Gold to aurostibite transformation and formation of Au-Ag-Sb phases: the Krásná Hora deposit, Czech Republic

2017 ◽  
Vol 81 (4) ◽  
pp. 987-999 ◽  
Author(s):  
Jiří Zachariáš ◽  
Matěj Němec
Keyword(s):  
Czech Republic ◽  
Solid State ◽  
Grain Boundaries ◽  
Native Gold ◽  
Diffusion Processes ◽  
Solid State Diffusion ◽  
State Diffusion

AbstractRare phases of the Au–Ag–Sb system were recognized in the Krásná Hora Sb-Au deposit (Sb 1.5–3 wt.%; Au 3–5 ppm), Czech Republic which correspond to auriferous dyscrasite (up to 7 at.% Au), auriferous allargentum (up to 34 at.% Au), and an unnamed phase with composition similar to the eutectics (E1, E2) of the experimental Au–Ag–Sb system. The dominant ore mineral is stibnite with rare native antimony, native gold and a Ag-Au alloy. Textural relationships are well established: stibnite (early) →gold → aurostibite → native antimony (late). Gold is present in four generations: Au-1 (0–15 at.% Ag) is the most abundant type; Au-2 (20–70 at.% Ag) forms thin rims along intra-grain boundaries of Au-1; Au-3 and Au-4 are rare and almost pure (∼0 at.% Ag). The formationof most of the Au-2 and of Au-Ag-Sb phases is associated with Ag-mobilization coupled with the Au-1 to aurostibite transformation via dissolution-precipitation and solid-state diffusion processes at temperatures <200°C.

Investigation of Solid State Diffusion Processes Involved in the Zinc Oxide Sulfidation Reaction

2016 ◽  
Vol 9 ◽  
pp. 100-110
Author(s):  
Kévin Perrin ◽  
David Chiche ◽  
Javier Perez-Pellitero ◽  
Olivier Politano ◽  
Sébastien Chevalier
Keyword(s):  
Zinc Oxide ◽  
Solid State ◽  
Reaction Kinetics ◽  
Diffusion Processes ◽  
Oxide Phase ◽  
Trivalent Cation ◽  
Solid State Diffusion ◽  
State Diffusion ◽  
Dynamics Simulations ◽  
The Impact

Sulfidation of undoped and aluminum doped zinc oxide materials has been performed by TGA under a H2S atmosphere in order to evaluate the impact of the doping element on sulfidation reaction kinetics and mechanism. The presence of aluminum seems to slow-down the reaction kinetics. This phenomenon might be explained by a modification of the solid state diffusion processes involved in ZnO sulfidation reaction and the related ZnS outward growth, assuming the presence of aluminum atoms inside ZnO and ZnS phases. In order to determine solid state diffusion mechanisms controlling the reaction kinetics, molecular dynamics simulations were performed using a Coulomb-Buckingham potential. Firstly, the diffusion of the different elements (Zn, O, S) was simulated for both the oxide and sulfide phases considering a vacancy mechanism. Secondly, simulations of the oxide phase doped by a trivalent cation were also performed. The results obtained in this preliminary work are presented and compared to the literature.

Exafs Studies of Grain Boundary Diffusion and Segregation

1986 ◽  
Vol 77 ◽  
Author(s):  
S. M. Heald ◽  
H. Chen ◽  
J. M. Tranquada
Keyword(s):  
Thin Film ◽  
Solid State ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Structural Information ◽  
Solid State Diffusion ◽  
Interface Reactions ◽  
Tin Bronze ◽  
State Diffusion

ABSTRACTThe dominant pathway for thin film interdiffusion and interface reactions is often via grain boundaries. We have made EXAFS measurements of grain boundary constituents for two systems: interdiffusion in Ag-Au bilay-ers and solid state reaction of Nb with a copper-tin bronze to form Nb3Sn. The Ag-Au results indicate that Au in saturated Ag grain boundaries has an environment similar to a dilute Au in Ag solution with reduced coordination. For the Nb-bronze reaction, the results for the Cu environment indicate distinct changes in the grain boundary environment when small amounts of Ti, Hf, Zr, and Ta are added to the starting Nb. Both results demonstrate the ability of EXAFS to probe grain boundary environments, and to provide important structural information in understanding solid state diffusion and interdiffusion in thin film systems.

