Al motion rates in levitated, molten Al2O3 samples, measured by pulsed gradient spin echo 27Al NMR

Robert F. Marzke; J. Piwowarczyk; P. F. McMillan; George Wolf

doi:10.1016/j.jeurceramsoc.2005.01.002

Al motion rates in levitated, molten Al₂O₃ samples, measured by pulsed gradient spin echo ²⁷Al NMR

Robert F. Marzke, J. Piwowarczyk, P. F. McMillan, George Wolf

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

Strong attenuation of ²⁷Al NMR signals has been observed in a magnetic field gradient, in beads of alumina melted by a CO₂ laser and levitated in flowing Ar. The standard NMR diffusivity measurement interpretation of the data leads to very large (∼1.5 × 10^-7 m²/s) effective diffusivity values, approximately independent of temperature between melting and 2500 °C. These high values and their weak temperature dependence contrast sharply with estimates of ionic diffusivity arising from the known, activated temperature dependences of molten alumina's viscosity and ²⁷Al NMR line width. Our anomalously large diffusivities are attributed to bulk displacive motions, which can be visually observed in the levitated molten beads and can lead to substantial Al displacements over experimental NMR time scales. Possible origins of these motions are briefly discussed.

Original language	English (US)
Pages (from-to)	1325-1332
Number of pages	8
Journal	Journal of the European Ceramic Society
Volume	25
Issue number	8 SPEC. ISS.
DOIs	https://doi.org/10.1016/j.jeurceramsoc.2005.01.002
State	Published - 2005

Keywords

AlO
Diffusion
NMR
Refractories
Spectroscopy

ASJC Scopus subject areas

Ceramics and Composites
Materials Chemistry

Access to Document

10.1016/j.jeurceramsoc.2005.01.002

Cite this

@article{971b7a7364e74abf92d92c2baae66c1e,

title = "Al motion rates in levitated, molten Al2O3 samples, measured by pulsed gradient spin echo 27Al NMR",

abstract = "Strong attenuation of 27Al NMR signals has been observed in a magnetic field gradient, in beads of alumina melted by a CO2 laser and levitated in flowing Ar. The standard NMR diffusivity measurement interpretation of the data leads to very large (∼1.5 × 10-7 m2/s) effective diffusivity values, approximately independent of temperature between melting and 2500 °C. These high values and their weak temperature dependence contrast sharply with estimates of ionic diffusivity arising from the known, activated temperature dependences of molten alumina's viscosity and 27Al NMR line width. Our anomalously large diffusivities are attributed to bulk displacive motions, which can be visually observed in the levitated molten beads and can lead to substantial Al displacements over experimental NMR time scales. Possible origins of these motions are briefly discussed.",

keywords = "AlO, Diffusion, NMR, Refractories, Spectroscopy",

author = "Marzke, {Robert F.} and J. Piwowarczyk and McMillan, {P. F.} and George Wolf",

note = "Funding Information: This work was co-funded by the National Science Foundation and the Air Force Office of Scientific Research, under NSF grant DRM01-116361. Additional support has been provided by AFOSR, under grant F4962-03-1-0346 and by the Research Corporation, under grant RA-0276. We wish to thank K. Schmidt for essential calculations in the design of the magnetic field gradient and shielding coils. We also thank R. Weber for many helpful discussions and suggestions.",

year = "2005",

doi = "10.1016/j.jeurceramsoc.2005.01.002",

language = "English (US)",

volume = "25",

pages = "1325--1332",

journal = "Journal of the European Ceramic Society",

issn = "0955-2219",

publisher = "Elsevier BV",

number = "8 SPEC. ISS.",

}

TY - JOUR

T1 - Al motion rates in levitated, molten Al2O3 samples, measured by pulsed gradient spin echo 27Al NMR

AU - Marzke, Robert F.

AU - Piwowarczyk, J.

AU - McMillan, P. F.

AU - Wolf, George

N1 - Funding Information: This work was co-funded by the National Science Foundation and the Air Force Office of Scientific Research, under NSF grant DRM01-116361. Additional support has been provided by AFOSR, under grant F4962-03-1-0346 and by the Research Corporation, under grant RA-0276. We wish to thank K. Schmidt for essential calculations in the design of the magnetic field gradient and shielding coils. We also thank R. Weber for many helpful discussions and suggestions.

PY - 2005

Y1 - 2005

N2 - Strong attenuation of 27Al NMR signals has been observed in a magnetic field gradient, in beads of alumina melted by a CO2 laser and levitated in flowing Ar. The standard NMR diffusivity measurement interpretation of the data leads to very large (∼1.5 × 10-7 m2/s) effective diffusivity values, approximately independent of temperature between melting and 2500 °C. These high values and their weak temperature dependence contrast sharply with estimates of ionic diffusivity arising from the known, activated temperature dependences of molten alumina's viscosity and 27Al NMR line width. Our anomalously large diffusivities are attributed to bulk displacive motions, which can be visually observed in the levitated molten beads and can lead to substantial Al displacements over experimental NMR time scales. Possible origins of these motions are briefly discussed.

AB - Strong attenuation of 27Al NMR signals has been observed in a magnetic field gradient, in beads of alumina melted by a CO2 laser and levitated in flowing Ar. The standard NMR diffusivity measurement interpretation of the data leads to very large (∼1.5 × 10-7 m2/s) effective diffusivity values, approximately independent of temperature between melting and 2500 °C. These high values and their weak temperature dependence contrast sharply with estimates of ionic diffusivity arising from the known, activated temperature dependences of molten alumina's viscosity and 27Al NMR line width. Our anomalously large diffusivities are attributed to bulk displacive motions, which can be visually observed in the levitated molten beads and can lead to substantial Al displacements over experimental NMR time scales. Possible origins of these motions are briefly discussed.

KW - AlO

KW - Diffusion

KW - NMR

KW - Refractories

KW - Spectroscopy

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