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Liquid-Phase Shock-Assisted Consolidation of Superconducting MgB2 Composites

Authors:
  • Tsulukidze Mining INstitute

Abstract

An original two-stage liquid-phase hot explosive compaction (HEC) procedure of Mg-B precursors above 900 ∘C provides the formation of superconductivity MgB2 phase in the whole volume of billets with maximal T c = 38.5 K without any further sintering. The liquid-phase HEC strongly increases the solid-state reaction rate similar to photostimulation, but in this case, due to the high penetrating capability of shock waves in a whole volume of cylindrical billets and consolidation of MgB2 precursors near to theoretical density allows one to produce bulk, long-body cylindrical samples important for a number practical applications.
1 23
Journal of Superconductivity and
Novel Magnetism
Incorporating Novel Magnetism
ISSN 1557-1939
J Supercond Nov Magn
DOI 10.1007/s10948-015-3007-8
Liquid-Phase Shock-Assisted Consolidation
of Superconducting MgB2 Composites
G.Mamniashvili, D.Daraselia,
D.Japaridze, A.Peikrishvili &
B.Godibadze
1 23
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J Supercond Nov Magn
DOI 10.1007/s10948-015-3007-8
ORIGINAL PAPER
Liquid-Phase Shock-Assisted Consolidation
of Superconducting MgB2Composites
G. Mamniashvili ·D. Daraselia ·D. Japaridze ·
A. Peikrishvili ·B. Godibadze
Received: 1 December 2014 / Accepted: 23 January 2015
© Springer Science+Business Media New York 2015
Abstract An original two-stage liquid-phase hot explosive
compaction (HEC) procedure of Mg-B precursors above
900 C provides the formation of superconductivity MgB2
phase in the whole volume of billets with maximal Tc=
38.5 K without any further sintering. The liquid-phase HEC
strongly increases the solid-state reaction rate similar to
photostimulation, but in this case, due to the high pene-
trating capability of shock waves in a whole volume of
cylindrical billets and consolidation of MgB2precursors
near to theoretical density allows one to produce bulk, long-
body cylindrical samples important for a number practical
applications.
Keywords HTSC ·MgB2·Liquid-phase ·Shock-assisted
consolidation ·Magnetometry
1 Introduction
The rapid development of research of the conductors based
on superconducting compound MgB2makes them a very
real prospect for technical applications at temperatures
below 30 K.
G. Mamniashvili ()
Andronikashvili Institute of Physics, Ivane Javakhishvili Tbilisi
State University, 6 Tamarashvili St., 0177, Tbilisi, Georgia
e-mail: mgrigor@rocketmail.com
D. Daraselia ·D. Japaridze
Ivane Javakhishvili Tbilisi State University, 3, Chavchavadze Ave.,
0128, Tbilisi, Georgia
A. Peikrishvili ·B. Godibadze
G. Tsulukidze Mining Institute, 7, Mindeli St.,
0186, Tbilisi, Georgia
Reported achievements of all higher values of the criti-
cal current density in wires and tapes at moderate magnetic
fields [1,2] lay out a strong hope that soon these conduc-
tors may be more economical at helium temperatures than
industrial wires and cables based on NbTi and Nb3Sn.
In the field of applied superconductivity, at temperatures
20–30 K, MgB2based conductors may seriously push out
industrial tape-based HTSC materials.
Main way for getting of MgB2is a solid-phase synthe-
sis in particular modifications. As example, one of quite
fruitful ones is the synthesis under high pressure [3]. As
high-temperature superconductor (HTSC) ceramics, com-
pound MgB2is brittle and therefore cannot be directly
manufactured in the form of wire or ribbon. The most
widely used method now to manufacture conductors based
on MgB2(as for HTSC ceramics) is the method “powder-
in-tube” (PIT) [4]. It is mainly used in two ways: in situ
and ex situ. In the in situ PIT method, thoroughly mixed
stoichiometric mixture of magnesium and boron powders
are pressed into a metallic tube, after which it runs into the
wire. Superconducting core of MgB2wire is a final result
of wire annealing in temperature range, usually, 600–950
C. In ex situ PIT method, in contrast, a metal tube filled
with already provisionally synthesized compound MgB2is
stretched into the wire.
Both options have their advantages and disadvantages.
