MORPHOLOGY AND COMPOSITION OF THE INTERFACE BOUNDARY OF SODIUM CHLORIDE SINGLE CRYSTALS WITH LEAD

Методами электронной микроскопии и рентгеноспектрального анализа исследована межфазная граница раздела жидкого свинца с хлоридом натрия после охлаждения и разрыва контакта. На поверхностях разрыва образцов обнаружено накопление поверхностно-активных примесей, содержащихся как объеме свинца, так и в хлориде натрия. Как показывают результаты рентгеноспектрального анализа, содержание примесей на поверхности подложки хлорида натрия превышает объемное содержание на несколько порядков. На поверхности свинца также наблюдается значительное накопление примесей кремния и индия. В исследованных образцах наблюдается анизотропия растекания жидкого свинца по поверхности монокристаллов хлорида натрия. Линия разрыва, затвердевшей капли свинца с монокристаллической поверхностью хлорида натрия ориентации (110), заметно отклоняются от круга. Кроме того, на электронно-микроскопическом изображении межфазной поверхности свинца после отрыва от подложки хлорида натрия ориентации (100), наблюдаются участки в виде «сигары», в которых обнаружено накопление примесей. Данные участки имеют ориентации, совпадающие с кристаллографическим направлением подложки. The interface between liquid lead and sodium chloride after cooling and breaking the contact was investigated by the electron microscopy and X-ray spectral analysis. Accumulation of surface-active impurities, contained both in the bulk of lead and in sodium chloride was found on the fracture surface of the samples. As shown by the results of the X-ray diffraction analysis, the content of impurities on the surface of the sodium chloride substrate exceeds the bulk content by several orders of magnitude. A significant accumulation of silicon and indium impurities is also observed on the lead surface. Anisotropy of spreading of liquid lead over the surface of sodium chloride monocrystals is observed in the studied samples. The separation line of a solidified lead droplet on the surface of sodium chloride with orientation (110) deviates noticeably from a circle. In addition, on the electron microscopic image of the lead interface after detachment from the substrate of sodium chloride of orientation (110), there are areas in the form of a «cigar», in which the accumulation of impurities was detected. The orientation of these regions coincides with the crystallographic direction of the substrate.

Black Agates from Paleoproterozoic Pillow Lavas (Onega Basin, Karelian Craton, NE Russia): Mineralogy and Proposed Origin

The present study provides the first detailed investigation of black agates occurring in volcanic rocks of the Zaonega Formation within the Onega Basin (Karelian Craton, Fennoscandian Shield). Three characteristic texture types of black agates were identified: monocentric concentrically zoning agates, polycentric spherulitic agates, and moss agates. The silica matrix of black agates is only composed of length-fast and zebraic chalcedony, micro- and macro-crystalline quartz, and quartzine. In addition to silica minerals, calcite, chlorite, feldspar, sulphides, and carbonaceous matter were also recognised. The black colour of agates is related to the presence of disseminated carbonaceous matter (CM) with a bulk content of less than 1 wt.%. Raman spectroscopy revealed that CM from black agates might be attributed to poorly ordered CM. The metamorphic temperature for CM from moss and spherulitic agates was determined to be close to 330 °C, whereas CM from concentrically zoning agates is characterised by a lower temperature, 264 °C. The potential source of CM in moss and spherulitic agates is associated with the hydrothermal fluids enriched in CM incorporated from underlaying carbon-bearing shungite rocks. The concentrically zoning agates contained heterogeneous CM originated both from the inter-pillow matrix and/or hydrothermal fluids.

Theoretical justification of the influence of change of dilaton and compression bonds of atoms of materials of machine parts on their tribological effect

The course of friction and wear processes in the surface layers of conjugations of machine parts is clarified on the basis of the idea of dilaton and compression bonds of atoms in the materials of parts. Dilaton-compression connections are random in nature, and therefore in this work the theory of destruction of parts by S.M. Zhurkov, thermodynamic and quantum physical approaches. The entropy at the macro-, meso- and microscopic levels and the local regions of the materials of conjugation of the parts subject to friction loading are considered. In the diagram of the state of atomic-molecular bonds the dependence curve Fi(ri) or Ti(ri) is considered and the analysis of transformations of bonds according to the specified diagram is carried out. From the point of view of solid state physics and tribophysics, the manifestation, evolution and consequences of the influence on the characteristics and properties of the friction zone of dilaton and compression bonds of material atoms are considered. Composite materials (composite coatings) are substantiated in more detail. This takes into account the assessment of the concept of material stresses in the friction zone, the ability to relax it, as well as the presence of the SD effect. The fracture process is associated with the modulus of elasticity of the components of the composite material and the bulk content of the filler. An appropriate condition is proposed, which determines the tribological efficiency of composite materials and coatings.

