Zone refining of zirconium in an electric field
The physical grounds and an experimental study of the efficiency of applying the zone recrystallization method in an electric field for zirconium refining from metal and gas-forming impurities are presented. The changes in the elemental composition, microhardness, and structure of the obtained ingot...
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| Date: | 2020 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2020
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| Cite this: | Zone refining of zirconium in an electric field / O.E. Kozhevnikov, M.M. Pylypenko, Yu.S. Stadnik, R.V. Azhazha // Problems of Atomic Science and Technology. — 2020. — № 1. — С. 27-34. — Бібліогр.: 15 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860268621927809024 |
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| author | Kozhevnikov, O.E. Pylypenko, M.M. Stadnik, Yu.S. Azhazha, R.V. |
| author_facet | Kozhevnikov, O.E. Pylypenko, M.M. Stadnik, Yu.S. Azhazha, R.V. |
| citation_txt | Zone refining of zirconium in an electric field / O.E. Kozhevnikov, M.M. Pylypenko, Yu.S. Stadnik, R.V. Azhazha // Problems of Atomic Science and Technology. — 2020. — № 1. — С. 27-34. — Бібліогр.: 15 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | The physical grounds and an experimental study of the efficiency of applying the zone recrystallization method in an electric field for zirconium refining from metal and gas-forming impurities are presented. The changes in the elemental composition, microhardness, and structure of the obtained ingots was investigated. It is shown that the application of the method can significantly reduce the content of interstitial impurities. Zirconium samples with a purity of 99.91 wt.% were obtained.
Представлено фізичне обґрунтування та експериментальне дослідження ефективності застосування методу зонної перекристалізації в електричному полі для рафінування цирконію від металевих та газоутворюючих домішок. Досліджено зміни елементного складу, мікротвердості та структури одержуваних злитків. Показано, що застосування методу дозволяє значно знизити вміст домішок впровадження і отримати зразки цирконію чистотою 99,91 мас.%.
Представлены физическое обоснование и экспериментальное исследование эффективности применения метода зонной перекристаллизации в электрическом поле для рафинирования циркония от металлических и газообразующих примесей. Исследованы изменения элементного состава, микротвердости и структуры получаемых слитков. Показано, что применение метода позволяет значительно снизить содержание примесей внедрения и получить образцы циркония чистотой 99,91 мас.%.
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| first_indexed | 2025-12-07T19:03:35Z |
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ISSN 1562-6016. PASТ. 2020. №1(125), p. 27-34.
UDC 669.296
ZONE REFINING OF ZIRCONIUM IN AN ELECTRIC FIELD
O.E. Kozhevnikov, M.M. Pylypenko, Yu.S. Stadnik, R.V. Azhazha
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: kozhevnikov@kipt.kharkov.ua
The physical grounds and an experimental study of the efficiency of applying the zone recrystallization method
in an electric field for zirconium refining from metal and gas-forming impurities are presented. The changes in the
elemental composition, microhardness, and structure of the obtained ingots was investigated. It is shown that the
application of the method can significantly reduce the content of interstitial impurities. Zirconium samples with a
purity of 99.91 wt.% were obtained.
INTRODUCTION
In the next 50 years, the thermal neutron reactors
will continue to occupy a dominant position among
nuclear power units. The base material for the active
zones of such reactors are zirconium-based alloys,
which have an optimal combination of nuclear,
corrosion, mechanical, thermal and other
physicochemical characteristics [1, 2].
The perfectioning of zirconium materials makes
possible to increase the efficiency of existing power
units, increase the fuel burnup depth, ensure operational
reliability and safety of nuclear installations, and extend
their design life.
The impurities in zirconium and its alloys, such as
O, C, Si, P, Mg, K, Ca, Cl, F, Ni, H, etc., even in small
quantities, have a negative effect on the structure,
physical and mechanical characteristics. This can lead to
a change in the mechanical and corrosion properties of
materials, to a change in the deformation and heat
treatment modes.
The development of new alloys and improvement of
the characteristics of existing zirconium alloys are
impossible without an in-depth study of the processes
for producing high purity zirconium. In this connection,
it is necessary to study the patterns of behavior of
metallic impurities and interstitial impurities during the
process of obtaining zirconium by physical methods, as
well as to study the effect of impurity composition on
the characteristics of the material.
