Sample records for rapid crystal growth

  1. Computer simulation of rapid crystal growth under microgravity (United States)

    Hisada, Yasuhiro; Saito, Osami; Mitachi, Koshi; Nishinaga, Tatau

    We are planning to grow a Ge single crystal under microgravity by the TR-IA rocket in 1992. The furnace temperature should be controlled so as to finish the crystal growth in a quite short time interval (about 6 min). This study deals with the computer simulation of rapid crystal growth in space to find the proper conditions for the experiment. The crystal growth process is influenced by various physical phenomena such as heat conduction, natural and Marangoni convections, phase change, and radiation from the furnace. In this study, a 2D simulation with axial symmetry is carried out, taking into account the radiation field with a specific temperature distribution of the furnace wall. The simulation program consists of four modules. The first module is applied for the calculation of the parabolic partial differential equation by using the control volume method. The second one evaluates implicitly the phase change by the enthalpy method. The third one is for computing the heat flux from surface by radiation. The last one is for calculating with the Monte Carlo method the view factors which are necessary to obtain the heat flux.

  2. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail:; Patki, Mugdha, E-mail: [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)


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

  3. Blocking rapid ice crystal growth through nonbasal plane adsorption of antifreeze proteins. (United States)

    Olijve, Luuk L C; Meister, Konrad; DeVries, Arthur L; Duman, John G; Guo, Shuaiqi; Bakker, Huib J; Voets, Ilja K


    Antifreeze proteins (AFPs) are a unique class of proteins that bind to growing ice crystal surfaces and arrest further ice growth. AFPs have gained a large interest for their use in antifreeze formulations for water-based materials, such as foods, waterborne paints, and organ transplants. Instead of commonly used colligative antifreezes such as salts and alcohols, the advantage of using AFPs as an additive is that they do not alter the physicochemical properties of the water-based material. Here, we report the first comprehensive evaluation of thermal hysteresis (TH) and ice recrystallization inhibition (IRI) activity of all major classes of AFPs using cryoscopy, sonocrystallization, and recrystallization assays. The results show that TH activities determined by cryoscopy and sonocrystallization differ markedly, and that TH and IRI activities are not correlated. The absence of a distinct correlation in antifreeze activity points to a mechanistic difference in ice growth inhibition by the different classes of AFPs: blocking fast ice growth requires rapid nonbasal plane adsorption, whereas basal plane adsorption is only relevant at long annealing times and at small undercooling. These findings clearly demonstrate that biomimetic analogs of antifreeze (glyco)proteins should be tailored to the specific requirements of the targeted application.

  4. Measurements of crystal growth kinetics at extreme deviations from equilibrium. [Rapid solidification processing

    Energy Technology Data Exchange (ETDEWEB)

    Aziz, M.J.


    We have measured solute trapping of Sn in Al over a wide enough range of velocities to make a quantitative test of theory. The Continuous Growth Model of Aziz is the only one-parameter model that fits the data. We have also measured the diffusive speed - the growth rate at which interfacial partitioning is in mid-transition between equilibrium partitioning and complete solute trapping - for several solutes in A1. We have found an inverse correlation between the equilibrium partition coefficient and the diffusive speed. Taken together, these results give us heretofore unprecedented predictive capability in modeling rapid solidification processing. We have also examined theoretically short-range diffusion-limited growth, characteristic of incomplete solute trapping, and interface-limited growth, characteristic of complete solute trapping, in alloy solidification and have shown that the two regimes fall naturally out of a single unified theory of solidification.

  5. Quartz crystal growth (United States)

    Baughman, Richard J.


    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 C. stepwise with a .DELTA.T of C., increasing the .DELTA.T to about C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  6. Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growth

    KAUST Repository

    Saidaminov, Makhsud I.


    Here we show the retrograde solubility of various hybrid perovskites through the correct choice of solvent(s) and report their solubility curves. Retrograde solubility enables to develop inverse temperature crystallization of FAPbX3 (FA = HC(NH2)2+, X = Br−/I−). FAPbI3 crystals exhibit a 1.4 eV bandgap – considerably narrower than their polycrystalline counterparts.

  7. Electronic crystal growth (United States)

    Sato, T.; Miyagawa, K.; Kanoda, K.


    Interacting atoms or molecules condense into liquid, and, when cooled further, they form a crystal. The time evolution of the atomic or molecular ordering has been widely studied as a nonequilibrium emergence of order from a supercooled liquid or a glass. Interacting electrons in a variety of correlated electron systems also form crystals, but observing the time evolution of electronic crystallization has been experimentally challenging. Here, working with an organic conductor exhibiting a supercooled charge liquid or charge glass as a metastable state, we observed electronic crystal growth through resistivity and nuclear magnetic resonance measurements. The temperature profile of the crystal growth is similar to those observed in classical systems and reveals two distinct regimes for the mechanism of electronic crystallization.

  8. Determination of crystal growth rates during rapid solidification of polycrystalline aluminum by nano-scale spatio-temporal resolution in situ transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zweiacker, K., E-mail:; Liu, C.; Wiezorek, J. M. K. [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 648 Benedum Hall, 3700 OHara Street, Pittsburgh, Pennsylvania 15261 (United States); McKeown, J. T.; LaGrange, T.; Reed, B. W.; Campbell, G. H. [Materials Science Division, Physical and Life Science Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94551 (United States)


    In situ investigations of rapid solidification in polycrystalline Al thin films were conducted using nano-scale spatio-temporal resolution dynamic transmission electron microscopy. Differences in crystal growth rates and asymmetries in melt pool development were observed as the heat extraction geometry was varied by controlling the proximity of the laser-pulse irradiation and the associated induced melt pools to the edge of the transmission electron microscopy support grid, which acts as a large heat sink. Experimental parameters have been established to maximize the reproducibility of the material response to the laser-pulse-related heating and to ensure that observations of the dynamical behavior of the metal are free from artifacts, leading to accurate interpretations and quantifiable measurements with improved precision. Interface migration rate measurements revealed solidification velocities that increased consistently from ∼1.3 m s{sup −1} to ∼2.5 m s{sup −1} during the rapid solidification process of the Al thin films. Under the influence of an additional large heat sink, increased crystal growth rates as high as 3.3 m s{sup −1} have been measured. The in situ experiments also provided evidence for development of a partially melted, two-phase region prior to the onset of rapid solidification facilitated crystal growth. Using the experimental observations and associated measurements as benchmarks, finite-element modeling based calculations of the melt pool evolution after pulsed laser irradiation have been performed to obtain estimates of the temperature evolution in the thin films.

  9. The growth of high density network of MOF nano-crystals across macroporous metal substrates - Solvothermal synthesis versus rapid thermal deposition (United States)

    Maina, James W.; Gonzalo, Cristina Pozo; Merenda, Andrea; Kong, Lingxue; Schütz, Jürg A.; Dumée, Ludovic F.


    Fabrication of metal organic framework (MOF) films and membranes across macro-porous metal substrates is extremely challenging, due to the large pore sizes across the substrates, poor wettability, and the lack of sufficient reactive functional groups on the surface, which prevent high density nucleation of MOF crystals. Herein, macroporous stainless steel substrates (pore size 44 × 40 μm) are functionalized with amine functional groups, and the growth of ZIF-8 crystals investigated through both solvothermal synthesis and rapid thermal deposition (RTD), to assess the role of synthesis routes in the resultant membranes microstructure, and subsequently their performance. Although a high density of well interconnected MOF crystals was observed across the modified substrates following both techniques, RTD was found to be a much more efficient route, yielding high quality membranes under 1 h, as opposed to the 24 h required for solvothermal synthesis. The RTD membranes also exhibited high gas permeance, with He permeance of up to 2.954 ± 0.119 × 10-6 mol m-2 s-1 Pa-1, and Knudsen selectivities for He/N2, Ar/N2 and CO2/N2, suggesting the membranes were almost defect free. This work opens up route for efficient fabrication of MOF films and membranes across macro-porous metal supports, with potential application in electrically mediated separation applications.

  10. Springer Handbook of Crystal Growth

    CERN Document Server

    Dhanaraj, Govindhan; Prasad, Vishwanath; Dudley, Michael


    Over the years, many successful attempts have been made to describe the art and science of crystal growth. Most modern advances in semiconductor and optical devices would not have been possible without the development of many elemental, binary, ternary, and other compound crystals of varying properties and large sizes. The objective of the Springer Handbook of Crystal Growth is to present state-of-the-art knowledge of both bulk and thin-film crystal growth. The goal is to make readers understand the basics of the commonly employed growth processes, materials produced, and defects generated. Almost 100 leading scientists, researchers, and engineers from 22 different countries from academia and industry have been selected to write chapters on the topics of their expertise. They have written 52 chapters on the fundamentals of bulk crystal growth from the melt, solution, and vapor, epitaxial growth, modeling of growth processes and defects, techniques of defect characterization as well as some contemporary specia...

  11. Problems of rapid growth. (United States)

    Kim, T D


    South Korea's export-oriented development strategy has achieved a remarkable growth record, but it has also brought 2 different problems: 1) since the country's exports accounted for about 1% of total world export volume, the 1st world has become fearful about Korea's aggressive export drive; and 2) the fact that exports account for over 30% of its total gross national product (GNP) exposes the vulnerability of South Korea's economy itself. South Korea continues to be a poor nation, although it is rated as 1 of the most rapidly growing middle income economies. A World Bank 1978 report shows Korea to be 28th of 58 middle income countries in terms of per capita GNP in 1976. Of 11 newly industrializing countries (NIC), 5 in the European continent are more advanced than the others. A recent emphasis on the basic human needs approach has tended to downgrade the concept of GNP. Korea has only an abundant labor force and is without any natural resources. Consequently, Korea utilized an export-oriented development strategy. Oil requirements are met with imports, and almost all raw materials to be processed into exportable products must be imported. To pay import bills Korea must export and earn foreign exchange. It must be emphasized that foreign trade must always be 2-way traffic. In order to export more to middle income countries like Korea, the countries of the 1st world need to ease their protectionist measures against imports from developing countries.

  12. Automated protein crystal growth facility (United States)

    Donald, Stacey

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

  13. China urges rapid growth

    Energy Technology Data Exchange (ETDEWEB)

    Hendry, S.


    This time last year China's paramount leader, Deng Xiaoping, launched the country on another bout of fast-paced economic growth and restructuring. After three years of riding out political and economic clampdown, foreign chemical companies were jerked awake by major changes in China's chemical industry. As the state becomes less involved with managing the economy, unleashing 12% gross national product growth, closer involvement with domestic factories has become attractive and essential. MCI officials say government funds will now be channeled toward clearing energy and transport bottlenecks, and chemical enterprises will be given more chance to turn a profit. They will be allowed to issue shares, seek foreign investment partners themselves, and bypass trading companies like China National Import-Export Corp. (Sinochem), the former state monopoly. Foreign analysts question whether China's finances and oil resources can support expansion. Even if they can, Cai estimates that ethylene imports will remain around the present level of 1 million tons. To further guarantee chemical supplies, China has invested in urea and polypropylene plants in the US and polystyrene plant in Hong Kong.

  14. Crystal growth of drug materials by spherical crystallization (United States)

    Szabó-Révész, P.; Hasznos-Nezdei, M.; Farkas, B.; Göcző, H.; Pintye-Hódi, K.; Erős, I.


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

  15. Phase diagrams and crystal growth (United States)

    Venkrbec, Jan


    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.

  16. Zeolite crystal growth in space (United States)

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


    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.

  17. Introduction to crystal growth and characterization

    CERN Document Server

    Benz, Klaus-Werner


    This new textbook provides for the first time a comprehensive treatment of the basics of contemporary crystallography and crystal growth in a single volume. The reader will be familiarized with the concepts for the description of morphological and structural symmetry of crystals. The architecture of crystal structures of selected inorganic and molecular crystals is illustrated. The main crystallographic databases as data sources of crystal structures are described. Nucleation processes, their kinetics and main growth mechanism will be introduced in fundamentals of crystal growth. Some phase d

  18. Measurements of Protein Crystal Face Growth Rates (United States)

    Gorti, S.


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

  19. Economic analysis of crystal growth in space (United States)

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


    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.

  20. Optical diagnostics of solution crystal growth (United States)

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


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

  1. Crystal growth of nanoscaled europium selenide having characteristic crystal shapes

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Atsushi; Adachi, Taka-aki [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Hasegawa, Yasuchika, E-mail: hasegawa@ms.naist.j [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Kawai, Tsuyoshi [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)


    Tetrapod-shaped EuSe nanocrystals were prepared through the thermal reduction of europium chloride an organic selenide complex, n-hexadecylamine, and two additives oleic acid and oleylamine. The obtained EuSe nanoparticles were characterized by X-ray diffraction (XRD). The crystal grain size from the XRD spectrum was estimated to be 50 nm. In contrast, observation of the transmission electron microscope (TEM) gave larger sized EuSe (average size: 200 nm). Anisotropic crystal-growth of EuSe nanocrystals was achieved by addition of a small amount of oleic acid in the crystal growth process.

  2. Microscopic kinetic model for polymer crystal growth (United States)

    Hu, Wenbing


    Linear crystal growth rates characterize the net result of competition between growth and melting at the liquid-solid interfaces. The rate equation for polymer crystal growth can be derived with a barrier term for crystal growth and with a driving force term of excess lamellar thickness, provided that growth and melting share the same rate-determining steps at the growth front. Such an ansatz can be verified by the kinetic symmetry between growth and melting around the melting point of lamellar crystals, as made in our recent dynamic Monte Carlo simulations. The profile of the growth/melting front appears as wedge-shaped, with the free energy barrier for intramolecular secondary crystal nucleation at its top, and with the driving force gained via instant thickening at its bottom. Such a scenario explains unique phenomena on polymer crystal growth, such as chain folding, regime transitions, molecular segregation of polydisperse polymers, self-poisoning with integer-number chain-folding of short chains, and colligative growth rates of binary mixtures of two chain lengths. Financial support from NNSFC No. 20825415 and NBRPC No. 2011CB606100 is acknowledged.

  3. Growth of single crystals of BaFe12O19 by solid state crystal growth (United States)

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


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

  4. A Genetic Analysis of Crystal Growth

    DEFF Research Database (Denmark)

    Brown, Stanley; Sarikaya, Mehmet; Johnson, E.


    growth. We have used the crystallization of gold as a model system and found polypeptides that control the morphology of the resulting gold crystals. Analysis of the crystallization process influenced by these polypeptides indicates they act catalytically by an acid mechanism. Our results suggest......The regulation of crystal morphology by proteins is often observed in biology. It is a central feature in the formation of hard tissues such as bones, teeth and mollusc shells. We have developed a genetic system in the bacterium Escherichia coli to study the protein-mediated control of crystal...

  5. Protein crystal growth (5-IML-1) (United States)

    Bugg, Charles E.


    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.

  6. Technology of gallium nitride crystal growth

    CERN Document Server

    Ehrentraut, Dirk; Bockowski, Michal


    This book deals with the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production. Leading experts from industry and academia report in a very comprehensive way on the current state-of-the-art of the growth technologies and optical and structural properties of the GaN crystals are compared.

  7. Experimental setup for rapid crystallization using favoured chemical ...

    Indian Academy of Sciences (India)

    The rapid crystallization of KH2PO4 (KDP) from solution is demonstrated at a rate up to ≈7.5 mm/day along [100] and 22 mm/day along [001] in a crystallizer of 5 l capacity, using accelerated crucible rotation technique (ACRT) and simulated platform geometry for controlling the hydrodynamic conditions. On an experimental ...

  8. Crystal Growth Behaviors of Silicon during Melt Growth Processes

    Directory of Open Access Journals (Sweden)

    Kozo Fujiwara


    Full Text Available It is imperative to improve the crystal quality of Si multicrystal ingots grown by casting because they are widely used for solar cells in the present and will probably expand their use in the future. Fine control of macro- and microstructures, grain size, grain orientation, grain boundaries, dislocation/subgrain boundaries, and impurities, in a Si multicrystal ingot, is therefore necessary. Understanding crystal growth mechanisms in melt growth processes is thus crucial for developing a good technology for producing high-quality Si multicrystal ingots for solar cells. In this review, crystal growth mechanisms involving the morphological transformation of the crystal-melt interface, grain boundary formation, parallel-twin formation, and faceted dendrite growth are discussed on the basis of the experimental results of in situ observations.

  9. Macromolecular Crystal Growth by Means of Microfluidics (United States)

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


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

  10. Convective flow effects on protein crystal growth (United States)

    Rosenberger, Franz


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

  11. Modeling the Growth Rates of Tetragonal Lysozyme Crystal Faces (United States)

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


    The measured macroscopic growth rates of the (110) and (101) faces of tetragonal lysozyme show an unexpectedly complex dependence on the supersaturation. The growth rates decay asymptotically to zero when the supersaturation is lowered to zero and increase rapidly when the supersaturation is increased. When supersaturations are increased still further the growth rates attain a maximum before starting to decrease. However, growth of these crystals is known to proceed by the classical dislocation and 2D nucleation growth mechanisms. This anomaly can be explained if growth is assumed to occur not by monomer units but by lysozyme aggregates. Analysis of the molecular packing of these crystals revealed that they were constructed of strongly bonded 4(sub 3) helices, while weaker bonds were responsible for binding the helices to each other. It follows that during crystal growth the stronger bonds are formed before the weaker ones. Thus, the growth of these crystals could be viewed as a two step process: aggregate growth units corresponding to the 4(sub 3) helix are first formed in the bulk solution by stronger intermolecular bonds and then attached to the crystal face by weaker bonds on dislocation hillocks or 2D islands. This will lead to a distribution of aggregates in the solution with monomers and lower order aggregates being predominant at low supersaturations and higher order aggregates being predominant at high supersaturations. If the crystal grows mostly by higher order aggregates, such as tetramers and octamers, it would explain the anomalous dependence of the growth rates on the supersaturation. Besides the analysis of molecular packing, a comprehensive analysis of the measured (110) and (101) growth rates was also undertaken in this study. The distribution of aggregates in lysozyme nutrient solutions at various solution conditions were determined from reversible aggregation reactions at equilibrium. The supersaturation was defined for each aggregate species

  12. Modeling Tetragonal Lysozyme Crystal Growth Rates (United States)

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


    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.

  13. Growth and Characterization of Tetraphenylphosphonium Bromide Crystal

    Directory of Open Access Journals (Sweden)

    Guangqiang Wang


    Full Text Available Multiple-phenyl phosphorous compounds are a group of chemical materials that have been used as reactants, pharmaceutical intermediates, extractants, and catalysts in organic synthetic reactions. However, the crystal growth of bulk crystals of multiple-phenyl phosphorous compounds, which may expand their applications in photonics technology, have been largely overlooked. In this article, the crystal growth of tetraphenylphosphonium bromide (TPPB has been studied in organic solvents and water. The crystal structures and crystallization features are analyzed by X-ray diffraction data. By a slow temperature-lowering method, a single-crystal of TPPB (2H2O with the size of 27 × 20 × 20 mm3 has been obtained in water. The basic thermal and optical properties were characterized. We find that the TPPB (2H2O crystal shows excellent transparent property in the near-IR region. Large Raman shifts and strong Raman scattering intensity indicate that TPPB is a potential candidate in Raman-scattering-based nonlinearity applications.

  14. Biomolecular Modification of Inorganic Crystal Growth

    Energy Technology Data Exchange (ETDEWEB)

    De Yoreo, J J


    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

  15. Crystal growth and physical properties of Ferro-pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Aswartham, Saicharan


    . Single crystals of KFe{sub 2}As{sub 2} were grown with two different fluxes, namely, FeAs-flux and KAs-flux. The superconducting transition is found to be at 3.8 K in both the crystals. The influence of doping with selected elements like Na, Rh, Co and Cr has been investigated systematically in KFe{sub 2}As{sub 2} single crystals. With Na-doping at the K-site, yield (K{sub 1-x}Na{sub x})Fe{sub 2}As{sub 2}; superconductivity is suppressed to lower temperatures. Substitution of Co and Cr at Fe site, yield K(Fe{sub 0.95}Co{sub 0.05}){sub 2}As{sub 2}, K(Fe{sub 0.95}Cr{sub 0.05}){sub 2}As{sub 2} superconductivity is rapidly killed. Single crystals of (Ba{sub 0.6}Eu{sub 0.4})(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} with x = 0, 0.05, 0.1, 0.15 and 0.2 were grown with solution growth technique using Fe-As flux and investigated with several physical measurements. The growth conditions are highly optimized to grow flux free large single crystals especially in case of BaFe{sub 2}As{sub 2} family. The high quality of the crystals were revealed by several physical properties, for e.g. single crystals of Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} are of the highest quality which was confirmed by the magnetic ac susceptibility which showed a very sharp superconducting transition.

  16. Growth rate study of canavalin single crystals (United States)

    Demattei, R. C.; Feigelson, R. S.


    The dependence on supersaturation of the growth rate of single crystals of the protein canavalin is studied. In the supersaturation ranges studied, the rate-limiting step for growth is best described by a screw dislocation mechanism associated with interface attachment kinetics. Using a ln-ln plot, the growth-rate data is found to fit a predictive relationship of the form G = 0.012 x the supersaturation to the 6.66, which, together with the solubility curves, allows the growth rate to be estimated under a variety of conditions.

  17. Growth of Organic Crystals by Ostwald Ripening (United States)

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


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

  18. Growth of single-crystal gallium nitride (United States)

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


    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.

  19. Flux growth of BPO 4 crystals (United States)

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


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

  20. Application of energy stability theory to problems in crystal growth (United States)

    Neitzel, G. P.; Jankowski, D. F.


    The use of energy stability theory to study problems in crystal growth is outlined and justified in terms of convection mechanisms. An application to the float zone process of crystal growth is given as an illustration.

  1. Crystallization and Growth of Colloidal Nanocrystals

    CERN Document Server

    Leite, Edson Roberto


    Since the size, shape, and microstructure of nanocrystalline materials strongly impact physical and chemical properties, the development of new synthetic routes to  nanocrystals with controlled composition and morphology is a key objective of the nanomaterials community. This objective is dependent on control of the nucleation and growth mechanisms that occur during the synthetic process, which in turn requires a fundamental understanding of both classical nucleation and growth and non-classical growth processes in nanostructured materials.  Recently, a novel growth process called Oriented Attachment (OA) was identified which appears to be a fundamental mechanism during the development of nanoscale  materials. OA is a special case of aggregation that provides an important route by which nanocrystals grow, defects are formed, and unique—often symmetry-defying—crystal morphologies can be produced. This growth mechanism involves reversible self-assembly of primary nanocrystals followed by reorientati...

  2. On the Nonequilibrium Interface Kinetics of Rapid Coupled Eutectic Growth (United States)

    Dong, H.; Chen, Y. Z.; Shan, G. B.; Zhang, Z. R.; Liu, F.


    Nonequilibrium interface kinetics (NEIK) is expected to play an important role in coupled growth of eutectic alloys, when solidification velocity is high and intermetallic compound or topologically complex phases form in the crystallized product. In order to quantitatively evaluate the effect of NEIK on the rapid coupled eutectic growth, in this work, two nonequilibrium interface kinetic effects, i.e., atom attachment and solute trapping at the solid-liquid interface, were incorporated into the analyses of the coupled eutectic growth under the rapid solidification condition. First, a coupled growth model incorporating the preceding two nonequilibrium kinetic effects was derived. On this basis, an expression of kinetic undercooling (∆ T k), which is used to characterize the NEIK, was defined. The calculations based on the as-derived couple growth model show good agreement with the reported experimental results achieved in rapidly solidified eutectic Al-Sm alloys consisting of a solid solution phase ( α-Al) and an intermetallic compound phase (Al11Sm3). In terms of the definition of ∆ T k defined in this work, the role of NEIK in the coupled growth of the Al-Sm eutectic system was analyzed. The results show that with increasing the coupled growth velocity, ∆ T k increases continuously, and its ratio to the total undercooling reaches 0.32 at the maximum growth velocity for coupled eutectic growth. Parametric analyses on two key alloy parameters that influence ∆ T k, i.e., interface kinetic parameter ( μ i ) and solute distribution coefficient ( k e ), indicate that both μ i and k e influence the NEIK significantly and the decrease of either these two parameters enhances the NEIK effect.

  3. Application of enthalpy model for floating zone silicon crystal growth (United States)

    Krauze, A.; Bergfelds, K.; Virbulis, J.


    A 2D simplified crystal growth model based on the enthalpy method and coupled with a low-frequency harmonic electromagnetic model is developed to simulate the silicon crystal growth near the external triple point (ETP) and crystal melting on the open melting front of a polycrystalline feed rod in FZ crystal growth systems. Simulations of the crystal growth near the ETP show significant influence of the inhomogeneities of the EM power distribution on the crystal growth rate for a 4 in floating zone (FZ) system. The generated growth rate fluctuations are shown to be larger in the system with higher crystal pull rate. Simulations of crystal melting on the open melting front of the polycrystalline rod show the development of melt-filled grooves at the open melting front surface. The distance between the grooves is shown to grow with the increase of the skin-layer depth in the solid material.

  4. Convective flow effects on protein crystal growth (United States)

    Rosenberger, Franz; Monaco, Lisa A.


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

  5. Features of beryllium aluminate crystal growth by the method of horizontally oriented crystallization (United States)

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


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

  6. Growth of the (001 face of borax crystals

    Directory of Open Access Journals (Sweden)

    Suharso Suharso


    Full Text Available he growth rates of borax crystals from aqueous solutions in the (001 direction at various relative supersaturations were measured using in situ cell optical microscopy method. The result shows that the growth mechanism of the (001 face of borax crystal at temperature of 20 °C is spiral growth mechanism.   Keywords: Growth mechanism, borax.

  7. Growth kinetics of sodium perborate from batch crystallization (United States)

    Söhnel, O.; Bravi, M.; Chianese, A.; Mazzarotta, B.


    The size distribution of sodium perborate crystals was continually monitored using a Malvern sizer during batch crystallization from aqueous solutions carried out under falling supersaturation established at the experiment onset. The growth rate was determined from the time shift of the crystal size distribution expressed in cumulative oversize numbers. The size independent overall growth rate was first order with respect to supersaturation for crystals larger than 150 μm. Crystals between 20 and 150 μm exhibited a significant size-dependent growth rate. Furthermore, the fraction of crystals smaller than 20 μm, formed by primary nucleation, grew extremely slowly or did not grow at all.

  8. Growth of lead molybdate crystals by vertical Bridgman method

    Indian Academy of Sciences (India)


    Crystal growth; Bridgman method; acousto-optic crystal; lead molybdate. 1. Introduction. Lead molybdate (PbMoO4, PMO) crystal is well known as an acousto-optic material with excellent properties such as higher acoustic–optic figure of merit and lower acoustic loss (Pinnow 1969). The crystal has attracted much interest for ...

  9. Fluid Physics and Macromolecular Crystal Growth in Microgravity (United States)

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


    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

  10. The impact of space research on semiconductor crystal growth technology (United States)

    Witt, A. F.


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

  11. Materials of construction for silicon crystal growth (United States)

    Leipold, M. H.; Odonnell, T. P.; Hagan, M. A.


    The performance of materials for construction and in contact with molten silicon for crystal growth is presented. The basis for selection considers physical compatibility, such as thermal expansion and strength, as well as chemical compatibility as indicated by contamination of the silicon. A number of new high technology materials are included as well as data on those previously used. Emphasis is placed on the sources and processing of such materials in that results are frequently dependent on the way a material is prepared as well as its intrinsic constituents.

  12. In-situ detection of growth striations by crystallization electromotive force measurement during Czochralski crystal growth (United States)

    Zhu, Yunzhong; Ma, Decai; Long, Siwei; Tang, Feng; Lin, Shaopeng; Wang, Biao


    Growth striations, as macrodefects of crystalline materials, are mainly caused by convection and temperature fluctuations in growth interface. For decades, striations have been widely regarded as an inherent problem. Even in the well-developed Czochralski method, the striation formation process is difficult to inspect in situ. In view of this long-standing issue, after systematically studying the temperature, weight, and output power during crystal growth and numerically modeling the growth process, we found that the regularity of the growth interface electromotive force (GEMF) is related to the distribution of striations. Furthermore, the GEMF quantifies interface fluctuations (711.2 s, 16.6 μm) and thermal hysteresis (107 s), presenting finer details than those provided by a thermocouple and a load cell. In this paper, GEMF is found to be an outstanding choice for monitoring the crystal growth status in real time. As an additional feedback, a new automatic control method could be developed for reducing growth striations and promoting crystal quality.

  13. Solid state single crystal growth of three-dimensional faceted LaFeAsO crystals (United States)

    Kappenberger, Rhea; Aswartham, Saicharan; Scaravaggi, Francesco; Blum, Christian G. F.; Sturza, Mihai I.; Wolter, Anja U. B.; Wurmehl, Sabine; Büchner, Bernd


    Solid state single crystal growth (SSCG) is a crystal growth technique where crystals are grown from a polycrystalline matrix. Here, we present single crystals of the iron pnictide LaFeAsO grown via SSCG using NaAs as a liquid phase to aid crystallization. The size of the as-grown crystals are up to 2 × 3 × 0.4 mm3. Typical for this method, but very uncommon for crystals of the pnictide superconductors and especially for the oxypnictides, the crystals show pronounced facets caused by considerable growth in c direction. The crystals were characterized regarding their composition, structure, magnetic, and thermodynamic properties. This sets the stage for further measurements for which single crystals are crucial such as any c axis and reciprocal space dependent measurements.

  14. Crystal shape 2D modeling for transient CZ silicon crystal growth (United States)

    Sabanskis, A.; Bergfelds, K.; Muiznieks, A.; Schröck, Th.; Krauze, A.


    A non-stationary axisymmetric model of Czochralski silicon single crystal growth is presented. The model describes transient behavior of crystal-melt, melt-gas and crystal-gas interfaces in connection with PID-based control of crystal diameter by changing crystal pulling velocity and heater power. To calculate significant crystal shape changes, unstructured finite element mesh is used in crystal and melt together with automatic element size control. Heater temperature changes are modeled with a simplified integral model. A numerical simulation example of start cone growth is given.

  15. Single crystal growth and anisotropic crystal-fluid interface tension in soft colloidal systems

    NARCIS (Netherlands)

    Nguyen, V.D.; Hu, Z.; Schall, P.


    We measure the anisotropy of the crystal-fluid interfacial free energy in soft colloidal systems. A temperature gradient is used to direct crystal nucleation and control the growth of large single crystals in order to achieve well-equilibrated crystal-fluid interfaces. Confocal microscopy is used to

  16. Flux growth and crystal structure of pyromorphite. (United States)

    Akao, A; Aoki, H; Innami, Y; Minamikata, S; Yamada, T


    Single crystals of pyromorphite, Pb5(PO4)3Cl, were grown by standard flux growth technique with excess lead chloride used as the flux. Pyromorphite was first prepared by heating an intimate mixture of lead hydrogen phosphate and lead chloride in the molar ratio 6:4 at 100 degrees C for 1 h. A mixture of 60 wt% of pyromorphite and 40 wt% of lead chloride was heated at 850 degrees C for 15 h and then cooled at the rate of 3.4 degrees C/h. Hexagonal prismatic crystals of length 1 mm were obtained. The chemical composition has close to the theoretical value. The crystal is hexagonal, space group P6(3)/m with a = 9.9981(8), c = 7.344(1) A and Z = 2. The structure was refined to R = 0.058 and Rw = 0.053 with 502 independent reflections. The structure is in principal the same as that of barium chlorapatite; the chlorine ions occupy the (0, 0, 0) position.

  17. Advances in the understanding of crystal growth mechanisms

    CERN Document Server

    Nishinaga, T; Harada, J; Sasaki, A; Takei, H


    This book contains the results of a research project entitled Crystal Growth Mechanisms on an Atomic Scale, which was carried out for 3 years by some 72 reseachers. Until recently in Japan, only the technological aspects of crystal growth have been emphasized and attention was paid only to its importance in industry. However the scientific aspects also need to be considered so that the technology of crystal growth can be developed even further. This project therefore aimed at understanding crystal growth and the emphasis was on finding growth mechanisms on an atomic scale.

  18. Growth rate dispersion in seeded batch D-xylose crystallization (United States)

    Gabas, N.; Biscans, B.; Laguérie, C.


    Laboratoire de Genie Chimique (URA CNRS 192), ENSIGC, Chemin de la Loge, F-31078 Toulouse Cedex, France Batch crystallization runs of D-xylose from aqueous solutions have been performed. Growth rate kinetics of xylose crystals have been evaluated from successive crystal size distribution records by means of a laser light scattering size analyser. The experiments have emphasized a broadening of the crystal size distribution during growth. Solutions to population balance equations have provided evidence for growth rate dispersion. A time-averaged growth rate equation as well as a growth rate diffusivity parameter have been identified.

  19. Residual Gases in Crystal Growth Systems (United States)

    Palosz, W.


    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.

  20. Structural evolution in the crystallization of rapid cooling silver melt

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Z.A., E-mail: [School of Physics and Electronics, Hunan University, Changsha 410082 (China); Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Dong, K.J.; Yu, A.B. [Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)


    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald’s rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid–solid phase transition. - Highlights: • A comprehensive structural analysis is conducted focusing on crystallization. • The involved atoms in our analysis are more than 90% for all samples concerned. • A series of distinct intermediate states are found in crystallization of silver melt. • A novelty icosahedron-saturated state breeds the metastable bcc state.

  1. Crystallization Kinetics of Organic–Inorganic Trihalide Perovskites and the Role of the Lead Anion in Crystal Growth

    KAUST Repository

    Moore, David T.


    © 2015 American Chemical Society. Methylammonium lead halide perovskite solar cells continue to excite the research community due to their rapidly increasing performance which, in large part, is due to improvements in film morphology. The next step in this progression is control of the crystal morphology which requires a better fundamental understanding of the crystal growth. In this study we use in situ X-ray scattering data to study isothermal transformations of perovskite films derived from chloride, iodide, nitrate, and acetate lead salts. Using established models we determine the activation energy for crystallization and find that it changes as a function of the lead salt. Further analysis enabled determination of the precursor composition and showed that the primary step in perovskite formation is removal of excess organic salt from the precursor. This understanding suggests that careful choice of the lead salt will aid in controlling crystal growth, leading to superior films and better performing solar cells.

  2. Organic crystal growth experiment facility (13-IML-1) (United States)

    Kanbayashi, Akio


    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.

  3. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth (United States)

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


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

  4. Beginner’s guide to flux crystal growth

    CERN Document Server

    Tachibana, Makoto


    This book introduces the principles and techniques of crystal growth by the flux method, which is arguably the most useful way to obtain millimeter- to centimeter-sized single crystals for physical research. As it is possible to find an appropriate solvent (“flux”) for nearly all inorganic materials, the flux method can be applied to the growth of many crystals ranging from transition metal oxides to intermetallic compounds. Both important principles and experimental procedures are described in a clear and accessible manner. Practical advice on various aspects of the experiment, which is not readily available in the literature, will assist the beginning graduate students in setting up the lab and conducting successful crystal growth. The mechanisms of crystal growth at an elementary level are also provided to better understand the techniques and to help in assessing the quality of the crystals. The book also contains many photographs of beautiful crystals with important physical properties of current inte...

  5. Crystal Growth Rate Dispersion: A Predictor of Crystal Quality in Microgravity? (United States)

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


    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.

  6. Rapid growth of hydroxyapatite nanoparticles using ultrasonic irradiation. (United States)

    Rouhani, Parvaneh; Taghavinia, Nima; Rouhani, Shohre


    A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 degrees C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to non-sonication condition. The comparison between the specific surface area of hydroxyapatite nanoparticles obtained by sonication and without sonication demonstrated that sonication increased the specific surface area from 63 m(2)/g to 107 m(2)/g and decreased the size of nanoparticles from 30 nm to 18 nm. Analysis on the pore structure demonstrated that the fractal structures obtained with and without sonication were considerably different. (c) 2010 Elsevier B.V. All rights reserved.

  7. Structural evolution in the crystallization of rapid cooling silver melt (United States)

    Tian, Z. A.; Dong, K. J.; Yu, A. B.


    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald's rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid-solid phase transition.

  8. Multiple gingival pregnancy tumors with rapid growth

    Directory of Open Access Journals (Sweden)

    Wei-Lian Sun


    Full Text Available Pregnancy gingivitis is an acute form of gingivitis that affects pregnant women, with a prevalence of 30%, possibly ranging up to 100%. Sometimes, pregnancy gingivitis shows a tendency toward a localized hyperplasia called gingival pyogenic granuloma. Pregnancy tumor is a benign gingival hyperplasia with the gingiva as the most commonly involved site, but rarely it involves almost the entire gingiva. A 22-year-old woman was referred to our clinic with a chief complaint of gingival swelling that had lasted for 2 days. The lesions progressed rapidly and extensively, and almost all the gingiva was involved a week later. Generalized erythema, edema, hyperplasia, a hemorrhagic tendency, and several typical hemangiomatous masses were noted. Pregnancy was denied by the patient at the first and second visits, but was confirmed 2 weeks after the primary visit. The patient was given oral hygiene instructions. She recovered well, and the mass gradually regressed and had disappeared completely at the end of 12 weeks of pregnancy, without recurrence. The gingival lesions were finally diagnosed as multiple gingival pregnancy tumors. The patient delivered a healthy infant. An extensive and rapid growth of gingival pregnancy tumors during the early first month of pregnancy is a rare occurrence that is not familiar to dentists, gynecologists, and obstetricians. Those practitioners engaged in oral medicine and periodontology, primary care obstetrics, and gynecology should be aware of such gingival lesions to avoid misdiagnosis and overtreatment.

  9. Crystal growth, electrical and photophysical properties of Tl2S ...

    Indian Academy of Sciences (India)

    871–885. Crystal growth, electrical and photophysical properties of Tl2S layered single crystals ... resultant crystals, the electrical properties (electrical conductivity and Hall effect) and steady-state photoconductivity were .... Block of wood, which was shaped in a triangle form. excessive heat loss, the temperature variation ...

  10. Physical Mechanisms of Crystal Growth Modification by Biomolecules (United States)

    De Yoreo, James J.


    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

  11. Protein Crystal Growth With the Aid of Microfluidics (United States)

    vanderWoerd, Mark


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

  12. Growth features of ammonium hydrogen d-tartrate single crystals

    Indian Academy of Sciences (India)


    Growth features of ammonium hydrogen d-tartrate single crystals. G SAJEEVKUMAR*, R RAVEENDRAN, ... Ammonium hydrogen d-tartrate (d-AHT) single crystals were grown in silica gel. The growth fea- tures of these .... tables 1 and 2 summarize the results of the experiments car- ried out. The tables indicate that with a ...

  13. Heating behavior and crystal growth mechanism in microwave field. (United States)

    Yang, Gang; Kong, Yan; Hou, Wenhua; Yan, Qijie


    A simple microwave solid-state reactor was designed on the basis of a domestic microwave oven by using graphite powder as heating medium. The heating behavior of the reactor was studied by using an on-line computer to monitor the real-time temperature during irradiation. It was found that the temperature (T) was related to the time (t) and that microwave power depended on the duty cycle (x) of microwave irradiation. Two empirical equations were proposed and could be applied to the similar microwave solid-state reactors. Four inorganic layered materials, LiV(3)O(8), KNb(3)O(8), KTiNbO(5), and KSr(2)Nb(3)O(10), were successfully synthesized in the designed reactor at a suitable heating rate and temperature that were fully controlled by the empirical equations. Characterization results of X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, and scanning (SEM) and transmission (TEM) electron microscopy indicated that the phases of samples prepared by traditional and microwave methods were in good agreement; nevertheless, the heating nature and the morphologies of products were quite different. The samples synthesized in the microwave field had crystallographic defects and showed an incompactly stacking structure of nanosheets. Due to the rapid formation of crystallites and different extended growth rate along the crystal axis of the products in microwave field, the crystal growth mechanism of layered metal oxides was not according to that of the traditional method and is briefly discussed.

  14. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry G.; Al-Jassim, Mowafak; Zhu, Kai; Zhou, Weilie; Berry, Joseph J.


    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 degrees C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 degrees C in +/-25 degrees C steps (150-200 degrees C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  15. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry; Al-Jassim, Mowafak M.; Zhu, Kai; Zhou, Weilie; Berry, J. J.


    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 °C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 °C in ±25 °C steps (150-200 °C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  16. Growth and Characterization on PMN-PT-Based Single Crystals

    Directory of Open Access Journals (Sweden)

    Jian Tian


    Full Text Available Lead magnesium niobate—lead titanate (PMN-PT single crystals have been successfully commercialized in medical ultrasound imaging. The superior properties of PMN-PT crystals over the legacy piezoelectric ceramics lead zirconate titanate (PZT enabled ultrasound transducers with enhanced imaging (broad bandwidth and improved sensitivity. To obtain high quality and relatively low cost single crystals for commercial production, PMN-PT single crystals were grown with modified Bridgman method, by which crystals were grown directly from stoichiometric melt without flux. For ultrasound imaging application, [001] crystal growth is essential to provide uniform composition and property within a crystal plate, which is critical for transducer performance. In addition, improvement in crystal growth technique is under development with the goals of improving the composition homogeneity along crystal growth direction and reducing unit cost of crystals. In recent years, PIN-PMN-PT single crystals have been developed with higher de-poling temperature and coercive field to provide improved thermal and electrical stability for transducer application.

  17. Growth and defects of explosives crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cady, H.H.


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

  18. Growth and defects of explosives crystals (United States)

    Cady, H. H.

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

  19. Growth and defects of explosives crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cady, H.H.


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

  20. Crystal growth: an anisotropic mass transfer process at the interface. (United States)

    Sun, Congting; Xue, Dongfeng


    Crystal growth is a dynamic physicochemical process, which depends on the multi-parameter synergetic control and directly determines the crystal features such as geometry and size. In this study, both thermodynamic and kinetic factors that determine inorganic single crystal growth are integrated by focusing on the mass transfer process at an interface. For the specific growth system, the integrated parameter is then classified to extract the critical control factors in anisotropic growth. The driving force of mass transfer essentially depends on the anisotropic chemical bonding architectures, leading to different concentration gradients along various [uvw] directions. Exquisitely controlling the chemical bonding architecture can therefore be used to regulate the mass transfer process of a compound in a straightforward manner, encompassing the origin of anisotropic growth as well as a variety of geometries in the formation of a multicomponent crystal.

  1. Crystal growth methods dedicated to low solubility actinide oxalates

    Energy Technology Data Exchange (ETDEWEB)

    Tamain, C., E-mail: [CEA, Nuclear Energy Division, Marcoule, RadioChemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Arab-Chapelet, B. [CEA, Nuclear Energy Division, Marcoule, RadioChemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Rivenet, M. [University Lille Nord de France, Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, ENSCL-USTL, B.P. 90108, F-59652 Villeneuve d’Ascq Cedex (France); Grandjean, S. [CEA, Nuclear Energy Division, Marcoule, RadioChemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Abraham, F. [University Lille Nord de France, Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, ENSCL-USTL, B.P. 90108, F-59652 Villeneuve d’Ascq Cedex (France)


    Two novel crystal growth syntheses dedicated to low solubility actinide-oxalate systems and adapted to glove box handling are described. These methods based on the use of precursors of either actinide metal or oxalic acid have been optimized on lanthanide systems (analogue of actinides(III)) and then assessed on real actinide systems. They allow the synthesis of several actinide oxalate single crystals, Am{sub 2}(C{sub 2}O{sub 4}){sub 3}(H{sub 2}O){sub 3}·xH{sub 2}O, Th(C{sub 2}O{sub 4}){sub 2}·6H{sub 2}O, M{sub 2+x}[Pu{sup IV}{sub 2−x}Pu{sup III}{sub x}(C{sub 2}O{sub 4}){sub 5}]·nH{sub 2}O and M{sub 1−x}[Pu{sup III}{sub 1−x}Pu{sup IV}{sub x}(C{sub 2}O{sub 4}){sub 2}·H{sub 2}O]·nH{sub 2}O. It is the first time that these well-known compounds are formed by crystal growth methods, thus enabling direct structural studies on transuranic element systems and acquisition of basic data beyond deductions from isomorphic (or not) lanthanide compounds. Characterizations by X-ray diffraction, UV–visible solid spectroscopy, demonstrate the potentialities of these two crystal growth methods to obtain oxalate compounds. - Graphical abstract: Two new single crystal growth methods dedicated to actinide oxalate compounds. - Highlights: • Use of diester as oxalate precursor for crystal growth of actinide oxalates. • Use of actinide oxide as precursor for crystal growth of actinide oxalates. • Crystal growth of Pu(III) and Am(III) oxalates. • Crystal growth of mixed Pu(III)/Pu(IV) oxalates.

  2. Crystal growth and magnetic properties of GdFeO3 crystals by floating zone method (United States)

    Wu, Anhua; Wang, Zhanliang; Wang, Bo; Ban, Xiaolei; Jiang, Linwen; Xu, Jun; Yuan, Shujuan; Cao, Shixun


    GdFeO3 and other rare earth substituted crystals with distorted orthorhombic pervoskite-like structure (space group Pbnm) have attracted much attention due to their remarkable magnetic properties of primary significance for technological applications. In the present work, the floating zone growth of GdFeO3 crystals has been systematically investigated and high quality GdFeO3 crystal was obtained by optimized process. The intrinsic magnetic properties of GdFeO3 crystal were investigated. GdFeO3 crystal displayed paramagnetic characteristic at low temperature, as temperature increased, a transition from paramagnetism to antiferromagnetism was observed.

  3. An observable protein crystal growth apparatus for studying the effects of microgravity on protein crystallization (United States)

    McPherson, Alexander; Malkin, Alexander J.; Kuznetsov, Yurii G.; Koszelak, Stan; Wells, Mark; Jenkins, Greg; Howard, Jeff; Lawson, Greg


    Macromolecular crystals during their growth, incorporate an extensive array of impurities which vary from individual molecules to large particles, and even microcrystals in the micron size range. AFM (atomic force microscopy) along with X-ray topology has shown that the density of defects and faults in most macromolecular crystals is several orders of magnitude higher than in conventional crystals. High defect and impurity density contributes, in turn, to a deterioration of both the mechanical and diffraction properties of crystals, thereby lessening their value for structural biology. In microgravity, access by impurities and aggregates to growing crystal surfaces is restricted due to the elimination of convention and to altered fluid transport properties. We designed, and have now completed construction of an instrument, the OPCGA (Observable Protein Crystal Growth Apparatus) that employs a fused optics, phase shift, Mach-Zehnder interferometer, along with polarized light, time lapse video microscopy to analyze the fluid environment around growing crystals. Using this device, which will ultimately be deployed on the International Space Station, we have, in thin cells on Earth, succeeded in directly visualizing macromolecule concentration gradients around growing protein crystals. This provides the first direct evidence that quasi-stable depletion zones formed around growing crystals in space may explain the improved quality of macromolecular crystals grown in microgravity. Further application of the interferometric technique will allow us to quantitatively describe the shapes, extent, and magnitudes of the concentration gradients and to evaluate their degree of stability. The OPCGA ultimately will be used by the broad crystal growth community to study, and quantitatively describe the development of a vast range of macromolecular crystals. This will have a significant impact on our understanding of crystal growth phenomena and our ability to improve and control

  4. Quartz crystal microbalance biosensor for rapid detection of aerosolized microorganisms (United States)

    Farka, Zdenĕk.; Kovár, David; Skládal, Petr


    Biological warfare agents (BWAs) represent the current menace of the asymmetric war. The early detection of BWAs, especially in the form of bioaerosol, is a challenging task for governments all around the world. Label-free quartz crystal microbalance (QCM) immunosensor and electrochemical immunosensor were developed and tested for rapid detection of BWA surrogate (E. coli) in the form of bioaerosol. Two immobilization strategies for the attachment of antibody were tested; the gold sensor surface was activated by cysteamine and then antibody was covalently linked either using glutaraldehyde, or the reduced antibodies were attached via Sulfo-SMCC. A portable bioaerosol chamber was constructed and used for safe manipulation with aerosolized microorganisms. The dissemination was done using a piezoelectric humidifier, distribution of bioaerosol inside the chamber was ensured using three 12-cm fans. The whole system was controlled remotely using LAN network. The disseminated microbial cells were collected and preconcentrated using the wetted-wall cyclone SASS 2300, the analysis was done using the on-line linked immunosensors. The QCM immunosensor had limit of detection 1×104 CFU·L-1 of air with analysis time 16 min, the whole experiment including dissemination and sensor surface regeneration took 40 min. In case of blank (disseminated sterile buffer), no signal change was observed. The electrochemical immunosensor was able to detect 150 CFU·L-1 of air in 20 min; also in this case, no interferences were observed. Reference measurements were done using particle counter Met One 3400 and by cultivation method on agar plates. The sensors have proved to be applicable for rapid screening of microorganisms in air.

  5. Growth of bulk single crystals of urea for photonic applications (United States)

    Saranraj, Arumugam; Sathiyadhas, Sahaya Jude Dhas; Jose, Michael; Martin Britto Dhas, Sathiyadhas Amalapusham


    We report the growth of technologically important urea crystals of record size (48 × 16 × 8 mm3) by doping sulfuric acid and employing slow evaporation technique. The grown crystal was identified by single crystal X-Ray diffraction and FTIR spectral analysis. Optical properties of the grown crystal were analyzed by UV-Vis spectrum and the presence of H2SO4 was confirmed by EDAX analysis. Thermogravimetric analysis, Differential Scanning Calorimetry and Photo acoustic studies were also carried out to determine the thermal properties of the grown crystal. The dielectric properties for wide range of frequencies (1 Hz to 1 MHz) at different temperatures (35, 40, 60, 80, 100 °C) were analyzed. The second harmonic conversion efficiency of the grown H2SO4 doped urea crystal was found to be 3.75 times higher than the commercially available KDP crystals. [Figure not available: see fulltext.

  6. Growth of bulk single crystals of urea for photonic applications (United States)

    Saranraj, Arumugam; Dhas, Sathiyadhas Sahaya Jude; Jose, Michael; Martin Britto Dhas, Sathiyadhas Amalapusham


    We report the growth of technologically important urea crystals of record size (48 × 16 × 8 mm3) by doping sulfuric acid and employing slow evaporation technique. The grown crystal was identified by single crystal X-Ray diffraction and FTIR spectral analysis. Optical properties of the grown crystal were analyzed by UV-Vis spectrum and the presence of H2SO4 was confirmed by EDAX analysis. Thermogravimetric analysis, Differential Scanning Calorimetry and Photo acoustic studies were also carried out to determine the thermal properties of the grown crystal. The dielectric properties for wide range of frequencies (1 Hz to 1 MHz) at different temperatures (35, 40, 60, 80, 100 °C) were analyzed. The second harmonic conversion efficiency of the grown H2SO4 doped urea crystal was found to be 3.75 times higher than the commercially available KDP crystals. [Figure not available: see fulltext.

