Mixed-conducting ceramic oxides have potential uses in high-temperature electrochemical applications such as solid oxide fuel cells, batteries, sensors, and oxygen-permeable membranes. The Sr-Fe-Co-O system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. Dense ceramic membranes made of this material can be used to separate high-purity oxygen from air without the need for external electrical circuitry, or to partially oxidize methane to produce syngas. Samples of Sr2Fe3-xCoxOy (with x = 0, 0.6, 1.0, and 1.4) were prepared by solid-state reaction method in atmospheres with various oxygen partial pressures (pO(2)) and were characterized by X-ray diffraction, scanning electron microscopy, and electrical conductivity testing. Phase components of the sample are dependent on cobalt concentration and pO(2). Electrical conductivity increases with increasing temperature and cobalt content in the material.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The objective of this research was to determine consumer preferences for tenderness, quality grade, origin, use of growth technologies, and price of beef, sirloin steak, specifically. Two hundred twenty three consumers participated. Of these, 96 consumers participated in a sensory tasting panel for sirloin steak before completing a choice set survey while the remaining 127 completed the choice set survey. A structural difference was found in the results between the two groups. The eating experience was found to be critical, altering the preferences of consumers. Consumers overstated their willingness-to-pay (WTP) for credence attributes before tasting the product. After tasting products, factors that influence the eating experience (tenderness, quality grade) still dominated as the most important and influential attributes on WTP. The lack of WTP premium or discount from the no tasting group for beef quality grade may indicate a lack of knowledge about the meaning of the grade terms “choice” and “select.” Sensory panel participants reported a significant WTP premium for Choice indicating they value that quality when they eat it. The use of no hormones and no antibiotics in production had a premium of $2.34/kg among the no tasting group, but after tasting the premium was reduced to $1.19/kg.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The mixed-conducting Sr-Fe-Co oxide has potential use as a gas separation membrane. Its superior oxygen transport reveals the feasibility of using oxide membranes in large-scale oxygen separation. Sr2Fe3-xCoxOy (with x = 0.0, 0.3, 0.6, and 1.0) samples were made by solid state reaction. To understand the oxygen transport mechanism in this system, conductivity and thermogravimetry experiments were conducted at high temperature in various oxygen partial pressure environments. The oxygen diffusion coefficient was determined from the time relaxation transient behavior of the specimen after switching the surrounding atmosphere. Mobility of the charge carrier was derived from relative conductivity and weight changes. X-ray diffraction experiments were carried out on these samples to determine their crystal structures.

We compare damage evolution in U3Si produced by neutron irradiation at 30°C and 350°C and measured by neutron diffraction. Initial studies found that increasing neutron irradiation dose at 30°C results in monotonic expansion of the a-axis and contraction of the c-axis that transforms the crystal structure from tetragonal to cubic [1]. Additional irradiation results in amorphization. Neutron irradiation at 350°C results in little change to the a-axis and expansion of the caxis.The complete alteration in lattice dilatation during irradiation is interpreted as due to modification of surviving defect configurations at the higher temperature. The high temperature lattice dilations can be explained by defect loop formation in the a-b plane. Confinement of lattice strain to the c-axis during irradiation at 350°C may be the mechanism that prevents the total lattice dilatation from exceeding the critical level required for amorphization.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Ni2MnGa has been the focus of multiple studies due to its unique ferromagnetic, magnetostrictive, thermal and magnetically controlled shape memory properties. At room temperature, the alloy has a Heusler alloy L2(1) type structure. A martensitic phase transition occurs upon cooling. It is highly desirable to develop and study the properties of alloys that exhibit the MSM effect at ambient conditions. In Ni-Mn-Ga compounds the exchange between Mn and Ga reduces the degree of order which makes neutron diffraction more sensitive to the crystallographic characterization and an ideal tool to study the effect of different thermal treatments on the structure. In this work the crystallography of several non-stoichiometric polycrystalline alloys synthesized and thermally treated were studied at several temperatures using pulsed neutron source at Argonne National Laboratory. The alloys were Ni2Mn1+xGa1-x compositions with x=-0.08, 0.0, 0.08 and 0.16. The sample were arc melted pellets and were studied as-cast and after several combinations of thermal treatments including isothermal annealing at 900 and 700 degrees C and cooling to room temperatures. It was found that the Mn rich non stoichiometric alloys (x=0.08 and 0.16) are unstable at 700 degrees C and fast cooling from 900 degrees C is essential in order to retain a homogeneous solid solution. These single-phase structures were found to have high level of chemical order, for that reason, ordering treatment is not necessary.