Growth of Silicon Carbide Filaments in Multicrystalline Silicon for Solar Cells

2009 ◽  
Vol 156-158 ◽  
pp. 35-40 ◽  
Author(s):  
Hans Joachim Möller ◽  
Claudia Funke ◽  
Jan Bauer ◽  
S. Köstner ◽  
H. Straube ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Solar Cells ◽  
Solid State ◽  
Grain Boundaries ◽  
Bulk Material ◽  
Casting Process ◽  
Carbon Diffusion ◽  
Solid State Diffusion ◽  
State Diffusion ◽  
Solid Liquid Interface

This work introduces two different approaches to explain the growth of silicon carbide (SiC) filaments, found in the bulk material and in grain boundaries of solar cells made from multicrystalline (mc) silicon. These filaments are responsible for ohmic shunts. The first model proposes that the SiC filaments grow at the solid-liquid interface of the mc-Si ingot, whereas the second model proposes a growth due to solid state diffusion of carbon atoms in the solid fraction of the ingot during the block-casting process. The melt interface model can explain quantitatively the observed morphologies, diameters and mean distances of SiC filaments. The modeling of the temperature- and time-dependent carbon diffusion to a grain boundary in the cooling ingot shows that solid state diffusion based on literature data is not sufficient to transport the required amount of approximately 3.4  1017 carbon atoms per cm2 to form typical SiC filaments found in grain boundaries of mc-Si for solar cells. However, possible mechanisms are discussed to explain an enhanced diffusion of carbon to the grain boundaries.

Specific Features of Statistical Analysis for Grain Nanostructures Formed by Solid-State Diffusion at Annealing

2021 ◽  
Vol 316 ◽  
pp. 527-532
Author(s):  
Alexey Stolbovsky
Keyword(s):  
Grain Size ◽  
Statistical Analysis ◽  
Standard Deviation ◽  
Solid State ◽  
Diffusion Processes ◽  
Average Crystallite Size ◽  
Solid State Diffusion ◽  
Mean Values ◽  
State Diffusion ◽  
Standard Distribution

Analysis of structure of Nb3Sn layers, formed by solid-state diffusion in Nb/Cu-Sn composites, has been carried out, using statistical analysis methods. The three different statistical models of grain size distributions, which consist of both a single logarithmic standard distribution and a combination of a logarithmic and a standard distribution with scale factors were considered. It was shown that, during the formation and further evolution of the structure by solid-state diffusion processes, there is a strong correlation between the average crystallite sizes and their deviations from mean values. The dependence of the standard deviation on the average crystallite size, calculated from parameters of logarithmic distribution, falls on the straight line with small deviations. Taking into consideration the relationship between the parameters of grain size distribution, one can conclude that an approximation with the model which involves the dependence between standard deviation of the standard distribution and the logarithmic one provides better accuracy, despite a little bit worse fitting quality of the experimental distributions.

Joining of Ti3SiC2 with Ti–6Al–4V Alloy

2002 ◽  
Vol 17 (1) ◽  
pp. 52-59 ◽  
Author(s):  
N.F. Gao ◽  
Y. Miyamoto
Keyword(s):  
Solid State ◽  
Rate Constant ◽  
Liquid State ◽  
Parabolic Rate Constant ◽  
Diffusion Path ◽  
Solid State Diffusion ◽  
Diffusion Controlled ◽  
State Diffusion ◽  
Rate Controlled ◽  
Higher Temperature

The joining of a Ti3SiC2 ceramic with a Ti–6Al–4V alloy was carried out at the temperature range of 1200–1400 °C for 15 min to 4 h in a vacuum. The total diffusion path of joining was determined to be Ti3SiC2/Ti5Si3Cx/Ti5Si3Cx + TiCx/TiCx/Ti. The reaction was rate controlled by the solid-state diffusion below 1350 °C and turned to the liquid-state diffusion controlled with a dramatic increase of parabolic rate constant Kp when the temperature exceeded 1350 °C. The TiCx tended to grow at the boundarywith the Ti–6Al–4V alloy at a higher temperature and longer holding time. TheTi3SiC2/Ti–6Al–4V joint is expected to be applied to implant materials.

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