Flat Plateau Region Research Articles

Modelling of nitrogen multi-energy ion implantation into WC-Co indexable knives for wood-based materials machining

Modelling of nitrogen multi-energy ion implantation into WC-Co indexable knives for wood-based materials machining. The paper presents the results of the modelling of multi-energy ion implantation processes of nitrogen to WC-Co indexable knives for wood-based materials machining. The modelling was performed for implantation of N++N2+ ions, for implanters without and with mass separation. Additionally, modelling for average charge state and for the extended implantation case was executed. The best results, i.e. flat and long plateau region and the most favourable plateau/multi ratio were obtained for N+ ions.

Compressive Properties of Al-Si Alloy Lattice Structures with Three Different Unit Cells Fabricated via Laser Powder Bed Fusion.

In the present study, in order to elucidate geometrical features dominating deformation behaviors and their associated compressive properties of lattice structures, AlSi10Mg lattice structures with three different unit cells were fabricated by laser powder bed fusion. Compressive properties were examined by compression and indentation tests, micro X-ray computed tomography (CT), together with finite element analysis. The truncated octahedron- unit cell (TO) lattice structures exhibited highest stiffness and plateau stress among the studied lattice structures. The body centered cubic-unit cell (BCC) and TO lattice structures experienced the formation of shear bands with stress drops, while the hexagon-unit cell (Hexa) lattice structure behaved in a continuous deformation and flat plateau region. The Hexa lattice structure densified at a smaller strain than the BCC and TO lattice structures, due to high density of the struts in the compressive direction. Static and high-speed indentation tests revealed that the TO and Hexa exhibited slight strain rate dependence of the compressive strength, whereas the BCC lattice structure showed a large strain rate dependence. Among the lattice structures in the present study, the TO lattice exhibited the highest energy absorption capacity comparable to previously reported titanium alloy lattice structures.

Hollow Glass Microspheres Filled Aluminum Syntactic Foam Made Through Stir-Casting Technique

Hollow Glass Microspheres (HGM) in the range of 10–20 vol. % were used as space holders for making syntactic aluminum foam having density 2.28–2.49 gm/cc using stir-casting technique. Aluminium alloys have already established their exceptional ability to sketch out the material for required properties. Aluminium alloy and its composites are one of the widely used materials for aeronautics and marine applications where high strength is expected from a low density material. So, an effort is made to enhance this lightness of aluminium alloy LM13 without affecting its strength by reinforcing it with Hollow Glass Microspheres (HGM). This synthesized syntactic foam, was characterized in terms of density and compressive deformation behaviour. It was noted that the syntactic foam behaves like a high strength aluminium foam under compressive deformation exhibiting flat plateau region in the stress–strain curves. The plateau stress of syntactic foam decreases with Hollow Glass Microspheres volume fraction vis-à-vis porosity.

Effect of composite electrode thickness on the electrochemical performances of all-solid-state li-ion batteries

Several ceramic half-cells with differing electrode composite thicknesses but identical formulations were assembled using the spark plasma sintering (SPS) technique, in order to conduct comparable investigations of their kinetic limitations. The SPS technique was used to assemble the composite electrode and the electrolyte together within a few minutes. NASICON-type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) ceramic was used as solid electrolyte, as it offers high ionic conductivity (3 × 10−4 S.cm−1 at 25 °C) with a Li+ transport number of 1. LiFePO4 active material was used as a model material; it offers an average flat potential of 3.45 V vs Li+/Li and a reasonably high theoretical capacity of 170 mAh.g−1. Surface capacity values (from 0.8 to 3.5 mAh.cm−2), which are proportional to electrode thickness, remained quite close to the initial values after more than 20 cycles, even for a 325 μm thick electrode (3.5 mAh.cm−2). The overpotential in the flat plateau region was proportional to the current density used, which means that it was dependent only on the cell’s ohmic drop. Performances were not limited by the ion transport into the solid electrolyte and composite electrode volume - as in classical Li-ion batteries - since the transport number of LAGP is one. Therefore, very thick electrode-enabling batteries with high-surface capacity can be considered.

