Energy Dispersive X-ray Diffraction Measurements Research Articles

Facile synthesis and optimization of graphene oxide reduction by annealing in hydrazine vapour in ambient air for potential application in perovskite solar cells

Graphene oxide (GO) was synthesized from graphite via a modified Hummer's method, followed by thermal and chemical reductions to produce reduced graphene oxide (RGO) samples at various temperatures. A suite of characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), UV-Visible Spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Hall effect measurements were employed to assess the structural, morphological, optical, and electrical properties of the samples. FTIR analysis confirmed the successful functionalization of graphite to GO and subsequent reduction to reduced graphene oxide, with peak intensities decreasing as the reduction temperature increased. UV-visible spectroscopy of GO showed a maximum absorption at 235 nm which confirmed the synthesis of GO while the reduction revealed a notable red shift in absorption peaks with increasing annealing temperature, and that signified a reduction in bandgap. XRD analyses demonstrated the removal of oxygen functional groups. The X-ray diffraction (XRD) analysis of GO showed diffraction at 2θ = 10.74° which revealed a fully oxidized graphene oxide with oxygen-containing functional groups, and hence an increase in interlayer spacing (d002) from 3.341 Å (graphite) to 8.228 Å (GO). Upon reduction, there is a gradual decrease in d002 from 8.228 Å (GO) to 3.387 Å (HRGO300), suggesting the gradual removal of intercalated oxygen molecules, and hence the gradual restoration of sp2 hybridisation in graphene. The EDS analysis revealed an increase in the carbon-to-oxygen (C/O) ratio from 1.78 in GO to 2.75 in HRGO300 as the annealing temperature for the reduction process increased which further confirmed the removal of oxygen functional groups. The Hall effect data showed hole mobility of 4.634 x101 (GO), 4.831 x101 (HRGO200), and 5.462 x100 (HRGO300) with conductivities of 8.985 x10-5 (GO), 1.087 x100 (HRGO200) and 1.791 x101 1/Ω cm, suggesting an increase in conductivity as the annealing temperature increased as revealed in the EDS. Out of the three samples identified as hole transport materials, the sample HRGO300 with the highest C/O ratio of 2.75 has the highest conductivity, and hence most suitable for application as hole transport material in perovskite solar cell.

Microstructural Investigations of Weld Deposits from Manganese Austenitic Alloy on X2CrNiMoN22-5-3 Duplex Stainless Steel

Duplex stainless steels are materials with high performance under mechanical stress and stress corrosion in chloride ion environments. Despite being used in many new applications such as components for offshore drilling platforms as well as in the chemical and petrochemical industry, the automotive industry, etc., they face issues of wear and hardness that limit current applications and prevent the creation of new use opportunities. To address these shortcomings, it is proposed to develop a hardfacing process by a special welding technique using a universal TIG source adapted for manual welding with a pulsed current, and a manganese austenitic alloy electrode as filler material. The opportunity to deposit layers of manganese austenitic steel through welding creates advantages related to the possibility of achieving high mechanical characteristics of this steel exclusively in the working area of the part, while the substrate material will not undergo significant changes in chemical composition. As a result of the high strain hardening rate, assisted mainly by mechanical twinning, manganese austenitic alloys having a face-centered cubic crystal lattice (f.c.c) and low stacking fault energy (SFE = 20–40 mJ/m2) at room temperature, exhibit high wear resistance and exceptional toughness. Following cold deformation, the hardness of the deposited metal increases to 465 HV5–490 HV5. The microstructural characteristics were investigated through optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Vickers hardness measurements (HV). The obtained results highlighted the feasibility of forming hard coatings on duplex stainless steel substrates.

