The Selection of Azeotropes at Ambient Pressure Drying of Aerogels
The representation of phase states in the multicomponent systems by graphical images is used for estimation of the LV (xL = xV) azeotrope influence on SLV and L = V equilibria. These theoretical investigations occurred from complications arising at an ambient pressure drying (APD) synthesis of trans...
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| Опубліковано в: : | Наносистеми, наноматеріали, нанотехнології |
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| Дата: | 2010 |
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Інститут металофізики ім. Г.В. Курдюмова НАН України
2010
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels / G.D. Nipan, O.A. Mykaylo, Young-Jei Oh // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2010. — Т. 8, № 3. — С. 701-712. — Бібліогр.: 15 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860189980174843904 |
|---|---|
| author | Nipan, G.D. Mykaylo, O.A. Young-Jei Oh |
| author_facet | Nipan, G.D. Mykaylo, O.A. Young-Jei Oh |
| citation_txt | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels / G.D. Nipan, O.A. Mykaylo, Young-Jei Oh // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2010. — Т. 8, № 3. — С. 701-712. — Бібліогр.: 15 назв. — англ. |
| collection | DSpace DC |
| container_title | Наносистеми, наноматеріали, нанотехнології |
| description | The representation of phase states in the multicomponent systems by graphical images is used for estimation of the LV (xL = xV) azeotrope influence on SLV and L = V equilibria. These theoretical investigations occurred from complications arising at an ambient pressure drying (APD) synthesis of transparent and crackfree bulk silica aerogels. During the empiric selection of azeotropic mixtures, the negative azeotropes advantage over positive ones for this goal is determined and substantiated in theory. As shown, the forecast must base not only on the critical points of components (L = V), in which liquid and vapour become indistinguishable, but also on the triple points of components (SLV–crystal—liquid—vapour). Using the P—T—x phase diagrams, the prediction of ways to reach a supercritical region at the ambient pressure is done. A good agreement between the theoretical results and experimental data is revealed.
Представлення фазових рівноваг у багатокомпонентних системах методою графічного зображення використовувалося для оцінки впливу азеотропу LV (xL = xV) на рівноваги SLV та L = V. Дані теоретичні дослідження виконувалися через виникнення ускладнень при синтезі прозорих і бездефектних кремнійових аероґелів способом атмосферного сушіння (APD). При емпіричному відборі азеотропних сумішей було визначено і теоретично обґрунтовано перевагу використання неґативних азеотропів над позитивними задля зазначеної мети. Показано, що прогноза має бути основаною не лише на критичних точках компонентів L = V, в яких рідина і пар стають нерозрізненними, але й на потрійних точках компонентів SLV (кристал—рідина—пар). У даній роботі з використанням P—T—x-фазових діяграм показано можливість досягнення надкритичної области за атмосферного тиску. Виявлено хорошу відповідність між теоретичними та експериментальними результатами.
Представление фазовых равновесий в многокомпонентных системах методом графического изображения использовано для оценки влияния азеотропа LV (xL = xV) на равновесия SLV и L = V. Данные теоретические исследования выполнялись по причине возникновения сложностей при синтезе прозрачных и бездефектных кремниевых аэрогелей способом атмосферной сушки (APD). При эмпирическом отборе азеотропных смесей определено и теоретически обосновано преимущество использования негативных азеотропов над позитивными для этой цели. Показано, что прогноз должен быть основан не только на критических точках компонентов L = V, в которых жидкость и пар становятся неразличимыми, но и
на тройных точках компонентов SLV (кристалл—жидкость—пар). В данной работе с использованием P—T—x-фазовых диаграмм показана возможность достижения сверхкритической области при атмосферном давлении. Обнаружено хорошее соответствие между теоретическими и экспериментальными результатами.
