7,852 research outputs found
Adsorption of cobalt(II) ion on prepared TiO2 adsorbents in high temperature water
No full textTiO2 adsorbents were prepared by hydrolysis of Ti(OC3H7)(4) followed by heat treatment of their hydroxides. Their structures were studied by X-ray diffractometry and Fourier transform infrared spectrometer as a function of preparation pH. The Co2+ adsorption characteristics of the adsorbent in high temperature water were investigated in a stirred autoclave. Co2+ adsorption capacity of the TiO2 adsorbent was determined to be 0.09 mEq/g adsorbent in 280 degrees C of high temperature water. The enthalpy change (Delta H degrees) of about 34 kJ/mol caused by the adsorption of Co2+ on the TiO2 indicates that the adsorption is endothermic in the experimental temperature range (150-280 degrees C). It was shown that specific surface area and surface OH groups of these adsorbents are not dominant factors for Co2+ adsorption on oxides at high temperature
Direct synthesis of W18O49 nanorods from W2N film by thermal annealing
No full textTungsten oxide nanorods were prepared from W2N film by a simple annealing method. W2N film was deposited on a Si( 100) substrate by chemical vapour deposition (CVD) at 450 degrees C, and then heating of the film at 600 - 700 degrees C produces a high density of tungsten oxide nanorods. The morphology, structure, composition and chemical binding states of the prepared nanorods were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) and transmission electron microscopy (TEM) measurements. XRD and TEM analysis showed that the grown nanorods were single-crystalline W18O49. According to XPS analysis, the W18O49 nanorods contained similar to 62% of W6+, similar to 28% of W5+, and similar to 10% of W4+. Field-emission measurements showed a low turn-on field of 9.5 V mu m(-1) for the W18O49 nanorods, indicating that they can be used as potential field emitters. Also, a synthesis reaction mechanism based on thermodynamics is proposed for the growth of tungsten oxide nanorods from W2N.X1142sciescopu
Thermochemistry of yavapaiite KFe(SO4)2: Formation and decomposition
No full textYavapaiite, KFe(SO4)2, is a rare mineral in nature, but its structure is considered as a reference for many synthetic compounds in the alum supergroup. Several authors mention the formation of yavapaiite by heating potassium jarosite above ca. 400°C. To understand the thermal decomposition of jarosite, thermodynamic data for phases in the K-Fe-S-O-(H) system, including yavapaiite, are needed. A synthetic sample of yavapaiite was characterized in this work by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal analysis. Based on X-ray diffraction pattern refinement, the unit cell dimensions for this sample were found to be a = 8.152 ± 0.001 Å, b = 5.151 ± 0.001 Å, c = 7.875 ± 0.001 Å, and β = 94.80°. Thermal decomposition indicates that the final breakdown of the yavapaiite structure takes place at 700°C (first major endothermic peak), but the decomposition starts earlier, around 500°C. The enthalpy of formation from the elements of yavapaiite, KFe(SO4)2, ΔH°f = −2042.8 ± 6.2 kJ/mol, was determined by high-temperature oxide melt solution calorimetry. Using literature data for hematite, corundum, and Fe/Al sulfates, the standard entropy and Gibbs free energy of formation of yavapaiite at 25°C (298 K) were calculated as S°(yavapaiite) = 224.7 ± 2.0 J.mol−1.K−1 and ΔG°f = −1818.8 ± 6.4 kJ/mol. The equilibrium decomposition curve for the reaction jarosite = yavapaiite + Fe2O3 + H2O has been calculated, at pH2O = 1 atm, the phase boundary lies at 219 ± 2°C
Enhanced field emission from density-controlled SiC nanowires
No full textSilicon carbide (SiC) nanowires were grown directly on Si substrates by thermal evaporation of WO3 and graphite powders at high temperature using NiO catalyst. The densities of the nanowires were controlled by varying the NiO catalyst concentration. The morphology, structure and composition of the nanowires were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, FTIR, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) measurements. The synthesized nanowires were single crystalline beta-SiC oriented along the [111] direction. Based on the experimental results, a possible growth mechanism was explained on the basis of solid-liquid-solid (SLS) growth model. Field emission measurements showed that the emission efficiency was strongly dependent on the density of SiC nanowires. Lowest turn-on field of 1.8 V mu m(-1) and highest field enhancement factor of 5.9 x 10(3) was observed for the medium density SiC nanowire sample. (C) 2008 Elsevier B.V. All rights reserved.X1152sciescopu
