Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite
The preliminary results of investigations of heat transfer in nanocomposites consisting of nanoparticles randomly distributed in solid carbon monoxide matrix are presented. In the experiment the thermal conductivity coefficient dependence on temperature for CO crystal with silica and palladium nanop...
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
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irk-123456789-1759472021-02-04T01:26:36Z Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite Nikonkov, R.V. Stachowiak, P. Jeżowski, A. Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) The preliminary results of investigations of heat transfer in nanocomposites consisting of nanoparticles randomly distributed in solid carbon monoxide matrix are presented. In the experiment the thermal conductivity coefficient dependence on temperature for CO crystal with silica and palladium nanoparticles of different size embedded in the crystal structure was determined over the temperature range 2.2–35 K by steady-state heat flow method. The results of the measurements were analyzed within the frame of relaxation time approximation. The analysis shows that lowering of the thermal conductivity of the nanocomposites relative to pure carbon monoxide crystal observed for both types of the investigated nanoparticles, palladium and silica, is caused mostly by scattering of phonons by boundaries of the nanoparticles. Additionally, the presence of the nanoinclusions promotes higher density of dislocations and influences the matrix lattice dynamics. Наведено попередні результати досліджень теплопереносу в нанокомпозитах, які містять наночастинки, що випадково розподілені у твердій матриці монооксиду вуглецю. Методом стаціонарного теплового потоку в температурному інтервалі 2,2–35 К визначено експериментальні залежності коефіцієнта теплопровідності від температури для кристалевого СО, що містить наночастинки оксиду кремнію та паладію різних розмірів. Результати вимірювань проаналізовано в рамках апроксимації часу релаксації. Аналіз показує, що зниження теплопровідності нанокомпозитів щодо чистого кристала монооксиду вуглецю, яке спостерігається для досліджених наночастинок паладію та оксиду кремнію, обумовлено головним чином розсіюванням фононів на границях наночастинок. Крім того, наявність нановключень сприяє більш високій щільності дислокацій і впливає на динаміку гратки матриці. Приведены предварительные результаты исследований теплопереноса в нанокомпозитах, содержащих наночастицы, случайным образом распределенные в твердой матрице монооксида углерода. Методом стационарного теплового потока в температурном интервале 2,2–35 К определены экспериментальные зависимости коэффициента теплопроводности от температуры для кристаллического СО, содержащего внедренные наночастицы оксида кремния и палладия различных размеров. Результаты измерений проанализированы в рамках аппроксимации времени релаксации. Анализ показывает, что понижение теплопроводности нанокомпозитов относительно чистого кристалла монооксида углерода, наблюдаемое для исследуемых наночастиц палладия и оксида кремния, обусловлено главным образом рассеянием фононов на границах наночастиц. Кроме того, наличие нановключений способствует более высокой плотности дислокаций и влияет на динамику решетки матрицы. 2019 Article Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite / R.V. Nikonkov, P. Stachowiak, A. Jeżowski // Физика низких температур. — 2019. — Т. 45, № 3. — С. 289-293. — Бібліогр.: 14 назв. — англ. 0132-6414 http://dspace.nbuv.gov.ua/handle/123456789/175947 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) |
| spellingShingle |
Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) Nikonkov, R.V. Stachowiak, P. Jeżowski, A. Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite Физика низких температур |
| description |
The preliminary results of investigations of heat transfer in nanocomposites consisting of nanoparticles randomly distributed in solid carbon monoxide matrix are presented. In the experiment the thermal conductivity coefficient dependence on temperature for CO crystal with silica and palladium nanoparticles of different size embedded in the crystal structure was determined over the temperature range 2.2–35 K by steady-state heat flow
method. The results of the measurements were analyzed within the frame of relaxation time approximation. The
analysis shows that lowering of the thermal conductivity of the nanocomposites relative to pure carbon monoxide crystal observed for both types of the investigated nanoparticles, palladium and silica, is caused mostly by
scattering of phonons by boundaries of the nanoparticles. Additionally, the presence of the nanoinclusions promotes higher density of dislocations and influences the matrix lattice dynamics. |
| format |
Article |
| author |
Nikonkov, R.V. Stachowiak, P. Jeżowski, A. |
| author_facet |
Nikonkov, R.V. Stachowiak, P. Jeżowski, A. |
| author_sort |
Nikonkov, R.V. |
| title |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| title_short |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| title_full |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| title_fullStr |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| title_full_unstemmed |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| title_sort |
influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite |
| publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| publishDate |
2019 |
| topic_facet |
Спеціальний випуск. “Proceedings of 12th International Conference on Cryocrystals and Quantum Crystals (CC-2018)” (Wrocław, Poland, August 26–31, 2018) |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/175947 |
| citation_txt |
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite / R.V. Nikonkov, P. Stachowiak, A. Jeżowski // Физика низких температур. — 2019. — Т. 45, № 3. — С. 289-293. — Бібліогр.: 14 назв. — англ. |
| series |
Физика низких температур |
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2025-07-15T13:33:25Z |
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2025-07-15T13:33:25Z |
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1837720043294556160 |
| fulltext |
Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3, pp. 289–293
Influence of different nanoparticles embedded
in crystalline carbon monoxide matrix on heat transfer
in the nanocomposite
R.V. Nikonkov, P. Stachowiak, and A. Jeżowski
Institute for Low Temperature and Structure Research, Polish Academy of Sciences,
PN 1410, 50-950 Wroclaw, Poland
E-mail: r.nikonkov@intibs.pl
Received October 24, 2018
The preliminary results of investigations of heat transfer in nanocomposites consisting of nanoparticles ran-
domly distributed in solid carbon monoxide matrix are presented. In the experiment the thermal conductivity co-
efficient dependence on temperature for CO crystal with silica and palladium nanoparticles of different size em-
bedded in the crystal structure was determined over the temperature range 2.2–35 K by steady-state heat flow
method. The results of the measurements were analyzed within the frame of relaxation time approximation. The
analysis shows that lowering of the thermal conductivity of the nanocomposites relative to pure carbon monox-
ide crystal observed for both types of the investigated nanoparticles, palladium and silica, is caused mostly by
scattering of phonons by boundaries of the nanoparticles. Additionally, the presence of the nanoinclusions pro-
motes higher density of dislocations and influences the matrix lattice dynamics.
Keywords: nanocomposite, thermal conductivity, phonon relaxation.
Introduction
For the recent two decades nanosize and nanostructured
objects are focus of tremendous scientific interest. The rea-
son for the interest is twofold: application motivated and
purely cognitive. The nanoobjects usually show very differ-
ent physical properties from those observed for their macro-
scopic counterparts. Some of the new properties make them
successfully utilizable in designing new devices or enhanc-
ing parameters of already produced ones. Since prevailing
majority of the devices work at ambient or higher tempera-
tures, the application motivated investigations of the proper-
ties of the nanostructures are mostly carried out in this tem-
perature region, see, e.g., [1–3]. The interest towards the
nanosize and nanostructured objects motivated by scientific
curiosity is directly related to their exceptional physical
properties and the investigations are carried out in wider
temperature range. On the wave of the nano-boom a lot of
theoretical works which try to describe and explain physical
phenomena in the nano-world have been done. Some of
them are devoted to analysis of vibrations of a crystalline
lattice in which nanosize particles were embedded. It
turned out, for example, that the effect of interaction of the
lattice vibrations with an individual nanoparticle strongly
depends on the shape of the nanoparticle, its material and
the ratio of the linear dimensions to the wave length [4–6].
Also the presence of numerous nanoparticles in a crystal-
line medium and hence effects of multiple or dependent
(correlated) elastic scattering of phonons by the nanoparti-
cles may affect the velocity and density of state of phonons
as well as influences the mean free path of phonons in not
a trivial way [7]. Additionally, the effects of both multiple
and dependent scattering increase with increasing volume
fraction of nanoparticles [7]. The mentioned above as well
as possibly other effects should influence, among other
physical properties, the heat transfer in a crystal with na-
noparticles embedded in its structure. In spite of numerous
investigations of nanoscale transport related problems, see,
e.g., [8] and references therein, the problem of interaction
of crystalline matrix phonons with foreign inclusions fea-
turing linear parameters comparable to the phonon wave
length, remains far from being understood.
In the current paper we present our preliminary results
of experimental investigations of the thermal conductivity
of model nanocomposites obtained from nanoparticles of
silica and palladium embedded in the crystalline matrix of
carbon monoxide. In our experiment the nanoparticles em-
bedded in the matrix made up relatively high fraction of
© R.V. Nikonkov, P. Stachowiak, and A. Jeżowski, 2019
R.V. Nikonkov, P. Stachowiak, and A. Jeżowski
the volume of the sample. The experiment was carried out
on a number of samples containing nanoparticles of different
mean linear dimensions. The choice of the nanocomposite
constituents was dictated by relative simplicity both of the
carbon monoxide matrix and the SiO2 and Pd nanopowders.
