CN102992772A - Preparation method of MgB2 superconducting wire - Google Patents
Preparation method of MgB2 superconducting wire Download PDFInfo
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- CN102992772A CN102992772A CN201210504677XA CN201210504677A CN102992772A CN 102992772 A CN102992772 A CN 102992772A CN 201210504677X A CN201210504677X A CN 201210504677XA CN 201210504677 A CN201210504677 A CN 201210504677A CN 102992772 A CN102992772 A CN 102992772A
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- magnesium
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- magnesium diboride
- diboride
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Abstract
The invention discloses a preparation method of an MgB2 superconducting wire. The preparation method comprises the steps of preparing magnesium diboride crystal as an inner core, including the steps of firstly, dissolving magnesium di-n-propyl alcohol and diborane in a nonpolar solvent, reacting to obtain magnesium borohydride, and separating impurities by a solid-liquid separation process; secondly, leading in argon to form protective atmosphere under standard pressure, and carrying out thermal decomposition on the obtained magnesium borohydride, so that magnesium borate is formed; encapsulating the magnesium diboride crystal inner core into metal, and drawing the inner core and the metal to obtain the superconducting wire with the magnesium diboride inner core. The magnesium diboride can be prepared by the preparation method under a reducing condition and prevented from being polluted by an oxide by-product, and the magnesium diboride inner core with small crystal particles and good degree of crystallinity is obtained, so as to prepare the superconducting wire with excellent performance.
Description
Technical field
The present invention relates to a kind of manufacture method of superconductivity wire, relate in particular to a kind of manufacture method that comprises the superconductivity wire of magnesium diboride.
Background technology
Along with the high speed development of science and technology, people more and more begin to utilize various superconductors, such as superconductive tape or superconducting line etc.Magnesium diboride has the highest transition temperature in metallic superconductor, because its transition temperature is high, if the magnesium diboride material purity of therefore making is good, can use by the liquid helium cooling.
In the prior art, a kind of magnesium diboride manufacture method that can industrial application is: make the mixture of element magnesium and element boron, then 800 ℃ of-1200 ℃ of temperature, stand furnaceman's skill under the condition of argon gas as shielding gas.This reaction is strong heat release.The method has following shortcoming, and pure magnesium diboride is not provided, and that is to say the magnesium diboride of anaerobic, but because MAGNESIUM METAL and boron have high avidity to oxygen, always has oxide impurity, and these oxide impurities have reduced the suitability as superconducting material.Thus, when industrial implementation the method, inevitable magnesium diboride oxide contaminating impurity almost.People can not be by removing oxide impurity with hydrogen reduction, and this is because because element boron can form hydroborons.
Another kind of magnesium diboride manufacture method comprises the mixture of making crystal magnesium and amorphous boron as preceding method, then carries out the mechanical alloying of raw material under argon gas.Reduced significantly thus temperature of reaction.The advantage of the method is, the MgB that this magnesium diboride wants beguine to make according to preceding method
2Be more suitable for as the powder filler for MgB 2 superconductor wire.But its shortcoming is that mechanical alloying is very slowly, and the impurity in the material has for example increased by wearing and tearing in addition.After furnaceman's skill, however must grind powder, although because powder is compared with the first traditional method with more fine particle generation, it always contains the coarse particles of crossing of signal portion.Product grinds and has improved again the share of impurity in the powder, consuming time and limit production ability for the second time.In order to make oxide impurity keep few as much as possible, also when grinding, adds product magnesium hydride.Also can before grinding, add the doping composition to this powder.
Therefore, it is good how to prepare purity, the magnesium diboride that impurity is few, and then make the targets that the superconductivity wire with excellent properties is the consistent pursuit of those skilled in the art.
Summary of the invention
The invention discloses a kind of MgB
2The manufacture method of superconductivity wire, this manufacture method can prepare magnesium diboride under reductive condition, prevent its oxide by-product contamination, and obtains the magnesium diboride inner core of the little and better crystallinity degree of crystal grain.
