Optical fiber coated Zinc Oxide (ZnO) nanorods decorated with Palladium (Pd) for hydrogen sensing

A novel hydrogen (H-2) sensor was developed using acid-etched optical fiber coated with zinc oxide (ZnO) nanorods. The sensing performance was done by comparing the acid-etched fiber coated with ZnO nanorods with and without decorated Palladium (Pd). The conventional optical single-mode fiber (SMF) with a diameter of 125 mu m has been modified as a transducing platform by etching it to 11 mu m diameter using hydrofluoric acid (HF) to enhance the evanescent field of the light propagates in the fiber core. The etched fiber was coated with ZnO nanorods via hydrothermal process by using seeding and growth solution method. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. Catalyst Palladium (Pd) was sputtered onto the ZnO nanorods to improve H-2 detection. The developed sensor operating temperature was found to be 150 degrees C that produces 6.36 dBm increase in response towards the 1% concentration of H-2 in synthetic air. It was then tested with different concentration of H-2. The sensor decorated with Pd has better performance in sensing compared to non-decorated Pd based on the output power versus time. The sensor best response and recovery times is 6 and 5 min respectively, for acid-etched optical fiber coated with ZnO nanorods decorated with Pd for 0.75% of H-2 concentrations at 150 degrees C. The results indicate the optical fiber sensor might improve the performance towards H-2 as oppose to the conventional electrical sensor

Single-mode fiber coated with zinc oxide (ZnO) nanorods for H2 gas sensor applications

A Hydrogen (H2) gas sensor was successfully developed using optical fiber coated with Zinc Oxide (ZnO) nanorods. The single-mode fiber (SMF) used as a sensing device has been prepared by etching the SMF fiber and coated with ZnO nanorods. The etching of the fiber was performed using hydrofluoric acid (HF) to enhance the evanescent field around the fiber core. The ZnO nanorods were prepared by hydrothermal method through seeding and growth solution technique. The diameter of cladding and core are 125 μm and 8 μm, respectively, before etching and goes down to 11μm after etching. Around 2 cm of ZnO nanorods were coated in the middle of the etched fiber. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. The developed sensor's response and recovery time were observed to be 7 min and 3 min, respectively, for a low concentration of 0.25% H2 gas. The aim of this study is to understand the gas sensing properties towards the spectral intensity variations in etched optical fiber coated with ZnO nanorods

Impulse response and electric field computation of various rod electrodes

Ionisation process has been known to occur in soil, when earth electrodes are subjected under high impulse conditions. In this paper, experimental results on impulse response of various earth electrodes, namely a conventional copper rod electrode, and three steel rods which had been in a form of solid, hollow and hollow with stamping of star shaped, is presented. Impulse tests were performed for a range of voltage magnitudes up to 300 kV. Computation of electric field is carried out with Finite Element Method (FEM) to obtain its profile, and determine the electric field values produced for each rod electrodes and peak currents. Experimental results show that little difference in its impulse resistance with increasing current magnitudes in these electrodes, which could be due to the critical electric value, Ec of the soil, and electric field of the rod electrode, which balances up its ionisation levels

Investigations on the Performance of Various Horizontal Ground Electrodes

Experimental work on grounding systems has shown that the characteristics of grounding systems under high impulse conditions are different than those obtained at steady-state conditions. Investigations on the grounding systems under high impulse conditions make it evident that ionization process could occur in soil, due to field enhancement in air voids in the soil. This process can lead to an ionization zone that reduces the impulse resistance of grounding systems (due to an enlargement of a virtually increased cross-sectional area) from its steady state. There have been many studies pointing towards the effect of various soils and the ground electrode’s arrangement on the reduction of impulse resistance from its steady state, and its decrease with increasing currents. It was, however, noted that very few studies on the effect of the configurations of horizontal ground electrodes have been performed by field measurements before. This work presents the experimental and simulated work of various configurations of ground electrodes, with spikes which are thought to enhance the ionization process in soil. In this paper, field measurement was set up, and the results of field measurements were applied with finite element method (FEM) to obtain the electric field values. It was demonstrated that with the addition of spike on the electrodes, a high electric field was computed. The time to peak current, discharged time and impulse impedance were also analyzed for various horizontal ground electrodes

Effect of high resistivity soil under high impulse currents

In this paper, experimental test results of several ground electrodes surrounded with gravelly soil medium subjected to high impulse currents were studied, to investigate the effect of confined soil surround electrodes. Ground resistance measurements were performed at low magnitude of voltage and current, where the results are compared to the impulse characteristics of ground electrodes. This paper shows a significant difference in the RDCvalues and impulse characteristics of ground electrodes when gravelly soil medium surrounded the ground electrode in comparison to the electrodes installed in natural soil. This indicates that the confined soil around the electrode has a major effect on the performance of ground electrodes, whether at steady state or under high impulse conditions. Equivalent circuit for each tested electrode was developed with personal simulation program with integrated circuit emphasis (PSPICE), where the effect of inductance was seen in the electrodes surrounded with gravelly soi

Investigations on the Performance of Grounding Device with Spike Rods (GDSR) with the Effects of Soil Resistivity and Configurations

In a recently published work, the characteristics of a new grounding device with spike rods (GDSR) with various arrangements of ground electrodes under high magnitude impulse currents (up to 16 kA), was investigated. In an earlier study, the ground electrodes were installed in low resistivity test media, with resistance at steady state (Rdc) values ranging from 11 Ω to 75 Ω. In practice, various soil resistivity, ranging from a few Ohm-metres to several kiloOhm-metres, have been reported in the standards. It is, therefore, necessary to investigate the characteristics of GDSR with different arrangements of ground electrodes in various soil resistivities under high impulse currents. In this present paper, six configurations of ground electrodes are used, installed at three different sites and subjected to high impulse conditions. Impulse test data of all the grounding systems are analyzed. The Finite Element Method (FEM) is used to compute the electric field values of the ground electrodes achieved. It is found that the highest electric field occurs in the presence of electrodes with the highest Rdc, soil resistivity and current magnitudes. This new data would be useful in bolstering the performance of GDSR in various types of soil resistivities, electrode arrangements and current magnitudes, which may allow for optimum design of grounding systems

Single-mode fiber coated with zinc oxide (ZnO) nanorods for H gas sensor applications

A Hydrogen (H2) gas sensor was successfully developed using optical fiber coated with Zinc Oxide (ZnO) nanorods. The single-mode fiber (SMF) used as a sensing device has been prepared by etching the SMF fiber and coated with ZnO nanorods. The etching of the fiber was performed using hydrofluoric acid (HF) to enhance the evanescent field around the fiber core. The ZnO nanorods were prepared by hydrothermal method through seeding and growth solution technique. The diameter of cladding and core are 125 µm and 8 µm, respectively, before etching and goes down to 11 µm after etching. Around 2 cm of ZnO nanorods were coated in the middle of the etched fiber. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. The developed sensor’s response and recovery time were observed to be 7 min and 3 min, respectively, for a low concentration of 0.25% H2 gas. The aim of this study is to understand the gas sensing properties towards the spectral intensity variations in etched optical fiber coated with ZnO nanorods. Keywords—hydrogen sensor; fiber-optic sensor; ZnO nanorods; hydrothermal metho