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1

Fluid mechanics in crystal growth - The 1982 Freeman scholar lecture  

Microsoft Academic Search

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

Simon Ostrach

1983-01-01

2

The Mechanism of Protein Crystal Growth from Lipid Layers  

Microsoft Academic Search

Two-dimensional (2D) crystals of proteins on lipid monolayers can initiate the formation of large three-dimensional (3D) crystals suitable for X-ray diffraction studies. The role of the 2D crystals in this process has not been firmly established. While it is likely that the 2D crystals serve as nuclei for epitaxial crystal growth, other mechanisms, such as non-specific nucleation induced by the

Sally A. Hemming; Alexey Bochkarev; Seth A. Darst; Roger D. Kornberg; Paul Ala; Daniel S. C. Yang; Aled M. Edwards

1995-01-01

3

The influence of precipitant concentration on macromolecular crystal growth mechanisms  

NASA Astrophysics Data System (ADS)

Atomic force microscopy was applied to investigate the influence of protein and precipitant (sodium-potassium tartrate) concentration on thaumatin crystal growth mechanisms. At constant protein concentration, a decrease of salt concentration from 0.8 to 0.085 M caused a transition of the crystal growth mechanism from two-dimensional nucleation to dislocation growth. At different, fixed concentrations of salt, the protein concentration, which does not induce multiple crystal nucleation, was increased from 8 to 60 mg/ml with corresponding increases in the tangential velocity of growth steps from 5 to 17.5 nm/s. Results from these experiments suggest that a highly concentrated protein solution, as might be found in a protein rich phase, may not induce crystal nucleation, but can promote crystal growth if screw dislocations are present in the crystal.

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

2001-11-01

4

Determining the Molecular Growth Mechanisms of Tetragonal Lysozyme Crystals  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

5

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

6

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

USGS Publications Warehouse

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

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

2000-01-01

7

Mechanisms of classical crystal growth theory explain quartz and silicate dissolution behavior  

E-print Network

Mechanisms of classical crystal growth theory explain quartz and silicate dissolution behavior-driven crystal growth was introduced that described growth kinetics in terms of fo through the same mecha- nistic theory of nucleation developed for mineral growth. In principle

Dove, Patricia M.

8

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

E-print Network

An interfacial energy mechanism for the complete inhibition of crystal growth by inhibitor for complete crystal-growth inhibition based on the thermodynamics of interfaces. The premise for our model or to a reduction in growth rate. The inhibition of crystal growth due to adsorption is impor- tant for both natural

Firoozabadi, Abbas

9

Physical Mechanisms of Crystal Growth Modification by Biomolecules  

NASA Astrophysics Data System (ADS)

During the process of biomineralization, living organisms use macromolecules to direct the nucleation and growth of a variety of inorganic materials. Because biomineral structures exhibit complex topologies, hierarchical design, and unique materials properties, an understanding of the underlying mechanisms of biomolecular controls over mineral growth presents an opportunity to develop new strategies towards synthesis of novel materials for applications across a wide range of technologies. Herein 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 calcium carbonate and calcium oxalate crystal surfaces during the growth are reviewed. The results show how the stereochemical relationships between additive and atomic step leads to modifications of crystal shape. In some cases, the inhibitory effects of strong binders are well-explained by a model of growth inhibition based on the classic Cabrera-Vermilyea theory, but updated to take into account the particular nature of biomolecular adsorption dynamics. The consequences include a positive feedback between peptide adsorption and step inhibition that results in bistable growth with rapid switching from fast to near-zero growth rates for very small changes in supersaturation. The phenomenon of biomolecule-induced growth acceleration is also reviewed and shown to be common to both the oxalate and carbonate systems. The source of acceleration is related to the activation barrier for solute attachment to steps. Finally, experimental and theoretical results are presented that suggest most biomineral phases can not be described by conventional models in which kink formation due to thermal fluctuations at step edges is rapid enough to ensure the availability of kinks. Instead, growth is kink-limited. As a consequence, biomolecule-step interactions cannot be interpreted with traditional thermodynamic models based on minimization of the Gibbs free energy. Instead these interactions follow a different mechanism determined by the kinetics of attachment and detachment. The general nature of these findings support the plausibility of their application to industrial systems.

De Yoreo, James J.

2010-07-01

10

Crystal Growth and Fluid Mechanics Problems in Directional Solidification  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

11

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

12

Crystal growth and fluid mechanics problems in directional solidification  

NASA Technical Reports Server (NTRS)

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?

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

1994-01-01

13

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

USGS Publications Warehouse

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

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

1998-01-01

14

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

USGS Publications Warehouse

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

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

1999-01-01

15

VO2 (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms  

NASA Astrophysics Data System (ADS)

Well crystallized VO2 (A) microrods were grown via a single step hydrothermal reaction in the presence of V2O5 and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO2 (A) micro rods. The structural and electronic transitions in VO2 (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversible intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO2 (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO2 (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO2 (M1) are described.

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

2014-05-01

16

An instrument for in situ growth rate characterization of mechanically strained crystals  

NASA Astrophysics Data System (ADS)

The crystal growth and dissolution characteristics of a certain material can be considerably influenced by the strain present in a growing (dissolving) crystal. Strain can be induced in various ways. One of the most common and always present in industrial processes, where attrition processes are always accompanied by generation of mechanical strain in a newly formed small crystal fragments, is mechanical stressing, in situ, during preparation and handling. To gain deeper insights into some aspects of this phenomenon, a sophisticated equipment is needed for in situ controlled stressing of extremely brittle and fragile crystals. For this purpose, we have developed an apparatus which comprises a specially designed straining cell coupled with a laser Michelson interferometer for growth rate measurements. The straining cell is designed to accommodate crystals that undergo fracture below 200 microstrains. The stress imposed on a crystal is computer controlled with a precision of approximately 5%. Details of the instrument are given together with two examples of straining in situ brittle paracetamol and plastic sodium nitrate crystals. The measured changes in growth rate of a paracetamol crystal, in the quasi linear region 0-70 kPa are estimated to be (-9.4±0.1)×10-11 m/s/kPa.

Zikic, A. M.; Ristic, R. I.; Sherwood, J. N.

1998-07-01

17

Growth, photoluminescence, thermal and mechanical behaviour of Ethyltriphenylphosphonium bromide dihydrate crystal  

NASA Astrophysics Data System (ADS)

Single crystal of Ethyltriphenylphosphonium bromide dihydrate (ETPB) was grown by slow evaporation solution growth technique. The grown crystal was confirmed by single crystal X-ray diffraction. The functional groups and vibrational frequencies were identified using FT-IR and FT-Raman spectral analyses. Optical properties were studied by UV-Visible and photoluminescence spectroscopic techniques to explore its efficacy towards device fabrication. Thermal characteristics of ETPB were studied using the TGA/DTA and DSC response curves. The mechanical behaviour of the grown crystal was studied using Vicker's microhardness tester and the work hardening coefficient was evaluated. The second harmonic generation of the title compound was tested by Kurtz-Perry powder technique.

Parthasarathy, M.; Gopalakrishnan, R.

2013-10-01

18

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

USGS Publications Warehouse

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

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

2000-01-01

19

New AFM Techniques for Investigating Molecular Growth Mechanisms of Protein Crystals  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

20

Total immersion crystal growth  

NASA Technical Reports Server (NTRS)

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.

Morrison, Andrew D. (inventor)

1987-01-01

21

Crystal growth mechanisms and morphological control of the prototypical metal-organic framework MOF-5 revealed by atomic force microscopy.  

PubMed

Crystal growth of the metal-organic framework MOF-5 was studied by atomic force microscopy (AFM) for the first time. Growth under low supersaturation conditions was found to occur by a two-dimensional or spiral crystal growth mechanism. Observation of developing nuclei during the former reveals growth occurs through a process of nucleation and spreading of metastable and stable sub-layers revealing that MOFs may be considered as dense phase structures in terms of crystal growth, even though they contain sub-layers consisting of ordered framework and disordered non-framework components. These results also support the notion this may be a general mechanism of surface crystal growth at low supersaturation applicable to crystalline nanoporous materials. The crystal growth mechanism at the atomistic level was also seen to vary as a function of the growth solution Zn/H(2)bdc ratio producing square terraces with steps parallel to the <100> direction or rhombus-shaped terraces with steps parallel to the <110> direction when the Zn/H(2)bdc ratio was >1 or about 1, respectively. The change in relative growth rates can be explained in terms of changes in the solution species concentrations and their influence on growth at different terrace growth sites. These results were successfully applied to the growth of as-synthesized cube-shaped crystals to increase expression of the {111} faces and to grow octahedral crystals of suitable quality to image using AFM. This modulator-free route to control the crystal morphology of MOF-5 crystals should be applicable to a wide variety of MOFs to achieve the desired morphological control for performance enhancement in applications. PMID:23055448

Cubillas, Pablo; Anderson, Michael W; Attfield, Martin P

2012-11-26

22

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

PubMed

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

Pileni, M P

2012-11-20

23

Growth mechanism of ZnO deposited by nitrogen mediated crystallization  

NASA Astrophysics Data System (ADS)

We investigate the growth mechanism of ZnO deposited by a nitrogen mediated crystallization (NMC) method. NMC is a method in which nitrogen is used to control nucleation via a nitrogen adsorption–desorption behavior. The growth of NMC-ZnO is classified into three stages, that is, the pre-nucleation stage, nucleation and grain growth stage for 4–30 nm in thickness, and coalescence stage for 31–100 nm in thickness. NMC-ZnO nucleation takes place in a very short period compared to that for conventional ZnO. Hence, NMC-ZnO has a uniform grain size distribution, flat surface with less spiky grains, and a longer lateral correlation length of the surface, leading to a larger grain size than in conventional ZnO. Utilizing this NMC-ZnO as a buffer layer, low resistive aluminum doped zinc oxide ZnO:Al (AZO) films are obtained at the buffer layer film thickness ranging from 4 to 30 nm. The lowest resistivity is 3.4 × 10−4 Ω cm for 90 nm thick AZO deposited on NMC-ZnO buffer layers of 10 and 30 nm in thickness.

Suhariadi, Iping; Shiratani, Masaharu; Itagaki, Naho

2014-09-01

24

Crystal growth and mechanical characterization of ZrMo2O8  

NASA Astrophysics Data System (ADS)

We report a fluxing technique for ZrMo2O8 single crystal growth. The volatility of MoO3 coupled with the limited temperature range of its stability with the liquid phase makes the single crystal growth of ZrMo2O8 a formidable challenge. Single crystal growth of ZrMo2O8 was carried out in a horizontal tubular furnace using a platinum boat and utilizing Li2MoO4 as a fluxing agent. The synthesized faceted crystals were up to 3 mm along the maximum dimension. Laue and single crystal X-ray diffraction confirmed the monoclinic crystal structure having a space group C 1 2/c 1 (S.G#15), and a single crystallographic domain within the crystals. Reduced elastic modulus and hardness were determined to be 108±4 GPa and 6.4±0.2 GPa respectively using nanoindentation. Appearance of additional peaks in Raman spectra of the indented region when compared with the fresh crystal indicated a possible pressure induced phase transformation during indentation.

Ahmad, Md. Imteyaz; Mohanty, Gaurav; Rajan, Krishna; Akinc, Mufit

2014-10-01

25

Liquid encapsulated crystal growth  

NASA Technical Reports Server (NTRS)

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.

Morrison, Andrew D. (Inventor)

1989-01-01

26

Liquid encapsulated crystal growth  

NASA Technical Reports Server (NTRS)

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.

Morrison, Andrew D. (inventor)

1987-01-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

28

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

PubMed

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

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

2014-12-10

29

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

SciTech Connect

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

Varjula, A. Jonie; Ramanand, A. [Department of Physics, Loyola College, Chennai 600034 (India); Das, S. Jerome [Department of Physics, Loyola College, Chennai 600034 (India)], E-mail: sjeromedas2004@yahoo.com

2008-02-05

30

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

NASA Astrophysics Data System (ADS)

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 (? 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.

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

2011-09-01

31

Physics of Crystal Growth  

NASA Astrophysics Data System (ADS)

Preface; List of symbols; 1. Morphology of a crystal surface; 2. Surface free energy, step free energy, and chemical potential; 3. The equilibrium crystal shape; 4. Growth and dissolution crystal shapes: Frank's model; 5. Crystal growth: the abc; 6. Growth and evaporation of a stepped surface; 7. Diffusion; 8. Thermal smoothing of a surface; 9. Silicon and other semiconducting materials; 10. Growth instabilities of a planar front; 11. Nucleation and the adatom diffusion length; 12. Growth roughness at long lengthscales in the linear approximation; 13. The Kardar-Parisi-Zhang equation; 14. Growth without evaporation; 15. Elastic interactions between defects on a crystal surface; 16. General equations of an elastic solid; 17. Technology, crystal growth and surface science; Appendices; References; Index.

Pimpinelli, Alberto; Villain, Jacques

1998-12-01

32

Studies on growth, spectral, optical and mechanical properties of new organic NLO crystal: guanidinium L-glutamate (GuGL).  

PubMed

Good optical quality single crystal of guanidinium l-glutamate is grown by slow evaporation solution growth technique. The cell parameters and crystallinity are determined from the single crystal and powder X-ray diffraction analysis. The formation of synthesized compound was confirmed by FT-IR and FT-Raman spectroscopic analysis. Wide band gap of 4.98eV with high transmittance up to 2000 nm is observed for the grown crystal in UV-Vis-NIR spectral analysis. The optical constants such as refractive index and extinction coefficient of the grown crystal are obtained as 2.1 and 8.64×10(-6) respectively. The nonlinear optical study reveals that the second harmonic generation efficiency of guanidinium l-glutamate is 2.8 times that of potassium dihydrogen phosphate (KDP). The mechanical stability of the grown crystal was analyzed by Vickers microhardness test and the results are discussed. PMID:22902572

Arumanayagam, T; Ananth, S; Murugakoothan, P

2012-11-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2003-01-01

34

Monitoring Crystal Growth From Solution  

NASA Technical Reports Server (NTRS)

Experimental system for monitoring growth of triglycine sulfate (TGS) crystals from solution is being studied. System consists of outer cell containing distilled water heated and stirred to maintain constant temperature to within plus or minus 0.1 degrees C, inner (growth) cell containing supersaturated solution of TGS, and seed crystal mounted in plastic-covered stainless-steel sting equiped with controlled cooling mechanism and temperature sensors.

Lal, R. B.

1982-01-01

35

Crystal growth of semiconductor bulk crystals  

SciTech Connect

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

Kakimoto, Koichi [Research Institute for Applied Mechanics, Kyushu University, 6-1, Kasuga-Koen, Kasuga, 816-8580 (Japan)

2010-07-22

36

Investigation on growth, structural, optical, thermal, dielectric and mechanical properties of organic L-prolinium trichloroacetate single crystals  

SciTech Connect

Graphical abstract: L-Prolinium trichloroacetate is 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 L-PTCA crystallizes in trigonal crystal system. The optical band gab is found to be 4.26 eV. Second harmonic conversion efficiency of L-PTCA has been found to be half that of KDP. Highlights: ? It deals with the synthesis, growth and characterization of L-PTCA an organic NLO crystal. ? Wide optical transparency window between 260 nm and 1100 nm. ? Thermal study reveals that the grown crystal is stable up to 127 °C. ? L-PTCA crystal exhibits the second order nonlinear optical properties. -- Abstract: A new organic nonlinear optical material L-prolinium trichloroacetate (L-PTCA) single crystal has been synthesized and grown by slow solvent evaporation technique at room temperature using water as solvent. Single-crystal X-ray diffractometer was utilized to measure unit cell parameters and to confirm lattice parameter. The powder X-ray diffraction pattern of the grown L-PTCA has been indexed. The modes of vibration of different molecular groups present in the sample were identified by the FTIR spectral analysis. The optical transmittance window and the lower cutoff wavelength of the L-PTCA have been identified by UV–vis–NIR studies. Thermal stability of the L-prolinium trichloroacetate was determined by TGA/DTA measurements. Dielectric measurements were carried out at various temperatures at frequency range 10–1 MHz. The mechanical properties of the grown crystals have been analyzed by Vickers microhardness method. The chemical etching studies were carried out on the grown crystals. Its SHG efficiency has been tested by Kurtz powder method.

Boopathi, K.; Rajesh, P. [Centre for Crystal Growth, SSN college of Engineering, Kalavakkam 603 110 (India)] [Centre for Crystal Growth, SSN college of Engineering, Kalavakkam 603 110 (India); Ramasamy, P., E-mail: ramasamyp@ssn.edu.in [Centre for Crystal Growth, SSN college of Engineering, Kalavakkam 603 110 (India)

2012-09-15

37

Crystal Growth and Design  

NSDL National Science Digital Library

An electronic version of this journal from the American Chemical Society is available for free through June 30, 2001. Crystal Growth and Design is "a new journal from the American Chemical Society, dedicated to publishing articles on the physical, chemical, and biological phenomena and processes related to crystal growth and design of new materials."

38

Crystal growth, structural, crystalline perfection, optical and mechanical properties of Nd3+ doped sulfamic acid (SA) single crystals  

NASA Astrophysics Data System (ADS)

Sulfamic acid (SA) single crystals, both pure and doped with 1, 2.5 and 5 mol% Nd, were grown successfully in an aqueous solution by the slow cooling method. Powder X-ray diffraction patterns were recorded to check the variation in the lattice parameters and phase of the crystals. The optical transparency was found to be higProd. Type: FTPhest (?80%) for the 1 mol% Nd3+ doped SA single crystal. The optical band gap was also calculated and found to be ?4.31, 4.20 and 3.67 eV. The influence of Nd3+ doping on the crystalline perfection was assessed by a high resolution X-ray diffractometer (HRXRD) and shows that the grown crystals could accommodate Nd3+ at the interstitial positions in the crystalline matrix of SA up to some critical concentration without any deterioration in the crystalline perfection. The etching studies were carried out and the etch pits densities were calculated. The mechanical property of grown single crystals was also studied.

Shkir, Mohd.; Riscob, B.; Ganesh, V.; Vijayan, N.; Gupta, Rahul; Plaza, J. L.; Dieguez, E.; Bhagavannarayana, G.

2013-10-01

39

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

NASA Astrophysics Data System (ADS)

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

Liang, Yuan-Chang; Zhong, Hua

2013-08-01

40

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

PubMed Central

In-Sn-O nanostructures with rectangular cross-sectional rod-like, sword-like, and bowling pin-like morphologies were successfully synthesized through self-catalytic growth. Mixed metallic In and Sn powders were used as source materials, and no catalyst layer was pre-coated on the substrates. The distance between the substrate and the source materials affected the size of the Sn-rich alloy particles during crystal growth in a quartz tube. This caused In-Sn-O nanostructures with various morphologies to form. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanostructures. The Sn doping and oxygen vacancies in the In2O3 crystals corresponded to the blue-green and yellow-orange emission bands of the nanostructures, respectively. PMID:23965167

2013-01-01

41

Protein crystal growth  

NASA Technical Reports Server (NTRS)

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.

2001-01-01

42

Studies on the growth, structural, optical, mechanical properties of 8-hydroxyquinoline single crystal by vertical Bridgman technique  

SciTech Connect

Highlights: {yields} Growth of bulk single crystal of 8-hydroxyquinoline (8-HQ) by vertical Bridgman technique for the first time. {yields} The crystalline perfection is reasonably good. {yields} The photoluminescence spectrum shows that the material is suitable for blue light emission. -- Abstract: Single crystal of organic nonlinear optical material, 8-hydroxyquinoline (8-HQ) of dimension 52 mm (length) x 12 mm (dia.) was grown from melt using vertical Bridgman technique. The crystal system of the material was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was examined by high-resolution X-ray diffraction study. Low angular spread around 400'' of the diffraction curve and the low full width half maximum values show that the crystalline perfection is reasonably good. The recorded photoluminescence spectrum shows that the material is suitable for blue light emission. Optical transmittance for the UV and visible region was measured and mechanical strength was estimated from Vicker's microhardness test along the growth face of the grown crystal.

Prabhakaran, SP. [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)] [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Velusamy, P.; Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)] [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

2011-11-15

43

Microgravity crystal growth  

NASA Technical Reports Server (NTRS)

Advanced finite element models are used to study three-dimensional, time-dependent flow and segregation in crystal growth systems. In this image of a prototypical model for melt and crystal growth, pathlines at one instant in time are shown for the flow of heated liquid silicon in a cylindrical container. The container is subjected to g-jitter disturbances along the vertical axis. A transverse magnetic field is applied to control them. Such computations are extremely powerful for understanding melt growth in microgravity where g-jitter drives buoyant flows. The simulation is part of the Theoretical Analysis of 3D, Transient Convection and Segregation in Microgravity Bridgman Crystal Growth investigation by Dr. Jeffrey J. Derby of the University of Mirnesota, Minneapolis.

2001-01-01

44

Crystal Growth Control  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

45

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

NASA Technical Reports Server (NTRS)

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

Brown, R. A.

1986-01-01

46

Quartz crystal growth  

DOEpatents

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.

Baughman, Richard J. (Albuquerque, NM)

1992-01-01

47

Crystal Growth from the Melt: A Review  

Microsoft Academic Search

This paper reviews four aspects of crystal growth theory: the nature of the rate-controlling process, the mechanism controlling molecular attachment onto the growing crystal surface, the nature of the crystal-melt interface, and the stability of planar interfaces relative to cellular interfaces. The rate-controlling process may be diffusion in the melt, heat flow, or the reaction at the crystal-melt interface. Diffusion

R. Jeuss Knrpnrnrcr

48

Zeolite crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

49

Protein Crystal Growth in Microgravity  

NASA Astrophysics Data System (ADS)

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 ? -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.

Delucas, Lawrence J.; Smith, Craig D.; Smith, H. Wilson; Vijay-Kumar, Senadhi; Senadhi, Shobha E.; Ealick, Steven E.; Carter, Daniel C.; Snyder, Robert S.; Weber, Patricia C.; Salemme, F. Raymond; Ohlendorf, D. H.; Einspahr, H. M.; Clancy, L. L.; Navia, Manuel A.; McKeever, Brian M.; Nagabhushan, T. L.; Nelson, George; McPherson, A.; Koszelak, S.; Taylor, G.; Stammers, D.; Powell, K.; Darby, G.; Bugg, Charles E.

1989-11-01

50

Protein crystal growth in microgravity  

NASA Technical Reports Server (NTRS)

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.

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

51

Protein crystals and their growth  

NASA Technical Reports Server (NTRS)

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

Chernov, Alexander A.

2003-01-01

52

Growth, optical, luminescence, thermal and mechanical behavior of an organic single crystal: 3-Acetyl-2-methyl-4-phenylquinolin-1-ium chloride.  

PubMed

A single crystal of 3-acetyl-2-methyl-4-phenylquinolin-1-ium chloride has grown by slow evaporation solution growth technique using ethanol as solvent. The structural, thermal, optical and mechanical property has studied for the grown crystal. Single crystal XRD revealed that the crystal belongs to monoclinic system with space group P21/c. The presences of Functional groups in the crystallized material have confirmed using the FTIR vibrational spectrum. The optical absorbance spectrum recorded from 190 to 1100nm shows the cut-off wavelength occurs at 371nm. The material shows its transparency in the entire region of the visible spectrum. The photoluminescence spectrum shows the ultraviolet and blue emission in the crystal. Thermogravimetric and differential thermal analysis reveal the thermal stability of the grown crystal. Etching study shows the grown mechanism and surface features of the crystal. Vickers microhardness studies have carried out on the (01-1) plane to understand the mechanical properties of the grown crystal. The hardness of the title compound increases on increasing the load. The Meyer's index number (n), and the stiffness constants for different loads has calculated and reported. PMID:24389003

Nirosha, M; Kalainathan, S; Sarveswari, S; Vijayakumar, V

2014-04-01

53

Protein crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

54

Growth, structural, spectral, mechanical and optical properties of pure and metal ions doped sulphamic acid single crystals.  

PubMed

Bulk single crystals of pure and metal ions (Mn(2+), Cu(2+) and Ni(2+)) doped sulphamic acid (SA) have been grown by conventional and unidirectional solution growth methods. Intensities of powder X-ray diffraction peaks of metal ions doped SA reveal that these dopants enhanced the crystallanity. The peak broadening and intensity variation in some frequency regions in FT-IR spectra show the incorporation of dopants in the SA lattice. Mn(2+) and Cu(2+) doped SA single crystals show high crystalline perfection (FWHM 5.5arcs) compared to pure and Ni(2+) metal ions doped SA crystals. The grown pure and Mn(2+), Cu(2+) and Ni(2+) ions doped SA crystals have transparency in the order SA>Mn:SA>Cu:SA>Ni:SA. The hardness value of Ni(2+) doped crystal is relatively less than that of the pure and other metal ions doped SA crystals. Pure and Ni(2+) ions doped SA crystals possess high dielectric constants than that of Cu(2+) and Mn(2+) ions doped crystals. From the SEM micrograph analyses, it is observed that the doping of these metal ions modify the surface morphology of the grown crystals. PMID:20493763

Ramesh Babu, R; Ramesh, R; Gopalakrishnan, R; Ramamurthi, K; Bhagavannarayana, G

2010-09-01

55

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

USGS Publications Warehouse

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

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

2002-01-01

56

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

NASA Astrophysics Data System (ADS)

4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6 × 2 × 3 mm3) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and 1H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV).

Dinakaran, Paul M.; Kalainathan, S.

