CN1562746A

CN1562746A - Burning preparation method for synthesizing power of magnesium diboride

Info

Publication number: CN1562746A
Application number: CN 200410029899
Authority: CN
Inventors: 韩欢庆; 褚征军; 刘桂荣; 陈飞雄; 卢惠民; 邱定蕃
Original assignee: Central Iron and Steel Research Institute; Advanced Technology and Materials Co Ltd; University of Science and Technology Beijing USTB
Current assignee: Central Iron and Steel Research Institute; Advanced Technology and Materials Co Ltd; University of Science and Technology Beijing USTB
Priority date: 2004-04-01
Filing date: 2004-04-01
Publication date: 2005-01-12
Anticipated expiration: 2024-04-01
Also published as: CN1247456C

Abstract

The invention is especially suited for prepn. method of magnesium hyboride powder by burning and compossing. Raw material powder is put into blendor to be mixed and then is send into combustion synthesizer to be process by evacuation, argon filling protection and reaction of burning and compossing, the created product is potched. The characteristic is that compounded raw material powder B2O3 and Mg are (wt%) 29-42 and 58-71, average paticle size of the powder is less than or equal to 30 um. The raw materials are processed by igniting to proceed high-temp. reaction, the reacted substance is potched in acidic liquid, then to be cleaned by adding 1-2 times water into the acidic liquid, finally, the potch liquid is removed by vacuum extract and filtering device.

Description

Preparation method for combustion synthesis of magnesium diboride powder

Field of the invention

The invention belongs to the field of preparation of metal ceramic powder. Is particularly suitable for the preparation method for synthesizing the magnesium diboride powder by combustion.

Background

In the use process of the current materials, magnesium diboride is found to be one of the metalate superconducting materials with the highest critical temperature and simple and stable so far, and the cermet powder material has the advantages of large coherence length, high grain boundary bearing critical current, simple crystal structure and the like, and is a cermet superconducting material with great development prospect. Up to now, for the production of this material (MgB)₂) The preparation method mainly comprises the steps of mixing magnesium powder and boron powder, placing the mixed powder in a reactor for heating reaction, wherein the synthesisreaction temperature is 800-950 ℃, the reaction time needs to be longer, and the synthesis reaction equation is as follows: (ii) a The preparation method has the disadvantages that (1) because the melting point (burning point) of the magnesium powder is low, magnesium is easy to volatilize in the heating process, the reaction container is prepared by precious materials such as quartz, tantalum, platinum and the like, and the reaction time for preparing the material is long and the repeatability is poor, so that the production in an industrial scale is difficult; (2) because the purity of the commercially available elemental boron powder or amorphous boron powder is low, generally only 85-95%, the high-purity MgB is difficult to prepare from the purity raw material₂Powder, so the raw material product must be subjected to a post purification treatment. (3) Because the simple substance boron powder or the amorphous boron powder is expensive and the unit price is 1600-2400 yuan/kg, the MgB is synthesized₂The raw material cost of the powder product is too high. (4) Also, the preparation process of the synthesis reaction is relatively high in temperature and long in time, and the obtained productThe particle size of the product powder is difficult to meet the use requirements, soSo as to limit the application field of the product.

Objects and summary of the invention

The invention aims to provide a preparation method for burning and synthesizing magnesium diboride powder, which has simple, reasonable and economic preparation process and can improve the product yield and reduce the production cost.

According to the purpose of the invention, the preparation method for synthesizing the magnesium diboride powder is mainly designed by adopting a self-propagating synthesis theory, and the chemical equation of the combustion synthesis reaction of the method is as follows: (ii) a Wherein x is 0-3. In the process of combustion synthesis reaction of magnesium diboride powder, because the Mg powder as a reducing agent has a certain amount of loss, a proper amount of supplementary Mg powder is added during batching, so that the reaction in the combustion replacement reduction process can be fully carried out. In addition, the reduction of B in the product should be taken into consideration₂O₃The residual amount is considered to be minimized and the MgB is suppressed₄And (5) generating equal transition phases.

