Effect of Si addition on the precipitation of Al<Superscript>2</Superscript>Cu-phase in Al-Cu-Si thin films

The effects of Si addition and of deposition temperature on the precipitation processes of Al²Cu (θ) and Si particles in Al-Cu-Si alloy films were studied with in-situ hot stage transmission electron microscopy (TEM). Deposition of an Al-1.5Cu-1.5Si (wt%) film at 305∘C, in the three-phase, Al(α)-Al²Cu-Si region resulted in formation of fine, uniformly distributed spherical θ -phase particles due to the coprecipitation of the θ and Si phase particles during deposition. For deposition in the two-phase, Al(α)-Si region (435∘C), fine θ -phase particles precipitated during wafer cooldown, while coarse Si nodules formed at the sublayer interface during deposition. In-situ heat treatment of the film revealed that excess Si existed in a supersaturated Al matrix. Si addition decreased film susceptibility to corrosion induced by the θ -phase precipitates, since extensive Cu segregation can be reduced by coprecipitation at 305∘C and the Al matrix supersaturated with Si reduced galvanic action with respect to the θ -phase precipitate.     

Thermal buckling behavior of composite laminated plates

Thermal buckling behavior of composite laminated plates was studied by making the use of finite element method. The thermal buckling mode shapes of cross-ply and angle-ply laminates with various E₁/E₂ ratios, aspect ratios, fiber angle, stacking sequence and boundary condition were studied in detail. The results indicate that the high E₁/E₂ and α₂/α₁ ratios of AS4/3501-6 and T 300/5208 laminates produce higher bending rigidity along the fiber direction and higher in-plane compressive force in a direction perpendicular to the fiber direction. Therefore, the higher thermal buckling mode shapes are formed. The thermal buckling mode that composite laminated plate will buckle into is mainly dependent on the E₁/E₂ ratio, α₂/α₁ ratio, fiber orientation and aspect ratio of the plate.     

Effects of surface modification of β-CaSiO3 on electrospun poly(butylene succinate)/β-CaSiO3 composite fibers

In this experiment, pure PBSU fibers, PBSU/12.5% β-CaSiO₃, and PBSU/25% β-CaSiO₃ composite fibers were fabricated by electrospinning. In order to investigate the effects of surface modification of β-CaSiO₃ on composite fibers, β-CaSiO₃ nanowires were surface esterified using dodecyl alcohol. SEM micrographs showed that composite materials with modified β-CaSiO₃ have homogeneous fibrous structures similar as that of pure PBSU fibers, while the fibers containing unmodified β-CaSiO₃ were inhomogeneous and much larger in diameter, and also junctions where β-CaSiO₃ agglomerated could be found. Mechanical testing showed that with the addition of unmodified β-CaSiO₃ into PBSU matrix, the tensile strength of fibrous materials decreased obviously, and the decrease degree increased with increased β-CaSiO₃ content. However, the tensile stresses of composite materials after surface modification of β-CaSiO₃ turned back and increased about 40% compared to those containing unmodified β-CaSiO₃. All of these results suggested surface modification of β-CaSiO₃ was an effective approach to obtain composite fibrous materials with better morphologies and enhanced mechanical properties, and this method is supposed to be feasible in other fibrous material systems.     

Uncertainty in particulate deposition for 1 microm AMAD particles in an adult lung model

The ICRP 66 lung model may be used to determine dose estimates for members of the public via the inhalation pathway. A significant source of uncertainty in internal dosimetric modelling is due to particulate deposition in regions of the respiratory tract. Uncertainties in estimates of particulate deposition are present because model input parameters have their own inherent variability. These sources of uncertainty need to be examined in an effort to understand better model processes and to estimate better the doses received by individuals exposed through the inhalation pathway. An improved understanding of the uncertainty in particulate deposition will further guide research efforts and improve our ability to quantify internal dose estimates. The ICRP 66 lung deposition model is most sensitive to breathing rate when 1 microm AMAD particles are inhaled by members of the public. Uncertainties in deposition fractions are shown to span an order of magnitude with their distributions varying by gender for a particular lung region. The largest fractional deposition occurs in the deep lung alveolar and extrathoracic regions.     

