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2005-05-01
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DEPUY ORTHOPAEDICS, INC. RANDOMIZED, MULTICENTER, TRIAL OF CERAMIC ...
... 40 401 ... records, clinical and office charts, laboratory notes, X-ray films, other subject ... head articulating with a metal alloy acetabular bearing insert. ...
Superstructure in nano-crystalline Al50Cu28Fe22 alloy
2005-07-14
This work reports the formation of nano- crystalline Al50Cu28Fe22 by high-energy milling. For obtaining the nano-crystalline material, the Al50Cu28Fe22 alloy synthesized through slow cooling of the molten alloy was subjected to ball milling, which was carried out in attritor mill at 400 rpm for 5 h, 10 h, 20 h, 40 h and 80 h with a ball to powder ratio 40 : 1 in hexane medium. The x-ray diffraction observation of ball-milled samples revealed that the milling duration of $5h$ to $40 hrs$ has led to the formation of nano-phase. The average crystallite size comprising the nano-phase has been found to be $\sim 17 nm$. When the nano-crystalline alloy, Al50Cu28Fe22 was vacuum annealed at a temperature of 500$^0C$ for 5 to 20 hrs, new structural phases representing superstructures of the parent nano-crystalline phase were found . The superstructure have been found to correspond to simple cubic with $a = \sqrt 2a_p$ and face central cubic with a = 2a_p (a_p = lattce parameter of parent nano-crystalline alloy). It has been proposed that the formation of different type of superstructure resulting due to different duration of ball milling followed by annealing is possibly governed by minimization of free energy of the disordered B2 phase.
Surface damage of molybdenum and TZM alloy under D/sup +/ impact
1977-01-01
The surface damage of polycrystalline molybdenum and TZM alloy under 40-, 60-, and 120-keV D/sup +/ impact has been investigated for irradiation in both pulsed and continuous mode for total doses varying from 1.7 x 10/sup 17/ to 2.2 x 10/sup 19/ ions/cm/sup 2/ and for target temperatures verying from ambient temperature to 400/sup 0/C. Analysis by scanning electron microscopy of the MO samples held at ambient temperatures during D/sup +/ irradiations in both pulsed and continuous modes revealed surface damage due to blistering for the 40-keV and 60-keV irradiations for doses ranging from 8.7 x 10/sup 17/ to 8.1 x 10/sup 18/ ions/cm/sup 2/, but no detectable damage for the 120-keV D/sup +/ irradiations for doses ranging from 4.3 x 10/sup 18/ to 2.2 x 10/sup 19/ ions/cm/sup 2/. This observed difference in the blistering behavior is attributed to the differences in the ambient target temperature for the 120-keV irradiation and both the 40- and 60-keV irradiations. For irradiations at temperatures above 300/sup 0/C, no blisters could be detected for any of the three energies. For similar irradiation conditions, TZM-alloy showed a reduction in blistering as compared to molybdenum.
Melt-spun Al70âX Si30Mn X (X=0, 3, 5, 7, 10) anode in lithium-ion batteries
2009-01-01
Al70âX Si30Mn X (X=0, 3, 5, 7, 10, mol%) ribbons were prepared by melt spinning. A supersaturated solid solution of Si and Mn in fcc Al and some microstructures consisting of nano grains were obtained. Some alloys with nano-sized grains exhibited high discharge capacities and favorable cycle properties. The capacity of more than 400 mAh/g could be obtained in melt-spun Al67Si30Mn3 alloy after 20 cycles and more than 300 mAh/g after 40 cycles. Li/Si and Li/Al compounds in the anodes of pure Al and pure Si were not detected in Al-Si-Mn alloys inserted by Li. It is considered that the formation of the supersaturated solid solution and refinement of microstructures have prevented the alloys from the forming the compounds with superfluous Li. As a result, the electrochemical properties have b...
Bulk metallic glass formation in the Pd-Ni-P and Pd-Cu-P alloy systems
1996-12-11
Bulk metallic glasses were prepared in the Pd-Ni-P and Pd-Cu-P systems using a fluxing technique. The formation of bulk amorphous Pd-Cu-P alloys was reported here for the first time. For both alloy systems, bulk glass formation requires maintaining the phosphorus content near 20 at.%. In the Pd-Ni-P system, 10-mm diameter amorphous Pd{sub x}Ni{sub 80{minus}x}P{sub 20} rods can be formed for 25 {le} x {le} 60. In the Pd-Cu-P system, 7-mm diameter amorphous Pd{sub x}Cu{sub 80{minus}x}P{sub 20} rods can be produced for 40 {le} x {le} 60. From all the ternary alloys studied, Pd{sub 40}Ni{sub 40}P{sub 20} has the highest glass formability, and 25-mm diameter amorphous cylinders, 50 mm in length, can be easily fabricated. The glass stability of the Pd-Ni-P system is wider than that of the Pd-Cu-P system. For most bulk Pd-Ni-P glasses, {Delta}T > 90 K. The {Delta}T values of bulk amorphous Pd-Cu-P alloys are considerably smaller, ranging from 27 to 73 K. The elastic constants of bulk amorphous Pd-Ni-P and Pd-Cu-P alloys were determined using a resonant ultrasound spectroscopy technique. The Pd-Ni-P glasses are slightly stiffer than the Pd-Cu-P glasses. Within each alloy system, the Young`s modulus and the bulk modulus show little change with alloy composition. Of all the bulk glass forming systems so far investigated, the ternary Pd-Ni-P system has the best glass formability. This alloy was one of the first bulk glasses discovered, yet it still remains the best in terms of glass formability. Upon replacing part of Ni by Cu, the critical cooling rates are expected to be further reduced.
2009-01-01
In order to obtain high-strength aluminium butt joints with corrosion resistance, ultrasonic soldering of A1070 rods was conducted using quasi-melting Sn-xZn (x = 23, 40, 82 mass%) hypereutectic alloy. Ultrasonic vibrations were applied at soldering temperatures ranging 220-300°C through A1070 rods without a solder bath. The tensile strength of the solder joints with Sn-23Zn or 40Zn alloy were higher than that of the joint soldered with Sn-9Zn eutectic alloy. The joints soldered with Sn-23Zn or 40Zn alloy showed the same strength as A1070 rods which employed the same heat treatment as the ultrasonic soldering process. The thickness of the hypereutectic solder layer in the joints was thicker than that of the Sn-9Zn solder layer because unmelted α-Zn solid solution ...
2009-01-01
Nanostructured Pt x Ni/C and Pt x Co/C catalysts (1 ⤠x ⤠3) containing from 27 to 40 wt % of metal with the average size of metal (alloy) particles from 2.6 to 4.7 nm are obtained using the methods of liquid-phase synthesis. Addition of a doping component is found to yield a decrease in the average nanoparticle sizes and an improved activity of materials in oxygen electroreduction reactions. The obtained catalysts are characterized by high specific activity as compared to commercial Pt/C materials. The stability of electrocatalysts to selective dissolution of the doping component is evaluated.
2006-10-07
The (Co,Ni)Al2O4 is an aluminum transition metals oxide which falls into the category of aluminate spinels. The synthesis of nano-crystalline spinels has been investigated extensively due to their potential applications such as a high-density magnetic recording, microwave devices magnetic fluids, ceramic pigment as well as a heterogeneous catalytic material. In the present study, attempts have been made to synthesise the nano-crystalline (Co,Ni)Al2O4 spinel powders by ball milling and subsequent annealing. An alloy of Al70 Ni15 Co15, exhibiting the formation of a complex intermetallic compound known as decagonal quasicrystals in the as-solidified condition, is selected as the starting material for mechanical milling. It is interesting to note that this alloy is close to the stoichiometry of aluminum and transition metal atoms required to form of the aluminate spinel. The milling was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 20:1 in hexane medium and the annealing was performed for 10, 20 and 40 h at 600 0 C in air in side the furnace in order to oxidize the decagonal phase and finally to form the spinel structures. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of nano-sized decagonal phase after milling and then (Co,Ni)Al2O4 spinel type structure from the nano-size decagonal phase during annealing. The average crystallite size has been found to be ~40 nm by XRD and TEM studies, the lattice strain is 0.6 %, and the lattice parameter is 8.0756 A . The ferromagnetic behaviour is also observed in the milled and the annealed samples.
2009-01-01
High-resolution electron microscopy was applied to analyze the continuous precipitated particles of the g-Mg17Al12 phase with Pitsch-Schrader OR in the heat-treated AZ91 alloy at 473K for 8h. The existence of a continuous precipitated particle with the Pitsch-Schrader OR including the selection of the habit plane and the growth direction in Mg-Al system is rationalized by the constrained coincidence site lattice/constrained complete pattern shift lattice (CCSL/CDSCL) model and the O-lattice theory.
2004-07-01
In continuation of efforts from last quarter, processing parameters, used in the formation of Pd-Cu alloy films, were being optimized in a drum (web) coater system with the goal of producing large-area, contiguous, pinhole-free films for H{sub 2} separation membranes. Since the (pre-treatment) functionality of the surface of the plastic backing material is sub-optimal, they tended to produce films in the drum coater that were either not contiguous (disseminates upon release from the polymer backing material) or contain pinholes. Alternative approaches, such as direct deposition onto thermally oxidized silicon wafers, have been attempted to yield pinhole-free films; i.e., formation of a poorly adherent Pd-Cu film on silicon will then directly release from the silicon substrate. Permeation characteristics of a 25 {micro}m-thick, Pd{sub 60}Cu{sub 40} alloy foil were conducted. After pre-treating the sample to stabilize the FCC {beta}-phase, the hydrogen permeability was determined to be 5.4 x 10{sup -5} cm{sup 3} cmcm{sup -2}s{sup -1}cm Hg{sup -1/2}. Thin, 1-3 {micro}m-thick Pd-Cu alloy films have been prepared on PS films and samples will be prepared and tested in the next quarter.
2009-01-01
The crystal structure and morphology of nitride precipitates developing in the matrix of a Fe-1.5 wt pct Cr-1.5 wt pct Al (Fe-1.6 at. pct Cr-3.1 at. pct Al) alloy upon gas nitriding were investigated. To this end, the nitrided zone was studied using metallographic methods, X-ray diffractometry (XRD), electron probe microanalysis (EPMA), microhardness measurement, and transmission electron microscopy (TEM), including high-resolution TEM (HRTEM), and scanning TEM (STEM). Furthermore, a nitrogen-absorption isotherm was determined, for use in characterizing the nature of the nitride-precipitation process. It could be shown that the expected equilibrium nitrides, cubic CrN and hexagonal AlN, do not develop. Instead, mixed Cr1âx Al x N nitride precipitates of the cubic, rock-salt structure typ...
http://hdl.handle.net/1947/2920
X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and potentiodynamic measurements have been made on chromate conversion-coated Al 2024-T3 alloy. X-ray photoelectron spectroscopy measurements indicated that the conversion coating had a surface of CrOOH and Cr(VI), enriched in ferricyanide. The bulk of the coating was an equal mixture of CrOOH and with significant levels of F- and Fe, the Cr latter implying the 2O3 presence of ferricyanide throughout the coating. Copper(II) ion was present at the interface between the conversion coating and the alloy, as well as Al3+ During ageing experiments, potentiodynamic measurements indicated that the corrosion current (icorr decreased from ~0.4 to ~0.04 uA cm-2 during the first 40 h after preparation but thereafter slowly increased. No significant changes were observed in the chemistry of the coating by XPS for ageing times longer than 40 h, although morphological changes were observed with SEM. As the coating aged, a network of microcracks developed across the surface. It is believed that Cr6+ is consumed in the process in which plugs of hydrated chromium oxide form at the base of these cracks. Other identifier: Surface and Interface Analysis 25 (4), pp. 223-234, 1997 Language: en_US
Zinc Treatment Effects on Corrosion Behavior of Alloy 600 in High Temperature, Hydrogenated Water
2004-11-16
Trace levels of soluble zinc(II) ions (30 ppb) maintained in mildly alkaline, hydrogenated water at 260 C were found to reduce the corrosion rate of Alloy 600 (UNS N06600) by about 40% relative to a non-zinc baseline test [2]. Characterizations of the corrosion oxide layer via SEM/TEM and grazing incidence X-ray diffraction confirmed the presence of a chromite-rich oxide phase and recrystallized nickel. The oxide crystals had an approximate surface density of 3500 {micro}m{sup -2} and an average size of 11 {+-} 5 nm. Application of X-ray photoelectron spectroscopy with argon ion milling, followed by target factor analyses, permitted speciated composition vs. depth profiles to be obtained. Numerical integration of the profiles revealed that: (1) alloy oxidation occurred non-selectively and (2) zinc(II) ions were incorporated into the chromite-rich spinel: (Zn{sub 0.55}Ni{sub 0.3}Fe{sub 0.15})(Fe{sub 0.25}Cr{sub 0.75}){sub 2}O{sub 4}. Spinel stoichiometry places the trivalent ion composition in the single phase oxide region, consistent with the absence of the usual outer, ferrite-rich solvus layer. By comparison with compositions of the chromite-rich spinel obtained in the non-zinc baseline test, it is hypothesized that zinc(II) ion incorporation was controlled by the equilibrium for 0.55 Zn{sup 2+}(aq) + (Ni{sub 0.7}Fe{sub 0.3})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}(s) {r_equilibrium} 0.40 Ni{sup 2+}(aq) + 0.15 Fe{sup 2+}(aq) + (Zn{sub 0.55}Ni{sub 0.3}Fe{sub 0.15})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}(s). It is estimated that only 8% of the Ni(II) ions generated during non-selective oxidation of the alloy were retained as Ni(II) in the corrosion layer; the remainder either recrystallized to Ni(0) (38%) or were released to the aqueous phase (54%).
2009-01-01
Immobilization of enzymes on porous inorganic materials is very important for biocatalysis and biotransformation. In this paper, nanoporous gold (NPG) was used as a support for lignin peroxidase (LiP) immobilization. NPG with a pore size of 40-50nm was prepared by dealloying Au/Ag alloy (50:50wt%) for 17h. By incubation with LiP aqueous solution, LiP was successfully immobilized on NPG. The optimal temperature of the immobilized LiP was ca. 40, 10degreeC higher than that of free LiP. After 2h incubation at 45degreeC, 55% of the initial activity of the immobilized LiP was still retained while the free LiP was completely deactivated. In addition, a high and sustainable LiP activity was achieved via in situ release of H2O2 by a co-immobilized glucose oxidase. The present co-immobilization sys...
2009-01-01
The amorphous alloy rods of (Zr53Cu30Ni9Al8)100-xSix (x=0.25, 0.5, 0.75, 1) with a diameter of 2-6mm were prepared by drop casting method in an Ar atmosphere. The thermal properties, including glass forming ability (GFA) and thermal stability during isothermal annealing of these amorphous alloys, and the mechanical properties have been systematic investigated by the combination of DSC, XRD, SEM, TEM, and compression test. The result of X-ray diffraction reveals that these entire (Zr53Cu30Ni9Al8)100-xSix alloy rods exhibit a typical amorphous diffraction pattern with only a broad maximum around 2 around 40 degree. Both Tg (glass transition temperature) and Tx (crystallization temperature) of these (Zr53Cu30Ni9Al8)100-xSix alloys increase with the silicon addition. In addition, both the acti...
