Table of contents

This paper discusses the possibility of determining, at the same time, both the electron density and temperature in a discharge produced at atmospheric pressure using the Stark broadening of lines spontaneously emitted by a plasma. This direct method allows us to obtain experimental results that are in good agreement with others previously obtained for the same type of discharge. Its advantages and disadvantages compared to other direct methods of diagnostics, namely Thomson scattering, are also discussed.

Effective destruction of Escherichia coli (E. coli) bacteria has been obtained in a flowing N₂–O₂ microwave post-discharge reactor. The sterilizing agents are the O atoms and the UV emissions of NOβ which are produced by N and O atoms recombination in the reactor. In the following plasma conditions: pressure 5 Torr, flow rate 1 L_n min⁻¹, microwave power of 100 W in a quartz tube of 5 mm, an O atom density of 2.5×10¹⁵ cm⁻³ is measured by NO titration in the post-discharge reactor with UV emission in a N₂–(5%)O₂ gas mixture. Full destruction of 10¹³ cfu ml⁻¹ E. coli is observed after a treatment time of 25 min.

Magnetic materials have been used with grain sizes down to the nanoscale for longer than any other type of material. This is because of a fundamental change in the magnetic structure of ferro- and ferrimagnetic materials when grain sizes are reduced. In these circumstances, the normal macroscopic domain structure transforms into a single domain state at a critical size which typically lies below 100 nm. Once this transformation occurs the mechanism of magnetisation reversal can only be via the rotation of the magnetisation vector from one magnetic easy axis to another via a magnetically hard direction. This change of reversal mechanism has led to a new class of magnetic materials whose properties and the basic underlying physical mechanism governing them were defined in a seminal work first published by E C Stoner and E P Wolhfarth in 1949.

As a consequence of this rotation mechanism, magnetic nanoparticles exist having coercivities which are highly controllable and lie between soft materials and normal permanent magnet materials. This ability to control coercivity in such particles has led to a number of significant technological advances, particularly in the field of information storage. The high value of information storage technology has meant that since the 1950s an enormous research and development effort has gone into techniques for the preparation of magnetic particles and thin films having well defined properties. Hence, certainly since the 1960s, a wide range of techniques to produce both metallic and oxide magnetic nanoparticles with sizes ranging from 4-100 nm has been developed.

The availability of this wide range of materials led to speculation from the 1960s onwards that they may have applications in biology and medicine. The fact that a magnetic field gradient can be used to either remotely position or selectively filter biological materials leads to a number of obvious applications. These applications fall broadly into two categories: those involving the use in-vivo and those involving the use of magnetic particles in-vitro. Obviously for safety reasons the development of in-vitro applications are more accessible. However, and somewhat ironically, the one application currently used on a significant scale involves the use of magnetic particles to produce a distortion in the magnetic field at a given site under examination via magnetic resonance imaging (MRI). The presence of the particles at a given site can alter the contrast of certain types of cells by several orders of magnitude, making visible objects that were hitherto difficult to image.

With the increasing sophistication of pharmaceuticals, the dramatic development of cell manipulation and even DNA sequencing, the possibility of using magnetic nanoparticles to improve the effectiveness of such technologies is obviously appealing. Hence there are proposals for drug delivery systems, particularly for anti-inflammatory agents and also for the use of magnetic separation technologies for rapid DNA sequencing.

A further and somewhat surprising application of magnetic nanoparticles lies in the production of controlled heating effects. Each cycle of a hysteresis loop of any magnetic material involves an energy loss proportional to the area of the loop. Hence if magnetic nanoparticles having the required coercivity are remotely positioned at a given site in the body, perhaps the site of a malignancy, then the application of an alternating magnetic field can be used to selectively warm a given area. It has been proposed that this simple physical effect could be used both to destroy cells directly or to induce a modest increase in temperature so as to increase the efficacy of either chemotherapy or radiotherapy.

