Structures and phase equilibria in the ternary Cu-As-Sb system

The PhD focus on the determination of the ternary Cu-As-Sb phase diagram in the copperrich corner of the system (64-100 at.% Cu). There are no works carried out on the Cu-As-Sb system yet; only the respective binary systems were studied [1-6]. The starting goal was to carry out not only the study of one isothermal section (i.e.: at 500 ºC or 600 ºC), but (and more ambitiously) to perform an investigation also as a function of temperature. This system is of particular importance for extractive metallurgy as copper mined from sulfosalt minerals, such as tetrahedrite, tennantite, and enargite (all so-called Fahlores), which are characterized by high concentrations of arsenic (As) and antimony (Sb). After starting the experimental work on the ternary Cu-As-Sb system, it became soon clear that the planned analyses would not have provided sufficient insight into the study of this system: it was quickly noted that some data reported for the Cu-As diagram were unreliably and the system was still lacking of fundamental data that were and are essential for the interpretation of results from the work on the ternary Cu-As-Sb system. Consequently, it has been decided to study formation, crystal structure and polymorphism of intermetallics of the Cu-As system (mostly Cu3As and Cu5As2; both reported dimorphic, each one with a low- and high-temperature structure). Then, it was also planned to possibly perform further and deeper analyses as crystal structure determinations and physical properties measurements. It is the aim of the PhD-research to: - Study the alloys in as-cast and annealed condition to understand phase formation, stability, the crystallo-chemical changes and transitions resulting from thermal treatments; - Determine the copper-rich corner of the Cu-As-Sb phase diagrams (64-100 at.% Cu); - Identify new phases and ternary compounds yet unknown, study their thermodynamic stability and crystal structure(s). - Plan (future) specific physical properties measurements, in view of identifying desirable and exploitable properties of either the binary or ternary compounds

Arsenic loss during metallurgical processing of arsenical bronze

The chemical composition of ancient copper-based metal changes over time due to repetitive recycling and mixing of old metal. Prehistoric copper usually contains impurities from the copper ores themselves, and some have been used as evidence of anthropomorphically induced chemical change. Research into these changes has historically relied upon the assumption of element loss linearity, which is highly misleading and in fact varies with a multitude of factors. To illustrate the complexity of such losses for prehistoric alloys, we have selected arsenical bronze (Cu-As alloys) for study. The mass loss of several Cu-As-alloys under reducing atmosphere was measured by DTA/TGA. From our comparison of the experimental results to thermodynamic calculations and literature data, it was unclear whether weight losses were solely caused by the elemental loss of arsenic. However, a prolonged time temperature-cycling run demonstrated that mainly arsenic volatilizes; hence, the non-linear mass loss from the alloy can be directly attributed to arsenic

Archaeometallurgical characterization of the earliest European metal helmets

Archaeometric analyses on conical and decorated cap helmets from the Bronze Age are presented. The helmets are dated to the 14–12th century BC according to associated finds in hoards. Alloy composition, material structure and manufacturing processes are determined and shed light on the earliest development of weaponry production in Central and Eastern Europe. Analyses were carried out using light and dark field microscopy, SEM–EDXS, PIXE, TOF-ND and PGAA. The results allowed reconstructing the manufacturing process, the differences between the cap of the helmets and their knobs (i.e. alloy composition) and the joining technique of the two parts