2013-07-01

57

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

PubMed

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

Dinakaran, Paul M; Kalainathan, S

2013-07-01

58

Growth, optical, mechanical and electrical properties of L-serine acetate: A promising semiorganic nonlinear optical crystal  

NASA Astrophysics Data System (ADS)

L-Serine Acetate (LSA) single crystal was successfully grown by slow solvent evaporation technique. Cell parameters are determined by single crystal X-ray diffraction study. Various functional groups presented in the crystal were confirmed by FT-IR Analysis. The transmission of the crystal was found by UV analysis and band gap energy of the grown crystal was also calculated. Dielectric constant and dielectric loss of the crystal was determined using dielectric studies. Hardness studies were employed to characterize the mechanical strength of the grown crystal. Nonlinear optical property has been studied by Kurtz Perry technique. The second harmonic generation conversion efficiency of the grown crystal shows the suitability of the grown crystal for frequency conversion applications. Due to a publication oversight, the PDF file of this article was accidentally substituted by a PDF file containing a different article. The PDF file of the correct article was published on June 12, 2013. AIP Publishing would like to apologize to the authors and editors for any inconvenience this may have caused.

Rajesh, K.; Kumar, P. Praveen; Zamara, A.; Thirugnanam, A.

2013-06-01

59

Direct flow crystal growth system  

DOEpatents

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.

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

1992-01-01

60

Protein crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

Delucas, Lawrence J.; Bugg, Charles E.

1991-01-01

61

What Variables Affect Crystal Growth?  

NSDL National Science Digital Library

Students investigate variables that may influence the growth of crystals which they have learned to make. There are two options for implementing this activity. The first is open-ended, with the students deciding what variables affect crystal growth and then deciding on the manipulating variables they would like to study. The second is prescriptive and explains to students how to test three variables in making crystals: temperature, method of mixing (such as shaking or stirring), and concentration.

62

Protein crystal growth in low gravity  

NASA Technical Reports Server (NTRS)

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

Feigelson, Robert S.

1987-01-01

63

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

PubMed

A new semi organic non linear optical polymeric crystal, bis (thiourea) silver (I) nitrate (TuAgN) with dimension 8×7×1.5 mm(3) has been successfully grown from aqueous solution by slow evaporation solution technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non centrosymmetric space group C2221. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Functional groups present in the crystal were analyzed qualitatively by infrared and Confocal Raman spectral analysis. Effects due to coordination of thiourea with metal ions were also discussed. Optical absorption study on TuAgN crystal shows the minimum absorption in the entire UV-Vis region and the lower cut off wavelength of TuAgN is found to be 318 nm. Thermal analysis shows that the material is thermally stable up to 180°C. The mechanical strength and its parameters of the grown crystal were estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 0.85 times that of KDP. PMID:24091346

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

2014-01-24

64

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

NASA Astrophysics Data System (ADS)

A new semi organic non linear optical polymeric crystal, bis (thiourea) silver (I) nitrate (TuAgN) with dimension 8 × 7 × 1.5 mm3 has been successfully grown from aqueous solution by slow evaporation solution technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non centrosymmetric space group C2221. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Functional groups present in the crystal were analyzed qualitatively by infrared and Confocal Raman spectral analysis. Effects due to coordination of thiourea with metal ions were also discussed. Optical absorption study on TuAgN crystal shows the minimum absorption in the entire UV-Vis region and the lower cut off wavelength of TuAgN is found to be 318 nm. Thermal analysis shows that the material is thermally stable up to 180 °C. The mechanical strength and its parameters of the grown crystal were estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 0.85 times that of KDP.

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

2014-01-01

65

Protein crystal growth - Growth kinetics for tetragonal lysozyme crystals  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

66

Crystal Growth by Evaporation  

NSDL National Science Digital Library

This activity introduces students to the idea that crystals 'grow' (crystallize or precipitate) and that minerals or rocks also form this way, providing a very general idea of the nature of magma (molten material that eventually crystallizes into igneous rocks). Using solutions mixed by the teacher, they will observe and sketch the formation of crystals of potassium dichromate and copper II acetate by placing drops of the solutions on microscope slides and drying them on a hot plate. Discussion questions are provided.

2005-10-06

67

Synthesis, growth, thermal, optical and mechanical properties of new organic NLO crystal: L-alanine DL-malic acid  

NASA Astrophysics Data System (ADS)

A new organic nonlinear optical crystal, L-alanine DL-malic acid (LADLMA), has been grown from aqueous solution by the slow cooling technique. L-alanine and DL-malic acid were used in the ratio 2:1 for synthesis. Crystals of size 24×13×8 mm 3 have been obtained in 26 days. Characterizations were carried out to study the structural, optical and mechanical properties of the grown crystals. Single crystal X-ray diffraction analysis shows that they belong to the orthorhombic system. To study the crystalline perfection of the grown crystals, high-resolution X-ray diffraction (HR-XRD) study was carried out. The vibrational frequencies of various functional groups have been derived from FTIR spectrum. Thermal behaviour of the crystal was investigated by TG-DTA analyses. Transmission spectrum has been recorded in the solution state and the cut-off frequency has been determined. Nonlinear optical property of the crystal has been confirmed using the Kurtz powder technique and a study of its second harmonic generation efficiency in comparison with KDP has been made. Knoop hardness test was carried out and its Young's modulus was calculated.

Jaikumar, D.; Kalainathan, S.; Bhagavanarayana, G.

2009-12-01

68

Crystal Growth Inside an Octant  

E-print Network

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 re-scaling 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 sub-leading 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.

Jason Olejarz; P. L. Krapivsky

2013-06-19

69

Plenum type crystal growth process  

DOEpatents

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.

Montgomery, Kenneth E. (Tracy, CA)

1992-01-01

70

Dynamically controlled crystal growth system  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

71

Effect of Antifreeze Glycoprotein in contact with ice interface on the growth mechanism of an ice crystal  

NASA Astrophysics Data System (ADS)

We study the effect of Antifreeze Glycoprotein in contact with ice interface on pattern formation of an ice crystal growing from AFGP solution. AFGP effects on ice crystal growth are completely opposite for basal and prismatic faces. Basal face of ice in pure water is governed by slow molecular rearrangements on the basal plane and is expressed as a second power of the supercooling at the interface. In the presence of AFGP molecules on the surface, the kinetic roughening transition from a smooth surface to a rough one occurs, and the growth rate is enhanced. Prismatic faces in pure water are controlled by transport of latent heat and are proportional to the supercooling at the interface. In the presence of AFGP molecules, the kinetic smoothing transition from a rough surface to smooth one occurs, and the growth rate is reduced. The effects relate to the anisotropic adsorption properties of AFGP molecules. In this study, we proposed a new model for the ice growth kinetics, in which a change of structure of water molecules near ice interface, i.e., hydrophobic interaction is taken into account instead of Gibbs-Thomson Effect caused by the pinning of a step by AFGP molecules.

Yokoyama, Etsuro; Furukawa, Yohsinori

2005-03-01

72

Crystal Growth - Fast and Slow  

NSDL National Science Digital Library

This lab is divided into two exercises that may be completed within a single three-hour session. The first exercise requires the mixture of aqueous solutions that will precipitate large euhedral crystals over the course of 1 to 2 weeks. These experiments are intended to mimic the slow growth of macroscopic minerals in thermal and chemical equilibrium. In the second exercise, students observe rapid growth of dendritic crystals in strongly undercooled solutions in order to visualize the disequilibrium growth processes that occur in the atmosphere, at chilled margins, and in highly supersaturated solutions.

73

Temperature Fluctuations During Crystal Growth  

NASA Technical Reports Server (NTRS)

Technique developed to deconvolve period and relative amplitude of fluctuations of heat flow inBridgman crystal growth. Temperature-measuring device with enough sensitivity and frequency response to make desired measurements inserted close as possible to substance monitored. Time-dependent temperature response recorded, and time domain response converted to frequency domain for further analysis. Fast fourier transform (FFT) of data on temperature oscillations shows particular behavior at some specific frequencies corresponding with striations, or defects observed on crystal. Useful procedure to help determine sources of some growth-induced crystalline defects. Other processes sensitive to small temperature fluctuations, such as diffusion, precipitation, and corrsion, benefit from technique.

Fripp, Archibald L., Jr.; Clark, Ivan O.; Debnam, William J., Jr.; Barber, Patrick G.; Crouch, Roger K.; Simchick, Richard T.

1988-01-01

74

Biomolecular Modification of Inorganic Crystal Growth  

NASA Astrophysics Data System (ADS)

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

De Yoreo, James J.

2007-06-01

75

Bridgman growth of large-aperture yttrium calcium oxyborate crystal  

SciTech Connect

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.

Wu, Anhua, E-mail: wuanhua@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

2012-09-15

76

A particle's eye view of crystallizer fluid mechanics  

Microsoft Academic Search

It has been recognized for some time that flow and mixing in industrial crystallizers has an effect on the kinetics of growth, nucleation and agglomeration and consequently on the crystal size distribution. Yet, a common assumption in population balance modelling is that the fluid mechanical environment experienced by growing crystals is uniform. In practice, however, industrial crystallizers provide extremely varied

Chris D Rielly; Andrew J Marquis

2001-01-01

77

Interfacial Mass Transport in Oxide Crystal Growth  

NASA Astrophysics Data System (ADS)

A space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystal in high temperature melts and solutions. Model experiments using transparent liquids such as KNbO3, Li2B4O7+KNbO3 were chosen to investigate effects of interfacial mass transport in oxide crystal growth. For the scaling of the coupled velocity, heat and concentration fields in KNbO3 crystal growth, a rotating growth process was performed and the widths of interfacial concentration, heat and momentum transition zones (The ``boundary layers'') are obtained, which are 7.5 × 10-3, and 8.6 × 10-2 and 4.4 × 10-1cm, respectively. Hence one can expect that interfacial concentration gradient will be confined to a narrow layer and in region of major concentration change at the interface. In order to study a mechanism based on the interfacial mass transport resulting from hydrodynamics, the growth of KNbO3 grain in high temperature Li2B4O7 and KNbO3 solution was studied. The result shows that the pivotal feature in the KNbO3 crystal growth is the initiated by KNbO3 solute surface tension gradient which is caused by the slow diffusion of KNbO3 solutes. Direct comparison of the model predictions and experimental observed phenomena demonstratre the predicitive capability of this model.

Jin, Wei Qing; Liang, Xin An; Cai, Li Xia; Pan, Zhi Lei; Tsukamoto, Katsuo

78

Modeling Elasticity in Crystal Growth  

E-print Network

A new model of crystal growth is presented that describes the phenomena on atomic length and diffusive time scales. The former incorporates elastic and plastic deformation in a natural manner, and the latter enables access to times scales much larger than conventional atomic methods. The model is shown to be consistent with the predictions of Read and Shockley for grain boundary energy, and Matthews and Blakeslee for misfit dislocations in epitaxial growth.

K. R. Elder; Mark Katakowski; Mikko Haataja; Martin Grant

2001-07-18

79

Journal of Crystal Growth 130 (1993) 553--566 jo~*~ o~ CRYSTAL North-Holland GROWTH  

E-print Network

Journal of Crystal Growth 130 (1993) 553--566 jo~*~ o~ CRYSTAL North-Holland GROWTH Simulation of the eddy current sensing of gallium arsenide Czochralski crystal growth Haydn N.G. Wadley and Kumar P crystal is convex, single crystal growth occurs. Emerging monolithic microwave integrated cir- However

Wadley, Haydn

80

Crystal growth in fused solvent systems  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

81

Observable Protein Crystal Growth Apparatus  

NASA Technical Reports Server (NTRS)

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

2001-01-01

82

(PCG) Protein Crystal Growth Canavalin  

NASA Technical Reports Server (NTRS)

(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.

1989-01-01

83

The history of crystal growth  

Microsoft Academic Search

A survey is given of the historical development of both theoretical and experimental knowledge from the early beginning to\\u000a the fifties of our century. The survey is completed by a full bibliography of the most relevant papers, a timetable, and a\\u000a list of conferences devoted to crystal growth.

J. Bohm

1985-01-01

84

Optical analysis of crystal growth  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

85

Growth Defects in Biomacromolecular Crystals  

NASA Technical Reports Server (NTRS)

NASA's ground based program confirmed close similarity between protein and small molecules crystal growth, but also revealed essential differences. No understanding exists as to why and when crystals grown in space are, in approx. 20 percent of cases, of higher quality. More rationale is needed in flight experiments. Ferritin crystals grown in space are 2.5 times cleaner than their terrestrial counterparts. This may occur because of the existence of a zone depleted with respect to impurities around a crystal growing in stagnant solution. This zone should appear since the distribution coefficient for homologous impurities exceeds unity. This impurity depletion zone hypothesis requires verification and development. Thorough purification from homologous impurities brought about resolution improvement from 2.6 to 1.8 angstroms for ferritin and from 2.6 to 2.0 angstroms for canavalin.

2003-01-01

86

Inhibition of heme crystal growth by antimalarials and other compounds: implications for drug discovery  

Microsoft Academic Search

During intraerythrocytic infection, Plasmodium falciparum parasites crystallize toxic heme released during hemoglobin catabolism. The proposed mechanism of quinoline inhibition of crystal growth is either by a surface binding or a substrate sequestration mechanism. The kinetics of heme crystal growth was examined in this work using a new high-throughput crystal growth determination assay based on the differential solubility of free vs.

Curtis Robert Chong; David Joseph Sullivan

2003-01-01

87

Laboratory studies of crystal growth in magma  

NASA Astrophysics Data System (ADS)

The proportions, compositions, and interrelationships among crystalline phases and glasses in volcanic rocks cryptically record pre-eruptive intensive conditions, the timing of changes in crystallization environment, and the devolatilization history of eruptive ascent. These parameters are recognized as important monitoring tools at active volcanoes and interpreting geologic events at prehistoric and remote eruptions, thus motivating our attempts to understand the information preserved in crystals through an experimental appoach. We are performing laboratory experiments in mafic, felsic, and intermediate composition magmas to study the mechanisms of crystal growth in thermochemical environments relevant to volcanic environments. We target features common to natural crystals in igneous rocks for our experimental studies of rapid crystal growth phenomena: (1) Surface curvature. Do curved interfaces and spongy cores represent evidence of dissolution (i.e., are they corrosion features), or do they record the transition from dendritic to polyhedral morphology? (2) Trapped melt inclusions. Do trapped liquids represent bulk (i.e., far-field) liquids, boundary layer liquids, or something intermediate, depending on individual species diffusivity? What sequence of crystal growth rates leads to preservation of sealed melt inclusions? (3) Subgrain boundaries. Natural phenocrysts commonly exhibit tabular subgrain regions distinguished by small angle lattice misorientations or "dislocation lamellae" and undulatory extinction. Might these crystal defects be produced as dendrites undergo ripening? (4) Clusters. Contacting clusters of polymineralic crystals are the building blocks of cumulates, and are ubiquitous features of mafic volcanic rocks. Are plagioclase and clinopyroxene aligned crystallographically, suggesting an epitaxial (surface energy) relationship? (5) Log-normal size distribution. What synthetic cooling histories produce "natural" distributions of crystal sizes, and are phenocrystic textures uniquely attributed to staged cooling? In addition, we seek to explore the limitations of the experimental approach. Which aspects of natural crystallization sequences are adequately reproduced in experimental charges, and which are compromised by the obligatory reduced temporal and spatial scales of crystal growth experiments? What are the implications of synthetic starting materials and thermal pre-treatments for nucleation, growth, heterophase equilibria, and textural maturation?

Hammer, J. E.; Welsch, B. T.; First, E.; Shea, T.

2012-12-01

88

The formation mechanism of grown-in defects in CZ silicon crystals based on thermal gradients measured by thermocouples near growth interfaces  

Microsoft Academic Search

The thermal distributions near the growth interface of 150 mm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) and edge (10 mm from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat flux balance equation. Using this fact, it is confirmed in

Takao Abe

2000-01-01

89

Journal of Crystal Growth 277 (2005) 578592 Nonlinear stability analysis of self-similar crystal growth  

E-print Network

Journal of Crystal Growth 277 (2005) 578­592 Nonlinear stability analysis of self-similar crystal-similarly growing crystals was demonstrated recently in our previous work (J. Crystal Growth 267 (2004) 703). Here. Crystal Growth 266 (2004) 552). This enables us to accurately simulate the long-time, nonlinear dynamics

Lowengrub, John

90

Efg Crystal Growth Apparatus And Method  

DOEpatents

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.

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

2003-05-13

91

Growth of single crystal diamond  

NASA Astrophysics Data System (ADS)

The subject of the research presented in this dissertation is the growth of single crystal diamond by microwave plasma chemical vapor deposition (CVD). Both heteroepitaxial and homoepitaxial growth methods have been examined, with emphasis on producing large diamond crystals of high structural and chemical perfection. By heteroepitaxy, epitaxial growth on a foreign substrate, diamond was grown on (001) Ir thin-film epitaxial buffer layers deposited on (001) strontium titanate (SrTiO3) by DC magnetron sputtering. To nucleate diamond on Ir, the Ir surface was bombarded with low energy ions extracted from the hydrocarbon plasma, a process known as DC biasing or bias-enhanced nucleation. Since this critical process is poorly understood, attention was paid to the spatial and temporal evolution of the Ir surface during the bias treatment. It was discovered that the biased Ir surface is etched on a surprisingly short time scale during which highly correlated nanopillars, 3-4 nm in height with mean separation 15 nm, emerge. The etching process is spatially non-uniform, propagating from substrate center to substrate edge in minutes. Diamond grew on Ir without an intervening phase. Lattice images revealed that interfacial strain from the 7% Ir-diamond lattice mismatch is largely relieved by misfit dislocations within 1 nm of the interface. It is suggested that the high nucleation density obtained with specific bias conditions is associated with the roughened Ir surface. To grow heteroepitaxial diamond as thick films, a two-step growth method was explored. This process involved the transfer of a thin heteroepitaxial diamond film, still attached to a substrate, to a second reactor where high growth rate conditions were possible. Characterization of films grown by this approach showed that the resulting diamond had much lower levels of internal strain, suggesting that the process could be used to grow diamond crystals of structural quality similar to natural diamond. In homoepitaxy, epitaxial growth on a substrate of the same material, diamond was deposited by CVD directly onto high-pressure, high-temperature Type Ib diamond substrates. Methods for removing substrate surface damage, as well as other imperfections, were devised by use of plasma etching. The characteristics and statistics of pits formed during etching were studied. Diamond growth methods were developed with the aim of minimizing the formation of various structural and chemical defects. To accomplish this, several growth parameters were varied, including substrate temperature, feed gas concentration, growth rate, substrate surface, microwave power, and reactor geometry. Regions of parameter space were found in which the diamond (001) surface remained smooth during growth, and complete suppression of instabilities that create hillocks or non-epitaxial crystallites was demonstrated. A great deal of information was obtained by interrupting growth, removing the crystal from the reactor for optical inspection, and then resuming the process with no apparent negative effects. Diamond crystals were grown on 3 x 3 mm2 substrates with thicknesses greater than 0.5 mm. The chemical purity of the crystals was such that it was impossible to observe signatures of substitutional nitrogen at the ppm level.

Regmi, Murari

92

Journal of Crystal Growth 266 (2004) 552567 Three-dimensional crystal growth--II: nonlinear simulation  

E-print Network

Journal of Crystal Growth 266 (2004) 552­567 Three-dimensional crystal growth--II: nonlinear previous analysis (J Crystal Growth 240 (2002) 267) of the linear evolution of non-spherical growing to be carried out in a laboratory in which a desired shape of a crystal is achieved and maintained during growth

Lowengrub, John

93

Crystal growth and dendritic solidification  

Microsoft Academic Search

The motion of complex solid\\/liquid boundaries in crystal growth is presently computed by a numerical model encompassing such physical effects as crystalline anisotropy, surface tension, molecular kinetics, and undercooling. The model recasts the equations of motion as a single, history-dependent boundary integral equation on the solid\\/liquid boundary, and moves the boundary by solving an equation formulated by Osher and Sethian

James A. Sethian; John Strain

1992-01-01

94

Crystal Growth Research in Space  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

95

Phase diagrams and crystal growth  

NASA Astrophysics Data System (ADS)

Phase diagrams are briefly treated as generalized property-composition relationships, with respect to crystal technology optimization. The treatment is based on mutual interaction of three systems related to semiconductors: (a) the semiconducting material systems, (b0 the data bank, (c) the system of crystallization methods. A model is proposed enabling optimatization on the path from application requirements to the desired material. Further, several examples of the selection as to the composition of LED and laser diode material are given. Some of molten-solution-zone methods are being successfully introduced for this purpose. Common features of these methods, the application of phase diagrams, and their pecularities compared with other crystallization methods are illustrated by schematic diagrams and by examples. LPE methods, particularly the steady-state LPE methods such as Woodall's ISM and Nishizawa's TDM-CVP, and the CAM-S (Crystallization Method Providing Composition Autocontrol in Situ) have been chosen as examples. Another approach of exploiting phase diagrams for optimal material selection and for determination of growth condition before experimentation through a simple calculation is presented on InP-GaP solid solutions. Ternary phase diagrams are visualized in space through calculation and constructions based on the corresponding thermodynamic models and anaglyphs. These make it easy to observe and qualitatively analyze the crystallization of every composition. Phase diagrams can be also used as a powerful tool for the deduction of new crystallization methods. Eutectic crystallization is an example of such an approach where a modified molten-solution-zone method can give a sandwich structure with an abrupt concentration change. The concentration of a component can range from 0 to 100% in the different solid phases.

Venkrbec, Jan

1980-04-01

96

Crystal growth and annealing method and apparatus  

DOEpatents

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.

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

2001-01-01

97

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

NASA Technical Reports Server (NTRS)

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.

Feigelson, R. S. (editor)

1986-01-01

98

Jurgen Geiser Simulation in crystal growth for SiC  

E-print Network

A S ¡ ¢ ¡ £ ¤¥ £ ¦ ¤ ¤§¨ ¤¥ ¢¥© ¥¡ £ ¢ ¡ ¨ ¦ ¤ ¢ ¤ ¦ ¨ ¥ ¦ ¤¥ ¢ ¤ ¢ ¨ ! £ ¤ © ¨ " ¤#¡ £ $ © ¨ % ¡ £ ¢ ¨ ¡ & ' & J¨urgen Geiser Simulation in crystal growth for SiC single crystal : Numerical Methods-dimensional and multi-physical problem in continuum mechanics for crystal growth process. · Task : Simulation of an apparatus of a complex crystal growth with heat- and temperature processes. · Model : Transmission Problem

Geiser, Juergen

99

Growth of Equally-Sized Insulin Crystals  

E-print Network

Guidelines for growing insulin crystals of a uniform size are formulated and tested experimentally. A simple theoretical model based on the balance of matter predicts the time evolution of the crystal size and supersaturation. The time dependence of the size is checked experimentally. The experimental approach decouples crystal nucleation and growth processes according to the classical nucleation-growth-separation principle. Strict control over the nucleation process is exerted. Crystalline substance dispersity is predetermined during the nucleation stage of a batch crystallization process. To avert nutrition competition during the crystal growth stage, the number density of nucleated crystals is preset to be optimal.

Nanev, Christo N; Hodzhaoglu, Feyzim V

2013-01-01

100

Journal of Crystal Growth 122 (1992) 286--292 j o, CRYSTAL North-Holland GROWTH  

E-print Network

Journal of Crystal Growth 122 (1992) 286--292 j o, CRYSTAL North-Holland GROWTH Derivatization-dimensional crystals of ribosomal particles Source Growth from °~ Cell dimensions (A) Resolution b) (A) 70S Thermus attached to whole ribosomes and to their small and large subunits prior to their crystallization. X

Yonath, Ada E.

101

Journal of Crystal Growth 130 (1993) 495--506 ~ o~ CRYSTAL North-Holland GROWTH  

E-print Network

Journal of Crystal Growth 130 (1993) 495--506 ~ o~ CRYSTAL North-Holland GROWTH Solidification-eutectic aqueous solutions of NH4CI is rather sensitive to the microscopic details of the crystal growth. As reported in the cooling from below and resulting crystal- first by Copley et al. [1], after an initial

Huppert, Herbert

102

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

NASA Astrophysics Data System (ADS)

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

Boopathi, K.; Ramasamy, P.

2014-11-01

103

Protein crystal growth in low gravity  

NASA Technical Reports Server (NTRS)

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.

Feigelson, Robert S.

1991-01-01

104

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

PubMed

An efficient amino acid family nonlinear optical single crystal L-phenylalanine-benzoic acid (LPB) was conveniently grown by slow evaporation technique at room temperature. The crystal system and the lattice parameters were analyzed by single crystal X-ray diffraction studies. The grown crystal has excellent transmission in the entire visible region and its lower cut-off wavelength was found to be 248 nm. The SHG efficiency of the grown crystal was found to be 1.6 times higher than that of KDP crystal. The Laser damage threshold value of LPB has been found to be 6.5 GW/cm(2). The sample was thermally stable up to 134°C. Microhardness, dielectric and AC/DC conductivity measurements were made along (001) plane and reported for the first time. Microhardness studies revealed that the sample belongs to hard nature. Frequency dependent dielectric constant was measured for different temperatures and found maximum dielectric constant of 14 for 363 K. Photoconductivity studies of LPB divulged its negative photoconducting nature. PMID:23747430

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

2013-10-01

105

Physical phenomena related to crystal growth in the space environment  

NASA Technical Reports Server (NTRS)

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.

Chu, T. L.

1973-01-01

106

Mechanically tunable photonic crystal lens  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

107

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

108

Protein Crystal Growth in Low Gravity. Annual Report January1 - December 31, 1986.  

National Technical Information Service (NTIS)

The solubility and growth mechanism of canavalin were studied, and the applicability of the Schlieren technique to protein crystal growth was investigated. Canavalin which may be crystallized from a basic solution by the addition of hydrogen (H+) ions was...