The effect of crystalline structure on molecular effect in ion-induced electron emission

The results of experimental and theoretical study of the molecular effect in ion-induced electron emission from single crystal and polycrystalline materials are presented. It has been found that the electron emission yield γ₂ under N₂⁺ bombardment of a single crystal shows a dependence on ion incidence angle θ, which is analogous to the anisotropy of the yield γ₁ under N⁺ impact. The ratio R₂(θ)=γ₂/2γ₁<1 exhibits, for single crystals, a drastic angular dependence, which was successfully described on the basis of electron sweeping-out mechanism by conjunction of both the sharp channeling at θ<ψ_L and the shadowing-caused bell-like pattern at θ>ψ_L, the Lindhard angle.     

Investigation on adhesion, interphases, and failure behaviour of cyclic butylene terephthalate (CBT)/glass fiber composites

Interphases exist in hybrid materials and significantly influence their mechanical performance. To find a bridge between the microscopic and macroscopic mechanical properties, this work investigates the microscopic nature of glass fiber surfaces and glass/CBT interphases in terms of topography, fractography, and adhesion properties. The variations in glass fiber surface properties result from the different sizings. Using the single fiber pull-out test, AFM, and ζ potential tests, it is shown that the interfacial bond strengths in CBT resin composites can vary depending on the kind of sizing formulation and properties. The greatest adhesion strength is achieved by aminosilane sizings with epoxy resin film former. The surface roughness of the fibers can be varied by sizings with different content and ζ potential values, which has no significant contribution to interphase adhesion strength from ‘mechanical interlocking’. For the systems with film formers, cohesive failure occurs and similar values of both interfacial adhesion strength, τ_d, and fracture energy release rate, G_ic, are obtained, in which τ_d approaches the shear yield strength of CBT matrix. A further enhancement of interfacial adhesion is limited by the mechanical properties and the non-homogeneous microstructure of CBT resin due to the less-than-perfect CBT polymerization.     

Effect of aggregates on the magnetization property of ferrofluids: A model of gaslike compression

The effect of field-induced aggregation of particles on the magnetization property of ferrofluids is investigated. From the viewpoint of energy, magnetizability of ferrofluids is more complicated than predicted by Langevin theory because the aggregation, i.e., the transition of ferrofluid microstructure, would consume the energy of the applied magnetic field. For calculating the effect of aggregates on the magnetization of ferrofluids, a model of gaslike compression (MGC) is proposed to simulate the evolution of the aggregate structure. In this model, the field-induced colloidal particles aggregating in ferrofluids is equivalent to the “gas of the particles” being compressed by the applied magnetic field. The entropy change of the ferrofluid microstructure is proportional to the particle volume fraction in field-induced aggregates φ_H. On the basis of the known behavior of ferrofluid magnetization and the aggregate structure determined from the present experiments, φ_H is obtained and found to depend on the aggregating characteristic parameter of ferrofluid particles γ in addition to the particle volume fraction in ferrofluids φ and the strength of applied magnetic field H. The effect of the nonmagnetic surface layer of ferrofluid particles is also studied. The theory of MGC conforms to our experimental results better than Langevin theory.     

Recovery of Pd from Spent Fuel: 1. Electrochemical Recovery of Palladium from Nitric Acid Solutions

The rate of cathodic deposition of palladium from nitrate solutions at a platinum electrode and the current efficiency of the process were studied as influenced by the concentrations of nitric acid, NaNO₃, U, and other admixtures. In the range of potential E from +0.5 to +0.25 V, the rate of Pd deposition from 1 M HNO₃ solution was 0.7–0.9 mg cm⁻² at current efficiency of about 70%. The degree of palladium recovery by cathodic deposition is more than 99% with the coefficient of separation from α- and β-emitting nuclides of 10²–10³.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 334–338.Original Russian Text Copyright © 2005 by Kirshin, Pokhitonov.     

