Chemomagnetic fields produced by solid combustion reactions

Article abstract of DOI:10.1063/1.124632

We report here the observation of chemomagnetism, generation of a magnetic field by rapid high-temperature solid reactions producing various oxides. The low-level transient magnetic fields were measured with a high-T_c superconducting quantum interference device magnetometer during the synthesis of both nonferromagnetic and ferromagnetic (ferrite) compounds. The magnetic field was most likely produced by chemoionization processes generated by the moving high-temperature reaction zone. The permanent magnetic field formed by the synthesis of ferromagnetic materials depended on the difference between the combustion temperature and the Curie temperature of the product.

Full text of DOI:10.1063/1.124632

Chemomagnetic fields produced by solid combustion reactions
M. D. Nersesyan, J. R. Claycomb, Q. Ming, J. H. Miller Jr. , J. T. Richardson, and Dan Luss
Citation: Applied Physics Letters 75, 1170 (1999); doi: 10.1063/1.124632
View online: http://dx.doi.org/10.1063/1.124632
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APPLIED PHYSICS LETTERS
VOLUME 75, NUMBER 8
23 AUGUST 1999
Chemomagnetic fields produced by solid combustion reactions
M. D. Nersesyana)
Department of Chemical Engineering, University of Houston, Houston, Texas 77204
J. R. Claycomb
Department of Physics and Texas Center for Superconductivity, University of Houston,
Houston, Texas 77204
Q. Ming
Department of Chemical Engineering, University of Houston, Houston, Texas 77204
J. H. Miller, Jr.
Department of Physics and Texas Center for Superconductivity, University of Houston,
Houston, Texas 77204
J. T. Richardson and Dan Lussb)
Department of Chemical Engineering, University of Houston, Houston, Texas 77204
͑Received 15 March 1999; accepted for publication 29 June 1999͒
We report here the observation of chemomagnetism, generation of a magnetic field by rapid
high-temperature solid reactions producing various oxides. The low-level transient magnetic fields
were measured with a high-Tc superconducting quantum interference device magnetometer during
the synthesis of both nonferromagnetic and ferromagnetic ͑ferrite͒ compounds. The magnetic field
was most likely produced by chemoionization processes generated by the moving high-temperature
reaction zone. The permanent magnetic field formed by the synthesis of ferromagnetic materials
depended on the difference between the combustion temperature and the Curie temperature of the
product. © 1999 American Institute of Physics. ͓S0003-6951͑99͒03034-X͔
During solid flame combustion a high-temperature front
propagates through a solid powder mixture converting it into
products.1,2 We studied the formation of magnetic fields dur-
ing high-temperature synthesis of two types of reacting solid
mixtures. Group 1 was comprised of nonferromagnetic solid
reactants yielding nonmagnetic oxides (BaTiO3, SrTiO3,
BaCrO3 /BaCrO4, and TiO2). Group 2 consisted of reactants
whose ferromagnetic products contained either iron or iron
oxides (Fe/Al2O3, NaFeO2, BaFe12O19, and SrFe12O19).
The experimental setup is shown schematically in Fig. 1.
A quartz tube ͑1 cm i.d., 6.5 cm long͒ with a mixture of
precursor chemicals ͑length between 1.0 and 6.5 cm͒ ͑a͒ is
placed into a thermally isolated enclosure ͑b͒ to protect the
high-Tc superconducting quantum interference device
͑SQUID͒. The low-level transient magnetic fields are mea-
sured by a high-Tc SQUID ͑Refs. 3 and 4͒ magnetometer
͑d͒, housed in a fiberglass G-10 liquid-nitrogen dewar ͑e͒
positioned about 1.0 cm above the sample. Liquid nitrogen
maintains the SQUID at 77 K. The sample is ignited with a
wooden match ͑c͒ through a hole in the heat shield. The
SQUID signal is transmitted through a cryogenic cable ͑f͒ to
outside electronics. High-permeability magnitude shielding
͑g͒ eliminates background noise. In some measurements the
SQUID signal passes a 5 Hz low-pass filter to decrease am-
bient noise. The combustion temperature and velocity are
determined by thermocouples placed at two positions along
the sample.
tants generated a weak ͑order of nT͒, rapidly oscillating mag-
netic field ͑Fig. 2͒. Experimental difficulties prevent simul-
taneous recording, and hence, comparison of the temperature
and magnetic signals. Table I reports the relation between
the combustion velocities ͑in a separate experiment͒ and
magnetic signals. The magnetic signal duration for nonferro-
magnetic materials were taken as the time between the de-
parture of the signal from its original ‘‘0’’ level until it re-
The temperature front during synthesis of group 1 reac-
a͒
Permanent address: Institute of Structural Macrokinetics and Materials Sci-
