| Metadata | Details |
|---|
| Publication Date | 2025-06-20 |
| Journal | IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA |
| Authors | B. P. Sorokin, Dmitry Yashin, D. A. Ovsyannikov, Mikhail Popov, B. A. Kulnitskiy |
| Analysis | Full AI Review Included |
- Ultrahard Phase Synthesis: The ultrahard amorphous Phase V of fullerite C60 was successfully synthesized at room temperature (RT) using quasi-hydrostatic pressure up to 25 GPa.
- Exceptional Stability: Phase V exhibits hardness greater than that of diamond and was confirmed to be stable and recoverable after the complete release of pressure at RT.
- Integrated Measurement System: A novel integrated system combining a Diamond Anvil Cell (DAC) with a built-in Microwave Bulk Acoustic Wave (BAW) resonator was used for in situ monitoring of structural changes.
- Acoustic Correlation: Changes in the relative frequency shift (Īf/f(P)) of the BAW resonator correlated precisely with known structural transitions in fullerite (IāII, IIIāIV, and the final transition to Phase V above 18 GPa).
- Structural Confirmation: Raman spectroscopy (KPC) and High-Resolution Transmission Electron Microscopy (HRTEM) confirmed the amorphous, 3D polymerized structure of Phase V, characterized by sp3 bonding.
- Technological Potential: The results provide a basis for developing scalable technology to synthesize ultrahard fullerite Phase V under potentially simpler, non-extreme thermodynamic conditions.
| Parameter | Value | Unit | Context |
|---|
| Initial Fullerite Purity | 99.99 | % | Molecular C60 crystals |
| Maximum Applied Pressure | Up to 25 | GPa | Quasi-hydrostatic compression in DAC |
| Synthesis Temperature | Room | Ā°C | All experiments performed at RT |
| Phase V Transition Pressure (Onset) | > 18 | GPa | Partial transformation to amorphous ultrahard phase |
| Phase III to IV Transition Pressure | ~ 8 | GPa | Observed via anomalies in Īf/f(P) curve |
| BAW Resonator Control Overtone Frequency | 1.3746 | GHz | Characteristic frequency used for acoustic monitoring |
| Hardness of Phase V | Greater than | N/A | Compared to diamond |
| Raman Excitation Wavelength | 532 | nm | Used for Raman spectroscopy (KPC) |
| Diamond Raman Line (Pressure Calibration) | 1332.5 | cm-1 | Used to determine pressure in situ |
| Characteristic Raman Line Shift (Phase V) | 1550-1600 | cm-1 | Broad, merged line indicating amorphous structure |
- High-Pressure Setup: Experiments utilized a Diamond Anvil Cell (DAC) to achieve pressures up to 25 GPa. Fullerite C60 powder was loaded into a tungsten (W) gasket.
- Integrated Acoustic Sensing: A Bulk Acoustic Wave (BAW) resonator, specifically a High-overtone BAW Resonator (HBAR) with an Al/ASN/Mo piezoelectric structure, was integrated onto the upper diamond anvil.
- Acoustic Measurement: A vector network analyzer (Agilent E5071C ENA) measured the amplitude-frequency characteristics (AFCs) of the BAW resonator in situ to track the relative frequency shift (Īf/f(P)) and Q-factor as pressure changed.
- Pressure Calibration: Pressure was determined simultaneously by measuring the shift of the 1332.5 cm-1 Raman line from the stressed tip of the diamond anvil (piezospectroscopy).
- Structural Monitoring (In Situ): Raman scattering spectroscopy (Renishaw in Via) was used to monitor the phase transitions of the fullerite sample, observing the characteristic merging and broadening of the Ag(2) line above 17.5 GPa.
- Compression Cycle: The sample underwent two full compression/decompression cycles (Pass 1 up to 24 GPa, Pass 2 up to 25 GPa) at room temperature, ensuring a quasi-equilibrium process over several tens of hours.
- Post-Synthesis Characterization: After pressure release, the recovered sample was analyzed using High-Resolution Transmission Electron Microscopy (HRTEM/ŠŠŠ-ŠŠ ) to confirm the amorphous, metastable structure of Phase V, including the presence of residual crystalline fragments.
- Superhard Materials Manufacturing: Direct synthesis of ultrahard amorphous carbon (Phase V C60) for use in industrial abrasives, cutting tools, and high-wear components, potentially replacing or supplementing synthetic diamond.
- High-Pressure Sensor Technology: Utilization of the integrated BAW resonator/DAC system for developing highly accurate, in situ pressure and material property sensors in extreme environments.
- Advanced Carbon Allotropes: Development of scalable production methods for 3D polymerized nanostructured carbon materials with superior mechanical properties (high bulk modulus, high stiffness).
- Thermal Management: Application of the synthesized amorphous carbon (known for high thermal conductivity in related literature) in advanced heat sinks and thermal interface materials for high-power electronics.
- Materials Research and Development: The methodology provides a pathway for synthesizing other novel high-pressure phases of carbon and related materials under less energy-intensive (room temperature) conditions.
View Original Abstract
Studies of the structure and properties of C60 fullerite phases, including ultrahard ones, continue to be relevant. Such interest is associated with the need to obtain large-scale samples suitable not only for comprehensive research, but also for expected practical applications. The complexity of the synthesis of such materials stimulates the search for new approaches in the field of materials science of nanostructured carbon materials and technologies for their production. The article describes studies of changes in the structure of C60 fullerite under high pressure at room temperature using microwave acoustics, Raman scattering and high-resolution transmission electron microscopy (HRTEM). To achieve pressure up to 25 GPa, a high-pressure chamber on diamond anvils with a built-in microwave resonator on a longitudinal bulk acoustic wave (BAW-resonator) was used. The Raman spectra of the stressed top of the diamond anvil and fullerite were used to determine both the pressure and the fullerite phase, respectively. The dependence of the relative frequency shift of the control overtone of the BAW-resonator at a frequency of f = 1.3746 GHz on the pressure as the Īf/f(P) was obtained. Features of the Īf/f(P) curve are associated with structural changes in fullerite, in particular, with the transitions of fullerite from the first to the second and from the third to the fourth phases. At a pressure above 18 GPa, a partial transformation into an amorphous ultrahard phase V is detected, in which fullerite has a hardness higher than that of diamond. The results of such methods as Raman, HRTEM and microwave acoustics confirm the stability of phase V at room temperature. The obtained results can be used, with appropriate scaling, to develop a technology for the synthesis of fullerite in the ultrahard phase V under simpler thermodynamic conditions. For citation: Sorokin B.P., Yashin D.V., Ovsyannikov D.A., Popov M.Yu., Kulnitskiy B.A., Asafiev N.O., Blank V.D. Synthesis of high-pressure phases at room temperature, structure and properties of fullerite C60. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 9. P. 66-74. DOI: 10.6060/ivkkt.20256809.10y.