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in subjects: "Nucleation"

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Activation Volume and Energy for Dislocation Nucleation in Multi-Principal Element Alloys

Paper describes study evaluating incipient plasticity in multi-principal element alloys, CoCrNi, CoCrFeMnNi, and Al0.1CoCrFeNi by nano-indentation and compared with pure Ni.

Date: February 23, 2019

Creator: Mridha, Sanghita; Sadeghilaridjani, Maryam & Mukherjee, Sundeep

Item Type: Article

Partner: UNT College of Engineering

open access

The Emerging Roles of mTORC1 in Macromanaging Autophagy

Review critically analyzes current literature to provide an integrated view of how rapamycin complex 1 (mTORC1) regulates various steps of the autophagy process.

Date: September 24, 2019

Creator: Dossou, Akpedje S. & Basu, Alakananda

Item Type: Article

Partner: UNT Health Science Center

open access

Nucleation and growth in electrodeposition of thin copper films on pyrolytic graphite

Electrodeposition of Cu on graphite electrodes was studied, with emphasis on nucleation. Various ex-situ and in-situ methods were investigated for determining the number density of nuclei. Two direct methods were studied (scanning electron microscopy and scanning tunneling microscopy); indirect determinations included Raman spectroscopy and analysis of potentiostatic current transients. Though some of the techniques correctly predicted the nucleation densities under special conditions, SEM was … more

Date: May 1, 1992

Creator: Kinaci, F. S. & Muller, R. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Large area silicon sheet task low-cost silicon solar array project. Fourth quarterly progress report, September 27, 1976--December 31, 1976

The seeded growth furnace with a slotted molybdenum susceptor has been operated during the past quarter. The susceptor design permits flat sheets of refractory materials to be used in making up the tray. Fused quartz and sapphire trays were used. Local surface cooling was obtained by means of a water-cooled cold finger. Seeded surface growth has been obtained in this furnace using a seed with (111) axis and (112) principal faces. The silicon grown out of solution has a region approximately 3 mm… more

Date: January 7, 1977

Creator: Garfinkel, M. & Hall, R. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Porous rigid-plastic materials containing rigid inclusions: yield function, plastic potential, and void nucleation

In this paper, the effect on constitutive behavior of the presence of rigid particles, embedded in and bonded to a rigid-plastic porous matrix, is examined. It is shown that the yield function is altered, and that the familiar concept of the yield function as a plastic potential must be used more carefully. The results also show how a void nucleation mechanism could destabilize, causing rapid bulk softening and failure.

Date: July 1, 1976

Creator: Gurson, A L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Continuum Theory of Ductile Rupture by Void Nucleation and Growth. Part I. Yield Criteria and Flow Rules for Porous Ductile Media

Widely used constitutive laws for engineering materials assume plastic incompressibility and no effect on yield of the hydrostatic component of stress. However, void nucleation and growth (and thus bulk dilatancy) are commonly observed in some processes which are characterized by large local plastic flow, such as ductile fracture. The purpose of this work is to develop approximate yield criteria and flow rules for porous (dilatant) ductile materials, showing the role of hydrostatic stress in pl… more

Date: September 1, 1975

Creator: Gurson, A. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Computer simulation of recrystallization in the presence of second phase particles

Recrystallization in the presence of inert second-phase particles has been simulated with a Monte Carlo technique. The technique is the same one as has been employed successfully to model grain growth, recrystallization and grain growth in the presence of second-phase particles. The results show that at low stored energies, the particles retard the growth of recrystallization nuclei and can prevent the recrystallization process from going to completion. At high enough stored energies, however, … more

Date: January 1, 1989

Creator: Rollett, A. D.; Srolovitz, D. J.; Doherty, R. D.; Anderson, M. P. & Grest, G. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nucleation and dynamics of vortices in type-II superconductors

The one- and two-dimensional Ginzburg-Landau equations are numerically integrated in a slab geometry, which is appropriate for comparison to experimental work done on films. When two-dimensional variations become energetically favorable, a vortex is found to nucleate and move to the center of the film with the Gibbs free energy decreasing during the process. An important process by which the energy is lowered during this nucleation procedure is found to be the savings in condensation energy ari… more

Date: March 1, 1977

Creator: Balley, R. E.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Effects of trapping and detrapping of helium on void nucleation

A model of steady-state void nucleation in the presence of mobile helium has recently been developed. The model is based on a reaction-rate formulation of nucleation theory and includes vacancy, interstitial, and gas capture; vacancy emission; and gas emission by three mechanisms--thermal detrapping, radiation displacement, and interstitial knockout of helium from voids ''filled'' with gas. The free (interstitial) helium concentration, the free-vacancy concentration, and nucleation rates are ca… more