|
| first_indexed | 2025-12-07T18:05:24Z |
| format | Article |
| fulltext |
701
PACS numbers:05.70.Ce, 64.60.F-,64.75.Cd,64.75.Jk,81.05.Rm,81.30.Dz, 82.70.Gg
The Selection of Azeotropes at Ambient Pressure Drying
of Aerogels
G. D. Nipan, O. A. Mykaylo*,**, and Young-Jei Oh**
Kurnakov Institute of General and Inorganic Chemistry, R.AS.,
Leninskii Prospekt, 31,
119991 Moscow, Russian Federation
*Uzhgorod National University,
Institute for Solid State Physics and Chemistry,
Pidhirna Str., 46,
88000 Uzhgorod, Ukraine
**Materials Science and Technology Division,
Korea Institute of Science and Technology,
Seoul, 136-791, Korea
The representation of phase states in the multicomponent systems by graphical
images is used for estimation of the LV (xL = xV) azeotrope influence on SLV and
L = V equilibria. These theoretical investigations occurred from complications
arising at an ambient pressure drying (APD) synthesis of transparent and crack-
free bulk silica aerogels. During the empiric selection of azeotropic mixtures, the
negative azeotropes advantage over positive ones for this goal is determined and
substantiated in theory. As shown, the forecast must base not only on the critical
points of components (L = V), in which liquid and vapour become indistinguisha-
ble, but also on the triple points of components (SLV–crystal—liquid—vapour).
Using the P—T—x phase diagrams, the prediction of ways to reach a supercritical
region at the ambient pressure is done. A good agreement between the theoreti-
cal results and experimental data is revealed.
Представлення фазових рівноваг у багатокомпонентних системах мето-
дою графічного зображення використовувалося для оцінки впливу азеот-
ропу LV (xL = xV) на рівноваги SLV та L = V. Дані теоретичні дослідження
виконувалися через виникнення ускладнень при синтезі прозорих і без-
дефектних кремнійових аероґелів способом атмосферного сушіння (APD).
При емпіричному відборі азеотропних сумішей було визначено і теорети-
чно обґрунтовано перевагу використання неґативних азеотропів над по-
зитивними задля зазначеної мети. Показано, що прогноза має бути осно-
ваною не лише на критичних точках компонентів L = V, в яких рідина і
пар стають нерозрізненними, але й на потрійних точках компонентів SLV
(кристал—рідина—пар). У даній роботі з використанням P—T—x-фазових
Наносистеми, наноматеріали, нанотехнології
Nanosystems, Nanomaterials, Nanotechnologies
2010, т. 8, № 3, сс. 701—712
© 2010 ІМФ (Інститут металофізики
ім. Г. В. Курдюмова НАН України)
Надруковано в Україні.
Фотокопіювання дозволено
тільки відповідно до ліцензії
702 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
діяграм показано можливість досягнення надкритичної области за атмо-
сферного тиску. Виявлено хорошу відповідність між теоретичними та ек-
спериментальними результатами.
Представление фазовых равновесий в многокомпонентных системах ме-
тодом графического изображения использовано для оценки влияния
азеотропа LV (xL = xV) на равновесия SLV и L = V. Данные теоретические
исследования выполнялись по причине возникновения сложностей при
синтезе прозрачных и бездефектных кремниевых аэрогелей способом ат-
мосферной сушки (APD). При эмпирическом отборе азеотропных смесей
определено и теоретически обосновано преимущество использования
негативных азеотропов над позитивными для этой цели. Показано, что
прогноз должен быть основан не только на критических точках компо-
нентов L = V, в которых жидкость и пар становятся неразличимыми, но и
на тройных точках компонентов SLV (кристалл—жидкость—пар). В дан-
ной работе с использованием P—T—x-фазовых диаграмм показана воз-
можность достижения сверхкритической области при атмосферном дав-
лении. Обнаружено хорошее соответствие между теоретическими и экс-
периментальными результатами.
Key words: nanostructures, sol—gel synthesis, azeotrope, critical point.
(Received 20 September, 2010)
1. INTRODUCTION
The remarkable material, nanostructure silica aerogel, was first created
by S. Kistler in 1931 [1] but saw just a little development for these years.
Wide applications of this material that possess high specific surface ar-
ea, high porosity, low density, low dielectric constant, and excellent
heat insulation properties [2, 3], terminates complications of its produc-
tion. There are many research works concerning aerogel properties and
manufacture. The most attention is paid to drying of aerogels to make
the production of these materials more profit making.
