Публікації, в яких представлені результати проекту |
064 Percolation of aligned dimers on a square lattice |
Автори: | Cherkasova, V.; Tarasevich, Y.; Lebovka, N. & Vygornitskii, N. | |
Реферат: | Percolation and jamming phenomena were investigated for anisotropic sequential deposition of dimers (particles occupying two adjacent adsorption sites) on a square lattice. The influence of dimer alignment on the electrical conductivity was examined. The percolation threshold for deposition of dimers was lower than for deposition of monomers. Nevertheless, the problem belongs to the universality class of random percolation. The lowest percolation threshold (pc = 0.562) was observed for isotropic orientation of the dimers. It was higher (pc = 0.586) in the case of dimers aligned strictly along one direction. The state of dimer orientation influenced the concentration dependence of the electrical conductivity. The proposed
model seems to be useful for description of the percolating properties of anisotropic conductors. | |
Ключові слова: | | |
Видання: | European Physical Journal | | | 2010,
205-209,англійська |
064 Liquid crystal dispersions of carbon nanotubes: dielectric, electro-optical and structural peculiarities |
Автори: | Dolgov, L.; Kovalchuk, O.; Lebovka, N.; Tomylko, S. & Yaroshchuk | |
Реферат: | 1. Introduction
2. Materials and methods
2.1. Liquid crystalline media and chiral dopant
2.2. Multiwalled carbon nanotubes
2.3. Preparation of LC-CNTs composites
2.4. Cells
2.5. Electro-optical measurements
2.6. Dielectric measurements
3. Dielectric studies of LC composites doped with carbon nanotubes
3.2. Dielectric spectra
3.3. Electrical conductivity: Intermediate frequency range
3.3.1. Percolation behavior
3.3.2. Temperature dependence and energy of activation
3.3.3. Hysteretic behavior and effect of positive temperature coefficient
3.4. Frequency and voltage dependence
3.5. Dielectric relaxation and near-electrode processes: Low frequency range (A)
3.6. High frequency dielectric relaxation: High frequency range C
4. Electro-optic studies of LC-CNTs composites
4.1. Reversible electro-optic response
4.2. Irreversible electro-optic response: effect of electro-optical memory
4.3. Enhancement of memory effect by chiral dopant
5. Structural peculiarities of LC-CNT composites and structural transformation under the applied field
5.1. Structural transformations in LC-CNTs composites without electrohydrodynamic flows
5.2. Structural transformations in the LC-CNT composites with electrohydrodynamic flows
5.3. Percolation structures of CNTs and mechanism of electro-optic memory
6. Conclusions
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Ключові слова: | | |
Видання: | Carbon Nanotubes, O.Marulanda, J. M., ed., (2010), In-Tech Vukovar, Croatia | | | 2010,
451-483,англійська |
064 Compacting of multiwalled carbon nanotubes at high centrifugal acceleration and in the presence of a surfactant |
Автори: | Lebovka, N.; Loginov, M. & Vorobiev, E. | |
Реферат: | This work is devoted to the compaction behavior of aqueous suspensions of multiwalled carbon nanotubes (MWCNTs) (1%wt) at high centrifugal acceleration and in the presence of a surfactant. The fast and slow processes in presence of a surfactant were identified in compression kinetic of MWCNT aggregates. The fast process was explained by formation of sediment and the slow process was identified as the processes of restructuring of the nanotube networks. The high compactness of sediments in the presence of a dispersant evidently reflected improvement of MWCNT packing assisted by a surfactant.
