Showing papers in "THE Coatings in 2020"
TL;DR: In this article, the concept and potential for application of new film-forming materials and management of food wastes from the fruit and vegetable industry, which can encounter problems in appropriate disposal.
Abstract: The development of edible films and coatings has seen remarkable growth in recent decades and is expected to have an important impact on the quality of food products in the coming years. This growth is attributed to the increasing knowledge of edible films and edible coating technology, as well as advances in material science and processing technology. Packaging is used in order to reduce synthetic packaging and can play a role as an eco-friendly biodegradable package or a protective coating on the food surface. A large amount of bio-based polymers have been used in the production of edible films and coatings. Novel sources of edible materials, as well as the novel processing techniques, are a subject of great interest due to their promising potential as innovative food packaging systems. This paper presents the concept and potential for application of new film-forming materials and management of food wastes from the fruit and vegetable industry, which can encounter problems in appropriate disposal. It summarizes the extensive knowledge about the new film-forming materials such as plant residues, flours and gums to show their protective effectiveness and suitability in various types of foods.
129 citations
TL;DR: In this paper, the authors present the process kinetics according to existing models of the discharge phenomena, as well as the influence of the process parameters on the process, and thus, on the resulting coating properties, eg, morphology and composition.
Abstract: Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO), is an innovative method in producing oxide-ceramic coatings on metals, such as aluminum, titanium, magnesium, zirconium, etc The process is characterized by discharges, which develop in a strong electric field, in a system consisting of the substrate, the oxide layer, a gas envelope, and the electrolyte The electric breakdown in this system establishes a plasma state, in which, under anodic polarization, the substrate material is locally converted to a compound consisting of the substrate material itself (including alloying elements) and oxygen in addition to the electrolyte components The review presents the process kinetics according to the existing models of the discharge phenomena, as well as the influence of the process parameters on the process, and thus, on the resulting coating properties, eg, morphology and composition
114 citations
TL;DR: In this article, the authors summarized current knowledge of growth defects in physical vapor deposition (PVD) coatings and discussed the effect of these defects on the quality of optical coatings, thin layers for semiconductor devices, and wear, corrosion, and oxidation resistant coatings.
Abstract: The paper summarizes current knowledge of growth defects in physical vapor deposition (PVD) coatings. A detailed historical overview is followed by a description of the types and evolution of growth defects. Growth defects are microscopic imperfections in the coating microstructure. They are most commonly formed by overgrowing of the topographical imperfections (pits, asperities) on the substrate surface or the foreign particles of different origins (dust, debris, flakes). Such foreign particles are not only those that remain on the substrate surface after wet cleaning procedure, but also the ones that are generated during ion etching and deposition processes. Although the origin of seed particles from external pretreatment of substrate is similar to all PVD coatings, the influence of ion etching and deposition techniques is rather different. Therefore, special emphasis is given on the description of the processes that take place during ion etching of substrates and the deposition of coating. The effect of growth defects on the functional properties of PVD coatings is described in the last section. How defects affect the quality of optical coatings, thin layers for semiconductor devices, as well as wear, corrosion, and oxidation resistant coatings is explained. The effect of growth defects on the permeation and wettability of the coatings is also shortly described.
110 citations
TL;DR: In this paper, the availability and application of polysaccharides from vegetal and marine biomass in coatings for foods packaging paper is discussed, and the extraction methods, chemical modification and combination routes of these biopolymers in coating for paper packaging are discussed.
Abstract: Paper and board show many advantages as packaging materials, but the current technologies employed to obtain adequate barrier properties for food packaging use synthetic polymers coating and lamination with plastic or aluminium foils—treatments which have a negative impact on packaging sustainability, poor recyclability and lack of biodegradability. Recently, biopolymers have attracted increased attention as paper coatings, which can provide new combinations in composite formulas to meet the requirements of food packaging. The number of studies on biopolymers for developing barrier properties of packaging materials is increasing, but only a few of them are addressed to food packaging paper. Polysaccharides are viewed as the main candidates to substitute oil-based polymers in food paper coating, due to their film forming ability, good affinity for paper substrate, appropriate barrier to gases and aroma, and positive effect on mechanical strength. Additionally, these biopolymers are biodegradable, non-toxic and act as a matrix for incorporation additives with specific functionalities for coated paper (i.e., active-antimicrobial properties). This paper presents an overview on the availability and application of polysaccharides from vegetal and marine biomass in coatings for foods packaging paper. The extraction methods, chemical modification and combination routes of these biopolymers in coatings for paper packaging are discussed.
84 citations
TL;DR: In this paper, visible-light photocatalysis of high-density polyethylene (HDPE) and low density polyethyleni (LDPE), in aqueous medium using a mesoporous N-TiO2 coating is proposed as an alternative for fighting MP pollution.