R. S. Feigelson

1987-01-01

109

Measurable characteristics of lysozyme crystal growth  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

110

Analytics of crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

111

Controlled growth of semiconductor crystals  

DOEpatents

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.

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

1992-01-01

112

Controlled growth of semiconductor crystals  

DOEpatents

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.

Bourret-Courchesne, E.D.

1992-07-21

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

114

Mechanics of Cell Growth  

PubMed Central

Cell growth describes an essential feature of biological tissues. This growth process may be modeled by using a set of relatively simple governing equations based on the axioms of mass and momentum balance, and using a continuum framework that describes cells and tissues as mixtures of a solid matrix, a solvent and multiple solutes. In this model the mechanics of cell growth is driven by osmotic effects, regulated by the cells’ active uptake of solutes and passive uptake of solvent. By accounting for the anisotropy of the cells’ cytoskeletal structures or extracellular matrix, as well as external constraints, a wide variety of growing shapes may be produced as illustrated in various examples. PMID:22904576

Ateshian, Gerard A.; Morrison, Barclay; Holmes, Jeffrey W.; Hung, Clark T.

2012-01-01

115

Advanced protein crystal growth programmatic sensitivity study  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

116

Effect of cobalt and DL-malic acid on the growth rate, crystalline perfection, optical, mechanical, dielectric, piezoelectric properties and SHG efficiency of ADP single crystals  

NASA Astrophysics Data System (ADS)

Effects of the additions of cobalt (II) acetate hexahydrate and DL-malic acid on the growth and various properties of ammonium dihydrogen orthophosphate single crystals grown by slow evaporation method have been studied. The grown crystals were subjected to UV-vis, microhardness, dielectric, piezoelectric, high resolution X-ray diffraction and SHG studies. UV spectra show good transparency in the entire visible region which is an essential requirement for a nonlinear optical crystal. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the crystals added with DL-malic acid compared to the pure and cobalt (II) acetate hexahydrate added crystals. Dielectric constant and dielectric loss were measured for the grown crystals for different frequencies and temperatures. It reveals that the DL-malic acid added ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals was analyzed using HRXRD. Good piezoelectric behaviour was observed for all the crystals. Preliminary measurements indicate that the second harmonic generation efficiency of the DL-malic acid doped crystals is greater than pure and cobalt (II) acetate hexahydrate added ADP.

Rajesh, P.; Ramasamy, P.; Kumar, Binay; Bhagavannarayana, G.

2010-05-01

117

Growth of triglycine sulfate (TGS) crystals by solution technique  

NASA Technical Reports Server (NTRS)

The growth of crystals from solution is greatly influenced by buoyancy driven convection. In a low-g environment, convection is greatly suppressed and diffusion becomes the predominant mechanism for thermal and mass transport. An experiment to grow TGS crystals by solution technique during the orbital Spacelab III mission has been designed. Crystals are grown by a new and unique technique of extracting heat from the crystal through a sting. The cooling at the sting tip is responsible for the desired supersaturation near the growing crystal. Calculations indicate that the cooled sting technique for solution crystal growth is necessary in low-g to maintain a maximum growth rate of 1 mm/day. Results of groundbased work in support of the flight experiment are discussed.

Lal, R. B.; Kroes, R. L.; Wilcox, W. R.

1982-01-01

118

Journal of Crystal Growth 129 (1993) 719--727 ~ CRYSTAL North-Holland GROWTH  

E-print Network

Journal of Crystal Growth 129 (1993) 719--727 ~ CRYSTAL North-Holland GROWTH Structural analysis-ray diffraction methods. Double crystal rocking curves from the as-deposited LT-GaAs show well defined interference fringes, indicating a high level of structural perfection. Triple crystal diffraction analysis

Woodall, Jerry M.

119

Growth of polyhedral crystals from supersaturated vapor  

E-print Network

We examine the growth of crystals from vapor. We assume that the Wulff shape is a prism with a hexagonal base. The Gibbs-Thomson correction on the crystal surface is included in the model. Assuming that the-initial crystal has an admissible shape we show local in time existence of solutions.

Przemyslaw Gorka

2007-03-26

120

Economic analysis of crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

121

Author's personal copy Selenium incorporation into calcite and its effect on crystal growth: An atomic force  

E-print Network

Author's personal copy Selenium incorporation into calcite and its effect on crystal growth Atomic force microscopy Crystal growth Selenium The atomic processes leading to calcite growth are still during growth as well as the growth mechanism. Among trace elements, selenium, in the form of oxyanions

122

Growth kinetics of tetragonal lysozyme crystals  

NASA Technical Reports Server (NTRS)

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.

Pusey, M.; Naumann, R.

1986-01-01

123

Calcite crystal growth orientation: implications for trace metal uptake into coccoliths  

E-print Network

Calcite crystal growth orientation: implications for trace metal uptake into coccoliths V. E. PAYNE inducing specific orientations of calcite crystal growth can cause the enrichment of cations larger than Ca growth on obtuse kink sites, causing calcite crystals elongated along their c-axes to form in a mechanism

Benning, Liane G.

124

Crystal Growth and Spectroscopy of Diglycine  

NASA Technical Reports Server (NTRS)

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

Taylor, Taravia M.

1995-01-01

125

Continuing adventures in lysozyme crystal growth. [in earth laboratory experiments  

NASA Technical Reports Server (NTRS)

Results obtained on the crystal nucleation and growth of lysozyme are presented. Special attention is given to the anion-protein binding, the nucleation kinetics, the mechanisms of aggregation, and the conditions that promote or inhibit lysozyme (110)-face growth rate. The emerging theory that is currently being used for data interpretation and for designing new experimental approaches is outlined.

Pusey, Marc L.

1992-01-01

126

Transport and Growth Kinetics in Microgravity Protein Crystal Growth  

NASA Technical Reports Server (NTRS)

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).

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

2002-01-01

127

Crystallization mechanism in melts of short n-alkane chains  

NASA Astrophysics Data System (ADS)

We study crystallization in a model system for eicosane (C20) by means of molecular dynamics simulation and identify the microscopic mechanisms of homogeneous crystal nucleation and growth. For the nucleation process, we observe that chains first align and then straighten. Then the local density increases and finally the monomer units become ordered positionally. The subsequent crystal growth process is characterized by a sliding-in motion of the chains. Chains preferably attach to the crystalline cluster with one end and then move along the stems of already crystallized chains towards their final position. This process is cooperative, i.e., neighboring chains tend to get attached in clusters rather than independently.

Anwar, Muhammad; Turci, Francesco; Schilling, Tanja

2013-12-01

128

Journal of Crystal Growth 267 (2004) 703713 Nonlinear theory of self-similar crystal growth and melting  

E-print Network

Journal of Crystal Growth 267 (2004) 703­713 Nonlinear theory of self-similar crystal growth analysis (J. Crystal Growth, 240 (2002) 267) and dynamical numerical simulations (J. Crystal Growth 240 (2003) in press). Here, we develop a nonlinear theory of self- similar crystal growth and melting

Lowengrub, John

129

VGF growth of germanium single crystals without crucible contact  

NASA Astrophysics Data System (ADS)

Experimental results on the vertical gradient freeze growth of germanium single crystals without crucible contact are presented. Two different approaches to establish a stable pressure difference necessary for avoiding the contact between crystal and crucible on solidification are described. Germanium crystals with a diameter of up to 3 in were grown almost without contact to the crucible wall. The effect of detachment is discussed with respect to the microscopical surface roughness and dislocation density of the grown crystals. In comparison to conventionally grown reference crystals the structural perfection of the detached-grown crystals is found to be much higher which can be attributed to the reduced thermal and thermo-mechanical stress in growth without wall contact.

Langheinrich, D.; Pätzold, O.; Raabe, L.; Stelter, M.

2010-08-01

130

Crack propagation driven by crystal growth  

SciTech Connect

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

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

2011-10-01

131

Synchrotron X-ray imaging for crystal growth studies  

NASA Astrophysics Data System (ADS)

The features associated with modern synchrotron radiation machines (intense and coherent beams) result in a substantial extension of X-ray imaging capabilities in terms of spatial and temporal resolution, phase contrast and 3D images. This allows crystal growth-related information to be obtained which is not available otherwise. After briefly describing the main synchrotron radiation based imaging techniques of interest, we give original examples illustrating the new capabilities for crystal growth: characterisation of crystals grown for applications, such as ice tri-crystals produced for mechanical deformation studies; SiC; crystalline silicon for solar photovoltaic cells; in situ and in real time studies of quasicrystal growth (AlPdMn); and ultrafast tomography for the study of the growth of dendrites in metallic alloys.

Baruchel, José; Di Michiel, Marco; Lafford, Tamzin; Lhuissier, Pierre; Meyssonnier, Jacques; Nguyen-Thi, Henri; Philip, Armelle; Pernot, Petra; Salvo, Luc; Scheel, Mario

2013-02-01

132

The crystal growth of barium flouride in aqueous solution  

NASA Astrophysics Data System (ADS)

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

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

1983-06-01

133

(PCG) Protein Crystal Growth on STS-26  

NASA Technical Reports Server (NTRS)

Mission Specialist George (Pinky) D. Nelson uses a 35 mm camera to photograph a protein crystal grown during the STS-26 Protein Crystal Growth (PCG-II-01) experiment. The protein crystal growth (PCG) carrier is shown deployed from the PCG Refrigerator/Incubator Mocule (R/IM) located in the middeck forward locker. The R/IM contained three Vapor Diffusion Apparatus (VDS) trays (one of which is shown). A total of sixty protein crystal samples were processed during the STS-26 mission.

1988-01-01

134

Optimal control of crystal growth processes  

NASA Astrophysics Data System (ADS)

This work focuses on the optimal control of two typical processes in the context of industrial crystal growth. First, the annealing of bulk GaAs crystals is considered and an optimal control problem is solved in order to find optimised heating profiles for the furnace. A reduced order model for the annealing furnace has been developed in order to speed up the optimisation algorithm. As a second application, our control algorithm is used to optimise a VGF-process for growing GaAs crystals: the growth rate of the GaAs crystal is maximised under side conditions for the resulting thermal stress.

Metzger, Michael

2001-08-01

135

Compatibility waves drive crystal growth on patterned substrates  

E-print Network

We explore the crystallization in a colloidal monolayer on a structured template starting from a few-particle nucleus. The competition between the substrate structure and that of the growing crystal induces a new crystal growth scenario. Unlike with the crystal growth in the bulk where a well-defined and connected crystal-fluid interface grows into the fluid, we identify a mechanism where a "compatibility wave" of the prescribed nucleus with the underlying substrate structure dictates the growth direction and efficiency. The growth process is strongly anisotropic and proceeds via transient island formation in front of an initial solid-fluid interface. We demonstrate the validity of this compatibility wave concept for a large class of substrate structures including a square-lattice and a quasicrystalline pattern. Dynamical density functional theory which provides a microscopic approach to the crystallization process is employed for colloidal hard spheres. Our predictions can be verified in experiments on confined colloids and also bear consequences for molecular crystal growth on structured substrates.

Tim Neuhaus; Michael Schmiedeberg; Hartmut Löwen

2013-07-08

136

Convective Flow Effects on Protein Crystal Growth.  

National Technical Information Service (NTIS)

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...

F. Rosenberger, L. A. Monaco

1995-01-01

137

The Growth of Large Single Crystals.  

ERIC Educational Resources Information Center

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)

Baer, Carl D.

1990-01-01

138

Research support for cadmium telluride crystal growth  

NASA Technical Reports Server (NTRS)

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.

Rosenberger, Franz; Banish, Michael

1993-01-01

139

Illusory spirals and loops in crystal growth  

PubMed Central

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

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

2013-01-01

140

Growth Of Oriented Crystals At Polymerized Membranes  

DOEpatents

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.

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

2000-01-25

141

Electrochemical Growth Of Crystals In Gels  

NASA Technical Reports Server (NTRS)

Nucleation and growth rates readily controlled. Technique developed to grow crystals by controlling rate of transfer of one component into crystallization volume. Method involves electrochemically controlled generation of one of precipitation species, coupled with diffusion barrier. New procedure, developed in connection with formation of lead tin telluride by reaction in gels of metal ions with telluride ions.

Barber, Patrick G.; Coleman, James

1988-01-01

142

Protein crystal growth (5-IML-1)  

NASA Technical Reports Server (NTRS)

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.

Bugg, Charles E.

1992-01-01

143

Interfacial Mass Transport in Oxide Crystal Growth  

Microsoft Academic Search

A space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystal in high temperature melts and solutions. Model experiments using transparent liquids such as KNbO3, Li2B4O7+KNbO3 were chosen to investigate effects of interfacial mass transport in oxide crystal growth. For the scaling of the coupled velocity, heat and concentration

Wei Qing Jin; Xin An Liang; Li Xia Cai; Zhi Lei Pan; Katsuo Tsukamoto

2002-01-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

145

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

PubMed

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

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

2014-06-01

146

Journal of Crystal Growth 275 (2005) e739e743 Crystal growth and characterization of the ruthenate  

E-print Network

Journal of Crystal Growth 275 (2005) e739­e743 p1/7 Crystal growth and characterization in the superconducting state of this material is still under debate. In this paper, we report about crystal growth.70._b; 74.70.Pq Keywords: A2. Floating zone technique; A2. Growth from melt; A2. Single crystal growth

Boyer, Edmond

147

Journal of Crystal Growth 240 (2002) 267276 Three-dimensional crystal growth--I: linear analysis and  

E-print Network

Journal of Crystal Growth 240 (2002) 267­276 Three-dimensional crystal growth--I: linear analysis; in: H.S. Peiser (Ed.), Crystal Growth, Pergamon, Oxford, 1967, p. 703) of the quasi stability; A2. Growth from melt; A2. Single crystal growth *Corresponding author. Tel: +1-612-625-0753; fax

Lowengrub, John

148

Growth, spectral, thermal, dielectric, mechanical, linear and nonlinear optical, birefringence, laser damage threshold studies of semi-organic crystal: dibrucinium sulfate heptahydrate.  

PubMed

Dibrucinium sulfate heptahydrate (DBSH), a semi-organic nonlinear optical material, has been synthesized and single crystals were grown from water-ethanol solution at room temperature up to dimensions of 10×7×2 mm(3). The unit cell parameters were determined from single crystal and powder X-ray diffraction studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) study. FTIR and Raman studies were performed to identify the functional groups present in the title compound. The activation energy (E), entropy (?S), enthalpy (?H) and Gibbs free energy (?G), of the thermal decomposition reaction have been derived from thermo gravimetric (TGA) and differential thermal (DTA) analysis curves, using Coats-Redfern method. The variation of dielectric properties of the grown crystal with respect to frequency has been investigated at different temperatures. Microhardness measurements revealed the mechanical strength of grown crystal. The optical parameters, the optical band gap E(g) and width of localized states Eu were determined using the transmittance data in the spectral range 200-800 nm. The relative second harmonic efficiency of the compound is found to be 1.4 times greater than that of KDP. Birefringence and Laser damage threshold studies were carried out for the grown crystal. PMID:23666350

Krishnan, P; Gayathri, K; Bhagavannarayana, G; Jayaramakrishnan, V; Gunasekaran, S; Anbalagan, G

2013-08-01

149

Modeling and design of PVT growth of silicon carbide crystals  

NASA Astrophysics Data System (ADS)

Physical vapor transport method (PVT) is an important technique for growing SiC bulk crystals, which is a promising semiconductor material for electrical and optoelectronic applications in the areas of high power, high temperature, high frequency and strong radiation. The ever-increasing demand for SiC substrates of high quality and large diameter has motivated extensive research effort on the growth of SiC boule using PVT method. The PVT growth process involves highly complex physics and elaborate system that significantly affect the rate of growth, growth area and defect density. This dissertation is aimed at developing a fundamental understanding of the growth process and identifying the foremost process conditions and parameters that affect crystal productivity and quality. To achieve this goal, we have developed a comprehensive model that involves major physical mechanisms of PVT growth, i.e. , transport of energy and vapor species, chemical reaction, growth kinetics, and anisotropic thermal stresses. Moreover, the multiplication of dislocation is integrated into this model to correlate thermal stresses to dislocation distribution. Through this work a relationship is established between the transport phenomena at the macroscale and defect development at the microscale. Finite volume method with adaptive non-orthogonal grid has been used for the thermal and mechanical calculations in the complex geometry. Using this integrated model, we have carried out numerical simulation of SiC growth process to predict the global temperature distribution in the furnace, the rate of growth and the shape of the as-grown crystals. In addition, the thermal stresses in the growing crystal and the dislocation distribution are also calculated. It is found that the temperature distribution in the induction-heated growth chamber is quite non-uniform. Under the growth temperatures, thermal radiation is the dominant heat transfer mode and accurate modeling is essential. The rate of growth and the shape of growth interface are closely related to the process parameters such as temperature distribution and pressure. For the system used in this thesis, the magnitude of the shear stress acting on the basal plane exceeds the estimated critical resolved shear stress in some portions of the crystal, which means thermal stress is a main cause of dislocations present in SiC bulk crystals. The dislocation distributions predicted using CRSS and A-H model are consistent. More importantly, the growth is a transient process; the geometry of the growing crystal and the temperature across the growth interface change appreciably, varying the growth rate, magnitude of thermal stress and the density of dislocation during the process. (Abstract shortened by UMI.)

Ma, Ronghui

2003-10-01

150

Solution growth of crystals in zero gravity  

NASA Technical Reports Server (NTRS)

A series of experiments will be performed in which triglycine sulfate (TGS) crystals will be grown by a low-temperature solution growth technique in the microgravity environment of the orbital Spacelab. Triglycine sulfate (TGS) crystals will be grown in the Fluid Experiment System (FES) facility on Spacelab 3 by slowly extracting heat at a controlled rate through a seed crystal of TGS suspended on an insulated sting in a saturated solution of TGS. The FES rack assembly designed for SL-3 is shown in Figure I-1, and a detailed view of the test cell layout is presented in Figure I-2. Variations in the liquid density, solution concentration and temperature around the growing crystal will be studied using a variety of techniques, such as schlieren, shadowgraph, and interferometric measurements. Growth in Earth gravity will also be studied by the same optical techniques, and in both cases the resulting crystalline features will be compared and correlated with the growth conditions.

Lai, R. B.

1982-01-01

151

Growth and defects of explosives crystals  

NASA Astrophysics Data System (ADS)

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.

Cady, H. H.

152

Organic Nanocrystals of the Resorcinarene Hexamer via Sonochemistry: Evidence of Reversed Crystal Growth Involving Hollow Morphologies  

PubMed Central

Nano- and micrometer scale crystals of a self-assembled hexamer have been synthesized via sonochemistry. The application of ultrasonic irradiation afforded hollow rhombic dodecahedron crystals of the C-methylcalix[4]resorcinarene hexamer. The formation of the hollow crystals is attributed to a reversed crystal growth mechanism heretofore only described in the synthesis of inorganic-based materials. PMID:22332828

Sander, John R. G.; Bucar, Dejan-Kresimir; Baltrusaitis, Jonas; MacGillivray, Leonard R.

2012-01-01

153

I. MATERIALS PREPARATION AND PROPERTIES. Section I. 1 : Crystal Growth.  

E-print Network

I. MATERIALS PREPARATION AND PROPERTIES. Section I. 1 : Crystal Growth. THE MELT-GROWTH of a preliminary LEC growth investigation. The charac- terization of the LEC crystals involves a survey of the main crystals. The growth of any large single crystal semiconductor with predetermined properties is an ultimate

Paris-Sud XI, Université de

154

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

NASA Astrophysics Data System (ADS)

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

Dinakaran, Paul M.; Kalainathan, S.

2013-03-01

155

Growth Modes and Energetics of 101 Face Lysozyme Crystal Growth  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

156

Sublimation Growth of Titanium Nitride Crystals  

SciTech Connect

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.

Du, Li [Kansas State University; Edgar, J H [Kansas State University; Kenik, Edward A [ORNL; Meyer III, Harry M [ORNL

2009-01-01

157

CRYSTAL GROWTH IN RAT ENAMEL  

Microsoft Academic Search

Observations have been made, using electron microscopy and x-ray diffraction, on the changes in crystal size and shape which occur in developing rodent enamel during minerali- zation. Small enamel pieces isolated from ground sections of rat molars and incisors were either embedded in methacrylate and sectioned with a diamond knife for electron micros- copy, or they were mounted intact on

M. U. Nylen; E. D. EANES; K.-A. OMNELL

1963-01-01

158

crystal: growth, crystal structure perfection, piezoelectric, and acoustic properties  

NASA Astrophysics Data System (ADS)

A five-component crystal of lanthanum-gallium silicate group La3Ga5.3Ta0.5Al0.2O14 (LGTA) was grown by the Czochralski method. The LGTA crystal possesses unique thermal properties and substitution of Al for Ga in the unit cell leads to a substantial increase of electrical resistance at high temperatures. The unit cell parameters of LGTA were determined by powder diffraction. X-ray topography was used to study the crystal structure perfection: the growth banding normal to the growth axis were visualized. The independent piezoelectric constants d 11 and d 14 were measured by X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves were studied by the double-crystal X-ray diffraction at the BESSY II synchrotron radiation source. The analysis of the diffraction spectra of acoustically modulated crystals permitted the determination of the velocity of acoustic wave propagation and the power flow angles in different acoustic cuts of the LGTA crystal.

Roshchupkin, Dmitry; Ortega, Luc; Plotitcyna, Olga; Irzhak, Dmitry; Emelin, Evgenii; Fahrtdinov, Rashid; Alenkov, Vladimir; Buzanov, Oleg

2014-09-01

159

Modeling Tetragonal Lysozyme Crystal Growth Rates  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

160

Protein Crystal Growth Dynamics and Impurity Incorporation  

NASA Technical Reports Server (NTRS)

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

Chernov, Alex A.; Thomas, Bill

2000-01-01

161

Method for solid state crystal growth  

DOEpatents

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.

Nolas, George S.; Beekman, Matthew K.

2013-04-09

162

Protein Crystal Growth Apparatus for Microgravity  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

163

Crystal growth under external electric fields  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

164

Drop deployment system for crystal growth apparatus  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

165

Phase-Field Simulations of Crystal Growth  

SciTech Connect

This course gives an elementary introduction to the phase-field method and to its applications for the modeling of crystal growth. Two different interpretations of the phase-field variable are given and discussed. It can be seen as a physical order parameter that characterizes a phase transition, or as a smoothed indicator function that tracks domain boundaries. Elementary phase-field models for solidification and epitaxial growth are presented and are applied to the dendritic growth of a pure substance and the step-flow growth on a vicinal surface.

Plapp, Mathis [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France)

2010-07-22

166

Book Reviews Crystal Growth Technology. Hans J. Scheel and  

E-print Network

Book Reviews Crystal Growth Technology. Hans J. Scheel and Tsuguo Fukuda Eds., John Wiley & Sons selected review papers from the First International School on Crystal Growth Technology held in 1998. Topics include some of the fundamentals of crystal growth, methods of character- ization, crystal

Regel, Liya L.

167

Physica D 138 (2000) 282301 Spiral crystal growth  

E-print Network

Physica D 138 (2000) 282­301 Spiral crystal growth Peter Smereka Department of Mathematics Communicated by H. Müller-Krumbhaar Abstract We numerically study the spiral mode of crystal growth using; Crystal growth; Interacting spirals 1. Introduction It is well documented that crystals grow in spiral

Smereka, Peter

168

Growth of equiaxed dendritic crystals settling in an undercooled melt  

E-print Network

176 Growth of equiaxed dendritic crystals settling in an undercooled melt A. Badillo and C direction relative to the crystal. The average of the measured tip growth velocities of all six dendrite the crystal. Understanding the growth of such equiaxed dendritic crystals is crucial for modeling evolution

Beckermann, Christoph

169

A Convection Chamber for Measuring Ice Crystal Growth Dynamics  

E-print Network

A Convection Chamber for Measuring Ice Crystal Growth Dynamics Kenneth G. Libbrecht1 and Helen C the growth of ice crystals from water vapor in the presence of a background gas. Crystals grow in free fall the growth and morphology of ice crystals over a broad range of conditions, as a function of temperature

Libbrecht, Kenneth G.

170

An Apparatus for Growth of Small Crystals From Solutions.  

ERIC Educational Resources Information Center

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)

Mitrovic, Mico M.

1995-01-01

171

Convective flow effects on protein crystal growth  

NASA Technical Reports Server (NTRS)

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

Rosenberger, Franz; Monaco, Lisa A.

1994-01-01

172

ELSEVIER Journal of Crystal Growth 164 (1996) 248-255 ,........ CRYSTAL  

E-print Network

ELSEVIER Journal of Crystal Growth 164 (1996) 248-255 ,........ CRYSTAL GROWTH Initial growth. / Journal of Crystal Growth 164 (1996) 248-255 249 varies from 0.36-0.37% for x = 0 to 1 (aGa P = 5.4505 A Abstract The nucleation and growth of AI ~GaI_ ,.P grown by metalorganic molecular beam epitaxy

Florida, University of

173

Method for crystal growth control  

DOEpatents

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.

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

1981-01-01

174

Crystal Growth in the Presence of Surface Melting and Impurities: An Explanation of Snow Crystal Growth Morphologies  

E-print Network

Crystal Growth in the Presence of Surface Melting and Impurities: An Explanation of Snow Crystal Pasadena, California 91125 Abstract. We examine the molecular dynamics of crystal growth in the presence crystal formation has to do with changes in the growth morphology with temperature. As shown in Figure 1

Libbrecht, Kenneth G.

