Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites

Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepar...

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Autores principales:	Andrej Opálek, Štefan Emmer, Roman Čička, Naďa Beronská, Peter Oslanec, Jaroslav Kováčik
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	metal matrix composites hot isostatic pressing thermal expansion Schapery model Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85
Acceso en línea:	https://doaj.org/article/dfd62d18f8d1433e850a15026add9cb2
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spelling	oai:doaj.org-article:dfd62d18f8d1433e850a15026add9cb22021-11-25T18:16:17ZStructure and Thermal Expansion of Cu−90 vol. % Graphite Composites10.3390/ma142270891996-1944https://doaj.org/article/dfd62d18f8d1433e850a15026add9cb22021-11-01T00:00:00Zhttps://www.mdpi.com/1996-1944/14/22/7089https://doaj.org/toc/1996-1944Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10<sup>−6</sup> K<sup>−1</sup> for HIPed pure copper to 4.9 × 10<sup>−6</sup> K<sup>−1</sup> for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu–graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu–graphite composites when more than 30 vol. % graphite is present.Andrej OpálekŠtefan EmmerRoman ČičkaNaďa BeronskáPeter OslanecJaroslav KováčikMDPI AGarticlemetal matrix compositeshot isostatic pressingthermal expansionSchapery modelTechnologyTElectrical engineering. Electronics. Nuclear engineeringTK1-9971Engineering (General). Civil engineering (General)TA1-2040MicroscopyQH201-278.5Descriptive and experimental mechanicsQC120-168.85ENMaterials, Vol 14, Iss 7089, p 7089 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	metal matrix composites hot isostatic pressing thermal expansion Schapery model Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85
spellingShingle	metal matrix composites hot isostatic pressing thermal expansion Schapery model Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85 Andrej Opálek Štefan Emmer Roman Čička Naďa Beronská Peter Oslanec Jaroslav Kováčik Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
description	Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10<sup>−6</sup> K<sup>−1</sup> for HIPed pure copper to 4.9 × 10<sup>−6</sup> K<sup>−1</sup> for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu–graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu–graphite composites when more than 30 vol. % graphite is present.
format	article
author	Andrej Opálek Štefan Emmer Roman Čička Naďa Beronská Peter Oslanec Jaroslav Kováčik
author_facet	Andrej Opálek Štefan Emmer Roman Čička Naďa Beronská Peter Oslanec Jaroslav Kováčik
author_sort	Andrej Opálek
title	Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
title_short	Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
title_full	Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
title_fullStr	Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
title_full_unstemmed	Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites
title_sort	structure and thermal expansion of cu−90 vol. % graphite composites
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/dfd62d18f8d1433e850a15026add9cb2
work_keys_str_mv	AT andrejopalek structureandthermalexpansionofcu90volgraphitecomposites AT stefanemmer structureandthermalexpansionofcu90volgraphitecomposites AT romancicka structureandthermalexpansionofcu90volgraphitecomposites AT nadaberonska structureandthermalexpansionofcu90volgraphitecomposites AT peteroslanec structureandthermalexpansionofcu90volgraphitecomposites AT jaroslavkovacik structureandthermalexpansionofcu90volgraphitecomposites
_version_	1718411411293470720

Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites

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