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Sample records for crystal growth mechanisms

  1. Determining the Molecular Growth Mechanisms of Tetragonal Lysozyme Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    Studies of the growth of tetragonal lysozyme crystals employing atomic force microscopy (AFM) have shown the advantages of this technique in investigating the growth mechanisms of protein crystals [1]. The resolution of these studies was in the micron range, which revealed surface features such as the occurrence of dislocations and 2D nucleation islands, similar to those found in inorganic systems. They clearly showed that the crystals grew by these surface growth mechanisms. However, the studies also revealed some surprising features, such as bimolecular growth step heights and pronounced growth anisotropies on the (110) face, which could not be explained. In previous studies we employed Periodic Bond Chain (PBC) theory to tetragonal lysozyme crystal growth and found that the crystals were constructed by strongly bonded molecular chains forming helices about the 43 axes [2,3]. The helices were connected to each other with weaker bonds. The growth process was shown to proceed by the formation of these 43 helices, resulting in bimolecular growth steps on the (110) face. It was also shown to explain many other observations on tetragonal lysozyme crystal growth. Although PBC analysis is not a new technique [4], it has not been widely used as the mechanisms predicted from it could not be experimentally verified. In this study the growth process of these crystals was investigated, particularly for the (110) face, employing some newly developed high resolution AFM techniques. These techniques allowed individual lysozyme molecules on the crystal faces to be resolved and predictions from PBC analyses to be tested. The analyses had shown that of the two possible packing arrangements on (110) faces, only one would actually occur. Employing the first of the newly developed techniques, these faces were scanned by high resolution AFM. The resulting images were then compared with the theoretically constructed images for the two possible packing arrangements on the (110) face. The theoretical images were constructed by convolution of the crystal surface shape obtained from crystallographic data with the AFM tip shape. The comparison confirmed the prediction that the molecular packing arrangement of these faces corresponded to that for complete 43 helices. The second AFM technique that was developed was used to follow the growth process by measuring the dimensions of individual growth units on the (110) face. Linescans across a growth step, performed near the saturation limit of the crystals, allowed the growth unit dimensions to be measured. These measurements showed that growth on the (110) face proceeded by the formation of new 43 helices from the addition of at least tetramer units in the [110] direction. In the [001] direction growth proceeded by the addition of various aggregate units corresponding to the 4(sub 3) helices.

  2. Fluid mechanics in crystal growth - The 1982 Freeman scholar lecture

    NASA Technical Reports Server (NTRS)

    Ostrach, S.

    1983-01-01

    An attempt is made to unify the current state of knowledge in crystal growth techniques and fluid mechanics. After identifying important fluid dynamic problems for such representative crystal growth processes as closed tube vapor transport, open reactor vapor deposition, and the Czochralski and floating zone melt growth techniques, research results obtained to date are presented. It is noted that the major effort to date has been directed to the description of the nature and extent of bulk transport under realistic conditions, where bulk flow determines the heat and solute transport which strongly influence the temperature and concentration fields in the vicinity of the growth interface. Proper treatment of near field, or interface, problems cannot be given until the far field, or global flow, involved in a given crystal growth technique has been adequately described.

  3. The mechanism of growth of quartz crystals into fused silica

    NASA Technical Reports Server (NTRS)

    Fratello, V. J.; Hays, J. F.; Spaepen, F.; Turnbull, D.

    1980-01-01

    It is proposed that the growth of quartz crystals into fused silica is effected by a mechanism involving the breaking of an Si-O bond and its association with an OH group, followed by cooperative motion of the nonbridging oxygen and the hydroxyl group which results in the crystallization of a row of several molecules along a crystalline-amorphous interfacial ledge. This mechanism explains, at least qualitatively, all the results of the earlier experimental study of the dependence of quartz crystal growth upon applied pressure: large negative activation volume; single activation enthalpy below Si-O bond energy; growth velocity constant in time, proportional to the hydroxyl and chlorine content, decreasing with increasing degree of reduction, and enhanced by nonhydrostatic stresses; lower pre-exponential for the synthetic than for the natural silica.

  4. Crystal growth mechanisms of the (0 1 0) face of ?-lactose monohydrate crystals

    NASA Astrophysics Data System (ADS)

    Dincer, T. D.; Ogden, M. I.; Parkinson, G. M.

    2009-04-01

    The growth rates of the (0 1 0) face of ?-lactose monohydrate crystals were measured at 30, 40 and 50 C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The mechanisms of growth were investigated. Spiral growth was found to be the mechanism of growth up to a critical relative supersaturation ( s-1) crit=1.9 at 30 C. Above the critical relative supersaturation, the crystal growth mechanisms were predicted to change. All growth models fit equally well to the growth rates. No two-dimensional nucleation was observed above critical supersaturation by AFM. On the other hand increased step height and roughness on the edges of steps were observed. It was concluded that the growth mechanism of the (0 1 0) face of ?-lactose monohydrate crystal is spiral growth. A parabolic relationship was obtained below critical supersaturation followed by a linear relationship with relative supersaturation.

  5. An assessment of calcite crystal growth mechanisms based on crystal size distributions

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.; Hoch, A.R.; Reddy, M.M.

    2000-01-01

    Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth. All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial ? = 20, where ? = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial ? = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (? >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances. The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism was established and maintained during the constant-composition experiments. CSDs having shapes intermediate between lognormal and Ostwald also were generated by varying the initial levels of supersaturation (initial ? = 28.2 to 69.2) in rapidly mixed solutions. Lognormal CSDs were observed for natural calcite crystals that are found in septarian concretions occurring in southeastern Colorado. Based on the model described above, these CSDs indicate initial growth by surface control, followed by supply-controlled growth. Thus, CSDs may be used to deduce crystal growth mechanisms from which geologic conditions early in the growth history of a mineral can be inferred. Conversely, CSD shape can be predicted during industrial crystallization by applying the appropriate conditions for a particular growth mechanism.

  6. Mechanisms of protein and virus crystal growth: An atomic force microscopy study of Canavalin crystallization

    SciTech Connect

    Land, T.A.; De Yoreo, J.J.; Malkin, A.J.; Kutznesov, Y.G.; McPherson, A.

    1995-03-10

    The evolution of surface morphology and step dynamics during growth of single crystals of the protein Canavalin and of the cubic satellite tobacco mosaic virus crystals (STMV) have been investigated by in situ atomic force microscopy. These two crystals were observed to grow by very different mechanisms. Growth of Canavalin occurs on complex vicinal hillocks formed by multiple, independently acting screw dislocations. Small cluster were observed on the terraces. STMV on the other hand, was observed to grow by 2D nucleation of islands. No dislocations were found on the crystal. The results are used to determine the growth mechanisms and estimate fundamental materials parameters. The images also illustrate the important mechanism of defect incorporation and provide insight to the processes that limit the growth rate and uniformity of these crystals.

  7. Molecular View of Protein Crystal Growth: Molecular Interactions, Surface Reconstruction and Growth Mechanism

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Li, Huayu; Konnert, John H.; Pusey, Marc L.

    2000-01-01

    Studies of the growth and molecular packing of tetragonal lysozyme crystals suggest that there is an underlying molecular growth mechanism, in addition to the classical one involving screw dislocation/2D) nucleation growth. These crystals are constructed by strongly bonded molecular chains forming helices about the 43 axes. The helices are connected to each other by weaker bonds. Crystal growth proceeds by the formation of these 4(sub 3) helices, which would explain some unexpected observations by earlier investigators, such as bimolecular growth steps on the (110) face. Another consequence of these molecular considerations is that only one of two possible packing arrangements could occur on the crystal faces and that their growth unit was at least a tetramer corresponding to the 4(sub 3) helix. Two new high resolution atomic force microscopy (AFM) techniques were developed to directly confirm these predictions on tetragonal lysozyme crystals. Most earlier investigations of protein crystal growth with AFM were in the low resolution mode which is adequate to investigate the classical growth mechanisms, but cannot resolve molecular features and mechanisms. Employing the first of the newly developed techniques, high resolution AFM images of the (110) face were compared with the theoretically constructed images for the two possible packing arrangements on this face. The prediction that the molecular packing arrangement of these faces corresponded to that for complete 4(sub 3) helices was confirmed in this manner. This investigation also showed the occurrence of surface reconstruction on protein crystals. The molecules on the surface of the (110) face were found to pack closer along the 4(sub 3) axes than those in the interior. The second new AFM technique was used to follow the growth process by measuring the dimensions of individual growth units on the (110) face. Linescans across a growth step, performed near the saturation limit of the crystals, allowed the growth unit dimensions to be measured as they were being incorporated into the crystal. These measurements showed that growth on the (110) face proceeded by the formation of new 4(sub 3) helices from the addition of many growth units of at least tetramer size. This is the first time that a time-resolved AFM technique has been used to observe individual molecular events during crystal growth.

  8. Crystal Growth and Fluid Mechanics Problems in Directional Solidification

    NASA Technical Reports Server (NTRS)

    Tanveer, S.; Baker, G. R.; Foster, M. R.

    1996-01-01

    An investigation of a more complete theoretical understanding of convection effects in a vertical Bridgman apparatus is described. The aim is to develop a clear understanding of scalings of various features of dendritic crystal growth in the case that both the surface energy and undercooling are small.

  9. Growth of (101) Faces of Tetragonal Lysozyme Crystals: Determination of the Growth Mechanism

    NASA Technical Reports Server (NTRS)

    Li, Meirong; Nadarajah, Arunan; Pusey, Marc L.

    1998-01-01

    Measurements of the macroscopic growth rates of the (101) face of tetragonal lysozyme crystals indicate an unusual dependence on the supersaturation (Forsythe, Nadarajah & Pusey, 1998), similar to that observed for the (110) face. As done before for the (110) face, in this study the surface packing arrangement for the (101) face was constructed, based on earlier microscopic observations and theoretical analysis of the internal molecular packing. This allowed the minimum growth unit for this face to be identified as a tetramer corresponding to a single turn of helices centered about the 4(sub 3) axes, and the minimum growth step to be of unimolecular height. A macroscopic mathematical model for the growth of the (101) face was developed, based on the formation of aggregate growth units in solution and the addition of a unit to the crystal face by dislocation and two-dimensional nucleation mechanisms. The calculations showed that the best fits were obtained for tetramer or octamer growth units in this model, indicating that average size of the growth unit participating in the growth process was between these two sizes.

  10. VO{sub 2} (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms

    SciTech Connect

    Rao Popuri, Srinivasa; Artemenko, Alla; Labrugere, Christine; Miclau, Marinela; Villesuzanne, Antoine; Pollet, Michal

    2014-05-01

    Well crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal reaction in the presence of V{sub 2}O{sub 5} and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO{sub 2} (A) micro rods. The structural and electronic transitions in VO{sub 2} (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversible intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO{sub 2} (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO{sub 2} (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO{sub 2} (M1) are described. - Graphical abstract: Using a single step and template free hydrothermal synthesis, well crystallized VO{sub 2} (A) microrods were prepared and the P4/ncc space group was assigned to the room temperature crystal structure. Reversible and irreversible phase transitions among different VO{sub 2} polymorphs were identified and their progressive nature was highlighted. Attempts to increase the microrods size, involving layer by layer formation mechanisms, are presented. - Highlights: Highly crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal process. The P4/ncc space group was determined for VO{sub 2} (A) at room temperature. The electronic structure and progressive nature of the structural phase transition were investigated. A weak coupling between structural and electronic phase transitions was identified. Different crystallite morphologies were discussed in relation with growth mechanisms.

  11. Crystal growth and fluid mechanics problems in directional solidification

    NASA Technical Reports Server (NTRS)

    Tanveer, Saleh; Baker, Gregory R.; Foster, Michael R.

    1994-01-01

    Broadly speaking, our efforts have been concentrated in two aspects of directional solidification: (A) a more complete theoretical understanding of convection effects in a Bridgman apparatus; and (B) a clear understanding of scalings of various features of dendritic crystal growth in the sensitive limit of small capillary effects. For studies that fall within class A, the principal objectives are as follows: (A1) Derive analytical formulas for segregation, interfacial shape and fluid velocities in mathematically amenable asymptotic limits. (A2) Numerically verify and extend asymptotic results to other ranges of parameter space with a view to a broader physical understanding of the general trends. With respect to studies that fall within class B, the principal objectives include answering the following questions about dendritic crystal growth: (B1) Are there unsteady dendrite solutions in 2-D to the completely nonlinear time evolving equations in the small surface tension limit with only a locally steady tip region with well defined tip radius and velocity? Is anisotropy in surface tension necessary for the existence of such solutions as it is for a true steady state needle crystal? How does the size of such a local region depend on capillary effects, anisotropy and undercooling? (B2) How do the different control parameters affect the nonlinear amplification of tip noise and dendritic side branch coarsening?

  12. Mechanisms of protein and virus crystal growth: An atomic force microscopy study of canavalin and STMV crystallization

    SciTech Connect

    Land, T.A.; De Yoreo, J.J.; Malkin, A.J.; Kutznesov, Yu.G.; McPherson, A.

    1996-05-01

    The evolution of surface morphology and step dynamics during growth of rhombohedral crystals of the protein canavalin and crystals of the cubic satellite tobacco mosaic virus (STMV) have been investigated for the first time by in situ atomic force microscopy. These two crystals were observed to grow by very different mechanisms. Growth of canavalin occurs on complex vicinal hillocks formed by multiple, independently acting screw dislocations. Small clusters were observed on the terraces. STMV on the other hand, was observed to grow by 2D nucleation of islands. No dislocations were found on the crystal. The results are used to determine the growth mechanisms and estimate the fundamental materials parameters. The images also illustrate the important mechanism of defect incorporation and provide insight to the processes that limit the growth rate and uniformity of these crystals.

  13. Deducing growth mechanisms for minerals from the shapes of crystal size distributions

    USGS Publications Warehouse

    Eberl, D.D.; Drits, V.A.; Srodon, J.

    1998-01-01

    Crystal size distributions (CSDs) of natural and synthetic samples are observed to have several distinct and different shapes. We have simulated these CSDs using three simple equations: the Law of Proportionate Effect (LPE), a mass balance equation, and equations for Ostwald ripening. The following crystal growth mechanisms are simulated using these equations and their modifications: (1) continuous nucleation and growth in an open system, during which crystals nucleate at either a constant, decaying, or accelerating nucleation rate, and then grow according to the LPE; (2) surface-controlled growth in an open system, during which crystals grow with an essentially unlimited supply of nutrients according to the LPE; (3) supply-controlled growth in an open system, during which crystals grow with a specified, limited supply of nutrients according to the LPE; (4) supply- or surface-controlled Ostwald ripening in a closed system, during which the relative rate of crystal dissolution and growth is controlled by differences in specific surface area and by diffusion rate; and (5) supply-controlled random ripening in a closed system, during which the rate of crystal dissolution and growth is random with respect to specific surface area. Each of these mechanisms affects the shapes of CSDs. For example, mechanism (1) above with a constant nucleation rate yields asymptotically-shaped CSDs for which the variance of the natural logarithms of the crystal sizes (??2) increases exponentially with the mean of the natural logarithms of the sizes (??). Mechanism (2) yields lognormally-shaped CSDs, for which ??2 increases linearly with ??, whereas mechanisms (3) and (5) do not change the shapes of CSDs, with ??2 remaining constant with increasing ??. During supply-controlled Ostwald ripening (4), initial lognormally-shaped CSDs become more symmetric, with ??2 decreasing with increasing ??. Thus, crystal growth mechanisms often can be deduced by noting trends in ?? versus ??2 of CSDs for a series of related samples.

  14. Crystal growth mechanisms in miarolitic cavities in the Lake George ring complex and vicinity, Colorado

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.

    1999-01-01

    The Crystal Peak area of the Pikes Peak batholith, near Lake George in central Colorado, is world-renowned for its crystals of amazonite (the blue-green variety of microcline) and smoky quartz. Such crystals, collected from individual miarolitic pegmatites, have a remakably small variation in crystal size within each pegmatite, and the shapes of plots of their crystal size distributions (CSDs) are invariably lognormal or close to lognormal in all cases. These observations are explained by a crystal growth mechanism that was governed initially by surface-controlled kinetics, during which crystals tended to grow larger in proportion to their size, thereby establishing lognormal CSDs. Surface-controlled growth was followed by longer periods of supply controlled growth, during which growth rate was predominantly size-independent, consequently preserving the lognormal shapes of the CSDs and the small size variation. The change from surface- to supply controlled growth kinetics may have resulted from an increasing demand for nutrients that exceeded diffusion limitations of the system. The proposed model for crystal growth in this locality appears to be common in the geologic record, and can be used with other information, such as isotopic data, to deduce physico-chemical conditions during crystal formation.

  15. Investigation of virus crystal growth mechanisms by {ital in} {ital situ} atomic force microscopy

    SciTech Connect

    Malkin, A.J.; Land, T.A.; Kuznetsov, Y.G.; McPherson, A.; DeYoreo, J.J.

    1995-10-02

    For the first time, virus crystal growth dynamics and morphology have been investigated in real time on the nanometer scale. Individual monomers on the (111) face of cubic satellite tobacco mosaic virus (STMV) crystals were resolved and used to determine crystal packing. Growth of STMV proceeded by two- and three-dimensional nucleation to formed ``stacks`` of islands. No dislocations were observed. Small islands provided an estimate of critical radius size and the free energy of the step edge, {alpha}. Step advancement rates were used to determinate the kinetic coefficient {beta}. Images illustrate mechanisms for defect incorporation and suggest factors that limit growth rate and uniformity.

  16. Crystal growth and mechanical hardness of In2Se2.7Sb0.3 single crystal

    NASA Astrophysics Data System (ADS)

    Patel, Piyush; Vyas, S. M.; Patel, Vimal; Pavagadhi, Himanshu; Solanki, Mitesh; Jani, Maunik P.

    2015-08-01

    The III-VI compound semiconductors is important for the fabrication of ionizing radiation detectors, solid-state electrodes, and photosensitive heterostructures, solar cell and ionic batteries. In this paper, In2Se2.7 Sb0.3 single crystals were grown by the Bridgman method with temperature gradient of 60 C/cm and the growth velocity 0.5cm/hr. The as-grown crystals were examined under the optical microscope for surface study, a various growth features observed on top free surface of the single crystal which is predominant of layers growth mechanism. The lattice parameters of as-grown crystal was determined by the XRD analysis. A Vickers' projection microscope were used for the study of microhardness on the as-cleaved, cold-worked and annealed samples of the crystals, the results were discussed, and reported in detail.

  17. Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal

    NASA Astrophysics Data System (ADS)

    Sudhahar, S.; Krishna Kumar, M.; Sornamurthy, B. M.; Mohan Kumar, R.

    2014-01-01

    Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications.

  18. Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal.

    PubMed

    Sudhahar, S; Krishna Kumar, M; Sornamurthy, B M; Mohan Kumar, R

    2014-01-24

    Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications. PMID:24184578

  19. TEM investigation of the microporous compound VSB-1: Building units and crystal growth mechanisms

    SciTech Connect

    Colmont, Marie Terasaki, Osamu

    2007-03-15

    Surface fine structure and structural defects in the open framework material VSB-1 have been investigated by electron microscopy. Crystal growth phenomena are proposed by a building unit model: (i) a unit is formed by two building units; (ii) they are linked to form first channels; and (iii) the whole network is grown via a layer-by-layer growth mechanism. A planar defect was observed in high-resolution transmission electron microscope (HRTEM) image taken with the [0001] incidence, and diffuse streaks related to the presence of defects were observed in a series of electron diffraction (ED) patterns. The microstructure model derived from the defect structure gives information on crystal growth. These defects highlight an open site that could be the pillar of a new crystal growth process. The study of defects and crystal growth is important in understanding physical properties such as catalytic or magnetic properties, and in synthesising a new open framework structure. - Graphical abstract: TEM investigation of the microporous compound VSB-1 evidenced defects and information about building units and crystal growth. As usually observed for microporous materials, the crystal growth via a layer by layer mechanism.

  20. Ex situ atomic force microscopy studies of growth mechanisms of cadmium mercury thiocyanate crystals

    NASA Astrophysics Data System (ADS)

    Jiang, X. N.; Xu, D.; Sun, D. L.; Yuan, D. R.; Lu, M. K.; Guo, S. Y.; Zhang, G. H.

    2002-01-01

    Ex situ atomic force microscopy (AFM) has been used to investigate the growth mechanisms of the cadmium mercury thiocyanate, CdHg(SCN) 4 (CMTC), crystal. Simultaneous spiral dislocation controlled growth and two-dimensional (2D) nucleation growth have been observed on {1 1 0} faces of the CMTC crystal grown at 30C at supersaturations ?=0.24 and 0.01. Circular or irregular 2D nuclei have been observed at the large step terraces generated by the spiral dislocation sources. The combination of spiral controlled growth and 2D nucleation growth expedites the growth rate of the large steps leading to the pile-up of elementary steps. When the CMTC crystal is grown at 30C and supersaturation ?=0.01, a multiple growth mechanism is found. Two-dimensional nuclei have been observed to coexist with dislocation spiral hillocks as well as multilayer stacks. The appearance of 2D nuclei as well as several 3D nuclei is assumed to result from the direct association of some solute aggregations in the growth solution. It is notable that the surface morphology of the multilayer stacks is greatly changed by multiple scanning. This is attributed to restructuring of the crystal surface due to an internal energy increase caused by multiple scanning.

  1. Structural Correspondence of the Oriented Attachment Growth Mechanism of Crystals of the Pharmaceutical Dirithromycin.

    PubMed

    Liang, Zuozhong; Wang, Yuan; Wang, Wei; Han, Xianglong; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong

    2015-12-29

    The oriented attachment (OA) mechanism is promising for designing novel nanomaterials, yet an intensive understanding of the relationship between the crystal structure and attachment orientation is still lacking. In this work, we report layered hexagonal crystals of the pharmaceutical dirithromycin (DIR) containing multiple layers fabricated via a solvothermal method for a certain period of time at 40 C. These elongated hexagonal crystals experience an OA that is preferentially on the face (001) of the initial crystals to assemble the final crystals into layered stacks. Through agreement with molecular modeling calculations, we predicted the final crystal growth morphology and confirmed the favored attachment surface based on the energy change ?E following an OA event. These simulation results at the molecular level yielded good agreement with the crystal growth experiments. This study demonstrates the critical importance of combining experiments with a computational approach to understand the intrinsic molecular details of the OA growth mechanism of other compounds and to design nanomaterials with a desirable morphology and physical and chemical properties. PMID:26632998

  2. Hydrothermal crystallization of barium titanate: Mechanisms of nucleation and growth

    NASA Astrophysics Data System (ADS)

    Chun, Chang-Min

    Barium titanate is synthesized under hydrothermal conditions by the reaction of a variety of titania precursors with aqueous solutions of Ba(OH)sb2 at 80spC. Particles processed at relatively low concentrations of Ba(OH)sb2 are micro-sized and highly aggregated, but increasing concentrations cause the particle size to decrease, resulting in nanometer-sized and fairly monodispersed particles. The change in particle size and morphology at various Ba(OH)sb2 concentrations is controlled by the dissolution of titania and precipitation of BaTiOsb3. In order to explain the origin of "raspberry-like" BaTiOsb3 particles and the generation of hierarchically ordered BaTiOsb3 aggregate comprised of primary, crystalline particles, which exhibit an unusually high degree of crystallographic alignment, the role of colloidal stability and therefore controlled aggregation of precipitated primary particles is taken into account. Formation of SrTiOsb3 on BaTiOsb3 particles reveal that two different morphologies for the growing SrTiOsb3 exists and that the form taken by SrTiOsb3 depends on the degree of supersaturation. In concentrated solutions, homogeneous nucleation and aggregation growth occur. In dilute solutions, heterogeneous nucleation and continuous growth of SrTiOsb3 promote epitaxial growth. BaTiOsb3 particles prepared by the alkoxide (Ti(OCsb3Hsb7)sb4) -hydroxide (Ba(OH)sb2) route under hydrothermal conditions show that secondary processed such as aggregation and recrystallization are important to control the particle size and morphology. Particle clustering, and rearrangement of nanometer-sized BaTiOsb3 particles, and particulate uniformity can then be explained in terms of solution reactions and colloidal behavior.

  3. Modification of crystal growth mechanism of yttrium oxalate in metastable solution

    NASA Astrophysics Data System (ADS)

    Sung, Min-Hyun; Kim, Joon-Soo; Kim, Woon-Soo; Hirasawa, Izumi; Kim, Woo-Sik

    2002-02-01

    In the seeded crystallization of yttrium oxalate from a metastable supersaturated solution, the growth mechanism was observed to become modified by variations in agitation and additive concentration. From the desupersaturation curve, the crystal growth rate was estimated and described using a power law of supersaturation ( RT= Kg? Cp). Without an additive in the metastable solution, the overall growth rate coefficient, Kg, increased with an increase in the agitation speed while the growth rate order, p, was almost independent of the agitation speed. When the additive sodium tripolyphosphate was used to inhibit crystal growth, the desupersaturation in the solution was substantially retarded and the growth rate order varied up to about 2.5 with an increase in the additive concentration. Using a two-step growth model, the kinetic parameter dependencies of the crystal growth of yttrium oxalate, such as the mass transfer coefficient, surface integration order, and surface integration coefficient, were estimated in relation to the agitation speed and additive concentration. The mass transfer coefficient increased with an increase in the agitation, whereas the surface integration coefficient was independent of the agitation speed. However, as the additive concentration in the solution increased, the surface integration coefficient was reduced while the mass transfer coefficient remained almost invariant. The change in the rate-determining step by the additive was examined using an effectiveness factor. It was shown that the effect of the additive on the surface integration followed a Langmuir type isotherm.

  4. Mechanisms of function by AF(G)Ps in ice crystal growth prevention, modification and recrystallization

    NASA Astrophysics Data System (ADS)

    Yeh, Yin

    2009-03-01

    Antifreeze activity by proteins and glycoproteins is a form of biomineralization process. Contrasting to covalent or ionic crystals, these hydrogen-bonded molecular crystals (ice) have much weaker crystalline bonding energy profiles. Thus, when interacting with proteins that are equally easy to change in conformation by variations of the hydrophilic/hydrophobic environment, some unique findings are suggestive that local conditions play significant roles in the activity level of these proteins or glycoproteins as they affect ice crystal growth, modification and recrystallization. We review some of these experiments and provide ideas for their functioning mechanisms.

  5. Kinetics and mechanisms of crystal growth inhibition of indomethacin by model precipitation inhibitors

    NASA Astrophysics Data System (ADS)

    Patel, Dhaval

    Supersaturating Drug Delivery Systems (SDDS) could enhance oral bioavailability of poorly water soluble drugs (PWSD). Precipitation inhibitors (PIs) in SDDS could maintain supersaturation by inhibiting nucleation, crystal growth, or both. The mechanisms by which these effects are realized are generally unknown. The goal of this dissertation was to explore the mechanisms underpinning the effects of model PIs including hydroxypropyl beta-cyclodextrins (HP-beta-CD), hydroxypropyl methylcellulose (HPMC), and polyvinylpyrrolidone (PVP) on the crystal growth of indomethacin, a model PWSD. At high degrees of supersaturation (S), the crystal growth kinetics of indomethacin was bulk diffusion-controlled, which was attributed to a high energy form deposited on the seed crystals. At lower S, indomethacin growth kinetics was surface integration-controlled. The effect of HP-beta-CD at high S was successfully modeled using the reactive diffusion layer theory. The superior effects of PVP and HPMC as compared to HP-beta-CD at high S were attributed to a change in the rate limiting step from bulk diffusion to surface integration largely due to prevention of the high energy form formation. The effects of PIs at low S were attributed to significant retardation of the surface integration rate, a phenomenon that may reflect the adsorption of PIs onto the growing surface. PVP was selected to further understand the relationship between adsorption and crystal growth inhibition. The Langmuir adsorption isotherm model fit the adsorption isotherms of PVP and N-vinylpyrrolidone well. The affinity and extent of adsorption of PVP were significantly higher than those of N-vinylpyrrolidone, which was attributed to cooperative interactions between PVP and indomethacin. The extent of PVP adsorption on a weight-basis was greater for higher molecular weight PVP but less on a molar-basis indicating an increased percentage of loops and tails for higher molecular weight PVPs. PVP significantly inhibited indomethacin crystal growth at high S as compared to N-vinylpyrrolidone, which was attributed to a change in the growth mechanism resulting in a change in the rate limiting step from bulk diffusion to surface integration. Higher molecular weight PVPs were better inhibitors than lower molecular weight PVPs, which was attributed to a greater crystal growth barrier provided by a thicker adsorption layer.

  6. Advanced Crystal Growth Technology

    SciTech Connect

    Land, T A; Hawley-Fedder, R A

    2005-03-01

    Although the fundamental mechanism of crystal growth has received and continues to receive deserved attention as a research activity, similar research efforts addressing the need for advanced materials and processing technology required to grow future high quality crystals has been sorely lacking. The purpose of this research effort is to develop advanced rapid growth processing technologies and materials suitable for providing the quality of products needed for advanced laser and photonics applications. In particular we are interested in developing a methodology for growing high quality KDP crystals based on an understanding of the fundamental mechanisms affecting growth. One problem in particular is the issue of control of impurities during the growth process. Many unwanted impurities are derived from the growth system containers and can adversely affect the optical quality and aspect ratio (shape) of the crystals. Previous studies have shown that even trace concentrations ({approx}10{sup -9} M) of impurities affect growth and even 'insignificant' species can have a large impact. It is also known that impurities affect the two growth faces of KDP very differently. Traces of trivalent metal impurities such as Fe{sup 3+}, Cr{sup 3+}, and Al{sup 3+} in solution are known to inhibit growth of the prismatic {l_brace}100{r_brace} faces of KDP while having little effect on the growth of the pyramidal {l_brace}101{r_brace} faces. This differentiation opens the possibility of intentionally adding select ions to control the aspect ratio of the crystal to obtain a more advantageous shape. This document summarizes our research efforts to improve KDP crystal growth. The first step was to control unwanted impurity addition from the growth vessel by developing an FEP liner to act as a barrier to the glass container. The other focus to develop an understanding of select impurities on growth rates in order to be able to use them to control the habit or shape of the crystal for yield improvement.

  7. Mechanism of abnormally slow crystal growth of CuZr alloy

    NASA Astrophysics Data System (ADS)

    Yan, X. Q.; L, Y. J.

    2015-10-01

    Crystal growth of the glass-forming CuZr alloy is shown to be abnormally slow, which suggests a new method to identify the good glass-forming alloys. The crystal growth of elemental Cu, Pd and binary NiAl, CuZr alloys is systematically studied with the aid of molecular dynamics simulations. The temperature dependence of the growth velocity indicates the different growth mechanisms between the elemental and the alloy systems. The high-speed growth featuring the elemental metals is dominated by the non-activated collision between liquid-like atoms and interface, and the low-speed growth for NiAl and CuZr is determined by the diffusion across the interface. We find that, in contrast to Cu, Pd, and NiAl, a strong stress layering arisen from the density and the local order layering forms in front of the liquid-crystal interface of CuZr alloy, which causes a slow diffusion zone. The formation of the slow diffusion zone suppresses the interface moving, resulting in much small growth velocity of CuZr alloy. We provide a direct evidence of this explanation by applying the compressive stress normal to the interface. The compression is shown to boost the stress layering in CuZr significantly, correspondingly enhancing the slow diffusion zone, and eventually slowing down the crystal growth of CuZr alloy immediately. In contrast, the growth of Cu, Pd, and NiAl is increased by the compression because the low diffusion zones in them are never well developed.

  8. User's Guide to Galoper: A Program for Simulating the Shapes of Crystal Size Distributions from Growth Mechanisms - and Associated Programs

    USGS Publications Warehouse

    Eberl, Dennis D.; Drits, V.A.; Srodon, J.

    2000-01-01

    GALOPER is a computer program that simulates the shapes of crystal size distributions (CSDs) from crystal growth mechanisms. This manual describes how to use the program. The theory for the program's operation has been described previously (Eberl, Drits, and Srodon, 1998). CSDs that can be simulated using GALOPER include those that result from growth mechanisms operating in the open system, such as constant-rate nucleation and growth, nucleation with a decaying nucleation rate and growth, surface-controlled growth, supply-controlled growth, and constant-rate and random growth; and those that result from mechanisms operating in the closed system such as Ostwald ripening, random ripening, and crystal coalescence. In addition, CSDs for two types weathering reactions can be simulated. The operation of associated programs also is described, including two statistical programs used for comparing calculated with measured CSDs, a program used for calculating lognormal CSDs, and a program for arranging measured crystal sizes into size groupings (bins).

  9. New AFM Techniques for Investigating Molecular Growth Mechanisms of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    Atomic Force Microscopy (AFM) has emerged as a powerful technique for investigating protein crystal growth. Earlier AFM studies were among the first to demonstrate that these crystals grew by dislocation and 2D nucleation growth mechanisms [1]. These investigations were restricted to the micron range where only surface features, such as dislocation hillocks and 2D islands are visible. Most AFM instruments can scan at higher resolutions and have the potential to resolve individual protein molecules at nanometer ranges. Such scans are essential for determining the molecular packing arrangements on crystal faces and for probing the growth process at the molecular level. However, at this resolution the AFM tip influences the image produced, with the resulting image being a convolution of the tip shape and the surface morphology [2]. In most studies this problem is resolved by deconvoluting the image to obtain the true surface morphology. Although deconvolution routines work reasonably well for simple one- dimensional shapes, for complex surfaces this approach does not produce accurate results. In this study we devised a new approach which takes advantage of the precise molecular order of crystal surfaces, combined with the knowledge of individual molecular shapes from the crystallographic data of the protein and the AFM tip shape. This information is used to construct expected theoretical AFM images by convoluting the tip shape with the constructed crystal surface shape for a given surface packing arrangement. By comparing the images from actual AFM scans with the constructed ones for different possible surface packing arrangements, the correct packing arrangement can be conclusively determined. This approach was used in this study to determine the correct one from two possible packing arrangements on (I 10) faces of tetragonal lysozyme crystals. Another novel AFM technique was also devised to measure the dimension of individual growth units of the crystal faces. Measuring these units was not attempted before and most studies have assumed that the growth unit consisted of individual protein molecules. The linescan mode of AFM instruments allows the crystal surface to be scanned along a single line. By scanning across a growth step an image showing the motion of the step is obtained. Normally such an image shows a straight line for continuous and constant step velocity. In this study by increasing the scan rate and by decreasing the step velocity (by decreasing the supersaturation), we were able to capture images of individual growth events, shown by jump discontinuities in the step line. By suitable integration of the image the growth unit dimension in the scanned direction can be obtained. Since multiple units can be involved in the growth process it is necessary to collect a statistically relevant sample before drawing conclusions about the growth mechanism. This technique was successfully employed to obtain the dimensions of growth units for the (110) face, showing that they consisted of various aggregates corresponding to the 43 helices in the crystal structure.

  10. Total immersion crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (inventor)

    1987-01-01

    Crystals of wide band gap materials are produced by positioning a holder receiving a seed crystal at the interface between a body of molten wide band gap material and an overlying layer of temperature-controlled, encapsulating liquid. The temperature of the layer decreases from the crystallization temperature of the crystal at the interface with the melt to a substantially lower temperature at which formation of crystal defects does not occur, suitably a temperature of 200 to 600 C. After initiation of crystal growth, the leading edge of the crystal is pulled through the layer until the leading edge of the crystal enters the ambient gas headspace which may also be temperature controlled. The length of the column of liquid encapsulant may exceed the length of the crystal such that the leading edge and trailing edge of the crystal are both simultaneously with the column of the crystal. The crystal can be pulled vertically by means of a pulling-rotation assembly or horizontally by means of a low-angle withdrawal mechanism.

  11. Growth, Mechanical, Thermal and Spectral Properties of Cr3+?MgMoO4 Crystal

    PubMed Central

    Li, Lingyun; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

    2012-01-01

    This paper reports the growth, mechanical, thermal and spectral properties of Cr3+?MgMoO4 crystals. The Cr3+?MgMoO4 crystals with dimensions up to 30 mm18 mm14 mm were obtained by TSSG method. The absorption cross-sections of 4A2?4T1 and 4A2?4T2 transitions are 12.9410?20 cm2 at 493 nm and 7.8910?20 cm2 at 705 nm for E//Ng, respectively. The Cr3+?MgMoO4 crystal shows broad band emission extending from 750 nm to 1300 nm with peak at about 705 nm. The emission cross-section with FWHM of 188 nm is 119.8810?20 cm2 at 963 nm for E//Ng. The investigated results showed that the Cr3+?MgMoO4 crystal may be regarded as a potential tunable laser gain medium. PMID:22291935

  12. Growth, mechanical, thermal and spectral properties of Cr3+:MgMoO4 crystal.

    PubMed

    Li, Lingyun; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

    2012-01-01

    This paper reports the growth, mechanical, thermal and spectral properties of Cr(3+):MgMoO(4) crystals. The Cr(3+):MgMoO(4) crystals with dimensions up to 30 mm18 mm14 mm were obtained by TSSG method. The absorption cross-sections of (4)A(2)?(4)T(1) and (4)A(2)?(4)T(2) transitions are 12.9410(-20) cm(2) at 493 nm and 7.8910(-20) cm(2) at 705 nm for E//N(g), respectively. The Cr(3+):MgMoO(4) crystal shows broad band emission extending from 750 nm to 1300 nm with peak at about 705 nm. The emission cross-section with FWHM of 188 nm is 119.8810(-20) cm(2) at 963 nm for E//N(g). The investigated results showed that the Cr(3+):MgMoO(4) crystal may be regarded as a potential tunable laser gain medium. PMID:22291935

  13. Supra- and nanocrystallinity: specific properties related to crystal growth mechanisms and nanocrystallinity.

    PubMed

    Pileni, M P

    2012-11-20

    The natural arrangement of atoms or nanocrystals either in well-defined assemblies or in a disordered fashion induces changes in their physical properties. For example, diamond and graphite show marked differences in their physical properties though both are composed of carbon atoms. Natural colloidal crystals have existed on earth for billions of years. Very interestingly, these colloidal crystals are made of a fixed number of polyhedral magnetite particles uniform in size. Hence, opals formed of assemblies of silicate particles in the micrometer size range exhibit interesting intrinsic optical properties. A colorless opal is composed of disordered particles, but changes in size segregation within the self-ordered silica particles can lead to distinct color changes and patterning. In this Account, we rationalize two simultaneous supracrystal growth processes that occur under saturated conditions, which form both well-defined 3D superlattices at the air-liquid interface and precipitated 3D assemblies with well-defined shapes. The growth processes of these colloidal crystals, called super- or supracrystals, markedly change the mechanical properties of these assemblies and induce the crystallinity segregation of nanocrystals. Therefore, single domain nanocrystals are the primary basis in the formation of these supracrystals, while multiply twinned particles (MTPs) and polycrystals remain dispersed within the colloidal suspension. Nanoindentation measurements show a drop in the Young's moduli for interfacial supracrystals in comparison with the precipitated supracrystals. In addition, the value of the Young's modulus changes markedly with the supracrystal growth mechanism. Using scanning tunneling microscopy/spectroscopy, we successfully imaged very thick supracrystals (from 200 nm up to a few micrometers) with remarkable conductance homogeneity and showed electronic fingerprints of isolated nanocrystals. This discovery of nanocrystal fingerprints within supracrystals could lead to promising applications in nanotechnology. PMID:23003577

  14. Mechanism for diamond nucleation and growth on single crystal copper surfaces implanted with carbon

    NASA Technical Reports Server (NTRS)

    Ong, T. P.; Xiong, Fulin; Chang, R. P. H.; White, C. W.

    1992-01-01

    The nucleation and growth of diamond crystals on single-crystal copper surfaces implanted with carbon ions is studied. Microwave plasma-enhanced chemical-vapor deposition is used for diamond growth. The single-crystal copper substrates were implanted either at room or elevated temperature with carbon ions prior to diamond nucleation. This procedure leads to the formation of a graphite film on the copper surface which greatly enhances diamond crystallite nucleation. A simple lattice model is constructed for diamond growth on graphite as 111 line (diamond) parallel to 0001 line (graphite) and 110 line (diamond) parallel to 1 1 -2 0 (graphite).

  15. Growth of ice discs from the vapor and the mechanism of habit change of ice crystals

    NASA Technical Reports Server (NTRS)

    Keller, V. W.; Mcknight, C. V.; Hallett, J.

    1980-01-01

    Ice crystals nucleated on a liquid nitrogen cooled glass fiber grow first as thin disks which subsequently transform to plates and columns as they thicken and extend to regions of higher supersaturation. Crystals are often found to be dislocation-free, which suggests that growth results from surface nucleation, the habit depending on preferential nucleation in an adsorbed multilayer on basal or prism face.

  16. Mechanism of Rare Earth Incorporation and Crystal Growth of Rare Earth Containing Type-I Clathrates

    PubMed Central

    2015-01-01

    Type-I clathrates possess extremely low thermal conductivities, a property that makes them promising materials for thermoelectric applications. The incorporation of cerium into one such clathrate has recently been shown to lead to a drastic enhancement of the thermopower, another property determining the thermoelectric efficiency. Here we explore the mechanism of the incorporation of rare earth elements into type-I clathrates. Our investigation of the crystal growth and the composition of the phase Ba8–xRExTMySi46–y (RE = rare earth element; TM = Au, Pd, Pt) reveals that the RE content x is mainly governed by two factors, the free cage space and the electron balance. PMID:26823658

  17. Change of morphology and growth mechanism of thin n-paraffin crystals induced by homologous impurities

    NASA Astrophysics Data System (ADS)

    van Hoof, P. J. C. M.; van Enckevort, W. J. P.; Schoutsen, M.; Bennema, P.; Liu, X. Y.

    1998-02-01

    In situ optical and birefringence measurements were applied in observing the crystallisation of very thin (⩾ 1.1 μm) n-paraffin crystals. Next, homologue impurities were found to reduce the crystal thickness even further to approximately 0.4 μm. As such thin crystals are very sensitive to adsorption of (sub-) micron particles (e.g. dust particles) a new type of growth, i.e. "particle-induced rough growth", is induced. This growth is akin to the growth of steps in the presence of immobile impurities adsorbed on the surface. The measured mean distance between the obstructing (sub-) micron particles (12 μm) is used to calculate the surface energy (36 mJ/m 2) of the top and bottom faces of the n-paraffin crystals. And it was shown that this is a reasonable value for the surface energy of {{0 0 1}} faces of n-paraffin crystals. Further, it was shown that at fixed concentrations the saturation temperatures for thin crystals are different from those for thick crystals. These results can be explained in terms of a Gibbs-Thomson effect.

  18. An interfacial energy mechanism for the complete inhibition of crystal growth by inhibitor adsorption

    NASA Astrophysics Data System (ADS)

    Anklam, Mark R.; Firoozabadi, Abbas

    2005-10-01

    We present a unified model for complete crystal-growth inhibition based on the thermodynamics of interfaces. The premise for our model is that the adsorption of inhibitor leads to a reduction in interfacial tension or edge energy for the crystal surface or step, respectively. In our formulation, the work to add a layer or grow a step increases due to the difference in interfacial tensions or edge energies for surfaces with and without an adsorbed inhibitor. For a large enough difference in interfacial tensions or edge energies, complete inhibition of growth is realized when the total work does not decrease as more crystals are formed. We demonstrate that our model can provide a theoretical description of critical subcooling data for ice with antifreeze proteins and glycoproteins, critical subcooling data for hydrates and ionic crystals, and critical supersaturation data for various crystal systems.

  19. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (inventor)

    1987-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into and adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  20. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1989-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into an adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  1. Determining the Molecular Growth Mechanisms of Protein Crystal Faces by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Li, Huayu; Pusey, Marc L.

    1999-01-01

    A high resolution atomic force microscopy (AFM) study had shown that the molecular packing on the tetragonal lysozyme (110) face corresponded to only one of two possible packing arrangements, suggesting that growth layers on this face were of bimolecular height. Theoretical analyses of the packing also indicated that growth of this face should proceed by the addition of growth units of at least tetramer size corresponding to the 43 helices in the crystal. In this study an AFM linescan technique was devised to measure the dimensions of individual growth units on protein crystal faces as they were being incorporated into the lattice. Images of individual growth events on the (110) face of tetragonal lysozyme crystals were observed, shown by jump discontinuities in the growth step in the linescan images as shown in the figure. The growth unit dimension in the scanned direction was obtained from these images. A large number of scans in two directions on the (110) face were performed and the distribution of lysozyme growth unit sizes were obtained. A variety of unit sizes corresponding to 43 helices, were shown to participate in the growth process, with the 43 tetramer being the minimum observed size. This technique represents a new application for AFM allowing time resolved studies of molecular process to be carried out.

  2. Crystal growth, structural, thermal and mechanical behavior of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals.

    PubMed

    Mahadevan, M; Ramachandran, K; Anandan, P; Arivanandhan, M; Bhagavannarayana, G; Hayakawa, Y

    2014-12-10

    Single crystals of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) have been grown successfully from the solution of l-arginine and 4-nitrophenol. Slow evaporation of solvent technique was adopted to grow the bulk single crystals. Single crystal X-ray diffraction analysis confirms the grown crystal has monoclinic crystal system with space group of P21. Powder X-ray diffraction analysis shows the good crystalline nature. The crystalline perfection of the grown single crystals was analyzed by HRXRD by employing a multicrystal X-ray diffractometer. The functional groups were identified from proton NMR spectroscopic analysis. Linear and nonlinear optical properties were determined by UV-Vis spectrophotometer and Kurtz powder technique respectively. It is found that the grown crystal has no absorption in the green wavelength region and the SHG efficiency was found to be 2.66 times that of the standard KDP. The Thermal stability of the crystal was found by obtaining TG/DTA curve. The mechanical behavior of the grown crystal has been studied by Vicker's microhardness method. PMID:24967545

  3. Growth, thermal and mechanical properties of new nonlinear optical barium bis-paranitrophenolate paranitrophenol tetrahydrate single crystal

    SciTech Connect

    Varjula, A. Jonie; Ramanand, A.; Das, S. Jerome

    2008-02-05

    Barium bis paranitrophenolate paranitrophenol tetrahydrate, a new semiorganic nonlinear optical single crystal has been grown by slow evaporation solution growth technique at room temperature of 30 deg. C. Crystal of dimensions of 29 mm x 11 mm x 5 mm was obtained in a period of 30 days. X-ray diffraction analysis reveal the newness of the crystal structure belonging to the orthorhombic class with lattice parameters a = 19.899(5) A, b = 28.019(8) A, c = 10.745(4) A and {alpha} = {beta} = {gamma} = 90{sup o}. The grown crystal is examined for its nonlinear optical nature with Kurtz powder technique after being sieved for particle sizes between 5 and 100 {mu}m and analyzed for its thermal and mechanical properties. The effective nonlinear optical coefficient being 16 times greater than that of KDP crystal, good thermal stability up to 120 deg. C with the Meyer's constant n < 2 helps fashion the crystal towards device geometry.

  4. Mercury iodide crystal growth

    NASA Technical Reports Server (NTRS)

    Cadoret, R.

    1982-01-01

    The purpose of the Mercury Iodide Crystal Growth (MICG) experiment is the growth of near-perfect single crystals of mercury Iodide (HgI2) in a microgravity environment which will decrease the convection effects on crystal growth. Evaporation and condensation are the only transformations involved in this experiment. To accomplish these objectives, a two-zone furnace will be used in which two sensors collect the temperature data (one in each zone).

  5. Physics of Crystal Growth

    NASA Astrophysics Data System (ADS)

    Pimpinelli, Alberto; Villain, Jacques

    1999-02-01

    This text discusses the physical principles of how and why crystals grow. It introduces the fundamental properties of crystal surfaces at equilibrium, and describes simple models and basic concepts of crystal growth including diffusion, thermal smoothing of a surface, and applications to semiconductors. It also covers more complex topics such as kinetic roughness, growth instabilities, and elastic effects, as well as the crucial contributions of crystal growth in electronics during this century. The book focuses on growth using molecular beam epitaxy. Throughout, the emphasis is on the role played by modern statistical physics. Informative appendices, interesting exercises and an extensive bibliography reinforce the text.

  6. Mechanism for enhanced single-crystal GaN growth in the C-assisted Na-flux method

    NASA Astrophysics Data System (ADS)

    Kawamura, Takahiro; Imabayashi, Hiroki; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Mori, Yusuke; Morikawa, Yoshitada

    2016-01-01

    First-principles molecular dynamics simulations are used to examine the effect of C addition in Na-flux growth of GaN. The mechanism for suppression of polycrystalline growth and the enhancement of single-crystal growth was identified by systematically calculating activation free energies for the formation and dissociation of CN bonds. The energy barrier for CN dissociation in a GaNa melt is ?3 eV; thus, dissociation is inhibited and the growth of polycrystals is suppressed. However, at kink sites at a Na/GaN interface with excess Ga atoms, the barrier is only ?1.0 eV, allowing CN dissociation and growth of GaN single crystals.

  7. Polymorphic polytypic transition induced in crystals by interaction of spirals and 2D growth mechanisms

    NASA Astrophysics Data System (ADS)

    Aquilano, Dino; Veesler, Stphane; Astier, Jean Pierre; Pastero, Linda

    2003-01-01

    The relationship between crystal polymorphism and polytypism can be revealed by surface patterns through the interlacing of the growth spirals. Simple high-symmetry structures as SiC, ZnS, CdI2 and more complex low-symmetry layered structures as n-paraffins, n-alcohols and micas are concerned with polymorphic-polytypic transition. In this paper, we will show for the first time, through in situ AFM observations and X-ray diffractometry, that a protein polymorph (P2 12 12 1?-amylase) locally changes, during growth, to a monoclinic P2 1 polytype, thanks to the screw dislocation activity. The interplay between spiral steps and 2D nuclei of the polytypes coexisting in the same crystalline individual allows to foresee the consequences on the crystal quality. The discussion is extended to other mineral and biological molecules and a new general rule is proposed to explain the interactions between surface patterns and the bulk crystal structure.

  8. Detection and a possible mechanism of magnetic field effect on the crystal growth of sedimentary calcium carbonate.

    PubMed

    Azuma; Tajima; Ishizu; Yokoi; Mori

    2000-07-01

    Sedimentary calcium carbonate was grown at a physiological pH6.8 from a mixture of equivolume of 70 mM Ca(NO(3))(2) and 70 mM NaHCO(3) aqueous solution. The kinetics of the crystal growth was monitored by means of turbidity measurement. The apparent absorption is gradually increased with the elapsed time after the mixing and reaches its maximum at t(max). The average t(max) is significantly decreased from =467 s (for n=13 runs) to 408 s (n=13) by application of the static magnetic field (SMF) of H=400 mT to the precipitating solution. The application of SMF at 120 s later the mixing shows the same =396 s (n=9) as that of 408 s. It has been thus detected that the application of SMF is ineffective in the stage of the nucleation or the earlier stage of the crystal growth but effective in the Ostwald ripening stage of the growth nucleus or the later stage of the crystal growth where large numbers of the growing crystalline particles seem greater than a few hundred nanometers. A possible mechanism for the SMF effect is as follows. An ion escaping from the growing crystal surface with a certain 'migration velocity' due to a random walk process has significant probability to drift onto the identical surface or at least the identical crystal by means of Lorentz force, because the translational displacement of the crystal during a cycle of the cyclotron motion of the ion is smaller than the size of the growing crystal. This type of drift results in the suppression of re-dissolution of the ions on the growing surface and in the acceleration of the growth in the later stage of the crystal growth. The undetected SMF effect in the earlier stage of the crystal growth can be partly attributed to the re-dissolution due to the thermodynamic instability of the small nuclei which predominates over the presumable SMF effect. This can be partly ascribed to the large translational displacement of the small particle. The application of this mechanism to an oscillating magnetic field will predict the presence of a window for the frequency of the oscillating magnetic field. PMID:10927185

  9. Crystal growth of semiconductor bulk crystals

    SciTech Connect

    Kakimoto, Koichi

    2010-07-22

    This course is aimed at showing how to grow bulk crystals by using several methods. The course involves the following points. The growth methods of Bridgman and Czochralski will be introduced. The course also focuses on the mechanism of some processes with consideration of the basic phenomenon. Experimental and numerical examples of the methods will also be introduced.

  10. Self-catalytic crystal growth, formation mechanism, and optical properties of indium tin oxide nanostructures

    NASA Astrophysics Data System (ADS)

    Liang, Yuan-Chang; Zhong, Hua

    2013-08-01

    In-Sn-O nanostructures with rectangular cross-sectional rod-like, sword-like, and bowling pin-like morphologies were successfully synthesized through self-catalytic growth. Mixed metallic In and Sn powders were used as source materials, and no catalyst layer was pre-coated on the substrates. The distance between the substrate and the source materials affected the size of the Sn-rich alloy particles during crystal growth in a quartz tube. This caused In-Sn-O nanostructures with various morphologies to form. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanostructures. The Sn doping and oxygen vacancies in the In2O3 crystals corresponded to the blue-green and yellow-orange emission bands of the nanostructures, respectively.

  11. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1993-01-01

    Proteins account for 50% or more of the dry weight of most living systems and play a crucial role in virtually all biological processes. Since the specific functions of essentially all biological molecules are determined by their three-dimensional structures, it is obvious that a detailed understanding of the structural makeup of a protein is essential to any systematic research pertaining to it. At the present time, protein crystallography has no substitute, it is the only technique available for elucidating the atomic arrangements within complicated biological molecules. Most macromolecules are extremely difficult to crystallize, and many otherwise exciting and promising projects have terminated at the crystal growth stage. There is a pressing need to better understand protein crystal growth, and to develop new techniques that can be used to enhance the size and quality of protein crystals. There are several aspects of microgravity that might be exploited to enhance protein crystal growth. The major factor that might be expected to alter crystal growth processes in space is the elimination of density-driven convective flow. Another factor that can be readily controlled in the absence of gravity is the sedimentation of growing crystal in a gravitational field. Another potential advantage of microgravity for protein crystal growth is the option of doing containerless crystal growth. One can readily understand why the microgravity environment established by Earth-orbiting vehicles is perceived to offer unique opportunities for the protein crystallographer. The near term objectives of the Protein Crystal Growth in a Microgravity Environment (PCG/ME) project is to continue to improve the techniques, procedures, and hardware systems used to grow protein crystals in Earth orbit.

  12. Near-liquidus growth of feldspar spherulites in trachytic melts: 3D morphologies and implications in crystallization mechanisms

    NASA Astrophysics Data System (ADS)

    Arzilli, Fabio; Mancini, Lucia; Voltolini, Marco; Cicconi, Maria Rita; Mohammadi, Sara; Giuli, Gabriele; Mainprice, David; Paris, Eleonora; Barou, Fabrice; Carroll, Michael R.

    2015-02-01

    The nucleation and growth processes of spherulitic alkali feldspar have been investigated in this study through X-ray microtomography and electron backscatter diffraction (EBSD) data. Here we present the first data on Shape Preferred Orientation (SPO) and Crystal Preferred Orientation (CPO) of alkali feldspar within spherulites. The analysis of synchrotron X-ray microtomography and EBSD datasets allowed us to study the morphometric characteristics of spherulites in trachytic melts in quantitative fashion, highlighting the three-dimensional shape, preferred orientation, branching of lamellae and crystal twinning, providing insights about the nucleation mechanism involved in the crystallization of the spherulites. The nucleation starts with a heterogeneous nucleus (pre-existing crystal or bubble) and subsequently it evolves forming "bow tie" morphologies, reaching radially spherulitic shapes in few hours. Since each lamella within spherulite is also twinned, these synthetic spherulites cannot be considered as single nuclei but crystal aggregates originated by heterogeneous nucleation. A twin boundary may have a lower energy than general crystal-crystal boundaries and many of the twinned grains show evidence of strong local bending which, combined with twin plane, creates local sites for heterogeneous nucleation. This study shows that the growth rates of the lamellae (10- 6-10- 7 cm/s) in spherulites are either similar or slightly higher than that for single crystals by up to one order of magnitude. Furthermore, the highest volumetric growth rates (10- 11-10- 12 cm3/s) show that the alkali feldspar within spherulites can grow fast reaching a volumetric size of ~ 10 ?m3 in 1 s.

  13. Crystal growth and crystallography

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  14. Mechanisms for Species-Selective Oriented Crystal Growth at Organic Templates

    SciTech Connect

    Kewalramani,S.; Kim, K.; Evmenenko, G.; Zschack, P.; Karapetrova, E.; Bai, J.; Dutta, P.

    2007-01-01

    Langmuir monolayers floating on supersaturated aqueous subphases can act as templates for the growth of oriented inorganic films--a 'bioinspired' nucleation process. We have performed in situ grazing incidence x-ray diffraction studies of the selective nucleation of BaClF and BaF2 under fatty acid monolayers. The arrangement of the fatty acid headgroups, the monolayer charge, and ion-specific effects all play important roles in selecting the inorganic species. When the monolayer is in a neutral state, both BaClF and BaF2 nucleate at the interface and are well aligned, but when the monolayer headgroup is deprotonated, only oriented BaF2 grows at the interface. We also observe an enhanced alignment of BaF2 crystals during growth from highly supersaturated solutions, presumably due to reorganization of preformed crystals at the organic template. These results show that a delicate interplay between multiple factors governs the oriented growth of inorganic films at organic templates.

  15. Rapid crystallization of faujasitic zeolites: mechanism and application to zeolite membrane growth on polymer supports.

