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Various nanosilica characteristics depend on hydrophobization strongly affecting interfacial phenomena. Is it possible to prepare hydrophilic samples with hydrophobic silica (AM1) alone and in blends with hydrophilic one (A-300)? It can be done with addition of a small amount of water to the powders which then are mechanically treated.Nanosilicas were characterized using adsorption, desorption, microscopic, spectroscopic, and quantum chemistry methods.The powders wetted at h = 0.3-3.0 g of water per gram of dry solids have increased bulk density. Samples are in gel-like state at h = 4-5 g/g. Water interaction energy with nanoparticles nonmonotonically depends on h (maximal at h = 3 g/g). Upon mechanical treatment of wetted blends (h 1.5 g/g), separated AM1 structures are absent. At greater h values, blend reorganization occurs to form AM1 aggregates covered by A-300 shells. Organics can displace water from mesovoids toward narrower pores inaccessible for larger molecules or into larger voids to reduce the contact area between immiscible liquids. Freezing point depression caused by confined space and dissolution effects is affected by the blend organization.

The formation of a composite system based on equal amounts of hydrophobic, porous polymethylsiloxane and hydrophilic nanosilicon A-300 was studied. It is shown that during the formation of a composite system the specific surface of the material is significantly reduced, which is due to the close contact between hydrophobic and hydrophilic particles. When water is added to the composite system, in the process of homogenization under conditions of dosed mechanical loading, the effect of nanocoagulation is manifested – the formation of nanosized particles of hydrated silica inside the polymethylsiloxane matrix, recorded on TEM microphotographs. When measuring the value of the interfacial energy of PMS and PMS/A-300 composite by low-temperature 1H NMR spectroscopy, it was found that the effect of nanocoagulation is manifested in a decrease (compared to the original PMS) energy of water interaction with the surface of the composite obtained under small mechanical conditions. its growth when using high mechanical loads. In the process, the binding of water in heterogeneous systems containing PMS, pyrogenic nanosilica (A-300), water and surfactants – decamethoxine (DMT) was studied. Composite systems were created using metered mechanical loads. It is shown that when filling the interparticle gaps of PMS by the method of hydrosealing, the interphase energy of water in the interparticle gaps of hydrophobic PMS with the same hydration is twice the interfacial energy of water in hydrophilic silica A-300. This is due to the smaller linear dimensions of the interparticle gaps in PMS compared to A-300. In the composite system, A-300/PMS/DMT/H2O there are non-additive growth of binding energy of water, which is probably due to the formation, under the influence of mechanical stress in the presence of water, microheterogeneous areas consisting mainly of hydrophobic and hydrophilic components (microcoagulation). Thus, with the help of mechanical loads, you can control the adsorption properties of composite systems and create new materials with unique adsorption properties.

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.

The aim of this review paper was to analyze investigation results on interfacial and temperature behaviors of nonpolar and polar adsorbates interacting with individual and complex fumed metal or metalloid oxides (FMO), initial and subjected to various treatments or chemical functionalization and compared to such porous adsorbents as silica gels, precipitated silica, mesoporous ordered silicas, and polymeric composites. Note that the particulate morphology of FMO depends strongly not only the flame reaction conditions but also on the types and amounts of reagents, as well their distribution in the flame. Therefore, complex nanooxides can include core-shell nanoparticles, (CSNP) of 50-200 nm in size with titania or alumina cores and silica or alumina shells in contrast to simple and smaller nanoparticles of individual FMO. CSNP could be destroyed under high-pressure cryogelation (HPCG) or mechanochemical activation (MCA). These treatments as well simple hydrocompaction (controlled wetting-drying) affect the structure of aggregates of nanoparticles and agglomerates of aggregates, resulting in their becoming more compacted. The analysis shows that complex FMO could be more sensitive to external actions than simple nanooxides such as fumed silica. Any treatment of ‘soft’ FMO affects the interfacial and temperature behaviors of polar and nonpolar adsorbates. Rearrangement of secondary particles and surface functionalization affect the freezing-melting point depression of adsorbates. For some adsorbates, open hysteresis loops became readily apparent in adsorption-desorption isotherms. Clustering of adsorbates bound in pores causes reduced changes in enthalpy during phase transitions (freezing, fusion). Freezing point depression and melting point elevation cause significant hysteresis freezing-melting effects for adsorbates bound to initial and treated FMO in textural pores (voids between nanoparticles in secondary structures). Relaxation phenomena for both low- and high-molecular weight adsorbates or of filled polymeric composites are affected by the morphology of primary particles, structural organization of secondary particles of differently treated or functionalized FMO, content of adsorbates, co-adsorption order, and temperature.

