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The impact of chemical reactions on the thermal boundary conductance (TBC) of Au/metal contact/β-Ga2O3 layered samples as a function of contact thickness is investigated using high-throughput thermoreflectance measurements. A maximum in TBC of 530 ± 40 (260 ± 25) MW/m2 K is discovered for a Cr (Ti) contact at a thickness of 2.5 (5) nm. There is no local maximum for a Ni contact, for which the TBC saturates at 410 ± 35 MW/m2 K for thicknesses greater than 3 nm. Relative to the Au/β-Ga2O3 interface, which has a TBC of 45 ± 7 MW/m2 K, these nanoscale contacts enhance TBC by factors of 6 to 12. The TBC maximum only exists for metals capable of forming oxides that are enthalpically favorable compared to β-Ga2O3. The formation of Cr2O3, via oxygen removal from the β-Ga2O3 substrate, is confirmed by TEM analysis. The reaction-formed oxide layer reduces the potential TBC and leads to the maximum, which is followed by a plateau at a lower value, as its thickness saturates due to passivation. Many advanced materials are prone to similar chemical reactions, impacting contact engineering and thermal management for a variety of applications.

Metal amorphous nanocomposites (MANCs) offer lower losses than silicon steels and higher saturation inductions than amorphous alloys. Their application in motors will require a detailed understanding of their mechanical properties. Co74.6Fe2.7Mn2.7Nb4Si2B14 was studied by nanoindentation and tensile testing to determine hardness, elongation, Young's modulus, ultimate tensile strength (UTS), and Poisson's ratio. Young's modulus was observed to increase with crystallization at 50 MPa, and then decrease when annealing under applied stress. Annealing at even higher stress resulted in no significant change in Young's modulus. This trend was replicated in nanohardness results. The UTS and elongation decrease with crystallization and show a large increase in standard deviation. Reduction in UTS and elongation has been attributed to embrittlement, as well as the high surface roughness of the ribbon material. Poisson's ratio remained relatively constant at 0.31–0.33 for all samples. X-ray diffraction (XRD) was performed on annealed samples, revealing fine nanocrystals. Profilometry indicates significant surface roughness, which contribute to reduction of UTS and elongation. Hardness, UTS, and elongation compare favorably to existing materials, but embrittlement of the material needs to be addressed to allow use in electric motor applications.

The impact of chemical reactions on the thermal boundary conductance (TBC) of Au/metal contact/β-Ga

Reduced titanomagnetite solid solutions, xFe2TiO4 - (1 - x)Fe3O4, with 0.5 ≤ × ≤ 1, were synthesized by sintering in 99.996% pure flowing argon. Samples showed a systematic variation in the second phase amount as a function of x. A wustite second phase primarily forms near the surface of titanomagnetite pellets. The amount of wustite decreases with increasing Ti concentration. XRD data confirms that samples with x > 0.8 have less than 1% wustite. M(T) curves were measured by vibrating sample magnetometer (VSM). A magnetization hump is observed in M(T) during heating and explained by ferrimagnetic phases formed by exsolution and precipitation processes. These phases were identified as titanomaghemite and magnetite by fitting M(T) cooling curves with a multi-phase Brillouin function.

Oxy-fuel combustion is burning a fuel in oxygen rather than air for ease of capture of CO2 from for reuse or sequestration. Corrosion issues associated with the environment change (replacement of much of the N2 with CO2 and higher sulfur levels) from air- to oxy-firing were examined. Alloys studied included model Fe–Cr alloys and commercial ferritic steels, austenitic steels, and nickel base superalloys. The corrosion behavior is described in terms of corrosion rates, scale morphologies, and scale/ash interactions for the different environmental conditions. Evidence was found for a threshold for severe attack between 10−4 and 10−3 atm of SO3 at 700 °C.