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Ключові слова: | | |
Видання: | FILTECH 2011, Wiesbaden Germany | | | 2011,
273-277,англійська |
064 Electroosmotic Flow in Micro and Nanosized Systems |
Автори: | Lebovka, N. I. & Alexeev O.L. | |
Реферат: | CONTENTS
6.1 Introduction
6.2 Structure of the Interface Between Solid Surface and Electrolyte Solution
6.3 Fundamentals of Electroosmosis
6.4 Electroosmotic Dewatering
6.5 Soil Remediation
6.6 Microfluidic Transport Devices
6.7 Conclusion
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Ключові слова: | | |
Видання: | in Monography: Starov, V. M., ed., (2010), Nano-Science: Colloidal and Interfacial Aspects, CRC Press, Taylor & Francis Group | | | 2010,
129-164,англійська |
064 Microstructural, rheological, and conductometric studies of multiwalled carbon nanotube suspensions in glycerol |
Автори: | Bulavin, L.; Lebovka, N.; Kyslyi, Y.; Khrapatyi, S.; Goncharuk, A.; Mel'nyk, I. & Koval'chuk, V. | |
Реферат: | Optical microscopy studies of electrical conductivity and rheological properties (in the cone-plate geometry) of glycerol suspensions filled with multiwalled carbon nanotubes (MWCNTs) have been fulfilled. The researches were carried out in the intervals of temperature T = 283 333 K andMWCNT concentration C = 01 wt%. MWCNTs in glycerol are demonstrated to have a strong tendency toward the aggregation, so that “primary” MWCNT aggregates
persist even after the intensive ultrasound homogenization. Typical percolation phenomena accompanied by an enhancement of the electrical conductivity and the viscosity are observed at an increase of the MWCNT concentration. The concentration percolation threshold is identified at C = Cp 0:1 wt%, and the scaling behavior in a vicinity of the percolation threshold is found to be characterized by the conductivity exponent t = 2:70:3, which is somewhat higher than a value typical of the random percolation problem. The introduction of MWCNTs in glycerol resulted in the appearance of thixotropic behavior related to the fracture of MWCNT aggregates under shear. An anomalous rheological behavior is observed at a high MWCNT concentration, C = 1 wt%, which testifies to the destruction of the H-bond network in glycerol induced by MWCNTs. The dependences of the activation energies of the ionic electric conductivity and a viscous flow on the MWCNT concentration are estimated. | |
Ключові слова: | | |
Видання: | Ukrainian Journal of Physics (Ukrains'kyi Fizychnyi Zhurnal) | | | 2011,
217-224,англійська |
064 Effect of surfactant addition on the mwnt suspensions stability in organic solvents |
Автори: | Gigiberya, V. A.; Ar‘ev, I. A. & Lebovka, N. I. | |
Реферат: | It is shown that multi-walled carbon nanotubes (MWNT) form stable suspensions
in isopropanol solvent as a result of influence of ultra-sound in the weight range of
concentrations from 0.0001% to 1% by weight. Nonionic surfactant Triton X-165 affects
the microstructure of the MWNT aggregates in isopropanol, a small amount of surfactant
increase the intervals between the aggregates and accelerate the sedimentation
process. MWNT suspension in and toluene shows unstable behavior, their total precipitation
time is less than 104 sec. Addition of 0.4% Triton X-165 to suspension of MWNT
in p-xylene leads to its stabilization. Also, addition of 0.6% Triton X-165 leads to partial
stabilization of suspensions of MWNT in toluene.
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Ключові слова: | multi-walled carbon nanotubes, surfactant, Triton X-165, sedimentation, isopropyl alcohol, p-xylene, toluene | |
Видання: | In A. Pogrebnjak; T. Lyutyy & S. Protsenko, ed., 'Nanomaterials: applications & properties' | | | 2011,
105-108,англійська |
064 Phase behaviour, microstructure, and percolation of poly(ethylene glycol) filled by multiwalled carbon nanotubes and organophilic montmorillonite |
Автори: | Lebovka, N.; Lysenkov, E.; Goncharuk, A.; Gomza, Y.; Klepko, V. & Boiko, Y. | |
Реферат: | This work studies phase behavior, microstructure and percolation of the poly(ethylene glycol) (PEG), filled by multiwalled
carbon nanotubes (MWCNTs), organo-modified montmorillonite (OMMT), and their mixtures, using differential scanning
