Table of contents

Solid particle erosion of metals and alloys at elevated temperature is governed by the nature of the interaction between erosion and oxidation, which, in turn, is determined by the thickness, pliability, morphology, adhesion characteristics and toughness of the oxide scale. The main objective of this paper is to critically review the present state of understanding of the elevated temperature erosion behaviour of metals and alloys. First of all, the erosion testing at elevated temperature is reviewed. This is followed by discussion of the essential features of elevated temperature erosion with special emphasis on microscopic observation, giving details of the erosion–oxidation (E–O) interaction mechanisms. The E–O interaction has been elaborated in the subsequent section. The E–O interaction includes E–O maps, analysis of transition criteria from one erosion mechanism to another mechanism and quantification of enhanced oxidation kinetics during erosion. Finally, the relevant areas for future studies are indicated.

The optimization of the linear, first-order, Faraday effect in absorbing, ultra-thin, magnetic films is considered both analytically and by numerical simulations. Enhancement using one-dimensional magnetophotonic crystals is considered in parallel with a discussion of the principles of enhancement through an appreciation of the optical resonances that occur in the Fabry–Perot etalon. Simple formulae are presented for the approximate upper limits of enhancement and the associated photometric parameters of the system that accompany optimal conditions. For a 1 nm thick cobalt layer the degree of enhancement is approximately a factor of 4 greater than can be achieved with a single layer. The validity of the formulations is confirmed by numerical simulations based on the use of cobalt as the magnetic medium.

The magnetocaloric effect (MCE) is studied in CeFe₂ and Ru-doped CeFe₂ alloys with dc magnetization measurements. The pure CeFe₂ compound shows a distinct peak in MCE around the paramagnetic to ferromagnetic transition. In Ru-doped CeFe₂ alloys there is a further transition from the ferromagnetic to antiferromagnetic state at low temperatures. This latter magnetic transition gives rise to a relatively large inverse MCE. A comparative study of the MCE associated with two different magnetic transitions is made and the possible role of a structural transition in the inverse MCE is discussed.

We investigated one dimensional magnetophotonic crystals consisting of a cavity containing a magnetic layer between two Bragg reflectors. This structure can be made very efficient to obtain a localized mode with enhanced Faraday rotation. In this paper, the parameters of the magnetic layer (thickness and position within the cavity) were systematically varied in order to find theoretically the most efficient structure according to a figure-of-merit. A significant enhancement of the Faraday rotation, θ_F, by a factor of twelve is found compared with a single cobalt layer. Our calculations show the possibility of using this huge enhancement for ultrathin magnetic layer studies. The experimental spectrum of the ellipsometric parameter tan(Ψ) agrees with the calculated results.

FePt and FePtCu thin films with a fixed thickness of 50 nm have been prepared by magnetron sputtering. The atomic ratio of Fe to Pt atoms was accurately controlled by dc co-sputtering. After vacuum annealing for 20 min at 350 °C, a coercive force of about 605 kA m⁻¹ is obtained in the Fe₅₂Pt₄₈ thin films with an ordering parameter around 0.87. The ordering parameter of the L1₀ phase is not enhanced by the addition of Cu to Fe₅₂Pt₄₈ films. On the contrary, the ordering process is improved by the addition of Cu to the Pt-rich or stoichiometric thin films. To keep the ordering of FePt films at a low annealing temperature, the lower the Fe content, the more addition of Cu is needed. It is found that the L1₀ phase can be obtained after annealing at 350 °C for 20 min only for films with the ratio of (FeCu) to Pt being in the range of 1.1–1.2.

(BiFeO₃)_1−x–(PbTiO₃)_x solution films have been prepared on LaNiO₃/SiO₂/Si substrates by the sol–gel process at an annealing temperature of 500 °C. X-ray diffraction patterns indicate that a cubic phase transition occurs in the film with x = 0.1. Cross section scanning shows the thickness of the films is about 470 nm. Coexistent ferroelectricity and magnetism at room temperature are observed by measuring ferroelectricity and magnetism. The study of ferroelectricity indicates that the remnant polarization and applicable drive field are increased by the ratio x of PbTiO₃. The film with x = 0.05 has the maximum saturation magnetization. In addition, dielectric property as a function of frequency is studied.

