Papers by Anthony Bruce Murphy
Journal of Physics D: Applied Physics, 2017
Welding in the World, 2009
Handbook of Fluid Dynamics, Second Edition, 2016
Welding in the World, 2010
IEEJ Transactions on Power and Energy, 2013
Nature Communications, 2017
Thermal chemical vapour deposition techniques for graphene fabrication, while promising, are thus... more Thermal chemical vapour deposition techniques for graphene fabrication, while promising, are thus far limited by resource-consuming and energy-intensive principles. In particular, purified gases and extensive vacuum processing are necessary for creating a highly controlled environment, isolated from ambient air, to enable the growth of graphene films. Here we exploit the ambient-air environment to enable the growth of graphene films, without the need for compressed gases. A renewable natural precursor, soybean oil, is transformed into continuous graphene films, composed of single-to-few layers, in a single step. The enabling parameters for controlled synthesis and tailored properties of the graphene film are discussed, and a mechanism for the ambient-air growth is proposed. Furthermore, the functionality of the graphene is demonstrated through direct utilization as an electrode to realize an effective electrochemical genosensor. Our method is applicable to other types of renewable precursors and may open a new avenue for low-cost synthesis of graphene films.
QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY, 2013
Scientific reports, Jan 9, 2016
Cold atmospheric-pressure plasma (CAP) is a relatively new method being investigated for antimicr... more Cold atmospheric-pressure plasma (CAP) is a relatively new method being investigated for antimicrobial activity. However, the exact mode of action is still being explored. Here we report that CAP efficacy is directly correlated to bacterial cell wall thickness in several species. Biofilms of Gram positive Bacillus subtilis, possessing a 55.4 nm cell wall, showed the highest resistance to CAP, with less than one log10 reduction after 10 min treatment. In contrast, biofilms of Gram negative Pseudomonas aeruginosa, possessing only a 2.4 nm cell wall, were almost completely eradicated using the same treatment conditions. Planktonic cultures of Gram negative Pseudomonas libanensis also had a higher log10 reduction than Gram positive Staphylococcus epidermidis. Mixed species biofilms of P. aeruginosa and S. epidermidis showed a similar trend of Gram positive bacteria being more resistant to CAP treatment. However, when grown in co-culture, Gram negative P. aeruginosa was more resistant to...
Physical Review Letters, Sep 1, 1994
A description of demixing that is mathematically simple and physically transparent is introduced.... more A description of demixing that is mathematically simple and physically transparent is introduced. The dominant demixing process at high temperatures in an atmospheric-pressure nitrogen-argon arc is predicted to be that associated with frictional forces. Spectroscopic measurments of the mass fraction distribution, which provide experimental confirmation of this demixing effect, are presented. It is shown that demixing can act to either increase or decrease the mass fraction of nitrogen as temperature increases, depending on the gas composition.
Surface and Coatings Technology, Dec 1, 2010
ABSTRACT Although the LTE assumption is effective to evaluate high temperature region in the arc ... more ABSTRACT Although the LTE assumption is effective to evaluate high temperature region in the arc column in Gas Tungsten Arc (GTA) which is a kind of a transfer-type plasma torch, it is difficult to apply it to low temperature region such as the fringe of the arc column or an electrical sheath due to decrease of collision frequency. Especially, in order to consider the effect of chemical reaction between the arc plasma and the surface of the anode material, non-equilibrium property of the arc plasma should be considered without the LTE assumption, since it is required to understand precise property of the arc plasma close to the anode surface. Therefore, we have developed non-equilibrium simulation model of GTA. In this paper, the reliability of the model was confirmed for comparing the simulation result with the experimental result. Furthermore, it was found that the thickness of non-equilibrium region in case of 150A is approximately 0.3mm near the anode surface and that in case of 50A exceeds 1mm.
Journal of Plasma Physics, Nov 30, 1989
ABSTRACT
Plasma Chem Plasma Process, 2010
A modeling study is conducted to investigate the effect of hydrogen content in propellants on the... more A modeling study is conducted to investigate the effect of hydrogen content in propellants on the plasma flow, heat transfer and energy conversion characteristics of low-power (kW class) arc-heated hydrogen/nitrogen thrusters (arcjets). 1:0 (pure hydrogen), 3:1 (to simulate decomposed ammonia), 2:1 (to simulate decomposed hydrazine) and 0:1 (pure nitrogen) hydrogen/nitrogen mixtures are chosen as the propellants. Both the gas flow
Transactions of J W R I, Dec 1, 2007
A gas tungsten arc in argon is modeled taking into account the contamination of the plasma by the... more A gas tungsten arc in argon is modeled taking into account the contamination of the plasma by the metal vapor from the weld pool surface. The whole region of gas tungsten arc welding, namely the tungsten cathode, arc plasma and weld pool, is treated using a unified numerical model. A viscosity approximation is used to express the diffusion coefficient in terms of the viscosities of the argon gas and the iron vapor. The time-dependent two-dimensional distributions of temperature, velocity and iron vapor concentration are predicted, together with the weld penetration as function of time for a 150 A arc at atmospheric pressure.
