Ahmad Hamdan

Ahmad Hamdan
Université de Montréal | UdeM · Department of Physics

PhD

About

74
Publications
8,398
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
625
Citations

Publications

Publications (74)
Article
Repetitive discharges in dielectric liquid are involved in many technological applications. The relatively poor reproducibility of such discharges, induced by significant modification of experimental conditions (electrode and liquid), hinders the understanding of their fundamental dynamics and optimizing processes. In this paper, we study the elect...
Article
A streamer discharge is a highly reactive and dynamic non-thermal plasma. It has been used in many applications, including environmental remediation, medicine, and material processing. Although the physics of streamer discharges in gaseous media is well understood, its interaction with a solid and liquid dielectric surfaces remains under investigat...
Article
Full-text available
Silicon carbide (SiC) has been widely used in many applications, which require high mechanical endurance or high electrical resistance. It also serves as a basic material for light emitting diodes. Here, we present an in-liquid plasma method to produce SiC nanoparticles. A sustained spark-discharge in a dielectric liquid, which is energized by a na...
Article
Discharge in dielectric liquid is an active field of research involved in many technological applications. Such multiple discharges are often applied during an experiment and that the electrode and liquid are altered by these stochastically behaving discharges. Therefore, it is important to address the variation of discharge characteristics as a fu...
Article
In this study, spark discharges are generated in liquid heptane that is in contact with an immiscible solution of silver nitrate. The results demonstrate that the discharges produced at 22 kV voltage amplitude and 500 ns pulse width change the color of both liquids and lead to the formation of nanoparticles. Most particles collected from heptane ar...
Article
Full-text available
Spark discharge in hydrocarbon liquids is considered a promising method for the synthesis of various nanomaterials, including nanocomposites. In this study, copper–carbon particles were synthesized by generating spark discharges between two Cu electrodes immersed in heptane, cyclohexane, or toluene. The synthesized particles were characterized usin...
Article
Discharges in liquid hydrocarbons produce submicrometric particles with a graphitic shell. In this study, discharges are generated between two Cu electrodes immersed in various liquid hydrocarbons, and the produced particles are characterized by various techniques. The obtained results indicate that the thickness of the particle shell increases wit...
Article
Electrical discharges in liquids are considered an efficient and ecological technique of nanoparticle synthesis via controlled erosion of electrodes. Herein, we use spark discharges between Co–Co, Ni–Ni, Co–Ni, or Ni–Co electrodes immersed in distilled water to synthesize Co and/or Ni nanoparticles, as well as their oxides. When mixed electrodes ar...
Article
The reforming of hydrocarbons has gained much interest as a means to upgrade low-grade fuels and to produce value-added chemicals. Plasmas have been considered one of the potential ways to reform fuels to achieve more effective and cleaner combustion, particularly by producing various hydrocarbons, hydrogen carriers, and oxygenates as well as synga...
Article
In this paper we describe the growth mechanism leading to the selective synthesis of 2D-like CuO nanoparticle agglomerates via pulsed electrical discharges in water. By adjusting the voltage and pulse width, we selected four experimental conditions: 5 kV/100 ns, 5 kV/500 ns, 20 kV/100 ns and 20 kV/500 ns. In these conditions, we obtained agglomerat...
Article
Full-text available
Metal oxide nanomaterials, including copper oxide, have attracted great attention due to their unique physical and chemical properties that are dependent on particle size and morphology. In this study, we propose an alternative technique for the synthesis of 2D mesoporous CuO agglomerates that is both efficient and ecological. This technique is bas...
Article
This article studies the possibility to design high-voltage pulser to sustain spark discharges in dielectric liquid using cheap and simple design. A spark pulser based on a zero-voltage switch oscillating circuit is used to power a high-voltage transformer. Sparks are ignited between copper electrodes in deionized water. The influence of input volt...
Article
Pulsed electrical discharges in dielectric liquids are intensively studied due to the wide range of applications in which they are implicated. Despite the simplicity of the experimental manipulation of these discharges, the underlying fundamental physics is relatively complex. In this study, we use the electrical characteristics, voltage and curren...
