Table of contents

The application of thermal barrier coatings (TBCs) to components with internal cooling in the hot gas stream of gas turbine engines has facilitated a steep increase in the turbine entry temperature and the associated increase in performance and efficiency of gas turbine engines. However, TBCs are susceptible to various life limiting issues associated with their operating environment including erosion, corrosion, oxidation, sintering and foreign object damage (FOD).

This is a review paper that examines various degradation and erosion mechanisms of TBCs, especially those produced by electron beam physical vapour deposition (EB-PVD). The results from a number of laboratory tests under various impact conditions are discussed before the different erosion and FOD mechanisms are reviewed. The transitions between the various erosion mechanisms are discussed in terms of the D/d ratio (contact area diameter/column diameter), a relatively new concept that relates the impact size to the erosion mechanism. The effects of ageing, dopant additions and calcium–magnesium–alumina–silicates on the life of TBCs are examined. It is shown that while ageing increases the erosion rate of EB-PVD TBCs, ageing of plasma sprayed TBCs in fact lowers the erosion rate. Finally modelling of EB-PVD TBCs is briefly introduced.

Ferromagnet–metal-type composites, La_0.7Ca_0.3MnO₃(LCMO)–Cu, have been fabricated by a three-step route. We got LCMO powder using the conventional solid state method. Then, LCMO powders coated by Cu are obtained using a novel electroless plating technique, in which the contents of copper are controlled by changing the plating time. Finally these powders are pelletized and then sintered at different temperatures in argon. The powders coated by Cu are characterized by x-ray powder diffraction and scanning electron microscope. The temperature dependence of resistivity and the magnetoresistance in the applied field of 3000 Oe are measured. It is observed that the metal–insulator transition temperature (Tp) is improved above 20 K approximately up to 280 K compared with that of LCMO powder using the conventional solid state method without being coated by Cu; meanwhile, a second broad peak occurs in low temperature in the resistivity-temperature curve when sintering temperature is changed. Also an anisotropic magnetoresistance effect is observed.

The magnetic properties of anatase Ti_1−xMn_xO₂ (0 < x < 0.06) films prepared by sol–gel spin coating annealed in air and vacuum have been investigated. Room temperature ferromagnetism was observed in all the films. Enhancement of ferromagnetism is revealed in the films annealed in vacuum. The magnetic moment of the films annealed in vacuum, at 300 K, is 0.285 ± 0.004 μ_B/Mn for Ti_0.9618Mn_0.0382 O₂ and 0.366 ± 0.005 μ_B/Mn for Ti_0.9409 Mn_0.0591O₂. It is believed that the enhanced ferromagnetism could be due to the formation of oxygen vacancies and/or defects.

A new kind of two-dimensional (2D) photonic crystals conforming to the 6-fold hybrid triangular configuration formed by holographic lithography is proposed. The relations between their photonic band gap (PBG) properties and their specific holographic designs for both the inverse and the normal structures are systematically investigated. Computations have shown that a series of complete band gaps of large sizes exist over a wide range of system parameters for inverse structures; especially, when the dielectric constant ε = 13.6, the optimized relative PBG can reach 24.1%, among the highest in all 2D structures. Furthermore, complete PBGs can also be obtained in normal structures of this kind even with a much lower dielectric constant contrast such as 5.3 : 1. The evolutions of band gap maps of these structures and their dependence on the structure parameters are demonstrated. The transverse electric and magnetic light propagations are simulated to prove the existence of complete band gaps in normal structures of low dielectric constant and their potential use as waveguides.

A memory device has been fabricated using an AgI film sandwiched between a Pt film and an Ag film with the lateral size of the device scaled down to 300 nm. The AgI film was made by the iodination of the Ag film at room temperature and under ambient pressure. The switching between high- and low-resistance states can be realized by applying voltages of different polarities. The switching can be performed under the application of voltage pulses with a 100 Hz frequency for ∼10³ times. The switching times are in the order of microseconds and the retention time is about a week. The switching effects are explained as the electrochemical growth and dissolution of Ag in AgI.