    PubMed

    Severance, Michael; Wang, Bo; Ramasubramanian, Kartik; Zhao, Lin; Ho, W S Winston; Dutta, Prabir K

    2014-06-17

    Zeolites are microporous, crystalline aluminosilicates with the framework made up of T-O-T (T = Si, Al) bonds and enclosed cages and channels of molecular dimensions. Influencing and manipulating the nucleation and growth characteristics of zeolites can lead to novel frameworks and morphologies, as well as decreased crystallization time. In this study, we show that manipulating the supersaturation during synthesis of zeolite X/Y (FAU) via dehydration led to extensive nucleation. Controlled addition of water to this nucleated state promotes the transport of nutrients, with a 4-fold increase in the rate of crystal growth, as compared to conventional hydrothermal process. Structural signature of the nucleated state was obtained by electron microscopy, NMR, and Raman spectroscopy. This extensively intermediate nucleated state was isolated and used as the starting material for zeolite membrane synthesis on porous polymer supports, with membrane formation occurring within an hour. With this time frame for growth, it becomes practical to fabricate zeolite/polymer membranes using roll-to-roll technology, thus making possible new commercial applications. PMID:24758695

  16. Studies on growth defects and mechanical properties of nonlinear optical crystal: L-arginine hydrofluoride

    NASA Astrophysics Data System (ADS)

    Pal, Tanusri; Kar, Tanusree

    2005-03-01

    Chemical etching technique has been used for the first time to reveal dislocation structure of the cleavage plane of L-arginine hydrofluoride monohydrate (LAHF). Selective behaviour of the etchants for revealing macrosteps and cooperating spirals has been demonstrated. Presence of growth spirals on (1 0 0) face indicates that growth of this face is governed by screw dislocation mechanism. Microhardness measurement reveals that LAHF is harder than LAP.

  17. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Atomic force microscopy uses laser technology to reveal a defect, a double-screw dislocation, on the surface of this crystal of canavalin, a major source of dietary protein for humans and domestic animals. When a crystal grows, attachment kinetics and transport kinetics are competing for control of the molecules. As a molecule gets close to the crystal surface, it has to attach properly for the crystal to be usable. NASA has funded investigators to look at those attachment kinetics from a theoretical standpoint and an experimental standpoint. Dr. Alex McPherson of the University of California, Irvine, is one of those investigators. He uses X-ray diffraction and atomic force microscopy in his laboratory to answer some of the many questions about how protein crystals grow. Atomic force microscopy provides a means of looking at how individual molecules are added to the surface of growing protein crystals. This helps McPherson understand the kinetics of protein crystal growth. McPherson asks, How fast do crystals grow? What are the forces involved? Investigators funded by NASA have clearly shown that such factors as the level of supersaturation and the rate of growth all affect the habit [characteristic arrangement of facets] of the crystal and the defects that occur in the crystal.

  18. The secrets of crystal growth

    SciTech Connect

    De Yoreo, J.; Land, T.

    1996-11-01

    Lawrence Livermore researchers are using the atomic-force microscope (AFM) to elucidate the growth mechanisms and three-dimensional structures of widely different solution-based crystals on the nanometer (billionth-of-a-meter) scale. Much of the AFM work has been in support of the Laser Programs` need to better understand KDP (potassium dihydrogen phosphate) crystal growth because of its direct impact on advanced lasers such as the National Ignition Facility. A second avenue of research has focused on the growth of solution-based crystals of biological macromolecules, specifically the protein canavalin and the satellite tobacco mosaic virus. The AFM images have revealed how solution-based crystals grow and how they are affected by impurities, defects, and solution conditions. The results are likely to affect many disciplines and technologies, from pharmaceuticals to materials synthesis.

  19. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1989-01-01

    The mechanisms involved in protein crystallization and those parameters which influence the growth process and crystalline perfection were studied. The analysis of the flows around growing crystals is detailed. The preliminary study of the growth of isocitrate lyase and the crystal morphologies found are discussed. Preliminary results of controlled nucleation studies are presented.

  20. Crystal Growth Control

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Batur, Celal; Bennett, Robert J.

    1997-01-01

    We present an innovative design of a vertical transparent multizone furnace which can operate in the temperature range of 25 C to 750 C and deliver thermal gradients of 2 C/cm to 45 C/cm for the commercial applications to crystal growth. The operation of the eight zone furnace is based on a self-tuning temperature control system with a DC power supply for optimal thermal stability. We show that the desired thermal profile over the entire length of the furnace consists of a functional combination of the fundamental thermal profiles for each individual zone obtained by setting the set-point temperature for that zone. The self-tuning system accounts for the zone to zone thermal interactions. The control system operates such that the thermal profile is maintained under thermal load, thus boundary conditions on crystal growth ampoules can be predetermined prior to crystal growth. Temperature profiles for the growth of crystals via directional solidification, vapor transport techniques, and multiple gradient applications are shown to be easily implemented. The unique feature of its transparency and ease of programming thermal profiles make the furnace useful for scientific and commercial applications for the determination of process parameters to optimize crystal growth conditions.

  1. Bridgman crystal growth

    NASA Technical Reports Server (NTRS)

    Carlson, Frederick

    1990-01-01

    The objective of this theoretical research effort was to improve the understanding of the growth of Pb(x)Sn(1-x)Te and especially how crystal quality could be improved utilizing the microgravity environment of space. All theoretical growths are done using the vertical Bridgman method. It is believed that improved single crystal yields can be achieved by systematically identifying and studying system parameters both theoretically and experimentally. A computational model was developed to study and eventually optimize the growth process. The model is primarily concerned with the prediction of the thermal field, although mass transfer in the melt and the state of stress in the crystal were of considerable interest. The evolution is presented of the computer simulation and some of the important results obtained. Diffusion controlled growth was first studied since it represented a relatively simple, but nontheless realistic situation. In fact, results from this analysis prompted a study of the triple junction region where the melt, crystal, and ampoule wall meet. Since microgravity applications were sought because of the low level of fluid movement, the effect of gravitational field strength on the thermal and concentration field was also of interest. A study of the strength of coriolis acceleration on the growth process during space flight was deemed necessary since it would surely produce asymmetries in the flow field if strong enough. Finally, thermosolutal convection in a steady microgravity field for thermally stable conditions and both stable and unstable solutal conditions was simulated.

  2. Fluid mechanics and mass transfer in melt crystal growth: Analysis of the floating zone and vertical Bridgman processes

    NASA Technical Reports Server (NTRS)

    Brown, R. A.

    1986-01-01

    This research program focuses on analysis of the transport mechanisms in solidification processes, especially one of interest to the Microgravity Sciences and Applications Program of NASA. Research during the last year has focused on analysis of the dynamics of the floating zone process for growth of small-scale crystals, on studies of the effect of applied magnetic fields on convection and solute segregation in directional solidification, and on the dynamics of microscopic cell formation in two-dimensional solidification of binary alloys. Significant findings are given.

  3. Growth, structural, optical, thermal and mechanical studies on 4-Aminopyridinium monophthalate: A novel nonlinear optical crystal

    NASA Astrophysics Data System (ADS)

    Marudhu, G.; Krishnan, S.; Palanichamy, M.

    2016-03-01

    A novel nonlinear optical crystal of 4-Aminopyridinium monophthalate (4-APMP) was grown by slow evaporation technique using methanol as solvent. Single crystal X-ray diffraction analysis confirms that the grown crystal belongs to orthorhombic system. The presence of functional groups was qualitatively determined by FTIR analysis. The optical absorption studies reveal very low absorption in the entire visible region. The fluorescence emission spectrum shows the emission is in blue region. The thermal stability of the grown crystal is found to be around 197.2 °C. The SHG efficiency of the grown crystal is found to be 1.1 times than that of KDP crystals.

  4. A comparative study on growth, structural, optical, thermal and mechanical properties of undoped and dye doped bis glycine cadmium chloride single crystals

    NASA Astrophysics Data System (ADS)

    Raju, B.; Saritha, A.; Bhagavannarayana, G.; Hussain, K. A.

    2011-06-01

    Dye inclusion crystals have attracted researchers in the context of crystal growth for applications in solid state lasers. Attempt to grow tris glycine cadmium chloride (TGCC) crystals yielded bis glycine cadmium chloride crystals. Single crystals of bis glycine cadmium chloride (BGCC) and organic dye, namely xylenol orange tetra sodium salt (XO) doped BGCC crystals, were grown from aqueous solutions by slow evaporation technique from the mixture of an aqueous solution of glycine and cadmium chloride in 3:1 molar ratio at a constant temperature of 35 °C. The grown crystals are up to the dimension of 20×20×5 mm 3. Characterization of the crystals was made using a single crystal X-ray diffractometer for obtaining the structure. The crystal is monoclinic with P2 1/ n space group. High-resolution X-ray diffraction (HRXRD) was used to evaluate crystalline perfection. Perfection of the undoped crystals is higher than those of the dye doped crystals. Thermal stability of the crystals is tested from differential scanning calorimetry. There is only one endothermic peak, indicating melting point. The optical transparency range of the crystals was identified from the UV-vis spectrum. Functional groups present in the crystals were studied by FT-IR spectral analysis. The mechanical strength of the crystals, measured by Vickers microhardness, and it has increased due to the presence of dye in the crystals.

  5. Quartz crystal growth

    DOEpatents

    Baughman, Richard J. (Albuquerque, NM)

    1992-01-01

    A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  6. Measurements of Protein Crystal Face Growth Rates

    NASA Technical Reports Server (NTRS)

    Gorti, S.

    2014-01-01

    Protein crystal growth rates will be determined for several hyperthermophile proteins.; The growth rates will be assessed using available theoretical models, including kinetic roughening.; If/when kinetic roughening supersaturations are established, determinations of protein crystal quality over a range of supersaturations will also be assessed.; The results of our ground based effort may well address the existence of a correlation between fundamental growth mechanisms and protein crystal quality.

  7. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-01

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized. PMID:21721131

  8. Growth, spectral, thermal, optical, mechanical and etching studies of L-lysine semi-maleate (L-LSM) single crystals

    NASA Astrophysics Data System (ADS)

    Vasudevan, V.; Renuka, N.; Ramesh Babu, R.; Ramamurthi, K.

    2015-02-01

    Organic nonlinear optical material, L-lysine semi-maleate (L-LSM) single crystals were grown by slow cooling solution growth technique. The crystal system of grown L-LSM was confirmed by single crystal and powder X-ray diffraction analyzes. Functional groups of the grown crystal have been identified by Fourier Transform Infrared spectral analysis. The proton and carbon NMR spectral studies confirm the presence of hydrogen and carbon in the grown L-LSM. The melting and thermal decomposition temperatures of the crystal were determined using thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Optical transparency, second harmonic generation efficiency, micro hardness, dielectric constant and loss, refractive index and birefringence have also been measured. Further, the growth patterns and dislocations present in the grown crystal are studied.

  9. Zeolite crystal growth in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Thompson, Robert W.; Dixon, Anthony G.

    1991-01-01

    The growth of large, uniform zeolite crystals in high yield in space can have a major impact on the chemical process industry. Large zeolite crystals will be used to improve basic understanding of adsorption and catalytic mechanisms, and to make zeolite membranes. To grow large zeolites in microgravity, it is necessary to control the nucleation event and fluid motion, and to enhance nutrient transfer. Data is presented that suggests nucleation can be controlled using chemical compounds (e.g., Triethanolamine, for zeolite A), while not adversely effecting growth rate. A three-zone furnace has been designed to perform multiple syntheses concurrently. The operating range of the furnace is 295 K to 473 K. Teflon-lined autoclaves (10 ml liquid volume) have been designed to minimize contamination, reduce wall nucleation, and control mixing of pre-gel solutions on orbit. Zeolite synthesis experiments will be performed on USML-1 in 1992.

  10. Coating effects on crack growth in a single crystal nickel based alloy during thermo-mechanical fatigue

    SciTech Connect

    Bressers, J.; Timm, J.; Martinez-Esnaola, J.M.; Martin-Meizoso, A.

    1996-12-31

    Single crystal specimens of the nickel based alloy SRR99 with [001] orientation are subjected to TMF cycling between 300 C and 1,050 C, using a {minus}135{degree} lag between temperature and mechanical strain, and various R ratios. The in-situ observation of the test specimen by means of a computer vision system during TMF testing enables the initiation of microcracks to be detected when cracks have reached lengths of approximately 30 {micro}m at the surface. High densities of point initiated micro-cracks are generated during the early stages of the TMF life. Crack increment measurements reveal marked differences between the growth rates of individual micro-cracks. The presence of a nickel-aluminide coating consistently reduces the TMF life, due largely to higher growth rates of the main crack in the substrate. In order to estimate the influence of initial crack distribution and density on life, a two dimensional crack shielding model is incorporated in a computer program which is used to simulate the growth of interacting, parallel surface cracks. The effect of various parameters, including the density and the initial distribution of the microcracks, on the life spent to grow a crack to a pre-defined length, are discussed and the model predictions are compared with the experimental observations.

  11. Crystal growth of artificial snow

    NASA Technical Reports Server (NTRS)

    Kimura, S.; Oka, A.; Taki, M.; Kuwano, R.; Ono, H.; Nagura, R.; Narimatsu, Y.; Tanii, J.; Kamimiytat, Y.

    1984-01-01

    Snow crystals were grown onboard the space shuttle during STS-7 and STS-8 to facilitate the investigation of crystal growth under conditions of weightlessness. The experimental design and hardware are described. Space-grown snow crystals were polyhedrons looking like spheres, which were unlike snow crystals produced in experiments on Earth.

  12. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Delucas, Lawrence J.; Smith, Craig D.; Smith, H. Wilson; Vijay-Kumar, Senadhi; Senadhi, Shobha E.; Ealick, Steven E.; Carter, Daniel C.; Snyder, Robert S.

    1989-01-01

    The crystals of most proteins or other biological macromolecules are poorly ordered and diffract to lower resolutions than those observed for most crystals of simple organic and inorganic compounds. Crystallization in the microgravity environment of space may improve crystal quality by eliminating convection effects near growing crystal surfaces. A series of 11 different protein crystal growth experiments was performed on U.S. Space Shuttle flight STS-26 in September 1988. The microgravity-grown crystals of gamma-interferon D1, porcine elastase, and isocitrate lyase are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth.

  13. The mechanism of growth-twin formation in zincblende crystals: new insights from a study of magnetic liquid encapsulated Czochralski-grown InP single crystals

    NASA Astrophysics Data System (ADS)

    Chung, H.; Dudley, M.; Larson, D. J.; Hurle, D. T. J.; Bliss, D. F.; Prasad, V.

    1998-04-01

    Synchrotron white beam X-ray topography (SWBXT) [1, 2][M. Dudley, in: Mater Res. Soc. Symp. Proc., vol. 307, 1993, p. 213; Encyclopedia of Applied Physics, vol. 21, 1997, p. 533] combined with chemical etching and Nomarski optical microscopy have been employed to investigate the phenomenon of twinning in sulfur-doped, MLEC-grown <1 0 0> InP single crystals. Results confirm the prediction of Hurle [3, 4][Sir Charles Frank, OBE, FRS; on 80th Birthday tribute, 1991, p. 188; J. Crystal Growth 147 (1995) 239] that twins nucleate in regions where {1 1 1} edge facets are anchored to the three-phase boundary (TPB), and that twinning produces a {1 1 1} external facet on the shoulder region of crystal. The critical factor controlling the point at which the twin nucleates is observed to be the appearance of a {1 1 5} external shoulder facet which is then converted to the {1 1 1} external shoulder facet upon twinning. Based on the observation of both anchored edge facets and twinning at shoulder angles of approximately 74, ?max, the maximum in the range of angles, ? (where ? is the angle between the edge facet and the extension of the crystal surface, or shoulder), over which edge facets can be expected to be trapped at the TPB, as presented by Hurle, has been increased, from 86.5 to 112, by modifying approximations made concerning the relevant physical parameters for the particular case of S-doped InP. A correction is made to an error in Hurle: the most dangerous grow-out angle for the occurrence of twinning in <1 0 0> oriented crystals, is 74.2 and not 35.5. Also Hurle predicted that, in crystals with diamond cubic or zincblende structures, the range of ? angles for edge facet pinning should encompass 70.5(3) for twinning to be possible. This is here extended to the statement that it should encompass either 70.5(3) and/or 109.47. Incidences of twinning were also observed to occur by a similar mechanism but one which involved the conversion of a {1 1 4} external shoulder facet to a {1 1 0} one.

  14. Crystal Shape Evolution in Detached Bridgman Growth

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    2013-01-01

    Detached (or dewetted) Bridgman crystal growth defines that process in which a gap exists between a growing crystal and the crucible wall. Existence of the gap provides several advantages, including no sticking of the crystal to the crucible wall, reduced thermal and mechanical stresses, reduced dislocations, and no heterogeneous nucleation by the crucible. Numerical calculations are used to determine the conditions in which a gap can exist. According to crystal shape stability theory, only some of these gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. Depending on the initial conditions and growth parameters, the crystal shape will evolve towards the crucible wall, towards a stable gap width, or towards the center of the crucible, collapsing the meniscus. The effect of a tapered crucible on dynamic stability is also described

  15. Crystal Shape Evolution in Detached Bridgman Growth

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    2013-01-01

    Detached (or dewetted) Bridgman crystal growth defines that process in which a gap exists between a growing crystal and the crucible wall. Existence of the gap provides several advantages, including no sticking of the crystal to the crucible wall, reduced thermal and mechanical stresses, reduced dislocations, and no heterogeneous nucleation by the crucible. Numerical calculations are used to determine the conditions in which a gap can exist. According to crystal shape stability theory, only some of these gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. Depending on the initial conditions and growth parameters, the crystal shape will evolve towards the crucible wall, towards a stable gap width, or towards the center of the crucible, collapsing the meniscus. The effect of a tapered crucible on dynamic stability is also described.

  16. Protein Crystals and their Growth

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    Recent results on binding between protein molecules in crystal lattice, crystal-solution surface energy, elastic properties and strength and spontaneous crystal cracking are reviewed and discussed in the first half of this paper (Sea 2-4). In the second par&, some basic approaches to solubility of proteins are followed by overview on crystal nucleation and growth (Sec 5). It is argued that variability of mixing in batch crystallization may be a source for scattering of crystal number ultimately appearing in the batch. Frequency at which new molecules join crystal lattice is measured by kinetic coefficient and related to the observable crystal growth rate. Numerical criteria to discriminate diffusion and kinetic limited growth are discussed on this basis in Sec 7. In Sec 8, creation of defects is discussed with the emphasis on the role of impurities and convection on macromolecular crystal I;erfection.

  17. Protein crystals and their growth

    NASA Technical Reports Server (NTRS)

    Chernov, Alexander A.

    2003-01-01

    Recent results on the associations between protein molecules in crystal lattices, crystal-solution surface energy, elastic properties, strength, and spontaneous crystal cracking are reviewed and discussed. In addition, some basic approaches to understanding the solubility of proteins are followed by an overview of crystal nucleation and growth. It is argued that variability of mixing in batch crystallization may be a source of the variation in the number of crystals ultimately appearing in the sample. The frequency at which new molecules join a crystal lattice is measured by the kinetic coefficient and is related to the observed crystal growth rate. Numerical criteria used to discriminate diffusion- and kinetic-limited growth are discussed on this basis. Finally, the creation of defects is discussed with an emphasis on the role of impurities and convection on macromolecular crystal perfection.

  18. Protein crystal growth in space

    NASA Technical Reports Server (NTRS)

    Bugg, C. E.; Clifford, D. W.

    1987-01-01

    The advantages of protein crystallization in space, and the applications of protein crystallography to drug design, protein engineering, and the design of synthetic vaccines are examined. The steps involved in using protein crystallography to determine the three-dimensional structure of a protein are discussed. The growth chamber design and the hand-held apparatus developed for protein crystal growth by vapor diffusion techniques (hanging-drop method) are described; the experimental data from the four Shuttle missions are utilized to develop hardware for protein crystal growth in space and to evaluate the effects of gravity on protein crystal growth.

  19. A unique growth mechanism of donut-shaped Mg-Al layered double hydroxides crystals revealed by AFM and STEM-EDX

    NASA Astrophysics Data System (ADS)

    Budhysutanto, W. N.; Van Den Bruele, F. J.; Rossenaar, B. D.; Van Agterveld, D.; Van Enckevort, W. J. P.; Kramer, H. J. M.

    2011-03-01

    Donut-like crystals of Mg-Al layered double hydroxides (LDH) are synthesized using a hydrothermal method with microwave heating. This morphology provides enlargement of the specific surface area of the {h k 0} faces, needed for adsorption application. The growth mechanism for donut-shaped crystals is proposed on the basis of AFM and STEM-EDX images. The nucleation of Mg-Al LDH starts on the amorphous surface of spherical MgO particles, which have a much lower solubility compared to the aluminum trihydroxides at the synthesis pH (?11). The outgrowing nucleus provides re-entrant corners on both sides. These are preferential sites for the addition of new growth units, allowing lateral growth of the LDH crystal encircling the MgO particles. The dissolving MgO provides the supersaturation needed for growth and once it is depleted, a donut-like structure remains.

  20. MCT crystal growth

    NASA Astrophysics Data System (ADS)

    Baird, James K.

    1988-02-01

    Convection and segregation in directional solidification and crystal growth by the Bridgman-Stockbarger technique are traditionally treated by assuming axisymmetric thermal condition on the ampoule wall. It is, however, difficult to achieve such a condition in an experimental setup. Any deviation from an axisymmetric temperature field on the wall of a vertical ampoule represents a horizontal temperature gradient. The horizontal density gradient that results from thermal expansion in the melt under this condition must lead on earth to some buoyance-driven convection, no matter what the axial (vertical) temperature distribution that is imposed on the melt. The magnitude of such convective flows for conditions representative of the MSFC mercury-cadmium-telluride (MCT) Bridgman setup is studied.

  1. MCT crystal growth

    NASA Technical Reports Server (NTRS)

    Baird, James K.

    1988-01-01

    Convection and segregation in directional solidification and crystal growth by the Bridgman-Stockbarger technique are traditionally treated by assuming axisymmetric thermal condition on the ampoule wall. It is, however, difficult to achieve such a condition in an experimental setup. Any deviation from an axisymmetric temperature field on the wall of a vertical ampoule represents a horizontal temperature gradient. The horizontal density gradient that results from thermal expansion in the melt under this condition must lead on earth to some buoyance-driven convection, no matter what the axial (vertical) temperature distribution that is imposed on the melt. The magnitude of such convective flows for conditions representative of the MSFC mercury-cadmium-telluride (MCT) Bridgman setup is studied.

  2. Crystal growth apparatus

    NASA Astrophysics Data System (ADS)

    Herrmann, Frederick T.; Herren, Blair J.

    1990-04-01

    This invention relates generally to crystal growth devices, and more particularly to a device in which protein crystals are grown in a hanging drop. The drop is suspended from a surface positioned in the interior of an enclosure which is sealably coupled via a valve to a vessel containing solvent used in the drop. A second opening in the enclosure is coupled via a valve to a vessel containing a selected desiccant material. The valve may be fully or partially opened to add a selected quantity of solvent in a vapor phase to the drop, and the valve may be fully or partially opened to cause a selected quantity of solvent to evaporate from the drop. The process is monitored by a camera, and in conjunction with a graduated pattern superimposed over the drop, relative volumes of the drop are determined. Alternately, the process may be automated by using a computer coupled to servo motors, which in turn are coupled to and operate a cap and valves, respectively. The computer is responsive to a detection device which detects changes of light passing through the drop from the light source.

  3. Nucleation kinetics, growth, crystalline perfection, mechanical, thermal, optical and electrical characterization of brucinium 2-carboxy-6-nitrophthalate dihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Krishnan, P.; Gayathri, K.; Sivakumar, N.; Gunasekaran, S.; Anbalagan, G.

    2014-06-01

    Single crystals of brucinium 2-carboxy-6-nitrophthalate dihydrate (B2C6ND) have been grown by the slow evaporation solution technique at room temperature using water-ethanol (1:1) mixed solvent. The metastable zone width and induction period have been experimentally determined for the growth conditions. Nucleation kinetics and fundamental growth parameters such as surface free energy, critical radius and critical free energy change are also evaluated according to the experimental data. The crystal system and the lattice parameters have been confirmed by single crystal X-ray diffraction. The crystalline perfection of the grown B2C6ND crystals has been characterized by HRXRD method. Optical band gap and Urbach tail width of the sample have been studied employing UV-Vis absorption spectroscopy. The Vickers microhardness number (Hv), yield strength (?v) and stiffness constant (C11) of the grown crystal have been evaluated. The dielectric permittivity and dielectric loss of the grown B2C6ND crystal have been investigated as a function of frequency in the temperature range 313-353 K. The laser damage threshold value of B2C6ND crystal was estimated to be 2.8 GW/cm2 using a Nd:YAG laser.

  4. Characterization and modeling of illite crystal particles and growth mechanisms in a zoned hydrothermal deposit, Lake City, Colorado

    USGS Publications Warehouse

    Bove, D.J.; Eberl, D.D.; McCarty, D.K.; Meeker, G.P.

    2002-01-01

    Mean thickness measurements and crystal-thickness distributions (CTDs) of illite particles vary systematically with changes in hydrothermal alteration type, fracture density, and attendant mineralization in a large acid-sulfate/Mo-porphyry hydrothermal system at Red Mountain, near Lake City, Colorado. The hydrothermal illites characterize an extensive zone of quartz-sericite-pyrite alteration beneath two deeply rooted bodies of magmatic-related, quartz-alunite altered rock. Nineteen illites from a 3000 ft vertical drill hole were analyzed by XRD using the PVP-10 intercalation method and the computer program MudMaster (Bertaut-Warren-Averbach technique). Mean crystallite thicknesses, as determined from 001 reflections, range from 5-7 nanometers (nm) at depths from 0-1700 ft, then sharply increase to 10-16 nm at depths between 1800-2100 ft, and decrease again to 4-5 nm below this level. The interval of largest particle thickness correlates strongly with the zone of most intense quartz-sericite-pyrite alteration (QSP) and attendant high-density stockwork fracturing, and with the highest concentrations of Mo within the drill core. CTD shapes for the illite particles fall into two main categories: asymptotic and lognormal. The shapes of the CTDs are dependent on conditions of illite formation. The asymptotic CTDs correspond to a nucleation and growth mechanism, whereas surface-controlled growth was the dominant mechanism for the lognormal CTDs. Lognormal CTDs coincide with major through-going fractures or stockwork zones, whereas asymptotic CTDs are present in wallrock distal to these intense fracture zones. The increase in illite particle size and the associated zone of intense QSP alteration and stockwork veining was related by proximity to the dacitic magma(s), which supplied both reactants and heat to the hydrothermal system. However, no changes in illite polytype, which in other studies reflect temperature transitions, were observed within this interval.

  5. Direct flow crystal growth system

    DOEpatents

    Montgomery, Kenneth E. (Tracy, CA); Milanovich, Fred P. (Lafayette, CA)

    1992-01-01

    A crystal is grown in a constantly filtered solution which is flowed directly into the growing face of a crystal. In a continuous flow system, solution at its saturation temperature is removed from a crystal growth tank, heated above its saturation temperature, filtered, cooled back to its saturation temperature, and returned to the tank.

  6. High density protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rouleau, Robyn (Inventor); Delucas, Lawrence (Inventor); Hedden, Douglas Keith (Inventor)

    2004-01-01

    A protein crystal growth assembly including a crystal growth cell and further including a cell body having a top side and a bottom side and a first aperture defined therethrough, the cell body having opposing first and second sides and a second aperture defined therethrough. A cell barrel is disposed within the cell body, the cell barrel defining a cavity alignable with the first aperture of the cell body, the cell barrel being rotatable within the second aperture. A reservoir is coupled to the bottom side of the cell body and a cap having a top side is disposed on the top side of the cell body. The protein crystal growth assembly may be employed in methods including vapor diffusion crystallization, liquid to liquid crystallization, batch crystallization, and temperature induction batch mode crystallization.

  7. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): a potential NLO material.

    PubMed

    Dinakaran, Paul M; Kalainathan, S

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6×2×3 mm(3)) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and (1)H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV). PMID:23624038

  8. Dendritic crystal growth in pure materials

    NASA Astrophysics Data System (ADS)

    Glicksman, M. E.; Lupulescu, A. O.

    2004-03-01

    Dendritic growth is a fundamental crystal growth phenomenon accompanying most casting and solidification processes, and, occasionally, occurring during the growth of single crystals, where it is detrimental to crystalline quality. Dendrites are the ubiquitous crystal form in freezing alloys and supercooled melts, because their shapes are most suited for efficient heat and mass transfer at small scales. Dendritic scales are typically the smallest length scales of interest in ingots and castings, typically associated with: (1) chemical processes, such as microsegregation, (2) thermal processes, for example, latent heat release, and (3) mechanical processes, for instance, the volume change during phase transformation. All of these processes operate at the dendritic solid-melt interface. Understanding dendritic growth is therefore considered essential for controlling basic solidification and crystal growth processes. A brief history of dendrites will be sketched, showing how the subject of dendritic solidification evolved to its present status as a modern sub-field of general crystal growth. The comprehensive understanding of dendrites and developing a predictive capability of practical utility to the crystal grower, however, remain as works in progress. The subject of dendritic growth will be presented on the basis of heat and mass transfer, capillarity effects at the solid-melt interface, and interfacial dynamics, including morphological stability, and side-branching dynamics. Experimental verification of dendritic scaling laws using microgravity experimentation is included as a brief attempt to encapsulate this important subject within crystal growth science.

  9. Protein crystal growth in space

    NASA Technical Reports Server (NTRS)

    Delucas, Lawrence J.; Bugg, Charles E.

    1991-01-01

    Studies of protein crystal growth in the microgravity environment in space are described with special attention given to the crystal growth facilities and the techniques used in Space Shuttle experiments. The properties of large space-grown crystals of gamma interferon, elastase, lathyros ochrus lectin I, and few other proteins grown on various STS flights are described. A comparison of the microgravity-grown crystals with the bast earth-grown crystals demonstrated that the space-grown crystals are more highly ordered at the molecular level than their earth-grown counterparts. When crystallization conditions were optimized, the microgravity-grown protein crystals were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolution than their earth-grown counterparts.

  10. Structure, crystal growth, optical and mechanical studies of poly bis (thiourea) silver (I) nitrate single crystal: a new semi organic NLO material.

    PubMed

    Sivakumar, N; Kanagathara, N; Varghese, B; Bhagavannarayana, G; Gunasekaran, S; Anbalagan, G

    2014-01-24

    A new semi organic non linear optical polymeric crystal, bis (thiourea) silver (I) nitrate (TuAgN) with dimension 871.5 mm(3) has been successfully grown from aqueous solution by slow evaporation solution technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non centrosymmetric space group C2221. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Functional groups present in the crystal were analyzed qualitatively by infrared and Confocal Raman spectral analysis. Effects due to coordination of thiourea with metal ions were also discussed. Optical absorption study on TuAgN crystal shows the minimum absorption in the entire UV-Vis region and the lower cut off wavelength of TuAgN is found to be 318 nm. Thermal analysis shows that the material is thermally stable up to 180C. The mechanical strength and its parameters of the grown crystal were estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 0.85 times that of KDP. PMID:24091346

  11. Protein crystal growth - Growth kinetics for tetragonal lysozyme crystals

    NASA Technical Reports Server (NTRS)

    Pusey, M. L.; Snyder, R. S.; Naumann, R.

    1986-01-01

    Results are reported from theoretical and experimental studies of the growth rate of lysozyme as a function of diffusion in earth-gravity conditions. The investigations were carried out to form a comparison database for future studies of protein crystal growth in the microgravity environment of space. A diffusion-convection model is presented for predicting crystal growth rates in the presence of solutal concentration gradients. Techniques used to grow and monitor the growth of hen egg white lysozyme are detailed. The model calculations and experiment data are employed to discuss the effects of transport and interfacial kinetics in the growth of the crystals, which gradually diminished the free energy in the growth solution. Density gradient-driven convection, caused by presence of the gravity field, was a limiting factor in the growth rate.

  12. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1987-01-01

    The solubility and growth mechanism of canavalin were studied, and the applicability of the Schlieren technique to protein crystal growth was investigated. Canavalin which may be crystallized from a basic solution by the addition of hydrogen (H+) ions was shown to have normal solubility characteristics over the range of temperatures (5 to 25 C) and pH (5 to 7.5) studied. The solubility data combined with growth rate data gathered from the seeded growth of canavalin crystals indicated that the growth mechanism at high supersaturation ratios (>1.28) is screw dislocation like. A Schlieren apparatus was constructed and flow patterns were observed in Rochelle salt (sodium potassium tartrate), lysozyme, and canavalin. The critical parameters were identified as the change in density with concentration (dp/dc) and the change in index of refraction with concentration (dn/dc). Some of these values were measured for the materials listed.

  13. Interface control and snow crystal growth

    NASA Astrophysics Data System (ADS)

    Li, Jessica; Schaposnik, Laura P.

    2016-02-01

    The growth of snow crystals is dependent on the temperature and saturation of the environment. In the case of dendrites, Reiter's local two-dimensional model provides a realistic approach to the study of dendrite growth. In this paper we obtain a new geometric rule that incorporates interface control, a basic mechanism of crystallization that is not taken into account in the original Reiter model. By defining two new variables, growth latency and growth direction, our improved model gives a realistic model not only for dendrite but also for plate forms.

  14. Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    In order to rapidly and efficiently grow crystals, tools were needed to automatically identify and analyze the growing process of protein crystals. To meet this need, Diversified Scientific, Inc. (DSI), with the support of a Small Business Innovation Research (SBIR) contract from NASA s Marshall Space Flight Center, developed CrystalScore(trademark), the first automated image acquisition, analysis, and archiving system designed specifically for the macromolecular crystal growing community. It offers automated hardware control, image and data archiving, image processing, a searchable database, and surface plotting of experimental data. CrystalScore is currently being used by numerous pharmaceutical companies and academic and nonprofit research centers. DSI, located in Birmingham, Alabama, was awarded the patent Method for acquiring, storing, and analyzing crystal images on March 4, 2003. Another DSI product made possible by Marshall SBIR funding is VaporPro(trademark), a unique, comprehensive system that allows for the automated control of vapor diffusion for crystallization experiments.

  15. Automated protein crystal growth facility

    NASA Technical Reports Server (NTRS)

    Donald, Stacey

    1994-01-01

    A customer for the protein crystal growth facility fills the specially designed chamber with the correct solutions, fills the syringes with their quenching solutions, and submits the data needed for the proper growth of their crystal. To make sure that the chambers and syringes are filled correctly, a NASA representative may assist the customer. The data needed is the approximate growth time, the growth temperature, and the desired crystal size, but this data can be changed anytime from the ground, if needed. The chambers are gathered and placed into numbered slots in special drawers. Then, data is entered into a computer for each of the chambers. Technicians map out when each chamber's growth should be activated so that all of the chambers have enough time to grow. All of this data is up-linked to the space station when the previous growth session is over. Anti-vibrational containers need to be constructed for the high forces encountered during the lift off and the landing of the space shuttle, and though our team has not designed these containers, we do not feel that there is any reason why a suitable one could not be made. When the shuttle reaches the space station, an astronaut removes a drawer of quenched chambers from the growth facility and inserts a drawer of new chambers. All twelve of the drawers can be replaced in this fashion. The optical disks can also be removed this way. The old drawers are stored for the trip back to earth. Once inside the growth facility, a chamber is removed by the robot and placed in one of 144 active sites at a time previously picked by a technician. Growth begins when the chamber is inserted into an active site. Then, the sensing system starts to determine the size of the protein crystal. All during the crystal's growth, the customer can view the crystal and read all of the crystal's data, such as growth rate and crystal size. When the sensing system determines that the crystal has reached the predetermined size, the robot is told to pick up a syringe filled with the correct quenchant solution and inject it into the chamber to stop the crystal growth. The chamber is then removed from the active site and placed into its original storage slot. Another chamber is then placed into the active site and the process is repeated in all of the active sites until all of the chambers have complted their growth. After ninety days (the scheduled time between shuttle visits), the crystal growth is completed, and the old drawers are replaced with new ones. Once the customer extracts the crystals, the chambers are retrieved for future customers.

  16. Studies on the growth, spectral, structural, electrical, optical and mechanical properties of Uronium 3-carboxy-4-hydroxybenzenesulfonate single crystal for third-order nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Silambarasan, A.; Krishna Kumar, M.; Thirunavukkarasu, A.; Md Zahid, I.; Mohan Kumar, R.; Umarani, P. R.

    2015-05-01

    Organic Uronium 3-carboxy-4-hydroxybenzenesulfonate (UCHBS) nonlinear optical single crystal was grown by solution growth technique. The solubility and nucleation studies were performed for UCHBS at different temperatures 30, 35, 40, 45, 50 and 55 C. The crystal structure of UCHBS was elucidated from single crystal X-ray diffraction study. High resolution X-ray diffraction technique was employed to study the perfection and internal defects of UCHBS crystal. Infrared and Raman spectra were recorded to analyze the vibrational behavior of chemical bonds and its functional groups. The physico-chemical changes, stability and decomposition stages of the UCHBS compound were established by TG-DTA studies. The dielectric phenomenon of UCHBS crystal was studied at different temperatures with respect to frequency. Linear optical properties of transmittance, cut-off wavelength, band gap of UCHBS were found from UV-visible spectral studies. Third-order nonlinear optical susceptibility, nonlinear refractive index, nonlinear optical absorption coefficient values were measured by Z-scan technique. The mechanical properties of UCHBS crystal was studied by using Vicker's microhardness test. The growth features of UCHBS crystal were analyzed from etching studies.

  17. Plenum type crystal growth process

    DOEpatents

    Montgomery, Kenneth E. (Tracy, CA)

    1992-01-01

    Crystals are grown in a tank which is divided by a baffle into a crystal growth region above the baffle and a plenum region below the baffle. A turbine blade or stirring wheel is positioned in a turbine tube which extends through the baffle to generate a flow of solution from the crystal growing region to the plenum region. The solution is pressurized as it flows into the plenum region. The pressurized solution flows back to the crystal growing region through return flow tubes extending through the baffle. Growing crystals are positioned near the ends of the return flow tubes to receive a direct flow of solution.

  18. Plenum type crystal growth chamber

    SciTech Connect

    Montgomery, K.E.

    1990-12-31

    Crystals are grown in a tank which is divided by a baffle into a crystal growth region above the baffle and a plenum region below the baffle. A turbine blade or stirring wheel is positioned in a turbine tube which extends through the baffle to generate a flow of solution from the crystal growing region to the plenum region. The solution is pressurized as it flows into the plenum region. The pressurized solution flows back to the crystal growing region through return flow tubes extending through the baffle. Growing crystals are positioned near the ends of the return flow tubes to receive a direct flow of solution.

  19. Plenum type crystal growth chamber

    NASA Astrophysics Data System (ADS)

    Montgomery, K. E.

    1990-10-01

    Crystals are grown in a tank which is divided by a baffle into a crystal growth region above the baffle and a plenum region below the baffle. A turbine blade or stirring wheel is positioned in a turbine tube which extends through the baffle to generate a flow of solution from the crystal growing region to the plenum region. The solution is pressurized as it flows into the plenum region. The pressurized solution flows back to the crystal growing region through return flow tubes extending through the baffle. Growing crystals are positioned near the ends of the return flow tubes to receive a direct flow of solution.

  20. Crystal Growth Using MEPHISTO

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III

    1999-01-01

    The shuttle flight experiment "In Situ Monitoring of Crystal Growth Using MEPHISTO" was accomplished during STS-87 as part of the fourth flight of the United States Microgravity Payload (USMP-4), which was flown from November 19 to December 5, 1997. The data returned from that flight are just now beginning to yield quantitative results. This project is an international collaboration: the furnace system known as MEPHISTO was built in France by CNES (French National Space Agency) and CEA (French Atomic Energy Commission); the principal investigator, Prof. Reza Abbaschian, is from the University of Florida at Gainesville; and numerical and analytical modeling support includes collaborators from the University of New South Wales, Australia, the University of Wisconsin at Milwaukee, the National Institute of Standards and Technology, and the NASA Lewis Research Center. MEPHISTO is a French acronym that translates into English as Materials for the Study of Interesting Phenomena of Solidification on Earth and in Orbit. Since this was the fourth flight of the MEPHISTO furnace, the experiment is referred to as MEPHISTO-4. MEPHISTO-4 was a directional solidification experiment that studied the liquid-to-solid transformation of bismuth alloyed with tin. Directional solidification is a freezing technique common to the processing of the electronic materials used in integrated circuits and detectors, such as silicon and germanium. When liquids are frozen on Earth, they must be cooled. The cooling causes stirring because of density variations in the liquid. This stirring, known as natural convection, influences the quality of the resulting solid. During freezing, regions of high and low concentrations of tin are created. This introduces another important phenomenon: diffusion, or the movement by molecular action of matter from regions of high concentration to regions of lower concentration. In MEPHISTO-4, it is tin that diffuses from the high-concentration region in front of the solid-liquid interface to more distant low-concentration regions.

  1. Dynamically controlled crystal growth system

    NASA Technical Reports Server (NTRS)

    Bray, Terry L. (Inventor); Kim, Larry J. (Inventor); Harrington, Michael (Inventor); DeLucas, Lawrence J. (Inventor)

    2002-01-01

    Crystal growth can be initiated and controlled by dynamically controlled vapor diffusion or temperature change. In one aspect, the present invention uses a precisely controlled vapor diffusion approach to monitor and control protein crystal growth. The system utilizes a humidity sensor and various interfaces under computer control to effect virtually any evaporation rate from a number of different growth solutions simultaneously by means of an evaporative gas flow. A static laser light scattering sensor can be used to detect aggregation events and trigger a change in the evaporation rate for a growth solution. A control/follower configuration can be used to actively monitor one chamber and accurately control replicate chambers relative to the control chamber. In a second aspect, the invention exploits the varying solubility of proteins versus temperature to control the growth of protein crystals. This system contains miniature thermoelectric devices under microcomputer control that change temperature as needed to grow crystals of a given protein. Complex temperature ramps are possible using this approach. A static laser light scattering probe also can be used in this system as a non-invasive probe for detection of aggregation events. The automated dynamic control system provides systematic and predictable responses with regard to crystal size. These systems can be used for microgravity crystallization projects, for example in a space shuttle, and for crystallization work under terrestial conditions. The present invention is particularly useful for macromolecular crystallization, e.g. for proteins, polypeptides, nucleic acids, viruses and virus particles.

  2. Oscillatory growth for twisting crystals.

    PubMed

    Ibaraki, Shunsuke; Ise, Ryuta; Ishimori, Koichiro; Oaki, Yuya; Sazaki, Gen; Yokoyama, Etsuro; Tsukamoto, Katsuo; Imai, Hiroaki

    2015-05-18

    We demonstrate the oscillatory phenomenon for the twisting growth of a triclinic crystal through in situ observation of the concentration field around the growing tip of a needle by high-resolution phase-shift interferometry. PMID:25892326

  3. Czochralski crystal growth: Modeling study

    NASA Technical Reports Server (NTRS)

    Dudukovic, M. P.; Ramachandran, P. A.; Srivastava, R. K.; Dorsey, D.

    1986-01-01

    The modeling study of Czochralski (Cz) crystal growth is reported. The approach was to relate in a quantitative manner, using models based on first priniciples, crystal quality to operating conditions and geometric variables. The finite element method is used for all calculations.

  4. Interplay between size and crystal structure of molybdenum dioxide nanoparticles--synthesis, growth mechanism, and electrochemical performance.

    PubMed

    Koziej, Dorota; Rossell, Marta D; Ludi, Bettina; Hintennach, Andreas; Novk, Petr; Grunwaldt, Jan-Dierk; Niederberger, Markus

    2011-02-01

    A detailed study is presented on the formation of MoO(2) nanoparticles from the dissolution of the precursor to the final rodlike product, with a focus on the exploration of the inorganic reaction occurring ahead of the nucleation step, and interplay between size and crystal structure of MoO(2). In situ X-ray absorption spectroscopy experiments show that the crystallization and the growth process of MoO(2) nanorods is initiated by rapid reduction of the MoO(2) Cl(2) precursor in benzyl alcohol and acetophenone. This reaction triggers the nucleation of 2 nm MoO(2) particles with spherical shape and hexagonal crystal structure. The transformation from spheres into rods emerges as a complex process driven by oriented attachment. High-resolution transmission electron microscopy and X-ray diffraction results provide evidence that the 2 nm particles first aggregate into 5-20 nm-large oriented assemblies. The increase in particle size induces the phase transition from hexagonal to the less symmetrical monoclinic crystal structure, and finally the transformation into rods. Is it shown that electrodes for lithium-ion batteries based on MoO(2) nanorods have a long-term cycling life. The specific discharge capacity even after 200 cycles at a discharge rate of 1 C is about 300 Ah kg(-1) . PMID:21294267

  5. Ultraslow growth rates of giant gypsum crystals

    PubMed Central

    Van Driessche, A. E. S.; García-Ruíz, J. M.; Tsukamoto, K.; Patiño-Lopez, L. D.; Satoh, H.

    2011-01-01

    Mineralogical processes taking place close to equilibrium, or with very slow kinetics, are difficult to quantify precisely. The determination of ultraslow dissolution/precipitation rates would reveal characteristic timing associated with these processes that are important at geological scale. We have designed an advanced high-resolution white-beam phase-shift interferometry microscope to measure growth rates of crystals at very low supersaturation values. To test this technique, we have selected the giant gypsum crystals of Naica ore mines in Chihuahua, Mexico, a challenging subject in mineral formation. They are thought to form by a self-feeding mechanism driven by solution-mediated anhydrite-gypsum phase transition, and therefore they must be the result of an extremely slow crystallization process close to equilibrium. To calculate the formation time of these crystals we have measured the growth rates of the {010} face of gypsum growing from current Naica waters at different temperatures. The slowest measurable growth rate was found at 55 °C, 1.4 ± 0.2 × 10-5 nm/s, the slowest directly measured normal growth rate for any crystal growth process. At higher temperatures, growth rates increase exponentially because of decreasing gypsum solubility and higher kinetic coefficient. At 50 °C neither growth nor dissolution was observed indicating that growth of giant crystals of gypsum occurred at Naica between 58 °C (gypsum/anhydrite transition temperature) and the current temperature of Naica waters, confirming formation temperatures determined from fluid inclusion studies. Our results demonstrate the usefulness of applying advanced optical techniques in laboratory experiments to gain a better understanding of crystal growth processes occurring at a geological timescale. PMID:21911400

  6. High-purity silicon crystal growth

    NASA Technical Reports Server (NTRS)

    Ciszek, T.

    1984-01-01

    Crystal growth parameter effects on minority carrier lifetime and solar cell efficiencies were investigated using high purity techniques such as float zoning. Study objectives include the following: (1) optimize dopants and minority carrier lifetime in FZ material for high efficiency silicon solar cell applications; (2) improve the understanding of lifetime degradation mechanisms (point defects, impurities, thermal history, surface effects, etc.), and (3) crystallographic defect characterization of float zone and ribbon crystals via X-ray topography.

  7. Bulk crystal growth, optical, mechanical and ferroelectric properties of new semiorganic nonlinear optical and piezoelectric Lithium nitrate monohydrate oxalate single crystal

    NASA Astrophysics Data System (ADS)

    Dalal, Jyoti; Kumar, Binay

    2016-01-01

    New semiorganic nonlinear optical single crystals of Lithium nitrate oxalate monohydrate (LNO) were grown by slow evaporation solution technique. Single crystal X-ray diffraction study indicated that LNO crystal belongs to the triclinic system with space group P1. Various functional groups present in the material were identified by FTIR and Raman analysis. UV-vis study showed the high transparency of crystals with a wide band gap 5.01 eV. Various Optical constants i.e. Urbach energy (Eu), extinction coefficient (K), refractive index, optical conductivity, electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data which have applications in optoelectronic devices. A sharp emission peak was found at 438 nm in photoluminescence measurement, which revealed suitability of crystal for fabricating violet lasers. In dielectric studies, a peak has been observed at 33 C which is due to ferroelectric to paraelectric phase transition. Piezoelectric charge coefficients (d33 = 9.2 pC/N and g33) have been calculated, which make it a suitable for piezoelectric devices applications. In ferroelectric studies, a saturated loop was found in which the values of coercive field and remnant polarization were found to be 2.18 kV/cm and 0.39 ?C/cm2, respectively. Thermal behavior was studied by TGA and DSC studies. The relative SHG efficiency of LNO was found to be 1.2 times that of KDP crystal. In microhardness study, Meyer's index value was found to be 1.78 which revealed its soft nature. These optical, dielectric, piezoelectric, ferroelectric, mechanical and non-linear optical properties of grown crystal establish the usefulness of this material for optoelectronics, non-volatile memory and piezoelectric devices applications.

  8. A study of crystal growth by solution technique

    NASA Technical Reports Server (NTRS)

    Lal, R. B.

    1981-01-01

    The mechanism of crystal growth by solution technique was studied. A low temperature solution crystal growth setup was developed. Crystals of triglycine sulfate (TGS) were grown using this arrangement. Some additional tasks were performed toward fabrication of experiments for future space flight.

  9. Two puzzling aspects of protein crystal growth

    NASA Technical Reports Server (NTRS)

    Grant, M. L.; Saville, D. A.

    1988-01-01

    A study is presented of several mechanisms which may reduce crystal growth rates and or terminate crystal growth. It is found that salt gradients which change the local chemical potential of the protein are insufficient to account for the slow crystal growth rates which have been reported. Contaminants which adsorb protein from solution may reduce the effective protein concentration, but the impurity's concentration and its affinity for protein are unknown. Association of protein molecules in bulk solution can reduce the monomer concentration significantly, but extant theory and experiment are not sensitive enough to determine the actual concentration of aggregates in solution. For systems of interest, shear-induced effects were found to be too weak to interfere with normal binding of incoming protein molecules. Although we found that most crystal growth occurs in a regime where both interfacial kinetics and diffusion influence crystal growth, the role of mass transfer rates on the terminal size of crystals is unknown, primarily because no data exist which cover the size range of interest (0.1 mm to 1 mm in length).

  10. Hydrothermal Growth of Polyscale Crystals

    NASA Astrophysics Data System (ADS)

    Byrappa, Kullaiah

    In this chapter, the importance of the hydrothermal technique for growth of polyscale crystals is discussed with reference to its efficiency in synthesizing high-quality crystals of various sizes for modern technological applications. The historical development of the hydrothermal technique is briefly discussed, to show its evolution over time. Also some of the important types of apparatus used in routine hydrothermal research, including the continuous production of nanosize crystals, are discussed. The latest trends in the hydrothermal growth of crystals, such as thermodynamic modeling and understanding of the solution chemistry, are elucidated with appropriate examples. The growth of some selected bulk, fine, and nanosized crystals of current technological significance, such as quartz, aluminum and gallium berlinites, calcite, gemstones, rare-earth vanadates, electroceramic titanates, and carbon polymorphs, is discussed in detail. Future trends in the hydrothermal technique, required to meet the challenges of fast-growing demand for materials in various technological fields, are described. At the end of this chapter, an Appendix 18.A containing a more or less complete list of the characteristic families of crystals synthesized by the hydrothermal technique is given with the solvent and pressure-temperature (PT) conditions used in their synthesis.

  11. A study of crystal growth by solution technique. [triglycine sulfate single crystals

    NASA Technical Reports Server (NTRS)

    Lal, R. B.

    1979-01-01

    The advantages and mechanisms of crystal growth from solution are discussed as well as the effects of impurity adsorption on the kinetics of crystal growth. Uncertainities regarding crystal growth in a low gravity environment are examined. Single crystals of triglycine sulfate were grown using a low temperature solution technique. Small components were assembled and fabricated for future space flights. A space processing experiment proposal accepted by NASA for the Spacelab-3 mission is included.

  12. Biomolecular Modification of Inorganic Crystal Growth

    NASA Astrophysics Data System (ADS)

    De Yoreo, James J.

    2007-06-01

    The fascinating shapes and hierarchical designs of biomineralized structures are an inspiration to materials scientists because of the potential they suggest for biomolecular control over materials synthesis. Conversely, the failure to prevent or limit tissue mineralization in the vascular, skeletal, and urinary systems is a common source of disease. Understanding the mechanisms by which organisms direct or limit crystallization has long been a central challenge to the biomineralization community. One prevailing view is that mineral-associated macromolecules are responsible for either inhibiting crystallization or initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineralizing surfaces. In particular, biomolecules that present carboxyl groups to the growing crystal have been implicated as primary modulators of growth. Here we review the results from a combination of in situ atomic force microscopy (AFM) and molecular modeling (MM) studies to investigate the effect of specific interactions between carboxylate-rich biomolecules and atomic steps on crystal surfaces during the growth of carbonates, oxalates and phosphates of calcium. Specifically, we how the growth kinetics and morphology depend on the concentration of additives that include citrate, simple amino acids, synthetic Asp-rich polypeptides, and naturally occurring Asp-rich proteins found in both functional and pathological mineral tissues. The results reveal a consistent picture of shape modification in which stereochemical matching of modifiers to specific atomic steps drives shape modification. Inhibition and other changes in growth kinetics are shown to be due to a range of mechanisms that depend on chemistry and molecular size. Some effects are well described by classic crystal growth theories, but others, such as step acceleration due to peptide charge and hydrophylicity, were previously unrealized. Finally, we show that the molecular scale observations are well correlated with macroscopic growth rate data.

  13. Biomolecular Modification of Inorganic Crystal Growth

    SciTech Connect

    De Yoreo, J J

    2007-04-27

    The fascinating shapes and hierarchical designs of biomineralized structures are an inspiration to materials scientists because of the potential they suggest for biomolecular control over materials synthesis. Conversely, the failure to prevent or limit tissue mineralization in the vascular, skeletal, and urinary systems is a common source of disease. Understanding the mechanisms by which organisms direct or limit crystallization has long been a central challenge to the biomineralization community. One prevailing view is that mineral-associated macromolecules are responsible for either inhibiting crystallization or initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineralizing surfaces. In particular, biomolecules that present carboxyl groups to the growing crystal have been implicated as primary modulators of growth. Here we review the results from a combination of in situ atomic force microscopy (AFM) and molecular modeling (MM) studies to investigate the effect of specific interactions between carboxylate-rich biomolecules and atomic steps on crystal surfaces during the growth of carbonates, oxalates and phosphates of calcium. Specifically, we how the growth kinetics and morphology depend on the concentration of additives that include citrate, simple amino acids, synthetic Asp-rich polypeptides, and naturally occurring Asp-rich proteins found in both functional and pathological mineral tissues. The results reveal a consistent picture of shape modification in which stereochemical matching of modifiers to specific atomic steps drives shape modification. Inhibition and other changes in growth kinetics are shown to be due to a range of mechanisms that depend on chemistry and molecular size. Some effects are well described by classic crystal growth theories, but others, such as step acceleration due to peptide charge and hydrophylicity, were previously unrealized. Finally, we show that the molecular scale observations are well correlated with macroscopic growth rate data.

  14. Observable Protein Crystal Growth Apparatus

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This diagram shows a cross sectrion of the fluid volume of an individual cell in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

  15. (PCG) Protein Crystal Growth Canavalin

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Canavalin. The major storage protein of leguminous plants and a major source of dietary protein for humans and domestic animals. It is studied in efforts to enhance nutritional value of proteins through protein engineerings. It is isolated from Jack Bean because of it's potential as a nutritional substance. Principal Investigator on STS-26 was Alex McPherson.

  16. Optical analysis of crystal growth

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Passeur, Andrea; Harper, Sabrina

    1994-01-01

    Processing and data reduction of holographic images from Spacelab presents some interesting challenges in determining the effects of microgravity on crystal growth processes. Evaluation of several processing techniques, including the Computerized Holographic Image Processing System and the image processing software ITEX150, will provide fundamental information for holographic analysis of the space flight data.

  17. Bridgman growth of large-aperture yttrium calcium oxyborate crystal

    SciTech Connect

    Wu, Anhua; Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei

    2012-09-15

    Highlights: ► YCOB is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. ► Large size crystal growth is key technology question for YCOB crystal. ► YCOB crystals 3 in. in diameter were grown with modified vertical Bridgman method. ► It is a more effective growth method to obtain large size and high quality YCOB crystal. -- Abstract: Large-aperture yttrium calcium oxyborate YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.

  18. Crystal growth in fused solvent systems

    NASA Technical Reports Server (NTRS)

    Ulrich, D. R.; Noone, M. J.; Spear, K. E.; White, W. B.; Henry, E. C.

    1973-01-01

    Research is reported on the growth of electronic ceramic single crystals from solution for the future growth of crystals in a microgravity environment. Work included growth from fused or glass solvents and aqueous solutions. Topics discussed include: crystal identification and selection; aqueous solution growth of triglycine sulphate (TGS); and characterization of TGS.

  19. Growth and dielectric, mechanical, thermal and etching studies of an organic nonlinear optical L-arginine trifluoroacetate (LATF) single crystal

    SciTech Connect

    Arjunan, S.; Mohan Kumar, R.; Mohan, R.; Jayavel, R.

    2008-08-04

    L-arginine trifluoroacetate, an organic nonlinear optical material, has been synthesized from aqueous solution. Bulk single crystal of dimension 57 mm x 5 mm x 3 mm has been grown by temperature lowering technique. Powder X-ray diffraction studies confirmed the monoclinic structure of the grown L-arginine trifluoroacetate crystal. Linear optical property of the grown crystal has been studied by UV-vis spectrum. Dielectric response of the L-arginine trifluoroacetate crystal was analysed for different frequencies and temperatures in detail. Microhardness study on the sample reveals that the crystal possesses relatively higher hardness compared to many organic crystals. Thermal analyses confirmed that the L-arginine trifluoroacetate material is thermally stable upto 212 deg. C. The etching studies have been performed to assess the perfection of the L-arginine trifluoroacetate crystal. Kurtz powder second harmonic generation test confirms the nonlinear optical properties of the as-grown L-arginine trifluoroacetate crystal.

  20. Crystal growth of drug materials by spherical crystallization

    NASA Astrophysics Data System (ADS)

    Szab-Rvsz, P.; Hasznos-Nezdei, M.; Farkas, B.; Gcz?, H.; Pintye-Hdi, K.; Er?s, I.