Common procedure for transparent silica aerogels production in our
case included two-step sol—gel process using tetraethyl orthosilicate
(TEOS) (Aldrich, USA), as a silica precursor and isopropanol (Junsei, Ja-
pan) as a solvent. Isopropanol was exchanged than with n-butanol (Jun-
sei), and the gel surface was modified using 5% volume solution of tri-
methylchlorosilane (TMCS) (Alfa Aesar) in n-butanol. Next, the solvent
was exchanged in some steps with binary azeotropes like pore fluids.
Actually, the process of aerogels obtaining by azeotropic mixtures
evaporation on the final stages of ambient pressure drying has not been
reported in the literature. Authors [4] used the water—ethanol azeo-
trope as the solvent just in prime stage of synthesis for the production
of low-density silica gel. This material was prepared by the classical
two-step sol—gel method developed by Deshpande, Brinker and Scherer
THE SELECTION OF AZEOTROPES AT AMBIENT PRESSURE DRYING OF AEROGELS703
[5, 6], which includes the ambient pressure drying stage. This process
demonstrated the existence a greater total pore volumes and more
mesopores > 50 Å in samples in comparison with the supercritical dry-
ing one. The main purpose of the azeotrope using [7] was to bind water
inside pores after sol—gel process, because their appearance finally
leads to increasing of the capillary pressure and then, during the
thermal drying, to the cracking of aerogels.
Authors of [8] used azeotrope mixtures of water and n-butanol-
saturated hydrocarbon (hexane, heptane, octane or nonane) for the
first time on the stage of washing. In three steps, gels were washed
successively with a 3:1 mixture of n-butanol and a saturated hydrocar-
bon, with a 1:1 mixture of n-butanol and a saturated hydrocarbon, fi-
nally, with only the saturated hydrocarbon. Per se, they had used azeo-
trope water, which necessarily remains inside of aerogel pores after
sol—gel process. Further, in the process of the choice of other suitable
azeotropic mixtures, first we could attempt to predict ways to get in a
supercritical region at ambient pressure. Physical properties data of
azeotropic mixtures were given from Azeotrope Databank by J. W.
Ponton and by book of John A. Dean [9]; we used the results of investi-
gations of the negative azeotrope for the methanol—propanal system in
the methanol-rich region [10].
2. THEORY
This prediction was made using the well-known method of the phase di-
agrams, which is the graphical representation of the equilibria between
the thermodynamically distinct phases. The main design principles were
created by Van der Waals [11]. Then, this method was highly developed
and it is a very powerful tool for predicting the state of a system under
different conditions [12]. It was determined with the accumulation of
experimental material that the prognosis can be based not only on the
critical points of components, in which liquid and vapour become indis-
tinguishable, but also on the triple points of components at which three
phases (solid, liquid and vapour) of that substance coexist in thermody-
namical equilibrium. In most cases, the phenomenon of azeotropy [13] is
examined only within the framework of the liquid—vapour equilibrium
LV and its characteristic features. Usually, there are extremes on the T—
x isobars of the boiling or on P—x isotherms of the evaporation. In addi-
tion, the interaction between azeotropic and solid—liquid equilibria SL
for several binary organic systems was investigated [14]. It was just the
partial investigations, but for the extensions of thermodynamic models,
a reliable knowledge of the phase equilibria behaviour as a whole is re-
quired. The experimental determination of the gas solubility in the liq-
uid phase along the SLV solid—liquid—vapour equilibrium line of some
binary system was established, and these data plotted as P—T and T—x
704 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
projections of the SLV-equilibrium line [15].
However, within the framework of the P—T—x-phase diagram of the
binary systems (where P–pressure, T–temperature, x–an independ-
ent co-ordinate of composition), the contiguity line of liquid L and va-
pour V surfaces corresponds to the LV azeotrope (more precisely
xL = xV). This line does not need to be a straight line; furthermore, it is
a segment, limited from one side by the surface of SLV monovariant
equilibrium of crystal—liquid—vapour, and from the other side, in the
simplest case, by the L = V curve, connecting the critical points of pure
components. The most obvious case relates to the P—T projection of P—
T—x phase diagram. If layering of liquid and equilibrium with partici-
pation of the crystalline phase and fluid is absent, the azeotrope xL = xV
is enclosed between VLS (SLV) and L = V lines (see Fig. 1). Certainly,
the presence of azeotrope influences VLS (SLV) and L = V line shapes.
