Johnson Matthey Technology Review - Volume 68, Issue 1, 2024

Ruthenium targets were prepared by vacuum hot pressing of ruthenium powder with different morphologies. Ruthenium films were then deposited on a SiO2/Si(100) substrate for different times by radio frequency (RF) magnetron sputtering. The relationship in terms of the microstructure and electrical properties between the ruthenium targets and resultant films at different conditions were studied by means of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe. The results showed that parameters such as the average deposition rate, surface roughness, crystallisation properties and growth rate were directly related to the homogeneity of the microstructure of the ruthenium targets, but there was no correlation between the crystal orientations of the films and the targets. Moreover, the resistivity of ruthenium films was positively correlated with that of the ruthenium targets.

Globally, transport is responsible for 23% of energy-related carbon dioxide emissions and 80% of these emissions are attributable to road transport. Significant transformations, including extensive electrification of the sector, are necessary to achieve climate change goals. To understand new energy vehicle (NEV) policy research, we explore the status, knowledge base and research frontiers of NEV policy research by studying 355 papers collected from the Web of Science™ (WoS) Core Collection database. We map NEV policy research trends and knowledge structure development using knowledge domain technology and bibliometric techniques. The knowledge base analysis shows that: (a) NEV policy formation and evaluation; (b) policy incentives and consumer adoption; and (c) consumer preferences towards NEV adoption are all essential knowledge foundations in NEV policy research and development (R&D). The efficiency of NEV policy, cost-effectiveness of alternative fuel vehicles (AFVs), consumer preferences for NEV adoption, hydrogen energy and fuel cell vehicles, climate policy and CO2 emissions are five main lines of research in NEV policy studies. With the highest number of publications from Tsinghua University, China is the most active country in NEV policy research. Energy Policy, Sustainability and Journal of Cleaner Production are the core journals and Energy and Fuels and Environmental Sciences are the core disciplines of NEV policy research. The findings of this analysis help policymakers and researchers to navigate the literature on NEV, provide a clear map of existing works, identify the gaps and recommend promising avenues for future studies.

The propagation of ultrasonic waves in the hexagonal closed packed (hcp) structured lanthanide metal titanium has been investigated in the temperature range 300–1000 K. For this, initially the higher-order elastic constants (second-order elastic constants (SOECs) and third-order elastic constants (TOECs)) were computed using the Lennard-Jones interaction potential model. With the help of SOECs, other elastic moduli such as Young’s modulus (Y), bulk modulus (B), shear modulus (G), Poisson’s ratio (σ) and Pugh’s ratio (B/G) were computed using the Voigt-Reuss-Hill approximation. Three types of orientation-dependent ultrasonic velocities, including Debye average velocities, were evaluated using the calculated SOECs and density of titanium in the same temperature range. Thermophysical properties such as lattice thermal conductivity, thermal relaxation time, thermal energy density, specific heat at constant volume and acoustic coupling constant were evaluated under the same physical conditions. The ultrasonic attenuation due to phonon-phonon interaction is most significant under the chosen physical conditions. The ultrasonic properties of titanium are correlated with thermophysical properties to understand the microstructural features and nature of the material.

The elastic, mechanical, thermophysical and ultrasonic properties of platinum group metal (pgm) carbides XC (X = rhodium, palladium, iridium) have been investigated at room temperature. The Coulomb and Born-Mayer potential model was used to compute second- and third-order elastic constants (SOECs and TOECs) at 0 K and 300 K. The obtained values of SOECs were used to evaluate mechanical properties such as Young’s modulus, bulk modulus, shear modulus, Pugh’s indicator, Zener anisotropic constant and Poisson’s ratio at room temperature. The materials show brittle nature as the value of Pugh’s indicator for pgm carbides is ≤1.75. The values of SOECs were used to compute the ultrasonic velocities along <100>, <110> and <111> directions for the longitudinal and shear modes of wave propagation. Further, the values of Debye temperature, thermal conductivity, specific heat per unit volume, energy density, average value of ultrasonic Grüneisen parameter, thermal relaxation time and non-linear parameter were calculated with the help of SOECs, TOECs, ultrasonic velocities, density and molecular weight. Finally, the ultrasonic attenuation due to phonon-phonon interaction and due to thermoelastic relaxation mechanisms were calculated with the use of all associated parameters. The calculated values of elastic, mechanical, thermophysical and ultrasonic properties are compared with available literature and discussed.