Abstract: Microplastics (MPs), which are small plastic debris of ≤5 mm size, are polluting the oceans with negative consequences for their biota. In this work, visible-light photocatalysis of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) MPs in aqueous medium using a mesoporous N–TiO2 coating is proposed as an alternative for fighting MP pollution. Spherical primary HDPE MPs were extracted from commercially available facial scrubs, while film-shaped secondary LDPE MPs were obtained from a plastic bag. For each plastic, two different sizes were tested. Degradation was measured by mass-loss and carbonyl-index (CI) calculation. The results obtained reveal that the photocatalytic degradation of HDPE and LDPE MPs using an N–TiO2 coating was affected by the size and shape of the MPs. Smaller MPs led to higher degradation, while film-shaped MPs led to lower degradation that was related to a poorly illuminated and oxygenated reaction medium. These results set the basis for further investigation on the on the design of more effective photocatalytic-reaction systems for decreasing MP inputs to the environment.
75 citations
TL;DR: In this article, an up-to-date holistic review of the natural fiber reinforced composites (NFRCs) is presented, which facilitates a clear understanding of the behavior of the composites along with the constituent materials.
Abstract: The increasing global environmental concerns and awareness of renewable green resources is continuously expanding the demand for eco-friendly, sustainable and biodegradable natural fibre reinforced composites (NFRCs). Natural fibres already occupy an important place in the composite industry due to their excellent physicochemical and mechanical properties. Natural fibres are biodegradable, biocompatible, eco-friendly and created from renewable resources. Therefore, they are extensively used in place of expensive and non-renewable synthetic fibres, such as glass fibre, carbon fibre and aramid fibre, in many applications. Additionally, the NFRCs are used in automobile, aerospace, personal protective clothing, sports and medical industries as alternatives to the petroleum-based materials. To that end, in the last few decades numerous studies have been carried out on the natural fibre reinforced composites to address the problems associated with the reinforcement fibres, polymer matrix materials and composite fabrication techniques in particular. There are still some drawbacks to the natural fibre reinforced composites (NFRCs)—for example, poor interfacial adhesion between the fibre and the polymer matrix, and poor mechanical properties of the NFRCs due to the hydrophilic nature of the natural fibres. An up-to-date holistic review facilitates a clear understanding of the behaviour of the composites along with the constituent materials. This article intends to review the research carried out on the natural fibre reinforced composites over the last few decades. Furthermore, up-to-date encyclopaedic information about the properties of the NFRCs, major challenges and potential measures to overcome those challenges along with their prospective applications have been exclusively illustrated in this review work. Natural fibres are created from plant, animal and mineral-based sources. The plant-based cellulosic natural fibres are more economical than those of the animal-based fibres. Besides, these pose no health issues, unlike mineral-based fibres. Hence, in this review, the NFRCs fabricated with the plant-based cellulosic fibres are the main focus.
73 citations
TL;DR: In this paper, the effects of two biopolymers (Ch, Ia) and incorporated TBE (containing phenolic compounds and carotenoids) were studied regarding the physical and antimicrobial properties of films; in addition, their influence on the total phenolic content, viscosity, and flow behavior on the film-forming solutions was investigated.
Abstract: Active films were prepared from poly(vinyl alcohol) (PVA) blended with itaconic acid (Ia), and with chitosan (Ch), enriched with tomato processing by-products extract (TBE) in order to develop new bioactive formulations for food packaging. The effects of two biopolymers (Ch, Ia) and of the incorporated TBE—containing phenolic compounds and carotenoids—were studied regarding the physical and antimicrobial properties of films; in addition, their influence on the total phenolic content, viscosity, and flow behavior on the film-forming solutions was investigated. The results showed increased physical properties (diameter, thickness, density, weight) of the films containing the TBE versus their control. TBE and Ch conferred significant antimicrobial effects to PVA films toward all the tested microorganisms, whereas the best inhibition was registered against S. aureus and P. aeruginosa, with a minimum inhibitory concentration of <0.078 mg DW/mL. The Ia-PVA films also exhibited some antibacterial activity against P. aeruginosa (2.5 mg DW/mL). The total phenolic content of the film-forming solutions presented the highest values for the TBE and Ch-added PVA samples (0.208 mg gallic acid/100 mL film-forming solution). These results suggest that the PVA + Ch film containing TBE can be used for the development of intelligent and active food packaging materials.
71 citations
TL;DR: In this paper, a review on the anodic oxide protection layer principles and requirements for aerospace application, the effect of the anodizing process parameters, as well as the importance of process steps taking place before and after anodicizing are discussed.
