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Sample records for growth crystal field

  1. 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.

  2. Electromagnetic Field Effects in Semiconductor Crystal Growth

    NASA Technical Reports Server (NTRS)

    Dulikravich, George S.

    1996-01-01

    This proposed two-year research project was to involve development of an analytical model, a numerical algorithm for its integration, and a software for the analysis of a solidification process under the influence of electric and magnetic fields in microgravity. Due to the complexity of the analytical model that was developed and its boundary conditions, only a preliminary version of the numerical algorithm was developed while the development of the software package was not completed.

  3. Semiconductor Crystal Growth in Static and Rotating Magnetic fields

    NASA Technical Reports Server (NTRS)

    Volz, Martin

    2004-01-01

    Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a

  4. Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

  5. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Schweizer, M.; Cobb, S. D.; Walker, J. S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). The RMF has a marked affect on the interface shape, changing it from concave to nearly flat. The onset of time-dependent flow instabilities occurs when the critical magnetic Taylor number is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The critical magnetic Taylor number is a sensitive function of the aspect ratio and, as the crystal grows under a constant applied magnetic field, the induced striations change from nonperiodic to periodic, undergo a period-doubling transition, and then cease to exist. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.

  6. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Szofran, F. R.; Cobb, S. D.; Schweizer, M.; Walker, J. S.

    2005-01-01

    A series of (100)-oriented gallium-doped germanium crystals has been grown by the vertical Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c)) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. Tm(sup c) decreases as the aspect ratio of the melt increases, and approaches the theoretical limit expected for an infinite cylinder. Intentional interface demarcations are introduced by pulsing the RMF on and off The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased.

  7. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Walker, J. S.; Schweizer, M.; Cobb, S. D.; Szofran, F. R.

    2004-01-01

    A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The experimental data indicate that Tm(sup c) increases as the aspect ratio of the melt decreases. Modeling calculations predicting Tm(sup c) as a function of aspect ratio are in reasonable agreement with the experimental data. The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.

  8. Application of magnetic fields in industrial growth of silicon single crystals

    NASA Astrophysics Data System (ADS)

    von Ammon, W.; Gelfgat, Yu.; Gorbunov, L.; Mulbauer, A.; Muiznieks, A.; Makarov, Y.; Virbulis, J.; Muller, G.

    2006-12-01

    The use of magnetic fields for the growth of semiconductor crystals has already been considered many decades ago. As early as in 1966, Chedzey et al te{1} and Utech et al te{2} reported about InSb crystals grown in a horizontal boat under the influence of a magnetic field. They found a suppression of temperature fluctuations in the InSb melt and a decrease of growth variations (striations) in the crystal. In 1970, Witt et al te{3} applied a static transverse (horizontal) magnetic field to the Czochralski (CZ) growth of InSb crystals. 10 years later, in 1980, the transverse field was also used for the CZ growth of silicon single crystals te{4,5}. Since then, the method has received considerable attention over the years. One of the major driving forces for introducing magnetic fields in the industrial CZ growth of silicon crystals was the request by the semiconductor industry to replace floating zone (FZ) grown crystals, which had been the preferred substrate material for the manufacturing of high power devices, by low oxygen CZ crystals te{6}. The reason for this changeover was the fact that the FZ method in the early 80's could not follow the rapid crystal diameter increase as required by the industry, namely, the switch from 4" to 5" diameter in the early 80's. The application of magnetic fields to the CZ technique (MCZ) allowed the growth of low oxygen crystals with the required diameter and having similar properties as the FZ grown crystals. Figs 12, Refs 59.

  9. 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.

  10. A phase-field model coupled with lattice kinetics solver for modeling crystal growth in furnaces

    SciTech Connect

    Lin, Guang; Bao, Jie; Xu, Zhijie; Tartakovsky, Alexandre M.; Henager, Charles H.

    2014-02-02

    In this study, we present a new numerical model for crystal growth in a vertical solidification system. This model takes into account the buoyancy induced convective flow and its effect on the crystal growth process. The evolution of the crystal growth interface is simulated using the phase-field method. Two novel phase-field models are developed to model the crystal growth interface in vertical gradient furnaces with two temperature profile setups: 1) fixed wall temperature profile setup and 2) time-dependent temperature profile setup. A semi-implicit lattice kinetics solver based on the Boltzmann equation is employed to model the unsteady incompressible flow. This model is used to investigate the effect of furnace operational conditions on crystal growth interface profiles and growth velocities. For a simple case of macroscopic radial growth, the phase-field model is validated against an analytical solution. Crystal growth in vertical gradient furnaces with two temperature profile setups have been also investigated using the developed model. The numerical simulations reveal that for a certain set of temperature boundary conditions, the heat transport in the melt near the phase interface is diffusion dominant and advection is suppressed.

  11. Models of Mass Transport During Microgravity Crystal Growth of Alloyed Semiconductors in a Magnetic Field

    NASA Technical Reports Server (NTRS)

    Ma, Nancy

    2003-01-01

    Alloyed semiconductor crystals, such as germanium-silicon (GeSi) and various II-VI alloyed crystals, are extremely important for optoelectronic devices. Currently, high-quality crystals of GeSi and of II-VI alloys can be grown by epitaxial processes, but the time required to grow a certain amount of single crystal is roughly 1,000 times longer than the time required for Bridgman growth from a melt. Recent rapid advances in optoelectronics have led to a great demand for more and larger crystals with fewer dislocations and other microdefects and with more uniform and controllable compositions. Currently, alloyed crystals grown by bulk methods have unacceptable levels of segregation in the composition of the crystal. Alloyed crystals are being grown by the Bridgman process in space in order to develop successful bulk-growth methods, with the hope that the technology will be equally successful on earth. Unfortunately some crystals grown in space still have unacceptable segregation, for example, due to residual accelerations. The application of a weak magnetic field during crystal growth in space may eliminate the undesirable segregation. Understanding and improving the bulk growth of alloyed semiconductors in microgravity is critically important. The purpose of this grant to to develop models of the unsteady species transport during the bulk growth of alloyed semiconductor crystals in the presence of a magnetic field in microgravity. The research supports experiments being conducted in the High Magnetic Field Solidification Facility at Marshall Space Flight Center (MSFC) and future experiments on the International Space Station.

  12. Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    1996-01-01

    A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

  13. The Effect of a Rotating Magnetic Field on Flow Stability During Crystal Growth

    NASA Technical Reports Server (NTRS)

    Volz, Martin P.; Mazuruk, K.

    2000-01-01

    The effect of a rotating magnetic field on the stability of flow in crystal growth configurations has been experimentally modeled using liquid gallium contained in a finite cylinder and heated from below. Several distinct flow regions were determined as a function of the Rayleigh and Hartmann numbers. At low values of the Rayleigh and Hartmann numbers, a region of stationary flow exists. As the rotating magnetic field is increased, the critical Rayleigh number bounding the stationary flow region can increase by a factor of 10. However, the rotating magnetic field itself induces an instability at a critical value of the Hartmann number independent of the Rayleigh number. In the stationary flow region, the rotating magnetic field can induce fluid motion with velocities several orders of magnitude larger than typical semiconductor crystal growth velocities. Thus, a rotating magnetic field can be used to achieve the benefits of forced convection without triggering deleterious instabilities.

  14. Three-dimensional control of crystal growth using magnetic fields

    NASA Astrophysics Data System (ADS)

    Dulikravich, George S.; Ahuja, Vineet; Lee, Seungsoo

    1993-07-01

    Two coupled systems of partial differential equations governing three-dimensional laminar viscous flow undergoing solidification or melting under the influence of arbitrarily oriented externally applied magnetic fields have been formulated. The model accounts for arbitrary temperature dependence of physical properties including latent heat release, effects of Joule heating, magnetic field forces, and mushy region existence. On the basis of this model a numerical algorithm has been developed and implemented using central differencing on a curvilinear boundary-conforming grid and Runge-Kutta explicit time-stepping. The numerical results clearly demonstrate possibilities for active and practically instantaneous control of melt/solid interface shape, the solidification/melting front propagation speed, and the amount and location of solid accrued.

  15. Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

    PubMed

    Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

    2016-01-19

    We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.

  16. Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

    PubMed

    Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

    2016-01-19

    We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process. PMID:26695105

  17. 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.

  18. 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.

  19. A binary phase field crystal study for liquid phase heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Lu, Yanli; Peng, Yingying; Chen, Zheng

    2016-09-01

    The liquid phase heteroepitaxial growth on predefined crystalline substrate is studied with binary phase field crystal (PFC) model. The purpose of this paper focuses on changes of the morphology of epitaxial films, influences of substrate vicinal angles on epitaxial growth, characteristics of islands growth on both sides of the substrate as well. It is found that the morphology of epitaxial films undergoes the following transitions: layer-by-layer growth, islands formation, mismatch dislocations nucleation and climb towards the film-substrate interface. Meanwhile, the density of steps and islands has obviously direct ratio relations with the vicinal angles. Also, preferential regions are found when islands grow on both sides of the substrate. For thinner substrate, the arrangement of islands is more orderly and the appearance of preferential growth is more obvious than that of thicker substrate. Also, the existing of preferential regions is much more valid for small substrate vicinal angles in contrast for big substrate vicinal angles.

  20. 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.

  1. Polymorphism, crystal nucleation and growth in the phase-field crystal model in 2D and 3D.

    PubMed

    Tóth, Gyula I; Tegze, György; Pusztai, Tamás; Tóth, Gergely; Gránásy, László

    2010-09-15

    We apply a simple dynamical density functional theory, the phase-field crystal (PFC) model of overdamped conservative dynamics, to address polymorphism, crystal nucleation, and crystal growth in the diffusion-controlled limit. We refine the phase diagram for 3D, and determine the line free energy in 2D and the height of the nucleation barrier in 2D and 3D for homogeneous and heterogeneous nucleation by solving the respective Euler-Lagrange (EL) equations. We demonstrate that, in the PFC model, the body-centered cubic (bcc), the face-centered cubic (fcc), and the hexagonal close-packed structures (hcp) compete, while the simple cubic structure is unstable, and that phase preference can be tuned by changing the model parameters: close to the critical point the bcc structure is stable, while far from the critical point the fcc prevails, with an hcp stability domain in between. We note that with increasing distance from the critical point the equilibrium shapes vary from the sphere to specific faceted shapes: rhombic dodecahedron (bcc), truncated octahedron (fcc), and hexagonal prism (hcp). Solving the equation of motion of the PFC model supplied with conserved noise, solidification starts with the nucleation of an amorphous precursor phase, into which the stable crystalline phase nucleates. The growth rate is found to be time dependent and anisotropic; this anisotropy depends on the driving force. We show that due to the diffusion-controlled growth mechanism, which is especially relevant for crystal aggregation in colloidal systems, dendritic growth structures evolve in large-scale isothermal single-component PFC simulations. An oscillatory effective pair potential resembling those for model glass formers has been evaluated from structural data of the amorphous phase obtained by instantaneous quenching. Finally, we present results for eutectic solidification in a binary PFC model. PMID:21386517

  2. Phase-field study of crystal growth in three-dimensional capillaries: Effects of crystalline anisotropy.

    PubMed

    Debierre, Jean-Marc; Guérin, Rahma; Kassner, Klaus

    2016-07-01

    Phase-field simulations are performed to explore the thermal solidification of a pure melt in three-dimensional capillaries. Motivated by our previous work for isotropic or slightly anisotropic materials, we focus here on the more general case of anisotropic materials. Different channel cross sections are compared (square, hexagonal, circular) to reveal the influence of geometry and the effects of a competition between the crystal and the channel symmetries. In particular, a compass effect toward growth directions favored by the surface energy is identified. At given undercooling and anisotropy, the simulations generally show the coexistence of several growth modes. The relative stability of these growth modes is tested by submitting them to a strong spatiotemporal noise for a short time, which reveals a subtle hierarchy between them. Similarities and differences with experimental growth modes in confined geometry are discussed qualitatively. PMID:27575207

  3. Phase-field study of crystal growth in three-dimensional capillaries: Effects of crystalline anisotropy

    NASA Astrophysics Data System (ADS)

    Debierre, Jean-Marc; Guérin, Rahma; Kassner, Klaus

    2016-07-01

    Phase-field simulations are performed to explore the thermal solidification of a pure melt in three-dimensional capillaries. Motivated by our previous work for isotropic or slightly anisotropic materials, we focus here on the more general case of anisotropic materials. Different channel cross sections are compared (square, hexagonal, circular) to reveal the influence of geometry and the effects of a competition between the crystal and the channel symmetries. In particular, a compass effect toward growth directions favored by the surface energy is identified. At given undercooling and anisotropy, the simulations generally show the coexistence of several growth modes. The relative stability of these growth modes is tested by submitting them to a strong spatiotemporal noise for a short time, which reveals a subtle hierarchy between them. Similarities and differences with experimental growth modes in confined geometry are discussed qualitatively.

  4. Ultrathin single-crystal ZnO nanobelts: Ag-catalyzed growth and field emission property

    NASA Astrophysics Data System (ADS)

    Xing, G. Z.; Fang, X. S.; Zhang, Z.; Wang, D. D.; Huang, X.; Guo, J.; Liao, L.; Zheng, Z.; Xu, H. R.; Yu, T.; Shen, Z. X.; Huan, C. H. A.; Sum, T. C.; Zhang, H.; Wu, T.

    2010-06-01

    We report the growth of ultrathin single-crystal ZnO nanobelts by using a Ag-catalyzed vapor transport method. Extensive transmission electron microscopy and atomic force microscopy measurements reveal that the thickness of the ultrathin ZnO nanobelts is ~ 2 nm. Scanning electron microscopy and post-growth annealing studies suggest a '1D branching and 2D filling' growth process. Our results demonstrate the critical role of catalyst in the deterministic synthesis of nanomaterials with the desired morphology. In addition, these ultrafine nanobelts exhibit stable field emission with unprecedented high emission current density of 40.17 mA cm - 2. These bottom-up building blocks of ultrathin ZnO nanobelts may facilitate the construction of advanced electronic and photonic nanodevices.

  5. Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field

    NASA Technical Reports Server (NTRS)

    Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar

    2000-01-01

    This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.

  6. High Resolution Numerical Model of Optically Heated Float-Zone Crystal Growth with Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Huang, Yue; Houchens, Brent

    2008-11-01

    During optically heated float-zone crystal growth processing, thermocapillary forces drive a flow in the melt. This steady, axisymmetric base flow is susceptible to instabilities, resulting in defects as the final crystal is solidified from the melt. To damp these instabilities, a magnetic field is employed. The stability of this flow, neglecting buoyancy, is studied with a full-zone model. The velocity and temperature fields are calculated by a spectral collocation method using Chebyshev polynomials as basis functions. Obtaining accurate base flows is crucial to the success of the subsequent stability analysis. A 2nd order vorticity transport representation is compared with a 4th order stream function representation. At low Hartmann numbers, the results are in good agreement. However, as resolution demands increase, the 2nd order vorticity transport formulation yields a better numerical representation by avoiding large computational errors caused by 4th and 3rd derivatives of Chebyshev terms in the 4th order stream function representation. This allows the stability analysis to be carried out at larger Hartmann numbers, where the critical thermocapillary Reynolds number is much greater.

  7. 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.

  8. 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.

  9. 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.

  10. Growth of dopamine crystals

    NASA Astrophysics Data System (ADS)

    Patil, Vidya; Patki, Mugdha

    2016-05-01

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  11. The Design of a Transparent Vertical Multizone Furnace: Application to Thermal Field Tuning and Crystal Growth

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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 in scientific and commercial applications for determining the optimized process parameters for crystal growth.

  12. A three-dimensional phase field model coupled with lattice kinetics solver for modeling crystal growth in furnaces with accelerated crucible rotation and traveling magnetic field

    SciTech Connect

    Lin, Guang; Bao, Jie; Xu, Zhijie

    2014-11-01

    In this study, which builds on other related work, we present a new three-dimensional numerical model for crystal growth in a vertical solidification system. This model accounts for buoyancy, accelerated crucible rotation technique (ACRT), and traveling magnetic field (TMF) induced convective flow and their effect on crystal growth and the chemical component's transport process. The evolution of the crystal growth interface is simulated using the phase field method. A semi-implicit lattice kinetics solver based on the Boltzmann equation is employed to model the unsteady incompressible flow. A one-way coupled concentration transport model is used to simulate the component fraction variation in both the liquid and solid phases, which can be used to check the quality of the crystal growth.

  13. 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.

  14. Volatilize-controlled oriented growth of the single-crystal layer for organic field-effect transistors.

    PubMed

    Zhao, Haoyan; Li, Dong; Dong, Guifang; Duan, Lian; Liu, Xiaohui; Wang, Liduo

    2014-10-14

    We demonstrate a solution method of volatilize-controlled oriented growth (VOG) to fabricate aligned single crystals of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) on a Si/SiO2 substrate. Through controlling the evaporation rate of the solvent, large-area-aligned single-crystal layers can be achieved on several substrates at the same time, covering over 90% on 2 × 1 cm substrates. The method provides a low-cost, maneuverable technology, which has potential to be used in batch production. We find that the atmosphere of the solvent with high dissolving capacity is in favor of aligned single-crystal growth. Besides, the growth mechanism of the VOG method is investigated in this paper. Top-contact organic field-effect transistors based on the single crystals of TIPS pentacene are achieved on a Si/SiO2 substrate. The optimal device exhibits a field-effect mobility of 0.42 cm(2) V(-1) s(-1) and an on/off current ratio of 10(5). Our research indicates that the VOG method is promising in single-crystal growth on a Si/SiO2 substrate for commercial production.

  15. An unforeseen polymorph of coronene by the application of magnetic fields during crystal growth

    NASA Astrophysics Data System (ADS)

    Potticary, Jason; Terry, Lui R.; Bell, Christopher; Papanikolopoulos, Alexandros N.; Christianen, Peter C. M.; Engelkamp, Hans; Collins, Andrew M.; Fontanesi, Claudio; Kociok-Köhn, Gabriele; Crampin, Simon; da Como, Enrico; Hall, Simon R.

    2016-05-01

    The continued development of novel drugs, proteins, and advanced materials strongly rely on our ability to self-assemble molecules in solids with the most suitable structure (polymorph) in order to exhibit desired functionalities. The search for new polymorphs remains a scientific challenge, that is at the core of crystal engineering and there has been a lack of effective solutions to this problem. Here we show that by crystallizing the polyaromatic hydrocarbon coronene in the presence of a magnetic field, a polymorph is formed in a β-herringbone structure instead of the ubiquitous γ-herringbone structure, with a decrease of 35° in the herringbone nearest neighbour angle. The β-herringbone polymorph is stable, preserves its structure under ambient conditions and as a result of the altered molecular packing of the crystals, exhibits significant changes to the optical and mechanical properties of the crystal.

  16. An unforeseen polymorph of coronene by the application of magnetic fields during crystal growth

    PubMed Central

    Potticary, Jason; Terry, Lui R.; Bell, Christopher; Papanikolopoulos, Alexandros N.; Christianen, Peter C. M.; Engelkamp, Hans; Collins, Andrew M.; Fontanesi, Claudio; Kociok-Köhn, Gabriele; Crampin, Simon; Da Como, Enrico; Hall, Simon R.

    2016-01-01

    The continued development of novel drugs, proteins, and advanced materials strongly rely on our ability to self-assemble molecules in solids with the most suitable structure (polymorph) in order to exhibit desired functionalities. The search for new polymorphs remains a scientific challenge, that is at the core of crystal engineering and there has been a lack of effective solutions to this problem. Here we show that by crystallizing the polyaromatic hydrocarbon coronene in the presence of a magnetic field, a polymorph is formed in a β-herringbone structure instead of the ubiquitous γ-herringbone structure, with a decrease of 35° in the herringbone nearest neighbour angle. The β-herringbone polymorph is stable, preserves its structure under ambient conditions and as a result of the altered molecular packing of the crystals, exhibits significant changes to the optical and mechanical properties of the crystal. PMID:27161600

  17. Thermoelectric Magnetohydrodynamic Flow During Crystal Growth with a Moderate or Weak Magnetic Field

    NASA Technical Reports Server (NTRS)

    Khine, Y. Y.; Walker, John S.; Szofran, Frank R.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    This paper treats a steady, axisymmetric melt motion in a cylindrical ampoule with a uniform, axial magnetic field and with an electric current due to a radial temperature variation along the crystal-melt interface, where the values of the absolute thermoelectric power for the crystal and melt are different. The radial component of the thermoelectric current in the melt produces an azimuthal body force, and the axial variation of the centrifugal force due to the azimuthal motion drives a meridional circulation with radial and axial velocities. For moderate magnetic field strengths, the azimuthal velocity and magnetic field produce a radial induced electric field which partially cancels the Seebeck electromotive force in the melt, so that the thermoelectric current and the melt motion are coupled. For weak magnetic fields, the thermoelectric current is decoupled from the melt motion, which is an ordinary hydrodynamic flow driven by a known azimuthal body force. The results show how the flow varies with the strength of the magnetic field and with the magnitude of the temperature variation along the crystal-melt interface. They also define the parameter ranges for which the simpler weak-field decoupled analysis gives accurate predictions.

  18. Shaped Crystal Growth

    NASA Astrophysics Data System (ADS)

    Tatartchenko, Vitali A.

    Crystals of specified shape and size (shaped crystals) with controlled crystal growth (SCG) defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section shaping technique (CST) grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the

  19. 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.

  20. 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.

  1. 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.

  2. Numerical model of protein crystal growth in a diffusive field such as the microgravity environment.

    PubMed

    Tanaka, Hiroaki; Sasaki, Susumu; Takahashi, Sachiko; Inaka, Koji; Wada, Yoshio; Yamada, Mitsugu; Ohta, Kazunori; Miyoshi, Hiroshi; Kobayashi, Tomoyuki; Kamigaichi, Shigeki

    2013-11-01

    It is said that the microgravity environment positively affects the quality of protein crystal growth. The formation of a protein depletion zone and an impurity depletion zone due to the suppression of convection flow were thought to be the major reasons. In microgravity, the incorporation of molecules into a crystal largely depends on diffusive transport, so the incorporated molecules will be allocated in an orderly manner and the impurity uptake will be suppressed, resulting in highly ordered crystals. Previously, these effects were numerically studied in a steady state using a simplified model and it was determined that the combination of the diffusion coefficient of the protein molecule (D) and the kinetic constant for the protein molecule (β) could be used as an index of the extent of these depletion zones. In this report, numerical analysis of these depletion zones around a growing crystal in a non-steady (i.e. transient) state is introduced, suggesting that this model may be used for the quantitative analysis of these depletion zones in the microgravity environment. PMID:24121357

  3. Faceted growth of primary Al{sub 2}Cu crystals during directional solidification in high magnetic field

    SciTech Connect

    Li, Chuanjun; Ren, Zhongming; Shen, Yu; Wang, Qiuliang; Dai, Yinming; Wang, Hui

    2013-10-21

    The high magnetic field is widely used to modify the crystal morphology. In this work, the effect of the magnetic field on growing behavior of faceted crystals in the Al-40 wt. %Cu alloy was investigated using directional solidification technique. It was found that the faceted growth of primary Al{sub 2}Cu phase was degraded and the primary spacing was reduced upon applying the magnetic field. Additionally, the length of the mushy zone first decreased and then increased with increase of the magnetic field intensity. The quantitative analysis reveals that the shear stress induced by the fluid motion is insufficient to break the atom bonds at the solid-liquid interface. However, both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause dendrites to fracture and reduce the primary spacing. The two effects also weaken the faceting growth. Moreover, the instability of the solid-liquid interface is generated by the TEMF, which further leads to degrade the faceted growth. The length of mushy zone was changed by the TEMC and reached the minimum in the magnetic field of 0.5 T, which is in good agreement with the predicted value (0.83 T)

  4. Quartz crystal growth

    DOEpatents

    Baughman, Richard J.

    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.

  5. 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.

  6. 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.

  7. Crystal Field Handbook

    NASA Astrophysics Data System (ADS)

    Newman, D. J.; Ng, Betty

    2007-09-01

    List of contributors; Preface; Introduction; 1. Crystal field splitting mechanisms D. J. Newman and Betty Ng; 2. Empirical crystal fields D. J. Newman and Betty Ng; 3. Fitting crystal field parameters D. J. Newman and Betty Ng; 4. Lanthanide and actinide optical spectra G. K. Liu; 5. Superposition model D. J. Newman and Betty Ng; 6. Effects of electron correlation on crystal field splitting M. F. Reid and D. J. Newman; 7. Ground state splittings in S-state ions D. J. Newman and Betty Ng; 8. Invariants and moments Y. Y. Yeung; 9. Semiclassical model K. S. Chan; 10. Transition intensities M. F. Reid; Appendix 1. Point symmetry D. J. Newman and Betty Ng; Appendix 2. QBASIC programs D. J. Newman and Betty Ng; Appendix 3. Accessible program packages Y. Y. Yeung, M. F. Reid and D. J. Newman; Appendix 4. Computer package CST Cz. Rudowicz; Bibliography; Index.

  8. Crystal growth of CdTe in space and thermal field effects on mass flux and morphology

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1988-01-01

    The primary, long-range goals are the development of vapor phase crystal growth experiments, and the growth of technologically useful crystals in space. The necessary ground-based studies include measurements of the effects of temperature variations on the mass flux and crystal morphology in vapor-solid growth processes. For in-situ mass flux measurements dynamic microbalance techniques will be employed. Crystal growth procedures and equipment will be developed to be compatible with microgravity conditions and flight requirements. Emphasis was placed on the further development of crystal growth and the investigation of relevant transport properties of CdTe. The dependence of the mass flux on source temperature was experimentally established. The CdTe synthesis and pretreatment procedures are being developed that yield considerable improvements in mass transport rates, and mass fluxes which are independent of the amount of source material. A higher degree of stoichiometric control of CdTe than before was achieved during this period of investigation. Based on this, a CdTe crystal growth experiment, employing physical vapor transport, yielded very promising results. Optical microscopy and X-ray diffraction studies revealed that the boule contained several large sized crystal grains of a high degree of crystallinity. Further characterization studies of CdTe crystals are in progress. The reaction chamber, furnace dimensions, and ampoule location of the dynamic microbalance system were modified in order to minimize radiation effects on the balance performance.

  9. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Rosenblum, William M.; Delucas, Lawrence J.; Wilson, William W.

    1989-01-01

    Major advances have been made in several of the experimental aspects of protein crystallography, leaving protein crystallization as one of the few remaining bottlenecks. As a result, it has become important that the science of protein crystal growth is better understood and that improved methods for protein crystallization are developed. Preliminary experiments with both small molecules and proteins indicate that microgravity may beneficially affect crystal growth. For this reason, a series of protein crystal growth experiments using the Space Shuttle was initiated. 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. Various optical techniques are being utilized to monitor the crystal growth process from the incipient or nucleation stage and throughout the growth phase. The eventual goal of these studies is to develop a system which utilizes optical monitoring for dynamic control of the crystallization process.

  10. Computational analyses of crystal growth

    NASA Technical Reports Server (NTRS)

    Dakhoul, Youssef M.

    1987-01-01

    Two important aspects of Hg/Cd/Te crystal growth processes are discussed. First, the thermal field and second, the fluid movement in the melt zone. The thermal analysis includes numerical calculation of axisymmetric heat conduction within the sample. It also includes a three-dimensional radiation model to calculate the radiative heat exchange between the furnace and the crystal as determined by the complex geometry of the furnace and the adiabatic shield. The thermal analysis also includes a crystal conductivity which is dependent on temperature and composition. To tackle the fluid flow aspect of the problem, an attempt was made to use a newly developed incompressible flow code based on the slight compressibility, and hence the finite sound speed, of all real fluids.

  11. Physical vapor transport crystal growth

    NASA Technical Reports Server (NTRS)

    Yoel, Dave W.; Anderson, Elmer; Wu, Maw-Kuen; Cheng, H. Y.

    1987-01-01

    The goals of this research are two-fold: to study effective means of growing ZnSe crystals of good optical quality and to determine the advantages of growing such crystals in microgravity. As of this date the optimal conditions for crystal growth have not been determined. However, successful growth runs were made in two furnances and the results are given.

  12. 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.

  13. 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)

  14. 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.

  15. 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.

  16. 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.

  17. Concentrating colloids with electric field gradients. I. Particle transport and growth mechanism of hard-sphere-like crystals in an electric bottle.

    PubMed

    Leunissen, Mirjam E; Sullivan, Matthew T; Chaikin, Paul M; van Blaaderen, Alfons

    2008-04-28

    This work concerns the use of electric field gradients to manipulate the local particle concentration in a hard-sphere-like suspension. Inside a specially designed "electric bottle," we observed our colloids to collect in the regions of lowest field strength ("negative dielectrophoresis"). This allows for the use of larger field gradients and stronger dielectrophoretic forces than in the original electric bottle design, which was based on positive dielectrophoresis [M. T. Sullivan et al., Phys. Rev. Lett. 96, 015703 (2006)]. We used confocal scanning laser microscopy to quantitatively follow the time-dependent change in the particle density and the suspension structure. Within a few days, the dielectrophoretic compression was seen to initiate a heterogeneouslike growth of large single crystals, which took place far out-of-equilibrium. The crystals had a random hexagonal close-packed structure and displayed an intriguing growth mechanism, during which the entire crystal was continuously transported, while growing both on the "high-field" and the "low-field" sides, although at different rates. After switching off the electric field, the compressed crystals were found to relax to a lower packing fraction and melt, at a much slower rate than the crystal growth. Besides revealing the particular (far out-of-equilibrium) crystal growth mechanism in these electric bottles, our observations also shed light on the role of the different particle transport processes in the cell and some of the relevant tuning parameters. This is useful for different types of experiments, for instance, focusing more on melting, homogeneous crystallization, or the glass transition.

  18. Direct flow crystal growth system

    DOEpatents

    Montgomery, Kenneth E.; Milanovich, Fred P.

    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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. Surrogate Seeds For Growth Of Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.

    1989-01-01

    Larger crystals of higher quality grown. Alternative method for starting growth of crystal involves use of seed crystal of different material instead of same material as solution. Intended for growing single-crystal proteins for experiments but applicable in general to growth of crystals from solutions and to growth of semiconductor or other crystals from melts.

  4. Plenum type crystal growth process

    DOEpatents

    Montgomery, Kenneth E.

    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.

  5. Crystal growth inside an octant.

    PubMed

    Olejarz, Jason; Krapivsky, P L

    2013-08-01

    We study crystal growth inside an infinite octant on a cubic lattice. The growth proceeds through the deposition of elementary cubes into inner corners. After rescaling by the characteristic size, the interface becomes progressively more deterministic in the long-time limit. Utilizing known results for the crystal growth inside a two-dimensional corner, we propose a hyperbolic partial differential equation for the evolution of the limiting shape. This equation is interpreted as a Hamilton-Jacobi equation, which helps in finding an analytical solution. Simulations of the growth process are in excellent agreement with analytical predictions. We then study the evolution of the subleading correction to the volume of the crystal, the asymptotic growth of the variance of the volume of the crystal, and the total number of inner and outer corners. We also show how to generalize the results to arbitrary spatial dimension. PMID:24032777

  6. 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.

  7. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Carter, Daniel

    1992-01-01

    The overall scientific goals and rationale for growing protein crystals in microgravity are discussed. Data on the growth of human serum albumin crystals which were produced during the First International Microgravity Laboratory (IML-1) are presented. Potential scientific advantages of the utilization of Space Station Freedom are discussed.

