The stability of the hydrophobic properties of coatings with textured surfaces made of polytetrafluoroethylene and ultra-high molecular weight polyethylene during storage, as well as during prolonged contact with water and aqueous solutions of sodium chloride has been studied. Polymeric coatings were applied to the surface of a polyethylene terephthalate track-etched membrane by electron-beam deposition to produce composite membranes for water desalination. It is found that polytetrafluoroethylene coatings tend to age under the influence of real environmental condi-tions and gradually lose their hydrophobic properties. The water contact angle of these coatings decreases during storage samples of composite membranes. In contrast, the water contact angle of ultra-high molecular weight polyethylene coatings practically does not change during storage of membrane samples. A study of the stability of polymeric coatings during prolonged contact of composite membranes with water and aqueous solutions of sodium chloride showed that coatings made of ultra-high molecular weight polyethylene are stable both in water and in aqueous solutions of sodium chloride. Polytetrafluoroethylene coatings are more stable to the action of aqueous salt solutions than water.

The crystal structure of superprotonic conductor caesium hydrogen sulfate phosphate [Cs4(HSO4)3(H2PO4)] have been analyzed using neutron diffraction methods. Additionally, its structure and surface layers have been investigated using atomic force microscopy. From the diffraction data obtained, Fourier syntheses of neutron scattering densities were calculated, and the localization of hydrogen atoms and the parameters of three types of hydrogen bonds in the crystal structure were accurately determined. Correlation of surface characteristics of samples obtained by atomic force microscopy with their crystal structure is shown.

The surface properties and chemical structure of nanosized coatings deposited on the surface of polyethylene terephthalate track-etched membranes by magnetron sputtering of ultrahigh molecular weight polyethylene and polytetrafluoroethylene in a vacuum have been studied. Application of coatings leads to hydrophobization of surface of the original membranes, the degree of which depends on the type of polymer used for sputtering and the coating thickness. The use of this modification method causes smoothing of structural inhomogeneities of the surface layer of membranes, which is explained by the deposition of coatings in the pore channels at a certain depth from the inlet and the overlap of pores on the surface of modified membranes. In addition, the deposition of coatings on the surface of track-etched membranes leads to a change in the shape of pores. The pore diameter decreases significantly on the modified side and remains unchanged on the untreated side of the membrane, while the membrane pores acquire an asymmetrical (conical) shape. The study of chemical structure of coatings using X-ray photoelectron spectroscopy showed that they contain oxygen-containing functional groups owing to oxidation of the polymer matrix. The developed composite membranes can be used in membrane distillation processes for seawater desalination.

Research subject. Crystals of hydrogen-containing compounds belonging to the superprotonic family. Aim. To obtain knowledge about regular relations between composition, atomic structure, real structure and physical properties of materials, with the purpose of elucidating processes occurring in condensed state and forming the basis for modification of known or obtaining new compounds. Materials and methods. Experimental data were obtained using a set of complementary physical methods, including structural analysis using X-rays, synchrotron radiation and neutrons, optical microscopy, and atomic force microscopy. Results. Experimental data on the atomic structure, real structure, and physical properties of superprotonic crystals, including systems of hydrogen bonds and their changes, were obtained. Conclusions. The physical properties of superprotonic crystals are significantly affected by hydrogen bonding systems and their changes, primarily by the formation of dynamically disordered hydrogen bonds with energetically equivalent positions of hydrogen atoms. When carrying out diagnostics of crystalline samples, account should be taken of their real structure, including the structure of surface layers and the presence of crystallization water. These factors may affect the measured physical parameters, the boundaries of existence of phases, the formation of a multiphase state under variations in temperature.