ence, Russian Academy of Sciences.
b͒
Electronic mail: Dluss@uh.edu
FIG. 1. Experimental setup for chemomagnetic measurements.
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0003-6951/99/75(8)/1170/3/$15.00 1170 © 1999 American Institute of Physics
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Appl. Phys. Lett., Vol. 75, No. 8, 23 August 1999
Nersesyan et al.
1171
FIG. 3. Magnetic signals of the reaction Fe2O3ϩ2Al˜2FeϩAl2O3.
rites, and chromites.7,8 The peroxide’s ͑or perchlorite’s͒ de-
composition in the preheating ͑pre-front͒ zone7,8 may
generate short-lived atomic and anionic oxygen and peroxide
ions.9,10 Ions also form by fuel oxidation ͑Ti, Si, Al, Fe, or
Cr3ϩ, to Cr6ϩ in reaction between Cr2O3 and BaO2) in the
combustion zone and by reactions among various intermedi-
ates in the postcombustion zone. The observed chemomag-
netic fields are, most likely, generated by the intense
chemoionization processes11 during the combustion. Tran-
sient local excesses of negatively and positively charged ions
͑for example, in the prefront and front zones͒ and their rela-
tive motions ͑caused by different diffusivities͒ may contrib-
ute to the oscillatory behavior of the magnetic field. In addi-
tion, velocity fluctuations of the moving reaction front may
generate oscillations of the magnetic field.
The magnitude of the transient magnetic field produced
during the combustion of the second groups of reactants was
similar to that created during the synthesis of the nonferrite
products. A major difference is that the transient magnetic
field formed during SHS of ferromagnetic ͑ferrite͒ materials
may lead to a permanent magnetic field. For example, SHS
of SrFe12O19 created a 2000 nT field. The possible occur-
rence of such an effect was mentioned in Ref. 12. The am-
plitude of the magnetic signal formed by the termite reaction:
FIG.
2.
Magnetic
signals
of
the
reactions:
͑a͒
SrO2ϩ0.4Tiϩ0.6TiO2˜SrTiO3 and ͑b͒ Tiϩ5.5TiO2ϩ0.5NaClO4˜TiO2
ϩ0.5NaCl.
turns ͑after combustion͒ to its original level. For
ferromagnetic materials, the duration was taken as the time
between the initial increase in field magnitude until it stabi-
lized to its final, constant value. For highly exothermic reac-
tions ͑formation of either BaTiO3, SrTiO3, SrSiO3 with cal-
culated adiabatic temperature exceeding 3000 °C͒, the fast
moving front generated a relatively large magnetic field
͑with a large peak͒, followed by a small amplitude, postcom-
bustion, decaying oscillatory magnetic field ͓Fig. 2͑a͔͒. This
magnetic signal usually persisted after the high-temperature
front exited the sample ͑Table I͒, indicating that postcombus-
tion processes may generate a magnetic field. For mildly
exothermic reactions ͑such as a highly diluted Ti͒ the mag-
netic signal included many high-frequency oscillations ͓Fig.
2͑b͔͒. The corresponding duration of the magnetic signal is
close to that of the front movement in the sample. A mag-
netic signal was formed during the oxidation of Ti by
NaClO4 only while the temperature front was within the
sample. Since neither the reactants nor products of the group
1 mixtures were ferromagnetic, the magnetic field disap-
peared after completion of the combustion and postcombus-
tion processes.
Fe2O3ϩ2Al˜2FeϩAl2O3,
͑1͒
was twice that of the permanent magnetic field ͑2.3 nT͒ gen-
erated by the product ͑Fig. 3͒. The oscillations lasted for
about 1.3 s, roughly equal to the sojourn of the temperature
front in the sample, as no postcombustion processes occurred
in this case. The magnetic signals observed following the
synthesis of the ferromagnetic materials were strongly af-
fected by the difference between the combustion and product
Curie temperatures. When the combustion temperature
greatly exceeded the Curie temperature, the magnetic field
decayed after the combustion wave exited the sample. After
Previous studies5,6 found that solid combustion produces
a time-varying electric field in and around the combustion
front. Multiple reactions and ionization processes occur dur-
ing the formation of complex oxides, such as titanates, fer-
TABLE I. Reactions schemas, maximum oscillation magnitude of magnetic field (BЌ), magnetic signal dura-
tion (t), front propagating duration (tf), combustion temperature (T), and velocity ͑U͒.
BЌ
t
T
U
tf
Reaction schemas
͑nT͒
͑s͒
͑s͒
͑°C͒
͑mm/s͒
BaO2ϩ0.4Tiϩ0.6TiO2˜BaTiO3
SrO2ϩ0.4Tiϩ0.6TiO2˜SrTiO3
6.5
2.7
1.6
0.8
0.7
1.4
4.3
8.8
6.5
9.5
0.7
1.3
1.5
6.6
9.5
3200a
3200a
3100a
755
93.3
51.0
43.3
1.8
SrO2ϩ0.4Siϩ0.6SiO2˜SrSiO3
BaO2ϩ0.5Cr2O3˜BaCrO4 /BaCrO3
Tiϩ5.5TiO2ϩ0.5NaClO4˜TiO2ϩ0.5NaCl
1340
3.7
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aCalculated value.
155.33.16.124 On: Tue, 25 Nov 2014 06:37:07

