Sintering Behavior of Ba2CaWO6-Doped-Tungsten

1993 ◽  
Vol 322 ◽  
Author(s):  
J.A. Ruud ◽  
B.P. Bewlay
Keyword(s):  
Grain Boundary ◽  
Mass Loss ◽  
Boundary Diffusion ◽  
Activation Energies ◽  
Grain Boundary Diffusion ◽  
Sintering Behavior ◽  
Densification Mechanism ◽  
Early Stages ◽  
Kinetics Of

AbstractThe sintering behavior of Ba2CaWO6 co-sintered with W powder was investigated. Measurements of density and mass loss of sintered compacts showed that the Ba2CaWO6-doped-W had a lower density than undoped W and that there was little volatilization of Ba2CaWO6 at temperatures below 1750 °C. The activation energies for densification of Ba2CaWO6-doped-W and undoped W were both measured to be 389 kJ/mol, which indicates the same densification mechanism, grain boundary diffusion, operated for both materials. The reduced densification kinetics of the Ba2CaWO6-doped-W was probably due to increased coarsening in the early stages of sintering.

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

Oxygen Self-Diffusion In Mgo Grain Boundaries

1994 ◽  
Vol 357 ◽  
Author(s):  
Michael Liberatore ◽  
Bernhardt J. Wuensch
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Experimental Error ◽  
Boundary Diffusion ◽  
High Energy ◽  
Activation Energies ◽  
Grain Boundary Diffusion ◽  
Low Energy ◽  
Enhanced Diffusion ◽  
Self Diffusion

AbstractOxygen grain boundary diffusion has been studied in low energy (∑5, ∑13) and high energy (asymmetric 16° tilt) MgO grain boundaries. Enhanced diffusion of oxygen was observed in all boundaries, but more so in the general, high energy boundary, by 1 - 2 orders of magnitude. This supports the theory that the better the atomic registry between the adjoining grains the lower the diffusivities in the grain boundary. Also the activation energies for bulk and grain boundary diffusion (in the ∑13 boundaries) were found to be equal to within experimental error. (≈ 3.9eV)

scholarly journals The oxidation kinetics of thin nickel films between 250 and 500 °C

2017 ◽  
Vol 19 (13) ◽  
pp. 9045-9052 ◽  
Author(s):  
Y. Unutulmazsoy ◽  
R. Merkle ◽  
D. Fischer ◽  
J. Mannhart ◽  
J. Maier
Keyword(s):  
Grain Boundary ◽  
Oxidation Kinetics ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Diffusion Controlled ◽  
Ni Oxidation ◽  
Thin Nickel ◽  
P Diffusion ◽  
Kinetics Of ◽  
Nio Films

Diffusion controlled Ni oxidation is enhanced by fast grain boundary diffusion in growing nanocrystalline NiO films.

Thermal Degradation of Tantalum-Nickel Thin Film Couples

1995 ◽  
Vol 382 ◽  
Author(s):  
M. H. Tabacniks ◽  
A.J. Kellock ◽  
J.E.E. Baglin ◽  
K.R. Coffey ◽  
J.K. Howard ◽  
...  
Keyword(s):  
Thin Film ◽  
Thermal Degradation ◽  
Grain Boundary ◽  
Boundary Diffusion ◽  
Thermal Conditions ◽  
Metal Films ◽  
Grain Boundary Diffusion ◽  
Helium Flow ◽  
Magnetic Performance ◽  
Kinetics Of

ABSTRACTMultilayered metal films including such couples as Ta-Permalloy (Ni80Fe20) play a key role in magnetic recording sensors, where it is important to preserve the integrity of the thin permalloy layer under thermal conditions during processing and subsequent service. Earlier work1 has indicated a fast grain boundary diffusion of Ta in Ni films at temperatures as low as 250°C. In this paper, we report measurements of the kinetics of this diffusion, in the temperature range 300–400°C. For this work, layered Ni/Ta systems were prepared under controlled conditions, annealed in a helium-flow furnace, and characterized by RBS, AES, XRD and SEM. The possible consequences of diffusion on magnetic performance are also discussed.

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