Graphene for Antimicrobial and Coating Application

Graphene is a versatile compound with several outstanding properties, providing a combination of impressive surface area, high strength, thermal and electrical properties, with a wide array of functionalization possibilities. This review aims to present an introduction of graphene and presents a comprehensive up-to-date review of graphene as an antimicrobial and coating application in medicine and dentistry. Available articles on graphene for biomedical applications were reviewed from January 1957 to August 2020) using MEDLINE/PubMed, Web of Science, and ScienceDirect. The selected articles were included in this study. Extensive research on graphene in several fields exists. However, the available literature on graphene-based coatings in dentistry and medical implant technology is limited. Graphene exhibits high biocompatibility, corrosion prevention, antimicrobial properties to prevent the colonization of bacteria. Graphene coatings enhance adhesion of cells, osteogenic differentiation, and promote antibacterial activity to parts of titanium unaffected by the thermal treatment. Furthermore, the graphene layer can improve the surface properties of implants which can be used for biomedical applications. Hence, graphene and its derivatives may hold the key for the next revolution in dental and medical technology.

Bond Characteristics and Experimental Behavior of Textured Epoxy-coated Rebars Used in Concrete Bridge Decks

The deterioration of bridge decks is a problem typically associated with the corrosion of the reinforcing steel. This issue was partially controlled during the 1970s with the incorporation of the epoxy-coating protection system. However, research later demonstrated that the smooth surface resulting from the epoxy-coating application reduces most of the friction between the rebar and the surrounding concrete. Consequently, forces acting on the rib faces are reconfigured in such a way that the radial components increase, triggering the early development of cracks. To mitigate both the reduction of bonding and the formation of cracks, the Illinois Department of Transportation proposed a new type of coated bars: textured epoxy-coated (TEC) bars. Over the last few years, different projects have been executed to understand and improve the characteristics of TEC rebars. This report is a continuation of research performed at the University of Illinois Urbana-Champaign to evaluate the bond behavior of TEC bars. The experimental program starts by characterizing, qualitatively and quantitatively, the roughness of the TEC rebars. Next, their bond-slip interaction embedded in concrete is evaluated through pull-out tests. Finite element models of these tests are developed to validate the behavior observed as the textured reinforcement loses anchorage with concrete. Based on these results, the experimental program then aims to study the impact of the drying shrinkage, temperature change, and flexural demands on two large-scale bridge deck specimens reinforced, individually, with TEC and standard epoxy-coated bars. The results collected from both specimens using digital image correlation and strain gauges are compared to explore the differences exhibited by the traditional and the new type of reinforcement coatings in terms of stress distribution in bridge decks. Finally, given the specialized equipment and time-consuming procedure needed to calculate the roughness parameters of TEC bars, an empirical, weight-based approach is developed as a rapid method for assessing the rebars’ roughness on-site.

Effect of Resin Coating on Surface Roughness and Microhardness of High Viscous Glass Ionomer Cements

High viscous glass ionomer cement (HVGIC) was recently developed for atraumatic restorative treatment (ART). However, its moisture sensitivity remains a limitation thus protective coating application is recommended. This study investigated the effect of resin coating on the surface roughness and microhardness of two HVGICs (Riva Self Cure HVGIC [RV] and Equia® Forte Fil [EQ]) conditioned in food-simulating liquids (FSLs). Fifty standard disc-shaped samples were fabricated using customised stainless-steel mould (10 × 2 mm). Coating was applied on top surface of all samples and subsequently divided into five groups: air (control), distilled water, 0.02 N citric acid, heptane and 50% ethanol-water solution. The samples were conditioned in FSLs at 37°C for seven days. Subsequently, the surface roughness and microhardness of samples were measured using optical profilometry and microhardness tester, respectively. SEM analysis was done for qualitative observation of surface morphological changes. Data were analysed using one-way ANOVA, two-way ANOVA and posthoc Tukey’s test (α = 0.05). Interestingly, the results revealed that surface roughness was significantly influenced by FSLs immersion, presence of coating and the materials itself (p < 0.001). The lowest surface roughness was found on control coated samples: RV (50.98±4.25) nm and EQ (62.77±3.92) nm, while the highest values seen on uncoated surfaces in citric acid: RV (505.26±31.10) nm and EQ (350.33±15.36) nm. RV samples had the lowest microhardness of 54.97±2.48 Vickers hardness number (VHN) post-immersion in citric acid. In conclusion, with the exception of RV conditioned in heptane and ethanol, the uncoated HVGICs generally had higher surface roughness than the coated HVGICs. HVGICs conditioned in citric acid showed the most significant increase in surface roughness and reduction in microhardness.

