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Topic Review
Pearlescent Pigments
Pigments are substances used to modify the colour of a material, which, unlike dyes, are insoluble both in common solvents and binders. Pigments can be either organic or inorganic, though the latest type is the most used and widespread for industry applications.
  • 9.7K
  • 01 Nov 2020
Topic Review
Prehistoric Paintings in Magura Cave
The paintings are made of bat guano applied over limestone, therefore two sets of laboratory specimens were considered: stone specimens and stone specimens covered with a layer of sterilized bat guano. The two investigated treatments were a commercial product based on ethyl silicate (“ES”) and a solution of diammonium hydrogen phosphate (“DAP”), aimed at forming calcium phosphates. The results of the study indicate that both treatments were able to increase mechanical properties of stone, the increase being higher for “DAP”. Both consolidants caused acceptable color changes, but the “ES” treatment significantly decreased stone wettability, water absorption and water vapor permeability, while the “DAP” treatment slightly affected those properties. In the stone+guano specimens, the presence of the guano layer affected the penetration of the consolidants, thus partly reducing their effectiveness. Compared to the stone samples, the guano layer experienced a more intense color change, alongside visible cracking. However, the adopted methodology to replicate the cave paintings was not completely successful, as the so-deposited guano layer was very prone to detachment when dry, unlike cave paintings. Future work will be dedicated to assess the consolidant performance onto samples that resemble even more closely the conditions of the cave paintings, by improving the methodology for the guano layer deposition and by contaminating specimens with soluble salts before consolidant application.
  • 6.8K
  • 02 Nov 2020
Topic Review Peer Reviewed
Porcelain Enamel Coatings
Porcelain enamel is an inorganic-type coating, which is applied to metals or glass for both decorative and functional purposes. This coating is a silica-based solidified glass mass obtained by high-temperature firing (temperature can range between 450 and 1200 °C depending on the substrate). Porcelain enamel coatings differ from ceramic coatings mainly by their glass structure and dilatation coefficient, and from organic paints mainly by the inorganic nature of the matrix and the chemical bond that exists between the coating and the substrate. 
  • 6.6K
  • 18 Apr 2022
Topic Review
Lipid Membrane
The biological lipid membrane is the key element for the maintenance of cell architecture and physiology. Lipid membranes act as a barrier separating the inner cellular space from the outer environment and further helping in the transmission of signals across the cell boundary. The correct composition and structure of cell membranes define key pathophysiological aspects of cells.
  • 6.3K
  • 23 Dec 2020
Topic Review
Ti Nitrides and Ti Silicides
The diffusion of nitrogen into TiSi2 films of low electrical resistivity, deposited on complementary metal oxyde semiconductor (CMOS) and Schottky diodes components increases their performances. TiN acts as a good diffusion barrier, gate material, Schottky barrier contact...Both TiSi2 and TiN are synthesized in Ti films coated on Si wafers and processed in an expanding microwave plasma producing nitrogen species such as NHx...This process promotes the chemical reactions at the surface of the metal. The growth of both compounds give rise to two competing processes which are thermodynamically and kinetically controlled. Ti films, 250 nm thick, processed at 600°C for  30 min, only consist of TiSi2 crystallites and TiN of amorphous structure. TiN crystallizes at 800°C and grows at the expense of TiSi2 according to thermodynamic data. 
  • 5.4K
  • 30 Oct 2020
Topic Review
Lotus-Leaf-Inspired Biomimetic Coatings
A universal infrastructural issue is wetting of surfaces; millions of dollars are invested annually for rehabilitation and maintenance of infrastructures including roadways and buildings to fix the damages caused by moisture and frost. The biomimicry of the lotus leaf can provide superhydrophobic surfaces that can repel water droplets, thus reducing the penetration of moisture, which is linked with many deterioration mechanisms in infrastructures, such as steel corrosion, sulfate attack, alkali-aggregate reactions, and freezing and thawing. In cold-region countries, the extent of frost damage due to freezing of moisture in many components of infrastructures will be decreased significantly if water penetration can be minimized. Consequently, it will greatly reduce the maintenance and rehabilitation costs of infrastructures.