The process of crystallization from melt is one of the
basic ways of refining metals and semiconductor
materials. Typically, they are used on the final stage for
purification from low concentrations of impurities.
During the zone melting (ZM) of refractory metals in a
vacuum it is takes place a refining as a result of the
impurity separation between the melt and the solid
phase during directional crystallization, as well as due
to the evaporation of volatile impurities.
An electrotransport is used to deep refining of
metals in the solid and liquid states. The method is
based on the ability of the solution components to the
directional displacement under an applied electric direct
current.
The aim of this work was the physical grounds and
experimental study of the impurity behavior in during
the zirconium refining process by zone recrystallization
method in an electric field (ZMEF), the obtaining high
purity zirconium specimens and studying its structure
and microhardness.
MATERIALS AND RESEARCH METHODS
The principle of zone refining is based on the
different solubility of impurities in the liquid and solid
phases of the base material. An important characteristic
in the process description is the impurity distribution
coefficient is k, which is the ratio of the impurity
concentration in the solid phase CS to the concentration
in the melt CL [3]:
k = CS / CL. (1)
It is distinguish between the concepts of equilibrium
distribution coefficient k0 and effective distribution
coefficient ke. The equilibrium coefficient k0 is usually
determined from the “base-impurity” state diagrams or
by the ratio of the maximum solubility of an impurity to
its concentration at the point of invariant transformation.
However, with such estimation methods, k0 values can
be calculated only in the case of a significant
concentration of impurities in the base material.
When calculating the equilibrium distribution
coefficient k0 in the case of low impurity concentrations
it is convenient to use the theoretical methods of
calculations based on the thermodynamic constants of
the equation of ideal solutions. According to this
concept it be can use the Schroeder-Le Chatelier
equation:
.
11
ln
GbS TTR
H
C
CL (2)
Then
L
S
C
C
e and ./1
0
ek
In the formula (2) CL and CS are the concentration
values of the impurity in the liquid and solid phases of
the main component, ΔH is the molar heat of fusion of
the impurity (J/mol), R is the universal gas constant
(R=8.314 J/(mol∙K)), Тb is the melting temperature of
the basic substance, ТG is the estimated value of the
melting temperature of the base-impurity alloy, which is
selected from the state diagram.
For phase diagrams characterized by a continuous
series of solid solutions, peritectic-type diagrams
throughout the concentration range, as well as for
impurities whose diagrams with the base metal are
unknown, ТG is chosen equal to the melting temperature
of the impurity element. In the case of phase diagrams
with a number of eutectic and peritectic transformations
value ТG is selected in order to meet the minimum
transformation temperature of eutectic or peritectic type
[4].
When conducting zone melting process, moving
solidification front pushes dissolved impurity faster than
it can evenly distributed in the melt. Before
crystallization front occurs enriched impurity region
called the diffusion layer. The diffusion layer thickness
δ is dependent on the impurity diffusion capacity, the
melt viscosity, the nature of the fluid motion, and the
crystallization speed and it can be changed depending
on the conditions of the melt mixing.
Therefore, the main characteristic of zone impurity
separation process is the effective distribution
coefficient ke, which can be expressed by the Burton-
Prim-Slichter formula [3]:
,
1
1
1
1
0
d
e v
e
k
k
(3)
where v is the zone speed, δ is the diffusion layer
thickness, and d is the impurity diffusion coefficient in
the melt.
The value of the diffusion coefficient d for most
metals is equal 5·10
-5
cm
2
/s approximately. The depth of
the diffusion layer δ in the case of moderate mixing of
the melt in the liquid zone is assumed to be 0.01 cm.
Therefore, δ/d ≈ 200 s/cm. The ratio vδ/d is called the
reduced crystallization rate and is a dimensionless
quantity.
Having determined the k0 values by formula (2), it
becomes possible to calculate the value of the effective
separation coefficient of the impurity ke according to
formula (3).
In the case of the melting of refractory metals in
vacuum it is occurs the refining process by substance
separating during recrystallization and evaporation
process of gas-formative impurities (oxygen, carbon,
nitrogen, hydrogen) as well as from those metallic
impurities which have a high vapor pressure at the
melting temperature of the base material. The pressure
of saturated zirconium vapor at a melting point
Тb = 2125 K is 2.6·10
-3
Pa. The steam tension of a large
number of metals at temperatures above 2000 К reaches
10…10
4
Pa, which leads to their intense evaporation [5].