2009-01-01
The passive film composition of Mg0.9-xTi0.1PdxNi (x=0.04, 0.06, 0.08, 0.1) hydrogen storage alloys after 40 charge-discharge cycles has been investigated by means of X-ray photoelectron spectroscopy (XPS) in combination with Ar+ sputtering technology. With the XPSPEAK software, high resolution spectra of alloy elements and oxygen were deconvolved into individual peaks. Composites formed by metal elements and their relative contents were also deduced. It was found that the composites originated from Mg and Ni were mainly in the form of their oxides and hydroxides, which existed at the top surface of alloys. With the increase of sputtering depth, the hydroxides of Mg and Ni gradually disappeared while corresponding oxides dominated their passive products. According to the analysis results o...
2009-01-01
The as-received hot band (2.54-mm thick) of a continuous cast (CC) AA 3004 Al alloy was cold rolled at reductions, ranging from 25 to 90 pct, and subsequently annealed at 510 °C for 4 hours. Some of these specimens had been annealed at 420 °C for 3 hours with a heating rate of 1 °C/min prior to cold rolling. It was found that the sample with the prior heat treatment exhibited a P orientation ({011} Formula Not Shown ) of 28 pct in volume fraction, stronger than that (23 pct) in the sample without the prior heat treatment, after 90 pct cold rolling and final recrystallization. The transmission electron microscopy (TEM) observations revealed that the prior heat treatment generated very densely distributed Al6(Mn,Fe) precipitates, which could pin dislocations and grain boundaries ...
1980-05-01
Work on the HTGR Helium Compatibility Task accomplished during the period March 31, 1977 through September 30, 1979, is documented in this report. Emphasis is on the results and analyses of creep data to 10,000 h and the detailed metallurgical evaluations performed on candidate alloy specimens tested for up to 10,000 h. Long-term creep and unstressed aging data in controlled-impurity helium and in air at 800, 900, and 1000/sup 0/C are reported for alloys included in the program in FY-76, including the wrought solid-solution-strengthened alloys, Hastelloy X, Hastelloy S, RA 333, and HD 556, and the centrifugally cast austenitic alloys, HK 40, Supertherm, Manaurite 36X, Manaurite 36XS, and Manaurite 900.
Subtask 12D3: Fracture properties of V-5Cr-5Ti Alloy
1995-03-01
The purpose of this research is to investigate the effect of heat treatment on microstructure and fracture toughness of a V-5Cr-5Ti alloy in the range -50-100{degrees}C. Fracture toughness and impact tests were performed on a V-5Cr-5Ti alloy. Specimens annealed at 1125{degrees}C for 1 h and furnace cooled in a vacuum of 1.33 x 10{sup -5} Pa were brittle at room temperature (RT) and experienced a mixture of intergranular and cleavage fracture. Fracture toughness (J{sub IQ}) at RT was 52 kJ/m{sup 2} and the impact fracture energy (IFE) was 6 J. The IFE at -100{degrees}C was only 1 J. While specimens exhibited high fracture toughness at 100{degrees}C (J{sub IQ} is 485 kj/m{sup 2}), fracture was a mixture of dimple and intergranular failure, with intergranular fracture making up 40% of the total fracture surface. The ductile to brittle transition temperature (DBTT) was estimated to be about 20{degrees}C. When some specimens were given an additional annealing at 890{degrees}C for 24 h, they became very ductile at RT and fractured by microvoid coalescence. The J{sub IQ} value increased from 52 kJ/m{sup 2} to {approximately}1100 kJ/m{sup 2}. The impact test failed to fracture specimens at RT due to a large amount of plastic deformation. 7 refs., 1 fig., 6 tabs.
Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen
2008-11-15
Full Text Available.Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not enhance the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4 – 9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values.
http://www.deakin.edu.au/dro/view/DU:30006434
An austenitic Ni-30 wt pct Fe alloy, with a stacking-fault energy and deformation characteristics similar to those of austenitic low-carbon steel at elevated temperatures, has been used to examine the defect substructure within austenite deformed by single-pass strip rolling and to identify those features most likely to provide sites for intragranular nucleation of ultrafine ferrite in steels. Samples of this alloy and a 0.095 wt pct C-1.58Mn-0.22Si-0.27Mo steel have been hot rolled and cooled under similar conditions, and the resulting microstructures were compared using transmission electron microscopy (TEM), electron diffraction, and X-ray diffraction. Following a single rolling pass of ∼40 pct reduction of a 2mm strip at 800 °C, three microstructural zones were identified throughout its thickness. The surface zone (of 0.1 to 0.4 mm in depth) within the steel comprised a uniform microstructure of ultrafine ferrite, while the equivalent zone of a Ni-30Fe alloy contained a network of dislocation cells, with an average diameter of 0.5 to 1.0 µm. The scale and distribution and, thus, nucleation density of the ferrite grains formed in the steel were consistent with the formation of individual ferrite nuclei on cell boundaries within the austenite. In the transition zone, 0.3 to 0.5 mm below the surface of the steel strip, discrete polygonal ferrite grains were observed to form in parallel, and closely spaced “rafts” traversing individual grains of austenite. Based on observations of the equivalent zone of the rolled Ni-30Fe alloy, the ferrite distribution could be correlated with planar defects in the form of intragranular microshear bands formed within the deformed austenite during rolling. Within the central zone of the steel strip, a bainitic microstructure, typical of that observed after conventional hot rolling of this steel, was observed following air cooling. In this region of the rolled Ni-30Fe alloy, a network of microbands was observed, typical of material deformed under plane-strain conditions. Publisher: Minerals, Metals & Materials Society Relation: isMemberOf: School of Engineering and Technology collection; isMemberOf: ERA cluster 3 : Engineering and Environmental Sciences collection Coverage: 2000-08-31 Language: eng Rights: Springer
2004-01-01
We present adaptive finite element simulations of dendritic and eutectic solidification in binary and ternary alloys. The computations are based on a recently formulated phase-field model that is especially appropriate for modelling non-isothermal solidification in multicomponent multiphase systems. In this approach, a set of governing equations for the phase-field variables, for the concentrations of the alloy components and for the temperature has to be solved numerically, ensuring local entropy production and the conservation of mass and inner energy. To efficiently perform numerical simulations, we developed a numerical scheme to solve the governing equations using a finite element method on an adaptive non-uniform mesh with highest resolution in the regions of the phase boundaries. Simulation results of the solidification in ternary Ni$_{60}$Cu$_{40-x}$Cr$_{x}$ alloys are presented investigating the influence of the alloy composition on the growth morphology and on the growth velocity. A morphology diagram is obtained that shows a transition from a dendritic to a globular structure with increasing Cr concentrations. Furthermore, we comment on 2D and 3D simulations of binary eutectic phase transformations. Regular oscillatory growth structures are observed combined with a topological change of the matrix phase in 3D. An outlook for the application of our methods to describe AlCu eutectics is given.
2009-01-01
The high-temperature creep deformation and fracture behavior of a directionally solidified Ni-base superalloy DZ951 have been investigated over a wide stress range of 110 to 880 MPa at high temperatures (700 °C to 1000 °C). In this article, the detailed creep deformation and fracture mechanism have been studied. The results show that the creep curves exhibit strong temperature dependence. From transmission election microscopy (TEM) observations, it is suggested that the deformation mechanism is temperature dependent and mainly consists of three dislocation-controlling mechanisms: stacking faults and dislocation-pair shearing, dislocation bowing, and dislocation climbing. It is found that the fracture mode of DZ951 alloy changes from cleavagelike fracture at low temperature to ductile ...
http://espace.library.uq.edu.au/view/UQ:57515
An experimental white cast iron with the unprecedented fracture tough ness of 40 MPa m(1/2) is currently being studied to determine the mechanisms of toughening. This paper reports the investigation of the role of strain-induced martensitic (SIM) transformation. The dendritic microconstituent in the toughened alloy consists primarily of retained austenite, with precipitated M(7)C(3) carbides and some martensite. Refrigeration experiments and differential scanning calorimetry (DSC) were used to demonstrate, firstly, that this retained austenite has an ''effective'' sub-ambient M(S) temperature and, secondly, that SIM transformation can occur at ambient temperatures. Comparison between room temperature and elevated temperature K-Ic tests showed that the observed SIM produces a transformation toughening response in the alloy, contributing to, but not fully accounting for, its high tough ness. SIM as a mechanism for transformation toughening has not previously been reported for white cast irons. Microhardness traverses on crack paths and X-ray diffraction (XRD) on fracture surfaces confirmed the interpretation of the K-Ic experiments. Further DSC and quantitative XRD showed that, as heat-treatment temperature is varied, there is a correlation between fracture toughness and the volume fraction of unstable retained austenite. Relation: isMemberOf Publications of the School of Engineering
http://handle.unsw.edu.au/1959.4/26174
In the global search for renewable sources of energy, hydrogen is a promising candidate in transportation and electronic applications. Carbon nanotubes (CNTs) have the largest hydrogen storage capacity among the hydrogen storage materials known at present. The Ni-MH battery can be used to store and then discharge large amounts of hydrogen reversibly by using hydrogen storage materials as negative electrode. The electrochemical hydrogen storage performances of metal hydride electrodes with different levels of multi wall carbon nanotubes (20%, 15%, 10%, 5% and 2% of Ni-MH battery's active materials) has been investigated under similar charge-discharge conditions. Electrochemical test cell consisted of a single hydrogen storage negative electrode sandwiched between two NiOOH/Ni(OH)2 positive electrodes. A 6M aqueous KOH solution was used as electrolyte. Electrochemical properties such as specific discharge capacity, high rate charge-discharge capability and cycle life stability have been investigated. The morphology and structure of negative electrode material were examined by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Chemical analysis of the hydrogen storage alloy was performed using electron probe microanalysis, electron diffraction spectroscopy and induced coupled plasma spectroscopy analysis. Hydrogen absorption-desorption properties were measured in terms of pressure-composition-isotherm curves. It has been found in this study that the presences of CNTs significantly enhanced the overall electrochemical properties of the Ni-MH battery. Maximum specific discharge capacity was observed for 5% CNTs electrode reaching 243 mAh/g, whereas 0% CNTs could only reach 229 mAh/g. High rate charge and discharge capabilities of 5% CNTs electrodes were ~ 241% and 250% higher than the corresponding values for 0% CNTs electrode. Furthermore, the differences in electrochemical hydrogen storage of CNTs with different diameters of 10-20 nm, 20-40 nm, 40-60 nm, and 60-100 nm were investigated. Electrochemical results demonstrated that CNTs with different diameters showed a large variation in the electrochemical hydrogen storage capability under the similar experimental condition. A comparison between electrodes with different CNTs studies was carried out in order to optimize nanotubes choices for Ni-MH battery. It was found that smaller tube diameters, 20-40 nm and 5% CNTs negative electrode showed the best electrochemical properties of Ni-MH battery system. Publisher: Awarded by:University of New South Wales. School of Materials Science and Engineering Language: EN Rights: Copyright Humara Sultana; http://unsworks.unsw.edu.au/copyright
Stacking dependent disordering processes in Gd/Co/Pt(111) studied with surface x-ray diffraction
2008-01-01
Disordering processes induced by Gd overlayers on 15 atomic layers thick Co films grown on top of a Pt(111) surface have been studied in situ by surface x-ray diffraction. They have been investigated in two structurally different Co layers deposited at different substrate temperatures: a film grown at 220 K consisting of a mixture of hcp and fcc crystallites plus some disordered stacking, and another one grown at room temperature containing more disorder and fcc crystallites only. Gd induced disordering has been found to be dependent on the structure of the Co film since cubic fcc crystallites are more sensitive to disordering than hexagonal ones. In addition, Gd deposition causes a reduction in about 0.5% in the Co interatomic distance in the layer plane, which arises from relaxation of stress in the film. The stress is mainly concentrated in fcc grains, which are more strained in the film plane than hcp ones. Furthermore, Co grains having the substrate fcc stacking sequence are majority in the Co films, and they are more stable against disordering than the corresponding fcc twin ones, suggesting some kind of long-range interaction stabilizing the majority stacking. These structural modifications induced by the Gd overlayers affect the magnetism of the film, as evidenced by the hysteresis loops measured by magneto-optical Kerr effect, probing the Co magnetization, and by resonant x-ray scattering at the Pt L-III edge, sensitive to the Pt magnetization at the Co/Pt interface. It has been found that the Gd overlayer changes the magnetization of the whole Co film, increasing significantly its coercive field for thick enough Gd overlayers and reducing the amplitude of the loops. These changes are compatible with the formation of a disordered Co-Gd alloy with reduced magnetic moment for the Co atoms, and they affect the whole Co film down to the Pt interface. All these results illustrate how surface x-ray diffraction can be used to characterize in detail alloying processes happening in thin films of binary systems, especially in those containing heterogeneous mixtures of different phases.
Ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline yttria-stabilized zirconia
2009-01-01
Thermally stable, stoichiometric, cubic yttria-stabilized zirconia (YSZ) thin-film electrolytes have been synthesized by reactive pulsed dc magnetron sputtering from a ZrâY (80/20 at. %) alloy target. Films deposited at floating potential had a texture. Single-line profile analysis of the 111 x-ray diffraction peak yielded a grain size of ~20 nm and a microstrain of ~2% regardless of deposition temperature. Films deposited at 400 °C and selected bias voltages in the range from â70 to â200 V showed a reduced grain size for higher bias voltages, yielding a grain size of ~6 nm and a microstrain of ~2.5% at bias voltages of â175 and â200 V with additional incorporation of argon. The films were thermally stable; very limited grain coarsening was observed up to an annealing temperature of 800 °C. Temperature-dependent impedance spectroscopy analysis of the YSZ films with Ag electrodes showed that the in-plane ionic conductivity was within one order of magnitude higher in films deposited with substrate bias corresponding to a decrease in grain size compared to films deposited at floating potential. This suggests that there is a significant contribution to the ionic conductivity from grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.14 and 1.30 eV. ©2009 American Institute of Physics
http://espace.library.uq.edu.au/view/UQ:2812
Distribution of nickel and minor elements such as Au, Ag, Fe, Co, Cu, As, and Sb between the Ni-S alloy and the CaO-Al2O3 based slag phases in a magnesia crucible was studied at 1873 K. Partial pressure of SO2 was controlled at 10.1 kPa, while partial pressures of O2 and S2 ranged between the point of NiO precipitation (po2 of 10.1 Pa) and the point at which Ni3S2 is formed (ps2 of 4.0 kPa). The nickel content in the slag and the sulfur and oxygen contents in the metal at a given po2 or pso2 decrease when the temperature is increased from 1773 to 1873 K. The distribution ratios of iron, cobalt, and copper, defined by (wt pct X in slag)/{wt pct X in alloy}, where X is the minor element in the slag, have larger values than that of nickel, while the values of Au, Ag, Sb, and As are lower than that of nickel. The distribution behavior of nickel and minor elements is discussed based on the concept of oxidic and sulfidic dissolution. Coverage: 2004-01-01T00:00:00Z
http://espace.library.uq.edu.au/view/UQ:163080
Hydroxyapatite (HA) is synthesized through acid-base reaction by adding an aqueous solution of orthophosphoric acid to an aqueous solution of calcium hydroxide maintained at 40, 80 and 100°C. X-ray diffraction of the precipitate particles revealed HA as the predominant phase in all the temperatures and that the morphology of the particles changed from needle-shaped at 40°C to spheroid at 100°C. The changes in the morphology with temperature were analyzed taking into account the driving force for the HA precipitation and the super saturation level of Ca2+and PO43-ions with respect to HA. It appears that the effect of temperature on morphology is less pronounced compared to that of super saturation level. The analysis also indicated that the super saturation level of the reactants, especially the concentration of Ca2+ions, played a predominant role on the precipitate morphology for this classical acid-base reaction. Publisher: IEEE Relation: isMemberOf Excellence in Research Australia (ERA) - Collection; isMemberOf Australian Institute for Bioengineering and Nanotechnology Publications
http://espace.library.uq.edu.au/view/UQ:162982
Hydroxyapatite (HA) is synthesized by a wet chemical route using calcium hydroxide and ortho-phosphoric acid at various temperatures (40, 80, and 100 °C). X-ray diffraction of the precipitate particles revealed HA as the predominant phase (>99%) with a small amount of β-tricalcium phosphate. Fourier transform infrared spectroscopy indicated the presence of carbonate substitution, which decreased with increasing temperature. Transmission electron microscopy observations revealed needle-shaped particles with a high aspect ratio at 40 °C, which changed to spheroidal when the precipitation temperature was increased to 100 °C. The changes in the morphology with temperature were analyzed taking into account the driving force for the HA precipitation and the supersaturation level of Ca2+ and PO43- ions with respect to HA. The analysis indicated that the supersaturation level of the reactants, especially the concentration of Ca2+ ions, played a predominant role on the precipitate morphology for this classical acid−base reaction. Publisher: American Chemical Society Relation: isMemberOf Excellence in Research Australia (ERA) - Collection; isMemberOf Australian Institute for Bioengineering and Nanotechnology Publications
http://espace.library.uq.edu.au/view/UQ:162944
The formation of biologically equivalent carbonate-containing apatite on the surface of synthetic hydroxyapatite (HA) is an important step leading to good bone healing. In this study, HA-reinforced polyetheretherketone (PEEK) composites were prepared by homogeneous mixing of HA and PEEK powders, compaction, and pressureless sintering. The bioactivity of HA/PEEK composite with 10, 20, 30 and 40 vol% HA was evaluated by immersing the composite disks in the simulated body fluid (SBF) for up to 4 weeks. The surface of composite with 40 vol% HA was covered by a layer of bone-like apatite just after 3 days of immersion, while 10 vol% HA was covered only after 28 days. This apatite layer was characterized by SEM, thin film X-ray diffractometer, attenuated total reflectance–Fourier transform infrared spectrometer (FTIR)/FTIR. Introducing a concept called apatite-forming capacity of SBF, growth kinetics of the apatite layer on the surface of the composite disks was carried out. The growth rate constant increased with HA volume fraction of the composite, suggesting that the bioactivity of the HA/PEEK composite increases with increasing HA volume fraction in the composite. ; ; ; ; Publisher: Elsevier Relation: isMemberOf Excellence in Research Australia (ERA) - Collection; isMemberOf Australian Institute for Bioengineering and Nanotechnology Publications
Uranium chloride extraction of transuranium elements from LWR fuel
1991-12-31
A process of separating transuranium actinide values from uranium values present in spent nuclear oxide fuels containing rare earth and noble metal fission products as well as other fission products is disclosed. The oxide fuel is reduced with Ca metal in the presence of Ca chloride and a U-Fe alloy which is liquid at about 800{degrees}C to dissolve uranium metal and the noble metal fission product metals and transuranium actinide metals and rare earth fission product metals leaving Ca chloride having CaO and fission products of alkali metals and the alkali earth metals and iodine dissolved therein. The Ca chloride and CaO and the fission products contained therein are separated from the U-Fe alloy and the metal values dissolved therein. The U-Fe alloy having dissolved therein reduced metals from the spent nuclear fuel is contacted with a mixture of one or more alkali metal or alkaline earth metal halides selected from the class consisting of alkali metal or alkaline earth metal and Fe or U halide or a combination thereof to transfer transuranium actinide metals and rare earth metals to the halide salt leaving the uranium and some noble metal fission products in the U-Fe alloy and thereafter separating the halide salt and the transuranium metals dissolved therein from the U-Fe alloy and the metals dissolved therein.
Thermal analysis of selected tin-based lead-free solder alloys
2009-01-01
The Sn-Ag-Cu alloys have favourable solderability and wetting properties and are, therefore, being considered as potential lead-free solder materials. In the present study, tin-based Sn-Ag-Cu and Sn-Ag-Cu-Bi alloys were studied in detail by a differential scanning calorimetry (DSC) and thermodynamic calculations using the CALPHAD approach. The amount of the alloying elements in the materials was chosen to be close to the respective eutectic composition and the nominal compositions were the following: Sn-3.7Ag-0.7Cu, Sn-1.0Ag-0.5Cu-1Bi (in wt.%). Thermal effects during melting and solidifying were experimentally studied by the DSC technique. The microstructure of the samples was determined by the light microscopy and the composition of solidified phases was obtained by the energy-dispersive X-ray spectroscopy, respectively. The solidification behaviour under equilibrium conditions was simulated using the Thermo-Calc software package. This approach enabled us to obtain the enthalpy of cooling for each alloy and to compare its temperature derivative with the experimental DSC curves.
2008-12-01
Peri-prosthetic infections are notoriously difficult to treat as the biomaterial implant is ideal for bacterial adhesion and biofilm formation, resulting in decreased antibiotic sensitivity....Full Text Available
2008-12-01
Full Text Available.Peri-prosthetic infections are notoriously difficult to treat as the biomaterial implant is ideal for bacterial adhesion and biofilm formation, resulting in decreased antibiotic sensitivity. Previously, we reported that vancomycin covalently attached to a Ti alloy surface (Vanc-Ti) could prevent bacterial colonization. Herein we examine the effect of this Vanc-Ti surface on Staphylococci epidermidis, a Gram-positive organism prevalent in orthopaedic infections. By direct colony counting and fluorescent visualization of live bacteria, S. epidermidis colonization was significantly inhibited on Vanc-Ti implants. In contrast, the gram negative organism Escherichia coli readily colonized the Vanc-Ti rod, suggesting retention of antibiotic specificity. By histochemical and SEM analysis, Vanc-Ti prevented S. epidermidis biofilm formation, even in the presence of serum. Furthermore, when challenged multiple times with S. epidermidis, Vanc-Ti rods resisted bacterial colonization. Finally, when S. epidermidis was continuously cultured in the presence of Vanc-Ti, the bacteria maintained a Vanc sensitivity equivalent to the parent strain. These findings indicate that antibiotic derivatization of implants can result in a surface that can resist bacterial colonization. This technology holds great promises for the prevention and treatment of periprosthetic infections.
2009-01-01
The influence of Cu(OH)2 addition in 7 mol/L KOH alkaline electrolyte on the electrochemical properties of La0.75Mg0.25Ni3.5 hydrogen storage alloy electrode was investigated in the testing temperature range of from 25 deg. C to -40 deg. C in this paper. XRD Rietveld analyses shows that the La0.75Mg0.25Ni3.5 hydrogen storage alloy consists of LaNi5 phase, (La, Mg)2Ni7 phase and (La,Mg)Ni3 phase. The maximum discharge capacity and the high-rate dischargeability (HRD) of the La0.75 Mg0.25Ni3.5 alloy electrode both decrease with decreasing testing temperature, which mainly due to the slower hydrogen transfer in the bulk of the alloy and the lower electrocatalytic activity at lower ... >>
The magnetism and magnetotransport properties of doped perovskite LaMn sub 1 sub - sub x Zn sub x O sub 3 (x = 0.05, 0.10, 0.15, 0.20, 0.30, 0.40) have been studied. All samples exhibit insulating behaviour under zero field and a 6 T field (except for x = 0.05, the weak insulating-metallic transition occurs near T sub C under zero field), but there is a paramagnetic-ferromagnetic (PM-FM) transition and a large MR effect near T sub C. The rho- T curves are fitted well by a semiconductor-like model. We suggest that the MnO sub 6 octahedron is contorted by zinc doping and that this contortion will influence the Jahn-Teller (JT) distortion of Mn sup 3 sup +. The e sub g carrier has to overcome the energy gap caused by the difference between the JT distortions induced by Mn sup 3 sup + in the non-contorted MnO sub 6 octahedrons and the contorted ones. Infrared spectra and Raman spectra confirmed our ideas. In addition, the magnetism was investigated by ESR and M-T measurements. The Zn doping suppresses the PM-FM transition and T sub C decreases with the increase of dopant. For x = 0.30 and 0.40, there exists cluster-glass behaviour in the low-temperature range.
1997-04-01
The yield and maximum strengths of an irradiated series of isotopically tailored ferritic alloys were evaluated using the shear punch test. The composition of three of the alloys was Fe-12Cr-1.5Ni. Different balances of nickel isotopes were used in each alloy in order to produce different helium levels. A fourth alloy, which contained no nickel, was also irradiated. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys, and as expected, the strength of the alloys decreased with increasing irradiation temperature. Helium itself, up to 75 appm over 7 dpa appears to have little effect on the mechanical properties of the alloys.
2009-01-01
Toxicity of hexavalent chromium (Cr6+) was focused on with a publication of EU RoHS directive, a novel method to determine hexavalent chromium is developed. It is a combination of energy dispersion X-ray fluorescence spectrometry (EDXRF), spot test, alkali digestion and UV-vis spectrophotometric analysis. First, by EDXRF screening, the presence or absence of element Cr was established. Spot test was followed to identify the valent state of chromium because Cr6+ and Cr3+ normally coexist. After alkali digestion, Cr(VI) was separated without an undersired Cr(VI)-Cr(III) interconversions. With a color reagent (DPC) to chelated with Cr(VI), the solution was finally detected by a UV-vis spectrophotometer at a wavelength of 540 nm which is the basis of analyzing Cr(VI) quantitatively. Some parameters affecting analyses were studied. ... >>
The bone diagnostic instrument II: Indentation distance increase
2008-06-01
The bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo....Full Text Available
The bone diagnostic instrument II: Indentation distance increase
2008-06-01
Full Text Available.The bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. Such measurements could contribute to the overall assessment of bone fragility in the future. Here, we describe an improved BDI, the Osteoprobe II™. In the Osteoprobe II™, the probe assembly, which is designed to penetrate soft tissue, consists of a reference probe (a 22 gauge hypodermic needle) and a test probe (a small diameter, sharpened rod) which slides through the inside of the reference probe. The probe assembly is inserted through the skin to rest on the bone. The distance that the test probe is indented into the bone can be measured relative to the position of the reference probe. At this stage of development, the indentation distance increase (IDI) with repeated cycling to a fixed force appears to best distinguish bone that is more easily fractured from bone that is less easily fractured. Specifically, in three model systems, in which previous mechanical testing and∕or tests reported here found degraded mechanical properties such as toughness and postyield strain, the BDI found increased IDI. However, it must be emphasized that, at this time, neither the IDI nor any other mechanical measurement by any technique has been shown clinically to correlate with fracture risk. Further, we do not yet understand the mechanism responsible for determining IDI beyond noting that it is a measure of the continuing damage that results from repeated loading. As such, it is more a measure of plasticity than elasticity in the bone.
We report the results of a series of X-ray measurements on a 3.1 mm sup 2 , 2.5 mm thick CdZnTe detector carried out at the BESSY II and HASYLAB synchrotron radiation facilities. The detector energy response function was found to be linear over the energy range 2.3-100 keV with an average rms non-linearity of 0.6%, consistent with statistics. At room temperature, under full-area illumination, the FWHM energy resolution was 1.6 keV at 5.9 keV rising to 2.9 keV at 59.54 keV. At a reduced detector temperature of -20 deg. C, these fall to 380 and 818 eV FWHM, respectively. Under pencil beam illumination, the measured energy resolution at 2.5 keV was 360 eV FWHM rising to 1558 eV at 100 keV. By best fitting the expected resolution function to the experimental data, we derive a value for the Fano factor of (0.099+-0.02). Cooling the detector to -50 deg. C, resulted in no noticeable difference in DELTA E above 60 keV, but a 40% reduction at energies <10 keV. At 5.9 keV, the measured resolution under full-area illumination using an sup 5 sup 5 Fe source was found to be approx 10% broader than that measured at an equivalent energy using a 50 mu m diameter pencil beam of synchrotron radiation. However, at 59.54 keV there was no statistical difference between pencil beam and full-area illumination, indicating uniform cystallinity and stoichiometry in the bulk. For energies <50 keV, the measured energy-loss spectra display symmetric photopeaks, becoming increasing tailed at higher energies due to hole trapping. The spatial uniformity of the detector was investigated by raster scanning a 50x50 mu m sup 2 , 10 keV monoenergetic X-ray beam across the active area. Apart from a few localized areas, the detector response was found to uniform at the few percent level, consistent with statistics
Tensile and impact properties of iron-aluminum alloys
1993-12-31
Tensile and impact tests have been conducted on specimens from a series of five heats of iron-aluminum alloys. These results have been compared to data for the iron aluminide alloy FA-129. The transition temperatures of all of the Fe{sub 3}Al-based alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys [based on Fe-8Al (wt %)] had lower transition temperatures and higher upper-shelf energy levels than the Fe{sub 3}Al-type alloys. The reduced aluminum alloy with yttrium showed excellent tensile properties, with a room temperature total elongation of 40%, and a very high upper-shelf energy level. Despite the high tensile ductility at room temperature, the transition temperature of the yttrium-containing alloy was still about 150 C, compared to approximately 300 C for FA-129. In general, the microstructures were coarse and anisotropic. The fracture processes were dominated by second-phase particles.
1998-03-01
The tensile strength and ductility of unirradiated CuAl25 IG0 and CuCrZr alloys decreased continuously with increasing temperature up to 350 deg C. Fracture toughness of unirradiated CuAl25 IG0 alloy decreased continuously with increasing temperature from 20 deg C to 350 deg C whereas the fracture toughness of unirradiated CuCrZr alloy remained almost constant at temperatures up to 100 deg C, was decreased significantly at 200 deg C and slightly increased at 350 deg C. Fracture toughness of HIP joints were lower than that of corresponding copper alloy and fracture path in HIP joint specimen was always within copper alloy side of the joint. Neutron irradiation to a dose level of 0.3 dpa resulted in hardening and reduction in uniform elongation to about 2-4% at 200 deg C in both copper alloys. At higher temperatures softening was observed and uniform elongation increased to about 5% and 16% for CuAl25 IG0 and CuCrZr alloys, respectively. Fracture toughness of CuAl25 IG0 alloy reduced markedly due to neutron irradiation in the temperature range from 20 deg C to 350 deg C. The fracture toughness of the irradiated CuCrZr alloy also decreased in the range from 20 deg C to 350 deg C, although it remained almost unaffected at temperatures below 200 deg C and decreased significantly at 350 deg C when compared with that of unirradiated CuCrZr alloy. (orig.)
