KIM, Young-Kuk (Ga-102, Hanhyokukhwa APT. 448-1, Hoisung-don, Masan-si Gyeongsangnam-do 630-020, KR)
KO, Jae-Woong (101-601 Hanlim Elicion APT, Namyang-dong Changwon-si, Gyeongsangnam-do 641-091, KR)
CHUNG, Kook-Chae (RM207, Korea Institute of Machinery & Materials APT. Gaeumjeong-don, Changwon-si Gyeongsangnam-do 641-110, KR)
YOO, Jai-Moo (1 Daedong APT, Sangnam-dong Changwon-si, Gyeongsangnam-do 641-010, 18-1903, KR)
KIM, Young-Kuk (Ga-102, Hanhyokukhwa APT. 448-1, Hoisung-don, Masan-si Gyeongsangnam-do 630-020, KR)
KO, Jae-Woong (101-601 Hanlim Elicion APT, Namyang-dong Changwon-si, Gyeongsangnam-do 641-091, KR)
CHUNG, Kook-Chae (RM207, Korea Institute of Machinery & Materials APT. Gaeumjeong-don, Changwon-si Gyeongsangnam-do 641-110, KR)
Claims:
1. An apparatus for manufacturing a superconducting wire using a wet chemical process, comprising: a metal layer formation part for forming a metal layer having biaxial orientation through electroplating; a buffer layer formation part for forming a buffer layer on the metal layer through the wet chemical process while maintaining biaxial orientation of the metal layer, thus obtaining a wire having a buffer layer; and a superconducting layer formation part for forming a superconducting layer on the wire having a buffer layer through the wet chemical process while maintaining biaxial orientation of the wire having a buffer layer, thus manufacturing the superconducting wire.
2. The apparatus according to claim 1, wherein the superconducting layer formation part comprises a winding portion for winding the superconducting wire.
3. The apparatus according to claim 1, wherein the metal layer formation part comprises: an electroplating portion, which includes a cathode having biaxial orientation, an anode for providing positive potential, a current supply source for supplying current to the cathode and anode, and an electroplating bath containing an electroplating solution in which the cathode and anode are dipped; a water washing bath for washing the metal layer separated from the cathode of the electroplating portion; and a dryer for drying the metal layer washed in the water washing bath.
4. The apparatus according to claim 3, wherein the metal layer is formed of nickel or alloys of nickel and at least one selected from among iron, copper, tungsten, chromium, manganese, vanadium, and tin.
5. The apparatus according to claim 1, wherein the buffer layer formation part comprises: a buffer layer coater for applying a precursor solution on the metal layer formed using the metal layer formation part through the wet chemical process while maintaining the biaxial orientation of the metal layer; and a buffer layer heater for heating the precursor solution, applied using the 5 buffer layer coater, to cure it.
6. The apparatus according to any one of claims 1 to 5, wherein the wet chemical process is any one selected from among metal-organic deposition, electroless plating, and electroplating. 0
7. The apparatus according to claim 6, wherein the buffer layer is formed of at least one selected from among LaAlO 3 , YSZ, SrTiO 3 , NiO, LaMnO 3 , La 2 Zr 2 O 7 , MgO, CeO 2 , BaTiO 3 , TiN, LaGaO 3 , Sm 2 O 3 , La 2 O 3 , Tb 2 O 3 , Y 2 O 3 , Gd 2 Zr 2 O 7 , and Sm 2 Zr 2 O 7 . 5
8. The apparatus according to claim 7, wherein the superconducting layer comprises at least one of YBa 2 Cu 3 O 7-X and REBa 2 Cu 3 O 7-X (RE=Sm, Eu, Gd, Dy, Ho, Er, Yb), and has biaxial orientation.
0 9. The apparatus according to claim 8, wherein the metal layer formed using the metal layer formation part is continuously passed through the buffer layer formation part and the superconducting layer formation part by guide rollers, thus manufacturing the superconducting wire.
5 10. A method of manufacturing a superconducting wire using a wet chemical process, comprising: a metal layer formation step of forming a metal layer having biaxial orientation through electroplating; a buffer layer formation step of forming a buffer layer on the metal layer O formed in the metal layer formation step through the wet chemical process while maintaining biaxial orientation of the metal layer, thus preparing a wire having a buffer layer; and a superconducting layer formation step of forming a superconducting layer on the wire having a buffer layer through the wet chemical process while maintaining biaxial orientation of the wire having a buffer layer, thus manufacturing the superconducting wire.
