Peritectic phase

Label all parts of the peritectic phase diagram (Fig. 3.15.10b) for solid—liquid equilibria at constant pressure. State what happens as liquids of compositions a, b, c, d, and e are cooled from temperature Tx to temperature T2. Read approximate values of T and x off the graph. 

Peritectics are observed in mixed saturated-unsaturated systems. Figure 17.12(c) is a theoretical peritectic phase diagram. Several authors have reported mixtures of SOS and SOO to exhibit peritectic behavior (Rossell 1976). The peritectic mixture contained 24%SOS melted at 27.4°C, determined using differential thermal analysis. Table 17.4 list common phase behaviors of binary mixtures for different triacyl-glycerides adapted from Rossell (1967). 

Table 17.4. Phase behavior of binary mixtures of triacylglycerides adapted from Rossell (1967). (M) represents monotectic phase behavior, (E) represents euteetie phase behavior and (P) represents peritectic phase behavior.

Stoiehiometrie VN undergoes a phase transition into a tetragonal phase below 205 K. At a composition of around VNo.80, a transition into a tetragonal phase occurs at 500 °C. Two different versions of the phase diagram at temperatures below 500 °C have been reported, " one with a eutectic and one with a peritectic phase reaction between tetragonal VNo.83 and 5-VNi-x. 

Construct a set of free energy curves that lead to the formation of the compound peritectic phase diagram depicted in Fig. 3.16.8. 

The solubility of alkaline earth metals in molten alkali metals is limited. The elements of the third group of the periodic table of elements are still less soluble in alkali metals, only the aluminium-lithium system is an exception. This system contains two intermetallic phases, LiAl and the peritectic phase Li9Al4, and solid alloys of both metals are of technical importance. The metals of the fourth group have a better solubility in alkali metals. They tend to form intermetallics. Some of the liquid alloys have found technical interest. 

Alloys with low r value (i.e., high concentration of calcium and low-tin content) have fine-grain structure. Figure 4.38 shows the correlation between corrosion rate and calcium content for Pb—Ca—Sn alloys with 0.5 or 1.5 wt% Sn content [18]. With increase of calcium content in the alloy, the r value decreases and the corrosion rate increases. When the Sn content is increased from 0.5 to 1.5 wt%, the r value increases from 7.1 to 21.4 at the peritectic phase composition of the ternary alloy and the corrosion rate decreases. 

FIGURE 6.39 (a) Peritectic phase diagram, b) Schematic illustration of phase formation... 

Oxygen, a halogen, and a main group element. Phase diagrams for LaOI-AI(A = Na Rb) systems determined by Tupoleva et al. (1988) by DTA and X-ray diffraction suggest formation of the peritectic phases A2LaOl3, A = Na-Rb, and Rb2La303l5. However, structural data were not presented. 

Schematic showing the construction of a peritectic phase diagram from free energy curves.

---