scholarly journals Ostwald Ripening of Platinum Nanoparticles Confined in a Carbon Nanotube/Silica-Templated Cylindrical Space

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Cintia Mateo-Mateo ◽  
Carmen Vázquez-Vázquez ◽  
Moisés Pérez-Lorenzo ◽  
Verónica Salgueiriño ◽  
Miguel A. Correa-Duarte
Keyword(s):  
Carbon Nanotube ◽  
Platinum Nanoparticles ◽  
Metallic Nanoparticles ◽  
Ostwald Ripening ◽  
Size Distributions ◽  
Confined Space ◽  
Sintering Process ◽  
Particle Size Distributions ◽  
Final Particle ◽  
Ostwald Ripening Mechanism

Sintering of nanoparticles mediated by an Ostwald ripening mechanism is generally assessed examining the final particle size distributions. Based on this methodology, a general approach for depositing platinum nanoparticles onto carbon nanotubes in solution has been employed in order to evaluate the sintering process of these metallic nanoparticles at increasing temperatures in a carbon nanotube/silica-templated confined space.

Three Dimensional Monte Carlo Simulation of Isotropic Coarsening of Particles in Liquid Phase

2007 ◽  
Vol 558-559 ◽  
pp. 1115-1120
Author(s):  
Suk Bin Lee ◽  
Anthony D. Rollett
Keyword(s):  
Particle Size ◽  
Monte Carlo ◽  
Liquid Phase ◽  
Ostwald Ripening ◽  
Monte Carlo Model ◽  
Liquid Phase Sintering ◽  
Three Dimensions ◽  
Average Particle ◽  
Size Distributions ◽  
Particle Size Distributions

Coarsening of particles during liquid phase sintering is known to be an example of Ostwald ripening. This coarsening process, in a fully wetting system, is simulated in three dimensions with a kinetic Monte Carlo model. The results from the simulation for microstructures, kinetics and particle size distributions are compared to available experimental findings. It is found that the average particle volume increases linearly with time and that the particle size distributions are consistent with those obtained experimentally, as in the W-Ni-Fe and Sn-Pb systems.

Composition Fluctuations in the Ostwald Ripening

2008 ◽  
Vol 277 ◽  
pp. 187-192
Author(s):  
G.V. Lutsenko ◽  
Andriy Gusak
Keyword(s):  
Computer Simulation ◽  
Particle Size ◽  
Large Volume ◽  
Ostwald Ripening ◽  
Volume Fraction ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Two Phase ◽  
Large Volume Fraction ◽  
Composition Fluctuations

The Ostwald ripening of a two-phase binary alloy has been considered for case of “large” volume fraction of precipitating phase. The approach is proposed in which the composition fluctuations into the vicinity of particles are considered. In this approach the evolution of particle size distributions is analyzed using the computer simulation.

Effect of the High Energy Milling in the Crystallite Size of WC-Co

2008 ◽  
Vol 591-593 ◽  
pp. 131-134 ◽  
Author(s):  
G.B. Pinto ◽  
S.R.S. Soares ◽  
Uilame Umbelino Gomes ◽  
Rubens Maribondo Nascimento ◽  
Antonio Eduardo Martinelli ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Milling Time ◽  
Hard Metal ◽  
High Energy ◽  
Size Distributions ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
Particle Size Distributions ◽  
High Energy Milling ◽  
Grinding Media

High-energy milling has been used for production of nano-structured WC-Co powders. During the High-Energy Milling, the powders suffer severe high-energy impacts in the process of ball-to-ball and ball-to-vial wall collisions of the grinding media. Hard metal produced from nanostructured powders have better mechanical properties after appropriate sintering process. During the milling the particles size of WC and Co can be reduced and plastic deformed. In the present work, a mixture of WC-10%Co was produced by high energy milling. The starting powders of the WC (0.87 μm - Wolfran Bergau) and Co (0.93 μm - H.C.Starck) were used to produce the hard metal. The influence of the milling time on the particle size distributions and in the lattice strain was investigated. Milling time of the 2, 10, 20, 50, 70, 100 and 150 hours were used. The powders after milling were characterized by X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM). The results show that 10 h milling were enough to reduce the crystallite size of WC and the increase of the milling time reduces the crystallite size.

