The influence of interfaces and water uptake on the dielectric response of epoxy-cubic boron nitride composites (original) (raw)
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IET Nanodielectrics, 2018
The epoxy resin was filled with nano-BN, surface treated, and untreated nano-SiO 2. Measurements of dielectric spectroscopy cover the range of frequency from 10 −2 to 10 5 Hz and will relate to the hydration of samples. It was observed from the results that permittivity of pure epoxy was strongly affected by the water absorptions and a bit of temperature. Then it will allow us to extract the influence of water absorption on dielectric properties and proposed a relatively reliable method by using Monte-Carlo simulation to estimate the average thickness of water shell or related relaxation peak of epoxy nanocomposites with spherical particles. At the end, the authors experimentally demonstrated the existence of two layer structure of water shell and concluded that surface treatment is able to reduce the water uptake, however, no obvious impact on modifying its effects on dielectric properties due to the limitation of thickness of tightly bonded layer. The 'hydrophobic' performance of BN nanocomposites is much better than silica ones, especially the no formation of water shell around the particles, and may be more suitable for application under environment with humidity.
Dielectric Properties of Filled Composites of Epoxy Resin
Journal of Basic & Applied Sciences, 2014
The addition of fillers in composite of epoxies, improves the dielectric response of the epoxies. The dielectric properties of unfilled and filled composites of epoxy resins have been studied as a function of thickness in the frequency range 10-1 Hz to 10 5 Hz at room temperature. The response of the unfilled samples shows that the composites behave as an insulator for all thickness. In filled composites at small thickness (0.32 mm) the response shows a loss peak in low frequency regime. The peak is broader than the Debye loss peak which is obscured by the dc conductance. At frequencies greater than p the response shows a well defined power law behaviour after the subtraction of C. Similar behaviour has been observed at different thickness.
Influence of water absorption on dielectric properties of epoxy SiO2 and BN nanocomposites
2015 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), 2015
It is well known that epoxy resins would absorb water when left in ambient conditions. A number of hydrophilic nano-particles also absorb water, like nano-SiO 2 , because of their surface hydroxyl groups resulting from the manufacture process. The water uptake will affect dielectric properties of the nanocomposites. However there was conflict report on the amount of water uptake by the unfilled and nano-filled epoxy resin systems. In the present paper, the epoxy resin was filled with surface treated, as well as, untreated nano-SiO 2 and nano-BN. The relative humidity is controlled by the desiccator (dry samples), de-ionized(100% RH) water and climate chamber. The dielectric properties will relate to the hydration of samples. Measurements of dielectric spectroscopy cover the range of frequency from 10-2-10 5 Hz. Dielectric spectroscopy also showed different capacitance and permittivity at low frequencies, as well as tanδ, which depend on the hydration and temperature. It was observed from the results that permittivity, capacitance and tanδ of pure epoxy were strongly affected by the water absorptions. All these results are used to analyse how different variables, like surface treatment, filler type and filler loading concentration, can influence the water absorption. It will allow us to extract the influence of water absorption on dielectric properties of epoxy nanocomposites.
Influence of filler loading on dielectric properties of epoxy-ZnO nanocomposites
IEEE Transactions on Dielectrics and Electrical Insulation, 2009
Experimental investigations into the dielectric properties of epoxy-ZnO nanocomposites at different filler loadings reveal few unique behaviors (at certain filler loadings) and also advantageous characteristics in contrast to the properties obtained for the corresponding microcomposites. Results demonstrate that in nanocomposites, it is possible to achieve lower values of permittivity and tanδ with respect to unfilled epoxy over a wide frequency range. Analysis of the results attributes this interesting observation to the interaction dynamics between the epoxy chains and the ZnO nanoparticles at the interfacial area. The dc volume resistivities and ac dielectric strengths of nanocomposites were also experimentally determined in the present study and the obtained characteristics are found to be different as compared to the results obtained for microcomposites. The volume fraction and nature of the interfaces in the bulk of the composites seem to influence this difference in the examined dielectric properties of the nanocomposites.
On the Dielectric Properties of Epoxy Filled with Glass Microspheres and Boron Nitride
2012
With rapid development of the electronic information industry, better properties are required for substrate and packaging materials, such as high thermal conductivity, low coefficients of thermal expansion (CTE), low dielectric constant and high thermal stability. Polymers, such as polyethylene, epoxy and polyamide are ordinarily used as these materials due to their high resistivity, low dielectric constant and excellent processability. However, these polymers suffer from disadvantages such as low thermal conductivity, high CTE, low stiffness and strength. To offset these deficiencies, adding inorganic particles to a polymer is a versatile method. This method synergistically integrates the advantages of polymers and inorganic fillers; and thus, the thermal, electrical and mechanical properties of the composites can be improved by properly selecting the fillers, their shape, size and concentration [1]. The dielectric properties including the dielectric constant (D k) play an important role in the proper functioning of the electronic circuit board substrates. As the working frequency of electronic appliances increases, signal intensity losses become more sensitive. Therefore, small D k is demanded for substrates in high frequency ABSTRACT Most semiconductor devices are packaged in epoxy polymer composites to reduce thermal expansion-coefficient. However high thermal conductivity as well as low dielectric fillers are required for high heat output devices in near future for electronic packaging and printed circuit boards as hardened neat epoxy in spite of its good mechanical strength, often cannot satisfy this demand due to its low thermal conductivity. In view of this, in the present work, solid glass microsphere (SGM) with Boron Nitride (BN) filled hybrid epoxy composites, with BN content ranging from 0 to 10 vol% in epoxy reinforced with 20 vol% of SGM have been prepared with an objective to study the effect of BN on the dielectric as well as thermal properties of the composites. Dielectric constant measurements are made for these composites using a HIOKI-3532-50 Hi Tester Elsier Analyzer with an applied Ac voltage of 500mv in the frequency range of 1 kHz to 1 MHz. In our previous study it is also noticed that the thermal conductivity of the composites decreased with increase in SGM content which is not desirable. Thus, in order to obtain relatively high thermal conductivity and low dielectric constant at the same time, fillers like AlN or BN which have high thermal conductivity can be added to the polymer in addition to the SGMs.
