# Low Temperature Reactivity of Aluminum Nanopowders with Liquid Water

Vincent Sarou-Kanian, Samir Ouazar, Pablo Escot Bocanegra, Christian

Chauveau, Iskender Gökalp

► To cite this version:

Vincent Sarou-Kanian, Samir Ouazar, Pablo Escot Bocanegra, Christian Chauveau, Iskender Gökalp. Low Temperature Reactivity of Aluminum Nanopowders with Liquid Water. 3rd European combustion meeting (ECM 2007), Apr 2007, Chania, Greece. hal-03991888

HAL Id: hal-03991888

https://cnrs.hal.science/hal-03991888

Submitted on 16 Feb 2023

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Distributed under a Creative Commons Attribution 4.0 International License
# Low Temperature Reactivity of Aluminum Nanopowders with Liquid Water

<figure><img src="image_2.png" /></figure>

V. Sarou-Kanian*, S. Ouazar, P. Escot Bocanegra, C. Chauveau, I. Gökalp

Institut de Combustion, Aérothermique, Réactivité et Environnement,
Centre National de la Recherche Scientifique
1C, avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France

sarou@cnrs-orleans.fr

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CENTRE NATIONAL
DE LA RECHERCHE
SCIENTIFIQUE

## 1 - Introduction

* Aluminum nanoparticles react with water and produces hydrogen.

* As hydrogen is envisaged as an alternative energy vector, is it possible to consider Ultrafine Aluminum Powder (UFP) as a in situ hydrogen source ?

## 2 - Objectives of the present work

* Understanding of the macrokinetics of the hydroxidation of aluminum.

* Measurements of the H₂ gas release rate as a function of time and temperature.

* Investigating the effect of salt water compared to pure water.

## 3 - Experimental setup

<figure><img src="image_4.png" /></figure>

### Operating Conditions

* Isothermal conditions during experiment

* Temperature parameter range [45 – 90 °C]

* Alex powder, air passivated (100 nm mean diameter)

* Mixture composition fixed as:

* 60 g distilled water

* 0.1 g of Alex powder

* Saline solution 3% w. (KCl or NaCl)

### Experimental Techniques

* Temperature → Thermocouple

graduated test-tube
Mass flowmeter

* H₂ gas release →

* Transmission electron microscopy

* X-ray diffraction

## 4 - Results

* X-ray analyses of the solid reaction residues reveal aluminum oxyhydroxide AlOOH (boehmite)

* Gas-phase chromatography confirms the production of gas dihydrogen (H₂)

* Al(s) + 2 H₂O(l) → AlO(OH)(s) + 3/2 H₂(g)

<figure><img src="image_5.png" /><figcaption>Diffraction diagram of the Al+H₂O reaction residues.</figcaption></figure>

●: AlOOH (JCPDS 00-049-0133);

□: Al (JCPDS 01-085-1327)

<figure><img src="image_6.png" /><figcaption>Example of an experimental result at T=72°C</figcaption></figure>

* Reaction starts after an induction period (t<sub>ind</sub>)

* After this period, instantaneous H₂ flow rate increases rapidly, exhibits a maximum then decreases.

* S-shaped gas evolution for the total volume of hydrogen observed.

* Temperature dependence of the induction period.

* Rat'ko et al [2] suggest that this induction period corresponds to the hydration of the natural oxide film (Al₂O₃).

* The theoretical value of maximum gas release (1350 cm³ H₂/g Al) is not reached, but conversion is quasi-complete.

<figure><img src="image_7.png" /><figcaption>Gas evolution process in water for different temperatures</figcaption></figure>

* Induction time and maximal flow rate follow an Arrhenius law.

* t<sub>ind</sub> for saline solutions are higher than for pure water, with lower W<sub>max</sub>.

<figure><img src="image_8.png" /></figure>

$$W_{\text{max}} = W_{\text{max}}^{\infty} \cdot \exp\left(\frac{-Ea}{RT}\right)$$

<table><thead><tr><th>Solution</th><th>W<sub>max</sub><sup>∞</sup><br>(cm<sup>3</sup>/g/min)</th><th>Ea<br>(kJ/mol)</th></tr></thead><tbody><tr><td>H<sub>2</sub>O, present work</td><td>1.90 10<sup>14</sup></td><td>77 ± 1.5</td></tr><tr><td>H<sub>2</sub>O, Ivanov et al. [1]</td><td>7.93 10<sup>15</sup></td><td>89 ± 1.5</td></tr><tr><td>H<sub>2</sub>O, Lur'e et al. [3]</td><td>3.02 10<sup>14</sup></td><td>85 ± 4.3</td></tr><tr><td>NaCl, KCl solutions, present work</td><td>7.70 10<sup>11</sup></td><td>62 ± 3.5</td></tr></tbody></table>

$$t_{\text{ind}} = t_{\text{ind}}^{\infty} \cdot \exp\left(\frac{-Ea}{RT}\right)$$

<table><thead><tr><th>Solution</th><th>t<sub>ind</sub><sup>∞</sup> (s)</th><th>Ea (kJ/mol)</th></tr></thead><tbody><tr><td>H<sub>2</sub>O</td><td>6.41 10<sup>-11</sup></td><td>-79.9 ± 4.1</td></tr><tr><td>NaCl, KCl solutions</td><td>1.12 10<sup>-10</sup></td><td>-80.4 ± 4.3</td></tr></tbody></table>

<figure><img src="image_9.png" /></figure>

## 5 - TEM Analysis

* Quenching of the reaction by freezing mixture samples at different times.

* Samples are then analyzed by TEM.

<figure><img src="image_10.png" /></figure>

## 6 - Conclusions

* The temperature dependence and the influence of salinity have been investigated on the low temperature reactivity of aluminum nanoparticles with water.

* The production of hydrogen is preceded by an induction period corresponding to the hydration-dissolution-precipitation of the oxide film initially covering the particles.

* This induction period is thermally activated (Ea= -80 kJ/mol).

* The hydrogen released by the reaction (hydroxidation) is characterized by W<sub>max</sub>, which is also thermally activated with similar values of Ea found in the literature.

* The hydroxidation of the nanopowder is slowed down in the presence of chloride ions.

### References

[1] V.G. Ivanov, M.N. Safronov, O.V. Gravilyuk, Combust. Explos. Shock Waves, 37 (2001) 173.

[2] E. Rat'ko, V.E. Romanenkov, E.V. Bolotnikova, Z.V. Krupen'kina, Kinetics and Catalysis, 45 (2004) 141.

[3] B.A. Lur'e, A.N. Chernyshov, N.N. Perova, B.S. Svetlov, Kinet. Katal., 17 (1976) 1453.