calorimentry (DSC), X-ray diffraction (XRD), electrical conductivity, and analysis of microscopic images. The DSC
and XRD data showed a noticeable decrease of PEG crystallinity with increase of nanofiller content. Filling of PEG by
MWCNTs was accompanied by a percolation threshold at&0.1 wt%, and the estimated electrical conductivity exponent
(t¼1.770.07) was typical for the random percolation networks. The similar threshold behavior, but with higher
percolation threshold &0.5–1.0 wt%, was observed for PEG filled by OMMT. The observed effect of OMMT-enhanced
dispersion of MWCNTS in PEG at a high level of loading by nanoparticles offers | |
Ключові слова: | poly(ethylene glycol), multiwalled carbon nanotubes, organo-modified montmorillonite, crystallinity, percolation | |
Видання: | Journal of Composite Materials 45(24), 2555-2566. | | | 2011,
2555-2566,англійська |
064 Percolation transition and the anisotropy of electrical conductivity in the nanocomposite systems, filled with particles of anisotropic shape with a core- permeable shell structure |
Автори: | Lebovka, N.; Vygornitsky, N. & Goncharuk, A. | |
Реферат: | The percolation behavior of nanocomposite systems filled by
particles of anisotropic shape with a core – permeable shell
structure was studied using computer simulation methods. The
two-dimensional composite system was formed accounting
for mutual correlation of spatial distributions and using continual version of the random sequential adsorption model. The percolation transition in the studied systems was suppressed by formation of the jamming state. The percolation was observed when the width of permeable conductive shell
exceeded some minimal threshold value. This threshold value
was increasing with aspect ration increase. For orientationally
ordered composites, the anisotropy of electrical conductivity
was observed. It was increasing with increase of the aspect
ratio of filler concentration. | |
Ключові слова: | nonacomposites, percolation, electrical conductivity anisotropy, computer simulation | |
Видання: | Nanostructured Materials Science | | | 2011,
57-65,російська |
064 Influence of organo-clay on electrical and mechanical properties of PP/MWCNT/OC nanocomposites |
Автори: | Levchenko, V.; Mamunya, Y.; Boiteux, G.; Lebovka, M.; Alcouffe, P.; Seytre, G. & Lebedev, E. | |
Реферат: | The electrical, thermal and mechanical properties of nanocomposites, based on polypropylene (PP) filled by multi-walled carbon nanotubes (MWCNTs) and organo-clay (OC), were studied with the purpose of finding out the effect of OC on the microstructure of MWCNTs dispersion and PP/MWCNT/OC composites. It was found that addition of organo-clay nanoparticles improved nanotube dispersion and enhanced electrical properties of PP/MWCNT nanocomposites. Addition of organo-clay (MWCNT/OC ratio was 1/1) reduced the percolation threshold of PP/MWCNT nanocomposites from /c = 0.95 vol.% to /c = 0.68 vol.% of carbon nanotubes, while the level of conductivity became 2–4 orders of magnitude higher.
The DSC and DMA analyses have shown that the influence of organo-clay on the thermal and mechanical properties of material was not significant in composites with both fillers
as compared to PP/OC. Such an effect can be caused by stronger interaction of OC with carbon nanotubes than with polymer matrix. | |
Ключові слова: | | |
Видання: | European Polymer Journal 47(7), 1351-1360. | | | 2011,
1351-1360,англійська |
064 Aggregation of clay platelets in nematic liquid crystal, 5CB: Microstructure, electrical conductivity and rheological investigations |
Автори: | Shaydyuk, Y.; Puchkovska, G.; Goncharuk, A. & Lebovka, N. | |
Реферат: | The microstructure, electrical conductivity and rheological properties of a nematic liquid crystal (5CB) doped at
concentrations up to 4.5 wt% of montmorillonite (MMT) or organomontmorillonite (OMMT) clay nanoplatelets,
were investigated at temperatures between 293 and 310 K. Microscopy and electrical conductivity assessment
revealed noticeable differences in aggregation in MMT and OMMT suspensions, MMT nanoplatelets showing
a strong tendency to aggregation. The incubation of 5CB in the presence of MMT initially produced loose aggregation,
followed by the formation of compact aggregates. The latter had practically no influence on the surrounding
