The use of gold for artefact productions underwent substantial developments during Iron Age in we... more The use of gold for artefact productions underwent substantial developments during Iron Age in western Europe, with the diversification of alloy compositions and the introduction of new technologies and aesthetics. This work presents a detailed study of a Late Iron Age earring from the western Iberian Peninsula and a discussion taking into consideration the alloys and technologies used at the time. The earring has a complex structure, composed of block- and strip-twisted wires and granulation. Characterization by multifocus optical microscopy, portable X-ray fluorescence spectrometry (pXRF), micro-XRF and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were performed to obtain information on the chemical composition and manufacturing techniques. Results show that the earring was manufactured with wires and granules made of a silver-rich alloy, covered with a gold-rich layer 45 μm thick on average, which acted as an external coating making the entire earrin...
This paper presents a comprehensive study of the evidence for ancient tin mining at the Ervedosa ... more This paper presents a comprehensive study of the evidence for ancient tin mining at the Ervedosa mine (Vinhais, Portugal). The geological context of the site indicates a rich cassiterite (SnO2) deposit, which was subject to mining in the twentieth century. Some ancient mining and ore processing stone tools were recovered during the twentieth century mining operations, namely one hammer, one pounder, one flat anvil and five small tools used both as pounders and crushing anvils, evidencing prehistoric mining activities. XRF and SEM–EDS chemical analyses were performed on primary and secondary cassiterite samples from the mining site, demonstrating the abundance and chemical heterogeneity of the tin (Sn) ores. The stone tools can be ascribed to Bronze Age or, at the latest, Early Iron Age (2nd millennium to the first half of 1st millennium BCE) by comparison with similar tools from other Iberian and European archaeological contexts. High-resolution photogrammetric 3D models of the tools are made available in this study. The historical descriptions of the findings and the research made on the technical archives about the mine allowed correlating the tools to mining in a primary context, focused on rich quartz veins in granitic or greisen bedrock, rather than mining in a secondary context. XRF and SEM–EDS analyses performed on the stone material and on surface adherences support their identification as specific types of hard rocks, such as granite, amphibolite and quartzite, and allowed the detection of Sn-rich adherent particles, confirming their use for Sn-material processing. The potential relation between the cassiterite resources and the local later prehistoric (Bronze Age to Early Iron Age) settlement pattern is also discussed. The results raise awareness and provide relevant data about the existence of tin mining in primary contexts during later prehistoric times in the NW Iberian Peninsula.
espanolPresentamos el resultado del trabajo iniciado en el contexto de una investigacion etnoarqu... more espanolPresentamos el resultado del trabajo iniciado en el contexto de una investigacion etnoarqueologica sobre las explotaciones mineras en epoca contemporanea en el termino municipal de A Gudina (SE de la provincia de Ourense, Galicia). Se documento la realizacion de un proceso artesanal de reduccion de casiterita, resultando una aportacion documental extraordinaria con respecto a las potencialidades de reduccion directa de estano cuando se procesan minerales de muy alta ley, como es el caso de la casiterita del grupo minero de Barxa. En el presente trabajo se aportan resultados de estudios analiticos de los materiales resultantes del proceso con el objetivo de estudiar el grado de pureza del estano producido, y, eventualmente, de relacionar los minerales utilizados con las escorias y el metal obtenido. El resultado permite plantear diversos aspectos en relacion a los modelos propuestos de obtencion de estano y bronce en la Prehistoria hasta la actualidad, y a las posibilidades in...
Transactions of the Indian Institute of Metals, 2021
Recently, severe plastic deformation (SPD) is recognized as a very efficient processing technique... more Recently, severe plastic deformation (SPD) is recognized as a very efficient processing technique for the fabrication of bulk nanostructured (ns)/ultrafine-grained materials. High-speed high-pressure torsion (HSHPT) process, an SPD method, is used as a novel approach to produce ultrafine grains in memory materials. The influence of HSHPT process variables on some Cu-based shape memory alloys (SMAs) is explored and discussed. This paper also envisages providing a comparative study of significant microstructural evolutions and features that are introduced by HSHPT processing. The plastic deformation mechanisms of the copper-based SMAs are investigated from macrostructural and microstructural points of view using optical and scanning electron microscopic techniques. In addition, significant grain size reduction brought about by the process is attested by X-ray diffraction and transmission electron microscopy. The transition temperatures have been determined by differential scanning calorimetry.
OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
The goal of the work is to comparatively assess the effect of laser irradiation on the surface of... more The goal of the work is to comparatively assess the effect of laser irradiation on the surface of shape memory alloys for several less common alloy families. The effect of pulsed laser impingement on the composition of NiTi shape memory alloys is analyzed for different compositions and manufacturing paths, with the aim to locally reduce the Ni content and/or to use the laser as a precise selective tool to generate structural reinforcements in a partially sintered shape memory alloy prepared by mechanical alloying. For a Ni-Ti-Hf alloy, the superficial layer formed as a result of the surface re-melting shows major Ni loss. Fe-Mn-Si-Cr shape memory alloys revealed major oxidations that are drastically affecting the properties as a result of interaction with the laser beam, while for the Co-Ni-Ga alloys only minor compositional changes have been detected.
A numerical study of quenching (in oil and water) of steel cylinders is carried out to determine ... more A numerical study of quenching (in oil and water) of steel cylinders is carried out to determine the effect of composition changes on the radial profile of the residual stresses. The numerical model takes into account only the martensitic transformation. As a first approach, the composition change has been limited to the carbon content and this has been considered to influence only the M s temperature, the martensitic transformation strain, the yield stress and the strain hardening coefficient (these last two, just for the martensite phase). The composition oscillations representative of micro-segregation bands have been simulated by a sinusoidal fluctuation between 0.35 and 0.45 %C, the average value being 0.4 %C. The sinusoidal composition oscillations have led to very significant fluctuations of the axial residual stress around the calculated value for the constant carbon content (equal to 0.4 %C). The present study clearly shows that the analysis of residual stress measurements in comparison with calculated results must not neglect the disturbing influence of localised composition changes, even when these seem to be not relevant.
Advances in Materials Science and Engineering, 2013
Superelastic shape memory alloys are difficult to machine by thermal processes due to the facilit... more Superelastic shape memory alloys are difficult to machine by thermal processes due to the facility for Ti oxidation and by mechanical processes due to their superelastic behavior. In this study, femtosecond lasers were tested to analyze the potential for machining NiTi since femtosecond lasers allow nonthermal processing of materials by ablation. The effect of processing parameters on machining depth was studied, and material removal rates were computed. Surfaces produced were analyzed under SEM which shows a resolidified thin layer with minimal heat affected zones. However, for high cutting speeds, that is, for short interaction times, this layer was not observed. A depletion of Ni was seen which may be beneficial in biomedical applications since Ni is known to produce human tissue reactions in biophysical environments.
The technological features of the grave goods from Anta do Malhão and Soalheironas perfectly fit ... more The technological features of the grave goods from Anta do Malhão and Soalheironas perfectly fit the metallurgical tradition of communities inhabiting the Southwestern Iberia during a period of transition from the 3rd to the 2nd millennium BC. Arsenical copper alloys began to be used for prestige goods of the 3rd millennium BC, becoming the standard for artefacts of the 2nd millennium BC, thus indicating the growing awareness of MBA metallurgists of the aesthetic and practical value of this silvery alloy.The work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds by Portuguese Foundation for Science and Technology under the projects UID/Multi/04349/2013 and POCI-01-0145-FEDER-007688:UID/CTM/50025. Authors acknowledge the use of the micro-EDXRF spectrometer from Department of Conservation and Restoration (FCT-NOVA).N/
The use of gold for artefact productions underwent substantial developments during Iron Age in we... more The use of gold for artefact productions underwent substantial developments during Iron Age in western Europe, with the diversification of alloy compositions and the introduction of new technologies and aesthetics. This work presents a detailed study of a Late Iron Age earring from the western Iberian Peninsula and a discussion taking into consideration the alloys and technologies used at the time. The earring has a complex structure, composed of block- and strip-twisted wires and granulation. Characterization by multifocus optical microscopy, portable X-ray fluorescence spectrometry (pXRF), micro-XRF and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were performed to obtain information on the chemical composition and manufacturing techniques. Results show that the earring was manufactured with wires and granules made of a silver-rich alloy, covered with a gold-rich layer 45 μm thick on average, which acted as an external coating making the entire earrin...