In work [5], a novel method of photostimulated solid-
state synthesis of oxide materials was developed, enabling
a dramatic increase of the solid-state reaction speed. The
rate of solid-state reaction appears to be approximately
two orders of magnitude higher compared with ordinary
high-temperature solid-state reaction performed in furnace.
Experimental results given in [5] provide evidence of the
photostimulated nature of performed solid-state reaction
and demonstrate the possibility of production of HTSC and
Author's personal copy
J Supercond Nov Magn
Fig. 1 Experimental setup [8]
CMR oxides by light that is usually limited by the sam-
ple thickness; one could expect that this method could be
particularly effective in the preparation of oxide films hav-
ing a high-technological importance.
The current paper presents the first results of inves-
tigation of properties of superconducting MgB2samples,
obtained by hot explosive compaction (HEC) method. By
this method, similar effect for increasing the speed of solid-
state reaction as in case of using the photostimulated solid-
state synthesis was obtained. Besides it, due to the high
penetrating capability of shock waves generated by explo-
sion with intensity of compression 10 GPa, this method
allows one to fabricate bulk, high-density, and long-body
cylindrical billets with length near to 200 mm and diameter
up to 30 mm. The HECs of cylindrical billets were con-
ducted using half-automatic explosive device created at the
Tsulukidze Institute of Mining, allowing one to consolidate
different composition precursors near the theoretical density
within the temperature range 20–1200 C and with intensity
of loading 5–10 GPa.
The described HEC method also allows one to produce
multilayer cylindrical tubes (pipes) when gap between the
two metallic layers (e.g., Cu) is filled by superconducting
MgB2composites which could find important applications
for production of superconducting cables for simultaneous
transport of hydrogen and electrical power in hybrid MgB2-
based electric power transmission lines filled with liquid
hydrogen [6].
Attempts to synthesize MgB2using self-propagating
high-temperature synthesis (SHS method) have been also
reported [7].
However, the explosive compaction method to obtain
highly dense MgB2materials from Mg and B powders had
not been employed until 2008 [8].
Explosive compaction of powders is a widely used cost-
effective fabrication process due to its many advantages.
The process results in compacts of very good interparti-
cle bonding. The explosive compaction technique is based
on the propagation of shock waves produced by a detonat-
ing explosive, transmitting the waves through a thin steel
cylindrical container to powder [8].
In this method, high shock pressure with duration of a
few microseconds can be developed. Consolidation of the
powder is caused by the container wall motion, accelerating
towards the central axis of the container after detonation.
An initial compressive stress wave is generated by explo-
sion, followed by a sequence of wave reflections leading to
collapse of the container and consequently of its content.
The result of this process is a dense compact provided
that an adequate energy is released by explosion and trans-
ferred to the powder. The lack of sufficient energy leads to
a highly porous material.
In [8], MgB2samples were prepared using the PIT
method, while the densification of materials was carried out
under explosive loading. The experimental setup is shown
in Fig. 1.
The explosive was placed in a cylindrical tube made of
PVC and the whole arrangement was mounted on a specially
designed 25-mm-thick steel plate which acted as a shock
wave absorber. The ends of the steel container were filled
with MgO powder and sealed with two plastic lids. MgO
powder was used to avoid losing a part of Mg or B pow-
der, since at the explosion, an amount of the tube content is
blown into the air together with the plastic lids.
Fig. 2 SEM micrograph of Mg flakes and B powder compact before
sintering [8]
Author's personal copy
J Supercond Nov Magn
Fig. 3 a Traces of oxidation are
observed on the microstructures
(light places). bMagnetic
moment temperature
dependence measurements in
zero-field-cooled (ZFC) and
field-cooled (FC) modes,
showing the superconducting
transition at temperature near
37 K
The experiments were performed in an explosion-proof
room built on special foundation using PETN plastic explo-
sive with mass 350 g. A section of the sample after the
explosive compaction is shown in Fig. 2.
Since the explosive process is of a very small time
duration and the maximum temperature inside of the steel
container during the explosive consolidation did not exceed
250 C, which is significantly lower than the melting point
of Mg at 650 C (2000 C for B), therefore Mg and B could
not react to produce the MgB2phase. To produce MgB2,
obtained compacts were heated up to 630 C with a tem-
perature rise 5 K/min in argon atmosphere. The temperature
remained constant at 630 C for 30 min, and then slowly
rose to 960 C (with rate 1 K/min) where it stayed for
90 min.