inter-aggregate regions. In the case of OMMT, a greater degree of integration of the nanoplatelets was observed
within the liquid crystal structure of 5CB, resulting in a noticeable effect on electrical conductivity and activation
energy of the composite material. Thixotropy was observed in suspensions of 5CB composites formed with either
MMT or OMMT. A composite of 5CB with OMMT also exhibited anomalous viscous thinning at shear rates
below 100 s−1. A structural model is suggested to explain this behaviour. | |
Ключові слова: | liquid crystal; 5CB; organophilic nanoplatelets; viscosity; electrical conductivity; microstructure | |
Видання: | Liquid Crystals | | | 2011,
,англійська |
064 Electro-optical memory of a nematic liquid crystal doped by multi-walled carbon nanotubes |
Автори: | Dolgov, L.; Yaroshchuk, O.; Tomylko, S. & Lebovka, N. | |
Реферат: | A pronounced irreversible electro-optical response (memory effect) has been recently observed for nematic
liquid crystal (LC) EBBA doped by multi-walled carbon nanotubes (MWCNTs) near the percolation threshold of
the MWCNTs (0.02÷0.05 wt. %). It is caused by irreversible homeotropic-to-planar reorientation of LC in an
electric field. This feature is explained by electro-hydrodynamically stimulated dispergation of MWCNTs in LC
and by the formation of a percolation MWCNT network which acts as a spatially distributed surface stabilizing
the planar state of the LC. This mechanism is confirmed by the absence of memory in the EBBA/MWCNT composites,
whose original structure is fixed by a polymer. The observed effect suggests new operation modes for
the memory type and bistable LC devices, as well as a method for in situ dispergation of carbon nanotubes in
LC cells. | |
Ключові слова: | carbon nanotubes, liquid crystal, memory effect | |
Видання: | Condensed Matter Physics | | | 2012,
1-8,англійська |
064 The Stability of Suspensions of Multilayer Carbon Nanotubes in Organic Solvents in the Presence of Triton X_165 |
Автори: | Gigiberiya, V. A.; Ar’ev, I. A. & Lebovka, N. I. | |
Реферат: | The stability of suspensions of multilayer carbon nanotubes in isopropanol, toluene, and pxylene
has been studied. Suspensions of multilayer carbon nanotubes in isopropanol (unlike those in toluene and
pxylene) display high aggregation stability, which is explained by the formation of repulsive solvation layers
as a result of interactions between the polar solvent and nanotube surface. The addition of a nonionic surfac
tant, Triton X165, noticeably increases aggregate sizes and accelerates sedimentation processes in nanotube
suspensions in isopropanol, while, in toluene and pxylene, the aggregate sizes decrease and the nanotube
suspensions are stabilized.
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Ключові слова: | | |
Видання: | Colloid Journal (Kolloidnyi Zhurnal) | | | 2012,
665-670,англійська |
064 Microstructure and electrical conductivity of hybrid liquid crystalline composites including 5CB, carbon nanotubes and clay platelets |
Автори: | Lebovka, N.; Goncharuk, A.; Bezrodna, T.; Chashechnikova, I. & Nesprava, V. | |
Реферат: | The microstructure and electrical conductivity of 4-pentyl-4-cyanobiphenyl (5CB) liquid crystal (LC) filled with
multiwalled carbon nanotubes (NTs), organophilic montmorillonite (OM) clay platelets or their hybrid mixture
OMNT were studied in the temperature range 290–350 K. The OMs were prepared by organic modification of
montmorillonites obtained from different mineral deposits. In general, the samples 5CB+OMNT containing OM
demonstrated more homogeneous distribution of filler particles than the samples 5CB+NT with the same amount
of nanotubes. For the OM based on montmorillonite from Pyzhevsk deposit (Ukraine) we obtained that change of
OMNT filler concentration from 1 to 4.5 wt% resulted in transition from the well developed nanoparticle network
to the structure of isolated agglomerates. This was accompanied by an increase (1% of OMNT filler) and a decrease
(4.5% of OMNT filler) of electrical conductivity in more than one order of magnitude as compared with the
5CB+NT composite with the same amount of nanotubes. The microstructure and electrical conductivity of the
composites were also dependent on the geological origin of the clay minerals.
