Pressure Effect on the Solid I−Liquid and Solid III−Solid I Equilibrium Forms of Cyclohexane

Shigematsu, Koji; Honda, Hideki; Kumagai, Toru; Takahashi, Yoshinori

doi:10.1021/cg900507w

Cited by 10 publications

(18 citation statements)

References 30 publications

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“…Liquids usually crystallize at a defined pressure. Many organic solvents have been crystallized via pressure, including odd-numbered normal alkanes (carbon number: 9, 11 and 13) 8 , cyclohexane 9 and carbon tetrachloride 10 . However, the properties of crystallized p -xylene remain unknown.…”

Section: Resultsmentioning

confidence: 99%

Pressure-Induced Crystallization and Phase Transformation of Para-xylene

Bai

Liu

et al. 2017

Sci Rep

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Static pressure is an alternative method to chemical pressure for tuning the crystal structure, bonds, and physical properties of materials, and is a significant technique for the synthesis of novel materials and fundamental research. In this letter, we report the crystallization and phase transformation of p-xylene under high pressure. Our optical micrographic observations and the appearance of lattice modes in the Raman and infrared (IR) spectra indicated that p-xylene crystallizes at ∼0.1 GPa. The X-ray diffraction (XRD) pattern at 0.84 GPa suggests that the crystallized p-xylene had a monoclinic phase with the Cc(9) space group. The sharp shrinkage of the lattice at ~13 GPa and the solid state of the decompressed sample we observed suggests a new crystalline phase of p-xylene. The in situ XRD showed that the new crystalline phase was still a monoclinic structure but with a different space group of C2(5), indicating that a phase transition occurred during further compression. The mass spectrometry experiment confirmed phase transition polymerization, with mainly trimer and tetramer polymers. Our findings suggest an easy and efficient method for crystallizing and polymerizing p-xylene under high pressure.

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Section: Resultsmentioning

confidence: 99%

Pressure-Induced Crystallization and Phase Transformation of Para-xylene

Bai

Liu

et al. 2017

Sci Rep

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“…9,10 We improved the pressure measurement with a precision of less than ±0.01 GPa using a reference light of a Ne spectrum peak. 11 See ref 11 for the detailed description of the measurement apparatus procedure of the RFT.…”

Section: ■ Experimental Apparatus and Proceduresmentioning

confidence: 99%

“…We confined a small amount of the n -pentadecane liquid in the hole (diameter: 0.6 mm) of a Pt-5%Au gasket (thickness: 0.5 mm), interposed between the upper and lower diamond faces of the DAC. A ruby ball (diameter: 0.134 mm) was enclosed together with n -pentadecane liquid for pressure measurement by the ruby fluorescence technique (RFT). , We improved the pressure measurement with a precision of less than ±0.01 GPa using a reference light of a Ne spectrum peak . See ref for the detailed description of the measurement apparatus procedure of the RFT.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

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Bidirectional Transformations of n-Pentadecane between Low-Pressure and High-Pressure Phases

Shigematsu

Chiba

Sawamura

et al. 2016

Crystal Growth & Design

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We optically observed the transformation between the solid phases of SII and SI of n-pentadecane of which a p–T diagram has a parallel and wide gap between the coexistence lines between liquid-SI and between SI–SII. We were able to grow an SII crystal in the liquid by cooling or compression, and subsequently filled the high-pressure specimen vessel with the SII crystal. The transformation to SI crystals in the SII crystal started after successive cooling or compression. Final compression transformed again all the SI crystals to the SII crystal. At the growth of an SII crystal in the liquid, we measured the SII-liquid equilibrium pressures and temperatures, which were located below the coexisting lines of the SI and liquid phases in the p–T diagram. We found that the SII crystal of n-pentadecane is stable even below the coexisting line between the SI and liquid. We elucidate thermodynamically the stabilities of the SI and SII phases based on the variations of some thermodynamic functions calculated from the measurements of the p–T diagram and the molar volume variation. Finally, we proposed a new arrangement among the planes of the Gibbs energy of the SII, SI, and liquid phases of n-pentadecane in the G–p–T diagram.

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“…Both polymorphism and order-disorder transformation are the peculiarities of molecular crystals which include not only odd normal alkanes but also carbon tetrachloride [9] and cyclohexane [10]. These peculiarities are brought about by the following features of molecular crystals: very weak intermolecular forces, which are the bonding forces of the crystals, very stable conformations of the molecules, which are formed by the covalent bonds between C-C, C-H, and C-Cl atoms.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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While we optically observed the pressure-induced transformation between the solid phases of SII and SI of n-heptadecane, of which p-T diagram has a parallel and wide gap between the coexistence lines between liquid-SI and between SI-SII (the same as that of n-pentadecane), we found that the SII crystal of n-heptadecane is stable even below the coexisting line between the SI and liquid, as is that of n-pentadecane. Fortunately, we can easily distinguish the SI crystal, of which morphology shows a hexagonal thin plate with very round corners, from the SII crystal, of which morphology shows a long and narrow pillar-like form in the liquid. Here, we report on the epitaxial growth of SI filmy crystals of n-heptadecane on its SII crystal in the p-T condition of 40 MPa and 30 °C. Although we could not observe the epitaxial growth of n-pentadecane, we could observe the clear epitaxial growth of n-heptadecane in the mixed liquid of n-pentadecane and n-heptadecane. Growth suppression by n-pentadecane brings about clear crystal shapes. Moreover, the epitaxially growing SI filmy crystals of n-heptadecane form a disk-like vessel which put its pillar-like SII crystal between the filmy crystals. If several billion years ago this vessel had been formed in a mixed drop of normal alkanes drifting about above the bottom of a deep sea, where the p-T condition was 40 MPa and 30 °C, the vessel might be seen as a cradle of primitive life.

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Pressure Effect on the Solid I−Liquid and Solid III−Solid I Equilibrium Forms of Cyclohexane

Cited by 10 publications

References 30 publications

Pressure-Induced Crystallization and Phase Transformation of Para-xylene

Pressure-Induced Crystallization and Phase Transformation of Para-xylene

Bidirectional Transformations of n-Pentadecane between Low-Pressure and High-Pressure Phases

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

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