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Silicon nitrides, deposited by capacitively coupled plasma (CCP)-type plasma enhanced atomic layer deposition (PEALD), are generally applied to today’s nanoscale semiconductor devices, and are currently being investigated in terms of their potential applications in the context of flexible displays, etc. During the PEALD process, 13.56 MHz rf power is generally employed for the generation of reactive gas plasma. In this study, the effects of a higher plasma generation frequency of 162 MHz on both plasma and silicon nitride film characteristics are investigated for the purpose of silicon nitride PEALD, using bis(diethylamino)silane (BDEAS) as the silicon precursor, and N2 plasma as the reactant gas. The PEALD silicon nitride film deposited using the 162 MHz CCP exhibited improved film characteristics, such as reduced surface roughness, a lower carbon percentage, a higher N/Si ratio, a lower wet etch rate in a diluted HF solution, lower leakage current, and higher electric breakdown field, and more uniform step coverage of the silicon nitride film deposited in a high aspect ratio trench, as compared to silicon nitride PEALD using 13.56 MHz CCP. These improved PEALD silicon nitride film characteristics are believed to be related to the higher ion density, higher reactive gas dissociation, and lower ion bombardment energy to the substrate observed in N2 plasma with a 162 MHz CCP.

Insulation systems in liquefied natural gas carriers (LNGCs) are vulnerable to sloshing impact and fatigue loads because of waves. If gas leaks into the primary barrier, the flexible secondary barrier (FSB) prevents the leakage of gas in this system. The fatigue strength of a composite FSB largely depends on the behavior of its materials. In this study, a new containment system is proposed for the FSB with the use of aramid fibers to improve its fatigue strength by replacing the conventional E-glass with aramid ones. In its manufacturing, the ratio of aramid to E-glass fibers was varied for an optimum design of the FSB. Fatigue tests showed that the FSB with aramid fibers was superior to that with E-glass ones.

In order to investigate the effect of buffer layer on the superconducting properties of MgB2, behaviors of electron-phonon coupling (EPC) in MgB2 thin films with various thicknesses of ZnO buffer layer on two different substrates Al2O3 and Hastelloy were studied. As the ZnO thickness increases, the values of Tc of MgB2 films on two substrates show opposite behaviors. Sharply decreased and then saturated Tc of ~38K is observed on Al2O3 substrates while an abrupt increase of Tc with no tendency of decrease is obtained on Hastelloy substrates. These Tc behaviors are closely related to the E2g phonon hardening/softening inside MgB2 which may be induced from a lattice distortion caused by an introduction of ZnO buffer layer. The electron-E2g coupling provides a dominant contribution to EPC from all phonon modes, however, it shows a very weak dependence on ZnO thickness to explain the Tc behavior of our samples. Therefore, in order to establish a mechanism of ZnO buffer layer influencing Tc of MgB2 films, contribution from other phonon modes needs to be considered. Understanding the effect of ZnO buffer layer on the EPC and the Tc behavior opens a possibility to obtain an optimal condition for ZnO buffer layer of MgB2 for the field of application.

Pm-Si:H which has improved optical and transport properties as well as stability compared to hydrogenated amorphous silicon is studied. In order to understand the effect of the growth temperature on pm-Si:H films, hydrogen bonding and stability were analyzed in this work. Samples grown at different temperatures were compared and a change on the films morphology and structure was observed. HRTEM images evidence nanocrystals with approximate size of 9 nm. A growth surface reorganization was observed at an almost constant deposition rate. Increasing the deposition temperature leads to a more ordered, compact and smooth structure of the pm-Si:H films. Hydrogen interaction with the growing surface is related to the deposition temperature, changing the growth of the amorphous matrix due to hydrogen surface diffusion into lower energy and more stable positions. The total hydrogen in the film is reduced as temperature increases and hydrogen becomes more tightly bonded, which changes in a non monotonous way how the nanocrystals are incorporated and their environment. The optoelectronic properties of the films are directly related to the incorporation of hydrogen and whether it is weakly or tightly bonded. A diminution of the optical gap of the pm-Si:H films in the range from 1.71 to 1.65 eV was observed with the increase of the deposition temperature in the range from 175 to 275 °C.

