C. S. Wong

University of Malaya | UM · Department of Physics

An experimental study to investigate the effect of an external magnetic field on the propagation of ion-acoustic waves (IAWs) has been carried out in hydrogen plasma containing two-temperature electrons and dust grains. It is a first step in understanding the propagation properties of IAWs in such an environment. A low-pressure hot cathode discharg...

An experimental study to investigate the effect of an external magnetic field on the propagation of ion-acoustic waves (IAWs) has been carried out in hydrogen plasma containing two-temperature electrons and dust grains. A low-pressure hot cathode discharge method is opted for plasma production. The desired two electron groups with distinct temperat...

50 Hz argon glow discharge plasma was used to treat the surface of polycarbonate (PC) and polypropylene (PP). These materials were treated for 10 min under low pressure of 0.3 mbar. Static water contact angle measurement showed there was a decrease in the contact angle on the surfaces of polymers after plasma treatment. X-ray Photoelectron Spectros...

Atmospheric pressure plasma jets (APPJ) have been established as suitable sources of low-temperature and non-equilibrium plasmas. In this paper, an atmospheric pressure plasma jet sustained in argon gas has been used to modify the surface properties of the Polyethylene terephthalate (PET) samples. The surface properties of the untreated and plasma...

This research work reports the results concerning the generation of Dielectric Barrier Discharge (DBD) and Atmospheric Pressure Glow Discharge (APGD) in different gases at atmospheric pressure and the study of its electrical and optical properties. The discharge has been produced by using three different power supplies. (i) High voltage (0-20 kV) A...

The present work reports the results of surface modification of different polymers; Polypropylene (PP), Polyethylene terephthalate (PET) and Polytetrafluoroethylene (PTFE) and textiles; Dynema SB21, Dynema SB51 and Dynema SB71 in order to improve their hydrophilic properties. Using a high voltage (0-20 kV) power supply operating at 27 kHz, atmosphe...

This research work reports the results concerning the generation of dielectric barrier discharge (DBD) and its use for the treatment of drinking water collected from different sources in Kathmandu Valley, Nepal. The discharge has been produced by applying AC high voltage (up to 20 kV peak-to-peak) source of frequency 10-30 kHz across annular electr...

This paper reports an investigation on the effects of atmospheric pressure plasma treatment (APPT) and ultraviolet treatment (UVT) on the wettability of polycarbonate (PC) surface. A high voltage (0-20 kV) power supply operating at 27 kHz was used to generate a dielectric barrier discharge consisting of two parallel electrodes with a discharge gap...

Low temperature plasmas generated under atmospheric pressure condition has been gaining popularity for the surface treatment of materials due to their many advantages over conventional methods of treatment. This paper reports the study of surface modification of Polyethylene Terephthalate (PET) and Polypropylene (PP) by using atmospheric pressure d...

Plasma technology forms the backbone of many modern industries today in the field of electronics, agriculture, medicine as well as environmental remediation sectors. However, plasma systems for industrial applications can be expensive to set up with the need for ultralow pressure operation and sophisticated power sources. With the goal of developin...

This chapter examines some of the key fundamentals of planar radio frequency inductively coupled plasmas (or RF ICPs) including the various modes of operation, hysteresis between modes, power balance of the plasma operating states and dynamics of the source electromagnetic fields in the presence of plasma. These properties are discussed with the de...

Gas discharge plasmas, also known as low-temperature plasmas, have drawn much attention in past few decades because of their importance in many technological developments. In this chapter, recent development in producing cost effective plasmas at atmospheric pressure has been introduced along with a brief description of low pressure gas discharge....

In this paper, a technique for the determination of electron temperatures and electron densities in atmospheric pressure argon/air discharge by the analysis of optical emission spectra (OES) is reported. The discharge is produced using a high voltage (0-20 kV) power supply operating at a frequency of 27 kHz in parallel electrode system, with glass...

We investigate the face-to-face collision between multisolitons in spin-1/2 quantum plasma. It is studied in the framework of the model proposed by Marklund et al in Phys. Rev. E76, 067401 (2007). This study is done with the help of the extended Poincare–Lighthill–Kno (PLK) method. The extended PLK method is also used to obtain two Korteweg–de Vrie...

