Showing papers in "THE Coatings in 2018"
TL;DR: In this paper, a review of the improvements already studied in order to optimize the sputtering PVD process, trying to relate these improvements with the industrial requirements as a function of product development and market demand is presented.
Abstract: Physical vapour deposition (PVD) is a well-known technology that is widely used for the deposition of thin films regarding many demands, namely tribological behaviour improvement, optical enhancement, visual/esthetic upgrading, and many other fields, with a wide range of applications already being perfectly established. Machining tools are, probably, one of the most common applications of this deposition technique, sometimes used together with chemical vapour deposition (CVD) in order to increase their lifespan, decreasing friction, and improving thermal properties. However, the CVD process is carried out at higher temperatures, inducing higher stresses in the coatings and substrate, being used essentially only when the required coating needs to be deposited using this process. In order to improve this technique, several studies have been carried out optimizing the PVD technique by increasing plasma ionization, decreasing dark areas (zones where there is no deposition into the reactor), improving targets use, enhancing atomic bombardment efficiency, or even increasing the deposition rate and optimizing the selection of gases. These studies reveal a huge potential in changing parameters to improve thin film quality, increasing as well the adhesion to the substrate. However, the process of improving energy efficiency regarding the industrial context has not been studied as deeply as required. This study aims to proceed to a review regarding the improvements already studied in order to optimize the sputtering PVD process, trying to relate these improvements with the industrial requirements as a function of product development and market demand.
217 citations
TL;DR: In this paper, the micro-arc oxidation (MAO) and physical vapor deposition-thermal evaporation (PVD-TE) techniques were combined for dental implant applications.
Abstract: The bioactive and anti-bacterial Cu-based bioceramic TiO2 coatings have been fabricated on cp-Ti (Grade 2) by two-steps. These two-steps combine micro-arc oxidation (MAO) and physical vapor deposition–thermal evaporation (PVD-TE) techniques for dental implant applications. As a first step, all surfaces of cp-Ti substrate were coated by MAO technique in an alkaline electrolyte, consisting of Na3PO4 and KOH in de-ionized water. Then, as a second step, a copper (Cu) nano-layer with 5 nm thickness was deposited on the MAO by PVD-TE technique. Phase structure, morphology, elemental amounts, thickness, roughness and wettability of the MAO and Cu-based MAO coating surfaces were characterized by XRD (powder- and TF-XRD), SEM, EDS, eddy current device, surface profilometer and contact angle goniometer, respectively. The powder- and TF-XRD spectral analyses showed that Ti, TiO2, anatase-TiO2 and rutile-TiO2 existed on the MAO and Cu-based MAO coatings’ surfaces. All coatings’ surfaces were porous and rough, owing to the presence of micro sparks through MAO. Furthermore, the surface morphology of Cu-based MAO was not changed. Also, the Cu-based MAO coating has more hydrophilic properties than the MAO coating. In vitro bioactivity and in vitro antibacterial properties of the coatings have been investigated by immersion in simulated body fluid (SBF) at 36.5 °C for 28 days and bacterial adhesion for gram-positive (S. aureus) and gram-negative (E. coli) bacteria, respectively. The apatite layer was formed on the MAO and Cu-based MAO surfaces at post-immersion in SBF and therefore, the bioactivity of Cu-based MAO surface was increased to the MAO surface. Also, for S. aureus and E. coli, the antibacterial properties of Cu-based MAO coatings were significantly improved compared to one of the uncoated MAO surfaces. These results suggested that Cu-based MAO coatings on cp-Ti could be a promising candidate for biomedical dental implant applications.
140 citations
TL;DR: In this article, different conductive metal nanomaterials are introduced, and the challenges facing methods of thin film deposition and applications of thin films as conductive coatings are investigated, as well as the application of conductive materials in thin-film applications.
Abstract: With ever-increasing demand for lightweight, small, and portable devices, the rate of production of electronic and optoelectronic devices is constantly increasing, and alternatives to the current heavy, voluminous, fragile, conductive and transparent materials will inevitably be needed in the future. Conductive metal nanomaterials (such as silver, gold, copper, zinc oxide, aluminum, and tin) and carbon-based conductive materials (carbon nanotubes and graphene) exhibit great promise as alternatives to conventional conductive materials. Successfully incorporating conductive nanomaterials into thin films would combine their excellent electrical and optical properties with versatile mechanical characteristics superior to those of conventional conductive materials. In this review, the different conductive metal nanomaterials are introduced, and the challenges facing methods of thin film deposition and applications of thin films as conductive coatings are investigated.
