研究目的
To develop and test a novel internally heated diamond anvil cell (DAC) for X-ray absorption spectroscopy (XAS) experiments under high pressure and high temperature conditions, enabling fast heating and cooling rates to study dynamics such as melting and crystallization.
研究成果
The developed internally heated DAC demonstrated excellent performance for XAS experiments under extreme pressure and temperature conditions, with fast heating and cooling rates. Preliminary results on selenium showed structural changes indicative of phase transitions, including evidence of a semiconductor-metal transition in the liquid phase. Further improvements and analyses are needed for broader applications.
研究不足
The study encountered technical issues such as pressure drift during slow heating cycles and potential sample position variations. The device is limited to temperatures up to about 1300 K and pressures achievable with DACs, and may face challenges with sample size and diamond glitches in XAS spectra.
1：Experimental Design and Method Selection:
The study involved designing and modifying a commercial diamond anvil cell (DAC) to include an internal graphite heater for high-temperature XAS experiments. Finite-element simulations were used to model temperature distributions. XAS and XRD techniques were employed for structural analysis under extreme conditions.
2：Sample Selection and Data Sources:
Elemental selenium (Se) was used as the test sample, mixed with NaCl powder as a pressure medium and marker. Data were collected at synchrotron beamlines (ODE at SOLEIL and EXAFS at Elettra).
3：List of Experimental Equipment and Materials:
Diamond anvil cell (modified commercial BETSA cell), graphite foil heater, nano-polycrystalline diamond anvils, TiB2 seats, HT glue (Pyrofeu R Ref. 4928), type K thermocouple, Delta SM15-200D power supply, vacuum chamber, XAS and XRD setups at synchrotron beamlines.
4：Experimental Procedures and Operational Workflow:
The DAC was assembled with the graphite heater and tested in a vacuum chamber. Temperature and pressure were controlled and measured using thermocouples and XRD for pressure calibration. XAS and XRD data were collected during heating and cooling cycles, with specific attention to sample stability and pressure drift.
5：Data Analysis Methods:
XAS spectra were analyzed for near-edge features and shifts, while XRD patterns were used to identify phase changes and pressure through the equation of state of NaCl.
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power supply
Delta SM15-200D
Delta
Provided electrical power to the graphite heater.
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diamond anvil cell
BETSA
BETSA
High-pressure device for XAS experiments, modified with internal heating for high-temperature applications.
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graphite foil
Used as an internal heater in the DAC to achieve high temperatures.
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nano-polycrystalline diamond anvils
Anvils for the DAC to reduce glitches in XAS spectra.
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TiB2 seats
Seats for the diamond anvils, resistant to high temperatures.
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HT glue
Pyrofeu R Ref. 4928
High-temperature glue used to fix components in the DAC.
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thermocouple
type K
Temperature measurement in the DAC.
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vacuum chamber
Housed the DAC to prevent deterioration at high temperatures.
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XAS beamline
ODE
Synchrotron SOLEIL
Used for energy-dispersive XAS measurements.
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XRD detector
MAR detector
MAR
Used for X-ray diffraction measurements to monitor pressure and phase changes.
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