Sintering and mechanical properties of β‐SiC powder obtained from waste tires

Plasma synthesized SiC powder obtained from quartz and carbonaceous residue of waste tires was successfully sintered at 1925 ℃ by pressureless liquid-phase method using yttria and alumina as sintering aids (T-SiC). Comparison with sintered SiC obtained from commercial powder (C-SiC) put in evidence of similar sintered density (98%T.D.), but much finer microstructure of T-SiC than that of C-SiC. T-SiC also showed higher flexural strength than C-SiC both at room temperature (508 vs. 458 MPa) and at 1500 ℃ (280 vs. 171 MPa). Difference in liquid phase was responsible for the differences in hardness and fracture toughness. The high value of the Young's modulus of T-SiC (427 MPa) confirmed the high degree of sinterability of this powder and that it can be a promising candidate for structural applications with high added value. © 2016, The Author(s)

Steam gasification of waste tyre: Influence of process temperature on yield and product composition

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Dopamine sensor in real sample based on thermal plasma silicon carbide nanopowders

Silicon carbide nanopowders (SiC_PL) were prepared via thermal plasma synthesis. The electrocatalytic activity of the SiC_PL coated glassy carbon electrode (GCE) towards the electrochemical oxidation of dopamine (DA), ascorbic acid (AA), and uric acid (UA), was characterized by cyclic voltammetry (CV), in 0.1 M phosphate buffer solution (PBS) at pH 7. The peaks of oxidation for DA, AA, and UA result well separated on the modified electrode in contrast with the behavior shown on bare GCE. A low limit of detection (LOD) of 0.043 μM was found at the SiC_PL coated GCE. In a real sample, the recovery rates of the added compound were 98.8%, 106.5% and 100.7%, indicating a potential for the SiC_PL electrode to determine DA in real conditions. The results of the characterization as supercapacitor electrode show that the specific capacitance for SiC_PL is of 151.2 F/g at 0.12 A/g. After 2.5 × 10 5 cycles SiC electrode still retains about 90% of its initial capacitance showing good stability

Supercapacitor Electrodes Made of Exhausted Activated Carbon-Derived SiC Nanoparticles Coated by Graphene

Graphene has been obtained at atmospheric pressure and low temperature on exhausted activated carbon-derived SiC nanoparticles. The graphene’s growth, traced by online analyzers, has been obtained from an external source of carbon, in particular by methane/hydrogen chemical vapor deposition (CVD). Recycled SiC has been chosen as growth substrate to carry out a convenient process and to increase the added value of the recycled, combining the favorable properties of different substances. Therefore, the SiC powder and the composite material obtained have been carefully characterized by the combined use of different techniques and tested as supercapacitor electrodes. The results show a very high capacitances up to 114.7 F/g for SiC alone and three times higher in the presence of graphene with an excellent cycle stability

Remote estimation of grassland gross primary production during extreme meteorological seasons

Different models driven by remotely sensed vegetation indexes (VIs) and incident photosynthetically active radiation (PAR) were developed to estimate gross primary production (GPP) in a subalpine grassland equipped with an eddy covariance flux tower. Hyperspectral reflectance was collected using an automatic system designed for high temporal frequency acquisitions for three consecutive years, including one (2011) characterized by a strong reduction of the carbon sequestration rate during the vegetative season. Models based on remotely sensed and meteorological data were used to estimate GPP, and a cross-validation approach was used to compare the predictive capabilities of different model formulations. Vegetation indexes designed to be more sensitive to chlorophyll content explained most of the variability in GPP in the ecosystem investigated, characterized by a strong seasonal dynamic. Model performances improved when including also PARpotential defined as the maximal value of incident PAR under clear sky conditions in model formulations. Best performing models are based entirely on remotely sensed data. This finding could contribute to the development of methods for quantifying the temporal variation of GPP also on a broader scale using current and future satellite sensors.JRC.H.4-Monitoring Agricultural Resource

Using digital repeat photography and eddy covariance data to model grassland phenology and photosynthetic CO2 uptake

The continuous and automated monitoring of canopy phenology is of increasing scientific interest for the multiple implications of vegetation dynamics on ecosystem carbon and energy fluxes. For this purpose we evaluated the applicability of digital camera imagery for monitoring and modeling phenology and physiology of a subalpine grassland over the 2009 and 2010 growing seasons. We tested the relationships between color indices (i.e. the algebraic combinations of RGB brightness levels) tracking canopy greenness extracted from repeated digital images against field measurements of green and total biomass, leaf area index (LAI), greenness visual estimation, vegetation indices computed from continuous spectroradiometric measurements and CO2 fluxes observed with the eddy covariance technique. A strong relationship was found between canopy greenness and (i) structural parameters (i.e., LAI) and (ii) canopy photosynthesis (i.e. Gross Primary Production; GPP). Color indices were also well correlated with vegetation indices typically used for monitoring landscape phenology from satellite, suggesting that digital repeat photography provides high-quality ground data for evaluation of satellite phenology products. We demonstrate that by using canopy greenness we can refine phenological models (Growing Season Index, GSI) by describing canopy development and considering the role of ecological factors (e.g., snow, temperature and photoperiod) controlling grassland phenology. Moreover, we show that canopy greenness combined with radiation use efficiency (RUE) obtained from spectral indices related to photochemistry (i.e., scaled Photochemical Reflectance Index) or meteorology (i.e., MOD17 RUE) can be used to predict daily GPP. Building on previous work that has demonstrated that seasonal variation in the structure and function of plant canopies can be quantified using digital camera imagery, we have highlighted the potential use of these data for the development and parameterization of phenological and RUE models, and thus point toward an extension of the proposed methodologies to the dataset collected within PhenoCam Network.JRC.H.2-Climate change and air qualit