Then slow cooling was performed to 700 C (1 K/min)
and at end the physical cool-down to ambient temperature.
Synthesis of MgB2in this case was initialized during
sintering, when melting of the surface layer of Mg and
following diffusion of B into Mg started. Gradually, melting
not only on the surface region but also of the interior of Mg
grains was performed as temperature rose and diffusion was
completed leading to a fine MgB2material as confirmed by
XRD patterns.
The porosity of samples appeared to be nearly zero,
indicating the importance of the explosive compaction tech-
nique when fabricating MgB2from Mg and B powders.
2 Experimental Results and Their Discussion
In this work, we have applied the innovative hot explo-
sive consolidation (HEC) method to fabricate high-dense
cylindrical billets of MgB2near to theoretical density with
perfect structure and high superconductive characteristics.
The offered method allows just after HEC to avoid a tedious
and several hour-long sintering procedure in the argon or
helium gas flow [9].
Fig. 4 Views of billets before
(a) and after the HEC procedure
at 1000 C and loading intensity
10 GPa (b)
Author's personal copy
J Supercond Nov Magn
Fig. 5 Temperature
dependences of the zero-field-
cooled (ZFC) and field-cooled
(FC) magnetic moment for HEC
MgB2composites at 1000 C
with intensity of loading 10 GPa
in magnetic field 20 Oe
The novelty of proposed nonconventionalapproach relies
on the fact that the consolidation of solid high-dense, long-
body cylindrical MgB2billets from submicrometer-sized
Mg and B powder blends is performed in two stages:
(1.) At the first stage, a preliminary explosive compression
of the precursors is carried out at room temperature
with a loading intensity of 5–10 GPa to increase the
initial density and to activate surfaces in the powder
blend.
(2.) At the second stage, the same already predensified
cylindrical sample is reloaded by a primary explosive
shock wave with a loading intensity of 10 GPa, but at
temperatures about 1000 C.
The first successful HEC of Mg-B powder blends was
performed at temperature 1000 C well above the melting
point of Mg phase at loading intensity 10 GPa, providing
critical temperature of superconducting transition Tcnear
37 K (Fig. 3b).
The mentioned confirms the important role of temper-
ature in formation of superconductive MgB2phase in the
whole volume of the sample and corresponds with literature
data, where only after sintering processes above 900 Cthe
formation of MgB2phase with Tc=40 K there took place.
The difference of Tcbetween the HEC and sintered MgB2
composites may be explained with a rest of nonreacted
Mg and B phases or existing of some oxides in precursors
(Fig. 3a).
The mentioned could be checked by increasing HEC tem-
perature or application of further sintering processes. The
careful selection of initial Mg and B phases is important
too, and in case of consolidation, Mg-B precursors with the
abovementioned corrections, the chance to increase Tcin the
HEC samples essentially increases.
In Fig. 4, the views of MgB2billets in steel jackets
after the previous densification (Fig. 4a) and after the HEC
procedure (Fig. 4b) are shown.
In further experiments, the application of pure Mg and
crystalline and amorphous B powder blend prevented the
formation of MgO in HEC billets and increased Tcof the
obtained MgB2composites up to 38.5 K (Fig. 5) in case of
pure amorphous boron powder without any post-sintering of
obtained samples.
For these samples, traces of oxidation (light places) on
microstructures were not observed (Fig. 6).
The experiments for HEC of precursors were performed
under and above the melting point of Mg phase. The con-
solidation was carried out at 500, 700, 950, and 1000 C
temperatures with the loading intensity 10 GPa.
It was experimentally established that the comparatively
low-temperature consolidations at 500 and 700 Cgiveno
results, and the obtained compacts have no superconducting
properties.
The application of higher temperatures and consolidation
at 1000 C provides formation of MgB2composition in the
whole volume of HEC billets with maximal value Tc=38.5
K without any further sintering procedure and corresponds
to literature with Tc=40 K.
In case of changed stoichiometry between the Mg
and B and HEC of MgB1.8composites at same 1000
C temperature leads to reducing the Tcdown to 35 K
(Fig. 7).
Fig. 6 Microstructures of the
HEC MgB2composites HEC at
1000 C and loading intensity
10 GPa from pure Mg and B
powder blends
Author's personal copy
J Supercond Nov Magn
Fig. 7 Magnetic moment temperature dependences in zero-field-
cooled (ZFC) and field-cooled (FC) modes at changed stoichiometry
between Mg and B phases
The difference of Tcbetween the HEC and sintered
MgB2compositions may be explained with rest nonreacted
Mg and B phases or existing some oxides in precursors.
