Impact and high strain rate delamination characteristics of carbon fibre epoxy composites

Delamination mechanisms and energy dissipation of carbon fibre epoxy composites under impact and high strain rate conditions are studies in terms of a new experimental set-up. The test set-up is designed to separate the Mode-I, -II and mixed mode delamination resistance so that relevant mechanisms can be studied in greater detail. The impact specimens consist of 18 × 18 mm laminated composite pieces bonded to steel bars to form the impact specimens with the normal Charpy and Izod specimen geometry. The impact energy dissipation is recorded and taken as a dynamic delamination toughness measurement, and the transition from the pure Mode-I to Mode-II through the mixed mode delamination is measured. Detailed delamination surface examinations by scanning electron microscopy (SEM) show that different failure mechanisms are involved in the dynamic and usual quasi-static delamination processes. The influence of chopped Kevlar fibres used as low cost interlaminar reinforcement on the energy dissipation is also studied.     

Electric Double‐Layer Capacitor Based on an Ionic Clathrate Hydrate

Herein, we suggest a new approach to an electric double‐layer capacitor (EDLC) that is based on a proton‐conducting ionic clathrate hydrate (ICH). The ice‐like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me₄NOH ? 5 H₂O show a high specific capacitance, reversible charge–discharge behavior, and a long cycle life. The ionic‐hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre‐treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more‐favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems.     

Asymmetric Total Synthesis of (+)‐Bermudenynol,a C15 Laurencia Metabolite with a Vinyl Chloride Containing Oxocene Skeleton,through Intramolecular Amide Enolate Alkylation

A substrate‐controlled asymmetric total synthesis of (+)‐bermudenynol, a compact and synthetically challenging C₁₅ Laurencia metabolite that contains several halogen atoms, is reported. The oxocene core, which contains a vinyl chloride, was constructed by an efficient and highly stereoselective intramolecular amide enolate alkylation (IAEA). This result showcases the broad utility of the IAEA methodology as a useful alternative for cases in which the ring‐closing metathesis is inefficient.     

A tiling proof of Euler’s Pentagonal Number Theorem and generalizations

The Ramanujan Journal - In two papers, Little and Sellers introduced an exciting new combinatorial method for proving partition identities which is not directly bijective. Instead, they consider...     

Finite element analysis of quasistatic crack propagation in brittle media with voids or inclusions

A three-level finite element scheme is proposed for simulation of crack propagation in heterogeneous media including randomly distributed voids or inclusions. To reduce total degrees of freedom in the view of mesh gradation, the entire domain is categorized into three regions of different-level meshes: a region of coarse-level mesh, a region of intermediate-level mesh, and a region of fine-level mesh. The region of coarse-level mesh is chosen to be far from the crack to treat the material inhomogeneities in the sense of coarse-graining through homogenization, while the region near the crack is composed of the intermediate-level mesh to model the presence of inhomogeneities in detail. Furthermore, the region very near the crack tip is refined into the fine-level mesh to capture a steep gradient of elastic field due to the crack tip singularity. Variable-node finite elements are employed to satisfy the nodal connectivity and compatibility between the neighboring different-level meshes. Local remeshing is needed for readjustment of mesh near the crack tip in accordance with crack growth, and this is automatically made according to preset values of parameters determining the propagation step size of crack, and so the entire process is fully automatic. The effectiveness of the proposed scheme is demonstrated through several numerical examples. Meanwhile, the effect of voids and inclusions on the crack propagation is discussed in terms of T-stresses, with the aid of three-level adaptive scheme.     

Electrochemical properties of nanostructured lanthanum strontium manganite cathode fabricated by electrostatic spray deposition

Electrostatic spray deposition was applied to prepare nanoporous lanthanum strontium manganite (LSM) films with high specific surface area (37.34 m²/g) for the cathode application in solid oxide fuel cell (SOFC). The electrochemical characteristics were investigated at a temperature range from 546 to 777 °C and oxygen partial pressure from 0.01 to 1.0 atm. The diffusion of atomic oxygen and oxygen ion transfer from three-phase boundary to the YSZ electrolyte were found to be the rate-determining steps for oxygen reduction reaction on LSM cathode. The polarization resistance of the LSM prepared using electrostatic spray deposition decreased from 15 to 1.2 Ωcm² with increasing temperature from 546 to 777 °C and the activation energy was 0.81 eV. It was demonstrated that the ESD method offers a promising approach for the preparation of electrochemically active nanoporous layers, particularly applicable for solid oxide fuel cells.     