  8. 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.

  9. 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.

  10. Crystal growth in salt efflorescence

    NASA Astrophysics Data System (ADS)

    Zehnder, Konrad; Arnold, Andreas

    1989-09-01

    Salt efflorescences strongly affect wall paintings and other monuments. The external factors governing the crystal habits and aggregate forms are studied phenomenologically in laboratory experiments. As salt contaminated materials dry, slats crystallize forming distinct sequences of crystal habits and aggregate forms on and underneath the surfaces. Four phases may be distinguished: (1) Large individual crystals with equilibrium forms grow immersed in a thick solution film; (2) granular crusts of small isometric crystals grow covered by a thin solution film; (3) fibrous crusts of columnar crystals grow from a coherent but thin solution film so that the crystals are in contact with solution only at their base; (4) whiskers grow from isolated spots of very thin solution films into the air. The main factor governing these morphologies is the humidity of the substrate. A porous material cracks while granular crystals (approaching their equilibrium forms) grow within the large pores. As the fissures widen, the habits pass into columnar crystals and then into whiskers. Because this succession corresponds to the crystallization sequence on the substrate surface it can be traced back to the same growth conditions.

  11. (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.

  12. 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.

  13. 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.

  14. Development of the β-BaB2O4 crystal growth technique in the heat field of three-fold axis symmetry

    NASA Astrophysics Data System (ADS)

    Kokh, A. E.; Bekker, T. B.; Vlezko, V. A.; Kokh, K. A.

    2011-03-01

    In our earlier works we have shown the efficiency of β-BaB2O4 crystal growth in the heat field of three-fold axis symmetry. In order to involve the whole body of the high temperature solution in the convective motion it is very important to achieve vertical temperature distribution with the ‘hot points' at the lower part of the growth crucible. At the same time to prevent crystal overgrowth and contact with the crucible wall, the temperature of the latter at the high temperature solution surface must be higher than the crystallization temperature. In order to accomplish such temperature distribution two-zone heating furnace with three heating sectors in each zone has been developed. Load commutator executes power distribution on heating sectors during the growth run. We suppose that developed heating furnace and the system of thermoregulation allow one to achieve stable thermo-gravitational convection in the whole body of high temperature solution, thus substantially delaying the onset of constitutional undercooling.

  15. 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.

  16. Influence of peripheral vibrations and traveling magnetic fields on VGF growth of Sb-doped Ge crystals

    NASA Astrophysics Data System (ADS)

    Dropka, Natasha; Frank-Rotsch, Christiane; Rudolph, Peter

    2016-11-01

    We performed 3D numerical and experimental studies to assess the potential of peripheral low frequency mechanical vibrations for improving the homogeneity of Sb-doped 4″ Ge crystals grown by vertical gradient freeze (VGF). For this study, a novel bell-shaped graphite vibrator was developed for the generation of the axial vibrations in the direction of three-phase junction. Melt stirring by downward traveling magnetic field (TMF) was used as a benchmark. The results showed superiority of peripheral vibrations to TMF stirring concerning radial and longitudinal doping distribution and initial stirring rate. Experimentally observed standing free surface waves in Ge were caused by shielding effect of the vibrator on TMF.

  17. 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.

  18. Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

    NASA Astrophysics Data System (ADS)

    Tao, Yang; Zheng, Chen; Jing, Zhang; Yongxin, Wang; Yanli, Lu

    2016-03-01

    By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. Project supported by the National Natural Science Foundation of China (Grant Nos. 54175378, 51474176, and 51274167), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7261), and the Doctoral Foundation Program of Ministry of China (Grant No. 20136102120021).

  19. Crystal growth and annealing method and apparatus

    DOEpatents

    Gianoulakis, Steven E.; Sparrow, Robert

    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.

  20. 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.

  1. Dendritic Growth in Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Martin, Joshua; Garg, Shila

    2000-03-01

    The experimental study of the onset of electrohydrodynamic convection (EHC) through a dendritic growth is reported. If a magnetic Freedericksz-distorted liquid crystal of negative dielectric anisotropy is subjected to an electric field parallel to the magnetic field, EHC sets in through the nucleation of dendrites [1,2]. Measurements of tip speeds of the dendrites as a function of applied voltage at a fixed magnetic field are made. The goal is to explore the effect of the magnetic and electric fields on the dendritic growth. In addition, pattern dynamics is monitored once the final state of spatio-temporal chaos is reached by the system. [1] J. T. Gleeson, Nature 385, 511 (1997). [2] J. T. Gleeson, Physica A 239, 211 (1997). This research was supported by NSF grants DMR 9704579 and DMR 9619406.

  2. Amazing growth of helium crystal facets

    NASA Astrophysics Data System (ADS)

    Tsymbalenko, V. L.

    2015-11-01

    This review systematizes experimental data from the study of two unusual phenomena: the superslow growth of a perfect, growth-defect-free crystal facet, and the abrupt transition of a crystal facet to an anomalous state with a growth rate greater by two to three orders of magnitude than the normal value (the 'burstlike growth effect').

  3. 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.

  4. 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.

  5. 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.

  6. Protein single crystal growth under microgravity

    NASA Astrophysics Data System (ADS)

    Littke, Walter; John, Christina

    1986-08-01

    Crystal growth conditions for proteins under microgravity were investigated with two model compounds (β-galactosidase and lysozyme). The single crystals obtained have been found to be significantly larger than those prepared in the same environment on earth.

  7. 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.

  8. Controlled growth of semiconductor crystals

    DOEpatents

    Bourret-Courchesne, Edith D.

    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.

  9. Preparation for microgravity science investigation of compound semiconductor crystal growth

    NASA Technical Reports Server (NTRS)

    Fripp, A. L.; Debnam, W. J.; Clark, I. O.; Crouch, R. K.; Carlson, F. M.

    1985-01-01

    Preparatory work on Bridgman directional solidification (BDS) of PbSnTe crystals prior to microgravity crystal growth experiments on Shuttle flights are reported. Gravitational effects become important in crystal growth when density gradients are present. The situation is critical in BDS of PbSnTe because of the necessity of obtaining homogeneous compositional distributions, which can be disturbed when convective processes occur. Numerical models have been defined which quantify the effects of convection in the crystal growth solution. The models were verified by earth-based crystal-growth tests in a two-zone furnace using equal concentrations of each of the elements. Data are provided to demonstrate the differences in composition among crystals grown at different orientations to the gravitational field vector.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. (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.

  16. 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.

  17. 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.

  18. 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.

  19. Crystal field and magnetic properties

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1977-01-01

    Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

  20. Effect of Interaction of the Temperature Field and Supersaturation on the Morphology of the Solid-Vapor Interface in Crystal Growth by Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Grasza, K.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    An in-situ study of the morphology of the solid-vapor interface during iodine crystal growth was done. The conditions for terrace growth, flat faces formation and retraction, competition between sources of steps, formation of protrusions, surface roughening, and defect overgrowth are demonstrated and discussed.

  1. 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.

  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. 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.

  4. 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

  5. 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.

  6. Growth kinetics of tetragonal lysozyme crystals

    NASA Technical Reports Server (NTRS)

    Pusey, M.; Naumann, R.

    1986-01-01

    A method for immobilizing protein crystals in small volumes to determine growth rates on various faces is applied to study the growth kinetics of the (100) face of tetragonal hen-egg white lysozyme crystals at different degrees of bulk saturation. In normal gravity, transport is found to be dominated by convection for crystal sizes larger than a few microns, while in a microgravity environment, transport is diffusion-limited for sizes up to a few mm. It is found that convection can be significant even in microgravity for crystals approaching cm sizes, and that lysozyme growth is limited by surface kinetics in normal gravity.

  7. Sublimation growth of aluminum nitride crystals

    NASA Astrophysics Data System (ADS)

    Gu, Z.; Du, L.; Edgar, J. H.; Nepal, N.; Lin, J. Y.; Jiang, H. X.; Witt, R.

    2006-12-01

    The crystal growth of AlN unseeded on a tungsten crucible lid and seeded on a polycrystalline AlN wafer is compared. AlN crystals with a preferential (0 0 0 1) orientation were achieved in both methods, as demonstrated by electron backscattering diffraction. The AlN grain size increased with the thickness of the AlN crystals. Seeded growth produced larger grains than unseeded growth (average grain size of less than 500 μm compared to 2-3 mm). Photoluminescence confirmed the high quality of the resultant AlN crystals.

  8. Growth of semicarbazone of benzophenone single crystals

    NASA Astrophysics Data System (ADS)

    Vijayan, N.; Ramesh Babu, R.; Gopalakrishnan, R.; Dhanuskodi, S.; Ramasamy, P.

    2002-03-01

    Semicarbazone of benzophenone single crystals have been grown by slow evaporation solution growth technique. The grown crystals have been characterized using XRD, melting point, FT-IR and UV-Vis spectra analyses. The X-ray diffraction analysis reveals that the crystal belongs to the triclinic crystal system and space group P1. From FT-IR studies it is found that the compound possesses both free and hydrogen bonded N-H stretching modes. The hydrogen bonded N-H stretching mode is found to be the major driving force for packing of molecules in the crystals. The transparency of the grown crystals has been confirmed using UV-Vis spectra.

  9. 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.

  10. 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.

  11. Crystal growth and melting in NiZr alloy: Linking phase-field modeling to molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Guerdane, M.; Wendler, F.; Danilov, D.; Teichler, H.; Nestler, B.

    2010-06-01

    We compare results from molecular dynamics simulations with those from phase-field modeling concerning the solidification and melting kinetics of a planar [NicZr1-c]liquid-Zrcrystal interface. Our study is an illustration that both approaches may predict the same quantitative physical description when the key parameters calculated within the atomistic molecular dynamics approach are used to construct the mesoscopic phase-field model. We show in this way that a thermodynamic consistent phase-field model can be applied down to the range of atomic structure. At the same time, molecular dynamics simulation seems to be capable to treat correctly relaxation dynamics, driven by thermodynamic forces, in a nonequilibrium state of solidification and melting. We discuss, in particular, how the free energy from atomistic calculations is used to design the phase dependent free-energy density in the phase-field model. Bridging the gap between both simulation approaches contributes to a better understanding of the thermodynamic and kinetic processes underlying the solidification and melting processes in alloys out of chemical equilibrium. The effective thermodynamic enhancement of the diffusivity through the strong negative enthalpy of mixing in the NiZr solution is discussed.

  12. 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).

  13. Materials discovery through crystal growth

    NASA Astrophysics Data System (ADS)

    zur Loye, Hans-Conrad

    2016-04-01

    The discovery of new materials and associated desirable properties has been a driving force behind chemical innovation for centuries. When we look at some of the many recent technological advances, and how widespread and significant their impact has been, we appreciate how much they have relied on new materials. The increase in hard drive storage capacity due to new giant magneto-resistive materials, the ever-shrinking cell phone due to improved microwave dielectric materials, the enhancement in lithium battery storage capacity due to new intercalation materials, or the improved capacitor due to new ferroelectric materials are all excellent examples. How were these materials discovered? While there is no single answer, in all cases there was a First-Material, the archetype in which the phenomenon was first observed, the one that led to further investigations and the subsequent preparation of improved 2nd or 3rd generation materials. It is this First-Material, the archetype, that was discovered - often via crystal growth.

  14. 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.

  15. Crystal growth of calcium oxalate monohydrate

    NASA Astrophysics Data System (ADS)

    Singh, R. P.; Gaur, S. S.; Sheehan, M. E.; Nancollas, G. H.

    1988-02-01

    The kinetics of crystal growth of calcium oxalate monohydrate has been investigated up to very large extents of growth over a range of supersaturations maintained using the Constant Composition technique. It is suggested that the initial rapid growth of aged seed crystals resulting in marked lattice perfection, reduces the density of growth sites on the crystal surfaces. A method for the preparation of perfected crystallites of calcium oxalate monohydrate through pregrowth of aged crystals has been developed. At large extents of growth with respect to initial seed crystals ( > 200% for aged crystals and 30-60% for pregrown crystals), the rates of crystallization at constant supersaturation undergo marked increases accompanying the formulation of secondary nuclei. These nucleation thresholds depend both upon supersaturation and upon the initial specific surface area of the crystallites and may be important factors in the formation of calcium oxalate stones in vivo. Experiments in whole urine suggest that the kinetics of growth, secondary nucleation, aggregation and cementation of particles may be important factors in kidney stone formation.

  16. Growth of single crystals of BaFe12O19 by solid state crystal growth

    NASA Astrophysics Data System (ADS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-10-01

    Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

  17. Effects of impurities on crystal growth in fructose crystallization

    NASA Astrophysics Data System (ADS)

    Chu, Y. D.; Shiau, L. D.; Berglund, K. A.

    1989-10-01

    The influence of impurities on the crystallization of anhydrous fructose from aqueous solution was studied. The growth kinetics of fructose crystals in the fructose-water-glucose and fructose-water-difructose dianhydrides systems were investigated using photomicroscopic contact nucleation techniques. Glucose is the major impurity likely to be present in fructose syrup formed during corn wet milling, while several difructose dianhydrides are formed in situ under crystallization conditions and have been proposed as a cause in the decrease of overall yields. Both sets of impurities were found to cause inhibition of crystal growth, but the mechanisms responsible in each case are different. It was found that the presence of glucose increases the solubility of fructose in water and thus lowers the supersaturation of the solution. This is probably the main effect responsible for the decrease of crystal growth. Since the molecular structures of difructose dianhydrides are similar to that of fructose, they are probably "tailor-made" impurities. The decrease of crystal growth is probably caused by the incorporation of these impurities into or adsorption to the crystal surface which would accept fructose molecules in the orientation that existed in the difructose dianhydride.

  18. Asteroid core crystallization by inward dendritic growth

    NASA Technical Reports Server (NTRS)

    Haack, Henning; Scott, Edward R. D.

    1992-01-01

    The physics of the asteroid core crystallization process in metallic asteroids is investigated, with special attention given to the initial conditions for core crystallization, the manner of crystallization, the mechanisms acting in the stirring of the liquid, and the effects of elements such as sulfur on crystallization of Fe-Ni. On the basis of theoretical considerations and the published data on iron meteorites, it is suggested that the mode of crystallization in asteroid core was different from the apparent outward concentric crystallization of the earth core, in that the crystallization of asteroidal cores commenced at the base of the mantle and proceeded inward. The inward crystallization resulted in complex dendritic growth. These dendrites may have grown to lengths of hundreds of meters or perhaps even as large as the core radius, thereby dividing the core into separate magma chambers.

  19. 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.

  20. Close-spaced crystal growth and characterization of BP crystals

    NASA Astrophysics Data System (ADS)

    Schmitt, J. O.; Edgar, L. J. H.; Liu, L.; Nagarajan, R.; Szyszko, T.; Podsiadlo, S.; Wojciech, G.

    2005-02-01

    The present study was undertaken to determine if boron phosphide (BP) crystals could be produced by a simple technique, close-spaced vapor transport (CVST). This technique has proven very successful in achieving very high growth rates for a wide variety of materials including ZnSe, AlN, and SiC. Both silicon (100) and sapphire substrates were used for the CSVT growth. The resulting films were characterized by Raman spectroscopy. Sublimation of BP powder from 1050 to 1450 °C in an argon atmosphere produced a range of deep orange colour, single and polycrystalline BP crystals. The crystal size increased and the crystal density decreased with increasing temperature. Well-faceted crystals were produced at an intermediate temperature of 1200 °C. At temperatures higher then 1450 °C no BP crystals were grown. Only a fibrous mass of fine whiskers, loosely attached to the substrate were produced. The peak position of the Raman LO mode of the BP crystals was shifted to higher wavenumbers than the BP powder source, suggesting that the crystals were compressively strained.

  1. Growth Of Oriented Crystals At Polymerized Membranes

    DOEpatents

    Charych, Deborah H. , Berman, Amir

    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. 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.

  3. 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.

  4. 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)

  5. (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.

  6. A Multiscale simulation method for ice crystallization and frost growth

    NASA Astrophysics Data System (ADS)

    Yazdani, Miad

    2015-11-01

    Formation of ice crystals and frost is associated with physical mechanisms at immensely separated scales. The primary focus of this work is on crystallization and frost growth on a cold plate exposed to the humid air. The nucleation is addressed through Gibbs energy barrier method based on the interfacial energy of crystal and condensate as well as the ambient and surface conditions. The supercooled crystallization of ice crystals is simulated through a phase-field based method where the variation of degree of surface tension anisotropy and its mode in the fluid medium is represented statistically. In addition, the mesoscale width of the interface is quantified asymptotically which serves as a length-scale criterion into a so-called ``Adaptive'' AMR (AAMR) algorithm to tie the grid resolution at the interface to local physical properties. Moreover, due to the exposure of crystal to humid air, a secondary non-equilibrium growth process contributes to the formation of frost at the tip of the crystal. A Monte-Carlo implementation of Diffusion Limited Aggregation method addresses the formation of frost during the crystallization. Finally, a virtual boundary based Immersed Boundary Method (IBM) is adapted to address the interaction of ice crystal with convective air during its growth.

  7. 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.

  8. On growth rate hysteresis and catastrophic crystal growth

    NASA Astrophysics Data System (ADS)

    Ferreira, Cecília; 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.

  9. Growth mode of polyethylene single crystals

    SciTech Connect

    Toda, A.; Tanzawa, Y.; Nakagawa, Y.

    1995-12-01

    The growth kinetics and morphology of polyethylene single crystals of narrow molecular weight fractions is reviewed. Single crystals grown from the melt show two types of morphology in the lateral habits; a lenticular shape elongated in the direction of the b-axis (type A) and a truncated lozenge with curved edges of the (100) growth faces (type B). The change in the lateral habits occurs in the vicinity of a transition in the supercooling dependence of growth rate along the b-axis direction. This talk will discuss the mechanism of the change in morphology and growth mode.

  10. 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

  11. 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

  12. 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

  13. Ultraslow growth rates of giant gypsum crystals.

    PubMed

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

    2011-09-20

    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.

  14. 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

  15. Field emission and growth of fullerene nanotubes

    SciTech Connect

    Rinzler, A.G.; Hafner, J.H.; Nilolaev, P.; Colbert, D.T.; Smalley, R.E.

    1994-11-01

    Efforts to control the growth of individual carbon nanotubes from nanotube seed crystals have led to a characterization of their field-induced electron emission behavior. The application of a bias voltage in the growth apparatus was motivated by the prolific formation of nanotubes in the carbon are growth method, in which the electric field appears to play a central role. The authors report here the ability to achieve various tube tip configurations by the controlled application of voltage, heat and chemicals to an individual nanotube, and that these states are well characterized by the emission currents they induce.

  16. Crystal growth and furnace analysis

    NASA Technical Reports Server (NTRS)

    Dakhoul, Youssef M.

    1986-01-01

    A thermal analysis of Hg/Cd/Te solidification in a Bridgman cell is made using Continuum's VAST code. The energy equation is solved in an axisymmetric, quasi-steady domain for both the molten and solid alloy regions. Alloy composition is calculated by a simplified one-dimensional model to estimate its effect on melt thermal conductivity and, consequently, on the temperature field within the cell. Solidification is assumed to occur at a fixed temperature of 979 K. Simplified boundary conditions are included to model both the radiant and conductive heat exchange between the furnace walls and the alloy. Calculations are performed to show how the steady-state isotherms are affected by: the hot and cold furnace temperatures, boundary condition parameters, and the growth rate which affects the calculated alloy's composition. The Advanced Automatic Directional Solidification Furnace (AADSF), developed by NASA, is also thermally analyzed using the CINDA code. The objective is to determine the performance and the overall power requirements for different furnace designs.

  17. 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).

  18. (PCG) Protein Crystal Growth Isocitrate Lyase

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Isocitrate Lyase. 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 for STS-26 was Charles Bugg.

  19. (PCG) Protein Crystal Growth Isocitrate Lysase

    NASA Technical Reports Server (NTRS)

    1989-01-01

    (PCG) Protein Crystal Growth Isocitrate Lysase. 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 on STS-26 was Charles Bugg.

  20. 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.

  1. Sublimation Growth of Titanium Nitride Crystals

    SciTech Connect

    Du, Li; Edgar, J H; Kenik, Edward A; Meyer III, Harry M

    2009-01-01

    The sublimation-recondensation growth of titanium nitride crystal with N/Ti ratio of 0.99 on tungsten substrate is reported. The growth rate dependence on temperature and pressure was determined, and the calculated activation energy is 775.8 29.8kJ/mol. The lateral and vertical growth rates changed with the time of growth and the fraction of the tungsten substrate surface covered. The orientation relationship of TiN (001) || W (001) with TiN [100] || W [110], a 45o angle between TiN [100] and W [100], occurs not only for TiN crystals deposited on W (001) textured tungsten but also for TiN crystals deposited on randomly orientated tungsten. This study demonstrates that this preferred orientational relationship minimizes the lattice mismatch between the TiN and tungsten.

  2. A phase-field-crystal model for liquid crystals.

    PubMed

    Löwen, Hartmut

    2010-09-15

    On the basis of static and dynamical density functional theory, a phase-field-crystal model is derived which involves both the translational density and the orientational degree of ordering as well as a local director field. The model exhibits stable isotropic, nematic, smectic A, columnar, plastic-crystalline and orientationally ordered crystalline phases. As far as the dynamics is concerned, the translational density is a conserved order parameter while the orientational ordering is non-conserved. The derived phase-field-crystal model can serve for use in efficient numerical investigations of various nonequilibrium situations in liquid crystals.

  3. Macromolecular Crystal Growth by Means of Microfluidics

    NASA Technical Reports Server (NTRS)

    vanderWoerd, Mark; Ferree, Darren; Spearing, Scott; Monaco, Lisa; Molho, Josh; Spaid, Michael; Brasseur, Mike; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    We have performed a feasibility study in which we show that chip-based, microfluidic (LabChip(TM)) technology is suitable for protein crystal growth. This technology allows for accurate and reliable dispensing and mixing of very small volumes while minimizing bubble formation in the crystallization mixture. The amount of (protein) solution remaining after completion of an experiment is minimal, which makes this technique efficient and attractive for use with proteins, which are difficult or expensive to obtain. The nature of LabChip(TM) technology renders it highly amenable to automation. Protein crystals obtained in our initial feasibility studies were of excellent quality as determined by X-ray diffraction. Subsequent to the feasibility study, we designed and produced the first LabChip(TM) device specifically for protein crystallization in batch mode. It can reliably dispense and mix from a range of solution constituents into two independent growth wells. We are currently testing this design to prove its efficacy for protein crystallization optimization experiments. In the near future we will expand our design to incorporate up to 10 growth wells per LabChip(TM) device. Upon completion, additional crystallization techniques such as vapor diffusion and liquid-liquid diffusion will be accommodated. Macromolecular crystallization using microfluidic technology is envisioned as a fully automated system, which will use the 'tele-science' concept of remote operation and will be developed into a research facility for the International Space Station as well as on the ground.

  4. 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.

  5. Czochralski silicon crystal growth: Modeling and simulation study

    NASA Astrophysics Data System (ADS)

    Javidi, Massoud

    Czochralski (CZ) crystal growth process is a widely used technique in the manufacturing of silicon crystals and other semiconductor materials such as germanium (Ge) and gallium arsenide (GaAs). The ultimate goal for the Integrated Circuit (IC) industry is to have the highest quality substrate. There is a huge interest to manipulate the thermal field in both the melt and crystal and control the melt convection and crystal-annealing rate in order to reduce growth striations, impurity and dopant inhomogeneity concentrations, excess point defects generation at interface, and micro defects nucleation and growth within the growing crystal. The objective of this investigation has been to facilitate and spearhead the development of a simple/efficient simulation tool for the accurate prediction of global thermal and flow fields and the melt-crystal interface position in the CZ process. The numerical algorithm employs a rectangular (fixed or non-uniform) mesh for enhanced computational efficiency and an enthalpy-based technique for interface tracking. Turbulent flow in the melt is accounted for by utilizing a K-ε model. Radiative heat transfer is modeled in a lumped parameter sense without appreciably compromising on solution accuracy to further allow for CPU times savings. The simulation tool is validated in a number of benchmark flows such as Wheeler's problem. For the CZ crystal growth process, an entire growth cycle has been computed and reliable predictions for the evolution of interface position, and flow/thermal field characteristics have been obtained. The enhanced CPU efficiency of the approach developed here could help integrate it into on-line control strategies.

  6. 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

  7. Method for solid state crystal growth

    DOEpatents

    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.

  8. Growth of oriented molecular sieve crystals on organophosphonate films

    NASA Astrophysics Data System (ADS)

    Feng, S.; Bein, T.

    1994-04-01

    THE successful construction of complex organic/inorganic bio-mimetic systems1-3has demonstrated the great power of supra-molecular pre-organization and templating in controlling crystal growth4. For instance, polar organic surfaces or surface-attached polar groups can induce the formation of thin films of iron oxide5. It would be of great interest, for the design of novel devices such as sensors or catalyst membranes6, to be able to control the growth on surfaces of porous crystals with oriented channels: such channels could, for example, control the access of molecules to the surface of a field-effect transistor in a sensor device. Films and membranes with non-oriented channels have been prepared by depositing or growing zeolite7-12 crystals on metal or metal-oxide supports13-21 in one case21, pre-grown crystals of an aluminophosphate zeolite were oriented by application of an electric field. Here we report the oriented growth of crystals of a zinco-phosphate zeolite on gold surfaces modified with metal phosphonate multilayer films. We attribute the high degree of orientation (>90%) to a strong affinity between the phosphonic acid groups of the phosphate multilayer and the (111) faces of the growing crystals.

  9. 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.

  10. 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

  11. Drop deployment system for crystal growth apparatus

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    A crystal growth apparatus is presented. It utilizes a vapor diffusion method for growing protein crystals, and particularly such an apparatus wherein a ball mixer is used to mix the fluids that form a drop within which crystals are grown. Particular novelty of this invention lies in utilizing a ball mixer to completely mix the precipitate and protein solutions prior to forming the drop. Additional novelty lies in details of construction of the vials, the fluid deployment system, and the fluid storage system of the preferred embodiment.

  12. 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

  13. 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

  14. 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

  15. Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization

    NASA Astrophysics Data System (ADS)

    Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

    2016-03-01

    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.

  16. Fluorination of Metal Phthalocyanines: Single-Crystal Growth, Efficient N-Channel Organic Field-Effect Transistors, and Structure-Property Relationships

    PubMed Central

    Jiang, Hui; Ye, Jun; Hu, Peng; Wei, Fengxia; Du, Kezhao; Wang, Ning; Ba, Te; Feng, Shuanglong; Kloc, Christian

    2014-01-01

    The fluorination of p-type metal phthalocyanines produces n-type semiconductors, allowing the design of organic electronic circuits that contain inexpensive heterojunctions made from chemically and thermally stable p- and n-type organic semiconductors. For the evaluation of close to intrinsic transport properties, high-quality centimeter-sized single crystals of F16CuPc, F16CoPc and F16ZnPc have been grown. New crystal structures of F16CuPc, F16CoPc and F16ZnPc have been determined. Organic single-crystal field-effect transistors have been fabricated to study the effects of the central metal atom on their charge transport properties. The F16ZnPc has the highest electron mobility (~1.1 cm2 V−1 s−1). Theoretical calculations indicate that the crystal structure and electronic structure of the central metal atom determine the transport properties of fluorinated metal phthalocyanines. PMID:25524460

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Convective flow effects on protein crystal growth

    NASA Astrophysics Data System (ADS)

    Rosenberger, Franz; Monaco, Lisa A.

    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

  2. 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

  3. Method for crystal growth control

    DOEpatents

    Yates, Douglas A.; Hatch, Arthur E.; Goldsmith, Jeff M.

    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.

  4. 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.

  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. 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).

  7. 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.

  8. (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.

  9. Simulated morphological landscape of polymer single crystals by phase field model

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Shi, Tongfei; Chen, Jizhong; An, Lijia; Jia, Yuxi

    2008-11-01

    The novel phase field model with the "polymer characteristic" was established based on a nonconserved spatiotemporal Ginzburg-Landau equation (TDGL model A). Especially, we relate the diffusion equation with the crystal growth faces of polymer single crystals. Namely, the diffusion equations are discretized according to the diffusion coefficient of every lattice site in various crystal growth faces and the shape of lattice is selected based on the real proportion of the unit cell dimensions. Spatiotemporal growth of syndiotactic polypropylene single crystals during isothermal crystallization has been investigated theoretically based on this phase field model. Two dimensional numerical calculations are performed to elucidate the faceted single crystal growth including square, rectangular, lozenge-shaped, and hexagonal single crystals. Our simulated patterns are in good agreement with the experimental morphologies, and the physical origin of polymer single crystal growth is discussed.

  10. Patterned growth of single-crystal 3, 4, 9, 10-perylenetetracarboxylic dianhydride nanowire arrays for field-emission and optoelectronic devices.

    PubMed

    Pan, Huanhuan; Zhang, Xiujuan; Yang, Yang; Shao, Zhibin; Deng, Wei; Ding, Ke; Zhang, Yu; Jie, Jiansheng

    2015-07-24

    3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) organic nanostructures possess extraordinary electronic and optoelectronic properties. However, it remains a challenge to achieve patterned growth of PTCDA nanowire (NW) arrays for integrated device applications. Here, we demonstrated the high-density, large-area, uniform, and cross-aligned growth of single-crystalline PTCDA NW arrays by using Au nanoparticles (NPs) as the growth templates. The high surface energy of Au NPs led to the cross-aligned growth of organic NWs, enabling the growth of PTCDA NW arrays with any desirable patterns by pre-patterning the Au films on a Si substrate. The PTCDA NW arrays as field emitters show good performance with a large emission current density and high emission stability. Furthermore, photodetectors based on PTCDA NW arrays were constructed via a simple in-situ growth approach, which exhibited high sensitivity to a wideband light ranging from 400-800 nm and surpassed the individual NW-based photodetectors in terms of higher photocurrent and faster response speed. Successful applications of PTCDA NW arrays in field emission and photodetectors show a great potential application of organic NW arrays in future efficient electronic and optoelectronic devices. PMID:26135069

  11. Apparatus for monitoring crystal growth

    DOEpatents

    Sachs, Emanual M.

    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.

  12. Method of monitoring crystal growth

    DOEpatents

    Sachs, Emanual M.

    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.

  13. 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

    " 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.

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

    NASA Astrophysics Data System (ADS)

    Chernov, A. A.

    2010-07-01

    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.

  15. 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.

  16. 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.

  17. Growth of single crystals by vapor transport

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1978-01-01

    The primary objectives of the program were to establish basic vapor transport and crystal growth properties and to determine thermodynamic, kinetic and structural parameters relevant to chemical vapor transport systems for different classes of materials. An important aspect of these studies was the observation of the effects of gravity-caused convection on the mass transport rate and crystal morphology. These objectives were accomplished through extensive vapor transport, thermochemical and structural studies on selected Mn-chalcogenides, II-VI and IV-VI compounds.

  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. Flux growth of BPO 4 crystals

    NASA Astrophysics Data System (ADS)

    Li, Zhihua; Wu, Yicheng; Fu, Peizhen; Pan, Shilie; Chen, Chuangtian

    2004-10-01

    Single crystals of BPO4 with sizes up to 15×10×12 mm3 were grown by top-seeded solution growth method using Li2O-Li4P2O7 as fluxes. The components volatilized from the melt were characterized by the method of X-ray powder diffraction. The defects of grown crystals have also been investigated. The measured ultraviolet cutoff edge of BPO4 was about 130 nm. Its density was 2.82 g/cm3 determined using drainage method.

