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1

Podstawy teoretyczne ruchu ciepła i wilgoci w twardniejącym betonie

Ślusarek J.

Cement Wapno Beton

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2012

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R. 17/79, nr 5

286-294

PL

Beton jest materiałem porowatym, w którym pory kapilarne są częściowo wypełnione wodą. W materiałach takich zachodzi zjawisko jednoczesnego przenoszenia ciepła przez przenoszenie unoszenie i promieniowanie. Ciepło jest także przenoszone wraz z dyfundującą parą wodną oraz migrującą wodą. Tak więc, równocześnie z wymianą ciepła zachodzi w twardniejącym betonie transport wilgoci. W pracy omówiono podstawowe zależności wiążące te procesy oraz podano ich opis matematyczny co pozwoliło na wyprowadzenie sprzężonego równania bilansu wody i ciepła w twardniejącym betonie.

EN

Concrete is a capillary porous material in which pores are partially filled with water. In such materials the phenomenon of simultaneous heat transport by conduction, convection and radiation occurs. Heat is also transported by diffusing water vapour and migrating water. Thus simultaneously with heat exchange the moisture is transported in hardening concrete. In the paper the fundamental functions linking these processes are discussed and their mathematical description is presented which gave the possibility to derive the completed balance equation for water and heat in the hardening concrete.

2

Proeutectic crystallisation in hypereutectic silumins modified with Al-CuP-Me master alloys

Piątkowski J.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 4

195-198

EN

Using thermal analyses TA and ATD, within a narrow range of the crystallisation period, i.e. until reaching an equilibrium temperature, the occurrence of exothermic effect was stated. Most probably, the said effect is due to a proeutectic crystallisation of \alfa phase or of \beta phase crystals. The said effect was observed to occur only in alloys after the process of modification with an addition of high-melting point elements. Complex inoculants of Al-CuP-Me (Me = Mo, Co, Cr, Nb, TiB, W) type cause hardening of silumins, due to the formation of new phases of the AlxMey type, which can act as substrates for the nucleation of \alfa dendrites and crystals of \beta phase. The experiments carried out on castings solidifying with different rates of heat transfer have proved that proeutectic crystallisation does not occur when free solidification conditions (microspheres) are provided. This fact can be related to the heat transfer rate.

3

Coefficient of crystal lattice matching as a parameter of substrate - crystal structure compatibility in silumins

Piątkowski J.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 4

191-194

EN

Adding high-melting point elements (Mo, Nb, Ni, Ti, W) to complex silumins results in hardening of the latter ones, owing to the formation of new intermetallic phases of the AlxMey type, with refinement of dendrites in \alfa solution and crystals in \beta phase. The hardening is also due to the effect of various inoculants. An addition of the inoculant is expected to form substrates, the crystal lattice of which, or some (privileged) lattice planes and interatomic spaces should bear a strong resemblance to the crystal nucleus. To verify this statement, using binary phase equilibria systems, the coefficient of crystal lattice matching, being one of the measures of the crystallographic similarity, was calculated. A compatibility of this parameter (up to 20%) may decide about the structure compatibility between the substrate and crystal which, in turn, is responsible for the effectiveness of alloy modification. Investigations have proved that, given the temperature range of their formation, the density, the lattice type, and the lattice parameter, some intermetallic phases of the AlxMey type can act as substrates for the crystallisation of aluminium and silicon, and some of the silumin hardening phases.