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Author: Admin | 2025-04-28
Epitaxial layers, allowing for the realization of ZnO-based electronic and optoelectronic devices. ZnO has several advantages over gallium nitride (GaN) in the application range however, the most important being its larger exciton binding energy and the ability to grow single crystal substrates. Other favorable aspects of ZnO include its broad chemistry leading to many opportunities for wet chemical etching, low power threshold for optical pumping, radiation hardness, and biocompatibility. Together, these properties of ZnO make it an ideal candidate for a variety of devices ranging from sensors through to ultra-violet laser diodes and nanotechnology-based devices such as displays.The stability of titanium oxide nanotube arrays at elevated temperatures was studied in dry oxygen as well as dry and humid argon environments. The tubes crystallized in the anatase phase at a temperature of about 280 °C irrespective of the ambient. Anatase crystallites formed inside the tube walls and transformed completely to rutile at about 620 °C in dry environments and 570 °C in humid argon. No discernible changes in the dimensions of the tubes were found when the heat treatment was performed in oxygen. However, variations of 10% and 20% in average inner diameter and wall thickness, respectively, were observed when annealing in a dry argon atmosphere at 580 °C for 3 h. Pore shrinkage was even more pronounced in humid argon environments. In all cases the nanotube architecture was found to be stable up to approximately 580 °C, above which oxidation and grain growth in the titanium support disrupted the overlying nanotube array. Magda TitiriciMarkus AntoniettiArne ThomasHollow spheres of crystalline metal oxides were synthesized in a simple one-pot synthesis via a hydrothermal approach. Various metal salts were dissolved together with carbohydrates in water, and the mixtures were heated to 180 °C in an autoclave. During the hydrothermal treatment, carbon spheres are formed with metal ions incorporated into their hydrophilic shell. The removal of carbon via calcination yields hollow metal oxide spheres. Using this process, we can produce a wide range of metal oxide hollow spheres that are not accessible via sol−gel chemistry. In this paper, we report the synthesis of Fe2O3,
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