Two-phase composites LCBMO/Pd_x were synthesized using the sol–gel technique followed by the solid-state reaction. Pd addition induces a remarkable decrease in resistivity, which is mainly related to the improvement of grain boundaries/surfaces caused by the segregation of Pd. The resistivity data for all samples follow the adiabatic small-polaron-hopping model at high temperature above the Curie temperature T_C, while in the low temperature region, they are proportional to T², reflecting that the electron–electron scattering mechanism is dominant in the ferromagnetic metallic state. In addition, Pd addition induces a large enhancement of room temperature magnetoresistance (MR). Especially for the x = 0.27 sample, an extra large magnetoresistance over 170% is obtained at 10 kOe and 289 K. This is the largest MR obtained at room temperature in all kinds of colossal magnetoresistance (CMR) materials. The good conductivity and polarizing effect of Pd are responsible for the enhancement of MR. The former leads to the decrease in resistivity and the latter induces a large number of spin clusters.

Yb³⁺ : NaGd(WO₄)₂ single crystal with dimensions Ø30 × 60 mm² has been grown by the Czochralski method. XRPD experimental results show that the as-grown Yb³⁺ : NaGd(WO₄)₂ crystal belongs to the tetragonal system and the I4₁/a space group. The high crystalline quality of the as-grown Yb³⁺ : NaGd(WO₄)₂ crystals was confirmed by HRXRD. The effective segregation coefficient of the Yb element in Yb³⁺ : NaGd(WO₄)₂ crystal growth was measured to be 0.812 using the x-ray fluorescence method. Subsequently, the thermal properties were systematically studied by measuring the thermal expansion, specific heat and thermal diffusion coefficients. The density of the as-grown Yb³⁺ : NaGd(WO₄)₂ crystal at 22 °C was measured by using the buoyancy method with a resulting value of 7.143 g cm⁻³ and almost linearly decreases as the temperature increases due to the thermal expansion. Comparing the thermal properties of several tungstate crystals, we find that the Yb³⁺ : NaGd(WO₄)₂ crystal possesses relatively larger anisotropic thermal expansion and specific heat but smaller thermal conductivity than those of other tungstate crystals.

CuFeSe₂ thin films have been grown by selenization of a CuFe alloy precursor. The CuFe alloy has been obtained by successive evaporation of thin Cu/Fe/Cu... layers on glass substrates heated at 550 °C. After deposition the metal alloy precursor is polycrystalline and there is an interdiffusion of metals all along the thickness. The atomic ratio Cu/Fe was varied from 0.8 to 1.15. The metal alloy precursor is selenized in a vacuum chamber; after heating at 550 °C it is exposed to selenium vapour (evaporation rate 3–4 nm s⁻¹ for 45 min).

At the end of the process only CuFeSe₂ diffraction peaks are visible in the x-ray diagram. The films exhibit a (112) preferential orientation. The scanning electron microscope (SEM) visualization of the films shows that films are composed of well-faceted grains. The Cu-rich films are slightly porous while the Fe-rich are more homogeneous.

The SEM study shows that the thickness of the grains is of the same order of magnitude as that of the CuFeSe₂ films.

Electrical measurements have shown that Cu-rich films are n-type with a room temperature resistivity of (5–9) × 10² Ω cm, while Fe-rich films are p-type with a room temperature resistivity of (3–5) × 10¹ Ω cm. It is shown that the electrical properties of the films are controlled by the grain boundary scattering effect.