  20. Crystal growth and annealing for minimized residual stress

    DOEpatents

    Gianoulakis, Steven E.

    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.

  1. 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.

  2. 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.

  3. Convective flow effects on protein crystal growth

    NASA Astrophysics Data System (ADS)

    Rosenberger, Franz; Monaco, Lisa A.

    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.

  4. 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.

  5. (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.

  6. (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.

  7. 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.

  8. CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

    PubMed

    De Yoreo, James J; Gilbert, Pupa U P A; Sommerdijk, Nico A J M; Penn, R Lee; Whitelam, Stephen; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D; Navrotsky, Alexandra; Banfield, Jillian F; Wallace, Adam F; Michel, F Marc; Meldrum, Fiona C; Cölfen, Helmut; Dove, Patricia M

    2015-07-31

    Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. PMID:26228157

  9. Optical Investigation of Nanoconfined Crystal Growth

    NASA Astrophysics Data System (ADS)

    Kohler, F.; Dysthe, D. K.

    2015-12-01

    Crystals growing in a confined space exert forces on their surroundings. This crystallization force causes deformation of solids and is therefore particularly relevant for the comprehension of geological processes such as replacement and weathering [1]. In addition, these forces are relevant for the understanding of damages in porous building materials caused by crystallization, which is of great economical importance and fundamental for methods that can help to preserve our cultural heritage [2,3]. However, the exact behavior of the growth and the dissolution process in close contact to an interface are still not known in detail. The crystallization, the dissolution and the transport of material is mediated by a nanoconfined water film. We observe brittle NaClO3 crystals growing against a glass surface by optical methods such as reflective interference contrast microscopy (RICM) [4]. In order to carefully control the supersaturation of the fluid close to the crystal interface, a temperature regulated microfluidic system is used (fig. A). The interference based precision of RICM enables to resolve distance variations down to the sub nanometer range without any unwanted disturbances by the measuring method. The combination of RICM with a sensitive camera allows us to observe phenomena such as periodic, wavelike growth of atomic layers. These waves are particularly obvious when observing the difference between two consecutive images (fig. B). In contradiction to some theoretical results, which predict a smooth interface, some recent experiments have shown that the nanoconfined growth surfaces are rough. In combination with theoretical studies and Kinetic Monte Carlo simulations we aim at providing more realistic descriptions of surface energies and energy barriers which are able to explain the discrepancies between experiments and current theory. References:[1] Maliva, Diagenetic replacement controlled by force of crystallization, Geology, August (1988), v. 16 [2] G

  10. 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.

  11. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study

    NASA Astrophysics Data System (ADS)

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-05-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection.

  12. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study.

    PubMed

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-05-23

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection.

  13. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study.

    PubMed

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-01-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection. PMID:27210816

  14. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study

    PubMed Central

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-01-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection. PMID:27210816

  15. The Biological Macromolecule Crystallization Database and NASA Protein Crystal Growth Archive.

    PubMed

    Gilliland, G L; Tung, M; Ladner, J

    1996-01-01

    The NIST/NASA/CARB Biological Macromolecule Crystallization Database (BMCD), NIST Standard Reference Database 21, contains crystal data and crystallization conditions for biological macromolecules. The database entries include data abstracted from published crystallographic reports. Each entry consists of information describing the biological macromolecule crystallized and crystal data and the crystallization conditions for each crystal form. The BMCD serves as the NASA Protein Crystal Growth Archive in that it contains protocols and results of crystallization experiments undertaken in microgravity (space). These database entries report the results, whether successful or not, from NASA-sponsored protein crystal growth experiments in microgravity and from microgravity crystallization studies sponsored by other international organizations. The BMCD was designed as a tool to assist x-ray crystallographers in the development of protocols to crystallize biological macromolecules, those that have previously been crystallized, and those that have not been crystallized.

  16. Efg Crystal Growth Apparatus And Method

    SciTech Connect

    Mackintosh, Brian H.; Ouellette, Marc

    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.

  17. Convective flow effects on protein crystal growth

    NASA Technical Reports Server (NTRS)

    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.

  18. 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.

  19. Convective diffusion in protein crystal growth

    NASA Technical Reports Server (NTRS)

    Baird, J. K.; Meehan, E. J., Jr.; Xidis, A. L.; Howard, S. B.

    1986-01-01

    A protein crystal modeled as a flat plate suspended in the parent solution, with the normal to the largest face perpendicular to gravity and the protein concentration in the solution adjacent to the plate taken to be the equilibrium solubility, is studied. The Navier-Stokes equation and the equation for convective diffusion in the boundary layer next to the plate are solved to calculate the flow velocity and the protein mass flux. The local rate of growth of the plate is shown to vary significantly with depth due to the convection. For an aqueous solution of lysozyme at a concentration of 40 mg/ml, the boundary layer at the top of a 1-mm-high crystal has a thickness of 80 microns at 1 g, and 2570 microns at 10 to the -6th g.

  20. 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.

  1. Bulk crystal growth of scintillator materials for gamma ray detectors

    NASA Astrophysics Data System (ADS)

    Aggarwal, Mohan

    2008-10-01

    Within the past few years, it has been demonstrated that several new rare earth halide scintillation detector crystals such as cerium doped lanthanum bromide (LaBr3:Ce) have high output and improved energy deposit to light linearity and thus they can substantially enhance the performance of the next generation of gamma ray detectors. These detectors have a variety of applications in NASA hard x-ray and gamma ray missions, high energy physics, home land security and medical imaging applications. This cerium doped lanthanum bromide crystal has ˜1100% the light output of BGO, resulting in better energy resolution than conventional scintillators. This is equivalent to 60000 photons per MeV of deposited energy. This new series of scintillator materials promise to usher a breakthrough in the field, if sufficiently large and clear crystals of this material can be grown. These halides however are highly hygroscopic and hence pose some difficulty in growing crystals. Efforts are being made to grow this and other materials in this family of crystals and successful results have been achieved. An overview of the challenges encountered during the synthesis and melt crystal growth of these rare earth halide scintillators shall be presented.

  2. 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.

  3. 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

  4. Crystal growth kinetics of the two-step model

    NASA Astrophysics Data System (ADS)

    Tai, Clifford Y.; Lin, Chiu-Hsiung

    1987-03-01

    The single crystal technique was used to measure the growth rate of the potassium alum (111) face and the magnesium sulfate (110) face. The two-step model was found appropriate to describe the growth kinetics with the surface integration order of two for potassium alum crystal and of one for magnesium sulfate crystal. The individual rate constants, Kd and Kr, were determined accordingly.

  5. 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.

  6. The influence of internal crystal perfection on growth rate dispersion in a continuous suspension crystallizer

    NASA Astrophysics Data System (ADS)

    Zacher, U.; Mersmann, A.

    1995-01-01

    The objective of the work presented here is to demonstrate the influence of induced lattice strain on growth behaviour of potassium alum crystals in a continuously operated mixed suspension mixed product removal (MSMPR) crystallizer. Therefore crystal size distributions in the crystallizer and individual growth velocities, especially of small particles (initial size 20-60 μm) in a flow-through cell, were simultaneously determined. Moreover Laue diffraction patterns of crystals withdrawn from the MSMPR crystallizer were carried out indicating lattice deformation and strain. Most crystals exhibit constant crystal growth (CCG) behaviour with significant growth rate dispersion. The mean growth rate of small particles in the sub-sieve size range is considerably smaller than the mean rate of product sized crystals at constant supersaturation. Small potash alum crystals show a clear tendency of increased lattice strain with increasing supersaturation which can be explained by the refaceting process of attrition nuclei in the crystallizer. The average amount of induced strain in crystals having the same growth history is obviously related to crystal size. Only slightly strained particles with sufficiently high growth rates will reach the product size range in the MSMPR crystallizer.

  7. Crystal fields in UO2 - revisited

    SciTech Connect

    Nakotte, Heinz; Rajatram, R; Mcqueeney, R J; Lander, G H; Robinson, R A

    2009-01-01

    We performed inelastic neutron scattering (INS) in order to re-investigate the crystal-field ground state and the level splitting in UO{sub 2}. Previous INS studies on UO{sub 2} by Amorelli et al. [Physical Review B 15, 1989, 1856] uncovered four excitations at low temperatures in the 150-180 meV range. Considering the dipole-allowed transitions, only three of these transitions could be explained by the published crystal-field model. Our INS results on a different UO{sub 2} sample revealed that the unaccounted peak at about 180 meV is a spurious one, and thus not intrinsic to UO{sub 2}. In good agreement with Amoretti's results, we corroborated that the ground-state of UO{sub 2} is the {Lambda}{sub 5} triplet, and we computed that the fourth- and six-order crystal field parameters are V{sub 4} = -116 meV and V{sub 6} = 26 meV, respectively. We also studied the INS response of the non-magnetic U{sub 0.4}Th{sub 0.6}O{sub 2}. The splitting for this thorium-doped compound is similar to the one of UO{sub 2}, which orders antiferromagnetically at low temperatures. Therefore, we can conclude that magnetic interactions only weakly perturb the energy level splitting, which is dominated by strong crystal fields.

  8. An automated protein crystal growth facility on the space station

    NASA Technical Reports Server (NTRS)

    Herrmann, Melody

    1988-01-01

    The need is addressed for an automated Protein Crystal Growth experiment on the Space Station and how robotics will be integrated into the system design. This automated laboratory system will enable several hundred protein crystals to grow simultaneously in microgravity and will allow the major variables in protein crystal growth to be monitored and controlled during the experiment. Growing good quality crystals is important in determining the complete structure of the protein by X-ray diffraction. This information is useful in the research and development of medicines and other important medical and biotechnological products. Previous Protein Crystal Growth experiments indicate that the microgravity environment of space allows larger crystals of higher quality to be grown as compared to the same crystals grown on the ground. It is therefore important to have a laboratory in space where protein crystals can be grown under carefully controlled conditions so that a crystal type can be reproduced as needed.

  9. 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.

  10. Investigation of growth of AgX tabular crystals.

    PubMed

    Larichev, T A; Kagakin, E I

    1998-07-15

    The process of tabular crystal formation during physical ripening of fine AgX (X=Br,I) emulsions is investigated. The tabular crystal growth is realized simultaneously via two mechanisms: ionic and coalescent. The relative contribution of those mechanisms to the tabular crystal growth is determined by the conditions of the physical ripening. It is possible to control the size and shape uniformity of the final AgX tabular crystals by adjusting the relative contributions of these mechanisms.

  11. Nephrocalcin isoforms coat crystal surfaces and differentially affect calcium oxalate monohydrate crystal morphology, growth, and aggregation

    NASA Astrophysics Data System (ADS)

    Kurutz, Josh W.; Carvalho, Mauricio; Nakagawa, Yasushi

    2003-08-01

    Calcium oxalate crystals were grown in the presence of each of the four isoforms of nephrocalcin (NC), a urinary protein proposed to inhibit kidney stone growth. Crystal size, morphology, and surface topography were assessed using optical microscopy, Coulter counter measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). All crystals grown in the presence of NC isoforms were calcium oxalate monohydrates (COMs). Crystals formed in the presence of NC-A were smaller than control crystals, which were grown without NC, according to optical and SEM results, suggesting that NC-A restricts crystal growth. In contrast, samples grown with NC-C and NC-D exhibit more large crystals and several crystal aggregates, suggesting that NC-C and -D promote crystal growth and aggregation. Crystals grown with NC-B are not significantly larger or smaller than controls. AFM images of the crystals reveal significantly different surface textures on the control crystals relative to those grown with NC isoforms, indicating that NC acts by coating nascent calcium oxalate crystals. These are the first reported AFM images that show topography of NC-coated crystals. These findings suggest that NC isoforms have distinct interactions with different COM crystal faces, which may be responsible for their different effects on crystal growth and morphology.

  12. 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.

  13. Consistent Hydrodynamics for Phase Field Crystals.

    PubMed

    Heinonen, V; Achim, C V; Kosterlitz, J M; Ying, See-Chen; Lowengrub, J; Ala-Nissila, T

    2016-01-15

    We use the amplitude expansion in the phase field crystal framework to formulate an approach where the fields describing the microscopic structure of the material are coupled to a hydrodynamic velocity field. The model is shown to reduce to the well-known macroscopic theories in appropriate limits, including compressible Navier-Stokes and wave equations. Moreover, we show that the dynamics proposed allows for long wavelength phonon modes and demonstrate the theory numerically showing that the elastic excitations in the system are relaxed through phonon emission. PMID:26824543

  14. Growth of urea crystals by physical vapor transport

    NASA Technical Reports Server (NTRS)

    Feigelson, R. S.; Route, R. K.; Kao, T.-M.

    1985-01-01

    This work demonstrates that high optical quality crystals of urea can be grown by the physical vapor transport method. The unique features of this method are compared with growth from methanol/water solutions. High growth rates, exceeding 2.5 mm/day, were achieved, and cm-size optical quality single crystals were obtained. Details of the growth technique and the physical properties of the crystals are presented.

  15. Crystal growth of calcium sulphate dihydrate at low supersaturation

    NASA Astrophysics Data System (ADS)

    Christoffersen, M. R.; Christoffersen, J.; Weijnen, M. P. C.; Van Rosmalen, G. M.

    1982-08-01

    The growth rate of calcium sulphate dihydrate crystals, gypsum, in aqueous suspension has been shown to be screw dislocation controlled in the supersaturation range 1.03< {C}/{C s}<1.15 . Constant composition experiments show that the overall rate of growth decreases with increasing mass of the crystals. A combination of normal spiral growth, growth of cooperating spirals with non-parallel Burgers vectors, and growth of grain boundary spirals, together with partial outgrowth of concave parts of the crystals, can explain the rate of growth found for different preparations of gypsum crytals.

  16. In-situ Optical Waveguides for Monitoring and Modifying Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gibson, Ursula; Osterberg, Ulf

    2004-01-01

    The use of electric fields in the growth of protein crystals was investigated, both theoretically and experimentally. We used dc, ac and optical fields to change the spatial distribution of proteins. Dc fields had only local effects, due to the conductivity of the growth solution. We found that for low frequency fields, movement of the buffer and salt ions dominated, and that for high frequency ac fields, &electrophoretic effects could be useful for relocating growing protein crystals. The most promising result was that for optical fields, a large gradient in the field could be used to capture a crystal, and observe growth in-situ. This concept could be developed into an experimental setup compatible with automated x-ray diffraction measurements in microgravity.

  17. Surface-engineered growth of AgIn₅S₈ crystals.

    PubMed

    Lai, Chia-Hung; Chiang, Ching-Yeh; Lin, Po-Chang; Yang, Kai-Yu; Hua, Chi Chung; Lee, Tai-Chou

    2013-05-01

    The growth of semiconductor crystals and thin films plays an essential role in industry and academic research. Considering the environmental damage caused by energy consumption during their fabrication, a simpler and cheaper method is desired. In fact, preparing semiconductor materials at lower temperatures using solution chemistry has potential in this research field. We found that solution chemistry, the physical and chemical properties of the substrate surface, and the phase diagram of the multicomponent compound semiconductor have a decisive influence on the crystal structure of the material. In this study, we used self-assembled monolayers (SAMs) to modify the silicon/glass substrate surface and effectively control the density of the functional groups and surface energy of the substrates. We first employed various solutions to grow octadecyltrichlorosilane (OTS), 3-mercaptopropyl-trimethoxysilane (MPS), and mixed OTS-MPS SAMs. The surface energy can be adjusted between 24.9 and 50.8 erg/cm(2). Using metal sulfide precursors in appropriate concentrations, AgIn5S8 crystals can be grown on the modified substrates without any post-thermal treatment. We can easily adjust the nucleation in order to vary the density of AgIn5S8 crystals. Our current process can achieve AgIn5S8 crystals of a maximum of 1 μm in diameter and a minimum crystal density of approximately 0.038/μm(2). One proof-of-concept experiment demonstrated that the material prepared from this low temperature process showed positive photocatalytic activity. This method for growing crystals can be applied to the green fabrication of optoelectronic materials.

  18. On Favorable Thermal Fields for Detached Bridgman Growth

    NASA Technical Reports Server (NTRS)

    Stelian, Carmen; Volz, Martin P.; Derby, Jeffrey J.

    2009-01-01

    The thermal fields of two Bridgman-like configurations, representative of real systems used in prior experiments for the detached growth of CdTe and Ge crystals, are studied. These detailed heat transfer computations are performed using the CrysMAS code and expand upon our previous analyses [14] that posited a new mechanism involving the thermal field and meniscus position to explain stable conditions for dewetted Bridgman growth. Computational results indicate that heat transfer conditions that led to successful detached growth in both of these systems are in accordance with our prior assertion, namely that the prevention of crystal reattachment to the crucible wall requires the avoidance of any undercooling of the melt meniscus during the growth run. Significantly, relatively simple process modifications that promote favorable thermal conditions for detached growth may overcome detrimental factors associated with meniscus shape and crucible wetting. Thus, these ideas may be important to advance the practice of detached growth for many materials.

  19. 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.

  20. 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 ( σ = 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).

  1. 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.

  2. Flux free growth of superconducting FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Maheshwari, P. K.; Joshi, L. M.; Gahtori, Bhasker; Srivastava, A. K.; Gupta, Anurag; Patnaik, S. P.; Awana, V. P. S.

    2016-07-01

    We report flux free growth of superconducting FeSe single crystals by an easy and versatile high temperature melt and slow cooling method for first time. The room temperature x-ray diffraction (XRD) on the surface of the piece of such obtained crystals showed single [101] plane of β-FeSe tetragonal phase. The bulk powder XRD, being obtained by crushing the part of crystal chunk showed majority (∼87%) β-FeSe tetragonal (space group P4/nmm) and minority (∼13%) δ-FeSe hexagonal (space group P63/mmc) crystalline phases. Detailed high resolution transmission electron microscope images along with selected area electron diffraction showed the abundance of both majority β-FeSe and minority δ-FeSe phases. Both transport (ρ-T) and magnetization exhibited superconductivity at below around 10 K. Interestingly, the magnetization signal of these crystals is dominated by the magnetism of minority δ-FeSe magnetic phase, and hence the isothermal magnetization at 4 K was seen to be ferromagnetic like. Transport (ρ-T) measurements under magnetic field showed superconductivity onset at below 12 K, and ρ = 0 (T c) at 9 K. Superconducting transition temperature (T c) decreases with applied field to around 6 K at 7 T, with dT c/dH of ∼0.4 K T‑1, giving rise to an H c2(0) value of around 50 , 30 and 20 T for normal resistivity ρ n = 90%, 50% and 10% respectively, which are calculated from conventional one band Werthamer–Helfand–Hohenberg equation. FeSe single crystal activation energy is calculated from thermally activated flux flow model which is found to decreases with field from 12.1 meV for 0.2 T to 3.77 meV for 7 T.

  3. Calcium oxalate crystal growth in human urinary stones

    SciTech Connect

    Kim, K.M.; Johnson, F.B.

    1981-01-01

    Calcium oxalate stones are very common and increasing. Crystal growth is no less important than the crystal nucleation in the pathogenesis of stone formation. The crystal growth was studied in human calcium oxalate stones by a combined electron microscopy and x-ray diffraction. The main mode of weddellite growth was interpenetration twinning of tetrahedral bipyramids. Bipyramids may form as initial crystal seeds, develop from anhedral crystals (crystals which lack flat symmetric faces) of spherular or mulberry shape, develop on the surface of preformed bipyramids by spiral dislocation mechanisms, or develop on whewellite crystal by heterogeneous nucleation and epitaxy. Heterogeneous nucleations of whewellite on weddellite, and calcium apatite on whewellite were also observed. Whewellite grew mainly by parallel twinning. Interpenetration twinning was exceptional. Transformation of anhedral to euhedral (completely bounded by flat faces that are set ar fixed angles to one another) whewellite occurred by parallel fissurations followed by brick wall like stacking of the crystals, while euhedral transformation of weddellite occurred by protrusion of bipyramids frm anhedral crystal surface. Occasionally, an evidence of crystal dissolution was noted. Although an aggregation of crystals is believed to play a pivotal role in stone nidus formation, growth in size of the formed crystals, and twinning and epitactic crystal intergrowth apparently play a significant role in the obstructive urinary stone formation.

  4. 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).

  5. Crystal growth of Ba 3BP 3O 12 with BPO 4-NaF flux

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Jun; Wang, Hong; Hu, Guan-Qin; Chen, Hao-Hong; Yang, Xin-Xin; Zhao, Jing-Tai

    2010-04-01

    Single crystals of Ba 3BP 3O 12 with size of 10×8×2 mm 3 have been grown by the top-seeded solution growth (TSSG) method using BPO 4-NaF mixture as the flux. The crystals were characterized by X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and transmittance spectrum. Ba 3BP 3O 12 single crystal exhibits wide transparency in the range 250-800 nm. The preparation process of starting materials and the effect of flux on the crystal growth were discussed.

  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. Simulation of the flow and mass transfer for KDP crystals undergoing 2D translation during growth

    NASA Astrophysics Data System (ADS)

    Zhou, Chuan; Li, Mingwei; Hu, Zhitao; Yin, Huawei; Wang, Bangguo; Cui, Qidong

    2016-09-01

    In this study, a novel motion mode for crystals during growth, i.e., 2D translation, is proposed. Numerical simulations of flow and mass transfer are conducted for the growth of large-scale potassium dihydrogen phosphate (KDP) crystals subjected to the new motion mode. Surface supersaturation and shear stress are obtained as functions of the translational velocity, distance, size, orientation of crystals. The dependence of these two parameters on the flow fields around the crystals is also discussed. The thicknesses of the solute boundary layer varied with translational velocity are described. The characteristics of solution flow and surface supersaturation distribution are summarized, where it suggests that the morphological stability of a crystal surface can be enhanced if the proposed 2D translation is applied to crystal growth.

  8. Nucleation and crystal growth in laser patterned lines in glasses

    NASA Astrophysics Data System (ADS)

    Komatsu, Takayuki; Honma, Tsuyoshi

    2016-07-01

    Laser-induced crystallization is a new method for the design and control of the crystallization of glasses and opens a new door in the study of nucleation and crystal growth in glasses. Nonlinear optical Sm-doped -BaB2O4 (-BBO) crystal lines were patterned by continuous wave Yb:YVO4 fiber laser (wavelength 1080 nm) in 8Sm2O3-42BaO-50B2O3 glass as an example, and nucleation and crystal growth behaviors in the laser-patterned bending and crossing lines were examined. It was confirmed that the growth of c-axis oriented -BBO crystals follows along the laser scanning direction even if laser scanning direction changes. The model of self-organized homo-epitaxial crystal growth was demonstrated for the orientation of -BBO crystals at the crossing point of two lines, in which the first crystal line at the crossing point acts as nucleation site for the second crystal line. This study proposes a new crystal growth technology.

  9. Using Magnetic Fields to Control Convection during Protein Crystallization: Analysis and Validation Studies

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F. W.

    2004-01-01

    The effect of convection during the crystallization of proteins is not very well understood. In a gravitational field, convection is caused by crystal sedimentation and by solutal buoyancy induced flow and these can lead to crystal imperfections. While crystallization in microgravity can approach diffusion limited growth conditions (no convection), terrestrially strong magnetic fields can be used to control fluid flow and sedimentation effects. In this work, we develop the analysis for magnetic flow control and test the predictions using analog experiments. Specifically, experiments on solutal convection in a paramagnetic fluid were conducted in a strong magnetic field gradient using a dilute solution of Manganese Chloride. The observed flows indicate that the magnetic field can completely counter the settling effects of gravity locally and are consistent with the theoretical predictions presented. This phenomenon suggests that magnetic fields may be useful in mimicking the microgravity environment of space for some crystal growth ana biological applications where fluid convection is undesirable.

  10. Reinvestigation of growth of 'L-valine zinc sulphate' crystal.

    PubMed

    Srinivasan, Bikshandarkoil R; Jyai, Rita N

    2014-01-01

    A reinvestigation of the growth of l-valine zinc sulphate crystal is reported. The slow evaporation of an aqueous solution containing l-valine and zinc sulphate heptahydrate results in the fractional crystallization of l-valine and not the organic inorganic hybrid nonlinear optical l-valine zinc sulphate crystal, as reported by Puhal Raj and Ramachandra Raja (2012).

  11. 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.

  12. Growth and properties of Lithium Salicylate single crystals

    SciTech Connect

    Zaitseva, N; Newby, J; Hull, G; Saw, C; Carman, L; Cherepy, N; Payne, S

    2009-02-13

    An attractive feature of {sup 6}Li containing fluorescence materials that determines their potential application in radiation detection is the capture reaction with slow ({approx}< 100 keV) neutrons: {sup 6}Li + n = {sup 4}He + {sup 3}H + 4.8MeV. The use of {sup 6}Li-salicylate (LiSal, LiC{sub 6}H{sub 5}O{sub 3}) for thermal neutron detection was previously studied in liquid and polycrystalline scintillators. The studies showed that both liquid and polycrystalline LiSal scintillators could be utilized in pulse shape discrimination (PSD) techniques that enable separation of neutrons from the background gamma radiation. However, it was found that the efficiency of neutron detection using LiSal in liquid solutions was severely limited by its low solubility in commonly used organic solvents like, for example, toluene or xylene. Better results were obtained with neutron detectors containing the compound in its crystalline form, such as pressed pellets, or microscopic-scale (7-14 micron) crystals dispersed in various media. The expectation drown from these studies was that further improvement of pulse height, PSD, and efficiency characteristics could be reached with larger and more transparent LiSal crystals, growth of which has not been reported so far. In this paper, we present the first results on growth and characterization of relatively large, a cm-scale size, single crystals of LiSal with good optical quality. The crystals were grown both from aqueous and anhydrous (methanol) media, mainly for neutron detection studies. However, the results on growth and structural characterization may be interesting for other fields where LiSal, together with other alkali metal salicylates, is used for biological, medical, and chemical (as catalyst) applications.

  13. Unstable vicinal crystal growth from cellular automata

    NASA Astrophysics Data System (ADS)

    Krasteva, A.; Popova, H.; KrzyŻewski, F.; Załuska-Kotur, M.; Tonchev, V.

    2016-03-01

    In order to study the unstable step motion on vicinal crystal surfaces we devise vicinal Cellular Automata. Each cell from the colony has value equal to its height in the vicinal, initially the steps are regularly distributed. Another array keeps the adatoms, initially distributed randomly over the surface. The growth rule defines that each adatom at right nearest neighbor position to a (multi-) step attaches to it. The update of whole colony is performed at once and then time increases. This execution of the growth rule is followed by compensation of the consumed particles and by diffusional update(s) of the adatom population. Two principal sources of instability are employed - biased diffusion and infinite inverse Ehrlich-Schwoebel barrier (iiSE). Since these factors are not opposed by step-step repulsion the formation of multi-steps is observed but in general the step bunches preserve a finite width. We monitor the developing surface patterns and quantify the observations by scaling laws with focus on the eventual transition from diffusion-limited to kinetics-limited phenomenon. The time-scaling exponent of the bunch size N is 1/2 for the case of biased diffusion and 1/3 for the case of iiSE. Additional distinction is possible based on the time-scaling exponents of the sizes of multi-step Nmulti, these are 0.36÷0.4 (for biased diffusion) and 1/4 (iiSE).

  14. Preliminary investigations of protein crystal growth using the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Delucas, L. J.; Suddath, F. L.; Snyder, R.; Naumann, R.; Broom, M. B.; Pusey, M.; Yost, V.; Herren, B .; Carter, D.

    1986-01-01

    Four preliminary Shuttle experiments are described which have been used to develop prototype hardware for a more advanced system that will evaluate effects of gravity on protein crystal growth. The first phase of these experiments has centered on the development of micromethods for protein crystal growth by vapor-diffusion techniques (using a space version of the hanging-drop method) and on dialysis using microdialysis cells. Results suggest that the elimination of density-driven sedimentation can effect crystal morphology. In the dialysis experiment, space-grown crystals of concanavalin B were three times longer and 1/3 the thickness of earth-grown crystals.

  15. 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

  16. 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.

  17. Holographic instrumentation for monitoring crystal growth in space

    NASA Technical Reports Server (NTRS)

    Trolinger, James D.; Lal, Ravindra B.; Batra, Ashok K.

    1990-01-01

    Measurement requirements and candidates for measuring crystal growth in space are described, emphasizing holographic instrumentation. Existing instrumentation planned for the IML-1 Spaceflight is described along with advanced concepts for future application which incorporate diode lasers, fiber optics, and holographic optical elements. Particle image displacement velocimetry in crystal growth chambers is described.

  18. 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.

  19. Model experiments for the Czochralski crystal growth technique

    NASA Astrophysics Data System (ADS)

    Cramer, A.; Pal, J.; Gerbeth, G.

    2013-03-01

    A lot of the physical and the numerical modeling of Czochralski crystal growth is done on the generic Rayleigh-Bénard system. To better approximate the conditions in a Czochralski puller, the influences of a rounded crucible bottom, deviations of the thermal boundary conditions from the generic case, crucible and/or crystal rotation, and the influence of magnetic fields are often studied separately. The present contribution reviews some of these topics while concentrating on studies of the flow and related temperature fluctuations in systems where a rotating magnetic field (RMF) was applied. The three-dimensional convective patterns and the resulting temperature fluctuations will be discussed both for the mere buoyant case and for the application of an RMF. It is shown that a system between a Rayleigh-Bénard and a more realistic configuration, which is still cylindrical but whose surface is partially covered by a crystal model, behaves much the same as a Rayleigh-Bénard system. An RMF can be used to damp the temperature fluctuations. Secondly, a more Czochralski-like system is examined. It turns out that the RMF does not provide the desired damping of the temperature fluctutions in the parameter range considered.

  20. Direct observation of interface instability during crystal growth

    NASA Technical Reports Server (NTRS)

    Tiller, W. A.; Feigelson, R. S.; Elwell, D.

    1982-01-01

    The general aim of this investigation was to study interface stability and solute segregation phenomena during crystallization of a model system. Emphasis was to be placed on direct observational studies partly because this offered the possibility at a later stage of performing related experiments under substantially convection-free conditions in the space shuttle. The major achievements described in this report are: (1) the development of a new model system for fundamental studies of crystal growth from the melt and the measurement of a range of material parameters necessary for comparison of experiment with theory. (2) The introduction of a new method of measuring segregation coefficient using absorption of a laser beam by the liquid phase. (3) The comparison of segregation in crystals grown by gradient freezing and by pulling from the melt. (4) The introduction into the theory of solute segregation of an interface field term and comparison with experiment. (5) The introduction of the interface field term into the theories of constitutional supercooling and morphological stability and assessment of its importance.

  1. Natural growth habit of bulk AlN crystals

    NASA Astrophysics Data System (ADS)

    Epelbaum, B. M.; Seitz, C.; Magerl, A.; Bickermann, M.; Winnacker, A.

