Aqueous two-phase system (ATPS), also called "water-in-water" emulsion, is a multicomponent system (aqueous droplets dispersed in a continuous aqueous phase), formed after gently mixing two aqueous solutions of immiscible polymers. It allows the formation of different compartments without adding any organic solvent, according to a green process. Nevertheless, the kinetic stability of ATPS is generally difficult to control. Phase diagrams, which express the concentration of a polymer as a function of that of the other in solution, are used to characterise ATPS and to determine conditions for preparing emulsions from selected polymers. In this study, dextran and polyethylene oxide aqueous mixtures with different processing parameters are investigated. Phase diagrams are generated through two automatic methods (Turbiscan and LUMiSizer® technologies) and a manual one. With the diagrams obtained, it is concluded that the purity of polyethylene oxide affects the ATPS, whereas the use of polymers in powder or in solution form has no effect. In view of this result, it is allowed to prepare ATPS formulation by a simple one-step process from polymers in powder form.

Being an effective sintering enhancer boron is gaining relevance for obtaining high density PM steels. Thermodynamic calculations are an important tool for studying the roll of alloying elements in the formation of a liquid during sintering. In the present work, the system Fe-Cr-B was obtained by combining up to date thermodynamic descriptions for the subsystems Fe-Cr, Cr-B and B-Cr. The calculations were carried out with Thermo-Calc software to predict isothermal sections for the ternary diagram for 1210 and 1250°C. The analysis of the isothermal sections indicates that the solid phases in equilibrium with the liquid are M2B and a-BCC solid solution. The generation of the liquid is based on a eutectic reaction (Lða+(FeCr)2B) involving the mixed borides previously formed. On the other hand, simulations for PM steels with constant boron but higher chromium content allowed realising that the formation of the liquid may be completely inhibited, within the temperature range under consideration, as materials with too high Cr/Fe ratios are used. This study was also supported by selected experiments which were in excellent agreement with the thermodynamic calculations.

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