Ultra-soft X-ray emission spectroscopy was used to study the distribution of Op-, Sisd- and Alsd- valence electrons in (SiO2)x(Al2O3)1-x (x = 0.8, x = 0.7) powder mixtures after mechanical treatment. An increase in atomic charges has been measured and can be explained by the transfer of electrons from Si/Al to O atoms in split Opπ-binding states and the formation of the weak long (O O)π bonds between the surface atoms of the contacted powder nanoparticles. Scanning and transmission electron microscopy images show an enhanced agglomeration of the nanoparticles of both SiO2 and Al2O3 oxides, but no changes in the crystalline parameters have been measured using X-ray diffraction. An increase in charge capacities of lithium ion power sources with 0.8SiO2–0.2Al2O3 electrode has been observed during cycling. At the same time, a decrease of the charge capacities with the 0.7SiO2–0.3Al2O3 electrode has been measured. The results are discussed in terms of an increase in the binding energy of electrons in the Op-states, which prevents the recombination and irreversible reactions of lithium with electrode atoms. Otherwise, due to cycling, electron population increase of in non-binding states near the valence band top contributes to the recombination ability of Li+ ions and leads to a decrease in the charge capacity.

The electronic structure of MxOy/SiO2 (M = Mg, Cu) inorganic nanocomposites was investigated using ultrasoft X-ray emission (USXES) and X-ray photoelectron spectroscopy (XPS) methods. The XPS core-...

The effects of water pre-adsorbed onto hydro-compacted hydrophilic nanosilica A-300 and its blend with hydrophobic AM1 (dimethyldichlorosilane hydrophobized A-300) on methane adsorption depend on the amounts of water (h = 0.005−0.25 g per gram of dry solids) and the AM1/A-300 ratio (1:1, 3:1, and 5:1), as well on the pretreatment conditions. The interfacial and temperature behaviors of co-adsorbed water and methane were analyzed using low-temperature 1H NMR spectroscopy (for static samples), cryoporometry, and quantum chemistry. The structural, morphological, and textural characteristics of the materials were studied using 1H MAS and 29Si CP/MAS NMR spectroscopy, infrared spectroscopy, SEM, TEM, and nitrogen adsorption. It is unexpected that 1H NMR signal of methane increases with increasing temperature. This could be occurred due to enhanced molecular mobility and structure changes in mobile water and ice clusters bound in voids between silica nanoparticles in their aggregates, as well because of changes in the textural characteristics of the pretreated blends. The maximal adsorption of methane (38 mg/g at 285 K) is observed for AM1/A-300 (3:1) hydrated at h = 0.1 g/g. An increase or decrease in the content of hydrophobic nanosilica AM1 in the blends, as well the bound water amount, results in a decrease in the methane adsorption, but hydro-compaction of the blends results in increased methane adsorption.

Adsorption of metal species Ba(II), Sr(II), Zn(II), Ca(II), and Mg(II) and anions Cl−, Br−, and I− at a surface of unmodified and partially silylated nanosilica A-300 was studied in aqueous media upon changes in the degree of substitution of silanols to trimethylsilyl groups (ΘTMS) at ΘTMS = 0.272–0.483. The cation adsorption increases in series Sr(II)

Initial Al-100 and hydro-compacted amorphous/crystalline nanoalumina cAl-100 alone or in blends with hydrophobic amorphous nanosilica AM1 were characterized using low-temperature 1H NMR and IR spectroscopies, adsorption, XRD, DSC, microscopy, and cryoporometry. Mechanical treatment of weakly hydrated (0.5 g/g) nanooxides results in their hydro-compaction changing many of the material characteristics. There is overlapping of confined space effects for water bound in voids between nanoparticles with effects caused by the colligative properties of aqueous solution of trifluoroacetic acid in a chloroform medium. The interfacial phenomena determine the temperature behavior of bound water/ice depending on dispersion media features. Contact area between unfrozen water and nanooxide surface is smaller than the specific surface area due incomplete water filling of voids between hydrophilic/hydrophobic nanoparticles. In composites with cAl-100/AM1, there is a tendency of diminution of the contact area of water with hydrophobic nanosilica AM1 and hydrophobic chloroform immiscible with water. This effect changes the temperature behavior of water, which becomes more strongly bound to hydrophilic alumina. The observed effects can be of importance upon practical applications of nanooxide based composites.

The morphological and textural characteristics of hydro-compacted nanosilicas (wetted by various water amounts in the range of hcp = 0.3–5.0 g per gram of dry silica, and then dried) were analyzed using low-temperature 1H NMR spectroscopy, SAXS, SEM, TEM, IR spectroscopy, and nitrogen adsorption methods. The results of the hydro-compaction of nanosilica A-300 depend strongly on the hcp value, which can be varied to control reorganization of secondary and ternary structures formed by nanoparticles. The compaction is accompanied by non-monotonic changes in the textural characteristics; however, the nanoparticles per se are practically not affected by the treatment. At hcp ≤ 1 g/g, the reorganization of secondary/ternary structures does not lead to diminution of the specific surface area (SBET); however, at hcp ≥ 1.5 g/g, the SBET value decreases, but the pore volume increases despite the empty volume of the powder decreases from 21.8 cm3/g for initial A-300 (bulk density ρb = 0.045 g/cm3) to 3.45 cm3/g on compaction at hcp = 4.5 g/g (ρb = 0.256 g/cm3). The structural reorganization of hydro-compacted powders is possible after addition of new water amount. This suggests that the chemical bonds between neighboring nanoparticles do not practically form upon the hydro-compaction. Thus, hydro-compacted nanosilica can lose a dust-forming property but remains active with respect to nanoparticles mobility and possibility of reorganization of the secondary structures with nanoparticles.

