The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements ...The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements are carried out with an alternating current at a frequency of 1 kHz using the measuring bridge E-20. Measurements are carried out at temperature range 300 - 450 K, irradiated at doses of 50, 100 and 150 kGy. It is revealed that in all irradiated samples with increasing volumetric filler content increase the dielectric characteristics of composites PE + x vol%. TlGaSe2. Temperature variation of the dielectric parameters, after gamma irradiation are the result of occurring in the electron-ion and polarization at the interface of the matrix polymer with filler of TlGaSe2.展开更多
Two different morphologies of ZnO（lotus-shaped, rod-shaped） and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy（SEM） a...Two different morphologies of ZnO（lotus-shaped, rod-shaped） and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. Fourier transform infrared spectroscopy（FT-IR）, thermal gravimetry（TG）, and X-ray diffraction（XRD） were also used to characterize the chemical structures and phase composites of ZnO and ZnO/PVDF composite materials. Breakdown voltage, dielectric constant and dielectric loss of ZnO/PVDF composite materials were also tested. Microstructure analysis showed that ZnO nanoparticles dispersed uniformly in the matrix. And the dielectric constant expresses a significantly improvement while the dielectric loss and breakdown voltage expresses no significant change. Moreover, dielectric constant keeps an improvement tendency with increasing content of ZnO.展开更多
Composite materials, by nature, are universally dielectric. The distribution of the phases, including voids and cracks, has a major influence on the dielectric properties of the composite materials. The dielectric rel...Composite materials, by nature, are universally dielectric. The distribution of the phases, including voids and cracks, has a major influence on the dielectric properties of the composite materials. The dielectric relaxation behavior measured by Broadband Dielectric Spectroscopy (BbDS) is often caused by interfacial polarization, which is known as Maxwell-Wagner-Sillars polarization that develops because of the heterogeneity of the composite materials. A prominent mechanism in the low frequency range is driven by charge accumulation at the interphases between different constituent phases. In our previous work, we observed in-situ changes in dielectric behavior during static tensile testing, and also studied the effects of applied mechanical and ambient environments on composite material damage states based on the evaluation of dielectric spectral analysis parameters. In the present work, a two dimensional conformal computational model was developed using a COMSOL™multi-physics module to interpret the effective dielectric behavior of the resulting composite as a function of applied frequency spectra, especially the effects of volume fraction, the distribution of the defects inside of the material volume, and the influence of the permittivity and Ohmic conductivity of the host materials and defects.展开更多
Natural rubber based composites containing different carbon nanofillers (fullerenes, carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)) at different concentrations have been prepared. Their dielectric properti...Natural rubber based composites containing different carbon nanofillers (fullerenes, carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)) at different concentrations have been prepared. Their dielectric properties (dielectric permittivity, dielectric loss) have been studied in the 1 - 12 GHz frequency range. Some factors (electromagnetic field frequency, fillers concentration, fillers intrinsic structure) influencing the dielectric behavior of the composites have been investigated. The dielectric properties of the developed natural rubber composites containing conductive fillers (fullerenes, CNTs, GNPs) indicate that these composites can be used as broadband microwave absorbing materials.展开更多
In this work, the polytetrafluoroethylene (PTFE)-based composite substrates were manufactured by mixing, calendering, hot-pressing sintering. The composition of all the samples was PTFE, SiO2 and chopped E-glass fiber...In this work, the polytetrafluoroethylene (PTFE)-based composite substrates were manufactured by mixing, calendering, hot-pressing sintering. The composition of all the samples was PTFE, SiO2 and chopped E-glass fibers. The effects of content of E-glass fibers on the properties of the SiO2 filled PTFE composites were investigated, including density, water absorption, dielectric properties (εr, tanδ), coefficient of thermal expansion (CTE) and temperature coefficient of dielectric constant (τε). The compositions of inorganic materials mixture are (62 ? x) % SiO2 + x % E-glass fiber (x: mass ratio to composites, x = 0, 1, 1.5, 2, 2.5, 3). The results show that as the content of E-glass fibers is 2.5 wt.%, this composite obtains optimal properties, including excellent dielectric properties (εr^2.9123, tanδ~0.0011), acceptable water absorption of 0.075%, temperature coefficient of dielectric constant of 10 ppm/?C and coefficient of thermal expansion of 15.87 ppm/?C.展开更多
文摘The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements are carried out with an alternating current at a frequency of 1 kHz using the measuring bridge E-20. Measurements are carried out at temperature range 300 - 450 K, irradiated at doses of 50, 100 and 150 kGy. It is revealed that in all irradiated samples with increasing volumetric filler content increase the dielectric characteristics of composites PE + x vol%. TlGaSe2. Temperature variation of the dielectric parameters, after gamma irradiation are the result of occurring in the electron-ion and polarization at the interface of the matrix polymer with filler of TlGaSe2.
