Reoxidation of Ni‐ and Ni‐Fe‐Alloys by Al2O3‐SiO2 Refractory Materials

Reactions at the refractory/melt interface during ingot casting of Ni‐ and Ni‐Fe‐alloys were studied. The casts were performed using different alumino‐silicate bricks as refractory materials. Samples taken from the casting channel before and after casting were investigated using light and scanning electron microscopy with XPS. Thermodynamic calculations were performed with FactSage and the results were compared with the results from industrial tests. After the melt has infiltrated the surface layer of the bricks, refractory corrosion starts with an attack of Mn and Mg of the melt on SiO₂ and Fe₂O₃ of the refractory bonding matrix. Despite the presence of elements with higher oxygen affinity in the melt, low‐melting alumino‐silicate phases are predominantly built by the reaction with Mn and Mg. In a second step this liquid phase either traps non‐metallic inclusions from the melt or, at higher contents of Zr, Ti, Mg, Y etc. in the melt, causes massive reoxidation and inclusion formation. The refractory materials investigated show an increasing trend for reoxidation with an increasing amount of SiO₂ in glassy phases of the refractory bonding matrix. By the use of a refractory material with higher mullite content in the bonding matrix or by use of alumina bricks a strong reoxidation of the melt and intense inclusion formation can be avoided. These observations are also valid for other alloys with higher contents of elements with high affinity to oxygen.     

Highly Stable and Stretchable Conductive Films through Thermal‐Radiation‐Assisted Metal Encapsulation

Stretchable conductors are the basic units of advanced flexible electronic devices, such as skin‐like sensors, stretchable batteries and soft actuators. Current fabrication strategies are mainly focused on the stretchability of the conductor with less emphasis on the huge mismatch of the conductive material and polymeric substrate, which results in stability issues during long‐term use. Thermal‐radiation‐assisted metal encapsulation is reported to construct an interlocking layer between polydimethylsiloxane (PDMS) and gold by employing a semipolymerized PDMS substrate to encapsulate the gold clusters/atoms during thermal deposition. The stability of the stretchable conductor is significantly enhanced based on the interlocking effect of metal and polymer, with high interfacial adhesion (>2 MPa) and cyclic stability (>10 000 cycles). Also, the conductor exhibits superior properties such as high stretchability (>130%) and large active surface area (>5:1 effective surface area/geometrical area). It is noted that this method can be easily used to fabricate such a stretchable conductor in a wafer‐scale format through a one‐step process. As a proof of concept, both long‐term implantation in an animal model to monitor intramuscular electric signals and on human skin for detection of biosignals are demonstrated. This design approach brings about a new perspective on the exploration of stretchable conductors for biomedical applications.     

Covalent‐Organic‐Framework‐Based Li–CO2 Batteries

Covalent organic frameworks (COFs) are an emerging class of porous crystalline materials constructed from designer molecular building blocks that are linked and extended periodically via covalent bonds. Their high stability, open channels, and ease of functionalization suggest that they can function as a useful cathode material in reversible lithium batteries. Here, a COF constructed from hydrazone/hydrazide‐containing molecular units, which shows good CO₂ sequestration properties, is reported. The COF is hybridized to Ru‐nanoparticle‐coated carbon nanotubes, and the composite is found to function as highly efficient cathode in a Li–CO₂ battery. The robust 1D channels in the COF serve as CO₂^– and lithium‐ion‐diffusion channels and improve the kinetics of electrochemical reactions. The COF‐based Li–CO₂ battery exhibits an ultrahigh capacity of 27 348 mAh g^?1 at a current density of 200 mA g^?1, and a low cut‐off overpotential of 1.24 V within a limiting capacity of 1000 mAh g^?1. The rate performance of the battery is improved considerably with the use of the COF at the cathode, where the battery shows a slow decay of discharge voltage from a current density of 0.1 to 4 A g^?1. The COF‐based battery runs for 200 cycles when discharged/charged at a high current density of 1 A g^?1.     

Chemically Exfoliated VSe2 Monolayers with Room‐Temperature Ferromagnetism

Among van der Waals layered ferromagnets, monolayer vanadium diselenide (VSe₂) stands out due to its robust ferromagnetism. However, the exfoliation of monolayer VSe₂ is challenging, not least because the monolayer flake is extremely unstable in air. Using an electrochemical exfoliation approach with organic cations as the intercalants, monolayer 1T‐VSe₂ flakes are successfully obtained from the bulk crystal at high yield. Thiol molecules are further introduced onto the VSe₂ surface to passivate the exfoliated flakes, which improves the air stability of the flakes for subsequent characterizations. Room‐temperature ferromagnetism is confirmed on the exfoliated 2D VSe₂ flakes using a superconducting quantum interference device (SQUID), X‐ray magnetic circular dichroism (XMCD), and magnetic force microscopy (MFM), where the monolayer flake displays the strongest ferromagnetic properties. Se vacancies, which can be ubiquitous in such materials, also contribute to the ferromagnetism of VSe₂, although density functional theory (DFT) calculations show that such effect can be minimized by physisorbed oxygen molecules or covalently bound thiol molecules.     

