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991.
Zeynep Münteha Şahin Erdinç Doğancı S. Zeki Yıldız Murat Tuna Faruk Yılmaz Yusuf Yerli Mesut Görür 《Synthetic Metals》2010,160(17-18):1973-1980
Two-armed poly(?-caprolactone) (TAPCL) polymers were successfully synthesized via the ring opening polymerization (ROP) of ?-caprolactone (?-CL) using the Schiff's base complexes [Cu(SAEE)2] (1) and [Ni(SAEE)2] (2), which have two hydroxyl functional groups, as the two-site initiators and tin(II) 2-ethylhexanoate (Sn(Oct)2) as the catalyst in bulk at 115 °C. The Schiff's base complexes (1 and 2) were synthesized by utilizing the concentrated template synthesis method starting from salicyl aldehyde, 2-(2-aminoethoxy) ethanol and related metal acetate salts. The synthesized TAPCL polymers were characterized by GPC, FTIR, UV–vis, and electron paramagnetic resonance (EPR). The molecular weights of TAPCL polymers linearly increased with increasing molar ratio of the monomer to the initiator. The results obtained from FTIR, UV–vis, and EPR studies indicated that TAPCL polymers had the Schiff's base complexes at the junction point of PCL arms. The crystallization behavior of TAPCL was studied by using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Thermal behavior of TAPCL was also investigated by thermogravimetrical analysis (TGA). 相似文献
992.
A.E. Ersundu G. Karaduman M. Çelikbilek N. Solak S. Aydin 《Journal of the European Ceramic Society》2010,30(15):3087-3092
The stability of δ-TeO2 phase was studied in binary TeO2–WO3, TeO2–CdO and ternary TeO2–WO3–CdO glasses. The samples were prepared by heating high purity powder mixtures of TeO2, WO3 and/or CdO to 800 °C in a platinum crucible with a closed lid, holding for 30 min and quenching in water bath. Differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the thermal, phase and microstructural properties of the δ-TeO2 phase. The addition of CdO into the tellurite glasses increased the stability range of the δ-TeO2 phase up to higher temperature values and expanded the compositional δ-TeO2 formation range. The formation of δ-TeO2 phase in the binary systems was observed for samples containing 5–10 mol% WO3 and 5–15 mol% CdO. However, for the ternary TeO2–WO3–CdO system the formation of δ-TeO2 phase was determined in a wider compositional range. 相似文献
993.
Petr Olegovich Vasiliev Arto Ojuva Jekabs Grins Lennart Bergström 《Journal of the European Ceramic Society》2010,30(14):2977-2983
Hierachically porous monoliths of ZSM-5 and Y zeolites have been prepared by pulsed current processing (PCP). The densification behaviour and structural characteristics during rapid thermal treatment of the zeolites have been determined and related to the influence of the Si:Al ratio on the thermal stability of the zeolites. Monoliths of macroscopic shape can be prepared with an insignificant loss of surface area and micropore volume when the PCP-treatment was performed at temperatures below a critical maximum PCP temperature (TPCP). Full-profile fittings of the powder X-ray diffraction patterns showed that the lattice strain of zeolite Y increases rapidly above the critical TPCP while the ZSM-5 zeolites undergo a phase transition from orthorhombic to monoclinic. The use of a novel ceramic processing route for the production of the zeolite monoliths that do not significantly influence the structural characteristics and surface area of the starting materials has a potential to be of importance in catalysis and gas separation applications. 相似文献
994.
Inclusions in commercial low and medium carbon ferromanganese 总被引:1,自引:0,他引:1
Thobias Sjöqvist Pär Jönsson Öystein Grong 《Metallurgical and Materials Transactions A》2001,32(5):1049-1056
The microstructures of commercial low and medium carbon ferromanganese have been studied by optical microscopy and electron
microprobe techniques. Element analysis and mapping have been performed on impurities in the matrix and nonmetallic inclusions
present. The results show that the most common nonmetallic inclusion is managanese oxide, followed by complex compounds of
managanese oxide, silicon oxide, and manganese sulfide. The different inclusions have been assessed according to the SS 111116
method. It follows that over 85 pct of the present nonmetallic inclusions are manganese oxides and that the amount of manganese
oxide inclusions is inversely proportional to the carbon content in standard refined ferromanganese. 相似文献
995.