In work [6] the purification results of iodide
zirconium by crucibleless floating zone method with the
evaporation of metal and gas-forming impurities was
analyzed. It was noted that a good degree of purification
from volatile metal impurities was achieved at high
zone velocities. For this impurities the saturated vapor
pressure p0 at the melting point of zirconium is quite
high (> 1·10
-1
Pa). The melting at a speed of 16 or 8
mm/min allowed to significantly reduce the content of
Al, Ca, Cu, Fe, Mn, Ni, Si, Ti, Cr and other metals.
For purification from refractory metal impurities and
impurities that have a low saturated vapor pressure at
the melting point of zirconium, a multistage zone
recrystallization is required. Multiple passes with low
velocity (4, 2, and 1 mm/min) will reduce their
concentrations.
Theoretical postulates of refining process of
substances under effect of direct electric field were
considered in a number of books and articles [7–9]. An
application of direct electric current to metal sample
leads to moving both the matrix ions and impurity ones
in a certain direction (to anode or cathode). The direct
electric current, which passing through the phase
boundary, changes the value of the effective distribution
coefficient ke. It happens due to the addition to the
diffusion flow of the electrotransport component.
In general, the resultant force F, which acts on the
impurity ion in the base metal substrate, can be
expressed as:
,* EZEnLeZF (4)
where Z is the ion charge; e is the electron
charge; n is the concentration of conduction ions; L is
the mean free pass of electron; σ is the cross-section for
scattering of electrons; E is the electric field intensity;
Z
* is the effective ion charge (Z
*
= Z – |e|nLσ).
The value of Z
* can be determined from the
expression:
,
*
De
UkT
Z (5)
where U is the ion mobility; D is the ion self-diffusion
coefficient; T is the temperature; k is the Boltzmann
constant [10].
Depending on the sign of Z
*
, the resultant force F
can be directed to the cathode (Z
*
> 0), to the anode
(Z
*
<0) or to be equal to zero (Z
*
= 0).
The value of the impurity ion mobility U is
dependent on the properties of system and the
temperature. In general, the relative mobility of ions is
determined by the expression ΔU = (v′1 – v′2)/E, where
v′1 and v′2 are the movement speeds of the impurity ions
and a main component, respectively; E is the electric
field intensity. In the case of dilute solutions the speed
of solvent movement v′2 is actually equal to zero, and
the expression for the impurity ion mobility can be
represented in the form as:
U = v′ / E. (6)
Equation (4) for the effective distribution coefficient
of the impurity in the case of zone melting in an electric
field becomes:
v
vv
e
v
v
k
v
v
De
k
'
1
1
'
1
1
1
'
1
0
'
, (7)
where D is the diffusion coefficient of the impurity ion,
v′ is the velocity of the impurity ion.
The value of the effective coefficient ke under
conditions of applying an electric field is mainly
affected by such processes: 1) displacement of
impurities with k0 < 1 during zone recrystallization; 2)
the influence of the flux arising due to different mobility
of the base ions and impurity ions (the magnitude of the
flux is proportional to v′) [3].
Thus, under the influence of an electric field, the
magnitude of ke can change. This makes it possible to
obtain the following results: 1) the value of ke can be
changed, and thus there is increase of the efficiency of
refining; 2) the value of ke can be made smaller than
unity (even for those cases where k0 > 1), which makes
it possible to refine from impurities during
recrystallization.
It should be noted that when performing calculations
according to formula (7), some effects are not taken into
account, which may occur at the “liquid-solid” interface
and may affect the magnitude of ke. For example, the
Peltier effect (heat generation or absorption at the phase
boundary) is not considered. In this case an additional
impurity flow occurs, caused by diffusion under a
thermal gradient field, and this may affect the efficiency
of cleaning.
In the work [11], there was a study of the
displacement of interstitial impurities in the low-
temperature and high-temperature solid phases of
zirconium under the influence of a constant electric
current. The alloys with a high content of oxygen,
carbon and nitrogen were prepared by the arc melting
method. The bars in the form of wires were having
dimensions of 6.6 cm in length and 0.26 cm in diameter.
Many hours of annealing was applied at various
temperatures under conditions of transmission of
electric current with these bars. As a result of studying
the impurity composition of the samples, the effective
charge Z
*
, mobility U, displacement velocity v′, and
diffusion coefficient D for carbon, nitrogen and oxygen
ions were calculated. The interstitial impurities were
displaced to the anode during electric transport. It was
allowed to determine the value and sign of the effective
ion charge (Z
*
< 0).
