation of the sum of the mass and the value of TiB₂Mass m of silicon required for Mo reaction in Mo biscuit₁With MoSi₂Mass m of₂；

Mo+2Si→MoSi₂(1.1)

(c) Calculating the volume of the air hole:

(I) measurement of TiB₂Mass M of the Mo biscuit₁According to TiB₂TiB in-Mo Mixed powder₂Mass percentage of W₂Calculating TiB₂TiB in-Mo biscuit₂Calculating the mass of TiB₂Volume V of₁；

(II) according to MoSi₂Mass m of₂Calculating MoSi₂Volume V of₂；

(III) measurement of TiB₂Volume V of the Mo green body, volume V of the pores₃＝V-V₁-V₂；

Volume of air hole V₃I.e. filling TiB₂-the volume of silicon required for the pores in the Mo biscuit;

(d) according to the filling of TiB₂-the volume of silicon required for pores in the Mo biscuit, calculating the TiB fill₂Mass m of silicon required for pores in the Mo biscuit₃；

(e) Mass M of actual silicon_{Oozing out}100-200% of theoretical mass M, because in the vacuum infiltration process, the temperature is higher, and the molten silicon is partially evaporated;

namely M_{Oozing out}＝M×(100％～200％)＝(m₁+m₃)×(100％～200％)。

The specific calculation formula is as follows:

$m_1=\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si};$

$m_2=\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+M_1\×W_1;$

$V_3=V-\frac{M_1\×W_2}{{\mathrm{\ρ}}_{{\mathrm{TiB}}_2}}-\frac{m_2}{{\mathrm{\ρ}}_{{\mathrm{MoSi}}_2}};$

m₃＝ρ_si×V₃；

practical dosage M of infiltration agent Si required in the process of preparing titanium boride-based composite cathode material_{Oozing out}The general formula is:

wherein M is_{Oozing out}The actual dosage of the infiltration agent Si required in the process of preparing the titanium boride-based composite cathode material; m is the theoretical mass of a required infiltration agent Si in the process of preparing the titanium boride-based composite cathode material; m₁Is TiB₂-the mass of the Mo biscuit; w₁Is TiB₂-Mo in the Mo mixed powder accounts for mass percent; ar (Ar)_MoIs the relative atomic mass of Mo; ar (Ar)_SiIs the relative atomic mass of Si; rho_siIs the density of Si; v is TiB₂-volume of Mo biscuit; w₂Is TiB₂TiB in-Mo Mixed powder₂The mass percentage of the components is calculated;is TiB₂(ii) a density of (d);is MoSi₂The density of (c).

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅。

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 14GPa, the bending strength of 231MPa and the fracture toughness of 4.09 MPa.m^1/2The open porosity was 0.22%, and the bulk density was 3.61g/cm³The relative density was 98.01%, and the resistivity was 9.67 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 3.

Example 2

A titanium boride-based composite cathode material is prepared from TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 9; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 9, metal Mo powder and absolute ethyl alcohol are 1: 10.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; carrying out the bonding on the materialsSieving to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂9% of the total mass of the Mo mixed powder, and the binder is a polyvinylpyrrolidone aqueous solution with the mass percentage concentration of 4%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at the normal temperature of 150MPa for 10s, drying at the temperature of 300 ℃ for 12h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1500 ℃ at the speed of 8 ℃/min, and then the temperature is kept for 60 min.

Wherein,

the calculation method of the required Si mass of the infiltration agent in the process of preparing the titanium boride-based composite cathode material is the same as that described in example 1.

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅；

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 15GPa, the bending strength of 195MPa and the fracture toughness of 4.14 MPa-m^1/2The open porosity was 0.16%, and the bulk density was 3.63g/cm³The relative density was 97.02%, and the resistivity was 7.76 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 4.

Example 3

Titanium boride-based composite cathodeMaterial of TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 5.67; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 5.67, metal Mo powder and absolute ethyl alcohol are 1: 6.67.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂8% of the total mass of the Mo mixed powder, and the binder is a polyvinylpyrrolidone aqueous solution with the mass percentage concentration of 5%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at normal temperature for 10s, drying at 250 ℃ for 14h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1550 ℃ at the speed of 6 ℃/min, and then the temperature is kept for 50 min.

Wherein,

the calculation method of the required Si mass of the infiltration agent in the process of preparing the titanium boride-based composite cathode material is the same as that described in example 1.

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅；

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 17GPa, the bending strength of 202MPa and the fracture toughness of 4.05 MPa-m^1/2An open porosity of 0.23% and a bulk density of 3.70g/cm³The relative density was 98.21% and the resistivity was 1.27 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 5.

Example 4

A titanium boride-based composite cathode material is prepared from TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 4; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 4, metal Mo powder and absolute ethyl alcohol are 1: 5.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder;sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂7% of the total mass of the Mo mixed powder, wherein the binder is a carboxymethyl cellulose aqueous solution with the mass percentage concentration of 6%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at the normal temperature of 250MPa for 10s, drying at the temperature of 200 ℃ for 16h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1600 ℃ at the speed of 5 ℃/min, and then the temperature is preserved for 40 min.

