CN102190311A - Method for preparing MgB2 superconducting material on basis of Mg(BH4)2 precursor - Google Patents
Method for preparing MgB2 superconducting material on basis of Mg(BH4)2 precursor Download PDFInfo
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- CN102190311A CN102190311A CN 201010124702 CN201010124702A CN102190311A CN 102190311 A CN102190311 A CN 102190311A CN 201010124702 CN201010124702 CN 201010124702 CN 201010124702 A CN201010124702 A CN 201010124702A CN 102190311 A CN102190311 A CN 102190311A
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Abstract
The invention discloses a method for preparing MgB2 superconducting material on the basis of a Mg(BH4)2 precursor. The method comprises the following steps: heating Mg(BH4)2 powder used as a precursor in vacuum or inert atmosphere to 400-500 DEG C, and maintaining the temperature for a period of time to obtain the MgB2 superconducting material. The method has the advantages of simple equipment, high synthesis speed and low cost, can be used for preparing MgB2 powder, block and film at low temperature, avoids the high-temperature requirement and nonuniformity of the traditional powder preparation methods, and is easy for industrial mass production; in addition, the prepared product has excellent superconductivity.
Description
Technical field
The present invention relates to the superconductor technology field, relate in particular to preparation magnesium diboride (MgB
2) method of superconductor material.
Background technology
Magnesium diboride (MgB
2) be temp. superconductive material in find at the beginning of calendar year 2001 a kind of novel, be the highest metallic compound superconductor of critical temperature up to now, its superconducting transition temperature reaches 39K.MgB
2Superconductor is the same with the alloy type superconductor, does not have tangible anisotropy, makes it can to avoid in power transmission application the loss that causes owing to anisotropy, and its normal state resistivity is lower, and this is to the stability requirement particularly advantageous in the superconductor applications.Pure MgB
2Upper critical field H
C2Between 2 to 6 teslas (T); Critical current density J under the null field condition
c=10
8A/cm
2In addition, adulterated MgB
2The upper critical field H of superconductor
C2Can be up to 60 to 70 teslas, and its current capacity under High-Field also improves a lot.MgB
2Owing to have higher transition temperature, bigger coherence length, higher upper critical field, and crystal boundary does not exist weak connection, advantage such as simple in structure, with low cost, very potentially replace traditional first kind superconducting wire large-scale application in the near future on medical nmr imaging technique, in addition, also be with a wide range of applications at aspects such as superconducting power, electron device and national defence.
Utilize solid reaction process that magnesium powder (Mg) and boron powder (B) are pressed 1: 2 mixed uniform mixing sintering, this is to prepare MgB at present
2The ordinary method of powder and bulk.But Mg, B fusing point are widely different, and the saturation vapour pressure of adding Mg is higher, are easy to gasification, make MgB
2Structure seem simply, its building-up process is but comparatively complicated.Preparation high quality, high performance MgB
2The superconducting sample key is to prepare the particle of superfine Mg powder and B powder, and creates high Mg vapour pressure.Problem in the actual fabrication can reduce 4 points: one, if the Mg powder is too thin, meet oxygen meeting spontaneous combustion, and danger is very big; Its two, Mg is the high metallic element of a kind of equilibrium vapor pressure, under 200 ℃, just begin the distillation; Its three, the hardness of B is very high, micron-sized B powder price up to 60 yuan/gram; Its four, the B powder is from producing, through links such as storage, transportations, by the time the boron powder is used to prepare MgB
2During superconductor, often the boron powder has been in serious oxidized state.This just makes with the MgB of ordinary method preparation
2Powder and bulk cost an arm and a leg, and in the prepared material a large amount of spaces are arranged, and cause density lower, reduce MgB
2Current capacity.Various countries are engaged in MgB
2The scientific worker of research wishes to find a kind of Mg and B of can making at the mixed uniformly technology and equipment of atom level.How to avoid needed high temperature of conventional powder preparation method and ununiformity, simultaneously simple and easy and economic preparation MgB
2Powder is MgB
2The key subjects that superconductor material practicability need solve.Adopt precursor in situ to decompose and make highly active Mg and B can overcome the deficiency that has the preparation method now in the even mixing of atom level, but the acquisition of presoma is again a worldwide difficult problem.
Magnesium borohydride (Mg (BH
4)
2) be just to have synthesized recently a kind of important boron hydride of pure phase (referring to 1.J.Materials Chemistry 2007,17,3496-3503; 2.Chem.Vap.Deposition 2007,13,414-419 etc.).With sodium borohydride (NaBH
4) and magnesium chloride (MgCl
2) be raw material, after mixing, ball milling adds back flow reaction in the ether solvent, can obtain magnesium borohydride and sodium chloride (NaCl), filter and the desolventizing ether with proper method again, can obtain Mg (BH
4)
2Powder.Because NaBH
4And MgCl
2But be low-cost suitability for industrialized production reagent, so Mg (BH
4)
2Preparation has the characteristics of simple and easy economy.