Date: January 1, 1977

Creator: Hall, B. O. & Wiedersich, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microstructural simulations of dynamic recrystallization

A Monte Carlo model for the simulation of static recrystallization and grain growth has been adapted for dynamic recrystallization by adding recrystallization nuclei and stored energy continuously with time. The results of the simulations have shown that many of the essential features of dynamic recrystallization are reproduced. The stored energy of the system, which may be interpreted as the flow stress, goes through a maximum and then decays, monotonically under some conditions and otherwise … more

Date: January 1, 1989

Creator: Rollett, A. D.; Srolovitz, D. J. & Luton, M. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanisms for the deposition of thin metallic films by laser driven gas phase reactions

Gas phase processing makes laser deposition over large areas possible but homogeneous nucleation of large atomic clusters must be avoided if films are to be produced. Clusters can be highly variable in size from a few atoms to significant fractions of a micrometer. If conditions do not allow for complete quenching of the clusters produced in the gas phase, these clusters can arrive at the substrate with sufficient energy to self sinter into homogeneous films which are substantially different fr… more

Date: January 1, 1986

Creator: Jervis, T. R.; Menon, S. K.; Joyce, E. L. & Carroll, D. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fatigue crack morphology in 304 stainless steel cycled at constant stress amplitude. [Nucleation and propagation modes]

A study is made to determine which modes of nucleation and propagation are operating during elevated temperature fatigue of 304 stainless steel. Cracks are nucleated at coarse slip bands, and microstructural features such as inclusions and grain boundaries are not important either as sites of initiation or as obstacles to propagation. One of the major effects of stress amplitude is that the number of cracks nucleated increases rapidly in part because increasing the stress amplitude increases th… more

Date: January 1, 1977

Creator: Turner, A. P. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Large area silicon sheet task low-cost silicon solar array project. Fifth quarterly progress report, January 1, 1977--April 1, 1977

The seeded growth furnace with the slotted molybdenum susceptor has been operated during the past quarter. Flat sheets of sapphire were used as the tray, and local cooling at the tin-silicon alloy surface was provided by a symmetric water-cooled jet. The silicon surface growth obtained during the past quarter has been consistently polycrystalline. This poor growth is attributed to impurities in the seeded growth furnace, caused by leakage into the system. Two sources have been identified: deter… more

Date: April 12, 1977

Creator: Garfinkel, M. & Hall, R. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Effect of carbon on void formation in neutron-irradiated nickel. [Trapping mechanism, nucleation suppression]

A study was made of neutron irradiation at 110/sup 0/C producing octahedral voids in high purity nickel samples containing up to 84 wt ppm carbon. The kinetics of void size, formation, and density with increasing carbon content is discussed. It was found that the effect of carbon was mainly to suppress void nucleation, with little or no effect on void growth. Also a trapping mechanism is proposed. There are 64 references. (JFP)

Date: February 1, 1977

Creator: Sorensen, S. M., Jr.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Relative stability of silicon self-interstitial defects

{l_brace}311{r_brace} defects and dislocation loops are formed after ion-implantation and annealing of a silicon wafer. Recent Transmission Electron Microscopy studies by Li and Jones have shown that sub-threshold dislocation loops nucleate from {l_brace}311{r_brace} defects. In our study, the conjugate gradient method with the Stillinger Weber potential is used to relax different configurations such as {l_brace}311{r_brace} defects with a maximum of five chains and perfect dislocation loops. F… more

Date: April 11, 2000

Creator: Subramanian, G; Jones, K S; Law, M E; Caturla, M J; Theiss, S & Diaz de la Rubia, T

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Investigation of Gettering Mechanisms in Crystalline Silicon: Final Subcontract Report, 21 July 1997--30 September 2003

In this investigation, various aspects of the mechanisms of gettering contaminant impurities away from device active regions in Si have been systematically conducted. Also systematically studied are the modeling of electrical activity of metallic precipitates in Si based on the Schottky effect. With these studies, our knowledge of gettering in Si and on the electrical activity of metallic precipitates in Si has become substantially complete in the sense that interpretations of major experimenta… more

Date: May 1, 2004

Creator: Tan, T. Y.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Three-Dimensional Analysis of Voids in AM60B Magnesium Tensile Bars Using Computed Tomography Imagery

In an effort to increase automobile fuel efficiency as well as decrease the output of harmful greenhouse gases, the automotive industry has recently shown increased interest in cast light metals such as magnesium alloys in an effort to increase weight savings. Currently several magnesium alloys such as AZ91 and AM60B are being used in structural applications for automobiles. However, these magnesium alloys are not as well characterized as other commonly used structural metals such as aluminum. … more

Date: May 1, 2001

Creator: Waters, A M

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

LORENTZ PHASE IMAGING AND IN-SITU LORENTZ MICROSCOPY OF PATTERNED CO-ARRAYS.

