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Al 6061 alloy is widely used for commercial applications in the transportation

Layered two-dimensional transition metal dichalcogenides, due to their semiconducting nature and large surface-to-volume ratio, have created their own niche in the field of gas sensing. Their large recovery time and accompanied incomplete recovery result in inferior sensing properties. Here, we report a composite-based strategy to overcome these issues. In this study, we report a facile double-step synthesis of a MoS 2 /SnO 2 composite and its successful use as a superior room-temperature ammonia sensor. Contrary to the pristine nanosheet-based sensors, the devices made using the composite display superior gas sensing characteristics with faster response. Specifically, at room temperature (30° C), the composite-based sensor exhibited excellent sensitivity (10%) at an ammonia concentration down to 0.4 ppm along with the response and recovery times of 2 and 10 s, respectively. Moreover, the device also exhibited long-term durability, reproducibility, and selectivity toward ammonia against hydrogen sulfide, methanol, ethanol, benzene, acetone, and formaldehyde. Sensor devices made on quartz and alumina substrates with different roughnesses have yielded almost an identical response, except for slight variations in response and recovery transients. Further, to shed light on the underlying adsorption energetics and selectivity, density functional theory simulations were employed. The improved response and enhanced selectivity of the composite were explicitly discussed in terms of adsorption energy. Lowdin charge analysis was performed to understand the charge transfer mechanism between NH 3 , H 2 S, CH 3 OH, HCHO, and the underlying MoS 2 /SnO 2 composite surface. The long-term durability of the sensor was evident from the stable response curves even after 2 months. These results indicate that hydrothermally synthesized MoS 2 /SnO 2 composite-based gas sensors can be used as a promising sensing material for monitoring ammonia gas in real fields.

Mathematical models for tracking the melting of cored wire during its injection into the steel bath have been developed in the past though important aspects of the formulations have not been discussed in sufficient detail. As a result, it is difficult to use the results of these models to derive benefits for a specific steel melting shop.A general purpose mathematical model has been developed at R & D, Tata Steel, using the finite difference approach with a fully implicit scheme to simulate the process of cored wire injection taking into account the different operating practices encountered in the steel shop. Numerical simulation of this kind of problem, involving moving boundary, typically suffers from the limitation that the progressive solidification of frozen layers that takes place is not made part of the thermal balance till it attains the size of a full node and thus the heat gained or lost by this "partial node" is not accounted for till such time. An alternative numerical formulation has been developed to rectify this.Owing to the difficulty in making a direct validation, this model has been verified through a novel approach. This work suggests that the use of different wire dimensions (13-18 mm diameter and 0.4-0.6 mm casing), depending on the steel grades to be processed, is necessary in order to extract the maximum benefit.KEY WORDS: mathematical model; steelmaking; calcium treatment; cored wire; injection metallurgy; deoxidation; alloy addition.

As a typical volatile organic compound (VOC), N,N-dimethylformamide (DMF) is a popular solvent and tracer for environmental air quality monitoring. Highly selective detection with low electrical noise, quick response/recovery times, and superior sensitivity at room temperature against VOCs, especially at the parts per billion (ppb) level, continues to be a significant challenge in gas-sensing applications. To address the issue, herein we demonstrate an MoSe2/multiwalled carbon nanotube composite based chemiresitor sensor for the detection of DMF. MoSe2 with a layered sheetlike structure supports MWCNTs to enhance the specific surface area, thereby increasing the sensitivity (down to 0.1 ppm for DMF) and selectivity and improving the response over a wider range of relative humidities (30–80%). The composite-based sensor shows good sensitivity (12.3% for 5 ppm of DMF), better selectivity, and faster response (65 s) and recovery (90 s) times in comparison to the MoSe2 sensor (192, 392 s), respectively, and a consistent response over 35 days. Density functional theory simulations were employed to understand the adsorption process and sensing mechanism. An analysis revealed a negative adsorption energy of −716 meV, implying that the adsorption process is spontaneous and exothermic. Further, charge transfer (0.013 e) using the Bader scheme confirms the process to be physisorption in nature. The results were further supported using an electrochemical impedance spectroscopy analysis. These results indicate the great potential of the composite for selective and stable sensing of DMF over a wider range of relative humidities. The present work suggests that a composite of MoSe2 with MWCNTs could be useful to design DMF sensors with improved sensitivity and selectivity under various environmental conditions.