Novel bulk triaxial residual stress mapping in an additive manufactured bridge sample by coupling energy dispersive X-ray diffraction and contour method measurements

A novel approach for determining triaxial residual stress states by coupling energy dispersive X-ray diffraction and contour method measurements is provided and validated in a Ti‐5Al‐5V‐5Mo‐3Cr additive manufactured (AM) bridge sample. Synchrotron X-ray diffraction (SXRD) can provide relatively fine spatial resolution (on the order of 10–100 µm) for mapping 3D elastic strain fields within a sample. However, for samples with dimensions larger than one or two centimeters the path length can get prohibitive as both constant wavelength and energy dispersive SXRD are based upon transmission measurements. As an example, for a plate-like sample geometry where the thickness is limited (less than a centimeter) it is trivial to measure the longitudinal and height direction elastic strain components with excellent in-plane spatial resolution (∼100 µm) and a somewhat lower through-thickness resolution (10–15 times larger) but obtaining the through thickness component is often not possible as the beam path must be parallel to one of the large dimensions of the plate. While small samples of low Z-number alloys (e.g., Ti or Al) allow determination of the three elastic strain components, this is often not the case for higher Z alloys (e.g., Fe or Ni) or large samples where some strain components can be indeterminable. To overcome these limitations, this work applies a combination of synchrotron X-ray diffraction and the contour method (a mechanical relaxation technique), to determine the triaxial stress state. This novel combination is demonstrated and validated in a relatively small additive manufactured sample where all three orthogonal strain components are accessible via X-ray diffraction for stress determination. The paper also explores methods for determining the strain-free lattice parameter, typically obtained from a small stress-free reference sample. This work shows that a small size AM sample is not stress free, producing unreliable magnitudes of strain and stress. Instead, a strain-free lattice parameter is determined using residual stress equilibrium conditions, which gives consistent strain and stress trends for both X-ray diffraction (alone) and the new diffraction-contour coupling technique. This demonstrates that the coupling technique can be confidently applied to samples to determine stress when path length (size or Z-number) prohibit determination of three orthogonal strain components via diffraction.

Towards Energy Dense Rechargeable Batteries Utilizing Zn and Cu

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.1 However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with Zn in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Alternatively, compensating for capacity loss with additional Cu metal provided for very high areal capacities (∼40 mA h/cm2) and energy densities (∼260 W h/L), despite only 65% active material cathode loadings and ∼10% Zn anode utilization; however, preliminary tests indicated these batteries were prone to shorting.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where ~ 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can affect the battery cycling mechanism and may have future roles increasing performance.Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, and ion selective polymers in enabling reversible Zn/Cu based batteries. In addition, the general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be discussed.A near-term goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While the laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.N. Schorr et al. ACS Applied Energy Mater. 2021, 4, 7, 7073–7082. https://doi.org/10.1021/acsaem.1c01133.D. J. Arnot et al. J. Power Sources 2022, 529, 231168. https://doi.org/10.1016/j.jpowsour.2022.231168.

Fabrication of superhydrophobic aluminum with enhanced anticorrosive property

The current work mainly introduces a facile method to obtain superhydrophobic aluminum with a hierarchical micro-nanostructure by a combination strategy of anodizing, chemical etching, and surface modification using SiO2@PDMS coating via a simple chemical vapor deposition (CVD) method. Scanning electron microscopy (SEM), energy dispersive X-ray (EDS), EDS-mapping, X-ray diffraction (XRD) and water contact angle (WCA) measurements have been performed to characterize the surface morphology, chemical composition, phase structure, and wetting property of the surfaces, respectively. The SEM results showed that by anodizing a network of cylindrical nanoporous is formed. By etching, the diameter of these pores increases and surface modification using CVD causes the deposition of SiO2@PDMS nanoparticles over them. The WCA measurements showed that the samples of the anodized and anodized-etched aluminum after modifying with SiO2@PDMS nanoparticles become superhydrophobic with values of 153° and 154°, respectively. The corrosion resistance of samples was analyzed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The results displayed that the charge transfer resistance of the superhydrophobic surface of modified anodized-etched aluminum is 16700 kΩ cm2, which is 900 times higher than that of pure aluminum. Also, the positive shift of 0.385 V in corrosion potential and reduction of more than 3 orders of magnitude in corrosion current are observed compared with aluminum. All results show a significant improvement in the corrosion protection of Al due to anodizing and surface modification with superhydrophobic coating. This method is suggested as a simple technique to creating aluminum with superhydrophobic surfaces in industry.

