Composite materials based on a ceramic matrix of polycarbosilane and iron-containing nanoparticles

Abstract

Composite materials comprised of a ceramic matrix with metal-containing nanoparticles were prepared by sintering iron (II) oxalate and polycarbosilane. The chemical composition of the material can be controlled by a sintering process. Sintering in inert atmosphere leads to reduction of the sample and metal iron formation (a-Fe, carbide). Formation of iron oxides requires calcination procedure in series (argon and air) for removing by products. The air-sintering materials consist mainly of oxide phases, but also contain metal iron. The prepared samples were characterized by the: SEM, TEM, XRD and EMR techniques and the Mössbauer spectroscopy. It was shown unique behavior that iron containing particles after calcination in air decreased from 5-30 nm to 2–5 nm due to interaction with matrix under air atmosphere.

Full text

Ceramics International 48 (2022) 37410–37422
Available online 13 September 2022
0272-8842/© 2022 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Composite materials based on a ceramic matrix of polycarbosilane and
iron-containing nanoparticles
G. Yu Yurkov
a
,
b
, D.A. Pankratov
c
, Yu.A. Koksharov
d
, Ye.A. Ovtchenkov
d
, A.V. Semenov
a
,
*
,
R.A. Korokhin
a
, G.I. Shcherbakova
e
, L.V. Gorobinskiy
b
, E.A. Burakova
f
, A.V. Korolkov
b
,
D.S. Ryzhenko
b
, V.I. Solodilov
a
a
N.N. Semenov Federal Research Center of Chemical Physics, Russian Academy of Sciences, 119334, Moscow, Russia
b
Bauman Moscow State Technical University, BMSTU, 2-nd Baumanskaya, 5, Moscow, 105005, Russia
c
Faculity of Chemistry, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia
d
Faculity of Physics, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia
e
State Research Institute for Chemistry and Technology of Organoelement Compounds, Moscow, 105005, Russia
f
Tambov State Technical University, Tambov, 392000, Russia
ARTICLE INFO
Keywords:
Chemical synthesis
Nanostructured materials
Metal matrix composite
ABSTRACT
Composite materials comprised of a ceramic matrix with metal-containing nanoparticles were prepared by
sintering iron (II) oxalate and polycarbosilane. The chemical composition of the material can be controlled by a
sintering process. Sintering in inert atmosphere leads to reduction of the sample and metal iron formation (a-Fe,
carbide). Formation of iron oxides requires calcination procedure in series (argon and air) for removing by
products. The air-sintering materials consist mainly of oxide phases, but also contain metal iron. The prepared
samples were characterized by the: SEM, TEM, XRD and EMR techniques and the M¨
ossbauer spectroscopy. It was
shown unique behavior that iron containing particles after calcination in air decreased from 5-30 nm to 2–5 nm
due to interaction with matrix under air atmosphere.
1. Introduction
Materials based on iron oxide are widely used in different applica-
tions. Several recent tendencies for applications on Fe
x
O
y
particles are:
environmental (as an example, removing of dyes from waste-water) [1],
agro chemistry (as a mineral fertilizing of cultivated plants) [2], medical
(boron-neutron capture therapy) [3], catalysis [4], composite materials
with controllable electrodynamic properties [5]. Iron-based complex
oxides or ferrites are the most important class of magnetic materials and
are widely discussed among researchers. The materials have got various
practical applications as magnets with high coercivity and remnant
magnetization [6]. The electrodynamic properties of the materials are
proven to be dependent both on the concentration of ferromagnetic
particles in the composite and their size, as well as on the properties of
the matrix [5]. The polymer composition is used for the creation of
nanosized ceramic which is durable at high temperatures with oxidation
tolerance. Ceramic shave next types: threads, matrix, complex special
barrier coatings, powders. The advantages of the application of polymer
precursors may be presented here: the negligible amount of uncontrolled
impurities, high adhesion on the edge bre-matrix, possibility of the
ceramic modelling of micro and macro structures on the stage of the
ceramic precursor, ability to adjust the physical form of the nal product
without ultra-high temperatures and pressures [7]. Several reports are
used polymer as a matrix: phenol-formaldehyde resin of the novolac
type [5], high- and low pressure polyethylene [8,9]. The iron oxide
nanoparticles can be produced by various techniques: hydrothermal
method [10,11], precipitation [11], ultrasound assisted green synthesis
[12], co-precipitation method [13,14], sonochemical method [15],
microwave-assisted synthesis [16], mechanochemical methods [17,18],
and others [19,20].
Silicon carbide is an important non-oxide ceramic which has diverse
industrial applications due to its outstanding properties, such as very
high hardness and strength, chemical, and thermal stability, high
melting point, oxidation resistance, high erosion resistance, excellent
thermal shock resistance. The material may be produced by pyrolysis
from preceramic polymer, for example, polycarbosilane [21,22]. The
* Corresponding author.
E-mail address: cemen9856@gmail.com (A.V. Semenov).
Contents lists available at ScienceDirect
Ceramics International
journal homepage: www.elsevier.com/locate/ceramint
https://doi.org/10.1016/j.ceramint.2022.09.096
Received 8 March 2022; Received in revised form 13 June 2022; Accepted 8 September 2022

Ceramics International 48 (2022) 37410–37422
37411
material based on polycarbosilane ceramic matrix can stabilize cobalt
ferrite nanoparticles [23].
The aim of this work is the possibility of preparing the material with
combine properties of silicon-based ceramic and magnetic properties of
iron oxide compounds under certain temperatures and annealing time.
It’s expected to have a variety of potential applications, such as mag-
netic data storage, electromagnetic solutions, and so on.
2. Experimental
2.1. Ceramic preparation
The method for PCS synthesis was previously described in the liter-
ature [23]. It requires readily available precursors and typical chemical
laboratory equipment.
Polycarbosilane – (PCS) as produced by "State Research Institute for
Chemistry and Technology of Organoelement Compounds". The process
lasts 30–40 h. The rst stage is the decomposition and rearrangement of
polydimethylsilane (PDMS) at 350–430◦С (with a controlled
temperature rise) and 0.4 MPa resulting in formation of raw PCS. The
second stage is the polycondensation at 390–425◦С and residual pres-
sure of 0.2–0.4 kPa with removal of low-boiling components in accor-
dance with the scheme. PCS was used as a 50 % solution at toluene.
Other compounds were purchased with high chemical purity and used
without any additional purication.
Ceramic samples of nanoparticles of iron ferrite (Fe
3
O
4
) were pre-
pared by the thermal decomposition method. Solution of iron (II) oxa-
late at the water - C
2
H
5
OH mixture was added to the solution of PCS in
toluene (50 %) at 240◦C at argon atmosphere with the removal of sol-
vent and reaction by-products at ambient pressure. The ratio of FeC
2
O
4
to the PCS was 1:5 by weight correspondingly. The composite was
divided into four parts: unsintered one, sintered at 800◦C for 2 h in air,
sintered at 800◦C for 2 h in argon, the last part of the composite was
sintered at the same temperature and the same time in argon followed by
air. The temperature rate and time of sintering were chosen on the basis
Fig. 1. TEM micrographs of individual iron oxide nanoparticles in the ceramic
matrix before sintering.