Wherein,

the calculation method of the required Si mass of the infiltration agent in the process of preparing the titanium boride-based composite cathode material is the same as that described in example 1.

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅；

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 18GPa, the bending strength of 229MPa and the fracture toughness of 4.38 MPa-m^1/2An open porosity of 0.29% and a bulk density of 3.74g/cm³The relative density was 98.16%, and the resistivity was 1.12 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 6.

Example 5

Titanium borideBased on a composite cathode material consisting of TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 3; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 3, metal Mo powder and absolute ethyl alcohol are 1: 4.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂6% of the total mass of the Mo mixed powder, and the binder is a polyvinyl alcohol aqueous solution with the mass percentage concentration of 7%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at normal temperature for 10s, drying at 150 ℃ for 18h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1650 ℃ at the speed of 4 ℃/min, and then the temperature is preserved for 20 min.

Wherein,

the calculation method of the required Si mass of the infiltration agent in the process of preparing the titanium boride-based composite cathode material is the same as that described in example 1.

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅；

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 18GPa, the bending strength of 238MPa and the fracture toughness of 4.54 MPa-m^1/2An open porosity of 0.27% and a bulk density of 3.81g/cm³The relative density was 98.65% and the resistivity was 1.35 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 7; the X-ray diffraction pattern of the titanium boride-based composite cathode material prepared in this example is shown in fig. 1 (a); in the present example, a scanning electron micrograph of the titanium boride-based composite cathode material and an EDS analysis chart of each region are shown in FIG. 2, (c) is a scanning electron micrograph of the titanium boride-based composite cathode material, and (d) is TiB₂EDS composition analysis chart of the region, (e) MoSi₂EDS component analysis chart of region (f) is EDS component analysis chart of Si region.

Example 6

A titanium boride-based composite cathode material is prepared from TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 2.33; the Si content was calculated from the Mo content and the pore volume, and was determined specifically according to formula (1).

The preparation method of the titanium boride-based composite cathode material comprises the following steps:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder:

mixing TiB₂Powder, a,Uniformly mixing metal Mo powder and absolute ethyl alcohol to obtain a mixed material, drying the mixed material to remove the absolute ethyl alcohol, and preparing the TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is 1: 2.33, metal Mo powder and absolute ethyl alcohol are 1: 3.33.

(2) According to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂5% of the total mass of the Mo mixed powder, and the binder is polyvinylpyrrolidone aqueous solution with the mass percentage concentration of 8%;

(3) putting the mould pressing material into a mould, carrying out mould pressing forming, keeping the pressure of the mould pressing forming at the normal temperature for 5s, drying at the temperature of 80 ℃ for 20h after mould pressing forming, and obtaining TiB₂-a Mo biscuit;

(4) placing silicon particles with the particle size of 0.1-10 mm in TiB in a graphite vacuum heating furnace₂Upper surface of Mo biscuit, TiB₂Carrying out vacuum infiltration by taking the-Mo biscuit as a framework and Si as an infiltration agent to obtain a titanium boride-based composite cathode material; wherein the vacuum infiltration parameters are as follows: the vacuum degree is less than or equal to 200Pa, the temperature is raised to 1650 ℃ at the speed of 3 ℃/min, and then the temperature is preserved for 10 min.

Wherein,

the calculation method of the required Si mass of the infiltration agent in the process of preparing the titanium boride-based composite cathode material is the same as that described in example 1.

The phase composition of the titanium boride-based composite cathode material prepared in this example was TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅；

The titanium boride-based composite cathode material prepared in the embodiment has the Vickers hardness of 20GPa, the bending strength of 264MPa and the fracture toughness of 4.34 MPa-m^1/2The open porosity was 0.36%, and the bulk density was 4.02g/cm³The relative density was 98.16%, and the resistivity was 8.69 × 10^-7Ω·m。

The scanning electron micrograph of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 8; the X-ray diffraction pattern of the titanium boride-based composite cathode material prepared in this example is shown in FIG. 1 (b).

By combining the X-ray diffraction pattern and the EDS composition analysis, FIGS. 3 to 8 are scanning electron micrographs of the composite materials of examples 1 to 6 under different addition amounts of Mo, and the light gray area in the pictures is TiB₂Region, white region is MoSi₂The region, dark gray area is the Si region. As can be seen from FIGS. 3 to 8, as the Mo content increases, Mo reacts with Si to form MoSi₂Increased amount of (i.e. MoSi in the figure)₂The corresponding white area shows a more obvious increasing trend; in addition, as the Mo content increases, the dispersion uniformity of the raw material Mo powder increases.

