Thermal conductivity of H2O‐CH3OH mixtures at high pressures - Implications for the dynamics of icy super‐Earths outer shells
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-09-30 |
| Journal | Journal of Geophysical Research Planets |
| Authors | Wen‐Pin Hsieh, Frédéric Deschamps |
| Institutions | Institute of Earth Sciences, Academia Sinica |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: High-Pressure Thermophysical Measurements using MPCVD Diamond
Section titled “Technical Analysis and Documentation: High-Pressure Thermophysical Measurements using MPCVD Diamond”Executive Summary
Section titled “Executive Summary”This research utilizes advanced high-pressure techniques to determine the thermal conductivity ($k$) and sound velocity ($v_{l}$) of H${2}$O-CH${3}$OH mixtures, critical data for modeling the thermal evolution of icy super-Earths. The findings underscore the necessity of ultra-high-quality diamond material for extreme environment research.
- Core Achievement: Measurement of thermal conductivity and sound velocity of H${2}$O-CH${3}$OH mixtures up to 12 GPa using a Diamond Anvil Cell (DAC) coupled with Time Domain Thermoreflectance (TDTR) and Stimulated Brillouin Scattering (SBS).
- Critical Finding: The presence of 5-20 wt% methanol (CH${3}$OH) substantially reduces the thermal conductivity of high-pressure ice VII phases by a factor of 2 to 5 compared to pure H${2}$O.
- Planetary Implication: This reduction in thermal conductivity induces a twofold decrease in the power transported by convection within icy super-Earth mantles, significantly influencing planetary thermal history.
- Methodology: The experiment relies on precise thermal measurements using an 80 nm Aluminum (Al) film deposited on a muscovite mica substrate within the DAC, requiring exceptional optical access and mechanical stability provided by the diamond anvils.
- 6CCVD Relevance: Replicating or extending this high-fidelity research requires high-purity, low-defect Single Crystal Diamond (SCD) for DAC windows, which 6CCVD supplies with custom dimensions and integrated metalization capabilities.
Technical Specifications
Section titled “Technical Specifications”Data extracted from the research paper detailing the experimental parameters and key results.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Achieved | 12 | GPa | H${2}$O-CH${3}$OH mixtures (Ice VII phase) |
| Thermal Conductivity (Pure H$_{2}$O, avg) | 5.0 | W m-1 K-1 | Average value in 2-12 GPa range |
| Thermal Conductivity (H${2}$O-10 wt% CH${3}$OH, avg) | 2.0 | W m-1 K-1 | Average value in 2-12 GPa range |
| Thermal Conductivity Reduction Factor | 2 to 5 | N/A | Due to 5-20 wt% CH$_{3}$OH in Ice VII phase |
| Convective Power Transport Reduction | Factor of 2 | N/A | Due to 10 wt% CH$_{3}$OH presence |
| Sound Velocity Reduction Factor | 1.4 | N/A | Due to CH$_{3}$OH presence |
| TDTR Modulation Frequency | 8.7 | MHz | Pump beam modulation |
| Al Film Thickness (Transducer) | 80 | nm | Coated on muscovite mica substrate |
| Muscovite Mica Thickness | 20 | µm | Reference substrate/thermal insulator |
| DAC Diamond Culet Size | 500 | µm | Sample chamber size |
| Pressure Measurement Uncertainty | ±0.1 | GPa | Determined by ruby fluorescence |
Key Methodologies
Section titled “Key Methodologies”The experiment combined high-pressure generation via DAC with advanced optical thermophysical measurement techniques.
- High-Pressure Generation: A symmetric Diamond Anvil Cell (DAC) with 500 µm culets was used to compress H${2}$O-CH${3}$OH mixtures up to 12 GPa at room temperature.
- Transducer Preparation: A 20 µm thick muscovite mica substrate was coated with an 80 nm thick Aluminum (Al) film, which serves as the thermal transducer for laser energy absorption.
- Pressure Monitoring: Pressure was accurately determined in situ using the fluorescence spectrum of a ruby ball loaded within the DAC.
- Thermal Conductivity Measurement (TDTR): Time Domain Thermoreflectance was employed. A pump beam, electrooptically modulated at 8.7 MHz, heated the Al film, while a time-delayed probe beam monitored the resulting temperature variations via changes in optical reflectivity.