Here, it also should be emphasized that solid CO, belonging
to the so-called N2 type solids, is very well-known dielectric
crystal.
At equilibrium vapor pressure solid CO appears, de-
pending on the temperature, in one of two structural phas-
es. In the temperature range 61.57–68.09 K the CO crystal
shows a structure in which the linear molecules precess
over their mass centers located in an hcp lattice nodes. This
is the so-called β-phase of the crystal. At 61.57 K the crys-
tal undergoes a structural phase transition: below this tem-
perature it exists in orientationally-ordered fcc structure,
known as the α-phase. The axes of the molecules are ori-
ented along space diagonals of the elementary cubic cell.
Due to the asymmetry of CO molecule, the molecules are
displaced a little from the regular lattice positions. This
structure belongs to the space group P213 [9]. Despite nu-
merous theoretical propositions [9], an existence of a low-
temperature phase of long-range ordering of carbon mon-
oxide dipoles in the α-phase was not confirmed. To the
contrary, almost all experiments carried out so far have
indicated disordering of the molecules down to tempera-
tures below 1 K. Such a glassy state in the dipole subsys-
tem of orientationally ordered phase of the CO crystal is
also seen in the thermal conductivity of the crystal [10].
Experiment
In our experiment the thermal conductivity of cryocrystal
nanocomposites was determined by steady-state heat flow
method in the temperature range from 2.2 to 35 K. The
methodology of the measurement and its technical aspect
have been described in details in our previous paper [11].
The central part of the experimental setup was an am-
poule made from glass tube of an inner diameter of 6 mm, a
wall thickness of 1 mm and a length of 50 mm. To the ends
of the tube two caps made of copper were fixed with epoxy
and two germanium resistance thermometers spaced 10 mm
from each other were glued to the cell cylindrical wall. The
lower one was mounted 10 mm above the bottom of the
ampoule. To the top cap an electric gradient heater was at-
tached. Through the cap a thin-wall stainless steel capillary
ran. The capillary allowed to pump out the cell or fill it with
carbon monoxide gas and thermal exchange gaseous helium.
During the experiment the bottom cap rested in a copper
base of controlled temperature.
For obtaining the nanocomposite samples, gaseous car-
bon monoxide of 99.999% purity and amorphous silica ox-
ide as well as amorphous palladium nanoparticles of differ-
ent size were used. The SiO2 nanopowders featured
nanoparticles of linear dimension of about 5, 18, 42, 162 nm
while the Pd nanoparticles — 6, 8, 10, 12, 18 and 24 nm.
The nanoparticle volume fraction in the investigated samples
(the ratio of the volume taken by the nanoparticle to the vol-
ume of the sample) was approximately 7% for CO–SiO2 and
14% for CO–Pd nanocomposites, regardless of the linear
dimension of the nanoparticles. The volume fraction was
determined by precise weighting of the nanopowder filling
the volume of the ampoule.
For each sample the powder was placed inside the cell
to fully fill the tube after the bottom cap was fixed to the
ampoule. Then the upper cap was also glued and the as-
sembled cell was installed in the measuring chamber of the
cryostat. At the beginning of the experiment the tempera-
ture of the cell was lowered to a little bit above the triple
point temperature of carbon monoxide and the gas was let
to the cell, whereupon the condensation to its liquid phase
began. During the condensation the temperature of the up-
per part of the cell was maintained a few Kelvins higher
than the temperature of the bottom so that the liquid gradu-
ally filled the cell from its bottom to the top. Finally, the
temperature of the bottom of the ampoule was slowly low-
ered — the liquid solidified forming carbon monoxide SiO2
or carbon monoxide Pd cryocrystal nanocomposite. Cooling
rate during the crystal growth was 3 K/h. After crystalliza-
tion the nanocomposite was cooled down to the tempera-
ture of the thermal conductivity measurement at the cool-
ing rate of 6 K/h.
In the process of determination of the thermal conduc-
tivity two distorting factors were taken into account: (i) the
parasitic temperature gradient being a result of the heat
radiation due to the temperature mismatch of the LHe
thermal shield of the measuring cell and the sample and
(ii) the heat transported by the cell glass wall. To determine
the first one, the measurements of the parasitic temperature
gradient was carried out at various temperatures for each of
the samples. As for the second one, the measurement of the
dependence of the thermal conductivity coefficient of empty
cell was performed in a separate experiment.