    2004-05-01

    Growth conditions for self-nucleation and subsequent growth of bulk AlN crystals by sublimation are presented. With increasing growth temperature, the natural habit of AlN crystals changes from needle-like to prismatic and then turns to thick asymmetric platelet. The best-formed platelet crystals up to 14×7×2 mm 3 in size exhibit a number of atomically smooth surfaces. Growth morphology and crystal quality were found to be strongly influenced by the polar nature of AlN. Al-terminated faces produce mirror-like facets and transparent material of high crystalline quality, whereas development of N-terminated faces leads to opaque and defective sectors in grown crystals. It is suggested that the most successful seeded growth of AlN can be achieved along Al-terminated (0 0 0 1) , ( 1¯ 0 1 2) and non-polar ( 1¯ 0 1 0) faces.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Şahin, Ö.; Özdemir, 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.

  4. Growth rate measurements of lysozyme crystals under microgravity conditions by laser interferometry.

    PubMed

    Yoshizaki, Izumi; Tsukamoto, Katsuo; Yamazaki, Tomoya; Murayama, Kenta; Oshi, Kentaro; Fukuyama, Seijiro; Shimaoka, Taro; Suzuki, Yoshihisa; Tachibana, Masaru

    2013-10-01

    The growth rate vs. supersaturation of a lysozyme crystal was successfully measured in situ together with the crystal surface observation and the concentration measurements onboard the International Space Station. A Michelson-type interferometer and a Mach-Zehnder interferometer were, respectively, employed for real-time growth rate measurements and concentration field measurements. The hardware development, sample preparation, operation, and analysis methods are described.

  5. Classical growth of hard-sphere colloidal crystals

    NASA Astrophysics Data System (ADS)

    Ackerson, Bruce J.; Schätzel, Klaus

    1995-12-01

    The classical theory of nucleation and growth of crystals is examined for concentrated suspensions of hard-sphere colloidal particles. The work of Russel is modified, extended, and evaluated, explicitly. Specifically, the Wilson-Frenkel growth law is modified to include the Gibbs-Thomson effect and is evaluated numerically. The results demonstrate that there is a critical nucleus radius below which crystal nuclei will not grow. A kinetic coefficient determines the maximum growth velocity possible. For large values of this coefficient, quenches to densities above the melting density show interface limited growth with the crystal radius increasing linearly with time. For quenches into the coexistence region the growth is diffusion limited, with the crystal radius increasing as the square root of elapsed time. Smaller values of the kinetic coefficient produce long lived transients which evidence quasi-power-law growth behavior with exponents between one half and unity. The smaller kinetic coefficients also lead to larger crystal compression. Crystal compression and nonclassical exponents have been observed in recent experiments. The theory is compared to data from small angle scattering studies of nucleation and growth in suspensions of hard colloidal spheres. The experimental nucleation rate is much larger than the theoretically predicted value as the freezing point is approached but shows better agreement near the melting point. The crystal growth with time is described reasonably well by the theory and suggests that the experiments are observing long lived transient rather than asymptotic growth behavior. (c) 1995 The American Physical Society

  6. 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)

  7. 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

  8. Protein and virus crystal growth on international microgravity laboratory-2.

    PubMed Central

    Koszelak, S; Day, J; Leja, C; Cudney, R; McPherson, A

    1995-01-01

    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. The method used 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 30 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. It is postulated that the establishment of quasi-stable depletion zones around crystals growing in microgravity are responsible for self-regulated and more ordered growth. Images FIGURE 1 FIGURE 2 FIGURE 6 PMID:7669890

  9. 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.

  10. The growth and dissolution of ammonium perchlorate crystals in a fluidized bed crystallizer

    NASA Astrophysics Data System (ADS)

    Tanrikulu, S. Ü.; Eroğlu, I.; Bulutcu, A. N.; Özkar, S.

    1998-11-01

    The growth and the dissolution of ammonium perchlorate crystals were studied in pure and in sodium chloride containing aqueous solutions, in a fluidized bed crystallizer. The presence of sodium chloride in the solution reduced the growth and the dissolution rates of ammonium perchlorate crystals. The growth rates were interpreted in terms of supersaturation levels. The orders and rate constants were reported. The effectiveness factors were estimated from the growth rate data to evaluate the relative magnitude of the two resistances in series, diffusion and integration. The controlling mechanism is mainly by diffusion for the crystal growth of ammonium perchlorate in pure aqueous solution. However, both diffusion and integration steps affect the growth of ammonium perchlorate crystals in the presence of sodium chloride in solution.

  11. Characterization of the Bridgman crystal growth process by radiographic imaging

    NASA Technical Reports Server (NTRS)

    Fripp, Archibald L.; Debnam, W. J.; Woodell, G. W.; Berry, R. F.; Simchick, R. T.; Sorokach, S. K.; Barber, P. G.

    1991-01-01

    Elemental (Ge) and alloy (PbSnTe) crystal growth that is monitored via radiography to reveal both the interface position and the shape in real time is discussed for both seeded and unseeded growth. It is concluded that the interface position and the actual growth rate of a Bridgman grown crystal is dependent on the growth conditions. The actual growth rate which is a strong function of the degree of supercooling exceeded the pull rate by a factor of greater than two. The interface shape changed from concave to flat to convex during the growth.

  12. Crystal growth and application of large size YCOB crystal for high power laser

    NASA Astrophysics Data System (ADS)

    Wu, Anhua; Xu, Jun; Zheng, Yanqing; Liang, Xiaoyan

    2014-10-01

    Yttrium calcium oxyborate YCa4O(BO3)3 (YCOB) is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. It is regards the important candidate frequency conversion material for the high-average power laser system. In this work, we described our effort to achieve the successful growth of large size YCOB single crystals, and the crystal quality of large size YCOB crystal grown by the Bridgman method. The OPCPA application of YCOB element was also introduced simply. The results confirmed that Bridgman technology can be used for the growth of large size YCOB crystal as an alternative to Czochralski method.

  13. Specific features of seeding and growth of bulk polar crystals

    NASA Astrophysics Data System (ADS)

    Tsvetkov, E. G.; Tyurikov, V. I.

    2000-07-01

    Formal analysis of seeding and growth of crystals exhibiting spontaneous polarization has been attempted using lithium iodate (α-LiIO 3) and barium metaborate (β-BaB 2O 4) as representative materials grown from aqueous and high-temperature solutions, respectively. We suggest that the specific growth features of nonlinear optical α-LiIO 3 and β-BaB 2O 4 crystals are being determined by formation and evolutionary restructuring of a double electric layer (DEL) at the growth interface. Both composition and structure of the DEL are governed by potential-determining ions of the growth medium as well as by the nature of crystal polarization and its properties. We have found that the composition and structure of the DEL together with the magnitude and direction of spontaneous polarization of the seed (crystal) predetermine the macrotwinning boundaries during seeding and subsequent stages of crystal growth as well as the formation of microtwin structures of various sizes. Similar reasoning is applied to possible crystal asymmetry, cellular growth, extinction of growth, etc. Model concepts of seeding and growth of bulk polar crystals are discussed.

  14. 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.

  15. 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.

  16. Growth of AlN single crystals by modified PVT

    NASA Astrophysics Data System (ADS)

    Wu, Honglei; Zheng, Ruisheng; Meng, Shu; Guo, Yuan

    2008-11-01

    Growth of AlN single crystals is achieved by physical vapor transport (PVT) in the reverse cone tungsten crucible, which is induction-heated, for obtaining proper sublimation rate and ensuring effective heat and mass transport. In the experiment, there is a little hole at the center of crucible lid where the temperature is lower than the periphery, and there is a tungsten cover on the lid. A self-seeded AlN single crystal is grown due to the anisotropic growth property of AlN crystals and limitation of the hole. During the following growth, the crystal as a seed becomes a large size and high quality single crystal. By modified PVT, separate AlN single crystals with diameters of larger than 2mm on the crucible lid have been obtained successfully for the first time.

  17. 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.

  18. Oxidation and crystal field effects in uranium

    NASA Astrophysics Data System (ADS)

    Tobin, J. G.; Yu, S.-W.; Booth, C. H.; Tyliszczak, T.; Shuh, D. K.; van der Laan, G.; Sokaras, D.; Nordlund, D.; Weng, T.-C.; Bagus, P. S.

    2015-07-01

    An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (U O2) , uranium trioxide (U O3) , and uranium tetrafluoride (U F4) . A discussion of the role of nonspherical perturbations, i.e., crystal or ligand field effects, will be presented.

  19. Oxidation and crystal field effects in uranium

    SciTech Connect

    Tobin, J. G.; Booth, C. H.; Shuh, D. K.; van der Laan, G.; Sokaras, D.; Weng, T. -C.; Yu, S. W.; Bagus, P. S.; Tyliszczak, T.; Nordlund, D.

    2015-07-06

    An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (UO2), uranium trioxide (UO3), and uranium tetrafluoride (UF4). As a result, a discussion of the role of non-spherical perturbations, i.e., crystal or ligand field effects, will be presented.

  20. 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.

  1. Stability of Magnetically-Suppressed Solutal Convection In Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Leslie, F. W.; Ramachandran, N.

    2005-01-01

    The effect of convection during the crystallization of proteins is not very well understood. In a gravitational field, convection is caused by crystal sedimentation and by solutal buoyancy induced flow and these can lead to crystal imperfections. While crystallization in microgravity can approach diffusion limited growth conditions (no convection), terrestrially strong magnetic fields can be used to control fluid flow and sedimentation effects. In this work, a theory is presented on the stability of solutal convection of a magnetized fluid in the presence of a magnetic field. The requirements for stability are developed and compared to experiments performed within the bore of a superconducting magnet. The theoretical predictions are in good agreement with the experiments and show solutal convection can be stabilized if the surrounding fluid has larger magnetic susceptibility and the magnetic field has a specific structure. Discussion on the application of the technique to protein crystallization is also provided.

  2. 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.

  3. Growth and surface topography of WSe2 single crystal

    NASA Astrophysics Data System (ADS)

    Dixit, Vijay; Vyas, Chirag; Pataniya, Pratik; Jani, Mihir; Pathak, Vishal; Patel, Abhishek; Pathak, V. M.; Patel, K. D.; Solanki, G. K.

    2016-05-01

    Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe2 were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe2 crystals. Single crystalline nature of the crystals was confirmed by SAED.

  4. 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 Ω = 20, where Ω = 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 Ω = 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 (Ω >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

  5. 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 β, controlling the increase in time of the typical slope of the pattern, M ˜tβ, 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.

  6. Colloidal Crystal Growth Monitored By Bragg Diffraction Interference Fringes

    PubMed Central

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

    2010-01-01

    We monitor 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 (111) 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 to 90 μM NaCl concentrations the fcc crystals first linearly grow at rates between 1.9 and 4.2 μm/sec 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 μM NaCl concentrations. Increasing NaCl concentrations slows the fcc CCA growth rate consistent with the expectation of the classical Wilson-Frenkel growth theory. The final thickness of wall nucleated CCA is determined by the competition between growth of heterogeneously and homogenously nucleated CCA and increases with higher NaCl concentrations. PMID:20542277

  7. 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.

  8. 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).

  9. 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.

  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. 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 μm 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 β 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.

  12. Nanoscale-driven crystal growth of hexaferrite heterostructures for magnetoelectric tuning of microwave semiconductor integrated devices.

    PubMed

    Hu, Bolin; Chen, Zhaohui; Su, Zhijuan; Wang, Xian; Daigle, Andrew; Andalib, Parisa; Wolf, Jason; McHenry, Michael E; Chen, Yajie; Harris, Vincent G

    2014-11-25

    A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25-40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals was found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ∼150 K for Co2Y ferrite, compared to 5-10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on a wide bandgap semiconductor GaN. The demonstration of the nanostructure materials-based "system on a wafer" architecture is a critical milestone to next generation microwave integrated systems. It is also practical that future microwave integrated systems and their magnetic performances could be tuned by an electric field because of the magnetoelectricity of hexaferrites.

  13. A study of solution crystal growth in LOW-g (2-IML-1)

    NASA Technical Reports Server (NTRS)

    Lal, Ravindra B.

    1992-01-01

    During the International Microgravity Laboratory-1 (IML-1) mission it is planned to grow triglycine sulfate (TGS) crystals from aqueous solution using the modified Fluids Experiment System (FES). A special cooled sting technique will be used for solution crystal growth. The objectives of the experiment are as follows: (1) to grow crystals of TGS using the modified FES; (2) to perform holographic interferometric tomography of the fluid field in three dimensions; (3) to study the fluid motion due to g-jitter by multiple exposure holography of tracer particles; and (4) to study the influence of g-jitter on the growth rate.

  14. Growth of protein crystals suspended in a closed loop thermosyphon

    NASA Astrophysics Data System (ADS)

    Nyce, Thomas A.; Rosenberger, Franz

    1991-03-01

    The quality of protein crystals often suffers from their growth at a liquid or solid surface. A novel solution growth method was developed to alleviate this problem. A growing crystal is suspended in a specially configured upflow of supersaturated nutrient, which is provided by the effect of fluid buoyancy in a closed loop thermosyphon. The flow rate and supersaturation are controlled by the temperature distribution in the thermosyphon, while contact of the crystal with the wall during growth is practically eliminated. The method was applied to the growth of lysozyme single crystals, with surprising results. While the orthorhombic form of lysozyme grew readily to the suspension limit of this particular apparatus (1.5 mm), the tetragonal form grew only to a maximum size less than 0.1 mm. Seed crystals of tetragonal lysozyme introduced into stagnant batch controls did not experience the growth cessation that the suspended crystals did. A likely cause of this growth cessation is the fluid shear forces on the suspended crystals.

  15. Ames Lab 101: Single Crystal Growth

    ScienceCinema

    Schlagel, Deborah

    2016-07-12

    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

    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.

  17. Growth of shaped single crystals of proteins

    NASA Astrophysics Data System (ADS)

    Moreno, Abel; Rondón, Deyanira; García-Ruiz, Juan Ma.

    1996-09-01

    We present a procedure for obtaining protein single crystals that fill the capillary tubes in which they grow. The implementation was typical of the gel acupuncture method and the four different proteins are used as examples: lysozyme (HEW), thaumatin I, ferritin and insulin. Rod- and prismatic-shaped protein single crystals of these four proteins were grown inside capillary tubes of 0.2, 0.3, 0.5 mm in diameter and, for the case of lysozyme, up to 1.2 mm in diameter. The maximum length measured along the long axes of the rod crystals was 1.6 mm again for lysozyme crystals. It was observed that, once the capillary tube was filled, the crystal continues to grow by diffusion of the precipitating agent throughout the porous network formed by the protein crystal structure. We also discuss the possibility of growing these cylinders of crystalline proteins by the addition of protein solution to the mother liquor through the upper end of the glass capillary while the precipitating agent diffuses through the protein crystal itself. X-ray diffraction patterns confirm the single crystal character of the protein rods.

  18. Phase-field-crystal model for fcc ordering.

    PubMed

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to <111> and <200> reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  19. Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.

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

    DOE PAGESBeta

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

    2015-03-30

    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 themore » growth of crystals to significant dimensions that are now relevant to NMC are revisited. We report that these include experimental strategies utilizing solubility diagrams, ripening effects, classical crystallization techniques, microgravity and theoretical considerations.« less

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

    SciTech Connect

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

    2015-03-30

    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. We report that these include experimental strategies utilizing solubility diagrams, ripening effects, classical crystallization techniques, microgravity and theoretical considerations.

  2. Growth and characterization of DAST crystal with large-thickness

    NASA Astrophysics Data System (ADS)

    Cao, Lifeng; Teng, Bing; Zhong, Degao; Hao, Lun; Sun, Qing

    2016-10-01

    Highly nonlinear optical 4-N, N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystals with large surface and thickness was grown by the slope nucleation technology with slow-cooling in a high concentration solution. The structure and composition of the crystal were confirmed by X-ray diffraction (XRD). The surface morphology of the crystal was characterized by optical microscope. Growth layers were observed on the (001) surface and several isolated "island layers" were also found. The mechanism of crystal growth was analyzed. Etching behavior of the (001) and (00 1 bar) faces of the crystal was studied with methanol, respectively. Optical properties of the crystal were also characterized by UV-vis-NIR spectrometer. The dielectric constants and the dielectric loss were tested by impedance analyzer.

  3. 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.

  4. 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.

  5. Crystal growth of compound semiconductors in a low-gravity environment (InGaAs crystals) (M-22)

    NASA Technical Reports Server (NTRS)

    Tatsumi, Masami

    1993-01-01

    Compound semiconductor crystals, such as gallium arsenide and indium phosphide crystals, have many interesting properties that silicon crystals lack, and they are expected to be used as materials for optic and/or electro-optic integrated devices. Generally speaking, alloy semiconductors, which consist of more than three elements, demonstrate new functions. For example, values of important parameters, such as lattice constant and emission wavelength, can be chosen independently. However, as it is easy for macroscopic and/or microscopic fluctuations of composition to occur in alloy semiconductor crystals, it is difficult to obtain crystals having homogeneous properties. Macroscopic change of composition in a crystal is caused by the segregation phenomenon. This phenomenon is due to a continuous change in the concentration of constituent elements at the solid-liquid interfacing during solidification. On Earth, attempts were made to obtain a crystal with homogeneous composition by maintaining a constant melt composition near the solid-liquid interface, through suppression of the convection flow of the melt by applying a magnetic field. However, the attempt was not completely successful. Convective flow does not occur in microgravity because the gravity in space is from four to six orders of magnitude less than that on Earth. In such a case, mass transfer in the melt is dominated by the diffusion phenomenon. So, if crystal growth is carried out at a rate that is higher than the rate of mass transfer due to this phenomenon, it is expected that crystals having a homogeneous composition will be obtained. In addition, it is also possible that microscopic composition fluctuations (striation) may disappear because microscopic fluctuations diminish in the absence of convection. We are going to grow a bulk-indium gallium arsenide (InGaAs) crystal using the gradient heating furnace (GHF) in the first material processing test (FMPT). The structure of the sample is shown where In

  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. Apparatus for single ice crystal growth from the melt.

    PubMed

    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 0.8 ml cylindrical volume. A triple window arrangement was used to minimize temperature gradients and allow for up to 10 mm working distance objective lens. Temperature could be established to within +/-10 mK in as little as 3.5 min and controlled to within +/-2 mK after 15 min for at least 10 h. 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.

  8. Nucleation and structural growth of cluster crystals

    NASA Astrophysics Data System (ADS)

    Leitold, Christian; Dellago, Christoph

    2016-08-01

    We study the nucleation of crystalline cluster phases in the generalized exponential model with exponent n = 4. Due to the finite value of this pair potential for zero separation, at high densities the system forms cluster crystals with multiply occupied lattice sites. Here, we investigate the microscopic mechanisms that lead to the formation of cluster crystals from a supercooled liquid in the low-temperature region of the phase diagram. Using molecular dynamics and umbrella sampling, we calculate the free energy as a function of the size of the largest crystalline nucleus in the system, and compare our results with predictions from classical nucleation theory. Employing bond-order parameters based on a Voronoi tessellation to distinguish different crystal structures, we analyze the average composition of crystalline nuclei. We find that even for conditions where a multiply occupied fcc crystal is the thermodynamically stable phase, the nucleation into bcc cluster crystals is strongly preferred. Furthermore, we study the particle mobility in the supercooled liquid and in the cluster crystal. In the cluster crystal, the motion of individual particles is captured by a simple reaction-diffusion model introduced previously to model the kinetics of hydrogen bonds.

  9. Nucleation and structural growth of cluster crystals.

    PubMed

    Leitold, Christian; Dellago, Christoph

    2016-08-21

    We study the nucleation of crystalline cluster phases in the generalized exponential model with exponent n = 4. Due to the finite value of this pair potential for zero separation, at high densities the system forms cluster crystals with multiply occupied lattice sites. Here, we investigate the microscopic mechanisms that lead to the formation of cluster crystals from a supercooled liquid in the low-temperature region of the phase diagram. Using molecular dynamics and umbrella sampling, we calculate the free energy as a function of the size of the largest crystalline nucleus in the system, and compare our results with predictions from classical nucleation theory. Employing bond-order parameters based on a Voronoi tessellation to distinguish different crystal structures, we analyze the average composition of crystalline nuclei. We find that even for conditions where a multiply occupied fcc crystal is the thermodynamically stable phase, the nucleation into bcc cluster crystals is strongly preferred. Furthermore, we study the particle mobility in the supercooled liquid and in the cluster crystal. In the cluster crystal, the motion of individual particles is captured by a simple reaction-diffusion model introduced previously to model the kinetics of hydrogen bonds. PMID:27544116

  10. 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.

  11. Containerless protein crystal growth technology: Electrostatic multidrop positioner

    NASA Technical Reports Server (NTRS)

    Rhim, Won-Kyu

    1990-01-01

    A brief discussion of containerless protein crystal growth in space and a diagram of the electrostatic multidrop positioner are presented. A picture of lysome crystals growing in a drop and a graph of levitation voltage versus time (minutes) are also presented.

  12. Crystal growth and roughening of solid D{sub 2}

    SciTech Connect

    Kozioziemski, B.J.; Collins, G.W.; Bernat, T.P.

    1997-03-26

    Near the triple point, growth shapes of vapor deposited hexagonal close packed D{sub 2} crystals reveal two crystal orientations contain facets which persist up to the melt. This observation is in contrast with previous experiments on rare gas solids and H{sub 2} where the highest T{sub r} measured is 0.8 T{sub tp}.

  13. Chamber Design For Slow Nucleation Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Pusey, Marc Lee

    1995-01-01

    Multiple-chamber dialysis apparatus grows protein crystals on Earth or in microgravity with minimum of intervention by technician. Use of multiple chambers provides gradation of nucleation and growth rates.

  14. 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.

  15. 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.

  16. (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.

  17. 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.

  18. 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.

  19. 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.

  20. 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)

  1. Growth Kinetics and Morphology of Barite Crystals Derived from Face-Specific Growth Rates

    DOE PAGESBeta

    Godinho, Jose R. A.; Stack, Andrew G.

    2015-03-30

    Here we investigate the growth kinetics and morphology of barite (BaSO4) crystals by measuring the growth rates of the (001), (210), (010), and (100) surfaces using vertical scanning interferometry. Solutions with saturation indices 1.1, 2.1, and 3.0 without additional electrolyte, in 0.7 M NaCl, or in 1.3 mM SrCl2 are investigated. Face-specific growth rates are inhibited in the SrCl2 solution relative to a solution without electrolyte, except for (100). Contrarily, growth of all faces is promoted in the NaCl solution. The variation of face-specific rates is solution-specific, which leads to a. change of the crystal morphology and overall growth ratemore » of crystals. The measured face-specific growth rates are used to model the growth of single crystals. Modeled crystals have a morphology and size similar to those grown from solution. Based on the model the time dependence of surface area and growth rates is analyzed. Growth rates change with time due to surface area normalization for small crystals and large growth intervals. By extrapolating rates to crystals with large surfaces areas, time-independent growth rates are 0.783, 2.96, and 0.513 mmol∙m-2∙h-1, for saturation index 2.1 solutions without additional electrolyte, NaCl, and SrCl2, respectively.« less

  2. Growth Kinetics and Morphology of Barite Crystals Derived from Face-Specific Growth Rates

    SciTech Connect

    Godinho, Jose R. A.; Stack, Andrew G.

    2015-03-30

    Here we investigate the growth kinetics and morphology of barite (BaSO4) crystals by measuring the growth rates of the (001), (210), (010), and (100) surfaces using vertical scanning interferometry. Solutions with saturation indices 1.1, 2.1, and 3.0 without additional electrolyte, in 0.7 M NaCl, or in 1.3 mM SrCl2 are investigated. Face-specific growth rates are inhibited in the SrCl2 solution relative to a solution without electrolyte, except for (100). Contrarily, growth of all faces is promoted in the NaCl solution. The variation of face-specific rates is solution-specific, which leads to a. change of the crystal morphology and overall growth rate of crystals. The measured face-specific growth rates are used to model the growth of single crystals. Modeled crystals have a morphology and size similar to those grown from solution. Based on the model the time dependence of surface area and growth rates is analyzed. Growth rates change with time due to surface area normalization for small crystals and large growth intervals. By extrapolating rates to crystals with large surfaces areas, time-independent growth rates are 0.783, 2.96, and 0.513 mmol∙m-2∙h-1, for saturation index 2.1 solutions without additional electrolyte, NaCl, and SrCl2, respectively.

  3. Liquid nitrogen dewar for protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Gaseous Nitrogen Dewar apparatus developed by Dr. Alex McPherson of the University of California, Irvine for use aboard Mir and the International Space Station allows large quantities of protein samples to be crystallized in orbit. The specimens are contained either in plastic tubing (heat-sealed at each end). Biological samples are prepared with a precipitating agent in either a batch or liquid-liquid diffusion configuration. The samples are then flash-frozen in liquid nitrogen before crystallization can start. On orbit, the Dewar is placed in a quiet area of the station and the nitrogen slowly boils off (it is taken up by the environmental control system), allowing the proteins to thaw to begin crystallization. The Dewar is returned to Earth after one to four months on orbit, depending on Shuttle flight opportunities. The tubes then are analyzed for crystal presence and quality

  4. 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.

  5. In situ observation of elementary growth processes of protein crystals by advanced optical microscopy.

    PubMed

    Sazaki, Gen; Van Driessche, Alexander E S; Dai, Guoliang; Okada, Masashi; Matsui, Takuro; Otálora, Fermin; Tsukamoto, Katsuo; Nakajima, Kazuo

    2012-07-01

    To start systematically investigating the quality improvement of protein crystals, the elementary growth processes of protein crystals must be first clarified comprehensively. Atomic force microscopy (AFM) has made a tremendous contribution toward elucidating the elementary growth processes of protein crystals and has confirmed that protein crystals grow layer by layer utilizing kinks on steps, as in the case of inorganic and low-molecular-weight compound crystals. However, the scanning of the AFM cantilever greatly disturbs the concentration distribution and solution flow in the vicinity of growing protein crystals. AFM also cannot visualize the dynamic behavior of mobile solute and impurity molecules on protein crystal surfaces. To compensate for these disadvantages of AFM, in situ observation by two types of advanced optical microscopy has been recently performed. To observe the elementary steps of protein crystals noninvasively, laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM) was developed. To visualize individual mobile protein molecules, total internal reflection fluorescent (TIRF) microscopy, which is widely used in the field of biological physics, was applied to the visualization of protein crystal surfaces. In this review, recent progress in the noninvasive in situ observation of elementary steps and individual mobile protein molecules on protein crystal surfaces is outlined.

  6. 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

  7. Lattice Boltzmann simulation of water isotope fractionation during ice crystal growth in clouds

    NASA Astrophysics Data System (ADS)

    Lu, Guoping; DePaolo, Donald J.

    2016-05-01

    We describe a lattice Boltzmann (LB) method for simulating water isotope fractionation during diffusion-limited ice crystal growth by vapor deposition from water-oversaturated air. These conditions apply to the growth of snow crystals in clouds where the vapor composition is controlled by the presence of both ice crystals and water droplets. Modeling of water condensation with the LB method has the advantage of allowing concentration fields to evolve based on local conditions so that the controls on grain shapes of the condensed phase can be studied simultaneously with the controls on isotopic composition and growth rate. Water isotope fractionation during snow crystal growth involves kinetic effects due to diffusion of water vapor in air, which requires careful consideration of the boundary conditions at the ice-vapor interface. The boundary condition is relatively simple for water isotopes because the molecular exchange rate for water at the interface is large compared to the crystal growth rate. Our results for the bulk crystal isotopic composition are consistent with simpler models using analytical solutions for radial geometry. However, the model results are sufficiently different for oxygen isotopes that they could affect the interpretation of D-excess values of snow and ice. The extent of vapor oversaturation plays a major role in determining the water isotope fractionation as well as the degree of dendritic growth. Departures from isotopic equilibrium increase at colder temperatures as diffusivity decreases. Dendritic crystals are isotopically heterogeneous. Isotopic variations within individual snow crystals could yield information on the microphysics of ice condensation as well as on the accommodation or sticking coefficient of water associated with vapor deposition. Our results are ultimately a first step in implementing LB models for kinetically controlled condensation or precipitation reactions, but needs to be extended also to cases where the

  8. 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.

  9. Rapid growth of thin and flexible organic semiconductor single crystal Anthracene by solution growth technique for device fabrication

    NASA Astrophysics Data System (ADS)

    Thirupugalmani, K.; Shanmugam, G.; Kannan, V.; Brahadeeswaran, S.

    2015-03-01

    Growth of thin and flexible organic semiconductor crystal Anthracene (AN) has been achieved in a very short duration. This simple, yet an effective approach was serendipitously found to yield high quality crystal with typical dimensions of 22×23×0.15-0.50 mm3 within a duration of about 30 min whereas a conventional method could take about 7-10 days to achieve similar dimensions. Further, these crystals were seen swirling and settling down slowly at the bottom of the growth flask. These factors were favorably utilized to place the Anthracene crystals firmly on prefabricated flexible substrates when they were kept in different heights within the solutions. This systematic approach also facilitated the fabrication of organic field effect transistor (OFET) and the results obtained were encouraging.

  10. 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

  11. Influence of Polymers on the Crystal Growth Rate of Felodipine: Correlating Adsorbed Polymer Surface Coverage to Solution Crystal Growth Inhibition.

    PubMed

    Schram, Caitlin J; Taylor, Lynne S; Beaudoin, Stephen P

    2015-10-20

    The bioavailability of orally administered drugs that exhibit poor aqueous solubility can be enhanced with the use of supersaturating dosage forms. Stabilization of these forms by preventing or inhibiting crystallization in solution is an important area of study. Polymers can be used to stabilize supersaturated systems; however, the properties that impact their effectiveness as crystal growth rate inhibitors are not yet fully understood. In this study, the impact of various polymers on the crystal growth rate of felodipine and the conformation of these polymers adsorbed to crystalline felodipine was investigated in order to gain a mechanistic understanding of crystal growth inhibition. It was determined that polymer hydrophobicity impacted polymer adsorption as well as adsorbed polymer conformation. Polymer conformation impacts its surface coverage, which was shown to directly correlate to the polymer's effectiveness as a growth rate inhibitor. By modeling this correlation, it is possible to predict polymer effectiveness given the surface coverage of the polymer.

  12. 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.

  13. Advanced protein crystal growth flight hardware for the Space Station

    NASA Technical Reports Server (NTRS)

    Herrmann, Frederick T.

    1988-01-01

    The operational environment of the Space Station will differ considerably from the previous short term missions such as the Spacelabs. Limited crew availability combined with the near continuous operation of Space Station facilities will require a high degree of facility automation. This paper will discuss current efforts to develop automated flight hardware for advanced protein crystal growth on the Space Station. Particular areas discussed will be the automated monitoring of key growth parameters for vapor diffusion growth and proposed mechanisms for control of these parameters. A history of protein crystal growth efforts will be presented in addition to the rationale and need for improved protein crystals for X-ray diffraction. The facility will be capable of simultaneously processing several hundred protein samples at various temperatures, pH's, concentrations etc., and provide allowances for real time variance of growth parameters.

  14. Skylab experiments on semiconductors and alkali halides. [single crystal growth

    NASA Technical Reports Server (NTRS)

    Lundquist, C. A.

    1974-01-01

    The space processing experiments performed during the Skylab missions included one on single crystal growth of germanium selenide and telluride, one on pure and doped germanium crystals, two on pure and doped indium antimonide, one on gallium-indium-antimony systems, and one on a sodium chloride-sodium fluoride eutectic. In each experiment, three ampoules of sample were processed in the multipurpose electric furnace within the Skylab Materials Processing Facility. All were successful in varying degrees and gave important information about crystal growth removed from the effects of earth surface gravity.

  15. 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.