Chemical Composition and Petrogenetic Implications of Eudialyte-Group Mineral in the Peralkaline Lovozero Complex, Kola Peninsula, Russia

Lovozero complex, the world’s largest layered peralkaline intrusive complex hosts gigantic deposits of Zr-, Hf-, Nb-, LREE-, and HREE-rich Eudialyte Group of Mineral (EGM). The petrographic relations of EGM change with time and advancing crystallization up from Phase II (differentiated complex) to Phase III (eudialyte complex). EGM is anhedral interstitial in all of Phase II which indicates that EGM nucleated late relative to the main rock-forming and liquidus minerals of Phase II. Saturation in remaining bulk melt with components needed for nucleation of EGM was reached after the crystallization about 85 vol. % of the intrusion. Early euhedral and idiomorphic EGM of Phase III crystalized in a large convective volume of melt together with other liquidus minerals and was affected by layering processes and formation of EGM ore. Consequently, a prerequisite for the formation of the ore deposit is saturation of the alkaline bulk magma with EGM. It follows that the potential for EGM ores in Lovozero is restricted to the parts of the complex that hosts cumulus EGM. Phase II with only anhedral and interstitial EGM is not promising for this type of ore. Nor is the neighboring Khibiny complex despite a bulk content of 531 ppm of Zr. Khibiny only has interstitial and anhedral EGM. The evolution of the Lovozero magma is recorded in the compositions EGM up through a stratigraphy of 2400 m in Phase II and III of the complex, and distinct in elements like rare earth elements (REE), Sr, Ba, Th, U, Rb, Mn, Fe. The compositional evolution reflects primarily fractional crystallization processes within the magma chamber itself in combination with convective magma flow and layering by precipitation of minerals with different settling velocities. The suggested mechanism for the formation of the EGM deposits is flotation of very small, suspended EGM crystals in the convective magma and concentration below the roof of the magma chamber. Phase III EGM is enriched in total REE (1.3%) and in HREE (Ce/Yt = 8.8) and constitutes a world class deposit of REE in the million tons of Phase III eudialyte lujavrites.

Elastic, inelastic and time constant measurement for M102 (AL–C–O) dispersions-reinforced aluminum alloys

Purpose. To conduct an experimental study on M102 aluminum alloy bulk content characterization under cyclic loadings for precision applications such as balance machines, optical, and laser instruments. M102 (AL-C-O) dispersion-reinforced aluminum alloy was chosen because of its ability to withstand temperatures beyond 200C and has a better strength than precipitation-hardened Al alloys at room temperature. A CNC milling machine is used to manufacture test samples with longitudinal machining directions. A constant time interval is set for the fabric a quarter-hour span, which is based on the investigation of inelastic and plastic deformations in the nanoscale. Methodology. An electromagnetic test instrument applies a tensile stress range of 10 to 145 N/mm2 to samples with particular shape. It should be noted that interferometers and capacitive sensors were used to measure all forms of deformations with and without loading. The experiments are carried out in a temperature-stable environment of 30.5 C; measurements are taken within a residual strain range of 10 microns. Findings. The results obtained show that results for inelastic deformations for samples of longitudinal cuts direction at 30.5 C were measured under 150 N/mm2 stress as 500 nm inelastic deformation and 100 nm plastic deformation were measured, which is much higher than aluminum alloy studied before at room temperature (20 C). Furthermore, it was found that the time constant of the M102 (ALCO) aluminum alloy samples was double times higher than that for other samples, Originality. For the first time, a study has been conducted on inelastic and plastic deformations in the nanoscale for characterization of M102 aluminum alloy bulk content under cyclic loadings for precision applications. Practical value. One of the main factors affecting the using of other materials than steel in precision applications such as balance machines, optical, and laser instruments is measurement and determination of inelastic, plastic and time constant of the process of delamination of materials of different aluminum alloys since they are nonmagnetic, are easily machined and shaped. This will bring new products and opportunities for these materials.

