INTL. SYMP. ON COMPOSITE, CERAMIC AND NANO MATERIALS PROCESSING, CHARACTERIZATION AND APPLICATIONS

Aiming at the realization of improved corrosion resistance against local corrosion damages, zinc hybrid coatings are obtained and characterized. They are electrodeposited on low carbon steel substrates, and contain embedded polymeric core-shell nanocontainers (NCs) with corrosion inhibitor benzotriazole (BTA). Rod-like hematite cores are coated by alternate adsorption of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylic acid) (PAA) using layer-by-layer assembly technique. Benzotriazole is entrapped in NCs in an assembly step, and the NCs are incorporated into the metal coating matrix via electrodeposition process [1-3].
The protective characteristics of the hybrid coatings in a model medium of 5% NaCl solution are analyzed by means of potentiodynamic polarization curves (PDP), polarization resistance (Rp) measurements, and electrochemical impedance spectroscopy (EIS) for definite periods of time. XPS method is applied to type the newly appeared products after corrosion treatment, and XRD investigations present the structural peculiarities of the hybrid coatings. The latter demonstrate enhanced corrosion resistance in neutral corrosion medium compared to ordinary zinc coatings.

Thus far, solar cells are the main component for efficiently converting energy from the sun to electricity. To generate light from electric energy to the optical energy, LEDs are the main devices. The light reflection of the optical interface in these two devices is the main barrier to enhance the efficiency of the devices.
In this study, we demonstrate a cost-effective method of depositing anti-reflection coatings on glass [1], GaAs [2], sapphire [3] and GaN wafers [4]. The anti-reflection layers are formed by monolayer of microspheres. The deposition is realized by dip coating method. For GaN LEDs, the microspheres can enhance the external efficiency (the output coupling of the light). The microspheres deposited on sapphire before the crystal growth can ameliorate the crystal quality of the GaN to improve the electric property of the GaN LED. The coating is also used on the glass to enhance the transmission of the light at the interface in the OLEDs. The microspheres deposited on GaAs-based solar cell can enhance the transmission of the light into the materials to improve the efficiency.
We demonstrate theoretically and experimentally the concept and the devices using the monolayer of the microspheres. We have developed a novel technique to deposit the monolayer of microspheres on any flat wafers without the limit of the wafer size. We will show the monolayers of microspheres on 2-inch sapphire wafer and 4-inch silicon wafer.

Environments that contain volcanic ashes can lead to serious damage of static and rotating elements of the jet engine. The mechanism standing behind the issue are complex, and concern not only erosion processes but also chemical interactions in elevated temperature reaching up to 1500°C [1]. Volcanic ash melts inside the engine, and in such a form hits the surface of the blade/vane. Nowadays, the most commonly used thermal and environmental barrier coatings (TBC/EBC) for turbine blades is yttrium stabilized zirconia dioxide (YSZ) [2,3]. It is a part of a whole coating consisting of two interacting layers, namely bond coat and top coat. The main role of the bond coat is to provide proper adhesion to sustain all the other surface parameters responsible for the efficiency of the whole blade. As the YSZ is characterized by proper thermal properties, it does not provide sufficient chemical resistance to the volcanic ash environment [3,4]. Thus, the research presented in the paper aims to develop a technology for manufacturing a coating that would be resistant to not only erosion, but also to chemical meaning in complex environments. This paper presents a step-by-step technology of EB-PVD, thermal, and plasma spraying processes leading to the manufacture of environmental barrier coatings based on YSZ and gadolinium zirconate (GZO). The coating obtained in the research were analysed by means of optical and electron microscopy, which allows a full description of their structure.

