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Alloy Composition (alloy + composition)
Selected AbstractsEffect of Ti addition on magnetic properties of TbCu7 -type Sm-Fe-Co-Mn system nitridesELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2008Hiroshi Yamamoto Abstract To support the development of high-performance isotropic bonded magnets, experiments were carried out to investigate the effect of Ti addition on the magnetic properties of Sm-Fe-Co-Mn system nitride compounds with TbCu7 -type structure. Sm10(Fe0.9Co0.1)89.5,xMn0.5Tix (x=0 to 1.0) alloy ribbons were prepared by the single-roller rapid-quenching method. The effects of alloy composition and of heat treatment and nitriding conditions on the magnetic properties were examined. The optimum preparation conditions of the compounds were as follows. Composition: {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2; roller speed: 50 m/s; heat treatment: 700°C×60 min in high-purity Ar gas; nitriding conditions: 420°C×15 h in high-purity N2 gas. Typical magnetic properties of the obtained compound powders were Jr = 0.97 T, HcJ = 730.8 kA/m,(BH)max = 140.0 kJ/m3 (17.6 MGOe), Tc=500°C. XRD, TEM photographs, and recoil loops of the hysteresis curve demonstrated that this sample had the characteristics of an exchange spring magnet. The value of (BH)max for the isotropic compression molding bonded magnet prepared from the {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2 powder was 94.8 kJ/m3 (11.9 MGOe) at a bonded magnet density of 6.07 Mg/m3. The reversible temperature coefficient of Jr was ,(Jr)=,0.04%/°C and the temperature coefficient of HcJ in the range from 25°C to 125°C obtained by linear extrapolation was ,(HcJ)=,0.40%/°C. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(7): 25,31, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10124 [source] Nanocrystalline Electroplated Cu,Ni: Metallic Thin Films with Enhanced Mechanical Properties and Tunable Magnetic BehaviorADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Eva Pellicer Abstract Nanocrystalline 3,µm thick Cu1,xNix (0.45,,,x,,,0.87) films are electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates, from a citrate- and sulphate-based bath containing sodium lauryl sulphate and saccharine as additives. The films exhibit large values of reduced Young's modulus (173,<,Er,<,192,GPa) and hardness (6.4,<,H,<,8.2,GPa), both of which can be tailored by varying the alloy composition. The outstanding mechanical properties of these metallic films can be ascribed to their nanocrystalline nature,as evidenced by X-ray diffraction, transmission electron microscopy, and atomic force microscopy,along with the occurrence of stacking faults and the concomitant formation of intragranular nanotwins during film growth. Due to their nanocrystalline character, these films also show very low surface roughness (root mean square deviation of around 2,nm). Furthermore, tunable magnetic properties, including a transition from paramagnetic to ferromagnetic behavior, are observed when the Ni percentage is increased. This combination of properties, together with the simplicity of the fabrication method, makes this system attractive for widespread technological applications, including hard metallic coatings or magnetic micro/nano-electromechanical devices. [source] Bioaccessibility studies of ferro-chromium alloy particles for a simulated inhalation scenario: A comparative study with the pure metals and stainless steelINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 3 2010Klara Midander Abstract The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large research effort was therefore conducted to generate quantitative bioaccessibility data for particles of ferro-chromium alloys compared with particles of the pure metals and stainless steel exposed at in vitro conditions in synthetic biological media of relevance for particle inhalation and ingestion. All results are presented combining bioaccessibility data with aspects of particle characteristics, surface composition, and barrier properties of surface oxides. Iron and chromium were the main elements released from ferro-chromium alloys upon exposure in synthetic biological media. Both elements revealed time-dependent release processes. One week exposures resulted in very small released particle fractions being less than 0.3% of the particle mass at acidic conditions and less than 0.001% in near pH-neutral media. The extent of Fe released