Performance of radar absorbing nanocomposites by waveguide measurements

Sol-gel synthesis has been investigated in order to produce stoichiometric compositions of Ba3Co2Fe24O41 (Co2Z) at lower calcination temperatures, using citric acid as quelant complex. Using this method, Co2Z ferrite could be synthesized at 950 °C, about 400 °C lower than that of conventional method. Nanocomposites (80:20% weight) of this ferrite with polychloroprene (CR) were obtained for the microwave absorption measurements by mixing, molding and curing mixtures of Ba3Co2Fe24O41 powders with polychloroprene and the additives of vulcanization. The microwave absorption measurements was carried out using the Transmission/Reflection method for the S and X-Ku bands and showed the best performance as Radar Absorber Material (RAM) in 8.0-16.0 GHz range. Thus, the material can be used by reducing the radar signature of the Brazilian Frigates' superstructures

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved