scholarly journals Evidence for a High Temperature Whisker Growth Mechanism Active in Tungsten during In Situ Nanopillar Compression

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2429
Author(s):  
Gowtham Jawaharram ◽  
Christopher Barr ◽  
Khalid Hattar ◽  
Shen Dillon
Keyword(s):  
Growth Mechanism ◽  
Laser Heating ◽  
Whisker Growth ◽  
Heating Surface ◽  
Surface Oxidation ◽  
Temperature Deformation ◽  
Compression Tests ◽  
Transmission Electron ◽  
Increasing Temperature

A series of nanopillar compression tests were performed on tungsten as a function of temperature using in situ transmission electron microscopy with localized laser heating. Surface oxidation was observed to form on the pillars and grow in thickness with increasing temperature. Deformation between 850 °C and 1120 °C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2O3-stabilized ZrO2 indenter. The constraint imposed by the surface oxidation is hypothesized to underly this mechanism for localized plasticity, which is generally the so-called whisker growth mechanism. The results are discussed in context of the tungsten fuzz growth mechanism in He plasma-facing environments. The two processes exhibit similar morphological features and the conditions under which fuzz evolves appear to satisfy the conditions necessary to induce whisker growth.

In situ transmission electron microscope measurements of solid Al-solid Pb and solid Al-liquid Pb surface-energy anisotropy in rapidly solidified Al-5% Pb (by mass)

1987 ◽  
Vol 414 (1847) ◽  
pp. 499-507 ◽  
Keyword(s):  
Electron Microscope ◽  
Melting Point ◽  
Surface Energy ◽  
Transmission Electron Microscope ◽  
Room Temperature ◽  
Transmission Electron ◽  
Increasing Temperature ◽  
Rapidly Solidified ◽  
Al Matrix

Alloys of Al-5% Pb and Al-5% Pb-0.5% Si (by mass) have been manufactured by rapid solidification and then examined by transmission electron microscopy. The rapidly solidified alloy microstructures consist of 5-60 nm Pb particles embedded in an Al matrix. The Pb particles have a cube-cube orientation relation with the Al matrix, and are cub-octahedral in shape, bounded by {100} Al, Pb and {111} Al, Pb facets. The equilibrium Pb particle shape and therefore the anisotropy of solid Al-solid Pb and solid Al-liquid Pb surface energies have been monitored by in situ heating in the transmission electron microscope over the temperature range between room temperature and 550°C. The ani­sotropy of solid Al-solid Pb surface energy is constant between room temperature and the Pb melting point, with a {100} Al, Pb surface energy about 14% greater than the {111} Al, Pb surface energy, in good agreement with geometric near-neighbour bond energy calculations. The {100} AI, Pb facet disappears when the Pb particles melt, and the anisotropy of solid Al-liquid Pb surface energy decreases gradually with increasing temperature above the Pb melting point, until the Pb particles become spherical at about 550°C.

Effect of Temperature and Vapor-phase Encapsulation on Particle Growth and Morphology

1999 ◽  
Vol 14 (4) ◽  
pp. 1664-1671 ◽  
Author(s):  
Sheryl H. Ehrman ◽  
Maria I. Aquino-Class ◽  
Michael R. Zachariah
Keyword(s):  
Particle Size ◽  
Vapor Phase ◽  
Particle Growth ◽  
Effect Of Temperature ◽  
Transmission Electron Micrograph ◽  
Transmission Electron ◽  
Size And Morphology ◽  
Silicon And Germanium ◽  
Increasing Temperature

The effect of in situ vapor phase salt-encapsulation on particle size and morphology was systematically investigated in a sodium co-flow/furnace reactor. The temperature of the furnace was varied, and the primary particle size and degree of agglomeration of the resulting silicon and germanium particles were determined from transmission electron micrograph images of particles sampled in situ. Particle size increased with increasing temperature, a trend expected from our understanding of particle formation in a high-temperature process in the absence of an encapsulant. Germanium, which coalesces faster than silicon, formed larger particles than silicon at the same temperatures, also in agreement with observations of particle growth in more traditional aerosol processes. At the highest temperatures, unagglomerated particles were formed, while at low temperatures, agglomerated particles were formed, with agglomerate shape following the shape of the salt coating.