from ferro-chromium alloy particles was significantly lower compared with particles of pure Fe, whereas Cr was released to a very low and similar extent as from particles of pure Cr and stainless steel. Low release rates are a result of a surface oxide with passive properties predominantly composed of chromium(III)-rich oxides and silica and, to a lesser extent, of iron(II,III)oxides. Neither the relative bulk alloy composition nor the surface composition can be used to predict or assess the extent of metals released in different synthetic biological media. Ferro-chromium alloys cannot be assessed from the behavior of their pure metal constituents. Integr Environ Assess Manag 2010;6:441,455. © 2009 SETAC [source] Mechanical Behavior and Failure Analysis of Prosthetic Retaining Screws after Long-Term Use In Vivo.JOURNAL OF PROSTHODONTICS, Issue 3 2008Microhardness Analysis, Part 2: Metallurgical Abstract Purpose: This study involved testing and analyzing multiple retrieved prosthetic retaining screws after long-term use in vivo to: (1) detect manufacturing defects that could affect in-service behavior; (2) characterize the microstructure and alloy composition; and (3) further characterize the wear mechanism of the screw threads. Materials and Methods: Two new (control) screws from Nobel Biocare (NB) and 18 used (in service 18,120 months) retaining screws [12 from NB and 6 from Sterngold (SG)] were: (1) metallographically examined by light microscopy and scanning electron microscopy (SEM) to determine the microstructure; (2) analyzed by energy dispersive X-ray (EDX) microanalysis to determine the qualitative and semiquantitative average alloy and individual phase compositions; and (3) tested for Vickers microhardness. Results: Examination of polished longitudinal sections of the screws using light microscopy revealed a significant defect in only one Group 4 screw. No significant defects in any other screws were observed. The defect was considered a "seam" originating as a "hot tear" during original casting solidification of the alloy. Additionally, the examination of longitudinal sections of the screws revealed a uniform homogeneous microstructure in some groups, while in other groups the sections exhibited rows of second phase particles. The screws for some groups demonstrated severe deformation of the lower threads and the bottom part of the screw leading to the formation of crevices and grooves. Some NB screws were comprised of Au-based alloy with Pt, Cu, and Ag as alloy elements, while others (Groups 4 and 19) were Pd-based with Ga, Cu, and Au alloy elements. The microstructure was homogeneous with fine or equiaxed grains for all groups except Group 4, which appeared inhomogeneous with anomalous grains. SG screws demonstrated a typical dendritic structure and were Au-based alloy with Cu and Ag alloy elements. There were differences in the microhardness of gold alloy screws from NB and SG as well as palladium alloy screws from NB. Conclusions: Significant differences within NB retaining screws and between NB and SG screws were found for microstructure, major alloy constituents, and microhardness. [source] Optimization of Bragg reflectors in AlGaAs/GaAs VCSELsLASER PHYSICS LETTERS, Issue 5 2005V. M. N. Passaro Abstract In this paper a detailed investigation of the distributed Bragg reflectors in GaAs-based vertical cavity surface emitting lasers is presented. The influence of layer doping concentration, number of periods, oxide aperture and AlxGa1,xAs alloy composition on output emission power and threshold current has been found. Both oxidized and non oxidized structures have been considered. A number of interpolation curves are extracted and presented for design and fabrication purposes. Although the results are presented for GaAs-based structures, the theoretical approach is very general. