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PRODID:https://murmitoyen.com/events/vanille/udem/
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UID:69dc02e22ebf1
DTSTAMP:20260412T163858
DTSTART:20170223T103000
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20170223T113000
URL:https://murmitoyen.com/events/vanille/udem/detail/750059-discharges-in-
 liquids-applications-for-nanomaterial-synthesis-ahmad-hamdan-kaust
LOCATION:Université de Montréal - Pavillon Claire-McNicoll\, 2900\, chemi
 n de la Tour\, Montréal\, QC\, Canada\, H3T 1J6
SUMMARY:Discharges in liquids: applications for nanomaterial synthesis - Ah
 mad Hamdan (KAUST)
DESCRIPTION:Discharges in liquids: applications for nanomaterial synthesis 
 Ahmad Hamdan King Abdullah University of Science and Technology (KAUST) Sa
 udi Arabia
\nabstract: 
\nIn this seminar\, our recent experimental work 
 on discharges in dielectric liquids will be presented. Several physical ph
 enomena\, such as pre-breakdown\, discharge ignition\, discharge-channel o
 pening\, and shock wave emission\, occur within the time interval extendin
 g from the application of an electric field to the liquid until its breakd
 own (t < 200 ns). The breakdown is followed by the formation of an oscilla
 ting gas bubble in the gap. This latter was experimentally studied by high
 -speed imaging techniques and by modeling to estimate the pressure in the 
 plasma at t ~0. We demonstrate that each discharge creates simultaneously 
 one impact at the anode and one at the cathode\, and that the diameter of 
 the impact can be controlled by the charge injected. At this stage\, the e
 nergy dissipation due to each physical phenomenon is estimated. In the cas
 e of discharges in liquid heptane with platinum-aluminum electrodes\, we f
 ound that the energy dissipated in the plasma channel is more than 90% of 
 the total injected energy. Note that the energy distribution between the p
 hysical phenomena is very sensitive to the experimental conditions\, such 
 as the electrodes’ nature and liquid’s properties.
\nDischarges in liq
 uids were used for the synthesis of nanomaterial. Depending on the electro
 de nature and liquid composition\, different families of nanomaterial were
  synthesized via electrode erosion and liquid dissociation / polymerizatio
 n. For instance\, using platinum electrodes and heptane liquid\, we succes
 sfully synthesized nanocomposite material: nanoparticles of Pt embedded in
  a matrix of hydrogenated carbon. In the case of discharges in liquid nitr
 ogen with lead (Pb) electrodes\, a new crystallographic phase of 2D-nanost
 ructures has been synthesized.
\nIn order to further increase the efficien
 cy of discharges in liquid\, we developed techniques based on the discharg
 e in bi-phasic media. The first technique is the injection of gaseous bubb
 les in the liquid\, which facilitates the breakdown due to the low density
  of the gas compared to that of the liquid. The second technique is the us
 e of mixture of two dielectric liquids with different dielectric permittiv
 ity. We will show that the control of the interface position of the two li
 quids with respect to the anode tip will improve the discharge characteris
 tics. We will also show\, in particular\, that discharge at the interface 
 of water- hexamethyldisilazane can be applied to the synthesis of hydrogen
 ated SiOC nanoparticles\, with production rate up to 10 mg/minute.
\n 
\n
 Web site of Dr. Hamdan.
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