Multichromic polymers based on pyrene clicked thienylpyrrole

In this study, the effect of pendant pyrene on the optical and electronic properties of poly(2,5‐dithienylpyrrole)s was studied. For this purpose a new pyrene coupled 2,5‐dithienylpyrrole derivative (SNS‐pyrene) was synthesized through click reaction. SNS‐pyrene was electrochemically polymerized and its electrochemical and optical properties were investigated by electrochemical and optical techniques. The polymer had a band gap of 3.36 eV and displayed light green to blue color variation upon oxidation in less than 2.48 s. Additionally, electrochemical copolymerization of SNS‐pyrene with 3,4‐ethylenedioxythiophene was achieved whilst a detailed investigation was performed on the effect of electrochemical polymerization conditions on the optoelectronic properties of the copolymers. Studies revealed that the copolymers exhibit multichromic reversible redox behavior with lower band gaps and shorter switching times than their parent polymer, P(SNS‐pyrene) © 2014 Society of Chemical Industry.     

Micromechanical modeling of particulate-filled composites using micro-CT to create representative volume elements

International Journal of Mechanics and Materials in Design - A method based on X-ray micro-CT was introduced to create realistic representative volume elements (RVE) for particulate-filled...     

Determination of the relative leaching kinetics of Cu, Rh, Ru and Ir during the sulphuric acid pressure leaching of leach residue derived from Ni-Cu converter matte enriched in platinum group metals

Hydrometallurgical process routes are typically used for separation of platinum group metals (PGMs) from base metals in Ni-Cu converter matte. Nickel dissolution is primarily achieved in the first stage leach (high pressure or atmospheric leaching, or a combination of the two), which is followed by second stage high pressure sulphuric acid/oxygen leaching to dissolve copper and the remaining nickel. PGMs are recovered from the leaching residue, and their dissolution must hence be limited. The leaching of base metals in the first stage has been characterised, but there is a limited understanding of the behaviour of metals, and more specifically PGMs, in the second stage pressure leach. This research presents the results of laboratory work performed to investigate the kinetics of leaching in the second stage pressure leach. The influence of key operating parameters such as the temperature, pressure, and initial acid concentration on PGM dissolution was investigated.     

The performance of PCD tools in high-speed milling of Ti6Al4V

Tool performance of conventional tools is poor and a major constraint when used in milling titanium alloys at elevated cutting speeds. At these high cutting speeds, the chemical and mechanical properties of Ti6Al4V cause complex wear mechanisms. In this paper, a fine-grain polycrystalline diamond (PCD) end mill tool was tested, and its wear behavior was studied. The performance of the PCD tool has been investigated in terms of tool life, cutting forces, and surface roughness. The PCD tool yielded longer tool life than a coated carbide tool at cutting speeds above 100?m/min. A slower wear progression was found with an increase in cutting speeds, whereas the norm is an exponential increase in tool wear at elevated speeds. Observations based on scanning electron microscope (SEM) and energy dispersive spectroscopy (EDAX) analysis suggest that adhesion of the workpiece is the wear main type, after which degradation of the tools accelerates probable due to the combined effect of high temperature degradation coupled with abrasion.     

The Liquidus in Cu–O–CaO System at Metallic Copper Saturation up to 1698 K

We present experimental results for the liquidus of the pseudo binary system Cu₂O–CaO at metallic copper saturation up to 1698 K in steps of 25 K. In this study, we quantified the liquidus (on the CaO side of the binary) by the equilibration, quench, and analysis technique, with Cu₂O, CaO, and Cu as the only primary crystalline phases. Experiments were conducted in an atmosphere of pure argon up to the critical temperature (1618 K) in the Cu–O system. Above this temperature, experiments were performed at a fixed oxygen pressure of (P_O2 = 1.01 kPa). Equilibrated specimens were quenched in ice‐cold water. We then quantified the liquid chemical compositions by means of energy‐dispersive X‐ray spectroscopy and electron probe micro‐analyzer. Results from this study reveal that below the critical point, some previous studies have overestimated CaO solubility amounts in the molten phase of the system, by up to 4.35 wt% CaO. Thermodynamic modeling of systems containing this binary should therefore also account for this variance.     

Micro‐ and nanoscale structures of mesiodens dentin: Combined study of FTIR and SAXS/WAXS techniques

A mesiodens is the most common type of supernumerary tooth present in conjunction to normal dentition. A mesiodens may commonly occur in the central region of the upper or lower jaw. A mesiodens is different from normal teeth in terms of structure and shape. The aim of this study is to evaluate the micro‐ and nanoscale structural properties of mesiodens dentin by combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and Fourier transform infrared (FTIR) spectroscopy. Five freshly extracted, noncarious mesiodens and five normal dentin disks prepared from human incisor teeth were compared. Using FTIR, the phosphate‐to‐amide I, carbonate‐to‐phosphate, and carbonate‐to‐amide I band area ratios and the crystallinity index were quantified. SAXS/WAXS were used to study the nanostructure of mesiodens. An increase in the mineral content in the mesiodens dentin with respect to the normal group was found. Crystallinity was also significantly increased and the protein content decreased in the mesiodens dentin compared with that of normal dentin. SAXS/WAXS results revealed that mesiodens dentin has a more calcified tissue. Further, SAXS analysis revealed a nonuniform distribution of dentin fibrils in mesiodens. Microsc. Res. Tech., 78:52–58, 2015. © 2014 Wiley Periodicals, Inc.     

Further Increase of T c in Y-Ba-Cu-O Superconductors

This paper presents the synthesis and characterization of three new Y-based high temperature-superconducting compounds having relatively higher transition temperature T _c compared with that of the Y-123, Y-124, and Y-247. The electrical resistivity measurements indicate the onset critical temperatures as high as 98 K. Atomic compositions of these new Y-Ba-Cu-O superconductors are Y₂Ba₃Cu_5.2O _x , Y₂Ba₅Cu₉O _x , and YBa₄Cu₅O _x . The X-ray analysis has shown that they have a similar crystalline structure as Y-123 phases.     

Predicting crack propagation with peridynamics: a comparative study

The fidelity of the peridynamic theory in predicting fracture is investigated through a comparative study. Peridynamic predictions for fracture propagation paths and speeds are compared against various experimental observations. Furthermore, these predictions are compared to the previous predictions from extended finite elements (XFEM) and the cohesive zone model (CZM). Three different fracture experiments are modeled using peridynamics: two experimental benchmark dynamic fracture problems and one experimental crack growth study involving the impact of a matrix plate with a stiff embedded inclusion. In all cases, it is found that the peridynamic simulations capture fracture paths, including branching and microbranching that are in agreement with experimental observations. Crack speeds computed from the peridynamic simulation are on the same order as those of XFEM and CZM simulations. It is concluded that the peridynamic theory is a suitable analysis method for dynamic fracture problems involving multiple cracks with complex branching patterns.