The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimat...The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equationproposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease firstas the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Snlarger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by adecrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9) and(Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9))_(0.97)Sn_3 was evaluated by Kissinger equation. It is noted that the Sn addition increases theactivation energies for glass transition and crystallization, implying that the higher thermal stability can be obtainedby appropriate addition of Sn.展开更多
Undercooling of Sn droplets in different atmospheres was studied by fast scanning calorimetry(FSC)at cooling rate of 1,000 K/s.It is found that the undercooling decreased with increasing partial pressure of oxygen.Ran...Undercooling of Sn droplets in different atmospheres was studied by fast scanning calorimetry(FSC)at cooling rate of 1,000 K/s.It is found that the undercooling decreased with increasing partial pressure of oxygen.Randomly distributed SnO2islands were observed to form on the droplet surface,which likely has promoted the heterogeneous surface nucleation.As the partial pressure of oxygen changes,the nucleation rate and growth of SnO2led to different oxide islands,which resulted in various potential catalytic sites for the nucleation of the molten Sn droplet.The results showed that the nucleation process of the Sn droplets was sensitive to the solidification environment,and therefore the atmosphere should be taken into account in the study of the nucleation behavior of the single Sn droplets.展开更多
The commercial market of Sn–Pb solder is gradually decreasing due to its toxicity,calling for Pb-free substitute materials.Sn–Ag alloy is a potential candidate in terms of good mechanical property.The major problema...The commercial market of Sn–Pb solder is gradually decreasing due to its toxicity,calling for Pb-free substitute materials.Sn–Ag alloy is a potential candidate in terms of good mechanical property.The major problematic issue of using Sn–Ag is their high melting temperature,consequently this study is dedicated to lowering the melting temperature of Sn3.5Ag(wt%)alloy by developing nanomaterials using a chemical reduction approach.The resultant nanocrystalline Sn3.5Ag is characterized by field emission scanning electron microscope.The size dependence of the melting temperature is discussed based on differential scanning calorimetry results.We have reduced the melting temperature to 209.8°C in the nanocrystalline Sn3.5Ag of(32.4±8.0)nm,compared to*221°C of the bulk alloy.The results are consistent with the prediction made by a relevant theoretical model,and it is possible to further lower the melting temperature using the chemical reduction approach developed by this study.展开更多
文摘The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equationproposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease firstas the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Snlarger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by adecrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9) and(Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9))_(0.97)Sn_3 was evaluated by Kissinger equation. It is noted that the Sn addition increases theactivation energies for glass transition and crystallization, implying that the higher thermal stability can be obtainedby appropriate addition of Sn.
基金supported by the National Natural Science Foundation of China (51171105, 50971086)the Shanghai Higher Education 085 Connotation Construction Project in Shanghai University
文摘Undercooling of Sn droplets in different atmospheres was studied by fast scanning calorimetry(FSC)at cooling rate of 1,000 K/s.It is found that the undercooling decreased with increasing partial pressure of oxygen.Randomly distributed SnO2islands were observed to form on the droplet surface,which likely has promoted the heterogeneous surface nucleation.As the partial pressure of oxygen changes,the nucleation rate and growth of SnO2led to different oxide islands,which resulted in various potential catalytic sites for the nucleation of the molten Sn droplet.The results showed that the nucleation process of the Sn droplets was sensitive to the solidification environment,and therefore the atmosphere should be taken into account in the study of the nucleation behavior of the single Sn droplets.
基金supported by the National Natural Science Foundation of China(50971086,51171105)
文摘The commercial market of Sn–Pb solder is gradually decreasing due to its toxicity,calling for Pb-free substitute materials.Sn–Ag alloy is a potential candidate in terms of good mechanical property.The major problematic issue of using Sn–Ag is their high melting temperature,consequently this study is dedicated to lowering the melting temperature of Sn3.5Ag(wt%)alloy by developing nanomaterials using a chemical reduction approach.The resultant nanocrystalline Sn3.5Ag is characterized by field emission scanning electron microscope.The size dependence of the melting temperature is discussed based on differential scanning calorimetry results.We have reduced the melting temperature to 209.8°C in the nanocrystalline Sn3.5Ag of(32.4±8.0)nm,compared to*221°C of the bulk alloy.The results are consistent with the prediction made by a relevant theoretical model,and it is possible to further lower the melting temperature using the chemical reduction approach developed by this study.
