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Conductivity in cured epoxy resins containing a biphenyl unit
(Wydawnictwo Politechniki Łódzkiej, 2010) Włodarska, Magdalena; Izdebski, Marek; Bąk, Grzegorz; Mossety-Leszczak, Beata; Galina, Henryk
Conductivity of two epoxy matrices based on the same monomer was compared. The epoxy monomer had symmetric structure and contained the biphenyl group which induced additional phase transitions in the pure material. Two amines responsible for different curing mechanisms were used to prepare the matrices. Wide ohmic regions were observed in both materials but quite high activation energy results in quick drop of conductivity at low temperatures and the materials can be treated as good isolators below 100°C. The obtained results are comparable with traditional epoxy resins.
Curing process and the curing product of a nematic epoxy resin containing ester groups
(Wydawnictwo Politechniki Łódzkiej, 2007) Włodarska, Magdalena; Mossety-Leszczak, Beata; Bąk, Grzegorz; Galina, Henryk
Curing process and the product of curing of one liquid crystalline epoxy monomer with a standard omine were examined. The reactions were monitored by DSC measurement and dielectric spectroscopy. Progress of curing of the examined mixture at different temperatures was shown. Influence of curing conditions on the final product was discussed and compared with other similar systems. DSC thermograms of the curing product were also analysed.
Dielectric and optical properties of liquid crystal 1H6Bi
(Wydawnictwo Politechniki Łódzkiej, 2012) Wojciechowski, Marek; Tykarska, Marzena; Bąk, Grzegorz
Recently synthesized antiferroelectric liquid crystal 1H6Bi shows special optical properties related to change in handedness of the ferroelectric helix. The broadband dielectric measurements of this compound has been carried out, a number of dielectric relaxation modes corresponding to various temperatures and LC phases have been detected. The characteristic parameters of these modes are presented and compared with the optical data.
Dielectric properties of ferrielectric subphase of liquid crystal MHPOPB
(Wydawnictwo Politechniki Łódzkiej, 2013) Wojciechowski, Marek; Tykarska, Marzena; Bąk, Grzegorz
The antiferroelectric liquid crystal with relatively broad temperature range of ferrielectric subphase was chosen for dielectric investigations of this subphase. In the ferrielectric subphase, collective molecular motions were registered as a ferrielectric Goldstone mode. Theory of ferroelectric Goldstone mode was applied to the registered ferrielectric subphase to obtain rotational viscosity.
Dispersive charge transport in hopping systems under open-circuit conditions: computer simulation
(Wydawnictwo Politechniki Łódzkiej, 2012) Bąk, Grzegorz
Applicability of the theories describing the discharge in thin-film insulators under open-circuit conditions for dispersive hopping systems is the subject of this paper. It is shown by means of computer simulation that the drift mobility obtained from application of the theories for such systems is underestimated. The computer simulation was carried out for a thin film system in which the charge transport is dominated by hopping of charge carriers among localized states in a narrow band at the Fermi level. The way of interpretation of the discharge under opencircuit conditions in such systems is suggested. The simulation results have also been applied for interpretation of the open-circuit discharge in thin diamond-like carbon films.
Electric conductivity in epoxy matrix with nanoparticles
(Wydawnictwo Politechniki Łódzkiej, 2012) Włodarska, Magdalena; Partyka, Michał; Bąk, Grzegorz; Mossety-Leszczak, Beata; Galina, Henryk; Florjańczyk, Zbigniew; Łokaj, Krzysztof
This work presents results of DC conductivity measurements obtained for epoxy matrices with different concentration of the nanofiller. In the first step, optimal curing conditions were determined - which turned out to be similar to those established for a plain epoxy matrix. In order to confirm stability of the matrix, measurements of the current-time dependency were made, which clearly show both the chemical and electric stabilization at the given temperature. All the obtained materials appeared to be good insulators with high activation energy. It was observed that the activation energy decreases slightly with increasing concentration of the nanofiller.
Space-charge-limited currents as an indicator of non-uniform charge traps distribution in thin film dielectrics: numerical solutions
(Wydawnictwo Politechniki Łódzkiej, 2012) Bąk, Grzegorz
Space charge limited currents in inhomogeneous thin film insulating systems are studied by means of numerical methods. Calculations for two spatial distribution of traps are presented. The results confirm that the influence of charge traps at the emitter is much stronger than those at the collector. The case of illumination of the emitter is also analyzed. It turns out that it is possible to find the valued of parameter describing the exponential decay of trap distribution at the emitter and the surface trap concentration for the case of illuminated sample. The paper summarizes the data concerning possibility of determination of trap distribution at the emitter in thin film insulators using photo-enhanced space-charge-limited current measurements.