# Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor

^{*}

## Abstract

**:**

## 1. Introductions

## 2. Pressure-Sensitive Paint

#### 2.1. Basic Principles of PSP

#### 2.2. Anodized-Aluminum Pressure-Sensitive Paint Characteristics

## 3. Experimental Apparatus

#### 3.1. Materials and Luminophore Solution

- (1)
- Pre-treatmentPure aluminum samples were soaked into 3% sodium hydroxide solution a few minutes. Pure aluminum plates were rinsed with distilled water after the soaking process. Then, the plates were dried in vacuum desiccators for several hours.
- (2)
- AnodizationTwo types of electrolytes, sulfuric acid and phosphoric acid, were used in the anodizing process. The post-treatment process is different for the electrolyte. The samples were anodized with a constant current density of 12.5 mA/cm${}^{2}$. The sample was connected to the anode in 1 molar sulfuric acid in 10 ${}^{\circ}\mathrm{C}$ or 1 molar phosphoric acid in 30 ${}^{\circ}\mathrm{C}$. After the anodization process, the samples were rinsed with distilled water and dried in vacuum desiccators for several hours in a vacuum desiccator.
- (3)
- Post-treatmentThe anodized samples were soaked into 3% phosphoric acid for 20 min at a constant temperature (20–30 ${}^{\circ}\mathrm{C}$) in the case of fabrication by using the sulfuric acid electrolyte or 60 min at a constant temperature (20–30 ${}^{\circ}\mathrm{C}$) in the case of fabrication by using the phosphoric acid electrolyte. Then, the samples were then rinsed with distilled water and dried in vacuum desiccators for several hours.
- (4)
- Luminophore adsorptionThe sample is dipped into the luminophore (${\mathrm{H}}_{2}\mathrm{TCPP}$) solution for 100 s. Then, the sample is quickly rinsed with pure acetone and the inhomogeneous adsorption of luminophore is reduced. Finally, it is dried at least overnight in a vacuum desiccator.

#### 3.2. Fluorescence Spectroscopy

#### 3.3. Static Calibration Chamber

#### 3.4. Laser and Camera for Laser Photodegradation

#### 3.5. Picosecond Laser and Streak Camera

#### 3.6. Resonance Tube

#### 3.7. Shock Tube

## 4. Results and Discussions

#### 4.1. Static Characteristics

#### 4.1.1. Excitation and Emission Spectrum

#### 4.1.2. Luminescence Lifetime

#### 4.1.3. Signal Intensity

#### 4.1.4. Pressure and Temperature Sensitivities

#### 4.1.5. Photodegradation

#### 4.1.6. Solvent Resistance

#### 4.2. Dynamic Characteristics

#### 4.2.1. Resonance Tube

#### 4.2.2. Shock Tube Experiment

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 8.**Luminescence lifetime of ${\mathrm{H}}_{2}\mathrm{TCPP}$ on the reference at atmospheric conditions.

**Figure 13.**Influence of fabrication conditions on photodegradation characteristics at P = 100 kPa and T = 293 K.

**Figure 16.**Bode plots of the AA-PSP at atmospheric pressure and ${T}_{ref}=293\left[K\right]$: (

**a**) gain and (

**b**) phase with fitting curves.

Sample Name | ${\mathbf{SA}}_{\mathbf{Ru}}$ | ${\mathbf{SA}}_{\mathbf{T}10}$ | ${\mathbf{SA}}_{\mathbf{T}20}$ | ${\mathbf{SA}}_{\mathbf{T}30}$ | ${\mathbf{SA}}_{\mathbf{C}0.01}$ | ${\mathbf{SA}}_{\mathbf{C}0.9}$ | ${\mathbf{PA}}_{\mathbf{T}20}$ | ${\mathbf{PA}}_{\mathbf{T}30}$ | ${\mathbf{PA}}_{\mathbf{T}60}$ |
---|---|---|---|---|---|---|---|---|---|

Electrolyte | Sulfuric acid | Phosphoric acid | |||||||

Pores diameter (nm) | 20–100 | 165 | |||||||

Anodization time (min) | 20 | 10 | 20 | 30 | 20 | 20 | 20 | 30 | 60 |

Layer thickness (µm) | 4.9 | 1.7 | 4.9 | 8.5 | 4.9 | 4.9 | 4 | 4.9 | 9.8 |

Luminophore | Ru(dpp)_{3} | ${\mathrm{H}}_{2}\mathrm{TCPP}$ | |||||||

Luminophore concentration (mM *) | 0.1 | 0.01 | 0.9 | 0.1 |

Sample | ${\mathbf{SA}}_{\mathbf{T}10}$ | ${\mathbf{SA}}_{\mathbf{T}20}$ | ${\mathbf{SA}}_{\mathbf{T}30}$ | ${\mathbf{SA}}_{\mathbf{C}0.01}$ | ${\mathbf{SA}}_{\mathbf{C}0.9}$ | ${\mathbf{PA}}_{\mathbf{T}20}$ | ${\mathbf{PA}}_{\mathbf{T}30}$ | ${\mathbf{PA}}_{\mathbf{T}60}$ |
---|---|---|---|---|---|---|---|---|

