Advanced Materials Research Vol. 872

Abstract: The possibility of bimetallic Ni-Mo nitrides usage as the catalysts in carbon dioxide hydrogenation reaction was examined in this work. Powders were synthesized through thermo-programmed reduction of precursor, which was produced by evaporation of the metal-containing solution. Specimens were investigated by x-ray diffraction, thermogravimetry, low-temperature nitrogen adsorption and scanning electron microscopy. It is shown that final powders provide CO₂ conversion of 29 % for contact time of 0.26 s.

Abstract: Foam catalysts have physicochemical, gas-dynamic and catalytic characteristics exceeding the indices of the traditional granular and honeycomb catalysts. Nanopowders have high catalytic activity due to high surface area and special electronic state. Catalysts of new structural type nanopowders supported on foam metals and foam ceramics - have been tested in the process of deep oxidation of organic substances.

Abstract: The results of the development of combined process for production of dimethyl ether (CuO/ZnO/Al₂O₃) and methanol dehydration (γ-Al₂O₃, zeolite (ZSM-5 type) with a silicate modulus (М) 20, 30, 60, 80, 100, and 200) are presented. The experiments on the influence of the catalysts loading and catalytic conditions were carried out (Р=3 MPa, Н₂/СО=2, Т=553 К). It was established that the use of ZSM-5 zeolite catalysts with silicate modulus of 30 allows obtaining the yield of dimethyl ether up to 39%. It was stated that catalytic systems were stable during 180 h.

Abstract: The mechanism of the Н₂, СО, СО₂, СН₃ОН, (CH₃)₂O interaction with the surfaces of CuO/ZnO/Al₂O₃ and γ-Al₂O₃ was investigated using temperature-programmed desorption method with mass spectrometry detection. It was shown that desorption of the main process components takes place in the temperature range between 373 and 673 K, which corresponds to the temperature range for catalytic studies. Methanol dehydration takes place over the surface of γ-Al₂O₃ catalyst with formation of dimethyl ether at Т_max = 553 К, which is the optimal temperature for synthesis of dimethyl ether from CO and H₂ over industrial catalysts with layered loadings. The desorption energies of the gases were calculated.

Abstract: Copper single crystals grown according to the Bridgman method and having their axes [] or [11 aligned with the normal load axis were processed by dry sliding. As shown, sliding-induced severe plastic deformation occurred in the subsurface of single crystals and caused formation of a lip by mechanism of texture formation. The SEM structure of this lip was found to be composed of fragments with their shapes dependent on the single crystal orientation with respect to normal load and friction force.

Abstract: The aim of the study is to design wear-resistant and extrudable polymeric composites based on mixture of UHMWPE+PP with increased tribotechnical characteristics for the wide application in friction units of machine parts and mechanisms as well as using the polymeric resin developed for obtaining nanocomposites. Adding of block copolymer PP-b LLDPE to UHMWPE is motivated by the necessity to increase the adhesion between the incompatible polymeric components of the mixture. It is shown that wear intensity of the polymer-polymeric composites UHMWPE+n wt.% PP-b-LLDPE is reduced at filling UHMWPE by the block copolymer. In doing so, an important technological characteristic of UHMWPE specific extrusion pressure (proportional to the melt flow index) is improved (is lowered). Nanocomposites on the basis of the given matrix have shown wear resistance of 3-4 times higher in contrast with pure UHMWPE. Permolecular structure and wear track surfaces of nanocomposites on the basis of polymer-polymeric matrix (UHMWPE+10 wt.% PP-b-LLDPE) were investigated. The mechanism of the wear of nanocomposites is discussed.

Abstract: The experimental results for manufacturing ceramics from industrial boron carbide powder with 10 wt% of ultradispersed fraction of a powder of the same composition by spark plasma sintering have been presented. Under optimal process conditions such sintering results in a decrease of the sintering temperature and synthesis time, and the addition of ultradispersed fraction increases microhardness and fracture toughness of the ceramics.

Abstract: This paper considers the issues of building a model of the cluster organization of Al₂O₃ on principles immediately associated with the involvement of a non-Euclidian technique of describing. As a model space which most adequately describes the internal structure of a real crystal, a finite closed space with elliptic metric and constant positive Gaussian curvature (K=1) was chosen, which assumes the realization of lattice systems in compliance with Fedorov groups of transformations. An algorithm for generating the cluster structures is presented, which determines the sequence of filling of the model space with cations and anions, taking into account the symmetry of a microstructure (a Fedorov group) and the electrostatic parameters of ions. Calculations are given of the geometrical sizes of nanoand microcrystalline complexes of Al₂O₃, taking into account the structural features of their formation at the cluster level. Practical applications connected with improving the structural characteristics of crystalline materials are discussed.

Abstract: Formation of cracks in the lateral indentation of brittle ceramic materials is described in several researches [1, 2]. Occurrence of such cracks and the associated side small cracks formed at the surface of the sample in the form of "petals" was observed and analyzed in this research on the samples of boron carbide ceramics and monocrystalline silicon. The experimental results for the determination of the sequence, the direction and nature of crack propagation, the size and shape of areas of spall fracture surface formed at indentation of monocrystalline silicon and polycrystalline boron carbide samples by scanning electron microscopy are presented. A comparison of the experimental results with the modeling results of indentation zone deformation, as well as analytical evaluation of the shapes and the maximum size of the spall fracture zones have been carried out, which showed good coincidence.