23 research outputs found

    THERMAL PROPERTIES AND HOMOGENITY RANGE OF Bi24+xCo2-xO39 CERAMICS

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    Samples with different Bi2O3/Co2O3 ratio were prepared by ceramic route. Based on the results of DTA, XRD and SEM – EDX a section of phase diagram of the Bi–Co–O diagram in air atmosphere was calculated using the FactSage software. The sillenite structure of Bi24+xCo2-xO39 was confirmed and described. The Rietveld analysis confirmed SEM – EDX results. The heat capacity and enthalpy increments of Bi24Co2O39 were measured by differential scanning calorimetry (DSC) from 258 K to 355 K and by the drop calorimetry from 573 K to 973 K. Above room temperature the temperature dependence of the molar heat capacity in the form Cpm = (1467.87 + 0.299410 · T – 15888378 · T-2) J K-1 mol-1 was derived by least-squares method from the experimental data

    ZnO thin films prepared by spray-pyrolysis technique from organo-metallic precursor

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    Presented experiments utilize methanolic solution of zinc acetyl-acetonate as a precursor and sapphire (001) as a substrate for deposition of thin films of ZnO. The X-ray diffraction analysis revealed polycrystalline character of prepared films with preferential growth orientation along c-axis. The roughness of prepared films was assessed by AFM microscopy and represented by roughness root mean square (RMS) value in range of 1.8 - 433 nm. The surface morphology was mapped by scanning electron microscopy showing periodical structure with several local defects. The optical transmittance spectrum of ZnO films was measured in wavelength range of 200-1000 nm. Prepared films are transparent in visible range with sharp ultra-violet cut-off at approximately 370 nm. Raman spectroscopy confirmed wurtzite structure and the presence of compressive stress within its structure as well as the occurrence of oxygen vacancies. The four-point Van der Pauw method was used to study the transport prosperities. The resistivity of presented ZnO films was found 8 × 10–2 Ω cm with carrier density of 1.3 × 1018 cm–3 and electron mobility of 40 cm2 V–1 s–1

    Biogeographical patterns and determinants of invasion by forest pathogens in Europe

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    A large database of invasive forest pathogens (IFPs) was developed to investigate the patterns and determinants of invasion in Europe. Detailed taxonomic and biological information on the invasive species was combined with country-specific data on land use, climate, and the time since invasion to identify the determinants of invasiveness, and to differentiate the class of environments which share territorial and climate features associated with a susceptibility to invasion. IFPs increased exponentially in the last four decades. Until 1919, IFPs already present moved across Europe. Then, new IFPs were introduced mainly from North America, and recently from Asia. Hybrid pathogens also appeared. Countries with a wider range of environments, higher human impact or international trade hosted more IFPs. Rainfall influenced the diffusion rates. Environmental conditions of the new and original ranges and systematic and ecological attributes affected invasiveness. Further spread of established IFPs is expected in countries that have experienced commercial isolation in the recent past. Densely populated countries with high environmental diversity may be the weakest links in attempts to prevent new arrivals. Tight coordination of actions against new arrivals is needed. Eradication seems impossible, and prevention seems the only reliable measure, although this will be difficult in the face of global mobility
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