Letteratura scientifica selezionata sul tema "Quenched-in fluorite type structure"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Quenched-in fluorite type structure".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "Quenched-in fluorite type structure"
1
Webster, Nathan A. S., Chris D. Ling e Frank J. Lincoln. "Structure–property relationships in fluorite-type Bi2O3–Yb2O3–PbO solid-electrolyte materials". Powder Diffraction 29, S1 (21 novembre 2014): S73—S77. http://dx.doi.org/10.1017/s0885715614001079.
Testo completoAbstract (sommario):
New quenched-in face-centred cubic fluorite-type materials were synthesised in the Bi2O3–Yb2O3–PbO system. After annealing in air at 500 °C for up to 200 h, each material underwent a conductivity-lowering structural transformation, thus making them unsuitable for use as solid electrolytes in solid-oxide fuel cells. For example, (BiO1.5)0.80(YbO1.5)0.17(PbO)0.03 underwent a fluorite- to Bi17Yb7O36-type orthorhombic transformation, indicative of long-range cation ordering, and (BiO1.5)0.80(YbO1.5)0.11(PbO)0.09 underwent a fluorite- to β-Bi2O3-type tetragonal transformation, indicative of long-range 〈001〉 oxide-ion vacancy ordering.
2
Landa-Cánovas, Á. R., Eladio Vila, Jorge Hernández-Velasco, Jean Galy e Alicia Castro. "Transmission Electron Microscopy Study of Low Mo-content Bi-Mo-O Phases". Microscopy and Microanalysis 18, S5 (agosto 2012): 71–72. http://dx.doi.org/10.1017/s1431927612013013.
Testo completoAbstract (sommario):
δ-Bi2O3, a material with a fluorite-type structure, is one of the best solid-state oxygen-ion conductors. It is a high-temperature form that cannot be quenched to room temperature. However, doping with small amounts of transition metal oxides preserves the δ-Bi2O3 structure at low temperature and retains its anionic conduction properties. The Bi2O3–MoO3 materials are interesting because of their functional properties, chiefly as catalysts and as good ionic conductors. All the phases in this system are related to the fluorite structure except Bi2MoO6 which shows an Aurivillius-type structure.
3
Sorokin, N. I. "Polarizability of Fluoride Ions in Fluorides with Fluorite-Type Structure". Crystallography Reports 45, n. 6 (novembre 2000): 976. http://dx.doi.org/10.1134/1.1327662.
Testo completo
4
Lucid, Aoife K., Aoife C. Plunkett e Graeme W. Watson. "Predicting the Structure of Grain Boundaries in Fluorite-Structured Materials". Johnson Matthey Technology Review 63, n. 4 (1 ottobre 2019): 247–54. http://dx.doi.org/10.1595/205651319x15598975874659.
Testo completoAbstract (sommario):
Interfaces are a type of extended defect which govern the properties of materials. As the nanostructuring of materials becomes more prevalent the impact of interfaces such as grain boundaries (GBs) becomes more important. Computational modelling of GBs is vital to the improvement of our understanding of these defects as it allows us to isolate specific structures and understand resulting properties. The first step to accurately modelling GBs is to generate accurate descriptions of the structures. In this paper, we present low angle mirror tilt GB structures for fluorite structured materials (calcium fluoride and ceria). We compare specific GB structures which are generated computationally to experimentally known structures, wherein we see excellent agreement. The high accuracy of the method which we present for predicting these structures can be used in the future to predict interfaces which have not already been experimentally identified and can also be applied to heterointerfaces.
5
Withers, RL, JG Thompson, PJ Barlow e JC Barry. "The Defect Fluorite Phase in the ZrO2-PrO1.5 System and Its Relationship to the Structure of Pyrochlore". Australian Journal of Chemistry 45, n. 9 (1992): 1375. http://dx.doi.org/10.1071/ch9921375.
Testo completoAbstract (sommario):
A detailed transmission electron microscope and X-ray powder diffraction study has been made of the so-called 'defect fluorite' phase field in the ZrO2-PrO1.5 system and of its close relationship to the pyrochlore solid solution field in the same system. Even for the lowest possible PrO1.5 content within the 'defect fluorite' phase field, it is clear that the sharp Bragg reflections characteristic of the underlying fluorite average structure are accompanied by some of the 'satellite reflections' characteristic of the pyrochlore solid solution field. As the PrO1.5 content increases, these satellite reflections increase systematically in intensity as well as sharpening very considerably. It is shown that this 'defect fluorite' phase field cannot be adequately described either in terms of random point defects within an average fluorite-type matrix or in terms of a diphasic texture of pyrochlore domains embedded coherently into a fluorite matrix, but must be regarded as enuinely intermediate between these two end-member structures and of commensurately modulated fluorite type. A group theoretical approach is used to propose a model for the structural deviation from the underlying fluorite average structure.