175

Book ReViews Crystal Growth Technology: From Fundamentals and  

E-print Network

Book ReViews Crystal Growth Technology: From Fundamentals and Simulation to Large-Scale Production-3-527-31762-2. This book contains 19 selected reviews from the Third International Workshop on Crystal Growth Technology on melt growth of large crystals of commercial importance, with little coverage of solution growth

Regel, Liya L.

176

Developing Quantitative, Multiscale Models for Microgravity Crystal Growth  

Microsoft Academic Search

Crystal growth conducted under microgravity conditions has had a profound impact on improving our under- standing of melt crystal growth processes. Here, we present a brief history of microgravity crystal growth and discuss the development of appropriate models to interpret and optimize these growth experiments. The need for increased model realism and predictive capa- bility demands new approaches for describing

J. J. Derby; Yong-Il Kwon; Arun Pandy; Paul Sonda; Andrew Yeckel; Thomas Jung; A. Georg Muller

2006-01-01

177

Spacelab 3 vapor crystal growth experiment  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

178

Growth of single-crystal gallium nitride  

NASA Technical Reports Server (NTRS)

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

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

1970-01-01

179

Growth of deformation twins in zinc crystals  

Microsoft Academic Search

The incorporation of slip dislocations at the coherent twin boundary has been analysed for the (112) [111] type twins in hexagonal close-packed zinc crystal by applying matrix algebra. The effects of the various dislocation incorporation processes on the growth and untwinning of the existing twin are discussed from the geometric and the energetic points of view. The results indicate that

Man Hyong Yoo; Chuan-Tseng Wei

1966-01-01

180

Crystal growth in a microgravity environment  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

181

Apparatus for monitoring crystal growth  

DOEpatents

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.

Sachs, Emanual M. (Watertown, MA)

1981-01-01

182

Method of monitoring crystal growth  

DOEpatents

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.

Sachs, Emanual M. (Watertown, MA)

1982-01-01

183

The kinetics of nucleation and crystal growth and scaling laws for magmatic crystallization  

Microsoft Academic Search

Magmatic crystallization depends on the kinetics of nucleation and crystal growth. It occurs over a region of finite thickness called the crystallization interval, which moves into uncrystallized magma. We present a dimensional analysis which allows a simple understanding of the crystallization characteristics. We use scales for the rates of nucleation and crystal growth, denoted by Im and Ym respectively. The

Genevieve Brandeis; Claude Jaupart

1987-01-01

184

A Kinetic Model To Simulate Protein Crystal Growth in an Evaporation-Based Crystallization Platform  

E-print Network

A Kinetic Model To Simulate Protein Crystal Growth in an Evaporation-Based Crystallization Platform of drops that will result in gel formation. We test this model with experimental crystal growth data of hen egg white lysozyme for which crystal nucleation and growth rate parameters are known from other

Kenis, Paul J. A.

185

ELSEVIER Journal of Crystal Growth 171 (1997) 442-446 j........ CRYSTAL  

E-print Network

ELSEVIER Journal of Crystal Growth 171 (1997) 442-446 j........ CRYSTAL G R O W T H Epitaxial polycrystalline structures were established on Si(111) substrates. The excellent crystal growth of the permalloy The crystal growth of permalloy films was carried out by vacuum product molecular beam epitaxy (MBE-930

Huang, Jung-Chun

186

Journal of Crystal Growth 250 (2003) 499515 Induction time in crystallization of gas hydrates  

E-print Network

Journal of Crystal Growth 250 (2003) 499­515 Induction time in crystallization of gas hydrates Dimo crystallite growth rate and the induction time in hydrate crystallization. These expressions are used Keywords: A1. Crystallization; A1. Growth rate; A1. Induction time; A1. Nucleation; B1. Gas Hydrates; B1

Firoozabadi, Abbas

187

Laser crystallization and localized growth of nanomaterials for solar applications  

NASA Astrophysics Data System (ADS)

Laser-assisted localized growth of semiconducting nanostructures is reported. As is the case of conventional crystal growth, localized laser enables three kinds of crystal growth: (1) melt growth (recrystallization) of amorphous silicon nanopillars by pulsed laser; (2) vapor growth (chemical vapor deposition) of germanium nanowires; (3) solution growth (hydrothermal growth) of zinc oxide nanowires. The results not only demonstrate programmable and digital fabrication of laser-assisted crystal growth, but also reveal unusual growth chacracteristics (grain morphologies, growth kinetics). Related to solar applications, it is suggested that these structures can act as epitaxial seeds for growth of coarse grains and as multi-spectral centers for enhanced and engineered light absorption.

In, Jungbin; Ryu, Sang-Gil; Lee, Daeho; Ahn, Sanghoon; Zheng, Andy Cheng; Hwang, David Jae-Seok; Grigoropoulos, Costas P.

2013-09-01

188

High-purity silicon crystal growth investigations  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

189

Mechanical instabilities of homogeneous crystals  

Microsoft Academic Search

Elastic stability criteria are derived for homogeneous lattices under arbitrary but uniform external load. These conditions depend explicitly on the applied stress and reduce, in the limit of vanishing load, to the criteria due to Born, involving only the elastic constants of the crystal. By demonstrating the validity of our results through a comparison of the analysis of an fcc

Jinghan Wang; Ju Li; Sidney Yip; Simon Phillpot; Dieter Wolf

1995-01-01

190

Crystal growth and furnace analysis  

NASA Technical Reports Server (NTRS)

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.

Dakhoul, Youssef M.

1986-01-01

191

Critical Supersaturation for Ice Crystal Growth: Laboratory Measurements and Atmospheric Modeling Implications  

Microsoft Academic Search

An improved understanding of ice crystal growth, particularly at low temperatures, is much in demand for the advancement of numerical modeling of atmospheric processes. Cirrus models must contend with the complexity of ice crystals growing in cold temperatures, low pressures, low supersaturations, and with multiple nucleation mechanisms. Recent observations have allowed increasingly realistic parameterizations of cirrus ice crystal microphysics, but

N. Magee; A. Moyle; D. Lamb

2003-01-01

192

Method of controlling defect orientation in silicon crystal ribbon growth  

NASA Technical Reports Server (NTRS)

The orientation of twinning and other effects in silicon crystal ribbon growth is controlled by use of a starting seed crystal having a specific (110) crystallographic plane and (112) crystallographic growth direction.

Leipold, M. H. (inventor)

1978-01-01

193

ELSEVIER Journal of Crystal Growth 179 (1997)297-308 j........ CRYSTAL  

E-print Network

ELSEVIER Journal of Crystal Growth 179 (1997)297-308 j........ CRYSTAL GROWTH Numerical reserved PII S0022-0248(97)00087-0 #12;298 D.I'E Mackowski et al. / Journal of Crystal Growth 179 (1997 a numerical investigation of the effects of thermal creep on the growth process in axisymmetric, binary

Walker, D. Greg

194

Convective flow effects on protein crystal growth  

NASA Technical Reports Server (NTRS)

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.

Rosenberger, Franz; Monaco, Lisa A.

1993-01-01

195

Protein crystal growth in low gravity  

NASA Technical Reports Server (NTRS)

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.

Feigelson, Robert S.

1994-01-01

196

Crystal growth and annealing for minimized residual stress  

DOEpatents

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.

Gianoulakis, Steven E. (Albuquerque, NM)

2002-01-01

197

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

198

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

199

Growth of Single Crystal Tungsten Nanorods by Oblique Angle Sputter Deposition Tansel Karabacak, Pei-I Wang, Gwo-Ching Wang, and Toh-Ming Lu  

E-print Network

Growth of Single Crystal Tungsten Nanorods by Oblique Angle Sputter Deposition Tansel Karabacak explained our #12;results by a competitive growth mechanism between the crystal structures that had the predicted growth mechanism, detailed crystal phase information for the very early stages of growth

Wang, Gwo-Ching

200

Mechanical Characterization of Partially Crystallized Sphere Packings  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

201

Mechanical characterization of partially crystallized sphere packings.  

PubMed

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

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

2014-10-01

202

Mechanical instabilities of homogeneous crystals  

SciTech Connect

Elastic stability criteria are derived for homogeneous lattices under arbitrary but uniform external load. These conditions depend explicitly on the applied stress and reduce, in the limit of vanishing load, to the criteria due to Born, involving only the elastic constants of the crystal. By demonstrating the validity of our results through a comparison of the analysis of an fcc lattice under hydrostatic tension with direct molecular-dynamics simulation, we show that crystal stability under stress (ideal strength) is not a question only of material property, and that even qualitative predictions require the inclusion of the effects of applied stress. General implications of our findings, as well as relevance to stability phenomena in melting, polymorphism, crack nucleation, and solid-state amorphization, are discussed.

Wang, J.; Li, J.; Yip, S. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Phillpot, S.; Wolf, D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1995-11-01

203

Crystal Splitting in the Growth of Bi2S3  

SciTech Connect

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.

Tang, Jing; Alivisatos, A. Paul

2006-06-15

204

High-purity silicon crystal growth investigations  

NASA Technical Reports Server (NTRS)

The study of silicon sheet material requirements for high efficiency solar cells is reported. Research continued on obtaining long lifetime single crystal float zone silicon and on understanding and reducing the mechanisms that limit the achievement of long lifetimes. The mechanisms studied are impurities, thermal history, point defects, and surface effect. The lifetime related crystallographic defects are characterized by X-ray topography and electron beam induced current.

Ciszek, T. F.; Hurd, J. L.; Schuyler, T.

1985-01-01

205

Crystal growth, stability and photoluminescence studies of tetra aqua diglycine magnesium (II) hexa aqua magnesium (II) bis sulfate crystal  

NASA Astrophysics Data System (ADS)

Single crystals of tetra aqua diglycine magnesium (II) hexa aqua magnesium (II) bis sulfate have been grown from saturated aqueous solution by slow evaporation solution growth technique. The solubility of the title compound in water at various temperatures has been determined. Single-crystal X-ray diffraction analyses reveal that the title compound crystallizes in triclinic system with space group P1¯. Fourier transform infrared spectral analyses confirm the presence of functional groups in the grown crystal. The thermal stability of the grown crystal has been investigated by thermogravimetric and differential scanning calorimetric analysis. It indicates that the material is stable upto 100 °C. The crystalline perfection of the grown crystal has been evaluated by high-resolution X-ray diffraction technique. Vickers microhardness measurements indicate the mechanical strength of the grown crystal. Photoluminescence of the grown crystal has been investigated and it reveals that the crystal has blue-violet fluorescence emission.

Senthil Murugan, G.; Ramasamy, P.

2011-03-01

206

Journal of Crystal Growth 271 (2004) 128133 Growth of strontium barium niobate  

E-print Network

Journal of Crystal Growth 271 (2004) 128­133 Growth of strontium barium niobate: the liquidus. Czochralski method; A2. Growth from the melt; A2. Single crystal growth; B1. Niobates; B2. Ferroelectric;crystal growth at such a composition is greatly facilitated, practically all publications up to now deal

Osnabrück, Universität

207

Lead isotope variation with growth zoning in a galena crystal  

USGS Publications Warehouse

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

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

1963-01-01

208

Microrobotic Streak Seeding For Protein Crystal Growth CUCS04104  

E-print Network

Microrobotic Streak Seeding For Protein Crystal Growth CUCS­041­04 Atanas Georgiev 1 Peter Allen 1 that consists of picking individual protein crystal from growth solution the purpose X­ray data collection) transferred protein solution that optimized their growth. building high­throughput protein crystal production

209

Optimal solutions for a free boundary problem for crystal growth  

E-print Network

Optimal solutions for a free boundary problem for crystal growth Pekka Neittaanm¨ aki Thomas I. Seidman Abstract. We consider a free boundary problem modeling the growth/dissolution of a crystal boundary problem corresponding to a model of growth (dissolution) of a radially symmetric crystal grain

Seidman, Thomas I.

210

Cloud structure and crystal growth in nimbostratus clouds. Mengistu Wolde*  

E-print Network

1 Cloud structure and crystal growth in nimbostratus clouds. Mengistu Wolde* , Gabor Vali-mail: mengistu.wolde@nrc.ca. #12;2 Abstract Cloud structure and crystal growth in two nimbostratus were examined made available by large scale lifting was taken up by depositional growth of the ice crystals

Vali, Gabor

211

Engineered Growth of Organic Crystalline Films Using Liquid Crystal Solvents  

E-print Network

S-1 Engineered Growth of Organic Crystalline Films Using Liquid Crystal Solvents F. Scott Wilkinson into the growing crystals. All experiments involving pentacene were performed under inert gas. Substrates typically crystals and, to a certain point, the density of crystals (i.e. number of crystals per unit area). Once

Patrick, David L.

212

Oriented growth of cadmium telluride crystals from the vapor phase  

Microsoft Academic Search

The effect of the temperature of crystallization, the magnitude of mass transfer, and the structure of the seed crystal on the oriented growth of cadmium telluride crystals from the vapor was studied. Crystals oriented in the <110>, <111>, and <112> directions were grown in the temperature interval 1130-1330 K from the vapor of cadmium telluride crystals. The maximum possible rates

L. A. Klinkova; S. A. Erofeeva

1988-01-01

213

Mechanics and growth of tissues  

NASA Astrophysics Data System (ADS)

During development or during tumor growth, cells organize collectively by cell division and apoptosis in a tissue. The aim of our work is to build up theoretical tools based on non-equilibrium statistical mechanics and continuum mechanics to describe the mechanical properties of tissues and to apply them to various biologically relevant situations. We first show that because of the coupling between cell division and the local stress, a tissue can be considered as a visco-elastic liquid at time scales larger than the cell division time. We then show recent model experiments on cell aggregates showing the effect of mechanical stress on tissue growth. Finally, we use the hydrodynamic description to discuss the steady state structure of villis which are the protrusions of the surface of the intestine. We describe the formation of villis as a buckling instability of a polar cell monolayer. Similar instabilities occur as well for tube-like cellular structures such as arteries.

Joanny, Jean-Francois

2013-03-01

214

(PCG) Protein Crystal Growth Gamma-Interferon  

NASA Technical Reports Server (NTRS)

(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.

1989-01-01

215

Journal of Crystal Growth 304 (2007) 114117 Single crystal growth of YbRh2Si2 using Zn flux  

E-print Network

Journal of Crystal Growth 304 (2007) 114�117 Single crystal growth of YbRh2Si2 using Zn flux-temperature solution technique, using Zn flux and followed by a decanting process. As opposed from the crystals growth: A1. Growth from high-temperature solutions; A1. Single crystal; B2. YbRh2Si2 1. Introduction YbRh2Si

Broholm, Collin Leslie

216

Crystallization Mechanism of Hard Sphere Glasses  

NASA Astrophysics Data System (ADS)

In supercooled liquids, vitrification generally suppresses crystallization. Yet some glasses can still crystallize despite the arrest of diffusive motion. This ill-understood process may limit the stability of glasses, but its microscopic mechanism is not yet known. Here we present extensive computer simulations addressing the crystallization of monodisperse hard-sphere glasses at constant volume (as in a colloid experiment). Multiple crystalline patches appear without particles having to diffuse more than one diameter. As these patches grow, the mobility in neighboring areas is enhanced, creating dynamic heterogeneity with positive feedback. The future crystallization pattern cannot be predicted from the coordinates alone: Crystallization proceeds by a sequence of stochastic micronucleation events, correlated in space by emergent dynamic heterogeneity.

Sanz, Eduardo; Valeriani, Chantal; Zaccarelli, Emanuela; Poon, W. C. K.; Pusey, P. N.; Cates, M. E.

2011-05-01

217

A unified description of attachment-based crystal growth.  

PubMed

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

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

2014-07-22

218

Third-harmonic generation and growth mechanism of vanadyl-phthalocyanine single crystals prepared on KBr substrate by molecular beam epitaxy  

Microsoft Academic Search

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr (100) substrate by molecular beam epitaxy (MBE). The second and third-harmonic generations of nonlinear optical thin films are proportional to the square of the thickness. Therefore, it is important to prepare a large nonlinear optical single crystal. However, the conditions to prepare a large nonlinear optical single crystal are not well understood

A. Maeda; N Okumura; H Furuhashi; T Yoshikawa; Y Uchida; K Kojima; A Ohashi; S Ochiai; M Ieda; T Mizutani

1999-01-01

219

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

220

Modeling of Continuum Transport and Meso-Scale Kinetics during Solution Crystal Growth  

NASA Astrophysics Data System (ADS)

Solution crystal growth is widely applied in many industries and fundamental research, and it is employed to crystallize materials ranging from inorganic molecules, small organic molecules, to large organic molecules. However, despite the broad application, fundamental factors regarding this crystal growth process are not well understood. In this thesis, numerical models are developed to study the influences of macro-scale mass transfer limitations and meso-scale growth kinetics on solution crystal growth. A parallel, finite element model is implemented to compute three-dimensional fluid flow and mass transfer during crystal growth and is especially applied to the growth systems in Atomic Force Microscopy fluid cells. This work assesses the parametric sensitivity of growth conditions to factors such as the strength of flow, the frequency of scanning motion, the size of the crystal, and the kinetics of the growing surface. Accounting for such effects will be very important to understand solution crystal growth and to interpret AFM measurements of growth dynamics. Additionally, a simplified two-dimensional numerical model focused on the region near the growing crystal surface and the AFM cantilever was developed based on the calculated results of the three-dimensional model. With this two-dimensional model, we provide basic understanding of the fluid flow and mass transfer where the AFM measurements were made, and simplified the revision of AFM measurements interpretation. A fundamental theoretical model based on the phase-field approach is developed to simulate nano-scale island growth and spiral step growth on crystal surfaces in a supersaturated liquid and is validated by comparison to zinc oxide nanowires synthesis experiments. Results obtained by this work help to explain how experimental factors affect the crystal growth and crystal microstructures and the correlation between island growth and spiral growth mechanisms.

Wang, Wei

221

Numerical Simulations for spiral crystal growth with impurity, interlaced spiral  

E-print Network

Numerical Simulations for spiral crystal growth with impurity, interlaced spiral and variable, then the crystal may need extremely high driving force around screw dislocation. #12;Hollow core type growth r ·Variable driving force by distance from a screw dislocation ·Wisker like growth ·Hollow core like growth

Ishii, Hitoshi

222

The Effect of Protein Impurities on Lysozyme Crystal Growth  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

223

Physical vapor transport growth of bulk aluminum nitride crystals  

NASA Astrophysics Data System (ADS)

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 interruption. In multiple growth experiments at ˜2100°C, 67 kPa and a ˜1°C/mm temperature gradient in the vapor phase centimeter-sized single crystalline AlN was obtained. Reflection X-ray diffraction patterns showed that the strain decreased as the grain size increased. Elemental analysis confirmed low impurity levels in the grown material. Luminescence and absorption spectra showed good optical quality of the grown AlN crystals.

Noveski, Vladimir

224

Crystal growth within a phase change memory cell  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

225

Synthesis, growth, structural, optical, spectral, thermal and mechanical studies of 4-methoxy 4-nitrostilbene (MONS): a new organic nonlinear optical single crystal.  

PubMed

4-Methoxy 4-nitrostilbene (MONS), a new organic nonlinear optical material has been synthesized. Based on the solubility data good quality single crystal with dimensions up to 38×11×3 mm(3) has been grown by slow evaporation method using ethyl methyl ketone (MEK) as a solvent. Powder XRD confirms the crystalline property and also the diffraction planes have been indexed. The lattice parameters for the grown MONS crystals were determined by using single crystal X-ray diffraction analysis and it reveals that the crystal lattice system is triclinic. The crystalline perfection of the grown crystals has been analysed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectrum for powdered MONS sample confirms the functional groups present in the grown crystal. The UV-vis absorption spectrum has been recorded in the range of 190-1100 nm and the cut off wavelength 499 nm has been determined. The optical constants of MONS have been determined through UV-vis-NIR spectroscopy. The MONS crystals were further subjected to other characterizations. i.e., (1)H NMR, TG/DTA, photoluminescence and microhardness test. The Kurtz and Perry powder technique confirms the NLO property of the grown crystal and the SHG efficiency of MONS was found to be 1.55× greater than that of KDP crystal. PMID:22929904

Dinakaran, Paul M; Bhagavannarayana, G; Kalainathan, S

2012-11-01

226

Roughness effect on the overall growth rate of sucrose crystals  

NASA Astrophysics Data System (ADS)

The roughness effect on crystal growth rate was investigated at 35C in a fluidized bed crystallizer and in a batch crystallizer. The crystallization of sucrose in pure aqueous solutions was the study subject. The results show that the sucrose crystals exhibit time-dependent growth rate. The overall growth rate decreased continually with time until a constant value was reached, that corresponds to a decrease of 40% considering the experiments of 13 and 63 min duration in the fluidized bed crystallizer. The decrease of the growth rates with the contact time between crystals and supersaturated solution was interpreted in terms of the increase of surfaces' roughness. According to SEM micrographs, the surface roughness increases significantly with residence time and supersaturation. The roughness appears to be the result of faulty integration of growth clusters in the crystal surface. The batch experiments show that the surface roughness acts like a strong impurity. The results were interpreted according to the Kubota-Mullin model.

Ferreira, A.; Faria, N.; Rocha, F.

2008-01-01

227

Growth Shape of Isotactic Polystyrene Crystals in Thin Films  

E-print Network

The crystal growth of isotactic polystyrene (it-PS) is investigated in very thin, 11 nm thick films. The it-PS crystals grown in the thin films show quite different morphology from that in the bulk. With decreasing crystallization temperature, the branching morphology in a diffusion field appears: dendrite and compact seaweed. The branching morphology is formed through a morphological instability caused by the gradient of film thickness around a crystal; the thicker the film thickness, the larger the lateral growth rate of crystals. Regardless of the morphological change, the growth rate as well as the lamellar thickness depends on crystallization temperature as predicted by the surface kinetics.

Ken Taguch; Hideki Miyaji; Kunihide Izumi; Akitaka Hoshino; Yoshihisa Miyamoto; Ryohei Kokawa

2001-03-13

228

Oriented growth of cadmium telluride crystals from the vapor phase  

SciTech Connect

The effect of the temperature of crystallization, the magnitude of mass transfer, and the structure of the seed crystal on the oriented growth of cadmium telluride crystals from the vapor was studied. Crystals oriented in the <110>, <111>, and <112> directions were grown in the temperature interval 1130-1330 K from the vapor of cadmium telluride crystals. The maximum possible rates of growth of single crystals and the activation energy of the growth process in the temperature interval studied in the directions <110>, <111>, and <112> (522, 372, and 334 kJ/mole, respectively) were determined.

Klinkova, L.A.; Erofeeva, S.A.

1988-08-01

229

Alloy Semiconductor Crystal Growth Under Microgravity  

SciTech Connect

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.

Hayakawa, Yasuhiro; Arivanandhan, Mukannan; Rajesh, Govindasamy; Tanaka, Akira [Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu, Shizuoka 432-8011 (Japan); Ozawa, Tetsuo [Shizuoka Institute of Science and Technology, 2200-2 Toyozawa, Fukuroi, Shizuoka 437-8555 (Japan); Okano, Yasunori [Graduate School of Engineering Science, Osaka University, 1-3 Machiganeyama, Osaka 560-8531 (Japan); Sankaranarayanan, Krishnasamy [Alagappa University, Karaikudi, Tamilnadu (India); Inatomi, Yuko [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan)

2010-12-01

230

Fluid Physics and Macromolecular Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

231

Crystal growth kinetics of the two-step model  

NASA Astrophysics Data System (ADS)

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.

Tai, Clifford Y.; Lin, Chiu-Hsiung

1987-03-01

232

Numerical studies of convective transport associated with crystal growth in mirrogravity  

NASA Technical Reports Server (NTRS)

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

Ramachandran, N.

1992-01-01

233

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

PubMed Central

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

Valenzuela, Carlos Diaz; Carriedo, Gabino A.; Valenzuela, Maria L.; Zuniga, Luis; O'Dwyer, Colm

2013-01-01

234

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

USGS Publications Warehouse

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

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

2003-01-01

235

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

NASA Astrophysics Data System (ADS)

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 ?m) 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.

Zacher, U.; Mersmann, A.

1995-01-01

236

Numerical computations of facetted pattern formation in snow crystal growth  

E-print Network

Facetted growth of snow crystals leads to a rich diversity of forms, and exhibits a remarkable sixfold symmetry. Snow crystal structures result from diffusion limited crystal growth in the presence of anisotropic surface energy and anisotropic attachment kinetics. It is by now well understood that the morphological stability of ice crystals strongly depends on supersaturation, crystal size and temperature. Until very recently it was very difficult to perform numerical simulations of this highly anisotropic crystal growth. In particular, obtaining facet growth in combination with dendritic branching is a challenging task. We present numerical simulations of snow crystal growth in two and three space dimensions using a new computational method recently introduced by the authors. We present both qualitative and quantitative computations. In particular, a linear relationship between tip velocity and supersaturation is observed. The computations also suggest that surface energy effects, although small, have a larg...

Barrett, John W; Nürnberg, Robert

2012-01-01

237

Residual Gases in Crystal Growth Systems  

NASA Technical Reports Server (NTRS)

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.

Palosz, W.

2003-01-01

238

Optimization of heating conditions during Cz BGO crystal growth  

NASA Astrophysics Data System (ADS)

We have studied the effect of geometrical and physical parameters of additional lower heater on thermal conditions during BGO growth by the Czochralski technique, in particular, on keeping flat melt/crystal interface during the whole growth process. Numerical simulation by CGSim software was used as an efficient tool for the analysis. After revealing optimal growth conditions and hot zone design by modeling, we have modified experimental growth setup and successfully improved crystal growth process in close agreement to modeling predictions.

