The Influence of Interface Structures on the Conducting Properties of Zirconia (ZrO2)-Based Solid Electrolytes

Zirconia-based materials are the solid electrolytes used as the principal component of solid oxide fuel cells. The present generation of fuel cell designs incorporates self-supporting thin films (80–100 m) of the electrolyte on which various coatings of electrode are applied. The operating temperature of the cell is currently in the range 800–1000°C, and understanding the interface structures associated with these structurally complex components at these temperatures remains a constant challenge. Incremental changes in conductivity brought on by interface modifications can have a large influence on the viability of any particular system for commercial application. This review outlines the influence that a number of interface structures associated specifically with zirconia-based electrolytes have on the ionic conductivity. These include grain boundary structures, structures within grains, and the influence of additives. In addition, the effect of long-term anneals on the various interfaces is addressed. In each case, the combination of ionic conductivity measurements with detailed analytical electron microscopy has provided the clues as to how the various interface structures influence the physical properties of the solid electrolyte ceramic.     

Plasma spraying induced changes of calcium phosphate ceramic characteristics and the effect onin vitro stability

Plasma spraying is a commonly used technique to apply thin calcium phosphate ceramic coatings. Special consideration is given to retaining the original structure of CPC particles. However, changes are possible. Thus this study focused on plasma spraying induced changes in material characteristics of commercial coatings and their influence onin vitro dissolution. All analysed coatings were found to undergo significant plasma spraying induced changes in phase composition, crystal structure, and specific surface area. The phase transformations depended on the starting particle characteristics. Specifically, -TCP transformed to -TCP. HA was dehydroxylated and transformed to oxyhydroxyapatite (OHA), and partly decomposed to -TCP and tetra calcium phosphate. These transformations lead to a considerable increase ofin vitro dissolution rates at physiological pH.     

Phase transformation in martensite of Cu-12.4% Al

Phase transformations in a Cu-AI alloy which was in the martensitic state were examined by the use of differential thermal analysis. The influence of the speed of temperature changes on the character of the phase transformation was determined. The new sequence of phase transformations in martensite is discussed and related to the physical properties (the shape memory effect). Characteristic temperatures and heats of transformation in the alloy are also estimated.     

Nondestructive evaluation of ferromagnetic materials by a “magnetometer like” experimental arrangement

The paper presents experimental results regarding the influence of mechanical stresses and thermal treatments on the Barkhausen noise and magnetization characteristic of MolyPermalloy and MuMetal ferromagnetic samples. The samples are different in stress magnitude and localization and in their thermal history. The level of Barkhausen noise and the changes in magnetization characteristic are estimated by measuring the sensitivity and transduction gain of magnetometer like coils configurations which employ the studied ferromagnetic samples as their nonlinear ferromagnetic cores. The present method is unique in the sense that the two factors (one factor is related to the internal magnetic noise, and the other one is related to the form of the magnetic characteristic) are obtained by employing a single relatively simple experimental arrangement. Various types of stresses, which are different in magnitude and localization, become distinguishable one from the other, when considering their differential effects on the two factors. Several possible experimental arrangements are shown.     

Microstructural changes induced in linear polyethylene by plastic deformation (rolling)

Mechanical spectrometry and differential scanning calorimetry analysis completed by wideangle X-ray diffraction and density measurements were performed on linear polyethylene in order to characterize the influence of a plastic deformation (rolling) on the microstructure. Thus, rolling performed at room temperature results in the breaking of the thicker lamellae. The changes in the microstructure in polyethylene induced by rolling are in agreement with those suggested by other authors. A phenomenological model, applied to the relaxations exhibited by polyethylene, allows quantitative analysis of the microstructural changes due to plastic deformation. Thus, rolling induces an increase in the interactions between phases through an increase in the number of tie molecules connecting the broken crystallites. Moreover, rolling results in an increase of crystallographic defect concentration within the crystalline phase and this plastic deformation induces phase transformation from orthorhombic to monoclinic lattice, which is preferentially developed for thicker lamellae.     

Experimental investigation into the compressive strength development of cemented paste backfill containing Nano-silica

This paper investigates the influence of Nano-silica (NS) addition on the consistency and compressive strength development of cemented paste backfill (CPB). Tetraethyl-Orthosilicate (TEOS) was used as the precursor of Nano-silica along with ether-based Polycarboxylate superplasticizer (PCS). Two binder types (Portland cement and Slag-cement) and different amounts of TEOS (0.7–14% by mass of binder) with and without PCS are examined for 3, 7, 14, and 28 days curing time. Uniaxial compression tests for unconfined compressive strength (UCS) determination, slump height measurement, changes in gravimetric water content, and differential thermogravimetric analysis (DTG) were used to assess the influence of NS and admixtures (TEOS-PCS) on CPB performance. The results of this experimental study indicate that the addition of approximately 5% TEOS along with 0.5% PCS (by mass of binder) provide the best compressive strengths that can also be anticipated through the higher amount of calcium silicate hydrate (CSH) on DTG curves. It is also noticeable that the positive influence of NS is more evident when the amount of binder was decreased. The addition of PCS to CPB containing NS improved both the consistency of the mixture and the compressive strength development of CPB.     

