Iryna Sulym | Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine (original) (raw)

Papers by Iryna Sulym

Research paper thumbnail of Surface Properties of Silica–MWCNTs/PDMS Composite Coatings Deposited on Plasma Activated Glass Supports

Applied sciences, Oct 5, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Superhydrophobic MWCNTs/PDMS-nanocomposite materials: Preparation and characterization

Physicochemical Problems of Mineral Processing, Sep 9, 2019

The surface morphology, structure and hydrophobicity of low-and high-molecular weight poly(dimeth... more The surface morphology, structure and hydrophobicity of low-and high-molecular weight poly(dimethylsiloxane) (PDMS) fluids physically adsorbed onto multi-walled carbon nanotubes (MWCNTs) at different weight percentages (5, 10, 20 and 40 wt.%), were studied employing X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and measurements of contact angle with water. It was found that MWCNTs agglomerate forming voids between tubes of a broad range, while adsorption of the polymer from a hexane solution results in the expected wrapping of nanotubes with PDMS chains and, further, in filling voids, as represented by SEM data. ATR-FTIR was used to investigate the possible structural changes in the polymer nanocomposites. Based on the contact angle measurements via water drop shape analysis, MWCNTs/PDMS nanocomposites were characterized as a stable, superhydrophobic materials with the maximum contact angle (CA) equal to 152° at CPDMS = 40 wt.%.

Research paper thumbnail of Interfacial behavior of water bound to zirconia/nanosilica with adsorbed poly(dimethylsiloxane)

Colloids and Surfaces A: Physicochemical and Engineering Aspects, Jun 1, 2013

ABSTRACT The behavior of water bound to silica/zirconia (2.4 wt.%) (at hydration of 50 mg/g) bare... more ABSTRACT The behavior of water bound to silica/zirconia (2.4 wt.%) (at hydration of 50 mg/g) bare or with adsorbed poly(dimethylsiloxane) (PDMS) (5 wt.%) strongly changes in chloroform medium in comparison with air. PDMS and CDCl3 stimulate an increase in size of water structures (clusters, domains) to reduce the contact area (Suw) between water and hydrophobic polymer or weakly polar solvent. Adsorbed water does not completely cover the oxide surface in air since the surface area in contact with unfrozen water is Suw = 63 m2/g at the specific surface area of 290 m2/g. The Suw value decreases by 5–10 times for samples with PDMS in the chloroform or chloroform–acetonitrile dispersion media.

Research paper thumbnail of Nanooxide/Polymer Composites with Silica@PDMS and Ceria–Zirconia–Silica@PDMS: Textural, Morphological, and Hydrophilic/Hydrophobic Features

Nanoscale Research Letters, Feb 27, 2017

SiO 2 @PDMS and CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites were prepared and studied using nitrogen a... more SiO 2 @PDMS and CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites were prepared and studied using nitrogen adsorptiondesorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), measurements of advancing and receding contact angles with water, and microcalorimetry. The pore size distributions indicate that the textural characteristics change after oxide modification by poly(dimethylsiloxane) (PDMS). Composites are characterized by mainly mesoporosity and macroporosity of aggregates of oxide nanoparticles or oxide@PDMS nanoparticles and their agglomerates. The FT-IR spectra show that PDMS molecules cover well the oxide surface, since the intensity of the band of free silanols at 3748 cm −1 decreases with increasing PDMS concentration and it is absent in the IR spectrum at C PDMS ≥ 20 wt% that occurs due to the hydrogen bonding of the PDMS molecules to the surface hydroxyls. SEM images reveal that the inter-particle voids are gradually filled and aggregates are rearranged and increase from 20 to 200 nm in size with the increasing polymer concentration. The highest hydrophobicity (contact angle θ = 140°at C PDMS = 20-40 wt%) is obtained for the CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites. The heat of composite immersion in water shows a tendency to decrease with increasing PDMS concentration.

Research paper thumbnail of Silica-Supported Titania–Zirconia Nanocomposites: Structural and Morphological Characteristics in Different Media

Nanoscale Research Letters, Feb 29, 2016

A series of TiO 2-ZrO 2 /SiO 2 nanocomposites were synthesized using a liquid-phase method and ch... more A series of TiO 2-ZrO 2 /SiO 2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It was revealed that the component ratio and calcination temperature affect the phase composition of nanocomposites. Composites TiZrSi1 (TiO 2 :ZrO 2 :SiO 2 = 3:10:87) and TiZrSi2 (10:10:80) calcined at 1100°С demonstrate the presence of t-ZrO 2 crystallites in TiZrSi1 and ZrTiO 4 phase in TiZrSi2. The samples calcined at 550°С were amorphous as it was found from XRD data. According to the Raman spectra, the bands specific for anatase are observed in TiZrSi2. According to XPS data, Zr and Ti are in the highest oxidation state (+4). Textural analysis shows that initial silica is mainly meso/macroporous, but composites are mainly macroporous. The particle size distributions in aqueous media showed a tendency of increasing particle size with increasing TiO 2 content in the composites.

