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High energy density magnets .400 kJ/m are increasingly used in many applications. Conventional casting techniques for sintered magnets reveal the formation of a high quantity of a-Fe and large Nd-rich regions. New techniques, like strip casting, produce homogeneous and fine scaled microstructures and are already used for producing high (BH)max magnets. The fast cooling rate during strip casting suppresses the formation of a-Fe dendrites and of large Nd-rich pockets. Directional solidification causes a formation of columnar grains containing a typical arrangement of hard magnetic Nd2Fe14B regions and Nd-rich regions. The Nd regions occur as intragranular platelets as well as intergranular phases. Intragranular lamellae show a periodicity which corresponds to a eutectoidal solidification according to the composition of the liquid and are directed parallel to the temperature gradient during solidification. The lamellae show an average width of 150 nm, a spacing of 3 mm, and a length up to the size of the hard magnetic grains. The fine separation of the hard magnetic and Nd phases is advantageous for the milling of the alloy after hydrogen decripitation and improves sinterability of magnets. Although the microstructure of strip cast alloys is much finer than that of ordinary cast alloys, the alignment of the powder is not deteriorated and Br is not reduced due to a sufficient large interlamellar spacing between the Nd-rich platelets that enables the formation of single crystal powder particles after milling. © 1998 American Institute of Physics. @S0021-8979~98!18911-9#

The microstructure and the magnetic properties of melt-spun Au100-xCox (x = 6.5, 16.7, 28.4) were investigated. The eutectic decomposition allows one to synthesize a lamellar microstructure. Changes of the size distribution and shape of the Co precipitates during annealing influence the magnetic behavior and the transport properties of the investigated samples.

Sintered magnets were prepared from jet‐milled and hydrogen‐decrepitated jet‐milled Nd‐Fe‐B:(Cu,Nb) powder. The HD process started after heating the cast material up to 200 °C. A single‐step annealing treatment at 525 °C improved the magnetic properties of all samples. Magnets prepared from the jet‐milled powder required a short time sintering (

Ga-doped Nd-Fe-B sintered magnets show an improved wetting behavior of the liquid phase during sintering and the formation of additional Ga-containing intergranular phases. Nb forms precipitates within the hard magnetic grains and enhances the coercivity. In the as-sintered magnets, a new Nd-rich Ga-containing region which contains Nd/sub 3/Ga and Nd/sub 5/Ga/sub 3/ is found. This region is formed from the liquid phase during cooling. In addition, the delta -phase occurs in the annealed magnets. Nb is found in the hexagonal NbFeB intergranular boride and in small Nb-containing precipitates within the hard magnetic phase. There is no Nb detected in the Nd-rich phases. >

In this study the cross-sectional nanoindentation (CSN) technique has been employed to investigate the adhesion behavior of Titanium-Tungsten (TiW) thin films in various thicknesses on silicon substrate. Furthermore, the nanoindentation-induced blister (NIB) technique has been implemented on the same samples to evaluate the adhesion energy of the films with a different approach. The adhesion energy release rate of these thin films, derived by these two techniques, revealed a good agreement. Accordingly, the results show that as the thickness of the TiW layer increases, the adhesion toughness of the film decreases. It was suggested that three factors might be responsible for the superior adhesion strength of thin films with lower thicknesses: higher surface energy due to the smaller mean grain size; higher constraint from the substrate, which causes inferior fracture toughness of the coating and facilitates crack deflection from interface to surface; and, energy dissipation due to decohesion. The thickness dependency of the transition between delamination and decohesion mechanism in thin films has also been discussed and modelled.

Co-substituted Nd-Fe-B magnets show an increased Curie temperature. The coercivity of these magnets is reduced due to the formation of Co-rich phases. In addition to the hard magnetic phase the Nd-rich intergranular phase exists, which results in bad corrosion resistance. In (Nd,Dy)-(Fe,Co)-B:Al type magnets doped with V, (V/sub 1-x/Fe/sub x/)/sub 3/B/sub 2/ intergranular phases and precipitates with Si/sub 2/U/sub 3/ structure and a Nd-rich Co-containing phase partly replacing the Nd-rich phase were found. X-ray microanalysis shows that in (Nd,Dy)-(Fe,Co)-B:(Al,V) magnets Dy is mainly dissolved in the hard magnetic phase. Comparison with W-doped Nd-Fe-B magnets shows that W also forms an intergranular WFeB phase with Co/sub 2/Si-structure and precipitates within the hard magnetic phase with presumably the same composition. >