Quaternary Cr–V–C–N films were deposited on Si wafers through a hybrid system of arc ion plating and sputtering techniques in an Ar/N2/CH4 gaseous mixture. In this work, the effects of vanadium on the microstructural evolution, mechanical properties and friction mechanism of Cr–V–C–N films were investigated. The results showed that quaternary Cr–V–C–N films consisted of nanosized crystallites of (Cr,V)(C,N) and amorphous VCN phases. The Cr–10·4 at-%V–C–N film possessed the higher hardness value of 34 GPa, compared to the 27 GPa of a Cr(C,N) film. Additionally, the friction coefficients of the Cr–V–C–N films were reduced from 0·38 for the Cr–C–N film to 0·27 for the Cr–10·4 at-%V—C–N film. Atomic force microscopy (AFM) and Auger electron spectroscopy (AES) analyses also revealed that the amorphous phase VCN phases played a role in reducing the friction coefficients of the films. The a-VCN phase (vanadium rich) was believed to cause a tribochemical reaction with ambient air during the wear process.

Porous three-layer mullite/alumina composites with a gradient in porosity and pore size were produced by a tertiary-butyl alcohol ice template technique. The porous products sintered at 1300–1500°C showed two types of pores, i.e. interconnected, unidirectional macro-pore channels and micrometre sized pores in the walls surrounding the pore channels. The layered materials showed superior compressive strength when compared with monolithic blocks, possibly due to the development of alternating layered structure with a gradient porosity and crack deflection along interlayer.

This paper reports the heating performance of the previously reported 4th generation shoe-insole-based hydraulic electromagnetic energy harvester (HEEH) [1] in connection with a micromachined polysilicon heater & a commercial copper heater [2]. The HEEH produced 455.77mW of power by using a 4-channel configuration under an actuation frequency of 3Hz. It was integrated with two types of heaters to produce temperature rises of 2.0 & 3.2°C and the heating rates of 12.0 & 1.6°C/min, respectively, from polysilicon (0.15×0.1mm2, 6.05e−6s of the thermal time constant) and copper heaters (78×28mm2, 8.31s of the thermal time constant). Such heating performance of the HEEH is the 1st results of its kind by energy harvester [3, 4, 5].

Cryogenic milling process is more effective in generating nano- and micro-size particles than conventional high-energy mechanical milling in terms of their size and processing time needed as the cryogenic temperature lowers the activation energy for elastic fracture and minimizes agglomeration among particles. Following the previous success in fabricating uniform chalcopyrite CuInSe 2 nanoparticles using the cryogenic milling process, this study has deposited CuInS 2 thin films through a particle-based, non-vacuum sequential process that includes the preparation of precursor particles using a cryogenic milling process. The paste formulated with the particles was coated on Mo-deposited glass substrate and subsequently sulfurized under S/H 2 /Ar atmosphere. The chalcopyrite CuInS 2 thin films were successfully made after sulfurization at the substrate temperature of 550 °C in 30 min. Optimization of pre-baking step prior to sulfurization was critical in achieving dense morphology of the films and the residual oxygen in the nanoparticles was efficiently removed by its reduction reaction with H 2 during the sulfurization process. While the cryogenic milling process can effectively produce particles in a short period of time, preventing agglomeration, further study is necessary to understand the effect of structural and morphological properties of the starting materials on the final outcome from the cryogenic milling process.

As an alloying element to increase the resistance to softening during tempering, silicon content was modified to investigate its effect on the microstructure and properties of 100Cr6 bearing steel. It turned out that increasing the silicon content brought about two difficulties in the manufacturing process, promoting the decarburisation during heating and/or hot rolling and retarding the spheroidisation of cementite. The maximum size of non-metallic inclusions was predicted to reduce evidently with increasing silicon content, although the total oxygen content in steels was nearly the same. There has been no fine carbide precipitation during tempering that can be attributed to the increasing silicon content, leading to the stabilisation of retained austenite due to the diffusion of carbon atoms from martensite. As a result, the new Si modified high carbon chromium bearing steel showed superior rolling contact fatigue characteristics to conventional steel.

We investigated the effect of the electrode on the resistive switching property of (Cu, Zn, Pt)-Cu2S-W structures to clarify the role of metallic ions and electrodes in forming conductive paths in solid-electrolytes and also to improve the switching property. Notably, Zn-Cu2S-W and Pt-Cu2S-W structures that lack of oxidizable metal electrodes exhibited bipolar switching characteristics, and practically preferable switching properties with appropriately higher a turn-ON voltage and resistance were achieved for Zn-Cu2S-W in comparison to Cu-Cu2S-W with too low turn-ON voltage. In contrast, the degrading evolution of switching was observed in Pt-Cu2S-W. A simplified but convincing model is also suggested and discussed to explain the observations.