Tunable optical and semiconducting properties of eco-friendly-prepared reduced graphene oxide.

Wide bandgap oxidized graphenes have garnered particular interest among the materials explored for these applications because of their exceptional semiconducting and optical properties. This study aims to investigate the tunability of the related properties in reduced graphene oxide (rGO) for potential use in energy conversion, storage, and optoelectronic devices. To accomplish this, we scrutinized crucial parameters of the synthesis process such as reduction time and temperature. Our findings demonstrate that controlling these parameters makes it possible to customize the optical bandgap of reduced graphene oxide within a range of roughly 2.2eV-1.6eV. Additionally, we observed that reduced graphene oxide has strong and superior absorption in the visible region, which is attributable to the existence of OFGs and defects. Notably, our results indicate that the absorption coefficients of reduced graphene oxide are up to almost three times higher (7426mlmg-1 m-1) than those observed in dispersions of exfoliated graphene and graphene oxide (GO). To complement our findings, we employed several spectroscopic and morphological characterizations, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrical measurements. The implications of our results are significant for the development and design of future semiconductors for energy conversion and optoelectronic applications.

Progress Towards the Development and Understanding of Energy Dense Rechargeable Batteries Utilizing Zn and Cu

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with Zn in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Alternatively, compensating for capacity loss with additional Cu metal provided for very high areal capacities (∼40 mA h/cm2) and energy densities (∼260 W h/L), despite only 65% active material cathode loadings and ∼10% Zn anode utilization; preliminary tests indicated these batteries were prone to shorting.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where ~ 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can affect the battery cycling mechanism and may have future roles increasing performance. Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, and ion selective polymers in enabling reversible Zn/Cu based batteries. In addition, the general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be discussed.The goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While the laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.N. B. Schorr et al. Rechargeable Alkaline Zinc/Copper Oxide Batteries. ACS Applied Energy Mater. 2021, 4, 7, 7073–7082. https://doi.org/10.1021/acsaem.1c01133.D. J. Arnot et al. Rechargeable Alkaline Zn-Cu Batteries Enabled by Carbon Coated Cu/Bi Particles. J. Power Sources 2022, 529, 231168. https://doi.org/10.1016/j.jpowsour.2022.231168.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Laser cleaning process of high-pressure turbine blade: Characterization and removal of surface contaminants

Laser cleaning has been introduced as an effective method for removing contaminants from the surface of a turbine blade. In this investigation, a continuous wave fiber laser with a power density of 7.96 × 106 W/cm2, a wavelength of 1064 nm, and a focusing distance of 305 mm under an argon gas was applied. The used laser removed CaO-MgO-Al2O3-SiO2 (CMAS) as contaminants from the Y2O3-stabilized ZrO2 layer of a thermal barrier coating (TBC) on a high-pressure turbine blade made of a nickel-based superalloy substrate. At first, the characterization of the CMAS and TBC properties, such as thickness, roughness, and morphology, as well as phase identifications were performed. CMAS on the high-pressure turbine blade (HPTB) surface had a mixture of granular and plate structures. The major imperfections of the surface of the out-of-service HPTB were infiltration of CMAS into the TBC, chemical interaction between CMAS and the TBC, transverse cracks, delamination of the TBC, structural changes of the TBC, separation of YSZ from TGO, and deformation of the TBC on the pressure side and the leading edge of HPTB. The main aim of this work was to remove non-infiltrated CMAS from the TBC coating through the laser cleaning process. Then, various parameters of the laser cleaning process such as power and scanning speed were investigated. After that, various analyses of laser-cleaned samples such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), optical microscopy (OM), X-ray diffraction (XRD), thickness test, and roughness measurement were accomplished for the optimum parameters of the laser cleaning process. Finally, the mechanism involved in the laser cleaning process to remove the contamination was presented in detail. The results demonstrated that the optimum parameters of the laser cleaning process to completely eliminate targeted contaminants were a power density of 7.16 × 106 W/cm2, a scanning speed of 0.01 mm/s, and a focusing distance of 305 mm under an argon gas atmosphere.

