DOCSLIB.ORG

A Study on Metallurgy and Corrosion of Ancient Copper-Based Artefacts from the Portuguese Territory

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Study on Metallurgy and Corrosion of Ancient Copper-Based Artefacts from the Portuguese Territory ELIN MARIA SOARES DE FIGUEIREDO A STUDY ON METALLURGY AND CORROSION OF ANCIENT COPPER-BASED ARTEFACTS FROM THE PORTUGUESE TERRITORY LISBOA 2010 nº de arquivo “copyright” ELIN MARIA SOARES DE FIGUEIREDO A STUDY ON METALLURGY AND CORROSION OF ANCIENT COPPER-BASED ARTEFACTS FROM THE PORTUGUESE TERRITORY Dissertação apresentada para a obtenção do Grau de Doutor em Conservação e Restauro, especialidade Ciências da Conservação, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia LISBOA 2010 Acknowledgments I would like to express my gratitude and sincere thanks to my supervisors M. Fátima Araújo (Instituto Tecnológico e Nuclear, ITN) and Rui J.C. Silva (Faculdade de Ciências e Tecnologia – Universidade Nova de Lisboa, FCT-UNL) for giving me the opportunity to be involved in the study of ancient metals, particularly to participate in the project Metallurgy and Society in Late Bronze Age Central Portugal (METABRONZE), as well as for the general supervision of my PhD project. I’m also grateful to João C. Senna-Martinez (Faculdade de Letras – Universidade de Lisboa, FL-UL), the METABRONZE project coordinator. Thanks are also due to all the people and institutions that provided items for study and guided me thought the contextual interpretation of them, namely: João C. Senna-Martinez (UNIARQ-FL-UL and Associação Terras Quentes) for the Fraga dos Corvos artefacts; João C. Senna-Martinez and João L. Inês Vaz (Universidade Católica) for the Baiões/Santa Luzia cultural group artefacts; Ana A. Melo, Luís Raposo and Ana Isabel Santos (Museu Nacional de Arqueologia) for the Pragança artefacts; Raquel Vilaça (Faculdade de Letras – Universidade de Coimbra) for the Medronhal artefacts; Mário V. Gomes (Faculdade de Ciências Sociais e Humanas – UNL) for the Escoural artefacts; and Miguel Pessoa (Museu da Villa Romana do Rabaçal) for the Penela spear-head. I would also like to thank all my colleagues from ITN, CENIMAT/I3N-FCT-UNL and DCR-FCT- UNL, for all the exchange of ideas, knowledge and interesting discussions, which contributed to the development of this work. Special thanks are to Pedro Valério, M. João Furtado, António M. Monge Soares and Francisco M. Braz Fernandes, with whom I worked in close collaboration numerous times. Special thanks are also due to my family and close friends, for all the support and companionship. Finally, I’m grateful for the following financial supports: • PhD grant (SFRH/BD/27358/2006) awarded by the Portuguese Foundation for Science and Technology (FCT-MCTES) for the period of 2007-2010; • METABRONZE grant (2006) and project funded by FCT-MCTES (POCTI/HAR/58678/2004) for the period of 2006-2009; • International Conference Attending grant awarded by the Fundação Calouste Gulbenkian for the attendance of the conference “Archaeometallurgy in Europe” in 2007; • and CENIMAT/I3N-FCT-UNL funding by FCT-MCTES for the attendance of the conference “V International Materials Symposium” in 2009. ii Resumo Nesta tese de doutoramento foram estudados artefactos metálicos de diversas tipologias e vários restos de produção metalúrgica provenientes de vários sítios arqueológicos do território Português, cobrindo um período cronológico de cerca de 3 milénios, desde o Calcolítico à Idade do Ferro. Grande parte dos materiais estudados provêm de colecções museológicas emblemáticas, tais como as do Castro de Pragança e de Baiões. Com este estudo pretendeu-se obter uma perspectiva geral da metalurgia antiga do território oeste peninsular, assim como informação pormenorizada da metalurgia em cada sítio arqueológico. Pretendeu-se também efectuar uma apreciação da corrosão dos metais