Carbon formation and gasification on metals. Bulk diffusion mechanism: A reassessment

2011 ◽  
Vol 178 (1) ◽  
pp. 110-116 ◽  
Author(s):  
L.S. Lobo ◽  
J.L. Figueiredo ◽  
C.A. Bernardo
Keyword(s):  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Carbon Formation

ChemInform Abstract: Carbon Formation and Gasification on Metals. Bulk Diffusion Mechanism: A Reassessment

ChemInform ◽  
2012 ◽  
Vol 43 (12) ◽  
pp. no-no
Author(s):  
L. S. Lobo ◽  
J. L. Figueiredo ◽  
C. A. Bernardo
Keyword(s):  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Carbon Formation

scholarly journals Dynamic Observation of Interfacial IMC Evolution and Fracture Mechanism of Sn2.5Ag0.7Cu0.1RE/Cu Lead-Free Solder Joints during Isothermal Aging

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 831 ◽  
Author(s):  
Di Zhao ◽  
Keke Zhang ◽  
Ning Ma ◽  
Shijie Li ◽  
Chenxiang Yin ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fracture Mechanism ◽  
Isothermal Aging ◽  
Solder Joints ◽  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Cu Substrate ◽  
Dynamic Observation ◽  
Free Solder ◽  
The Relationship

Dynamic observation of the microstructure evolution of Sn2.5Ag0.7Cu0.1RE/Cu solder joints and the relationship between the interfacial intermetallic compound (IMC) and the mechanical properties of the solder joints were investigated during isothermal aging. The results showed that the original single scallop-type Cu6Sn5 IMC gradually evolved into a planar double-layer IMC consisting of Cu6Sn5 and Cu3Sn IMCs with isothermal aging. In particular, the Cu3Sn IMC grew towards the Cu substrate and the solder seam sides; growth toward the Cu substrate side was dominant during the isothermal aging process. The growth of Cu3Sn IMC depended on the accumulated time at a certain temperature, where the growth rate of Cu3Sn was higher than that of Cu6Sn5. Additionally, the growth of the interfacial IMC was mainly controlled by bulk diffusion mechanism, where the activation energies of Cu6Sn5 and Cu3Sn were 74.7 and 86.6 kJ/mol, respectively. The growth rate of Cu3Sn was slightly faster than that of Cu6Sn5 during isothermal aging. With increasing isothermal aging time, the shear strength of the solder joints decreased and showed a linear relationship with the thickness of Cu3Sn. The fracture mechanism of the solder joints changed from ductile fracture to brittle fracture, and the fracture pathway transferred from the solder seam to the interfacial IMC layer.

Non-Destructive Method of Diffusion Parameters Determination in Solids

2005 ◽  
Vol 237-240 ◽  
pp. 438-443 ◽  
Author(s):  
O.B. Bodnar ◽  
I.M. Aristova ◽  
A.A. Mazilkin ◽  
A.N. Chaika ◽  
L.N. Pronina
Keyword(s):  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Surface Concentration ◽  
Initial Distribution ◽  
Dopant Atom ◽  
X Ray Diffraction ◽  
Diffusion Parameters ◽  
Transmission Electron ◽  
Radiation Damages ◽  
Non Destructive

Diffusion of nitrogen implanted in tungsten and molybdenum single crystals has been investigated at temperature about 0.3 Tm (Tm is the melting point). Existence of several dopant atom fluxes is found in subsurface region of the ion implanted material. The diffusion coefficients of the nitrogen connected with the radiation damages and that with the bulk diffusion mechanism are determined. Change of the nitrogen surface concentration has been measured by Auger electron spectroscopy. Initial distribution of the nitrogen and diffusion profiles for various annealing time have been determined by secondary-ion mass-spectroscopy technique. Transmission electron microscopy and X-ray diffraction investigations were used to study the microstructure and phase state of the implanted samples.

Catalysis with Inorganic Membranes

MRS Bulletin ◽  
1994 ◽  
Vol 19 (4) ◽  
pp. 34-39 ◽  
Author(s):  
M.P. Harold ◽  
C. Lee ◽  
A.J. Burggraaf ◽  
K. Keizer ◽  
V.T. Zaspalis ◽  
...  
Keyword(s):  
Thin Film ◽  
Pore Size ◽  
Diffusion Mechanism ◽  
Knudsen Diffusion ◽  
Bulk Diffusion ◽  
Molecular Transport ◽  
Mean Free Path ◽  
Specific Interactions ◽  
Inorganic Membranes ◽  
Introductory Article

Catalytic inorganic membranes are among the most challenging and intriguing porous materials. Consisting of a thin film of mesoporous or microporous inorganic material deposited on a macroporous material, catalytic membranes are multifunctional materials that must be engineered for both chemical and physical properties. New approaches to carrying out chemical reactions are possible by tailoring the membrane catalytic activity and selectivity, permselectivity, and other thin film properties. Readers are referred to several recent reviews of inorganic membranes, in particular, Zaspalis and Burggraaf, Armor, Gellings and Bouwmeister, Hsieh, Stoukides, and Tsotsis et al.Inorganic membranes are most conveniently classified according to pore size (see introductory article). Of particular importance is the ratio of the pore size to the molecular mean free path (MFP). Decreasing pore dimensions lead to increased selectivity with corresponding loss of permeability. Macroporous membranes have a pore size much larger than the MFP, leading to molecular (bulk) diffusion or viscous flow. Knudsen diffusion dominates in the mesoporous regime, where the pore size is comparable to the MFP. In addition, surface diffusion of the molecules along the pore walls may contribute, leading to an enhanced flux of the adsorbed species along the walls. The microporous regime is encountered when the pore size is comparable to the molecules. This regime makes possible much higher permselectivities, which depend on both molecular size and specific interactions with the solid. Finally, in dense membranes, molecular transport occurs through a solution-diffusion mechanism, which also involves specific interactions between the solute and membrane.

Electromigration Lifetimes of Single Crystal Aluminum Lines with Different Crystallographic Orientations

1994 ◽  
Vol 338 ◽  
Author(s):  
Y.-C. Joo ◽  
C.V. Thompson
Keyword(s):  
Activation Energy ◽  
Single Crystal ◽  
Diffusion Mechanism ◽  
Failure Mechanisms ◽  
Bulk Diffusion ◽  
Time To Failure ◽  
Interface Diffusion ◽  
Test Conditions ◽  
Service Conditions ◽  
Crystallographic Orientations

ABSTRACTNear-bamboo interconnects are susceptible to failure either at polygranular clusters or within bamboo grains (transgranular failure). Polygranular failure mechanisms are often dominant in lines with near-bamboo structures at test conditions, but at service conditions, transgranular failure mechanisms are expected to dominate. In order to study the temperature and current density dependence as well as the crystallographic dependence of these transgranular failure mechanisms, it is necessary to isolate them from other mechanisms. To do this, we have studied single crystal Al lines on oxidized silicon.We have tested lifetimes of passivated and unpassivated Al single crystal lines with various textures. In both passivated and unpassivated lines, the median time to failure, t50, was found to be texture-dependent, with t50(l11) > t50(133) > t50(110), and with t50(111) ∼ 10×t50(110). The activation energy for failure for both passivated and unpassivated (110) single crystal lines was about 1 eV. This value differs from that of aluminum bulk diffusion (1.4 eV), suggesting that interface diffusion is the dominant diffusion mechanism in these lines, and perhaps in bamboo regions of near-bamboo lines as well.

Study of Oxygen Diffusion in Polycrystalline ZnO by SIMS

2009 ◽  
Vol 289-292 ◽  
pp. 523-530
Author(s):  
Antônio Claret Soares Sabioni ◽  
Antônio Márcio J.M. Daniel ◽  
Anne Marie Huntz ◽  
Wilmar Barbosa Ferraz ◽  
François Jomard
Keyword(s):  
Grain Boundary ◽  
Oxygen Pressure ◽  
Diffusion Coefficients ◽  
Effective Charge ◽  
Oxygen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Interstitial Oxygen ◽  
Exchange Method

Oxygen diffusion coefficients were measured in polycrystalline ZnO by means of the gas-solid exchange method using the isotope 18O as the oxygen tracer. The diffusion annealings were performed at 892oC and 992oC, in an Ar+18O2 atmosphere under oxygen partial pressures from 0.1 to 1atm. After the diffusion annealings, the 18O diffusion profiles were established by secondary ion mass spectrometry (SIMS). Increasing the oxygen pressure leads to an increase of the oxygen diffusion in ZnO. The bulk diffusion coefficients depends on oxygen pressure according to , at 882oC, or , at 992oC, which indicates that the oxygen bulk diffusion mechanism should preferentially take place by means of interstitial oxygen having a null effective charge. The grain boundary diffusion coefficients show little dependence on oxygen pressure at 882oC, given by , which should correspond to a diffusion mechanism by means of interstitial oxygen, with a double negative charge, but at 992oC this dependence is corresponding to a diffusion mechanism by interstitial oxygen having a null effective charge. The results also show that the grain boundary is a fast path for the oxygen diffusion in polycrystalline ZnO.

scholarly journals Carbon Formation at High Temperatures (550–1400 °C): Kinetics, Alternative Mechanisms and Growth Modes

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 465 ◽  
Author(s):  
Luís Sousa Lobo ◽  
Sónia A. C. Carabineiro
Keyword(s):  
Catalyst Surface ◽  
Bulk Diffusion ◽  
Carbon Formation ◽  
Carbon Structure ◽  
Graphene Layers ◽  
Rate Determining Step ◽  
Growth Modes ◽  
Higher Temperature ◽  
Hybrid Carbon ◽  
Gas Pressures

This Note aims at clarifying the alternative mechanisms of carbon formation from gases at temperatures above 550 °C. Both the growth of carbon nanotubes (CNTs) by a hybrid route, and of graphene layers deposition by a pyrolytic route are analyzed: the transition had no influence in apparent kinetics, but the carbon structure was totally different. The transition temperature from hybrid to pyrolytic growth varies with the gas pressure: higher temperature transition was possible using lower active gas pressures. The rate-determining step concept is essential to understanding the behavior. In catalytic and hybrid carbon formation, the slower step controls and determines kinetics. In the pyrolytic region, the faster step dominates, and carbon bulk diffusion is blocked: layers of graphene cover the external catalyst surface. It is easier to optimize CNTs growth (rate, shape, properties) knowing the details of the alternative mechanisms operating.

scholarly journals Explaining Bamboo-Like Carbon Fiber Growth Mechanism: Catalyst Shape Adjustments above Tammann Temperature

2020 ◽  
Vol 6 (2) ◽  
pp. 18 ◽  
Author(s):  
Luís Sousa Lobo ◽  
Sónia A.C. Carabineiro
Keyword(s):  
Melting Point ◽  
Metal Nanoparticles ◽  
Bulk Diffusion ◽  
Pyrolytic Carbon ◽  
Metal Nanoparticle ◽  
Carbon Formation ◽  
Graphene Layers ◽  
Nanoparticle Shape ◽  
C Fibers ◽  
Nano Catalyst

The mechanism of bamboo-like growth behavior of carbon fibers is discussed. We propose that there is a requirement to have this type of growth: operation above the Tammann temperature of the catalyst (defined as half of the melting point). The metal nanoparticle shape can then change during reaction (sintering-like behavior) facilitating carbon nanotube (CNT) growth, adjusting geometry. Using metal nanoparticles with a diameter below 20 nm, some reduction of the melting point (mp) and Tammann temperature (TTa) is observed. Fick’s laws still apply at nano scale. In that range, distances are short and so bulk diffusion of carbon (C) atoms through metal nanoparticles is quick. Growth occurs under catalytic and hybrid carbon formation routes. Better knowledge of the mechanism is an important basis to optimize growth rates and the shape of bamboo-like C fibers. Bamboo-like growth, occurring under pyrolytic carbon formation, is excluded: the nano-catalyst surface in contact with the gas gets quickly “poisoned”, covered by graphene layers. The bamboo-like growth of boron nitride (BN) nanotubes is also briefly discussed.

Interdiffusion Studies in the Co-Sb System

2020 ◽  
Vol 27 ◽  
pp. 35-39
Author(s):  
Amudha Armugam ◽  
Ravi Raju ◽  
Varun Baheti
Keyword(s):  
Crystal Structure ◽  
Electron Microscope ◽  
Electron Probe ◽  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Diffusion Couples ◽  
Homologous Temperature ◽  
The Difference ◽  
High Homologous Temperature ◽  
Scanning Electron

CoSb based compounds have gained much importance in the fields of thermoelectric devices. In this work, we have conducted the solid–state conventional bulk diffusion couple experiments. To study the phase evolutions, Co/Sb diffusion couples are annealed at 450–550 °C. The interdiffusion zone is analysed using field emission gun equipped scanning electron microscope and the composition measurements are done in electron probe micro−analyser to confirm the growth of various product phases. The marker experiment indicates that the CoSb3 phase grows mainly by diffusion of Sb in the binary Co–Sb system. Growth of the CoSb3 phase is discussed based on assessment correlating the difference in mobilities of species with the high homologous temperature, crystal structure of the phase, and the concept of sublattice diffusion mechanism in line compounds.

scholarly journals Mechanism of Catalytic CNTs Growth in 400–650 °C Range: Explaining Volcano Shape Arrhenius Plot and Catalytic Synergism Using both Pt (or Pd) and Ni, Co or Fe

2019 ◽  
Vol 5 (3) ◽  
pp. 42 ◽  
Author(s):  
Luis Sousa Lobo
Keyword(s):  
Surface Reaction ◽  
Arrhenius Plot ◽  
Bulk Diffusion ◽  
Initial Surface ◽  
Carbon Formation ◽  
Reaction Orders ◽  
Higher Temperature ◽  
Carbon Nanotube Growth ◽  
Nanotube Growth ◽  
Surface Decomposition

The Arrhenius plot of catalytic carbon formation from olefins on Ni, Co, and Fe has a volcano shape in the range 400–550 °C with reaction orders 0 (at lower T: Below ~500 °C) and one (at higher T: Above ~500 °C) at each side of the maximum rate. The reaction follows a catalytic route with surface decomposition of the gas (olefin) on the catalyst nanoparticle, followed by the bulk diffusion of carbon atoms and carbon nanotube growth on the opposite side. At the higher temperature region (500–550 °C), the initial surface reaction step controls the rate and the reaction order is one, both in olefins and hydrogen (H). This confirms that H is essential for the surface reaction to occur. This is very valuable information to get faster CNT growth rate at relatively low temperatures. The apparent activation energy observed must correspond with the surface reaction Ea corrected for the temperature dependence of the two molecules involved (olefin and H). Adding a noble metal (Pt, Pd) to the carbon formation catalyst is frequently found to increase the reaction rate further. This effect has been described as an H spillover since 1964. However, there is evidence that the bulk diffusion of H atoms prevails and does not “spillover” the surface diffusion. Diffusion of H atoms through the solids involved is easy, and the H atoms remain single (“independent”) until emerging on a surface.

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