The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202101948.

No abstract

Hollow spheres made from titanium dioxide (TiO 2) are interesting structures because of their high surface area and low density, combined with semiconducting properties of the TiO 2. However, the synthesis is still challenging because of the high reactivity of the titania precursors. Here, we present a simple, reproducible, and scalable way to synthesize TiO 2 hollow spheres in the micrometer/sub-micrometer size range comprising three steps: synthesis of polystyrene template particles, growth of TiO 2 shells, and calcination to hollow spheres. We investigate the importance of adjusting the seed particle surface functionalization via the appropriate choice of comonomer during the dispersion polymerization. An aging step and a calcination process at low temperatures are mandatory to retain the particle integrity during the seed particle removal. We provide a detailed characterization of each step of this process including electron microscopy, small angle X-ray scattering, and simultaneous thermal analysis.

Dedicated to Prof. Dr. Josef Breu on the occasion of his 60 th birthday.Silicon carbide (SiC) particles are exciting structures because of their hardness, chemical inertness, and dielectric properties. In particular, their absorption/emission properties in the midinfrared range render them suitable structures for ambient temperature thermal emitters. However, the synthesis of uniform, spherical structures is still challenging. Here, we present a robust synthesis procedure based on carbothermal reduction of silica precursor particles. With an isotropic shrinkage of ~30 %, the spherical particle shape and uniformity are retained. Furthermore, we outline the influence of the gas atmosphere during the carbothermal treatment and demonstrate the successful conversion to SiC by electron microscopy, X-ray diffraction, thermal and optical analysis.