Commercially pure α-Ti was serial sectioned using a Xe plasma focused ion beam (PFIB) scanning electron microscope and orientation maps were obtained on the parallel layers by electron backscatter ...diffraction. The orientations and shapes of 13,900 grains and 92,100 grain faces were characterized. The mean number of faces per grain was 14.2. The grain boundaries were classified according to the three misorientation parameters and two grain boundary orientation parameters. There were more grain boundaries with 180°-twist and 180°-tilt character than expected in a random distribution. Furthermore, grain boundary planes with prismatic orientations were more common than those with basal orientations. The grain boundary with the greatest relative area had a 28°/0001 misorientation and (314¯0) and (72¯5¯0) grain boundary planes. Compared to earlier instruments with Ga-ion sources, the milling speed of the PFIB makes it possible to collect ten times more data in a comparable time.
Display omitted
Atomic force microscopy was used to measure the dimensions of grain‐boundary thermal grooves on the surfaces of Al2O3, 100 ppm Y‐doped Al2O3, and 500 ppm Y‐doped Al2O3 ceramics heated at temperatures ...between 1350°C and 1650°C. The measurements were used to estimate the relative grain‐boundary energies as a function of temperature. The relative grain‐boundary energies of Al2O3 decrease slightly with increased temperature. When the doped samples were heated, there was an overall increase in the grain‐boundary energy, attributed to a reduction in the grain boundary excess at higher temperature. The overall trend of increasing grain‐boundary energy was interrupted by abrupt reductions in grain‐boundary energy between 1450°C and 1550°C. In the same temperature range, there is an abrupt increase in the grain‐boundary mobility that is associated with a complexion transition. When the 100 ppm Y‐doped sample was cooled, there was a corresponding increase in the relative grain‐boundary energy at the same complexion transition temperature, indicating that the transition is reversible.
The dihedral angles at grain boundary thermal grooves in SrTiO3 were measured and used to determine the relative grain boundary energy at several temperatures where the grain growth rate constant ...displays anti-thermal properties (it decreases with increasing temperature). The measurements indicate that at temperatures in the anti-thermal region (1390 °C–1400 °C), the average grain boundary energy is less than at a lower temperature (1350 °C) where grain boundaries move more rapidly. Three-dimensional electron backscatter diffraction was used to measure the geometries of internal triple junctions in a sample where the slow and fast grain boundaries co-exist. Based on the dihedral angles at triple junctions, the ratio of the energies of slow boundaries to fast boundaries is 0.86. The results indicate that at temperatures between 1350 °C and 1425 °C, the higher and lower energy boundaries coexist. The coexistence of the two boundary types in this temperature range is likely because there is a range of grain boundary energies and the temperature at which a boundary transforms from the slow type to the fast type depends on its grain boundary energy.
Display omitted
The grain boundary character distribution (GBCD) of a 100-nm-thick Al thin film was measured as a function of annealing time by transmission electron microscopy-based crystal orientation mapping and ...compared to a bulk material with a grain size of 23 μm. The most significant difference between the thin film and bulk GBCDs is the concentration of Σ3 boundaries (boundaries with a misorientation of 60° around 111), which were mostly coherent twins. The length fraction of Σ3 boundaries in the as-deposited thin film is 0.245, more than ten times the length fraction in the bulk sample (0.016). Although the concentrations of Σ3 boundaries are very different in the two samples, the population distributions are strongly correlated for all misorientations except Σ3. The results indicate that the characteristic GBCD develops at grain sizes as small as 109 nm. Annealing the thin film samples at 400 °C for 30 min or more leads to a strong 〈111〉 grain orientation texture and a decrease in the concentration of Σ3 grain boundaries. Grain size distributions for the samples in the current study show good agreement with prior reports that used image-based methods.
By mapping grain orientations on parallel serial sections of a SrTiO3 ceramic, it was possible to reconstruct three‐dimensional orientation maps containing more than 3000 grains. The grain boundaries ...were approximated by a continuous mesh of triangles and mean curvatures were determined for each triangle. The integral mean curvatures of grain faces were determined for all grains. Small grains with fewer than 16 neighbors mostly have positive mean curvatures while larger grains with more than 16 neighbors mostly have negative mean curvatures. It is also possible to correlate the mean curvature of individual triangles with the crystallographic characteristics of the grain boundary. The mean curvature is lowest for grain boundaries with (100) orientations and highest for grain boundaries with (111) orientations. This trend is inversely correlated to the relative areas of grain boundaries and directly correlated to the relative grain boundary energy. The direct correlation between the energy and curvature is consistent with the expected behavior of grain boundaries made up of singular orientations. Furthermore, because both the relative energy and curvature of grain boundaries with (100) orientations are minima in the distributions, these boundaries also have the lowest driving force for migration.
Thin-film solar cells based on polycrystalline Cu(In,Ga)Se2 absorbers exhibit record conversion efficiencies of up to 22.6%. There is still a lack of a quantitative connection between the ...grain-boundary character distribution (GBCD) and the corresponding electrical and optoelectronic properties. The present work uses microstructural data from a CuInSe2 thin film acquired by electron backscatter diffraction (EBSD) to evaluate the GBCD. The most prominent features of the GBCD of CuInSe2 are Σ3 twin boundaries and the Σ9 and Σ27a symmetric tilt grain boundaries. Moreover, combining EBSD with electron-beam-induced current and cathodoluminescence (measurements on the same identical area) on a CuInSe2/Mo/glass stack provide the means to relate the grain-boundary character with the corresponding electrical and optoelectronic signals across the grain boundary. In part, determining this relationship is accomplished by means of correlation analysis using measurement data from more than 100 grain boundaries. However, the crystallographic, electrical and optoelectronic data showed no strong correlations, which is attributed to atomic reconstruction found in atomic planes adjacent to planar defects in polycrystalline CuInSe2 thin films and corresponding reductions of excess charge densities at these defects.