Claims (10)

1. The titanium boride-based composite cathode material is characterized by comprising TiB₂The powder, the metal Mo powder and Si are compounded; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder is (1: 2) - (1: 19); the Si content was calculated from the Mo content and pore volume:

in the titanium boride-based composite cathode material, the mass M general formula of Si is as follows:

$M=\[\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+{\mathrm{\ρ}}_{Si}\left(V-\frac{M_1\×W_2}{{\mathrm{\ρ}}_{{\mathrm{TiB}}_2}}-\frac{\frac{2M_1\×W_1}{{\mathrm{Ar}}_{Mo}}\·{\mathrm{Ar}}_{Si}+M_1\×W_1}{{\mathrm{\ρ}}_{{\mathrm{MoSi}}_2}}\right)\]$

wherein, the mass of Si in the M titanium boride-based composite cathode material; m₁Is TiB₂-the mass of the Mo biscuit; w₁Is TiB₂-Mo in the Mo mixed powder accounts for mass percent; ar (Ar)_MoIs the relative atomic mass of Mo; ar (Ar)_SiIs the relative atomic mass of Si; rho_SiIs the density of Si; v is TiB₂-volume of Mo biscuit; w₂Is TiB₂TiB in-Mo Mixed powder₂The mass percentage of the components is calculated;is TiB₂(ii) a density of (d);is MoSi₂The density of (c).

2. The method of claim 1The titanium boride-based composite cathode material is characterized in that the phase composition of the titanium boride-based composite cathode material is TiB₂、MoSi₂、Si、Mo₂B、Ti₃B₄And TiB₅₅。

3. The titanium boride-based composite cathode material as claimed in claim 1, wherein the titanium boride-based composite cathode material has a vickers hardness of 14 to 21GPa, a bending strength of 195 to 265MPa, and a fracture toughness of 4.0 to 4.6mpa.m^1/2An open porosity of 0.1 to 0.4% and a bulk density of 3.6 to 4.1g/cm³The relative density is 97.02% -98.65%, the resistivity is 1.12 × 10^-7～9.67×10^-7Ω.m。

4. The titanium boride-based composite cathode material of claim 1 wherein said TiB₂The purity of the powder is more than 98 percent, and the granularity is less than or equal to 0.5 mm; the purity of the metal Mo powder is more than 99 percent, and the granularity is less than or equal to 50 mu m; the granularity of the Si is 0.1-10 mm.

5. The method for preparing the titanium boride-based composite cathode material of claim 1, comprising the steps of:

(1) according to the proportion, TiB₂Preparing TiB from powder and metal Mo powder₂-Mo mixed powder;

(2) according to the proportion, TiB₂Uniformly mixing the-Mo mixed powder with a binder to obtain a binder; sieving the bonding material to obtain bonding material particles with the granularity of 24-80 meshes as a die pressing material, wherein the bonding agent accounts for TiB₂5-10% of the total mass of the-Mo mixed powder;

(3) compression molding is carried out on the molded material under the pressure of 100-350 MPa, and drying is carried out for 10-20 h at the temperature of 80-350 ℃ after compression molding, so as to obtain TiB₂-a Mo biscuit;

(4) mixing TiB₂Carrying out vacuum infiltration by taking-Mo biscuit as a framework and Si as an infiltration agent to obtain the titanium boride-based composite cathode material(ii) a Wherein the vacuum infiltration parameter is that the temperature is increased to 1450-1650 ℃ at the speed of 3-10 ℃/min, then the temperature is kept for 10-70 min, and the actual consumption of Si is 100-200% of the theoretical mass.

6. The method for preparing a titanium boride-based composite cathode material as claimed in claim 5, wherein in the step (1), TiB₂The preparation method of the-Mo mixed powder comprises the following steps: mixing TiB₂Uniformly mixing the powder, the metal Mo powder and the absolute ethyl alcohol to obtain a mixed material, drying the mixed material at 100-300 ℃ for 4-10 hours to remove the absolute ethyl alcohol, and preparing TiB₂-Mo mixed powder; wherein, according to the mass ratio, the metal Mo powder and the TiB₂Powder (1: 2) to (1: 19), metal Mo powder and absolute ethyl alcohol (1: 3) to (1: 20).

7. The titanium boride-based composite cathode material as claimed in claim 5, wherein the binder is an aqueous solution of polyvinyl alcohol, polyvinylpyrrolidone or carboxymethylcellulose, and the concentration of the binder is 3 to 8% by mass.

8. The method for preparing titanium boride-based composite cathode material as claimed in claim 5, wherein in the step (2), the TiB₂the-Mo mixed powder and the adhesive are mixed by a manual mixing or mechanical mixing mode, and during the mixing process, the adhesive material naturally forms granular adhesive material.

9. The method for preparing the titanium boride-based composite cathode material as claimed in claim 5, wherein in the step (3), the compression molding material is subjected to compression molding, the compression molding temperature is normal temperature, and the pressure is maintained for 5-15 s.

10. The method for preparing titanium boride-based composite cathode material as claimed in claim 5, wherein in the step (4), the vacuum infiltration is pressureless vacuum infiltration; the equipment adopted by the vacuum infiltration is a graphite vacuum heating furnace; the vacuum degree of the vacuum infiltration is less than or equal to 200 Pa.