Grenoble Institute of Technology

About: Grenoble Institute of Technology is a education organization based out in Grenoble, France. It is known for research contribution in the topics: Hyperspectral imaging & Geology. The organization has 3427 authors who have published 5345 publications receiving 137158 citations. The organization is also known as: Grenoble INP.

Dielectric properties of polyacrylate thick films used in sensors and actuators

Abstract: Dielectric polymers are emerging electro-active materials used in high performance applications such as micropumps, robots and artificial muscles. The development of such applications requires the use of models taking into account the electrical parameters of the material. However, there is still some controversy over the dielectric constant of the most widely used dielectric polymer (VHB 4910, 3M, USA). In this paper, we present an exhaustive study relating to changes in the dielectric constant of VHB 4910 over wide frequency and temperature ranges. We found that the permittivity was a function of: frequency, temperature, the nature of the electrodes and the pre-stress applied to material. Mechanisms of dielectric polarization (β-relaxation) explain the behaviour in temperature and frequency of this parameter. The use of silver grease-compliant electrodes induces an increase in the dielectric constant which moves to a value of 5.4 (against 4.7 with gold electrodes). A pre-strain applied to the material shows a reduction up to 15% in the value of the dielectric constant. Short-range dipolar relaxation, local mechanical constraints in the material and a possible crystallization of material induced by the stretching are suggested to explain these behaviours. Analytic equations of the dielectric constant according to the temperature and pre-strain are then proposed and used to validate the behaviour of these materials for actuator and scavenger devices.

Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics

Abstract: Recently, a new approach to atomic layer deposition (ALD) has been developed that doesn't require vacuum and is much faster than conventional ALD. This is achieved by separating the precursors in space rather than in time. This approach is most commonly called Spatial ALD (SALD). In our lab we have been using/developing a novel atmospheric SALD system to fabricate active components for new generation solar cells, showing the potential of this novel technique for the fabrication of high quality materials that can be integrated into devices. In this minireview we will introduce the basics of SALD and illustrate its great potential by highlighting recent results in the field of photovoltaics.

Starch Nanocrystal Stabilized Pickering Emulsion Polymerization for Nanocomposites with Improved Performance

Abstract: Latex/starch nanocrystal (SNC) nanocomposite dispersions were successfully synthesized via a one-step surfactant-free Pickering emulsion polymerization route using SNC as the sole stabilizer. The effect of the SNC content, initiator type and comonomer on the particle size, colloidal stability, and film properties were investigated. Both HCl and H2SO4-hydrolysed starch nanocrystals, each bearing different surface charges, were used as Pickering emulsion stabilizing nanoparticles. SNCs from HCl hydrolysis were found to provide a better stabilization effect, giving rise to a polymer dispersion with a lower average particle size. The mechanistic aspects of the Pickering emulsion polymerization were also discussed. Nanocomposites formed by film-casting the polymer Pickering emulsions showed better mechanical properties and optical transparency than those obtained by blending the polymer emulsion with a nanocrystal dispersion, showing the one-pot route to nanocomposite precursors to be doubly advantageous. Ther...

Nonlocal Coupled Tensor CP Decomposition for Hyperspectral and Multispectral Image Fusion

Abstract: Hyperspectral (HS) super-resolution, which aims at enhancing the spatial resolution of hyperspectral images (HSIs), has recently attracted considerable attention. A common way of HS super-resolution is to fuse the HSI with a higher spatial-resolution multispectral image (MSI). Various approaches have been proposed to solve this problem by establishing the degradation model of low spatial-resolution HSIs and MSIs based on matrix factorization methods, e.g., unmixing and sparse representation. However, this category of approaches cannot well construct the relationship between the high-spatial-resolution (HR) HSI and MSI. In fact, since the HSI and the MSI capture the same scene, these two image sources must have common factors. In this paper, a nonlocal tensor decomposition model for hyperspectral and multispectral image fusion (HSI-MSI fusion) is proposed. First, the nonlocal similar patch tensors of the HSI are constructed according to the MSI for the purpose of calculating the smooth order of all the patches for clustering. Then, the relationship between the HR HSI and the MSI is explored through coupled tensor canonical polyadic (CP) decomposition. The fundamental idea of the proposed model is that the factor matrices in the CP decomposition of the HR HSI’s nonlocal tensor can be shared with the matrices factorized by the MSI’s nonlocal tensor. Alternating direction method of multipliers is used to solve the proposed model. Through this method, the spatial structure of the MSI can be successfully transferred to the HSI. Experimental results on three synthetic data sets and one real data set suggest that the proposed method substantially outperforms the existing state-of-the-art HSI-MSI fusion methods.

Mechanical properties of natural rubber nanocomposites reinforced with cellulosic nanoparticles obtained from combined mechanical shearing, and enzymatic and acid hydrolysis of sisal fibers

Abstract: In a previous work (Siqueira et al. 2010b) the preparation of cellulosic nanoparticles from sisal fibers using different processing routes, viz. a combination of mechanical shearing, acid and enzymatic hydrolysis was reported. It was shown that the pre-enzymatic hydrolysis treatment of bleached sisal pulp helps the preparation of well individualized rod-like nanocrystals. An amorphous polymer (natural rubber—NR) was chosen as model matrix to investigate the effect of these nanoparticles on the thermo-mechanical properties of nanocomposites. Both tensile tests and dynamic mechanical analyses showed improved stiffness for all nanocomposites. The enzymatic treatment allowed production of a huge range of cellulosic nanoparticles which provided completely different mechanical properties to NR matrix.