In this study, a total of 21 elements were determined from PM2.5 and PM10 samples collected at one subway station using INAA and XRF. In order to assess the pollution status and distribution characteristics in a subway station, the absolute concentration levels, concentration ratios, and crustal enrichment factors of these elements were analyzed. PM2.5 concentrations in the subway station varied in the range of 24.8 to 72.6 μg m−3 (average ± standard deviation: 42.6 ± 10.6 μg m−3), while those of PM10 from 38.0 to 101 μg m−3 (67.2 ± 15.5 μg m−3). The relative contribution of elemental components in each particle fraction accounted for about 42 and 44%, respectively. Out of all metals, Fe was predominant to represent about 29 and 27% of each particle fraction. In contrast, the crustal sources were estimated to contribute to about 3.7 and 2.3% of the total Fe concentrations, respectively. Thus, one can conclude that considerable quantities of airborne Fe particles originated mainly from subway sources, probably due to the wearing of the steel products like wheel, rail, brake, etc.

The present study concerns laser-assisted springback correction for a stamped part comprising a curved U-channel. To determine laser irradiation conditions, bending deformation induced by the laser scanning was predicted using a coupled thermo-mechanical finite element (FE) analysis. To validate and tune the results of analysis, a laser bending experiment was performed. The required magnitude of bending angle for springback correction was determined through a stamping analysis followed by a springback analysis. From the series of thermo-mechanical FE analyses, a simple relationship between bending angle and laser scanning length was constructed. A simple method of springback correction which uses the constructed relationship is proposed in this work.

A microanalytical characterization of cast magnesium alloys of eutectic origin based on the Mg–Al–Ca ternary matrix system has been carried out in order to investigate the influence of alloying elements on their microstructure as well as microchemistry-processing-microstructural relations using structure-sensitive techniques of electron microscopy, mechanical spectroscopy (internal friction), X-ray diffractometry, and advanced microanalytical methods including electron probe compositional analysis. Following the data obtained here there is direct correlation of microstructure with creep properties of the new experimental magnesium alloys. The creep and heat-induced properties of the multicomponent magnesium alloys containing low range of inexpensive additions of titanium (0.07–0.2%) or strontium (of about 1.8%) are defined by resulting structure dynamically formed during creep strain (up to 200 h). It is noteworthy that Ti as novel alloying element competes for creep resistance and cost with Sr and attracts as-cast desirable properties minimizing solute effects at ambient temperatures because of the pinning of slowly moving dislocations with the binding energy no more then 0.3 eV as well as because of stress-induced strengthening. The Ti and Sr solute atmosphere dragging is believed to be the rate-controlling mechanism responsible for radical improvement of creep resistance and long-term strength in the newly developed magnesium alloys at elevated temperatures. The new experimental alloys are superior to commercial alloys AZ91D, AE42, and AS21 following their creep resistance, long-term strength, heat resistance, and castability because of their novel microstructure having desirable engineering properties for structural applications (creep strain ec less than 0.3–0.4% at 423 K and 70 MPa for 200 h; έc ~ 10−9 s−1). The newly developed magnesium alloys with improved castability could be used in die-casting technology and automobile (powertrain) industry for manufacturing of components and parts which are difficult to cast with more desirable microstructure.

Nanometre sized hydroxyapatite grains improve bioactivity and improve osteoblast functions, and are better than the micron sized hydroxyapatite. The surface of titanium can be modified to coat nanosized hydroxyapatite by electrochemical deposition from electrolytes containing calcium and phosphorus precursors. Recently, ultrasonic agitation has been employed to obtain thin coatings of hydroxyapatite. This coating contains nanosized apatite that shows a promising osteoblast cell activity. Moreover, titanium oxide nanotubes have attracted the attention of various researchers due to the increased exploitation of specific functional properties of TiO2 in various applications. TiO2 nanotubes have been formed by anodic oxidation in fluoride based acid electrolytes and these have thicknesses of up to a maximum of 500 nm. Use of fluoride containing glycerol electrolyte is shown to produce smooth tubes of very high aspect ratio. Ultrasonic agitation of the electrolyte has also been employed to produce good...