1172
Appl. Phys. Lett., Vol. 75, No. 8, 23 August 1999
Nersesyan et al.
generated a combustion temperature of 560 °C, which is be-
low the product Curie temperature of 600 °C. The magnetic
field in this case monotonically increased to its final value
͓Fig. 4͑b͔͒. Qualitatively similar magnetic signals were ob-
served during the synthesis of the hard ferrites BaFe12O19
and SrFe12O19.
One should not attempt at correlate the magnetic field
magnitudes with the combustion temperatures and/or veloci-
ties of different systems as other factors may affect it, such
as the specific reaction mechanisms, solid mixture composi-
tions, etc. A meaningful comparison must be carried out for
the same system, similar to that done for sodium ferrite. We
are conducting such a study.
This work was supported by grants from the NSF to the
Materials Research Science and Engineering Center at the
University of Houston, the State of Texas to TSCUH and the
Texas Higher Education Coordinating Board Advanced
Technology Program ͑ATP͒, and a Robert A. Welch Foun-
dation grant ͑E-1221͒.
FIG. 4. Magnetic signals of the reactions: ͑a͒ 0.5Na2O2ϩFe˜4NaFeO2 and
͑b͒ 2Na2O2ϩFeϩ1.5Fe2O3˜4NaFeO2 .
the sample cooled below the Curie temperature, spontaneous
magnetization of the product generated a permanent mag-
netic field, as illustrated in Fig. 4͑a͒ for the reaction
1 A. G. Merzhanov, in Combustion and Plasma Synthesis of High-
Temperature Materials, edited by Z. A. Munir and J. B. Holt ͑VCH, New
York, 1990͒, pp. 1–53.
2 Z. A. Munir and U. Anselmi-Tamburini, Mater. Sci. Rep. 3, 277 ͑1989͒.
3
Na2O2ϩ2Fe˜2NaFeO2.
͑2͒
IMAG system by Conductus, San Diego, CA.
4 D. Koelle, A. H. Miklich, F. Ludwig, E. Daulster, D. T. Nemeth, and J.
Clarke, Appl. Phys. Lett. 63, 2271 ͑1993͒.
The corresponding combustion and product Curie tempera-
tures were 1210 and 600 °C, respectively.13 The change in
the sign of the measured magnetic field from positive to
negative observed in Fig. 4 is not clear at present. A defini-
tive explanation will require more extensive experimental
and theoretical modeling studies. A plausible explanation is
that the exterior and interior of the sample cool to the Curie
temperature at different times and the direction of spontane-
ous magnetization of these regions may not necessarily be
the same. The qualitative features of the magnetic signal
were rather different when the combustion temperature was
less than the product Curie temperature. For example, when
the reactants in reaction ͑2͒ were diluted with Fe2O3, the
reaction
5 V. A. Kudryashov, A. S. Mukasyan, and I. A. Filomonov, J. Mater. Synth.
Process. 4, 353 ͑1996͒.
6 Y. G. Morozov, M. V. Kuznetsov, M. D. Nersesyan, and A. G. Merzha-
nov, Dokl. Akad. Nauk SSSR 351, 780 ͑1997͒.
7 A. G. Merzhanov and M. D. Nersesyan, J. Vses. Chem. O-va im. Men-
deleeva, D. M. 35, 700 ͑1990͒ ͑in Russian͒.
8 Q. Ming, M. D. Nersesyan, K. Ross, J. T. Richardson, and D. Luss, Com-
bust. Sci. Technol. 128, 279 ͑1997͒.
9 I. I. Volnov, The Peroxides of Alkaline and Earth-Alkaline Metals ͑Nauka,
Moscow, 1988͒, p. 156.
10 Handbook of Inorganic Chemistry, edited by R. A. Lidin ͑Begell House,
New York, 1995͒.
11 J. Lawton and P. Weinberg, Electrical Aspects of Combustion ͑Oxford
University Press, New York, 1969͒.
12 P. B. Avakyan, M. D. Nersesyan, and A. G. Merzhanov, Am. Ceram. Soc.
Bull. 75, 50 ͑1996͒.
13 Concise Encyclopedia of Magnetic and Superconducting Materials, edited
by J. E. Evtts ͑Pergamon, New York, 1992͒, p. 203.
Na2O2ϩ0.5Feϩ0.75Fe2O3˜2NaFeO2,
͑3͒
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