基金Funded by the National Natural Science Foundation of China(51677045)the Natural Science Foundation of Heilongjiang Province of China(E201224)
文摘Two different morphologies of ZnO（lotus-shaped, rod-shaped） and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. Fourier transform infrared spectroscopy（FT-IR）, thermal gravimetry（TG）, and X-ray diffraction（XRD） were also used to characterize the chemical structures and phase composites of ZnO and ZnO/PVDF composite materials. Breakdown voltage, dielectric constant and dielectric loss of ZnO/PVDF composite materials were also tested. Microstructure analysis showed that ZnO nanoparticles dispersed uniformly in the matrix. And the dielectric constant expresses a significantly improvement while the dielectric loss and breakdown voltage expresses no significant change. Moreover, dielectric constant keeps an improvement tendency with increasing content of ZnO.
文摘Composite materials, by nature, are universally dielectric. The distribution of the phases, including voids and cracks, has a major influence on the dielectric properties of the composite materials. The dielectric relaxation behavior measured by Broadband Dielectric Spectroscopy (BbDS) is often caused by interfacial polarization, which is known as Maxwell-Wagner-Sillars polarization that develops because of the heterogeneity of the composite materials. A prominent mechanism in the low frequency range is driven by charge accumulation at the interphases between different constituent phases. In our previous work, we observed in-situ changes in dielectric behavior during static tensile testing, and also studied the effects of applied mechanical and ambient environments on composite material damage states based on the evaluation of dielectric spectral analysis parameters. In the present work, a two dimensional conformal computational model was developed using a COMSOL™multi-physics module to interpret the effective dielectric behavior of the resulting composite as a function of applied frequency spectra, especially the effects of volume fraction, the distribution of the defects inside of the material volume, and the influence of the permittivity and Ohmic conductivity of the host materials and defects.
文摘Natural rubber based composites containing different carbon nanofillers (fullerenes, carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)) at different concentrations have been prepared. Their dielectric properties (dielectric permittivity, dielectric loss) have been studied in the 1 - 12 GHz frequency range. Some factors (electromagnetic field frequency, fillers concentration, fillers intrinsic structure) influencing the dielectric behavior of the composites have been investigated. The dielectric properties of the developed natural rubber composites containing conductive fillers (fullerenes, CNTs, GNPs) indicate that these composites can be used as broadband microwave absorbing materials.
文摘In this work, the polytetrafluoroethylene (PTFE)-based composite substrates were manufactured by mixing, calendering, hot-pressing sintering. The composition of all the samples was PTFE, SiO2 and chopped E-glass fibers. The effects of content of E-glass fibers on the properties of the SiO2 filled PTFE composites were investigated, including density, water absorption, dielectric properties (εr, tanδ), coefficient of thermal expansion (CTE) and temperature coefficient of dielectric constant (τε). The compositions of inorganic materials mixture are (62 ? x) % SiO2 + x % E-glass fiber (x: mass ratio to composites, x = 0, 1, 1.5, 2, 2.5, 3). The results show that as the content of E-glass fibers is 2.5 wt.%, this composite obtains optimal properties, including excellent dielectric properties (εr^2.9123, tanδ~0.0011), acceptable water absorption of 0.075%, temperature coefficient of dielectric constant of 10 ppm/?C and coefficient of thermal expansion of 15.87 ppm/?C.
