The first- and second-order isothermal phase transitions in Fe3Ga-type compounds

2019 ◽  
Vol 75 (6) ◽  
pp. 1024-1033 ◽  
Author(s):  
Anatoly M. Balagurov ◽  
Nataliya Yu. Samoylova ◽  
Ivan A. Bobrikov ◽  
Sergey V. Sumnikov ◽  
Igor S. Golovin
Keyword(s):  
Isothermal Annealing ◽  
Early Stage ◽  
Structural Features ◽  
Nucleation And Growth ◽  
Second Order ◽  
Constant Growth Rate ◽  
Phase Nucleation ◽  
Kinetics Of ◽  
Constant Growth

Structural features and kinetics of the transition between ordered metastable b.c.c.-derived D03 and equilibrium f.c.c.-derived L12 phases of Fe–xGa alloys (x = 27.2% and 28.0%) have been analyzed by in situ real-time neutron diffraction during isothermal annealing in the temperature range 405–470°C. It has been revealed that the transition proceeds with alternation of the first- and second-order phase transformations according to a D03 → A2 → A1 → L12 scheme, where A2 and A1 are disordered b.c.c. and f.c.c. structures. Deformations of the crystal lattice that arise due to these transitions are determined. The kinetics of the L12 phase nucleation and growth were analyzed in the frame of the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model; however, only the early stage of the D03 → L12 transition is well described by the JMAK equation. The value of the Avrami exponent corresponds to the constant growth rate of the new L12 phase and decreasing nucleation rate in the Fe–27.2Ga alloy and indicates the presence of pre-existing nucleation centres of the L12 phase in the Fe–28.0Ga alloy.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

GROWTH OF OXIDE LAYER ON GERMANIUM (011) SUBSTRATE UNDER DRY AND WET ATMOSPHERES

1999 ◽  
Vol 06 (06) ◽  
pp. 1053-1060 ◽  
Author(s):  
N. TABET ◽  
J. AL-SADAH ◽  
M. SALIM
Keyword(s):  
Simple Model ◽  
Oxide Film ◽  
Growth Kinetics ◽  
Photoelectron Spectroscopy ◽  
Early Stage ◽  
X Ray ◽  
Apparent Thickness ◽  
Different Temperatures ◽  
Kinetics Of

X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the oxidation of (011) Ge substrates. The sample surfaces were CP4-etched, then annealed in situ, at different temperatures, for various durations. Dry and wet atmospheres were used. The oxidation rate during the early stage was increased by the presence of moisture in the atmosphere. A simple model was used to define and determine an apparent thickness of the oxide film from XPS measurements. The time dependence of the apparent thickness is consistent with a partial coverage of the surface by oxide islands. The growth kinetics of the oxide islands obeys a nearly cubic law.

Recrystallization of AA1050 Studied by 3DXRD

2006 ◽  
Vol 519-521 ◽  
pp. 1569-1578
Author(s):  
Dorte Juul Jensen
Keyword(s):  
Single Crystals ◽  
High Energy ◽  
Nucleation And Growth ◽  
X Rays ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
X Ray ◽  
3 Dimensional ◽  
Kinetics Of

By 3 dimensional X-ray diffraction (3DXRD) using high energy X-rays from synchrotron sources it is possible to study in-situ the nucleation and growth during recrystallization. In this paper it is described and discussed how 3DXRD can supplement EBSP measurements of nucleation and growth. Three types of studies are considered: i) orientation relationships between nuclei and parent deformed matrix, ii) recrystallization kinetics of individual bulk grains and iii) filming of growing grains in deformed single crystals.

