Table of contents

The compressive stress in diamond films formed by hot filament chemical vapour deposition is reduced by implantation of carbon ions into alumina substrates before the deposition of diamond films. It is found that the stress in the diamond films decreases linearly with the increment of the C⁺ implantation dose. The reason for the decrease in the compressive stress is explained in terms of the offset by the residual compressive stress in the alumina substrates, which is caused by the ion pre-implantation.

Hydrocarbon fuels have specific energy contents some two orders of magnitude greater than any electrical storage device. They therefore proffer an ideal source in the universal quest for compact, lightweight, long-lasting alternatives for batteries to power the ever-proliferating electronic devices. The motivation lies in the need to power, for example, equipment for infantry troops, for weather stations and buoys in polar regions which need to signal their readings intermittently to passing satellites, unattended over long periods, and many others. Fuel cells, converters based on miniaturized gas turbines, and other systems under intensive study, give rise to diverse practical difficulties. Thermoelectric devices are robust, durable and have no moving parts, but tend to be exceedingly inefficient. We propose regenerative combustion systems which mitigate this impediment and are likely to make high performance small-scale thermoelectric power generation applicable in practice. The efficiency of a thermoelectric generating system using preheat when operated between ambient and 1200 K is calculated to exceed the efficiency of the best present day thermoelectric conversion system by more than 20%.

The advanced characteristics of synchrotron x-ray sources make it possible to implement radiology with powerful and innovative approaches. We review in simple terms the conceptual background of such approaches, then we present a number of selected examples. The practical tests concern life-sciences specimens as well as materials-science systems.

The microwave properties of chromium-doped mono-crystalline yttrium aluminium garnet (Y₃Al₅O₁₂ : YAG) were determined between 6 K and room temperature. It exhibited very strong microwave losses near 15.5 GHz. The mechanism producing the losses was found to follow standard Curie law behaviour below 30 K. In combination with the thermal expansion of the material, the magnetic characteristics produced turning points in the mode frequency-temperature dependence at 60 K. Analysis showed that the Cr³⁺ doping into the dielectric lattice resulted in an anisotropic paramagnetic susceptibility, which was resolvable at temperatures below 77 K. Room temperature data also indicated anisotropic susceptibility due to Cr³⁺ ions with the addition of another species with a loss peak near 20 GHz. Zero field splitting of the ground state energy level equivalent to 0.76 K and an excited state energy level 29 K above the ground state of the Cr³⁺ ions was confirmed. The lifetime of the excited state was found to be very temperature dependent and below 100 K was dominated by the Raman two-phonon scattering process.

Magnetic insulation is the only practicable form of insulation for much equipment used in ultrahigh pulsed-power work, including transmission lines and plasma opening switches. It has not however so far been successfully exploited in the transformers that are necessarily involved, and the first proposed design that appeared more than 30 years ago raised apparently insuperable problems.

The two novel arrangements for a magnetically insulated transformer described in this paper overcome the problems faced by the earlier designs and also offer considerable scope for development in a number of important areas. Theoretical justification is given for their insulating properties, and this is confirmed by proof-of-principle results obtained from a small-scale experimental prototype in which magnetic insulation was demonstrated at up to 100 kV.

The photostability of rhodamine 6G, rhodamine 610 and pyrromethene 567 in solutions, wet-gel and dried sol-gel host media has been determined. A method for the synthesis of xerogel monoliths has been modified to reduce the preparation time for the doped sol-gel samples, and high optical quality sol-gel samples doped with laser dyes have been prepared. A high efficiency and photostability is observed for xanthene laser dyes in wet and dried sol-gel phases but not for a pyrromethene laser dye.

For the first time for a ZnGeP₂ crystal, the three-wave interaction of picosecond pulses was considered as the difference frequency generation. The group velocities and absorption of radiation were taken into account in performing a spectral analysis. The calculations of a radiation pulse were made for the following parameters of a CO₂ laser: 100-1.25 ps and 15-1100 GW cm^-2. At the 804.5 µm wavelength of difference frequency, the spectral characteristics have been obtained and the pulse power has been found as a function of crystal length. The half-cycle pulse generation is possible at a particular crystal length.

The hexagonal wurtzite GaN nanowires embedded in the nanochannels of anodic alumina membrane were achieved by the direct reaction of Ga vapour with a constant flowing ammonia atmosphere. X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy were used to measure the size and structures of the samples. The Raman scattering spectrum of ordered GaN nanowires was studied. The Raman spectrum of the GaN nanowire arrays is consistent with the hexagonal wurtzite structure GaN, in agreement with XRD observation. The E₂(high), E₁(TO), and A₁(TO) phonon frequencies at 563, 553, and 529 cm^-1 show the low-energy shifts, respectively. The shifts and band broadening of the Raman modes result from the nanosize effect.