Research paper thumbnail of Highly dispersed silica-supported ceria–zirconia nanocomposites: Preparation and characterization

Surfaces and Interfaces, Dec 1, 2016

Abstract Ternary CeO 2 –ZrO 2 /SiO 2 nanocomposite oxides were synthesized by a liquid-phase meth... more Abstract Ternary CeO 2 –ZrO 2 /SiO 2 nanocomposite oxides were synthesized by a liquid-phase method and subjected to thermal treatment at 550 °C. The physicochemical characterization of the obtained nanosized systems was carried out by various techniques, namely: X-ray diffraction (XRD), nitrogen adsorption–desorption, Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The XRD measurements revealed the presence of cubic phase Zr 0.4 Ce 0.6 O 2 in CZS1 (CeO 2 :ZrO 2 :SiO 2 = 3:10:87) and CZS2 (CeO 2 :ZrO 2 :SiO 2 = 10:10:80) samples. The crystallinity of this phase slightly increased with increasing ceria content in nanocomposites. Raman spectra indicated the presence of oxygen vacancies in the case of CZS2 and an absence displacement of oxygen ions from their normal lattice positions in both of the samples. XPS data indicated a significant quantity of Ce 3+ ions present in the composites, which is greater in the CZS2 composite. In the case of CZS systems the TEM–HRTEM results showed well-dispersed nanosized Zr–Ce–oxides over the surface of amorphous SiO 2 . All the characterization techniques revealed that silica does not form any compounds with the dispersed Zr–Ce-oxides. The prepared materials were tested in catalytic reaction of CO oxidation in the presence of H 2 and it was shown that CZS2 system had better performance than CZS1 one.

Research paper thumbnail of Structural and hydrophobic–hydrophilic properties of nanosilica/zirconia alone and with adsorbed PDMS

Applied Surface Science, Oct 1, 2011

Two nanosilica A-300/zirconia (SZ) composites at zirconia content C ZrO 2 = 5 and 20 wt.% were sy... more Two nanosilica A-300/zirconia (SZ) composites at zirconia content C ZrO 2 = 5 and 20 wt.% were synthesized using a wet impregnation method with zirconium acetylacetonate as a precursor. The specific surface area of SZ is larger than that of A-300 because zirconia is composed of nanoparticles (crystallites of 4 nm in average size at C ZrO 2 = 20 wt.%) smaller than those of the initial silica (d av ≈ 11 nm). A-300 and SZ modified by polydimethylsiloxane (PDMS at molecular weight 1700 and 7960) in amounts of 5, 10, 15, 20 and 40 wt.% remained in the powder state with aggregates of primary particles smaller than those of A-300. SZ is more hydrophilic than silica but PDMS/SZ is more hydrophobic (maximum hydrophobic at C PDMS 15-20 or 40 wt.%) than PDMS/A-300.

Research paper thumbnail of Interfacial phenomena in core–shell nanocomposites of PDMS adsorbed onto low specific surface area fumed silica nanooxides: Effects of surface modification

Polymer, Jun 1, 2015

Coreeshell structured nanocomposites of polydimethylsiloxane (PDMS) adsorbed onto low specific su... more Coreeshell structured nanocomposites of polydimethylsiloxane (PDMS) adsorbed onto low specific surface area fumed silica nanoparticles were studied employing structure (nitrogen adsorption edesorption, IPSD), morphology (SEM), thermal (DSC) and dielectric (BDS) techniques. The study focuses on the effects of porosity characteristics on polymer structure and dynamics at the filler interface. To that aim, roughness and porosity characteristics of silica were modified, prior to polymer adsorption, with nanozirconia grafting. The initial particles (15e150 nm in diameter) were found to aggregate and disperse well in the volume of nanocomposites, while nanozirconia grafting resulted in increased volume of the voids. PDMS was adsorbed both in the inner space of the voids and onto external surfaces of the aggregates. According to BDS and DSC the fraction of polymer chains at interfaces increases with nanozirconia modification and the respective dynamics (a int relaxation) and cooperativity are enhanced. The results were interpreted in terms of increasing of the number of polymereparticle contact points on the modified surfaces, as compared to the unmodified ones. Finally, the characteristics of interfacial polymer (fraction, dynamics, polarizability) were interpreted employing models which involve bimodal chain conformations and increased order (orientation) of the polymer chains at the interfaces.

Research paper thumbnail of Morphology, crystallization and rigid amorphous fraction in PDMS adsorbed onto carbon nanotubes and graphite

Polymer, Mar 1, 2018

Morphology and thermal transitions of low-molecular weight polydimethylsiloxane (PDMS) adsorbed o... more Morphology and thermal transitions of low-molecular weight polydimethylsiloxane (PDMS) adsorbed onto carbon nanotubes (CNTs) and micrometric colloidal graphite sheets (CG) were studied employing SEM, isothermal nitrogen adsorption-desorption and calorimetry techniques. The CNTs were found to agglomerate forming voids between tubes of a broad range, while adsorption of the polymer from a solution results in the expected wrapping of CNTs by PDMS chains and, further, in filling of voids, as documented by SEM and by reduction in specific surface area, S BET. By employing three different thermal protocols in differential scanning calorimetry (DSC) measurements, namely, fast cooling, slow cooling and isothermal annealing of crystallization, direct and indirect filler effects on PDMS mobility (glass transition temperature, T g , mobile amorphous fraction, MAF), crystallization temperature, T c , and crystalline fraction (CF) were followed. Results were further evaluated in terms of the rigid amorphous fraction, RAF, and the respective contributions of crystals, RAF crystal , and of filler-polymer interfaces, RAF filler. CNTs were found to increase the rate and degree of crystallization of PDMS, while RAF seems to correlate with a previously proposed fraction of polymer ordered at the interface with CNTs for the uncrystallized samples and with CF for the semicrystalline samples. CG particles interact at a lesser extent with PDMS (less RAF filler), while their presence results in suppression of rate and degree of crystallization (i.e. opposite effects than those of CNTs), so that contributions to RAF could be

