Thermal Conductivity of Helium and Argon at High Pressure and High Temperature

At a Glance

Metadata	Details
Publication Date	2022-09-26
Journal	Materials
Authors	Wen‐Pin Hsieh, Yi‐Chi Tsao, Chun‐Hung Lin
Institutions	Institute of Earth Sciences, Academia Sinica, National Taiwan University
Citations	6
Analysis	Full AI Review Included

Technical Documentation & Analysis: High P-T Thermal Transport in DACs

Executive Summary

This research provides critical data on the thermal conductivity ($\Lambda$) of Helium (He) and Argon (Ar) under extreme pressure-temperature (P-T) conditions, directly impacting the design and thermal modeling of Diamond Anvil Cell (DAC) experiments and planetary science.

Core Achievement: Precise measurement of He and Ar thermal conductivity up to 55.2 GPa and 973 K using Time-Domain Thermoreflectance (TDTR) coupled with an Externally Heated DAC (EHDAC).
Methodology: Ultrafast pump-probe TDTR technique applied to an Aluminum (Al) thermal transducer deposited on a borosilicate glass substrate within the DAC.
He Findings: Liquid He $\Lambda$ exhibits a positive dependence on both pressure (P^0.86) and temperature (T^0.45), a behavior contrasting with typical crystalline dielectrics.
Ar Findings: Solid Ar $\Lambda$ shows a strong positive pressure dependence (P^1.25) but a sharp negative temperature dependence (T^-1.37), typical of phonon-dominated transport.
Modeling Impact: The results significantly improve the accuracy of modeling heat transfer dynamics and temperature profiles within DACs loaded with He or Ar pressure media.
6CCVD Relevance: The study underscores the necessity of high-performance, thermally stable materials (like MPCVD diamond) for substrates and thermal management in extreme P-T environments.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Pressure (He)	55.2	GPa	Solid hcp phase, Room Temperature
Maximum Pressure (Ar)	49	GPa	Solid phase, Room Temperature
Maximum Temperature	973	K	Fixed pressure measurements (He at 10.2 GPa, Ar at 19 GPa)
He $\Lambda$ (Liquid) Pressure Dependence	P^0.86 (±0.048)	Exponent	Room Temperature
He $\Lambda$ (Solid hcp) Pressure Dependence	P^0.72 (±0.045)	Exponent	Room Temperature
He $\Lambda$ (Liquid) Temperature Dependence	T^0.45 (±0.036)	Exponent	Fixed at 10.2 GPa
Ar $\Lambda$ (Solid) Pressure Dependence	P^1.25 (±0.025)	Exponent	Room Temperature
Ar $\Lambda$ (Solid) Temperature Dependence	T^-1.37 (±0.005)	Exponent	Fixed at 19 GPa
Thermal Transducer Thickness	~90	nm	Thermally evaporated Al film
Substrate Thickness	~10	µm	Borosilicate glass (D 263® Teco)
TDTR Repetition Rate	80	MHz	Ti:sapphire laser
TDTR Modulation Frequency	8.7	MHz	Pump beam

Key Methodologies

The thermal conductivity measurements were performed using a highly specialized TDTR setup integrated with a high P-T DAC system.

Substrate Preparation: A thin sheet of borosilicate glass (D 263® Teco) was polished to approximately 10 µm thickness to serve as the reference substrate.
Transducer Deposition: A ~90 nm-thick Aluminum (Al) film was thermally evaporated onto the glass substrate, functioning as the thermal transducer for the TDTR measurement.
DAC Assembly: A symmetric DAC (300 µm culet) was used, equipped with a Rhenium (Re) gasket to contain the sample and pressure medium.
Pressure Medium Loading: High-purity He or Ar gas (99.9999%) was loaded into the DAC, acting as both the material under study and the pressure medium.
P-T Control: Simultaneous high P-T conditions were achieved using an Externally Heated DAC (EHDAC) combined with a gas membrane to control pressure in situ during heating, minimizing thermal pressure effects.
Pressure Monitoring: Ruby balls placed next to the substrate were monitored via pressure-shifted fluorescence or Raman spectroscopy to characterize pressure in situ.
TDTR Measurement: An ultrafast optical pump-probe method was employed, utilizing a Ti:sapphire laser (785 nm, 80 MHz repetition rate). The pump beam was modulated at 8.7 MHz to induce temperature oscillation in the Al film.
Data Acquisition: Heat diffusion dynamics were monitored by measuring the variation of the probe beam’s reflected intensity, specifically the in-phase (V_in) and out-of-phase (V_out) components, using a fast Si photodiode and lock-in amplifier.