The authors explained the divergence in the
calculated and experimental data on the concentration of
interstitial impurities by the absorption of residual gases
from the chamber atmosphere.
In the studies presented below, the process of
zirconium refining was carried out by the method of
zone recrystallization in an electric field. The
description of the process and the experimental setup
was considered in detail in the article [12].
Zirconium obtained in the course of industrial iodide
refining was used as a starting material for experiments
(with a purity of 99.8 wt.%).
The results of the impurity content in zirconium
were obtained by laser mass spectrometry. The analysis
used an energy analyzer EMAL-2. The limiting
sensitivity of the method of analysis for metallic
impurities was ~ 10
-5
10
-6
at.%.
The use of a LECO TC-600 gas analyzer made it
possible to determine the content of nitrogen and
oxygen in the samples with an accuracy of 5·10
-8
at.%.
The device was calibrated with certified LECO samples.
Visual viewing of thin sections and photographing
of the grain structure was carried out using an MMP-4
microscope.
Microhardness was measured on a PMT-3
microhardness meter at loads of 0.05 and 0.1 kG. The
microhardness numbers were recorded in ten
measurements; the measurement error did not exceed
5 %.
RESULTS AND DISCUSSION
Analysis of the state diagrams of “zirconium-
impurity” binary systems allows to conclude that for the
Zr-O and Zr-O cases, the value of k0 > 1. So, up to the
oxygen content of 10 % and nitrogen 4.4 %, the melting
point of the alloy increases with increasing of impurity
concentration (Fig. 1).
a b c
Fig. 1. The state diagrams for systems Zr-O (a), Zr-N (b), and Zr-С (c)
It is characteristic of the Zr-C diagram that, to a
carbon concentration of 12 %, the melting point of
the alloy decreases, and in this case k0 < 1 [13].
In the samples with whose it was carried out the
refining in the present work, the concentration of
interstitial impurities (oxygen, carbon, nitrogen) was
less than 0.3%. Therefore, in the diagrams, a region
with a low impurity concentration was considered.
The distribution coefficients for metallic impurities
and interstitial impurities in zirconium were calculated
taking into account the thermodynamic constants of the
ideal solution equation. By the formula (2), the values
of the equilibrium coefficient k0 are calculated. To
calculate the value of the effective coefficient kе,
formula (3) was used.
The calculations took into account the value of the
melting point of zirconium Тb = 2125 K, Тm is element
melting point, ТG is estimated value of the melting
temperature of the base-impurity alloy, ΔH is the molar
heat of fusion of the impurity, the ratio δ/d ≈ 200 s/cm,
and the melting speed v = 0.0033 cm/s.
The results are presented in Table 1, in which k0
values were taken from the reference book [14] for
comparison.
Table 1
The results of calculating the equilibrium and effective coefficients for impurities in zirconium
Element Тm, К ТG, К
ΔH,
kJ/mol
k0 k0 [14] k е
Oxygen – 2243 96 1.33 > 1 1.15
Carbon – 2093 110 0.91 – 0.95
Nitrogen – 2153 83,736 1.06 > 1 1.03
Hafnium 2500 2500 25.1 1.23 > 1 1.1
Aluminum 933.5 933.5 10.75 0.46 < 0.42 0.62
Iron 1812 1201 13.8 0.54 0.27 0.70
Calcium 1112 1112 9.2 0.62 – 0.76
Silicon 1687 1643 50.6 0.43 < 1 0.59
Molybdenum 2890 1826 28 0.77 0.39 0.87
Nickel 1728 1233 17.61 0.49 < 1 0.65
Titanium 1943 1808 18.8 0.83 < 1 0.90
Chromium 2136 1605 21 0.68 < 1 0.80
Refining of zirconium was carried out by the method
of vacuum electron beam melting in an electric field,
turned on against the zone. With this option of
connecting the field, the ions of interstitial impurities,
characterized by a negative value of Z
*
, were shifted to
the positive pole (anode). Moreover, the movement of
ions coincided with the motion direction of the liquid
zone. The effectiveness of the ZMEF process with this
method of connecting an electric field was previously
confirmed when working with hafnium materials [15].
Using the recommendations of the article [11] (the
values of effective charge Z
*
and of the diffusion
coefficient of the impurity ion D) the mobility of the
impurity ion U were calculated using formula (5).
