Cobalt

Prior to the eighteenth century, cobalt was exclusively employed as a colouring agent for vitreous materials, and its use appears to be concurrent with the earliest large-scale production of glass during the Late Bronze Age (LBA). LBA cobalt deposits with a distinctive elemental signature have been identified in the oases of the western Egyptian desert, while cobalt mines in Kashan (Iran) and in the Erzgebirge (Germany) are known to have been exploited during the later Middle Ages. For most of the first millennium BCE and CE, however, the identity of cobalt sources and their supply patterns remain elusive. The aim of this study is to characterise the chemical composition of cobalt colorants used during the first millennium CE. Compositional variations indicate the use of different raw materials and/or production processes, which in turn has implications for the underlying exchange networks. Using mainly correlations between cobalt, nickel and zinc as discriminants, our results show that the compositional signature of cobalt underwent two major changes. An increase in the CoO/NiO ratios occurs between the late fourth and the beginning of the sixth century, while a new zinc-rich source of cobalt begins to be exploited during the second half of the eighth century in the Islamic world.

Naples assumed an important political and economic role within the region of Campania during the late antique period. LA-ICP-MS data of 285 glass tesserae from the catacomb of San Gennaro in Naples confirm that the surge in building activities in the late fourth and early fifth century CE was accompanied by imports of new materials for the production of mosaic tesserae. Our results from Naples identify a substantial number of Jalame-like Levantine glasses for which there is no parallel within the Italian Peninsula. Only few scattered examples of this type of base glass are found among the published data from Aquileia, Ravenna and the Villa of Faragola, pointing to a link between the supply of glass and the sites' connectivity and economic strength. This seems to have changed after the fifth century. Elemental analyses, combined with SEM-EDS and micro-Raman indicate that the mosaics dating from the fourth to the eighth/ninth century CE in the catacombs of San Gennaro were overwhelmingly made from reused first-to fourth-century Roman base glasses opacified with calcium antimonate. The reuse and recycling of Roman glass and Roman tesserae is a common feature of mosaic assemblages in Italy more generally. The definition of a Roman spectrum tesserae reference group revealed this dependence on old Roman material throughout the first millennium CE.

Layered lithium nickel manganese cobalt oxides, Li(NixMnyCoz)O2 where x + y + z = 1 (NMCs), have been studied extensively due to their higher capacity, less toxicity and lower cost compared to LiCoO2. However, widespread market penetration of NMCs as cathodes for Li-ion batteries (LIBs) is impeded by their poor capacity retention and low rate capability. Coatings provide an effective solution to these problems. This article focuses on review of the recent advancements in coatings of NMCs from the mechanism viewpoint. This is the first time that coatings on NMCs are reviewed based on their functionalities and mechanisms through which the electrochemical properties and performance of NMCs have been improved. To provide a comprehensive understanding of the functions and mechanisms offered by coatings, the following functions and mechanisms are reviewed individually: (i) scavenging HF in the electrolyte, (ii) scavenging water molecules in the electrolyte and thus suppressing HF propagation during charge/discharge cycles, (iii) serving as a buffer layer to minimize HF attack on NMCs and suppress side reactions between NMCs and the electrolyte, (iv) hindering phase transitions and impeding loss of lattice oxygen, (v) preventing microcracks in NMC particles to keep participation of most NMC material in lithiation/de-lithiation, and (vi) enhancing the rate capability of NMC cathodes. Finally, the personal perspectives on outlook are offered with an aim to stimulate further discussion and ideas on the rational design of coatings for durable and high performance NMC cathodes for the next generation LIBs in the near future.

The trade of glass beads has long been assumed to have been under Islamic dominance during the early centuries following the Arab conquest of the Middle East, judged by the prevalence of Islamic beads in the archaeological contexts from Viking Scandinavia to medieval Morocco. This paper explores the impact of the Byzantine-Slavic transition on the use and by extension trade of glass beads in the Balkans from the seventh to the ninth century CE. A series of 48 glass beads and 4 vessel fragments from two excavated sites in modern day Albania have been analysed morphologically, technologically and chemically by LA-ICP-MS. The seventh-century beads from Lezha have typological parallels among central European assemblages and are made from recycled natron-type glass. The presence of a high lead-iron-natron variant is of particular interest as it potentially reflects a regional production. The ninth-century beads from Komani are made from soda-rich plant ash glass from the eastern Mediterranean and Mesopotamia and correspond to an Islamic typology. The chronological and geographical differences are reflected in the distinctive cobalt sources used for the two groups. While the beads from Lezha are coloured with a cobalt not correlated with any particular element, the cobalt source of the Komani samples is associated with zinc, typical of Islamic glass making. It thus appears that the supply of beads during the seventh century when the Balkans were under Slavic occupation relied on regional production and recycled material, and that a long-distance trade with the eastern Mediterranean was revived following the Byzantine re-conquest of the southeastern Adriatic in the ninth century. Intriguingly, the Albanian finds confirm the Islamic control of the production and trade of glass beads during this period and highlight the mediatory role of the Byzantine Empire.