Fig. 2. TEM micrograph nanosized iron oxide particles in the ceramic matrix
sintered in air.
Fig. 3. TEM micrograph nanosized iron oxide particles in the ceramic matrix
sintered in argon.
Fig. 4. SEM micrographs of individual iron oxide nanoparticles in the ceramic
matrix before sintering.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37412
of our research [23] where similar materials based on PCS and cobalt
ferrite (CoFe
2
O
4
) were synthesized.
2.2. Sample characterization
Transmission electron microscopy (TEM) was used to conrm the
presence of nanoparticles in the material and determine their sizes. The
studies were performed using a JEOL JEM 1011 microscope, with an
accelerating voltage of 80 kV and instrument constant of 80 cm.
SEM micrographs and EDS spectra of the samples prepared in this
study were recorded on a JEOL JSM 6380-LA scanning electron micro-
scope (with a 1 nA current and 20 kV accelerating voltage) equipped
with a JED 2300 energy dispersive X-ray analyzer.
X-ray diffraction patterns were recorded on a Shimadzu diffractom-
eter equipped with a GP-13 powder diffraction accessory and BSV21–Cu
X-ray tube. The Cu K
α
1
(1.540598 Å) line was extracted from the radi-
ation spectrum using a Ni-lter. The PDF2 database by ICDD (2010) was
used as a reference.
M¨
ossbauer absorption spectra were recorded on a МS1104ЕM ex-
press M¨
ossbauer spectrometer produced by CJSC “Kordon” (Rostov-on-
Don). The source of γ-radiation was
57
Со in the metallic Rh matrix, with
the activity of 30 mCi, produced by RITVERC GmbH (Saint Petersburg).
Blended powder samples enclosed in a plastic cell were placed into a
vacuum cryostat. The spectra were recorded at room temperature (298
±3 K), and at temperature of liquid nitrogen (77.5 ±0.5 K). The
reproducibility of the spectra was ensured by comparing the spectra of
the same sample recorded at room temperature before vacuuming and
after the freezing-heating loop. The spectra were recorded with a noise/
signal ratio from 2.5 to 1.1%. Mathematical processing of M¨
ossbauer
spectra was performed for high-resolution spectra (1024 points) using
SpectRelax 2.8 software. The spectra were decomposed into symmetric
doublets and sextets with a controlled ratio between line widths and
intensities. The chemical shifts are provided relative to
α
-Fe.
EMR spectra were recorded at room temperature using a Varian-E4
X-band spectrometer. Magnetic measurements were performed using
EG&G PARC 155 vibrating sample magnetometer. The dependencies M
(H) were measured at room temperature in the elds up to 0.5 T.
3. Results and discussion
3.1. TEM
TEM micrograph of the unsintered sample made of iron ferrite and
ceramic matrix (Fig. 1) contains particles with sizes ranging from 5 to
Fig. 5. SEM micrograph nanosized iron oxide particles in the ceramic matrix
sintered in air.
Fig. 6. SEM micrograph nanosized iron oxide particles in the ceramic matrix
sintered in argon.
Fig. 7. Element composition of iron oxide nanoparticles in the ceramic matrix before sintering, according toTable 1.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37413
Fig. 8. Element composition of iron oxide nanoparticles in the ceramic matrix after sintering in air,according toTable 2.
Fig. 9. Element composition of iron oxide nanoparticles in the ceramic matrix after sintering in argon, according toTable 3.
Fig. 10. X-Ray diffraction pattern of iron oxide nanoparticles in the ceramic matrix before sintering.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37414
30 nm as well as larger then conglomerates formed by stacked particles.
TEM micrograph of the sample sintered in air (Fig. 2) contains
multiple small (2–5 nm) particles scattered uniformly throughout the
matrix as well as separate particles with a size up to 25 nm.
TEM micrograph of the sample sintered in argon contains nano-
particles with sizes ranging from 5 to 15 nm evenly dispersed in the
matrix (Fig. 3). It was shown a decrease in the average nanoparticle size
after sintering.
3.2. SEM
The TEM data comply with the morphology determined by SEM
(Figs. 4–6). As follows from X-ray spectral data (Figs. 7–9), the relative
content of Fe and C changes after sintering in argon or air. Sintering in
air results in the removal of the remaining solvent and low-molecular
materials from the blend as they are burned out. The molar ratio C/Fe
drastically reduces from 68 to 4 after sintering in air. The sintering in
Fig. 11. X-Ray diffraction pattern of iron oxide nanoparticles in the ceramic matrix after sinteringargon.
Fig. 12. X-Ray diffraction pattern of iron oxide nanoparticles in the ceramic matrix after sintering in air.
Fig. 13. X-Ray diffraction pattern of iron oxide nanoparticles in the ceramic matrix after sintering in argon and air.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37415
argon changes the C/Fe ratio in much less amount from 68 to 55.
3.3. XRD
X-ray diffraction is used to determine the composition of the samples.
X-ray diffraction patterns of the samples are shown (Figs. 10–13) for
unsintered samples, sintered in different atmospheres: argon, argon
followed by sintering air, air respectively. The diffraction patterns of the
unsintered sample (Fig. 10) reveal the peaks attributable to Iron(III)
Oxalate - Fe
2
(C
2
O
4
)
3
, - Iron(II) Oxalate FeC
2
O
4
, Iron(II) Oxalate Hydrate
- FeC
2
O
4
*2H
2
O (ICDD PDF: 14–762, 14–807, 22–635 respectively). It
indicates that the synthesis temperature is too lower for the total
decomposition of iron oxalate.
The X-ray pattern of the sample sintered in argon (Fig.11) contains
peaks attributable to different compounds: metal alpha iron –
α
Fe;
austenite - solid solution of iron (with an alloying element carbon) – Fe
+C; - iron silicide - Fe
3
Si; iron carbide - Fe
3
C (ICDD PDF: 6–696,
31–619, 35–519, 35–772). The chemical composition of the sample
shows that iron is reduced by the excess of the organic matrix, and is not
oxidized due to lack of oxygen.
The sample sintered in air (Fig.12) has some reduced form of iron.
The X-ray pattern of the sample shows several peaks correspond to the
different states of oxidation: iron -
α
Fe; magnetite – Fe
3
O
4
; hematite –
α
Fe
2
O
3
; Fayalite - Fe
2
SiO
4
(ICDD PDF: 6–696, 19–629, 33–664, 34–178).
One calcination procedure is not enough for complete oxidation, prob-
ably, due to kinetic factors.
The X-ray pattern of the sample sintered in argon followed by sin-
tering in air (Fig.13) contains peaks corresponding to the oxidized form
of iron: magnetite – Fe
3
O
4
; and hematite –
α
Fe
2
O
3
(ICDD PDF: 19–629,
33–664) [24]. Calcination in air of the sintered sample leads to deep
oxidation of the material.
3.4. M¨
ossbauer spectroscopy
M¨
ossbauer spectra of the unsintered sample have three resonance
lines at the two temperatures. The lines are different by intensities and
width. The intensities are strongly increased by the lowering of the
temperature. Such behavior is typical for metalorganic coordination
compounds with molecular crystal lattice [25,26].
