Method for synthesizing lanthanum hexaboride nano powder by solid-phase reaction under low temperature

A technology of lanthanum hexaboride and nanopowder, which is applied in the field of preparation of lanthanum hexaboride materials, can solve the problems of high energy consumption, high temperature requirements, and high cost of raw materials, and achieve low reaction temperature, simple and easy-to-control process, and high product quality. good shape effect

Inactive Publication Date: 2009-08-12
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] At present, the common methods for preparing lanthanum hexaboride are: elements are directly synthesized at 1800°C (J.R.Rea et al. The formation of calcium and certain rare-earth hexaboride single crystals. European Journal of Crystal Growth, J.Cryst.Growth 11(1971) 110 112), carbothermal reduction of rare earth oxides (B.Post, et al. Borides of rare earth metals. Journal of the American Chemical Society, J.Am.Chem.Soc.78(1956) 1800-1802), boron thermal reduction (G.H.Olsen et al. People, Single-crystal growth of mixed (La, Eu, Y, Ce, Ba, Cs) hexaborides for thermionic emission. European Journal of Crystal Growth J. CrystalGrowth 44 (1978) 287-290), but these methods require higher temperature, generally At around 1000°C (or above), the energy consumption is higher and the cost of raw materials is also higher

Method used

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  • Method for synthesizing lanthanum hexaboride nano powder by solid-phase reaction under low temperature
  • Method for synthesizing lanthanum hexaboride nano powder by solid-phase reaction under low temperature
  • Method for synthesizing lanthanum hexaboride nano powder by solid-phase reaction under low temperature

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Experimental program
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Effect test

Embodiment 1

[0025] Embodiment 1: The superfine powder based on LaB6 nano cubes is prepared by reacting lanthanum oxide, magnesium powder, iodine and boric acid.

[0026] Take 0.8g of lanthanum oxide, 2.5g of magnesium powder, 3.7g of iodine, and 1.86g of boric acid into a 25ml special stainless steel reaction kettle, seal it and place it in a resistance crucible boiler. React for half an hour; stop heating, cool the reaction kettle to room temperature naturally; open the kettle, add the obtained product to water, wash with hot dilute hydrochloric acid solution, centrifuge and dry, and obtain the pure phase of LaB 6 powder.

[0027] Cu Kα rays (wavelength λ=1.5418 The scanning step speed is 0.08° / sec) as the diffraction light source for X-ray diffraction analysis of the product.

[0028] figure 1 The X-ray diffraction spectrum of the product was prepared by reacting at different temperatures for half an hour with 0.8g lanthanum oxide, 2.5g magnesium powder, 3.7g iodine and 1.86g. Depe...

Embodiment 2

[0030] Example 2: Raw material ratio as described in Example 1, respectively at 170°C, 200°C, 300°C, 400°C, prolonging the reaction time to 12 hours, preparing LaB 6 Ultrafine powder based on nano cubes.

[0031] image 3 The X-ray diffraction spectrum of the product was prepared by reacting 0.8g lanthanum oxide, 2.5g magnesium powder, 3.7g iodine and 1.86g boric acid at different temperatures for 12 hours.

[0032] Depend on image 3 It can be seen that in the X-ray diffraction spectrum, 20 has 10 strong diffraction peaks at 10-80 degrees, and all the diffraction peaks can be indexed as cubic LaB 6 , the position and intensity are consistent with the results of the standard powder diffraction card (JCPDS 34-0427).

[0033] The TEM photo of the product obtained at 170°C is as follows Figure 4 , showing that the nano-LaB6 powder particles are small, and the size is about 300nm.

Embodiment 3

[0034] Embodiment 3: preparation process as described in embodiment 1, difference is that raw material uses 0.3g amorphous boron powder, 1.16g sodium borohydride, 1.0g boron trioxide respectively to replace the boric acid in embodiment 1 as boron source, and Correspondingly adjust the amount of Mg to 0.694g, 0.5g, and 1.0g, respectively, and react at 500°C for 12 hours to prepare LaB 6 Ultrafine powder.

[0035] Figure 5 The X-ray diffraction spectrum of the product was prepared by using amorphous boron powder, sodium borohydride, and boron trioxide as the boron source at 500°C for 12 hours. Depend on Figure 5 It can be seen that all diffraction peaks can be indexed as cubic LaB 6 , the position and intensity are consistent with the results of the standard powder diffraction card (JCPDS 34-0427).

[0036] From boron trioxide (B 2 o 3 ) as a TEM photo of the product obtained as a boron source Figure 6 , showing nano-LaB 6 The powder particles are small and uniform in...

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Abstract

The invention relates to a method for preparing lanthanum hexaboride nano-powder by solid phase reaction at low temperature. The method comprises: lanthanum source, metallic reducing agent, halogenating agent and boron source are sealed in a high-pressure autoclave for reaction at the temperature of 170-500 DEG C for 30 minutes-3 days; the head product is treated by acid to remove impurity, and then is filtered and dried, so that pure phase lanthanum hexaboride powder is obtained and has the particle size within the range of 100-1500nm. Compared with the existing boron thermal, carbon thermal, boron carbide technologies and the like, the method has low reaction temperature as well as simple and easy control process, the obtained product has better appearance, and the material is low in price, so that the method is convenient for commercial process.

Description

technical field [0001] The invention belongs to the technical field of preparation of lanthanum hexaboride materials, in particular to the synthesis of lanthanum hexaboride (LaB 6 ) method of powder material. Background technique [0002] Lanthanum hexaboride has a CsCl structure with Pm3m symmetry, in which the La atom occupies the central position of the Cs atom, and the La atom is surrounded by eight B 6 octahedron around. This covalent bond composed of boron leads to the high mechanical properties, high thermal stability, and high chemical stability of lanthanum hexaboride. For the trivalent rare earth metal La, B 6 The network structure needs two electrons to stabilize its structure, so it has a surplus of electrons, which is usually a conductor. Other properties of lanthanum hexaboride such as high melting and boiling point, low work function, etc. are also derived from its structural characteristics. LaB 6 It is a very important thermionic emission material and ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B35/04
Inventor 钱逸泰王连成马小健徐立强
Owner SHANDONG UNIV
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