11. The method according to claim 10, wherein the metal layer formation step is conducted by electroplating the metal layer on a surface of a cathode having biaxial orientation to perform deposition to achieve biaxial orientation, and then separating it from the cathode.
12. The method according to claim 11, wherein the metal layer is formed of nickel or alloys of nickel and at least one selected from among iron, copper, tungsten, chromium, manganese, vanadium, and tin.
13. The method according to claim 10, wherein the buffer layer formation step is conducted such that the buffer layer has biaxial orientation and is formed into one or more layers on the metal layer having biaxial orientation using any one wet chemical process selected from among electroplating, electroless plating, and organic chemical deposition.
14. The method according to claim 13, wherein the buffer layer formation step using organic chemical deposition is conducted by applying a precursor solution composed mainly of a metal salt or a chelating agent on the metal layer and then heating the metal layer, coated with the precursor solution for a buffer layer, to 500~1300°C for a period of time ranging from 10 min to 1 hour in an inert gas atmosphere containing 4-10% hydrogen gas.
15. The method according to claim 14, wherein the buffer layer is formed of at least one selected from the group consisting of LaAlO 3 , YSZ, SrTiO 3 , NiO, LaMnO 3 , La 2 Zr 2 O 7 , MgO, CeO 2 , BaTiO 3 , TiN, LaGaO 3 , Sm 2 O 3 , La 2 O 3 , Tb 2 O 3 , Y 2 O 3 , Gd 2 Zr 2 O 7 , and Sm 2 Zr 2 O 7 .
16. The method according to claim 10, wherein the superconducting layer formation step is conducted such that the superconducting layer is formed on the buffer layer to have biaxial orientation through the wet chemical process.
17. The method according to claim 16, wherein the superconducting layer formation step is conducted by applying a precursor solution composed of a superconducting metal and a metal salt on a wire having a buffer layer, heating the wire having a buffer layer coated with the precursor solution for a superconducting layer at 300~600°C in a pure oxygen atmosphere containing moisture to calcine the precursor solution for the superconducting layer so as to form a precursor thin film, and post-heating the wire having a buffer layer on which the precursor thin film is formed at 700~850°C for a period of time ranging from 10 min to 3 hours in an inert gas atmosphere containing 10-10000 ppm oxygen to form the precursor thin film into the superconducting layer.
18. The method according to claim 17, wherein the superconducting layer comprises at least one of YBa 2 Cu 3 O 7-X and REBa 2 Cu 3 O 7 - X (RE=Sm, Eu, Gd, Dy, Ho, Er, Yb), and has biaxial orientation.
19. The method according to any one of claims 10 to 18, wherein the metal layer formation step, the buffer layer formation step, and the superconducting layer formation step are continuously conducted. |
APPARATUS AND METHOD OF MANUFACTURING SUPER CONDUCTING TAPES USING WET CHEMICAL PROCESS
Technical Field
The present invention relates, in general, to the manufacture of superconducting wires, and more particularly, to an apparatus and method for manufacturing a superconducting wire using a wet chemical process, in which a metal layer, a buffer layer and a superconducting layer are sequentially manufactured using only a wet chemical process, without rolling and post- heating processes for conferring biaxial orientation to the metal layer or intermediate layer, thus manufacturing an oxide superconducting wire.
Background Art
Typically represented by YBa 2 Cu 3 0 7-x , oxide superconducting wires have excellent current transport properties and superior critical current properties in strong magnetic fields. Thus, in the future, such a superconducting wire is expected to realize small sizes, high efficiencies and high capacitances of large power machines upon application to power cables, industrial motors, power generators, etc.
FIG. 1 is a cross-sectional view showing an oxide superconducting wire. As shown in FIG. 1 , the oxide superconducting wire includes a metal substrate A, a buffer layer B, and a superconducting layer C. Since the current transport properties vary greatly depending on the orientation of crystals in a superconductor, the crystals of the superconductor should be arranged to have high biaxial orientation, so as to manufacture a superconducting wire having a high critical current density (Jc). Thus, attempts have been successfully made to induce biaxial orientation of crystals of a superconductor using a highly oriented metal substrate of { 100}<l 00>.
Presently, with the goal of preparing a biaxially oriented metal substrate required for manufacturing a superconducting wire, a RABiTS (Rolling-assisted
Biaxially Textured Substrate) process developed by ORNL (Oak Ridge National
Lab.), USA, is mainly used. The RABiTS process is a method of preparing a biaxially oriented substrate for YBCO-based superconducting wires by rolling
and post-heating a metal substrate. The rolling/post-heating processes are advantageous because a substrate having uniform biaxial orientation can be prepared on a large scale, but suffers because large equipment is required for rolling and recrystallization heating. Further, due to problems related to the rolling process, such as the generation of cracks and non-uniform thickness, the rolling and post-heating processes must be precisely controlled to prepare a biaxially oriented metal substrate having a thickness of 100 μm or less.
