Jobin K. Antony

Bio: Jobin K. Antony is an academic researcher from Rajagiri. The author has contributed to research in topics: Plasma & Laser ablation. The author has an hindex of 5, co-authored 18 publications receiving 86 citations. Previous affiliations of Jobin K. Antony include Indian Institute of Technology Madras.

Understanding the mechanism of nano-aluminum particle formation by wire explosion process using optical emission technique

Abstract: Nano-aluminum particles are produced by a wire explosion process in different inert gas ambience. It is observed that generated particles have different sizes and it follows log–normal probability distribution. The particle size produced by the wire explosion process varies depending on the thermal conductivity of the medium and the operating pressure of the gas. To understand the mechanism of nano-particle formation, the optical-emission spectroscopic technique is used for measuring characteristics of plasma generated during the wire explosion process. Strong emission lines were observed from the species formed during the wire explosion process. Plasma temperatures are estimated based on local thermal equilibrium principle and using Al emission lines. Plasma temperature of more than 8000 K is observed in an Ar ambient. The optical emission study clearly indicates that the intensity of plasma increases with an increase in the ambient pressure. Further, it is observed that an increase in the pressure of the gas, the plasma temperature also increases. The study shows that the plasma temperature in the He gas is lesser than in the Ar gas. The plasma temperature due to the discharge plays a significant role on nano-particle formation. In addition, it is observed that irrespective of polarity, emission characteristics are almost the same.

Single laser based dual-wavelength ablation technique for emission enhancement during LIBS

Abstract: In this paper, a novel method of the dual-wavelength (laser-induced breakdown spectroscopy LIBS) technique using a single laser system is proposed and demonstrated. Experiments are performed using a pulsed Nd3+ : YAG laser with a pair of 355–1064 nm and also with 532–1064 nm. The shorter wavelength laser is used for ablation and plasma formation, and the fundamental wavelength (1064 nm) is used for plasma re-excitation. The proposed dual-wavelength LIBS technique is used for lunar simulant samples under different ambient pressure conditions. Various characteristic parameters, such as the emission line-intensity enhancement, plasma temperature, lifetime and plasma area, are studied. Experimental studies clearly showed the emission line-intensity enhancement up to a factor of 3. Emission lifetime showed a longer sustained emission with an increase of up to 33% for the dual-wavelength approach. A theoretical simulation based on the hydrodynamic equations is also performed for dual-wavelength ablation and re-excitation. The estimated plasma temperature and ablation plume-front velocity clearly showed an increase in dual wavelength, which is in agreement with the experimental results.

Design and Simulation of a Micro Hotplate Using COMSOL Multiphysics for MEMS Based Gas Sensor

Abstract: Micro Hotplate (MHP) is one of the main components in micro-sensors, especially in gas sensors. A MHP should have low power consumption, low thermal mass and better temperature uniformity. The metal oxide gas sensors utilize the properties of surface adsorption to detect changes in resistance as a function of varying concentration of different gases. In order to detect to detect the resistive changes, the temperature must be in the requisite temperature range over the heater area. The sensitivity and response time of the sensor are dependent on the operating temperature of the MHP. Making proper design is of critical importance. In this paper, the geometric optimization of the heater structure to achieve high temperature uniformity by performing analysis using COMSOL Multiphysics 5.0, a Finite Element Analysis (FEA) package is done. Electro-Thermo-Mechanical(ETM) analysis is done to review the temperature and stress distribution over the MHP. Two dimensional structure of five different patterns of MHP, namely single Meander, double Meander, fan shape, rectangle shape, and porous structure are designed and simulations are done. Their temperature profiles are compared and porous structure is found to have low power consumption and better temperature uniformity. Three dimensional design and simulation of Meander and porous structures are also done and their temperature and displacement profiles are compared. The effect of various materials and thickness of heating element on the temperature, displacement, and power consumption of the MHP is evaluated. The porous structure is found to be best suitable for designing a gas sensor with high sensitivity and low power consumption. Then a gas sensor with high sensitivity is designed using this porous structure of MHP and ETM simulation is done.

Modeling of laser induced breakdown spectroscopy for very low-pressure conditions

Abstract: Laser Induced Breakdown Spectroscopy (LIBS) can be considered as a prominent technology for compositional analysis of materials in low-pressure space applications. In space applications, usually LIBS is conducted in a low-pressure environment and proper understanding of the plasma parameters is significant for any improvement in the system. A model is developed to describe the heating and subsequent melting, vaporization and ionization of a target material during LIBS process. A numerical model based on one-dimensional thermal conductivity equation is being used to simulate the target evaporation and a hydrodynamic model is used to simulate plume expansion. Further, an experimental approach of measuring spectral emission from the ablation plume using emission spectroscopy and estimating the plasma state, such as the ionization species, and average plasma temperature, is investigated. An important result of this work is that for different ambient conditions, laser ablation plume dynamics can be estimated.

Modified MAC unit for low power high speed DSP application using multipler with bypassing technique and optimized adders

Abstract: Braun multiplier is one of the parallel array multipliers, which is used for unsigned numbers multiplication. This paper aims at an optimization of power and delay of Braun multiplier by using bypassing technique and modification of adders. The dynamic power of a multiplier can be reduced by using bypassing techniques and delay can be reduced by replacing ripple carry adder in the last stage of full adders by optimized adders in different logics, Double pass transistor logic (DPL) and Transmission Gate (TG). Different logic style adders are designed and implemented in 0.13μm CMOS technology and its functional parameters are compared and the best result is incorporated in the column bypassed Braun multiplier. The new multiplier is used to implement a MAC unit which is more efficient.