Delta ferrite formation and evolution during slab processing from an 80-ton industrial heat of AISI 304 austenitic stainless steel

Although delta ferrite is a very common phase in most austenitic stainless steels, studies about its formation and evolution during slab processing from industrial heats of tens of tons are scarce. The main objective of this research is to study the evolution of delta ferrite (quantity, chemical composition, morphology, and distribution) along the production route from the cast slab to the coil of an industrial heat of 80 tons of 304 stainless steel. Samples were extracted after the following processing steps: continuous casting, first and second hot-rolling pass, and solution-heat-treating, arriving at the final commercial condition. Sample analyses were carried out with several complementary microstructural characterization techniques: optical microscopy, scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction, and magnetic measurements of delta ferrite content (feritscope). Thermocalc® indicates that the present continuous cast slab solidifes according to the FA (ferrite-austenite) mode and the final microstructure should be completely austenitic in equilibrium conditions. Nevertheless, delta ferrite is detected along the processing steps, indicating that the steel is out of phase equilibrium. The ferrite content measured after solidification varies significantly across the as-cast slab thickness. Lower values are detected on the surfaces, followed by a gradual increase when moving into the slab, reaching a peak, and finally decreasing at the slab center. This pattern of delta ferrite content is named “M type” distribution. The average content of delta ferrite decreases after each subsequent processing step, namely the two hot-rolling passes and the solution heat-treating.

Oxidation Behaviour of New Nickel-Base Superalloys with Varying Aluminium: Niobium Ratio

New Ni-base superalloys with higher temperature capability are required for future, more efficient gas turbine engines. In designing such alloys, careful consideration is required of the elemental concentrations to ensure that a suitable balance of mechanical properties and environmental resistance is obtained. In this study, the oxidation resistance of a series of new Ni-base superalloys with varying Al:Nb ratio has been assessed through long-term exposures in air at elevated temperature. The oxide scale was characterised using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and quantitative measurements of oxide scale dimensions. The alloys were found to form continuous chromia scales at 700 °C and outperformed several current commercial superalloys. However, following exposure at 800 °C, significant microstructural degradation was observed due to precipitation of the δ phase.

High temperature oxidation of SiC-coated Fe-Cr-Al-Mo alloys in muffle and concentrated solar furnaces

The maximal temperature of a solar receiver is limited by its resistance to oxidation, thermal cycling and mechanical stresses as it is a key component of solar power plant with a central tower. Currently used Ni-based alloys cannot heat the air coolant at temperatures beyond 1000 K due to the severe oxidation that may affect the surfaces exposed to air at high temperatures, affecting the solar absorptivity of the receiver. A SiC coating should protect a high temperature metallic alloy from oxidation and improve its solar absorptivity, only if the accommodation between the metallic substrate and the ceramic coating is optimized to prevent the coating from cracking and peeling due to the thermal expansion of the assemblage. To reduce the interfacial stresses, SiC was deposited using High Temperature Chemical Vapor Deposition on a pre-oxidized Fe-Cr-Al-Mo alloy, so that a 2µm-thick alumina layer could work as an accommodation layer. The oxidations performed in muffle and solar furnaces (associated to ex situ characterizations using scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping, X-ray diffraction, and room-temperature normal spectral emissivity measurements) have demonstrated that this multilayer structure could support long-term oxidation and thermal stresses up to1400 K without significant changes regarding the spectral emissivity, but the coating peels if the sample is treated at 1600 K. The multilayer structure can therefore work beyond the current working point of solar receivers, nevertheless the accommodation still has to be improved in case of accidental exposures to higher solar fluxes.