- Sound Velocity Measurement (SBS): Time domain stimulated Brillouin scattering was used to measure the Brillouin frequency ($f_{B}$), which is directly related to the longitudinal sound velocity ($v_{l}$) and elastic constants of the high-pressure ice phases.
- Thermal Modeling: Thermal conductivity was derived by comparing the measured ratio of the in-phase and out-of-phase signals (-V${in}$/V${out}$) to calculations based on a thermal model accounting for bidirectional heat flow.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD provides the specialized MPCVD diamond materials and precision engineering services necessary to enable and advance high-pressure thermophysical research, such as the TDTR/SBS measurements conducted in this study.
Applicable Materials
Section titled “Applicable Materials”The foundation of high-pressure TDTR/SBS experiments is the quality of the diamond anvil. These applications demand materials with exceptional optical transparency, low defect density, and high mechanical strength.
| Research Requirement | 6CCVD Material Solution | Key Benefit |
|---|---|---|
| High-Pressure Anvils | Optical Grade Single Crystal Diamond (SCD) | Ultra-low defect density ensures maximum mechanical integrity up to 12 GPa and beyond. |
| Optical Access | SCD Polished to Ra < 1 nm | Minimizes laser scattering and absorption, crucial for high-fidelity TDTR and SBS measurements. |
| Thermal Management | High Purity SCD (Type IIa) | Excellent thermal properties and minimal background absorption for precise thermal modeling. |
Customization Potential
Section titled “Customization Potential”The paper highlights the use of an 80 nm Al film transducer and a 500 µm culet size. 6CCVD offers integrated services to meet these exact specifications, streamlining the experimental setup for researchers.
- Custom Metalization Services: 6CCVD offers internal, high-precision deposition of thin-film metal stacks directly onto the diamond surface.
- We can replicate the required 80 nm Al film or provide alternative transducer layers (e.g., Ti/Pt/Au, W) with nanometer-scale thickness control, optimizing thermal coupling and reflectivity for TDTR/SBS.
- Precision Diamond Fabrication: While the paper used 500 µm culets, 6CCVD provides custom dimensions for SCD plates and wafers up to 500 µm thick, and PCD plates up to 125 mm in diameter.
- We offer custom laser cutting and shaping to meet specific DAC geometry requirements, ensuring perfect fit and alignment for high-pressure systems.
- Advanced Polishing: For the optical measurements required by TDTR and SBS, surface quality is paramount.
- 6CCVD guarantees SCD polishing to Ra < 1 nm, ensuring the highest quality optical interface for pump and probe beams.
Engineering Support
Section titled “Engineering Support”The modeling of heat transfer in icy super-Earths requires precise material parameters, often involving complex pressure- and temperature-dependent properties.
- Expert Consultation: 6CCVD’s in-house PhD team specializes in high-pressure physics and thermal management. We can assist researchers in selecting the optimal diamond material grade and designing custom metalization stacks for similar High-Pressure Thermophysical Measurement projects (e.g., measuring $k$ of H$_{2}$O-volatile mixtures at temperatures up to 1000 K, as suggested for future work).
- Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure your critical SCD components arrive safely and promptly, regardless of your research location.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Thermal conductivity of H 2 O‐volatile mixtures at extreme pressure‐temperature conditions is a key factor to determine the heat flux and profile of the interior temperature in icy bodies. We use time domain thermoreflectance and stimulated Brillouin scattering combined with diamond anvil cells to study the thermal conductivity and sound velocity of water (H 2 O)‐methanol (CH 3 OH) mixtures to pressures as high as 12 GPa. Compared to pure H 2 O, the presence of 5-20 wt % CH 3 OH significantly reduces the thermal conductivity and sound velocity when the mixture becomes ice VI‐CH 3 OH and ice VII‐CH 3 OH phases at high pressures, indicating that the heat transfer is hindered within the icy body. We then apply these results to model the heat transfer through the icy mantles of super‐Earths, assuming that these mantles are animated by thermal convection. Our calculations indicate that the decrease of thermal conductivity due to the presence of 10 wt % CH 3 OH induces a twofold decrease of the power transported by convection.