Mark H. Carpenter Jan Nordström David Gottlieb 《Journal of scientific computing》2010,45(1-3):118-150
A general interface procedure is presented for multi-domain collocation methods satisfying the summation-by-parts (SBP) spatial discretization convention. Unlike more traditional operators (e.g. FEM) applied to the advection-diffusion equation, the new procedure penalizes the solution and the first p derivatives across the interface. The combined interior/interface operators are proven to be pointwise stable, and conservative, although accuracy deteriorates for p≥2. Penalties between two different sets of variables are compared (motivated by FEM primal and flux formulations), and are shown to be equivalent for certain choices of penalty parameters. Extensive validation studies are presented using two classes of high-order SBP operators: (1) central finite difference, and (2) Legendre spectral collocation. 相似文献
996.
Extraction of ground spruce sapwood with pressurized hot water in an accelerated solvent extractor (ASE) at 170°C during 20, 60, and 100 min resulted in isolation of galactoglucomannans and aromatic substances, including lignin. The isolated lignin preparations were characterized by spectrometric (UV, FT-IR, 1H NMR, liquid and solid-state 13C NMR), chromatographic (RP-HPLC, HP-SEC, GC-FID, and GC-MS), conventional pyrolysis, thermally assisted hydrolysis, and methylation techniques in tandem with GC-MS, and classical wet chemistry (methoxyl groups, total and phenolic hydroxyl groups, derivatization followed by reductive cleavage—DFRC). The content of β-O-4 bonds in isolated lignins was similar to that in MWL and their proportion decreased with extraction time. The oxidation of isolated lignins and content of total hydroxyl groups were significantly increased with extraction time. The lignin structure underwent condensation and demethylation reactions during hot-water extraction. The induction of new phenylcoumaran substructures was proposed in isolated lignins. 相似文献
997.
True biaxial tests of granular materials are investigated by applying the principle of minimal dissipation and comparing to
two dimensional contact dynamics simulations. It is shown that the macroscopic steady state manifested by constant stress
ratio and constant volume is the result of the ever changing microscopic structure which minimizes the dissipation rate. The
shear band angle in the varying shear band structures is found to be constant. We also show that introducing friction on the
walls reduces the degeneracy of the optimal shear band structures to one for a wide range of parameters which gives a non-constant
stress ratio curve with varying aspect ratio that can be calculated. 相似文献
998.
999.
0-18 nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nafion 117 membranes, and used as thin spacer electrolyte layers between the Nafion and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 °C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activity is seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte. 相似文献
1000.
ARIES-RS is one of the major magnetic fusion energy reactor designs that uses a blanket having vanadium alloy structure cooled
by lithium [1, 2]. It is a deuterium–tritium (DT) fusion driven reactor, having a fusion power of 2170 MW [1, 2]. This study presents the neutronic analysis of the ARIES-RS fusion reactor using heavy metal molten salts in which Li2BeF4 as the main constituent was mixed with increased mole fractions of heavy metal salt (ThF4 or UF4) starting by 2 mol.% up to 12 mol.%. Neutron transport calculations were carried out with the help of the SCALE 4.3 system
by solving the Boltzmann transport equation with the XSDRNPM code in 238 neutron groups and a S
8–P
3 approximation. According to the numerical results, tritium self-sufficiency was attained for the coolants, Flibe with 2%
UF4 or ThF4 and 4% UF4. In addition, higher energy multiplication values were found for the salt with UF4 compared to that with ThF4. Furthermore, significant amount of high quality nuclear fuel was produced to be used in external reactors. 相似文献