To avoid dependence on conventional raw materials, global emphasis has been placed on obtaining alternative plant celluloses and the chemical synthesis of cellulose. The use of synthetically derived cellulose as a precursor for cellulose nitrates (NCs) is currently absent in global practice, which underscores the undoubted relevance of this research. Cellulose nitrate (NC) was synthesized in a 138% actual yield by nitration of synthetic cellulose (SC)-a new type of cellulose-prepared by electropolymerization from an aqueous glucose solution in the presence of catalytic tungsten-vanadium heteropolyacid of the 1-12 series with the chemical formula H6[PW10V2O40]: a nitrogen content of 11.83%, a viscosity of 198 mPa·s, a high solubility of 91% in an alcohol-ether solvent, and an ash content of 0.05%. SEM provided a general concept of the morphological structure of SC and SC-derived NC. The initial SC consisted of flat, curly fibers with a smooth surface approximately 10-20 μm wide, with no aggregation observed. The fibers of SC-derived NC had a cylindrical shape with a diameter of up to 25 μm and a rough surface. FT-IR spectroscopy revealed that SC and SC-derived NC have the main functional groups characteristic of classical cellulose (3346, 2901, 1644, 1429, 1162, and 1112 cm-1) and nitrate esters of cellulose (1650, 1278, 832, 747, and 689 cm-1), respectively. For the first time, a full-profile analysis discovered that SC is made up of the monoclinic phase of cellulose Iβ with an antiparallel chain arrangement. SC with a crystallinity index (CrI) of 81-86% was shown to undergo amorphization upon nitration, with the CrI declining to 17% and the crystallite sizes decreasing from 44 × 62 × 59 × 94 Å to 29 × 62 × 26 × 38 Å. Coupled TGA/DTA revealed that SC exhibits a high-temperature endothermic peak of decomposition of 374 °C, with a weight loss of 84%. The thermostable SC-derived NC exhibits a high onset temperature of intense decomposition of 200 °C and an exothermic peak of 208 °C, with a weight loss of 88%, and is characterized by a high specific heat of decomposition of 7.74 kJ/g. This study provides new insights into the functionalization of SC with a high degree of polymerization, expanding the classical concepts of cellulose nitration.

Nanocrystalline cellulose (NCC) was successfully obtained from two Arctic brown algae species, Laminaria digitata and Saccharina latissima. The production process involved a sequential extraction of non-cellulosic compounds, an environmentally friendly bleaching process with hydrogen peroxide, and subsequent acidic hydrolysis, resulting in the formation of nanosized rod-like particles. Comprehensive assessments were conducted to evaluate the influence of hydrolysis conditions, specifically using hydrochloric and sulfuric acids, on the key characteristics of the nanocellulose. The resulting NCC was characterized using various techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA, DTG), scanning electron microscopy (SEM), laser diffraction, and low-temperature nitrogen sorption. The obtained algal NCC demonstrated a yield of 76–91%, a degree of polymerization of 150–230 units, and a crystallinity index of 69–80%. The choice of acid during the production significantly influenced the thermal stability, particle size distribution, and porous properties of the samples. Remarkably, the algal NCC, acquired in the form of stable gel-like suspensions, exhibited robust stability during extended storage. These materials showcase promising potential for applications in biomedicine, serving as versatile components for hydro/aerogels, matrices, and fillers in the development of advanced medical dressings.

On the basis of X-ray diffraction experiment data the atomic molecular configuration in the short-range order region of amorphous nitrocellulose from Miscanthus is constructed by the computer simulation technique using the HyperChem 8 program. It is shown that the arrangement of atoms in the short-range order region of amorphous nitrocellulose is satisfactorily described by a cluster composed of nine nitrocellulose chains, two cellulose I chains twisted by an angle of 72°, and two untwisted cellulose I chains. Each chain contains ten glucose residues. In the final cluster, the above-mentioned chains form an approximately hexagonal layer in projection on plane ab with a distance between them being 12.2 Å. In projection on plane bc , the dimensions of the final cluster are 28 Å along axis b and 54 Å along axis c . The total number of atoms is 3300, and the degree of polymerization is 130; the formula unit of the asymmetric fragment is [C 6 H 7.24 O 2 (OH) 0.92 (ONO 2 ) 2.08 ] 130 . The result reliability is proved by the fact that the experimental curve of X-ray scattering intensity distribution I ( s ) and the corresponding curve calculated for the cluster coincide with an accuracy of up to 7.5%.