Clearly this area of potential technology is highly novel and offers many exciting possibilities for future developments. The area is relatively young and highly multidisciplinary, requiring a range of scientific knowledge from inorganic chemistry involved in the preparation of the nanoparticles, through biochemistry and medical science to allow for their functionalisation, and of course the basic physics of how the properties of the magnetic particles can best be brought to bear. In consequence it is not possible for a single author to be able to produce an overview of such a wide range of disciplines in a single paper. Therefore, in this issue of Journal of Physics D: Applied Physics we have commissioned three separate reviews from leading groups in Western Europe covering in some detail the preparation of magnetic nanoparticles, their functionalisation with appropriate biomolecules for different applications and a review of the fundamental underlying physics behind the technology. We hope that this somewhat unusual combination of review articles in an applied physics journal will be of benefit to all those in the scientific community with interests in this area.

We are most grateful to all the authors of the three papers for their contribution to this issue of Journal of Physics D: Applied Physics and in particular for their willingness to coordinate their submissions so as to enable this cluster of review articles to appear in a single issue.

The physical principles underlying some current biomedical applications of magnetic nanoparticles are reviewed. Starting from well-known basic concepts, and drawing on examples from biology and biomedicine, the relevant physics of magnetic materials and their responses to applied magnetic fields are surveyed. The way these properties are controlled and used is illustrated with reference to (i) magnetic separation of labelled cells and other biological entities; (ii) therapeutic drug, gene and radionuclide delivery; (iii) radio frequency methods for the catabolism of tumours via hyperthermia; and (iv) contrast enhancement agents for magnetic resonance imaging applications. Future prospects are also discussed.

This review is focused on describing state-of-the-art synthetic routes for the preparation of magnetic nanoparticles useful for biomedical applications. In addition to this topic, we have also described in some detail some of the possible applications of magnetic nanoparticles in the field of biomedicine with special emphasis on showing the benefits of using nanoparticles. Finally, we have addressed some relevant findings on the importance of having well-defined synthetic routes to produce materials not only with similar physical features but also with similar crystallochemical characteristics.

Magnetic nanoparticles have been proposed for use as biomedical purposes to a large extent for several years. In recent years, nanotechnology has developed to a stage that makes it possible to produce, characterize and specifically tailor the functional properties of nanoparticles for clinical applications. This has led to various opportunities such as improving the quality of magnetic resonance imaging, hyperthermic treatment for malignant cells, site-specific drug delivery and the manipulation of cell membranes. To this end a variety of iron oxide particles have been synthesized. A common failure in targeted systems is due to the opsonization of the particles on entry into the bloodstream, rendering the particles recognizable by the body's major defence system, the reticulo-endothelial system. This review discusses each of the above bio-applications of such magnetic nanoparticles and details some of the main recent advances in biological research.

We apply the periodic time-dependent Ginzburg–Landau model to study vortex distribution in type-II superconductors with a point-like defect and square pinning array. A defect site will pin vortices, and a periodic pinning array with right geometric parameters, which can be any form designed in advance, shapes the vortex pattern as external magnetic field varies. The maximum length over which an attractive interaction between a pinning centre and a vortex extends is estimated to be about 6.0ξ. We also derive spatial distribution expressions for the order parameter, vector potential, magnetic field and supercurrent induced by a point defect. Theoretical results and numerical simulations are compared with each other and they are consistent.

Polycrystalline samples of nominal La_2/3Ca_1/3Mn_1−xCu_xO₃ (x = 0% and 4%) were fabricated by a sol–gel method following sintering treatments at temperature T_s ranging between 1000°C and 1300°C. Experiments indicate that doping Cu does not cause a change in crystalline structure, but strongly affects transport and magnetoresistance (MR) properties. For lower T_s, when a low magnetic field of H = 0.3 T, is applied, the x = 0 samples show typical intergrain MR behaviour with a monotonic increase in MR₀(≡ Δρ/ρ(H = 0)) on cooling; while for the x = 4% samples, in addition to intergrain MR, a characteristic feature similar to colossal MR (CMR) is observed near the insulator–metal transition. The maximum MR with a value ∼80% of that for H = 0.3 T is obtained in the sample prepared at 1100°C, which is comparable to the intrinsic CMR response usually observed in large fields of the order of several teslas.

