Chem 263 Winter 2015 Problem Set #3 Due: Mar 6 1. Sketch the phase diagram of the NiO-Al2O3 system from 1500-2200 °C using the following information. NiO melts at 1985 °C. Al2O3 melts at 2070 °C. There is a single compound, NiAl2O4, that melts congruently at 2100 °C. Eutectics occur at two points: 15% Al2O3, 1875 °C and 90% Al2O3, 1980 °C. NiO forms a solid solution with a maximum Al2O3 content of 5%. The nickel spinel also forms a solid solution for Al-rich compositions up to 35% NiO, 65% Al2O3, but no solid solution forms for Ni-rich compositions. 2. Sketch a phase diagram for a system A-B that has the following features. Three binary compounds are present, A4B, AB, and AB3. A4B melts incongruently to give A plus liquid. AB melts congruently. AB3 has an upper limit of stability. 3. For the phase diagram shown in West Ch. 7, Figure 7.16, describe the reactions that would be expected to occur upon equilibrium cooling of a melt of composition 48% A and 52% B. How might the product differ if the melt is cooled rapidly? 4. Construct a triangular grid for representing three-component phase diagrams. Let the three components be Na2O, CaO, and SiO2. Mark on your triangle, using a mole% scale, the compositions of the following phases: Na2SiO3, Na2Si2O5, CaSiO3, Ca3Si2O7, Ca2SiO4, Ca3SiO5, Na2CaSiO4, Na2Ca3Si6O16, Na2Ca2Si3O9, Na4CaSi3O9, Na2CaSi5O12. 5. a) Label each of the fields in the following simplified phase diagram, except the tiny one on the right. b) Use the Phase Rule to determine the degrees of freedom at points L, P and E. c) Envision this system as a slowly cooling magma chamber. Start with a liquid of bulk composition d. In the circles below, show schematically the appearance of the system at temperatures T3 + 0.01°C, T3 - 0.01°C, T4 and T5. When drawing, think about the crystallization process, not just the numbers! Also, try to portray the proportions of phases somewhat correctly. In the blanks, list the phases present, and the amount & composition of each. Not every text line will be needed. d) Given a solid of composition Mg2Si2O6, at what temperature will the solid first melt? What will be the product(s) of melting? What are their compositions?
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