Nowadays humidity sensors are used in every industry, such as in food, pharmaceuticals [1], medicine, [2] and agriculture [3, 4]. These commercial humidity sensors are quite expensive, complicated in operation, and have low sensitivity and stability because of the materials used as a sensing element [5]. It is difficult to maintain their operational cost, power losses, sensitivity and stability [4]. Therefore, it is essential for a sensor to have high sensitivity and stability, low cost, small hysteresis, wide linear range, simple operation, short response, and short recovery time [5, 6]. Electrical conduction is affected significantly by dipoles of water molecules, which makes it important for researchers to investigate the magnitude of change in impedance and capacitance of the samples with respect to varying relative humidity. The investigation becomes more important for composite materials due to the contribution of properties by two or more ingredients. Changing the constituting ratio of the ingredients in the composites results in modification of properties in composite materials. The choice of compatible ingredients is also important to fabricate stable samples so as to overcome the degradation processes [7].
The present work demonstrates a humidity sensor based on a composite of polythieno [3,4-b]-thiophene-co-benzodithiophene (PTB7) and [6,6]-phenyl-C-butyric-acid methyl ester (PCBM). The capacitive type humidity sensor is fabricated using simple cost effective spin coating approach in the Al/ PTB7:PCBM/Al surface type geometry with different ratios of PTB7: PCBM i.e., 1:0, 1.5:1, 1:1, 1:1.5 and 0:1 respectively. The sensing behavior of the prepared devices has been observed at ~1V of AC operational bias over a wide range of relative humidity i.e. 20-95 % RH. The sensors are also examined at different frequencies i.e., 100 Hz, 1 kHz, 10 kHz and 100 kHz. The optimum frequency and volumetric ratio are selected as 100 Hz and 1.5:1 (PTB7:PCBM). The sensor shows better sensitivity of 1.325 nF/%RH with negligible hysteresis. The composite sensor indicates remarkable improvement in the sensing behavior as compared to single material based sensors. These properties make it a potential candidate for the state-of-the-art sensor applications.

Catalysts based on the Vanadia-Titania system are widely used for the abatement of pollutants, particularly nitrogen oxides (NOx) in the exhaust gases of industrial plants. Their mechanism of operation is based on the catalytic reduction reaction of nitrogen oxides with ammonia (SCR). In this paper, two commercial catalysts based on the V-W-Ti system of very similar nominal compositions were compared. The two samples were analyzed in the fresh state and after a period of operation in a waste-gas plant of a waste-to-energy plant. The materials were first characterized from the chemical-structural point of view through instrumental techniques such as X-ray fluorescence (XRF), X-ray diffractometry (XRD), IR spectroscopy (FT-IR), SEM scanning electron microscopy observations with analysis EDS, measurement of pore size and specific surface area through nitrogen adsorption / desorption and BET technique. Subsequently, the catalytic properties of the new and used catalysts in the NH3-SCR reaction were evaluated. The results of the analyzes showed that the samples are both made of a titanium matrix in the form of anatase, reinforced with glass fibers, used as a support for the active phases based on V and W. The percentages of vanadium are practically the same for both systems, while the tungsten percentage is very different. The specific surface also has very similar values for the two fresh catalysts. The tests of catalytic activity, on the other hand, have given very different results; in particular, the performance of one of the two catalysts decays much faster than the other. The kinetic measurements show that the decay is not due to a specific surface decrease, due to the presence of precipitates, but due to a difference in initial activity between the two catalysts, linked to the different tungsten content.

Effects of Ifon clay, various additives, and sintering temperature on the phase development and physico-mechanical properties of mullite-carbon ceramic composite were investigated. Powders of Ifon clay, kaolin from Okpella, and graphite of known mineralogical composition were thoroughly blended in a ball mill for 3 hours at a speed of 60 rev/min using a predetermined ratio. From the blended powders, standard samples were produced by uniaxial compression. This was followed by sintering in an electric furnace at 1400°C, 1500°C and 1600°C for one hour. The sintered samples were characterized for various physical and mechanical properties. The phases developed in the sample during sintering were also investigated using X-ray diffractometer (XRD). Morphology and microanalysis of the sintered ceramic composite samples were determined using ultrahigh resolution field emission scanning electron microscope (UHR-FESEM) equipped with energy dispersive spectroscopy (EDS). It was observed that the Ifon clay addition to the sample favours the formation of microcline over mullite at temperatures between 1400°C and 1500°C in sample A. As the sintering temperature increases to 1600°C, there is the formation of mullite phase and pores in sample A [1]. For sample B, 10% SiC served as nucleating point for SiC around 1400°C [2, 3]. 10% TiO₂ led to the development of 2.5% TiC at 1500°C which increased to 6.8% at 1600°C. Ifon clay in the sample led to the development of anorthite and microcline in the samples. 10% TiO₂ is effective as anti-oxidant for graphite up to 1500°C in sample C [3]. For sample D, the addition of TiO₂ and SiC in the sample led to the formation of TiC in the sample at 1400°C and 1600°C. This takes place through high temperature solid state reaction (reaction sintering) of TiO₂ and SiC. This also contributes to the reduction in the apparent porosity of the sample with increased sintering temperature [4, 5]. The presence of titania in the sample does not favour the stability of anorthite beyond 1400°C. The formation of 50.6 % mullite in the sample at 1500°C gave it the highest cold crushing strength and absorbed energy. The sample D sintered at 1500°C is considered optimal.