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Field study on superheater tubes in the loop seal of a wood fired CFB plantMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2004A. Nafari Abstract Two full scale superheaters were exposed in the loop seal of a 30 MW wood-fired CFB plant in Nässjö, Sweden, for one firing season each. Some austenitic steel tubes from the first tube bundle were reinstalled in the second superheater. The superheater tubes were made from one ferritic steel, X10 (Fe8.8Cr) and three austenitic steels; Esshete 1250 (Fe15Cr9Ni6Mn), 347H (Fe17Cr11Ni) and AC66 (Fe27Cr32Ni). Commercial coatings mainly on iron, nickel and carbide base were deposited on some of the X10 and 347H tubes. The material wastage kinetics was non-linear showing that pure corrosion and not erosion-corrosion is the major degradation mechanism in the loop seal. It is however clear that the environment is not very aggressive and the corrosion attack on the uncoated tubes is very small. The largest oxide thickness was only about 150 ,m recorded on the X10 alloy. The austenitic steels mainly suffered from internal corrosion and grain boundary corrosion, the extent and distribution of which strongly depended on the alloy composition. Generally, it was more pronounced in the regions with the thinnest deposit layers. Eight out of 17 coating qualities tested were unaffected by the exposure. Corrosion was only recorded on the lowest alloyed iron based coatings. The only coatings which could not resist the conditions in the loop seal were the carbide containing Metco 3006 and Metco 3007, where severe oxidation and delamination took place. Also the thermally sprayed Inconel 625 coating delaminated, but this was rather due to a mechanical failure resulting from thermal expansion. [source] Atomic layer epitaxy of GaMnAs on GaAs(001)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007M. Ozeki Abstract A self-limiting mechanism in atomic layer epitaxy (ALE) has been investigated for the heterogrowth of GaMnAs on GaAs(001) substrate. In the ALE, trimethylgallium, bismethylcyclopentadienylmanganese and trisdimethylaminoarsine were used as source materials of gallium, manganese and arsenic atoms, respectively. Although the growth of GaMnAs was carried out at a high growth temperature of 500 °C, a distinct self-limiting mechanism was observed for the manganese alloy composition up to 6% and the epitaxial layer had no indications of including MnAs phase. The layer showed an atomically flat surface morphology reflecting the self-limiting growth. The self-limiting mechanism was largely affected by the lattice mismatch between GaMnAs epitaxial layer and GaAs substrate. When the manganese alloy composition exceeded 7%, the self-limiting mechanism was broken and MnAs precipitates were observed in the epitaxial layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth kinetics of AlxGa1,xN layers (0 < x < 1) in plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010A. M. Mizerov Abstract Comparative study of growth kinetics of the AlxGa1-xN (x = 0-1) layers of different polarity, grown by plasma assisted molecular beam epitaxy (PA MBE) under different growth conditions (substrate temperature, group III to activated nitrogen and Al to Ga flux ratios) and on different buffer layers, is presented. The 60 °C higher temperature stability of N-face AlGaN layers is detected. The strong influence of elastic stress on growth kinetics of metal-polar AlxGa1-xN (x > 0.2) layers is observed and discussed. It was found that two-dimensional growth of AlGaN films of the same composition on different buffer layers at TS = 700 °C can be achieved at different group III surface enrichment, the AlGaN(0001)/c-Al2O3 films exhibiting the atomically smooth surface at group III to activated nitrogen flux ratio FIII/FN *gradually increased from 1.3 to 2 with the x variation from 0.1 to 0.8. In this case the alloy composition is controlled by the variation of Al flux only (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Defects and structure of µc-SiOx:H deposited by PECVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Lihong Xiao Abstract Electronic transport and paramagnetic defects detected by Electron Spin Resonance (ESR) in both intrinsic and Effect of strain and alloy composition inhomogeneity on the electronic and optical properties of III-nitride semiconductorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2008Nikos Skoulidis Abstract Using the empirical tight binding method with a sp3s* basis for the first neighbour interactions and only p,p interactions for the second neighbours, we calculated the optical properties near the fundamental gap of cubic GaxAl1,xN alloys for x<0.33 grown on a substrate whose lattice constant varies from the lattice constant of cubic AlN to GaN. We found that the spectra of the fully relaxed alloy have a tail with onset energy at the indirect gap of AlN and an edge at the direct gap of the alloy which follows the Vegard's law within 0.1 eV. The maximum of band gap for each alloy composition is found for a substrate with the lattice