Development of a microwave calorimeter for simultaneous thermal analysis, infrared spectroscopy and dielectric measurements

Nesbitt, A.; Navabpour, Parnia; Degamber, B.; Nightingale, C.; Mann, Tim; Fernando, Gerard Franklyn; Day, Richard

doi:10.1088/0957-0233/15/11/018

Cited by 35 publications

(31 citation statements)

References 41 publications

(108 reference statements)

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“…DSC results confirmed that the composite panels fabricated using this profile were fully cured. Determination of the cure cycle for microwave processing was based on the dielectric properties of the neat resin, as they were measured according to the cavity perturbation technique [30]. Fig.…”

Section: Resultsmentioning

confidence: 99%

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

Papargyris

Day

Nesbitt

et al. 2008

Composites Science and Technology

132

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2008) "Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating". Composites Science and Technology,, [1854][1855][1856][1857][1858][1859][1860][1861] Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating AbstractMicrowave processing holds great potential for improving current composite manufacturing techniques, substantially reducing cure cycle times, energy requirements and operational costs. In this paper, microwave heating was incorporated into the resin transfer moulding technique. Through the use of microwave heating, a 50% cure cycle time reduction was achieved. The mechanical and physical properties of the produced carbon fibre/epoxy composites were compared to those manufactured by conventional resin transfer moulding. Mechanical testing showed similar values of flexural moduli and flexural strength for the two types of composites after normalisation of the corresponding data to a common fibre volume fraction. A 9% increase of the interlaminar shear strength (ILSS) was observed for the microwave cured composites. This enhancement in ILSS is attributed to a lowering of resin viscosity in the initial stage of the curing process, which was also confirmed via scanning electron microscopy by means of improved fibre wetting and less fibre pull-out. Furthermore, both types of composites yielded minimal void content ( properties of the produced carbon fibre/epoxy composites were compared to those manufactured by conventional resin transfer moulding. Mechanical testing showed similar values of flexural moduli and flexural strength for the two types of composites after normalisation of the corresponding data to a common fibre volume fraction. A 9% increase of the interlaminar shear strength (ILSS) was observed for the microwave cured composites. This enhancement in ILSS is attributed to a lowering of resin viscosity in the initial stage of the curing process, which was also confirmed via scanning electron microscopy by means of improved fibre wetting and less fibre pull-out. Furthermore, both types of composites yielded minimal void content (<2%). Dynamic mechanical thermal analysis revealed comparable glass transition temperatures for composites produced by both methods. A 15 °C shift in the position of the ȕ-transition peak was observed between thermally and microwave cured composites, suggesting an alteration in the cross-linking path followed.

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Section: Resultsmentioning

confidence: 99%

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

Papargyris

Day

Nesbitt

et al. 2008

Composites Science and Technology

132

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“…Microwave heating of the sample was achieved using a smaller cavity (radius 58 mm; height 77 mm) increasing the power supplied to the cavity in between measurements using an amplifier driven by the output from the network analyser so as to achieve the required temperature program [12]. The sample holder was modified so that conventional heating could be applied using a hot air jacket around the specimen.…”

Section: Methodsmentioning

confidence: 99%

Hysteresis in the β–α phase transition in silver iodide

Binner

Dimitrakis

Price

et al. 2006

J Therm Anal Calorim

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IntroductionSilver iodide can exist in three crystal polymorphs at atmospheric pressure [1]. Below 147°C the b-phase is stable; this has a wurtzite structure with the iodide ions arranged in a hexagonal close packed structure and with the silver ions occupying a sublattice of interstitial tetrahedral sites. Above 147°C silver iodide undergoes a crystalline transition to the high temperature a-phase, which has a body centred cubic arrangement of iodine ions with the silver ions distributed over a sublattice of interstitial sites whose number exceeds the occupancy of silver ions. This phase is stable up to the melting temperature of 555°C. Also present below 147°C is the metastable g-phase which differs from the b-phase in that it has a zinc blende structure with the iodide ions occupying a cubic close packed lattice. This can be viewed as a defect b-phase structure in which the iodide ions are layered ABABAB rather than ABCABC. Migration of Ag + though the disordered cationic lattice gives rise to exceptionally high ionic conductivity of the a-AgI phase [2]. The ordering of Ag + has been studied using computer simulations and it is the tendency of the cations to condense into a locally monoclinic arrangement which is unstable relative to the hexagonal (wurtzite) structure which is proposed as the driving force for the a-b phase transition [3].Previous investigators have reported the heat capacity of silver iodide using conventional and AC calorimetry [4,5]. These measurements have been carried out in heating only whereas Hanaya et al. have reported DSC studies on heating and cooling of the stabilisation of a-AgI by incorporating AgI inside porous silica [6]. In this work the nucleation of the low temperature phase is claimed to be inhibited by the reduction in AgI particle size. For bulk AgI claims have been made that the b-a phase transition can be made to occur around 100°C when the specimen is heated by microwave radiation rather than be conventional heating [7]. In this particular case, multi-phonon coupling between the electromagnetic field and vibrational motions within the AgI crystal are conjectured to stabilise the high temperature form in the same way that mechanical stress by reduction in particle size might also achieve the same effect. An alternative mechanism is the so-called 'ponderomotive effect' whereby microwave-excited ionic currents become locally rectified at interfaces (such as grain boundaries) so as to promote mass transport [8]. In the case of AgI there is no bulk diffusion of material during its structural transformation but it is not unreasonable to propose that this process might promote the formation of a-AgI.This work reports studies on the silver iodide a-b phase transition by conventional and modulated-temperature calorimetry. We also report dielectric property measurements under conventional and microwave heating. ExperimentalThe silver iodide powder (99.999%, Acros Organics) used for these studies was made into pellets with a density of 4.9±0.3 g cm -3 , i.e. 83% of theoretical d...

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“…Modern microwave-heating technologies still rely solely on the room-temperature examination of the structure, microstructure, and properties of materials before and after microwave heating. The few previous attempts to follow in situ the evolution of materials during microwave heating [8][9][10][11][12][13] were part of the sustained effort to clarify the occurrence and nature of nonthermal contributions to mass transport [i.e., solely due to the application of high-frequency electromagnetic (EM) fields]. 7,[14][15][16] The enhancement of atomic diffusion under EM field application is known as the "microwave effect."…”

Section: Introductionmentioning

confidence: 99%

In situ synchrotron radiation monitoring of phase transitions during microwave heating of Al–Cu–Fe alloys

et al. 2008

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The effect of rapid microwave heating has so far been evaluated mainly by comparing the state of materials before and after microwave exposure. Yet, further progress critically depends on the ability to follow the evolution of materials during ultrafast heating in real time. We describe the first in situ time-resolved monitoring of solid-state phase transitions during microwave heating of metallic powders using wide-angle synchrotron radiation diffraction. Single-phase Al-Cu-Fe quasicrystal powders were obtained by microwave heating of nanocrystalline alloy precursors at 650°C in <20 s.

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Development of a microwave calorimeter for simultaneous thermal analysis, infrared spectroscopy and dielectric measurements

Cited by 35 publications

References 41 publications

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

Hysteresis in the β–α phase transition in silver iodide

In situ synchrotron radiation monitoring of phase transitions during microwave heating of Al–Cu–Fe alloys

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