MgB of the present invention
2The manufacture method of superconductivity wire comprises the steps:
Preparation magnesium diboride xln, as inner core, it comprises the steps:
At first, two n-propyl alcohol magnesium and diboron hexahydride are dissolved in the non-polar solvent, reaction obtains magnesium borohydride, impurity is separated non-polar solvent pentane preferably wherein, hexane, heptane, octane by solid-liquid isolation method; More preferably heptane or octane;
Secondly, under standard pressure, pass into argon gas and form protective atmosphere, with resulting magnesium borohydride thermolysis, so that form boronation magnesium, and wherein, preferred 500 ℃-1000 ℃ of the temperature of thermolysis, more preferably 500 ℃-600 ℃;
Magnesium diboride xln inner core is encapsulated in the metal;
Above-mentioned inner core and metal wire-drawing are obtained having the superconducting line of magnesium diboride inner core.
Preferably, this metal is copper.
Embodiment
In order to make those skilled in the art more clearly understand technical scheme of the present invention, describe the manufacture method of this superconducting line in detail below by embodiment.
MgB of the present invention
2The manufacture method of superconductivity wire comprises the steps:
The first, preparation magnesium diboride xln, as inner core, preparation magnesium diboride xln comprises the steps:
At first, two n-propyl alcohol magnesium are dissolved in the non-polar solvent, wherein non-polar solvent can be pentane, hexane, heptane, octane; The preferred octane that uses.
Two n-propyl alcohol magnesium are responsive for oxygen and moisture, so it always contains magnesium oxide or magnesium hydroxide.If relatively nonpolar two n-propyl alcohol magnesium are dissolved in the described solvent, two n-propyl alcohol magnesium enter in the solution so, and oxide impurity for example magnesium oxide and magnesium hydroxide since their polar character do not enter in the solution.Undissolved component will by known solid/liquid separation method, for example be separated from two n-propyl alcohol magnesium solutions by filtration or centrifugation.Obtained the solution of two n-propyl alcohol magnesium of oxide-free impurity, the diboron hexahydride of gaseous state is introduced in this solution, reaction obtains two (normal-butyl) boron and magnesium borohydride.
Employed diboron hexahydride is at oxygen-free and moisture in nature, generates boron oxide or boric acid because of it and oxygen or moisture reaction.By forming magnesium borohydride with the diboron hexahydride reaction, magnesium borohydride is separated out in this solvent as polar salt.The a small amount of three organic radical boron R3 that form simultaneously or boric acid ester are because its nonpolar dissolving in this non-polar solvent.By again being separated, for example by filtering, the solid-state magnesium borohydride of pure oxide-free impurity will be obtained.This magnesium borohydride can be used when the second step thermolysis.During whole method, must be noted that strict isolating oxygen and moisture.
Secondly, under standard pressure, pass into argon gas and form protective atmosphere, with resulting magnesium borohydride thermolysis, so that form boronation magnesium.
The pyrolysis of magnesium borohydride is to carry out in the scope of 250 ℃-1600 ℃ of temperature, preferably carries out in the scope of 500 ℃-1000 ℃ of temperature.The pyrolysis about 500 ℃-600 ℃ in temperature is particularly preferred.Produced the magnesium diboride of non-crystalline state to partial crystallization.In the situation according to magnesium diboride of the present invention, reaction wants beguine much higher according to the situation of the crystallization magnesium diboride of prior art for the friendly of mixing.Compare with the magnesium diboride according to the method manufacturing of routine, magnesium diboride constructed in accordance also has higher sintering activity.
The pressure of pyrolytic reaction is standard pressure preferably; Under standard pressure, preferably use argon gas to form protective atmosphere.Alternatively, also can use hydrogen excess pressure.If the pyrolysis of magnesium borohydride is carried out, cause so the reversed reaction for this compound formation reaction under high vacuum.The result has produced again magnesium hydride and diboron hexahydride.Preferred consideration has the reactor of moving-bed as the reactor of magnesium borohydride pyrolysis under the standard pressure.Example for this reason comprises rotary kiln or fluidized-bed reactor, alternatively, also can use the reactor with quiescent bed.
