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Topic Review
Thin-Film Materials by RF Sputtering
We report on the development of several different thin-film material systems prepared by RF magnetron sputtering at Edith Cowan University nanofabrication labs. While focusing on the RF sputtering process optimizations for new or the previously underexplored material compositions and multilayer structures, we disclose several unforeseen material properties and behaviours. We communicate research results related to the design, prototyping, and practical fabrication of high-performance magneto-optic (MO) materials, oxide based sensor components, and transparent heat regulation coatings for advanced construction and solar windows.
  • 2.5K
  • 30 Oct 2020
Topic Review
Bismuth Ferrite
Bismuth ferrite was first discovered to harness its ferroelectric and magnetoelectric properties; the bulk BFO prepared in the 1960s–1970s were marred with high conductivity and secondary phases, which resulted in the loss of motivation over the years. It was not until the early 2000s that the research in single crystals, high-quality BFO thin films, and ceramics brought back researchers into BFO. It is an ABO3 type perovskite compound that crystalizes into the rhombohedral R3c group, hence possessing multiferroic properties due to its noncentrosymmetric nature. In ABO3, perovskite A is Bismuth (Bi) and occupies the corner of the perovskite unit cell, B is iron (Fe), the central atom with an oxygen octahedral arrangement. There is a tilting of oxygen octahedral, which doubles the pseudocubic unit cell giving rhombohedral unit cell. There is an equivalence between pseudocubic unit cell, rhombohedral and hexagonal unit cell representation and hence Figure 2 gives the hexagonal representation. The ferroelectric Curie temperature (TC) of BFO is as high as ~1103 K and antiferromagnetic Neel temperature (TN) is ~643 K. It exhibits a weak net magnetization as the G- type magnetic ordering with an incommensurate cycloidal spin structure having a periodicity of 62 nm. The chemical substitution of A and B sites are considered as one of the alternatives for enhancing the net magnetization via disruption of the cycloidal chain
  • 2.5K
  • 04 Feb 2023
Topic Review
Laser Melting Deposition
Ceramics and ceramic-reinforced metal matrix composites (CMMCs) demonstrate high wear resistance, excellent chemical inertness, and exceptional properties at elevated temperatures. These characteristics are suitable for their utilization in biomedical, aerospace, electronics, and other high-end engineering industries. The aforementioned performances make them difficult to fabricate via conventional manufacturing methods, requiring high costs and energy consumption. To overcome these issues, laser additive manufacturing (LAM) techniques, with high-power laser beams, were developed and extensively employed for processing ceramics and ceramic-reinforced CMMCs-based coatings. In respect to other LAM processes, laser melting deposition (LMD) excels in several aspects, such as high coating efficiency and lower labor cost. Nevertheless, difficulties such as poor bonding between coating and substrate, cracking, and reduced toughness are still encountered in some LMD coatings.
  • 2.4K
  • 24 Mar 2021
Topic Review
Multivariable Formulation of Surfactant-Oil-Water Systems
Surfactant-Oil-Water (SOW) systems are found in nature and synthetic products. They usually result in two immiscible phases, e.g., for two liquids, a water phase (often a brine), and an oily phase (which could be extremely complex as petroleum). Surfactant partitions between the two phases according to some physicochemical rules due to molecular interactions. There is a very particular formulation case in which SOW systems can form three immiscible phases, that is, two excess phases (water and oil) in equilibrium with a  so-called middle phase (because of an intermediate density that places it in the middle of a test tube). This middle phase is a so-called bicontinuous microemulsion which has no droplets dispersed in an external phase as a typical emulsion, but a complex single-phase structure similar to a disordered liquid crystal. When stirred, SOW systems can form multiple dispersed systems that can be described as macroemulsions or nanoemulsions depending on the drop size (O/W or W/O) or multiple emulsions (w/O/W or o/W/O) with droplets inside larger drops. Since the beginnings of the 20th century with Bancroft’s rule, the properties of these systems have been related to many thermodynamic variables, generally with one effect at a time. Nowadays, the generalized physicochemical concept of SOW systems with many formulation variables involved allows to make predictions in various application cases, even for very complex systems, as in enhanced oil recovery (EOR), crude oil dehydration, paints, foods, cosmetics and pharmaceutical formulations, that requires the control on 6-8 variables or even more. This is mainly because of the presence of mixtures of oils from linear alkanes to triglycerides or complex molecules perfumes, or a mixture of salts with cations from sodium to calcium or aluminum, and anions like chloride to phosphate. The complexity is even worse with mixtures of very different surface-active species, resulting in non-linear interactions.