According to formula (6) it was possible to calculate the
movement velocity of the impurity ion v′. The
calculation of the effective coefficient k′e for interstitial
impurities in the case of ZMEF was carried out
according to formula (7).
In the estimations it was taken into account that in
the liquid phase of the main material the values of the
mobility of the impurity ion U, diffusion coefficient D,
effective charge Z
*
may differ from the values
characteristic of the low-temperature α- and high-
temperature β-phases of zirconium. In particular, the
values of U and D can increase significantly. The
estimates of the values of these parameters for the liquid
phase of zirconium have not been carried out
previously. Therefore, the calculations performed in the
work can only give an indicative estimates of the values.
In the calculation the characteristic parameter values
for the experiment were used: the electric field intensity
Е = 0.013 V/cm, melting speed v = 0.066 cm/s. The
calculation results are presented in Table 2.
Table 2
The calculation results of the ZMEF parameters for interstitial impurities in zirconium
Impurity Z
* U, 10
-5
,
cm
2
/(V·s)
D, 10
-6
,
cm
2
/s
| v′ |, 10
-7
,
cm/s
k е
at ZM
k′e k′e
Oxygen - 1 1.8 3.3 2.34 1.15 1.01 0.99
Carbon - 0.2 0.9 8.25 1.17 0.95 0.96 0.95
Nitrogen - 0.7 1.2 3.14 1.56 1.03 1.01 0.99
The calculations k´е for ZMEF show that for gas-
forming impurities with a negative value of the effective
charge Z
*
, refining will proceed more efficiently when
an electric field is applied against the direction of the
zone melting course. The values of the effective
coefficient for oxygen and nitrogen in this case can
change and become less than unity. This shows the
possibility of refining from these impurities during
electric transport.
In preparation for experimental work, preforms were
previously cut from a bar of iodide zirconium with a
diameter of 20 mm. The bar was cut lengthwise into
four segments with a length of 150 to 300 mm using
electric spark cutting.
The preparation of refined samples at the
crucibleless zone melting facility was carried out under
various conditions. Before the start of the process or
during the experiment, it was possible to change:
1) the vacuum conditions from 1∙10
-1
to 1∙10
-4
Pa,
2) the melting speed from 16 to 1 mm/min,
3) the number of passes from one to five,
4) the value of the potential difference between the
cathode of the electron beam gun and the ingot from 4
to 10 kV,
5) the direction of the electric field along or against
the course of zone melting,
6) the value of the constant electric current passing
through the sample is from 20 to 100 A.
The stages of high-temperature heating (from half an
hour to 2 hours) and of zone melting of the workpiece at
a speed of 16 mm/min made it possible to obtain a
cylindrical ingot.
The meltings with high (16 or 8 mm/min) and low
speed (4, 2, and 1 mm/min) reduced the content of both
metallic impurities and interstitial impurities in
zirconium significantly [6].
The complex methodology of the refining process
included the application of thermal cycling (heating and
cooling of the ingot in the polymorphic temperature
range α-β transformations) at the final stage. This
procedure contributed to the increase in grain size.
Zone melting in an electric field was carried out with
zirconium ingots round in cross section with a zone
velocity of 2 to 8 mm/min.
The refining of Zr during ZMEF occurred as a result
of the simultaneous passage of several physical
processes:
1) evaporation of impurities during zone melting in
vacuum;
2) the displacement of metallic impurities, as well as
oxides and carbides, in the end part of the sample during
recrystallization;
3) the movement of ions of interstitial impurities to
the anode.
Photos of the initial iodide zirconium and the sample
refined by the ZMEF method are presented in Fig. 2.
The ingot was obtained as a result of three passes ZM
and two ZMEF.
a b
Fig. 2. The shapes of the initial iodide zirconium (a) and the metal ingot refined by the ZMEF method (b)
Samples in the form of tablets were cut out from the
middle (cleanest) part of the refined ingot for
conducting elemental composition and metallography
studies (6 mm high and 8 mm in diameter). The results
of the analysis of the content of impurities in the
zirconium samples before and after refining are given in
Table 3. The bottom row of the table shows the
calculation of the efficiency of the zone melting process
with electric transport (in relation to the concentration
of impurities in the initial metal to the concentration in
the refined material).
