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Method for synthesizing crystallites and block crystals of nitride by multistep reaction in-situ under hydrothermal condition

A nitride and microcrystalline technology, applied in the direction of nitrogen-metal/silicon/boron binary compounds, etc., can solve the problems of many reducing agents, difficult reactivity, difficult reaction process, etc., to achieve pollution elimination, wide applicability, Controllable effect

Inactive Publication Date: 2005-08-24
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The previous preparation technology has applied for an invention patent (application number 02110066.7), but this method has some defects: for example, due to the one-time addition of the reaction raw materials, the nucleation process of the product is very random, which makes the grain size distribution wide and uniform The reactivity of various raw materials is difficult to match with each other, so the reaction process is difficult to control, which makes the crystallization integrity of nitride grains poor; the reducing agent used produces more by-products, which is harmful to nitride nanocrystals and bulk crystal contamination, etc.

Method used

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  • Method for synthesizing crystallites and block crystals of nitride by multistep reaction in-situ under hydrothermal condition
  • Method for synthesizing crystallites and block crystals of nitride by multistep reaction in-situ under hydrothermal condition
  • Method for synthesizing crystallites and block crystals of nitride by multistep reaction in-situ under hydrothermal condition

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0048] Embodiment 1. prepare BN nanopowder

[0049] Using hydrazine hydrate as a reducing agent, boric acid and sodium azide react to synthesize boron nitride under hydrothermal conditions. The chemical reaction in water is as follows:

[0050] (a)

[0051] (b)

[0052] (c)

[0053] (d)

[0054] (e)

[0055] (In the reaction formula, those with "*" represent highly active atoms)

[0056] The specific operation process is as follows:

[0057] First weigh 3.1g of boric acid and add it to a conical flask with a capacity of 250ml, then add 100ml of deionized water and stir to dissolve the boric acid. After continuing to stir for 30 minutes, a transparent solution with a concentration of 0.5 mol / L was obtained. Under the condition of continuous stirring, add 9.80g of sodium azide, continue stirring to make it all dissolve. Add 2.86ml of hydrazine hydrate while stirring to obtain a transparent homogeneous solution. The above mixed solution was ...

Embodiment 2

[0059] Embodiment 2. prepare BN nanopowder

[0060] The specific operation process is the same as in Example 1, the difference is that 9.8gNaN is replaced with 6.8g trimethylamine in this example 3 , and the filling ratio of the reactor was 30%, the temperature of the reaction system was rapidly raised to 400° C. (50° C. / minute), and the total reaction was 24 hours, and the rest remained unchanged.

[0061] Figure 4 is the X-ray diffraction pattern (XRD) of the BN sample prepared by the rapid heating method. There is only one diffraction packet in the picture, this is because the rapid temperature rise makes the raw material decompose too fast, resulting in uncontrollable reaction process, resulting in mostly amorphous products; Figure 5 is the Fourier transform infrared spectrum of the sample. From the results of this experiment, it is known that rapid heating is unfavorable for the crystallization and growth of grains.

Embodiment 3

[0062] Embodiment 3. prepare BN micron powder

[0063] The types and proportions of the raw materials used are exactly the same as in Example 1, except that the filling rate of the reactor is 60% in this example, and the reaction temperature is raised to 220°C at a rate of 0.2-0.4°C / min for 144 hours.

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Abstract

A process for preparing microcrystal and bulk crystal of nitride by in-situ multi-step reaction in hydrothermal condition features that in constant temp and pressure condition, the raw materials are supplemented into reaction system continuously or multiple times for controlling the generation of crystal nuclears and the growth of crystals, and a novel reducer (hydrazine hydrate) is used to prevent the pollution of by-product to microcrystal and crystal. Its advantage is uniform granularity.

Description

(1) Technical field [0001] The invention relates to a method for preparing nitride micropowder and bulk crystals by utilizing multi-step in-situ reactions under hydrothermal conditions, and belongs to the technical field of growth of nanometer materials and crystal materials. (2) Background technology [0002] Boron nitride (BN) is a typical III-V covalent compound, which has multiple phases of hexagonal, cubic, close-packed hexagonal and orthorhombic phases. Atoms in hexagonal BN pass through sp 2 Bonded, with a layered structure similar to graphite; cubic BN and orthogonal BN are based on sp 3 Bonded, with a tetrahedral network structure. The close-packed hexagonal phase is a high-pressure phase of BN with sp 3 Bonding and diamond-like properties. [0003] Hexagonal BN micropowders have attracted widespread attention due to their high thermal conductivity, good chemical stability, and excellent lubricating properties. Hexagonal BN is currently widely used in nano-lubr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B21/06
Inventor 崔得良于美燕郝宵鹏刘振刚蒋民华
Owner SHANDONG UNIV
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