Employer involvement in eldercare: an organizational adaptation perspective.

Social and demographic changes represent an important environmental challenge to organizations. Recent demographic changes in the United States have increased the potential importance of "eldercare" benefits in the workplace. In this research, I elaborate a number of important organizational and environmental determinants that influence the recognition and interpretation of eldercare issues and relate these considerations to the level of employer involvement in the care of elderly dependents, or eldercare.     

Superconductivity of thin Nb3Sn films under tensile stress

Thin Nb₃Sn films on bendable quartz substrates have been prepared by different methods. These films exhibit an initial tensile stress. Bending the samples by two methods under known conditions results in quantitative changes of tensile stress and in relative changes of the superconducting transition temperature. On the average a “tension coefficient” of about $$\Delta T_c /\Delta \sigma \approx - 5 \times 10^{ - 3} K/kp mm^{ - 2} $$ has been found for all samples. A certain influence of the preparation conditions has been observed. The results are in fairly good agreement with similar types of earlier measurements.     

Anisotropy of ultra-high modulus polymers drawn through a die

The influence of processing conditions on the microhardness of ultra-oriented linear polyethylene (LPE) and polyoxymethylene (POM) produced by drawing the material through a heated conical die has been examined. After indentation with a squarebased diamond the die-drawn rods exhibit an anisotropic impression which can be related primarily to a local elastic recovery of the material surface parallel to the fibre axis. It is found that the microindentation anisotropy MH is a unique function of the actual draw ratio achieved, which depends on the drawing speed. A correlation between MH and elastic modulus has also been found. These results confirm that the changes in structure with increasing draw ratio increase the elastic stiffness and improve the recovery behaviour. These changes in structure involve an increase in the number of taut tie molecules or intercrystalline bridges which leads to the increased modulus, and also produce a more effective oriented molecular network which gives rise to improved recovery behaviour. TheMH /E ratio shows for these die drawn materials values 10^–2 which are in the vicinity of those obtained for steel. The fibril orientation is partially destroyed at the die walls through friction effects giving rise to an anisotropy value at the surface which is smaller than that within the core of the die-drawn fibres. Finally the present data also emphasize the influence of the die dimensions on the anisotropy value.     

Flow into an Arterial Branch Model

Arterial branches are found to be a major site for formation of arterial plaque. In this study, several of the main parameters that influence the local flow into an arterial branch model are investigated. In particular, the role of the local geometric parameters of the bifurcation on the overall flow is thought to be interesting. How the changes in the bifurcation geometry influence the distribution of axial wall shear and pressure in the model, is investigated. The major geometric factors influencing this flow are the bifurcation area ratio and angle. The flow in a large number of geometric variations of the branch model is numerically simulated. The models at several branch area ratios in the range of 0·4≤ AR≤ 2·0 are considered. In the above range of area ratios, a range of branch opening half-angle of is also studied. The flow in the above models is calculated for the inlet-flow Reynolds numbers of 250, 500, 1000, and 2000. The asymmetric mass flow into the branches by imposing different exit pressures at the branch outlets is also investigated. Area ratio seems to have the largest influence on the flow within the physiologically relevant range of the parameters considered. Increasing the area ratio can lead to relatively large flow separation in the vicinity of the bifurcation region. At higher values of the opening angle of the bifurcation, the possibility and severity of flow separation at the appropriate wall location increases. Having asymmetric mass flow into different branches also increases the chance of separation at the opening of the constricted branch. The relative influence of the convective acceleration of the flow, as represented by the value of the flow Reynolds number, is also investigated. The particular value of the area ratio or bifurcation angle, necessary to initiate flow separation, is influenced by the Reynolds number of the incoming flow in the mother tube. In particular, the influence of all these parameters on flow properties and their relative importance is quantified. The relation between the influence of these parameters on the flow and the formation of some vascular diseases reported in the literature, is also examined.     

