Electron microscopic study on high-pressure induced deformation of nano-TiO<sub>2</sub>
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-12-03 |
| Journal | Acta Physica Sinica |
| Authors | Fei Wang, Quanjun Li, Kuo Hu, Bingbing Liu |
| Institutions | Jilin University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Pressure Induced Deformation in Nano-TiOā
Section titled āTechnical Documentation & Analysis: High-Pressure Induced Deformation in Nano-TiOāāReference: Wang Fei, Li Quan-Jun, Hu Kuo, Liu Bing-Bing. Electron microscopic study on high-pressure induced deformation of nano-TiOā. Acta Physica Sinica, Vol. 72, No. 3 (2023) 036201.
Executive Summary
Section titled āExecutive SummaryāThis research successfully utilized high-quality diamond anvils in a Diamond Anvil Cell (DAC) to investigate the pressure-induced phase transformation and plastic deformation mechanisms of anatase TiOā nanospheres.
- High-Pressure Synthesis: The visible-light active $\alpha$-PbOā phase of TiOā was successfully synthesized and stabilized at ambient pressure following compression up to 31.9 GPa.
- Deformation Mechanism: Microstructural analysis confirmed that high pressure induces plastic deformation in TiOā nanospheres, characterized by mechanisms similar to those found in metals: deformation twins and stacking fault slip.
- Critical Size Effect: A significant size effect was observed: submicron grains (500-1000 nm) formed parallel, lens lamellar deformation twins, while smaller nanocrystalline grains (10-150 nm) formed complex fan-shaped multiple twins, indicating size-dependent hardening.
- Material Requirement: The experiment relied critically on the mechanical integrity and optical transparency of the diamond anvils to achieve and sustain pressures exceeding 30 GPa.
- Novel Material Pathway: The findings provide a new experimental direction for preparing twin-rich $\alpha$-PbOā TiOā high-pressure phases, potentially enhancing both photocatalytic efficiency and mechanical strength.
- 6CCVD Relevance: This application directly validates the need for high-purity, custom-fabricated Single Crystal Diamond (SCD) plates, a core offering of 6CCVD, for extreme high-pressure research.
Technical Specifications
Section titled āTechnical SpecificationsāThe following hard data points were extracted from the experimental results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Applied Pressure | 31.9 | GPa | Compression cycle peak |
| $\alpha$-PbOā Phase Stability Pressure | 1.3 | GPa | Stable phase upon decompression |
| Anatase $\rightarrow$ Zircon-type Transition Pressure | 14.6 | GPa | Observed during compression |
| Zircon-type $\rightarrow$ $\alpha$-PbOā Transition Pressure | 7.7 | GPa | Observed during decompression |
| Submicron Grain Size Range | 500-1000 | nm | Exhibited lens lamellar twins |
| Nanocrystalline Grain Size Range | 10-150 | nm | Exhibited fan-shaped multiple twins |
| DAC Anvil Culet Diameter | 300 | Āµm | Used for high-pressure compression |
| Gasket Material / Hole Diameter | 304 Stainless Steel / 100 | Āµm | Sample chamber dimensions |
| Raman Excitation Wavelength | 514 | nm | Used for in-situ phase monitoring |
| Anatase Eg(1) Raman Shift | 144 | cm-1 | Key vibration mode |
Key Methodologies
Section titled āKey MethodologiesāThe high-pressure synthesis and characterization relied on precise control of the DAC environment and advanced electron microscopy techniques.
- Sample Preparation: Used 99.9% pure anatase TiOā nanospheres (Alfa Aesar).
- High-Pressure Setup: Employed a Diamond Anvil Cell (DAC) utilizing 300 Āµm culet diameter diamond anvils and a 304 stainless steel gasket (100 Āµm hole).
- Pressure Medium: TiOā powder was loaded directly without a pressure-transmitting medium, resulting in non-hydrostatic stress conditions.
- Pressure Calibration: Pressure was monitored in-situ using the ruby fluorescence method.
- Compression Cycle: Samples were compressed up to $\approx$ 30 GPa and subsequently decompressed to ambient pressure.
- In-situ Analysis: Phase transitions were tracked using high-pressure Raman spectroscopy (Renishaw InVia) with a 514 nm laser source.
- Ex-situ Sample Extraction: Post-compression samples were extracted from the DAC chamber using a dual-beam electron microscope (FEI scios) via Focused Ion Beam (FIB) milling to prepare cross-section TEM lamellae.