3 Conclusion
The liquid-phase HEC of Mg-B precursors above 900 C
provides formation of the MgB2phase in the whole volume
of billets with maximal Tc=38.5 K.
The type of applied B powder has influence on the final
result of superconductive characteristics of MgB2and in
the case of amorphous B precursors better results are fixed
(38.5 K against 37.5) than in the case of crystalline B
powder.
The purity of precursors is an important factor, and exist-
ing of oxygen in the form of oxidized phases in precursors
leads to reduced Tcand uniformity of the HEC billets.
The hot shock wave consolidation procedure increases
strongly the solid-state reaction rate similar to the
photostimulation, but in difference to it allows one to pro-
duce bulk samples of different geometries that are important
for practical applications.
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Author's personal copy
... The novelty of the proposed nonconventional approach relies on the fact that the consolidation of the coarse (under 10-15 µ) Mg-2B blend powders was performed in two stages [9]. The explosive pre-densification of the powders was made at room temperatures. ...
... The heating billet is fixed in the furnace by an opening and closing mechanism (6). After reaching the necessary temperature the opening (6) sheet opens the furnace and billet moves through the feeding cylindrical system (9)(10)(11) to the explosive charge set-up (17). After receiving the signal that the billet passed through the feeding system and is located in final position (13), the detonation takes place and explosive compression of heated billets occurs. ...
... As reported in Refs. [9,12,13], the application of low temperatures up to 900°C and HSWC of Mg-2B precursors in steel containers did not give results. In spite of the high density and uniform distribution of phases, they did not obtain superconductive characteristics. ...
... The novelty of the proposed nonconventional approach relies on the fact that the consolidation of the samples from coarse (under 10-15 µ) Mg-2B blend powders was performed in two stages [9]. The explosive pre-densification of the powders was made at room temperatures. ...
... The heating billet is fixed in the furnace by an opening and closing mechanism (6). After reaching the necessary temperature the opening (6) sheet opens the furnace and the billet moves through the feeding system (9)(10)(11) to the explosive charge set-up (17). After receiving the signal that the billet passed through the feeding system and is located in final position (13), the detonation takes place and explosive compression of heated billets occurs. ...
... In order to evaluate the superconductive characteristics of obtained billets the magnetic moment temperature dependence in zero-field-cooled (ZFC) and field-cooled (FC) modes depending on experimental conditions and type of boron precursors were investigated. As reported in [9,12] the application of low temperatures up to 900 0 C and HEC of Mg-2B precursors in steel containers did not give results. In spite of high density and uniform distribution of phases they did not obtain superconductive characteristics. ...
Article
Full-text available
The original hot shock wave assisted consolidation method combining high temperature was applied with the two-stage explosive process without any further sintering to produce superconducting materials with high density and integrity. The consolidation of MgB2 billets was performed at temperatures above the Mg melting point and up to 1000oC in partially liquid condition of Mg-2B blend powders. The influence of the type of boron (B) isotope in the composition on critical temperature and superconductive properties was evaluated. An example of a hybrid Cu-MgB2–Cu superconducting tube is demonstrated and conclusions are discussed.
... The [6] paper presents first results of investigation of properties of superconducting MgB2 samples, obtained by hot explosive compaction (HEC) method. By this method, similar effect for increasing the speed of solid-state reaction as in case of using the photostimulated solid-state synthesis was obtained. ...
... .a-Traces of oxidation are observed on the microstructures (light places). b-Magnetic moment temperature dependence measurements in zero-field-cooled (ZFC) and field-cooled (FC) modes, showing the superconducting transition at temperature near 37 K[6]. ...
... Temperature dependences of the zero-field cooled (ZFC) and field-cooled (FC) magnetic moment for HEC MgB2 composites at 1000 •C with intensity of loading 10 GPa in magnetic field 20 Oe For these samples, traces of oxidation (light places) on microstructures were not observed(Fig. 5.)Microstructures of the HEC MgB2 composites HEC at 1000•C and loading intensity 10 GPa from pure Mg and B powder blends[6] ...