The random error of the thermal conductivity measure-
ment at low temperatures did not exceed 1.5%, whereas
above 20 K it increased to 3%, mostly due to effects con-
nected with spurious heat leaks. The systematic error did not
exceed 3%.
Results
Figures 1 and 3 show our measurement results of the
dependences of the thermal conductivity coefficient k for
carbon monoxide based nanocomposites with palladium
spherical nano-admixtures and with silica nanoparticles of
different size on temperature. Both of the obtained families
of the temperature dependences of k dispaly the shape
typical for a dielectric crystal. Generally, impurities cause
a decreasing of total thermal conductivity of the investi-
gated nanocomposites when compared to pure crystal of
carbon monoxid [10].
290 Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite
The thermal conductivity of the nanocomposites depends
on the nanoparticles size and the dependence is not mono-
tonic. Initially the thermal conductivity decreases with in-
creasing nano-spheres diameter and after achieving certain
“critical” particles size, for which the phonon scattering
reaches its maximum (and the thermal conductivity reaches
its minimum), further increasing of particles size causes an
increase of samples thermal conductivity, see Figs. 2 and 4.
Here it should be noticed that for the samples with SiO2
nanoparticles the size-effect is clear however not as promi-
nent as for the CO–Pd nanostructure.
In all cases the thermal conductivity at higher tempera-
tures (T > 20 K) aspire to the same value, the value of the
thermal conductivity of pure CO crystal.
Taking into account that the characteristics of the used
nanoadmixtures (the type of the material, the linear dimen-
sions and the volume fraction) are strongly different from
each other and that their effect on the total thermal conduc-
tivity of the samples is similar (compare Figs. 2 and 4), one
can assume, that the material of the sample matrix gives
the decisive contribution to the thermal conductivity. The
impurities cause only some extra effects in the matrix.
Therefore, the results of the measurements were ana-
lyzed using the Callaway method [12]. In this approach
each mechanism of elastic scattering of phonons is repre-
sented by its characteristic relaxation time. The thermal
conductivity of a dielectric crystal can be written as a sum
1 2k k k= + , (1)
where
( )
/3 4
3
1 2 2
0
e
,
2 e 1
T x
CB B
x
xk kk T dx
v
θ τ =
π −
∫
(2)
Fig. 1. (Color online) Temperature dependences of thermal con-
ductivity of carbon monoxide nanocomposite with palladium
nanoparticles of different linear dimensions: 6 nm (), 8 nm (),
10 nm (), 12 nm () and 18 nm (). For the comparison purpose
the data for pure CO were also shown () [10]. Solid lines are ap-
proximations of the experimental data with the expression (10).
Fig. 2. The thermal conductivity (at the maximum of the thermal
conductivity curve) of carbon monoxide based nanocomposite as
a function of palladium nanoparticle size.
Fig. 3. (Color online) Thermal conductivity of carbon monoxide
nanocomposite with SiO2 nanoparticles of different linear dimen-
sions: 5 nm (), 18 nm (), 42 nm (), 162 nm ().
Fig. 4. The thermal conductivity (at the maximum of the thermal
conductivity curve) of CO-based nanocomposite as a function of
silica nano-inclusions size.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 291
R.V. Nikonkov, P. Stachowiak, and A. Jeżowski
and
( )
( )
2
/ 4
2
3 0
3
2 2 / 4
2
0
e
e 1
2 e
e 1
T x
C
xn
B B
T x
C
xn r
x dx
k kk T
v x dx
θ
θ
τ
τ − =
π τ
τ τ −
∫
∫
, (3)
where 4 2 3/ 2BG k v= π , / Bx k T= ω ; 103.3θ = K is Debye
temperature of carbon monoxide crystal, iτ is relaxation time
of phonon scattering, ( )( ) 1/33 32 / 3 1225.5l tv v v
−− − == + ms–1
is phonon propagation velocity averaged over longitudinal
lv and transversal tv polarizations [9], and ω is phonon
frequency.
Assuming additivity of the effects of scattering, the to-
tal relaxation rate 1
C
−τ may be written down as a sum of the
relaxation rates of the resistive 1
r
−τ and normal 1
n
−τ proc-
esses:
1 1 1
C r n
− − −τ = τ + τ , (4)
where
1 1 1 1 1
r b p d U
− − − − −τ = τ + τ + τ + τ (5)
and the quantities
1 b ba−τ = , (6)
1 4 4 p pa x T−τ = , (7)
1 d da xT−τ = , (8)
[ ]1 2 3
1 2 exp /U U Ua x T a T−τ = − (9)
are relaxation rates of phonon scattering by grain bounda-
ries, point defects, dislocation strain fields and three-phonon
U-processes, respectively.