- Microstructural Characterization: High-Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) (JEOL JEM-2200FS) were used to analyze the morphology, deformation twins, and stacking faults of the recovered $\alpha$-PbOā phase.
6CCVD Solutions & Capabilities
Section titled ā6CCVD Solutions & CapabilitiesāThis research highlights the critical role of high-quality diamond materials in achieving extreme pressure conditions necessary for novel material synthesis and fundamental physics studies. 6CCVD is uniquely positioned to supply the foundational diamond components and advanced processing required to replicate and extend this work.
Applicable Materials for High-Pressure Research
Section titled āApplicable Materials for High-Pressure ResearchāTo replicate the 30+ GPa pressures achieved in this study, researchers require diamond anvils fabricated from the highest quality material.
| Application Requirement | 6CCVD Material Recommendation | Rationale |
|---|---|---|
| High-Pressure Anvils (> 30 GPa) | Optical Grade Single Crystal Diamond (SCD) | SCD offers superior hardness, thermal conductivity, and optical transparency across the visible spectrum, essential for in-situ Raman and ruby fluorescence measurements under extreme non-hydrostatic stress. |
| High P-T Experiments (Future Work) | Boron-Doped Diamond (BDD) Plates | BDD acts as a conductive material, enabling the integration of micro-heaters or electrodes directly onto the anvil surface for high P-T synthesis or electrical transport measurements. |
| Large-Volume Synthesis | Polycrystalline Diamond (PCD) Plates | For scaling up high-pressure synthesis beyond the DAC scale, 6CCVD offers PCD plates up to 125 mm in diameter, providing robust material for larger-volume high-pressure apparatus. |
Customization Potential
Section titled āCustomization PotentialāThe success of DAC experiments hinges on the precision and customization of the diamond components. 6CCVD provides comprehensive services tailored to high-pressure science.
- Custom Dimensions: While the paper used 300 Āµm culets, 6CCVD can supply SCD plates up to 500 Āµm thick and PCD wafers up to 125 mm in diameter, serving as ideal precursors for custom anvil fabrication (e.g., Boehler-Almax, Toroidal, or custom culet geometries).
- Precision Polishing: Achieving uniform pressure distribution is critical. 6CCVD offers ultra-high precision polishing for SCD (Ra < 1 nm) and inch-size PCD (Ra < 5 nm), minimizing surface defects that could lead to catastrophic failure at GPa pressures.
- Advanced Metalization: For integrating electrical functionality (e.g., micro-heaters for high P-T synthesis or electrodes for in-situ conductivity measurements), 6CCVD offers internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu deposition. This is crucial for extending the current research to study the electrical properties of the synthesized $\alpha$-PbOā phase.
Engineering Support
Section titled āEngineering Supportā6CCVDās in-house PhD team specializes in the material science of CVD diamond and can assist researchers in optimizing material selection for similar High-Pressure Phase Transformation projects. We ensure the diamond material meets the stringent requirements for mechanical stability, optical clarity, and thermal management under extreme conditions.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The high-pressure <i>Ī±</i>-PbO<sub>2</sub> phase of TiO<sub>2</sub> has suitable band gap and photocatalytic capability in the visible light range, which is an environmentally friendly and efficient photocatalytic material. In this work, <i>Ī±</i>-PbO<sub>2</sub> phase of TiO<sub>2</sub> is obtained by the pressure-relief treatment of anatase nanospheres through using diamond anvil cell, and transmission electron microscope (TEM) observation shows the obvious deformation of TiO<sub>2</sub> nanospheres. High-esolution TEM shows that there are a large number of stacking faults along the [100] direction and deformation twins in the grain. Specifically, the deformation twin band with lens lamellar structure is formed in the submicron grain. The fan-shaped multiple deformation twins are formed in the nanocrystalline grains. This study shows that anatase TiO<sub>2</sub> can be deformed under high pressure, and its micro mechanism of deformation is similar to metalās, mainly including deformation twins and stacking fault slip. There is obvious size effect in the formation of deformation twins. These results provide a new breakthrough point for the study of the size effect of high-pressure phase transformation of TiO<sub>2</sub>, and also point out an experimental direction for preparing the twin high-pressure <i>Ī±</i>-PbO<sub>2</sub> phase.