arqueológicos, nomeadamente das ligas de bronze (Cu-Sn). Para tal foram efectuadas análises elementares e microestruturais utilizando vários métodos analíticos, tais como a espectrometria de fluorescência de raios X dispersiva de energias (FRX), micro-FRX, microscopia óptica e electrónica de varrimento. Os principais resultados do estudo da corrosão demonstraram que a decuprificação é o principal fenómeno de corrosão dos bronzes arqueológicos, mas que o fenómeno inverso, o da destanificação, poderá ocorrer em casos particulares. Foi também verificado que estes fenómenos podem ter uma influência muito significativa nos resultados das análises elementares superficiais efectuadas por FRX, devido à espessura das camadas de corrosão, que podem atingir os 500 µm. Foi observado que a corrosão interna, nomeadamente a intergranular, pode ser muito pronunciada nos artefactos com uma microestrutura mais heterogénea, ou seja, naqueles menos sujeitos a trabalhos termo-mecânicos. Adicionalmente, foram relatadas particularidades da corrosão a longo prazo, como a corrosão selectiva das fases α ou δ e a presença de cobre metálico redepositado nas zonas de corrosão mais internas. Os principais resultados do estudo arqueometalúrgico demonstraram que durante o período Calcolítico foram utilizados cobres bastante puros, com a excepção do elemento As, sendo que durante o Bronze Final o bronze binário com teores relativamente constantes de estanho (média de ~13% Sn) e com ocasionais impurezas de Pb, As e Sb se tenha tornado dominante, passando o cobre a ser utilizado esporadicamente em artefactos onde se pretenderia um aproveitamento das suas propriedades particulares. Ao contrário de outras regiões do ocidente Europeu, os bronzes ternários parecem surgir tardiamente, já durante a Idade do Ferro. A moldagem dos artefactos maiores e de formas mais complexas (p. ex. pontas de lança, machados, anéis fechados) seria feita em molde sendo aplicados apenas alguns trabalhos termo-mecânicos de acabamento, enquanto que os objectos mais pequenos (p. ex. cinzéis, punções, fíbulas simples, anéis abertos) seriam fabricados a partir de pré-formas obtidas em molde, como barras, através de trabalhos termo-mecânicos por vezes muito intensos. iii Abstract In the present thesis metallic artefacts of various typologies and diverse materials related to metallurgical operations were studied. The items are from various sites in the Portuguese territory, covering a period of circa 3 millennia, from Chalcolithic to Iron Age. A large part of the studied items belong to emblematic museum collections, as the Castro de Pragança and the Baiões ones. The aim of the present study is to provide a general view of the ancient metallurgy in the Western territory of the Iberian Peninsula, as well as detailed information on the metallurgy of each archaeological site. It was also aimed an evaluation of the corrosion of archaeological metals, namely bronzes (Cu-Sn alloys). Accordingly, elemental analysis and microstructural examinations were made, combining diverse analytical techniques as energy dispersive X-ray fluorescence spectrometry (EDXRF), micro-EDXRF, optical microscopy and scanning electron microscopy. The main results of the corrosion study showed that decuprification is the main corrosion phenomena among the bronzes, but that destannification can also occur in particular cases. It was found that these phenomena can have a major influence in the results of superficial EDXRF elemental analysis, mainly due to the thickness of the corrosion layers that can reach 500 µm. It was also found that the most internal corrosion, namely the intergranular corrosion, can be very pronounced among the artefacts with a heterogeneous microstructure, i.e. mainly among those that were less subjected to thermo- mechanical processing. Additionally, particular long-term corrosion phenomena were described, as the preferential corrosion of α or δ phase and the presence of redeposited metallic copper in the most internal corrosion regions. The main results of the archaeometallurgical study showed that during the Chalcolithic period relatively pure coppers were used (with exception for the presence of As), and that during Late Bronze Age binary bronze with relatively constant tin contents (average of ~13 wt.