Single-Site Metal–Organic Framework and Copper Foil Tandem Catalyst for Highly Selective CO2 Electroreduction to C2H4

Tandem catalysis is a promising way to break the limitation of linear scaling relationship for enhancing efficiency, and the desired tandem catalysts for electrochemical CO₂ reduction reaction (CO₂RR) are urgent to be developed. Here, a tandem electrocatalyst created by combining Cu foil (CF) with a single-site Cu(II) metal–organic framework (MOF), named as Cu–MOF–CF, to realize improved electrochemical CO₂RR performance, is reported. The Cu–MOF–CF shows suppression of CH₄, great increase in C₂H₄ selectivity (48.6%), and partial current density of C₂H₄ at −1.11 V versus reversible hydrogen electrode. The outstanding performance of Cu–MOF–CF for CO₂RR results from the improved microenvironment of the Cu active sites that inhibits CH₄ production, more CO intermediate produced by single-site Cu–MOF in situ for CF, and the enlarged active surface area by porous Cu–MOF. This work provides a strategy to combine MOFs with copper-based electrocatalysts to establish high-efficiency electrocatalytic CO₂RR.     

Effects of ball burnishing parameters on surface finish—A literature survey and discussion

Ball burnishing, a plastic deformation process, is becoming more popular as a finishing operation. A literature survey and discussion on the effects of the various types of burnishing (normal, vibratory and ultrasonic) and related parameters—force, speed, feed-rate, lubrication, ball material and diameter, workpiece material, pre-machined roughness and frequency of oscillation—on the final surface roughness are presented. The effect is an interaction between the process parameters with burnishing force and feed-rate as the two most significant factors. A particular surface finish can be obtained by appropriate selection of the parameters     

Intrathalline Metabolite Profiles in the Lichen <Emphasis Type="Italic">Argopsis friesiana</Emphasis> Shape Gastropod Grazing Patterns

Lichen-gastropod interactions generally focus on the potential deterrent or toxic role of secondary metabolites. To better understand lichen-gastropod interactions, a controlled feeding experiment was designed to identify the parts of the lichen Argopsis friesiana consumed by the Subantarctic land snail Notodiscus hookeri. Besides profiling secondary metabolites in various lichen parts (apothecia, cephalodia, phyllocladia and fungal axis of the pseudopodetium), we investigated potentially beneficial resources that snails can utilize from the lichen (carbohydrates, amino acids, fatty acids, polysaccharides and total nitrogen). Notodiscus hookeri preferred cephalodia and algal layers, which had high contents of carbohydrates, nitrogen, or both. Apothecia were avoided, perhaps due to their low contents of sugars and polyols. Although pseudopodetia were characterized by high content of arabitol, they were also rich in medullary secondary compounds, which may explain why they were not consumed. Thus, the balance between nutrients (particularly nitrogen and polyols) and secondary metabolites appears to play a key role in the feeding preferences of this snail.     

Dynamical observation of bamboo-like carbon nanotube growth

The growth dynamics of bamboo-like multiwalled carbon nanotubes (BCNTs) via catalytic decomposition of C2H2 on Ni catalyst at 650 degrees C was observed in real time using an in situ ultrahigh vacuum transmission electron microscope. During BCNT growth, the shape of the catalyst particle changes constantly but remains metallic and crystalline. Graphene sheets (bamboo knots) within the nanotube preferentially nucleate on the multistep Ni-graphite edges at the point where the graphene joins the catalyst particle, where it is stabilized by both the graphene walls and the Ni catalyst surface. The growth of a complete inner graphene layer growth prior to contraction of the Ni catalyst particle due to restoring cohesive forces will result in a complete BCNT knot whereas partial growth of the inner wall will lead to an incomplete BCNT knot.     

Comparative disinfection of poliovirus by bromine chloride and chlorine in a model contact chamber

The effectiveness of BrCl vs chlorine as a disinfectant of poliovirus was evaluated using a model contact chamber capable of automatically treating water at the rate of 4 gal min⁻ to simulate conditions at an operating wastewater treatment plant. The results show that in clean tap water both BrCl and chlorine are effective in inactivating poliovirus. However, in the presence of NH₄Cl or 10% sewage effluent, BrCl was demonstrated to be superior to chlorine as a disinfectant of poliovirus.     

Optimizing label-free DNA electrical detection on graphene platform

The anodized epitaxial graphene (EG) electrode demonstrates a high level of performance for electrochemical impedance as well as differential pulse voltammetry detection of immobilized DNA and free DNA, respectively, at solid-liquid interfaces. On the anodized EG surface, because of the presence of oxygen functionalities as well as π conjugated domains, the anchoring of the DNA probe can be achieved by either covalent grafting or noncovalent π-π stacking readily. The effect of different binding modes on the sensitivity of the impedimetric sensing was investigated. Equivalent circuit modeling shows that the sensitivity of EG to DNA hybridization is controlled by changes in the resistance of the molecular layer as well as the space charge layer. The linear dynamic detection range of EG for DNA oligonucleotides is in the range of 5.0 × 10(-14) to 1 × 10(-6) M. In addition, with the use of differential pulse voltammetry, single stranded DNA, fully complimentary DNA, as well as single nucleotide polymorphisms can be differentiated on anodized EG by monitoring the oxidation signals of individual nucleotide bases.