constant of the fully relaxed alloy. When the substrate composition is such that induces negative tetragonal strain on the alloy (,xx<0) the energy band gap is mainly affected by the alloy composition while for ,xx>0 the alloy composition has a limited effect. The total effect of substrate and alloy composition in the calculated range on the band gap can be as much as 0.4 eV and is mainly due to the valence band shift as the conduction band is only slightly affected by the substrate or the alloy composition. This band gap change is adequate to explain the experimentally observed double photoluminescence peak of open quantum dots. The energy separation of the double peak is 0.1 eV and one peak can be attributed to the tetragonically strained wetting layer and the other to the fully relaxed quantum dots. Furthermore the present results can be used to estimate any possible stoichiometric inhomogeneity and help design structures with specific energies for the pair of peaks. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007Tetuso Narita Abstract The diffusion of Ga species in gas phase as well as on the surface are studied in selective area growth of AlGaN in low pressure metalorganic vapor phase epitaxy. The experiments were performed on a trapezoidal stripe with (0001) facet on the top and (1-101) facet on the sides. It was found that the ridge growth on the facets were sensitive to the growth pressure, in agreement with numerical results. At a low pressure of 100 Torr, we got a uniform thickness of AlGaN alloy, but the alloy composition was not uniform. Exponential variation of the composition gave the effective diffusion length of Ga on the order of 0.7 ,m which was independent of the growth pressure. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence and electrophysical characterization of AlxGa1,xN epilayersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006V. I. Kozlovsky Abstract Cathodoluminescence (CL) of metalorganic vapor phase epitaxy (MOVPE) grown AlxGa1,xN epilayers on sapphire has been studied with x from 0.23 to 0.38. CL spectra of undoped and Si-doped AlGaN epilayers with the same alloy composition grown on thick GaN buffers have been compared. The free electron concentration in the doped samples has been measured to (1-1.6) × 1017 cm,3 with a mobility of 84-115 cm2/Vs. CL spectra have been compared with deep level transient spectroscopy spectra. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Innovative Katalysatoren zur oxidativen Dehydrierung in der Gasphase , Metallische KurzfasernCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 6 2004R. Brüning Abstract Metallische Kurzfasern in ausgesuchter Legierungszusammensetzung und Gefügestruktur wurden auf ihre katalytische Aktivität bei der oxidativen Dehydrierung (ODH) von Propan zu Propen und von Isopropanol zu Aceton untersucht. Die über das Schmelzextraktions-Verfahren hergestellten Kurzfasern wurden einer intensiven Charakterisierung ihrer werkstoffseitigen Eigenschaften unterworfen. Dabei kamen lichtmikroskopische, DSC-, XRD-, REM- und EDX-Untersuchungen zum Einsatz, um Zusammenhänge zwischen der Werkstoffzusammensetzung, dem Gefüge und den katalytischen Eigenschaften zu ermitteln. Es werden ausgewählte Ergebnisse zur Temperaturabhängigkeit des Propan-Umsatzes bzw. der Propen-Selektivität präsentiert. So wurde Propen bei einem Propan-Umsatz von mehr als 50,% mit einer Ausbeute von 35,% gebildet. Auch die Selektivoxidation von Isopropanol zu Aceton erfolgte mit attraktiven Ausbeuten von über 80,%. Die Ergebnisse insgesamt belegen das hohe Innovationspotenzial der Metallfaserwerkstoffe. Innovative Catalysts for Oxidative Dehydration Reactions in the Gas Phase , Metallic Short Fibres The catalytic activity of metallic short fibres with chosen alloy composition and texture was investigated in the oxidative dehydration (ODH) of propane to yield propene, and of isopropanol to yield acetone. The short fibres were synthesised using a melt extraction process and the properties of the fibres were intensely characterised. A correlation between the structure and the catalytic activity of the material was established. Thus, light-optical microscopic-, DSC-, XRD-, REM- and EDX-methods were used to characterise the fibres. Selective results of the dependency of the temperature on the propane conversion are presented in this work. A yield of more than 35,% propene is obtained at a propane conversion of 50,%. The ODH of isopropanol to acetone