As a matter of fact, normal processes are only signifi-
cant for the thermal conductivity of crystals of high quality
and at low temperatures [13]. Otherwise, the normal proc-
esses are much less frequent then other phonon scattering
processes and do not contribute noticeably to the dielectric
crystal heat transfer. Therefore, for strongly defected crys-
tal, 1
n
−τ can be neglected and then the Eq. (1) reduces to the
so-called expression of Debye:
( )
/3 4
3
2 2
0
e
2 e 1
T x
CB B
x
xk kk T dx
v
θ τ =
π −
∫
. (10)
We have fitted the Debye equation, by varying ia pa-
rameters of relaxation times (6)–(9), to the experimentally
obtained data of the thermal conductivity temperature de-
pendence of the nanocomposites. The results of the best
match for samples of solid CO containing palladium nano-
particles were shown in Fig. 1 by solid black lines and the
parameters were collected in Table 1. The same information,
displayed in the same way, for the CO crystal with silica
nanoparticles embedded in its structure was given in Fig. 3
and Table 2.
Table 1. Best fit phonon relaxation rate parameters obtained
by Debye equation for the CO crystals containing palladium
nanoparticles. In the fitting procedure scattering of phonons by
crystal grain boundaries (ab), point defects (ap), dislocation strain
fields (ad) and by phonons in U-processes (aU1, aU2) were taken
into account
Nanocomposite
Parameter
ab ap ad aU1 aU2
CO+Pd (6 nm) 5.61·108 1.31·104 2.23·106 1.27·107 19.9
CO+Pd (8 nm) 3.55·109 1.83·104 1.00·106 6.07·106 6.0
CO+Pd (10 nm) 3.14·108 1.11·104 1.79·107 1.08·107 18.0
CO+Pd (12 nm) 3.09·108 1.17·104 2.93·106 1.11·107 21.2
CO+Pd (18 nm) 1.67·108 1.27·104 3.08·105 9.87·106 21.1
Table 2. Values of the parameters ab, ap, ad, aU1, aU2 of equa-
tion (10), for which the experimentally obtained dependence of
the thermal conductivity of the investigated nanocomposites is
best approximated
Nanocomposite
Parameter
ab ap ad aU1 aU2
Pure CO 2.47·104 3.81·104 1.21·104 7.27·106 32.8
CO+SiO2 (5 nm) 1.88·108 1.78·104 1.82·106 1.91·107 25.6
CO+SiO2 (18 nm) 1.85·108 2.09·104 2.02·105 1.03·107 26.2
CO+SiO2 (42 nm) 2.92·108 2.81·104 2.72·106 1.33·107 24.1
CO+SiO2 (162 nm) 1.81·108 3.54·104 6.35·106 2.05·107 26.6
The solid lines in Figs. 1 and 3 show that the approxima-
tion of the experimental data with the applied thermal con-
ductivity model is satisfactory. Therefore one can get some
information from the analysis of the numerical values dis-
played in Tables 1 and 2. First of all, it should be noticed
that the effect of introduction of the nanoparticle into the
structure of carbon monoxide crystalline matrix on phonon
relaxation rates is qualitatively the same for both investi-
gated nano-powders, palladium and silica. The most promi-
nent effect is observed for scattering of phonons by grain
boundaries. While for pure CO crystal 1 4~ 10b
−τ s–1, for the
nano-powder doped ones 1 8~ 10b
−τ s–1. Such tremendous
increase of frequency of phonon scattering in this mecha-
nism should be understood as not caused by structural grain
boundaries but rather diffuse scattering of phonons by
boundary of the two media: carbon monoxide and palladium
or silica. Point defect (Rayleigh) scattering is almost insensi-
tive to the presence of the nanoparticles. This is because the
nanoparticles can act as point defect only for long-wave
phonons which do not contribute noticeably to the thermal
292 Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3
Influence of different nanoparticles embedded in crystalline carbon monoxide matrix on heat transfer in the nanocomposite
conductivity, at least in the investigated temperature re-
gion. The significant increase of da for the nanoparticles
doped crystal relatively to the pure solid CO indicates that
the presence of the nano-powders promotes creation of
dislocations. Finally, the difference of 1Ua and 2Ua param-
eters, between those obtain for pure carbon monoxide crys-
tal and the investigated nanocomposites, may be related to
the difference of pure and doped matrix lattice dynamics.