139 citations
TL;DR: In this paper, a review of the starch-based ECs used to preserve the main properties of fruits and vegetables in postharvest conditions as well as the different factors affecting the coating efficiency, such as surface properties or incorporation of antifungal compounds.
Abstract: Considerable research has focused on the control of the physiological activity of fruits and vegetables in postharvest conditions as well as microbial decay. The use of edible coatings (ECs) carrying active compounds (e.g., antimicrobials) represents an alternative preservation technology since they can modify the internal gas composition by creating a modified atmosphere through the regulation of the gas exchange (oxygen, carbon dioxide, volatiles) while also limiting water transfer. Of the edible polymers able to form coating films, starch exhibits several advantages, such as its ready availability, low cost and good filmogenic capacity, forming colourless and tasteless films with high oxygen barrier capacity. Nevertheless, starch films are highly water sensitive and exhibit limited water vapour barrier properties and mechanical resistance. Different compounds, such as plasticizers, surfactants, lipids or other polymers, have been incorporated to improve the functional properties of starch-based films/coatings. This paper reviews the starch-based ECs used to preserve the main properties of fruits and vegetables in postharvest conditions as well as the different factors affecting the coating efficiency, such as surface properties or incorporation of antifungal compounds. The great variability in the plant products requires specific studies to optimize the formulation of coating forming products.
129 citations
TL;DR: In this article, a carboxymethyl cellulose/sodium alginate/chitosan composite film was obtained by immersing the film in a solution of a cross-linking agent, CaCl2, and air-drying the resulting material.
Abstract: A sodium alginate/chitosan solution was prepared by dissolving sodium alginate, chitosan, and glycerol in an acetic acid solution. This solution was then combined with a sodium carboxymethyl cellulose solution and the mixture was cast onto a glass plate and dried at a constant temperature of 60 °C. Then, a carboxymethyl cellulose/sodium alginate/chitosan composite film was obtained by immersing the film in a solution of a cross-linking agent, CaCl2, and air-drying the resulting material. First, the most advantageous contents of the three precursors in the casting solution were determined by a completely random design test method. Thereafter, a comprehensive orthogonal experimental design was applied to select the optimal mass ratio of the three precursors. The composite film obtained with sodium alginate, sodium carboxymethyl cellulose, and chitosan contents of 1.5%, 0.5%, and 1.5%, respectively, in the casting solution displayed excellent tensile strength, water vapor transmission rate, and elongation after fracture. Moreover, the presence of chitosan successfully inhibited the growth and reproduction of microorganisms. The composite film exhibited antibacterial rates of 95.7% ± 5.4% and 93.4% ± 4.7% against Escherichia coli and Staphylococcus aureus, respectively. Therefore, the composite film is promising for antibacterial food packaging applications.
109 citations
TL;DR: In this article, the authors provide a comprehensive understanding of the preparation and anti-icing applications of the super-hydrophobic coatings applied on the surface of aircrafts, and discuss the current research progress on the wetting theories of superhydrophobicity.
Abstract: Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of flight due to the damage of aerodynamic shape. This review article provides a comprehensive understanding of the preparation and anti-icing applications of the superhydrophobic coatings applied on the surface of aircrafts. The first section introduces the hazards of aircraft icing and the underlying formation mechanisms of ice on the surface of aircrafts. Although some current anti-icing and de-icing strategies have been confirmed to be effective, they consume higher energy and lead to some fatigue damages to the substrate materials. Considering the icing process, the functional coatings similar to lotus leaf with extreme water repellency and unusual self-cleaning properties have been proposed and are expected to reduce the relied degree on traditional de-icing approaches and even to replace them in near future. The following sections mainly discuss the current research progress on the wetting theories of superhydrophobicity and main methods to prepare superhydrophobic coatings. Furthermore, based on the bouncing capacity of impact droplets, the dynamic water repellency of superhydrophobic coatings is discussed as the third evaluated parameter. It is crucial to anti-icing applications because it describes the ability of droplets to rapidly bounce off before freezing. Subsequently, current studies on the application of anti-icing superhydrophobic coatings including the anti-icing mechanisms and application status are introduced in detail. Finally, some limitations and issues related to the anti-icing applications are proposed to provide a future outlook on investigations of the superhydrophobic anti-icing coatings.
103 citations
TL;DR: In this article, methods to improve the dispersion of graphene and dispersion mechanisms that have been developed in recent years are reviewed, and the advantages and disadvantages of various methods are compared and analyzed.
