The effect of proton irradiation with a power of 1·1017 units/cm2 and an energy of 2 MeV on the structure and properties of composite ceramics of the composition ZrO2–SiO2–Al2O3 is shown. It has been established that at this irradiation dose, the phase composition of the ceramic does not change. Calculations using X-ray diffraction methods have shown that proton irradiation creates compressive stresses (stresses of the 1st kind) ranging from ~–1 to –2 GPa on the surface of field ceramics, while microstresses (stresses of the 2nd kind) are practically absent. Analysis of SEM images of the ceramic surface after irradiation showed a chaotic arrangement of macropores in the t–ZrO2 matrix, while pores in zircon particles are located exclusively along the boundaries of inclusions. A decrease in the level of hardness and density in ceramics after proton treatment was noted due to the formation of a large number of pores.

The paper presents an analysis of the effect of processing powders with high hydrostatic pressure (HHP) (300, 500, 700 MPa) and stabilized zirconium dioxide (ZrO2 + 3 mol.% Y2O3, (YSZ)) doping on the compaction of metastable nanopowders mixture with γ+θ-Al2O3 + n% YSZ (n = 0, 1, 5, 10, 15wt.%) composition during sintering. The behavior of nanopowders at the initial stage of sintering was studied by dilatometry at a constant heating rate of 5 °C/min, in temperature range from 20 °C to 1500 °C. It has been determined that sintering of compacts occurs in two stages: compaction of γ + θ-Al2O3 (Ⅰ-st stage metastable phases), compaction of the stable α-Al2O3 (ⅠⅠ-nd stage), accompanied by inhibition between them. An “effect of mutual protection against crystallization” of powder mixtures was determined using the X-ray diffraction method. This is characteristic of systems obtained by co-precipitation. A connection between the above mentioned inhibition and an increase in the YSZ additive was found. That, also, correlates to the effect of “mutual protection against crystallization” of Al2O3 – YSZ powder mixtures. A study of the mechanisms and activation energies of γ+θ-Al2O3 + n% YSZ systems’ (n = 0, 1, 5, 10, 15 wt.%) sintering depending on the YSZ additive amount and the HHP value showed that a dopant and pressure increase leads to activation energy decrease of the initial sintering stage, and the prevailing sintering mechanism is volumetric diffusion in corundum grains. Also, the work shows that for γ+θ-Al2O3 + ≥5wt.% YSZ systems, the optimal compaction pressure is HHP ≥ 500 MPa, which corresponds to the transition of the sintering mechanism from grain-boundary diffusion to volumetric diffusion.

One of the ways to develop methods for effective and economical synthesis of carbon nanostructures from the plant raw materials is to use the energy of the microwave electromagnetic field for pyrolytic transformations of biomass. Combining microwave irradiation and pyrolysis process is a new solution with several advantages that increase the efficiency of the biomass processing and determine the prospects of the microwave pyrolysis in obtaining carbon nanoproducts. In this work, the conditions for catalytic synthesis of carbon nanotubes through the microwave pyrolysis of cellulose, a major component of biomass, were studied. The objective of the present investigation is to evaluate the effect of a binary nickel-iron catalyst supported on a carbon substrate on synthesis of carbon nanostructures. This process involves the use of organic additives, such as glucose and thiourea, which are intended to prevent oxidative reactions in the system and maintain the activity of the catalyst. Experiments were carried out by treating the mixture of reagents with the microwave radiation with a frequency of 2450 MHz and a power of 1000 W for 10-12 minutes. The synthesis samples were characterized by X-ray phase analysis and transmission electron microscopy. In all experiments, the formation of multi-walled carbon nanotubes and few-layer graphene particles was observed. It was experimentally found that the used catalyst showed great activity in the microwave synthesis of carbon nanotubes in the presence of glucose.

