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For many industrial applications, the simultaneous presence in a material of different functional properties is necessary. The main interest lies in making a single material more versatile and durable, less fragile and more efficient. In this study, two concomitant properties in the same material were mainly studied: resistance to cracking and the increase in its hydrophobic properties. The chosen process was the sol-gel route due to its versatility and the ease of formulating materials from various precursors in order to obtain (multi)functional materials. In this paper, sol-gel coatings were prepared with tetraethoxysilane, methyltrimethoxysilane and diethoxydimethylsilane as precursors. Tetraethoxysilane was mainly used to improve the material's mechanical properties, especially hardness, and silicon oil was added to improve its hydrophobic behavior. The integration of silicon oil was monitored via 29Si NMR. Microstructural characterizations were carried out to correlate the multi-scale properties with the microstructure of the derived films. Young's modulus and hardness were measured to highlight the effect of key formulation parameters on the mechanical strength of the coatings. The synergistic effect of these precursors is underlined as well as the beneficial effect of silicon oil (generated in situ or precondensed). [ABSTRACT FROM AUTHOR]

Bi-functional water-soluble polymers have been investigated as bonding layers (BL) on aluminum surfaces to promote the adhesion of adhesives for structural bonding applications in the automotive sector. The BLs are located at the interface between two parts: the aluminum substrate and the adhesive (an epoxy-dicyandiamide). The formation and the morphology are studied mainly by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Many process parameters have been investigated such as: i) long or short immersion time in the treatment baths containing the polymers, ii) formulation using three different concentrations. The performances of the BLs under these different operating conditions are evaluated via several mechanical tests: micro-scratch, three-point bending, single lap shear. Results were compared with results obtained with already existing products, launched for the same application, surface treatment prior to structural adhesive bonding of aluminum in transportation. [ABSTRACT FROM AUTHOR]

Silica and silica-based materials with tunable functionalities are frequently encountered in low-k material applications, porous membranes, and microelectonic devices. In the present study, an innovative O 2 /O 3 assisted CVD process for the deposition of such films at moderate temperature is presented, based on a dual precursor chemistry from hexamethyldisilazane (HMDS) and tetraethyl orthosilicate (TEOS). Films with tunable carbon content were obtained through variation of the HMDS flow ratio. A comprehensive FT-IR study reveals the transition of the material from a SiO x C y H type film containing -CH 3 moieties, to a methyl-free SiO x film with the increase of the temperature. At the same time the water contact angle of 81.0° at 400 °C is decreased to 52.8° at 550 °C, related to the absence of methyl moieties in the latter. Ion beam analysis (IBA) confirms the lack of carbon in the films when deposition temperatures are equal to or exceed 500 °C. The resistance to liquid corrosion is investigated as a function of the deposition temperature; SiO x type films present a low Pliskin etching rate of 15 Å.s−1, with this value increasing to 60 Å.s−1 for the SiO x C y :CH 3 films produced at the lower temperatures. It is found that the addition of HMDS to a TEOS chemistry can be utilized to modulate the film composition from SiO x to SiO x C y H and by such, tune the film functional properties, in particular its etching rate, opening the way to the development of new sacrificial films. • Dual-precursor chemical vapor deposition of SiOx and SiOxCy:CH3 from TEOS and HMDS • Tunable carbon incorporation from SiOxCy:CH3 to SiOx through HMDS addition • Enhanced film-etching rate by addition of HMDS in a TEOS/O2/O3 chemistry • Adjustable wettability, constant film hardness and modulus from SiOxCy:CH3 to SiOx [ABSTRACT FROM AUTHOR]