Determining the Temperature Coefficient of Reference Resistors

The influence of temperature on electrical resistance of standard resistors is presented within this paper. Electrical resistance is like any other quantity temperature dependent. This dependence is specified with the temperature coefficient, which gives the relative change of resistance with temperature. The level of resistance change is not linear as it changes with temperature, and therefore the coefficient is temperature dependent as well. At a certain temperature, its value is equal to zero—the stationary point. Use of the standard resistor at this exact temperature or in a narrow interval around it greatly reduces the influence of temperature on electrical resistance, even if the thermal conditions are not optimal. Measurements of temperature coefficient were taken on a group of standard resistors of the same type in a wide temperature range, and the temperature of the stationary point was determined. Measurements were taken by placing the resistors in an oil bath and changing its set point temperature from 18 \({^{\circ }}\hbox {C}\) to 38 \({^{\circ }}\hbox {C}\). Electrical resistance of each resistor was measured using a resistance bridge, which had its reference resistor placed in a separate thermal enclosure at a constant temperature.     

Influence of preliminary cyclic plastic deformation on crack resistance

The influence of preliminary (before crack origin) cyclic plastic deformation by tension-compression (R = _min/_max = –1 on the brittle fracture resistance of 15Kh2MFA heat resistant steel in two conditions was investigated. The preliminary loading was done at 293 K and the fracture at 123 and 293 K. It was established that in the case of relatively short preliminary deformation the change in static fracture toughness is caused by a change in yield strength as the result of the Bauschinger effect. However, with an increase in cyclic deformation the total irreversibly dispersed specific energy of inelastic deformation and the structural changes in the material are the determining factor. A physically based method is proposed for prediction of the influence of preliminary cyclic plastic deformation on the brittle fracture resistance of cyclically softening steels.Institute of Problems of Strength of the Academy of Sciences of the Ukrainian SSR, Kiev. Leningrad. Translated from Problemy Prochnosti, No. 11, pp. 14–20, November, 1989.     

An investigation about thin films of poly[2-methoxy-5-(2′-ethyl-hexyloxy) phenylene vinylene] (MEH-PPV) prepared by Langmuir-Schaefer technique

The Langmuir monolayer behaviour of poly[(2-methoxy-5-(2-ethyl-hexyloxy) phenylene vinylene] (MEH-PPV) conducting polymer was investigated at air-water interface at different subphases containing anions. A uniform deposition of MEH-PPV monolayers was shown by UV-visible, electrochemical techniques, where the influence of anions on redox properties was investigated by cyclic voltammetric surveying. The nature of anions revealed significant changes in redox properties of the MEH-PPV LS films. The photoelectrochemical response of MEH-PPV LS conducting polymer was also investigated at length.     

Effect of order-disorder transformation modes on the anomalous yield behaviour of Fe3Al intermetallic compounds

Compression tests were performed to clarify the effects of transformation modes on the anomalous yield behaviour of hypo- and hyper-stoichiometric Fe₃Al alloys which show a first- and a second-order transition, respectively. There were great differences in the anomalous yield behaviour depending on the transformation modes. In the first-order transformation alloy, changes in the degree of order played an important role before phase separation, while precipitation of phase had a great influence on the anomalous behaviour after phase separation. In contrast, only the change in the degree of order was a dominant factor in the second-order transformation alloy.     

Impact of substrate temperature on rapid solidification of an Al-Cu eutectic alloy

An aluminium-copper eutectic alloy has been subjected to rapid solidification, utilising the gun technique, with different substrate temperatures to evaluate its influence on the cooling rate and microstructure. At all temperatures, the microstructure is essentially non-uniform and consists of metastable solid solution (with decomposition products) as well as eutectic regions. The solid state decomposition of the metastable solid solution is strongly dependent on the substrate temperature and leads to the formation of different metastable precipitates and consequent changes in microstructure. The origin of the different microstructures is discussed.On leave at Carnegie-Mellon University, Pittsburgh, PA, USA.     

Electrically excited, localized infrared emission from single carbon nanotubes

Carbon nanotube field-effect transistors (CNTFETs) produce band gap derived infrared emission under both ambipolar and unipolar transport conditions. We demonstrate here that heterogeneities/defects in the local environment of a CNTFET perturb the local potentials and, as a result, the characteristic bias dependent motion of the ambipolar light emission. Such defects can also introduce localized infrared emission due to impact excitation by carriers accelerated by a voltage drop at the defect. The correlation of the change in the motion of the ambipolarlight emission and of the stationary electroluminescence with the electrical characteristics of the CNTFETs shows that stationaryelectroluminescence can identify "environmental defects" in carbon nanotubes and help evaluate their influence on electrical transport and device operation. A number of different defects are studied involving local dielectric environment changes (partially polymer-covered nanotubes), nanotube-nanotube contacts in looped nanotubes, and nanotube segments close to the electronic contacts. Random defects due to local charging are also observed.     