The experimental spectrum can be satisfactorily described as a su-
perposition of two independent distribution functions of quadrupole
splitting and isomer shifts for doublets (Fig. 14). It corresponds to iron
atoms at different oxidation states (Table. 4). Iron(II) compounds at the
high spin state and octahedral oxygen environment [27] are described
by three modal distribution functions (Fig. 14). The most intense mode
of the function corresponds to a dehydrated form of iron(II) oxalate [28]
(Table. 4). The medium mode with a peak area around 7 % (Table 1)
obviously relates to original iron(II) oxalate dehydrate [29,30]. The
third mode with minimal area, probably, corresponds to the interme-
diate of the iron oxalate dehydration process [31]. Iron(III) compounds
[32] are presented by the second distribution - one, but asymmetric
mode with high dispersion. The mode describes initial products of
thermal decomposition of iron(II) oxalate [33–35] which may be the
different hydrated form of iron(III) oxalate [36,37]. The presence of iron
oxalates in oxidation states of +2 and +3 are completely correlated with
the X-ray data of the sample described above.
M¨
ossbauer spectra of the sintered in argon sample have a large set of
resonance lines with different intensives (Fig. 15). The spectra can be
described as a superposition of ten subspectra of four different iron
contained phases. The three phases correspond to metal iron (Table. 5).
The most intense sextet attributes to metal iron -
α
-Fe [38]. The inner
part of the sextet is distorted by the presence of satellite subspectra iron
atoms at the lattice of alloy with composition:
α
-Fe
1-x
A
x
. The crystal
lattice of the alloy has iron atoms for which surrounded by 1, 2, or more
iron atoms by atoms of another element are replaced [39–41]. Spectrum
parameters for these iron atoms are similar to subspectrumN◦1 param-
eters. The difference can be explained as a chemical shift and the
effective magnetic eld value. They are differenced from the original
values by n*dδ and -n*dH (where n – is the number of the satellite, dF is
the value difference for M¨
ossbauer parameter F (Table. 5). The ratio of
satellite intense values is dened as binominal distribution dependent
on x (part of impurities) [42]. (Lower in Table 5 and Fig. 16 satellite with
an intense value higher than 0,1 % are shown only). In the present work,
the inuence of the changing number of iron atoms only at the rst
coordination sphere (it has eight atoms) is taken into account during the
experimental spectra investigation. Implementation of the model with a
second coordination sphere [43] (it contains 6 atoms) does not lead to a
decrease in normal functional at chi-square –
χ
2
and does not change
parameter x (the parameter which describes the number of impurities) -
α
-Fe
0.8
A
0.2
. That is why the second sphere is not described in the current
investigation. It is possible to guess, that the alloy is a solid solution of Si
in metal Fe [44,45] -
α
-Fe
0.8
Si
0.2
. The occurrence of the iron silicide is
X-ray powder diffraction is shown as impurities to the main component –
iron. It is possible that iron silicide is not an absolutely stoichiometric
compound, it has some defects with an ultimate form of a solution of Si
in Fe (see Table 4).
The third metal phase is shown as a high intense resonance line in the
spectrum center and it is shown as the singlet #10 (Table. 5). The metal
Fig. 14. M¨
ossbauer spectra and the distribution functions of the quadrupole
splitting at 78 and 298 K for the unsintered sample.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37416
phase corresponds to the metastable face-centered cubic lattice of metal
iron - γ-Fe [46,47].
The rest 40 % of the spectrum is described as a couple of sextets. They
describe iron atoms in the two different crystalline lattice positions of
θ-Fe
3
C [5,42,48].
M¨
ossbauer spectra of the sample sintered in argon and air and the
sample sintered only at air have complicated combined types (Fig. 16). A
higher number of the resonance line with smaller widths are occurred
for the sample sintered only at air compare to the sample sintered in
argon and air. However, a larger part of the spectra can be described by
components from the common phases. A subspectrum N◦1 related to
α
-Fe
2
O
3
[49,50] appears in the both samples (Tabl. 6). The higher width
of the resonance line and absence of Morin transition at hematite for the
sample sintered in series in argon and air is proof of high defectiveness
or the phase [38]. A subspectra N◦2–4 (Table 6) group describes solid
state solution magnetite-maghemite (Fe
3
O
4
- γ-Fe
2
O
3
) for the both
samples [51]. The solution can be presented as formula Fe
3-δ
O
4
, where
0 ≤δ ≤1/3 is the coefcient of nonstoichiometry. The coefcient shows
the degree of the partial oxidation state of magnetite [38,52]. For the
low temperature spectra of the sample sintered only at air a higher value
of the isomer shifts of subspectra shows the smaller degree of the partial
Fig. 15. M¨
ossbauer spectra obtained at 298 K and 78 K of the sintered in argon sample and their model description with the numbering of subspectra according
to Table 5.
Table 1
Element composition of iron oxide nanoparticles in the ceramic matrix before
sintering.
Element/transition Energy, keV Weight, % Atomic, %
C K 0.277 62.20 74.73
O K 0.525 17.85 16.10
Si K 1.739 15.71 8.07
Fe K 6.398 4.24 1.10
Total, % – 100.00 100.00
Table 2
Element composition of iron oxide nanoparticles in the ceramic matrix after
sintering in air.
Element/transition Energy, keV Weight, % Atomic, %
C K 0.277 11.60 18.63
O K 0.525 48.43 58.88
Si K 1.739 25.82 17.73
Fe K 6.398 13.76 4.75
Total,% – 100.00 100.00
Table 3
Element composition of iron oxide nanoparticles in the ceramic matrix after
sintering in argon.
Element/transition Energy, keV Weight, % Atomic, %
C K 0.277 51.74 67.46
O K 0.525 16.23 15.89
Si K 1.739 27.67 15.43
Fe K 6.398 4.37 1.22
Total,% – 100.00 100.00
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37417
oxidation state. It is needed to relate this phase the doublet #7 (Tabl. 3)
too. The intensity of the doublet has strong temperature dependence.
This dependence is characteristic of the superparamagnetic state of iron
oxides.
A higher difference of the spectrum for the sample sintered in air is
the presence of subspectra correspond to the metal iron (
α
-Fe) and iron
silicate
α
-Fe
2
SiO
4
[53]. A smaller degree of the oxidation state of
magnetite may be explained by the existence of a kinetic barrier. The
barrier has occurred during the sintering procedure of iron oxalate in the
ceramic matrix. During the procedure, some gases (such as CO and
others) are involved in chemical reactions with iron compounds. The
reactions lead to the formation of iron with oxidation state +2 and
0 (metal iron). In contrast, the gas byproducts are removed on the rst
step (sintering in argon) during the sintering of the sample sintered in
argon and air. The next sintering in air leads to the oxidation of iron
compounds.
3.5. Magnetic properties
The eld dependence of magnetization M(H) measured at room
temperature also demonstrates that behaviour is different for the sam-
ples based on iron nanoparticles in the matrix before sintering, sintering
either in air or argon (Fig. 17). The sample before sintering is para-
magnetic. The sintered samples are ferromagnetic compounds. The co-
ercive force (
μ
0
H
c
) of the sample sintered in air is 0.01 T, and the
remnant magnetization (M
r
) is ca. 1.5 A*m
2
/kg. The saturation takes
place at magnetic induction B =0.5 T, the achieved saturation magne-
tization (Ms) is 9 A*m
2
/kg. The coercive force (
μ
0
H
c
) of the sample
sintered in argon is 0.01 T, and the remnant magnetization (M
r
) is ca. 3
A*m
2
/kg. A weak saturation of the M(H) curve for this sample may
indicate the presence of a large proportion of superparamagnetic
particles.