  7. Recent advances in crystal growth of selected oxides by Czochralski method (United States)

    Pajaczkowska, Anna


    Czochralski crystal growth method is discussed. Crystals of polycomponent oxides of pseudoperovskite structure are grown using convex interface, low gradient of temperature, and low growth and rotation rates. The knowledge of the crystal structure, morphology of crystals, and the attachment energy of faces allows us to design the crystal growth process. The change of color in ABCO4 type crystal is related to oxygen point defects. The selected crystals are discussed as substrate crystals for high Tc superconductor thin layers.

  8. Zeolite Crystal Growth (ZCG) Flight on USML-2 (United States)

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


    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.

  9. Theory of the intermediate stage of crystal growth with applications to insulin crystallization (United States)

    Barlow, D. A.


    A theory for the intermediate stage of crystal growth, where two defining equations one for population continuity and another for mass-balance, is used to study the kinetics of the supersaturation decay, the homogeneous nucleation rate, the linear growth rate and the final distribution of crystal sizes for the crystallization of bovine and porcine insulin from solution. The cited experimental reports suggest that the crystal linear growth rate is directly proportional to the square of the insulin concentration in solution for bovine insulin and to the cube of concentration for porcine. In a previous work, it was shown that the above mentioned system could be solved for the case where the growth rate is directly proportional to the normalized supersaturation. Here a more general solution is presented valid for cases where the growth rate is directly proportional to the normalized supersaturation raised to the power of any positive integer. The resulting expressions for the time dependent normalized supersaturation and crystal size distribution are compared with experimental reports for insulin crystallization. An approximation for the maximum crystal size at the end of the intermediate stage is derived. The results suggest that the largest crystal size in the distribution at the end of the intermediate stage is maximized when nucleation is restricted to be only homogeneous. Further, the largest size in the final distribution depends only weakly upon the initial supersaturation.

  10. Growth and characterization of nonlinear optical single crystals: bis ...

    Indian Academy of Sciences (India)


    Experimental. 2.1 Synthesis and crystal growth of BCT and C4MB. Cyclohexylamine, terephthalic acid and para-methoxy benzoic acid reagents were the starting materials used to synthesise the title compounds. BCT crystal was grown by. *Author for correspondence (, ...

  11. Growth features of ammonium hydrogen d-tartrate single crystals

    Indian Academy of Sciences (India)

    Ammonium hydrogen -tartrate (-AHT) single crystals were grown in silica gel. The growth features of these crystals with variation of parameters like specific gravity of the gel, gel pH, acid concentrations, concentration of the feed solution and gel age were studied in detail.

  12. Crystal growth and comparison of vibrational and thermal properties ...

    Indian Academy of Sciences (India)

    Single crystals of urea thiourea mercuric sulphate (UTHS) and urea thiourea mercuric chloride (UTHC), semi-organic nonlinear optical materials, were grown by low-temperature solution growth technique by slow evaporation method using water as the solvent. Good quality single crystals were grown within three weeks.

  13. Crystal nucleation and dendrite growth of metastable phases in undercooled melts

    Energy Technology Data Exchange (ETDEWEB)

    Herlach, Dieter, E-mail: [Institut fuer Materialphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt, D-51170 Koeln (Germany)


    Research highlights: > Homogenous nucleation. > Effects of convection on dendrite growth kinetics. > Description of disorder trapping validated by experiment. - Abstract: An undercooled melt possesses an enhanced free enthalpy that opens up the possibility to crystallize metastable crystalline solids in competition with their stable counterparts. Crystal nucleation selects the crystallographic phase whereas the growth dynamics controls microstructure evolution. We apply containerless processing techniques such as electromagnetic and electrostatic levitation to containerlesss undercool and solidify metallic melts. Owing to the complete avoidance of heterogeneous nucleation on container-walls a large undercooling range becomes accessible with the extra benefit that the freely suspended drop is direct accessible for in situ observation of crystallization far away from equilibrium. Results of investigations of maximum undercoolability on pure zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Rapid dendrite growth is measured as a function of undercooling by a high-speed camera and analysed within extended theories of non-equilibrium solidification. In such both supersaturated solid solutions and disordered superlattice structure of intermetallics are formed at high growth velocities. A sharp interface theory of dendrite growth is capable to describe the non-equilibrium solidification phenomena during rapid crystallization of deeply undercooled melts. Eventually, anomalous growth behaviour of Al-rich Al-Ni alloys is presented, which may be caused by forced convection.

  14. Computing the crystal growth rate by the interface pinning method

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Hummel, Felix; Dellago, Christoph


    An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two......-phase configurations are stabilized by adding a spring-like bias field coupling to an order-parameter that discriminates between the two phases. Crystal growth is a Smoluchowski process and the crystal growth rate can, therefore, be computed from the terminal exponential relaxation of the order parameter. The approach...... from first principles. A generalized version of the method may be used for computing the rates of crystal nucleation or other rare events....

  15. Direction-specific interactions control crystal growth by oriented attachment

    National Research Council Canada - National Science Library

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


    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment...

  16. Definition study for temperature control in advanced protein crystal growth (United States)

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


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

  17. Direction-specific interactions control crystal growth by oriented attachment

    DEFF Research Database (Denmark)

    Li, Dongsheng; Nielsen, Michael H; Lee, Jonathan R.I.


    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy...... initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment....

  18. Solubility and peculiarities of the yttrium-aluminium borate crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Azizov, A.V.; Leonyuk, N.I.; Rezvyj, V.R.; Timchenko, T.I.; Belov, N.V. (Moskovskij Gosudarstvennyj Univ. (USSR))

    The nature of crystallization media and crystallization peculiarities of YAl/sub 3/(BO/sub 3/)/sub 4/ yttrium-alluminium borate (YAB) were investigated. The investigation of YAB solubility was conducted in the melts of two different compositions: 88.1K/sub 2/Mo/sub 2/O/sub 10/-3.5V/sub 2/O/sub 3/-8.4B/sub 2/O/sub 3/ (1) and 89.5K/sub 2/Mo/sub 3/O/sub 10/ - - 10.5B/sub 2/O/sub 3/ (2) at 1060-900 deg C. The YAB crystals obtained from different crystallization media had different habit and morphology. The revealed peculiarities are significant for the choice of the YAB crystal growing conditions on orientated seedings: more rapid growth can be exercised along the (0001) face from the solution in the melt (2).

  19. Imaging System For Measuring Macromolecule Crystal Growth Rates in Microgravity (United States)

    Corder, Eric L.; Briscoe, Jeri


    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

  20. Crystal growth and reflectivity studies of Zn1–xMnxTe crystals

    Indian Academy of Sciences (India)

    Single crystals of Zn1–MnTe were prepared by vertical Bridgman crystal growth method for different concentrations of Mn. Chemical analysis and reflectivity studies were carried out for compositional and band structure properties. Microscopic variation in composition between starting and end compounds was observed ...

  1. Dendritic Growth of Hard-Sphere Crystals. Experiment 34 (United States)

    Russel, W. B.; Chaikin, P. M.; Zhu, Ji-Xiang; Meyer, W. V.; Rogers, R.


    Recent observations of the disorder-order transition for colloidal hard spheres under microgravity revealed dendritic crystallites roughly 1-2 mm in size for samples in the coexistence region of the phase diagram. Order-of-magnitude estimates rationalize the absence of large or dendritic crystals under normal gravity and their stability to annealing in microgravity. A linear stability analysis of the Ackerson and Schaetzel model for crystallization of hard spheres establishes the domain of instability for diffusion-limited growth at small supersaturations. The relationship between hard-sphere and molecular crystal growth is established and exploited to relate the predicted linear instability to the well-developed dendrites observed.

  2. Protein crystal growth and the International Space Station (United States)

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


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

  3. The growth and dissolution of sodium perborate crystals in a fluidized bed crystallizer (United States)

    Chianese, A.; Condò, A.; Mazzarotta, B.


    The growth and dissolution rates of sodium perborate (SPB) crystals in aqueous solutions were measured by means of a fluidized bed apparatus. The influence on the overall growth rate of the concentration of sodium metaborate (SMB) in aqueous solutions, in the range 0-4.7 wt%, of the temperature, between 18 and 28° C, and of the crystal size, in the range 0.27-0.72 mm was investigated. By determining properly the surface-volume shape factor of the crystals, markedly dendritic, the independence of the overall growth rate on the crystal size results, whereas both the dissolution and growth phenomenon are greatly affected by the presence of SMB in solution.

  4. Analysis of Monomer Aggregation and Crystal Growth Rates of Lysozyme (United States)

    Nadarajah, Arunan


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

  5. Fluid mechanics in crystal growth - The 1982 Freeman scholar lecture (United States)

    Ostrach, S.


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

  6. Advanced crystal growth techniques for thallium bromide semiconductor radiation detectors (United States)

    Datta, Amlan; Becla, Piotr; Guguschev, Christo; Motakef, Shariar


    Thallium Bromide (TlBr) is a promising room-temperature radiation detector candidate with excellent charge transport properties. Currently, Travelling Molten Zone (TMZ) technique is widely used for growth of semiconductor-grade TlBr crystals. However, there are several challenges associated with this type of crystal growth process including lower yield, high thermal stress, and low crystal uniformity. To overcome these shortcomings of the current technique, several different crystal growth techniques have been implemented in this study. These include: Vertical Bridgman (VB), Physical Vapor Transport (PVT), Edge-defined Film-fed Growth (EFG), and Czochralski Growth (Cz). Techniques based on melt pulling (EFG and Cz) were demonstrated for the first time for semiconductor grade TlBr material. The viability of each process along with the associated challenges for TlBr growth has been discussed. The purity of the TlBr crystals along with its crystalline and electronic properties were analyzed and correlated with the growth techniques. Uncorrected 662 keV energy resolutions around 2% were obtained from 5 mm x 5 mm x 10 mm TlBr devices with virtual Frisch-grid configuration.

  7. Single crystal growth of the intermetallic compound InPd (United States)

    Hahne, Michael; Gille, Peter


    Quite recently intermetallic compounds have been investigated as catalysts for heterogeneous catalysis as they can be highly active regarding a specific reaction and often show advantages in selectivity and long-term stability. The intermetallic phase InPd (CsCl structure type) is considered to be a possible catalyst for methanol steam reforming. Single crystals are needed to study the basic processes of catalysis. Using the Czochralski technique, InPd single crystals were grown from In-rich solutions as to reduce the vapor pressure of In. The crystals show some unusual rough surface morphology and gradients concerning the main components composition. By adjusting the growth parameters like growth temperature and growth rate we succeeded to get inclusion-free single crystals.

  8. Crystal growth of CVD diamond and some of its peculiarities

    CERN Document Server

    Piekarczyk, W


    Experiments demonstrate that CVD diamond can form in gas environments that are carbon undersaturated with respect to diamond. This fact is, among others, the most serious violation of principles of chemical thermodynamics. In this $9 paper it is shown that none of the principles is broken when CVD diamond formation is considered not a physical process consisting in growth of crystals but a chemical process consisting in accretion of macro-molecules of polycyclic $9 saturated hydrocarbons belonging to the family of organic compounds the smallest representatives of which are adamantane, diamantane, triamantane and so forth. Since the polymantane macro-molecules are in every respect identical with $9 diamond single crystals with hydrogen-terminated surfaces, the accretion of polymantane macro- molecules is a process completely equivalent to the growth of diamond crystals. However, the accretion of macro-molecules must be $9 described in a way different from that used to describe the growth of crystals because so...

  9. Crystallization and activation of silicon by microwave rapid annealing (United States)

    Kimura, Shunsuke; Ota, Kosuke; Hasumi, Masahiko; Suzuki, Ayuta; Ushijima, Mitsuru; Sameshima, Toshiyuki


    A combination of the carbon-powder absorber with microwave irradiation is proposed as a rapid heat method. 2-μm-diameter carbon powders with a packing density of 0.08 effectively absorbed 2.45 GHz 1000-W-microwave and heated themselves to 1163 °C for 26 s. The present heat treatment recrystallized n-type crystalline silicon surfaces implanted with 1.0 × 10^{15}hbox {-cm}^{-2}-boron and phosphorus atoms with crystalline volume ratios of 0.99 and 0.93, respectively, by microwave irradiation at 1000 W for 20 s. Activation and carrier generation were simultaneously achieved with a sheet resistivity of 62 Ω / hbox {sq}. A high photo-induced-carrier effective lifetime of 1.0 × 10^{-4} s was also achieved. Typical electrical current-rectified characteristic and solar cell characteristic with an efficiency of 12.1 % under 100-mW/cm2-air-mass-1.5 illumination were obtained. Moreover, heat treatment with microwave irradiation at 1000 W for 22 s successfully crystallized silicon thin films with thicknesses ranging from 2.4 to 50 nm formed on quartz substrates. Nano-crystalline cluster structure with a high volume ratio of 50 % was formed in the 1.8-nm (initial 2.4-nm)-thick silicon films. Photoluminescence around 1.77 eV was observed for the 1.8-nm-thick silicon films annealed at 260 °C in 1.3 × 106-Pa-H2O-vapor for 3 h after the microwave heating.

  10. Crystallization of lysozyme from lysozyme - ovalbumin mixtures: Separation potential and crystal growth kinetics (United States)

    Maosoongnern, Somchai; Flood, Chalongsri; Flood, Adrian E.; Ulrich, Joachim


    Lysozyme was successfully separated from mixtures of lysozyme and ovalbumin by crystallization. The purity of the lysozyme product is more than 98%, the remaining activity is greater than 97%, and the yields of the crystal products were greater than 80%. The experimental conditions used were varied to study the effect of the operating parameters on the growth kinetics of lysozyme crystal and the separation ability of the process. The growth rates of lysozyme are second order with respect to the relative supersaturation. Therefore the growth kinetics of the crystallization process is controlled by the surface integration mechanism. The calculated growth rate constants were 5.4×10-6 cm/h and 2.5×10-6 cm/h for the crystallization process at 20 °C and 10 °C, respectively. There is no significant effect of the ovalbumin impurity up to the concentration of 67.5% ovalbumin (based on total protein) on the growth kinetics of lysozyme. Changing the NaCl concentration from 4% to 3% had no effect on the growth kinetics of lysozyme, although this does change the solubility and therefore the yield. The calculated activation energy was 53.08 kJ/mol which supports the hypothesis that the crystallization process is controlled by the surface integration mechanism.

  11. High-thermal-gradient Superalloy Crystal Growth (United States)

    Pearson, D. D.; Anton, D. L.; Giamei, A. F.


    Single, (001)-oriented crystals of PWA 1480 were processed in alumina/silica shell molds in a laboratory high gradient furnace. The furnace employs a graphite resistance heated element, a radiation baffle, and a water cooled radiation trap below the baffle. All crystals were grown in vacuum (10 torr) and all heat transfer was radiative. The element is constructed with a variable cross section that is tapered just above the baffle to maximize heat input and therefore thermal gradient. A maximum alloy temperature of 1600 C was used. A thermal gradient of 130 deg C/cm was recorded at 1370 C just above the solidus of the PWA 1480 alloys. Crystal bars with 14.4 and 17.5 mm diameters were grown in alumina/silica shell molds. Each crystal was started from a 1.6 mm pencil seed at a rate of 76 mm/hr and slowly accelerated to a rate of 200 mm/hr under computer control. Volume percent porosity and average pore size were measured as functions of distance in representative bars. Low cycle fatigue behavior and stress rupture properties were determined.

  12. Limit growth of ice crystals under different temperature oscillations levels in nile Tilapia

    Directory of Open Access Journals (Sweden)

    Mirko Salomon Chávez GUTIÉRREZ

    Full Text Available Abstract The degenerative effect of temperature fluctuations during storage time is a critical condition that needs to be quantitatively characterized in products where drip losses are appreciable. In this work, real storage conditions were reproduced using freezers modified to cause 3 levels of temperature fluctuation (± 0, ± 3, ± 5; ± 7 during storage of Tilapia (Oreochromis sp, at temperature of –18 °C. The fast frozen tilapia muscle (freezing cabinet was chosen to quantify the growth of ice crystals according to temperature fluctuations. The identification of crystals in the optical microscope as well as histological treatments and measurements using specific software has shown that the growth of ice crystals in the first days of storage follows an asymptote, whose final value is conditioned only by the level of temperature fluctuations regardless of initial diameter, which begins storage. It has also been found that the growth of crystals formed during rapid freezing rapidly develops according to temperature fluctuations to which the product has been subjected. This work also identified statistically significant differences in the equivalent diameter of crystals formed at the four proposed levels of temperature fluctuation with significance level of p < 0.05.

  13. Crystal growth and comparison of vibrational and thermal properties ...

    Indian Academy of Sciences (India)

    86, No. 3. — journal of. March 2016 physics pp. 719–722. Comments on: “Crystal growth and comparison of vibrational and thermal properties of semi-organic nonlinear optical materials” ... and urea ligands, the title paper by Gunasekaran et al [1] reporting on the growth of the so-called urea thiourea mercuric chloride ...

  14. Molecular modifiers reveal a mechanism of pathological crystal growth inhibition (United States)

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


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

  15. Ice Crystal Growth Rates Under Upper Troposphere Conditions (United States)

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


    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.

  16. Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment (United States)

    Su, Ching-Hua


    A low gravity material experiment will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). There are two sections of the flight experiment: (I) crystal growth of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, by physical vapor transport (PVT) and (II) melt growth of CdZnTe by directional solidification. The main objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the grown crystals as results of buoyancy-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. This talk will focus on the ground-based studies on the PVT crystal growth of ZnSe and related ternary compounds. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  17. Bridgman growth of bismuth tellurite crystals

    Indian Academy of Sciences (India)

    The photorefractive crystal, Bi2TeO5, was grown by the modified Bridgman method for the first time. High purity Bi2O3 and TeO2 were used as starting materials and were mixed thoroughly with molar ratio of Bi2O3/TeO2 = 1 : 1. Platinum crucible was fabricated with a seed well of 10 mm in diameter and several folds were ...

  18. Crystal growth of fluorides for optical applications

    Energy Technology Data Exchange (ETDEWEB)

    Shimamura, K.; Sato, H.; Bensalah, A.; Sudesh, V.; Fukuda, T. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Machida, H. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Tokin Corp., Saitama (Japan); Sarukura, N. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Institute for Molecular Science, Okazaki (Japan)


    Ce-doped and undoped LiCaAlF{sub 6}, LiSrAlF{sub 6}, LiYF{sub 4}, LiLuF{sub 4} and KMgF{sub 3} single crystals were grown by the Czochralski technique under CF{sub 4} atmosphere. The effective distribution coefficients of Ce{sup 3+} in LiCaAlF{sub 6}, LiSrAlF{sub 6}, LiYF{sub 4} and LiLuF{sub 4} were determined to be 0.031, 0.028, 0.116 and 0.054, respectively. Laser output energy of 60 mJ and 27mJ were obtained using the grown Ce:LiCaAlF{sub 6} and Ce:LiLuF{sub 4} single crystals, respectively. Undoped LiCaAlF{sub 6} and KMgF{sub 3} single crystals showed a transmission edge at 112 nm and 115 nm, respectively. (orig.)

  19. Reinvestigation of growth of thiourea urea zinc sulfate crystal. (United States)

    Srinivasan, Bikshandarkoil R; Naik, Teja A; Tylczyński, Zbigniew; Priolkar, K R


    Reinvestigation of the growth of thiourea urea zinc sulfate crystal is reported. Aqueous reaction of thiourea, urea and zinc sulfate in 1:1:1 mol ratio results in the formation of the well known [Zn(tu)3(SO4)] (1) (tu=thiourea) crystal and not the 'so called' novel semiorganic nonlinear optical thiourea urea zinc sulfate (2) crystal, as claimed by Redrothu Hanumantha Rao, S. Kalainathan, Spectroscopic investigation, nucleation, growth, optical, thermal and second harmonic studies of novel semi-organic nonlinear optical crystal - Thiourea urea zinc sulfate, Spectrochim. Acta A97 (2012) 456-463. In this work, we demonstrate the usefulness of elemental analytical data, infrared and NMR spectra and X-ray powder pattern, for accurate product characterization. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Crystal growth of organics for nonlinear optical applications (United States)

    Singh, N. B.; Mazelsky, R.


    The crystal growth and characterization of organic and inorganic nonlinear optical materials were extensively studied. For example, inorganic crystals such as thallium arsenic selenide were studied in our laboratory for several years and crystals in sizes over 2.5 cm in diameter are available. Organic crystals are suitable for the ultraviolet and near infrared region, but are relatively less developed than their inorganic counterparts. Very high values of the second harmonic conversion efficiency and the electro-optic coefficient were reported for organic compounds. Single crystals of a binary organic alloy based on m.NA and CNA were grown and higher second harmonic conversion efficiency than the values reported for m.NA were observed.

  1. Growth, crystalline perfection and characterization of benzophenone oxime crystal (United States)

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

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

  2. Defect reduction in seeded aluminum nitride crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Bondokov, Robert T.; Schowalter, Leo J.; Morgan, Kenneth; Slack, Glen A; Rao, Shailaja P.; Gibb, Shawn Robert


    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  3. Molecular simulation of crystal growth in n-eicosane (United States)

    Waheed, N.; Lavine, M. S.; Rutledge, G. C.


    Molecular dynamics is used to obtain crystal growth rates for a model n-alkane. A united atom model of bulk n-eicosane exhibits an observable phase change from an amorphous phase to a close-packed hexagonal phase, in the presence of a crystal surface. Rates are calculated from the translation of the order-disorder transition in the simulation cell as a function of time. The temperature dependence of crystallization is analyzed in terms of Ziabicki's rate model, and behavior is considered in light of more coarse-grained models.

  4. Calcium oxalate crystal growth modification; investigations with confocal Raman microscopy (United States)

    McMulkin, Calum J.; Massi, Massimiliano; Jones, Franca


    Confocal Raman Microscopy (CRM) in combination with a photophysical investigation has been employed to give insight into the interaction between calcium oxalate monohydrate (COM) and a series of tetrazole containing crystal growth modifier's (CGM's), in conjunction with characterisation of morphological changes using scanning electron and optical microscopy. The tetrazole CGM's were found to interact by surface adsorption with minimal morphological changes to the COM crystals however, significant interactions via chemisorption were observed; it was discovered that the chemisorption is sufficiently strong for aggregation of the tetrazole species to occur within the crystal during crystallisation.

  5. Czochralski silicon crystal growth: Modeling and simulation study (United States)

    Javidi, Massoud

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

  6. Organisational Factors of Rapid Growth of Slovenian Dynamic Enterprises

    Directory of Open Access Journals (Sweden)

    Pšeničny Viljem


    Full Text Available The authors provide key findings on the internal and external environmental factors of growth that affect the rapid growth of dynamic enterprises in relation to individual key organisational factors or functions. The key organisational relationships in a growing enterprise are upgraded with previous research findings and identified key factors of rapid growth through qualitative and quantitative analysis based on the analysis of 4,511 dynamic Slovenian enterprises exhibiting growth potential. More than 250 descriptive attributes of a sample of firms from 2011 were also used for further qualitative analysis and verification of key growth factors. On the basis of the sample (the study was conducted with 131 Slovenian dynamic enterprises, the authors verify whether these factors are the same as the factors that were studied in previous researches. They also provide empirical findings on rapid growth factors in relation to individual organisational functions: administration - management - implementation (entrepreneur - manager - employees. Through factor analysis they look for the correlation strength between individual variables (attributes that best describe each factor of rapid growth and that relate to the aforementioned organisational functions in dynamic enterprises. The research findings on rapid growth factors offer companies the opportunity to consider these factors during the planning and implementation phases of their business, to choose appropriate instruments for the transition from a small fast growing firm to a professionally managed growing company, to stimulate growth and to choose an appropriate growth strategy and organisational factors in order to remain, or become, dynamic enterprises that can further contribute to the preservation, growth and development of the Slovenian economy

  7. Growth and characterization of nonlinear optical crystal - Semicarbazide Picrate (United States)

    Raja, R.; Seshadri, S.; Santhanam, V.; Vedhavalli, D.


    Good-optical-quality single crystals of Semicarbazide Picrate (SP), a new organic charge transfer molecular complex salt, were successfully synthesized and grown by the slow evaporation solution growth technique. The grown crystal is analyzed by various instrumentation techniques. The structure of the grown crystal as determined by single crystal XRD diffraction analysis. The presence of functional groups in the SP crystals is confirmed by FT-IR vibrational analysis. The optical transparency has been studied using UV-vis spectrophotometer. The relative second harmonic generation (SHG) efficiency measurements reveal that the SP crystals is a efficient nonlinear optical (NLO) material having an activity 1.4 times as that of the reference material potassium dihydrogen phosphate. The TG/DTA thermal analyses reveal the purity of the sample and no decomposition is observed up to the melting point. The mechanical properties of the crystal are examined by Vicker's microhardness test. The dielectric permittivity, dielectric loss and AC conductivity of the crystal are measured at various temperatures.

  8. Crystal growth of sulfide materials from alkali polysulfide liquids (United States)

    White, W. B.


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

  9. Studying of crystal growth and overall crystallization of naproxen from binary mixtures. (United States)

    Kaminska, E; Madejczyk, O; Tarnacka, M; Jurkiewicz, K; Kaminski, K; Paluch, M


    Broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) were applied to investigate the molecular dynamics and phase transitions in binary mixtures composed of naproxen (NAP) and acetylated saccharides: maltose (acMAL) and sucrose (acSUC). Moreover, the application of BDS method and optical microscopy enabled us to study both crystallization kinetics and crystal growth of naproxen from the solid dispersions with the highest content of modified carbohydrates (1:5wt ratio). It was found that the activation barriers of crystallization estimated from dielectric measurements are completely different for both studied herein mixtures. Much higher E a (=205kJ/mol) was obtained for NAP-acMAL solid dispersion. It is probably due to simultaneous crystallization of both components of the mixture. On the other hand, lower value of E a in the case of NAP-acSUC solid dispersion (81kJ/mol) indicated, that naproxen is the only crystallizing compound. This hypothesis was confirmed by X-ray diffraction studies. We also suggested that specific intermolecular dipole-dipole interactions between active substance and excipient may be an alternative explanation for the difference between activation barrier obtained for NAP-acMAL and NAP-acSUC binary mixtures. Furthermore, optical measurements showed that the activation energy for crystal growth of naproxen increases in binary mixtures. They also revealed that both excipients: acMAL and acSUC move the temperature of the maximum of crystal growth towards lower temperatures. Interestingly, this maximum occurs for nearly the same structural relaxation time, which is a good approximation of viscosity, for all samples. Finally, it was also noticed that although naproxen crystallizes to the same polymorphic form in both systems, there are some differences in morphology of obtained crystals. Thus, the observed behavior may have a significant impact on the bioavailability and dissolution rate of API produced in that way

  10. Rapid crystallization of externally produced ions in a Penning trap

    CERN Document Server

    Murboeck, T; Birkl, G; Noertershaeuser, W; Thompson, R C; Vogel, M


    We have studied the cooling dynamics, formation process and geometric structure of mesoscopic crystals of externally produced magnesium ions in a Penning trap. We present a cooling model and measurements for a combination of buffer gas cooling and laser cooling which has been found to reduce the ion kinetic energy by eight orders of magnitude from several hundreds of eV to micro-eV and below within seconds. With ion numbers of the order of 1000 to 100000, such cooling leads to the formation of ion Coulomb crystals which display a characteristic shell structure in agreement with theory of non-neutral plasmas. We show the production and characterization of two-species ion crystals as a means of sympathetic cooling of ions lacking a suitable laser-cooling transition.

  11. Supercritical fluid crystallization of griseofulvin: crystal habit modification with a selective growth inhibitor. (United States)

    Jarmer, Daniel J; Lengsfeld, Corinne S; Anseth, Kristi S; Randolph, Theodore W


    Poly (sebacic anhydride) (PSA) was used as a growth inhibitor to selectively modify habit of griseofulvin crystals formed via the Precipitation with a compressed-fluid antisolvent (PCA) process. PSA and griseofulvin were coprecipitated within a PCA injector, which provided efficient mixing between the solution and compressed antisolvent process streams. Griseofulvin crystal habit was modified from acicular to bipyramidal when the mass ratio of PSA/griseofulvin in the solution feed stream was griseofulvin and PSA particles, and gave results consistent with a selective growth inhibition mechanism. SEM micrographs showed regions on griseofulvin crystals where PSA microparticles had preferentially adsorbed. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) analysis of the griseofulvin crystals indicated no changes in the crystalline form after the habit modification. Powder compressibility decreased from 49 +/- 3% to 28 +/- 7% with the modification in crystal habit. No change in the physical stability of the processed powder was observed after being stored at 25 degrees C/60% RH and 40 degrees C/70% RH for 23 days. Despite the change in crystal habit, griseofulvin crystals achieved 100% dissolution within 60 min in a simulated gastric fluid. (c) 2005 Wiley-Liss, Inc.

  12. Linking Crystal Populations to Dynamic States: Crystal Dissolution and Growth During an Open-System Event (United States)

    Bergantz, G. W.; Schleicher, J.; Burgisser, A.


    The identification of shared characteristics in zoned crystals has motivated the definition of crystal populations. These populations reflect the simultaneous transport of crystals, heat and composition during open-system events. An obstacle to interpreting the emergence of a population is the absence of a way to correlate specific dynamic conditions with the characteristic attributes of a population. By combining a boundary-layer diffusion controlled model for crystal growth/dissolution with discrete-element magma dynamics simulations of crystal-bearing magmas, the creation of populations can be simulated. We have implemented a method that decomposes the chemical potential into the thermal and compositional contributions to crystal dissolution/growth. This allows for the explicit treatment of thermal inertia and thermal-compositional decoupling as fluid circulation stirs the system during an open-system event. We have identified three distinct dynamic states producing crystal populations. They are based on the volume fraction of crystals. In a mushy system, thermal and compositional states are tightly linked as the volume involved in the mixing is constrained by the so-called mixing bowl (Bergantz et al., 2015). The mixing bowl volume is a function of the visco-plastic response of the mush and the intrusion width, not by the progressive entrainment of the new intrusion as commonly assumed. Crystal dissolution is the dominate response to input of more primitive magma. At the other endmember, under very dilute conditions, thermal and compositional conditions can become decoupled, and the in-coming magma forms a double-diffusive low-Re jet. This can allow for both dissolution and growth as crystals circulate widely into an increasingly stratified system. A middle range of crystal concentration produces a very complex feedback, as sedimenting crystals form fingers and chains that interact with the incoming magma, break-up the entrainment with chaotic stirring and add

  13. Growth of large detector crystals. CRADA final report

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A. [Oak Ridge National Lab., TN (United States); Samuelson, S. [Deltronic Crystal Industries, Dover, NJ (United States)


    In the course of a collaborative research effort between L.A. Boatner of Oak Ridge National Laboratory and Prof. Alex Lempicki of the Department of Chemistry of Boston University, a new highly efficient and very fast scintillator for the detection of gamma-rays was discovered. This new scintillator consists of a single crystal of lutetium orthophosphate (LuPO{sub 4}) to which a small percentage of trivalent cerium is added as an activator ion. The new lutetium orthophosphate-cerium scintillator was found to be superior in performance to bismuth germanium oxide--a material that is currently widely used as a gamma-ray detector in a variety of medical, scientific, and technical applications. Single crystals of LuPO{sub 4} and related rare-earth orthophosphates had been grown for a number of years in the ORNL Solid State Division prior to the discovery of the efficient gamma-ray-scintillation response of LuPO{sub 4}:Ce. The high-temperature-solvent (flux-growth) method used for the growth of these crystals was capable of producing crystals in sizes that were adequate for research purposes but that were inadequate for commercial-scale production and widespread application. The CRADA between ORNL and Deltronic Crystal Industries of Dover, NJ was undertaken for the purpose of investigating alternate approaches, such as top-seeded-solution growth, to the growth of LuPO{sub 4}:Ce scintillator crystals in sizes significantly larger than those obtainable through the application of standard flux-growth methods and, therefore, suitable for commercial sales and applications.

  14. Growth of Tungsten Bronze Family Crystals (United States)


    Keesrer. Mater Res BuL 15 t]s , 13(5the discussions on this. research b\\ Profesor .f J[19] R R Neurgaonkar W.K Cot.s and J R (Oi,’e- I-errocl. s otncs 35...L" tic . 22 𔃻 als, demonstrated’ the growth of excellent qual;tv bronze !N’BO.0. substrates using thie LPL and sputtering techniques. C.Car. to gt

  15. Growth, spectral and thermal studies of ibuprofen crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ramukutty, S.; Ramachandran, E. [Department of Physics, Thiruvalluvar College, Papanasam (India)


    RS -Ibuprofen was crystallized for the first time in silica gel under suitable pH conditions by reduction of solubility method. The grown crystals were characterized by single crystal X-ray diffraction and density measurement. The functional groups present in the crystal were identified using Fourier transform infrared spectroscopy. Optical bandgap energy of ibuprofen was estimated as 3.19(3) eV from UV-Vis spectrum. Thermogravimetric analysis revealed that ibuprofen is thermally stable upto 102.9 C and the initial loss of mass was due to evaporation only. Morphological study showed that the growth is prominent along b-axis and the prominent face is {l_brace}100{r_brace}. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. In Situ μGISAXS: II. Thaumatin Crystal Growth Kinetic (United States)

    Gebhardt, Ronald; Pechkova, Eugenia; Riekel, Christian; Nicolini, Claudio


    The formation of thaumatin crystals by Langmuir-Blodgett (LB) film nanotemplates was studied by the hanging-drop technique in a flow-through cell by synchrotron radiation micrograzing-incidence small-angle x-ray scattering. The kinetics of crystallization was measured directly on the interface of the LB film crystallization nanotemplate. The evolution of the micrograzing-incidence small-angle x-ray scattering patterns suggests that the increase in intensity in the Yoneda region is due to protein incorporation into the LB film. The intensity variation suggests several steps, which were modeled by system dynamics based on first-order differential equations. The kinetic data can be described by two processes that take place on the LB film, a first, fast, process, attributed to the crystal growth and its detachment from the LB film, and a second, slower process, attributed to an unordered association and conversion of protein on the LB film. PMID:20713011

  17. Transient natural convection heat and mass transfer in crystal growth (United States)

    Han, Samuel S.


    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.

  18. Phase field simulations of ice crystal growth in sugar solutions

    NARCIS (Netherlands)

    Sman, Van Der R.G.M.


    We present the first model ever, that describes explicitly ice crystal growth in a sugar solution during freezing. This 2-D model uses the phase field method, supplemented with realistic, and predictive theories on the thermodynamics and (diffusion) kinetics of this food system. We have to make

  19. Growth morphology of zinc tris (thiourea) sulphate crystals

    Indian Academy of Sciences (India)

    The growth morphology of crystals of zinc tris(thiourea) sulphate (ZTS) is investigated experimentally, and computed using the Hartman–Perdok approach. Attachment energies of the observed habit faces are calculated for determining their relative morphological importance. A computer code is developed for carrying out ...

  20. Page 1 . Growth of single crystals in silica gels 133 ...

    Indian Academy of Sciences (India)

    Glockber D A and Soest J E 1969 J. Chem. Phys. 51 3143. Henisch H K 1970 Crystal growth in gels (Pennsylvania : University Press). Henisch H K, Dennis J and Honoka J I 1965 J. Phys. Chem. Solids 26 439. Joshi M S and Antony A V 1978 J. Mater. Sci, 13 939. Shiojiri M., Kaito C, Saito Y, Murakami M and Kawamoto J ...

  1. Modelling of transport phenomena and defects in crystal growth ...

    Indian Academy of Sciences (India)

    ... transport and defect phenomena involoved in the growth process with the ultimate aim of integrating them into a comprehensive numerical model. The sources of dislocation nucleation in the growing crystal are discussed, and the propagation and multiplication of these under the action of thermal stresses is discussed.

  2. Selective crystal growth of polymorphs and crystal-to-crystal thermal phase transition of non-peripherally alkyl-substituted phthalocyanine and tetrabenzotriazaporphyrin (United States)

    Ohmori, Masashi; Nakano, Chika; Fujii, Akihiko; Shimizu, Yo; Ozaki, Masanori


    Selective crystal growth of polymorphs and crystal-to-crystal thermal phase transition of non-peripherally alkyl-substituted macrocycle molecules, such as octapentylphthalocyanine (C5PcH2), octahexylphthalocyanine (C6PcH2), and octahexyltetrabenzotriazaporphyrin (C6TBTAPH2) have been investigated. Two types of single crystals, called α-type and β-type, were separately grown by controlling the recrystallization conditions, and the crystal structures were determined by single-crystal X-ray structure analysis. The irreversible crystal-to-crystal thermal phase transition from α-type to β-type were observed by the differential scanning calorimetry and temperature-controlled X-ray structure analysis. The selective crystal growth of the α-type or β-type and the irreversible crystal-to-crystal thermal phase transition have been discussed by taking the alkyl-substituent distribution into consideration.

  3. Low-Temperature and Rapid Growth of Large Single-Crystalline Graphene with Ethane. (United States)

    Sun, Xiao; Lin, Li; Sun, Luzhao; Zhang, Jincan; Rui, Dingran; Li, Jiayu; Wang, Mingzhan; Tan, Congwei; Kang, Ning; Wei, Di; Xu, H Q; Peng, Hailin; Liu, Zhongfan


    Future applications of graphene rely highly on the production of large-area high-quality graphene, especially large single-crystalline graphene, due to the reduction of defects caused by grain boundaries. However, current large single-crystalline graphene growing methodologies are suffering from low growth rate and as a result, industrial graphene production is always confronted by high energy consumption, which is primarily caused by high growth temperature and long growth time. Herein, a new growth condition achieved via ethane being the carbon feedstock to achieve low-temperature yet rapid growth of large single-crystalline graphene is reported. Ethane condition gives a growth rate about four times faster than methane, achieving about 420 µm min(-1) for the growth of sub-centimeter graphene single crystals at temperature about 1000 °C. In addition, the temperature threshold to obtain graphene using ethane can be reduced to 750 °C, lower than the general growth temperature threshold (about 1000 °C) with methane on copper foil. Meanwhile ethane always keeps higher graphene growth rate than methane under the same growth temperature. This study demonstrates that ethane is indeed a potential carbon source for efficient growth of large single-crystalline graphene, thus paves the way for graphene in high-end electronical and optoelectronical applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Crystal growth and property characterization for PIN–PMN–PT ternary piezoelectric crystals

    Directory of Open Access Journals (Sweden)

    Jian Tian


    Full Text Available Binary piezoelectric crystal Pb(Mg1/3Nb2/3O3–PbTiO3 (PMN–PT has excellent dielectric and piezoelectric properties, which has led to the commercialization for medical ultrasound imaging. Recently, there is a growing demand for piezoelectric crystals with improved thermal and electrical properties. Ternary piezoelectric crystals Pb(In1/2Nb1/2O3–Pb(Mg1/3Nb2/3O3–PbTiO3 (PIN–PMN–PT have increased depoling temperature and coercive field than binary PMN–PT. To better understand the ternary crystal system and improve crystal properties, we systematically investigated crystal growth of PIN–PMN–PT with modified Bridgman method. Like PMN–PT, PIN–PMN–PT crystals have excellent piezoelectric properties (e.g., k33 ~ 0.87–0.92, d33 ~ 1000–2200 pm/V. Higher PIN content leads to ~40°C increase in depoling temperature and more than doubling of coercive field(~7.0 kV/cm. Such improvements are advantageous for applications where high temperature and/or high-drive are needed.

  5. Control of crystal growth in water purification by directional freeze crystallization (United States)

    Conlon, William M. (Inventor)


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

  6. Curved faces in polymer crystals with asymmetrically spreading growth patches (United States)

    Ungar, Goran


    Polymer crystals often have curved faces. Understanding such morphology is of major interest since it allows distinction between fundamentally different theories of polymer crystallization. E.g. Sadler's ``roughness-pinning'' theory assumes that the curvature is a result of roughening transition on lateral faces. It has since been shown by Mansfield that the curvature can be explained quantitatively, essentially within the Lauritzen-Hoffman nucleation theory. However, the step propagation rates v implied in their treatment are substantially lower than predicted by the LH theory. The retardation appears to be due to the ``self-poisoning'' or ``pinning'' effect of incorrect chain attachment, effectively demonstrated by the extreme cases of growth rate minima in long-chain monodisperse n-alkanes. Recently crystals of poly(vinylidene fluoride) and alkanes C162H326 and C198H398 have been found with habits that can be best described as bounded by curved 110 faces. The interesting feature is the asymmetry of the curvature: while the faces are curved at one end, they are straight at the other. We carried out mathematical analysis of the curvature, generalizing the Mansfield model. We suggest that such asymmetric curvature arises from the propagation rates to the left, vl, and to the right, vr, being different because of the lack of mirror bisecting planes such as (110). By solving appropriate equations with moving boundaries, we obtained the shape of the growth front y(x,t). Calculated crystal habits gave excellent fits to the observed growth shapes of a-axis lenticular crystals of long alkanes and PVDF, as well as of single crystals of PEO. This explains some hitherto poorly understood morphologies and, in principle, allows independent measurements of step initiation and propagation rates in all polymers.

  7. Thin film modeling of crystal dissolution and growth in confinement (United States)

    Gagliardi, Luca; Pierre-Louis, Olivier


    We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.

  8. Experimental setup for rapid crystallization using favoured chemical ...

    Indian Academy of Sciences (India)


    tors (3005 type), the output of which drives the d.c. motor. M3. The solution of ... to motor M1 prevents rapid temperature fluctuations and hence ensures very good temperature control. The thermostatic bath is heated with an infrared lamp I at the base of the unit and ... through chains of hydrogen bonds and these polymers.

  9. Growth of bulk single crystals of organic materials for nonlinear optical devices - An overview (United States)

    Penn, Benjamin G.; Cardelino, Beatriz H.; Moore, Craig E.; Shields, Angela W.; Frazier, D. O.


    Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

  10. Crystal growth and characterization of REFeAsO (RE = La, Nd) and LaFePO

    Energy Technology Data Exchange (ETDEWEB)

    Adamski, Agnes; Abdel-Hafiez, Mahmoud; Krellner, Cornelius [Physikalisches Institut, Goethe Universitaet, D-60438 Frankfurt am Main (Germany)


    Since the discovery of iron-based superconductors, much effort was put on the crystal growth of the various systems and their characterization. Although, the initial flurry of activities was mainly performed on the 1111 systems, the focus has been rapidly shifted towards other materials, were large high-quality crystals are available. In contrast, the growth of sizeable high-quality single crystals of 1111 compounds is extremely challenging, slowing down the scientific progress in this type of compounds. Here we report on the crystal growth of 1111-type materials under ambient pressure conditions and by using the flux technique. The influence of the material to flux ratio was systematically studied. Subsequently, the obtained samples were analyzed with powder diffractometry, electron microscope, energy dispersive X-ray analysis, Laue diffractometry and magnetic measurements to analyze the structural and magnetic properties.

  11. Rapid Population Growth and its Implication for Malawi

    African Journals Online (AJOL)

    Worldwide concern has recently focused on the negative aspects of rapid population growth for the' future as regards natural and non-renewable re- sources, energy and the environment. A United. Nations sponsored international conference on. "Environment and Development" was held in Brazil. inJune 1992 to focus ...

  12. Nanoparticle-mediated nonclassical crystal growth of sodium fluorosilicate nanowires and nanoplates

    Directory of Open Access Journals (Sweden)

    Hongxia Li


    Full Text Available We observed nonclassical crystal growth of the sodium fluorosilicate nanowires, nanoplates, and hierarchical structures through self-assembly and aggregation of primary intermediate nanoparticles. Unlike traditional ion-by-ion crystallization, the primary nanoparticles formed first and their subsequent self-assembly, fusion, and crystallization generated various final crystals. These findings offer direct evidences for the aggregation-based crystallization mechanism.

  13. Page 1 Electrolytic growth and properties of AHT crystals 189 Figure ...

    Indian Academy of Sciences (India)

    Figure 2. AHT orthorhombic disphenoidal crystal and needle habit crystals grown in electrolytic cell. º. ; : 5 ...] l. : Table 1. Typical growth parameters for orthorhombic disphenoidal and long needle habit. AHT crystals. Period of. Current crystallization. (mA) (days) Size and habit of grown crystals. 0-05 6 Needles, 9 mm length.

  14. Screening and Crystallization Plates for Manual and High-throughput Protein Crystal Growth (United States)

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


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

  15. Fundamental Studies of Crystal Growth of Microporous Materials (United States)

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


    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

  16. Crystal growth within a phase change memory cell. (United States)

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


    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.

  17. Mathematical modeling and numerical simulation of Czochralski Crystal Growth

    Energy Technology Data Exchange (ETDEWEB)

    Jaervinen, J.; Nieminen, R. [Center for Scientific Computing, Espoo (Finland)


    A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)

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

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


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

  19. Growth of (101) Faces of Tetragonal Lysozyme Crystals: Measured Growth Rate Trends (United States)

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


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

  20. Single crystal growth of europium and ytterbium based intermetallic ...

    Indian Academy of Sciences (India)

    to dissolve the excess metal flux. Due to its low melting temperature of 156.6. ◦. C, indium is an ideal metal for use as a reactive flux (self- flux condition). It has widely been used for the synthe- sis and crystal growth of indium-rich binary and ternary indides. In many cases, a slight excess of indium sig- nificantly increases the ...

  1. Growth of crystalline semiconductor materials on crystal surfaces

    CERN Document Server

    Aleksandrov, L


    Written for physicists, chemists, and engineers specialising in crystal and film growth, semiconductor electronics, and various applications of thin films, this book reviews promising scientific and engineering trends in thin films and thin-films materials science. The first part discusses the physical characteristics of the processes occurring during the deposition and growth of films, the principal methods of obtaining semiconductor films and of reparing substrate surfaces on which crystalline films are grown, and the main applications of films. The second part contains data on epitaxial i

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

    Directory of Open Access Journals (Sweden)

    Finnegan Michael P


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

  3. Hydroxyapatite crystal deposition causing rapidly destructive arthropathy of the hip joint

    Directory of Open Access Journals (Sweden)

    Jae-Hyuk Yang


    Full Text Available Destructive arthropathy of the hip joint can be attributed to various etiologies like rheumatoid arthritis, aseptic necrosis of the femur head, Charcot′s joint, subacute septic arthritis, and tubercular arthritis. A disease that results in much rapid destruction of the hip joint and is not associated with clinical syndrome of above mentioned disease has been reported way back in 1970. However, no evidence-based study has been published to support hydroxyapatite (HA crystals as a probable cause of rapidly destructive arthropathy of the hip joint. We report a case with microscopic and biochemical confirmation of HA crystal deposition causing destructive arthropathy of the hip joint.

  4. Economic Growth of a Rapidly Developing Economy: Theoretical Formulation

    Directory of Open Access Journals (Sweden)

    Oleg Sergeyevich Sukharev


    Full Text Available The subject matter of the article is the description of economic growth. Modern economy is characterized by a high rate of changes. These changes are the limiting parameters of modern development, which requires a modification of the basic models of growth, the substantiation of the expediency and necessity of a rapid development strategy. In a simple mathematical form, the statement of the problem of economic growth in the “green economy” is examined, in which the costs of environmental measures are not considered a priori as hampering economic development (as it is common for a number of modern neoclassical and neo-Keynesian growth models. The methodological basis of the article are the econometric approach and modelling method. The article has a theoretical character. The main hypothesis supposes that the rapid development strategy cannot make an adequate development strategy under certain conditions, but may be acceptable in other its specific conditions. In this sense, the important growth conditions are the availability of resources, the effectiveness of institutions and the current economic structure, the technological effectiveness of economy, as well as the conditions of technological development (“green economy” and the path of such development. In the article, on the theoretical level of analysis, the substantiation of the adequacy of the rapid development strategy for an economic system is given, whose goal is to achieve the standard of living of the countryleader. Based on the assumptions introduced, the period for which the rapid development strategy might be implemented and the economic lag of the country might be reduced from the country-leader is determined. The conditions that ensure the impact of innovations on the rate of economic development are summarized. The introduced range of dependencies and relations can be useful for the elaboration of the theory of innovation development and for the formation of a new

  5. Magnetic Control in Crystal Growth from a Melt (United States)

    Huang, Yue

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

  6. Population priorities: the challenge of continued rapid population growth. (United States)

    Turner, Adair


    Rapid population growth continues in the least developed countries. The revisionist case that rapid population could be overcome by technology, that population density was advantageous, that capital shallowing is not a vital concern and that empirical investigations had not proved a correlation between high population growth and low per capita income was both empirically and theoretically flawed. In the modern world, population density does not play the role it did in nineteenth-century Europe and rates of growth in some of today's least developed nations are four times than those in nineteenth-century Europe, and without major accumulation of capital per capita, no major economy has or is likely to make the low- to middle-income transition. Though not sufficient, capital accumulation for growth is absolutely essential to economic growth. While there are good reasons for objecting to the enforced nature of the Chinese one-child policy, we should not underestimate the positive impact which that policy has almost certainly had and will have over the next several decades on Chinese economic performance. And a valid reticence about telling developing countries that they must contain fertility should not lead us to underestimate the severely adverse impact of high fertility rates on the economic performance and prospects of many countries in Africa and the Middle East.

  7. In vitro crystallization, characterization and growth-inhibition study of urinary type struvite crystals (United States)

    Chauhan, Chetan K.; Joshi, Mihir J.


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

  8. Acquisition of Single Crystal Growth and Characterization Equipment

    Energy Technology Data Exchange (ETDEWEB)

    Maple, M. Brian; Zocco, Diego A.


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

  9. Regional Rapid Growth in Cities and Urbanization in Thailand

    Directory of Open Access Journals (Sweden)

    Thanadorn Phuttharak


    Full Text Available This article aims to investigate the driving forces affecting regional rapid growth in Thailand, along with its impact, to understand the dynamics of urbanization and how it affects cities. The study selected UdonThani Province, Thailand, as a case study. This study collected data from academic and semi-academic documents, semi-structured interviews, participatory and non-participatory observations, and group discussion. The informants were residents within municipalities, government, and private officers related to city development, and NGOs. The results found that the driving forces affecting regional rapid growth in UdonThani province include: 1 historic events from World War II to the Cold War; 2 events during the Vietnam War; 3 Capitalist policies; and 4 the establishment of the ASEAN Economic Community (AEC. The study also found impacts of regional rapid growth in UdonThani province including 1 land use change; 2 economic and societal change; 3 road and traffic problems; and 4 waste disposal problems.

  10. Growth and Characterization of Lead-free Piezoelectric Single Crystals

    Directory of Open Access Journals (Sweden)

    Philippe Veber


    Full Text Available Lead-free piezoelectric materials attract more and more attention owing to the environmental toxicity of lead-containing materials. In this work, we review our first attempts of single crystal grown by the top-seeded solution growth method of BaTiO3 substituted with zirconium and calcium (BCTZ and (K0.5Na0.5NbO3 substituted with lithium, tantalum, and antimony (KNLSTN. The growth methodology is optimized in order to reach the best compositions where enhanced properties are expected. Chemical analysis and electrical characterizations are presented for both kinds of crystals. The compositionally-dependent electrical performance is investigated for a better understanding of the relationship between the composition and electrical properties. A cross-over from relaxor to ferroelectric state in BCTZ solid solution is evidenced similar to the one reported in ceramics. In KNLSTN single crystals, we observed a substantial evolution of the orthorhombic-to-tetragonal phase transition under minute composition changes.