Cycle life and hydrogen storage properties of mechanical alloyed Ca1−xZrxNi5−yCry; (x = 0, 0.05 and y = 0, 0.1)

CaNi5–based alloys have been synthesized by mechanical alloying followed by isothermal annealing. The formation of the CaNi5 structure occurred when the milled powders were heated at 800 °C under vacuum for 3 h. The abundance of CaNi5 phase in the alloys ranges from 60 to 70 wt.%. Replacement of Zr into the Ca site reduces the unit cell volume of CaNi5 whilst replacement of Cr into the Ni site slightly increases the unit cell volume. The hydrogen storage capacity of all substituted alloys is decreased and the hydrogen sorption plateau regions are narrowed compared to those of pure CaNi5. Substitution of Zr into the Ca site extinguishes the flat plateau region unlike replacement of Cr into the Ni site where a flat plateau is maintained. The reaction enthalpy ΔH for both absorption and desorption are directly proportional to the unit cell volume of the alloys. The hydrogen storage capacity of all alloys rapidly decays for the first 50 cycles at 85 °C followed by a more gradual decline after 50 further cycles. The hydrogen storage capacity of the alloys after 200 cycles is in the range of 65–75% of the initial capacity.

Removal of Cadmium from Aqueous Solution Using Castor Seed Hull: A Kinetic and Equilibrium Study

AbstractThe effects of various parameters such as initial concentration, adsorbent loading, pH, and contact time on kinetics and equilibrium of adsorption of Cd2+ metal ion from its aqueous solution by castor seed hull (CSH) and also by activated carbon have been investigated by batch adsorption experiments. The amount of adsorption increases with initial metal ion concentration, contact time, solution pH, and the loading of adsorbent for both the systems. Kinetic experiments indicate that adsorption of cadmium metal ion on both CSH and on activated carbon consists of three steps – a rapid adsorption of cadmium metal ion, a transition phase, and an almost flat plateau region. This has also been confirmed by the intraparticle diffusion model. The lumped kinetic results show that the cadmium adsorption process follows a pseudo‐second order rate law. The kinetic parameters including the rate constant are determined at different initial metal ion concentrations, pH, amount, and type of adsorbent, respectively. The Langmuir and Freundlich adsorption isotherm models are used to describe the experimental data. The Langmuir model yields a better correlation coefficient than the other model. A comparison of the monolayer adsorption capacity (qm) of CSH, activated carbon, and several other reported adsorbents has been provided. The value of separation factor (RL) calculated from the Langmuir equation also gives an indication of favorable adsorption of the metal ion. From comparative studies, it has been found that CSH is a potentially attractive adsorbent than commercial activated carbon for cadmium metal ion (Cd2+) removal.

Cenosphere filled aluminum syntactic foam made through stir-casting technique

Cenospheres in the range of 30–50 vol.% were used as space holders for making syntactic aluminum foam having density 1.5–1.9 gm/cc using stir-casting technique. The synthesized syntactic foam (SF) was characterized in terms of microstructures, hardness and compressive deformation behaviour. It was noted that the SF behaves like a high strength aluminium foam under compressive deformation exhibiting flat plateau region in the stress–strain curves. The plateau stress of SF decreases with cenosphere volume fraction vis-à-vis porosity following a power law relationship. But, the densification strain increases linearly with cenosphere volume fraction.

Effect of sample sizes in terahertz emission from intrinsic Josephson junctions in cuprate HTSC

Effect of sample sizes in electromagnetic wave emission from intrinsic Josephson junctions is investigated numerically. By using material parameters of Bi2Sr2CaCu2O8, emission frequency becomes as large as 1THz for a few dozens of layers. Frequencies at intensity peaks can be described well as the in-phase cavity resonance of transverse plasma. As the sample width increases, peak intensity gradually increases and then saturates. When the width exceeds a critical size, intensity peak becomes almost flat and such plateau region broadens as the width further increases. These behaviors can be explained by the mixing of two nearby cavity modes.

Processing and mechanical properties of magnesium foams

An open-cellular magnesium foam has been manufactured by using powder metallurgy technology basing on space holder fillers in the present study. Depending on the volume fraction and the diameter of the carbamide particles, the porosity and pore size can be controlled in the range of 40–80% and 0.5–2.0 mm, respectively. Quasi-static compressive tests indicate that the mechanical behavior of the present magnesium foam is in good agreement with the Gibson–Ashby model when the porosity is over 45%. The most outstanding mechanical feature, however, may be its long and flat plateau region that is favorable for energy absorbing applications.