The temperature behavior of water bound to compacted nanosilica cA-300 alone or in mixture with hydrophobic nanosilica AM1 alone or with addition of human serum albumin (HSA) or tannin was compared for different dispersion media (air, CDCl3 alone or with addition of HCl or trifluoroacetic acid, TFAA) using low-temperature 1H NMR spectroscopy and cryoporometry. There is overlapping of the confined space effects for water bound in voids between silica nanoparticles with the effects caused by the colligative properties of aqueous solutions of TFAA or HCl. These phenomena determine the temperature behavior of bound water unfrozen at T

Nanoporous microspheres with divinylbenzene (DVB), styrene (St), and lignin were synthesized by an emulsion-suspension polymerization method. Several types of lignins were used: (1) kraft lignin be ...

The heat of immersion and surface properties of hydroxyapatite initial and modified (containing Ca, P, and CO32−) and composites with fumed oxides were examined using microcalorimetry. The microcalorimetric measurements showed a regular decrease in the heat of immersion in water per area unit with an increase in the specific surface area of samples. The nitrogen adsorption/desorption isotherms were used to estimate the textural characteristics of the materials studied.

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, SBET. 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, Tg, mobile amorphous fraction, MAF), crystallization temperature, Tc, and crystalline fraction (CF) were followed. Results were further evaluated in terms of the rigid amorphous fraction, RAF, and the respective contributions of crystals, RAFcrystal, and of filler-polymer interfaces, RAFfiller. 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 RAFfiller), 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 separated in that case. For both cases of filler, changes in RAF correlate well with those in the SBET value of initial particles. This result supports previous observations in nanocomposites based on PDMS of various low molecular weights adsorbed onto metal oxide nanoparticles with a wide range of SBET.

Methane adsorption onto hydrated (0.1 g/g) initial and compacted nanosilica A-50 and compacted A-50/hydrophobic AM1 (based on nanosilica A-300) and water behavior vs. temperature were analyzed using 1H NMR and theoretical methods. Methane adsorption increases with temperature because of changes in structure of mobile water. Stronger compaction of A-50 than that of A-50/AM1 (due to negative effect of AM1 preventing formation of tight contacts between A-50 nanoparticles) leads to decrease in adsorption of methane onto dense A-50 alone. These effects cause the difference in temperature behavior of bound water.

It has been assumed that nanoparticle/aggregate/agglomerate structure, texture and surface characteristics of hydrophobic nanosilica AM1 treated with certain amounts of arginine and water may provide better conditions for methane adsorption compared to AM1 alone. Nanosilica and composites are characterized using adsorption, desorption, microscopic, spectroscopic, XRD, SAXS, and quantum chemistry methods. The 1H NMR spectroscopy (at 200–283 K) and cryoporometry (T

A variety of unmodified and modified fumed silica A-300 and silica/titania (ST20 and ST76 at 20 and 76 wt.% of titania, respectively) was prepared to analyze features of their interactions with polar and nonpolar adsorbates. The materials were studied using nitrogen adsorption-desorption, ethanol evaporation kinetics, infrared (IR) spectroscopy, thermogravimetry (TG), photon correlation spectroscopy, differential scanning calorimetry (DSC), DSC and TG thermoporometry, and quantum chemistry. Changes in surface structure of modified nanooxides with increasing hydrophobization degree (Θ MS ) from 20% to 100% have a strong affect on the textural characteristics of the materials and adsorption-desorption of various adsorbates. Confined space effects enhanced due to the location of adsorbates in narrow voids between nanoparticles lead to freezing-melting point depression for bound polar and nonpolar adsorbates. The behavior of particles of modified nanooxides in aqueous and water/ethanol media is strongly altered due to enhanced aggregations with increasing value of Θ MS . All of these change are non-monotonic functions of Θ MS which affects (i) rearrangement of nanoparticles, (ii) interactions with polar and nonpolar adsorbates, (iii) location of adsorbates in voids of different sizes, (iv) the clustering of adsorbates and formation of nearly bulk structures.

Solid phase extraction of aliphatic and aromatic explosives (nitrate esters, nitramines and nitroaromatics) on Ni-, NiCo- and Co- carbon composites was studied. It was shown that the composites could be used as materials tailored for effective extraction of explosives from aqueous samples (spiked lake water) and their selective elution − desorption with acetonitrile (aliphatic explosives), and dimethylformamide (aromatic explosives). The composites were obtained from phenol-formaldehyde resin as a carbon precursor using a mechanochemical method and pyrolysis at 800 °C. The structure and morphology of the nanocomposites were characterized using nitrogen adsorption, Raman spectroscopy, XRD, SEM, and TEM methods It came out that particles of the composites consist of metal core coated with relatively uniform graphitic layers of several nanometers in thickness. It was ascertained that texture and porosity of the composites are strongly depended on the applied metal, e.g. mesoporosity ot the samples increases in the line of Ni − NiCo − Co composite.

Wastewaters containing organic and inorganic contaminants such as dyes, heavy metal ions, salts, and surfactants are considered to be a serious environmental problem in human society. Adsorption is the most popular technique for wastewater treatment. In this paper, a new mesoporous silica-alumina oxide (97% SiO 2 , 3% Al 2 O 3 ) synthesized by pyrogenic method was proposed as a sorbent for acid (C.I. Acid Orange 7), reactive (C.I. Reactive Black 5) and direct (C.I. Direct Blue 71) dyes as well as for heavy metal (Co(II), Cu(II), Ni(II), Zn(II)) ions removal from the aqueous solutions and wastewaters. The batch method was employed. The parameters such as phases contact time (1–360 min), initial metal and dyes concentrations (10, 20, 30 mg/L), effect of hydrochloric acid concentration (0.1–6.0 M), anionic surfactant (0.1–1.0 g/L) and salt (5–20 g NaCl/L) as well as wastewater decolorization were studied. The kinetic and equilibrium studies were also performed. An equilibrium time of 1 min and >240 min was required for the adsorption of heavy metal ions and dyes onto mixed oxide, respectively. The experimental data were better fitted to the Freundlich equation than to the Langmuir one. The potentiometric titrations indicated that dyes and heavy metal ions adsorption influence the structure of electrical double layer at the mixed oxide - liquid interface which was evidenced by changes in the solid surface charge density. The results showed that the mixed oxide could be an effective adsorbent especially for heavy metal ions removal from aqueous and industrial wastewaters.

Interfacial effects in polymer nanocomposites (PNCs) of poly(dimethylsiloxane) (PDMS) and titania, prepared by in-situ generation of titania nanoparticles in the presence of crosslinked PDMS (sol-gel PNCs) and by adsorption of linear PDMS on fumed crystalline titania nanoparticles (core-shell PNCs), were comparatively investigated by DSC and by two dielectric techniques, broadband dielectric spectroscopy (BDS) and thermally stimulated depolarization currents (TSDC). The PNCs are characterized by the presence of hydrogen bonding interactions between the oxygens in the backbone of PDMS and the hydroxyls on the oxide surface. DSC results show that a fraction of polymer in an interfacial layer in the PNCs is immobilized making no contribution to the glass transition, whereas it shows reduced segmental mobility with respect to the bulk by dielectric techniques. The results are quantified in terms of the fraction of polymer with restricted mobility (the interfacial fraction), the thickness of the corresponding interfacial layer and the temperature dependence of restricted and bulk segmental mobility. The interfacial fraction is larger in the sol-gel PNCs, in agreement with a larger surface to volume ratio, whereas the interfacial dynamics is slower and less cooperative for the core-shell PNCs. Compared with similar PDMS/silica PNCs studied previously, interfacial effects are more pronounced in the titania based PNCs.

The increasing availability of various types of technical lignins as result of the emergence of new biorefinery technologies has boosted the interest in the commercialization of lignin-based materi ...

Novel stable ZnO photocatalyst prepared via simple high-thermal processing of resorcinol-formaldehyde/zinc acetate mixture was synthesized for photocatalytic purposes. As a reference, pure ZnO was obtained using Zn(CH3CO2)2. The UV–vis spectra demonstrate an intensive absorption of composite ZnO within the visible region, in contrast to pure ZnO (white). The kinetic parameters of the diclofenac sodium photodecomposition reaction reflect higher activity of composite ZnO unlike pure ZnO and P25 (Evonik). Comparative study of bisphenol A degradation during Advanced Oxidation Processes involving ZnO and visible light irradiation demonstrated outstanding role of synthesized photocatalyst.

Interactions of human serum albumin (10 wt% H 2 O and 0.3 wt% sodium caprylate) with doxorubicin hydrochloride (1 wt%) were studied alone or with addition of HCl (3.6 wt% HCl) using 1 H NMR spectroscopy. A model of hydrated HSA/12DOX was calculated using PM7 method with COSMO showing large variations in the binding constant depending on structural features of DOX/HSA complexes. DOX molecules/ions displace bound water from narrow intramolecular voids in HSA that leads to diminution of freezing-melting point depression of strongly bound water (SBW). Structure of weakly bound water (WBW) depends much weaker on the presence of DOX than SBW because a major fraction of DOX is bound to adsorption sites of HSA. Addition of HCl results in strong changes in structure of macromolecules and organization of water in hydration shells of HSA (i.e., mainly SBW) and in the solution (i.e., WBW + non-bound bulk water).

