Development of a new suspension electrolyte based on methane-sulphonic acid for the electrodeposition of Cu–TiO2 composites

Electrodeposition of composite coatings based on copper is a promising direction in the creation of advanced materials for multifunctional purposes. An important area of composites application is to use them in the treatment systems for gas emissions and wastewater. It is advisable to use semiconductor oxide materials, in particular titanium dioxide, as the photocatalysts in the photo destruction of organic pollutants of wastewater. The structural features of wastewater treatment equipment require that titanium dioxide particles should be fixed in a rigid matrix. Resolving the task of fixing photosensitive elements at the surface of a certain configuration implies the electrodeposition of coatings by composites, in particular Cu–TiO2. An important factor affecting the functional characteristics of composites and their manufacturing technology is the nature of the electrolyte. It has been shown that the electrodeposition of Cu–TiO2 composites from methane-sulfonate electrolytes makes it possible to reduce the coagulation of the dispersed phase and to obtain coatings with a high content of titanium dioxide from a suspension solution containing no more than 4 g/l of TiO2. It was established that the content of the dispersed phase in the composite made at a current density of 2 A/dm2 and the concentration of titanium dioxide in the electrolyte at the level of 4 g/l is 1.3 % by weight, which is twice as much as when using a sulfate electrolyte. It has been shown that the increase in the content of the dispersed phase in the coatings from 0.1 to 1.3 % by weight is accompanied by an increase in the degree of photo destruction of the colorant from 6 to 15.5 %. The micro-hardness of coatings increases, in this case, by 30 %. The proposed electrolyte to make the Cu–TiO2 composites is an important contribution to the development of the synthesis of wear-resistant high-performance photocatalysts for treating wastewater from organic pollutants

SYNTHEIS OF NI IMPREGNATED HYPERCROSSLINKED POLYSTERENE FOR CATALITIC HYDROGENATION OF D-GLUCOSE

Development of efficient catalysts is in focus of modern chemical technology for production of fine chemicals. D-sorbitol is widely used as sweetener, food additive and fuel compound is typically produced by D-glucose hydrogenation over Ni-Reney catalyst. However, this catalyst is characterized by not sufficient stability and selectivity to D-sorbitol formation. The described study is devoted to synthesis of nickel containing hypercrosslinked polystyrene for D-glucose hydrogenation process. Hypercrosslinked polystyrene is one of the representatives of crosslinked polymers with rigid matrix applicable for metal nanoparticles synthesis. However, hypercrosslinked polystyrene is characterized by high surface hydrophobicity that prevent impregnation of high amount of active metal over it surface. To overcome this disadvantage hypercrosslinked polystyrene was modified by hydrogen peroxide, chlorine and ammonia. A series of nickel based catalyst theoretically containing 25wt.% of nickel were synthesized. Modification of hypercrosslinked polystyrene results in appropriate increase in surface concentration of active metal. Synthesized Ni based catalysts were characterized by comparable Ni loading varying from 20.1 wt.% to 23.2 wt.%. Some increase in Ni loading can be subscribed to presence of surface-active groups in a case of modified hypercrosslinked polystyrene application. Mesopores surface area decrease from 126 m2/g to 69 m2/g in case of catalysts on modified hypercrosslinked polystyrene. Catalytic hydrogenation of D-glucose over synthesized Ni-containing catalysts showed considerable increase in turnover frequency (TOF) for all samples compare to commonly used Reney type nickel. Increase in TOF can be subscribed to appropriate increase of active metal surface concentration. Beside, some increase in catalyst selectivity to sorbitol took place. Considerable improvement of selectivity to sorbitol can be explained by increasing of desired D-glucose hydrogenation reaction rate, while reaction rate of D-glucose isomerization process to D-fructose remain the same. The achieved TOF for most active catalyst was found to be 0.27 s-1 and catalysts selectivity to D-sorbitol 98%.