  16. Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

    SciTech Connect

    Raghavan, C.M.; Sankar, R.; Mohan Kumar, R.; Jayavel, R.

    2008-02-05

    Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern.

  17. Characterization of crystal growth using a spiral nucleation model

    NASA Astrophysics Data System (ADS)

    Martins, P. M.; Rocha, F.

    2007-08-01

    Classical concepts of two-dimensional nucleation and spiral growth are used together with recent findings on the dynamics of dislocation spirals to derive a new crystal growth model. Initial growth nuclei result from the organization of adsorbed molecules in spirals around surface dislocations. The energetic barrier for the activation of the spiral nuclei is considerably lower than the admitted by classical two dimensional nucleation models. Stable nuclei evolve into bigger growth hillocks in supersaturated media through the incorporation of adsorbed units into their steps. The displacement velocity of steps during solution and vapour growth is calculated by different kinetic approaches, taking into consideration the distinct role of surface diffusion in each process, and avoiding known limitations of conventional theories. A generalized expression is obtained relating the crystal growth rate with main variables such as supersaturation, temperature, crystal size, surface topology and interfacial properties. At the end of the paper, the crystallization kinetics of sucrose measured at 40 °C is interpreted in the light of the new perspectives resulting from the proposed model. The application example illustrates how to estimate interfacial and topological properties from the experimental crystal growth results.

  18. Protein crystal growth and the International Space Station.

    PubMed

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

    1999-05-01

    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.

  19. 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.

  20. Growth and morphology of AlN crystals

    NASA Astrophysics Data System (ADS)

    Yazdi, G. R.; Syväjärvi, M.; Yakimova, R.

    2006-09-01

    This study focused on growth dependencies, morphological forms and initial nucleation of aluminium nitride (AlN) crystals. Epitaxial layers of AlN have been grown on 4H-SiC substrates by sublimation recondensation in a radio frequency (RF) heated graphite furnace. Both AlN nuclei size and growth rate increased as temperature was increased and decreased as the pressure was increased. The results of these effects are different kinds of surface morphology. We have observed three modes of AlN single crystals: plate-like, columnar and needle-like. Optical microscopy and scanning electron microscopy (SEM) along with atomic force microscopy (AFM) were used to characterize the crystal surface morphology. Cathodoluminescence (CL) and x-ray diffraction (XRD) were applied to determine crystal quality and crystallographic orientation of the grown crystals.

  1. Floating zone crystal growth and phase equilibria - A review

    NASA Astrophysics Data System (ADS)

    Kimura, Shigeyuki; Kitamura, Kenji

    1992-06-01

    The thermal-imaging floating zone technique can be used to grow crystals of yttrium iron garnet aluminum-doped yttrium orthoferrite and magnetite, which represent peritectic compounds, solid-solution crytals, and atmosphere-sensitive materials, respectively. The reactions involved in floating zone crystal growth are explained on the basis of phase diagrams. A review of crystal growth reports, including unpublished findings by the present authors, demonstrates how the crystallization processes, the reaction with the ambient atmosphere, and the composition variation in the obtained crystals can be explained or controlled on the basis of phase equilibrium. The floating zone technique is applicable to a variety of materials and remains a handy tool for materials research; however, its industrial application may be limited.

  2. Lattice Boltzmann scheme for crystal growth in external flows.

    PubMed

    Medvedev, Dmitry; Kassner, Klaus

    2005-11-01

    A composite phase-field lattice-Boltzmann scheme is used to simulate dendritic growth from a supercooled melt, allowing for heat transport by both diffusion and convection. The phase-transition part of the problem is modelled by the phase-field approach of Karma and Rappel, whereas the flow of the liquid is computed by the lattice-Boltzmann-BGK (LBGK, referring to Bhatnagar, Gross, and Krook) method into which interactions with solid and thermal convection are incorporated. For simplicity, we have so far restricted ourselves to the symmetric model. Heat transport is simulated via the multicomponent LBGK method. Depending on the level of anisotropy and undercooling, dendrites or doublons are obtained in our simulations. Crystal growth in a shear flow is considered for different flow velocities and undercoolings. Doublons turn out to be robust against the perturbation imposed by a shear flow and display interesting dynamic behavior, quite different from that of dendrites. In addition, the influence of a parallel flow on the operating state of the tip of dendrites is studied. To complement information from selection theories such as the one presented by Bouissou and Pelcé, we measure selected growth characteristics of dendrites as a function of a flow imposed parallel to the growth direction, for intermediate undercoolings. The observed dependencies are compatible with power law behavior, if the undercooling is not too high. It is shown that for sufficiently large flow velocities, an oncoming flow can lead to tip oscillations of the dendrite and, consequently, to the generation of coherent side branches. PMID:16383781

  3. Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves

  4. Study of growth of single crystal ribbon in space

    NASA Technical Reports Server (NTRS)

    Wood, V. E.; Markworth, A. J.

    1975-01-01

    The technical feasibility is studied of growing single-crystal silicon ribbon in the space environment. Procedures are described for calculating the electromagnetic fields produced in a silicon ribbon by an rf shaping coil. The forces on the ribbon and the degree of shaping to be expected are determined. The expected steady-state temperature distribution in the ribbon is calculated in the one-dimensional approximation. Calculations on simplified models indicate, that lack of flatness of the shaped ribbon and excessive heating of the melt by the eddy currents induced by the shaping fields may pose problems. An analysis of the relative effects of various kinds of forces other than electromagnetic showed that in the space environment capillarity forces would dominate, and that the shape of the melt is thus principally determined by the shape of any solids with which it comes in contact. This suggests that ribbon may be produced simply by drawing between parallel wires. A concept is developed for a process of off-angle growth, in which the ribbon is pulled at an angle to the solidification front. Such a process promises to offer increased growth rate, better homogeneity, and thinner ribbon.

  5. 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

  6. 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.

  7. A novel method for measurement of crystal growth rate

    NASA Astrophysics Data System (ADS)

    Kim, Do Yeon; Yang, Dae Ryook

    2013-06-01

    A new method for measurement of crystal growth rate is proposed, in an attempt to make the measuring of growth rate more convenient than the existing methods. In this newly proposed method, the point of nucleation under a constant cooling rate condition was measured as changing the amount of seeds. The growth kinetics parameters were then estimated using the experimental data to match the points of nucleation. Experiments were performed with potash alum in the water system and growth kinetic parameters were estimated. Compared with existing results, the proposed method showed tolerable discrepancy in the growth kinetic parameters. The proposed method can be an alternative technique for measurement of growth rate.

  8. Molecular modifiers reveal a mechanism of pathological crystal growth inhibition.

    PubMed

    Chung, Jihae; Granja, Ignacio; Taylor, Michael G; Mpourmpakis, Giannis; Asplin, John R; Rimer, Jeffrey D

    2016-08-25

    Crystalline materials are crucial to the function of living organisms, in the shells of molluscs, the matrix of bone, the teeth of sea urchins, and the exoskeletons of coccoliths. However, pathological biomineralization can be an undesirable crystallization process associated with human diseases. The crystal growth of biogenic, natural and synthetic materials may be regulated by the action of modifiers, most commonly inhibitors, which range from small ions and molecules to large macromolecules. Inhibitors adsorb on crystal surfaces and impede the addition of solute, thereby reducing the rate of growth. Complex inhibitor-crystal interactions in biomineralization are often not well elucidated. Here we show that two molecular inhibitors of calcium oxalate monohydrate crystallization--citrate and hydroxycitrate--exhibit a mechanism that differs from classical theory in that inhibitor adsorption on crystal surfaces induces dissolution of the crystal under specific conditions rather than a reduced rate of crystal growth. This phenomenon occurs even in supersaturated solutions where inhibitor concentration is three orders of magnitude less than that of the solute. The results of bulk crystallization, in situ atomic force microscopy, and density functional theory studies are qualitatively consistent with a hypothesis that inhibitor-crystal interactions impart localized strain to the crystal lattice and that oxalate and calcium ions are released into solution to alleviate this strain. Calcium oxalate monohydrate is the principal component of human kidney stones and citrate is an often-used therapy, but hydroxycitrate is not. For hydroxycitrate to function as a kidney stone treatment, it must be excreted in urine. We report that hydroxycitrate ingested by non-stone-forming humans at an often-recommended dose leads to substantial urinary excretion. In vitro assays using human urine reveal that the molecular modifier hydroxycitrate is as effective an inhibitor of nucleation of

  9. 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

  10. 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:

  11. Crystal growth and dielectric, mechanical, electrical and ferroelectric characterization of n-bromo succinimide doped triglycine sulphate crystals

    NASA Astrophysics Data System (ADS)

    Rai, Chitharanjan; Byrappa, K.; Dharmaprakash, S. M.

    2011-09-01

    Single crystals of triglycine sulphate (TGS) doped with n-bromo succinimide (NBS) were grown at ambient temperature by the slow evaporation technique. An aqueous solution containing 1-20 mol% of n-bromo succinimide as dopant was used for the growth of NBSTGS crystals. The incorporation of NBS in TGS crystals has been qualitatively confirmed by FTIR spectral data. The effect of the dopant on morphology and crystal properties was investigated. The cell parameters of the doped crystal were determined by the powder X-ray diffraction technique. The dielectric constant of NBS doped TGS crystal was calculated along the ferroelectric direction over the temperature range of 30-60 °C. The dielectric constant of NBSTGS crystals decrease with the increase in NBS concentration and considerable shift in the phase transition temperature ( TC) towards the higher temperature observed. Pyroelectric studies on doped TGS were carried out to determine the pyroelectric coefficient. The emergence of internal bias field due to doping was studied by collecting P- E hysteresis data. Temperature dependence of DC conductivity of the doped crystals was studied and gradual increase in the conductivity with the increase of dopant concentration was observed. The activation energy (Δ E) calculated was found to be lower in both the ferroelectric and the paraelectric phases for doped crystals compared to that of pure TGS. The micro-hardness studies were carried out at room temperature on thin plates cut perpendicular to the b-axis. Less doped TGS crystals show higher hardness values compared to pure TGS. Piezoelectric measurements were also carried out on 010 plates of doped TGS crystals at room temperature.

  12. The growth of graphite phase on an iridium field electron emitter

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2016-06-01

    The growth of graphite on the surface of an iridium tip in pyrolysis of benzene to give a ribbed crystal has been found by the methods of field electron and desorption microscopy. The formation of a graphite crystal results in the electric field factor increasing. The adsorption of alkali metals on the surface of graphite is accompanied by the intercalation effect.

  13. 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.

  14. Growth Mechanism of the (110) Face of Tetragonal Lysozyme Crystals

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    The measured macroscopic growth rates of the (110) face of tetragonal lysozyme show an unexpectedly complex dependence on the supersaturation. In earlier studies it has been shown that an aggregate growth unit could account for experimental growth-rate trends. In particular molecular packing and interactions in the growth of the crystal were favored by completion of the helices along the 4, axes. In this study the molecular orientations of the possible growth units and the molecular growth mechanism were identified. This indicated that growth was a two-step process: aggregate growth units corresponding to the 4, helix are first formed in the bulk solution by stronger intermolecular bonds and then attached to the crystal face by weaker bonds. A more comprehensive analysis of the measured (110) growth rates was also undertaken. They were compared with the predicted growth rates from several dislocation and two-dimensional nucleation growth models, employing tetramer and Octamer growth units in polydisperse solutions and monomer units in monodisperse solutions. The calculations consistently showed that the measured growth rates followed the expected model relations with octamer growth units, in agreement with the predictions from the molecular level analyses.

  15. 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.

  16. Macromolecular crystal growth experiments on International Microgravity Laboratory--1.

    PubMed Central

    Day, J.; McPherson, A.

    1992-01-01

    Macromolecular crystal growth experiments, using satellite tobacco mosaic virus (STMV) and canavalin from jack beans as samples, were conducted on a US Space Shuttle mission designated International Microgravity Laboratory--1 (IML-1), flown January 22-29, 1992. Parallel experiments using identical samples were carried out in both a vapor diffusion-based device (PCG) and a liquid-liquid diffusion-based instrument (CRYOSTAT). The experiments in each device were run at 20-22 degrees C and at colder temperatures. Crystals were grown in virtually every trial, but the characteristics of the crystals were highly dependent on the crystallization technique employed and the temperature experience of the sample. In general, very good results, based on visual inspection of the crystals, were obtained in both PCG and CRYOSTAT. Unusually impressive results were, however, achieved for STMV in the CRYOSTAT instrument. STMV crystals grown in microgravity by liquid-liquid diffusion were more than 10-fold greater in total volume than any STMV crystals previously grown in the laboratory. X-ray diffraction data collected from eight STMV crystals grown in CRYOSTAT demonstrated a substantial improvement in diffraction quality over the entire resolution range when compared to data from crystals grown on Earth. In addition, the extent of the diffraction pattern for the STMV crystals grown in space extended to 1.8 A resolution, whereas the best crystals that were ever grown under conditions of Earth's gravity produced data limited to 2.3 A resolution. Other observations indicate that the growth of macromolecular crystals is indeed influenced by the presence or absence of gravity. These observations further suggest, consistent with earlier results, that the elimination of gravity provides a more favorable environment for such processes. PMID:1303744

  17. High-Pressure Geoscience Special Feature: Dynamic pressure-induced dendritic and shock crystal growth of ice VI

    NASA Astrophysics Data System (ADS)

    Lee, Geun Woo; Evans, William J.; Yoo, Choong-Shik

    2007-05-01

    Crystal growth mechanisms are crucial to understanding the complexity of crystal morphologies in nature and advanced technological materials, such as the faceting and dendrites found in snowflakes and the microstructure and associated strength properties of structural and icy planetary materials. In this article, we present observations of pressure-induced ice VI crystal growth, which have been predicted theoretically, but had never been observed experimentally to our knowledge. Under modulated pressure conditions in a dynamic-diamond anvil cell, rough single ice VI crystal initially grows into well defined octahedral crystal facets. However, as the compression rate increases, the crystal surface dramatically changes from rough to facet, and from convex to concave because of a surface instability, and thereby the growth rate suddenly increases by an order of magnitude. Depending on the compression rate, this discontinuous jump in crystal growth rate or "shock crystal growth" eventually produces 2D carpet-type fractal morphology, and moreover dendrites form under sinusoidal compression, whose crystal morphologies are remarkably similar to those predicted in theoretical simulations under a temperature gradient field. The observed strong dependence of the growth mechanism on compression rate, therefore, suggests a different approach to developing a comprehensive understanding of crystal growth dynamics.

  18. 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-α 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.

  19. 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.

  20. Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    2003-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.

  1. 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.

  2. 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.

  3. Confined Crystal Growth in Space. Deterministic vs Stochastic Vibroconvective Effects

    NASA Astrophysics Data System (ADS)

    Ruiz, Xavier; Bitlloch, Pau; Ramirez-Piscina, Laureano; Casademunt, Jaume

    directional solidification under microgravity", Journal of Crystal Growth 303 (2007) 262 -268. [2] X. Ruiz, P. Bitlloch, L. Ramé ırez-Piscina, J. Casademunt, "Solid segregation induced by stochastic acceleration fields", ELGRA News 26 (2009) 217.

  4. 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.

  5. Controlling Growth Orientation of Phthalocyanine Films by Electrical Fields

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Banks, C. E.; Frazier, D. O.; Ila, D.; Muntele, I.; Penn, B. G.; Sharma, A.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Organic Phthalocyanine films have many applications ranging from data storage to various non-linear optical devices whose quality is affected by the growth orientation of Phthalocyanine films. Due to the structural and electrical properties of Phthalocyanine molecules, the film growth orientation depends strongly on the substrate surface states. In this presentation, an electrical field up to 4000 V/cm is introduced during film growth. The Phthalocyanine films are synthesized on quartz substrates using thermal evaporation. An intermediate layer is deposited on some substrates for introducing the electrical field. Scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy are used for measuring surface morphology, film structure, and optical properties, respectively. The comparison of Phthalocyanine films grown with and without the electrical field reveals different morphology, film density, and growth orientation, which eventually change optical properties of these films. These results suggest that the growth method in the electrical field can be used to synthesized Phthalocyanine films with a preferred crystal orientation as well as propose an interaction mechanism between the substrate surface and the depositing molecules. The details of growth conditions and of the growth model of how the Phthalocyanine molecules grow in the electrical field will be discussed.

  6. Molecular modifiers reveal a mechanism of pathological crystal growth inhibition

    NASA Astrophysics Data System (ADS)

    Chung, Jihae; Granja, Ignacio; Taylor, Michael G.; Mpourmpakis, Giannis; Asplin, John R.; Rimer, Jeffrey D.

    2016-08-01

    Crystalline materials are crucial to the function of living organisms, in the shells of molluscs, the matrix of bone, the teeth of sea urchins, and the exoskeletons of coccoliths. However, pathological biomineralization can be an undesirable crystallization process associated with human diseases. The crystal growth of biogenic, natural and synthetic materials may be regulated by the action of modifiers, most commonly inhibitors, which range from small ions and molecules to large macromolecules. Inhibitors adsorb on crystal surfaces and impede the addition of solute, thereby reducing the rate of growth. Complex inhibitor-crystal interactions in biomineralization are often not well elucidated. Here we show that two molecular inhibitors of calcium oxalate monohydrate crystallization—citrate and hydroxycitrate—exhibit a mechanism that differs from classical theory in that inhibitor adsorption on crystal surfaces induces dissolution of the crystal under specific conditions rather than a reduced rate of crystal growth. This phenomenon occurs even in supersaturated solutions where inhibitor concentration is three orders of magnitude less than that of the solute. The results of bulk crystallization, in situ atomic force microscopy, and density functional theory studies are qualitatively consistent with a hypothesis that inhibitor-crystal interactions impart localized strain to the crystal lattice and that oxalate and calcium ions are released into solution to alleviate this strain. Calcium oxalate monohydrate is the principal component of human kidney stones and citrate is an often-used therapy, but hydroxycitrate is not. For hydroxycitrate to function as a kidney stone treatment, it must be excreted in urine. We report that hydroxycitrate ingested by non-stone-forming humans at an often-recommended dose leads to substantial urinary excretion. In vitro assays using human urine reveal that the molecular modifier hydroxycitrate is as effective an inhibitor of nucleation

  7. Molecular modifiers reveal a mechanism of pathological crystal growth inhibition

    NASA Astrophysics Data System (ADS)

    Chung, Jihae; Granja, Ignacio; Taylor, Michael G.; Mpourmpakis, Giannis; Asplin, John R.; Rimer, Jeffrey D.

    2016-08-01

    Crystalline materials are crucial to the function of living organisms, in the shells of molluscs, the matrix of bone, the teeth of sea urchins, and the exoskeletons of coccoliths. However, pathological biomineralization can be an undesirable crystallization process associated with human diseases. The crystal growth of biogenic, natural and synthetic materials may be regulated by the action of modifiers, most commonly inhibitors, which range from small ions and molecules to large macromolecules. Inhibitors adsorb on crystal surfaces and impede the addition of solute, thereby reducing the rate of growth. Complex inhibitor–crystal interactions in biomineralization are often not well elucidated. Here we show that two molecular inhibitors of calcium oxalate monohydrate crystallization—citrate and hydroxycitrate—exhibit a mechanism that differs from classical theory in that inhibitor adsorption on crystal surfaces induces dissolution of the crystal under specific conditions rather than a reduced rate of crystal growth. This phenomenon occurs even in supersaturated solutions where inhibitor concentration is three orders of magnitude less than that of the solute. The results of bulk crystallization, in situ atomic force microscopy, and density functional theory studies are qualitatively consistent with a hypothesis that inhibitor–crystal interactions impart localized strain to the crystal lattice and that oxalate and calcium ions are released into solution to alleviate this strain. Calcium oxalate monohydrate is the principal component of human kidney stones and citrate is an often-used therapy, but hydroxycitrate is not. For hydroxycitrate to function as a kidney stone treatment, it must be excreted in urine. We report that hydroxycitrate ingested by non-stone-forming humans at an often-recommended dose leads to substantial urinary excretion. In vitro assays using human urine reveal that the molecular modifier hydroxycitrate is as effective an inhibitor of

  8. 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 -10°C and -25°C, 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

  9. 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-γ 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-γ 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

  10. 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-γ 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-γ 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

  11. 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-γ 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-γ 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.

  12. Control of nucleation and growth in protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Meehan, Edward J.

    1988-01-01

    The potential advantages of nucleation and growth control through temperature, rather than the addition of precipitants or removal of solvent, are discussed. A simple light scattering arrangement for the characterization of nucleation and growth conditions in solutions is described. The temperature dependence of the solubility of low ionic strength lysozyme solutions is applied in preliminary nucleation and growth experiments.

  13. Growth of aluminum nitride bulk crystals by sublimation

    NASA Astrophysics Data System (ADS)

    Liu, Bei

    The commercial potential of III-nitride semiconductors is already being realized by the appearance of high efficiency, high reliability, blue and green LEDS around the world. However, the lack of a native nitride substrate has hindered the full-realization of more demanding III-nitride devices. To date, single aluminum nitride (AlN) crystals are not commercially available. New process investigation is required to scale up the crystal size. New crucibles stable up to very high temperatures (˜2500°C) are needed which do not incorporate impurities into the growing crystals. In this thesis, the recent progresses in bulk AlN crystal growth by sublimation-recondensation were reviewed first. The important physical, optical and electrical properties as well as chemical and thermal stabilities of AlN were discussed. The development of different types of growth procedures including self-seeding, substrate employed and a new "sandwich" technique were covered in detail. Next, the surface morphology and composition at the initial stages of AlN grown on 6H-SiC (0001) were investigated. Discontinuous AlN coverage occurred after 15 minutes of growth. The initial discontinuous nucleation of AlN and different lateral growth of nuclei indicated discontinuous AIN direct growth on on-axis 6H-SiC substrates. At the temperature in excess of 2100°C, the durability of the furnace fixture materials (crucibles, retorts, etc.) remains a critical problem. The thermal and chemical properties and performance of several refractory materials, including tantalum carbide, niobium carbide, tungsten, graphite, and hot-pressed boron nitride (HPBN), in inert gas, as well as under AIN crystal growth conditions were discussed. TaC and NbC are the most stable crucible materials in the crystal growth system. HPBN crucible is more suitable for AlN self-seeding growth, as crystals tend to nucleate in thin colorless platelets with low dislocation density. Finally, clear and colorless thin platelet Al

  14. 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.

  15. Crystal growth of mixed AlN-SiC bulk crystals

    NASA Astrophysics Data System (ADS)

    Filip, Octavian; Bickermann, Matthias; Epelbaum, Boris M.; Heimann, Paul; Winnacker, Albrecht

    2010-09-01

    Bulk AlN-SiC mixed single crystals are prepared by sublimation growth employing pure AlN or mixed AlN-SiC sources and 6H-SiC seed crystals. As the growth temperature is increased from 1900 to 2050 °C, using seeds with different off-axis orientations, inclined up to 42° from the basal plane toward the (0 1 -1 0)-plane, or using different source materials, crystals with different Si/C contents are obtained. Dependent on the Si and/or C content, crystal coloration changes from yellowish to greenish to blackish. Modification in crystals' coloration and corresponding changes in below band-gap optical absorption and cathodoluminescence spectra are discussed.

  16. 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

  17. Crystal growth furnace with trap doors

    DOEpatents

    Sachs, Emanual M.; Mackintosh, Brian H.

    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.

  18. 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.

  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. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  1. 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.

  2. Epitaxial growth of germanium thin films on crystal silicon substrates by solid phase crystallization

    NASA Astrophysics Data System (ADS)

    Isomura, Masao; Kanai, Mikuri

    2015-04-01

    We have investigated the solid phase crystallization (SPC) of amorphous germanium (a-Ge) precursors on single crystalline silicon (c-Si) substrates as seed layers and successfully obtained the epitaxial growth of Ge. The n-type (100) Si substrate is most suitable for preferential growth following the substrate orientation, because the velocity of preferential growth is higher than those on the other substrates and preferential growth is completed before random nucleation. The impurity contamination in the a-Ge precursors probably enhances random nucleation. The epitaxial growth is disturbed by the impurity contamination at a relatively high SPC temperature in the intrinsic and p-type Si substrates with the (100) orientation and the n-type and intrinsic Si substrates with the (111) orientation, because the lower velocity of preferential growth allows random crystallization. Almost no epitaxial growth is observed on the p-type (111) Si substrates even when low-impurity a-Ge precursors are used.

  3. Pathways to self-organization: Crystallization via nucleation and growth.

    PubMed

    Jungblut, S; Dellago, C

    2016-08-01

    Crystallization, a prototypical self-organization process during which a disordered state spontaneously transforms into a crystal characterized by a regular arrangement of its building blocks, usually proceeds by nucleation and growth. In the initial stages of the transformation, a localized nucleus of the new phase forms in the old one due to a random fluctuation. Most of these nuclei disappear after a short time, but rarely a crystalline embryo may reach a critical size after which further growth becomes thermodynamically favorable and the entire system is converted into the new phase. In this article, we will discuss several theoretical concepts and computational methods to study crystallization. More specifically, we will address the rare event problem arising in the simulation of nucleation processes and explain how to calculate nucleation rates accurately. Particular attention is directed towards discussing statistical tools to analyze crystallization trajectories and identify the transition mechanism. PMID:27498980

  4. Growth of mercuric iodide single crystals from dimethylsulfoxide

    DOEpatents

    Carlston, Richard C.

    1976-07-13

    Dimethylsulfoxide is used as a solvent for the growth of red mercuric iodide (HgI.sub.2) crystals for use in radiation detectors. The hygroscopic property of the solvent allows controlled amounts of water to enter into the solvent phase and diminish the large solubility of HgI.sub.2 so that the precipitating solid collects as well-defined euhedral crystals which grow into a volume of several cc.

  5. 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.

  6. 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.

  7. 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.

  8. Growth, crystalline perfection and characterization of benzophenone oxime crystal

    NASA Astrophysics Data System (ADS)

    Rajasekar, M.; Muthu, K.; Meenatchi, V.; Bhagavannarayana, G.; Mahadevan, C. K.; Meenakshisundaram, SP.

    Single crystals of benzophenone oxime (BPO) have been grown by slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the crystal belongs to monoclinic system and cell parameters are, a = 9.459 Å, b = 8.383 Å, c = 26.690 Å, v = 2115 Å3 and β = 92.807°. The structure and the crystallinity of the materials were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by FT-IR analysis. The TG/DSC studies reveal the purity of the material and the crystals are transparent in the entire visible region having a lower optical cut-off at ˜300 nm. The crystalline perfection was evaluated by high-resolution X-ray diffraction (HRXRD). The crystal is further characterized by Kurtz powder technique, dielectric studies and microhardness analysis.

  9. Anomalous growth of single ice crystals in solution

    NASA Technical Reports Server (NTRS)

    Gill, W. N.

    1979-01-01

    It is shown that major discrepancies exist between experiments and theory for ice crystal growth from solution. Accurate data, taken in a microgravity environment, approximate analytical models, and exact (probably numerical) models all are needed to advance our understanding of ice crystal growth phenomena. A new approximate semi-empirical theory is presented which predicts that a relatively sharp transition from natural convection control to diffusion control for ice growth in pure water occurs at a subcooling of about 10 C (a reduced temperature difference of about 0.125). No reliable data exist to test this prediction. The theory also predicts qualitatively the growth of ice in NaCl solution in which maxima in the growth rates are observed at various levels of subcooling.

  10. Growth and birefringence studies of semi organic non-linear optical LHB single crystal

    NASA Astrophysics Data System (ADS)

    Jayaramakrishnan, V.; Prasanyaa, T.; Haris, M.; Bhoopathi, G.

    2015-02-01

    In the last few decades nonlinear optical materials are getting attention in the field of optical data storage, telecommunication, second harmonic generation (SHG) and optical signal processing, etc. In the present work we are reporting the single crystal growth of L-Histidine with hydro-bromic acid. The L-Histidine bromide (LHB) single crystals have been harvested from the solution in a span of 34 days by adopting slow cooling solution growth technique. The grown crystals have been subjected to powder X-ray diffraction studies to identify the cell parameters and structure. The crystalline perfection has been defined by rocking curve (HRXRD) analysis. Optical transmission spectra reveal the optical properties of the grown crystals. The Modified channel spectrum (MCS) method has been adopted for the study of spectral dependence of linear birefringence over the wavelength range 480-620 nm. The second harmonic generation efficiency was tested by using Kurtz and Perry method, keeping KDP as reference.

  11. Growth of single crystals of mercuric iodide (HgI/sub 2/) in spacelab III

    SciTech Connect

    Van Den Berg, L.; Schnepple, W.F.

    1981-01-01

    Continued development of a system designed to grow crystals by physical vapor transport in the environment of Spacelab III will be described, with special emphasis on simulation of expected space conditions, adjustment of crystal growth parameters, and on board observation and control of the experiment by crew members and ground personnel. A critical factor in the use of mercuric iodide for semiconductor detectors of x-rays and gamma-rays is the crystalline quality of the material. The twofold purpose of the Spacelab III experiment is therefore to grow single crystals with superior electronic properties as an indirect result of the greatly reduced gravity field during the growth, and to obtain data which will lead to improved understanding of the vapor transport mechanism. The experiments planned to evaluate the space crystals, including gamma-ray diffractometry and measurements of stoichiometry, lattice dimensions, mechanical strength, luminescense, and detector performance are discussed.

  12. Crystal growth simulations of H(2)S hydrate.

    PubMed

    Liang, Shuai; Kusalik, Peter G

    2010-07-29

    In this paper, we report a molecular simulation study exploring the crystal growth behavior of H(2)S hydrates within two-phase (H(2)S hydrate crystal and H(2)S aqueous solution) and three-phase (H(2)S hydrate crystal, liquid H(2)S, and H(2)S aqueous solution) systems. The microscopic mechanisms of growth, as well as the interfacial properties during the heterogeneous crystal growth process, are probed. We find that the H(2)S hydrate can be grown at a higher rate than methane hydrates under comparable conditions (Vatamanu, J.; Kusalik, P. G. J. Phys. Chem. B 2006, 110, 15896). The three-phase simulations, which also allow us to identify the simulation conditions on the experimental phase diagram, demonstrate that the present models reasonably reproduce the phase behavior of this system. We find that the crystal interface has a strong affinity for water molecules. We observed a relatively low level of defects in the newly formed H(2)S hydrate crystal.

  13. 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.

  14. Density Functional Theory of Crystal Growth: Lennard-Jones Fluids

    NASA Astrophysics Data System (ADS)

    Shen, Yu Chen; Oxtoby, David

    1996-03-01

    We employ an extension of density functional theory to the dynamics of phase transitions in order to study the velocities of crystal growth and melting at planar undercooled and superheated crystal-melt interfaces. The free energy functional we use has a square-gradient form, with the parameters for a Lennard-Jones interaction potential determined by a modified weighted density approximation (MWDA) applied locally through the liquid-solid interface. We explore the role of the density change on freezing in crystal and melt growth, and discover a significant asymmetry between freezing and melting both close to and far from the equilibrium freezing point. The behavior of the superheated solid is governed by the close proximity of a spinodal, whereas in the undercooled liquid there is no evidence for a spinodal and the growth at large undercoolings is affected instead by the density deficit that appears in front of the growing interface.

  15. 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.

  16. 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.

  17. 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.

  18. Rapid growth of α-LiIO3 crystal

    NASA Astrophysics Data System (ADS)

    Rubakha, V. I.; Puchkov, A. V.