A series of silica gels (Si-40, Si-60, Si-100) and related carbon–silica gels, prepared by carbonization of CH2Cl2 at a surface of silica gels at 550 °C, characterized using FTIR/PAS, SEM/EDX, and nitrogen adsorption, was investigated upon interactions with polar (water, dimethylsulfoxide), weakly polar (chloroform), and nonpolar (n-hexane, n-decane, benzene, toluene) adsorbates using adsorption and differential scanning calorimetry methods. Features of confined space effects, such as freezing/melting point depression and melting delay, depend strongly on pore sizes, pore wall structure, type and amount of adsorbates, and the degree of pore filling. Melting curves of both polar and nonpolar adsorbates bound in broad pores (Si-60 and Si-100 based materials) can include two–three peaks around melting point, but for Si-40-based materials, a number of similar peaks is smaller. This occurs due to step-by-step melting of frozen structures located in broader pores and the absence of similar effects in narrower pores. The present study shows that complex carbon–silica gel adsorbents can be more effective adsorbents than simple silica gels due to the presence of a number of surface sites of various polarity and structure.

This work deals with effects of polymer molecular weight, Wm, below the entanglement threshold, Wm,e, on molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto silica particles, employing differential scanning calorimetry (DSC) and two dielectric techniques: broadband dielectric spectroscopy (BDS) and thermally stimulated depolarization currents (TSDC). The rigid amorphous polymer fraction at interfaces, RAFint, was found suppressed for larger Wm by all techniques in qualitative agreement with each other. Results on RAFint were supported by evaluating, for the first time, the coverage of hydroxyls at the surfaces of nanoparticles by polymer chains (S relaxation). The mobility of interfacial polymer (αint relaxation) was followed by BDS and TSDC, showing suppression of dynamics and cooperativity with decreasing Wm. We suggest that interfacial polymer fraction and dynamics are dominated by the concentration of polymer–particle contact points, the latter increasing for smaller Wm due to more free ch...

Adsorption modification of fumed silica by polymers allows effective changes in the properties and characteristics of complex materials. The efficiency of both well-known liquid-phase adsorption modification methods, such as adsorption under equilibrium and impregnation conditions, as well as the gas-phase modification, have been compared to that of gas-phase solvato-stimulated adsorption modification (GSSAM) developed by the authors. It has been shown that structure of medicinal polymers (poly(vinyl pyrrolidone), poly(ethylene oxide), poly(vinyl alcohol), carboxymethylcellulose) adsorbed onto a silica surface was practically independent of the method of silica modification. However, the differences are significant with respect to the efficiency of liquid-phase and gas-phase processes in comparison to GSSAM, especially from practical and technological points of view. The set of the GSSAM characteristics allows us to consider this method as an environmentally friendly, green technology.

Differently functionalized silica nanoparticles are the best fillers for various polymers, for example, liner, branched, cross-linked, polar/nonpolar, ionic, etc. There are numerous modifiers of silica fillers, and among them silanes are the best ones to create stable functionalities since stable Si–O–Si bonds are formed. Some functionalities can be cross-linked with polymers or take part in polymerization reactions. In situ synthesized silica nanoparticles in polymeric (or a monomer mix) media give another effective pathway to produce hybrid nanocomposites for various applications.

Disperse polymethylsiloxane (PMS) alone and in a mixture with highly disperse nanosilica A-300 was studied as a dry powder and a hydrogel located in various dispersion media (air, chloroform alone and with addition of trifluoroacetic acid) using low-temperature 1H NMR spectroscopy, cryoporometry, thermogravimetry, nitrogen adsorption, microscopy, infrared spectroscopy, and quantum chemistry. The powders of dried PMS and PMS/A-300 can be easily rehydrated upon strong stirring with added water. The slurry properties depend on mechanical treatment features due to stronger compaction of the secondary structures with increasing mechanical loading. The organization of bound water (at a constant hydration degree h = 1 g/g) depends strongly on the dispersion media (because chloroform can displace water from narrow interparticle voids into broader ones or into pores inaccessible for larger CDCl3 molecules) and mechanical loading reorganizing aggregates of PMS and A-300 nanoparticles ( 1 μm) of aggregates. The PMS/nanosilica blends could be of interest from a practical point of view due to additional control of the textural and structural characteristics determining efficiency of sorbents with respect to low- and high-molecular weight compounds depending on the dispersion media that is of importance, e.g., for medical applications.

Freeze-dried multi-layer graphene oxide (MLGO), produced from natural flake graphite using ionic hydration method, demonstrates strong interactions of functionalized carbon sheets with polar or nonpolar adsorbates or co-adsorbates depending on the characteristics of dispersion media. Interactions of MLGO with a mixture of water and n-decane in chloroform media provide specific surface area (Su) in contact with unfrozen liquids greater than 1000 m2/g corresponding to stacks with 3–5 carbon layers. Electrostatic interactions between functionalized carbon sheets in dried MLGO are very strong. Therefore, nonpolar molecules (benzene, decane, nitrogen) cannot penetrate between the sheets. Water molecules can effectively penetrate between the sheets, especially if MLGO is located in weakly polar CDCl3 medium. In this case, n-decane molecules (co-adsorbate) can also penetrate into the sheet stacks and locate around nonpolar fragments of the sheets. The Su value of MLGO being in contact with unfrozen water can reach 360 m2/g, but upon co-adsorption of water with decane Su = 930 m2/g, i.e., hydrophobic interactions of the mentioned fragments with decane are stronger that with co-adsorbed water. Water alone (0.25 or 0.5 g/g) bound to MLGO in a mixture with fumed silica A-300 in air or CDCl3 media can provide Su = 30–50 m2/g. Pores in wetted MLGO or MLGO/A-300 mainly correspond to mesopores. Nanosilica does not provide significant opening of the MLGO sheet stacks during their mechanical mixing.

