lee moo montgomery stephen hofer (4 résultats)

Wraps. Etat : Very good. Presumed First Edition, First printing. Staplebound. 65, [3] pages. Tables. Figures. Formulae. Appendices, References. Specimens of poled and unpoled ''chem-prep'' PNZT ceramic from batch HF1035 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions at -55, 25, and 75 C. The objective of this experimental study was to characterize the mechanical properties and conditions for the ferroelectric (FE) to antiferroelectric (AFE) phase transformations of this ''chem-prep'' PNZT ceramic to aid grain-scale modeling efforts in developing and testing realistic response models for use in simulation codes. As seen from a previously characterized material (batch HF803), poled ceramic from HF1035 was seen to undergo anisotropic deformation during the transition from a FE to an AFE phase. Also, the phase transformation was found to be permanent for the two low temperature conditions, whereas the transformation can be completely reversed at the highest temperature. The rates of increase in the phase transformation pressures with temperature were practically identical for both unpoled and poled PNZT HF1035 specimens. We observed that temperature spread the phase transformation over mean stress analogous to the observed spread over mean stress due to shear stress. Additionally, for poled ceramic samples, the FE to AFE phase transformation was seen to occur when the normal compressive stress, acting perpendicular to a crystallographic plane about the polar axis, equals the hydrostatic pressure at which the transformation otherwise takes place.

Wraps. Etat : Good. Presumed First Edition, First printing. x, 74 pages plus back cover. Illustrations (most with color). References. Velobound. Format is approximately 8.5 inches by 11 inches. Unlimited Release. Ink note on front cover. Mailing label on back. Sandia is currently developing a lead-zirconate-titanate ceramic 95/5-2Nb (or PNZT) from chemically prepared ('chem-prep') precursor powders. Previous PNZT ceramic was fabricated from the powders prepared using a 'mixed-oxide' process. The specimens of unpoled PNZT ceramic from batch HF803 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions within the temperature range of -55 to 75 C and pressures to 500 MPa. The objective of this experimental study was to obtain mechanical properties and phase relationships so that the grain-scale modeling effort can develop and test its models and codes using realistic parameters. The stress-strain behavior of 'chem-prep' PNZT under different loading paths was found to be similar to that of 'mixed-oxide' PNZT. The phase transformation from ferroelectric to antiferroelectric occurs in unpoled ceramic with abrupt increase in volumetric strain of about 0.7 % when the maximum compressive stress, regardless of loading paths, equals the hydrostatic pressure at which the transformation otherwise takes place. The stress-volumetric strain relationship of the ceramic undergoing a phase transformation was analyzed quantitatively using a linear regression analysis. The pressure (P{sub T1}{sup H}) required for the onset of phase transformation with respect to temperature is represented by the best-fit line, P{sub T1}{sup H} (MPa) = 227 + 0.76 T (C). We also confirmed that increasing shear stress lowers the mean stress and the volumetric strain required to trigger phase transformation. At the lower bound of the tested temperature range, the phase transformation is irreversible. At the upper bound (75 C), the phase transformation is completely reversible as the stress causing phase transformation is removed.

Wraps. Etat : Very good. Presumed First Edition, First printing. 85, [1] pages plus back cover. Illustrations (most with color). References. Staplebound. Format is approximately 8.5 inches by 11 inches. Unlimited Release. Specimens of poled 'chem-prep' PNZT ceramic from batch HF803 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions at three temperatures of -55, 25, and 75 C and pressures up to 500 MPa. The objective of this experimental study was to obtain the electro-mechanical properties of the ceramic and the criteria of FE (Ferroelectric) to AFE (Antiferroelectric) phase transformations so that grain-scale modeling efforts can develop and test models and codes using realistic parameters. The poled ceramic undergoes anisotropic deformation during the transition from a FE to an AFE structure. The lateral strain measured parallel to the poling direction was typically 35 % greater than the strain measured perpendicular to the poling direction. The rates of increase in the phase transformation pressures per temperature changes were practically identical for both unpoled and poled PNZT HF803 specimens. We observed that the retarding effect of temperature on the kinetics of phase transformation appears to be analogous to the effect of shear stress. We also observed that the FE-to-AFE phase transformation occurs in poled ceramic when the normal compressive stress, acting perpendicular to a crystallographic plane about the polar axis, equals the hydrostatic pressure at which the transformation otherwise takes place.

Velobound. Etat : Very good. Presumed First Edition, First printing. x, 74 pages, plus covers. Tables. Figures (some with color). References Appendices A. - D. Rear cover has mailing label and ink notation. Sandia is currently developing a lead-zirconate-titanate ceramic 95/5-2Nb (or PNZT) from chemically prepared ("chem-prep") precursor powders. Previous PNZT ceramic was fabricated from the powders prepared using a "mixed-oxide" process. The specimens of unpoled PNZT ceramic from batch HF803 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions within the temperature range of -55 to 75°C and pressures to 500 MPa. The objective of this experimental study was to obtain mechanical properties and phase relationships so that the grain-scale modeling effort can develop and test its models and codes using realistic parameters. The stress-strain behavior of "chem-prep" PNZT under different loading paths was found to be similar to that of "mixed-oxide" PNZT. The phase transformation from ferroelectric to antiferroelectric occurs in unpoled ceramic with abrupt increase in volumetric strain of about 0.7 % when the maximum compressive stress, regardless of loading paths, equals the hydrostatic pressure at which the transformation otherwise takes place. The stress-volumetric strain relationship of the ceramic undergoing a phase transformation was analyzed quantitatively using a linear regression analysis. The pressure (PT1 H) required for the onset of phase transformation with respect to temperature is represented by the best-fit line, PT1 H (MPa) = 227 + 0.76 T (°C). We also confirmed that increasing shear stress lowers the mean stress and the volumetric strain required to trigger phase transformation. At the lower bound (-55°C) of the tested temperature range, the phase transformation is permanent and irreversible. However, at the upper bound (75°C), the phase transformation is completely reversible as the stress causing phase transformation is removed.