Dispersion Dynamics of Clustered Particles by Centrifugal Force

In this paper an approach is proposed to solve the problem of aggregation in nanomaterials through the mean of rotational separation aiming to quickly disperse clustered nanoparticles while not affecting their purity. If it is possible, this approach may replace the current mean of mechanical mixing, which may cause impurities issues. The hypothesis is that the centrifugal force due to rotational velocity acting on the nanoparticles can overcome the cohesive force between the nanoparticles, therefore dispersing the clustered nanoparticles. The experimental mean is to put different spheres connected by different types of glues imitating different nanoparticle clusters into centrifuges imitating the swivel plate. The results from both the theoretical model and the experiment show that for a cluster with a cohesive force of 1.75N, a rotational velocity of about 800rad./s is required to disperse the cluster. While for a cluster with a cohesive force of 0.25N and the same mass and position, a rotational velocity of about 150 rad./s is required to disperse the cluster. Except for the cohesive force, the mass and position of the nanoparticle on the swivel plate also have a large effect on the required rotational velocity. The observation of the physical mechanism of the dispersion has also shown that while using this way, the cluster is dispersed slowly with small parts separated from it. Therefore, this way can also eliminate re-clustering problems of nanoparticles.

The Acoustic Performance of Expanded Perlite Composites Reinforced with Rapeseed Waste and Natural Polymers

Lignocelluloses residues from the post-harvest crop are receiving great scientific attention nowadays. Generally, the composite materials based on lignocelluloses waste present low density and weight, and better insulation properties compared with those petroleum-based. This study presents the results of experimental investigations regarding soundproofing capabilities for a composite material based on expanded perlite (EP) and natural polymers matrix (starch) reinforced with rapeseed stalks waste. The preparation of light-weight samples of composites was performed at room temperature through a mechanical mixing process of EP with starch polymers and rapeseed residues until optimum moisture content composition was obtained. Rapeseed stalks long fibers were avoided through the preliminary dry grinding procedure, and the composite was air-dried at room temperature for 48 h. Four samples of composites with different ratio of EP and rapeseed waste were considered. The evaluation of sample sound insulation characteristics was performed using the transfer-matrix method based on a four-microphone acoustic impedance tube. The paper concludes that the proposed composite provides comparative sound insulation capabilities to actual materials, with few particular aspects presented within the paper. Thus, these new materials are promising as a viable alternative to the actual large-scale utilization solutions in soundproofing applications.

COMPOSITES BASED ON CALCIUM PHOSPHATES AND COPPER NANOPARTICLES

Боргидридным методом с использованием полимерных стабилизаторов (полиэтиленгликоля, поливинилпирролидона) синтезированы наночастицы меди. Методом оптической спектроскопии установлено, что наибольшей стабильностью (до 1,5 месяца) обладают наночастицы меди, полученные при мольном соотношении Cu /полимер 1:3 - 6. Показано, что в отсутствии полимера либо при его небольшом содержании (мольное соотношение Cu /полимер 1:1) происходит агрегирование образующихся наночастиц и выпадение осадка, содержащего медь и ее оксиды (CuO, CuO). Механическим смешиванием аморфизированных фосфатов кальция (в порошковой и гелевой форме) и наночастиц меди (в виде коллоидного раствора) получен порошковый композит, содержащий фазы CaCuH(PO) и CuPOOH . Выявлено, что при совместном осаждении фосфатов кальция и наночастиц меди происходит встраивание ионов меди в кристаллическую решетку фосфатов кальция с образованием смешанных кислых и средних солей. Copper nanoparticles were synthesized by the borohydride method using polymer stabilizers (polyethylene glycol, polyvinylpyrrolidone). It was found by optical spectroscopy that copper nanoparticles obtained at a molar ratio Cu / polymer of 1: (3 - 6) have the highest stability (up to 1.5 months). It was shown that in the absence of polymer or at its low content (molar ratio Cu / polymer 1:1), the resulting nanoparticles aggregate and a precipitate forms containing copper and its oxides (CuO, CuO). By mechanical mixing of amorphized calcium phosphates (in powder and gel form) and copper nanoparticles (in the form of a colloidal solution), a powder composite containing CaCuH(PO) and CuPOOH phases was obtained. It was shown that during the coprecipitation of calcium phosphates and copper nanoparticles, copper ions are incorporated into the crystal lattice of calcium phosphates with the formation of mixed acidic and medium salts.

