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

Cover of: Crystal growth of CdTe in space and thermal field effects on mass flux and morphology |

Published by National Aeronautics and Space Administration in [Washington, DC .

Written in English

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Subjects:

  • Materials -- Effect of space environment on.,
  • Cadmium compounds.

Edition Notes

Book details

StatementH, Wiedemeier.
SeriesNASA-CR -- 183263., NASA contractor report -- NASA CR-183263.
ContributionsUnited States. National Aeronautics and Space Administration.
The Physical Object
FormatMicroform
Pagination1 v .
ID Numbers
Open LibraryOL15295009M

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Get this from a library. Crystal growth of CdTe in space and thermal field effects on mass flux and morphology. [H Wiedemeier; United States. National Aeronautics and Space Administration.]. The dependence of the mass flux on source temperature was experimentally established.

The CdTe synthesis and pretreatment procedures are being developed that yield considerable improvements in mass transport rates, and mass fluxes which are independent of the amount of source material. A higher degree of stoichiometric control of CdTe than before was achieved during this period of investigation.

Based on this, a CdTe crystal growth Author: H. Wiedemeier. Secondly, CdTe also has a low critical-resolved shear stress (CRSS) for slip. Hence CdTe is exposed to greater thermal stress during crystal growth, and this stress has a proportionately greater effect than in many other materials.

A third factor is the low stability of the sphalerite form of CdTe. The thermal fields of two Bridgman-like configurations, representative of real systems used in prior experiments for the detached growth of CdTe and Ge crystals, are : Carmen Stelian. Exploratory crystal growth is a fundamental and practical aspect of materials chemistry that can result in the discovery of new materials exhibiting desired and even unexpected physical properties.

The process involves control over the size, morphology and exposed surface features of crystals, as well as the discovery of materials with novel compositions that crystallize in new structure types.

OF COMMERCIAL CRYSTAL GROWTH IN SPACE ANNUAL REPORT September 1, to Aug growth of bulk mercury halide and cadmium telluride crystals. A laser doppler CRYSTAL GROWTH OF CdTe IN SPACE AND THERMAL FIELD EFFECTS ON MASS FLUX AND MORPHOLOGY (Rensselaer Polytechnic Institute).

MANAGEMENT SUMMARY. Rudolph and Kakimoto have outlined various means of controlling uniformity and stability of crystal growth from the melt by complementing internal parameters (e. g., temperature field, pressure, growth velocity, etc.) by external influences, for example, mechanical, electrical, and mechanical fields.

Stirring during crystal growth can often be essential to enhance solute transport through the growth fluid, to. The thermal conductivity, electrical conductivity, and Seebeck coefficient of a vapor-grown CdTe and two melt-grown Cd Zn Te crystals, including In-doped CZT and un-doped CZT samples, were measured from room temperature to o C.

The measured thermal conductivity of CdTe was higher than the two CdZnTe samples in the low temperature range and the three sets of. condition is the prime factor controlling the deposition process. Growth of crystals can be conside red to compress these steps [28 ].

Achievement of super saturation or super cooling. Formation of crystal nucleus of microscopic size. Successive growth of crystals to yield distinct faces. CRYSTAL GROWTH TECHN IQUES. These should be labeled and then placed where they will not be disturbed.

Students will examine the crystals the next day with hand lenses and with the field microscopes, recording results in their science notebooks.

Variable 2. Students will investigate the effect of stirring or shaking crystal-making solution on crystal growth. Abstract. This frontier article focuses on the use of flux crystal growth for the preparation of new actinide containing materials, reviews the history of flux crystal growth of uranium containing phases, and highlights the recent advances in the field.

Specifically, we discuss how recent developments in f-element materials, fueled by accelerated materials discovery via crystal growth, have led to the. The majority of experimenters have reported about the strange detachment of samples from the crucibles during Bridgman crystal growth in space.

This so-called detached growth can take several aspects, including bubbles at the interface between sample and crucible, large decrease of the sample diameter (often called necking), and a constant small gap between the crystal and the crucible. The response of molecular crystal structures to changes in externally applied conditions such as temperature and pressure are the result of a complex balance between strong intramolecular bonding, medium strength intermolecular interactions such as hydrogen bonds, and weaker intermolecular van der Waals contacts.

At high pressure the additional thermodynamic requirement to fill space. Crystal Growth in Space Objective Investigate how crystals form when materials transition from their liquid to their solid state.

NASA Challenge You are a scientist astronaut working in the laboratory of the International Space Station. Use the materials below to grow the largest crystal you can to help scientists on earth design a new medicine.

The presence of crystal defects in the material can change the mechanical, physical as well as the optical properties of material. Defect can affect the strength of the material. Crystal growth and lattice parameters of rare- earth doped yttrium phosphate, arsenate and vanadate prepared by the oscillating temperature flux technique.

Cryst. In general, crystal growth involves a phase transformation i.e. change of a substance from one state to another. The basic conditions under which the crystal growth.

occurs are given below. a change from the liquid phase to the solid occurs by crystallization from a melt or a solution. Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors.

Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited. New authors in Crystal Growth & Design are making important contributions to the field and the community.

Read the Virtual Issue. View Virtual Issues from Crystal Growth & Design. Effect of Radius on Crystal Structure Selection in III–V Nanowire Growth.

Erik K. Mårtensson. Handbook of Crystal Growth, 2nd Edition Volume IIA (Basic Technologies) presents basic growth technologies and modern crystal cutting methods.

Particularly, the methodical fundamentals and development of technology in the field of bulk crystallization on both industrial and research scales are explored. After an introductory chapter on the formation of minerals, ruling historically the basic crystal.