Characteristic Features of Hydroxystearic Acid Monolayers at the Air/Water Interface

The effect of high NaCl concentrations in the aqueous subphase on the structure and phase properties of selected n-hydroxystearic acid monolayers is studied. The surface pressure−area (π−A) isotherms, the BAM (Brewster angle microscopy) images of the condensed phase domains, and the lattice structures obtained by GIXD (grazing incidence X-ray diffraction) of 2-, 9-, 11-, and 12-hydroxystearic acid monolayers spread on 1 M NaCl aqueous pH 3 subphase are determined. Large differences exist between the monolayer characteristics of stearic acid OH-substituted near the COOH-group (2-position) when both groups act as a monopolar entity and those OH-substituted in the mid-position of the alkyl chain (9-, 11-, 12-position) when the molecule has bipolar character. The π−A isotherms of the bipolar hydroxystearic acid monolayers have an extended flat plateau region only slightly dependent on temperature. In the case of 2-hydroxystearic acid monolayers, first at T > 30 °C an inclined small “plateau” region, which is ...

Effect of hydroxyl group position and system parameters on the features of hydroxystearic Acid monolayers.

The characteristic features of hydroxystearic acid monolayers OH-substituted in the mid position of the alkyl chain deviate considerably from those of the usual nonsubstituted stearic acid. The phase behavior, domain morphology, and two-dimensional lattice structure of 9-, 11-, and 12-hydroxystearic acids are studied, using pi-A isotherms, Brewster angle microscopy (BAM), and grazing incidence X-ray diffraction (GIXD), to obtain detailed information on the effect of the exact position of the OH-substitution. The pi-A isotherms of all three hydroxyoctadecanoic acids have an extended flat plateau region, the extension of which only slightly decreases with the increase of temperature. At the same temperature, the extension of the plateau region increases and the plateau pressure decreases from 9-hydroxyoctadecanoic acid to 12-hydroxyoctadecanoic acid. The absolute -DeltaH and -DeltaS values for the phase transition increase slightly from 9-hydroxyoctadecanoic acid to 12- hydroxyoctadecanoic acid and indicate differences in the ordering of the condensed phase under consideration of the special reorientation mechanism of these bipolar amphiphiles at the fluid/condensed phase transition. The morphology of the condensed phase domains formed in the fluid/condensed coexistence region is specific for the position of the OH-substitution of the alkyl chain, just as the lattice structures of the condensed monolayer phase. 11-hydroxyoctadecanoic acid monolayers form centered rectangular lattices with the chain tilt toward the NNN (next nearest neighbor) direction, and 12-hydroxyoctadecanoic acid monolayers have an oblique lattice over the entire pressure range. A special feature of 9-hydroxystearic acid monolayers is the phase transition between two condensed phases observed in the pi-A isotherm of 5 degrees C at approximately 18 mN/m, where the centered rectangular lattice shows a NNN/NN transition. The morphology of the condensed phase domains formed in the fluid/condensed coexistence region, just as the lattice structures of the condensed monolayer phase, reveal the high specifity of the monolayer feature of the bipolar hydroxystearic acids OH-substituted in the mid position.

Hydrogen and Pd-clusters

Isotherms of Pd–H clusters with different sizes differ from bulk isotherms: they show a largely enhanced solubility in the low-concentration regime. The isotherms resemble those of bulk above the critical point, they show no flat plateau region, but a slope. However, the existence of a hysteresis gives evidence for a phase transition even in small Pd–H clusters. Structural studies of 6.0 nm clusters show a transition between two cubic phases. 3.8 nm Pd–H clusters always show an icosahedral structure in the low and high concentration regime. For an intermediate size of 5.0 nm Pd–H clusters, the lattice structure changes during H-absorption, from cubic to, most probably, icosahedral. The slope in the cluster isotherm’s two-phase region is here attributed to stress emerging between the surfactant shell and the cluster during hydrogen-loading.

