The dynamics of texture formation, changes in crystal structure, and stress accommodation mechanisms have been studied in perovskite-type R3¯c rhombohedral LaCoO3 during uniaxial compression using in-situ neutron diffraction. The in-situ neutron diffraction revealed the complex crystallographic changes causing the texture formation and significant straining along certain crystallographic directions during compression, which are responsible for the appearance of hysteresis and non-linear ferroelastic deformation in the LaCoO3 perovskite. The irreversible strain after the first loading was connected with the appearance of non-recoverable changes in the intensity ratio of certain crystallographic peaks, causing non-reversible texture formation. However, in the second loading/unloading cycle, the hysteresis loop was closed and no further irrecoverable strain appeared after deformation. The significant texture formation is responsible for an increase in the Young's modulus of LaCoO3 at high compressive stresses, ranging from 76 GPa at the very beginning of the loading to 194 GPa at 900 MPa at the beginning of the unloading curve.

Articles you may be interested inIn-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture developmentCalculations of elastic constants and development of elastic anisotropy under uniaxial compression in originally isotropic polycrystalline LaCoO 3 perovskite are reported. The lattice strains in individual (hkl) planes as well as average lattice strain were determined both for planes oriented perpendicular and parallel to the loading direction using in-situ neutron diffraction. Utilizing average lattice strains as well as lattice strains along the a and c crystallographic directions, an attempt was made to determine Poisson's ratio of LaCoO 3 , which was then compared with that measured using an impulse excitation technique. The elastic constants were calculated and Young's moduli of LaCoO 3 single crystal in different crystallographic directions were estimated. V C 2014 AIP Publishing LLC. [http://dx.

This paper presents the mechanical behavior of LaCoO 3 and La 0.8 Ca 0.2 CoO 3 ceramics under fourpoint bending in which the two cobaltites are subjected to a low stress of ~8 MPa at temperatures

The purpose of this study is to assess the impact of a newly developed modules, Interactive Web-Based Visualization Tools for Gluing Undergraduate Fuel Cell Systems Courses system (IGLU), on learning motivations of engineering students using two samples (n1=144 and n2=135) from senior engineering classes. The multivariate analysis results revealed that the participants had a significant increase in their learning motivation after the treatment with the IGLU modules. This result was cross-validated with the two samples, in which the motivation mean posttest scores are significantly higher than the mean pretest scores, systematically (Sample 1: the mean score is increased by 2.09 [.32, 3.87] points, p = .021; Sample 2: the mean score is increased by 1.38 [.14, 2.61] points, p = .029). With the use of instructional technology prevailing in current university courses, the education initiative of the IGLU system and the assessment of its impact on student learning motivation provide us information to improve the modules to serve a more diverse student body. It will greatly help the development of engineering educational curriculum. With regards to the statistical inference, it is desirable to conduct further studies with a quasi-experiment control group design to assess the program effect focusing on student learning and its associations with student learning motivations and learning styles.

The study of domain wall movement and texture formation in ferroelastic LaCoO 3 perovskite under constant applied compressive stress has been performed using in situ neutron diffraction. It was established that under constant applied compressive stress the domain walls show mobility that may lead both to the shrinkage (creep strain) and to the expansion (negative creep strain) of LaCoO 3 perovskite. The domain wall movement and texture formation can be explained by the availability, mobility, and interaction of twins, stacking faults, antiphase boundaries, dislocations, and point defects, such as oxygen vacancies and their complexes as well as impurity atoms. The equation of motion was used to describe the possible mechanisms of domain wall movement under applied stress, and it was determined that the available solutions of this equation allow both for the shrinkage (creep strain) and for the expansion (negative creep strain) of LaCoO 3 perovskite to occur.