Twenty-six tesserae (red, orange, yellow, light amber, green, blue and white) from the balneum of the villa at Faragola (Ascoli Satriano, Foggia) have been examined by colorimetry, ICP–MS, ICP–OES and SEM–EDS. Different types of calcareous sands have been used as the source of silica (network former), also providing the stabilizing agent. A natron-type soda source served as the network modifier; however, the use of a sodium-rich plant ash and the recycling process have been hypothesized for the production of two tesserae (FT 1 red and FT 3 orange). The colouring and opacifying agents were Cu oxide (cuprite, orange), metallic copper (red), Pb antimonates (yellow), Ca antimonates (white), a mixture of copper (Cu2+) and Pb antimonates (green), a mixture of cobalt (Co2+) or copper (Cu2+) and Ca antimonates (blue). The light amber tesserae should owe their colour to iron (Fe3+) alone or associated with sulphide (S2−) and Ca antimonates. It is likely that the Faragola tesserae were locally produced in a secondary glass workshop

Much has been written in recent years about the urgency to develop new technologies that meet ambitious targets for more efficient energy infrastructure with reduced reliance on fossil fuels. There has also been growing recognition that mineral scarcity can hamper the speed of key technologies being developed. The dominance of China as a global supplier of many technology minerals and the Chinese government’s ability to constrain supply has led to a focus on the international trade dimensions of the challenge. The United States, Japan, the European Union and South Korea have all been keenly focused on securing mineral supply for their domestic industries through a range of initiatives. These efforts have included the World Trade Organization dispute resolution mechanism; research investment in alternative and more widely available materials where possible; and considering strategic stockpiles of minerals from internal sources that harken back to Cold War era strategies for material security.
In this report, we argue that a neglected area in addressing the mineral scarcity challenge is the private sector’s current trajectory for geological mineral exploration of key minerals and innovative initiatives on material efficiency and recycling where possible. We term this approach Smart Mineral Enterprise Development (SMED) which entails a partnership between public and private entities to consider pathways whereby public sector data sharing on geology can be coupled with research innovations in the private sector both upstream and downstream of mineral supply. Just as smart energy grids harness efficiencies in electricity supply and demand through a dynamic process of communication, SMED processes can do the same for key technological bottlenecks in mineral supply. We focus on cobalt to highlight the bottlenecks; identify alternative supply sources based on current exploration and recycling technologies; propose ways in which the international legal framework could be adapted to promote investments in critical minerals; and consider ways by which the public sector can assist the private sector in developing a SMED process that would bring forth more efficient and effective entrepreneurial activity to meet our green technology needs.

Both the electrical and the dielectric properties of the Al/Co-doped polyvinyl alcohol/p-Si metal-polymer-semiconductor (MPS) structure have been studied using temperature-dependent admittance-voltage (C/G-V) measurements at temperatures below room temperature at 300 kHz. The C-V plot indicates two peaks for each temperature corresponding to inversion and accumulation regions, respectively. The first peak was attributed to a particular distribution of interface traps (D it ), and the second was attributed to the series resistance (R s ) and interfacial polymer layer. G/ω-V plots show almost U-shape behavior for all temperatures and a crossing at almost 3 V. Such behavior of the G/ω-V plots may be attributed to the lack of free charge at low temperatures. After this intersection point, while the value of the capacitance (C) starts decreasing, the G/ω continues to increase. The temperature-dependent real and imaginary parts of the dielectric constant (ε′, ε″) and of the electric modulus (M′, M″), as well as the ac electrical conductivity (σ ac ), of structure were obtained using C and G data before and after the intersection point (at 2 and 6 V), respectively. Experimental results show that the ε′, ε″, loss tangent (tan δ), σ ac , M′, and M″ values were strong functions of the temperature and the applied bias voltage. In addition, G/ω-T and ε″-T plots show two different behaviors, one before and the other after the intersection point.


, loss tangent (tanδ), σac, M

,
and M

values were strong functions of the temperature and the applied bias voltage. In addition,
G/ω-T and ε

-T plots show two different behaviors, one before and the other after the intersection
point.

Monodisperse and stable cobalt ferrite (CoFe2O4) nanoparticles (5.4 nm) have been produced, coated with monoand difunctional phosphonic and hydroxamic acids, and fully characterized (using thermogravimetric analysis (TGA), dynamic light scattering (DLS), IR spectroscopy, transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) measurements). Cobalt leakage of the coated nanoparticles has been also studied. Magnetic measurements show the possible applications in hyperthermia at low frequencies, and for this reason, water-soluble coated CoFe2O4 can be seen as a first step toward the obtainment of novel systems for biomagnetic applications.

Cobalt metallic films are the subject of an ever-expanding academic and industrial interest for incorporation into a multitude of new technological applications. This report reviews the state-of-the art chemistry and deposition techniques for cobalt thin films, highlighting innovations in cobalt metal-organic chemical vapor deposition (MOCVD), plasma and thermal atomic layer deposition (ALD), as well as pulsed MOCVD technologies, and focusing on cobalt source precursors, thin and ultrathin film growth processes, and the resulting effects on film composition, resistivity and other pertinent properties.