It was found that the high decomposition temperature of amorphous Al(OH)3 makes it possible to sinter corundum ceramics directly from aluminum hydroxide, bypassing the stage of its preliminary thermal dehydration. Using the cold isostatic pressing method at 200, 600, and 1000 MPa, compacts with densities of 62, 69, and 79

Thermally expanded graphite (TEG) is a vermicular-structured carbon material that can be prepared by heating expandable graphite compounds. Liquid phase exfoliation of TEG obtained from graphite nitrate cointercalation compounds (GNCCs) with organic substances allows obtaining dispersions of carbon nanoparticles, namely few-layer graphenes as well as small graphene structural fragments. This paper presents the results of complex investigations of structural features of triple GNCCs with acetic acid, formic acid, ethyl acetate and acetonitrile as well as TEGs on their base. X-Ray powder diffraction and scanning electron microscopy were used for studied GNCCs and TEGs characterization. GNCCs were used as a source for thermally expanded graphite which can be considered as perspective precursor for graphene and related structures. Morphology of the carbon nanoparticles formed from corresponded TEGs by liquid phase exfoliation in tert-butanol assisted with sonication is discussed. The most promising results were observed for the TEG sample obtained from a triple GNCC with acetic acid and acetonitrile.

The paper presents results of the study of the structure and physico-mechanical properties of ceramics composits α-Al2O3 + n Y2O3 (n = 0; 0.5; 1; 1.5; 2; 3; 4; 5 wt.%) based on the basis of polymorphic modifications γ+θ-Al2O3 depending on the concentration of the Y2O3 doping impurity and the annealing temperature of the powder mixtures (800 and 900°C). The effect of mutual protection against crystallization was discovered, which results in mutual inhibition of crystallization processes in Al2O3–Y2O3 powder systems. By X-ray diffraction analysis, the formation of a phase of yttrium-aluminum garnet Y3Al5O12 (YAG) in ceramics has been established. The dependence of the mechanical characteristics of the materials under study on the amount and size of the formed phase YAG has been revealed.

The influence of combined plastic deformation, including methods of intense plastic deformation and traditional metal forming, on the structure and mechanical properties of M1 copper was studied. It has been shown that combined processing helps to increase the dimensional uniformity of hardness across the cross-section of the workpiece and contributes to the refinement of microstructure elements. Thus, with an increase in the equivalent degree of deformation, the level of mechanical properties of M1 copper increases accordingly.

The results of studying the influence of high hydrostatic pressure (HHP) on the structure formation and prop-erties of composite ceramics of the Al2O3-ZrO2 + 3mol% Y2O3 (YSZ) system, based on the metastable Al2O3 phase, are presented in this work. The phase composition of the powders, the structure, physical and mechanical properties of the Al2O3 -YSZ ceramics were studied taking into account the YSZ concentration and the pressing pressure. We have found that various crystallization processes occur during the sintering of ceramics and two types of structure are realized: aggregate-hardened and disperse-hardened, depending on the HHP value. It is shown that the processing of compacts under HHP conditions at 600-700 MPa prevents the formation of ag-glomerates of YSZ grains in the intergranular space of Al2O3, and the maximum values of physical and me-chanical characteristics are achieved at concentrations of 10 and 15% YSZ and HHP values of 700 MPa.

Аннотация: Показано, что предварительная подготовка образцов влияет на структуру и свойства оксида графита и частично восстановленного оксида графита при их исследовании физическими методами.Способ высушивания оксида графита как последний этап синтеза определяет его морфологию и структурные свойства.При высушивании методом сублимации фиксируется состояние оксида графита в водной суспензии до начала процесса самоупорядочивания его листов, данные рентгеноструктурного анализа свидетельствуют о его рентгеноаморфном состоянии, внешний вид высушенного оксида графита -светло-желтый порошок

The growing demand for carbon nanotubes, which are typical representatives of the class of carbon nanomaterials and have unique physical and chemical properties, necessitates the search for available and renewable hydrocarbon resources for their production and development of an energy-efficient and a highly productive synthesis method. The prospects of using lignocellulosic biomass and its wastes as a carbon source for the synthesis of carbon nanotubes by means of microwave catalytic pyrolysis are considered. The expediency of research in this direction is emphasized. It is noted that one of the parameters responsible for the process of pyrolytic synthesis of carbon nanotubes is the concentration of microwave radiation absorber, which determines pyrolysis temperature. The effect of changing the concentration of microwave absorber in reaction mixture on the catalytic synthesis of multi-walled carbon nanotubes during microwave pyrolysis of cellulose has been studied. It is shown that a change in the microwave acceptor content from 10 to 30% is accompanied by an increase in the concentration of multi-walled carbon nanotubes of disordered morphology in reaction mixture. A two-stage pyrolysis-synthesis process is suggested. The results of transmission electron microscopy and X-ray phase analysis of the obtained products are considered.