As methods of manufacturing a superconducting wire using an oxide superconductor, a technique of forming an intermediate layer having controlled crystal orientation on a long metal tape and then sequentially forming a buffer layer and an oxide superconducting layer on the intermediate layer has been proposed. As a typical example of the superconducting tape-shaped wire thus obtained, useful is a tape-shaped wire obtained by depositing stable zirconia (YSZ) having crystal orientation controlled using IBAD (Ion Beam-Assisted Deposition) on a Hastelloy tape while maintaining c-axis orientation to the tape and a-axis and b-axis matching (in-plane orientation) to the tape and then forming a Y 123 (YBa 2 Cu 3 0 7 . x )-based oxide superconducting film on the zirconia layer through laser abrasion. However, in the IBAD process, the control of the crystal orientation of the intermediate layer necessary for manufacturing the superconducting wire should be realized in a high vacuum, and therefore expensive high-vacuum equipment should be used, and the film production rate is inferior.
Further, in the presently used oxide superconducting wire manufacturing process, the rolling/post-heating process or IBAD process is mainly adopted to confer biaxial orientation to the metal layer or intermediate layer. In order to form the buffer layer and the superconducting layer on the prepared substrate, a high-vacuum process, such as sputtering, laser abrasion, heat deposition or metal-organic chemical vapor deposition, or a wet chemical process such as metal-organic deposition (MOD), may be employed. Since the high- vacuum process is conducted in a high vacuum of 10 "5 Pa or less, expensive high-vacuum equipment and highly developed high-vacuum technique are needed, undesirably deteriorating process stability, essential for the practical use of superconducting wires, and negating economic benefits.
On the other hand, the wet chemical process such as MOD does not need to be conducted in a high vacuum, and merely consists of coating and heat
treatment, hence generating economic benefits. In addition, recently, oxide superconducting wires, having critical current values of 380 A/cm on a short wire and 160 A/cm or more on a long wire having a length of 85 m, have been developed by forming a superconducting layer on a metal substrate that is prepared through rolling/post-heating processes, using an MOD process. In this way, the MOD process is regarded as excellent from the point of view of economic benefits and wire performance.
The oxide superconducting wire is composed of a plurality of highly oriented crystal layers. Such a multilayered wire is manufactured through a plurality of process steps. In the case where the plurality of process steps is required as in manufacturing the superconducting wire, it is preferred that the steps progress continuously without interruption in order to realize excellent productivity and economic benefits. However, in methods of manufacturing oxide superconducting wires developed to date, there is big trouble in continuously conducting the process of preparing a substrate and the process of forming a buffer layer or a superconducting layer, so that realizing a continuous superconducting wire manufacturing process is impossible. In particular, even if the MOD process is applied, since the substrate preparation process needs a plurality of steps for mechanical processing and post-heat treatment, all of the process steps for manufacturing the oxide superconducting wire are difficult to continuously conduct. Therefore, conventional methods of manufacturing an oxide superconducting wire are disadvantageous because each batch must be separately wound on the corresponding winding reel for every process step, and must then be transferred to subsequent process equipment. The lattice orientation of the metal substrate may be controlled through an electroplating process, in addition to a rolling process and a recrystallization process. If the electroplating process is used to manufacture a metal substrate for a superconducting wire, the biaxially oriented substrate may be continuously prepared through a simpler process and at a lower preparation cost compared to conventional methods, in which large numbers of the rolling and high- temperature heating processes should be repeatedly performed. Further, the electroplating process, acting as a wet chemical process, enables the preparation of a substrate suitable for an MOD process for the formation of a buffer layer and a superconducting layer of a superconducting wire, and is preferable from the point of view of realization of a continuous process. However, since the
electroplating process merely induces uniaxial orientation, the resultant metal layer has a fibrous texture. Thus, almost all of the metal plated layers are known to have high orientation to the c-axis of the metal lattice but to have no orientation to the a-axis or b-axis thereof. However, the biaxial orientation may be induced upon application of an external magnetic field during a plating process, which is disclosed in Korean Patent No. 352976 and US Patent No. 6,346,181. This method is novel in that an electroplated layer having biaxial orientation is obtained by appropriately controlling the position of the electrode in the plating bath and the arrangement of a magnetic field, but is disadvantageous because the extent of biaxial orientation is lower than that of a substrate resulting from conventional rolling/heating processes.
