Multiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA‐b‐PDMAEMA‐b‐P2VP‐b‐PDMAEMA‐b‐PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2‐vinylpyridine) (P2VP). Furthermore, these are end‐capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self‐assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase‐separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin‐coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.

Electrophoretic deposition (EPD) was employed to coat yttria-stabilised zirconia (YSZ) on Fecralloy. Various non-aqueous solvents were utilised to achieve smooth crack-free YSZ coatings. The EPD parameters, including solvent type, sedimentation height, zeta potential, particle size, pH and deposition weight, were studied. The micro-structural evolution and mechanical properties of the coatings were studied by the field emission scanning electron microscopy and micro-hardness, respectively. It was found that coatings obtained from 0.4 g L−1 I2 acetyl–acetone were uniform, smooth and crack free. Also they had narrow particle size distributions and higher zeta potential in the suspension. The experimental results revealed that suspension stability was a requirement for obtaining high-quality coatings and deposition yield for stable suspensions was higher; however, particle coagulation resulted in coatings with low green density and poor sinter ability. A transition in deposition mechanism from linear to parabolic was observed during EPD where deposition rate was decreased by time. GRAPHICAL ABSTRACT

No abstract

Nanostructure yttria-stabilized zirconia (nano-YSZ) /Al2O3 composite coatings were deposited on Inconel super-alloy substrates by electrophoretic deposition. Aluminum and nano-YSZ particles were utilized for reaction bonding at high temperatures. After aluminum oxidation at 650℃, sintering process was carried out at temperature ranges of 1100–1250℃. It was found that the presence of aluminum in the green coatings improves bonding and also compensates for the coatings’ volume shrinkage during sintering. The average crystallite sizes for all sintering temperatures were laid on a nanometric scale. Crystallite sizes of various YSZ/Al2O3 nanocomposite coatings were calculated via Scherer’s formula and the measures were in a reasonable agreement with the field-emission scanning electron microscopic results. The average grain size increased from 52.4 nm at 1100℃ for YSZ, to 68.3 nm at 1250℃ for YSZ/Al2O3 nanocomposite coatings. The nanocomposite coatings, which sintered at 1250℃ for 4 h exhibited an optimized self-crack healing capacity with lesser microcrack content.

No abstract