6
Shiraki, Koichi, Taku Tsuchiya e Shigeaki Ono. "Structural refinements of high-pressure phases in germanium dioxide". Acta Crystallographica Section B Structural Science 59, n. 6 (25 novembre 2003): 701–8. http://dx.doi.org/10.1107/s0108768103021761.
Testo completoAbstract (sommario):
Recently, there has been substantial interest in the new high-pressure polymorphs of GeO2 synthesized in the laboratory. Previous investigators reported the synthesis of `CaCl2-type', `α-PbO2-type' and `pyrite-type (modified-fluorite-type)' GeO2 at pressures of 30–130 GPa in laser-heated diamond anvil cells. In order to provide definitive information about the new high-pressure polymorphs, we performed Rietveld refinements of the structures. The structure refinements confirm that two of these high-pressure phases do have the α-PbO2-type and pyrite-type (modified-fluorite-type) structures.
7
Ye, Fei, Ding Rong Ou e Toshiyuki Mori. "Microstructural Evolution in a CeO2-Gd2O3 System". Microscopy and Microanalysis 18, n. 1 (15 dicembre 2011): 162–70. http://dx.doi.org/10.1017/s1431927611012396.
Testo completoAbstract (sommario):
AbstractMicrostructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.
8
Rossell, HJ, M. Leblanc, G. Ferey, DJM Bevan, DJ Simpson e MR Taylor. "On the Crystal Structure of Bi2Te4O11". Australian Journal of Chemistry 45, n. 9 (1992): 1415. http://dx.doi.org/10.1071/ch9921415.
Testo completoAbstract (sommario):
Bi2Te4O11 is monoclinic, space group P21/n; the lattice parameters derived from a Guinier powder pattern ( Si standard) are: a = 6.9909(3), b = 7.9593(3), c = 18.8963(8) � , β = 95.176(3)�, Z = 4, V = 1047.15 �. The structure was solved independently from both single-crystal X-ray data and a combination of X-ray and neutron powder data. It is an anion-deficient superstructure of fluorite in which can be recognized the ordered intergrowth of fluorite-type Bi2Te2O7 and rutile-type Te2O4. Lone-pair electrons are stereochemically active.
9
Achary, S. N., S. J. Patwe e A. K. Tyagi. "Powder XRD study of Ba4Eu3F17: A new anion rich fluorite related mixed fluoride". Powder Diffraction 17, n. 3 (settembre 2002): 225–29. http://dx.doi.org/10.1154/1.1477198.
Testo completoAbstract (sommario):
The compound Ba4Eu3F17 was prepared by heating pre-dried BaF2 and EuF3 (4:3) at 800 °C for 8 h in static vacuum. The colorless polycrystalline product obtained was characterized by Rietveld refinement of the observed powder diffraction data with a starting model of Ba4Y3F17. The title compound Ba4Eu3F17 crystallizes in rhombohedral lattice with lattice parameters, a=11.1787(4) and c=20.5789(10) Å, Z=3 (Space group R 3, No. 148). The Ba4Eu3F17 structure can be described as an ordered anion-rich fluorite type structure with the formation of Eu6F37 clusters. There are two crystallographically distinct Ba (CN=10, 11) and one distinct Eu (CN=8). The typical Ba(1)–F, Ba(2)–F, and Eu–F bond lengths range from 2.56 to 2.83 Å, 2.54 to 3.25 Å, and 2.24 to 2.49 Å, respectively. The salient feature of the structure is that the EuF8 polyhedra share their corner to form a cubo-octahedron of fluoride ions. The cubic BaF8 polyhedra of BaF2 are modified to Ba(1)–F10 and Ba(2)–F11 polyhedra in this structure. The cubo-octahedron encloses extra fluorine F(8) inside it.
10
Kennedy, Brendan, Peter Blanchard, Emily Reynolds e Zhaoming Zhang. "Transformation from pyrochlore to fluorite by diffraction and X-ray spectroscopy". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C234. http://dx.doi.org/10.1107/s2053273314097654.