Modification of hydroxyapatite coating in the presence of adipic acid for Mg-based implant application

This study investigated the role of adipic acid (AA) in improving the anti-corrosion performance and in-vitro bioactivity of hydroxyapatite coating applied on AZ31 Mg alloy. Firstly, hydroxyapatite (HA) coating was applied on the AZ31 Mg alloy. In the next step, the optimized hydroxyapatite-based coating, modified with adipic acid by direct addition and post-treatment methods. Corrosion behavior of uncoated sample and different coated samples were studied by Electrochemical Impedance Spectroscopy (EIS) and Direct Current (DC) Polarization techniques. Surface characterization was examined by Field Emission Scanning Electron Microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD) and contact angle measurements. According to the contact angle results, all coated samples reveal high hydrophilic behavior. Additionally, the XRD analysis confirms the formation of hydroxyapatite crystals in all coated samples and the presence of the AA in HA + AA and HA − AA coatings does not change the crystal structure of the hydroxyapatite. Electrochemical studies display that the Rp value of HA coating is increased from 3630 Ω.cm2 to 10784 Ω.cm2 by the direct addition method also by the post-treatment method the polarization resistance reached 10294 Ω.cm2. In addition, an in-vitro bioactivity assessment was performed in a simulated body fluid (SBF). Based on FE-SEM studies, a protective layer of AA is formed on HA coating by the post-treatment method which improves the anti-corrosion behavior efficiently. The results showed that the adipic acid-modified hydroxyapatite coatings by direct addition and post-treating methods display better anti-corrosion properties and bioactivity compared to the optimal hydroxyapatite coating.

(Invited, Digital Presentation) The Discovery and Development of Rechargeable Zn/CuO Batteries

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.1 However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline zinc-based batteries are a strong candidate for electrical grid storage applications due to zinc’s high capacity (820 mAh/g), established materials supply chain and low cost.1 Alkaline-based cells are generally considered safe and do not have the temperature limitations of Li-ion or Pb-acid batteries, thereby removing the need for complicated thermal management control strategies and providing for simpler systems with lower integration costs. To realize the highest energy density batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. Historically Zn has been paired with MnO2 (616 mAh/g), CuO (674 mAh/g) and S (1675 mAh/g) cathodes to produce energy dense primary batteries. If reversibility can be proven for these conversion cathodes, they would be enticing candidates for grid storage systems.In this presentation, we will report on the development of electrochemically reversible conversion cathodes for alkaline Zn-batteries. Specifically, we will focus on copper oxide-based cathodes and their use in alkaline Zn/CuO batteries with application for large scale grid storage.2 Sandia has recently developed rechargeable alkaline Zn/CuO batteries with very high areal capacities of ~ 40 mAh/cm2 and energy densities of > 200 Wh/L. This is among the highest ever energy density reported for a laboratory scale alkaline Zn–based battery using a conversion cathode. In this example, the rechargeability is enabled by the addition of a bismuth (Bi2O3) additive that facilitates the electrochemical reversibility of Cu2O and Cu(OH)2 species. Data collected from a variety of techniques, including cyclic voltammetry (CV), rotating ring-disk electrode (RRDE) voltammetry, electrochemical impedance spectroscopy (EIS), electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and operando energy-dispersive X-ray diffraction measurements will be presented to elucidate the role of the additive in enabling reversibility in Zn/CuO batteries. In addition, the general challenges of achieving high-capacity Zn anodes and the pairing of two high-capacity conversion electrodes to form the battery, each which cycles through the formation of soluble “-ate” complexes [i.e., cuprate, Cu(OH)4 2- and zincate, Zn(OH)4 2-] will also be covered.The goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While these laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Electrical and microstructural evaluation of ZnO varistor ceramics with different CaSiO3 contents

