Magnetite (Fe3O4) nanoparticles (NPs) are attractive nanomaterials in the field of material science, chemistry, and physics because of their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Various structures of Fe3O4 NPs with different sizes, geometries, and nanoarchitectures have been synthesized, and the related properties have been studied with targets in multiple fields of applications, including biomedical devices, electronic devices, environmental solutions, and energy applications. Tailoring the sizes, geometries, magnetic properties, and functionalities is an important task that determines the performance of Fe3O4 NPs in many applications. Therefore, this review focuses on the crucial aspects of Fe3O4 NPs, including structures, synthesis, magnetic properties, and strategies for functionalization, which jointly determine the application performance of various Fe3O4 NP-based systems. We first summarize the recent advances in the synthesis of magnetite NPs with different sizes, morphologies, and magnetic properties. We also highlight the importance of synthetic factors in controlling the structures and properties of NPs, such as the uniformity of sizes, morphology, surfaces, and magnetic properties. Moreover, emerging applications using Fe3O4 NPs and their functionalized nanostructures are also highlighted with a focus on applications in biomedical technologies, biosensing, environmental remedies for water treatment, and energy storage and conversion devices.

No abstract

No abstract

No abstract

No abstract

No abstract

Micro-electrical discharge machining milling is a promising method to fabricate three-dimensional microshapes owing to its negligible cutting force and high-dimensional accuracy achievable. In order to machine intricate features, it requires the application of computer-aided manufacturing software to automatically generate the motion pattern for the electrode. Although most commercial computer-aided manufacturing systems cater for conventional milling, they cannot be directly applied for micro-electrical discharge machining milling due to the electrode wear issue and the existence of machining gap. This article presents these process-related issues and proposes an approach in customizing the conventional milling computer-aided manufacturing software for micro-electrical discharge machining milling of three-dimensional intricate shapes. The results show that it is feasible to utilize the current computer-aided manufacturing software to automatically generate tool paths for three-dimensional micro-electrical discharge machining milling by appropriately considering the tool wear and the inherent machining gap. In addition, further control parameters are also considered to achieve fine finish machining condition called simultaneous micro-electrical discharge/electrochemical milling. Different intricate three-dimensional microshapes are produced and evaluated to demonstrate the capability of this approach.

We herein present an alternative geometry of nanostructured carbon cathode capable of obtaining a low turn-on field, and both stable and high current densities. This cathode geometry consisted of a micro-hollow array on planar carbon nanostructures engineered by femtosecond laser. The micro-hollow geometry provides a larger edge area for achieving a lower turn-on field of 0.70 V/µm, a sustainable current of approximately 2 mA (about 112 mA/cm2) at an applied field of less than 2 V/µm. The electric field in the vicinity of the hollow array (rim edge) is enhanced due to the edge effect, that is key to improving field emission performance. The edge effect of the micro-hollow cathode is confirmed by numerical calculation. This new type of nanostructured carbon cathode geometry can be promisingly applied for high intensity and compact electron sources.