Testo completoAbstract (sommario):
We have studied the long-range average and local structures in a number of zirconium containing materials of the type A2B2O7 ( A = Ln or Y; B = Zr, Hf or Sn) using synchrotron X-ray and neutron powder diffraction and X-ray absorption spectroscopy. Studies of the system Gd2-xTbxZr2O7 include neutron diffraction data, obtained at λ ≍ 0.497 Å to minimise absorption, not only provide evidence for independent ordering of the anion and cation sublattices, but also suggest that the disorder transition across the pyrochlore-defect fluorite boundary of Ln2Zr2O7 is rather gradual. In general we observe that while the diffraction data indicate a clear phase transition from ordered pyrochlore to disordered defect-fluorite at specific compositions corresponding to a critical ionic radius ratio of the A and B cations (rA/rB) x ~ 1.0-1.2, X-ray absorption near-edge structure (XANES) results reveal a gradual structural evolution across the compositional range. These findings provide experimental evidence that the local disorder occurs long before the pyrochlore to defect-fluorite phase boundary as determined by X-ray diffraction, and the extent of disorder continues to develop throughout the defect-fluorite region. Where possible the experimental results were supplemented by ab initio atomic scale simulations, which provide a mechanism for disorder to initiate in the pyrochlore structure. Further, the coordination numbers of the cations in both the defect-fluorite and pyrochlore structures were predicted, and the trends agree well with the experimental XANES results. X-ray absorption measurements at the Zr L3-edge, which showed a gradual increase in the effective coordination number of the Zr from near 6-coordinate in the pyrochlore rich samples to near 7-coordinate in the defect fluorites.
Tesi sul tema "Quenched-in fluorite type structure"
1
Webster, Nathan A. S. "New fluorite-type Bi2O3-based solid electrolytes : characterisation, conductivity and crystallography". University of Western Australia. School of Biomedical and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0092.
Testo completoAbstract (sommario):
[Truncated abstract] New, double-doped, Bi2O3-based materials in the Bi2O3 Ln2O3 PbO (Ln = La, Nd, Er and Yb) and Bi2O3 WO3 PbO systems were prepared using solid-state reactions. For the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems, the air-quenchable compositional domain of the fcc fluorite-type phase was partially established. Temperature dependent conductivity measurements were performed on these quenched-in fluorite-type materials using AC impedance spectroscopy. Conductivity at 750[degrees Celsius] generally increased with increasing Pb2+/Ln3+ and decreasing (Ln3++Pb2+)/Bi3+ ratios. The material (BiO1.5)0.70(ErO1.5)0.15(PbO)0.15 had a conductivity of 0.66 [plus-minus] 0.05 S cm-1 at 750[degrees Celsius], placing it among the most highly conductive Bi2O3-based materials, and was the best new fluorite-type material from a combined conductivity and structural stability viewpoint. Some of the new materials in the Bi2O3 La2O3 PbO and Bi2O3 Nd2O3 PbO systems appeared to have the quenched-in fluorite type structure based on powder X-ray diffraction data. These materials had very high conductivities at 750[degrees Celsius] of `~ 1 S cm-1, but underwent rapid symmetry lowering transformations during heating, thus making them unsuitable for use as solid electrolytes. The fluorite-type structure was not air-quenchable in the Bi2O3 WO3 PbO system, for the compositions synthesised. Room temperature neutron powder diffraction data were collected for quenched-in fluorite-type materials in the (BiO1.5)0.80(LnO1.5)0.20-x(PbO)x, Ln = Er and Yb, x = 0, 0.03, 0.06 and 0.09, and (BiO1.5)0.97-y(ErO1.5)y(PbO)0.03, y = 0.27, 0.17 and 0.12, series. ... This suggests that Pb2+ dopant cations occupy face-centre positions in the fcc unit cell, and the Pb2+ lone pair electrons are likely to be orientated towards an oxide ion vacancy in an adjacent tetrahedral site. Pb2+/oxide ion vacancy interactions affect the migration of oxide ions/oxide ion vacancies through the structure, and are responsible for the significantly larger activation energy for oxide ion migration in the Pb2+-doped materials relative to the Pb2+-free materials. For example, the activation energies of (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03 and 0.06, were 1.50 [plus-minus] 0.02 and 1.54 [plus-minus] 0.02 eV, respectively, while the activation energy for (BiO1.5)0.80(ErO1.5)0.20 was 1.25 [plus-minus] 0.04 eV. Long-term annealing of the quenched in fluorite-type materials in the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems at 500 and 600[degrees Celsius] resulted in conductivity lowering structural transformations, making these materials unsuitable for practical use as solid electrolytes at these temperatures. For example, the materials (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03, 0.06 and 0.09, underwent a fluorite-type to tetragonal transformation during annealing at 500[degrees Celsius] due to <100> oxide ion vacancy ordering, and the rate of conductivity decay at 500[degrees Celsius] increased with increasing Pb2+/Er3+ ratio. Long-term annealing experiments at 500[degrees Celsius] performed on air quenched (Bi2O3)0.705(Er2O3)0.245(WO3)0.050 showed that the disordered fluorite-type structure of this material was not fully stabilised, as evidenced by the presence of superlattice reflections in selected area electron diffraction patterns for the material annealed for 2000 hours, and a gradual conductivity decay after ~ 150 hours annealing.