In the present study, the impact of CaSiO3 addition on microstructure and electrical characteristics of a ZnO-based varistor system was investigated. The ceramic materials were prepared by solid-state reaction route by varying the CaSiO3 concentrations (0, 3, 6, 9, 12, and 15 wt%) and sintered at 1300 °C. Characterization of the pelletized samples was carried out by density measurement, scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and current density-electric field characteristics measurement. The growth of ZnO grain was restrained with the introduction of CaSiO3; the average grain size decreases from 18.09 to 10.85 μm, whereas their relative density increases up to 99.79%. Structural results indicated the existence of the CaSiO3-rich phase without any other secondary phase formation. It is also revealed that different CaSiO3 contents significantly affect the electrical properties, prominently in the sample with 12 wt% CaSiO3 addition. The maximal value of the nonlinear coefficient, breakdown voltage, and barrier height acquired in this work were 4.41, 0.80 V/mm, and 0.691 eV, respectively, along with a sharp decline in leakage current density to 373.93 μA/cm2. Further increase in CaSiO3 content (15 wt%) eventually caused a deterioration in varistor behavior.

Green synthesis of gold nanoparticles using Gracilaria crassa leaf extract and their ecotoxicological potential: Issues to be considered

The use of vegetal species for gold nanoparticles (AuNPs) biosynthesis can constitute an alternative to replacing the extensive use of several hazardous chemicals commonly used during NPs synthesis and, therefore, can reduce biological impacts induced by the release of these products into the natural environment. However, the “green nanoparticles” and/or “eco-friendly nanoparticles” label does not ensure that biosynthesized NPs are harmless to non-target organisms. Thus, we aimed to synthesize AuNPs from seaweed Gracilaria crassa aqueous extract through an eco-friendly, fast, one-pot synthetic route. The formation of spherical, stable, polycrystalline NPs with a diameter of 32.0 nm ± 4.0 nm (mean ±SEM) was demonstrated by UV–vis spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy, energy-dispersive X-ray and X-ray diffraction measurement, and Fourier-transform infrared spectroscopy analysis. In addition, different phytocomponents were identified in the biosynthesized AuNPs, using Gas Chromatography-Mass Spectrometry (GC-MS). However, both G. crassa aqueous extract and the biosynthesized AuNPs showed high ecotoxicity in Anopheles stephensi larvae exposed to different concentrations. Therefore, our study supports the potential of seaweed G. crassa as a raw material source for AuNPs biosynthesis while also shedding light on its ecotoxicological potential, which necessitates consideration of its risk to aquatic biota.

The effect of porosity on the mechanical properties of Ti–8Nb–8Zr–8Cu alloy

The present study investigated the mechanical performance of Ti–8Nb–8Zr–8Cu (at.-%) alloys containing different porosity levels. Metallographic examination and phase analysis of samples was performed by scanning electron microscope (SEM), optical microscopy (OM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) measurements. The mechanical properties were detected by uniaxial compression test, micro and macro hardness measurements. The wear behaviour was determined by a dry wear test on the bulk sample. The ultimate compressive strength decreased from 1077.30 to 344.65 MPa with 50% porosity and the modulus of elasticity from 15.6 to 9.5 GPa. These values show that it may be suitable for bone replacement considering the stress shield effect.

Anti-corrosion characteristics of FeCO3 and Fe Ca Mg CO3 scales on carbon steel in high-PT CO2 environments