The pyrolytic reaction of magnesium borohydride has following advantage:
Evaporate in the argon gas stream when the 50-250 ℃ of temperature with the body solvent of giving of magnesium atom coordination.Yet magnesium borohydride is stable for decomposition under the occasion of this temperature.Therefore in this sense, magnesium borohydride and do not descend plane defect for the adducts of body solvent also namely plays Decomposition when magnesium borohydride is decomposed, and the latter just decomposes being higher than 250 ℃ of temperature.
During pyrolytic reaction, only form hydrogen as unique by product.Therefore the formation of oxide impurity can not form oxygen during the pyrolysis or not have oxygen to participate in pyrolytic reaction, owing to can pollute.
The Hydrogen Energy that forms easily separate with the solid magnesium diboride as gas.Do not use solvent or auxiliary agent in this external this step, described solvent or auxiliary agent occupy the supraconductivity that formed magnesium diboride surface also randomly sprays thus gas and affects magnesium diboride.Under the occasion of the method according to this invention, avoided at the very start the surface to be occupied, therefore can not form reaction product or by product.Therefore from this respect, the formation of hydrogen is verified to be desirable.
Easy and the fully pyrolysis of magnesium borohydride.Pyrolysis just begins in about 250 ℃ of temperature.Pyrolysis by magnesium borohydride form magnesium diboride reaction heat effect with formed by element that to compare be relative low.When making the magnesium diboride that supplies superconductor applications, this situation is useful.Temperature or heat effect that magnesium diboride forms reaction are lower, and then the granularity of resulting magnesium diboride and crystal growth are just lower, and the degree of crystallinity of magnesium diboride is just poorer.According to the graceful law of tower, if the temperature of mixture is positioned near the theoretical fusing point, then crystal growth is just large especially.Therefore high heat effect has promoted crystal growth.But for superconductor applications of the present invention, alap granularity is preferred.
Formed magnesium diboride has following advantage, also is that it produces with fine particle, and needn't grinds subsequently again, because during pyrolytic reaction, sintering does not occur for it, and it can be directly as the material for the filling wire.Because wearing and tearing, grinding steps also means pollution.Resulting magnesium diboride has the size-grade distribution D of single mode
100≤ 15 microns, preferred D
100≤ 10 microns.
Magnesium diboride constructed in accordance is unbodied or partial crystallization.Therefore magnesium diboride amorphous or partial crystallization of the present invention has at the most 25% weight, preferred 15% weight at the most, and the crystal share of 10% weight at the most particularly preferably.In contrast, the non-crystalline state magnesium diboride that does not contain remarkable share according to the magnesium diboride of prior art crystallization.
Compare with the crystallization magnesium diboride of the almost exclusiveness of prior art, magnesium diboride constructed in accordance has the more advantage of high ductibility.Fill wire by wire drawing and rollingly add man-hour at the powder that is filled with magnesium diboride, this material property is important.Magnesium diboride constructed in accordance has the higher current capacity of magnesium diboride of making than prior art in addition.
Magnesium diboride oxide-free impurity made according to the method for the present invention has the oxygen level of paramount 2000ppm, the oxygen level of preferred paramount 500ppm, the particularly preferably oxygen level of paramount 100ppm.
Mix with gas according to the present invention, in the magnesium borohydride pyrolysis step, sneak into described gas to shielding gas.Therefore can reach the particularly preferred distribution of doping agent, namely reach desirable " sosoloid ".Doping carbon can realize at the gas that makes shielding gas be rich in release carbon when decomposing during the pyrolytic process.Suitable gas is for example acetylene, ethene, propane and butane.The preferred acetylene that uses.
Consider various methyl-monosilanes for mixing with silico-carbo, it produces silicon carbide when pyrolysis, randomly together with excessive element.Methyl-monosilane is preferably tetramethylsilane and tetramethyl-silicoethane.This external enwergy is used other compound, particularly gas, and when pyrolytic process, other compound can be decomposed into needed hotchpotch on the other hand.
