Calorimetric Studies of the Mg-Pt System.

Area of Science:

• Materials Science
• Thermodynamics
• Physical Chemistry

Background:

• Accurate thermodynamic data is essential for understanding alloy formation and predicting material properties.
• Previous studies have limited data on the thermodynamic properties of magnesium-platinum (Mg-Pt) intermetallic phases.

Purpose of the Study:

• To determine the limiting partial enthalpy of platinum (Pt) in liquid tin (Sn) and aluminum (Al) baths.
• To experimentally determine the standard enthalpies of formation for Mg-Pt intermetallic phases using solution calorimetry.
• To compare experimental results with theoretical calculations (ab initio and Miedema's model).

Main Methods:

• Solution calorimetry was employed to measure enthalpy changes.
• Magnesium-platinum alloys were prepared using mechanical alloying.
• X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for material characterization.

Main Results:

• Negative limiting partial enthalpies of Pt in Sn (-126.0 ± 3.4 kJ/mol at 931 K, -126.3 ± 3.5 kJ/mol at 1033 K) and Al (-217.9 ± 1.2 kJ/mol at 1036 K) were measured.
• Standard enthalpies of formation (kJ/mol·at.) were determined for Mg₆Pt (-29.5 ± 1.8), Mg₃Pt (-53.9 ± 1.6), Mg₂Pt (-65.2 ± 0.4), MgPt (-78.7 ± 2.1), MgPt₃ (-44.5 ± 0.4), and MgPt₇ (-26.4 ± 1.0).
• Miedema's model provided less exothermic values compared to experimental and ab initio data.

Conclusions:

• The study provides novel, experimentally determined thermodynamic data for Mg-Pt alloys.
• Calorimetric measurements offer a reliable basis for validating theoretical thermodynamic models.
• The obtained data are crucial for advancing the understanding and application of Mg-Pt systems.