occurred with attractive yields of over 80,%. The results demonstrate the high innovative potential of the metal fibre materials. [source] TEM Study of Precipitates in Melt-Spun Mg-Zn-Y-La Alloys,ADVANCED ENGINEERING MATERIALS, Issue 6 2005J. Rao Recently, nano-crystalline MgZn1Y2 alloys exhibiting excellent tensile yield strength elongation ratio have been developed as a consequence of preliminary investigations of alloy compositions using melt-spun ribbons. Their results show that the novel long-period hexagonal atomic configurations in the Mg-Ln-Zn alloys as well as the atomic scale enrichment of Ln and Zn elements into the misfit atomic array sites indicates the possibility that a high-strength Mg-based alloy is developed by the control of the novel structure and the atomic scale segregation mode. [source] A small-angle neutron scattering study of fine-scale NbC precipitation kinetics in the ,-Fe,Nb,C systemJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2006F. Perrard The fine-scale precipitation of NbC in ferrite has been quantitatively characterized in the temperature range 873,1073,K for two alloy compositions, containing respectively 800,p.p.m. Nb and 400,p.p.m. Nb (by weight). Transmission electron microscopy (TEM) has revealed that the precipitates are located on dislocations, and have a plate-like morphology with an average aspect ratio between 2 and 3. Small-angle neutron scattering (SANS) has been systematically used to determine the precipitation kinetics. The validity of the quantitative SANS measurements of size and volume fraction has been assessed by TEM image analysis and chemical dissolution experiments. The precipitation kinetics is observed to depend strongly on temperature but to be similar for the two alloy compositions. From the measurements, it is inferred that precipitate nucleation is extremely rapid, in relation to the nature of the nucleation sites. A time,temperature transformation diagram is built from the kinetic data, showing a maximum reaction rate between 973 and 1073,K. [source] Effects of indium incorporation in AlGaN on threading dislocation densityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005H. Kang Abstract A comparison of dislocation densities in AlGaN and InAlGaN with approximately similar alloy compositions was completed. A systematic series of the AlGaN layers with concentration of 17% Aluminum were grown by metal-organic chemical vapor deposition with trace amounts of indium incorporated into the layers. X-ray diffraction analysis by Williamson Hall plot and reciprocal space mapping was employed to investigate columnar structure in these layers. It was found that lateral coherence length, related to threading dislocation, was systematically varied with Indium content. The lateral coherence length increased with the consequence that the threading dislocation density decreased as Indium content increased, which indicated that even small amounts of indium incorporation could improve crystalline quality. The results are in good agreement with etch pit density study using AFM. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microstructure of ball milled and compacted Co,Ni,Al alloys from the , rangeJOURNAL OF MICROSCOPY, Issue 2 2009W. MAZIARZ Summary Two powder alloys from the , phase region of compositions Co28.5Ni36.5Al35 and Co35Ni30Al35 were ball milled for 80 h in a high energy ball mill. The formation of amorphous structure was observed after 40 h of milling and further milling did not change their structure. The analytical and high-resolution transmission electron microscopy (TEM, HREM) examination of powder structure showed that nanoparticles of L10 phase of size of about 5 nm were present within the amorphous matrix. The vacuum hot pressing of the milled powders under pressure of 400 MPa at 700°C for 12 min resulted in the formation of compacts with density of about 70% of the theoretical one. The additional heat treatment at 1300°C for 6 h followed by water quenching, led to significant improvement of density and induced the martensitic transformation manifested by a broad heat effect. The characteristic temperatures of the transformation were determined using DSC measurements, which revealed only small differences within the examined alloys compositions. TEM structure studies of heat-treated alloys allowed to identify the structure of an ordered , (B2) phase and L10 martrensite. [source]
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