Selected articles from various sources

of previously synthesized nanoscaled donor-doped perovskite powder with ..
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with a perovskite-structured compound (CH 3 ..

The purpose of the work is to characterize and systematize the phase-mineral transformations and chemical interactions in the inorganic matter during combustion of Bulgarian coals from 6 coal basins - Sofia (S), Maritza West (MW), Maritza East (ME), Bobov Dol (BD), Balkan (B) and Pernik (P) [32]. The methodological approach used includes a parallel investigation of coals and their products obtained during coal heating from 100 to 1600 °C using a temperature step of 100 °C in air and for a fixed holding time of 0.5 h. A complex of analytical methods and procedures (separation, thermal treatment, optical microscopy, SEM, TEM, X-ray powder diffraction, DTA-TGA, various chemical analyses, ash-fusion test, etc.) was used. The most important results achieved can be grouped as follows: 1) Phase-mineral and chemical classification of the coals and coal ashes are studied. It was found that the coals have low (S, MW, ME) or high (BD, B, P) detrital abundance and carbonate (S, BD), sulphide-sulphate (MW, ME, B) or mixed (P) authigenic mineralization. The coal ashes belong to 4 chemical types, namely: calferrisialic (S, MW), sialoferric (ME), sialoferricalcic (BD, B) and sialic (P); while the phase composition of these ashes are of a low (S, MW, ME) or high (BD, B, P) silicate concentration and oxyhydroxide (S, BD, B, P) or sulphate (MW, ME) tendency. 2) The behavior of organic and inorganic matter during heating is discussed. The behavior of 39 major and minor minerals and phases of primary and secondary origin in the products obtained during oxidation and combustion of the coals studied was characterized up to 1600 °C. 3) The phase-mineral transformations and chemical interactions are studied. The processes of oxidation and burning of the organic matter, transformation of minerals and solid phases, and the interactions between them, as well as the processes taking place in solutions and melts that induce the formation of solid products during oxidation and combustion of the coals are systemized. The temperature intervals for such processes were described. The coal ashes studied have low (S, MW, ME), medium (BD, B) and high melting (P) ash-fusion temperatures. The phase transformations responsible for these ash-fusion temperatures were identified. 4) An attempt is made for additional explanation and prediction of some technological (fouling, slagging, abrasion, corrosion and less effective combustion of coals in power plants) and environmental (stack emissions of sulphur and trace elements, and contaminated waters that transport the waste products from power stations) problems related to the combustion of Bulgarian coals.

24/12/2017 · Microwave Assisted Synthesis and Characterization of Perovskite ..
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based perovskite materials: Chemical structure ..

Abstract:
Supercapacitors are electrochemical energy storage devices that combine the high energy-storage-capability of conventional batteries with the high power-delivery-capability of conventional capacitors. In this contribution we will show the results of our group recently obtained on supercapacitors with electrodes obtained using mixtures of carbonaceous nanomaterials (carbon nanotubes (CNTs), graphite, graphene, oxidised graphene). The electrode fabrication has been performed using a new dynamic spray-gun based deposition process set-up at Thales Research and Technology (patented). First, we systematically studied the effect of the relative concentrations of Multi-Walled Carbon Nanotubes (MWCNTs) and graphite on the energy and power density. We obtained a power increase of a factor 2.5 compared to barely MWCNTs based electrodes for a mixture composed by 75% of graphite. This effect is related with the improvement of the mesoporous distribution of the composites and to the increase of the conductance as pointes out by Coleman et al. After these results, we decided to test water as a solvent in order to reduce the heating temperature and to obtain a green type process without toxic solvents. To achieve stable suspensions we oxidised the graphene and the CNTs before putting them in water. We observed that changing the Graphene Oxide concentrations we obtained different value of capacitance and energy. The best results were obtained with 90% of GO and 10% of CNTs. We obtained 120F/g and a power of 30kW/Kg. The importance of these results is that it is the first time that these performances have been obtained for graphene related materials using an industrial fabrication suitable technique that can be implemented in roll-to-roll production. In this way we were able to fabricate stable suspensions in less than one hour compared to three days using NMP. All these results demonstrate the strong potential to obtaining high performance devices using an industrially suitable fabrication technique. Finally, new results using mixtures of Carbon nanofibers and graphene will be shown. These new composite allow to use ionic liquid as electrolytes and so to increase dramatically the energy stored in the device without reducing the power.

Process for the synthesis of crystalline ceramic powders of perovskite ..
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The chemical compositions of the epidote type minerals studied are plotted in the figure in terms of (REE+Y+Th+U) against the total Al (p.f.u.) (Fig. 1.). As seen, the points corresponding to the allanite under study lies between the regions of I- and S-type granitoids (according to Broska et al., 2000), thus suggesting that the primary magma had been mixed (S- + I-types). Epidote-I is of an intermediate epidote-clinozoisite-allanite composition corresponding well to the composition trend observed for allanite. At the same time, the composition of postmagmatic epidote (epidote-II) is close to that of proper epidote, containing about 25 mol.% of clinozoisite.

27/05/2016 · Development of Mn-based perovskite materials: Chemical structure and ..
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the perovskite type structure ..

Abstract:
The ordered porous anodic aluminum oxide (AAO) is one of the famous nano-templates usedas etching mask for pattern transfer and for synthesis of nanocomposite materials for wideapplications. Conventional AAO templates were synthesized using two-step potentiostaticmethod of direct current anodization (DCA) at low temperature (0-10°C) to avoid dissolutioneffect. In this talk, the synthesis and characteristics of AAO using conventionallow-temperature anodization and an effective method of room-temperature hybrid pulseanodization (HPA) are presented for the comparison. The HPA with normal-positive andsmall-negative voltages for AAO synthesis can be accomplished at relatively hightemperature of 15-25°C for enhancing AAO characteristics from both the cheap low-purity(99%) and costly high-purity (99.997%) aluminum foils. The pore distribution uniformity andcircularity of AAO by HPA is much better than DCA due to its effective cooling at hightemperature. The impurity effect on AAO characteristics is also discussed. HPA is differentfrom the traditional pulse-anodization with alternating both high and low positive potentialdifferences (/currents) or both one-positive and one-zero potential differences. HPA not onlymerits manufacturing convenience and cost reduction but also promotes pore distributionuniformity of AAO at severe conditions of low-purity Al foils and high temperature. Someapplication in humidity sensing, photoluminescence and SERS will be presented.