In this chapter, the generation of plasma by gaseous electrical discharge will be discussed. Townsend Theory of electrical breakdown of gases will be explained. Various types of discharge, including to corona discharge, glow discharge and arc discharge and the characteristics of the plasmas produced will be introduced. The electrical power sources...

Some of the fundamental basic concepts useful for the understanding of plasma will be introduced and explained in this chapter. These include particle collision and the fundamental processes that may occur as a consequence of collision between particles, the concept of Debye shielding, plasma sheath formation at the surface of object placed inside...

In this chapter, some of the basic diagnostic techniques that are useful for studying various types of plasmas are described. These include electrical measurements (discharge current and voltage across the plasma), spectroscopic measurements, the Langmuir (electric) probe, X-ray and neutron measurements.

In this chapter, the principle of operation, experimental setup as well as some results obtained from research work carried out by the authors and collaborators based on several small plasma devices will be discussed briefly.

Segregation and mixing of granular materials are complex processes and are not fully understood. Motivated by industrial need, we performed a simulation using the discrete element method to study size segregation of a binary mixture of granular particles in a horizontal rotating drum. Particles of two different sizes were poured into the drum until...

The development of a non-thermal plasma jet with a capillary configuration working at atmospheric pressure is reported in this paper. The plasma jet is powered by a power source with frequency of several kilohertz. The working gas is argon. The plasma obtained has been characterized by optical emission spectroscopic measurements and electrical meas...

A review of research work carried out at University of Malaya Plasma Technology Research Centre.

The dynamic features of dust acoustic waves in a four-component dusty plasma with non-thermal ions are investigated applying the bifurcation theory of planar dynamical systems. Employing the Galilean transformation, basic equations are reduced to a planar dynamical system. Existence of solitary and periodic waves is presented for the dynamical syst...

The aim of the present work was the study of the surface modification of polymers and textiles in order to improve their hydrophilic properties. Atmospheric pressure argon glow discharges were applied for the surface modification of four different types of polymers: low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalet (PET...

In this study, polycaprolactone (PCL) film, a high potential material used in biomedical applications, was treated by air plasma prior to a conjugation by carbodiimide cross-linking with various types of proteins, including type A gelatin, type B gelatin, and collagen hydrolysate. The properties of modified PCL films were characterized by X-ray pho...

A modular typed dielectric barrier discharge (DBD) device is designed and tested for air and water remediation. The module is made of a number of DBD tubes that can be arranged in series or parallel. Each of the DBD tubes comprises inner electrode enclosed with dielectric barrier and arranged as such to provide a gap for the passage of gases. Non-t...

This book presents some fundamental aspects of plasma technology that are important for beginners interested to start research in the area of plasma technology . These include the properties of plasma, methods of plasma generation and basic plasma diagnostic techniques. It also discusses several low cost plasma devices, including pulsed plasma sour...

In this paper, the results of electrical characterization of DBD generated in air, nitrogen and argon at atmospheric pressure were analyzed. Filamentary mode and homogeneous DBD mode of discharge were studied. Glow-arc discharge mode was also studied by means of electrical characterization without using the dielectric barrier between the electrodes...

Background. Syngnathid fishes produce three kinds of sounds, named click, growl and purr. These sounds are generated by different mechanisms to give a consistent signal pattern or signature which is believed to play a role in intraspecific and interspecific communication. Commonly known sounds are produced when the fish feeds (click, purr) or is un...

Sound dataset

The head-on collisions and overtaking collisions of dust acoustic multi-solitons in a dusty plasma with qnonextensive velocity distributed ions are studied applying the Extended Poincare-Lighthill Kuo(EPLK) method and using the results of Hirota’s direct method. The EPLK method is used to derive two separate Korteweg-de Vries (KdV) equations where...

Dust grains’ potential variation is presented by using a non-equilibrium complex (dusty) plasma following the Vasyliunas Cairns (VC)-distribution, in which the components such as the electrons, ions [positive and negative], and dust grains have negative charge. For this reason, mathematical statement of currents is solved for dust grains having neg...

Nonthermal atmospheric pressure plasmas are suitable for inactivation of bacteria and killing cancer cells. These plasmas produce highly energetic electrons that efficiently dissociate molecular gases (N2, O2 in air) to generate reactive radical species (OH, O, NO, etc.) that induce cell death. Operating the nonthermal plasma at atmospheric pressur...