Synthesis, characterization and modeling of high quality ferromagnetic Cr-doped AlN thin films
2002-12-18
We report a theoretical and experimental investigation of Cr-doped AlN. Density functional calculations predict that the isolated Cr t2 defect level in AlN is 1/3 full, falls approximately at midgap, and broadens into an impurity band for concentrations over 5%. Substitutional Al1-xCrxN random alloys with 0.05 <= x <= 0.15 are predicted to have Curie temperatures over 600 K. Experimentally, we have characterized and optimized the molecular beam epitaxy thin film growth process, and observed room temperature ferromagnetism with a coercive field, Hc, of 120 Oersted. The measured magnetic susceptibility indicates that over 33% of the Cr is magnetically active at room temperature and 40% at low temperature.
2004-01-22
We present a study of the superconducting properties (Tc and Hc2) in the solid solution (TMTSF)2ClO4(1−x)ReO4x with a ReO−4 anion concentration up to x = 6%. The dramatic suppression of Tc when the residual resistivity is increased upon alloying with no modification of the Fermi surface is the signature of non-conventional superconductivity . This behaviour strongly supports p or d wave pairing in quasi one dimensional organic superconductors. The determination of the electron lifetime in the normal state at low temperature confirms that a single particle Drude model is unable to explain the temperature dependence of the conductivity and that a very narrow zero frequency mode must be taken into account for the interpretation of the transport properties.
Substitutional alloy of Ce and Al
2009-02-24
The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered...Full Text Available
Substitutional alloy of Ce and Al
2009-02-24
Full Text Available.The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce3Al intermetallic compound >15 GPa or the Ce3Al metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L3-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions.
Study on the Formation of Nano tau 3 Phase by Mechanical Alloying
2006-10-07
In the present investigation the pure elemental powder mixture of Al (70 at%) Ni (15 at %), Cu (15 at %) was mechanically milled in an attritor ball mill for 10, 20, 40, 60, 80 and 100 hours in hexane medium at 400 rpm. The isothermal annealing of 100 h mechanically milled powder has been done at 700 0C for 20, 40 and 60 hours. The mechanically alloyed powders are characterized using X-ray diffraction, differential thermal analysis and transmission electron microscopy techniques. It was observed that mechanical alloying led to the formation of nano tau 3 phases in Al70 Cu15Ni15 after 80 h of milling. In the case of 100 h MM and subsequent annealing at 700 0 C for 20, 40 and 60 h, powder exhibited the formation of tau 3 phases with bigger grain sizes. The phase formation and transformations in the above systems have been discussed based.
2009-01-01
The structure and electrochemical kinetics properties of La0.90-xCexPr0.05Nd0.05Ni3.90Co0.40Mn0.40Al0.30 (x = 0.10, 0.20, 0.30, 0.40, 0.50) hydrogen storage alloys have been investigated. XRD shows that the alloys consist of LaNi5 phase with hexagonal CaCu5 structure. With increase in Ce content, the parameter a and cell volume decrease remarkably, but the parameter c increases slightly. The limiting current density IL and the hydrogen diffusion coefficient D increase, and the exchange current density I0 increases firstly from 201.4 mA/g (x = 0.10) to 277.9 mA/g (x = 0.30) and then decreases to 208.5 mA/g (x = 0.50). Meanwhile, high rate dischargeability (HRD) at 1440 mA/g increases from 44.1% (x = 0.10) to 59.9% (x = ... >>
Study on defect state and tritium behavior in neutron-irradiated Li-Al alloy
1999-07-01
Li-Al alloy was selected as a target material for tritium production, because of its high thermal conductivity, which prevents the temperature rise of the target during irradiation. Here, the proposed Al-12.7 at.% {sup 6}Li alloy is composed of {alpha} - (Al) and {beta} - (intermetallic compound {beta}-LiAl) phases. {beta}-LiAl is a unique compound that contains a large amount of Li-vacancy (maximum 4 at.%), but its defect structure has not been confirmed. In this alloy, almost {sup 6}Li are contained in the {beta}-phase. In order to clarify the behavior of tritium which is produced by the {sup 6}Li(n, {alpha}){sup 3}H reaction in this alloy, the tritium behavior in the {beta}-phase, i.e., the {beta}-LiAl crystal was examined. Further, in order to clarify the defect structure of {beta}-LiAl, the carrier scattering model for the lattice defects was proposed and the experimental data of the electrical resistivity was analyzed. On the basis of the carrier scattering model, the resistivity of {beta}-LiAl before and after neutron irradiation was consistently explained, and the unknown concentration (maximum 0.8 at.%) of the defect complex in {beta}-LiAl was determined. As mentioned above, the tritium behavior in the neutron-irradiated {sup 6}Li-Al alloy was clarified in consideration of the defect structure of {beta}-LiAl. The temperature to extract the tritium from the {sup 6}Li-Al alloy was determined and the alloy was applied to the tritium production of 37 TBq (1,000 Ci) scale. (J.P.N.)
Study of the high temperature characteristics of hydrogen storage alloys
In this work, the phase structure of as-cast and melt-spun (MmY)/sub 1/(NiCoMnAl)/sub 5/ alloys (the content of yttrium is 0-2.5wt.%) and their electrochemical properties were studied with regard to discharge capacity at different temperatures (30-80 degrees C) and cycling life at 30 degrees C. It is found that the substitution of yttrium increase the electrochemical capacity of the compounds and decrease the difference in capacity between as-cast and as-quenched compounds at 30 degrees C. When increasing the yttrium concentration from 0 to 2.5wt.%, the cycling life of both the as-cast and the melt- spun compounds deteriorated, although the latter have a slightly longer cycle life than the former. The remarkable feature of the alloys obtained by yttrium substitution is the improvement of the high temperature electrochemical properties. It shows that the stability of the hydrides is increased. Compared with the as-cast alloys, the melt-spun ribbons have higher electrochemical charge /discharge capacity in the range of 40-80 degrees C, especially in the temperature range 70-80 degrees C. In addition, the electrochemical capacities of the melt-spun alloys showed more recovery than the as-cast alloys after charging/discharging at high temperature. This is ascribed to the better oxidation resistance. The analysis of the potential curves illustrate that the improvement of the charging/discharging efficiency for the melt-spun ribbons with yttrium substitution is ascribed to a flatter and lower hydride- formation potential as well as to a higher hydrogen evolution potential. XRD indicates that less lattice strain and defects and more anisotropy existed in melt-spun alloys. This could be beneficial to the improvement of the cycling durability and anti-corrosion properties.
Studies on PEM Fuel Cell Noble Metal Catalyst Dissolution
2009-01-01
A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium dissolution, and membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were found to dissolve in 1 M sulfuric acid solution and the solubility increased exponentially with the potential cycle upper limit. 2-20% Pt (depending on catalyst type) was found dissolved during the experiment; in the same condition, 30 up to 100% Ru (depending on catalyst type) was found lost. Faster dissolution of ruthenium compared to platinum in the alloy type catalyst was also confirmed by X-ray diffraction measurement. Dissolution of carbon supported catalyst was found one order of magnitude higher than none-supported catalyst. Other factors like media acidity, chloride content and oxygen partial pressure all turned out to influence the noble metal dissolution. Degradation of the polyfluorinated sulfonic acid membrane electrolyte was also found to be an important source of increased acidity in the triple phase boundary, and consequently dissolution of the noble metal catalysts.
2008-01-01
Energy-dispersive X-ray fluorescence spectrometer (EDXRF) with primary radiation monochromatized by LiF(200) crystal was developed. In the constructed spectrometer, the radiation from the Ag target X-ray tube operated at 50 kV and 40 mA excites the secondary target (Cu, Se, Zr or Mo). The characteristic radiation (Cu Kalpha, Se Kalpha, Zr Kalpha or Mo Kalpha) of the target is monochromatized with LiF(200) crystal and excites elements in the analyzed sample. The X-ray spectra are collected by thermoelectrically cooled Si-PIN detector with resolution of 145 eV at 5.9 keV. The pinhole collimator placed in front of the X-ray detector allows reducing size of the analyzed area. Quantitative analysis is performed using standardless fundamental parameters (FP) method. ... >>
Spin-dependent electron dynamics and recombination in GaAs(1-x)N(x) alloys at room temperature
2006-12-27
We report on both experimental and theoretical study of conduction-electron spin polarization dynamics achieved by pulsed optical pumping at room temperature in GaAs(1-x)N(x) alloys with a small nitrogen content (x = 2.1, 2.7, 3.4%). It is found that the photoluminescence circular polarization determined by the mean spin of free electrons reaches 40-45% and this giant value persists within 2 ns. Simultaneously, the total free-electron spin decays rapidly with the characteristic time ~150 ps. The results are explained by spin-dependent capture of free conduction electrons on deep paramagnetic centers resulting in dynamical polarization of bound electrons. We have developed a nonlinear theory of spin dynamics in the coupled system of spin-polarized free and localized carriers which describes the experimental dependencies, in particular, electron spin quantum beats observed in a transverse magnetic field.
SHIELDING CHARACTERISTICS OF TERNARY BISMUTH, LEAD AND TIN ALLOYS
2008-01-01
Radiation shields are widely used in radiotherapy to protect critical organs and avoid normal tissue to be exposed to unnecessary irradiation. In recent years, cadmium has been recognized as a source of environmental pollution. The present study was carried out to compare between two groups used in shielding during radiotherapy. The first group contained standard alloys used in Mansoura University and National Cancer Institute of Cairo University, Egypt. The second group was the prepared alloys. Some of these alloys containing cadmium (Bi50Pb27Sn13Cd10 and Bi50Pb40Cd10) and the other alloys were cadmium free (containing bismuth, lead and tin ternary with different concentrations). The attenuation coefficient of the two groups has been compared to that of the control material ... >>
Recovery in aluminium
2006-01-01
In the present thesis the development of a unique experimental method for volume characterisation of individual embedded crystallites down to a radius of 150 nm is presented. This method is applied to in-situ studies of recovery in aluminium. The method is an extension of 3DXRD microscopy, an X-ray diffraction technique for studies of the evolution of grains within polycrystalline materials. The much smaller volume of the crystallites of interest here in comparison to grains implies that the existing method is not applicable due to overlap of diffraction spots. In this work this obstacle is overcome by the combined use of X-ray micro focusing optics, new scanning algorithms and the use of foils. The ratio of foil thickness to crystallite size should be at least 10 such that the central ones are situated in a bulk environment. To avoid thermal drifts, gold reference markers are deposited onto the sample. The X-ray fluorescence from these markers defnes the position of the crystallites with respect to the beam to within 1 ¹m. Two types of data analysis approaches have been developed. The first one generates apparent size distributions of an ensemble of crystallites. These may be converted to true size distributions by stereological tools. Uniquely, this method enables in situ studies of the evolution in size distribution - at a specific sample location - with good statistics (5000-20000 per 20 minutes). The second approach generates growth curves (volume vs. time) of individual crystallites. This involves at all times 1) separating a given diffraction spot from neighbouring spots originating from other crystallites and 2) measuring the complete integrated intensity of the spot (as this is related to volume). This image analysis problem is formulated in a 5D observational space, where growth curves are represented as strings. To identify the strings a combination of a 5D connected component type algorithm and multi-peak fitting was found to be superior. The first use of the method was a study of recovery of a deformed aluminium alloy (AA1050). The aluminium alloy was deformed by cold rolling to a thickness reduction of 38%. The sample was annealed at 300±C for 3 hours. From the statistical analysis of the size distribution most of the recovery was found to occur during the first 3 minutes of annealing. Growth curves are presented for nine individual subgrains. A difference is observed between these experimental data and predictions from curvature-driven grain growth models. The observed individual subgrains showed no evidence of rotation. In outlook, several synchrotrons are presently developing nano-X-ray beams. Applying the methodology developed in this thesis to these beams will enable in-situ studies of the dynamics of bulk crystalline nano-structures down to the scale of »20 nm.
Reconstruction of chronic aseptic sternal pseudoarthrosis after median sternotomy: initial experience with the Ley prosthesis
2008-01-01
It has previously been reported that the Ley prosthesis, a 0.5-mm-thick titanium alloy plate designed for reconstruction and stabilization of the unstable sternotomy, leads to shorter hospital stay and reduces the need for further surgical procedures in patients with postoperative mediastinitis after open heart surgery. We report our initial experience with the Ley prosthesis in patients with chronic aseptic sternotomy dehiscence. The study included 6 male patients (age 42-80 years) with opiate-derivate-dependent intractable pain and significantly reduced quality of life caused by noninfected sternal pseudoarthrosis and unstable sternotomy with large sternal bone tissue deficit. Four of the patients had undergone various surgical fixation procedures 8 days to 12 months after the primary operation. The patients were treated with reconstruction and stabilization of the sternum with the Ley prosthesis 10 to 40 months after the primary operation. In 1 patient bone transplantation was used. No immediate peri- or postoperative complications were observed, and all patients were discharged 4 to 11 days after surgery. One patient who received a bone transplant developed wound infection, and the prosthesis was removed 5 weeks after implantation. At 6-month follow-up all sternotomies were found stable, and patients reported that pain had decreased and quality of life was significantly improved. Our results demonstrate that the Ley prosthesis can be safely and efficiently used for the reconstruction and stabilization of the sternum in patients with intractable pain caused by noninfected postoperative sternal dehiscence and large sternal bone tissue deficit.
Radiation effects in the aluminium alloys irradiated with neutrons
2009-01-01
Full text: Materials of fuel elements for water cooled nuclear reactors are exposed to simultaneous action of an ionizing radiation, temperature and yields of water radiolysis. In particular, irradiation by fast neutrons (En> 0.1 MeV) in research reactors influences mainly the mechanical properties of aluminium alloys, increasing their strength and reducing the plasticity. Radiation can essentially affect the stability of the heat-generating assembly material, changing its structure state. The structure change may also be the result of post-radiation ageing. This paper presents the results of studying the influence of reactor neutrons (research reactor of INP AS RU) on microstructure, electrical characteristics and length changes of SAV-1 and AMG-2 aluminium alloys used in nuclear industry. These alloys are low-alloyed solid solutions and ... >>
Positive Contrast Visualization of Nitinol Devices using Susceptibility Gradient Mapping
2008-09-01
MRI visualization of devices is traditionally based on the signal loss due to T2* effects originating from the local susceptibility differences. To visualize nitinol devices...Full Text Available
Positive Contrast Visualization of Nitinol Devices using Susceptibility Gradient Mapping
2008-09-01
Full Text Available.MRI visualization of devices is traditionally based on the signal loss due to T2* effects originating from the local susceptibility differences. To visualize nitinol devices with positive contrast a recently introduced post processing method is adapted to map the induced susceptibility gradients. This method operates on regular gradient echo MR images and maps the shift in k-space in a (small) neighborhood of every voxel by Fourier analysis followed by a center of mass calculation. The quantitative map of the local shifts generates the positive contrast image of the devices, while areas without susceptibility gradients render a background with noise only. The positive signal response of this method depends only on the choice of the voxel neighborhood size. The properties of the method are explained and the visualization of a nitinol wire and two stents are shown for illustration.