  11. Stability of amorphous pharmaceutical solids: crystal growth mechanisms and effect of polymer additives. (United States)

    Sun, Ye; Zhu, Lei; Wu, Tian; Cai, Ting; Gunn, Erica M; Yu, Lian


    We review recent progress toward understanding and enhancing the stability of amorphous pharmaceutical solids against crystallization. As organic liquids are cooled to become glasses, fast modes of crystal growth can emerge. One such growth mode, the glass-to-crystal or GC mode, occurs in the bulk, and another exists at the free surface, both leading to crystal growth much faster than predicted by theories that assume diffusion defines the kinetic barrier of crystallization. These phenomena have received different explanations, and we propose that GC growth is a solid-state transformation enabled by local mobility in glasses and that fast surface crystal growth is facilitated by surface molecular mobility. In the second part, we review recent findings concerning the effect of polymer additives on crystallization in organic glasses. Low-concentration polymer additives can strongly inhibit crystal growth in the bulk of organic glasses, while having weaker effect on surface crystal growth. Ultra-thin polymer coatings can inhibit surface crystallization. Recent work has shown the importance of molecular weight for crystallization inhibitors of organic glasses, besides "direct intermolecular interactions" such as hydrogen bonding. Relative to polyvinylpyrrolidone, the VP dimer is far less effective in inhibiting crystal growth in amorphous nifedipine. Further work is suggested for better understanding of crystallization of amorphous organic solids and the prediction of their stability.

  12. Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars (United States)

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


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

  13. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei


    crystals will be discussed in Chapter 3 and 4. Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios and free standing growth. As the other major part of work of this dissertation, explorative work on growing organolead halide perovskite monocrystalline films and further their application in solar cells will be discussed in Chapter 5.

  14. Development of SiC Large Tapered Crystal Growth (United States)

    Neudeck, Phil


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

  15. Delta L: An Apparatus for Measuring Macromolecular Crystal Growth Rates in Microgravity (United States)

    Judge, Russell A.; Whitaker, Ann F. (Technical Monitor)


    In order to determine how macromolecule crystal quality improvement in microgravity is related to crystal growth characteristics, is was necessary to develop new hardware that could measure the crystal growth rates of a population of crystals growing under the same solution conditions. As crystal growth rate is defined as the change or delta in a defined dimension or length (L) of a crystal over time, the hardware was named Delta L. Delta L consists of fluids, optics, and data acquisition, sub-assemblies. Temperature control is provided for the crystal growth chamber. 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 (ISS). Delta L prototype hardware has been assembled. This paper will describe an overview of the design of Delta L and present preliminary crystal growth rate data.

  16. Bovine gallbladder mucin accelerates cholesterol monohydrate crystal growth in model bile. (United States)

    Afdhal, N H; Niu, N; Gantz, D; Small, D M; Smith, B F


    Gallbladder mucin accelerates cholesterol crystal nucleation, an early step in the pathogenesis of gallstones. To examine the role of gallbladder mucin in postnucleation gallstone maturation, the influence of mucin on cholesterol monohydrate crystal growth was studied in a novel model system. Cholesterol crystals of a uniform size were incubated in model biles at 37 degrees C with varying cholesterol saturation indices. Crystal size was quantitated by measuring the width and length of individual crystals under polarizing light microscopy and calculating average crystal area. Crystal growth was dependent on the degree of cholesterol supersaturation of bile. Bovine gallbladder mucin (0.5-8 mg/mL) accelerated crystal growth in supersaturated model bile in a concentration- and time-dependent fashion compared with control incubations with bovine serum albumin or model bile alone (P < 0.05). Cholesterol crystal growth was accompanied by a progressive decrease in cholesterol saturation and an increase in total cholesterol crystal mass. Crystal growth was also accompanied by a decrease in total crystal number, suggesting net transfer of cholesterol to larger crystals. The acceleration of cholesterol crystal growth by gallbladder mucin may be of pathophysiological importance in the postnucleation maturation of cholesterol gallstones.

  17. Crystal growth of bismuth(V) oxides from hydroxide fluxes (United States)

    Bharathy, M.; Khalsa, Hargobind S.; Smith, Mark D.; zur Loye, H.-C.


    The first example of a 2 H-perovskite related A3A'BiO 6 oxide, (Sr 2.59Ba 0.41)NaBiO 6, with two different divalent cations on the A site, was synthesized in a reactive, mixed strontium-, barium-, sodium-hydroxide flux. (Sr 2.59Ba 0.41)NaBiO 6 crystallizes in the space group R3¯c, with a = 9.9839(2) Å and c = 11.8008(4) Å. Crystals of isostructural oxides, Sr 3NaBiO 6 and Sr 3LiBiO 6, were also obtained from reactive Sr(OH) 2, NaOH and LiOH fluxes. Sr 3NaBiO 6 and Sr 3LiBiO 6 crystallize in the space group R3¯c with a = 9.9193(2) Å, c = 11.7473(5) Å and a = 9.9293(2) Å, c = 11.4188(5) Å, respectively. In addition, we report the crystal growth of a strontium bismuth oxyhydroxide, Sr 4(BiO 6)(OH), isolated from a reactive Sr(OH) 2 flux contained in sealed silver tubes. Sr 4(BiO 6)(OH) crystallizes in the monoclinic space group, P2 1 with a = 6.9429(8) Å, b = 6.1286(7) Å, c = 9.2746(10) Å, and β = 102.176(2)°. The structure consists of layers of connected SrO x polyhedra, with isolated BiO 6 octahedra located in every second Sr-O layer.

  18. Czochralski growth of crystals - Simple models for growth rate and interface shape (United States)

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


    A simple model for the crystal growth by the Czochralski (CZ) process has been proposed based on semiquantitative arguments. The model provides empirical relationships for the dependence of the pulling rate and the interface shape on the important process variables such as crystal radius, crucible temperature, height of the melt level, and the height of the exposed portion of the crucible wall. The parameters of the model can be evaluated by matching the results obtained from a detailed mathematical model of the CZ process or from extensive experimental data. The model has, therefore, the potential application for determining the best process conditions and for on-line control and optimization of the crystal puller to grow crystals with constant diameter and nearly planar interface.

  19. Incidence of crystal growth conditions on the formation of macroscopic liquid inclusions in ciclopirox crystals (United States)

    Waldschmidt, Audrey; Dupray, Valérie; Berton, Benjamin; Couvrat, Nicolas; Petit, Samuel; Coquerel, Gérard


    Using an accurate and rigorous protocol, the crystal growth behavior in solution of the antifungal drug ciclopirox was investigated with the aim to identify the experimental factors responsible for the appearance of macroscopic inclusions of saturated solution. Counterintuitively, these inclusions are produced only when the relative supersaturation is below a critical threshold; simultaneously the crystals exhibit a hexagonal morphology. An increase in the driving force leads to a rod-shaped morphology without inclusion and without any change of the crystal phase, as confirmed by X-ray diffraction. The correlation between this morphological transition and the occurrence of liquid inclusions could be rationalized by considering the associated change of growth rates of {(1 1 1)} and {(1 1 -1)} faces. However, the nature of the solvent, the presence of impurities and diffusion in solution appeared to have no detectable incidence on the formation of liquid inclusions, inducing that the presumed contribution of a chemical adsorption phenomenon—side products or solvents—could not be established.

  20. Inclusion free cadmium zinc tellurium and cadmium tellurium crystals and associated growth method (United States)

    Bolotnikov, Aleskey E [South Setauket, NY; James, Ralph B [Ridge, NY


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

  1. Rapid thermal chemical vapor deposition growth of nanometer-thin SiC on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Steckl, A.J.; Li, J.P. (Univ. of Cincinnati, OH (United States))


    Rapid thermal chemical vapor deposition growth of [beta]-SiC ultrathin films on Si (100) was achieved using the carbonization reaction of the silicon substrate with C[sub 3]H[sub 8] gas. Growth rates of 0.5-2 nm s[sup -1] have been achieved at 1100-1300degC using C[sub 3]H[sub 8] flow rates of 7-9 standard cm[sup 3] min[sup -1]. X-ray and electron diffraction indicate single-crystal growth. Therefore nanometer-scale SiC films can be grown by controlling the reaction time to a few seconds. The activation energy at atmospheric pressure is 3.12 eV. The growth rate was found to decrease significantly at higher C[sub 3]H[sub 8] flow rates, leading to films of constant thickness beyond a certain critical reaction time. Using this regime of self-limiting growth, SiC films of 3-5 nm have been grown with relatively little sensitivity to the growth time. (orig.).

  2. On the origin of radiation growth of hcp crystals

    Energy Technology Data Exchange (ETDEWEB)

    Golubov, Stanislav I [ORNL; Barashev, Aleksandr [University of Liverpool; Stoller, Roger E [ORNL


    The aim of the present work is to study theoretically the radiation growth (RG) of hcp-type materials with a particular focus on the effect of one-dimensionally (1-D) migrating clusters of self-interstitial atoms (SIAs), which are steadily produced in displacement cascades under neutron or heavy-ion irradiation. A reaction-diffusion model is developed for the description of RG in single hcp-type metallic crystals. The model reproduces all RG stages observed in neutron-irradiated annealed samples of pure Zr and Zr alloys, such as high strain rate at low, strain saturation at intermediate and breakaway growth at relatively high irradiation doses. In addition, it accounts for the striking observations of negative strains in prismatic directions and coexistence of vacancy- and SIA-type prismatic loops. The role of cold work in RG behavior and alignment of the vacancy-type loops along basal planes are revealed and the maximum strain rate is estimated.

  3. A preliminary review of organic materials single crystal growth by the Czochralski technique (United States)

    Penn, B. G.; Shields, A. W.; Frazier, D. O.


    The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed.

  4. Growth inhibition of struvite crystals in the presence of herbal extract Commiphora wightii. (United States)

    Chauhan, C K; Joshi, M J; Vaidya, A D B


    Struvite is one of the components of urinary stone. Large number of people is suffering from urinary stones (calculi) problem all over the globe. These stones can grow rapidly forming "staghorn-calculi", which is more painful urological disorder. Therefore, it is of prime importance to study the growth and inhibition of Struvite crystals. This in vitro study has been carried out in the presence of herbal extract of Commiphora wightii by using single diffusion gel growth technique. Sodium metasilicate solution of specific gravity 1.05 and an aqueous solution of ammonium dihydrogen phosphate of 0.5 M concentration were mixed so that the pH value 7.0 could be set. After the gelation, equal amount of supernatant solutions comprising of pure 1.0 M magnesium acetate as well as the mixtures of magnesium acetate and the herbal extract solutions of 0.5 and 1% concentrations of C. wightii were gently poured on the set gels. From the study of growth and inhibition behavior of Struvite crystals, it was found that C. wightii inhibits the growth of the Struvite. This study incorporates multidisciplinary interests and may be used for formulating the strategy for prevention or dissolution of urinary stones.

  5. Controlled Growth of Organic Semiconductor Films Using Liquid Crystal Solvents (United States)

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


    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.

  6. Polygenic Risk, Rapid Childhood Growth, and the Development of Obesity (United States)

    Belsky, Daniel W.; Moffitt, Terrie E.; Houts, Renate; Bennett, Gary G.; Biddle, Andrea K.; Blumenthal, James A.; Evans, James P.; Harrington, HonaLee; Sugden, Karen; Williams, Benjamin; Poulton, Richie; Caspi, Avshalom


    Objective To test how genomic loci identified in genome-wide association studies influence the development of obesity. Design A 38-year prospective longitudinal study of a representative birth cohort. Setting The Dunedin Multidisciplinary Health and Development Study, Dunedin, New Zealand. Participants One thousand thirty-seven male and female study members. Main Exposures We assessed genetic risk with a multilocus genetic risk score. The genetic risk score was composed of single-nucleotide polymorphisms identified in genome-wide association studies of obesity-related phenotypes. We assessed family history from parent body mass index data collected when study members were 11 years of age. Main Outcome Measures Body mass index growth curves, developmental phenotypes of obesity, and adult obesity outcomes were defined from anthropometric assessments at birth and at 12 subsequent in-person interviews through 38 years of age. Results Individuals with higher genetic risk scores were more likely to be chronically obese in adulthood. Genetic risk first manifested as rapid growth during early childhood. Genetic risk was unrelated to birth weight. After birth, children at higher genetic risk gained weight more rapidly and reached adiposity rebound earlier and at a higher body mass index. In turn, these developmental phenotypes predicted adult obesity, mediating about half the genetic effect on adult obesity risk. Genetic associations with growth and obesity risk were independent of family history, indicating that the genetic risk score could provide novel information to clinicians. Conclusions Genetic variation linked with obesity risk operates, in part, through accelerating growth in the early childhood years after birth. Etiological research and prevention strategies should target early childhood to address the obesity epidemic. PMID:22665028

  7. Growth of BPO4 single crystals from Li2Mo3O10 flux (United States)

    Xu, Guogang; Li, Jing; Han, Shujuan; Guo, Yongjie; Wang, Jiyang


    Transparent single crystal of BPO4 with a typical sizes of 5 × 7 × 9 mm3 have been grown by the top-seeded solution growth (TSSG) slow-cooling method using Li2Mo3O10 as the flux. X-ray powder diffraction result shows that the as-grown crystal was well crystallized and indexed in a tetragonal system. The processing parameters and the effects of the flux on the crystal growth were investigated.

  8. Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique (United States)


    develop a new single crystal growth method which is suitable to grow chemically uniform and large “n- and p-type doped” perovskite single crystals...boundary are also fabricated using diffusion bonding process of two single crystal plates. These results demonstrate that the SSCG (solid-state...that can be used to develop new non-linear dielectrics for high-voltage and high-power applications. A major need is to better understand their

  9. Simple geometry for diffusion limited protein crystal growth: harnessing gravity to suppress convection

    NARCIS (Netherlands)

    Poodt, P.W.G.; Heijna, M.C.R.; Schouten, A.; Gros, P.; van Enckevort, W.J.P.; Vlieg, E.


    A new upside-down geometry is proposed to achieve the beneficial effects of microgravity crystal growth by making use of buoyant forces instead of compensating for them. We show by growth experiments on sodium chlorate and lysozyme that crystal growth in an upside-down geometry leads to the

  10. Deterministic patterned growth of high-mobility large-crystal graphene: a path towards wafer scale integration (United States)

    Miseikis, Vaidotas; Bianco, Federica; David, Jérémy; Gemmi, Mauro; Pellegrini, Vittorio; Romagnoli, Marco; Coletti, Camilla


    We demonstrate rapid deterministic (seeded) growth of large single-crystals of graphene by chemical vapour deposition (CVD) utilising pre-patterned copper substrates with chromium nucleation sites. Arrays of graphene single-crystals as large as several hundred microns are grown with a periodicity of up to 1 mm. The graphene is transferred to target substrates using aligned and contamination- free semi-dry transfer. The high quality of the synthesised graphene is confirmed by Raman spectroscopy and transport measurements, demonstrating room-temperature carrier mobility of 21 000 cm2 V-1 s-1 when transferred on top of hexagonal boron nitride. By tailoring the nucleation of large single-crystals according to the desired device geometry, it will be possible to produce complex device architectures based on single-crystal graphene, thus paving the way to the adoption of CVD graphene in wafer-scale fabrication.

  11. Growth and characterization of urea sulphamic acid single crystals (United States)

    Chinnasamy, E.; Senthil, S.


    Single crystal of Urea Sulphamic acid (USA) single crystals were grown and harvested successfully at room temperature by slow solvent evaporation method. The cell parameters of the grown crystal were determined by single crystal X-ray diffraction analysis. The presence of various functional groups in the crystal is confirmed by FT-IR analysis. The optical transmission study reveals the transparency of the crystal and its optical band gap is found to be 4.74 eV. The crystal quality can be further examined by the time resolved Photoluminescence Spectroscopy. Laser damage threshold study was also carried for the grown crystal.

  12. Mn3O4 nano-sized crystals: Rapid synthesis and extension to ...

    Indian Academy of Sciences (India)

    Mn3O4 nano-sized crystals: Rapid synthesis and extension to preparation of nanosized LiMn2O4 materials. XIAO-LING CUI, YONG-LI LI, SHI-YOU LI. ∗. , GUO-CUN SUN, JIN-XIA MA,. LU ZHANG, TIAN-MING LI and RONG-BO MA. College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, ...

  13. Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method (United States)

    Choi, J.; Cruz, Magda; Metzl, R.; Wang, W. S.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.


    A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

  14. Growth of cadmium oxide whiskers on cadmium sulphide single crystals with copper as growth activator

    Energy Technology Data Exchange (ETDEWEB)

    Koparanova, N.; Simov, S. (Bylgarska Akademiya na Naukite, Sofia. Inst. po Fizika na Tvyrdoto Tyalo); Genchev, D. (Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika); Metchenov, G. (Research Inst. of Criminalistics and Criminology, Sofia (Bulgaria))


    Some results on the growth and morphology of cadmium oxide whiskers, obtained on cadmium sulphide single crystals with copper as a growth activator, are presented in this work. Cadmium oxide whiskers have been obtained on brace 112-bar0 brace faces of cadmium sulphide plates with a copper layer deposited in advance. The whiskers grew during the annealing of the plates in a weak stream of technically pure argon at temperatures 670 to 730 deg C for 15 min to 3.5 h. Details about the procedure have been given elsewhere. The composition and morphology of the whiskers have been studied by an X-ray microanalyser JEOL 35 DDS and a scanning electron microscope JEOL, JSM 35. The optical microscopic observations have shown that after annealing, a gray-black granular layer is formed on the cadmium sulphide single crystals and this layer can easily be separated from the crystal substrate. Under the granular layer the crystal is heavily damaged. The whiskers grow on the granular layer and they are coloured yellow-brown or red-brown. The maximum whisker length attains several hundreds of micrometres and in some cases up to 1 mm or more.

  15. Rapid crystallization of WS{sub 2} films assisted by a thin nickel layer: An in situ energy-dispersive X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Ellmer, K.; Seeger, S. [Hahn-Meitner-Institut Berlin, Dept. Solare Energetik, Glienicker Str. 100, 14109 Berlin (Germany); Mientus, R. [Opto-Transmitter-Umweltschutz-Technologie e.V., Koepenicker Str. 325b, 12555 Berlin (Germany)


    By rapid thermal crystallization of an amorphous WS{sub 3+x} film, deposited by reactive magnetron sputtering at temperatures below 150 C, layer-type semiconducting tungsten disulfide films (WS{sub 2}) were grown. The rapid crystallization was monitored in real-time by in situ energy-dispersive X-ray diffraction. The films crystallize very fast (>40 nm/s), provided that a thin nickel film acts as nucleation seeds. Experiments on different substrates and the onset of the crystallization only at a temperature between 600 and 700 C points to the decisive role of seeds for the textured growth of WS{sub 2}, most probably liquid NiS{sub x} drops. The rapidly crystallized WS{sub 2} films exhibit a pronounced (001) texture with the van der Waals planes oriented parallel to the surface, leading to photoactive layers with a high hole mobility of about 80 cm{sup 2}/Vs making such films suitable as absorbers for thin film solar cells. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Wafer-scale single-crystal perovskite patterned thin films based on geometrically-confined lateral crystal growth (United States)

    Lee, Lynn; Baek, Jangmi; Park, Kyung Sun; Lee, Yong-Eunkoo; Shrestha, Nabeen K.; Sung, Myung M.


    We report a facile roll-printing method, geometrically confined lateral crystal growth, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovskite thin films. Geometrically confined lateral crystal growth is based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent. The striking feature of this method is that the instant crystallization of the feeding solution under geometrical confinement leads to the unidirectional lateral growth of single-crystal perovskites. Here, we fabricated single-crystal perovskites in the form of a patterned thin film (3 × 3 inch) with a high carrier mobility of 45.64 cm2 V-1 s-1. We also used these single-crystal perovskite thin films to construct solar cells with a lateral configuration. Their active-area power conversion efficiency shows a highest value of 4.83%, which exceeds the literature efficiency values of lateral perovskite solar cells.

  17. Wafer-scale single-crystal perovskite patterned thin films based on geometrically-confined lateral crystal growth (United States)

    Lee, Lynn; Baek, Jangmi; Park, Kyung Sun; Lee, Yong-EunKoo; Shrestha, Nabeen K.; Sung, Myung M.


    We report a facile roll-printing method, geometrically confined lateral crystal growth, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovskite thin films. Geometrically confined lateral crystal growth is based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent. The striking feature of this method is that the instant crystallization of the feeding solution under geometrical confinement leads to the unidirectional lateral growth of single-crystal perovskites. Here, we fabricated single-crystal perovskites in the form of a patterned thin film (3 × 3 inch) with a high carrier mobility of 45.64 cm2 V−1 s−1. We also used these single-crystal perovskite thin films to construct solar cells with a lateral configuration. Their active-area power conversion efficiency shows a highest value of 4.83%, which exceeds the literature efficiency values of lateral perovskite solar cells. PMID:28691697

  18. In-Situ Crystallization of a Lithium Disilicate Glass--Effect of Pressure on Crystal Growth Rate (United States)

    Fuss, T.; Ray, C. S.; Lesher, C. E.; Day, D. E.


    Crystallization of a Li2O.2SiO2 (LS2) glass subjected to a uniform hydrostatic pressure of 4.5 GPa and 6 GPa was investigated up to a temperature of 750 C. The density of the compressed glass is about 2% greater at 4.5 GPa than at 1 atm and, depending upon the processing temperature, up to 10% greater at 6 GPa. Crystal growth rates investigated as a function of temperature and pressure show that lithium disilicate crystal growth is an order of magnitude slower at 4.5 GPa than 1 atm resulting in a shift of +45 C (plus or minus 10 C) in the growth rate curve at high pressure compared to 1 atm condition. At 6 GPa lithium disilicate crystallization is suppressed entirely, while a new high pressure lithium metasilicate crystallizes at temperatures 95 C (plus or minus 10 C) higher than those reported for lithium disilicate crystallization at 1 atm. The decrease in crystal growth rate with increasing pressure for lithium disilicate glass up to 750 C is related to an increase in viscosity with pressure associated with fundamental changes in glass structure accommodating densification.

  19. Coupling between Molecular Mobility and Kinetics of Crystal Growth in a Hydrogen-Bonded Liquid

    DEFF Research Database (Denmark)

    Sanz, Alejandro; Niss, Kristine


    rate. The coupling between dynamic properties, such as dielectric α relaxation time, viscosity, and self-diffusion coefficient, and the characteristic crystal growth time is analyzed. We find that the crystal growth time scales with the glycerol’s self-diffusion coefficient as taucryst ∝ D−0......Our aim here is to gain new insight into the nature of the crystalline phase formed in supercooled glycerol near the glass transition temperature and to establish the interrelationship between the kinetics of crystal growth and fundamental dynamic properties. The liquid’s dynamics...... of the crystalline phase from preexisting nuclei, in such a way that the observed kinetics is dominated by the crystal growth step. Our experimental results are discussed in terms of the classical theory of crystallization which predicts a significant correlation between the liquid’s diffusion and the crystal growth...

  20. Growth-melt asymmetry in ice crystals under the influence of spruce budworm antifreeze protein

    Energy Technology Data Exchange (ETDEWEB)

    Pertaya, Natalya [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); Celik, Yeliz [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); DiPrinzio, Carlos L [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); Wettlaufer, J S [Department of Geology and Geophysics, Yale University, New Haven, CT 06520-8109 (United States); Davies, Peter L [Department of Biochemistry, Queen' s University, Kingston, ON K7L 3N6 (Canada); Braslavsky, Ido [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)


    Here we describe studies of the crystallization behavior of ice in an aqueous solution of spruce budworm antifreeze protein (sbwAFP) at atmospheric pressure. SbwAFP is an ice binding protein with high thermal hysteresis activity, which helps protect Choristoneura fumiferana (spruce budworm) larvae from freezing as they overwinter in the spruce and fir forests of the north eastern United States and Canada. Different types of ice binding proteins have been found in many other species. They have a wide range of applications in cryomedicine and cryopreservation, as well as the potential to protect plants and vegetables from frost damage through genetic engineering. However, there is much to learn regarding the mechanism of action of ice binding proteins. In our experiments, a solution containing sbwAFP was rapidly frozen and then melted back, thereby allowing us to produce small single crystals. These maintained their hexagonal shapes during cooling within the thermal hysteresis gap. Melt-growth-melt sequences in low concentrations of sbwAFP reveal the same shape transitions as are found in pure ice crystals at low temperature (-22 deg. C) and high pressure (2000 bar) (Cahoon et al 2006 Phys. Rev. Lett. 96 255502); while both growth and melt shapes display faceted hexagonal morphology, they are rotated 30 deg. relative to one another. Moreover, the initial melt shape and orientation is recovered in the sequence. To visualize the binding of sbwAFP to ice, we labeled the antifreeze protein with enhanced green fluorescent protein (eGFP) and observed the sbwAFP-GFP molecules directly on ice crystals using confocal microscopy. When cooling the ice crystals, facets form on the six primary prism planes (slowest growing planes) that are evenly decorated with sbwAFP-GFP. During melting, apparent facets form on secondary prism planes (fastest melting planes), leaving residual sbwAFP at the six corners of the hexagon. Thus, the same general growth-melt behavior of an apparently

  1. Growth of single-crystal YAG fiber optics. (United States)

    Nie, Craig D; Bera, Subhabrata; Harrington, James A


    Single-crystal YAG (Y3Al5O12) fibers have been grown by the laser heated pedestal growth technique with losses as low as 0.3 dB/m at 1.06 μm. These YAG fibers are as long as about 60 cm with diameters around 330 μm. The early fibers were grown from unoriented YAG seed fibers and these fibers exhibited facet steps or ridges on the surface of the fiber. However, recently we have grown fibers using an oriented seed to grow step-free fibers. Scattering losses made on the fibers indicate that the scattering losses are equal to about 30% of the total loss.

  2. Growth of 2-amino-5-chlorobenzophenone single crystal by ...

    Indian Academy of Sciences (India)

    Abstract. Organic single crystals of 2-amino-5-chlorobenzophenone (2A5CB) were grown by Microtube Czochral- ski method using Microtube as a seed. The grown crystals were characterized by single crystal and powder X-ray diffraction. The functional groups of the grown crystal were found using Fourier transform ...

  3. Growth of 2-amino-5-chlorobenzophenone single crystal by ...

    Indian Academy of Sciences (India)

    Organic single crystals of 2-amino-5-chlorobenzophenone (2A5CB) were grown by Microtube Czochralski method using Microtube as a seed. The grown crystals were characterized by single crystal and powder X-ray diffraction. The functional groups of the grown crystal were found using Fourier transform infrared ...

  4. The Averaged Face Growth Rates of lysozyme Crystals: The Effect of Temperature (United States)

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


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

  5. Single crystal: Urea bisthiourea sodium acetate synthesis, growth and characterization (United States)

    Manickam, R.; Srinivasan, G.


    Crystals of urea bisthiourea sodium acetate (UBTSA) were successfully grown from an aqueous solution by slow evaporation method at room temperature. Recrystallization process was used to increase the purity of the grown crystal. The grown crystals were characterized by single crystal XRD, FT-Raman, UV and TGA/DTA analysis. Structure and unit cell parameters were determined by single crystal XRD. Functional groups of grown crystal and their modes of vibration were identified using FT-Raman spectral analysis. Absorbance percentage of the grown crystal was studied using UV analysis. Thermo gravimetric analysis and differential thermal analysis reveal that the good thermal stability of the material.

  6. Measuring Carbon and Oxygen Isotope Uptake into Inorganic Calcite using Crystal Growth Experiments (United States)

    Baker, E. B.; Watkins, J. M.


    Carbon and oxygen isotopes measured on natural calcite crystals provide a record of paleo-environment conditions. Despite the importance of measuring stable isotopes in calcite for paleo-environment reconstructions, there is neither a general theory nor an experimental data set that fully separates the effects of pH, temperature, and precipitation rate on isotope discrimination during calcite growth. Many stable isotope studies of calcite have focused on either carbon or oxygen isotope compositions individually, but few have measured both carbon and oxygen isotope uptake in the same set of crystals. We are precipitating inorganic calcite across a range in temperature, pH, and precipitation rate to guide the development of a general theory for combined carbon and oxygen isotope uptake into calcite crystals grown on laboratory timescales. In our experiments, dissolved inorganic carbon (DIC) is added to an aqueous solution (15 mM CaCl2 + 5 mM NH4Cl) by CO2 bubbling. Once a critical supersaturation is reached, calcite crystals nucleate spontaneously and grow on the beaker walls. A key aspect of this experimental approach is that the δ13C of DIC is relatively constant throughout the crystal growth period, because there is a continuous supply of DIC from the CO2-bearing bubbles. Carbonic anhydrase, an enzyme promoting rapid equilibration of isotopes between DIC and water, was added to ensure that the solution remained isotopically equilibrated during calcite growth. We have conducted experiments at T = 25°C and pH = 8.3 - 9.0. We observe that the fractionation of oxygen isotopes between calcite and water decreases with increasing pH, consistent with available data from experiments in which the enzyme carbonic anhydrase was used. Our results for carbon isotopes extend the available data set, which previously ranged from pH 6.62 to 7.75, to higher pH. At pH 8.3, we observe that calcite is isotopically heavier than DIC with respect to carbon isotopes by about 0.25‰. At

  7. Investigation on the bulk growth of α-LiIO 3 single crystals and the ...

    Indian Academy of Sciences (India)


    Jul 26, 2017 ... the crystal growth rate several times with the conservation of crystal quality was demonstrated [17]. ... salt was increased by successive recrystallization process and solution was prepared using the ... pH 10 in comparison to the synthesized salt at pH 2 for the further studies. α-LiIO3 crystals grown at pH 10 ...

  8. Crystal growth iron based pnictide compounds; Kristallzuechtung eisenbasierter Pniktidverbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Nacke, Claudia


    The present work is concerned with selected crystal growth method for producing iron-based superconductors. The first part of this work introduces significant results of the crystal growth of BaFe{sub 2}As{sub 2} and the cobalt-substituted compound Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} with x{sub Nom} = 0.025, 0.05, 0.07, 0.10 and 0.20. For this purpose a test procedure for the vertical Bridgman method was developed. The second part of this work contains substantial results for growing a crystal of LiFeAs and the nickel-substituted compound Li{sub 1-δ}Fe{sub 1-x}Ni{sub x}As with x{sub Nom} = 0.015, 0.025, 0.05, 0.06, 0.075 and 0.10. For this purpose a test procedure for the melt flow process has been developed successfully. [German] Die vorliegende Arbeit befasst sich mit ausgewaehlten Kristallzuechtungsverfahren zur Herstellung eisenbasierter Supraleiter. Der erste Teil dieser Arbeit fuehrt wesentliche Ergebnisse der Kristallzuechtung von BaFe{sub 2}As{sub 2} sowie der Cobalt-substituierten Verbindung Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} mit x{sub Nom} =0.025, 0.05, 0.07, 0.10 und 0.20 auf. Hierzu wurde eine Versuchsdurchfuehrung fuer das vertikale Bridgman-Verfahren konzipiert, mit welcher erfolgreich Kristalle dieser Zusammensetzungen gezuechtet wurden. Der zweite Teil dieser Arbeit enthaelt wesentliche Ergebnisse zur Kristallzuechtung von LiFeAs sowie der Nickel-substituierten Verbindung Li{sub 1-δ}Fe{sub 1-x}Ni{sub x}As mit x{sub Nom} = 0.015, 0.025, 0.05, 0.06, 0.075 und 0.10. Hierfuer wurde erfolgreich eine Versuchsdurchfuehrung fuer das Schmelzfluss-Verfahren entwickelt.

  9. Predicting crystal growth via a unified kinetic three-dimensional partition model (United States)

    Anderson, Michael W.; Gebbie-Rayet, James T.; Hill, Adam R.; Farida, Nani; Attfield, Martin P.; Cubillas, Pablo; Blatov, Vladislav A.; Proserpio, Davide M.; Akporiaye, Duncan; Arstad, Bjørnar; Gale, Julian D.


    Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal-organic frameworks, calcite, urea and L-cystine.

  10. Rapid black hole growth under anisotropic radiation feedback (United States)

    Sugimura, Kazuyuki; Hosokawa, Takashi; Yajima, Hidenobu; Omukai, Kazuyuki


    Discovery of high-redshift (z > 6) supermassive black holes (BHs) may indicate that the rapid (or super-Eddington) gas accretion has aided their quick growth. Here, we study such rapid accretion of the primordial gas on to intermediate-mass (102-105 M⊙) BHs under anisotropic radiation feedback. We perform two-dimensional radiation hydrodynamics simulations that solve the flow structure across the Bondi radius, from far outside of the Bondi radius down to a central part that is larger than a circum-BH accretion disc. The radiation from the unresolved circum-BH disc is analytically modelled considering self-shadowing effect. We show that the flow settles into a steady state, where the flow structure consists of two distinct parts: (1) bipolar ionized outflowing regions, where the gas is pushed outward by thermal gas pressure and super-Eddington radiation pressure, and (2) an equatorial neutral inflowing region, where the gas falls towards the central BH without affected by radiation feedback. The resulting accretion rate is much higher than that in the case of isotropic radiation, far exceeding the Eddington-limited rate to reach a value slightly lower than the Bondi one. The opening angle of the equatorial inflowing region is determined by the luminosity and directional dependence of the central radiation. We find that photoevaporation from its surfaces set the critical opening angle of about 10° below which the accretion to the BH is quenched. We suggest that the shadowing effect allows even stellar-remnant BHs to grow rapidly enough to become high-redshift supermassive BHs.

  11. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.


    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  12. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Energy Technology Data Exchange (ETDEWEB)

    Morherr, Antonia, E-mail: [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Witt, Sebastian [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Chernenkaya, Alisa [Graduate School Materials Science in Mainz, 55128 Mainz (Germany); Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bäcker, Jan-Peter [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Schönhense, Gerd [Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bolte, Michael [Institut für anorganische Chemie, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Krellner, Cornelius [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany)


    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F{sub x}, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  13. Second harmonic chalcone crystal: Synthesis, growth and characterization

    Energy Technology Data Exchange (ETDEWEB)

    D' Silva, E.D., E-mail: [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India); Narayan Rao, D. [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, Bangalore 560080 (India); Butcher, Ray J. [Department of Chemistry, Howard University, Washington, DC 20059 (United States); Rajnikant [Department of Physics and Electronics, University of Jammu, Jammu Tawi 180006 (India); Dharmaprakash, S.M. [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India)


    The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.

  14. Trigonal crystals of glucose isomerase require thymol for their growth and stability (United States)

    Chayen, N. E.; Lloyd, L. F.; Collyer, C. A.; Blow, D. M.


    The growth of trigonal bypyramidal crystals of Arthrobacter glucose isomerase is only possible in the presence of thymol at a concentration exceeding 2.5mM; at lower thymol concentrations rectangular and rhombic crystals are formed. When thymol is removed from the supernatant of trigonal crystals, they fall apart and recrystallise as rectangles or rhombs. The disordering can be reversed if thymol is reintroduced before the trigonal crystals have dispersed, but the other crystal forms are stable in thymol. During the disintegration of trigonal crystals the supernatant concentration of protein is increased.

  15. A Simple Inexpensive Bridgman-Stockbarger Crystal Growth System for Organic Materials (United States)

    Choi, J.; Aggarwal, M. D.; Wang, W. S.; Metzl, R.; Bhat, K.; Penn, Benjamin G.; Frazier, Donald O.


    Direct observation of solid-liquid interface is important for the directional solidification to determine the desired interface shape by controlling the growth parameters. To grow good quality single crystals of novel organic nonlinear optical materials, a simple inexpensive Bridgman-Stockbarger (BS) crystal growth system has been designed and fabricated. Two immiscible liquids have been utilized to create two zones for this crystal growth system. Bulk single crystals of benzil derivative and n-salicylidene-aniline have been successfully grown in this system. The optimum lowering rate has been found to be 0.1 mm/h for the flat interface. Results on the crystal growth and other parameters of the grown crystals are presented.

  16. Single crystal growth in spin-coated films of polymorphic phthalocyanine derivative under solvent vapor

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, T.; Ohmori, M.; Ramananarivo, M. F.; Fujii, A., E-mail:; Ozaki, M. [Division of Electrical, Electronic, and Information Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)


    The effects of solvent vapor on spin-coated films of a polymorphic phthalocyanine derivative were investigated. Growth of single crystal films via redissolving organic films under solvent vapor was revealed by in situ microscopic observations of the films. X-ray diffraction measurement of the films after exposing to solvent vapor revealed the phase transition of polymorphs under solvent vapor. The direction of crystal growth was clarified by measuring the crystal orientation in a grown monodomain film. The mechanism of crystal growth based on redissolving organic films under solvent vapor was discussed in terms of the different solubilities of the polymorphs.

  17. Growth and characterization of L-Lysine adipate crystal (United States)

    Ramya, K.; Saraswathi, N. T.; Raja, C. Ramachandra


    Nonlinear optical crystals of L-Lysine adipate were grown by liquid diffusion method at room temperature. The lattice parameters were determined by single crystal X-ray diffraction analysis. Fourier Transform Infrared and Raman spectral studies were carried out to confirm functional groups present in the crystal. Optical property of crystal was examined by UV-vis-NIR studies. Molecular structure of grown crystal was established using 1H NMR and 13C NMR studies. Thermal stability and decomposition were analyzed using Thermo Gravimetric and Differential Thermal analysis. Second harmonic generation efficiency of crystal was determined by Kurtz Perry powder technique.

  18. Growth rate analysis of gibbsite single crystals growing from aqueous sodium aluminate solutions

    NARCIS (Netherlands)

    Sweegers, C.; Meekes, H.L.M.; Enckevort, W.J.P. van; Hiralal, I.D.K.; Rijkeboer, A.


    In-situ optical microscopy was used to measure the growth rate of gibbsite single crystals growing from aqueous sodium aluminate solutions. The growth rate was measured for various crystal faces, i.e., {100} and {001} faces in case of twinned hexagons and {110} faces for single crystalline lozenges.

  19. Understanding self-poisoning phenomenon in crystal growth of short-chain polymers

    NARCIS (Netherlands)

    Ma, Yu; Qi, Bo; Ren, Yijin; Ungar, Goran; Hobbs, Jamie K; Hu, Wenbing


    Flexible polymers crystallize with chain folding, which shows a unique phenomenon called self-poisoning. As a result, minima in crystal growth rates of strictly monodisperse short-chain polymers are observed near the temperatures of transitions from extended-chain to once-folded-chain growth, from

  20. Functional Durability of a Quartz Crystal Microbalance Sensor for the Rapid Detection of Salmonella in Liquids from Poultry Packaging

    National Research Council Canada - National Science Library

    Olsen, Eric


    .... A rapid, sensitive (350 +/- 150 cells ml/cm) quartz crystal microbalance biosensor, layered with heat-treated anti-Salmonella-phospholipid monolayers by the Langmuir-Blodgett technique, has been evaluated by immersion testing in chicken exudate...

  1. Interface Shape and Growth Rate Analysis of Se/GaAs Bulk Crystals Grown in the NASA Crystal Growth Furnace (CGF) (United States)

    Bly, J. M.; Kaforey, M. L.; Matthiesen, D. H.; Chait, A.


    Selenium-doped gallium arsenide, Se/GaAs, bulk crystals have been grown on earth using NASA's crystal growth furnace (CGF) in preparation for microgravity experimentation on the USML-2 spacelab mission. Peltier cooling pulses of 50 ms duration, 2040 A magnitude, and 0.0033 Hz frequency were used to successfully demark the melt-solid interface at known times during the crystal growth process. Post-growth characterization included interface shape measurement, growth rate calculation, and growth rate transient determinations. It was found that the interface shapes were always slightly concave into the solid. The curvature of the seeding interfaces was typically 1.5 mm for the 15 mm diameter samples. This was in agreement with the predicted interface shapes and positions relative to the furnace determined using a numerical model of the sample/ampoule/cartridge assembly (SACA).

  2. Rapid thermal annealing and crystallization mechanisms study of silicon nanocrystal in silicon carbide matrix

    Directory of Open Access Journals (Sweden)

    Wan Zhenyu


    Full Text Available Abstract In this paper, a positive effect of rapid thermal annealing (RTA technique has been researched and compared with conventional furnace annealing for Si nanocrystalline in silicon carbide (SiC matrix system. Amorphous Si-rich SiC layer has been deposited by co-sputtering in different Si concentrations (50 to approximately 80 v%. Si nanocrystals (Si-NC containing different grain sizes have been fabricated within the SiC matrix under two different annealing conditions: furnace annealing and RTA both at 1,100°C. HRTEM image clearly reveals both Si and SiC-NC formed in the films. Much better "degree of crystallization" of Si-NC can be achieved in RTA than furnace annealing from the research of GIXRD and Raman analysis, especially in high-Si-concentration situation. Differences from the two annealing procedures and the crystallization mechanism have been discussed based on the experimental results.

  3. Crystal front shape control by use of an additional heater in a Czochralski sapphire single crystal growth system (United States)

    Hur, Min-Jae; Han, Xue-Feng; Choi, Ho-Gil; Yi, Kyung-Woo


    The quality of sapphire single crystals used as substrates for LED production is largely influenced by two defects: dislocation density and bubbles trapped in the crystal. In particular, the dislocation density has a higher value in sapphire grown by the Czochralski (CZ) method than by other methods. In the present study, we predict a decreased value for the convexity and thermal gradient at the crystal front (CF) through the use of an additional heater in an induction-heated CZ system. In addition, we develop a solute concentration model by which the location of bubble formation in CZ growth is calculated, and the results are compared with experimental results. We further calculate the location of bubble entrapment corresponding with the use of an additional heater. We find that sapphire crystal growth with an additional heater yields a decreased thermal gradient at the CF, together with decreased CF convexity, improved energy efficiency, and improvements in terms of bubble formation location.

  4. Crystal growth, electrical and photophysical properties of Tl2S ...

    Indian Academy of Sciences (India)

    The Tl2S compound was prepared in a single crystal form using a special local technique, and the obtained crystals were analysed by X-ray diffraction. For the resultant crystals, the electrical properties (electrical conductivity and Hall effect) and steady-state photoconductivity were elucidated in this work. The electrical ...

  5. Crystal growth and structural analysis of zirconium sulphoselenide ...

    Indian Academy of Sciences (India)

    The grown crystals were examined under optical zoom microscope for their surface topography study. Hall effect measurements were carried out on grown crystals at room temperature. The negative value of Hall coefficient implies that these crystals are -type in nature. The conductivity is found to decrease with increase of ...

  6. Extracellular matrix protein in calcified endoskeleton: a potential additive for crystal growth and design (United States)

    Azizur Rahman, M.; Fujimura, Hiroyuki; Shinjo, Ryuichi; Oomori, Tamotsu


    In this study, we demonstrate a key function of extracellular matrix proteins (ECMPs) on seed crystals, which are isolated from calcified endoskeletons of soft coral and contain only CaCO 3 without any living cells. This is the first report that an ECMP protein extracted from a marine organism could potentially influence in modifying the surface of a substrate for designing materials via crystallization. We previously studied with the ECMPs from a different type of soft coral ( Sinularia polydactyla) without introducing any seed crystals in the process , which showed different results. Thus, crystallization on the seed in the presence of ECMPs of present species is an important first step toward linking function to individual proteins from soft coral. For understanding this interesting phenomenon, in vitro crystallization was initiated in a supersaturated solution on seed particles of calcite (1 0 4) with and without ECMPs. No change in the crystal growth shape occurred without ECMPs present during the crystallization process. However, with ECMPs, the morphology and phase of the crystals in the crystallization process changed dramatically. Upon completion of crystallization with ECMPs, an attractive crystal morphology was found. Scanning electron microscopy (SEM) was utilized to observe the crystal morphologies on the seeds surface. The mineral phases of crystals nucleated by ECMPs on the seeds surface were examined by Raman spectroscopy. Although 50 mM Mg 2+ is influential in making aragonite in the crystallization process, the ECMPs significantly made calcite crystals even when 50 mM Mg 2+ was present in the process. Crystallization with the ECMP additive seems to be a technically attractive strategy to generate assembled micro crystals that could be used in crystals growth and design in the Pharmaceutical and biotechnology industries.

  7. Progress in art and science of crystal growth and its impacts on modern society (United States)

    Nishinaga, Tatau


    The impacts of the progress in the art and science of crystal growth on human life are reviewed. Even before the invention of the transistor, quartz and corundum crystals were used as crystal oscillators and jewel bearings, respectively. However, a major impact of crystal growth on society was experienced with the invention of the transistor, which required high-purity and perfect germanium crystals. Once the importance of crystal growth was clearly recognized, the science of crystal growth also extensively developed. The growth of single crystalline silicon allows us to produce integrated circuits, which are used in all the electronic devices in everyday use. The technological developments in the growth of compound semiconductors have also had a large impact on society through the inventions of the laser diode for optical communication and the p-n junction nitride light-emitting diode toward the realization of a less energy-intensive society. The latter invention was awarded the 2014 Nobel Prize in Physics. Finally, future aspects of crystal growth are discussed.

  8. Crystal growth and properties of novel organic nonlinear optical crystals of 4-Nitrophenol urea

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, M. Krishna, E-mail:; Ponnusamy, S.; Muthamizhchelvan, C.


    Single crystals of 4-Nitrophenol urea have been grown from water using slow evaporation technique at constant temperature, with the vision to improve the properties of the crystals. The unit cell parameters of the grown crystals were determined by single crystal and powder X-Ray diffraction. FTIR studies reveals the presence of different vibrational bands. The Optical studies confirmed that the crystal is transparent up to 360 nm .TGA and DSC studies were carried out to understand the thermal behavior of crystals. The SHG studies show the suitability of the crystals for NLO applications. The etching studies were carried out to study the behavior of the crystals under different conditions.These studies reveal that the crystals of 4-Nitrophenol urea are suitable for device applications. - Highlights: • 4-Nitrophenol urea crystals of dimensions 14 mm × 1 mm were grown. • UV–Visible studies indicate the crystal is transparent in the region of 370–800 nm. • Thermal studies show the crystal starts decomposing at 170 °C. • SHG studies indicate that the crystals have NLO efficiency 3.5 times that of KDP.

  9. Crystal Growth Inhibitors for the Prevention of L-Cystine Kidney Stones Through Molecular Design

    Energy Technology Data Exchange (ETDEWEB)

    Rimer, Jeffrey D.; An, Zhihua; Zhu, Zina; Lee, Michael H.; Goldfarb, David S.; Wesson, Jeffrey A.; Ward, Michael D. (NY Univ.); (MCW)


    Crystallization of L-cystine is a critical step in the pathogenesis of cystine kidney stones. Treatments for this disease are somewhat effective but often lead to adverse side effects. Real-time in situ atomic force microscopy (AFM) reveals that L-cystine dimethylester (L-CDME) and L-cystine methylester (L-CME) dramatically reduce the growth velocity of the six symmetry-equivalent {l_brace}100{r_brace} steps because of specific binding at the crystal surface, which frustrates the attachment of L-cystine molecules. L-CDME and L-CME produce L-cystine crystals with different habits that reveal distinct binding modes at the crystal surfaces. The AFM observations are mirrored by reduced crystal yield and crystal size in the presence of L-CDME and L-CME, collectively suggesting a new pathway to the prevention of L-cystine stones by rational design of crystal growth inhibitors.

  10. Crystal growth of ZrW2O8 and its optical and mechanical characterization (United States)

    Imteyaz Ahmad, Md.; Mohanty, Gaurav; Cambrea, Lee R.; Harris, Daniel C.; Rajan, Krishna; Akinc, Mufit


    ZrW2O8 is known for its isotropic negative thermal expansion over a wide of range of temperature from -272 to 777 °C. However, ZrW2O8 melts incongruently at 1257 °C and is stable only over a short temperature interval between 1105 and 1257 °C. This makes the growth of single crystals a formidable challenge. In order to study the intrinsic properties of this compound, a repeatable, viable single crystal growth strategy is required. Here we report a simple, self-seeding, self-fluxing single crystal growth process which resulted in single crystals of ZrW2O8 up to about 4 mm in size. Grown crystals were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Mechanical properties of the crystals were studied using nanoindentation.

  11. Modeling the effect of crystal and crucible rotation on the interface shape in Czochralski growth of piezoelectric langatate crystals (United States)

    Stelian, C.; Nehari, A.; Lasloudji, I.; Lebbou, K.; Dumortier, M.; Cabane, H.; Duffar, T.


    Single La3Ga5.5Ta0.5O14 (LGT) crystals have been grown by using the Czochralski technique with inductive heating. Some ingots exhibit imperfections such as cracks, dislocations and striations. Numerical modeling is applied to investigate the factors affecting the shape of the crystal-melt interface during the crystallization of ingots having 3 cm in diameter. It was found that the conical shape of the interface depends essentially on the internal radiative exchanges in the semi-transparent LGT crystal. Numerical results are compared to experimental visualization of the growth interface, showing a good agreement. The effect of the forced convection produced by the crystal and crucible rotation is numerically investigated at various rotation rates. Increasing the crystal rotation rate up to 50 rpm has a significant flattening effect on the interface shape. Applying only crucible rotation enhances the downward flow underneath the crystal, leading to an increased interface curvature. Counter rotation between the crystal and the crucible results in a distorted shape of the interface.

  12. Crystal growth, electronic structure and luminescence properties of Nb/Yb co-doped RbTiOPO4 crystals (United States)

    Liu, Jian; Li, Ziqing; Zhu, Pengfei; Duan, Xiulan


    Nb/Yb co-doped RbTiOPO4 (RTP) crystals were successfully grown by a top-seeded solution growth method from two different kinds of flux systems. 5%Nb/3%Yb: RTP crystal with more transparency was obtained from the mixed solvent containing MoO3. The chemical composition was analyzed by Electron Probe Microanalyzer (EPMA), and the result indicated that co-doping of Nb and Yb into RTP can greatly increase the concentration of Yb in RTP crystal. The addition of MoO3 into self-flux system can improve the quality of as-grown crystals, but it is not helpful to introduce Yb into crystal. The electronic structures of Nb/Yb: RTP crystals were analyzed using X-ray photoelectron spectra (XPS). The results show that the binding energy difference between O 1s and P 2p levels (ΔBE (O-P)) increases firstly with the increase of Yb content, and then decreases with Nb content increasing, which is associated with the covalency change of O-P bonds in crystals. However, the doping has little influence on the chemical bond properties of O-Ti. The FL spectra of Nb/Yb: RbTiOPO4 crystals were also analyzed, and five emission peaks characteristic of Yb3+ ions were observed.