Effect of the crab waist and of the micro-beta on the beam–beam instability

We calculate the luminosity and the strengths of the beam–beam resonances for colliders with large horizontal crossing angles. Achievable luminosities of such colliders can reach high values provided that the number of particles in colliding beams can be increased while the vertical β-function can be decreased till the mini-beta range. The crab waist option of the optics in the interaction region decreases (or, even vanishes) the strengths of two-dimensional betatron weak–strong beam–beam resonances and of their synchro-betatron satellites provided that β-functions at the interaction point can be decreased till the micro-beta range. This can help to increase the achievable value of the collider luminosity.     

Hybrid lattice particle modeling: Theoretical considerations for a 2D elastic spring network for dynamic fracture simulations

A new hybrid lattice particle modeling (HLPM) scheme is proposed. The particle–particle interaction is derived from lattice modeling (LM) theory, whereas the computational scheme follows particle modeling (PM) technique. The newly proposed HLPM considers different particle interaction schemes, involving not only particles in the nearest neighborhood, but also the second nearest neighborhood. Different mesh structures with triangular or rectangular unit cells can be used. The current paper is concerned with the mathematical derivations of elastic interaction between contiguous particles in 2D lattice networks, accounting for different types of linkage mechanism and different shapes of lattice. Axial (α) and combined axial-angular (α − β) models are considered. Derivations are based on the equivalence of strain energy stored in a unit cell with its associated continuum structure in the case of in-plane elasticity. Conventional PM technique was restricted to a fixed Poisson’s ratio and had a strong bias in crack propagation direction, as a result of the geometry of the adopted lattice network. The current HLPM is free from the above-mentioned deficiencies and can be applied to a wide range of impact and dynamic fracture failure problems. Although the current analysis is based on the linear elastic spring model, inelastic considerations can be easily implemented, as HLPM has the same force interaction scheme as PM, based on the Lennard–Jones potential.     

Combinatorial synthesis and rapid characterization of Mo1−xSnx (0x1) thin films

Thin films of Mo_1−xSn_x, continuously and linearly mapped for 0<x<1, have been prepared by d.c. magnetron sputter deposition under various growth conditions. X-ray diffraction results indicate that as x in high-pressure deposited Mo_1−xSn_x increases from 0 to approximately 0.45, the bcc lattice expands and no new phases are formed. At low deposition pressures, Mo₃Sn, a β-tungsten structured phase, is formed along with the bcc Mo–Sn solid solution for 0.1<x<0.3. The variation of the lattice parameter for this intermetallic phase also indicates that solid solutions, possibly of the form Mo_3+ySn, are being formed. These materials are of special interest as anode candidates in lithium-ion batteries.     

The preparation, surface modification, and characterization of metallic α-Fe nanoparticles

α-Fe nanoparticles were prepared by reduction of Fe²⁺ using potassium borohydride in a simple ethanol/water system in the presence of surfactant. The in-situ modification of particles was carried out by taking advantage of a modifying solution containing Ni²⁺. The structure and size of the particles were investigated by X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM) and electron diffraction (ED). Results showed that the in-situ electrochemical reaction between α-Fe nanoparticles and Ni²⁺ resulted in the formation of stable multilayer composite nanostructure. The cores of composite nanostructure were α-Fe.     

