Chapter 10, Problem 10.69P

Interpretation Introduction

(a)

Interpretation:

The liquidus temperature, solidus temperature and freezing range for equimolar MgO-FeO ceramic are to be determined.

Concept Introduction:

The formula to calculate the wt% from the given mol% for ceramic containing components $1\text{ and }2$ is:

  ${\left(\text{wt\%}\right)}_1=\frac{\left[{\left(\text{mol\%}\right)}_1\times \left({\text{M}}_1\right)\right]}{\left[{\left(\text{mol\%}\right)}_1\times \left({\text{M}}_1\right)+{\left(\text{mol\%}\right)}_2\times \left({\text{M}}_2\right)\right]}\times 100$ ...... (1)

Here, ${\left(\text{mol\%}\right)}_1\text{ and }{\left(\text{mol\%}\right)}_2$ are the mole percent of the components present in the ceramic, and ${\text{M}}_1{\text{ and M}}_2$ are the molecular weights of the components.

On the temperature-composition graph of a ceramic, the curve above which the ceramic exist in the liquid phase is the liquidus curve. The temperature at this curve is maximum known as liquidus temperature at which the crystals in the ceramic can coexist with its melt in the thermodynamic equilibrium.

Solidus curve is the locus of the temperature on the temperature composition graph of a ceramic, beyond which the ceramic is completely in solid phase. The temperature at this curve is minimum known as solidus temperature at which the crystals in the ceramic can coexist with its melt in the thermodynamic equilibrium.

Freezing range for a ceramic is the difference of the liquidus and the solidus temperature of a ceramic. In this range, the ceramic melt starts to crystallize at liquidus temperature and solidifies when reaches solidus temperature.

Interpretation Introduction

(b)

Interpretation:

The phases present, their compositions and their amounts for equimolar MgO-FeO ceramic at ${1800}^{\circ }\text{C}$ are to be determined.

Concept Introduction:

On the temperature-composition graph of a ceramic, the curve above which the ceramic exist in the liquid phase is the liquidus curve. The temperature at this curve is the maximum temperature at which the crystals in the ceramic can coexist with its melt in the thermodynamic equilibrium.

Solidus curve is the locus of the temperature on the temperature composition graph of aceramic, beyond which the ceramic is completely in solid phase.

Between the solidus and liquidus curve, the ceramic exits in a slurry form in which there is both crystals as well as ceramic melt.

Solidus temperature is always less than or equal to the liquidus temperature.

Amount of each phase in wt% is calculated using lever rule. At a particular temperature and ceramic composition, a tie line is drawn on the phase diagram of the ceramic between the solidus and liquidus curve. Then the portion of the lever opposite to the phase whose amount is to be calculated is considered in the formula used as:

  $\text{Phase wt\%}=\frac{\text{opposite arm of lever}}{\text{total length of the tie line}}\times 100$ ...... (2)