Abstract: Graphene, as a reinforcement for composite materials, has become a focus recently. However, the dispersion of graphene in composite materials is a problem that has been difficult to solve for a long time, which makes it difficult to produce and use graphene-reinforced composites on a large scale. Herein, methods to improve the dispersion of graphene and dispersion mechanisms that have been developed in recent years are reviewed, and the advantages and disadvantages of various methods are compared and analyzed. On this basis, the dispersion methods and mechanisms of graphene are prospected, which lays the foundation for graphene application and preparation.
98 citations
TL;DR: In this paper, the latest achievements in the field of copper oxide thin film gas sensors are presented and discussed, and several methods and deposition techniques are shown with their advantages and disadvantages for commercial applications.
Abstract: In this work, the latest achievements in the field of copper oxide thin film gas sensors are presented and discussed. Several methods and deposition techniques are shown with their advantages and disadvantages for commercial applications. Recently, CuO thin film gas sensors have been studied to detect various compounds, such as: nitrogen oxides, carbon oxides, hydrogen sulfide, ammonia, as well as several volatile organic compounds in many different applications, e.g., agriculture. The CuO thin film gas sensors exhibited high 3-S parameters (sensitivity, selectivity, and stability). Furthermore, the possibility to function at room temperature with long-term stability was proven as well, which makes this material very attractive in gas-sensing applications, including exhaled breath analysis.
90 citations
TL;DR: A review of the latest advances in the field of plasma-assisted deposition of ion-substituted hydroxyapatite thin films, highlighting the state of the art, the limitations, potentialities, open challenges, and the future scenarios for their application is presented in this article.
Abstract: Plasma sprayed coatings composed of stoichiometric hydroxyapatite have been extensively used to improve integration of metallic implants in the host bone, as hydroxyapatite (HA) is normally regarded as similar to the mineralized phase of bone. However, these coatings exhibited several drawbacks that limited their success. On the one hand biological apatite is a carbonated-HA, containing significant amounts of foreign ions, having low crystallinity and a small crystals size. This means that it differs from stoichiometric HA in terms of composition, stoichiometry, crystallinity degree, crystal size/morphology and, as a direct consequence, solubility, and ions release in the peri-implant environment. On the other hand, thick plasma sprayed coatings can undergo cracking and delamination and are scarcely uniform. For these reasons, research is pushing into two directions: (i) Increasing the similarity of apatite coatings to real bone, and (ii) exploring deposition by alternative plasma assisted techniques, allowing to achieve thin films, and having superior adhesion and a better control over the coating composition. In this article, we review the latest advances in the field of plasma-assisted deposition of ion-substituted hydroxyapatite thin films, highlighting the state of the art, the limitations, potentialities, open challenges, and the future scenarios for their application.
82 citations
TL;DR: In this paper, two different types of paperboard produced from primary and secondary cellulosic fibers were coated using renewable materials, such as alginate and chitosan, and comprehensive barrier measurements showed multifunctional barrier properties of these two biomaterials.
Abstract: Paper-based food packaging materials are widely used, renewable, and biodegradable. Because of its porous structure, paper has poor or no barrier performance against grease, water vapor, water, and volatile organic compounds. Moreover, recycled paperboard can be a source of organic residuals that are able to migrate into packed food. Two different types of paperboard produced from primary and secondary cellulosic fibers were coated using renewable materials, such as alginate and chitosan, and comprehensive barrier measurements showed multifunctional barrier properties of these two biomaterials. Both paper substrates were successfully coated using a draw-down coater, and the measured air permeability of the coated samples was 0 mL·min−1. Grease resistance was improved, while it was possible to reduce water vapor transmission, the migration of mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons (MOSH/MOAH), and the permeation of volatile compounds for both paper substrates when compared with uncoated substrates. Wettability and water absorptiveness of chitosan- and alginate-coated papers were found to be substrate-dependent properties, and could be significantly affected by bio-based coatings. In summary, industrially produced paperboard was upgraded by coating it with the naturally biodegradable biopolymers, alginate and chitosan, thus achieving extraordinary barrier performance for various applications within the packaging industry.
70 citations
TL;DR: In this paper, a bionanocomposite based on chitosan reinforced with sodium montmorillonite (MMT) and incorporated with ginger essential oil (GEO) was used to extend shelf life of perishable food.