Kolesnikov, A. V.; Galenin, E. P.; Sidletskiy, O. Ts.; Kalaev, V. V.

2014-12-01

239

Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth  

NASA Technical Reports Server (NTRS)

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.

Mazuruk, Konstantin; Ramachandran, Narayanan

1998-01-01

240

Crystal growth by solvent evaporation and characterization of metronidazole  

NASA Astrophysics Data System (ADS)

Single crystals of metronidazole were crystallized by the slow solvent evaporation method and used as seeds to grow bulk crystals of size 8.0×6.5×2.0 mm3 using top-seeded submerged solution growth. The crystals were characterized using single crystal X-ray diffraction. Fourier transform infrared spectral analysis was made for the absorption bands of various functional groups present in the crystal. UV-vis absorption spectrum was used to identify the presence of nitroimidazole in metronidazole. Morphology study revealed that the growth is prominent along the c-axis and the prominent face is {010}. Thermal stability and thermal decomposition were analyzed using thermo calorimetry.

Ramukutty, S.; Ramachandran, E.

2012-07-01

241

Growth of urea crystals by physical vapor transport  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

242

Indium antimonide crystal growth experiment M562. [Skylab weightless conditions  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

243

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

USGS Publications Warehouse

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

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

2003-01-01

244

Journal of Crystal Growth 241 (2002) 220230 Driving force for crystallization of gas hydrates  

E-print Network

Journal of Crystal Growth 241 (2002) 220­230 Driving force for crystallization of gas hydrates Dimo by R. Kern Abstract A general expression is derived for the supersaturation for crystallization of one and in the hydrate crystal. Expressions for the supersaturation are obtained for solutions supersaturated

Firoozabadi, Abbas

245

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

NASA Astrophysics Data System (ADS)

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.

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

2003-08-01

246

Synthesis, growth, spectral, thermal, mechanical and optical properties of 4-chloro-4'dimethylamino-benzylidene aniline crystal: a third order nonlinear optical material.  

PubMed

An organic nonlinear optical material, 4-chloro-4'dimethylamino-benzylidene aniline (CDMABA), was synthesized by the condensation of the p-chloroaniline and p-dimethylaminobenzaldehyde. Solubility of CDMABA was determined in acetone at different temperatures. Single crystals were grown by the solvent evaporation method from acetone solution at room temperature. Grown crystal was subjected to FTIR, FT-Raman and (1)H NMR spectral analyses to confirm the synthesized compound. The range and percentage of optical transmission was ascertained by recording UV-vis-NIR spectrum. Thermal properties were investigated by Thermo Gravimetric, Differential Thermal and Differential Scanning Calorimetric analyses. High Resolution X-ray Diffractometry (HRXRD) was employed to evaluate the perfection of the grown crystal. The third order nonlinear optical parameters (nonlinear refractive index and nonlinear absorption coefficient) were derived by the Z-scan technique. PMID:19616991

Leela, S; Ramamurthi, K; Bhagavannarayana, G

2009-09-15

247

Growth rate dispersion of single potassium alum crystals  

NASA Astrophysics Data System (ADS)

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

Lacmann, Rolf; Tanneberger, Ulrike

1995-01-01

248

Kinetic mechanism of chain folding in polymer crystallization  

NASA Astrophysics Data System (ADS)

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

Stepanow, S.

2014-09-01

249

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

NASA Technical Reports Server (NTRS)

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

Kanbayashi, Akio

1992-01-01

250

A chain mechanism for flagellum growth.  

PubMed

Bacteria swim by means of long flagella extending from the cell surface. These are assembled from thousands of protein subunits translocated across the cell membrane by an export machinery at the base of each flagellum. Unfolded subunits then transit through a narrow channel at the core of the growing flagellum to the tip, where they crystallize into the nascent structure. As the flagellum lengthens outside the cell, the rate of flagellum growth does not change. The mystery is how subunit transit is maintained at a constant rate without a discernible energy source in the channel of the external flagellum. We present evidence for a simple physical mechanism for flagellum growth that harnesses the entropic force of the unfolded subunits themselves. We show that a subunit docked at the export machinery can be captured by a free subunit through head-to-tail linkage of juxtaposed amino (N)- and carboxy (C)-terminal helices. We propose that sequential rounds of linkage would generate a multisubunit chain that pulls successive subunits into and through the channel to the flagellum tip, and by isolating filaments growing on bacterial cells we reveal the predicted chain of head-to-tail linked subunits in the transit channel of flagella. Thermodynamic analysis confirms that links in the subunit chain can withstand the pulling force generated by rounds of subunit crystallization at the flagellum tip, and polymer theory predicts that as the N terminus of each unfolded subunit crystallizes, the entropic force at the subunit C terminus would increase, rapidly overcoming the threshold required to pull the next subunit from the export machinery. This pulling force would adjust automatically over the increasing length of the growing flagellum, maintaining a constant rate of subunit delivery to the tip. PMID:24213633

Evans, Lewis D B; Poulter, Simon; Terentjev, Eugene M; Hughes, Colin; Fraser, Gillian M

2013-12-12

251

Growth and characterization of L-tryptophan doped KDP crystals  

NASA Astrophysics Data System (ADS)

Potassium Dihydrogen Phosphate crystals are one of the most popular crystals used for Non-linear Optical applications. Most of the amino acids also exhibit NLO properties. The effect of doping of one of the amino acids, L-tryptophan in KDP crystals has been investigated. Pure and L-tryptophan doped KDP crystals were grown by slow solvent evaporation solution growth technique. Good quality transparent crystals were obtained. Doping of L-tryptophan in KDP crystal was confirmed by FT-IR spectroscopy studies. The value of second harmonic generation efficiency and optical transmission in UV-Vis spectra increased as doping of L-tryptophan increased in KDP crystals.

Parikh, K. D.; Dave, D. J.; Parekh, B. B.; Joshi, M. J.

2013-06-01

252

Journal of Crystal Growth 127 (1993) 499--502 ~ 0~ CRYSTAL North-Holland GROWT H  

E-print Network

Journal of Crystal Growth 127 (1993) 499--502 ~ 0~ CRYSTAL North-Holland GROWT H Two be incorporated in GaAs and AIGaAs epilayers. By switching the growth mode at these low substrate temperatures. This was followed barriers. A film structure with As clusters in the by the growth of quantum well structures

Woodall, Jerry M.

253

Growth of TiO 2 ribbon single crystals by edge-defined film-fed growth method  

NASA Astrophysics Data System (ADS)

Shaped uniform width TiO2 ribbon single crystals have been successfully grown by the edge-defined, film-fed growth (EFG) method. A feature of this growth is a periodic change in ribbon width, which occurs under a non-uniform temperature distribution and/or too high a die top temperature. Examination of the growth mechanisms of the TiO2 ribbon crystal has revealed that the periodic change is closely connected with a decrease in the radiative heat transfer in the growing crystal. The periodic change can be suppressed by improved growth conditions on the uniform temperature distribution and the precise temperature control of the die top. Observation of X-ray topographs shows that a uniform width ribbon crystal is free from small angle grain boundaries on the ribbon edge.

Machida, Hiroshi; Hoshikawa, Keigo; Fukuda, Tsuguo

1993-03-01

254

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

PubMed

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

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

2006-08-15

255

Continuum Mechanics of Line Defects in Liquid Crystals and Liquid Crystal Elastomers A. Acharya and K. Dayal Continuum Mechanics of Line Defects in Liquid Crystals  

E-print Network

Continuum Mechanics of Line Defects in Liquid Crystals and Liquid Crystal Elastomers A. Acharya and K. Dayal Continuum Mechanics of Line Defects in Liquid Crystals and Liquid Crystal Elastomers Amit Abstract This paper generalizes the Ericksen-Leslie continuum model of liquid crystals to allow for dynam

Acharya, Amit

256

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

257

Magnetic Control in Crystal Growth from a Melt  

NASA Astrophysics Data System (ADS)

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

Huang, Yue

258

Manipulation of droplet and crystal growth by Paul effect  

Microsoft Academic Search

Crystal growth in the microgravity is attracting attention for material science because it is possible to produce a uniform crystal. A purpose of this research is to manipulate a small droplet with a diameter of nano-micro meters by Paul effect and to vaporize for producing a crystal. In case a cylindrical electrode between cap-electrodes is charged, a micro particle of

Y. Otani; Y. Mizutani; Y. Yamabe

2010-01-01

259

Investigation on Growth and Surface Analysis of DAST Single Crystals  

SciTech Connect

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

Thomas, Tina; Vijay, R. Jerald; Gunaseelan, R.; Sagayaraj, P. [Department of Physics, Loyola College, Chennai - 600 034 (India)

2011-07-15

260

Mechanically Tunable Negative-Index Photonic Crystal Lens  

E-print Network

Mechanically Tunable Negative-Index Photonic Crystal Lens Volume 2, Number 6, December 2010 Y. Cui;Mechanically Tunable Negative-Index Photonic Crystal Lens Y. Cui,1;2 V. A. Tamma,1 J.-B. Lee,2 and W. Park1 1 systems (MEMS)-enabled mechanically tunable negative-index photonic crystal lens, which was comprised of 2

Lee, Jeong-Bong

261

Growth and Characterization of Chalcogenide Crystals by Vapour Method  

NASA Astrophysics Data System (ADS)

A horizontal linear gradient two zone furnace was designed and employed to grow single crystals of indium telluride by Physical Vapour Deposition (PVD) method. It was calibrated for various trials including, series and parallel combinations of coils, and set temperatures. Systematic growth runs for chalcogenide crystals were performed by varying the source and growth temperatures. Crystals of different sizes and morphologies were obtained. The morphology and chemical analysis of the grown crystals were investigated by Scanning Electron Microscope (SEM) and Energy Dispersive Analysis using X-rays (EDAX). The hardness of the crystals was estimated using a Vickers microhardness tester.

Reshmi, P. M.; Kunjomana, A. G.; Chandrasekharan, K. A.

2011-07-01

262

Crystal growth and characterization of 9,10-diphenylanthracene  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

263

Inorganic and protein crystal growth - Similarities and differences  

NASA Technical Reports Server (NTRS)

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

Rosenberger, F.

1986-01-01

264

Oscillatory zoning: a pathological case of crystal growth  

Microsoft Academic Search

A new theory of oscillatory zoning in naturally grown plagioclase crystals is presented. This describes explicitly the coupling between the interface kinetics and the diffusion of chemical species in the melt. The crystal growth rate R responds with a finite delay time to concentration changes at the interface. Thus the growth rate cannot be simply some function of the supersaturation.

Claude J. Allègre; Ariel Provost; Claude Jaupart

1981-01-01

265

Holographic instrumentation for monitoring crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

266

Growth rate dispersion of single potassium alum crystals  

Microsoft Academic Search

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

Rolf Lacmann; Ulrike Tanneberger

1995-01-01

267

Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals  

NASA Astrophysics Data System (ADS)

Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals.

Nirmala, L. Ruby; Prakash, J. Thomas Joseph

2013-06-01

268

Issues in the growth of bulk crystals of infrared materials  

NASA Technical Reports Server (NTRS)

Attention is given to the relevant criteria governing materials choice in the growth of IR optoelectronic bulk single crystals of III-V and II-VI alloy and I-III-VI2 compound types. The most important considerations concern the control of crystal purity, microstructural perfection, stoichiometry, and uniformity during crystal growth, as well as the control of surface properties in wafer fabrication. Specific examples are given to illustrate the problems encountered and their preferred solutions.

Bachmann, K. J.; Golowsky, H.

1987-01-01

269

Growth of Triglycine Sulfate (TGS) crystals aboard Spacelab-3  

NASA Technical Reports Server (NTRS)

An experiment to study the growth of single crystals of triglycine sulfate (NH2CH2COOH)3 H2SO4 (TGS) was successfully carried out on the Spacelab-3 mission during April 29 to May 6, 1985. Two crystals of TGS were grown during the flight, using a specially developed cooled sting technique of solution crystal growth. For the first time in any flight experiment the growth was monitored on-board as well as on ground by video-schlieren technique. Hundreds of holograms were taken for the solution/crystal interaction during the growth process. Preliminary results indicate that the optical system worked very well and the quality of reconstructed holograms is satisfactory. The cooled sting technique was successfully demonstrated. Holographic interferograms indicate convection free, diffusion limited growth. Some of the preliminary results of crystal quality are also presented.

Lal, R. B.; Aggarwal, M. D.; Batra, A. K.; Kroes, R. L.; Wilcox, William R.; Trolinger, James R.; Cirino, Philip

1987-01-01

270

Effect of impurities on crystal growth rate of ammonium pentaborate  

NASA Astrophysics Data System (ADS)

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.

?ahin, Ö.; Özdemir, M.; Genli, N.

2004-01-01

271

Step flow and polytype transformation in growth of 4H-SiC crystals  

NASA Astrophysics Data System (ADS)

4H-SiC crystals containing polytype defects are investigated by optical microscopy, atomic force microscopy, and Raman scattering, aiming at understanding the mechanism of polytype transformation during growth processes. It is observed that the crystal surfaces around the facet are uneven and contain many macroscopic triangular domains, consisting of wide triangular terraces and giant macrosteps. Nucleation and growth on the wide terraces are demonstrated to be responsible for the polytype transformation. A possible polytype transformation mechanism is put forward, which can explain the stabilizing effect of nitrogen on 4H-SiC growth.

Liu, Chunjun; Chen, Xiaolong; Peng, Tonghua; Wang, Bo; Wang, Wenjun; Wang, Gang

2014-05-01

272

Controlled Growth of Organic Semiconductor Films Using Liquid Crystal Solvents  

NASA Astrophysics Data System (ADS)

Interest in using organic semiconductors in applications such as large area displays, photovoltaic devices, and RFID tags stems in part from their prospects for enabling significantly reduced manufacturing costs compared to traditional inorganic semiconductors. However many of the best performing prototype devices produced so far have involved expensive or time-consuming fabrication methods, such as the use of single crystals or thin films deposited under high vacuum conditions. We present a new approach for growing low molecular weight organic crystalline films at ambient conditions based on a vapor-liquid-solid growth mechanism using thermotropic nematic liquid crystal (LC) solvents. Tetracene is deposited via atmospheric-pressure sublimation onto substrates coated by a LC layer oriented using rubbed polyimide, producing films that are highly crystalline, with large grain sizes, and possessing macroscopic uniaxial orientation. This poster will describe the growth mechanism, discuss the effects of processing conditions such as LC layer thickness, substrate temperature and flux rate, and compare the results to a model of diffusion limited aggregation accounting for the finite thickness of the solvent layer.

Bufkin, Kevin; Ohlson, Brooks; Hillman, Ben; Johnson, Brad; Patrick, David

2008-03-01

273

Controlled Growth of Organic Semiconductor Films Using Liquid Crystal Solvents  

NASA Astrophysics Data System (ADS)

Interest in using organic semiconductors in applications such as large area displays, photovoltaic devices, and RFID tags stems in part from their prospects for enabling significantly reduced manufacturing costs compared to traditional inorganic semiconductors. However many of the best performing prototype devices produced so far have involved expensive or time-consuming fabrication methods, such as the use of single crystals or thin films deposited under high vacuum conditions. We present a new approach for growing low molecular weight organic crystalline films at ambient conditions based on a vapor-liquid-solid growth mechanism using thermotropic nematic liquid crystal (LC) solvents. Tetracene is deposited via atmospheric-pressure sublimation onto substrates coated by a LC layer oriented using rubbed polyimide, producing films that are highly crystalline, with large grain sizes, and possessing macroscopic uniaxial orientation. This poster will describe the growth mechanism, discuss the effects of processing conditions such as LC layer thickness, substrate temperature and flux rate, and compare the results to a model of deposition-diffusion aggregation accounting for the finite thickness of the solvent layer.

Bufkin, Kevin; Ohlson, Brooks; Hillman, Ben; Johnson, Brad; Patrick, David

2008-05-01

274

Continuum models of crystal growth from atomic beams with and without desorption  

Microsoft Academic Search

Continuum equations appropriate to describe crystal growth from atom beams are derived in various cases. When desorption is important, the growth is described on very long lengthscales by the Kardar-Parisi-Zhang equation, but should be corrected for shorter lengthscales where surface diffusion is the dominant mechanism. In the absence of desorption, an important effect at sufficiently low temperature comes from the

J. Villain

1991-01-01

275

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

NASA Astrophysics Data System (ADS)

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

Murugan, G. Senthil; Ramasamy, P.

2014-04-01

276

Kinetic Roughening Transition and Energetics of Tetragonal Lysozyme Crystal Growth  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

277

Kinetics of crystal growth of mirabilite in aqueous supersaturated solutions  

NASA Astrophysics Data System (ADS)

The crystallization of sodium sulfate decahydrate (Na 2SO 4·10H 2O, mirabilite) from supersaturated solutions was investigated using stable supersaturated solutions seeded with mirabilite seed crystals. The experiments were done in batch, stirred reactors in which the supersaturated solutions were prepared either by dissolution of sodium sulfate anhydrous at 32 °C followed by cooling to 18 or 20 °C or by mixing equal volumes of equimolar ammonium sulfate and sodium hydroxide solutions at 20 °C. Inoculation of the solutions supersaturated only with respect to mirabilite with seed crystals was accompanied with temperature increase of the thermostated solution. Despite the fact that crystal growth was initiated with seed crystals, the process started past the lapse of induction times inversely proportional to the solution supersaturation. The rates of crystal growth were measured both from the temperature rise and from the concentration-time profiles, which were linearly correlated. The measured crystal growth rates showed a parabolic dependence on supersaturation at low supersaturations. For higher values this dependence changed to linear, a behavior consistent with the BCF spiral crystal growth model. The morphology of the crystals growing at 20 °C showed typical prismatic habit, while at 18 °C when crystallized from cooled sodium sulfate solutions changes in the crystal habit to a leaf like morphology were observed.

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

2012-01-01

278

Universality classes for unstable crystal growth  

NASA Astrophysics Data System (ADS)

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

Biagi, Sofia; Misbah, Chaouqi; Politi, Paolo

2014-06-01

279

Ground Based Program for the Physical Analysis of Macromolecular Crystal Growth  

NASA Technical Reports Server (NTRS)

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

Malkin, Alexander J.

1998-01-01

280

Solution Growth of Crystals in Zero-Gravity  

NASA Technical Reports Server (NTRS)

In a low-g environment, buoyancy driven convection effects in solution crystal growth are greatly reduced and, thus, one can study diffusion mass transport which in 1-g is masked by convective phenomena. Crystals of triglycine sulfate (TGS) will be grown aboard the Spacelab 3 mission, using a specially developed Fluids Experiments System (FES). The objectives of the experiment are: (1) to develop a technique for solution crystal growth in a low-g environment, (2) to characterize the growth environment provided by an orbiting spacecraft and to determine the influence of the environment on the growth behavior, and (3) to determine how gravity in a low-gravity environment influences the properties of a resulting TGS crystal. Single crystals of TGS have been grown using conventional low-temperature solution crystal growth method and the growth process has been extensively characterized. Various physical properties of TGS solution have been measured. Also, a unique technique of growing solution growth crystals by extracting heat at a programmed rate from the crystal through a semi-insulating sting has been developed and tested in 1-g environment.

Lal, R. B.; Kroes, R. L.

1985-01-01

281

Crystal Growth And Characterization Of Oxides Host Crystals For Tunable Lasers  

NASA Astrophysics Data System (ADS)

Crystal growth of titanium doped sapphire crystals is described. Effects of growth atmosphere, titanium concentration, dopant oxidation state are described. Growth of garnet hosts gadolinium scandium gallium garnet and gadolinium scandium aluminum garnet doped with chromium is described. Effects of impurities on optical characteristics of chromium doped garnets are described, as well as approach leading to improvement of optical quality. Growth of magnesium and yttrium aluminates and their doping with titanium is described.

Kokta, Milan R.

1987-03-01

282

Synthesis and crystallization mechanism of europium-titanate Eu2Ti2O7  

NASA Astrophysics Data System (ADS)

The synthesis of nanocrystalline europium-titanate pyrochlore Eu2Ti2O7 by a generic sol gel approach is presented. The size of the formed nanocrystals was tailored from 20 nm to 100 nm. The nucleation process and the crystallization mechanism were studied. The activation energies of the crystallization process and crystal growth were calculated. It was found; from the calculated Avrami's parameters; that the crystallization process starts by homogenous nucleation followed by three dimensional growth. The activation energies of the crystallization process were about 700 kJ mol-1. The energy of nanocrystal growth was 26.5±3.9 kJ mol-1. The results present fundamental information about the crystallization behavior of RE2Ti2O7 prepared by the condensation of titanium alkoxides with inorganic salts of rare-earth elements.

Mrázek, Jan; Surýnek, Martin; Bakardjieva, Snejana; Buršík, Ji?í; Kašík, Ivan

2014-04-01

283

Calcite crystal growth rate inhibition by polycarboxylic acids  

USGS Publications Warehouse

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.

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

2001-01-01

284

Needs and Opportunities in Crystal Growth.  

ERIC Educational Resources Information Center

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)

Mroczkowski, Stanley

1980-01-01

285

Growth of large birefringent ?-BBO crystal  

Microsoft Academic Search

Sr2+-doped ?-BBO crystals have been grown by Czochralski method. The ?-BBO crystal is highly perfect, colorless and without any cracks and without any scattering particles if examined under He–Ne laser.

Shaofan Wu; Guofu Wang; Jianling Xie; Xiquan Wu; Yangfen Zhang; Xiang Lin

2002-01-01

286

Vapor Growth and Characterization of Cr-Doped ZnSe Crystals  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

287

Simulation of crystal growth from Lennard-Jones solutions  

Microsoft Academic Search

We simulate crystal growth from solution using the Monte Carlo method in the semigrand-isobaric-isothermal ensemble. All crystals are grown in the face-centered-cubic (100) direction, while varying the solubility and temperature. This enables us to change the growth mode from linear to nonlinear. In order to simulate at time scales necessary for growth from solution, we devised and used smart Monte

H. E. A. Huitema; B. van Hengstum; J. P. van der Eerden

1999-01-01

288

Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

289

Spatiotemporal growth of faceted and curved single crystals  

PubMed

The spatiotemporal growth of single crystals in a crystalline polymer has been investigated theoretically based on a nonconserved time dependent Ginzburg-Landau equation (known as TDGL model A). In the description of the total free energy, a double-well local free energy density signifying metastability of crystal ordering is combined with a nonlocal free energy term representing an interface gradient. The resulting nonlinear reaction diffusion equation after renormalization possesses a solitary wave property. Two-dimensional numerical calculations were performed to elucidate the faceted single crystal growth including square, rectangular, diamond-shaped, and curved single crystals. A three-dimensional simulation was also undertaken for the emergence of diamond-shaped single crystals in polyethylene. Of particular importance is that the model field parameters can be linked directly to the material parameters of polyethylene single crystals. Simulation with various elements of the interface gradient coefficient tensor captures various topologies of polymer single crystals. PMID:11088211

Kyu; Mehta; Chiu

2000-04-01

290

Critical Supersaturation for Ice Crystal Growth: Laboratory Measurements and Atmospheric Modeling Implications  

NASA Astrophysics Data System (ADS)

An improved understanding of ice crystal growth, particularly at low temperatures, is much in demand for the advancement of numerical modeling of atmospheric processes. Cirrus models must contend with the complexity of ice crystals growing in cold temperatures, low pressures, low supersaturations, and with multiple nucleation mechanisms. Recent observations have allowed increasingly realistic parameterizations of cirrus ice crystal microphysics, but these observations need to be supplemented by a fundamental understanding of growth processes affecting low-temperature crystals. Several experimental studies have demonstrated that certain ice crystals require a minimum "critical" supersaturation before exhibiting detectable growth. These crystals are presumed to be essentially defect-free, preventing vicinal hillock growth at the site of crystal dislocations. In the case of crystal growth by spiral dislocation, advancement of faces begins as soon as supersaturation is present. The finding of conditional critical supersaturations have analogies in other materials (metals, semiconductors, potassium dihydrogen phosphate) and are thermodynamically predicted given a two-dimensional nucleation growth mechanism. Previous measurements have determined the critical supersaturation for ice as a function of temperature and crystallographic face from 0 to --15° C with extrapolation to --30° C. For both basal and prism faces, critical supersaturation is seen to increase with decreasing temperature, suggesting that low-temperature, low-supersaturation processes are most likely to be affected by this critical contingency. We present laboratory results to verify and extend prior critical supersaturation measurements using a novel approach for supersaturation generation, control, and measurement. The crystals are grown on the tip of a fine glass fiber ( ˜10 microns in diameter) under varying conditions of temperature, pressure, and saturation. Supersaturation is generated when a pre-saturated airflow passes over a coil of ice warmed by electrical resistance upstream from the growing crystal. Supersaturation is determined by a system of differential thermocouples calibrated to sulfuric acid drop size measurements. Measurements follow those made in earlier studies, but also extend to temperatures of --45° C, mimicking conditions found in some high altitude clouds.

Magee, N.; Moyle, A.; Lamb, D.

2003-12-01

291

[Mechanism of crystal deposition in the joints].  

