64 research outputs found
Quantum nucleation in a single-chain magnet
The field sweep rate (v=dH/dt) and temperature (T) dependence of the
magnetization reversal of a single-chain magnet (SCM) is studied at low
temperatures. As expected for a thermally activated process, the nucleation
field (H_n) increases with decreasing T and increasing v. The set of H_n(T,v)
data is analyzed with a model of thermally activated nucleation of
magnetization reversal. Below 1 K, H_n becomes temperature independent but
remains strongly sweep rate dependent. In this temperature range, the reversal
of the magnetization is induced by a quantum nucleation of a domain wall that
then propagates due to the applied field.Comment: 5 pages, 4 figure
Synthesis, magnetic behaviour, and X-ray structures of dinuclear copper complexes with multiple bridges. Efficient and selective catalysts for polymerization of 2,6-dimethylphenol
5 pagesInternational audienceThe use of a potentially tridentate mono-anionic bridging ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)- propan-2-ol (bdmpp-H), in assembling new dimeric copper complexes with interesting magnetic properties has been investigated. The reaction of copper hydroxide or copper acetate with phenyl phosphinic acid or diphenyl phosphinic acid in the presence of bdmpp-H produces the dinuclear complexes [Cu(bdmpp)(ppi)]2 (1) and [Cu(bdmpp)(dppi-H)]2(dppi)2 (2) (ppi-H = phenylphosphinic acid; dppi-H = diphenylphosphinic acid), respectively. The products have been characterized with the help of analytical, thermal, and spectroscopic (IR, UV-vis, and EPR) techniques. Single crystal X-ray diffraction studies of 1 and 2 reveal that the two bdmpp ligands hold together the dimeric copper unit in each complex through l-O alkoxide and the pyrazolyl nitrogen ligating centers. Two phenyl phosphinate ligands additionally bridge the dicopper core in 1 to result in octahedral coordination geometry around each metal ion. The diphenyl phosphinic acid acts as a terminal ligand in 2, and thus completes a square pyramidal geometry around each copper ion. Both complexes show a very short Cu · · · Cu separation (3.001 and 3.065A˚ for 1 and 2, respectively). The investigation of the magnetic properties reveals the efficiency of the double alkoxide bridge between the two paramagnetic copper ions to mediate strong antiferromagnetic interactions [J/kB =−620(5) K (−431(4) cm−1) and −685(5) K (−476(4) cm−1) for 1 and 2, respectively]. Compounds 1 and 2, along with a few other copper phosphate complexes, were tested as catalysts for the oxidative polymerization of 2,6-dimethylphenol; 1 and 2 were found to be efficient catalysts with an increased selectivity for the formation of the polyphenylene ether. However a related mononuclear octahedral copper complex [Cu(imz)4(dtbp)2] (dtbp-H = di-tert-butylphosphate) was found to be more efficient
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Advanced coal-fueled industrial cogeneration gas turbine system
Advances in coal-fueled gas turbine technology over the past few years, together with recent DOE-METC sponsored studies, have served to provide new optimism that the problems demonstrated in the past can be economically resolved and that the coal-fueled gas turbine can ultimately be the preferred system in appropriate market application sectors. The objective of the Solar/METC program is to prove the technical, economic, and environmental feasibility of a coal-fired gas turbine for cogeneration applications through tests of a Centaur Type H engine system operated on coal fuel throughout the engine design operating range. The five-year program consists of three phases, namely: (1) system description; (2) component development; (3) prototype system verification. A successful conclusion to the program will initiate a continuation of the commercialization plan through extended field demonstration runs
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Advanced coal-fueled industrial cogeneration gas turbine system
The objective of the Solar/METC program is to prove the technical, economic, and environmental feasibility of coal-fired gas turbine for cogeneration applications through tests of a Centaur Type H engine system operated on coal fuel throughout the engine design operating range. This quarter, work was centered on design, fabrication, and testing of the combustor, cleanup, fuel specifications, and hot end simulation rig. 2 refs., 59 figs., 29 tabs
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Advanced coal-fueled industrial cogeneration gas turbine system. Annual report, June 1990--June 1991
Advances in coal-fueled gas turbine technology over the past few years, together with recent DOE-METC sponsored studies, have served to provide new optimism that the problems demonstrated in the past can be economically resolved and that the coal-fueled gas turbine can ultimately be the preferred system in appropriate market application sectors. The objective of the Solar/METC program is to prove the technical, economic, and environmental feasibility of a coal-fired gas turbine for cogeneration applications through tests of a Centaur Type H engine system operated on coal fuel throughout the engine design operating range. The five-year program consists of three phases, namely: (1) system description; (2) component development; (3) prototype system verification. A successful conclusion to the program will initiate a continuation of the commercialization plan through extended field demonstration runs
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Full-scale and bench-scale testing of a coal-fueled gas turbine system
Components for a coal-fueled industrial gas turbine were developed and tested at both benchscale and full-scale. The components included a two stage slagging combustor, a particulate rejection impact separator (PRIS), and a secondary particulate filter. The Integrated Bench Scale Test Facility (IBSTF) was used for the filter tests ana some of the PRIS testing. Full-scale combustor testing has been carried-out both with and without the PRIS. Bench-scale testing has included evaluating the feasibility of on-site CWM preparation, developing a water-cooled impactor and an extended run with new secondary candle filters
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