Summary of the invention
The purpose of this invention is to provide a kind of with Mg (BH
4)
2For the presoma thermal decomposition prepares MgB
2The method of superconductor.
Technical scheme of the present invention is as follows:
A kind of MgB for preparing
2The method of superconductor is with Mg (BH
4)
2Be presoma, heat Mg (BH under vacuum condition or in the inert atmosphere
4)
2Powder to 400 ℃～500 ℃ keeps this temperature a period of time to obtain MgB
2Superconductor.
Said method both can carry out also can carrying out under the protection of inert gas under vacuum condition, if carry out under vacuum condition, required to be evacuated to air pressure≤10Pa; If under the protection of inert gas, carry out, gas pressure there is not special requirement, usually be controlled at below the 5atm.
In the aforesaid method, described temperature is advisable with 400 ℃～500 ℃, is preferably 430 ℃～450 ℃.Mg (BH
4)
2Presoma is heated rear decomposition and produces hydrogen and the mixed uniformly Mg of atom level and B, and insulation makes Mg, B reaction obtain MgB
2Superconductor, temperature retention time is advisable with 1h～24h, is preferably 3h～5h.Decompose the hydrogen of generation to MgB
2Not impact of formation, can create on the contrary reducing atmosphere and play the effect that prevents that product is oxidized, so in course of reaction, need not to discharge hydrogen.Mg (BH
4)
2Decomposition rate very fast, the effect of insulation is that Mg and B are fully reacted, the insulation 3h after MgB
2Production rate just can reach more than 95%.
Above-mentioned based on Mg (BH
4)
2Presoma hot preparation MgB
2The method of superconductor has been utilized Mg (BH
4)
2The atomic ratio of middle Mg, B is 1: 2, and catabolite hydrogen is the characteristics of loss from system easily, and is simply ingenious.Presoma Mg (BH
4)
2The quality of quality (mainly being purity and granularity) directly has influence on effective enforcement of this method.Mg (BH
4)
2Presoma should have littler particle size and very big purity, and the General Requirements particle size is micron order (for example: the particle diameter distribution scope is at 500nm～50 μ m), and purity is greater than 95%.
Mg (BH
4)
2The preparation method of presoma can be as follows: boron hydride and the salt that contains magnesium elements ball milling under hydrogen shield are mixed, join then back flow reaction in the water-free organic solvent, filtration after reaction finishes is got the filtrate drying and is obtained Mg (BH
4)
2Powder.
Above-mentioned synthetic Mg (BH
4)
2The raw material boron hydride of presoma can be sodium borohydride, potassium borohydride, calcium borohydride, lithium borohydride etc., and the salt that contains magnesium elements can be anhydrous magnesium chloride, anhydrous magnesium bromide, anhydrous magnesium iodide etc.After the factors such as comprehensive cost, reactive behavior, by product processing, being preferably sodium borohydride and Magnesium Chloride Anhydrous reacts, and both mol ratios were advisable with 2: 1～2.3: 1, were preferably 2.05: 1.
Above-mentioned mechanical milling process is in order to increase the reaction system energy, tentatively to obtain required product Mg (BH
4)
2And accessory substance.Mechanical milling process preferably carries out with planetary ball mill in airtight ball grinder, hydrogen pressure is advisable with 2bar～10bar, be preferably 5bar, ratio of grinding media to material (mass ratio of reactant and steel ball) was advisable with 20: 1～100: 1, being preferably is 40: 1, and rotating speed is advisable with 200 rev/mins～600 rev/mins, is preferably 300 rev/mins, the ball milling time is more than 5 hours, is preferably 10 hours.
The organic solvent that above-mentioned back flow reaction is used is preferably ether, and commercial ether dewaters with the sodium Metal 99.5 silk and re-uses.Contain Mg (BH with what ball milling obtained
4)
2Mixture add in the ether after dewatering, heated solution is to the boiling point of ether, back flow reaction obtains Mg (BH
4)
2Diethyl ether solution and accessory substance precipitation.Reaction is filtered after finishing, and leaves and takes filtrate and carries out heat drying, obtains Mg (BH
4)
2Powder.Wherein reflux time is more than 24 hours, is preferably 60 hours, and drying temperature is advisable with 180 ℃～200 ℃, is preferably 190 ℃, and be preferably 2 hour greater than 1 hour time of drying.