Article
Electrical discharge in liquids is a research field that has great potential in environmental and technological applications. Depending on the experimental conditions (liquid nature, interelectrodes distance, applied voltage, pulse width, etc.), various discharge modes can be obtained. The involved physical processes have relatively fast spatiotemp...
Article
Full-text available
Nanomaterial synthesis is a hot research subject that has been extensively studied in the last two decades. Recently, plasmas in liquid systems have been proposed as an efficient means of synthesizing various types of nanomaterials. The formation processes implicate many physical and chemical phenomena that take place at the electrode surface, as w...
Article
Full-text available
In the present study, Cu-based nanomaterials are synthesized by initiating spark discharges between two copper electrodes immersed in de-ionized water. The electrical conductivity of water is varied by adding HCl at very low concentrations. The discharge and water properties are determined by measuring the current-voltage waveforms and monitoring w...
Article
Full-text available
Plasma-induced water treatment is a novel water treatment technique that has shown high efficiency and flexibility. Although the electrical conductivity of impure water varies depending on the degree of pollution, its influence on plasma treatment efficiency is not well understood. In this study, we investigate the fundamentals of a microwave plasm...
Article
Full-text available
Plasma in- or in-contact-with liquid is an emerging technology that has high potential for use in liquid treatment applications. Due to the simultaneous production of highly reactive species, plasmas can efficiently eliminate pollutants that are difficult to remove using conventional methods. In this study, we investigate an AC-driven air plasma in...
Article
Plasma in or in‐contact with liquids is a research field that has great potential in the treatment of wastewater. Today, efforts are focused on finding a plasma source that can efficiently remove persistent pollutants from water. In this study, we evaluate the effectiveness of a microwave plasma jet, in TIAGO (Torche à Injection Axiale sur Guide d'...
Conference Paper
Full-text available
Microwave plasma jet (MWPJ) in water is a promising setup for water treatment as it is an electrodeless plasma device. Using a surfatron at a 2.45 GHz, plasma is generated in a quartz tube and injected in water. The propagation of the MWPJ in water is highly dependent on the experimental parameters, namely the microwave power, gas composition and f...
Conference Paper
Full-text available
Plasma-liquid interactions have great potential for numerous applications, including environmental remediation. The simultaneous physical and chemical phenomena, induced by plasma, have synergetic effect and can be used in water treatment, among other applications. In this paper, we study an AC discharge in air using pin-to-water geometry. Our resu...
Article
Full-text available
Plasma–liquid interactions have gained escalated interests over the last decade due to their potentials in many applications. The simultaneous generation of physicochemical phenomena of interest promotes itself to the top of the promising technologies for liquid processing. Here, we study the physics of a microwave plasma jet (MWPJ) submerged into...
Article
Full-text available
Plasmas in- or in-contact with liquids have been extensively investigated due to their high potential for a wide range of applications including, but not limited to, water treatment, material synthesis and functionalization, bio-medical applications, and liquid fuel reformation. Recently, we successfully developed a discharge using two immiscible l...
Article
Full-text available
We present a new method for achieving chemical reactions induced by plasmas with liquids - an in-liquid arc plasma jet system - designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility o...
Article
A simple method to synthesise hexagonal lead sheets, which belong to the class of two-dimensional materials, is proposed. These objects are collected on a substrate located under two lead electrodes, between which nanosecond-pulsed spark discharges are ignited in liquid nitrogen. The hexagonal sheets are single crystals produced by gas phase conden...
Article
Full-text available
A high-density plasma in a pin-to-pin configuration was sustained in liquid organosilicon precursors (hexamethyldisiloxane, tetraethyl orthosilicate, and tetramethylcyclotetrasiloxane) by the application of a high-voltage at a frequency of 1 kHz and a duty cycle of 30%. For all organosilicon precursors investigated, the current-voltage characterist...
Article
Full-text available
We studied composite wires assembled from electric field-driven nanoparticles in a dielectric liquid (heptane) to elucidate the exact processes and controlling factors involved in the synthesis of the multi-phase nanocomposites. Filamentary wires are synthesized by a two-step process: (1) abundant nanoparticle production, mostly of carbonaceous typ...
