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Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride

Producing bulk AlN with grain sizes in the nano regime and measuring its thermal conductivity is an important milestone in the development of materials for high energy optical applications. We present the synthesis and subsequent densification of nano-AlN powder to produce bulk nanocrystalline AlN....

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Autores principales: Duarte, Matthew A., Mishra, Vivek, Dames, Chris, Kodera, Yasuhiro, Garay, Javier E.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8509186/
https://www.ncbi.nlm.nih.gov/pubmed/34639962
http://dx.doi.org/10.3390/ma14195565
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author Duarte, Matthew A.
Mishra, Vivek
Dames, Chris
Kodera, Yasuhiro
Garay, Javier E.
author_facet Duarte, Matthew A.
Mishra, Vivek
Dames, Chris
Kodera, Yasuhiro
Garay, Javier E.
author_sort Duarte, Matthew A.
collection PubMed
description Producing bulk AlN with grain sizes in the nano regime and measuring its thermal conductivity is an important milestone in the development of materials for high energy optical applications. We present the synthesis and subsequent densification of nano-AlN powder to produce bulk nanocrystalline AlN. The nanopowder is synthesized by converting transition alumina (δ-Al(2)O(3)) with <40 nm grain size to AlN using a carbon free reduction/nitridation process. We consolidated the nano-AlN powder using current activated pressure assisted densification (CAPAD) and achieved a relative density of 98% at 1300 °C with average grain size, [Formula: see text] ~125 nm. By contrast, high quality commercially available AlN powder yields densities ~75% under the same CAPAD conditions. We used the 3-ω method to measure the thermal conductivity, κ of two nanocrystalline samples, 91% dense, [Formula: see text] = 110 nm and 99% dense, [Formula: see text] = 220 nm, respectively. The dense sample with 220 nm grains has a measured κ = 43 W/(m·K) at room temperature, which is relatively high for a nanocrystalline ceramic, but still low compared to single crystal and large grain sized polycrystalline AlN which can exceed 300 W/(m·K). The reduction in κ in both samples is understood as a combination of grain boundary scattering and porosity effects. We believe that these are finest [Formula: see text] reported in bulk dense AlN and is the first report of thermal conductivity for AlN with ≤220 nm grain size. The obtained κ values are higher than the vast majority of conventional optical materials, demonstrating the advantage of AlN for high-energy optical applications.
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spelling pubmed-85091862021-10-13 Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride Duarte, Matthew A. Mishra, Vivek Dames, Chris Kodera, Yasuhiro Garay, Javier E. Materials (Basel) Article Producing bulk AlN with grain sizes in the nano regime and measuring its thermal conductivity is an important milestone in the development of materials for high energy optical applications. We present the synthesis and subsequent densification of nano-AlN powder to produce bulk nanocrystalline AlN. The nanopowder is synthesized by converting transition alumina (δ-Al(2)O(3)) with <40 nm grain size to AlN using a carbon free reduction/nitridation process. We consolidated the nano-AlN powder using current activated pressure assisted densification (CAPAD) and achieved a relative density of 98% at 1300 °C with average grain size, [Formula: see text] ~125 nm. By contrast, high quality commercially available AlN powder yields densities ~75% under the same CAPAD conditions. We used the 3-ω method to measure the thermal conductivity, κ of two nanocrystalline samples, 91% dense, [Formula: see text] = 110 nm and 99% dense, [Formula: see text] = 220 nm, respectively. The dense sample with 220 nm grains has a measured κ = 43 W/(m·K) at room temperature, which is relatively high for a nanocrystalline ceramic, but still low compared to single crystal and large grain sized polycrystalline AlN which can exceed 300 W/(m·K). The reduction in κ in both samples is understood as a combination of grain boundary scattering and porosity effects. We believe that these are finest [Formula: see text] reported in bulk dense AlN and is the first report of thermal conductivity for AlN with ≤220 nm grain size. The obtained κ values are higher than the vast majority of conventional optical materials, demonstrating the advantage of AlN for high-energy optical applications. MDPI 2021-09-25 /pmc/articles/PMC8509186/ /pubmed/34639962 http://dx.doi.org/10.3390/ma14195565 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Duarte, Matthew A.
Mishra, Vivek
Dames, Chris
Kodera, Yasuhiro
Garay, Javier E.
Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title_full Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title_fullStr Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title_full_unstemmed Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title_short Processing and Thermal Conductivity of Bulk Nanocrystalline Aluminum Nitride
title_sort processing and thermal conductivity of bulk nanocrystalline aluminum nitride
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8509186/
https://www.ncbi.nlm.nih.gov/pubmed/34639962
http://dx.doi.org/10.3390/ma14195565
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