The orientation growth and angle-dependent photoluminescence (PL) of nitrogen-doped SnO₂ films grown on Si substrate by reactive magnetron sputtering have been studied. It was found that the orientation of the nitrogen-doped SnO₂ films depends strongly on their thickness, and a highly [1 1 0]-oriented film was achieved with a seed layer. An angle-dependent PL of the [1 1 0]-oriented films was observed, and the PL peak position shifts towards the longer wavelength side and the PL peak width decreases as the observation angle decreases. This angle-dependent PL was attributed to the Fabry–Pérot optical interference effect.

Lanthanum hexaboride(LaB₆) films have been deposited on silicon tip field emitters by electron-beam evaporation. The field emission characteristics are studied in a diode test cell in a vacuum system. The experimental results show that the field emission stability of the LaB₆-coated Si-tip FEA can be improved and the emission current is significantly enhanced to 75 µA, in contrast to pure Si-tip FEA of 500 nA and Mo-coated Si-tip FEA of 300 nA with 1500 V applied to the anode. Furthermore, even at low vacuum (>1.5 × 10⁻⁵ Torr) it still exhibits good emission properties and strong ability to withstand ion bombardment. This LaB₆-coated Si-tip FEA is an excellent electronic candidate, in particular a fit for travelling-wave tubes, klystrons and other large vacuum apparatus.

Electrical breakdown and water surface deformation in a metal pin–water electrode system with dc applied voltages is studied for small inter-electrode distances (2–12 mm). The radius of curvature of the metal pin is 0.5 cm to exclude corona before breakdown at these small inter-electrode spacings. Calculations of the water surface deformation as a function of the applied voltage and initial inter-electrode spacing are compared with measurements of the water elevation. For distances smaller than 7 mm the calculated stability limit of the water surface corresponds with the experimentally obtained breakdown voltage. It is proved with fast CCD images and calculations of the electrical field distribution that the water surface instability triggers the electrical breakdown in this case. The images show that at breakdown the water surface has a Taylor cone-like shape. At inter-electrode distance of 7 mm and larger the breakdown voltage is well below the water stability limit and the conductive channel at breakdown is formed between the pin electrode and the static water surface. Both cases are discussed and compared.

We report the output characteristics of a saturated capillary discharge 46.9 nm Ne-like Ar soft x-ray laser obtained with relatively low main discharge current of less than 20 kA, with the lowest being 9 kA. The 20 cm long and 3 mm diameter alumina capillary channel was filled with argon in the region 0.1–0.4 mbar and was driven by a current pulse with a quarter-cycle duration of about 40 ns. The laser pulse duration generated was about 1.3 ns, with a gain coefficient of 1.2 cm⁻¹.

The 1.315 µm [I(²P_1/2) → I(²P_3/2)] transition of atomic iodine in the chemical oxygen–iodine laser (COIL) is pumped by sequential reactions of I₂ and I with O₂(¹Δ). In electrically pumped systems (eCOILs), electron impact excitation of O₂ produces the O₂(¹Δ) and also produces O atoms through dissociative excitation. The O atoms, through reactions with I₂, I(²P_1/2) and I(²P_3/2), lead to dissociation of I₂, quenching of the upper laser level and removal of the lower laser level. While dissociating I₂ is potentially beneficial, quenching of the upper laser level is detrimental and so management of the O atom density is necessary to maximize laser gain. In this regard, NO and NO₂ additives have been used to manage the O atom density by cyclically reacting with O and I. In this paper, results from a computational investigation of eCOIL systems using plug flow and two-dimensional models are discussed where NO and NO₂ additives are used. The system is a flowing plasma sustained in He/O₂/NO mixtures with downstream injection of NO₂ followed by injection of I₂. We found that addition of NO and NO₂ is effective in managing the density of O atoms and maximizing gain by minimizing quenching of the upper laser level. We found that by optimizing the additives, laser gain can be maximized even though O₂(¹Δ) densities may be lower due to the management of quenching and dissociation reactions.

In this work, a non-equilibrium mathematical model for an air inductively coupled plasma torch with a supersonic nozzle is developed without making thermal and chemical equilibrium assumptions. Reaction rate equations are written, and two coupled energy equations are used, one for the calculation of the translational–rotational temperature T_hr and one for the calculation of the electro-vibrational temperature T_ev. The viscous dissipation is taken into account in the translational–rotational energy equation.