PHYSICO-TRIBOLOGICAL ANND WEAR MECHANISM CHARACTERISTICS OF HYBRID REINFFORCED Al6063 MATRIX COMPOSITES

The development of engineering materials is continuously attracting attention from scientists and engineers for numerous engineering applications. The physical properties and wear mechanism of aluminium (Al 6063) matrix reinforced with silicon carbide (SiC) and palm kernel shell ash (PKSA) particulates at different weight ratios ranging from 0 to 10 wt.% with 2 wt.% intervals were investigated. The liquid route of double stir casting was employed in synthesizing the composites. The wear experiment was conducted using the Taber-type wear abrasion machine. The worn surfaces were examined using scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS), while the intermetallic phases were examined using the x-ray diffractometer (XRD). From the result, the increase in PKSA and SiC lowered and improved the density of the composites, respectively. The percentage porosity values (2 - 2.4%) obtained in this study were found to be within the acceptable limit of less than 4% for metal matrix composites castings. The mass loss and wear index increased owing to the rotating speed and applied load increase, resulting from the occurrence of mechanical mixing between the contacting surface of the sample disk and the machined disc. Adhesive and abrasive wear mechanisms were the major mechanisms observed in this study.

Emergence of uniform linearly-arranged micro-droplets entrapping DNA and living cells through water/water phase-separation

Living cells maintain their lives through self-organization in an environment crowded with a rich variety of biological species. Recently, it was found that micro-droplets containing biomacromolecules, which vary widely in size, are generated accompanied by water/water phase-separation by simple mechanical mixing of an aqueous solution with binary polymers. Here, we report that cell-sized droplets of nearly the same size are generated as a linear array within a glass capillary upon the introduction of a binary polymer solution of polyethylene glycol (PEG) and dextran (DEX). Interestingly, when DNA molecules are added to the polymer solution, stable droplets entrapping DNA molecules are obtained. Similarly, living cells are entrapped spontaneously for the linearly-arranged cell-sized droplets. This simple method for generating micro-droplets entrapping DNA and also living cells is expected to stimulate further study on the self-construction of protocells and micro organoids.

Research and development of commercially viable lubricants to intensify working life of marine diesel engines and cylinder piston group in internal combustion engines

The paper presents the results of studying the influence of variable characteristics of lubricating oils for marine diesel engines (concentration of layered friction modifier in lubricating oil, viscosity of lubricating oil, contact pressure in the friction zone) on the tribological parameters of parts of the cylinder-piston group of marine diesel engines. There are considered the aspects of increasing the reliability and wear resistance of the cylinder-piston group of marine diesel engines when a layered friction modifier is added to the base lubricating oil in a concentration of 1.5 vol.%. There have been carried out the comparative tribological studies of M-16G2CS lubricating oil including an additive based on molybdenum diselenide. Dependences of the wear of parts of the cylinder-piston group of a marine engine on different parameters of the studied lubricants are shown. The wear rate of experimental samples in conditions of variable characteristics of lubricants has been studied. According to the tribological studies of lubricants and structural materials, the tribological rating of lubricating compositions containing M16G2CS marine engine oil as a base and a layered friction modifier - molybdenum diselenide as a tribologically active additive was built. The test tool for the antiwear ability of lubricants is a friction machine of an original design with abraded samples according to the “ball-cylinder” contact scheme. Mechanical mixing of the lubricating medium of “oil + additive” type on the RPU-0.8-55A rotary-pulsating unit was one of the variable parameters in the tests. The tribological efficiency of the studied antiwear additive varies depending on the type of mixing of the additive solution before adding to the base lubricating oil and makes 13-54% (the difference in the diameter of the wear spot of the sample) for mechanical mixing, and for rotary-pulsation mixing - 45-56%.

