Augusta Lima - Academia.edu (original) (raw)

Papers by Augusta Lima

Research paper thumbnail of Gold nanoparticles in ancient and contemporary ruby glass

Journal of Cultural Heritage, 2008

Gold ruby glass was made by irradiating a soda-lime-silicate glass with ca. 0.2 weight % of gold ... more Gold ruby glass was made by irradiating a soda-lime-silicate glass with ca. 0.2 weight % of gold with gamma rays and further heating instead of using a reducing agent such as stannous oxide. Different colours were obtained by controlling the temperature and heating times. A comparison of this process to develop ruby glass with the conventional ones is discussed. Ruby glass was also made by dissolving gold metal in soda-lime-silicate glass and using stannous oxide at 1500 C. The colour of the gold ruby glass is due to the presence of gold nanoparticles.

Research paper thumbnail of Chemical analysis of 17th century Millefiori glasses excavated in the Monastery of Sta. Clara-a-Velha, Portugal: comparison with Venetian and façon-de-Venise production

Journal of Archaeological Science, 2012

A set of ten Millefiori glass fragments dating from the 17th century, originated from archaeologi... more A set of ten Millefiori glass fragments dating from the 17th century, originated from archaeological excavations carried out at the Monastery of Sta. Clara-a-Velha (Coimbra, Portugal), were characterized by X-ray electron probe microanalysis (EPMA), Raman microscopy and UVeVisible absorption spectroscopy. All glasses are of soda-lime-silica type. The use of coastal plant ash is suggested by the relatively high content of MgO, K 2 O and P 2 O 5 , as well as by the presence of chlorine. Tin oxide or calcium antimonate were the opacifiers used in the opaque glasses, cobalt in the blue glasses, copper in the turquoise glasses, iron in the yellow and greenish glasses, and iron and copper were found in the opaque red and aventurine glasses. Based on the concentrations of alumina and silica four different sources of silica were identified, allowing the classification of the glasses into the following compositional groups: low alumina (<2 wt%), which includes a sub-group of cristallo samples with SiO 2 > 70 wt%, medium alumina (2e3 wt %), high alumina (3e6 wt%) and very high alumina (>6 wt%). Comparison with genuine Venetian and façon-de-Venise compositions showed that two fragments are of Venetian production, one of Venetian or Spanish production and the remaining are of unknown provenance. In two fragments the glass of the decoration is probably Venetian or Spanish but the glass used in the body is also of unknown provenance.

Research paper thumbnail of Uranium glass in museum collections

Journal of Cultural Heritage, 2008

The presence of uranium glass objects in museum and private collections has raised radiation prot... more The presence of uranium glass objects in museum and private collections has raised radiation protection concerns resulting from possible exposure to ionizing radiation emitted by this type of object. Fourteen glass objects with different uranium contents were studied. Dose rates (b þ g radiation) were measured with a beta/gamma probe at several distances from the glass objects. In general, the determined dose rates did not raise any concern as long as some precautions were taken. Radon ( 222 Rn), usually the most important contributor for the overall natural dose exposure resulting from radium ( 226 Ra) decay in the uranium natural series, was also evaluated and it was found to be within the background values. Non-invasive analyses of the uranium content were made using micro-EDXRF analysis, measuring the radiation emitted by the objects and fluorescence spectroscopy.

Research paper thumbnail of Gold nanoparticles in ancient and contemporary ruby glass

Journal of Cultural Heritage, 2008

Gold ruby glass was made by irradiating a soda-lime-silicate glass with ca. 0.2 weight % of gold ... more Gold ruby glass was made by irradiating a soda-lime-silicate glass with ca. 0.2 weight % of gold with gamma rays and further heating instead of using a reducing agent such as stannous oxide. Different colours were obtained by controlling the temperature and heating times. A comparison of this process to develop ruby glass with the conventional ones is discussed. Ruby glass was also made by dissolving gold metal in soda-lime-silicate glass and using stannous oxide at 1500 C. The colour of the gold ruby glass is due to the presence of gold nanoparticles.

Research paper thumbnail of Chemical analysis of 17th century Millefiori glasses excavated in the Monastery of Sta. Clara-a-Velha, Portugal: comparison with Venetian and façon-de-Venise production

Journal of Archaeological Science, 2012

A set of ten Millefiori glass fragments dating from the 17th century, originated from archaeologi... more A set of ten Millefiori glass fragments dating from the 17th century, originated from archaeological excavations carried out at the Monastery of Sta. Clara-a-Velha (Coimbra, Portugal), were characterized by X-ray electron probe microanalysis (EPMA), Raman microscopy and UVeVisible absorption spectroscopy. All glasses are of soda-lime-silica type. The use of coastal plant ash is suggested by the relatively high content of MgO, K 2 O and P 2 O 5 , as well as by the presence of chlorine. Tin oxide or calcium antimonate were the opacifiers used in the opaque glasses, cobalt in the blue glasses, copper in the turquoise glasses, iron in the yellow and greenish glasses, and iron and copper were found in the opaque red and aventurine glasses. Based on the concentrations of alumina and silica four different sources of silica were identified, allowing the classification of the glasses into the following compositional groups: low alumina (<2 wt%), which includes a sub-group of cristallo samples with SiO 2 > 70 wt%, medium alumina (2e3 wt %), high alumina (3e6 wt%) and very high alumina (>6 wt%). Comparison with genuine Venetian and façon-de-Venise compositions showed that two fragments are of Venetian production, one of Venetian or Spanish production and the remaining are of unknown provenance. In two fragments the glass of the decoration is probably Venetian or Spanish but the glass used in the body is also of unknown provenance.

Research paper thumbnail of Uranium glass in museum collections

Journal of Cultural Heritage, 2008

The presence of uranium glass objects in museum and private collections has raised radiation prot... more The presence of uranium glass objects in museum and private collections has raised radiation protection concerns resulting from possible exposure to ionizing radiation emitted by this type of object. Fourteen glass objects with different uranium contents were studied. Dose rates (b þ g radiation) were measured with a beta/gamma probe at several distances from the glass objects. In general, the determined dose rates did not raise any concern as long as some precautions were taken. Radon ( 222 Rn), usually the most important contributor for the overall natural dose exposure resulting from radium ( 226 Ra) decay in the uranium natural series, was also evaluated and it was found to be within the background values. Non-invasive analyses of the uranium content were made using micro-EDXRF analysis, measuring the radiation emitted by the objects and fluorescence spectroscopy.