  13. Crystal growth of Ba 3BP 3O 12 with BPO 4-NaF flux (United States)

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


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

  14. Floating zone growth and characterization of Ca 2Fe 2O 5 single crystals (United States)

    Maljuk, A.; Strempfer, J.; Lin, C. T.


    We report the growth of inclusion and sub-grain free Ca 2Fe 2O 5 (CFO) single crystals by the floating zone method. Single crystals were successfully obtained with volumes of up to 1.0 cm 3. The X-ray rocking curve of the CFO single crystal has the full-width at half-maximum (FWHM) of 0.065°. The oxygen content in the as-grown CFO single crystal was measured by the thermo-gravimetric (TG) method in Ar/H 2 flow. Two magnetic transitions at T1≈140 K and T2≈60 K were observed in the CFO crystal.

  15. Growth and microtopographic study of CuInSe{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail:; Deshpande, M. P. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat - 388120 (India); Tailor, J. P. [Applied Physics Department, S.V.N.I.T., Surat, Gujarat - 395007 (India)


    The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

  16. Novel Design Integrating a Microwave Applicator into a Crystallizer for Rapid Temperature Cycling. A Direct Nucleation Control Study (United States)


    The control of nucleation in crystallization processes is a challenging task due to the often lacking knowledge on the process kinetics. Inflexible (predetermined) control strategies fail to grow the nucleated crystals to the desired quality because of the variability in the process conditions, disturbances, and the stochastic nature of crystal nucleation. Previously, the concept of microwave assisted direct nucleation control (DNC) was demonstrated in a laboratory setup to control the crystal size distribution in a batch crystallization process by manipulating the number of particles in the system. Rapid temperature cycling was used to manipulate the super(under)saturation and hence the number of crystals. The rapid heating response achieved with the microwave heating improved the DNC control efficiency, resulting in halving of the batch time. As an extension, this work presents a novel design in which the microwave applicator is integrated in the crystallizer, hence avoiding the external loop though the microwaves oven. DNC implemented in the 4 L unseeded crystallizer, at various count set points, resulted in strong efficiency enhancement of DNC, when compared to the performance with a slow responding system. The demonstrated crystallizer design is a basis for extending the enhanced process control opportunity to other applications. PMID:28729813

  17. Inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate. (United States)

    Damodaran, Srinivasan


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

  18. Growth and Characterization of Morpholium Cadmium Acetoperchlorate Single Crystal

    Directory of Open Access Journals (Sweden)

    D. Shyamala


    Full Text Available In the search for novel crystal with promising nonlinear optical properties an attempt is made to grow morpholium cadmium aceto-perchlorate single crystals. The title compound is synthesized by slow evaporation technique at room temperature. The powder X-ray diffraction pattern has been recorded and the various planes of reflections are identified. The transmittance spectrum of the crystal in the UV–Vis region has been obtained. Using the FTIR spectrum, the vibrational modes of the crystal is analysed and the presence of cadmium in the crystal is confirmed. Thermogravimetric analysis and differential thermal analysis studies have been done to assess the thermal stability of the grown crystal. The dielectric measurement for the crystal is carried out in the range of 50 Hz to 5 MHz for three different temperatures 40ºC, 80ºC and 120ºC to study the electrical nature of the grown crystal. The nonlinear optical property of the grown crystal is confirmed.

  19. Crystal growth, structural, optical, thermal and dielectric properties of lithium hydrogen oxalate monohydrate single crystal (United States)

    Chandran, Senthilkumar; Paulraj, Rajesh; Ramasamy, P.


    The vibrational groups of the lithium hydrogen oxalate monohydrate have been investigated by FTIR and FT- Raman analyses. It has low absorbance in the UV-Vis-NIR region. The laser damage threshold study confirms that the material withstands upto 30 mJ with time of 7 s, after that circular dot damage is seen on the surface. The dark region of the surface damage spot occurs due to the thermal effects. The material is thermally stable upto 93 °C and there is no weight loss below this temperature. The dielectric studies were carried out at the frequency regions of 1 kHz-1 MHz and different temperatures from 40 °C to 80 °C. Semi-organic non-linear optical (NLO) single crystal lithium hydrogen oxalate monohydrate has been grown by slow evaporation solution growth technique. The Hirshfeld surface analysis was performed to understand the different intermolecular interactions in the title compound. The fingerprint plots contain the highest portion of H⋯O/O⋯H (48.3%) interactions.

  20. Introducing uncertainty analysis of nucleation and crystal growth models in Process Analytical Technology (PAT) system design of crystallization processes. (United States)

    Samad, Noor Asma Fazli Abdul; Sin, Gürkan; Gernaey, Krist V; Gani, Rafiqul


    This paper presents the application of uncertainty and sensitivity analysis as part of a systematic model-based process monitoring and control (PAT) system design framework for crystallization processes. For the uncertainty analysis, the Monte Carlo procedure is used to propagate input uncertainty, while for sensitivity analysis, global methods including the standardized regression coefficients (SRC) and Morris screening are used to identify the most significant parameters. The potassium dihydrogen phosphate (KDP) crystallization process is used as a case study, both in open-loop and closed-loop operation. In the uncertainty analysis, the impact on the predicted output of uncertain parameters related to the nucleation and the crystal growth model has been investigated for both a one- and two-dimensional crystal size distribution (CSD). The open-loop results show that the input uncertainties lead to significant uncertainties on the CSD, with appearance of a secondary peak due to secondary nucleation for both cases. The sensitivity analysis indicated that the most important parameters affecting the CSDs are nucleation order and growth order constants. In the proposed PAT system design (closed-loop), the target CSD variability was successfully reduced compared to the open-loop case, also when considering uncertainty in nucleation and crystal growth model parameters. The latter forms a strong indication of the robustness of the proposed PAT system design in achieving the target CSD and encourages its transfer to full-scale implementation. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Zirconate Pyrochlore Frustrated Magnets: Crystal Growth by the Floating Zone Technique

    Directory of Open Access Journals (Sweden)

    Monica Ciomaga Hatnean


    Full Text Available This article reviews recent achievements on the crystal growth of a new series of pyrochlore oxides—lanthanide zirconates, which are frustrated magnets with exotic magnetic properties. Oxides of the type A 2 B 2 O 7 (where A = Rare Earth, B = Ti, Mo have been successfully synthesised in single crystal form using the floating zone method. The main difficulty of employing this technique for the growth of rare earth zirconium oxides A 2 Zr 2 O 7 arises from the high melting point of these materials. This drawback has been recently overcome by the use of a high power Xenon arc lamp furnace for the growth of single crystals of Pr 2 Zr 2 O 7 . Subsequently, large, high quality single crystals of several members of the zirconate family of pyrochlore oxides A 2 Zr 2 O 7 (with A = La → Gd have been grown by the floating zone technique. In this work, the authors give an overview of the crystal growth of lanthanide zirconates. The optimum conditions used for the floating zone growth of A 2 Zr 2 O 7 crystals are reported. The characterisation of the crystal boules and their crystal quality is also presented.


    Directory of Open Access Journals (Sweden)

    Suharso Suharso


    Full Text Available The growth rates of borax single crystals from aqueous solutions at various flow rates in the (001 direction were measured using in situ cell method. From the growth rate data obtained, the growth rate distribution of borax crystals was investigated using Minitab Software and SPSS Software at relative supersaturation of 0807 and temperature of 25 °C. The result shows that normal, gamma, and log-normal distribution give a reasonably good fit to GRD. However, there is no correlation between growth rate distribution and flow rate of solution.   Keywords: growth rate dispersion (GRD, borax, flow rate

  3. Origin of enhanced crystal growth kinetics near Tg probed with indomethacin polymorphs. (United States)

    Wu, Tian; Yu, Lian


    Using three crystal polymorphs of indomethacin (IMC), we tested two interpretations of the enhanced crystal growth kinetics near the glass transition temperature Tg. This enhancement refers to the stronger temperature dependence of liquid viscosity eta than crystal growth rate (corrected for thermodynamic driving force). This enhancement is attributed in the first interpretation to an increase of the number of preferred interfacial growth sites with decreasing temperature and, in the second interpretation, to the breakdown of the Stokes-Einstein relation in deeply supercooled liquids. We measured the growth rates of the IMC polymorphs (alpha, gamma, and delta) from Tg + 9 K (Tg = 314 K) to near the respective melting points. From Tg + 19 K to Tg + 69 K, the growth rates of the polymorphs changed by 10(4) fold but displayed the same temperature dependence (eta-0.78) after corrections for thermodynamic driving forces. These results argue for a liquid-state origin of the enhanced growth kinetics. Below ca. Tg + 19 K, delta IMC continued to grow in the same spherulite morphology but alpha and gamma IMC grew in different, fiberlike morphologies and, if measured consistently, at faster rates. We conclude that the liquid dynamics of IMC controls its crystal growth kinetics over a wide range of temperatures but changes of growth morphologies near Tg also lead to apparent acceleration of growth of certain polymorphs. This work also extended a previous study of D-sorbitol to lower temperatures to enable a broader analysis of crystal growth kinetics of organic molecules near Tg.

  4. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)


    tartaric acid content of the gel is completely exhausted partly through the formation of calcium tartrate crystals and partly through the demonstrable loss of tartaric acid to the solution at the top in the gel region close to the super- natant liquid. Normally, many small crystals grow in the gel medium and only a few of them are ...

  5. Crystal growth and optical properties of 4-aminobenzophenone (ABP) (United States)

    Li, Zhengdong; Wu, Baichang; Su, Genbo; Huang, Gongfan


    Bulk crystals of 4-aminobenzophenone (ABP) were grown from organic solution. The crystal structure was determined by X-ray analysis. The refractive indices were determined by the method of prism minimum deviation. Some effective nonlinear-optical coefficients deff were measured. A blue second-harmonic emission with wavelengths of 433 and 460 nm were observed during laser diode pumping.

  6. Crystal growth and morphology of calcium oxalates and carbonates

    NARCIS (Netherlands)

    Heijnen, W.M.M.


    The main purpose of the research described in this thesis is to establish a relationship between the crystal structure and morphology of calcium oxalate and calcium carbonate crystals grown from aqueous solutions. Starting point is the PBC (Periodic Bond Chain) theory formulated by Hartman and

  7. Growth mechanism, dielectric, elastic and thermal properties of zinc cadmium thiocyanate crystal as a potential piezoelectric crystal (United States)

    Lü, Yadong; Liu, Xitao; Wang, Xinqiang; Gao, Zeliang; Yin, Xin; Yuan, Kangkang; Xu, Chonghe; Wang, Lin; Zhang, Guanghui; Zhu, Luyi; Xu, Dong


    Bulk single crystals of zinc cadmium thiocyanate, ZnCd(SCN)4 (ZCTC) with dimensions of 51 × 15 × 12 and 28 × 13 × 12 mm3 have been obtained. Growth habits were investigated, two-dimensional nucleation growth mechanism and crystal twinning defect were observed from the as-grown crystals. The thermal diffusivities were measured, and then thermal conductivities were calculated with values decreasing from 1.3683 to 0.8739 Wṡm-1ṡK-1 and 0.8496 to 0.5356 Wṡm-1ṡK-1 as the temperature increasing from 303 to 423 K, along the a- and c-directions, respectively. The relative dielectric constants and elastic compliance constants at room temperature were determined. Meanwhile, first-principles calculation was used to calculate elastic constants.

  8. Czochralski crystal growth and aluminum segregation coefficient in yttrium gallium aluminum garnet (United States)

    Dabkowski, A.; Berkowski, M.; Jasiołek, G.


    The aluminum distribution coefficient and the amount of octahedral yttrium aluminum gallium garnet single crystals obtained by the Czochralski method have been determined from lattice constant variations during crystal growth. The value of the aluminum distribution coefficient was close to 2 for those parts of the crystal with a convex solid-liquid interface and it was close to 1 for those with a flat solid-liquid interface. The large difference between these values can be explained by chemical stresses in the crystal in the meltback region and small changes of the lattice constant in the part of crystal with a flat solid-liquid interface. Single crystals of yttrium aluminum gallium garnet with a lattice constant appropriate for LPE film growth of yttrium gallium garnet have been grown.

  9. Carbon agent chemical vapor transport growth of Ga2O3 crystal (United States)

    Jie, Su; Tong, Liu; Jingming, Liu; Jun, Yang; Guiying, Shen; Yongbiao, Bai; Zhiyuan, Dong; Youwen, Zhao


    Beta-type gallium oxide (β-Ga2O3) is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga2O3 crystals. In this work, crystal growth of Ga2O3 has been carried out by chemical vapor transport (CVT) method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga2O3 crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural (XRD) and optical (Raman spectroscopy, photoluminescence spectrum) properties of the CVT-Ga2O3 crystal are presented. Project supported by the National Natural Science Foundation of China (Nos. 61474104, 61504131).

  10. Existence of thickness threshold for crystal growth rate of ascorbic acid from its thin solution film (United States)

    Yamazaki, Yoshihiro; Yoshino, Hiroki; Kikuchi, Mitsunobu; Kashiwase, Sakiko


    Growth rate of ascorbic acid crystal domains from its aqueous solution film depends on the film thickness. Existence of a thickness threshold is experimentally confirmed below which growth rate becomes quite low and is considered to almost stop. This threshold is one of the essential factors for the dynamical transition between uniform and rhythmic growth modes.

  11. Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dhanaraj, P.V. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Rajesh, N.P., E-mail: [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Sundar, J. Kalyana; Natarajan, S. [Department of Physics, Madurai Kamaraj University, Madurai 625 021 (India); Vinitha, G. [Department of Physics, Crescent Engineering College, Chennai 600 048 (India)


    Highlights: {yields} Good quality crystals of nicotinium trifluoroacetate in monoclinic system were grown for first time. {yields} Nicotinium trifluoroacetate crystal exhibits third order nonlinear optical properties. {yields} The optical spectrum of nicotinium trifluoroacetate crystal reveals the wide transmission in the entire range with cutoff wavelength at 286 nm. {yields} Nicotinium trifluoroacetate is a low dielectric constant material. - Abstract: An organic material, nicotinium trifluoroacetate (NTF) was synthesized and single crystals in monoclinic system were grown from aqueous solution for the first time. Its solubility and metastable zone width were estimated. The crystal structure of NTF was analyzed to reveal the molecular arrangements and the formation of hydrogen bonds in the crystal. High-resolution X-ray diffraction rocking curve measurements were performed to analyze the structural perfection of the grown crystals. Functional groups in NTF were identified by Fourier transform infrared spectral analysis. Thermal behaviour and stability of NTF were studied by thermogravimetric and differential thermal analysis and differential scanning calorimetry. Mechanical and dielectric properties of NTF crystals were analyzed. Optical studies reveal that NTF crystals are transparent in the wavelength range 286-1100 nm. The third order nonlinear optical parameters of NTF were derived by the Z-scan technique.

  12. A Low-Cost System Based on Image Analysis for Monitoring the Crystal Growth Process. (United States)

    Venâncio, Fabrício; Rosário, Francisca F do; Cajaiba, João


    Many techniques are used to monitor one or more of the phenomena involved in the crystallization process. One of the challenges in crystal growth monitoring is finding techniques that allow direct interpretation of the data. The present study used a low-cost system, composed of a commercial webcam and a simple white LED (Light Emitting Diode) illuminator, to follow the calcium carbonate crystal growth process. The experiments were followed with focused beam reflectance measurement (FBRM), a common technique for obtaining information about the formation and growth of crystals. The images obtained in real time were treated with the red, blue, and green (RGB) system. The results showed a qualitative response of the system to crystal formation and growth processes, as there was an observed decrease in the signal as the growth process occurred. Control of the crystal growth was managed by increasing the viscosity of the test solution with the addition of monoethylene glycol (MEG) at 30% and 70% in a mass to mass relationship, providing different profiles of the RGB average curves. The decrease in the average RGB value became slower as the concentration of MEG was increased; this reflected a lag in the growth process that was proven by the FBRM.

  13. A Low-Cost System Based on Image Analysis for Monitoring the Crystal Growth Process

    Directory of Open Access Journals (Sweden)

    Fabrício Venâncio


    Full Text Available Many techniques are used to monitor one or more of the phenomena involved in the crystallization process. One of the challenges in crystal growth monitoring is finding techniques that allow direct interpretation of the data. The present study used a low-cost system, composed of a commercial webcam and a simple white LED (Light Emitting Diode illuminator, to follow the calcium carbonate crystal growth process. The experiments were followed with focused beam reflectance measurement (FBRM, a common technique for obtaining information about the formation and growth of crystals. The images obtained in real time were treated with the red, blue, and green (RGB system. The results showed a qualitative response of the system to crystal formation and growth processes, as there was an observed decrease in the signal as the growth process occurred. Control of the crystal growth was managed by increasing the viscosity of the test solution with the addition of monoethylene glycol (MEG at 30% and 70% in a mass to mass relationship, providing different profiles of the RGB average curves. The decrease in the average RGB value became slower as the concentration of MEG was increased; this reflected a lag in the growth process that was proven by the FBRM.

  14. Acousto-optical phonon excitation in piezoelectric wurtzite slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten


    This paper presents a theoretical investigation of phonon dispersion in piezoelectric slabs of hexagonal crystal symmetry (wurtzite). Specifically we solve the fully coupled dispersion relations in a GaN free standing quantum well by varying the crystal growth direction from the [001] axis...

  15. A monte carlo study of dislocation growth and etching of crystals

    NARCIS (Netherlands)

    Cuppen, H.M.; van Veenendaal, E.; van Suchtelen, J.; van Enckevort, W.J.P.; Vlieg, E.


    It is well known that screw dislocations are step sources that allow crystals to grow at low driving forces. Growth is accelerated at the outcrop of a screw dislocation generating a spiral hillock. This makes the intersection of a screw dislocation and a crystal surface a so-called velocity source.

  16. Microscopic Rate Constants of Crystal Growth from Molecular Dynamic Simulations Combined with Metadynamics

    Directory of Open Access Journals (Sweden)

    Dániel Kozma


    Full Text Available Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design.

  17. Growth and study of some gel grown group II single crystals of iodate

    Indian Academy of Sciences (India)


    such compounds on account of its unique advantages in terms of crystals produced and the simplicity of the pro- cess (Armington and O'Connar 1968; Ranadive ... using glacial acetic acid and sodium meta silicate having different pH values. The chemicals used for growth of doped and undoped barium iodate crystals were.

  18. Lattice Boltzmann simulation of water isotope fractionation during ice crystal growth in clouds (United States)

    Lu, Guoping; DePaolo, Donald J.


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

  19. Reinvestigation of growth of urea thiosemicarbazone monohydrate crystal (United States)

    Srinivasan, Bikshandarkoil R.; Raghavaiah, Pallepogu; Nadkarni, V. S.


    The reaction of urea with thiosemicarbazide in 1:1 mole ratio in aqueous solution does not result in the formation of urea thiosemicarbazone monohydrate crystal, as reported by Hanumantharao, Kalainathan and Bhagavannarayana [Spectrochim. Acta A91 (2012) 345-351]. A reinvestigation of the reported reaction reveals that the crystal obtained is the starting material namely thiosemicarbazide, which has been unambiguously confirmed with the aid of infrared and 1H NMR spectra and single crystal X-ray structure determination. Analysis of 1H NMR spectrum reveals that thiosemicarbazide exhibits thione-thiol tautomerism in solution. In contrast, thiosemicarbazide exists as the thione tautomer in the solid state.

  20. Effect of surface charge distribution on the crystal growth of sodium perborate tetrahydrate (United States)

    Sahın, Ömer; Nusret Bulutcu, A.


    Growth and dissolution rates of sodium perborate crystals have been measured in a flow-type single-crystal cell. Sodium perborate grows dendritically at any level of supersaturation and shows growth and dissolution rate dispersion. Both the growth and dissolution rates of sodium perborate were found to be controlled by surface charge distribution which is represented by applied voltages in an electrostatic separator. It was determined that high surface charge dominates the crystal growth rate when compared with low surface charge under identical conditions. The results obtained showed that the formation of dendritic structure is not a function of supersaturation but a function of surface charge. The rate of dissolution of a crystal with a high surface charge is greater than that with a low surface charge.

  1. Monitoring and Characterization of Crystal Nucleation and Growth during Batch Crystallization

    NARCIS (Netherlands)

    Kadam, S.S.


    Batch crystallization is commonly used in pharmaceutical, agrochemical, specialty and fine chemicals industry. The advantages of batch crystallization lie in its ease of operation and the relatively simple equipment that can be used. On the other hand a major disadvantage associated with it is the

  2. Crystal growth of semiconductors in microgravity; Bisho juryokuka no handotai kessho seicho

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, K. [Nippon Telegraph and Telephone Corp., Tokyo (Japan)


    Most of crystal growth methods handle liquids or gases except recrystallizing methods of solids. Since the effect of a microgravity appears as macro-change in motion or form of liquids or gases, effective use of microgravity environment can produce high-quality crystals which have been never obtained on the earth. Based on major experiments on crystal growth of the 1990s, this paper outlines the effect of a microgravity on crystal growth, and some future issues. The space crystal growth experiments of III-V group compound semiconductors were carried out using International Microgravity Laboratory (IML), Fuwatto`92, Chinese reusable satellite, and Free Flyer (SFU). Melts, liquids and gases were used as materials for these crystal growth experiments. These experiments aimed at production of high-quality crystals by using the effects of non-convection, non- buoyancy, non-sedimentation, non-static pressure and isolated floating under microgravity environment. Systematic researches are most important toward the coming era of an international space base. 27 refs., 3 figs.

  3. Growth of ninhydrin single crystal and its characterization (United States)

    Uma Devi, T.; Lawrence, N.; Ramesh Babu, R.; Ramamurthi, K.; Bhagavannarayana, G.


    A novel organic nonlinear optical crystal ninhydrin having good optical quality was grown by solution technique using aqua solution. The quality of the crystal was also examined by high-resolution X-ray diffraction study. Solubility studies were made at different temperatures. Functional groups present in the grown material were identified from the vibrational frequencies of recorded FTIR spectrum. Transmittance of the crystal was recorded using the UV-vis-NIR spectrophotometer. From the thermal analysis it was observed that the material exhibits single sharp melting point. The fluorescence spectrum of ninhydrin was recorded. The Vicker's microhardness values were measured for the grown crystal. Second harmonic generation conversion efficiency estimated using Kurtz and Perry method is about five times that of KDP.

  4. A versatile low-cost Czochralski crystal growth system for nonlinear optical organic materials (United States)

    Aggarwal, M. D.; Wang, W. S.; Shields, Angela W.; Penn, Benjamin G.; Frazier, Donald O.


    A versatile low-cost Czochralski system for pulling crystals from melt has been described. It is designed for low melting, transparent, and nonlinear optical materials. One of the most important novel feature of this crystal growth system is that the entire growth process including the solid-liquid interface can be viewed from any direction. Another is the use of an after-heater to reduce excess heat loss from the surface of the melt.

  5. Hydrothermal Crystal Growth of Lithium Tetraborate and Lithium Gamma-Metaborate (United States)


    Characterization of Neutron-Induced Defects in Isotopically Enriched Lithium Tetraborate,” Master’s thesis, Air Force Institute of Technology, 2011. [11] O...HYDROTHERMAL CRYSTAL GROWTH OF LITHIUM TETRABORATE AND LITHIUM γ-METABORATE THESIS Jeffrey J. Graham, Captain, USAF AFIT-ENP-14-M-12 DEPARTMENT OF...not subject to copyright protection in the United States. AFIT-ENP-14-M-12 HYDROTHERMAL CRYSTAL GROWTH OF LITHIUM TETRABORATE AND LITHIUM γ

  6. Bridgman growth and scintillation properties of calcium tungstate single crystal (United States)

    Wang, Zhenhai; Jiang, Linwen; Chen, Yaping; Chen, Peng; Chen, Hongbing; Mao, Rihua


    CaWO4 single crystal with large size was grown by Bridgman method. The results of transmission spectra show that the transmittance of CaWO4 crystal reaches 79-85% in 320-800 nm wavelength range. The refraction index is near 1.80 in visible and infrared region. CaWO4 crystal shows a broad emission band centered at 424 nm under X-ray excitation and centered at 416 nm under ultraviolet (λex = 280 nm) excitation. The decay kinetics of CaWO4 single crystal shows double-exponential decay with fast decay constant τ1 = 5.4 μs and slow decay constant τ2 = 177.1 μs. The energy resolution of CaWO4 crystal was found to be 31.6% in the net peak of 545.9 channel. Meanwhile, the absolute output is at the lever of 19,000 ± 1000 photons/MeV. The results indicate the scintillator of CaWO4 single crystal has great potential in the applications of high-energy physics and nuclear physics due to its high light output and great energy resolution.

  7. Growth of bulk GaN crystal by Na flux method (United States)

    Imade, M.; Miyoshi, N.; Yoshimura, M.; Kitaoka, Y.; Sasaki, T.; Mori, Y.


    In this paper, we reported the recent advances in the growth of GaN crystals on GaN templates and spontaneously nucleated GaN seeds by Na flux method. In the growth on GaN templates, it was clarified that the growth mode could be controlled by changing the flux composition. Based on the changes in the growth mode under different flux compositions, a growth sequence that is effective for the growth of thick GaN substrates with a low dislocation density was proposed. In the growth on pyramidal GaN seeds, we investigated the dependence of the growth rate, crystallinity and the growth habit on the flux composition. Results showed that a low Ga composition was preferred to grow high-crystallinity prismatic GaN crystals with a high growth rate. When a spontaneously nucleated GaN seed was used, a bulk GaN crystal with a hexagonal pillar consisting of six m-facets, and its length and diameter were 10 mm and 8 mm, respectively, was obtained. Furthermore, we found that the addition of Ca and Li to Ga-Na melt improved transparency of GaN crystals grown on pyramidal GaN seeds.

  8. The growth of a cubic, single phase, Cd 0.6Mn 0.4Te single crystal by the vertical gradient freeze method (United States)

    Azoulay, M.; Raizman, A.; Weingarten, R.; Shacham, H.; Feldstein, H.


    The growth of CdMnTe single crystals faces some difficulties due to the phase transition in the solid state at high temperatures, just after solidification. To overcome this problem, it has been suggested to grow the crystals from a Te-rich solution by the traveling heater method at a lower temperature than that of growth from the melt, or alternatively to grow the crystal from the melt at high axial thermal gradient near the interface. In this paper, we present for the first time the growth of cubic, single phase, CdxMn1-xTe single crystals by the vertical gradient freeze technique under a very low axial thermal gradient in the melt (3°C/cm) and high manganese content (x ≈ 40%). The solidification stage is characterized by a rapid cooling of the crystal through the phase transition temperature region, followed by annealing at about 800°C. The crystal exhibits a very high crystalline perfection, as measured by the double-crystal X-ray rocking curves with a full width at half maximum of 30 arc sec and low optical losses of about 1 dB/mm between 650 and 820 nm with λ-cutoff at 630 nm. Further magneto-optical properties are currently examined for a possible application in devices.

  9. Delta L: An Apparatus for Measuring Macromolecule Crystal Growth Rates in Microgravity (United States)

    Judge, Russell A.; Whitaker, Ann F. (Technical Monitor)


    Strongly diffracting high quality macromolecule crystals of suitable volume are keenly sought for X-ray diffraction analysis so that high-resolution molecular structure data can be obtained. Such data is of tremendous value to medical research, agriculture and commercial biotechnology. In previous studies by many investigators microgravity has been reported in some instances to improve biological macromolecule X-ray crystal quality while little or no improvement was observed in other cases. A better understanding of processes effecting crystal quality improvement in microgravity will therefore be of great benefit in optimizing crystallization success in microgravity. In ground based research with the protein lysozyme we have previously shown that a population of crystals grown under the same solution conditions, exhibit a variation in X-ray diffraction properties (Judge et al., 1999). We have also observed that under the same solution conditions, individual crystals will grow at slightly different growth rates. This phenomenon is called growth rate dispersion. For small molecule materials growth rate dispersion has been directly related to crystal quality (Cunningham et al., 1991; Ristic et al., 1991). We therefore postulate that microgravity may act to improve crystal quality by reducing growth rate dispersion. If this is the case then as different, Materials exhibit different degrees of growth rate dispersion on the ground then growth rate dispersion could be used to screen which materials may benefit the most from microgravity crystallization. In order to assess this theory the Delta L hardware is being developed so that macromolecule crystal growth rates can be measured in microgravity. Crystal growth rate is defined as the change or delta in crystal size (defined as a characteristic length, L) over time; hence the name of the hardware. Delta L will consist of an optics, a fluids, and a data acquisition sub-assemblies. The optics assembly will consist of a

  10. Nucleation Kinetics, Growth and Characterization Studies of a Diamagnetic Crystal-Zinc Sulphate Heptahydrate (ZSHH

    Directory of Open Access Journals (Sweden)

    R. Kanagadurai


    Full Text Available Solubility, metastable zone width and induction period measurements have been performed on zinc sulphate heptahydrate (ZSHH. Interfacial tension values determined from induction period measurements have been used for the evaluation of the nucleation parameters such as radius of critical nucleus and the free energy of formation of critical nucleus. ZSHH crystallizes in the orthorhombic structure. Crystals of diamagnetic zinc sulphate heptahydrate have been grown by temperature lowering solution growth technique with the optimized growth parameters. The as-grown ZSHH crystals were characterized by the powder X-ray diffraction, UV-VIS absorption and transmittance, FT-IR absorption, TG-DTA, microhardness and etching studies.

  11. Effect of supersaturation on hillock of directional Growth of KDP crystals. (United States)

    Liu, Fa-Fu; Yu, Guang-Wei; Zhang, Li-Song; Li, Liang; Wang, Bo; Gan, Xiao-Yu; Ren, Hong-Kai; Zhou, Hai-Liang; Zhu, Li-Li; Ji, Shao-Hua; Xu, Ming-Xia; Liu, Bao-An; Xu, Xin-Guang; Gu, Qing-Tian; Sun, Xun


    KDP single crystals were grown in aqueous solution by using "point seeds" with a defined crystallographic direction of 59° to the Z axis. When hillock slopes on the (100) face of KDP crystals were measured within the supersaturation (σ) range of 0 dislocation on the (100) face of KDP crystals was observed at σ = 0.04, characterized by large holes with micro-steps and step bunching inside, the formation of which were analyzed. The result verified that the reversed growth appears to occur within hollow channels found on growth hillocks.

  12. Size effects on void growth in single crystals with distributed voids

    DEFF Research Database (Denmark)

    Borg, Ulrik; Niordson, Christian Frithiof; Kysar, J.W.


    The effect of void size on void growth in single crystals with uniformly distributed cylindrical voids is studied numerically using a finite deformation strain gradient crystal plasticity theory with an intrinsic length parameter. A plane strain cell model is analyzed for a single crystal...... with three in-plane slip systems. It is observed that small voids allow much larger overall stress levels than larger voids for all the stress triaxialities considered. The amount of void growth is found to be suppressed for smaller voids at low stress triaxialities. Significant differences are observed...

  13. Basic ammonothermal growth of bulk GaN single crystal using sodium mineralizers (United States)

    Shim, Jang Bo; Kim, Gun Hwan; Lee, Young Kuk


    Basic ammonothermal growth of GaN crystals was studied. We examined the effect of different sodium-based mineralizers, including sodium amide, sodium azide, and sodium metal, on the growth rate and quality of the as-grown GaN crystals. Ammonothermally grown GaN crystal in sodium metal mineralizer showed significant increase in both the growth rate and quality of the as-grown GaN crystals. The full-width half-maximum values of the as-grown GaN crystal using sodium metal mineralizer were 270 arcsec for Ga face and 88 arcsec for N face. Also, we reported approximately 2 in. GaN crystals using sodium metal mineralizer. Ammonothermally grown GaN crystal showed higher chemical stability than HVPE-grown GaN crystal after H3PO4 etching at 160 °C for 2 h. The dark spot density in cathodoluminescence image was measured at the level of 1 × 105/cm2.

  14. Crystal growth of an organic non-linear optical material from the vapour phase

    CERN Document Server

    Hou, W


    Due to the potential applications of organic non-linear optical materials in the areas of optical processing and communication, the investigation of the crystal growth of new organic NLO materials has been an active field for the last 20 years. For such uses it is necessary to produce single crystals of high quality and perfection, free of strain and defects. When crystals are grown from the solution and the melt, solvent and the decomposition component in the melt can introduce impurities and imperfection to the as-grown crystals. For crystals grown from vapour phase, in the absence of the solvent, this cannot occur and the method promises to yield single crystals of higher quality. Despite this attraction, little attention has been paid to the vapour phase growth of organic NLO crystals. It was with this in mind that the following investigation was carried out. Using Methyl p-hydroxybenzoate (p-MHB), a potential organic NLO material, a comparison investigation was made of its crystal growth from both the va...

  15. An instrument for in situ growth rate characterization of mechanically strained crystals (United States)

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


    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.


    Directory of Open Access Journals (Sweden)

    Suharso Suharso


    Full Text Available The growth rates of borax crystals from aqueous solutions in the (010 direction at various flow rates were measured. The observed variations of the growth rate can be represented by a normal distribution.  It was found that there is no correlation between growth rate distribution and solution flow under these experimental conditions.   Keywords: Growth rate dispersion (GRD, borax, flow rate

  17. Measurement of crystal growth velocity in a melt-quenched phase-change material. (United States)

    Salinga, Martin; Carria, Egidio; Kaldenbach, Andreas; Bornhöfft, Manuel; Benke, Julia; Mayer, Joachim; Wuttig, Matthias


    Phase-change materials are the basis for next-generation memory devices and reconfigurable electronics, but fundamental understanding of the unconventional kinetics of their phase transitions has been hindered by challenges in the experimental quantification. Here we obtain deeper understanding based on the temperature dependence of the crystal growth velocity of the phase-change material AgInSbTe, as derived from laser-based time-resolved reflectivity measurements. We observe a strict Arrhenius behaviour for the growth velocity over eight orders of magnitude (from ~10 nm s(-1) to ~1 m s(-1)). This can be attributed to the formation of a glass at elevated temperatures because of rapid quenching of the melt. Further, the temperature dependence of the viscosity is derived, which reveals that the supercooled liquid phase must have an extremely high fragility (>100). Finally, the new experimental evidence leads to an interpretation, which comprehensively explains existing data from various different experiments reported in literature.

  18. Effects of buoyancy-driven convection on nucleation and growth of protein crystals. (United States)

    Nanev, Christo N; Penkova, Anita; Chayen, Naomi


    Protein crystallization has been studied in presence or absence of buoyancy-driven convection. Gravity-driven flow was created, or suppressed, in protein solutions by means of vertically directed density gradients that were caused by generating suitable temperature gradients. The presence of enhanced mixing was demonstrated directly by experiments with crustacyanin, a blue-colored protein, and other materials. Combined with the vertical tube position the enhanced convection has two main effects. First, it reduces the number of nucleated hen-egg-white lysozyme (HEWL) crystals, as compared with those in a horizontal capillary. By enabling better nutrition from the protein in the solution, convection results in growth of fewer larger HEWL crystals. Second, we observe that due to convection, trypsin crystals grow faster. Suppression of convection, achieved by decreasing solution density upward in the capillary, can to some extent mimic conditions of growth in microgravity. Thus, impurity supply, which may have a detrimental effect on crystal quality, was avoided.

  19. Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Karthi, S., E-mail:; Girija, E. K., E-mail: [Department of Physics, Periyar University, Salem - 636011 (India)


    Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - Π - acceptor - Π - donor (D-Π-A-Π-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

  20. Growth of BPO 4 single crystals from Li 2O-MoO 3 flux (United States)

    Zhang, Shufeng; Zhang, Erpan; Fu, Peizhen; Wu, Yicheng


    A new flux system, Li 2O-MoO 3, has been applied to growing BPO 4 single crystals. Transparent BPO 4 single crystals with sizes up to 31×18×16 mm 3 have been successfully grown from the new flux by the top-seeded solution growth method. The viscosity of solution using this new flux decreased significantly compared with that of previously utilized Li 4P 2O 7-Li 2O flux. The solubility was measured and favorable concentration for BPO 4 crystal growth was in the range of 55-64%. The powder SHG effect of as-grown BPO 4 crystal was observed and its intensity was about twice as large as that of KDP. The laser damage threshold of BPO 4 crystal at λ=1.064 nm and τ=8.0 ns is about 10.3 GW/cm 2.

  1. Hydrothermal growth and characterization of aluminum-doped ZnO bulk crystals (United States)

    Wang, Buguo; Mann, Matthew; Claflin, Bruce; Snure, Michael; Look, David C.


    Bulk ZnO crystals were grown by the hydrothermal technique with Al2O3 added to the solution in an attempt to obtain Al-doped ZnO crystals. Aluminum and indium co-doped ZnO were also grown by the same technique. Adding Al2O3 to the growth solution has a significant impact on the ZnO growth ⎯ either preventing overgrowth and dissolving the seed growth or degrading the crystalline quality; nevertheless, the resulting crystals of both Al:ZnO and Al/In:ZnO are highly conductive, similar to In and Ga doped ZnO crystals, with a resistivity approaching 0.01 Ω cm, as revealed by temperature-dependent Hall-effect measurements. Photoluminescence spectra at 18 K show Al0-bound-exciton peak energies of 3.3604 eV on the Zn face and 3.3609 eV on the O face for the Al-doped ZnO crystals. Similarly both an Al0- bound-exciton peak at 3.3604 eV and an In0-bound-exciton peak at 3.3575 eV were found on the Al/In-co-doped crystals. The electrical properties of all group III doped ZnO crystals grown hydrothermally are compared with each other and with Al:ZnO obtained by other growth methods.

  2. Role of internal radiation during Czochralski growth of YAG and Nd:YAG crystals

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Jyotirmay; Muralidhar, Krishnamurthy [Department of Mechanical Engineering, Indian Institute of Technology, Kanpur 208016 (India)


    Crystals of YAG and Nd:YAG are grown from their molten state by the Czochralski technique. Oxide crystals are semi-transparent to infrared radiation. In many instances, radiation losses from the bulk of the crystal and melt are quite large. The scattering of radiation in doped melts can be significant during the growth process. The present study is a numerical simulation of flow and heat transfer during the growth of YAG and Nd:YAG crystals in a Czochralski process. The importance of radiation in the growth process has been examined. The heat flux in the melt comprises of contributions from conduction, advection and radiation. The radiative portion of heat transfer comprises of internal absorption, emission and scattering. It has been calculated in the present work by solving the radiative transfer equation (RTE) simultaneously with the conservation of energy equation. The Czochralski domain is considered to be an isotropically scattering gray medium. The radiative properties are assumed to be independent of wavelength and temperature. The boundaries are taken as diffusely emitting and reflecting opaque surfaces. The results obtained in the present study clearly show that the losses calculated by including internal radiation are higher, when compared to surface radiation alone. In addition, the temperature distribution develops skewness with respect to the crystal axis and thereby influences the shape of the melt-crystal interface. Calculations incorporating the bulk radiation model also show the importance of enclosure conditions for controlling the crystal growth process. (authors)

  3. Two new bismuth thiourea bromides: crystal structure, growth, and characterization. (United States)

    Li, Ming; Li, R K


    Crystals of two new bismuth thiourea bromides, bismuth trithiourea bromide (Bi[CS(NH2)2]3Br3, BTB) and bismuth protonated-hexathiourea bromide (Bi[CS(NH2)2H]6Br9, BHB), have been successfully grown from hydrobromic acid solution with different pH values by slow evaporation. Single crystal X-ray diffraction reveals that BTB is isostructural to its Cl-analog crystallizing in a monoclinic space group Cc with unit cell dimensions of a = 8.6238(7) Å, b = 12.2506(11) Å, c = 15.5040(13) Å, β = 90.7810(10)° and Z = 4. In contrast, BHB crystallizes in a trigonal space group R3[combining macron]c with unit cell dimensions of a = b = 12.748(17) Å, c = 40.45(11) Å, and Z = 6. The protonation of the thiourea in BHB is confirmed by the structure solution, IR and Raman spectroscopy. The UV diffuse reflection spectra clearly indicate that both of the two crystals have good optical transparency in the range below 2000 nm. Both compounds decompose above 190 °C, and BHB melts at around 140 °C while BTB possesses a phase transition at 145 °C as indicated by thermogravimetric (TG) and differential thermal analysis (DTA).

  4. Growth of homogeneous Nd:LGGG single crystal plates by edge-defined film-fed growth method (United States)

    Mu, Wenxiang; Jia, Zhitai; Yin, Yanru; Hu, Qiangqiang; Li, Yang; Tao, Xutang


    Device-size Nd3+:(LuxGd1-x)3Ga5O12 (Nd:LGGG) single crystal plates have been grown by edge-defined film-fed growth (EFG) method for the first time. The problems encountered during the crystal growth have been discussed and solved, resulting in a single crystal plate with a length of 180 mm. In particular, the evaporation loss of Ga2O3 composition during the crystal growing has been depressed efficiently by using an Ir lid. The crystal perfection was confirmed by X-ray rocking curve with a FWHM of the 32 arcsec, meaning a high crystalline quality. It was very interesting to find that the distribution of Nd3+ in the crystal grown by EFG method was more homogeneous than that in Cz method, benefitting from the larger segregation coefficient of Nd3+ in EFG method. The thermal conductivity was measured to be 8.1 W m-1 K-1 at room temperature. All the properties showed that the Nd:LGGG crystal plates grown by EFG method were promising for high power laser application.

  5. Studies on growth and spectral characterization of diglycine fumarate monohydrate single crystals (United States)

    Antony Joseph, A.; Ramachandra Raja, C.


    Single crystals of organic optical material, diglycine fumarate monohydrate (DGFM) has been synthesized and grown from solution by slow evaporation solution growth method. Purity of synthesized materials was increased by continuous recrystallization. The lattice parameters of the grown crystals are observed by X-ray diffraction method and the crystal system of grown crystal is identified as monoclinic. The optical transparency range has been investigated by UV-Vis-NIR spectroscopy method in the range between 190 and 1100 nm. The presence of different modes of vibrations is analyzed using FT-IR technique. The carbon and hydrogen atmosphere in molecular structure of DGFM is investigated using FT-NMR method. The thermogravimetrrc analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) analysis shows that the grown crystal has very good thermal stability up to 263 °C. The Kurtz-Perry powder SHG test has done for grown crystals.

  6. Growth and characterization of pure and KCl doped zinc thiourea chloride (ZTC) single crystals. (United States)

    Ruby Nirmala, L; Thomas Joseph Prakash, J


    Potassium Chloride (KCl) as an additive is added into zinc thiourea chloride solution in a small amount (1M%) by the method of slow evaporation solution growth technique at room temperature to get a new crystal. Due to the doping of the impurities on the crystals, remarkable changes in the physical properties were obtained. The grown crystals have been subjected to different instrumentation methods. The incorporation of the amount of potassium and zinc in the crystal lattices has been determined by AAS method. The lattice dimensions have been identified from single crystal X-ray diffraction measurements. The presence of functional group for the grown crystals has been identified by FTIR analysis. The optical, thermal and mechanical behaviors have been assessed by UV-Vis, TG/DTA and Vickers hardness methods respectively. The presence of dislocations of atoms has been identified by etching studies. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Rapid growth of phosphorus-rich olivine in mantle xenolith from Middle Atlas Mountains (Morocco, Africa) (United States)

    Baziotis, Ioannis; Mavrogonatos, Konstantinos; Flemetakis, Stamatios; Papoutsa, Angeliki; Klemme, Stephan; Berndt, Jasper; Asimow, Paul


    Phosphorus(P)-rich zones in olivine may reflect incorporation of P in excess of equilibrium partitioning during rapid growth (e.g. Milman-Barris et al. 2008). We investigated a mantle xenolith from Middle Atlas Mountains (Morocco) by optical microscopy and electron microprobe. It contains spinel-bearing lherzolite and orthopyroxenite layers, cross-cut by veins dominated by glass and secondary phases including P-rich olivines. The host lava, presumed to be alkali basalt (El Messbahi et al. 2015), is present on the margins of the hand sample but not included in our thin section. The studied melt veins (MV) generally contain Ol+Gl+Cpx+Pl+Spl±Ap. Olivines in the MV have (Fo72.1-83.4) with 0.02-0.3 wt.% P2O5; olivines with P2O5 >0.1 wt.% are Fo75.3 -82.8. Some olivine grains are inclusion-free; others contain rounded glass inclusions or subhedral spinel or ilmenite inclusions. Olivines is generally found in contact with plagioclase and glass. Glass (5-15 vol%) has variable composition with P2O5 up to 1.52 wt.%, K2O 1.65-2.37 wt%, CaO 6.39-9.55 wt%, Na2O 0.78-6.70 wt% and SiO2 45.2-49.6 wt%. Where glass is in contact with matrix olivine, Fe-rich outer rims on olivine indicate mineral-melt reaction. In MgO variation diagrams, glass compositions display a coherent single trend for all oxides, with the exception of a discrete low-Na group. Clinopyroxene is present both as isolated subhedral to euhedral crystals within the MV and as replacive rims on matrix minerals. Very fine-grained dendritic clinopyroxene quench crystals up to 10 μm long are also present. Plagioclase occurs as prismatic, flow-oriented crystals parallel or sub-parallel to the layering. Spinel shows anhedral and euhedral shapes and occurs both as inclusions in olivine and as discrete grains associated with plagioclase and glass. Spinel in contact with glass shows a spongy outer rim and normal zonation towards Fe-rich rim compositions. Apatite is found mostly as very small crystals embedded in glass. High

  8. Growth Rate and Morphology of a Single Calcium Carbonate Crystal on Polysulfone Film Measured with Time Lapse Raman Micro Spectroscopy

    NARCIS (Netherlands)

    Liszka, B.; Lenferink, Aufrid T.M.; Otto, Cornelis


    The growth of single, self- nucleated calcium carbonate crystals on a polysulfone (PSU) film was investigated with high resolution, time lapse Raman imaging. The Raman images were acquired on the interface of the polymer with the crystal. The growth of crystals could thus be followed in time. PSU is

  9. Investigation on nucleation kinetics, growth and characterization of urea oxalic acid-ferroelectric single crystal (United States)

    Dhivya, R.; Ezhil Vizhi, R.; Rajan Babu, D.


    Nucleation and growth kinetics renders the information about the crystal growth process, which can be adopted to grow large size crystals. Urea oxalic acid was synthesized by slow evaporation method. Solubility was analyzed gravimetrically and it was observed that it exhibits positive temperature coefficient of solubility which is suitable for bulk growth. Metastable zonewidth was observed by adopting polythermal method. Induction period was measured by isothermal method for the saturation temperature by varying the degrees of supersaturation. Based on the classical theory of nucleation, the other nucleation parameters such as interfacial energy, Gibbs critical free energy and radius of critical nuclei were calculated. Urea oxalic acid (UOA) was synthesized and subsequently grown by a slow cooling technique. Single crystal X-ray diffraction study confirms that the crystal belongs to a monoclinic system. Dielectric analysis affirms the ferroelectric property of the material and the results were further discussed in detail.

  10. Growth and surface morphology of ErFeO3 single crystal (United States)

    Chang, Fenfen; Yuan, Shujuan; Wang, Yabin; Zhan, Sheng; Cao, Shixun; Wu, Anhua; Xu, Jun


    ErFeO3 single crystal 7 mm in diameter and up to 70 mm in length has been grown by the floating zone technique using a four-mirror image furnace. Particular attention was given to the surface morphology of different cross-sections of the single crystal perpendicular to the growth direction. There are many cracks, bubbles, and precipitations on the cross-sections of the crystal observed by scanning electron microscopy. The thermal stress induced by the high growth rate might play an important role in the formation of the cracks. The bubbles might be mainly caused by high growth rate and the voids within the sintered feed rod. The energy-dispersive X-ray spectroscopy analysis indicates that there is Fe deficiency in the crystal especially in the precipitations.

  11. Investigating calcite growth rates using a quartz crystal microbalance with dissipation (QCM-D) (United States)

    Cao, Bo; Stack, Andrew G.; Steefel, Carl I.; DePaolo, Donald J.; Lammers, Laura N.; Hu, Yandi


    Calcite precipitation plays a significant role in processes such as geological carbon sequestration and toxic metal sequestration and, yet, the rates and mechanisms of calcite growth under close to equilibrium conditions are far from well understood. In this study, a quartz crystal microbalance with dissipation (QCM-D) was used for the first time to measure macroscopic calcite growth rates. Calcite seed crystals were first nucleated and grown on sensors, then growth rates of calcite seed crystals were measured in real-time under close to equilibrium conditions (saturation index, SI = log ({Ca2+}/{CO32-}/Ksp) = 0.01-0.7, where {i} represent ion activities and Ksp = 10-8.48 is the calcite thermodynamic solubility constant). At the end of the experiments, total masses of calcite crystals on sensors measured by QCM-D and inductively coupled plasma mass spectrometry (ICP-MS) were consistent, validating the QCM-D measurements. Calcite growth rates measured by QCM-D were compared with reported macroscopic growth rates measured with auto-titration, ICP-MS, and microbalance. Calcite growth rates measured by QCM-D were also compared with microscopic growth rates measured by atomic force microscopy (AFM) and with rates predicted by two process-based crystal growth models. The discrepancies in growth rates among AFM measurements and model predictions appear to mainly arise from differences in step densities, and the step velocities were consistent among the AFM measurements as well as with both model predictions. Using the predicted steady-state step velocity and the measured step densities, both models predict well the growth rates measured using QCM-D and AFM. This study provides valuable insights into the effects of reactive site densities on calcite growth rate, which may help design future growth models to predict transient-state step densities.

  12. Crystal growth and characterization of SnS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Trifonova, E.P.; Yanchev, I.Y. [St. Kliment Ohridski Univ. of Sofia (Bulgaria). Faculty of Physics; Stoyanova, V.B. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Physical Chemistry; Mandalidis, S.; Kambas, K.; Anagnostopoulos, A.N. [Aristotle Univ., Thessaloniki (Greece)


    SnS{sub 2} crystals were grown by the stoichiometric composition technique (total synthesis). After their stoichiometrical investigation, they were characterized by means of (1) X-ray diffraction, which gave the following results for their structure: space group D{sub 3d}{sup 3} {minus} P{bar 3}ml, lattice parameters a = 3.646 {angstrom} and c = 5.879 {angstrom}; (2) scanning electron microscopy, which revealed the layered structure of the crystals; and (3) microhardness measurements, which were performed for the first time on this material. The obtained results are consistent with the reported values for the energy gap and melting point of this material.