The present invention is by proper temperature heat treated Mg (BH
4)
2Presoma can obtain MgB
2Superconductor material.Mg (BH wherein
4)
2As adopting solwution method, raw material prepares prepared Mg (BH take boron hydride and magnesium salts
4)
2The size of presoma is micron order, and its diameter distribution is at 0.5 μ m～2 μ m, and majority is about 1 μ m, has littler particle size and very big purity.Such Mg (BH
4)
2Presoma can lower temperature in thermal decomposition process decomposes that to obtain atomic ratio be 1: 2 Mg and B, the more important thing is that catabolite is that mixing and the reactivity of atomic level is bigger, thereby has greatly improved preparation MgB
2The efficient of superconductor.Utilize Mg (BH
4)
2Presoma can prepare at low temperature with in the short time MgB
2Powder, bulk and film have the advantage that equipment is simple, aggregate velocity is fast, and production cost are low, product superconducting property excellence, avoided the needed high temperature of conventional powder preparation method and inhomogeneities, than being easier to realize industrialized mass production, had a good application prospect.
Description of drawings
Fig. 1 is the Mg (BH of embodiment 1 preparation
4)
2The X-ray diffractogram of presoma.
Fig. 2 is the Mg (BH of embodiment 1 preparation
4)
2The differential scanning calorimetric curve of presoma thermal decomposition process.
Fig. 3 be embodiment 1 preparation based on Mg (BH
4)
2The MgB of presoma
2The transmission electron microscope photo of superconductor.
Fig. 4 be embodiment 1 preparation based on Mg (BH
4)
2The MgB of presoma
2The energy spectrum analysis of superconductor.
Fig. 5 be embodiment 2 measure based on Mg (BH
4)
2The MgB of presoma
2The intensity of magnetization of superconductor and the relation curve of temperature.
Fig. 6 is the partial enlarged drawing of Fig. 5 in temperature is the 30-37K scope.
Embodiment
By the following examples the present invention is done describing in further detail, but the scope that does not limit the present invention in any way.Embodiment 1, based on Mg (BH
4)
2Precursor synthesizes MgB
2Superconductor
(1) with sodium borohydride and the anhydrous magnesium chloride ratio with 2.05: 1; join in the ball grinder; the hydrogen that vacuumizes rear adding 5bar pressure is made protection atmosphere, is that 40: 1, rotating speed are to use planetary type ball-milling instrument ball milling 10 hours under 300 rev/mins the condition in ratio of grinding media to material, obtains containing Mg (BH
4)
2Mixture.
What (2) ball milling is obtained contains Mg (BH
4)
2Mixture join in the ether after dewatering with the sodium metal silk, heated solution is to the boiling point of ether, the reaction in 60 hours that refluxes obtains Mg (BH
4)
2Diethyl ether solution and accessory substance precipitation.Filtrate is left and taken in filtration, and 190 ℃ of heat dryings obtained pure Mg (BH in 2 hours
4)
2Powder.
(3) do protective atmosphere with Ar gas, with pure Mg (BH
4)
2Powder is heated to 420 ℃, decomposes to produce hydrogen and the mixed uniformly Mg of atom level and B, is incubated 2 hours and makes the further reaction of Mg, B obtain MgB
2Superconductor.
Fig. 1 is the product Mg (BH of above-mentioned experimental procedure (2)
4)
2The XRD of presoma (X-ray diffraction) figure can see clearly that with the prepared sample of reference material contrast be purity greater than 95% pure phase.
Fig. 2 is above-mentioned experimental procedure (2) product Mg (BH
4)
2The differential scanning calorimetric curve of presoma thermal decomposition process can be seen Mg (BH
4)
2Presoma decomposes before 400 ℃ fully, obtains mixing Mg and the B of atomic level.
Fig. 3 is above-mentioned experimental procedure (3) product MgB
2The TEM of superconducting material (transmission electron microscope) figure, Fig. 4 are that its EDX (power spectrum) analyzes, and can see MgB
2Length scale is 5-10 μ m, and the width size is about 0.5 μ m, and ultimate analysis is Mg and B more than 95%, and small amount of impurities unit have O, Na, Cl.
Embodiment 2, based on Mg (BH
4)
2The MgB of presoma
2The superconductivity of superconductor detects
With embodiment 1 preparation based on Mg (BH
4)
2The MgB of presoma
2Powder is put in the gyromagnetic material M-T chart recording instrument after grinding evenly in agate mortar, measures MgB under the unsaturated state
2The parameters such as the intensity of magnetization of powder, remanent magnetization, coercive field are strong, squareness ratio, curie point, and the relation curve of describing the intensity of magnetization (M) and temperature (T).