Thus, in order to overcome the above problems encountered upon manufacturing the oxide superconducting wire and maximize the productivity of the oxide superconducting wire for realization of actual use thereof, there are urgently required an inexpensive apparatus and method for manufacturing an oxide superconducting wire, capable of realizing a continuous manufacturing process and generating economic benefits.
Disclosure of the Invention
Technical tasks to be solved by the invention
Accordingly, the present invention has been devised to solve the problems mentioned above, and an object of the present invention is to provide an apparatus and method for manufacturing a superconducting wire using a wet chemical process, in order to enable the continuous manufacture of the superconducting wire, which has been conventionally regarded as unrealizable, by conducting the process of manufacturing an oxide superconducting wire using only a wet chemical process such as electroplating, electroless plating, or MOD.
Technical Solution
In order to accomplish the above object, the present invention provides an apparatus for manufacturing a superconducting wire using a wet chemical process, comprising a metal layer formation part for forming a metal layer having biaxial orientation through electroplating; a buffer layer formation part for forming a
buffer layer on the metal layer through a wet chemical process while maintaining the biaxial orientation of the metal layer, thus obtaining a wire having a buffer layer; and a superconducting layer formation part for forming a superconducting layer on the wire having a buffer layer through a wet chemical process while maintaining the biaxial orientation of the wire having a buffer layer, thus manufacturing the superconducting wire.
The superconducting layer formation part may include a winding portion for winding the superconducting wire.
The metal layer formation part may include an electroplating portion, which is composed of a cathode having biaxial orientation, an anode for providing positive potential, a current supply source for supplying current to the cathode and anode, and an electroplating bath containing an electroplating solution in which the cathode and anode are dipped; a water washing bath for washing the metal layer separated from the cathode of the electroplating portion; and a dryer for drying the metal layer washed in the water washing bath.
The buffer layer formation part may include a buffer layer coater for applying a precursor solution on the metal layer formed using the metal layer formation part through a wet chemical process while maintaining the biaxial orientation of the metal layer; and a buffer layer heater for heating the precursor solution applied using the buffer layer coater to cure it.
The wet chemical process may be any one selected from among MOD, electroless plating, and electroplating.
In addition, the present invention provides a method of manufacturing a superconducting wire using a wet chemical process, comprising a metal layer formation step of forming a metal layer having biaxial orientation through electroplating; a buffer layer formation step of forming a buffer layer on the metal layer formed in the metal layer formation step through a wet chemical process while maintaining the biaxial orientation of the metal layer, thus preparing a wire having a buffer layer; and a superconducting layer formation step of forming a superconducting layer on the wire having a buffer layer through a wet chemical process while maintaining the biaxial orientation of the wire having a buffer layer, thus manufacturing the superconducting wire.
The metal layer formation step may be conducted by electroplating the metal layer on the surface of a cathode having biaxial orientation to perform deposition to achieve biaxial orientation and then separating it from the cathode.
The buffer layer formation step may be conducted such that the buffer layer has biaxial orientation and is formed into one or more layers on the metal layer having biaxial orientation using any one wet chemical process selected from among electroplating, electroless plating, and organic chemical deposition. In the case where the organic chemical deposition process is selected from among the above wet chemical processes, the buffer layer formation step may be conducted by applying a precursor solution, composed mainly of a metal salt or a chelating agent, on the metal layer and then heating the metal layer, coated with the precursor solution for a buffer layer, to 500-1300°C for a period of time ranging from 10 min to 1 hour in an inert gas atmosphere containing 4-10% hydrogen gas.
The superconducting layer formation step may be conducted by applying a precursor solution composed mainly of a superconducting metal and a metal salt on the wire having a buffer layer, heating the wire having a buffer layer coated with the precursor solution for a superconducting layer at 300~600°C in a pure oxygen atmosphere containing moisture to calcine the precursor solution for a superconducting layer so as to form a precursor thin film, and post-heating the wire having a buffer layer on which the precursor thin film is formed at 700~850°C for a period of time ranging from 10 min to 3 hours in an inert gas atmosphere containing 10-10000 ppm oxygen to form the precursor thin film into the superconducting layer.