Abstract: Aluminum alloys used for aerospace applications provide good strength to weight ratio at a reasonable cost but exhibit only limited corrosion resistance. Therefore, a durable and effective corrosion protection system is required to fulfil structural integrity. Typically, an aerospace corrosion protection system consists of a multi-layered scheme employing an anodic oxide with good barrier properties and a porous surface, a corrosion inhibited organic primer, and an organic topcoat. The present review covers published research on the anodic oxide protection layer principles and requirements for aerospace application, the effect of the anodizing process parameters, as well as the importance of process steps taking place before and after anodizing. Moreover, the challenges of chromic acid anodizing (CAA) substitution are discussed and tartaric-sulfuric acid anodizing (TSA) is especially highlighted among the environmentally friendly alternatives.
70 citations
TL;DR: In this article, the authors review the fundamentals of fungal decay, staining and mold processes, then use these fundamentals as the basis for a discussion of the fungal attack of wood.
Abstract: Wood durability researchers have long described fungal decay of timber using the starkly simple terms of white, brown and soft rot, along with the less destructive mold and stain fungi. These terms have taken on an almost iconic meaning but are only based upon the outward appearance of the damaged timber. Long-term deterioration studies, as well as the emerging genetic tools, are showing the fallacy of simplifying the decay process into such broad groups. This paper briefly reviews the fundamentals of fungal decay, staining and mold processes, then uses these fundamentals as the basis for a discussion of fungal attack of wood in light of current knowledge about these processes. Biotechnological applications of decay fungi are reviewed, and an overview is presented on how fungi surmount the protective barriers that coatings provide on surfaces. Advances in biochemical analyses have, in some cases, radically altered our perceptions of how wood is degraded, and even the relationships between fungal species, while other new findings have reinforced traditional perspectives. Suggestions for future research needs in the coatings field relative to enhanced fungal and environmental protection are presented.
70 citations
TL;DR: In this article, the use of these coated tools in recent scientific researches was collected, highlighting some novel advances in the nanocomposite and diamond coatings area, as these coatings are seeing a growing use in the industry, with very satisfactory results, with performance and tool-life increase.
Abstract: The milling process is one of the most used processes in the manufacturing industry. Milling, as a process, as evolved, with new machines and methods being employed, in order to obtain the best results consistently. Milling tools have also seen quite an evolution, from the uncoated high-speed steel tool, to the now vastly used, coated tools. Information on the use of these coated tools in recent scientific researches was collected. The coatings that are currently being researched are going to be presented, highlighting some novel advances in the nanocomposite and diamond coatings area, as these coatings are seeing a growing use in the industry, with very satisfactory results, with performance and tool-life increase. Wear mechanism of various types of coatings are also a popular topic on recent research, as the cutting behavior of these coated tools provides valuable information on the tool’s-life. Furthermore, analysis of these mechanisms enables for the selection of the best coating type for the correct application. Recently, the employment of coated tools paired with sustainable lubrication methods as seen some use. As this presents the opportunity to enhance the coated tool’s and the process’s performance, obtaining better results, in terms of better tool-life and better surface finish quality, in a more sustainable fashion.
70 citations
TL;DR: In this paper, an ensemble of convolutional neural networks (without a pooling layer) based on probability fusion for automated pavement crack detection and measurement was proposed, and the results show that the proposed method can be effectively applied for crack measurement.
Abstract: Automated pavement crack detection and measurement are important road issues. Agencies have to guarantee the improvement of road safety. Conventional crack detection and measurement algorithms can be extremely time-consuming and low efficiency. Therefore, recently, innovative algorithms have received increased attention from researchers. In this paper, we propose an ensemble of convolutional neural networks (without a pooling layer) based on probability fusion for automated pavement crack detection and measurement. Specifically, an ensemble of convolutional neural networks was employed to identify the structure of small cracks with raw images. Secondly, outputs of the individual convolutional neural network model for the ensemble were averaged to produce the final crack probability value of each pixel, which can obtain a predicted probability map. Finally, the predicted morphological features of the cracks were measured by using the skeleton extraction algorithm. To validate the proposed method, some experiments were performed on two public crack databases (CFD and AigleRN) and the results of the different state-of-the-art methods were compared. To evaluate the efficiency of crack detection methods, three parameters were considered: precision (Pr), recall (Re) and F1 score (F1). For the two public databases of pavement images, the proposed method obtained the highest values of the three evaluation parameters: for the CFD database, Pr = 0.9552, Re = 0.9521 and F1 = 0.9533 (which reach values up to 0.5175 higher than the values obtained on the same database with the other methods), for the AigleRN database, Pr = 0.9302, Re = 0.9166 and F1 = 0.9238 (which reach values up to 0.7313 higher than the values obtained on the same database with the other methods). The experimental results show that the proposed method outperforms the other methods. For crack measurement, the crack length and width can be measure based on different crack types (complex, common, thin, and intersecting cracks.). The results show that the proposed algorithm can be effectively applied for crack measurement.