Fungi commonly found in municipal water can participate in natural biofilm formation on the surface of galvanised steel despite the toxic effect of zinc. Depending on the age of the biofilm, fungal diversity may vary. To examine this hypothesis, natural biofilm formation was allowed on galvanised steel surfaces over six months in a model recirculating water system. Fungal colonies with different morphologies were obtained monthly from biofilm and water samples and then identified by both morphological and molecular approaches. In addition, the biofilm layer was examined by electrochemical impedance spectroscopy (EIS) analysis and scanning electron microscopy (SEM). It was determined that fungi were included in the naturally aging biofilm formed on galvanised steel surfaces during the experiment. The diversity and the number of fungi in the biofilm and water changed over the experiment. All fungi isolated from the biofilm and water were found to be members of the Ascomycota phylum. F. oxysporum was the first fungus to be involved in the biofilm formation process and was one of the main inhabitants of the biofilm together with Penicillium spp. In addition, EIS data showed that the structure of the biofilm changed as it aged. The results of this study may lead to a better understanding of naturally aging biofilms involving fungi in municipal water systems, as well as the development of new strategies for effective disinfection of fungi based on biofilm age.

The improved bulk and surface function of manufactured implants has advanced implantation procedures, leading to a decline in surgical risks. Many current techniques discussed in the literature are related to additive manufacturing (AM) of lightweight implants based on reliable, precise, flexible scaffolds and capable of mimicking bone properties while incorporating other useful features. These techniques have evolved for the production of a variety of biocompatible materials. AM has progressed beyond prototype to full-scale manufacturing of metals, polymers and ceramic products. However, metallic implants often fail in vivo due to biocorrosion and deterioration, limiting implant longevity. This study reviews current trends and approaches to enhancing the surface corrosion resistance of porous metallic implants and the effect of interfacial films on biological activity. The art of porous metallic implants manufactured by AM and their biocorrosion behaviour are discussed. This review also evaluates future trends and perspectives in additively manufactured synthetic orthopaedic implants porous with enhanced surface morphology.

Noble metals are key to various research fields and noble metal nanomaterials are directly relevant to optics, catalysis, medicine, sensing and many other applications. Rhodium-based nanomaterials have been less studied than metals such as gold, silver or platinum. There have been many improvements in characterisation tools over the years and knowledge about rhodium chemistry and nanomaterials is growing rapidly. Rhodium nanoparticles are widely used as catalysts for automotive emissions control and for hydrogen and oxygen precipitation reactions in electrolytic cells. Novel applications in electronics, anticancer drugs and aerospace are being revisited. In Part I of this two-part review, we cover different strategies for the synthesis of rhodium films and nanoparticles.

Part I of this review covered the synthesis methods for synthesis of rhodium films and nanoparticles (1). In Part II, we review the literature on the current and potential applications of rhodium and rhodium alloy films and nanoparticles in catalysis, components for the glass, chemical and electronic industries, thermal sensors and anticancer drugs.

State-of-the-art proton exchange membrane (PEM) electrolysers employ iridium-based catalysts to facilitate oxygen evolution at the anode. To enable scale-up of the technology to the terawatt level, further improvements in the iridium utilisation are needed, without incurring additional overpotential losses or reducing the device lifetime. The research community has only recently started to attempt systematic benchmarking of catalyst stability. Short term electrochemical methods alone are insufficient to predict catalyst degradation; they can both underestimate and overestimate catalyst durability. Complementary techniques, such as inductively coupled plasma-mass spectrometry (ICP-MS), are required to provide more reliable assessment of the amount of catalyst lost through dissolution. In Part I, we critically review the state of the art in probing degradation of iridium-based oxide catalysts.

Part I (1) introduced state-of-the-art proton exchange membrane (PEM) electrolysers with iridium-based catalysts for oxygen evolution at the anode in green hydrogen applications. Aqueous model systems and full cell testing were discussed along with proton exchange membrane water electrolyser (PEMWE) catalyst degradation mechanisms, types of iridium oxide, mechanisms of iridium dissolution and stability studies. In Part II, we highlight considerations and best practices for the investigation of activity and stability of oxygen evolution catalysts via short term testing.

Coating surfaces with bioactive glass can be defined as depositing fine bioactive glasses on biomaterial substrates. Cobalt-chromium is a viable alternative to stainless steel for long-term applications with superior ductility. The mechanical properties of cobalt-chromium alloys are high strength with elastic modulus of 220–2300 GPa, more significant than the 30 GPa of bones. Combining metals and bioactive glass results in high biocompatibility and improved bioactivity of implant surfaces. In addition, it triggers new bone tissue to regenerate through osteogenesis and mineralisation. However, implantation failure still occurs and requires surgery revision due to a lack of adequate bone bonding and delamination at the coating surface of the implant. The current review summarises the adhesion between bioactive glass coatings and cobalt-chromium substrates applied through electrophoretic deposition (EPD).