2
Brigden, Clive. "A study of the synthesis chemistry, structure formation and characterization of all-silica, aluminium-, scandium- and copper-containing MFI and BEA type zeolites synthesized in fluoride and caustic media". Thesis, University of Wolverhampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542315.
Testo completoCapitoli di libri sul tema "Quenched-in fluorite type structure"
1
Danko, Stefania J., e Hiroshi Suzuki. "The Use of Metal Fluoride Compounds as Phosphate Analogs for Understanding the Structural Mechanism in P-type ATPases". In P-Type ATPases, 195–209. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-3179-8_19.
Testo completo
2
Lupei, V., A. Lupei e I. Ursu. "Structure and Luminescence Properties of U6+ Centers in Alkali and Alkaline Earth Fluorides". In Spectroscopy of Solid-State Laser-Type Materials, 560. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4613-0899-7_27.
Testo completo
3
"Fluoride Contaminated Groundwater". In Nano-Phytoremediation Technologies for Groundwater Contaminates, 31–54. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-5225-9016-3.ch004.
Testo completoAbstract (sommario):
In this chapter, the authors explore Fluoride (F) in groundwater as a major issue of water pollution. Geo-statistical analysis of groundwater quality in Newai Tehsil (India) has been done in order to identify the possible spatial distribution of water quality parameters and to assess the spatial dependence of water properties with the help of principal component analysis (PCA) structure. Two types of maps (spatial map and principal component map) of groundwater quality have been developed. A field experiment was conducted to investigate the effect of different Fluoride (F) concentration combined with Pseudomonas fluorescens (P.F) on Prosopis juliflora plant. The field design was used as completely randomized block design with three replicates. The study revealed that parameters were found to be positively and highly correlated with principal component. Low and high values (with their acceptable limit) have also been displayed over each spatial map. Plants treated with P. fluorescens showed the highest F uptake in root, shoot, and leaves tissues were 33.14, 19.41, and 15.15 mg kg-1 after 120 days, respectively. Both total bioaccumulation factor (BF) and translocation factor (TF) were obtained above one (i.e., 1.06 and 1.04). This confirmed the high accumulation and translocation of F in plant tissues. The F uptake efficiency of plant was enhanced to 67.7%, and plant biomass was increased to 57.03%. The present study will be beneficial for researchers working towards further improvement of F phytoremediation technology.
4
Herbert, Bruce E., e Paul M. Bertsch. "A 19F and 2H NMR Spectroscopic Investigation of the Interaction Between Nonionic Organic Contaminants and Dissolved Humic Material". In Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0009.
Testo completoAbstract (sommario):
Interaction between nonionic organic contaminants (NOC) and natural organic matter strongly influences the fate and transport of NOC in the environment. Microscopic descriptions of NOC-organic matter interaction have been developed based on macroscopic observations of NOC sorption to organic matter and organic solute transport under varying conditions. These models include the partitioning concept describing NOC sorption to organic matter and the concept of intra-organic matter diffusion used to account for nonequilibrium organic solute transport; however, little microscopic information exists to validate them. NMR may be a powerful method to gain information and insight concerning NOC-organic matter interaction. Chemical shifts, linewidths, and the magnitude of spin-spin couplings exhibited in the NMR spectra of a given nucleus are dependent on the characteristics of the surrounding media and therefore can be used to study the NOC-organic matter interaction. NMR characterization of the chemical interaction between NOC and organic matter can potentially provide information on important aspects of the sorption mechanism. This information may be useful to explain the influence of organic matter characteristics on NOC sorption and the mechanisms controlling nonequilibrium sorption of NOC to organic matter and mineral phases, and to evaluate different conceptual models of natural humic material, including the polymer concept, where humics are considered to be flexible linear polyelectrolytes, and the micelle concept, which considers humics to be aggregates of simple organic compounds, oligomers, and humic molecules ultimately forming micellar-type structures. NMR has been used to study the interactions of small organic solutes with macromolecules and organized organic assemblies. Fluorine-19 NMR has been particularly useful to study these interactions because this magnetically active nucleus is 100% abundant, has a high sensitivity (83% of 1H) and large chemical shift range, and exhibits no background signal. Several NMR studies have followed the interactions between fluorinated anesthetics and phospholipids, sodium dodecyl sulfate (SDS) micelles, and intact rabbit brain tissue. Generally, these studies have indicated both that sorption sites are less polar than aqueous solutions and that there is decreased mobility of the sorbed solute. Fluorine-19 NMR has also been used to characterize the interactions between fluorine-containing ligands, such as fluorotryptophan, and human serum albumin (HSA).
5
Mark, James E., Harry R. Allcock e Robert West. "Introduction". In Inorganic Polymers. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195131192.003.0005.