The global abundance and availability of oat hulls make them a promising feedstock to produce a unique type of cellulose, the bacterial one. This is the first study examining how a chemical pretreatment method of oat hulls influences the yield and properties of bacterial cellulose (BC) in extended cultivation. Here we employed our own pretreatment methods that use dilute HNO3 and NaOH solutions in one and two stages, a total of four pretreatment methods. Further technological stages were performed in the same manner: pulps were enzymatically hydrolyzed with commercial enzymes CelloLux-A and BrewZyme BGX, and biosynthesis of BC was run using the Medusomyces gisevii Sa-12 symbiotic culture. A two-stage (HNO3 + NaOH) pretreatment of oat hulls was found to afford a biologically good medium and increase the BC yield 1.8−3.2-fold compared to the other pretreatments used. A pretreatment method of oat hulls determined the BC yield and degree of polymerization. However, a pretreatment method had no impact on the highest crystallinity index and allomorph Iα content of all the BC samples, which is explained by Medusomyces gisevii Sa-12 used. The crystallinity index and allomorph Iα content, as measured by X-ray diffractometry, are proposed for use as BC quality assessment criteria.

The structure of amorphous-crystalline titanite obtained by mechanical activation was studied by X-ray diffraction and simulation methods. The short-range order characteristics were calculated using Finbak-Warren's method. It was found that the coordination numbers of metal atoms decreased as the result of titanite grinding. The atomic configurations of short-range order of ground titanite were constructed by translation of titanite unit cell. The theoretical X-ray patterns were calculated using Debye's method and were compared with the experimental curves. The structure of ground titanite in the mill with centrifugal factor 40 g was described satisfactorily by the model of mechanical mixture of clusters containing 2016 atoms, disordered during the molecular dynamics with clusters containing 12096 atoms. The increase of grinding intensity led to the sharp decrease of sizes of small cluster.

To maintain the competitiveness of Russia in the world market, a strategically important task for manufacturers of high-energy cellulose ethers is to find a worthy alternative to cotton and sulfite cellulose. The two most optimum solutions to replacement of conventional resources to overcome the existing problem can be discriminated: alternative easily renewable plant-based feedstocks and their synthetic analogues as replacements. The present study investigates if two conceptually different feedstocks-the grain-processing waste, oat hulls, and synthetic cellulose derived by electropolymerization-can be used as the precursor of cellulose nitrates. The comparative analysis of the cellulose samples established that the synthetic cellulose sample exhibits a higher quality and a more homogeneous morphological structure of cellulosic fibers, as opposed to the cellulose sample isolated from oat hulls. X-ray diffraction discovered that both celluloses match cellulose I beta and the crystallinity values are over 60%, namely, 77.0% for synthetic cellulose and 64.4% for oat-hull cellulose. The resultant cellulose nitrates have the following basic properties: 11.61-11.74% nitrogen content, 93-200 mPa center dot s viscosity, and the same solubility in alcohol-ether mixture at 91%. The morphological features of the cellulose nitrates obtained from both feedstocks were characterized by scanning electron microscopy. FTIR Fourier spectroscopy confirmed the synthesized products to be low-substituted nitric-acid cellulose esters. The crystallinity values calculated from the X-ray patterns by two ways were 4.7-10.0% for the oat-hull cellulose nitrates and 7.0-13.0% for the synthetic cellulose-derived cellulose nitrates, that is, the cellulose is amorphous as a result of nitration. The d-spacing in the X-ray diffraction patterns of the crystalline component of the cellulose nitrates was shown to be consistent with the literature data for the pseudo-orthorhombic phase of cellulose trinitrate. The findings reported justify the expediency of using the new alternative sources as the precursor of cellulose nitrates, with synthetic cellulose being of choice.

