Browsing by Author "Adedipe, Adedayo Mayowa"

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    Investigation of thermodynamic properties of liquid binary alloys
    (Federal University of Technology, Owerri, 2019-11) Adedipe, Adedayo Mayowa
    A complex formation model has been used to study the thermodynamic properties of Bi-Sb at 1200k, Bi-Sn at 905k and Sb-Sn at 600k binary liquid alloys. The research reveals that Bi-Sb and Sb-Sn alloys are weakly ordered systems and compound forming liquid alloys (hetero-coordinated) i.e., unlike atoms of Bi-Sb and Sb-Sn pairing as nearest neighbors, while Bi-Sn is not a compound forming alloy but exhibit phase segregation (homocoordinated) i.e., like atoms of Bi-Sn pairing as nearest neighbors. The fitted and experimental values of the free energy of mixing of the three alloys compare well with each other at the temperature of interest. The value of 𝑔⁄𝑅𝑇 (a measure of the formation of a complex in each alloy) in Bi-Sb and Sb-Sn are greater than zero, which shows that none of the two alloys has a strong tendency to form complexes, while the value for Bi-Sn is less than zero. The values of the Gibbs free energy of mixing, 𝐺𝑀⁄𝑅𝑇 for Bi-Sb, Bi-Sn and Sb-Sn are found to be negative at all concentrations with a maximum value of -0.907, -0.640 and 0.926 respectively and are all symmetry at equiatomic composition (i.e c = 0.5). The concentrationconcentration fluctuation 𝑆𝐶(0) values for both Bi-Sb and Sb-Sn are less than the 𝑆𝐶𝐶 ideal (𝑆𝑐𝑐 𝑖𝑑(0)) values with a maximum value of 0.174 at c = 0.4 and 0.172 at c = 0.5 which justify that they are compound forming alloys. While BiSn 𝑆𝐶(0) exhibits a maximum value of 0.289 at c = 0.5, and greater than the ideal value and exhibited phase separation. Bi-Sb and SbSn shows negative and minimum values for Warren-Cowley short-range order parameter 𝛼1 as 𝛼1 𝑚𝑖𝑛 = −0.0391 at c= 0.6 and 0.0391 at c = 0.5 respectively, these value is quite small compared to the value of 𝛼1 for a complete ordering which is 𝛼1 𝑚𝑖𝑛 = −1.0 and this implies a tendency towards clustering and indicates a weakly pronounced hetero-coordination. Bi-Sn exhibited a maximum value for Warren-Cowley shortrange order parameter 𝛼1 as 𝛼1 𝑚𝑎𝑥 = 0.0680, this value is quite big compared to the value of 𝛼1 for complete order which is 1 𝑚𝑖𝑛 = −1.0, this implies a high tendency towards segregation and indicates a strong pronounced homocoordination. In addition, it is observed that computed values and experimental values of this quantity are in very good agreement both in BiSb, Bi-Sn and Sb-Sn alloys. From the thermodynamic properties, Bi-Sb and Sb-Sn are more suitable to be used as solders than Bi-Sn because they are compound forming alloys.