Testo completoAbstract (sommario):
A polymer is a very-long-chain macromolecule in which hundreds or thousands of atoms are linked together to form a one-dimensional array. The skeletal atoms usually bear side groups, often two in number, which can be as small as hydrogen, chlorine, or fluorine atoms or as large as aryl or long-chain alkyl units. Polymers are different from other molecules because the long-chain character allows the chains to become entangled in solution or in the solid state or, for specific macromolecular structures, to become lined up in regular arrays in the solid state. These molecular characteristics give rise to solid-state materials properties, such as strength, elasticity, fiber-forming qualities, or film-forming properties, that are not found for small molecule systems. The molecular weights of polymers are normally so high that, for all practical purposes, they are nonvolatile. These characteristics underlie the widespread use of polymers in all aspects of modern technology. Attempts to understand the relationship between the macromolecular structure and the unusual properties characterize much of the fundamental science in this field. Polymers are among the most complicated molecules known. They may contain thousands of atoms in the main chain, plus complex clusters of atoms that form the side groups attached to the skeletal units. How, then, can we depict such molecules in a manner that is easy to comprehend? First, an enormous simplification can be achieved if we remember that most synthetic polymers contain a fairly simple structure that repeats over and over down the chain. This simplest repetitive structure is known as the repeating unit, and it provides the basis for an uncomplicated representation of the structure of the whole polymer. For example, suppose that a polymer consists of a long chain of atoms of type A, to which are attached side groups, R. The polymer chain can be represented by the formula shown in 1.1. The two horizontal lines represent the bonds of the main chain. The brackets (or parentheses) indicate that the structure repeats many times. The actual number of repeating units present is normally not specified, but is represented by the subscript, n.
6
Jolivet, Jean-Pierre. "Titanium, Manganese, and Zirconium Dioxides". In Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0011.
Testo completoAbstract (sommario):
The dioxides of titanium (TiO2), manganese (MnO2), and zirconium (ZrO2) are important materials because of their technological uses. TiO2 is used mainly as white pigment. Because of its semiconducting properties, TiO2, in its nanomaterial form, is also used as an active component of photocells and photocatalysis for self-cleaning glasses and cements . MnO2 is used primarily in electrode materials. ZrO2 is used in refractory ceramics, abrasive materials, and stabilized zirconia as ionic conductive materials stable at high temperature. Many of these properties are, of course, dependent on particle size and shape (§ Chap. 1). Dioxides of other tetravalent elements with interesting properties have been studied elsewhere in this book, especially VO2, which exhibits a metal–isolator transition at 68°C, used, for instance, in optoelectronics (§ 4.1.5), and silica, SiO2 (§ 4.1.4), which is likely the most ubiquitous solid for many applications and uses. Aqueous chemistry is of major interest in synthesizing these oxides in the form of nanoparticles from inorganic salts and under simple, cheap, and environmental friendly conditions. However, as the tetravalent elements have restricted solubility in water (§ 2.2), metal–organic compounds such as titanium and zirconium alkoxides are frequently used in alcoholic solution as precursors for the synthesis of TiO2 and ZrO2 nanoparticles. An overview of the conversion of alkoxides into oxides is indicated about silica formation (§ 4.1.4), and since well-documented works have already been published, these compounds are not considered here. The crystal structures of most MO2 dioxides are of TiO2 rutile type for hexacoordinated cations (e.g., Ti, V, Cr, Mn, Mo, W, Sn, Pb) and CaF2 fluorite type for octacoordinated, larger cations (e.g., Zr, Ce), but polymorphism is common. Some dioxides of elements such as chromium and tin form only one crystalline phase. So, hydrolysis of SnCl4 or acidification of stannate [Sn(OH)6]2− leads both to the same rutile-type phase, cassiterite, SnO2. Many other dioxides are polymorphic, especially TiO2, which exists in three main crystal phases: anatase, brookite, and rutile; and MnO2, which gives rise to a largely diversified crystal chemistry.
Atti di convegni sul tema "Quenched-in fluorite type structure"
1
Kaneko, H., Y. Naganuma, S. Taku, K. Ouchi, N. Hasegawa e Y. Tamaura. "Solar H2 Production From a Two-Step Water Splitting Process With Metal (Fe, Ni) Doped Ceria". In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54281.