    2014-09-01

    A fundamental possibility of significantly increasing the growth rate of α-LiIO3 crystals without the formation of visible defects in them is demonstrated. The corresponding equipment is designed and a technique for obtaining intermediate-size samples is developed. The crystals grown with an average rate of up to 4 mm/days along the Z axis are of high enough quality to be used as materials of optical elements for laser frequency doubling. α-LiIO3 crystals have been grown both in an open volume via natural faceting and in a rectangular habit, where growth occurs basically through the pyramid (101) face. It is shown that that amount of limiting impurities in the raw material used can be reduced and that the applicability of this material for rapid growth can be verified.

  19. Crystal splitting in the growth of Bi2S3.

    PubMed

    Tang, Jing; Alivisatos, A Paul

    2006-12-01

    Bi2S3 nanostructures with a sheaflike morphology are obtained via reaction of bismuth acetate-oleic acid complex with elemental sulfur in 1-octadecence. These structures may form by the splitting crystal growth mechanism, which is known to account for the morphology some mineral crystals assume in nature. By control of the synthetic parameters, different shapes are obtained, analogous to those which have been observed to occur by crystal splitting in minerals. These new and complex Bi2S3 nanostructures are characterized by transmission and scanning electron microscopy, and electron and X-ray diffraction.

  20. 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.

  1. Adaptive temperature profile control of a multizone crystal growth furnace

    NASA Technical Reports Server (NTRS)

    Batur, C.; Sharpless, R. B.; Duval, W. M. B.; Rosenthal, B. N.

    1991-01-01

    An intelligent measurement system is described which is used to assess the shape of a crystal while it is growing inside a multizone transparent furnace. A color video imaging system observes the crystal in real time, and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.

  2. Crystal growth of cadmium oxide from the vapor phase

    SciTech Connect

    Shimada, S.; Nomura, S.; Kodaira, K.; Matsushita, T.

    1987-10-01

    Single crystals of CdO were grown at temperatures of 930/sup 0/ to 1080/sup 0/C from the vapor phase by air oxidation of Cd vapors which were generated at a constant rate by reaction of CdO with graphite. A prolonged growth up to 70 h at 1030/sup 0/C produced a crystal conglomerate with a maximum size of 13.5 mm. The electrical resistivity and electron density of the crystal in the direction of <100> were 5x10/sup -4/ ..cap omega...cm and 1.3x10/sup 20/cm/sup 3/, respectively, at 20/sup 0/C.oefficients

  3. Modelling the growth of triglycine sulphate crystals in Spacelab 3

    NASA Technical Reports Server (NTRS)

    Yoo, Hak-Do; Wilcox, William R.; Lal, Ravindra; Trolinger, James D.

    1988-01-01

    Two triglycine sulphate crystals were grown from an aqueous solution on the Spacelab 3 mission. Using a diffusion coefficient of 0.00002 sq cm/sec, a computer simulation gave reasonable agreement between experimental and theoretical crystal sizes and interferometric lines in the solution near the growing crystal. This diffusion coefficient is larger than most measured values, possibly due to fluctuating accelerations on the order of 0.001 g. The average acceleration was estimated to be less than 10 to the -6th g. At this level buoyancy-driven convection is predicted to add approximately 20 percent to the steady-state growth rate.

  4. Growth of large zeolite crystals in space

    SciTech Connect

    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 do not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

  5. 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.

  6. Enhancing the volume and the optical quality of hen egg-white lysozyme crystals by coupling the salt concentration gradient crystallization method with a magnetic field

    PubMed Central

    Magay, Elena; Cho, Sang Jin; Kim, Shin Ae

    2012-01-01

    The effect of coupling the salt concentration gradient crystallization method with the use of the paramagnetic salt MnCl2 and a magnetic field is reported. The use of a simple magnetic device is proposed to have a significant effect on hen egg-white lysozyme crystal growth. Large single crystals greater than 10 mm3 in volume with optical perfection were consistently obtained in this study. PMID:22997475

  7. 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.

  8. Crystal growth of sulfide materials from alkali polysulfide liquids

    NASA Technical Reports Server (NTRS)

    White, W. B.

    1979-01-01

    The fluids experiment system was designed for low temperature solution growth, nominally aqueous solution growth. The alkali polysulfides, compositions in the systems Na2S-S and K2S-S form liquids in the temperature range of 190 C to 400 C. These can be used as solvents for other important classes of materials such as transition metal and other sulfides which are not soluble in aqueous media. Among these materials are luminescent and electroluminescent crystals whose physical properties are sensitive functions of crystal perfection and which could, therefore, serve as test materials for perfection improvement under microgravity conditions.

  9. Growth morphologies and optical properties of LTA single crystal.

    PubMed

    Liu, Xiaojing; Ren, Miaojuan; Chen, Gang; Wang, Peiji

    2013-12-01

    Atomic force microscopy (AFM) has been used to study the growth morphologies of l-threonine acetate (abbreviated as LTA) crystal. Spiral growth hillocks and typical step patterns are described and discussed. Nuclei with various shapes often distribute at the larger step terraces. Eventually, in order to investigate microscopic second order nonlinear optical properties of LTA crystals, the molecular dipole moment (μ), polarizability (α), and first hyperpolarizability (β) were computed using a series of basis sets including polarized and diffuse functions at the framework of Hartree-Fock and density functional theory methods. The study is helpful to the further development of l-threonine analogs with improved nonlinear optical properties.

  10. 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.

  11. Dendritic crystal growth in pure /sup 4/He

    SciTech Connect

    Franck, J.P.; Jung, J.

    1986-08-01

    Dendritic crystal growth of pure hcp and fcc /sup 4/He was observed at pressures between 210 and 6500 bar. Dendrite morphology depends on fluid supercooling and crystal phase. At large supercooling, dendrites with side arms are observed, whereas at low supercooling dendrites grow without side arms. The morpholpogy of hcp /sup 4/He dendrites is strongly influenced by crystalline anisotropy. Comparison with present theories of dendrite growth show good agreement with the power law dependencies of velocity, tip radius, and Peclet number on supercooling. Numerically, theory predicts much larger velocities than are observed. The stability parameter sigma is found to be much smaller than theoretically predicted.

  12. Crystal growth by precipitation under microgravity

    NASA Technical Reports Server (NTRS)

    Authier, A.; Lefaucheux, F.; Robert, M. C.

    1979-01-01

    The importance of understanding the mechanisms associated with defect generation during growth and the influence of gravity is stressed. An experiment is described. The advantages of adapting this experiment to the FES are then discussed. A brief survey of the ground based research under way is given.

  13. Some features of two commercial softwares for the modeling of bulk crystal growth processes

    NASA Astrophysics Data System (ADS)

    Santailler, J. L.; Duffar, T.; Théodore, F.; Boiton, P.; Barat, C.; Angelier, B.; Giacometti, N.; Dusserre, P.; Nabot, J. P.

    1997-10-01

    Two commercial codes, FIDAP and MARC, have been used to model a number of crystal growth processes in collaboration with industrial and research teams. Examples of global and local simulations in the field of heat transfer, hydrodynamics, chemistry and mechanics are given and the results are compared to experimental measurements, with good agreement as a rule. This establishes that such codes can be used to help improve crystal growth processes, while full global transient models still belong to software specifically written in order to model crystal growth. Emphasis is put on the necessity to validate the numerical results by comparison with experiments and to have a clear understanding of the physical laws hidden behind the software.

  14. 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.

  15. The dynamic nature of crystal growth in pores

    PubMed Central

    Godinho, Jose R. A.; Gerke, Kirill M.; Stack, Andrew G.; Lee, Peter D.

    2016-01-01

    The kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocities predominate and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks. PMID:27615371

  16. The dynamic nature of crystal growth in pores

    DOE PAGESBeta

    Godinho, Jose R. A.; Gerke, Kirill M.; Stack, Andrew G.; Lee, Peter D.

    2016-09-12

    We report that the kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocities predominatemore » and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Lastly, accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks.« less

  17. The dynamic nature of crystal growth in pores.

    PubMed

    Godinho, Jose R A; Gerke, Kirill M; Stack, Andrew G; Lee, Peter D

    2016-01-01

    The kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocities predominate and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks. PMID:27615371

  18. The dynamic nature of crystal growth in pores

    NASA Astrophysics Data System (ADS)

    Godinho, Jose R. A.; Gerke, Kirill M.; Stack, Andrew G.; Lee, Peter D.

    2016-09-01

    The kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocities predominate and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks.

  19. Effects of magnetic fields on dissolution of arthritis causing crystals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Y.; Iwasaka, M.

    2015-05-01

    The number of gout patients has rapidly increased because of excess alcohol and salt intake. The agent responsible for gout is the monosodium urate (MSU) crystal. MSU crystals are found in blood and consist of uric acid and sodium. As a substitute for drug dosing or excessive water intake, physical stimulation by magnetic fields represents a new medical treatment for gout. In this study, we investigated the effects of a magnetic field on the dissolution of a MSU crystal suspension. The white MSU crystal suspension was dissolved in an alkaline solution. We measured the light transmission of the MSU crystal suspension by a transmitted light measuring system. The magnetic field was generated by a horizontal electromagnet (maximum field strength was 500 mT). The MSU crystal suspension that dissolved during the application of a magnetic field of 500 mT clearly had a higher dissolution rate when compared with the control sample. We postulate that the alkali solution promoted penetration upon diamagnetic rotation and this magnetic field orienting is because of the pronounced diamagnetic susceptibility anisotropy of the MSU crystal. The results indicate that magnetic fields represent an effective gout treatment approach.

  20. 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 100°C and 150°C 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.

  1. 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.

  2. Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

    SciTech Connect

    Koizumi, H.; Uda, S.; Fujiwara, K.; Nozawa, J.; Tachibana, M.; Kojima, K.

    2014-10-06

    X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

  3. 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.

  4. 2D modeling of the regeneration surface growth on crystals

    NASA Astrophysics Data System (ADS)

    Thomas, V. G.; Gavryushkin, P. N.; Fursenko, D. A.

    2012-11-01

    A physical model is proposed to describe the growth of regeneration surfaces (flat crystal surfaces that are not parallel to any possible faces). According to this model, the change in the growth rate of a regeneration surface during its evolution and the decrease in the number of subindividuals forming the growth front can be explained by the implementation of two types of geometric selection: within each subindividual (the absorption of rapidly growing faces by slowly growing ones) and between subindividuals (when subindividuals absorb each other). A numerical modeling of the growth of the regeneration surface (30.30.19) of potassium alum crystals showed quantitative agreement between the model proposed and the experimental data.

  5. 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.

  6. Crystal Growth of II-VI Semiconducting Alloys by Directional Solidification

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Su, Ching-Hua; Cobb, Sharon D.; Scripa, Rosalia A.; Sha, Yi-Gao

    1999-01-01

    This research study is investigating the effects of a microgravity environment during the crystal growth of selected II-VI semiconducting alloys on their compositional, metallurgical, electrical and optical properties. The on-going work includes both Bridgman-Stockbarger and solvent growth methods, as well as growth in a magnetic field. The materials investigated are II-VI, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se, where x is between 0 and 1 inclusive, with particular emphasis on x-values appropriate for infrared detection and imaging in the 5 to 30 micron wavelength region. Wide separation between the liquidus and solidus of the phase diagrams with consequent segregation during solidification and problems associated with the high volatility of one of the components (Hg), make the preparation of homogeneous, high-quality, bulk crystals of the alloys an extremely difficult nearly an impossible task in a gravitational environment. The three-fold objectives of the on-going investigation are as follows: (1) To determine the relative contributions of gravitationally-driven fluid flows to the compositional redistribution observed during the unidirectional crystal growth of selected semiconducting solid solution alloys having large separation between the liquidus and solidus of the constitutional phase diagram; (2) To ascertain the potential role of irregular fluid flows and hydrostatic pressure effects in generation of extended crystal defects and second-phase inclusions in the crystals; and, (3) To obtain a limited amount of "high quality" materials needed for bulk crystal property characterizations and for the fabrication of various device structures needed to establish ultimate material performance limits. The flight portion of the study was to be accomplished by performing growth experiments using the Crystal Growth Furnace (CGF) manifested to fly on various Spacelab missions.

  7. Effect of Co2+ doping on solubility, crystal growth and properties of ADP crystals

    NASA Astrophysics Data System (ADS)

    Ganesh, V.; Shkir, Mohd.; AlFaify, S.; Yahia, I. S.

    2016-09-01

    Bulk size crystal growth of ADP with different concentrations doping of cobalt (Co2+) has been done by low cost slow evaporation technique at ambient conditions. The solubility measurement was carried out on pure and doped crystals and found that the solubility is decreasing with doping concentrations. The presence of Co2+ ion in crystalline matrix of ADP has been confirmed by structural, vibrational and elemental analyses. Scanning electron microscopic study reveals that the doping has strong effect on the quality of the crystals. The optical absorbance and transmission confirms the enhancement of quality of ADP crystals due to Co2+ doping and so the optical band gap. Further the dislocation, photoluminescence, dielectric and mechanical studies confirms that the properties of grown crystals with Co2+ doping has been enriched and propose it as a better candidate for optoelectronic applications.

  8. Accumulated distribution of material gain at dislocation crystal growth

    NASA Astrophysics Data System (ADS)

    Rakin, V. I.

    2016-05-01

    A model for slowing down the tangential growth rate of an elementary step at dislocation crystal growth is proposed based on the exponential law of impurity particle distribution over adsorption energy. It is established that the statistical distribution of material gain on structurally equivalent faces obeys the Erlang law. The Erlang distribution is proposed to be used to calculate the occurrence rates of morphological combinatorial types of polyhedra, presenting real simple crystallographic forms.

  9. 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.

  10. The Growth of Protein Crystals Using McDUCK

    NASA Technical Reports Server (NTRS)

    Ewing, Felicia; Wilson, Lori; Nadarajah, Arunan; Pusey, Marc

    1998-01-01

    Most of the current microgravity crystal growth hardware is optimized to produce crystals within the limited time available on orbit. This often results in the actual nucleation and growth process being rushed or the system not coming to equilibrium within the limited time available. Longer duration hardware exists, but one cannot readily pick out crystals grown early versus those which nucleated and grew more slowly. We have devised a long duration apparatus, the Multi-chamber Dialysis Unit for Crystallization Kinetics, or McDUCK. This apparatus-is a series of protein chambers, stacked upon a precipitant reservoir chamber. All chambers are separated by a dialysis membrane, which serves to pass small molecules while retaining the protein. The volume of the Precipitant chamber is equal to the sum of the volumes of the protein chamber. In operation, the appropriate chambers are filled with precipitant solution or protein solution, and the McDUCK is placed standing upright, with the precipitant chamber on the bottom. The precipitant diffuses upwards over time, with the time to reach equilibration a function of the diffusivity of the precipitant and the overall length of the diffusion pathway. Typical equilibration times are approximately 2-4 months, and one can readily separate rapid from slow nucleation and growth crystals. An advantage on Earth is that the vertical precipitant concentration gradient dominates that of the solute, thus dampening out solute density gradient driven convective flows. However, large Earth-grown crystals have so far tended to be more two dimensional. Preliminary X-ray diffraction analysis of lysozyme crystals grown in McDUCK have indicated that the best, and largest, come from the middle chambers, suggesting that there is an optimal growth rate. Further, the improvements in diffraction resolution have been better signal to noise ratios in the low resolution data, not an increase in resolution overall. Due to the persistently large crystals

  11. 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.

  12. Identification and control of a multizone crystal growth furnace

    NASA Technical Reports Server (NTRS)

    Batur, C.; Sharpless, R. B.; Duval, W. M. B.; Rosenthal, B. N.; Singh, N. B.

    1992-01-01

    This paper presents an intelligent adaptive control system for the control of a solid-liquid interface of a crystal while it is growing via directional solidification inside a multizone transparent furnace. The task of the process controller is to establish a user-specified axial temperature profile and to maintain a desirable interface shape. Both single-input-single-output and multi-input-multi-output adaptive pole placement algorithms have been used to control the temperature. Also described is an intelligent measurement system to assess the shape of the crystal while it is growing. A color video imaging system observes the crystal in real time and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.

  13. Polymer-mediated growth of crystals and mesocrystals.

    PubMed

    Cölfen, Helmut

    2013-01-01

    Polymers are important additives for the control of mineralization reactions in both biological and bioinspired mineralization. The reason is that they allow for a number of interactions with the growing crystals and even amorphous minerals. These can substantially influence the way the mineral grows on several levels. Already in the prenucleation phase, polymers can control the formation of prenucleation clusters and subsequently the nucleation event. Also, polymers can control whether the further crystallization follows a classical or nonclassical particle-mediated growth path. In this chapter, the main ways in which polymers can be used to control a crystallization reaction will be highlighted. In addition, polymers that are useful for this purpose and the experimental conditions suitable for directing a crystallization reaction into the desired direction through the use of polymers will be described.

  14. Second harmonic generation and crystal growth of new chalcone derivatives

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Dharmaprakash, S. M.; Ramakrishna, K.; Fun, Hoong-Kun; Sai Santosh Kumar, R.; Narayana Rao, D.

    2007-05-01

    We report on the synthesis, crystal structure and optical characterization of chalcone derivatives developed for second-order nonlinear optics. The investigation of a series of five chalcone derivatives with the second harmonic generation powder test according to Kurtz and Perry revealed that these chalcones show efficient second-order nonlinear activity. Among them, high-quality single crystals of 3-Br-4'-methoxychalcone (3BMC) were grown by solvent evaporation solution growth technique. Grown crystals were characterized by X-ray powder diffraction (XRD), laser damage threshold, UV-vis-NIR and refractive index measurement studies. Infrared spectroscopy, thermogravimetric analysis and differential thermal analysis measurements were performed to study the molecular vibration and thermal behavior of 3BMC crystal. Thermal analysis does not show any structural phase transition.

  15. Epitaxial growth of single crystal films

    NASA Technical Reports Server (NTRS)

    Lind, M. D.; Kroes, R. L.; Immorlica, A. A., Jr.

    1981-01-01

    An experiment in gallium arsenide liquid phase epitaxy (LPE) on a flight of the SPAR 6 is described. A general purpose LPE processor suitable for either SPAR or Space Transportation System flights was designed and built. The process was started before the launch, and only the final step, in which the epitaxial film is grown, was performed during the flight. The experiment achieved its objectives; epitaxial films of reasonably good quality and very nearly the thickness predicted for convection free diffusion limited growth were produced. The films were examined by conventional analytical techniques and compared with films grown in normal gravity.

  16. 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.

  17. Crystal growth and optical properties of rare earth calcium oxoborates

    NASA Astrophysics Data System (ADS)

    Vivien, Daniel; Aka, Gérard; Kahn-Harari, Andrée; Aron, Astrid; Mougel, Frédéric; Bénitez, Jean-Marie; Ferrand, Bernard; Klein, Régine; Kugel, Godefroy; Nain, Nicole Le; Jacquet, Michèle

    2002-04-01

    This paper begins with a historical report of the discovery of Ca 4REO(BO 3) 3 (RECOB), a new family of nonlinear optic (NLO) materials. It presents the crystal growth and some physical characteristics related to their use in NLO applications. Then the NLO properties of GdCOB and YCOB are reviewed and the influence of some cationic substitutions is described.

  18. 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.

  19. 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.

  20. Direct observation of crystal growth from solution using optical investigation of a growing crystal face

    NASA Technical Reports Server (NTRS)

    Lal, Ravindra

    1994-01-01

    The first technical report for the period 1 Jan. 1993 till 31 Dec. 1993 for the research entitled, 'Direct observation of crystal growth from solution using Optical Investigation of a growing crystal Face' is presented. The work on the project did not start till 1 June 1993 due to the non-availability of the required personnel. The progress of the work during the period 1 June 1993 till the end of 1993 is described. Significant progress was made for testing various optical diagnostic techniques for monitoring crystal solution. Some of the techniques that are being tested are: heterodyne detection technique, in which changes in phase are measured as a interferometric function of time/crystal growth; a conventional technique, in which a fringe brightness is measured as a function of crystal growth/time; and a Mach-Zehnder interferometric technique in which a fringe brightness is measured as a function of time to obtain information on concentration changes. During the second year it will be decided to incorporate the best interferometric technique along with the ellipsometric technique, to obtain real time in-situ growth rate measurements. A laboratory mock-up of the first two techniques were made and tested.

  1. The effect of nucleation and crystal growth on isotope fractionation

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Gaetani, G. A.; Liu, C.; Hu, P.; Cohen, A. L.

    2011-12-01

    A set of "free-drift" experiments is conducted to precipitate aragonites from seawater at controlled temperature (25-55oC) and CO2 degassing rate in the lab. These experiments help to calibrate a coupled degassing-nucleation-crystal growth model, which not only can reproduce measured pH and alkalinity over the course of the experiments, but also predict crystal size within a factor of two of the measured values, the activation energy of the precipitation reaction constant to be 24.3±1.3 kJ/mol, the surface energy of aragonite crystals that is consistent with estimation by atomistic simulation and crystal morphology. Forward simulation of our precipitation experiments using calibrated parameters reveal the supersaturation of seawater arrives at a critical value (~13-50 in our experiment) before nucleation initiates and when the concentration of the total dissolved inorganic carbon (DIC) reduces to that of Ca. This result cannot be explained by classical nucleation theory (CNT), but is consistent with recently proposed "two-step" nucleation model, implying solution chemistry determines when the nucleation starts but the surface properties of crystal (surface energy and crystal morphology) determine the size of the crystal. It also requires not only carbonate ions but all other DIC species within a sphere of a-few-micron radius actively participate into the nucleation process. This model is then used as a framework to understand oxygen and Mg isotope fractionation between carbonates and fluid. Our results suggest nucleation and crystal growth will affect isotope fractionation at different levels depending on experimental conditions. A quantitative analysis using our model can help reconcile the isotope fractionation factors determined by various experimental approaches.

  2. 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.

  3. Slow crack growth in single-crystal silicon.

    PubMed

    Connally, J A; Brown, S B

    1992-06-12

    Time-dependent crack growth has been measured on a precracked, single-crystal silicon cantilever beam 75 micrometers long that was excited at resonance. Growth of the precrack changes the resonant frequency of the beam, which is correlated to crack length. The measured steady-state crack growth rate was as slow as 2.9 x 10(-13) meter per second, although the apparatus can measure crack growth rates as low as 10(-15) meter per second. It is postulated that static fatigue of the native surface silica layer is the mechanism for crack growth. These experiments demonstrate the possibility of rate-dependent failure of silicon devices and the applicability of linear elastic fracture mechanics to small-scale micromechanical devices. The results indicate that slow crack growth must therefore be considered when evaluating the reliability of thin-film silicon structures.

  4. Device and method for screening crystallization conditions in solution crystal growth

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor)

    1995-01-01

    A device and method for detecting optimum protein crystallization conditions and for growing protein crystals in either 1g or microgravity environments comprising a housing, defining at least one pair of chambers for containing crystallization solutions is presented. The housing further defines an orifice therein for providing fluid communication between the chambers. The orifice is adapted to receive a tube which contains a gelling substance for limiting the rate of diffusive mixing of the crystallization solutions. The solutions are diffusively mixed over a period of time defined by the quantity of gelling substance sufficient to achieve equilibration and to substantially reduce density driven convection disturbances therein. The device further includes endcaps to seal the first and second chambers. One of the endcaps includes a dialysis chamber which contains protein solution in which protein crystals are grown. Once the endcaps are in place, the protein solution is exposed to the crystallization solutions wherein the solubility of the protein solution is reduced at a rate responsive to the rate of diffusive mixing of the crystallization solutions. This allows for a controlled approach to supersaturation and allows for screening of crystal growth conditions at preselected intervals.

  5. Device and Method for Screening Crystallization Conditions in Solution Crystal Growth

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor)

    1997-01-01

    A device and method for detecting optimum protein crystallization conditions and for growing protein crystals in either 1 g or microgravity environments comprising a housing defining at least one pair of chambers for containing crystallization solutions. The housing further defines an orifice therein for providing fluid communication between the chambers. The orifice is adapted to receive a tube which contains a gelling substance for limiting the rate of diffusive mixing of the crystallization solutions. The solutions are diffusively mixed over a period of time defined by the quantity of gelling substance sufficient to achieve equilibration and to substantially reduce density driven convection disturbances therein. The device further includes endcaps to seal the first and second chambers. One of the endcaps includes a dialysis chamber which contains protein solution in which protein crystals are grown. Once the endcaps are in place. the protein solution is exposed to the crystallization solutions wherein the solubility of the protein solution is reduced at a rate responsive to the rate of diffusive mixing of the crystallization solutions. This allows for a controlled approach to supersaturation and allows for screening of crystal growth conditions at preselected intervals.

  6. Breadboard activities for advanced protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Banish, Michael

    1993-01-01

    The proposed work entails the design, assembly, testing, and delivery of a turn-key system for the semi-automated determination of protein solubilities as a function of temperature. The system will utilize optical scintillation as a means of detecting and monitoring nucleation and crystallite growth during temperature lowering (or raising, with retrograde solubility systems). The deliverables of this contract are: (1) turn-key scintillation system for the semi-automatic determination of protein solubilities as a function of temperature, (2) instructions and software package for the operation of the scintillation system, and (3) one semi-annual and one final report including the test results obtained for ovostatin with the above scintillation system.

  7. Controlled deposition or organic semiconductor single crystals and its application in field-effect transistors

    NASA Astrophysics Data System (ADS)

    Liu, Shuhong

    single crystals are selectively nucleated on patterned templates of carbon nanotube (CNT) bundles. Several organic semiconductor materials are successfully patterned, including p-type pentacene, tetracene, sexiphenylene, and sexithiophene, as well as n-type tetracyanoquinodimethane. This study suggests that the selective growth of crystals onto patterned carbon nanotubes is most likely due to the coarse topography of the CNT bundles. Moreover, I observe that the crystals nucleate from CNT bundles and grow onto CNT bundles in a conformal fashion. The crystal growth can be directly applied onto transistor source-drain electrodes and arrays of organic single-crystal field effect transistors are demonstrated. To investigate the impact of CNTs on device performance, CNT bundles are incorporated into thin-film FETs and a mobility enhancement of organic semiconductors is observed. In the third approach, organic single crystals with well controlled sizes and shapes are successfully grown using patterned Au films as templates. It is observed that sexithiophene crystals nucleate from the edge or the top surface of Au films and then grow two dimensionally on SiO2 surface. The sizes and shapes of sexithiophene crystals are precisely determined by that of the Au patterns. After removing Au templates, large arrays of sexithiophene crystals with controlled sizes and various shapes such as stripes, squares, hexagons, etc. are achieved. Top-contact FETs made of sexithiophene ribbons are demonstrated. Besides organic single crystals, Au templates can also act as templates to pattern vapor- and solution-deposited organic semiconductor thin films. Patterned organic thin-film FETs exhibit superior performance compared to unpatterned devices. Finally, oriented growth of organic semiconductor single crystals on templates with various features is studied. On substrates with aligned features, such as friction-transferred poly(tetrafluoroethylene) thin films, organic semiconductor thin films

  8. Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum.

    PubMed

    Li, Jinhua; Menguy, Nicolas; Gatel, Christophe; Boureau, Victor; Snoeck, Etienne; Patriarche, Gilles; Leroy, Eric; Pan, Yongxin

    2015-02-01

    Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral-octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.

  9. Floating zone crystal growth of selected R2PdSi3 ternary silicides

    SciTech Connect

    Xu, Yiku; Frontzek, Matthias D; Mazilu, Irina; Loeser, W; Behr, G; Buechner, Bernd; Liu, L

    2011-01-01

    Substitution of various rare earths R within the class of R2PdSi3 single crystals with hexagonal AlB2-type crystallographic structure reveals the systematic dependence of anisotropic magnetic properties governed by the interplay of crystal-electric field effects and magnetic two-ion interactions. Here we compare the floating zone (FZ) crystal growth with radiation heating of compounds with R = Tb, Tm, Pr, and Gd. The congruent melting behavior enabled moderate growth velocities of 3 to 5 mmh-1. The preferred growth directions are close to the basal plane of the hexagonal unit cell. The composition of the crystals, except of Tb2PdSi3, is slightly Pd-depleted with respect to the nominal composition 16.7 at.% Pd. Thin precipitates of RSi secondary phases were detected in the crystal matrix. Their phase fraction can be diminished by growth from Pd-rich melt compositions and annealing treatments. The compounds exhibit antiferromagnetic order below the N el temperatures TN: 23.6 K (Tb2PdSi3), 1.8 K (Tm2PdSi3), 2.17 K (Pr2PdSi3) and 22 K (Gd2PdSi3) with different grades of magnetic anisotropy.

  10. Electrochemical liquid-liquid-solid (ec-LLS) crystal growth: a low-temperature strategy for covalent semiconductor crystal growth.

    PubMed

    Fahrenkrug, Eli; Maldonado, Stephen

    2015-07-21

    This Account describes a new electrochemical synthetic strategy for direct growth of crystalline covalent group IV and III-V semiconductor materials at or near ambient temperature conditions. This strategy, which we call "electrochemical liquid-liquid-solid" (ec-LLS) crystal growth, marries the semiconductor solvation properties of liquid metal melts with the utility and simplicity of conventional electrodeposition. A low-temperature liquid metal (i.e., Hg, Ga, or alloy thereof) acts simultaneously as the source of electrons for the heterogeneous reduction of oxidized semiconductor precursors dissolved in an electrolyte as well as the solvent for dissolution of the zero-valent semiconductor. Supersaturation of the semiconductor in the liquid metal triggers eventual crystal nucleation and growth. In this way, the liquid electrolyte-liquid metal-solid crystal phase boundary strongly influences crystal growth. As a synthetic strategy, ec-LLS has several intrinsic features that are attractive for preparing covalent semiconductor crystals. First, ec-LLS does not require high temperatures, toxic precursors, or high-energy-density semiconductor reagents. This largely simplifies equipment complexity and expense. In practice, ec-LLS can be performed with only a beaker filled with electrolyte and an electrical circuit capable of supplying a defined current (e.g., a battery in series with a resistor). By this same token, ec-LLS is compatible with thermally and chemically sensitive substrates (e.g., plastics) that cannot be used as deposition substrates in conventional syntheses of covalent semiconductors. Second, ec-LLS affords control over a host of crystal shapes and sizes through simple changes in common experimental parameters. As described in detail herein, large and small semiconductor crystals can be grown both homogeneously within a liquid metal electrode and heterogeneously at the interface of a liquid metal electrode and a seed substrate, depending on the particular

  11. Electrochemical liquid-liquid-solid (ec-LLS) crystal growth: a low-temperature strategy for covalent semiconductor crystal growth.

