Page 9 - ICIFMS
P. 9

201-002
                  Mechanical spectroscopy for the investigation of materials for energy applications
                  Paolone, A.(1); Palu mbo, O.(1); Trequattrini, F.(2);
                  (1) CNR-ISC; (2) S;
                  Presenter: Annalisa Paolone (CNR-ISC)
                  Keyword: mechanical spectroscopy, materials for energy applications, tension modulus,
                  local dynamics
                  Abstract:
                  Storage and transformation of energy is one of the priorities for the future. The basis for
                  improvements in this field is the synthesis and characterization of new materials with
                  better performances in energy devices. In order to achieve optimized applications, a deep
                  knowledge of the basic physical and chemical properties of these compounds is needed.
                  In  this  framework,  we  conducted  an  investigation  of  many  materials  with  potential
                  applications  in  the  field  of  energy  storage  and  conversion  by  means  of  mechanical
                  spectroscopy. Our investigations exploited the full potential of mechanical spectroscopy:
                  in  fact,  both  the  real  and  the  imaginary  part  of  mechanical  modulus  can  give  useful
                  information about applicative materials. Indeed, on one side, in applications there a need
                  of optimized mechanical properties of materials; for example, we measured the tension
                  modulus of polymeric membranes useful as polymeric electrolyte membranes of fuel cells
                  and its evolution with the addition of inorganic fillers. Moreover, both  the shear and
                  tension  modulus  of  cellulose  based  membranes,  intended  as  water  compatible,  gel
                  electrolytes, are reported. Finally, we investigated the changes induced by a hot pressing
                  process of the tension modulus and of the electrolyte uptake of electrospun polymeric
                  membranes  used  as  separators  in  lithium  batteries.  On  the  other  side,  mechanical
                  spectroscopy can provide useful parameters of the local motion of atoms and defects or
                  of the occurrence of phase transitions. In the field of electrodes  materials for lithium
                  batteries,  LiMn1.5Ni0.5O4  was  investigated  by  mechanical  spectroscopy  in  order  to
                  study the manganese dynamics. An intense thermally activated peak, detectable only in
                  off-stoichiometric samples, was attributed to a polaronic conduction due to an electron
                  transfer from Mn3+ to a Mn4+, and the consequent motion of the Jahn–Teller lattice
                  distortion. In order to have a good fit of the experimental data, the Jonscher model for
                  ionic dynamics was adopted for the first time in this spinel structure. A value of about 0.3
                  eV for the energy barrier of the polaronic conduction was obtained. Moreover, in the last
                  years  we  investigated  ionic  liquids  (ILs)  by  means  of  mechanical  spectroscopy.  ILs
                  present peculiar physical and chemical properties: an extremely low vapor pressure, a
                  high ionic conductivity, a high thermal, chemical and electrochemical stability, a high
                  thermal capacity and a good solvent capacity. Due to these peculiarities, ILs have been
                  proposed for a large variety of applications in chemistry and physics, such as electrolytes
                  for  electrochemical  devices,  lubricants,  ingredients  for  pharmaceuticals  and  heat
                  exchangers.  By  modifying  the  method  of  measurement  of  a  Dynamical  Mechanical
                  Analyzer, we could measure relaxation processes occurring in the liquid phase, due to the
                  internal  movements  of  the  composing  ions.  Moreover,  one  can  easily  detect  phase
                  transitions  towards  solid  phases.  Due  to  the  occurrence  of  vitrification  at  low
                  temperatures in most ILs, proper theoretical models for the relaxation peaks should be
                  considered. A survey of the results obtained in this field will be presented. REFERENCES






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