Achraf Ghorbal

Localized Electrografting of Vinylic Monomers on a Conducting Substrate by Means of an Integrated Electrochemical AFM Probe

Combinations of scanning electrochemical microscopy (SECM) with other scanning probe microscopy techniques, such as atomic force microscopy (AFM), show great promise for directing localized modification, which is of great interest for chemical, biochemical and technical applications. Herein, an atomic force scanning electrochemical microscope is used as a new electrochemical lithographic tool (L-AFM-SECM) to locally electrograft, with submicrometer resolution, a non-conducting organic coating on a conducting substrate.

The in-situ characterization and structuring of electrografted polyphenylene films on silicon surfaces. An AFM and XPS study.

An atomic force microscope was used so as to structure by nanofriction films of polynitrophenylene electrografted on substrates of n-type silicon (100) with the native oxide on the top of the surface. AFM measurements of thin films thickness have been carried out in the electrolytic solution for different applied potentials during the electrografting. This investigation allows (i) to determine the relationship between the applied potential and the final thickness of electrografted polyphenylene films and (ii) to specify how the thin layers grow. XPS analysis confirmed the AFM observations on (i) the effective shaving of the grafted polymer chains under mechanical stress and (ii) the existence of a potential threshold for electrografting a polyphenylene film on silicon oxide surfaces. The presence of a residual film in the rubbed zone was attributed to stronger interactions between the first electrografted layer and the native oxide of silicon (through Si-C or/and Si-O-C bonds) than those insuring the cohesion of the multilayer (C-C and C-N bonds).

Nano-friction of polystyrene : the role of the surface chemistry

The purpose of this study is to analyse the influence of the chemical contribution on the nano-friction of polystyrene. The role of interfacial interactions is analysed by comparing friction between the polymer and hydrophobic AFM tip (methyl-terminated grafted layer) and hydrophilic tip (hydroxyl-terminated tip) as a function of sliding velocity and normal force. Nano-friction experiments are achieved by using atomic force microscopy (AFM) in torsion mode. Amorphous atactic polystyrene films are prepared by spin coating a solution onto a smooth and rigid substrate (silicon wafer). Two amorphous atactic polystyrene, varying by their different molecular weights are used. Experimental results show that the friction coefficients measured with hydroxylated tip are always larger than those obtained with non-treated tip (intermediate value) and hydrophobic tip (lower friction), indicating a relationship between nano-friction and interfacial interactions. The dependence of frictional force on velocity is consequent, with a great increase of friction with speed in the case of the hydroxylated tip. A higher friction is obtained for the higher molecular weight polystyrene in contact with hydroxylated tips. However, differences between both polymers become negligible in the case of non-treated and hydrophobic tips.

Nano-Electrochemistry and Nano-Electrografting with an Original Combined AFM-SECM

This study demonstrates the advantages of the combination between atomic force microscopy and scanning electrochemical microscopy. The combined technique can perform nano-electrochemical measurements onto agarose surface and nano-electrografting of non-conducting polymers onto conducting surfaces. This work was achieved by manufacturing an original Atomic Force Microscopy-Scanning ElectroChemical Microscopy (AFM-SECM) electrode. The capabilities of the AFM-SECM-electrode were tested with the nano-electrografting of vinylic monomers initiated by aryl diazonium salts. Nano-electrochemical and technical processes were thoroughly described, so as to allow experiments reproducing. A plausible explanation of chemical and electrochemical mechanisms, leading to the nano-grafting process, was reported. This combined technique represents the first step towards improved nano-processes for the nano-electrografting.

Experimental Investigation of Palm Fiber Surface Treatment Effect on Thermal, Acoustical, and Mechanical Properties of a New Bio-Composite

This work presented an experimental investigation on the use of a bio-composite as an insulating material in building. During the past few years, many projects have tried to create new composites with a high insulating properties, essentially thermal, which plays an important role in buildings energy efficiency (Chikhi et al. in Energy Build 66:267–273, 2013).

Nano-Wear of Polystyrene in Contact With Hydrophilic and Hydrophobic Substrates: Influence of Interfacial Interactions

The aim this study is to analyse the influence of interfacial interactions in the nano-wear behaviour of polymers. Studies will be focussed on the analysis of the transfer layer induced by the friction of a polystyrene cylinder in contact with a flat and smooth substrate. In order to change the nature of interfacial interactions, two different substrates are used. The first one is a hydrophilic silicon wafer (hydroxylated by a piranha treatment) and the second one is a hydrophobic silicon wafer, obtained by a chemical grafting with a CH3 terminated silane. Friction experiments are performed with a translation tribometer which measures the tangential force between the polymer and the substrate for controlled normal force and friction rate. The transfer layer is analysed using atomic force microscopy (AFM) and IR spectroscopy (reflection mode) Tentative correlations between transfer layer characteristics and interfacial properties are proposed.Copyright