${S}_{P}$ | 0.437 | 0.499 | 0.544 | 0.505 | 0.485 | 0.331 | 0.377 | 0.505 |

$(\%/\mathrm{kPa})$ | ||||||||

${S}_{T}$ | 1.461 | 0.526 | 0.815 | 0.726 | 0.774 | 0.104 | 0.072 | 0.091 |

$(\%/\mathrm{K})$ |

Sample | ${\mathbf{SA}}_{\mathbf{T}10}$ | ${\mathbf{SA}}_{\mathbf{T}20}$ | ${\mathbf{SA}}_{\mathbf{T}30}$ | ${\mathbf{SA}}_{\mathbf{C}0.01}$ | ${\mathbf{SA}}_{\mathbf{C}0.9}$ | ${\mathbf{PA}}_{\mathbf{T}20}$ | ${\mathbf{PA}}_{\mathbf{T}30}$ | ${\mathbf{PA}}_{\mathbf{T}60}$ |
---|---|---|---|---|---|---|---|---|

${I}_{d\mathrm{LED}}$ | 0.010 | 0.051 | −0.009 | 0.062 | 0.066 | 0.146 | 0.152 | 0.034 |

$(\%/\mathrm{min})$ | ||||||||

${I}_{d\mathrm{Laser}}$ | ||||||||

$(\times {10}^{-5}\%/\mathrm{pulse})$ | ||||||||

$N=$ 1,000,000 | 0.93 | 1.07 | 1.31 | 1.26 | 1.28 | 1.59 | 1.77 | 1.29 |

$N=$ 2,000,000 | 0.57 | 0.63 | 0.87 | 0.78 | 0.77 | 1.04 | 1.12 | 0.81 |

Sample No. | ${\mathbf{SA}}_{\mathbf{T}30:\mathbf{pd}}$ | ${\mathbf{SA}}_{\mathbf{T}30:\mathbf{ar}}$ | ${\mathbf{PA}}_{\mathbf{T}60:\mathbf{pd}}$ | ${\mathbf{PA}}_{\mathbf{T}60:\mathbf{ar}}$ |
---|---|---|---|---|

${S}_{P}$ | 0.482 | 0.644 | 0.520 | 0.624 |

$(\%/\mathrm{kPa})$ | ||||

${S}_{T}$ | 9.32 × ${10}^{-2}$ | 2.35 × ${10}^{-2}$ | 0.839 | 0.125 |

$(\%/\mathrm{K})$ | ||||

Signal intensity | 1 | 0.81 | 1 | 0.80 |

Sample | ${\mathbf{SA}}_{\mathbf{T}10}$ | ${\mathbf{SA}}_{\mathbf{T}20}$ | ${\mathbf{SA}}_{\mathbf{T}30}$ | ${\mathbf{PA}}_{\mathbf{T}60}$ |
---|---|---|---|---|

Estimated cut-off frequency (kHz) | 15.0 | 12.5 | 9.0 | 15.2 |

Diffusion coefficient (m${}^{2}$/s) | $1.05\times {10}^{-7}$ | $7.25\times {10}^{-7}$ | $1.58\times {10}^{-6}$ | $3.53\times {10}^{-6}$ |

Theoretical diffusion coefficient (m${}^{2}$/s) | $2.40\times {10}^{-7}$ | $2.40\times {10}^{-7}$ | $2.40\times {10}^{-7}$ | $7.51\times {10}^{-7}$ |

Sample | Mach Number of Normal Shock Wave | The Time Constant (µs) | The 90% Rise Time (µs) |
---|---|---|---|

${\mathrm{SA}}_{\mathrm{T}20}$ | 1.41 | 4.87 | 11.2 |

${\mathrm{PA}}_{\mathrm{T}60}$ | 1.63 | 2.60 | 5.99 |

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## Share and Cite

**MDPI and ACS Style**

Oka, Y.; Nagata, T.; Kasai, M.; Ozawa, Y.; Asai, K.; Nonomura, T.
Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor. *Sensors* **2022**, *22*, 6401.
https://doi.org/10.3390/s22176401

**AMA Style**

Oka Y, Nagata T, Kasai M, Ozawa Y, Asai K, Nonomura T.
Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor. *Sensors*. 2022; 22(17):6401.
https://doi.org/10.3390/s22176401

**Chicago/Turabian Style**

Oka, Yoshinori, Takayuki Nagata, Miku Kasai, Yuta Ozawa, Keisuke Asai, and Taku Nonomura.
2022. "Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor" *Sensors* 22, no. 17: 6401.
https://doi.org/10.3390/s22176401