Using the neutron time-of-flight (TOF) technique, we have examined the reason for the dramatic departure of experimental results from the Darwin and Ewald reflectivity functions in the far wings. The scattering from Si(111) single- and triple-bounce crystals set up at the Bragg angle θB=24.4° was dispersed in time-of-flight in the wavelength range 0.3<λ<3.0Å. The experiment reveals admixture of the single-scattered Bragg peaks and thermal diffuse scattering (TDS) originating at λ<0.6Å in the spectrum registered from a triple-bounce crystal. Our study explains the discrepancy between the theory and the experimental results reported in many neutron studies and proves the validity of the Darwin and Ewald theories in the far wings.

The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the as-cast specimen was composed of \( {\left\{ {{\text{001}}} \right\}}{\left\langle {{\text{100}}} \right\rangle } \), \( {\left\{ {{\text{001}}} \right\}}{\left\langle {{\text{110}}} \right\rangle } \), \( {\left\{ {{\text{011}}} \right\}}{\left\langle {{\text{100}}} \right\rangle } \), and \( {\left\{ {{\text{011}}} \right\}}{\left\langle {{\text{110}}} \right\rangle } \), which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants (\( {\left\{ {{\text{110}}} \right\}}{\left\langle {{\text{001}}} \right\rangle } \)and \( {\left\{ {{\text{100}}} \right\}}{\left\langle {{\text{001}}} \right\rangle } \)) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent Bain-distortion energy.

We have measured the lattice constants and Debye–Waller factors of ZrC from 12 to 1600 K using neutron diffraction. The data have been analyzed with the Grüneisen equation of state using an existing procedure for the Debye–Waller factors and a new procedure for the CTE that takes the temperature dependence of the elastic stiffness into account. The results of these measurements are in good agreement with previous measurements and with recent calculations. We have used the results of our measurements to estimate the melting point of ZrC with the Lindemann rule and obtain an estimate of 4000 K, in good agreement with the measured melting point of 3700 K of this highly refractory material. This last result demonstrates the importance of anharmonic effects in determining the melting point.

Neutron diffraction was used to study the structure of ternary NiAl + M (M = Ni, Fe, Cc) alloys. The experiment confirmed the predictions by first-principle calculations on site preference by solute atoms. Moreover, a universal structural transformation was observed below 20 K in alloys where Al is partially replaced by M. The extra peaks at low-temperatures do not match those from known martensite phases, but are well indexed by a cubic structure. A possible mechanism for the low-temperature phase is discussed. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We report here that the ball-milling process induces the phase transformation from the tetragonal structure to the disordered face-centered-cubic structure in Ni2MnGa ferromagnetic shape-memory alloys. The in situ high-energy x-ray diffraction analyses reveal that an intermediate phase, which is characterized by amorphous structure, controls the transformation kinetics during the postannealing process. Completely different from their coarse-grained counterparts, the ferromagnetic Ni2MnGa nanoparticles undergo various sequences of structural transitions that are tailored by the crystallite size, atomic order, and intrinsic magnetic structure.

The authors report complementary use of high-energy x-ray and neutron diffraction to probe the local atomic structure in a Zr-based bulk metallic glass. By analyzing the partial coordination numbers, the authors demonstrate the presence of multiple types of solute-centered clusters in the multicomponent glass and efficient packing of the amorphous structure at atomic scale. The authors’ findings provide a basis for understanding how local structures change during phase transformation and mechanical deformation of multicomponent amorphous alloys.