From the other side, the existence of extremes on these lines is neces-
sary, but insufficient condition for existence of the azeotrope. We
would set constant P, T co-ordinates for the triple and critical points of
components A and B, and examine the interrelation of the azeotrope
xL = xV on the SL monovariant line and the L = V critical curve.
3. RESULTS AND DISCUSSION
We can use, for the convenience, P—T projections and T—x key isobaric
sections for the analysis of different variants. We should take into the
consideration the fact that order of phases at the heterogeneous equi-
libria is very important and agree that it will be certain increase of the
B component content.
I. The positive azeotrope appears in the A—B system and components
are mutually soluble without restriction in all of phase states.
A and B triple points for pure components, also KA and KB critical
points are marked on the P—T projection (Fig. 1, a). The positions of
critical points are specially chosen [11].
AKA and BKB lines correspond to evaporation of liquids based on pure
components. Lines going out from A and B points straight up to the di-
rection of high temperatures represent the melting, and the ones move
away to the direction of low temperatures correspond to the sublimation
of crystals based on pure components. The AB curve is the only mono-
variant line of binary system and consists of two parts: ANLV, with the
LVS order of phases, and BNLV, with the VLS order of ones. In the NLV
conditional non-variant point, being near to Pmax, a maximum of pres-
sure of the monovariant curve, compositions of liquid and vapour are
identical, and from it, the xL = xV line of azeotrope begins, which is
stopped in the KAZ critical point placed near-by a maximum of pressure
of the KAKB critical curve.
Dashed lines on the P—T projection (Fig. 1, a) are imaged isobars and
THE SELECTION OF AZEOTROPES AT AMBIENT PRESSURE DRYING OF AEROGELS705
their proper T—x isobaric sections (Fig. 1, b). Let us consider six key
isobars.
1. There is only the sublimation of the continuous solid solution S at
P1 < PB and, in the same time, vapour V enriched by the B component.
2. The solid solution S begins to melt from the PB < P2 < PA interval at
constant pressures, area of liquid L, enriched by the B component, appears
on the T—x section and the node of the VLS three-phase equilibrium arises.
3. Due to the melting of the solid solution on basis of the A compo-
Fig. 1.
706 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
nent, the second local area of liquid L and another LVS node appear in
PA < P3 < PNLV interval.
4. Finally, typical T—x isobars for positive azeotropes with a mini-
mum of the pressure in the LV equilibrium appear at PNLV < P4 < PKA.
5. With the further increasing of pressure, fluid F appears at the
beginning, for compositions enriched by the A component in the inter-
val PKB < P5 < PKAZ.
6. Then, fluid F appears for compositions enriched by the B compo-
nent under achievement the PKB < P6 < PKAZ interval of pressure.
Further, with the growth of pressure, areas of fluids extend, but,
firstly, the minimum disappears at PKAZ, and then, at Pmax, the equilibri-
um LV disappears for KAKB, and the area of fluid F becomes continuous.
Evidently, in the case of positive-azeotropes using, it is possible to
reach the fluid area only at pressures higher than P of the critical points
of constituent components.
II. The positive azeotrope appears in the A—B system and components
restrictedly mutually soluble in the crystalline state.
It should be noted that triple and critical points for pure components
remain on the P—T projection (Fig. 2, a), and, accordingly, some lines
are stored too: the evaporation, the melting and the sublimation lines
for pure components, and the KAKB critical curve. There are four mono-
variant lines: SALV, VLSB, SAVSB, and SALSB appeared in place of one
monovariant line of the two-component system. The mutual solubility in
the crystalline state is insignificant; therefore, vapour pressure in the
SAVSB equilibrium is an additive summation of vapour pressures for
pure components. The invariant equilibrium in the N(SAVLSB) point has
the eutectic character and the xL = xV azeotrope line starts in the NLV in-
variant point on the AN line. There is the change of the order phases
SALV ⇔ SAVL in the NLV point, which is near-by a maximum of the pres-
sure. We can analyse T—x-isobar sections (Fig. 2, b).
Similar to the previous case (Fig. 1, a), the dashed lines mark isobars
on the P—T projection, and their T—x-isobaric sections are resulted on
(Fig. 2, b).
