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Acoustic attenuation modeling in porous and composite materials
INSA Centre Val de Loire, Blois
GREMAN
Acoustics Applied Physics 
Full Description:

The study of the porous media in the GREMAN laboratory has begun in 2011 into the thematic of the ultrasonic characterization of complex media. More precisely, this study focused on the porous silicon, which is already largely studied in the GREMAN laboratory, and already 3 Phd thesis have been initiated in this field. The main goal of this study is the nondestructive evaluation of this material to lead to its integration in several systems (RF filters, CMUT and sensors).

The first Phd thesis, defended in 2013, has shown that the ultrasonic characterization allows to retrieve parameters of the porous layer such as its thickness and its porosity. Moreover, it has also been shown that the attenuation is very high in this material, which is an interesting feature in order to limit the undesired wave propagation in the CMUT transducer and enhance their sensitivity. This parameter is also essential in the Surface Acoustic Wave (SAW) sensors (tuning
of the sensitivity) or in the backing of piezoelectric transducers.

 Therefore, This Phd thesis focuses on the estimation of the attenuation of porous material, according to the shape and the porosity, in order to model and simulate the wave propagation into the porous material. This simulation will be used to simulate complex systems, such as CMUT transducers or SAW sensors, in order to optimize them.

The modeling of porous material needs a homogenization step, taking in account the shape of the pores, the porosity and the parameters of the saturating fluid. This step allows to obtain complex mechanical constants which integrate the losses. These mechanical constants can be used in poroelastic models in order to simulate the wave propagation in the porous layers and estimate the whole attenuation occurring in the porous material in the cases of bulk waves or surface waves. Moreover this modeling can be extended to composite materials made from the filling of
porous materials. In fact, several researchers have shown that the filling of porous silicon can tune the mechanical parameters and its study can be useful to optimize attenuation.

Finally, taking account of the attenuation can be really useful to improve the characterization of many others porous materials studied in the GREMAN laboratory, such as mesostructured
metallic oxides or porous ceramics.

Keywords : Porous silicon, composite, acoustic attenuation, SAW sensors, modeling,  poroelasticity

 

Candidate profile: The candidate must have an academic knowledge in the field of applied physics or acoustics. Some competences in instrumentation, modeling or microelectronics will be appreciated.

Candidature procedure: Send a curriculum vitae and a motivation letter before the 15th april 2016

 

 



Posted on: 09 March 2016Deadline to apply: 15 April 2016Start Date: 01 October 2016 Duration: 36 months
The Fund category is Public Funding - Region (State) and the salary is 20-25k€ annual gross
Doctoral School is Energy - materials - earth and universe sciences in the Centre Region.

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