Testo completoAbstract (sommario):
Solar H2 production by the two-step water splitting process with thermochemical reaction has been proposed to convert solar energy into chemical energy. We succeeded in repeating the cyclic two-step water splitting process composed of the O2-releasing and H2-generation reactions with metal (Fe, Ni) doped ceria. The metal doped ceria with low content of metal ion (Fe3+, Ni2+) formed a solid solution with fluorite-type structure between ceria (CeO2) and metal oxide (Fe2O3, NiO). The empirical formula of the solid solution was Ce1-αMαO2−δ (M = Fe, Ni), and it was assumed that the high reactivity on the two-step water splitting process was due to an oxygen deficiency in the solid solution. The metal doped ceria with different Ce:M mole ratio (Ce:M = 0.97:0.03–0.7:0.3) was prepared through the combustion method. The two-step water-splitting process with metal doped ceria proceeded at 1673K for the O2-releasing reaction and at 1273K for the H2-generation reaction by irradiation of an infrared imaging lamp for a solar simulator. The amounts of H2 gas evolved in the H2-generation reaction with Fe-doped ceria and Ni-doped ceria with different Ce:M (M = Fe, Ni) mole ratio were 0.97–1.8 and 1.7–2.5 cm3/g, respectively, and the evolved H2/O2 ratios were approximately equaled to 2 of the stoichiometric value. The amounts of H2 and O2 gases evolved in the two-step water splitting process varied with the Ce:M mole ratio in the metal doped ceria. It was suggested that the O2-releasing and H2-generation reactions with metal doped ceria was repeated with the reduction and oxidation of Ce4+-Ce3+ enhanced by the presence of Fe or Ni ions. Furthermore, the O2-releasing reaction with Ni-doped ceria proceeded under a high O2 partial pressure atmosphere (pO2 = 0.05 atm) and at the temperature of 1773K. The progress of the O2-releasing reaction under a high pO2 indicates that metal doped ceria can be applicable for the rotary-type solar reactor developed by Tokyo Tech group for solar H2 production.
2
Xu, Jian, Marcelo J. Dapino, Daniel Gallego Perez e Derek Hansford. "Acoustic Sensor With PVDF Micro-Pillars and Patterned Electrodes". In ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-475.
Testo completoAbstract (sommario):
This paper addresses the design and theoretical analysis of a new type of millimeter-size acoustic sensor that uses Polyvinylidene Fluoride (PVDF) micro-pillars and patterned electrodes. The sensor has the potential to achieve 100x the sensitivity of existing commercial sensors in combination with a dynamic range of 181dB and a frequency bandwidth of at least 100 kHz. A constrained optimization algorithm has been developed as a function of geometric parameters (sensor footprint, diameter and height of the micro-pillars, gap between pillar edges, number of pillars) and electrical parameters of the sensor and conditioning amplifier.
3
Khodaparast, Payam, e Zoubeida Ounaies. "On the Dielectric and Mechanical Behavior of Metal Oxide-Modified PVDF-Based Nanocomposites". In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3302.
Testo completoAbstract (sommario):
Nanoparticle modified polymers have promise as hybrid materials that exhibit properties beyond those predicted by mixing law theories. In the case of metal-oxide nanoparticles in a polymer, it is expected that multifunctional properties of the obtained nanocomposite, including dielectric and mechanical, will be dominated by presence of interface rather than predicted by the inherent properties of individual components. This paper will focus on understanding the role of different types of nanoparticles, namely, titania, silica and alumina and a polymer matrix, Polyvinylidene fluoride (PVDF) in affecting the final dielectric and mechanical properties.
4
Tang, Haixiong, Henry A. Sodano e Yirong Lin. "Enhanced Energy Storage in Nanocomposites Through Aligned PZT Nanowires". In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5141.
Testo completoAbstract (sommario):
Nanocomposites consisting of a piezoceramic inclusion and polymer matrix offer a combination of electromechanical coupling with high toughness and ductility inherent to polymers. There is a wide range of applications for these types of materials due to their intrinsic piezoelectric and dielectric properties, such as vibration sensing, actuation, energy harvesting and capacitive energy storage. However, the relatively low piezoelectric strain coefficient and dielectric permittivity of these nanocomposites significantly limit their application in energy conversion and energy storage applications. There are mainly two coupled to improve the dielectric permittivity and electromechanical properties of piezoceramic nanocomposites, namely higher aspect ratio active inclusions and alignment of inclusions in the direction of the applied electric field. Previously, we have demonstrated that using higher aspect ratio lead zirconate titanate (PZT) nanowires (NWs) could significantly enhance the energy density and d33 coupling as compared to the samples with lower aspect ratio PZT nanorods [11]. In this paper, we will show that orientation of PZT NWs also influences energy storage capability of nanocomposite. Nanocomposites with aligned PZT NWs in the direction of the applied electric field show increased dielectric permittivity and energy density as compared to those with randomly dispersed inclusions. PZT NWs are hydrothermally synthesized, dispersed into a polyvinylidene fluoride (PVDF), cast into a film and then aligned through uniaxial stretching. Scanning electric microscopy (SEM) shows the PZT NWs are successfully aligned in direction of stretching. This work demonstrates that the energy storage and conversion capability of the nanocomposite can be significantly enhanced through the alignment of PZT NWs in the direction of the applied electric field. The findings of this research could lead to broad interest due to demonstration of developing piezoceramic nanocomposites with enhanced dielectric and electromechanical properties for next generation energy storage and conversion devices.