It is shown by physical methods that the preliminary preparation of samples affects the structure and properties of graphite oxide and partially reduced graphite oxide. The graphite oxide drying technique as the last synthesis stage determines its morphology and structural properties. At drying by sublimation method, the state of graphite oxide in aqueous suspension before the beginning of the process of self-ordering of its sheets is fixed, the data of X-ray diffraction analysis testifies its X-ray amorphous state, the dried graphite oxide appearance is a light yellow powder. Drying of graphite oxide aqueous suspensions at temperatures above room temperature is accompanied by the ordering of the graphite oxide structure under the action of the surface tension and Van der Waals forces with the dark brown film formation. It is shown by scanning and transmission microscopy methods that the method of separation of partially reduced graphite oxide from glass substrates, on which the product is dried, can lead to the formation of wrinkled or roll-shaped structures. When graphite oxide is examined by transmission electron microscopy, even a short exposure to ultrasound (used in the conventional method of depositing the material on a copper grid prior to examination) results in wrinkling and partial curling of the edges of graphite oxide nanoparticles. Mechanical grinding of graphite oxide leads to disordered graphite oxide structure and to the interplanar spacing increase.

The effect of doping with silicon and aluminum oxides on the process of structure formation of ceramics based on yttrium-stabilized zirconium dioxide is investigated. Using the X-ray diffraction, internal friction, 4-point bending, and electron microscopy methods, it is shown that in the system of the powder system ZrO2+3 mol.% Y2O3 (YSZ)+n wt.% SiO2 + 2wt% Al2O3 (n = 3, 5, 7, 9) a decrease in the size of CSR to 26 nm is observed. It is established that the formation of a new phase in the form of zirconium orthosilicate (ZrSiO4) is observed in ceramics based on these powders. The amount of the new phase increases with the increase in the amount of silicon oxide SiO2 in the initial powders. It is shown that the presence of the ZrSiO4 phase in ceramics leads to a significant improvement in the physical and mechanical characteristics in comparison with the initial composition of YSZ. Optimal structure and improved mechanical properties were obtained at n = 5 (wt.% SiO2).

We report structural and luminescence properties of the spinel MgAl2O4:Sm3+ nanophosphors (with Sm3+ content of 0.03, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 3.0 wt%.) synthesized by a co-precipitation method. The X-ray phase analysis and transmission electron microscopy show that the size of the MgAl2O4:Sm3+ nanoparticles varies from 5 nm to 6 nm at a synthesis temperature of 700 degrees C and from 7 nm to 15 nm at 1000 degrees C. We demonstrate that the samples synthesized at 700 degrees C with a samarium content of 1.5 wt% are the most promising candidates for use as orange phosphors. We show that near-surface rare-earth ion segregation arises in the nanoparticles with an average size of 10 nm and the Sm concentrations of 1.0 wt% and 1.5 wt%. Simulation of the MgAl2O4:Sm3+ luminescence spectrum by the modified crystal field theory (MCFT) indicates that Sm ions occupy both octahedral and tetrahedral positions. Complexes with broken bonds, non-equivalent bonds, and complexes with vacancies are revealed and confirmed by EPR studies and theoretical calculations. We demonstrate that the most intense transitions arise in tetrahedral and octahedral complexes with vacancies. The enhancement of the emission efficiency caused by the distortions of the Sm3+ coordination complexes competes with the luminescence quenching caused by surface segregation.

To expand the number of possible precursors of carbon nanoparticles, i.e., low-layer graphenes and nanoscrolls, binary and ternary graphite nitrate cointercalation compounds (GNCCs) with formic and acetic acid esters have been synthesized. X-ray powder diffraction data have demonstrated that the obtained GNCCs are stage II and IV intercalation compounds. It has been shown that the use of ethyl formate or an ethyl acetate/butyl acetate mixture as organic cointercalants leads to an increase in the height of the layer filled with intercalants as compared with graphite nitrate. Dispersions of carbon nanoparticles (low-layer graphenes and nanoscrolls) were obtained by sonication-assisted liquid-phase exfoliation of studied GNCCs in ethanol. The morphology of the obtained nanoparticles has been studied by transmission electron microscopy.