In the present invention, the metal layer may be formed of nickel or alloys of nickel and at least one selected from among iron, copper, tungsten, chromium, manganese, vanadium, and tin. Further, the buffer layer may be formed of at least one selected from among LaAlO 3 , YSZ, SrTiO 3 , NiO, LaMnO 3 , La 2 Zr 2 O 7 , MgO, CeO 2 , BaTiO 3 , TiN, LaGaO 3 , Sm 2 O 3 , La 2 O 3 , Tb 2 O 3 , Y 2 O 3 , Gd 2 Zr 2 O 7 , and Sm 2 Zr 2 O 7 .
Further, the superconducting layer may be formed to have biaxial orientation through the wet chemical process on the buffer layer and may comprise at least one of YBa 2 Cu 3 0 7 . x and REBa 2 Cu 3 0 7 . x (RE=Sm, Eu, Gd, Dy, Ho, Er, Yb).
In the present invention, the metal layer formation step, the buffer layer formation step, and the superconducting layer formation step may be continuously conducted. That is, the metal layer formed using the metal layer formation part is preferably transferred to the buffer layer formation part through a guide roller,
after which the precursor solution for a buffer layer is applied and then heated to form the buffer layer, which is then transferred to the superconducting layer formation part through another guide roller, after which the precursor solution for a superconducting layer is applied, calcined and then post-heated to form the superconducting layer, thereby manufacturing the superconducting wire, which is then wound on the winding reel.
Hereinafter, a detailed description will be given of the present invention, with reference to the appended drawings.
FIG. 2 is a view showing an apparatus for manufacturing a superconducting wire using a wet chemical process, according to the present invention, and FIG. 3 is a flowchart showing a process of manufacturing a superconducting wire through a wet chemical process using the apparatus of FIG. 2, according to the present invention.
As shown in FIG. 2, the apparatus for manufacturing the superconducting wire of the present invention comprises a metal layer formation part 10 for forming a metal layer having excellent biaxial orientation through electroplating, a buffer layer formation part 20 for forming a wire having a buffer layer by applying a precursor solution for a buffer layer on the metal layer formed using the metal layer formation part through a wet chemical process and then heating it while maintaining the biaxial orientation of the metal layer, and a superconducting layer formation part 30 for forming a superconducting wire by applying a precursor solution containing a superconducting metal element on the wire having a buffer layer formed using the buffer layer formation part 20 through a wet chemical process, and then calcining and post-heating it. The metal layer formation part 10 includes an electroplating portion 16 for forming the metal layer through electroplating, a water washing bath 17 for washing the metal layer m formed using the electroplating portion 16, and a dryer 18 for drying the metal layer m washed in the water washing bath 17 by hot blasting. Further, the electroplating portion 16 is composed of an electroplating bath 15 containing an electroplating solution 13, a cathode 11 dipped in the electroplating solution 13 of the electroplating bath for depositing metal ions present in the electroplating solution 13 to have high biaxial orientation so as to form the metal layer m while being separated from the cathode, an anode 12 for providing positive potential required for plating, and a current supply source 14
for supplying current to the cathode 11 and anode 12. In the case where the metal ions are deposited using the cathode 11 having biaxial orientation, the biaxial orientation of the cathode 11 is transferred to the metal, resulting in the metal layer having high biaxial orientation. As such, the metal layer is formed of nickel or alloys of nickel and at least one selected from among iron, copper, tungsten, chromium, manganese, vanadium, and tin.
The method of preparing a metal plated layer having high biaxial orientation through electroplating is specifically disclosed in Korean Patent No. 10-0516126, related to 'a method of manufacturing a metal plated layer having biaxial texture', and a detailed description thereof is omitted.
The buffer layer formation part 20 includes a buffer layer coater 21 for applying the precursor solution for a buffer layer on the metal layer m supplied from the dryer 18 of the metal layer formation part 10 through a wet chemical process, and a buffer layer heater 22 for heating the precursor solution applied on the metal layer m using the buffer layer coater 21 to cure it so as to produce the wire b having a buffer layer.
The superconducting layer formation part 30 includes a superconducting layer coater 31 for applying the precursor solution containing the metal element for a superconducting layer and the metal salt on the wire b having a buffer layer supplied from the buffer layer formation part 20, a superconducting layer heater
32 which is provided after the superconducting layer coater 31 for calcining the precursor solution containing the metal element for a superconducting layer applied on the wire b having a buffer layer using the superconducting layer coater 31, and a superconducting layer post-heater 33 for forming a cured superconducting wire s through heat treatment subsequent to calcination. Further, a winding reel 34 for winding the superconducting wire s is provided after the superconducting layer post-heater 33.