5
Li, D. S., L. Cheng e C. M. Gosselin. "Active Control of Sound Radiation Into Enclosures Using Structural Error Sensors". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33614.
Testo completoAbstract (sommario):
Active control of vibration and sound inside a structure-surrounded enclosure leads to many applications such as noise control inside vehicle cabins. Despite the extensive research carried out in the last two decades, ANVC technology is still in its infancy and has not yet been introduced massively in practical engineering applications. One of the problems to be resolved is that most of presently used techniques require the use of microphones inside the cavity, which is not practical in many situations. In addition, due to the coupling between the vibrating structure and the confined enclosure, demand for more robust control strategy is apparent. This paper tackles the aforementioned problem using a benchmark system in which only PVDF (Polymer polyvinylidene fluoride) sensors are used on the structural surface. A new method based on genetic algorithms is developed for sensor design. This design process ensures a proper consideration of the acoustic energy in the enclosure without the direct use of acoustic sensors inside the cavity. Roughly speaking, the sensor is designed to capture the most radiating motion of the structure via an automatic optimization process. In the proposed method, Genetic Algorithms and the least quadratic square optimal theory are organically combined together. For each configuration of error sensors, the amplitude of control forces, which can either be point forces or excitation generated by piezoceramic actuators, is first determined by minimizing the sum of the squared outputs of error sensors using the least quadratic square optimal theory. Then with the optimal amplitude of control forces, the acoustic potential energy of the sound cavity is computed and used as the evaluation criteria in the evolution process. Using Genetic Algorithms, the optimal configuration of the error sensors can be determined. A cylindrical shell with an internal floor partition is used as an example to illustrate the effectiveness of the proposed approach. To increase the computational efficiency, the structural surface is assumed to be covered with strip-typed PVDF sensors along both the circumferential and longitudinal directions. Both numerical and experimental results show the great effectiveness of the proposed GA-based design method. The sound reduction is achieved not only at the design frequency but also at most frequencies in the low frequency range. The proposed method demonstrates great merits in sensor design for complex structures.
6
Faria, Hugo, Clara Frias, Orlando Fraza˜o, Pedro Vieira e Anto´nio Torres Marques. "Development and Validation of Online Monitoring Techniques for Composite Overwrapped Pressure Vessels". In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25812.
Testo completoAbstract (sommario):
In this research programme, methodologies for structural health monitoring (SHM) of composite overwrapped pressure vessels (COPV) were addressed. This works fit in the development of a COPV laboratorial prototype incorporating non-destructive sensing technologies, in order to detect and identify critical aspects that can occur during operation, aiming to reduce possible unwanted and unpredicted failures. Fibre Bragg grating (FBG) optical sensors and polyvinylidene Fluoride (PVDF) polymeric piezoelectric were the selected sensing technologies. These sensors were embedded in the liner-composite interface during its manufacturing and monitored the prototype while being tested under cyclic internal pressure loading. The data collected from the different sensors type were compared. The Analysis of the data, together with the assessment to the suitability of the two sensing technologies in SHM applications are discussed.
7
Tada, Masaru, Toshihiko Ishihara, Hiroshi Kaneko e Yutaka Tamaura. "O2 Releasing Reactivity of Ceria-Based Reactive Ceramics on Irradiation of Concentrated Solar Beam for Solar Hydrogen Production". In ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90460.
Testo completoAbstract (sommario):
In the present paper, different types of metal doped ceria CeO2-MOx (M = Sc, Y, Dy, Zr and Hf) with fluorite structures have been prepared with a complex polymerization method. The O2-releasing potential of prepared samples was evaluated at 1773 K for two-step water splitting process. The partially oxygen defected CeO2-MO1.5 mixed oxides (M = Sc3+, Y3+ and Dy3+) exhibited an enhancement of the O2 evolution due to the crystal-chemical effect that cation with smaller ionic radius (Sc3+, Y3+ and Dy3+) mitigate the volume expansion of crystal lattice resulted in the reduction of Ce4+ with smaller ionic radius into Ce3+ with larger ionic radius. The CeO2-MO2 (M = Zr4+ and Hf4+) produced larger amount of O2 than that for CeO2-MO1.5 mixed oxides, since CeO2-MO2 has no oxygen vacancy. While the ionic radii of Zr4+ and Hf4+ are almost equal, the higher O2-releasing reactivity of Ce0.9Hf0.1O2 than that of Ce0.9Zr0.1O2 is explained in terms of ionicity of M-O bond. Thus, it was found that both ionic radius and ionicity play important role in the O2-releasing reaction.