The enhancement of structural anisotropy and magnetic anisotropy in ferrite films, Fe_3−xM_xO₄ (M = Fe, Co, Mn), which were deposited on glass substrates from aqueous solutions by thin liquid film (TLF) method at a low temperature (358 K), was compared in x-ray diffraction, conversion electron Mössbauer spectroscopy, and vibrating sample magnetometer measurements. The experimental results showed that the highly coercive Fe_3−xCo_xO₄ films, maximum coercivity of 0.21 T at room temperature, have a preferential growing direction along the magnetic easy axis of the magnetite, ⟨111⟩. While anisotropy was enhanced by the addition of Co²⁺ ions in the reaction solution, no enhancement was observed in the TLF-films of Fe₃O₄ and Fe_3−xMn_xO₄. The enhanced anisotropy is probably caused by the extra stabilization energy of the Co²⁺ ions in the octahedral sites of the spinel and the interactions between the Co²⁺ ions in the spinel. The alternating deposition of metal ions and oxide ions in TLF process, which is a simulation of the atomic layer deposition, may help the alignment. The most anisotropic TLF film was Fe_2.59Co_0.41O₄.

The angular dependence of magnetization reversal in square nanomagnets has been studied by means of micromagnetic simulations. Small nanosquares (L ⩽ 20l_ex, l_ex = (A/2πM_s)^1/2) exhibit quasi-coherent reversal and a monotonic decrease in the switching time as the applied field angle deviates from being anti-parallel to the initial magnetization. It is found that the non-uniformities in the magnetization slow down the reversal process, whereas the thinness induced demagnetizing field fastens it. Large nanosquares (L = 40l_ex) present a peak in the angular dependence of the switching time due to the occurrence of a highly symmetric metastable state consisting of two 180° domain walls. Depending on the applied field direction, this state is annihilated via a change in the sense of rotation in the inner region of the nanosquare or via the penetration of two vortices at the element edges.

Hysteresis loop measurements using magnetooptic Kerr effect magnetometry in the low frequency region and magnetization dynamics measurements using high frequency permeametry are carried out to study the exchange anisotropy in Ni₈₁Fe₁₉/Ir₂₂Mn₇₈ bilayers. These two measurement techniques provide different exchange anisotropies for bilayers with thin Ir₂₂Mn₇₈ films. The observations can be understood by assuming that the AF grains break into domains due to the interface random field. By analysing the results from these two techniques, the interface coupling strength and the magnetic properties of the bilayers can be quantitatively determined.

A resolution-tunable double-crystal analyser was successfully applied, for the first time, to angle-resolved x-ray imaging. Tuning the resolution between 0.5'' and 2.3'' was done with small loss of peak intensity using a Si(220) double-crystal analyser. The angle-resolved images of a housefly were recorded on nuclear emulsion plates at various angular resolutions. Several methods to improve the angular resolution of the analyser are also proposed.

We study theoretically semiconductor optical amplifier (SOA) length effects on gain dynamics when a short saturating pulse (pump) is either co- or counter-propagative with the probe. More specifically, we focus our attention on SOA recovery dynamics and gain overshoot. Analysis is also given when the input probe power and input pump energy are increased for different SOA lengths.

By considering a monochromatic plane wave obliquely incident upon a planar layer of S-20 photocathode material, deposited upon a non-absorbing glass substrate, the distribution of optical power absorbed within the layer can be resolved. This is important to the question of photocathode efficiency, as the absorbed light excites photoelectrons within the photocathode which then may pass from the photocathode into the vacuum of the photomultiplier tube and be collected and multiplied. The calculation uses the measured complex permittivity of an extended red S-20 photocathode in the wavelength range, 375–900 nm. The results show that thin film effects are important within the photocathode, as they give rise to interesting power absorption profiles. This information is invaluable in predicting optimum photocathode thickness for wavelength selective applications. Electromagnetic waves that are obliquely incident upon the photocathode are also considered in both transverse electric and transverse magnetic polarizations.