Effect of precipitates on damping capacity and mechanical properties of Ti–6Al–4V alloy

The present study was concerned with the effects of over-aging on damping property and fracture toughness in Ti–6Al–4V alloy. Damping property and toughness become important factors for titanium implants, which have big modulus difference between bone and implant, and need high damping capacity for bone-implant compatability. Widmanstätten, equiaxed, and bimodal microstructures containing fine α₂ (Ti₃Al) particles were obtained by over-aging a Ti–6Al–4V alloy. Over-aging heat treatment was conducted for 200 h at 545 °C. Fracture toughness, Charpy impact, and bending vibration tests were conducted on the unaged and the over-aged six microstructures, respectively. Charpy absorption energy and apparent fracture toughness decreased as over-aging was done, even if the materials were strengthened by precipitation of very fine and strong α₂-Ti₃Al particles. On the other hand, damping properties were enhanced by over-aging in Widmanstätten and equiaxed microstructures, but was weakened in bimodal microstructure due to the softening of tempered martensite and the decreasing of elastic difference between tempered martensite and α phase contained α₂ particles, etc. These data can provide effective information to future work about internal damping and fracture properties of Ti–6Al–4V alloy.     

Relating microtexture and dynamic micro hardness in an extruded AA8090 alloy and AA8090-8 vol% SiCp composite

The present study involves combined measurements of microtexture and dynamic ultra micro hardness (DUH) in hot extruded AA8090 aluminum alloy and its composite reinforced with 8 vol% SiC_p. Both the materials show strong crystallographic fiber textures—111 and 001. The dynamic micro hardness shows a clear pattern of difference between these two fiber textures, 111 oriented grains being harder and stiffer. The difference in θ/d between the fibers, where θ and d are the average cell misorientation and cell size, respectively, was marginal in the alloy and thus cannot explain the observed hardness difference. The hardness difference can be explained from the difference in Taylor factors between the respective fibers. Elastic stiffness values estimated from microtexture and DUH follow a similar trend qualitatively.     

Slip Correction Measurements of Certified PSL Nanoparticles Using a Nanometer Differential Mobility Analyzer (Nano-DMA) for Knudsen Number From 0.5 to 83

The slip correction factor has been investigated at reduced pressures and high Knudsen number using polystyrene latex (PSL) particles. Nano-differential mobility analyzers (NDMA) were used in determining the slip correction factor by measuring the electrical mobility of 100.7 nm, 269 nm, and 19.90 nm particles as a function of pressure. The aerosol was generated via electrospray to avoid multiplets for the 19.90 nm particles and to reduce the contaminant residue on the particle surface. System pressure was varied down to 8.27 kPa, enabling slip correction measurements for Knudsen numbers as large as 83. A condensation particle counter was modified for low pressure application. The slip correction factor obtained for the three particle sizes is fitted well by the equation: C = 1 + Kn (α + β exp(−γ/Kn)), with α = 1.165, β = 0.483, and γ = 0.997. The first quantitative uncertainty analysis for slip correction measurements was carried out. The expanded relative uncertainty (95 % confidence interval) in measuring slip correction factor was about 2 % for the 100.7 nm SRM particles, about 3 % for the 19.90 nm PSL particles, and about 2.5 % for the 269 nm SRM particles. The major sources of uncertainty are the diameter of particles, the geometric constant associated with NDMA, and the voltage.     

Microwave-assisted route for synthesis of nanosized metal oxides

Microwave-assisted route for the synthesis of nanomaterials has gained importance in the field of synthetic technology because of its faster, cleaner and cost effectiveness than the other conventional and wet chemical methods for the preparation of metal oxide nanoparticles. In the present work, synthesis of metal oxide nanoparticles viz., γ-Fe₂O₃, NiO, ZnO, CuO and Co-γ-Fe₂O₃ were carried out by microwave-assisted route through the thermal decomposition of their respective metal oxalate precursors employing polyvinyl alcohol as a fuel. The metal oxide nanoparticles are then characterized for their size and γ to α (in γ-Fe₂O₃) transition and structure by employing powder X-ray diffraction (XRD) pattern, high-temperature X-ray diffraction (HTXRD) pattern and Fourier transform infrared (FT-IR) spectral studies. The morphology of the samples ranged from nanorods to irregular-shaped particles for different metal oxide samples on the basis of scanning electron microscopy and transmission electron microscopy images. Frequency-dependent dielectric study of the ferrite samples (γ-Fe₂O₃ and Co-Fe₂O₃) showed a similar behaviour, where the dielectric constant decreased rapidly with increase in frequency. Possible explanation for this behaviour is given.     