The crystallisation of glasses based on eutectic compositions in the system Li2O-Al2O3-SiO2

Structural transformations have been studied in glasses related in composition to the binary eutectic between lithium metasilicate and -spodumene. Crystallisation processes and changes in microstructure during the controlled heating of the glasses have been followed using X-ray diffraction, electron microscopy, high temperature microscopy, thermal analysis and electron spin resonance spectroscopy.The influence exerted by titanium dioxide on the phase relationships, crystal growth rates and micromorphology of the polycrystalline products of heat-treatment has been investigated and the findings used as a basis for proposals on the rôle of TiO₂ during nucleation and crystal growth.     

Granular sphere-chain relaxation dynamics to interpret polymer-nanocomposite glass transition temperatures

Free volume and polymer chain architecture play important roles in controlling the glass transition temperature \(T_g\) of polymer nanocomposites. Various changes in \(T_g\) with respect to nanoparticle (NP) loading have been reported, depending, in part, on whether there are attractive or repulsive interactions between the polymer and NPs. However, even with no enthalpic interaction, there are ostensible changes in \(T_g\) that must be attributed to topological factors, such as chain stiffness and nanoparticle size. Here we adopt a macroscopic granular model to help understand frustrated dynamics in glassy polymer nanocomposites. Mixtures of granular chains with spherical inclusions were prepared with prescribed sphere size, chain length, and mixture composition. We measured the time to reach a close–packed, jammed state when these composites were subjected to controlled mechanical shaking. The compaction dynamics reveal that spherical inclusions profoundly influence the chain relaxation dynamics. In the long-chain limit, increasing the NP loading furnishes a minimum in the chain relaxation time, which may be loosely associated with an intermediate minimum in \(T_g\) with respect to nanoparticle loading for polymer nanocomposites. This minimum occurs for spheres having different sizes, but only at concentrations where the characteristic sphere separation is comparable to the chain loop size. This observation may explain the variety of contrasting trends that have been found in the literature for the dependence of \(T_g\) on nanoparticle loading in polymeric nanocomposites.     

Properties of high-alumina cement reinforced with alkali resistant glass fibres

The changes in the mechanical properties of cement composites made from high-alumina cement and Cem-FIL AR-glass fibres kept in three different environments up to 10 years are described. While the flexural and impact properties of the composite remained largely unaffected with time in a relatively dry atmosphere, in wet conditions a reduction in strength takes place. In natural weather the 10 year modulus of rupture and impact strength values are 22.8 MIN m^–2 and 6.7 KJ m^–2, respectively, corresponding to the 28 day values of 41.2 MN m^–2 and 22.8 KJ m^–2. These values are significantly better than the corresponding results obtained with Portland cement composites made from Cem-FIL fibres. High-alumina cement composites reinforced by E-glass fibre lose a very large proportion of their flexural and impact strength under wet conditions. The strength reduction with time observed for glass fibre reinforced high-alumina cement composites can be related to two sources: (a) the reduction in the strength of the glass fibre due to chemical corrosion and (b) conversion of the matrix. The latter has greater influence on those composite properties that are matrix controlled such as the Young's modulus whereas any significant reduction in fibre tensile strength is reflected in a corresponding loss in composite tensile and bending strength. Matrix conversion may also influence the fibre-matrix bond.     

Characterization of polyethylene/EPDM/silicon dioxide multicomponent composites by solid-state dynamic mechanical spectroscopy

Various composites of polyethylene, ethylene propylene diene rubber (EPDM), and filler are milled and analysed by solid-state dynamic mechanical spectroscopy. The filler used is silicon powder with an oxidized surface. This filler is a model for materials with siliceous surfaces. The torsion pendulum measurements show that the multicomponent composites exhibited complex viscoelastic behaviour. For composites of polyethylene and silicon dioxide, there is evidence of particle-particle interactions. In composites which include polyethylene, rubber and filler, interactions of the polyethylene and especially of the rubber with the filler surface are significant. Treatment of the filler surface with gamma-aminopropyltriethoxysilane (-APS) or gamma-methacryloxypropyltrimethoxysilane (-MPS) has a significant influence on the resultant composite dynamic mechanical spectrum. Maleic anhydride grafting of the EPDM rubber also changes the character of the composites. These composites appear to exhibit complex morphologies, which may be controlled to a certain extent by filler surface treatment and grafting to the rubber. There is evidence for a chemical reaction between the maleic anhydride modification of the EPDM and -APS during processing on the roll mill. Prediction of the composite properties using the extended van der Poel model is qualitatively useful.