RAFT-Mediated Emulsion Polymerization of Styrene in Water using a Reactive Polymer Nanoreactor

2009 ◽  
Vol 62 (11) ◽  
pp. 1528 ◽  
Author(s):  
Carl N. Urbani ◽  
Michael J. Monteiro
Keyword(s):  
Particle Size ◽  
Diblock Copolymer ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Final Particle ◽  
Reactive Polymer ◽  
Highly Active ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
And Control

We have demonstrated a nanoreactor methodology to produce polystyrene nanoparticles with narrow molecular weight distributions (MWD) and control over the final particle size distributions. Our reactive thermoresponsive diblock copolymer nanoreactor is an ideal setting to carry out otherwise difficult reversible addition–fragmentation chain transfer (RAFT)-mediated polymerizations, resulting in surfactant-free nanoparticles that can be tuned to size and MWD. By confining the MacroRAFT agent within the nanoreactor, the poor P(DMA68-b-NIPAM73)-SC(=S)SC4H9 (PNIPAM) leaving group on the MacroCTA behaves as a highly active MacroCTA through kinetic rather than thermodynamic control. The Mn was close to theory with low polydispersity indices (PDIs) (<1.2). The particle size increased with the ratio of styrene to nanoreactors and with very narrow particle size distributions. However, we found that there was a limited amount of styrene monomer that can be encapsulated into the nanoreactor, leading to polymerizations stopping well before full conversion. This problem was overcome through the addition of a non-reactive thermoresponsive diblock copolymer, which resulted in Mns close to 340 K and low PDIs. Manuscript received: 15 April 2009. Manuscript accepted: 15 July 2009.

Evidence of Ostwald ripening related recrystallization of diagenetic chlorites from reservoir rocks offshore Norway

Clay Minerals ◽  
1991 ◽  
Vol 26 (2) ◽  
pp. 169-178 ◽  
Author(s):  
J. S. Jahren
Keyword(s):  
Ostwald Ripening ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Temperature Dependent ◽  
X Ray ◽  
Reservoir Rocks ◽  
Transmission Electron ◽  
Crystal Core ◽  
Higher Temperature ◽  
Scanning Electron

AbstractChemical variations in individual chlorite crystals of diagenetic origin delineated by energy dispersive X-ray spectroscopy (EDS) in a transmission electron microscope (TEM) indicate a temperature dependent chemical zonation in each grain. Silicon decreases and Al increases with higher temperature resulting in a decreasing Si/Al ratio away from the crystal core reflecting the time and rate of the crystal growth. Chlorite particle-size distributions obtained by scanning electron microscopy (SEM) give steady state profiles which suggests that the chlorite growth is controlled by a grain coarsening process related to Ostwald ripening.

scholarly journals Practical Limits for Two Fundamental Approaches to Designing Particle Size Distributions to Address a Specific Physical Property like Viscosity

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3047
Author(s):  
Richard D. Sudduth
Keyword(s):  
Particle Size ◽  
Physical Property ◽  
Design Approach ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Initial Particle ◽  
Initial Particle Size ◽  
Final Particle ◽  
Straight Line

It has previously been shown that optimum particle size distributions with a maximum packing fraction can be achieved from a straight line plot of the accumulated sum of particle volume fractions versus the square root of particle size. This study addresses practical limits for two dominant fundamental approaches to designing particle size distributions to address the effect on a specific physical property such as viscosity. The two fundamental approaches to obtain such a straight line would include: the first design approach would be generated utilizing the same initial particle size, Dmin, but by using different ultimate particle sizes, Dmax. The second design approach would be generated where each distribution starts with the same initial particle size, Dmin, and ends with the same ultimate particle size, Dmax. The first design approach is particularly useful to identify the possible slopes available based on the smallest and largest particle sizes available. The second design approach can be utilized to identify the preferred ratio between particles, Z, and the number of different particle sizes, n, to be utilized in the final particle blend. The extensive empirical experimental evaluations of particle size distributions generated by McGeary were then utilized to confirm the limits.

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