Geometric Design of Heterogeneous Nucleation Sites on Biocompatible Surfaces

2013 ◽  
Vol 13 (8) ◽  
pp. 3835-3841 ◽  
Author(s):  
Vilmalí López-Mejías ◽  
Allan S. Myerson ◽  
Bernhardt L. Trout
Keyword(s):  
Heterogeneous Nucleation ◽  
Geometric Design ◽  
Nucleation Sites

Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability

1999 ◽  
Vol 5 (S2) ◽  
pp. 778-779
Author(s):  
R.W Carpenter ◽  
W Braue ◽  
M.J. Kim
Keyword(s):  
Silicon Nitride ◽  
Heterogeneous Nucleation ◽  
Radiation Stability ◽  
Silicon Oxynitride ◽  
Minor Constituent ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Nucleation Sites ◽  
Heterogeneous Formation ◽  
A Minor

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.

Refinement Effect and Mechanism of AZ31 Magnesium Alloy by Electromagnetic Stirring under the Effect of Grain-Refiner

2013 ◽  
Vol 631-632 ◽  
pp. 556-561 ◽  
Author(s):  
Sheng Yuan Gao ◽  
Shi Lian Qu ◽  
Yue Yuan ◽  
Bao Qin Fu
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Heterogeneous Nucleation ◽  
Holding Time ◽  
Electromagnetic Stirring ◽  
Az31 Magnesium Alloy ◽  
Grain Refiner ◽  
Nucleation Sites ◽  
Continuously Cast ◽  
Refinement Effect

The effects of electromagnetic stirring and Al4C3grain refiner on the grain refinement of semi-continuously cast AZ31 magnesium alloy were discussed in this investigation. The results indicate that electromagnetic stirring has effective refining effect on the grain size of AZ31 magnesium alloy under the effect of Al4C3grain refiner. Electromagnetic stirring can “activate” the Al4C3particles, resulting in more heterogeneous nucleation sites for the primary α-Mg grains. But, longer holding time can “inactivate” the Al4C3particles, and the optimal experimental holding time is 60 min in the present investigation. The activated rate of the electromagnetic under the experimental condition ρ2=1.65%.

Precisely controlled heterogeneous nucleation sites for TiO2crystal growth

CrystEngComm ◽  
2014 ◽  
Vol 16 (32) ◽  
pp. 7502 ◽  
Author(s):  
Shuang Yang ◽  
Yu Hou ◽  
Bo Zhang ◽  
Xiao Hua Yang ◽  
Haimin Zhang ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Nucleation Sites

scholarly journals Microbubbles as Heterogeneous Nucleation Sites for Crystallization in Continuous Microfluidic Devices

Langmuir ◽  
2018 ◽  
Vol 35 (1) ◽  
pp. 60-69 ◽  
Author(s):  
Naghmeh Fatemi ◽  
Zhengya Dong ◽  
Tom Van Gerven ◽  
Simon Kuhn
Keyword(s):  
Heterogeneous Nucleation ◽  
Microfluidic Devices ◽  
Nucleation Sites

Master Alloys for Grain Refinement

2019 ◽  
Author(s):  
Xiaoming Wang
Keyword(s):  
Grain Refinement ◽  
Heterogeneous Nucleation ◽  
Aluminum Matrix ◽  
Industrial Applications ◽  
Hard Particles ◽  
Nucleation Sites ◽  
Major Disadvantage ◽  
Master Alloys ◽  
Volume Production ◽  
Low Volume

Master alloys are routinely added into aluminum melts before casting for grain refinement purposes. The widely used master alloys contain titanium and boron in the forms of Al3Ti and TiB2 particles in an aluminum matrix. Upon addition into aluminum melts, Al3Ti dissolves into the aluminum melts and promotes the heterogeneous nucleation of the α-Al grains while restricting the growth of α-Al grains through a constitutional cooling effect in solidification. Meanwhile, TiB2 is stable and acts as a substrate for the heterogeneous nucleation of α-Al grains through a layer of Al3Ti on the surface. Sharing these in common, different mechanisms for the grain refinement of aluminum by Al-Ti-B-type master alloys have been proposed. Another kind of popular master alloys is Al-Ti-C, which is used in a lesser extent for the grain refinement of Al alloys containing elements that are poisoning Al-Ti-B master alloys. Titanium and carbon exist as Al3Ti and TiC particles. TiC is not as stable as TiB2 and decomposes in aluminum melts. TiC in Al-Ti-C therefore acts as heterogeneous nucleation sites for α-Al grains similar to TiB2. However, the fading of Al-Ti-C master alloys is irreversible, which is the major disadvantage of Al-Ti-C master alloys. Al-Ti master alloys do not contain hard particles and are used industrially for products that are sensitive to hard TiB2 and TiC particles. There are also other master alloys that show high grain refinement potentials in lab tests but have never been used industrially for mainly low-volume production and high costs. This article gives an overview of the grain refinement of aluminum by master alloys with an emphasis on Al-Ti-B master alloys, from the production to the industrial applications of the master alloys.

