Differential Scanning Calorimeter Apparatus Research Articles

Chaotic parameters and their role in quantifying noise in the output signals from UV, TGA and DSC apparatus

Two fractal dimensions and the Liapunov exponent (LE) have been applied to detect noisy output signals from UV spectrophotometer (UV), thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) apparatus of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid ([emim][EtSO4]). The data collected from these three pieces of equipment were classified before calculating LE, regularization (RD) and box dimensions (BD). The RD and LE are able individually to detect and quantify noisy output signals with a mean error value less than 5% in all cases tested. Given that the LE can be calculated using a really simple method, this chaotic parameter has been selected as the most suitable to detect noise of signals from these apparatus.

Nucleation and growth of the α′ martensitic phase in Pu–Ga alloys

In a Pu–2.0 at.% Ga alloy, it is observed experimentally that the amount of the martensitic α′ product formed upon cooling the metastable δ phase below the martensite burst temperature ( M b) is a function of the holding temperature and holding time of a prior conditioning (“annealing”) treatment. Before subjecting a sample to a cooling and heating cycle to form and revert the α′ phase, it was first homogenized for 8 h at 375 °C to remove any microstructural memory of prior transformations. Subsequently, conditioning was carried out in a differential scanning calorimeter apparatus at temperatures in the range between −50 and 370 °C for periods of up to 70 h to determine the holding time and temperature that produced the largest volume fraction of α′ upon subsequent cooling. Using transformation peak areas (i.e., the heats of transformation) as a measure of the amount of α′ formed, the largest amount of α′ was obtained following holding at 25 °C for at least 6 h. Additional time at 25 °C, up to 70 h, did not increase the amount of subsequent α′ formation. At 25 °C, the Pu–2.0 at.% Ga alloy is below the eutectoid transformation temperature in the phase diagram and the expected equilibrium phases are α and Pu 3Ga, although a complete eutectoid decomposition of δ to these phases is expected to be extremely slow. It is proposed here that the influence of the conditioning treatment can be attributed to the activation of α-phase embryos in the matrix as a beginning step toward the eutectoid decomposition, and we discuss the effects of spontaneous self-irradiation accompanying the Pu radioactive decay on the activation process. Subsequently, upon cooling, certain embryos appear to be active as sites for the burst growth of martensitic α′ particles, and their amount, distribution, and potency appear to contribute to the total amount of martensitic product formed. A modeling approach based on classic nucleation theory is presented to describe the formation of α-phase embryos during conditioning. The reasons why the holding times during conditioning become eventually ineffective in promoting more α′ formation on cooling are discussed in terms of the differences in the potency of the embryos created in the δ matrix during conditioning and in terms of growth-impeding volume strains in the matrix resulting from an increasing number of martensite particles, thus opposing further growth. It is suggested that the disparate amounts of the α′ formation reported in the literature following various studies may be in part a consequence of the fact that conditioning times at ambient temperatures are inevitably involved in any handling of radioactive samples prior to testing.

Cs–V Catalysts for the Combustion of Diesel Particulate

The soot combustion process, promoted by some promising diesel particulate combustion catalysts based on Cs and V oxides (Cs2O, Cs3VO4, Cs4V2O7, Cs2O · V2O5, CsVO3, Cs2V4O11, V2O5), is discussed on the grounds of an experimental test campaign involving reaction runs in micro-reactors (temperature-programmed conditions) and in a differential scanning calorimeter apparatus. Such investigations led to define the roles of the Cs and V species in these catalysts as well as to identify the Cs3VO4 catalyst as the most active.

A new DSC for high heating and cooling rates measurements

A new differential scanning calorimeter(DSC) for high and adjustable heating and cooling rates (up to 200 K/min) and a wide temperature range of measurement (230 – 1050 K) has been developed. Performance and applicability of the new DSC apparatus were examined for precipitation reactions in aluminum alloys. This apparatus, developed mainly for the study of metals and alloys, will also be useful for the study of other materials.