arXiv subjects

Jagannath Devkota

Publications and source records attributed to Jagannath Devkota.

5 recordsLinked to original sources

arXiv2023

A Disposable Soft Magnetic Ribbon Based Sensor for Corrosion Monitoring

We present a new approach for real-time monitoring of chemical corrosion based on the radio-frequency (RF) impedance technology and soft ferromagnetic ribbons. The impedance (Z) of a commercial magnetic ribbon was measured in real time for 5 mul of drop-casted HNO3 of various concentrations. Variations in the concentration of the drop-casted acid were assessed by considering the difference in Z with and without the acid treatment. We found a large and linear increase in deltaZ and a large linear decrease in measurement time with the acid concentration, which are ideal for developing disposable chemical sensors for strength estimation of corrosive chemicals and for monitoring of a time-dependent chemical corrosion process. Since the ribbon used is commercially available at low cost and the measurement system is quick and low power consuming, the proposed sensor can be used as an easy, quick, and low-cost chemical probe in industries and environmental hazard management purposes.

physics.app-ph↗

arXiv2020

An 860 MHz Wireless Surface Acoustic Wave Sensor with a Metal-Organic Framework Sensing Layer for CO2 and CH4

Wireless and passive surface acoustic wave (SAW) devices with nanoporous metal-organic framework (MOF) sensing layers are attractive gas sensors for applications in many fields such as energy industries and air pollution control. Here, we report on enhancing the sensitivity and detection limit of zeolitic imidazolate framework-8 (ZIF-8) MOF-coated SAW reflective delay line mass sensors by increasing the operating frequency for sensitive detection of carbon dioxide (CO2) and methane (CH4) at ambient conditions. In particular, we show at least four times higher sensitivity of an 860 MHz (4-μm periodicity) SAW reflective delay line coated with a 240 nm thick ZIF-8 compared to the sensitivity of a 430 MHz (8-μm periodicity) otherwise identical sensor device to the targeted gases. The detection limits of the higher frequency wireless devices for CO2 and CH4 were estimated to be 0.91 vol-% and 7.01 vol-%, respectively. The enhanced sensitivity for higher frequency devices is explained in terms of the frequency dependent acoustic wave energy confinement.

physics.app-ph↗

arXiv2019

Study on Sub monolayer Epitaxy Growth under Anisotropic Detachment

We have performed Kinetic Monte Carlo simulation to study the effect of diffusion anisotropy and bonding anisotropy on island formation at different temperatures during the sub-monolayer film growth in Molecular Beam Epitaxy. We use simple cubic solid on solid model and event based Bortz, Kalos and Labowitch (BKL) algorithm on Kinetic Monte Carlo method to simulate the physical phenomena. We have found that surface anisotropy has no significant role on island elongation however it influences on the island morphology, growth exponent and island size distribution. Elongated islands were obtained when bonding anisotropy was included.

cond-mat.mtrl-sci↗

arXiv2019

Effects of substrate anisotropy and edge diffusion on submonolayer growth during molecular beam epitaxy: A Kinetic Monte Carlo study

We have performed Kinetic Monte Carlo simulation work to study the effect of diffusion anisotropy, bonding anisotropy and edge diffusion on island formation at different temperatures during the sub-monolayer film growth in Molecular Beam Epitaxy. We use simple cubic solid on solid model and event based Bortz, Kalos and Labowitch (BKL) algorithm on the Kinetic Monte Carlo method to simulate the physical phenomena. We have found that the island morphology and growth exponent are found to be influenced by substrate anisotropy as well as edge diffusion, however they do not play a significant role in island elongation. The growth exponent and island size distribution are observed to be influenced by substrate anisotropy but are negligibly influenced by edge diffusion. We have found fractal islands when edge diffusion is excluded and compact islands when edge diffusion is included.

cond-mat.mtrl-sci↗

arXiv2018

Zeolitic imidazolate framework-coated acoustic sensors for room temperature detection of carbon dioxide and methane

Integration of nanoporous materials such as metal organic frameworks (MOFs) with sensitive transducers can result robust sensing platforms for monitoring gases and chemical vapors for a range of applications. Here, we report on an integration of the zeolitic imidazolate framework-8 (ZIF-8) MOF with surface acoustic wave (SAW) and thickness shear mode quartz crystal microbalance (QCM) devices to monitor carbon dioxide(CO2)and methane (CH4) at ambient conditions. The MOF was directly coated on the custom fabricated Y-Z LiNbO3 SAW delay lines (operating frequency,f0 = 436 MHz)and AT-cut Quartz TSM resonators (resonant frequency, f0 = 9 MHz) and the devices were tested for various gases in N2 at ambient condition. The devices were able to detect the changes in CO2 or CH4 concentrations with relatively higher sensitivity to CO2, which was due to its higher adsorption potential and heavier molecular weight. The sensors showed full reversibility and repeatability which were attributed to the physisorption of the gases into the MOF and high stability of the devices. Both types of the sensors showed linear responses relative to changes in the binary gas compositions thereby allowing to construct calibration curves which correlated well with the expected mass changes in the sorbent layer based on mixed-gas gravimetric adsorption isotherms measured on bulk samples.For 200 nm thick films, the SAW sensitivity to CO2 and CH4 were 1.44x10^-6/vol-%, respectivel yagainst the QCM sensitivities 0.24x10^-6/vol-% and 1x10^-8/vol-%,respectively which were evaluated as the fractional change in the signal. The SAW sensors were also evaluated for 100 nm - 300 nm thick films, the sensitivities of which were found to increase with the thickness due to the increased number of pores for adsorption of larger amount of gases. Also, the SAW devices had a good wireless response for detecting gases remotely.

physics.app-ph↗