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.

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.

scholarly journals Hydrogenative Cyclization of Levulinic Acid to γ-Valerolactone with Methanol and Ni-Fe Bimetallic Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1096
Author(s):  
Ligang Luo ◽  
Xiao Han ◽  
Qin Zeng
Keyword(s):  
Photoelectron Spectroscopy ◽  
Levulinic Acid ◽  
Hydrogen Donor ◽  
Effect Of Temperature ◽  
X Ray ◽  
Transmission Electron ◽  
Ft Ir ◽  
Temperature Programmed

A series of Ni-Fe/SBA-15 catalysts was prepared and tested for the catalytic hydrogenation of levulinic acid to γ-valerolactone, adopting methanol as the only hydrogen donor, and investigating the synergism between Fe and Ni, both supported on SBA-15, towards this reaction. The characterization of the synthesized catalysts was carried out by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), H2-TPD (hydrogen temperature-programmed desorption), XPS (X-ray photoelectron spectroscopy), and in situ FT-IR (Fourier transform–infrared spectroscopy) techniques. H2-TPD and XPS results have shown that electron transfer occurs from Fe to Ni, which is helpful both for the activation of the C=O bond and for the dissociative activation of H2 molecules, also in agreement with the results of the in situ FT-IR spectroscopy. The effect of temperature and reaction time on γ-valerolactone production was also investigated, identifying the best reaction conditions at 200 °C and 180 min, allowing for the complete conversion of levulinic acid and the complete selectivity to γ-valerolactone. Moreover, methanol was identified as an efficient hydrogen donor, if used in combination with the Ni-Fe/SBA-15 catalyst. The obtained results are promising, especially if compared with those obtained with the traditional and more expensive molecular hydrogen and noble-based catalysts.

The Properties of YSZ-Ni-Cr Cermet Fabricated by Sol-Gel Method

2012 ◽  
Vol 535-537 ◽  
pp. 787-790
Author(s):  
Shu Lan Guo ◽  
Min Wang ◽  
Su Hua Lv ◽  
Jia Li ◽  
Xian Chang Du
Keyword(s):  
Particle Size ◽  
Sol Gel ◽  
Hot Press ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Particle Size And Morphology ◽  
Size And Morphology ◽  
Increasing Temperature ◽  
Hot Press Sintering

The properties of YSZ-Ni-Cr cermet fabricated by Sol-Gel Method（YSZ-Ni-Cr powder was synthesized by coprecipitation method at 850°C for 2 h and was processed into YSZ-Ni-Cr cermet by hot-press sintering at 1350°C for 1 h）was explored. The identification of phases was carried out using a X-ray diffractometer (XRD). The particle size and morphology was determined by electron microscopys(SEM/TEM) The conductivity had a tendency to decrease with increasing temperature. This behavior can be accounted for that there are two conduction paths through the cermet, an electronic path through the (Ni,Cr) metal phase and an ionic path through the ZrO2-Y2O3 phase.

Synthesis of Pt Nanoparticles and Nanorods by Microwave-assisted Solvothermal Technique

2006 ◽  
Vol 61 (12) ◽  
pp. 1566-1572 ◽  
Author(s):  
Dongsheng Li ◽  
Sridhar Komarneni
Keyword(s):  
Particle Size ◽  
Pt Nanoparticles ◽  
Transmission Electron Microscopy Image ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Microwave Assisted ◽  
Metal Sources ◽  
Transmission Electron ◽  
Particle Size And Morphology ◽  
Size And Morphology

Platinum nanoparticles and nanorods were synthesized by microwave-assisted solvothermal techniques. Changing the reaction conditions controlled particle size and morphology. The effects of the reaction conditions, such as the molar ratio of the polyvinylpyrrolidone (PVP) repeating unit to the metal sources, the concentration of metal sources, the reaction temperature, and the presence of distilled water were investigated. Nanoparticles of Pt were approximately 3 nm in size. Produced nanoparticles and nanorods were characterized by transmission electron microscopy. Image JTM software was used to calculate the particle size and size distribution.

The Effect of Grain Boundaries on Surface Diffusion Mediated-Planarization of Polycrystalline Cu Films

1995 ◽  
Vol 389 ◽  
Author(s):  
R.A. Brain ◽  
D.S. Gardner ◽  
D.B. Fraser ◽  
H.A. Atwater
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Surface Diffusion ◽  
Cross Sections ◽  
Boundary Surface ◽  
Surface Profile ◽  
Transmission Electron Micrograph ◽  
Cu Films ◽  
Transmission Electron

ABSTRACTIn situ, ultrahigh vacuum anneals were performed to induce Cu reflow at 500°C following deposition of Cu films and a Ta barrier layer on 1 μm wide by 1 μm deep trenches. Transmission electron micrograph cross-sections show profiles which suggest that grain boundaries and surface energy anisotropy significantly affect reflow. The extent of reflow is dependent on the structure of grain boundary-surface intersections, and the surface profile consists of regions of low curvature within grains and with sharp discontinuities in curvature at grain boundaries, a structure that inhibits surface diffusion. We present results showing how the surface diffusion mediated reflow varies with grain boundary groove angle and position, and compare these results with finite-element simulations that model surface diffusion-driven reflow.

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.

The Effect of Temperature on the Dispersion of a-Mangostin in PNIPAM Microgel System

2012 ◽  
Vol 9 (2) ◽  
pp. 21
Author(s):  
Madihah Ahmad ◽  
Bohari Yamin ◽  
Azwan Mat Lazim
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Electron Microscope ◽  
Spectroscopic Data ◽  
Effect Of Temperature ◽  
Garcinia Mangostana ◽  
Transmission Electron ◽  
Uv Visible ◽  
Microgel Solution ◽  
Increasing Temperature ◽  
Fluorescence Peak

a-Mangostin was extracted from the pericarp of the Malaysian local Garcinia mangostana linn., The structure was characterised by Infrared red, UV-Visible and Nuclear Magnetic Resonance spectroscopic data. The fluorescence peak at 500nm in ethanol was not observed in PNIPAM microgel solution. The increase of colloidal size of the gel in the presence of a-mangostin was studied by Dynamic Light Scattering and Transmission Electron Microscope. The size of the particle also increases with increasing temperature up to 45°C after which it began to shrink. The TEM micrograph at 45°C showed a uniformly structured pattern of the gel occurs in the range of the lowest solution critical temperature.

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