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Ключові слова: | 5CB; carbon nanotubes; electrical conductivity; liquid crystal; microstructure; montmorillonite;
organophilic clay
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Видання: | Liquid Crystals | | | 2012,
531-538,англійська |
064 Percolation behaviour of polypropylene glycol filled with multiwalled carbon nanotubes and Laponite |
Автори: | Lysenkov, E.; Lebovka, N.; Yakovlev, Y.; Klepko, V. & Pivovarova, N. | |
Реферат: | The percolation behaviour of the hybrid composites of polypropylene glycol (PPG) filled with multiwalled
carbon nanotubes (MWCNTs) and Laponite RD (Lap), or with MWCNTs and organo-modified Laponite
(LapO) was studied by wide angle X-ray diffraction (XRD), microscopic image analysis, and electrical conductivity
measurements. Cetyltrimethylammoniumbromide (CTAB) was used as an organo-modifier of
Laponite. The Lap and LapO were found to have rather different affinity to PPG. XRD data have evidenced
finite PPG integration inside Lap and complete exfoliation of LapO stacks in a PPG matrix. In PPG +
MWCNT composites containing no Lap or LapO, increase of MWCNT concentration above the critical
value Cp 0.4 wt% resulted in percolation. The value of the percolation threshold, Cp, was practically
the same for hybrid PPG + MWCNT + Lap composites. However, it noticeably decreased (Cp 0.2 wt%)
in PPG + MWCNT + LapO materials. The observed behaviour of the percolation threshold may be attributed
to the effects exerted by LapO on the size of MWCNT aggregates, state of their dispersion and
homogeneity of their spatial distribution. | |
Ключові слова: | A. Carbon nanotubes
A. Hybrid composites
A. Nanoclays
A. Nanocomposites
B. Electrical properties | |
Видання: | Composites Science and Technology 72(10), 1191-1195 | | | 2012,
1191-1195,англійська |
064 Small-angle neutron scattering of multiwalled carbon nanotubes in aqueous suspensions in presence of laponite platelets or cetyltrimethylammonium bromide |
Автори: | Bulavin, L. A.; Savenko, V. S.; Lebovka, N. I.; Kuklin, A. I.; Soloviov, D. V. & Ivankov, O. I. | |
Реферат: | The results of small angle neutron scattering (SANS) study of semidiluted 0.1 and 0.3 % wt aqueous suspensions of
multiwalled carbon nanotubes (MWCNTs) are reported. The additives of Laponite platelets or cationic surfactant
cetyltrimethylammonium bromide (CTAB) were used for enhancing the dispersion ability of MWCNTs. At high
values of wave vector q, (1 nm-1 < q < 3.5 nm-1) all samples exhibited behavior characteristic for rigid rods (i.e., q-1
variation of neutron scattering intensity was observed). At low values of q (0.1 nm-1 < q < 0.5 nm-1), the neutron
scattering intensity followed the power law q-α with exponent the α in the range of 1.2 - 2, depending on concentration
of the Laponite platelets or CTAB. Addition of Laponite platelets or CTAB allowed improvement of dispersion ability
of MWCNTs. The effects were optimal at the certain value of Laponite/MWCNTs ratio X ≈0.5 or CTAB concentration
(≈0.2 %wt). SANS also revealed existence of a mesh structure in MWCNT aggregates with characteristic mesh size of
≈7.4 nm and ≈6.3 nm in suspensions with concentration of 0.1 and 0.3 % wt of MWCNTs, respectively.
Keywords: SANS, elastic neutron scattering, nanotubes, Laponite platelets, CTAB. | |
Ключові слова: | | |
Видання: | Nuclear Physics and Atomic Energy | | | 2013,
372- 376,англійська |
064 Low temperature phase transformations in 4-cyano-4’-pentylbiphenyl (5CB) filled by multiwalled carbon nanotubes |
Автори: | Lebovka, N.; Melnyk, V.; Mamunya, Y.; Klishevich, G.; Goncharuk, A. & Pivovarova, N. | |
Реферат: | The effects of multiwalled carbon nanotubes (NTs) on low-temperature phase transformations in 5CB
were studied by means of differential scanning calorimetry (DSC), low-temperature photoluminescence
and measurements of electrical conductivity. The concentration of NTs was varied within 0–1 wt%
The experimental data, obtained for pure 5CB by DSC and measurements of photoluminescence in the
heating mode, evidenced the presence of two crystallization processes at T≈229 K and T≈262 K, which
correspond to Ca
1-Cb1
, and Cb1
-C2 phase transformations. Increase of temperature T from 10 K tо 229 K
provoked the red shift of photoluminescence spectral band that was explained by flattening of 5CB
molecule conformation. Moreover, the photoluminescence data allow to conclude that crystallization at
T≈229 K results in conformation transition to non-planar 5CB structure characteristic to ideal crystal.