A STUDY INTO THE COATING THICKNESS OF SHIP BALLAST TANKS

Ballast tanks are expected to be coated according to the IMO Performance Standard for Protective Coating regulations (PSPC15), in addition to the paint application requirements of the paint producer. In general, a coating system should consist of minimum two spray coats of light-colored epoxy coating on flat surfaces with a Nominal total Dry Film Thickness (NDFT) of 320 μm and 90% of all thickness measurements greater than, or equal to the NDFT and none of the remaining measurements below 0.9 x NDFT (the “90/10 rule”). Allegedly, the value of 320 μm in this PSPC15 rule may be misconstrued as a benchmark for coating application on flat surfaces, eventually leading to a non-PSPC15 compliance due to the resulting variation in coating thickness violating this 90/10 rule. This study indicates that over the years, the arithmetic mean in-situ DFT appears to be 498±18 μm and that too high and low thicknesses, below 288 μm and above 800 μm, were noted in the field. Analysis of a survey of ballast tank coating performance of ships indicates that too low thicknesses appear to be negatively impacting the average theoretical ballast tank performance. However, when an application mean DFT benchmark of 525 μm is used, the coating will almost surely comply to the 90/10 rule and the risk of falling below the 288 μm threshold is small, less than 2% in most cases. Consequently, using 320 μm as a mean DFT benchmark could result in a non-PSPC15 compliance with the in-situ ascertained coating thickness variation as this does not exclude coating thicknesses below 288 μm, which may then result in a significantly less than average theoretical coating performance. If the coating application is performed very evenly, the benchmark may be reduced to 429 μm with a probability of falling below 288 μm reduced to 0.1%. It should therefore be emphasized that the PSPC15 requirement is a coating system framework description, and that the requirement should be broadened to include a mean DFT as a coating applicator benchmark together with a clearly specified minimum and maximum DFT, in order to avoid any misinterpretations.

Blended PVA/PVP Electro spun nanofibers for Coating Application

The use of polymeric blended nanofibres is one of the recent applications in the food and liquid packaging. The current research aims to prepare the nanofibers coatings from the blend of polymeric materials via the electro spinning technique 0.08 weight ratio concentration of polyvinyl alcohol (PVA) dissolved in water, as well as, (0.2 weight ratio concentration ) of poly vinyl pyrrolidone (PVP) were used to obtain different volume proportions of (PVA:PVP) solutions include (100:0, 80:20,70:30, 50:50, 20:80, and 0:100). The electro spinning system was organized with pumping conditions (20 kV for the applied voltage, 20 cm pumping distance, 1ml/hr pumping rate) and a needle diameter with 0.4mm diameter. The properties of the polymeric solutions involve (viscosity, surface tension, and electrical conductivity of the liquid) were examined. A scanning electron microscope technique was used to study the surface properties of the prepared films, and the contact angle via the contact angle analyzer was examined. The results of a scanning electron microscope proved that the diameter of the nano fibers increases with increasing the concentration and viscosity of solutions and decreasing its electrical conductivity. Also, the results of the contact angle analyzer showed an increase the hydrophilic property via increasing percentage of polyvinylpyrrolidone.

Review—(Mn,Co)3O4-Based Spinels for SOFC Interconnect Coating Application

With the reduction of solid oxide fuel cell (SOFC) operating temperature to the range of 600 − 800℃, Cr-containing ferritic alloys have become the preferred interconnect material, which unfortunately are susceptible to continuous scale growth and Cr volatility at the SOFC operating temperatures. The (Mn,Co)3O4 spinel system is widely regarded as the most effective coating for SOFC interconnect protection, due to its high thermal and electrical conductivity, adequate coefficient of thermal expansion, and excellent Cr blocking capability. This article reviews the physical and chemical properties of the (Mn,Co)3O4-based spinels; different types of coating precursors and deposition techniques; and the effects of spinel composition, quality and thickness on the coating performance. It is concluded that the spinel coating composition, quality, and thickness are more critical than the coating process in affecting the overall coating performance.

