Wyniki wyszukiwania - BazTech

1

Equilibrium and non-equilibrium freezing of water in clay-water systems

Kozłowski T.

Civil and Environmental Engineering Reports

|

2009

|

No. 3

77-91

EN

The temperature of spontaneous nucleation Tsn and the equilibrium freezing point Tf were determined for six monomineral, homoionic clayey soils by use of the Differential Scanning Calorimetry (DSC) technique. The temperature of spontaneous nucleation Tsn was determined on the cooling run, as the initial temperature of the observed exothermic peak. The temperature of equilibrium freezing (or melting) Tf was comprehended as the initial temperature of the last non-zero thermal impulse in the diagram of real thermal impulses distribution q(T) obtained on warming.The supercooling was calculated as the difference between Tf and Tsn. The obtained results testify the strong dependency of the equilibrium freezing point Tf on the water content w. It has been proved that Tf can be expressed as a power function of water content wand the limit of plasticity with a high correlation coefficient (R=0.933) showing a good fit to the experimental data. In contrary, a scatter of results was observed for Tsn and [...], which could be related to the effect of factors other than the water content. The diagrams of the supercooling vs. the water content suggest a relationship with an extreme. The critical water content, Wcr at which the supercooling reaches a maximum, was found by use of a quadratic empirical model. For all the clay-water systems, the criitical water content Wcr occurs between the plastic limit Wp and the liquid limit W_L.'

2

Calorimetric examinations of austempered ductile iron ADI

Binczyk F., Furmanek J., Smolnicki T.

Archives of Foundry Engineering

|

2007

|

Vol. 7, iss. 4

5-8

EN

The study presents the results of calorimetric examinations during heating and cooling of austempered ductile iron ADI after austempering at temperatures of 280, 330 and 380°C. The samples for examinations were taken from cast rods of 20 and 60 mm diameter. Examinations were carried out on a differential scanning calorimeter, type Multi HTC S60. During heating, on a DSC curve one strong exothermic effect has been noted to occur (it does not occur in the case of common-grade cast iron), accompanied by two endothermic effects. The exothermic effect occurs within the range of about 20°C. Depending on the temperature of austempering treatment, its beginning falls to the temperatures from 469 to 490°C. The heat of this effect is proportional to the austenite content in ADI matrix after austempering. The endothermic effects are related with decomposition of pearlite (or bainite) and with phase transformation [...](ferrite as a constituent of ausferritic matrix.

3

Calorimetric analysis of heating and cooling process of nodular cast iron

Binczyk F., Tomaszewska A., Smoliński A.

Archives of Foundry Engineering

|

2007

|

Vol. 7, iss. 1

25-30

EN

The study presents the results of investigations of the thermal effects which take place during heating and cooling of samples of the nodular graphite cast iron taken from the stepped test casting of the wall thicknesses amounting to 5, 10, 15 and 20 mm. For investigations, a differential scanning calorimeter, type Multi HTC S60, was used. During heating, three endothermic effects related with pearlite decomposition, phase transformation "alpha -> ghama", and carbon dissolution in austenite were observed on a DSC diagram. During cooling, two exothermic effects related with phase transformation "ghama -> alpha¨ and pearlite formation were observed to consecutively take place on a DSC diagram. The values of the enthalpy of these processes differ and depend on the initial microstructure of the examined samples. The metallic matrix in 5 mm sample after the process of heating and cooling changes totally in favour of ferrite. The same effect, though less advanced in intensity, takes place in 10 mm sample, while in 15 and 20 mm samples the matrix constitution remains unchanged. The higher is the content of ferrite in samples, the stronger is the endothermic effect of the "alpha -> ghama" transformation and the weaker is the endothermic effect related with carbon dissolution in austenite. The total of the endothermic effects (heating) is reduced, while that of the exothermic effects (cooling) increases along with the increasing thickness of walls in a stepped test casting, from which samples for the investigations were taken.

4

Sytuacja fazowa ciekłych kryształów MBBA i EBPA

Bąk A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Fizyka

|

1998

|

z. 7 [164]

69-82

PL

Ciekły kryształ EBPA był badany za pomocą mikroskopu polaryzacyjnego i różnicowego kalorymetru skaningowego w zakresie temperatury -100--100°C, z różnym tempem chłodzenia i grzania próbki. Na podstawie obserwacji stwierdzono, że EBPA może występować w fazach. ciecz izotropowa, nematyk, metastabilny kryształ, który spontanicznie transformuje do fazy stabilnej. Stwierdzono również, że fazę metastabilną można zamrozić oraz oddzielnie stopić.

EN

Liquid trystal EBPA has been investigated using polarizing microscopy and differential scanning calorimetry (DSC) in the temperature range from -100 to 100°C, using several velocity of heating and cooling process. On the basis of these analysis it appeared that we can observe EBPA in the phases: isotropic liquid, nematic and metastable solid crystal which can be transformed to the stable crystal phase. We proved that metastable phase can be frozen and also melted separately.