Direct wafer bonding has increasingly become popular in the manufacture of microelectromechanical systems and semiconductor microelectronics components. The success of the bonding process is controlled by variables such as wafer flatness and surface preparation. In order to understand the effects of these variables, spontaneous planar crack propagation simulations were performed using the spectral scheme in conjunction with a cohesive zone model. The fracture-toughness on the bond interface is varied to simulate the effect of surface roughness (nanotopography) and patterning. Our analysis indicated that the energetics of crack propagation is sensitive to the local surface property variations. The patterned wafers are tougher (well bonded) than the unpatterned ones of the same average fracture-toughness.

We present a systematic study of the effects of post-fabrication annealing on the performance of photovoltaic devices that incorporate a photoactive donor–acceptor dispersed heterojunction system. Solar cells have been fabricated based on poly(3-octylthiophene) as donor (D) and single-wall carbon nanotubes as the electron acceptor (A) with a PEDOT:PSS hole transport layer. A post-fabrication annealing treatment was carried out at a temperature range of 40–200 °C. The best results were obtained at 120 °C; at this temperature the cell shows a short circuit current, I_sc = 0.5 mA cm⁻², an open circuit voltage, V_oc = 0.75 V and a fill factor, FF = 0.6, resulting in a power conversion efficiency of η = 0.22% under AM 1.5 (100 mW cm⁻²) white light illumination. The annealing treatment led to a doubling of the power conversion efficiency. This was attributed to a better charge carrier transport in the polymer matrix and more effective charge separation and collection.

We report space-and-time current spectroscopy for characterization of wide-gap semiconductors. The approach is based on the illumination of semiconductor material with an oscillating interference pattern formed of two light waves, one of which is phase modulated with frequency ω. The non-steady-state photocurrent flowing through the short-circuited semiconductor is the measurable quantity in this technique. The alternating current results from the periodic relative shifts of the photoconductivity and space charge electric field gratings which arise in the volume of the crystal under illumination. The experiments are carried out in photorefractive n-type Bi₁₂SiO₂₀, molecular SnS₂ and pyrolytic crystal of BN and the main parameters of the photoinduced carriers are determined.

Tomographic reconstruction of spatial profiles of the mercury atom density in the excited state 7 ³S₁ in high-frequency electrodeless lamps (HFELs) has been performed. The measurements of the Hg 546.1 nm line emission intensity have been made for the HFELs in argon–mercury mixture depending on the operation regime with different cold spot temperatures in the range 31–98 °C. The maximum entropy-based algorithm was applied for the reconstruction of local emission coefficients from the integrated intensities. The emission coefficients are directly related to the local values of the mercury atom density in the excited state 7 ³S₁, the upper state of the 546.1 nm transition. Such an investigation has been performed first for the HFEL. We have found that the emitting mercury atoms in the state 7 ³S₁ are concentrated in a thin layer located close to the lamp wall. The radial profiles have demonstrated a strong depletion of the population density in the state 7 ³S₁ from the lamp centre at high generator currents and low mercury vapour density. The obtained results are analysed theoretically in the context of the radial cataphoresis phenomenon. We found a qualitative agreement between the reconstructed density profiles and theoretical model predictions.

Experiments were carried out to investigate the removal of SO₂ and NOx from simulated glass manufacturing industry flue gas containing O₂, N₂, NO, NO₂, CO₂, SO₂ and H₂O using a sub-microsecond pulsed dielectric barrier discharge (DBD) at atmospheric pressure. Removal efficiencies of SO₂ and NOx (NO+NO₂) were achieved as a function of gas temperature for two specific energies and two initial NO, NO₂ and SO₂ concentrations. The higher SO₂ and NOx removal efficiencies were achieved in a gas stream containing 163 ppm of SO₂, 523 ppm of NO, 49 ppm of NO₂, 14% of CO₂, 8% of O₂, 16% of H₂O and N₂ as balance. The experimental results were evaluated using the energy cost or W-value (eV/molecule removed). About 100% of SO₂ and 36% of NOx were removed at a gas temperature of 100 °C with an energy cost of about 45 eV/molecule removed and 36 eV/molecule removed, respectively. These results indicate that DBD plasmas have the potential to remove SO₂ and NOx from gas streams without additives.