PubMed

The mechanism of crystal deposition in joints varies with the chemical nature of the crystal. Crystallisation of monosodium urate, characteristic of gout, requires a neutral pH and supersatured tissues, which is the basis for the clinical definition of the upper limit of normal blood uric acid level. The appearance of crystals also is dependent on time since crystallisation of monosodium urate is very slow. Inhibitory or promoting factors could intervene and explain rare cases of gout without hyperuricemia or the rapid crystallisation which seems to characterise some types of drug-induced gout. Crystal deposits of calcium pyrophosphate dihydrate form mainly in the cartilage where they seem favoured by ageing or by trauma, which could deplete cartilage of crystallisation inhibitors, notably proteoglycans. High pyrophosphate levels within cartilage also play an important role. The appearance of these pyrophosphates in the interstitial cartilagenous medium would be in large part due to the activity of an ectoenzyme, nucleoside triphosphate pyrophosphatase; increased activity of this ectoenzyme could be responsible for some chondrocalcinosis. Chronic hypercalcaemia can also be involved in the pathogenesis of cartilage deposition of calcium pyrophosphate dihydrate by raising the calcium-pyrophosphate product, or by decreasing the activity of alkaline phosphatase, an enzyme responsible for breakdown of extracellular pyrophosphates. The pathophysiology of calcium phosphate deposits is poorly understood. For some authors, these deposits occur within matrix vesicles, but for others, within collagen fibres. Increase in the calcium-phosphate product can also be a cause, for example, during renal osteodystrophy or vitamin D intoxication.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8178067

Bardin, T

1994-01-15

292

Colloidal Crystal Growth Monitored By Bragg Diffraction Interference Fringes  

PubMed Central

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 ?M NaCl concentrations the fcc crystals first linearly grow at rates between 1.9 and 4.2 ?m/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 ?M 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

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

2010-01-01

293

Passive particle dosimetry. [silver halide crystal growth  

NASA Technical Reports Server (NTRS)

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.

Childs, C. B.

1977-01-01

294

Hydrothermal crystal growth of yttrium and rare earth stabilized hafnia  

NASA Astrophysics Data System (ADS)

Single crystals of hafnia stabilized with yttrium, neodymium, holmium and erbium 0.25 mm in size were formed in hydrothermal solutions by spontaneous nucleation in 20 M KOH at 750 °C. Positive transport conditions were established at 650 °C using a single crystal of cubic zirconia as a substrate for growth of yttrium stabilized hafnia at a rate of 0.084 mm/week. During the study single crystals could only be formed with high concentrations of the stabilizer dopants by this method. This is the lowest synthesis temperature reported for any single crystal growth method of this refractory material.

Mann, Matthew; Kolis, Joseph

2010-01-01

295

Growth and characterisation of EDTA-added TGS crystals  

NASA Astrophysics Data System (ADS)

Triglycine sulfate (TGS) crystal with 1 wt% of EDTA (ETGS) addition was grown from aqueous solution by slow-cooling technique. The addition of EDTA enhanced the metastable zone width of TGS solution and, thereby, increased the growth rate of TGS crystal. The powder X-ray diffraction analysis showed a slight change in the cell parameter values of ETGS crystal. The presence of various functional groups in the grown crystal is identified from FTIR analysis. Optical transmission studies on ETGS crystal showed a lower UV cut-off of 237 nm and the transmission percentage of 95%. The dielectric studies were carried out to identify the phase transition temperature and to find the dielectric constant. The pyroelectric co-efficient was calculated, which increased slightly with EDTA addition in TGS. Piezoelectric studies were also done on the grown crystals. Microhardness studies carried out using Leitz-Weitzler hardness tester showed that the ETGS crystal was softer than pure TGS crystal.

Meera, K.; Claude, A.; Muralidharan, R.; Choi, C. K.; Ramasamy, P.

2005-12-01

296

Antifreeze Effect of Carboxylated ?-Poly-l-lysine on the Growth Kinetics of Ice Crystals.  

PubMed

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

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

2014-08-28

297

Growth of zeolite crystals in the microgravity environment of space  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

298

Contract crystal growth and fabrication services  

NASA Astrophysics Data System (ADS)

This program is intended to give the scientists at the Naval Research Laboratory the ability to evaluate new solid state laser crystals. The five crystals grown were gadolinium scandium gallium garnet (GSGG) doped with erbium and/or thulium. The presumed congruent composition for undoped GSGG is GD2.96Sc1.9Ga3.14O12. If it is assumed that the distribution coefficients are unity then the crystal compositions will be the same.

Randles, M. H.; Metzl, R.; Murrell, D. M.; Creamer, J. E.

1990-02-01

299

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

300

Modelling of Heat Transfer in Single Crystal Growth  

E-print Network

An attempt is made to review the heat transfer and the related problems encountered in the simulation of single crystal growth. The peculiarities of conductive, convective and radiative heat transfer in the different melt, solution, and vapour growth methods are discussed. The importance of the adequate description of the optical crystal properties (semitransparency, specular reflecting surfaces) and their effect on the heat transfer is stresses. Treatment of the unknown phase boundary fluid/crystal as well as problems related to the assessment of the quality of the grown crystals (composition, thermal stresses, point defects, disclocations etc.) and their coupling to the heat transfer/fluid flow problems is considered. Differences between the crystal growth simulation codes intended for the research and for the industrial applications are indicated. The problems of the code verification and validation are discussed; a brief review of the experimental techniques for the study of heat transfer and flow structu...

Zhmakin, Alexander I

2014-01-01

301

The effects of polydispersity and metastability on crystal growth kinetics  

E-print Network

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

John J. Williamson; R. Mike L. Evans

2012-08-19

302

Fluid Physics and Macromolecular Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

303

Ames Lab 101: Single Crystal Growth  

SciTech Connect

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.

Schlagel, Deborah

2013-09-27

304

Ames Lab 101: Single Crystal Growth  

ScienceCinema

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.

Schlagel, Deborah

2014-06-04

305

Improved Transparent Furnace For Crystal-Growth Experiments  

NASA Technical Reports Server (NTRS)

Novel design and fabrication process for transparent crystal-growing furnace developed. Design consists of one or more heater zones in which heating wire coiled around insides of quartz tubes. Ampoule of material supported inside furnace by guide wire. Crystal then grown by directional freezing of material in ampoule. Distinct feature of use of quartz is capability of direct visual observation of crystal-growth process during experiment. Study of transparent electronic materials conducted in new furnaces.

Rosenthal, Bruce N.; White, Steve; Kalinowski, Joseph M.

1989-01-01

306

Control of thermal conditions during crystal growth by inverse modeling  

NASA Astrophysics Data System (ADS)

A numerical modeling algorithm is developed which is able to calculate the powers of an arbitrary number of heaters in a crystal growth configuration in order to obtain a prescribed temperature distribution in a growing crystal. Such a mathematical procedure is called inverse modeling. The algorithm is implemented in our software system CrysVUN++ for global thermal simulation of crystal growth processes. The efficiency of this new strategy of inverse modeling is demonstrated by applying it to an industrial vertical gradient freeze (VGF) process for the growth of GaAs crystals with 3? diameter. As a result we obtain optimized growth conditions which will be discussed in comparison to the state of the art of VGF technology.

Kurz, M.; Müller, G.

2000-01-01

307

Growth of large single crystals of the orthorhombic paracetamol  

NASA Astrophysics Data System (ADS)

A new procedure for the growth of large (cm-range) single crystals of the metastable orthorhombic (s.g. Pcab) polymorph of paracetamol is described. The crystals were grown by very slow cooling of hot water solutions under the conditions, when the multiple nucleation was prevented. The samples were characterized by DSC and X-ray diffraction.

Mikhailenko, M. A.

2004-05-01

308

Crystal growth of lead carbonates: Influence of the medium and relationship between structure and habit  

NASA Astrophysics Data System (ADS)

The crystal-growth features of cerussite and hydrocerussite formed by two different chemical reactions are studied. With respect to the former, acid-vapour oxidation and latter carbonation of metallic lead produced a nanocrystalline precipitate for the lead carbonates. In the latter, cerussite and hydrocerusite are precipitated after mixing two mother solutions in liquid and solid porous media, forming diverse polyhedral morphologies. Crystal growth in gel medium gives rise to pseudo-cubic morphologies by the aggregation of one-micron-sized particles of cerussite. Skeletal morphologies composed of cyclically twinned crystals of cerussite also occur in gel-growth experiments. These morphologies were determined by kinetic factors, in particular by high supersaturation conditions that led to high growth rates. Kinetics also favoured the predominance of weak over strong interactions during crystal growth. The habit observed for cerussite crystals has been explained based on crystal-structure considerations and quantum-mechanical calculations. In particular, the crystal growth along the a direction in cyclically twinned crystals is explained by the binding forces between the CO32- molecular group and Pb2+, defining an uninterrupted chain of strong bonds along that direction. However, the preferred growth along the c direction observed for the cerussite crystal formed in gel media is here attributed to an intermolecular interaction through C-C bonds. The occurrence of a chemical bonding between the C atoms of the CO32- molecular groups aligned along the c direction is clearly shown by the theoretical analysis of the electron density with the quantum theory of atoms in molecules (QTAIM).

Sánchez-Navas, Antonio; López-Cruz, Olimpia; Velilla, Nicolás; Vidal, Isaac

2013-08-01

309

Protein Crystal Movements and Fluid Flows During Microgravity Growth  

NASA Technical Reports Server (NTRS)

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.

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

310

Zeolite Crystal Growth (ZCG) Flight on USML-2  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

311

Physical vapor transport growth of bulk aluminum nitride crystals  

Microsoft Academic Search

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

Vladimir Noveski

2004-01-01

312

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

PubMed Central

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

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

2013-01-01

313

Investigations on the Growth Kinetics of Mixed KDP: LAP and TGS: LAP Single Crystals  

NASA Astrophysics Data System (ADS)

Potassium dihydrogen phosphate (K H2 P04, abbreviated as KDP) and triglycine sulfate (NH2CH2COOH)3.H2S04 abbreviated as TGS) are the most extensively studied ferroelectric materials, which finds wide application in electro-optic and infrared detecting devices respectively. L-arginine phosphate monohydrate (C6H14N4O2H3P04.H2O, known as LAP) is a highly transparent monoclinic crystal with attractive properties for efficient frequency conversion of infrared lasers. It was thought interesting to explore the growth Kinetics of new mixed KDP: LAP and TGS: LAP crystals and study the properties of the resulting crystals. In this paper, we will report the growth morphology, optical and mechanical properties of these crystals. A new apparatus designed to study the in-situ mass transfer in growing crystals from solutions will also be described.

Batra, A. K.; Stephens, J.; Bhat, K.; Aggarwal, M. D.; Lal, R. B.

2002-10-01

314

Effect of storage temperature on crystal formation rate and growth rate of calcium lactate crystals on smoked Cheddar cheeses.  

PubMed

Previous studies have shown that storage temperature influences the formation of calcium lactate crystals on vacuum-packaged Cheddar cheese surfaces. However, the mechanisms by which crystallization is modulated by storage temperature are not completely understood. The objectives of this study were to evaluate the effect of storage temperature on smoked Cheddar cheese surfaces for (1) the number of discrete visible crystals formed per unit of cheese surface area; (2) growth rate and shape of discrete crystals (as measured by area and circularity); (3) percentage of total cheese surface area occupied by crystals. Three vacuum-packaged, random weight (?300 g) retail samples of naturally smoked Cheddar cheese, produced from the same vat of cheese, were obtained from a retail source. The samples were cut parallel to the longitudinal axis at a depth of 10mm from the 2 surfaces to give six 10-mm-thick slabs, 4 of which were randomly assigned to 4 different storage temperature treatments: 1, 5, 10°C, and weekly cycling between 1 and 10°C. Samples were stored for 30 wk. Following the onset of visible surface crystals, digital photographs of surfaces were taken every other week and evaluated by image analysis for number of discrete crystal regions and total surface area occupied by crystals. Specific discrete crystals were chosen and evaluated biweekly for radius, area, and circularity. The entire experiment was conducted in triplicate. The effects of cheese surface, storage temperature, and storage time on crystal number and total crystal area were evaluated by ANOVA, according to a repeated-measures design. The number of discrete crystal regions increased significantly during storage but at different rates for different temperature treatments. Total crystal area also increased significantly during storage, at rates that varied with temperature treatment. Storage temperature did not appear to have a major effect on the growth rates and shapes of the individual crystals that were chosen for analysis. The data indicated that the effect of storage temperature was complex, likely involving solubility changes, the formation of d(-) and l(+) lactic acid, and the occurrence of syneresis, which in turn affected the number of crystal formation sites and total crystal area on the cheese surface. PMID:23548293

Rajbhandari, P; Patel, J; Valentine, E; Kindstedt, P S

2013-06-01

315

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

SciTech Connect

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.

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

1981-01-01

316

Growth morphology of primary silicon in cast Al Si alloys and the mechanism of concentric growth  

NASA Astrophysics Data System (ADS)

Faceted growth of primary silicon crystals in cast hypereutectic aluminium-silicon alloys is studied by measurement of spacings between successive growth traces observed in microsections. A general equation, derived to specify conditions for stable growth of silicon crystal, is supported by spacing measurements. Some examples of departures from stable silicon growth are studied. Three stages in the development of faceted crystal growth are recognized, changing from spheroidal to faceted to unstable with increasing crystal diameter.

Wang, Ru-yao; Lu, Wei-hua; Hogan, L. M.

1999-11-01

317

Mechanics in Tumor Growth 1 Mechanics in Tumor Growth  

E-print Network

the extracellular matrix. As will be described in the following this process is affected by the stress applied some of the main feature of tumor growth and in particular the phenomena involving stress description, one can say that the cells forming a compact tumor, like other cells in the body, live

Preziosi, Luigi

318

(PCG) Protein Crystal Growth HIV Reverse Transcriptase  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

319

Imaging System For Measuring Macromolecule Crystal Growth Rates in Microgravity  

NASA Technical Reports Server (NTRS)

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

Corder, Eric L.; Briscoe, Jeri

2004-01-01

320

Protein crystal growth in low gravity  

NASA Technical Reports Server (NTRS)

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.

Feigelson, Robert S.

1992-01-01

321

Edge-controlled growth and kinetics of single-crystal graphene domains by chemical vapor deposition  

PubMed Central

The controlled growth of large-area, high-quality, single-crystal graphene is highly desired for applications in electronics and optoelectronics; however, the production of this material remains challenging because the atomistic mechanism that governs graphene growth is not well understood. The edges of graphene, which are the sites at which carbon accumulates in the two-dimensional honeycomb lattice, influence many properties, including the electronic properties and chemical reactivity of graphene, and they are expected to significantly influence its growth. We demonstrate the growth of single-crystal graphene domains with controlled edges that range from zigzag to armchair orientations via growth–etching–regrowth in a chemical vapor deposition process. We have observed that both the growth and the etching rates of a single-crystal graphene domain increase linearly with the slanted angle of its edges from 0° to ?19° and that the rates for an armchair edge are faster than those for a zigzag edge. Such edge-structure–dependent growth/etching kinetics of graphene can be well explained at the atomic level based on the concentrations of the kinks on various edges and allow the evolution and control of the edge and morphology in single-crystal graphene following the classical kinetic Wulff construction theory. Using these findings, we propose several strategies for the fabrication of wafer-sized, high-quality, single-crystal graphene. PMID:24297886

Ma, Teng; Ren, Wencai; Zhang, Xiuyun; Liu, Zhibo; Gao, Yang; Yin, Li-Chang; Ma, Xiu-Liang; Ding, Feng; Cheng, Hui-Ming

2013-01-01

322

Growth of eutectic silicon from primary silicon crystals in aluminium-silicon alloys  

SciTech Connect

Technological interest in aluminium-silicon alloys derives, fundamentally, from their excellent moulding properties provided by the presence of silicon. In addition, they possess high thermal and electrical conductivities and good corrosion resistance. The possibility of modification of their cast structure by adding small quantities of alkaline and alkaline-earth elements makes their mechanical characteristics very competitive. Metallographic observations of the structures of primary and eutectic silicon crystals, and their possible synergistic influence, provide useful data on the critical stages of formation and growth of eutectic silicon phase. The nucleation and growth of eutectic silicon, removed from the cooperative precipitation zone, induce refinement in crystal size and, therefore, an improvement of the mechanical properties of the moulded structure. The aim of this investigation was to observe the influence of primary silicon crystals on the nucleation and growth of eutectic silicon.

Criado, A.J.; Martinez, J.A.; Calabres, R. [Complutense Univ. of Madrid (Spain). Dept. of Materials Science and Metallurgical Engineering] [Complutense Univ. of Madrid (Spain). Dept. of Materials Science and Metallurgical Engineering

1997-01-01

323

Mathematical Existence of Crystal Growth with GibbsThomson Curvature E#ects 1  

E-print Network

Mathematical Existence of Crystal Growth with Gibbs­Thomson Curvature E#ects 1 by Fred Almgren 2 one type of growth of a crystal as it freezes from a cold melt. The crystal freezes (melts) as rapidly. CHAPTER 2. Ingredients of our model of crystal growth. 2.1 The ambient space. 2.2 Crystals. 2.3 Heat

Wang, Lihe

324

Inhibition of calcium oxalate monohydrate crystal growth using polyelectrolytes  

NASA Astrophysics Data System (ADS)

The effects of polyacrylic acid and poly(ethylene glycol-block-acrylic acid) copolymer on the growth of calcium oxalate monohydrate (COM), a common renal stone constituent, have been investigated in aqueous solutions at 37 °C. A constant composition method has been utilized to investigate the crystallization kinetics of COM. The results of the experiment show that the retardation in mass transport in growth process is controlled by the nature of the polymer and its concentration. Monoclinic COM crystals were shown to be major components in the absence of polymers. In the presence of polymers monoclinic COM crystals were smaller and some of the crystals were less elongated, and small number of crystals grew in the shape of three-dimensional hexagonal prisms. The data on the growth kinetics of crystals in the presence of polyelectrolytes were examined from the standpoint of adsorption models. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface.

Akyol, Emel; Öner, Mualla

2007-09-01

325

Bulk III-V compound semiconductor crystal growth  

SciTech Connect

This paper discusses the production of III-V compound semiconductor substrates characterized by structural perfection and chemical homogeneity. Special attention is given to the use of vertical-gradient-freeze (VGF) technique for producing large high-quality GaP, InP, and GaAs crystals. The characteristics of VGF-grown GaAs crystals are described, including the dislocation-count distribution, etch-pit density, and electrical properties. The VGF-grown crystals have very low levels of crystalline defects distributed uniformly throughout the crystal; growth striations are planar and are greatly reduced in comparison with those observed in materials produced by the liquid-encapsulated Czochralski method. Yields obtained with the VGF method compare favorably with those of other commercial crystal-growth processes. 9 refs.

Clemans, J.E.; Ejim, T.I.; Gault, W.A.; Monberg, E.M. (AT and T Bell Laboratories, Princeton, NJ (USA) AT and T Microelectronics, Reading, PA (USA) AT and T Bell Laboratories, Murray Hill, NJ (USA))

1989-02-01

326

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, H. C.; Lagowski, J.

1983-01-01

327

Lattice Boltzmann simulation of snow crystal growth in clouds  

NASA Astrophysics Data System (ADS)

The Lattice Boltzmann (LB) method can be used to simulate aspects of chemical reactions such as mineral precipitation from a fluid phase or condensation from a vapor phase. The LB method has the advantage of allowing the shape of the condensing phase to evolve depending on local conditions rather than being specified, so that the controls on condensed phase grain shape can be studied simultaneously with the controls on chemical composition and growth rate. We have used the LB approach to simulate the growth of ice crystals from water vapor-oversaturated air as a first step in developing methods for treating more complex chemical reaction problems, including isotopic effects. The formation of ice crystals (i.e., snow) in air is a classic problem in diffusion-limited crystal growth. There are many complexities, but the process is attractive for modeling purposes because it involves only one chemical component and there is abundant information on reaction kinetics and the relationships between crystal morphology and growth conditions. In this paper we describe the LB approach used, and address strategies for properly conserving mass at a surface of a growing "crystal," the scaling of the calculations to the actual physical problem, and the conditions for growth of dendritic versus compact crystals.

Lu, Guoping; Depaolo, Donald J.; Kang, Qinjun; Zhang, Dongxiao

2009-04-01

328

Czochralski growth of gallium indium antimonide alloy crystals  

SciTech Connect

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

Tsaur, S.C.

1998-02-01

329

Kinetics of non-isothermal crystallization process and activation energy for crystal growth in amorphous materials  

Microsoft Academic Search

An equation expressing the volume fraction,x, of crystals precipitating in a glass heated at a constant rate, a, was derived. When crystal particles grow m-dimensionally,x is expressed as In [- ln(1 -x)] = -n (na - 1.052mE\\/RT + Constant whereE is the activation energy for crystal growth andn is a numerical factor depending on the nucleation process. When the nuclei

Kazumasa Matusita; Takayuki Komatsu; Ryosuke Yokota

1984-01-01

330

Direct growth of self-crystallized graphene and graphite nanoballs with Ni vapor-assisted growth: From controllable growth to material characterization  

PubMed Central

A directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100°C via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12?nm at growth temperature of 1000°C to ~32?nm at growth temperature of 1100°C, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. By increasing growth pressure, the growth of graphite nano-balls was preferred rather than graphene growth. The detailed formation mechanisms of graphene and graphite nanoballs were proposed and investigated in detail. Optical and electrical properties of graphene layer were measured. The direct growth of the carbon-based materials with free of the transfer process provides a promising application at nanoelectronics. PMID:24810224

Yen, Wen-Chun; Chen, Yu-Ze; Yeh, Chao-Hui; He, Jr-Hau; Chiu, Po-Wen; Chueh, Yu-Lun

2014-01-01

331

Transient natural convection heat and mass transfer in crystal growth  

NASA Technical Reports Server (NTRS)

A numerical analysis of transient combined heat and mass transfer across a rectangular cavity is performed by a numerical method based on the SIMPLE algorithm. The physical parameters are selected to represent a range of possible crystal growth in solutions. Numerical results are compared with available experimental data to confirm the accuracy of the results. Good qualitative agreements are obtained for the average mass transfer rate across the cavity. Also, qualitative agreements are observed for the global development of thermal and solute fields. It is found that the thermal and solute fields become highly oscillatory when the thermal and solute Grashof numbers are large. Oscillations are probably caused by a number of different instability mechanisms. By reducing the gravity some of these instabilities were made to disappear at the lower Grashof numbers. Transient temperature and solute distribution near the crystal growing surface are highly non-uniform at the higher Grashof numbers. These non-uniformities are less severe in the reduced gravity environments but still exist. The effects of convection on the rate of average mass transfer are more than one order of magnitude higher than those of conduction in the range of Grashof numbers studied. Dependency of mass transfer rate on the Grashof number indicates that the convection effects many not be negligible even in the microgravity environments for the range of parameters investigated.

Han, Samuel S.

1988-01-01

332

Crystal growth and spectral properties of Sm:GGG crystal  

NASA Astrophysics Data System (ADS)

A Sm:GGG crystal was grown by the Czochralski method. The absorption and emission spectra of Sm:GGG were measured at room temperature. According to the Judd-Ofelt theory, the intensity parameters ?t ( t=2, 4, 6), spontaneous transition probabilities, branching ratio and radiative lifetime of 4G 5/2 state were calculated. The emission cross-sections of 567, 613, 662 and 710 nm were estimated. The decay curve of the 613 nm emission assigned to the 4G 5/2? 6H 7/2 transition was measured and the fluorescence lifetime was also determined.

Liu, Wenpeng; Zhang, Qingli; Sun, Dunlu; Luo, Jianqiao; Gu, Changjiang; Jiang, Haihe; Yin, Shaotang

2011-09-01

333

Aerodynamic Stability and the Growth of Triangular Snow Crystals K. G. Libbrecht and H. M. Arnold  

E-print Network

Aerodynamic Stability and the Growth of Triangular Snow Crystals K. G. Libbrecht and H. M. Arnold Department of Physics, California Institute of Technology Pasadena, California 91125 Keywords: Crystal growth, crystal morphology, ventilation effect, diffusion-limited growth, growth instabilities, crystal faceting

Libbrecht, Kenneth G.

334

A Critical Look at Ice Crystal Growth Data KENNETH G. LIBBRECHT1  

E-print Network

A Critical Look at Ice Crystal Growth Data KENNETH G. LIBBRECHT1 Norman Bridge Laboratory. I review published data relating to the growth of ice crystals from water vapor under various of the crystal growth dynamics of ice. 1 Introduction The growth of ice crystals from the vapor phase

Libbrecht, Kenneth G.

335

A Model for Tetragonal Lysozyme Crystal Nucleation and Growth  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

336

Crystal Growth and Characterization of Bil3  

NASA Technical Reports Server (NTRS)

Bismuth tri-iodide (BiI3) have been grown by physical vapor transport (PVT), and by the Bridgman (melt) method. These crystals along with pure and stoichiometric BiI3 powder have been investigated by differential scanning calorimetry (DSC). The DSC results show that pure BiI3 powder has no phase transition and melts around 408 C. While we found no evidence for the high temperature dissociation of BiI3, the DSC measurements show that crystals grown from melt method contain a significantly large amount of Bi-rich phases than crystals grown from PVT method, as indicated by phase transition detected at 270, 285, 298 and 336 C.

Hayes, Julia; Chen, Kuo-Tong; Burger, Arnold

1997-01-01

337

Ice Crystal Growth Rates Under Upper Troposphere Conditions  

NASA Technical Reports Server (NTRS)

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.

Peterson, Harold S.; Bailey, Matthew; Hallett, John

2010-01-01

338

Shallow Melt Apparatus for Semicontinuous Czochralski Crystal Growth  

DOEpatents

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.

Wang, T.; Ciszek, T. F.

2006-01-10

339

Synthesis, crystal growth and spectroscopic investigation of novel metal organic crystal: ?-alanine cadmium bromide monohydrate (?-ACBM).  