Mid-infrared light emitting diodes which exhibit more than 7 mW (pulsed) and 0.35 mW dc output power at 3.3 μm and at room temperature have been fabricated by liquid phase epitaxy using Pb as a neutral solvent. Using Pb solution an increase in pulsed output power of between two and three times was obtained compared with InAs light emitting diodes (LEDs) made using rare-earth gettering. The performance improvements were attributed to a reduction in residual carrier concentration arising from the removal of un-intentional donors and structure defects in the InAs active region material. These LEDs are well matched to the CH₄ absorption spectrum and potentially could form the basis of a practical infrared CH₄ gas sensor.

A pulsed Townsend technique was used to measure the electron drift velocity, the longitudinal diffusion, and the effective ionization coefficients, and the limiting field strength for the binary mixtures of SF₆ with Ar and Xe. This paper covered a wide range of the density-reduced electric field strength E/N between 50 and 700 Td (1 Townsend (Td) = 10⁻¹⁷ V cm²). The content of SF₆ in the gas mixtures was varied over the range 1–90%. For the SF₆–Ar mixture, the electron drift velocities were found to be higher than those for pure SF₆, and conversely for the SF₆–Xe mixture. The above can be explained in terms of the larger momentum transfer cross-section for electrons in Xe than in Ar. The limiting field strength for the SF₆–Xe mixture was found to be higher than that for the SF₆–Ar one, but still lower than that for the SF₆–N₂ mixture.

This paper presents a simple model of the fragment in the cathode electrical arc root taking into account the physical phenomena occuring on the cathode surface and the sheath. The goal is the obtainment of characteristics values of the heat flux, the electrons, and atoms density in the sheath. Computation is carried out on a one-dimensional model with a coupling between the equation obtained in the sheath and an enthalpy model of the cathode to describe the temperature evolution. In the modelling, we introduce a friction zone above the sheath edge to characterize the heavy particle interactions. Numerical simulation shows that the ionic friction phenomenon deriving from ion–atom collision regulates the heat flux lightening the surface, and the crucial necessity to obtain a good evaluation of the cross section of the charge exchange.

A new chemically generated plasma source is reported. The presence of gaseous Rb⁺ or K⁺ ions with thermally dissociated hydrogen formed a low applied temperature, extremely low voltage plasma called a resonant transfer or rt-plasma having strong vacuum ultraviolet emission. We propose an energetic catalytic reaction involving a resonant energy transfer between hydrogen atoms and Rb⁺ or 2K⁺ since Rb⁺ to Rb²⁺, 2K⁺ to K + K²⁺, and K to K³⁺ each provide a reaction with a net enthalpy equal to the potential energy of atomic hydrogen. Remarkably, a stationary inverted Lyman population was observed; thus, these catalytic reactions may pump a cw HI laser as predicted by a collisional radiative model used to determine that the observed overpopulation was above threshold.

A sensitive, spatially resolved optical absorption spectroscopy experiment using synchrotron radiation on metal-halide high intensity discharge (MH-HID) lamps was performed. This experiment was used to measure the absolute column densities of ground and excited level Sc atoms, ground level Sc⁺ ions, and ground level Na atoms in a 250 W MH-HID lamp during operation. The column densities were Abel inverted and used to determine the arc temperature as a function of radius and the absolute electron density as a function of radius. Although most of these measurements were made using a one-dimensional spectrally-multiplexed experiment, a two-dimensional spatially and spectrally multiplexed experiment has also been demonstrated. The absolute density and temperature maps from this experiment were used to determine the absolute near-infrared output power from the MH-HID lamp as described in the companion paper (Smith et al 2003).

A study of the near-infrared (IR) emission from the arc of a metal-halide high intensity discharge (MH-HID) lamp with a sodium/scandium chemistry is reported. Radiometrically calibrated spectra from 0.7 to 2.5 μm were recorded as a function of position on the arc tube of a 250 W lamp. These spectra were analysed to determine the relative densities of Na and Sc atoms and the arc temperature as a function of radius. Information from these spectra, combined with absorption measurements in the companion paper (Bonvallet and Lawler 2003), were used to determine the absolute output power in the near-IR from the MH-HID lamp.