The topography and wettability of low-density polyethylene (LDPE) were modified by an inductively coupled Ar plasma. The extent and mechanisms of surface modification were correlated with the ion energy fluence, determined from the ion density measured with a Langmuir probe. The ion energy fluence was varied in the range of (0.3–6.3) × 10⁵ J m⁻² by changing the sample distance from the plasma power source. Physical and chemical changes of the plasma-treated LDPE surfaces were evaluated with an atomic force microscope, goniometer and x-ray photoelectron spectrometer. Images of plasma-treated and chemically etched LDPE surfaces provided insight into the mechanisms responsible for the topography changes observed at different length scales in terms of the sample distance (ion energy fluence). A significant effect of the nanoscale roughness on the contact angle of LDPE was observed for high ion energy fluence. The results demonstrate a strong effect of the ion energy fluence on the modification of the surface morphology and wettability of plasma-treated polymer surfaces.

The plasma parameters in the IMPF (International Microgravity Plasma Facility) device for studying complex plasmas are determined with a 2D-scanning Langmuir probe system, which is suitable for operation on the International Space Station. The probe characteristics in low density, low pressure radio frequency (rf) discharges are evaluated in the framework of the radial-motion theory with corrections for collisions. A critical comparison between experimental values for plasma potential and ion density with SIGLO simulations (Kinema Software) is made, which yields good overall agreement. In particular, the shaping of the plasma profile by different rf power in the plasma centre and in an outer ring is well described. Small amounts of dust particles are used as a novel method to mark the boundary, where ion-drag force and electric field force are balanced. Again close agreement with simulation is found and demonstrates the applicability of the tracer technique as a quantitative diagnostic means.

The knowledge of transport coefficients is of interest in the modelling of flow in plasma processes and heat transfer. Calculations are performed in the temperature range of 9000–20 000 K and for different pressures (1, 3, 6 and 10 bar). The composition of e/C/H/N/O mixture plasmas is determined at equilibrium and four examples are studied: H₂O, CO₂, CO–H₂O and CH₄–air plasmas. First, the most recent data of potential interactions or elastic differential cross sections are carefully examined in order to choose the most appropriate ones to determine the collision integrals. Second, in this study devoted to high temperature calculations, we have restricted the species number to 12 (only atoms and atomic ions). Then we have tested the validity of our calculated composition and deduced that our transport properties are available for the temperature range of 9000–20 000 K at p = 1 bar and 11 000–20 000 K at p = 10 bar. Finally, the electrical conductivity, the viscosity and the total thermal conductivity are calculated for the four compositions and different pressures.

The coupling arc of twin-electrode TIG (T-TIG) is a particular kind of arc, which is achieved through the coupling of two arcs generated from two insulated electrodes in the same welding torch. It is therefore different from the single arc of conventional TIG in its physical characteristics. This paper studies the distribution of T-TIG coupling arc pressure, and analyses the influences of welding current, arc length, the distance between electrode tips and electrode shape upon arc pressure on the basis of experiment. It is expected that the T-TIG welding method can be applied in high efficiency welding according to its low arc pressure.

A homogeneous dielectric barrier discharge is generated by sub-microsecond square pulses. Two separate discharges per voltage pulse were observed, a primary discharge at the rising edge of the voltage pulse and a secondary discharge at the falling edge. Photos taken with a high-speed ICCD camera with an exposure time of 5 ns show that the evolution process of the first discharge (primary) is quite different from that of the second (secondary) discharge. The primary discharge starts from the bulk of the gap and the whole gap reaches its maximum emission intensity within 20 ns. Before the secondary discharge starts, there are weak emission layers next to both electrodes. The secondary discharge develops from the anode and expands towards the cathode, with the marked presence of a dark space adjacent to a weakly luminous cathode layer.