TL;DR: In this article, the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules are analyzed and a realistic industrial production process is analytically described.
Abstract: Among thin-film photovoltaic technology, cadmium telluride (CdTe) has achieved a truly impressive development that can commercially compete with silicon, which is still the king of the market. Solar cells made on a laboratory scale have reached efficiencies close to 22%, while modules made with fully automated in-line machines show efficiencies above 18%. This success represents the result of over 40 years of research, which led to effective and consolidated production processes. Based on a large literature survey on photovoltaics and on the results of research developed in our laboratories, we present the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules. The most common substrates, the constituent layers, their interaction, the interfaces and the different “tricks” necessary to obtain highly efficient devices will be analyzed. A realistic industrial production process will be analytically described. Moreover, environmental aspects, end-of-life recycling and the life cycle assessment of CdTe-based modules will be deepened and discussed.
TL;DR: In this article, the second phase of the mullite matrix composites has been used to improve the strength and toughness of the matrix, and the reinforcement mechanism of second phase has been discussed.
Abstract: Mullite has high creep resistance, low thermal expansion coefficient and thermal conductivity, excellent corrosion resistance and thermal shock resistance, and plays an important role in traditional ceramics and advanced ceramic materials. However, the poor mechanical properties of mullite at room temperature limit its application. In order to improve the strength and toughness of mullite, the current research focuses on the modification of mullite by using the second phase. The research status of discontinuous phase (particle, whisker, and chopped fiber) and continuous fiber reinforced mullite matrix composites is introduced, including preparation process, microstructure, and its main properties. The reinforcement mechanism of second phase on mullite matrix composites is summarized, and the existing problems and the future development direction of mullite matrix composites are pointed out and discussed.
TL;DR: In the last decades, the interest in the development of protective coatings for movable and immovable Cultural Heritage (CH) assets has decidedly increased as discussed by the authors, mainly motivated by the raising consciousness on preservation requirements for cultural artefacts and monuments.
Abstract: In the last decades, the interest in the development of protective coatings for movable and immovable Cultural Heritage (CH) assets has decidedly increased. This has been mainly prompted by the raising consciousness on preservation requirements for cultural artefacts and monuments, which has consequently determined the development of new protective products. From acrylic resins used at the end of the last century to the up-to-date biomaterials and nanoparticles employed nowadays, the research has made a giant step forward. This article reviews the progresses, the technical challenges, and the most recent advances in protective coatings for archaeological metal, glass, and stone artefacts. It aims at offering a comprehensive and critical overview of the progressions in conservation science and displaying how research has optimized polymers in order to solve deterioration problems. Attention is given to recently developed materials, hybrid coatings, and corrosion inhibitors. This work seeks to provide a reference point for future research and to offer a wide-ranging introduction on the newly available material technologies to restorers and conservators.
TL;DR: In this paper, several available coating techniques to coat metal alloys using bioactive glasses are described, with a special focus on thermal spraying, which nowadays is the most used to deposit coatings on metallic implants.
Abstract: Bioactive glasses are promising biomaterials for bone and tissue repair and reconstruction, as they were shown to bond to both hard and soft tissues stimulating cells towards a path of regeneration and self-repair. Unfortunately, due to their relatively poor mechanical properties, such as brittleness, low bending strength and fracture toughness, their applications are limited to non-load-bearing implants. However, bioactive glasses can be successfully applied as coatings on the surface of metallic implants to combine the appropriate mechanical properties of metal alloys to bioactivity and biocompatibility of bioactive glasses. In this review, several available coating techniques to coat metal alloys using bioactive glasses are described, with a special focus on thermal spraying, which nowadays is the most used to deposit coatings on metallic implants.
TL;DR: In this paper, a bio-based biodegradable films presented good antimicrobial activity, being the intrinsic antimicrobial properties of chitosan enhanced by the ZnO NPs added on the system.
Abstract: The advances on the development of novel materials capable to enhance the shelf life of food products may contribute to reduce the current worldwide food waste problem. Zinc oxide nanoparticles (ZnO NPs) are considered GRAS (Generally Recognized as Safe) by the Food and Drug Administration (FDA) and due to their good antimicrobial properties are suitable to be applied as active compounds in food packaging. ZnO NPs were synthesized to be tested in active bionanocomposites through an eco-friendlier route using apple peel wastes. This work aimed to develop bionanocomposites based on chitosan and incorporated with ZnO NPs to characterize its bioactivity via in vitro and in situ studies, using fresh poultry meat as the food matrix. Overall, bio-based biodegradable films presented good antimicrobial activity, being the intrinsic antimicrobial properties of chitosan enhanced by the ZnO NPs added on the system. When used as primary packaging of the meat, the samples protected with the films presented a decrease on the deterioration speed, which was represented by the preservation of the initial reddish color of the meat and reduction on the oxidation process and microbiological growth. The nanoparticles enhanced especially the antioxidant properties of the films and proved to be potential food preservatives agents to be used in active food packaging.