Influence of Thermocycling and Sealer Coating Application on Shore Hardness of Soft Denture Lining Material

BACKGROUND: One of the properties of the soft denture lining (SDL) material that needed to overcome the functional problems is softness. Loss of softness due to the aging process and to extend the duration of use, sealer coating was developed to maintain its softness. Sealer coating acts as mechanical barrier to provide protection against aging of SDL materials. AIM: This study aims to determine the influence of thermocycling and sealer coating application on the shore hardness of the acrylic-based and silicone-based auto-polymerizing soft denture lining materials. MATERIALS AND METHODS: Materials that were used in this study are acrylic-based auto-polymerizing SDL (Durabase Soft, Reliance Dental Manufacturing LLC, Illinois, USA) and silicone-based auto-polymerizing SDL (Mollosil, Detax GmbH, Ettlingen, Germany). In this study, we used monopoly as sealer coating for acrylic-based auto-polymerizing SDL and varnish for silicone-based auto-polymerizing SDL. Thermocycling was performed for 2000 cycles for a 2-year simulation time. For shore hardness test, a total of 40 discs shaped samples were made with a diameter of 35 mm and a thickness of 6 mm. The samples were divided into eight groups (n = 5), namely, the uncoated and non-thermocycling acrylic-based auto-polymerizing SDL, the coated and non-thermocycling acrylic-based auto-polymerizing SDL, the uncoated and thermocycling acrylic-based auto-polymerizing SDL, the coated and thermocycling acrylic-based auto-polymerizing SDL, the uncoated and non-thermocycling silicone-based auto-polymerizing SDL, the coated and non-thermocycling silicone-based auto-polymerizing SDL, the uncoated and thermocycling silicone-based auto-polymerizing SDL, and the coated and thermocycling silicone-based auto-polymerizing SDL. The hardness test was carried out using the shore A durometer. RESULTS: The obtained data were tested using the independent t-test with a significance level of p < 0.05. The results showed that there was a significant effect between coated and uncoated acrylic-based SDL group that underwent thermocycling and in the silicone-based SDL group. The study showed that the hardness value was lower in both coated acrylic-based and silicone-based SDL groups compared to the non-coated group, so it can be concluded that the sealer coating is able to protect the hardness of SDL material against aging with a thermocycling simulation. The results also showed that there was a significant effect of thermocycling on the hardness of the material both in the coated acrylic-based SDL group, the uncoated acrylic-based SDL group, and the uncoated silicone-based SDL group. Study also showed that there was no significant effect of thermocycling in the coated silicone-based SDL group. CONCLUSION: Based on the results, it can be concluded that the use of sealer coating can maintain the hardness properties of both acrylic-based SDL and silicon-based self-polymerizing SDL so that it can increase the durability of SDL materials. However, the effect of sealer coating in protecting the hardness of SDL materials against aging was more evident in the silicone-based SDL group.

Hydrogen Production in Methane Decomposition Reactor Using Solar Thermal Energy

This study investigates the decomposition of methane using solar thermal energy as a heat source. Instead of the direct thermal decomposition of the methane at a temperature of 1200 °C or higher, a catalyst coated with carbon black on a metal foam was used to lower the temperature and activation energy required for the reaction, and to increase the yield. To supply solar heat during the reaction, a reactor suitable for a solar concentrating system was developed. In this process, a direct heating type reactor with quartz was initially applied, and a number of problems were identified. An indirect heating type reactor with an insulated cavity and a rotating part was subsequently developed, followed by a thermal barrier coating application. Methane decomposition experiments were conducted in a 40 kW solar furnace at the Korea Institute of Energy Research. Conversion rates of 96.7% and 82.6% were achieved when the methane flow rate was 20 L/min and 40 L/min, respectively.