The superconducting wire manufacturing apparatus having the structure shown in FIG. 2 enables the manufacture of the superconducting wire by forming the metal layer having high biaxial orientation through electroplating without rolling or heating processes for conferring high biaxial orientation to the metal layer, and then sequentially depositing the buffer layer and superconducting layer thereon through a wet chemical process. Thus, the superconducting wire manufacturing apparatus of FIG. 2 is characterized in that the superconducting wire can be manufactured through a continuous process.
FIG. 3 is a flowchart showing the process of manufacturing the superconducting wire through a wet chemical process using the superconducting wire manufacturing apparatus of FIG. 2, according to the present invention.
The method of manufacturing the superconducting wire of the present invention is largely composed of 1) a metal layer formation process (S1~S3) of forming a metal layer having excellent biaxial orientation through electroplating,
2) a buffer layer formation process (S4-S5) of forming a buffer layer on the metal layer formed in the metal layer formation process through a wet chemical process such as electroplating or MOD while maintaining the biaxial orientation of the metal layer so as to form a wire having a buffer layer, and 3) a superconducting layer formation process (S6-S8) of forming a superconducting layer through a wet chemical process while maintaining the biaxial orientation of the wire having a buffer layer, thus manufacturing the superconducting wire.
The method of the present invention composed of the above steps is characterized in that the oxide superconducting wire can be manufactured using only the wet chemical process to realize economic benefits and a continuous process. That is, respective steps for manufacturing the oxide superconducting wire are conducted using the wet chemical process, and thus, the manufacturing process including respective steps can continuously progress, thereby enabling the manufacture of the oxide superconducting wire through the continuous process using the superconducting wire manufacturing apparatus of FIG. 2.
Respective processes of the method of manufacturing a superconducting wire using a wet chemical process of the present invention are described with reference to FIGS. 2 and 3. 1 ) Formation of Metal Layer through Electroplating
As disclosed in Korean Patent No. 10-0516126, the cathode 11 having high biaxial orientation is installed in the electroplating bath 15, and the metal layer is plated under conditions capable of transferring the biaxial orientation of the cathode to the metal layer and is then separated, thus forming a metal layer m having high biaxial orientation. As such, the resultant metal layer is formed of nickel or alloys of nickel and at least one selected from among iron, copper, tungsten, chromium, manganese, vanadium, and tin.
Particularly, as shown in FIG. 2, the anode 12 and the cathode 11 having high biaxial orientation are dipped in the plating solution 13 and the metal layer is grown on the cathode to have orientation the same as or similar to monocrystals
using the current supply source 14, and is then separated from the cathode, thus forming the metal layer. In order to separate the metal layer formed on the cathode through plating, before the plating process, the cathode is washed, dipped in an aqueous solution comprising 0~10 M lithium hydroxide, 0~10 M sodium hydroxide, 0-10 M potassium hydroxide, 0~10 M ammonia water, and 0-10 M hydrogen peroxide for a period of time ranging from ones of seconds to tens of minutes, washed with water, and then dried. Immediately before the cathode is treated in the aqueous solution, a process of smoothing the surface of the cathode through electrolytic polishing may be further carried out (Sl). The metal layer m separated in Sl is transferred to the water washing bath
17 to wash it with water (S2), and is then transferred to the dryer 18 to dry it (S3). 2) Formation of Buffer Layer through Wet Chemical Process The metal layer formed by the metal layer formation process including Sl -S3 is transferred to the buffer layer formation part 20 via a guide roller R4, coated with the precursor solution for a buffer layer through a wet chemical process using the buffer layer coater 21 (S4), and then heated using the buffer layer heater 22, thus forming the buffer layer (S5). As such, the buffer layer has biaxial orientation and is formed into one or more layers on the biaxially oriented metal layer, using any one wet chemical process selected from among electroplating, electroless plating, and organic chemical deposition. As the wet chemical process, MOD, electroless plating, or electroplating may be adopted. In particular, the use of MOD is preferable.
According to the MOD process, the precursor solution, which is composed mainly of a metal salt or metal alkoxide of carboxylic acid, nitric acid or hydrochloric acid, and a chelating agent, such as 2,4-pentanedione, ethanolamine, or amylamine, is applied on the biaxially oriented substrate formed by the metal layer formation process (S1-S3) (S4), and dried and post-heated using the buffer layer heater 22 (S5), thus obtaining an oxide or nitride buffer layer having induced biaxial orientation. The metal element contained in the precursor solution may vary depending on the kind of buffer layer, and examples thereof include La, Al, Cr, Mn, Ni, Sr, Ti, Zr, Sn, Cu, etc. In this case, examples of the solvent for use in the preparation of the precursor solution include methylalcohol, ethylalcohol, butanol, propanol, acetone, 2-octanol, etc. In the application step (S4), a coating
process, such as dip coating, slot die coating, gravure coating, or ink jet coating, may be adopted.