1. There is only the sublimation of the SA and SB limited solid solu-
tion at P1 < PB. There is the only SAVSB node.
2. The solid solution based on the B component begins melting at
constant pressures from the PB < P2 < PA interval and, accordingly, the
area of liquid L, enriched by the B component, appears on the T—x-
isobaric section. Furthermore, another node of the VLSB three-phase
equilibrium appears.
3. The second local area of liquid L, due to the melting of the solid
solution based on the A component, and the third node SALV appear in
the PA < P3 < PN interval.
4. Finally, SAVSB and VLSB equilibria disappear and SALSB and SAVL
ones appear in the PNLV < P4 < PKA interval due to the presence of the
THE SELECTION OF AZEOTROPES AT AMBIENT PRESSURE DRYING OF AEROGELS707
xL = xV azeotrope.
5. An interesting T—x isobar exists in a very narrow interval of pres-
sures. At the further increasing of the pressure in the PNLV < P5 < Pmax
interval, two nodes are realized with the same order of phases SALV, and
a minimum of the pressure appears in the LV divariant equilibrium.
6. Then, the T—x isobar acquires characteristic for the positive azeo-
tropes shape with a minimum of the pressure in the equilibrium at the
PNLV < P6 < PKA interval. Unlike the cross-section (Fig. 1, b, 6), fusion is
in the equilibrium not with the continuous solid solution, but with two
Fig. 2.
708 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
limited ones on basis of A and B components.
Further, the areas of fluids are broadening with the growth of the
pressure, and in the beginning, at PKAZ, a minimum disappears, and
then, at Pmax for KAKB, the LV equilibrium disappears, and the area of
fluid F becomes continuous.
Then, fluid F appears with growth of pressures for compositions en-
riched by the A component, then for compositions enriched by the B com-
ponent, and, finally, the area of fluid F becomes continuous (Fig. 1).
III. The negative azeotrope appears in the A—B system and components
mutually soluble without restriction in all of the phase states.
Existence of the negative azeotrope, in this case, is related to the
presence of a minimum of the pressure (Pmin) on the monovariant AB
curve [3]. More complex variant (Fig. 3, a), with Pmin and Tmax on the AB
curve has shown on P—T projection. The monovariant line consists of
three parts: ANLV with the VLS order of phases, NLVNSV with the LVS or-
der of ones, and BNSV with the LSV order of phases. Compositions of liq-
uid and vapour are identical in the NLV conditional invariant point, and
the xL = xV azeotrope line of the azeotrope begins from this point. Com-
positions of crystal and vapour are identical in the NSV conditional in-
variant point, and the xS = xV line of the congruent sublimation of crys-
tal begins from this point, get-away toward low pressures. The condition
of obligatory congruent sublimation of binary crystals explains the sta-
tistical predominance of positive azeotropes (Fig. 1), in which this con-
dition is absent, in the comparison with negative ones.
Let us consider key T—x isobars (Fig. 3, b, 1—6).
1. There is only the congruent sublimation of the continuous solid
solution S in the absence of liquid L at P1 < PNLV.
2. The local area of liquid L, capable to evaporate, appears from the
PNLV < P2 < PNSV interval at the constant pressures. At the same time,
there are two azeotropes: along with the congruent sublimation of the
solid solution S, there is the congruent evaporation of liquid L, richer
in the A component. There are the VLS and LVS nodes of the three-
phase equilibria.
3. The solid solution S halts the congruent sublimation in the
PNSV < P3 < PB interval, and for the high-temperature node, it changes
the order of phases to LSV on the T—x cross-section.
4. The pressure of the B triple point (PB < P4 < PA) is exceeded and
the area L spreads to the B component.
5. T—x-isobars with a minimum of pressure in the LV equilibrium,
characteristic for negative azeotropes, appear at PNLV < P5 < PKAZ.
6. The (T—x)6 isobar (PKAZ < P6 < PKA) holds the greatest interest, be-
cause fluid F appears in the wide interval of concentrations, at pres-
sures below the critical points pressures for pure components.
At the further increase of the pressure (PKA < P < PKB), fluid F first
spreads to the A component, and then, under reaching the P > PKB in-
THE SELECTION OF AZEOTROPES AT AMBIENT PRESSURE DRYING OF AEROGELS709
terval, the area of fluid becomes continuous.
