In-Situ Observation of the Formation of Fibrous Sulfur under High Pressure

Abstract

Sulfur (S) possesses the largest number of allotropes among all elements. Herein, the formation of fibrous S via two different synthesis paths (path 1: S-I → S-II → fibrous S; path 2: S-I → liquid S → a-S → S-II → fibrous S) was investigated through in-situ Raman spectroscopy and synchrotron X-ray diffraction (XRD) analyses in a diamond anvil cell (DAC). Raman spectroscopy revealed the kinetic transformations from S-I to S-II and liquid S to S-II under high temperature and high pressure, and an intermediate amorphous phase was observed during the phase transition of liquid S to S-II. By decompressing S-II to ∼0.9 GPa at room temperature, the fibrous S would be formed and recovered to ambient conditions regardless of the paths. However, the difference of synthesis paths would result in the distinct microstructures and mechanical properties of fibrous S in bulk polycrystalline forms synthesized by a large press. In particular, the bulk sample synthesized from path 2 was composed of numerous aligned ultrafine S nanofibers. The presence of intermediate amorphous phase and the microstructure difference of fibrous S might account for various contradictions among previously reported results.

Localized Corrosion of Stainless Steel Triggered by Typical Inclusions in NaCl Solution: Oxy-Sulfide and MnS

“…As can be seen from Figure 7 a that there is only one strong peak located at 279 cm −1 before immersion, which is the characteristic Raman line of MnS [ 45 ]. After immersion for about 7 d, the MnS peak disappeared and a new peak appeared at 471 cm −1 , which belongs to elemental sulfur [ 46 ]. The disappearance of the MnS peak implies the dissolution of MnS, leaving elemental sulfur as a product in the corrosion pit, which is consistent with the literature [ 7 , 10 ].…”

High-Performance Hydrogels via Alternate Compression–Decompression

“…In addition, high pressure can convert weak π bonds, van der Waals forces, and hydrogen bonds to strong covalent or ionic bonds and increase the coordination number. 19 In view of this, considering the thermodynamic equivalence between pressure and temperature, pressure may have a similar effect on the gelling of PVA. As reported by Mutsuo et al, the PVA gel can be obtained at a high pressure (1 GPa, 10 min).…”

“…From the liquefaction of gases to the solidification of liquids and then to multiple solid–solid phase transitions, pressure can provide versatile structural changes. In addition, high pressure can convert weak π bonds, van der Waals forces, and hydrogen bonds to strong covalent or ionic bonds and increase the coordination number . In view of this, considering the thermodynamic equivalence between pressure and temperature, pressure may have a similar effect on the gelling of PVA.…”

High-Pressure Nonequilibrium Dynamics on Second-to-Microsecond Time Scales: Application of Time-Resolved X-ray Diffraction and Dynamic Compression in Ice

“…Since the inception of the first dDAC, there have been many modifications and improvements to suit different purposes, such as high-temperature operation and increasing the compression rate. , In the past decade, the dynamic compression in the intermediate time scales has been used to investigate time-dependent high-pressure nonequilibrium dynamics, observing diverse physical phenomena. These include compression-rate kinetics, ,, formation of metastable phases, − crystal growth, − chemical reaction, and strain and stress . Relevant to the experiments that will be discussed below ( vide supra ) is the use of the double-membrane so the pressure can be systematically applied and reduced to control the compression and decompression processes at different rates .…”