2009
This paper looks at the dierences in dielectric response between epoxy resin com- posites with conventional and nanoscale alumina filler. Host material, namely bisphenol-A epoxy resin, is the same for all samples. Preparation of the samples is described in detail. Both filler types are treated in similar fashion to ensure comparability of the results. An even distribution of the alumina in case of the nanoscale filler was validated by means of transmis- sion electron microscopy. It is shown by means of dielectric spectroscopy how the particle size and preparation influence the material properties. Measurements were performed in a broad frequency range between 0.01 and 10 MHz, for temperatures between -20C and the glass transition temperature of the host material close to 120C. Possible explanations for the witnessed behavior are presented and the contributing factors discussed.
A Study on the Dielectric Properties of SGM-Filled Epoxy Composites
2012
Materials used for electronic packaging and printed circuit boards need to have multi- functional properties such as adequate thermal conductivity and controlled dielectric const. Hardened neat epoxy inspite of its good mechanical strength, often cannot satisfy this demand. In view of this, in the present work, Solid glass micro-sphere (SGM) filled Epoxy composites, with filler content ranging from 0 to 20 vol% have been prepared with an objective to modify the dielectric properties of the epoxy. Dielectric constant measurements are made for these composites using a HIOKI- 3532-50 Hi Tester Elsier Analyser with an applied Ac voltage of 500mv in the frequency range of 1kHz to 1 MHz. However in this study it is also noticed that that the thermal conductivity of the composites decreased with increase in SGM content which is not desirable. Thus, inorder to obtain relatively high thermal conductivity and low dielectric constant simultaneously, this paper suggests further addition of some...
Study of low weight % Filler on Dielectric Properties of MWNT-Epoxy Nanocomposites
An attempt is made to study the effect of low weight % Multiwall carbon nanotube (MWCNT) powder on dielectric properties of MWCNT reinforced epoxy composites. For that MWCNT (of different low weight %) reinforced epoxy composite were prepared by dispersing the MWCNT in resin. Samples were prepared by solution casting process and characterized for their dielectric properties such as dielectric constant (ε'), dielectric dissipation factor (tan δ) and AC conductivity (σac). The main objective is the investigation of the dielectric properties of the prepared samples at the low weight % of the filler at different temperatures and frequency. From the two mechanisms of electrical conduction, first the leakage current obtained by the formation of a percolation network in the matrix and the other by tunneling of electrons formed among conductors nearby (tunneling current); here we are getting conduction by the second mechanism. Generally, leakage current makes more contribution to conductivity than tunneling current. Dielectric dissipation factor at 250 Hz frequency is greater than all other frequencies and starts increasing from 60 °C. The peak height of the transition temperature decreases with increasing frequency. This study shows that the addition of a low weight % of MWCNT can modify considerably the electrical behaviour of epoxy nanocomposites without chemical functionalization of filler.
Dielectric characterisation of epoxy nanocomposite with barium titanate fillers
IET Nanodielectrics, 2020
High permittivity materials are currently in use for mitigation of electrical stress in high-voltage apparatus and energy storage systems. In this work, epoxy-based high permittivity nanocomposites with Barium titanate (BaTiO 3) nanofillers are considered, for the purpose of stress mitigation. Uniform dispersion of the fillers in the polymer up to 10% by volume is achieved. Apart from the use of as-received fillers, the effect of using surface-functionalised nanoparticles (with 3glycidoxypropyltrimethoxy-silane) before use is also investigated. The nanocomposite is characterised in terms of its complex permittivity, DC conductivity, short-term AC breakdown strength and space charge accumulation, to gauge its suitability for use in high-voltage insulation. Complex permittivity is measured using broadband dielectric spectroscopy over a broad frequency range of 1 mHz to 1 MHz. DC conductivity is studied from polarisation-depolarisation current measurements. Short-term AC breakdown strength tests are performed at power frequency (50 Hz). Space charge density along the sample thickness is obtained using pulsed electro-acoustic technique. A computational case-study is presented to show the feasibility of using the high permittivity nanocomposite for electric stress control in high-voltage equipment (viz., at mounting flanges of 69 kV bushings).