It is shown, that the magnetic properties of particles of Fe
3
O
4
are size
dependent. Nanoparticles of magnetite with sizes less than 20 nm are
superparamagnetic. The emergence of coercive force is shown for par-
ticles with sizes higher than 20 nm [54]. The Fe
3
O
4
particles with di-
mensions higher than 20 nm or other compounds may be in charge of
ferromagnetic behaviour in our case. The results of studying the eld
dependences of the magnetization M(H) are in good agreement with the
results obtained in M¨
ossbauer spectroscopy experiments. The data ob-
tained show that the unsintered sample contains mainly paramagnetic
iron phases, which are transformed into magnetic phases upon further
sintering. The sintering in argon produces large amounts of magnetic
particles.
3.6. EMR spectra
In order to obtain an analytical representation of the spectra, they
were decomposed into components described by the Tsallis function
(tsallian) [55,56].
Y’ ={−2A/(q−1)}{(2
q−1
−1) (H−H
R
)/Γ
2
}{1+(2
q−1
−1) ((H−H
R
)/Γ)
2
}
q/
(1−q)
+
+{−2A/(q−1)}{(2
q−1
−1) (H +H
R
)/Γ
2
}{1+(2
q−1
−1) ((H +H
R
)/Γ)
2
}
q/
(1−q)
H)
where A is the absorption line amplitude, H
R
is the resonance eld
strength, Γ is a relaxation rate parameter, q is a parameter which de-
termines the resonance line shape. Special cases of the tsallian are q =1
(gaussian) and q =2 (lorentzian). Lines with q >2 are called super-
lorentzians.
EMR spectra of three types of samples and decomposition into tsal-
lians are shown in (Figs. 18–21).
The method used herein for the EMR spectra decomposition into
tsallians is described in more detail elsewhere [23]. It is based on
minimization of the discrepancy between experimental and theoretical
spectra using a hybrid technique combining gradient descent and
Monte-Carlo methods.
Fig. 19 contains spectra of the sintered in argon followed by sintering
in air. The spectra can be decomposed into 3 components. The narrowest
(ΔH
pp
≈190 Oe) one has g
eff
=1.99 and it likely corresponds to the
paramagnetic Fe
3+
ions. The wider component (ΔH
pp
≈680 Oe) with
g
eff
=2.02 is typical for small or amorphous nanoparticles of maghemite
(Fe
2
O
3
, γ-Fe
2
O
3
) (a maghemite phase with complex composition will
have a similar component). The most intense component (super-Lor-
entzian) has ΔH
pp
≈780 Oe) with g
eff
=2.42. It probably relates to
magnetite (Fe
3
O
4
) particles or the magnetite phase.
The sintered in air sample has higher magnetization for maghemite
and magnetite components. Decomposition of the EMR spectra leads to a
shift of components to lower elds Fig. 20.
The EMR spectrum of the sintered in argon sample has a new very
intense and broad (ΔH
pp
≈5660 Oe) component with high magnetiza-
tion (Fig. 21). The component can be explained by the presence of Fe (0).
The maghemite phase is presented also on spectra by line with small
intensity.
The chemical compositions of prepared samples are in line with
known data for stabilized iron oxide nanoparticles. For example, the
chemical composition of iron contained nanoparticles is complex after
sintering without oxygen. An iron citrate sample was interacted with a
portion of phenol-formaldehyde resin, heated without oxygen access at
800◦C. The resulted mix has several components: carbon, Fe
3
O
4
, Fe
3
C,
Fe different types [3]. In our case, all mentioned iron compounds are
presented with additional FeSi compound, after sintering in argon. FeSi
is presented because we used polycarbosylane with Si.
The chemical forms of iron in the sintered in air sample are by
M¨
ossbauerspectra:
α
-Fe (2 at%) – also seen at X-ray powder diffraction,
FeSiO
4
(10 at%) - also seen at X-ray powder diffraction,
α
-Fe
2
O
3
(11 at
%) - also seen at X-ray powder diffraction, Fe
3
O
4
(75 at%) - also seen at
X-ray powder diffraction, Fe
+3
SPM
(2 at%) – impurities.
The chemical forms of iron in the sintered argon followed by
Table 4
Parameters of the M¨
ossbauer spectra recorded at 78 and 298 K for unsintered sample.
Temperature, K Subspectrum Mode Phase δ
da
Δ
d
=2
ε
d
Γ S
d
ΣS
d
mm/s %
298 1 1 Fe
2
(C
2
O
4
)
3
•xH
2
O 0.372 ±0.003 0.97 ±0.04 0.290 ±0.005 31.2 ±0.2 31.2 ±0.2
2 1 Fe(C
2
O
4
) 1.217 ±0.002 2.21 ±0.01 58.9 ±0.6 68.8 ±0.2
2 Fe(C
2
O
4
)•2H
2
O 1.254 ±0.004 1.74 ±0.04 6.9 ±0.7
3 Fe(C
2
O
4
)•xH
2
O 1.287 ±0.005 1.30 ±0.02 3.3 ±0.5
78 1 1 Fe
2
(C
2
O
4
)
3
•xH
2
O 0.456 ±0.005 0.99 ±0.03 0.317 ±0.004 30.4 ±0.3 30.4 ±0.3
2 1 Fe(C
2
O
4
) 1.323 ±0.003 2.62 ±0.01 56.9 ±0.8 69.6 ±0.3
2 Fe(C
2
O
4
)•2H
2
O 1.398 ±0.007 2.21 ±0.03 7.7 ±0.8
3 Fe(C
2
O
4
)•xH
2
O 1.52 ±0.01 1.56 ±0.04 5.1 ±0.6
a
δ
d
- isomer shift, Δ
d
=2
ε
d
- quadrupole splitting and S
d
- relative area for maximum of mode distribution functions, Γ - line width.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37418
Table 5
M¨
ossbauer spectra parameters and iron phase distribution in sintered in argon sample.