The “Black Pad” phenomenon referring to blackening of electrolessly plated nickel-phosphorous (Ni(P)) films after the immersion gold (IG) process was reproduced using pure chemicals for the first time. Chemical composition of the electrolyte most suitable for the black pad reproduction was proposed, and it was found that submicron scale nodular variation of the P content of the Ni(P) film induced potential differences large enough to drive galvanic corrosion when exposed to the electrolyte; gold cyanide solution in this case. Instead of conventional potential measurement techniques, corrosion couple experiments using Ni(P) films with different P content were performed to substantiate preferential corrosion, which occurred at the lower P side with the propensity of forming black pad getting more severe with the P content difference (ΔP) between films. Subsequent AFM analysis showed that variations of nodular shapes and curvatures among nodules led to submicron scale variations of the P content in the film, which could promote galvanic corrosion.

We studied the interaction between a surface modified glass prism and a thin film of PDMS (polydimethylsiloxane) elastomer using a shear adhesion test. The glass prism was chemically modified either by depositing a self-assembled silane monolayer (silanization) or by depositing a few layers of polyelectrolytes. The PDMS was modified only with the polyelectrolyte layers (PEL). While the interaction between the chemically modified glass prism and unmodified PDMS (free of any filler additive) is primarily dispersive, some specific interaction prevails when the PEL-modified glass prism contacts a commercial PDMS (i.e., Sylgard® 184) that has silica additives. The surfaces were examined with wettability analysis, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) that established the locus of failure. Water immersion tests show that the adhesion between PDMS and glass is stable under water for a long time when the interfacial interaction is mainly dispersive, whereas it deteriorates rapi...

A rigid-glass prism (square or rectangular base, rectangular cross-section) is sheared off a thin film of silicone elastomer bonded to a glass plate by applying a tangential force at various distances above the prism/elastomer interface. At a given tangential force, the prism starts to slide on the elastomeric film. As the sliding velocity, thus the frictional force, is progressively increased, an elastic instability develops at the interface that results in the formation of numerous bubbles. These bubbles, the lateral dimension of which is comparable to the thickness of the film, move across the interface with speeds 1000 times faster than the overall sliding speed of the glass prism against the PDMS film. It is found that the glass prism continues to slide on the elastomeric film as long as the applied shear stress is less than a critical value. During sliding, however, a normal stress is developed at the interface that decays from the front (i.e. where the force is applied) to the rear end of the prism. When the normal stress reaches a critical value, the prism comes off the film. The critical shear stress of fracture increases with the modulus of the film, but decreases with the thickness following a square root relationship, as is the case with the removal of rigid punches from thin elastomeric films by normal pull-off forces.

A new model for calculating the coefficients of thermal expansion, CTE, in all three coordinate directions is developed for composites containing aligned, axisymmetric elliptical particles, i.e., characterized by a single aspect ratio, that in the limit approximate the shapes of spheres, fibers and discs. This model is based on Elshelby's method but employs a somewhat different formulation than used in prior papers; a main advantage of the current approach is that it can be readily extended to composites based on ellipsoidal particles with no axes of symmetry, i.e., all three major axes are different, as recently demonstrated for modulus. CTE predictions for the simple case of axisymmetric particles are illustrated by calculations for glass particles in the shape of spheres, fibers and discs in an epoxy resin and are compared to those from the popular Chow theory. For spherical-shaped particles, the CTEs in all directions are the same and decrease modestly as the volume fraction of filler particles increases. As the particle aspect ratio increases from unity, the thermal expansion becomes anisotropic. The coefficient of longitudinal linear thermal expansion always decreases with increasing aspect ratio and filler loading due to the mechanical constraint of the filler. For aligned axisymmetric particles, the coefficients of linear thermal expansion are always the same in two directions. The values in the transverse direction may be higher or lower than that of the matrix depending on the values of aspect ratio and filler loading; these regions are mapped out for this particular set of matrix and filler properties. The two-dimensional constraints on matrix expansion caused by discs versus the one-dimensional effects of fibers cause quantitative differences in behavior for the two shapes.

