A.Z. Zhuk

Shock metamorphism of plagioclase and amphibole (Experimental data)

The shock metamorphism of plagioclase and amphibole of various chemical compositions from amphibolite and granulite facies schists was studied in experiments with shock wave loading of samples in steel recovery ampoules of plane geometry. A maximum shock pressure was reached after a few circulations of waves in the sample (stepwise shock wave compression) and varied within 26–52 GPa. The recovered samples were examined by the methods of scanning electron microscopy and microprobe and X-ray phase analysis. It is established that an increase in the F, Ti, and K concentrations in amphibole and a decrease in the Ca concentration in plagioclase make these minerals more stable with respect to shock waves. It is shown that the migration of some chemical elements, starting already at the solid phase stage of transformation in plagioclase and amphibole, is intensified at the stage of melting. It is established that isotropization of plagioclase occurs through two different mechanisms. At relatively low pressures, it is caused by the fragmentation of substance at the microlevel and is accompanied by the formation of maskelynite, a typical mineral of meteorites and astrobleme rocks. At higher pressures, isotropization is associated with melting-induced amorphization.

Hydrothermal liquefaction of microalgae to produce biofuels: state of the art and future prospects

The article presents a review of the state of the art and lines of research on hydrothermal liquefaction (HTL) of microalgae (MA). The main advantages of this technology for production of biofuel are that it does not require predrying of the feedstock and ensures a relatively high product yield—the ratio of the end product weight to the feedstock weight—owing to the fact that all the microalgal components, viz., lipids, proteins, and carbohydrates, are converted into biofuel. MA hydrothermal liquefaction is considered to be a promising technology for conversion of biomass and is a subject of a series of research studies and, judging by the available publications, the scope of research in this field is expanding currently. However, many significant problems remain unsolved. In particular, an active searched is being conducted for suitable strains that will ensure not only a high lipid yield—necessary to convert microalgae into biodiesel—but also higher biomass productivity and a higher biofuel yield; the chemical reactions that occur during the hydrothermal treatment are being studied; and the effect of significant process variables, such as temperature, heating rate, holdup time at the maximum temperature, biomass concentration in the water suspension, biochemical and elemental compositions of the microalgae, use of catalysts, etc., on the liquefaction processes is being studied. One of the urgent tasks is also the reduction of the nitrogen content in the resulting biofuel. Studies aimed at the development of a continuous process and rational heat-processing plants for thermal microalgal conversion are being conducted to increase the energy efficiency of the HTL process, in particular, to provide the heat recovery and separation of the end product.

Shock metamorphism of the graphite quasimonocrystal

Abstract Micro structure examination of graphite quasimonocrystal recovered after dynamic loading to pressure of 35-45 GPa was carried out. Only a small amount of cubic diamond and recrystalized graphite was detected. Most of the graphite (∼80 vol.%) remained in initial high orientation, but transformed to fine, grained phase with crystalite size 0.1-1 microns. Relaxation time of the transformation (∼ 10 ns) and the degree of the transformation (∼ 70-80 vol.%) were determined by means of measurements of the electrical resistivity during loading up to 26 GPa and following computer simulation of the results. We proposed that two simultaneous processes take place at pressures higher than 20 GPa: i) relatively slow diffusive graphite to diamond transformation localized in the zones with defect structure: ii) highly oriented graphite transforms to a diamond like phase with density of about 3.2 g/cm3 at zero pressure. This, transformation has fast, martensitic kinetics and is reversible.

An Electrochemical Generator Containing Cylindrical Aluminum-Air Cells

The article considers matters concerned with optimizing the design and technology of aluminum-air electrochemical generators for emergency and backup power supply to different consumers. The physicochemical principles used to construct such generators are briefly described. Owing to the absence of self-discharge in the energy storage mode, aluminum-air generators can remain in the waiting mode for a longer period of time as compared with electrochemical storage batteries or hydrogen-air fuel cells. The source is activated by adding water to it. To obtain better specific parameters of aluminum-air cells and improve their manufacturability, a cylindrical cell design is proposed. One-off cells and a battery have been developed, fabricated, and tested. The obtained results are compared with the data from testing a battery and cells having a flat design. The possibility of obtaining essentially better specific characteristics due to making a shift to a cylindrical design is shown. Owing to the proposed design, more efficient use of aluminum has been achieved along with simplifying the system for maintaining the thermal balance of the cell and battery. The article presents the results from testing a single aluminum-air cell and a four-cell battery, which showed the need to adjust the concentration of electrolyte in cells and batteries of this type. The obtained data are compared with the results from tests of previously fabricated aluminum-air elements of the classical flat design. For determining the prospects for using generators of this type, their technical and economic characteristics were compared with those of the main competing sources of emergency and backup power supply, including lead-acid and lithium-ion storage batteries, and with hydrogen-air electrochemical generators. The characteristic time of power source operation and the frequency of its coming into action for which the use of aluminum-air electrochemical generators is economically justified are determined, and recommendations on extending the range of these parameters are given.

Development and Study of Gas-Diffusion Cathodes in Cylindrical Cells of Air-Aluminum Electrochemical Generator

Possibility of substantially improving the specific characteristics of the cell of an air-aluminum electrochemical generator by passing to its cylindrical design is demonstrated. This made it possible to raise the efficiency of aluminum utilization and to simplify the system that maintains the thermal balance of a cell and an array. It was found that, to reach the best parameters of a cylindrical cell of an air-aluminum electrochemical generator, it is necessary to fabricate gas-diffusion cathodes on the basis of the following factors: type of carbon black (Timcal), type of activated carbon (UAF), and relative amounts of hydrophobized carbon black and activated carbon in the active layer (2.5: 1). The results obtained in the study and the achieved characteristics of the air-aluminum electrochemical generator demonstrated that it is possible in principle to use this generator as a portable backup and emergency power source and also in power supply of urban electrically powered automobiles.

Influence of solvent on the yield and chemical composition of liquid products of hydrothermal liquefaction of Arthrospira platensis as revealed by Fourier transform ion cyclotron resonance mass spectrometry

Yields of liquid products (bio-oil and residual organics in aqueous solution) of hydrothermal liquefaction (at 300℃ and 60 min) of own cultivated Arthrospira platensis using different solvents have been determined. Nonpolar hexane, moderately polar dichloromethane, and relatively more polar acetonitrile have been used. High-resolution mass spectrometry based on linear quadrupole ion trap and Fourier transform mass spectrometer (LTQ FT) has been used for liquid sample characterization. Concentration of bio-oil in a unit of solvent volume after solvent extraction took the following arrangement: acetonitrile > dichloromethane > hexane. Concentration of residual organics in a unit of aqueous solution after solvent extraction took the following arrangement: hexane >dichloromethane > acetonitrile. Yield of total organics was arranged as follows: hexane > dichloromethane > acetonitrile. Content of carbon in bio-oil was increased and the content of oxygen was decreased with the increasing of solvent polarity. From mass spectrometric analysis it was established that in the positive electrospray ionization (ESI) mode the compounds containing two nitrogen atoms dominate and the considerable portion of the compounds containing single nitrogen atom are also presented for both bio-oil and residual organics samples. In the negative ESI mode the compounds containing four oxygen atoms dominated except bio-oil obtained using hexane where the compounds containing two oxygen atoms dominated. Bio-oil fraction had highly saturated compounds with low double bond equivalent values while the compounds of the residual organics fraction had large double bond equivalent values.