The electro-vibrational energy equation also includes the pressure work of the electrons, the Ohmic heating power and the exchange due to elastic collision.

Higher order approximations of the Chapman–Enskog method are used to obtain better accuracy for transport properties, taking advantage of the most recent sets of collisions integrals available in the literature. The results obtained are compared with those obtained using a chemical equilibrium model and a one-temperature chemical non-equilibrium model. The influence of the power and the pressure chamber on the chemical and thermal non-equilibrium is investigated.

The paper reports the deterministic effects of a focusing electric field in improving the purity and yield of the arc-generated carbon nanotubes (CNTs). The method utilizes a focusing electrostatic field, which was superimposed on the arc symmetrically. The focusing voltage was varied from 0 to 1200 V at steps of 200 V and a number of cathode deposits, thus generated, were collected and thoroughly analysed in their totality with the help of weight balance, Raman spectroscopy, transmission electron microscopy and thermogravimetry. With the optimally configured focusing electric field, the arc generator is found to utilize nearly 85% of the consumed anode material, for converting into cathode deposit consisting of CNTs, as compared with about 35% in the conventional arc plasma method. The sample prepared under optimized conditions exhibited high oxidation temperature (851 °C) in the thermogravimetric analysis, negligible D band intensity along with a reduced G band line-width (14 cm⁻¹) in the Raman spectrum, confirming the presence of high purity CNTs with a high relative yield.

If a particle in an anisotropic plasma is replaced by a charge q₀ and a dipole p₀, without modifying the moment of the monopole and the dipole, the approximation method neglecting higher-order terms is not sufficient for describing the actual potential distribution around the particle. By introducing the concepts of the 'apparent' charge q and the 'apparent' dipole p in this paper, the surface potential of the particle caused by q₀ + p₀ and the sheath charge+dipole can be decided by q + p. If we assume that the dusty plasma has roughly equal moments of particle dipoles (+) and sheath dipoles (−), i.e. 'momentneutrality', besides the electroneutrality relation, the relationship between the actual moment and the 'apparent' moment can be acquired, and the potential around the particle can be calculated self-consistently. Based on the physical model, the electrostatic force on an isolated particle in an anisotropic plasma may be calculated and the pair interaction potential energy between particles or the coupling parameter can be acquired even for high κa values. Compared with other methods, the system is solvable analytically and thus yields clear insight into its physical behaviour.

First-order phase transition at a fluctuation stage into non-linear dissipative plasma-like media is considered. The clustering of new phase germs (or nucleation) is represented by stochastic Wiener processes. Brownian motion of clusters induced by a long-range potential of indirect (through acoustic phonons and Friedel's oscillation of electron density) interaction between one another is taken into account. Kinetic models for blistering materials in a controlled thermonuclear reactor and for melted metal thin film islands deposition during surface CVD modification are both put forward. The non-steady-state distribution of clusters versus their size and position in space is calculated using Ito–Stratonovich stochastic differential equations. Formation of radiation stimulated porosity layers in a lattice as well as liquid island chains on the surface are to be discussed as characteristics of phase transition at fluctuation stages as well as a new kind of self-organization phenomenon.

Swift heavy ion (SHI) irradiation experiments have been performed on as-deposited nanocrystalline cadmium sulfide (CdS) thin films by using 100 MeV Au⁸⁺ ions with 5 × 10¹² ions cm⁻². In addition, the as-deposited films were annealed at 300 °C in air for 1 h. Structural, optical and electrical properties of pristine (as-deposited), annealed and irradiated thin films were carried out by using x-ray diffraction (XRD), energy dispersive spectra, scanning electron microscopy, atomic force microscopy, UV-VIS spectroscopy and Arrhenius plots for resistivity and thermoemf, respectively. XRD shows the intrinsic peak of (0 0 2) for the hexagonal phase of CdS. After annealing and SHI irradiation this peak was enhanced drastically and dramatically, showing the dominant orientation in this plane. The grain growth observed in these two post-deposition processes was different. This resulted in a decrease in resistivity of the annealed and the irradiated samples by one and two orders from the pristine sample, respectively.