J Phys D Appl Phys, 2001
The calculation and measurement of the properties of thermal plasmas in mixtures of different gas... more The calculation and measurement of the properties of thermal plasmas in mixtures of different gases are reviewed. The calculation of composition, thermodynamic properties and transport coefficients is described. Particular attention is given to the calculation of diffusion coefficients, which is a significant problem in mixed-gas plasmas. The combined diffusion coefficient formulation is shown to be a useful method for the treatment of diffusion. Computational fluid dynamic modelling of thermal plasmas in gas mixtures is considered, using the examples of demixing in welding arcs, the turbulent mixing of atmospheric air into a plasma jet and a plasma waste destruction process. Diagnostic techniques for mixed-gas plasmas, in particular emission spectroscopy, laser scattering and laser-induced fluorescence, are discussed.
Journal of Physics D Applied Physics, Apr 13, 2011
This review paper presents historical perspectives, recent advances and future directions in the ... more This review paper presents historical perspectives, recent advances and future directions in the multidisciplinary research field of plasma nanoscience. The current status and future challenges are presented using a three-dimensional framework. The first and the largest dimension covers the most important classes of nanoscale objects (nanostructures, nanofeatures and nanoassemblies/nanoarchitectures) and materials systems, namely carbon nanotubes, nanofibres, graphene, graphene nanoribbons, graphene nanoflakes, nanodiamond and related carbon-based nanostructures; metal, silicon and other inorganic nanoparticles and nanostructures; soft organic nanomaterials; nano-biomaterials; biological objects and nanoscale plasma etching. In the second dimension, we discuss the most common types of plasmas and plasma reactors used in nanoscale plasma synthesis and processing. These include low-temperature non-equilibrium plasmas at low and high pressures, thermal plasmas, high-pressure microplasmas, plasmas in liquids and plasma-liquid interactions, high-energy-density plasmas, and ionized physical vapour deposition as well as some other plasma-enhanced nanofabrication techniques. In the third dimension, we outline some of the 'Grand Science Challenges' and 'Grand Socio-economic Challenges' to which significant contributions from plasma nanoscience-related research can be expected in the near future. The urgent need for a stronger focus on practical, outcome-oriented research to tackle the grand challenges is emphasized and concisely formulated as from controlled complexity to practical simplicity in solving grand challenges.
Ieee Transactions on Plasma Science, Sep 1, 2010
This paper focuses on the numerical investigation of arc plasma behavior in low-voltage circuit b... more This paper focuses on the numerical investigation of arc plasma behavior in low-voltage circuit breaker with arcsplitting process included. A 3-D simulation model of a certain type miniature circuit breaker product is built and calculated, which is based on magnetohydrodynamics theory. Aside from coupled electromagnetic and gas dynamic interactions being considered as usual, a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc roots. Thus, the arc-splitting process with ferromagnetic plates can be included. Arc motion is described in detail by the temperature distribution. Some interesting phenomena are observed in the simulation, such as the arc root jumping from contact to arc runner, the arc back commutation before splitting into series arcs by metallic plates, new arc root formation in splitting process, and, finally, the arc go across the splitter plates in the chamber. Moreover, the simulation result is compared with experimental result, which shows good agreement.
QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY, 2013
QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY, 2013
Physics of Plasmas, 2014
Dielectric breakdown properties of hot SF6-CO2 mixtures at temperatures of 300-3500K and pressure... more Dielectric breakdown properties of hot SF6-CO2 mixtures at temperatures of 300-3500K and pressures of 0.01-1.0MPa Phys. Plasmas 21, 053506 (2014); 10.1063/1.4876744 Modeling of inductively coupled plasma SF6/O2/Ar plasma discharge: Effect of O2 on the plasma kinetic properties J. Vac. Sci. Technol. A 32, 021303 (2014); 10.1116/1.4853675 Study of the dielectric breakdown properties of hot SF6-CF4 mixtures at 0.01-1.6MPa
Plasma Chemistry and Plasma Processing
Calculated values of the viscosity, thermal conductivity, and electrical conductivity of hydrogen... more Calculated values of the viscosity, thermal conductivity, and electrical conductivity of hydrogen and mixtures of argon and hydrogen at high temperatures are presented. Combined ordinary, pressure, temperature, and electric field diffusion coefficients are also given for the mixtures. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 300 to 30,000 K. The results are compared with those of previously published studies. Generally, the agreement is reasonable; those discrepancies that exist are attributed to the improved values of some of the collision integrals used here in calculating the transport coefficients.
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Papers by Anthony Bruce Murphy