Phonons
Mostrando 1-12 de 43 artigos, teses e dissertações.
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1. PHOSPHORUS INCORPORATION INTO MULTIWALLED CARBON NANOTUBES / INCORPORAÇÃO DE FÓSFORO EM NANOTUBOS DE CARBONO DE PAREDES MÚLTIPLAS
The thesis addresses the incorporation of phosphorus atoms into the structure of multi-walled carbon nanotubes (MWCNTs) grown by the Spray Pyrolysis method. To this end, the concentration of ferrocene in the precursor was fixed in 2,0 wt %, while the concentration of triphenylphosphine (Ph3P) was varied from 0,15 to 0,65 wt %. Scanning and transmission elect
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 25/08/2011
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2. Estudo de um sistema clÃssico de dipolos magnÃticos carregados em estruturas de bicamadas. / Study of a classical bilayer system of charged magnetic dipoles
Estudamos as estruturas e as propriedades dinÃmicas de um cristal clÃssico bidimensional (2D) em bicamadas de partÃculas dipolares magnÃticas carregadas em um arranjo no qual os dipolos sÃo perpendiculares Ãs camadas e com mesma densidade de partÃculas em cada camada. A energia do sistema à devido à interaÃÃo carga - carga (interaÃÃo coulom- bia
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 05/08/2010
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3. Estudo de parâmetros espectroscópicos de íons de Nd3+ no sistema vítreo SNAB (SiO2 Na2CO3 Al2O3 B2O3) nanoestruturado com nanocristais de CdS
In this work, experimental evidences have been observed for energy transfer from CdS nanocrystals, synthesized by the fusion method, to Nd3+ ions embedded in vitreous substrates (SNAB: SiO2 Na2O Al2O3 B2O3). These dot samples doped with neodymium have been investigated by combined optical absorption (OA), photoluminescence (PL), and time-resolved photolumine
Publicado em: 2010
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4. PROPRIEDADES VIBRACIONAIS E DIELÉTRICAS DA MULITA Bi2Mn4O10 / VIBRATIONAL PROPERTIES AND DIELECTRIC OF MULITA Bi2Mn4O10
In this work we investigated the vibrational properties of ceramics Bi2Mn4O10 (BMO) at room temperature by the Raman and Infrared spectroscopies, the phonons were classified by FG matrix method of Wilson. The dielectric properties of the material, in turn, were studied using the impedance spectroscopy in a range of 22 C to 275 C. Furthermore, static atomisti
Publicado em: 2010
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5. Efeitos de campo cristalino e rattling modes em skutterudites / Crystal field and rattling mode effects in skutterudites
This thesis addresses the general problem of crystall field effects and rattling modes in skut- terudite compounds. It employs, predominantly, the electron spin resonance technique (ESR or EPR, in the classical literature) aiming to probe the local point symmetry of the electronic states associated to the rare earth ions and the inohomogenities implied by th
Publicado em: 2010
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6. Estudo da interação elétron-fônon em nanotubos de carbono por Espectroscopia Raman Ressonante
In this work, we have used resonance Raman spectroscopy to the study of carbon nanotubes. We reviewed the literature concerning their structural, electronic and vibrational properties, emphasizing the role of many-body effects, particularly the electron-phonon interaction, on the latter two properties. We also reviewed how Raman spectroscopy can be applied t
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 01/09/2009
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7. Estudo das transiÃÃes de fase do RbBi0,31 3Nd0,02 W8/3O9, submetido a variaÃÃes de pressÃo hidrostÃtica e temperatura. / Studies of phase transitions of RbBi0,313Nd0,02W8/3O9 submit variation of hydrostatic pressure en temperature
Tungsten bronzes has attracted great attention owing to it is interesting physical properties. Hexagonal tungsten of the form AxWO3 (with A = K, Rb, Cs), are well know superconductors. The RbBi1/3W8/3O9 (RBW) material, belongs to the valence balanced hexagonal tungsten materials with ABxW3-xO9 stoichiometry (with A = Cs, K, Rb, Tl, and B = Bi, Nd, Ta, Zr, Sc
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 16/02/2009
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8. Nonlocal effects on the thermal behavior of non-crystalline solids
We argue that nonlocal effects represented by fractionary terms in the kinetic energy can be relevant to achieve a satisfactory phenomenological description of the thermal behavior of the specific heat of non-crystalline solids at very low temperature. We propose a simple model formed by the direct sum of two Hamiltonians, one of which is obtained by incorpo
Brazilian Journal of Physics. Publicado em: 2009-08
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9. Estudo do acoplamento spin-órbita de multipartículas confinadas em pontos quânticos semicondutores
Spin-orbit (SO) coupling provides a way for orbital degrees of freedom to influence spin states. As a result the spin dynamics is affected, thus making spin qubit (quantum version of bit, basic unit of information in the computational language) operations more complex. Furthermore, spin-orbit coupling leads to spin decoherence and relaxation due to phonons,
Publicado em: 2009
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10. Filtros acústicos em cristais fonônicos
In this work, we have studied the acoustic phonon wave propagation within the periodic and quasiperiodic superlattices of Fibonacci type. These structures are formed by phononic crystals, whose periodicity allows the raise of regions known as stop bands, which prevent the phonon propagation throughout the structure for specific frequency values. This p
Publicado em: 2009
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11. Phonon multiplexing through 1D chains
Recently, phonon propagation through atomic structures has become a relevant study issue. The most important applications arise in the thermal field, since phonons can carry thermal and acoustic energy. It is expected that technological advances will make possible the engineering of thermal paths according to convenience. A simple phonon multiplexer was anal
Brazilian Journal of Physics. Publicado em: 2008-12
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12. Controle e interação de fonons e fotons em fibras opticas de cristal fotonico / Control and interaction of phonons and photons in photonic crystal fibers
Techniques that may allow control and tight confinement of photons and phonons in photonic crystal fibers (PCFs) are investigated in this thesis. By means of robust numerical methods to solve Maxwell equations, a new kind of PCF with a tubular core is proposed. Simulations and experimental results show that such structure is able to confine light tighly insi
Publicado em: 2008