6CCVD Solutions & Capabilities

This research demonstrates the critical need for materials with exceptional thermal and mechanical stability for high P-T experiments. While the authors used borosilicate glass, 6CCVD’s MPCVD diamond offers superior performance, enabling researchers to push the boundaries of P-T conditions and reduce experimental uncertainty.

Research Requirement/Challenge	6CCVD Solution & Capability	Material Recommendation
Superior Thermal Management	Diamond’s ultra-high thermal conductivity (up to 2000 W m^-1 K^-1) is essential for minimizing thermal gradients and ensuring uniform temperature distribution within the EHDAC, a key challenge noted in the paper.	High Thermal Conductivity SCD (Single Crystal Diamond)
Custom Substrate Thickness	The experiment required a thin (~10 µm) substrate. 6CCVD offers precise thickness control for both SCD and PCD plates, ranging from 0.1 µm up to 500 µm, allowing for optimized thermal boundary conductance.	Optical Grade SCD Wafers (Custom thickness 0.1 µm - 500 µm)
High-Quality Transducer Deposition	The TDTR method relies on a high-quality metal film (~90 nm Al). 6CCVD provides internal, high-precision metalization services, including Au, Pt, Pd, Ti, W, and Cu, optimized for transducer stacks in pump-probe experiments.	Custom Metalization Services (e.g., Ti/Pt/Au stacks)
Ultra-Smooth Surface Finish	TDTR sensitivity requires extremely low surface roughness. 6CCVD guarantees superior polishing quality, minimizing scattering and improving measurement fidelity.	SCD Polishing: Ra < 1 nm
Large-Scale/High-Volume Experiments	For scaling up high P-T studies or developing larger DACs, 6CCVD provides large-area polycrystalline diamond (PCD) plates.	Inch-Size PCD Plates (Up to 125 mm diameter, Ra < 5 nm)

Engineering Support: The accurate determination of thermal transport properties in extreme environments, as demonstrated in this paper, is a core application area for 6CCVD. Our in-house PhD team specializes in material selection and customization for high P-T thermal transport, geophysics, and quantum systems research. We can assist researchers in transitioning from traditional substrates (like glass) to high-performance MPCVD diamond to enhance experimental accuracy and reliability.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Helium (He) and argon (Ar) are important rare gases and pressure media used in diamond-anvil cell (DAC) experiments. Their thermal conductivity at high pressure-temperature (P-T) conditions is a crucial parameter for modeling heat conduction and temperature distribution within a DAC. Here we report the thermal conductivity of He and Ar over a wide range of high P-T conditions using ultrafast time-domain thermoreflectance coupled with an externally heated DAC. We find that at room temperature the thermal conductivity of liquid and solid He shows a pressure dependence of P0.86 and P0.72, respectively; upon heating the liquid, He at 10.2 GPa follows a T0.45 dependence. By contrast, the thermal conductivity of solid Ar at room temperature has a pressure dependence of P1.25, while a T−1.37 dependence is observed for solid Ar at 19 GPa. Our results not only provide crucial bases for further investigation into the physical mechanisms of heat transport in He and Ar under extremes, but also substantially improve the accuracy of modeling the temperature profile within a DAC loaded with He or Ar. The P-T dependences of the thermal conductivity of He are important to better model and constrain the structural and thermal evolution of gas giant planets containing He.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma15196681

References

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