Investigations of interfacial and temperature behaviors of nonpolar and polar adsorbates interacting with individual and complex fumed metal or metalloid oxides (FMO), initial and subjected to various treatments or chemical functionalization and compared to such porous adsorbents as silica gels, precipitated silica, mesoporous ordered silicas, filled polymeric composites, were analyzed. Complex nanooxides include core-shell nanoparticles, CSNP (50-200nm in size) with titania or alumina cores and silica or alumina shells in contrast to simple and smaller nanoparticles of individual FMO. CSNP could be destroyed under high-pressure cryogelation (HPCG) or mechanochemical activation (MCA). These treatments affect the structure of aggregates of nanoparticles and agglomerates of aggregates, resulting in their becoming more compacted. The analysis shows that complex FMO could be more sensitive to external actions than simple nanooxides such as fumed silica. Any treatment of 'soft' FMO affects the interfacial and temperature behaviors of polar and nonpolar adsorbates. Rearrangement of secondary particles and surface functionalization affects the freezing-melting point depression of adsorbates. For some adsorbates, open hysteresis loops became readily apparent in adsorption-desorption isotherms. Clustering of adsorbates bound in textural pores in aggregates of nanoparticles (i.e., voids between nanoparticles in secondary structures) causes reduced changes in enthalpy during phase transitions (freezing, fusion, evaporation). Freezing point depression and melting point elevation cause significant hysteresis freezing-melting effects for adsorbates bound to FMO in the textural pores. Relaxation phenomena for both low- and high-molecular weight adsorbates or filled polymeric composites are affected by the morphology of primary particles, structural organization of secondary particles of differently treated or functionalized FMO, content of adsorbates, co-adsorption order, and temperature.

A novel approach is proposed to modify the porous structure and surface properties of the polymers used in solid-phase extraction. The approach involves soaking in water or acetone, followed by freezing in liquid nitrogen (77.4 K) and was employed for two polymeric materials: Amberlite XAD-7 and Amberlite XAD-16. Variations in the surface properties of the adsorbents were justified by the action of acetone and water as solvents affecting the textural and other characteristic of the materials. The initial and treated adsorbents were used in extraction of explosive nitramines from aqueous samples. The performed modifications of the polymer texture allow us to increase the recovery rate as compared with the initial adsorbents. The results were justified by the swelling of fragments of the polymers and by the additional process of sorption of nitramines. The results indicate that polymeric adsorbents can be easily modified by the soaking/freezing process and the materials can be achieved that prove usefulness for the effective separation of explosive nitramines from aqueous samples.

In this study, a set of CoFe 2 O 4 /SiO 2 /TiO 2 nanocomposites was synthesized. The total concentration of metals (Co + Fe) was varied from 3 to 9 mmol with respect to 1 g of SiO 2 . Titania was formed in two concentrations — 2 and 4 mmol/g. The structure of the samples was analyzed by application of XRD, UV–vis spectroscopy, magnetometry, SEM, low-temperature nitrogen adsorption–desorption and Mossbauer spectroscopy. Photocatalytic degradation of an organic model compound – carbamazepine (CBZ) – was studied in the presence of the nanocomposites under ultraviolet irradiation ( λ = 254 nm) in a batch reactor. Two types of media (distilled and tap water) were used. The X-ray diffraction patterns demonstrate the formation of CoFe 2 O 4 and TiO 2 (anatase). The studied materials reveal a better activity than commercial sample of P25 (Evonik) during degradation of carbamazepine (CBZ). It has been found that the type of water medium affects the CBZ decomposition differently: there is residual CBZ observed in distilled water in 60 min of treatment. Contrastingly, in tap water the total decomposition of CBZ took place. This may be due to the occurrence of Fe 3+ ions which stimulate the formation of active sites of chlorine dissolved in tap water.

Initial and treated silicas of different origin, such as fumed and precipitated silicas and silica gel, were studied using infrared spectroscopy, DSC, NMR, and adsorption methods. Mechanochemical activation (MCA) of fumed silica A-300 in a ball-mill or a microbreaker affects the structure of aggregates of nanoparticles and agglomerates of aggregates becoming more compacted. Any treatment of ‘soft’ nanosilica affects the interfacial behavior of polar and nonpolar adsorbates because the rearrangement of secondary particles affects the freezing–melting point depression. Clusterization of adsorbates bound in pores causes diminution of heat effects during phase transition (freezing or fusion). The freezing point depression and increasing melting point lead to the hysteresis in freezing–melting of adsorbates bound in pores. The study shows that fumed and precipitated silicas can be more sensitive to external actions, such as wetting–drying and MCA, than silica gels because of less dense packing of nanoparticles in the secondary structures. These effects should be considered upon applications of similar materials in different media.