The paper presents the results of studies of the structure and physical and mechanical properties of copper M0b after combined plastic deformation under different schemes of equal channel angular pressing (ECAP) and upsetting or ECAP and multi upsetting. Comparative characteristics of the structure, hardness and deformational decompaction of copper are given. Interesting to note that after ECAP and multi upsetting treatment, a deeper development of the structure has been observed.

Triple graphite nitrate cointercalation compounds (GNCCs) with acetic acid were synthesized, characterized by powder XRD and SEM methods, and used as a source of the thermally expanded graphite (TEG). Structural reorganization of graphite nitrate-acetate and triple GNCCs with acetic acid as a result of their exposition in air is discussed on the base of powder XRD data. Dispersions of carbon nanoparticles were prepared by liquid phase exfoliation of TEGs obtained from the GNCCs. It was demonstrated by TEM method that using of the studied TEGs as a source of carbon nanoparticles favours formation of few-layered graphene.

В работе представлены результаты исследования морфологии углеродных наночастиц, образующихся при жидкофазном расслоении терморасширенного графита в трет-бутаноле. Используемый в работе терморасширенный графит получен путем термического расширения соинтеркалата нитрата графита с уксусной и муравьиной кислотами в режиме термоудара при 500°С и 900 °С. Исходный соинтеркалант по данным рентгенофазового анализа представляет собой смесь соединений II-й и IV-й стадий интеркалирования. Методом просвечивающей электронной микроскопии установлено, что дисперсии углеродных наночастиц, образующиеся при расслоении терморасширенного графита в трет-бутаноле под действием ультразвука, содержат в основном малослойные графены, планарные размеры которых достигают 8 мкм. Обсуждается влияние условий получения терморасширенного графита на морфологию образующихся углеродных наночастиц. Дисперсии на основе терморасширенного графита, полученного при более низкой температуре, помимо малослойных графенов содержат также значительное количество аморфных углеродных частиц с планарными размерами до 100 нм. The paper presents the investigation results of the morphology of carbon nanoparticles formed during liquid-phase exfoliation of thermally expanded graphite in tert-butanol. The thermally expanded graphite used in this work was obtained by thermal expansion of graphite nitrate with acetic and formic acids in the thermal shock mode at 500 °C and 900 °C. Initial cointercalate was shown by powder X-ray diffraction analysis to be the mixture of the II and the IV stage intercalation compounds. It has been established by transmission electron microscopy that dispersions of carbon nanoparticles formed during the exfoliation of thermally expanded graphite in tert-butanol via sonication contain mainly few-layer graphenes, the planar dimensions of which reach 8 pm. The influence of the conditions for thermally expanded graphite obtaining on the morphology of resulting carbon nanoparticles is discussed. Dispersions based on thermally expanded graphite obtained at a lower temperature, in addition to few-layer graphenes, also contain a significant amount of amorphous carbon particles with planar sizes up to 100 nm.

Using the X-ray diffraction, internal friction, 4-point bending, and electron microscopy methods we have studied the structural compatibility and influence of Y2O3 and HfO2 dopants addition on the structure and phase composition of ZrO2 powders and ceramics based on them. The mechanical properties of ZrO2-Y2O3-HfO2 (YSZ) system have been investigated. It was determined that the similarity of the structure and properties of yttrium and hafnium oxides is not complete. The individual structural features of ZrO2, Y2O3, and HfO2 oxides reviled themselves during the formation of ternary systems of the YSZ-Hf type. Studies of the nY(2)O(3)-ZrO2 center dot mHf(2)O(3) system in the range of hafnium amount from 1 to 15 wt% and yttrium oxide concentration from 0 to 12 mol% showed the possibility of increase in the values of physical and mechanical properties of common two-component zirconium ceramics by the forming ternary systems of the YSZ-Hf type.