Internal oxidation of Cu-C and Ag-C composites

Gabrijela Čevnik (Author), Gorazd Kosec (Author), Ladislav Kosec (Author), Rebeka Rudolf (Author), Borut Kosec (Author), Ivan Anžel (Author)

Abstract

The internal oxidation in copper-carbon and silver-carbon composites occurs when they are exposed to air or oxygen at high temperature. Solubility of carbon in copper or in silver is very low. The kinetics of oxidation at high temperature and activation energy were determined and the mechanism of internal oxidation was analysed. The kinetics of internal oxidation was determined for both cases and it is depended from the diffusion of oxygen following parabolic time dependence according to Wagner's theory. The activation energy for Cu-C composite is 70.5 kJ/mol, and for Ag-C composite is 50.1 kJ/mol, what is in both cases close to the activation energy for the volume diffusion of oxygen in copper or in silver. In both cases gas products are formed during the internal oxidation of composites. In the internal oxidation zone pores, bubbles occur. The carbon oxidates directly with the oxygen from solid solution as long there is a contact, which breaks down with the presence of gas products. Then the oxidation occurs over the gas mixture of CO and CO2.

Keywords

internal oxidation;internal oxidation zone;composite;copper;silver;diffusion;kinetics;

Data

Language:	English
Year of publishing:	2008
Typology:	1.03 - Short Scientific Article
Organization:	UM FS - Faculty of Mechanical Engineering
UDC:	669.014
COBISS:	12150294
ISSN:	1408-7073
Parent publication:	RMZ - Materials and geoenvironment
Views:	1600
Downloads:	26
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary title:	Notranja oksidacija Cu-C in Ag-C kompozitov
Secondary abstract:	Pri visokih temperaturah kompoziti bakra in srebra z ogljikom na zraku ali v kisiku reagirajo po mehanizmu notranje oksidacije. Topnost ogljika v trdnem bakru in trdnem srebru je zelo majhna. Analizirali smo kinetiko oksidacije kompozitov, določili aktivacijsko energijo in mehanizem notranje oksidacije. Kinetika oksidacije je pri obeh skupinah materialov odvisna od difuzije kisika in sledi parabolični odvisnosti od časa v skladu z Wagnerjevo teorijo. Aktivacijska energija procesa je za kompozit Cu-C enaka 70,5 kJ/mol, za kompozit Ag-C pa 50,1 kJ/mol, kar je blizu aktivacijski energiji za volumsko difuzijo kisika v trdnem bakru oziroma srebru. Pri oksidaciji kompozita nastajajo plinski produkti. Oksidacija ogljika poteka neposredno s kisikom iz trdne raztopine, ko pa se zaradi nastanka plinske faze stik prekine, pa preko plinske zmesi CO in CO2.
Secondary keywords:	notranja oksidacija;cona notranje oksidacije;kompozit;baker;srebro;difuzija;kinetika;
URN:	URN:SI:UM:
Pages:	str. 1-6
Volume:	ǂVol. ǂ55
Issue:	ǂno. ǂ1
Chronology:	2008
ID:	8717764