Research paper thumbnail of Morphology and molecular dynamics investigation of PDMS adsorbed on titania nanoparticles: Effects of polymer molecular weight

European Polymer Journal, 2016

Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto ... more Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto three types of silica nanoparticles, namely St€ ober, fumed-pyrogenic, and silica gel, were studied employing scanning electron microscopy (SEM), isothermal nitrogen adsorptionedesorption, calorimetry (DSC) and broadband dielectric spectroscopy (BDS) techniques. The initial St€ ober particles (specific surface area S BET~2 40 m 2 /g) form a quite loose silica network with mainly textural pores of~12 nm in size. Fumed silica (S BET~2 60 m 2 /g) demonstrates denser aggregation and increased textural porosity (~11 nm), while silica gel (S BET~8 50 m 2 /g) exhibits tremendous intraparticle porosity (tubular-like pores of~6 nm). On adsorption of PDMS (at~20 and~30 wt%), the glass transition temperature (T g) decreases as compared to the bulk, while the glass transition step broadens. Results suggest loosened molecular packing of the polymer chains accompanied by a broadening of the range of relaxation times in the composites as compared to the neat polymer. On the other hand, the heat capacity step at glass transition is significantly suppressed in the composites, suggesting the formation of a rigid polymer fraction (RAF) at the interfaces with nanoparticles due to strong physical interaction (hydrogen bonding). RAF increases in the order St€ ober < fumed (A300) < silica gel, this increase following that of S BET , in agreement with results in previous work on silica/PDMS systems. Next to the segmental dynamics (a relaxation) of the bulk-like polymer related to the glass transition, BDS allowed the detection of a separate segmental-like relaxation of the polymer in the interfacial silica-PDMS zone. In terms of timescale the interfacial relaxation is almost identical for St€ ober and A300, and slightly faster for silica gel. Comparison of the results of the present work with previous results obtained with similar nanocomposites based on low molecular weight PDMS and silica, provides additional support to recently proposed 'S BET einterfacial dynamics' and 'chain packingepolymer dynamics' correlations.

Research paper thumbnail of Investigation of surface structure, electrokinetic and stability properties of highly dispersed Ho2O3–Yb2O3/SiO2 nanocomposites

Applied Nanoscience, Feb 13, 2021

A series of highly dispersed Ho2O3-Yb2O3/SiO2 nanocomposites was synthesized using a liquidphase ... more A series of highly dispersed Ho2O3-Yb2O3/SiO2 nanocomposites was synthesized using a liquidphase method and examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), and photon correlation spectroscopy (PCS). X-ray fluorescence spectrometry (XRF) confirmed a similar amount of weight percentage of Ho, Yb and Si oxides in the prepared samples.

Research paper thumbnail of Золь-гель синтез и оптические свойства кварцевых стекол, легированных переходными металлами

Разработан новый вариант золь-гель синтеза кварцевого стекла, активированного наночастицами оксид... more Разработан новый вариант золь-гель синтеза кварцевого стекла, активированного наночастицами оксидов переходных металлов. Полученное легированное стекло имеет высокую оптическую однородность, содержит ~ 0.3 % масс. ОН-групп и отличается повышенным показателем преломления по сравнению с чистым кварцевым стеклом. Введение Стекла, активированные ионами переходных металлов (ПМ), широко используются при производстве люминофоров, в лазерной технике, интегральной и волоконной оптике. Так, в качестве активного волоконного световода лазера, используются нити на основе кварцевого стекла с добавками Nd, Yb, Er, Ho, Tm [1]. Стекла, активированные ионами Ce 3+ и Tb 3+ , представляют интерес в качестве световых переизлучателей и катодолюминесцирующих экранов [2]. Стекловидные материалы, легированные Cr-содержащими наночастицами, проявляют спектральнолюминесцентные характеристики, подобные рубину [3]. Обычно легированное кварцевое стекло получают плавлением кремнезёмистого сырья высокой чистоты (t пл~1 665 °C) и активаторов. Попытки сохранить введенные в шихту наночастицы соединений активаторов оказались безуспешными из-за их растворения в расплаве [3]. С развитием золь-гель (ЗГ) технологии появилась возможность получения стекол, исключая стадию расплава, путем введения наночастиц на стадии золя. Источниками таких наночастиц могут служить модифицированные оксидами ПМ высокодисперсные кремнеземы. Возможность использования хромсодержащих кремнеземов для синтеза оптического Cr-стекла показана нами в предыдущих исследованиях [4]. Данная работа посвящена дальнейшей разработке ЗГ синтеза легированных наночастицами оксидов ПМ стекол и изучению их оптических свойств. Экспериментальная часть В работе использовали высокодисперсный кремнезем А-175 производства Калушского опытно-экспериментального завода Института химии поверхности им. А.А. Чуйко НАН Украины (ГОСТ 14922-77); модифицированные кремнеземы, синтезы которых разработаны нами и подробно описаны в [4-10], тетраэтоксисилан, ТЭОС, Si(OC 2 H 5) 4 , ОСЧ 14-5-ОП-1 (ТУ 6-09-5230-85) Ангарского завода химреактивов. Спектры в ИК области полированных стекол толщиной ~ 2 мм записывали с помощью спектрофотометра Specord M-80 (Германия). Коэффициенты преломления стекол измеряли на ноль-эллипсометре ЛЭФ-3М-1 с использованием в качестве