Individual and complex fumed nanooxides were studied using high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet-visible (UV–vis) spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, adsorption, desorption (evaporation), and quantum chemical methods. For mixed nanooxides in contrast to simple and small nanoparticles of individual silica or titania, complex core–shell nanoparticles (50–200 nm in size) with titania or alumina cores and silica or alumina shells can be destroyed under high-pressure cryogelation (HPCG), mechnochemical activation (MCA) that also affect the structure of aggregates of nanoparticles and agglomerates of aggregates becoming more compacted. This is accompanied by changes in color from white to beige of different tints and changes in the UV–vis spectra in the 300–600 nm range, as well as changes in crystalline structure of alumina. Any treatment of ‘soft’ nanooxides affects the interfacial behavior of polar and nonpolar adsorbates. For some of them, the hysteresis loops become strongly open. Rearrangement of secondary particles affects the freezing-melting point depression. Clusterization of adsorbates bound in pores causes diminution of heat effects during phase transition (freezing, fusion). Freezing point depression and increasing melting point cause significant hysteresis freezing-melting effects for adsorbates bound to oxide nanoparticles. The study shows that complex nanooxides can be more sensitive to external actions than simple nanooxides such as silica.

Kefir grains (KG) were studied using low-temperature 1 H NMR spectroscopy, DSC, and thermogravimetry to analyse the influence of the hydration degree on the properties of water bound in KG, as well as effects of dispersion media (air, weakly polar CDCl 3 , CDCl 3 + F 3 CCOOD) and temperature. An increase in water content added to dried KG results in changes in water structure and supramolecular organisation in bacteria, low- and high-molecular components of KG. Five types of water are observed in KG: (i) weakly associated water characterised by a low value of the chemical shift of proton resonance d H = 1–2 ppm; (ii) strongly associated water at d H = 4–5.5 ppm (similar to that of bulk water), (iii) weakly bound water frozen at 265 K

The quantum-chemical methods used for describing the processes at the surface of Diesel fuel droplets are summarised. Some results relevant to practical engineering application in Diesel engines, obtained previously, are summarised. Assuming that the droplets are so small that their interaction with individual molecules can be described using the methods of the kinetic gas theory (they can be considered as clusters/nanodrops), it was shown that the evaporation rate depends on partial pressures, temperature, and the sizes and masses of molecules and clusters/nanodrops. The results of the analysis of the collision processes between n-dodecane (approximation of Diesel fuel) molecules and clusters/nanodrops, based on the Dynamic Reaction Coordinate (DRC) method, are described. It is concluded that the probability of the attacking molecule sticking to a droplet is maximal if the molecular plane is parallel or almost parallel to the droplet surface. If the kinetic energy of the attacking molecules is high (greater than that corresponding to the boiling temperature) then it is expected that it will scatter and be removed from the cluster/nanodrop surface. The mechanisms of evaporation of microdrops and nanodrops are shown to involve rather different processes. In the case of microdrops, individual C12 molecules are evaporated from their surfaces, while in the case of nanodrops they can be disintegrated into clusters and individual molecules. The decrease in the likelihood of evaporation/condensation with temperature, predicted by the quantum-chemical (QC) approach, agrees with the prediction of the classical theory based on the MD simulations of n-dodecane molecules. The results of the estimation of the evaporation/condensation coefficient of n-dodecane molecules using the transition state theory (TST), based on the QC/DFT approach and taking into account the conformerisation of n-dodecane molecules, are summarised. It is shown that taking into account the QC effects leads to marginal modifications of the predicted evaporation/condensation coefficient, particularly at temperatures which are not close to the critical temperature.

Hydroxyapatite composite is a very important biomaterial, which can be applied in various life areas. Hydroxyapatite and its composites with fumed oxides ST20, AST1, Al2O3, A90, and A300 were prepared and studied using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy adsorption, potentiometric titration, quasi-elastic light scattering and zeta potential measurements. The values of pHpzc (the point of zero charge) and pHIEP (the isoelectric point) characteristic of the electrical double layer depend on the type of the fumed oxide matrix. Comparative studies of hydroxyapatite, fumed oxides and composites by adsorption and desorption of nitrogen, scanning electron microscopy and FTIR showed that in most cases composites have properties intermediate between hydroxyapatite and the oxides taken for the synthesis.