... The [6] paper presents first results of investigation of properties of superconducting MgB2 samples, obtained by hot explosive compaction (HEC) method. By this method, similar effect for increasing the speed of solid-state reaction as in case of using the photostimulated solid-state synthesis was obtained. ...
... .a-Traces of oxidation are observed on the microstructures (light places). b-Magnetic moment temperature dependence measurements in zero-field-cooled (ZFC) and field-cooled (FC) modes, showing the superconducting transition at temperature near 37 K[6]. ...
... Temperature dependences of the zero-field cooled (ZFC) and field-cooled (FC) magnetic moment for HEC MgB2 composites at 1000 •C with intensity of loading 10 GPa in magnetic field 20 Oe For these samples, traces of oxidation (light places) on microstructures were not observed(Fig. 5.)Microstructures of the HEC MgB2 composites HEC at 1000•C and loading intensity 10 GPa from pure Mg and B powder blends[6] ...
... The application of shock wave pressure proved to be an effective method to generate such superconducting interfaces [6]. The HSWC technology was recently successfully applied for the fast production of superconducting MgB 2 samples avoiding long-time solid state reaction procedures [7]. We present further the experimental results of study of the HTSC samples of Bi-Pb-Sr-Ca-Cu initial density and for activation of the surface of mixture particles. ...
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... Magnesium diboride can be synthesized in a variety of forms [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In the powder-in-tube (PIT) process [21], boron and magnesium powders are mixed and poured into a metal tube which is drawn into a wire and subsequently heated to kick off a high-temperature reaction between B and Mg. ...
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Bulk MgB2 superconductor was synthesized from elemental Mg–B blends employing Reactive Forging (RF)—thermal explosion mode of Self-propagating High-temperature Synthesis (SHS)—under a moderate pressure of 200 MPa. RF of the stoichiometric Mg–2B blend conducted at 800 °C yielded near-single-phase albeit porous (92% TD) MgB2, whereas RF at 1000 °C produced a fully dense material containing significant amounts of MgO and MgB4. The addition of 20–30 wt.% Mg to the starting blend improved material's consolidation behavior at 800 °C, as well as hindered the formation of MgB4 at 1000 °C. For all the compositions and RF conditions, the combustion temperature, Tcomb of approximately 1200 °C was measured. Plastic deformation at Tcomb of the ductile MgO phase and/or residual Mg resulted in full density consolidation of the synthesized material. In all the specimens, a superconducting transition was observed at 39 K regardless of their porosity and the amount of second phases. Above 39 K, the electrical resistivity of dense MgB2 specimens with residual metallic magnesium was 30 times lower than that of the 92% dense near-single-phase MgB2.
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We have fabricated a series of ex situ copper sheathed powder-in-tube MgB2 wires with 20% by volume Ag, Pb, In, and Ga metal added to the MgB2 powder. We find the transport critical current of these wires increases significantly with the addition of specific metals to the core filament. In particular, the critical current density (JC) of the MgB2/Ga(20%) wire is in excess of 5 × 104 A/cm2 at 10 K in self-field, nearly 50 times that of the MgB2/Ag(20%) wire. The temperature dependent JC of all wires is well described as an ensemble of clean S/N/S junctions in which the relevant parameters are the average thickness of the N layer, the critical temperature of the S layer, and a scaling term related to JC at zero temperature. Eliminating the differences in the filament microstructure as the primary cause of the enhanced JC, we suggest that JC is determined by the magnitude of the proximity effect induced superconductivity in the normal metal layer, which is known to be proportional to the electron–electron interaction in N. We present one-dimensional material specific calculations that support this, and zero-field cooled DC magnetic susceptibility data that confirm an increased number of well-connected superconducting grains exist in the composite wires that contain metal additions with large electron–electron interactions and long electron mean free paths.
Liquid-phase shock-assisted consolidation of superconducting MgB2 composites
  • A Peikrishvili
  • G Mamniashvili
  • E Chagelishvili
  • B Godibadze
  • M Tsiklauri
  • A Dgebuadze
  • V Peikrishvili
Peikrishvili, A., Mamniashvili, G., Chagelishvili, E., Godibadze, B., Tsiklauri, M., Dgebuadze, A., Peikrishvili, V.: Liquid-phase shock-assisted consolidation of superconducting MgB 2 composites. In: XII International Symposium on Explosive Production of New Materials: Science, Technology, Business, and Innovations (EPNM-2014), pp. 25-30, Cracow, Poland (2014)