Table 3
The results of elemental analysis of zirconium samples
Zirconium
The concentration, wt.%
Zr Hf O C N Al Fe Ni Cu Cr Si Ti
Initial 99.80 0.075 0.052 0.02 0.003 2·10
-4
0.008
0.004 9·10
-4
3·10
-3
2·10
-4
5·10
-4
ZM 99.87 0.052 0.026 0.012 0.0015 7·10
-5
7·10
-4
0.0023 2·10
-5
5·10
-5
7·10
-5
3·10
-4
ZMEF 99.91 0.05 0.016 0.01 0.001 4·10
-5
6·10
-4
0.002 2·10
-5
4·10
-5
2·10
-5
2·10
-4
Efficiency
ZMEF
1.5 3.3 2 3 5 11 2 45 75 10 2.5
The results of the analysis of the elemental
composition show an insignificant content in the refined
ingots of a number of metallic impurities that were
removed during the simultaneous passage of the
processes of evaporation, zone recrystallization, and
melting in an electric field. So, the aluminum
concentration was reduced by 5, iron – 11, nickel – 2,
copper – 45, chromium – 75, silicon – 10, titanium – 2.5
times.
Elemental analysis showed a slight decrease in
hafnium concentration (from 0.075 to 0.05 wt.%). The
content of molybdenum and niobium after melting did
not changed and remained at the level of 2·10
-4
and
1·10
-4
wt.% respectively.
The refining of zirconium from gas-forming
impurities occurred at various stages of the experiment.
So, hydrogen left in the form of gaseous molecules of
Н2, Н2О upon preliminary heating and zone melting at a
high speed. Carbon escaped in the form of CO and CO2
molecules. The refining process also occurred due to the
displacement of metal carbides into the end part of the
ingot. Nitrogen evaporated in the form of N2 gas
molecules during high-temperature heating and zone
melting.
A decrease in the oxygen content occurred at the
stages of heating and zone melting as a result of the
formation of gaseous molecules (CO, CO2, Н2О). The
purification from oxygen could also occur due to a
displacement upon recrystallization to the end of the
sample of refractory oxides (for example, ZrO2, HfO2).
In the purest zirconium samples the oxygen
concentration decreased by 3.3, nitrogen – 3, carbon – 2
times. The purity of the samples refined by the ZMEF
method was characterized by a value of 99.91 wt.% by
zirconium content.
a
b
c
Fig. 3. The microstructure of the samples of the initial
iodide zirconium (a), refined by the methods of ZM (b)
and ZMEF (c) materials
Fig. 3 presents photographs of the microstructure of
zirconium iodide, as well as samples cut from ingots
refined by the ZM and ZMEF methods.
Coarse grains elongated along the melting direction
with a length of 12 mm and a cross section of up to
4 mm were observed in the zone-melted material. After
recrystallization, twins were present in the grains. An
insignificant amount of impurities accumulated along
the grain boundaries (see Fig. 3,b).
After ZMEF in microphotographs it was possible to
see the presence of zirconium grains from 2 to 5 mm in
size, the borders are clean. The impurities were
redistributed from the boundaries along the body of the
grains. It can be explained by a consequence of the
influence of electric transport. In the micrograph (see
Fig. 3,c) one can see the output of the primary slip lines
along the prismatic planes { 0110 }.
The microhardness value for the samples of the
initial iodide zirconium varied within
Hμ = 980…1110 MPa. The scatter of values is due to
the multidirectional grain growth during iodide refining.
After zone recrystallization the grain of the material
became cleaner, impurities accumulated along the grain
boundaries. The grains were mainly aligned along the
direction of the zone melting (the deviation of the
normal vector to the base plane from the direction of
melting was from 0 to 15 degrees). The microhardness
value was Hμ = 930…980 MPa.
After melting in an electric field the spread of
microhardness values increased due to the redistribution
of impurities over the grain body
(Hμ = 880…1040 MPa) (Fig. 4).
Fig. 4. The microhardness value for the initial iodide
zirconium and materials after ZM and ZMEF
CONCLUSIONS
The physical substantiation of the refining process of
zirconium from metallic and interstitial impurities by
methods of zone melting and melting in an electric field
is presented. A technique was applied, including
vacuum crucibleless zone melting with electron-beam
heating, thermal cycling in the temperature range of
polymorphic transformation, and melting in an electric
field. It was made possible to obtain zirconium samples
with a purity of 99.91 wt.%. The concentration of
interstitial impurities was reduced significantly (oxygen
in 3.3, nitrogen – 3, carbon –2 times). The change in the
microstructure and microhardness of zirconium after
refining by zone melting and melting in an electric field
is studied.