Local surface potential measurements on alkoxy-substituted poly (p-phenylene ethynylene), poly (EHO-OPPE), as an electron transport material (ETM) and poly (triphenyl diamine), poly (TPD), as a hole transport material (HTM) and their blends in three different compositions (1 : 3, 1 : 1, 3 : 1) were performed by using scanning Kelvin force microscopy (SKFM). Simultaneously the topography of all surfaces was obtained using atomic force microscopy (AFM). In this paper, we propose a new principle for mapping out the local surface potential distributions of macrophase separated segments in the model polymer blend systems through the combined mode of intermittent contact AFM–SKFM techniques. The energetics and kinetics involved are also discussed in terms of potential distributions in the different phases of surface morphologies in the single-layered pristine as well as single-layered two component polymer blend systems. The experimental results provide considerable insight into the electrical/electronic properties of these ETM and HTM materials and reveal highly qualitative information for the first time to show a direct conformation of apparent work function difference between the ETM rich and HTM rich components. Finally, an attempt has been made to perform the combined approaches of valuable and high resolution complementary techniques such as scanning electron microscopy, absorption and photoluminescence spectra in order to correlate the observed contact potential difference/surface potential difference between the two rich ETM and HTM components obtained from microscopic and macroscopic scans.

Narrow band gap iron oxide semiconductor films were grown with the laser chemical vapour deposition (LCVD) and reactive pulsed laser deposition (RPLD) techniques. For LCVD, 10 and 18 nm thick films, with composition Fe₂O_3−x (0 ≤ x ≤ 1), were deposited from iron carbonyl vapours with an Ar⁺ laser. Their band gap (E_g) results were of 0.46 eV and 0.66 eV, respectively. For RPLD, an iron target was ablated in low pressure oxygen atmosphere (0.1–1 Pa) by a KrF excimer laser. A number of pulses (4000–8500) increasing with oxygen ambient pressure was used for each deposition. The film thickness increased with pulse number from 100 to 240 nm. E_g increased in the range 0.13–0.34 eV with increasing oxygen pressure during deposition. It is shown that both LCVD and RPLD are appropriate technologies for the deposition of narrow variable band gap iron oxide semiconductor thin films.

The epitaxial stabilization of SmNiO₃ (SNO) films grown by an injection MO-CVD process on (0 0 1) SrTiO₃ (STO) substrates is discussed. By means of high-resolution x-ray diffraction, we show for the first time that SNO can be stabilized on STO with a minor amount of secondary phases and with a layer thickness reaching several hundreds of nanometres. It is argued that this stabilization is achieved because the lattice mismatch between these two perovskites is not as high as expected (1.8% instead of 2.8%). Moreover, the well-known dissociation of the SNO phase into NiO and Sm₂O₃ has been clearly correlated with the relaxation of epitaxial strain which is driven by the formation of misfit dislocations.

The present study aims to investigate turbulent film condensation on an inclined tube with variable wall temperature. The analysis proceeds under the effects of liquid–vapour interfacial shear and eddy diffusivity. In order to forecast the results more exactly, a new theory model of local film shear stress (τ/τ_w) is presented in the paper. The numerical calculation is obtained by using Visual C⁺⁺.Net. The results show that the increase in the temperature amplitude will bring about a larger Nusselt number under high velocity vapour. Besides, the results present the optimal inclination angle of the tube in different wall temperature amplitudes.

The microstructure of zinc oxide thin films on silicon substrates grown by metalorganic chemical vapour deposition (MOCVD) was characterized. The cross-sectional bright-field transmission electron microscopy (TEM) image showed that small ZnO columnar grains were embedded into large columnar grains, and the selected-area electron diffraction pattern showed that the ZnO/Si thin films were nearly c-axis oriented. The deviation angle along the ZnO (0 0 0 1) direction with respect to the growth direction of Si (1 0 0) was no more than 5°. The [0 0 0 1]-tilt grain boundaries in ZnO/Si thin films were investigated symmetrically by plan-view high resolution TEM. The boundaries can be classified into three types: low-angle boundaries described as an irregular array of edge dislocations, boundaries of near 30° angle with facet structures and large-angle boundaries with symmetric structure which could be explained by a low Σ coincident site lattice structure mode. The research was useful to us for finding optimized growth conditions to improve ZnO/Si thin film quality.