PubMed

?-Alanine cadmium bromide monohydrate (?-ACBM), a new metal organic crystal has been grown from aqueous solution by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction analysis to determine the crystal structure. The ?-ACBM crystallized in monoclinic system with space group P2(1)/c. The presence of protons and carbons in the ?-alanine cadmium bromide monohydrate was confirmed by (1)H and (13)C nuclear magnetic resonance spectral analysis. The mode of vibration of different molecular groups present in ?-ACBM was identified by FT-IR spectral analysis. Transparency of crystals in UV-Vis-NIR region has also been studied. The thermal characteristics of as-grown crystals were analyzed using thermo gravimetric and differential thermal analyses. The magnetic property of the grown crystal was investigated using Vibrating Sample Magnetometer (VSM) at ambient temperature. The mechanical stability of ?-ACBM was evaluated by Vickers microhardness measurement. PMID:24691377

Renugadevi, R; Kesavasamy, R

2014-07-15

340

Synthesis, crystal growth and spectroscopic investigation of novel metal organic crystal: ?-Alanine cadmium bromide monohydrate (?-ACBM)  

NASA Astrophysics Data System (ADS)

?-Alanine cadmium bromide monohydrate (?-ACBM), a new metal organic crystal has been grown from aqueous solution by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction analysis to determine the crystal structure. The ?-ACBM crystallized in monoclinic system with space group P21/c. The presence of protons and carbons in the ?-alanine cadmium bromide monohydrate was confirmed by 1H and 13C nuclear magnetic resonance spectral analysis. The mode of vibration of different molecular groups present in ?-ACBM was identified by FT-IR spectral analysis. Transparency of crystals in UV-Vis-NIR region has also been studied. The thermal characteristics of as-grown crystals were analyzed using thermo gravimetric and differential thermal analyses. The magnetic property of the grown crystal was investigated using Vibrating Sample Magnetometer (VSM) at ambient temperature. The mechanical stability of ?-ACBM was evaluated by Vickers microhardness measurement.

Renugadevi, R.; Kesavasamy, R.

2014-07-01

341

A Critical Assessment of Protein Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

Experiments to grow higher diffraction quality protein crystals in the microgravity environment of an orbiting spacecraft are one of the most frequently flown space experiments. Ground-based research has shown that convective flows occur even about protein crystals growing in the Earth's gravitational field. Further, this research has shown that the resultant flow velocities can cause growth cessation, and probably affect the measured X-ray data quality obtained. How flow deleteriously affects protein crystal growth (PCG) is still not known, and is the subject of ongoing research. Failing a rational method for ameliorating flow effects on Earth, one can, through NASA and other nations space agency sponsored programs, carry out protein crystal growth in the microgravity environment of an orbiting spacecraft. Early first generation PCG hardware was characterized by a very low success rate and a steep design learning curve. Subsequent hardware designs have improved upon their predecessors. Now the crystal grower has a wide variety of hardware configurations and crystal growth protocols to choose from, many of which implement "standard" laboratory protein crystal growth methods. While many of these are first or early second generation hardware the success rate, defined as growing crystals giving data better than has been obtained on Earth, is at least 20% overall and may be considerably higher if one only considers latter experiments. There are a large number of protein crystals grown every year, with hundreds of structures determined. Those crystallized in microgravity represent a small proportion of this total, and there is concern that the costs of the microgravity PCG program(s) do not justify such limited returns. Empirical evidence suggests that optimum crystal growth conditions in microgravity differ from those determined on Earth, further exacerbating the chances of success. Microgravity PCG is probably best suited for "mature" crystallizations, where one has considerable experience with the particular macromolecular system and has reached an apparent limit in diffraction resolution. Under such circumstances the cost of one or two successful flight experiments may more than offset the equivalent cost of several years effort to obtain the same improvement in data quality.

Pusey, Marc

1997-01-01

342

Tooth enamel proteins enamelin and amelogenin cooperate to regulate the growth morphology of octacalcium phosphate crystals.  

PubMed

To examine the hypothetical cooperative role of enamelin and amelogenin in controlling the growth morphology of enamel crystals in the post-secretory stage, we applied a cation selective membrane system for the growth of octacalcium phosphate (OCP) in the truncated recombinant porcine amelogenin (rP148) with and without the 32kDa enamelin fragment. Enamelin alone inhibited the growth in the c-axis direction more than rP148, yielding OCP crystals with the smallest aspect ratio of all conditions tested. When enamelin was added to the amelogenin "gel-like matrix", the inhibitory action of the protein mixture on the growth of OCP in the c-axis direction was diminished, while that in the b-axis direction was increased. As a result, the length to width ratio (aspect ratio) of OCP crystal was markedly increased. Addition of enamelin to amelogenin enhanced the potential of amelogenin to stabilize the amorphous calcium phosphate (ACP) transient phase. The ratio of enamelin and amelogenin was crucial for stabilization of ACP and the growth of OCP crystals with larger aspect ratio. The cooperative regulatory action of enamelin and amelogenin was attained, presumably, through co-assembling of enamelin and amelogenin. These results have important implications in understanding the growth mechanism of enamel crystals with large aspect ratio. PMID:21483648

Iijima, Mayumi; Fan, Daming; Bromley, Keith M; Sun, Zhi; Moradian-Oldak, Janet

2010-11-01

343

Tooth enamel proteins enamelin and amelogenin cooperate to regulate the growth morphology of octacalcium phosphate crystals  

PubMed Central

To examine the hypothetical cooperative role of enamelin and amelogenin in controlling the growth morphology of enamel crystals in the post-secretory stage, we applied a cation selective membrane system for the growth of octacalcium phosphate (OCP) in the truncated recombinant porcine amelogenin (rP148) with and without the 32kDa enamelin fragment. Enamelin alone inhibited the growth in the c-axis direction more than rP148, yielding OCP crystals with the smallest aspect ratio of all conditions tested. When enamelin was added to the amelogenin “gel-like matrix”, the inhibitory action of the protein mixture on the growth of OCP in the c-axis direction was diminished, while that in the b-axis direction was increased. As a result, the length to width ratio (aspect ratio) of OCP crystal was markedly increased. Addition of enamelin to amelogenin enhanced the potential of amelogenin to stabilize the amorphous calcium phosphate (ACP) transient phase. The ratio of enamelin and amelogenin was crucial for stabilization of ACP and the growth of OCP crystals with larger aspect ratio. The cooperative regulatory action of enamelin and amelogenin was attained, presumably, through co-assembling of enamelin and amelogenin. These results have important implications in understanding the growth mechanism of enamel crystals with large aspect ratio. PMID:21483648

Iijima, Mayumi; Fan, Daming; Bromley, Keith M.; Sun, Zhi; Moradian-Oldak, Janet

2010-01-01

344

Polymer crystallization The objective of this laboratory is for you to explore the kinetics of polymer crystal growth and melting.  

E-print Network

the kinetics of polymer crystal growth and melting. Preparation Read the introduction of the paper on thin, the kinetics of crystal growth determines the overall rate of the phase transformation. For crystal growth from a melt, heat transfer plays an important role for metals, ceramics

Braun, Paul

345

Epitaxial growth, structure, and magnetism of epitaxial Ni80Fe20 single-crystal, bicrystal, and quad-crystal films  

E-print Network

Epitaxial growth, structure, and magnetism of epitaxial Ni80Fe20 single-crystal, bicrystal epitaxy MBE growth and structural and magnetic characterizations of high-quality single-crystal, bi the conclusion is made. II. SAMPLE PREPARATION AND MEASUREMENTS The crystal growth was carried out in a MBE

Huang, Jung-Chun

346

Novel protein crystal growth technology: Proof of concept  

NASA Technical Reports Server (NTRS)

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.

Nyce, Thomas A.; Rosenberger, Franz

1989-01-01

347

Data acquisition from a crystal growth furnace  

NASA Technical Reports Server (NTRS)

Digital acquisition from a furnace for growing the lead tin telluride crystal based on Asyst software is described. It is shown that the use of Asyst for the acquisition of experimental data makes it possible to handle large amounts of data and to drastically reduce the time required for displaying the data from several hours to less than 5 minutes.

Woodell, Glenn A.

1988-01-01

348

The effect of growth rate, diameter and impurity concentration on structure in Czochralski silicon crystal growth  

NASA Technical Reports Server (NTRS)

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.

Digges, T. G., Jr.; Shima, R.

1980-01-01

349

Commercial Protein Crystal Growth: Protein Crystallization Facility (CPCG-H)  

NASA Astrophysics Data System (ADS)

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.

DeLucas, Lawrence J.

2002-12-01

350

Protein Crystal Movements and Fluid Flows During Microgravity Growth  

NASA Technical Reports Server (NTRS)

The growth of protein crystals suitable for x-ray crystal structure analysis is an important topic. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and x-ray topographic images as well as the diffraction resolution limit and overall data quality. In yet another study, use of hanging drop vapour diffusion geometry on the IML-2 shuttle mission showed, again via CCD video monitoring, growing apocrustacyanin C(sub 1) protein crystal executing near cyclic movement, reminiscent of Marangoni convection flow of fluid, the crystals serving as "markers" of the fluid flow. A review is given here of existing results and experience over several microgravity missions. Some comment is given on gel protein crystal growth in attempts to 'mimic' the benefits of microgravity on Earth. Finally, the recent new results from our experiments on the shuttle mission LMS are described. These results include CCD video as well as interferometry during the mission, followed, on return to Earth, by reciprocal space mapping at the NSLS, Brookhaven, and full X-ray data collection on LMS and Earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C(sub 1) crystals are also described.

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

1998-01-01

351

A Microfluidic, High Throughput Protein Crystal Growth Method for Microgravity  

PubMed Central

The attenuation of sedimentation and convection in microgravity can sometimes decrease irregularities formed during macromolecular crystal growth. Current terrestrial protein crystal growth (PCG) capabilities are very different than those used during the Shuttle era and that are currently on the International Space Station (ISS). The focus of this experiment was to demonstrate the use of a commercial off-the-shelf, high throughput, PCG method in microgravity. Using Protein BioSolutions’ microfluidic Plug Maker™/CrystalCard™ system, we tested the ability to grow crystals of the regulator of glucose metabolism and adipogenesis: peroxisome proliferator-activated receptor gamma (apo-hPPAR-? LBD), as well as several PCG standards. Overall, we sent 25 CrystalCards™ to the ISS, containing ~10,000 individual microgravity PCG experiments in a 3U NanoRacks NanoLab (1U = 103 cm.). After 70 days on the ISS, our samples were returned with 16 of 25 (64%) microgravity cards having crystals, compared to 12 of 25 (48%) of the ground controls. Encouragingly, there were more apo-hPPAR-? LBD crystals in the microgravity PCG cards than the 1g controls. These positive results hope to introduce the use of the PCG standard of low sample volume and large experimental density to the microgravity environment and provide new opportunities for macromolecular samples that may crystallize poorly in standard laboratories. PMID:24278480

Carruthers Jr, Carl W.; Gerdts, Cory; Johnson, Michael D.; Webb, Paul

2013-01-01

352

Fluid Physics and Macromolecular Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

The first protein crystallization experiment in microgravity was launched in April, 1981 and used Germany's Technologische Experimente unter Schwerelosigkeit (TEXUS 3) sounding rocket. The protein P-galactosidase (molecular weight 465Kda) was chosen as the sample with a liquid-liquid diffusion growth method. A sliding device brought the protein, buffer and salt solution into contact when microgravity was reached. The sounding rocket gave six minutes of microgravity time with a cine camera and schlieren optics used to monitor the experiment, a single growth cell. In microgravity a strictly laminar diffusion process was observed in contrast to the turbulent convection seen on the ground. Several single crystals, approx 100micron in length, were formed in the flight which were of inferior but of comparable visual quality to those grown on the ground over several days. A second experiment using the same protocol but with solutions cooled to -8C (kept liquid with glycerol antifreeze) again showed laminar diffusion. The science of macromolecular structural crystallography involves crystallization of the macromolecule followed by use of the crystal for X-ray diffraction experiments to determine the three dimensional structure of the macromolecule. Neutron protein crystallography is employed for elucidation of H/D exchange and for improved definition of the bound solvent (D20). The structural information enables an understanding of how the molecule functions with important potential for rational drug design, improved efficiency of industrial enzymes and agricultural chemical development. The removal of turbulent convection and sedimentation in microgravity, and the assumption that higher quality crystals will be produced, has given rise to the growing number of crystallization experiments now flown. Many experiments can be flown in a small volume with simple, largely automated, equipment - an ideal combination for a microgravity experiment. The term "protein crystal growth" is often historically used to describe these microgravity experiments. This is somewhat inaccurate as the field involves the study of many varied biological molecules including viruses, proteins, DNA, RNA and complexes of those structures. For this reason we use the term macromolecular crystal growth. In this chapter we review a series of diagnostic microgravity crystal growth experiments carried out principally using the European Space Agency (ESA) Advanced Protein Crystallization Facility (APCF). We also review related research, both experimental and theoretical, on the aspects of microgravity fluid physics that affect microgravity protein crystal growth. Our experiments have revealed some surprises that were not initially expected. We discuss them here in the context of practical lessons learnt and how to maximize the limited microgravity opportunities available.

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

353

Controlled growth of single-crystal twelve-pointed graphene grains on a liquid cu surface.  

PubMed

The controlled fabrication of single-crystal twelve-pointed graphene grains is demonstrated for the first time by ambient pressure chemical vapor deposition on a liquid Cu surface. An edge-diffusion limited mechanism is proposed. The highly controllable growth of twelve-pointed graphene grains presents an intriguing case for the fundamental study of graphene growth and should exhibit wide applications in graphene-based electronics. PMID:25043403

Geng, Dechao; Meng, Lan; Chen, Bingyan; Gao, Enlai; Yan, Wei; Yan, Hui; Luo, Birong; Xu, Jie; Wang, Huaping; Mao, Zupan; Xu, Zhiping; He, Lin; Zhang, Zhiyong; Peng, Lianmao; Yu, Gui

2014-10-01

354

Determination of the activation energy for crystal growth by differential thermal analysis  

Microsoft Academic Search

A method for determining the activation energy for crystal growth was calculated on the basis of the heat balance in the differential thermal analysis (DTA) measurements and the mechanism of nucleation and growth. The theoretical analysis showed that the term ln[Cpd(dT)\\/dt+KdT] should be a linear function of l\\/T, whereCp is the heat capacity of sample and sample holder,K is the

K. Matusita; S. Sakka; Y. Matsui

1975-01-01

355

Journal of Crystal Growth 304 (2007) 399401 Growth of high quality, epitaxial InSb nanowires  

E-print Network

Journal of Crystal Growth 304 (2007) 399­401 Growth of high quality, epitaxial InSb nanowires Hyun March 2007 Communicated by R.M. Biefeld Available online 1 April 2007 Abstract The growth of InSb nanowires on an InSb(1 1 1) substrate in a closed system is described. A high density InSb nanowires

Wang, Zhong L.

356

Synthesis, crystal growth and characterization of nonlinear optical organic crystal: p-Toluidinium p-toluenesulphonate  

SciTech Connect

Graphical abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. p-TTS single crystal belongs to negative birefringence crystal. Second harmonic conversion efficiency of p-TTS has been found to be 1.3 times higher than that of KDP. Multiple shot surface laser damage threshold is determined to be 0.30 GW/cm{sup 2} at 1064 nm laser radiation. Highlights: Black-Right-Pointing-Pointer It deals with the synthesis, growth and characterization of p-TTS an organic NLO crystal. Black-Right-Pointing-Pointer Wide optical transparency window between 280 nm and 1100 nm. Black-Right-Pointing-Pointer Negative birefringence crystal and dispersion of birefringence is negligibly small. Black-Right-Pointing-Pointer Thermal study reveals that the grown crystal is stable up to 210 Degree-Sign C. Black-Right-Pointing-Pointer Multiple shot surface laser damage threshold is 0.30 GW/cm{sup 2} at 1064 nm laser radiation. -- Abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. The structural perfection of the grown p-TTS single crystal has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Fourier transform infrared spectral studies have been performed to identify the functional groups. The optical transmittance window and the lower cutoff wavelength of the grown crystals have been identified by UV-vis-IR studies. Birefringence of p-TTS crystal has been studied using channel spectrum measurement. The laser damage threshold value was measured using Nd:YAG laser. The second harmonic conversion efficiency of p-TTS has been determined using Kurtz powder technique. Thermo gravimetric and differential thermal analyses were used to study its thermal properties. Dielectric constant, dielectric loss and AC conductivity of the grown p-TTS single crystal has been studied.

Vijayakumar, P. [Centre for Crystal Growth, SSN College of Engineering, SSN Nagar, Tamilnadu 603110 (India)] [Centre for Crystal Growth, SSN College of Engineering, SSN Nagar, Tamilnadu 603110 (India); Anandha Babu, G., E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, SSN Nagar, Tamilnadu 603110 (India); Ramasamy, P. [Centre for Crystal Growth, SSN College of Engineering, SSN Nagar, Tamilnadu 603110 (India)] [Centre for Crystal Growth, SSN College of Engineering, SSN Nagar, Tamilnadu 603110 (India)

2012-04-15

357

Crystal growth furnace with trap doors  

NASA Technical Reports Server (NTRS)

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.

Sachs, Emanual M. (Inventor); Mackintosh, Brian H. (Inventor)

1982-01-01

358

Crystal growth furnace with trap doors  

DOEpatents

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.

Sachs, Emanual M. (Watertown, MA); Mackintosh, Brian H. (Lexington, MA)

1982-06-15

359

Czochralski growth of ?-BBO crystals under azimuthally anisotropic heating  

NASA Astrophysics Data System (ADS)

Crystal growth of ?-BBO in a modified low-gradient Czochralski furnace was performed. The distribution of temperature inside the furnace was described by a three-fold symmetry axis (L 3). The axial temperature gradient under the melt was ˜2 K/cm, while that inside the melt was almost equal to zero. A 36 mm thick sample of the grown crystal shows extremely low 0.05 cm -1 absorption coefficient at wavelengths >220 nm.

Kokh, Konstantin; Kokh, Alexander

2011-02-01

360

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, H. C.; Lagowski, J.

1980-01-01

361

Czochralski growth of ?-BBO crystals under azimuthally anisotropic heating  

Microsoft Academic Search

Crystal growth of ?-BBO in a modified low-gradient Czochralski furnace was performed. The distribution of temperature inside the furnace was described by a three-fold symmetry axis (L3). The axial temperature gradient under the melt was ?2K\\/cm, while that inside the melt was almost equal to zero. A 36mm thick sample of the grown crystal shows extremely low 0.05cm?1 absorption coefficient

Konstantin Kokh; Alexander Kokh

2011-01-01

362

Organo-thermal crystal growth of ?6 thiophene  

NASA Astrophysics Data System (ADS)

Organic solvents contained in sealed glass capsules in the temperature range 150-250°C can dissolve 0.5 to ˜ 18 wt% of moderate molecular weight organic oligomers often as much as 10-100 × previously reported solubility. We report solubilities of ?-hexathiophene (a promising thin film transistor material) as high as 18% and describe the growth of small crystals by slow cooling. This work suggests that previously recalcitrant organics may be grown as single crystals under "organo-thermal" conditions.

Laudise, R. A.; Bridenbaugh, P. M.; Kloc, Ch.; Jouppi, S. L.

1997-07-01

363

Fundamental Studies of Crystal Growth of Microporous Materials  

NASA Technical Reports Server (NTRS)

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.

Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

2002-01-01

364

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, H. C.; Lagowski, J.

1985-01-01

365

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, Harry C.; Lagowski, Jacek

1989-01-01

366

Rapid growth of ?-LiIO3 crystal  

NASA Astrophysics Data System (ADS)

A fundamental possibility of significantly increasing the growth rate of ?-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. ?-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.

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

2014-09-01

367

Numerical simulation of Cz crystal growth in rotating magnetic field with crystal and crucible rotations  

NASA Astrophysics Data System (ADS)

Three-dimensional numerical simulations were carried out to analyze the effect of crystal and crucible rotating directions on heat and oxygen transport in Czochralski crystal growth system under rotating magnetic field. A low-Reynolds number k-? model was used for the description of the turbulent processes. The computational results show that when rotations of crystal, melt and crucible are in the same direction, the oxygen concentration in the melt is the lowest and a low concentration crystal can be obtained. Under rotating magnetic field, the heat transport is dominated by lorentz force induced streaming field and the influence of crystal and crucible rotations on heat transport is weak. Moreover, the effect of crystal rotation on the melt turbulent flow and oxygen transport is stronger than that of crucible.

Zhou, Xiaoming; Huang, Hulin

2012-02-01

368

Crucibleless crystal growth and Radioluminescence study of calcium tungstate single crystal fiber  

NASA Astrophysics Data System (ADS)

In this article, single phase and high optical quality scheelite calcium tungstate single crystal fibers were grown by using the crucibleless laser heated pedestal growth technique. The as-synthesized calcium tungstate powders used for shaping seed and feed rods were investigated by X-ray diffraction technique. As-grown crystals were studied by Raman spectroscopy and Radioluminescence measurements. The results indicate that in both two cases, calcined powder and single crystal fiber, only the expected scheelite CaWO4 phase was observed. It was verified large homogeneity in the crystal composition, without the presence of secondary phases. The Radioluminescence spectra of the as-grown single crystal fibers are in agreement with that present in Literature for bulk single crystals, presented a single emission band centered at 420 nm when irradiated with ?-rays.

Silva, M. S.; Jesus, L. M.; Barbosa, L. B.; Ardila, D. R.; Andreeta, J. P.; Silva, R. S.

2014-11-01

369

A low temperature furnace for solution crystal growth on the International Space Station  

NASA Astrophysics Data System (ADS)

The Zeolite Crystal Growth Furnace Unit (ZCG-FU) is the first module in an integrated payload designed for low temperature crystal growth in solutions on the International Space Station (ISS). This payload is scheduled to fly on the ISS flight 7A.1 in an EXPRESS rack. Its name originated from early shuttle flight experiments limited to the growth of zeolite crystals but has since grown to include other materials of significant commercial interest using the solution method of crystal growth. Zeolites, ferroelectrics, piezeoelectrics and silver halides are some of the materials considered. The ZCG-FU experiment consists of a furnace unit and its electronic control system, and mechanically complex, crystal growth autoclaves suitable for use with a particular furnace and solution. The ZCG facility is being designed to grow into four independent furnaces controlled by IZECS (Improved Zeolite Electronic Control System). IZECS provides monitoring of critical parameters, data logging, safety monitoring, air-to-ground control and operator interfacing. It is suitable for controlling the four furnaces either individually or all at one time. It also contains the power management solid-state drivers and switches for the ZCG-FU furnace. The furnace contains 19 tubes operating at three different temperature zones. .

Baç, Nurcan; Harpster, Joseph; Maston, Robert A.; Sacco, Albert

2000-01-01

370

Adaptive temperature profile control of a multizone crystal growth furnace  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

371

Colloidal crystal growth at externally imposed nucleation clusters  

E-print Network

We study the conditions under which and how an imposed cluster of fixed colloidal particles at prescribed positions triggers crystal nucleation from a metastable colloidal fluid. Dynamical density functional theory of freezing and Brownian dynamics simulations are applied to a two-dimensional colloidal system with dipolar interactions. The externally imposed nucleation clusters involve colloidal particles either on a rhombic lattice or along two linear arrays separated by a gap. Crystal growth occurs after the peaks of the nucleation cluster have first relaxed to a cutout of the stable bulk crystal.

Sven van Teeffelen; Christos N. Likos; Hartmut Löwen

2008-02-15

372

Catalyzed growth of doped TGS single crystals for infrared applications  

NASA Astrophysics Data System (ADS)

Single crystals of triglycine sulphate (TGS) doped with Pr3+ Sm3+, Pd2+, Co2+, Pt4+ and PO43- with L-alanin were grown from aqueous solutions by means of the slow cooling method. Surface morphology, domain structure and P-E hysteresis loops have been investigated. The model of catalyzed growth of {001}and{101}crystal pyramids on the basis of metal-glycine complexes has been suggested. We have found on the basis of experimental results that TGS single crystals doped with Pt4+ and L-alanin are excellent materials for construction of infrared detectors.

Novotny, Jan; Zelinka, J.; Podvalova, Z.

2002-03-01

373

Modelling the growth of triglycine sulphate crystals in Spacelab 3  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

374

Zeolite crystal growth in space - What has been learned  

NASA Technical Reports Server (NTRS)

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.

Sacco, A., Jr.; Thompson, R. W.; Dixon, A. G.

1993-01-01

375

Growth and characterization of Cadmium Thiosemicarbazide Bromide crystals for antibacterial and nonlinear optical applications.  

PubMed

Semiorganic nonlinear optical crystals of Cadmium Thiosemicarbazide Bromide was grown by slow evaporation solution growth technique. The unit cell parameters were estimated by subjecting the crystals to single crystal X-ray diffraction. The grown crystals were subjected to Powder X-ray diffraction for analyzing the crystalline nature of the sample. FTIR studies reveal the functional groups and the optical characters were analyzed by UV-Vis spectral studies. Mechanical stability of the sample was assessed by Vicker's micro hardness test. The presence of surface dislocations was identified by chemical etching technique. Antibacterial study was carried out against ACDP declared harmful pathogens. SHG efficiency of CTSB crystal was tested using Nd: YAG laser and it was found to be ?1.8times that of potassium dihydrogen phosphate. PMID:25048404

Thomas Joseph Prakash, J; Martin Sam Gnanaraj, J

2015-01-25

376

Synthesis, growth and characterization of L-Phenylalanine-4-nitrophenol (LPNP) single crystal  

NASA Astrophysics Data System (ADS)

Single crystals of L-Phenylalanine-4-nitrophenol (LPNP) were synthesis and grown by slow cooling solution growth technique. The grown crystals have been subjected to various characterization techniques such as single crystal X-ray diffraction and Powder X-ray diffraction studies to confirm the lattice parameters. Transmittance of the grown crystals was analysed and optical band gap calculated to be 1.54 eV. Thermogravimetric analysis and differential thermal analysis showed that the compound decomposes beyond 170°C. Mechanical behavior of the grown LPNP crystal was analyzed by Vicker's microhardness test. The relative second harmonic efficiency of the compound is found to be 0.3 greater than that of KDP.

