Micrograph of the Month(s) from the Journal of Sol-Gel Science and Technology April/May

Each month, the ISGS Newsletter features an interesting and striking micrograph (or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given). If you know of any interesting images that might be suitable, please contact the ISGS Newsletter Editor for inclusion. The micrographs can be optical, SEM, TEM, AFM, etc, and a brief description of the samples should be provided.

The first series is taken from the work of Yamamoto, Shimoda, Sato, Nakaya, Ohshita and Gunji entitled “Preparation and film properties of polysiloxanes consisting of di- and quadra-functional hybrid units” (JSST, (2022); https://doi.org/10.1007/s10971-022-05806-z), which explores the mechanical properties of colourless, transparent gel films prepared from siloxane precursors containing both di- (D) and quadra-functional (Q) siloxane groups. Varying the arrangement of D and Q moieties within the precursor enabled the mechanical properties of the hybrids to be modulated, with Young’s modulus and fracture strengths of around 450 and 3.7 MPa being demonstrated.

The second series of micrographs is from the work of Chen, Tao, Shang, Ma, Li, Cao, Li, Li, Li, Xiao and Zhang. This paper, entitled “Rutile TiO2 nanorods grown on carbon nanotubes as high-performance lithium-ion batteries anode via one-dimensional electron pathways” (JSST, (2022); https://doi.org/10.1007/s10971-022-05835-8), explores the properties of rutile nanorods grown on carbon nanotubes via a microwave-assisted hydrothermal method. The intriguing morphologies obtained, which are illustrated in the micrographs below, yielded an initial discharge capacity of 315 mAh.g -1 at 0.3 C when the materials were used as anodes in lithium ion batteries. This was substantially higher than the corresponding values obtained for physically mixed rutile and CNT or pure rutile. Excellent cycling performance was also demonstrated, with 93 % of the initial capacity retained at 1C after 200 cycles. The enhanced performance was attributed to the shorter electron-transfer distances via the one-dimensional pathways established by the CNTs and TiO2 nanorods.

The third series of images is from the work of Muto, Amano, Tan, Yokoi, Kawamura and Matsuda entitled “Ordered arrays of electrostatically assembled SiO2 –SiO 2 composite particles by electrophoresis-induced stimulation” (JSST, (2022); https://doi.org/10.1007/s10971-022-05854-5). This paper explores the formation of electrostatically-assembled SiO2 -SiO 2 composite particles from ensembles of monodisperse 200 nm and 16 µm particles. Composite particles consisting of a 16 µm SiO 2 core decorated with the 200 nm SiO 2 particles (left image) were initially assembled using polyelectrolyte adsorption to control the surface charge of the core and decorating particles. The assembly of these exquisite composites was subsequently achieved by applying controlled AC and DC electric fields to yield 2D hexagonal close-packed structures (right image) or an AC field coupled with gravitational sedimentation to generate ordered 3D hexagonal close-packed arrays.

The final series of images is from the work of Mimura, Hamao, Itasaka, Liu and Hamamoto. This paper, entitled “Hydrothermal synthesis of perovskite-type solid electrolyte nanoplate” ((JSST, (2022); https://doi.org/10.1007/ s10971-022-05810-3), describes the synthesis of perovskite nanoplates with stoichiometry (A,La)TiO 3 (where A is either Li or Na). The phase purity of the nanoplates was modulated by the processing conditions employed, with a single-phase perovskite being obtained when NaOH was used as a mineraliser. The nanoplates had a thickness of around 10 nm and an average size of around 360 nm. Pellets fabricated from the nanoplatelets exhibited a conductivity of 3.8×10 -6 S/cm following sintering at 1000 oC, which was an order of magnitude higher than the corresponding values obtained using commercial powders with a more conventional morphology.