De-mixing of additives in a vertically-operated, ceramic DyI₃–CsI–Hg metal-halide arc lamp has been observed by examining the ratios of absolute elemental densities as a function of position. As the elemental densities have been obtained directly by x-ray induced fluorescence (Curry J J, Adler H G, Shastri S D and Lee W-K 2003 J. Appl. Phys.93 2359), this approach reveals the extent of mixing (or de-mixing) with no intervening assumptions about equilibrium, the local temperature, or the accuracy of partition functions. The metal additives in the arc studied show complex de-mixing. Depletion of Dy and Cs from the core is attributed to ambipolar cataphoresis. These same additives also exhibit a relative enhancement in a layer just outside the core before decreasing again toward the wall. Thermochemical data are used to derive radial distributions of molecular species given the experimentally obtained elemental densities and the gas temperature assuming a lamp operating pressure of 10⁶ Pa (10 atm).

Extreme ultraviolet spectroscopy was recorded on microwave discharges of helium with 2% hydrogen. Novel emission lines were observed with energies of q . 13.6 eV, q = 1, 2, 3, 7, 9, 11, or q . 13.6 eV, q = 4, 6, 8 less 21.2 eV corresponding to inelastic scattering of these photons by helium atoms due to excitation of He (1s²) to He (1s¹2p¹). The average hydrogen atom temperature was measured to be 180–210 eV versus ≈3 eV for pure hydrogen. The electron temperature T_e for helium–hydrogen was 30 500 ± 5% K compared to 7400±5% K for pure helium. Known explanations for the novel series of spectral lines and extraordinary broadening were ruled out.

Standard laser interferometry is used in dry etch fabrication of semiconductor and MEMS devices to measure etch depth, rate and to detect the process end point. However, many wafer materials, such as silicon are absorbing at probing wavelengths in the visible, severely limiting the amount of information that can be obtained using this technique. At infrared (IR) wavelengths around 1500 nm and above, silicon is highly transparent. In this paper we describe an instrument that can be used to monitor etch depth throughout a thru-wafer etch. The provision of this information could eliminate the requirement of an `etch stop' layer and improve the performance of fabricated devices.

We have added a further new capability by using tuneable lasers to scan through wavelengths in the near IR to generate an interference pattern. Fitting a theoretical curve to this interference pattern gives in situ measurement of film thickness. Whereas conventional interferometry would only allow etch depth to be monitored in real time, we can use a pre-etch thickness measurement to terminate the etch on a remaining thickness of film material.

This paper discusses the capabilities of, and the opportunities offered by, this new technique and gives examples of applications in MEMS and waveguides.

Applied voltage and gas pressure dependent electrical power deposition efficiencies in a short voltage pulse excited dielectric barrier discharge have been measured. The effect of time delay between the onset of gas breakdown, peak conduction current and the applied voltage pulse with increasing gas pressure leads to higher net power deposition at lower E/n, where E is the electric field and n is the gas density. An accurate measurement of the power deposition requires careful estimation of the displacement current with the applied voltage as the voltage time derivative dV/dt increases. The variation of optical emission intensity measurements of Ar 2p₁–1s₂, N₂ C–B and N₂⁺ B–X transitions with increasing gas pressure validated the conclusions reached from the time resolved electrical measurements.

This paper describes the use of dimensional analysis in investigating the effects of the electrical and the discharge configuration parameters on ozone production in oxygen, by means of a pulsed streamer discharge. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.

Low SF₆ content SF₆–N₂ mixtures have recently been proposed as a replacement for pure SF₆ in the insulation of gas insulated lines (GIL). Among the areas of investigation of such gas mixtures, their electrical decomposition under corona discharges must be studied considering the possible occurrence of such stress in GIL.

This paper presents data concerning the decomposition of high-pressure SF₆–N₂ (5 : 95) mixtures (400 kPa) submitted to negative dc coronas in the absence or presence of 0.3% H₂O or 0.3% O₂. The chemical stability of these mixtures is compared with that of SF₆–N₂ (10 : 90) mixtures or undiluted SF₆ investigated in the same conditions in a previous paper.

The corona discharges were generated with a point-to-plane set-up and the gaseous by-products were assayed by gas chromatography at the end of each run carried out over a range of transported charge covering 0–13 C. The following by-products were detected and assayed: SOF₄, SO₂F₂, (SF₄ + SOF₂), SO₂, S₂F₁₀, S₂O₂F₁₀, S₂O₃F₆, (SF₅)₂NF, NF₃ and N₂O.