In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO2 and O2. While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

In this work we present preliminary results on magnetization and remanence of synthetic pseudo-binary x(Fe2TiO4)-(1-x)(Fe3O4)(0.30

Ultrasound diagnosis of pediatric intussusception is feasible with limited operator training. The authors report the test characteristics of bedside ultrasound (BUS) for the diagnosis of pediatric intussusception at a single institution.Inclusion criteria were: 1) patients of 0-18 years old were seen in the pediatric emergency department (ED) with a clinical presentation suspicious for intussusception; 2) BUS was performed to identify intussusception and bedside impression documented in the medical record; 3) a "formal" diagnostic study (such as computed tomography, ultrasound, or barium enema) was performed by the radiology department after BUS was completed. Electronic medical record and ED BUS archive were screened for potentially eligible ED visits between January 1(st) 2009 to October 3(rd) 2012. These records were then reviewed to identify patients for inclusion in the study. All emergency physicians who performed the BUS had undergone a minimum of 1-hour didactic training on the use of BUS to diagnose pediatric intussusception.A total of 1 631 charts were reviewed, with 49 meeting inclusion criteria. Five of those were later excluded for incomplete documentation or lack of saved BUS images. The prevalence of intussusception was 23%. The mean age of the subjects was 31 months. BUS was 100% sensitive (95%CI 66%-100%) and 94% specific (95%CI 79%-99%) for detection of pediatric intussusception compared to radiology study results. Positive and negative likelihood ratios were 16.5 (95%CI 4.30%-63.21%) and 0 (95%CI 0-0) respectively.BUS is an accurate means of diagnosing acute intussusception in pediatric patients. Further study might be indicated to confirm such benefits.

Ulvospinel (Fe2TiO4) and titanomagnetites (TM) (pseudo-binary (1-x)Fe3O4xFe2TiO4 system, where, e. g. TM95 corresponds to x = 0.95) were made using a solid-state synthesis technique. For single phase titanomagnetites (x>0.75), our measured lattice constants extends the previous work of Wechesler to Ti-rich solid solutions, and extrapolates to a value of 8.531 A for single phase ulvospinel, agreeing closely to the literature value of 8.534 A. The lattice constants as a function of composition (x>0.75) were fit to a straight line with the equation y = 0.09x + 8.441. Grain sizes of single phase TM pellets of as-quenched and annealed samples were determined, showing that the grain size of the annealed samples grew noticeably after 100 hrs in Ar flow at 450 °C. For TM75, the grains grew from 11.7 μm to 15.4 μm. The ratios of grain sizes vary over the composition range, from 4% to 31%, suggesting coarsening driven by diffusional growth. In the samples that initially contained wustite as a second phase, there are grains with a lath microstructure with well-defined angles, indicating preferred orientations. Small amounts of Feor Ti-cation rich phases were observed to decorate the grain boundaries after long annealing. TiO2 formed on grain boundaries of TM75 annealed sample.

We have synthesized the antiferromagnetic mineral ulvospinel, Fe 2 TiO 4, in Ar to assess the role of inert atmosphere on phase formation and magnetic properties. We report the role of atmosphere on a possible phase transition and the magnetic properties of this mineral. Atmosphere dependent transformations of ulvospinel are observed with increasing temperature. Oxidation of ulvospinel to form metastable titanomaghemite is shown to occur at 300° in atmospheric conditions. Only slight titanomaghematitzation was observed in samples transformed under pressure in in situ temperature dependent X-ray experiments. Formation of ilmenite and hematite from ulvospinel was observed under high temperature, high pressure, and low oxygen atmosphere conditions. This work is supported by the National Science Foundation (NSF) through Award DMR1106943 and the Spanish National Space Program of R&D Externalization through the project PRI-PIBUS-2011-1150. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. Use of the HPCAT facility was supported by DOE-BES, DOE-NNSA (CDAC), NSF, DOD-TACOM, and the W. M. Keck Foundation. Use of the APS was supported by DOE-BES, under Contract DE-AC02-06CH11357. Peerreview

X-ray powder diffraction, simultaneous DSC/TGA and Mössbauer spectroscopy. Structural, thermal and magnetic properties. Cation distributions derived from isomer shifts. The xFe2TiO4-(1−x)Fe3O4 pseudo-binary systems (0≤x≤1) of ulvöspinel component were synthesized by solid-state reaction between ulvöspinel Fe2TiO4 precursors and commercial Fe3O4 powders in stochiometric proportions. Crystalline structures were determined by X-ray powder diffraction (XRD) and it was found that the as-obtained titanomagnetites maintain an inverse spinel structure. The lattice parameter a of synthesized titanomagnetite increases linearly with the increase in the ulvöspinel component. 57Fe room temperature Mössbauer spectra were employed to evaluate the magnetic properties and cation distribution. The hyperfine magnetic field is observed to decrease with increasing Fe2TiO4 component. The fraction of Fe2+ in both tetrahedral and octahedral sites increases with the increase in Ti4+ content, due to the substitution and reduction of Fe3+ by Ti4+ that maintains the charge balance in the spinel structure. For x in the range of 0 ≤x≤0.4, the solid solution is ferrimagnetic at room temperature. However, it shows weak ferrimagnetic and paramagnetic behavior for x in the range of 0.40.70, it only shows paramagnetic behavior, with the appearance of quadrupole doublets in the Mössbauer spectra. Simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TGA) studies showed that magnetite is not stable, and thermal decomposition of magnetite occurs with weight losses accompanying with exothermic processes under heat treatment in inert atmosphere. The work at Duquesne was supported by the National Science Foundation under grant DMR-0854794. Peerreview