MOCVD of tungsten nitride films using W(CO)(6) and NH3 for Cu diffusion barrier
No full textTungsten nitride (WNx) films were deposited by metalorganic chemical vapor deposition (MOCVD) using W(CO)(6) and NH3 in the growth temperature range from 250 to 500degreesC. The growth rate was 0.3similar to193 nm/min. The film resisitivity decreased from 950 to 590 muOmega cm, and the impurity concentration of C and O both decreased from 10 to below 5% upon the temperature rise. X-ray diffraction (XRD) analysis showed that the film structure changed from an amorphous-like structure to a W2N(200) phase dominant polycrystalline structure with the temperature rise. Sheet resistance measurements and XRD analysis showed that the WNx barrier of a 15 nm thickness blocked the Cu diffusion efficiently up to 600degreesC for 1 h annealing. (C) 2004 The Electrochemical Society.open111518sciescopu
Characterization of ZnO nanorod arrays fabricated on Si wafers using a low-temperature synthesis method
No full textZnO nanorod arrays fabricated on ZnO buffer layers on Si wafers were grown using a low-temperature solution method and were characterized by various techniques. Buffer layers were prepared using metal organic chemical vapor deposition and a sputter-oxidation method. Aligned ZnO nanorods were deposited at 90 degrees C on the substrates by a hydrothermal treatment using a zinc salt and aqueous ammonia solution. The ZnO nanorod arrays were characterized by scanning electron microscopy, x-ray diffraction., x-ray photoelectron spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. The as-grown ZnO nanorod arrays exhibited broad deep-level emission centered at similar to 564 nm. The intensity of the deep-level emission decreased and band edge emission centered at 379 nut appeared after air annealing. Samples annealed in hydrogen showed only band edge emission. (c) 2006 American Vacuum Society.open1148sciescopu
X-ray induced changes in immunostaining of proliferating cell nuclear antigen (PCNA) in V79 hamster fibroblasts
No full textBackground: Proliferating cell nuclear antigen (PCNA) ist a 36 kD protein that is involved in DNA-replication and -repair. For V79 hamster cells, a mutated p53 and a so-called "adaptive response", an improved radiation tolerance after pre-irradiation with low X-ray doses hours before definitive irradiation with higher doses have been reported. To better understand the role of PCNA after photon irradiation in vivo, using flow cytometry, we studied the immunochemical PCNA-staining in V79 cells after irradiation with 6-MeV photons with and without serum depletion and with and without low-dose pre-irradiation under different growth conditions. Material and Methods: Using V79 hamster cells, BrdUrd incorporation, total and DNA-bound PCNA were measured for exponential cells and for confluent cells at different times (up to 14 days) after reaching confluence. Cells were eith-er grown with medium containing 10% fetal calf serum (FCS) or 0.5% FCS. Six days after reaching confluence, cells were irradiated with 1 Gy land 8 Gy for non-serum-depleted cells) (6-MV photons, 2 Gy/min). Then, immunochemical PCNA-staining was measured by flow cytometry at 0, 30, 60 and 120 min after irradiation. For studying the adaptive response, exponentially growing cells and cells that were 6 days in confluence were pretreated with 0.01 Gy, reincubated for 5 h and then definitively treated with 1 Gy and harvested and processed as described above. Results: Four days after reaching confluence; DNA-bound PCNA and BrdUrd content were reduced to a minimum of <15% positive cells while total PCNA remained essentially unchanged. After irradiation with 1 Gy 6 days after reaching confluence, cells grown with 10% FCS showed a moderate but distinct transient increase in DNA-bound PCNA at 30 min after irradiation. After irradiation with 8 Gy, there was no clear increase at 30 min but a more distinct decrease at 60 min, implying that