A simple analytical method is proposed to predict the maximum plasma power for a torch of given geometry. Experiments were conducted on two torches of different diameters. The results indicate that reasonable estimates of plasma power can be made for a range of gas flow rates by monitoring the temperature rise at the final segment of the torch. It has also been shown that this method can be used as a design tool for the engineering scale-up of plasma torches.

It is clearly seen that the application of non-thermal plasmas (NTP) to remove NO_x from gas mixture containing a large amount of oxygen (O₂) is dominated by NO to NO₂ oxidation. Experiments have been conducted using a NTP generated by a nanosecond pulsed dielectric barrier discharge in synthetic exhaust gas, prepared from N₂, O₂, NO, H₂O, and C₃H₆, over a large range of gas temperature (20-300\r{}C). Results show that the NO_x removal rate significantly increased with increasing specific energy deposition. For example, at a temperature of 100\r{}C and an energy deposition of 27 J l^-1, 92% of the NO molecules have been removed. The W values for NO is dramatically reduced to values scaling from ≈15 eV at 27 J l^-1 down to ≈4 eV at 7 J l^-1. NO_x removal efficiency around 43% was obtained at a temperature of 260\r{}C and a space velocity of 60 000 h^-1 for a specific input energy of 27 J l^-1. W values for NO_x were less than ≈30 eV. Such treatments in exhaust gas with and without the presence of water vapour induced reactions leading to the production of a large variety of by-products such as acetaldehyde, propylene oxide, formic acid, methyl nitrate, and nitromethane.

Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO₃ thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant.

Optical and microstructural properties of polycrystalline CuGaTe₂ films deposited by three source co-evaporation technique are presented. Two characteristic bandgaps were detected at 1.24 and 1.69 eV corresponding to allowed direct transition and forbidden direct transition respectively. Microstructure was studied by x-ray diffraction (XRD) and SEM/TEM. Harris texture analysis of the XRD data indicated (112) to be the predominant orientation for stoichiometric composition of CuGaTe₂ films with Cu/Ga~1.0 whereas (204) orientation was most predominant for the off-stoichiometric films having excess Cu or excess Ga. Variation of Urbach tail width with Cu/Ga ratio was studied. The films had a rough surface, and the surface roughness of the films obtained from diffused reflectance measurement indicated a variation within 32-58 nm.

CdS nanoparticles with the size less than 2 nm were formed within the Langmuir-Blodgett (LB) films. Size distribution of CdS nanoparticles in different LB films and its further transformations were studied by UV-visible adsorption spectroscopy. The Lifshitz-Slezov diffusion model was generalized for the two-dimensional case, and the resulting time-dependent equations were simulated in order to explain the observed behaviour.

The process of thin film deposition from a gas phase in long narrow channels has been theoretically described. The analytical expressions have been derived for the function of coating thickness distribution along the channel for an arbitrary deposition mechanism. Universal quantitative criteria have been obtained which characterize the degree of coating thickness uniformity or conformal ability of the film-forming substance. The coating thickness distribution in any channel is shown to be described in relative coordinate system by universal distribution curve dependent on the process parameters only, but not on the shape and dimensions of a channel. The prospects of using the simulation results in different processes of coating deposition are discussed. The results obtained can be quantitatively applied to deposition processes of one-component coating such as poly-p-xylylene one. A method is proposed to improve the coating thickness uniformity applicable to various gas-phase deposition processes including deposition of poly-p-xylylenes with high limiting temperature of polymerization, such as PPX-C and PPX-D. The methods are also proposed to evaluate the main characteristics of the deposition process using film thickness distribution in narrow channels. The model is verified by experimental results.

For the thickness determination of thin coatings on substrate in scanning electron microscopy using x-ray energy dispersive spectrometry, a method called Auger formalism has been established in our laboratory. It consists of applying a formalism derived from that in the Auger spectroscopy which assumes a linear relationship between the signal intensity emitted by the coating and its thickness.

In this paper, a development of the Auger formalism in the case of heterogeneous coatings is presented. Using x-ray energy dispersive spectrometry, this method allows one to determine the atomic concentrations of the elements which composed the coating. The capability of the proposed method is illustrated by two different applications: a Ni-Cu film on titanium alloy substrate (academic specimen) and calcium phosphate film on titanium alloy substrate (prosthetic coating). An iterative procedure established for the proposed method is also presented. The results show that the Auger formalism may now be applied not only to simple coatings for thickness determination but also to the complex ones for concentration determination. And its use does not require the local knowledge of the substrate composition which is not accessible in the Auger spectroscopy.