  • 2.3K
  • 17 Aug 2021
Topic Review
Surface Treatment in PDMS-Microfluidic Devices
Microfluidic lab-on-a-chip cell culture techniques have been gaining popularity by offering the possibility of reducing the amount of samples and reagents with greater control over the cellular microenvironment. Polydimethylsiloxane (PDMS) is the commonly used polymer for microfluidic cell culture devices because of the cheap and easy fabrication techniques, non-toxicity, biocompatibility, high gas permeability, and optical transparency.
  • 2.3K
  • 07 Dec 2021
Topic Review
GaN(0001) Surfaces
Herein, the surface properties of gallium nitride (GaN) of the wurtzite form, (0001) oriented are presented. X-ray and UV photoelectron spectroscopies (XPS, UPS) were employed to show chemical and physical characters of the surface . Basic information about electronic structure of various doped GaN(0001) surfaces as well as surface Fermi level pinning are discussed.
  • 2.3K
  • 10 Feb 2021
Topic Review
Resistance of PVD Coatings
Due to the increasing maintenance costs of hydraulic machines related to the damages caused by cavitation erosion and/or erosion of solid particles, as well as in tribological connections, surface protection of these components is very important. Up to now, numerous investigations of resistance of coatings, mainly nitride coatings, such as CrN, TiN, TiCN, (Ti,Cr)N coatings and multilayer TiN/Ti, ZrN/CrN and TN/(Ti,Al)N coatings, produced by physical vapor deposition (PVD) method using different techniques of deposition, such as magnetron sputtering, arc evaporation or ion plating, to cavitation erosion, solid particle erosion and wear have been made. The results of these investigations, degradation processes and main test devices used are presented in this paper. An effect of deposition of mono- and multi-layer PVD coatings on duration of incubation period, cumulative weight loss and erosion rate, as well as on wear rate and coefficient of friction in tribological tests is discussed. It is shown that PVD coating does not always provide extended incubation time and/or improved resistance to mentioned types of damage. The influence of structure, hardness, residence to plastic deformation and stresses in the coatings on erosion and wear resistance is discussed. In the case of cavitation erosion and solid particle erosion, a limit value of the ratio of hardness (H) to Young’s modulus (E) exists at which the best resistance is gained. In the case of tribological tests, the higher the H/E ratio and the lower the coefficient of friction, the lower the wear rate, but there are also many exceptions
  • 2.2K
  • 13 Oct 2020
Topic Review
Diamond-Like Carbon Films
Diamond-like carbon (DLC) films have been extensively applied in industries owing to their excellent characteristics such as high hardness. In particular, there is a growing demand for their use as protective films for mechanical parts owing to their excellent wear resistance and low friction coefficient. DLC films have been deposited by various methods and many deviate from the DLC regions present in the ternary diagrams proposed for sp3 covalent carbon, sp2 covalent carbon, and hydrogen. Consequently, redefining the DLC region on ternary diagrams using DLC coatings for mechanical and electrical components is urgently required. Therefore, we investigate the sp3 ratio, hydrogen content, and other properties of 74 types of amorphous carbon films and present the classification of amorphous carbon films, including DLC. We measured the sp3 ratios and hydrogen content using near-edge X-ray absorption fine structure and Rutherford backscattering-elastic recoil detection analysis under unified conditions. Amorphous carbon films were widely found with nonuniform distribution. The number of carbon atoms in the sp3 covalent carbon without bonding with hydrogen and the logarithm of the hydrogen content were inversely proportional. Further, we elucidated the DLC regions on the ternary diagram, classified the amorphous carbon films, and summarized the characteristics and applications of each type of DLC.
  • 2.1K
  • 28 Sep 2021
Topic Review
Plasma electrolytic oxidation
Plasma electrolytic oxidation (PEO) is a promising method for the surface treatment of metals. The procedure takes place within passivating aqueous electrolytes under alternating current patterns and high process voltages. In so far suitable treatment parameters are chosen, this leads to the formation of protective ceramic coatings which technological properties can be adjusted within wide ranges. The article gives an brief introduction to this topic, concerning a historical overview and a summary of the application fields as well as the layer forming mechanisms and parameter dependencies of this process.
  • 2.1K
  • 21 Jul 2020
Topic Review
Graphene Oxide-Based Anticorrosive Coatings
Graphene oxide was extensively used in the last few years due to its remarkable assets and proved to have a significant contribution to composite materials. Concerning the graphene-based coatings, the synthesis methods, protective function, anticorrosion mechanism, feasible problems, and some methods to improve the overall properties were highlighted. Regarding the contribution of the nanostructure used to improve the capability of the material, several modification strategies for graphene oxide along with the synergistic effect exhibited when functionalized with other compounds were mainly discussed.
  • 2.1K
  • 10 Dec 2020
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