Authors:J. O. Santos, C. S. Munita, M. E. G. Valério, C. Vergne, and P. M. S. Oliveira
Chemistry fingerprint of materials helps determine provenance and technological production techniques, and, therefore, is
useful way to study interaction between prehistoric people. In this work 38 ceramic fragments from Justino and São José sites,
in Brazilian northeast, were analyzed using instrumental neutron activation analysis (INAA). The recognition of the compositionally
homogeneous group within of the database was performed by means of principal component (PC). The PC scores were calculated
on the matrix covariance of the log base 10 transformed concentration values, and grouping was sought in the PC scores using
Kernel Density Estimates (KDE). By using KDE from PC scores two chemically different groups were found. Discriminant analysis
was performed to assess the groups' validity. Despite of the pottery from Justino and São José sites present same technical
profile, different of the Tupiguarani and Aratu traditions, it was obtained that Justino and São José samples are constitute
of distinct ceramic pastes. This result can be understood in terms of the cultural influences in the preparation of the ceramic
past and that potteries analyzed are originate locally.
Authors:S. M. Sidel, F. A. Santos, V. O. Gordo, E. Idalgo, A. A. Monteiro, J. C. S. Moraes, and K. Yukimitu
Nucleation process and crystal growth for three samples of the (20-x)Li2O–80TeO2–xWO3 glass system were studied using X-ray diffraction and differential scanning calorimetry techniques. X-ray diffraction data confirmed the amorphous characteristic of the as-quenched samples and indicated the growth of crystalline phases formed due to the thermal treatment for annealed samples. These results reveal the presence of three distinct γ-TeO2, α-TeO2 and α-Li2Te2O5 crystalline phases in the TL sample, and two distinct α-TeO2 and γ-TeO2 crystalline phases in the TLW5 and TLW10 samples. The activation energy and the Avrami exponent were determined from DSC measurements. The activation energy values X-ray diffraction data of the TLW10 glass sample suggest that γ-TeO2 phase occur before the α-TeO2. The results obtained for the Avrami exponent point to that the nucleation process is volumetric and that the crystal growth is two or three-dimensional.