Investigation about Synthesis of Carbon Nanotubes with Various Structures Governed by Temperature and Relevant Growth Mechanism

2012 ◽  
Vol 499 ◽  
pp. 35-39
Author(s):  
Hai Peng Li ◽  
Jia Wei Fan ◽  
Hong Shui Wang ◽  
Li Hui Wang
Keyword(s):  
Carbon Nanotubes ◽  
Growth Mechanism ◽  
Chemical Vapor ◽  
Composite Powders ◽  
Catalyst Carrier ◽  
Transmission Electron ◽  
Multi Walled Carbon Nanotubes ◽  
Synthesis Of Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Multi-walled carbon nanotubes (CNTs)/Al in-situ composite powders over Al as catalyst carrier had been synthesized successfully using transition metal Ni by chemical vapor deposition. CNTs were mainly characterized by transmission electron microscopy. It was found that reaction temperature had great influences on the structures of carbon products obtained. Detailed discussions according to the structures of CNTs at different reaction temperatures were given. A deduced model for explaining the growth mechanism of CNTs governed by temperature was developed.

Investigations On In Situ Nanocrystallization And Magnetic Properties For Amorphous Fe78Si9B13 Ribbons

1999 ◽  
Vol 577 ◽  
Author(s):  
Xiangeheng Sun ◽  
A. Cabral-Prieto ◽  
M. Jose Yacaman ◽  
Wensheng Sun
Keyword(s):  
Amorphous Phase ◽  
Amorphous State ◽  
Field Pattern ◽  
Transmission Electron ◽  
Measurement Results ◽  
Optimum Annealing Temperature ◽  
Increasing Temperature ◽  
Differential Scanning Calorimeters ◽  
Nanocrystalline Phases

ABSTRACTThe amorphous state of ferromagnetic Fe78Si9B13 (Metglas 2605S-2) and its nanocrystallization were investigated by in situ transmission electron microscope (TEM), Xray diffraction (XRD), Mossbauer spectroscopy (MS), differential scanning calorimeters (DSC) and magnetic moment measurements. The Mössbauer spectrum exhibited an essentially symmetric hyperfine field pattern of 259KOe in as-quenched amorphous state at room temperature. The Curie and crystallization temperature were determined to be Tc=708K and Tx= 803K, respectively. The Tx value was in good agreement with DSC measurement results. The occupied fraction of the nanocrystalline phases of α-Fe(Si) and Fe2B at in situ optimum annealing temperature was about 57% and 43%, respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of nanocrystalline ferromagnetism, suggesting the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.

Growth Mechanism of Chains of Silicon Nanocrystallites

2000 ◽  
Vol 638 ◽  
Author(s):  
Hideo Kohno ◽  
Koji Tanaka ◽  
Seiji Takeda
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Growth Mechanism ◽  
Silicon Nanowires ◽  
Strong Evidence ◽  
Surface Oxidation ◽  
Transmission Electron ◽  
Wetting Property ◽  
Silicon Nanocrystallites

AbstractThe growth mechanism of chains of silicon nanocrystallites was investigated. Energy-filtered transmission electron microscopy observations provided strong evidence that the chains were formed as a result of surface oxidation of silicon nanowires. In addition, the periodic instability in the wetting property of molten catalysts was simulated numerically.

High-temperature Dislocation-precipitate Interactions in Al Alloys: An in situ Transmission Electron Microscopy Deformation Study

2005 ◽  
Vol 20 (7) ◽  
pp. 1792-1801 ◽  
Author(s):  
B.G. Clark ◽  
I.M. Robertson ◽  
L.M. Dougherty ◽  
D.C. Ahn ◽  
P. Sofronis
Keyword(s):  
High Temperature ◽  
Al Alloys ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Rate Limiting Step ◽  
Transmission Electron ◽  
Deformation Processes ◽  
Temperature Interaction ◽  
Rate Limiting

The fundamental processes controlling the high-temperature interaction of dislocations with precipitates in Al-alloys were investigated in real time by deforming specimens in situ in the transmission electron microscope at elevated temperature. The observations support a bypass mechanism involving the interaction of lattice dislocations with the precipitate–matrix interface dislocations, where the rate-limiting step in the interaction is the release of the dislocation from the particle. These observations are discussed in relation to high-temperature deformation processes and models.

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