Atmospheric pressure single electrode argon /oxygen plasma jet has been generated between a high-voltage electrode and the surrounding room air for treating thermally sensitive materials is reported. The discharge has been characterized by electrical and optical emission spectroscopic technique. The microplasma jet device operated by an electrical...

The dynamic motions of ion acoustic waves an unmagnetized plasma with superthermal (q-nonextensive) electrons are investigated employing the bifurcation theory of planar dynamical systems through direct approach. Using traveling wave transformation and initial conditions, basic equations are transformed to a planar dynamical system. Using numerical...

Acoustic signals of the tiger-tail seahorse (Hippocampus comes) during feeding were studied using wavelet transform analysis. The seahorse “click” appears to be a compounded sound, comprising three acoustic components that likely come from two sound producing mechanisms. The click sound begins with a low-frequency precursor signal, followed by a su...

Acoustic signals of the tiger-tail seahorse (Hippocampus comes) during feeding were studied using wavelet transform analysis. The seahorse “click” appears to be a compounded sound, comprising three acoustic components that likely come from two sound producing mechanisms. The click sound begins with a low-frequency precursor signal, followed by a su...

In vitro drug screening techniques provide rapid and easy to analyze data, while saving a lot of animals from being sacrificed. An important part of any In vitro drug screening platform is a biomaterial which promotes cell growth and proliferation. The potential of electrospun scaffolds made of polyhydroxybutyrate (PHB), poly (3-hydroxybutyric acid...

The present work addresses an important issue in micro- and nano-crystalline diamond (MCD/NCD) synthesized in microwave plasma assisted chemical vapor deposition system (MPCVD) which is the real-time monitoring of plasma parameters during the growth process. A computer controlled bipolar source-meter instrument was setup as a voltage source for the...

Synthesis of ZnO nanowires (NWs) using vapor phase transport (VPT) assisted with thermal evaporation of brass (CuZn) assisted by hotwire was presented. The effects of aliphatic alcohols such as methanol and ethanol as source of oxygen were investigated using field emission scanning electron microscope and X-ray diffraction (XRD). Significant change...

Atmospheric pressure non-thermal dielectric barrier discharges can be generated in different configurations for different applications. For sterilization, a parallel-plate electrode configuration with glass dielectric that discharges in air was used. Gram-negative bacteria ( Escherichia coli and Salmonella enteritidis) and Gram-positive bacteria (B...

A 2.2 kJ plasma focus device was analysed as an electron beam and an X-ray source that operates with argon gas refilled at a specific pressure. Time-resolved X-ray signals were observed using an array of PIN diode detectors, and the electron beam energy was detected using a scintillator-assisted photomultiplier tube. The resultant X-rays were inves...

Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) pr...

Acoustic signals of the tiger-tail seahorse (Hippocampus comes) during feeding were studied using wavelet transform analysis. The seahorse “click” appears to be a compounded sound, comprising three acoustic components that likely come from two sound producing mechanisms. The click sound begins with a low-frequency precursor signal, followed by a su...

The expected emission spectra of nitrogen and oxygen high density plasma have been studied for different conditions. Expected nitrogen and oxygen plasma spectra at certain electron temperature range have been plotted. Suitable electron temperature ranges for nitrogen and oxygen plasma soft X-ray emission and extreme ultraviolet emission have been i...

The effect of gas flow rate of helium and argon on the length of dielectric barrier discharge (DBD) jet generated under atmospheric pressure using an AC source is investigated. It is found that as the flow rate increases, the jet length increases up to a maximum length. Upon further increase in flow rate, it will cause the jet length to decrease. V...

An atmospheric pressure dielectric barrier discharge (DBD) system capable of operating under both positively biased voltage pulses at 500 Hz and sinusoidal AC voltage at 8.5 kHz was constructed. The 500 Hz operation produced DBD plasma that was visually more uniform, whilst optical emission from DBD at 8.5 kHz operation was more intense. Though the...

Hydroxyapatite has a chemical composition that closely resembles the mineral phase of natural hard tissues, making it a good material for use as a bone scaffold. Previous studies have demonstrated that the use of electrospun nanofibres that contain synthetic hydroxyapatite aids in bone regeneration. In this study, composite scaffolds of polycaprola...