The non-planar conformations were dominating in nematic phase, i.e., at T4297 K. Electrical conductivity
data for 5CB–NT composites revealed supplementary anomaly inside the stable crystalline phase C2,
identified earlier in the temperature range 229–296.8 K. It can reflect the influence of phase
transformation of 5CB in interfacial layers on the transport of charge carriers between NTs. | |
Ключові слова: | 5CB
Multiwalled carbon nanotube
DSC
Photoluminescence
Electrical conductivity
Solid crystalline polymorphism | |
Видання: | Physica E: Low-Dimensional Systems and Nanostructures 52, 65-69 (arXiv:1303.0569). | | | 2013,
65-69 ,англійська |
064 Sedimentation stability and aging of aqueous dispersions of Laponite in the presence of cetyltrimethylammonium bromide |
Автори: | Savenko, V.; Bulavin, L.; Rawiso, M.; Loginov, M.; Vorobiev, E. & Lebovka, N. I. | |
Реферат: | This work discusses the sedimentation stability and aging of aqueous suspensions of Laponite in the presence
of cetyltrimethylammonium bromide (CTAB). The concentration of Laponite was fixed at a constant level Cl = 2 %wt, which corresponds to the threshold between equilibrium gel IG1 and glass IG2 states. The concentration
of CTAB Cs was within 0–0.3 %wt. In the presence of CTAB, the Laponite aqueous suspensions were unstable
against sedimentation and separated into the upper and bottom layers (U and B layers, respectively). The
dynamic light-scattering technique has revealed that addition of CTAB even at a rather small concentration,
Cs = 0.0164 %wt (0.03 cation exchange capacity), induced noticeable changes in the aging dynamics of the
U layer. It was explained by equilibration of CTAB molecules that were initially nonuniformly distributed
between different Laponite particles. Accelerated stability analysis by means of analytical centrifugation with
rotor speed ω = 500–4000 rpm revealed three sedimentation regimes: continuous (I, Cs < 0.14 %wt), zonelike
(II, 0.14 < Cs < 0.2 %wt), and gel-like (III, Cs > 0.2 %wt). It was demonstrated that the B layer was “soft”
in the zonelike regime. The increase of ω resulted in its supplementary compressing and collapse of “soft”
sediment above certain critical centrifugal acceleration. The physical nature of the observed behavior, accounting
for enhancement of hydrophobic interactions between Laponite particles, is discussed. | |
Ключові слова: | | |
Видання: | Phys. Rev E 88, 052301 (arXiv:1305.6629). | | | 2013,
052301 ,англійська |
064 Regulation of dispersion of carbon nanotubes in mixture of good and bad solvents |
Автори: | Deriabina, O.; Lebovka, N.; Bulavin, L. & Goncharuk, A. | |
Реферат: | The microstructure and electrical conductivity of suspensions of multi-walled carbon nanotubes
(MWCNTs) in binary waterþ1-Cyclohexyl-2-pyrrolidone (CHP) liquid mixtures were studied in the
temperature interval of 253–318 K, in the heating and cooling cycles. The concentration of MWCNTs was
varied in the interval between 0 and 1 wt% and the content of water in a binary mixture X¼[water]/
([CHP]þ[water]) was varied within 0–1.0. The experimental data have shown that dispersing quality of
MWCNTs in a mixture of good (CHP) and bad (water) solvents may be finely regulated by adjustment of
composition of the CHPþwater mixtures. The aggregation ability of MWCNTs in dependence on X was
discussed. The surface of MWCNT clusters was highly tortuous, its fractal dimension df increased with
increase of X, approaching E1.9 at X-1. It was concluded that the surface tension is not suitable
characteristic for prediction of dispersion ability in the mixture of good and bad solvents. The electrical