This paper presents a numerical analysis of the flow and heat transfer characteristics of mixed convection in a micropolar fluid flowing along a vertical flat plate with conduction effects. The governing non-linear equations and their associated boundary conditions are first cast into dimensionless forms by a local non-similar transformation. The resulting equations are then solved using the cubic spline collocation method and the finite difference scheme. This study examines the effects of the buoyancy parameter, the conjugate heat transfer parameter, the micropolar parameter and the Prandtl number on the flow and the thermal fields. The results show that the conjugate heat transfer parameter has a significant influence on the fluid flow and heat transfer characteristics. The buoyancy parameter reduces the solid–liquid interfacial temperature but increases the skin friction factor and the local heat transfer rate. The effect of wall conduction on the local heat transfer rate, interfacial temperature and skin friction factor is found to be more pronounced in a system with a greater buoyancy effect. Finally, compared with the case of pure forced convection, a reduction in the interfacial temperature, an increase in the skin friction factor and an increase in the local heat transfer rate are obtained in the current mixed convection case.

This study applies a hybrid technique of the Laplace transform and finite-difference methods in conjunction with the least-squares method and experimental temperature data inside the test material to predict the unknown surface temperature, heat flux and absorptivity for various surface conditions in the laser surface heating process. In this study, the functional form of the surface temperature is unknown a priori and is assumed to be a function of time before performing the inverse calculation. In addition, the whole time domain is divided into several analysis sub-time intervals and then these unknown estimates on each analysis interval can be predicted. In order to show the accuracy of the present inverse method, comparisons are made among the present estimates, direct results and previous results, showing that the present estimates agree with the direct results for the simulated problem. However, the present estimates of the surface absorptivity deviate slightly from previous estimated results under the assumption of constant thermal properties. The effect of the surface conditions on the surface absorptivity and temperature is not negligible.

Amorphous hydrogenated carbon nitride (a-CN : H) films were deposited onto silicon (n-100) substrates by dual direct current radio frequency plasma enhanced chemical vapour deposition with CH₄ and N₂ as feedstock at different ratios. The composition and surface morphology of the films were characterized by means of x-ray photoelectron spectroscopy, Raman spectroscopy and atomic force microscopy; while the mechanical and tribological properties of the films were evaluated using nano-indentation and the UMT test system. It was found that the deposition rate of the films decreased significantly but the N/C ratio, the surface roughness and the I_D/I_G ratio of the films increased as the N₂/CH₄ flow ratio increased. The nano-hardness and adhesion strength of the films to the silicon substrate sharply increased at first and then decreased with increasing N₂/CH₄ flow ratio. Moreover, the wear resistance of the films varied with the N₂/CH₄ flow ratio. The structure transformation from an sp³-like to sp²-like carbon–nitrogen network in the deposited films was also revealed.

Sputter-deposited V-doped SrZrO₃ (SZO) films were deposited on textured LaNiO₃ (LNO) bottom electrodes to investigate the resistance switching properties and reliabilities. The microstructures of the SZO and LNO films were characterized by x-ray diffraction. The resistance of the Al/V-doped SZO/LNO sandwich structures can be reversibly switched by operating with dc bias voltages or voltage pulses. The device with [100] orientated SZO film had better resistance switching properties and the resistance ratio was more than 1000. The effect of thermal treatment on resistance switching properties was investigated and different behaviour of the two leakage-states was found. Finally, the reliability of the device was also investigated. The device with the properties of reversible resistance switching and non-destructive readout is suitable for nonvolatile memory application.

Thin films of BaTiO₃ were prepared by radio-frequency magnetron sputtering at substrate temperatures from 450 to 750 °C and analysed by x-ray diffraction, optical transmittance and Raman spectroscopy. The packing density of the films relative to the crystalline density increases from 0.75 at 450 °C to about 1 at 750 °C. At a substrate temperature of 450 °C, the film is nano-crystalline (5 to 20 nm) with big lattice expansion, large band gap and pronounced hexagonal Raman lines. This film is homogeneous in the thickness direction. Films prepared at higher temperatures exhibit perovskite peaks in the Raman spectrum and an optical band gap of 3.38 eV. At 600 °C, the film exhibits a pronounced two-phase growth with a porous nucleation layer of initial packing density of 0.78, a preferred (100)-orientation of the grains and minimum micro-strain. At 750 °C, the films are again homogeneous in the thickness direction, have nearly crystalline packing density and preferably (110)-oriented grains.