Plasma Membrane Area Increases with Spread Area by Exocytosis of a GPI-anchored Protein Compartment
2009-07-15
The role of plasma membrane (PM) area as a critical factor during cell motility is poorly understood, mainly due to an inability to precisely follow PM area dynamics. To address this fundamental question,...Full Text Available
Plasma Membrane Area Increases with Spread Area by Exocytosis of a GPI-anchored Protein Compartment
2009-07-15
Full Text Available.The role of plasma membrane (PM) area as a critical factor during cell motility is poorly understood, mainly due to an inability to precisely follow PM area dynamics. To address this fundamental question, we developed static and dynamic assays to follow exocytosis, endocytosis, and PM area changes during fibroblast spreading. Because the PM area cannot increase by stretch, spreading proceeds by the flattening of membrane folds and/or by the addition of new membrane. Using laser tweezers, we found that PM tension progressively decreases during spreading, suggesting the addition of new membrane. Next, we found that exocytosis increases the PM area by 40–60% during spreading. Reducing PM area reduced spread area, and, in a reciprocal manner, reducing spreadable area reduced PM area, indicating the interconnection between these two parameters. We observed that Golgi, lysosomes, and glycosylphosphatidylinositol-anchored protein vesicles are exocytosed during spreading, but endoplasmic reticulum and transferrin receptor-containing vesicles are not. Microtubule depolymerization blocks lysosome and Golgi exocytosis but not the exocytosis of glycosylphosphatidylinositol-anchored protein vesicles or PM area increase. Therefore, we suggest that fibroblasts are able to regulate about half of their original PM area by the addition of membrane via a glycosylphosphatidylinositol-anchored protein compartment.
Performance of a furnace for the high-field X-ray diffraction measurements at high temperature
2009-01-01
An X-ray powder diffraction system in high temperature and in high magnetic fields was developed, which was performed at temperature ranging from room temperature to 473 K in the magnetic fields up to 5 T. The temperature stability was within +-1 K for 8 hours. To examine the ability of the system, high field and high temperature X-ray diffraction measurements were carried out for a novel ferromagnetic shape alloy, Ni40Co10Mn34Al16. We observed a field-induced reverse transformation in the alloy. (author)
Oxidation of Fe–22Cr Coated with Co3O4: Microstructure Evolution and the Effect of Growth Stresses
2007-01-01
The oxidation behavior of a commercially available Feâ22Cr alloy coated with a Co3O4 layer by metal organicâchemical vapor deposition was investigated in air with 1% H2O at 1,173 K and compared to the oxidation behavior of the non-coated alloy. The oxide morphology was examined with X-ray diffraction, electron microscopy, and energy dispersive X-ray spectroscopy. Cr2O3 developed in between the Co3O4 coating and the alloy, while alloying elements of the substrate were incorporated into the coating. Particular attention was devoted to possible sources of growth stresses and the effect of the growth stresses on microstructure evolution in the scales that developed on the non-coated and the coated Feâ22Cr alloy. Microstructural features suggested that scale spallation on coated Feâ22Cr occurred as a result of superimposing thermal stresses during cooling onto the growth stresses, that had developed during oxidation.
2008-10-01
Full Text Available.Environmental and nutritional conditions that optimize the yield of hydrogen (H2) from water using a two-step photosynthesis/fermentation (P/F) process are reported for the hypercarbonate-requiring cyanobacterium “Arthrospira maxima.” Our observations lead to four main conclusions broadly applicable to fermentative H2 production by bacteria: (i) anaerobic H2 production in the dark from whole cells catalyzed by a bidirectional [NiFe] hydrogenase is demonstrated to occur in two temporal phases involving two distinct metabolic processes that are linked to prior light-dependent production of NADPH (photosynthetic) and dark/anaerobic production of NADH (fermentative), respectively; (ii) H2 evolution from these reductants represents a major pathway for energy production (ATP) during fermentation by regenerating NAD+ essential for glycolysis of glycogen and catabolism of other substrates; (iii) nitrate removal during fermentative H2 evolution is shown to produce an immediate and large stimulation of H2, as nitrate is a competing substrate for consumption of NAD(P)H, which is distinct from its slower effect of stimulating glycogen accumulation; (iv) environmental and nutritional conditions that increase anaerobic ATP production, prior glycogen accumulation (in the light), and the intracellular reduction potential (NADH/NAD+ ratio) are shown to be the key variables for elevating H2 evolution. Optimization of these conditions and culture age increases the H2 yield from a single P/F cycle using concentrated cells to 36 ml of H2/g (dry weight) and a maximum 18% H2 in the headspace. H2 yield was found to be limited by the hydrogenase-mediated H2 uptake reaction.
2008-10-01
Environmental and nutritional conditions that optimize the yield of hydrogen (H2) from water using a two-step photosynthesis/fermentation (P/F) process are reported for the hypercarbonate-requiring...Full Text Available
On line monitoring systems of MIICON Cu-10Ni alloy in brackish water
1998-12-31
The alloy ASTM B-III UNS C70600 (Cu-1ONi) has been extensively used for surface condenser tubes in power stations. However, there have been cases of Microbiologically Induced Corrosion (MIC) in this alloy caused by Sulfate-Reducing Bacteria (SRB). This paper presents the evaluation of Alloy C70600 in a dynamic monitoring system with one-way circulation using brackish water (Lake Maracaibo water) with and without chlorine treatment, for 3,6,8 and 12 months exposure period. The physical-chemical results indicated favorable conditions for microbial development with planktonic SRB present in the order of 107 cell/ml SEM, EDXA, WDX and XRD analysis evidenced organic and inorganic fouling, Cu{sub 2}S (Chalcocite) and Cu{sub 2}O (Cuprite) as the corrosion product and the characteristic MIC onset morphology. The electrochemical tests indicated that the corrosion current increased with the chlorine content (4.0 A/cm{sup 2}/0.0 ppm Cl{sub 2}, 6.0 u A/cm{sup 2}/0.1 ppm Cl{sub 2} and 16.0 A/cm{sup 2}/2.0 ppm Cl{sub 2}). Furthermore, the polarization curves did not show passivation of this alloy. All these results suggest that Alloy C70600 is not resistant to MIC in brackish water even with chlorine treatment. (Author)
On Fermi level pinning in the alloys based on the lead telluride doped with gallium
Effect of doping with gallium and fast electron irradiation on the galvanomagnetic properties of n-Pb sub 1 sub - sub x Ge sub x Te (0.04 <= x <= 0.06) alloys is investigated. The transformations the metal-type conductivity are obtained both by increasing the impurity content and under the electron irradiation. The conclusion has been drawn that Fermi level pinning by the impurity level does not take place while the doping with gallium as well as the electron irradiation may serve as effective mutually complementary tools for modifying of electrical properties of alloys
Neurological symptoms among dental assistants: a cross-sectional study
Full Text Available.BackgroundDental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure.MethodsAll dental assistants still at work and born before 1970 registered in the archives of a trade union in Hordaland county of Norway were invited to participate (response rate 68%, n = 41), as well as a similar number of randomly selected assistant nurses (response rate 87%, n = 64) in the same age group. The participants completed a self-administered, mailed questionnaire, with questions about demographic variables, life-style factors, musculoskeletal, neurological and psychosomatic symptoms (Euroquest).ResultsThe dental assistants reported significant higher occurrence of neurological symptoms; psychosomatic symptoms, problems with memory, concentration, fatigue and sleep disturbance, but not for mood. This was found by analyses of variance, adjusting for age, education, alcohol consumption, smoking and personality traits. For each specific neurological symptom, adjusted logistic regression analyses were performed, showing that these symptoms were mainly from arms, hands, legs and balance organs.ConclusionThere is a possibility that the higher occurrence of neurological symptoms among the dental assistants may be related to their previous work exposure to mercury amalgam fillings. This should be studied further to assess the clinical importance of the reported symptoms.
Neurological symptoms among dental assistants: a cross-sectional study
BackgroundDental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to...Full Text Available
Multiple-unit implant frames: one-piece casting vs. laser welding and brazing
2004-09-01
Full Text Available
MgB sub 2 superconductor: a review
Synthesis, structure and properties of the most intensively studied newly discovered intermetallic binary superconductor MgB sub 2 have been reviewed up to October, 2002. It has a hexagonal unit cell with cell parameters a approx 3.1432 A and c approx 3.5193 A. MgB sub 2 bulk samples synthesized under high pressure (approx 3.5 GPa) and high temperature (approx 1000 degC) has density approx 2.63 g/cm sup 3. The normal state carriers of MgB sub 2 are holes which have been established from the positive thermoelectric power and Hall coefficient measurements. The external pressure decreases the critical temperature (T sub c) with dT sub c /dP in the range of -1 to -2 K/GPa. The T sub c decreases rapidly by the doping of Mn, Li, Co, C, Al, Ni and Fe but increases slightly by Zn doping. However, no significant change of T sub c is observed by the doping of Si and Be. It is further noticed that the anisotropic ratio gamma(= H sub c sub 2 sup a sup b /H sub c sub 2 sup c) approx 1-5 with lower critical field (H sub c sub l) approx 25-48 mT and upper critical field, H sub c sub 2 (0) approx 40 T. The critical current density (J sub c) of it is as high as 1.3 x 10 sup 6 A cm sup - sup 2 in the self-field and 9.4 x 10 sup 4 Acm sup - sup 2 in a magnetic field of 2T at the temperature of 20 K. The most interesting feature of this superconductor is the appearance of two superconducting energy gaps one DELTA sub l approx 1.92 MeV and the other at DELTA sub 2 approx 3.45 MeV. From theoretical studies, it is found that MgB sub 2 superconductor has a minimum of the density of states (DOS) just above the Fermi level which can account for the decrease of T sub c with the increase of pressure. This review mainly deals with experimental results obtained by different research groups working on this new superconductor. Since more new and interesting results are expected in near future, critical theoretical analysis of the existing experimental data has not been made. It is hoped that it will done in the next review on this subject
Low-Temperature Aging Kinetics of a 15-Year Old Water-Quenched U-6wt.% Nb Alloy
2007-10-30
It is well known that U-6wt.% Nb (U-14at.% Nb) alloy has a microstructure containing martensitic phases supersaturated with Nb that can be obtained by rapid quenching the alloy from {gamma} (bcc)-field solid solution to room temperature. The high cooling rate forces the {gamma}-phase solid solution to transform to variants of the low-temperature {alpha} (orthorhombic) phase in which Nb is forced to retain in the supersaturated solid solution. However, the crystal lattice of supersaturated solution formed by rapid quenching is in unstable conditions and is severely distorted since the solubility of Nb in the {alpha} phase at room temperature is nearly zero under an equilibrium condition. Two variant phases, a monoclinic distortion of {alpha} phase that is designated as {alpha}{double_prime} martensite and a tetragonal distortion of {gamma} phase that is designated as {gamma}{sup o} phase, can form in the as-quenched alloy, as shown in Fig. 1. We have learned from our previous TEM studies on the low-temperature aging of a water-quenched U6Nb (WQ-U6Nb) alloy that there are two possible transformation pathways for phase decomposition of the alloy supersaturated with 14 at.% of Nb upon aging at temperatures below 200 C, i.e., (1) supersaturated solid solution {alpha}{double_prime} {yields} spinodal decomposition {yields} {alpha}{sub 1} (Nb-lean) + {alpha}{sub 2} (Nb-rich) at 200 C and (2) supersaturated solid solution {alpha}{double_prime} {yields} spinodal ordering {yields}{alpha}{double_prime}{sub po} (partially ordered phase) {yields} phase decomposition and precipitation {yields} {alpha} (U) + {alpha}{sub o} (U{sub 3}Nb) at ambient temperatures [1]. The mechanisms for the spinodal transformation occurred at 200 C and the spinodal ordering occurred at ambient temperatures are quite similar; both are caused by the composition modulation of Nb except that the wavelength ({lambda} {approx} 3 nm) of modulation for spinodal decomposition is larger than that ({lambda} {approx} 0.5 nm) of modulation for the spinodal ordering, as illustrated in Fig. 2. Since the Nb modulation for the spinodal ordering can occur within the unit cell of {alpha}{double_prime} phase through the nearest jumps of atoms along the [001] direction, the degree of long-range order (S) increases from 0 to 0.16 as a result of the Nb modulation, as illustrated in Fig. 3. As we accelerated the ordering transformation by thermal heating a 15-year old alloy at 200 C, decomposition of the {alpha}{double_prime}{sub po} phase into {alpha} (U) and a fully ordered {alpha}{sub o} (U{sub 3}Nb) phase occurred, as shown in Fig. 4. Figure 5 shows the results of microhardness measurement and TEM analysis of the microstructural evolution in the 15-old alloy samples thermally heated at 200 C. Here, it can be clearly seen that the {alpha}{double_prime}{sub po} phase with a swirl-shape feature of antiphase boundaries (APBs) vanishes upon heating with the formation of U{sub 3}Nb precipitates, which gives rise to the increase of microhardness (precipitation hardening). Figure 6 shows the changes of tensile properties of the 15-old alloy thermally heated at 200 C. It can be readily seen that in addition to the increase of tensile strength (precipitation hardening), the ductility reduces from {approx}40% to {approx}14% after heating for 96 hours. In view of these adverse changes in tensile properties upon aging, we accordingly pursued a precipitation kinetics study on the 15-year old WQ-U6Nb alloy in order to develop an empirical time-temperature-transformation model for predicting the remaining lifetime of the WQ-U6Nb alloy in the stockpile.
Isolation, biology and chemistry of the disorazoles: new anti-cancer macrodiolides
2009-05-01
The disorazoles comprise a family of 29 closely related macrocyclic polyketides isolated in 1994 from the fermentation broth of the gliding myxobacterium Sorangium cellulosum....Full Text Available
Isolation, biology and chemistry of the disorazoles: new anti-cancer macrodiolides
2009-05-01
Full Text Available.The disorazoles comprise a family of 29 closely related macrocyclic polyketides isolated in 1994 from the fermentation broth of the gliding myxobacterium Sorangium cellulosum. Disorazoles A1, E and C1 have shown exceptional biological activities toward inhibiting the proliferation of human cancer cell lines in picomolar and nanomolar concentrations through the disruption of microtubule polymerization. This review gives a brief introduction describing the biosynthesis and the significance of the disorazoles as a new class of microtubulin disruptors. Another portion of the review focuses on the biology of the disorazoles, specifically disorazole A1 and C1, and their antiproliferative efficacy against animal and human tumor cell lines, as well as the available SAR data. The majority of the discussion addresses synthetic efforts, including partial syntheses of various disorazoles and a summary of the total synthesis of disorazole C1.