Research paper thumbnail of Lipase immobilization on pristine and modified multi-walled carbon nanotubes

Research paper thumbnail of Lipase immobilization on pristine and modified carbon nanotubes in order to obtain an efficient and environmentally friendly biocatalysts

Research paper thumbnail of Золь-гель синтез и оптические свойства кварцевых стекол, легированных переходными металлами

A new variant of the sol-gel synthesis of the quartz glass activated with transition metal oxide ... more A new variant of the sol-gel synthesis of the quartz glass activated with transition metal oxide nanoparticles have been developed. The resulting doped glass has a high optical homogeneity, contains ~ 0.3 wt. % OH groups and different high refractive index compared to pure silica glass.

Research paper thumbnail of Structure of aluminosilicate-supported nickel and iron oxides nanocomposites in gaseous and aqueous media

Physicochemical Problems of Mineral Processing, 2021

A series of mixed oxides was synthesized by deposition of a guest phase on a highly dispersed oxi... more A series of mixed oxides was synthesized by deposition of a guest phase on a highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65-91 m 2 /g were selected as highly dispersed matrices. NiO/FexOy was deposited as a guest oxide using solvate-stimulated modification of a surface of fumed nanocarriers with nickel nitrate and iron(III) formate and subsequent heat treatment up to 600 °C to form NiO/FexOy. The aim of this work was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the behavior of the composites in gaseous and aqueous media using XRD, nitrogen adsorption and SEM/EDX, and quasi-elastic light scattering (QELS) methods. The lowtemperature nitrogen adsorption isotherms have a sigmoid shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area of composites varies from 65 to 120 m 2 /g. SEM data show denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30-60 nm range. According to QELS data, there is a tendency to form aggregates of 100 nm-10 µm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of NiO with crystallites of 7-23 nm in size, but the iron oxide reflexes were not identified for NiO-containing composites.

Research paper thumbnail of Particulate morphology of nanostructured materials

Himia, Fizika ta Tehnologia Poverhni, 2020

The aim of this study was to develop a technique to analyze the crystalline and particulate morph... more The aim of this study was to develop a technique to analyze the crystalline and particulate morphology of highly disperse complex metal and metalloid oxides, which include both crystalline and amorphous phases, using X-ray diffraction (XRD) data to compute crystallite size distributions (CSD) compared to the particles size distribution functions estimated from high-resolution transmission electron microscopy (TEM) images treated with specific software. Two versions of the XRD treatment methods were used: (i) full profile analysis (FPA) of whole XRD patterns with a self-consistent regularization (SCR) procedure using models for spherical and lamellar crystallites that allows us to estimate relative contributions of crystallites of different shapes; and (ii) analysis of main pure XRD lines with consideration of corrections on an instrumental line profile and background using a regularization procedure with models of spherical or lamellar crystallites. The XRD and TEM based approaches were tested to analyze the crystalline and particulate morphology of various disperse materials: complex (binary and ternary) fumed oxides with silica/alumina, silica/titania, and alumina/silica/titania including crystalline alumina and titania and amorphous silica; nanocomposites CeO 2-ZrO 2 /SiO 2 (10 : 10 : 80 wt.%) and TiO 2-ZrO 2 /SiO 2 (10 : 10 : 80 wt.%) including crystalline and amorphous phases and synthesized using a liquid-phase method and fumed silica A-300 as a substrate; and natural clays of complex composition including several crystalline phases. Obtained results show that the developed approaches to analyze the XRD patterns could be effectively used to compute the CSD in parallel with TEM image treatments, using specific software, for a deeper insight into crystalline and particulate morphology of various disperse materials.