The metal magnesium powder (Mg) is a commercially available industrial pure reagent, has the purity of 99 percent, and has the average grain diameter of less than or equal to 30 mu m, wherein the part with the grain diameter of less than or equal to 20 mu m accounts for more than 70 percent of the total amount of the metal magnesium powder. The proportion of the ingredients is 58-71%. The method has two functions, namely, the boron serves as a displacer to be combined with oxygen to precipitate monomer boron, and the reaction equation is as follows:

secondly, the boron is used as a reactant and combined with the precipitated monomer boron to generate MgB₂The reaction equation is as follows:

B₂O₃the powder is industrial grade high-purity powder, the purity is 99%, the average grain diameter is less than or equal to 30 mu m, and the proportion of ingredients is 29-42%. B is₂O₃As a source of boron as a reaction product of the present invention, it is easyThe separated boron monomer reacts with magnesium powder to generate MgB₂. MgO generated by the reaction and excessive Mg are removed by acid liquor such as hydrochloric acid, nitric acid or sulfuric acid, the concentration of the acid is 20-50%, and the adding amount is 1-2 times of the total powder amount. The reaction equations are respectively:

according to the above basic principle of the preparation method of the invention, the preparation method of the combustion synthesis magnesium diboride powder is provided, wherein the B with the set weight is firstly weighed₂O₃Mixing with Mg powder in a mixer, vacuumizing in a combustion synthesizer at vacuum degree of 10^-1-10^-2pa, removing interference gases such as nitrogen, oxygen and the like in the synthesizer; argon gas is introduced into the combustion synthesizer to 1-10MPa, so as to inhibit the volatilization of Mg in the combustion reduction reaction process. Igniting the reaction materials by an ignition coil in the combustion synthesizer to enable the reaction materials to generate self-propagating high-temperature synthesis reaction; along with the reaction, the temperature in the reactor can be gradually increased, and the gas pressure in the combustion synthesizer can be increased along with the expansion gas pressure, so that the volatilization of Mg element in the reaction process can be effectively inhibited. And after the reaction process is finished, taking out the generated product for rinsing. Slowly adding the reaction product into the prepared acidic rinsing liquid, uniformly stirring to ensure that the generated product can be fully reduced, stopping adding the reactant when the pH value of the acidic rinsing liquid is more than or equal to 6, adding 1-2 times of distilled water for dilution and stirring, and removing the rinsing solution through a vacuum filtration device to obtain the high-purity superfine MgB₂And (3) powder.

Compared with the prior art, the preparation method has the following characteristics:

(1) the preparation method of the invention adopts cheap B₂O₃Instead of expensive monomer boron to prepare MgB₂The method omits the process of preparing the monomer boron, combines the preparation of the monomer boron and the synthesis process of the magnesium diboride into a whole, shortens the production flow and obviously reduces the production cost of the magnesium diboride.

(2) The preparation method of the invention designs the MgB which has simple, reasonable and economic preparation process, can improve the yield and reduce the production cost according to the basic principle of combustion synthesis technology₂Preparation of powderThe preparation method is as follows. Compared with the heating synthesis process in the prior art, the preparation method of the invention can fully utilize the reaction heat release, can save 80-90% of electric energy, and has the efficiency obviously higher than that of the prior art.

(3) Because the combustion synthesis process of the preparation method can be completed in a short time and the pressure of the control gas in the reactor adopted by the method is also large, the preparation method can effectively inhibit the volatilization of the magnesium element in the material and simultaneously ensure the MgB after production₂Purity of the powder. The following Table 1 shows MgB produced by the preparation method of the present invention₂Powder, MgB synthesized directly with prior art processes₂The powder is obviously superior to the prior art by comparing various technical parameters and performances.

TABLE 1 MgB produced by the process of the present invention and the prior art₂Comparison of powder parameters

Contrasting content	Purity of	Oxygen content	Average particle diameter	Transition phase	Kilogram/cost
Contrasting content	Purity of	Oxygen content	Average particle diameter	Transition phase	Kilogram/cost	The invention	＞99％	＜1％	＜6μm	Micro-scale	200-
Existing methods	＜98％	＞2％	＞10μm	Much more	800-	The invention	＞99％	＜1％	＜6μm	Micro-scale	200-

Detailed description of the preferred embodiments

According to the inventionThe specific content of the preparation method for synthesizing the magnesium diboride powder is that three batches of MgB are prepared under the same preparation process condition according to different raw material proportioning ranges in the method of the invention₂The ingredients and preparation process parameters of the powder are listed in Table 2, and the powder B in the weight setting in Table 2 is weighed in the first step₂O₃And Mg powder are filled into a mixer to be mixed evenly, the powder is filled into a combustion synthesizer to be vacuumized, and then argon is filled into the combustion synthesizer. Igniting the reaction materials by an ignition coil in the combustion synthesizer to enable the reaction materials to generate self-propagating high-temperature synthesis reaction; along with the reaction, the temperature in the reactor can be gradually increased, and the gas pressure in the combustion synthesizer can be increased along with the expansion gas pressure, so that the volatilization of Mg element in the reaction process can be effectively inhibited. And after the reaction process is finished, taking out the generated product for rinsing. Slowly adding the reaction product into 45% hydrochloric acid rinsing solution, stirring to obtain product capable of being sufficiently reduced, stopping addingreactant when pH of the acid rinsing solution is 6.5,adding 2 times of distilled water for dilution and stirring, and then removing rinsing solution through a vacuum filtration device to obtain high-purity superfine MgB₂And (3) powder. For the sake of convenience of comparison, we also show the preparation process parameters of the comparison technique in table 2, the preparation method of the prior art is to place the mixture in a tungsten crucible in a heating furnace after mixing uniformly, vacuumize, fill argon, reduce the temperature at a rate of 5 ℃/min, preserve the temperature at 600 ℃ for 30min, then preserve the temperature at 800 ℃ for 60min, and then cool the mixture to room temperature along with the furnace. Table 3 also lists MgB produced by the examples of the present invention and the prior art₂The powder test results are shown in Table 3.

