Role of the oxygen partial pressure in the formation of composite Co-CoO nanoparticles by reactive aggregation

The magnetic properties of diluted films composed of nanocomposite Co-CoO nanoparticles (of ~8 nm diameter) dispersed in a Cu matrix have been investigated. The nanoparticles were formed in an aggregation chamber by sputtering at different Ar/O2 partial pressures (0-0.015). The exchange bias properties appear to be insensitive to the amount of O2 during their formation. However, the temperature dependence of the magnetization, M(T), exhibits two different contributions with relative intensities that correlate with the amount of O2. The magnetic results imply that two types of particles are formed, nanocomposite Co-CoO (determining the exchange bias) and pure CoO, as confirmed by transmission electron microscopy observations. Importantly, as the O2 partial pressure during the sputtering is raised the number of nanocomposite Co-CoO nanoparticles (exhibiting exchange bias properties) is reduced and, consequently, there is an increase in the relative amount of pure, antiferromagnetic CoO particles

Thermal comfort in office buildings

150 σ.Θερμική άνεση σε κτήρια. Παράγοντες που επηρεάζουν τη θερμική άνεση. Εφαρμογή σε χώρο γραφείων με χρήση του προγράμματος Ecotect Analysis 2010 της Autodesk.Thermal comfort in buildings. Factors that effect it. Application in office buildins using the Ecotect Analysis 2010 Autodesk.Φωκάς Ν. Φραγγή