The hard magnetic properties of hot‐worked R‐Fe‐B permanent magnets are improved by the addition of a minor amount of Cu (up to 2 at. %). Transmission electron microscope investigations show that the reason for the increase of the coercivity is the fact that Cu is mainly dissolved in the intergranular region separating the hard magnetic 2:14:1 grains. The results obtained are similar in Nd‐Fe‐B:Cu and Pr‐Fe‐B:Cu magnets. The intergranular region has been observed to consist of a eutectic consisting of two phases: the Nd‐or Pr‐rich phase and the orthorhombic NdCu‐ or PrCu‐phase. This corresponds to the eutectic decomposition of the liquid intergranular phase during cooling. It is suggested that the decrease of the melting temperature of the intergranular phase leads to a better wetting behavior and separation of the hard magnetic grains, and therefore to an enhancement of the coercivity.

The metal particle supported formation of In2O3 nanowires via molecule-based chemical vapour deposition is demonstrated. Results of electron microscopy investigations of the wire and the metal seed lead to the conclusion that the growth mechanism should be assigned to the VSS mechanism, which is very rare for the formation of oxide nanowires. The growth could be assigned to a quasi-epitaxial guidance by the gold growth seed facilitating the formation of nanowires from a solid particle.

The microstructure of melt-spun Au83.3Co16.7 and Au71.6Co28.4 ribbons is investigated by means of analytical and high-resolution electron microscopy. The as-quenched ribbons contain a multilayered lamellar eutectic within the grains and Co precipitates at grain boundaries. Cobalt-rich lamellae are found with growing direction 〈110〉 and an average width of 7.5 nm. The thickness of the Co-lamella parallel to [001] is larger in the sample with the higher Co-content. Annealing at 480 °C dissolves the eutectic and large Co particles are formed at grain boundaries and within the grains deteriorating the magnetic properties. Die Mikrostruktur von schnell abgekuhlten Au83.3Co16.7 und Au71.6Co28.4 Bandern wird mittels analytischer und hochauflosender Elektronenmikroskopie untersucht. Die nicht warmebehandelten Bander bestehen aus Kornern mit einem lamellaren Eutektikum und Co-Ausscheidungen an den Korngrenzen. Die Kobalt-reichen Lamellen wachsen in 〈110〉 Richtung und weisen eine mittlere Breite von 7,5 nm auf. In der 28,4 At% Co Probe ist die Dicke der Co-Lamellen parallel zu [001] groser als in der Probe mit geringerem Co-Gehalt. Eine Warmebehandlung bei 480 °C lost die Lamellenstruktur auf, fuhrt zur Bildung von grosen Co-Ausscheidungen an Korngrenzen und im Inneren der Korner und verschlechtert die magnetischen Eigenschaften.

Microstructural influence on saturation magnetization, remanence, coercivity and giant magnetoresistance (GMR) of melt-spun Au 1−x -Co x , (x = 0.65 and 0.284) ribbons in the as-quenched state and subsequently annealed at 480 °C has been investigated using analytical transmission electron microscopy. The evolution of the magnetic data with annealing time was found to be determined by the sequence of the formation of Co precipitates, their volume fraction, their particle size distribution and their morphology. GMR behavior was only measured for Au 73.6 Co 28.4 and is clearly caused by a lamellar eutectic with a structure similar to multilayers.

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We present a focused ion beam based technique for the synthesis of nanowires in room temperature ambient without using any additional material source. Based on the idea of a catalytic approach gallium antimonide and antimony nanowires were grown with diameters of about 20nm. We suppose that the intense focused ion beam exposure forms catalytic particles alloyed by the constituents of the growing nanowire in situ. In contrast to a broad class of techniques for nanowire growth neither heating of the sample nor any additional material source is required, thereby being compatible with on-chip microelectronics.

Giant magnetoresistance (GMR) has recently been achieved in multilayers as well as in granular alloys prepared by sputtering or melt spinning. In these granular alloys magnetic Co particles are usually embedded in a nonferromagnetic metallic matrix (Cu, Ag, Au) and have a statistical magnetic moment distribution. The GMR effect originates mainly from spin dependent scattering of conduction electrons within the ferromagnetic Co particles and at their interfaces and is controlled by the size distribution and the volume fraction of the Co particles as well as the roughness of the interfaces between the Co particles and the matrix. Au-Co was chosen as a model system to investigate systematically the microstructural influence on the transport properties. The large difference of the atomic scattering factors of Au and Co enables the distribution of ferromagnetic Co particles be distinguished by structure factor contrast. The eutectic decomposition in Au-Co (Liq. ⇔ Au + Co at TE = 995.6 °C and 28.4 at% Co) allows a multilayered structure in rapidly quenched Au-Co to be synthesized.