Whatever the type or the concentration of impurity added to the SF₆–N₂ mixtures the major compound groups, (SOF₄ + SO₂F₂) and (SF₄ + SOF₂ + SO₂), were formed with 5% SF₆ in quantities very close to those observed with 10% SF₆. However, the lesser production rates of S₂F₁₀, (SF₅)₂NF and NF₃ measured with the most dilute SF₆–N₂ mixtures makes the use of SF₆–N₂ (5 : 95) more advantageous than that of SF₆–N₂ (10 : 90) in all cases.

Considering the overall quantity of by-products formed in the presence of water or without any impurity added, it appears that SF₆–N₂ mixtures are, from this point of view, preferable to pure SF₆.

Excitation of dielectric barrier discharge xenon excimer lamps by unipolar short square pulses is studied in this paper. Two discharges with different polarity are excited by each voltage pulse (double discharge phenomenon). The primary discharge occurs at the top or at the rising flank of the applied unipolar square pulse, which is directly energized by the external circuit. The secondary discharge with the reversed polarity occurs at the falling flank or shortly after the falling flank end (zero external voltage) depending on the pulse width, which is energized by the energy stored by memory charges deposited by the primary discharge. Fast-speed ICCD imaging shows the primary discharge has a conic discharge appearance with a channel broadening on the anode side. This channel broadening increases with increasing the pulse top level. Only the anode-side surface discharge is observed in the primary discharge. The surface discharge on the cathode side which is present in bipolar sine voltage excitation is not observed. On the contrary, the secondary discharge has only the cathode-side surface discharge. The surface discharge on the anode side is not observed. The secondary discharge is much more diffuse than the primary discharge. Time-resolved emission measurement of double discharges show the secondary discharge emits more VUV xenon excimer radiation but less infrared (IR) xenon atomic emission than the primary discharge. It was found that the IR xenon atomic emission from the secondary discharge can be reduced by shortening the pulse width. The energy efficiency of unipolar-pulsed xenon excimer lamps (the overall energy efficiency of double discharges) is much higher than that obtained under bipolar sine wave excitation. The output VUV spectrum under unipolar pulse excitation is found to be identical to that under sine wave excitation and independent of injected electric power.

Erosion that occurred during arc shut down was investigated. The arc current was 200 A; the cathode was made of hafnium. Different gases were used: oxygen, nitrogen, and noble gases (argon, helium, and hydrogen–argon mixture). The gas pressure was 3 atm. It was shown that erosion in noble gases is higher compared to gases that create chemical compounds with hafnium (oxygen and nitrogen). The following model of arc-off erosion is suggested. An amount of plasma gas is diluted in the molten tip of the cathode. When the arc is terminated, the gas pressure in the cathode vicinity drops down. The diluted gas then leaves the molten puddle and carries some liquid material with it.

A transition from a negative regime to positive streamers in a guiding field has been studied. The apparatus is a simple parallel plane electrode arrangement that provides the uniform guiding field. Negative streamers were generated by a pulsed negative voltage of magnitude ≈5 kV and duration ≈270 ns applied to a trigger pin electrode placed in an aperture at the centre of the grounded electrode and insulated from it by air. It has been shown that the velocities of streamers was between 4×10⁴ and 1.5×10⁵ m s⁻¹ over an external guiding field range of 5.5–6.3 kV cm⁻¹. Results have been presented showing the variation of field in the mid-gap region and the characteristics of streamers. Optical observations have shown the light emission from the developing discharge to be non-linear.