New Insights on the Nickel State Deposited by Hydrazine Wet-Chemical Synthesis Route in the Ni/BCY15 Proton-Conducting SOFC Anode

Yttrium-doped barium cerate (BCY15) was used as an anode ceramic matrix for synthesis of the Ni-based cermet anode with application in proton-conducting solid oxide fuel cells (pSOFC). The hydrazine wet-chemical synthesis was developed as an alternative low-cost energy-efficient route that promotes ‘in situ’ introduction of metallic Ni particles in the BCY15 matrix. The focus of this study is a detailed comparative characterization of the nickel state in the Ni/BCY15 cermets obtained in two types of medium, aqueous and anhydrous ethylene glycol environment, performed by a combination of XRD, N2 physisorption, SEM, EPR, XPS, and electrochemical impedance spectroscopy. Obtained results on the effect of the working medium show that ethylene glycol ensures active Ni cermet preparation with well-dispersed nanoscale metal Ni particles and provides a strong interaction between hydrazine-originating metallic Ni and cerium from the BCY15 matrix. The metallic Ni phase in the pSOFC anode is more stable during reoxidation compared to the Ni cermet prepared by the commercial mechanical mixing procedure. These factors contribute toward improvement of the anode’s electrochemical performance in pSOFC, enhanced stability, and a lower degradation rate during operation.

Reactivity Study of Bimetallic Fe-Mn Oxides with Addition of TiO2 for Chemical Looping Combustion Purposes

The objective of the research was to prepare Mn-based materials for use as oxygen carriers and investigate their reactivity in terms of their applicability to energy systems. The family of Fe2O3-MnO2 with the addition of TiO2 was prepared by mechanical mixing method and calcination. Five samples with addition of Fe2O3 (20, 30, 35, and 50 wt.%) to MnO2 (65, 55, 50, 35, and 85 wt.%) with constant amount of inert TiO2 (15 wt.%) were prepared. The performance of TiO2 supported Fe-Mn oxides oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was evaluated. Thermogravimetric analysis was used for reactivity studies within a wide temperature range (800–1000 °C). Comprehensive characterization contained multipurpose techniques for newly synthesized materials. Moreover, post-reaction experiments considered morphology analysis by SEM, mechanical strength testing by dynamometry, and crystal phase study by XRD. Based on wide-ranging testing, the F50M35 sample was indicated as the most promising for gaseous fuel combustion via CLC at 850–900 °C temperature.

Studies on uranium recovery from a U-bearing Radoniów Dump

This work reports the possibility of uranium recovery from a post-mining uranium ore dump in Poland by a bioleaching method. The studies were conducted on the dump leaching model with the mass of 570 kg of uranium bearing mineral material from Radoniów pile and in the periodic bioreactor with a work volume of 80 dm3 and with mechanical mixing and aeration of the charge. The uranium concentration in the examined material was about 800 ppm. In this process, the consortium of microorganisms isolated from former mines was used. It was composed of the following microorganisms: Bacillius, Pseudomonas, Sphingomonas, Thiobacillus, Halothiobacillus, Thiomonas, and Geothrix. The efficiency of the uranium bioleaching process was 98% in the reactor, and a yield of 70% was obtained in the dump leaching model. The post-leaching solution contained significant amounts of uranium ions that were separated in two stages: (1) by ion chromatography and then (2) by a two-step precipitation method. The resulting solution was a source of ammonium diuranate, the precursor of yellowcake (uranium oxides).

Impacts of Landscape Evolution on Heterotrophic Carbon Loss in Intensively Managed Landscapes

Soil respiration that releases CO2 into the atmosphere roughly balances the net primary productivity and varies widely in space and time. However, predicting its spatial variability, particularly in intensively managed landscapes, is challenging due to a lack of understanding of the roles of soil organic carbon (SOC) redistribution resulting from accelerated soil erosion. Here we simulate the heterotrophic carbon loss (HCL)—defined as microbial decomposition of SOC—with soil transport, SOC surface redistribution, and biogeochemical transformation in an agricultural field. The results show that accelerated soil erosion extends the spatial variation of the HCL, and the mechanical-mixing due to tillage further accentuates the contrast. The peak values of HCL occur in areas where soil transport rates are relatively small. Moreover, HCL has a strong correlation with the SOC redistribution rate rather than the soil transport rate. This work characterizes the roles of soil and SOC transport in restructuring the spatial variability of HCL at high spatio-temporal resolution.