Morphology, thermal transitions and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto low specific surface area (25 m 2 /g) spherical-like titania (TiO 2 ) nanoparticles were studied employing adsorption–desorption nitrogen isotherms, morphology (SEM), calorimetry (DSC) and dielectric (BDS) techniques. The initial titania particles (crystallites of 40–140 nm in diameter) were found to aggregate forming voids of a broad range. PDMS was adsorbed in the interior of voids in aggregates and onto external surfaces of the aggregates. With nanoparticles content increasing an increase in the glass transition temperature, T g , is observed in DSC, accompanied by a broadening of the glass transition step and a decrease in the heat capacity step, Δ C p . According to BDS the interfacial polymer fraction is larger and exhibits slower dynamics ( α int relaxation) in the case of shorter PDMS chains (∼22 monomers/chain) as compared to longer chains (∼105 monomers/chain). Changes in the interfacial polymer fraction correlate well with changes in the specific surface area of the aggregates, as recorded by gas molecules adsorption–desorption, and with morphology (SEM). Comparison with previous results obtained with PDMS-based nanocomposites suggests that interfacial polymer fraction and dynamics are dominated by the concentration of polymer–particle contact points (increased for shorter chains due to more free chain ends), rather than by the strength of polymer–filler physical bonds.

A Discrete Component Model (DCM) is applied to study the heating and evaporation of suspended kerosene and kerosene surrogate droplets. The effects of natural convection are taken into account using the Churchill approximation, whilst the effects of heat addition from the supporting fibre are modelled using the assumption that heat supplied via the fibre is uniformly distributed within the droplet volume. The results of taking into account and ignoring the above effects are investigated. It is shown that the effect of supporting fibre can be ignored in the analysis of these droplets. In contrast, the effect of natural convection cannot be ignored. The time evolution of droplet radii predicted by the DCM, taking into account the effects of natural convection and supporting fibre, is shown to be close to experimental predictions of this parameter for gas temperatures in the range 500 °C to 700 °C. The heating and evaporation of kerosene droplets are compared with those for droplets of various kerosene surrogate fuels, including eleven surrogate fuels proposed in the literature, and two original compositions. Considering the balance between the heating and evaporation characteristics of droplets we conclude that those of the original surrogate SU1 and the modified Utah surrogate are the closest to those of kerosene droplets.

To improve structural characteristics of clays and neem leaf powder (NLP)/clay composites, nanosilica was used as an addition upon mechanical treatment. This results in composites with natural nanostructured materials (NNM) possessing improved structural characteristics and bioactivity. The blends based on NNM with crystalline kaolinite alone and kaolinite/α-quartz or calcite/α-quartz + clay and amorphous admixtures and additions with nanosilica or nanosilica/NLP were treated in a knife mill. The materials were characterized using TEM, SEM, XRD, 1H MAS and 29Si CP/MAS NMR, FTIR spectroscopy, elemental analysis, nitrogen adsorption, quantum chemistry, release of bioactive components and bactericidal effects against various bacteria. There are regularities in the characteristics depending on a type of NNM, particulate morphology and textural features of solids. The morphological and structural characteristics of components slightly changed in the blends because the treatment was performed using relatively low mechanical loading. Release of chlorophyll and anthocyanins is greater for NLP/A―300/NNM composites (especially characterized by minimal confined space effects) than for NLP alone. Some clays and composites demonstrate bactericidal activity tested against four types of bacteria. The morphological, textural, and structural characteristics of the NNM/A―300 and NNM/A―300/NLP systems, as well NLP transformation into a nanostructured state, allow one to expect high activity of the composites as bioactive systems interesting for practical applications in medicine and cosmetics.

Three polydimethylsiloxanes (PDMS200, PDMS1000, and PDMS12500 with numbers showing the viscosity values dependent on the molecular weight) were used for adsorption (14–95 wt% PDMS) onto unmodified and PDMS-modified (16.7 wt% PDMS using dimethyl carbonate (DMC) as a siloxane bond breaking reagent) nanosilica A-300. The materials were studied using microscopy, infrared spectroscopy, thermodesorption, calorimetry, ethanol and water/ethanol evaporation, nitrogen adsorption-desorption, and quantum chemical methods. The interfacial and temperature behaviors of a PDMS layer at a silica surface depend strongly on the type of bonding to silica particles, molecular weight and content of PDMS. Upon chemical bonding, shorter PDMS200 forms a denser coverage of the silica surface since SBET diminution is larger and residual free silanols are practically absent (the degree of free silanol substitution Θ > 0.95) in contrast to the reactions with PDMS1000/DMC or PDMS12500/DMC providing Θ = 0.60–0.63 at larger SBET values. Upon thermal decomposition of the PDMS layer, oxidation/depolymerization desorption gives a greater contribution than pure depolymerization destruction. An increase in the PDMS adsorption layer thickness leads to enhancement of the depolymerization contribution because the oxidation mainly occurs at the top of the layer, but the depolymerization can occur in the total PDMS layer. The adsorption, desorption, and evaporation processes of low-molecular weight probes at a surface of PDMS-modified nanosilica depend strongly on the type of bonding and content of PDMS. Thus, the most effective hydrophobization of nanosilica by PDMS/DMC could be carried out using the shortest polymer giving the shortest PDMS fragments upon the interaction with DMC that is of interest from a practical point of view.