Polyhydroxyalkanoates are bacterial biopolyesters having good biocompatibility and biodegradability. Poly[(R)-3-hydroxybutyric acid] is the least expensive/costly and most easily available member of this family. However, poly[(R)-3-hydroxybutyric acid] is very brittle because of its high crystallinity. Its poor processability poses limitations on i...

Non-thermal atmospheric pressure plasma jet can easily be generated via a coplanar-coaxial dielectric (quartz tube) barrier discharge configuration driven by AC high voltage source at 11 kHz frequency in flowing argon gas. The plasma jet was characterized by its physical dimension, electrical and optical emission properties. It was found that small...

In this work, stochastic behavior of atmospheric pressure dielectric barrier discharge (DBD) has been investigated. The experiment is performed in a DBD reactor consisting of a pair of stainless steel parallel plate electrodes powered by a 50Hz ac high voltage source. Current pulse amplitude distributions for different space gaps and the time separ...

X-ray point source generated by X-pinches on the compact pulsed power device PPG-2 of Tsinghua University is well suited for phase-contrast imaging of weakly X-ray absorbing organism. Using six sets of photoconducting devices each covered by a filter of specific transmittance curve, the X-ray radiation energy spectra from Mo-wire and W-wire X-pinch...

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered th...

Diffuse dielectric barrier discharge was first produced in 3-mm-thick air gap at atmospheric pressure using two plane parallel electrodes each covered by one specific alumina plate with a thickness of 2.3 mm. Based on the discharge photographs of 10 ns exposure time taken with an intensified CCD camera, the diffuse discharge was identified with Tow...

Zinc oxide (ZnO) nanowires (NWs) were synthesized using vapor phase transport (VPT) and thermal evaporation of Zn from CuZn. Time dependence of ZnO NWs growth was investigated for 5, 10, 15, 20, 25, and 30 minutes. Significant changes were observed from the field electron scanning electron microscopy (FESEM) images as well as from the X-ray diffrac...

Langmuir double probe is a very useful diagnostics for studying the plasma parameters at low pressure discharge and this paper reports the measurement of electron temperature (􀢀􀢋), ion saturation current (􀡵􀢙􀢇􀢚) and electron density (􀢔􀢋) in a low pressure DC glow discharge in air using I-V characteristics of double probe and the objective of the stu...

Articles you may be interested in Numerical simulation of carbon arc discharge for nanoparticle synthesis Phys. Plasmas 19, 073510 (2012); 10.1063/1.4737153 Iron oxide nanoparticles fabricated by electric explosion of wire: focus on magnetic nanofluids AIP Advances 2, 022154 (2012); 10.1063/1.4730405 Observation of nonlinear absorption and visible...

We presented combinations of vapor phase transport (VPT) of mixture of methanol and acetone and thermal evaporation of brass (CuZn) which contain in-situ three stages in obtaining un-doped and Mn-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by energy dispersive X-ray analysis (EDAX), field emission sc...

The dust acoustic Gardner solitons in a dusty plasma with q-nonextensive electrons in nonplaner geometry are reported. By deriving modified Gardner (MG) equation, the properties of nonplanar (cylindrical and spherical) dust acoustic solitary waves (DASWs) in an unmagnetized, collisionless, three component dusty plasma, whose constituents are negati...

This chapter reveals the surface functionalization of carbon nanotube (CNT) using oxygen–hydrogen (O 2 –H 2) gas mixture direct current (DC) glow discharge plasma technique for cathode/CNT–anode separation of 0.10 ± 0.01cm. During the (O 2 –H 2) gas mixture DC glow discharge, current–voltage (I–V) characteristic of gaseous species studied for vario...

Diffuse dielectric barrier discharge was first produced in 3-mm-thick air gap at atmospheric pressure using two plane parallel electrodes each covered by one specific alumina plate with a thickness of 2.3 mm. Based on the discharge photographs of 10 ns exposure time taken with an intensified CCD camera, the diffuse discharge was identified with Tow...