    2002-04-01

    One of the crystal growth processes is the production of crystal agglomerates by spherical crystallization. Agglomerates of drug materials were developed by means of non-typical (magnesium aspartate) and typical (acetylsalicylic acid) spherical crystallization techniques. The growth of particle size and the spherical form of the agglomerates resulted in formation of products with good bulk density, flow, compactibility and cohesivity properties. The crystal agglomerates were developed for direct capsule-filling and tablet-making.

  1. Compact Apparatus For Growth Of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C.; Miller, Teresa Y.

    1991-01-01

    Compact apparatus proposed specifically for growth of protein crystals in microgravity also used in terrestrial laboratories to initiate and terminate growth at prescribed times automatically. Has few moving parts. Also contains no syringes difficult to clean, load, and unload and introduces contaminant silicon grease into crystallization solution. After growth of crystals terminated, specimens retrieved and transported simply.

  2. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1988-01-01

    The solubility and growth of the protein canavalin, and the application of the schlieren technique to study fluid flow in protein crystal growth systems were investigated. These studies have resulted in the proposal of a model to describe protein crystal growth and the preliminary plans for a long-term space flight experiment. Canavalin, which may be crystallized from a basic solution by the addition of hydrogen (H+) ions, was shown to have normal solubility characteristics over the range of temperatures (5 to 25 C) and pH (5 to 7.5) studies. The solubility data combined with growth rate data gathered from the seeded growth of canavalin crystals indicated that the growth rate limiting step is a screw dislocation mechanism. A schlieren apparatus was constructed and flow patterns were observed in Rochelle salt (sodium potassium tartrate), lysozyme, and canavalin. The critical parameters were identified as the change in density with concentration (dp/dc) and the change in index of refraction with concentration (dn/dc). Some of these values were measured for the materials listed. The data for lyrozyme showed non-linearities in plots of optical properties and density vs. concentration. In conjunction with with W. A. Tiller, a model based on colloid stability theory was proposed to describe protein crystallization. The model was used to explain observations made by ourselves and others. The results of this research has lead to the development for a preliminary design for a long-term, low-g experiment. The proposed apparatus is univeral and capable of operation under microprocessor control.

  3. Crystal Growth Research in Space

    NASA Technical Reports Server (NTRS)

    Crouch, R. K.; Fripp, A. L.

    1985-01-01

    The objectives of this work are to develop growth techniques and theory leading to improved bulk growth of semiconductor single crystals. Ground based experiments will be complemented by experiments carried out in the low-g environment provided by the space shuttle. Analytical studies and laboratory investigations are being conducted to better define the causes of crystalline defects and inhomogeneities. The compound semiconductor lead-tin-telluride is being used as the modeling material. Theoretical techniques are being developed to predict the thermal and solutal fields which are present during bulk growth from a melt. Techniques for measuring the thermophysical properties of semiconductors at high temperatures have been developed. During the past year electrochemical etching techniques have been developed for delineation of inhomogeneous regions in crystals. Thermal diffusivity measurements have been completed for the solid and liquid phases of PbTe and PbSnTe. Preliminary results have been obtained on the effects on crystal morphology of gravity, interface shape and interaction between the melt and the container.

  4. Efg Crystal Growth Apparatus And Method

    DOEpatents

    Mackintosh, Brian H. (Concord, MA); Ouellette, Marc (Nashua, NH)

    2003-05-13

    An improved mechanical arrangement controls the introduction of silicon particles into an EFG (Edge-defined Film-fed Growth) crucible/die unit for melt replenishment during a crystal growth run. A feeder unit injects silicon particles upwardly through a center hub of the crucible/die unit and the mechanical arrangement intercepts the injected particles and directs them so that they drop into the melt in a selected region of the crucible and at velocity which reduces splashing, whereby to reduce the likelihood of interruption of the growth process due to formation of a solid mass of silicon on the center hub and adjoining components. The invention also comprises use of a Faraday ring to alter the ratio of the electrical currents flowing through primary and secondary induction heating coils that heat the crucible die unit and the mechanical arrangement.

  5. Sealed silica pressure ampoules for crystal growth

    NASA Technical Reports Server (NTRS)

    Holland, L. R.

    1984-01-01

    The properties of vitreous silica and the mechanics of thick walled pressure vessels are reviewed with regard to the construction of sealed silica crucibles such as are used in the growth of mercury-cadmium telluride crystals. Data from destructive rupture tests are reported, failure modes discussed, and recommendations for design given. Ordinary commercial clear vitreous silica from flame fused quartz can withstand a surface stress of 20 MPa or more in this application.

  6. Crystal growth and annealing method and apparatus

    DOEpatents

    Gianoulakis, Steven E. (Albuquerque, NM); Sparrow, Robert (North Brookfield, MA)

    2001-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

  7. Protein crystal growth in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1988-01-01

    Protein crystal growth is a major experimental problem and is the bottleneck in widespread applications of protein crystallography. Research efforts now being pursued and sponsored by NASA are making fundamental contributions to the understanding of the science of protein crystal growth. Microgravity environments offer the possibility of performing new types of experiments that may produce a better understanding of protein crystal growth processes and may permit growth environments that are more favorable for obtaining high quality protein crystals. A series of protein crystal growth experiments using the space shuttle was initiated. The first phase of these experiments was focused on the development of micro-methods for protein crystal growth by vapor diffusion techniques, using a space version of the hanging drop method. The preliminary space experiments were used to evolve prototype hardware that will form the basis for a more advanced system that can be used to evaluate effects of gravity on protein crystal growth.

  8. Effect of L-tyrosine on the solubility, growth, structural, optical, SHG, dielectric and mechanical properties of KDP single crystals

    NASA Astrophysics Data System (ADS)

    Boopathi, K.; Ramasamy, P.

    2014-11-01

    The effect of L-tyrosine doping on various properties of potassium dihydrogen phosphate single crystals grown by slow cooling along with seed rotation method has been investigated. The crystalline nature of the grown crystals has been analyzed by powder X-ray diffraction analysis. The presence of various functional groups is identified by Fourier transform spectroscopy. Optical transparency of the grown crystals has been analyzed by UV-Vis-NIR spectral analysis. 90% of transmittance was observed for L-tyrosine added potassium dihydrogen phosphate crystal. Thermal stability and micro hardness measurement was examined by TG-DTA and Vickers microhardness study. Second harmonic study was carried out using Kurtz and Perry method. Dielectric and laser damage threshold studies were carried out.

  9. Growth, thermal, dielectric and mechanical properties of L-phenylalanine-benzoic acid: A nonlinear optical single crystal

    NASA Astrophysics Data System (ADS)

    Tamilselvan, S.; Vimalan, M.; Vetha Potheher, I.; Rajasekar, S.; Jeyasekaran, R.; Antony Arockiaraj, M.; Madhavan, J.

    2013-10-01

    An efficient amino acid family nonlinear optical single crystal L-phenylalanine-benzoic acid (LPB) was conveniently grown by slow evaporation technique at room temperature. The crystal system and the lattice parameters were analyzed by single crystal X-ray diffraction studies. The grown crystal has excellent transmission in the entire visible region and its lower cut-off wavelength was found to be 248 nm. The SHG efficiency of the grown crystal was found to be 1.6 times higher than that of KDP crystal. The Laser damage threshold value of LPB has been found to be 6.5 GW/cm2. The sample was thermally stable up to 134 C. Microhardness, dielectric and AC/DC conductivity measurements were made along (0 0 1) plane and reported for the first time. Microhardness studies revealed that the sample belongs to hard nature. Frequency dependent dielectric constant was measured for different temperatures and found maximum dielectric constant of 14 for 363 K. Photoconductivity studies of LPB divulged its negative photoconducting nature.

  10. Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua (Inventor)

    2013-01-01

    The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

  11. Protein crystal growth; Proceedings of the First International Conference, Stanford University, CA, August 14-16, 1985

    NASA Technical Reports Server (NTRS)

    Feigelson, R. S. (Editor)

    1986-01-01

    Papers are presented on mechanisms of nucleation and growth of protein crystals, the role of purification in the crystallization of proteins and nucleic acids, and the effect of chemical impurities in polyethylene glycol on macromolecular crystallization. Also considered are growth kinetics of tetragonal lysozyme crystals, thermodynamic and kinetic considerations for crystal growth of complex molecules from solution, protein single-crystal growth under microgravity, and growth of organic crystals in a microgravity environment. Papers are also presented on preliminary investigations of protein crystal growth using the Space Shuttle, convective diffusion in protein crystal growth, and the growth and characterization of membrane protein crystals.

  12. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1991-01-01

    The objective of this research is to study the effect of low gravity on the growth of protein crystals and those parameters which will affect growth and crystal quality. The application of graphoepitaxy (artificial epitaxy) to proteins is detailed. The development of a method for the control of nucleation is discussed. The factor affecting the morphology of isocitrate lyase crystals is presented.

  13. Bending nanowire growth in solution by mechanical disturbance.

    PubMed

    Wang, Chao; Wei, Yujie; Jiang, Hongyuan; Sun, Shouheng

    2010-06-01

    The effect of mechanical disturbance on one-dimensional nanocrystal growth in solution phase is investigated by controlled growth of Au nanowires with and without stirring. While a static growth leads to straight, single-crystal Au nanowires, the mechanic disturbance by stirring tends to bend the nanowire growth, yielding nanowire kinks abundant in various types of crystal defects including dislocations, twin boundaries, and grain boundaries. Mechanical modeling and analysis is introduced to elucidate the nanowire growth mechanisms in these two conditions. The provided fundamental understanding of crystal defect formation at nanoscale could be applied to guide the development of advanced nanomaterials with shape control and unique mechanical properties. PMID:20499890

  14. Hanging drop crystal growth apparatus

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J. (Inventor); Witherow, William K. (Inventor); Carter, Daniel C. (Inventor); Bugg, Charles E. (Inventor); Suddath, Fred L. (Inventor)

    1990-01-01

    This invention relates generally to control systems for controlling crystal growth, and more particularly to such a system which uses a beam of light refracted by the fluid in which crystals are growing to detect concentration of solutes in the liquid. In a hanging drop apparatus, a laser beam is directed onto drop which refracts the laser light into primary and secondary bows, respectively, which in turn fall upon linear diode detector arrays. As concentration of solutes in drop increases due to solvent removal, these bows move farther apart on the arrays, with the relative separation being detected by arrays and used by a computer to adjust solvent vapor transport from the drop. A forward scattering detector is used to detect crystal nucleation in drop, and a humidity detector is used, in one embodiment, to detect relative humidity in the enclosure wherein drop is suspended. The novelty of this invention lies in utilizing angular variance of light refracted from drop to infer, by a computer algorithm, concentration of solutes therein. Additional novelty is believed to lie in using a forward scattering detector to detect nucleating crystallites in drop.

  15. Unidirectional growth of L-asparagine monohydrate single crystal: First time observation of NLO nature and other studies of crystalline perfection, optical, mechanical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Shakir, Mohd.; Riscob, B.; Maurya, K. K.; Ganesh, V.; Wahab, M. A.; Bhagavannarayana, G.

    2010-10-01

    L-asparagine monohydrate (LAM), a new amino acid single crystal, was grown by slow evaporation solution technique (SEST) as well as by recently invented Sankaranarayanan-Ramasamy (SR) method in aqueous medium. Using SR method, LAM single crystal of diameter 18 mm and length 52 mm was grown for the first time. The growth conditions were optimized and the maximum growth rate of 1.0 mm per day was observed for the SR crystal. The crystal structure was confirmed by powder XRD. The crystalline perfection was assessed by high resolution XRD and etching studies and found that the quality of the SR crystal is better than the SEST crystal. The UV-vis-NIR spectroscopic study revealed that the SR crystal has good optical transparency than that of SEST crystal. The relative second harmonic generation efficiency was measured and found to be 0.35 times to that of KDP. The laser damage threshold (LDT) was measured and found that the SR crystal has higher LDT value (5.76 GW cm -2) than SEST crystal (4.75 GW cm -2). The Vickers's microhardness and dielectric studies were also carried out and discussed.

  16. Controlled growth of semiconductor crystals

    DOEpatents

    Bourret-Courchesne, Edith D. (Richmond, CA)

    1992-01-01

    A method for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B.sub.x O.sub.y are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T.sub.m1 of the oxide of boron (T.sub.m1 =723.degree. K. for boron oxide B.sub.2 O.sub.3), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T.sub.m2 of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm.sup.2. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 .mu.m.

  17. Controlled growth of semiconductor crystals

    DOEpatents

    Bourret-Courchesne, E.D.

    1992-07-21

    A method is disclosed for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B[sub x]O[sub y] are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T[sub m1] of the oxide of boron (T[sub m1]=723 K for boron oxide B[sub 2]O[sub 3]), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T[sub m2] of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm[sup 2]. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 [mu]m. 7 figs.

  18. Reversed Crystal Growth of RHO Zeolitic Imidazolate Framework (ZIF)

    PubMed Central

    Self, Katherine; Telfer, Michael; Greer, Heather F.

    2015-01-01

    Abstract RHO zeolitic imidazolate framework (ZIF), Zn1.33(O.OH)0.33(nim)1.167(pur), crystals with a rhombic dodecahedral morphology were synthesized by a solvothermal process. The growth of the crystals was studied over time using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X‐ray diffraction (PXRD) and Brunauer–Emmett–Teller (BET) analyses, and a reversed crystal growth mechanism was revealed. Initially, precursor materials joined together to form disordered aggregates, which then underwent surface recrystallization forming a core–shell structure, in which a disordered core is encased in a layer of denser, less porous crystal. When the growth continued, the shell became less and less porous, until it was a layer of true single crystal. The crystallization then extended from the surface to the core over a six‐week period until, eventually, true single crystals were formed. PMID:26577835

  19. Physical phenomena related to crystal growth in the space environment

    NASA Technical Reports Server (NTRS)

    Chu, T. L.

    1973-01-01

    The mechanism of crystal growth which may be affected by the space environment was studied. Conclusions as to the relative technical and scientific advantages of crystal growth in space over earth bound growth, without regard to economic advantage, were deduced. It was concluded that the crucibleless technique will most directly demonstrate the unique effects of the greatly reduced gravity in the space environment. Several experiments, including crucibleless crystal growth using solar energy and determination of diffusion coefficients of common dopants in liquid silicon were recommended.

  20. Cluster Mechanism of Homogeneous Crystallization (Computer Study)

    NASA Astrophysics Data System (ADS)

    Belashchenko, D. K.

    2008-12-01

    A molecular dynamics (MD) study of homogeneous crystallization of liquid rubidium is conducted with an inter-particle pair potential. The equilibrium crystallization temperature of the models was 313 K. Models consisted of 500, 998, and 1968 particles in a basic cube. The main investigation method was as follows: to detect (along the MD run) the atoms with Voronoi polyhedrons (VP) of 0608 type (“0608-atoms,” as in a bcc crystal) and to detect the bound groups of 0608-atoms (“0608-clusters”) that could play the role of the seeds in crystallization. Full crystallization was observed only at temperatures lower than 185 K with the creation of a predominant bcc crystal. The crystallization mechanism of Rb models differs drastically from the mechanism adopted in classical nucleation theory. It consists of the growth of the total number of 0608-atoms on cooling and the formation of 0608-clusters, analogous to the case of coagulation of solute for a supersaturated two-component solution. At the first stage of the process the clusters have a very loose structure (something like medusa or octopus with many tentacles) and include inside atoms with other Voronoi polyhedron types. The dimensions of clusters quickly increase and approach those of the basic cube. 0608-atoms play the leading role in the crystallization process and activate the transition of the atoms involved in the 0608-coordination. The fast growth of the maximum cluster begins after it attains a critical size (about 150 0608-atoms). The fluctuations of cluster sizes are very important in the creation of a 0608-cluster of critical (threshold) size. These fluctuations are especially large in the interval from 180 K to 185 K.

  1. Growth, structural, optical and mechanical studies on acid mixed glycine metal salt (GABN) crystal as potential NLO material

    NASA Astrophysics Data System (ADS)

    Khandpekar, Mahendra M.; Dongare, Shailesh S.; Patil, Shirish B.; Pati, Shankar P.

    2012-03-01

    Transparent crystals of ?-glycine with ammonium nitrate and barium nitrate (GABN) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 11 7 4 mm 3 have been obtained in about 3-4 weeks time. The solubility of GABN has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 7.317 A.U, b = 12.154 A.U and c = 5.468 A.U with a unit cell volume 486.35 (A.U) 3. The presence of chemical components/groups has been identified by CHN, EDAX and NMR analysis. Comparative IR and Raman studies indicate a molecule with a lack of centre of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV Studies. Using a Nd-YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GABN is found to be 1.406 times of that of standard KDP. On exposure to light the GABN crystals are found to exhibit negative photoconductivity. I-V characteristics, SEM studies, dielectrics studies, and Vickers micro hardness measurement have been carried out.

  2. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1990-01-01

    The effect of low gravity on the growth of protein crystals and those parameters which will affect growth and crystal quality was studied. The proper design of the flight hardware and experimental protocols are highly dependent on understanding the factors which influence the nucleation and growth of crystals of biological macromolecules. Thus, those factors are investigated and the body of knowledge which has been built up for small molecule crystallization. These data also provide a basis of comparison for the results obtained from low-g experiments. The flows around growing crystals are detailed. The preliminary study of the growth of isocitrate lyase, the crystal morphologies found and the preliminary x ray results are discussed. The design of two apparatus for protein crystal growth by temperature control are presented along with preliminary results.

  3. Measurable characteristics of lysozyme crystal growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2005-01-01

    The behavior of protein crystal growth is estimated from measurements performed at both the microscopic and molecular levels. In the absence of solutal flow, it was determined that a model that balances the macromolecular flux toward the crystal surface with the flux of the crystal surface well characterizes crystal growth observed using microscopic methods. Namely, it was determined that the model provides accurate estimates for the crystal-growth velocities upon evaluation of crystal-growth measurements obtained in time. Growth velocities thus determined as a function of solution supersaturation were further interpreted using established deterministic models. From analyses of crystal-growth velocities, it was found that the mode of crystal growth varies with respect to increasing solution supersaturation, possibly owing to kinetic roughening. To verify further the hypothesis of kinetic roughening, crystal growth at the molecular level was examined using atomic force microscopy (AFM). From the AFM measurements, it was found that the magnitude of surface-height fluctuations, h(x), increases with increasing solution supersaturation. In contrast, the estimated characteristic length, xi, decreases rapidly upon increasing solution supersaturation. It was conjectured that the magnitude of both h(x) and xi could possibly determine the mode of crystal growth. Although the data precede any exact theory, the non-critical divergence of h(x) and xi with respect to increasing solution supersaturation was nevertheless preliminarily established. Moreover, approximate models to account for behavior of both h(x) and xi are also presented.

  4. Modelling the growth of feather crystals

    SciTech Connect

    Wood, H.J.; Hunt, J.D.; Evans, P.V.

    1997-02-01

    An existing numerical model of dendritic growth has been adapted to model the growth of twinned columnar dendrites (feather crystals) in a binary aluminium alloy, Examination of the effect of dendrite tip angle on growth has led to an hypothesis regarding the stability of a pointed tip morphology in these crystals.

  5. Compact spaceflight solution crystal-growth system

    NASA Technical Reports Server (NTRS)

    Trolinger, James D.; Lal, Ravindra; Vikram, Chandra; Witherow, William

    1991-01-01

    A versatile, miniaturized, stand alone, crystal solution growth chamber design is presented which is based on fiber optics, diode lasers, and holographic optical elements in conjunction with knowledge gained from previous Spacelab work. Diagnostics instrumentation is based on a crystal growth monitor, a growth/dissolution monitor with feedback, solution diagnostics, multiple wavelength holography, and single wavelength or color Schlieren with video recording.

  6. Analytics of crystal growth in space

    NASA Technical Reports Server (NTRS)

    Wilcox, W. R.; Chang, C. E.; Shlichta, P. J.; Chen, P. S.; Kim, C. K.

    1974-01-01

    Two crystal growth processes considered for spacelab experiments were studied to anticipate and understand phenomena not ordinarily encountered on earth. Computer calculations were performed on transport processes in floating zone melting and on growth of a crystal from solution in a spacecraft environment. Experiments intended to simulate solution growth at micro accelerations were performed.

  7. Mechanically tunable photonic crystal lens

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Tamma, V. A.; Lee, J.-B.; Park, W.

    2010-08-01

    We designed, fabricated and characterized MEMS-enabled mechanically-tunable photonic crystal lens comprised of 2D photonic crystal and symmetrical electro-thermal actuators. The 2D photonic crystal was made of a honeycomb-lattice of 340 nm thick, 260 nm diameter high-index silicon rods embedded in low-index 10 ?m thick SU-8 cladding. Silicon input waveguide and deflection block were also fabricated for light in-coupling and monitoring of focused spot size, respectively. When actuated, the electro-thermal actuators induced mechanical strain which changed the lattice constant of the photonic crystal and consequently modified the photonic band structure. This in turn modified the focal-length of the photonic crystal lens. The fabricated device was characterized using a tunable laser (1400~1602 nm) and an infrared camera during actuation. At the wavelength of 1450 nm, the lateral light spot size observed at the deflection block gradually decreased 40%, as applied current increased from 0 to 0.7 A, indicating changes in focal length in response to the mechanical stretching.

  8. (PCG) Protein Crystal Growth Horse Serum Albumin

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Horse Serum Albumin crystals grown during the USML-1 (STS-50) mission's Protein Crystal Growth Glovebox Experiment. These crystals were grown using a vapor diffusion technique at 22 degrees C. The crystals were allowed to grow for nine days while in orbit. Crystals of 1.0 mm in length were produced. The most abundant blood serum protein, regulates blood pressure and transports ions, metabolites, and therapeutic drugs. Principal Investigator was Edward Meehan.

  9. A study of the growth rates and growth habits of ice crystals in a solution of antifreeze (glyco) proteins

    NASA Astrophysics Data System (ADS)

    Li, Qianzhong; Luo, Liaofu

    1996-12-01

    The mechanism of the antifreeze glycoprotein/antifreeze protein interaction on the surface of ice is analyzed. The theory of ice crystal growth in an AF(G)P solution is presented. A quantitative calculation of the growth rates for gain growth has been obtained. The anisotropic growth habits and growth rates of ice crystals in an AF(G)P solution are explained.

  10. Crystallization seeds favour crystallization only during initial growth

    PubMed Central

    Allahyarov, E.; Sandomirski, K.; Egelhaaf, S.U.; Löwen, H.

    2015-01-01

    Crystallization represents the prime example of a disorder–order transition. In realistic situations, however, container walls and impurities are frequently present and hence crystallization is heterogeneously seeded. Rarely the seeds are perfectly compatible with the thermodynamically favoured crystal structure and thus induce elastic distortions, which impede further crystal growth. Here we use a colloidal model system, which not only allows us to quantitatively control the induced distortions but also to visualize and follow heterogeneous crystallization with single-particle resolution. We determine the sequence of intermediate structures by confocal microscopy and computer simulations, and develop a theoretical model that describes our findings. The crystallite first grows on the seed but then, on reaching a critical size, detaches from the seed. The detached and relaxed crystallite continues to grow, except close to the seed, which now prevents crystallization. Hence, crystallization seeds facilitate crystallization only during initial growth and then act as impurities. PMID:25975451

  11. Factors affecting the nascent structure and morphology of polyethylene obtained by heterogeneous ziegler-natta catalyst. III. Crystal morphology and growth mechanism

    NASA Astrophysics Data System (ADS)

    Muñoz-Escalona, A.; Parada, A.

    1980-02-01

    Following the change of morphology during growth of the nascent, crystalline polyethylene during the polymerization at different times and under different polymerization conditions, it was possible to show how a variety of morphologies already described in the literature are linked. Initially the polymer grows on the catalyst surface in form of dots which reach a diameter between 200-5000 Å depending on the polymerization conditions and on the activity of the catalyst active sites. As the polymerization continues, the dots grown and may cover the catalyst surface in case of a high enough concentration of growing polymer chains. The length of this initial period depends on the polymerization conditions. In the next reaction stage an increase of the polymerization rate occurs, due to fracturing of the catalyst particles, caused by mechanical effects from the growing polymer. If the polymerization continues at a high rate, a globular morphology appears with diameters ranging finally from 0.5 to 1.6 μm. Finally, the globular morphology goes to wormlike morphology as the polymerization continues. The wormlike morphology consists of a complex aggregation of ribbonlike crystal elements. The widths and thicknesses of the lamellae are irregular and range between 400-2000 Å and around 215 Å, respectively. The fibrillar cobweb morphology which is also observed results from a secondary effect due to stretching of the growing polymer mass. A folded-chain macroconformation is assumed for all crystals.

  12. Advanced protein crystal growth programmatic sensitivity study

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The purpose of this study is to define the costs of various APCG (Advanced Protein Crystal Growth) program options and to determine the parameters which, if changed, impact the costs and goals of the programs and to what extent. This was accomplished by developing and evaluating several alternate programmatic scenarios for the microgravity Advanced Protein Crystal Growth program transitioning from the present shuttle activity to the man tended Space Station to the permanently manned Space Station. These scenarios include selected variations in such sensitivity parameters as development and operational costs, schedules, technology issues, and crystal growth methods. This final report provides information that will aid in planning the Advanced Protein Crystal Growth Program.

  13. MCT crystal growth. Final report

    SciTech Connect

    Baird, J.K.

    1988-02-01

    Convection and segregation in directional solidification and crystal growth by the Bridgman-Stockbarger technique are traditionally treated by assuming axisymmetric thermal condition on the ampoule wall. It is, however, difficult to achieve such a condition in an experimental setup. Any deviation from an axisymmetric temperature field on the wall of a vertical ampoule represents a horizontal temperature gradient. The horizontal density gradient that results from thermal expansion in the melt under this condition must lead on earth to some buoyance-driven convection, no matter what the axial (vertical) temperature distribution that is imposed on the melt. The magnitude of such convective flows for conditions representative of the MSFC mercury-cadmium-telluride (MCT) Bridgman setup is studied.

  14. Investigation of crystal growth from solutions

    NASA Technical Reports Server (NTRS)

    Miyagawa, I.

    1975-01-01

    Growth of organic compounds from solution, in particular Rochelle salt and triglycine sulphate, was investigated. Ground-based experiments showed that gravity-driven convection currents in the growth solution influenced defect production in crystals, degraded ferroelectric quality, and indicated that an experiment done in a zero-gravity environment would be beneficial. A crystal of Rochelle salt was grown on board Skylab-4. The quality of this crystal was compared to earth-grown crystals and its unusual features were studied. A typical defect produced in this convection-free environment was a long straight tube extending in the direction of the c crystal axis. These tubes were much longer and more regularly arranged than in similar earth-grown crystals. The crystal was actually several crystals with corresponding axes parallel to each other. Ferroelectric hysteresis experiments showed that some parts of the crystal had many defects, while other parts were of extremely good quality.

  15. Nucleation and Convection Effects in Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Vekilow, Peter G.

    1998-01-01

    Our work under this grant has significantly contributed to the goals of the NASA supported protein crystallization program. We have achieved the main objectives of the proposed work, as outlined in the original proposal: (1) We have provided important insight into protein nucleation and crystal growth mechanisms to facilitate a rational approach to protein crystallization; (2) We have delineated the factors that currently limit the x-ray diffraction resolution of protein crystals, and their correlation to crystallization conditions; (3) We have developed novel technologies to study and monitor protein crystal nucleation and growth processes, in order to increase the reproducibility and yield of protein crystallization. We have published 17 papers in peer-reviewed scientific journals and books and made more than 15 invited and 9 contributed presentations of our results at international and national scientific meetings.

  16. Growth, thermal, mechanical, structural and optical properties of organic NLO crystals of novel cis-2,6-bis(2-chlorophenyl)-3,3-dimethylpiperidin-4-one

    NASA Astrophysics Data System (ADS)

    Ponnuswamy, S.; Mohanraj, V.; Ilango, S. S.; Thenmozhi, M.; Ponnuswamy, M. N.

    2015-02-01

    An organic NLO material viz., cis-2,6-bis(2-chlorophenyl)-3,3-dimethylpiperidin-4-one (2C3DMPO), has been synthesized and a slow evaporation technique was applied to produce a single crystal. X-ray diffraction study on the single crystal 2C3DMPO reveals a non-centro symmetric crystal, possessing a monoclinic space group P21 and prefers to adopt a chair conformation. The crystal has been characterised using UV, FT-IR and NMR spectral studies. Solubility study and mechanical study using micro hardness methods have also been carried out. Furthermore, the thermal stability of the crystal was established by TG/DTA. The second harmonic conversion efficiency of the crystal was determined using the Kurtz and Perry powder technique and the activity observed was 3.83 times greater than that of KDP.

  17. Economic analysis of crystal growth in space

    NASA Technical Reports Server (NTRS)

    Ulrich, D. R.; Chung, A. M.; Yan, C. S.; Mccreight, L. R.

    1972-01-01

    Many advanced electronic technologies and devices for the 1980's are based on sophisticated compound single crystals, i.e. ceramic oxides and compound semiconductors. Space processing of these electronic crystals with maximum perfection, purity, and size is suggested. No ecomonic or technical justification was found for the growth of silicon single crystals for solid state electronic devices in space.

  18. Optical diagnostics of solution crystal growth

    NASA Technical Reports Server (NTRS)

    Kim, Yongkee; Reddy, B. R.; George, Tharayil G.; Lal, Ravindra B.

    1995-01-01

    Solution crystal growth monitoring of LAP/TGS crystals by various optical diagnostics systems, such as conventional and Mach-Zehnder (M-Z) interferometers, optical heterodyne technique, and ellipsometry, is under development. The study of the dynamics of the crystal growth process requires a detailed knowledge of crystal growth rate and the concentration gradient near growing crystals in aqueous solution. Crystal growth rate can be measured using conventional interferometry. Laser beam reflections from the crystal front as well as the back surface interfere with each other, and the fringe shift due to the growing crystal yields information about the growth rate. Our preliminary results indicate a growth rate of 6 A/sec for LAP crystals grown from solution. Single wavelength M-Z interferometry is in use to calculate the concentration gradient near the crystal. Preliminary investigation is in progress using an M-Z interferometer with 2 cm beam diameter to cover the front region of the growing crystal. In the optical heterodyne technique, phase difference between two rf signals (250 KHZ) is measured of which one is a reference signal, and the other growth signal, whose phase changes due to a change in path length as the material grows. From the phase difference the growth rate can also be calculated. Our preliminary results indicate a growth rate of 1.5 A/sec. the seed and solution temperatures were 26.46 C and 27.92 C respectively, and the solution was saturated at 29.0 C. an ellipsometer to measure the growth rate and interface layer is on order from JOBIN YVON, France. All these systems are arranged in such a manner that measurements can be made either sequentially or simultaneously. These techniques will be adapted for flight experiment.

  19. Applications of Atomic Force Microscopy in Macromolecular Crystal Growth

    NASA Astrophysics Data System (ADS)

    McPherson, Alexander

    1997-03-01

    A series of protein and virus crystals was investigated, in situ, using atomic force microscopy. Most of the crystals grew principally on steps generated by two dimensional nucleation on surfaces, though some, such as canavalin, grew by development of spiral dislocations. Apoferritin grew by a rarely encountered mechanism, normal growth, usually associated only with melt or vapor phase crystallization. Cubic crystals of satellite tobacco mosaic virus (STMV) grew, at moderate to high levels of supersaturation, by the direct addition of three- dimensional nuclei followed by their rapid normal growth and lateral expansion, a mechanism not previously described to promote controlled and reproducible crystal growth from solutions. Biological macromolecules apparently utilize a more diverse range of growth mechanisms in their crystallization than any previously studied material. High resolution AFM analyses have allowed us to record the first, real time, in situ atomic force microscope images, on the nanometer scale, of the incorporation of molecules into the growth steps of crystals grown from solution. The molecular structure of the growth step edge and surface layer on the (101) faces of tetragonal thaumatin crystals were resolved. It was shown that, although the growth step height corresponds to the unit cell containing eight thaumatin molecules, its advancement occurs by the addition of individual protein molecules rather than molecular clusters. Models for the packing of molecules on the surface layer, and of the structure of the step edge were developed which agree well with experimental data. Again, using high resolution, in situ atomic force microscopy, the initial stages of the formation and development of two- and three-dimensional nuclei on the surface of protein crystals were recorded. From these we conclude that non crystalline aggregates, with short range order, present both on the crystal-solution interface, and in the volume of the solution, give rise to two- and three-dimensional crystalline nuclei respectively. The transition to a crystalline phase is guided by the underlying crystalline lattice.

  20. Thermal crystallization mechanism of silk fibroin protein

    NASA Astrophysics Data System (ADS)

    Hu, Xiao

    In this thesis, the thermal crystallization mechanism of silk fibroin protein from Bombyx mori silkworm, was treated as a model for the general study of protein based materials, combining theories from both biophysics and polymer physics fields. A systematic and scientific path way to model the dynamic beta-sheet crystallization process of silk fibroin protein was presented in the following sequence: (1) The crystallinity, fractions of secondary structures, and phase compositions in silk fibroin proteins at any transition stage were determined. Two experimental methods, Fourier transform infrared spectroscopy (FTIR) with Fourier self-deconvolution, and specific reversing heat capacity, were used together for the first time for modeling the static structures and phases in the silk fibroin proteins. The protein secondary structure fractions during the crystallization were quantitatively determined. The possibility of existence of a "rigid amorphous phase" in silk protein was also discussed. (2) The function of bound water during the crystallization process of silk fibroin was studied using heat capacity, and used to build a silk-water dynamic crystallization model. The fundamental concepts and thermal properties of silk fibroin with/without bound water were discussed. Results show that intermolecular bound water molecules, acting as a plasticizer, will cause silk to display a water-induced glass transition around 80C. During heating, water is lost, and the change of the microenvironment in the silk fibroin chains induces a mesophase prior to thermal crystallization. Real time FTIR during heating and isothermal holding above Tg show the tyrosine side chain changes only during the former process, while beta sheet crystallization occurs only during the latter process. Analogy is made between the crystallization of synthetic polymers according to the four-state scheme of Strobl, and the crystallization process of silk fibroin, which includes an intermediate precursor stage before crystallization. (3) The beta-sheet crystallization kinetics in silk fibroin protein were measured using X-ray, FTIR and heat flow, and the structure reveals the formation mechanism of the silk crystal network. Avrami kinetics theories, which were established for studies of synthetic polymer crystal growth, were for the first time extended to investigate protein self-assembly in multiblock silk fibroin samples. The Avrami exponent, n, was close to two for all methods, indicating formation of beta sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in most synthetic homopolymers. A microphase separation pattern after chymotrypsin enzyme biodegradation was shown in the protein structures using scanning electron microscopy. A model was then used to explain the crystallization of silk fibroin protein by analogy to block copolymers. (4) The effects of metal ions during the crystallization of silk fibroin was investigated using thermal analysis. Advanced thermal analysis methods were used to analyze the thermal protein-metallic ion interactions in silk fibroin proteins. Results show that K+ and Ca2+ metallic salts play different roles in silk fibroin proteins, which either reduce (K+) or increase (Ca2+ ) the glass transition (Tg) of pure silk protein and affect the thermal stability of this structure.

  1. Diffusion, Viscosity and Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Myerson, Allan S.

    1996-01-01

    The diffusivity of TriGlycine Sulfate (TGS), Potassium Dihydrogen Phosphate (KDP), Ammonium Dihydrogen Phosphate (ADF) and other compounds of interest to microgravity crystal growth, in supersaturated solutions as a function of solution concentration, 'age' and 'history was studied experimentally. The factors that affect the growth of crystals from water solutions in microgravity have been examined. Three non-linear optical materials have been studied, potassium dihydrogen phosphate (KDP), ammonium dihydrogen phosphate (ADP) and triglycine sulfate (TGC). The diffusion coefficient and viscosity of supersaturated water solutions were measured. Also theoretical model of diffusivity and viscosity in a metastable state, model of crystal growth from solution including non-linear time dependent diffusivity and viscosity effect and computer simulation of the crystal growth process which allows simulation of the microgravity crystal growth were developed.

  2. Crystal Growth and Spectroscopy of Diglycine

    NASA Technical Reports Server (NTRS)

    Taylor, Taravia M.

    1995-01-01

    Raman and infrared spectra have been obtained for alpha-diglycine (C4H8N2O3) single crystals. These dipeptide crystals are being grown as a models system for protein crystal growth studies. There have been previous Raman measurements on diglycine powder samples recorded, but there is no reference to measurements on oriented diglycine single crystals. Diglycine can grow in one of three forms, alpha, beta, or gamma.

  3. Salt-induced aggregation of lysozyme: Implications for crystal growth

    NASA Technical Reports Server (NTRS)

    Wilson, Lori J.

    1994-01-01

    Crystallization of proteins is a prerequisite for structural analysis by x-ray crystallography. While improvements in protein crystals have been obtained in microgravity onboard the U.S. Space Shuttle, attempts to improve the crystal growth process both on the ground and in space have been limited by our lack of understanding of the mechanisms involved. Almost all proteins are crystallized with the aid of a precipitating agent. Many of the common precipitating agents are inorganic salts. An understanding of the role of salts on the aggregation of protein monomers is the key to the elucidation of the mechanisms involved in protein crystallization. In order for crystallization to occur individual molecules must self-associate into aggregates. Detection and characterization of aggregates in supersaturated protein solutions is the first step in understanding salt-induced crystallization.

  4. Transport and Growth Kinetics in Microgravity Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Otalora, F.; Garcia-Ruiz, J. M.; Carotenuto, L.; Castagnolo, D.; Novella, M. L.; Chernov, A. A.

    2002-01-01

    The dynamic coupling between mass transport and incorporation of growth units into the surface of a crystal growing from solution in microgravity is used to derive quantitative information on the crystal growth kinetics. To this end, new procedures for experiment preparation, interferometric data processing and model fitting have been developed. The use of experimental data from the bulk diffusive maw transport together with a model for steady state stagnant crystal growth allows the detailed quantitative understanding of the kinetics of both the concentration depletion zone around the crystal and the growth of the crystal interface. The protein crystal used in the experiment is shown to be growing in the mixed kinetic regime (0.2 x 10(exp -6) centimeters per second less than beta R/D less than 0.9 x 10(exp -6) centimeters per second).

  5. Macromolecular crystal growth in microgravity

    NASA Astrophysics Data System (ADS)

    McPherson, Alexander

    1996-03-01

    Two T=1 and one T=3 plant viruses, along with a protein were crystallized in microgravity during the International Microgravity Laboratory-2 (IML-2) mission in July of 1994 (Koszelak, et al. 1995). The method employed was liquid-liquid diffusion in the European Space Agency's Advanced Protein Crystallization Facility (APCF). Distinctive alterations in the habits of Turnip Yellow Mosaic Virus (TYMV) crystals and hexagonal canavalin crystals were observed. Crystals of cubic Satellite Tobacco Mosaic Virus (STMV) more than thirty times the volume of crystals grown in the laboratory were produced in microgravity. X-ray diffraction analysis demonstrated that both crystal forms of canavalin and the cubic STMV crystals diffracted to significantly higher resolution and had superior diffraction properties as judged by relative Wilson plots.

  6. Analysis of Monomer Aggregation and Crystal Growth Rates of Lysozyme

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan

    1996-01-01

    This project was originally conceived to analyze the extensive data of tetragonal lysozyme crystal growth rates collected at NASA/MSFC by Dr. Marc L. Pusey's research group. At that time the lack of analysis of the growth rates was hindering progress in understanding the growth mechanism of tetragonal lysozyme and other protein crystals. After the project was initiated our initial analysis revealed unexpected complexities in the growth rate behavior. This resulted in an expansion in the scope of the project to include a comprehensive investigation of the growth mechanisms of tetragonal lysozyme crystals. A discussion of this research is included as well a list of presentations and publications resulting from the research. This project contributed significantly toward the education of several students and fostered extensive collaborations between investigators.

  7. Mechanisms for the Crystallization of ZBLAN

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Tucker, Dennis S.; Kaukler, William; Antar, Basil

    2003-01-01

    The objective of this ground based study is to test the hypothesis that shear thinning (the non-Newtonian response of viscosity to shear rate) is a viable mechanism to explain the observation of enhanced glass formation in numerous low-g experiments. In 1-g, fluid motion results from buoyancy forces and surface tension driven convection. This fluid flow will introduce shear in undercooled liquids in 1-g. In low-g it is known that fluid flows are greatly reduced so that the shear rate in fluids can be extremely low. It is believed that some fluids may have weak structure in the absence of flow. Very small shear rates could cause this structure to collapse in response to shear resulting in a lowering of the viscosity of the fluid. The hypothesis of this research is that: Shear thinning in undercooled liquids decreases the viscosity, increasing the rate of nucleation and crystallization of glass forming melts. Shear in the melt can be reduced in low-g, thus enhancing undercooling and glass formation. The viscosity of a model glass (lithium di-silicate, L2S) often used for crystallization studies has been measured at very low shear rates using a dynamic mechanical thermal analyzer. Our results are consistent with increasing viscosity with a lowering of shear rates. The viscosity of L2S may vary as much as an order of magnitude depending on the shear rate in the temperature region of maximum nucleation and crystal growth. Classical equations for nucleation and crystal growth rates, are inversely related to the viscosity and viscosity to the third power respectively. An order of magnitude variation in viscosity (with shear) at a given temperature would have dramatic effects on glass crystallization Crystallization studies with the heavy metal fluoride glass ZBLAN (ZrF2-BaF2-LaF3-AlF3-NaF) to examine the effect of shear on crystallization are being initiated. Samples are to be melted and quenched under quiescent conditions at different shear rates to determine the effect on crystallization. The results from this study are expected to advance the current scientific understanding of glass formation in low-g and glass crystallization under glass molding conditions and will improve the scientific understanding of technological processes such as fiber pulling, bulk amorphous alloys, and glass fabrication processes.

  8. Protein-crystal growth experiment (planned)

    NASA Technical Reports Server (NTRS)

    Fujita, S.; Asano, K.; Hashitani, T.; Kitakohji, T.; Nemoto, H.; Kitamura, S.

    1988-01-01

    To evaluate the effectiveness of a microgravity environment on protein crystal growth, a system was developed using 5 cubic feet Get Away Special payload canister. In the experiment, protein (myoglobin) will be simultaneously crystallized from an aqueous solution in 16 crystallization units using three types of crystallization methods, i.e., batch, vapor diffusion, and free interface diffusion. Each unit has two compartments: one for the protein solution and the other for the ammonium sulfate solution. Compartments are separated by thick acrylic or thin stainless steel plates. Crystallization will be started by sliding out the plates, then will be periodically recorded up to 120 hours by a still camera. The temperature will be passively controlled by a phase transition thermal storage component and recorded in IC memory throughout the experiment. Microgravity environment can then be evaluated for protein crystal growth by comparing crystallization in space with that on Earth.

  9. Crack propagation driven by crystal growth

    SciTech Connect

    A. Royne; Paul Meaking; A. Malthe-Sorenssen; B. Jamtveit; D. K. Dysthe

    2011-10-01

    Crystals that grow in confinement may exert a force on their surroundings and thereby drive crack propagation in rocks and other materials. We describe a model of crystal growth in an idealized crack geometry in which the crystal growth and crack propagation are coupled through the stress in the surrounding bulk solid. Subcritical crack propagation takes place during a transient period, which may be very long, during which the crack velocity is limited by the kinetics of crack propagation. When the crack is sufficiently large, the crack velocity becomes limited by the kinetics of crystal growth. The duration of the subcritical regime is determined by two non-dimensional parameters, which relate the kinetics of crack propagation and crystal growth to the supersaturation of the fluid and the elastic properties of the surrounding material.

  10. The crystal growth of barium flouride in aqueous solution

    NASA Astrophysics Data System (ADS)

    Barone, J. P.; Svrjcek, D.; Nancollas, G. H.

    1983-06-01

    The kinetics of growth of barium flouride seed crystals were investigated in aqueous solution at 25C using a constant composition method, in which the supersaturation and ionic strength were maintained constant by the addition of titrants consisting of barium nitrate and potassium flouride solutions. The rates of reaction, studied over a range of supersaturation (? ? 0.4 to 1.0), were interpreted in terms of crystal growth models. A spiral growth mechanism best describes the data, and scanning electron microscopy indicates a three-dimensional growth. In the presence of inorganic additives such as phosphate, however, induction periods precede a morphological two-dimensional crystallization. Coulter Counter results show little crystal agglomeration.

  11. The Nucleation and Growth of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    2004-01-01

    Obtaining crystals of suitable size and high quality continues to be a major bottleneck in macromolecular crystallography. Currently, structural genomics efforts are achieving on average about a 10% success rate in going from purified protein to a deposited crystal structure. Growth of crystals in microgravity was proposed as a means of overcoming size and quality problems, which subsequently led to a major NASA effort in microgravity crystal growth, with the agency also funding research into understanding the process. Studies of the macromolecule crystal nucleation and growth process were carried out in a number of labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. Based upon experimental evidence, as well as simple starting assumptions, we have proposed that crystal nucleation occurs by a series of discrete self assembly steps, which 'set' the underlying crystal symmetry. This talk will review the model developed, and its origins, in our laboratory for how crystals nucleate and grow, and will then present, along with preliminary data, how we propose to use this model to improve the success rate for obtaining crystals from a given protein.

  12. Combustion growth of large diamond crystals

    NASA Astrophysics Data System (ADS)

    Wang, X. H.; Zhu, W.; von Windheim, J.; Glass, J. T.

    1993-03-01

    This paper reports the successful growth of optically transparent, individual diamond crystals up to millimeter diameters on silicon substrates by oxygen-acetylene combustion flames at atmospheric pressure. The growth process consisted of three steps: (i) achieve a suitable nucleation density by pretreating the as-received Si substrate in an acetylene-rich flame (oxygen-to-acetylene ratio Rf = 0.95) for about 30 min at a downstream position (7-10 mm away from the tip of the flame inner cone); (ii) grow crystals up to 200 ?m in diameter in an annular area on the substrate at Rf = 0.98 and a substrate-to-tip of the flame inner cone distance of 2 mm; (iii) move the preferred crystals from the annular region into either the central core region of the flame feather or near the edge of the flame feather for further growth up to millimeter diameters under carefully controlled conditions. The final step of moving the crystals into a different growth region was necessary to avoid extensive secondary nucleation and structural defects. The key factor for diamond crystals to grow up to millimeter diameters was to maintain the growth conditions at the growing surface constant throughout the process. It was found that the crystal surface temperature, which was the most sensitive and also one of the most critical parameters, could be effectively maintained constant by decreasing the total gas flow rate as growth continued. Both the crystal growth orientations and the amount of nitrogen impurity incorporated in the diamond lattice were closely related to the crystal surface temperature. It is believed that the gas flow dynamics, or more specifically, the boundary layer thickness, played an important role in the growth and morphological development of large diamond crystals.

  13. Crystal growth and characterization of MnTe single crystals

    NASA Astrophysics Data System (ADS)

    de Melo, O.; Leccabue, F.; Pelosi, C.; Sagredo, V.; Chourio, M.; Martin, J.; Bocelli, G.; Calestani, G.

    1991-03-01

    The growth of MnTe single crystals by means of a chemical transport technique using iodine as a transport agent is reported. A detailed thermodynamical study of MnTe-I 2 system has been undertaken in order to define the best growth conditions. Moreover, structural, magnetic and electrical properties are reported and discussed.

  14. On growth rate hysteresis and catastrophic crystal growth

    NASA Astrophysics Data System (ADS)

    Ferreira, Ceclia; Rocha, Fernando A.; Damas, Ana M.; Martins, Pedro M.

    2013-04-01

    Different crystal growth rates as supersaturation is increasing or decreasing in impure media is a phenomenon called growth rate hysteresis (GRH) that has been observed in varied systems and applications, such as protein crystallization or during biomineralization. We have recently shown that the transient adsorption of impurities onto newly formed active sites for growth (or kinks) is sensitive to the direction and rate of supersaturation variation, thus providing a possible explanation for GRH [6]. In the present contribution, we expand on this concept by deriving the analytical expressions for transient crystal growth based on the energetics of growth hillock formation and kink occupation by impurities. Two types of GRH results are described according to the variation of kink density with supersaturation: for nearly constant density, decreasing or increasing supersaturation induce, respectively, growth promoting or inhibiting effects relative to equilibrium conditions. This is the type of GRH measured by us during the crystallization of egg-white lysozyme. For variable kink density, slight changes in the supersaturation level may induce abrupt variations in the crystal growth rate. Different literature examples of this so-called 'catastrophic' crystal growth are discussed in terms of their fundamental consequences.

  15. (PCG) Protein Crystal Growth Porcine Elastase

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Porcine Elastase. This enzyme is associated with the degradation of lung tissue in people suffering from emphysema. It is useful in studying causes of this disease. Principal Investigator on STS-26 was Charles Bugg.

  16. Silicon carbide - Progress in crystal growth

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony

    1987-01-01

    Recent progress in the development of two processes for producing large-area high-quality single crystals of SiC is described: (1) a modified Lely process for the growth of the alpha polytypes (e.g., 6H SiC) initially developed by Tairov and Tsvetkov (1978, 1981) and Ziegler et al. (1983), and (2) a process for the epitaxial growth of the beta polytype on single-crystal silicon or other substrates. Growth of large-area cubic SiC on Si is described together with growth of defect-free beta-SiC films on alpha-6H SiC crystals and TiC lattice. Semiconducting qualities of silicon carbide crystals grown by various techniques are discussed.

  17. The Growth of Large Single Crystals.

    ERIC Educational Resources Information Center

    Baer, Carl D.

    1990-01-01

    Presented is an experiment which demonstrates principles of experimental design, solubility, and crystal growth and structure. Materials, procedures and results are discussed. Suggestions for adapting this activity to the high school laboratory are provided. (CW)

  18. Illusory spirals and loops in crystal growth.

    PubMed

    Shtukenberg, Alexander G; Zhu, Zina; An, Zhihua; Bhandari, Misha; Song, Pengcheng; Kahr, Bart; Ward, Michael D

    2013-10-22

    The theory of dislocation-controlled crystal growth identifies a continuous spiral step with an emergent lattice displacement on a crystal surface; a mechanistic corollary is that closely spaced, oppositely winding spirals merge to form concentric loops. In situ atomic force microscopy of step propagation on pathological L-cystine crystals did indeed show spirals and islands with step heights of one lattice displacement. We show by analysis of the rates of growth of smaller steps only one molecule high that the major morphological spirals and loops are actually consequences of the bunching of the smaller steps. The morphology of the bunched steps actually inverts the predictions of the theory: Spirals arise from pairs of dislocations, loops from single dislocations. Only through numerical simulation of the growth is it revealed how normal growth of anisotropic layers of molecules within the highly symmetrical crystals can conspire to create features in apparent violation of the classic theory. PMID:24101507

  19. Research support for cadmium telluride crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Banish, Michael

    1993-01-01

    Work performed during the period 11 Feb. 1992 to 10 Aug. 1993 on research support for cadmium telluride crystal growth is reported. Work on chemical impurity characterization and mass spectroscopy is described.

  20. Protein crystal growth (5-IML-1)

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1992-01-01

    Proteins (enzymes, hormones, immunoglobulins) account for 50 pct. or more of the dry weight of most living systems. A detailed understanding of the structural makeup of a protein is essential to any systematic research pertaining to it. Most macromolecules are extremely difficult to crystallize, and many otherwise exciting projects have terminated at the crystal growth stage. In principle, there are several aspects of microgravity that might be exploited to enhance protein crystal growth. The major factor is the elimination of density driven convective flow. Other factors that can be controlled in the absence of gravity is the sedimentation of growing crystals in a gravitational field, and the potential advantage of doing containerless crystal growth. As a result of these theories and facts, one can readily understand why the microgravity environment of an Earth orbiting vehicle seems to offer unique opportunities for the protein crystallographer. This perception has led to the establishment of the Protein Crystal Growth in a Microgravity Environment (PCG/ME) project. The results of experiments already performed during STS missions have in many cases resulted in large protein crystals which are structurally correct. Thus, the near term objective of the PCG/ME project is to continue to improve the techniques, procedures, and hardware systems used to grow protein crystals in Earth orbit.

  1. Growth Of Oriented Crystals At Polymerized Membranes

    DOEpatents

    Charych, Deborah H. (Albany, CA), Berman, Amir (Ben-Shiva, IL)

    2000-01-25

    The present invention relates to methods and compositions for the growth and alignment of crystals at biopolymeric films. The methods and compositions of the present invention provide means to generate a variety of dense crystalline ceramic films, with totally aligned crystals, at low temperatures and pressures, suitable for use with polymer and plastic substrates.

  2. Crystallization of authentic recombinant human growth hormone

    SciTech Connect

    Jones, N.D.; DeHoniesto, J.; Tackitt, P.M.; Becker, G.W.

    1987-05-01

    Large single crystals of natural-sequence recombinant human growth hormone (rhGH) have been grown from a medium containing polyethylene glycol and a non-ionic detergent, ..beta..-octyl glucoside. The identity of the crystals was confirmed by gel electrophoresis and anion exchange chromatography.

  3. Convection effects in protein crystal growth

    NASA Technical Reports Server (NTRS)

    Roberts, Glyn O.

    1988-01-01

    Protein crystals for X-ray diffraction study are usually grown resting on the bottom of a hanging drop of a saturated protein solution, with slow evaporation to the air in a small enclosed cell. The evaporation rate is controlled by hanging the drop above a reservoir of water, with its saturation vapor pressure decreased by a low concentration of a passive solute. The drop has a lower solute concentration, and its volume shrinks by evaporation until the molecular concentrations match. Protein crystals can also be grown from a seed crystal suspended or supported in the interior of a supersaturated solution. The main analysis of this report concerns this case because it is less complicated than hanging-drop growth. Convection effects have been suggested as the reason for the apparent cessation of growth at a certain rather small crystal size. It seeems that as the crystal grows, the number of dislocations increases to a point where further growth is hindered. Growth in the microgravity environment of an orbiting space vehicle has been proposed as a method for obtaining larger crystals. Experimental observations of convection effects during the growth of protein crystals have been reported.

  4. Growth and optical, thermal, mechanical and surface morphology studies of semiorganic nonlinear optical material: Dichlorobis (l-proline) zinc (II) crystal.

    PubMed

    Anbuselvi, D; Jayaraman, D; Arul Martin Mani, J; Joseph, V

    2014-06-01

    The organometallic nonlinear optical material Dichlorobis (l-proline) zinc (II) (DCBPZ) was crystallized using solution growth technique. XRD data reveal that the grown crystal belongs to orthorhombic system with space group P212121. The crystals were characterized using UV-vis-NIR, FTIR and NMR spectral studies, SEM-EDAX analysis and Atomic force microscopy (AFM), thermal and microhardness studies. Photoconductivity measurements were made to understand the response of the grown material to the visible light. The SHG efficiency of DCBPZ was also measured using Kurtz and Perry powder technique. It is observed that the NLO activity of DCBPZ is found to be twice that of KDP due to improved linear and nonlinear optical properties of the material. PMID:24637277

  5. Crystallization mechanisms of stoichiometric monomethylhydrazinewater mixtures

    NASA Astrophysics Data System (ADS)

    Clavaguera, N.; Palumbo-Romand, V.; Ferriol, M.; Cohen-Adad, M. T.

    1997-09-01

    Lights scattering measurements of crystallization under the isothermal regime of stoichiometric mixtures of CH 3NHNH 2H 2O, in the temperature range 180-200 K are modeled as nucleation-growth of the two crystalline forms, stable and metastable, that result as crystallization products. The modeling procedure is founded on the JohnsonMelhAvramiKomolgorov model with introduction of the competition between interface and diffusion growth limiting mechanisms. The nucleation and growth kinetics, and in particular the optimum temperature range for both nucleation and growth have been deduced from calorimetric analysis of the process under continuous heating of previously annealed samples at selected temperatures. The calculation presented here agrees with the experimental results and evidences the importance of: (a) heterogeneous nucleation, (b) diffusion-controlled growth in the last stages of crystallization process and (c) co-crystallization of both crystalline forms in the temperature range 150-200 K.

  6. Growth of organic benzimidazole (BMZ) single crystal by vertical Bridgman technique and its structural, spectral, thermal, optical, mechanical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Muthuraja, A.; Kalainathan, S.

    2015-09-01

    Benzimidazole (BMZ) single crystal was successfully grown by the vertical Bridgman technique (VBT). The crystal system was identified and lattice parameters have been measured from the powder X-ray diffraction (PXRD) measurement. Fourier transforms infrared spectral studies have been carried out to find out the functional groups of BMZ crystal. The optical transmittance and the cut-off wavelength of BMZ were identified using UV-Vis NIR studies and the cut-off wavelength was found to be 294 nm. The dielectric permittivity and dielectric loss as a function of frequency and temperature was measured for the grown BMZ crystal. Vickers microhardness analysis was carried out to identify the mechanical stability of the grown crystal. Chemical etching study was carried out using different etchants and the etch pit density (EPD) was calculated and compared. The third order nonlinear optical property of BMZ crystal was studied by using Z-scan technique with He-Ne laser (632.8 nm). The magnitude of nonlinear refractive index (n2), nonlinear absorption (?) and third order nonlinear susceptibility (?3) have been found to be in the range of 10-11 m2/W, 10-4 m/W and 10-5 esu respectively. Photoluminescence spectrum was recorded using a xenon lamp in the range of 330-585 nm and it exhibits ultraviolet light emission.