In this work, we describe the homo- and hetero-epitaxial growth of hexagonal and cubic Mg_xZn_1−xO thin films on lattice matched substrates of c-Al₂O₃, ZnO, MgO and SrTiO₃. The crystalline quality, composition and epitaxial nature of the alloy films are obtained by x-ray diffraction and Rutherford backscattering spectroscopy (RBS) techniques. The RBS channeling yields are in the range 3–8% for homoepitaxial and hetero-epitaxial thin films. The metal–semiconductor–metal and ultraviolet detectors were fabricated on hexagonal and cubic Mg_xZn_1−xO thin films and the leakage current and UV-visible rejection ratio are correlated with the epitaxial relationship between the film and substrates.

Structural and surface morphology studies of MnF₂ epitaxial layers have been performed by x-ray diffraction and atomic force microscopy (AFM). MnF₂ layers of different thicknesses (0.12–1.25 µm) were grown by MBE on Si(0 0 1) substrates with the deposited CaF₂-buffer layer having a ⟨1 1 0⟩ orientation and a grooved and ridged surface. X-ray diffraction patterns in the 10°–60° angular range have been measured. Profiles of diffraction peaks in two directions—parallel and normal to the diffraction vector—as well as the intensity distribution around 2 2 0 reciprocal lattice points were obtained. It was found that the metastable orthorhombic phase of α-PbO₂ type with [1 1 0] growth direction dominates in the films; a much smaller portion of the stable rutile type phase was also detected, though it increases with the film thickness. As follows from the x-ray diffraction data, the films have a mosaic block structure. Parameters of the crystallites were determined using the Williamson–Hall analysis of angular width of the diffraction peaks. It was obtained that the crystallites of the orthorhombic phase have an elongated shape oriented along the direction of the CaF₂ ridges. The AFM study confirms a regular distribution of the orthorhombic crystallites and shows the appearance of some irregular shaped crystallites on the top of the thick MnF₂ films.

The interface microstructure in a simulated sandwich structure of Ni base-metal electrode and BaTiO₃ dielectric has been studied by transmission electron microscopy. Some Ni grains have been oxidized to NiO; most of them although coarsened and poorly densified remained Ni metal. NiO formed during the reoxidation step at 1000 °C because the partial pressure of oxygen (pO₂ ≈ 10⁻⁶ atm) in the controlled-sintering atmosphere was higher than the thermodynamic equilibrium value of pO₂ = 4.68 × 10⁻¹¹ atm. Crystallographic orientation relationships between NiO and BaTiO₃ at the interface were determined. The BaTiO₃–NiO interface was both twist and tilt boundaries that are characterized by dislocations of a mixed nature with Burgers vectors b = ½ ⟨0 0 1⟩ and ½ ⟨1 1 0⟩ and ⟨1 1 1⟩, described in the indices of pseudo-cubic BaTiO₃. Dislocation loops were also found in BaTiO₃ as well as along the NiO–BaTiO₃ interface; the latter with was a vacancy loop formed by condensation of intrinsic Schottky defects. The Ni–BaTiO₃ interface is built on and a configuration with opposite-charged ions stacked upon each other was energetically more favourable. The lattice mismatch was accommodated by misfit partials with b = ½ ⟨1 1 0⟩ that were dissociated from perfect dislocations with b = ⟨1 1 0⟩ probably by glide in on the metal–dielectric interface.

Transparent conducting CuCrO₂ thin films were prepared by pulsed laser deposition (PLD) from a nanocrystalline CuCrO₂ target. The derived CuCrO₂ films were highly c-axis oriented deposited at 800 K. The microstructural, electrical as well as optical properties were studied. It was found that the films were relatively smooth and behaved as semiconductors. The energy band of the CuCrO₂ films is constructed based on the Mott–Davis model in order to investigate the conduction mechanism. The transmittances of the films in the visible region are about 60–80% with direct band gaps of about 3.2 eV. The results suggested that CuCrO₂ films could be successfully prepared by the PLD method, which can broaden the applications of the transparent conducting oxide films.