Abstract: Active packaging incorporated with natural extracts is a promising technology to extend shelf life of perishable food. Therefore, this study aimed to produce a bionanocomposite based on chitosan reinforced with sodium montmorillonite (MMT) and incorporated with ginger essential oil (GEO). In vitro activity was assessed through migration assay and antimicrobial study against foodborne bacteria. Phenolic compounds were diffused within 48 h of contact, and retained some of their antioxidant activity. Films demonstrated antimicrobial activity against both Gram-positive and -negative bacteria tested. The effect on the shelf life of fresh poultry meat was determined on samples wrapped in the biopolymers and stored under refrigeration for 15 days, through physicochemical and microbiological analyses. Compared to unwrapped poultry meat, samples wrapped in the bionanocomposites showed a reduction in microorganisms count of 1.2–2.6 log CFU/g, maintained color and pH values and thiobarbituric acid reactive substances (TBARS) index increased at a lower rate, extending fresh poultry meat shelf life. The incorporation of GEO enhanced the biopolymer activity, by reducing lipid oxidation and microbiological growth of the poultry meat. In contrast, reinforcement with MMT imprisoned the active compounds in the polymeric chain, hindering its activity. In conclusion, the bionanocomposites tested represent promising substitutes to commercial and unsustainable plastic films.
TL;DR: In this paper, the effect of principal deposition parameters, including deposition pressure, temperature, Cr-target voltage, and Ar/O2 ratio, on both the structure and mechanical properties of chromium oxide coatings was investigated.
Abstract: Appropriate conditions for depositing hard Cr2O3 coatings by reactive sputtering techniques have yet to be defined. To fill this gap, the effect of principal deposition parameters, including deposition pressure, temperature, Cr-target voltage, and Ar/O2 ratio, on both the structure and mechanical properties of chromium oxide coatings was investigated. A relationship between processing, structure, and the mechanical properties of chromium oxide coatings was established. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the morphology, structure, and chemical compositions of the coatings that were prepared. An optical profilometer was employed to measure both the roughness and thickness of the coatings. The hardness and Young’s modulus of the coatings both as-deposited and after annealing conditions were measured by nanoindentation. The results showed that depositing hard Cr2O3 coatings is a highly critical task, requiring special deposition conditions. Cr2O3 coatings with a high hardness of approximately 25 GPa could be achieved at room temperature, at a low pressure of 1.6 × 10−1 Pa, where Cr-target voltage and oxygen content were 260 V and between 15–25 vol % of total gas, respectively. A dense stoichiometric Cr2O3 structure was found to be responsible for the high chromium oxide coating hardness observed.
TL;DR: In this article, a review focusing mostly on the decorative and wearable applications, and aiming to create a bridge between the past knowledge and the future direction that electrodeposition is taking, is presented.
Abstract: Electroplating processes are widely employed in industrial environments for a large variety of metallic coatings, ranging from technological to decorative applications. Even if the galvanic electrodeposition is certainly a mature technology, new concepts, novel applications, environmental legislation and the new material requirements for next-generation devices make the scientific research in this field still very active. This review focuses mostly at the decorative and wearable applications, and aims to create a bridge between the past knowledge and the future direction that this process, i.e., electrodeposition, is taking. Both the theoretical fundamentals as well as some of the most widespread practical applications—limited to metallic and alloy coatings—are explored. As an integral part of the industrial process, we take a look at the main techniques thought which the quality control of deposits and surfaces is carried out. Finally, global industrial performance and research directions towards sustainable solutions are highlighted.
TL;DR: What the authors need to do to achieve the goal of running a majority of cars on renewable solar energy, after clarification of the difference to conventional photovoltaic technology is listed.
Abstract: A car-roof photovoltaic has enormous potential to change our society With this technology, 70% of a car can run on the solar energy collected by the solar panel on its roof Unfortunately, it is not a simple extension of conventional photovoltaic technology This paper lists what we need to do to achieve the goal of running a majority of cars on renewable solar energy, after clarification of the difference to conventional photovoltaic technology In addition to technological development, standardization will be important and this list was made highlighting standardization
TL;DR: In this paper, the authors investigated the shiny thin film with a metallic tactile covering of nanoparticles over the surface of a rotating disk and found that the film thickness process highly depends on the process of evaporation, which takes some time to settle on the disk surface.