% Sn) and impurities as Pb, As and Sb was the main material used, being unalloyed copper only used sporadically to produce particular items where the properties of this metal were an advantage. Differing from other Western European regions, ternary bronzes seem to have a later appearance, i.e. during Iron Age. The shaping of large and more complex artefacts (e.g. spear heads, axes, closed rings) was done in the mould, being needed just some final thermo-mechanical processing. On the other hand, smaller and simpler items (e.g. chisels, awls, simple fibulae, open rings) were produced by shaping pre-defined forms, as cast bars, through thermo-mechanical processes that could be very intense, as those that include various cycles of deformation and annealing. iv Symbols and Notations BA Bronze Age BCS British Chemical Standards BF Bright Field (in OM observations) BSE Backscattered secondary emission (in SEM-EDS analysis) CA Copper Age CCB Centro Cultural de Belém CENIMAT Centro de Investigação em Materiais CSG Castro de Nossa Senhora da Guia de Baiões CSR Crasto de São Romão DAS (Secondary) Dendritic Arm Spacing DCM Departamento de Ciências dos Materiais DCR Departamento de Conservação e Restauro DF Dark Field (in OM observations) EBA Early Bronze Age EIA Early Iron Age ESC Povoado do Escoural EDXRF Energy Dispersive X-Ray Fluorescence FC Fraga dos Corvos FCT Faculdade de Ciências e Tecnologia FCT-MCTES Fundação para a Ciência e Tecnologia – Ministério da Ciência, Tecnologia e Ensino Superior FD Figueiredo das Donas I3N Instituto de Nanoestruturas, Nanomodelação e Nanofabricação IA Iron Age IP Iberian Peninsula IPA
Load more

Recommended publications
  • Planting Power ... Formation in Portugal.Pdf
    Promotoren: Dr. F. von Benda-Beckmann Hoogleraar in het recht, meer in het bijzonder het agrarisch recht van de niet-westerse gebieden. Ir. A. van Maaren Emeritus hoogleraar in de boshuishoudkunde. Preface The history of Portugal is, like that of many other countries in Europe, one of deforestation and reafforestation. Until the eighteenth century, the reclamation of land for agriculture, the expansion of animal husbandry (often on communal grazing grounds or baldios), and the increased demand for wood and timber resulted in the gradual disappearance of forests and woodlands. This tendency was reversed only in the nineteenth century, when planting of trees became a scientifically guided and often government-sponsored activity. The reversal was due, on the one hand, to the increased economic value of timber (the market's "invisible hand" raised timber prices and made forest plantation economically attractive), and to the realization that deforestation had severe impacts on the environment. It was no accident that the idea of sustainability, so much in vogue today, was developed by early-nineteenth-century foresters. Such is the common perspective on forestry history in Europe and Portugal. Within this perspective, social phenomena are translated into abstract notions like agricultural expansion, the invisible hand of the market, and the public interest in sustainably-used natural environments. In such accounts, trees can become gifts from the gods to shelter, feed and warm the mortals (for an example, see: O Vilarealense, (Vila Real), 12 January 1961). However, a closer look makes it clear that such a detached account misses one key aspect: forests serve not only public, but also particular interests, and these particular interests correspond to specific social groups.