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Article received 24.10.2019
ЗОННОЕ РАФИНИРОВАНИЕ ЦИРКОНИЯ В ЭЛЕКТРИЧЕСКОМ ПОЛЕ
О.Е. Кожевников, Н.Н. Пилипенко, Ю.С. Стадник, Р.В. Ажажа
Представлены физическое обоснование и экспериментальное исследование эффективности применения
метода зонной перекристаллизации в электрическом поле для рафинирования циркония от металлических и
газообразующих примесей. Исследованы изменения элементного состава, микротвердости и структуры
получаемых слитков. Показано, что применение метода позволяет значительно снизить содержание
примесей внедрения и получить образцы циркония чистотой 99,91 мас.%.
ЗОННЕ РАФІНУВАННЯ ЦИРКОНІЮ В ЕЛЕКТРИЧНОМУ ПОЛІ
О.Є. Кожевніков, М.М. Пилипенко, Ю.С. Стаднік, Р.В. Ажажа
Представлено фізичне обґрунтування та експериментальне дослідження ефективності застосування
методу зонної перекристалізації в електричному полі для рафінування цирконію від металевих та
газоутворюючих домішок. Досліджено зміни елементного складу, мікротвердості та структури одержуваних
злитків. Показано, що застосування методу дозволяє значно знизити вміст домішок впровадження і
отримати зразки цирконію чистотою 99,91 мас.%.
http://link.springer.com/journal/11663
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| id | nasplib_isofts_kiev_ua-123456789-194341 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T19:03:35Z |
| publishDate | 2020 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Kozhevnikov, O.E. Pylypenko, M.M. Stadnik, Yu.S. Azhazha, R.V. 2023-11-22T15:45:51Z 2023-11-22T15:45:51Z 2020 Zone refining of zirconium in an electric field / O.E. Kozhevnikov, M.M. Pylypenko, Yu.S. Stadnik, R.V. Azhazha // Problems of Atomic Science and Technology. — 2020. — № 1. — С. 27-34. — Бібліогр.: 15 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/194341 669.296 The physical grounds and an experimental study of the efficiency of applying the zone recrystallization method in an electric field for zirconium refining from metal and gas-forming impurities are presented. The changes in the elemental composition, microhardness, and structure of the obtained ingots was investigated. It is shown that the application of the method can significantly reduce the content of interstitial impurities. Zirconium samples with a purity of 99.91 wt.% were obtained. Представлено фізичне обґрунтування та експериментальне дослідження ефективності застосування методу зонної перекристалізації в електричному полі для рафінування цирконію від металевих та газоутворюючих домішок. Досліджено зміни елементного складу, мікротвердості та структури одержуваних злитків. Показано, що застосування методу дозволяє значно знизити вміст домішок впровадження і отримати зразки цирконію чистотою 99,91 мас.%. Представлены физическое обоснование и экспериментальное исследование эффективности применения метода зонной перекристаллизации в электрическом поле для рафинирования циркония от металлических и газообразующих примесей. Исследованы изменения элементного состава, микротвердости и структуры получаемых слитков. Показано, что применение метода позволяет значительно снизить содержание примесей внедрения и получить образцы циркония чистотой 99,91 мас.%. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Pure materials and the vacuum technologies Zone refining of zirconium in an electric field Зонне рафінування цирконію в електричному полі Зонное рафинирование циркония в электрическом поле Article published earlier |
| spellingShingle | Zone refining of zirconium in an electric field Kozhevnikov, O.E. Pylypenko, M.M. Stadnik, Yu.S. Azhazha, R.V. Pure materials and the vacuum technologies |
| title | Zone refining of zirconium in an electric field |
| title_alt | Зонне рафінування цирконію в електричному полі Зонное рафинирование циркония в электрическом поле |
| title_full | Zone refining of zirconium in an electric field |
| title_fullStr | Zone refining of zirconium in an electric field |
| title_full_unstemmed | Zone refining of zirconium in an electric field |
| title_short | Zone refining of zirconium in an electric field |
| title_sort | zone refining of zirconium in an electric field |
| topic | Pure materials and the vacuum technologies |
| topic_facet | Pure materials and the vacuum technologies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/194341 |
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