Direct Observations of the Growth of Sputtered Silver on Substrates of Graphite and Muscovite MICA

1976 ◽  
Vol 34 ◽  
pp. 648-649
Author(s):  
J. S. Maa ◽  
J. I. Lee ◽  
Thomas E. Hutchinson
Keyword(s):  
Surface Defects ◽  
Chemical Interaction ◽  
Early Stage ◽  
Ion Beam ◽  
Substrate Surface ◽  
Nucleation And Growth ◽  
Graphite Substrate ◽  
Short Period ◽  
Silver Islands

The nucleation and growth of sputtered thin films are controlled by several important factors such as nucleus mobility, substrate surface defects, substrate/ overgrowth chemical interaction, and residual gasses, which depend upon the properties of substrate-overgrowth materials and/or the deposition conditions. The effects of nucleus mobility and substrate surface defects on the nucleation and growth of in situ ion beam sputtered thin silver films have been investigated in detail using in situ electron microscopy. Silver has been sputter deposited on the basal plane of single crystal graphite substrate at temperatures ranging from 350°C to 500°C. The results obtained show that the deposition process in the case of silver on graphite is controlled by the nucleus mobility on the substrate surface. The silver islands with sizes of 20Å to 100Å at the early stage of growth are highly mobile on the graphite substrate. The migration of silver islands from one position to another occurs in a very short period of time and the distance of the island migration varies from less than 100Å to several hundred angstroms, as shown in Figure la and lb.

Nucleation and Growth Kinetics of ZnO Nanoparticles Studied by in Situ Microfluidic SAXS/WAXS/UV–Vis Experiments

Langmuir ◽  
2019 ◽  
Vol 35 (36) ◽  
pp. 11702-11709 ◽  
Author(s):  
Maria Herbst ◽  
Eddie Hofmann ◽  
Stephan Förster
Keyword(s):  
Growth Kinetics ◽  
Zno Nanoparticles ◽  
Nucleation And Growth ◽  
Kinetics Of

In situ non-aqueous nucleation and growth of next generation rare-earth-free permanent magnets

2015 ◽  
Vol 17 (2) ◽  
pp. 1070-1076 ◽  
Author(s):  
Hyojung Yoon ◽  
Aoran Xu ◽  
George E. Sterbinsky ◽  
Dario A. Arena ◽  
Ziying Wang ◽  
...  
Keyword(s):  
Rare Earth ◽  
Room Temperature ◽  
Permanent Magnets ◽  
Bulk Material ◽  
Nucleation And Growth ◽  
Time Resolved ◽  
Energy Product ◽  
Formation Kinetics ◽  
Kinetics Of

In situ time resolved XAS measurements are applied to investigate the phase formation kinetics of metastable cobalt carbide nanoparticles using polyol reduction chemistry. The resulting material exhibits an energy product of greater than 20.7 kJ m−3 at room temperature before compaction, a vastly improved coercivity compared to pure bulk material.

scholarly journals Action of Chlorhexidine Digluconate against Yeast and Filamentous Forms in an Early-Stage Candida albicans Biofilm

2002 ◽  
Vol 46 (11) ◽  
pp. 3522-3531 ◽  
Author(s):  
Peter A. Suci ◽  
Bonnie J. Tyler
Keyword(s):  
Candida Albicans ◽  
Biofilm Formation ◽  
Early Stage ◽  
Cell System ◽  
Accurate Estimation ◽  
Interfacial Region ◽  
In Situ Method ◽  
The Difference ◽  
Kinetics Of

ABSTRACT An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded onto the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.

Structural Re-Organization Kinetics of Nanocrystalline Pt Films during In Situ Annealing

2012 ◽  
Vol 323-325 ◽  
pp. 149-154 ◽  
Author(s):  
Wolfgang Gruber ◽  
Sujoy Chakravarty ◽  
Carsten Baehtz ◽  
Harald Schmidt
Keyword(s):  
Activation Energy ◽  
Bragg Peak ◽  
Isothermal Annealing ◽  
Direct Proof ◽  
In Situ Xrd ◽  
Columnar Grains ◽  
Pt Films ◽  
Heating Up ◽  
Kinetics Of

In this work we investigated the structural re-organization of thin nanocrystalline Pt films in the temperature range between 250 °C and 400 °C by in-situ XRD, GIXRD and XRR synchrotron experiments. A re-orientation of (111) atomic planes and a relaxation of residual stress occurs. After heating up, Bragg peak fringes can be observed in the diffractograms. They are a direct proof that the Pt films are built of (111) columnar grains which essentially reach the whole film thickness of about 40 nm. During isothermal annealing a relaxation of the dispersion parameter of the atomic planes takes place which is associated with an activation energy of (0.4 ± 0.1) eV.

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