Relaxation-Induced Gettering of Metal Impurities in Silicon: Microscopic Properties of Effective Gettering Sites

1992 ◽  
Vol 262 ◽  
Author(s):  
M. Seibt
Keyword(s):  
Heterogeneous Nucleation ◽  
Point Of View ◽  
Homogeneous Precipitation ◽  
The Core ◽  
Heterogeneous Precipitation ◽  
Metal Impurities ◽  
Cobalt Nickel ◽  
Fundamental Point ◽  
Nucleation Sites ◽  
High Incorporation

ABSTRACTSome gettering processes like internal gettering or backside damage gettering base on heterogeneous precipitation of metal impurities at defects in pre-de ter mined parts of silicon wafers during cooling from high temperatures. We consider microscopic properties of effective heterogeneous nucleation sites for cobalt, nickel and copper impurities from the fundamental point of view of suicide precipitate formation. We follow the basic concept that such gettering sites are defects which allow fast precipitation, i.e. which remove kinetic limitations known from homogeneous precipitation of these impurities at small supersaturation. For Co and Ni it follows that distorted lattice sites in the core of dislocations may establish high incorporation rates of interstitial atoms into suicide particles, whereas for Cu sinks for silicon self-interstitials are suitable gettering sites.

Nucleation Dynamics of Water Nanodroplets

2014 ◽  
Vol 20 (2) ◽  
pp. 407-415 ◽  
Author(s):  
Dipanjan Bhattacharya ◽  
Michel Bosman ◽  
Venkata R.S.S. Mokkapati ◽  
Fong Yew Leong ◽  
Utkur Mirsaidov
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gold Nanoparticles ◽  
Heterogeneous Nucleation ◽  
Flat Surface ◽  
Nucleation And Growth ◽  
Length Scale ◽  
Transmission Electron ◽  
Nucleation Sites

AbstractThe origin of the condensation of water begins at the nanoscale, a length-scale that is challenging to probe for liquids. In this work we directly image heterogeneous nucleation of water nanodroplets by in situ transmission electron microscopy. Using gold nanoparticles bound to a flat surface as heterogeneous nucleation sites, we observe nucleation and growth of water nanodroplets. The growth of nanodroplet radii follows the power law: R(t)~(t−t0)β, where β~0.2−0.3.

scholarly journals Microstructural Improvement of Eutectic Al + Mg2Si Phases on Al–Zn–Si–Mg Cast Alloy with TiB2 Particles Additions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2902
Author(s):  
Byungjoo Kim ◽  
Jihoon Hwang ◽  
Yongho Park ◽  
Youngcheol Lee
Keyword(s):  
Crystal Structure ◽  
Aluminum Alloys ◽  
Heterogeneous Nucleation ◽  
Cast Alloy ◽  
Mg2si Phase ◽  
Phase Modification ◽  
Polarizing Microscope ◽  
Nucleation Sites ◽  
Tib2 Particles

In this study, the effects of adding TiB2 particles to eutectic Al + Mg2Si phases in aluminum alloys were analyzed. The eutectic Al + Mg2Si phases were modified effectively when a large amount of TiB2 was added, and changes in the shape, size, and distribution of the eutectic Al + Mg2Si phases were confirmed using a polarizing microscope and FE-SEM. The crystal structure of the TiB2 particles and Mg2Si phases were analyzed using HR-TEM, and the analysis confirmed that the TiB2 particles can act as heterogeneous nucleation sites. This paper intends to clarify the principle of phase modification of the eutectic Al + Mg2Si phases by TiB2 particles and proposes a new mechanism to improve Mg2Si phase modification when TiB2 particles are added.

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