  7. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1993-01-01

    This Final Technical Report for NASA Grant NAG8-774 covers the period from April 27, 1989 through December 31, 1992. It covers five main topics: fluid flow studies, the influence of growth conditions on the morphology of isocitrate lyase crystals, control of nucleation, the growth of lysozyme by the temperature gradient method and graphoepitaxy of protein crystals. The section on fluid flow discusses the limits of detectability in the Schlieren imaging of fluid flows around protein crystals. The isocitrate lyase study compares crystals grown terrestrially under a variety of conditions with those grown in space. The controlling factor governing the morphology of the crystals is the supersaturation. The lack of flow in the interface between the drop and the atmosphere in microgravity causes protein precipitation in the boundary layer and a lowering of the supersaturation in the drop. This lowered supersaturation leads to improved crystal morphology. Preliminary experiments with lysozyme indicated that localized temperature gradients could be used to nucleate crystals in a controlled manner. An apparatus (thermonucleator) was designed to study the controlled nucleation of protein crystals. This apparatus has been used to nucleate crystals of materials with both normal (ice-water, Rochelle salt and lysozyme) and retrograde (horse serum albumin and alpha chymotrypsinogen A) solubility. These studies have lead to the design of an new apparatus that small and more compatible with use in microgravity. Lysozyme crystals were grown by transporting nutrient from a source (lysozyme powder) to the crystal in a temperature gradient. The influence of path length and cross section on the growth rate was demonstrated. This technique can be combined with the thermonucleator to control both nucleation and growth. Graphoepitaxy utilizes a patterned substrate to orient growing crystals. In this study, silicon substrates with 10 micron grooves were used to grow crystals of catalase, lysozyme and canavalin. In all cases, the crystals grew oriented to the substrate. The supersaturation needed for nucleation and growth was lower on the patterned substrates. In some cases, isolated, large crystals were grown.

  8. Crystal growth under heat field rotation conditions

    NASA Astrophysics Data System (ADS)

    Kokh, Alexandr E.; Kononova, Nadegda G.

    2000-05-01

    Rotation of the heat field which is applied to the outer walls of a crystallizer or growth crucible, provides a contact-free induction of forced convection (i.e. flow azimuthal component) in a medium of crystallization. Thus, the stirring of a melt or solution is gained without the direct effect of a rotating crystal, or crucible, or various mixers. This allows to simplify crystallization and to escape vibration and other excitations. The circular movement of a heat field by the perimeter of a growing crystal, which proceeds at a certain amplitude and frequency, provides the formation of a structurally perfect single crystal. An original heating furnace provides the rotation of the heat field. Thermal control of this furnace allows maintainance of a necessary temperature in a growth zone with high precision; it is possible to set the amplitude and frequency of thermal oscillation in a wide range of values. This technique was tested for the growth of nonlinear-optical CLBO crystals from a high-temperature melt-solution and KDP crystals from a water solution.

  9. Growth and defects of explosives crystals

    NASA Astrophysics Data System (ADS)

    Cady, H. H.

    Large single crystals of PETN, RDX, and TNT can be grown easily from evaporating ethyl acetate solutions. The crystals all share a similar type of defect that may not be commonly recognized. The defect generates conical faces, ideally mosaic crystals, and may account for the 'polymorphs' of TNT and detonator grades of PETN. TATB crystals manufactured by the amination of trichlorotrinitrobenzene in dry toluene entrain two forms of ammonium chloride. One of these forms causes 'worm holes' in the TATB crystals that may be the reason for its unusually low failure diameters. Strained HMX crystals form mechanical twins that can spontaneously revert back to the untwinned form when the straining force is removed. Large strains or temperatures above 100 C lock in the mechanical twins.

  10. Stability limits for the horizontal ribbon growth of silicon crystals

    NASA Astrophysics Data System (ADS)

    Daggolu, Parthiv; Yeckel, Andrew; Bleil, Carl E.; Derby, Jeffrey J.

    2013-01-01

    A rigorous, thermal-capillary model, developed to couple heat transfer, melt convection and capillary physics, is employed to assess stability limits of the HRG system for growing silicon ribbons. Extending the prior understanding of this process put forth by Daggolu et al. [Thermal-capillary analysis of the horizontal ribbon growth of silicon crystals, Journal of Crystal Growth 355 (2012) 129-139], model results presented here identify additional failure mechanisms, including the bridging of crystal onto crucible, the spilling of melt from the crucible, and the undercooling of melt at the ribbon tip, that are consistent with prior experimental observations. Changes in pull rate, pull angle, melt height, and other parameters are shown to give rise to limits, indicating that only narrow operating windows exist in multi-dimensional parameter space for stable growth conditions that circumvent these failure mechanisms.

  11. Growth Modes and Energetics of 101 Face Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, L.

    2004-01-01

    From analyses of lysozyme 101 face growth rate data using a 2D nucleation model for layer-by-layer growth, we find the effective barrier for crystal growth to be gamma = 1.0 +/- 0.2 x 10(exp -13) erg/molecule. The magnitude of the effective barrier is 2.4 +/- 0.5 k(sub beta)T, at 22 C. We also find that beyond a critical solution supersaturation, sigma(sub c), crystal growth rates are more accurately described by a kinetic roughening hypothesis. Beyond sigma(sub c), crystals grow by the continuous addition of molecules anywhere on the crystal surface rather than layer-by-layer. The magnitude of the critical supersaturation (sigma(sub c), = 1.7 +/- 0.2) for a crossover from a layer-by-layer to continuous growth is found to be statistically independent of the solution conditions that vary with buffer pH, temperature or precipitant concentration. Using the experimentally determined values for gamma and sigma(sub c), we find the crystal growth unit to be comprised of 7 +/- 3 molecules. The energy barrier, E(sub c), for the continuous addition of the growth Units is 6.2 +/- 0.3 x 10(exp -13) erg/molecule or 15 +/1 1 k(sub beta)T at 22C.

  12. Synthesis, growth, structural, spectral, linear and nonlinear optical and mechanical studies of a novel organic NLO single crystal 4-Bromo 4-Nitrostilbene (BONS) for nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Dinakaran, Paul M.; Kalainathan, S.

    2013-03-01

    Single crystal of 4-Bromo 4-Nitrostilbene (BONS), a new organic nonlinear optical material was synthesized and crystals were grown with dimensions up to 8 6 3 mm3 from ethyl methyl ketone (EMK) solvent by slow evaporation method. Single crystal X-ray diffractometer was used to measure the unit cell parameters and confirmed the BONS structure as orthorhombic with the space group P212121. The sample has been subjected to powder X-ray diffraction to identify the crystalline nature and the prominent peaks were indexed. The functional groups were identified from Fourier transform infrared (FTIR) spectral analysis. Proton NMR analysis confirms the protonation in the structure of the title compound. Optical behaviour of BONS has been observed by UV-Vis absorption spectral analysis which shows the low cut off wavelength lies at 405 nm and found that the energy band gap of the crystal is 2.90 eV. Thermal stability of the material has been confirmed by TG/DTA analyses. The BONS compound formation analyzed by mass spectroscopic analysis. The mechanical strength of the crystal was found using Vickers microhardness measurement. The laser damage threshold (LDT) for the grown crystal was measured by using Nd:YAG laser. Photoluminescence spectrum indicated green light emission at 515.44 nm. The Kurtz powder second harmonic generation test shows that the BONS crystal (1.5 V) is a very potential NLO candidate for optical generation and it has SHG efficiency 69 times greater than that of KDP (21.7 mV).

  13. Convective flow effects on protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1995-01-01

    During the fifth semi-annual period under this grant we have pursued the following activities: (1) Characterization of the purity and further purification of lysozyme solutions, these efforts are summarized in Section 2; (2) Crystal growth morphology and kinetics studies with tetragonal lysozyme, our observation on the dependence of lysozyme growth kinetics on step sources and impurities has been summarized in a manuscript which was accepted for publication in the Journal of Crystal Growth; (3) Numerical modelling of the interaction between bulk transport and interface kinetics, for a detailed summary of this work see the manuscript which was accepted for publication in the Journal of Crystal Growth; and (4) Light scattering studies, this work has been summarized in a manuscript that has been submitted for publication to the Journal of Chemical Physics.

  14. Effects of Crystal Microstructure on Epitaxial Growth

    NASA Astrophysics Data System (ADS)

    Amar, Jacques G.; Family, Fereydoon

    1996-03-01

    In the past, Monte Carlo simulations of epitaxial growth have used simple solid-on-solid (SOS) models to simulate the crystalline structure of both the substrate and the growing crystal. These models have produced results in the early stages of growth in good agreement with experiments for a number of quantities, including the island density and island-size distribution. For multilayer growth, however, there exists a competition between microscopic effects such as the Ehrlich-Schwoebel step barrier and the crystalline microstructure. Therefore, the crystal structure and geometry are important in determining the evolution of epitaxial morphology. We present the results of large-scale realistic kinetic Monte Carlo simulations of multilayer epitaxial growth on fcc(100) and bcc(100) surfaces. The influence of crystal structure on the formation and coarsening of mounds and facets will be discussed. We also discuss and compare our results with recent experiments.

  15. Research support for cadmium telluride crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1995-01-01

    The growth of single crystals of zinc selenide was carried out by both closed ampoule physical vapor transport and effusive ampoule physical vapor transport (EAPVT). The latter technique was shown to be a much more efficient method for the seeded growth of zinc selenide, resulting in higher transport rates. Furthermore, EAPVT work on CdTe has shown that growth onto (n 11) seeds is advantageous for obtaining reduced twinning and defect densities in II-VI sphalerite materials.

  16. Growth and characterization of large CLBO crystals

    NASA Astrophysics Data System (ADS)

    Yuan, Xin; Shen, Guangqiu; Wang, Xiaoqing; Shen, Dezhong; Wang, Guiling; Xu, Zuyan

    2006-07-01

    A high optical quality Cesium lithium borate (CLBO) crystal with dimensions of 146×132×118 mm was grown by the Kyropoulos method. The 4th harmonic generation of a frequency doubled Nd:YAG laser, from 532 to 266 nm, was carried out with a CLBO crystal doubler, and an average output power of 28.4 W was achieved at 266 nm. Polished surfaces were etched to reveal the cracking mechanism of CLBO crystals. Through observation and comparison of the surface etching patterns, it is proved that CLBO crystals crack under chemical attack by water molecules penetrating from the (1 0 0) and (0 1 0) crystallographic planes.

  17. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function of temperature.

  18. Modeling Tetragonal Lysozyme Crystal Growth Rates

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2003-01-01

    Tetragonal lysozyme 110 face crystal growth rates, measured over 5 orders of magnitude in range, can be described using a model where growth occurs by 2D nucleation on the crystal surface for solution supersaturations of c/c(sub eq) less than or equal to 7 +/- 2. Based upon the model, the step energy per unit length, beta was estimated to be approx. 5.3 +/- 0.4 x 10(exp -7) erg/mol-cm, which for a step height of 56 A corresponds to barrier of approx. 7 +/- 1 k(sub B)T at 300 K. For supersaturations of c/c(sub eq) > 8, the model emphasizing crystal growth by 2D nucleation not only could not predict, but also consistently overestimated, the highest observable crystal growth rates. Kinetic roughening is hypothesized to occur at a cross-over supersaturation of c/c(sub eq) > 8, where crystal growth is postulated to occur by a different process such as adsorption. Under this assumption, all growth rate data indicated that a kinetic roughening transition and subsequent crystal growth by adsorption for all solution conditions, varying in buffer pH, temperature and precipitant concentration, occurs for c/c(sub eq)(T, pH, NaCl) in the range between 5 and 10, with an energy barrier for adsorption estimated to be approx. 20 k(sub B)T at 300 K. Based upon these and other estimates, we determined the size of the critical surface nucleate, at the crossover supersaturation and higher concentrations, to range from 4 to 10 molecules.

  19. Protein Crystal Growth Dynamics and Impurity Incorporation

    NASA Technical Reports Server (NTRS)

    Chernov, Alex A.; Thomas, Bill

    2000-01-01

    The general concepts and theories of crystal growth are proven to work for biomolecular crystallization. This allowed us to extract basic parameters controlling growth kinetics - free surface energy, alpha, and kinetic coefficient, beta, for steps. Surface energy per molecular site in thermal units, alpha(omega)(sup 2/3)/kT approx. = 1, is close to the one for inorganic crystals in solution (omega is the specific molecular volume, T is the temperature). Entropic restrictions on incorporation of biomolecules into the lattice reduce the incorporation rate, beta, by a factor of 10(exp 2) - 10(exp 3) relative to inorganic crystals. A dehydration barrier of approx. 18kcal/mol may explain approx. 10(exp -6) times difference between frequencies of adding a molecule to the lattice and Brownian attempts to do so. The latter was obtained from AFM measurements of step and kink growth rates on orthorhombic lysozyme. Protein and many inorganic crystals typically do not belong to the Kossel type, thus requiring a theory to account for inequivalent molecular positions within its unit cell. Orthorhombic lysozyme will serve as an example of how to develop such a theory. Factors deteriorating crystal quality - stress and strain, mosaicity, molecular disorder - will be reviewed with emphasis on impurities. Dimers in ferritin and lysozyme and acetylated lysozyme, are microheterogeneous i.e. nearly isomorphic impurities that are shown to be preferentially trapped by tetragonal lysozyme and ferritin crystals, respectively. The distribution coefficient, K defined as a ratio of the (impurity/protein) ratios in crystal and in solution is a measure of trapping. For acetylated lysoyzme, K = 2.15 or, 3.42 for differently acetylated forms, is independent of both the impurity and the crystallizing protein concentration. The reason is that impurity flux to the surface is constant while the growth rate rises with supersaturation. About 3 times lower dimer concentration in space grown ferritin and lysozyme crystals might be examples explaining higher quality of the space grown protein crystal. Depletion of solution with respect to isomorphic impurities around a growing crystal may be K times deeper than with respect to the crystallizing protein.

  20. Method for solid state crystal growth

    SciTech Connect

    Nolas, George S.; Beekman, Matthew K.

    2013-04-09

    A novel method for high quality crystal growth of intermetallic clathrates is presented. The synthesis of high quality pure phase crystals has been complicated by the simultaneous formation of both clathrate type-I and clathrate type-II structures. It was found that selective, phase pure, single-crystal growth of type-I and type-II clathrates can be achieved by maintaining sufficient partial pressure of a chemical constituent during slow, controlled deprivation of the chemical constituent from the primary reactant. The chemical constituent is slowly removed from the primary reactant by the reaction of the chemical constituent vapor with a secondary reactant, spatially separated from the primary reactant, in a closed volume under uniaxial pressure and heat to form the single phase pure crystals.

  1. Protein Crystal Growth Apparatus for Microgravity

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor); Dowling, Timothy E. (Inventor)

    1997-01-01

    Apparatus for growing protein crystals under microgravity environment includes a plurality of protein growth assemblies stacked one above the other within a canister. Each of the protein growth assemblies includes a tray having a number of spaced apart growth chambers recessed below an upper surface. the growth chambers each having an upstanding pedestal and an annular reservoir about the pedestal for receiving a wick and precipitating agents. A well is recessed below the top of each pedestal to define a protein crystal growth receptacle. A flexible membrane is positioned on the upper surface of each tray and a sealing plate is positioned above each membrane, each sealing plate having a number of bumpers corresponding in number and alignment to the pedestals for forcing the membrane selectively against the upper end of the respective pedestal to seal the reservoir and the receptacle when the sealing plate is forced down.

  2. Space-based crystal growth and thermocapillary flow

    NASA Technical Reports Server (NTRS)

    Shen, Yong-Hong

    1994-01-01

    The demand for larger crystals is increasing especially in applications associated with the electronic industry, where large and pure electronic crystals (notably silicon) are the essential material to make high-performance computer chips. Crystal growth under weightless conditions has been considered an ideal way to produce bigger and hopefully better crystals. One technique which may benefit from a microgravity environment is the float-zone crystal-growth process, a containerless method for producing high-quality electronic material. In this method, a rod of material to be refined is moved slowly through a heating device which melts a portion of it. Ideally, as the melt resolidifies it does so as a single crystal which is then used as substrate for building microelectronic devices. The possibility of contamination by contact with other material is reduced because of the 'float' configuration. However, since the weight of the material contained in the zone is supported by the surface-tension force, the size of the resulting crystal is limited in Earth-based productions; in fact, some materials have properties which prevent this process from being used to manufacture crystals of reasonable size. Consequently, there has been a great deal of interest in exploiting the microgravity environment of space to grow larger size crystals of electronic material using the float-zone method. In addition to allowing larger crystals to be grown, a microgravity environment would also significantly reduce the magnitude of convection induced by buoyancy forces during the melting state. This type of convection was once thought to be at least partially responsible for the presence of undesirable nonuniformities--called striations--in material properties observed in float-zone material. However, past experiments on crystal growth under weightless conditions found that even with the absence of gravity, the float-zone method sometimes still results striations. It is believed that another mechanism is playing a dominant role in the microgravity environment.

  3. Convective flow effects on protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Monaco, Lisa A.

    1994-01-01

    The long-term stability of the interferometric setup for the monitoring of protein morphologies has been improved. Growth or dissolution of a crystal on a 100 A scale can now be clearly distinguished from dimensional changes occurring within the optical path of the interferometer. This capability of simultaneously monitoring the local interfacial displacement at several widely-spaced positions on the crystal surface with high local depth resolution, has already yielded novel results. We found with lysozyme that (1) the normal growth rate is oscillatory, and (2) the mean growth step density is greater at the periphery of a facet than in its center. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied for a wide range of crystallization conditions. A nucleation-growth-repartitioning model was developed to interpret the large body of data in a unified way. The results strongly suggests that (1) the ion to lysozyme ratio in the crystal depends mostly on kinetic rather than crystallographic parameters, and (2) lysozyme crystals possess a salt-rich core with a diameter on the order of 10 microns. The computational model for diffusive-convective transport in protein crystallization (see the First Report) has been applied to a realistic growth cell geometry, taking into account the findings of the above repartitioning studies. These results show that some elements of a moving boundary problem must be incorporated into the model in order to obtain a more realistic description. Our experimental setup for light scattering investigations of aggregation and nucleation in protein solutions has been extensively tested. Scattering intensity measurements with a true Rayleigh scatterer produced systematically increased forward scattering, indicating problems with glare. These have been resolved. Preliminary measurements with supersaturated lysozyme solutions revealed that the scatterers grow with time. Work has begun on a computer program for the unified evaluation of simultaneously obtained, multi-angle static and dynamic light scattering data.

  4. Modeling the Growth Rates of Tetragonal Lysozyme Crystal Faces

    NASA Technical Reports Server (NTRS)

    Li, Meirong; Nadarajah, Arunan; Pusey, Marc L.

    1998-01-01

    The measured macroscopic growth rates of the (110) and (101) faces of tetragonal lysozyme show an unexpectedly complex dependence on the supersaturation. The growth rates decay asymptotically to zero when the supersaturation is lowered to zero and increase rapidly when the supersaturation is increased. When supersaturations are increased still further the growth rates attain a maximum before starting to decrease. However, growth of these crystals is known to proceed by the classical dislocation and 2D nucleation growth mechanisms. This anomaly can be explained if growth is assumed to occur not by monomer units but by lysozyme aggregates. Analysis of the molecular packing of these crystals revealed that they were constructed of strongly bonded 4(sub 3) helices, while weaker bonds were responsible for binding the helices to each other. It follows that during crystal growth the stronger bonds are formed before the weaker ones. Thus, the growth of these crystals could be viewed as a two step process: aggregate growth units corresponding to the 4(sub 3) helix are first formed in the bulk solution by stronger intermolecular bonds and then attached to the crystal face by weaker bonds on dislocation hillocks or 2D islands. This will lead to a distribution of aggregates in the solution with monomers and lower order aggregates being predominant at low supersaturations and higher order aggregates being predominant at high supersaturations. If the crystal grows mostly by higher order aggregates, such as tetramers and octamers, it would explain the anomalous dependence of the growth rates on the supersaturation. Besides the analysis of molecular packing, a comprehensive analysis of the measured (110) and (101) growth rates was also undertaken in this study. The distribution of aggregates in lysozyme nutrient solutions at various solution conditions were determined from reversible aggregation reactions at equilibrium. The supersaturation was defined for each aggregate species with respect to its concentration at saturation in order to apply growth rate models to this process. The measured growth rates were then compared with the predicted ones from several dislocation and 2D nucleation growth models, employing tetramer and octamer growth units in polydisperse solutions and monomer units in monodisperse solutions. For the (110) face, the calculations consistently showed that the measured growth rates followed the expected model relations with octamer growth units. For the (101) face, it is not possible to obtain a clear agreement between the predicted and measured growth rates for a single growth unit as done for the (110) face. However, the calculations do indicate that the average size of the growth unit is between a tetramer and an octamer. This suggests that tetramers, octamers and other intermediate size growth units all participate in the growth process for this face. These calculations show that it is possible to model the macroscopic protein crystal growth rates if the molecular level processes can be account for, particularly protein aggregation processes in the bulk solution. Our recent investigations of tetragonal lysozyme crystals employing high resolution atomic force microscopy scans have further confirmed the growth of these crystals by aggregate growth units corresponding to 4(sub 3) helices.

  5. Crystal growth under external electric fields

    SciTech Connect

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-10-06

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  6. Crystal growth under external electric fields

    NASA Astrophysics Data System (ADS)

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-10-01

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostaticallyeither through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  7. High quality factor single-crystal diamond mechanical resonators

    NASA Astrophysics Data System (ADS)

    Ovartchaiyapong, P.; Pascal, L. M. A.; Myers, B. A.; Lauria, P.; Bleszynski Jayich, A. C.

    2012-10-01

    Single-crystal diamond is a promising material for microelectromechanical systems (MEMs) because of its low mechanical loss, compatibility with extreme environments, and built-in interface to high-quality spin centers. But its use has been limited by challenges in processing and growth. We demonstrate a wafer bonding-based technique to form diamond on insulator, from which we make single-crystal diamond micromechanical resonators with mechanical quality factors as high as 338 000 at room temperature. Variable temperature measurements down to 10 K reveal a nonmonotonic dependence of quality factor on temperature. These resonators enable integration of single-crystal diamond into MEMs technology for classical and quantum applications.

  8. Mechanical Properties Of Large Sodium Iodide Crystals

    NASA Technical Reports Server (NTRS)

    Lee, Henry M.

    1988-01-01

    Report presents data on mechanical properties of large crystals of thallium-doped sodium iodide. Five specimens in shape of circular flat plates subjected to mechanical tests. Presents test results for each specimen as plots of differential pressure versus center displacement and differential pressure versus stress at center. Also tabulates raw data. Test program also developed procedure for screening candidate crystals for gamma-ray sensor. Procedure eliminates potentially weak crystals before installed and ensures material yielding kept to minimum.

  9. Growth technology of piezoelectric langasite single crystal

    NASA Astrophysics Data System (ADS)

    Uda, Satoshi; Wang, Shou-Qi; Konishi, Nozomi; Inaba, Hitoshi; Harada, Jiro

    2005-02-01

    Although langasite (La 3Ga 5SiO 14) is an incongruent material, it can directly grow from the "pseudo-congruent melt" via the Czochralski method using a langasite seed crystal when the appropriate supercooling is provided. This may be explained by the extension of the univariant line of langasite+liquid into the primary phase field of Ga-containing lanthanum silicate. Free energies serving to solute transport, growth kinetics, surface creation and defect generation are summed up to be the total supercooling necessary for growth which may be larger for the formation of Ga-containing lanthanum silicate and smaller for langasite than the actual supercooling. The growth technology of 4-in-size crystal along [0 1 1 1] is optimized by understanding (i) the importance of the prior annealing of the melt to acquire the suitable supercooling for growth, (ii) the transform of the unstable growth interface, (0 1 1 1), into the complex of more stable principal planes, and (iii) the necessity of the accurate evaluation method to examine the homogeneity of the grown crystal. Issues of (i) and (ii) are interrelated. Physical crystal properties at high temperature are also demonstrated.

  10. Sublimation Crystal Growth of Yttrium Nitride

    SciTech Connect

    Du, Li; Edgar, J H; Meisner, Roberta Ann; Bakalova-hadjikrasteva, Silvia; Kuball, M

    2010-01-01

    The sublimation recombination crystal growth of bulk yttrium nitride crystals is reported. The YN source material was prepared by reacting yttrium metal with nitrogen at 1200 C and 800 Torr total pressure. Crystals were produced by subliming this YN from the source zone, and recondensing it from the vapor as crystals at a lower temperature (by 50 C). Crystals were grown from 2000 to 2100 C and with a nitrogen pressure from 125 to 960 Torr. The highest rate was 9.64 10 5 mol/h (9.92 mg/h). The YN sublimation rate activation energy was 467.1 21.7 kJ/mol. Individual crystals up to 200 m in dimension were prepared. X-ray diffraction confirmed that the crystals were rock salt YN, with a lattice constant of 4.88 . The YN crystals were unstable in air; they spontaneously converted to yttria (Y2O3) in 2 4 h. A small fraction of cubic yttria was detected in the XRD of a sample exposed to air for a limited time, while non-cubic yttria was detected in the Raman spectra for a sample exposed to air for more than 1 h.

  11. An Apparatus for Growth of Small Crystals From Solutions.

    ERIC Educational Resources Information Center

    Mitrovic, Mico M.

    1995-01-01

    Describes an apparatus for crystal growth that was designed to study growth kinetics of small crystals from solutions and to obtain crystals of various substances. Describes the use of the apparatus in laboratory practical experiments in the field of crystal growth physics within the course "Solid State Physics". (JRH)

  12. Method for crystal growth control

    DOEpatents

    Yates, Douglas A. (Burlington, MA); Hatch, Arthur E. (Waltham, MA); Goldsmith, Jeff M. (Medford, MA)

    1981-01-01

    The growth of a crystalline body of a selected material is controlled so that the body has a selected cross-sectional shape. The apparatus is of the type which includes the structure normally employed in known capillary die devices as well as means for observing at least the portion of the surfaces of the growing crystalline body and the meniscus (of melt material from which the body is being pulled) including the solid/liquid/vapor junction in a direction substantially perpendicular to the meniscus surface formed at the junction when the growth of the crystalline body is under steady state conditions. The cross-sectional size of the growing crystalline body can be controlled by determining which points exhibit a sharp change in the amount of reflected radiation of a preselected wavelength and controlling the speed at which the body is being pulled or the temperature of the growth pool of melt so as to maintain those points exhibiting a sharp change at a preselected spatial position relative to a predetermined reference position. The improvement comprises reference object means positioned near the solid/liquid/vapor junction and capable of being observed by the means for observing so as to define said reference position so that the problems associated with convection current jitter are overcome.

  13. Convective flow effects on protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Monaco, Lisa A.

    1994-01-01

    A high-resolution microscopic interferometric setup for the monitoring of protein morphologies has been developed. Growth or dissolution of a crystal can be resolved with a long-term depth resolution of 200 A and a lateral resolution of 2 microns. This capability of simultaneously monitoring the interfacial displacement with high local depth resolution has yielded several novel results. We have found with lysozyme that (1) the normal growth rate is oscillatory, and (2) depending on the impurity content of the solution, the growth step density is either greater or lower at the periphery of a facet than in its center. The repartitioning of Na plus and Cl minus ions between lysozyme solutions and crystals was studied for a wide range of crystallization conditions. A nucleation-growth-repartitioning model was developed, to interpret the large body of data in unified way. The results strongly suggest that (1) the ion to lysozyne ratio in the crystal depends mostly on kinetic rather than crystallographic parameters, and (2) lysozyme crystals possess a salt-rich core with a diameter electron microscopy results appear to confirm this finding, which could have far-reaching consequences for x-ray diffraction studies. A computational model for diffusive-convective transport in protein crystallization has been applied to a realistic growth cell geometry, taking into account the findings of the above repartitioning studies and our kinetics data for the growth of lysozyme. The results show that even in the small cell employed, protein concentration nonuniformities and gravity-driven solutal convection can be significant. The calculated convection velocities are of the same order to magnitude as those found in earlier experiments. As expected, convective transport, i.e., at Og, lysozyme crystal growth remains kinetically limited. The salt distribution in the crystal is predicted to be non-uniform at both 1g and 0g, as a consequence of protein depletion in the solution. Static and dynamic light scattering studies in undersaturated and supersaturated solutions have been performed. Diffusivities in undersaturated solutions, were found to vary with lysozyme concentrations. Depending on the salt concentration, the diffusivities either increase or decrease. Interestingly, the corresponding static scattering intensities behave oppositely, Our current analysis indicates that these changes are inconsistent with aggregation in undersaturated solutions. However, the data are compatible with concentration-dependent changes of the interactions between protein and salt.

  14. Interaction between Convection and Heat Transfer in Crystal Growth

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Crystals are integral components in some of our most sophisticated and rapidly developing industries. Single crystals are solids with the most uniform structures that can be obtained on an atomic scale. Because of their structural uniformity, crystals can transmit acoustic and electromagnetic waves and charged particles with essentially no scattering or interferences. This transparency, which can be selectively modified by controlled additions of impurities known as dopants, is the foundation of modern electronic industry. It has brought about widespread application of crystals in transistors, lasers, microwave devices, infrared detectors, magnetic memory devices, and many other magnets and electro-optic components. The performance of a crystal depends strongly on its compositional homogeneity. For instance, in modern microcircuitry, compositional variations of a few percent (down to a submicron length scale) can seriously jeopardize predicted yields. Since crystals are grown by carefully controlled phase transformations, the compositional adjustment in the solid is often made during growth from the nutrient. Hence, a detailed understanding of mass transfer in the nutrient is essential. Moreover, since mass transfer is often the slowest process during growth, it is usually the rate limiting mechanism. Crystal growth processes are usually classified according to the nature of the parent phase. Nevertheless, whether the growth occurs by solidification from a melt (melt growth), nucleation from a solution (solution growth), condensation from a vapor (physical vapor transport) or chemical reaction of gases (chemical vapor deposition), the parent phase is a fluid. As is with most non-equilibrium processes involving fluids, liquid or vapor, fluid motion plays an important role, affecting both the concentration and temperature gradients at the soli-liquid interface.

  15. Optical monitoring of protein crystal growth

    NASA Technical Reports Server (NTRS)

    Choudry, A.

    1988-01-01

    The possibility of using various optical techniques for detecting the onset of nucleation in protein crystal growth was investigated. Direct microscopy, general metrologic techniques, light scattering, ultraviolet absorption, and interferometry are addressed along with techniques for determining pH value. The necessity for collecting basic data on the optical properties of the growth solution as a prerequisite to the evaluation of monitoring techniques is pointed out.

  16. Method of monitoring crystal growth

    DOEpatents

    Sachs, Emanual M. (Watertown, MA)

    1982-01-01

    A system and method are disclosed for monitoring the growth of a crystalline body from a liquid meniscus in a furnace. The system provides an improved human/machine interface so as to reduce operator stress, strain and fatigue while improving the conditions for observation and control of the growing process. The system comprises suitable optics for forming an image of the meniscus and body wherein the image is anamorphic so that the entire meniscus can be viewed with good resolution in both the width and height dimensions. The system also comprises a video display for displaying the anamorphic image. The video display includes means for enhancing the contrast between any two contrasting points in the image. The video display also comprises a signal averager for averaging the intensity of at least one preselected portions of the image. The value of the average intensity, can in turn be utilized to control the growth of the body. The system and method are also capable of observing and monitoring multiple processes.

  17. Apparatus for monitoring crystal growth

    DOEpatents

    Sachs, Emanual M. (Watertown, MA)

    1981-01-01

    A system and method are disclosed for monitoring the growth of a crystalline body from a liquid meniscus in a furnace. The system provides an improved human/machine interface so as to reduce operator stress, strain and fatigue while improving the conditions for observation and control of the growing process. The system comprises suitable optics for forming an image of the meniscus and body wherein the image is anamorphic so that the entire meniscus can be viewed with good resolution in both the width and height dimensions. The system also comprises a video display for displaying the anamorphic image. The video display includes means for enhancing the contrast between any two contrasting points in the image. The video display also comprises a signal averager for averaging the intensity of at least one preselected portions of the image. The value of the average intensity, can in turn be utilized to control the growth of the body. The system and method are also capable of observing and monitoring multiple processes.

  18. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

    1999-01-01

    The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

  19. A clarified gel for crystal growth

    NASA Technical Reports Server (NTRS)

    Barber, P. G.; Simpson, N. R.

    1985-01-01

    A procedure for preparing clarified sodium silicate gels suitable for crystal growth is described. In the method described here, the silicate stock is clarified by pretreating it with cation exchange resins before preparing the gels. Also, a modified recipe is proposed for preparing gels to achieve improved transparency.

  20. (PCG) Protein Crystal Growth Isocitrate Lysase

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Comparison of Earth grown and Space grown Isocitrate Lysase crystals. Target enzyme for fungicides. A better understanding of this enzyme should lead to the discovery of more potent fungicides to treat serious crop diseases such as rice blast. It regulates the flow of metabolic intermediates required for cell growth. Principal Investigator was Charles Bugg.

  1. Growth of Organic Crystals by Ostwald Ripening

    NASA Technical Reports Server (NTRS)

    Egbert, W.; Podsiadly, C.; Naumann, R.

    1985-01-01

    The objective of this investigation is to evaluate the growth of various organic crystals by chemical precipitation and Ostwald ripening. Six precipitation reactors were flown on STS-51A. Five of the reactors contained proprietary materials. The sixth contained urea dissolved in ethanol with toluene as the precipitating agent. The size distribution will be analyzed and compared with a similar model being developed.

  2. Spacelab 3 vapor crystal growth experiment

    NASA Technical Reports Server (NTRS)

    Schnepple, W.; Vandenberg, L.; Skinner, N.; Ortale, C.

    1987-01-01

    The Space Shuttle Challenger, with Spacelab 3 as its payload, was launched into orbit April 29, 1985. The mission, number 51-B, emphasized materials processing in space, although a wide variety of experiments in other disciplines were also carried onboard. One of the materials processing experiments on this flight is described, specifically the growth of single crystals of mercuric iodide by physical vapor transport.

  3. Crystal growth furnace safety system validation

    NASA Technical Reports Server (NTRS)

    Mackowski, D. W.; Hartfield, R.; Bhavnani, S. H.; Belcher, V. M.

    1994-01-01

    The findings are reported regarding the safe operation of the NASA crystal growth furnace (CGF) and potential methods for detecting containment failures of the furnace. The main conclusions are summarized by ampoule leak detection, cartridge leak detection, and detection of hazardous species in the experiment apparatus container (EAC).

  4. Growth of single-crystal gallium nitride

    NASA Technical Reports Server (NTRS)

    Clough, R.; Richman, D.; Tietjen, J.

    1970-01-01

    Use of ultrahigh purity ammonia prevents oxygen contamination of GaN during growth, making it possible to grow the GaN at temperatures as high as 825 degrees C, at which point single crystal wafers are deposited on /0001/-oriented sapphire surfaces.

  5. Crystal growth in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Kroes, Roger L. (Inventor); Reiss, Donald A. (Inventor); Lehoczky, Sandor L. (Inventor)

    1992-01-01

    Gravitational phenomena, including convection, sedimentation, and interactions of materials with their containers all affect the crystal growth process. If they are not taken into consideration they can have adverse effects on the quantity and quality of crystals produced. As a practical matter, convection, and sedimentation can be completely eliminated only under conditions of low gravity attained during orbital flight. There is, then, an advantage to effecting crystallization in space. In the absence of convection in a microgravity environment cooling proceeds by thermal diffusion from the walls to the center of the solution chamber. This renders control of nucleation difficult. Accordingly, there is a need for a new improved nucleation process in space. Crystals are nucleated by creating a small localized region of high relative supersaturation in a host solution at a lower degree of supersaturation.

  6. Polymer crystallization mechanism through a mesomorphic state

    NASA Astrophysics Data System (ADS)

    Konishi, Takashi; Sakatsuji, Waki; Fukao, Koji; Miyamoto, Yoshihisa

    2011-10-01

    The isothermal crystallization from the molten state of poly(butylene terephthalate) is studied by differential scanning calorimetry and small-angle x-ray scattering. The relations among the crystallization temperature, lamella thickness, and melting temperature give two equilibrium transition temperatures. We propose a model of crystalline lamella formation through a mesomorphic state at the growth front by which these equilibrium transition temperatures are interpreted as the transition temperature between the mesophase and the crystal, and the one between the melt and the crystal of infinitely thick lamellae. These results show that the mesomorphic state plays a key role in the ordering process of polymers.

  7. How Chain-Folding Crystal Growth Determines the Thermodynamic Stability of Polymer Crystals.

    PubMed

    Jiang, Xiaoming; Reiter, Gnter; Hu, Wenbing

    2016-01-28

    Chain-folding is a habit of polymer crystallization, which yields limited lamellar thickness of polymer crystals and thus determines their thermodynamic stability. We performed dynamic Monte Carlo simulations of a lattice polymer model with chain-folded lamellar crystal growth stopped by a critical spacing of two parallel-oriented bars. We confirmed the critical spacing as minimum lamellar thickness (lmin) proposed previously in the Lauritzen-Hoffman (LH) model; however, the temperature dependence of excess lamellar thickness beyond lmin appears opposite to the prediction of the LH model. Moreover, it reproduces Strobl et al.'s experimental observations, but our lattice-model approach rules out any mesophase hypothesis. We proposed a kinetic model combining intramolecular secondary nucleation and stem elongation to explain this temperature-dependence behavior, which reconciles the controversial arguments on the microscopic mechanism of lamellar crystal growth of polymers. PMID:26720595

  8. Surface Phenomena and Parameters of Crystal Growth: Simple Basics

    SciTech Connect

    Chernov, A. A.

    2010-07-22

    Basic concepts of crystal growth and their practical use to semi-quantitatively estimate growth processes are explained: surface energy and free energy, driving force of crystallization, atomically rough vs smooth interface structure and the corresponding normal vs layer-by-layer growth modes, application of the activated complex concept to derive kinetic coefficient characterizing crystal growth rate at a given driving force. The Reader is supposed to be familiar with general physics and chemistry. No specific knowledge in crystal growth is required.

  9. Nucleation and growth control in protein crystallization

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Nyce, Thomas A.; Meehan, Edward J.; Sowers, Jennifer W.; Monaco, Lisa A.

    1990-01-01

    The five topics summarized in this final report are as follows: (1) a technique for the expedient, semi-automated determination of protein solubilities as a function of temperature and application of this technique to proteins other than lysozyme; (2) a small solution cell with adjustable temperature gradients for the growth of proteins at a predetermined location through temperature programming; (3) a microscopy system with image storage and processing capability for high resolution optical studies of temperature controlled protein growth and etching kinetics; (4) growth experiments with lysozyme in thermosyphon flow ; and (5) a mathematical model for the evolution of evaporation/diffusion induced concentration gradients in the hanging drop protein crystallization technique.

  10. On the elementary processes of protein crystallization: Bond selection mechanism

    NASA Astrophysics Data System (ADS)

    Nanev, Christo N.

    2014-09-01

    The paper explores the application of bond selection mechanism (BSM) in protein crystal growth; previously, BSM was employed to explain the slow rate of protein crystal nucleation, equilibrium crystal shape and energy barrier in nucleus formation (C.N. Nanev, Prog. Cryst. Growth Charact. Mater. 59 (2013) 133-169). Now, the elementary growth processes are considered from BSM perspective and the crystal growth shape is tackled, the latter resulting from a strong directional kinetic anisotropy in step advancement rates in different crystallographic directions. The most significant surface patterns of growing protein crystals, such as two-dimensional nuclei and growth spiral shapes observed by atomic force microscopy (AFM), are also considered. The activation barrier associated with entering of a protein molecule into the kink site is evaluated and the start of the kinetic roughening is established. Crystal lattice bond energies are estimated (being well above the thermal energy, kBT) from the supersaturation dependence of 2D- into 1D-nuclei transformation.

  11. Bridgman growth of paratellurite single crystals

    NASA Astrophysics Data System (ADS)

    Veber, P.; Mangin, J.; Strimer, P.; Delarue, P.; Josse, C.; Saviot, L.

    2004-09-01

    The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120 mm long and 25 mm in diameter were obtained under a temperature gradient of 10C cm-1 and translation rates lower than 0.6 mm h-1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth proceeds. Gas bubbles and dark inclusions rejected to the periphery in the upper part of the crystal are observed to lay preferentially in (1 0 0), (0 0 1), (1 1 bar 0) and (1 1 2) crystallographic planes. Among them, SEM and microprobe analyses evidenced the presence of metallic platinum, while micro-Raman experiments allowed to assess oxygen as being actually the gas content of occluded bubbles, originated at the crucible wall through Pt-induced dissociation of Te-O bonds.

  12. Inclusion free cadmium zinc tellurium and cadmium tellurium crystals and associated growth method

    DOEpatents

    Bolotnikov, Aleskey E. (South Setauket, NY); James, Ralph B. (Ridge, NY)

    2010-07-20

    The present disclosure provides systems and methods for crystal growth of cadmium zinc tellurium (CZT) and cadmium tellurium (CdTe) crystals with an inverted growth reactor chamber. The inverted growth reactor chamber enables growth of single, large, high purity CZT and CdTe crystals that can be used, for example, in X-ray and gamma detection, substrates for infrared detectors, or the like. The inverted growth reactor chamber enables reductions in the presence of Te inclusions, which are recognized as an important limiting factor in using CZT or CdTe as radiation detectors. The inverted growth reactor chamber can be utilized with existing crystal growth techniques such as the Bridgman crystal growth mechanism and the like. In an exemplary embodiment, the inverted growth reactor chamber is a U-shaped ampoule.

  13. Drop deployment system for crystal growth apparatus

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H. (Inventor); Snyder, Robert S. (Inventor); Pusey, Marc L. (Inventor)

    1992-01-01

    This invention relates to a crystal growth apparatus (10) generally used for growing protein crystals wherein a vapor diffusion method is used for growing the crystals. In this apparatus, a precipitating solution and a solution containing dissolved crystalline material are stored in separate vials (12, 14), each having a resilient diaphragm (28) across one end and an opening (24) with a puncturable septum (26) thereacross at an opposite end. The vials are placed in receptacles (30) having a manifold (41) with a manifold diaphragm (42) in contact with the vial diaphragm at one end of the receptacle and a hollow needle (36) for puncturing the septum at the other end of the manifold. The needles of each vial communicate with a ball mixer (40) that mixes the precipitate and protein solutions and directs the mixed solution to a drop support (64) disposed in a crystal growth chamber (16), the drop support being a tube with an inner bevelled surface (66) that provides more support for the drop (68) than the tubes of the prior art. A sealable storage region (70) intermediate the drop support and mixer provides storage of the drop (68) and the grown crystals.

  14. High-purity silicon crystal growth investigations

    NASA Technical Reports Server (NTRS)

    Ciszek, T. F.; Schuyler, T.; Hurd, J. L.; Fearheiley, M.; Evans, C.; Elder, R.

    1986-01-01

    Information is given on evaporation and segregation contributions to impurity profiles of floating zone crystals (FZ); high-purity silicon float zoning (FZ); minority-carrier lifetime measurement of heavily doped silicon crystals; the effect of some crystal growth parameters on minority-carrier lifetime; and defect investigations by X-ray topography in graphical and tabular form. It was concluded that evaporation contributes substantially to impurity reduction when FZ or cold-crucible growth is conducted in a vacuum; boron and gallium may be more favorable dopants than indium or aluminum for obtaining high minority-carrier lifetimes; minority-carrier lifetimes greater than 100 microseconds are feasible at a 2 times 10 to the 17th power cm-3 doping level; minority-carrier lifetime decreases with increasing crystal cooling rate and also with the presence of dislocations; the method used to clean silicon feed rods affects lifetime; and microdefect densities in dislocation-free FZ crystals appear to be lower with Ga doping than with B doping.

  15. Growth of (101) Faces of Tetragonal Lysozyme Crystals: Measured Growth Rate Trends

    NASA Technical Reports Server (NTRS)

    Forsythe, Elizabeth L.; Nadarajah, Arunan; Pusey, Marc L.

    1998-01-01

    Earlier extensive measurements of the growth rates of the (110) face of tetragonal lysozyme crystals had shown unexpected dependencies on the supersaturation. In this study similar growth rate measurements were done for the (101) faces of the crystals. The data show a similar dependence on the supersaturation, becoming appreciable only at high supersaturations, reaching a maximum value and then decreasing. As reported in earlier studies, the (101) growth rates are larger at low supersaturations than the (110) growth rates at the same conditions, and smaller at high supersaturations. These trends suggest that the growth mechanism of the (101) is similar to that of the (110) face, involving the addition of lysozyme aggregates formed in solution, but with a growth unit smaller than that of the (110) face.

  16. Growth of (101) faces of tetragonal lysozyme crystals: measured growth-rate trends

    NASA Technical Reports Server (NTRS)

    Forsythe, E. L.; Nadarajah, A.; Pusey, M. L.

    1999-01-01

    Previous extensive measurements of the growth rates of the (110) face of tetragonal lysozyme crystals have shown unexpected dependencies on the supersaturation. In this study, similar growth-rate measurements were performed for the (101) faces of the crystals. The data show a similar dependence on the supersaturation, becoming appreciable only at high supersaturations, reaching a maximum value and then decreasing. The (101) growth rates are larger at low supersaturations than the (110) growth rates under the same conditions and are smaller at high supersaturations. These trends suggest that the growth mechanism of the (101) face is similar to that of the (110) face: both processes involve the addition of multimeric growth units formed in solution, but the average size of the units for the (101) face is likely to be smaller than for the (110) face.

  17. In situ observation of mono-molecular growth steps on aqueous solution grown crystals and the transport of molecules to the crystals

    NASA Technical Reports Server (NTRS)

    Tsukamoto, Katsuo

    1987-01-01

    Direct in situ observation of mono-molecular growth steps on a crystal growing in an aqueous solution became possible. The combination of this method with high resolution Schlieren methods or interferometry, permits the growth mechanism of crystals to be investigated directly. Since the observation of growth steps on crystals is the most direct and sensitive way for investigating a crystal growth mechanism, it would contribute to revealing fundamental differences between the growth in space and on Earth. The method was recently extended to in situ observation of the growth processes at high temperatures (1800K).

  18. FNAS/advanced protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1992-01-01

    A scintillation method is presented for determination of the temperature dependence of the solubility, S(T), of proteins in 50-100 micro-l volumes of solution. S(T) data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. The resulting kinetics and equilibrium information was used for dynamic control, that is the separation of nucleation and growth stages in protein crystallization. Individual lysozyme and horse serum albumin crystals were grown in 15-20 micro-l solution volumes contained in x-ray capillaries.

  19. Convective flow effects on protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Monaco, Lisa A.

    1993-01-01

    The experimental setup for the in-situ high resolution optical monitoring of protein crystal growth/dissolution morphologies was substantially improved. By augmenting the observation system with a temperature-controlled enclosure, laser illumination for the interferometric microscope, and software for pixel by pixel light intensity recording, a height resolution of about two unit cells for lysozyme can now be obtained. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied. Quite unexpectedly, it was found that the longer crystals were in contact with their solution, the lower was their ion content. The development of a model for diffusive-convective transport and resulting distribution of the growth rate on facets was completed. Results obtained for a realistic growth cell geometry show interesting differences between 'growth runs' at 1g and 0g. The kinematic viscosity of lysozyme solutions of various supersaturations and salt concentrations was monitored over time. In contrast to the preliminary finding of other authors, no changes in viscosity were found over four days. The experimental setup for light scattering investigations of aggregation and nucleation in protein solutions was completed, and a computer program for the evaluation of multi-angle light scattering data was acquired.

  20. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1994-01-01

    This research involved (1) using the Atomic Force Microscope (AFM) in a study on the growth of lysozyme crystals and (2) refinement of the design of the Thermonucleator which controls the supersaturation required for the nucleation and growth of protein crystals separately. AFM studies of the (110) tetragonal face confirmed that lysozyme crystals grow by step propagation. There appears to be very little step pile up in the growth regimes which we studied. The step height was measured at = 54A which was equal to the (110) interpane spacing. The AFM images showed areas of step retardation and the formation of pits. These defects ranged in size from 0.1 to 0.4 mu. The source of these defects was not determined. The redesign of the Thermonucleator produced an instrument based on thermoelectric technology which is both easier to use and more amenable to use in a mu g environment. The use of thermoelectric technology resulted in a considerable size reduction which will allow for the design of a multi-unit growth apparatus. The performance of the new apparatus was demonstrated to be the same as the original design.

  1. Crystal growth and annealing for minimized residual stress

    DOEpatents

    Gianoulakis, Steven E. (Albuquerque, NM)

    2002-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing.

  2. Mechanisms, kinetics, impurities and defects: consequences in macromolecular crystallization

    PubMed Central

    McPherson, Alexander; Kuznetsov, Yurii G.

    2014-01-01

    The nucleation and growth of protein, nucleic acid and virus crystals from solution are functions of underlying kinetic and thermodynamic parameters that govern the process, and these are all supersaturation-dependent. While the mechanisms of macromolecular crystal growth are essentially the same as for conventional crystals, the underlying parameters are vastly different, in some cases orders of magnitude lower, and this produces very different crystallization processes. Numerous physical features of macromolecular crystals are of serious interest to X-ray diffractionists; the resolution limit and mosaicity, for example, reflect the degree of molecular and lattice order. The defect structure of crystals has an impact on their response to flash-cooling, and terminal crystal size is dependent on impurity absorption and incorporation. The variety and extent of these issues are further unique to crystals of biological macromolecules. All of these features are amenable to study using atomic force microscopy, which provides direct images at the nanoscale level. Some of those images are presented here. PMID:24699728

  3. Crystal Splitting in the Growth of Bi2S3

    SciTech Connect

    Tang, Jing; Alivisatos, A. Paul

    2006-06-15

    Novel Bi{sub 2}S{sub 3} nanostructures with a sheaf-like morphology are obtained via reaction of bismuth acetate-oleic acid complex with elemental sulfur in 1-octadecence. We propose these structures form by the splitting crystal growth mechanism, which is known to account for the morphology some mineral crystals assume in nature. By controlling the synthetic parameters, different forms of splitting, analogous to observed in minerals, are obtained in our case of Bi{sub 2}S{sub 3}. These new and complex Bi{sub 2}S{sub 3} nanostructures are characterized by TEM, SEM, XRD and ED.

  4. Subtilisin surface properties and crystal growth kinetics

    NASA Astrophysics Data System (ADS)

    Pan, Xiaojing; Bott, Rick; Glatz, Charles E.

    2003-07-01

    Our previous study showed that the solubility and crystal growth rate of the protein subtilisin changed with the substitution of small numbers of surface amino acid residues. Structural and energetic comparisons of crystal structures of two subtilisin mutants were conducted to explore the reason for changes in the growth rate of subtilisin crystals. Unique lattice contact patches were determined for the two mutants. The loss of solvent accessible surface area (ASA), the average hydrophobicity and the number of hydrogen bonds and salt bridges were calculated to quantify surface properties of the contact patches. The structural comparison showed that the three amino acid mutations (Purafect ?Properase ) are all in contact patches and provide extra atomic contacts. For Properase subtilisin, the number of contacting residues and the loss of ASA increased. Binding energetic calculations, based on the detailed protein structures, were performed to determine non-electrostatic interaction contributions for the required crystallographic orientation and the number of energetically favored, false-binding orientations. The agreement and disparity between molecular structure and macroscopic crystallization behavior are discussed.

  5. Lead isotope variation with growth zoning in a galena crystal

    USGS Publications Warehouse

    Cannon, R.S., Jr.; Pierce, A.P.; Delevaux, M.H.

    1963-01-01

    A large crystal of lead sulfide from Picher, Oklahoma, has significant differences in isotopic composition of lead in successive growth zones. Lead isotope ratios in the parent ore-fluid evidently changed with time during crystal growth. The growth history of this crystal, interpreted quantitatively, points to a tentative hypothesis of genesis of Mississippi Valley deposits of lead and zinc.

  6. Studying Crystal Growth With the Peltier Effect

    NASA Technical Reports Server (NTRS)

    Larsen, David J., Jr.; Dressler, B.; Silberstein, R. P.; Poit, W. J.

    1986-01-01

    Peltier interface demarcation (PID) shown useful as aid in studying heat and mass transfer during growth of crystals from molten material. In PID, two dissimilar "metals" solid and liquid phases of same material. Current pulse passed through unidirectionally solidifying sample to create rapid Peltier thermal disturbance at liquid/solid interface. Disturbance, measured by thermocouple stationed along path of solidification at or near interface, provides information about position and shape of interface.

  7. Dendritic Growth Velocity of Ice Crystals

    NASA Technical Reports Server (NTRS)

    Ohsaka, K.; Trinh, E. H.

    1997-01-01

    The dendritic growth velocity of ice crystals is measured at undercooling levels between 5-8.5 K using a unique apparatus. The result shows that the measured velocities are smaller that the theoretical prediction based on the thermal diffusion theory with the scalling constant, Q= 0.025, which has been shown to agree with the experimental results at lower undercooling levels between 0.4 -2.5 K.

  8. (PCG) Protein Crystal Growth Gamma-Interferon

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Gamma-Interferon. Stimulates the body's immune system and is used clinically in the treatment of cancer. Potential as an anti-tumor agent against solid tumors as well as leukemia's and lymphomas. It has additional utility as an anti-ineffective agent, including antiviral, anti-bacterial, and anti-parasitic activities. Principal Investigator on STS-26 was Charles Bugg.

  9. (PCG) Protein Crystal Growth Human Serum Albumin

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Human Serum Albumin. Contributes to many transport and regulatory processes and has multifunctional binding properties which range from various metals, to fatty acids, hormones, and a wide spectrum of therapeutic drugs. The most abundant protein of the circulatory system. It binds and transports an incredible variety of biological and pharmaceutical ligands throughout the blood stream. Principal Investigator on STS-26 was Larry DeLucas.

  10. Determination of growth and breakage kinetics of L-threonine crystals

    NASA Astrophysics Data System (ADS)

    Bao, Ying; Zhang, Jinlong; Yin, Qiuxiang; Wang, Jingkang

    2006-03-01

    The crystal growth and breakage kinetics of L-threonine by evaporation crystallization were studied at the laboratory scale using a 1200 ml crystallizer with draft tube. Evaporation experiments were carried out at three different temperatures and three different stirrer speeds. Crystal breakage phenomena were demonstrated by image analysis and evolution of crystal size distribution. Breakage of binary uniform distribution and volume-independent growth kinetics were extracted by moment method. Moreover, the breakage and growth kinetics were proved to be appropriate for L-threonine/water evaporation process using numeric simulation. The growth kinetic parameters indicated that diffusion should be the rate-controlling step of crystal growth, and higher temperature higher growth rate. The higher exponent of agitation speed for breakage kinetics indicated that the removal of fragments stimulated by stirring should be the main breakage mechanism.

  11. ICCG-10: Tenth International Conference on Crystal Growth. Oral presentation abstracts

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Oral presentation abstracts from the tenth International Conference on Crystal Growth (ICCG) (Aug. 16-21, 1992) are provided. Topics discussed at the conference include superconductors, semiconductors, nucleation, crystal growth mechanisms, and laser materials. Organizing committees, ICCG advisory board and officers, and sponsors of the conference are also included.

  12. ICCG-10: Tenth International Conference on Crystal Growth. Poster presentation abstracts

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Poster presentation abstracts from the tenth International Conference on Crystal Growth (ICCG) (Aug. 16-21, 1992) are provided. Topics discussed at the conference include crystal growth mechanisms, superconductors, semiconductors, laser materials, optical materials, and biomaterials. Organizing committees, ICCG advisory board and officers, and sponsors of the conference are also included.

  13. Mechanical characterization of partially crystallized sphere packings.

    PubMed

    Hanifpour, M; Francois, N; Vaez Allaei, S M; Senden, T; Saadatfar, M

    2014-10-01

    We study grain-scale mechanical and geometrical features of partially crystallized packings of frictional spheres, produced experimentally by a vibrational protocol. By combining x-ray computed tomography, 3D image analysis, and discrete element method simulations, we have access to the 3D structure of internal forces. We investigate how the network of mechanical contacts and intergranular forces change when the packing structure evolves from amorphous to near perfect crystalline arrangements. We compare the behavior of the geometrical neighbors (quasicontracts) of a grain to the evolution of the mechanical contacts. The mechanical coordination number Z(m) is a key parameter characterizing the crystallization onset. The high fluctuation level of Z(m) and of the force distribution in highly crystallized packings reveals that a geometrically ordered structure still possesses a highly random mechanical backbone similar to that of amorphous packings. PMID:25325661

  14. The Averaged Face Growth Rates of lysozyme Crystals: The Effect of Temperature

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Forsythe, Elizabeth L.; Pusey, Marc L.

    1995-01-01

    Measurements of the averaged or macroscopic face growth rates of lysozyme crystals are reported here for the (110) face of tetragonal lysozyme, at three sets of pH and salt concentrations, with temperatures over a 4-22 C range for several protein concentrations. The growth rate trends with supersaturation were similar to previous microscopic growth rate measurements. However, it was found that at high super-saturations the growth rates attain a maximum and then start decreasing. No 'dead zone' was observed but the growth rates were found to approach zero asymptotically at very low super-saturations. The growth rate data also displayed a dependence on pH and salt concentration which could not be characterized solely by the super-saturation. A complete mechanism for lysozyme crystal growth, involving the formation of an aggregate growth unit, mass transport of the growth unit to the crystal interface and faceted crystal growth by growth unit addition, is suggested. Such a mechanism may provide a more consistent explanation for the observed growth rate trends than those suggested by other investigators. The nutrient solution interactions leading to the formation of the aggregate growth unit may, thus, be as important as those occurring at the crystal interface and may account for the differences between small molecule and protein crystal growth.

  15. A unified description of attachment-based crystal growth.

    PubMed

    Zhang, Hengzhong; De Yoreo, James J; Banfield, Jillian F

    2014-07-22

    Crystal growth is one of the most fundamental processes in nature. Understanding of crystal growth mechanisms has changed dramatically over the past two decades. One significant advance has been the recognition that growth does not only occur atom by atom, but often proceeds via attachment and fusion of either amorphous or crystalline particles. Results from recent experiments and calculations can be integrated to develop a simple, unified conceptual description of attachment-based crystal growth. This enables us to address three important questions: What are the driving forces for attachment-based growth? For crystalline particles, what enables the particles to achieve crystallographic coalignment? What determines the surface on which attachment occurs? We conclude that the extent of internal nanoparticle order controls the degree of periodicity and anisotropy in the surrounding electrostatic field. For crystalline particles, the orienting force stemming from the electrostatic field can promote oriented attachment events, although solvent-surface interactions modulate this control. In cases where perfect crystallographic alignment is not achieved, misorientation gives rise to structural defects that can fundamentally modify nanomaterial properties. PMID:25000275

  16. Enhancing the Mechanical Properties of Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  17. Unsteady-state transfer of impurities during crystal growth of sucrose in sugarcane solutions

    NASA Astrophysics Data System (ADS)

    Martins, P. M.; Ferreira, A.; Polanco, S.; Rocha, F.; Damas, A. M.; Rein, P.