Abstract: The current effort is devoted to investigate the shiny thin film with a metallic tactile covering of nanoparticles over the surface of a rotating disk. To decorate, glowing silver and gold particles were chosen. Four illustrative base liquids, namely (i) ethanol, (ii) methanol, (iii) ethylene-glycol, and (iv) water were considered with different geometries, which have great importance in industrial usage. An emphasis on comparative multi nanofluid analysis was used to make a sound judgment on which one of the fluids best suited the metallic glittering process of spin coating. The film thickness process highly depends on the process of evaporation, which takes some time to settle on the disk’s surface. It was found that of the base fluids, the best choices were ethanol alloys with silver. Hence, one can conclude that from an experimental point of view, if silver alloy is used for coating, then only those liquids can be considered that exhibit ethanol-like properties. The impact of pertinent parameters with different aspects are graphically illustrated in each case.
TL;DR: In this paper, a discussion of current trends and challenges in cellulose aerogel research for thermal insulation are presented, gathered from studies reported within the last five years, and a brief description of cellulose/silica aerogels.
Abstract: Cellulose-based aerogels hold the potential to become a cost-effective bio-based solution for thermal insulation in buildings. Low thermal conductivities (<0.025 W·m−1·K−1) are achieved through a decrease in gaseous phase contribution, exploiting the Knudsen effect. However, several challenges need to be overcome: production energy demand and cost, moisture sensitivity, flammability, and thermal stability. Herein, a description and discussion of current trends and challenges in cellulose aerogel research for thermal insulation are presented, gathered from studies reported within the last five years. The text is divided into three main sections: (i) an overview of thermal performance of cellulose aerogels, (ii) an identification of challenges and possible solutions for cellulose aerogel thermal insulation, and (iii) a brief description of cellulose/silica aerogels.
TL;DR: In this paper, the authors analyzed the behavior of thin films of Reiner-Philippoff fluid in the changeable heat transmission and radiation over a time-dependent stretching sheet in 2D.
Abstract: The current investigation is carried out on the thin film flow of Reiner-Philippoff fluid of boundary-layer type. We have analyzed the flow of thin films of Reiner-Philippoff fluid in the changeable heat transmission and radiation over a time-dependent stretching sheet in 2D. The time-dependent governing equations of Reiner-Philippoff fluid model are simplified with the help of transformation of similarity variables. To investigate the behavior of the Reiner-Philippoff fluid with variable stretching surface for different physical effects, we considered thermophoresis and Brownian motion parameters in the flow. The Homotopy Analysis Method is implemented in the reduced model to achieve a solution of the original problem. A numerical convergence of the implemented method is also analyzed. The behavior of temperature, velocity, and concentration profiles have been investigated with the variation of skin friction, Nusselt number, and Sherwood number. A comparative graphical survey is presented for the velocity gradient, under different parameters. An analytical analysis is presented for the time-dependent parameter over thin film flow. The results we obtained are better than the previously available results. For the survey, the physical representation of the embedded parameters, like, β depends on the stretching parameter ζ , and the Reiner-Philippoff fluid parameter ϵ are discussed in detail and plotted graphically. Prandtl number P r , Brownian motion parameter N b , thermophoretic number N t , and Schmidt number S c are presented by graphs and discussed in detail.
TL;DR: In this paper, a flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor by a low-temperature combustion synthesis (LCS) method using nitric acid (HNO3), urea (CO(NH2)2), boric acid(H3BO3), and glucose (C6H12O6·H2O) as starting materials.
Abstract: Flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor. The precursor was prepared by a low-temperature (350 °C) combustion synthesis (LCS) method using nitric acid (HNO3), urea (CO(NH2)2), boric acid (H3BO3), and glucose (C6H12O6·H2O) as starting materials. The precursor consists of B2O3 and amorphous carbon and the morphology is composed of blocks with average diameters of about 10 μm by statistical methods using SEM at different fields. Then BN was synthesized at 900 °C in NH3 at a heating rate of 5 °C min−1. The as-prepared BN possesses a flake morphology and high specific surface area up to 936 m2 g−1. It also has high density structural defects and abundant –NH2/–OH groups. The surface groups improve its water wettability and electronegativity, which contributes to the rapid and selective adsorption performance, especially towards the cationic dyes. When 4 mg of the sample was added into a 100 mL RhB solution with an initial concentration of 5 mg L−1, 95% of the RhB was removed within 1 min and the adsorption capacity is 125 mg g−1. Importantly, the sample can be regenerated by heating at 400 °C in air.
TL;DR: In this paper, a general classification for thin-film thermoelectric materials varied by material compositions, and temperature properties depended on different measurement technique, with the hope that they can inspire further development of novel thermoe-lectric applications and hold unique promise for future electronics and miniature accessories.