  13. Effect of zinc acetate addition on crystal growth, structural, optical, thermal properties of glycine single crystals

    Directory of Open Access Journals (Sweden)

    S. Anbu Chudar Azhagan


    Full Text Available In the present study, γ-glycine has been crystallized by using zinc acetate dihydrate as an additive for the first time by slow solvent evaporation method. The second harmonic conversion efficiency of γ-glycine crystal was determined using Kurtz and Perry powder technique and was found to be 3.66 times greater than that of standard inorganic material potassium dihydrogen phosphate (KDP. The analytical grade chemicals of glycine and zinc acetate dihydrate were taken in six different molar ratios: 1:0.2, 1:0.4, 1:0.6, 1:0.7, 1:0.8, and 1:0.9 respectively to find out the γ-polymorph of glycine. The lower molar concentration of zinc acetate yield only α-polymorph where as the higher molar concentration of zinc acetate inhibits the γ-polymorph of glycine which was confirmed by single crystal XRD and powder XRD studies. Inductively coupled plasma optical emission spectrometry (ICP-OES was carried out to quantify the concentration of zinc element in the grown glycine single crystals. The concentration of zinc element in the presence of grown γ-glycine single crystal is found to be 0.73 ppm. UV–Visible–NIR transmittance spectra were recorded for the samples to analyse the transparency in visible and near infrared region (NIR. The optical band gap Eg was estimated for γ-glycine single crystal using UV–Visible–NIR study. Functional groups present in the samples were identified by FTIR spectroscopic analysis. Differential scanning calorimetry technique was employed to determine the phase transition, thermal stability and melting point of the grown crystal.

  14. Inferring the effects of compositional boundary layers on crystal nucleation, growth textures, and mineral chemistry in natural volcanic tephras through submicron-resolution imaging

    Directory of Open Access Journals (Sweden)

    Georg F. Zellmer


    Full Text Available Crystal nucleation and growth are first order processes captured in volcanic rocks and record important information about the rates of magmatic processes and chemical evolution of magmas during their ascent and eruption. We have studied glass-rich andesitic tephras from the Central Plateau of the Southern Taupo Volcanic Zone by electron- and ion-microbeam imaging techniques to investigate down to sub-micrometre scale the potential effects of compositional boundary layers (CBLs of melt around crystals on the nucleation and growth of mineral phases and the chemistry of crystal growth zones. We find that CBLs may influence the types of mineral phases nucleating and growing, and growth textures such as the development of swallowtails. The chemistry of the CBLs also has the capacity to trigger intermittent overgrowths of nanometre-scale bands of different phases in rapidly growing crystals, resulting in what we refer to as cryptic phase zoning. The existence of cryptic phase zoning has implications for the interpretation of microprobe compositional data, and the resulting inferences made on the conditions of magmatic evolution. Identification of cryptic phase zoning may in future lead to more accurate thermobarometric estimates and thus geospeedometric constraints. In future, a more quantitative characterization of CBL formation and its effects on crystal nucleation and growth may contribute to a better understanding of melt rheology and magma ascent processes at the onset of explosive volcanic eruptions, and will likely be of benefit to hazard mitigation efforts.

  15. A new rapid colourimetric method for testing Mycobacterium tuberculosis susceptibility to isoniazid and rifampicin: a crystal violet decolourisation assay

    Directory of Open Access Journals (Sweden)

    Ahmet Yilmaz Coban


    Full Text Available The aim of this study was to investigate the performance of a new and accurate method for the detection of isoniazid (INH and rifampicin (RIF resistance among Mycobacterium tuberculosis isolates using a crystal violet decolourisation assay (CVDA. Fifty-five M. tuberculosis isolates obtained from culture stocks stored at -80ºC were tested. After bacterial inoculation, the samples were incubated at 37ºC for seven days and 100 µL of CV (25 mg/L stock solution was then added to the control and sample tubes. The tubes were incubated for an additional 24-48 h. CV (blue/purple was decolourised in the presence of bacterial growth; thus, if CV lost its colour in a sample containing a drug, the tested isolate was reported as resistant. The sensitivity, specificity, positive predictive value, negative predictive value and agreement for INH were 92.5%, 96.4%, 96.1%, 93.1% and 94.5%, respectively, and 88.8%, 100%, 100%, 94.8% and 96.3%, respectively, for RIF. The results were obtained within eight-nine days. This study shows that CVDA is an effective method to detect M. tuberculosis resistance to INH and RIF in developing countries. This method is rapid, simple and inexpensive. Nonetheless, further studies are necessary before routine laboratory implementation.

  16. Crystal growth, FTIR and thermal characterization of bis ...

    Indian Academy of Sciences (India)

    The grown crystals were characterized by elemental analysis, powder X-ray diffraction, thermal analysis, nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infra-red spectroscopy (FTIR) techniques. The chemical composition of the compound was revealed by elemental analysis and its crystallinity was ...

  17. Crystal growth, FTIR and thermal characterization of bis ...

    Indian Academy of Sciences (India)

    Quaternary phosphonium salts can be made into casts with commercially available polymeric sus- pension to form membranes for the mass transport of cations, anions and neutral species. [14]. However, no attempt has been made so far to crystallize these compounds and check their suitability for industrial applications.

  18. Phonon-enhanced crystal growth and lattice healing (United States)

    Buonassisi, Anthony; Bertoni, Mariana; Newman, Bonna


    A system for modifying dislocation distributions in semiconductor materials is provided. The system includes one or more vibrational sources for producing at least one excitation of vibrational mode having phonon frequencies so as to enhance dislocation motion through a crystal lattice.

  19. Crystal growth and structural analysis of zirconium sulphoselenide ...

    Indian Academy of Sciences (India)


    tion on the lattice parameter, unit cell volume and X-ray density in the series of ZrSxSe3–x single crystals have been studied and found to decrease in all these parameters with rise in sulphur proportion. The grown cry- stals were examined under optical zoom microscope for their surface topography study. Hall effect ...

  20. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    . Calcium formate mixed with formic acid was taken as the supernatant solution. It was observed that the nucleation density was reduced and the size of the crystals was improved to a large extent compared to the conventional way of growing ...

  1. Growth morphology of zinc tris(thiourea) sulphate crystals

    Indian Academy of Sciences (India)

    [7] P Hartman, in Morphology of crystals edited by I Sunagawa (Terra Scientific Publishing Co.,. Tokyo, 1987) p. 269. [8] R Docherty, G Clydesdale, K J Roberts and P Bennema, J. Phys. 24, 89 (1991). [9] G D Andreeti, L Cavalca and A Musatti, Acta Cryst. B24, 683 (1968). [10] M Ramanadham, P U M Sastry, H Rajagopal ...

  2. Lattice Boltzmann Simulation of Water Isotope Fractionation During Growth of Ice Crystals in Clouds (United States)

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


    The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically- symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over-saturation, determines crystal morphology, there are no existing quantitative models that directly relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be a direct relationship between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D Lattice-Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. The input parameters needed are the isotope-dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the sticking coefficient (or accommodation coefficient) for ice is uncertain. The ratio D/k is a length that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions using a dimensionless Damkohler number

  3. Crystal structure control in Au-free self-seeded InSb wire growth

    Energy Technology Data Exchange (ETDEWEB)

    Mandl, Bernhard; Dick, Kimberly A; Deppert, Knut [Department of Solid State Physics, Lund University, S-22 100 Lund (Sweden); Kriegner, Dominik; Keplinger, Mario; Bauer, Guenther; Stangl, Julian, E-mail: [Institute of Solid State- and Semiconductor Physics, Johannes Kepler University Linz, A-4040 Linz (Austria)


    In this work we demonstrate experimentally the dependence of InSb crystal structure on the ratio of Sb to In atoms at the growth front. Epitaxial InSb wires are grown by a self-seeded particle assisted growth technique on several different III-V substrates. Detailed investigations of growth parameters and post-growth energy dispersive x-ray spectroscopy indicate that the seed particles initially consist of In and incorporate up to 20 at.% Sb during growth. By applying this technique we demonstrate the formation of zinc-blende, 4H and wurtzite structure in the InSb wires (identified by transmission electron microscopy and synchrotron x-ray diffraction), and correlate this sequential change in crystal structure to the increasing Sb/In ratio at the particle-wire interface. The low ionicity of InSb and the large diameter of the wire structures studied in this work are entirely outside the parameters for which polytype formation is predicted by current models of particle seeded wire growth, suggesting that the V/III ratio at the interface determines crystal structure in a manner well beyond current understanding. These results therefore provide important insight into the relationship between the particle composition and the crystal structure, and demonstrate the potential to selectively tune the crystal structure in other III-V compound materials as well.

  4. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Willatzen, Morten; Duggen, Lars


    -growth direction, and will be jointly excited by electrical stimulus. We demonstrate this for an electrically excited freestanding slab for two cases of high-symmetry crystal-growth directions and finally show the impact of the Drude model for permittivity on the phonon dispersion. In particular, it is verified...

  5. Control of melt-crystal interface shape during sapphire crystal growth by heat exchanger method (United States)

    Wu, Ming; Liu, Lijun; Ma, Wencheng


    We numerically investigate the melt-crystal interface shape during the early stage of the solidification process when the crystal diameter increases. The contact angle between the melt-crystal interface and the crucible bottom wall is found obtuse during this stage, which is unfavorable for the crystal quality. We found that the obtuse contact angle is caused by the thermal resistance difference between the sapphire crystal and melt as well as the insufficient cooling effect of the crucible bottom. Two approaches are proposed to suppress the obtuse contact angle. The first approach is to increase the emissivity of the outer surface of crucible bottom. The second approach is to install a heat shield near the crucible bottom. The reduction of the emissivity of the heat shield is also favorable for the suppression of the obtuse contact angle. Compared with the increase of the emissivity of the crucible bottom, the installation of a heat shield is a more effective approach to prevent the appearance of an obtuse contact angle for the sake of reliability since a molybdenum heat shield can be reused and will not induce other impurities.

  6. A Rationale for System-Dependent Advantages and Disadvantages of Solution Crystal Growth at Low Gravity (United States)

    Rosenberger, Franz; Vekilov, Peter G.; Lin, Hong; Alexander, J. Iwan D.


    Protein crystallization experiments at reduced gravity have yielded crystals that, depending on the specific material, are either superior or inferior in their structural perfection compared to counterparts grown at normal gravity. A reduction of the crystals' quality due to their growth at low gravity cannot be understood from existing models. Our experimental investigations of the ground-based crystallization of the protein lysozyme have revealed pronounced unsteady growth layer dynamics and associated defect formation under steady external conditions. Through scaling analysis and numerical simulations we show that the observed fluctuations originate from the coupling of bulk transport with non-linear interface kinetics under mixed kinetics-transport control of the growth rate. The amplitude of the fluctuations is smallest when either transport or interfacial kinetics dominate the control of the crystallization process. Thus, depending on the specific system, crystal quality may be improved by either enhancing or suppressing the transport in the solution. These considerations provide, for the first time, a material-dependent rationale for the advantages, as well as the disadvantages, of reduced gravity for (protein) crystallization.

  7. Advances in the Growth and Characterization of Relaxor-PT-Based Ferroelectric Single Crystals

    Directory of Open Access Journals (Sweden)

    Jun Luo


    Full Text Available Compared to Pb(Zr1−xTixO3 (PZT polycrystalline ceramics, relaxor-PT single crystals offer significantly improved performance with extremely high electromechanical coupling and piezoelectric coefficients, making them promising materials for piezoelectric transducers, sensors and actuators. The recent advances in crystal growth and characterization of relaxor-PT-based ferroelectric single crystals are reviewed in this paper with emphases on the following topics: (1 the large crystal growth of binary and ternary relaxor-PT-based ferroelectric crystals for commercialization; (2 the composition segregation in the crystals grown from such a solid-solution system and possible solutions to reduce it; (3 the crystal growth from new binary and ternary compositions to expand the operating temperature and electric field; (4 the crystallographic orientation dependence and anisotropic behaviors of relaxor-PT-based ferroelectriccrystals; and (5 the characterization of the dielectric, elastic and piezoelectric properties of the relaxor-PT-based ferroelectriccrystals under small and large electric fields.

  8. Effect of monomer composition on crystal growth by resin containing bioglass. (United States)

    Hashimoto, Masanori; Iijima, Masahiro; Nagano, Futami; Ohno, Hiroki; Endo, Kazuhiko


    This study evaluated the effect of resin monomer composition on crystal growth at the interface between the resin/bioglass composites and water. Light-cured resin that contained 2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl], 2-hydroxyethyl methacrylate, and triethylene glycol dimethacrylate with different compositions were used. Resin/bioglass composites were prepared with 40 mass% bioglass and 60 mass% resin. The resin/bioglass composites were stored in deionized distilled water for 24 h (control group) or 3-12 months (experimental groups). After water storage, the disk surfaces were examined by light- and scanning electron microscopy. Chemical states of the crystals were analyzed by laser-Raman spectroscopy and micro-X-ray diffractometry. The microscopic analysis showed crystal on the resin disks surface after six months of water storage for hydrophilic resins. However, there was no crystal formation in the control and the experimental groups of specimens of hydrophobic resins. Raman analysis showed the chemical states of the crystals formed on the resin matrix and bioglass to be different. The micro-X-ray analysis of crystals on resin disks identified them to be calcium carbonate. This crystal formation occurred in water instead of simulated body fluid. In conclusion, the resin monomer compositions affected the ability to induce crystal growth on the surfaces of disks containing bioglass. (c) 2010 Wiley Periodicals, Inc.

  9. Effects of gallic acid on the morphology and growth of hydroxyapatite crystals. (United States)

    Tang, Bei; Yuan, He; Cheng, Lei; Zhou, Xuedong; Huang, Xuelian; Li, Jiyao


    This study was designed to explore the effect of gallic acid (GA, one of the ingredients of chemical compounds from galla chinensis) on the morphology and growth of hydroxyapatite crystals. The crystals was produced by mixing CaCl2 and KH2PO4 with or without GA (4g/L) at room temperature for 3, 12, 24h and 3, 7, 14 days. Subsequently, the micro-structure, morphology and composition of the crystals were investigated via SEM, XRD, ATR-FTIR and fluorescence microscopy. The mineral phase was hydroxyapatite in both groups after 14 days, but their processes and the morphology were completely different. The crystals from groups utilizing GA for 14 days were urchin-like, while loose needle-like crystals were observed in groups without GA. XRD results indicated that GA might limit the growth of the crystals, mainly on the 002 direction. The results of ATR-FTIR and fluorescence microscopy revealed that the unique structures might caused by the participation of GA during crystals formation. GA might affect and participate into the formation of the hydroxyapatite, and regulate the morphology and structure of the crystals, to enhance the remineralization process. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Communication and The Challenges of Rapid Population Growth in ...

    African Journals Online (AJOL)

    These factors include religious beliefs, customs and traditions, among others. The discourse also examined the various communication types in Africa and their appropriateness in educating Africans and their governments on the need to control high rate of population growth. Ironically, medical facilities available in African ...

  11. Ribosomal crystallography: from crystal growth to initial phasing (United States)

    Thygesen, J.; Krumbholz, S.; Levin, I.; Zaytzev-Bashan, A.; Harms, J.; Bartels, H.; Schlünzen, F.; Hansen, H. A. S.; Bennett, W. S.; Volkmann, N.; Agmon, I.; Eisenstein, M.; Dribin, A.; Maltz, E.; Sagi, I.; Morlang, S.; Fua, M.; Franceschi, F.; Weinstein, S.; Böddeker, N.; Sharon, R.; Anagnostopoulos, K.; Peretz, M.; Geva, M.; Berkovitch-Yellin, Z.; Yonath, A.


    Preliminary phases were determined by the application of the isomorphous replacement method at low and intermediate resolution for structure factor amplitudes collected from crystals of large and small ribosomal subunits from halophilic and thermophilic bacteria. Derivatization was performed with dense heavy atom clusters, either by soaking or by specific covalent binding prior to the crystallization. The resulting initial electron density maps contain features comparable in size to those expected for the corresponding particles. The packing arrangements of these maps have been compared with motifs observed by electron microscopy in positively stained thin sections of embedded three-dimensional crystals, as well as with phase sets obtained by ab-initio computations. Aimed at higher resolution phasing, procedures are being developed for multi-site binding of relatively small dense metal clusters at selected locations. Potential sites are being inserted either by mutagenesis or by chemical modifications to facilitate cluster binding to the large halophilic and the small thermophilic ribosomal subunits which yield crystals diffracting to the highest resolution obtained so far for ribosomes, 2.9 and 7.3 Å, respectively. For this purpose the surfaces of these ribosomal particles have been characterized and conditions for quantitative reversible detachment of selected ribosomal proteins have been found. The corresponding genes are being cloned, sequenced, mutated to introduce the reactive side-groups (mainly cysteines) and overexpressed. To assist the interpretation of the anticipated electron density maps, sub-ribosomal stable complexes were isolated from H50S. One of these complexes is composed of two proteins and the other is made of a stretch of the rRNA and a protein. For exploiting the exposed parts of the surface of these complexes for heavy atom binding and for attempting the determination of their three-dimensional structure, their components are being produced

  12. Effect of solvents on the bulk growth of 4-aminobenzophenone single crystals: A potential material for blue and green lasers (United States)

    Natarajan, V.; Usharani, S.; Arivanandhan, M.; Anandan, P.; Hayakawa, Y.


    Although 4-aminobenzophenone (4-ABP) is the best derivative of benzophenone with 260 times higher second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP), growth of high quality bulk crystal still remains a difficult task. In the present work, the effect of solvents on solubility and growth aspects of 4-ABP was investigated to grow inclusion free 4-ABP crystals. The growth processes were discussed based on solute-solvent interaction in two different growth media of ethyl acetate and ethanol. The growth rate and thereby solvent inclusions are relatively higher in ethyl acetate grown crystal than the crystal grown from ethanol. The structural, thermal and optical properties of 4-ABP crystals were studied. The enthalpy of 4-ABP melting process was estimated from differential thermal analysis. The optical transmission study shows that 4-ABP crystals grown from ethanol has high transparency compared to ethyl acetate grown sample due to solvent inclusion in the later crystal.

  13. Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy (United States)

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


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

  14. Growth, structural and characterization of a novel third order nonlinear optical Benzimidazolium Maleate single crystal (United States)

    Amudha, M.; Muthu, S.; Gunasekaran, B.; Praveen Kumar, P.


    Good optical quality single crystals of Benzimidazolium Maleate (BML), a new organic charge transfer molecular complex salt, were grown successfully by the slow evaporation solution growth technique using deionised water as solvent at room temperature. The grown crystals of BML were characterised by single crystal X-ray diffraction (XRD) and powder XRD which confirm that the crystal belongs to monoclinic system with the centrosymmetric space group P21/n. The presence of functional groups in the grown crystal was confirmed by Fourier transform infrared spectral analysis. The BML crystal is thermally stable up to 147.7 °C and it is found by TG-DTA analysis. The transparency of the crystal was identified using UV-Vis spectrophotometer. Vickers microhardness analysis shows the mechanical stability of the grown crystal. The dependence of dielectric properties with frequency and temperature were also studied. Nonlinear optical absorption coefficient determined from open aperture Z-scan analysis revealed that the BML crystal can serve as a promising candidate for optical limiting applications.

  15. The Bridgman method growth and spectroscopic characterization of calcium fluoride single crystals

    Directory of Open Access Journals (Sweden)

    Elswie Ibrahim Hana


    Full Text Available It must be noted that the main objective of this study was to obtain single crystals of calcium fluoride - CaF2, and after that the crystals were characterized with various spectroscopic methods. The crystals were grown using the Bridgman technique. By optimizing growth conditions, oriented CaF2 crystals up to 20 mm in diameter were grown. Number of dislocations in CaF2 crystals was 5×104 - 2×105 per cm2. Selected CaF2 single crystal is cut into several tiles with the diamond saw. The plates were polished, first with the silicon carbide, then the paraffin oil, and finally with a diamond paste. The obtained crystal wаs studied by Raman and infrared -IR spectroscopy. The crystal structure is confirmed by X-ray diffraction (XRD. One Raman and two IR optical modes predicted by group theory are observed. A low photoluminescence testifies that the concentration of oxygen defects within the host CaF2 is small. All performed investigations show that the obtained CaF2 single crystal has good optical quality, which was the goal of this work. [Projekat Ministarstva nauke Republike Srbije, br. III 45003 i br. TR34011

  16. Crystal growth and magnetic property of YFeO3 crystal

    Indian Academy of Sciences (India)

    Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 200235, China; Department of Physics, Shanghai University, Shanghai 200444, China; State Key Laboratory of Crystal Material, Shandong ...

  17. Crystal growth, crystal structure, vibrational spectroscopy, linear and nonlinear optical properties of guanidinium phosphates (United States)

    Němec, Ivan; Matulková, Irena; Held, Peter; Kroupa, Jan; Němec, Petr; Li, Dongxu; Bohatý, Ladislav; Becker, Petra


    Of the three guanidinium phosphates GuH2PO4 (space group P21/c), Gu2HPO4·H2O (space group P 4 bar 21 c) and Gu3PO4· 3/2 H2O (space group Cc) crystal structures and a vibrational spectroscopy study are presented. Large single crystals of GuH2PO4 and Gu2HPO4·H2O are grown. Refractive indices and their dispersion in the wavelength range 365 nm - 1083 nm are determined and used for the analysis of phase matching conditions for collinear SHG in the case of the non-centrosymmetric crystals of Gu2HPO4·H2O. The crystals are not phase-matchable within their transmission range. Both independent components of the SHG tensor of Gu2HPO4·H2O, determined by the Maker fringe method, are given, with d14 = 0.23 pm/V and d36 = 0.22 pm/V. In addition, the thermal stability and the anisotropy of thermal expansion of GuH2PO4 and Gu2HPO4·H2O is reported.

  18. Crystal growth and magnetic property of YFeO3 crystal

    Indian Academy of Sciences (India)

    taken by ferromagnetic garnets for magnetic bubble devices. However, their highest domain wall motion velocity (at up ... Voids, bubbles, twins and optical den- sity variations are commonly observed in crystals ..... The authors would like to acknowledge the financial sup- port from the National Natural Science Foundations ...

  19. A rare large right atrial myxoma with rapid growth rate. (United States)

    Kelly, Shawn C; Steffen, Kelly; Stys, Adam T


    Atrial myxomas are the most common benign intracavitary cardiac neoplasms. They most frequently occur in the left atrium. Right atrial tumors are rare, comprising 20 percent of myxomas achieving an incidence of 0.02 percent. Due to their rarity, right atrial tumor development and associated clinical symptoms has not been well described. The classical clinical triad for the presentation of left atrial myxomas--heart failure, embolic events, and constitutional symptoms--may not be applicable to right sided tumors. Also, natural development of myxoma is not well described, as surgical resection is the common practice. Previously ascribed growth rates of myxomas refer mostly to left atrial ones, as right atrial tumors are rare. We present a case of right atrial myxoma with growth rates exceeding those previously described.

  20. Metallic nanofilms on single crystal silicon: Growth, properties and applications

    Directory of Open Access Journals (Sweden)

    Nikolay I. Plusnin


    We have considered theoretical viewpoints and reviewed experimental data on the growth and properties of metallic nanofilms (including multilayered ones on silicon, and also provided a brief review of their applications. The films consist either of atomic-sized, quabquantum sized and quantum sized layers. We have suggested a low temperature film growth technology based on freezing growing layers during deposition by maintaining a low temperature of the substrate and using an atomic beam with a reduced heat power. The technology uses a specially shaped deposition system in which the distance between the source and the substrate is comparable to their size or smaller. Furthermore, we use a special time sequence of deposition that provides for a reduced substrate surface temperature due to greater intervals between deposition pulses. This growth method of atomically thin films and multilayered nanofilms excludes interdiffusion between the layers, reduces three-dimensional growth rate and relatively increases lateral layer growth rate.

  1. Rapid population growth and environmental degradation: ultimate versus proximate factors. (United States)

    Shaw, R P


    This philosophical review of 2 arguments about responsibility for and solutions to environmental degradation concludes that both sides are correct: the ultimate and the proximal causes. Ultimate causes of pollution are defined as the technology responsible for a given type of pollution, such as burning fossil fuel; proximate causes are defined as situation-specific factors confounding the problem, such as population density or rate of growth. Commoner and others argue that developed countries with low or negative population growth rates are responsible for 80% of world pollution, primarily in polluting technologies such as automobiles, power generation, plastics, pesticides, toxic wastes, garbage, warfaring, and nuclear weapons wastes. Distortionary policies also contribute; examples are agricultural trade protection, land mismanagement, urban bias in expenditures, and institutional rigidity., Poor nations are responsible for very little pollution because poverty allows little waste or expenditures for polluting, synthetic technologies. The proximal causes of pollution include numbers and rate of growth of populations responsible for the pollution. Since change in the ultimate cause of pollution remains out of reach, altering the numbers of polluters can make a difference. Predictions are made for proportions of the world's total waste production, assuming current 1.6 tons/capita for developed countries and 0.17 tons/capita for developing countries. If developing countries grow at current rates and become more wealthy, they will be emitting half the world's waste by 2025. ON the other hand, unsustainable population growth goes along with inadequate investment in human capital: education, health, employment, infrastructure. The solution is to improve farming technologies in the 117 non-self-sufficient countries, fund development in the most unsustainable enclaves of growing countries, break institutionalized socio-political rigidity in these enclaves, and focus on

  2. Physical modelling of temperature fluctuations in a high aspect ratio model of the Czochralski crystal growth (United States)

    Pal, J.; Cramer, A.; Grants, I.; Eckert, S.; Gerbeth, G.


    A low temperature liquid metal model of the Czochralski (CZ) crystal growth process is considered experimentally for a high aspect ratio. Temperature fluctuations close to the edge of the model crystal are studied under the action of a rotating magnetic field (RMF) and/or rotation of the model crystal. A rotation of thermal structures is observed which loses its periodicity at sufficiently high strengths of the RMF. This finding is in qualitative agreement with previous findings in Rayleigh-Bénard (RB) cells. Opposing to that more generic case, the remaining amplitude of the temperature fluctuations stays significantly higher. I.e., the suppression of the fluctuations, which are detrimental to the growth of a mono-crystal, is weaker in the model under investigation.

  3. Synthesis, growth, spectral, optical and thermal studies of thiourea family crystal: TTPB (United States)

    Subashini, A.; Rajarajan, K.; Sagadevan, Suresh


    In the present work, bulk size single crystal of tetrakis thiourea potassium bromide [K(N2H4CS)4Br]; (TTPB) has been grown from an aqueous solution using slow evaporation solution growth method. The XRD result proved that the compound crystallize in tetragonal crystal system with space group P41. The FT-IR spectrum of TTPB has clearly identified the functional groups of thiourea in the resulting compound. The TG-DTA and DSC studies have been carried out on the grown sample of TTPB and the results are reported. The etching and scanning electron microscope studies were also carried out to understand the growth pattern and surface morphology of TTPB. The spectral, optical and thermal studies of TTPB are compared with the similar thiourea complex crystal [K(N2H4CS)4I]; (TTPI) and reported.

  4. Determining the Molecular Growth Mechanisms of Protein Crystal Faces by Atomic Force Microscopy (United States)

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


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

  5. Crystal growth and characterization of Marokite CaMn 2O 4+δ (United States)

    White, B. D.; dos Santos, C. A. M.; Souza, J. A.; McClellan, K. J.; Neumeier, J. J.


    Centimeter-sized single crystals of CaMn 2O 4+δ, commonly known as Marokite, were grown using the floating-zone method. The growth conditions are reported along with a discussion of a simple method for polycrystalline rod preparation, which differs from the typical cold isostatic pressure procedure. Crystal characterization was determined by powder X-ray diffraction, back-reflection Laue diffraction, iodometric titration, energy-dispersive X-ray spectrometry, and vibrating sample magnetometry. Polycrystalline rods, composed of stoichiometric Marokite, were found to produce crystals with CaMnO 3 as a secondary impurity phase as revealed by magnetic measurements and powder diffraction. Crystals grown from polycrystalline rods with excess manganese oxide produced single crystals of high quality without impurity phases.

  6. Growth and Faraday rotation characteristics of Tb2Sn2O7 crystal (United States)

    Guo, F. Y.; Wan, Q. P.; Hou, Y.; Zhang, L. Z.; Fu, H.; Chen, J. Z.


    Tb2Sn2O7 (TSO) single crystals have been grown by the top-seeded solution growth (TSSG) method using a Na2B4O7-NaF mixture as the flux. In this paper, the morphology of as-grown TSO crystals is briefly described and the valences of terbium and tin in crystal were analyzed by X-ray photoelectron spectroscopy. The transmission spectrum was measured in the wavelength range of 400-1600 nm at room temperature and the Faraday rotation of a TSO crystal was investigated at 532, 633 and 1064 nm wavelengths by the extinction method. Results show that TSO crystals exhibit typical paramagnetism when the temperature is above 2 K and have a larger Verdet constant than that reported for TGG.

  7. Tabular silver halide crystals prepared by controlled Ostwald growth in the presence of dimethyl sulphoxide

    Energy Technology Data Exchange (ETDEWEB)

    Dyonizy, A.; Nowak, P.; Mora, C.; Krol-Gracz, A.; Michalak, E. [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze St. Wyspianskiego 27, 50-370 Wroclaw (Poland)


    The results of research in the size and shape of silver bromide crystals precipitated by the Ostwald controlled growth method at the presence of dimethyl sulphoxide were presented in the paper. The silver bromide crystals were produced in the form of microcrystal suspension stabilised by gelatine. In the course of the synthesis of crystals, the constant concentration of dimethyl sulphoxide, concentration of excessive bromide ions and the constant ionic strength were achieved. The tabular crystals of silver bromide with their average size of 50 {mu}m and their aspect ratio equal to 100 were obtained by means of this method. The suspensions of flat silver bromide crystals produced in this manner can be used in the production of high-sensitivity materials. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Growth of CdZnTe Crystals for Radiation Detector Applications by Directional Solidification (United States)

    Su, Ching-Hua


    Advances in Cadmium Zinc Telluride (Cd(sub 1-x)Zn(sub x)Te) growth techniques are needed for the production of large-scale arrays of gamma and x-ray astronomy. The research objective is to develop crystal growth recipes and techniques to obtain large, high quality CdZnTe single crystal with reduced defects, such as charge trapping, twinning, and tellurium precipitates, which degrade the performance of CdZnTe and, at the same time, to increase the yield of usable material from the CdZnTe ingot. A low gravity material experiment, "Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment", will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). One section of the flight experiment is the melt growth of CdZnTe ternary compounds. This talk will focus on the ground-based studies on the growth of Cd(sub 0.80)Zn(sub 0.20)Te crystals for radiation detector applications by directional solidification. In this investigation, we have improved the properties that are most critical for the detector applications (electrical properties and crystalline quality): a) Electrical resistivity: use high purity starting materials (with reproducible impurity levels) and controlled Cd over pressure during growth to reproducibly balance the impurity levels and Cd vacancy concentration b) Crystalline quality: use ultra-clean growth ampoule (no wetting after growth), optimized thermal profile and ampoule design, as well as a technique for supercool reduction to growth large single crystal with high crystalline quality

  9. Growth and study of mixed crystals of Ca–Cd iodate

    Indian Academy of Sciences (India)


    on account of its unique advantages in terms of crystals produced and the simplicity of the process (Armington and O'Connar 1968; Blank and Brenner 1969; ... glacial acetic acid and sodium meta silicate having different. pH values. The chemicals used for growth of mixed iodate crystals were CH3COOH, Na2SiO3⋅9H2O, ...

  10. Vapor Growth of Mercuric Iodide Tetragonal Prismatic Crystals (United States)


    5.40 Gas chromatograph for thermal desorption of n- eicosane (n-C20H42) . . . . 93 5.41 Background subtracted ATR-IR spectrum of processed low M̄w...n-Alkanes Three types of alkanes were used for various growth runs: n-hexatriacontane (C36H74), n-tetracontane (C24H50), and n- eicosane (C20H42). The...hexatriacontane n-C36H74 98% Sigma Aldrich n-tetracosane n-C24H50 99% Sigma Aldrich n- eicosane n-C20H42 99% Sigma Aldrich 4.7 Growth with Ketones HgI2 growth

  11. Effect of convective flow on stable dendritic growth in rapid solidification of a binary alloy (United States)

    Galenko, P. K.; Danilov, D. A.; Reuther, K.; Alexandrov, D. V.; Rettenmayr, M.; Herlach, D. M.


    A model for anisotropic growth of a dendritic crystal in a binary mixture under non-isothermal conditions is presented. A criterion for a stable growth mode is given for the dendrite tip as a function of the thermal Péclet number and the ratio between the velocities of dendrite growth and solute diffusion in the liquid bulk. Limiting cases of known criteria for anisotropic dendrite growth at low and high growth Péclet numbers are provided. The inclusion of forced convective flow extends the range of theoretical predictions, especially to low growth velocities, thus eliminating systematic discrepancies between earlier models and observed experimental data, as shown by a comparison of model predictions with measured growth velocities in Ti-55 at% Al alloys solidified under electromagnetic levitation.

  12. Growth experiment of organic metal crystal in low gravity (M-21) (United States)

    Anzai, Hiroyuki


    The purpose of this experiment is to grow large, high-quality single crystals of the organic metal (TMTTF-TCNQ) by the diffusion method without thermal fluctuation due to convection and gravitational sedimentation, and to evaluate the difference in properties between such crystals grown in low gravity and the ones obtained on Earth. The expected results may fix several physical properties of TMTTF-TCNQ, lead to the discovery of new phenomena, and enable us to analyze diffusion processes in a precise way. The result will contribute to the development of research on organic metals and, generally, on crystal growth.

  13. Method for single crystal growth of photovoltaic perovskite material and devices

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jinsong; Dong, Qingfeng


    Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

  14. Enhancement of heat transfer in Czochralski growth of silicon crystals with a chemical cooling technique (United States)

    Ding, Junling; Liu, Lijun; Zhao, Wenhan


    The cost of producing single-crystalline silicon with the Czochralski method can be reduced by promoting the crystal size and/or crystal pulling rate. However, more latent heat of solidification needs to be released from the melt-crystal (m-c) interface during the crystal growth process. In this study, the C-CO2 chemical endothermic reaction is proposed as a novel and efficient cooling technique to solve this problem. Compared with the conventional gas cooling method, C-CO2 endothermic reaction method can significantly enhance the heat transfer in the crystal at the m-c interface. It was found that the heat transfer is more enhanced with a chemical reaction of smaller activation energy, and the m-c interface becomes flatter. The influence of the carbon concentration in the chemical reactive gas flow on the heat removal in the crystal at the m-c interface is also investigated. The cooling effect is significantly increased with the increase in the carbon concentration when it is small. However, when the carbon concentration in the reactive gas is high, the cooling effect just increases slightly. The research demonstrates that the proposed chemical endothermic reaction is a promising cooling technique to be applied in CZ-Si crystal growth with large size/high pulling rate.

  15. Equipment and methods for rapid analysis of PWO full-sized scintillation crystal radiation hardness during mass production

    CERN Document Server

    Drobychev, G Yu; Fedorov, A; Korzhik, M V; Lecoq, P; Lopatik, A; Missevitch, O V; Peigneux, J P; Singovsky, A V; Zouevski, R F


    The mass production of lead tungstate crystals (PWO) for the Compact Muon Solenoid (CMS) Project at CERN began at the Bogoroditsk Techno- Chemical Plant (BTCP, Tula Region, Russia) in 2000. Mass production technology, developed in recent years, is based on a set of methods and instrumentation for crystal growth and machining, as well as quality control and certification of crystals. One of the most crucial categories of tolerances is the radiation hardness of crystals. Control of the PWO radiation hardness during the mass production phase requires a reliable, easy-to-use measuring tool with high productivity. A semiautomatic spectrometric setup for PWO radiation hardness monitoring was developed and tested at CERN. After final crosschecks, the setup was put into operation at BTCP. (13 refs).

  16. Rapid growth of left atrial myxoma after radiofrequency ablation. (United States)

    Rubio Alvarez, José; Martinez de Alegria, Anxo; Sierra Quiroga, Juan; Adrio Nazar, Belen; Rubio Taboada, Carola; Martinez Comendador, José Manuel


    Atrial myxoma is the most common benign tumor of the heart, but its appearance after radiofrequency ablation is very rare. We report a case in which an asymptomatic, rapidly growing cardiac myxoma arose in the left atrium after radiofrequency ablation. Two months after the procedure, cardiovascular magnetic resonance, performed to evaluate the right ventricular anatomy, revealed a 10 × 10-mm mass (assumed to be a thrombus) attached to the patient's left atrial septum. Three months later, transthoracic echocardiography revealed a larger mass, and the patient was diagnosed with myxoma. Two days later, a 20 × 20-mm myxoma weighing 37 g was excised. To our knowledge, the appearance of an atrial myxoma after radiofrequency ablation has been reported only once before. Whether tumor development is related to such ablation or is merely a coincidence is uncertain, but myxomas have developed after other instances of cardiac trauma.

  17. Crystal growth and evaluation of silicon for VLSI and ULSI

    CERN Document Server

    Eranna, Golla


    PrefaceAbout the AuthorIntroductionSilicon: The SemiconductorWhy Single CrystalsRevolution in Integrated Circuit Fabrication Technology and the Art of Device MiniaturizationUse of Silicon as a SemiconductorSilicon Devices for Boolean ApplicationsIntegration of Silicon Devices and the Art of Circuit MiniaturizationMOS and CMOS Devices for Digital ApplicationsLSI, VLSI, and ULSI Circuits and ApplicationsSilicon for MEMS ApplicationsSummaryReferencesSilicon: The Key Material for Integrated Circuit Fabrication TechnologyIntroductionPreparation of Raw Silicon MaterialMetallurgical-Grade SiliconPuri

  18. Development of low-cost silicon crystal growth techniques for terrestrial photovoltaic solar energy conversion (United States)

    Zoutendyk, J. A.


    Because of the growing need for new sources of electrical energy, photovoltaic solar energy conversion is being developed. Photovoltaic devices are now being produced mainly from silicon wafers obtained from the slicing and polishing of cylindrically shaped single crystal ingots. Inherently high-cost processes now being used must either be eliminated or modified to provide low-cost crystalline silicon. Basic to this pursuit is the development of new or modified methods of crystal growth and, if necessary, crystal cutting. If silicon could be grown in a form requiring no cutting, a significant cost saving would potentially be realized. Therefore, several techniques for growth in the form of ribbons or sheets are being explored. In addition, novel techniques for low-cost ingot growth and cutting are under investigation.

  19. The influence of biuret on the growth kinetics of urea crystals from aqueous solutions (United States)

    Davey, R.; Fila, W.; Garside, J.


    The growth kinetics of urea in the [001] and [110] directions are presented for both pure solutions and solutions containing up to 6% biuret. This impurity is formed during the synthesis of urea and acts as a powerful habit modifier. In pure solutions urea grows very quickly in the [001] but very slowly in the [110] direction. As a result long needle-like crystals are produced. In the presence of biuret [001] growth is dramatically reduced while [110] growth is virtually unaffected, so producing a crystal with a much lower length: breadth ratio. The influence of biuret is explained by the replacement of two urea molecules in the crystal lattice by a biuret molecule. The resulting disruption of the (001) face leaves insufficient NH 2-groups to satisfy the hydrogen bonding linkages.

  20. Surfaces Self-Assembly and Rapid Growth of Amyloid Fibrils (United States)

    Lin, Yichih; Petersson, E. James; Fakhraai, Zahra


    The mechanism of surface-mediated fibrillization has been considered as a key issue in understanding the origins of the neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. In vitro, amyloid proteins fold through nucleation-elongation process. There is a critical concentration for early nucleating stage. However, some studies indicate that surfaces can modulate the fibril's formation under physiological conditions, even when the concentration is much lower than the critical concentration. Here, we use a label-free procedure to monitor the growth of fibrils across many length scales. We show that near a surface, the fibrillization process appears to bypass the nucleation step and fibrils grow through a self-assembly mechanism instead. We control and measure the pre-fibrillar morphology at different stages of this process on various surfaces. The interplay between the surface concentration and diffusion constant can help identify the detailed mechanisms of surface-mediated fibril growth, which remains largely unexplored. Our works provide a new insight in designing new probes and therapies. Supported by the National Institute On Aging of the National Institutes of Health under Award Number P30AG010124.

  1. Dynamics of the phase transition boundary in the presence of nucleation and growth of crystals (United States)

    Alexandrov, D. V.


    Nucleation and growth of crystals in a moving metastable layer of phase transition is analyzed theoretically. The integro-differential equations for the density distribution function and system metastability are solved analytically on the basis of a previously developed approach (Alexandrov and Malygin 2013 J. Phys. A: Math. Theor. 46 455101) in cases of the kinetic and diffusionally controlled regimes of crystal growth. The Weber-Volmer-Frenkel-Zel’dovich and Meirs nucleation kinetics are considered. It is shown that the phase transition boundary propagates with time as α\\sqrt{t}+\\varepsilon Z_1(t) , where Z_1(t)=β t7/2 and Z_1(t)=β t2 in cases of kinetic and diffusionally controlled growth regimes. The growth rate constants α and β as well as parameter ɛ are found analytically. The phase transition boundary in the presence of particle nucleation and growth moves slower than in cases without nucleation.

  2. Crystal growth and reflectivity studies of Zn1–xMnxTe crystals

    Indian Academy of Sciences (India)


    Stifter D, Bonanni A, Garcia-Rocha M, Schmid M, Hingerl K and Sitter H 1999 J. Cryst. Growth 201 132. Veera Brahmam K 2002 Studies in semimagnetic semiconduc- tors: Growth and characterization of Zn1–xMnxTe, Ph. D. Thesis, Sri Venkateswara University, Tirupati. Yodershort D R, Debska U and Furdyna J K 1985 J.

  3. Automatic Control System for the High Pressure CdTe Crystal Growth Furnace

    Directory of Open Access Journals (Sweden)

    Petr Praus


    Full Text Available CdTe and (CdZnTe bulk single crystals have been widely used as substrates for MBE and LPE epitaxy of infrared (HgCdTe as well as gamma- and X-ray detectors. The Cd1-xZnxTe (x = 0.04-0.1 single crystals with diameter up to 100 mm and height at most 40 mm were prepared in our laboratory in a vertical arrangement by gradual cooling of the melt (the Vertical Gradient Freezing method. Achievement of excellent crystal quality required full control of Cd pressure during the growth process and application of high Cd pressures (up to 4 bar at growth temperature. An electronic control system was designed to control both temperature and internal pressure of two zones CZT crystal growth furnace by using two high performance PID controllers/setpoint programmers. Two wire current loop serial communication bus was used for the data exchange and computer control of the furnace electronics setup. Control software was written to supervise the crystal growth process and to collect all important data and parameters.

  4. Ultrasound Flow Mapping for the Investigation of Crystal Growth. (United States)

    Thieme, Norman; Bonisch, Paul; Meier, Dagmar; Nauber, Richard; Buttner, Lars; Dadzis, Kaspars; Patzold, Olf; Sylla, Lamine; Czarske, Jurgen


    A high energy conversion and cost efficiency are keys for the transition to renewable energy sources, e.g., solar cells. The efficiency of multicrystalline solar cells can be improved by enhancing the understanding of its crystallization process, especially the directional solidification. In this paper, a novel measurement system for the characterization of flow phenomena and solidification processes in low-temperature model experiments on the basis of ultrasound (US) Doppler velocimetry is described. It captures turbulent flow phenomena in two planes with a frame rate of 3.5 Hz and tracks the shape of the solid-liquid interface during multihour experiments. Time-resolved flow mapping is performed using four linear US arrays with a total of 168 transducer elements. Long duration measurements are enabled through an online, field-programmable gate array (FPGA)-based signal processing. Nine single US transducers allow for in situ tracking of a solid-liquid interface. Results of flow and solidification experiments in the model experiment are presented and compared with numerical simulation. The potential of the developed US system for measuring turbulent flows and for tracking the solidification front during a directional crystallization process is demonstrated. The results of the model experiments are in good agreement with numerical calculations and can be used for the validation of numerical models, especially the selection of the turbulence model.

  5. Fast growth of n-type 4H-SiC bulk crystal by gas-source method (United States)

    Hoshino, Norihiro; Kamata, Isaho; Tokuda, Yuichiro; Makino, Emi; Kanda, Takahiro; Sugiyama, Naohiro; Kuno, Hironari; Kojima, Jun; Tsuchida, Hidekazu


    Fast growth of n-type 4H-SiC crystals was attempted using a high-temperature gas-source method. High growth rates exceeding 9 mm/h were archived at a seed temperature of 2550 °C, although the formation of macro-step bunching caused doping fluctuation and voids in the grown crystal. We investigated a trade-off between growth-rate enhancement and macro-step formation and how to improve the trade-off. By controlling the growth conditions, the growth of highly nitrogen-doped 4H-SiC crystals without the doping fluctuation and void formation were accomplished under a high growth rate exceeding 3 mm/h, maintaining the density of threading screw dislocations in the same level with the seed crystal. The influence of growth parameters on nitrogen incorporations into grown crystals was also surveyed.

  6. Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Weidong, E-mail: [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhong, Jiasong [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhao, Yinsheng [Pan Asia Technical Automotive Center Co. Ltd., Shanghai 201201 (China); Zhao, Binyu [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); Dong, Yongjun [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Zhang, Zhimin; Chen, Zhaoping; Liu, Bingfeng [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China)


    Highlights: Black-Right-Pointing-Pointer The YAG:Ce,Mn single crystal was well synthesized by the Czochralski (CZ) method. Black-Right-Pointing-Pointer The emission intensity of the sample has been influenced after annealing. Black-Right-Pointing-Pointer Annealed in the air at 1200 Degree-Sign C was the most optimal annealing condition. Black-Right-Pointing-Pointer The single crystal could be used in the white light LED which emitted by blue light. - Abstract: The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300-500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

  7. Growth and thermoelectric properties of p-type layered GaTe single crystals (United States)

    Vu, Thi Hoa; Pham Anh, Tuan; Duong Anh, Tuan; Nguyen van, Quang; Cho, Sunglae

    Gallium Telluride (GaTe) crystal is a member of chalcogenide crystal family as same as two-dimensional (2D) semiconductors. As for GaTe, the high dissymmetry between intra- and inter bond strengths can give rise to a strong scattering of the charge carriers by optical phonon polarized perpendicular to the layers, so thermal conductivity can be reduced. However, due to the difficulty in growth of large-size high quality crystals, it is one of the less investigated materials. In this talk, we report on the crystal structure and thermoelectric properties of p-type GaTe single crystals. The sample was obtained by the vertical temperature gradient method. The single crystal structure was determined by XRD and FE-SEM measurement. Thermoelectric and transport properties both along and perpendicular to the layered planes were evaluated in the temperature range from 20 to 400 K. We observed very high positive Seebeck coefficients in GaTe single crystal. Maximum values are about 2000 and 843 for in-plane and perpendicular direction, respectively. The results indicate a p-type semiconductor in GaTe single crystal. We will discuss on temperature and direction dependent power factor value of p-type GaTe in detail.

  8. Mediation of calcium oxalate crystal growth on human kidney epithelial cells with different degrees of injury

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Shen [Graduate School of Southern Medical University, Guangzhou 510515 (China); Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Su Zexuan, E-mail: [The First Affiliated Hospital, Jinan University, Guangzhou 510632 (China); Yao Xiuqiong; Peng Hua; Deng Suiping [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Ouyang Jianming, E-mail: [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China)


    The current study examined the role of injured human kidney tubular epithelial cell (HKC) in the mediation of formation of calcium oxalate (CaOxa) crystals by means of scanning electronic microscopy and X-ray diffraction. HKC was injured using different concentrations of H{sub 2}O{sub 2}. Cell injury resulted in a significant decrease in cell viability and superoxide dismutase (SOD) concentration and an increase in the level of malondialdehyde (MDA) and expression of osteopontin (OPN). Injured cells not only promote nucleation and aggregation of CaOxa crystals, but also induce the formation of calcium oxalate monohydrate (COM) crystals that strongly adhere to cells. These results imply that injured HKCs promote stone formation by providing more nucleating sites for crystals, promoting the aggregation of crystals, and inducing the formation of COM crystals. - Graphical abstract: Injured cells promote nucleation and aggregation of CaOxa crystals, induce the formation of calcium oxalate monohydrate (COM) crystals. Highlights: Black-Right-Pointing-Pointer A direct nucleation and growth of CaOxa crystals on both normal and injured cells. Black-Right-Pointing-Pointer Stronger green fluorescence, i.e. OPN expression, was seen on the injury cell surface Black-Right-Pointing-Pointer Injured cells promote nucleation and aggregation of CaOxa crystals. Black-Right-Pointing-Pointer Injured cells induce the formation of calcium oxalate monohydrate crystals. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} decrease cell viability in a dose-dependent manner at 0.1-1 mmol/L.

  9. MOCVD epitaxial growth of single crystal GaN, AlN and AlxGa1-xN (United States)

    Matloubian, M.; Gershenzon, M.


    Ga begins to deposit from a stream of trimethylgallium (TMG) in H2 at a minimum temperature of 475‡C. Addition of sufficient amounts of NH2 results in the growth of textured polycrystalline GaN on basal plane sapphire substrates above 500‡C. A minimum temperature of 800‡C is required for the epitaxial growth of GaN on the substrate. Under similar conditions, but with the TMG replaced with trimethylaluminum (TMA), polycrystalline A1N begins forming at 400‡C (in the absence of NH3,, the TMA starts pyrolyzing at 300‡C), but single crystal growth of A1N requires a temperature of at least 1200‡C. Epitaxial single crystal layers of Alx Ga1-x N can be grown in the temperature range 800-1200‡C, tne minimum temperature being approximately proportional to x, but preferential deposition of A1N on the hot walls of the reactor (>400‡C) precludes precise control of the alloy composition. This predeposition of A1N can be retarded by keeping the walls below 400‡C by using a water-cooled jacket, by rapid flow-rates, or by injecting the TMA through a nozzle close to the surface of the substrate.

  10. Hydrothermal vents in Lake Tanganyika harbor spore-forming thermophiles with extremely rapid growth

    DEFF Research Database (Denmark)

    Elsgaard, Lars; Prieur, Daniel


    and peptone. The optimum temperature for growth was 60 °C, while minimum and maximum temperatures were 40 and 75 °C. The pH response was alkalitolerant with optimum pH at 7.4 and 8.5 depending on the growth medium. The distinct feature of rapid proliferation and endospore formation may allow the novel...

  11. Accelerated crack growth rate at low Delta K in a single crystal superalloy (United States)

    Telesman, Jack; Ghosn, Louis


    The low Delta K crack growth behavior of a single crystal of the PWA 1480 nickel-based superalloy was investigated. The crystal was tested in the near (100) orientation with the side faces being in the near (001) orientation. Although in the higher Delta K region the fatigue crack growth (FCG) behavior is rather normal, at Delta K of about 8 MPa sq rt m, a transition occurs where the FCG rate appears to be independent of Delta K. This region is found to continue until Delta K of about 2.5 MPa sq rt m, where the FCG rate again decreases with decreasing Delta K.

  12. Single Crystal Growth of URu2Si2 by the Modified Bridgman Technique

    Directory of Open Access Journals (Sweden)

    Andrew Gallagher


    Full Text Available We describe a modified Bridgman growth technique to produce single crystals of the strongly correlated electron material URu2Si2 and its nonmagnetic analogue ThRu2Si2. Bulk thermodynamic and electrical transport measurements show that the properties of crystals produced in this way are comparable to those previously synthesized using the Czochralski or conventional molten metal flux growth techniques. For the specimens reported here, we find residual resistivity ratios R R R = ρ 300 K / ρ 0 as large as 116 and 187 for URu2Si2 and ThRu2Si2, respectively.

