Home – Home – Jornals – Advanced Search

We consider geochemistry of Neoproterozoic metavolcanosedimentary rocks of the Bozdak Group in southern Ulutau (Central Kazakhstan) and present the first results of U-Pb LA-ICP-MS dating of clastic zircons and Sm-Nd isotope data. Isotope-geochemical and geochronological studies have shown that the Bozdak Group rocks resulted from the destruction of igneous and metamorphic complexes mostly of Neoproterozoic age with the participation of Archean and Paleoproterozoic rocks. The lower boundary of sedimentation is dated at 800 Ma. The obtained isotope-geochemical data on the Bozdak Group basaltoids suggest their formation on thick continental crust with the participation of subduction fluid.

Acoustic emission (AE) from laboratory samples of coarse-grained granite hit by a dropped weight at temperatures from 20 to 500 °C is recorded within a frequency range of 80 kHz-4 MHz. The time series of AE signals bear information on the size of primary defects, since the AE frequency is proportional to the growth rate of microcracks and inversely proportional to their lengths. According to AE data obtained in this study, impact fracture of granite produces cracks at grain boundaries at temperatures below 400 °C and additional defects inside grains at 400 °C and higher. The reason is that overheated water-vapor inclusions increase pressure in the grain interior, which affects the mechanic behavior of granite.

The synthesis conditions of multi-walled carbon nanotubes (MWCNTs) indirectly determine their application potential through the decisive role in the characteristics of individual tubes: diameter distribution, structure and defectiveness of graphene walls, the amount of metal impurities and amorphous carbon. In the present work, we have studied the influence of the catalyst composition and synthesis conditions on the diameter distribution and the structure of nanotube walls. We have observed the influence of the particle size for MWCNT synthesis ( i.e. size effect) on catalytic activity by ex situ and in situ techniques: in situ X-ray diffraction on synchrotron radiation (SRXRD), gas chromatography, and ex situ transmission electron microscopy. The data obtained by in situ SRXRD are in agreement with the results collected using laboratory tubular fix-bed catalytic reactor allowing thereby extending the applicability of the approach. For the first time we have shown the increase of the fraction of graphene walls in the total MWCNT diameter with time.

Magnetic nanoparticles and those doped with rare-earth metal ions having spinel structure were synthesized, possessing the average particles size of 11.3-13.4 nm. According to Mossbauer spectroscopy data it can be concluded that prepared iron oxide nanoparticles are γ-Fe₂O₃. For materials containing rare-earth elements the decrease of octahedral component surface was observed in comparison to non-doped material, what can be explained by Eu³⁺, Sm³⁺ и Gd³⁺ ions occupying the octahedral position.

The crystal, local and electronic structure of complex oxides Ln₂Hf₂O₇ (Ln = Gd, Tb, Dy) formed as result of annealing of amorphous mixed hydroxides LnHf(OH)₇x n H₂O (precursors) have been studied using a set of modern local-sensitive techniques of structural analysis based on the interaction of synchrotron radiation with condensed matter (XAFS spectroscopy, PDF analysis, anomalous X-ray diffraction). It was shown that the thermal treatment of precursors in the temperature range 600-700°C/3 h induces the formation of nanocrystallites with the fluorite structure characterized by the considerable inequivalence of local surrounding of Ln³⁺ and Hf⁴⁺ cations. It was found that the cation ordering of the pyrochlore type takes place in nanocrystals of gadolinium hafnate Gd₂Hf₂O₇ and terbium hafnate Tb₂Hf₂O₇. The phase transition fluorite - pyrochlore goes through the formation of the pyrochlore nanodomains in the matrix of well-crystallized fluorite. In the case of Gd₂Hf₂O₇ the formation of the pyrochlore local structure is completed at annealing temperature ~1000-1200°C/3 h and at > 1300°C/3 h the pyrochlore phase is detected by the diffraction techniques. In Tb₂Hf₂O₇ the process of the pyrochlore phase formation exhibits the more complex behavior. Nanocrystals of dysprosium hafnate Dy₂Hf₂O₇ retain the structure of defect fluorite in the whole temperature range of the heat treatment (up to 1600°C).

In this paper, a study of pure and doped samarium magnetite nanoparticles synthesized using a microwave synthesis in aqueous solution was performed. The shape, size and structure of the pure and samarium doped magnetite nanoparticles were determined by X-ray diffraction, transmission electron microscopy, X-ray absorption spectroscopy and Mössbauer spectroscopy. The magnetic properties of the nanoparticles were investigated using a vibrating sample magnetometer. It was found that the samarium doped magnetite nanoparticles were superparamagnetic with high saturation magnetization. The doping with a small amount of samarium allowed to reduce the size of nanoparticles, their size distribution, increase resistance to oxidation and improve their magnetic characteristics.

The use of the modern installations with the synchrotron radiation allowed obtaining the information about the dynamics of rapid transformation of adamantane into diamond within 2 ms under shock-wave action with nanosecond time resolution. The yield of diamond was 30%. An explanation of adamantane-diamond transformation is proposed. Hydrogen evolved during adamantane decomposition easily diffuses over diamond lattice. However, during synthesis time (~1 μs) hydrogen does not have enough time to go out of diamond particles. Experiment was made at accelerate complex VEPP-3/VEPP-4.

The present study deals with the electronic structure of the bioactive anticancer drugs based on platinum (II) complexes: cisplatin PtCl₂(NH₃)₂, carboplatin PtC₆H₁₂N₂O₄ and oxaliplatin PtC₈H₁₄N₂O_4, which are being used in cancer treatment. The purpose of the work wasto examine the molecular and electronic structure of platinum (II) coordination complexes when they undergo hydrolysis, which is crucialin order to better understand their antitumor properties. The density functional theory (DFT) was used to investigate the electronic structureof the platinum (II) complexes under study. The process of hydrolysis was simulated, and the structure and geometry of hydrolyzed platinum complexes were determined. The electronic structure, energy levels of occupied and unoccupied MOs and the distribution of the total and partial electron density of states (DOS) were shown and the UV-Vis and oscillation spectra of the hydrolyzed platinum(II) complexes were calculated. The theoretical calculations were verified by the experimentally obtained data by applying the method of X-ray absorption at PtL₃-edge as well as UV-Vis and IR spectroscopic techniques.

The compressibility of γ-K₂CO₃ within the pressure range of 0.001-23.3 kbar and room temperature was determined by in situ synchrotron powder diffraction measurements in diamond anvil cell. The modification of the diffraction pattern was fixed at P > 23.3 kbar. This modification can be explained by a reconstructive phase transition. The amorphization of the high pressure phase was fixed on decompression.

The work is devoted to the experimental study of coronene C₂₄H₁₂ at high pressure and room temperature using in situ X-ray diffraction in a diamond anvil cell. The high-pressure phase P 2/ m of coronene was found at 0.9 GPa, the PV -equation of state for P2/m coronene phase was defined to 4 GPa: K₀ = 10.8(3) GPa, K₀'= 7. At 5.9 GPa partial amorphization of coronene was observed. After the decompression to ambient pressure the high-pressure phase P2/m was preserved, that can be related with partial amorphization.