Temperature,
K
78 298
# Phase δ
a
Dδ Δ =2
ε Г
exp
H
eff
dH S# Σ S# δ dδ Δ =2
ε Г
exp
H
eff
dH S# Σ S#
mm/s kOe % mm/s kOe %
1
α
-Fe 0.126 ±
0.001
−0.006 ±
0.003
0.332 ±
0.006
338.6 ±
0.1
29.2 ±0.8 29.2 ±
0.8
0.003 ±
0.002
0.010 ±
0.005
0.39 ±
0.01
330.0 ±
0.2
27 ±1 27 ±1
2
α
-Fe
1-
x
A
x
0.126 ±
0.001
0.016 ±
0.003
0.01 ±0.01 0.32 ±
0.03
338.6 ±
0.1
14.4 ±
0.8
2.2 ±0.5 13.5 ±
0.6
0.003 ±
0.002
0.046 ±
0.005
−0.05 ±
0.01
0.32 ±
0.03
330.0 ±
0.2
16
±1
3.2 ±0.9 16.5 ±
0.9
3 0.141 ±
0.003
324.2 ±
0.8
4.51 ±
0.03
0.049 ±
0.005
314.2 ±
1
5.84 ±
0.05
4 0.157 ±
0.007
310 ±2 3.98 ±
0.02
0.096 ±
0.009
298 ±2 4.62 ±
0.04
5 0.17 ±
0.01
295 ±2 2.00 ±
0.01
0.14 ±0.01 282 ±3 2.09 ±
0.02
6 0.19 ±
0.01
281 ±3 0.630 ±
0.004
0.19 ±0.02 266 ±4 0.589 ±
0.005
7 0.20 ±
0.02
267 ±4 0.127 ±
0.001
0.23 ±0.02 250 ±5 0.106 ±
0.001
8 θ-Fe
3
C 0.315 ±
0.001
0.008 ±
0.002
0.266 ±
0.006
252.6 ±
0.2
13.0 ±0.1 13.0 ±
0.1
0.200 ±
0.002
0.020 ±
0.003
0.37 ±
0.01
210.5 ±
0.4
24 ±1 24 ±1
9 0.315 ±
0.001
0.008 ±
0.002
0.394 ±
0.007
242.8 ±
0.2
25.9 ±0.1 25.9 ±
0.1
0.200 ±
0.002
0.020 ±
0.003
0.34 ±
0.02
197.4 ±
0.6
13 ±2 13 ±2
10 γ-Fe 0.039 ±
0.001
0.437 ±
0.004
18.4 ±0.1 18.4 ±
0.1
−0.069 ±
0.002
0.512 ±
0.005
19.4 ±0.2 19.4 ±
0.2
x
b
0.20 ±0.02 0.18 ±0.02
a
δ – chemical shift; Δ =2
ε
– quadrupole splitting;
Г
exp
– line width; H
eff
– hyperne magnetic eld; S – site # area.
b
x - parameter for
α
-Fe
1-x
A
x
.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37419
Fig. 16. M¨
ossbauer spectra obtained at 78 K (a, c) and 298 K (b, d) of samples the sintered in Ar and air (a, b) or sintered in only air (c, d) and their model description
with the numbering of subspectra according to Table 6.
Table 6
M¨
ossbauer spectra parameters of samples the sintered in Ar and air or sintered in only air.
Temperature,К 78 298
Sample # Phase δ
a
Δ =2
ε Г
exp
H
eff
S# δ Δ =2
ε Г
exp
H
eff
S#
mm/s kOe % mm/s kOe %
Ar +air 1
α
-Fe
2
O
3
0.48 ±
0.01
0.03 ±0.01 0.42 ±
0.01
544.9 ±
0.4
19 ±1 0.40 ±
0.01
−0.08 ±
0.01
0.45 ±
0.02
510.7 ±
0.4
12.2 ±
0.9
2 Fe
3-δ
O
4
0.49 ±
0.01
−0.09 ±
0.01
0.48 ±
0.02
525.0 ±
0.7
25 ±2
3 0.37 ±
0.01
0.01 ±0.01 0.37 ±
0.01
507.1 ±
0.3
25 ±2 0.27 ±
0.01
0.00 ±0.01 0.49 ±
0.02
485.4 ±
0.2
31 ±3
4 0.42 ±
0.01
−0.06 ±
0.02
0.82 ±
0.05
486 ±2 20 ±2 0.33 ±
0.01
−0.03 ±
0.01
1.46 ±
0.09
455 ±4 40 ±2
7 Fe
+3
SPM
0.40 ±
0.02
1.19 ±0.04 1.32 ±
0.08
11.4 ±
0.4
0.34 ±
0.01
0.76 ±0.01 0.77 ±
0.05
17 ±2
Air 1
α
-Fe
2
O
3
0.49 ±
0.01
0.20 ±0.02 0.38 ±
0.02
537.3 ±
0.5
10.7 ±
0.6
0.38 ±
0.01
−0.20 ±
0.01
0.31 ±
0.01
512.0 ±
0.1
19.6 ±
0.6
2 Fe
3-δ
O
4
0.48 ±
0.01
−0.18 ±
0.01
0.31 ±
0.01
528.3 ±
0.2
19 ±1
3 0.44 ±
0.01
−0.04 ±
0.01
0.63 ±
0.02
508.9 ±
0.7
20.8 ±
0.9
0.35 ±
0.01
−0.16 ±
0.01
0.54 ±
0.02
491.5 ±
0.5
15.9 ±
0.8
4 0.53 ±
0.01
−0.11 ±
0.02
1.36 ±
0.04
456 ±1 35 ±1 0.39 ±
0.01
−0.10 ±
0.01
1.28 ±
0.03
452 ±1 33 ±1
5
α
-Fe 0.14 ±
0.01
−0.04 ±
0.02
0.30 ±
0.01
339.4 ±
0.8
2.4 ±0.4 0.00 ±
0.01
−0.07 ±
0.02
0.31 ±
0.01
328.9 ±
0.8
2.6 ±0.4
6
α
-Fe
2
SiO
4
1.28 ±
0.01
3.07 ±0.01 0.30 ±
0.01
10.2 ±
0.2
1.15 ±
0.01
2.80 ±0.01 0.35 ±
0.01
13.9 ±
0.2
7 Fe
+3
SPM
0.48 ±
0.02
0.85 ±0.03 0.47 ±
0.06
2.1 ±0.3 0.39 ±
0.01
0.91 ±0.01 0.45 ±
0.01
14.9 ±
0.2
a
δ – chemical shift; Δ =2
ε
– quadrupole splitting;
Г
exp
– line width; H
eff
– hyperne magnetic eld; S – site # area.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37420
sintering in air sample are by M¨
ossbauer spectra:
α
-Fe
2
O
3
(19 at%) - also
seen at X-ray powder diffraction and EMR spectra, Fe
3
O
4
(70 at%) - also
seen at X-ray powder diffraction and EMR spectra, Fe
+3
SPM
(11 at%) –
impurities.
The observed reduction of iron during the heating in argon or air is
not unique for thermal treatment of iron nanoparticles. The formation of
metal iron and mostly iron carbide occurs during heating of iron nitrate
and chitosan matrix at 600 ◦C. If the reaction mixture treated at lower
temperatures (300 – 500 ◦C) than oxidized forms or iron are formed
[57].
The size of iron contained particles is dependent on the type of
particles and the way it is synthesized and stabilized. Several ranges of
unsintered iron oxide particles are known: 20–90 nm [1], 10–40 nm [2],
30–150 nm [3]. The matrix stabilization leads to smaller particle size:
3–5 nm [4], 5–30 nm current job. It was shown in current work, that
calcination in air in matrix was able to produce very small particles
around 2–5 nm. The size of the particles is smaller than known ultrane
doped Fe
2
O
3
2–5 nm compare to 4,5 nm [5]. The samples sintered in air
or argon proved to be very stable and kept small particle sizes, in
contrast to resin matrix. The iron contained sample with resin matrix
after sintering in inert atmosphere has particle sizes 10–100 nm with
average size of 60–80 nm for iron compounds prepared from iron nitrate
[6].