Understanding magnetic structures and properties of patterned and ordinary magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The key feature to such success is the ability to achieve visual quantitative information on domain configurations with a maximum ''magnetic'' resolution. Several methods have been developed to meet these demands (Kerr and Faraday effects, differential phase contrast microscopy, magnetic force microscopy, … more

Date: August 3, 2003

Creator: VOLKOV,V. V. ZHU,Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Carbon Nanotube Atomic Force Microscopy for Proteomics and Biological Forensics

The Human Genome Project was focused on mapping the complete genome. Yet, understanding the structure and function of the proteins expressed by the genome is the real end game. But there are approximately 100,000 proteins in the human body and the atomic structure has been determined for less than 1% of them. Given the current rate at which structures are being solved, it will take more than one hundred years to complete this task. The rate-limiting step in protein structure determination is th… more

Date: January 1, 2002

Creator: Noy, A.; De Yoreo, J. J. & Malkin, A. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Surface Dynamics during Environmental Degradation of Crystal Surfaces

Using in situ optical microscopy and scattering measurements, we have followed the evolution of surface morphology during etching and measured surface etching rates as a function of humidity and undersaturation. From our experiments to date we have developed the following picture of etch pit formation on KDP crystal surfaces. Pit formation is characterized by a nucleation and growth process: the introduction of water creates a condition of undersaturation at the crystal surface. The equilibrium… more

Date: February 21, 2001

Creator: Whitman, P; DeYoreo, J; Land, T; Miller, E; Suratwala, T; Thorsness, C et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

''The Incubation Period for Void Swelling and its Dependence on Temperature, Dose Rate, and Dislocation Structure Evolution''

Void swelling in structural materials used for nuclear reactors is characterized by an incubation period whose duration largely determines the usefulness of the material for core components. Significant evolution of the dislocation and void microstructures that control radiation-induced swelling can occur during this period. Thus, a theory of incubation must treat time-dependent void nucleation in combination with dislocation evolution, in which the sink strengths of voids and dislocations chan… more

Date: June 13, 2002

Creator: Surh, M. P.; Sturgeon, J. B. & Wolfer, W. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A study of transient particle coarsening

Efforts were concentrated on numerically modeling the time-dependent particle coarsening (Ostwald ripening) process. Four models were included: Lifshsitz-Slyozov-Wagner, Brailsford and Wynblatt, Marqusee and Ross, and Marder. The simulations monitored the particle size distribution (PSD) as a function of time; initial PSDs were derived from classical nucleation theory. The ripening kinetics can be represented as a plot of the second moment of normalized PSD vs time. A geometric correction facto… more

Date: October 19, 1992

Creator: Hoyt, J. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Boron Addition to Model Austenitic Steels and void Nucleation

Fe-15Cr-16Ni, -0.25Ti, -500appmB, and -0.25Ti-500appmB have been irradiated in FFTF/MOTA over a wide range of dose rate which covers more than two orders difference in magnitude, within the very limited temperature range of 387-444 C. The effects of dose rate and boron addition on swelling are examined. Lower dose rates increase the swelling by shortening the incubation dose for swelling. Addition of boron does not significantly change the swelling nor the dose rate dependence of swelling for b… more

Date: October 30, 2003

Creator: Okita, T; Wolfer, W G; Garner, F A & Sekimura, N

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nanoscale Twinning and Martensitic Transformation in Shock-Deformed BCC Metals

Shock-induced twinning and martensitic transformation in BCC-based polycrystalline metals (Ta and U-6wt%Nb) have been observed and studied using transmission electron microscopy (TEM). The length-scale of domain thickness for both twin lamella and martensite phase is found to be smaller than 100 nm. While deformation twinning of {l_brace}112{r_brace}<111>-type is found in Ta when shock-deformed at 15 GPa, both twinning and martensitic transformation are found in Ta when shock-deformed at … more

Date: March 22, 2005

Creator: Hsiung, L L

Item Type: Article

Partner: UNT Libraries Government Documents Department