scholarly journals Substitution and diffusion of Cr2+ and Cr3+ in synthetic forsterite and natural olivine at 1200–1500 °C and 1 bar

2018 ◽  
Vol 220 ◽  
pp. 407-428 ◽  
Author(s):  
M.C. Jollands ◽  
H.St.C. O'Neill ◽  
J. Van Orman ◽  
A.J. Berry ◽  
J. Hermann ◽  
...  
Keyword(s):  
Natural Olivine ◽  
And Diffusion

Coupled inter-site reaction and diffusion: Rapid dehydrogenation of silicon vacancies in natural olivine

2019 ◽  
Vol 262 ◽  
pp. 220-242 ◽  
Author(s):  
Michael C. Jollands ◽  
Elias Kempf ◽  
Jörg Hermann ◽  
Othmar Müntener
Keyword(s):  
Site Reaction ◽  
Natural Olivine ◽  
And Diffusion ◽  
Reaction And Diffusion

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Growth of hematite by surface oxidation of olivine

1988 ◽  
Vol 46 ◽  
pp. 800-801
Author(s):  
S. McKernan ◽  
C. B. Carter
Keyword(s):  
Electron Microscope ◽  
Surface Oxidation ◽  
Thin Foil ◽  
Nucleation And Growth ◽  
Ion Milling ◽  
Annealed Material ◽  
Thin Foils ◽  
Natural Olivine ◽  
Approximate Composition ◽  
Second Phases

The oxidation of natural olivine has previously been performed on bulk samples and the reactions followed by preparation of TEM specimens from the annealed material. These results show that below ∼1000°C hematite and amorphous silica are formed, particularly around dislocations. At higher temperatures magnetite and some enstatite-like phase are formed. In both cases the olivine is left almost totally Fe depleted. By performing the oxidation on characterized thin TEM specimens it is possible to obtain more information on the nucleation and growth of the second phases formed. The conditions in a thin foil, however, are very different from those in the bulk especially with regard to surface effects. The nucleation of precipitates in particular may be expected to occur differently in these thin foils than in the bulk.TEM specimens of natural olivine (approximate composition Mg+Fe+Si2o4) which had been annealed at 1000°C for 1 hr were prepared by mechanical polishing and dimpling, followed by Ar ion milling to perforation. The specimens were characterized in the electron microscope and then heated in air in alumina boats to 900°C for between 30 and 180 minutes.

Ordering and diffusion in II-VI/III-VI alloys with structural vacancies

1997 ◽  
Vol 101-103 (1-2) ◽  
pp. 479-487
Author(s):  
H v. Wensierski
Keyword(s):  
And Diffusion

NMR-Study of Structure and Diffusion Processes in Li3N

1980 ◽  
Vol 41 (C6) ◽  
pp. C6-28-C6-31 ◽  
Author(s):  
R. Messer ◽  
H. Birli ◽  
K. Differt
Keyword(s):  
Diffusion Processes ◽  
Nmr Study ◽  
And Diffusion
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