Research paper thumbnail of Study of rheological properties of vaseline oil suspensions of fumed silica modified with poly(dimethylsiloxane)

Hìmìâ, fìzіka ta tehnologìâ poverhnì, Sep 30, 2019

Research paper thumbnail of FABRICATION AND SPECTROSCOPIC INVESTIGATIONS OF SOL-GEL QUARTZ GLASSES CO-DOPED WITH Er3+/Yb3+ IONS

Research paper thumbnail of Er3+ and Yb3+ cations in silica sol-gel glasses: structural-adsorption and morphological characteristics

Research paper thumbnail of Surface Properties of Silica–MWCNTs/PDMS Composite Coatings Deposited on Plasma Activated Glass Supports

Applied sciences, Oct 5, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Superhydrophobic MWCNTs/PDMS-nanocomposite materials: Preparation and characterization

Physicochemical Problems of Mineral Processing, Sep 9, 2019

The surface morphology, structure and hydrophobicity of low-and high-molecular weight poly(dimeth... more The surface morphology, structure and hydrophobicity of low-and high-molecular weight poly(dimethylsiloxane) (PDMS) fluids physically adsorbed onto multi-walled carbon nanotubes (MWCNTs) at different weight percentages (5, 10, 20 and 40 wt.%), were studied employing X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and measurements of contact angle with water. It was found that MWCNTs agglomerate forming voids between tubes of a broad range, while adsorption of the polymer from a hexane solution results in the expected wrapping of nanotubes with PDMS chains and, further, in filling voids, as represented by SEM data. ATR-FTIR was used to investigate the possible structural changes in the polymer nanocomposites. Based on the contact angle measurements via water drop shape analysis, MWCNTs/PDMS nanocomposites were characterized as a stable, superhydrophobic materials with the maximum contact angle (CA) equal to 152° at CPDMS = 40 wt.%.

Research paper thumbnail of Interfacial behavior of water bound to zirconia/nanosilica with adsorbed poly(dimethylsiloxane)

Colloids and Surfaces A: Physicochemical and Engineering Aspects, Jun 1, 2013

ABSTRACT The behavior of water bound to silica/zirconia (2.4 wt.%) (at hydration of 50 mg/g) bare... more ABSTRACT The behavior of water bound to silica/zirconia (2.4 wt.%) (at hydration of 50 mg/g) bare or with adsorbed poly(dimethylsiloxane) (PDMS) (5 wt.%) strongly changes in chloroform medium in comparison with air. PDMS and CDCl3 stimulate an increase in size of water structures (clusters, domains) to reduce the contact area (Suw) between water and hydrophobic polymer or weakly polar solvent. Adsorbed water does not completely cover the oxide surface in air since the surface area in contact with unfrozen water is Suw = 63 m2/g at the specific surface area of 290 m2/g. The Suw value decreases by 5–10 times for samples with PDMS in the chloroform or chloroform–acetonitrile dispersion media.

Research paper thumbnail of Nanooxide/Polymer Composites with Silica@PDMS and Ceria–Zirconia–Silica@PDMS: Textural, Morphological, and Hydrophilic/Hydrophobic Features

Nanoscale Research Letters, Feb 27, 2017

SiO 2 @PDMS and CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites were prepared and studied using nitrogen a... more SiO 2 @PDMS and CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites were prepared and studied using nitrogen adsorptiondesorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), measurements of advancing and receding contact angles with water, and microcalorimetry. The pore size distributions indicate that the textural characteristics change after oxide modification by poly(dimethylsiloxane) (PDMS). Composites are characterized by mainly mesoporosity and macroporosity of aggregates of oxide nanoparticles or oxide@PDMS nanoparticles and their agglomerates. The FT-IR spectra show that PDMS molecules cover well the oxide surface, since the intensity of the band of free silanols at 3748 cm −1 decreases with increasing PDMS concentration and it is absent in the IR spectrum at C PDMS ≥ 20 wt% that occurs due to the hydrogen bonding of the PDMS molecules to the surface hydroxyls. SEM images reveal that the inter-particle voids are gradually filled and aggregates are rearranged and increase from 20 to 200 nm in size with the increasing polymer concentration. The highest hydrophobicity (contact angle θ = 140°at C PDMS = 20-40 wt%) is obtained for the CeO 2-ZrO 2-SiO 2 @PDMS nanocomposites. The heat of composite immersion in water shows a tendency to decrease with increasing PDMS concentration.

Research paper thumbnail of Silica-Supported Titania–Zirconia Nanocomposites: Structural and Morphological Characteristics in Different Media

Nanoscale Research Letters, Feb 29, 2016

A series of TiO 2-ZrO 2 /SiO 2 nanocomposites were synthesized using a liquid-phase method and ch... more A series of TiO 2-ZrO 2 /SiO 2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It was revealed that the component ratio and calcination temperature affect the phase composition of nanocomposites. Composites TiZrSi1 (TiO 2 :ZrO 2 :SiO 2 = 3:10:87) and TiZrSi2 (10:10:80) calcined at 1100°С demonstrate the presence of t-ZrO 2 crystallites in TiZrSi1 and ZrTiO 4 phase in TiZrSi2. The samples calcined at 550°С were amorphous as it was found from XRD data. According to the Raman spectra, the bands specific for anatase are observed in TiZrSi2. According to XPS data, Zr and Ti are in the highest oxidation state (+4). Textural analysis shows that initial silica is mainly meso/macroporous, but composites are mainly macroporous. The particle size distributions in aqueous media showed a tendency of increasing particle size with increasing TiO 2 content in the composites.