電池材料 Ｖ‐Ｔｉ‐Ｚｒ‐Ｎｉ系プロチウム吸蔵合金のニッケル水素電池の負極としての電気化学特性

We have developed the new compositional V-7.4at%Ti-7.4at%Zr-7.4at%Ni alloys that consist of BCC as main phase, and C14 Laves phases along grain boundary. They have the flat plateau region in the PCT curves and 2.0mass% protium absorption-desorption capacity. This paper investigates electrochemical characteristics of V-7.4at%Ti-7.4at%Zr-7.4at%Ni protium absorbing alloys as metal hydride electrodes. The electrodes which were prepared by mixing as-cast alloys with 300mass% Ni powder show 372mAh/g discharge capacity at 10mA/g discharge current. This result indicates that V-7.4at%Ti-7.4at%Zr-7.4at%Ni alloys work as metal hydride electrodes. It was found that the electrodes which were prepared by mixing as-cast alloys with Ni powder and heat-treated for 1h at 873K can discharge by the protium that can't desorb in a gas reaction.

New Vanadium-based Protium Absorbing Alloys with Laves Phases Along Grain Boundary

Vanadium or V-based solid solution type alloys with a BCC crystal structure are known to absorb the high capacity of protium but not to desorb completely. This paper tried to find new compositional V-based high density protium storage alloys, with the starting composition of V2.5M1 (M=Al, Co, Fe, Mn, Ni, Ti, Zr).It was found that the best composition among studied alloys is V3.5(Zr1⁄3Ti1⁄3Ni1⁄3) where the alloys consist of the BCC phase with the C14 type Laves phase along the grain boundary. The V3.5(Zr1⁄3Ti1⁄3Ni1⁄3) heat-treated alloys have about 2.0 mass% protium storage capacity of the 3rd cycle and have the flat plateau region in the PCT curves. The V70Zr1Ti12Cr17 alloys show higher protium capacity of nearly 2.5 mass% protium as well as flat plateau region. In the present investigations, it was found that the Zr substitution was very effective for easier activation, better plateau region and higher protium capacity, by forming the C14 Laves phase as minor phases in the BCC major matrix phase for various V-based alloys such as V–Ti–Ni (Cr) alloys.

Applicability of Slug Interference Tests for Hydraulic Characterization of Unconfined Aquifers: (1) Analytical Assessment

AbstractSlug interference responses within unconfined aquifers are characterized by an initial wave or “hump,” which is followed by a flat transitional plateau region and then by a declining, recessional limb segment. The shape and amplitude of the initial wave are primarily controlled by the elastic characteristics (i.e., S) and degree of anisotropy within the aquifer, while transmissivity is the principal parameter affecting the transmission (i.e., arrival time) of the slug interference response. Wellbore storage and delayed‐yield effects tend to attenuate the test response. The transitional and late‐time recessional segments are significantly influenced by the aquifer's specific yield. In addition, test well/aquifer relationships, e.g., observation well distance, aquifer thickness, and well depth/aquifer penetration, also strongly affect slug interference characteristics. The sensitivity of the propagated response to test well/aquifer relationships indicates that slug interference tests can be designed to maximize the expected response for aquifer property characterization.

Effect of the brittle‐ductile transition on the topography of compressive mountain belts on Earth and Venus

The Coulomb critical taper model has been very successful in explaining the large‐scale topography of a number of terrestrial accretionary wedges; however, this model is limited to cases of purely brittle‐frictional deformation. In this paper we extend the range of applicability of the critical taper model by explicitly including the effects of temperature‐dependent ductile deformation. The new model includes temperature‐dependent power law flow, an assumed velocity field, and linear thermal gradients in the atmosphere and within the crust. Flexural isostasy is also incorporated so that the decollement geometry is computed as a response to the applied load of the wedge material. We assume that ductile deformation within the decollement zone is controlled primarily by diffusion flow, whereas ductile deformation within the wedge itself is controlled by dislocation creep. The topographic profiles predicted by the model are very similar to those of a number of fold‐and‐thrust belts on both Earth and Venus. A typical wedge profile includes three distinctive topographic regions: a narrow taper toe, where both the wedge and the decollement zone deform in a brittle‐frictional manner; a region of relatively steep slope, where the wedge base deforms ductilely and the decollement zone is still frictional; and a flat plateau region, where both the wedge base and the decollement zone are deforming by ductile flow. We have applied the model to two fold‐and‐thrust belts on Venus (Maxwell Montes and Uorsar Rupes) and to the Andes on Earth, and we find good agreement between observed and predicted topography using reasonable parameter values. The model accounts for the observed positive correlation between relief and elevation of Venusian fold‐and‐thrust belts on the basis of different thermal environments at different elevations. It is also able to explain the first‐order differences between terrestrial and Venusian fold‐and‐thrust belts; fundamentally, this difference is due to a combination of the lower temperatures and the presence of water on Earth.

