Notched-tensile properties under high-pressure gaseous hydrogen: Comparison of pipeline steel X70 and austenitic stainless type 304L, 316L steels

The effect of high-pressure gaseous H₂ on the fracture behavior of pipeline steel X70 and austenitic stainless steel type 304L and 316L was investigated by means of notched-tensile tests at 10 MPa H₂ gas and various test speed. The notch tensile strength of pipeline X70 steel and austenitic stainless steels were degraded by gaseous H₂, and the deterioration was accompanied by noticeable changes in fracture morphology. The loss of notch tensile strength of type 316L and X70 steels was comparable, but type 304L was more susceptible to hydrogen embrittlement than the others. In the X70 steel, hydrogen embrittlement increased as test speed decreased until the test speed reached 1.2 × 10^?3 mm/s, but the effect of test speed was not significant in 304L and 316L steels.     

Surface modification of polyimide and polysulfone membranes by ion beam for gas separation

The surface carbonization of polyimide (PI) and polysulfone (PSf) by ion beam has been performed to adapt the carbon molecular sieve properties on the skin of the polymeric membranes without the deformation of the membrane structure. In order to control the structure of membrane skin and to improve gas transport properties, the irradiation conditions, such as the dosage and the source of ion beams, have been varied. The ideal separation factor of CO₂ over N₂ through the surface‐modified PI and PSf membranes increased threefold compared to those of the untreated, pristine membranes, whereas the permeability decreased with almost two orders of magnitude. This appears to be due to the fact that the structure of membrane skin has been changed to a barrier layer. The formation of barrier layer was confirmed by comparing the calculated values of a simple resistance model with the experimental results, and the estimated permeability of this barrier was 10⁻⁴ barrer. It was concluded that ion beam irradiation could provide a useful tool for improving selectivity for gas separation membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1554–1560, 2000     

An experimental study for qualifying hydrogen compatibility of austenitic stainless steel under low temperature

Journal of Mechanical Science and Technology - Hydrogen compatibility of materials refers to the ability to exhibit reliable mechanical integrity and a probability of failure in a given...     

Development of bandwidth-enhanced X–Ku band reflectarray antenna using a novel design strategy

This paper reports the development of a reflectarray (RA) antenna using overlapping tri-resonance phase distribution to produce enhanced bandwidth performance in X/Ku band frequencies. The RA with square aperture (24 cm) operating from 11 to 15.8 GHz is constructed using unit cells with concentric Malta cross and square ring developed on Diclad substrate isolated from the ground through a 2.5-mm air layer. Variation in the concentric element's size along with the length of the delay line connected to the square ring offers a 518° phase range. The distribution of the 529 RA elements is done using the phase variations observed at 12, 13, and 14 GHz. The optimized design of the proposed antenna offers a simulated peak gain of 27.43 dBi at 12 GHz and a 1-dB gain bandwidth of 38%. The experimental validation of the fabricated prototype exhibits a peak gain of 27.4 dBi at 12 GHz with a sidelobe level (SLL), and cross-polarization level less than −15.6 dB, and −28 dB respectively, and a 1-dB gain bandwidth of 37%. The enhanced performance characteristics of the proposed X/Ku wideband reflectarray antenna befit the uplink and downlink operations of fixed satellite services (FSS).     

High-Speed Operation of Electrochemical Logic Circuits Depending on 3D Construction of Transistor Architectures

The emergence of organic electrochemical transistors (OECTs) has opened a new era of printable electronics and bioelectronics, due to their unique advantages including innately superior transconductance and biocompatibility. Despite the foreseeable advancements available from their further implementations in fundamental logic circuitry, however, insufficient operation speeds and short compatibilities to scaling-down have so far hindered advanced integrations other than biosensing and biosignal amplifications. Here, a 3D-construction-dependent operational analysis of OECTs is reported, with which an all-vertical architectural design enabled unprecedentedly high operating speed and a facile expansion to large-area and high-density 3D crossbar arrays. A simple vertical channel architecture completed with solid-state Ag/AgCl top-gate electrodes enables an ultrafast redistribution of ions within channels, yielding a state-of-the-art operation frequency reaching 12 MHz V⁻¹. Various printed logic circuit arrays, including NOT, NAND, and NOR gates, with high stability and reproducibility.     