Abstract: Thermoelectric technology has the ability to convert heat directly into electricity and vice versa With the rapid growth of portable and wearable electronics and miniature devices, the self-powered and maintenance of free thermoelectric energy harvester is highly desired as a potential power supply Thin film thermoelectric materials are lightweight, mechanically flexible, and they can be synthesized from abundant resources and processed with a low-cost procedure, which offers the potential to develop the novel thermoelectric devices and hold unique promise for future electronics and miniature accessories Here, a general classification for thin film thermoelectric materials varied by material compositions, and thermoelectric properties depended on different measurement technique Several new flexible thermoelectric strategies are summarized with the hope that they can inspire further development of novel thermoelectric applications
TL;DR: In this paper, nine different surface modifications of cellulose nanofibrils (CNF) with 3-aminopropyl triethoxysilane (ATS) by using three different solvent systems (water, ethanol, and a mixture of both) were investigated.
Abstract: Nine different surface modifications of cellulose nanofibrils (CNF) with 3-aminopropyl triethoxysilane (ATS) by using three different solvent systems (water, ethanol, and a mixture of both) were investigated. The effect of reaction conditions, such as silane to cellulose ratio and solvent type were evaluated to determine their contribution to the extent of the silane modification. Nanofibril properties were evaluated by infrared spectroscopy, powder X-ray diffraction, surface free energy, thermogravimetry, 13C and 29Si nuclear magnetic resonance, and electronic microscopy. The influence of the solvent in the solvolysis of the silane was reflected in the presence or absence of ethoxy groups in the silane. On the other hand, whereas the surface modification was increased directly proportionally to silane ratio on the reaction, the aggregation of nanofibrils was also increased, which can play a negative role in certain applications. The increment of silane modification also had substantial repercussions on the crystallinity of the nanofibrils by the addition of amorphous components to the crystalline unit; moreover, silane surface modifications enhanced the hydrophobic character of the nanofibrils.
TL;DR: In this paper, a review on the mechanism of the thermal growth method and different synthesis methods, where epitaxial growth, chemical vapor deposition, plasma-enhanced chemical vapor, and combustion are discussed in detail based on this mechanism.
Abstract: A common belief proposed by Peierls and Landau that two-dimensional material cannot exist freely in a three-dimensional world has been proved false when graphene was first synthesized in 2004. Graphene, which is the base structure of other carbon materials, has drawn much attention of scholars and researchers due to its extraordinary electrical, mechanical and thermal properties. Moreover, methods for its synthesis have developed greatly in recent years. This review focuses on the mechanism of the thermal growth method and the different synthesis methods, where epitaxial growth, chemical vapor deposition, plasma-enhanced chemical vapor deposition and combustion are discussed in detail based on this mechanism. Meanwhile, to improve the quality and control the number of graphene layers, the latest research progress in optimizing growth parameters and developmental technologies has been summarized. The strategies for synthesizing high-quality and large-scale graphene are proposed and an outlook on the future synthesis direction is also provided.
TL;DR: The chemistry involved in some conversion coatings processing has been known for over 100 years as mentioned in this paper, however, recent advances in chemical processing, changes in the components used for vehicle body structures, environmental considerations and costs have prompted the automobile industry to embrace new conversion coating technologies.
Abstract: Automotive conversion coatings consist of layers of materials that are chemically applied to the body structures of vehicles before painting to improve corrosion protection and paint adhesion. These coatings are a consequence of surface-based chemical reactions and are sandwiched between paint layers and the base metal; the chemical reactions involved distinctly classify conversion coatings from other coating technologies. Although the tri-cationic conversion coating bath chemistry that was developed around the end of the 20th century remains persistent, environmental, health, and cost issues favor a new generation of greener methods and materials such as zirconium. Environmental forces driving lightweight material selection during automobile body design are possibly more influential for transitioning to zirconium than the concerns regarding the body coating process. The chemistry involved in some conversion coatings processing has been known for over 100 years. However, recent advances in chemical processing, changes in the components used for vehicle body structures, environmental considerations and costs have prompted the automobile industry to embrace new conversion coatings technologies. These are discussed herein along with a historical perspective that has led to the use of current conversion coatings technologies. In addition, future directions for automobile body conversion coatings are discussed that may affect conversion coatings in the age of multi-material body structures.
TL;DR: In this paper, the antifriction properties of polyurethane (PU)/graphene (Gr) composite coatings were evaluated using a tribometer with a ball-on-disc mode at room temperature.