AISI H13 is an excellent hot work tool steel commonly used for manufacturing dies. These dies are subjected to working conditions with continuous cyclic thermo-mechanical loading, which results into surface failure of dies. So in order to enhance the service life of the die, surface hardening by electron beam is proposed. In this paper, effect of electron beam scanning speed on the hardening case depth of an AISI H13 sample was studied. Microstructure of EB hardened layer has been characterized by optical microscope. The tribological performance of hardening was investigated by pin on disk wear testing. It is found that effective case depth increases with decrease in the scanning speed.

Simple (LaMnO₃ and LaCoO₃) and complex hybrid perovskites (LaCo_xMn_1-xO₃) were synthesized, and their catalytic functionality and thermal/chemical durability were investigated in a comparative manner. Structural properties as well as catalytic behavior of these hybrid perovskite structures were examined comprehensively, using a multitude of in-situ and ex-situ characterization techniques such as XRD, BET, TEM-EDX, STEM, ICP-MS, TPR, and ex-situ and in-situ XANES, and were compared to that of LaMnO₃ and LaCoO₃ benchmark systems. Adsorption and desorption properties of NOx species examined by in-situ FTIR and TPD revealed a superior NOx storage capacity (NSC) and thermal stability for LaCo_0.7Mn_0.3O₃ and LaCo_0.8Mn_0.2O₃ hybrid perovskites as compared to that of LaMnO₃ and LaCoO₃.TPR and in-situ XANES results suggested that Mn addition enhances thermal stability by suppressing the sintering of Co at high temperatures and enhances NOx storage by increasing the number of NOx adsorption sites. Ex-situ XANES and XPS results suggested that Mn addition alters the oxidation state of Mn and Co via Mn³⁺+ Co³⁺ -> Mn⁴⁺ +Co²⁺ leading to a stoichiometrically defective but functionally enhanced structure. Hybrid perovskites were also found to facilitate N-O bond activation. NOx TPD results point out that treatment with H₂(g) further enhances the NSC of hybrid perovskites due to the formation of oxygen vacancies and OH^- radicals. These results suggest that B-site cations of perovskites play a crucial role both in catalytic activity and stability. Current findings reveal valuable molecular-level insights regarding the origins of the fine-tunable redox/catalytic behavior of mixed perovskite systems, which could be applicable to a large variety of catalytic systems to enhance catalytic activity, structural durability, and selectivity.

The use of fluorescence in many chemical applications often requires extrinsic fluorophores, especially when intrinsic fluorescence of the molecule of interest is weak or in a spectral region that is prone to interference in the matrix. Introducing extrinsic fluorophores in the molecule of interest may require chemistry that utilizes a reagent that is less environmentally friendly or may require significant amounts of the fluorescent dyes. This is especially true if a fluorophore is used to authenticate the origin of industrial products, such as hydrocarbons, paints, etc. This is due to the fact that the fluorescence intensity of a single molecular label or reporting group can be relatively weak, requiring a larger amount of chemicals per unit product. Frequently the product itself may cause quenching of the fluorophore. All these concerns may be alleviated by encapsulating fluorophores in silica nanoparticles. Silica nanoparticles are biologically and environmentally friendly and can be designed for many applications. Covalently copolymerized dyes in silica nanoparticles are free from leaching; even non-covalently encapsulated dyes are often virtually free of leaching. The outside of the silica nanoparticles can be designed to mach the product chemistry, and can be hydrophobic or hydrophilic or anything between. The encapsulated dye can serve as a simple reporting label or as a sophisticated molecular probe. Due to the large number of dye molecules that can be encapsulated in a single silica nanoparticle, the number of labels are very small, requiring minimal amount of chemicals. Silica nanoparticle synthesis is conducive for the introduction of covalently copolymerized fluorescent dyes by using modified TEOS reactive analogues that are inexpensive and widely available. The outside layer of the silica nanoparticle surface that can be modified by regrowth technique can also serve as chemical reagent or sensor. This study reports how copolymerized silica nanoparticles can be made using a wide array of fluorophores and how its surface properties were modified by adding hydrophobic or hydrophilic molecules to achieve compatibility. Surface hydrophobicity controlled fluorescent silica nanoparticles are excellent candidates for many applications, including sensitive analytical detections. Copolymerization of multiple dyes or other molecules will also be discussed to achieve large Stokes' shift using fluorescence energy transfer.