The systems with the limited mutual solubility in the crystalline state
and the systems, in which compounds appear, are of particular interest.
IV. The negative azeotrope and the crystalline phase based on the AB
compound, which sublimates and melts congruently, appears in the A—B
system.
On the P—T projection (Fig. 4, a), except for the triple and critical
points for pure components, invariant points of eutectic equilibria are
Fig. 3.
710 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
present: N1 (VSALSAB) and N2 (SABLSBV), and NLV, NSV, NSL conditional
invariant points. Accordingly, the monovariant lines appear. Two of
them are co-sublimation of two crystalline phases VSASAB and SABSBV
(get-away toward low pressures from N1 and N2), also SALSAB and SABLSB
co-melting lines (vertical ones spreading toward high pressures from N1
and N2), and three lines of crystal—liquid—vapour: AN1 (VSAL), N1N2
(VLSAB) and BN2 (LSBV). The N1N2 monovariant line with the change of
phases order: VLSAB ⇔ VSABL ⇔ SABVL ⇔ SABLV in points NSL, NSV, and
NLV, from which xSAB = xL, xSAB = xV, and xL = xV azeotropes lines start, is
of particular interest.
Mutual solubility of A and B components in the crystalline state is
insignificant. We can consider T—x-isobaric sections (Fig. 4, b).
1. There is the incongruent sublimation of SA and SB limited solid
solutions, and the congruent sublimation of the SAB binary crystalline
phase at P1 < PN2. There two nodes exist: VSASAB and SABSBV.
2. The solid solution, rich in the A component, begins to melt at con-
stant pressures from the PN2 < P2 < PB interval. The area of liquid L ap-
pears and instead of the SABSBV node SABLSB, LSBV and SABLV nodes
appear on the T—x section.
3. The area of liquid L spreads to B component, and the LSBV node
disappears in the PB < P3 < PN1 interval.
4. Then, liquid L rich with the B component begins the congruent
evaporation, besides, the PN1 pressure is exceeded and liquid L rich
with the A component appears at PNLV < P4 < PNSV.
5. An interesting T—x isobar exists in PNSV < P5 < PNSL narrow inter-
val of pressures. The binary crystalline phase melts incongruently,
liquid L rich with the B component evaporates congruently, aiming to
unite with liquid L based on the A component.
6. The T—x isobar acquires a characteristic form for negative azeo-
tropes with a minimum of the pressure at P6 > PNSL. There is the con-
gruent melting of the AB binary phase at low temperatures.
Further, with increase of pressures, fluid F appears, similar to the
previous case.
4. CONCLUSION
It is clear that the graphical phase-diagrams method makes possible
to improve experimental information concerning the equilibrium
states. Usually, it is used in the research and industrial development to
save large amounts of time and resources by reducing the experimental
work and by making thermodynamic predictions available especially
for the multicomponent systems.
It has ascertained experimentally that the application of positive aze-
otropes initially could not be very successful, because the pressure above
them is higher than above pure components in isothermal conditions.
THE SELECTION OF AZEOTROPES AT AMBIENT PRESSURE DRYING OF AEROGELS711
Apparently, it is possible to get in the supercritical region for nega-
tive azeotropes at pressures below critical points of pure components.
We have used some binary negative azeotropic mixtures like pore fluids
in our experimental work and obtained transparent, crack-free bulk
samples of silica aerogels. It would pay to try other compounds for aero-
gels production, such as triple azeotropic mixtures. We are sure that
there will be a great number of the additional phenomena related to the
presence of the third component. As it has been noticed earlier, the sys-
Fig. 4.
712 G. D. NIPAN, O. A. MYKAYLO, and Young-Jei OH
tems that possess the limited mutual solubility in the crystalline state
and those, in which the chemical compounds appear, are of significant
practical interest. It is possible to expect the considerable decline of the
evaporation pressure of liquid—vapour azeotrope, as compared to the
evaporation of liquid components. Such systems exist, but they are
scantily known now.
ACKNOWLEDGMENTS
The financial support received from the Korean Federation of Sciences
and Technology Societies (KOFST) under Brain Pool Program is grate-
fully acknowledged.
