NASA Scientific and Technical Aerospace Reports

provide a more complete representation of shear effects that are no longer negligible even in thin piezoelectric beams. In
addition, the effects of varying piezoelectric properties through-the-thickness of the beam are shown to provide additional
benefits in minimizing the induced deformations and stresses.
Author
Piezoelectricity; Shape Control; Smart Materials; Functionally Gradient Materials; Actuators
20040111986 NASA Marshall Space Flight Center, Huntsville, AL, USA
Steps in Solution Growth: Revised Gibbs-Thomson Law, Turbulence and Morphological Stability
Chernov, A. A.; Rashkovich, L. N.; Vekilov, P. G.; [2004]; 1 pp.; In English; ICCG-14, 9-14 Aug. 2004, Grenoble, France;
No Copyright; Avail: Other Sources; Abstract Only
Two groups of new phenomena revealed by AFM and high resolution optical interferometry on crystal faces growing from
solutions will be discussed. 1. Spacing between strongly polygonized spiral steps with low less than 10(exp -2) kink density
on lysozyme and K- biphtalate do not follow the Burton-cabrera-Frank theory. The critical length of the yet immobile first
Short step segment adjacent to a pinning defect (dislocation, stacking fault) is many times longer than that following from the
step free energy. The low-kink density steps are typical of many growth conditions and materials, including low temperature
gas phase epitaxy and MBE. 2. The step bunching pattern on the approx. 1 cm long { 110) KDP face growing from the
turbulent solution flow (Re (triple bonds) 10(exp 4), solution flow rate approx. 1 m/s) suggests that the step bunch height does
not increase infinitely as the bunch path on the crystal face rises, as is usually observed on large KDP crystals. The mechanism
controlling the maximal bunch width and height is based on the drag of the solution depleted by the step bunch down thc
solution stream. It includes splitting, coagulation and interlacing of bunches
Derived from text
Crystal Growth; Lysozyme; Molecular Beam Epitaxy; Coagulation; Bunching
20040111988 NASA Marshall Space Flight Center, Huntsville, AL, USA
Detached Growth of Germanium by Directional Solidification
Palosz, W.; Volz, M.; Cobb, S.; Motakef, S.; Szofran, F. R.; [2004]; 1 pp.; In English; 14th International Conference on Crystal
Growth in Conjunction with the 12th International Conference on Vapor Growth and Epitaxy (XIV ICCG/XII ICVGE, 9-13
Aug. 2004, Grenoble, France; Original contains black and white illustrations; No Copyright; Avail: Other Sources; Abstract
Only
Detached crystal growth technique (dewetting) offers improvement in the quality of the grown crystals by preventing
sticking to the walls of the crucible and thus reducing the possibility of parasitic nucleation and formation of lattice defects
upon cooling. One of the factors relevant for the phenomena is the pressure differential across the meniscus at the crystal-melt
interface. We investigated this effect experimentally. The growth took place in closed ampoules under the pressure of an inert
gas (forming gas: 96% Ar + 4% H2). The pressure above the melt was adjustable and allowed for a control of the pressure
difference between the top and bottom menisci. The crystals were characterized, particularly by taking profilometer
measurements along the grown crystals surface. The effects of the experimental conditions on the detachment were compared
with those predicted based on the theory of Duffar et al.
Author
Germanium; Crystal Defects; Crystal Growth; Directional Solidification (Crystals)
20040120936 Westinghouse Savannah River Co., Aiken, SC, USA
Impact of Higher Waste Loading on Glass Properties: The Effects of Uranium and Thorium
Peelr, D. K.; Edwards, T. B.; 2003; In English
Report No.(s): DE2004-820001; WSRC-TR-2003-00386; No Copyright; Avail: National Technical Information Service
(NTIS)
In this study, glasses are designed or selected to assess the impacts of U3O8 and ThO2 on various glass properties of
interest. More specifically, glasses were fabricated in which Th replaced U (on a molar basis) to assess the impact of ThO2
on the durability response (as measured by the Product Consistency Test ) and viscosity. Based on the measured normalized
boron release values, the results indicated that the Th-enriched glasses were less durable than their U-based counterparts.
Although molar substitution of Th or U had a negative impact, all of the glasses were more durable than the Environmental
Assessment glass - the highest release being 7.39 g/L as compared to 16.695 g/L as reported for EA. With respect to model
predictions, THERMO(TM) predicts that a molar substitution of thorium for uranium should increase glass durability.
However, these data suggest that the signs and/or magnitudes of the Gi values associated with U3O8 and ThO2 are
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