the increase might occur earlier in the time course at higher doses. Total cellular PCNA and BrdUrd uptake were constant during the first 2 hours after irradiation. In cells that were kept with serum depleted medium for 6 days after reaching confluence, total PCNA was reduced and no changes in either DNA-bound PCNA or BrdUrd-uptake were observed after irradiation. When cells were primed with a dose of 0.01 Gy 5 h before subsequent treatment with 1 Gy, neither for exponentially growing cells nor for those in confluence a significant difference in the detected amount of PCNA (total and DNA-bound) or BrdUrd was observed when compared to cells treated without a priming dose. Conclusions: The moderate X-ray induced DNA association of PCNA is indicative for ongoing DNA repair but appears to require serum stimuli. However, this p53-independent pathway involving PCNA does not seem to be the most relevant for survival in these rodent cells that tolerate much residual damage. Furthermore, no adaptive response for DNA-association of PCNA could be detected in V79 cells
Finite element simulation of the plastic collapse of closed-cell aluminum foams with X-ray computed tomography
No full textThe detailed deformation and plastic collapse mechanisms of closed-cell Al foams under uniaxial compressive loading, which govern the energy absorption capacity of the foam material, are analyzed with the method of finite elements and experimental measurements. A three-dimensional (3D) finite element (FE) model for a real closed-cell Al foam specimen fabricated via the direct foaming route is constructed by employing the micro-focus X-ray CT system, the 3D reconstruction program, the 3D scanned data processing software, and the commercially available mesh generation program. Finite element analysis is subsequently carried Out using the constructed FE model to explore the deformation and collapse mechanisms of the foam specimen, and the numerical predictions are compared with the experimentally measured results. From this research, it is found that all increase in the 0.2% offset yield stress considerably increases the magnitude of the plateau stress, whereas a decrease in the power-law hardening exponent not only increases the magnitude of the plateau stress but also modifies the shape of the plateau stage. Also, it is found that an increase in the 0.2% offset yield stress with a decrease in the power-law hardening exponent dramatically increases the magnitude of the plateau stress. (C) 2010 Elsevier Ltd. All rights reserved
Thermal decomposition and desorption of diethylamido of tetrakis (diethylamido) zirconium (TDEAZr) on Si(100)
No full textThe thermal decomposition pathway and desorption of diethylamido of tetrakis(diethylamido)zirconium [TDEAZr, Zr(N(C2H5)(2))(4)] on Si(100) were studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). During TPD experiments, ethylethyleneimine (C2H5N=CHCH3), diethylamine [NH(C2H5)(2)], acetonitrile (CH3CN), ethylene (C2H4) and hydrogen (H-2) desorbed as the main decomposition products of diethylamido, which was chemisorbed on Si(100) through the scission of the zirconium-diethylamido bond in TDEAZr. After TPD runs, the formation of silicon carbide and silicon nitride was observed on the surface by XPS, indicating that a complete decomposition of diethylamido proceeded. This could be a reaction pathway of C, N incorporation in the thin film growth using TDEAZr as a Zr precursor.X112sciescopu
Human rights : would our rights be better protected in or out of Europe?
No full textTo understand the implications of Brexit for fundamental rights protection, it is important to distinguish between two legal Europes. The primary human rights regime in Europe is the European Convention on Human Rights (ECHR) – a treaty drawn up by the Council of Europe, which is an older organisation than the EU with a much wider membership. The UK ratified the ECHR in 1951, and since 1966, UK citizens have been able to take cases alleging breaches of Convention rights to the European Court of Human Rights (ECtHR) in Strasbourg. In 1998, the ECHR was incorporated into the UK’s legal systems by the Human Rights Act (HRA) and the devolution statutes, thereby enabling Convention rights to be enforced in UK courts as well
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