Impact of Cation Intercalation on the Electronic Structure of Ti3C2Tx MXenes in Sulfuric Acid

Intercalation in Ti3C2Tx MXene is essential for a diverse set of applications such as water purification, desalination, electrochemical energy storage, and sensing. The interlayer spacing between the Ti3C2Tx nanosheets can be controlled by cation intercalation; however, the impact of intercalation on the Ti3C2Tx MXene chemical and electronic structures is not well understood. Herein, we characterized the electronic structure of pristine, Li , Na , K , and Mg intercalated Ti3C2Tx MXenes dispersed initially in water and 10 mM sulfuric acid H2SO4 using X ray absorption spectroscopy XAS . The cation intercalation is found to dramatically influence the chemical environment of Ti atoms. The Ti oxidation of the MXene increases progressively upon intercalation of cations of larger sizes after drying in air, while interestingly a low Ti oxidation is observed for all intercalated MXenes after dispersion in diluted H2SO4. In situ XAS at the Ti L edge was conducted during electrochemical oxidation to probe the changes in the Ti oxidation state in the presence of different cations in H2SO4 aqueous electrolyte. By applying the sensitivity of the Ti L edge to probe the oxidation state of Ti atoms, we demonstrate that cation intercalation and H2SO4 environment significantly alter the Ti3C2Tx surface chemistr

HTS current lead using a composite heat pipe

This paper discusses the design and fabrication of HTS current leads being built by Los Alamos to supply power to a demonstration HTS coil which will operate in a vacuum cooled by a cryocooler. Because vapor cooling is not an option for this application the leads must be entirely conductively cooled. In the design of HTS current leads for this type of application, it is desirable to intercept part of the heat load at an intermediate temperature. This thermal intercept or connection must be electrically insulating but thermally conductive, two mutually exclusive properties of most candidate solid materials. To achieve this end we incorporate a composite nitrogen heat pipe, constructed of conducting and non-conducting materials, to provide efficient thermal communication and simultaneously, electrical isolation between the lead and the intermediate temperature heat sink. Another important feature of the current lead design is the use of high Jc thick film superconductors deposited on a non-conducting substrate to reduce the conductive heat leak through the lower portion of the lead. Two flexible electrical conductors are incorporated to accommodate handling, assembly and the dissimilar expansion coefficients of the various materials

Spatially resolved X ray absorption spectroscopy investigation of individual cation intercalated multi layered Ti3C2Tx MXene particles

Ti3C2Tx MXene is a two dimensional 2D material possessing highly active hydrophilic surfaces coupled with high metallic conductivity. Cations intercalation between the Ti3C2Tx nanosheets has a significant role in many applications such as water purification, desalination, and electrochemical energy storage. The pseudocapacitive charging mechanism involving surface redox reactions at the Ti3C2Tx surface enables higher energy densities than electrical double layer capacitors, and higher power densities than batteries. In this context, the oxidation state of surface Ti atoms involved in redox reactions has a high impact on the capacitance of Ti3C2Tx MXene and this can be impacted by cation intercalation. Thus, the electronic structure of multi layered Ti3C2Tx particles is investigated by X ray absorption XA spectroscopy, while also benefitting from a high spatial resolution of 30 nm from X ray photoemission electron microscopy. In this work, the XA spectra from multi layered intercalated Ti3C2Tx particles of different thicknesses were recorded at the Ti L and O K edges. The Ti oxidation state in pristine, Li , and Mg intercalated Ti3C2Tx was found to be thickness dependent, while Na and K intercalated Ti3C2Tx particles did not reveal differences upon changing thickness. This work demonstrates thickness dependent modification of the MXene surface chemistry upon cation intercalation in different individual Ti3C2Tx particle

Metal Cation Pre Intercalated Ti3C2Tx MXene as Ultra High Areal Capacitance Electrodes for Aqueous Supercapacitors