Rajalakshmi, M.; Indirajith, R.; Gopalakrishnan, R.

2012-06-01

377

Mechanics of instability-related delimination growth  

NASA Technical Reports Server (NTRS)

Local buckling of a delaminated group of plies can lead to higher interlaminar stresses and delamination growth. The mechanics of instability-related delamination growth (IRDG) had been described previously for the through-width delamination. This paper describes the mechanics of IRDG for the embedded delamination subjected to either uniaxial or axisymmetric loads. The mechanics of IRDG are used to explain the dramatic differences in strain-energy release rates observed for the through-width, the axisymmetrically loaded embedded delamination, and the uniaxially loaded embedded delamination.

Whitcomb, John D.

1988-01-01

378

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, H. C.; Lagowski, J.

1984-01-01

379

Interface stability and defect formation during crystal growth  

SciTech Connect

Unidirectional solidification experiments have been carried out in organic crystals with the aim of improving our knowledge on the effects of constraints on the interface morphology and to increase our understanding of the growth of anisotropic materials. The experimental information shows that lateral constraints such as a sharp change in the cross-sectional area in the solid liquid interface path, can produce important changes in the microstructure if the interface morphology is planar, cellular or dendritic. The study of anisotropic materials cover several topics. It is first shown that slight anisotropy does not influence the dendrite tip selection criterion. This conclusion is obtained from the analysis of the relationship between tip radius and velocity for dendrites growing under the steady state condition for two different materials, CBr{sub 4} and C{sub 2}Cl{sub 6}, which have different surface energy anisotropy values. The values of the dendrite operating parameters {sigma}* are compared with the predictions of the solvability theory and the morphological stability theory. The experiments show better agreement with the latter theory. Critical experiments have been designed and carried out to find the response functions which determine the composition and temperature of the interface as a function of velocity in faceted materials. The experiments, carried out in Napthalene-Camphor system, indicate a strong temperature dependence of the planar interface growth which can be correlated with the step growth mechanism. Experiments on the interface instability show an important dependence on the crystallographic orientation. Unidirectional solidification experiments in zone refined Napthalene confined in very thin cells (gap size {le} 50 {mu}m) have proven to be a good method to study the defect production at the solid liquid interface. 118 refs., 90 figs., 5 tabs.

Fabietti, L.M.R.

1991-01-08

380

Methane hydrate crystallization mechanism from in-situ particle sizing  

SciTech Connect

A new experimental setup that makes possible in-situ determinations of the population density function of the methane hydrate particles during its crystallization in a pressurized reactor is used. Thanks to this equipment, new results can be obtained, in particular concerning the granular aspects of the crystallization processes and the influence of the stirring rate. These results are discussed in the framework of a model including gas absorption, primary and secondary nucleation, crystal growth, agglomeration, and breakage. From this discussion, the relevant processes and parameters of methane hydrate crystallization can be determined and quantified.

Herri, J.M. [Ecole des Mines de Saint-Etienne (France)] [Ecole des Mines de Saint-Etienne (France); [Institut Francais du Petrole, Rueil-Malmaison (France); Pic, J.S.; Gruy, F.; Cournil, M. [Ecole des Mines de Saint-Etienne (France)] [Ecole des Mines de Saint-Etienne (France)

1999-03-01

381

Growth of large zeolite crystals in space  

NASA Technical Reports Server (NTRS)

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.

Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

1988-01-01

382

Unidirectional growth of Methyl 2-amino-5-bromobenzoate crystal by Sankaranarayanan-Ramasamy method and its characterization  

NASA Astrophysics Data System (ADS)

Bulk single crystal of Methyl 2-amino-5-bromobenzoate (M2A5B) nonlinear optical single crystal of size 60 mm length and 15 mm diameter was successfully grown from solution by Unidirectional growth method of Sankaranarayanan-Ramasamy (SR) for the first time in the literature. The growth conditions were optimized and the growth rate of 1.5 mm per day was observed for the SR grown crystal. The crystal system and its lattice parameters were confirmed by single crystal X-ray diffraction studies. The UV-vis transmission, Photoluminescence, Chemical Etching And Mechanical behavior of M2A5B were studied for conventional and SR methods grown crystals and compared. The second harmonic generation efficiency of M2A5B was confirmed by Kurtz-Perry powder method.

Parthasarathy, M.; Gopalakrishnan, R.

2013-06-01

383

Crystal Growth Simulations: a new Mathematical Model based on the Minkowski  

E-print Network

Crystal Growth Simulations: a new Mathematical Model based on the Minkowski Sum of Sets Alessandra. Realistic crystal growth simulators can give information on what would be the surface structure of a crystal the mother phase, that we assume to be gaseous, to the crystal (solid) phase. Specifically, Growth Units

Villa, Elena

384

Growth of High Quality A N Single Crystals and Their Optical Properties  

E-print Network

Growth of High Quality A N Single Crystals and Their Optical Properties M. strassburgl, J a two-step growth process in a TaN crucible. Crystal defects and the effect of incorporated impurities,2,3]. Hence, the growth and crystal quality opiimhtion of buk AiN crystals is of primary importance

Nabben, Reinhard

385

Modelling of 3D Melt Flow in Czochralski Crystal Growth Petr Knobloch 1 and Lutz Tobiska  

E-print Network

Modelling of 3D Melt Flow in Czochralski Crystal Growth Petr Knobloch 1 and Lutz Tobiska Otto to the crystal growth velocity and maintain the melt free surface in a constant position. The crystal growth]) is the mostly used technique for producing semiconductor single crystals, the most important of which

Knobloch, Petr

386

Effects of substrate crystallographic orientations on crystal growth and microstructure development in laser  

E-print Network

Effects of substrate crystallographic orientations on crystal growth and microstructure development in laser surface-melted superalloy single crystals. Mathematical modeling of single-crystal growth that the substrate orientation has a predominant effect on crystal growth pattern, and simultaneously influences

DuPont, John N.

387

Self-Organized Growth of Complex Nanotube Patterns on Crystal Surfaces  

E-print Network

Self-Organized Growth of Complex Nanotube Patterns on Crystal Surfaces Ernesto Joselevich-organized growth directed by well-defined crystal surfaces, or "nanotube epitaxy". We identify three different to "nanotube epitaxy" Epitaxy generally refers to the "growth of a crystal of one material on the crystal base

Joselevich, Ernesto

388

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Lagowski, J.

1981-01-01

389

Visual Simulation of Ice Crystal Growth  

Microsoft Academic Search

The beautiful, branching structure of ice is one of the most striking visual phenomena of the winter landscape. Yet there is little study about modeling this effect in computer graphics. In this paper, we present a novel approach for visual simulation of ice growth. We use a numerical simulation technique from computational physics, the \\

Theodore Kim; Ming C. Lin

2003-01-01

390

A framework for optimization of crystal growth processes applied to VGF growth of fluorides  

NASA Astrophysics Data System (ADS)

We develop a flexible framework for optimization of crystal growth processes. This framework is based on an accurate and robust process model and combines two optimization loops. Adapting of model parameters and optimizing of process parameters.

Backofen, Rainer; Voigt, Axel; Wulff-Molder, Dirk

2005-02-01

391

Lattice Boltzmann Simulation of Isotope Kinetics in Crystal Growth  

NASA Astrophysics Data System (ADS)

There is useful information that comes from isotopic variations resulting from micro-scale processes in the formation of methane hydrate, ice and mineral crystals. Most previous work on isotopic effects resulting from phase changes has used continuum models. This study is aimed at the development of computational tools using the lattice Boltzmann (LB) method to simulate isotopic fractionation during evaporation, condensation and crystal growth. The model relates isotopic fractionation to the chemical saturation state of the growth medium, fluid flow, diffusion and reaction associated with the phase transformations. The effect of reaction relative to that of diffusion is described with a Damkohler number, Da = kr h/D, where kr is the local reaction-rate constant, h is the length dimension of the model domain, and D is the diffusivity. The parameter values are chosen to represent realistic values in natural environments. At low Damkohler numbers, compact "crystals" are formed whereas at high Da, dendritic crystals form. The fractal dimensions of the grown crystals are computed. In situations where molecular isotopomers have different diffusion coefficients, the resultant isotopic ratios of the crystals differ strongly from the equilibrium values when Da values are high and less when Da values are low. The isotopic fractionation can be directly related to crystal morphology, saturation state, and fluid flow. LB simulation provides a novel alternative method to evaluate isotopic kinetics in natural systems, and may be particularly useful for better understanding isotopic effects associated with microphysical processes such as vapor depositional growth of ice crystals in clouds and chemical reactions on atmospheric aerosols.

Lu, G.; Depaolo, D. J.; Kang, Q.; Zhang, D.

2005-12-01

392

Journal of Crystal Growth 281 (2005) 364369 Flux growth and characterization of lead-free piezoelectric  

E-print Network

-free piezoelectric single crystal [Bi0.5(Na1Ã?xKx)0.5]TiO3 Xiujie Yia,b , Huanchu Chena,Ã?, Wenwu Caoc , Minglei Zhaod Available online 13 June 2005 Communicated by M. Schieber Abstract Lead-free piezoelectric single crystal melting during growth. Superior piezoelectric and electromechanical properties were found in these lead

Cao, Wenwu

393

Crystal growth of device quality GaAs in space  

NASA Technical Reports Server (NTRS)

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.

Gatos, H. C.; Lagowski, J.

1986-01-01

394

2D modeling of the regeneration surface growth on crystals  

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

395

Dislocation Elimination in Czochralski Silicon Crystal Growth Revealed by White X-ray Topography Combined with Topo-tomographic Technique  

Microsoft Academic Search

We have examined the neck of a large-diameter [001]-oriented Czochralski silicon crystal by synchrotron white X-ray topography combined with a topo-tomographic technique in order to explain the mechanism of dislocation elimination due to Dash necking in industrial-scale crystal growth. In the portion where the grown crystal was transformed from a dislocated region to a dislocation-free region, dislocation half loops were

Seiji Kawado; Satoshi Iida; Kentaro Kajiwara; Yoshifumi Suzuki; Yoshinori Chikaura

2007-01-01

396

Chiral Symmetry Breaking in Crystal Growth: Is Hydrodynamic Convection Relevant?  

NASA Technical Reports Server (NTRS)

The effects of mechanical stirring on nucleation and chiral symmetry breaking have been investigated for a simple inorganic molecule, sodium chlorate (NaClO3). In contrast to earlier findings, our experiment suggests that the symmetry breaking may have little to do with hydrodynamic convection. Rather the effect can be reasonably accounted for by mechanical damage to incipient crystals. The catastrophic events, creating numerous small 'secondary' crystals, produce statistical domination of one chiral species over the other. Our conclusion is supported by a number of observations using different mixing mechanisms.

Martin, B.; Tharrington, A.; Wu, Xiao-Lun

1996-01-01

397

Numerical Modeling of Physical Vapor Transport in Contactless Crystal Growth Geometry  

NASA Technical Reports Server (NTRS)

Growth from the vapor under conditions of limited contact with the walls of the growth ampoule is beneficial for the quality of the growing crystal due to reduced stress and contamination which may be caused by interactions with the growth container. The technique may be of a particular interest for studies on crystal growth under microgravity conditions: elimination of some factors affecting the crystal quality may make interpretation of space-conducted processes more conclusive and meaningful. For that reason, and as a part of our continuing studies on 'contactless' growth technique, we have developed a computational model of crystal growth process in such system. The theoretical model was built, and simulations were performed using the commercial computational fluid dynamics code, (CFD) ACE. The code uses an implicit finite volume formulation with a gray discrete ordinate method radiation model which accounts for the diffuse absorption and reflection of radiation throughout the furnace. The three-dimensional model computes the heat transfer through the crystal, quartz, and gas both inside and outside the ampoule, and mass transport from the source to the crystal and the sink. The heat transport mechanisms by conduction, natural convection, and radiation, and mass transport by diffusion and convection are modeled simultaneously and include the heat of the phase transition at the solid-vapor interfaces. As the thermal boundary condition, temperature profile along the walls of the furnace is used. For different thermal profiles and furnace and ampoule dimensions, the crystal growth rate and development of the crystal-vapor and source-vapor interfaces (change of the interface shape and location with time) are obtained. Super/under-saturation in the ampoule is determined and critical factors determining the 'contactless' growth conditions are identified and discussed. The relative importance of the ampoule dimensions and geometry, the furnace dimensions and its temperature, and the properties of the grown material are analyzed. The results of the simulations are compared with related experimental results on growth of CdTe, CdZnTe, ZnTe, PbTe, and PbSnTe crystals by this technique.

Palosz, W.; Lowry, S.; Krishnam, A.; Przekwas, A.; Grasza, K.

1998-01-01

398

Kinetics of Crystal Growth From Silicate Melts: Anorthite and Diopside  

Microsoft Academic Search

Rates of linear crystal growth have been measured for diopside and anorthite growing from their own melts by using a microscope heating stage. Rates were obtained for undercoolings of as little as 13øC. The rates are higher for diopside than for anorthite. Maximum growth rates observed are 1.5 X 10 -' cm\\/s (AT = 194øC) for anorthite and 2.2 X

R. James Kirkpatrick; Gilpin R. Robinson; James Fred Hays

1976-01-01

399

Fabrication of whispering gallery mode cavity using crystal growth  

E-print Network

We developed a new method for fabricating crystalline whispering gallery mode cavities based on laser-heated pedestal growth. We fabricated sapphire cavities and obtained a Q factor of 16000 with a cavity whose diameter was about 240 um. We showed numerically that the cross-sectional shape of the cavity is sensitive to the cavity Q, and we controlled it successfully by changing the growth condition in the molten zone, without significantly degrading the crystal structure.

Kudo, Hiroshi; Kato, Takumi; Yokoo, Atsushi; Tanabe, Takasumi

2013-01-01

400

Growth and properties of benzil doped benzimidazole (BMZ) single crystals  

SciTech Connect

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Sukumar, M. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India) [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Shakir, Mohd. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Bhagavannarayana, G. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)

2010-09-15

401

Solid state growth mechanisms for carbon nanotubes  

Microsoft Academic Search

The mechanisms by which carbon nanotubes nucleate and grow remain poorly understood. This paper reviews the models which have been proposed to explain nanotube growth in the arc-evaporation and laser-vaporisation processes. Many of the early models assumed that growth is a gas phase phenomenon but there is growing experimental evidence that the formation of both multiwalled and single-walled tubes involves

Peter J. F. Harris; J. J. Thomson

2007-01-01

402

Mechanisms That Determine the Electronic Dielectric Constants of Ionic Crystals  

Microsoft Academic Search

The very old and widely accepted theory for the electronic dielectric constants of ionic crystals assumes that intra-ionic excitations dominate in the crystal whereby polarizabilities of individual ions may be identified and tabulated. It is shown here that this assumption is unfounded and leads to inconsistencies and unphysical results. In turn I present theoretical and experimental evidence that the mechanism

Sokrates T. Pantelides

1975-01-01

403

Mechanical characterization of ibuprofen, naproxen, and their spherically crystallized products  

Microsoft Academic Search

The objectives of this study were to establish a rational basis for choosing parameters for conducting the tensile strength and indentation hardness test on pharmaceutical compacts, to describe the changes in tableting indices based on the different parameters, to develop a method to spherically crystallize ibuprofen, and to compare the mechanical and micromeritic properties of spherically crystallized ibuprofen and naproxen

Stephen R. Anderson

1997-01-01

404

Band gaps in phononic crystals: Generation mechanisms and interaction effects  

E-print Network

generation and detection in microstructure devices Rev. Sci. Instrum. 82, 104905 (2011) Interpillar phononicsBand gaps in phononic crystals: Generation mechanisms and interaction effects C. Croënne, E. J. S band structure in a two-dimensional phononic crystal plate J. Appl. Phys. 110, 123503 (2011) Phonon

Page, John

405

Crystal growth in porous materials—I: The crystallization pressure of large crystals  

Microsoft Academic Search

A critical review of the existing literature on the pressure exerted by growing crystals in porous materials reveals that a number of different equations are in use. A derivation of an equation for the crystallization pressure based on the chemical potentials of the loaded and the unloaded faces of a growing crystal is provided. The equation obtained is compared to

Michael Steiger

2005-01-01

406

Growth of paratellurite crystals: effect of axial temperature gradient on the quality of the crystals  

Microsoft Academic Search

Paratellurite (TeO2) crystals have been grown under different temperature gradients (10–15, 15–20, 20–25 and 50–60°C\\/cm) employing resistive and induction heating systems. The growth parameters were optimized for each gradient range to harvest good quality crystals. The problems of constitutional supercooling and cracking were avoided by employing suitable rotation and pulling rates. The effect of melt depth in the crucible on

S. Kumaragurubaran; D Krishnamurthy; C Subramanian; P Ramasamy

2000-01-01

407

Protein crystal growth in microgravity: Temperature induced large scale crystallization of insulin  

NASA Technical Reports Server (NTRS)

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.

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

408

Research Progress on Growth of UV Nonlinear Optical Borate Crystals.  

National Technical Information Service (NTIS)

In this paper, a description of research advance on the growth of some important uv nonlinear optical crystals, such as BBO LBO and KBBF etc., which were first invented and developed by our institute during the past decade is given. The review consists of...

T. Dingyuan

1996-01-01

409

Nucleation, crystal growth and the thermal regime of cooling magmas  

Microsoft Academic Search

Crystallization at the margin of a quiet cooling magma has been studied numerically, taking into account the kinetics of crystalligation. The variables are the latent heat value, the growth and nucleation functions, the initial magma temperature, and the thermal contrast between magma and country rock. We have investigated a wide range of values for these parameters corresponding to natural conditions.

Geneviéve Brandeis; Claude Jaupart; Claude J. Allégre

1984-01-01

410

Modeling snow crystal growth III: three-dimensional snowfakes  

E-print Network

We introduce a three-dimensional, computationally feasible, mesoscopic model for snow crystal growth, based on diffusion of vapor, anisotropic attachment, and a semi-liquid boundary layer. Several case studies are presented that faithfully emulate a wide variety of physical snowflakes.

Janko Gravner; David Griffeath

2007-11-26

411

Transient natural convection heat and mass transfer in crystal growth  

NASA Technical Reports Server (NTRS)

A numerical analysis of transient combined heat and mass transfer across a rectangular cavity is performed. The physical parameters are selected to represent a range of possible crystal growth in solutions. Good agreements with measurement data are observed. It is found that the thermal and solute fields become highly oscillatory when the thermal and solute Grashof numbers are large.

Han, Samuel S.

1990-01-01

412

Application of heat pipe technology to crystal growth  

NASA Astrophysics Data System (ADS)

Heat pipes are highly efficient heat exchangers with effective thermal conductivities several orders of magnitude higher than those of the best metallic conductors. The principle, design and construction of heat pipes are discussed together with specific examples of applications to crystal growth for heat transfer and to obtain isothermal and multizone temperature profiles.

Steininger, Jacques; Reed, Thomas B.

1972-05-01

413

Morphological stability and fluid dynamics of vapor crystal growth  

NASA Technical Reports Server (NTRS)

Research on morphological stability and fluid dynamics of crystal growth is discussed. Interfacial heat and mass transfer research is discussed. The finding of surface roughening is a precursor to a solid-solid phase transition was further quantified. Progress was obtained with the mass spectroscopic characterization of GeSe-Ge I sub 4.

Rosenberger, F. E.

1984-01-01

414

Crewmember working on the spacelab Zeolite Crystal Growth experiment.  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

415

Crewmember working on the mid deck Zeolite Crystal Growth experiment.  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

416

Bacteria can promote calcium oxalate crystal growth and aggregation.  

PubMed

Our previous report showed that uropathogenic bacteria, e.g., Escherichia coli, are commonly found inside the nidus of calcium oxalate (CaOx) kidney stones and may play pivotal roles in stone genesis. The present study aimed to prove this new hypothesis by direct examining CaOx lithogenic activities of both Gram-negative and Gram-positive bacteria. CaOx was crystallized in the absence (blank control) or presence of 10(5) CFU/ml E. coli, Klebsiella pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae. Fragmented red blood cell membranes and intact red blood cells were used as positive and negative controls, respectively. The crystal area and the number of aggregates were measured to initially screen for effects of bacteria on CaOx crystal growth and aggregation. The data revealed that all the bacteria tested dramatically increased the crystal area and number of crystal aggregates. Validation assays (spectrophotometric oxalate-depletion assay and an aggregation-sedimentation study) confirmed their promoting effects on both growth (20.17 ± 3.42, 17.55 ± 2.27, 16.37 ± 1.38, and 21.87 ± 0.85 % increase, respectively) and aggregation (57.45 ± 2.08, 51.06 ± 5.51, 55.32 ± 2.08, and 46.81 ± 3.61 % increase, respectively) of CaOx crystals. Also, these bacteria significantly enlarged CaOx aggregates, with the diameter greater than the luminal size of distal tubules, implying that tubular occlusion might occur. Moreover, these bacterial effects were dose-dependent and specific to intact viable bacteria, not intact dead or fragmented bacteria. In summary, intact viable E. coli, K. pneumoniae, S. aureus, and S. pneumoniae had significant promoting effects on CaOx crystal growth and aggregation. This functional evidence supported the hypothesis that various types of bacteria can induce or aggravate metabolic stone disease, particularly the CaOx type. PMID:23334195

Chutipongtanate, Somchai; Sutthimethakorn, Suchitra; Chiangjong, Wararat; Thongboonkerd, Visith

2013-03-01

417

Czochralski growth of heavily tin-doped Si crystals  

NASA Astrophysics Data System (ADS)

Heavily tin (Sn)-doped Si crystals in a concentration up to 4×1019 cm-3 were grown by the Czochralski method. Variation of Sn concentration in the crystals was well expressed by the Pfann equation using a segregation coefficient of k=0.016. From the occurrence of growth interface instability and the appearance of Sn precipitates in the grown crystals, the solubility limit of Sn was considered to be around 5×1019 cm-3. Interstitially dissolved oxygen Oi was presented at a concentration of 8-9×1017 cm-3 in the grown Sn-doped crystals. The FT-IR absorption peak relating to a Si-Oi-Si quasi-molecule at 1106 cm-1 showed preferential occupation of Oi at the bond-centered position of Si-Si. The Oi peak shifted to the lower wave number side with increasing Sn concentration in Si, implying expansion of the Si-Si bond.

Yonenaga, I.; Taishi, T.; Inoue, K.; Gotoh, R.; Kutsukake, K.; Tokumoto, Y.; Ohno, Y.

2014-06-01

418

Crystal nucleation and near-epitaxial growth in nacre  

E-print Network

Nacre, the iridescent inner lining of many mollusk shells, interests materials scientists because of its unique brick-and-mortar periodic structure at the sub-micron scale and its remarkable resistance to fracture. However, it remains unclear how nacre forms. Here we present 20-nm, 2{\\deg}-resolution Polarization-dependent Imaging Contrast (PIC) images of shells from 15 species, mapping nacre tablets and their orientation patterns, showing where crystals nucleate and how they grow in nacre. In all shells we found stacks of co-oriented aragonite (CaCO3) tablets arranged into vertical columns or staggered diagonally. Only near the nacre-prismatic boundary are disordered crystals nucleated, as spherulitic aragonite. Overgrowing nacre tablet crystals are most frequently co-oriented with the underlying spherulitic aragonite or with another tablet, connected by mineral bridges. Therefore aragonite crystal growth in nacre is epitaxial or near-epitaxial, with abrupt or gradual changes in orientation, with c-axes with...

Olson, Ian C; Tamura, Nobumichi; Kunz, Martin; Gilbert, Pupa U P A

2013-01-01

419

Aluminium segregation of TiAl during single crystal growth  

SciTech Connect

{gamma}-TiAl single crystals have been successfully prepared by an induction-heated cold crucible Czochralski technique which offers more flexibility than vertical float zoning. Compositional analysis of the Czochralski grown single crystals indicates a homogeneous composition after initial transition; and the average composition is close to the peritectic composition. However, {gamma}-TiAl single crystals prepared by vertical float zoning show a small aluminium segregation profile along the growth direction; and the average composition of the as-grown crystals is close to that of the starting alloy. Compositional analysis further demonstrated the banded structure with alternative single {gamma}-phase and {alpha}{sub 2} + {gamma} lamellar regions in the vertical float zoned Ti-54 at.% Al.

Bi, Y.J.; Abell, J.S. [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials] [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials

1997-09-15

420

Growth and characterization of rare earths doped triglycine sulfate crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in values of dielectric constant and pyroelectric coefficient is observed while the dielectric loss has increased. Using these parameters, figure-of-merits for their use in infrared sensors have also been reported and compared with pure TGS crystal. The Vickers's hardness of doped TGS crystals along (0 1 0) crystallographic face has increased.

Batra, A. K.; Guggilla, Padmaja; Cunningham, Dewanna; Aggarwal, M. D.; Lal, R. B.

2006-01-01

421

Applications of Mechanical Vapor Recompression to Evaporation and Crystallization  

E-print Network

Over the past 10-15 years, mechanical vapor recompression (MVR) has become the preferred system in many industrial evaporation and crystallization applications, because of its economy and simplicity of operation. In most instances, the need...

Outland, J. S.

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