Abstract
Clay-based nanostructured multilayers, such as clay-polymer multilayers and clay-oxide multilayers, have attracted growing attention owing to their remarkable mechanical properties and promising application in various fields. In this paper, synthesis of a new kind of nanostructured clay-oxide multilayers by layer-by-layer self-assembly was explored. Nano-mechanical characterization of 18 clay-based multilayer samples, prepared under as-deposited (i.e., air-dried) and annealing conditions at 400 °C/600 °C with different precursor cations and multilayer structure, were carried out using nanoindentation testing, atomic force microscopy (AFM), and X-ray diffraction (XRD). The influencing factors, including as-deposited and annealing conditions and clay concentrations on the mechanical properties were analyzed. Results show that all of the multilayers exhibit high bonding strength between interlayers. Higher modulus and hardness of clay-based multilayers were obtained with lower clay concentrations than that with higher clay concentrations. Different relationships between the modulus and hardness and the annealing temperature exist for a specific type of clay-oxide multilayer. This work offers the basic and essential knowledge on design of clay-based nanostructured multilayers by layer-by-layer self-assembly.
Highlights
Clay-based nanostructured multilayers have attracted growing attentions owing to their remarkable mechanical properties and promising application in various fields, such as protective coatings, micro/nanodevices, electronic memory structures and advanced optical and electro-optical devices, etc. [5,6,7]
The clay-zirconia multilayers were fabricated by sequentially dipping a Si/SiO2 substrate in the exfoliated nano-clay suspension and a zirconia cationic precursor solution followed by annealing at elevated temperatures
The typical indentation load-displacement curves and indent impressions of (SnO2-MMT)30 and (ZrO2-MMT-SnO2-MMT)15 multilayers are shown in Figures 3 and 4, respectively
Summary
Clay-based nanostructured multilayers (e.g., clay-polymer multilayers and clay-oxide multilayers [1,2,3,4]) have attracted growing attentions owing to their remarkable mechanical properties and promising application in various fields, such as protective coatings, micro/nanodevices, electronic memory structures and advanced optical and electro-optical devices, etc. [5,6,7]. Nanostructured clay-oxide multilayers prepared by the LbL self-assembly technique has been reported by Chen and Zhang et al [15,16,17] In these studies, the exfoliated clay platelet (montmorillonite, MMT) having a high aspect ratio with thickness in nanometer scale and bearing negative surface charges is used as an anionic component. It was found that nanoscale LbL growth is achievable, and the annealed films remain uniform and crack-free. This indicates that a variety of nanostructured clay-oxide multilayers with graded functionalities can be conveniently manufactured via changing the composition or concentration of oxide cationic precursor solutions periodically or continuously
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