Research paper thumbnail of Highly dispersed silica-supported ceria–zirconia nanocomposites: Preparation and characterization

Surfaces and Interfaces, Dec 1, 2016

Abstract Ternary CeO 2 –ZrO 2 /SiO 2 nanocomposite oxides were synthesized by a liquid-phase meth... more Abstract Ternary CeO 2 –ZrO 2 /SiO 2 nanocomposite oxides were synthesized by a liquid-phase method and subjected to thermal treatment at 550 °C. The physicochemical characterization of the obtained nanosized systems was carried out by various techniques, namely: X-ray diffraction (XRD), nitrogen adsorption–desorption, Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The XRD measurements revealed the presence of cubic phase Zr 0.4 Ce 0.6 O 2 in CZS1 (CeO 2 :ZrO 2 :SiO 2 = 3:10:87) and CZS2 (CeO 2 :ZrO 2 :SiO 2 = 10:10:80) samples. The crystallinity of this phase slightly increased with increasing ceria content in nanocomposites. Raman spectra indicated the presence of oxygen vacancies in the case of CZS2 and an absence displacement of oxygen ions from their normal lattice positions in both of the samples. XPS data indicated a significant quantity of Ce 3+ ions present in the composites, which is greater in the CZS2 composite. In the case of CZS systems the TEM–HRTEM results showed well-dispersed nanosized Zr–Ce–oxides over the surface of amorphous SiO 2 . All the characterization techniques revealed that silica does not form any compounds with the dispersed Zr–Ce-oxides. The prepared materials were tested in catalytic reaction of CO oxidation in the presence of H 2 and it was shown that CZS2 system had better performance than CZS1 one.

Research paper thumbnail of Structural and hydrophobic–hydrophilic properties of nanosilica/zirconia alone and with adsorbed PDMS

Applied Surface Science, Oct 1, 2011

Two nanosilica A-300/zirconia (SZ) composites at zirconia content C ZrO 2 = 5 and 20 wt.% were sy... more Two nanosilica A-300/zirconia (SZ) composites at zirconia content C ZrO 2 = 5 and 20 wt.% were synthesized using a wet impregnation method with zirconium acetylacetonate as a precursor. The specific surface area of SZ is larger than that of A-300 because zirconia is composed of nanoparticles (crystallites of 4 nm in average size at C ZrO 2 = 20 wt.%) smaller than those of the initial silica (d av ≈ 11 nm). A-300 and SZ modified by polydimethylsiloxane (PDMS at molecular weight 1700 and 7960) in amounts of 5, 10, 15, 20 and 40 wt.% remained in the powder state with aggregates of primary particles smaller than those of A-300. SZ is more hydrophilic than silica but PDMS/SZ is more hydrophobic (maximum hydrophobic at C PDMS 15-20 or 40 wt.%) than PDMS/A-300.

Research paper thumbnail of Interfacial phenomena in core–shell nanocomposites of PDMS adsorbed onto low specific surface area fumed silica nanooxides: Effects of surface modification

Polymer, Jun 1, 2015

Coreeshell structured nanocomposites of polydimethylsiloxane (PDMS) adsorbed onto low specific su... more Coreeshell structured nanocomposites of polydimethylsiloxane (PDMS) adsorbed onto low specific surface area fumed silica nanoparticles were studied employing structure (nitrogen adsorption edesorption, IPSD), morphology (SEM), thermal (DSC) and dielectric (BDS) techniques. The study focuses on the effects of porosity characteristics on polymer structure and dynamics at the filler interface. To that aim, roughness and porosity characteristics of silica were modified, prior to polymer adsorption, with nanozirconia grafting. The initial particles (15e150 nm in diameter) were found to aggregate and disperse well in the volume of nanocomposites, while nanozirconia grafting resulted in increased volume of the voids. PDMS was adsorbed both in the inner space of the voids and onto external surfaces of the aggregates. According to BDS and DSC the fraction of polymer chains at interfaces increases with nanozirconia modification and the respective dynamics (a int relaxation) and cooperativity are enhanced. The results were interpreted in terms of increasing of the number of polymereparticle contact points on the modified surfaces, as compared to the unmodified ones. Finally, the characteristics of interfacial polymer (fraction, dynamics, polarizability) were interpreted employing models which involve bimodal chain conformations and increased order (orientation) of the polymer chains at the interfaces.

Research paper thumbnail of Morphology, crystallization and rigid amorphous fraction in PDMS adsorbed onto carbon nanotubes and graphite

Polymer, Mar 1, 2018

Morphology and thermal transitions of low-molecular weight polydimethylsiloxane (PDMS) adsorbed o... more Morphology and thermal transitions of low-molecular weight polydimethylsiloxane (PDMS) adsorbed onto carbon nanotubes (CNTs) and micrometric colloidal graphite sheets (CG) were studied employing SEM, isothermal nitrogen adsorption-desorption and calorimetry techniques. The CNTs were found to agglomerate forming voids between tubes of a broad range, while adsorption of the polymer from a solution results in the expected wrapping of CNTs by PDMS chains and, further, in filling of voids, as documented by SEM and by reduction in specific surface area, S BET. By employing three different thermal protocols in differential scanning calorimetry (DSC) measurements, namely, fast cooling, slow cooling and isothermal annealing of crystallization, direct and indirect filler effects on PDMS mobility (glass transition temperature, T g , mobile amorphous fraction, MAF), crystallization temperature, T c , and crystalline fraction (CF) were followed. Results were further evaluated in terms of the rigid amorphous fraction, RAF, and the respective contributions of crystals, RAF crystal , and of filler-polymer interfaces, RAF filler. CNTs were found to increase the rate and degree of crystallization of PDMS, while RAF seems to correlate with a previously proposed fraction of polymer ordered at the interface with CNTs for the uncrystallized samples and with CF for the semicrystalline samples. CG particles interact at a lesser extent with PDMS (less RAF filler), while their presence results in suppression of rate and degree of crystallization (i.e. opposite effects than those of CNTs), so that contributions to RAF could be