    2009-07-01

    In this work, we present growth rate data of sucrose crystals in the presence of impurities that can be used by both sugar technologists and crystal growth scientists. Growth rate curves measured in a pilot-scale evaporative crystallizer suggest a period of slow growth that follows the seeding of crystals into supersaturated technical solutions. The observed trend was enhanced by adding typical sugarcane impurities such as starch, fructose or dextran to the industrial syrups. Maximum growth rates of sucrose resulted at intermediate rather than high supersaturation levels in the presence of the additives. The effects of the additives on the sucrose solubility and sucrose mass transfer in solution were taken into account to explain the observed crystal growth kinetics. A novel mechanism was identified of unsteady-state adsorption of impurities at the crystal surface and their gradual replacement by the crystallizing solute towards the equilibrium occupation of the active sites for growth. Specifically designed crystallization experiments at controlled supersaturation confirmed this mechanism by showing increasing crystal growth rates with time until reaching a steady-state value for a given supersaturation level and impurity content.

  18. Convective flow effects on protein crystal growth

    NASA Astrophysics Data System (ADS)

    Rosenberger, Franz; Monaco, Lisa A.

    1995-01-01

    During the fourth semi-annual period under this grant we have pursued the following activities: (1) crystal growth morphology and kinetics studies with tetragonal lysozyme. These clearly revealed the influence of higher molecular weight protein impurities on interface shape; (2) characterization of the purity and further purification of lysozyme solutions. These efforts have, for the first time, resulted in lysozyme free of higher molecular weight components; (3) continuation of the salt repartitioning studies with Seikagaku lysozyme, which has a lower protein impurity content that Sigma stock. These efforts confirmed our earlier findings of higher salt contents in smaller crystals. However, less salt is in corporated into the crystals grown from Seikagaku stock. This strongly suggests a dependence of salt repartitioning on the concentration of protein impurities in lysozyme. To test this hypothesis, repartitioning studies with the high purity lysozyme prepared in-house will be begun shortly; (4) numerical modelling of the interaction between bulk transport and interface kinetics. These simulations have produced interface shapes which are in good agreement with out experimental observations; and (5) light scattering studies on under- and supersaturated lysozyme solutions. A consistent interpretation of the static and dynamic data leaves little doubt that pre-nucleation clusters, claimed to exist even in undersaturated solutions, are not present. The article: 'Growth morphology response to nutrient and impurity nonuniformities' is attached.

  19. Step Crowding Effects Dampen the Stochasticity of Crystal Growth Kinetics.

    PubMed

    Lutsko, James F; Van Driessche, Alexander E S; Durn-Olivencia, Miguel A; Maes, Dominique; Sleutel, Mike

    2016-01-01

    Crystals grow by laying down new layers of material which can either correspond in size to the height of one unit cell (elementary steps) or multiple unit cells (macrosteps). Surprisingly, experiments have shown that macrosteps can grow under conditions of low supersaturation and high impurity density such that elementary step growth is completely arrested. We use atomistic simulations to show that this is due to two effects: the fact that the additional layers bias fluctuations in the position of the bottom layer towards growth and by a transition, as step height increases, from a 2D to a 3D nucleation mechanism. PMID:26799026

  20. Step Crowding Effects Dampen the Stochasticity of Crystal Growth Kinetics

    NASA Astrophysics Data System (ADS)

    Lutsko, James F.; Van Driessche, Alexander E. S.; Durn-Olivencia, Miguel A.; Maes, Dominique; Sleutel, Mike

    2016-01-01

    Crystals grow by laying down new layers of material which can either correspond in size to the height of one unit cell (elementary steps) or multiple unit cells (macrosteps). Surprisingly, experiments have shown that macrosteps can grow under conditions of low supersaturation and high impurity density such that elementary step growth is completely arrested. We use atomistic simulations to show that this is due to two effects: the fact that the additional layers bias fluctuations in the position of the bottom layer towards growth and by a transition, as step height increases, from a 2D to a 3D nucleation mechanism.

  1. Accelerated protein crystal growth by protein thin film template

    NASA Astrophysics Data System (ADS)

    Pechkova, Eugenia; Nicolini, Claudio

    2001-11-01

    A new method based on Langmuir-Blodgett (LB) technology is presented for the template stimulation of protein crystal growth. The new approach allows the acceleration of the hen egg white lysozyme (HEWL) crystal growth rate in comparison with such a classical vapour diffusion method as hanging drop. Protein thin films were coated on the cover slide of the common crystallization plates. Lysozyme crystal growth was observed on the LB thin films of HEWL.

  2. Protein-induced morphological transitions in KCl crystal growth.

    PubMed

    Szab, Blint; Vicsek, Tams

    2003-01-01

    We investigated the formation of KCl crystals on a glass surface by phase contrast, fluorescent, and atomic force microscopy on the micrometer scale and observed interesting morphological transitions as a function of the experimental conditions. The presence of proteins in the solution from which the salt crystals grow during the drying up leads to complex microscopic patterns of crystals, some of which are analogous to those commonly observed on the macroscopic scale. We tested the effect of tubulin, FITC-labeled albumin, and IgG on the morphology of crystals grown either slowly or fast. A rich variety of protein-specific and concentration-dependent morphologies was found and described by a morphological diagram. We give a phenomenological interpretation, which can explain the growth of complex patterns. Fluorescent images prove that a protein layer covers the surface of the KCl structures. We propose that this layer reduces the anisotropy of the effective surface tension during growth. The tip splitting fractal regime is attributed to the decrease of anisotropy. Further possible mechanisms, which can cause a morphological transition, are also discussed. We found elongated saw-toothed crystals induced by proteins, especially IgG, and identified their structure. PMID:12636533

  3. Growth and adhesion properties of monosodium urate monohydrate (MSU) crystals

    NASA Astrophysics Data System (ADS)

    Perrin, Clare M.

    The presence of monosodium urate monohydrate (MSU) crystals in the synovial fluid has long been associated with the joint disease gout. To elucidate the molecular level growth mechanism and adhesive properties of MSU crystals, atomic force microscopy (AFM), scanning electron microscopy, and dynamic light scattering (DLS) techniques were employed in the characterization of the (010) and (1-10) faces of MSU, as well as physiologically relevant solutions supersaturated with urate. Topographical AFM imaging of both MSU (010) and (1-10) revealed the presence of crystalline layers of urate arranged into v-shaped features of varying height. Growth rates were measured for both monolayers (elementary steps) and multiple layers (macrosteps) on both crystal faces under a wide range of urate supersaturation in physiologically relevant solutions. Step velocities for monolayers and multiple layers displayed a second order polynomial dependence on urate supersaturation on MSU (010) and (1-10), with step velocities on (1-10) generally half of those measured on MSU (010) in corresponding growth conditions. Perpendicular step velocities on MSU (010) were obtained and also showed a second order polynomial dependence of step velocity with respect to urate supersaturation, which implies a 2D-island nucleation growth mechanism for MSU (010). Extensive topographical imaging of MSU (010) showed island adsorption from urate growth solutions under all urate solution concentrations investigated, lending further support for the determined growth mechanism. Island sizes derived from DLS experiments on growth solutions were in agreement with those measured on MSU (010) topographical images. Chemical force microscopy (CFM) was utilized to characterize the adhesive properties of MSU (010) and (1-10). AFM probes functionalized with amino acid derivatives and bio-macromolecules found in the synovial fluid were brought into contact with both crystal faces and adhesion forces were tabulated into histograms for comparison. AFM probes functionalized with -COO-, -CH3, and -OH functionalities displayed similar adhesion force with both crystal surfaces of MSU, while adhesion force on (1-10) was three times greater than (010) for -NH2+ probes. For AFM probes functionalized with bovine serum albumin, adhesion force was three times greater on MSU (1-10) than (010), most likely due to the more ionic nature of (1-10).

  4. The Effect of Protein Impurities on Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Judge, Russell A.; Forsythe, Elizabeth L.; Pusey, Marc L.

    1998-01-01

    While bulk crystallization from impure solutions is used industrially as a purification step for a wide variety of materials, it is a technique that has rarely been used for proteins. Proteins have a reputation for being difficult to crystallize and high purity of the initial crystallization solution is considered paramount for success in the crystallization. Although little is written on the purifying capability of protein crystallization or of the effect of impurities on the various aspects of the crystallization process, recent published reports show that crystallization shows promise and feasibility as a purification technique for proteins. In order to further examine the issue of purity in macromolecule crystallization this study investigates the effect of the protein impurities, avidin, ovalbumin and conalbumin, at concentrations up to 50%, on the solubility, crystal face growth rates and crystal purity, of the protein lysozyme. Solubility was measured in batch experiments while a computer controlled video microscope system was used to measure the f {101} and {101} lysozyme crystal face growth rates. While little effect was observed on solubility and high crystal purity was obtained (>99.99%), the effect of the impurities on the face growth rates varied from no effect to a significant face specific effect leading to growth cessation, a phenomenon that is frequently observed in protein crystal growth. The results shed interesting light on the effect of protein impurities on protein crystal growth and strengthen the feasibility of using crystallization as a unit operation for protein purification.

  5. Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Brebrick, Robert F.; Volz, Martin P.; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin P.; Shih, Hung-Dah

    2001-01-01

    Crystal growth by vapor transport has several distinct advantages over melt growth techniques. Among various potential benefits from material processing in reduced gravity the followings two are considered to be related to crystal growth by vapor transport: (1) elimination of the crystal weight and its influence on the defect formation and (2) reduction of natural buoyancy-driven convective flows arising from thermally and/ or solutally induced density gradient in fluids. The previous results on vapor crystal growth of semiconductors showed the improvements in surface morphology, crystalline quality, electrical properties and dopant distribution of the crystals grown in reduced gravity as compared to the crystals grown on Earth. But the mechanisms, which are responsible for the improvements and cause the gravitational effects on the complicated and coupled processes of vapor mass transport and growth kinetics, are not well understood.

  6. Transport Processes in Solution Crystal Growth

    NASA Technical Reports Server (NTRS)

    Chai, A. T.

    1985-01-01

    The objective of this effort is to conduct fundamental research in reduced gravity on transport processes occurring during solution crystal growth. Experimental techniques will be developed to monitor and control key parameters at the interface between a growing crystal and the solution from which it grows. Techniques developed will lead to an in-space experiment in the Shuttle. The focus will be on non-incursive ground-based laboratory measurements of model systems and the definition of requirements for space experimentation. Initially, aqueous solutions will be used for easier control and instrumentation. Model systems with imposed steady flows and simplified boundary conditions will be studied for characterization. Various nonincursive measurement techniques are being investigated for proper applications in a newly built laboratory capable of flow visualization, laser Doppler velocimetry, Schlieren photography, specklegram, holographic interferometry, and Raman spectroscopy.

  7. Alloy Semiconductor Crystal Growth Under Microgravity

    SciTech Connect

    Hayakawa, Yasuhiro; Arivanandhan, Mukannan; Rajesh, Govindasamy; Tanaka, Akira; Ozawa, Tetsuo; Okano, Yasunori; Sankaranarayanan, Krishnasamy; Inatomi, Yuko

    2010-12-01

    Microgravity studies on the dissolution and crystallization of In{sub x}Ga{sub 1-x}Sb have been done using a sandwich combination of InSb and GaSb as the starting material using the Chinese recoverable satellite. The same type of experiment was performed under 1G gravity condition for comparison. From these experiments and the numerical simulation, it is found that the shape of the solid/liquid interface and composition profile in the solution was found to be significantly affected by gravity. GaSb seed was dissolved faster than GaSb feed even though the GaSb feed temperature was higher than that of GaSb seed temperature. These results clearly indicate that solute transport due to gravity affects dissolution and growth processes of alloy semiconductor bulk crystals.

  8. The effect of microgravity on protein crystal growth

    NASA Technical Reports Server (NTRS)

    Mcpherson, Alexander; Greenwood, Aaron; Day, John

    1991-01-01

    Based on the results of microgravity crystallization experiments using the protein canavalin aboard four separate U.S. Space Shuttle missions, visual observations and diffraction data are presented that support the contention that protein crystals of improved quality can be obtained in a microgravity environment. With canavalin, no significant increase in resolution was noted, but an overall improvement in diffraction quality, as judged by statistical analyses of the data, was clear. This improvement in quality may be due primarily to the elimination of defects and dislocations rather than an overall enhancement of order. The mechanism for this improvement may be microgravity-stabilized depletion zones that develop around growing crystals that establish and maintain optimal growth conditions more rapidly following nucleation. Such zones would be destroyed by convective flow effects in earth's gravity.

  9. Protein crystal growth with a two-liquid system and stirring solution.

    PubMed

    Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-01-01

    We developed two novel methods for growing large, high-quality protein crystals. A two-liquid system enables the convenient extraction of protein crystals without causing mechanical damage due to growth at the interface between two liquids. Since this system does not require limitations on solution volume, it is also suitable for the seed technique, and for growing large crystals. Another new concept is the mild stirring of the solution using the Floating And Stirring Technique (FAST) and the Micro-stirring technique. When compared to conventional techniques, both techniques result in a reduced number of crystals, as well as the growth of large crystals. PMID:14646151

  10. Crystal growth formation in melt extrudates.

    PubMed

    Bruce, Caroline; Fegely, Kurt A; Rajabi-Siahboomi, Ali R; McGinity, James W

    2007-08-16

    The purpose of the study was to investigate the physical state of hot-melt extruded guaifenesin tablets containing either Acryl-EZE or Eudragit L100-55 and to study the physicochemical factors influencing crystal growth of guaifenesin on the surface of the extrudates. The powder mixtures containing Acryl-EZE were extruded on a single-screw Randcastle Microtruder at 20rpm and at temperatures of 90, 95, 110 degrees C (zones 1, 2, 3, respectively) and 115 degrees C (die), before being manually cut into tablets (250+/-5mg). Extrudates containing Eudragit L100-55, TEC and guaifenesin were extruded at temperatures ranging from 60 to 115 degrees C. Modulated differential calorimetry (DSC) was used to demonstrate the plasticizing effect of guaifenesin on Eudragit L100-55. Powder X-ray diffraction (PXRD) showed that while the drug powder is crystalline, extrudates containing up to 25% drug exhibited an amorphous diffraction profile. Extrudates containing higher drug concentrations showed an amorphous profile with some crystalline peaks corresponding to guaifenesin, indicating that the limit of solubility of drug in the matrix had been exceeded. Scanning electron microscopy was used to demonstrate that drug crystallization was a surface phenomenon and dependent on the drug concentration. In vitro dissolution testing showed no effect of surface crystallization of guaifenesin on drug release rates of extruded matrix tablets. The influence of hydrophilic polymeric additives including PVP K25, polycarbophil, PEG 3,350, poloxamer 188 or poly(ethylene oxide) as crystal growth inhibitors was investigated at a level of 10% based on the drug content. The extent of crystal growth was reduced for all additives. Complete drug release in pH 6.8 phosphate buffer was prolonged from 4h in extrudates containing Acryl-EZE and guaifenesin to 8h in extrudates containing Eudragit L100-55, TEC and guaifenesin. Drug release in extrudates containing Eudragit L100-55 and guaifenesin was not affected by the presence of hydrophilic additives present at 10% based on the drug content. In vitro drug release studies showed no significant change during storage for up to 6 months at 25 degrees C/60% relative humidity and 40 degrees C/75% relative humidity. PMID:17524578

  11. The impact of space research on semiconductor crystal growth technology

    NASA Technical Reports Server (NTRS)

    Witt, A. F.

    1983-01-01

    Crystal growth experiments in reduced gravity environment and related ground-based research have contributed significantly to the establishment of a scientific basis for semiconductor growth from the melt. NASA-sponsored research has been instrumental in the introduction of heat pipes for heat and mass transfer control in crystal growth and in the development of magnetic field induced melt stabilization, approaches primarily responsible for recent advances in crystal growth technology.

  12. Crystal growth within a phase change memory cell.

    PubMed

    Sebastian, Abu; Le Gallo, Manuel; Krebs, Daniel

    2014-01-01

    In spite of the prominent role played by phase change materials in information technology, a detailed understanding of the central property of such materials, namely the phase change mechanism, is still lacking mostly because of difficulties associated with experimental measurements. Here, we measure the crystal growth velocity of a phase change material at both the nanometre length and the nanosecond timescale using phase-change memory cells. The material is studied in the technologically relevant melt-quenched phase and directly in the environment in which the phase change material is going to be used in the application. We present a consistent description of the temperature dependence of the crystal growth velocity in the glass and the super-cooled liquid up to the melting temperature. PMID:25000349

  13. In situ monitoring of crystal growth by reflectance difference spectroscopy

    NASA Astrophysics Data System (ADS)

    Colas, E.; Aspnes, D. E.; Bhat, R.; Studna, A. A.; Harbison, J. P.; Florez, L. T.; Koza, M. A.; Keramidas, V. G.

    1991-01-01

    Reflectance difference spectroscopy (RDS) is a surface analysis technique that was invented in 1985 by Aspnes. Here, we give a summary of its application to crystal growth techniques which gave new and valuable real time information about the growth process. Also, this information was obtained in-situ, in molecular beam epitaxy (MBE) and organometallic chemical vapor deposition (OMCVD) crystal growing setups which are routinely used to produce high quality device structures. The application of RDS to OMCVD allowed us to develop a "textbook" like model of growth kinetics, which includes two independent microscopic mechanisms, i.e. adsorption (at -26 kcal/mol) of the reacting molecule (trimethylgallium (TMG) in the case of GaAs), followed by its decomposition (at 39 kcal/mol) on the growing GaAs surface. Our model includes an effect called steric hindrance, associated with the large size of the TMG molecule. This study represents the first direct quantitative evaluation of the catalytic effect of the GaAs surface for the decomposition of TMG. We discuss implications of the model both for growth in the ALE mode as well as for conventional OMCVD growth and comment on the relative importance of surface and gas phase reactions. The application of RDS to MBE revealed remarkable details about the complex intermediate steps that surfaces undergo during growth and enabled to extract directly surface dielectric functions. Finally, applications of the technique as well as results obtained in a number of laboratories where RDS is currently being developed are discussed.

  14. Growth of shaped sapphire crystals using automated weight control

    NASA Astrophysics Data System (ADS)

    Kurlov, V. N.; Rossolenko, S. N.

    1997-04-01

    The automated control systems have been developed for the growth of various sapphire crystals by edge-defined film-fed growth (EFG) and noncapillary shaping (NCS) methods. Automated crystal weight control is based on the analysis of the behaviour of the mass rate deviation at all stages of the growth process (seeding, crystal expansion, stationary growth, in-situ cross-sectional changing). The maintenance of the mass rate deviation in a certain range provides the crystal quality control as well as crystal shape control.

  15. Fluid Physics and Macromolecular Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Pusey, M.; Snell, E.; Judge, R.; Chayen, N.; Boggon, T.

    2000-01-01

    The molecular structure of biological macromolecules is important in understanding how these molecules work and has direct application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these flows. Buoyancy driven convection results from density differences between the bulk solution and fluid close to the crystal surface which has been depleted of macromolecules due to crystal growth. Schlieren photograph of a growing lysozyme crystal illustrating a 'growth plume' resulting from buoyancy driven convection. Both sedimentation and buoyancy driven convection have a negative effect on crystal growth and microgravity is seen as a way to both greatly reduce sedimentation and provide greater stability for 'depletion zones' around growing crystals. Some current crystal growth hardware however such as those based on a vapor diffusion techniques, may also be introducing unwanted Marangoni convection which becomes more pronounced in microgravity. Negative effects of g-jitter on crystal growth have also been observed. To study the magnitude of fluid flows around growing crystals we have attached a number of different fluorescent probes to lysozyme molecules. At low concentrations, less than 40% of the total protein, the probes do not appear to effect the crystal growth process. By using these probes we expect to determine not only the effect of induced flows due to crystal growth hardware design but also hope to optimize crystallization hardware so that destructive flows are minimized both on the ground and in microgravity.

  16. Features of beryllium aluminate crystal growth by the method of horizontally oriented crystallization

    NASA Astrophysics Data System (ADS)

    Gurov, V. V.; Tsvetkov, E. G.; Kirdyashkin, A. G.

    2003-09-01

    The method of horizontally oriented (one-dimensional) crystallization (HOC) was applied for growth of chrome-doped beryllium aluminate (alexandrite) single crystals. The stratified hydrodynamic structure of melt in the boat-like crystallization container that predetermines major features of crystal growth was revealed by model experiment. Patterns of (1 2 0), (1 3 0), and (1 0 0) growth sectors of crystal volume and zones of preferred entrapment of gas-melt inclusions as well as efficient distribution coefficient of chrome on crystallization (inversion included) and distribution behavior of dopant along the grown crystals are illustrated and discussed. Occurrence of metal microinclusions of crystallization container material (Mo) in grown alexandrite crystals is analyzed. It is shown that alexandrite crystals grown by the HOC method have some advantages compared to the crystals grown by the Czochralski method.

  17. Residual Gases in Crystal Growth Systems

    NASA Technical Reports Server (NTRS)

    Palosz, W.

    2003-01-01

    Residual gases present in closed ampoules may affect different crystal growth processes. That seems to be particularly true under microgravity conditions where, due to weightlessness of the melt, the gases may lead to detached solidification and/or formation of voids and bubbles, as observed in the past. For that reason a good understanding and control of formation of residual gases is important for an optimum design and meaningful interpretation of crystal growth experiments. Our extensive experimental and theoretical studies of the subject, summarized in this paper, include degassing of silica glass and generation of gases from different source materials. Different materials processing conditions, like outgassing under vacuum, annealing in hydrogen, resublimation, different material preparation procedures, multiple annealings, different processing times, and others were applied and their effect on the amount and composition of gas were analyzed. The experimental results were interpreted based on theoretical calculations on diffusion in silica glass and source materials and thermochemistry of the system. Procedures for a reduction of the amount of gas are also discussed.

  18. Preferred growth orientation of biomimetic apatite crystals

    NASA Astrophysics Data System (ADS)

    Müller, Frank A.; Müller, Lenka; Caillard, Daniel; Conforto, Egle

    2007-06-01

    Simulated body fluid (SBF) solutions are widely used for in vitro bioactivity tests and to coat bioinert materials with biomimetic calcium phosphates. In this study, a SBF solution was used to precipitate hydroxy carbonated apatite (HCA) with a general formula Ca 10-x(HPO 4) x-y(CO 3) y(PO 4) 6-x(OH) 2-x on a bioactive titanium surface. X-ray diffraction (XRD) as well as cross-sectional transmission electron microscopy (TEM) analyses revealed that the biomimetically derived crystallites show a preferred growth orientation in direction of their c-axis and perpendicular to the surface of the bioactive substrate. This growth behaviour as well as the measured crystal dimensions ranging from 5×10×20 to 5×20×100 nm are very similar to that found in the mineral part of mammalian bone, where the c-axes of plate-shaped apatite crystals are well aligned with the long axes of the collagen fibrils.

  19. Solid State Pathways to Complex Shape Evolution and Tunable Porosity during Metallic Crystal Growth

    PubMed Central

    Valenzuela, Carlos Díaz; Carriedo, Gabino A.; Valenzuela, María L.; Zúñiga, Luis; O'Dwyer, Colm

    2013-01-01

    Growing complex metallic crystals, supported high index facet nanocrystal composites and tunable porosity metals, and exploiting factors that influence shape and morphology is crucial in many exciting developments in chemistry, catalysis, biotechnology and nanoscience. Assembly, organization and ordered crystallization of nanostructures into complex shapes requires understanding of the building blocks and their association, and this relationship can define the many physical properties of crystals and their assemblies. Understanding crystal evolution pathways is required for controlled deposition onto surfaces. Here, complex metallic crystals on the nano- and microscale, carbon supported nanoparticles, and spinodal porous noble metals with defined inter-feature distances in 3D, are accomplished in the solid-state for Au, Ag, Pd, and Re. Bottom-up growth and positioning is possible through competitive coarsening of mobile nanoparticles and their site-specific crystallization in a nucleation-dewetted matrix. Shape evolution, density and growth mechanism of complex metallic crystals and porous metals can be imaged during growth. PMID:24026532

  20. Numerical studies of convective transport associated with crystal growth in mirrogravity

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.

    1992-01-01

    Information on numerical studies of convective transport associated with crystal growth in microgravity is given in viewgraph form. Inferences drawn from the research are that protein crystals seem to grow at much larger relative supersaturations than small molecule crystals; growth rate is limited by attachment kinetics more than by transport; attachment kinetics are apparently influenced by convective flows, although the mechanism is uncertain; acceleration levels required to achieve D/L growth within Space Station Freedom specifications may not be achievable on manned vehicles; and D/L transport can help minimize incorporation of impurities, but growth cessation cannot be explained.

  1. Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Ramachandran, Narayanan

    1998-01-01

    The role of step geometry in two-dimensional stationary volume diff4sion process used in crystal growth kinetics models is investigated. Three different interface shapes: a) a planar interface, b) an equidistant hemispherical bumps train tAx interface, and c) a train of right angled steps, are used in this comparative study. The ratio of the super-saturation to the diffusive flux at the step position is used as a control parameter. The value of this parameter can vary as much as 50% for different geometries. An approximate analytical formula is derived for the right angled steps geometry. In addition to the kinetic models, this formula can be utilized in macrostep growth models. Finally, numerical modeling of the diffusive and convective transport for equidistant steps is conducted. In particular, the role of fluid flow resulting from the advancement of steps and its contribution to the transport of species to the steps is investigated.

  2. On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.

    2003-01-01

    Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (??2) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum crystals, proportionate growth occurs in stirred systems, whereas constant growth occurs in non-stirred systems. Accordingly, the mechanism for proportionate growth is hypothesized to be related to the supply of reactants to the crystal surface by advection, whereas constant growth is related to supply by diffusion. Paradoxically, micrometer-sized calcite crystals showed proportionate growth both in stirred and in non-stirred systems. Such growth presumably results from the effects of convection and Brownian motion, which promote an advective environment and hence proportionate growth for minute crystals in non-stirred systems, thereby indicating the importance of solution velocity relative to crystal size. Calcite crystals grown in gels, where fluid motion was minimized, showed evidence for constant, diffusion-controlled growth. Additional investigations of CSDs of naturally occurring crystals indicate that proportionate growth is by far the most common growth law, thereby suggesting that advection, rather than diffusion, is the dominant process for supplying reactants to crystal surfaces.

  3. Special phase transformation and crystal growth pathways observed in nanoparticles†

    PubMed Central

    Gilbert, Benjamin; Zhang, Hengzhong; Huang, Feng; Finnegan, Michael P; Waychunas, Glenn A; Banfield, Jillian F

    2003-01-01

    Phase transformation and crystal growth in nanoparticles may happen via mechanisms distinct from those in bulk materials. We combine experimental studies of as-synthesized and hydrothermally coarsened titania (TiO2) and zinc sulfide (ZnS) with thermodynamic analysis, kinetic modeling and molecular dynamics (MD) simulations. The samples were characterized by transmission electron microscopy, X-ray diffraction, synchrotron X-ray absorption and scattering, and UV-vis spectroscopy. At low temperatures, phase transformation in titania nanoparticles occurs predominantly via interface nucleation at particle–particle contacts. Coarsening and crystal growth of titania nanoparticles can be described using the Smoluchowski equation. Oriented attachment-based crystal growth was common in both hydrothermal solutions and under dry conditions. MD simulations predict large structural perturbations within very fine particles, and are consistent with experimental results showing that ligand binding and change in aggregation state can cause phase transformation without particle coarsening. Such phenomena affect surface reactivity, thus may have important roles in geochemical cycling.

  4. Crystal growth by solvent evaporation and characterization of metronidazole

    NASA Astrophysics Data System (ADS)

    Ramukutty, S.; Ramachandran, E.

    2012-07-01

    Single crystals of metronidazole were crystallized by the slow solvent evaporation method and used as seeds to grow bulk crystals of size 8.06.52.0 mm3 using top-seeded submerged solution growth. The crystals were characterized using single crystal X-ray diffraction. Fourier transform infrared spectral analysis was made for the absorption bands of various functional groups present in the crystal. UV-vis absorption spectrum was used to identify the presence of nitroimidazole in metronidazole. Morphology study revealed that the growth is prominent along the c-axis and the prominent face is {010}. Thermal stability and thermal decomposition were analyzed using thermo calorimetry.

  5. Vapor Crystal Growth International Microgravity Laboratory (IML-1)

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Vapor Crystal Growth System developed in IML-1, Mercuric Iodide Crystal grown in microgravity FES/VCGS (Fluids Experiment System/Vapor Crystal Growth Facility). During the mission, mercury iodide source material was heated, vaporized, and transported to a seed crystal where the vapor condensed. Mercury iodide crystals have practical uses as sensitive X-ray and gamma-ray detectors. In addition to their excellent optical properties, these crystals can operate at room temperature, which makes them useful for portable detector devices for nuclear power plant monitoring, natural resource prospecting, biomedical applications, and astronomical observing.

  6. Inorganic chemistry: Movies of a growth mechanism

    NASA Astrophysics Data System (ADS)

    Walton, Krista S.

    2015-07-01

    A microscopy technique has been used to study the formation and growth of crystals of porous solids known as metal-organic frameworks in real time. The findings will aid the design of methods for making these useful compounds.

  7. Morphological stability and kinetics in crystal growth from vapors

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1990-01-01

    The following topics are discussed: (1) microscopy image storage and processing system; (2) growth kinetics and morphology study with carbon tetrabromide; (3) photothermal deflection vapor growth setup; (4) bridgman growth of iodine single crystals; (5) vapor concentration distribution measurement during growth; and (6) Monte Carlo modeling of anisotropic growth kinetics and morphology. A collection of presentations and publications of these results are presented.

  8. Comment on "Evaluation of X-ray diffraction methods for determining the crystal growth mechanisms of clay minerals in mudstones, shales and slates," by L. N. Warr and D. R. Peacor

    USGS Publications Warehouse

    Eberl, D.D.; Srodon, J.; Drits, V.A.

    2003-01-01

    A recent paper by Warr and Peacor (2002) suggested that our use of the Bertaut-Warren-Averbach technique (MudMaster computer program) for studying changes in crystallite thickness distributions (CTDs) of clay minerals during diagenesis and very low-grade metamorphism is not reliable because it is dependent on many variables which can not be fully controlled. Furthermore, the authors implied that the measured shapes of CTDs cannot be used with confidence to deduce crystal growth mechanisms and histories for clays, based on our CTD simulation approach (using the Galoper computer program). We disagree with both points, and show that the techniques are powerful, reliable and useful for studying clay mineral alteration in rocks. ?? 2003 Schweiz. Mineral. Petrogr. Ges.

  9. Indium antimonide crystal growth experiment M562. [Skylab weightless conditions

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Witt, A. F.

    1974-01-01

    It was established that ideal diffusion controlled steady state conditions, never accomplished on earth, were achieved during the growth of Te-doped InSb crystals in Skylab. Surface tension effects led to nonwetting conditions under which free surface solidification took place in confined geometry. It was further found that, under forced contact conditions, surface tension effects led to the formation of surface ridges (not previously observed on earth) which isolated the growth system from its container. In addition, it was possible, for the first time, to identify unambiguously: the origin of segregation discontinuities associated with facet growth, the mode of nucleation and propagation of rotational twin boundaries, and the specific effect of mechanical-shock perturbations on segregation. The results obtained prove the advantageous conditions provided by outer space. Thus, fundamental data on solidification thought to be unattainable because of gravity-induced interference on earth are now within reach.

  10. CVD growth of single-crystal monolayer graphene on H-terminated germanium surface

    NASA Astrophysics Data System (ADS)

    Whang, Dongmok

    2015-03-01

    Large-area graphene has been grown by catalytic chemical vapor deposition (CVD) on various metal substrates. However, the uniform growth of single-crystal graphene over wafer-scale areas remains a challenge toward the commercial realization of various electronic, photonic, mechanical, and other devices based upon the outstanding properties of graphene. In this talk, we present the growth of single-crystal monolayer graphene on hydrogen-terminated germanium (Ge) surface. A single-crystal Ge substrate is a promising candidate for the growth of single-crystal graphene, because of (i) its catalytic activity for the catalytic decomposition of the formation of graphitic carbon on the surface; (ii) the extremely low solubility of carbon in Ge even at its melting temperature, enabling growth of complete monolayer graphene; (iii) the anisotropic atomic arrangement of single crystal Ge surface, enabling aligned growth of multiple seeds; (iv) the availability of a large area single-crystal surface via epitaxial Ge growth on Si wafers. We observed that well-defined atomic arrangement on the single crystal Ge surface enabled aligned growth of multiple seeds which can merge to single crystal graphene. Furthermore very weak van der Waals interaction between graphene and underlying Ge surface enabled facile dry transfer of graphene and recycling the Ge/Si wafer for continuing growth.

  11. Growth rate dispersion of single potassium alum crystals

    NASA Astrophysics Data System (ADS)

    Lacmann, Rolf; Tanneberger, Ulrike

    1995-01-01

    The dispersion of growth rates is a lively discussed matter. However, still no acceptable explanation exists for the reason of the phenomenon describing that crystals of the same size growing under the same constant environmental conditions (as supersaturation, temperature and hydrodynamics) might grow with different rates. The individual face-specific growth rates of potassium aluminium alum crystals (diameter 1-3 mm) have been directly determined at different supersaturations ( ? = 0.5-5%). It was found that the order of growth rates of the appearing faces of unhurt and hurt crystals is {111} < {100{ < {110{. Further experiments have shown that face-specific growth rates of unhurt crystals (out of evaporation crystallization) are lower than those of hurt crystals (out of batch crystallization experiments).

  12. Organic crystal growth experiment facility (13-IML-1)

    NASA Technical Reports Server (NTRS)

    Kanbayashi, Akio

    1992-01-01

    The interesting nature of metal-like organic compounds composed of charge transfer complexes has been recently realized. Crystals of these complexes can usually be grown by the solution crystallization method. It is difficult to grow such organic crystals on Earth, especially from the chemical reactions through diffusion controlled process in the solutions, because of gravitational disturbances, or sedimentation. The International Microgravity Lab. (IML-1) Organic Crystal Growth with G-Gitter Preventive Measure (OCGP) experiment is expected to grow a single crystal large enough to allow its intrinsic physical properties to be measured and its detailed crystal structure to be determined. This experiment also attempts to assess the experimental conditions including the microgravity environment for further study of the fundamental process of solution crystallization, nucleation, and growth from supersaturated phases including chemical reactions. Microgravity disturbances, G-jitter, may be an important environmental factor in the experimental method to assess. The vibration damping effects on organic crystal growth can be carefully studied.

  13. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    NASA Astrophysics Data System (ADS)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.

    2010-12-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  14. Helical Growth of Aluminum Nitride: New Insights into Its Growth Habit from Nanostructures to Single Crystals

    PubMed Central

    Zhang, Xing-Hong; Shao, Rui-Wen; Jin, Lei; Wang, Jian-Yu; Zheng, Kun; Zhao, Chao-Liang; Han, Jie-Cai; Chen, Bin; Sekiguchi, Takashi; Zhang, Zhi; Zou, Jin; Song, Bo

    2015-01-01

    By understanding the growth mechanism of nanomaterials, the morphological features of nanostructures can be rationally controlled, thereby achieving the desired physical properties for specific applications. Herein, the growth habits of aluminum nitride (AlN) nanostructures and single crystals synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport process were investigated by transmission electron microscopy. The detailed structural characterizations strongly suggested that the growth of AlN nanostructures including AlN nanowires and nanohelixes follow a sequential and periodic rotation in the growth direction, which is independent of the size and shape of the material. Based on these experimental observations, an helical growth mechanism that may originate from the coeffect of the polar-surface and dislocation-driven growth is proposed, which offers a new insight into the related growth kinetics of low-dimensional AlN structures and will enable the rational design and synthesis of novel AlN nanostructures. Further, with the increase of temperature, the growth process of AlN grains followed the helical growth model. PMID:25976071

  15. Specific mass increment and nonequilibrium crystal growth

    NASA Astrophysics Data System (ADS)

    Martyushev, Leonid M.; Terentiev, Pavel S.

    2013-09-01

    Unsteady nonequilibrium crystallization of ammonium chloride from an aqueous solution resulting in the formation of irregular, so-called seaweed, structures is experimentally investigated. It is shown that specific increment of mass for the coexisting structures (or parts thereof) is the same and changes with time (t) according to the power law a/t-b, where the factor a=1.87±0.09 and the factor b is determined by the system relaxation time. The normalization of the power law to the total time of structure growth allows obtaining a universal law that describes the specific mass increment with time for both seaweed and dendrite structures (including the non-coexisting ones).

  16. Recombinant sea urchin vascular endothelial growth factor directs single-crystal growth and branching in vitro.

    PubMed

    Knapp, Regina T; Wu, Ching-Hsuan; Mobilia, Kellen C; Joester, Derk

    2012-10-31

    Biomineralization in sea urchin embryos is a crystal growth process that results in oriented single-crystalline spicules with a complex branching shape and smoothly curving surfaces. Uniquely, the primary mesenchyme cells (PMCs) that construct the endoskeleton can be cultured in vitro. However, in the absence of morphogenetic cues secreted by other cells in the embryo, spicules deposited in PMC culture lack the complex branching behavior observed in the embryo. Herein we demonstrate that recombinant sea urchin vascular endothelial growth factor (rVEGF), a signaling molecule that interacts with a cell-surface receptor, induces spiculogenesis and controls the spicule shape in PMC culture. Depending on the rVEGF concentration, PMCs deposit linear, "h"- and "H"-shaped, or triradiate spicules. Remarkably, the change from linear to triradiate occurs with a switch from bidirectional crystal growth parallel to the calcite c axis to growth along the three a axes. This finding has implications for our understanding of how cells integrate morphogenesis on the multi-micrometer scale with control over lattice orientation on the atomic scale. The PMC model system is uniquely suited to investigate this mechanism and develop biotechnological approaches to single-crystal growth. PMID:23066927

  17. State-of-the-art of ZnO bulk crystal growth

    NASA Astrophysics Data System (ADS)

    Fukuda, T.; Mikawa, Y.; Ehrentraut, D.

    2007-02-01

    Zinc oxide (ZnO) crystals can be grown by vapor phase transport, hydrothermal solution growth, and high pressure melt growth. Three inch size single crystal has been demonstrated by the hydrothermal growth technique. We will emphasis on the hydrothermal technology of large size ZnO crystal. Material characteristics are discussed and compared to ZnO fabricated from vapor phase and melt growth. A route to obtain high-quality, single-crystalline ZnO films with mechanically untouched surfaces is employed to screen the doping of ZnO under the conditions of growth near the thermodynamic equilibrium. Future trends in ZnO crystal growth technology will be discussed.

  18. Growth of faceted 123 crystals in superconductive YBCO/Ag composites fabricated by infiltration-growth method

    NASA Astrophysics Data System (ADS)

    Mori, N.; Dateki, K.; Hirao, T.; Ogi, K.

    2006-10-01

    Growth process and structures of faceted 123 (YBa2Cu3O7-X) crystals fabricated by conventional unidirectional solidification and infiltration-growth method were studied experimentally and numerically to clarify the formation mechanism of the solidification structures of YBCO/Ag composites. Sample size was almost unchanged during the infiltration-growth process, since molten Ba-Cu-O with a small amount of Y and Ag was just infiltrated into pores in pre-sintered porous primary phase: 211 (Y2BaCuO5) with Ag and then it was cooled to grow 123 crystal. Solidified samples had uniform distribution of primary phase and Ag particles in peritectic 123 crystals. The critical transition condition of macrostructures from columnar to equiaxed structures, and the freezing front temperature of 123 crystal during solidification were clarified. The formation processes of macro/microstructure of faceted 123 crystals were simulated, and the results compared with the experimental ones.

  19. Growth aspects of semi-organic nonlinear optical ?-arginine tetrafluoroborate single crystals

    NASA Astrophysics Data System (ADS)

    Babu, D. Rajan; Jayaraman, D.; Kumar, R. Mohan; Ravi, G.; Jayavel, R.

    2003-03-01

    Single crystals of L-arginine tetrafluoroborate ( L-AFB), a semi-organic NLO material, have been grown from aqueous solution. Since L-AFB is known to form highly viscous solution in water, growth by slow cooling has been difficult for optical quality crystals. In this study, highly transparent L-AFB crystals have been successfully grown by slow evaporation by keeping the saturated solution under special condition. The grown crystals were subjected to structural, optical and mechanical property studies. XRD studies reveal that L-AFB crystals possess orthorhombic structure. Fourier transform infrared absorption studies confirm the chemical constituents and presence of functional groups in the grown crystals. L-AFB crystals possess a higher hardness values compared to other semi-organic crystals. The linear and nonlinear optical properties of the grown crystals have also been studied.

  20. Acquisition of Single Crystal Growth and Characterization Equipment

    SciTech Connect

    Maple, M. Brian; Zocco, Diego A.

    2008-12-09

    Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As a result, many user facilities are not being used optimally. The number of proficient crystal growers is too small. In addition, insufficient attention is being paid to the enterprise of finding new and interesting materials, which is the driving force behind much of condensed matter research and, ultimately, technology. While a detailed assessment of this situation is clearly needed, enough evidence of a problem already exists to compel a general consensus that the situation must be addressed promptly. This final report describes the work carried out during the last four years in our group, in which a state-of-the-art single crystal growth and characterization facility was established for the study of novel oxides and intermetallic compounds of rare earth, actinide and transition metal elements. Research emphasis is on the physics of superconducting (SC), magnetic, heavy fermion (HF), non-Fermi liquid (NFL) and other types of strongly correlated electron phenomena in bulk single crystals. Properties of these materials are being studied as a function of concentration of chemical constituents, temperature, pressure, and magnetic field, which provide information about the electronic, lattice, and magnetic excitations at the root of various strongly correlated electron phenomena. Most importantly, the facility makes possible the investigation of material properties that can only be achieved in high quality bulk single crystals, including magnetic and transport phenomena, studies of the effects of disorder, properties in the clean limit, and spectroscopic and scattering studies through efforts with numerous collaborators. These endeavors will assist the effort to explain various outstanding theoretical problems, such as order parameter symmetries and electron-pairing mechanisms in unconventional superconductors, the relationship between superconductivity and magnetic order in certain correlated electron systems, the role of disorder in non-Fermi liquid behavior and unconventional superconductivity, and the nature of interactions between localized and itinerant electrons in these materials. Understanding the mechanisms behind strongly correlated electron behavior has important technological implications.

  1. Crystal growth and properties of Yb:FAP laser crystal

    NASA Astrophysics Data System (ADS)

    Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

    2005-04-01

    A large and transparent Yb:FAP crystal with dimensions up to ?30 mm85 mm has been grown by the Czochralski method. The preparation of the raw material has been investigated. X-ray power diffraction studies of Yb:FAP crystal confirm that the as-grown crystal is isostructural with the FAP crystal. The crystalline quality has been studied using X-ray rocking curve analysis. The segregation coefficient of Yb 3+ in the Yb:FAP crystal has been also determined. Linear thermal expansion coefficients in [0 0 1] and [1 0 0] directions have been measured in the 30-800 C temperature range.

  2. Inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate.

    PubMed

    Damodaran, Srinivasan

    2007-12-26

    The inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate produced by papain action was studied. The ice crystal growth was monitored by thermal cycling between -14 and -12 degrees C at a rate of one cycle per 3 min. It is shown that the hydrolysate fraction containing peptides in the molecular weight range of about 2000-5000 Da exhibited the highest inhibitory activity on ice crystal growth in ice cream mix, whereas fractions containing peptides greater than 7000 Da did not inhibit ice crystal growth. The size distribution of gelatin peptides formed in the hydrolysate was influenced by the pH of hydrolysis. The optimum hydrolysis conditions for producing peptides with maximum ice crystal growth inhibitory activity was pH 7 at 37 degrees C for 10 min at a papain to gelatin ratio of 1:100. However, this may depend on the type and source of gelatin. The possible mechanism of ice crystal growth inhibition by peptides from gelatin is discussed. Molecular modeling of model gelatin peptides revealed that they form an oxygen triad plane at the C-terminus with oxygen-oxygen distances similar to those found in ice nuclei. Binding of this oxygen triad plane to the prism face of ice nuclei via hydrogen bonding appears to be the mechanism by which gelatin hydrolysate might be inhibiting ice crystal growth in ice cream mix. PMID:18044830

  3. Kinetic mechanism of chain folding in polymer crystallization

    NASA Astrophysics Data System (ADS)

    Stepanow, S.

    2014-09-01

    I develop a kinetic mechanism to explain chain folding in polymer crystallization which is based on the competition between the formation of stems, which is due to frequent occupations of trans states along the chains in the supercooled polymer melt, and the random coil structure of the polymer chains. Setting equal the average formation time of stems of length dl with the Rouse time of a piece of polymer of the same arc length dl yields a lower bound for the thickness of stems and bundles. The estimated lamellar thickness is inversely proportional to the supercooling. The present approach emphasizes the importance of repulsive interactions in polymer crystallization, which are expected to be responsible for the logarithmic lamellar thickening and the increase of lamellar thickness with pressure. An expression for the growth rate for formation and deposition of stems is derived by considering the growth as a dynamic multistage process.

  4. Protein Crystal Growth With the Aid of Microfluidics

    NASA Technical Reports Server (NTRS)

    vanderWoerd, Mark

    2003-01-01

    Protein crystallography is one of three well-known methods to obtain the structure of proteins. A major rate limiting step in protein crystallography is protein crystal nucleation and growth, which is still largely a process conducted by trial-and-error methods. Many attempts have been made to improve protein crystal growth by performing growth in microgravity. Although the use of microgravity appears to improve crystal quality in some attempts, this method has been inefficient because several reasons: we lack a fundamental understanding of macromolecular crystal growth in general and of the influence of microgravity in particular, we have to start with crystal growth conditions in microgravity based on conditions on the ground and finally the hardware does not allow for experimental iteration without reloading samples on the ground. To partially accommodate the disadvantages of the current hardware, we have used microfluidic technology (Lab-on-a-Chip devices) to design the concept of a more efficient crystallization device, suitable for use on the International Space Station and in high-throughput applications on the ground. The concept and properties of microfluidics, the application design process, and the advances in protein crystal growth hardware will be discussed in this presentation. Some examples of proteins crystallized in the new hardware will be discussed, including the differences between conventional crystallization versus crystallization in microfluidics.

  5. In vitro crystallization, characterization and growth-inhibition study of urinary type struvite crystals

    NASA Astrophysics Data System (ADS)

    Chauhan, Chetan K.; Joshi, Mihir J.

    2013-01-01

    The formation of urinary stones, known as nephrolithiasis or urolithiasis, is a serious, debilitating problem throughout the world. Struvite—NH4MgPO4·6H2O, ammonium magnesium phosphate hexahydrate, is one of the components of urinary stones (calculi). Struvite crystals with different morphologies were grown by in vitro single diffusion gel growth technique with different growth parameters. The crystals were characterized by powder XRD, FT-IR, thermal analysis and dielectric study. The powder XRD results of struvite confirmed the orthorhombic crystal structure. The FT-IR spectrum proved the presence of water of hydration, metal-oxygen bond, N-H bond and P-O bond. For thermal analysis TGA, DTA and DSC were carried out simultaneously. The kinetic and thermodynamic parameters of dehydration/decomposition process were calculated. Vickers micro-hardness and related mechanical parameters were also calculated. The in vitro growth inhibition studies of struvite by the juice of Citrus medica Linn as well as the herbal extracts of Commiphora wightii, Boerhaavia diffusa Linn and Rotula aquatica Lour were carried out and found potent inhibitors of struvite.

  6. Crystal Growth Rate Dispersion: A Predictor of Crystal Quality in Microgravity?

    NASA Technical Reports Server (NTRS)

    Kephart, Richard D.; Judge, Russell A.; Snell, Edward H.; vanderWoerd, Mark J.

    2003-01-01

    In theory macromolecular crystals grow through a process involving at least two transport phenomena of solute to the crystal surface: diffusion and convection. In absence of standard gravitational forces, the ratio of these two phenomena can change and explain why crystal growth in microgravity is different from that on Earth. Experimental evidence clearly shows, however, that crystal growth of various systems is not equally sensitive to reduction in gravitational forces, leading to quality improvement in microgravity for some crystals but not for others. We hypothesize that the differences in final crystal quality are related to crystal growth rate dispersion. If growth rate dispersion exists on Earth, decreases in microgravity, and coincides with crystal quality improvements then this dispersion is a predictor for crystal quality improvement. In order to test this hypothesis, we will measure growth rate dispersion both in microgravity and on Earth and will correlate the data with previously established data on crystal quality differences for the two environments. We present here the first crystal growth rate measurement data for three proteins (lysozyme, xylose isomerase and human recombinant insulin), collected on Earth, using hardware identical to the hardware to be used in microgravity and show how these data correlate with crystal quality improvements established in microgravity.

  7. Investigation on Growth and Surface Analysis of DAST Single Crystals

    SciTech Connect

    Thomas, Tina; Vijay, R. Jerald; Gunaseelan, R.; Sagayaraj, P.

    2011-07-15

    We have explored the growth of bulk size N, N-dimethylamino-N'-methylstilbazolium p-toluenesulphonate (DAST) using slope nucleation method. The grown crystal was characterized by single crystal X-ray diffraction (XRD), and CHN analyses. The surface morphology of the crystal was analyzed using Scanning electron microscopy (SEM).

  8. The inhibition of calcium carbonate crystal growth by the cysteine-rich Mdm2 peptide.

    PubMed

    Dalas, E; Chalias, A; Gatos, D; Barlos, K

    2006-08-15

    The crystal growth of calcite, the most stable calcium carbonate polymorph, in the presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in the ring finger configuration), has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized calcite crystals in solutions supersaturated only with respect to this calcium carbonate salt. The kinetic results indicated a surface diffusion spiral growth mechanism. The presence of the Mdm2 peptide inhibited the crystal growth of calcite by 22-58% in the concentration range tested, through adsorption onto the active growth sites of the calcite crystal surface. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k(aff)=147x10(4) dm(3)mol(-1), a(ads)=0.29. PMID:16678843

  9. Growth phenomena in the surface layer and step generation from the edges of faceted crystals

    SciTech Connect

    Carman, L; Smolsky, I; Zaitseva, N P

    1999-07-29

    The mechanism of growth step generation from the edges of faceted crystals obtained from experimental results with KDP crystals is described. It shows that growth from the crystal edges is initiated by the deviation of the edges from their crystallographic orientation and formation of incomplete shapes of singular facets. The conditions for formation of the incomplete faceted shapes during dislocation growth are considered. It is shown that the process of step generation from the edges is determined by the mutual positions of the vicinal slopes on the adjacent faces.

  10. Magnetic Control in Crystal Growth from a Melt

    NASA Astrophysics Data System (ADS)

    Huang, Yue

    Control of bulk melt crystal growth techniques is desirable for producing semiconductors with the highest purity and ternary alloys with tunable electrical properties. Because these molten materials are electrically conducting, external magnetic fields are often employed to regulate the flow in the melt. However, complicated by the coupled flow, thermal, electromagnetic and chemical physics, such magnetic control is typically empirical or even an educated guess. Two magnetic flow control mechanisms: flow damping by steady magnetic fields, and flow stirring by alternating magnetic fields, are investigated numerically. Magnetic damping during optically-heated float-zone crystal growth is modeled using a spectral collocation method. The Marangoni convection at the free melt-gas interface is suppressed when exposed to a steady axial magnetic field, measured by the Hartmann number Ha. As a result, detrimental flow instabilities are suppressed, and an almost quiescent region forms in the interior, ideal for single crystal growth. Using normal mode linear stability analyses, dominant flow instabilities are determined in a range applicable to experiments (up to Ha = 300 for Pr = 0.02, and up to Ha = 500 for Pr = 0.001). The hydrodynamic nature of the instability for small Prandtl number Pr liquid bridges is confirmed by energy analyses. Magnetic stirring is modeled for melt crystal growth in an ampule exposed to a transverse rotating magnetic field. Decoupled from the flow field at small magnetic Reynolds number, the electromagnetic field is first solved via finite element analysis. The flow field is then solved using the spectral element method. At low to moderate AC frequencies (up to a few kHz), the electromagnetic body force is dominant in the azimuthal direction, which stirs a steady axisymmetric flow primarily in the azimuthal direction. A weaker secondary flow develops in the meridional plane. However, at high AC frequencies (on the order of 10 kHz and higher), only the flow within a skin depth is directly stirred due to the magnetic shielding effect. By regulating the flow in the melt, magnetic control can improve grown-crystal properties in new materials, and achieve economically viable growth rates for production of novel crystalline semiconductors.

  11. Luminescence labeling and dynamics of growth active crystal surface structures

    NASA Astrophysics Data System (ADS)

    Bullard, Theresa Vivian

    One aspect of the multifaceted proposal by A. G. Cairns-Smith (CS), that imperfect crystals have the capacity to act as primitive genes by transferring the disposition of their imperfections from one crystal to another, is investigated. An experiment was designed in a model crystalline system unrelated to the composition of the pre-biotic earth but suited to a well-defined test. Plates of potassium hydrogen phthalate were studied in order to ascertain whether, according to CS, parallel screw dislocations could serve as an information store with cores akin to punches in an old computer card. Evidence of screw dislocations was obtained from their associated growth hillocks through differential interference contrast microscopy, atomic force microscopy, and luminescence labeling of hillocks in conjunction with confocal laser scanning microscopy. Inheritance was evaluated by the corresponding patterns of luminescence developed in 'daughter' crystals grown from seed in the presence of fluorophores. The dispositions and evolution of growth active hillock patterns were quantified by fractal correlation analysis and statistical analysis. Along the way, we came to realize that transferring information encoded in the disposition of screw dislocations is complicated by several factors that lead to 'mutations' in the information stored in the pattern of defects. These observations forced us to confront the fundamental mechanisms that give rise to screw dislocations. It became clear that inter-hillock correlations play a significant role in the appearance of new dislocations through growth, and cause the overall pattern of hillocks to be non-random. Tendencies for clustering and correlations along various crystallographic directions were observed. Investigations into the dye-crystal surface chemistries and interactions with hillock steps also ensued through a combination of experimental techniques and force-field calculations. It was established that certain dye molecules not only recognize some propagating steps as opposed to others, but preferentially choose between kinks propagating in opposing directions on the same step. Beyond providing the first experimental test of the CS proposal, this work is aimed at understanding the nucleation, evolution, and impurity interactions of growth-induced screw dislocations, a necessary ingredient for the growth of crystals at low supersaturation.

  12. Kyropolous crystal growth of silicon for solar cell applications

    NASA Astrophysics Data System (ADS)

    Ravishankar, P. S.

    1985-11-01

    For the first time, the Kyropolous crystal growth method was used to grow single crystal silicon ingots. The ingots were of relatively low dislocation density (less than 10,000/sq cm). Solar cell efficiency in excess of 13 percent and comparable to Czochralski single crystal control cells was demonstrated. A novel remelt releasing technique was developed in order to avoid the use of the traditional ingot release agents that tend to interact with the crystal growth process, which in turn leads to the breakdown of the single crystal character.

  13. Crystal growth and characterization of 9,10-diphenylanthracene

    NASA Astrophysics Data System (ADS)

    van Loef, Edgar V.; Mukhopadhyay, Sharmistha; Zaitseva, Natalia; Payne, Steve; Shah, Kanai S.

    2012-08-01

    In this paper we report on the crystal growth and characterization of 9,10-diphenylanthracene. Crystals of 9,10-diphenylanthracene (DPA) were grown by the solution growth technique as well as the vertical Bridgman method. In case of the solution growth technique, several organic solvents were investigated including heptane, cyclohexane, toluene, and p-xylene. The largest crystals of the highest quality were obtained from toluene and xylene. In the case of vertical Bridgman, evacuated silica ampoules were used to grow large single crystals of DPA. Crystals grown by this method exhibit excellent scintillation properties. Radioluminescence spectra of DPA crystals exhibit a broad emission band peaking at 475 nm. DPA crystals show high light yields of up to 20,000 ph/MeV and a fast scintillation decay of less than 20 ns. Fast neutron detection was achieved using a 252Cf source.

  14. Space manufacturing in an automated crystal growth facility

    NASA Technical Reports Server (NTRS)

    Quinn, Alberta W.; Herrmann, Melody C.; Nelson, Pamela J.

    1989-01-01

    An account is given of a Space Station Freedom-based robotic laboratory system for crystal growth experiments; the robot must interface with both the experimental apparatus and such human input as may be required for control and display. The goal of the system is the simultaneous growth of several hundred protein crystals in microgravity. The robot possesses six degrees-of-freedom, allowing it to efficiently manipulate the cultured crystals as well as their respective growth cells; the crystals produced are expected to be of sufficiently high quality for complete structural determination on the basis of XRD.

  15. Inorganic and protein crystal growth - Similarities and differences

    NASA Technical Reports Server (NTRS)

    Rosenberger, F.

    1986-01-01

    Transport and interface kinetic concepts for the design and control of inorganic crystal growth experiments are reviewed, and their applications and limitations in protein crystal growth are considered. It is suggested that the interfacial concentration gradients are steeper for faster crystallization, and that the interfacial concentration distributions for the protein and the precipitant can differ significantly. Results show that uniformity in crystal composition and steady-state conditions in growth kinetics are favored by larger sample size, since surface-tension gradients drive strong in microgravity experiments and in small samples on earth.