TABLE 2 Process parameters in the examples of the invention

Parameter(s) Serial number Example 1	B₂O₃ Proportioning	Mg powder Proportioning	Ingredients Measurement of	Vacuum Degree of rotation	Fill with Ar Initial pressure	Fill with Ar Peak pressure	Reaction of Time of day
	B₂O₃ Proportioning	Mg powder Proportioning	Ingredients Measurement of	Vacuum Degree of rotation	Fill with Ar Initial pressure	Fill with Ar Peak pressure	Reaction of Time of day	30％	70％	6kg	10^-2Pa	3Mpa	8Mpa	25S
	Example 2	35％	65％	6kg	10^-2Pa	3Mpa	10Mpa	30％	70％	6kg	10^-2Pa	3Mpa	8Mpa	25S	20S
Example 3	Example 2	35％	65％	6kg	10^-2Pa	3Mpa	10Mpa	40％	60％	6kg	10^-2Pa	3Mpa	6Mpa	30S	20S
Example 3	Example 4	47.8％	52.2％	0.5kg	10^-2Pa	100pa	/	40％	60％	6kg	10^-2Pa	3Mpa	6Mpa	30S	2 hours

TABLE 3 comparison of the final properties of the inventive examples with the prior art products

Practice of Example (b)	After synthesis Weight (D)	Acid picklingRear end Weight (D)	MgB₂ Colour(s)	Purity of	MgB₄ Phase (C)	Average Particle size
Practice of Example (b)	After synthesis Weight (D)	Acid picklingRear end Weight (D)	MgB₂ Colour(s)	Purity of	MgB₄ Phase (C)	Average Particle size	Example 1	5.92kg	1.56kg	Brown black	99.2％	Micro-scale	4.3μm
Example 2	5.98kg	1.62kg	Brown black	99.5％	Is free of	2.6μm	Example 1	5.92kg	1.56kg	Brown black	99.2％	Micro-scale	4.3μm
Example 2	5.98kg	1.62kg	Brown black	99.5％	Is free of	2.6μm	Example 3	5.94kg	1.54kg	Brown black	99.3％	Micro-scale	5.4μm
Example 4	485g	/	Brown black	94.6％	7％	16.6μm	Example 3	5.94kg	1.54kg	Brown black	99.3％	Micro-scale	5.4μm

Claims

1. A process for preparing magnesium diboride powder by combustion synthesis includes such steps as weighing B₂O₃And Mg powder are filled into the mixer to be uniformly mixed, the powder is filled into the combustion synthesizer to be vacuumized and aerated for protection, then the reaction material is ignited by the ignition coil in the combustion synthesizer to be subjected to self-propagating high-temperature synthesis reaction, and after the reaction process is finished, the generated product is taken out to be rinsed, which is characterized in that:

(1) raw material B₂O₃And the Mg powder is mixed in a set proportion of B in percentage by weight₂O₃29-42% of powder and 58-71% of Mg powder;

(2) in the raw materials B₂O₃And the average grain diameter of Mg powder is less than or equal to 30 mu m;

(3) after the powder material is uniformly mixed, the powder material is placed into a combustion synthesizer, and firstly the vacuum degree is pumped to 10^-1-10^-2pa, filling argon to 1-10 Mpa;

(4) the combustion synthesizer is used for igniting reaction raw materials through an ignition coil to generate a high-temperature synthesis reaction;

(5) rinsing the reaction product in a rinsing liquid with the acid concentration of 20-50%, wherein the addition amount of the rinsing liquid is 1-2 times of the total powder amount;

(6) when the pH value of the acid liquor is more than or equal to 6 after rinsing, adding 1-2 times of distilled water for rinsing, and removing the rinsing solution by using a vacuum filtration device.

2. The method according to claim 1, wherein the powder having a particle size of less than 10 to 20 μm in the raw Mg powder accounts for 70% or more of the total amount of the Mg powder.

3. The preparation method according to claim 1, wherein the acidic rinsing solution used for the reaction product is any one of hydrochloric acid, nitric acid and sulfuric acid,