Bio-Based Composites from Industrial By-products and Wastes as Raw Materials

Innovative bio-based composites combining humins as biorefinery by-product with keratin or lignin as wastes or industrial side-products were developed. The bio-composites were prepared using three types of matrix formulations allowing the synthesis of elastic to rigid thermosets. These matrices were combined with chicken feathers powder, non-woven chicken feathers mat or lignin to produce bio-composites. A maximum quantity of bio-fillers was used, around 10 wt.%. The effect of the bio-fillers on the matrix’s crosslinking was studied by rheology and DSC. Then, the obtained materials were analyzed by TGA, DMA, tensile tests, water absorption and SEM. The results show a very good compatibility of the humins matrix with the bio-fillers, without any preliminary modification of the matrix, that is exceptional for the point of view of a composite. The overall performances of the neat matrix were maintained or improved through the composites. Therefore, bio-composites with potentially interesting thermal and mechanical properties have been synthesized. In the case of the elastic ductile matrix the Young’s modulus value was improved from 1 to 22 MPa, while for the rigid matrix the increase was from 106 to 443 or 667 MPa, in the case of composites with non-woven chicken feathers mat or lignin. To our knowledge this is the first study combining humins matrix with keratin. The obtained bio-composites are sustainable materials linked via the used raw materials to the circular economy and biomass valorization.

Catalysis by a rigid enzyme

Many enzymes are dynamic entities, sampling conformational states that are relevant for catalytic activity. Crystal structures of catalytic intermediates suggest, however, that not all enzymes require structural changes for activity. The single-domain enzyme xylanase from Bacillus circulans (BCX) is involved in the degradation of hemicellulose. We demonstrate that BCX in solution undergoes minimal structural changes during catalysis. NMR spectroscopy results show that the rigid protein matrix provides a frame for fast substrate binding in multiple conformations, accompanied by slow, enzyme induced substrate distortion. Therefore, we propose a model in which the rigid enzyme takes advantage of substrate flexibility to induce a conformation that facilitates catalysis.One Sentence SummaryThe rigid matrix of BCX uses substrate flexibility in Michaelis complex formation.

MELT DROPS MOVEMENT OVER SEMICONDUCTOR SURFACES CONTROLLED BY ELECTRIC FIELD

The problems of molten zones formation and their subsequent migration over material surface are of interest from the viewpoint of developing novel technological methods of forming microelectronic structures. Such drops can be used as primary working elements of microlenses and reflectors, displays, weighers. The aim of this work was experimental studying processes of electromigration of molten silver- and aluminum-based inclusions over surfaces of germanium and aluminum semiconductor crystals. The issues of formation and motion of molten drops over the surfaces of silicon and germanium semiconductor crystals are considered within the framework of the electrocapillary approach. It is shown by an example of Ge-Ag and Si-Al systems that accelerated migration is related to the contribution of an electrocapillary component that relates surface tension force of melt drops to electric potential difference at the interface. The experiment consisted in applying metal grain to the surface of the samples and vacuuming the chamber where excessive pressure and the surface temperature were created. Migration of inclusions by powerful current pulses was initiated. An analysis of the effect of direct current on a drop of melt deposited on the surface of a crystalline matrix was made. An analysis of the droplet composition was carried out using the AES method, the results of which showed the relationship between silver and germanium concentrations. Quantitative evaluations are given for migration rates in systems under direct current flow as well as under pulsed current loads. During the experiment, it was found that the energy required to detach the droplet from the rigid matrix was not consumed. The value of the surface charge transfer density was estimated. The results of the work can be used to develop new technological methods for the formation of microelectronic structures and their use for practical purposes.

Working Body for Deformation of Thin-Walled Pipe Billets

In this paper we consider different types of working bodies and fillers used in the manufacture of hydro-gas systems of aircraft from thin-walled pipe billets, and also explored the advantages and disadvantages of liquid, fusible, solid, elastic, loose and combined fillers in the deformation of pipe segments by means of distribution, crimping, forming and flexible. As a result of the research, a device for distributing pipe billets along a rigid matrix and a working body made of granular polyurethane and ice, the main advantages of which are: good rheological properties (fast flow); high ductility and viscosity; high ability to transfer pressure throughout the metal zone; ability to withstand high compression load; ease of entry into the workpiece and removal from the finished part; low production costs.