    [Show full text]
  • Bat Specialist Screening Study of the 2Nd 765 Kv Kappa – Sterrekus Powerline
    Bat Specialist Screening Study of the 2nd 765 kV Kappa – Sterrekus Powerline Prepared for Eskom Holdings SOC Prepared by 2021-05-17 Kappa- Sterrekus Powerline Specialist Screening Report: Bats Page ii Bat Specialist Screening Study of the 2nd 765 kV Kappa – Sterrekus Powerline Date 2021-05-17 Authors Reviewers Miguel Mascarenhas Joana Santos Craig Campbell Technical Coordination Helena Coelho Joana Santos Joao Paula Miguel Mascarenhas Kappa- Sterrekus Powerline Specialist Screening Report: Bats Page iii Table of Contents 1 Introduction .................................................................................................................. 1 1.1 Project Background ............................................................................................................................. 1 1.1.1 Background ............................................................................................................................. 1 1.1.2 Strategic Environmental Assessment for Power Corridors ..................................................... 3 1.2 Objectives of the Bat Screening Report .............................................................................................. 3 1.3 Terms of Reference for Bat Study ...................................................................................................... 4 2 Project Description ....................................................................................................... 4 2.1 Corridor Alignments ...........................................................................................................................
    [Show full text]
  • Publicado Public Policy Portuguese Journal Vol2 N2 2017
    ISSN 2183-8992 Volume 2, Number 2, 2017 Special Issue: Sustaining small and medium-size towns: policies and prospects Teresa de Noronha and Eric Vaz Guest Editors 1 Public Policy Portuguese Journal, Volume 2, Number 2, 2017 1 Public Policy Portuguese Journal Aims and Scope Public Policy Portuguese Journal aims to publish high-quality theoretical, empirical, applied or policy- oriented research papers on public policy. We will enforce a rigorous, fair and prompt refereeing process. The geographical reference in the name of the Journal only means that the Journal is an initiative of Portuguese scholars. Editors Paulo Neto, Universidade de Évora, Portugal. Maria Manuel Serrano, Universidade de Évora, Portugal. Editorial Board Adriano Pimpão - Universidade do Algarve, Faculdade de Economia e Assembleia Intermunicipal do Algarve | Ana Lúcia Sargento - Instituto Politécnico de Leiria, Escola Superior de Tecnologia e Gestão e Centro de Investigação em Gestão para a Sustentabilidade | Annette Bongardt - London School of Economics and Political Science, European Institute, e Academic Steering Committee of the European Studies Centre of St Antony’s College, Oxford University | António Ferreira Gomes - Organisation for Economic Co-operation and Development (OECD) | António Manuel Figueiredo - Universidade do Porto, Faculdade de Economia e Quarternaire Portugal | António Oliveira das Neves - Instituto de Estudos Sociais e Económicos (IESE) | Artur Rosa Pires - Universidade de Aveiro, Departamento de Ciências Sociais, Políticas e do Território, e
    [Show full text]
  • WP2 Report Aveiro
    DELIVERABLE D2.1b The Ria de Aveiro Lagoon Current knowledge base and knowledge gaps © H. Queiroga Deliverable D2.1b Title The Ria de Aveiro Lagoon – Current knowledge base and knowledge gaps Author(s) Alves FL, Soares J, Sousa LP, Department of Environment and Planning & CESAM, University of Aveiro, Portugal Baggett S, Gooch G, Hendry S, IHP-HELP Centre for Water Law, Policy and Science, University of Dundee, Scotland, UK Lillebø AI, Department of Biology & CESAM, University of Aveiro, Portugal Report No. LAGOONS Report No. D2.1b This report should be cited as: LAGOONS. 2012. The Ria de Aveiro Lagoon – Current knowledge base and knowledge gaps. LAGOONS Report D2.1b. 52pp. Organisation name of lead contractor for this deliverable University of Aveiro, Portugal No. of pages 52 Due date of deliverable: 30.09.2012 Actual date of deliverable: 11.10.2010 Dissemination level1 PU Key words Ria de Aveiro, lagoon, coastal zone management, climate change, river basin, management <Other> Title of project: Integrated water resources and coastal zone management in European lagoons in the context of climate change Instrument: Contract number: 283157 Start date of project: October 2011 Duration: 36 months Disclaimer The information provided and the opinions given in this publication are not necessarily those of the authors or the EC. The authors and publisher assume no liability for any loss resulting from the use of this report. 1 PU Public PP Restricted to other programme participants (including the Commission Services) RE Restricted to a group specified
    [Show full text]