AlN/Ti/TiN/DLC layers more than 1 µm thick have been prepared by plasma-based ion implantation sequentially with nitrogen/titanium/nitrogen and titanium/carbon on 2024 aluminium alloy. On the basis of our previous AlN/Ti/TiN/DLC layers, new AlN/Ti/TiN/DLC layers thicken by thickening the 'TiN' layer and the diamond-like (DLC) film. The structures of the new layers have been characterized by XPS, AFM and Raman spectrum. The new layers exhibit improved composition and structure gradients at the interface in addition to a thicker 'TiN' layer and DLC film than the previous ones and hence display significant improvements in surface hardness and tribological properties. Also, their surface topography, DLC structure, nanohardness, stress and tribological properties as a function of the DLC film thickness have been discussed.

In this paper, we develop a sensitive optical method to monitor the surface roughness in the investigation of surfaces. By applying this method to measure the RMS surface roughness of various surfaces, we found RMS values which are comparable to those obtained by atomic force microscopy measurements. In addition, we present a simple empirical model to calculate the RMS surface roughness which shows very good agreement with the surface roughness measurements taken by the method reported in this paper. Finally, the application of our method to the study of the LO-phonon mode of CdS suggests that its intensity is dominated by the surface roughness. This roughness dependent behaviour of the CdS LO-phonon mode is experimentally confirmed by using an excitation wavelength near its E₀ transition.

Molecular dynamics simulations using the embedded atom method (EAM) potential are carried out to study the nanoimprint of copper single crystal. The effects of mould taper angle, mould tooth spacing and crystal orientation on the deformation behaviour, dislocation movement and imprint force are investigated. A four-stage deformation is observed for the mould with a small taper angle, while it cannot be clearly identified for the mould with a large taper angle. The four-stage deformation is: (1) a purely elastic deformation with a rapid increase of imprint force, (2) dislocation nucleation with a small drop of imprint force, (3) local pile-up of dislocations with a second rapid increase of imprint force, and (4) active dislocation movement with almost a plateau of imprint force. Among the three imprint surfaces of (0 0 1), (1 1 0) and (1 1 1), it is found that the (0 0 1) surface results in the lowest imprint force and the (1 1 1) surface results in the highest one. It is also observed that the pattern transfer on the (1 1 1) surface is less accurate than on the (0 0 1) and (1 1 0) surfaces. It is shown that the smaller the mould tooth spacing, the stronger is the interaction of the stress fields in the substrate, which results in more obvious influence on the material deformation, the dislocation movement and the imprint force.

Thin films were fabricated by glancing angle deposition (GLAD), a technique providing accurate control of the nanoscale geometry in the film. We demonstrate the ability of GLAD to create structures with a sinusoidal refractive index variation in the direction normal to the film surface. The structural periodicity prevents the transmission of light over a wide optical spectrum, creating a photonic stopband. By changing the parameters of the GLAD technique, a set of titanium dioxide films have been created exhibiting stopbands in desired spectral locations. Films with a predefined defect in the periodicity have also been designed and fabricated using the GLAD technique. Optical measurements of these samples have shown that the incorporation of a uniaxial defect layer into the film leads to the appearance of a transmittance peak within the stopband. We have performed finite-difference time-domain simulations of light transmission through the optical filters and calculated the photonic dispersion relation of idealized structures. By changing the geometry of the defect, the ability to control the location and width of the transmittance peak in the spectrum has been demonstrated. The theoretical results obtained demonstrate very good agreement with experimental measurements and allow one to make accurate predictions of the optical properties of GLAD fabricated thin films.

We have deposited magnetite thin films using the pulsed laser deposition technique from a α-Fe₂O₃ target on different substrates (Si (1 1 1), GaAs (1 0 0), Al₂O₃ (0 0 1) and amorphous float glass (FG)) without any buffer layer at a substrate temperature of 450 °C. These films have been characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ac magnetic susceptibility and four-probe resistivity. The XRD results of these films show highly (1 1 1) oriented growth and single phase nature of Fe₃O₄ films on all substrates. Fe 2p core level x-ray photoelectron spectra and Raman spectra reveal the formation of Fe₃O₄ throughout the thickness of the films. All films show a Verwey transition at or around 120 K. It is observed that the oriented growth of Fe₃O₄ films takes place along the [1 1 1] direction on these substrates, which have either a huge lattice mismatch or no matching at all (as in FG) with Fe₃O₄.

The effect of platinum (Pt) on the leakage currents of lead barium zirconate (PBZ) films was studied. The leakage current is reduced by two orders of magnitude by Pt doping. The transport mechanisms of PBZ films are also analysed. The leakage mechanism is found to change from interface-limited conduction to mixed conduction after Pt doping. It is proposed that the internal stresses suppress the leakage current and change the conduction mechanism. The stresses are considered to be caused by lattice distortion due to the presence of Pt inside the PBZ films, which is confirmed by XPS and Raman spectrum.

The thermal conductivity, thermal diffusivity and heat capacity per unit volume of sedimentary rocks (limestones) taken from Nammal Gorge sections, Western Salt Range, Pakistan, have been measured simultaneously using the transient plane source technique. The temperature dependence of thermal transport properties was studied in the temperature range 293 to 443 K. Different relations for the estimation of thermal conductivity are applied. A proposal for the prediction of thermal conductivity as a function of temperature is also given. It is observed that the values of effective thermal conductivity predicted by the proposed model are in agreement with the experimental thermal conductivity data within 8%. Furthermore, the errors in experimental calculations of thermal conductivity, thermal diffusivity and volumetric heat capacity are around 5%, 7% and 10%, respectively.

There have been many attempts to develop expressions for thermal conductivity (λ) as a function of liquid content (θ) in granular media such as powders, gravel and soil. We present a new approach based upon a cubic array of solid spheres, with liquid capillary bridges surrounding the solid–solid contacts. Numerical results agree with analytical solutions for the endpoints. For small filling angles (low liquid contents, such that menisci do not coalesce) and for a fixed conductivity ratio α ≡ λ_solid/λ_liquid = λ_liquid/λ_gas, we find a simple relationship λ (θ) = λ (θ = 0) + aθ^b, where the prefactor and exponent are simple functions of α. The power-law relationship also holds for compressed spheres, if the dry conductivity λ (θ = 0) is adjusted for the new porosity. While the results are not trivially applicable to real granular media, they provide a quantitative explanation for the observed phenomenon in soils of the rapid rise in conductivity caused by the addition of a small volume of liquid.

A new simple equation for the effective permittivity of particle-filled composites is presented. The equation does not involve any free parameters in addition to the volume fraction of inclusions, the semi-axes of ellipsoidal inclusions and the permittivities of materials. Alternatively, instead of semi-axes, the percolation threshold can be used as a parameter. It is derived in a similar manner as the Maxwell Garnett mixing equation, but by including an enhanced background permittivity effect when the volume filling ratio of inclusions increase. The result is a mixing equation which has the Maxwell Garnett mixing equation as a low volume filling ratio limit, but which approaches the Bruggeman mixing equation as the volume fraction of inclusions increases. The mixing equation is compared with classical mixing formulae, and to numerical simulations and measurements from the literature.

β-Zn₄Sb₃ is a promising thermoelectric material for energy conversion applications due to its exceptional low thermal conductivity. In this report, the effect of In substitution on thermoelectric properties and β to α/α' phase transition of indium doped compounds (Zn_1−xIn_x)₄Sb₃ (x = 0–0.02) were investigated at temperatures from 5 to 310 K. The results indicated that low-temperature (T < 300 K) thermal conductivity λ of the doped β-(Zn_1−x In_x)₄Sb₃ (x ≠ 0) reduced remarkably as compared with that of Zn₄Sb₃ presumably due to enhanced impurity (dopant) scattering of phonons. Direct current electrical resistivity ρ and thermopower S were found to decrease and then increase moderately with the increase in the In content, which could be ascribed to the introduction of donors due to substitution of In³⁺ for Zn²⁺, leading to increased electron contribution. Moreover, it was found that the β to α/α' phase transition of Zn₄Sb₃ was completely prohibited by In doping, implying that In was substituted predominantly for interstitial Zn and hindered their ordering. In addition, the thermoelectric figure of merit (=S²T/ρλ, where T is temperature) of the doped compound β-(Zn_1−xIn_x)₄Sb₃ (x ≠ 0) was smaller than that of Zn₄Sb₃ at the low temperatures because of substantial decrease in their thermopower, suggesting that In substitution for Zn in Zn₄Sb₃ is not beneficial for raising its low-temperature thermoelectric properties.