Growth and Morphology of Crystals reason for that rock-crystals took a variety of polyhedral forms was growth rate anisotropy, i.e. growth rates were different in different crystallographic directions (5). The concept of “growth rate anisotropy” is the most basic concept of the present day’s science of crystal growth.

The effect of a strong magnetic field on protein crystal growth is a new research field. Here, we review research on protein crystallization in magnetic fields, including magnetic orientation of protein crystals, magnetic control of effective gravity on earth, formation of protein crystals in various effective gravity, magnetic improvement in crystal quality, magnetic increase in viscosity of.

growth rate of crystals grown from the flux is generally more than hundred times slower than in melt growth. Furthermore, crystals prepared from the flux using stationary crucibles are typically of small size due to multi nucleation, although the size can be improved using.

crystal growth, will be discussed. Finally crystals possess an internal structure, an external shape and consequently a finite size (or size distribution in the case of a quantity of crystals). These parameters determine many bulk properties of a given crystalline material, such as dissolution rate, bio-availability, color, flow properties etc.

The book also focuses on the determination of density scale-height profiles, geomagnetic effects in the exosphere, and gravity waves and tidal winds in the equatorial thermosphere. The selection is a dependable source of data for readers interested in space research. Flux Crystal Species Flux Controlling gradients (i.e., Thermal fluctuations, 10 fs Growth time, hr.

Furnace -scale Complicated geometry Ampoule-scale Fluid mechanics Atomic-scale Liquid configuration analysis on many scales crystal growth system Melt Gas Hotter Cooler Crystal. The crystal may also be removed and its mass measured on a balance. Periodically observe the fluid flow associated with the crystal’s growth by directing the light beam of a slide projector through the box to a projection screen.

Observe plumes around the shadow of the crystal. Convection currents in the growth solution distort the light. Higashitani et al. () studied the effects of magnetic field on formation of CaCO 3 crystals from the reaction between solutions of CaCl 2 and Na 2 CO 3, having found that (1) the nucleation frequency of CaCO 3 crystals is suppressed but the growth of crystals is accelerated, if the exposed magnetic flux density is greater than about T.

Above: The surface of this crystal grown by the Bridgman method is visibly smoother where it was detached from the container wall. The "hands off" growth of detached Bridgman crystals creates fewer defects in the crystals' internal structure.

Image courtesy MSFC. Szofran explains: "When crystal growth takes place in contact with the container wall, the container pushes on the crystal.

Crystal defect, imperfection in the regular geometrical arrangement of the atoms in a crystalline solid. These imperfections result from deformation of the solid, rapid cooling from high temperature, or high-energy radiation (X-rays or neutrons) striking the solid. Located at single points, along.

the effect of crystal faces like {} and {} and the relaxation of structure on surfaces while calculating the growth morphology. These faces correspond to large inter-planer spacing and required due consideration. On the other hand, Ashley et al. [14] have considered above facet while computing the growth morphology but they predicted the.

Journal of Crystal Growth (v, #1) Contents IWMCG-5 (v-viii). Preface (). A bottom–up multiscale view of point-defect aggregation in silicon by Talid Sinno (). A multiscale computational framework is presented for modeling and simulation of point-defect aggregation in crystalline silicon.

Large-scale molecular dynamics simulations. T1 - Effects of magnetic fields on crystal growth. AU - Kao, A. AU - Pericleous, K. AU - Patel, M. AU - Voller, Vaughan R. PY - /11/4. Y1 - /11/4. N2 - The effects of a constant uniform magnetic field on thermoelectric currents during dendritic solidification were investigated using a two-dimensional enthalpy based numerical model.

tween space groups: a useful tool in crystal chemistry, published inshowed the way to the application of crystallographic group theory in crystal chemistry. The present book is based on this article and on his manuscripts for several courses on this.

Crystals grown in space do not suffer this problem due to the lack of gravity, although the acceleration of a spacecraft or the movements of astronauts can still cause defects to develop in. crystal growth process has been instrumental in the discovery of the majority of these new materials.

This frontier article focuses on the use of flux crystal growth for the preparation of new actinide containing materials, reviews the history of flux crystal growth of uranium containing phases, and highlights the recent advances in the field.

Excursus: Microstructure of a casting. Polygonal crystal growth also explains the typical three-zone microstructure of a solidified casting block (primary microstructure).Such a casted block is also called the vicinity of the mold wall, a very fine-grained structure with roundish grains (globulites) forms due to the strong isotropic undercooling caused by the cool mold wall (zone I).

Analysis of a three-dimensional phase-field model for solidification under a magnetic field effect. André Ferreira e Pereira and Gabriela Planas. Investigating the Effects of Anisotropic Mass Transport on Dendrite Growth in High Energy Density Lithium Batteries.

Theory of Crystal Growth Morphology. Robert F. Sekerka. Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth.

A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to. Since the growth of ice crystals results in greater order, or a decrease in entropy, some have attempted to justify the theory of evolution by an analogy to crystal growth.

This paper will discuss ice crystal growth, the second law of thermodynamics, and. Two-dimensional (2D) transient numerical simulations are performed to investigate the evolution of the thermal and flow fields during the growth of multi-crystalline silicon ingots with two different silicon feedstock capacities, kg and kg.

The simulation results show that there are differences in the structure of the melt flow. In the kg case, there is a reduction in the.Crystal growth is the increase in size (or more accurately “characteristic length”) of crystals as solute is deposited from solution. The relationship between supersaturation, nucleation, and growth is defined by a well-known set of (somewhat simplified) equations first outlined by Nyvlt (Journal of Crystal Growth, Volumes 3–4, 3.

Crystal Growth Once a small crystal seed has formed, (either from homogeneous or heterogeneous nucleation), it will continue to grow by advancing the crystal/liquid interface. Here the obstacle is no longer the creation of new interface but is limited more by the rate at which molecules can move in, align and grow new crystal layers.

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