The time evolution of the inhomogeneous curing process of polystyrene emulsions is studied using a variant of the conventional photoacoustic (PA) technique. The thermal effusivity, as a function of time, is determined in order to monitor the sintering process of a styrene emulsion in different steps of the manufacturing procedure. PA measurements of thermal effusivity show a sigmoidal growth as a function of time during the curing process. The parameterization of these curves permits the determination of the characteristic curing time and velocity of the process. A decreasing of the curing time and an increasing curing velocity for the final steps of the manufacturing process are observed. The feasibility of our approach and its potentiality for the characterization of other curing process are discussed.

Using a torsion pendulum, the features of spontaneous twisting of several ferroelastic crystals at a temperature variation near the phase transition points have been studied as a function of a crystallographic orientation, a thermal and mechanical history, and an external static shear stress. It was assumed that a torque arises at the Curie point because of the specific domain structure organization resulted in the predominant formation of that certain domain types.

The Pb(Zr,Ti)O₃ (PZT) ceramics with Zr/Ti ratios of 30/70, 52/48 and 70/30 and the PZT(52/48) ceramics doped with La, Ta and Co at various percent were prepared by a standard solid-state reaction method, respectively. Internal friction and modulus were measured as a function of temperature at low frequencies by using a inverted torsion pendulum. Two internal friction peaks (P₁ and P₂), related to oxygen vacancies and domain walls, respectively, were observed in all the undoped PZT ceramics with different Zr/Ti ratios. In addition, a minimum in modulus associated with a phase transition internal friction peak appearing at Curie temperature was observed in all samples. The effects of the Zr/Ti ratios and some dopants (such as La, Ta and Co) on the internal frictions were investigated. The internal friction results indicate the changes of the concentration of oxygen vacancies and the domain structure with the variations of Zr/Ti ratios and dopants, which will be helpful in the utilities of the PZT ceramics.

Laser Doppler interferometry has been used to determine the strain and piezoelectric response of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) electrostrictive ceramics as a function of electric fields up to 4 MV m^-1, frequencies between 0.1 Hz and 2.5 kHz and DC bias fields up to 3 MV m^-1. The strain and polarization of PMN-15 with a composition of 0.9PMN-0.1PT and PMN-38 with a composition of 0.85PMN-0.15PT both produced by TRS ceramics, have been measured at room temperature. The strain and polarization responses of PMN-15 ceramics under an electric field up to 4 MV m^-1 have been fitted to a polynomial model. The results suggest that a quadratic dependence of strain on polarization is not valid for large electric fields and that higher-order terms must be included. Our measurements showed that the effective piezoelectric coefficient, d₃₃, of PMN-15 ceramics had a maximum value of 800 pm V^-1 at a bias field of 0.67 MV m^-1 and had little frequency dependence in the frequency range from 1 Hz up to 2.5 kHz. PMN-38 ceramic showed a maximum d₃₃ of 1200 pm V^-1 at a bias field of 0.43 MV m^-1 and the d₃₃ of this material showed a clear frequency dependence from 1 Hz up to 2.5 kHz.

This paper presents a physico-chemical and an electrical study of a low-density polyethylene used in cable insulation. The first part deals with the effect of temperature on morphology and the consequences on the conduction properties. Next, the influence of cross-linking by-products and antioxidant is studied. The analysis of the current measurements had led us to retain the Nath and Perlman model for the conduction mechanism in our films. The good agreement between theory and experiment in the high-field region allows us to evaluate a parameter related to the trap site separation distance whose variation with temperature and morphology is analysed.

Thermally stimulated luminescence of natural mineral petalite (LiAlSi₄O₁₀) crystals was investigated and the possible electron/hole traps responsible for thermoluminescence (TL) emission were identified using optical absorption and electron paramagnetic resonance (EPR) measurements. The glow curves for natural samples, obtained with a heating rate of 4C s^-1, show two glow peaks at 160°C and 330°C. Pre-annealed and subsequently irradiated samples give rise to three glow peaks at 175°C, 340°C and 435°C. An isochronal thermal study established correlation between the first glow peak and Ti³⁺-like trap centre and E'₁-centre and Al-O^--Al-like recombination centres. The second TL peak at 340°C may be related to the E'₁ centres formed on irradiation. A mechanism for the observed TL is suggested.

