Recent development in lead-free perovskite piezoelectric bulk materials

Photocatalytic approaches, that is the reaction of light-produced charge carriers at a semiconductor surface with their environment, currently attract an extremely wide scientific interest. This is to a large extent due to the high expectations: i) to convert sunlight directly into an energy carrier (H(2)), ii) to stimulate chemical synthetic reactions, or iii) to degrade unwanted environmental pollutants. Since the early reports in 1972, TiO(2) has been the most investigated photocatalytic material by far; this originates from its outstanding electronic properties that allow for a wide range of applications. Not only the material, but also its structure and morphology, can have a considerable influence on the photocatalytic performance of TiO(2). In recent years, particularly 1D (or pseudo 1D) structures such as nanowires and nanotubes have received great attention. The present Review focuses on TiO(2) nanotube arrays (and similar structures) that grow by self-organizing electrochemistry (highly aligned) from a Ti metal substrate. Herein, the growth, properties, and applications of these tubes are discussed, as well as ways and means to modify critical tube properties. Common strategies are addressed to improve the performance of photocatalysts such as doping or band-gap engineering, co-catalyst decoration, junction formation, or applying external bias. Finally, some unique applications of the ordered tube structures in various photocatalytic approaches are outlined.

A Review of Photocatalysis using Self-organized TiO2 Nanotubes and Other Ordered Oxide Nanostructures

One dimensional nanostructured materials

http://ntur.lib.ntu.edu.tw/bitstream/246246/96860/1/88.pdf

Review of titania nanotubes synthesized via the hydrothermal treatment: Fabrication, modification, and application

Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

Nanotubular titanates and titania, with an external diameter of around 8 nm and a wall thickness of about 1 nm, were synthesised by hydrothermal processing. Their morphological and structural properties were characterised by TEM and XRD, respectively, and their thermal stability was evaluated. The formation of nanotubular products was due to hydrothermal treatment, rather than washing process, but the pH values of washing solutions could determine the composition of the products. Sodium titanates, hydrogen titanates and titania nanotubes could be synthesised, respectively, via changing the pH value of washing solutions and the heat-treatment temperature. The nanotubes remained in their shape at 400 °C, fused together at 600 °C, and completely lost their nanotubular shape to give aggregated anatase nano-particles at 800 °C.

Synthesis and characterisation of nanotubular titanates and titania

Microstructure and properties of silicon carbide whisker reinforced zirconium diboride ultra-high temperature ceramics

BiFeO 3 ferrite ceramics were synthesized by spark plasma sintering (SPS) and conventional solid-state synthesis in conjunction with high-energy ball milling. They were evaluated by different characterization techniques such as X-ray diffraction, scanning electron microscopy, and dielectric, ferroelectric and magnetic measurements. The 750 °C-SPS prepared ceramic samples possessed a single perovskite structure and they were compared with the conventionally synthesized ones. The relative density and average grain size were approximately 95% and 300 nm for the conventionally prepared ones. In comparison with the conventionally synthesized ceramics, the SPS-prepared ones exhibited improved dielectric, ferroelectric and magnetic properties. These should be associated with high-density, fine-grained and uniform microstructure created by SPS in conjunction with high-energy ball milling, which could be a promising technique for fabricating high-quality BiFeO 3 multiferroic ceramics.

A comparative study of dielectric, ferroelectric and magnetic properties of BiFeO3 multiferroic ceramics synthesized by conventional and spark plasma sintering techniques

ZrB 2 –SiCw composites were prepared through hot-pressing at a low temperature of 1800 °C, and Al 2 O 3 plus Y 2 O 3 were added as sintering aids. Analysis revealed that additives may react with impurities (i.e. surface oxygen impurities and residual metallic impurities) to form a transient liquid phase, thus promote the sintering and densification of ZrB 2 –SiCw composites. The content of additives was found to have a significant influence on the sinterability, microstructure and mechanical properties of ZrB 2 –SiCw composites. ZrB 2 –SiCw composite prepared with a small amount of additives (3 vol.%) provided the optimal combination of microstructure (relative density of 98.3%) and excellent properties, including flexural strength of 783 MPa and fracture toughness of 6.7 MPa m 1/2 . With further addition of additives, SiC whiskers were inclined to gather together and be enveloped by excessive liquids to form core-rim-like structures, which lead to little decrease in mechanical properties.

Ling Weng

Papers

Synthesis and characterisation of nanotubular titanates and titania

Microstructure and properties of silicon carbide whisker reinforced zirconium diboride ultra-high temperature ceramics

A comparative study of dielectric, ferroelectric and magnetic properties of BiFeO3 multiferroic ceramics synthesized by conventional and spark plasma sintering techniques

Densification, microstructure and mechanical properties of ZrB2–SiCw ceramic composites

The effect of B4C on the microstructure and thermo-mechanical properties of HfB2-based ceramics