8
Zhang, Sheng, Shanbin Shi, Xiao Wu, Xiaodong Sun e Richard Christensen. "Double-Wall Natural Draft Heat Exchanger Design for Tritium Control in FHRs". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67844.
Testo completoAbstract (sommario):
Tritium control is potentially a critical issue for Fluoride salt-cooled High-temperature Reactors (FHRs) and Molten Salt Reactors (MSRs). Tritium production rate in these reactors can be significantly higher compared to that in Light Water Reactors (LWRs). Tritium is highly permeable at high temperatures through reactor structures, especially. Therefore, heat exchangers with large heat transfer areas in FHRs and MSRs provide practical paths for the tritium generated in the primary salt migrating into the surroundings, such as Natural Draft Heat Exchangers (NDHXs) in the direct reactor auxiliary cooling system (DRACS), which are proposed as a passive decay heat removal system for these reactors. A double-wall heat exchanger design was proposed in the literature to significantly minimize the tritium release rate to the environment in FHRs. This unique shell and tube heat exchanger design adopts a three-fluid design concept and each of the heat exchanger tube consists of an inner tube and an outer tube. Each of these tube units forms three flow passages, i.e., the inner channel, annular channel, and outer channel. While this type of heat exchangers was proposed, few such heat exchangers have been designed in the literature, taking into account both heat and tritium mass transfer performance. In this study, a one-dimensional heat and mass transfer model was developed to assist the design of a double-wall NDHX for FHRs. In this model, the molten salt and air flow through the inner and outer channels, respectively. A selected sweep gas acting as a tritium removal medium flows in the annular channel and takes tritium away to minimize tritium leakage to the air flowing in the outer channel. The heat transfer model was benchmarked against a Computational Fluid Dynamics (CFD) code, i.e., ANSYS Fluent. Good agreement was obtained between the model simulation and Fluent analysis. In addition, the heat and mass transfer models combined with non-dominated sorting in generic algorithms (NSGA) were applied to investigate a potential NDHX design in Advanced High-Temperature Reactor (AHTR), a pre-conceptual FHR design developed by the Oak Ridge National Laboratory. A double-wall NDHX design using inner and outer fluted tubes was therefore optimized and compared with a single-wall design in terms of performance and economics.
9
Andersson, Mats, Akichika Yamaguchi e Hua Wang. "Imaging of gasoline-like sprays with planar laser-induced exciplex fluorescence using a stereoscopic imaging system". In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5023.
Testo completoAbstract (sommario):
The role of the fuel injection systems in direct injected gasoline engines is to achieve a suitable fuel vapordistribution, homogeneous or with some degree of stratification, while avoiding unwanted effects such as wall wetting. Planar laser-induced exciplex fluorescence (PLIEF) is a method suitable for the characterization of such sprays since it enables separate imaging of both vapor and liquid phase of fuel simultaneously. In this study a hollow-cone spray generated with an outwards-opening piezo-actuated injector is investigated, with the injector mounted in a constant volume, constant pressure spray chamber with quartz windows, providing a controlled steady test environment. N-hexane is used as surrogate fuel of gasoline, together with exciplex-forming fluorescence tracers - fluorobenzene and diethylmethylamine. Fluorescence excitation is carried out with a parallel laser sheet from the fourth harmonic light of a Nd:YAG-laser (266 nm) running at 10 Hz. Exciplex fluorescence images from liquid phase and monomer fluorescence spray images from vapor phase can be acquired by a single UV-sensitive CMOS camera equipped with a stereoscope having filters selectively transmitting monomer fluorescence at 295 nm and exciplex fluorescence at 355 nm. Since the fluorescence is strongly quenched by oxygen, most of the experiments were carried out in a nitrogen atmosphere.Images were recorded during the injection and at various time steps after the end of the injection, and typical spray development for this type of injector was observed, i.e. the fuel forms an expanding cone, the sheet breaks up to form a vortex structure and the vortices continue to expand after the end of the injection. Fuel vapor is firstly observed at the same locations as the liquid drops, and is then accumulated into the center of the vortices. In addition, penetration of liquid phase and vapor phase are found to be very similar. Various injection pressures have been tested, which shows that increasing the fuel pressure from 10 to 20 MPa results in a larger vortex structure. The fuel evaporation can be followed by studying the evolution of the monomer and exciplex fluorescence as a function of time. At room temperature the vaporization is found to be very slow, but above 40°C there is a noticeablepresence of vapor at the end of the injection, and at higher temperatures, the vaporization goes even faster.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5023