conductivity data evidenced the presence of a fuzzy-type percolation with multiple thresholds in the
systems under investigation. This behavior was explained by formation of different percolation networks
in dependence of MWCNT concentration. | |
Ключові слова: | Water
1-Cyclohexyl-2-pyrrolidone (CHP)
Multiwalled carbon nanotubes (NTs)
Suspension
Electrical conductivity
Percolation | |
Видання: | Physica E 59, 150-157 (arXiv:1304.5679). | | | 2014,
150-157,англійська |
064 Effects of hydrodynamic retardation and interparticle interactions on the self-assembly in a dryingdroplet containing suspended solid particles |
Автори: | Lebovka, N. I.; Khrapatiy, S.; Melnyk, R. & Vygornitskii | |
Реферат: | Self-assembly of particles, suspended in a drying droplet, were studied by the Monte Carlo method. The
Brownian diffusion of particles was simulated accounting for the effect of hydrodynamic retardation and
interparticle interactions. The model allowed for explaining formation of the “coffee ring” patterns even without
accounting for the radial flows towards the three-phase contact line. Morphologies of the drying patterns and
their dependence on interparticle interactions and concentration of particles are discussed. | |
Ключові слова: | | |
Видання: | Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 89, 052307 | | | 2014,
052307,англійська |
064 Drying of sessile droplets of Laponite based aqueous nano fluids |
Автори: | Lebovka, N. I.; Gigiberiya, V. A.; Tarasevich, Y. Y.; Vodolazskaya, I. V. & Bondarenko, O. P. | |
Реферат: | tFormation of the ring-like pattern by nano-particles of the desiccated droplet of a laponite-based aqueousnanofluid (the well known ‘coffee-ring effect’) is studied. The temperature was controlled and fixed(T = 300 K). The laponite concentration was controlled and varied in order to investigate its effect onthe pattern formation. It was observed that the coffee-ring effect vanishes if concentration of laponiteexceeds 5%. A simple model for analysis of colloidal sessile droplet desiccation is proposed. The modeldescribes correctly dynamics of the drying droplet profile and the final shape of the dried film (deposit).The model is based on the mass conservation law and reasonable assumption that deposit (gel phase)prevents the flows. | |
Ключові слова: | Laponite Nanofluid Sessile droplet Evaporation Coffee-ring effect Desiccation Modeling Mass conservationa | |
Видання: | Colloids and Surfaces A: Physicochemical and Engineering Aspects 462, 5263.52–63 | | | 2014,
52–63,англійська |
064 Hybrid Multiwalled Carbon Nanotube − Laponite Sorbent for Removal of Methylene Blue From Aqueous Solutions |
Автори: | Loginov, M.; Lebovka, N. & Vorobiev, E. | |
Реферат: | The article discusses adsorption of methylene blue dye by novel hybrid sorbent consisting of Laponite and
multiwalled carbon nanotubes. The sorbent was obtained by sonication of the aqueous suspensions of
nanotubes at different concentrations of Laponite. The methods of the methylene blue adsorption,
dead-end membrane filtration and environmental scanning electron microscopy were used for the sorbent
characterization.
It may be concluded from the results of filtration and adsorption experiments that sonication of mixed
aqueous suspensions of Laponite and multiwalled carbon nanotubes leads to the formation of hybrid particles
(ML-particles) with a core–shell structure. The size and the shape of hybrid particles were determined
by nanotubes, while their adsorption properties were determined by Laponite particles attached
to the surface of nanotubes. The Laponite content in hybrid particles was corresponding to the Laponite
to nanotubes ratio in the initial suspension XL = 0–1.