Laser-induced breakdown spectroscopy.

Abstract: ■ CONTENTS General Information: Books, Reviews, and Conferences 640 Fundamentals 641 Interaction of Laser Beam with Matter 641 Factors Affecting Laser Ablation and LaserInduced Plasma Formation 642 Influence of Target on the Laser-Induced Plasmas 642 Influence of Laser Parameters on the LaserInduced Plasmas 643 Laser Wavelength (λ) 643 Laser Pulse Duration (τ) 643 Laser Pulse Energy (E) 645 Influence of Ambient Gas on the Laser-Induced Plasmas 645 LIBS Methods 647 Double Pulse LIBS 647 Femtosecond LIBS 651 Resonant LIBS 652 Ranging Approaches 652 Applications 654 Surface Inspection, Depth Profiling, and LIBS Imaging 654 Cultural Heritage 654 Industrial Analysis 655 Environmental Monitoring 656 Biomedical and Pharmaceutical Analysis 658 Security and Forensics 659 Analysis of Liquids and Submerged Solids 660 Space Exploration and Isotopic Analysis 662 Space Exploration 662 Isotopic Analysis 662 Conclusions and Future Outlook 663 Author Information 664 Corresponding Author 664 Notes 664 Biographies 664 Acknowledgments 664 References 664

Microhotplates for metal oxide semiconductor gas sensor applications—towards the CMOS-MEMS monolithic approach

Abstract: The recent development of the Internet of Things (IoT) in healthcare and indoor air quality monitoring expands the market for miniaturized gas sensors. Metal oxide gas sensors based on microhotplates fabricated with micro-electro-mechanical system (MEMS) technology dominate the market due to their balance in performance and cost. Integrating sensors with signal conditioning circuits on a single chip can significantly reduce the noise and package size. However, the fabrication process of MEMS sensors must be compatible with the complementary metal oxide semiconductor (CMOS) circuits, which imposes restrictions on the materials and design. In this paper, the sensing mechanism, design and operation of these sensors are reviewed, with focuses on the approaches towards performance improvement and CMOS compatibility.

Combustion of HTPB-Based Solid Fuels Loaded with Coated Nanoaluminum

Abstract: Nanoaluminum powder (nAl, nominal size of particles 50 nm and 100 nm), obtained by electrical explosion of wires, was passivated by air and coated by several different protective organic reagents to assess the effects on ballistics of nAl-loaded hydroxyl-terminated polybutadiene (HTPB)-based solid fuel with respect to pure HTPB baseline. The nAl samples were characterized by transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), and chemical analysis on active aluminum content (Al°) content and added to HTPB-based solid fuels for hybrid propulsion. Combustion tests were carried out burning central-perforated single-port cylindrical samples in a 2D radial burner. Data analysis was performed to obtain a continuous time-resolved regression rate. Coated nAl particles may significantly improve the ballistics of HTPB + nAl formulations burning in gaseous oxygen, with respect to pure HTPB. All investigated formulations with nAl exhibit increase of instantaneous regression rate (up to 89% maximum),...

Effect of self-absorption correction on LIBS measurements by calibration curve and artificial neural network

Abstract: In this paper, laser-induced breakdown spectroscopy (LIBS) technique is used for concentration prediction of six elements of Mn, Si, Cu, Fe, Zn, and Mg in seven Al samples by two approaches of artificial neural network (ANN) and standard calibration curve. ANN is utilized as a new technique for determination and classification of various materials and elements in LIBS method. In this study, a few spectra of six aluminum standards with known concentrations are used for training of ANN. It should be noted that the mentioned network is not on trial and error basis, but it is a self-organized network. Calibration curve method, which is implemented in represented paper, determines certain relation between concentration and intensity. Then, the calibration curve and ANN methods obtained by six samples are used for prediction of the elements of the seventh standard sample in order to check the accuracy of these methods and make a comparison. In both approaches, a self-absorption correction is applied for high concentrations species and an improvement in prediction of two methods is seen. Results illustrate that at high concentrations except for Si, ANN shows a better prediction with a lower relative error compared to calibration curve approach after self-absorption correction. Primitive study without any self-absorption correction shows that ANN and calibration curve predictions with the best result are related to Fe with R 2 = 0.99 % having the minimum errors.

Enhancement of laser-induced Fe plasma spectroscopy with dual-wavelength femtosecond double-pulse

Abstract: In this paper, we propose and demonstrate a study of Fe plasma using collinear dual-wavelength femtosecond double-pulse laser-induced breakdown spectroscopy (LIBS) with a fundamental wavelength (800 nm) and a second harmonic wavelength (400 nm) from Ti:sapphire laser. By varying the time separation of the dual-wavelength femtosecond double-pulse, the experimental results clearly show the signal enhancement up to a factor of 10 and more than 10 times, in comparison with it at 0 ps time separation. The electron temperature and electron density are analyzed as the basic parameters of plasma properties, and they are respectively based on the theory of Boltzmann plot and Stark broadening. It proves that dual-wavelength femtosecond double-pulse LIBS is excellent for enhancing the emission intensity of the signal.