Effect of gamma irradiation on the density, glass transition temperature and electrical conductivity of lithium borosilicate glasses with alumina addition

In this study, the composites prepared from polyimide (PI) and polyaniline (PANI) were radiated with electron beam (EB) at the radiation doses of 0, 50, 150, 200, and 300 kGy. The electrical conductivity and thermal properties of the radiated composites were determined and compared with those of the composites doped with 6M HCl. The results revealed that the electrical conductivity was enhanced from 3.42 x 10-16 S/cm (untreated polyimide without polyaniline) to 6.97 x 10-5 S/cm when the PI/PANI composite was doped with HCl at 10 phr of PANI; furthermore, the conductivity was increased to 2.16 x 10-4 S/cm for the composite at 10 phr of PANI with radiation dose of 200 kGy. In addition, it was found that the glass transition temperature of the composite was increased with the increase of PANI content for either EB radiation method or protonic acid doping method. It could be noted that the electrical conductivity values of the radiated composites were higher than those of composites doped with HCl at the same PANI content.

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Characterization of Thermo-Electric Interface Material with Carbon Nanotubes

MRS Proceedings ◽

10.1557/proc-1056-hh12-06-ff13-06-gg15-06 ◽

2007 ◽

Vol 1056 ◽

Author(s):

Piyush R Thakre ◽

Yordanos Bisrat ◽

Dimitris C Lagoudas

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotubes ◽

Electrical Conductivity ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Epoxy Matrix ◽

Loss Modulus ◽

Single Wall Carbon Nanotubes ◽

Electrical Percolation

ABSTRACTAn approach has been presented in the current work to fabricate and characterize nanocomposite systems for optimizing electrical and thermal properties without sacrificing mechanical properties. An epoxy matrix based nanocomposite system has been processed with different volume fractions of carbon nanotubes. The purpose was to tailor macroscale properties to meet competing performance requirements in microelectronics industy. The nanofiller consisted of comparatively low cost XD grade carbon nanotubes (XD-CNTs) that are optimized for electrical properties. This system was compared with another system consisting of single wall carbon nanotubes (SW-CNTs) as nano-reinforcements in epoxy matrix. The electrical percolation threshold (about seven orders of magnitude increase in electrical conductivity) measured by dielectric spectroscopy was found to be at lower loading weight fraction of SWCNTs (0.015 weight %) as compared to XD-CNTs (0.0225 weight %). However, the electrical conductivity after percolation was higher for XD-CNTs reinforced epoxy with respect to SW-CNTs filled nanocomposites. The governing mechanisms for this phenomenon were investigated using transmission optical microscope. The enhancement in thermal conductivity, measured using differential scanning calorimetry, was found to be moderate at lower weight loadings corresponding to electrical percolation. However, a 90% improvement in thermal conductivity was observed for 0.3 weight percent of XD-CNTs. Dynamic mechanical analysis was performed to measure the storage and loss modulus along with the glass transition temperature. No significant change in modulus values and glass transition temperature was measured for nanocomposites varied filler contents with respect to neat matrix.

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On Fluidization of Borosilicate Glasses in Intense Radiation Fields

ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management, Volume 1 ◽

10.1115/icem2009-16055 ◽

2009 ◽

Author(s):

Michael Ojovan ◽

Guenter Mo¨bus ◽

Jim Tsai ◽

Stuart Cook ◽

Guang Yang

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Viscous Flow ◽

Electron Irradiation ◽

Amorphous Materials ◽

Flow Behaviour ◽

High Electron ◽

Borosilicate Glasses ◽

Glassy Materials

The viscosity is rate-limiting for many processes in glassy materials such as homogenisation and crystallisation. Changes in the viscous flow behaviour in conditions of long-term irradiation are of particular interest for glassy materials used in nuclear installations as well as for nuclear waste immobilising glasses. We analyse the viscous flow behaviour of oxide amorphous materials in conditions of electron-irradiation using the congruent bond lattice model of oxide materials accounting for the flow-mediating role of broken bonds termed configurons. An explicit equation of viscosity was obtained which is in agreement with experimental data for non-irradiated glasses and shows for irradiated glasses, first, a significant decrease of viscosity, and, second, a stepwise reduction of the activation energy of flow. An equation for glass-transition temperature was derived which shows that irradiated glasses have lower glass transition temperatures. Intensive electron irradiation of glasses causes their fluidisation due to non-thermal bond breaking and can occur below the glass transition temperature. Due to surface tension forces fluidisation of glasses at enough high electron flux densities can result in modification of nano-size volumes and particles such as those experimentally observed under TEM electron beams.

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