In this paper, the influence of different laser power and scanning speed on the microstructure of laser remelted as-sprayed hydroxyapatite (HA) coatings was studied and the optimum technological parameters were obtained. The morphologies, elements and phase analysis of both sprayed and remelted coatings were examined by means of electron probe microanalysis, x-ray diffraction and so on. The results show that the plasma sprayed coatings could be improved by laser remelting and the optimum technological parameters are that the laser power is 600 W and the scanning speed is 11.2 mm s⁻¹. In the technological condition, the remelted coating which has compact columnar and cellular dendritic crystal consists of HA, α-TCP, CaO and TiO₂ phases, and the Ca/P ratio of the coating is the most approximate to that of HA. When increasing the laser power and slowing the scanning speed, the structure of the coating will become much coarser and the Ca/P ratio will deviate more from that of HA. On the contrary, if the laser power is reduced and the scanning speed is accelerated, the influence of technological parameters of laser remelting on the sprayed coating will be weakened.

Crack-free germanosilicate films, 3.6 µm-thick and containing up to 70 mol% germanium dioxide, which are inaccessible through the conventional sol–gel process, were fabricated using tetraethyl orthogermanate (TEOG) and diethylorthosilicate (DEOS) as precursors for germania and silica, respectively. The studies using viscosity, TEM and SEM revealed that DEOS contributed largely to stabilizing the GeO₂–SiO₂ sol and suppressing crack formation in thick films. XRD study showed that the films remained amorphous after being sintered at 600 °C in air for 60 min and annealed at 550 °C under a flowing H₂/N₂ atmosphere for 120 min. An intense absorption band at around 241 nm was distinctly observed in the films. The intensity of this absorption band was found to be effectively bleached by UV illumination. Weak photoluminescence emission bands which originated from the neutral oxygen di-vacancy were detected near 375 and 275 nm. Therefore, the 5 eV absorption band observed in this work was mainly caused by the neutral oxygen monovacancy. A saturated absorptivity change of the UV-bleachable band after prolonged illumination was found to be 389 cm⁻¹ for 70GeO₂–30SiO₂ films.

Inorganic scintillators are important elements of a new type of cryogenic phonon scintillation detector (CPSD) being developed for single particle detection. These detectors, exhibiting superior energy resolution and the ability to identify the type of interaction in an event, are considered to be the next generation of instrumentation in the search for extremely rare events. This paper presents the latest results of our research on cryogenic scintillators for CPSD applications in the search for dark matter. The paper gives a description of the concept of direct dark matter detection and the operation principles of CPSD, discusses the major material requirements and summarizes the results of investigations over a wide temperature range of the luminescence and scintillation properties of tungstates (CaWO₄ and ZnWO₄), molybdates (CaMoO₄, MgMoO₄ and CdMoO₄) and Ti-doped Al₂O₃.

We report the dielectric response of Ca_2−xPr_xMnO₄ (x = 0 and 0.25). Specifically, their intrinsic dielectric constants are calculated by impedance spectroscopy from the values of the obtained bulk capacitances. For Ca₂MnO₄, that does not show charge-order, the measured intrinsic dielectric constant is 14. The Pr doping induces charge-order in the system, and also a noteworthy increase in , that reaches a value of ∼220 for x = 0.25, unusual in these kind of oxides. This result provides a new link between both phenomena.