• Anti-corrosion capabilities of FeCO 3 and Fe x Ca y Mg z CO 3 scales were compared. • FIB and µCT were applied to reveal the pore characteristics within the scales. • General corrosion rate is closely related to the available active surface areas. • FeCO 3 scales provide superior anti-corrosion protection than Fe x Ca y Mg z CO 3 scales. Corrosion products formed on carbon steel can be considered as naturally occurring anti-corrosion scales. However, relationships between porosity and anti-corrosion characteristics of such scales remain poorly understood. In this study, characterisation data derived from Focus ion beam (FIB) and X-ray micro-computed tomography (μCT) techniques, combined with image processing algorithms, were applied to reveal the porosity, pore connectivity and pore size distribution within FeCO 3 and Fe x Ca y Mg z CO 3 (where x + y + z = 1) scales on a X65 carbon steel substrate. The formation kinetics, chemistry and anti-corrosion capabilities of both scales were also systematically evaluated by Scanning electron microscopy (SEM) coupled with Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), profilometry and electrochemical measurements. The results demonstrate that FeCO 3 scales can reduce the availability of active surface areas more efficiently with their lower porosity on the steel surface, providing superior anti-corrosion performance than Fe x Ca y Mg z CO 3 scales. This study elucidates the effects of ubiquitous cations on the formation and relative protectiveness of corrosion product scales, as well as their effectiveness to protect against corrosion.

An ultrasensitive electrochemical sensing platform based on silver nanoparticle-anchored 3D reduced graphene oxide for rifampicin detection.

A facile strategy has been reported to anchor silver nanoparticles (Ag NPs) onto three-dimensional reduced graphene oxide (3D rGO) via a green and simple method. An accurate and reliable electrochemical sensing platform based on Ag NPs/3D rGO was designed for the ultrasensitive detection of rifampicin (RIF). The morphology and features of Ag NPs/3D rGO were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical measurements. The interface of the modified electrode presented effective electrical activity for the analysis of RIF due to the large electrochemically active surface area and excellent electron transport ability. The sensor exhibited a good linear relationship in the range of 0.01 nM-45 μM and a low detection limit of 0.810 nM (S/N = 3). Crucially, the fabricated Ag NPs/3D rGO sensor was successfully utilized to assess RIF in human blood, drug and aquatic product samples. This sensing platform exhibited outstanding electrochemical performance for RIF detection and showed great potential application in clinical diagnosis, pharmaceutical and food-related fields.

Solide State Diffusion Bonding of Al6061-SiC Nanocomposites

Aluminium matrix composites are both strong and lightweight, and are limited in their applications due to the proper choice of welding process. Conventional welding that is based on fusion at the welded joint is not suitable because it leads to the formation of certain defects at the welded joint. For this reason, solid-state welding such as diffusion bonding is one of the suitable joining methods, as there will be no melting of any of the constituents. The solid-state diffusion bonding at 520° C of Al6061-SiC nanocomposites was investigated. This composite material was made by powder metallurgy, where aluminium alloy Al6061 was selected as the base metal, and SiC nanoparticles with an average size of 50 nm were added as reinforced particles. The effects of bonding time on the microstructures and mechanical properties of the welded material were investigated. The main characterisation techniques were optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, x-ray diffraction, and microhardness measurements. We have found that increasing the holding time up to 3 h at 520° C strengthens the weldability of the two basic composite materials and increases their hardness. X-ray diffraction analysis did not reveal any new phase during diffusion welding; it is considered one of the advantages of using the solid-state diffusion welding technique for the assembly of this kind of composite material. The welding success of this composite material widens its field of use, such as the automotive or space industry, because it is a light material with high mechanical properties.

Evaluation of extremely steep residual stress gradients based on a combined approach using laboratory-scale equipment.

Surface treatments characterized by rapid heating and cooling (e.g. laser hardening) can induce very steep residual stress gradients in the direct vicinity of the area being treated. These gradients cannot be characterized with sufficient accuracy by means of the classical sin2Ψ approach applying angle-dispersive X-ray diffraction. This can be mainly attributed to limitations of the material removal method. In order to resolve residual stress gradients in these regions without affecting the residual stress equilibrium, another angle-dispersive approach, i.e. the universal plot method, can be used. A novel combination of the two approaches (sin2Ψ and universal plot) is introduced in the present work. Prevailing limits with respect to profiles as a function of depth can be overcome and, thus, high-resolution surface layer characterization is enabled. The data obtained are discussed comprehensively in comparison with results elaborated by energy-dispersive X-ray diffraction measurements.