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Rapid preparation method of LaB6 polycrystalline bulk cathode material

A cathode material and crystal block technology, which is applied in the field of rare earth boride cathode materials, can solve problems such as poor mechanical properties and emission properties of products, unfavorable large-scale industrial production and application, and complicated nano-powder preparation process, etc., to achieve large-scale Industrial production, improved mechanical and emission properties, and short sintering time

Inactive Publication Date: 2009-03-11
BEIJING UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] At present, LaB is usually prepared by hot pressing or cold pressing sintering method. 6 Polycrystalline blocks, and the above methods all have high sintering temperature (2000-2300 ° C), long sintering time (2-10h), and the prepared product is not dense enough (relative density is lower than 90%), resulting in the mechanical properties of the product and Poor launch performance limits its range of applications
Chinese patent ZL200610012297.9 provides an in-situ synthesis of high-purity nanocrystalline LaB 6 The preparation method of the block is divided into two steps. First, the nano-lanthanum hydride powder is prepared by the hydrogen arc evaporation condensation method, and then the lanthanum hydride powder is mixed with the B powder, and the SPS reaction is used for sintering. The sintering temperature is 1150-1400 ° C. Prepare LaB under the conditions of pressure 30-50MPa and holding time 2-10min 6 Cathode material, but the nano powder preparation process of this method is complicated, and the output is low, the cost is high, and it is not conducive to large-scale industrial production and application

Method used

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  • Rapid preparation method of LaB6 polycrystalline bulk cathode material
  • Rapid preparation method of LaB6 polycrystalline bulk cathode material

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] LaB 6 The powder is loaded into a graphite mold, and after being pressurized and compacted, it is put into an SPS sintering furnace for sintering. The sintering process is as follows: the axial pressure is 30MPa, the atmosphere is high-purity argon gas (purity 99.999%), and the temperature is increased at 90°C / min. The rate of temperature rise, the sintering temperature is 1400 ° C, the holding time is 20 min, and the furnace is cooled to room temperature to obtain LaB 6 Polycrystalline bulk.

[0014] from figure 1 It can be seen that the sintered bulk crystallizes well and is LaB 6 Single phase structure. from figure 2 It can be seen that LaB 6 The grains are uniform, and the fracture mode of the sample is transgranular fracture, which helps to increase the flexural strength of the sample. The relative density of the sample reaches 90.5%, and the Vickers hardness reaches 1548kg / mm 2 , the flexural strength reaches 167.4MPa. The emission current density of the ...

Embodiment 2

[0016] LaB 6 The powder is put into a graphite mold, and after being pressurized and compacted, it is put into an SPS sintering furnace for sintering. The sintering process is as follows: the axial pressure is 40 MPa, the atmosphere is high-purity argon gas (purity 99.999%), and the temperature is increased at a temperature of 150°C / min. The rate of heating, the sintering temperature is 1500 ° C, the holding time is 10 min, and the furnace is cooled to room temperature to obtain LaB 6 Polycrystalline bulk.

[0017] LaB 6 The polycrystalline bulk was analyzed as LaB by X-ray diffraction 6 Single phase structure. The relative density of the sample reaches 92.6%, and the Vickers hardness reaches 1580kg / mm 2 , the flexural strength reaches 195.6MPa. The emission current density of the sample reaches 16.63A / cm at 1520℃ 2 , the work function is 2.40eV.

Embodiment 3

[0019] LaB 6 The powder is put into a graphite mold, and after being pressurized and compacted, it is put into an SPS sintering furnace for sintering. The sintering process is as follows: the axial pressure is 50MPa, the vacuum is evacuated to 5Pa, and the temperature is increased at a heating rate of 200℃ / min. The sintering temperature is 1700 ℃, the holding time is 5min, and the furnace is cooled to room temperature to obtain LaB 6 Polycrystalline bulk.

[0020] LaB 6 The polycrystalline bulk was analyzed as LaB by X-ray diffraction 6 Single phase structure. The relative density of the sample reaches 96.5%, and the Vickers hardness reaches 1720kg / mm 2 , the flexural strength reaches 203.2MPa. The emission current density of the sample reaches 16.98A / cm at 1520℃ 2 , the work function is 2.40eV.

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Abstract

The invention discloses a method for quickly preparing bulk LaB6 polycrystal cathode material, and belongs to the technical field of rare earth boride hot cathode material. The prior preparation technology of LaB6 cathode material has the problems of high sintering temperature, long sintering time, and complicated process and so on. The method is as follows: LaB6 powder is placed in a mould, compacted and placed in a SPS sintering furnace to be sintered under the conditions of an applied pressure of from 30 to 50 Mpa, an atmosphere of high-purity argon gas or vacuum with a vacuum degrees more than 5Pa, temperature raise at a speed of from 90 to 200 DEG C / min, a sintering temperature of between 1400 and 1700 DEG C, and a temperature holding period of from 5 to 20 minutes, and then the bulk LaB6 polycrystal cathode material is obtained as the furnace cools down. The method of the invention lowers the sintering temperature, reduces sintering time and simplifies process while improving the mechanical property and emission property of LaB6 cathode material.

Description

technical field [0001] The invention belongs to the technical field of rare earth boride cathode materials, in particular to a rapid preparation of LaB by spark plasma sintering (SPS). 6 Methods of polycrystalline bulk cathode materials. Background technique [0002] LaB 6 It is one of the cathodes with the best performance among rare earth hexaboride cathodes. It has the ideal characteristics of low work function, high melting point, high hardness, high thermal stability and chemical stability as cathode materials. Furthermore, compared to other hot cathodes, LaB 6 It also has many advantages such as high emission current density, resistance to ion bombardment, good resistance to poisoning, and long service life. Now it has been successfully used in plasma sources, scanning electron microscopes, transmission electron microscopes, electron beam exposure machines, electron beam welders, Auger It has broad application prospects in various equipment such as energy spectromet...

Claims

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Application Information

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IPC IPC(8): C01B35/04
Inventor 张久兴周身林刘丹敏
Owner BEIJING UNIV OF TECH
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