A long laminar plasma jet has adjustable high-temperature region length, small temperature and velocity gradients in the axial direction, low noise emission and weak entrainment of ambient air into the jet, and thus it has potential applications in materials processing. A three-dimensional modelling approach is used in this paper to study the spatial distributions of plasma parameters in the long laminar plasma jet for the case with and without lateral injection of particulate matter and its carrier gas. The combined diffusion coefficient method is employed in the modelling to treat the diffusion of ambient air into the plasma jet. Typical computed distributions of temperature, velocity and species concentration in the jet are presented using the long laminar argon plasma jet issuing into ambient air as a calculation example. It is shown that similarly to the turbulent plasma jet case, the long laminar plasma jet has good enough stiffness to endure the impact of the laterally injected carrier gas, although the laminar jet assumes slight deflection from its original geometrical axis in the injection plane due to the action of laterally injected carrier gas. The three-dimensional effects caused by the lateral carrier-gas injection on the jet characteristics and thus on the particle moving trajectories and heating histories are shown to be appreciable. Particulate matter can be fed into the high-temperature region of the laminar plasma jet with the aid of the carrier gas.

We obtain an effective parametrization of the bulk electronic structure of InP within the tight-binding scheme. Using these parameters, we calculate the electronic structure of InP clusters with the size ranging up to 7.5 nm. The calculated variations in the electronic structure as a function of the cluster size is found to be in excellent agreement with experimental results over the entire range of sizes, establishing the effectiveness and transferability of the obtained parameter strengths.

Quantification of low Z elements like oxygen by energy-dispersive x-ray spectrometry requires x-rays absorption correction even the in the case of thin films analysis in scanning transmission electron microscope. Absorption correction needs the knowledge of the sample local mass thickness. The purpose of this paper is to propose a method which allows the obtainment of the sample local mass thickness and then permits the quantification of all the elements of the sample using the quantification ratio method. Combining electron energy loss spectroscopy measured relative specimen thickness, and x-rays characteristic peaks intensities, we determine with an iterative process the local mass thickness and the absorption corrected elemental weight concentrations. We validate our method with four standard samples (SiO, SiO₂, CaSiO₃ and Li₄SiO₄) by the determination of the O/Si atomic ratio. We also ensure the method by analysing a native bioactive glass sample of known composition and of inhomogeneous mass thickness.

Room temperature deposition of biaxially textured yttria-stabilized zirconia (YSZ) films on amorphous glass substrates was successfully achieved by conventional pulsed-laser deposition. The influence of the surrounding gases, their pressure and the deposition time on the structure of the films was studied. A columnar growth process was revealed based on the experimental results. The grown biaxial texture appears as a kind of substrate independence, which makes it possible to fabricate in-plane aligned YSZ films on various substrates.

Au/Pd bimetallic nanoparticles, even with core–shell structure, were synthesized by successive and simultaneous sonochemical irradiation of their metal precursors in ethylene glycol, respectively. In the successive method, Pd clusters or nanoparticles are first obtained by reduction of Pd(NO₃)₂, followed by adding HAuCl₄ solution. As a result, Au-core/Pd-shell structured particles are formed, instead of Pd-core/Au-shell as usually expected. The successive method is more effective than the simultaneous one in the formation of the core–shell structure. Detailed investigation with optical absorption spectroscopy suggested that the pre-formed Pd atoms or clusters have a reduction effect on Au³⁺ ions and the post-formation of Pd-shell can damp the surface plasmon resonance of Au nanoparticles. Theoretical absorption spectra based on Mie-like model for core–shell structured particles yield excellent agreement with the experimental results.

Effects of uniaxial stress on the dielectric properties of ceramics in lead magnesium niobate–lead zirconate titanate (PMN–PZT) system are investigated. The ceramics with a formula (x)Pb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.52Ti_0.48)O₃ or (x)PMN–(1 − x)PZT when x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 are prepared by a conventional mixed-oxide method. Phase formation behaviour and microstructural features of these ceramics are studied by x-ray diffraction and scanning electron microscopy methods, respectively. The dielectric properties under the uniaxial stress of the PMN–PZT ceramics are observed at stress levels up to 5 MPa using a uniaxial compressometer. It is found that with increasing applied stress the dielectric constant of the PZT-rich compositions increases slightly, while that of the PMN-rich compositions decreases. On the other hand, the dielectric loss tangent for most of the compositions first rises and then drops with increasing applied stress.