We demonstrated the RF integrated noise suppressor and thin-film inductor using ferromagnetic film. The transmission parameter (S 21) of the integrated noise suppressor was compared with that of the nonintegrated noise suppressor. The magnitude of signal attenuation at the resonance point was greatly increased by the integration up to −30 and −57 dB for the 1-µm-thick and 2-µm-thick CoNbZr films, respectively. The closed magnetic circuit type GHz-drive integrated spiral inductors were fabricated with a four-turn and 380 × 380 µm2 two-port-type inductor with ground guards, which consisted of a sandwich 2-µm-thick Cu coil in between a patterned 1-µm-thick CoNbZr film. The 10/3 (line/space [µm]) designs with 2-µm-thick SiO2 insulating layers exhibited a quality factor Q = 14.7, being highest among the published data at 1 GHz.

An instrumented indentation technique (IIT) appears to be a promising alternative to conventional stress measurement methods, particularly for welds with rapid microstructural gradients, because it has high spatial resolution and is non-destructive. The technique is used to characterize the residual stress of a friction stir-welded joint of API X80 steel. The indentation load–depth curve is significantly affected by the presence of residual stress and the stress-induced load change at a given penetration is converted to a quantitative stress value through an analytical model. All indentation test results show good agreement with those from an energy-dispersive X-ray diffraction performed to assess the validity of the IIT. In addition, the microstructures in various regions of the friction stir-welded joint and their effects on local microhardness are discussed.

Shelled peanut kernels were hydraulically pressed, reconstituted, and fried to investigate the effects of applied pressure, holding time, and initial depth of peanuts in the cylinder on percent oil removed (Y), percent broken kernels (B), and over-expansion ability (E). In general, Y, B, E, and the apparent density of pressed peanut cake increased with the applied pressure in the compression strain range of 0.3 – 0.7 and it was possible to develop the respective empirical correlations. Typical stress-strain diagrams for peanuts exhibited nonlinear relationships indicating a small degree of elasticity upon unloading. The swelling rate constants of pressed peanuts during reconstitution appeared to be proportional to the percent oil removed.

When two thin soft elastomeric films are separated from each other, an elastic instability develops at the interface. Although similar instability develops for the case of a soft film separating from a rigid adherent, there are important differences in the two cases. For the single-film case, the wavelength of instability is independent of any material properties of the system, and it scales only with thickness of the film. For the two-film case, a co-operative instability mode develops, which is a non-linear function of the thicknesses and the elastic moduli of both films. We investigate the development of such instability by energy minimization procedures. Understanding the nature of this instability is important, as it affects the adhesive compliance of the system and thus the energy release rate in the debonding of soft interfaces.

A novel approach for the numerical simulation of the development of crystallinity and birefringence on the spinline was proposed. The approach was based on the calculation of elastic recovery and crystalline and amorphous orientation functions without making any assumption about freezing. To model crystallization, the amorphous orientation function and the flow effect on the equilibrium melting temperature elevation due to the entropy reduction between the oriented and unoriented melts were incorporated. The crystalline orientation function was calculated from the frozen-in elastic recovery. The entropy change and frozen-in elastic recovery calculation were based on a nonlinear viscoelastic constitutive Eq. with the crystallinity and temperature dependent viscosity and relaxation time. The crystalline and amorphous contributions to the overall birefringence were obtained from the crystalline orientation function and the flow birefringence, respectively. The temperature, diameter, density, and birefringence profile in both low- and high-speed spun PET fibers were predicted and compared with the experimental data from literature. Theoretical predictions were found to be in agreement with the published experimental data.

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

Aluminum (2 wt %) doped zinc oxide (AZO) films are prepared by ion beam sputtering method on glass substrates with very low substrate deposition temperature below 150 °C. The results of Hall effect measurements showed the decrease in resistivity (2.6×10−3–7.3×10−4 Ω cm) came from an increase in mobility and carrier concentration as substrate deposition temperature increased. We confirmed the decrease of resistivity, which resulted from the formation of oxygen deficiency (ZnO1−x) as substrate deposition temperature increased. The increase of Hall mobility and carrier concentration was also influenced by increases in crystallinity and grain growth of AZO films as substrate deposition temperature increased. The optical transmission of AZO increased from 70% to 80% with increasing substrate deposition temperature. The surface morphology analysis by atomic force microscopy showed the decrease of surface roughness might be related to the development of optical properties.