This paper will discuss in detail the adequate microstructural structures for magnetic recording. The maximum coercivity is obtained for single domain size particles [1], also known as Stoner-Wohlfarth particles. It was found that the squareness of hysteresis is improved with texture optimization, which is relevant as good squareness of hysteresis is an important issue for the magnetic recording industry. Detailed overviews on the texture effects of Stoner-Wohlfarth particles, as well as the effects of particle interaction, are given and discussed in detail. Additionally, modifications of the Stoner-Wohlfarth model, and the Callen-Liu-Cullen [2] model are analyzed. The spring effect observed in hysteresis curves of isotropic nanocrystalline materials can be explained with the Stoner-Wohlfarth model. Theories for magnetostic coupling between particles are also reviewed.

In general, the optical properties of nano-dispersive structures are very different from the properties of the bulk materials, and depend on the following structural parameters: the occupancy of the volume of the ultrafine medium with nanoparticles (q); the size and shape of the particles (f); the order of the particles; and the properties of the medium and surrounding nanoparticles (λ₀) [1,2]. This was predictable because these structures contain from some atoms to thousands of atoms and take a middle place between atoms and massive substances, and subsequently, they have properties different from both of them. In the present paper, using the discontinuous Ni films as examples, we consider theoretically and experimentally the influence of the structural parameters on the optical properties of the ultrafine structures. In this work, the optical properties of nano-dispersive structures are represented within the theoretical Maxwell-Garnett model [3,4]. The behavior of the optical spectra of thin Ni films was explained in the framework of the effective medium approximation in two cases: q<0.5 and 0.5< q<1. In this approach, an effective refractive index (n-ik) of the nano-dispersive structures can be calculated as a function of the λ₀, q, and particle shapes. These calculations proved a good agreement between the experimental results and the theoretical calculations.

The work presents the results of studies on the manufacture of multilayered ceramic shell molds the drying processes, including the selection of the proper slurries. The molds are intended for precision casting, especially in the aircraft industry [1-2]. The investigations included the selection of the optimum technological parameters of the casting slurries suitable for the first (inner) and structural layers of the mold, so that the entire surfaces of the wax mold models were covered uniformly with the successive layers (the first layer and seven structural layers) of specified thickness and porosity. The porosity of the layer was investigated by using computed X-ray tomography. By using a profilometer, surface roughness of the wax models and first ceramics layers were examined. Based on the conducted tests, it was found that the use of a thermal imaging camera enables precise determination of the drying time of the layers of ceramic shell molds.

Precision investment casting is one of the longest known superalloys forming techniques. Nowadays, it is primarily used to manufacture precision castings with high surface quality. It is widely utilized in the aircraft industry for jet engines turbine blades production. Fabrication of multilayer ceramic casting mold is a complicated and time consuming process, which is also burdened with high risk of failure due to the their cracking during wax pattern melting process [1,2]. This work presents studies concerning applicability of a thermo-visual camera in ceramic shells molds cooling process. Moreover, ceramic materials and slurries have been investigated. There were slurries prepared for near-model (first layer) and construction layers of a shell mold. Using the pre-prepared slurries, the ceramic near-model (first layer) and construction layers were made on a wax pattern. Cooling was tested with the thermo-visual camera in the 300Ai-40Ai°C temperature range.

This article presents research results on modern ceramic materials used for the manufacturing of critical elements in aircraft engine hot zones, by using investment casting technology. Investment casting using multi-layered ceramic moulds is commonly used in the production of aircraft components. This technology allows precise reproduction of geometrically complex spatial shapes. The quality requirements that the final product must meet, which are extremely and increasingly rigorous, necessitate a permanent solution for technologically complex problems related to castings defects that are dependent on the ceramic mould's technological quality. Prevention of casting defects is accomplished by optimizing the parameters of the metallurgical process, and by improving structural and technological construction of the mould. On the other hand, to limit the defects coming from the mould's technological quality, one should correctly select technical and auxiliary materials for constructing self-supporting ceramic moulds and the parameters of the manufacturing process.