A series of LiNbO3:Er ([Er] = 0.08-2.71 wt%) crystals were grown due to one technology in a single technological cycle. A near-stoichiometric lithium niobate (NSLN) was grown as a control. Concentration dependences of LiNbO3:Er and NSLN crystals structure characteristics were studied. A full-profile analysis of polycrystals X-ray patterns was used to analyze models of LiNbO3:Er atom structure. Structure characteristics of LiNbO3:Er crystals are compares with that of NSLN crystal. Optical and atomic-force microscopy were used to study growth irregular and regular domain microstructures and periodic nano-structures in as-grown LiNbO3:Er crystals.

A series of LiNbO 3 :Tb crystals ([Tb] = 0.1–2.89 wt %) and nominally pure lithium niobate crystals of congruent (LiNbO 3cong ) and almost stoichiometric compositions (LiNbO 3near stoich ) were grown. The concentration relationships of physicochemical and structural properties of LiNbO 3 :Tb crystals are studied. The structural parameters of LiNbO 3 :Tb crystals are compared with those of LiNbO 3cong and LiNbO 3near stoich .

The results of X-ray diffraction analysis of bacterial nanocellulose (BNC), synthesized by Komagataeibacter xylinus В-12429 and Komagataeibacter xylinus В-12431 producers in enzymatic hydrolyzates of miscanthus, oat hull, and synthetic nutrient medium, are presented. It is found by full-profile analysis that the dominant component in all BNC samples studied, independent of the producer and nutrient medium, is allomorph Іα, whose content varies from 96 to 100%. The following characteristics of the supramolecular structure of the samples have been determined: the degree of crystallinity, sizes of elementary fibrils and the shape of their cross section, and the coherence length of elementary fibrils along the fibril axis.

МИНИСТЕРСТВО НАУКИ И ВЫСШЕГО ОБРАЗОВАНИЯ РФБийский технологический институт (филиал) федерального государственного бюджетного образовательного учреждения высшего образования «Алтайский

A series of LiNbO3:Tb ([Tb] = 0.1–2.89 wt%) and a nominally pure near-stoichiometric (NSLN) crystals have been grown. Concentration dependences physico-chemical and structure characteristics LiNbO3:Tb of different composition has been studied.

The article presents a study of the influence of three drying methods (vacuum drying, freeze-drying and supercritical drying) on the physicochemical properties and macroscopic structure of Arctic brown algae cellulose. It shows that freeze-died and supercritically dried algal celluloses have lower thermal stability due to the predominance of the metastable Iα phase in them, degree of crystallinity of 48–69% and a fibrillar surface. Freeze-dried cellulose and especially supercritically dried cellulose have a larger specific surface area (up to 186 m2/g) and a developed mesoporous structure with the average pore diameter of 13.81–14.81 nm.

X-ray diffraction results of short-range order in nanoscale powders of silicon nitride obtained by plasma-chemical synthesis are presented. It is shown that the most probable structure of nanopowder silicon nitride can be characterized by a model of a disordered network of SiN4tetrahedra.

Abstract An influence of hyper-hardening on structure and mechanical properties of ceramic solid solutions (SS) Li0.12Na0.88Ta y Nb1– y O3 with tantalum concentrations у = 0.05; 0.25; 0.4 has been revealed. The researched was carried out using X-ray diffraction and scanning probe microscopy methods. Two ferroelectric phases co-exist in initial non-hardened SS Li0.12Na0.88Ta y Nb1– y O3: hexagonal R3cH and rhombic P21ma. A symmetric rhombic phasePbnm prevails in hardened samples. Hyper-hardening has been established to sufficiently increase micro-hardness and surface strength of SSLi0.12Na0.88Ta y Nb1– y O3ceramic samples.