Decreasing of the iron particle size during sintering in air is not
common for nanoparticles. It is known that iron nanoparticles increase
size from 4 nm to 25 nm after heating at 800◦C [57], but in our case the
particle size decrease to 2–5 nm. The reason for different nanoparticle
behaviour can be kinetic factors such as chemical reactions, mass and
heat transfer effects.
Fig. 17. Hysteresis loop M(H) recorded at 298 K for the sample comprised of
iron oxide nanoparticles in the ceramic matrix before sintering and after sin-
tering in either air or argon. Specic magnetization M is normalized to the
iron content.
Fig. 18. Experimental EMR spectra of the samples after sintering in air, argon,
or argon followed by sintering in air.
Fig. 19. Decomposition of the EMR spectrum of the sample sintered in argon
followed by sintering in air.
Fig. 20. Decomposition of the EMR spectrum of a sample after sintering in air.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37421
4. Conclusions
Methods for the preparation of composite materials based on iron
nanoparticles stabilized in the matrix by pyrolysis of iron precursor
polycarbosilane was worked out under certain temperatures and
annealing time. The size and product composition depend on the sin-
tering procedure. The thermal treatment, especially in argon, increases
remnant magnetization of the composites, evidenced by a larger hys-
teresis loop area. It was shown, that EMR spectra, X-ray diffraction
analysis are sensitive to structural changes and magnetic properties. The
methods can be recommended for samples investigation. It is shown that
sintering in argon leads to the reduction of iron compounds. The full
oxidation of iron to iron oxides needs at least two sintering procedures,
for example, sintering in argon followed by sintering in air; the one
sintering procedure in air is not enough for total oxidation of iron due to
kinetic factors (decomposition of the ceramic matrix provides an excess
of reducing agent such as hydrogen, carbon monoxide and so on …). The
completed work describes the thermal transformation of the composite
material in the different atmospheres, and the variation of the material
structure lets create a technology of composite material preparation
with designed particle formulation.
Preparing the material under different technological parameters will
be investigated.
Declaration of competing interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Acknowledgements
This work was performed as part of a State Task from the RF Ministry
of Science and Higher Education.
References
[1] D. Manojlovi´
c, K. Lelek, G. Rogli´
c, D. Zherebtsov, V. Avdin, K. Buskina,
C. Sakthidharan, S. Sapozhnikov, M. Samodurova, R. Zakirov, D.M. Stankovi´
c,
Efciency of homely synthesized magnetite: carbon composite anode toward
decolorization of reactive textile dyes, Int. J. Environ. Sci. Technol. 17 (2020),
https://doi.org/10.1007/s13762-020-02654-8.
[2] M.M. Anuchina, D.A. Pankratov, D.P. Abroskin, N.A. Kulikova, D.T. Gabbasova, D.
N. Matorin, D.S. Volkov, I.V. Perminova, Estimating the Toxicity and Biological
Availability for Interaction Products of Metallic Iron and Humic Substances, vol.
74, Moscow University Soil Science Bulletin, 2019, https://doi.org/10.3103/
S0147687419050028.
[3] D.I. Tishkevich, I.V. Korolkov, A.L. Kozlovskiy, M. Anisovich, D.A. Vinnik, A.
E. Ermekova, A.I. Vorobjova, E.E. Shumskaya, T.I. Zubar, S.V. Trukhanov, M.
V. Zdorovets, A.V. Trukhanov, Immobilization of boron-rich compound on Fe3O4
nanoparticles: stability and cytotoxicity, J. Alloys Compd. 797 (2019), https://doi.
org/10.1016/j.jallcom.2019.05.075.
[4] T.N. Rostovshchikova, M.S. Korobov, D.A. Pankratov, G.Y. Yurkov, S.P. Gubin,
Catalytic conversions of chloroolens over iron oxide nanoparticles 2.
Isomerization of dichlorobutenes over iron oxide nanoparticles stabilized on the
surface of ultradispersed poly(tetrauoroethylene), Russ. Chem. Bull. 54 (2005)
1425–1432, https://doi.org/10.1007/S11172-005-0422-1.
[5] D.S. Klygach, M.G. Vakhitov, D.A. Pankratov, D.A. Zherebtsov, D.S. Tolstoguzov,
Z. Raddaoui, S. el Kossi, J. Dhahri, D.A. Vinnik, A.V. Trukhanov, MCC: specic of
preparation, correlation of the phase composition and electrodynamic properties,
J. Magn. Magn Mater. 526 (2021), https://doi.org/10.1016/j.jmmm.2020.167694.
[6] A.V. Trukhanov, D.A. Vinnik, E.A. Tromov, V.E. Zhivulin, O.V. Zaitseva, S.
V. Taskaev, D. Zhou, K.A. Astapovich, S.V. Trukhanov, Y. Yang, Correlation of the
Fe content and entropy state in multiple substituted hexagonal ferrites with
magnetoplumbite structure, Ceram. Int. 47 (2021), https://doi.org/10.1016/j.
ceramint.2021.03.088.
[7] Z. Ren, C. Gervais, G. Singh, Fabrication and characterization of silicon
oxycarbidebre-mats via electrospinning for high temperature applications, RSC
Adv. 10 (2020), https://doi.org/10.1039/D0RA04060F.
[8] A.S. Fionov, G.Yu Yurkov, V.v. Kolesov, D.A. Pankratov, E.A. Ovchenkov,
YuA. Koksharov, Composite material based on iron-containing nanoparticles for
applications in the problems of electromagnetic compatibility, J. Commun.
Technol. Electron. 57 (2012), https://doi.org/10.1134/S1064226912040079.
[9] G.Y. Yurkov, A.S. Fionov, A.V. Kozinkin, Y.A. Koksharov, Y.A. Ovtchenkov, D.
A. Pankratov, O.V. Popkov, V.G. Vlasenko, Y.A. Kozinkin, M.I. Biryukova, N.
A. Taratanov, V.M. Bouznik, Synthesis and physicochemical properties of
composites for electromagnetic shielding applications: a polymeric matrix
impregnated with iron- or cobalt-containing nanoparticles, J. Nanophotonics 6
(2012), https://doi.org/10.1117/1.JNP.6.061717.
[10] P. Bhavani, C.H. Rajababu, M.D. Arif, I.V.S. Reddy, N.R. Reddy, Synthesis of high
saturation magnetic iron oxide nanomaterials via low temperature hydrothermal
method, J. Magn. Magn Mater. 426 (2017), https://doi.org/10.1016/j.
jmmm.2016.09.049.
[11] A. Lassoued, M.S. Lassoued, B. Dkhil, S. Ammar, A. Gadri, Synthesis,
photoluminescence and Magnetic properties of iron oxide (
α
-Fe2O3) nanoparticles
through precipitation or hydrothermal methods, Phys. E Low-dimens. Syst.
Nanostruct. 101 (2018), https://doi.org/10.1016/j.physe.2018.04.009.
[12] K. Sathya, R. Saravanathamizhan, G. Baskar, Ultrasound assisted phytosynthesis of
iron oxide nanoparticle, Ultrason. Sonochem. 39 (2017), https://doi.org/10.1016/
j.ultsonch.2017.05.017.