GaMnN magnetic thin films were grown using a single GaN precursor of Et2Ga(N3)NH2C(CH3)3, and their structural and magnetic properties were investigated. The GaN layers were grown with c-axis texture orientation. The films, however, revealed a great improvement in the crystallinity upon in-situ and ex-situ annealing at higher temperatures. Incorporation of Mn, however, randomized the growth direction as revealed by investigations of X-ray diffraction and transmission electron microscopy. For high Mn flux, a cubic second phase, Mn3GaN, has precipitated. It is a structure seldom observed in other conventional molecular beam epitaxy growth. It, however, offered a high conductivity to the GaMnN matrix. The precipitated films showed a uniaxial anisotropy in the magneto-transport. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We study thermal annealing effects on the size and composition variations of indium-aggregated clusters in two InGaN thin films with photoluminescence (PL) in the yellow and red ranges. The methods of investigation include optical measurement, nanoscale material analysis, and theoretical calculation. Such a study is important for determining the relation between the band gap and the average indium content of InGaN. In one of the samples, the major part of the PL spectrum is shifted from the yellow band into the blue range upon thermal annealing. In the other sample, after thermal annealing, a broad spectrum covering the whole visible range is observed. Cathodo-luminescence (CL) spectra show that the spectral changes occur essentially in the photons emitted from the shallow layers of the InGaN films. Photon emission spectra from the deeper layers are essentially unaffected by thermal annealing. The spectral changes upon thermal annealing are mainly attributed to the general trend of cluster size reduction....

Valence states and electronic structures of Cr-doped Nd½A½MnO₃ (NAMO; A=Ca, Sr) manganites have been investigated using x-ray absorption spectroscopy (XAS) and high-resolution photoemission spectroscopy (PES). All the Cr-doped NAMO systems exhibit the clear metallic Fermi edges in the Mn e_g PES spectra near E_F. The spectral intensity at E_F is higher for Cr-doped Nd½Sr½MnO₃ (NSMO) than for Cr-doped Nd½Ca½MnO₃ (NCMO), reflecting the stronger metallic nature for NSMO than for NCMO. The measured Cr 2p XAS spectra are found to be very similar to that of Cr₂O₃, indicating that Cr ions in Cr-doped NAMO are in the trivalent Cr³+ states (t³_(2g)). The Cr 2p XAS data are consistent with the Cr 3d PES spectra located at ~1.3 eV below EF and having no emission near E_F.

We compared the optical and material properties of two high-indium InGaN thin layers between the as-grown and post-growth thermally annealed conditions. In one of the samples, the major part of photoluminescence spectrum was shifted from the original yellow band into the blue range upon thermal annealing. Cathodo-luminescence (CL) spectra showed that the spectral shift occurred essentially in the photons emitted from a shallow layer of the InGaN film. The deeper layer in the as-grown film contributed blue emission because it had been thermally annealed during the growth of the shallow layer. The spectral shift was mainly attributed to the shrinkage of cluster size through spinodal decomposition upon thermal annealing. The attribution was supported by the observations in the CL, X-ray diffraction (XRD), time-resolved photoluminescence (TRPL) and, high–resolution transmission electron microscopy (HRTEM) results. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The upper critical field Hc2 for the fields perpendicular and parallel to Mg and B planes of the magnesium diboride is presented in the temperature range from 5.4 K up to Tc as obtained by comparison of high-field magnetotransport, ac-susceptibility and specific heat measurements. The onset of the finite resistivity yields Hc2, while the end of the resistive transition to the normal state is due to surface effects. Hc2 perpendicular to the planes reveals a conventional temperature dependence with μ0Hc2⊥ab(0) = 3.5 T but the parallel critical field with μ0Hc2||ab(0) = 17 T has a positive curvature at temperatures above 20 K. Consequently, the anisotropy factor Γ = Hc2||ab/Hc2⊥ab is temperature dependent with Γ equal to 4.8 at low temperatures and about 2 near Tc. The angular dependence of the upper critical field of an elliptic form is obtained at several temperatures.

Using magnetization, magneto-transport and single-crystal specific heat measurements we have determined the superconducting phase diagram of MgB 2 . The superconducting anisotropy γ changes monotonously from a value of around 2 near T c to above 4.5 at 22 K. For H||c a pronounced peak effect in the critical current occurs at the upper critical field. We present a strong evidence for a surface superconducting state for H||c which might account for the wide spread in reported values of the superconducting anisotropy γ.