This article presents materials that highlight the bioengineering potential of polymeric systems of natural origin based on biodegradable polysaccharides, with applications in creating modern products for localized wound healing. Exploring the unique biological and physicochemical properties of polysaccharides offers a promising avenue for the atraumatic, controlled restoration of damaged tissues in extensive wounds. The study focused on alginate, pectin, and a hydrogel composed of their mixture in a 1:1 ratio. Atomic force microscopy data revealed that the two-component gel exhibits greater cohesion and is characterized by the presence of filament-like elements. The dynamic light scattering method indicated that this structural change results in a reduction in the damping of acoustic modes in the gel mixture compared to the component gels. Raman spectroscopy research on these gels revealed the emergence of new bonds between the components’ molecules, contributing to the observed effects. The biocompatibility of the gels was evaluated using dental pulp stem cells, demonstrating that all the gels exhibit biocompatibility.

Polynaphthoylenebenzimidazoles containing functional sulfo groups were synthesized by a one-step method in a sulfuric acid medium with oleum. A polymer-analogous transformation of these polymers with aqueous solutions of metal salts (K, Ca, and Cr) was carried out. Their chemical structure was characterized by FTIR, NMR, and elemental analysis. Polymer salt coatings were deposited on QCM sensor surfaces by electron beam-induced vacuum deposition. The morphology of the coatings was characterized by AFM. It was shown that the coatings formed from a series of polymer salts have different adsorption activity in acetaminophen–water solution compared to distilled water. The QCM results indicate that sensor signal correlates with polymer coating thickness, morphology, and its chemical composition.

Сублимация энергетических материалов имеет ключевое значение для их применения и детектирования. Исследование сублимации с помощью атомно-силовой микроскопии (АСМ) позволяет отслеживать изменения объема отдельных микрочастиц и таким образом анализировать соединения, не подходящие для классических методов исследования. Тем не менее результаты АСМ-исследования в значительной степени могут зависеть от морфологии образца и условий эксперимента. Данная работа посвящена определению влияния морфологической структуры образца, материала подложки и механического воздействия АСМ-зондом на наблюдаемые при нагреве морфологические изменения частиц пентаэритрита тетранитрата (ТЭН) на различных подложках с целью установления условий проведения корректной оценки энтальпии сублимации с помощью АСМ. Установлено, что одновременно с сублимацией на некоторых образцах может протекать перекристаллизация ТЭН, доминирующая до 55 ◦C и искажающая результаты измерений, индикатором которой служит повышение объема частиц в интервале45-60 ◦C. Показано, что в отсутствие перекристаллизации результаты АСМ позволяют корректно оценить энтальпию сублимации вещества, если средняя высота исследуемых частиц превышает 280 ± 30 нм. В целом, метод АСМ позволяет проводить исследования с использованием очень малой массы вещества(менее 10 мкг) при сравнительно низкой температуре, что открывает возможность исследовать высокочувствительные соединения или низколетучие термостабильные материалы, а также анализировать новые соединения с неизвестными свойствами, синтезированные в малом количестве.

Single crystals of [K1-x(NH4)x]3H(SO4)2 (x ≥ 0.57) grown in the K3H(SO4)2-(NH4)3H(SO4)2-H2O water-salt system are studied. The atomic structure including H atoms was determined at room temperature using X-ray structural analysis. [K1-x(NH4)x]3H(SO4)2 (x ≥ 0.57) crystals have trigonal symmetry and disordered hydrogen-bond networks at ambient conditions similar to the high-temperature phases of K3H(SO4)2, (NH4)3H(SO4)2 and other superprotonic compounds M3H(AO4)2. Impedance measurements performed on single crystals show high values of conductivity characteristic for superprotonic phases. Using the methods of impedance spectroscopy and atomic force microscopy, a significant anisotropy of the conductivity of crystals has been detected. It was also shown that there is a qualitative correlation of bulk and local conductivity measured for samples of the same composition and orientation at room temperature, which is due to the peculiarities of their crystal structure.

The influence of a permanent magnetic field on macro- and nanoscopic properties of triglycine sulfate (TGS) crystals with impurity chromium (TGS-Cr) has been investigated. This work continues the previous studies of magnetically induced effects in ferroelectrics. A specific feature of TGS crystals is the presence of a nanoscale relief on a polar (010) cleavage; this nanorelief is a qualitative characteristic of the crystal defect structure. It is shown that the exposure of a crystal in a magnetic field of 2 T leads to a change in its dielectric properties, accompanied by a long-term transformation of the nanorelief. The results obtained are indicative of a magnetically induced change in the defect crystal structure. A qualitative difference is found between the magnetically induced effects in TGS-Cr crystals and undoped TGS crystals. The relationship between the magnetically induced effects and structural defects is discussed.