TL;DR: The main polymer-based strategies to develop antibacterial coatings are summarized, with the aim of these coatings being to avoid the bacteria proliferation by controlling the antibacterial mechanisms involved and enhancing long-term stability.
Abstract: Biomedical devices have become essential in the health care. Every day, an enormous number of these devices are used or implanted in humans. In this context, the bacterial contamination that could be developed in implanted devices is critical since it is estimated that infections kill more people than other medical causes. Commonly, these infections are treated with antibiotics, but the biofilm formation on implant surfaces could significantly reduce the effectiveness of these antibiotics since bacteria inside the biofilm is protected from the drug. In some cases, a complete removal of the implant is necessary in order to overcome the infection. In this context, antibacterial coatings are considered an excellent strategy to avoid biofilm formation and, therefore, mitigate the derived complications. In this review, the main biomaterials used in biomedical devices, the mechanism of biofilm formation, and the main strategies for the development of antibacterial coatings, are reviewed. Finally, the main polymer-based strategies to develop antibacterial coatings are summarized, with the aim of these coatings being to avoid the bacteria proliferation by controlling the antibacterial mechanisms involved and enhancing long-term stability.
TL;DR: A review of the use of edible films/coating with different compositions with a focus on natural compounds from plants, and an assessment of their mechanical and physicochemical features can be found in this paper.
Abstract: In recent years, food packaging has evolved from an inert and polluting waste that remains after using the product toward an active item that can be consumed along with the food it contains. Edible films and coatings represent a healthy alternative to classic food packaging. Therefore, a significant number of studies have focused on the development of biodegradable enveloping materials based on biopolymers. Animal and vegetal proteins, starch, and chitosan from different sources have been used to prepare adequate packaging for perishable food. Moreover, these edible layers have the ability to carry different active substances such as essential oils—plant extracts containing polyphenols—which bring them considerable antioxidant and antimicrobial activity. This review presents the latest updates on the use of edible films/coatings with different compositions with a focus on natural compounds from plants, and it also includes an assessment of their mechanical and physicochemical features. The plant compounds are essential in many cases for considerable improvement of the organoleptic qualities of embedded food, since they protect the food from different aggressive pathogens. Moreover, some of these useful compounds can be extracted from waste such as pomace, peels etc., which contributes to the sustainable development of this industry.
TL;DR: In this article, a review article summarized the concept of scale, various green scale inhibitors, types, mechanisms, comparative performance, significance, and future aspects of green scale inhibitor, which will shed light and be helpful for professionals working in the oil and gas industries.
Abstract: In the present time, more often, it has been seen that scaling has grown as widely and caused problems in the oilfield industry. Scaling is the deposition of various salts of inorganic/organic materials due to the supersaturation of salt-water mixtures. Many works have been proposed by researchers using different methods to solve the problem, of which scale inhibition is one of them. The scale inhibitors, particularly for antiscaling, have derived from natural and synthetic polymers. Among different polymers, inorganic and organic compounds (polyphosphates, carboxylic acid, ethylenediaminetetraacetic acid (EDTA), etc.) can effectively manage the oilfield scales of which many are toxic and expansive. Scale inhibitors of alkaline earth metal carbonate and sulfates and transition metal sulfide are commonly used in oilfield applications. Scale inhibition of metallic surfaces is an essential activity in technical, environmental, economic, and safety purposes. Scale inhibitors containing phosphorus appear to have significant achievements in the inhibition process despite its toxicity. However, phosphorus-based inhibitors can serve as supplements prompting eutrification difficulties. Besides these increasing environmental concerns, green scale inhibitors are renewable, biodegradable, and ecologically acceptable that has been used to prevent, control, and retard the formation of scale. Considering the facts, this review article summarized the concept of scale, various green scale inhibitors, types, mechanisms, comparative performance, significance, and future aspects of green scale inhibitors, which will shed light and be helpful for the professionals working in the oil and gas industries.
TL;DR: In this paper, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi2Se3 thin films prepared using a stoichiometric Bi 2Se3 target and a Se-rich target are investigated.
Abstract: In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi2Se3 thin films prepared using a stoichiometric Bi2Se3 target and a Se-rich Bi2Se5 target are investigated. The Bi2Se3 films were grown on InP(111) substrates by using pulsed laser deposition. X-ray diffraction results revealed that all the as-grown thin films exhibited were highly c-axis-oriented Bi2Se3 phase with slight shift in diffraction angles, presumably due to slight stoichiometry changes. The energy dispersive X-ray spectroscopy analyses indicated that the Se-rich target gives rise to a nearly stoichiometric Bi2Se3 films, while the stoichiometric target only resulted in Se-deficient and Bi-rich films. Atomic force microscopy images showed that the films’ surfaces mainly consist of triangular pyramids with step-and-terrace structures with average roughness, Ra, being ~2.41 nm and ~1.65 nm for films grown with Bi2Se3 and Bi2Se5 targets, respectively. The hardness (Young’s modulus) of the Bi2Se3 thin films grown from the Bi2Se3 and Bi2Se5 targets were 5.4 GPa (110.2 GPa) and 10.3 GPa (186.5 GPa), respectively. The contact angle measurements of water droplets gave the results that the contact angle (surface energy) of the Bi2Se3 films obtained from the Bi2Se3 and Bi2Se5 targets were 80° (21.4 mJ/m2) and 110° (11.9 mJ/m2), respectively.
TL;DR: In this paper, the substitution of plastic packaging with natural materials based on biopolymers and, implicitly, of sodium alginate, with or without other natural additions, is discussed.
Abstract: The amount of plastics used globally today exceeds a million tonnes annually, with an alarming annual growth. The final result is that plastic packaging is thrown into the environment, and the problem of waste is increasing every year. A real alternative is the use bio-based polymer packaging materials. Research carried out in the laboratory context and products tested at the industrial level have confirmed the success of replacing plastic-based packaging with new, edible or completely biodegradable foils. Of the polysaccharides used to obtain edible materials, sodium alginate has the ability to form films with certain specific properties: resistance, gloss, flexibility, water solubility, low permeability to O2 and vapors, and tasteless or odorless. Initially used as coatings for perishable or cut fresh fruits and vegetables, these sodium alginate materials can be applied to a wide range of foods, especially in the meat industry. Used to cover meat products, sodium alginate films prevent mass loss and degradation of color and texture. The addition of essential oils prevents microbial contamination with Escherichia coli, Salmonella enterica, Listeria monocytogenes, or Botrytis cinerea. The obtained results promote the substitution of plastic packaging with natural materials based on biopolymers and, implicitly, of sodium alginate, with or without other natural additions. These natural materials have become the packaging of the future.
TL;DR: In this paper, the photocatalytic activity (PCA) of ZnO/graphitic carbon nitride g-C3N4 (g-CN) composite material for methylene blue (MB) degradation under visible-light irradiation (VLI) was examined.
Abstract: We examine the photocatalytic activity (PCA) of ZnO/graphitic carbon nitride g-C3N4 (g-CN) composite material for methylene blue (MB) degradation under visible-light irradiation (VLI). The polymeric g-CN materials were fabricated by the pyrolysis of urea and thiourea. More importantly, ZnO/g-CN nanostructured composites were fabricated by adding the different mounts (60, 65, 70, and 75 wt.%) of g-CN into ZnO via the simple hydrothermal process. Among fabricated composites, the 75% ZnO/g-CN nanocomposites displayed a superior PCA for MB degradation, which were ~three-fold an enhancement over the pure ZnO nanoparticles. The fabricated materials have been evaluated by X-ray diffraction (XRD), UV-Vis, Fourier transform infrared (FT-IR) spectroscopy, and electron microscopy. More importantly, the photodegradation of MB could get 98% in ZnO/g-CN could be credited to efficient separation of photo-induced charge carriers between ZnO and g-CN. Also, the recycling efficiency of the as-prepared composites was studied for multiple cycles, which shows that the photocatalysts are stable and suitable to carry out photocatalytic degradation in the logistic mode. Additionally, the probable photocatalytic mechanism has also discussed. The synthetic procedure of ZnO/g-CN based materials can be used in numerous fields such as environmental and in energy storage applications.
TL;DR: In this paper, the impact of different physical parameters on the velocity, the temperature, the Nusselt number, and the skin friction coefficient is shown, and it was observed that the ferromagnetic case gained maximum thermal conductivity, as compared to the ferrimagnetic case.