Display omitted
Display omitted
•An approach to characterize complexion transition kinetics is presented.•The fundamentals of bulk phase and complexion TTT diagrams are compared.•Avrami-type analysis quantifies the ...time dependence of complexion transitions.•Newly constructed complexion TTT diagrams enable engineered microstructures.•Future challenges and recommendations for complexion TTT diagrams are discussed.
Grain boundaries and other interfaces can undergo complexion transitions from one thermodynamic state to another, resulting in discontinuous changes in interface properties such as diffusivity, mobility, and cohesive strength. The kinetics of such complexion transitions has been largely overlooked until recently. Just as with bulk phase transformations, complexion transition kinetics can be represented on time-temperature-transformation (TTT) diagrams. An experimental complexion TTT diagram is presented here for polycrystalline Eu-doped spinel annealed at 1400–1800°C. This material developed a microstructure with a bimodal grain size distribution, indicating that a complexion transition occurs within this temperature range. The time and temperature dependence of this complexion transition was analyzed and used to produce a grain-boundary complexion TTT diagram for this system. Complexion TTT diagrams have the potential to be remarkably useful tools for manipulating the properties of internal interfaces in polycrystalline metals and ceramics. The development of experimental complexion TTT diagrams is likely to have an important impact on the field of grain-boundary engineering, and hence the development of these experimental diagrams should be an intense area of focus in the coming years.
Bloodless pediatric cardiac surgery requiring the use of cardiopulmonary bypass (CPB) remains a challenge for the entire operating room (OR) team. The amount of circulating blood volume to pump prime ...volume mismatch of small patients results in hemodilution that frequently results in transfusion of allogeneic blood products. Patients of families of the Jehovah’s Witness (JW) faith reject the use of these products because of religious beliefs. Our institution is a referral center for children of JW families because we have developed techniques to minimize blood loss with the hope of performing bloodless pediatric cardiac surgery whenever possible. These techniques include preoperative treatment with erythropoietin, intraoperative acute normovolemic hemodilution, CPB circuit miniaturization, ultrafiltration during and after CPB, limiting blood gas analyses or other unnecessary blood draws, and using hemostatic agents during and after CPB. We present the case of a 4-day-old patient of the JW faith weighing 2.7 kg with transposition of the great arteries and an intact ventricular septum who underwent an arterial switch operation. The patient received no allogeneic blood product administration throughout the entire hospitalization. The patient’s first hematocrit in the OR was 43%, lowest hematocrit on bypass was 15%, and first hematocrit in the cardiothoracic intensive care unit post-procedure was 21%. The patient was discharged on post-op day nine with a hematocrit of 36%.
Abstract
By mapping grain orientations on parallel serial sections of a SrTiO
3
ceramic, it was possible to reconstruct three‐dimensional orientation maps containing more than 3000 grains. The grain ...boundaries were approximated by a continuous mesh of triangles and mean curvatures were determined for each triangle. The integral mean curvatures of grain faces were determined for all grains. Small grains with fewer than 16 neighbors mostly have positive mean curvatures while larger grains with more than 16 neighbors mostly have negative mean curvatures. It is also possible to correlate the mean curvature of individual triangles with the crystallographic characteristics of the grain boundary. The mean curvature is lowest for grain boundaries with (100) orientations and highest for grain boundaries with (111) orientations. This trend is inversely correlated to the relative areas of grain boundaries and directly correlated to the relative grain boundary energy. The direct correlation between the energy and curvature is consistent with the expected behavior of grain boundaries made up of singular orientations. Furthermore, because both the relative energy and curvature of grain boundaries with (100) orientations are minima in the distributions, these boundaries also have the lowest driving force for migration.
Bloodless pediatric cardiac surgery requiring the use of cardiopulmonary bypass (CPB) remains a challenge for the entire operating room (OR) team. The amount of circulating blood volume to pump prime ...volume mismatch of small patients results in hemodilution that frequently results in transfusion of allogeneic blood products. Patients of families of the Jehovah’s Witness (JW) faith reject the use of these products because of religious beliefs. Our institution is a referral center for children of JW families because we have developed techniques to minimize blood loss with the hope of performing bloodless pediatric cardiac surgery whenever possible. These techniques include preoperative treatment with erythropoietin, intraoperative acute normovolemic hemodilution, CPB circuit miniaturization, ultrafiltration during and after CPB, limiting blood gas analyses or other unnecessary blood draws, and using hemostatic agents during and after CPB. We present the case of a 4-day-old patient of the JW faith weighing 2.7 kg with transposition of the great arteries and an intact ventricular septum who underwent an arterial switch operation. The patient received no allogeneic blood product administration throughout the entire hospitalization. The patient’s first hematocrit in the OR was 43%, lowest hematocrit on bypass was 15%, and first hematocrit in the cardiothoracic intensive care unit post-procedure was 21%. The patient was discharged on post-op day nine with a hematocrit of 36%.
PDF
