Electronic properties of Mg2NiH4-x across the metal-to-insulator transition for industrial hydrogen sensing
Event details
| Date | 21.09.2017 |
| Hour | 10:30 › 11:30 |
| Speaker |
Dr. Dook van Mechelen ABB Corporate Research Baden-Dättwil, Switzerland |
| Location | |
| Category | Conferences - Seminars |
ChE-605 - Highlights in Energy Research seminar series
Optical hydrogen sensors have a promising future in a society where hydrogen detection becomes increasingly essential. The traditional use of Pd as sensing material is disadvantaged by its small optical contrast and low sensitivity. A solution is found by complex metal hydrides that are structurally disordered and manifest a metal-to-insulator transition. The amorphous structure offers the sensor’s reversibility and reproducibility. The metal-to-insulator transition translates through the electronic properties into an optical change that is uniquely linked to the hydrogen content, thereby avoiding cross sensitivity from the application environment.
In this talk I first present an optical and transport study on the metal-to-insulator transition in Mg-Ni-H. Experimentally, a significant electron renormalization is observed that increases towards the insulating phase. The lacking Drude weight is recovered in a series of mid-infrared bands. DFT calculations show that band flattening due to a decreasing hydrogen vacancy concentration cannot account for the observed mass. The calculations further suggest the presence of in-gap Ni 3d states that are hybridized with Mg and H. Transitions involving these states cause infrared spectral weight that qualitatively corresponds to the experiment.
Subsequently, I discuss the materials science of making Mg-Ni-H amorphous by using the properties of Ni-Zr. The last part of the talk demonstrates the way from the basic electronic properties to a functional hydrogen sensor, where the hydrogen content is determined from the infrared behavior using fiber optic telecom technologies. Eventually I show the behavior of an amorphous complex metal-hydride in its industrial environment such an oil-filled power transformer.
The seminar can be followed remotely by joining the online Cisco WebEx meeting (connection possible 15 minutes before the talk).
See here the documentation how to install the Cisco WebEx add-on on your computer.
Optical hydrogen sensors have a promising future in a society where hydrogen detection becomes increasingly essential. The traditional use of Pd as sensing material is disadvantaged by its small optical contrast and low sensitivity. A solution is found by complex metal hydrides that are structurally disordered and manifest a metal-to-insulator transition. The amorphous structure offers the sensor’s reversibility and reproducibility. The metal-to-insulator transition translates through the electronic properties into an optical change that is uniquely linked to the hydrogen content, thereby avoiding cross sensitivity from the application environment.
In this talk I first present an optical and transport study on the metal-to-insulator transition in Mg-Ni-H. Experimentally, a significant electron renormalization is observed that increases towards the insulating phase. The lacking Drude weight is recovered in a series of mid-infrared bands. DFT calculations show that band flattening due to a decreasing hydrogen vacancy concentration cannot account for the observed mass. The calculations further suggest the presence of in-gap Ni 3d states that are hybridized with Mg and H. Transitions involving these states cause infrared spectral weight that qualitatively corresponds to the experiment.
Subsequently, I discuss the materials science of making Mg-Ni-H amorphous by using the properties of Ni-Zr. The last part of the talk demonstrates the way from the basic electronic properties to a functional hydrogen sensor, where the hydrogen content is determined from the infrared behavior using fiber optic telecom technologies. Eventually I show the behavior of an amorphous complex metal-hydride in its industrial environment such an oil-filled power transformer.
The seminar can be followed remotely by joining the online Cisco WebEx meeting (connection possible 15 minutes before the talk).
See here the documentation how to install the Cisco WebEx add-on on your computer.
Practical information
- General public
- Free