The deformation behavior of Cu single crystal has been investigated by synchrotron radiation. The variation point of slope in the difference of glide strains corresponds to the exchange point of Schmid's factor of the secondary slip systems. This phenomenon may be originated by the interaction between the primary and secondary slip systems.

A new surface modification technique, the so-called ion-assisted reaction (IAR), has been developed; such modification of polymer surfaces offers many industrial applications. The addition of new functional groups on polymer surfaces and permanent hydrophilic polymer surfaces (water contact angle below 30° and surface energy 60-70 mJ/m2) have been accomplished by IAR treatment. The formation of functional groups is significantly dependent on the flow rate of the reactive gas, the irradiating ion dose, and the ion beam energy. Improvements in wettability and surface energy are primarily attributed to the increase of polar characteristics due to the formation of functional groups such as —(C=O), —(C=O)—O—, —(C—O)—, etc. The characteristics of the IAR treatment have been reviewed, with outstanding results regarding the wettability and adhesion of various polymers such as PMMA, PC, PP, PS, PI, PVDF, and PTFE.

Asymmetric rolling, in which the circumferential velocities of working rolls are different, imposes shear deformation and in turn shear deformation textures to sheets through the thickness. A component of ND//〈111〉 in the shear deformation textures can improve the plastic strain ratios of aluminum sheets. In order to understand the evolution of ND//〈111〉, the strain histories and distributions in the sheets and the texture evolution during the asymmetric rolling have been measured and calculated. The shear deformation texture can vary with the ratio of shear to normal strain increments. As the ratio increases from zero to infinity, the texture moves from the plane strain compression texture (β fiber) to the ideal shear deformation texture consisting of {001}〈110〉, {111}〈110〉, and {111}〈112〉. The ratio increases with rolling reduction per pass in asymmetric rolling. However, it is practically difficult to develop a rolling reduction per pass high enough to obtain the ideal shear deformation texture. Imposing the positive and negative shear deformations on the sheet by reversal of the shearing direction can give rise to the ideal shear deformation texture.

Mesoscale disordered materials are ubiquitous in industry and in the environment. Any fundamental understanding of the transport and mechanical properties of such materials must follow from a thorough understanding of their structure. However, in the overwhelming majority of cases, experimental characterization of such materials has been limited to first- and second-order structural correlation functions, i.e., the mean filling fraction and the structural autocorrelation function. We report here the successful combination of synchrotron x-ray microtomography and image processing to determine the full three-dimensional real-space structure of a model disordered material, a granular bed of relatively monodisperse glass spheres. Specifically, we determine the center location and the local connectivity of each granule. This complete knowledge of structure can be used to calculate otherwise inaccessible high-order correlation functions. We analyze nematic order parameters for contact bonds to characterize the geometric anisotropy or fabric induced by the sample boundary conditions. Away from the boundaries we find short-range bond orientational order exhibiting characteristics of the underlying polytetrahedral structure.

The purpose of this study was to estimate the absorbed dose distribution of Ho-166 endovascular beta irradiation using an angio-catheter. The liquid form of Ho-166 was produced at the Korea Atomic Energy Research Institute (KAERI) by an (n,gamma) reaction. Ho-166 has a half-life of 26.8 h and emits a high-energy beta particle with a maximum energy of 1.85 MeV. GafChromic film was used for the estimation of the absorbed dose of beta particles. A Co-60 teletherapy source and a 6 MV photon beam from a linear accelerator were used to generate dose-optical density calibration curves. The exposed films were read using a videodensitometer. With a modified micrometer, the film was positioned accurately on the surface of the balloon in water. The balloon was filled with Ho-166 solution to a pressure of 4 atm. Several film exposures were made with varying irradiation times and activities. The radiation absorbed dose rates were 1.02, 0.51 and 0.35 Gy x min(-1) x GBq(-1) x ml(-1) at the balloon surface, 0.5 and 1 mm from the balloon surface, respectively. The absorbed dose distribution revealed that Ho-166 is a good source for endovascular irradiation as the beta range is very short, avoiding unnecessary irradiation of normal tissue. A clinically applicable irradiation and duration of exposure were achievable utilizing our system.