Wire explosion process has long been studied due to its ability to produce nanoparticles with high purity, high energy efficiency and feasibility to be used for mass production. In general, a high power pulsed current is passed through a thin wire to vaporize the wire by Joule heating. Plasma will be formed thereafter when the supplied energy is su...

The dust-acoustic shock waves have been theoretically investigated using reductive perturbation technique. An unmagnetized four-component dusty plasma system consisting of nonextensive q-distributed electrons, Boltzmann distributed ions, and negatively as well as positively charged dust particles has been considered. The solution of Burgers equatio...

The electrical characteristics of a filamentary dielectric barrier discharge (DBD) are studied experimentally and numerically. The DBD system which has parallel plate electrodes geometry is powered by a 50 Hz power supply and operated at atmospheric air. A dynamic electric circuit model considering the discharge region and the non-discharge region...

The discharge dynamics in an atmospheric pressure dielectric barrier discharge (DBD) is studied in a DBD reactor consisting of a pair of stainless steel parallel plate electrodes. The DBD discharge has been generated by a 50Hz ac high voltage power source. The high-speed intensified charge coupled device camera is used to capture the images of fila...

The X-ray emission characteristics of a vacuum spark device operated with anode materials of various atomic numbers were studied. The temporal evolution of the X-ray emission was recorded by using five channels of high-speed PIN X-ray diodes. A time-integrated X-ray spectrometer was used to record the spectral distribution of the X-ray emission. Th...

In this paper, we summarise the efforts of our group in the development of cost effective plasma devices for applications in the treatment of materials, in particular bio-medical materials.

Diagnostics of ion beam emission from a 3 kJ Mather-type plasma focus device have been performed for deuterium discharge at low pressure regime. Deuterium plasma focus was found to be optimum at pressure of 0.2 mbar. The energy spectrum and total number of ions per shot from the pulsed ion beam are determined by using biased ion collectors, Farada...

Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at op...

The effects of experimental parameters on the emission of Extreme Ultra Violet (EUV) from plasma produced by vacuum spark discharge using Tin as anode material were studied. The operating pressure for all the experiments carried out was maintained at below 10−4 mbar. The discharge voltage tested was from 10 kV to 25 kV. The inter-electrode distance...

In this paper, experimental results on atmospheric pressure argon dielectric barrier discharge (DBD) have been presented. The discharge was generated using a high voltage (0 to 20 kV) power supply operating at frequency of 10 to 30 kHz and was studied by means of electrical and optical measurements. A homogeneous and steady discharge was observed b...

In this work, the metallic capillary discharge is operated with two different ambients: air and argon. In the experiments reported here, the chamber is first evacuated to 10−5 mbar. The discharge is initiated by the transient hollow cathode effect generated electron beam, with either air ambient or argon ambient at 10−4 mbar. The bombardment of el...

Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies

The radiation emission in a 2.2 kJ Mather-type dense plasma focus device is investigated using a five channel BPX65 PIN diode spectrometer. Estimated X-ray associated with the hollow anode without and with target in Argon gas medium is compared. At optimum conditions, the radiation emission from the system is found to be strongly influenced with t...

Radiation emission in a 2.2 kJ Mather-type plasma focus device is investigated using a five channel BPX65 PIN diode spectrometer. At optimum condition, radiation emission from the system is found to be strongly influenced in hollow anode and filling gas pressure. Maximum X-ray yield in 4p sr has been obtained in case of hollow anode in argon gas me...

Heating of neutral gas in inductively coupled plasma (ICP) is known to result in neutral gas depletion. In this work, this effect is considered in the simulation of the magnetic field distribution of a 13.56 MHz planar coil ICP. Measured electron temperatures and densities at argon pressures of 0.03, 0.07 and 0.2 mbar were used in the simulation wh...

a b s t r a c t Crystallization of hydrogenated amorphous silicon thin films with irradiation by using a dense plasma focus ion beam source has been investigated. The effects of the energetic ion beam irradiation on the surface morphological, structural and optical properties of the as-prepared a-Si:H thin films were investigated with field emissio...

Dynamic light scattering (DLS) technique is a simple and yet powerful technique for characterizing particle properties and dynamics in complex liquids and gases, including dusty plasmas. Intensity fluctuation in DLS experiments often studied using correlation analysis with assumption that the fluctuation is statistically stationary. In this study,...