Because distributing, its high purity and thin uniform particle size be used for valuably superconduction according to magnesium diboride of the present invention.Use in this case the wire with magnesium diboride inner core.
In order to obtain having the plain conductor of magnesium diboride inner core, for the chemical reaction that reaches boron and magnesium becomes magnesium diboride, by introduce the mixture of element boron and magnesium in metal shell, then wire drawing and thermal treatment subsequently can access such wire.
Except the share of high amorphous boron, the oxygen of demanding purity, particularly low levels, nitrogen, anionic impurity such as chlorion or fluorion also have common metallic impurity such as alkali and alkaline earth metal ions ion and other metal ion.Reach equally lower granularity, do not have excessive individual particle, because this individual particle can cause the fracture of wire when wire drawing, impurity can cause lower current capacity.
In addition, excessive individual particle hinders boron and the complete chemical reaction formation of magnesium magnesium diboride.Traditional commercially available boron normally obtains with magnesium reduction by boron trioxide, so that there is the demand of the boron that is further purified commercially available routine, makes it possible to produce extra high-quality product.
The method according to this invention and the magnesium diboride that obtains is particularly suitable for making superconducting line, because it is because high purity, size-grade distribution and low granularity have been eliminated many shortcomings of prior art uniformly.
The manufacture method of high performance superconducting line of the present invention also comprises, second, the prepared according to the methods of the invention magnesium diboride is closed in the metal shell, and preferably, this metal is copper.The 3rd, then obtained having the wire of metal shell and magnesium diboride inner core by wire drawing.Magnesium diboride xln by the method preparation has the purity height, particle diameter is little, and therefore the uniform advantage of particle diameter adopts this magnesium diboride xln as the inner core of superconducting line, and conductivity is excellent, will be used widely as superconducting line of new generation.
Certainly; the present invention also can have other various embodiments; in the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make according to the present invention various corresponding changes and distortion, but these corresponding changes and distortion all should belong to the protection domain of the appended claim of the present invention.
Claims (4)
1. MgB
2The manufacture method of superconductivity wire is characterized in that the method comprises the steps:
The first, preparation magnesium diboride xln, as inner core, it comprises the steps:
At first, two n-propyl alcohol magnesium and diboron hexahydride are dissolved in the non-polar solvent, reaction obtains magnesium borohydride, impurity is separated non-polar solvent pentane preferably wherein, hexane, heptane, octane by solid-liquid isolation method;
Secondly, under standard pressure, pass into argon gas and form protective atmosphere, with resulting magnesium borohydride thermolysis, so that form boronation magnesium, wherein, the temperature of thermolysis is 500 ℃-1000 ℃;
The second, magnesium diboride xln inner core is encapsulated in the metal;
Three, above-mentioned inner core and metal wire-drawing are obtained having the superconducting line of magnesium diboride inner core.
2. MgB as claimed in claim 1
2The manufacture method of superconductivity wire is characterized in that, described non-polar solvent is octane.
3. MgB as claimed in claim 1
2The manufacture method of superconductivity wire is characterized in that, the temperature of described thermolysis is 500 ℃-600 ℃.
4. MgB as claimed in claim 1
2The manufacture method of superconductivity wire is characterized in that, described metal is copper.
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| CN201210504677XA CN102992772A (en) | 2012-11-30 | 2012-11-30 | Preparation method of MgB2 superconducting wire |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102209686A (en) * | 2008-11-11 | 2011-10-05 | H.C.施塔克股份有限公司 | Magnesium diboride |
| 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 |
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- 2012-11-30 CN CN201210504677XA patent/CN102992772A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102209686A (en) * | 2008-11-11 | 2011-10-05 | H.C.施塔克股份有限公司 | Magnesium diboride |
| 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 |
Non-Patent Citations (2)
| Title |
|---|
| 郭峥山等: "溶液法制备MgB2超导膜研究", 《真空科学与技术学报》 * |
| 陈君儿等: "配位氢化物储氢材料g（BH4）2的研究进展", 《材料科学与工程学报》 * |
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Application publication date: 20130327 |