Parameters for the Adsorption of Tungsten from Metatungstate Solution on to Alumina

The adsorption of tungsten from aqueous solutions of ammonium metatungstate on to alumina has been studied, an adsorption isotherm at 20°C being obtained. The isotherm had a sigmoidal shape and reached a flat plateau region at an adsorbed concentration of 100 mg W/g Al2O3 within the range of initial concentrations used (up to 70,000 ppm W). A proposed relationship between the adsorbed concentration and the equilibrium solution concentration has enabled the adsorption equilibrium parameters to be estimated. Impregnation of flat thin layers of alumina with concentrated tungstate solutions (5,100, 31,200 and 72,800 ppm W) has also been studied. Fits between the experimental tungsten concentration profiles and those obtained via a theoretical model of the impregnation phenomena allowed the adsorption kinetic parameters to be obtained. These parameters are useful in predicting the concentration profiles resulting from the pore-filling impregnation of pellets provided a suitable theoretical model is employed.

Detection of low energy neutrals by a channel electron multiplier

A method for determining relative channel electron multiplier (CEM) detection efficiencies for low energy neutrals using the technique of direct recoiling is described. The method uses time-of-flight analysis of low-energy atoms recoiling from an energetic ion/surface collision. The system used for demonstration is 1–10 keV Ne + scattering from a polyimide resin surface, producing H and C recoils. The behavior of the CEM detection efficiency γ can be divided into two regions: A flat plateau region is observed at high velocity while below a specific velocity, ν H = 4.4 × 10 7 and ν C = 3.2 × 10 7 cm/s, γ decreases linearly with velocity with slope dγ dν = 6.4 × 10 −8 s/cm . This behavior is discussed in terms of secondary electron emission by a kinetic ejection process.

Effects of the substrate on the response of pyroelectric detectors

In our studies dealing with a theoretical analysis on the response of pyroelectric detectors, it has been found that for substrate-attached pyroelectric detectors, the current responsivity falls off with decreasing frequency below a certain frequency due to the flow of heat out of the pyroelectric crystal into the substrate. The rate of the falloff depends on the thermal conductivity of the substrate. The higher the thermal conductivity, the faster the rate of the falloff. The current responsivity flattens out in a lower intermediate frequency range of 10-2to 102Hz. In this flat plateau region, the smaller the substrate thermal capacity, the higher the current responsivity. The theoretical analysis agrees with the experimental results using LiTaO 3 detectors mounted on silicon substrates.

Studies on the aggregation behaviour of some direct dyes in aqueous solutions

Physicochemical properties of the two direct dyes ChrysophenineG and Chlorazol Sky Blue FF in aqueous solutions, have been studied using solubility and electrical conductivity methods. The results indicate that in aqueous solutions, both dyes in the presence of added sodium chloride start forming aggregates at a critical dye concentration. This critical concentration is a function of the temperature and the concentration of added sodium chloride. An analysis of the conductivity data shows that in all solutions containing dye aggregates the concentration of single dye ions is constant and equal to the critical cocentration. Since the solubility of ChrysophenineG unlike that of Chlorazol Sky Blue FF, is very small in the presence of added sodium chloride, the solubility product principle has been used to experimentally determine mean ionic activity coefficients for the dye ions. These values have been compared with activity coefficients calculated using a suitable form of theDebye-Huckel expression. The results indicate that ChrysophenineG in aqueous solutions behaves as a strong unaggregated 1∶2 valence type electrolyte in dilute solutions below the critical concentration for aggregate formation. Finally, a close correlation has been shown to exist between the critical dye concentrations for aggregate formation and the equilibrium dye bath concentrations at which the aqueous solution adsorption isotherms for these dyes on cotton, viscose and cuprammonium rayon fibres show a marked change in slope leading to the formation of a flat plateau region.