[13] A. Lazzarini, R. Colaiezzi, M. Passacantando, F. D’Orazio, L. Arrizza, F. Ferella,
M. Crucianelli, Investigation of physico-chemical and catalytic properties of the
coating layer of silica-coated iron oxide magnetic nanoparticles, J. Phys. Chem.
Solid. 153 (2021), https://doi.org/10.1016/j.jpcs.2021.110003.
[14] K. Petcharoen, A. Sirivat, Synthesis and characterization of magnetite
nanoparticles via the chemical co-precipitation method, Mater. Sci. Eng., B 177
(2012), https://doi.org/10.1016/j.mseb.2012.01.003.
[15] A. Hassanjani-Roshan, M.R. Vaezi, A. Shokuhfar, Z. Rajabali, Synthesis of iron
oxide nanoparticles via sonochemical method and their characterization,
Particuology 9 (2011), https://doi.org/10.1016/j.partic.2010.05.013.
[16] T.A. Lastovina, A.P. Budnyk, S.P. Kubrin, A.v. Soldatov, Microwave-assisted
synthesis of ultra-small iron oxide nanoparticles for biomedicine, Mendeleev
Commun. 28 (2018), https://doi.org/10.1016/j.mencom.2018.03.019.
[17] P.A. Calder´
on Bedoya, P.M. Botta, P.G. Bercoff, M.A. Fanovich, Magnetic iron
oxides nanoparticles obtained by mechanochemical reactions from different solid
precursors, J. Alloys Compd. 860 (2021), https://doi.org/10.1016/j.
jallcom.2020.157892.
[18] B. Medina, M.G. Verd´
erioFressati, J.M. Gonçalves, F.M. Bezerra, F.A. Pereira
Scacchetti, M.P. Mois´
es, A. Bail, R.B. Samulewski, Solventless preparation of
Fe3O4 and Co3O4 nanoparticles: a mechanochemical approach, Mater. Chem.
Phys. 226 (2019), https://doi.org/10.1016/j.matchemphys.2019.01.043.
[19] A.G. Roca, L. Guti´
errez, H. Gavil´
an, M.E. Fortes Brollo, S. Veintemillas-Verdaguer,
M. del P. Morales, Design strategies for shape-controlled magnetic iron oxide
nanoparticles, Adv. Drug Deliv. Rev. 138 (2019), https://doi.org/10.1016/j.
addr.2018.12.008.
[20] C. Song, W. Sun, Y. Xiao, X. Shi, Ultrasmall iron oxide nanoparticles: synthesis,
surface modication, assembly, and biomedical applications, Drug Discov. Today
24 (2019), https://doi.org/10.1016/j.drudis.2019.01.001.
[21] S. Kaur, R. Riedel, E. Ionescu, Pressureless fabrication of dense monolithic SiC
ceramics from a polycarbosilane, J. Eur. Ceram. Soc. 34 (2014), https://doi.org/
10.1016/j.jeurceramsoc.2014.05.002.
[22] F. Süß, T. Schneider, M. Frieß, R. Jemmali, F. Vogel, L. Klopsch, D. Koch,
Combination of PIP and LSI processes for SiC/SiC ceramic matrix composites, Open
Ceramics 5 (2021), https://doi.org/10.1016/j.oceram.2021.100056.
[23] G.Y. Yurkov, K.A. Shashkeev, S.v. Kondrashov, O.v. Popkov, G.I. Shcherbakova, D.
v. Zhigalov, D.A. Pankratov, E.A. Ovchenkov, Y.A. Koksharov, Synthesis and
magnetic properties of cobalt ferrite nanoparticles in polycarbosilane ceramic
Fig. 21. Decomposition of the EMR spectrum of a sample after sintering
in argon.
G.Y. Yurkov et al.

Ceramics International 48 (2022) 37410–37422
37422
matrix, J. Alloys Compd. 686 (2016) 421–430, https://doi.org/10.1016/J.
JALLCOM.2016.06.025.
[24] E.M. Kostyukhin, Synthesis of magnetite nanoparticles upon microwave and
convection heating, Russ. J. Phys. Chem. A 92 (2018), https://doi.org/10.1134/
S0036024418120233.
[25] D.A. Pankratov, V.D. Dolzhenko, R.A. Stukan, Y.F. al Ansari, E.v. Savinkina, Y.
M. Kiselev, Investigation of iron(III) complex with crown-porphyrin, Hyperne
Interact. 222 (2013), https://doi.org/10.1007/s10751-011-0378-5.
[26] L.I. Rodionova, N.E. Borisova, A.v. Smirnov, V.v. Ordomsky, A.A. Moiseeva, D.
A. Pankratov, Binuclear iron complexes with acyclic Schiff bases based on 4-tert-
butyl-2,6-diformylphenol: synthesis, properties, and use in catalytic partial
oxidation of isobutane, Russ. Chem. Bull. 62 (2013), https://doi.org/10.1007/
s11172-013-0164-4.
[27] D.A. Pankratov, M¨
ossbauer study of oxo derivatives of iron in the Fe2O3-Na2O2
system, Inorg. Mater. 50 (2014), https://doi.org/10.1134/S0020168514010154.
[28] M. Hermanek, R. Zboril, M. Mashlan, L. Machala, O. Schneeweiss, Thermal
behaviour of iron(ii) oxalate dihydrate in the atmosphere of its conversion gases,
J. Mater. Chem. 16 (2006), https://doi.org/10.1039/b514565a.
[29] M.C. D’Antonio, A. Wladimirsky, D. Palacios, L. Coggiolaa, A.C. Gonz´
alez-Bar´
o, E.
J. Baran, R.C. Mercader, Spectroscopic investigations of iron(II) and iron(III)
oxalates, J. Braz. Chem. Soc. 20 (2009), https://doi.org/10.1590/S0103-
50532009000300006.
[30] M.A. Gabal, Non-isothermal decomposition of NiC2O4–FeC2O4 mixture aiming at
the production of NiFe2O4, J. Phys. Chem. Solid. 64 (2003), https://doi.org/
10.1016/S0022-3697(03)00163-X.
[31] D. Xue, F. Li, Y. Kong, J. Yang, Phase transformation of FeC2O4 ⋅ 2H2O heat
treated in, J. Phys. Chem. Solid. 57 (1996), https://doi.org/10.1016/0022-3697
(95)00249-9.
[32] F.F.H. Arag´
on, J.A.H. Coaquira, S.W. da Silva, R. Cohen, D.G. Pacheco-Salazar, L.C.
C.M. Nagamine, Fe content effects on structural, electrical and magnetic properties
of Fe-doped ITO polycrystalline powders, J. Alloys Compd. 867 (2021), https://
doi.org/10.1016/j.jallcom.2021.158866.
[33] M.A. Gabal, A.A. El-Bellihi, S.S. Ata-Allah, Effect of calcination temperature on Co
(II) oxalate dihydrate–iron(II) oxalate dihydrate mixture, Mater. Chem. Phys. 81
(2003), https://doi.org/10.1016/S0254-0584(03)00137-8.
[34] P.K. Gallagher, C.R. Kurkjian, A study of the thermal decomposition of some
complex oxalates of iron(III) using the M¨
ossbauer effect, Inorg. Chem. 5 (1966),
https://doi.org/10.1021/ic50036a013.