    PubMed

    Fahrenkrug, Eli; Maldonado, Stephen

    2015-07-21

    This Account describes a new electrochemical synthetic strategy for direct growth of crystalline covalent group IV and III-V semiconductor materials at or near ambient temperature conditions. This strategy, which we call "electrochemical liquid-liquid-solid" (ec-LLS) crystal growth, marries the semiconductor solvation properties of liquid metal melts with the utility and simplicity of conventional electrodeposition. A low-temperature liquid metal (i.e., Hg, Ga, or alloy thereof) acts simultaneously as the source of electrons for the heterogeneous reduction of oxidized semiconductor precursors dissolved in an electrolyte as well as the solvent for dissolution of the zero-valent semiconductor. Supersaturation of the semiconductor in the liquid metal triggers eventual crystal nucleation and growth. In this way, the liquid electrolyte-liquid metal-solid crystal phase boundary strongly influences crystal growth. As a synthetic strategy, ec-LLS has several intrinsic features that are attractive for preparing covalent semiconductor crystals. First, ec-LLS does not require high temperatures, toxic precursors, or high-energy-density semiconductor reagents. This largely simplifies equipment complexity and expense. In practice, ec-LLS can be performed with only a beaker filled with electrolyte and an electrical circuit capable of supplying a defined current (e.g., a battery in series with a resistor). By this same token, ec-LLS is compatible with thermally and chemically sensitive substrates (e.g., plastics) that cannot be used as deposition substrates in conventional syntheses of covalent semiconductors. Second, ec-LLS affords control over a host of crystal shapes and sizes through simple changes in common experimental parameters. As described in detail herein, large and small semiconductor crystals can be grown both homogeneously within a liquid metal electrode and heterogeneously at the interface of a liquid metal electrode and a seed substrate, depending on the particular

  12. A numerical study of transient heat and mass transfer in crystal growth

    NASA Technical Reports Server (NTRS)

    Han, Samuel Bang-Moo

    1987-01-01

    A numerical analysis of transient heat and solute transport across a rectangular cavity is performed. Five nonlinear partial differential equations which govern the conservation of mass, momentum, energy and solute concentration related to crystal growth in solution, are simultaneously integrated by a numerical method based on the SIMPLE algorithm. Numerical results showed that the flow, temperature and solute fields are dependent on thermal and solutal Grashoff number, Prandtl number, Schmidt number and aspect ratio. The average Nusselt and Sherwood numbers evaluated at the center of the cavity decrease markedly when the solutal buoyancy force acts in the opposite direction to the thermal buoyancy force. When the solutal and thermal buoyancy forces act in the same direction, however, Sherwood number increases significantly and yet Nusselt number decreases. Overall effects of convection on the crystal growth are seen to be an enhancement of growth rate as expected but with highly nonuniform spatial growth variations.

  13. Physical vapor transport growth of bulk aluminum nitride crystals

    NASA Astrophysics Data System (ADS)

    Noveski, Vladimir

    The most promising substrates for III-Nitride devices---bulk aluminum nitride (AlN) crystals were grown by seeded and self-seeded methods in sandwich sublimation configuration in nitrogen atmosphere. The growth was performed in an inductively heated reactor, which was designed and assembled during the course of this project. In the theoretical study of mass transfer effects on the crystal growth rate a one-dimensional model was developed assuming diffusion of Al species as rate limiting step. Estimation and validation of model parameters were completed by experiments carried out at temperature 1800--2400°C, pressure 55--105 kPa and temperature gradient in the vapor phase 1--4°C. Crystal growth rates ˜1 mm/h, viable for commercial production and very good uniformity in the plane of growth were achieved. Two typical issues during the seeded growth on SiC were identified: (1) the formation of voids, and (2) the formation of cracks. A viable process window of temperatures, growth times and source-to-seed distances was identified in which these issues could be overcome and single crystalline AIN was deposited on 200--300 mm2 SiC seeds. X-ray diffraction confirmed a single crystalline nature of the grown material, and scanning electron microscopy (SEM) and optical microscopy revealed the step-flow growth mechanism. Grain expansion in the growth direction during self-seeded studies indicated a possibility of achieving single crystalline AlN of significant size starting from a polycrystalline material. Growth interruption and seed preparation were introduced to preserve the crucible integrity and provide conditions for one-dimensional transport. The use of an inverted temperature gradient during initial stages and sintering of the AlN powder source helped eliminating the secondary nucleation, which had been identified to be an issue during the growth on previously polished AlN seeds. X-ray topography and optical microscopy confirmed the epitaxial re-growth after

  14. Study of Fluid Flow Control In Protein Crystallization Using Strong Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F.; Ciszak, E.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in 'microgravity', researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  15. Switching plastic crystals of colloidal rods with electric fields

    PubMed Central

    Liu, Bing; Besseling, Thijs H.; Hermes, Michiel; Demirörs, Ahmet F.; Imhof, Arnout; van Blaaderen, Alfons

    2014-01-01

    When a crystal melts into a liquid both long-ranged positional and orientational order are lost, and long-time translational and rotational self-diffusion appear. Sometimes, these properties do not change at once, but in stages, allowing states of matter such as liquid crystals or plastic crystals with unique combinations of properties. Plastic crystals/glasses are characterized by long-ranged positional order/frozen-in-disorder but short-ranged orientational order, which is dynamic. Here we show by quantitative three-dimensional studies that charged rod-like colloidal particles form three-dimensional plastic crystals and glasses if their repulsions extend significantly beyond their length. These plastic phases can be reversibly switched to full crystals by an electric field. These new phases provide insight into the role of rotations in phase behaviour and could be useful for photonic applications. PMID:24446033

  16. Comparison of the spiral growth modes of silicon-face and carbon-face silicon carbide crystals

    NASA Astrophysics Data System (ADS)

    Seiss, M.; Ouisse, T.; Chaussende, D.

    2013-12-01

    We have studied the dependence of the terrace width of growth spirals on local supersaturation during the growth of on-axis silicon carbide (SiC) crystals. Local supersaturation is adjusted by changing the residual argon gas pressure inside the sublimation growth chamber. Whereas Si-face crystals seem to partly verify the model of Burton, Cabrera and Frank, we found that on C-face crystals, the terrace width is independent of supersaturation. In contrast to previously reported data obtained from KDP crystals, we cannot ascribe our result to hollow-core dislocations or micropipes, as the observed growth spirals arose from independent and closed, unit or double-unit screw dislocations. Besides, we checked that neither the finite growth area nor the influence of the stress field of the dislocation can explain our data.

  17. Growth of a single crystal ribbon in space

    NASA Technical Reports Server (NTRS)

    Padovani, F. A.; Voltmer, F. W.

    1973-01-01

    Three critical technological areas associated with adapting the method of pulling signal crystal silicon ribbon to a space environment were investigated. Basic parameters such as the magnitude of the forces required and the coupling between thermal and force are discussed. The design of a ribbon puller is described, and the problems encountered are also discussed. The force fields in the vicinity of a coil were characterized and results of attempts to pull ribbon are described. The results of the one experiment to grow a conventional float zone crystal in an external static magnetic field are presented.

  18. Crystal settling and crystal growth caused by Ostwald Ripening in a terrestrial magma ocean under rotation

    NASA Astrophysics Data System (ADS)

    Maas, C.; Moeller, A.; Hansen, U.

    2013-12-01

    at the bottom of the magma ocean. At the equator we find three regimes (see A. Möller, U. Hansen (2013)) depending on the rotation strength. At low rotation a high fraction of silicate crystals settle at the bottom. At higher rotation the crystals form a thick layer in the bottom 1/3 of box. At high rotation all crystals are suspended and we observe a ribbon structure in the middle of the box. With a second model we investigate growing and shrinking of crystals by Ostwald Ripening and include formation and melting. In general we observe the same behaviour and regimes as described above, however due to Ostwald Ripening the evolution of crystal radius with time depends on the strength of rotation and on the orientation of the rotation axis. Very first results show that at the pole the growth of the silicate crystals is limited. The resulting small radius leads to a slow crystal settling. At the equator the crystals are able to grow larger than at the pole and therefore settle faster. This could lead to an asymmetrical crystallization of the magma ocean. In an extreme case due to the different settling times this could lead to a well mixed mantle at the pole whereas at the equator the mantle could be strongly differentiated after the solidification of the magma ocean.

  19. On anisotropy function in crystal growth simulations using Lattice Boltzmann equation

    NASA Astrophysics Data System (ADS)

    Younsi, Amina; Cartalade, Alain

    2016-11-01

    In this paper, we present the ability of the Lattice Boltzmann (LB) equation, usually applied to simulate fluid flows, to simulate various shapes of crystals. Crystal growth is modeled with a phase-field model for a pure substance, numerically solved with a LB method in 2D and 3D. This study focuses on the anisotropy function that is responsible for the anisotropic surface tension between the solid phase and the liquid phase. The anisotropy function involves the unit normal vectors of the interface, defined by gradients of phase-field. Those gradients have to be consistent with the underlying lattice of the LB method in order to avoid unwanted effects of numerical anisotropy. Isotropy of the solution is obtained when the directional derivatives method, specific for each lattice, is applied for computing the gradient terms. With the central finite differences method, the phase-field does not match with its rotation and the solution is not any more isotropic. Next, the method is applied to simulate simultaneous growth of several crystals, each of them being defined by its own anisotropy function. Finally, various shapes of 3D crystals are simulated with standard and nonstandard anisotropy functions which favor growth in <100>-, <110>- and <111>-directions.

  20. Susceptor for EFG crystal growth apparatus

    DOEpatents

    Menna, Andrew A.

    1996-09-03

    An improved susceptor for a crucible/die assembly for growing tubular crystalline structures by the EFG process is provided. The crucible/die assembly comprises a die having a substantially polygonally-shaped top end surface for supporting a film of silicon feed material that is replenished from a melt in the crucible through capillary action. A hollow crystalline body is grown from the film of silicon material on the top end surface of the die. The heat susceptor is made of graphite or similar material, and has a peripheral configuration similar to that of the die. Further, the upper surface of the heat susceptor has a central land and a plurality of circumferentially-spaced upwardly extending projections. The central land thermally contacts a central portion of the lower surface of the crucible/die, and the projections thermally contact the lower surface of the crucible/die at its corners, whereby a temperature distribution is provided that permits growth of hollow bodies having more nearly constant thickness walls.

  1. Twin-mediated crystal growth: an enigma resolved

    NASA Astrophysics Data System (ADS)

    Shahani, Ashwin J.; Gulsoy, E. Begum; Poulsen, Stefan O.; Xiao, Xianghui; Voorhees, Peter W.

    2016-06-01

    During crystal growth, faceted interfaces may be perturbed by defects, leading to a rich variety of polycrystalline growth forms. One such defect is the coherent Σ3 {111} twin boundary, which is widely known to catalyze crystal growth. These defects have a profound effect on the properties of many materials: for example, electron-hole recombination rates strongly depend on the character of the twin boundaries in polycrystalline Si photovoltaic cells. However, the morphology of the twinned interface during growth has long been a mystery due to the lack of four-dimensional (i.e., space and time resolved) experiments. Many controversial mechanisms have been proposed for this process, most of which lack experimental verification. Here, we probe the real-time interfacial dynamics of polycrystalline Si particles growing from an Al-Si-Cu liquid via synchrotron-based X-ray tomography. Our novel analysis of the time evolution of the interfacial normals allows us to quantify unambiguously the habit plane and grain boundary orientations during growth. This, when combined with direct measurements of the interfacial morphology provide the first confirmation of twin-mediated growth, proposed over 50 years ago. Using the insights provided by these experiments, we have developed a unified picture of the phenomena responsible for the dynamics of faceted Si growth.

  2. Twin-mediated crystal growth: an enigma resolved

    PubMed Central

    Shahani, Ashwin J.; Gulsoy, E. Begum; Poulsen, Stefan O.; Xiao, Xianghui; Voorhees, Peter W.

    2016-01-01

    During crystal growth, faceted interfaces may be perturbed by defects, leading to a rich variety of polycrystalline growth forms. One such defect is the coherent Σ3 {111} twin boundary, which is widely known to catalyze crystal growth. These defects have a profound effect on the properties of many materials: for example, electron-hole recombination rates strongly depend on the character of the twin boundaries in polycrystalline Si photovoltaic cells. However, the morphology of the twinned interface during growth has long been a mystery due to the lack of four-dimensional (i.e., space and time resolved) experiments. Many controversial mechanisms have been proposed for this process, most of which lack experimental verification. Here, we probe the real-time interfacial dynamics of polycrystalline Si particles growing from an Al-Si-Cu liquid via synchrotron-based X-ray tomography. Our novel analysis of the time evolution of the interfacial normals allows us to quantify unambiguously the habit plane and grain boundary orientations during growth. This, when combined with direct measurements of the interfacial morphology provide the first confirmation of twin-mediated growth, proposed over 50 years ago. Using the insights provided by these experiments, we have developed a unified picture of the phenomena responsible for the dynamics of faceted Si growth. PMID:27346073

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

    NASA Astrophysics Data System (ADS)

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

    1992-06-01

    The 4 solution growth experiments on the LDEF were presented thoroughly elsewhere. The CaCO3-experiment, and to a certain extent also the TTF-TCNQ-experiments yielded useful results. In Jan. 1992, the next series of solution growth experiments were sent to ESA for shipment to KSC. As on the LDEF, the SGF (solution growth facility) of the EURECA-1 contains 4 large experiments. From the beginning, the planning and developments were introduced. Still, the basic concept was maintained, and the CaCO3-experiment, that showed the best results on the LDEF, will now be repeated with improved technology and in larger scale on the EURECA-1. The contents of the 4 SGF experiments are as follows: (1) growth of calcium-carbonate crystals; (2) formation and transformation of tri-calcium-phosphate; (3) growth of zeolite crystals; and (4) soret coefficient measurements (diffusion). The scientific background for the choice of experiments and the major improvements of the SGF are reviewed. Furthermore, some ideas on basic microgravity solution growth experimentation from ESA's newly established EWG (Expert Working Group) on solution growth are reported.

  4. Experiment MA-028 crystal growth. [low gravity manufacturing of single crystals from Apollo/Soyuz Test Project

    NASA Technical Reports Server (NTRS)

    Lind, D. M.

    1976-01-01

    A crystal growth experiment is reported on orbital space flights. The experiment was performed during the Apollo-Soyuz Test Project. The Crystal Growth Experiment assessed a novel process for growing single crystals of insoluble substances by allowing two or more reactant solutions to diffuse toward each other through a region of pure solvent in zero gravity. The experiment was entirely successful and yielded crystals of about the expected size, quality, and number.

  5. Method for minimizing convection during crystal growth from solution

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J. (Inventor)

    1985-01-01

    Disclosed is a method and apparatus for growing in a gravitational field a microscopic crystal from a solution. Solution is held in a vertical chamber which is relatively thin, the thin dimension being generally perpendicular to the vertical. There is a substrate crystal disposed at either the upper or lower end of the chamber and the crystal grows from this substrate crystal in one direction. In accordance with this invention, the temperature conditions of the solution are controlled so that as the crystal forms the effects of buoyant convection within the solution are minimized. This is accomplished in two different ways depending upon whether the crystal is grown from the upper or lower end of the chamber. When grown from the upper end of the chamber, the temperature of the solution is controlled so that it remains essentially isothermal so that there is essentially no heat loss from the solution. When the crystal is grown from the lower end of the chamber, the temperatures of the solution is controlled so that there is a differential in temperature throughout the solution which provides a positive thermal gradient within the chamber.

  6. Crystal growth methods dedicated to low solubility actinide oxalates

    NASA Astrophysics Data System (ADS)

    Tamain, C.; Arab-Chapelet, B.; Rivenet, M.; Grandjean, S.; Abraham, F.

    2016-04-01

    Two novel crystal growth syntheses dedicated to low solubility actinide-oxalate systems and adapted to glove box handling are described. These methods based on the use of precursors of either actinide metal or oxalic acid have been optimized on lanthanide systems (analogue of actinides(III)) and then assessed on real actinide systems. They allow the synthesis of several actinide oxalate single crystals, Am2(C2O4)3(H2O)3·xH2O, Th(C2O4)2·6H2O, M2+x[PuIV2-xPuIIIx(C2O4)5]·nH2O and M1-x[PuIII1-xPuIVx(C2O4)2·H2O]·nH2O. It is the first time that these well-known compounds are formed by crystal growth methods, thus enabling direct structural studies on transuranic element systems and acquisition of basic data beyond deductions from isomorphic (or not) lanthanide compounds. Characterizations by X-ray diffraction, UV-visible solid spectroscopy, demonstrate the potentialities of these two crystal growth methods to obtain oxalate compounds.

  7. Consideration of the condensation processes of thin films in the crystal substrate's potential field

    NASA Astrophysics Data System (ADS)

    Tupik, V. A.; Margolin, V. I.; Trong Su, Chu

    2016-07-01

    The condensation process of a single particle in an ideal crystal substrate's potential field is considered. The optimal deposition path and the potential barrier of deposited particle's motion are shown. Some computer modeling examples of thin film's growth process were carried out on the basis of the implemented programs. A fractal analysis of obtained thin films was made, on the basis of which the possibility of estimating the performance of thin film's growth process will be discussed.

  8. Crystal growth of enzymes in low gravity (L-5)

    NASA Technical Reports Server (NTRS)

    Morita, Yuhei

    1993-01-01

    Recent developments in protein engineering have expanded the possibilities of studies of enzymes and other proteins. Now such studies are not limited to the elucidation of the relationship between the structure and function of the protein. They also aim at the production of proteins with new and practical functions, based on results obtained during investigation of structure and function. For continuing research in this field, investigation of the tertiary structure of proteins is important. X-ray diffraction of single crystals of protein is usually used for this purpose. The main difficulty is the preparation of the crystals. The theme of the research is to prepare such crystals at very low gravity, with the main purpose being to obtain large single crystals of proteins suitable for x-ray diffraction studies.

  9. III-V semiconductor solid solution single crystal growth

    NASA Technical Reports Server (NTRS)

    Gertner, E. R.

    1982-01-01

    The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

  10. 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.

  11. In situ atomic force microscopy of layer-by-layer crystal growth and key growth concepts

    NASA Astrophysics Data System (ADS)

    Rashkovich, L. N.; de Yoreo, J. J.; Orme, C. A.; Chernov, A. A.

    2006-12-01

    Contradictions that have been found recently between the representations of classical theory and experiments on crystal growth from solutions are considered. Experimental data show that the density of kinks is low in many cases as a result of the low rate of their fluctuation generation, the Gibbs-Thomson law is not always applicable in these cases, and there is inconsistency with the Cabrera-Vermilyea model. The theory of growth of non-Kossel crystals, which is to be developed, is illustrated by the analysis of the experimental dependence of the growth rate on the solution stoichiometry.

  12. Control of crystal growth in water purification by directional freeze crystallization

    NASA Technical Reports Server (NTRS)

    Conlon, William M. (Inventor)

    1996-01-01

    A Directional Freeze Crystallization system employs an indirect contact heat exchanger to freeze a fraction of liquid to be purified. The unfrozen fraction is drained away and the purified frozen fraction is melted. The heat exchanger must be designed in accordance with a Growth Habit Index to achieve efficient separation of contaminants. If gases are dissolved in the liquid, the system must be pressurized.

  13. Relationship between appearance crystalline planes and growth temperatures during sublimation growth of AlN crystals

    NASA Astrophysics Data System (ADS)

    Li, Juan; Hu, Xiaobo; Jiang, Shouzhen; Ning, Lina; Wang, Yingmin; Chen, Xiufang; Xu, Xiangang; Wang, Jiyang; Jiang, Minhua

    2006-07-01

    Self-seeded growth of aluminum nitride single crystals in BN crucible was conducted by sublimation method. It was found that the growth temperature played a critical role in the determination of the crystal morphologies and the appearance crystalline planes. The (0 0 0 1) and pseudo ( 1 1 2¯ 0) planes were often present at low and high temperature, respectively. The self-seeded crystals possess high structural quality which were assessed by high resolution X-ray diffractometry with a full-width at half-maximum of 35.76 arcsec. Step flow mechanism for the growth of AlN similar to SiC growth was confirmed with the aid of atomic force microscopy.

  14. Crystal growth in a three-phase system: diffusion and liquid-liquid phase separation in lysozyme crystal growth.

    PubMed

    Heijna, M C R; van Enckevort, W J P; Vlieg, E

    2007-07-01

    In the phase diagram of the protein hen egg-white lysozyme, a region is present in which the lysozyme solution demixes and forms two liquid phases. In situ observations by optical microscopy show that the dense liquid droplets dissolve when crystals grow in this system. During this process the demixed liquid region retracts from the crystal surface. The spatial distribution of the dense phase droplets present special boundary conditions for Fick's second law for diffusion. In combination with the cylindrical symmetry provided by the kinetically roughened crystals, this system allows for a full numerical analysis. Using experimental data for setting the boundary conditions, a quasi-steady-state solution for the time-dependent concentration profile was shown to be valid. Comparison of kinetically rough growth in a phase separated system and in a nonseparated system shows that the growth kinetics for a three-phase system differs from a two-phase system, in that crystals grow more slowly but the duration of growth is prolonged.

  15. Morphological stability and fluid dynamics of vapor crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, F. E.

    1985-01-01

    Progress is reported in establishing the capabilities of thermal deflection spectroscopy for measurements of the concentration field around a growing crystal. Work was completed on the inclusion of the next nearest neighbor interaction into a surface roughness model and the resulting formalism was applied to copper, zinc, and lead. Other work in mass spectroscopy and vapor transport is discussed.

  16. Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics

    NASA Technical Reports Server (NTRS)

    Kim, Soojin; Myerson, Allan S.

    1996-01-01

    The crystal growth rates of NH4H2PO4, KH2PO4, (NH4)2SO4, KAl(SO4)2 central dot 12H2O, NaCl, and glycine and the nucleation rates of KBr, KCl, NaBr central dot 2H2O, (NH4)2Cl, and (NH4)2SO4 were expressed in terms of the fundamental driving force of crystallization calculated from the activity of supersaturated solutions. The kinetic parameters were compared with those from the commonly used kinetic expression based on the concentration difference. From the viewpoint of thermodynamics, rate expressions based on the chemical potential difference provide accurate kinetic representation over a broad range of supersaturation. The rates estimated using the expression based on the concentration difference coincide with the true rates of crystallization only in the concentration range of low supersaturation and deviate from the true kinetics as the supersaturation increases.

  17. 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.

  18. Liquid drop stability for protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Owen, Robert B.; Broom, Beth H.; Snyder, Robert S.; Daniel, Ron

    1987-01-01

    It is possible to grow protein crystals for biomedical research in microgravity by deploying a protein-rich solution from a syringe, forming a drop in which crystallization can occur with the proper degree of supersaturation. Drop stability is critical to the success of this research, due to the large drop sizes which can be achieved in space. In order to determine the type of syringe tips most suitable to support these large drops, tests were performed during brief periods of weightlessness onboard the NASA KC-135 low-gravity simulation aircraft. The drops were analyzed using three simple models in which the samples were approximated by modified pendulum and spring systems. It was concluded that the higher frequency systems were the most stable, indicating that of the syringes utilized, a disk-shaped configuration provided the most stable environment of low-gravity protein crystal growth.

  19. Modelling the growth of triglycine sulphate crystals in Spacelab 3

    NASA Technical Reports Server (NTRS)

    Yoo, Hak-Do; Wilcox, William R.; Lal, Ravindra; Trolinger, James D.

    1988-01-01

    Two triglycine sulphate crystals were grown from an aqueous solution in Spacelab 3 aboard a Space Shuttle. Using a diffusion coefficient of 0.00002 sq cm/s, a computerized simulation gave reasonable agreement between experimental and theoretical crystal sizes and interferometric lines in the solution near the growing crystal. This diffusion coefficient is larger than most measured values, possibly due to fluctuating accelerations on the order of .001 g (Earth's gravity). The average acceleration was estimated to be less than .000001 g. At this level, buoyancy driven convection is predicted to add approx. 20 percent to the steady state growth rate. Only very slight distortion of the interferometric lines was observed at the end of a 33 hr run. It is suggested that the time to reach steady state convective transport may be inversely proportional to g at low g, so that the full effect of convection was not realized in these experiments.

  20. 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

  1. Modeling and control of the Czochralski crystal growth process

    NASA Astrophysics Data System (ADS)

    Martinez, Denise Marie

    The Czochralski process is a method of pulling crystal from the melt that is widely used by the semiconductor industry. The current breadth of this industry makes the method indespensible. The International Technology Roadmap for Semiconductors forecasts the use of 35 nm technology on 64 Gbit DRAM and 10 GHz processor speeds by the end of this decade. This implies the need for higher quality crystals, and therefore improved growth systems. Furthermore, industry has noted a problem with rapid pull rate variation contributing to structural defects in the grown crystals. It was proposed by industry to investigate elimination of the pull rate as a control input. The current state of the system as well as the predicted path of the industry served to motivate development of a new control scheme. The first objective of this work was to develop or enhance a first-principles based model of the process. This model must be kept at a manageable order to accommodate online simulation while still capturing the dominant process physics. The model must also be formulated as a time differential equation in order to apply the desired control theories. The second objective of this work was to answer industry's question regarding elimination of pull rate as a manipulated input. The final objective of this work was to use the model to design a new control algorithm. The control development includes consideration of the time delay between heater and the crystal. The work is based on silicon growth, but the developments are kept as generic as possible for future application to other materials. Data from industry crystal growths as well as experimental results reported in literature will be used to gauge the effectiveness of the new designs.

  2. A comparative study of the influence of buoyancy driven fluid flow on GaAs crystal growth

    NASA Technical Reports Server (NTRS)

    Kafalas, J. A.; Bellows, A. H.

    1988-01-01

    A systematic investigation of the effect of gravity driven fluid flow on GaAs crystal growth was performed. It includes GaAs crystal growth in the microgravity environment aboard the Space Shuttle. The program involves a controlled comparative study of crystal growth under a variety of earth based conditions with variable orientation and applied magnetic field in addition to the microgravity growth. Earth based growth will be performed under stabilizing as well as destabilizing temperature gradients. The boules grown in space and on earth will be fully characterized to correlate the degree of convection with the distribution of impurities. Both macro- and micro-segregation will be determined. The space growth experiment will be flown in a self-contained payload container through NASA's Get Away Special program.

  3. Crystal growth, spectral, structural and optical studies of π-conjugated stilbazolium crystal: 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate.

    PubMed

    Krishna Kumar, M; Sudhahar, S; Bhagavannarayana, G; Mohan Kumar, R

    2014-05-01

    Nonlinear optical (NLO) organic compound, 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate was synthesized by reflux method. The formation of molecular complex was confirmed from (1)H NMR, FT-IR and FT-Raman spectral analyses. The single crystals were grown by slow evaporation solution growth method and the crystal structure and atomic packing of grown crystal was identified. The morphology and growth axis of grown crystal were determined. The crystal perfection was analyzed using high resolution X-ray diffraction study on (001) plane. Thermal stability, decomposition stages and melting point of the grown crystal were analyzed. The optical absorption coefficient (α) and energy band gap (E(g)) of the crystal were determined using UV-visible absorption studies. Second harmonic generation efficiency of the grown crystal was examined by Kurtz powder method with different particle size using 1064 nm laser. Laser induced damage threshold study was carried out for the grown crystal using Nd:YAG laser. PMID:24531108

  4. Electrochemical growth of linear conducting crystals in microgravity

    NASA Technical Reports Server (NTRS)

    Cronise, Raymond J., IV

    1988-01-01

    Much attention has been given to the synthesis of linear conducting materials. These inorganic, organic, and polymeric materials have some very interesting electrical and optical properties, including low temperature superconductivity. Because of the anisotropic nature of these compounds, impurities and defects strongly influences the unique physical properties of such crystals. Investigations have demonstrated that electrochemical growth has provided the most reproducible and purest crystals. Space, specifically microgravity, eliminates phenomena such as buoyancy driven convection, and could permit formation of crystals many times purer than the ones grown to date. Several different linear conductors were flown on Get Away Special G-007 on board the Space Shuttle Columbia, STS 61-C, the first of a series of Project Explorer payloads. These compounds were grown by electrochemical methods, and the growth was monitored by photographs taken throughout the mission. Due to some thermal problems, no crystals of appreciable size were grown. The experimental results will be incorporated into improvements for the next 2 missions of Project Explorer. The results and conclusions of the first mission are discussed.

  5. Investigation of Vibrational Control of the Bridgman Crystal Growth Technique

    NASA Technical Reports Server (NTRS)

    Fedoseyev, Alexandre I.; Alexander, J. I. D.; Feigelson, R. S.; Zharikov, E. V.; Ostrogorsky, A. G.; Marin, C.; Volz, M. P.; Kansa, E. J.; Friedman, M. J.

    2001-01-01

    The character of natural buoyant convection in rigidly contained inhomogeneous fluids can be drastically altered by vibrating the container. Vibrations are expected to play a crucial influence on heat and mass transfer onboard the International Space Station (ISS). It is becoming evident that substantial vibrations will exist on the ISS in the wide frequency spectrum. In general, vibrational flows are very complex and governed by many parameters. In many terrestrial crystal growth situations, convective transport of heat and constituent components is dominated by buoyancy driven convection arising from compositional and thermal gradients. Thus, it may be concluded that vibro-convective flow can potentially be used to influence and even control transport in some crystal growth situations.

  6. Direction-Specific Interactions Control Crystal Growth by Oriented Attachment

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Nielsen, Michael H.; Lee, Jonathan R. I.; Frandsen, Cathrine; Banfield, Jillian F.; De Yoreo, James J.

    2012-05-01

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.

  7. Crystallization in supercooled liquid Cu: Homogeneous nucleation and growth

    SciTech Connect

    E, J. C.; Wang, L.; Luo, S. N.; Cai, Y.; Wu, H. A.

    2015-02-14

    Homogeneous nucleation and growth during crystallization of supercooled liquid Cu are investigated with molecular dynamics simulations, and the microstructure is characterized with one- and two-dimensional x-ray diffraction. The resulting solids are single-crystal or nanocrystalline, containing various defects such as stacking faults, twins, fivefold twins, and grain boundaries; the microstructure is subject to thermal fluctuations and extent of supercooling. Fivefold twins form via sequential twinning from the solid-liquid interfaces. Critical nucleus size and nucleation rate at 31% supercooling are obtained from statistical runs with the mean first-passage time and survival probability methods, and are about 14 atoms and 10{sup 32} m{sup −3}s{sup −1}, respectively. The bulk growth dynamics are analyzed with the Johnson-Mehl-Avrami law and manifest three stages; the Avrami exponent varies in the range of 1–19, which also depends on thermal fluctuations and supercooling.

  8. Some New Observations on Activation Energy of Crystal Growth for Thermally Activated Crystallization.

    PubMed

    Mehta, N; Kumar, A

    2016-02-18

    Calorimetric study of glass/crystal phase transformation in disordered semiconductors is a significant tool for understanding their crystallization kinetics. Such studies provide the basis for practical application of glasses. Differential scanning calorimetry (DSC) is one of the advanced techniques for the analysis of thermally induced crystallization in glassy or amorphous systems. We are reporting the nonisothermal DSC measurements on four amorphous systems of Se70Te30 alloy with Ag, Cd, Sb, and Zn as chemical modifiers. In general, the rate constant (K) shows Arrhenian dependence on temperature (T), i.e., K = K0 exp (-Eg/RT) where Eg is the activation energy of crystal growth and K0 is called the pre-exponential factor of rate constant. In the present work, an experiment is designed to see the effect of composition on the activation energy of crystal growth. We have found Meyer-Neldel relation (MNR) between Eg and K0 for present systems. Another interesting feature of present work is the observation of further relation between Meyer-Neldel prefactor and Meyer-Neldel energy.