INSPEC Accession Number: 12261756 Titanomagnetites offer a rich system to explore the role of fine microstructure on magnetic properties. They are important minerals in basalts, and are commonly found on the moon and Mars. Here magnetic measurements were used to monitor decomposition and phase evolution in the pseudo-binary Fe 2 TiO 4 -Fe 3 O 4 solid solution system. The phases appearing in the decomposition are a strongly magnetic magnetite and a weakly magnetic Ti-rich spinel. For the 40, 50, and 60 at% Fe 2 TiO 4 compounds (balance Fe 3 O 4 ) explored here, a metastable solid solution is nonmagnetic at temperatures where decomposition kinetics can be monitored in reasonable experimental times. The magnetization of magnetite formed by the decomposition offers a direct measure of the volume fraction transformed. Time-dependent magnetization measurements were used to monitor the kinetics of decomposition and compared to models for spinodal decomposition and nucleation and growth kinetics for compositions outside the spinodes. The fine microstructure resulting from spinodal decomposition and exchange bias mechanisms for coupling, may be important in understanding the remnant state of these minerals on Mars This work was supported in part by the NSF under Grants DMR0804020 and DMR1106943, as well as the Spanish National Space Program (DGI-MEC), Project MEIGA-MET-NET, Grant PJE-09001. The authors wish to acknowledge S. Paticopolous for help in sample synthesis and testing. As well as J. Wolf and T. Nuhfer of the J. Earl and Mary Roberts Center for Materials Characterization. Peerreview

M-type barium hexaferrite films have been grown by liquid phase epitaxy and examined by x-ray diffraction,scanning electron microscopy, atomic force microscopy, and conventional and Lorentz-mode transmission electron microscopy(TEM). These films exhibit a diamond chevron shaped “brick wall” microstructure with c-axis oriented hexaferrite platelets. The films are oriented with their c axes in-plane, and parallel to the M-plane sapphire substrate, and exhibit a 30° rotation about the c axis with respect to the substrate. Rocking curves showed (20−20) and (22−40) FWHM values of 1.09° and 1.56°, respectively, for the thinner of two samples, and 0.31° and 0.50° for the thicker sample. The magnetic domain structures have been characterized by Lorentz-mode TEM and the domain walls were found to be pinned to small angle tilt boundaries. Using the measured rocking curve values, the effect of the overall crystalline misorientation on the dispersion of the magnetocrystalline anisotropy of the samples is estimated to be less than half a percent.

Processes for making well ordered L10 FePt thin films with root-mean-square surface roughness close to 0.4 nm, perpendicular anisotropy greater than 5 kOe and perpendicular squareness near 1 using a deposition temperature of 390 °C have been developed. In this study, we focused on reducing the ordering temperature and smoothness of L10 FePt films, while achieving good perpendicular magnetic properties by using MgO/CrRu/TiN or MgO/CrRu/Pt seed layers on Si/SiO2 substrates. It was found that the chemical ordering of L10 FePt films is strongly affected by the insertion of a sputtered MgO seed layer, and the CrRu (002) texture on a (002) textured MgO seed layer is substantially improved at high DC power. In order to prevent Cr diffusion, TiN and Pt films were inserted between the CrRu and FePt films. It was found that the smoothness, L10 FePt ordering, and perpendicular magnetic properties were strongly improved by the TiN barrier layer compared to the Pt barrier layer. Increased TiN thickness improved the perpendicular magnetic anisotropy due to the reduced lattice misfit between the CrRu and L10 FePt films.