  13. (Li1−xFexOHFeSe Superconductors: Crystal Growth, Structure, and Electromagnetic Properties

    Directory of Open Access Journals (Sweden)

    Guo-Yong Zhang


    Full Text Available This review focuses on the growth of high-quality (Li1−xFexOHFeSe single crystals by a hydrothermal method using floating-zone-grown AxFe2−ySe2 (A = K, Rb, and Cs as precursors. The structure, superconductivity, and magnetic behavior of the obtained crystals are highly influenced by the growth conditions, such as time, temperature, and composition. A phase diagram with temperature against the c-lattice constant is summarized including the antiferromagnetic spin density wave, superconducting, and paramagnetic phases.

  14. Growth and characterization of single crystal insulators on silicon (United States)

    Schowalter, Leo J.; Fathauer, Robert W.


    An overview of the growth and characterization of epitaxial insulators on semiconductors is presented. The potential applications include semiconductor-on-insulator structures, three-dimensional and/or high-density integrated circuits, optoelectronic applications such as integrated waveguides and improved gate insulators. The growth and physical characterization of epitaxial fluorides on semiconductors are discussed. Consideration is also given to the epitaxial overgrowth of epitaxial metal layers with CaF2 as well as to the formation of a novel superlattice of Ca particles in epitaxial CaF2.

  15. New Crystal-Growth Methods for Producing Lattice-Matched Substrates for High-Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A.


    This effort addressed the technical problem of identifying and growing, on a commercial scale, suitable single-crystal substrates for the subsequent deposition of epitaxial thin films of high temperature semiconductors such as GaN/AlN. The lack of suitable lattice-matched substrate materials was one of the major problem areas in the development of semiconducting devices for use at elevated temperatures as well as practical opto-electronic devices based on Al- and GaN technology. Such lattice-matched substrates are necessary in order to reduce or eliminate high concentrations of defects and dislocations in GaN/AlN and related epitaxial thin films. This effort concentrated, in particular, on the growth of single crystals of ZnO for substrate applications and it built on previous ORNL experience in the chemical vapor transport growth of large single crystals of zinc oxide. This combined expertise in the substrate growth area was further complemented by the ability of G. Eres and his collaborators to deposit thin films of GaN on the subject substrates and the overall ORNL capability for characterizing the quality of such films. The research effort consisted of research on the growth of two candidate substrate materials in conjunction with concurrent research on the growth and characterization of GaN films, i.e. the effort combined bulk crystal growth capabilities in the area of substrate production at both ORNL and the industrial partner, Commercial Crystal Growth Laboratories (CCL), Naples, Florida, with the novel thin-film deposition techniques previously developed in the ORNL SSD.

  16. A simple high-pressure furnace for liquid-encapsulated Bridgman/Stockbarger crystal growth (United States)

    Ciszek, T. F.; Evans, C. D.


    This paper describes a simple, internally-heated high pressure furnace for liquid-encapsulated synthesis and melt growth at temperatures up to 1200 C and pressures up to 100 bar. The hot zone is contained in a 102-mm-ID x 127-mm-OD x 508-mm-long tubular vessel made of 304-series stainless steel. The vessel is externally water cooled and has self-sealing O-ring end closures. A Kanthal A-1 wire heating element provides a uniform-temperature synthesis zone and a gradient for crystal growth. The 38-mm-ID hot zone requires less than 1 kW power for 1200 C operation. The furnace power level is varied by a triac circuit that operates from stabilized 110-V ac line voltage at less than 10 A current. Motor-driven power ramping is provided for stationary crystal growth in a moving temperature gradient. Alternatively, the temperature gradient can be maintained constant while the crucible is lowered with a steeper-motor driven lead screw. Some applications of the furnace for synthesis and crystal growth of Cu(x)Ag(1-x)InSe2 and crystal growth of InP are described.

  17. The Way towards Ultrafast Growth of Single-Crystal Graphene on Copper. (United States)

    Zhang, Zhihong; Xu, Xiaozhi; Qiu, Lu; Wang, Shaoxin; Wu, Tianwei; Ding, Feng; Peng, Hailin; Liu, Kaihui


    The exceptional properties of graphene make it a promising candidate in the development of next-generation electronic, optoelectronic, photonic and photovoltaic devices. A holy grail in graphene research is the synthesis of large-sized single-crystal graphene, in which the absence of grain boundaries guarantees its excellent intrinsic properties and high performance in the devices. Nowadays, most attention has been drawn to the suppression of nucleation density by using low feeding gas during the growth process to allow only one nucleus to grow with enough space. However, because the nucleation is a random event and new nuclei are likely to form in the very long growth process, it is difficult to achieve industrial-level wafer-scale or beyond (e.g. 30 cm in diameter) single-crystal graphene. Another possible way to obtain large single-crystal graphene is to realize ultrafast growth, where once a nucleus forms, it grows up so quickly before new nuclei form. Therefore ultrafast growth provides a new direction for the synthesis of large single-crystal graphene, and is also of great significance to realize large-scale production of graphene films (fast growth is more time-efficient and cost-effective), which is likely to accelerate various graphene applications in industry.

  18. The role of step edge diffusion in epitaxial crystal growth

    NARCIS (Netherlands)

    Schinzer, S.; Kinne, M.; Biehl, M.; Kinzel, W.


    The role of step edge diffusion (SED) in epitaxial growth is investigated. To this end we revisit and extend a recently introduced simple cubic solid-on-solid model, which exhibits the formation and coarsening of pyramid or mound-like structures. By comparing the limiting cases of absent, very fast

  19. Equipment and methods for rapid analysis of PWO full size scintillation crystals radiation hardness at mass production

    CERN Document Server

    Annenkov, A N; Drobychev, G Yu; Fedorov, A; Ivankin, P; Korzhik, M V; Lecoq, P; Ligun, V; Lopatik, A; Matveev, L; Missevitch, O V; Zouevski, R F; Peigneux, J P; Sigovski, A


    This year an extensive R&D on lead tungstate crystals has entered into the pre-production phase at the Bogoroditsk Techno-Chemical Plant (BTCP). Laboratory small-scale PWO crystal growth technology, which has been tuned and optimised over the last years, is transforming now into an industrial technology of mass production. This mass production technology is based on a set of methods and instrumentation for crystal growth, machining, crystal quality control and certification. According to the specification on lead tungstate pre-production crystals, one of the most important categories of tolerance is the radiation hardness. Control of the PWO radiation hardness at the pre-production phase requires reliability and an easy to use measuring tool with a high productivity. A semi- automatic spectrometric setup for PWO radiation hardness monitoring has been developed and tested at the X5 CERN irradiation facility. After final crosschecks the setup was set into operation at the BTCP. Together with several other m...

  20. Crystal growth and mechanical hardness of In{sub 2}Se{sub 2.7}Sb{sub 0.3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Piyush, E-mail:; Vyas, S. M., E-mail:; Patel, Vimal; Pavagadhi, Himanshu [Department of Physics, School of Science, Gujarat University, Ahmedabad, Gujarat, India-380009 (India); Solanki, Mitesh [panditdindayal Petroleum University, Gandhinagar. Gujarat (India); Jani, Maunik P. [BITS Edu Campus, Varnama, Vadodara, Gujarat (India)


    The III-VI compound semiconductors is important for the fabrication of ionizing radiation detectors, solid-state electrodes, and photosensitive heterostructures, solar cell and ionic batteries. In this paper, In{sub 2}Se{sub 2.7} Sb{sub 0.3} single crystals were grown by the Bridgman method with temperature gradient of 60 °C/cm and the growth velocity 0.5cm/hr. The as-grown crystals were examined under the optical microscope for surface study, a various growth features observed on top free surface of the single crystal which is predominant of layers growth mechanism. The lattice parameters of as-grown crystal was determined by the XRD analysis. A Vickers’ projection microscope were used for the study of microhardness on the as-cleaved, cold-worked and annealed samples of the crystals, the results were discussed, and reported in detail.

  1. Influence of controlling vibrations on heat transfer in floating zone crystal growth* (United States)

    Fedyushkin, A. I.

    The crystal growth processes of monocrystals are strongly vibrational sensitive systems and in particular it concerns to a floating zone method as presence of a free surface and two fronts of crystallization and melting that aggravate it The given work is devoted to numerical investigations of the influence of controlling vibrations on heat transfer during crystal growth by floating zone technique Normal and weightless environment conditions are considered Mathematical simulation is performed on the numerical solutions of basis unsteady Navier-Stokes equations for incompressible fluid flows and energy equation 2D axisymmetric geometry was used in model Marangoni convection and radiation condition on the curvature free surface were taken in account The calculations of the shape of a free surface of a liquid zone and influences on it of a corner of wetting force of weight and size of factor of a superficial tension are carried out The simulations of convective heat transfer for real curvature free surface of a liquid zone with and without the taking into account of the following factors parameters of radiation rotations natural and Marangoni convection and vibrations are carried out The given calculations are carried out for semiconductors melts with Prandtl number Pr 1 and for oxides Pr 1 The influence of vibrations of a crystal on melt flow and on the wide of dynamic and thermal boundary layers at melt-crystal interface is studied The action of vibrations on an enhancement of heat fluxes at the melt crystal interface is shown

  2. A numerical study of transient heat and mass transfer in crystal growth (United States)

    Han, Samuel Bang-Moo


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

  3. A niching genetic algorithm applied to optimize a SiC-bulk crystal growth system (United States)

    Su, Juan; Chen, Xuejiang; Li, Yuan; Pons, Michel; Blanquet, Elisabeth


    A niching genetic algorithm (NGA) was presented to optimize a SiC-bulk crystal growth system by PVT. The NGA based on clearing mechanism and its combination method with heat transfer model for SiC crystal growth were described in details. Then three inverse problems for optimization of growth system were carried out by NGA. Firstly, the radius of blind hole was optimized to decrease the radial temperature gradient along the substrate while the center temperature on the surface of substrate is fixed at 2500 K. Secondly, insulation materials with anisotropic thermal conductivities were selected to obtain much higher growth rate as 600, 800 and 1000 μm/h. Finally, the density of coils was also rearranged to minimize the temperature variation in the SiC powder. All the results were analyzed and discussed.

  4. Three-parameter distribution function fit to growth rate dispersion among small crystals (United States)

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


    This paper considers the advantages of using a three-parameter fit to both log-normal and gamma distributions rather than the two parameter fit normally used for the statistical treatment of growth rate dispersion among small crystals. It discusses the distribution functions, the procedure of searching for location parameters and the optimal number of bins for the best log-normal and gamma fits. As an example, the three-parameter fit is applied to results of the growth rate distributions of small paracetamol crystals. It is shown that the application of three-parameter distributions yields both a better fit to the experimental data than the two-parameter ones and the potential for a compound statistical treatment of growth, zero-growth and dissolution among small particles.

  5. Growth of Faceted Crystals in a Snow Cover, (United States)


    as 1.25 in. (3.18 cm). The growth of depth hoar as well as other fac- eted grains was observed in the laboratory by de Quervain (1958) where the...and Colleagues (1955), de Quervain (1963), Yen (1969), and Palm and Tveitereid (1979) have calculated the vapor movement associated with a temperature...ide Quervain 1954, Bader 1962). However, in a seasonal snow cover, where temperature gradients are imposed by nature, we observe that the destruction of

  6. CrystaL Growth and Mechanical Properties of Semiconductor Alloys. (United States)


    these approaches with the following specific studies: an attempt to grow thick films of GaPAs by isothermal vapor phase epitaxy (ISOVPE); Vickers...for understanding the complex plastic behavior in semiconductors. III. Growth of GaPAs epitaxial layers The isothermal vapor phase epitaxial (ISOVPE...films of GaPAs using a GaAs wafer as the substrate and polycrystalline GaP as the source. The experiment was performed at 6750 C for 70 hours. There was

  7. Synthesis, crystal growth and studies on non-linear optical property of new chalcones (United States)

    Sarojini, B. K.; Narayana, B.; Ashalatha, B. V.; Indira, J.; Lobo, K. G.


    The synthesis, crystal growth and non-linear optical (NLO) property of new chalcone derivatives are reported. 4-Propyloxy and 4-butoxy benzaldehydes were made to under go Claisen-Schmidt condensation with 4-methoxy, 4-nitro and 4-phenoxy acetophenones to form corresponding chalcones. The newly synthesized compounds were characterized by analytical and spectral data. The Second harmonic generation (SHG) efficiency of these compounds was measured by powder technique using Nd:YAG laser. Among tested compounds three chalcones showed NLO property. The chalcone 1-(4-methoxyphenyl)-3-(4-propyloxy phenyl)-2-propen-1-one exhibited SHG conversion efficiency 2.7 times that of urea. The bulk crystal of 1-(4-methoxyphenyl)-3-(4-butoxyphenyl)-2-propen-1-one (crystal size 65×28×15 mm 3) was grown by slow-evaporation technique from acetone. Microhardness of the crystal was tested by Vicker's microhardness method.

  8. Use of anomolous thermal imaging effects for multi-mode systems control during crystal growth (United States)

    Wargo, Michael J.


    Real time image processing techniques, combined with multitasking computational capabilities are used to establish thermal imaging as a multimode sensor for systems control during crystal growth. Whereas certain regions of the high temperature scene are presently unusable for quantitative determination of temperature, the anomalous information thus obtained is found to serve as a potentially low noise source of other important systems control output. Using this approach, the light emission/reflection characteristics of the crystal, meniscus and melt system are used to infer the crystal diameter and a linear regression algorithm is employed to determine the local diameter trend. This data is utilized as input for closed loop control of crystal shape. No performance penalty in thermal imaging speed is paid for this added functionality. Approach to secondary (diameter) sensor design and systems control structure is discussed. Preliminary experimental results are presented.

  9. The growth of multicomponent Sm, Lu, Ca, and Ge-substituted yig bulk crystals (United States)

    Nevšriva, M.; šSimšsová, J.; Pollert, E.; šCermák, J.


    Bulk garnet crystals of (Y, Sm, Lu, Ca) 3(Fe, Ge) 5 O 12 composition were grown from PbO-B 2O 3 based melts by an ACRT technique. The homogeneity of garnet composition along the growth axis was investigated as a function of the rotation regime. The solubility of individual melt components was studied and compared with the results obtained for the growth of epitaxial garnet films by LPE.

  10. Residual Gases in Crystal Growth Systems: Their Origin, Magnitude, and Dependence on the Processing Conditions (United States)

    Palosz, W.


    Residual gases present in closed ampoules may affect different crystal growth processes. Their presence may affect techniques requiring low pressures and affect the crystal quality in different ways. For that reason a good understanding and control of formation of residual gases may be important for an optimum design and meaningful interpretation of crystal growth experiments. Our extensive experimental and theoretical study includes degassing of silica glass and generation of gases from various 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.

  11. Crystal Growth of HgZnTe Alloy by Directional Solidification in Low Gravity Environment (United States)

    Su, Ching-Hua; Sha, Yi-Gao; Lehoczky, S. L.; Szofran, F. R.; Gillies, D. C.; Scripa, R. N.; Cobb, S. D.; Wang, J. C.


    An Hg(0.84)Zn(0.16)Te alloy crystal was back-melted and partially re-solidified during the first United States Microgravity Laboratory mission in the Marshall Space Flight Center's Crystal Growth Furnace. The experiment was inadvertently terminated at about 30% of planned completion. Nonetheless, it was successfully demonstrated that a HgZnTe alloy ingot partially grown and quenched on the ground can be back-melted and re-grown in space under nearly steady-state growth conditions. An identical "ground-truth" experiment was performed following the mission and a comparison between the properties of the crystals is described. The results indicate the importance of residual microgravity acceleration (less than or approx. equal to 0.4 micro-grams) even in the sub-microgravity range for the slow solidification velocities and large density gradients.

  12. Prediction of dislocation generation during Bridgman growth of GaAs crystals (United States)

    Tsai, C. T.; Yao, M. W.; Chait, Arnon


    Dislocation densities are generated in GaAs single crystals due to the excessive thermal stresses induced by temperature variations during growth. A viscoplastic material model for GaAs, which takes into account the movement and multiplication of dislocations in the plastic deformation, is developed according to Haasen's theory. The dislocation density is expressed as an internal state variable in this dynamic viscoplastic model. The deformation process is a nonlinear function of stress, strain rate, dislocation density and temperature. The dislocation density in the GaAs crystal during vertical Bridgman growth is calculated using a nonlinear finite element model. The dislocation multiplication in GaAs crystals for several temperature fields obtained from thermal modeling of both the GTE GaAs experimental data and artificially designed data are investigated.

  13. Growth and PhysioChemical Properties of Second-Order Nonlinear Optical L-Threonine Single Crystals

    Directory of Open Access Journals (Sweden)

    G. Ramesh Kumar


    Full Text Available The present aim of the paper is to grow and to study the various properties of L-threonine amino acid single crystal in various aspects. Crystal growth of L-threonine single crystals has been carried out with the help of crystallization kinetics. pH and deuteration effects on the properties of the grown crystals have been studied and the results presented in a lucid manner. The various second-order NLO parameters were evaluated using anharmonic oscillator model. Particle and ion irradiation effects on structural, optical, and surface properties of the crystals have also been studied in detail.

  14. Growth and study of barium oxalate single crystals in agar gel

    Indian Academy of Sciences (India)

    Keywords. Barium oxalate; agar gel; XRD; IR; TGA/DTA. Abstract. Barium oxalate was grown in agar gel at ambient temperature. The effect of various parameters like gel concentration, gel setting time and concentration of the reactants on the growth of these crystals was studied. Prismatic platy shaped spherulites and ...

  15. Automatic Stand Modeling of Casting Rate Influence on Solid Phase Growth of Round Ingot inside Crystallizer

    Directory of Open Access Journals (Sweden)

    A. N. Chichko


    Full Text Available The method of calculation and results of computer dynamics modeling of solid ingot skin in a crystallizer are presented in the paper. The paper shows influence of ingot drawing rate on dynamics of solid ingot skin growth in the continuous casting machine at steel grades used at Republic Unitary Enterprise «Belarussian Metallurgical Works» (BMZ.

  16. Cryomicroscopic determination of ice crystal growth in the system 2,4-pentanediol/water (United States)

    Mehl, Patrick M.


    The system 2,4-pentanediol/water is studied using differential scanning calorimetry and cryomicroscopy. The phase diagram at low temperatures is presented. Ice crystal growth rates are calculated from direct cryomicroscopic observations. These rates are found to be proportional to the ratio of the supercooling to the viscosity of the solution.

  17. Bridgman growth and defects of Nd : Sr3Ga2Ge4O14 laser crystals

    Indian Academy of Sciences (India)


    . ... Nd3+ : SGG crystal; Bridgman method; EPMA; inclusion; dislocation. ... A pair of Pt–. Pt/Rh thermocouples was installed in the tube to measure the temperature of the melt near the top of the seed. The. Bridgman growth was carried out in a ...

  18. Crystal growth, structure and magnetic properties of Sm 3 Ni 5 Al 19 ...

    Indian Academy of Sciences (India)

    Crystal growth, structure and magnetic properties of Sm3Ni5Al19: A compound in the Sm2n+mNi4n+mAl15n+4m homologous series. Udumula Subbarao Aloke Kumar Ghosh Sumanta Sarkar Sebastian C Peter. Special issue on Chemical Crystallography Volume 126 Issue 5 September 2014 pp 1605-1613 ...

  19. Identification of a macromolecular crystal growth inhibitor in human urine as osteopontin

    DEFF Research Database (Denmark)

    Sørensen, Steen; Justesen, S J; Johnsen, A H


    Macromolecules occurring in human urine inhibit the growth and/or aggregation of calcium oxalate crystals and may prevent the formation of kidney stones. Attention has focused particularly on proteins, as these seem to be most responsible for the inhibitory activity; three proteins, nephrocalcin...

  20. Effects of ionic inflow and organic matrix on crystal growth of octacalcium phosphate; relevant to tooth enamel formation (United States)

    Iijima, Mayumi; Moriwaki, Yutaka


    The mechanism of the lengthwise and oriented growth of enamel apatite crystals was studied on the basis of a hypothesis that (1) enamel crystals grow initially as octacalcium phosphate (OCP) as a precursor of apatite and (2) a one-directional Ca 2+ ion supply from the ameloblasts promotes the lengthwise and oriented growth of the crystals. To test this, OCP crystals were grown in a model system of enamel formation, where a cation selective membrane was used to control the Ca 2+ ion diffusion, at 37°C and at pH 6.3-7.4. The lengthwise and oriented growth of OCP was enhanced by the Ca influx from the membrane. H + ion enhanced while F -, Mg 2+ and CO 32- ions decreased the growth in the c-axis direction. F - induced an epitaxial overgrowth of apatite on the (1 0 0) of OCP, embedding an OCP lamella in the center of a crystal. When 5% polyacrylamide gel was attached to the membrane, OCP grew in long plate-like or ribbon-like crystals at pHs between 6.5 and 7.4. The length of these crystals was greater than that of those grown on the membrane without gel. The crystal size decreased with an increase in gel concentration from 5 to 20%. When a thin slice of tendon was used in place of the membrane, long OCP crystals grew along the collagen fibrils; these crystals were oriented with their axis of elongation perpendicular to the direction of ionic inflow. The size of crystals grown inside the collagenous matrix was much smaller than the size of crystals formed outside of the matrix and on the membrane. Thus, crystal growth was regulated by ionic diffusion and the matrix. When there were no constituents which regulated the growth direction, OCP crystals tended to grow along the direction of ionic inflow.

  1. The Growth and Properties of Lead-Free Ferroelectric Single Crystals

    Directory of Open Access Journals (Sweden)

    Xiaobing Li


    Full Text Available Much attention is drawn to the preparation, structure and properties investigation of lead-free ferroelectrics for the next generation of piezoelectric devices. (Na0.5Bi0.5TiO3-BaTiO3 (NBT-BT lead-free solid solution piezoelectric single crystals with composition x in the range of 0–0.05 as a materials with high piezoelectric properties were successfully grown from platinum crucible by using the top-seeded solution growth (TSSG method. The dimensions of NBT-BT crystal is Ø40 × 10 mm2. X-ray powder diffraction patterns reveal that the crystal structure of NBT-BT crystal changes from rhombohedral to tetragonal symmetry with increasing amounts of BT(x. The dielectric, ferroelectric and piezoelectric properties of NBT-BT crystals with different compositions near the morphotropic phase boundary (MPB were studied systematically. Ions (Mn, Eu, Zn doped NBT and NBT-BT 95/5 crystals were also grown and studied. In addition, their piezoelectric and ferroelectric properties are investigated. Further, a high-quality and large-sized (K0.25Na0.75NbO3 (KNN25/75 single crystal has been achieved by a carefully controlled TSSG method. The dimensions of the as-grown KNN25/75 single crystal reached up to Ø30 × 10 mm2. The obtained KNN crystals provided us a superb material for the dielectric, piezoelectric, ferroelectric and electromechanical coupling property characterization along different orientations.

  2. Rapid growth reduces cold resistance: evidence from latitudinal variation in growth rate, cold resistance and stress proteins. (United States)

    Stoks, Robby; De Block, Marjan


    Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. Larvae of the damselfly Ischnura elegans from two univoltine northern and two multivoltine southern populations were reared at three temperatures and after emergence given a cold shock. Cold resistance, measured by chill coma recovery times in the adult stage, was lower in the southern populations. The faster larval growth rates in the southern populations contributed to this latitudinal pattern in cold resistance. In accordance with their assumed role in cold resistance, Hsp70 levels were lower in the southern populations, and faster growing larvae had lower Hsp70 levels. Yet, individual variation in Hsp70 levels did not explain variation in cold resistance. WE PROVIDE EVIDENCE FOR A NOVEL COST OF RAPID GROWTH: reduced cold resistance. Our results indicate that the reduced cold resistance in southern populations of animals that change voltinism along the latitudinal gradient may not entirely be explained by thermal selection per se but also by the costs of time constraint-induced higher growth rates. This also illustrates that stressors imposed in the larval stage may carry over and shape fitness in the adult stage and highlights the importance of physiological costs in the evolution of life-histories at macro-scales.

  3. Rapid crystallization of a-Si:H films with various silicon-to-hydrogen bonding configurations using rapid energy transfer annealing

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y.-L. [Department of Electrical Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)]. E-mail:; Chang, Y.-C. [Department of Electrical Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)


    Hydrogenated amorphous silicon (a-Si:H) films were prepared by changing substrate temperature of plasma-enhanced chemical vapor deposition to induce different contents of monohydride and polyhydride bonds, which were then crystallized into polysilicon (poly-Si) films by rapid energy transfer annealing. Fourier transform infrared and transmission spectra show that the formation of numerous polyhydride bonds increases the hydrogen content and reduces the refractive index of a-Si:H films. The rise in the concentration of polyhydride bonds in as-deposited a-Si:H films can result in the increase of ultraviolet reflectance, small peak shift, and change in full width at half maximum of Raman scattering and X-ray diffraction peaks of the obtained poly-Si films after annealing. These results demonstrate that high-concentration polyhydride bonds can promote the rapid crystallization of a-Si:H and obtain high-crystallinity poly-Si films. Transmission electron microscopy identifies that the poly-Si films have the typical dendrite-like grain structure.

  4. Sono-crystallization kinetics of K2SO4: Estimation of nucleation, growth, breakage and agglomeration kinetics. (United States)

    Bari, Atul H; Chawla, Aseem; Pandit, Aniruddha B


    Application of ultrasound in crystallization has showed improved process characteristics. Although several attempts have been made in the past to study the sono-crystallization kinetics, only nucleation and crystal growth were considered, neglecting breakage and agglomeration of crystals. In this study, an attempt is made for the estimation of the kinetic parameters of all the phenomena occurring simultaneously during sono-crystallization. For this, both conventional and ultrasonic crystallization of K2SO4-water system has been reported. Sono-crystallization experiments were carried out using ultrasonic horn operating at 20 kHz frequency. Reduction in the induction time, reduction in metastable zone width (MSZW), narrowing of crystal size distribution (CSD) were the key observations of sono-crystallization experiments. Population balance equations (PBE) were used to model the crystallization system and the various kinetic parameters have been estimated. The kinetic parameters obtained for conventional crystallization and sonocrystallization were compared. The estimated parameters suggest an increase in nucleation and breakage rate during sono-crystallization. Growth rates were observed to be of the same order of magnitude for both conventional and sonocrystallization. While agglomeration during sono-crystallization was found to be negligible. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Ultrafast growth of single-crystal graphene assisted by a continuous oxygen supply (United States)

    Xu, Xiaozhi; Zhang, Zhihong; Qiu, Lu; Zhuang, Jianing; Zhang, Liang; Wang, Huan; Liao, Chongnan; Song, Huading; Qiao, Ruixi; Gao, Peng; Hu, Zonghai; Liao, Lei; Liao, Zhimin; Yu, Dapeng; Wang, Enge; Ding, Feng; Peng, Hailin; Liu, Kaihui


    Graphene has a range of unique physical properties and could be of use in the development of a variety of electronic, photonic and photovoltaic devices. For most applications, large-area high-quality graphene films are required and chemical vapour deposition (CVD) synthesis of graphene on copper surfaces has been of particular interest due to its simplicity and cost effectiveness. However, the rates of growth for graphene by CVD on copper are less than 0.4 μm s-1, and therefore the synthesis of large, single-crystal graphene domains takes at least a few hours. Here, we show that single-crystal graphene can be grown on copper foils with a growth rate of 60 μm s-1. Our high growth rate is achieved by placing the copper foil above an oxide substrate with a gap of ∼15 μm between them. The oxide substrate provides a continuous supply of oxygen to the surface of the copper catalyst during the CVD growth, which significantly lowers the energy barrier to the decomposition of the carbon feedstock and increases the growth rate. With this approach, we are able to grow single-crystal graphene domains with a lateral size of 0.3 mm in just 5 s.

  6. Distributions of crystals and gas bubbles in reservoir ice during winter growth period

    Directory of Open Access Journals (Sweden)

    Zhi-jun LI


    Full Text Available In order to understand the dominant factors of ice physical properties for ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were done, in the stages of fast ice growth and steady ice growth. These ice samples were used to observe ice crystals and gas bubbles in ice, and to measure ice density. Vertical profiles of the ice crystal type, ice crystal size, gas bubble shape and size, gas bubble content, as well as ice density were ontained. The results reveal that the upper part of the samples is granular ice and the lower part is columnar ice, the average grain size increases along ice depth and keeps steady within fast and steady ice growth stages; the shape of gas bubbles in ice upper layer is spherical with higher total content, and the shape in the middle and lower layers is cylinder with lower total content; the gas bubble size and content are active along with the ice growth stage; ice density decreases with the gas content increasing.

  7. Silicon impurity as a possible growth-regime indicator for LiNbO3 crystals

    Energy Technology Data Exchange (ETDEWEB)

    Erdei, S.; Szaller, Z.; Raksanyi, K.; Matok, G.


    The influence of Si concentration and temperature regimes on the visually observable properties of LiNbO3 single crystals grown by Czochralski method was studied. Si concentration measurements were carried out and minima in the radial and axial distribution curves have been established. An upper estimate is given for the equilibrium distribution coefficient of Si in LiNbO3. A direct correlation has been found between the degree of opacity and the Si concentration. The variation of the Grashof number during growth and a correlated modification of the structure of the concentration layer width, implying a position dependent fulfilment of the Hurle-Bardsley criterium for constitutional super cooling, accounts reasonably well with the visually observable properties of the opaque regions appearing in the course of crystal growth. The use of Si as an overall indicator for the characterization of growth regimes is discussed.

  8. Quantitative description of morphological transitions in diffusion-limited growth of xenon crystals (United States)

    Singer, H. M.; Bilgram, J. H.


    Changes of growth morphologies are induced by a perturbation of the temperature distribution in the surrounding of a growing xenon crystal. Apart from the dendritic morphology seaweed and doublon morphologies are found. We present a method which quantitatively describes growth morphologies by means of rotational, scale, and translational invariant transformations. Evolutions of growth morphologies are represented as paths in the morphology space. The presented method could be of some use for other fields of research where qualitative and quantitative information of different classes of images has to be identified.

  9. Single crystal growth of ZrW2O8 by hydrothermal route (United States)

    Xing, Qifeng; Xing, Xianran; Yu, Ranbo; Du, Ling; Meng, Jian; Luo, Jun; Wang, Dan; Liu, Guirong


    Single crystals of ZrW2O8 were prepared by the hydrothermal route followed by a heat treatment at 550 °C. XRD, FT-IR, TG-DTA, TEM and SEM were employed to characterize the precursor ZrW2O7(OH)2(H2O)2 and the final product ZrW2O8. The precursor ZrW2O7(OH)2(H2O)2 critically influenced the crystal size of ZrW2O8. The growth of ZrW2O7(OH)2(H2O)2 crystals was restrained with increasing acidity. The addition of ZrW2O8 seeds facilitates and accelerates the nucleation of ZrW2O7(OH)2(H2O)2 crystals. XRD patterns and TEM images showed that ZrW2O7(OH)2(H2O)2 crystals grew under hydrothermal conditions along [2 0 0] and [3 1 0] directions. The pure phase of ZrW2O8 crystals could be obtained by hydrothermal route at the lowest sintering temperature of 300 °C.

  10. About Small Streams and Shiny Rocks: Macromolecular Crystal Growth in Microfluidics (United States)

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


    We are developing a novel technique with which we have grown diffraction quality protein crystals in very small volumes, utilizing chip-based, microfluidic ("LabChip") technology. With this technology volumes smaller than achievable with any laboratory pipette can be dispensed with high accuracy. We have performed a feasibility study in which we crystallized several proteins with the aid of a LabChip device. The protein crystals are of excellent quality as shown by X-ray diffraction. The advantages of this new technology include improved accuracy of dispensing for small volumes, complete mixing of solution constituents without bubble formation, highly repeatable recipe and growth condition replication, and easy automation of the method. We have designed a first LabChip device specifically for protein crystallization in batch mode and can reliably dispense and mix from a range of solution constituents. We are currently testing this design. Upon completion additional crystallization techniques, such as vapor diffusion and liquid-liquid diffusion will be accommodated. Macromolecular crystallization using microfluidic technology is envisioned as a fully automated system, which will use the 'tele-science' concept of remote operation and will be developed into a research facility aboard the International Space Station.

  11. Halogen-free vapor phase epitaxy for high-rate growth of GaN bulk crystals (United States)

    Nakamura, Daisuke; Kimura, Taishi; Horibuchi, Kayo


    Here, we propose a halogen-free vapor phase epitaxy (HF-VPE) technique to grow bulk GaN single crystals. This technique employs the simplest reaction for GaN synthesis (reaction of Ga vapor with NH3) and can potentially achieve a high growth rate, a prolonged growth duration, a high crystal quality, and a low cost. The analyses of thick HF-VPE-GaN layers grown under optimized growth conditions revealed that high-quality crystals, both in terms of dislocation density and impurity concentration, are obtained at high growth rates of over 100 µm/h.

  12. Homoepitaxial growth of GaN crystals by Na-flux dipping method (United States)

    Sato, Taro; Nakamura, Koshi; Imanishi, Masayuki; Murakami, Kosuke; Imabayashi, Hiroki; Takazawa, Hideo; Todoroki, Yuma; Matsuo, Daisuke; Imade, Mamoru; Maruyama, Mihoko; Yoshimura, Masashi; Mori, Yusuke


    The realization of low-dislocation-density bulk GaN crystals is necessary for use in the fabrication of future high-power devices with low power consumption. In this study, we attempted the regrowth of low-dislocation-density (104-105 cm-2) GaN substrates to fabricate thick and low-dislocation-density GaN crystals using the dipping technique with the Na-flux method. In the growth using this dipping technique, the generation of dislocations at the interface between the GaN substrate and the regrowth layer was prevented, and we succeeded in fabricating thick and low-dislocation-density GaN crystals. In the growth without the dipping technique, the surface of the GaN substrate demonstrated meltback immediately before the growth, and dislocations were newly generated. These results indicate that the Na-flux dipping technique has potential use for the fabrication of low-dislocation-density bulk GaN crystals.

  13. Growth and characterization of CdTe single crystals for radiation detectors

    CERN Document Server

    Funaki, M; Satoh, K; Ohno, R


    To improve the productivity of CdTe radiation detectors, the crystal growth by traveling heater method (THM) as well as the quality of the fabricated detectors were investigated. In the THM growth, optimization of the solvent volume was found to be essential because it affects the shape of the growth interface. The use of the slightly tilted seed from B was also effective to limit the generation of twins having different directions. Single-crystal (1 1 1) wafers, larger than 30x30 mm sup 2 were successfully obtained from a grown crystal of 50 mm diameter. Pt/CdTe/Pt detectors of dimensions 4x4x2 mm sup 3 , fabricated from the whole crystal ingot, showed an energy resolution (FWHM of 122 keV peak from a sup 5 sup 7 Co source) between 6% and 8%. Similarly, Pt/CdTe/In detectors of dimensions 2x2x0.5 mm sup 3 showed a resolution better than 3%. These characteristics encourage the practical applications of various types of CdTe detectors.

  14. Crystal growth, resistivity and Hall effect of the delafossite metal PtCoO$_2$


    Kushwaha, Pallavi; Moll, Philip J.W.; Nandi, Nabhanila; Mackenzie, Andrew P.


    We report single crystal growth of the delafossite oxide PtCoO$_2$, and basic transport measurements on single crystals etched to well-defined geometries using focused ion beam techniques. The room temperature resistivity is 2.1 $\\mu\\Omega$ cm, and the Hall coefficient is consistent with the existence of one free electron per Pt. Although the residual resistivity ratio is greater than fifty, a slight upturn of resistivity is seen below 15 K. The angle dependence of the in-plane magnetoresista...

  15. Directory of crystal growth and solid state materials production and research

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, T.F.; Battle, G.C.; Keesee, A.M. (comps.)


    This directory lists only those who returned questionnaires distributed by the Research Materials Information Center during 1978. The directory includes, in addition to crystal growers, those preparing starting materials for crystal growth and ultrapure noncrystalline research specimens. It also includes responses from those characterizing, or otherwise studying, the properties of materials provided by others. The international coverage of the directory is limited to the United States, Argentina, Australia, Bulgaria, Canada, Czechoslovakia, Egypt, Finland, East Germany, Hungary, India, Israel, Japan, Mexico, Poland, Romania, South Africa, Taiwan, Yugoslavia, and Zaire.

  16. Crystal Growth of Thiol-Stabilized Gold Nanoparticles by Heat-Induced Coalescence

    Directory of Open Access Journals (Sweden)

    Moon SookYoung


    Full Text Available Abstract A monolayer of dodecanethiol-stabilized gold nanoparticles changed into two-dimensional and three-dimensional self-organized structures by annealing at 323 K. Subsequent crystal growth of gold nanoparticles occurred. Thiol molecules, although chemisorbed, form relatively unstable bonds with the gold surface; a few thiols desorbed from the surface and oxidized to disulfides at 323 K, because the interaction energy between thiol macromolecules is larger than that between a thiol and a nanoparticle. The gold nanoparticles approached each other and grew into large single or twinned crystals because of the van der Waals attraction and the heat generated by the exothermic formation of disulfides.

  17. Nonclassical crystallization in vivo et in vitro (II): Nanogranular features in biomimetic minerals disclose a general colloid-mediated crystal growth mechanism. (United States)

    Rodríguez-Navarro, Carlos; Ruiz-Agudo, Encarnación; Harris, Joe; Wolf, Stephan E


    Recent research has shown that biominerals and their biomimetics (i) typically form via an amorphous precursor phase, and (ii) commonly display a nanogranular texture. Apparently, these two key features are closely related, underlining the fact that the formation of biominerals and their biomimetics does not necessarily follow classical crystallization routes, and leaves a characteristic nanotextural imprint which may help to disclose their origins and formation mechanisms. Here we present a general overview of the current theories and models of nonclassical crystallization and their applicability for the advance of our current understanding of biomineralization and biomimetic mineralization. We pay particular attention to the link between nonclassical crystallization routes and the resulting nanogranular textures of biomimetic CaCO 3 mineral structures. After a general introductory section, we present an overview of classical nucleation and crystal growth theories and their limitations. Then, we introduce the Ostwald's step rule as a general framework to explain nonclassical crystallization. Subsequently, we describe nonclassical crystallization routes involving stable prenucleation clusters, dense liquid and solid amorphous precursor phases, as well as current nonclassical crystal growth models. The latter include oriented attachment, mesocrystallization and the new model based on the colloidal growth of crystals via attachment of amorphous nanoparticles. Biomimetic examples of nanostructured CaCO 3 minerals formed via these nonclassical routes are presented which help us to show that colloid-mediated crystal growth can be regarded as a wide-spread growth mechanism. Implications of these observations for the advance in the current understanding on the formation of biomimetic materials and biominerals are finally outlined. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Sang-gil; Kim, Eunpa; Grigoropoulos, Costas P., E-mail: [Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Allen, Frances I.; Minor, Andrew M. [Department of Materials Science and Engineering, University of California, Berkeley, California 94720-1740 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hwang, David J. [Department of Mechanical Engineering, Stony Brook University, Stony Brook, New York 11794 (United States)


    We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ∼10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystal growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.

  19. Segregation of Ge in B and Ge codoped Czochralski-Si crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Arivanandhan, Mukannan, E-mail: [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Gotoh, Raira; Fujiwara, Kozo; Uda, Satoshi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Hayakawa, Yasuhiro [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan)


    Highlights: • Effective segregation of Ge in B and Ge codoped Czochralski-Si crystal growth was analyzed. • The equilibrium segregation coefficient of Ge was calculated. • The experimentally results were analytically analyzed using partitioning theory. - Abstract: The segregation of Ge in B and Ge codoped Czochralski (CZ)-Si crystal growth was investigated. The concentration of Ge in heavily Ge codoped CZ-Si was measured by electron probe micro analysis (EPMA) and X-ray fluorescence spectroscopy. The effective segregation coefficient of Ge (k{sub eff}) was calculated by fitting the EPMA data to the normal freezing equation, and by taking the logarithmic ratio of the Ge concentrations at the seed and tail of the ingots (top to bottom approach). The k{sub eff} of Ge increased from 0.30 to 0.55, when the initial Ge concentration in the Si melt (C{sub L(o)}{sup Ge}) was increased from 3 × 10{sup 19} to 3 × 10{sup 21} cm{sup −3}. To avoid cellular growth, the crystal pulling rate was decreased for heavily Ge codoped crystal growth (C{sub L(o)}{sup Ge} > 3 × 10{sup 20} cm{sup −3}). The equilibrium segregation coefficient (k{sub 0}) of Ge was calculated by partitioning theory, and was smaller than the experimentally estimated k{sub eff}. The variation of k{sub eff} from k{sub 0} was discussed based on Ge clustering in the heavily Ge codoped crystal, which led to changes in the bonding and strain energies caused by the incorporation of Ge into Si.

  20. Peptides of Matrix Gla protein inhibit nucleation and growth of hydroxyapatite and calcium oxalate monohydrate crystals.

    Directory of Open Access Journals (Sweden)

    Maria Goiko

    Full Text Available Matrix Gla protein (MGP is a phosphorylated and γ-carboxylated protein that has been shown to prevent the deposition of hydroxyapatite crystals in the walls of blood vessels. MGP is also expressed in kidney and may inhibit the formation of kidney stones, which mainly consist of another crystalline phase, calcium oxalate monohydrate. To determine the mechanism by which MGP prevents soft-tissue calcification, we have synthesized peptides corresponding to the phosphorylated and γ-carboxylated sequences of human MGP in both post-translationally modified and non-modified forms. The effects of these peptides on hydroxyapatite formation and calcium oxalate crystallization were quantified using dynamic light scattering and scanning electron microscopy, respectively. Peptides YGlapS (MGP1-14: YγEpSHEpSMEpSYELNP, YEpS (YEpSHEpSMEpSYELNP, YGlaS (YγESHESMESYELNP and SK-Gla (MGP43-56: SKPVHγELNRγEACDD inhibited formation of hydroxyapatite in order of potency YGlapS > YEpS > YGlaS > SK-Gla. The effects of YGlapS, YEpS and YGlaS on hydroxyapatite formation were on both crystal nucleation and growth; the effect of SK-Gla was on nucleation. YGlapS and YEpS significantly inhibited the growth of calcium oxalate monohydrate crystals, while simultaneously promoting the formation of calcium oxalate dihydrate. The effects of these phosphopeptides on calcium oxalate monohydrate formation were on growth of crystals rather than nucleation. We have shown that the use of dynamic light scattering allows inhibitors of hydroxyapatite nucleation and growth to be distinguished. We have also demonstrated for the first time that MGP peptides inhibit the formation of calcium oxalate monohydrate. Based on the latter finding, we propose that MGP function not only to prevent blood-vessel calcification but also to inhibit stone formation in kidney.

  1. The rapid analysis of fungal growth in the presence of inhibitory effects


    Williams, Tyson


    For fungal contamination of foodstuffs, there are no fast, reliable, automated techniques to examine growth, nor have any predictive models been developed to describe the growth in the same way as for bacteria. Traditional plating methods can take 3 to 7 days to get adequate results depending on the fungal species utilised and well over a month for challenge testing, an unacceptable delay especially for the food industry. In this study two rapid analysis techniques were investi...

  2. Demonstrated rapid growth of a corpus callosum cavernous angioma within a short period of time. (United States)

    Ozer, E; Yücesoy, K; Kalemci, O


    Cavernous angiomas are uncommon central nervous system vascular malformations. They occur in the corpus callosum very rarely. In this study we report a case of corpus callosum cavernous angioma which demonstrated rapid growth within a short period of time. Corpus callosum cavernous angiomas have distinct features regarding growth and should be treated more carefully by giving more importance to surgical removal rather than a conservative approach.

  3. Crystal Growth, Characterization and Fabrication of Cadmium Zinc Telluride-based Nuclear Detectors (United States)

    Krishna, Ramesh M.

    In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials such as uranium and plutonium. One of the most promising semiconductor materials being considered to create a convenient, field-deployable nuclear detector is cadmium zinc telluride (CdZnTe, or CZT). CZT is a ternary semiconductor compound which can detect high-energy gamma-rays at room temperature. It offers high resistivity (≥ 1010 O-cm), a high band gap (1.55 eV), and good electron transport properties, all of which are required for a nuclear radiation detector. However, one significant issue with CZT is that there is considerable difficulty in growing large, homogeneous, defect-free single crystals of CZT. This significantly increases the cost of producing CZT detectors, making CZT less than ideal for mass-production. Furthermore, CZT suffers from poor hole transport properties, which creates significant problems when using it as a high-energy gamma-ray detector. In this dissertation, a comprehensive investigation is undertaken using a successful growth method for CZT developed at the University of South Carolina. This method, called the solvent-growth technique, reduces the complexity required to grow detector-grade CZT single crystals. It utilizes a lower growth temperature than traditional growth methods by using Te as a solvent, while maintaining the advantages of

  4. Effect of Mannitol on Nucleation and Crystal Growth of Amorphous Flavonoids: Implications on the Formation of Nanocrystalline Solid Dispersion. (United States)

    Shete, Ganesh; Modi, Sameer R; Bansal, Arvind Kumar


    In this work, we studied crystallization kinetics of amorphous hesperetin (HRN) and naringenin (NRN) alone, and in 1:1 proportion with mannitol at Tg + 15 K. Crystallization rate of NRN was found to be significantly higher than HRN. Mannitol accelerated crystallization of HRN as well as NRN. NRN exhibited higher crystallization rate than HRN, in presence of mannitol, as well. Finke-Watzky model was used to deconvolute the crystallization kinetics data into nucleation and crystal growth rate constant. HRN alone had 9.56 × 10(9) times faster nucleation rate and 1.88 times slower crystal growth than NRN alone. Mannitol increased nucleation and crystal growth rate of HRN as well as NRN. In presence of mannitol, HRN possessed 1.34 × 10(10) times faster nucleation rate and 1.70 times slower crystal growth rate than NRN. Differences in crystallization behavior of HRN and NRN were explained by their thermodynamic properties. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  5. Synthesis and single crystal growth of perovskite semiconductor CsPbBr3 (United States)

    Zhang, Mingzhi; Zheng, Zhiping; Fu, Qiuyun; Chen, Zheng; He, Jianle; Zhang, Sen; Chen, Cheng; Luo, Wei


    As a typical representative of all-inorganic lead halide perovskites, cesium lead bromine (CsPbBr3) has attracted significant attention in recent years. The direct band gap semiconductor CsPbBr3 has a wide band gap of 2.25 eV and high average atomic number (Cs: 55, Pb: 82 and Br: 35), which meet most of the requirements for detection of X- and γ-ray radiation, such as high attenuation, high resistivity, and significant photoconductivity response. However, the growth of large volume CsPbBr3 single crystals remains a challenge. In this paper, the synthesis of CsPbBr3 polycrystalline powders by a chemical co-precipitation method was investigated and the optimum synthesis conditions were obtained. A large CsPbBr3 single crystal of 8 mm diameter and 60 mm length was obtained by a creative electronic dynamic gradient (EDG) method. X-ray diffraction (XRD) patterns and X-ray rocking curve showed that the CsPbBr3 crystal preferentially oriented in the (1 1 0) direction and had a low dislocation density and small residual stress in the crystal. The IR and UV-Vis transmittance and temperature-dependent photoluminescence (PL) spectra showed the crystal had a good basic optical performance. The almost linear current-voltage (I-V) curves implied good ohmic contact between the electrodes and crystal surfaces. The resistivity of the crystal was calculated 109-1010 Ω cm. The above results showed that the quality of the obtained crystal had met the demand of optoelectronic applications.

  6. On the origin of surface imposed anisotropic growth of salicylic and acetylsalicylic acids crystals during droplet evaporation. (United States)

    Przybyłek, Maciej; Cysewski, Piotr; Pawelec, Maciej; Ziółkowska, Dorota; Kobierski, Mirosław


    In this paper droplet evaporative crystallization of salicylic acid (SA) and acetylsalicylic acid (ASA) crystals on different surfaces, such as glass, polyvinyl alcohol (PVA), and paraffin was studied. The obtained crystals were analyzed using powder X-ray diffraction (PXRD) technique. In order to better understand the effect of the surface on evaporative crystallization, crystals deposited on glass were scraped off. Moreover, evaporative crystallization of a large volume of solution was performed. As we found, paraffin which is non-polar surface promotes formation of crystals morphologically similar to those obtained via bulk evaporative crystallization. On the other hand, when crystallization is carried out on the polar surfaces (glass and PVA), there is a significant orientation effect. This phenomenon is manifested by the reduction of the number of peaks in PXRD spectrum recorded for deposited on the surface crystals. Noteworthy, reduction of PXRD signals is not observed for powder samples obtained after scraping crystals off the glass. In order to explain the mechanism of carboxylic crystals growth on the polar surfaces, quantum-chemical computations were performed. It has been found that crystal faces of the strongest orientation effect can be characterized by the highest surface densities of intermolecular interactions energy (IIE). In case of SA and ASA crystals formed on the polar surfaces the most dominant faces are characterized by the highest adhesive and cohesive properties. This suggests that the selection rules of the orientation effect comes directly from surface IIE densities.

  7. Growth kinetics and motion of thaumatin crystals during USML-2 and LMS microgravity missions and comparison with earth controls (United States)

    Lorber, B.; Ng, J. D.; Lautenschlager, P.; Giegé, R.


    As part of a study of the effects of microgravity on protein crystallization, the growth of tetragonal crystals of thaumatin was monitored by CCD-time-lapse video in environments where convection is negligible. In Space Shuttle missions entitled United States Microgravity Laboratory-2 and Life and Microgravity Sciences, free interface diffusion and dialysis techniques were utilized to grow crystals in the advanced protein crystallization facility (APCF). Ng et al. (Acta Crystallogr. D 53 (1997) 724) have shown that the crystals recovered in these experiments are of superior crystallographic quality (at the level of their diffraction intensity, resolution, and mosaicity) with regard to earth controls. Here, the number of crystals, their size, growth rate, and protein solubility in microgravity were compared with data of dialysis experiments performed in parallel on earth. Image analysis shows that in microgravity about one-quarter to half of the crystals have nucleated and grown in the bulk of the solution, the remaining being attached to the walls of crystallization vessels. The growth of free-floating crystals was 2.5 times faster, has resulted in 15-fold larger crystals, and consumed more protein than that of attached crystals in earth controls. Distances between immobile free-floating crystals in microgravity were related to the size of the latter. Experimental results are in favor of a correlation between more favorable growth parameters in microgravity and better diffraction properties. The displacements of free-floating crystals at various velocities and in various directions on unrelated trajectories are indicative of drift and stirring motion. On the basis of an overview of reactors monitored on four APCF missions some forces causing motion are proposed. Advantages of crystallization in microgravity are discussed and recommendations for future experiments given.

