Authors:T. Devièse, M. Colombini, M. Regert, B. Stuart, and J. Guerbois
The use of thermogravimetric analysis–mass spectrometry (TGMS) to study the state of preservation of archaeological bones
has been investigated. As part of a collaborative multi-analytical study, bones exhumed from graves of the late Roman period
in France and Italy were examined. A decrease in organic matter for the archaeological bones compared to that for new bone
was confirmed, demonstrating that diagenesis of aged bones can be detected using TGMS. Different amounts of collagen were
determined for bones from different graves and could, for the majority of specimens, be correlated with the visually observed
Authors:A. Onishi, P. Thomas, B. Stuart, J. Guerbois, and S. Forbes
In order to investigate the potential of thermal analysis for the determination of post-mortem age, rib bone specimens were
collected from the remains of a number of slaughtered pigs that were allowed to decompose in the Australian bush in a controlled
site under a range of conditions for time periods ranging from 1 to 5 years. The bone specimens were cut in cross-section
with the compact bone collected for analysis. TG-MS curves were collected by heating bone samples to 1100°C in an argon atmosphere.
The TG-MS data showed significant differences for the pig bone specimens derived from the different environments and showed
trends in peak size correlating with age. The reported data suggest that TG-MS has significant potential for the identification
of origin as well as the ageing of skeletal remains in a forensic context.
Authors:A. Onishi, P. Thomas, B. Stuart, J. Guerbois, and S. Forbes
A challenge for forensic examiners is the
ageing and characterisation of bone fragments or decomposed skeletal remains.
Due to the sensitivity of thermal methods to morphological states, thermal
analysis has been selected as a technique which could overcome the difficulties.
In this preliminary study, TG-MS was applied to the characterisation of bone
fragments derived from the compact bone of pig rib specimens. TG-MS curves
were collected by heating bone samples to 1000C in an argon atmosphere.
Under these conditions, both the organic and inorganic phases decomposed,
producing a variety of organic fragments and carbon dioxide. Pyrolysis of
the organic phase, which is composed predominantly of collagen, occurred resulting
in the observation of ion fragments up to 110 amu. Selected fragments were
monitored and their observation is discussed in terms of the decomposition
of both the collagen phase and the inorganic carbonated hydroxyapatite phase.
Authors:L. Brown, A. Ray, P. Thomas, and J. Guerbois
Naturally occurring opals from three different regions in Australia were studied for their thermal characteristics. All the
opals showed initial expansion followed by contraction in thermomechanical analysis (TMA) although the temperature at which
the change from expansion to contraction occurred depended on their provenance. Thermogravimetric analysis (TG) revealed different
rates and temperatures of dehydration for these opals. A general correlation between the temperature at which there was a
zero thermal expansion and that of the maximum rate of dehydration was observed. A dehydration–sintering mechanism is proposed
with the effect of sintering being more pronounced following total dehydration.
Authors:P. Thomas, J.-P. Guerbois, G. Russell, and B. Briscoe
The degradation of poly(vinyl alcohol) was investigated using TG analysis and Fourier transform infrared spectroscopy to determine
the effect of atmosphere on the process of degradation. In the spectra, four vibrational modes were identified that characterised
the major steps of the degradation process. These were the O-H, C-H, C=O and C=C stretching modes. The mechanism observed
for degradation in an inert atmosphere was in accordance with the accepted mechanism of elimination followed by pyrolisation.
Evidence of conjugated polyenes, however, was not observed. For the air atmosphere, oxidation in both steps of the degradation
process was observed.
Authors:H. Connan, A. Ray, P. Thomas, and J.-P. Guerbois
The utilisation of fired clay-brick waste is of interest in the manufacture
of building products due to both socio-economic and technological reasons.
Autoclaving is an established process for manufacturing calcium silicate-based
building products that affords rapid strength development. Clay-brick waste
represents a source of alternative silica, which is more reactive than conventionally
used silica and also contains alumina. This paper presents data on the effect
of lowering the autoclaving temperature from commonly practised 180 to 170°C
on OPC-quartz blends containing clay-brick fines as direct replacement of
quartz at 4.3, 8.6 and 12.9 mass percentages. The hydration products of autoclaved
OPC-quartz blends with clay-brick fines were characterised using simultaneous
DTA-TG in combination with other methods.
Authors:B. Liu, P. Thomas, A. Ray, and J. Guerbois
of MgO obtained from calcination of magnesium carbonate at different temperatures
has been investigated by means of hydration in a constant relative humidity
environment at 40°C for periods up to 24 days. Natural magnesite and AR
grade basic MgCO3 calcined in the range of 500–1000°C
was characterised in terms of surface area, crystallite size, morphology,
and hydration rate.
It was found that the hydration rate is dependent
on the surface area and crystallite size where temperature was the main variable
affecting them. The most reactive MgO was produced at the lowest calcination
temperature with the highest surface area and the smallest crystallite size.
The basic MgO specimens showed higher degree of hydration compared to the
natural MgO specimens due to the smaller surface area and larger crystallite
size. The low MgO content of the starting natural magnesite is also attributable
to the lower reactivity. This preliminary study serves as a mean to investigate
potential utilisation of reactive MgO as a supplementary cementitious material
in eco-friendly cements.
Authors:R. White, P. Thomas, M. Philips, R. Wuhrer, and J. Guerbois
The deleterious interaction
of some traditional sulphide artists pigments and copper ions results in the
formation of black copper sulphides, in particular, covellite (CuS), and,
hence, the discolouration of valuable artworks. In this paper the interaction
of malachite, a source of copper(II) ions, with the pigment cadmium yellow,
a sulphide pigment comprising of a solid solution of cadmium and zinc sulphides,
is investigated by XRD and TG-MS. XRD showed the presence of the copper sulphide
and cadmium carbonate phases, produced by a simple ion exchange mechanism.
TG-MS showed the complexity of the range of metastable phases produced. The
identification of these phases, however, requires further work.
Authors:J. Lawry, A. Ray, D. Klimesch, P. Thomas, J.-P. Guerbois, and J. Harrison
Summary Due to growing environmental concerns and the need to use less energy-intensive building products, alternatives and improvements to Portland cement (PC) are being actively researched worldwide. Use of supplementary materials is now a common practice where PC is the predominant component of inorganic building products. This study aims to investigate the potential of magnesia (MgO), derived from a naturally occurring raw material magnesite, as a supplementary material. Results from mortar samples prepared with 10 and 20% replacements of ordinary Portland cement (OPC) by MgO are presented. DTA-TG was used to study and characterise the hydration behaviour of MgO in OPC environment after 3, 7, 14, 28, 56 and 90 days of moist curing. Microstructural and compressive strength determinations providing additional information on the influence of hydrated phases are also reported.