In our laboratory, we combine accurate electromagnetic radiation (EMR) measurements during fracture of rocks (carbonate and igneous) and transparent materials (glass, PMMA and glass ceramics) with careful fractographic methods. A critical analysis of experimental observations, accumulated here during the last decade together with supporting material from the works of other authors are used in this study to demonstrate the failure of all current models to explain the properties of EMR arising from fracture. The basic elements of a new model are proposed. These are (a) the EMR amplitude increases as long as the crack continues to grow, since new atomic bonds are severed and their contribution is added to the EMR. As a result, the atoms on both sides of the bonds are moved to `non-equilibrium' positions relative to their steady state ones and begin to oscillate collectively in a manner similar to Debye model bulk oscillations—`surface vibrational optical waves'; (b) when the crack halts, the waves and the EMR pulse amplitude decay by relaxation. These basic elements are already enough to describe the characteristics of the experimentally obtained isolated individual EMR pulses. These characteristics include the shape of the EMR pulse envelope, and the frequency, time duration and rise–fall time of the pulse.

The theory of the modal expansion method for the transient electromagnetic fields inside a closed region is reviewed. Although the concept of modal expansion is well known in the theory of electromagnetism, this formulation may make it more comprehensive where the scope of applicability, the effect of surface excitations, and the introduction of real modal fields to avoid complex notations in the time-domain formulation is concerned. It can be shown that, without resorting to the explicit expression for the quasi-static solution, which should be used to satisfy the inhomogeneous boundary conditions, the transient responses of EM fields inside a closed region could be expressed explicitly in terms of the natural modes of the system. This formulation assumes an arbitrarily inhomogeneous anisotropic material, volume and surface sources of arbitrary temporal and spatial dependence, and arbitrary initial electric and magnetic field distributions. For simplicity, the effects of losses are neglected in this formulation.

The characteristics of the laser-induced plasma encountered in laser welding are investigated using a new three-dimensional modelling approach. A simplified keyhole model is employed to couple with our previous plasma plume model, and thus both the plasma inside a blind keyhole and the plasma plume issuing from the keyhole can be treated simultaneously. Investigations include the effects on the laser-induced plasma characteristics of many factors, including the velocity of metal vapour leaving from the keyhole bottom, the velocity of the shielding gas injected coaxially with the laser beam, the velocity and location of the assisting gas injected laterally with respect to the workpiece, and the energy absorption and radiation heat loss of the laser-induced plasma. Typical computed distributions of temperature, velocity and vapour concentration within the plasma are presented with the continuous-wave CO₂ laser welding of iron workpiece as the calculation example. It is shown that the high-temperature core of the laser-induced plasma is mostly located inside the blind keyhole or near the keyhole top for the cases under study. The metal-vapour/shielding-gas momentum ratio plays an important role in determining the height of the plasma plume, and the plume height decreases with increasing shielding-gas velocity. The laterally injected assisting gas may also significantly affect the laser-induced plasma characteristics and thus can be used to control the unfavourable effect of the laser-induced plasma on the laser welding process. The predicted temperatures of the laser-induced plasma are reasonably consistent with corresponding experimental data.

We extend the Rayleigh method for the calculation of the effective conductivity to three-phase composite materials. The materials under study consist of two types of circular cylinders in a periodic arrangement embedded in a matrix. Highly accurate values for lattice sums were obtained using algorithms which have been recently developed. A series of explicit formulations, which are used to facilitate the calculation of the effective conductivity of the composites under study, are reported. We also perform a series of numerical calculations to study the behaviour of these composites.

In much pulsed power experimentation a capacitor bank is discharged into an inductive load, but although sufficient energy may be available in the capacitors their voltage rating may considerably exceed that necessary for the load and the current delivered during the experiment may accordingly be too low. This paper describes a novel design of air-cored transformer that has been used as an interfacing or matching device in such a situation, where peak load currents between 1 and 2 MA were required.

Design considerations led to the use of an air-cored autotransformer connection wound with copper sheet conductors. Although thick wide conductors and clamping are needed to prevent deformation due to high magnetic pressure, the transformer is nevertheless relatively simple, easy to make, lightweight and inexpensive.

This paper describes the design and the winding arrangement of the transformer that was constructed, and presents typical experimental results.