Preparation of nano single crystal lanthanum hexaboride and application of nano single crystal lanthanum hexaboride in electron microscope filament preparation

A nano-single crystal, lanthanum boride technology, applied in nanotechnology, boron/boride, metal boride, etc., can solve the problem of inability to mass industrial production, current efficiency not higher than 50%, borides not easy to be continuous, etc. problems, to achieve broad industrialization prospects, low cost, and the effect of improving the consistency of single crystal particle size

Inactive Publication Date: 2015-12-30
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the existing shortcomings cannot be ignored: (1) several boride phases may be generated; (2) the preparation of boride by molten salt electrolysis is not easy to be continuous, because most of the electrolysis products are insulators, which are attached near the cathode, preventing the electrolysis from continuing conduct
(3) The molten salt electrolysis method generally has the disadvantage of low current efficiency, and the current efficiency is not higher than 50%.
However, pulse current sintering also has disadvantages such as uneven discharge, difficulty in product quality control, and inability to mass industrial production.

Method used

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  • Preparation of nano single crystal lanthanum hexaboride and application of nano single crystal lanthanum hexaboride in electron microscope filament preparation

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] Embodiment 1: take lanthanum oxide and lithium borohydride as the synthesis of lanthanum boride of raw material

[0039] Weigh 0.001 moles (0.326g) of lanthanum oxide and 0.006 moles (0.26g) of lithium borohydride according to the molar ratio of lanthanum and boron being 1:6 (La:B=1:6) and add them to the ball mill jar, and ball mill at 400rpm After 16 hours, a mechanical mixture of lanthanum oxide and lithium borohydride was obtained, which was placed in a reactor, heated from room temperature to 300° C. at a heating rate of 2° C. / min, and then kept for 2 hours.

[0040] La 2 o 3 +12LiBH 4 →2LaB 6 +3Li 2 O+6LiH+21H 2

[0041] Release hydrogen gas, cool to room temperature and wash with water. During water washing, LiH reacts with water to generate hydrogen and lithium hydroxide. Lithium hydroxide is dissolved in water, centrifuged, and vacuum-dried at 80°C to obtain nano single crystal lanthanum boride.

Embodiment 2

[0042] Embodiment 2: take lanthanum hydroxide and sodium borohydride as the synthesis of lanthanum boride of raw material

[0043] Weigh 0.001 mole (0.19g) of lanthanum hydroxide and 0.006 mole (0.227g) of sodium borohydride as the molar ratio of lanthanum to boron is 1:6 (La:B=1:6) After ball milling for 2 hours, a mechanical mixture of lanthanum hydroxide and sodium borohydride was obtained, which was placed in a reactor at a heating rate of 2°C / min and heated to 500°C for 2 hours.

[0044] La(OH) 3 +6NaBH 4 →LaB 6 +3Na 2 O+13.5H 2

[0045] Release the hydrogen gas, cool to room temperature and wash with water. During water washing, sodium oxide reacts with water to form sodium hydroxide. Sodium hydroxide is dissolved in water, centrifuged, and vacuum-dried at 80°C to obtain nano single crystal lanthanum boride.

Embodiment 3

[0046] Embodiment 3: take lanthanum carbonate and potassium borohydride as the synthesis of lanthanum boride of raw material

[0047] Weigh 0.01 mole (0.458g) of lanthanum carbonate and 0.06 mole (0.646g) of potassium borohydride as the molar ratio of lanthanum and boron is 1:6 (La:B=1:6) and add them to the ball mill jar, and ball mill at 400rpm After 2 hours, a mechanical mixture of lanthanum carbonate and potassium borohydride was obtained, which was placed in a reactor and heated to 700°C at a heating rate of 2°C / min for 2 hours.

[0048] La 2 (CO 3 ) 3 +12KBH 4 →2LaB 6 +3K 2 CO 3 +6KH+21H 2

[0049] Release hydrogen gas, cool to room temperature and wash with water. KH reacts with water to generate hydrogen and potassium hydroxide during water washing. Potassium hydroxide is dissolved in water, centrifuged, and vacuum-dried at 80°C to obtain nano single crystal lanthanum boride.

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Abstract

The invention relates to the field of field emission materials, and aims at providing the preparation of nano single crystal lanthanum hexaboride and the application of the nano single crystal lanthanum hexaboride in the electron microscope filament preparation. The preparation comprises the following steps: weighing lanthanum compounds and alkali metal boron hydride powder, and performing ball-milling to obtain a mechanical mixture; placing the mechanical mixture into a reactor, heating up to 300 to 700 DEG C from the room temperature at the heating rate of 2 DEG C per minute, then performing heat preservation for 2 hours and releasing hydrogen; then cooling, washing, separating and performing vacuum drying at the temperature of 80 DEG C to obtain the nano single crystal lanthanum hexaboride. According to the preparation, the synthesis temperature of lanthanum hexaboride is greatly decreased, the quality management during the industrial production of the lanthanum hexaboride is facilitated, the single crystal particle size consistency of the lanthanum hexaboride is improved, and the quality management of large-scale production is facilitated. The raw material cost is low, the energy consumption is low, and the preparation process is easy and simple. When the nano single crystal lanthanum hexaboride is used for preparing an electron microscope filament, low work function, low volatility and low resistance are realized; the mechanical strength is high, and the chemical stability is good, so that an electron microscope image is more clear, the cost is lower and the service life is prolonged greatly.

Description

technical field [0001] The invention relates to the field of field emission materials, and relates to a preparation method of nano single crystal lanthanum boride, in particular to a preparation method of nano single crystal lanthanum boride field emission material with low reaction temperature, mild reaction conditions and low energy consumption. Effectively improve the field emission intensity and life of the lanthanum boride electron microscope filament. Background technique [0002] Lanthanum boride is a reddish-purple crystal with a very high melting point of 2715°C, above which lanthanum boride decomposes. Insoluble in water and acid at room temperature. Usually, lanthanum trioxide and borax are dissolved in a suitable molten salt, and electrolyzed by a graphite anode at high temperature to deposit lanthanum hexaboride on a graphite or steel cathode. Due to its high melting point and high thermal electron radiation energy, it can replace high melting point metals and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B35/04H01J1/304H01J9/02B82Y40/00
Inventor 刘宾虹李洲鹏
Owner ZHEJIANG UNIV
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