  8. Chemical vapor deposition growth of large grapheme single crystal from ethanol (United States)

    Chen, Xiao; Zhao, Pei; Chiashi, Shohei; Maruyama, Shigeo


    Ethanol as a precursor has proven effective in the chemical vapor deposition (CVD) synthesis of graphene on both Ni foils and Cu capsule substrates. For applications of graphene in field effect transistors or as transparent conducting electrodes, larger singe-crystal graphene without any grain boundaries shows superior electrical performance and has attracted enormous interests. Here we report a protocol to synthesize large graphene single crystals (up to 600 μm) using ethanol as precursor on commercially-available polycrystalline Cu foils. We explored the mechanism by studying the influences of different growth parameters such as pressure, flow rate and temperature. Low partial pressure and low flow rate of ethanol is essential in achieving low nucleation density over the metal surface and therefore large graphene grains can be obtained. We found that growth temperature dramatically affects the crystallinity and the growth rate of graphene grains. Moreover, this CVD growth of large graphene single crystals involves no electro-polishing or annealing treatments to the metal surface, presenting a significant simplification to the current graphene synthesis process.

  9. Dynamic light scattering study of inhibition of nucleation and growth of hydroxyapatite crystals by osteopontin.

    Directory of Open Access Journals (Sweden)

    John R de Bruyn

    Full Text Available We study the effect of isoforms of osteopontin (OPN on the nucleation and growth of crystals from a supersaturated solution of calcium and phosphate ions. Dynamic light scattering is used to monitor the size of the precipitating particles and to provide information about their concentration. At the ion concentrations studied, immediate precipitation was observed in control experiments with no osteopontin in the solution, and the size of the precipitating particles increased steadily with time. The precipitate was identified as hydroxyapatite by X-ray diffraction. Addition of native osteopontin (nOPN extracted from rat bone caused a delay in the onset of precipitation and reduced the number of particles that formed, but the few particles that did form grew to a larger size than in the absence of the protein. Recombinant osteopontin (rOPN, which lacks phosphorylation, caused no delay in initial calcium phosphate precipitation but severely slowed crystal growth, suggesting that rOPN inhibits growth but not nucleation. rOPN treated with protein kinase CK2 to phosphorylate the molecule (p-rOPN produced an effect similar to that of nOPN, but at higher protein concentrations and to a lesser extent. These results suggest that phosphorylations are critical to OPN's ability to inhibit nucleation, whereas the growth of the hydroxyapatite crystals is effectively controlled by the highly acidic OPN polypeptide. This work also demonstrates that dynamic light scattering can be a powerful tool for delineating the mechanism of protein modulation of mineral formation.

  10. Distributions of crystals and gas bubbles in reservoir ice during growth period

    Directory of Open Access Journals (Sweden)

    Zhi-jun Li


    Full Text Available In order to understand the dominant factors of the physical properties of ice in ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were conducted in the fast and steady ice growth stages. Ice pieces were used to observe ice crystals and gas bubbles in ice, and to measure the ice density. Vertical profiles of the type and size of ice crystals, shape and size of gas bubbles, and gas bubble content, as well as the ice density, were obtained. The results show that the upper layer of the ice pieces is granular ice and the lower layer is columnar ice; the average crystal size increases with the ice depth and remains steady in the fast and steady ice growth stages; the shape of gas bubbles in the upper layer of ice pieces is spherical with higher total content, and the shape in the middle and lower layers is cylinder with lower total content; the gas bubble size and content vary with the ice growth stage; and the ice density decreases with the increase of the gas bubble content.

  11. Growth morphology of tetragonal ABCO 4 compounds: theory and observations on Czochralski grown crystals (United States)

    Woensdregt, C. F.; Janssen, H. W. M.; Gloubokov, A.; Pajaczkowska, A.


    Tetragonal ABCO 4 compounds, where A  Sr, Ca, B  rare earth elements and C  Ga or Al, are potential substrate candidates for high-frequency superconducting films. The Hartman-Perdok theory (HPT) explains the relation between crystal structure and morphology and provides the atomic surface topology of the crystalline interface. Theoretical growth forms can be constructed from computed attachment energies, Ehkla, which is assumed to be directly proportional to the growth rate for F faces. HPT has been applied to CaYAlO 4 as a model for all ABCO 4 compounds with a K 2NiF 4 crystal structure. F forms are {002}, {101}, {103}, {110}, {112}. {200}, {211} and {213}. The theoretical growth form is planar following {001} with {101} and {110} as lateral forms. At lower effective charges on oxygen, qO, the growth forms are still tabular, but the order of importance of lateral forms changes as function of qO. When the ions on the slice boundaries are ordered, {110} will be absent for the model with the formal charges and replaced by {112} in the case of models with less negative oxygen charges. As-grown crystals show often inhomogeneities in color parallel to the {110} interface. This can be explained by the surface topology of {110}.

  12. Crystal structures, anisotropic growth, and optical properties: controlled synthesis of lanthanide orthophosphate one-dimensional nanomaterials. (United States)

    Yan, Ruoxue; Sun, Xiaoming; Wang, Xun; Peng, Qing; Li, Yadong


    The fundamental understanding of the relationship between crystal structure and the dynamic processes of anisotropic growth on the nanoscale, and exploration of the key factors governing the evolution of physical properties in functional nanomaterials, have become two of the most urgent and challenging issues in the fabrication and exploitation of functional nanomaterials with designed properties and the development of nanoscale devices. Herein, we show how structural and kinetic factors govern the tendency for anisotropic growth of such materials under hydrothermal conditions, and how the crystal structure and morphology influence the optical properties of Ln3+-doped nanocrystals. The synthesis of phase-pure and single-crystalline monoclinic, hexagonal, and tetragonal one-dimensional LnPO4 nanostructures of different aspect ratios by means of kinetically controlled hydrothermal growth processes is demonstrated. It is shown that the tendency for anisotropic growth under hydrothermal conditions can be enhanced simply by modifying the chemical potentials of species in the reaction solution through the use of carefully selected chelating ligands. A systematic study of the photoluminescence of various Eu3+-doped lanthanide phosphates has revealed that the optical properties of these nanophosphors are strongly dependent on their crystal structures and morphologies.

  13. Measurement of Microscopic Growth Rates in Float-Zone Silicon Crystals (United States)

    Dold, P.; Schweizer, M.; Benz, K. W.; Rose, M. Franklin (Technical Monitor)


    Time dependent convective flows during crystal growth of doped semiconductors lead to fluctuations of the composition, so called dopant striations. In general, it is difficult to decide which is the main mechanism for the generation of these striations, it might be either the fluctuation of the concentration field in the melt and the extent of the solute boundary layer ahead of the solid-liquid interface or a variation of the growth velocity. Direct access to the concentration field is rather complicated to achieve, especially considering the high process temperature and the chemical activity of liquid silicon. The contribution of growth rate fluctuations to the formation of compositional fluctuations can be determined by measuring microscopic growth rates. The classical method of current pulses requires electrical feed-throughs and good electrical contacts, both are critical issues for the growth of high purity silicon crystals. Using a radiation based heating system, the heating power can be modulated very fast and effectively. We added to the normal heater power a sinusoidal off-set in the frequency range of 1 to 10 Hz, generating a narrow spaced weak rippling in the grown crystals which are superposed to the dopant striations caused by natural and by thermocapillary convection. The pulling speed was varied between 1 and 4mm/min. The microscope images of etched crystals slices have been analyzed by peak-search algorithms (measuring the spacing between each artificially induced marker) and by FFT. Performing growth experiments under a time-dependent flow regime, fluctuations of the microscopic growth velocity of Delta(v)/v(sub average) up to 50% have been measured. Damping the time-dependent convection by the use of an axial, static magnetic field of 500mT, the microscopic growth rate became constant within the resolution limit of this method. The results will be discussed using analytical methods for the calculation of microscopic growth velocity and by

  14. Spiral and target patterns in bivalve nacre manifest a natural excitable medium from layer growth of a biological liquid crystal. (United States)

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


    Nacre is an exquisitely structured biocomposite of the calcium carbonate mineral aragonite with small amounts of proteins and the polysaccharide chitin. For many years, it has been the subject of research, not just because of its beauty, but also to discover how nature can produce such a superior product with excellent mechanical properties from such relatively weak raw materials. Four decades ago, Wada [Wada K (1966) Spiral growth of nacre. Nature 211:1427] proposed that the spiral patterns in nacre could be explained by using the theory Frank [Frank F (1949) The influence of dislocations on crystal growth. Discuss Faraday Soc 5:48-54] had put forward of the growth of crystals by means of screw dislocations. Frank's mechanism of crystal growth has been amply confirmed by experimental observations of screw dislocations in crystals, but it is a growth mechanism for a single crystal, with growth fronts of molecules. However, the growth fronts composed of many tablets of crystalline aragonite visible in micrographs of nacre are not a molecular-scale but a mesoscale phenomenon, so it has not been evident how the Frank mechanism might be of relevance. Here, we demonstrate that nacre growth is organized around a liquid-crystal core of chitin crystallites, a skeleton that the other components of nacre subsequently flesh out in a process of hierarchical self-assembly. We establish that spiral and target patterns can arise in a liquid crystal formed layer by layer through the Burton-Cabrera-Frank [Burton W, Cabrera N, Frank F (1951) The growth of crystals and the equilibrium structure of their surfaces. Philos Trans R Soc London Ser A 243:299-358] dynamics, and furthermore that this layer growth mechanism is an instance of an important class of physical systems termed excitable media. Artificial liquid crystals grown in this way may have many technological applications.

  15. Rapid yet accurate first principle based predictions of alkali halide crystal phases using alchemical perturbation

    CERN Document Server

    Solovyeva, Alisa


    We assess the predictive power of alchemical perturbations for estimating fundamental properties in ionic crystals. Using density functional theory we have calculated formation energies, lattice constants, and bulk moduli for all sixteen iso-valence-electronic combinations of pure pristine alkali halides involving elements $A \\in \\{$Na, K, Rb, Cs$\\}$ and $X \\in \\{$F, Cl, Br, I$\\}$. For rock salt, zincblende and cesium chloride symmetry, alchemical Hellmann-Feynman derivatives, evaluated along lattice scans of sixteen reference crystals, have been obtained for all respective 16$\\times$15 combinations of reference and predicted target crystals. Mean absolute errors (MAE) are on par with density functional theory level of accuracy for energies and bulk modulus. Predicted lattice constants are less accurate. NaCl is the best reference salt for alchemical estimates of relative energies (MAE $<$ 40 meV/atom) while alkali fluorides are the worst. By contrast, lattice constants are predicted best using NaF as a re...

  16. Governing Rapid Growth in Asia: State-led Development in Historical Perspective

    NARCIS (Netherlands)

    T-W. Ngo (Tak-Wing)


    textabstractRapid growth in Asia has often been explained in terms of effective policies pursued by a “developmental state”. In particular, countries in East Asia are said to be characterized by the presence of a strong state with technocratic capacity and social embeddedness. This inaugural address

  17. Nitric Acid and Benomyl Stimulate Rapid Height Growth of Longleaf Pine (United States)

    A.G. Kais; R.C. Hare; J.P. Barnett


    Rapid height growth of longleaf pine seedlings, important to production of uniform, even-aged stands, can be promoted by controlling brown-spot needle blight and weed competition, and by increasing soil fertility. Root systems of container-grown longleaf pine seedlings were dip-treated in either benomyl/clay mix (10 percent a.i. benomyl) or clay control and planted...

  18. A comparison of test statistics for the recovery of rapid growth-based enumeration tests

    NARCIS (Netherlands)

    van den Heuvel, Edwin R.; IJzerman-Boon, Pieta C.

    This paper considers five test statistics for comparing the recovery of a rapid growth-based enumeration test with respect to the compendial microbiological method using a specific nonserial dilution experiment. The finite sample distributions of these test statistics are unknown, because they are

  19. Social Disruption and Rapid Community Growth: An Explication of the "Boom-Town" Hypotheses. (United States)

    Thompson, James G.; And Others

    Recent case studies of social effects of rapid community growth associated with energy development in the western states have relied primarily on qualitative data with limited use of agency records, population surveys, and other secondary sources. While providing the first essential step in the orderly development of a scientific approach to…

  20. Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal (United States)

    Shan, Pai; Sun, Tongqing; Chen, Hong; Liu, Hongde; Chen, Shaolin; Liu, Xuanwen; Kong, Yongfa; Xu, Jingjun


    Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4. PMID:27126353

  1. Nucleation and crystal growth behavior of nepheline in simulated high-level waste glasses

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Amoroso, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Mcclane, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)


    The Savannah River National Laboratory (SRNL) has been tasked with supporting glass formulation development and process control strategies in key technical areas, relevant to the Department of Energy’s Office of River Protection (DOE-ORP) and related to high-level waste (HLW) vitrification at the Waste Treatment and Immobilization Plant (WTP). Of specific interest is the development of predictive models for crystallization of nepheline (NaAlSiO4) in HLW glasses formulated at high alumina concentrations. This report summarizes recent progress by researchers at SRNL towards developing a predicative tool for quantifying nepheline crystallization in HLW glass canisters using laboratory experiments. In this work, differential scanning calorimetry (DSC) was used to obtain the temperature regions over which nucleation and growth of nepheline occur in three simulated HLW glasses - two glasses representative of WTP projections and one glass representative of the Defense Waste Processing Facility (DWPF) product. The DWPF glass, which has been studied previously, was chosen as a reference composition and for comparison purposes. Complementary quantitative X-ray diffraction (XRD) and optical microscopy confirmed the validity of the methodology to determine nucleation and growth behavior as a function of temperature. The nepheline crystallization growth region was determined to generally extend from ~ 500 to >850 °C, with the maximum growth rates occurring between 600 and 700 °C. For select WTP glass compositions (high Al2O3 and B2O3), the nucleation range extended from ~ 450 to 600 °C, with the maximum nucleation rates occurring at ~ 530 °C. For the DWPF glass composition, the nucleation range extended from ~ 450 to 750 °C with the maximum nucleation rate occurring at ~ 640 °C. The nepheline growth at the peak temperature, as determined by XRD, was between 35 - 75 wt.% /hour. A maximum nepheline growth rate of ~ 0.1 mm/hour at 700 °C was measured for the DWPF

  2. Effect of Gravity Level on the Particle Shape and Size During Zeolite Crystal Growth (United States)

    Song, Hong-Wei; Ilebusi, Olusegun J.; Sacco, Albert, Jr.


    A microscopic diffusion model is developed to represent solute transport in the boundary layer of a growing zeolite crystal. This model is used to describe the effect of gravity on particle shape and solute distribution. Particle dynamics and crystal growth kinetics serve as the boundary conditions of flow and convection-diffusion equations. A statistical rate theory is used to obtain the rate of solute transport across the growing interface, which is expressed in terms of concentration and velocity of solute species. Microgravity can significantly decrease the solute velocity across the growing interface compared to its earth-based counterpart. The extent of this reduction highly depends on solute diffusion constant in solution. Under gravity, the flow towards the crystal enhances solute transport rate across the growing interface while the flow away from crystals reduces this rate, suggesting a non-uniform growth rate and thus an elliptic final shape. However, microgravity can significantly reduce the influence of flow and obtain a final product with perfect spherical shape. The model predictions compare favorably with the data of space experiment of zeolites grown in space.

  3. Growth of congruent-melting lithium tantalate crystal with stoichiometric structure by MgO doping (United States)

    Fujii, Shunsuke; Uda, Satoshi; Maeda, Kensaku; Nozawa, Jun; Koizumi, Haruhiko; Fujiwara, Kozo; Kajigaya, Tomio


    Lithium tantalate (LT) is an oxide material whose congruent composition differs from its stoichiometric composition in the Li2O-Ta2O5 binary system. Ionic species in the LT melt are segregated during crystal growth, even at the congruent composition, which leads to crystallization electromotive force (C-EMF) at the solid-liquid. On the other hand, when a compound has a stoichiometric structure at the congruent composition, such segregation does not occur. By employing a new concept of stoichiometry of a material where the activity of any constituent element could be unity, we developed a new lithium tantalate with MgO doping, cs-MgO:LT (Li2O:Ta2O5:MgO=40.8:50.0:9.2), that is stoichiometric and coincident with the congruent composition. Because of this coincidence, cs-MgO:LT does not yield C-EMF and does not show segregation during growth even for ionic species. A bulk crystal was grown from the melt of the cs-MgO:LT composition via the Czochralski (CZ) method, and it showed excellent compositional homogeneity, proved by the constant distribution of the Curie temperature throughout the crystal.

  4. Formation and Growth Mechanism of Globular Crystal of ADC12 Aluminum Alloy by Near-Liquidus Squeeze Casting

    Directory of Open Access Journals (Sweden)

    Shao-zhu Wang


    Full Text Available A new method of near-liquidus squeeze casting (NLSC, which obtains globular crystal, has been developed. The research focuses on the formation and growth mechanism of globular crystals of ADC12 alloy by NLSC. Globular crystal transforms into rosette crystal, average grain size (AGS increases, and average globular coefficient (ASC decreases with the rise of pouring temperature. But AGS decreases to 17.8 μm directly and ASC increases directly to 0.46 when the pouring temperature is 650°C. NLSC globular crystal of different sizes (AGS is 22.5 μm; ASC is 0.73 distributes uniformly in matrix. Heterogeneous nucleation grows on the solid particles of metal walls and fusing grains. The formation and growth modes of globular crystal include normal grain growth, annexation of small globular crystal, and fracture and spherulization of rosette crystal. NLSC globular crystal critical radius is inversely proportional to degree of supercooling. The pressure has very little influence on critical radius by increase of melting point and thermal conductivity, but it affects critical radius greatly by changing the degree of supercooling. NLSC globular crystal has no enough time to exceed the critical radius.

  5. Crystal growth, optical spectroscopy and laser action of Tm3+-doped monoclinic magnesium tungstate. (United States)

    Zhang, Lizhen; Lin, Haifeng; Zhang, Ge; Mateos, Xavier; Serres, Josep Maria; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin; Wang, Yicheng; Loiko, Pavel; Vilejshikova, Elena; Yumashev, Konstantin; Lin, Zhoubin; Chen, Weidong


    We report on the crystal growth, spectroscopic investigation and laser performance of Tm3+-doped monoclinic magnesium tungstate (Tm:MgWO4), for the first time, to the best of our knowledge. A high-quality crystal has been grown by the top seeded solution growth method. The relevant spectroscopic properties are characterized in terms of absorption, luminescence and Raman spectroscopy. Judd-Ofelt (J-O) analysis is performed to evaluate the spontaneous emission probabilities and the radiative lifetimes. The absorption, stimulated-emission and gain cross-section spectra are determined for the principal light polarizations. The first laser action in the 2 μm spectral range is demonstrated in the regime of continuous-wave operation with a maximum output power of 775 mW and a slope efficiency of 39%.

  6. Step-height standards based on the rapid formation of monolayer steps on the surface of layered crystals

    Energy Technology Data Exchange (ETDEWEB)

    Komonov, A.I. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Prinz, V.Ya., E-mail: [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Seleznev, V.A. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Kokh, K.A. [Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences (IGM SB RAS), pr. Koptyuga 3, Novosibirsk 630090 (Russian Federation); Shlegel, V.N. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences (NIIC SB RAS), pr. Lavrentieva 3, Novosibirsk 630090 (Russian Federation)


    Highlights: • Easily reproducible step-height standard for SPM calibrations was proposed. • Step-height standard is monolayer steps on the surface of layered single crystal. • Long-term change in surface morphology of Bi{sub 2}Se{sub 3} and ZnWO{sub 4} was investigated. • Conducting surface of Bi{sub 2}Se{sub 3} crystals appropriate for calibrating STM. • Ability of robust SPM calibrations under ambient conditions were demonstrated. - Abstract: Metrology is essential for nanotechnology, especially for structures and devices with feature sizes going down to nm. Scanning probe microscopes (SPMs) permits measurement of nanometer- and subnanometer-scale objects. Accuracy of size measurements performed using SPMs is largely defined by the accuracy of used calibration measures. In the present publication, we demonstrate that height standards of monolayer step (∼1 and ∼0.6 nm) can be easily prepared by cleaving Bi{sub 2}Se{sub 3} and ZnWO{sub 4} layered single crystals. It was shown that the conducting surface of Bi{sub 2}Se{sub 3} crystals offers height standard appropriate for calibrating STMs and for testing conductive SPM probes. Our AFM study of the morphology of freshly cleaved (0001) Bi{sub 2}Se{sub 3} surfaces proved that such surfaces remained atomically smooth during a period of at least half a year. The (010) surfaces of ZnWO{sub 4} crystals remained atomically smooth during one day, but already two days later an additional nanorelief of amplitude ∼0.3 nm appeared on those surfaces. This relief, however, did not further grow in height, and it did not hamper the calibration. Simplicity and the possibility of rapid fabrication of the step-height standards, as well as their high stability, make these standards available for a great, permanently growing number of users involved in 3D printing activities.

  7. Rapid growth reduces cold resistance: evidence from latitudinal variation in growth rate, cold resistance and stress proteins.

    Directory of Open Access Journals (Sweden)

    Robby Stoks

    Full Text Available BACKGROUND: Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. METHODOLOGY/PRINCIPAL FINDING: Larvae of the damselfly Ischnura elegans from two univoltine northern and two multivoltine southern populations were reared at three temperatures and after emergence given a cold shock. Cold resistance, measured by chill coma recovery times in the adult stage, was lower in the southern populations. The faster larval growth rates in the southern populations contributed to this latitudinal pattern in cold resistance. In accordance with their assumed role in cold resistance, Hsp70 levels were lower in the southern populations, and faster growing larvae had lower Hsp70 levels. Yet, individual variation in Hsp70 levels did not explain variation in cold resistance. CONCLUSIONS/SIGNIFICANCE: WE PROVIDE EVIDENCE FOR A NOVEL COST OF RAPID GROWTH: reduced cold resistance. Our results indicate that the reduced cold resistance in southern populations of animals that change voltinism along the latitudinal gradient may not entirely be explained by thermal selection per se but also by the costs of time constraint-induced higher growth rates. This also illustrates that stressors imposed in the larval stage may carry over and shape fitness in the adult stage and highlights the importance of physiological costs in the evolution of life-histories at macro-scales.

  8. Heteroepitaxy, an Amazing Contribution of Crystal Growth to the World of Optics and Electronics


    Vladimir L. Tassev


    Advances in Electronics and Optics are often preceded by discoveries in Crystal Growth theory and practice. This article represents in retrospect some of the most significant contributions of heteroepitaxy in these and some other areas—the strong impact of the three modes of heteroepitaxy on microelectronics and quantum optics, the big “push” of PENDEO epitaxy in development of Light Emitting Diodes, etc. A large part of the text is dedicated to heteroepitaxy of nonlinear optical materials gr...

  9. Mechanism of Ice Crystal Growth Habit and Shape Instability Development Below Water Saturation. (United States)


    of food he consumes is dependent upon water. For this basic reason, the obtainment of water has been the cardinal objective of the human race...and human error make an accurate determination of the ice crystal growth history difficult. For this reason, researchers 14 have attempted to...the emmissivity of ice, and Ti and Tj are the average temperatures in degrees Kelvin of the top and bottom plates. The last is the heat conductio

  10. Synthesis, deposition and crystal growth of CZTS nanoparticles onto ceramic tiles

    Directory of Open Access Journals (Sweden)

    Ivan Calvet


    Full Text Available The work presents a simple solvothermal method for CZTS nanoparticles preparation using hexadecylamine (HDA as a capping agent. The as-prepared CZTS powder was deposited as ink using Doctor Blade technique onto ceramic tile, as a substrate substituting the typical soda-lime glass. The as-prepared film was thermal treated at different temperatures in order to enhance the thin film crystallinity. CZTS crystal growth onto ceramic tile was obtained successfully for the first time.

  11. Nucleation kinetics and growth aspects of semi organic non-linear optical bis thiourea cadmium acetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sankar, R.; Raghavan, C.M.; Jayavel, R. [Crystal Growth Centre, Anna University, Chennai-600 025 (India)


    Nucleation parameters such as metastable zone width, induction period and interfacial energy have been determined for the aqueous solution growth of bis thiourea cadmium acetate (BTCA) single crystals. Solubility of BTCA has been determined for various temperatures. Metastable zone width and induction period values have been estimated in order to optimize the growth parameters. The interfacial tension values derived from experimentally determined induction period are found to be comparable with theoretical values. Bulk crystals of BTCA have been grown using the optimized growth parameters. The grown crystals have been subjected to structural, optical and mechanical property studies. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Transient from crystallization to fractal growth observed in both boar bile and SnI sub 2 vapour

    CERN Document Server

    Zhang Ji Zhong; Xie An Jian


    A visual transient of the growth mechanism from crystallization to fractal growth was observed clearly in a drop of boar bile. The growing crystals were replaced by treelike fractal structures during solidification of the sample. It is fascinating to compare the transient with the result observed in SnI sub 2 vapour. They were completely identical, and revealed that under certain conditions a linear growth could be transferred spontaneously into nonlinear growth. It may be possible to consider the transient as a 'bridge' between linear and nonlinear growth, and to develop a quantitative expression of transient dynamics.

  13. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Willatzen, Morten; Duggen, Lars


    -growth direction, and will be jointly excited by electrical stimulus. We demonstrate this for an electrically excited freestanding slab for two cases of high-symmetry crystal-growth directions and finally show the impact of the Drude model for permittivity on the phonon dispersion. In particular, it is verified...... that the piezoelectric effect leads to a drastically enhanced coupling of acoustic and optical phonon modes and increase in the local phonon density of states near the plasma frequency where the permittivity approaches zero....

  14. Growth of n-alkane films on a single-crystal substrate

    DEFF Research Database (Denmark)

    Wu, Z. U.; Ehrlich, S. N.; Matthies, B.


    reveal that growth of all films is preempted between two and three layers by nucleation of bulk particles oriented with a single bulk crystal plane parallel to the film. In the case of butane, the bulk particles also have a fixed azimuthal relationship with the film resulting in complete epitaxy.......The structure and growth mode of alkane films (n-C/sub n/H/sub 2n+2/; n=4, 6, 7) adsorbed on a Ag(111) surface have been investigated by synchrotron X-ray scattering. New models are proposed for the butane (n=4) and hexane (n=6) monolayer and butane bilayer structures. Specular reflectivity scans...

  15. Crystal Growth of Ca3Nb(Ga1−xAlx3Si2O14 Piezoelectric Single Crystals with Various Al Concentrations

    Directory of Open Access Journals (Sweden)

    Yuui Yokota


    Full Text Available Ca3Nb(Ga1−xAlx3Si2O14 (CNGAS single crystals with various Al concentrations were grown by a micro-pulling-down (µ-PD method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction.

  16. Rapid self-assembly of brush block copolymers to photonic crystals

    National Research Council Canada - National Science Library

    Benjamin R. Sveinbjörnsson; Raymond A. Weitekamp; Garret M. Miyake; Yan Xia; Harry A. Atwater; Robert H. Grubbs


    .... In this report, we demonstrate the rapid self-assembly of brush block copolymers to nanostructures with photonic bandgaps spanning the entire visible spectrum, from ultraviolet (UV) to near infrared (NIR...

  17. Acceleration of Crystal Growth of Amorphous Griseofulvin by Low-Concentration Poly(ethylene oxide): Aspects of Crystallization Kinetics and Molecular Mobility. (United States)

    Shi, Qin; Zhang, Chen; Su, Yuan; Zhang, Jie; Zhou, Dongshan; Cai, Ting


    This study aims to investigate the crystallization behavior and molecular dynamics of amorphous griseofulvin (GSF) in the presence of low-concentration poly(ethylene oxide) (PEO). We observe that the addition of 3% w/w PEO remarkably increases the crystal growth rate of GSF by two orders of magnitude in both the supercooled liquid and glassy states. The liquid dynamics of amorphous GSF in the presence and absence of PEO are characterized by dielectric spectroscopy. With an increase of the PEO content, the α-relaxation times of the systems decrease, indicating the increase of global molecular mobility. The couplings between molecular mobility and crystallization kinetics of GSF systems show strong time-dependences below Tg. The overlapping of α-relaxation times of GSF in presence and absence of PEO as a function of Tg/T suggest the "plasticization" effect of PEO additives. However, the crystallization kinetics of amorphous GSF containing low-concentration PEO do not overlap with those of pure GSF on a Tg/T scale. The remarkable accelerating effect of crystal growth of amorphous GSF by low-concentration PEO can be partially attributed to the increase of global mobility. The high segmental mobility of PEO is expected to strongly affect the crystal growth rates of GSF. These findings are relevant for understanding and predicting the physical stability of amorphous pharmaceutical solid dispersions.

  18. Fast and slow crystal growth kinetics in glass-forming melts

    Energy Technology Data Exchange (ETDEWEB)

    Orava, J.; Greer, A. L., E-mail: [WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan and Department of Materials Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)


    Published values of crystal growth rates are compared for supercooled glass-forming liquids undergoing congruent freezing at a planar crystal-liquid interface. For the purposes of comparison pure metals are considered to be glass-forming systems, using data from molecular-dynamics simulations. For each system, the growth rate has a maximum value U{sub max} at a temperature T{sub max} that lies between the glass-transition temperature T{sub g} and the melting temperature T{sub m}. A classification is suggested, based on the lability (specifically, the propensity for fast crystallization), of the liquid. High-lability systems show “fast” growth characterized by a high U{sub max}, a low T{sub max} / T{sub m}, and a very broad peak in U vs. T / T{sub m}. In contrast, systems showing “slow” growth have a low U{sub max}, a high T{sub max} / T{sub m}, and a sharp peak in U vs. T / T{sub m}. Despite the difference of more than 11 orders of magnitude in U{sub max} seen in pure metals and in silica, the range of glass-forming systems surveyed fit into a common pattern in which the lability increases with lower reduced glass-transition temperature (T{sub g} / T{sub m}) and higher fragility of the liquid. A single parameter, a linear combination of T{sub g} / T{sub m} and fragility, can show a good correlation with U{sub max}. For all the systems, growth at U{sub max} is coupled to the atomic/molecular mobility in the liquid. It is found that, across the diversity of glass-forming systems, T{sub max} / T{sub g} = 1.48 ± 0.15.

  19. Step-height standards based on the rapid formation of monolayer steps on the surface of layered crystals (United States)

    Komonov, A. I.; Prinz, V. Ya.; Seleznev, V. A.; Kokh, K. A.; Shlegel, V. N.


    Metrology is essential for nanotechnology, especially for structures and devices with feature sizes going down to nm. Scanning probe microscopes (SPMs) permits measurement of nanometer- and subnanometer-scale objects. Accuracy of size measurements performed using SPMs is largely defined by the accuracy of used calibration measures. In the present publication, we demonstrate that height standards of monolayer step (∼1 and ∼0.6 nm) can be easily prepared by cleaving Bi2Se3 and ZnWO4 layered single crystals. It was shown that the conducting surface of Bi2Se3 crystals offers height standard appropriate for calibrating STMs and for testing conductive SPM probes. Our AFM study of the morphology of freshly cleaved (0001) Bi2Se3 surfaces proved that such surfaces remained atomically smooth during a period of at least half a year. The (010) surfaces of ZnWO4 crystals remained atomically smooth during one day, but already two days later an additional nanorelief of amplitude ∼0.3 nm appeared on those surfaces. This relief, however, did not further grow in height, and it did not hamper the calibration. Simplicity and the possibility of rapid fabrication of the step-height standards, as well as their high stability, make these standards available for a great, permanently growing number of users involved in 3D printing activities.

  20. Study of morphology and crystal growth behaviour of nanoclay-containing biodegradable polymer blend thin films using atomic force microscopy

    CSIR Research Space (South Africa)

    Malwela, T


    Full Text Available Thin films of unmodified and nanoclay-modified polylactide/poly(butylene succinate) (PLA/PBS) blends were prepared on a glass substrate with a spin coater. The morphology and crystal growth behaviours for the films, crystallized at different...

  1. Adsorption of Polyvinylpyrrolidone and its Impact on Maintenance of Aqueous Supersaturation of Indomethacin via Crystal Growth Inhibition. (United States)

    Patel, Dhaval D; Anderson, Bradley D


    This study explored the adsorption and crystal growth inhibitory effects of polyvinylpyrrolidone (PVP) on indomethacin crystals in an aqueous medium. A solution depletion method was used to construct adsorption isotherms of PVPs with different molecular weights and N-vinylpyrrolidone onto indomethacin crystals. The affinity for and extent of maximum adsorption of PVP on indomethacin crystals were significantly higher than that of N-vinylpyrrolidone, which was attributed to cooperative interactions between PVP and the surface of indomethacin. The extent of PVP adsorption onto indomethacin crystals in terms of mg/m(2) was greater for higher molecular weight PVP but less on a molar basis indicating an increased percentage of loops and tails for the higher molecular weight PVP. PVP significantly inhibited the crystal growth of indomethacin at a high degree of supersaturation as compared with N-vinylpyrrolidone, which was attributed to a change in indomethacin crystal growth mechanism leading to a change in the rate limiting step from bulk diffusion to surface integration. Higher molecular weight PVPs are better inhibitors of the crystal growth of indomethacin than lower molecular weight PVPs, which was attributed in part to a greater barrier for surface diffusion of indomethacin provided by a thicker adsorption layer of PVP. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  2. The effect of pigeon yolk sac fluid on the growth behavior of calcium carbonate crystals. (United States)

    Song, Juan; Cheng, Haixia; Shen, Xinyu; Tong, Hua


    Previous experiments have proved that thermodynamically unstable calcium carbonate vaterite can exist for long periods in the yolk sac of a pigeon embryo. The aim of this article was to demonstrate the effect of in vitro mineralization of yolk sac fluid on calcium carbonate by direct precipitation. Experiments were conducted using pigeon yolk sac fluid and using lecithin extracted from pigeon yolk sac fluid as a control to investigate the regulating effects of the organic components in the embryo on the formation of the calcium carbonate precipitate. Multiple characterization methods were employed to study the various morphological patterns, sizes, crystal growth, and crystal phase transformations of the calcium carbonate precipitates as regulated by the yolk sac fluid extracted at different stages of incubation. The experimental results demonstrate that as the incubation proceeds towards the later stages, the composition and environmental features of the yolk sac fluid become more favorable for the formation of relatively unstable calcium carbonate phases with high energies of the vaterite state. The experiments conducted with extracted lecithin as the template for crystal growth yielded similar results. A large amount of organic molecules with polar functional groups carried by the yolk sac fluid have strong effects and can both initially induce the crystallization and regulate the aggregation of calcium carbonate. Furthermore, this regulation process is found to be closely related to the lecithin contained in yolk sac fluid. These observations confirm the changes in yolk sac fluid composition during incubation have significant effects on the production of vaterite, which implicates the calcium transport during embryo growth. © 2015 Poultry Science Association Inc.

  3. Optical imaging of the growth kinetics and polar morphology of zinc tris(thiourea) sulphate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dinakaran, S.; Das, S.J. [Department of Physics, Loyola College, University of Madras, Chennai - 600034 (India); Verma, S.; Kar, S.; Bartwal, K.S. [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore - 452013 (India)


    Growth kinetics of zinc tris(thiourea) sulphate (ZTS) single crystals was imaged in two different growth geometries using laser shadowgraphy technique. Growth rates of the {l_brace}010{r_brace} and {l_brace}001{r_brace} faces were computed as a function of supersaturation. The time evolution of polar morphology of ZTS crystal based on the growth rates is presented. Except (00 anti 1) face, all the other three faces are found to have a dead zone resulting in large induction period of growth. The anisotropy in the growth rates of the (001) and (00 anti 1) faces was very high, resulting in polar morphology. Different chemical environments on two sides of the (001) slice are suggested as the possible cause for the polar morphology of the crystals. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Unidirectional growth of L-lysine L-lysinium dichloride nitrate (L-LLDN) single crystals by the SR method

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Ramesh Babu, R., E-mail: [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)


    Bulk semi-organic single crystals of L-lysine L-lysinium dichloride nitrate (L-LLDN) were grown by Sankaranarayanan-Ramasamy (SR) method. The experimental parameters involved in the present work are discussed in detail. The cut-off wavelength and the transmittance of the crystal were determined by UV-vis-NIR spectral analysis. Mechanical stability of the crystal was determined by Vickers microhardness tester. Refractive index of the crystal was measured using Brewster's angle method. A simple interferometric technique was used for measuring birefringence of the crystal. The frequency dependent dielectric constant ({epsilon}{sub r}) and dielectric loss (tan {delta}) were also measured. The results were analyzed for the L-LLDN crystals grown by both conventional and unidirectional methods. -- Research highlights: {yields} Growth of bulk L-LLDN single crystals by unidirectional solution growth method for the first time. {yields} Unidirectionally grown crystals have less defects. {yields} The double refraction was observed in unidirectionally grown L-LLDN single crystal. {yields} The unidirectionally grown L-LLDN crystal has better physical properties.

  5. The impact of nanoclay on the crystal growth kinetics and morphology of biodegradable poly(ethylene succinate) composite

    CSIR Research Space (South Africa)

    Bandyopadhyay, J


    Full Text Available The impact of nanoclay on the isothermal crystal growth kinetics and morphology of biodegradable poly(ethylene succinate) (PES) is reported. A PES composite (PESNC) containing 5 wt% organically modified montmorillonite, was prepared via solvent...

  6. Investigating the crystal growth behavior of biodegradable polymer blend thin films using in situ atomic force microscopy

    CSIR Research Space (South Africa)

    Malwela, T


    Full Text Available This article reports the crystal growth behavior of biodegradable polylactide (PLA)/poly[(butylene succinate)-co-adipate] (PBSA) blend thin films using atomic force microscopy (AFM). Currently, polymer thin films have received increased research...

  7. Growth, structural, thermal, dielectric and optical studies on HBST crystal: A potential THz emitter (United States)

    Ma, Yuzhe; Teng, Bing; Cao, Lifeng; Zhong, Degao; Ji, Shaohua; Teng, Fei; Liu, Jiaojiao; Yao, Yuan; Tang, Jie; Tong, Jiaming


    The efficient organic nonlinear optical material 4-hydroxy benzaldehyde-N-methyl 4-stilbazolium tosylate (HBST) was grown from methanol by slope nucleation method combined with slow cooling (SNM-SC) for the first time. The optimum growth conditions based on the cooling rate was further investigated. The single crystal X-ray diffraction (XRD) revealed that the chromophores of HBST crystal make an angle of about 33° with respect to the a-axis, which is close to the optimum of Terahertz (THz)-wave generation and electro-optics applications. NMR and FT-IR spectral studies have been performed to ascertain various functional groups present in the sample. Futhermore, the thermal stability and decomposition stages were analyzed through TG-DTA and DSC techniques. The dielectric constant and dielectric loss of HBST crystal have been studied. Critical optical properties like the absorption coefficient, refractive index, cut-off wavelength and band gap energy were calculated. Photoluminescence (PL) exication studies indicated green emission occured at 507 nm. All the results of HBST crystal make it a promising candidate in the fields of optoelectronic and the generation of THz.

  8. Crystal growth and second harmonic generation efficiency of a chalcone derivative

    Energy Technology Data Exchange (ETDEWEB)

    Meenatchi, V.; Muthu, K.; Rajasekar, M.; Meenakshisundaram, SP., E-mail:


    Single crystals of (2E,6E)-2-(4-fluorobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone (FBMBC) have been grown by a slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the FBMBC belongs to triclinic system and the cell parameters are a=9.790(6) Å, b=12.08(7) Å, c=14.09(9) Å and V=1577 Å{sup 3}. The structure and the crystallinity of the material were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by Fourier transform infrared spectral analysis. The scanning electron microscopy study reveals the surface morphology of the as-grown crystal. Thermogravimetric/differential thermal analysis studies reveal the purity of the material and the crystals are transparent in the visible region having a low optical cut-off at ∼475 nm. The second harmonic generation efficiency of FBMBC is estimated by the Kurtz and Perry technique. Theoretical calculations were performed using the Hartree–Fock method with 6-31 G(d,p) as the basis set to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values.

  9. High-pressure growth and characterization of bulk MnAs single crystals (United States)

    Zhigadlo, Nikolai D.


    Bulk single crystals of manganese arsenide (MnAs) were grown from melt at 1 GPa and 1100 °C by using a cubic-anvil, high-pressure, and high-temperature technique. The as-grown black colored crystals extracted from solidified lump exhibit a plate-like morphology, with flat surfaces and maximum dimensions up to ∼3 × 2 × 0.5 mm3. The hexagonal crystal structure at room temperature was confirmed by X-ray diffraction [B81, space group P63/mmc, No 194, Z = 2, a = 3.7173(4) Å, b = 3.7173(4) Å, c = 5.7054(8) Å, and V = 68.277(16) Å3]. Temperature-dependent magnetization measurements reveal the occurrence of a first-order ferro- to paramagnetic transition at Tc = 318.5 K accompanied by a hysteresis of ∼9 K. The successful growth of relatively large crystals reported here might be extended to various substituted analogues of MnAs, thus opening new possibilities for further exploration of this interesting system.

  10. Crystal growth and characterization of CeFe{sub 1-x}Ru{sub x} PO

    Energy Technology Data Exchange (ETDEWEB)

    Balle, Tanita; Kliemt, Kristin; Krellner, Cornelius [Goethe Universitaet Frankfurt, Kristall- und Materiallabor (Germany)


    CeRuPO is a one of the few heavy fermion systems, which order ferromagnetically at low temperatures (T{sub C} = 15 K), because of dominant RKKY-interaction. CeFePO on the other hand shows no long-range magnetic order even at low temperatures because of dominant Kondo effect (T{sub K} = 10 K). By substituting CeFePO with ruthenium we can reach a quantum critical point, at which the RKKY-interaction and the Kondo effect are equally strong. To study the quantum critical point, and to enlighten the question if the order stays ferromagnetically down to lowest temperatures, high quality crystals are needed. Here, the growth and characterization of the single crystals will be discussed. We obtained mm-sized single crystals of the unsubstituted CeRuPO and CeFePO by a modified Bridgeman method using tin as a flux. The quality of the crystals was verified by Powder-X-Ray-Diffraction, energy dispersive X-ray spectroscopy and Laue backscattering.

  11. Self-Assembled Biosensors on a Solid Interface for Rapid Detection and Growth Monitoring of Bacteria

    CERN Document Server

    Kinnunen, Paivo; Craig, Elizabeth; Brahmasandra, Sundu; McNaughton, Brandon H


    Developing rapid methods for pathogen detection and growth monitoring at low cell and analyte concentrations is an important goal, which numerous technologies are working towards solving. Rapid biosensors have already made a dramatic impact on improving patient outcomes and with continued development, these technologies may also help limit the emergence of antimicrobial resistance and reduce the ever expanding risk of foodborne illnesses. One technology that is being developed with these goals in mind is asynchronous magnetic bead rotation (AMBR) biosensors. Self-assembled AMBR biosensors have been demonstrated at water/air and water/oil interfaces, and here, for the first time, we report on self-assembled AMBR biosensors used at a solid interface. The solid interface configuration was used to measure the growth of Escherichia coli with two distinct phenomena at low cell concentrations: firstly, the AMBR rotational period decreased and secondly, the rotational period increased after several division times. Ta...

  12. Wafer-scale growth of large arrays of perovskite microplate crystals for functional electronics and optoelectronics. (United States)

    Wang, Gongming; Li, Dehui; Cheng, Hung-Chieh; Li, Yongjia; Chen, Chih-Yen; Yin, Anxiang; Zhao, Zipeng; Lin, Zhaoyang; Wu, Hao; He, Qiyuan; Ding, Mengning; Liu, Yuan; Huang, Yu; Duan, Xiangfeng


    Methylammonium lead iodide perovskite has attracted intensive interest for its diverse optoelectronic applications. However, most studies to date have been limited to bulk thin films that are difficult to implement for integrated device arrays because of their incompatibility with typical lithography processes. We report the first patterned growth of regular arrays of perovskite microplate crystals for functional electronics and optoelectronics. We show that large arrays of lead iodide microplates can be grown from an aqueous solution through a seeded growth process and can be further intercalated with methylammonium iodide to produce perovskite crystals. Structural and optical characterizations demonstrate that the resulting materials display excellent crystalline quality and optical properties. We further show that perovskite crystals can be selectively grown on prepatterned electrode arrays to create independently addressable photodetector arrays and functional field effect transistors. The ability to grow perovskite microplates and to precisely place them at specific locations offers a new material platform for the fundamental investigation of the electronic and optical properties of perovskite materials and opens a pathway for integrated electronic and optoelectronic systems.

  13. Crystal growth and magnetic characterization of a tetragonal polymorph of NiNb2O6 (United States)

    Munsie, T. J. S.; Millington, A.; Dube, P. A.; Dabkowska, H. A.; Britten, J.; Luke, G. M.; Greedan, J. E.


    A previously unidentified polymorph of nickel niobate, NiNb2O6, was grown and stabilized in single crystalline form using an optical floating zone furnace. Key parameters of the growth procedure involved use of a slight excess of NiO (1.2% by mol), an O2 atmosphere and a growth rate of 25 mm/h. The resulting boule consisted of a polycrystalline exterior shell of the columbite structure - columbite is the thermodynamically stable form of NiNb2O6 under ambient conditions - and a core region consisting of transparent yellow-green single crystals up to 5 mm×2 mm×1 mm in dimension of the previously unidentified phase. The crystal structure, solved from single crystal x-ray diffraction data, is described in the P42/n space group. Interestingly, this is not a subgroup of P42/mnm, the rutile space group. The Ni2+ ions form layers which are displaced such that interlayer magnetic frustration is anticipated. Magnetic susceptibility data shows a broad maximum at approximately 22 K and evidence for long range antiferromagnetic order at approximately 14 K, obtained by Fisher heat capacity analysis as well as heat capacity measurements. The susceptibility data for T > 25 K are well fit by a square lattice S = 1 model, consistent with the Ni sublattice topology.

  14. Green Fluorescent Protein as a Model for Protein Crystal Growth Studies (United States)

    Agena, Sabine; Smith, Lori; Karr, Laurel; Pusey, Marc


    Green fluorescent protein (GFP) from jellyfish Aequorea Victoria has become a popular marker for e.g. mutagenesis work. Its fluorescent property, which originates from a chromophore located in the center of the molecule, makes it widely applicable as a research too]. GFP clones have been produced with a variety of spectral properties, such as blue and yellow emitting species. The protein is a single chain of molecular weight 27 kDa and its structure has been determined at 1.9 Angstrom resolution. The combination of GFP's fluorescent property, the knowledge of its several crystallization conditions, and its increasing use in biophysical and biochemical studies, all led us to consider it as a model material for macromolecular crystal growth studies. Initial preparations of GFP were from E.coli with yields of approximately 5 mg/L of culture media. Current yields are now in the 50 - 120 mg/L range, and we hope to further increase this by expression of the GFP gene in the Pichia system. The results of these efforts and of preliminary crystal growth studies will be presented.

  15. Chd1 is essential for the high transcriptional output and rapid growth of the mouse epiblast


    Guzman-Ayala, Marcela; Sachs, Michael; Koh, Fong Ming; Onodera, Courtney; Bulut-Karslioglu, Aydan; Lin, Chih-Jen; Wong, Priscilla; Nitta, Rachel; Song, Jun S.; Ramalho-Santos, Miguel


    The pluripotent mammalian epiblast undergoes unusually fast cell proliferation. This rapid growth is expected to generate a high transcriptional demand, but the underlying mechanisms remain unknown. We show here that the chromatin remodeler Chd1 is required for transcriptional output and development of the mouse epiblast. Chd1−/− embryos exhibit proliferation defects and increased apoptosis, are smaller than controls by E5.5 and fail to grow, to become patterned or to gastrulate. Removal of p...

  16. Rapid growth and childhood obesity are strongly associated with lysoPC(14:0). (United States)

    Rzehak, Peter; Hellmuth, Christian; Uhl, Olaf; Kirchberg, Franca F; Peissner, Wolfgang; Harder, Ulrike; Grote, Veit; Weber, Martina; Xhonneux, Annick; Langhendries, Jean-Paul; Ferre, Natalia; Closa-Monasterolo, Ricardo; Verduci, Elvira; Riva, Enrica; Socha, Piotr; Gruszfeld, Dariusz; Koletzko, Berthold


    Despite the growing interest in the early-origins-of-later-disease hypothesis, little is known about the metabolic underpinnings linking infant weight gain and childhood obesity. To discover biomarkers reflective of weight change in the first 6 months and overweight/obesity at age 6 years via a targeted metabolomics approach. This analysis comprised 726 infants from a European multicenter randomized trial (Childhood Obesity Programme, CHOP) for whom plasma blood samples at age 6 months and anthropometric data up to the age of 6 years were available. 'Rapid growth' was defined as a positive difference in weight within the first 6 months of life standardized to WHO growth standards. Weight change was regressed on each of 168 metabolites (acylcarnitines, lysophosphatidylcholines, sphingomyelins, and amino acids). Metabolites significant after Bonferroni's correction were tested as predictors of later overweight/obesity. Among the overall 19 significant metabolites, 4 were associated with rapid growth and 15 were associated with a less-than-ideal weight change. After adjusting for feeding group, only the lysophosphatidylcholine LPCaC14:0 remained significantly associated with rapid weight gain (β = 0.18). Only LPCaC14:0 at age 6 months was predictive of overweight/obesity at age 6 years (OR 1.33; 95% CI 1.04-1.69). LPCa14:0 is strongly related to rapid growth in infancy and childhood overweight/obesity. This suggests that LPCaC14:0 levels may represent a metabolically programmed effect of infant weight gain on the later obesity risk. However, these results require confirmation by independent cohorts. © 2014 S. Karger AG, Basel.

  17. Research on crystal growth by using pressure as a control parameter; Atsuryoku seigyo ni yoru kessho seicho ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)



    This research project aims to establish a technique for crystal growth using pressure as a principal control parameter, and combining it with a microgravity condition, to develop a novel process material fabrication. Since the solubility of materials depends on pressure, it is possible to control a supersaturated condition for crystal growth by changing pressure. The growth condition can be controlled precisely, which is not possible by conventional methods that vary temperature and other factors. On the other hand, because a concentration diffusing field is formed autonomically around crystals in association with their growth, density convection is generated under gravity as a result of difference in the concentrations, making the growth conditions severely complex and uncontrollable. Ideal crystal growth condition control may be possible if the pressure control is performed under micro-gravity by which generation of the density convection can be suppressed. Realization has been achieved on in-situ observation by using high-magnification microscope which uses a diamond anvil cell, development of a hydraulic type optic pressure cell, and a high- speed crystal growing technology by means of pressure control utilizing the cell. New findings were also obtained on effects of pressure on crystal forms, and the pressure induced solid phase transfer mechanism. 67 refs., 49 figs., 3 tabs.

  18. Bulk Growth of 2-6 Crystals in the Microgravity Environment of USML-1 (United States)

    Gillies, Donald C.; Lehoczky, Sandor L.; Szofran, Frank R.; Larson, David J.; Su, Ching-Hua; Sha, Yi-Gao; Alexander, Helga A.