Research paper thumbnail of Morphology and molecular dynamics investigation of PDMS adsorbed on titania nanoparticles: Effects of polymer molecular weight

European Polymer Journal, 2016

Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto ... more Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto three types of silica nanoparticles, namely St€ ober, fumed-pyrogenic, and silica gel, were studied employing scanning electron microscopy (SEM), isothermal nitrogen adsorptionedesorption, calorimetry (DSC) and broadband dielectric spectroscopy (BDS) techniques. The initial St€ ober particles (specific surface area S BET~2 40 m 2 /g) form a quite loose silica network with mainly textural pores of~12 nm in size. Fumed silica (S BET~2 60 m 2 /g) demonstrates denser aggregation and increased textural porosity (~11 nm), while silica gel (S BET~8 50 m 2 /g) exhibits tremendous intraparticle porosity (tubular-like pores of~6 nm). On adsorption of PDMS (at~20 and~30 wt%), the glass transition temperature (T g) decreases as compared to the bulk, while the glass transition step broadens. Results suggest loosened molecular packing of the polymer chains accompanied by a broadening of the range of relaxation times in the composites as compared to the neat polymer. On the other hand, the heat capacity step at glass transition is significantly suppressed in the composites, suggesting the formation of a rigid polymer fraction (RAF) at the interfaces with nanoparticles due to strong physical interaction (hydrogen bonding). RAF increases in the order St€ ober < fumed (A300) < silica gel, this increase following that of S BET , in agreement with results in previous work on silica/PDMS systems. Next to the segmental dynamics (a relaxation) of the bulk-like polymer related to the glass transition, BDS allowed the detection of a separate segmental-like relaxation of the polymer in the interfacial silica-PDMS zone. In terms of timescale the interfacial relaxation is almost identical for St€ ober and A300, and slightly faster for silica gel. Comparison of the results of the present work with previous results obtained with similar nanocomposites based on low molecular weight PDMS and silica, provides additional support to recently proposed 'S BET einterfacial dynamics' and 'chain packingepolymer dynamics' correlations.

Research paper thumbnail of Investigation of surface structure, electrokinetic and stability properties of highly dispersed Ho2O3–Yb2O3/SiO2 nanocomposites

Applied Nanoscience, Feb 13, 2021

A series of highly dispersed Ho2O3-Yb2O3/SiO2 nanocomposites was synthesized using a liquidphase ... more A series of highly dispersed Ho2O3-Yb2O3/SiO2 nanocomposites was synthesized using a liquidphase method and examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), and photon correlation spectroscopy (PCS). X-ray fluorescence spectrometry (XRF) confirmed a similar amount of weight percentage of Ho, Yb and Si oxides in the prepared samples.

Research paper thumbnail of Золь-гель синтез и оптические свойства кварцевых стекол, легированных переходными металлами

Разработан новый вариант золь-гель синтеза кварцевого стекла, активированного наночастицами оксид... more Разработан новый вариант золь-гель синтеза кварцевого стекла, активированного наночастицами оксидов переходных металлов. Полученное легированное стекло имеет высокую оптическую однородность, содержит ~ 0.3 % масс. ОН-групп и отличается повышенным показателем преломления по сравнению с чистым кварцевым стеклом. Введение Стекла, активированные ионами переходных металлов (ПМ), широко используются при производстве люминофоров, в лазерной технике, интегральной и волоконной оптике. Так, в качестве активного волоконного световода лазера, используются нити на основе кварцевого стекла с добавками Nd, Yb, Er, Ho, Tm [1]. Стекла, активированные ионами Ce 3+ и Tb 3+ , представляют интерес в качестве световых переизлучателей и катодолюминесцирующих экранов [2]. Стекловидные материалы, легированные Cr-содержащими наночастицами, проявляют спектральнолюминесцентные характеристики, подобные рубину [3]. Обычно легированное кварцевое стекло получают плавлением кремнезёмистого сырья высокой чистоты (t пл~1 665 °C) и активаторов. Попытки сохранить введенные в шихту наночастицы соединений активаторов оказались безуспешными из-за их растворения в расплаве [3]. С развитием золь-гель (ЗГ) технологии появилась возможность получения стекол, исключая стадию расплава, путем введения наночастиц на стадии золя. Источниками таких наночастиц могут служить модифицированные оксидами ПМ высокодисперсные кремнеземы. Возможность использования хромсодержащих кремнеземов для синтеза оптического Cr-стекла показана нами в предыдущих исследованиях [4]. Данная работа посвящена дальнейшей разработке ЗГ синтеза легированных наночастицами оксидов ПМ стекол и изучению их оптических свойств. Экспериментальная часть В работе использовали высокодисперсный кремнезем А-175 производства Калушского опытно-экспериментального завода Института химии поверхности им. А.А. Чуйко НАН Украины (ГОСТ 14922-77); модифицированные кремнеземы, синтезы которых разработаны нами и подробно описаны в [4-10], тетраэтоксисилан, ТЭОС, Si(OC 2 H 5) 4 , ОСЧ 14-5-ОП-1 (ТУ 6-09-5230-85) Ангарского завода химреактивов. Спектры в ИК области полированных стекол толщиной ~ 2 мм записывали с помощью спектрофотометра Specord M-80 (Германия). Коэффициенты преломления стекол измеряли на ноль-эллипсометре ЛЭФ-3М-1 с использованием в качестве