Solid state of a new flavonoid derivative DA-6034

DA-6034 is a new synthetic flavonoid known to possess anti-inflammatory activity. The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of DA-6034. Six crystal forms, one hydrate form and five solvates, of DA-6034 have been isolated by recrystallization and characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and powder X-ray diffractometry (PXRD). From the DSC and TG data it was confirmed that Form 1 is monohydrate; Form 2 is DMSO solvate; Form 3 is 1/2 DMSO solvate; Form 4 is 1/2 methyl ethyl ketone solvate; Form 5 is 1.5 H₂O, 1/2 acetic acid solvate; Form 6 is 1/2 H₂O, 1/4 butanol solvate. The PXRD patterns of the six crystal forms were different respectively. In the dissolution studies in pH 6.8 ± 0.05 buffer at 37 ± 0.5 °C, the solubility of solvates was higher than that of Form 1.     

Asymmetric Total Synthesis of (+)‐Bermudenynol,a C15 Laurencia Metabolite with a Vinyl Chloride Containing Oxocene Skeleton,through Intramolecular Amide Enolate Alkylation

A substrate‐controlled asymmetric total synthesis of (+)‐bermudenynol, a compact and synthetically challenging C₁₅ Laurencia metabolite that contains several halogen atoms, is reported. The oxocene core, which contains a vinyl chloride, was constructed by an efficient and highly stereoselective intramolecular amide enolate alkylation (IAEA). This result showcases the broad utility of the IAEA methodology as a useful alternative for cases in which the ring‐closing metathesis is inefficient.     

Recycling process of spent battery modules in used hybrid electric vehicles using physical/chemical treatments

The physical treatment/chemical treatments for recycling of spent lithium-ion battery modules in used hybrid electric vehicles as cathodic active materials were performed. The result by physical treatment showed that over 95 % valuable metals such as Co, Li, Ni, and Mn were concentrated in 65-mesh during a grinding time 2 min, while just 2.7 % Al was concentrated from spent lithium-ion batteries which were completely electric discharged after 70 min. Through reductive leaching with H₂O₂ and H₂SO₄, leaching efficiency of valuable metals with 65-mesh powder was almost 99 % Co, Mn, Ni, and Li under the conditions of 2 M H₂SO₄, 5 vol% H₂O₂, 60 °C, 300 rpm, 50 g/500 mL, and 2 h. After removing some impurities such as Cu, Al, and Fe, the leaching solutions containing Co, Mn, Ni, and Li could be utilized for manufacturing the precursor of cathodic active material of Li-ion battery. The precursor was manufactured by co-precipitation from the filtrate after calibration of Co, Mn, and Ni concentration adding NaOH and NH₄OH under the conditions over pH 11, 30 °C, 150 rpm, and 24 h. To maintain the pH, 11 is most important level for making homogeneous spherical Co–Mn–Ni hydroxide.     

Influence of primary ion species on the secondary cluster ion emission process from SAMs of hexadecanethiol on gold

In order to investigate the secondary cluster ion emission process of organo-metallic compounds under keV ion bombardment, self-assembled monolayers (SAMs) of alkanethiols on gold are ideal model systems. In this experimental study, we focussed on the influence of the primary ion species on the emission processes of gold-alkanethiolate cluster ions from a hexadecanethiol SAM on gold. For this purpose, we carried out time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements using the following primary ion species and acceleration voltages: Ar⁺, Xe⁺, SF₅⁺ (10 kV), Bi⁺, Bi₃⁺(25 kV), Bi₃²⁺, Bi₅²⁺, Bi₇²⁺ (25 kV).It is well known that molecular ions M⁻ and gold-alkanethiolate cluster ions Au_xM_y⁻ with M = S-(CH₂)₁₅-CH₃, x − 3 ≤ y ≤ x + 1, x, y > 0, show intense peaks in negative mass spectra. We derived yields Y_SI exemplarily for the molecular ions M⁻ and the gold-hexadecanethiolate cluster ions Au_y+1M_y⁻ up to y = 8 and found an exponentially decreasing behaviour for increasing y-values for the cluster ions.In contrast to the well-known increase in secondary ion yield for molecular secondary ions when moving from lighter to heavier (e.g. Ar⁺ to Xe⁺) or from monoatomic to polyatomic (e.g. Xe⁺ to SF₅⁺) primary ions, we find a distinctly different behaviour for the secondary cluster ions. For polyatomic primary ions, there is a decrease in secondary ion yield for the gold-hexadecanethiolate clusters whereas the relative decrease of the secondary ion yield ξ_Y with increasing y remains almost constant for all investigated primary ions.