This paper presents a comprehensive study of the evidence for ancient tin mining at the Ervedosa ... more This paper presents a comprehensive study of the evidence for ancient tin mining at the Ervedosa mine (Vinhais, Portugal). The geological context of the site indicates a rich cassiterite (SnO2) deposit, which was subject to mining in the twentieth century. Some ancient mining and ore processing stone tools were recovered during the twentieth century mining operations, namely one hammer, one pounder, one flat anvil and five small tools used both as pounders and crushing anvils, evidencing prehistoric mining activities. XRF and SEM–EDS chemical analyses were performed on primary and secondary cassiterite samples from the mining site, demonstrating the abundance and chemical heterogeneity of the tin (Sn) ores. The stone tools can be ascribed to Bronze Age or, at the latest, Early Iron Age (2nd millennium to the first half of 1st millennium BCE) by comparison with similar tools from other Iberian and European archaeological contexts. High-resolution photogrammetric 3D models of the tools are made available in this study. The historical descriptions of the findings and the research made on the technical archives about the mine allowed correlating the tools to mining in a primary context, focused on rich quartz veins in granitic or greisen bedrock, rather than mining in a secondary context. XRF and SEM–EDS analyses performed on the stone material and on surface adherences support their identification as specific types of hard rocks, such as granite, amphibolite and quartzite, and allowed the detection of Sn-rich adherent particles, confirming their use for Sn-material processing. The potential relation between the cassiterite resources and the local later prehistoric (Bronze Age to Early Iron Age) settlement pattern is also discussed. The results raise awareness and provide relevant data about the existence of tin mining in primary contexts during later prehistoric times in the NW Iberian Peninsula.
espanolPresentamos el resultado del trabajo iniciado en el contexto de una investigacion etnoarqu... more espanolPresentamos el resultado del trabajo iniciado en el contexto de una investigacion etnoarqueologica sobre las explotaciones mineras en epoca contemporanea en el termino municipal de A Gudina (SE de la provincia de Ourense, Galicia). Se documento la realizacion de un proceso artesanal de reduccion de casiterita, resultando una aportacion documental extraordinaria con respecto a las potencialidades de reduccion directa de estano cuando se procesan minerales de muy alta ley, como es el caso de la casiterita del grupo minero de Barxa. En el presente trabajo se aportan resultados de estudios analiticos de los materiales resultantes del proceso con el objetivo de estudiar el grado de pureza del estano producido, y, eventualmente, de relacionar los minerales utilizados con las escorias y el metal obtenido. El resultado permite plantear diversos aspectos en relacion a los modelos propuestos de obtencion de estano y bronce en la Prehistoria hasta la actualidad, y a las posibilidades in...
Transactions of the Indian Institute of Metals, 2021
Recently, severe plastic deformation (SPD) is recognized as a very efficient processing technique... more Recently, severe plastic deformation (SPD) is recognized as a very efficient processing technique for the fabrication of bulk nanostructured (ns)/ultrafine-grained materials. High-speed high-pressure torsion (HSHPT) process, an SPD method, is used as a novel approach to produce ultrafine grains in memory materials. The influence of HSHPT process variables on some Cu-based shape memory alloys (SMAs) is explored and discussed. This paper also envisages providing a comparative study of significant microstructural evolutions and features that are introduced by HSHPT processing. The plastic deformation mechanisms of the copper-based SMAs are investigated from macrostructural and microstructural points of view using optical and scanning electron microscopic techniques. In addition, significant grain size reduction brought about by the process is attested by X-ray diffraction and transmission electron microscopy. The transition temperatures have been determined by differential scanning calorimetry.
OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
The goal of the work is to comparatively assess the effect of laser irradiation on the surface of... more The goal of the work is to comparatively assess the effect of laser irradiation on the surface of shape memory alloys for several less common alloy families. The effect of pulsed laser impingement on the composition of NiTi shape memory alloys is analyzed for different compositions and manufacturing paths, with the aim to locally reduce the Ni content and/or to use the laser as a precise selective tool to generate structural reinforcements in a partially sintered shape memory alloy prepared by mechanical alloying. For a Ni-Ti-Hf alloy, the superficial layer formed as a result of the surface re-melting shows major Ni loss. Fe-Mn-Si-Cr shape memory alloys revealed major oxidations that are drastically affecting the properties as a result of interaction with the laser beam, while for the Co-Ni-Ga alloys only minor compositional changes have been detected.
A numerical study of quenching (in oil and water) of steel cylinders is carried out to determine ... more A numerical study of quenching (in oil and water) of steel cylinders is carried out to determine the effect of composition changes on the radial profile of the residual stresses. The numerical model takes into account only the martensitic transformation. As a first approach, the composition change has been limited to the carbon content and this has been considered to influence only the M s temperature, the martensitic transformation strain, the yield stress and the strain hardening coefficient (these last two, just for the martensite phase). The composition oscillations representative of micro-segregation bands have been simulated by a sinusoidal fluctuation between 0.35 and 0.45 %C, the average value being 0.4 %C. The sinusoidal composition oscillations have led to very significant fluctuations of the axial residual stress around the calculated value for the constant carbon content (equal to 0.4 %C). The present study clearly shows that the analysis of residual stress measurements in comparison with calculated results must not neglect the disturbing influence of localised composition changes, even when these seem to be not relevant.
Advances in Materials Science and Engineering, 2013
Superelastic shape memory alloys are difficult to machine by thermal processes due to the facilit... more Superelastic shape memory alloys are difficult to machine by thermal processes due to the facility for Ti oxidation and by mechanical processes due to their superelastic behavior. In this study, femtosecond lasers were tested to analyze the potential for machining NiTi since femtosecond lasers allow nonthermal processing of materials by ablation. The effect of processing parameters on machining depth was studied, and material removal rates were computed. Surfaces produced were analyzed under SEM which shows a resolidified thin layer with minimal heat affected zones. However, for high cutting speeds, that is, for short interaction times, this layer was not observed. A depletion of Ni was seen which may be beneficial in biomedical applications since Ni is known to produce human tissue reactions in biophysical environments.
The technological features of the grave goods from Anta do Malhão and Soalheironas perfectly fit ... more The technological features of the grave goods from Anta do Malhão and Soalheironas perfectly fit the metallurgical tradition of communities inhabiting the Southwestern Iberia during a period of transition from the 3rd to the 2nd millennium BC. Arsenical copper alloys began to be used for prestige goods of the 3rd millennium BC, becoming the standard for artefacts of the 2nd millennium BC, thus indicating the growing awareness of MBA metallurgists of the aesthetic and practical value of this silvery alloy.The work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds by Portuguese Foundation for Science and Technology under the projects UID/Multi/04349/2013 and POCI-01-0145-FEDER-007688:UID/CTM/50025. Authors acknowledge the use of the micro-EDXRF spectrometer from Department of Conservation and Restoration (FCT-NOVA).N/
XIX Congress of Sociedade Portuguesa de Materiais e X International Symposium on Materials, 2019
Grave goods were recovered by archaeological excavations at two burial sites in southern Portugal... more Grave goods were recovered by archaeological excavations at two burial sites in southern Portugal: Anta do Malhão and Soalheironas.
Uploads
Papers by Rui J . C . Silva