Abstract: This article explores the impact of a magnetic dipole on the heat transfer phenomena of different nano-particles Fe (ferromagnetic) and Fe3O4 (Ferrimagnetic) dispersed in a base fluid ( 60 % water + 40 % ethylene glycol) on micro-polar fluid flow over a stretching sheet. A magnetic dipole in the presence of the ferrities of nano-particles plays an important role in controlling the thermal and momentum boundary layers. The use of magnetic nano-particles is to control the flow and heat transfer process through an external magnetic field. The governing system of partial differential equations is transformed into a system of coupled nonlinear ordinary differential equations by using appropriate similarity variables, and the transformed equations are then solved numerically by using a variational finite element method. The impact of different physical parameters on the velocity, the temperature, the Nusselt number, and the skin friction coefficient is shown. The velocity profile decreases in the order Fe (ferromagnetic fluid) and Fe3O4 (ferrimagnetic fluid). Furthermore, it was observed that the Nusselt number is decreasing with the increasing values of boundary parameter ( δ ) , while there is controversy with respect to the increasing values of radiation parameter ( N ) . Additionally, it was observed that the ferromagnetic case gained maximum thermal conductivity, as compared to ferrimagnetic case. In the end, the convergence of the finite element solution was observed; the calculations were found by reducing the mesh size.
TL;DR: In this article, the authors presented analytical solutions of pumping flow of third-grade nanofluid and described the effects of double diffusion convection through a compliant curved channel, including the presence of Brownian motion and thermophoresis, and concluded that fluid becomes hotter with increase in regular buoyancy ratio and a modified Dufour parameter, but a decrease in temperature is observed for the buoyancy parameter.
Abstract: Nanofluids are potential heat transfer fluids with improved thermophysical properties and heat transfer performance. Double diffusion convection plays an important role in natural processes and technical applications. The effect of double convection by diffusion is not limited to oceanography, but is also evident in geology, astrophysics, and metallurgy. For such a vital role of such factors in applications, the authors have presented the analytical solutions of pumping flow of third-grade nanofluid and described the effects of double diffusion convection through a compliant curved channel. The model used for the third-grade nanofluid includes the presence of Brownian motion and thermophoresis. Additionally, thermal energy expressions suggest regular diffusion and cross-diffusion terms. The governing equations have been constructed for incompressible laminar flow of the non-Newtonian nanofluid along with the assumption of long wavelength. The obtained analytical expressions for velocity, temperature, and nanoparticle concentration have been sketched for various considerable parameters. The effects of regular buoyancy ratio, buoyancy parameter, modified Dufour parameter, and Dufour-solutal Lewis number have been analyzed along with wall properties and pumping characteristics. This study concludes that fluid becomes hotter with increase in regular buoyancy ratio and a modified Dufour parameter, but a decrease in temperature is observed for the buoyancy parameter. Moreover, the solutal concentration is behaving inversely against the Defour-Solutal Lewis number.
TL;DR: In this paper, the current state-of-the-art in the application of graphene in the field of protective coatings is presented, which provides detailed discussions about the protective properties of graphene coatings deposited by different methods, graphene-based organic coatings, the modification of graphenebased coatings and the effects of graphene functionalization on the corrosion resistance of the coating.
Abstract: Due to the excellent properties of graphene, including flexibility that allows it to adjust to the curvature of the substrate surface, chemical inertness, and impermeability, graphene is used as an anticorrosion layer. In this review, we present the current state-of-the-art in the application of graphene in the field of protective coatings. This review provides detailed discussions about the protective properties of graphene coatings deposited by different methods, graphene-based organic coatings, the modification of graphene-based coatings, and the effects of graphene functionalization on the corrosion resistance of protective coatings.
TL;DR: In this article, a mathematical illustration of an application to endoscopy by incorporating hybrid nanoparticles and an induced magnetic field with a rheological fluid model for more realistic results is presented.
Abstract: Present theoretical investigation is a mathematical illustration of an application to endoscopy by incorporating hybrid nanoparticles and an induced magnetic field with a rheological fluid model for more realistic results. Rheological fluid behavior is characterized by the Ostwald-de-Waele power-law model. A hybrid nanofluid mechanism is considered comprising platelet-shaped nanoparticles since nanoparticles are potential drug transportation tools in biomedical applications. Moreover, ciliary activity is encountered regarding their extensive applications in performing complex functions along with buoyancy effects. An endoscope is inserted inside a ciliated tube and peristalsis occurred due to ciliary activity in the gap between tube and endoscope. A non-Newtonian model is developed by mathematical formulation which is tackled analytically using homotopy analysis. The outcomes are interpreted graphically along with the pressure rise and streamlining configuration for the case of negligible inertial forces and long wavelength. A three-dimensional graphical interpretation of axial velocity is studied as well. Moreover, tables are prepared and displayed for a more physical insight.
TL;DR: The aim of this review is to present an updated overview of the most recent and common coating materials used for the microencapsulation of probiotics, as well as the involved techniques and the results of research studies, providing a useful knowledge basis to identify challenges, opportunities, and future trends around coating materials involved in the probiotic microencapulation.