Differential algebraic method is a powerful and promising technique in computer numerical analysis. When applied to nonlinear dynamics systems, the arbitrary high-order transfer properties of the systems can be computed directly with high precision. In this paper, the principle of differential algebra is applied to study on the time of flight (TOF) property of electron optical systems and their arbitrary order TOF transfer properties can be numerically calculated out. As an example, TOF transfer properties of a uniform magnetic sector field analyzer have been studied by differential algebraic method. Relative errors of the first-order and second-order TOF transfer coefficients of the magnetic sector field analyzer are of the order 10^-11 or smaller compared with the analytic solutions. It is proved that differential algebraic TOF method is of high accuracy and very helpful for high-order TOF transfer property analysis of electron optical systems.

The formation and stability of stationary laser weld keyholes are investigated using a numerical simulation. The effect of multiple reflections in the keyhole is estimated using the ray tracing method, and the free surface profile, flow velocity and temperature distribution are calculated numerically. In the simulation, the keyhole is formed by the displacement of the melt induced by evaporation recoil pressure, while surface tension and hydrostatic pressure oppose cavity formation. A transition mode having the geometry of the conduction mode with keyhole formation occurs between the conduction and keyhole modes. At laser powers of 500 W and greater, the protrusion occurs on the keyhole wall, which results in keyhole collapse and void formation at the bottom. Initiation of the protrusion is caused mainly by collision of upward and downward flows due to the pressure components, and Marangoni flow has minor effects on the flow patterns and keyhole stability.

Electric-field dependent ion mobility is calculated in the framework of the two-temperature displaced-distribution theory. The considered approach provides a better accuracy than the conventional approach based on (the first approximation in) the two-temperature theory and is better justified for the case of heavy ions, while being not much more complicated than the conventional approach. Calculated ion mobilities are in good agreement with experimental data.

Chemical mechanical polishing (CMP) is a key technique for wafer global planarization. Many studies have been conducted in recent years to analyse the slurry flow between a pad and a wafer due to its importance in CMP processing. In these studies, however, the grains in the slurry were not considered. Thus this investigation uses a grain flow model to analyse the slurry flow between wafer and pad. The proposed model predicts the film thickness of the slurry flow with various convex wafer curvature radius under a variety of the CMP parameters including load, rotation speed and grain size. The theoretical results compare well with experimental data in the literature. This study elucidates grain flow during CMP processing and further contributes to understanding of the CMP mechanism.

By application of dielectrophoresis neuronal cells can be trapped successfully. Several trapping experiments have been performed using a quadrupole electrode structure at different amplitudes (1, 3, and 5 V_pp) and frequencies (10-50 MHz). Due to the high conductivity of the suspending medium negative dielectrophoretic forces are created. The dielectrophoretic force is determined by the gradient of the electric field. However, the electrode-liquid interfaces are responsible for decreased electric field strengths, and thus decreased field gradients, inside the medium, especially at lower frequencies. Circuit modelling is used to determine the frequency-dependent electric field inside the medium.

The creation of an electric field in high conductivity of the medium results in local heating, which in turn induces fluid flow. This flow also drives the neurons and was found to enhance the trapping effect of the dielectrophoretic force. With the use of finite element modelling, this aspect was investigated. The results show that the dielectrophoretic force is dominating just above the substrate. When the upward dielectrophoretic force is large enough to levitate the cells, they may be dragged along with the fluid flow. The result is that more cells may be trapped than expected on the basis of dielectrophoresis alone.

Ti₃SiC₂ exhibits a unique combination of ceramic and metallic properties suitable for both electrical and mechanical application. With high-temperature stability, high electrical and thermal conductivity and resistance to oxidation, Ti₃SiC₂ has proven promising as a contact layer for high power SiC semiconductors. However, until recently, synthesis of this material has proven difficult without appreciable quantities (<2 vol{%}) of impurity phases, namely TiC_1-x and Ti₅Si₃C_x. As such, many properties of this compound are as yet unknown. In this paper, a comparable analysis of Ti₃SiC₂ and associated compounds, TiC and Ti₅Si₃C_x has been performed using both x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Assessing impurity sensitivities for each technique, XRD was shown to readily identify impurities of TiC and Ti₅Si₃C_x within Ti₃SiC₂ at <2 wt{%}. Although XPS could not independently resolve these impurities, its use resulted in the detection of a complex oxide structure on Ti₃SiC₂. It was speculated that it was composed of mixed C-Ti-C-O and Si-Ti-C-O bond chemistries. In a comparison of TiC, Ti₅Si₃C_x and Ti₃SiC₂, differences in oxide states suggest that oxidation is chemically dissimilar for all the three compounds. However, upon etching, the binding energies of Ti₃SiC₂ and Ti₅Si₃C_x were shown to be very similar. It may be concluded that a concurrent analysis of both XRD and XPS was essential for identifying the overall surface chemistry of Ti₃SiC₂.