In the paper ‘‘Crystal structure and zinc location in the BaZnFe6O11 Y-type hexagonal ferrite’’ by Collomb et al. [1], the detailed list of atomic positions gives the fractional coordinate location of the Me5 atom at the 18h symmetry site as x: 0.50317, y: –0.50317, and z: 0.19073 in a hexagonal cell. We believe this to be a typographical error, and that the fractional coordinate for the z-position should be approximately z: 0.109. The Y-type hexagonal ferrite has the space group symmetry R-3m. When this symmetry is applied to the positions given in the paper, using CrystalMaker software, the center to center distance between the Me5 atoms and the O5 atoms is only 0.27 A, an unrealistic number. In the paper, the closest-approach distance between Me5 and O5 atoms is listed as 2.048 A. Since the R-3m symmetry of the system is well-documented, the issue must lie with either the oxygen or metal atom fractional coordinate. Since the oxygen positions are consistent with the placement of the other oxygen layers in the unit cell, the misalignment appears to be in the Me5 position. Another paper on Y-type

Sputter-deposited W films with nominal thicknesses between 5 and 180 nm were prepared by varying the base pressure prior to film deposition and by including or not including sputtered SiO2 encapsulation layers. X-ray and electron diffraction studies showed that single phase, polycrystalline α-W could be achieved in as-deposited films as thin as 5 nm. The stress state in the as-deposited films was found to be inhomogeneous. Annealing resulted in stress relaxation and reduction of resistivity for all films, except the thinnest, unencapsulated film, which agglomerated. In-plane film grain sizes measured for a subset of the annealed films with thicknesses between 5 and 180 nm surprisingly showed a near constant value (101–116 nm), independent of film thickness. Thick-film (≥120 nm) resistivity values as low as 8.6 μΩ cm at 301 K were obtained after annealing at 850 °C for 2 h. Film resistivities were found to increase with decreasing film thicknesses below 120 nm, even for films which are fully A2 α-W with no metastable, A15 β-W evident. Sputter-deposited W films with nominal thicknesses between 5 and 180 nm were prepared by varying the base pressure prior to film deposition and by including or not including sputtered SiO2 encapsulation layers. X-ray and electron diffraction studies showed that single phase, polycrystalline α-W could be achieved in as-deposited films as thin as 5 nm. The stress state in the as-deposited films was found to be inhomogeneous. Annealing resulted in stress relaxation and reduction of resistivity for all films, except the thinnest, unencapsulated film, which agglomerated. In-plane film grain sizes measured for a subset of the annealed films with thicknesses between 5 and 180 nm surprisingly showed a near constant value (101–116 nm), independent of film thickness. Thick-film (≥120 nm) resistivity values as low as 8.6 μΩ cm at 301 K were obtained after annealing at 850 °C for 2 h. Film resistivities were found to increase with decreasing film thicknesses below 120 nm, even for films which are fully A2 α-W with no...

We report on new high-saturation induction, high-temperature nanocomposite alloys with reduced glass formers. The amounts of the magnetic transition metals and early transition metal growth inhibitors were systematically varied to determine trade-offs between higher inductions and fine microstructures with consequently lower magnetic losses. Alloys of nominal composition (Fe65Co35)79.5+xNb4−xB13Si2Cu1.5 (x=0–4) were cast into a 28 mm wide, 20 μm thick ribbon from which toroidal cores were wound. Inductions and magnetic losses were measured after nanocrystallization and stress relief. We report technical magnetic properties: permeability, maximum induction, remanence ratio, coercive field, and high frequency magnetic losses as a function of composition and annealing temperature for these alloys. Of note is the development of maximum inductions in excess of 1.76 T in cores made of alloys with the x=4 composition and maximum inductions in excess of 1.67 T in alloys with the x=3 composition, which also exhibit power losses smaller than 10 W/kg at 0.2 T induction levels in 20 kHz fields. We discuss optimization of induction with chemistry and correlate the microstructures with losses.

(Fe50Co50)97V2Nb1nanoparticles were synthesized in an induction plasma torch and oxidized isochronally at temperatures between room temperature (RT) and 900 °C. The particles exhibited three stages of oxidation present at different temperatures. The initial oxide layer was nearly Co-free, beginning at 3 nm at RT, and Co appeared to oxidize separately from the iron.Iron cations were determined to be the mobile species during oxidation, yielding a progressively more Co-rich core as oxidation progressed, decreasing from an average diameter of 42 to 25 nm, while the oxide tripled in size. At 350 °C, the particles exhibited a less dense core, and at 900 °C the particles were observed to have changed morphology completely with some sintering, forming completely oxidized particles with an average diameter three times the as received size.