By Fig. 5 and Fig. 6 as seen, the specific magnetising moment becomes negative value from 0.000 about 35K, and the temperature range about 5K has a tangible bust.This curve shows based on Mg (BH
4)
2The MgB of presoma
2Superconductor demonstrates the superconduction diamagnetism about 35K, namely change superconducting phase into.In addition, if further control Mg (BH
4)
2The content of the O in the presoma, Na, Cl impurity increases preparation MgB
2Reaction temperature in the process and reaction time, so MgB
2The superconducting property of superconductor also can further improve.
Claims (10)
1. one kind prepares MgB
2The method of superconductor is with Mg (BH
4)
2Be presoma, heat Mg (BH under vacuum condition or in the inert atmosphere
4)
2Powder to 400 ℃～500 ℃ keeps this temperature a period of time to obtain MgB
2Superconductor.
2. the method for claim 1 is characterized in that, described vacuum condition is to be evacuated to air pressure≤10Pa.
3. the method for claim 1 is characterized in that, keeps temperature 1h～24h of 400 ℃～500 ℃.
4. the method for claim 1 is characterized in that, Mg (BH
4)
2The particle size of powder is micron order, and purity is greater than 95%.
5. such as the arbitrary described method of claim 1～4, it is characterized in that, prepare Mg (BH by following method
4)
2Powder: boron hydride and the salt that contains magnesium elements ball milling under hydrogen shield are mixed, join then back flow reaction in the water-free organic solvent, filtration after reaction finishes is got the filtrate drying and is obtained Mg (BH
4)
2Powder.
6. method as claimed in claim 5 is characterized in that, described hydroborate is sodium borohydride, POTASSIUM BOROHYDRIDE, hydroboration calcium or lithium borohydride; The described salt that contains magnesium elements is Magnesium Chloride Anhydrous, anhydrous magnesium bromide or anhydrous magnesium iodide.
7. method as claimed in claim 6 is characterized in that, described hydroborate is a sodium borohydride, and the described salt that contains magnesium elements is Magnesium Chloride Anhydrous, and the mol ratio of the two was with 2: 1～2.3: 1.
8. method as claimed in claim 5 is characterized in that, mechanical milling process is to carry out with planetary ball mill in airtight ball grinder, hydrogen pressure 2bar～10bar, ratio of grinding media to material 20: 1～100: 1, rotating speed is with 200 rev/mins～600 rev/mins, and ball milling is more than 5 hours.
9. method as claimed in claim 5 is characterized in that, the organic solvent of back flow reaction is an ether, and back flow reaction is after-filtration more than 24 hours.
10. method as claimed in claim 5 is characterized in that, 180 ℃～200 ℃ dried filtrate obtain Mg (BH
4)
2Powder.
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| CN102190311B CN102190311B (en) | 2013-03-06 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102496680A (en) * | 2011-11-28 | 2012-06-13 | 西部超导材料科技有限公司 | Preparation method of carbon-doped magnesium diboride superconducting tape |
| CN104576914A (en) * | 2015-01-26 | 2015-04-29 | 北京大学 | MgB2/BN/MgB2 Josephson junction and preparation method thereof |
| CN115440435A (en) * | 2022-09-30 | 2022-12-06 | 西安聚能医工科技有限公司 | MgB 2 Method for preparing superconducting powder |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1329370A (en) * | 2001-07-16 | 2002-01-02 | 西北有色金属研究院 | MgB2 superconducting material and its preparation method |
| CN101168442A (en) * | 2007-09-25 | 2008-04-30 | 中国科学院电工研究所 | High-performance MgB2 superconducting material and preparation method thereof |
-
2010
- 2010-03-12 CN CN 201010124702 patent/CN102190311B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1329370A (en) * | 2001-07-16 | 2002-01-02 | 西北有色金属研究院 | MgB2 superconducting material and its preparation method |
| CN101168442A (en) * | 2007-09-25 | 2008-04-30 | 中国科学院电工研究所 | High-performance MgB2 superconducting material and preparation method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 《Journal of Materials Chemistry》 20070530 Krzysztof Chlopek,et.al. Synthesis and properties of magnesium tetrahydroborate, Mg(BH4)2 第3498页，3.1 合成步骤，第3501页，原位XRD部分，图6 1-10 第17卷, 第33期 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102496680A (en) * | 2011-11-28 | 2012-06-13 | 西部超导材料科技有限公司 | Preparation method of carbon-doped magnesium diboride superconducting tape |
| CN104576914A (en) * | 2015-01-26 | 2015-04-29 | 北京大学 | MgB2/BN/MgB2 Josephson junction and preparation method thereof |
| CN104576914B (en) * | 2015-01-26 | 2017-07-28 | 北京大学 | MgB2/BN/MgB2Josephson junction and preparation method thereof |
| CN115440435A (en) * | 2022-09-30 | 2022-12-06 | 西安聚能医工科技有限公司 | MgB 2 Method for preparing superconducting powder |
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