Two dimensional transition metal carbides and nitrides MXenes have demonstrated great potential as electrode materials for electrochemical energy storage systems. This is especially true for delaminated Ti3C2Tx, which already shows outstanding gravimetric and volumetric capacitance, with areal capacitance limited by thickness only a few microns . However, the performance of multilayer Ti3C2Tx has been more modest. Here, we report on using metal cation viz., Na , K , and Mg2 pre intercalated multilayer Ti3C2Tx as electrodes for aqueous supercapacitors. These electrodes are scalable and amenable to roll to roll manufacturing, with adjustable areal loadings of 5.2 to 20.1 mg cm2. K Ti3C2Tx exhibited the highest capacitances at different scan rates. A gravimetric capacitance comparable to that of delaminated MXene of up to 300 F g was achieved for multilayer K Ti3C2Tx but with an outstanding ultra high areal capacitance of up to 5.7 F cm2, which is 10 fold higher than the 0.5 F cm2 of delaminated MXene and exceeds the 4.0 F cm2 of microengineered MXene electrode

Magnetic separation for soil decontamination

High gradient magnetic separation (HGMS) is a physical separation process that is used to extract magnetic particles from mixtures. The technology is used on a large scale in the kaolin clay industry to whiten or brighten kaolin clay and increase its value. Because all uranium and plutonium compounds are slightly magnetic, HGMS can be used to separate these contaminants from non-magnetic soils. A Cooperative Research and Development Agreement (CRADA) was signed in 1992 between Los Alamos National Laboratory (LANL) and Lockheed Environmental Systems and Technologies Company (LESAT) to develop HGMS for soil decontamination. This paper reports progress and describes the HGMS technology

Beached bachelors: an extensive study on the largest recorded sperm whale <i>Physeter macrocephalus</i> mortality event in the North Sea

Between the 8th January and the 25th February 2016, the largest sperm whale Physeter macrocephalus mortality event ever recorded in the North Sea occurred with 30 sperm whales stranding in five countries within six weeks. All sperm whales were immature males. Groups were stratified by size, with the smaller animals stranding in the Netherlands, and the largest in England. The majority (n = 27) of the stranded animals were necropsied and/or sampled, allowing for an international and comprehensive investigation into this mortality event. The animals were in fair to good nutritional condition and, aside from the pathologies caused by stranding, did not exhibit significant evidence of disease or trauma. Infectious agents were found, including various parasite species, several bacterial and fungal pathogens and a novel alphaherpesvirus. In nine of the sperm whales a variety of marine litter was found. However, none of these findings were considered to have been the primary cause of the stranding event. Potential anthropogenic and environmental factors that may have caused the sperm whales to enter the North Sea were assessed. Once sperm whales enter the North Sea and head south, the water becomes progressively shallower (<40 m), making this region a global hotspot for sperm whale strandings. We conclude that the reasons for sperm whales to enter the southern North Sea are the result of complex interactions of extrinsic environmental factors. As such, these large mortality events seldom have a single ultimate cause and it is only through multidisciplinary, collaborative approaches that potentially multifactorial large-scale stranding events can be effectively investigated

Influenza A (H10N7) virus causes respiratory tract disease in harbor seals and ferrets

Avian influenza viruses sporadically cross the species barrier to mammals, including humans, in which they may cause epidemic disease. Recently such an epidemic occurred due to the emergence of avian influenza virus of the subtype H10N7 (Seal/H10N7) in harbor seals (Phoca vitulina). This epidemic caused high mortality in seals along the north-west coast of Europe and represented a potential risk for human health. To characterize the spectrum of lesions and to identify the target cells and viral distribution, findings in 16 harbor seals spontaneously infected with Seal/H10N7 are described. The seals had respiratory tract inflammation extending from the nasal cavity to bronchi associated with intralesional virus antigen in respiratory epithelial cells. Virus infection was restricted to the respiratory tract. The fatal outcome of the viral infection in seals was most likely caused by secondary bacterial infections. To investigate the pathogenic potential of H10N7 infection for humans, we inoculated the seal virus intratracheally into six ferrets and performed pathological and virological analyses at 3 and 7 days post inoculation. These experimentally inoculated ferrets displayed mild clinical signs, virus excretion from the pharynx and respiratory tract inflammation extending from bronchi to alveoli that was associated with virus antigen expression exclusively in the respiratory epithelium. Virus was isolated only from the respiratory tract. In conclusion, Seal/H10N7 infection in naturally infected harbor seals and experimentally infected ferrets shows that respiratory epithelial cells are the permissive cells for viral replication. Fatal outcome in seals was caused by secondary bacterial pneumonia similar to that in fatal human cases during influenza pandemics. Productive infection of ferrets indicates that seal/H10N7 may possess a zoonotic potential. This outbreak of LPAI from wild birds to seals demonstrates the risk of such occasions for mammals and thus humans