In order to study the effect of M substitution of transition elements on the structural properties of R₂Co_7−xM_xB₃ (R = Y, Gd; M = Ti, V, Cr) compounds, the phase stability and site preference are performed by using the pair potentials based on the lattice inversion technique. In R₂Co_7−xM_xB₃, M atoms substitute for Co with a strong preference for the 6i₁ sites and the order of site preference is 6i₁, 2c and 6i₂. Calculated lattice parameters are in good agreement with the experimental data. Moreover, the total and partial phonon densities of states are first evaluated for the R₂Co₇B₃ compounds with the hexagonal Ce₂Co₇B₃-type structure.

Thin films of Ba(Ti,Zr)O₃ containing about 65% Zr have been grown using rf magnetron sputtering with various substrate temperatures (500–700 °C). All of them display ferroelectric relaxor features at low temperature (T < 200 K), namely a frequency dependent maximum of the dielectric permittivity and dispersion on the low temperature side of the peak. This is the first time that such a behaviour has been evidenced in lead-free sputtered thin films.

Optical investigation has been conducted on chemically treated polyamide (nylon) 6 fibres using a strongly interacting solvent, dimethylformamide (DMF). A comparison has been carried out between the effect of solvent treatments and the effect of thermal treatment on the structure and properties of the fibres. The two-beam interference Pluta microscope is used to calculate the refractive indices parallel and perpendicular to the fibre axis and the birefringence. Optical and structural parameters related to the refractive indices and birefringence are evaluated. Crystallinity, specific refractivity of the isotropic dielectric, polarizability per unit volume and orientation functions are among the parameters obtained and plotted versus the time of treatment. Increases in the birefringence, crystallinity and orientation functions with time of treatment are obtained. The results indicate that DMF modifies the fibre structure and enhances its optical anisotropy. Moreover, immersion of the fibre samples in DMF prior to thermal treatment gives rise to different results for the optical and structural parameters than those immersed in DMF and thermally treated at the same time. The study revealed a considerable change in the molecular orientation of the nylon 6 fibres due to solvent and thermal treatments. This could enhance and expand their utilization in industrial applications.

There has been substantial interest in determining the thermo-physical properties of hydrocarbon fluids. We have used three different experimental techniques: ultrasonic interferometry to determine the velocity of compressional wave, differential scanning calorimetry to determine the specific heat and the Anton Paar density meter to determine the density of crude oil sample over a wide range of temperatures varying from 20 to 70 °C. These data are used in thermodynamic relations to evaluate the specific heat ratio, the Grüneisen parameter, the Debye temperature and the long wavelength limit of the structure factor. The packing fraction obtained for crude oil is found to be closer to the values of other dense liquid fluids.

The set of realizable refractive indices as a function of frequency is considered. For passive media we give bounds for the refractive index variation in a finite bandwidth. Special attention is given to the loss and index variation in the case of left-handed materials.

Nickel doped compounds (Ni_xTi_1−x)_1+yS₂ (0 ⩽ x ⩽ 0.06) were prepared by solid-state reaction, and their dc electrical and thermal conductivity and thermopower were investigated from 5 K to 310 K. The results indicated that Ni doping caused a metal-like to semiconductor-like behaviour transition; at low temperatures (T < ∼100 K) dc electrical conduction σ for (Ni_xTi_1−x)_1+yS₂ (x > 0) obeys Mott's 2D variable range hopping law, ln σ ∝ T^−1/3, indicating that TiS₂ possesses 2D transport characteristics. The appearance of Mott's 2D law could originate from potential disorder introduced by Ni substitution for Ti in S–Ti–S slabs, while the metal-to-semiconductor transition can be ascribed to de-degeneration through reduction in electron concentration due to Ni substitution. Experiments also indicated that both lattice thermal conductivity and carrier (mainly electron) thermal conductivity of the doped compounds decreased upon doping, which can be explained as the combined effects of substitution with intercalation of Ni and reduction of carrier concentration upon doping, respectively. The absolute Seebeck coefficient |S| was found to decrease after doping, which could be attributed to generation of some holes after Ni substitution for Ti. The figure of merit, ZT, of the doped compounds (Ni_xTi_1−x)_1+yS₂ (x > 0) decreased as compared with TiS₂ due to both a large increase in their resistivity and an obvious decrease in their Seebeck coefficient.

