Epitaxial Growth of n-Tridecane Low-Pressure Phase Filmy Crystal on Its High-Pressure Phase

Abstract

We measured the p−T diagrams of four odd normal alkanes including ntridecane, which have two equilibrium lines on which the orthorhombic (SII) and hexagonal (SI) solids coexist, and the SI and liquid coexist. The equilibrium lines of n-tridecane nearly overlap above 40 °C and separate from each other with temperatures decreasing less than 40 °C. We also show that the metastable area of SII of n-tridecane widely spreads below the SII−SI coexistence line. We focused on the reason why the metastable region of the SII crystal spreads, based on the transformational relationship between SI and SII and the unisotropies among the SI and SII singular interfaces. The SII crystal first appears from the liquid above 40 °C just after compression, due to the narrow stable region of the liquid−SI crystal system. When the temperature and pressure of the liquid−SII crystal system vary compared with those of the wide stable region of the liquid−SI crystal system, the filmy SI crystal can grow on its SII crystal in the liquid. Therefore, the arrangement and the wide area cause the epitaxial growth of SI filmy crystal on SII crystal.

A disk-like vessel formed with n-heptadecane low-pressure phase filmy crystals epitaxially growing during its high-pressure phase growth in the mixed liquid of n-pentadecane and n-heptadecane

“…The molecular weights of n-pentadecane and n-heptadecane are 0.21242 kg/mol Fig. 2 a Temperature dependences of SII-SI, SI-liquid, and SII-liquid equilibrium pressures for n-tridecane [5], n-pentadecane [4] and n-heptadecane. The equilibrium pressures of n-tridecane and n-pentadecane between SII-SI and SI-liquid phases were measured by both CPM and RFT.…”

“…We measured the phase transition pressures and temperatures of n-heptadecane by the cylinder-piston method (CPM), as previously reported [5]. We simultaneously measured the pressure dependences of the liquid, SI and SII of the n-heptadecane densities by CPM.…”

“…A single crystal then survived after several pressure adjustments, and which was used for our observation. Figure 2a shows the temperature dependences of the SII-SI, SI-liquid, and SII-liquid equilibrium pressures for n-tridecane (20-45 °C) [5], n-pentadecane (20-40 °C) [4] and n-heptadecane (25-40 °C). Those of SII-SI and SI-liquid of n-heptadecane were measured by both CPM and RFT, which were in correspondence.…”

“…In our research on odd normal alkanes, we first reported the epitaxial growth of the n-tridecane filmy SI crystal along the edge of its thick-pillar-like SII crystal in the liquid [6]. We also reported that the reason why the SI crystal can grow on the SII crystal in the liquid is that the metastable area of SII spreads widely below the SII-SI coexistence line in the p-T diagram of n-tridecane [5].…”

“…1) [1][2][3]. As the order-disorder transformation between the SI and SII is of great interest to us, we carried out the observations of the growths and transformations of n-tridecane and n-pentadecane [4][5][6].…”