研究目的
To develop and characterize PZT/PZT and PZT/BiT composite thick piezoelectric films using photochemical metal organic and infiltration deposition techniques for structural health monitoring in aerospace applications.
研究成果
The hybrid sol-gel PMOD and infiltration technique successfully produced crack-free, dense PZT/PZT and PZT/BiT composite thick films on curved superalloy substrates with improved dielectric, ferroelectric, and piezoelectric properties. The films showed high remnant polarization, permittivity, and piezoelectric coefficients, making them suitable for high-frequency structural health monitoring in aerospace applications. Future work could focus on optimizing the process for larger substrates and reducing porosity further.
研究不足
The deposition on curved substrates, especially larger blades, was challenging and required modifications like eliminating spin coating. The process involved multiple thermal cycles, which could induce stress or cracking if not controlled. Porosity and agglomeration issues were addressed but not fully eliminated. Measurement of transverse piezoelectric coefficients (e.g., d31) was difficult due to substrate curvature and film thinness.
1：Experimental Design and Method Selection:
A hybrid sol-gel technique combining photochemical metal organic deposition (PMOD) and infiltration was used to deposit composite piezoelectric films on curved superalloy substrates. The method involved suspending PZT-5A powder in PZT or BiT precursor solutions, with UV irradiation and thermal treatments to achieve crack-free, dense films.
2：Sample Selection and Data Sources:
Substrates included IN718 and IN738 nickel-based superalloy turbine blades, as well as Si and Pt/Si flat wafers for comparison. Samples were masked and prepared with bottom electrodes.
3：List of Experimental Equipment and Materials:
Equipment included spin coaters, hot plates, UV lamps (365 nm, 6 W), furnaces for annealing, thermal evaporation and sputtering systems for electrode deposition, SEM (FESEM JEOL JSM-600F), profilometer (Alpha-Step IQ), roughness tester (Perthometer M2), XRD (Rigaku D/MAX-2000), C-V analyzer (Keithley 590), and APC d33 meter. Materials included lead 2-ethylhexanoate, zirconium 2-ethylhexanoate, Ti-isopropoxide, bismuth 2-ethylhexanoate, hexane solvent, PZT-5A powder, gold, platinum, and Kapton tape.
4：Experimental Procedures and Operational Workflow:
The process involved: (a) Preparing precursor solutions with specific molar ratios. (b) Depositing layers by injection or spin coating at 1500 rpm, followed by drying at 200°C, UV irradiation for 10 min, pyrolysis at 400°C, and annealing at 700°C for each layer, repeated to achieve desired thickness (up to 100 μm). Infiltration steps involved alternating layers of precursor solution and powder suspension. (c) Depositing bottom and top electrodes using evaporation (Au) or sputtering (Pt). (d) Secondary annealing at 600°C for electrode bonding.
5：Data Analysis Methods:
Characterization included SEM for morphology, profilometry for thickness and roughness, XRD for crystalline structure, C-V hysteresis for dielectric properties, P-E hysteresis for ferroelectric properties, and d33 measurement for piezoelectric coefficients. Data were analyzed using standard methods and MATLAB for hysteresis loops.
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