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Title: DISLOCATIONS IN MO5SIB2 T2 PHASE

Abstract

No abstract prepared.

Authors:
; ;
Publication Date:
Research Org.:
Los Alamos National Lab., Los Alamos, NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
777915
Report Number(s):
LA-UR-01-2032
TRN: US200201%%8
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Apr 2001
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DISLOCATIONS; MOLYBDENUM BORIDES; MOLYBDENUM SILICIDES; PHASE STUDIES

Citation Formats

R. FIELD, J. COOLEY, and ET AL. DISLOCATIONS IN MO5SIB2 T2 PHASE. United States: N. p., 2001. Web.
R. FIELD, J. COOLEY, & ET AL. DISLOCATIONS IN MO5SIB2 T2 PHASE. United States.
R. FIELD, J. COOLEY, and ET AL. Sun . "DISLOCATIONS IN MO5SIB2 T2 PHASE". United States. doi:. https://www.osti.gov/servlets/purl/777915.
@article{osti_777915,
title = {DISLOCATIONS IN MO5SIB2 T2 PHASE},
author = {R. FIELD and J. COOLEY and ET AL},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Apr 01 00:00:00 EST 2001},
month = {Sun Apr 01 00:00:00 EST 2001}
}

Conference:
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  • The microstructure evolution involving Mo-B-Si as-solidified alloys with compositions in the Mo solid-solution(ss) + T2 two-phase field has been examined following arc-melting and rapid solidification processing (RSP). Several solidification pathways in the arc-melted alloys have been identified. Compositional segregation during conventional solidification results in the formation of additional phases such as borides in the arc-melted alloys which require a prolonged solid-state annealing to obtain equilibrated two-phase microstructures. The RSP methods employed, splat-quenching (SQ) and powder drop tube processing (DTP), allow for significant microstructural modifications that facilitate the attainment of uniform dispersions of Mo(ss) phase in a T2 phase matrix.
  • Abstract not provided.
  • An iterative algorithm has been developed to correct for distortions in echo planar images caused by short T2 components. The values of T2 are initially estimated from a set of images produced by the inverse Fourier transform of the geometric mean of Hermitian symmetric points. The estimated T2 values are then used to compute k-space data, which, when compared with the true data, provide error data sets and corresponding images to iteratively refine the estimates of T2. Images corrected for T2 decay are thereby generated at specified echo times. Computer simulation studies of several phantoms show good convergence under amore » variety of conditions. This procedure should enable wider data acquisition windows to be utilized in echo planar or spin echo images, leading to better resolution or better signal to noise ratio.« less
  • In proton MR imaging the determination of fundamental MR constants such as spin lattice (T1) and spin spin (T2) relaxation times is essential for an understanding of image contrast and for insight into the question of optimal field vis a vis disease state. Multislice, multiecho imaging is attractive because imaging time per slice is reduced; however, slice selecting radiofrequency (RF) pulses may cause interference from adjacent slices to the slice being imaged. This interference will cause incorrect relaxation time measurements and ''false'' image contrast between tissues which could result in improper diagnosis. To observe the effect of slice separation onmore » T1 and T2 the authors imaged bottles of various concentrations of MnCl/sub 2/, with T1 values ranging from 215 to 1003 msec and T2 values from 39 to 240 msec. For T1 determinations two sets of multi-slice images (5 slices with nominal thickness of 1 cm) were taken both with an echo time (TE) of 30 msec and repetition times (TR) of 500 and 2000 msec. Slice separation was varied from 0 to 1 cm in 0.25 cm intervals. Reliable T1 values were obtained only when the slice separation was 0.75 or 1 cm. When slice separation was less than this, the TR500 images showed severe reversals in expected contrast when outside slices were compared with central slices. The effect of slice separation on T2 relaxation was investigated using a 5 slice multiecho technique (8 echoes per slice) with TR of 1400 msec and TE varying from 30 to 240 msec in intervals of 30 msec and nominal thickness set at 1 cm. Acquisitions were taken for slice separations from 0 to 1 cm and accurate T2 values for all 5 slices were only obtained when slice separation was 1 cm.« less