This article reviews current primary analysis on twin boundaries defect at nano-regime. We emphasis essentially on studies that intent to understand, through modelling, experiments, or both, the origin and effects of twinning at elementary level. We foresee that, by imparting an extensive viewpoint on the happening progress in twinning, this analysis will pitch in the juncture for designing or tracing new metallic and semiconductor materials with modified alter properties like thermoelectric¹, mechanical², optical^3,4, ferroelectric and magnetic⁵ etc. Since it is nearly unworkable to slog with defect free or impurity free materials, it is vital to comprehend how defects and impurities modify the properties of the materials. To be specific, it is more necessary to differentiate between distinct types of impurities (defects) and decide if their existence is favourable or not, so that we can use it as per our requirement and can be used in different application by enhancing various properties of the material. We have analysed these issues and provided an updated overview of the current characterization tools able to identify and detect defects in different forms of materials, and also made an overview on the possible applications

At least almost half of the electric energy of the world is consumed by electric motors.Thus, there is big pressure on increasing the efficiency of electric motors, and rigorous specifications such as IE4 - (Super Premium Efficiency) are now requested by the European Union [1].
Electric vehicles need machines with very high efficiency, and this can be achieved with improved materials. For example, axial flux machines may use amorphous or nanocrystalline soft magnetic materials, and wind turbines can be improved with better magnetic materials. Off-shore wind turbines need to be without gearbox (i.e. direct drive) in order to reduce maintenance problems. Rare-earth magnets are necessary for direct drive wind turbines. Moreover, the correct choice of the magnetic materials can lead to significant weight reduction of the turbines, and thus the turbines can be built taller. Tall wind turbines are necessary because strong and constant winds are found at heights of about 150 meters or more. The proper choice of materials is essential for better motors and generators, which will ultimately reduce the energy consumption in the entire world. In this study, different possibilities of magnetic materials are discussed and compared.

Africa is facing a serious crisis, due to serious environmental degradation arising from the economic exploitation of its forests. A possible mitigating measure would be the development and provision of alternative cheap structural materials to replace timber.
A good cheap alternative material is plant fibre reinforced polymer composite. Use of rice husk fiber reinforced polymer composite minimizes environmental pollution due to characteristic biodegradability [1]. Engineering materials fail when loaded beyond their elastic limit by fracture or plastic deformation. Structures made from healable materials have significantly prolonged service life [2]. A rice husk fibre reinforced polypropylene composite will undergo failure that involves crack initiation, propagation, and complete fracture [3]. Rice husk fibre reinforced polypropylene composite forms a chemical or frictional bond, whose strength largely depends on strength of the interface [4].
In this research, rice husk fibres were prepared by hammer milling, heated to reduce moisture content and surface modification done to increase wettability by the matrix. Polypropylene wastes were shredded and used as matrix [5]. Composite test pieces were produced by film stacking technique and by injection moulding. Respective standards were applied during destructive testing and mechanical properties were compared with existing published results. The resulting strengths were: Tensile 85 MPa, bending 56 MPa, Compressive 178 MPa, impact 61 J/mm² and hardness BHN 480. These results gave mechanical performance sufficient to conclude that the reinforced composite material could be used to replace timber and save forests which are depleting.
The fractured test pieces were repaired / healed and then retested for respective mechanical properties. Percentage recovered strengths from tensile, impact and compressive strength tests were 81, 98.36 and 95 respectively. It could be concluded that repaired rice husk fibre reinforced polypropylene composites could be reused for their original specific structural functions thus further minimizing need for forest products for similar applications.

Nowadays, many industrial sectors, and among them transport, are intended to improve both mechanical and chemical properties of surfaces to increase their durability, such as thermochemical broadcast treatments; surface treatments by wet - chemical - electrochemical - plasma routes; inorganic, organic, and hybrid coatings, etc. Whether as support for the development and for the optimization of surface treatment in accordance with regulations (ex: REACH), or as a means of control and audit materials and failures, the electron spectroscopies show a real interest for R&D activity. It is thus now that the XPS and Auger spectroscopies, only dedicated to fundamental academic research in past decades, are making a remarkable contribution in the innovation of new processes for improvement of surfaces and facilitating their transfer to industry.
As part of (electro)chemical surface treatment of metal alloys, from the initial preparation of the substrate up to its protection by a thin coating, varied and complementary examples will come to account for the extraordinary potential of the electron spectroscopies. Spectral signature, whether from surface or in depth, or from chemical mapping survey (Figure 1), will have as many opportunities to identify phenomena at interfaces or to reveal unexpected behaviors. Different industrial issues will be reviewed, such as adhesion of rubber to steel in reinforcement material in belted radial tires, and eco-friendly anti-corrosion coatings for aircraft aluminum alloys.