[35] B.S. Randhawa, A. Pal Singh, R.P. Sharma, P.S. Bassi, Comparative study of solid
state reactivity between ferrous oxalate dihydrate and unsubstituted/substituted
aniline hydrochlorides, J. Radioanal. Nucl. Chem. 128 (1988), https://doi.org/
10.1007/BF02166646.
[36] H. Ahouari, G. Rousse, J. Rodríguez-Carvajal, M.-T. Sougrati, M. Sauban`
ere,
M. Courty, N. Recham, J.-M. Tarascon, Unraveling the structure of iron(III) oxalate
tetrahydrate and its reversible Li insertion capability, Chem. Mater. 27 (2015),
https://doi.org/10.1021/cm5043149.
[37] P.Yu Tyapkin, S.A. Petrov, A.P. Chernyshev, A.I. Ancharov, L.A. Sheludyakova, N.
F. Uvarov, Structural features of hydrate forms of iron(III) oxalate, J. Struct. Chem.
57 (2016), https://doi.org/10.1134/S0022476616060111.
[38] D.A. Pankratov, M.M. Anuchina, Nature-inspired synthesis of magnetic non-
stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic
medium, Mater. Chem. Phys. 231 (2019), https://doi.org/10.1016/j.
matchemphys.2019.04.022.
[39] W.E. Sauer, R.J. Reynik, Electronic and magnetic structure of dilute iron-base
alloys, J. Appl. Phys. 42 (1971), https://doi.org/10.1063/1.1660357.
[40] D. Grudinskyv, D. Zinoveev, A. Kondratiev, D. Lubyanoi, D. Pankratov, Reductive
smelting of neutralized red Mud for iron recovery and produced pig iron for heat-
resistant castings, Metals 10 (2019), https://doi.org/10.3390/met10010032.
[41] I. Vincze, I.A. Campbell, Mossbauer measurements in iron based alloys with
transition metals, J. Phys. F Met. Phys. 3 (1973), https://doi.org/10.1088/0305-
4608/3/3/023.
[42] P. Grudinsky, D. Zinoveev, D. Pankratov, A. Semenov, M. Panova, A. Kondratiev,
A. Zakunov, V. Dyubanov, A. Petelin, Inuence of sodium sulfate addition on iron
grain growth during carbothermic roasting of red Mud samples with different
basicity, Metals 10 (2020), https://doi.org/10.3390/met10121571.
[43] S.M. Dubiel, J. Cieslak, Short-range order in iron-rich Fe-Cr alloys as revealed by
M¨
ossbauer spectroscopy, Phys. Rev. B 83 (2011), https://doi.org/10.1103/
PhysRevB.83.180202.
[44] M.B. Stearns, Internal magnetic elds, isomer shifts, and relative abundances of the
various Fe sites in FeSi alloys, Phys. Rev. 129 (1963), https://doi.org/10.1103/
PhysRev.129.1136.
[45] H. Tokoro, S. Fujii, Y. Kobayashi, S. Muto, The growth of carbon coating layers on
iron particles and the effect of alloying the iron with silicon, J. Alloys Compd. 509
(2011), https://doi.org/10.1016/j.jallcom.2010.10.124.
[46] J. Ding, H. Huang, P.G. McCormick, R. Street, Magnetic properties of martensite-
austenite mixtures in mechanically milled 304 stainless steel, J. Magn. Magn
Mater. 139 (1995), https://doi.org/10.1016/0304-8853(95)90034-9.
[47] K. Haneda, Z.X. Zhou, A.H. Morrish, T. Majima, T. Miyahara, Low-temperature
stable nanometer-size fcc-Fe particles with no magnetic ordering, Phys. Rev. B 46
(1992), https://doi.org/10.1103/PhysRevB.46.13832.
[48] G. G.LeCaer, J.M. Dubois, J.P. Senateur, Etude par spectrom´
etrieM¨
ossbauer des
carbures de Fer Fe3C et Fe5C2, J. Solid State Chem. 19 (1976), https://doi.org/
10.1016/0022-4596(76)90145-6.
[49] S.J. Oh, D.C. Cook, H.E. Townsend, Characterization of iron oxides commonly
formed as corrosion products on steel, Hyperne Interact. 112 (1998), https://doi.
org/10.1023/A:1011076308501.
[50] A.Yu Romanchuk, S.N. Kalmykov, A.v. Egorov, Y.v. Zubavichus, A.A. Shiryaev, O.
N. Batuk, S.D. Conradson, D.A. Pankratov, I.A. Presnyakov, Formation of
crystalline PuO2+⋅nH2O nanoparticles upon sorption of Pu(V,VI) onto hematite,
Geochem. Cosmochim. Acta 121 (2013), https://doi.org/10.1016/j.
gca.2013.07.016.
[51] D.A. Pankratov, M.M. Anuchina, F.M. Spiridonov, G.G. Krivtsov, Fe3 – δO4
nanoparticles synthesized in the presence of natural polyelectrolytes, Crystallogr.
Rep. 65 (2020), https://doi.org/10.1134/S1063774520030244.
[52] G. Niraula, J.A.H. Coaquira, F.H. Aragon, B.M. GaleanoVillar, A. Mello, F. Garcia,
D. Muraca, G. Zoppellaro, J.M. Vargas, S.K. Sharma, Tuning the shape, size, phase
composition and stoichiometry of iron oxide nanoparticles: the role of phosphate
anions, J. Alloys Compd. 856 (2021), https://doi.org/10.1016/j.
jallcom.2020.156940.
[53] I. Choe, R. Ingalls, J.M. Brown, Y. Sato-Sorensen, M¨
ossbauer studies of iron silicate
spinel at high pressure, Phys. Chem. Miner. 19 (1992), https://doi.org/10.1007/
BF00202313.
[54] S. Klomp, C. Walker, M. Christiansen, B. Newbold, D. Griner, Y. Cai, P. Minson,
J. Farrer, S. Smith, B.J. Campbell, R.G. Harrison, K. Chesnel, Size-dependent
crystalline and magnetic properties of 5–100 nm Fe ₃ O ₄ nanoparticles:
superparamagnetism, verwey transition, and FeO–Fe ₃ O ₄ core–shell formation,
IEEE Trans. Magn. 56 (2020), https://doi.org/10.1109/TMAG.2020.3018154.
[55] D.F. Howarth, J.A. Weil, Z. Zimpel, Generalization of the lineshape useful in
magnetic resonance spectroscopy, J. Magn. Reson. 161 (2003), https://doi.org/
10.1016/S1090-7807(02)00195-7.
[56] YuA. Koksharov, Application of Tsallis functions for analysis of line shapes in
electron magnetic resonance spectra of magnetic nanoparticles, Phys. Solid State
57 (2015) 2011–2015, https://doi.org/10.1134/S1063783415100121.
[57] A.A. Vasil’ev, D.G. Muratov, G.N. Bondarenko, E.L. Dzidziguri, M.N. Emov, G.
P. Karpacheva, Synthesis of iron and cobalt nanoparticles in an IR-pyrolyzed
chitosan matrix, Russ. J. Phys. Chem. A 92 (2018), https://doi.org/10.1134/
S0036024418100369.
G.Y. Yurkov et al.