Entropy-Driven Self-Healing of Metal Oxides Assisted by Polymer-Inorganic Hybrid Materials.

Enabling self-healing of materials is crucially important for saving resources and energy in numerous emerging applications. While strategies for the self-healing of polymers are advanced, mechanisms for semiconducting inorganic materials are scarce due to the lack of suitable healing agents. Here a concept for the self-healing of metal oxides is developed. This concept consists of metal oxide nanoparticle growth inside the bulk of halogenated polymers and their subsequent entropy-driven migration to externally induced defect sites, leading to recovery of the defect. Herein, it is demonstrated that the pool of self-healing materials is expanded to include semiconductors, thereby increasing the reliability and sustainability of functional materials through the use of metal oxides. It is revealed that electrical properties of tin-doped indium oxide can be partially restored upon healing. Such properties are of immediate interest for the further development of transparent flexible electrodes.

ALD coating of centrifugally spun polymeric fibers and postannealing: case study for nanotubular TiO2 photocatalyst.

This work describes the synthesis of highly photocatalytically active TiO2 tubes (TiTBs) by combining centrifugal spinning and atomic layer deposition (ALD). Poly(vinyl pyrrolidone) (PVP) fibers were first produced by centrifugal spinning and subsequently coated with TiO2 with various film thicknesses in a fluidized bed ALD reactor. After annealing of the TiO2 ALD coated PVP fibers, TiO2 tubes (TiTBs) with excellent textural properties and diameters in the range from approx. 170 to 430 nm were obtained. The morphology and structure of all TiTBs were investigated by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller analysis (BET). Liquid phase photocatalysis was conducted to determine the photocatalytic activity of the TiTBs. The photocatalytic activity of the TiTBs obtained after 50 TiO2 ALD cycles (degradation rate 0.123 min-1) was twice that of the reference TiO2 P25. The underlying reasons for the remarkable photocatalytic performance were textural properties of the resulting tubes along with suitable crystallinity, embedded within the 1D tubular morphology. The herein presented proof-of-concept approach paves a way for the processing of various polymeric fibers into various tubular nanostructures.

Copper-Stabilized Si/Au Nanowhiskers for Advanced Nanoelectronic Applications.

We report here the growth and functional properties of silicon-based nanowhisker (NW) diodes produced by the vapor-liquid-solid process using a pulsed laser deposition technique. For the first time, we demonstrate that this method could be employed to control the size and shape of silicon NWs by using a two-component catalyst material (Au/Cu ≈ 60:1). During the NW growth, copper is distributed on the outer surface of the NW, whereas gold sticks as a droplet to its top. The length of NWs is defined by the total amount of copper in the catalyst alloy droplet. The measurements of the electrical transport properties revealed that in contact with the substrate, individual NWs demonstrate typical I-V diode characteristics. Our approach can become an important new tool in the design of novel electronic components.

Protective radiolucent aluminium oxide coatings for beryllium X-ray optics.

Beryllium, being one of the most transparent materials to X-ray radiation, has become the material of choice for X-ray optics instrumentation at synchrotron radiation sources and free-electron laser facilities. However, there are concerns due to its high toxicity and, consequently, there is a need for special safety regulations. The authors propose to apply protective coatings in order to seal off beryllium from the ambient atmosphere, thus preventing degradation processes providing additional protection for users and prolonging the service time of the optical elements. This paper presents durability test results for Be windows coated with atomic-layer-deposition alumina layers run at the European Synchrotron Radiation Facility. Expositions were performed under monochromatic, pink and white beams, establishing conditions that the samples could tolerate without radiation damage. X-ray treatment was implemented in various environments, i.e. vacuum, helium, nitrogen, argon and dry air at different pressures. Post-process analysis revealed their efficiency for monochromatic and pink beams.