Due to the presence of Laponite in the sorbent, its adsorbing capacity was much higher as compared to
the adsorbing capacity of pure nanotubes, and it was directly proportional to the Laponite content. This
sorbent may be used either as a purifying additive or as a filtering layer if it is deposited on the surface of
a supporting membrane. Due to relatively large size of hybrid particles, they can be easily separated from
the purified solution by filtration or centrifugation. | |
Ключові слова: | Multiwalled carbon nanotubes
Laponite
Hybrid sorbent
Dye
Adsorption
Purification
Filtration | |
Видання: | Journal of Colloid and Interface Science 431(1), 241-249. | | | 2014,
241-249,англійська |
064 Liquid crystal suspensions of carbon nanotubes assisted by organically modified Laponite nanoplatelets |
Автори: | Tomylko, S.; Kovalchuk, O.; Yaroshchuk, O. & Lebovka, N. | |
Реферат: | We present a simple and effective approach for dispersion of carbon nanotubes (CNTs) into
liquid crystals (LCs), suitable for a wide range of CNT concentrations (60.1 wt.%). It consists
in doping of LC+CNT suspensions with Laponite, which shows high affinity to the nanotubes.
The organo-modified Laponite platelets surround CNTs and hamper their aggregation.
At the same time, they do not hinder orientational ordering of CNTs imposed by LC
matrix. This approach avoids problems of direct organo-modification of CNTs, associated
with worsening of their unique properties. The increased dispersion degree results in drastic
changes in dielectric and electro-optical characteristics of the suspensions. Dispersing
and insulating effects of the Laponite platelets on CNTs lead to the absence of classical percolation
of conductivity, linear growth of dielectric constant with CNT concentration, as
well as reduction of Frederiks threshold and significant growth of contrast ratio of the
E7+CNTs suspensions. | |
Ключові слова: | | |
Видання: | Carbon 68, 389-398 | | | 2014,
389-398,англійська |
064 Laponite assisted dispersion of carbon nanotubes in water |
Автори: | Loginov, M.; Lebovka, N. & Vorobiev, E. | |
Реферат: | The ability of Laponite to stabilize aqueous suspensions of multiwalled carbon nanotubes (MWCNTs) was investigated with the help of analytical centrifugation, microscopic image analysis, and measurements of electrical conductivity of hybrid Laponite. +. MWCNT suspensions. The impact of nanotube concentration C n (0.0025-0.5. wt%) and Laponite/MWCNTs ratio X (varied within 0-1. wt/wt) on the properties of Laponite. +. MWCNT hybrid suspensions was discussed. It was observed that sonication of MWCNTs at critical minimal concentration of Laponite X c≈ 0.25 ± 0.05 resulted in efficient dispersion and formation of stabilized suspensions of individual nanotubes. The stabilization of nanotubes in the presence of Laponite was explained by adsorption of Laponite particles and formation of a hydrophilic charged shell on the surface of nanotubes. Increase of MWCNT concentration above the critical value resulted in percolation and formation of spatially extended electrically conductive networks of particles. | |
Ключові слова: | Laponite
Multiwalled carbon nanotubes (MWCNTs)
Aqueous suspensions
Ultrasonication
Stabilization
Analytical centrifugation
Electrical conductivity
Percolation | |
Видання: | Journal of Colloid and Interface Science, 2012, 365, 127-136 | | | 2012,
127-136 ,англійська |
Конференції, семінари, читання, на яких представлені результати проекту |
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064 2.4. Колоїдні нанорозмірні системи Мета:Дослідження процесів структуроутворення, перколяції, агрегаційної стійкості і самоорганізації наночастинок з високим ступенем анізотропної форми в різних дисперсійних середовищах, розробка методів синтезу та створення на їх основі нових типів функціональних композиційних матеріалів. Очікувані результати:Випуск нового виду продукції: матеріалів Етап 1:Структуроутворення в суспензіях наночастинок при врахуванні процесів ексфоліації і компактизації Етап 2:Структуроутворення в суспензіях, що включають суміші анізотропних наночастинок Етап 3:Підсилення диспергації вуглецевих нанотрубок у воді при використанні нанопласти-нок лапоніту Етап 4:Мікроструктура колоїдних суспензій на основі бінарних наповнювачів, вплив розподілу наночастинок за розміром і формою Етап 5:Процеси часової реорганізації структури суспензій в залежності від способу їх приготування, складу і наявності стабілізаторів, фазового стану, в’язкості середовища і температури. Розробка рекомендацій для прогнозування та підвищення їх стабільності.
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