We present a spectroscopic ellipsometry study of the optical anisotropies at energies above and below a crossing point at {approx_equal}2 eV in the optical conductivity of Bi{sub 1-x}Ca{sub x}MnO{sub 3} crystals. Below T{sub co}, we observe a sudden increase of the low-frequency dielectric function, reflecting charge ordering. Moreover, we find a gradual development in the high-frequency dielectric function, primarily influenced by orbital effects, which suggest that fluctuations associated with short-range orbital ordering precede charge ordering. (c) 2000 The American Physical Society.

Highly epitaxial CrSi 2 films were grown on Si(111) substrate by Cr deposition on Si(111)-(7×7) surface at 450°C followed by in situ annealing at 900–1100°C in ultrahigh vacuum. CrSi 2 (001) plane was grown parallel to the Si(111) plane with a CrSi 2 // Si matching face relationship. The valence band (VB photoemission for the 1200-Å-thick CrSi 2 was measured at room temperature and 20 K by using synchrotron radiation (hν=20–120 eV). Overall shapes of the two energy distribution curves (EDC's) were similar. Two peaks were observed in the EDC's corresponding to the bonding and the nonbonding Cr -d states in the CrSi 2. The onset of the VB photoemission measured at 20 K was located at about 0.32 eV below Fermi level, due to the energy band gap opening at low temperature.

We investigated dc and ac susceptibilities of Pr0.63Sr0.37MnO3 and Nd0.7Sr0.3MnO3 single crystals. Surprisingly, real components of the ac susceptibility of both samples are frequency dependent below TC , indicating competition between ferromagnetic and antiferromagnetic interactions even in the ferromagnetic phase. We also found evidence of rare-earth moment ordering at low temperatures. Our ac susceptibility data suggest strongly that ferromagnetic phases of the two samples are of different nature. By comparing the resistivity data with the susceptibility results near TC , we propose that the order parameter of magnetic origin should be coupled to the other degrees of freedom in the case of Nd0.7Sr0.3MnO3. @S0163-1829~99!01646-X#

The deformation behaviour of pure copper single crystals has been investigated by scanning electron microscopy and synchrotron radiation using the in situ reflection Laue method. Two types of sample with the same orientation of tensile axes, but with different crystallographic orientations in the directions of the width and thickness of the samples, have been studied. They showed different characteristics of deformation behaviour, such as the activated slip systems, the movement of the tensile axis, and the mode of fracture.

{ital F}-center formation by monochromatic x rays has been studied above and below the bromine and rubidium {ital K}-absorption edges in crystals of RbBr. The x-ray beam from a double silicon crystal monochromator on an undulator at the Advanced Photon Source was used to produce these point defects, which were detected by a sensitive laser-induced luminescence method. Experiments were carried out over a wide range of monochromatic x-ray intensity, with emphasis on the nearly linear initial slope of defect formation with exposure. No significant increase in {ital F}-center formation efficiency was found upon crossing the bromine {ital K} edge, which indicates that additional Auger-cascade mechanisms do not appreciably add to the usual multiple ionization electron-hole recombination processes known to generate point defects. {copyright} {ital 1999} {ital The American Physical Society}

We investigated temperature-dependent optical conductivity spectra of a ${\mathrm{Nd}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ single crystal. We found that polishing and surface scattering effects on the ${\mathrm{Nd}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ crystal surfaces could significantly distort the optical responses, especially in the mid-infrared region. However, oxygen annealing and gold normalization processes seemed to remedy the distortions. We found that the spectral weight of ${\mathrm{Nd}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ in the metallic state might be composed of a Drude carrier term and a strong incoherent mid-infrared absorptions. The temperature dependence of the spectral weight suggests that the electron-lattice coupling should be important in optical properties of colossal magnetoresistance manganites.

To conduct plasma research with a steady-state high magnetic field, a magnetic mirror system with a pair of superconducting magnets (SCMs), named Superconducting Magnet Plasma Research Facility (SPRF), is under development. Major components of the system are a pair of NbTi solenoid SCMs, two cryostats, a plasma chamber, and a dc power supply. Each SCMs is separated by 1-m distance and operated at 800 A. The magnetic flux density on the axis of the SPRF is 0.23 T at the mid point and 3.1 T at the magnet center, which gives the mirror ratio of 13.4. In this paper, we describe the design consideration of SPRF, including the development activities of the magnets and the cryostats. Also, the test results of the magnets and the cryostats are described.