At this stage of industry development, composite nanostructure materials are widely used. Among them, materials containing carbides and borides of metals TiB₂ / TiC and ZrB₂ / ZrC are especially notable.
In this presented work, the task is to perform a complete thermodynamics analysis — FTA (Full thermodynamics analysis) [1] on the process of receiving carbides and boride of the titanium and zirconium (Ti-B-O-C, Zr-B-O-C), and on the basis of this analysis of experimental studies of nano-structured composite materials.
The innovation of the work is studying the physical and chemical bases of high-temperature processes of receiving carbides and borides of the specified systems, that will give the chance of carrying out the minimum quantity of experiments.
FTA of the Ti-B-O-C system in vacuum for the following structures is carried out: 2TiO₂+B₂O₃+8C=TiB₂+TiC+7CO (1); 2ZrO₂+B₂O₃+8C=ZrB₂+ZrC+7СО (2).
On the basis of this analysis, experimental research is carried out on receiving composite materials TiB₂ / TiC and ZrB₂ / ZrC. X-ray diffraction patterns of the obtained powders indicate that in general, mixes TiB₂/TiC and ZrB₂/ZrC result.

We discuss the structural and thermoelectric properties of the layered compounds K_xRhO₂ [1] in comparison to isostructural and isovalent Na_xCoO₂. The optimized structure of K_1/2RhO₂ exhibits a remarkable deviation of the c/a ratio from the experimental result as well as from c/a ratios of related compounds. This indicates that a hydrated phase of K_xRhO₂ exists and the experimental structure determination refers to this hydrated phase. The calculated Seebeck coefficient of pristine K_1/2RhO₂ amounts to 50*10^-6 V/K at 300 K, which is close to the experimental value of 40*10^-6 V/K. More importantly, we observe high values for the Seebeck coefficient and power factor for hydrated K_xRhO₂ in the whole temperature range from 0 to 700 K. At 100 K we find for hydrated K_7/8RhO₂ a value of Z = 3*10^-3 K^-1, which is the highest power factor observed at this temperature. It exceeds also the exceptionally high value of Na_0.88CoO₂ by more than 50%. Our results, hence, demonstrate that hydration is an effective approach to modify the lattice parameters and, as a result, enhance the thermoelectric performance. The Na_xRhO₂ oxides [2] are found to form a new class of materials with exciting thermoelectric features, even outperforming the 2H phases of the K_xRhO₂ system. In the latter the optimal thermoelectric performance is achieved at low temperature, whereas the modified stacking of the atomic layers in the 3R phases of Na_xRhO₂ results in a reduced interlayer coupling and, in turn, in a dramatically enhanced thermoelectric response in the technologically relevant high temperature range. We find that Na vacancies in Na_xRhO₂ avoid clustering and that the RhO₆ octahedra are modified depending on the amount of Na deficiency. Analysis of the induced changes in the density of states close to the Fermi level indicates that the Rh^3+d d_3z2-r2 states control the transport properties of the compounds. A substantial figure of merit of 0.35 at 580 K is found in hydrated Na_0.83RhO₂ due to the enhanced effective mass of the charge carriers. In general, the figure of merit can be further increased by reduction of the Na vacancy concentration to increase the resistivity.

Corrosion of engineering alloys and its mitigation measures cost any developed economy ~4% of their GDP (i.e., ~$8b annually to Australia and ~$250b to USA). Traditional measures such as development of corrosion-resistant alloys and conventional coatings have not always provided durable corrosion resistance, particularly in highly demanding situations. Thus, a novel and disruptive approach is immensely commercially attractive. This presentation will discuss graphene coating as a disruptive approach to durable corrosion resistance [1-2], chronological evolution of the field, and success in circumventing the related challenges.
The presenter's group demonstrated that just 1-2 atomic layers of graphene coating can improve corrosion resistance of copper (Cu) by two orders of magnitude in an aggressive chloride solution (similar to seawater) [2]. However, the improvement in corrosion resistance of Cu due to graphene coating vary remarkably in different studies, i.e., from >2 orders of magnitude [2], to only 10 times [3] to little improvement [4]. In fact, a few subsequent studies [5,6] have categorically demonstrated graphene coated Cu to show remarkably inferior long-term oxidation resistance to bare Cu. The presenter's recent investigations [7,8] have provided mechanistic understanding of such variabilities. The group also had considerable success in circumventing the factors/challenges that contributed to the development of deleterious defects in graphene film that trigger accelerated corrosion (instead of protection) as reported in other studies [5,6]. The graphene developed the most recent studies [7,8] have been demonstrated to provided durable corrosion resistance to nickel [7] (see Figure 1) and copper [8]. However, developing graphene on most common engineering alloys (e.g., mild steel) by CVD poses a few fundamental scientific challenges that this presentation will discuss.