Investigation of the deformation structure in an aluminium magnesium alloy by high angular resolution three-dimensional X-ray diffraction
2007-01-01
Investigation of the deformation structure in an aluminium magnesium alloy by high angular resolution three-dimensional X-ray diffraction
2007-01-01
Interfacial Behavior of Cholesterol, Ergosterol, and Lanosterol in Mixtures with DPPC and DMPC
2008-09-01
Full Text Available.Binary mixtures of cholesterol, ergosterol, and lanosterol with phosphatidylcholines differing in the length of the saturated acyl chains, viz 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-myristoyl-sn-glycero-3-phosphocholine (DMPC), were analyzed using a Langmuir balance for recording force-area (π-A) and surface potential-area (ψ-A) isotherms. A progressive disappearance of the liquid expanded–liquid condensed transition was observed in mixed monolayers with DPPC after the increase in the content of all three sterols. For fluid DMPC matrix, no modulation of the monolayer phase behavior due to the sterols was evident with the exception of lanosterol, for which a pronounced discontinuity between mole fractions of X = 0.3 and X = 0.75 was discernible in the compression isotherms. Condensing and expanding effects in force-area (π-Ā) isotherms due to varying Xsterols and differences in the monolayer physical state were assessed from the values for the interfacial compression moduli. Surface potential measurements support the notion that cholesterol and ergosterol, but not lanosterol, reduce the penetration of water into the lipid monolayers. Examination of the excess free energy of mixing revealed an enhanced stability of binary monolayers containing cholesterol compared to those with ergosterol or lanosterol; the differences are emphasized in the range of surface pressure values found in natural membranes.
Interfacial Behavior of Cholesterol, Ergosterol, and Lanosterol in Mixtures with DPPC and DMPC
2008-09-01
Binary mixtures of cholesterol, ergosterol, and lanosterol with phosphatidylcholines differing in the length of the saturated acyl chains, viz 1,2-dipalmitoyl-sn-glycero-3-phosphocholine...Full Text Available
Inter-diffusion between Co3O4 coatings and the oxide scale on Fe-22Cr
2007-01-01
The oxidation behaviour of a commercially available Fe-22Cr alloy coated with a Co3O4 layer by spray-painting or plasma-spraying was investigated at 1173K in air with 1% H2O and compared to the oxidation behaviour of the non-coated alloy. The oxide morphology was examined with X-ray diffraction, electron microscopy, and energy dispersive X-ray spectroscopy. Cr2O3 developed in-between the Co3O4 coating and the alloy, whilst alloying elements of the substrate were incorporated in the coating, regardless of the deposition method. The coatings reduced the growth rate of the Cr2O3 layer as well as the evolution in contact resistance with time between two Fe-22Cr plates sandwiched around a Pt-mesh. SiO2 developed as particles within the alloy during oxidation of the Co3O4 spray-painted samples, whereas SiO2 was identified as an interfacial layer between Cr2O3 and the alloy after oxidation of the Co3O4 plasma-sprayed and the non-coated samples. The difference in morphology is suggested to be an effect of SiO2 nucleation assisted by Kirkendall void formation.
2006-01-01
Background: The problem of geometrical aspects of field matching was investigated very extensively in 1980's and earlier. In the 1990's accelerators were equipped with asymmetric jaws that solve the problem in most cases. However, it is still not possible to have homogeneous dose distribution in the matching region if two beams with different penumbra are matched, which is the case if a photon beam and an electron beam are matched. Aim: To improve the matching of photon and electron fields in IHS technique with individual block. Materials/Methods: Three individual blocks made from Wood's alloy were designed with the angles of the lateral wall at 2.2, 6.5 and 9.0 degrees. Profiles of photon beams of the energy of 6 MV were measured on a Mevatron KD2 with a PTW field analyser with diamond detector for the typical beam size used in the IHS technique (20 x 20 cm2). The ... >>
Improvement on the light yield of a high-Z inorganic scintillator GSO(Ce)
Cerium-doped gadolinium silicic dioxide crystal, GSO(Ce), is a high-Z non-hydroscopic scintillator that gives higher light yield than BGO, and can potentially replace NaI(Tl), CsI(Tl) and BGO in many applications. Its production cost, however, has been substantially higher than any of them, while its energy resolution has been worse than that of NaI(Tl) or CsI(Tl). The merit did not overcome these deficiencies except in limited applications. We developed a low background phoswich counter (the well-type phoswich counter) for the Hard X-ray Detector of the Astro-E project based on GSO scintillator. In the developmental work, we have succeeded in improving the light yield of GSO(Ce) by 40-50%. For energies above 500 keV, a large GSO(Ce) crystal (4.5 cmx4.5phi cm) now gives energy resolution comparable to or better than the best NaI(Tl) when read out with a phototube. With a small GSO(Ce) crystal (5x5x5 mm sup 3) and a photodiode, an energy resolution comparable to or better than the best CsI(Tl) has been obtained. With this improved performance, we find that the much higher photopeak efficiency and the shorter scintillation decay time of GSO(Ce) offsets its higher cost for many applications. We summarize our past developmental work to decrease radioactive contamination and to increase light yield of GSO(Ce) for astronomical hard X-ray detection. Included also are measurements done after the unsuccessful launch of the Astro-E mission. The work is still continuing for the remake version of Astro-E Hard X-ray Detector.
Hybrid Spintronic Structures With Magnetic Oxides and Heusler Alloys
2008-01-01
Hybrid spintronic structures, integrating half-metallic magnetic oxides and Heusler alloys with their predicted high spin polarization, are important for the development of second-generation spintronics with high-efficient spin injection. We have synthesized epitaxial magnetic oxide Fe3O4 on GaAs(100) and the unit cell of the Fe3O4 was found to be rotated by 45 degrees to match the gallium arsenide GaAs. The films were found to have a bulk-like moment down to 3-4 nm and a low coercivity indicating a high-quality magnetic interface. The magnetization hysteresis loops of the ultrathin films are controlled by uniaxial magnetic anisotropy. The dynamic response of the sample shows a heavily damped precessional response to the applied field pulses. In the Heusler alloy system of Co-2 MnGa on GaAs, we found that the magnetic moment was reduced for thicknesses down to 10 nm, which may account for the lower than expected spin-injection efficiency from the spin-light-emitting diode structures. Using the element-specific technique of X-ray magnetic circular dichroism (XMCD), the reduced spin moments were found to originate from the Mn rather than the Co atoms, and the improvement of the interface is thus needed to increase the spin injection efficiency in this system. Further studies of the I-Vcharacteristics of Fe3O4/GaAs(100) and Fe3O4/MgO/GaAs(100) show that the Fe3O4-based spintronic structures have a well-defined Schottky or tunneling barrier of moderate barrier height, which is encouraging for high-efficient spin injection.
2008-06-01
The inbred FVB mouse strain is used extensively in cancer research. Transgenic mice with an FVB/N background in which the expression of green fluorescent protein is under the control of various promoters...Full Text Available
2008-06-01
Full Text Available.The inbred FVB mouse strain is used extensively in cancer research. Transgenic mice with an FVB/N background in which the expression of green fluorescent protein is under the control of various promoters have been used widely for the last decade. However, little is known about the incidence and characteristics of spontaneous tumors in these mice. In addition, only a few tumor lines have been established for use in this particular mouse strain. Our aim was to initiate a database of spontaneous tumors in our retired FVB/N breeders, analyze the histopathologic characteristics of these tumors, and establish novel tumor lines in vivo and in vitro. A total of 234 (40 male, 194 female) breeder mice were observed during their natural lifespans. The incidence of spontaneous tumors was 45.0% in male mice and 52.8% in female mice. All tumors in male mice were lung alveolar–bronchiolar (AB) neoplasms, except for 1 testis interstitial cell tumor. In female mice, histopathologic examination revealed 48 lung AB tumors, 27 mammary gland tumors, 13 ovarian tumors, and 14 other tumors. Several of these spontaneous tumors have been transplanted into FVB/N mice. One mammary adenocarcinoma (MCaP0008) and 1 lung AB carcinoma (LAP0297) were successfully transplanted subcutaneously and passaged serially in vivo. Subsequently, we established cell lines from both tumors, which were maintained in monolayer in vitro. Both of the grafted tumors and cell lines are tumorigenic in VEGFP-GFP/FVB and Tie2P-GFP/FVB mice. Establishment of these novel tumor lines will benefit both in vivo and in vitro studies on the pathophysiology of cancer in this relatively new but widely used mouse strain.
High-pressure synchrotron studies on TiO sub 2 -II nanocrystallite doped with SnO sub 2
We have studied the high-pressure and high-temperature behaviour of alpha-PbO sub 2 -type TiO sub 2 -SnO sub 2 (5 mol%) nanocomposite up to 62.3 GPa and 1700 K in a laser-heated diamond-anvil cell by means of synchrotron energy-dispersive x-ray diffraction. We found that it transforms to the baddeleyite phase at 19.4 GPa at room temperature. This phase was stable up to about 40 GPa. At 62.3 GPa and 1700 K, the diffraction pattern showed that there exists another nonquenchable phase. We discussed the mechanisms for these high-pressure transformations in alpha-PbO sub 2 -type TiO sub 2 -SnO sub 2 (5 mol%) nanocomposite.
Gold Nanocages: Synthesis, Properties, and Applications
2008-12-01
Full Text Available.Conspectus Noble-metal nanocages represent a novel class of nanostructures with hollow interiors and porous walls. They are prepared using the remarkably simple galvanic replacement reaction between solutions containing metal precursor salts and Ag nanostructures prepared by polyol reduction. The electrochemical potential difference between the two species drives the reaction, with the reduced metal depositing on the surface of the Ag nanostructure. In our most studied example involving HAuCl4 as the metal precursor, the resultant Au epitaxially deposits on the surface of the Ag nanocubes, adopting their cubic structure. Concurrent with this deposition, the interior Ag is oxidized and removed, together with alloying and dealloying, to produce hollow and eventually porous structures that we commonly refer to as Au nanocages. This approach has proven versatile, with a wide range of morphologies – including nanorings, prism-shaped nanoboxes, nanotubes, and multiple-walled nanoshells or nanotubes – being produced by changing the shape of the initial Ag template. Besides Au-based structures, Pt- and Pd-containing hollow nanostructures have been prepared by switching the metal salt precursors to Na2PtCl4 or Na2PdCl4, respectively.Additionally, we have found it easy to tune both the composition and localized surface plasmon resonance (LSPR) of the metal nanocages by simply changing the amount of metal precursor added to the suspension of Ag nanocubes. In this way, we are developing these structures for biomedical and catalytic applications. As the Au nanocages are predicted by discrete dipole approximations (DDA) to have large absorption cross-sections and their LSPR can be tuned into the near-infrared where the attenuation of light by blood and soft tissue is greatly reduced, they are attractive for biomedical applications in which the selective absorption of light at great depths is desirable. For example, we have explored their use as contrast enhancement agents for both optical coherence tomography (OCT) and photoacoustic tomography (PAT), with improvements being observed in each case. As the Au nanocages have large absorption cross-sections, they are also effective photothermal transducers, which when targeted to cancer cells could provide a therapeutic effect by selectively killing them by hyperthermia. Our in vitro work illustrates the feasibility of this technique as a less invasive form of cancer treatment.
Gold Nanocages: Synthesis, Properties, and Applications
2008-12-01
Conspectus Noble-metal nanocages represent a novel class of nanostructures with hollow interiors...Full Text Available
Giant magnetoresistance in melt spun Cu85Co10Ni5
2009-01-01
CuCoNi rapidly solidified alloys are interesting because they display giant magnetoresistance (GMR). In the present work a Cu85Co10Ni5 alloy has been synthesized by melt spinning and analysed for GMR. The ribbons obtained have been annealed at different temperatures and the evolution of the crystal structure with annealing has been studied by X-ray diffraction. The. ne microstructure has been observed by TEM and related to the magnetic properties, investigated in a vibrating sample magnetometer. In the studied composition the magnetoresistance was found to be lower than in binary CuCo alloys without Ni addition. (C) 2008 Elsevier B.V. All rights reserved.
Fixation and Bone Remodeling Around a Low Stiffness Stem in Revision Surgery
2008-02-01
Full Text Available.Femoral stems with reduced stiffness have the potential of decreasing stress shielding and could be an alternative in revision surgery when restoration of bone stock is required. We retrospectively reviewed 38 patients (40 stems) with a central core of cobalt-chromium surrounded by a polymer and an outer titanium mesh layer containing a proximal coating of hydroxyapatite/tricalcium phosphate; 30 of the 38 patients (32 hips) had a minimum 2-year followup. We impacted morselized allograft around the stem in 28 of 32 revisions. Repeated radiostereometric examinations showed medial, distal, and posterior migration (median, 0.21 mm, 0.17 mm, and 0.96 mm, respectively) of the femoral head center for up to 6 months followed by stabilization. Measurements of bone mineral density in the seven Gruen zones at 6 months revealed either a decrease (down to a median of 3%), no change, or a slight increase (up to 5%) followed by a further increase up to 2 years in three of the regions (2, 3, and 5). Conventional radiography at 2 years demonstrated graft remodeling and incomplete radiolucent lines in 19 hips, mainly in Regions 1 and 7. Two hips were reoperated on as a result of dislocation, but none of the stems had been revised.Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Fixation and Bone Remodeling Around a Low Stiffness Stem in Revision Surgery
2008-02-01
Femoral stems with reduced stiffness have the potential of decreasing stress shielding and could be an alternative in revision surgery when restoration of bone stock is required. We retrospectively...Full Text Available
Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy
2001-09-12
It is well established that Al-Zn-Mg-(Cu) aluminum alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are commonly used to increase HEAC resistance at the expense of strength. Overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). When freshly bared coupons of AA 7050 are exposed to 90 C, 90% RH air, hydrogen ingress follows inverse-logarithmic-type kinetics and is equivalent for underaged (HEAC susceptible) and overaged (HEAC resistant) tempers. However, when the native oxide is allowed to form (24 hrs in 25 C, 40% RH lab air) prior to exposure to 90 C, 90% RH air, underaged alloy shows significantly greater hydrogen ingress than the overaged alloy. Humid air is a very aggressive environment producing local ({approx}1{micro}m) hydrogen concentrations in excess of 10,000 wt. ppm at 90 C. In the copper bearing alloy, overaging also effects the apparent diffusivity of hydrogen. As AA 7050 is aged from underaged {yields} peak aged {yields} overaged, the activation energy for hydrogen diffusion increases and the apparent diffusivity for hydrogen decreases, In the low copper alloy, overaging has little effect on hydrogen diffusion. Comparison of the apparent activation energies for hydrogen diffusion and for K independent (stage II) crack growth rate in 90% RH air between 25 and 90 C indicates that hydrogen transport kinetics are responsible for the decreased crack growth rate of overaged AA 7050 relative to the peak aged temper.