Growth and characterisation of wide-bandgap,I-VII optoelectronic materials on silicon

γ-CuCl is a wide-bandgap (E_g = 3.395 eV), direct bandgap, semiconductor material with a cubic zincblende lattice structure. Its lattice constant, a_CuCl = 0.541 nm, means that the lattice mismatch to Si (a_Si = 0.543 nm) is < 0.5%. γ-CuCl on Si—the growth of a wide-bandgap, direct bandgap, optoelectronics material on silicon substrates is a novel material system, with compatibility to current Si based electronic/optoelectronics technologies.The authors report on early investigations consisting of the growth of polycrystalline, CuCl thin films with layer thicknesses of 100 nm to 1 μm on Si (100), Si (111), and quartz substrates by physical vapour deposition. X-ray diffraction (XRD) studies indicate that CuCl grows preferentially in the (111) direction but an epitaxial alignment with the substrate is also detected to a lesser extent in the case of Si (100). Photoluminescence (PL) and Cathodoluminescence (CL) reveal a strong room temperature Z₃ excitonic emission at ≈387 nm. X-ray microanalysis and XRD are used to investigate the effect of heat treatments on the CuCl thin films after deposition in the temperature range of 50 to 430∘C, (melting point of CuCl ≈ 430∘C). It is a found that a reaction occurs with Si on heating above 250∘C forming SiCl₄ and Cu.     

Electronic structure of the filled tetrahedral compound LiCdP and zinc–blende InP: Application of the interstitial insertion rule

We report on first principles studies of the electronic properties of the filled tetrahedral compound LiCdP and zinc–blende InP, using the full potential linearized augmented plane wave method within the local density approximation. The total energy calculations show that the α phase (Li⁺ near the anion) to be more stable than the β one (Li⁺ near the cation) for the LiCdP. The conduction band valleys follow the Γ–L–X ordering of increasing energy for β-LiCdP and InP, and the Γ–X–L one for α–LiCdP. The conduction band modifications are discussed and found to obey the interstitial insertion rule except for the Γ state of β-LiCdP. The valence charge density analysis shows that the Cd–P bond is covalent whereas the Li–P and the Li–Cd ones in α and β phases, respectively, are ionic.     

Fibrous insulations with transparent cover for passive use of solar energy

Fibrous thermal insulation protected by a transparent pane instead of an opaque cover applied to the exterior of house walls exhibits an improved efficiency. The fibrous layer and the house wall behind it are heated upon absorption of solar radiation and thermal leakage from the interior of the house is significantly reduced. The transparently covered fibrous insulation is well suited to retrofit old residential and commercial buildings. The optimal design parameters for the fibrous layer are as follows: thickness, 5 cm; density, 10kg-m^–3; fiber diameter, 20n; and albedo in the visible, _vis> 0.9.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Preparation and characterization of regenerated fiber from the aqueous solution of Bombyx mori cocoon silk fibroin

The regenerated silk fibers with high strength and high biodegradability were prepared from the aqueous solution of Bombyx mori silk fibroin from cocoons with wet spinning method. Although the tensile strength of the regenerated silk fibroin fiber, 210 MPa is still half of the strength of native silk fiber, the diameter of the fiber is about 100 μm which is suitable for monofilament of suture together with high biodegradability. The high concentration (30%, w/v) of the aqueous solution of the silk fibroin which corresponds to the high concentration in the middle silkgland of silkworm was obtained. This was performed by adjusting the pH of the aqueous solution to 10.4 which corresponds to pK_a value of the OH group of Tyr residues in the silk fibroin. The mixed solvent, methanol/acetic acid (7:3 in volume ratio) was used as coagulant solvent for preparing the regenerated fiber. The structural change of silk fibroin fiber by stretching was monitored with both ¹³C solid state NMR and X-ray diffraction methods, indicating that the high strength of the fiber is related with the long-range orientation of the silk fibroin chain with β-sheet structure.