The interaction of a laser generated surface acoustic wave with a surface crack has been simulated in detail by the finite element method, where a surface notch of rectangular shape has been introduced to represent the fatigue crack for the convenience of modelling. It is shown that four distinct reflected components are present in the captured waveforms; the first component is the direct reflection of a compressive pulse from the left side of the notch, while the second one is assumed to be the Rayleigh wave converted from the laser generated compressive wave when it impacts the left face of the notch. The arrival time of the third peak has demonstrated clearly that it comes from the direct reflection of an initial Rayleigh wave on the near side of the notch. The origin of the last component has been assumed to be the mode conversion occurring at the base of the notch, which is based on the fact that the deeper the notch the longer the arrival time of the fourth peak.

This paper deals with a thin liquid metal layer submitted to an ac magnetic field. Experimentally, we have noticed that even if the system (inductor+liquid metal) is axisymmetric, when an ac magnetic field is applied the symmetry is broken. The observed deformations of the liquid metal are in three dimensions. Therefore, our aim is to investigate this deformation using a numerical method as boundary element method in three dimensions.

Numerical and experimental investigations have been carried out on transport of particles in an electrostatic travelling field. A three-dimensional hard-sphere model of the distinct element method was developed to simulate the dynamics of particles. Forces applied to particles in the model were the Coulomb force, the dielectrophoresis force on polarized dipole particles in a non-uniform field, the image force, gravity and the air drag. Friction and repulsion between particle–particle and particle–conveyer were included in the model to replace initial conditions after mechanical contacts. Two kinds of experiments were performed to confirm the model. One was the measurement of charge of particles that is indispensable to determine the Coulomb force. Charge distribution was measured from the locus of free-fallen particles in a parallel electrostatic field. The averaged charge of the bulk particle was confirmed by measurement with a Faraday cage. The other experiment was measurements of the differential dynamics of particles on a conveyer consisting of parallel electrodes to which a four-phase travelling electrostatic wave was applied. Calculated results agreed with measurements, and the following characteristics were clarified. (1) The Coulomb force is the predominant force to drive particles compared with the other kinds of forces, (2) the direction of particle transport did not always coincide with that of the travelling wave but changed partially. It depended on the frequency of the travelling wave, the particle diameter and the electric field, (3) although some particles overtook the travelling wave at a very low frequency, the motion of particles was almost synchronized with the wave at the low frequency and (4) the transport of some particles was delayed to the wave at medium frequency; the majority of particles were transported backwards at high frequency and particles were not transported but only vibrated at very high frequency.

Tailoring of weld attributes based on scientific principles remains an important goal in welding research. The current generation of unidirectional laser keyhole models cannot determine sets of welding variables that can lead to a particular weld attribute such as specific weld geometry. Here we show how a computational heat transfer model of keyhole mode laser welding can be restructured for systematic tailoring of weld attributes based on scientific principles. Furthermore, the model presented here can calculate multiple sets of laser welding variables, i.e. laser power, welding speed and beam defocus, with each set leading to the same weld pool geometry. Many sets of welding variables were obtained via a global search using a real number-based genetic algorithm, which was combined with a numerical heat transfer model of keyhole laser welding. The reliability of the numerical heat transfer calculations was significantly improved by optimizing values of the uncertain input parameters from a limited volume of experimental data. The computational procedure was applied to the keyhole mode laser welding of the 5182 Al–Mg alloy to calculate various sets of welding variables to achieve a specified weld geometry. The calculated welding parameter sets showed wide variations of the values of welding parameters, but each set resulted in a similar fusion zone geometry. The effectiveness of the computational procedure was examined by comparing the computed weld geometry for each set of welding parameters with the corresponding experimental geometry. The results provide hope that systematic tailoring of weld attributes via multiple pathways, each representing alternative welding parameter sets, is attainable based on scientific principles.