2009-01-01
Electrorefining in molten LiCl-KCl eutectic-based salt is one of the key separation steps in the pyrochemical treatment of spent nuclear fuels. The actinides are separated from the bulk of the fission products by electrochemical transport in the molten salt electrolyte. Pure U is deposited onto a solid cathode, while group actinides (U, Pu, Np, and Am) are deposited into a liquid cadmium cathode (LCC). The LCC technology takes advantage of the low chemical activities of transuranics (TRU) elements in the liquid Cd phase to accomplish this separation. However, rare earth (RE) fission products have similar thermodynamic properties to those of TRU elements in a molten salt/liquid Cd system and are, therefore, subject to also entering the Cd phase. The degree to which RE contamination of the actinide product will occur needs to be predicted for analysis of the overall pyrochemical ... >>
Environmental and Geometrical Conditions to Sustain Crevice Corrosion in Alloy 22
2006-11-10
Alloy 22 (N06022) is highly resistant to localized corrosion. Under aggressive environmental conditions Alloy 22 may be susceptible to crevice corrosion in hot chloride (Cl{sup -}) solutions. The objective of the present work was to explore the environmental and geometrical conditions for crevice corrosion to occur. Electrochemical tests were performed using PCA and prismatic mill annealed Alloy 22 specimens in chloride solutions. Crevice corrosion current density was found to be a function of applied potential. i{sub CREV} values ranged from 40 {micro}A/cm{sup 2} to 20 mA/cm{sup 2}. Such low values of current density explained the absence of pitting corrosion in Alloy 22 at any potential. Decreasing of the effective diffusion distance in a propagating crevice is thought to cause crevice corrosion stifling or repassivation after long anodic polarization. Crevice corrosion breakdown potential is expected to decrease with potential scan rate, approaching repassivation potential for low scan rates. The lowest corrosion potential of Alloy 22 in hydrochloric acid solutions at which active corrosion exists was proposed as the lowest possible repassivation potential for crevice corrosion.
Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen
2008-11-15
Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with...Full Text Available
Element specific investigation of ultrathin Co2MnGa/GaAs heterostructures
2007-01-01
We have used x-ray magnetic circular dichroism to study the element specific magnetic properties of ultrathin films of the Heusler alloy Co2MnGa at room temperature. Nine films were grown by molecular beam epitaxy on GaAs substrates and engineered to vary in stoichiometry as Co1.86Mn0.99Ga1, Co1.95Mn0.98Ga1, and Co1.97Mn0.96Ga1, with thicknesses of 5.3, 7.6, and 9.7 nm, and were capped with Al to prevent oxidization. Sum rule analysis revealed magnetic moments significantly lower than the values predicted theoretically, especially in the case of the Mn total magnetic moment. The results do not support the hypothesis that a large magnetic moment is transferred from Co to Mn, and may suggest that diffusion and reacted layers at ultrathin thicknesses can effect the establishment of a full Heusler structure.
2009-04-07
Recent studies have shown that high pressure (P) induces the metallization of the Fe2+–O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS)...Full Text Available
2009-04-07
Full Text Available.Recent studies have shown that high pressure (P) induces the metallization of the Fe2+–O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate and oxide phases at the deep planetary interiors. Hematite (Fe2O3) is an important magnetic carrier mineral for deciphering planetary magnetism and a proxy for Fe in the planetary interiors. Here, we present synchrotron Mössbauer spectroscopy and X-ray diffraction combined with ab initio calculations for Fe2O3 revealing the destruction of magnetic ordering at the hematite → Rh2O3-II type (RhII) transition at 70 GPa and 300 K, and then the revival of magnetic ordering at the RhII → postperovskite (PPv) transition after laser heating at 73 GPa. At the latter transition, at least half of Fe3+ ions transform from LS to HS and Fe2O3 changes from a semiconductor to a metal. This result demonstrates that some magnetic carrier minerals may experience a complex sequence of magnetic ordering changes during impact rather than a monotonic demagnetization. Also local Fe enrichment at Earth's core-mantle boundary will lead to changes in the electronic structure and spin state of Fe in silicate PPv. If the ultra-low-velocity zones are composed of Fe-enriched silicate PPv and/or the basaltic materials are accumulated at the lowermost mantle, high electrical conductivity of these regions will play an important role for the electromagnetic coupling between the mantle and the core.
Electrochemical dissolution of surface alloys in acids: Thermodynamic trends from first-principles calculations
2007-01-01
A simple procedure is introduced to use periodic Density Functional Theory calculations to estimate trends in the thermodynamics of surface alloy dissolution in acidic media. With this approach, the dissolution potentials for solute metal atoms embedded in the surface layer of various host metals (referenced to the dissolution potential of the solute in its pure, metallic form) are calculated. Periodic trends in the calculated potentials are found to be related to trends in surface segregation energies of the various solute/host pairs. The effects of water splitting and concomitant hydroxyl adsorption on the dissolution potentials are also considered; these effects do not change the potentials for highly oxophilic solutes embedded in less active hosts, but they do decrease the dissolution potential for more inert solutes on oxophilic hosts. Finally, the dissolution of Pt "skin" layers from Pt3X (X = Fe, Co, and Ni) bulk alloys is analyzed; the Pt skins are found to be stabilized compared to pure Pt.
temperatures and in zero field an activated form of the conductivity is observed. In applied magnetic fields (B > 50 mT) Efros-ShkIovskii variable range hopping is observed in the insulating phase. These results are attributed to the formation of a hard gap in the density of states, having a magnetic origin. At higher fields an insulator-metal phase transition occurs. In the metallic phase the conductivity can be described by a quantum correction to the zero temperature conductivity due to the effect of electron-electron interactions. Results obtained before and after illumination are consistent with scaling theory of electron localisation, having a critical exponent close to unity, indicative of the importance of electron-electron interactions. A reduction in the value of the critical field is seen after increasing the carrier density (B sub c = 2.0 and 1.3 T for n = 3.3 and 3.8 x 10 sup 1 sup 7 cm sup - sup 3 respectively). At low temperatures an anisotropy in the resistivity has been measured for samples in the spin glass phase. Magnetoresistance measurements have shown results consistent with previous measurements, in addition to a large, low field component that is attributed to the effect of magnetic field on electrons in the variable range hopping regime. Electrical transport and magnetic measurements have been made on n-Cd sub 1 sub - sub x Mn sub x Te (0.047 n sub c. At low
Effects of as-cast and wrought Cobalt-Chrome-Molybdenum and Titanium-Aluminium-Vanadium alloys on cytokine gene expression and protein secretion in J774A.1 macrophages.
2007-01-01
Insertion of metal implants is associated with a possible change in the delicate balance between pro- and anti-inflammatory proteins, probably leading to an unfavourable predominantly pro-inflammatory milieu. The most likely cause is an inappropriate activation of macrophages in close relation to the metal implant and wear-products. The aim of the present study was to compare surfaces of as-cast and wrought Cobalt-Chrome-Molybdenum (CoCrMo) alloys and Titanium-Aluminium-Vanadium (TiAlV) alloy when incubated with mouse macrophage J774A.1 cell cultures. Changes in pro- and anti-inflammatory cytokines (TNF-alpha, IL-6, IL-alpha, IL-1beta, IL-10) and proteins known to induce proliferation (M-CSF), chemotaxis (MCP-1) and osteogenesis (TGF-beta, OPG) were determined by ELISA and Real Time reverse transcriptase - PCR (Real Time rt-PCR). Lactate dehydrogenase (LDH) was measured in the medium to asses the cell viability. Surface properties of the discs were characterised with a profilometer and with energy dispersive X-ray spectroscopy. We here report, for the first time, that the prosthetic material surface (non-phagocytable) of as-cast high carbon CoCrMo reduces the pro-inflammatory cytokine IL-6 transcription, the chemokine MCP-1 secretion, and M-CSF secretion by 77%, 36%, and 62%, respectively. Furthermore, we found that reducing surface roughness did not affect this reduction. The results suggest that as-cast CoCrMo alloy is more inert than wrought CoCrMo and wrought TiAlV alloys and could prove to be a superior implant material generating less inflammation which might result in less osteolysis.
Effect of cerium ion implantation on the oxidation behavior of zircaloy-4 at 500 degree sign C
In order to investigate the oxidation behavior changes of zircaloy-4 induced by cerium ion implantation using a MEVVA source at an energy of 40 keV with a dose range from 1x10 sup 1 sup 6 to 1x10 sup 1 sup 7 ions/cm sup 2 at the maximum temperature of 130 degree sign C, weight gain curves of the different specimens including as-received zircaloy-4 and cerium-implanted zircaloy-4 were measured after oxidation in air at 500 degree sign C for 100 min. It was obviously found that a significant improvement was achieved in the oxidation behavior of cerium ion implanted zircaloy-4 compared with that of the as-received zircaloy-4. The depth profile of the element composition in the surface region of the samples was obtained by Auger electron spectroscopy, and the valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy. Glancing angle X-ray diffraction employed to examine the phase transformation in the oxide films showed that the addition of cerium transformed the phase from monoclinic zirconia to hexagonal zirconia. Finally, the mechanism of the improvement of the oxidation behavior is discussed.
Diffuse scattering measurements of static atomic displacements in crystalline binary solid solutions
1997-09-01
Diffuse x-ray scattering from crystalline solid solutions is sensitive to both local chemical order and local bond distances. In short-range ordered alloys, fluctuations of chemistry and bond distances break the long-range symmetry of the crystal within a local region and contribute to the total energy of the alloy. Recent use of tunable synchrotron radiation to change the x-ray scattering contrast between elements has greatly advanced the measurement of bond distances between the three kinds of atom pairs found in crystalline binary alloys. The estimated standard deviation on these recovered static displacements approaches {+-}0.001 {angstrom} (0.0001 nm) which is an order of magnitude more precise than obtained with EXAFS. In addition, both the radial and tangential displacements can be recovered to five near neighbors and beyond. These static displacement measurements provide new information which challenges the most advanced theoretical models of binary crystalline alloys. 29 refs., 8 figs., 2 tabs.
Development of explosion welding (EXW) technique and characterisation of EXW joints
1997-05-01
The integrity of the EXW copper alloy stainless steel compound plates were examined by ultrasonic examination. The metallurgical structure and mechanical performance of the copper stainless steel joints were characterised using tensile, fatigue, creep, shear and fracture resistance tests at ambient and elevated temperatures. The results indicate that explosion welding can be applied in manufacturing fully bonded copper stainless steel compound plates with adequate bond strength. In the tensile and fatigue testing the failure mode of the bond specimens was primarily a ductile failure of copper alloy both at ambient and at elevated temperature indicating that the bond strength was higher than the strength of copper alloy. However, the failure mode in creep fatigue and creep testing at elevated temperatures changed to interfacial failure propagating along the bond interface. The observation that specific loading conditions at elevated temperatures can induce a bond failure at low stress levels indicates that creep behaviour of copper alloy may have a major role in failure mechanisms of copper alloy stainless steel compound structures under ITER operation conditions. Creep behaviour of copper alloy and copper alloy stainless steel compound specimens and structures at elevated temperatures requires more detailed studies and experimental work. (orig.)
Dehydrogenation in lithium borohydride/conventional metal hydride composite based on a mutual catalysis
2009-01-01
The dehydrogenation of LiBH4 ball-milled with hydrogenated 40Tiâ15Mnâ15Crâ30V alloy was investigated. It was found that there is a mutual catalysis between the two hydrides, lowering the temperature of hydrogen release from both hydrides. In the case of 1h milled LiBH4/40Tiâ15Mnâ15Crâ30V with a mass ratio of 1:4, the peak temperatures of 40Tiâ15Mnâ15Crâ30V and LiBH4 were decreased to 195 and 390°C, respectively, which are 77 and 50°C lower than the respective hydride on its own.
DEVELOPMENT OF ODS HEAT EXCHANGER TUBING
2002-04-01
Work continued on three major tasks of this project--increasing the circumferential strength of MA956 tubing, joining of the MA956 alloy, and determination of the high temperature corrosion limits of the MA956 alloy. With respect to increasing the circumferential strength of a MA956 tube, all of the cold working operations (0, 10, 20, 30, 40%) and annealing treatments (1000, 1150, 1300 C) have been completed. The sample microstructures produced by this processing continue to be analyzed with TEM results providing valuable information on the strengthening mechanism of this alloy. Creep testing to determine the ''stress threshold'' curves for this alloy continues. Regarding joining of the MA956 alloy, additional welds were produced with the friction welding and transient liquid phase bonding techniques. And finally, laboratory high temperature corrosion testing of the material continues in both fluid-side and fire-side simulated environments.
DEVELOPMENT OF ODS HEAT EXCHANGER TUBING
2001-07-01
Work continued on three major tasks of this project--increasing the circumferential strength of the MA956 tube, joining of the MA956 alloy, and determination of the high temperature corrosion limits of the MA956 alloy. With respect to increasing the circumferential strength of a MA956 tube, an additional 120 MA956 rods have been extruded (total of 180 rods) using 16:1 and 10:1 extrusion ratios and extrusion temperatures of 1000, 1075, 1150, and 1200 C. Also, approximately 40 cold work (0, 10, 20, 30, 40%) plus annealing treatments (1000, 1150, 1300 C) have been completed with sample microstructure presently being analyzed. Also, creep testing to determine the ''stress threshold'' curves for this alloy continues. Regarding joining of the alloy MA956, work continued on the friction welding, magnetic impulse welding, explosive welding, and transient liquid phase bonding, with joints produced using the friction, magnetic impulse and explosive welding techniques. And finally, fluid-side high temperature corrosion tests of the material have been initiated.
Cochlear Implants:System Design, Integration and Evaluation
2008-01-01
Full Text Available.As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120,000 persons worldwide; half of which being pediatric users who are able to develop nearly normal language. Biomedical engineers have played a central role in the design, integration and evaluation of the cochlear implant system, but the overall success is a result of collaborative work with physiologists, psychologists, physicians, educators, and entrepreneurs. This review presents broad yet in-depth academic and industrial perspectives on the underlying research and ongoing development of cochlear implants. The introduction accounts for major events and advances in cochlear implants, including dynamic interplays among engineers, scientists, physicians, and policy makers. The review takes a system approach to address critical issues from design and specifications to integration and evaluation. First, the cochlear implant system design and specifications are laid out. Second, the design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator and electrode arrays. Third, system integration and functional evaluation are presented with respect to safety, reliability, and challenges facing the present and future cochlear implant designers and users. Finally, issues beyond cochlear implants are discussed to address treatment options for the entire spectrum of hearing impairment as well as to use the cochlear implant as a model to design and evaluate other similar neural prostheses such as vestibular and retinal implants.
Cochlear Implants:System Design, Integration and Evaluation
2008-01-01
As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120,000 persons worldwide; half of which being pediatric users who are able to develop...Full Text Available
Cobalt-chromium-molybdenum alloy causes metal accumulation and metallothionein up-regulation in rat liver and kidney.