Abstract: The consumption of probiotics has been associated with a wide range of health benefits for consumers. Products containing probiotics need to have effective delivery of the microorganisms for their consumption to translate into benefits to the consumer. In the last few years, the microencapsulation of probiotic microorganisms has gained interest as a method to improve the delivery of probiotics in the host as well as extending the shelf life of probiotic-containing products. The microencapsulation of probiotics presents several aspects to be considered, such as the type of probiotic microorganisms, the methods of encapsulation, and the coating materials. The aim of this review is to present an updated overview of the most recent and common coating materials used for the microencapsulation of probiotics, as well as the involved techniques and the results of research studies, providing a useful knowledge basis to identify challenges, opportunities, and future trends around coating materials involved in the probiotic microencapsulation.
TL;DR: This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity and describes two types of surface modifications: additive and subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo.
Abstract: The main aim of bone tissue engineering is to fabricate highly biocompatible, osteoconductive and/or osteoinductive biomaterials for tissue regeneration. Bone implants should support bone growth at the implantation site via promotion of osteoblast adhesion, proliferation, and formation of bone extracellular matrix. Moreover, a very desired feature of biomaterials for clinical applications is their osteoinductivity, which means the ability of the material to induce osteogenic differentiation of mesenchymal stem cells toward bone-building cells (osteoblasts). Nevertheless, the development of completely biocompatible biomaterials with appropriate physicochemical and mechanical properties poses a great challenge for the researchers. Thus, the current trend in the engineering of biomaterials focuses on the surface modifications to improve biological properties of bone implants. This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity. The article describes two types of surface modifications: (1) Additive and (2) subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo. The review article summarizes known additive modifications, such as plasma treatment, magnetron sputtering, and preparation of inorganic, organic, and composite coatings on the implants. It also presents some common subtractive processes applied for surface modifications of the biomaterials (i.e., acid etching, sand blasting, grit blasting, sand-blasted large-grit acid etched (SLA), anodizing, and laser methods). In summary, the article is an excellent compendium on the surface modifications and development of advanced osteoconductive and/or osteoinductive coatings on biomaterials for bone regeneration.
TL;DR: In this article, the composites were investigated by X-ray photoelectron spectroscopy (XPS), XRD, Fourier transform infrared (FTIR), and transmission electron microscopy (TEM).
Abstract: Graphene oxide–titanium (GO-Ti) composite materials were fabricated using GO as a precursor and then anchoring nano titanium (Nano-Ti) particles on GO sheets with the help of a silane coupling agent. Then, the coating samples were prepared by dispersing GO, Nano-Ti particles, and GO-Ti in an epoxy resin at a low weight fraction of 1 wt %. The GO-Ti composites were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The dispersibility and anti-corrosion mechanism of the coatings were studied by sedimentation experiments, electrochemical impedance spectroscopy (EIS), SEM, and salt spray tests. The mechanical properties of the coatings were analyzed by friction and wear tests. The results showed that the Nano-Ti particles were successfully loaded on the GO surface by chemical bonds, which made GO-Ti composites exhibit better dispersibility in the epoxy than GO. Compared with Nano-Ti particles and GO, the GO-Ti composite exhibited significant advantages in improving the corrosion resistance of epoxy coatings at the same contents, which was attributed to the excellent dispersibility, inherent corrosion resistance, and sheet structure. Among the different proportions of composite materials, the GO-Ti (2:1) material exhibited the best dispersibility and corrosion resistance. In addition, the composite material also greatly improved the wear resistance of the coating.
TL;DR: A survey on hydrophobic surface treatments of concrete can be found in this paper, where the authors highlight the huge variety of compounds and formulations utilized, and the different performances reached in terms of water contact angle, water absorption, chloride penetration, and, rarely reported, anti-icing/icephobic action.
Abstract: In this review, we present a survey on hydrophobic surface treatments of concrete, important protection tools against deterioration and corrosion phenomena. In the frame of a standardized distinction in coatings, pore blockage, and impregnation methods, we highlight the huge variety of compounds and formulations utilized, and the different performances reached in terms of water contact angle, water absorption, chloride penetration, and, rarely reported, anti-icing/icephobic action. Our view covers the spectrum of the surface treatments, but also makes a comparison with hydrophobic bulk modifications of concrete, procedures often utilized as well; further, novel proposals of more sustainable routes are presented. We note that coating and impregnation, preferably when based on polyurethane and silane/siloxane, respectively, appear more effective against water ingress. The achieved wetting character is hydrophobic or, at most, overhydrophobic. Superhydrophobic coatings for concrete have been obtained by embedding nano-powders in hydrophobic emulsions, allowing to add a nanotexture to the preexisting complex roughness of the material. Concrete treated with this type of coating has also recently shown a pronounced icephobic character, a parameter that goes beyond the freeze–thaw characterization usually conducted on cement-based materials.