The method for the determination of dissolved methane in water using the system based on a tubular selective membrane permeable to volatile organic substances and impermeable to liquid water is proposed. Purified air is passed through the membrane tube immersed in water. The air inside the tube is saturated with methane dissolved in water, which diffuses through the tube wall. Methane concentration is measured in the air passing through the membrane tube using a semiconductor metal oxide sensor. The sensitivity threshold and the response time of the system are estimated.

Проведено исследование поверхностных и электрохимических свойств трековой мембраны из полиэтилентерефталата, на одну из сторон которой методом плазмохимического осаждения из газовой фазы смеси силана и закиси азота наносили наноразмерные покрытия из диоксида кремния. Показано, что осаждение слоя диоксида кремния на поверхность мембраны приводит к созданию композиционных мембран, обладающих в растворах электролитов асимметрией проводимости.

Vaporization is an important aspect of the performance and detection of energetic materials. While the traditional techniques concentrate on bulk property changes during sublimation, atomic force microscopy (AFM) offers the possibility to track particle volume changes under heating. Ideally, this will enable the investigation of chemicals that are challenging to study using conventional vaporization analysis methods, i.e., those having low thermal stability and/or low volatility. However, prior studies have demonstrated that novel structural effects at the nanoscale may interfere with sublimation mass loss. The present work aims to provide a comprehensive investigation of the sublimation of pentaerythritol tetranitrate (PETN) thin films with respect to the measurement parameters, the heating technique, the sample composition, and the type of the substrate. We observed the low-temperature recrystallization of thin-film islands during heating together with the sublimation process; this was demonstrated by the unexpected local increase in volume with temperature. Overall, AFM allows us to set up a precise nanoscale vaporization experiment and, in some instances, to obtain a reliable estimate of the sublimation enthalpy. However, it is crucial to consider the sample's morphology as well as any concurrent structural transformations in order to ensure the validity of the results.

The results of comprehensive studies of structural and phase transformations in (K 0.43 (NH 4 ) 0.57 ) 3 H(SO 4 ) 2 superprotonic crystals under the influence of atmospheric moisture are presented. The real structure, composition, and thickness of the modified surface layers have been analyzed using scanning electron microscopy and X-ray microscopy. The local characteristics of nanostructures, formed on the freshly cleaved (001) crystal surface subjected to the electrostatic effect, have been investigated by conductive atomic force microscopy. A correlation has been established between the time changes in the structure, composition, and magnitude of the electrostatic potential of the crystal surface. The results are considered in the context of evaluation of the chemical stability of the samples and searching for the ways to optimize the compositions and functional properties of superprotonic compounds.

Surface properties of superprotonic (K1-x(NH4)(x))(3)H(SO4)(2) (x >= 0.57) single crystals and their evolution under humidity were studied by optical polarization microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDXS). Traditional method of atomic force microscopy (AFM) and sophisticated methods such as Kelvin probe force microscopy (KPFM) and scanning capacitance force microscopy (SCFM) were also used. Fresh and aged cleavage surfaces perpendicular and parallel to the c axis of the trigonal superprotonic phase were examined. The effect of air humidity on the surface morphology, surface conductivity, surface potential and surface capacitance was studied. The influence of material composition and surface orientation was considered. During ageing for 430 h, the (001) sample surfaces, initially stepped, were smoothened, surface electric potential changed from negative greater than a hundred of millivolts in absolute value to positive of about 80 mV, and a modified layer containing new crystal phases was formed.