Bacterial cellulose (BC) was synthesized from biomass of Miscanthus grown in West Siberia. Miscanthus biomass was pretreated at atmospheric pressure with 4 wt.% solutions of HNO3 and NaOH in one and two stages. The effect of four methods of the pretreatment of the feedstock on BC yield and properties was examined. The resultant pulps were subjected to enzymatic hydrolysis with commercial CelloLux-A and BrewZyme BGX enzymes. Biosynthesis of BC was run under static and non-sterile conditions using Medusomyces gisevii Sa-12. The two-stage pretreatment of Miscanthus biomass gave a 20 % increase in BC production compared to the single stage pretreatment. The resultant BC exhibited a high crystallinity index (88-93 %) and an extraordinarily high content of allomorph I alpha (99-100 %), irrespective of the pretreatment method; therefore, it has been revealed for the first time that the Medusomyces gisevii Sa-12 symbiotic culture is capable of self-standardization against the quality of produced BC.

Lithium niobate single crystals of congruent composition and doped with various impurities are investigated using Raman spectroscopy and X-ray analysis. Raman scattering spectra and X-ray diffraction (XRD) patterns of the studied crystals contain weak reflections forbidden by the R3c space group of symmetry. These superstructure lines are not associated with a new crystalline phase. It is found that neither the increasing of nonstoichiometry of the grown crystals, nor increasing the concentration of dopants, nor the type of dopant, nor the doping method of batch affect the intensity and position of the additional reflections on the XRD patterns. The frequencies and the intensities of the superfluous lines in the Raman spectra are also independent of these parameters. It can be caused by the formation of a superstructural hexagonal sublattice with a double unit cell parameter due to the ordering of defects.

Nominally pure congruent LiNbO 3 crystal and LiNbO 3 :ZnO ([ZnO] ~ 5.4–6.4 mol % in the melt) crystals of different genesis are studied using photoinduced light scattering, laser conoscopy, and X-ray diffraction (method of moments). The photorefractive properties and optical and structural uniformity are analyzed. It is found that LiNbO 3 :ZnO crystals obtained by direct solid phase doping have the best optical and structural uniformity, the lowest photorefractive sensitivity, and a high compositional uniformity along the polar axis. Crystals obtained by homogeneous doping are compositionally uniform, although their optical and structural uniformity is worse than those of LiNbO 3 :ZnO crystals obtained by direct solid phase doping. Anomalies of conoscopic patterns are caused by the presence of charged structural defects in LiNbO 3 :ZnO crystals and the distortion of the optical indicatrix induced by mechanical stresses and compositional inhomogeneity of the crystals. High temperature annealing in short-circuited state of LiNbO 3 :ZnO crystals with high dopant concentration leads to healing of charged defects and improvement of optical characteristics in general. The distribution coefficient for LiNbO 3 :ZnO crystals obtained by the homogeneous doping method is significantly higher than that for the crystals obtained by the direct solid phase doping method.

Changes in a structural state of homogeneous doped lithium niobate crystals with magnesium in the region of 5 mol. % were studied by X-ray diffraction methods. It was found that the changes in the structure of LiNbO3: Mg occured not only in the region of the impurity defect, but also in the region of the main motive of the structure. Bond lengths in the octahedra of the main motive and the Nb–Li distance along the polar axis of the crystal changed. The magnesium introduced into the vacant lithium octahedron distorted the shape of the octahedron more strongly than niobium.

Currently, cellulose is one of the most requested natural polymers and the material has a wide range of industrial applications. The most studied and extensively used source of cellulose are coniferous and deciduous wood. At the same time, taking into account the structural and chemical properties of the biopolymer, the influence on the formation of nano-, micro- and macro-characteristics, and the conditions of its biosynthesis, the industry increasingly pay attention to its alternative sources, including algae. In this work, a protein-polysaccharide complex, where cellulose is the principal component, was isolated from samples of brown algae samples collected from the White and Yellow Seas. The structural features of the brown algae cellulose complexes were studied using classical physicochemical methods, as well as FTIR spectroscopy, X-ray spectroscopy, and scanning electron microscopy Analyses revealed stable phase Iβ forms of cellulose predominated in arctic brown algal samples, and the degree of crystallinity of the cellulose product was 54–59%. Scanning electron microscopy revealed that the compound has a fibrous structure, which is most pronounced in samples derived from arctic kelp. These results expand our understanding of use of algal cellulose and macrophytes as a valuable raw material for the production of sorption and composite cellulose-based materials.