The influence of small additions of Ga and Nb on the magnetic and microstructural properties of sintered and melt-spun FeNdB based magnets was analyzed. New intergranular phases and precipitates improve the magnetic decoupling thus enhancing the critical fields μ 0 H c up to 2.5 T in melt-spun Fe 72 Nd 17 B 7.5 Ga 1.5 Nb 2 .

Giant magnetoresistance (GMR) of up to 65% at room temperature has been achieved in Cu/Co multilayers, far exceeding the 2.5% arising from permalloy, which is presently used in magnetoresistive read heads. The GMR effect is not restricted to multilayered structures only and has been also discovered in heterogeneous CulxCox thin films. At present, experimentally determined and statistically significant microstructural parameters, e.g., Co particle size distribution, composition of Co particles and Co matrix concentration, are still not available for Cu1-xCox films or melt-spun ribbons because of two reasons. First, the small difference in atomic scattering factors of Cu and Co and secondly, the Ashby-Brown contrast, which is expected for coherent precipitates, is not observed. The large volume fraction of Co precipitates results in overlap and cancellation of their strain fields. To overcome limitations in imaging Co precipitates, melt-spun AU1-xCox ribbons have been investigated regarding their GMR. AuCo has a similar phase diagram (Fig. 1) compared with CuCo, but it has the advantage of a large difference in atomic scattering factors of Au and Co. As a consequence Co-rich precipitates can be directly identified by their mass contrast.

The study of next generation high energy accelerators based on 16T dipoles has emphasized the need for higher performance, cost-effective Nb3Sn superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density (Jc) of 1500A/mm2 at 16T and 4.2K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this article, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first stage Jc milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize Jc. The study of next-generation high-energy accelerators based on 16 T dipoles has emphasized the need for higher performance, cost-effective Nb$_3$Sn superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density ($J_c$) of 1500 A/mm2 at 16 T and 4.2 K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this paper, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first-stage $J_c$ milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize $J_c$.

Due to the rapid development of packaging industry accelerated reliability testing for evaluation of lifetime of electronic components are increasingly utilized. In addition to common active thermal cycling procedures, accelerated mechanical fatigue testing provides a new possibility to assess the reliability of microelectronic components, mainly due to the significantly shorter duration of testing time. In this investigation we have used an ultrasonic fatigue testing system in combination with a special experimental set-up for qualification and lifetime determination of microelectronic interconnects. Using this technique, fatigue life of Al wire bonded interconnects were determined and S-N curves (shear stress as a function of loading cycles) up to N = 1 0 9 were plotted. Three dimensional elasto-plastic FEM simulations were performed to determine the distributions of shear stress and plastic strain generated during cyclic fatigue in the bond area. Furthermore, the FEM model was employed to predict the lifetime of wire-bonds. The results were correlated to the lifetime curves of similar bonds obtained by power cycling tests. Detailed microstructural investigations were performed by means of EBSD -SEM to study the evolution of microstructure of the interconnects subjected to thermal and mechanical fatigue loading. This study demonstrates the applicability of accelerated mechanical fatigue testing as an alternative to time consuming thermal cycling for qualification of microelectronic interconnects.

Although considerable research has been dedicated to the synthesis and characterization of lead-free nanoparticle solder alloys, only very little has been reported on the reliability of the respective joints. In fact, the merit of nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature has always been challenged when compared with conventional solder joints, especially in terms of inferior solderability due to the oxide shell commonly present on the nanoparticles, as well as due to compatibility problems with common fluxing agents. Correspondingly, in the current study, Sn-Ag-Cu (SAC) nanoparticle alloys were combined with a proper fluxing vehicle to produce prototype nanosolder pastes. The reliability of the solder joints was successively investigated by means of electron microscopy and mechanical tests. As a result, the optimized condition for employing nanoparticles as a competent nanopaste and a novel procedure for surface treatment of the SAC nanoparticles to diminish the oxide shell prior to soldering are being proposed.

We here report an improved experimental technique for the determination of Young׳s modulus and uniaxial strength of extracellular bone matrix at the single micrometer scale, giving direct access to the (homogeneous) deformation (or strain) states of the tested samples and to the corresponding mechanically recoverable energy, called potential or elastic energy. Therefore, a new protocol for Focused Ion Beam milling of prismatic non-tapered micropillars, and attaching them to a rigid substrate, was developed. Uniaxial strength turns out as at least twice that measured macroscopically, and respective ultimate stresses are preceded by hardening elastoplastic states, already at very low load levels. The unloading portion of quasi-static load–displacement curves revealed Young׳s modulus of 29 GPa in bovine extracellular bone matrix. This value is impressively confirmed by the corresponding prediction of a multiscale mechanics model for bone, which has been comprehensively validated at various other observation scales, across tissues from the entire vertebrate animal kingdom.