  16. Simulation of jet cooling effects on Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1986-01-01

    The effects of cooling the crystal side surface by blowing a jet of an inert gas are examined in detail for Czochralski crystal growth. A combined model of the crystal + melt, which incorporates the detailed radiation calculations, the shape of the melt-gas meniscus, predicts the growth rate and the crystal-melt interface shape, is used for this study. The convective heat transfer coefficient for the jet is estimated from the correlation available in the literature. The effect of the jet cooling on the interface shape and the pulling rate is significant. The crystal diameter as well as the interface shape tend to be more stable in the environment of the rapid cooling of the crystal by the jet. The crystal diameter or the interface shape can be easily controlled by adjusting the gas flow rate through the jet. This gives the Czochralski pulling an additional degree of freedom facilitating the control of crystal diameter and interface shape.

  17. Crystal growth in fused solvent systems. [in space environment

    NASA Technical Reports Server (NTRS)

    Ulrich, D. R.; Noval, B. A.; White, W. B.; Spear, K. E.; Henry, E. C.

    1974-01-01

    The successful nucleation of bismuth germanate, B12GeO20 on a high quality seed and the growth of regions of single crystals of the same orientation of the seed are reported. Lead germanate, Pb5Ge3O11 was also identified as a ferroelectric crystal with large electrooptic and nonlinear optic constants. Solvent criteria, solvent/development, and crystal growth are discussed, and recommendations for future studies are included.

  18. Universality classes for unstable crystal growth

    NASA Astrophysics Data System (ADS)

    Biagi, Sofia; Misbah, Chaouqi; Politi, Paolo

    2014-06-01

    Universality has been a key concept for the classification of equilibrium critical phenomena, allowing associations among different physical processes and models. When dealing with nonequilibrium problems, however, the distinction in universality classes is not as clear and few are the examples, such as phase separation and kinetic roughening, for which universality has allowed to classify results in a general spirit. Here we focus on an out-of-equilibrium case, unstable crystal growth, lying in between phase ordering and pattern formation. We consider a well-established 2+1-dimensional family of continuum nonlinear equations for the local height h(x,t) of a crystal surface having the general form ?th(x,t)=-?.[j(?h)+?(?2h)]: j (?h) is an arbitrary function, which is linear for small ?h, and whose structure expresses instabilities which lead to the formation of pyramidlike structures of planar size L and height H. Our task is the choice and calculation of the quantities that can operate as critical exponents, together with the discussion of what is relevant or not to the definition of our universality class. These aims are achieved by means of a perturbative, multiscale analysis of our model, leading to phase diffusion equations whose diffusion coefficients encapsulate all relevant information on dynamics. We identify two critical exponents: (i) the coarsening exponent, n, controlling the increase in time of the typical size of the pattern, L tn; (ii) the exponent ?, controlling the increase in time of the typical slope of the pattern, M t?, where M ?H/L. Our study reveals that there are only two different universality classes, according to the presence (n =1/3, ? =0) or the absence (n =1/4, ? >0) of faceting. The symmetry of the pattern, as well as the symmetry of the surface mass current j (?h) and its precise functional form, is irrelevant. Our analysis seems to support the idea that also space dimensionality is irrelevant.

  19. Shallow melt apparatus for semicontinuous czochralski crystal growth

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2006-01-10

    In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

  20. Effect of impurities on crystal growth rate of ammonium pentaborate

    NASA Astrophysics Data System (ADS)

    ?ahin, .; zdemir, M.; Genli, N.

    2004-01-01

    The effect of sodium chloride, borax and boric acid of different concentrations on the growth rate of ammonium pentaborate octahydrate crystals (APBO) was measured and was found to depend on supersaturation in a fluidized bed crystallizer. The presence of impurities in APBO solution increases the growth rate compared with growth from pure solution. It was found that the presence of sodium chloride, borax and boric acid decreases the reaction rate constant kr, while it increases the mass-transfer coefficient, K, of APBO crystals. In pure aqueous solution, the crystal growth rate of APBO is mainly controlled by diffusion. However, both diffusion and integration steps affect the growth rate of APBO crystals in the presence of sodium chloride, borax and boric acid. The mass-transfer coefficient, K, reaction rate constant, kr and reaction order, r were calculated from general mass-transfer equation by using genetic algorithm method making no assumption.

  1. Kinetic Roughening Transition and Energetics of Tetragonal Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    Interpretation of lysozyme crystal growth rates using well-established physical theories enabled the discovery of a phenomenon possibly indicative of kinetic roughening. For example, lysozyme crystals grown above a critical supersaturation sigma, (where supersaturation sigma = ln c/c(sub eq), c = the protein concentration and c(sub eq) = the solubility concentration) exhibit microscopically rough surfaces due to the continuous addition of growth units anywhere on the surface of a crystal. The rate of crystal growth, V(sub c), for the continuous growth process is determined by the continuous flux of macromolecules onto a unit area of the crystal surface, a, from a distance, xi, per unit time due to diffusion, and a probability of attachment onto the crystal surface, expressed. Based upon models applied, the energetics of lysozyme crystal growth was determined. The magnitudes of the energy barriers of crystal growth for both the (110) and (101) faces of tetragonal lysozyme crystals are compared. Finally, evidence supportive of the kinetic roughening hypothesis is presented.

  2. The inhibition of crystal growth of mirabilite in aqueous solutions in the presence of phosphonates

    NASA Astrophysics Data System (ADS)

    Vavouraki, A. I.; Koutsoukos, P. G.

    2016-02-01

    The formation of sodium sulfate decahydrate (Mirabilite) has been known to cause serious damages to structural materials both of modern and of historical buildings. Methods which can retard or completely suppress the development of mirabilte crystals are urgently needed especially as remedies or preventive measures for the preservation of the built cultural heritage. In the present work we present results on the effect of the presence of phosphonate compounds on the kinetics of crystal growth from aqueous supersaturated solutions at 18 °C using the seeded growth technique. The phosphonate compounds tested differed with respect to the number of ionizable phosphonate groups and with respect to the number of amino groups in the respective molecules. The crystal growth process was monitored by the temperature changes during the exothermic crystallization of mirabilite in the stirred supersaturated solutions. The crystal growth of mirabilite in the presence of: (1-hydroxyethylidene)-1, 1-diphosphonic acid (HEDP), amino tri (methylene phosphonic acid) (ATMP), hexamethylenediaminetetra (methylene)phosphonic acid (HTDMP), and diethylene triamine penta(methylene phosphonic acid)(DETPMP) over a range of concentrations between 0.1-5% w/w resulted in significant decrease of the rates of mirabilite crystal growth. All phosphonic compounds tested reduced the crystallization rates up to 60% in comparison with additive-free solutions. The presence of the test compounds did not cause changes of the mechanism of crystal growth which was surface diffusion controlled, as shown by the second order dependence of the rates of mirabilite crystal growth on the relative supersaturation. The excellent fit of the measured rates to a kinetic Langmuir-type model suggested that the activity of the tested inhibitors could be attributed to the adsorption and subsequent reduction of the active crystal growth sites of the seed crystals. In all cases, the inhibitory activity was reduced with increasing solution supersaturation, while the presence of DETPMP, which showed the best inhibition activity, showed the least reduction of inhibition with increasing supersaturation.

  3. Needs and Opportunities in Crystal Growth.

    ERIC Educational Resources Information Center

    Mroczkowski, Stanley

    1980-01-01

    Presents a survey of the scientific basis for single crystals production, discussing some of the theoretical and experimental advances in the area. Future prospects for semiconductors, magnetic lasers, nonlinear optics, piezoelectrics, and other crystals are surveyed. (Author/CS)

  4. Autocatalytic Decomposition Mechanisms in Energetic Molecular Crystals

    NASA Astrophysics Data System (ADS)

    Kuklja, Maija; Rashkeev, Sergey

    2009-06-01

    Atomic scale mechanisms of the initiation of chemical processes in energetic molecular crystals, which lead to the decomposition and ultimately to an explosive chain reaction, are still far from being understood. In this work, we investigate the onset of the initiation processes in two high explosive crystals - diamino-dinitroethylene (DADNE) and triamino- trinitrobenzene (TATB). We found that an autocatalytic decomposition mechanism is likely to take place in DADNE crystal that consists of corrugated, dashboard-shaped molecular layers. The presence of a dissociated NO2 group in the interstitial space between two layers induces a significant shear-strain between these layers, which, in turn, facilitates the further dissociation of NO2 groups from surrounding molecules through lowering the C-NO2 decomposition barrier. Unlike this, in TATB (that consists of flat, graphite-like molecular layers), an interstitial NO2 group positioned between two layers tends to produce a tensile stress (rather than a shear-strain), which leads to local molecular disorder in these layers without any significant modification of the C-NO2 decomposition barrier. The observed differences between the two materials are discussed in terms of their structural, electronic, and chemical properties.

  5. Synthesis, crystal growth, solubility, structural, optical, dielectric and microhardness studies of Benzotriazole-4-hydroxybenzoic acid single crystals

    NASA Astrophysics Data System (ADS)

    Silambarasan, A.; Krishna Kumar, M.; Thirunavukkarasu, A.; Mohan Kumar, R.; Umarani, P. R.

    2015-06-01

    Organic Benzotriazole-4-hydroxybenzoic acid (BHBA), a novel second-order nonlinear optical single crystal was grown by solution growth method. The solubility and nucleation studies were performed for BHBA crystal at different temperatures 30, 35, 40 45 and 50 C. Single crystal X-ray diffraction study reveals that the BHBA belongs to Pna21 space group of orthorhombic crystal system. The crystal perfection of BHBA was examined from powder and high resolution X-ray diffraction analysis. UV-visible and photoluminescence spectra were recorded to study its transmittance and excitation, emission behaviors respectively. Kurtz powder second harmonic generation test reveals that, the frequency conversion efficiency of BHBA is 3.7 times higher than that of potassium dihydrogen phosphate (KDP) crystal. The dielectric constant and dielectric loss values were estimated for BHBA crystal at various temperatures and frequencies. The mechanical property of BHBA crystal was studied on (110), (010) and (012) planes by using Vicker's microhardness test. The chemical etching study was performed on (012) facet of BHBA crystal to analyze its growth feature.

  6. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  7. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

    1999-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the application of the magnetic field leads to a significant reduction in fluid flow, with improved homogeneity of composition. The field strength required to suppress flow increases with diameter of the material. The 8 mm diameter sample used here was less than the upper diameter limit for a ST magnet. The configuration for USMP-4 was changed so that the material was seeded and other processing techniques were also modified. It was decided to examine the effects of a strong magnetic field under the modified configuration and parameters. A further change from USMP-2 was that a different composition of material was grown, namely with 0.152 mole fraction of cadmium telluride rather than the 0.200 of the USMP-2 experiment. The objective was to grow highly homogeneous, low defect density material of a composition at which the conduction band and the valence band of the material impinge against each other. As indicated, the furnace was contaminated during the mission. As a result of solid debris remaining in the furnace bore, the cartridge in this experiment, denoted as SL1-417, was significantly bent during the insertion phase. During translation the cartridge scraped against the plate which isolates the hot and cold zones of the furnace. Thermocouples indicated that a thermal assymetry resulted. The scraping in the slow translation or crystal growth part of the processing was not smooth and it is probable that the jitter was sufficient to give rise to convection in the melt. Early measurements of composition from the surface of the sample have shown that the composition varies in an oscillatory manner.

  8. Nucleation and Growth of Discotic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Zhengdong; Wang, Xuezhen; Zhang, Lecheng; Shinde, Abhijeet; Liquid Crystals of Nanoplates in Microgravity Team

    2015-03-01

    We investigate the nucleation and growth of liquid crystals of plate-shaped charged zirconium phosphate (ZrP) monolayers with various sizes, temperature and salt concentrations. The smaller the platelets size, or the higher the temperature, or the higher the salt concentration (from 0 to 0.6M), the faster the Isotropic-Nematic (I-N) separation took place. We established the I-N transition phase diagram of charged platelets in the temperature verse volume fraction plane, and discovered that N phase can be melted by increasing temperature, and coexistent samples are more sensitive to polydispersity at higher temperature and higher concentrations. We also found that salt concentration in the ZrP suspensions contributed to the formation of an apparently twisted phase. This work is supported by NSF (DMR-1006870) and NASA (NASA-NNX13AQ60G). X.Z. Wang acknowledges support from the Mary Kay O'Connor Process Safety Center (MKOPSC) at Texas A&M University.

  9. Ground Based Program for the Physical Analysis of Macromolecular Crystal Growth

    NASA Technical Reports Server (NTRS)

    Malkin, Alexander J.

    1998-01-01

    During the past year we have focused on application of in situ Atomic Force Microscopy (AFM) for studies of the growth mechanisms and kinetics of crystallization for different macromolecular systems. Mechanisms of macrostep formation and their decay, which are important in understanding of defect formation, were studied on the surfaces of thaumatin, catalase, canavalin and lysozyme crystals. Experiments revealed that step bunching on crystalline surfaces occurred either due to two- or three-dimensional nucleation on the terraces of vicinal slopes or as a result of uneven step generation by complex dislocation sources. No step bunching arising from interaction of individual steps in the course of the experiment was observed. The molecular structure of the growth steps for thaumatin and lipase crystals were deduced. It was further shown that growth step advance occurs by incorporation of single protein molecules. In singular directions growth steps move by one-dimensional nucleation on step edges followed by lateral growth. One-dimensional nuclei have different sizes, less then a single unit cell, varying for different directions of step movement. There is no roughness due to thermal fluctuations, and each protein molecule which incorporated into the step remained. Growth kinetics for catalase crystals was investigated over wide supersaturation ranges. Strong directional kinetic anisotropy in the tangential step growth rates in different directions was seen. The influence of impurities on growth kinetics and cessation of macromolecular crystals was studied. Thus, for catalase, in addition to pronounced impurity effects on the kinetics of crystallization, we were also able to directly observe adsorption of some impurities. At low supersaturation we repeatedly observed filaments which formed from impurity molecules sedimenting on the surfaces. Similar filaments were observed on the surfaces of thaumatin, canavalin and STMV crystals as well, but the frequency was low compared with catalase crystallization. Cessation of growth of xylanase and lysozyme crystals was also observed and appeared to be a consequence of the formation of dense impurity adsorption layers. Attachment: "An in situ AFM investigation of catalase crystallization", "Atomic force microscopy studies of living cells: visualization of motility, division, aggregation, transformation, and apoptosis", AFM studies on mechanisms of nucleation and growth of macromolecular crystals", and "In situ atomic force microscopy studies of surface morphology, growth kinetics, defect structure and dissolution in macromolecular crystallization".

  10. Passive particle dosimetry. [silver halide crystal growth

    NASA Technical Reports Server (NTRS)

    Childs, C. B.

    1977-01-01

    Present methods of dosimetry are reviewed with emphasis on the processes using silver chloride crystals for ionizing particle dosimetry. Differences between the ability of various crystals to record ionizing particle paths are directly related to impurities in the range of a few ppm (parts per million). To understand the roles of these impurities in the process, a method for consistent production of high purity silver chloride, and silver bromide was developed which yields silver halides with detectable impurity content less than 1 ppm. This high purity silver chloride was used in growing crystals with controlled doping. Crystals were grown by both the Czochalski method and the Bridgman method, and the Bridgman grown crystals were used for the experiments discussed. The distribution coefficients of ten divalent cations were determined for the Bridgman crystals. The best dosimeters were made with silver chloride crystals containing 5 to 10 ppm of lead; other impurities tested did not produce proper dosimeters.

  11. Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2003-01-01

    Lysozyme crystal growth rates over 5 orders of magnitude in range can be described using a layer-by-layer model where growth occurs by 2D nucleation on the crystal surface. Based upon the 2D nucleation model of layer growth, the effective barrier for growth was determined to be gamma = 1.3 plus or minus 0.3 x 10(exp -13) erg/molecule, corresponding to a barrier of 3.2 plus or minus 0.7 k(sub B)T, at 22 C. For solution supersaturation, In c/c(sub eq) greater than or equal to 1.9 plus or minus 0.2, the nucleation model would not predict or consistently estimate the highest observable crystal growth rates. As such, a kinetic roughening hypothesis where crystal growth occurs by a continuous mode was implemented for all growth rate data obtained above In c(sub r)/c(sub eq) greater than or equal to 2. That is, independent of the solution conditions that vary with either buffer pH, temperature or precipitant concentration, crystal growth occurs by the continuous addition of molecules anywhere on the crystal surface, above a roughening solution supersaturation. The energy barrier, E(sub c), for the continuous growth process is determined as 6.1 plus or minus 0.4 x 10(exp -13) erg/molecule or 15 plus or minus 1 k(sub B)T at 22 C.

  12. Numerical computations of faceted pattern formation in snow crystal growth

    NASA Astrophysics Data System (ADS)

    Barrett, John W.; Garcke, Harald; Nrnberg, Robert

    2012-07-01

    Faceted growth of snow crystals leads to a rich diversity of forms with remarkable sixfold symmetry. Snow crystal structures result from diffusion-limited crystal growth in the presence of anisotropic surface energy and anisotropic attachment kinetics. It is by now well understood that the morphological stability of ice crystals strongly depends on supersaturation, crystal size, and temperature. Until very recently it was very difficult to perform numerical simulations of this highly anisotropic crystal growth. In particular, obtaining facet growth in combination with dendritic branching is a challenging task. We present numerical simulations of snow crystal growth in two and three spacial dimensions using a computational method recently introduced by the present authors. We present both qualitative and quantitative computations. In particular, a linear relationship between tip velocity and supersaturation is observed. In our computations, surface energy effects, although small, have a pronounced effect on crystal growth. We compute solid plates, solid prisms, hollow columns, needles, dendrites, capped columns, and scrolls on plates. Although all these forms appear in nature, it is a significant challenge to reproduce them with the help of numerical simulations for a continuum model.

  13. Crystal Growth of Germanium-Silicon Alloys on the ISS

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2015-01-01

    A series of Ge(1-x)Si(x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The experiments are part of the investigation "Influence of Containment on the Growth of Silicon-Germanium" (ICESAGE). The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. This meniscus can exist over a much larger range of processing parameters in microgravity and the meniscus is more stable under microgravity conditions. The plans for the flight experiments will be described.

  14. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    SciTech Connect

    Murugan, G. Senthil Ramasamy, P.

    2014-04-24

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  15. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    NASA Astrophysics Data System (ADS)

    Murugan, G. Senthil; Ramasamy, P.

    2014-04-01

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P21. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d33 co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  16. Vapor Growth and Characterization of Cr-Doped ZnSe Crystals

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, Shari; Volz, M. P.; Matyi, R.; George, M. A.; Chattopadhyay, K.; Burger, A.; Lehoczky, S. L.

    1999-01-01

    Cr-doped ZnSe single crystals were grown by a self-seeded physical vapor transport technique in both vertical (stabilized) and horizontal configurations. The source materials were mixtures of ZnSe and CrSe. Growth temperatures were in the range of 1140-1150 C and the furnace translation rates were 1.9-2.2 mm/day. The surface morphology of the as-grown crystals was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Different features of the as-grown surface of the vertically and horizontally grown crystals suggest that different growth mechanisms were involved in the two growth configurations. The [Cr] doping levels were determined to be in the range of 1.8-8.3 x 10 (exp 19) cm (exp -3) from optical absorption measurements. The crystalline quality of the grown crystals were examined by high-resolution triple-crystal X-ray diffraction (HRTXD) analysis.

  17. Growth and studies of cyclohexylammonium 4-methoxy benzoate single crystal for nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Sathya, P.; Gopalakrishnan, R.

    2015-06-01

    Cyclohexylammonium 4-Methoxy Benzoate (C4MB) was synthesised and the functional groups were confirmed by FTIR analysis. The purified C4MB (by repeated recrystallisation) was used for single crystal growth. Single crystal of cyclohexylammonium 4-methoxy benzoate was successfully grown by slow evaporation solution growth method at ambient temperature. Structural orientations were determined from single crystal X-ray diffractometer. Optical absorption and cut off wavelength were identified by UV-Visible spectroscopy. Thermal stability of the crystal was studied from thermogravimetric and differential thermal analyses curves. Mechanical stability of the grown crystal was analysed by Vicker's microhardness tester. The Second Harmonic Generation (SHG) study revealed that the C4MB compound exhibits the SHG efficiency 3.3 times greater than KDP crystal.

  18. Analysis of ice crystal growth for a crystal surface containing adsorbed antifreeze proteins

    NASA Astrophysics Data System (ADS)

    Grandum, Svein; Yabe, Akira; Nakagomi, Kazuya; Tanaka, Makoto; Takemura, Fumio; Kobayashi, Yasunori; Frivik, Per-Erling

    1999-09-01

    The adsorption of antifreeze protein (AFP) molecules to the ice crystal surface during melt growth from an AFP solution results in disturbance of the growth kinetics at the surface interface. In this paper, the growth pattern related to the potential for crystal growth as well as the crystal surface topography have been studied. The crystal shape and size were found to be strongly dependent on the supercooling in the crystal's surrounding liquid. In between a transition temperature and the freezing temperature, needle-type crystals were formed, growing rapidly in the c-axis direction. The surface was investigated using a scanning tunneling microscope (STM) and a systematic groove/ridge pattern aligned 65° (±5°) to the hexagonal side on one bipyramidal plane observed with length and width similar to the size of the AFP molecule. The depth of the grooves, ranging from 2 to 10 nm indicates the curvature of ice.

  19. Colloidal crystal growth monitored by Bragg diffraction interference fringes.

    PubMed

    Bohn, Justin J; Tikhonov, Alexander; Asher, Sanford A

    2010-10-15

    We monitored the crystal growth kinetics of crystallization of a shear melted crystalline colloidal array (CCA). The fcc CCA heterogeneously nucleates at the flow cell wall surface. We examined the evolution of the (1 1 1) Bragg diffraction peak, and, for the first time, quantitatively monitored growth by measuring the temporal evolution of the Bragg diffraction interference fringes. Modeling of the evolution of the fringe patterns exposes the time dependence of the increasing crystal thickness. The initial diffusion-driven linear growth is followed by ripening-driven growth. Between 80 and 90 microM NaCl concentrations the fcc crystals first linearly grow at rates between 1.9 and 4.2 microm/s until they contact homogeneously nucleated crystals in the bulk. At lower salt concentrations interference fringes are not visible because the strong electrostatic interactions between particles result in high activation barriers, preventing defect annealing and leading to a lower crystal quality. The fcc crystals melt to a liquid phase at >90 microM NaCl concentrations. Increasing NaCl concentrations slow the fcc CCA growth rate consistent with the expectation of the classical Wilson-Frenkel growth theory. The final thickness of wall-nucleated CCA, that is determined by the competition between growth of heterogeneously and homogenously nucleated CCA, increases with higher NaCl concentrations. PMID:20542277

  20. Universality classes for unstable crystal growth.

    PubMed

    Biagi, Sofia; Misbah, Chaouqi; Politi, Paolo

    2014-06-01

    Universality has been a key concept for the classification of equilibrium critical phenomena, allowing associations among different physical processes and models. When dealing with nonequilibrium problems, however, the distinction in universality classes is not as clear and few are the examples, such as phase separation and kinetic roughening, for which universality has allowed to classify results in a general spirit. Here we focus on an out-of-equilibrium case, unstable crystal growth, lying in between phase ordering and pattern formation. We consider a well-established 2+1-dimensional family of continuum nonlinear equations for the local height h(x,t) of a crystal surface having the general form ∂_{t}h(x,t)=-∇·[j(∇h)+∇(∇^{2}h)]: j(∇h) is an arbitrary function, which is linear for small ∇h, and whose structure expresses instabilities which lead to the formation of pyramidlike structures of planar size L and height H. Our task is the choice and calculation of the quantities that can operate as critical exponents, together with the discussion of what is relevant or not to the definition of our universality class. These aims are achieved by means of a perturbative, multiscale analysis of our model, leading to phase diffusion equations whose diffusion coefficients encapsulate all relevant information on dynamics. We identify two critical exponents: (i) the coarsening exponent, n, controlling the increase in time of the typical size of the pattern, L∼t^{n}; (ii) the exponent β, controlling the increase in time of the typical slope of the pattern, M∼t^{β}, where M≈H/L. Our study reveals that there are only two different universality classes, according to the presence (n=1/3, β=0) or the absence (n=1/4, β>0) of faceting. The symmetry of the pattern, as well as the symmetry of the surface mass current j(∇h) and its precise functional form, is irrelevant. Our analysis seems to support the idea that also space dimensionality is irrelevant. PMID:25019732

  1. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  2. Morphologies of Pentacene Crystals Obtained by Physical Vapor Growth Technique

    NASA Astrophysics Data System (ADS)

    Sadaharu Jo,; Mitsuru Takenaga,

    2010-07-01

    Three kinds of morphologies were observed in the pentacene crystals obtained by physical vapor growth, such as the whisker-type morphology, the plateletlike morphology with large parallelogram planes, and the plateletlike morphology with large dendritic planes. Plateletlike crystals have a common basal (001) plane, despite possessing different morphologies, that is, either the parallelogram or dendritic planes. The results of white-beam X-ray diffraction analysis revealed that the crystal qualities depended on the growth condition rather than on the crystal morphology.

  3. Large-size germanium crystal growth for rare event physics

    NASA Astrophysics Data System (ADS)

    Mei, Dongming; Wang, Guojian; Mei, Hao; Guan, Yutong; Yang, Gang; Govani, Jayesh; Cubed Collaboration

    2014-09-01

    Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the crystalline structure. With knowledge gained from the pioneers in the field of crystal growth, the researchers have developed a novel technique to grow detector-grade crystals. In this paper, we will report detector-grade large-size germanium crystal growth at the University of South Dakota. Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the crystalline structure. With knowledge gained from the pioneers in the field of crystal growth, the researchers have developed a novel technique to grow detector-grade crystals. In this paper, we will report detector-grade large-size germanium crystal growth at the University of South Dakota. DE-FG02-10ER46709 and the state of South Dakota.

  4. Crystal growth of organic energetic materials: pentaerythritol tetranitrate

    NASA Astrophysics Data System (ADS)

    Zhang, Gengxin; Weeks, Brandon; Zhang, Xin

    2012-09-01

    The energy output performance and thermal stability of organic energetic materials have a strong dependence on the porosity, particle morphology, and micro-scale crystal structure. This paper reviews the growth habit of pure pentaerythritol tetranitrate (PETN) crystals and the effect of metal impurities on microcrystal morphology of PETN films. The pure crystal growth shows that PETN molecules diffuse on the surface and nucleate in a two-dimensional layer-by-layer fashion; the final structure is controlled by the deposition flux. Also, the effect of metal cation impurities has a strong impact on the thermal stability and crystal structure, and is dependent on the doping level.

  5. Pulsation processes at hydrothermal crystal growth (beryl as example)

    NASA Astrophysics Data System (ADS)

    Thomas, Victor G.; Demin, Sergey P.; Foursenko, Dmitry A.; Bekker, Tatjana B.

    1999-10-01

    The experiments on beryl hydrothermal growth showed that spontaneously formed growth zonality in crystals can be explained by sporadic temperature fluctuations at 0.7C amplitude. Model experiments under normal conditions proved that such temperature fluctuations in the growth medium can be generated in hydrothermal growth processes. They are due to the pulsation character of heat-mass transfer in autoclave. The model is suggested to explain the hydrothermal crystal growth as a result of the instant local overcooling of the diffusion layer when they are in contact with the cold portions of hydrothermal solution.

  6. Method For Growth of Crystal Surfaces and Growth of Heteroepitaxial Single Crystal Films Thereon

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony (Inventor); Larkin, David J. (Inventor); Neudeck, Philip G. (Inventor); Matus, Lawrence G. (Inventor)

    2000-01-01

    A method of growing atomically-flat surfaces and high quality low-defect crystal films of semiconductor materials and fabricating improved devices thereon is discussed. The method is also suitable for growing films heteroepitaxially on substrates that are different than the film. The method is particularly suited for growth of elemental semiconductors (such as Si), compounds of Groups III and V elements of the Periodic Table (such as GaN), and compounds and alloys of Group IV elements of the Periodic Table (such as SiC).

  7. Synthesis and crystallization mechanism of europium-titanate Eu2Ti2O7

    NASA Astrophysics Data System (ADS)

    Mrzek, Jan; Surnek, Martin; Bakardjieva, Snejana; Burk, Ji?; Kak, Ivan

    2014-04-01

    The synthesis of nanocrystalline europium-titanate pyrochlore Eu2Ti2O7 by a generic sol gel approach is presented. The size of the formed nanocrystals was tailored from 20 nm to 100 nm. The nucleation process and the crystallization mechanism were studied. The activation energies of the crystallization process and crystal growth were calculated. It was found; from the calculated Avrami's parameters; that the crystallization process starts by homogenous nucleation followed by three dimensional growth. The activation energies of the crystallization process were about 700 kJ mol-1. The energy of nanocrystal growth was 26.53.9 kJ mol-1. The results present fundamental information about the crystallization behavior of RE2Ti2O7 prepared by the condensation of titanium alkoxides with inorganic salts of rare-earth elements.

  8. Michelson interferometric studies of protein and virus crystal growth

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Yu. G.; Malkin, A. J.; Greenwood, A.; McPherson, A.

    1996-09-01

    In situ laser Michelson interferometry was utilized to investigate the growth kinetics and surface morphology in canavalin, thaumatin, and turnip yellow mosaic virus (TYMV) crystallization. Interferometric patterns and kinetic measurements from growing macromolecular crystals as small as 20 ?m were obtained. This study shows that for the crystallization of canavalin, dislocations are the sources of growth steps on the surfaces of growing crystals. Supersaturation dependencies of the normal growth rates, tangential growth step velocities, and the slopes of the dislocation hillocks were determined. The kinetic coefficient ? was estimated for canavalin grown from two different precipitant systems to be 3.2 10 -4 and 5.3 10 -4 cm s -1, respectively. The change in activities of dislocation sources under different growth conditions was analyzed.

  9. Silicon isotope fractionation during FZ growth of silicon crystals

    NASA Astrophysics Data System (ADS)

    Morishita, Y.; Satoh, H.

    2003-01-01

    We have carried out evaporation and crystal growth experiments, and precisely determined silicon isotopic ratios for the run products of the experiments using the ims-1270 SIMS with multicollectors at the Geological Survey of Japan. The silicon isotope fractionation factor between vapor and melt under vacuum was determined to be 0.9821 at a temperature of 1680 C, while that under 10 5 Pa of Ar was 0.9947. The SIMS microanalysis revealed isotopic zoning in a single silicon crystal which was produced during its growth. It is inferred that the silicon isotopic ratios in a silicon crystal during the floating zone growth were controlled by the growth conditions such as the growth and rotation rates as well as the fractionation factor between the crystal and its melt.

  10. Growth of high-strength protein crystals with nanofibers

    NASA Astrophysics Data System (ADS)

    Matsuoka, Miki; Kakinouchi, Keisuke; Adachi, Hiroaki; Maruyama, Mihoko; Sugiyama, Shigeru; Nakabayashi, Iori; Tsuchikura, Hiroshi; Kuwahara, Atsushi; Sano, Satoshi; Yoshikawa, Hiroshi Y.; Takahashi, Yoshinori; Yoshimura, Masashi; Matsumura, Hiroyoshi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Takano, Kazufumi

    2016-03-01

    Here, we present a novel method of growing protein crystals with nanofibers. Protein crystals were grown by incorporating nanofibers. No obvious differences were observed in diffraction data between fiber-containing and as-grown crystals. The fiber-containing crystals displayed an increased tolerance to osmotic shock caused by soaking in 25% ethanol or 40% dimethyl sulfoxide. This means that the method allowed us to easily increase the crystal mechanical stability. Because the method is very simple, it will provide a variety of possibilities for protein crystallization.

  11. Growth of zeolite crystals in the microgravity environment of space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

    1986-01-01

    Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

  12. Specificity of growth inhibitors and their cooperative effects in calcium oxalate monohydrate crystallization.

    PubMed

    Farmanesh, Sahar; Ramamoorthy, Sriram; Chung, Jihae; Asplin, John R; Karande, Pankaj; Rimer, Jeffrey D

    2014-01-01

    The molecular recognition and interactions governing site-specific adsorption of growth inhibitors on crystal surfaces can be tailored in order to control the anisotropic growth rates and physical properties of crystalline materials. Here we examine this phenomenon in calcium oxalate monohydrate (COM) crystallization, a model system of calcification with specific relevance for pathological mineralization. We analyzed the effect of three putative growth inhibitors--chondroitin sulfate, serum albumin, and transferrin--using analytical techniques capable of resolving inhibitor-crystal interactions from interfacial to bulk scales. We observed that each inhibitor alters surface growth by adsorbing on to distinct steps emanating from screw dislocations on COM surfaces. Binding of inhibitors to different crystallographic faces produced morphological modifications that are consistent with classical mechanisms of layer-by-layer crystal growth inhibition. The site-specific adsorption of inhibitors on COM surfaces was confirmed by bulk crystallization, fluorescent confocal microscopy, and atomic force microscopy. Kinetic studies of COM growth at varying inhibitor concentrations revealed marked differences in their efficacy and potency. Systematic analysis of inhibitor combinations, quantified via the combination index, identified various binary pairings capable of producing synergistic, additive, and antagonistic effects. Collectively, our investigation of physiologically relevant biomolecules suggests potential roles of COM inhibitors in pathological crystallization and provides guiding principles for biomimetic design of molecular modifiers for applications in crystal engineering. PMID:24313314

  13. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

    2001-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

  14. Sizes and spatial relationships of crystals in granitic plutons: Exploring the crystallization gaps, heterogeneous nucleation, and mechanical clustering of crystals

    NASA Astrophysics Data System (ADS)

    Špillar, V.; Dolejš, D.

    2012-04-01

    Quantitative measurements on magmatic textures provide an important insight into nucleation and growth rates as well as mechanical effects such as crystal settling and melt extraction in magma reservoirs. Crystal size distribution (CSD) measurements and spatial analysis are routinely applied to dilute volcanic suspensions but comparable data on holocrystalline multiphase plutonic rocks are uncommon. We present quantitative description of CSDs and spatial relationships for all rock-forming minerals from an intrusive suite of the Fichtelgebirge/Smrčiny granite batholith in central Europe. This composite body represents two spatially unrelated chambers, consisting of peraluminous biotite, two-mica, and tourmaline-muscovite granites, crystallized as texturally diverse batches covering equigranular, serial porphyritic, and hiatal porphyritic fine- to coarse-grained types. All granite samples exhibit straight to concave-up CSDs in the natural log of population density vs. crystal size projection. Straight CSDs were only found in fine-grained biotite-rich granites representing early crystallizing roof facies of the batholith. For all other samples, the slope decreases from -65 to nearly 0 mm-1 as grain size increases. The curvature can result from superposition of two quasilinear segments. It cannot be produced by two separate crystallization events because the population of larger grains is about 10 times more abundant by volume than the fine one. Instead, we propose that the concave-up CSDs developed in situ, with enhanced nucleation and/or reduced growth rates during the final stage of solidification. Spatial analysis and measurements of contact relationships reveal significant clustering of crystals except near the roof of the batholith. The clustering index decreases to 0.6 for the smallest crystals (random = 1), Ripley's Ľ-function reaches 0.8 mm, and the clusters are mineral sensitive: pairs of like phases appear to be more clustered than the unlike pairs. The observed parameters were reproduced by a three-dimensional numerical model with time-dependent nucleation and growth rates, and with variable degree of clustering induced by changing the ratio of homogeneous vs. heterogeneous nucleation rate, between

  15. Ames Lab 101: Single Crystal Growth

    SciTech Connect

    Schlagel, Deborah

    2013-09-27

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  16. Ames Lab 101: Single Crystal Growth

    ScienceCinema

    Schlagel, Deborah

    2014-06-04

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  17. The effects of polydispersity and metastability on crystal growth kinetics

    NASA Astrophysics Data System (ADS)

    Williamson, John J.; Evans, R. Mike L.

    We investigate the effect of metastable gas-liquid (G-L) separation on crystal growth in a system of either monodisperse or slightly size-polydisperse square well particles, using a simulation setup that allows us to focus on the growth of a single crystal. Our system parameters are such that, inside the metastable G-L binodal, a macroscopic layer of the gas phase "coats" the crystal as it grows, consistent with experiment and theoretical free energy considerations. Crucially, the effect of this metastable G-L separation on the crystal growth rate depends qualitatively on whether the system is polydisperse. We measure reduced polydispersity and qualitatively different local size ordering in the crystal relative to the fluid, proposing that the required fractionation is dynamically facilitated by the gas layer. Our results show that polydispersity and metastability, both ubiquitous in soft matter, must be considered in tandem if their dynamical effects are to be understood.

  18. Antifreeze effect of carboxylated ε-poly-L-lysine on the growth kinetics of ice crystals.

    PubMed

    Vorontsov, Dmitry A; Sazaki, Gen; Hyon, Suong-Hyu; Matsumura, Kazuaki; Furukawa, Yoshinori

    2014-08-28

    Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated ε-poly-L-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units. PMID:25113284

  19. Application of porous interface on segregation in Czochralski crystal growth

    NASA Astrophysics Data System (ADS)

    Asadian, M.; Saeedi, H.

    2016-02-01

    The aim of this paper is to develop a model for the solute segregation in Czochralski crystal growth based on similarity solution. In this model, the effect of crystal growth rate for the wide range of Schmidt (Sc) numbers on boundary layer is considered. We utilize a variable R = V0 / ?{ ? ? } which represents the ratio of growth velocity (V0) to stirring velocity (?{ ? ? }). Since both crystal rotation rate and growth velocity are almost varied in order to control the growth process, the parameter R can be used as a scale of optimization for the various growth conditions. The analyses show that the effective segregation coefficient (keff) is related to the parameter R. In the end, the results are utilized in the Czochralski configuration to determine the equilibrium segregation coefficient (k0) and Sc number evaluated and compared with experimental data.

  20. Apparatus for single ice crystal growth from the melt

    NASA Astrophysics Data System (ADS)

    Zepeda, Salvador; Nakatsubo, Shunichi; Furukawa, Yoshinori

    2009-11-01

    A crystal growth apparatus was designed and built to study the effect of growth modifiers, antifreeze proteins and antifreeze glycoproteins (AFGPs), on ice crystal growth kinetics and morphology. We used a capillary growth technique to obtain a single ice crystal with well-defined crystallographic orientation grown in AFGP solution. The basal plane was readily observed by rotation of the capillary. The main growth chamber is approximately a 0.8ml cylindrical volume. A triple window arrangement was used to minimize temperature gradients and allow for up to 10mm working distance objective lens. Temperature could be established to within ±10mK in as little as 3.5min and controlled to within ±2mK after 15min for at least 10h. The small volume growth chamber and fast equilibration times were necessary for parabolic flight microgravity experiments. The apparatus was designed for use with inverted and side mount configurations.

  1. Growth of large KDP crystals in the form of plates

    SciTech Connect

    Beriot, E; Tatartchenko, V

    1998-05-01

    This paper suggests a new technique of growth-oriented KDP crystals in the form of plates. The technique includes: using small oriented seeds spaced between two parallel platforms with a rapid growth of crystals between these two platforms, in a tank containing a KDP solution. As a result, crystals in the form of plates can be obtained. The thickness of the crystal plate depends on the distance between platforms. The horizontal dimensions of the plate depend on the volume of solution and the diameter of the platforms. The orientation of the plates are defined by the orientation of the seed. KDP crystals in the form of plates of two orientations are grown. The peculiarities of morphology and some characteristics of crystals are discussed.

  2. Large-volume protein crystal growth for neutron macromolecular crystallography.

    PubMed

    Ng, Joseph D; Baird, James K; Coates, Leighton; Garcia-Ruiz, Juan M; Hodge, Teresa A; Huang, Sijay

    2015-04-01

    Neutron macromolecular crystallography (NMC) is the prevailing method for the accurate determination of the positions of H atoms in macromolecules. As neutron sources are becoming more available to general users, finding means to optimize the growth of protein crystals to sizes suitable for NMC is extremely important. Historically, much has been learned about growing crystals for X-ray diffraction. However, owing to new-generation synchrotron X-ray facilities and sensitive detectors, protein crystal sizes as small as in the nano-range have become adequate for structure determination, lessening the necessity to grow large crystals. Here, some of the approaches, techniques and considerations for the growth of crystals to significant dimensions that are now relevant to NMC are revisited. These include experimental strategies utilizing solubility diagrams, ripening effects, classical crystallization techniques, microgravity and theoretical considerations. PMID:25849493

  3. Fluid Physics and Macromolecular Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Pusey, M.; Snell, E.; Judge, R.; Chayen, N.; Boggon, T.; Helliwell, J.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The molecular structure of biological macromolecules is important in understanding how these molecules work and has direct application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these flows.

  4. Imaging and interferometric analysis of protein crystal growth

    NASA Astrophysics Data System (ADS)

    Raghunandan, Ranjini; Gupta, Anamika Sethia; Muralidhar, K.

    2008-04-01

    Protein crystals are grown under controlled temperature, concentration and vapor pressure conditions, usually by vapor diffusion, liquid-liquid diffusion and dialysis techniques. The present study examines the effects of protein concentration, drop size and reservoir height on the crystal growth of Hen Egg White Lysozyme (HEWL). Crystals are grown by the hanging drop vapor diffusion method using Modular VDX TM Plates. Due to the vapor pressure difference created between the protein drop and the reservoir, evaporation takes place till equilibrium is attained. Crystal formation takes place after a certain level of supersaturation is attained when the protein precipitates out in crystalline form. The observations revealed that the growth is faster for higher lysozyme concentration, smaller drop sizes and larger reservoir heights. The morphology of the crystals is viewed during the growth process using stereomicroscope. The number of crystals formed is the maximum for higher concentrations, drop sizes and reservoir heights. When the number of crystals formed is less, the size of the crystals is comparatively larger. The effect of evaporation of water vapor from the protein drop into the reservoir is studied using Mach-Zehnder interferometry. The recorded interferograms and shadowgraph images indicate the diffusion of condensed water into the reservoir. The radius of the drop is determined using the shadowgraph images of the growth process. The radius decreases with evaporation and the rate of decrease of radius is highest for higher protein concentrations, smaller drop sizes and larger reservoir heights.

  5. Protein Crystal Movements and Fluid Flows During Microgravity Growth

    NASA Technical Reports Server (NTRS)

    Boggon, Titus J.; Chayen, Naomi E.; Snell, Edward H.; Dong, Jun; Lautenschlager, Peter; Potthast, Lothar; Siddons, D. Peter; Stojanoff, Vivian; Gordon, Elspeth; Thompson, Andrew W.; Zagalsky, Peter F.; Bi, Ru-Chang; Helliwell, John R.

    1997-01-01

    The growth of protein crystals suitable for X-ray crystal structure analysis is an important topic. The methods of protein crystal growth are under increasing study whereby different methods are being compared via diagnostic monitoring including Charge Coupled Device (CCD) video and interferometry. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and X-ray topographic images as well as the diffraction resolution limit and overall data quality. Choice of a liquid-liquid linear crystal growth geometry and microgravity can yield a spatial stability of growing crystals and fluid, as seen in protein crystallization experiments on the unmanned platform EURICA. A review is given here of existing results and experience over several microgravity missions. The results include CCD video as well as interferometry during the mission, followed, on return to earth, by rocking curve experiments and full X-ray data collection on LMS and earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C(sub 1) crystals are also described.

  6. Zeolite Crystal Growth (ZCG) Flight on USML-2

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Bac, Nurcan; Warzywoda, Juliusz; Guray, Ipek; Marceau, Michelle; Sacco, Teran L.; Whalen, Leah M.

    1997-01-01

    The extensive use of zeolites and their impact on the world's economy has resulted in many efforts to characterize their structure, and improve the knowledge base for nucleation and growth of these crystals. The zeolite crystal growth (ZCG) experiment on USML-2 aimed to enhance the understanding of nucleation and growth of zeolite crystals, while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16 day - USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. The external surfaces of zeolite A, X, and Silicalite crystals grown in microgravity were smoother (lower surface roughness) than their terrestrial controls. Catalytic studies with zeolite Beta indicate that crystals grown in space exhibit a lower number of Lewis acid sites located in micropores. This suggests fewer structural defects for crystals grown in microgravity. Transmission electron micrographs (TEM) of zeolite Beta crystals also show that crystals grown in microgravity were free of line defects while terrestrial/controls had substantial defects.

  7. Growth of nonlinear optical ?-glycine crystals

    NASA Astrophysics Data System (ADS)

    Bhat, M. Narayan; Dharmaprakash, S. M.

    2002-03-01

    Bulk crystals of ?-glycine have been grown at ambient temperature from aqueous solution in the presence of small amount of sodium chloride. The chemical composition of the grown crystal was determined by CHN analysis and infrared spectroscopy. The ?-phase was confirmed by powder XRD, single crystal XRD and differential scanning calorimetry. It was observed that ?-glycine generates second harmonic frequency of an Nd:YAG laser operating at 1064 nm. The second harmonic sconversion efficiency of ?-glycine is comparable with that of potassium dihydrogen phosphate.

  8. (PCG) Protein Crystal Growth HIV Reverse Transcriptase

    NASA Technical Reports Server (NTRS)

    1992-01-01

    HIV Reverse Transcriptase crystals grown during the USML-1 (STS-50) mission using Commercial Refrigerator/Incubator Module (CR/IM) at 4 degrees C and the Vapor Diffusion Apparatus (VDA). Reverse transcriptase is an enzyme responsible for copying the nucleic acid genome of the AIDS virus from RNA to DNA. Studies indicated that the space-grown crystals were larger and better ordered (beyond 4 angstroms) than were comparable Earth-grown crystals. Principal Investigators were Charles Bugg and Larry DeLucas.

  9. Simulation study of twisted crystal growth in organic thin films.

    PubMed

    Fang, Alta; Haataja, Mikko

    2015-10-01

    Many polymer and organic small-molecule thin films crystallize with microstructures that twist or curve in a regular manner as crystal growth proceeds. Here we present a phase-field model that energetically favors twisting of the three-dimensional crystalline orientation about and along particular axes, allowing morphologies such as banded spherulites, curved dendrites, and "s"- or "c"-shaped needle crystals to be simulated. When twisting about the fast-growing crystalline axis is energetically favored and spherulitic growth conditions are imposed, crystallization occurs in the form of banded spherulites composed of radially oriented twisted crystalline fibers. Due to the lack of symmetry, twisting along the normal growth direction leads to heterochiral banded spherulites with opposite twist handedness in each half of the spherulite. When twisting is instead favored about the axis perpendicular to the plane of the substrate and along the normal growth direction under diffusion-limited single-crystalline growth conditions, crystallization occurs in the form of curved dendrites with uniformly rotating branches. We show that the rate at which the branches curve affects not only the morphology but also the overall kinetics of crystallization, as the total crystallized area at a given time is maximized for a finite turning rate. PMID:26565254

  10. Simulation study of twisted crystal growth in organic thin films

    NASA Astrophysics Data System (ADS)

    Fang, Alta; Haataja, Mikko

    2015-10-01

    Many polymer and organic small-molecule thin films crystallize with microstructures that twist or curve in a regular manner as crystal growth proceeds. Here we present a phase-field model that energetically favors twisting of the three-dimensional crystalline orientation about and along particular axes, allowing morphologies such as banded spherulites, curved dendrites, and "s"- or "c"-shaped needle crystals to be simulated. When twisting about the fast-growing crystalline axis is energetically favored and spherulitic growth conditions are imposed, crystallization occurs in the form of banded spherulites composed of radially oriented twisted crystalline fibers. Due to the lack of symmetry, twisting along the normal growth direction leads to heterochiral banded spherulites with opposite twist handedness in each half of the spherulite. When twisting is instead favored about the axis perpendicular to the plane of the substrate and along the normal growth direction under diffusion-limited single-crystalline growth conditions, crystallization occurs in the form of curved dendrites with uniformly rotating branches. We show that the rate at which the branches curve affects not only the morphology but also the overall kinetics of crystallization, as the total crystallized area at a given time is maximized for a finite turning rate.

  11. Transport modes during crystal growth in a centrifuge

    NASA Technical Reports Server (NTRS)

    Arnold, William A.; Wilcox, William R.; Carlson, Frederick; Chait, Arnon; Regel', Liia L.

    1992-01-01

    Flow modes arising under average acceleration in centrifugal crystal growth, the gradient of acceleration, and the Coriolis force are investigated using a fully nonlinear three-dimensional numerical model for a centrifugal crystal growth experiment. The analysis focuses on an examination of the quasi-steady state flow modes. The importance of the gradient acceleration is determined by the value of a new nondimensional number, Ad.

  12. Definition study for temperature control in advanced protein crystal growth

    NASA Technical Reports Server (NTRS)

    Nyce, Thomas A.; Rosenberger, Franz; Sowers, Jennifer W.; Monaco, Lisa A.

    1990-01-01

    Some of the technical requirements for an expedient application of temperature control to advanced protein crystal growth activities are defined. Lysozome was used to study the effects of temperature ramping and temperature gradients for nucleation/dissolution and consecutive growth of sizable crystals and, to determine a prototype temperature program. The solubility study was conducted using equine serum albumin (ESA) which is an extremely stable, clinically important protein due to its capability to bind and transport many different small ions and molecules.

  13. Crystal growth from the vapor in low gravity environments

    SciTech Connect

    Santandrea, R.P.

    1985-01-01

    Effects of earth's gravity on fluids and gases are discussed. Crystal growth in microgravity has been studied since the first Skylab mission. Crystal growth from the vapor has been accomplished in space using the chemical vapor transport method, and the principles behind this method and the results obtained in space are discussed, particularly in the germanium chalcogenide systems. Chemical vapor deposition in space offer promising applications. (DLC)

  14. Nacre biomineralisation: A review on the mechanisms of crystal nucleation.

    PubMed

    Nudelman, Fabio

    2015-10-01

    The wide diversity of biogenic minerals that is found in nature, each with its own morphology, mechanical properties and composition, is remarkable. In order to produce minerals that are optimally adapted for their function, biomineralisation usually occurs under strict cellular control. This control is exerted by specialised proteins and polysaccharides that assemble into a 3-dimensional organic matrix framework, forming a microenvironment where mineral deposition takes place. Molluscs are unique in that they use a striking variety of structural motifs to build their shells, each made of crystals with different morphologies and different calcium carbonate polymorphs. Much of want is known about mollusc shell formation comes from studies on the nacreous layer, or mother-of-pearl. In this review, we discuss two existing models on the nucleation of aragonite crystals during nacre formation: heteroepitaxial nucleation and mineral bridges. The heteroepitaxial nucleation model is based on the identification of chemical functional groups and aragonite-nucleating proteins at the centre of crystal imprints. It proposes that during nacre formation, each aragonite tablet nucleates independently on a nucleation site that is formed by acidic proteins and/or glycoproteins adsorbed on the chitin scaffold. The mineral bridges model is based on the identification of physical connections between the crystals in a stack, which results in a large number of crystals across several layers sharing the same crystallographic orientation. These observations suggest that there is one nucleation event per stack of tablets. Once the first crystal nucleates and reaches the top interlamellar matrix, it continues growing through pores, giving rise to the next layer of nacre, subsequently propagating into a stack. We compare both models and propose that they work in concert to control crystal nucleation in nacre. De novo crystal nucleation has to occur at least once per stack of aligned crystals, and is induced by nucleation sites. We suggest that further growth is controlled both by mineral bridges and nucleation sites. Finally, we discuss the role of amorphous calcium carbonate precursor in nacre formation. PMID:26205040

  15. Growth and characterization of lead bromide crystals

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Gottlieb, M.; Henningsen, T.; Hopkins, R. H.; Mazelsky, R.; Glicksman, M. E.; Coriell, S. R.; Santoro, G. J.; Duval, W. M. B.

    1992-01-01

    Lead(II) bromide was purified by a combination of directional freezing and zone-refining methods. Differential thermal analysis of the lead bromide showed that a destructive phase transformation occurs below the melting temperature. This transformation causes extensive cracking, making it very difficult to grow a large single crystal. Energy of phase transformation for pure lead bromide was determined to be 24.67 cal/g. To circumvent this limitation, crystals were doped by silver bromide which decreased the energy of phase transformation. The addition of silver helped in achieving the size, but enhanced the inhomogeneity in the crystal. The acoustic attenuation constant was almost identical for the pure and doped (below 3000 ppm) crystals.

  16. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1992-01-01

    A study is presented of the crystallization of isocitrate lyase (ICL) and the influence of the lack of thermal solutal convection in microgravity on the morphology of ICL crystals is discussed. The latest results of studies with thermonucleation are presented. These include the nucleation of a protein with retrograde solubility and an unknown solubility curve. A new design for a more microgravity compatible thermonuclear is presented.

  17. Computational Models for Crystal Growth of Radiation Detector Materials: Growth of CZT by the EDG Method

    SciTech Connect

    Derby, Jeffrey J.; Gasperino, David

    2008-07-01

    Crystals are the central materials element of most gamma radiation detection systems, yet there remains surprisingly little fundamental understanding about how these crystals grow, how growth conditions affect crystal properties, and, ultimately, how detector performance is affected. Without this understanding, the prospect for significant materials improvement, i.e., growing larger crystals with superior quality and at a lower cost, remains a difficult and expensive exercise involving exhaustive trial-and-error experimentation in the laboratory. Thus, the overall goal of this research is to develop and apply computational modeling to better understand the processes used to grow bulk crystals employed in radiation detectors. Specifically, the work discussed here aims at understanding the growth of cadmium zinc telluride (CZT), a material of long interest to the detector community. We consider the growth of CZT via gradient freeze processes in electrodynamic multi-zone furnaces and show how crucible mounting and design are predicted to affect conditions for crystal growth. (authors)

  18. Follow up on the crystal growth experiments of the LDEF

    NASA Technical Reports Server (NTRS)

    Nielsen, K. F.; Lind, M. D.

    1993-01-01

    The results of the 4 solution growth experiments on the LDEF have been published elsewhere. Both the crystals of CaCO3, which were large and well shaped, and the much smaller TTF-TCNQ crystals showed unusual morphological behavior. The follow up on these experiments was begun in 1981, when ESA initiated a 'Concept Definition Study' on a large, 150 kg, Solution Growth Facility (SGF) to be included in the payload of EURECA-1, the European Retrievable Carrier. This carrier was a continuation of the European Spacelab and at that time planned for launch in 1987. The long delay of the LDEF retrieval and of subsequent missions brought about reflections both on the concept of crystal growth in space and on the choice of crystallization materials that had been made for the LDEF. Already before the LDEF retrieval, research on TTF-TCNQ had been stopped, and a planned growth experiment with TTF-TCNQ on the SGF/EURECA had been cancelled. The target of the SGF investigation is now more fundamental in nature. None of the crystals to be grown here are, like TTF-TCNQ, in particular demand by science or industry, and the crystals only serve the purpose of model crystals. The real purpose of the investigation is to study the growth behavior. One of the experiments, the Soret Coefficient Measurement experiment is not growing crystals at all, but has it as its sole purpose to obtain accurate information on thermal diffusion, a process of importance in crystal growth from solution.

  19. Initial development of a high-pressure crystal growth facility: Center director's discretionary fund

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Lehoczky, S. L.; Cobb, S. D.; Gillies, D. C.

    1993-01-01

    A low-cost, flexible, high-pressure (600 psi) system for crystal growth and related thermophysical properties measurements was designed, assembled, and tested. The furnace system includes a magnetically coupled translation mechanism that eliminates the need for a high-pressure mechanical feedthru. The system is currently being used for continuing crystal growth experiments and thermophysical properties measurements on several material systems including Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se.

  20. Thermal effects in the anomalous growth of helium crystals

    SciTech Connect

    Tsymbalenko, V. L.

    2006-12-15

    Variations in pressure and thermal response have been synchronously measured beginning from the moment of nucleation of a helium crystal, at the onset of anomalously fast growth and during this growth, and in the course of relaxation to the normal kinetics. The measurements were performed at temperatures within 0.4-0.7 K in a range of pressures from the boundary of the anomalous growth region up to an overpressure of {delta}P {approx} 25 mbar. A superconductor bolometer with an rms noise of about 10 {mu}K was used as the fast-response thermal sensor. Temperature variations related to changes in the pressure and the heat dissipation during crystal growth were observed. The upper boundary of possible variations in the internal energy of the crystal is estimated as 1-20% of the excess energy of the system prior to the onset of anomalous growth.

  1. Modeling of Macroscopic/Microscopic Transport and Growth Phenomena in Zeolite Crystal Solutions Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Gatsonis, Nikos A.; Alexandrou, Andreas; Shi, Hui; Ongewe, Bernard; Sacco, Albert, Jr.

    1999-01-01

    Crystals grown from liquid solutions have important industrial applications. Zeolites, for instance, a class of crystalline aluminosilicate materials, form the backbone of the chemical process industry worldwide, as they are used as adsorbents and catalysts. Many of the phenomena associated with crystal growth processes are not well understood due to complex microscopic and macroscopic interactions. Microgravity could help elucidate these phenomena and allow the control of defect locations, concentration, as well as size of crystals. Microgravity in an orbiting spacecraft could help isolate the possible effects of natural convection (which affects defect formation) and minimize sedimentation. In addition, crystals will stay essentially suspended in the nutrient pool under a diffusion-limited growth condition. This is expected to promote larger crystals by allowing a longer residence time in a high-concentration nutrient field. Among other factors, the crystal size distribution depends on the nucleation rate and crystallization. These two are also related to the "gel" polymerization/depolymerization rate. Macroscopic bulk mass and flow transport and especially gravity, force the crystals down to the bottom of the reactor, thus forming a sedimentation layer. In this layer, the growth rate of the crystals slows down as crystals compete for a limited amount of nutrients. The macroscopic transport phenomena under certain conditions can, however, enhance the nutrient supply and therefore, accelerate crystal growth. Several zeolite experiments have been performed in space with mixed results. The results from our laboratory have indicated an enhancement in size of 30 to 70 percent compared to the best ground based controls, and a reduction of lattice defects in many of the space grown crystals. Such experiments are difficult to interpret, and cannot be easily used to derive empirical or other laws since many physical parameters are simultaneously involved in the process. At the same time, however, there is increased urgency to develop such an understanding in order to more accurately quantify the process. In order to better understand the results obtained from our prior space experiments, and design future experiments, a detailed fluid dynamic model simulating the crystal growth mechanism is required. This will not only add to the fundamental knowledge on the crystallization of zeolites, but also be useful in predicting the limits of size and growth of these important industrial materials. Our objective is to develop macro/microscopic theoretical and computational models to study the effect of transport phenomena in the growth of crystals grown in solutions. Our effort has concentrated so far in the development of separate macroscopic and microscopic models. The major highlights of our accomplishments are described.