The initiation of energetic materials by mechanical stimuli is a critical stage of their functioning, but remains poorly understood. Using atomic force microscopy (AFM) we explore the microscopic initiation behavior of four prototypical energetic materials: 3,4-dinitropyrazole, ε-CL-20, α-PETN and picric acid. Along with the various chemical structures, these energetic compounds cover a range of application types: a promising melt-cast explosive, the most powerful energetic compound in use, a widespread primary explosive, and a well-established nitroaromatic explosive from the early development of energetics. For the softest materials (picric acid and 3,4-dinitropyrazole), the surfaces were found to behave dynamically, quickly rearranging in response to mechanical deformation. The pit created by nanoscale friction stimulation on the surface of 3,4-dinitropyrazole doubled in volume upon aging for half an hour. Over the same time frame, a similar pit on the picric acid surface increased in volume by more than seven-fold. Remarkably, increased humidity was found to reduce the rate of surface rearrangement, potentially offering an origin for the desensitization of energetic materials when wetted. Finally, we identify an inverse correlation between the surface dynamics and mechanical sensitivity of our test energetic compounds. This strongly suggests that surface dynamics influence a material's ability to dissipate excess energy, acting as a buffer towards mechanical initiation.

Single crystals of (K1‒x(NH4)x)3H(SO4)2 (x ≥ 0.57) solid solutions have been studied by electrical atomic force microscopy. At 296 K, the local current–voltage characteristics of trigonal superprotonic phases were measured for the samples with different concentrations of K and NH4 cations as a function of the c axis orientation, and anisotropy of conductivity was established. The degree of the dependence of the conduction properties on the composition is determined. The temporal changes in the morphology, potential, and surface capacitance derivatives of the (001) (K0.43(NH4)0.57)3H(SO4)2 surface were traced and evaluated when the samples were held in air under conditions of constant humidity and temperature.

A technique for studying the local elastic properties of inhomogeneous ferroelectrics has been proposed by the example of growth striations in triglycine sulfate crystals, layer-by-layer doped with chromium and L-α-alanine impurities. The data on the width and impurity compositions of stripes were obtained by X-ray fluorescence analysis and X-ray topography. The positions of the boundaries of the stripes emerging at the surface and the domain structure morphology were determined by the methods of correlation electrical atomic-force microscopy. The force curves were measured and Young’s moduli were calculated for impurity-free and doped crystal stripes using contact atomic-force spectroscopy. The introduction of impurity decreases Young’s modulus: the difference was found to be 20–25 and 12–14% for chromium and L-α-alanine, respectively.

Работа посвящена изучению реакции поверхности отдельных кристаллов пикриновой кислоты на наномасштабное механическое воздействие с целью понимания процессов, лежащих в основе инициирования энергетических материалов (ЭМ). С помощью методов атомно-силовой микроскопии (АСМ) реализованы три вида локального механического воздействия: наноиндентирование, воздействие трением и ударом. Установлено, что наноразмерное воздействие на кристалл приводит к исчезновению материала его поверхности. Кроме того обнаружено, что реакция на механическое воздействие неодинакова для различных граней кристалла. Также выяснено, что при повышении влажности наблюдаемый эффект замедляется, что, вероятно, связано с взаимодействием поверхности пикриновой кислоты с водой.

High-lignin content cellulose nanofibrils (LCNF) were successfully prepared from thermomechani-cal pulp through TEMPO-catalyzed oxidation, followed by ultrasonic treatment. Preparation protocols of the LCNFs included use of the mild pre-hydrolysis of the thermomechanical pulp and adjustment of sodium hypochlorite loading for the samples with the 23.8 and 14.1 wt.% lignin content, resulting in the increase of the carboxyl group content from 0.70 to 1.24 mmol/g. LCNFs had a diameter of 14 +/- 5 nm (AFM evalua-tion); and the LCNF morphology was affected by contents of both lignin and carboxyl groups. The translucent LCNF films were prepared by solution casting technique. They exhibited the heightened water contact angle of 75-82 degrees, an increased thermal stability up to 275 degrees C compared to lignin-free cellulose nanofibril films (39 degrees and 203 degrees C, respectively), and excellent UV-blocking ability in a wide spectrum range from 200 to 375 nm. The said LCNFs can be successfully used for manufacturing the packaging materials and/or making the biopolymer composites.