  9. Two-step crystal growth mechanism during crystallization of an undercooled Ni50Al50 alloy

    NASA Astrophysics Data System (ADS)

    An, Simin; Li, Jiahao; Li, Yang; Li, Shunning; Wang, Qi; Liu, Baixin

    2016-08-01

    Crystallization processes are always accompanied by the emergence of multiple intermediate states, of which the structures and transition dynamics are far from clarity, since it is difficult to experimentally observe the microscopic pathway. To insight the structural evolution and the crystallization dynamics, we perform large-scale molecular dynamics simulations to investigate the time-dependent crystallization behavior of the NiAl intermetallic upon rapid solidification. The simulation results reveal that the crystallization process occurs via a two-step growth mechanism, involving the formation of initial non-equilibrium long range order (NLRO) regions and of the subsequent equilibrium long range order (ELRO) regions. The formation of the NLRO regions makes the grains rather inhomogeneous, while the rearrangement of the NLRO regions into the ELRO regions makes the grains more ordered and compact. This two-step growth mechanism is actually controlled by the evolution of the coordination polyhedra, which are characterized predominantly by the transformation from five-fold symmetry to four-fold and six-fold symmetry. From liquids to NLRO and further to ELRO, the five-fold symmetry of these polyhedra gradually fades, and finally vanishes when B2 structure is distributed throughout the grain bulk. The energy decrease along the pathway further implies the reliability of the proposed crystallization processes.

  10. Two-step crystal growth mechanism during crystallization of an undercooled Ni50Al50 alloy

    PubMed Central

    An, Simin; Li, Jiahao; Li, Yang; Li, Shunning; Wang, Qi; Liu, Baixin

    2016-01-01

    Crystallization processes are always accompanied by the emergence of multiple intermediate states, of which the structures and transition dynamics are far from clarity, since it is difficult to experimentally observe the microscopic pathway. To insight the structural evolution and the crystallization dynamics, we perform large-scale molecular dynamics simulations to investigate the time-dependent crystallization behavior of the NiAl intermetallic upon rapid solidification. The simulation results reveal that the crystallization process occurs via a two-step growth mechanism, involving the formation of initial non-equilibrium long range order (NLRO) regions and of the subsequent equilibrium long range order (ELRO) regions. The formation of the NLRO regions makes the grains rather inhomogeneous, while the rearrangement of the NLRO regions into the ELRO regions makes the grains more ordered and compact. This two-step growth mechanism is actually controlled by the evolution of the coordination polyhedra, which are characterized predominantly by the transformation from five-fold symmetry to four-fold and six-fold symmetry. From liquids to NLRO and further to ELRO, the five-fold symmetry of these polyhedra gradually fades, and finally vanishes when B2 structure is distributed throughout the grain bulk. The energy decrease along the pathway further implies the reliability of the proposed crystallization processes. PMID:27486073

  11. Two-step crystal growth mechanism during crystallization of an undercooled Ni50Al50 alloy.

    PubMed

    An, Simin; Li, Jiahao; Li, Yang; Li, Shunning; Wang, Qi; Liu, Baixin

    2016-01-01

    Crystallization processes are always accompanied by the emergence of multiple intermediate states, of which the structures and transition dynamics are far from clarity, since it is difficult to experimentally observe the microscopic pathway. To insight the structural evolution and the crystallization dynamics, we perform large-scale molecular dynamics simulations to investigate the time-dependent crystallization behavior of the NiAl intermetallic upon rapid solidification. The simulation results reveal that the crystallization process occurs via a two-step growth mechanism, involving the formation of initial non-equilibrium long range order (NLRO) regions and of the subsequent equilibrium long range order (ELRO) regions. The formation of the NLRO regions makes the grains rather inhomogeneous, while the rearrangement of the NLRO regions into the ELRO regions makes the grains more ordered and compact. This two-step growth mechanism is actually controlled by the evolution of the coordination polyhedra, which are characterized predominantly by the transformation from five-fold symmetry to four-fold and six-fold symmetry. From liquids to NLRO and further to ELRO, the five-fold symmetry of these polyhedra gradually fades, and finally vanishes when B2 structure is distributed throughout the grain bulk. The energy decrease along the pathway further implies the reliability of the proposed crystallization processes. PMID:27486073

  12. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Singh, Ramsharan; Doolittle, John, Jr.; Payra, Pramatha; Dutta, Prabir K.; George, Michael A.; Ramachandran, Narayanan; Schoeman, Brian J.

    2003-01-01

    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: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

  13. Nucleation and convection effects in protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz (Principal Investigator)

    1996-01-01

    The following activities are reported on: repartitioning of NaCl and protein impurities in lysozyme crystallization; dependence of lysozyme growth kinetics on step sources and impurities; facet morphology response to nonuniformities in nutrient and impurity supply; interactions in undersaturated and supersaturated lysozyme solutions; heterogeneity determination and purification of commercial hen egg white lysozyme; nonlinear response of layer growth dynamics in the mixed kinetics-bulk transport regime; development of a simultaneous multiangle light scattering technique; and x-ray topography of tetragonal lysozyme grown by the temperature-control technique.

  14. Methods for growth of relatively large step-free SiC crystal surfaces

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2002-01-01

    A method for growing arrays of large-area device-size films of step-free (i.e., atomically flat) SiC surfaces for semiconductor electronic device applications is disclosed. This method utilizes a lateral growth process that better overcomes the effect of extended defects in the seed crystal substrate that limited the obtainable step-free area achievable by prior art processes. The step-free SiC surface is particularly suited for the heteroepitaxial growth of 3C (cubic) SiC, AlN, and GaN films used for the fabrication of both surface-sensitive devices (i.e., surface channel field effect transistors such as HEMT's and MOSFET's) as well as high-electric field devices (pn diodes and other solid-state power switching devices) that are sensitive to extended crystal defects.

  15. Synthesis, crystal structure, crystal growth and physical properties of N,N-diethyl anilinium picrate

    NASA Astrophysics Data System (ADS)

    Subramaniyan @ Raja, R.; Anandha Babu, G.; Ramasamy, P.

    2011-11-01

    Crystalline substance of N,N-diethyl anilinium picrate (NNDEAP) has been synthesized and single crystals of NNDEAP were successfully grown for the first time by the slow evaporation solution growth technique at room temperature with dimensions 14×10×10 mm3. The formation of the new crystal has been confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystal was analyzed by high resolution X-ray diffraction (HRXRD) measurements. The functional groups of NNDEAP have been identified by Fourier transform infrared spectral studies. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have also been carried out and the thermal behavior of NNDEAP has been studied. The UV-vis-NIR studies have been carried out to identify the optical transmittance and the cut off wavelength of NNDEAP is identified. The dielectric loss and the dielectric constant as a function of frequency and temperature were measured for the grown crystal and the nature of variation of dielectric constant εr and dielectric losses (tan δ) were studied. Vicker's hardness test has been carried out on NNDEAP to measure the load dependent hardness. The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser.

  16. In situ observation of containerless protein crystallization by magnetically levitating crystal growth

    NASA Astrophysics Data System (ADS)

    Maki, Syou; Tanimoto, Yoshifumi; Udagawa, Chikako; Morimoto, Shotaro; Hagiwara, Masayuki

    2016-03-01

    We report on the results of the crystal growth of hen-egg lysozyme by magnetically levitating crystals in a small amount of buffer solution. The concentrations of lysozyme and the precipitating agent (gadolinium chloride) were 6.53 wt % and 0.362 mol/kg, respectively. Gadolinium chloride, which induces the magneto-Archimedes effect, was utilized to levitate the crystals with Bz · (dBz/dz) = 22.46 T2/m, where Bz is the vertical (z) component of the magnetic flux density vector. Although the collected crystals were small, we succeeded in maintaining the levitation of the crystals into a specific place in the liquid phase from the beginning of nucleation. In situ observation revealed that a state of pseudo-weightlessness was generated in the vicinity of the magnet bore edge, and small crystals were concentrated inside the domain moving along an hourglass-shaped surface. We found by numerical computations that the formation of the hourglass-shaped domain is attributable to the radial component of the magnetic force.

  17. Growth, morphology, structure and characterization of L-histidinium dihydrogen arsenate orthoarsenic acid single crystal.

    PubMed

    Tyagi, Nidhi; Sinha, Nidhi; Yadav, Harsh; Kumar, Binay

    2016-08-01

    L-Histidinium dihydrogen arsenate orthoarsenic acid (LHAS) crystals were grown by the slow evaporation method. Single-crystal X-ray diffraction confirms monoclinic structure. The growth rates of various planes of LHAS crystals were estimated by morphological study. Hirshfeld surface and fingerprint plots were analyzed to investigate the intermolecular interactions at 0.002 a.u. present in the crystal structure. The functional groups and phase behavior of the compound are studied by FTIR spectroscopy and differential scanning calorimetry (DSC). A ferroelectric to paraelectric phase transition at 307 K was observed in dielectric studies. The piezoelectric charge coefficients of the grown crystal were found to be 2 pC/N. The values of coercive field (Ec), remnant polarization (Pr) and spontaneous polarization (Ps) in the hysteresis loop are found to be 5.236 kV cm(-1), 0.654 µC cm(-2) and 2.841 µC cm(-2), respectively. Piezoelectricity and ferroelectricity are reported for the first time in LHAS crystals. The mechanical strength was confirmed from microhardness study and void volume. Due to the low value of the dielectric constant, and good piezoelectric and ferroelectric properties, LHAS crystals can be used in microelectronics, sensors and advanced electronic devices.

  18. Growth, morphology, structure and characterization of L-histidinium dihydrogen arsenate orthoarsenic acid single crystal.

    PubMed

    Tyagi, Nidhi; Sinha, Nidhi; Yadav, Harsh; Kumar, Binay

    2016-08-01

    L-Histidinium dihydrogen arsenate orthoarsenic acid (LHAS) crystals were grown by the slow evaporation method. Single-crystal X-ray diffraction confirms monoclinic structure. The growth rates of various planes of LHAS crystals were estimated by morphological study. Hirshfeld surface and fingerprint plots were analyzed to investigate the intermolecular interactions at 0.002 a.u. present in the crystal structure. The functional groups and phase behavior of the compound are studied by FTIR spectroscopy and differential scanning calorimetry (DSC). A ferroelectric to paraelectric phase transition at 307 K was observed in dielectric studies. The piezoelectric charge coefficients of the grown crystal were found to be 2 pC/N. The values of coercive field (Ec), remnant polarization (Pr) and spontaneous polarization (Ps) in the hysteresis loop are found to be 5.236 kV cm(-1), 0.654 µC cm(-2) and 2.841 µC cm(-2), respectively. Piezoelectricity and ferroelectricity are reported for the first time in LHAS crystals. The mechanical strength was confirmed from microhardness study and void volume. Due to the low value of the dielectric constant, and good piezoelectric and ferroelectric properties, LHAS crystals can be used in microelectronics, sensors and advanced electronic devices. PMID:27484380

  19. Density functional theory of crystal growth: Lennard-Jones fluids

    NASA Astrophysics Data System (ADS)

    Shen, Yu Chen; Oxtoby, David W.

    1996-03-01

    We employ an extension of density functional theory to the dynamics of phase transitions in order to study the velocities of crystal growth and melting at planar undercooled and superheated crystal-melt interfaces. The free energy functional we use has a square-gradient form, with the parameters for a Lennard-Jones interaction potential determined by a modified weighted density approximation (MWDA) applied locally through the liquid-solid interface. We explore the role of the density change on freezing in crystal and melt growth, and discover a significant asymmetry between freezing and melting both close to and far from the equilibrium freezing point. The behavior of the superheated solid is governed by the close proximity of a spinodal, whereas in the undercooled liquid there is no evidence for a spinodal and the growth at large undercoolings is affected instead by the density deficit that appears in front of the growing interface. Comparisons are made with other density functional approaches and with computer simulations.

  20. Screening and Crystallization Plates for Manual and High-throughput Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Thorne, Robert E. (Inventor); Berejnov, Viatcheslav (Inventor); Kalinin, Yevgeniy (Inventor)

    2010-01-01

    In one embodiment, a crystallization and screening plate comprises a plurality of cells open at a top and a bottom, a frame that defines the cells in the plate, and at least two films. The first film seals a top of the plate and the second film seals a bottom of the plate. At least one of the films is patterned to strongly pin the contact lines of drops dispensed onto it, fixing their position and shape. The present invention also includes methods and other devices for manual and high-throughput protein crystal growth.

  1. Electric-field-tuned color in photonic crystal elastomers

    NASA Astrophysics Data System (ADS)

    Zhao, Qibin; Haines, Andrew; Snoswell, David; Keplinger, Christoph; Kaltseis, Rainer; Bauer, Siegfried; Graz, Ingrid; Denk, Richard; Spahn, Peter; Hellmann, Goetz; Baumberg, Jeremy J.

    2012-03-01

    Electrically tuned photonic crystals are produced by applying fields across shear-assembled elastomeric polymer opal thin films. At increasing voltages, the polymer opal films stretch biaxially under Maxwell stress, deforming the nanostructure and producing marked color changes. This quadratic electro-optic tuning of the photonic bandgap is repeatable over many cycles, switches within 100 ms, and bridges the gap between electro-active materials and photonic crystals.

  2. A Proposed Model for Protein Crystal Nucleation and Growth

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    How does one take a molecule, strongly asymmetric in both shape and charge distribution, and assemble it into a crystal? We propose a model for the nucleation and crystal growth process for tetragonal lysozyme, based upon fluorescence, light, neutron, and X-ray scattering data, size exclusion chromatography experiments, dialysis kinetics, AFM, and modeling of growth rate data, from this and other laboratories. The first species formed is postulated to be a 'head to side' dimer. Through repeating associations involving the same intermolecular interactions this grows to a 4(sub 3) helix structure, that in turn serves as the basic unit for nucleation and subsequent crystal growth. High salt attenuates surface charges while promoting hydrophobic interactions. Symmetry facilitates subsequent helix-helix self-association. Assembly stability is enhanced when a four helix structure is obtained, with each bound to two neighbors. Only two unique interactions are required. The first are those for helix formation, where the dominant interaction is the intermolecular bridging anion. The second is the anti-parallel side-by-side helix-helix interaction, guided by alternating pairs of symmetry related salt bridges along each side. At this stage all eight unique positions of the P4(sub3)2(sub 1),2(sub 1) unit cell are filled. The process is one of a) attenuating the most strongly interacting groups, such that b) the molecules begin to self-associate in defined patterns, so that c) symmetry is obtained, which d) propagates as a growing crystal. Simple and conceptually obvious in hindsight, this tells much about what we are empirically doing when we crystallize macromolecules. By adjusting the growth parameters we are empirically balancing the intermolecular interactions, preferentially attenuating the dominant strong (for lysozyme the charged groups) while strengthening the lesser strong (hydrophobic) interactions. In the general case for proteins the lack of a singularly defined

  3. Non-linear optical titanyl arsenates: Crystal growth and properties

    NASA Astrophysics Data System (ADS)

    Nordborg, Jenni Eva Louise

    Crystals are appreciated not only for their appearance, but also for their unique physical properties which are utilized by the photonic industry in appliances that we come across every day. An important part of enabling the technical use of optical devices is the manufacture of crystals. This dissertation deals with a specific group of materials called the potassium titanyl phosphate (KIP) family, known for their non-linear optical and ferroelectric properties. The isomorphs vary in their linear optical and dielectric properties, which can be tuned to optimize device performance by forming solid solutions of the different materials. Titanyl arsenates have a wide range of near-infrared transmission which makes them useful for tunable infrared lasers. The isomorphs examined in the present work were primarily RbTiOASO4 (RTA) and CsTiOAsO4 (CTA) together with the mixtures RbxCs 1-xTiOAsO4 (RCTA). Large-scale crystals were grown by top seeding solution growth utilizing a three-zone furnace with excellent temperature control. Sufficiently slow cooling and constant upward lifting produced crystals with large volumes useable for technical applications. Optical quality RTA crystals up to 10 x 12 x 20 mm were grown. The greater difficulty in obtaining good crystals of CTA led to the use of mixed RCTA materials. The mixing of rubidium and cesium in RCTA is more favorable to crystal growth than the single components in pure RTA and CTA. Mixed crystals are rubidium-enriched and contain only 20-30% of the cesium concentration in the flux. The cesium atoms show a preference for the larger cation site. The network structure is very little affected by the cation substitution; consequently, the non-linear optical properties of the Rb-rich isomorphic mixtures of RTA and CTA can be expected to remain intact. Crystallographic methods utilizing conventional X-ray tubes, synchrotron radiation and neutron diffraction have been employed to investigate the properties of the atomic

  4. Microstructural Studies on Bonds and Crystal Growth in a Snowpack

    NASA Astrophysics Data System (ADS)

    Adams, E. E.

    2002-12-01

    crystals that developed adopted the same crystal orientation as the substrate. Crystal habit is a function of the environment under which it is grown, based predominantly on temperature and supersaturation. This led to the hypothesis of a dominant grain growth theory whereby nucleation onto existing crystals optimally oriented for given conditions would dominate resulting in crystallographically oriented regions within a snowpack.

  5. Growth and Characterization of Graphene on Single Crystal Cu Substrates

    NASA Astrophysics Data System (ADS)

    Robinson, Z. R.; Tyagi, P.; Geisler, H.; Ventrice, C. A., Jr.; Bol, A. A.; Hannon, J. B.

    2012-02-01

    One of the key issues for the use of CVD graphene in device applications is the influence of defects on the transport properties of the graphene. Therefore, it is important to understand the influence of the substrate on the orientation of the graphene. Growth of graphene films on Cu(111) has the potential for producing films with a low defect density because of the hexagonal symmetry of the substrate and relatively small lattice mismatch, whereas growth on Cu(100) is expected to result in multi-domain growth because of its square symmetry. In this study, graphene films were grown on Cu single crystal substrates, and characterized with LEEM, LEED, SEM, AFM, and Raman spectroscopy. The clean Cu substrates were prepared by sputtering and annealing in UHV. For the initial growth studies, the samples were transferred to a tube furnace for graphene growth using a technique optimized for Cu foils. The UHV system has recently been modified with a button heater compatible with the conditions needed for graphene growth to enable in-situ growth and characterization.

  6. Crucible materials for growth of aluminum nitride crystals

    NASA Astrophysics Data System (ADS)

    Schlesser, R.; Dalmau, R.; Zhuang, D.; Collazo, R.; Sitar, Z.

    2005-07-01

    The growth of aluminum nitride (AlN) bulk crystals by sublimation of an AlN source requires elevated temperatures, typically in a range of 1800-2300 °C. These temperature requirements, combined with the chemically aggressive nature of the Al vapor, severely limit the choice of reactor hot-zone materials, and most notably, the selection of reaction crucibles. Aside from refractory elements, potentially promising compound materials include refractory nitrides, carbides, and borides. In this work, TaC crucibles were fabricated using a binderless sintering process and were tested in AlN bulk growth experiments. Elemental analysis of crystals grown in these crucibles revealed extremely low Ta contamination, below the analytical detection limit of 1 ppm by weight and C contamination levels as low as 50 ppm by weight; C contamination likely originated from sources unrelated to the crucible material. Crucibles were re-used in several consecutive growth runs; average crucible lifetimes exceeded 200 h at growth temperatures exceeding 2200 °C.

  7. A simple apparatus for controlling nucleation and size in protein crystal growth

    NASA Technical Reports Server (NTRS)

    Gernert, Kim M.; Smith, Robert; Carter, Daniel C.

    1988-01-01

    A simple device is described for controlling vapor equilibrium in macromolecular crystallization as applied to the protein crystal growth technique commonly referred to as the 'hanging drop' method. Crystal growth experiments with hen egg white lysozyme have demonstrated control of the nucleation rate. Nucleation rate and final crystal size have been found to be highly dependent upon the rate at which critical supersaturation is approached. Slower approaches show a marked decrease in the nucleation rate and an increase in crystal size.

  8. Phase-Field Crystal Modeling of Polycrystalline Materials

    NASA Astrophysics Data System (ADS)

    Adland, Ari Joel

    In this thesis, we use and further develop the phase-field crystal (PFC) method derived from classical density functional theory to investigate polycyrstalline materials. The PFC method resolves atomistic scale processes by tracking the evolution of the local time averaged crystal density field, thereby naturally describing dislocations and grian boundaries (GBs), but with a phenomenological incorporation of vacancy diffusion that accesses long diffusive time scales beyond the reach of MD simulations. We use the PFC method to investigate two technologically important classes of polycrystalline materials whose properties are strongly influenced by GB equilibrium and non-equilibrium properties. The first are structural polycyrstalline materials such as nickel based superalloys used for turbine blades. Those alloys can develop large defects known as "hot tears'' due to the lack of complete crystal cohesion and strain localization during the late stages of solidification. We investigate the equilibrium structure of symmetric tilt GBs at high homologous temperatures and identify a wide range of misorientation that leads to the formation of nanometer-thick intergranular films with liquid like properties. The phase transition character of this "GB premelting'' phenomenon is investigated through the quantitative computation of a disjoining thermodynamic potential in both pure materials and alloys, using body-centered-cubic Fe as a model system. The analysis of this potential sheds light on the physical origin of attractive and repulsive forces that promote and suppress crystal cohesion, respectively, and are found to be strongly affected by solute addition. Our equilibrium studies also reveal the existence of novel structural transitions of low angle GBs driven by the pairing of dislocations with both screw and edge character. Non-equilibrium PFC simulations in turn characterize the response of GBs to an applied shear stress, showing that intergranular liquid-like films

  9. Bulk Crystal Growth of Piezoelectric PMN-PT Crystals Using Gradient Freeze Technique for Improved SHM Sensors

    NASA Technical Reports Server (NTRS)

    Aggarwal, Mohan D.; Kochary, F.; Penn, Benjamin G.; Miller, Jim

    2007-01-01

    There has been a growing interest in recent years in lead based perovskite ferroelectric and relaxor ferroelectric solid solutions because of their excellent dielectric, piezoelectric and electrostrictive properties that make them very attractive for various sensing, actuating and structural health monitoring (SHM) applications. We are interested in the development of highly sensitive and efficient PMN-PT sensors based on large single crystals for the structural health monitoring of composite materials that may be used in future spacecrafts. Highly sensitive sensors are needed for detection of defects in these materials because they often tend to fail by distributed and interacting damage modes and much of the damage occurs beneath the top surface of the laminate and not detectable by visual inspection. Research is being carried out for various combinations of solid solutions for PMN-PT piezoelectric materials and bigger size crystals are being sought for improved sensor applications. Single crystals of this material are of interest for sensor applications because of their high piezoelectric coefficient (d33 greater than 1700 pC/N) and electromechanical coefficients (k33 greater than 0.90). For comparison, the commonly used piezoelectric ceramic lead zirconate titanate (PZT) has a d33 of about 600 pC/N and electromechanical coefficients k33 of about 0.75. At the present time, these piezoelectric relaxor crystals are grown by high temperature flux growth method and the size of these crystals are rather small (3x4x5 mm(exp 3). In the present paper, we have attempted to grow bulk single crystals of PMN-PT in a 2 inch diameter platinum crucible and successfully grown a large size crystal of 67%PMN-33%PT using the vertical gradient freeze technique with no flux. Piezoelectric properties of the grown crystals are investigated. PMN-PT plates show excellent piezoelectric properties. Samples were poled under an applied electric field of 5 kV/cm. Dielectric properties at a

  10. General hypothesis governing the growth of single-crystal nanowires

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2010-06-01

    The growth and growth rates of single-crystal nanowires by vapor phase mechanisms have been studied. A hypothesis has been proposed, which lays down foundation for the nanowire growth. It redefines the basic concepts of droplets from seeds and describes the fundamental basis of the adhesive properties of droplets. A set of droplet characteristics has been defined, a model in the framework of the hypothesis has been developed, and theoretical calculations have been performed. Experiments have also been carried out. Close correspondences between the theoretical and the experimental results lend support for the hypothesis and the model. Additional experimental evidences quantify the validity of the hypothesis. The calculated results resolve conflicts and controversies. They address the roles of catalysts in the growth of single-crystal nanowires. They shed light on the basic differences in the growth of thin and thick nanowires. They elucidate possible relationship between eutectic temperature and activation energy in the vapor-liquid-solid growth. They provide ground rules that govern the relative supplies of constituent vapor species for the growth of compound semiconductor nanowires. They explain how the same alloyed droplet (e.g., Au/Ga) is activated differently under the influence of different nonmetal elements of different nanowires (for example, As of GaAs, P of GaP, and N of GaN). They demonstrate, for example, that the nanowire growth may be achieved by means that creates thermodynamic imbalance and nanopores inside the seeds at temperatures far below the seed's melting temperature. Alloying in the vapor-solid-liquid mechanism is one such means where growth of even thick nanowires (radius of rD≥50 nm) is possible at temperatures far below the eutectic temperature. The hypothesis, is called the simple, novel, and malleable (SNM) hypothesis. This hypothesis, together with the model, appears to have solved the basic origin of the nanowire growth. It

  11. Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

    SciTech Connect

    Sankari, R. Siva; Perumal, Rajesh Narayana

    2014-04-24

    Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

  12. Development of SiC Large Tapered Crystal Growth

    NASA Technical Reports Server (NTRS)

    Neudeck, Phil

    2011-01-01

    Research Focus Area: Power Electronics, Temperature Tolerant Devices. Demonstrate initial feasibility of totally new "Large Tapered Crystal" (LTC) process for growing vastly improved large-diameter wide-band gap wafers. Addresses Targets: The goal of this research is to experimentally investigate and demonstrate feasibility of the key unproven LTC growth processes in SiC. Laser-assisted growth of long SiC fiber seeds. Radial epitaxial growth enlargement of seeds into large SiC boules. Uniqueness and Impacts open a new technology path to large-diameter SiC and GaN wafers with 1000-fold defect density improvement at 2-4 fold lower cost. Leapfrog improvement in wide band gap power device capability and cost.

  13. 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.

  14. Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Kah, L. C.; Kronyak, R. E.; Ming, D. W.; Grotzinger, J. P.; Schieber, J.; Sumner, D. Y.; Edgett, K. S.

    2015-01-01

    The Pahrump region (Gale Crater, Mars) marks a critical transition between sedimentary environments dominated by alluvial-to-fluvial materials associated with the Gale crater rim, and depositional environments fundamentally linked to the crater's central mound, Mount Sharp. At Pahrump, the Murray formation consists of an approximately 14-meter thick succession dominated by massive to finely laminated mudstone with occasional interbeds of cross-bedded sandstone, and is best interpreted as a dominantly lacustrine environment containing tongues of prograding fluvial material. Murray formation mudstones contain abundant evidence for early diagenetic mineral precipitation and its subsequent removal by later diagenetic processes. Lenticular mineral growth is particularly common within lacustrine mudstone deposits at the Pahrump locality. High-resolution MAHLI images taken by the Curiosity rover permit detailed morphological and spatial analysis of these features. Millimeter-scale lenticular features occur in massive to well-laminated mudstone lithologies and are interpreted as pseudomorphs after calcium sulfate. The distribution and orientation of lenticular features suggests deposition at or near the sediment-water (or sediment-air) interface. Retention of chemical signals similar to host rock suggests that original precipitation was likely poikilotopic, incorporating substantial amounts of the primary matrix. Although poikilotopic crystal growth is common in burial environments, it also occurs during early diagenetic crystal growth within unlithified sediment where high rates of crystal growth are common. Loss of original calcium sulfate mineralogy suggests dissolution by mildly acidic, later-diagenetic fluids. As with lenticular voids observed at Meridiani by the Opportunity Rover, these features indicate that calcium sulfate deposition may have been widespread on early Mars; dissolution of depositional and early diagenetic minerals is a likely source for both calcium

  15. 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?

  16. Ice crystal growth in a dynamic thermal diffusion chamber

    NASA Technical Reports Server (NTRS)

    Keller, V. W.

    1980-01-01

    Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.

  17. Controlling Molecular Growth between Fractals and Crystals on Surfaces.

    PubMed

    Zhang, Xue; Li, Na; Gu, Gao-Chen; Wang, Hao; Nieckarz, Damian; Szabelski, Paweł; He, Yang; Wang, Yu; Xie, Chao; Shen, Zi-Yong; Lü, Jing-Tao; Tang, Hao; Peng, Lian-Mao; Hou, Shi-Min; Wu, Kai; Wang, Yong-Feng

    2015-12-22

    Recent studies demonstrate that simple functional molecules, which usually form two-dimensional (2D) crystal structures when adsorbed on solid substrates, are also able to self-assemble into ordered openwork fractal aggregates. To direct and control the growth of such fractal supramolecules, it is necessary to explore the conditions under which both fractal and crystalline patterns develop and coexist. In this contribution, we study the coexistence of Sierpiński triangle (ST) fractals and 2D molecular crystals that were formed by 4,4″-dihydroxy-1,1':3',1″-terphenyl molecules on Au(111) in ultrahigh vacuum. Growth competition between the STs and 2D crystals was realized by tuning substrate and molecular surface coverage and changing the functional groups of the molecular building block. Density functional theory calculations and Monte Carlo simulations are used to characterize the process. Both experimental and theoretical results demonstrate the possibility of steering the surface self-assembly to generate fractal and nonfractal structures made up of the same molecular building block.

  18. Crystal growth and fluid mechanics problems in directional solidification

    NASA Astrophysics Data System (ADS)

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

    1994-08-01

    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?

  19. Controlling Molecular Growth between Fractals and Crystals on Surfaces.

    PubMed

    Zhang, Xue; Li, Na; Gu, Gao-Chen; Wang, Hao; Nieckarz, Damian; Szabelski, Paweł; He, Yang; Wang, Yu; Xie, Chao; Shen, Zi-Yong; Lü, Jing-Tao; Tang, Hao; Peng, Lian-Mao; Hou, Shi-Min; Wu, Kai; Wang, Yong-Feng

    2015-12-22

    Recent studies demonstrate that simple functional molecules, which usually form two-dimensional (2D) crystal structures when adsorbed on solid substrates, are also able to self-assemble into ordered openwork fractal aggregates. To direct and control the growth of such fractal supramolecules, it is necessary to explore the conditions under which both fractal and crystalline patterns develop and coexist. In this contribution, we study the coexistence of Sierpiński triangle (ST) fractals and 2D molecular crystals that were formed by 4,4″-dihydroxy-1,1':3',1″-terphenyl molecules on Au(111) in ultrahigh vacuum. Growth competition between the STs and 2D crystals was realized by tuning substrate and molecular surface coverage and changing the functional groups of the molecular building block. Density functional theory calculations and Monte Carlo simulations are used to characterize the process. Both experimental and theoretical results demonstrate the possibility of steering the surface self-assembly to generate fractal and nonfractal structures made up of the same molecular building block. PMID:26502984

  20. Length Selection in Dendritic Growth of Electrohydrodynamic Convection in a Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Gheorghiu, Nadina; Gleeson, J. T.

    2001-03-01

    Dendritic growth of electrohydrodynamic convection (EHC) with parallel magnetic field in a nematic liquid crystal (NLC) has been already subjected to one important experiment (J.T.Gleeson, Nature, 385, 511 (1997)). Further exploration of this interesting pattern-forming system is presented here. The most important question is: What sets the length scale for the dendrite? In order to find this, we use two control parameters in our experiment: the thickness d of the liquid crystal film, and the intensity H of the magnetic field. The first one is proportional to the pattern wavelength in the traditional EHC experiment, while the second determines the distance of externally imposed anisotropy, the magnetic coherence length ξ_m. By systematically varying d and ξ_m, we relate these two imposed lengths to those that characterize the dendrite: the tip radius of curvature ρ and the interface width w. An estimate of the critical field HC for the subcritical bifurcation is also provided.