  2. Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth.

    PubMed

    Celik, Yeliz; Drori, Ran; Pertaya-Braun, Natalya; Altan, Aysun; Barton, Tyler; Bar-Dolev, Maya; Groisman, Alex; Davies, Peter L; Braslavsky, Ido

    2013-01-22

    Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules. PMID:23300286

  3. Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth

    PubMed Central

    Celik, Yeliz; Drori, Ran; Pertaya-Braun, Natalya; Altan, Aysun; Barton, Tyler; Bar-Dolev, Maya; Groisman, Alex; Davies, Peter L.; Braslavsky, Ido

    2013-01-01

    Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules. PMID:23300286

  4. Vapor crystal growth studies of single crystals of mercuric iodide (3-IML-1)

    NASA Technical Reports Server (NTRS)

    Vandenberg, Lodewijk

    1992-01-01

    A single crystal of mercuric iodide (HgI2) will be grown during the International Microgravity Lab. (IML-1) mission. The crystal growth process takes place by sublimation of HgI2 from an aggregate of purified material, transport of the molecules in the vapor from the source to the crystal, and condensation on the crystal surface. The objectives of the experiment are as follow: to grow a high quality crystal of HgI2 of sufficient size so that its properties can be extensively analyzed; and to study the vapor transport process, specifically the rate of diffusion transport at greatly reduced gravity where convection is minimized.

  5. Imaging System For Measuring Macromolecule Crystal Growth Rates in Microgravity

    NASA Technical Reports Server (NTRS)

    Corder, Eric L.; Briscoe, Jeri

    2004-01-01

    In order to determine how macromolecule crystal quality improvement in microgravity is related to crystal growth characteristics, a team of scientists and engineers at NASA's Marshal Space Flight Center (MSFC) developed flight hardware capable of measuring the crystal growth rates of a population of crystals growing under the same conditions. As crystal growth rate is defined as the change or delta in a defined dimension or length (L) of crystal over time, the hardware was named Delta-L. Delta-L consists of three sub assemblies: a fluid unit including a temperature-controlled growth cell, an imaging unit, and a control unit (consisting of a Data Acquisition and Control Unit (DACU), and a thermal control unit). Delta-L will be used in connection with the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) inside the Microgravity Science Glovebox (MSG), onboard the International Space Station. This paper will describe the Delta-L imaging system. The Delta-L imaging system was designed to locate, resolve, and capture images of up to 10 individual crystals ranging in size from 10 to 500 microns with a point-to-point accuracy of +/- 2.0 microns within a quartz growth cell observation area of 20 mm x 10 mm x 1 mm. The optical imaging system is comprised of a video microscope camera mounted on computer controlled translation stages. The 3-axis translation stages and control units provide crewmembers the ability to search throughout the growth cell observation area for crystals forming in size of approximately 10 microns. Once the crewmember has selected ten crystals of interest, the growth of these crystals is tracked until the size reaches approximately 500 microns. In order to resolve these crystals an optical system with a magnification of 10X was designed. A black and white NTSC camera was utilized with a 20X microscope objective and a 0.5X custom designed relay lens with an inline light to meet the magnification requirement. The design allows a 500 pm crystal to be viewed in the vertical dimension on a standard NTSC monitor (4:3 aspect ratio). Images of the 10 crystals are collected periodically and stored in sets by the DACU.

  6. A kinetic model to simulate protein crystal growth in an evaporation-based crystallization platform

    SciTech Connect

    Talreja, S.; Kenis, P; Zukoski, C

    2007-01-01

    The quality, size, and number of protein crystals grown under conditions of continuous solvent extraction are dependent on the rate of solvent extraction and the initial protein and salt concentration. An increase in the rate of solvent extraction leads to a larger number of crystals. The number of crystals decreases, however, when the experiment is started with an initial protein concentration that is closer to the solubility boundary. Here we develop a kinetic model capable of predicting changes in the number and size of protein crystals as a function of time under continuous evaporation. Moreover, this model successfully predicts the initial condition of drops that will result in gel formation. We test this model with experimental crystal growth data of hen egg white lysozyme for which crystal nucleation and growth rate parameters are known from other studies. The predicted and observed rates of crystal growth are in excellent agreement, which suggests that kinetic constants for nucleation and crystal growth for different proteins can be extracted by applying a kinetic model in combination with observations from a few evaporation-based crystallization experiments.

  7. Preparation and crystal growth of rare earth and actinide intermetallics

    NASA Astrophysics Data System (ADS)

    Vogt, O.

    1985-05-01

    The need for high-purity samples in rare-earth and actinide research is extensively discussed. In many cases single crystals are of primary importance due to the large anisotropies encountered in these compounds. Purification methods for both, rare earth and actinide, metals are compared. Actinide research is hampered by reactivity, radioactivity, toxicity and scarcity of the elements. Out of the many possibilities crucible-free melt growth seems to be the most adequate technique to obtain high-quality single crystals. Some of the more spectacular results obtained in crystal growth of actinide intermetallics are mentioned.

  8. Crocodile: An automated apparatus for organic crystal growth from solution

    NASA Astrophysics Data System (ADS)

    Gonzalez, F.; Cunisse, M.; Perigaud, A.

    CROCODILE ( CROissance de Cristaux Organiques par DIffusion Liquide dans l' Espace) is a space instrument dedicated to crystal growth from solution. The selected material N (4 nitrophenyl) (L) prolinol (NPP) is the result of studies on organic crystal in the frame of an extended program initiated by CNES for many years. The apparatus was flown aboard PHOTON, an automatic satellite, in April 1990, for a flight duration of more than 15 days. This paper describes the instrument design, with emphasis on specific and original technology well adapted to crystal growth from solution, and extendable to any space experiment on fluids. Preliminary details of the flight campaign will also be discussed.

  9. CROCODILE: an automated apparatus for organic crystal growth from solution.

    PubMed

    Gonzalez, F; Cunisse, M; Perigaud, A

    1991-12-01

    CROCODILE (CROissance de Cristaux Organiques par DIffusion Liquide dans l'Espace) is a space instrument dedicated to crystal growth from solution. The selected material N (4 nitrophenyl) (L) prolinol (NPP) is the result of studies on organic crystal in the frame of an extended program initiated by CNES for many years. The apparatus was flown aboard PHOTON, an automatic satellite, in April 1990, for a flight duration of more than 15 days. This paper describes the instrument design, with emphasis on specific and original technology well adapted to crystal growth from solution, and extendible to any space experiment on fluids. Preliminary details of the flight campaign will also be discussed. PMID:11541155

  10. Growth mechanism of hydrogen clusters

    SciTech Connect

    Nickel, N.H.; Anderson, G.B.; Johnson, N.M.; Walker, J.

    1997-07-01

    It is demonstrated that the exposure of polycrystalline silicon (poly-Si) to monatomic hydrogen results in the formation of H clusters. These H stabilized platelets appear in the near-surface region (100 nm) and are predominantly oriented along {l_brace}111{r_brace} crystallographic planes. Platelet concentrations of {approx}5 x 10{sup 15}, 1.5 x 10{sup 16} -cm{sup {minus}3}, and 2.4 x 10{sup 17} cm{sup {minus}3} were observed in nominally undoped poly-Si, phosphorous doped poly-Si (P = 10{sup 17} cm{sup {minus}3}), and phosphorous doped single crystal silicon (P > 3 x 10{sup 18} cm{sup {minus}3}), respectively. Results obtained on doped c-Si demonstrate that platelet generation occurs only at Fermi-level positions of E{sub C} - E{sub F} < 0.4 eV.

  11. Protein crystal growth and the International Space Station

    NASA Technical Reports Server (NTRS)

    DeLucas, L. J.; Moore, K. M.; Long, M. M.

    1999-01-01

    Protein structural information plays a key role in understanding biological structure-function relationships and in the development of new pharmaceuticals for both chronic and infectious diseases. The Center for Macromolecular Crystallography (CMC) has devoted considerable effort studying the fundamental processes involved in macromolecular crystal growth both in a 1-g and microgravity environment. Results from experiments performed on more than 35 U.S. space shuttle flights have clearly indicated that microgravity can provide a beneficial environment for macromolecular crystal growth. This research has led to the development of a new generation of pharmaceuticals that are currently in preclinical or clinical trials for diseases such as cutaneous T-cell lymphoma, psoriasis, rheumatoid arthritis, AIDS, influenza, stroke and other cardiovascular complications. The International Space Station (ISS) provides an opportunity to have complete crystallographic capability on orbit, which was previously not possible with the space shuttle orbiter. As envisioned, the x-ray Crystallography Facility (XCF) will be a complete facility for growing protein crystals; selecting, harvesting, and mounting sample crystals for x-ray diffraction; cryo-freezing mounted crystals if necessary; performing x-ray diffraction studies; and downlinking the data for use by crystallographers on the ground. Other advantages of such a facility include crystal characterization so that iterations in the crystal growth conditions can be made, thereby optimizing the final crystals produced in a three month interval on the ISS.

  12. Molecular tagging velocimetry characterization of rapid KDP crystal growth

    SciTech Connect

    Maynes, D.

    2000-03-01

    Measurements of the tangential and axial velocities near the prism faces of a rotating mock crystal mounted on a rotating platform are presented. These measurements were made using molecular tagging velocimetry and are significant to the rapid growth of KDP crystals because they provide a description of the flow field and the evolution of the relative tangential and axial velocities near the prism faces and in the bulk flow region. These data represent the first measurements of fluid velocities around rotating crystal geometries, and thus provide a benchmark for future computer simulations of the crystal growth process at higher Re than previously obtainable. The measurements provide a temporal and spatial description of the evolving velocity field in the vicinity of a rotating crystal. Rotational conditions and locations on the prism faces where low shear rates are likely to occur, based on the measurements presented, are discussed qualitatively.

  13. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.

    1983-01-01

    GaAs device technology has recently reached a new phase of rapid advancement, made possible by the improvement of the quality of GaAs bulk crystals. At the same time, the transition to the next generation of GaAs integrated circuits and optoelectronic systems for commercial and government applications hinges on new quantum steps in three interrelated areas: crystal growth, device processing and device-related properties and phenomena. Special emphasis is placed on the establishment of quantitative relationships among crystal growth parameters-material properties-electronic properties and device applications. The overall program combines studies of crystal growth on novel approaches to engineering of semiconductor material (i.e., GaAs and related compounds); investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; and investigation of electronic properties and phenomena controlling device applications and device performance.

  14. Vapor growth of mercuric iodide tetragonal prismatic crystals

    NASA Astrophysics Data System (ADS)

    Ariesanti, Elsa

    The effect of polyethylene addition on the growth of mercuric iodide (HgI2) tetragonal prismatic crystals is examined. Three types of polyethylene powder are utilized: low molecular weight (Mw 4 x 103), ultra high molecular weight (Mw 3-6 x 1066), and spectrophotometric grade polyethylenes. Among these types of polyethylene, the low molecular weight polyethylene produces the most significant change in HgI2 morphology, with {110} being the most prominent crystal faces. Thermal desorption - gas chromatography/ mass spectroscopy (TD-GC/MS) studies show that thermal desorption of the low molecular weight polyethylene at 100C and 150C produce isomers of alkynes, odd nalkanes, and methyl (even-n) alkyl ketones. HgI2 growth runs with n-alkanes, with either neicosane, n-tetracosane, or n-hexatriacontane, cannot replicate the crystal shapes produced during growth with the low molecular weight polyethylene, whereas HgI2 growth runs with ketones, with either 3-hexadecanone or 14-heptacosanone, produce HgI2 tetragonal prismatic crystals, similar to the crystals grown with the low molecular weight polyethylene. C-O double bond contained in any ketone is a polar bond and this polar bond may be attracted to the mercury atoms on the top-most layer of the {110} faces through dipoledipole interaction. As a result, the growth of the {110} faces is impeded, with the crystals elongated in the [001] direction and bounded by the {001} faces along with large, prismatic {110} faces.

  15. Viscous Fingering and Dendritic Growth of Surface Crystallized Sr2TiSi2O8 Fresnoite

    PubMed Central

    Wisniewski, Wolfgang; Patschger, Marek; Rssel, Christian

    2013-01-01

    During the quenching of a melt with the composition 2SrOTiO22.75SiO2, cubic SrTiO3- and tetragonal Sr2TiSi2O8-crystals are formed at the surface. Subsequent crystal growth leads to dendritic fresnoite structures which become increasingly finer until the mechanism changes to viscous fingering during further cooling. In the final stages of this initial growth step, the crystal orientations of these dendrites systematically change. Due to a complete absence of bulk nucleation in this system, crystal growth is resumed upon reheating to 970C and fractal growth with the c-axis tilted by about 45 from the main growth direction is observed. The results are interpreted to confirm the link between viscous fingering and dendritic growth in the case of a true crystallization process. PMID:24356207

  16. Czochralski growth of gallium indium antimonide alloy crystals

    SciTech Connect

    Tsaur, S.C.

    1998-02-01

    Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub 1{minus}x}Sb{sub x}. Single crystals of Ga{sub 1{minus}x}In{sub x}Sb were grown with uniform compositions up to nearly 5 mole% InSb.

  17. Center for the development of commercial crystal growth in space

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.

    1989-01-01

    The second year of operation of the Center for Commercial Crystal Growth in Space is described. This center is a consortium of businesses, universities and national laboratories. The primary goal of the Center's research is the development of commercial crystal growth in space. A secondary goal is to develop scientific understanding and technology which will improve commercial crystal growth on earth. In order to achieve these goals the Center's research is organized into teams by growth technique; melt growth, solution growth, and vapor growth. The melt growth team is working on solidification and characterization of bulk crystals of gallium arsenide and cadmium telluride. They used high resolution X-ray topography performed at the National Synchrotron Light Source at Brookhaven National Laboratory. Streak-like features were found in the diffraction images of semi-insulating undoped LEC GaAs. These were shown to be (110) antiphase boundaries, which have not been reported before but appear to be pervasive and responsible for features seen via less-sensitive characterization methods. The results on CdTe were not as definitive, but indicate that antiphase boundaries may also be responsible for the double peaks often seen in X-ray rocking curves of this material. A liquid encapsulated melt zone system for GaAs has been assembled and techniques for casting feed rods developed. It was found that scratching the inside of the quartz ampoules with silicon carbide abrasive minimized sticking of the GaAs to the quartz. Twelve floating zone experiments were done.

  18. Spiral and target patterns in bivalve nacre manifest a natural excitable medium from layer growth of a biological liquid crystal

    PubMed Central

    Cartwright, Julyan H. E.; Checa, Antonio G.; Escribano, Bruno; Sainz-Daz, C. Ignacio

    2009-01-01

    Nacre is an exquisitely structured biocomposite of the calcium carbonate mineral aragonite with small amounts of proteins and the polysaccharide chitin. For many years, it has been the subject of research, not just because of its beauty, but also to discover how nature can produce such a superior product with excellent mechanical properties from such relatively weak raw materials. Four decades ago, Wada [Wada K (1966) Spiral growth of nacre. Nature 211:1427] proposed that the spiral patterns in nacre could be explained by using the theory Frank [Frank F (1949) The influence of dislocations on crystal growth. Discuss Faraday Soc 5:4854] had put forward of the growth of crystals by means of screw dislocations. Frank's mechanism of crystal growth has been amply confirmed by experimental observations of screw dislocations in crystals, but it is a growth mechanism for a single crystal, with growth fronts of molecules. However, the growth fronts composed of many tablets of crystalline aragonite visible in micrographs of nacre are not a molecular-scale but a mesoscale phenomenon, so it has not been evident how the Frank mechanism might be of relevance. Here, we demonstrate that nacre growth is organized around a liquid-crystal core of chitin crystallites, a skeleton that the other components of nacre subsequently flesh out in a process of hierarchical self-assembly. We establish that spiral and target patterns can arise in a liquid crystal formed layer by layer through the BurtonCabreraFrank [Burton W, Cabrera N, Frank F (1951) The growth of crystals and the equilibrium structure of their surfaces. Philos Trans R Soc London Ser A 243:299358] dynamics, and furthermore that this layer growth mechanism is an instance of an important class of physical systems termed excitable media. Artificial liquid crystals grown in this way may have many technological applications. PMID:19528636

  19. Protein crystal growth in microgravity: Status and commercial implications

    NASA Astrophysics Data System (ADS)

    Moore, Karen M.; Long, Marianna M.; Delucas, Lawrence J.

    1999-01-01

    Since 1985, The Center for Macromolecular Crystallography has conducted an extensive program of macromolecular crystal growth experiments in microgravity. This Center has designed and built crystal growth flight hardware that has an excellent productivity and reliability record. In addition, several other crystallography laboratories have conducted macromolecular crystal growth experiments in microgravity and developed hardware to house their experiments. These experiments have successfully demonstrated that the low gravity environment can be used to produce crystals of proteins and other macromolecules that are superior to crystals of the same compounds grown on earth. Improved, extended x-ray diffraction data collected from space-grown crystals has contributed to the solution of the three-dimensional structures of many proteins and has augmented structure-based drug design studies targeting several diseases and degenerative conditions. The production of produce high-quality crystals of medically relevant macromolecules is important because of the rapidly growing role of macromolecular crystallography in biology and medicine. Large, high-quality crystals are critical to solving the structures of biologically important macromolecules, but it is often difficult to obtain these crystals because of the physical and chemical properties of the compounds. Work by this and other crystallography laboratories has shown that conducting macromolecular crystallization experiments in the microgravity environment alleviates convection and sedimentation effects, and frequently results in crystals that yield x-ray diffraction data that is superior to their earth-grown counterparts. The improved diffraction data translates directly to faster, more accurate solutions to the three-dimensional structures of the target molecules.

  20. Mechanisms of growth cone repulsion

    PubMed Central

    Krull, Catherine E

    2010-01-01

    Research conducted in the last century suggested that chemoattractants guide cells or their processes to appropriate locations during development. Today, we know that many of the molecules involved in cellular guidance can act as chemorepellents that prevent migration into inappropriate territories. Here, we review some of the early seminal experiments and our current understanding of the underlying molecular mechanisms. PMID:20711492

  1. A Model for Tetragonal Lysozyme Crystal Nucleation and Growth

    NASA Technical Reports Server (NTRS)

    Pusey, Marc L.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Macromolecular crystallization is a complex process, involving a system that typically has 5 or more components (macromolecule, water, buffer + counter ion, and precipitant). Whereas small molecules have only a few contacts in the crystal lattice, macromolecules generally have 10's or even 100's of contacts between molecules. These can range from hydrogen bonds (direct or water-mediated), through van der Waals, hydrophobic, salt bridges, and ion-mediated contacts. The latter interactions are stronger and require some specificity in the molecular alignment, while the others are weaker, more prevalent, and more promiscuous, i.e., can be readily broken and reformed between other sites. Formation of a consistent, ordered, 3D structure may be difficult or impossible in the absence of any or presence of too many strong interactions. Further complicating the process is the inherent structural asymmetry of monomeric (single chain) macromolecules. The process of crystal nucleation and growth involves the ordered assembly of growth units into a defined 3D lattice. We suggest that for many macromolecules, particularly those that are monomeric, this involves a preliminary solution-phase assembly process into a growth unit having some symmetry prior to addition to the lattice, recapitulating the initial stages of the nucleation process. If this model is correct then fluids and crystal growth models assuming a strictly monodisperse nutrient solution need to be revised. This model has been developed from experimental evidence based upon face growth rate, AFM, and fluorescence energy transfer data for the nucleation and growth of tetragonal lysozyme crystals.

  2. Crystal growth of calcium apatites from dilute solutions

    NASA Astrophysics Data System (ADS)

    Moreno, E. C.; Varughese, K.

    1981-05-01

    The dependence of the kinetics of crystal growth of hydroxyapatite, HA, on concentration of seeds and degree of solution supersaturation is examined. Empirical relations are obtained between the initial rates of precipitation and the two aforementioned variables. The results clearly indicate that the precipitating phase, under the selected experimental conditions, is HA. The driving force for precipitation is the supersaturation with respect to this calcium phosphate. The data obtained from kinetic studies are consistent with the BCF theory of crystal growth which relates the mean linear rate of growth to the degree of supersaturation. This observation is also valid for systems in which the precipitating phases are fluoridated hydroxyapatites, Ca 5F x?(OH) 1- x(PO 4) 3, FHA. In this case, supersaturation is calculated with respect to the specific FHA precipitated. The degree of fluoridation, x, appears to be determined by the activity of hydrofluoric acid in solution which remains fairly constant during precipitation but varies for each initial fluoride concentration used. Studies are reported on the kinetics of crystal growth of HA in the presence of biological inhibitors. Two proline-rich proteins and a peptide, statherin, of salivary origin are powerful inhibitors of HA crystal growth. It appears that their mode of action is related to their adsorption onto the surface of apatite seeds. The results suggest that the adsorption sites are the same as the sites where crystal growth takes place.

  3. Impact of surfactants on the crystal growth of amorphous celecoxib.

    PubMed

    Mosquera-Giraldo, Laura I; Trasi, Niraj S; Taylor, Lynne S

    2014-01-30

    The purpose of this study was to investigate the impact of surfactants on the rate of crystal growth of amorphous celecoxib, both in the presence and absence of a polymer. Celecoxib is a poorly water-soluble non-steroidal anti-inflammatory drug. Such compounds may be formulated as amorphous solid dispersions to improve bioavailability, and solid dispersions can contain both a surfactant and a polymer. While the impact of polymers on crystal growth rates has been studied, the effect of surfactants is largely unexplored. Herein, the effect of sodium lauryl sulfate (SLS), sucrose palmitate and d-? tocopherol polyethylenglycol 1000 succinate (TPGS) at a 10% (w/w) concentration on the crystal growth rate of celecoxib was investigated. Linear crystal growth rates as a function of temperature (70-120 C) were measured using optical microscopy. The mixtures were characterized using differential scanning calorimetry (DSC), infrared spectroscopy, and X-ray diffraction. The results indicate that the surfactants increase the crystal growth rate of amorphous celecoxib. However, addition of polyvinyl pyrrolidone (PVP) helped to mitigate the increase in growth rates, although the ternary systems were highly complex. Thus it is clear that the impact of a surfactant on the physical stability of an amorphous solid dispersion should be considered during formulation. PMID:24333451

  4. Growth of bulk single crystals under applied magnetic field by liquid phase electroepitaxy

    NASA Astrophysics Data System (ADS)

    Sheibani, H.; Dost, S.; Sakai, S.; Lent, B.

    2003-11-01

    Binary (GaAs) and ternary (InGaAs) bulk single crystals have been grown by the growth process of liquid phase electroepitaxy (LPEE with and without the application of an external static magnetic field. Two significant achievements were made: first is the development of a new, improved LPEE system to grow, flat, thick and uniform single crystals of In 0.04Ga 0.96As, and the second is the significant improvement of the LPEE growth rate by the application of an external static magnetic field. Experiments performed under no magnetic field have shown that LPEE can grow large (thick) and flat single crystals of In 0.04Ga 0.96As with uniform composition. Experiments have also proved the reproducibility of LPEE growth of such single crystals in terms of crystal thickness, flatness, and compositional uniformity. It was possible to use higher electric current density levels (up to 7 A/cm 2) in spite of the achievement of large crystal thicknesses. Experiments conducted under various magnetic field levels have shown that the LPEE growth process at the 4.5 kG and lower magnetic field levels yields satisfactory growth. However, the growth experiments at higher magnetic field and electric current density levels were unsatisfactory and unstable. Although the crystals were still grown, large holes and unstable interfaces were observed in the grown crystals. However, lower magnetic field and electric current levels had very beneficial effects, namely flat growth interfaces and prolonged growth due to weak convection in the liquid zone, and a substantial increase in the growth rate (about up to 20 times higher at 4.5 kG and 7 A/cm 2 levels). Such a significant increase in the growth rate under a static magnetic field can be attributed to the positive effect of applied magnetic field on the mechanism of "electromigration". The performed electron probe micro analysis (EPMA) and the energy dispersive X-ray spectroscopy (EDS) measurements have shown that the indium composition distribution in grown crystals was uniform in both the radial and growth directions. Advances made through this work may be considered as a significant initial step towards the commercialization of the LPEE technique for growth of high-quality, bulk single crystals.

  5. High Thermal Conducting Boron Arsenide: Crystal Growth and Characterization

    NASA Astrophysics Data System (ADS)

    Lv, Bing; Lan, Yucheng; Wang, Xiqu; Zhang, Qian; Hu, Yongjie; Jacobson, Allan J.; Broido, David; Chen, Gang; Ren, Zhifeng; Chu, Ching-Wu

    2015-03-01

    Intrigued by recent calculations [Phys. Rev. Lett. 111, 025901(2013)] which predict a remarkably high thermal conductivity of ~ 2,000 Wm-1K-1 , comparable to that of diamond, in cubic boron arsenide (BAs) crystals, we have succeeded in synthesizing single crystals of BAs with a zinc blende structure and lattice parameters of a = 4.7830(7) characterized by X-ray single crystal diffraction and transmission electron microscopy (TEM). A relatively high thermal conductivity is obtained but still smaller than the predicted value. We attribute the difference of thermal conductivity value to the defect scattering associated with crystal twinning and As vacancies, verified both from experimental evidence and theoretical calculations. The predicted super-thermal-conductivity may be achieved in BAs single crystals with further improvement of crystal growth by removing the defects. Lawrence Berkeley National Laboratory, Berkeley California 94720.

  6. Transient natural convection heat and mass transfer in crystal growth

    NASA Technical Reports Server (NTRS)

    Han, Samuel S.

    1988-01-01

    A numerical analysis of transient combined heat and mass transfer across a rectangular cavity is performed by a numerical method based on the SIMPLE algorithm. The physical parameters are selected to represent a range of possible crystal growth in solutions. Numerical results are compared with available experimental data to confirm the accuracy of the results. Good qualitative agreements are obtained for the average mass transfer rate across the cavity. Also, qualitative agreements are observed for the global development of thermal and solute fields. It is found that the thermal and solute fields become highly oscillatory when the thermal and solute Grashof numbers are large. Oscillations are probably caused by a number of different instability mechanisms. By reducing the gravity some of these instabilities were made to disappear at the lower Grashof numbers. Transient temperature and solute distribution near the crystal growing surface are highly non-uniform at the higher Grashof numbers. These non-uniformities are less severe in the reduced gravity environments but still exist. The effects of convection on the rate of average mass transfer are more than one order of magnitude higher than those of conduction in the range of Grashof numbers studied. Dependency of mass transfer rate on the Grashof number indicates that the convection effects many not be negligible even in the microgravity environments for the range of parameters investigated.

  7. One-dimensional Growth of Zinc Crystals on a Liquid Surface

    PubMed Central

    Lu, Chenxi; Cheng, Yi; Pan, Qifa; Tao, Xiangming; Yang, Bo; Ye, Gaoxiang

    2016-01-01

    The catalyst-free growth of nanocrystals on various substrates at room temperature has been a long-standing goal in the development of material science. We report the growth of one-dimensional zinc nanocrystals on silicone oil surfaces by thermal evaporation method at room temperature (20 ± 2 °C). Uniform zinc nanorods with tunable size can be obtained. The typical length and width of the nanorods are 250–500 nm and 20–40 nm, respectively. The growth mechanism can be attributed to the effect of the liquid substrate and the preferential growth direction of the crystals. This result provides a novel and simple way to fabricate the precursors (zinc crystals) for preparation of Zn-based semiconductors and other metallic crystals on liquid substrates. PMID:26822226

  8. One-dimensional Growth of Zinc Crystals on a Liquid Surface

    NASA Astrophysics Data System (ADS)

    Lu, Chenxi; Cheng, Yi; Pan, Qifa; Tao, Xiangming; Yang, Bo; Ye, Gaoxiang

    2016-01-01

    The catalyst-free growth of nanocrystals on various substrates at room temperature has been a long-standing goal in the development of material science. We report the growth of one-dimensional zinc nanocrystals on silicone oil surfaces by thermal evaporation method at room temperature (20 ± 2 °C). Uniform zinc nanorods with tunable size can be obtained. The typical length and width of the nanorods are 250–500 nm and 20–40 nm, respectively. The growth mechanism can be attributed to the effect of the liquid substrate and the preferential growth direction of the crystals. This result provides a novel and simple way to fabricate the precursors (zinc crystals) for preparation of Zn-based semiconductors and other metallic crystals on liquid substrates.

  9. One-dimensional Growth of Zinc Crystals on a Liquid Surface.

    PubMed

    Lu, Chenxi; Cheng, Yi; Pan, Qifa; Tao, Xiangming; Yang, Bo; Ye, Gaoxiang

    2016-01-01

    The catalyst-free growth of nanocrystals on various substrates at room temperature has been a long-standing goal in the development of material science. We report the growth of one-dimensional zinc nanocrystals on silicone oil surfaces by thermal evaporation method at room temperature (20??2?C). Uniform zinc nanorods with tunable size can be obtained. The typical length and width of the nanorods are 250-500?nm and 20-40?nm, respectively. The growth mechanism can be attributed to the effect of the liquid substrate and the preferential growth direction of the crystals. This result provides a novel and simple way to fabricate the precursors (zinc crystals) for preparation of Zn-based semiconductors and other metallic crystals on liquid substrates. PMID:26822226

  10. Ice Crystal Growth Rates Under Upper Troposphere Conditions

    NASA Technical Reports Server (NTRS)

    Peterson, Harold S.; Bailey, Matthew; Hallett, John

    2010-01-01

    Atmospheric conditions for growth of ice crystals (temperature and ice supersaturation) are often not well constrained and it is necessary to simulate such conditions in the laboratory to investigate such growth under well controlled conditions over many hours. The growth of ice crystals from the vapour in both prism and basal planes was observed at temperatures of -60 C and -70 C under ice supersaturation up to 100% (200% relative humidity) at pressures derived from the standard atmosphere in a static diffusion chamber. Crystals grew outward from a vertical glass filament, thickening in the basal plane by addition of macroscopic layers greater than 2 m, leading to growth in the prism plane by passing of successive layers conveniently viewed by time lapse video.

  11. Shallow Melt Apparatus for Semicontinuous Czochralski Crystal Growth

    DOEpatents

    Wang, T.; Ciszek, T. F.

    2006-01-10

    In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

  12. High-thermal-gradient Superalloy Crystal Growth

    NASA Technical Reports Server (NTRS)

    Pearson, D. D.; Anton, D. L.; Giamei, A. F.

    1985-01-01

    Single, (001)-oriented crystals of PWA 1480 were processed in alumina/silica shell molds in a laboratory high gradient furnace. The furnace employs a graphite resistance heated element, a radiation baffle, and a water cooled radiation trap below the baffle. All crystals were grown in vacuum (10 torr) and all heat transfer was radiative. The element is constructed with a variable cross section that is tapered just above the baffle to maximize heat input and therefore thermal gradient. A maximum alloy temperature of 1600 C was used. A thermal gradient of 130 deg C/cm was recorded at 1370 C just above the solidus of the PWA 1480 alloys. Crystal bars with 14.4 and 17.5 mm diameters were grown in alumina/silica shell molds. Each crystal was started from a 1.6 mm pencil seed at a rate of 76 mm/hr and slowly accelerated to a rate of 200 mm/hr under computer control. Volume percent porosity and average pore size were measured as functions of distance in representative bars. Low cycle fatigue behavior and stress rupture properties were determined.

  13. Mechanisms of hematin crystallization and inhibition by the antimalarial drug chloroquine.

    PubMed

    Olafson, Katy N; Ketchum, Megan A; Rimer, Jeffrey D; Vekilov, Peter G

    2015-04-21

    Hematin crystallization is the primary mechanism of heme detoxification in malaria parasites and the target of the quinoline class of antimalarials. Despite numerous studies of malaria pathophysiology, fundamental questions regarding hematin growth and inhibition remain. Among them are the identity of the crystallization medium in vivo, aqueous or organic; the mechanism of crystallization, classical or nonclassical; and whether quinoline antimalarials inhibit crystallization by sequestering hematin in the solution, or by blocking surface sites crucial for growth. Here we use time-resolved in situ atomic force microscopy (AFM) and show that the lipid subphase in the parasite may be a preferred growth medium. We provide, to our knowledge, the first evidence of the molecular mechanisms of hematin crystallization and inhibition by chloroquine, a common quinoline antimalarial drug. AFM observations demonstrate that crystallization strictly follows a classical mechanism wherein new crystal layers are generated by 2D nucleation and grow by the attachment of solute molecules. We identify four classes of surface sites available for binding of potential drugs and propose respective mechanisms of drug action. Further studies reveal that chloroquine inhibits hematin crystallization by binding to molecularly flat {100} surfaces. A 2-?M concentration of chloroquine fully arrests layer generation and step advancement, which is ?10(4) less than hematin's physiological concentration. Our results suggest that adsorption at specific growth sites may be a general mode of hemozoin growth inhibition for the quinoline antimalarials. Because the atomic structures of the identified sites are known, this insight could advance the future design and/or optimization of new antimalarials. PMID:25831526

  14. Direct growth of self-crystallized graphene and graphite nanoballs with Ni vapor-assisted growth: From controllable growth to material characterization

    PubMed Central

    Yen, Wen-Chun; Chen, Yu-Ze; Yeh, Chao-Hui; He, Jr-Hau; Chiu, Po-Wen; Chueh, Yu-Lun

    2014-01-01

    A directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100°C via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12 nm at growth temperature of 1000°C to ~32 nm at growth temperature of 1100°C, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. By increasing growth pressure, the growth of graphite nano-balls was preferred rather than graphene growth. The detailed formation mechanisms of graphene and graphite nanoballs were proposed and investigated in detail. Optical and electrical properties of graphene layer were measured. The direct growth of the carbon-based materials with free of the transfer process provides a promising application at nanoelectronics. PMID:24810224

  15. A Critical Assessment of Protein Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    1997-01-01

    Experiments to grow higher diffraction quality protein crystals in the microgravity environment of an orbiting spacecraft are one of the most frequently flown space experiments. Ground-based research has shown that convective flows occur even about protein crystals growing in the Earth's gravitational field. Further, this research has shown that the resultant flow velocities can cause growth cessation, and probably affect the measured X-ray data quality obtained. How flow deleteriously affects protein crystal growth (PCG) is still not known, and is the subject of ongoing research. Failing a rational method for ameliorating flow effects on Earth, one can, through NASA and other nations space agency sponsored programs, carry out protein crystal growth in the microgravity environment of an orbiting spacecraft. Early first generation PCG hardware was characterized by a very low success rate and a steep design learning curve. Subsequent hardware designs have improved upon their predecessors. Now the crystal grower has a wide variety of hardware configurations and crystal growth protocols to choose from, many of which implement "standard" laboratory protein crystal growth methods. While many of these are first or early second generation hardware the success rate, defined as growing crystals giving data better than has been obtained on Earth, is at least 20% overall and may be considerably higher if one only considers latter experiments. There are a large number of protein crystals grown every year, with hundreds of structures determined. Those crystallized in microgravity represent a small proportion of this total, and there is concern that the costs of the microgravity PCG program(s) do not justify such limited returns. Empirical evidence suggests that optimum crystal growth conditions in microgravity differ from those determined on Earth, further exacerbating the chances of success. Microgravity PCG is probably best suited for "mature" crystallizations, where one has considerable experience with the particular macromolecular system and has reached an apparent limit in diffraction resolution. Under such circumstances the cost of one or two successful flight experiments may more than offset the equivalent cost of several years effort to obtain the same improvement in data quality.

  16. Hydrothermal crystal growth of the potassium niobate and potassium tantalate family of crystals

    SciTech Connect

    Mann, Matthew; Jackson, Summer; Kolis, Joseph

    2010-11-15

    Single crystals of KNbO{sub 3} (KN), KTaO{sub 3} (KT), and KTa{sub 1-x}Nb{sub x}O{sub 3} (x=0.44, KTN) have been prepared by hydrothermal synthesis in highly concentrated KOH mineralizer solutions. The traditional problems of inhomogeneity, non-stoichiometry, crystal striations and crystal cracking resulting from phase transitions associated with this family compounds are minimized by the hydrothermal crystal growth technique. Crystals of good optical quality with only minor amounts of metal ion reduction can be grown this way. Reactions were also designed to provide homogeneous distribution of tantalum and niobium metal centers throughout the KTN crystal lattice to maximize its electro-optic properties. Synthesis was performed at relatively low (500-660 {sup o}C) temperatures in comparison to the flux and Czochralski techniques. This work represents the largest crystals of this family of compounds grown by hydrothermal methods to date. -- Graphical Abstract:

  17. Commercial Protein Crystal Growth: Protein Crystallization Facility (CPCG-H)

    NASA Astrophysics Data System (ADS)

    DeLucas, Lawrence J.

    2002-12-01

    Within the human body, there are thousands of different proteins that serve a variety of different functions, such as making it possible for red blood cells to carry oxygen in our bodies. Yet proteins can also be involved in diseases. Each protein has a particular chemical structure, which means it has a unique shape. It is this three-dimensional shape that allows each protein to do its job by interacting with chemicals or binding with other proteins. If researchers can determine the shape, or shapes, of a protein, they can learn how it works. This information can then be used by the pharmaceutical industry to develop new drugs or improve the way medications work. The NASA Commercial Space Center sponsoring this experiment - the Center for Biophysical Sciences and Engineering at the University of Alabama at Birmingham - has more than 60 industry and academic partners who grow protein crystals and use the information in drug design projects.

  18. Synthesis, crystal growth and spectroscopic investigation of novel metal organic crystal: ?-alanine cadmium bromide monohydrate (?-ACBM).

    PubMed

    Renugadevi, R; Kesavasamy, R

    2014-07-15

    ?-Alanine cadmium bromide monohydrate (?-ACBM), a new metal organic crystal has been grown from aqueous solution by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction analysis to determine the crystal structure. The ?-ACBM crystallized in monoclinic system with space group P2(1)/c. The presence of protons and carbons in the ?-alanine cadmium bromide monohydrate was confirmed by (1)H and (13)C nuclear magnetic resonance spectral analysis. The mode of vibration of different molecular groups present in ?-ACBM was identified by FT-IR spectral analysis. Transparency of crystals in UV-Vis-NIR region has also been studied. The thermal characteristics of as-grown crystals were analyzed using thermo gravimetric and differential thermal analyses. The magnetic property of the grown crystal was investigated using Vibrating Sample Magnetometer (VSM) at ambient temperature. The mechanical stability of ?-ACBM was evaluated by Vickers microhardness measurement. PMID:24691377

  19. The effect of growth rate, diameter and impurity concentration on structure in Czochralski silicon crystal growth

    NASA Technical Reports Server (NTRS)

    Digges, T. G., Jr.; Shima, R.

    1980-01-01

    It is demonstrated that maximum growth rates of up to 80% of the theoretical limit can be attained in Czochralski-grown silicon crystals while maintaining single crystal structure. Attaining the other 20% increase is dependent on design changes in the grower, to reduce the temperature gradient in the liquid while increasing the gradient in the solid. The conclusions of Hopkins et al. (1977) on the effect of diameter on the breakdown of structure at fast growth rates are substantiated. Copper was utilized as the test impurity. At large diameters (greater than 7.5 cm), concentrations of greater than 1 ppm copper were attained in the solid (45,000 ppm in the liquid) without breakdown at maximum growth speeds. For smaller diameter crystals, the sensitivity of impurities is much more apparent. For solar cell applications, impurities will limit cell performance before they cause crystal breakdown for fast growth rates of large diameter crystals.

  20. Novel protein crystal growth technology: Proof of concept

    NASA Technical Reports Server (NTRS)

    Nyce, Thomas A.; Rosenberger, Franz

    1989-01-01

    A technology for crystal growth, which overcomes certain shortcomings of other techniques, is developed and its applicability to proteins is examined. There were several unknowns to be determined: the design of the apparatus for suspension of crystals of varying (growing) diameter, control of the temperature and supersaturation, the methods for seeding and/or controlling nucleation, the effect on protein solutions of the temperature oscillations arising from the circulation, and the effect of the fluid shear on the suspended crystals. Extensive effort was put forth to grow lysozyme crystals. Under conditions favorable to the growth of tetragonal lysozyme, spontaneous nucleation could be produced but the number of nuclei could not be controlled. Seed transfer techniques were developed and implemented. When conditions for the orthorhombic form were tried, a single crystal 1.5 x 0.5 x 0.2 mm was grown (after in situ nucleation) and successfully extracted. A mathematical model was developed to predict the flow velocity as a function of the geometry and the operating temperatures. The model can also be used to scaleup the apparatus for growing larger crystals of other materials such as water soluble non-linear optical materials. This crystal suspension technology also shows promise for high quality solution growth of optical materials such as TGS and KDP.

  1. Novel protein crystal growth technology: Proof of concept

    NASA Astrophysics Data System (ADS)

    Nyce, Thomas A.; Rosenberger, Franz

    1989-03-01

    A technology for crystal growth, which overcomes certain shortcomings of other techniques, is developed and its applicability to proteins is examined. There were several unknowns to be determined: the design of the apparatus for suspension of crystals of varying (growing) diameter, control of the temperature and supersaturation, the methods for seeding and/or controlling nucleation, the effect on protein solutions of the temperature oscillations arising from the circulation, and the effect of the fluid shear on the suspended crystals. Extensive effort was put forth to grow lysozyme crystals. Under conditions favorable to the growth of tetragonal lysozyme, spontaneous nucleation could be produced but the number of nuclei could not be controlled. Seed transfer techniques were developed and implemented. When conditions for the orthorhombic form were tried, a single crystal 1.5 x 0.5 x 0.2 mm was grown (after in situ nucleation) and successfully extracted. A mathematical model was developed to predict the flow velocity as a function of the geometry and the operating temperatures. The model can also be used to scaleup the apparatus for growing larger crystals of other materials such as water soluble non-linear optical materials. This crystal suspension technology also shows promise for high quality solution growth of optical materials such as TGS and KDP.

  2. Environmental Scanning Electron Microscopy of Ice Crystal Nucleation and Growth

    NASA Astrophysics Data System (ADS)

    Amaral, M.; Miller, A. L.; Magee, N. B.

    2012-12-01

    Ice crystal nucleation and growth are dual processes that can be studied uniquely through Environmental Scanning Electron Microscopy (ESEM). By utilizing differential pumping systems and a Peltier element to vary the vapor pressure and to achieve temperatures below the freezing point, respectively, it is possible to obtain supersaturated conditions relative to ice in the sample chamber of an Environmental Scanning Electron Microscope. Ice crystals were nucleated on a variety of atmospherically relevant substrates and grown in a pure water vapor environment in the chamber of a FEI-Quanta 200 ESEM. To initiate ice crystal nucleation, the Peltier element was set at a temperature between -10C and -25C, while the chamber water vapor pressure was adjusted to just below the frost point. Ice crystal nucleation and growth was then controlled by careful adjustments of chamber pressure and temperature, where high-magnification images of hexagonal ice crystals were acquired at nanoscale resolution. These images display prominent mesoscopic surface topography including linear strands, crevasses, islands, and steps. The surface features are seen to be ubiquitously present at all observed temperatures, at many supersaturated and subsaturated conditions, and on all crystal facets. Additionally, a pre-growth "shadow" resembling a dark spot sometimes appeared on areas of the sample stage immediately preceding ice crystal nucleation and growth. The observations represent the most highly magnified images of ice surfaces yet reported and significantly expand the range of ambient conditions where the features are conspicuous. New knowledge of the presence and characteristics of these features could transform the fundamental understanding of ice crystal growth kinetics and its physical parameterization in the context of atmospheric and cryospheric science. To the extent these observations are applicable to atmospheric ice, the results suggest that the radiative representation of ice and mixed-phase cloud properties in climate models could be markedly affected.

  3. A Microfluidic, High Throughput Protein Crystal Growth Method for Microgravity

    PubMed Central

    Carruthers Jr, Carl W.; Gerdts, Cory; Johnson, Michael D.; Webb, Paul

    2013-01-01

    The attenuation of sedimentation and convection in microgravity can sometimes decrease irregularities formed during macromolecular crystal growth. Current terrestrial protein crystal growth (PCG) capabilities are very different than those used during the Shuttle era and that are currently on the International Space Station (ISS). The focus of this experiment was to demonstrate the use of a commercial off-the-shelf, high throughput, PCG method in microgravity. Using Protein BioSolutions microfluidic Plug Maker/CrystalCard system, we tested the ability to grow crystals of the regulator of glucose metabolism and adipogenesis: peroxisome proliferator-activated receptor gamma (apo-hPPAR-? LBD), as well as several PCG standards. Overall, we sent 25 CrystalCards to the ISS, containing ~10,000 individual microgravity PCG experiments in a 3U NanoRacks NanoLab (1U = 103 cm.). After 70 days on the ISS, our samples were returned with 16 of 25 (64%) microgravity cards having crystals, compared to 12 of 25 (48%) of the ground controls. Encouragingly, there were more apo-hPPAR-? LBD crystals in the microgravity PCG cards than the 1g controls. These positive results hope to introduce the use of the PCG standard of low sample volume and large experimental density to the microgravity environment and provide new opportunities for macromolecular samples that may crystallize poorly in standard laboratories. PMID:24278480

  4. A microfluidic, high throughput protein crystal growth method for microgravity.

    PubMed

    Carruthers, Carl W; Gerdts, Cory; Johnson, Michael D; Webb, Paul

    2013-01-01

    The attenuation of sedimentation and convection in microgravity can sometimes decrease irregularities formed during macromolecular crystal growth. Current terrestrial protein crystal growth (PCG) capabilities are very different than those used during the Shuttle era and that are currently on the International Space Station (ISS). The focus of this experiment was to demonstrate the use of a commercial off-the-shelf, high throughput, PCG method in microgravity. Using Protein BioSolutions' microfluidic Plug Maker/CrystalCard system, we tested the ability to grow crystals of the regulator of glucose metabolism and adipogenesis: peroxisome proliferator-activated receptor gamma (apo-hPPAR-? LBD), as well as several PCG standards. Overall, we sent 25 CrystalCards to the ISS, containing ~10,000 individual microgravity PCG experiments in a 3U NanoRacks NanoLab (1U = 10(3) cm.). After 70 days on the ISS, our samples were returned with 16 of 25 (64%) microgravity cards having crystals, compared to 12 of 25 (48%) of the ground controls. Encouragingly, there were more apo-hPPAR-? LBD crystals in the microgravity PCG cards than the 1g controls. These positive results hope to introduce the use of the PCG standard of low sample volume and large experimental density to the microgravity environment and provide new opportunities for macromolecular samples that may crystallize poorly in standard laboratories. PMID:24278480

  5. Protein Crystal Movements and Fluid Flows During Microgravity Growth

    NASA Technical Reports Server (NTRS)

    Boggon, Titus J.; Chayen, Naomi E.; Snell, Edward H.; Dong, Jun; Lautenschlager, Peter; Potthast, Lothar; Siddons, D. Peter; Stojanoff, Vivian; Gordon, Elspeth; Thompson, Andrew W.; Zagalsky, Peter F.; Bi, Ru-Chang; Helliwell, John R.

    1998-01-01

    The growth of protein crystals suitable for x-ray crystal structure analysis is an important topic. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and x-ray topographic images as well as the diffraction resolution limit and overall data quality. In yet another study, use of hanging drop vapour diffusion geometry on the IML-2 shuttle mission showed, again via CCD video monitoring, growing apocrustacyanin C(sub 1) protein crystal executing near cyclic movement, reminiscent of Marangoni convection flow of fluid, the crystals serving as "markers" of the fluid flow. A review is given here of existing results and experience over several microgravity missions. Some comment is given on gel protein crystal growth in attempts to 'mimic' the benefits of microgravity on Earth. Finally, the recent new results from our experiments on the shuttle mission LMS are described. These results include CCD video as well as interferometry during the mission, followed, on return to Earth, by reciprocal space mapping at the NSLS, Brookhaven, and full X-ray data collection on LMS and Earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C(sub 1) crystals are also described.

  6. Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    2014-01-01

    A low gravity material experiment will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). There are two sections of the flight experiment: (I) crystal growth of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, by physical vapor transport (PVT) and (II) melt growth of CdZnTe by directional solidification. The main objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the grown crystals as results of buoyancy-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. This talk will focus on the ground-based studies on the PVT crystal growth of ZnSe and related ternary compounds. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  7. Vapor crystal growth technology development: Application to cadmium telluride

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Banish, Michael; Duval, Walter M. B.

    1991-01-01

    Growth of bulk crystals by physical vapor transport was developed and applied to cadmium telluride. The technology makes use of effusive ampoules, in which part of the vapor contents escapes to a vacuum shroud through defined leaks during the growth process. This approach has the advantage over traditional sealed ampoule techniques that impurity vapors and excess vapor constituents are continuously removed from the vicinity of the growing crystal. Thus, growth rates are obtained routinely at magnitudes that are rather difficult to achieve in closed ampoules. Other advantages of this effusive ampoule physical vapor transport (EAPVT) technique include the predetermination of transport rates based on simple fluid dynamics and engineering considerations, and the growth of the crystal from close to congruent vapors, which largely alleviates the compositional nonuniformities resulting from buoyancy driven convective transport. After concisely reviewing earlier work on improving transport rates, nucleation control, and minimization of crystal wall interactions in vapor crystal growth, a detail account is given of the largely computer controlled EAPVT experimentation.

  8. Crystal growth furnace with trap doors

    DOEpatents

    Sachs, Emanual M. (Watertown, MA); Mackintosh, Brian H. (Lexington, MA)

    1982-06-15

    An improved furnace is provided for growing crystalline bodies from a melt. The improved furnace is characterized by a door assembly which is remotely controlled and is arranged so as to selectively shut off or permit communication between an access port in the furnace enclosure and a hot zone within that enclosure. The invention is especially adapted to facilitate use of crystal growing cartridges of the type disclosed in U.S. Pat. No. 4,118,197.

  9. Crystal growth furnace with trap doors

    NASA Technical Reports Server (NTRS)

    Sachs, Emanual M. (Inventor); Mackintosh, Brian H. (Inventor)

    1982-01-01

    An improved furnace is provided for growing crystalline bodies from a melt. The improved furnace is characterized by a door assembly which is remotely controlled and is arranged so as to selectively shut off or permit communication between an access port in the furnace enclosure and a hot zone within that enclosure. The invention is especially adapted to facilitate use of crystal growing cartridges of the type disclosed in U.S. Pat. No. 4,118,197.

  10. Edge-controlled growth and kinetics of single-crystal graphene domains by chemical vapor deposition

    PubMed Central

    Ma, Teng; Ren, Wencai; Zhang, Xiuyun; Liu, Zhibo; Gao, Yang; Yin, Li-Chang; Ma, Xiu-Liang; Ding, Feng; Cheng, Hui-Ming

    2013-01-01

    The controlled growth of large-area, high-quality, single-crystal graphene is highly desired for applications in electronics and optoelectronics; however, the production of this material remains challenging because the atomistic mechanism that governs graphene growth is not well understood. The edges of graphene, which are the sites at which carbon accumulates in the two-dimensional honeycomb lattice, influence many properties, including the electronic properties and chemical reactivity of graphene, and they are expected to significantly influence its growth. We demonstrate the growth of single-crystal graphene domains with controlled edges that range from zigzag to armchair orientations via growth–etching–regrowth in a chemical vapor deposition process. We have observed that both the growth and the etching rates of a single-crystal graphene domain increase linearly with the slanted angle of its edges from 0° to ∼19° and that the rates for an armchair edge are faster than those for a zigzag edge. Such edge-structure–dependent growth/etching kinetics of graphene can be well explained at the atomic level based on the concentrations of the kinks on various edges and allow the evolution and control of the edge and morphology in single-crystal graphene following the classical kinetic Wulff construction theory. Using these findings, we propose several strategies for the fabrication of wafer-sized, high-quality, single-crystal graphene. PMID:24297886

  11. Fluid Physics and Macromolecular Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Helliwell, John R.; Snell, Edward H.; Chayen, Naomi E.; Judge, Russell A.; Boggon, Titus J.; Pusey, M. L.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The first protein crystallization experiment in microgravity was launched in April, 1981 and used Germany's Technologische Experimente unter Schwerelosigkeit (TEXUS 3) sounding rocket. The protein P-galactosidase (molecular weight 465Kda) was chosen as the sample with a liquid-liquid diffusion growth method. A sliding device brought the protein, buffer and salt solution into contact when microgravity was reached. The sounding rocket gave six minutes of microgravity time with a cine camera and schlieren optics used to monitor the experiment, a single growth cell. In microgravity a strictly laminar diffusion process was observed in contrast to the turbulent convection seen on the ground. Several single crystals, approx 100micron in length, were formed in the flight which were of inferior but of comparable visual quality to those grown on the ground over several days. A second experiment using the same protocol but with solutions cooled to -8C (kept liquid with glycerol antifreeze) again showed laminar diffusion. The science of macromolecular structural crystallography involves crystallization of the macromolecule followed by use of the crystal for X-ray diffraction experiments to determine the three dimensional structure of the macromolecule. Neutron protein crystallography is employed for elucidation of H/D exchange and for improved definition of the bound solvent (D20). The structural information enables an understanding of how the molecule functions with important potential for rational drug design, improved efficiency of industrial enzymes and agricultural chemical development. The removal of turbulent convection and sedimentation in microgravity, and the assumption that higher quality crystals will be produced, has given rise to the growing number of crystallization experiments now flown. Many experiments can be flown in a small volume with simple, largely automated, equipment - an ideal combination for a microgravity experiment. The term "protein crystal growth" is often historically used to describe these microgravity experiments. This is somewhat inaccurate as the field involves the study of many varied biological molecules including viruses, proteins, DNA, RNA and complexes of those structures. For this reason we use the term macromolecular crystal growth. In this chapter we review a series of diagnostic microgravity crystal growth experiments carried out principally using the European Space Agency (ESA) Advanced Protein Crystallization Facility (APCF). We also review related research, both experimental and theoretical, on the aspects of microgravity fluid physics that affect microgravity protein crystal growth. Our experiments have revealed some surprises that were not initially expected. We discuss them here in the context of practical lessons learnt and how to maximize the limited microgravity opportunities available.

  12. Polymer crystallization in a temperature gradient field with controlled crystal growth rate

    NASA Technical Reports Server (NTRS)

    Hansen, D.; Taskar, A. N.; Casale, O.

    1971-01-01

    A method is described for studying the influence of a temperature gradient on the crystallization of quiescent polymer melts. The apparatus used consists of two brass plates with embedded electrical resistance heaters and cooling coils. The crystallizations experiments were conducted by placing polymer specimens between the paltes, and manually adjusting heaters and cooling fluids for temperature control. Linear polyethylene, isotactic polyprophylene, and a high density polyethylene were used. It is concluded that the role of a temperature gradient in producing oriented crystallization is in producing conditions which lead the spherulitic growth pattern to proceed primarily in one direction. Steep gradients diminish the penetration of supercooling and favors oriented growth.

  13. Hydrothermal crystal growth of oxides for optical applications

    NASA Astrophysics Data System (ADS)

    McMillen, Colin David

    2007-12-01

    The manipulation of light has proven to be an integral part of today's technology-based society. In particular, there is great interest in obtaining coherent radiation in all regions of the optical spectrum to advance technology in military, medical, industrial, scientific and consumer fields. Exploring new crystal growth techniques as well as the growth of new optical materials is critical in the advancement of solid state optics. Surprisingly, the academic world devotes little attention to the growth of large crystals. This shortcoming has left gaps in the optical spectrum inaccessible by solid state devices. This dissertation explores the hydrothermal crystal growth of materials that could fill two such gaps. The first gap exists in the deep-UV region, particularly below 200 nm. Some materials such as LiB3O5 and beta-BaB2O4 can generate coherent light at wavelengths as low as 205 nm. The growth of these materials was explored to investigate the feasibility of the hydrothermal method as a new technique for growing these crystals. Particular attention was paid to the descriptive chemistry surrounding these systems, and several novel structures were elucidated. The study was also extended to the growth of materials that could be used for the generation of coherent light as low as 155 nm. Novel synthetic schemes for Sr2Be2B2O7 and KBe2BO 3F2 were developed and the growth of large crystals was explored. An extensive study of the structures, properties and crystal growth of related compounds, RbBe2BO3F2 and CsBe2BO 3F2, was also undertaken. Optimization of a number of parameters within this family of compounds led to the hydrothermal growth of large, high quality single crystal at rates suitable for large-scale growth. The second gap in technology is in the area of high average power solid state lasers emitting in the 1 mum and eye-safe (>1.5 mum) regions. A hydrothermal technique was developed to grow high quality crystals of Sc 2O3 and Sc2O3 doped with suitable lanthanide activator ions. Preliminary spectroscopic studies were performed and large crystals were again grown at rates suitable for commercial production. The synthesis of ultra-high purity Ln2O3 (Ln = Sc, Y, La-Lu) nanoparticles was also explored to advance the development of ceramic-based solid state lasers. Crystal growth is a complex task involving a great number of intricacies that must be understood and balanced. This dissertation has advanced the art and science of growing crystals, and documented the development of large, high quality crystals of advanced optical materials The materials and hydrothermal crystal growth techniques developed over the course of this work represent important progress toward controlling the optical spectrum.