Thermally stimulated luminescence (TSL) and conductivity (TSC) are considered using the classical insulator model that assumes one kind of active trap, one kind of inactive deep trap and one kind of recombination centre. Kinetic equations describing the model are solved numerically without and with the use of quasi-equilibrium (QE) approximation. The QE state is characterized by the parameter q_I = (dn_c/dt)/I_e, where dn_c/dt is the rate of change of free electron density, and I_e is the TSL intensity. The QE state parameter q_I, the relative recombination probability γ = I_e/(I_e + I_t) (I_t is the trapping intensity) and a new parameter called a quasi-stationary (QS) state parameter q* = q_Iγ = (dn_c/dt)/(I_e + I_t) are used for the analysis of the TSL and TSC. The QE and QS states are determined by conditions |q_I| ≪ 1 and, respectively, |q^*| ≪ 1. The TSL and TSC curves and the temperature dependences of q_I, q^*, γ the recombination lifetime and the occupancies of active traps and recombination centres are numerically calculated for five sets of kinetic parameters and different heating rates. These calculation results show that (1) the upper limit of the heating rate for the presence of the QS state appears at a higher heating rate than that for the QE state when the retrapping process is present, and (2) the TSL (TSC) curves in the QS state have properties similar to those for the TSL (TSC) curves in the QE state. Approximate formulae for calculation of the parameters q_I and q^* in the initial range of the TSL and TSC curves are derived and used in the heating-rate methods, proposed in this work, for determination of those parameters from the calculated TSL curves.

Tensoactive agents may decrease water absorption in clay products like adobes. They modify the characteristics of the surface of clay particles. Characterization of water diffusion through the pores of modified clays is important to apply appropriate surface modifiers and to improve their performance. We established a simple model for water diffusion in test samples of defined dimensions to estimate real physical parameters and their effect on water absorption. Adsorption mechanisms are examined based on experimental results. The fitting of the experimental data to the model provides a deep understanding of water adsorption in chemically modified clays. A better agreement between the model and the experimental data is achieved for complex molecules.

We report the results of detailed electrical resistivity variation with temperature at different twin configurations in Ni₄₉Mn₂₉Ga₂₂. It was noted that in the martensitic region (<300 K), the structural transition occurs in the range 200 K ≤ T ≤ 300 K and hence the measurements were made in this temperature range. By using compressive stress, different twin configurations of the crystal were obtained. The important findings of the measurements are that: (i) during the heating cycle the alloy undergoes an intermartensitic transformation, M to M'; around 270 K, the resistivity of M' is about 20% greater than that of M and depends upon the martensite variant distribution; (ii) the resistivity does not depend upon the number of twin boundaries present in the crystal, but instead depends upon the crystal orientation w.r.t. the direction of the current; and (iii) the temperature of the observed intermartensitic transition, T₁, is strongly dependent upon the number of twin boundaries; T₁ is found to be minimum for e₀ = 2.5%, when the number of twin boundaries is maximum.

Magnetoelectric (ME) composite ceramics of NiFe₂O₄ (NFO) and lead zirconate titanate (PZT) were synthesized by a simple in situ processing based on a sol–gel method followed by a conventional sintering. X-ray diffraction patterns and scanning electron microscopy images revealed that this processing can produce two pure phases simultaneously. The in situ grown magnetic NiFe₂O₄ grains were well dispersed in the PZT matrix. The results demonstrated an attractive ME response of about 28.5 V cm⁻¹ Oe⁻¹ in the 0.35 NiFe₂O₄/0.65PZT at a resonance frequency of around 287 kHz.

The capillary rise of liquid in the gap between two closely spaced parallel cylinders, whose radii may be identical or different, is modelled in this paper. On the basis of the minimum free energy principle and interfacial analysis, the vertical capillary rise of liquid at equilibrium was calculated as a function of distance of separation of the two cylinders. In order to validate our theory, a piece of experimental apparatus was designed and a series of experiments was conducted on it. Compared with the experimental data, our theoretical model gave a reasonably accurate prediction within experimental error except at a small separation of cylinders. Possible experimental errors were discussed. We also showed that the wicking height at equilibrium was nonlinear to the reciprocal of the hydraulic radius.