Abstract: This work contributes to the development and characterization of the corrosion resistance and antifriction properties of high performance polyurethane (PU)/graphene (Gr) composite coating. In this study, PU composite coatings containing 0, 2, 4 and 8 wt.% of Gr were prepared and evaluated using various corrosion and mechanical tests, namely electrochemical impedance spectroscopy, salt spray tests, cross-cut tape tests and dynamic mechanical analysis. Antifriction properties of the coatings were evaluated using a tribometer with a ball-on-disc mode at room temperature. The corrosion resistance and adhesion property of the PU coatings were found to be enhanced by adding 4 and 8 wt.% of Gr. The coefficient of friction revealed that the antifriction properties of the PU/Gr composite coatings were 61% lower than those of the conventional coating when the Gr content was increased to 8 wt.%.
TL;DR: In this paper, a review of the most successful ZnO thin-film based synthesis methods with both framework and textural porosities is presented, mainly focused on photocatalytic degradation of dyes, gas sensor fabrication and photoanodes for dye-sensitized solar cells.
Abstract: Zinc oxide (ZnO) thin films have been widely investigated due to their multifunctional properties, i.e., catalytic, semiconducting and optical. They have found practical use in a wide number of application fields. However, the presence of a compact micro/nanostructure has often limited the resulting material properties. Moreover, with the advent of low-dimensional ZnO nanostructures featuring unique physical and chemical properties, the interest in studying ZnO thin films diminished more and more. Therefore, the possibility to combine at the same time the advantages of thin-film based synthesis technologies together with a high surface area and a porous structure might represent a powerful solution to prepare ZnO thin films with unprecedented physical and chemical characteristics that may find use in novel application fields. Within this scope, this review offers an overview on the most successful synthesis methods that are able to produce ZnO thin films with both framework and textural porosities. Moreover, we discuss the related applications, mainly focused on photocatalytic degradation of dyes, gas sensor fabrication and photoanodes for dye-sensitized solar cells.
TL;DR: In this paper, the authors proposed the design and fabrication of flexible thin-film thermoelectric generators at a low manufacturing cost using a combination of electrodeposition and transfer processes.
Abstract: To reduce consumption for ambient assisted living (AAL) applications, we propose the design and fabrication of flexible thin-film thermoelectric generators at a low manufacturing cost. The generators were fabricated using a combination of electrodeposition and transfer processes. N-type Bi2Te3 films and p-type Sb2Te3 films were formed on a stainless-steel substrate employing potentiostatic electrodeposition using a nitric acid-based bath, followed by a transfer process. Three types of flexible thin-film thermoelectric generators were fabricated. The open circuit voltage (Voc) and maximum output power (Pmax) were measured by applying a temperature difference between the ends of the generator. The thin-film generators obtained using thermoplastic sheets with epoxy resin exhibited a Voc that was tens of millivolts. In particular, the contact resistance of the thin-film generator decreased when silver paste was inserted at the junctions between the n- and p-type films. The most flexible thin-film generator fabricated in this study exhibited a Pmax of 10.4 nW at a temperature difference of 60 K. The current performance of the generators was too low, but we innovated a combination process to prepare them. It is expected to increase the performance by further decreasing the micro-cracks and contact resistance in the generators.
TL;DR: In this article, the authors investigated the effectiveness of antimicrobial films and coatings applied to fresh fish and found that they inhibit the microbial growth and decrease the rate of fish nutrients degradation, thus preventing the formation of chemical metabolites.
Abstract: Fresh fish is extensively consumed and is one of the most-traded food commodities in the world. Conventional preservation technologies include vacuum and modified atmosphere packaging, but they are costly since requires capital investment. In the last decade, research has been directed towards the development of antimicrobial packaging systems, as an economical alternative to these. This paper outlines antimicrobial films and coatings applied so far on fresh fish, their efficacy against targeted microorganism/group and effects on chemical quality of the product. Findings show that edible films/coatings incorporated with different active agents applied to fresh fish are able to inhibit the microbial growth and decrease the rate of fish nutrients degradation, thus preventing the formation of chemical metabolites; a shelf-life extension of 6 to 13 days was obtained for fish fillets, depending on the species on which the active packaging materials were applied. The manufacturing use of these formulations could lead to a significant reduction in fish waste, consequently, a diminution of economic losses for fish traders and retailers. Therefore, their industrial production and commercialization could be an exploitable sector by the packaging industry.