Research paper thumbnail of Lipase immobilization on pristine and modified multi-walled carbon nanotubes

Research paper thumbnail of Lipase immobilization on pristine and modified carbon nanotubes in order to obtain an efficient and environmentally friendly biocatalysts

Research paper thumbnail of Золь-гель синтез и оптические свойства кварцевых стекол, легированных переходными металлами

A new variant of the sol-gel synthesis of the quartz glass activated with transition metal oxide ... more A new variant of the sol-gel synthesis of the quartz glass activated with transition metal oxide nanoparticles have been developed. The resulting doped glass has a high optical homogeneity, contains ~ 0.3 wt. % OH groups and different high refractive index compared to pure silica glass.

Research paper thumbnail of Structure of aluminosilicate-supported nickel and iron oxides nanocomposites in gaseous and aqueous media

Physicochemical Problems of Mineral Processing, 2021

A series of mixed oxides was synthesized by deposition of a guest phase on a highly dispersed oxi... more A series of mixed oxides was synthesized by deposition of a guest phase on a highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65-91 m 2 /g were selected as highly dispersed matrices. NiO/FexOy was deposited as a guest oxide using solvate-stimulated modification of a surface of fumed nanocarriers with nickel nitrate and iron(III) formate and subsequent heat treatment up to 600 °C to form NiO/FexOy. The aim of this work was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the behavior of the composites in gaseous and aqueous media using XRD, nitrogen adsorption and SEM/EDX, and quasi-elastic light scattering (QELS) methods. The lowtemperature nitrogen adsorption isotherms have a sigmoid shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area of composites varies from 65 to 120 m 2 /g. SEM data show denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30-60 nm range. According to QELS data, there is a tendency to form aggregates of 100 nm-10 µm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of NiO with crystallites of 7-23 nm in size, but the iron oxide reflexes were not identified for NiO-containing composites.

Research paper thumbnail of Particulate morphology of nanostructured materials

Himia, Fizika ta Tehnologia Poverhni, 2020

The aim of this study was to develop a technique to analyze the crystalline and particulate morph... more The aim of this study was to develop a technique to analyze the crystalline and particulate morphology of highly disperse complex metal and metalloid oxides, which include both crystalline and amorphous phases, using X-ray diffraction (XRD) data to compute crystallite size distributions (CSD) compared to the particles size distribution functions estimated from high-resolution transmission electron microscopy (TEM) images treated with specific software. Two versions of the XRD treatment methods were used: (i) full profile analysis (FPA) of whole XRD patterns with a self-consistent regularization (SCR) procedure using models for spherical and lamellar crystallites that allows us to estimate relative contributions of crystallites of different shapes; and (ii) analysis of main pure XRD lines with consideration of corrections on an instrumental line profile and background using a regularization procedure with models of spherical or lamellar crystallites. The XRD and TEM based approaches were tested to analyze the crystalline and particulate morphology of various disperse materials: complex (binary and ternary) fumed oxides with silica/alumina, silica/titania, and alumina/silica/titania including crystalline alumina and titania and amorphous silica; nanocomposites CeO 2-ZrO 2 /SiO 2 (10 : 10 : 80 wt.%) and TiO 2-ZrO 2 /SiO 2 (10 : 10 : 80 wt.%) including crystalline and amorphous phases and synthesized using a liquid-phase method and fumed silica A-300 as a substrate; and natural clays of complex composition including several crystalline phases. Obtained results show that the developed approaches to analyze the XRD patterns could be effectively used to compute the CSD in parallel with TEM image treatments, using specific software, for a deeper insight into crystalline and particulate morphology of various disperse materials.

Research paper thumbnail of Study of rheological properties of vaseline oil suspensions of fumed silica modified with poly(dimethylsiloxane)

Hìmìâ, fìzіka ta tehnologìâ poverhnì, Sep 30, 2019

Research paper thumbnail of FABRICATION AND SPECTROSCOPIC INVESTIGATIONS OF SOL-GEL QUARTZ GLASSES CO-DOPED WITH Er3+/Yb3+ IONS

Research paper thumbnail of Er3+ and Yb3+ cations in silica sol-gel glasses: structural-adsorption and morphological characteristics