Direct Observation of Contact Reaction Induced Ion Migration and its Effect on Non-Ideal Charge Transport in Lead Triiodide Perovskite Field-Effect Transistors

The migration of ionic defects and electrochemical reactions with metal electrodes remains one of the most important research challenges for organometal halide perovskite optoelectronic devices. There is still a lack of understanding of how the formation of mobile ionic defects impact charge carrier transport and operational device stability, particularly in perovskite field-effect transistors (FETs), which tend to exhibit anomalous device characteristics. Here, the evolution of the n-type FET characteristics of one of the most widely studied materials, Cs_0.05FA_0.17MA_0.78PbI_3, is investigated during repeated measurement cycles as a function of different metal source–drain contacts and precursor stoichiometry. The channel current increases for high work function metals and decreases for low work function metals when multiple cycles of transfer characteristics are measured. The cycling behavior is also sensitive to the precursor stoichiometry. These metal/stoichiometry-dependent device non-idealities are correlated with the quenching of photoluminescence near the positively biased electrode. Based on elemental analysis using electron microscopy the observations can be understood by an n-type doping effect of metallic ions that are created by an electrochemical interaction at the metal–semiconductor interface and migrate into the channel. The findings improve the understanding of ion migration, contact reactions, and the origin of non-idealities in lead triiodide perovskite FETs.     

Recent Advances in Structural Design of Efficient Near-Infrared Light-Emitting Organic Small Molecules

Organic light-emitting materials in the near-infrared (NIR) region are important to realize next-generation lightweight and wearable applications in bioimaging, photodynamic therapy, and telecommunications. Inorganic and organometallic light-emitting materials are expensive and toxic; thus, the development of purely organic light-emitting materials is essential. However, the development of highly efficient NIR light-emitting materials made of organic materials is still in its infancy. Therefore, this review outlines molecular design strategies for developing organic small-molecule NIR light-emitting materials with high emission efficiency that can overcome the energy-gap law to be applied to next-generation wearable devices. After briefly reviewing the basic knowledge required for the NIR emission of organic molecules, representative high-efficiency molecules reported over the past 5 years are classified according to their core moieties, and their molecular design, physical properties, and luminescence characteristics are analyzed. Further, the perspective and outlook regarding the development of next-generation high-efficiency NIR organic light-emitting materials are provided.     

Numerical sensitivity analysis of temperature-dependent reaction rate constants for optimized thermal conversion of high-density plastic waste into combustible fuels

The use of experimental rate constants for producing a high yield of liquid fuels from the pyrolysis of plastic waste is not widely accepted owing to a lack of compatibility between the different kinetic rate constants responsible for successful conversion reactions. In R software, the Arrhenius law can forecast the ideal combination of reaction rate constants and frequency factors and then perform sensitivity analysis on individual rate constants to estimate the selectivity and quantity of primary pyrolysis products. Sensitivity analysis is a way of determining the effectiveness of individual rate constants in the reaction. This research element is currently lacking in the literature for the cost-effective valorization of plastics into combustible fuels. We are the first to use R software to perform sensitivity analysis on specific rate constants by reducing or raising their initial values to a point where maximum oil yield is attainable in the temperature range of 340–370°C. The primary focus was to save time and cost of extracting empirical rate constants from experiments to produce commercial-scale pyrolytic oil. The H-abstraction, chain fission, polymerization, and scission reactions were chosen due to the high availability of free radicals for maximum oil production. The oil recovery rate improved drastically to 90% at the end of processing time, while the number of by-products gradually decreased. The k8 rate constant driven reaction is the best-suited condition for industrial-scale pyrolysis of high-density plastics into liquid fuels, with 74% improvement in oil production and 14% improvement in light wax during sensitivity analysis.