The post-heating process for the buffer layer is performed at 500-1300°C for a period of time ranging from 10 min to 1 hour in an argon or nitrogen 5 containing 4-10% hydrogen. As such, moisture of 5% or less may be further included in the reactive gas to ensure complete reaction of the buffer layer (S5).
The buffer layer thus obtained is formed of at least one selected from the group consisting Of LaAlO 3 , YSZ, SrTiO 3 , NiO, LaMnO 3 , La 2 Zr 2 O 7 , MgO, CeO 2 , BaTiO 3 , TiN, LaGaO 3 , Sm 2 O 3 , La 2 O 3 , Tb 2 O 3 , Y 2 O 3 , Gd 2 Zr 2 O 7 , and Sm 2 Zr 2 O 7 . 0 3) Formation of Superconducting Layer through Wet Chemical Process
The wire b having a buffer layer formed by the buffer layer formation process (S4, S5) is moved to the superconducting coater 31 via a guide roller R6, and is then coated with a precursor solution composed of a superconducting metal and a metal salt through a wet chemical process (S6). 5 The wet chemical process of S6 is performed through MOD. That is, the precursor solution, which comprises the metal element for a superconducting layer, for example, at least one metal element selected from among yttrium (Y), samarium (Sm), europium (Eu), neodymium (Nd), dysprosium (Dy), and gadolinium (Gd), and metal salts of barium (Ba) or copper (Cu), is applied on the O surface of the buffer layer formed in the previous process.
Upon preparation of the precursor solution, the metal salt is added in the form of carboxylate, halogenated carboxylate, acetylacetonate, nitrate, hydrochloride, etc., and the solvent used is exemplified by methylalcohol, ethylalcohol, butanol, propanol, acetone, 2-octanol, etc. In addition, with the 5 intention of achieving the stability of the solution, carboxylic acid, such as acetic acid, propionic acid or butyric acid, an amine compound, such as pyridine, Methanol amine or monoethanol amine, or β-diketone such as 2,4-pentanedione, may be added. For the application of the precursor solution (S6), a coating process, such as a dip coating process, a slot die coating process, a gravure O coating process, or an ink jet coating process, may be applied.
The wire b having a buffer layer coated with the precursor solution containing the superconducting metal element as mentioned above is transferred to the superconducting heater 32 to calcine it, such that the precursor solution containing the superconducting metal element is formed into a precursor thin film. 5 The calcination step (S7) is conducted at 300~600°C using a reactive gas
composed of pure oxygen containing moisture. The calcined precursor thin film is composed mainly of Y 2 O 3 , BaF 2 , or CuO (S7). As such, the resultant superconducting layer is formed of at least one of YBa 2 Cu 3 O 7-X and REBa 2 Cu 3 0 7-x (RE=Sm, Eu, Gd, Dy, Ho, Er, Yb) and has biaxial orientation. After the calcination of S7, the wire having the precursor thin film is moved to the superconducting layer post-heater 33. The wire having the precursor thin film provided in the superconducting layer post-heater 33 is subjected to post-heat treatment at 700~850°C for a period of time ranging from 10 min to 3 hours in an argon or nitrogen gas containing 10-10000 ppm oxygen, such that the precursor thin film is formed into the superconducting layer, leading to a superconducting wire s. As such, in order to remove fluorine from the precursor thin film, moisture of 10% or less may be added to the reactive gas (S 8).
After the heat treatment, the resultant oxide superconducting wire is wound on the winding reel 34 (S9), thereby completing the manufacturing process.
Advantageous Effects
According to the present invention, a high-temperature superconducting wire can be manufactured using only a wet chemical process, such as electroplating or MOD. Thus, it is possible to continuously conduct the manufacturing steps, and the manufacturing process from a biaxially oriented metal layer to a superconducting layer may progress continuously without an interruption.
Therefore, the manufacturing process rate of the present invention is maximized, compared to conventional processes. Further, in the present invention, economic benefits can be greatly exhibited by adopting only the wet chemical process without the need for rolling equipment or high-vacuum equipment required for conventional processes of manufacturing a high- temperature superconducting wire. In addition, since neither the rolling equipment nor the high- vacuum equipment for conventionally manufacturing a superconducting wire are required in the present invention, the manufacturing cost, equipment cost, and manufacturing rate are superior to those of conventional processes, thereby realizing actual use of oxide superconducting wires.