ASSESSMENT OF ANTHROPOGENIC POLLUTION OF SOILS IN CHERNIVTSI (UKRAINE) BY MAGNETIC SUSCEPTIBILITY AND HEAVY METAL CONTENT

The paper is devoted to spatial distribution of low-frequency magnetic susceptibility (χ) of surface sediments in Chernivtsi city as an informative indicator of geochemical contamination of the topsoil. The bulk content of heavy metals in urban soils and the correlations between the χ, frequency dependence of magnetic susceptibility (kfd) and the content of Cd, Mn, Cu, Ni, Pb, Zn were studied. Χ vary from 10∙10-8 to 1286∙10-8 m3/kg with a median value of 66∙10-8 m3/kg. In 20 % of samples χ exceeds the median value three times or more, indicating that the soil is contaminated with iron dust and magnetic particulate matter derived from anthropogenic aerosols. Priority contaminants of city soils are metals such as Pb and Zn, the bulk content of which exceeds the trigger concentration in the vast majority of samples. The χ revealed strong correlation with bulk content of Pb and Zn and the weaker one, but still statistically significant, with Cu and Cd. An additional criterion for the common anthropogenic origin of heavy metals and magnetic minerals in soils is the significant negative correlation coefficients between kfd and content of Zn, Pb, and Cu. So, it can be argued that the increase in Zn, Pb, and Cu content is accompanied by an increase in concentration of magnetic minerals in the multidomain state. The maps were produced, showing spatial distribution of χ and Pollution Load Index (PLI), calculated by three metals (Zn, Pb, and Cu). For 51 % of the samples, the PLI indicates no contamination, 35 % indicate moderate contamination,14 % are strongly contaminated. These results prove that surface sediment over a large area of the city require measures to reduce their toxicity. The correlation coefficient between χ and PLI makes 0.88, indicating χ as a quick indicator of geochemical soil contamination in the city of Chernivtsi.

Mineralogy, chemical composition and leachability of ash from biomass combustion and biomass–coal co-combustion

Ash samples from biomass combustion or co-combustion with coal were analysed. The aim of this study of ash was to determine its mineral and chemical composition, and the chemical composition of solutions obtained during one-step water extraction. Besides the chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS) were applied. The mineral and chemical composition of ash samples differ strongly. The content of heavy metals in the ash is generally low, but in some samples the limits of the content of some elements determined for fertilizers or soil amendments are exceeded. The relatively poor correlation between the concentration in leachate and bulk content in ash indicates that numerous elements are present in different forms in the studied samples. The results indicate that the potential use of biomass ash, or ash from biomass–coal co-combustion, requires complex studies that explore ash and leachates.

Effect of Proeutectoid Ferrite Morphology on the Microstructure and Mechanical Properties of Hot Rolled 60Si2MnA Spring Steel

The hot rolled 60Si2MnA spring steel was transformed to obtain different proeutectoid ferrite morphologies by different cooling rates after finish rolling through dynamic thermal simulation test. The coexistence relationship between proeutectoid ferrite and pearlite, and the effect of proeutectoid ferrite morphology on mechanical properties were systematically investigated. Results showed that the reticular proeutectoid ferrite could be formed by the cooling rates of 0.5–2 °C/s; the small, dispersed and blocky proeutectoid ferrite could be formed by the increased cooling rates of 3–5 °C/s; and the bulk content of proeutectoid ferrite decreased. The pearlitic colony and interlamellar spacing also decreased, the reciprocal of them both followed a linear relationship with the reciprocal of proeutectoid ferrite bulk content. Besides, the tensile strength, percentage of area reduction, impact energy and microhardness increased, which all follow a Hall–Petch-type relationship with the inverse of square root of proeutectoid ferrite bulk content. The fracture morphologies of tensile and impact tests transformed from intergranular fracture to cleavage and dimple fracture, and the strength and plasticity of spring steel were both improved. The results have been explained on the basis of proeutectoid ferrite morphologies–microstructures–mechanical properties relationship effectively.