Glassy carbon manufacture using rapid photonic curing

Journal of Materials Science - Photonic curing was explored as a rapid method for producing glassy carbon coatings, reducing processing time from ~?20 h for conventional thermal...     

Detection of transient-evoked otoacoustic emissions and the design of time windows

A new approach to the design of time windows is presented for detection of transient-evoked otoacoustic emissions (TEOAE). The windows are designed with reference to a minimum mean square error criterion involving the correlation properties of the ensemble of responses. Latency information is introduced in the detection process by windowing at different scales that result from wavelet decomposition. The significance of both subject- and population-specific time windows is investigated. The detection performance is evaluated on a health screen database consisting of 4989 records. The results show that the present approach to windowing yields a significantly better performance in separating normal-hearing subjects from hearing-impaired subjects when compared to detection based on unwindowed signals. With time windowing, the specificity increased with almost 15% at a fixed sensitivity of 90%.     

Energo-Mechanical Evaluation of Damage Growth and Fracture Initiation in Aviation Composite Structures

The aim of the present paper is to (1) highlight the results of laboratory damage detection and monitoring in the aviation composite materials, during a mechanical testing constituted of multiple loadings, and (2) obtain a detailed understanding of damage evolution of composite specimens with regard to impact energy. Woven 12-ply glass fiber and 16-ply carbon fiber–reinforced epoxy composites (GFRP 92 125/L285/287 and CFRP 98 131/L285/287) were used as less studied subjects in research. This study explored the resistance to cracking and delamination of glass and carbon fiber laminates with the same resin system under low-load conditions.     

The side effects of UV light stabilizer on properties of polypropylene based composite tape yarn

Initial consuming properties of polypropylene (PP) based composite tape yarns having different portions of ultraviolet (UV) light stabilizer are studied. In many cases, the samples with different portions of UV light stabilizer exhibit changes at level of initial properties, that is, the statistically significant side effects are obtained. When portion of the additive increases, the initial values of width, thickness and linear density of the modified samples are found to be reduced. The additions of UV light stabilizer also generate the statistically significant changes for the most tensile characteristics. The linear and second order polynomial equations are suggested to show the side effects on the properties. Some visual changes in morphology, that is, the differences in smoothness of the surfaces of the samples are also noticed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44400.     

Structural characterization of femtosecond laser modified regions inside sapphire

We report on structural characterization of sapphire photomodified by voids of sub-wavelength diameter surrounded by amorphised regions formed after exposure by tightly-focused femtosecond laser pulses of 800 nm wavelength and 150 fs duration at the single and double-pulse irradiation inside crystalline sapphire. Regrowth of a crystalline phase near the edge between the amorphous and crystalline phases was observed by transmission electron microscopy (TEM) in the case of double-pulse-irradiated locations. Regions patterned by single-pulse-induced voids inside sapphire were characterized by synchrotron X-ray diffraction (XRD) technique. The XRD patterns indicate presence of an expanded phase of the host crystal. The origin of structural changes observed in TEM and XRD is discussed and is consistent with fast thermal quenching.     

High Ion Conductive and Selective Membrane Achieved through Dual Ion Conducting Mechanisms

Conventional ion-selective membranes, that is ion-exchange and porous membranes, are unable to perform high conductivity and selectivity simultaneously due to the contradictions between their ion selecting and conducting mechanisms. In this work, a bifunctional ion-selective layer is developed via the combination of nanoporous boron nitride (PBN) and ion exchange groups from Nafion to achieve high ion conductivity through dual ion conducting mechanisms as well as high ion selectivity. A template-free method is adopted to synthesize flake-like PBN, which is further enmeshed with Nafion resin to form the bifunctional layer coated onto a porous polyetherimide membrane. The double-layer membrane exhibits excellent ion selectivity (1.49 × 10⁸ mS cm⁻³ min), which is 22 times greater than that of the pristine porous polyetherimide membrane, with outstanding ion conductivity (64 mS cm⁻¹). In a vanadium flow battery, the double-layer membrane achieves a high Coulombic efficiency of 97% and outstanding energy efficiency of 91% at 40 mA cm⁻² with a stable cycling performance for over 700 cycles at 100 mA cm⁻². PBN with ion exchange groups may therefore offer a potential solution to the limitation between ion selectivity and conductivity in ion-selective membranes.