Brief Description of Drawings
FIG. 1 is a view showing the laminated structure of an oxide superconducting wire; FIG. 2 is a view showing an apparatus for manufacturing a superconducting wire using a wet chemical process, according to the present invention;
FIG. 3 is a flowchart showing a process of manufacturing a superconducting wire using a wet chemical process, according to the present invention;
FIG. 4 is views showing the results of X-ray diffraction analysis of a nickel plated layer formed into a biaxially oriented metal layer by electroplating a nickel layer on the surface of a cathode having high biaxial orientation and then separating it therefrom, according to the present invention; FIG. 5 is views showing the results of X-ray diffraction pattern, θ-rocking curve and φ-scan of a CeO 2 buffer layer formed on the nickel plated layer of FIG. 4 through MOD; and
FIG. 6 is a view showing the critical current properties of a YBCO layer.
Best Mode for Carrying Out the Invention
A better understanding of the present invention may be obtained through the following example which is set forth to illustrate, but is not to be construed as the limit of the present invention. * Example
<Formation of Metal Layer>
A nickel layer was electroplated on the surface of a cathode having high orientation under the following conditions, and was then separated therefrom, thus manufacturing a biaxially oriented metal layer: Anode: Highly pure nickel plate
Cathode: Biaxially oriented nickel-tungsten alloy substrate ({100}<100> orientation)
Composition of nickel plating solution: 250 g/1 of nickel sulfaminate, 15 g/1 of nickel chloride, and 15 g/1 of boric acid Plating temperature: 50°C
Plating time: Nickel - 20 min
Average current density: 5 A/dm 2
FIG. 4 is views showing a resulting X-ray diffraction pattern for analyzing the extent of biaxial orientation of the metal plated layer. In order to evaluate the c-axis alignment of the plane (001) of the resultant metal layer, the θ-rocking curve was measured. The results are shown in FIG. 4a. As such, the half width of the peak was found to be 5.7°.
Further, to evaluate the biaxial texture, the φ-scan (phi scan) of nickel
(111) was measured. In the φ-scan of FIG. 4b measured at the ψ angle of 54.7°, the half width of the Ni plated layer was found to be 7.8°. As the results of X- ray diffraction pattern, the electroplated nickel layer was confirmed to have excellent orientation.
<Formation of Buffer Layer>
On the biaxially oriented nickel substrate resulting from electroplating, CeO 2 was formed through MOD under the following conditions:
Composition of precursor solution: 0.2 M Ce-acetylacetonate, 0.1 M triethanolamine
Solvent: Methanol
Coating process: Dip coating Post-heating conditions: 1000 0 C, 30 min, Ar/H 2 (4%) gas
FIG. 5 is views showing the results of X-ray diffraction pattern, θ- rocking curve, and φ-scan of the CeO 2 buffer layer formed on the nickel plated layer of FIG. 4 through MOD.
The X-ray diffraction pattern resulting from analysis of the biaxial orientation of the CeO 2 buffer layer is shown in FIG. 5a. From this, the peak of
CeO 2 (200) was seen to be obviously developed, and the orientation (TF) perpendicular to the surface of CeO 2 was determined to be excellent to the extent of about 0.9. In order to evaluate the c-axis alignment of the plane (001), the θ- rocking curve was measured. The results are given in FIG. 5b. The half width of the peak was 7.01°. In the φ-scan of FIG. 5c, measured at the ψ angle of
54.7°, the half width of the CeO 2 layer was 9.89°. From the X-ray diffraction pattern, the CeO 2 layer was found to epitaxially grow.
<Formation of Superconducting Layer>
YBa 2 Cu 3 O 7-X (YBCO) was formed through MOD under the following conditions:
Composition of precursor solution: Y-trifluoroacetate, Ba-trifluoroacetate, Cu-trifluoroacetate
Solvent: Methanol
Coating process: Dip coating Calcination conditions: 400°C, oxygen gas (containing 2% moisture)
Post-heating conditions: 780°C, Ar/O 2 (lOOppm) gas
FIG. 6 is a view showing the critical current properties of the YBCO layer acting as the superconducting layer. As shown in FIG. 6, the critical current of 8 A was measured at a line width of 7 mm. Therefore, it has been confirmed that the superconducting wire can be manufactured using only a wet chemical process, such as electroplating, electroless plating, or MOD.
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