    The first United States Microgravity Laboratory Mission (USML- 1) flew in June 1992 on the Space Shuttle Columbia. An important part of this SpaceLab mission was the debut of the Crystal Growth Furnace (CGF). Of the seven samples grown in the furnace, three were bulk grown 2-6 compounds, two of a cadmium zinc telluride alloy, and one of a mercury zinc telluride alloy. Ground based results are presented, together with the results of computer simulated growths of these experimental conditions. Preliminary characterization results for the three USML-1 growth runs are also presented and the flight sample characteristics are compared to the equivalent ground truth samples. Of particular interest are the effect of the containment vessel on surface features, and especially on the nucleation, and the effect of the gravity vector on radial and axial compositional variations and stress and defect levels.

  19. Growth, structural, optical, thermal and mechanical properties of cytosinium hydrogen selenite: A novel nonlinear optical single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Jaikumar, P. [PG & Research Department of Physics, National College (Autonomous), Tiruchirappalli, 620 001 Tamil Nadu (India); Sathiskumar, S. [Crystal Growth Laboratory, Department of Physics, Periyar EVR College (Autonomous), Tiruchirappalli, 620 023 Tamil Nadu (India); Balakrishnan, T., E-mail: [Crystal Growth Laboratory, Department of Physics, Periyar EVR College (Autonomous), Tiruchirappalli, 620 023 Tamil Nadu (India); Ramamurthi, K. [Crystal Growth & Thin Film laboratory, Department of Physics & Nanotechnology, SRM University, Kattankulathur, 603 203 Kancheepuram, Tamil Nadu (India)


    Highlights: • Growth of bulk single crystals of cytosinium hydrogen selenite (CHS) is reported. • Dielectric constant of CHS is measured as a function of Frequency and temperature. • Lower cut off value of UV–vis-NIR spectrum of CHS crystal is observed at 210 nm. • Meyer’s index value of CHS crystal calculated identifies it as a soft material. • Powder SHG efficiency of CHS is about 1.5 times that of KDP crystal. - Abstract: A novel nonlinear optical single crystal of cytosinium hydrogen selenite was grown from aqueous solution of cytosinium hydrogen selenite by slow solvent evaporation method at room temperature. The structural properties of grown crystal have been studied by single crystal and powder X-ray diffraction analysis. Presence of various functional groups was identified from Fourier transform infrared spectroscopy. The optical transmittance and absorbance spectra were recorded by UV–vis-NIR spectrometer and the grown crystal possesses good transparency in the entire visible region. The dielectric constant and dielectric loss of the crystal were calculated as a function of frequency at different temperatures. The mechanical strength of the cytosinium hydrogen selenite crystal was estimated using Vicker’s microhardness tester. Etch patterns of the cytosinium hydrogen selenite crystal were obtained using distilled water as etchant for different etching time. Second harmonic generation efficiency tested using Nd:YAG laser is about 1.5 times that of KDP.

  20. Reduction-induced inward diffusion and crystal growth on the surfaces of iron-bearing silicate glasses

    DEFF Research Database (Denmark)

    Liu, S.J.; Tao, H.Z.; Zhang, Y.F.


    first and then the growth of silica crystals on the glass surface. The type of alkaline earth cations has a strong impact on both the glass transition and the surface crystallization. In the Mg-containing glass, a quartz layer forms on the glass surface. This could be attributed to the fact that Mg2......We investigate the sodium inward diffusion (i.e., sodium diffusion from surface toward interior) in iron containing alkaline earth silicate glasses under reducing conditions around Tg and the induced surface crystallization. The surface crystallization is caused by formation of a silicate-gel layer...

  1. Control of parabolic PDEs with time-varying spatial domain: Czochralski crystal growth process (United States)

    Ng, James; Aksikas, Ilyasse; Dubljevic, Stevan


    This paper considers the optimal control problem for a class of convection-diffusion-reaction systems modelled by partial differential equations (PDEs) defined on time-varying spatial domains. The class of PDEs is characterised by the presence of a time-dependent convective-transport term which is associated with the time evolution of the spatial domain boundary. The functional analytic description of the PDE yields the representation of the initial and boundary value problem as a nonautonomous parabolic evolution equation on an appropriately defined infinite-dimensional function space. The properties of the time-varying evolution operator to guarantee existence and well posedness of the initial and boundary value problem are demonstrated which serves as the basis for the optimal control problem synthesis. An industrial application of the crystal temperature regulation problem for the Czochralski crystal growth process is considered and numerical simulation results are provided.

  2. Numerical computation of the linear stability of the diffusion model for crystal growth simulation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.; Sorensen, D.C. [Rice Univ., Houston, TX (United States); Meiron, D.I.; Wedeman, B. [California Institute of Technology, Pasadena, CA (United States)


    We consider a computational scheme for determining the linear stability of a diffusion model arising from the simulation of crystal growth. The process of a needle crystal solidifying into some undercooled liquid can be described by the dual diffusion equations with appropriate initial and boundary conditions. Here U{sub t} and U{sub a} denote the temperature of the liquid and solid respectively, and {alpha} represents the thermal diffusivity. At the solid-liquid interface, the motion of the interface denoted by r and the temperature field are related by the conservation relation where n is the unit outward pointing normal to the interface. A basic stationary solution to this free boundary problem can be obtained by writing the equations of motion in a moving frame and transforming the problem to parabolic coordinates. This is known as the Ivantsov parabola solution. Linear stability theory applied to this stationary solution gives rise to an eigenvalue problem of the form.

  3. Structure and Growth Control of Organic-Inorganic Halide Perovskites for Optoelectronics: From Polycrystalline Films to Single Crystals. (United States)

    Chen, Yani; He, Minhong; Peng, Jiajun; Sun, Yong; Liang, Ziqi


    Recently, organic-inorganic halide perovskites have sparked tremendous research interest because of their ground-breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light-emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high-quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three-dimensional large sized single crystals, two-dimensional nanoplates, one-dimensional nanowires, to zero-dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high-performance (opto)electronic devices.

  4. Crystal growth and characterization of semi-organic 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals for third-order nonlinear optical (NLO) applications (United States)

    Vediyappan, Sivasubramani; Arumugam, Raja; Pichan, Karuppasamy; Kasthuri, Ramachandran; Muthu, Senthil Pandian; Perumal, Ramasamy


    Semi-organic nonlinear optical (NLO) 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals have been grown by slow evaporation solution technique (SEST) with the growth period of 60 days. The single-crystal XRD analysis confirms the unit cell parameters of the grown crystal. The crystallinity of grown 2A5NPBr was analyzed by powder X-ray diffraction (PXRD) measurement. The presence of functional groups of 2A5NPBr crystal was confirmed by Fourier transform infrared (FTIR) spectrum analysis. The optical transmittance of the grown crystal was analyzed by UV-Vis-NIR analysis. It shows good transparency in the visible and NIR region and it is favorable for nonlinear optical (NLO) device applications. The chemical etching study was carried out and it reveals that the grown crystal has less dislocation density. The photoconductivity study reveals that the grown crystal possesses positive photoconductive nature. The thermal stability of the crystal has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The dielectric constant and dielectric loss as a function of frequency were measured. The electronic polarizability (α) of 2A5NPBr molecule has been calculated theoretically by different ways such as Penn analysis, Clausius-Mossotti relation, Lorentz-Lorenz equation, optical bandgap, and coupled dipole method (CDM). The obtained values of electronic polarizability (α) are in good agreement with each other. Laser damage threshold (LDT) of 2A5NPBr crystal has been measured using Nd:YAG laser with the wavelength of 1064 nm. Third-order nonlinear optical property of the grown crystal was studied by Z-scan technique using He-Ne laser of wavelength 632.8 nm.

  5. Single crystal growth and enhancing effect of glycine on characteristic properties of bis-thiourea zinc acetate crystal (United States)

    Anis, Mohd; Muley, G. G.


    A single crystal of glycine-doped bis-thiourea zinc acetate (G-BTZA) with a dimension of 15 × 6 × 4 mm3 has been grown using the slow solution evaporation technique. The structural parameters of the crystals were determined using the single crystal XRD technique. The increase in optical transparency of the doped BTZA crystal was ascertained in the range of 200 to 900 nm using UV-visible spectral analysis. The improved optical band gap of the G-BTZA crystal is found to be 4.19 eV, and vital optical constants have been calculated using the transmittance data. The influence of glycine on the mechanical parameters of the BTZA crystal has been investigated via microhardness studies. The thermal stability of pure and doped BTZA crystals has been determined by employing the thermogravimetric and differential thermal analysis technique. The improvement in the dielectric properties of the BTZA crystal after the addition of glycine has been evaluated in a temperature range of 30 to 120 °C at a frequency of 100 KHz. The SHG efficiency of the glycine-doped BTZA crystal is found to be much higher than KDP and BTZA crystal material in a Kurtz-Perry powder analysis.

  6. Can Solution Supersaturation Affect Protein Crystal Quality? (United States)

    Gorti, Sridhar


    The formation of large protein crystals of "high quality" is considered a characteristic manifestation of microgravity. The physical processes that predict the formation of large, high quality protein crystals in the microgravity environment of space are considered rooted in the existence of a "depletion zone" in the vicinity of crystal. Namely, it is considered reasonable that crystal quality suffers in earth-grown crystals as a result of the incorporation of large aggregates, micro-crystals and/or large molecular weight "impurities", processes which are aided by density driven convective flow or mixing at the crystal-liquid interface. Sedimentation and density driven convection produce unfavorable solution conditions in the vicinity of the crystal surface, which promotes rapid crystal growth to the detriment of crystal size and quality. In this effort, we shall further present the hypothesis that the solution supersaturatoin at the crystal surface determines the growth mechanism, or mode, by which protein crystals grow. It is further hypothesized that protein crystal quality is affected by the mechanism or mode of crystal growth. Hence the formation of a depletion zone in microgravity environment is beneficial due to inhibition of impurity incorporatoin as well as preventing a kinetic roughening transition. It should be noted that for many proteins the magnitude of neither protein crystal growth rates nor solution supersaturation are predictors of a kinetic roughening transition. That is, the kinetic roughening transition supersaturation must be dtermined for each individual protein.

  7. Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species (United States)

    Ma, E.; Lim, B. S.; Nicolet, M.-A.; Natan, M.


    The growth kinetics is characterized and the moving species is identified for the formation of Ni2Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a Si substrate. The interfacial Ni2Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350 450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni2Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni2Si formation.

  8. Growth of CdZnTe Crystals the Bridgman Technique with Controlled Overpressures of Cd (United States)

    Su, Ching-Hu; Lehoczky, S. L.


    Cd(1-x)Zn(x)Te crystals with x = 0.15 and 0.20, were grown in this study by closed-ampoule directional solidification (Bridgman) technique with a controlled Cd overpressure. The growth ampoule was made of quartz with inner diameter from 20 to 40 mm and a tapered length of 2.5 cm at the growth tip. Both unseeded and seeded growths were performed with total material charges up to 400 g. After the loading of starting CdZnTe material, a typical amount of 2 g of Cd was also loaded inside a Cd reservoir basket, which was attached beneath the seal-off cup. The ampoule was sealed off under a vacuum below lxl0(exp -5) Torr. The sealed ampoule was placed inside a 4-zone Bridgman furnace - a Cd reservoir zone with a heat-pipe furnace liner on the top, followed by a hot zone, a booster heating zone and a cold zone at the bottom. The Cd zone was typically 300 to 400 C below the hot zone setting. High resistivity material has been obtained without any intentional dopants but has been reproducibly obtained with In doping. The crystalline and the electrical properties of the crystals will be reported.

  9. Growth of large size lithium niobate single crystals of high quality by tilting-mirror-type floating zone method

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, Abdur Razzaque, E-mail: [Department of Physics, University of Rajshahi (Bangladesh)


    Large size high quality LiNbO{sub 3} single crystals were grown successfully by tilting-mirror-type floating zone (TMFZ) technique. The grown crystals were characterized by X-ray diffraction, etch pits density measurement, Impedance analysis, Vibrating sample magnetometry (VSM) and UV-Visible spectrometry. The effect of mirror tilting during growth on the structural, electrical, optical properties and defect density of the LiNbO{sub 3} crystals were investigated. It was found that the defect density in the crystals reduced for tilting the mirror in the TMFZ method. The chemical analysis revealed that the grown crystals were of high quality with uniform composition. The single crystals grown by TMFZ method contains no low-angle grain boundaries, indicating that they can be used for high efficiency optoelectronic devices. (author)

  10. Enhancement of lateral growth of the GaN crystal with extremely low dislocation density during the Na-flux growth on a point seed (United States)

    Hayashi, Masatoshi; Imanishi, Masayuki; Yamada, Takumi; Matsuo, Daisuke; Murakami, Kosuke; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Mori, Yusuke


    Recently, we developed a Na-flux point seed technique for fabrication of large-diameter gallium nitride (GaN) crystals with low dislocation density. It may be possible to further reduce the dislocation density of crystals fabricated by this technique by reducing the point-seed (PS) density, because one dislocation remains on the c face of each grain grown on each point seed. Therefore, in order to realize coalescence growth by using a Multi-PS-GaN substrate with a low PS density, namely a long interval between neighboring point seeds, the lateral growth of each grain grown on a point seed must be enhanced. We attempted to promote the lateral growth of GaN crystals grown on a point seed by decreasing the flux thickness. As a result, we realized a high growth rate of 80 μm/h along the a direction and a low aspect ratio by the Na-flux point seed technique. Moreover, almost no dislocations could be found in the lateral growth sector. Consequently, growth in a thin flux is applicable for the coalescence growth technique with low PS density and may be an outstanding approach for reducing the dislocation density in GaN crystals grown by the Na-flux coalescence growth technique.

  11. Adaptation of BAp crystal orientation to stress distribution in rat mandible during bone growth

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, T; Fujitani, W; Ishimoto, T [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871 (Japan); Umakoshi, Y [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaragi, 305-0471 (Japan)], E-mail:


    Biological apatite (BAp) c-axis orientation strongly depends on stress distribution in vivo and tends to align along the principal stress direction in bones. Dentulous mandible is subjected to a complicated stress condition in vivo during chewing but few studies have been carried out on the BAp c-axis orientation; so the adaptation of BAp crystal orientation to stress distribution was examined in rat dentulous mandible during bone growth and mastication. Female SD rats 4 to 14 weeks old were prepared, and the bone mineral density (BMD) and BAp crystal orientation were analyzed in a cross-section of mandible across the first molar focusing on two positions: separated from and just under the tooth root on the same cross-section perpendicular to the mesiodistal axis. The degree of BAp orientation was analyzed by a microbeam X-ray diffractometer using Cu-K{alpha} radiation equipped with a detector of curved one-dimensional PSPC and two-dimensional PSPC in the reflection and transmission optics, respectively. BMD quickly increased during bone growth up to 14 weeks, although it was independent of the position from the tooth root. In contrast, BAp crystal orientation strongly depended on the age and the position from the tooth root, even in the same cross-section and direction, especially along the mesiodistal and the biting axes. With increased biting stress during bone growth, the degree of BAp orientation increased along the mesiodistal axis in a position separated from the tooth root more than that near the tooth root. In contrast, BAp preferential alignment clearly appeared along the biting axis near the tooth root. We conclude that BAp orientation rather than BMD sensitively adapts to local stress distribution, especially from the chewing stress in vivo in the mandible.

  12. Nucleation and Crystal Growth in the Formation of Hierarchical Three-Dimensional Nanoarchitecture

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xudong [University of Wisconsin-Madison


    This project is to obtain fundamental understandings of the operation of the Ostwald-Lussac (OL) Law and the oriented attachment (OA) mechanism in nucleation and growth of TiO2 nanorods (NR) via surface-reaction-limited pulsed chemical vapor deposition (SPCVD) process. Three-dimensional (3D) NW networks are a unique type of mesoporous architecture that offers extraordinary surface area density and superior transport properties of electrons, photons, and phonons. It is exceptionally promising for advancing the design and application of functional materials for photovoltaic devices, catalysts beds, hydrogen storage systems, sensors, and battery electrodes. Our group has developed the SPCVD technique by mimicking the mechanism of atomic layer deposition (ALD), which effectively decoupled the crystal growth from precursor concentration while retaining anisotropic 1D growth. For the first time, this technique realized a 3D NW architecture with ultrahigh density and achieved ~4-5 times enhancement on photo-conversion efficiency. Through the support of our current DOE award, we revealed the governing role of the OL Law in the nucleation stage of SPCVD. The formation of NR morphology in SPCVD was identified following the OA mechanism. We also discovered a unique vapor-phase Kirkendall effect in the evolution of tubular or core-shell NR structures. These understandings opened many new opportunities in designing 3D NW architectures with improved properties or new functionalities. Specifically, our accomplishments from this project include five aspects: (1) Observation of the Ostwald-Lussac Law in high-temperature ALD. (2) Observation of vapor-solid Kirkendall effect in ZnO-to-TiO2 nanostructure conversion. (3) Development of highly-efficient capillary photoelectrochemical (PEC) solar-fuel generation. (4) Development of efficient and stable electrochemical protections for black silicon PEC electrodes. (5) Development of doped polymers with tunable electrical properties. This

  13. High-Temperature Crystal-Growth Cartridge Tubes Made by VPS (United States)

    Holmes, Richard; O'Dell, Scott; McKechnie, Timothy; Power, Christopher


    Cartridge tubes for use in a crystal growth furnace at temperatures as high as 1,600 deg. C have been fabricated by vacuum plasma spraying (VPS). These cartridges consist mainly of an alloy of 60 weight percent molybdenum with 40 weight percent rhenium, made from molybdenum powder coated with rhenium. This alloy was selected because of its high melting temperature (approximately equal.2,550 C) and because of its excellent ductility at room temperature. These cartridges are intended to supplant tungsten/nickel-alloy cartridges, which cannot be used at temperatures above approximately equal 1,300 C.

  14. Effect of Low-Concentration Polymers on Crystal Growth in Molecular Glasses: A Controlling Role for Polymer Segmental Mobility Relative to Host Dynamics. (United States)

    Huang, Chengbin; Powell, C Travis; Sun, Ye; Cai, Ting; Yu, Lian


    Low-concentration polymers can strongly influence crystal growth in small-molecule glasses, a phenomenon important for improving physical stability against crystallization. We measured the velocity of crystal growth in two molecular glasses, nifedipine (NIF) and o-terphenyl (OTP), each doped with four or five different polymers. For each polymer, the concentration was fixed at 1 wt % and a wide range of molecular weights was tested. We find that a polymer additive can strongly alter the rate of crystal growth, from a 10-fold reduction to a 10-fold increase. For a given polymer, increasing molecular weight slows down crystal growth and the effect saturates around DP = 100, where DP is the degree of polymerization. For all the systems studied, the polymer effect on crystal growth rate forms a master curve in the variable (Tg,polymer - Tg,host)/Tcryst, where Tg is the glass transition temperature and Tcryst is the crystallization temperature. These results support the view that a polymer's effect on crystal growth is controlled by its segmental mobility relative to the host-molecule dynamics. In the proposed model, crystal growth rejects impurities and creates local polymer-rich regions, which must be traversed by host molecules to sustain crystal growth at rates determined by polymer segmental mobility. Our results do not support the view that host-polymer hydrogen bonding plays a controlling role in crystal growth inhibition.

  15. He atom-surface scattering: Surface dynamics of insulators, overlayers and crystal growth

    Energy Technology Data Exchange (ETDEWEB)


    Investigations in this laboratory have focused on the surface structure and dynamics of ionic insulators and on epitaxial growth onto alkali halide crystals. In the later the homoepitaxial growth of NaCl/NaCl(001) and the heteroepitaxial growth of KBr/NaCl(001), NaCl/KBr(001) and KBr/RbCl(001) have been studied by monitoring the specular He scattering as a function of the coverage and by measuring the angular and energy distributions of the scattered He atoms. These data provide information on the surface structure, defect densities, island sizes and surface strain during the layer-by-layer growth. The temperature dependence of these measurements also provides information on the mobilities of the admolecules. He atom scattering is unique among surface probes because the low-energy, inert atoms are sensitive only to the electronic structure of the topmost surface layer and are equally applicable to all crystalline materials. It is proposed for the next year to exploit further the variety of combinations possible with the alkali halides in order to carry out a definitive study of epitaxial growth in the ionic insulators. The work completed so far, including measurements of the Bragg diffraction and surface dispersion at various stages of growth, appears to be exceptionally rich in detail, which is particularly promising for theoretical modeling. In addition, because epitaxial growth conditions over a wide range of lattice mismatches is possible with these materials, size effects in growth processes can be explored in great depth. Further, as some of the alkali halides have the CsCl structure instead of the NaCl structure, we can investigate the effects of the heteroepitaxy with materials having different lattice preferences. Finally, by using co-deposition of different alkali halides, one can investigate the formation and stability of alloys and even alkali halide superlattices.

  16. Metastable crystal growth of acetaminophen using solution-mediated phase transformation (United States)

    Mori, Yoichiro; Maruyama, Mihoko; Takahashi, Yoshinori; Yoshikawa, Hiroshi Y.; Okada, Shino; Adachi, Hiroaki; Sugiyama, Shigeru; Takano, Kazufumi; Murakami, Satoshi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Yoshimura, Masashi; Mori, Yusuke


    We report a new method of obtaining the metastable phase form II crystals of acetaminophen. Solution-mediated phase transformation (SMPT) from trihydrate into form II is utilized to obtain form II crystals. SMPT is triggered by seeding form II crystals into a saturated solution including trihydrate crystals, which are less stable than form II crystals. Form II seed crystals gradually grew at the expense of the dissolving trihydrate crystals, and finally, all the trihydrate crystals in solution were transformed into form II crystals in about 4 h. Thus, we conclude that SMPT is effective for the production of form II crystals.

  17. Dependence of the CaOx and MgOx Growth Rates on Solution Stoichiometry. Non-Kossel Crystal Approach (United States)

    Chernov, Alexander A.; Rashkovich, L. N.


    Experimental data on step rates on the CaOx and MgOx faces are presented and discussed in terms of non-Kossel crystal growth theory. The theory well describes the major feature - maximum of the growth rate in stoichiometric solution. More precise analyses is needed to fit details of this dependence.

  18. Growth and characterization of Tm-doped Y 2O 3 single crystals (United States)

    Mun, J. H.; Jouini, A.; Novoselov, A.; Guyot, Y.; Yoshikawa, A.; Ohta, H.; Shibata, H.; Waseda, Y.; Boulon, G.; Fukuda, T.


    The rare-earth sesquioxides (RE2O3, RE = Lu, Y and Sc) are promising host materials for solid-state lasers due to their low phonon energy and high thermal conductivity. On the other hand, Tm3+ and Yb3+ are preferable activators for advanced laser diode pumped solid-state lasers. In addition to that, Tm-doped materials can be used for eye-safe lasers application. Tm-doped Y2O3 single crystals were grown using the micro-pulling-down method. Crystals were transparent with gray and blue colors of 4.2 mm in diameter and 13-20 mm in length. The crystallinity was characterized using X-ray rocking curve analysis. Tm-doped Y2O3 single crystals have a good compositional homogeneity along the growth axis and their thermal conductivity was calculated from the measurements of thermal diffusivity, heat capacity and density. We have also recorded absorption, fluorescence spectra and measured fluorescence lifetimes as a function of the Tm content, we have found a very attractive fluorescence around the eye-safe wavelength of 1.9 mm which corresponds to a 3F4 → 3H6 transition of Tm3+.

  19. Sequential purification and crystal growth for the production of low cost silicon substrates (United States)

    Liaw, M.; Daragona, F. S.

    The objective of this program is to identify and develop low cost processing for fabricating large grain size polycrystalline silicon substrates. Metallurigical grade silicon (MG-Si) which is low cost and abundant for industrial usage was chosen as starting material. However, MG-Si cannot be used directly as substrates for solar cell fabrication for the following reasons: (1) it contains 1 to 2 percent metallic impurities, and (2) it is produced as irregular shapes with a fine grain structure. Various purification techniques have been reported. The techniques being studied under this program use direct methods for the purification of MG-Si. The process uses sequential steps of purification followed by crystal growth. The steps of sequential purification include: (1) leaching of MG-Si charge, (2) phase separation of nonsoluble impurities from molten silicon, (3) reactive gas treatment of molten silicon, (4) liquid liquid extraction (called slagging), and (5) impurity redistribution using ingot pulling. All the purification steps, with the exception of step (1), are performed in a consecutive manner using a crystal puller. The purified ingots will be produced in a desired ingot dimension and further recrystallization is not necessary. The theory and experimental results for each purification technique are presented. The relative effectiveness of the various steps are assessed and the most import step(s) are recommended. Finally the electrical characteristics of solar cells built on a thin epitaxial layer deposited on single pulled MG-Si substrates are discussed and compared to single crystal substrates.

  20. Air-Flow Navigated Crystal Growth for TIPS Pentacene-Based Organic Thin-Film Transistors

    Energy Technology Data Exchange (ETDEWEB)

    He, Zhengran [ORNL; Chen, Jihua [ORNL; Sun, Zhenzhong [ORNL; Szulczewski, Greg [University of Alabama, Tuscaloosa; Li, Dawen [ORNL


    6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene) is a promising active channel material of organic thin-film transistors (OTFTs) due to its solubility, stability, and high mobility. However, the growth of TIPS pentacene crystals is intrinsically anisotropic and thus leads to significant variation in the performance of OTFTs. In this paper, air flow is utilized to effectively reduce the TIPS pentacene crystal anisotropy and enhance performance consistency in OTFTs, and the resulted films are examined with optical microscopy, grazing-incidence X-ray diffraction, and thin-film transistor measurements. Under air-flow navigation (AFN), TIPS pentacene drop-cast from toluene solution has been observed to form thin films with improved crystal orientation and increased areal coverage on substrates, which subsequently lead to a four-fold increase of average hole mobility and one order of magnitude enhancement in performance consistency defined by the ratio of average mobility to the standard deviation of the field-effect mobilities.

  1. New insights from coral growth band studies in an era of rapid environmental change (United States)

    Lough, Janice M.; Cooper, Timothy F.


    The rapid formation of calcium carbonate coral skeletons (calcification) fuelled by the coral-algal symbiosis is the backbone of tropical coral reef ecosystems. However, the efficacy of calcification is measurably influenced by the sea's physico-chemical environment, which is changing rapidly. Warming oceans have already led to increased frequency and severity of coral bleaching, and ocean acidification has a demonstrable potential to cause reduced rates of calcification. There is now general agreement that ocean warming and acidification are attributable to human activities increasing greenhouse gas concentrations in the atmosphere, and the large part of the extra carbon dioxide (the main greenhouse gas) that is absorbed by oceans. Certain massive corals provide historical perspectives on calcification through the presence of dateable annual density banding patterns. Each band is a page in an environmental archive that reveals past responses of growth (linear extension, skeletal density and calcification rate) and provides a basis for prediction of future of coral growth. A second major line of research focuses on the measurement of various geochemical tracers incorporated into the growth bands, allowing the reconstruction of past marine climate conditions (i.e. palaeoclimatology). Here, we focus on the structural properties of the annual density bands themselves (viz. density; linear extension), exploring their utility in providing both perspectives on the past and pointers to the future of calcification on coral reefs. We conclude that these types of coral growth records, though relatively neglected in recent years compared to the geochemical studies, remain immensely valuable aids to unravelling the consequences of anthropogenic climate change on coral reefs. Moreover, an understanding of coral growth processes is an essential pre-requisite for proper interpretation of studies of geochemical tracers in corals.

  2. Large plasma-membrane depolarization precedes rapid blue-light-induced growth inhibition in cucumber (United States)

    Spalding, E. P.; Cosgrove, D. J.


    Blue-light (BL)-induced suppression of elongation of etiolated Cucumis sativus L. hypocotyls began after a 30-s lag time, which was halved by increasing the fluence rate from 10 to 100 micromoles m-2 s-1. Prior to the growth suppression, the plasma-membrane of the irradiated cells depolarized by as much as 100 mV, then returned within 2-3 min to near its initial value. The potential difference measured with surface electrodes changed with an identical time course but opposite polarity. The lag time for the change in surface potential showed an inverse dependence on fluence rate, similar to the lag for the growth inhibition. Green light and red light caused neither the electrical response nor the rapid inhibition of growth. The depolarization by BL did not propagate to nonirradiated regions and exhibited a refractory period of about 10 min following a BL pulse. Fluence-response relationships for the electrical and growth responses provide correlational evidence that the plasma-membrane depolarization reflects an event in the transduction chain of this light-growth response.

  3. Transient growth from the continuous spectrum of a high-speed rapidly-swirling jet (United States)

    Samanta, Arnab; Muthiah, Gopalsamy


    We investigate the possibility for short-time transient growths involving the helical modes of a rapidly-swirling, high-speed jet that has undergone a sub-critical transition via an axisymmetric vortex breakdown. The base flow is extracted from the time-averaged measurements, consisting of the recirculation bubble and its wake. A pseudospectrum analysis complements a local normal-mode based stability analysis in identifying the continuous spectrum, which is further split into a potential and freestream spectrum, where the non-orthogonality between the former type and the existing discrete stable modes is shown to be the main origin of strong transient growths in such flows. As the swirling flow develops post the bubble collapse, this potential mode spectrum widens, increasing the importance of transient growth inside the wake region. The local transient gains calculated at the wake confirms this, where strong growths far outstrips the exponential modal growth at shorter times, especially at the higher helical orders and smaller streamwise wavenumbers. These short-time transients are likely to be a necessary first-step toward the formation of a wavemaker region at the wake of such flows, leading to their eventual spiral breakdown.

  4. Is rapid growth in Internet usage environmentally sustainable for Australia? An empirical investigation. (United States)

    Salahuddin, Mohammad; Alam, Khorshed; Ozturk, Ilhan


    This study estimates the short- and long-run effects of Internet usage and economic growth on carbon dioxide (CO2) emissions using annual time series macro data for Australia for the period 1985-2012. Autoregressive distributive lag (ARDL) bounds and Gregory-Hansen structural break cointegration tests are applied. ARDL estimates indicate no significant long-run relationship between Internet usage and CO2 emissions, which implies that the rapid growth in Internet usage is still not an environmental threat for Australia. The study further indicates that higher level of economic growth is associated with lower level of CO2 emissions; however, Internet usage and economic growth have no significant short-run relationship with CO2 emissions. Financial development has both short-run and long-run significant positive association with CO2 emissions. The findings offer support in favor of energy efficiency gains and a reduction in energy intensity in Australia. However, impulse response and variance decomposition analysis suggest that Internet usage, economic growth and financial development will continue to impact CO2 emissions in the future, and as such, this study recommends that in addition to the existing measures to combat CO2 emissions, Australia needs to exploit the potential of the Internet not only to reduce its own carbon footprint but also to utilize information and communication technology (ICT)-enabled emissions abatement potential to reduce emissions in various other sectors across the economy, such as, power, renewable energy especially in solar and wind energy, agriculture, transport and service.

  5. Phosphorus and other trace elements from secondary olivine in composite mantle xenoliths (CMX) from Cima Volcanic Field (CVF; California, USA): implications for crystal growth kinetics (United States)

    Baziotis, Ioannis; Asimow, Paul; Ntaflos, Theodoros; Boyce, Jeremy; Koroneos, Antonios; Perugini, Diego; Liu, Yongsheng; Klemme, Stephan; Berndt, Jasper


    Phosphorus(P)-rich zones in olivine may reflect excess incorporation of P during rapid growth; zoning patterns may then record growth rate variations (Milman-Barris et al., 2008; Stolper et al., 2009). We report data on interior cuts of two CMX from alkali basalt flows (Mukasa & Wilshire, 1997) in the CVF with second-generation P-rich olivines. In Ci-1-196, a dark layer (~200 μm wide) between lherzolite and websterite is interpreted as a rapidly crystallized melt layer (ML), consisting of Ol+Gl+Pl+Spl+Cpx+Ap+Ilm. Glass (~15 vol%) is variable in composition (P2O5 ≤1.2 wt%, Li 8.22-20.0 ppm). Olivines in the layer have 0.03-0.62 wt% P2O5; P-rich Ol (P2O5 >0.1 wt%) are Fo85-89.3. The lowest P concentrations are consistent with equilibrium with liquid parental to Gl, but the higher concentrations are not. Li concentrations, zoned from 3.84 to 4.90 ppm (core-rim), indicate equilibrium incorporation during crystal growth from a small, evolving melt pool and preservation of this rapidly relaxing gradient. REEs are mostly consistent with equilibrium growth from liquids evolving towards the observed LREE-enriched glass. Most of the clinopyroxenes are diopsides with some augites. Apatite inclusions occur in the rim of P-rich Fo85 and in An54. In Ki-5-301, a dark-coloured area of irregular shape (~200 μm wide) is present along the contact between lherzolite and orthopyroxenite, consisting of Ol+Pl+Gl+Cpx+Spl+Ilm+Ap. It resembles a tabular dyke but is connected to melt-patches infiltrating the host rock. Widespread Glass in the layer has variable composition with two populations not related by fractional crystallization: 1) P2O5 1.02-1.09 wt% and 2) P2O51.62-2.35 wt% (a Gl inclusion in Ol has P2O5 3.57 wt% may have captured melt from the P-rich boundary layer at the interface with the rapidly growing olivine). REEs cluster in the same two groups. Li is as low as 3.66 ppm group 1 and 3-4× higher (9.64-13.3 ppm) in group 2. Olivine occurs as small idiomorphic crystals

  6. Formation and growth of crystal defects in directionally solidified multicrystalline silicon for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ryningen, Birgit


    Included in this thesis are five publications and one report. The common theme is characterisation of directionally solidified multicrystalline silicon for solar cells. Material characterisation of solar cell silicon is naturally closely linked to both the casting process and to the solar cell processing: Many of the material properties are determined by the casting process, and the solar cell processing will to some extend determine which properties will influence the solar cell performance. Solar grade silicon (SoG-Si) made by metallurgical refining route and supplied by Elkem Solar was directionally solidified and subsequently characterised, and a simple solar cell process was applied. Except from some metallic co-precipitates in the top of the ingot, no abnormalities were found, and it is suggested that within the limits of the tests performed in this thesis, the casting and the solar cell processing, rather than the assumed higher impurity content, was the limiting factor. It is suggested in this thesis that the main quality problem in multicrystalline silicon wafers is the existence of dislocation clusters covering large wafer areas. The clusters will reduce the effect of gettering and even if gettering could be performed successfully, the clusters will still reduce the minority carrier mobility and hence the solar cell performance. It has further been pointed out that ingots solidified under seemingly equal conditions might have a pronounced difference in minority carrier lifetime. Ingots with low minority carrier lifetime have high dislocation densities. The ingots with the substantially higher lifetime seem all to be dominated by twins. It is also found a link between a higher undercooling and the ingots dominated by twins. It is suggested that the two types of ingots are subject to different nucleation and crystal growth mechanisms: For the ingots dominated by dislocations, which are over represented, the crystal growth is randomly nucleated at the

  7. Oxidation-Assisted Crack Growth in Single-Crystal Superalloys during Fatigue with Compressive Holds (United States)

    Lafata, M. A.; Rettberg, L. H.; He, M. Y.; Pollock, T. M.


    The mechanism of oxidation-assisted growth of surface cracks during fatigue with compressive holds has been studied experimentally and via a model that describes the role of oxide and substrate properties. The creep-based finite element model has been employed to examine the role of material parameters in the damage evolution in a Ni-base single-crystal superalloy René N5. Low-cycle fatigue experiments with compressive holds were conducted at 1255 K and 1366 K (982 °C and 1093 °C). Interrupted and failed specimens were characterized for crack depth and spacing, oxide thickness, and microstructural evolution. Comparison of experimental to modeled hysteresis loops indicates that transient creep drives the macroscopic stress-strain response. Crack penetration rates are strongly influenced by growth stresses in the oxide, structural evolution in the substrate, and the development of γ ^' } denuded zones. Implications for design of alloys resistant to this mode of degradation are discussed.

  8. Oxidation-Assisted Crack Growth in Single-Crystal Superalloys during Fatigue with Compressive Holds (United States)

    Lafata, M. A.; Rettberg, L. H.; He, M. Y.; Pollock, T. M.


    The mechanism of oxidation-assisted growth of surface cracks during fatigue with compressive holds has been studied experimentally and via a model that describes the role of oxide and substrate properties. The creep-based finite element model has been employed to examine the role of material parameters in the damage evolution in a Ni-base single-crystal superalloy René N5. Low-cycle fatigue experiments with compressive holds were conducted at 1255 K and 1366 K (982 °C and 1093 °C). Interrupted and failed specimens were characterized for crack depth and spacing, oxide thickness, and microstructural evolution. Comparison of experimental to modeled hysteresis loops indicates that transient creep drives the macroscopic stress-strain response. Crack penetration rates are strongly influenced by growth stresses in the oxide, structural evolution in the substrate, and the development of γ ^' } denuded zones. Implications for design of alloys resistant to this mode of degradation are discussed.

  9. Cladding single crystal YAG fibers grown by laser heated pedestal growth (United States)

    Bera, Subhabrata; Nie, Craig D.; Harrington, James A.; Chick, Theresa; Chakrabarty, Ayan; Trembath-Reichert, Stephen; Chapman, James; Rand, Stephen C.


    Rare-earth doped single-crystal (SC) Yttrium Aluminum Garnet (YAG) fibers are excellent candidates for high power lasers. These SC fiber optics combine the favorable low Stimulated Brillouin Scattering (SBS) gain coefficient and excellent thermal properties to make them an attractive alternative to glass fiber lasers and amplifiers. Various rare-earth doped SC fibers have been grown using the laser heated pedestal growth (LHPG) technique. Several cladding methods, including in-situ and post-growth cladding techniques, are discussed in this paper. A rod-in-tube approach has been used by to grow a fiber with an Erbium doped SC YAG fiber core inserted in a SC YAG tube. The result is a radial gradient in the distribution of rare-earth ions. Post cladding methods include sol-gel deposited polycrystalline.

  10. High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

    KAUST Repository

    Saidaminov, Makhsud I.


    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization.

  11. Synthesis, structure, crystal growth and characterization of a novel semiorganic nonlinear optical L-proline lithium bromide monohydrate single crystal (United States)

    Sathiskumar, S.; Balakrishnan, T.; Ramamurthi, K.; Thamotharan, S.


    L-Proline lithium bromide monohydrate (LPLBM), a promising semiorganic nonlinear optical material, was synthesized and single crystals of LPLBM were grown from solution by slow evaporation technique. Single crystal X-ray structure solution reveals that the grown crystal belongs to monoclinic system with space group P21. Presence of various functional groups was identified by FT-IR and FT-Raman spectral analyses. UV-Vis-NIR spectroscopic study shows that the LPLBM crystal possesses 90% of transmittance in the range of 250-1100 nm. Vickers microhardness values, the dielectric constant and dielectric loss of the LPLBM crystal were reported. Elemental analysis by energy dispersive X-ray analysis shows the presence of carbon, nitrogen, oxygen and bromine. The surface morphology of the crystal was investigated using scanning electron microscopic study. The thermal stability of the LPLBM crystal was studied from TGA and DSC analysis. Second harmonic generation efficiency of the LPLBM crystal measured by Kurtz and Perry powder technique using Nd:YAG laser is about 0.3 times that of urea.

  12. Prenatal exposure to traffic pollution: associations with reduced fetal growth and rapid infant weight gain. (United States)

    Fleisch, Abby F; Rifas-Shiman, Sheryl L; Koutrakis, Petros; Schwartz, Joel D; Kloog, Itai; Melly, Steven; Coull, Brent A; Zanobetti, Antonella; Gillman, Matthew W; Gold, Diane R; Oken, Emily


    Prenatal air pollution exposure inhibits fetal growth, but implications for postnatal growth are unknown. We assessed weights and lengths of US infants in the Project Viva cohort at birth and 6 months. We estimated 3rd-trimester residential air pollution exposures using spatiotemporal models. We estimated neighborhood traffic density and roadway proximity at birth address using geographic information systems. We performed linear and logistic regression adjusted for sociodemographic variables, fetal growth, and gestational age at birth. Mean birth weight-for-gestational age z-score (fetal growth) was 0.17 (standard deviation [SD] = 0.97; n = 2,114), 0- to 6-month weight-for-length gain was 0.23 z-units (SD = 1.11; n = 689), and 17% had weight-for-length ≥95th percentile at 6 months of age. Infants exposed to the highest (vs. lowest) quartile of neighborhood traffic density had lower fetal growth (-0.13 units [95% confidence interval (CI) = -0.25 to -0.01]), more rapid 0- to 6-month weight-for-length gain (0.25 units [95% CI = 0.01 to 0.49]), and higher odds of weight-for-length ≥95th percentile at 6 months (1.84 [95% CI = 1.11 to 3.05]). Neighborhood traffic density was additionally associated with an infant being in both the lowest quartile of fetal growth and the highest quartile of 0- to 6-month weight-for-length gain (Q4 vs. Q1, odds ratio = 3.01 [95% CI = 1.08 to 8.44]). Roadway proximity and 3rd-trimester black carbon exposure were similarly associated with growth outcomes. For 3rd-trimester particulate matter (PM2.5), effect estimates were in the same direction, but smaller and imprecise. Infants exposed to higher traffic-related pollution in early life may exhibit more rapid postnatal weight gain in addition to reduced fetal growth.

  13. Ground-based research of LiIO3 and NaClO3 crystal growth under microgravity environment (United States)

    Song, Youting

    Ground-based research of LiIO3 and NaClO3 crystal growth under microgravity environment Youting Song*, Wanchun Chen, Xiaolong Chen Institute of Physics and Beijing National Lab-oratory for Condensed Matter Physics, Beijing, 100080 P. R. China The progress in ground-based research of LiIO3 and NaClO3 crystal growth under micro-gravity environment was reported. (a) A new apparatus used for growth of large size of LiIO3 crystals by the evaporation method has been developed, in which the hydrophobic poly-terafluorothytene micro-filtration (PEFT) film was used to resist the leakage of LiIO3 solution and control the growth rate of LiIO3 crystals along with CaCl2 adsorbent. The pore diameters of PEFT film should be between 0.1-1.0m, and the optimal weight of the adsorbent should be as three times as that of the solvent H2O evaporated. During crystal growth, the solution is re-plenished by a creeping pump to avoid separating the growing crystal from the solution. Using this technique we have obtained good quality LiIO3 crystals in the ground-based experiments. (b) The nucleating experiment of NaClO3 seed-induction was carried out in a ground-based en-vironment, and experimental results showed that seed-induction of NaClO3 played certainly a role of increasing crystal chiral enantiomer excess (cee), which will become the basis of contrast experiment under microgravity environment.

  14. Rapid Growth of Dermatofibrosarcoma Protuberans Associated with Bilateral Adrenalectomy for Cushing’s Syndrome

    Directory of Open Access Journals (Sweden)

    Sadanori Furudate


    Full Text Available We describe a 50-year-old Japanese patient with dermatofibrosarcoma protuberans (DFSP rapidly growing after bilateral adrenalectomy for Cushing’s syndrome that reduced the serum level of cortisol from 17.1 to 0.8 mg/dl. It is known that glucocorticoids decrease the transcriptions of the COL1A1 gene and the PDGFB gene, which is under the direct control of the COL1A1 gene in most DFSP. Therefore, the hypersecretion of glucocorticoids in Cushing’s syndrome might suppress the development of DFSP. To the best of our knowledge, this is the first case of rapid growth of DFSP that may be associated with bilateral adrenalectomy for Cushing’s syndrome.

  15. Crystal growth and characterization of third order nonlinear optical piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) single crystal (United States)

    Pichan, Karuppasamy; Muthu, Senthil Pandian; Perumalsamy, Ramasamy


    The organic single crystal of piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) was grown by slow evaporation solution technique (SEST) at room temperature. The lattice parameters of the grown crystal were confirmed by single crystal X-ray diffraction analysis. Functional groups of P4HBS crystal were confirmed by FTIR spectrum analysis. The optical quality of the grown crystal was identified by the UV-Vis NIR spectrum analysis. The grown crystal has good optical transmittance in the range of 410-1100 nm. In photoluminescence spectrum, sharp emission peaks are observed, which indicates the ultraviolet (UV) emission. The photoconductivity study reveals that the grown crystal has negative photoconductive nature. The thermal behaviour of the P4HBS crystal was investigated by thermogravimetric and differential thermal analysis (TG-DTA). The mechanical stability of grown crystal was analyzed and the indentation size effect (ISE) was explained by Hays-Kendall's (HK) approach and proportional specimen resistance model (PSRM). Chemical etching study was carried out and the etch pit density (EPD) was calculated. The dielectric constant (ε‧) and dielectric loss (tan δ) as a function of frequency were measured for the grown crystal. The solid state parameters such as valence electron, plasma energy, Penn gap and Fermi energy were evaluated theoretically for the P4HBS using the empirical relation. The estimated values are used to calculate the electronic polarizability. The third-order nonlinear optical properties such as nonlinear refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied by Z-scan technique at 632.8 nm using He-Ne laser.

  16. Applying shot boundary detection for automated crystal growth analysis during in situ transmission electron microscope experiments

    Energy Technology Data Exchange (ETDEWEB)

    Moeglein, W. A.; Griswold, R.; Mehdi, B. L.; Browning, N. D.; Teuton, J.


    In-situ (scanning) transmission electron microscopy (S/TEM) is being developed for numerous applications in the study of nucleation and growth under electrochemical driving forces. For this type of experiment, one of the key parameters is to identify when nucleation initiates. Typically the process of identifying the moment that crystals begin to form is a manual process requiring the user to perform an observation and respond accordingly (adjust focus, magnification, translate the stage etc.). However, as the speed of the cameras being used to perform these observations increases, the ability of a user to “catch” the important initial stage of nucleation decreases (there is more information that is available in the first few milliseconds of the process). Here we show that video shot boundary detection (SBD) can automatically detect frames where a change in the image occurs. We show that this method can be applied to quickly and accurately identify points of change during crystal growth. This technique allows for automated segmentation of a digital stream for further analysis and the assignment of arbitrary time stamps for the initiation of processes that are independent of the user’s ability to observe and react.

  17. Direct anisotropic growth of CdS nanocrystals in thermotropic liquid crystal templates for heterojunction optoelectronics. (United States)

    Yuan, Kai; Chen, Lie; Chen, Yiwang


    The direct growth of CdS nanocrystals in functional solid-state thermotropic liquid crystal (LC) small molecules and a conjugated LC polymer by in situ thermal decomposition of a single-source cadmium xanthate precursor to fabricate LC/CdS hybrid nanocomposites is described. The influence of thermal annealing temperature of the LC/CdS precursors upon the nanomorphology, photophysics, and optoelectronic properties of the LC/CdS nanocomposites is systematically studied. Steady-state PL and ultrafast emission dynamics studies show that the charge-transfer rates are strongly dependent on the thermal annealing temperature. Notably, annealing at liquid-crystal state temperature promotes a more organized nanomorphology of the LC/CdS nanocomposites with improved photophysics and optoelectronic properties. The results confirm that thermotropic LCs can be ideal candidates as organization templates for the control of organic/inorganic hybrid nanocomposites at the nanoscale level. The results also demonstrate that in situ growth of semiconducting nanocrystals in thermotropic LCs is a versatile route to hybrid organic/inorganic nanocomposites and optoelectronic devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Organic Crystal Growth Facility (OCGF) and Radiation Monitoring Container Device (RMCD) Groups in (United States)


    The primary payload for Space Shuttle Mission STS-42, launched January 22, 1992, was the International Microgravity Laboratory-1 (IML-1), a pressurized manned Spacelab module. The goal of IML-1 was to explore in depth the complex effects of weightlessness of living organisms and materials processing. Around-the-clock research was performed on the human nervous system's adaptation to low gravity and effects of microgravity on other life forms such as shrimp eggs, lentil seedlings, fruit fly eggs, and bacteria. Materials processing experiments were also conducted, including crystal growth from a variety of substances such as enzymes, mercury iodide, and a virus. The Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at the Marshall Space Flight Center (MSFC) was the air/ground communication channel used between the astronauts and ground control teams during the Spacelab missions. Featured are activities of the Organic Crystal Growth Facility (OCGF) and Radiation Monitoring Container Device (RMCD) groups in the SL POCC during the IML-1 mission.

  19. Effect of controlled crucible movement on melting process and carbon contamination in Czochralski silicon crystal growth (United States)

    Liu, Xin; Han, Xue-Feng; Nakano, Satoshi; Kakimoto, Koichi


    In Czochralski silicon (CZ-Si) crystal growth, packed Si chunks experience collapse and volume shrinkage during the melting process. The axial movements of the crucible and the melting of the Si feedstock lead to dynamic thermal and flow fields and affect mass transport. To study the effect of crucible movement on the melting process and carbon (C) contamination, the cases of fixed and lifting crucible were investigated by the transient global simulation with dynamic mesh deformation. The gap width between the gas-guide and the top surface of Si feedstock was kept constant during the crucible lifting process. Impurity and species transport in Si feedstock and argon gas was investigated for the cases with the fixed and lifting crucibles. The comparison of C accumulation processes indicated that the lifting crucible case resulted in higher C contamination than that found in the fixed crucible case. Furthermore, lifting crucible cases with different gap widths were investigated to elaborate strategies for controlling the crucible movement for its effect on the melting process and C contamination in CZ-Si crystal growth. It was observed that the optimum gap width for C reduction results from the trade-off between the back diffusion and gas convection.

  20. Screw dislocations in complex, low symmetry oxides: core structures, energetics, and impact on crystal growth. (United States)

    Shahsavari, Rouzbeh; Chen, Lu


    Determining the atomic structure and the influence of defects on properties of low symmetry oxides have long been an engineering pursuit. Here, we focus on five thermodynamically reversible monoclinic and orthorhombic polymorphs of dicalcium silicates (Ca2SiO3)-a key cement constituent-as a model system and use atomistic simulations to unravel the interplay between the screw dislocation core energies, nonplanar core structures, and Peierls stresses along different crystallographic planes. Among different polymorphs, we found that the α polymorphs (α-C2S) has the largest Peierls stress, corresponding to the most brittle polymorph, which make it attractive for grinding processes. Interestingly, our analyses indicate that this polymorphs has the lowest dislocation core energy, making it ideal for reactivity and crystal growth. Generally, we identified the following order in terms of grinding efficiency based on screw dislocation analysis, α-C2S > αH-C2S > αL-C2S > β-C2S > γ-C2S, and the following order in term of reactivity, α -C2S > αL-C2S > γ-C2S > αH-C2S > β-C2S. This information, combined with other deformation-based mechanisms, such as twinning and edge dislocation, can provide crucial insights and guiding hypotheses for experimentalists to tune the cement grinding mechanisms and reactivity processes for an overall optimum solution with regard to both energy consumption and performance. Our findings significantly broaden the spectrum of strategies for leveraging both crystallographic directions and crystal symmetry to concurrently modulate mechanics and crystal growth processes within an identical chemical composition.