Dielectric behavior of some aromatic polyimide films

Chişcă, Ştefan; Musteata, Valentina-Elena; Sava, Ion; Brumă, Maria

doi:10.1016/j.eurpolymj.2011.01.008

Cited by 137 publications

(91 citation statements)

References 43 publications

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“…As is shown in Figure 5, for all of the specimens, DC conductivity (σ dc ) exhibits a flat frequency plateau at lower frequencies, while AC conductivity, as a frequency-dependent behavior, presents itself at higher frequencies. This may be attributed to a hopping-type conduction at a high frequency range [39]. The general conductivity shows dispersion around the frequency of 10 3 Hz.…”

Section: Electric and Dielectric Properties Of Nickel-cobalt Oxide Namentioning

confidence: 85%

Structure and Physical Properties of NiO/Co3O4 Nanoparticles

Naseri

Dehzangi²,

Kamari

et al. 2016

Metals

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Abstract:The thermal treatment method was employed to prepare nickel-cobalt oxide (NiO/Co 3 O 4 ) nanoparticles. This method was attempted to achieve the higher homogeneity of the final product. Specimens of nickel-cobalt oxide were characterized by various experimental techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). X-ray diffraction results showed that there was no crystallinity in the predecessor, and it still had the amorphous phase. The formations of the crystalline phases of the nickel-cobalt oxide nanoparticles started from 350-500˝C, and the final products had different crystallite sizes ranging from 11-35 nm. Furthermore, the variation of DC conductivity (σ dc ), impedance, tangent loss (tgδ) and dielectric constant (ε 1 ) of the calcined specimens with frequency in the range of 10 2 -10 6 Hz was investigated. σ dc showed a value of 1.9ˆ10´6 S/m, 1.3ˆ10´6 S/m and 1.6ˆ10´6 S/m for the specimens calcined at 350, 400 and 450˝C, respectively. Additionally, a decrease in tgδ values with an increase in temperature was observed. Finally, the formed nanoparticles exhibited ferromagnetic behaviors, which were confirmed by using a vibrating sample magnetometer (VSM).

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Section: Electric and Dielectric Properties Of Nickel-cobalt Oxide Namentioning

confidence: 85%

Structure and Physical Properties of NiO/Co3O4 Nanoparticles

Naseri

Dehzangi²,

Kamari

et al. 2016

Metals

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“…This frequency independent process has been attributed to the removal of polar molecules (like absorbed water) [31]. At even higher temperatures, above 150°C for 7a and 7b and above 100°C for 7c, ε' and ε" increase abruptly, especially at low frequency.…”

Section: Study Of Dielectric Propertiesmentioning

confidence: 97%

High performance bismaleimide resins modified by novel allyl compounds based on polytriazoles

et al. 2012

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New poly(1,2,3-triazole)s functionalized with allyl groups were prepared by the 1,3-cycloaddition reaction (click reaction) of azido-imides to bispropargyl monomers containing allyl groups. The copolymers of 4,4'-bismaleimidodiphenylmethane with allylated polytriazoles were prepared and their properties investigated. Modified bismaleimide resins had excellent processing compared with neat bismaleimides, especially improved olubility and faster thermal polymerization rate. In addition, the new cured systems had good thermal and dielectric properties (dielectric constant at 1 kHz ranged between 3.09 and 3.39, except the polymer with aliphatic segment instead of the imide group that had a higher constant, namely 4.6).

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“…Dielectric relaxation spectroscopy provided information about the storage and dissipation components of the complex permittivity, namely, dielectric constant (ε ) and dielectric loss (ε ) of the hybrid polyimide films in a broad frequency and As reported for other polyimides [34,35] and generally for polymers, dielectric constant, ε , decreases with increasing frequency. The dielectric constant being dependent on the ability of polarizable units to align to the alternating electric field, it decreases with increasing frequency, since the orientation of dipole moments needs longer time than that corresponding to applied frequency.…”

Section: Dielectric Behaviormentioning

confidence: 98%

Insights into the physico-chemical behavior of CoCl2/polyimide hybrid materials

2016

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Hybrid fluorinated polyimide materials have been obtained by incorporation of various quantities of cobalt(II) chloride (CoCl 2 ) into polyimide matrix. Polycondensation reaction of equimolar amounts of 4,4′-diamino-3′3′-dimethyldiphenylmethane and 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride has been carried out to produce in the first stage a polyamidic acid solution in which CoCl 2 × 6H 2 O has been placed. Further thermal treatment of this system led to the corresponding imide structure filled with the halide salt. An exhaustive study was directed to the influence of Co 2+ ions on the modified polyimide behavior as a function of its surroundings. To survey the functional properties of as-obtained Co 2+ -containing polyimide systems, several techniques such as FTIR, UV-vis and broadband dielectric spectroscopy, differential scanning calorimetry, and thermogravimetric and scanning electron microscopy were employed. A special concern was directed to the study of the optical properties induced by the addition of CoCl 2 into polymer solutions and films. The magnetic response of the polyimide was investigated in correlation with the salt quantity embedded in the PI film. The variation of the real and imaginary parts of the hybrid films' dielectric permittivity was registered in a broad frequency and temperature range, from 10 to 10 6 Hz and from −130 to 230°C, respectively.

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Dielectric behavior of some aromatic polyimide films

Cited by 137 publications

References 43 publications

Structure and Physical Properties of NiO/Co3O4 Nanoparticles

Structure and Physical Properties of NiO/Co3O4 Nanoparticles

High performance bismaleimide resins modified by novel allyl compounds based on polytriazoles

Insights into the physico-chemical behavior of CoCl2/polyimide hybrid materials

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