2007-01-01
Cobalt-chromium-molybdenum (CoCrMo) metal-on-metal hip prosthesis has had a revival due to their excellent wear properties. However, particulate wear debris and metal ions liberated from the CoCrMo alloys might cause carcinogenicity, hypersensitivity, local and general tissue toxicity, genotoxicity and inflammation-generating qualities. Nine months after implanting small pieces of CoCrMo alloy intramuscularly and intraperitoneally in rats, we analysed the accumulation of metals with a multi-element analysis, and the levels of metallothionein I/II with real-time reverse transcriptase-polymerase chain reaction in liver and kidney. We found that metal ions are liberated from CoCrMo alloys and suggest that they are released by dissolucytosis, a process where macrophages causes the metallic surface to release metal ions. Animals with intramuscular implants accumulated metal in liver and kidney and metallohionein I/II were elevated in liver tissue. The present data do not tell whether kidney and liver are the primary target organs or what possible toxicological effect the different metal ions might have, but they show that metal ions are liberated from CoCrMo alloys that are not subjected to mechanical wear and that they accumulate in liver and kidney tissue. That the liberated metal ions affect the tissues is supported by an up-regulation of the detoxifying/pacifying metalloprotein I/II in the liver.
Cobalt-chromium-molybdenum alloy causes metal accumulation and metallothionein up-regulation in rat liver and kidney
2007-01-01
Clinical Experience of the Dynamic Stabilization System for the Degenerative Spine Disease
2008-05-01
ObjectiveThe aim of the present study was to assess the safety and efficacy of the dynamic stabilization system in the treatment of degenerative spinal diseases.MethodsThe...Full Text Available
Clinical Experience of the Dynamic Stabilization System for the Degenerative Spine Disease
2008-05-01
Full Text Available.ObjectiveThe aim of the present study was to assess the safety and efficacy of the dynamic stabilization system in the treatment of degenerative spinal diseases.MethodsThe study population included 20 consecutive patients (13 females, 7 males) with a mean age of 61±6.98 years (range 46-70) who underwent decompression and dynamic stabilization with the Dynesys system between January 2005 and August 2006. The diagnoses included spinal stenosis with degenerative spondylolisthesis (9/20, 45%), degenerative spinal stenosis (5/20, 25%), adjacent segmental disease after fusion (3/20, 15%), spinal stenosis with degenerative scoliosis (2/20, 10%) and recurrent intervertebral lumbar disc herniation (1/20, 5%). All of the patients completed the visual analogue scale (VAS) and the Korean version of the Oswestry Disability Index (ODI). The following radiologic parameters were measured in all patients : global lordotic angles and segmental lordotic angles (stabilized segments, above and below adjacent segments). The range of motion (ROM) was then calculated.ResultsThe mean follow-up period was 27.25±5.16 months (range 16-35 months), and 19 patients (95%) were available for follow-up. One patient had to have the implant removed. There were 30 stabilized segments in 19 patients. Monosegmental stabilization was performed in 9 patients (47.3%), 9 patients (47.3%) underwent two segmental stabilizations and one patient (5.3%) underwent three segmental stabilizations. The most frequently treated segment was L4-5 (15/30, 50%), followed by L3-4 (12/30, 40%) and L5-S1 (3/30, 10%). The VAS decreased from 8.55±1.21 to 2.20±1.70 (p<0.001), and the patients' mean score on the Korean version of the ODI improved from 79.58%±15.93% to 22.17%±17.24% (p<0.001). No statistically significant changes were seen on the ROM at the stabilized segments (p=0.502) and adjacent segments (above segments, p=0.453, below segments, p=0.062). There were no patients with implant failure.ConclusionThe results of this study show that the Dynesys system could preserve the motion of stabilized segments and provide clinical improvement in patients with degenerative spinal stenosis with instability. Thus, dynamic stabilization systems with adequate decompression may be an alternative surgical option to conventional fusion in selected patients.
2004-10-01
To overcome the issue of pinhole (defect) formation in membrane films over large areas, a process was developed and implemented for producing 6-12 {micro}m-thick, Pd-Cu alloy films on thermally oxidized silicon wafer substrates. The processing parameters on silicon are such that adhesion is poor and as-deposited Pd-Cu alloy films easily release from the oxidized silicon surface. Hydrogen permeation tests were conducted on 9 and 12 {micro}m-thick Pd-Cu alloy films and the hydrogen flux for 9 and 12 {micro}m-thick films were 16.8 and 8 cm{sup 3}(STP)/cm{sup 2} {center_dot} min respectively. The hydrogen permeability (corrected using data in McKinnley patent) of the 9 {micro}m-thick membrane is 7.4 {center_dot} 10{sup -5} cm{sup 3}(STP) {center_dot} cm/cm{sup 2} {center_dot} s {center_dot} cm Hg{sup 0.5} at 350 C and compares very well to permeability reported by McKinnley for a 62.5% Pd membrane; this permeability is {approx}56% of the value reported for a Pd-Cu alloy membrane with optimum 60% Pd composition. Using XRD, we confirmed the presence of a two-phase, {alpha}/{beta}, structure and that the composition of our membrane was slightly higher than the optimum composition. We are making adjustments to the compositions of the Pd-Cu alloy target in order to produce films next quarter that match the ideal Pd{sub 60}Cu{sub 40} composition.
Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture
2008-01-01
Early bone ongrowth secures long-term fixation of primary implants inserted without cement. Implant surfaces roughened with a texture on the micrometer scale are known to be osseoconductive. The aim of this study was to evaluate the bone formation at the surface of acid etched implants modified on the micro-scale. We compared implants with a nonparticulate texture made by chemical milling (hydrofluoric acid, nitric acid) (control) with implants that had a dual acid etched (hydrofluoric acid, hydrochloric acid) microtexture surface superimposed on the primary chemically milled texture. We used an experimental joint replacement model with cylindrical titanium implants (Ti-6Al-4V) inserted paired and press-fit in cancellous tibia metaphyseal bone of eight canines for 4 weeks and evaluated by histomorphometric quantification. A significant twofoldmedian increase was seen for bone ongrowth on the acid etched surface [median, 36.1% (interquartile range, 24.3-44.6%)] compared to the control [18.4% (15.6-20.4%)]. The percentage of fibrous tissue at the implant surface and adjacent bone was significantly less for dual acid textured implants compared with control implants. These results show that secondary roughening of titanium alloy implant surface by dual acid etching increases bone formation at the implant bone interface.
2008-07-01
This study evaluated 1) the efficacy of packing autologous fat grafts around temporomandibular joint (TMJ) total joint prosthetic reconstructions to prevent fibrosis and heterotopic bone formation and...Full Text Available
2008-07-01
Full Text Available.This study evaluated 1) the efficacy of packing autologous fat grafts around temporomandibular joint (TMJ) total joint prosthetic reconstructions to prevent fibrosis and heterotopic bone formation and 2) the effects on postsurgical joint mobility and jaw function. One hundred fifteen patients (5 males and 110 females) underwent TMJ reconstruction with total joint prostheses and simultaneous fat grafts (88 bilateral and 27 unilateral) for a total of 203 joints. The abdominal fat grafts were packed around the articulating portion of the joint prostheses after the fossa and mandibular components were stabilized. Patients were divided into two groups: group 1 (n = 76 joints) received Christensen total joint prostheses, and group 2 (n = 127 joints) received TMJ Concepts total joint prostheses. Clinical and radiographic assessments were performed before surgery, immediately after surgery, and at long-term follow-up. In group 1, maximal incisal opening (MIO) increased 3.5 mm, lateral excursions (LE) decreased 0.2 mm, and jaw function improved 1.9 levels. In group 2, MIO increased 6.8 mm, LE decreased 1.4 mm, and jaw function improved 2.4 levels. The improvement for MIO and patient perception of jaw function in both groups was statistically significant; no significant difference was found for LE. There was no radiographic or clinical evidence of heterotopic calcifications or limitation of mobility secondary to fibrosis in either group. Twenty-five Christensen prostheses (33%) were removed because of device failure and/or metal hypersensitivity; no fibrosis or heterotopic bone formation was seen at surgical removal. Four TMJ Concepts prostheses (3%) were removed because of metal hypersensitivity. In all instances, removal of the prostheses was unrelated to the autologous fat grafting. Ten patients (8.7%) developed complications involving the fat donor site: two patients (1.8%) developed abdominal cysts requiring surgery, and eight patients (6.9%) developed seroma formation requiring aspiration. Autologous fat transplantation is a useful adjunct to prosthetic TMJ reconstruction to minimize the occurrence of excessive joint fibrosis and heterotopic calcification, consequently providing improved range of motion and jaw function.
Augmentation of tibial plateau fractures with Trabecular Metal™: a biomechanical study
Full Text Available.BackgroundRestoration and maintenance of the plateau surface are the key points in the treatment of tibial plateau fractures. Any deformity of the articular surface jeopardizes the future of the knee by causing osteoarthritis and axis deviation. The purpose of this study is to evaluate the effect of Trabecular Metal (porous tantalum metal) on stability and strength of fracture repair in the central depression tibial plateau fracture.MethodSix matched pairs of fresh frozen human cadaveric tibias were fractured and randomly assigned to be treated with either the standard of treatment (impacted cancellous bone graft stabilized by two 4.5 mm screws under the comminuted articular surface) or the experimental method (the same screws supporting a 2 cm diameter Trabecular Metal (TM) disc placed under the comminuted articular surface). Each tibia was tested on a MTS machine simulating immediate postoperative load transmission with 500 Newton for 10,000 cycles and then loaded to failure to determine the ultimate strength of the construct.ResultsThe trabecular metal construct showed 40% less caudad displacement of the articular surface (1, 32 ± 0.1 mm vs. 0, 80 ± 0.1 mm) in cyclic loading (p < 0.05). Its mechanical failure occurred at a mean of 3275 N compared to 2650 N for the standard of care construct (p < 0, 05).ConclusionThe current study shows the biomechanical superiority of the trabecular metal construct compared to the current standard of treatment with regards to both its resistance to caudad displacement of the articular surface in cyclic loading and its strength at load to failure.
Augmentation of tibial plateau fractures with Trabecular Metal™: a biomechanical study
BackgroundRestoration and maintenance of the plateau surface are the key points in the treatment of tibial plateau fractures. Any deformity of the articular surface jeopardizes the...Full Text Available
Atomic structure of glassy Mg60Cu30Y10 investigated with EXAFS, x-ray and neutron diffraction, and reverse Monte Carlo simulations
2007-01-01
Short range order of amorphous Mg60Cu30Y10 was investigated by x-ray and neutron diffraction, Cu and Y K-edge x-ray absorption fine structure measurements, and the reverse Monte Carlo simulation technique. We found that Mg-Mg and Mg-Cu nearest neighbor distances are very similar to values found in crystalline Mg2Cu. The Cu-Y coordination number is 1.1±0.2, and the Cu-Y distance is ~4% shorter than the sum of atomic radii, suggesting that attraction between Cu and Y plays an important role in stabilizing the glassy state. Thermal stability and structure evolution upon annealing were also studied by differential scanning calorimetry and in situ x-ray powder diffraction. The alloy shows a glass transition and three crystallization events, the first and dominant one at 456  K corresponding to eutectic crystallization of at least three phases: Mg2Cu and most likely cubic MgY and CuMgY. ©2007 The American Physical Society
2008-05-01
Monolayers of a functional pulmonary surfactant (PS) can reach very low surface tensions well below their equilibrium value. The mechanism by which PS monolayers reach such low surface tensions and...Full Text Available
2008-05-01
Full Text Available.Monolayers of a functional pulmonary surfactant (PS) can reach very low surface tensions well below their equilibrium value. The mechanism by which PS monolayers reach such low surface tensions and maintain film stability remains unknown. As shown previously by fluorescence microscopy, phospholipid phase transition and separation seem to be important for the normal biophysical properties of PS. This work studied phospholipid phase transitions and separations in monolayers of bovine lipid extract surfactant using atomic force microscopy. Atomic force microscopy showed phospholipid phase separation on film compression and a monolayer-to-multilayer transition at surface pressure 40–50 mN/m. The tilted-condensed phase consisted of domains not only on the micrometer scale, as detected previously by fluorescence microscopy, but also on the nanometer scale, which is below the resolution limits of conventional optical methods. The nanodomains were embedded uniformly within the liquid-expanded phase. On compression, the microdomains broke up into nanodomains, thereby appearing to contribute to tilted-condensed and liquid-expanded phase remixing. Addition of surfactant protein A altered primarily the nanodomains and promoted the formation of multilayers. We conclude that the nanodomains play a predominant role in affecting the biophysical properties of PS monolayers and the monolayer-to-multilayer transition.
Applications and characteristics of imaging plates as detector in neutron radiography at SINQ
Imaging plate technique is a commonly accepted method in many fields as in medicine, biology and physics for detection of the distribution of beta- and gamma-radiation or X-rays on large areas. Recently a new type of imaging plate sensitive to neutrons has been developed. The storage layer is doped with gadolinium, which, after absorption of neutrons, produces radiation detectable by the same sensitive crystals used in conventional imaging plates. At the spallation neutron source, SINQ, at the Paul Scherrer Institut (CH) some of the characteristics of the neutron radiography station in combination with the imaging plate technique were investigated. The intensity distribution of the source was measured to check the accuracy for quantification of the image data. Also, the reproducibility of results obtained by this detection system was stated. For a test object, the high selectivity for different neutron absorption is demonstrated at details with low contrast. The obtainable spatial resolution was determined recording an image of a gadolinium edge, from which the line spread function and the modulation transfer function can be calculated. By use of conventional X-ray sensitive imaging plates the exposure time for a indirect detection method using a dysprosium foil can be reduced significantly. For the measurement of the latent image in the neutron activated foil it is sufficient to excite the imaging plate by the radiation of the isotope sup 1 sup 6 sup 5 sup m Dy with a short life time. The possibility to measure effective cross-sections of materials with pretty strong absorption by imaging plates as detector because of their high dynamic range was proved as well.
Analysis of sludge in the dissolver and survey of the behavior of zirconium molybdate
2009-01-01
In the aspects of reliable operation of spent nuclear fuel reprocessing plant, it is important to investigate the behavior of sludge generated in a dissolving process. In this paper we report on the analytical results of sludge obtained from the dissolver at the Tokai Reprocessing Plant (TRP) at first, and then the experimental results using simulated solutions to clarify the formation behavior of sludge. The composition of sludge in the dissolver after dissolution of PWR and ATR fuels at TRP was analyzed. The presence of zirconium molybdate was confirmed by the analysis of X-ray diffraction (XRD). This result indicate the compounds of Mo and Zr precipitates during the dissolution process. On the other hand, to clarify the formation behavior of the precipitates of zirconium molybdate, investigated the dependence of HNO3 concentration on the precipitation with Mo ... >>
The structure of the pseudo-binary mercury chalcogenide alloy HgSe_{0.7}S_{0.3} has been studied by means of X-ray and neutron powder diffraction at pressure up to 8.5 GPa. A phase transition from the cubic zinc blende structure to the hexagonal cinnabar structure was observed at P{\sim}1 GPa. The obtained structural parameters were used for the analysis of the geometrical relationship between the zinc blende and the cinnabar phases. The zinc blende-cinnabar phase transition is discussed in the framework of Landau theory of the phase transitions. It was found that the possible order parameter for the structural transformation is the spontaneous strain e_{4}. This assignment agrees with previously observed high pressure behaviour of the elastic constants of other mercury chalcogenides.
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