  • 5.2K
  • 11 Jun 2022
Topic Review
Niobium Oxides
Niobium oxides (NbO, NbO2, Nb2O5), being a versatile material has achieved tremendous popularity to be used in a number of applications because of its outstanding electrical, mechanical, chemical, and magnetic properties. NbxOy films possess a direct band gap within the ranges of 3.2–4.0 eV, with these films having utility in different applications which include; optical systems, stainless steel, ceramics, solar cells, electrochromic devices, capacitor dielectrics, catalysts, sensors, and architectural requirements. With the purpose of fulfilling the requirements of a vast variety of the named applications, thin films having comprehensive properties span described by film composition, morphology, structural properties, and thickness are needed.
  • 4.3K
  • 06 Jan 2021
Topic Review
Water Droplet Erosion
The term erosion is originally derived from the Latin word “rodere”, which means “to gnaw”, and used to indicate a form of materials wear (i.e. loss of material) that is caused by the impact of solid or liquid particles with sufficiently high speed. Liquid erosion can be divided into two types; cavitation erosion and liquid impingement erosion (LIE). The term Water droplet erosion (WDE) is commonly used to indicate liquid impingement erosion (LIE), where a progressive material loss is caused by the repetitive impact of high speed water droplets. WDE constitutes a major concern in many industries including aerospace and aviation, power generation industries particularly in gas turbines and steam turbines, nuclear power plants, and wind energy. Hence, WDE has become an important topic of research.
  • 3.6K
  • 23 Oct 2020
Topic Review Peer Reviewed
Active Edible Packaging
Active edible packaging is a food packaging made of comestible bioproducts and active compounds that interacts with the food. The bioproducts, usually biopolymers, must be recognized as safe and with characteristics to be consumed by humans—comestible—and not toxic and capable of carrying an active compound, like anti-browning agents, colorants, flavors, nutrients, antimicrobial and/or antioxidant compounds, in order to extend the product shelf-life, reduce contamination and maintain or even enhance the nutritional value.
  • 3.4K
  • 13 Apr 2022
Topic Review
Electron Transport Layer
The electron transport layer (ETL) acts as a function of collecting electrons and blocking the transport of holes to the FTO electrode in the PSC. The mesoporous structure of the ETL promotes the crystallization and film formation of perovskite and shortens the migration path of photogenerated electrons. A suitable ETL should have an energy band position that matches the perovskite material.
  • 3.3K
  • 10 Apr 2023
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.
  • 3.0K
  • 07 Dec 2021
Topic Review
2D Nanomaterials
Materials can be rightly characterized as 2D material or nanosheet if only one of its dimensions is in nano-size, they usually resemble a large sheet with one or few atomic thickness layers (more like a sheet of paper). This explains the fundamental characteristic of 2D materials and their unique properties that made them very attractive in tribological applications. Also, the method of preparation of the materials are highlighted.
  • 3.0K
  • 11 Nov 2021
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
  • 3.0K
  • 04 Feb 2023
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.
  • 2.9K
  • 10 Feb 2021
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.
  • 2.9K
  • 30 Oct 2020
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.
  • 2.7K
  • 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.
  • 2.7K
  • 17 Aug 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
  • 2.6K
  • 13 Oct 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.
  • 2.6K
  • 10 Dec 2020
Topic Review
AlCr-Based Coatings in Industrial Applications
AlCr-based hard nitride coatings with different chemical compositions and architectures have been successfully developed and applied over the last few decades. Coating properties are mainly influenced by deposition conditions and the Al/Cr content. The fcc structure is dominant for an Al-content up to Al0.7Cr0.3N and is preferred for most cutting applications. Different (AlCrX)N alloying concepts, including X = Si, W, B, V, have been investigated in order to enhance oxidation resistance and wear behaviour and to provide tribological properties. AlCr-based oxynitrides and even pure oxides (Al1−xCrx)2O3 with different crystalline structures have been explored. Multi- and nanolayered coatings within the AlCr materials system, as well as in combination with (TiSi)N, for example, have also been implemented industrially. The dominant deposition technology is the vacuum arc process. Recently, advanced high-power impulse magnetron sputtering (HiPIMS) processes have also been successfully applied on an industrial scale. 
  • 2.6K
  • 25 Mar 2021
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