The polarization resistance of lanthanum strontium ferrite thin film electrodes with and without additional Pt surface doping was compared directly after film growth by PLD employing in situ electrochemical impedance spectroscopy.

Ni nanoparticles supported on ZrO2 are a prototypical system for reforming catalysis converting methane to synthesis gas. Herein, we examine this catalyst on a fundamental level using a 2-fold approach employing industrial-grade catalysts as well as surface science based model catalysts. In both cases we examine the atomic (HRTEM/XRD/LEED) and electronic (XPS) structure, as well as the adsorption properties (FTIR/PM-IRAS), with emphasis on in situ/operando studies under atmospheric pressure conditions. For technological Ni–ZrO2 the rather large Ni nanoparticles (about 20 nm diameter) were evenly distributed over the monoclinic zirconia support. In situ FTIR spectroscopy and ex situ XRD revealed that even upon H2 exposure at 673 K no full reduction of the nickel surface was achieved. CO adsorbed reversibly on metallic and oxidic Ni sites but no CO dissociation was observed at room temperature, most likely because the Ni particle edges/steps comprised Ni oxide. CO desorption temperatures were in line with single crystal data, due to the large size of the nanoparticles. During methane dry reforming at 873 K carbon species were deposited on the Ni surface within the first 3 h but the CH4 and CO2 conversion hardly changed even during 24 h. Post reaction TEM and TPO suggest the formation of graphitic and whisker-type carbon that do not significantly block the Ni surface but rather physically block the tube reactor. Reverse water gas shift decreased the H2/CO ratio. Operando studies of methane steam reforming, simultaneously recording FTIR and MS data, detected activated CH4 (CH3 and CH2), activated water (OH), as well as different bidentate (bi)carbonate species, with the latter being involved in the water gas shift side reaction. Surface science Ni–ZrO2 model catalysts were prepared by first growing an ultrathin “trilayer” (O–Zr–O) ZrO2 support on an Pd3Zr alloy substrate, and subsequently depositing Ni, with the process being monitored by XPS and LEED. Apart from the trilayer oxide, there is a small fraction of ZrO2 clusters with more bulk-like properties. When CO was adsorbed on the (fully metallic) Ni particles at pressures up to 100 mbar, both PM-IRAS and XPS indicated CO dissociation around room temperature and blocking of the Ni surface by carbon (note that on the partially oxidized technological Ni particles, CO dissociation was absent). The Ni nanoparticles were stable up to 550 K but annealing to higher temperatures induced Ni migration through the ultrathin ZrO2 support into the Pd3Zr alloy. Both approaches have their benefits and limitations but enable us to address specific questions on a molecular level.

Mc 2009. Microscopy Conference, Graz, Austria. 30 August - 4 September 2009. First Joint Meeting Of Dreiländertagung And Multinational Congress On Microscopy.

EELS (electron energy loss spectrometry) in the transmission electron microscope (TEM) was used to determine the composition of a nanocrystalline magnetic specimen. The relative amounts of the hard magnetic phase Nd 2 Fe 14 B and the soft magnetic phase Fe 3 B at the point of measurement was measured by standard EELS quantification. In order to determine the structure of Fe 3 B present, the fine structure of the boron K -ionisation edge was analysed. Comparison of the experimental spectra with simulations of the fine structures based on the TELNES extension of the WIEN97 program package, a full potential linearised augmented plane wave approach to the calculation of electronic structure in crystals, shows that the tetragonal form of Fe 3 B is predominant.

We present a study conducted on binary Tube Type and ternary powder-in-tube Nb3Sn wires manufactured using the artificial pinning centres-internal oxidation method. All the specimens are doped with Zr: oxide nano-particles of this element are responsible for the pinning improvement, both by refining the A-15 grain-size and their own point-pinning contribution. Low-field J c magnetometry confirms that the hadron-hadron Future Circular Collider (FCC-hh) specifications are met by one ternary doped-sample. The differences in microstructure were assessed by scanning electron microscopy/transmission electron microscopy to clarify the reasons for the pinning improvement between the two generations. The deviations from the Dew Hughes model are also discussed, underlying some non-linear addition due to competition between the two pinning mechanisms. Finally, we show how the introduction of Ta as a ternary addition influences the A-15 phase by focusing on the radial inhomogeneities, evaluating the T c distribution and Sn composition gradients. The latter are used to model the currents, enabling us to evaluate the individual weights of the pinning mechanisms and their absolute contributions at the High Luminosity-Large Hadron Collider and FCC-hh dipoles operational points.