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| id | nasplib_isofts_kiev_ua-123456789-73140 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1816-5230 |
| language | English |
| last_indexed | 2025-12-07T18:05:24Z |
| publishDate | 2010 |
| publisher | Інститут металофізики ім. Г.В. Курдюмова НАН України |
| record_format | dspace |
| spelling | Nipan, G.D. Mykaylo, O.A. Young-Jei Oh 2015-01-05T15:08:36Z 2015-01-05T15:08:36Z 2010 The Selection of Azeotropes at Ambient Pressure Drying of Aerogels / G.D. Nipan, O.A. Mykaylo, Young-Jei Oh // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2010. — Т. 8, № 3. — С. 701-712. — Бібліогр.: 15 назв. — англ. 1816-5230 PACS numbers: 05.70.Ce, 64.60.F-, 64.75.Cd, 64.75.Jk, 81.05.Rm, 81.30.Dz, 82.70.Gg https://nasplib.isofts.kiev.ua/handle/123456789/73140 The representation of phase states in the multicomponent systems by graphical images is used for estimation of the LV (xL = xV) azeotrope influence on SLV and L = V equilibria. These theoretical investigations occurred from complications arising at an ambient pressure drying (APD) synthesis of transparent and crackfree bulk silica aerogels. During the empiric selection of azeotropic mixtures, the negative azeotropes advantage over positive ones for this goal is determined and substantiated in theory. As shown, the forecast must base not only on the critical points of components (L = V), in which liquid and vapour become indistinguishable, but also on the triple points of components (SLV–crystal—liquid—vapour). Using the P—T—x phase diagrams, the prediction of ways to reach a supercritical region at the ambient pressure is done. A good agreement between the theoretical results and experimental data is revealed. Представлення фазових рівноваг у багатокомпонентних системах методою графічного зображення використовувалося для оцінки впливу азеотропу LV (xL = xV) на рівноваги SLV та L = V. Дані теоретичні дослідження виконувалися через виникнення ускладнень при синтезі прозорих і бездефектних кремнійових аероґелів способом атмосферного сушіння (APD). При емпіричному відборі азеотропних сумішей було визначено і теоретично обґрунтовано перевагу використання неґативних азеотропів над позитивними задля зазначеної мети. Показано, що прогноза має бути основаною не лише на критичних точках компонентів L = V, в яких рідина і пар стають нерозрізненними, але й на потрійних точках компонентів SLV (кристал—рідина—пар). У даній роботі з використанням P—T—x-фазових діяграм показано можливість досягнення надкритичної области за атмосферного тиску. Виявлено хорошу відповідність між теоретичними та експериментальними результатами. Представление фазовых равновесий в многокомпонентных системах методом графического изображения использовано для оценки влияния азеотропа LV (xL = xV) на равновесия SLV и L = V. Данные теоретические исследования выполнялись по причине возникновения сложностей при синтезе прозрачных и бездефектных кремниевых аэрогелей способом атмосферной сушки (APD). При эмпирическом отборе азеотропных смесей определено и теоретически обосновано преимущество использования негативных азеотропов над позитивными для этой цели. Показано, что прогноз должен быть основан не только на критических точках компонентов L = V, в которых жидкость и пар становятся неразличимыми, но и
 на тройных точках компонентов SLV (кристалл—жидкость—пар). В данной работе с использованием P—T—x-фазовых диаграмм показана возможность достижения сверхкритической области при атмосферном давлении. Обнаружено хорошее соответствие между теоретическими и экспериментальными результатами. The financial support received from the Korean Federation of Sciences and Technology Societies (KOFST) under Brain Pool Program is gratefully acknowledged. en Інститут металофізики ім. Г.В. Курдюмова НАН України Наносистеми, наноматеріали, нанотехнології The Selection of Azeotropes at Ambient Pressure Drying of Aerogels Article published earlier |
| spellingShingle | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels Nipan, G.D. Mykaylo, O.A. Young-Jei Oh |
| title | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels |
| title_full | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels |
| title_fullStr | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels |
| title_full_unstemmed | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels |
| title_short | The Selection of Azeotropes at Ambient Pressure Drying of Aerogels |
| title_sort | selection of azeotropes at ambient pressure drying of aerogels |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/73140 |
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