HDPE based composites were produced with 10-20-30 and 40% composite mass of wood fiber. The coupling agents were epolene and
silane. The thermal behavior of composite samples was analyzed as a function of the coupling agent content, the exposure time
and the wood fibers content by means of differential scanning calorimetry. Calorimetric curves of all samples of first and
second heating shows a similar behavior. Some significant relation has been observed between the exposure time and the degree
of crystallinity for the same percentage of fiber samples. A linear relation between the melting enthalpy average vs. content
in cellulosic fibers is detected. Nevertheless, the fibers non-pretreated with coupling agent show a lower loss of crystallinity
of the HDPE matrix at low wood fiber content (10%). A slight diminution of the melting peak temperature is detected as increasing
the exposure time.
The alloys, Fe60Ni14Zr6B20 and Fe85Nb9B6, were produced by mechanical alloying. The formation of the nanocrystallites (about 40 nm) was detected by X-ray diffraction.
Furthermore, a slight oxygen presence (<3 at.%) was found by induced-coupled plasma and EDX microanalysis. After milling,
calorimetry scans show low temperature recovery process and several crystallization processes related with the crystal growth
and reordering of the crystalline phases. The apparent activation energies, 360 and 290 kJ mol-1, were determined by the Kissinger method. A mass increase (about 1 mass%) was detected by thermogravimetry.
Authors:J. Suñol, J. Farjas, R. Berlanga, and J. Saurina
A modified isoconversional method is applied to perform the kinetic analysis of non-isothermal processes. The solidification
process of a polyethylene glycol with a mean molecular of 4000 (PEG 4000) was here analyzed. It was stated that the Avrami
model provides a good description of the solidification process.
Temperature-cooling rate-transformation diagrams were constructed and there was a good agreement between experimental data
and the calculated T-CR-T curves. Moreover, morphological qualitative analysis has been performed by means of scanning electron
Authors:J. Bonastre, L. Escoda, A. González, J. Saurina, and J. Suñol
In this work three alloys, Fe74Nb6B20,
were obtained by mechanical alloying to analyze the influence of Ni content
on Fe–Nb–B alloy formation. Structural analysis by X-ray diffraction
(XRD) confirms that partial substitution of Fe by Ni favours the formation
during milling of a more disordered structure. Furthermore, thermal stability
study was performed by differential scanning calorimetry (DSC) because thermally
induced structural changes can affect soft magnetic behaviour. After 40 h
of milling time, all DSC curves show several exothermic effects on heating
associated to structural relaxation and crystallization. All alloys present
a crystallization process with associated activation energy values ranged
between 238 and 265 kJ mol–1 related to the
crystalline growth of the bcc-Fe rich phase. In alloys with Ni, a second crystallization
process appears at temperatures over 500°C with activation energies 397
(10% Ni alloy) and 385 kJ mol–1 (20% Ni alloy)
probably associated to the nucleation and crystalline growth of a new phase.
Authors:J. Suñol, J. Saurina, F. Carrasco, X. Colom, and F. Carrillo
Lyocell, modal and
viscose fibers were subjected to mercerization or to solar degradation. The
ulterior thermal degradation was analyzed by means of differential scanning
calorimetry (DSC). Thermal analysis shows wide exothermic processes that began
between 250 and 300C corresponding to the main thermal degradation and
are associated to a depolymerization and decomposition of the regenerated
cellulose. Thermal degradation was analyzed as a function of concentration
and time. Lyocell fiber is the most stable under thermal degradation conditions.
Furthermore, mercerized samples are initially more degraded and present a
lower thermal stability.
Authors:J. J. Suñol, D. Miralpeix, J. Saurina, F. Carrillo, and X. Colom
Summary New regenerated cellulose fibers were developed during the last decades as environmentally friendly systems. In this work, three fibers: lyocell, modal and viscose were subjected to an enzymatic treatment. Likewise, different lyocell fibers were washed in a Na2CO3 solution under severe conditions. Analysis was performed by means of differential scanning calorimetry, thermogravimetry and scanning electron microscopy. In all samples, at low temperature, water desorption was detected. Furthermore, thermal analysis shows wide exothermic processes that began between 250 and 300°C corresponding to the main thermal degradation and it is associated to a depolymerization and decomposition of the regenerated cellulose. It is accompanied with mass more than 60% mass loss. Kinetic analysis was performed and activation energy values 152-202 kJ mol-1 of the main degradation process are in agreement with literature values of cellulose samples.
Authors:R. Coll, L. Escoda, J. Saurina, J. Sánchez-Llamazares, B. Hernando, and J. Suñol
Three magnetic shape memory alloys: Mn50Ni50−xSnx (x = 5, 7.5, and 10) were produced as bulk polycrystalline ingots by arc melting. The structural austenite–martensite transformation
was checked by calorimetry. The transformation temperatures decrease as increasing the Sn content. The same trend is found
in the entropy and enthalpy changes related to the transformation. The control of the valence electron by atom e/a determines the transformation temperatures range in this kind of alloys and it is possible to develop alloys that can be
candidates in applications as sensors and actuators. Furthermore, X-ray diffraction was performed to check the crystalline
structure at room temperature.