  14. Electromagnetic induction heating for single crystal graphene growth: morphology control by rapid heating and quenching.

    PubMed

    Wu, Chaoxing; Li, Fushan; Chen, Wei; Veeramalai, Chandrasekar Perumal; Ooi, Poh Choon; Guo, Tailiang

    2015-01-01

    The direct observation of single crystal graphene growth and its shape evolution is of fundamental importance to the understanding of graphene growth physicochemical mechanisms and the achievement of wafer-scale single crystalline graphene. Here we demonstrate the controlled formation of single crystal graphene with varying shapes, and directly observe the shape evolution of single crystal graphene by developing a localized-heating and rapid-quenching chemical vapor deposition (CVD) system based on electromagnetic induction heating. Importantly, rational control of circular, hexagonal, and dendritic single crystalline graphene domains can be readily obtained for the first time by changing the growth condition. Systematic studies suggest that the graphene nucleation only occurs during the initial stage, while the domain density is independent of the growth temperatures due to the surface-limiting effect. In addition, the direct observation of graphene domain shape evolution is employed for the identification of competing growth mechanisms including diffusion-limited, attachment-limited, and detachment-limited processes. Our study not only provides a novel method for morphology-controlled graphene synthesis, but also offers fundamental insights into the kinetics of single crystal graphene growth. PMID:25762066

  15. Experimental techniques for determination of the role of diffusion and convection in crystal growth from solution

    NASA Technical Reports Server (NTRS)

    Zefiro, L.

    1980-01-01

    Various studies of the concentration of the solution around a growing crystal using interferometric techniques are reviewed. A holographic interferometric technique used in laboratory experiments shows that a simple description of the solution based on the assumption of a purely diffusive mechanism appears inadequate since the convection, effective even in reduced columns, always affects the growth.

  16. Growth of 3He crystals at different magnetic fields

    NASA Astrophysics Data System (ADS)

    Bueno, J.; Blaauwgeers, R.; Parshin, A. Y.; Jochemsen, R.

    2008-04-01

    Experiments on He3 crystal growth are carried out in magnetic field up 9T. The data are analyzed and compared with the results found at zero magnetic field. It is found that the interface and the crystal lattice couple weakly in the presence of an external magnetic field, and we can set an upper limit of the step energy of the ?110?, ?100? and ?211? facets at different magnetic fields.

  17. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.

    1980-01-01

    The apparatus and techniques used in effort to determine the relationships between crystal growth and electronic properties are described with emphasis on electroepitaxy and melt-grown gallium aresenide crystal. Applications of deep level transient spectroscopy, derivative photocapitance spectroscopy, and SEM-cathodoluminescene in characterizing wide bandgap semiconductors; determining photoionization in MOS, Schottky barriers, and p-n junctions; and for identifying inhomogeneities are examined, as well as the compensation of indium phosphide.

  18. Mechanisms Limiting Body Growth in Mammals

    PubMed Central

    Lui, Julian C.

    2011-01-01

    Recent studies have begun to provide insight into a long-standing mystery in biologywhy body growth in animals is rapid in early life but then progressively slows, thus imposing a limit on adult body size. This growth deceleration in mammals is caused by potent suppression of cell proliferation in multiple tissues and is driven primarily by local, rather than systemic, mechanisms. Recent evidence suggests that this progressive decline in proliferation results from a genetic program that occurs in multiple organs and involves the down-regulation of a large set of growth-promoting genes. This program does not appear to be driven simply by time, but rather depends on growth itself, suggesting that the limit on adult body size is imposed by a negative feedback loop. Different organs appear to use different types of information to precisely target their adult size. For example, skeletal and cardiac muscle growth are negatively regulated by myostatin, the concentration of which depends on muscle mass itself. Liver growth appears to be modulated by bile acid flux, a parameter that reflects organ function. In pancreas, organ size appears to be limited by the initial number of progenitor cells, suggesting a mechanism based on cell-cycle counting. Further elucidation of the fundamental mechanisms suppressing juvenile growth is likely to yield important insights into the pathophysiology of childhood growth disorders and of the unrestrained growth of cancer. In addition, improved understanding of these growth-suppressing mechanisms may someday allow their therapeutic suspension in adult tissues to facilitate tissue regeneration. PMID:21441345

  19. Synthesis, crystal growth and characterization of nonlinear optical organic crystal: p-Toluidinium p-toluenesulphonate

    SciTech Connect

    Vijayakumar, P.; Anandha Babu, G.; Ramasamy, P.

    2012-04-15

    Graphical abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. p-TTS single crystal belongs to negative birefringence crystal. Second harmonic conversion efficiency of p-TTS has been found to be 1.3 times higher than that of KDP. Multiple shot surface laser damage threshold is determined to be 0.30 GW/cm{sup 2} at 1064 nm laser radiation. Highlights: Black-Right-Pointing-Pointer It deals with the synthesis, growth and characterization of p-TTS an organic NLO crystal. Black-Right-Pointing-Pointer Wide optical transparency window between 280 nm and 1100 nm. Black-Right-Pointing-Pointer Negative birefringence crystal and dispersion of birefringence is negligibly small. Black-Right-Pointing-Pointer Thermal study reveals that the grown crystal is stable up to 210 Degree-Sign C. Black-Right-Pointing-Pointer Multiple shot surface laser damage threshold is 0.30 GW/cm{sup 2} at 1064 nm laser radiation. -- Abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. The structural perfection of the grown p-TTS single crystal has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Fourier transform infrared spectral studies have been performed to identify the functional groups. The optical transmittance window and the lower cutoff wavelength of the grown crystals have been identified by UV-vis-IR studies. Birefringence of p-TTS crystal has been studied using channel spectrum measurement. The laser damage threshold value was measured using Nd:YAG laser. The second harmonic conversion efficiency of p-TTS has been determined using Kurtz powder technique. Thermo gravimetric and differential thermal analyses were used to study its thermal properties. Dielectric constant, dielectric loss and AC conductivity of the grown p-TTS single crystal has been studied.

  20. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (1) Nature of the molecular units responsible for the crystal nuclei formation; (2) Nature of the nuclei and nucleation process; (3) Growth process of the nuclei into crystal; (4) Morphological control and size of the resulting crystal; (5) Surface structure of the resulting crystals; (6) Transformation of frameworks into other frameworks or condensed structures. The NASA-funded research described in this report focuses to varying degrees on all of the above issues and has been described in several publications. Following is the presentation of the highlights of our current research program. The report is divided into five sections: (1) Fundamental aspects of the crystal growth process; (2) Morphological and Surface properties of crystals; (3) Crystal dissolution and transformations; (4) Modeling of Crystal Growth; (5) Relevant Microgravity Experiments.

  1. Mechanics of instability-related delimination growth

    NASA Technical Reports Server (NTRS)

    Whitcomb, John D.

    1988-01-01

    Local buckling of a delaminated group of plies can lead to higher interlaminar stresses and delamination growth. The mechanics of instability-related delamination growth (IRDG) had been described previously for the through-width delamination. This paper describes the mechanics of IRDG for the embedded delamination subjected to either uniaxial or axisymmetric loads. The mechanics of IRDG are used to explain the dramatic differences in strain-energy release rates observed for the through-width, the axisymmetrically loaded embedded delamination, and the uniaxially loaded embedded delamination.

  2. Minimal physical requirements for crystal growth self-poisoning.

    PubMed

    Whitelam, Stephen; Dahal, Yuba Raj; Schmit, Jeremy D

    2016-02-14

    Self-poisoning is a kinetic trap that can impair or prevent crystal growth in a wide variety of physical settings. Here we use dynamic mean-field theory and computer simulation to argue that poisoning is ubiquitous because its emergence requires only the notion that a molecule can bind in two (or more) ways to a crystal; that those ways are not energetically equivalent; and that the associated binding events occur with sufficiently unequal probability. If these conditions are met then the steady-state growth rate is in general a non-monotonic function of the thermodynamic driving force for crystal growth, which is the characteristic of poisoning. Our results also indicate that relatively small changes of system parameters could be used to induce recovery from poisoning. PMID:26874500

  3. Minimal physical requirements for crystal growth self-poisoning

    NASA Astrophysics Data System (ADS)

    Whitelam, Stephen; Dahal, Yuba Raj; Schmit, Jeremy D.

    2016-02-01

    Self-poisoning is a kinetic trap that can impair or prevent crystal growth in a wide variety of physical settings. Here we use dynamic mean-field theory and computer simulation to argue that poisoning is ubiquitous because its emergence requires only the notion that a molecule can bind in two (or more) ways to a crystal; that those ways are not energetically equivalent; and that the associated binding events occur with sufficiently unequal probability. If these conditions are met then the steady-state growth rate is in general a non-monotonic function of the thermodynamic driving force for crystal growth, which is the characteristic of poisoning. Our results also indicate that relatively small changes of system parameters could be used to induce recovery from poisoning.

  4. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, Harry C.; Lagowski, Jacek

    1989-01-01

    The program on Crystal Growth of Device Quality GaAs in Space was initiated in 1977. The initial stage covering 1977 to 1984 was devoted strictly to ground-based research. By 1985 the program had evolved into its next logical stage aimed at space growth experiments; however, since the Challenger disaster, the program has been maintained as a ground-based program awaiting activation of experimentation in space. The overall prgram has produced some 80 original scientific publications on GaAs crystal growth, crystal characterization, and new approaches to space processing. Publication completed in the last three years are listed. Their key results are outlined and discussed in the twelve publications included as part of the report.

  5. Influence of residual gravity on crystal growth processes

    NASA Technical Reports Server (NTRS)

    Rosenberger, F.; Alexander, J. I. D.; Nadarajah, A.; Ouazzani, J.

    1990-01-01

    The effects of steady and time-dependent residual accelerations on representative melt and solution crystal growth systems have been investigated using numerical models. For the melt growth system, it was found that the lateral nonuniformity in crystal composition, depending on the particular operating conditions, can be very sensitive to the orientation of the steady component of the residual gravity vector down to 10 to the -6th g. Oscillatory residual accelerations (g-jitter) were found to lead to transients in the dopant distribution. For the solution growth, longtime simulations showed that at 10 to the -5th g, and the cooling rates used in Spacelab 3 experiments, diffusive transport dominates only in the beginning. Convective transport becomes increasingly significant after 3 to 5 hours, depending on the orientation of the crystal in the residual gravity field.

  6. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.

    1985-01-01

    The present program has been aimed at solving the fundamental and technological problems associated with Crystal Growth of Device Quality in Space. The initial stage of the program was devoted strictly to ground-based research. The unsolved problems associated with the growth of bulk GaAs in the presence of gravitational forces were explored. Reliable chemical, structural and electronic characterization methods were developed which would permit the direct relation of the salient materials parameters (particularly those affected by zero gravity conditions) to the electronic characteristics of single crystal GaAs, in turn to device performance. These relationships are essential for the development of optimum approaches and techniques. It was concluded that the findings on elemental semiconductors Ge and Si regarding crystal growth, segregation, chemical composition, defect interactions, and materials properties-electronic properties relationships are not necessarily applicable to GaAs (and to other semiconductor compounds). In many instances totally unexpected relationships were found to prevail.

  7. Nucleation and Convection Effects in Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1997-01-01

    Work during the second year under this grant (NAG8-1161) resulted in several major achievements. We have characterized protein impurities as well as microheterogeneities in the proteins hen egg white lysozyme and horse spleen apoferritin, and demonstrated the effects of these impurities on nucleation and crystallization. In particular, the purification of apoferritin resulted in crystals with an X-ray diffraction resolution of better than 1.8 A, i.e. a 1 A improvement over earlier work on the cubic form. Furthermore, we have shown, in association with studies of liquid-liquid phase separation, that depending on the growth conditions, lysozyme can produce all growth morphologies that have been observed with other proteins. Finally, in connection with our experimental and simulation work on growth step bunching, we have developed a system-dependent criterion for advantages and disadvantages of crystallization from solution under reduced gravity. In the following, these efforts are described in some detail.

  8. The growth of multicomponent oxide single crystals by Stepanov's technique

    NASA Astrophysics Data System (ADS)

    Ivleva, L. I.; Kuzminov, Iu. S.; Osiko, V. V.; Polozkov, N. M.

    1987-03-01

    Single crystals of LiNbO3, Sr(x)Ba(1-x)Nb2O6, Ca3(VO4), Bi12SiO20, Bi12GeO20, Bi4Ge3O12 and Nd3Ga5O12 were grown in an apparatus using RF heating of platinum crucibles in air. Stepanov's technique made it possible to increase by several times the rates of solidification needed to obtain optically homogeneous single crystals. Optimum crystallographic directions of pulling were experimentally determined for crystals from various symmetry groups. The shape of a growing crystal was related to the structural defects according to the Curie principle. The experimental data provided support for the growth of profiled multicomponent single crystals.

  9. Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization

    PubMed Central

    Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

    2016-01-01

    Organic semiconductors including rubrene, Alq3, copper phthalocyanine and pentacene are crystallized by the eutectic melt crystallization. Those organic semiconductors form good eutectic systems with the various volatile crystallizable additives such as benzoic acid, salicylic acid, naphthalene and 1,3,5-trichlorobenzene. Due to the formation of the eutectic system, organic semiconductors having originally high melting point (Tm > 300 °C) are melted and crystallized at low temperature (Te = 40.8–133 °C). The volatile crystallizable additives are easily removed by sublimation. For a model system using rubrene, single crystalline rubrene nanowires are prepared by the eutectic melt crystallization and the eutectic-melt-assisted nanoimpinting (EMAN) technique. It is demonstrated that crystal structure and the growth direction of rubrene can be controlled by using different volatile crystallizable additives. The field effect mobility of rubrene nanowires prepared using several different crystallizable additives are measured and compared. PMID:26976527

  10. Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization.

    PubMed

    Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

    2016-01-01

    Organic semiconductors including rubrene, Alq3, copper phthalocyanine and pentacene are crystallized by the eutectic melt crystallization. Those organic semiconductors form good eutectic systems with the various volatile crystallizable additives such as benzoic acid, salicylic acid, naphthalene and 1,3,5-trichlorobenzene. Due to the formation of the eutectic system, organic semiconductors having originally high melting point (Tm > 300 °C) are melted and crystallized at low temperature (Te = 40.8-133 °C). The volatile crystallizable additives are easily removed by sublimation. For a model system using rubrene, single crystalline rubrene nanowires are prepared by the eutectic melt crystallization and the eutectic-melt-assisted nanoimpinting (EMAN) technique. It is demonstrated that crystal structure and the growth direction of rubrene can be controlled by using different volatile crystallizable additives. The field effect mobility of rubrene nanowires prepared using several different crystallizable additives are measured and compared. PMID:26976527

  11. Crystal growth of organics for nonlinear optical applications

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Mazelsky, R.

    1993-01-01

    The crystal growth and characterization of organic and inorganic nonlinear optical materials were extensively studied. For example, inorganic crystals such as thallium arsenic selenide were studied in our laboratory for several years and crystals in sizes over 2.5 cm in diameter are available. Organic crystals are suitable for the ultraviolet and near infrared region, but are relatively less developed than their inorganic counterparts. Very high values of the second harmonic conversion efficiency and the electro-optic coefficient were reported for organic compounds. Single crystals of a binary organic alloy based on m.NA and CNA were grown and higher second harmonic conversion efficiency than the values reported for m.NA were observed.

  12. Analytics of crystal growth in space

    NASA Technical Reports Server (NTRS)

    Chang, C. E.; Lefever, R. A.; Wilcox, W. R.

    1975-01-01

    The variation of radial impurity distribution induced by surface tension driven flow increases as the zone length decreases in silicon crystals grown by floating zone melting. In combined buoyancy driven and surface tension driven convection at the gravity of earth, the buoyancy contribution becomes relatively smaller as the zone diameter decreases and eventually convection is dominated by the surface tension driven flow (in the case of silicon, for zones of less than about 0.8 cm in diameter). Preliminary calculations for sapphire suggest the presence of an oscillatory surface tension driven convection as a result of an unstable melt surface temperature that results when the zone is heated by a radiation heater.

  13. Growth of large zeolite crystals in space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

    1988-01-01

    Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

  14. Ground Based Program for the Physical Analysis of Macromolecular Crystal Growth

    NASA Technical Reports Server (NTRS)

    Malkin, Alexander J.

    1999-01-01

    In a reported period in situ atomic force microscopy was utilized in our laboratory to study mechanisms of growth and kinetics of crystallization of ten protein and virus crystals. These included canavalin, thaumatin, apoferritin, lipase, catalase, t-RNA, lysozyme, xylanase, turnip yellow mosaic virus (TYMV) and satellite tobacco mosaic virus (STMV). We have also designed and constructed in our laboratory both in situ conventional two-beam Michelson and phase shift Mach-Zenhder interferometers. Computer software for the processing of the interferometric images was developed as well. Interferometric techniques were applied for studies of growth kinetics and transport phenomena in crystallization of several macromolecular crystals. As a result of this work we have published 21 papers and have given many presentations at international and national meetings. A list of these publications and conference presentations is attached.

  15. Characterizing ice crystal growth behavior under electric field using phase field method.

    PubMed

    He, Zhi Zhu; Liu, Jing

    2009-07-01

    In this article, the microscale ice crystal growth behavior under electrostatic field is investigated via a phase field method, which also incorporates the effects of anisotropy and thermal noise. The multiple ice nuclei's competitive growth as disclosed in existing experiments is thus successfully predicted. The present approach suggests a highly efficient theoretical tool for probing into the freeze injury mechanisms of biological material due to ice formation during cryosurgery or cryopreservation process when external electric field was involved. PMID:19640138

  16. Zeolite crystal growth in space - What has been learned

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Thompson, R. W.; Dixon, A. G.

    1993-01-01

    Three zeolite crystal growth experiments developed at WPI have been performed in space in last twelve months. One experiment, GAS-1, illustrated that to grow large, crystallographically uniform crystals in space, the precursor solutions should be mixed in microgravity. Another experiment evaluated the optimum mixing protocol for solutions that chemically interact ('gel') on contact. These results were utilized in setting the protocol for mixing nineteen zeolite solutions that were then processed and yielded zeolites A, X and mordenite. All solutions in which the nucleation event was influenced produced larger, more 'uniform' crystals than did identical solutions processed on earth.

  17. Simulation of Gravity Effects on Bulk Crystal Growth with Effects on undercooling

    NASA Astrophysics Data System (ADS)

    Chuang, S.-H.; Lu, M.-F.

    For the production of a perfect single crystal by Bridgman, it is important to acquire the correct information about the heat transfer mechanism and to control the heat transfer in the Bridgman furnace. Because the quality of the crystal is closely related to its thermal history and the transport phenomena in the furnace. Ma et al. (2004) presented that faceting simulation of bulk crystal growth with undercooling method. Lan et al. (2003) developed a new model to study heat flow and facet formation in Bridgman growth with the undercooling satisfied the given growth mechanism. Considering the gravity effects added kinetic undercooling is thus developed. Heat conduction, convection and radiation are considered and coupled with the two-dimensional transient undercooling simulation. The solidification interface temperature is related to the undercooling along the interface and the melting temperature. In this investigation, we are going to apply the developed model to simulate interface in vertical Bridgman crystal growth process for yttrium aluminum garnet subjected to the normal gravity to microgravity. Also, it discusses the effect upon the shape and the propagation of the solidification crystal front.

  18. Study on crystal-melt interface shape of sapphire crystal growth by the KY method

    NASA Astrophysics Data System (ADS)

    Liu, Weina; Lu, Jijun; Chen, Hongjian; Yan, Wenbo; Min, Chunhua; Lian, Qingqing; Wang, Yunman; Cheng, Peng; Liu, Caichi; Xu, Yongliang

    2015-12-01

    In this article, the influence of the flow field structure and temperature gradient of forefront interface on the shape of crystal-melt interface which may reflect the interface stability were analyzed through the method of numerical simulation by using CGSim software. In order to get a suitable interface shape and grow high-quality sapphire crystal, the heater arrangement should be adjusted during the KY process. The results indicate that the effect of Marangoni convection cannot be neglected at the last stage, the crystal-melt interface is governed by the flow field structure and the temperature gradient in melt at the crystal-melt interface. The phenomenon of shoulder concave appears at the stage of shoulder turning and interface inversion appears at the last stage during the crystal growth is discussed. Adjusting heater arrangement may effectively optimize the shape of crystal-melt interface.

  19. Hanging drop crystal growth apparatus and method

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor); Smith, Robbie E. (Inventor)

    1989-01-01

    An apparatus (10) is constructed having a cylindrical enclosure (16) within which a disc-shaped wicking element (18) is positioned. A well or recess (22) is cut into an upper side (24) of this wicking element, and a glass cover plate or slip (28) having a protein drop disposed thereon is sealably positioned on the wicking element (18), with drop (12) being positioned over well or recess (22). A flow of control fluid is generated by a programmable gradient former (16), with this control fluid having a vapor pressure that is selectively variable. This flow of control fluid is coupled to the wicking element (18) where control fluid vapor diffusing from walls (26) of the recess (22) is exposed to the drop (12), forming a vapor pressure gradient between the drop (12) and the control fluid vapor. Initially, this gradient is adjusted to draw solvent from the drop (12) at a relatively high rate, and as the critical supersaturation point is approached (the point at which crystal nucleation occurs), the gradient is reduced to more slowly draw solvent from the drop (12). This allows discrete protein molecules more time to orient themselves into an ordered crystalline lattice, producing protein crystals which, when processed by X-ray crystallography, possess a high degree of resolution.

  20. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.

    1984-01-01

    The crystal growth, device processing and device related properties and phenomena of GaAs are investigated. Our GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor materials (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; (3) investigation of electronic properties and phenomena controlling device applications and device performance. The ground based program is developed which would insure successful experimentation with and eventually processing of GaAs in a near zero gravity environment.

  1. Mechanical Behavior and Processing of DS and Single Crystal Superalloys

    NASA Astrophysics Data System (ADS)

    Khan, T.; Caron, P.; Nakagawa, Y. G.

    1986-07-01

    This article examines mechanical anisotropy of single crystals, cold work induced surface recrystallization on directionally solidified (DS) materials, and the effect of temperature gradient in a DS furnace on the fatigue strength of single crystals. It draws attention to the highly anisotropic creep behavior of some modern single crystal alloys showing, in particular, extremely poor creep resistance in the <111> orientation. Effects of surface recrystallization on the creep strength are evaluated. The present work incites further investigation on heat treatments and alloy chemistry modifications in order to reduce the effect of mechanical anisotropy. Great care should be taken during the "mechanical" handling of DS or single crystal components to avoid surface recrystallization. HIP'ing or high gradient solidification are shown to be two possible ways for enhancing the durability and the fatigue strength of single crystal superalloys. In certain liquid fuel rocket engine applications, where hydrogen embrittlement of single crystal turbopump blades can be of concern, both these techniques can be useful.

  2. Ionic strength and ion ratio effects on the single crystal growth of calcium oxalate monohydrate

    SciTech Connect

    DeLong, J.D.; Briedis, D.M.

    1987-01-01

    Single crystal growth rates of calcium oxalate monohydrate, CaC/sub 2/O/sub 4/ . H/sub 2/O, were measured as a function of ionic strength and of calcium to oxalate free ion ratio. The photomicroscopic technique was used which allowed measurement of the growth rates of individual faces of single crystals. The amounts of reagents required to maintain a constant relative supersaturation of 3.7 for all experiments were determined using an iterative computer algorithm which allowed the use of various background electrolytes, ionic strength, and free ion ratios. For a range of ionic strengths of I = .0024 to 0.5 for each of the background electrolytes KCl, LiCl, and KClO/sub 4/, and a free ion ratio (Ca/sup 2+/)/(C/sub 2/O/sub 4//sup 2-/) = 1, facial growth rate showed a steady increase with ionic strength towards an asymptotic maximum. The curves of growth rate, R, versus ionic strength followed approximately the form R = k I/sup n/ with 0 < n < 1, suggesting a mechanism of growth enhancement with increasing ionic strength by compression of the electrical double layer at the crystal/solution interface. For a range of free ion ratios (Ca/sup 2+/)/(C/sub 2/O/sub 4//sup 2-/) = 0.01 to 100 and an ionic strength of I = 0.15 M, the observed growth rate showed a maximum at equimolar free ion conditions, with decreasing growth rates observed at lower and higher ion ratios. This growth rate maximum was not apparent under conditions with no added background electrolyte. These results indicate that relative supersaturation as usually used for crystal growth may not be the complete or appropriate driving force for describing electrolyte crystal growth.

  3. Interface stability and defect formation during crystal growth

    SciTech Connect

    Fabietti, L.M.R.

    1991-01-08

    Unidirectional solidification experiments have been carried out in organic crystals with the aim of improving our knowledge on the effects of constraints on the interface morphology and to increase our understanding of the growth of anisotropic materials. The experimental information shows that lateral constraints such as a sharp change in the cross-sectional area in the solid liquid interface path, can produce important changes in the microstructure if the interface morphology is planar, cellular or dendritic. The study of anisotropic materials cover several topics. It is first shown that slight anisotropy does not influence the dendrite tip selection criterion. This conclusion is obtained from the analysis of the relationship between tip radius and velocity for dendrites growing under the steady state condition for two different materials, CBr{sub 4} and C{sub 2}Cl{sub 6}, which have different surface energy anisotropy values. The values of the dendrite operating parameters {sigma}* are compared with the predictions of the solvability theory and the morphological stability theory. The experiments show better agreement with the latter theory. Critical experiments have been designed and carried out to find the response functions which determine the composition and temperature of the interface as a function of velocity in faceted materials. The experiments, carried out in Napthalene-Camphor system, indicate a strong temperature dependence of the planar interface growth which can be correlated with the step growth mechanism. Experiments on the interface instability show an important dependence on the crystallographic orientation. Unidirectional solidification experiments in zone refined Napthalene confined in very thin cells (gap size {le} 50 {mu}m) have proven to be a good method to study the defect production at the solid liquid interface. 118 refs., 90 figs., 5 tabs.

  4. Effect of the nature of impurities on the rate of axial growth of filamentary silicon crystals

    SciTech Connect

    Shchetinin, A.A.; Bubnov, L.I.; Kozenkov, O.D.; Tatarenkov, A.F.

    1988-03-01

    The authors studied the kinetics of axial growth of silicon in the standard chloride flow system using different initiating impurities and measured the contact angles of wetting of drops of the impurities on the apexes. The starting material was tetrachlorosilane transported by hydrogen, and gold, copper, and silver particles were used as the initiating impurities. The contact angles of drops of the impurities were determined with photographs of the apexes in a scanning electron microscope. The effect of the nature of impurities which initiate growth of filamentary silicon crystals according to the vapor-liquid-crystal mechanism on their axial growth rate is physical in nature and is due to the contact angle of wetting of the drop on the apex of the filamentary crystal and the solubility of the crystallizable material in the metal initiator.

  5. Wafer-scale growth of single-crystal monolayer graphene on reusable hydrogen-terminated germanium.

    PubMed

    Lee, Jae-Hyun; Lee, Eun Kyung; Joo, Won-Jae; Jang, Yamujin; Kim, Byung-Sung; Lim, Jae Young; Choi, Soon-Hyung; Ahn, Sung Joon; Ahn, Joung Real; Park, Min-Ho; Yang, Cheol-Woong; Choi, Byoung Lyong; Hwang, Sung-Woo; Whang, Dongmok

    2014-04-18

    The uniform growth of single-crystal graphene over wafer-scale areas remains a challenge in the commercial-level manufacturability of various electronic, photonic, mechanical, and other devices based on graphene. Here, we describe wafer-scale growth of wrinkle-free single-crystal monolayer graphene on silicon wafer using a hydrogen-terminated germanium buffer layer. The anisotropic twofold symmetry of the germanium (110) surface allowed unidirectional alignment of multiple seeds, which were merged to uniform single-crystal graphene with predefined orientation. Furthermore, the weak interaction between graphene and underlying hydrogen-terminated germanium surface enabled the facile etch-free dry transfer of graphene and the recycling of the germanium substrate for continual graphene growth. PMID:24700471

  6. Thermal Optimization of Growth and Quality in Protein Crystals

    NASA Technical Reports Server (NTRS)

    Wiencek, John M.

    1996-01-01

    Experimental evidence suggests that larger and higher quality crystals can be attained in the microgravity of space; however, the effect of growth rate on protein crystal quality is not well documented. This research is the first step towards providing strategies to grow crystals under constant rates of growth. Controlling growth rates at a constant value allows for direct one-to-one comparison of results obtained in microgravity and on earth. The overall goal of the project was to control supersaturation at a constant value during protein crystal growth by varying temperature in a predetermined manner. Applying appropriate theory requires knowledge of specific physicochemical properties of the protein solution including the effect of supersaturation on growth rates and the effect of temperature on protein solubility. Such measurements typically require gram quantities of protein and many months of data acquisition. A second goal of the project applied microcalorimetry for the rapid determination of these physicochemical properties using a minimum amount of protein. These two goals were successfully implemented on hen egg-white lysozyme. Results of these studies are described in the attached reprints.

  7. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Lagowski, J.

    1981-01-01

    Experimental and theoretical efforts in the development of crystal growth approaches, effective techniques for electronic characterization on a macro and microscale, and in the discovery of phenomena and processes relevant to GaAs device applications are reported. The growth of electron trap-free bulk GaAS with extremely low density of dislocations is described. In electroepitaxy, growth configuration which eliminates the substrate back-contact was developed. This configuration can be extended to the simultaneous growth on many substrates with a thin solution layer sandwiched between any two of them. The significant reduction of Joule heating effects in the configuration made it possible to realize the in situ measurement of the layer thickness and the growth velocity. Utilizing the advantages of electroepitaxy in achieving abrupt acceleration (or deceleration) of the growth it was shown that recombination centers are formed as a result of growth acceleration.

  8. Phase field modelling of strain induced crystal growth in an elastic matrix.

    PubMed

    Laghmach, Rabia; Candau, Nicolas; Chazeau, Laurent; Munch, Etienne; Biben, Thierry

    2015-06-28

    When a crystal phase grows in an amorphous matrix, such as a crystallisable elastomer, containing cross-links and/or entanglements, these "topological constraints" need to be pushed away from the crystal phase to allow further crystallization. The accumulation of these topological constraints in the vicinity of the crystal interface may store elastic energy and affect the phase transition. To evaluate the consequences of such mechanism, we introduce a phase field model based on the Flory theory of entropic elasticity. We show that the growth process is indeed sensibly affected, in particular, an exponential increase of the surface energy with the displacement of the interface is induced. This explains the formation of stable nano-crystallites as it is observed in the Strain Induced Crystallization (SIC) of natural rubber. Although simple, the model developed here is able to account for many interesting features of SIC, for instance, the crystallite shapes and their sizes which depend on the applied deformation. PMID:26133455

  9. Growth and characterization of Cadmium Thiosemicarbazide Bromide crystals for antibacterial and nonlinear optical applications.

    PubMed

    Thomas Joseph Prakash, J; Martin Sam Gnanaraj, J

    2015-01-25

    Semiorganic nonlinear optical crystals of Cadmium Thiosemicarbazide Bromide was grown by slow evaporation solution growth technique. The unit cell parameters were estimated by subjecting the crystals to single crystal X-ray diffraction. The grown crystals were subjected to Powder X-ray diffraction for analyzing the crystalline nature of the sample. FTIR studies reveal the functional groups and the optical characters were analyzed by UV-Vis spectral studies. Mechanical stability of the sample was assessed by Vicker's micro hardness test. The presence of surface dislocations was identified by chemical etching technique. Antibacterial study was carried out against ACDP declared harmful pathogens. SHG efficiency of CTSB crystal was tested using Nd: YAG laser and it was found to be ?1.8 times that of potassium dihydrogen phosphate. PMID:25048404

  10. Growth and characterization of Cadmium Thiosemicarbazide Bromide crystals for antibacterial and nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Thomas Joseph Prakash, J.; Martin Sam Gnanaraj, J.

    2015-01-01

    Semiorganic nonlinear optical crystals of Cadmium Thiosemicarbazide Bromide was grown by slow evaporation solution growth technique. The unit cell parameters were estimated by subjecting the crystals to single crystal X-ray diffraction. The grown crystals were subjected to Powder X-ray diffraction for analyzing the crystalline nature of the sample. FTIR studies reveal the functional groups and the optical characters were analyzed by UV-Vis spectral studies. Mechanical stability of the sample was assessed by Vicker's micro hardness test. The presence of surface dislocations was identified by chemical etching technique. Antibacterial study was carried out against ACDP declared harmful pathogens. SHG efficiency of CTSB crystal was tested using Nd: YAG laser and it was found to be ?1.8 times that of potassium dihydrogen phosphate.

  11. Phase field modelling of strain induced crystal growth in an elastic matrix

    NASA Astrophysics Data System (ADS)

    Laghmach, Rabia; Candau, Nicolas; Chazeau, Laurent; Munch, Etienne; Biben, Thierry

    2015-06-01

    When a crystal phase grows in an amorphous matrix, such as a crystallisable elastomer, containing cross-links and/or entanglements, these "topological constraints" need to be pushed away from the crystal phase to allow further crystallization. The accumulation of these topological constraints in the vicinity of the crystal interface may store elastic energy and affect the phase transition. To evaluate the consequences of such mechanism, we introduce a phase field model based on the Flory theory of entropic elasticity. We show that the growth process is indeed sensibly affected, in particular, an exponential increase of the surface energy with the displacement of the interface is induced. This explains the formation of stable nano-crystallites as it is observed in the Strain Induced Crystallization (SIC) of natural rubber. Although simple, the model developed here is able to account for many interesting features of SIC, for instance, the crystallite shapes and their sizes which depend on the applied deformation.

  12. A low temperature furnace for solution crystal growth on the International Space Station

    NASA Astrophysics Data System (ADS)

    Baç, Nurcan; Harpster, Joseph; Maston, Robert A.; Sacco, Albert

    2000-01-01

    The Zeolite Crystal Growth Furnace Unit (ZCG-FU) is the first module in an integrated payload designed for low temperature crystal growth in solutions on the International Space Station (ISS). This payload is scheduled to fly on the ISS flight 7A.1 in an EXPRESS rack. Its name originated from early shuttle flight experiments limited to the growth of zeolite crystals but has since grown to include other materials of significant commercial interest using the solution method of crystal growth. Zeolites, ferroelectrics, piezeoelectrics and silver halides are some of the materials considered. The ZCG-FU experiment consists of a furnace unit and its electronic control system, and mechanically complex, crystal growth autoclaves suitable for use with a particular furnace and solution. The ZCG facility is being designed to grow into four independent furnaces controlled by IZECS (Improved Zeolite Electronic Control System). IZECS provides monitoring of critical parameters, data logging, safety monitoring, air-to-ground control and operator interfacing. It is suitable for controlling the four furnaces either individually or all at one time. It also contains the power management solid-state drivers and switches for the ZCG-FU furnace. The furnace contains 19 tubes operating at three different temperature zones. .

  13. Micromechanisms of fatigue crack growth in a single crystal Inconel 718 nickel-based superalloy

    SciTech Connect

    Mercer, C.; Soboyejo, A.B.O.; Soboyejo, W.O. )

    1999-07-09

    The fatigue crack growth behavior of an experimental, single crystal alloy, of equivalent nominal chemical composition to Inconel 718 is presented. Fracture modes under cyclic loading were determined by scanning electron microscopy. The results of the fractographic analyses are presented on a fracture mechanism map that shows the dependence of the fatigue fracture mechanisms on the maximum stress intensity factor, K[sub max], and the stress intensity factor range, [Delta]K. Crack-tip deformation mechanisms associated with fatigue crack growth were studied using transmission electron microscopy. The relative effects of [Delta]K and K[sub max] on the fatigue crack growth behavior of this material are discussed within the context of a two-parameter crack growth law. The influence of grain boundaries on the fatigue crack growth resistance of materials such as Inconel 718 is also discussed in light of the results of this investigation.

  14. Crystal-growth Underground Breeding Extra-sensitive Detectors

    NASA Astrophysics Data System (ADS)

    Mei, Dongming

    2012-02-01

    CUBED (Center for Ultra-Low Background Experiments at DUSEL) collaborators from USD, SDSMT, SDSU, Sanford Lab, and Lawrence Berkeley National Laboratory are working on the development of techniques to manufacture crystals with unprecedented purity levels in an underground environment that may be used by experiments proposed for DUSEL. The collaboration continues to make significant progress toward its goal of producing high purity germanium crystals. High quality crystals are being pulled on a weekly basis at the temporary surface growth facility located on the USD campus. The characterization of the grown crystals demonstrates that the impurity levels are nearly in the range of the needed impurity level for detector-grade crystals. Currently, the crystals are being grown in high-purity hydrogen atmosphere. With an increase in purity due to the zone refining, the group expects to grow high-purity crystals by the end of 2011. The one third of the grown crystals will be manufactured to be detectors; the remaining will be fabricated in to wafers that have large applications in electro and optical devices as well as solar panels. This would allow the research to be connected to market and create more than 30 jobs and multi millions revenues in a few years.

  15. Crystal growth of device quality GaAs in space

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.

    1986-01-01

    It was established that the findings on elemental semiconductors Ge and Si regarding crystal growth, segregation, chemical composition, defect interactions, and materials properties-electronic properties relationships are not necessarily applicable to GaAs (and to other semiconductor compounds). In many instances totally unexpected relationships were found to prevail. It was further established that in compound semiconductors with a volatile constituent, control of stoichiometry is far more critical than any other crystal growth parameter. It was also shown that, due to suppression of nonstoichiometric fluctuations, the advantages of space for growth of semiconductor compounds extend far beyond those observed in elemental semiconductors. A novel configuration was discovered for partial confinement of GaAs melt in space which overcomes the two major problems associated with growth of semiconductors in total confinement. They are volume expansion during solidification and control of pressure of the volatile constituent. These problems are discussed in detail.

  16. The role of surface hydrolysis of ferricyanide anions in crystal growth of snowflake-shaped ?-Fe2O3.

    PubMed

    Liu, Zhong; Chiang, Chang-Yang; Li, Wu; Zhou, Wuzong

    2015-06-01

    Selective adsorption and surface hydrolysis of [Fe(CN)6](3-) anions on ?-Fe2O3 crystals was found to be a crucial process in the formation of a snowflake-like morphology, and the established mechanism is complementary to the classical theories of crystal growth. PMID:25959407

  17. Planet formation - Mechanism of early growth

    NASA Technical Reports Server (NTRS)

    Hartmann, W. K.

    1978-01-01

    Experiments in vacuum (approx. 0.5 to 1 mbar) and in air quantify mechanics of collisions, rebound, and fragmentation at low velocities (1-50 m/sec), under the conditions usually postulated for the preplanetary environment in the primitive solar nebula. Such collisions have been little studied experimentally. Contrary to widespread assumptions, accretionary growth of the largest meteoroid- and asteroid-sized bodies in a given swarm results spontaneously from the simple mechanics of these collisions, without other ad hoc sticking mechanisms. The smaller bodies in the swarm are less likely to grow. Granular surfaces form, either by gravitational collapse of dust swarms or by rapid formation of regolith surfaces on solid planetesimals; these surfaces strongly promote further growth by retarding rebound. Growth of large bodies increases modal collision velocities, causing fragmentation of smaller bodies and eventual production of interstellar dust as a by-product of planetesimal interactions.

  18. Modern trends in crystal growth and new applications of sapphire

    NASA Astrophysics Data System (ADS)

    Akselrod, Mark S.; Bruni, Frank J.

    2012-12-01

    We provide an overview of the latest market trends and modern competing methods of sapphire crystal growth and the application of sapphire wafers as LED substrates. Almost all methods of high temperature growth from the melt are suitable for sapphire production, but each of these methods has its advantages and disadvantages depending on the application and required finished product form factor. Special attention is paid to the review of defects and imperfections that allow the engineering of new active devices based on sapphire.

  19. Thermal-mechanical fatigue crack growth in aircraft engine materials

    NASA Astrophysics Data System (ADS)

    Dai, Yi

    1993-08-01

    This thesis summarizes the major technical achievements obtained as a part of a collaborative research and development project between Ecole Polytechnique and Pratt & Whitney Canada. These achievements include: (1) a thermal-mechanical fatigue (TMF) testing rig which is capable of studying the fatigue behaviors of gas turbine materials under simultaneous changes of temperatures and strains or stress; (2) an advanced alternative current potential drop (ACPD) measurement system which is capable of performing on-line monitoring of fatigue crack initiation and growth in specimen testing under isothermal and TMF conditions; (3) fatigue crack initiation and short crack growth data for the titanium specimens designed with notch features associated with bolt holes of compressor discs; (4) thermal-mechanical fatigue crack growth data for two titanium alloys being used in PWC engine components, which explained the material fatigue behavior encountered in full-scale component testing; (5) a complete fractographic analysis for the tested specimens which enhanced the understanding of the fatigue crack growth mechanisms and helped to establish an analytical crack growth model; and (6) application of the ACPD fatigue crack monitoring technique to single tooth firtree specimen (STFT) LCF testing of PWA 1480 single crystal alloy. Finally, a comprehensive discussion concerning the results pertaining to this research project is presented.

  20. Mechanical grain growth in nanocrystalline copper.

    PubMed

    Li, James C M

    2006-06-01

    Nanograined materials have some unusual properties. To maintain the small size of the grains, grain growth should be avoided. But recently grain growth has been observed under an indenter at liquid-nitrogen temperatures. Such grain growth has never been reported before. How can this happen and how can it be prevented? These questions are answered here using a simple tilt boundary. It is found that high purity and nonequilibrium structure are necessary conditions for mechanical grain growth. The material must be pure enough so that free dislocations are available to move out of the boundary. But the boundary should not be in the lowest-energy state so that extra dislocations are available to be emitted by stress. Based on these conditions, methods can be devised to avoid low temperature grain growth. PMID:16803250

  1. Growth Mechanism and Morphology of Hexagonal Boron Nitride.

    PubMed

    Zhang, Zhuhua; Liu, Yuanyue; Yang, Yang; Yakobson, Boris I

    2016-02-10

    Hexagonal boron nitride (h-BN) sheet is a structural analogue of graphene, yet its growth mechanism has been rarely studied, as complicated by its binary composition. Here, we reveal an atomistic growth mechanism for the h-BN islands by combining crystal growth theory with comprehensive first-principles calculations. The island shapes preferred by edge equilibrium are found to be inconsistent with experimental facts, which is in contrast to previous common views. Then the growth kinetics is explored by analyzing the diffusion and docking of boron and nitrogen atoms at the edges in a step-by-step manner of the nanoreactor approach. The determined sequence of atom-by-atom accretion reveals a strong kinetic anisotropy of growth. Depending on the chemical potential of constituent elements, it yields the h-BN shapes as equilateral triangles or hexagons, explaining a number of experimental observations and opening a way for the synthesis of quality h-BN with controlled morphology. The richer growth kinetics of h-BN compared to graphene is further extendable to other binary two-dimensional materials, notably metal dichalcogenides. PMID:26812169

  2. Chiral Symmetry Breaking in Crystal Growth: Is Hydrodynamic Convection Relevant?

    NASA Technical Reports Server (NTRS)

    Martin, B.; Tharrington, A.; Wu, Xiao-Lun

    1996-01-01

    The effects of mechanical stirring on nucleation and chiral symmetry breaking have been investigated for a simple inorganic molecule, sodium chlorate (NaClO3). In contrast to earlier findings, our experiment suggests that the symmetry breaking may have little to do with hydrodynamic convection. Rather the effect can be reasonably accounted for by mechanical damage to incipient crystals. The catastrophic events, creating numerous small 'secondary' crystals, produce statistical domination of one chiral species over the other. Our conclusion is supported by a number of observations using different mixing mechanisms.

  3. Growth of long sapphire crystals of optical quality

    NASA Astrophysics Data System (ADS)

    Kryvonosov, Ye. V.; Vyshnevskiy, S. D.; Lytvynov, L. A.

    2005-02-01

    The technological possibilities of the growth of optical-quality sapphire rods with a diameter of 12-20 mm and a length of 500-1000 mm by the Stepanov method (EFG) in argon medium at high-frequency heating of graphite heater were considered. The influence of crystallization rate and crystallographic growth direction on the optical quality of the crystals was investigated. The technological procedure of "cold" narrowing of the growing crystal at the beginning stage of seeding was proposed to improve crystals structure. It was shown that heat treatment of the grown crystal in a gas environment with neutral chemical potential leads to the destruction of optical color centers and scattering foreign-phase inclusions in its volume. It was shown that the main reason of color and scattering centers foundation in sapphire is anionic stoichiometry violation and the presence of uncontrollable impurities in the melt. To obtain long sapphire rods of optical quality, the crystallographic oriented growth [1 1 2 0] is preferred. In the process of growing a rod with a diameter of 14 mm, the depth of the surface-adjacent defective layer does not exceed 0.4 mm and the small-angle optical scattering does not have to be greater than 0.01 cm -1.

  4. Single crystal growth by gel technique and characterization of lithium hydrogen tartrate

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2015-02-01

    Single crystal growth of lithium hydrogen tartrate by gel encapsulation technique is reported. Dependence of crystal count on gel density, gel pH, reactant concentration and temperature are studied and the optimum conditions for these crystals are worked out. The stoichiometric composition of the grown crystals is determined using EDAX/AES and CH analysis. The grown crystals are characterized by X-ray diffraction, FTIR and Uv-Visible spectroscopy. It is established that crystal falls under orthorhombic system and space group P222 with the cell parameters as: a=10.971 , b=13.125 and c=5.101 ; ?=90.5o, ?=?=90. The morphology of the crystals as revealed by SEM is illustrated. Crystallite size, micro strain, dislocation density and distortion parameters are calculated from the powder XRD results of the crystal. UV-vis spectroscopy shows indirect allowed transition with an optical band gap of~4.83 eV. The crystals are also shown to have high transmittance in the entire visible region. Dependence of dielectric constant, dielectric loss and conductivity on frequency of the applied ac field is analyzed. The frequency-dependent real part of the complex ac conductivity is found to follow the universal dielectric response: ?ac (?)~?s. The trend in the variation of frequency exponent with frequency corroborates the fact that correlated barrier hopping is the dominant charge-transport mechanism in the present system.

  5. Numerical Modeling of Physical Vapor Transport in Contactless Crystal Growth Geometry

    NASA Technical Reports Server (NTRS)

    Palosz, W.; Lowry, S.; Krishnam, A.; Przekwas, A.; Grasza, K.

    1998-01-01

    Growth from the vapor under conditions of limited contact with the walls of the growth ampoule is beneficial for the quality of the growing crystal due to reduced stress and contamination which may be caused by interactions with the growth container. The technique may be of a particular interest for studies on crystal growth under microgravity conditions: elimination of some factors affecting the crystal quality may make interpretation of space-conducted processes more conclusive and meaningful. For that reason, and as a part of our continuing studies on 'contactless' growth technique, we have developed a computational model of crystal growth process in such system. The theoretical model was built, and simulations were performed using the commercial computational fluid dynamics code, (CFD) ACE. The code uses an implicit finite volume formulation with a gray discrete ordinate method radiation model which accounts for the diffuse absorption and reflection of radiation throughout the furnace. The three-dimensional model computes the heat transfer through the crystal, quartz, and gas both inside and outside the ampoule, and mass transport from the source to the crystal and the sink. The heat transport mechanisms by conduction, natural convection, and radiation, and mass transport by diffusion and convection are modeled simultaneously and include the heat of the phase transition at the solid-vapor interfaces. As the thermal boundary condition, temperature profile along the walls of the furnace is used. For different thermal profiles and furnace and ampoule dimensions, the crystal growth rate and development of the crystal-vapor and source-vapor interfaces (change of the interface shape and location with time) are obtained. Super/under-saturation in the ampoule is determined and critical factors determining the 'contactless' growth conditions are identified and discussed. The relative importance of the ampoule dimensions and geometry, the furnace dimensions and its temperature, and the properties of the grown material are analyzed. The results of the simulations are compared with related experimental results on growth of CdTe, CdZnTe, ZnTe, PbTe, and PbSnTe crystals by this technique.

  6. Solidification and crystal growth of solid solution semiconducting alloys

    SciTech Connect

    Lehoczky, S.L.; Szofran, F.R.

    1984-10-01

    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  7. Crewmember working on the mid deck Zeolite Crystal Growth experiment.

    NASA Technical Reports Server (NTRS)

    1992-01-01

    View showing Payload Specialist Bonnie Dunbar, in the mid deck, conducting the Zeolite Crystal Growth (ZCG) Experiment in the mid deck stowage locker work area. View shows assembly of zeolite sample in the metal autoclave cylinders prior to insertion into the furnace.

  8. Crewmember working on the spacelab Zeolite Crystal Growth experiment.

    NASA Technical Reports Server (NTRS)

    1992-01-01

    View showing Payload Specialists Bonnie Dunbar and Larry DeLucas in the aft section of the U. S. Microgravity Laboratory-1. Dunbar is preparing to load a sample in the Crystal Growth Furnace (CGF) Integrated Furnace Experiment Assembly (IFEA) in rack 9 of the Microgravity Laboratory. DeLucas is checking out the multi-purpose Glovebox Facility.

  9. Astronaut Wendy Lawrence monitors the Protein Crystal Growth experiment

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Astronaut Wendy B. Lawrence, flight engineer and mission specialist for STS-67, scribbles notes on the margin of a checklist while monitoring an experiment on the Space Shuttle Endeavour's middeck. The experiment is the Protein Crystal Growth (PCG), which takes up locker space near the Commercial Materials Dispersion Apparatus Instruments Technology Associates Experiment (CMIX, see decal upper left).

  10. Computing the crystal growth rate by the interface pinning method.

    PubMed

    Pedersen, Ulf R; Hummel, Felix; Dellago, Christoph

    2015-01-28

    An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two-phase configurations are stabilized by adding a spring-like bias field coupling to an order-parameter that discriminates between the two phases. Crystal growth is a Smoluchowski process and the crystal growth rate can, therefore, be computed from the terminal exponential relaxation of the order parameter. The approach is investigated in detail for the Lennard-Jones model. We find that the kinetic coefficient scales as the inverse square-root of temperature along the high temperature part of the melting line. The practical usability of the method is demonstrated by computing the kinetic coefficient of the elements Na and Si from first principles. A generalized version of the method may be used for computing the rates of crystal nucleation or other rare events. PMID:25637966

  11. Computing the crystal growth rate by the interface pinning method

    NASA Astrophysics Data System (ADS)

    Pedersen, Ulf R.; Hummel, Felix; Dellago, Christoph

    2015-01-01

    An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two-phase configurations are stabilized by adding a spring-like bias field coupling to an order-parameter that discriminates between the two phases. Crystal growth is a Smoluchowski process and the crystal growth rate can, therefore, be computed from the terminal exponential relaxation of the order parameter. The approach is investigated in detail for the Lennard-Jones model. We find that the kinetic coefficient scales as the inverse square-root of temperature along the high temperature part of the melting line. The practical usability of the method is demonstrated by computing the kinetic coefficient of the elements Na and Si from first principles. A generalized version of the method may be used for computing the rates of crystal nucleation or other rare events.

  12. Transient natural convection heat and mass transfer in crystal growth

    NASA Technical Reports Server (NTRS)

    Han, Samuel S.

    1990-01-01

    A numerical analysis of transient combined heat and mass transfer across a rectangular cavity is performed. The physical parameters are selected to represent a range of possible crystal growth in solutions. Good agreements with measurement data are observed. It is found that the thermal and solute fields become highly oscillatory when the thermal and solute Grashof numbers are large.

  13. Solidification and crystal growth of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  14. Morphological stability and fluid dynamics of vapor crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, F. E.

    1984-01-01

    Research on morphological stability and fluid dynamics of crystal growth is discussed. Interfacial heat and mass transfer research is discussed. The finding of surface roughening is a precursor to a solid-solid phase transition was further quantified. Progress was obtained with the mass spectroscopic characterization of GeSe-Ge I sub 4.

  15. Protein crystal growth in microgravity: Temperature induced large scale crystallization of insulin

    NASA Technical Reports Server (NTRS)

    Long, Marianna M.; Delucas, Larry J.; Smith, C.; Carson, M.; Moore, K.; Harrington, Michael D.; Pillion, D. J.; Bishop, S. P.; Rosenblum, W. M.; Naumann, R. J.

    1994-01-01

    One of the major stumbling blocks that prevents rapid structure determination using x-ray crystallography is macro-molecular crystal growth. There are many examples where crystallization takes longer than structure determination. In some cases, it is impossible to grow useful crystals on earth. Recent experiments conducted in conjuction with NASA on various Space Shuttle missions have demonstrated that protein crystals often grow larger and display better internal molecular order than their earth-grown counterparts. This paper reports results from three Shuttle flights using the Protein Crystallization Facility (PCF). The PCF hardware produced large, high-quality insulin crystals by using a temperature change as the sole means to affect protein solubility and thus, crystallization. The facility consists of cylinders/containers with volumes of 500, 200, 100, and 50 ml. Data from the three Shuttle flights demonstrated that larger, higher resolution crystals (as evidenced by x-ray diffraction data) were obtained from the microgravity experiments when compared to earth-grown crystals.

  16. Growth and characterization of ? and ?-glycine single crystals

    NASA Astrophysics Data System (ADS)

    Srinivasan, T. P.; Indirajith, R.; Gopalakrishnan, R.

    2011-03-01

    Single crystals of ?- and ?-glycine were grown by the slow evaporation solution growth method using deionised water as solvent. The ?-glycine was transformed to ?-glycine by addition of KNO3 as additive and both the forms of glycine single crystals were grown and the characteristic properties were studied and compared. From the single crystal XRD analysis the grown ?- and ?-glycine crystals are confirmed. The presence of the functional groups of ?- and ?-glycine was analyzed from the recorded FT-IR spectrum. The optical transmission was ascertained from UV-vis-NIR spectrum. The lower cut-off wavelengths of ?- and ?-glycine are 292 and 272 nm, respectively. The second harmonic generation relative efficiency was measured by the Kurtz and Perry powder technique. Group theoretical analysis predicts 120 vibrational optical modes in ?-glycine and 90 vibrational optical modes in ?-glycine. The TGA, DTA and dielectric studies were carried out to explore information about thermal and dielectric behavior, respectively, for ?- and ?-glycine.

  17. Growth and characterization of rare earths doped triglycine sulfate crystals

    NASA Astrophysics Data System (ADS)

    Batra, A. K.; Guggilla, Padmaja; Cunningham, Dewanna; Aggarwal, M. D.; Lal, R. B.

    2006-01-01

    Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in values of dielectric constant and pyroelectric coefficient is observed while the dielectric loss has increased. Using these parameters, figure-of-merits for their use in infrared sensors have also been reported and compared with pure TGS crystal. The Vickers's hardness of doped TGS crystals along (0 1 0) crystallographic face has increased.

  18. In Situ ?GISAXS: II. Thaumatin Crystal Growth Kinetic

    PubMed Central

    Gebhardt, Ronald; Pechkova, Eugenia; Riekel, Christian; Nicolini, Claudio

    2010-01-01

    The formation of thaumatin crystals by Langmuir-Blodgett (LB) film nanotemplates was studied by the hanging-drop technique in a flow-through cell by synchrotron radiation micrograzing-incidence small-angle x-ray scattering. The kinetics of crystallization was measured directly on the interface of the LB film crystallization nanotemplate. The evolution of the micrograzing-incidence small-angle x-ray scattering patterns suggests that the increase in intensity in the Yoneda region is due to protein incorporation into the LB film. The intensity variation suggests several steps, which were modeled by system dynamics based on first-order differential equations. The kinetic data can be described by two processes that take place on the LB film, a first, fast, process, attributed to the crystal growth and its detachment from the LB film, and a second, slower process, attributed to an unordered association and conversion of protein on the LB film. PMID:20713011

  19. Investigations of interstitial generations near growth interface depending on crystal pulling rates during CZ silicon growth by detaching from the melt

    NASA Astrophysics Data System (ADS)

    Abe, T.; Takahashi, T.; Shirai, K.; Zhang, X. W.

    2016-01-01

    In conventional CZ crystal growth, since formation of a cone tail takes a long time, from such a crystal to have been subject the long heat treatment it is not possible to observe actual distribution of vacancies (Vs) and interstitial atoms (Is) in a straight body of a crystal during growth. This experiment attempted to observe point defect distribution frozen by rapidly cooling a crystal that had been detached from a melt during growth to eliminate the effect of the time delay. Comparison between the experimental results of these specimens and the defect distributions of a conventionally pulled crystals revealed that Vs are introduced at a growth interface and the concentration of the Vs does not depend on the pulling rate. In addition, when the pulling rate is low, Is are generated by thermal stress which increases with increasing thermal gradient G because the amount of heat transfer by mass transfer is decreased and the crystal surface near the growth interface is cooled for longer period. As a result, the generation of Is due to the increase of the thermal stress is observed in an area referred to as an interstitial generation area (IGA) located above the vacancy region on the growth interface, where the crystal temperature is 1300 °C or more. This paper describes the recombination (Rc) mechanism by which these Is created in the IGA are recombined with Vs transformed through the growth interface, thereby creating an observable Rc area at a location where no defect can be detected.

  20. Crystal growth and characterization of semiorganic single crystals of L-histidine family for NLO applications

    NASA Astrophysics Data System (ADS)

    Anandan, Pandurangan; Jayavel, Ramasamy

    2011-05-01

    Single crystals of L-histidine hydrochloride monohydrate and tartaric acid mixed L-histidine hydrochloride monohydrate have been grown by slow evaporation solution growth technique from appropriate mixtures of respective chemicals. Single crystal and powder X-ray diffraction analyses, Fourier transform infrared, nuclear magnetic resonance spectral analysis, thermo-gravimetric (TG), differential thermal analysis (DTA) have been employed to characterize the as-grown crystals. It is observed to be a wide transparency window for both the crystals from 300 to 1000 nm, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd: YAG laser ( ?=1064 nm). The second harmonic generation conversion efficiency of the grown crystal shows the suitability for frequency conversion applications.