Article
Nanoparticles have unique properties and are useful in many applications. Efficient synthesis of high yields of nanoparticles remains a challenge. Here, we synthesized SiOC:H, a low-dielectric-constant material, by electrical discharge at the interface of hexamethyldisilazane and water. The nanoparticle production rate of our technique was ∼17 mg p...
Article
Anions in low-pressure magnetically confined Ar-C2H2 plasmas were investigated using the laser-induced photodetachment technique. In particular, the influence of the magnetic field (B) was studied. We observed that the density of negatively-charged species n - increases with B and slightly decreases when the C2H2 percentage grows. These phenomena a...
Article
We investigated the effect of a liquid's electrical conductivity (EC) on the physical characteristics of electrical discharges in liquids with gaseous bubbles. Argon gas was supplied into the liquid to form an array of gaseous bubbles in between two electrodes (a pin-to-hollow electrode setup). Methanol and water were considered as base liquids, re...
Article
In this paper, the ignition and development of a plasma created by pulsed surface wave discharges (PSWDs) was experimentally investigated using time-resolved imaging techniques and optical spectroscopy in helium at intermediate gas pressures between 5 and 50 Torr. We found that the ionization front moves at a few km s⁻¹ during the ignition phase an...
Article
Full-text available
Electric discharge in liquids is an emerging field of research, and is involved into various environmental applications (water purification, fuel reforming, nanomaterial synthesis, etc.). Increasing the treatment efficiency with simultaneous decreasing of the energy consumption are the main goals of today’s research. Here we present an experimental...
Article
Recently, an aqueous discharge reactor was developed to facilitate reformation of liquid fuels by in-liquid plasma. To gain a microscopic understanding of the physical elements behind this aqueous reactor, we investigate nanosecond discharges in liquid n-heptane with single and double gaseous bubbles in the gap between electrodes. We introduce disc...
Article
Electric discharge in liquids with bubbles can reduce the energy consumption, which increases treatment efficiency. We present an experimental study of nanosecond discharges in distilled water bubbled with the monoatomic gas argon and with the polyatomic gases methane, carbon dioxide, and propane. We monitor the time evolution of the voltage and cu...
Article
This paper presents a characterization study of carbon thin films grown on crystalline silicon substrates using a magnetized high-frequency discharge in argon–acetylene mixture at very low pressure. Thin films with different morphological structure are obtained. Depending on the gas pressure, acetylene percentage and process time, it is possible to...
Poster
Nanomaterials synthesized by plasmas in liquids have many applications in nanoscience [1]. Lead nanostructures can be used as sensors material [2] and could exhibit new properties in superconductivity [3]. In this work, original lead (Pb) nanostructures are grown by electrical discharges in liquid nitrogen and a special attention is paid to study t...
Article
Full-text available
The spatial variation of the characteristics of an aluminum plasma induced by a pulsed nanosecond XeCl laser is studied in this paper. The electron density and the excitation temperature are deduced from time- and space- resolved Stark broadening of an ion line and from a Boltzmann diagram, respectively. The influence of the gas pressure (from vacu...
Article
Full-text available
In this article, we present a comprehensive study of the plume dynamics of plasmas generated by laser ablation of an aluminum target. The effect of both ambient gas composition (helium, nitrogen or argon) and pressure (from ∼5 × 10−7 Torr up to atmosphere) is studied. The time- and space- resolved observation of the plasma plume are performed from...
Article
Here, we present the microscopic physical characteristics of nanosecond discharges with an array of bubbles in distilled water. In particular, applying a single high-voltage pulse, four delayed intensified charge-coupled device cameras successfully visualized four successive images during a single discharge event. We identified three distinctive mo...
Poster
Silicon nanoparticles can be synthesized by discharges in liquid nitrogen [1]. This system is easily adoptable in the preparation of large quantities and has the potential for low-cost production for application in photovoltaics or lithium rechargeable batteries. However, it turns out that size distributions lie in the range 10-20 nm and post-etchi...
Article
A stationary surface wave discharge is studied in helium gas at intermediate pressure. By optical emission spectroscopy, rotational temperatures derived from impurities molecular bands have been studied, as well as the excitation temperature from the Boltzmann plot method of helium lines, as a function of gas pressure, absorbed power and axial posi...
