Dynamic mechanical thermal analysis of aqueous sugar solutions containing fructose, glucose, sucrose, maltose and lactose

The glass transition of glucose, fructose, lactose, maltose and sucrose solutions at maximum cryo-concentration was studied by Dynamic Mechanical Thermal Analysis (DMTA), using the disc bending technique. The glass transition temperatures were determined from the peaks in the loss modulus E′′, which corresponds theoretically to the resonance point (Maxwell model) for several input frequencies. The frequency dependence was well described by both an Arrhenius-type model and by the WLF (Williams, Landel and Ferry) equation, yielding glass transition temperatures for an average molecular vibration time of 100 s, which were similar to published midpoint temperatures determined by DSC scans. Some sugar mixtures were studied, yielding results that were well described by the Gordon–Taylor equation, using literature data. The frequency dependence of the viscoelastic ratio was also well approximated by an Arrhenius-type equation, with activation energies similar to those of the glass transition temperature and corresponded well to published values of the endset of glass transition

Morphology and Properties in Blended Cements with Ceramic Wastes as a Pozzolanic Material

[EN] This paper describes the research run on ceramic materials, and more specifically fired clay roof tiles, ground to a fineness suitable for use as an active replacement for portland cements (PCs). The utilization of waste products from calcined clay roof tiles as a pozzolanic material in the cement manufacture is studied. One of the first materials used as pozzolans in the history was thermal-treated clay, a material similar to the calcined clay precast elements. For this study, the materials selected are clay products that have been eliminated for different reasons: a wrong temperature inside the kiln, dimensional and mechanical failures, and durability loss. The results showed that these products have good pozzolanic properties; at an early age, the pozzolanic activity was found to be higher than fly ash, although it was lower than silica fume. The morphology of clay tile–PC pastes are similar to the morphology of the pastes containing other pozzolanic materials. Hydrated calcium aluminate products are generated when the preparation method yields less compact pastes with a greater voids' volume to accommodate these products. The hydrated calcium aluminate phases were analyzed using scanning electronic microscopy and X-ray diffraction techniques.Peer reviewe

Thermal-tempering analysis of bulk metallic glass plates using an instant-freezing model

The viscoelastic nature of bulk metallic glasses (BMGs), their low thermal conductivity, and the fast cooling used in their processing subject them to thermal tempering. This process leads to a residual stress state in which compression on the surface is balanced by tension in the interior. For the first time, we have calculated such stresses in metallic glasses by adapting an analytical instant-freezing model previously developed for silicate glasses. This model has been demonstrated to be reasonably accurate in predicting the final residual stresses, although, due to its very nature, it neglects transient effects. For an infinite plate geometry and employing processing parameters often used for metallic glasses, we predict that significant residual stresses can be generated in these materials during thermal tempering. Preliminary measurements conducted using the layer-removal method yield compressive residual stress values close to model predictions