Since 1Ua is considered as a measure of phonon interaction
strength [14], the parameter bigger for the nanocomposite
testify to higher anharmonicity of the lattice vibration while
smaller 2Ua (being a measure of mean energy of a phonon
taking part in U-process) to lowering of the maximum fre-
quency vibrations of the matrix in such nanocomposites.
In conclusion, nanocomposites built from carbon mon-
oxide crystal with amorphous silica and palladium nano-
powders of different size embedded in the crystal structure
were obtained and determined their thermal conductivity
coefficient dependence on temperature in the temperature
range 2.2–35 K. Nano-impurities in the crystal cause a de-
creasing of total thermal conductivity of investigated nano-
composites compared to the pure crystal of carbon monox-
ide. Analysis of the experimental results shows that the
material of the sample matrix gives the decisive contribution
to the thermal conductivity and that the low thermal conduc-
tivity of the nanocomposites is caused mostly by scattering
of phonons by boundaries of the nanoparticles.
Acknowledgments
This work was supported by the National Science Centre
(Poland) grant nr. UMO-2013/08/M/ST3/00934.
_______
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Вплив наночастинок, введених в кристалічну
матрицю монооксиду вуглецю, на теплопереніс
в нанокомпозиті
R.V. Nikonkov, P. Stachowiak, A. Jeżowski
Наведено попередні результати досліджень теплоперено-
су в нанокомпозитах, які містять наночастинки, що випадко-
во розподілені у твердій матриці монооксиду вуглецю. Ме-
тодом стаціонарного теплового потоку в температурному
інтервалі 2,2–35 К визначено експериментальні залежності
коефіцієнта теплопровідності від температури для кристале-
вого СО, що містить наночастинки оксиду кремнію та пала-
дію різних розмірів. Результати вимірювань проаналізовано в
рамках апроксимації часу релаксації. Аналіз показує, що
зниження теплопровідності нанокомпозитів щодо чистого
кристала монооксиду вуглецю, яке спостерігається для дос-
ліджених наночастинок паладію та оксиду кремнію, обумов-
лено головним чином розсіюванням фононів на границях
наночастинок. Крім того, наявність нановключень сприяє
більш високій щільності дислокацій і впливає на динаміку
гратки матриці.
Ключові слова: нанокомпозит, теплопровідність, фононна
релаксація.
Влияние наночастиц, введенных
в кристаллическую матрицу монооксида углерода,
на теплоперенос в нанокомпозите
R.V. Nikonkov, P. Stachowiak, A. Jeżowski
Приведены предварительные результаты исследований
теплопереноса в нанокомпозитах, содержащих наночастицы,
случайным образом распределенные в твердой матрице мо-
нооксида углерода. Методом стационарного теплового пото-
ка в температурном интервале 2,2–35 К определены экспе-
риментальные зависимости коэффициента теплопроводности
от температуры для кристаллического СО, содержащего вне-
дренные наночастицы оксида кремния и палладия различных
размеров. Результаты измерений проанализированы в рамках
аппроксимации времени релаксации. Анализ показывает, что
понижение теплопроводности нанокомпозитов относительно
чистого кристалла монооксида углерода, наблюдаемое для
исследуемых наночастиц палладия и оксида кремния, обу-
словлено главным образом рассеянием фононов на границах
наночастиц. Кроме того, наличие нановключений способст-
вует более высокой плотности дислокаций и влияет на дина-
мику решетки матрицы.
Ключевые слова: нанокомпозит, теплопроводность, фонон-
ная релаксация.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2019, v. 45, No. 3 293
https://doi.org/10.1021/nl8031982
https://doi.org/10.1103/PhysRevB.84.035438
https://doi.org/10.1103/PhysRevB.84.035438
https://doi.org/10.1126/science.1156446
https://doi.org/10.1063/1.2188251
https://doi.org/10.1103/PhysRevB.9.4422
https://doi.org/10.1016/j.ijheatmasstransfer.2005.04.034
https://doi.org/10.1115/1.2194036
https://doi.org/10.1063/1.4832615
https://doi.org/10.1016/j.ssc.2014.07.020
https://doi.org/10.1016/j.ssc.2014.07.020
https://doi.org/10.1063/1.4922106
https://doi.org/10.1063/1.4922106
https://doi.org/10.1103/PhysRev.113.1046
https://doi.org/10.1103/PhysRevB.29.2709
Introduction
Experiment
Results
Acknowledgments
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