Article
The discharge between a platinum electrode and different metallic monolayers on a silicon substrate produced sub-micrometric structures. The scanning electron microscope images showed the formation of craters with cones, holes, corona, and other exotic structures. The atomic force microscopy images allowed evaluating the depth and height of these c...
Article
Full-text available
Synthesis of aluminium-containing nanoparticles (NPs) by electrical discharges was performed in three dielectric liquids (heptane, liquid nitrogen and water) with aluminium electrodes. The nature of the liquid plays an essential role in the synthesis yield and in the structural properties of NPs. Time-resolved optical emission spectroscopy of selec...
Article
Full-text available
Discharge–surface interaction in liquids includes many phenomena which are reviewed in this work. This is used to examine results in the area of nanoparticle synthesis and to propose a general sketch of formation mechanisms.
Article
Full-text available
Nanosecond-pulsed micro-discharges in heptane are studied by time-resolved imaging in pin-to-plate configuration. When a voltage of +5 kV is applied to the pin electrode, the discharge exhibits one maximum in light intensity. At +15 kV, filtered images show that up to three maxima can be identified. These maxima are associated with local electron-i...
Thesis
Dans ce document, nous présentons nos travaux sur les décharges dans l'heptane. L'une des conditions retenue pour ces études est le choix d'un gap micrométrique. Nous avons travaillé avec des gaps compris entre 10 et 150 µm qui correspondent à des tensions de claquage comprises entre 1 et 15 kV. Du claquage jusqu'à 1 µs, la décharge a été caractéri...
Article
Micro-gap discharges created in heptane between two platinum pin-electrodes produce platinum particles embedded in an amorphous carbon matrix which exhibits a short-range order. The platinum particles can be sorted by size. The largest ones (>100 nm in diameter) are created by emission of droplets from the liquid pool formed when the discharge hits...
Article
Full-text available
The determination of the initial pressure at the bubble wall created by a discharge in heptane for micro-gap conditions cannot be determined straightforwardly by modeling the time-oscillations of the bubble. The resolution of the Gilmore equation gives the same solutions beyond 1 μs typically for various sets of initial parameters, making impossibl...
Article
Full-text available
The main processes related to discharges between pin and plate electrodes in hydrocarbon liquid (heptane) are modelled for micro-gap (from 10 to 100 mu m) conditions. When a plasma channel hits the surface, a micro-crater is created. The different phenomena controlling the geometry (shape and dimension) of a single crater are described and included...
Article
Full-text available
Interaction of discharges in heptane with magnetron-sputtered thin films made of aluminum, copper or iron is studied in a pin-to-plate configuration. The behavior of discharges on thin films can be used to better understand the interaction of discharges with given surfaces and it might also improve the reproducibility of the impacts in order to bet...
Article
Full-text available
Discharges in heptane in pin‐to‐plate configuration are produced between a platinum wire and a (100)‐oriented silicon wafer coated by a carbon nanotube (CNT) carpet. This carpet is used to simulate the behavior of a nanostructured surface in electro‐discharge machining (EDM) where small protrusions on the surface could play a similar role. CNTs beh...
Article
Full-text available
Modes of energy dissipation in impacts made on various materials (Al, Cu, Fe, and Si) by discharges in heptane are investigated for micro-gap conditions. Bulk metals and thin films of 300 nm in thickness deposited on silicon wafers are used as samples. Positive high voltage pulses with nanosecond rise times make it possible to isolate a single disc...
Article
Full-text available
This paper explores the possibility of using AlN/sapphire piezoelectric bilayer structures for high-temperature SAW applications. To determine the temperature stability of AlN, homemade AlN/sapphire samples are annealed in air atmosphere for 2 to 20 h at temperatures from 700 to 1000°C. Ex situ X-ray diffraction measurements reveal that the microst...
Conference Paper
Full-text available
Interaction between streamer and 316L Stainless Steel substrate in heptane with microgaps gives craters with a very specific shape. The role of the Marangoni forces is stressed, a phenomenon which is generally neglected in EDM processes to describe the shape of the craters.