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Gradiental State in Polymer Nanocomposites

#G-2000


Development of Gradiental State in Polymer Nanocomposites and Creation of Sensors of New Generation with Desirable Gradient of Electrical and Magnetic Properties

Tech Area / Field

  • MAN-MAT/Engineering Materials/Manufacturing Technology
  • MAT-COM/Composites/Materials

Status
3 Approved without Funding

Registration date
17.02.2012

Leading Institute
Institute of Cybernetics, Georgia, Tbilisi

Supporting institutes

  • Tbilisi State University / Institute of Physics (Ge), Georgia, Tbilisi

Collaborators

  • University of Alacant, Spain, Alacant\nUniversidade de Coimbra, Portugal, Coimbra

Project summary

Investigations of the electro-physical properties of electrical conducting gradiently oriented polymer composites (GOPC) filled with carbon black, graphite and metal powders will be realized.
The project foresees the production of thin polymer films, the specific electrical volumetric conductance, magnetic and acoustic properties of which are depended on the film coordinates. The shape of films, temperature, direction of stretching and stretching rate effectively influence on the anisotropy of properties.
At using of combination of geometry, directions and rate of stretching it is possible to obtain the films, which mechanical, thermal, electrical, magnetic and acoustic properties will have desired values in dependence on the film coordinates.
The project foresees also the investigation of local densities of the films by ultrasound methods. Whereas the density of separate local regions of gradiently oriented films differs one from another and depends on the film coordinates, the rate of ultrasound will be respectively dependent on these ones. The changes of ultrasound rate will be dependent also on such factors as filler particles sizes and distribution of ones in the polymer matrix, environment temperature, phase transitions, etc. The irradiation of films will be conducted in rectangular directions to film plane and the intensity of sound passing through the film will be fixed in separate region of the film by detectors after passing of sound. Storage of signals obtained after detecting and processing them by means of computer will create the “picture” of distribution of local densities in the gradiently oriented polymer composite film.
Ferromagnetic fillers in the polymer composites give the determined magnetic and electrical properties to composite material. The decreasing of fillers particles sizes down to nano-sizes leads to decreasing of magnetic permeability and increasing of coercitive force. The particle becomes mono-domain (superparamagnetic state). The nano-particles attract each other and unite, single domains parameters change and, therefore, the formation and distribution in the polymer matrix are a very useful technological objective. The researches conducted by using of ultrasound in the films with gradient of density is very perspective development.
In the nanocomposite films the magnetoresistive effect is very sensitive to very little changes of geometry of gradiently oriented film. Therefore, the using of acoustic pulse echo method will allow us to obtain very useful information on the magnetoresistive effects, which is perspective for using of investigated materials in the microelectronics.
In the researches we will widely use the nuclear spin echo and electron paramagnetic resonance (EPR) methods, by means of which it will be measured spectra and the relaxation times and other parameters allowing one to investigate the magnetic and electrical structure of gradiently oriented polymer materials. Moreover, it can be obtained useful information on local magnetic parameters in the anisotropic polymer films filled with ferromagnetic fillers by spin echo methods.
The investigations mentioned above will be the basis for creation of sensors of a new generation based on gradiently oriented polymeric nanocomposite films using metallic and ferromagnetic nanopowder fillers for precision measuring of mechanical deformations and pressures, temperature, electrical, magnetic and electromagnetic fields, mass loading, etc, sensing of which will be conducted by means of variation of sensors local electrical resistance or magnetic and acoustic parameters.
Besides it, they could be used in sensors for the precision control of the concentration of ecologically important gases in atmosphere, such as hydrogen, oxygen and carbon oxides.
The application of gradiently oriented polymers containing above mentioned fillers for different type sensors is foreseen in the project, in particular in acoustic and resistance sensors.
As it is known at the beginning stage of fire and pyrolysis along with organic compounds there always observed the exit of carbon oxide (CO) and hydrogen (H2) gases. For their timely and selectively recording it is necessary to have simple for manufacturing and sufficiently fast sensors.
The project foresees to create new high-sensitive sensors operating by the following principles:
1. Change of conductivity at absorption of investigated gas molecules when the polymeric substrate is coated by a layer of nanoparticles (Pd, Pt, etc.).
2. The change of natural frequency and quality of some high-quality acoustic resonators when they are coated by nanocrystalline transition metal powders or layers, and GOPC films at gas absorption.
For this aim we developed original acoustic resonance spectrometers and devices where commercial quartz resonators could be used, thereby simplifying their exploitation.
We carried out previous experiments on the effectiveness of hydrogen absorption with Ni and Pt nanoparticle powders and on fabrication of quartz resonators with optimal parameters.
In the present project we propose to use also new method of obtaining high-quality acoustic resonances using recently developed by our group method of inductive excitation of magnetoacoustic resonances and domain-acoustic echo in magnetostrictive materials on basis of conventional NMR spectrometer. The high sensitivity of method is caused by the contactless nature of excitation of the high-quality magnetostrictive resonators.
For this aim we could use phase-coherent detection scheme of pulsed NMR spectrometers to accumulate weak signals. We propose to test new magnetostrictive materials with increased quality such as yttrium iron garnet with quality factor on order of value better than one of quartz. For the memorization of sensor signals it could be used stimulated domain-acoustic echo signals in magnetostrictive materials.
Gradiently oriented polymer nanocomposite films will be developed with fillers providing optimal selectivity and sensitivity of acoustic sensors. On this basis it could be created sensors combining the high selectivity with multifunctionality.


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