TL;DR: In this paper, a series of polydimethylsiloxane-modified polyurethane coatings were synthesized with various PDMS contents, using the solvent-free method.
Abstract: Polydimethylsiloxane (PDMS) could be used to improve the antifouling properties of the fouling release coatings based on polyurethane (PU). A series of polydimethylsiloxane-modified polyurethane coatings were synthesized with various PDMS contents, using the solvent-free method. The effects of PDMS content and seawater immersion on the chain structure and surface morphology were investigated by confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Based on the measurements of contact angles of deionized water and diiodomethane, surface free energies of the coatings were estimated according to the Owens two-liquid method. The PDMS-modified polyurethane exhibited lower surface free energy and a lower glass transition temperature than polyurethane. The presence of PDMS increased the degree of microphase separation, and enhanced the water resistance of the coatings. The optimum amount of PDMS reduced the elastic modulus and increased the ductility of the coating. The presence of PDMS benefited the removal of weakly attached organisms. Panel tests in the Yellow Sea demonstrated the antifouling activity of the PDMS-modified polyurethane.
TL;DR: In this article, a review discusses recent developments in the mechanical durability of super-hydrophobic coatings primarily used for anti-corrosion, and the testing procedures used for the measurement of corrosion and mechanical durability are presented.
Abstract: Engineered superhydrophobic coating for anti-corrosion applications is a subject of great significance at present. However, the use of superhydrophobic coatings for anti-corrosion applications is hindered by the mechanical durability in many cases. There is a need for an understanding not only of how to fabricate such surfaces, but also of the corrosion resistance and mechanical durability of those coatings. This review discusses recent developments in the mechanical durability of superhydrophobic coatings primarily used for anti-corrosion. First, superhydrophobicity is introduced with an emphasis on different wetting models. After that, this review classifies the nanofabrication methods based on the material and methods of surface functionalization. Furthermore, the testing procedures used for the measurement of corrosion and mechanical durability are presented. Finally, the mechanical durability and anti-corrosion performance of the developed superhydrophobic coatings are discussed.
TL;DR: In this paper, the porosity, microhardness and fracture toughness of the conventional, multimodal and nanostructured WC-12Co coatings with different WC sizes and distributions were measured.
Abstract: Conventional, multimodal and nanostructured WC-12Co coatings with different WC sizes and distributions were prepared by high velocity oxy-fuel spray (HVOF). The micrographs and structures of the coatings were analyzed by scanning electron microscope (SEM), X-ray diffractometer (XRD) et al. The porosity, microhardness and fracture toughness of the WC-Co coatings were measured. The coating resistance to cavitation erosion (CE) was investigated by ultrasonic vibration cavitation equipment and the cavitation mechanisms were explored. Results show that there is serious WC decarburization in nanostructured and multimodal WC-Co coatings with the formation of W2C and W phases. The nanostructured WC-Co coating has the densest microstructure with lowest porosity compared to the other two WC-Co coatings, as well as the highest fracture toughness among the three coatings. It was also discovered that the nanostructured WC-Co coating exhibits the best CE resistance and that the CE rate is approximately one-third in comparison with conventional coating.
TL;DR: In this paper, a 125mm-diameter eight-tohed end mill, with a mechanical fastening of ceramic inserts, was used as a cutting tool for milling hardened steel (102Cr6), and the effect of smoothing the microroughness and surface defects in comparison with uncoated inserts, which are characteristic of the abrasive processing of ceramics, was investigated.
Abstract: The main problem with ceramics used in cutting tools is related to the unpredictable failures caused by the brittle fracturing of ceramic inserts, which is critical for the intermittent milling of cyclic loading. A 125-mm-diameter eight-toothed end mill, with a mechanical fastening of ceramic inserts, was used as a cutting tool for milling hardened steel (102Cr6). For the experiments, square inserts of the Al2O3 + SiC ceramic were used and compared with the samples made of Al2O3 + TiC to confirm the obtained results. The samples were coated with diamond-like coating (DLC), TiZrN, and TiCrAlN coatings, and their bending strength and adhesion were investigated. Investigations into the friction coefficient of the samples and operational tests were also carried out. The effect of smoothing the microroughness and surface defects in comparison with uncoated inserts, which are characteristic of the abrasive processing of ceramics, was investigated and analyzed. The process developed by the authors of the coating process allows for the cleaning and activation of the surface of ceramic inserts using high-energy gas atoms. The impact of these particles on the cutting edge of the insert ensures its sharpening and reduces the radius of curvature of its cutting edges.