Kinetic Insight on Improved Chemi-Resistive Response of Hydrothermal Synthesized Pt Loaded TiO2 Nano-rods Toward Vapor Phase Isopropanol

Flower like microstructure composed of eccentrically grown vertically aligned titania nano-rods is prepared through spherical carbon template mediated hydrothermal route. Mechanistic pathways for the growth of said esthetic architecture is proposed by studying their phase formation behavior and morphological features. Chemi-resistive type sensing properties of prepared titania flowers for the detection of isopropanol are studied by varying the sensor operating temperature (225–300°C) and vapor concentration (10–200 ppm). Distinguishable sensitivity of titania flowers is identified for the detection of even 10 ppm isopropanol. Catalytic amount of Pt nano-particles (synthesized through chemical method) are introduced over prepared flower like titania to improve further their sensitivity. The plausible isopropanol sensing mechanism over TiO2 flowers as well as influence of operating temperature and role of Pt nanoparticles as chemical sensitizer in enhancing the response is explained. The current response transients of both the TiO2 flowers and their Pt modified counterpart for detecting low concentration (10–50 ppm) of isopropanol are modeled in accordance to Langmuir-Hinshelwood reaction mechanism and the rate constants for the respective surface reactions are estimated. The higher rate constant for the interaction of isopropanol over titania flowers than Pt modified counterparts is explained using the concept of decaying depleted layer during sensing

Peptide-based gel in environmental remediation: removal of toxic organic dyes and hazardous Pb2+ and Cd2+ ions from wastewater and oil spill recovery

A dipeptide-based synthetic amphiphile bearing a myristyl chain has been found to form hydrogels in the pH range 6.9–8.5 and organogels in various organic solvents including petroleum ether, diesel, kerosene, and petrol. These organogels and hydrogels have been thoroughly studied and characterized by different techniques including high-resolution transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and rheology. It has been found that the xerogel obtained from the peptide gelator can trap various toxic organic dyes from wastewater efficiently. Moreover, the hydrogel has been used to remove toxic heavy metal ions Pb2+ and Cd2+ from wastewater. Dye adsorption kinetics has been studied, and it has been fitted by using the Freundlich isotherm equation. Interestingly, the gelator amphiphilic peptide gels fuel oil, kerosene, diesel, and petrol in a biphasic mixture of salt water and oil within a few seconds. This indicates that these gels not only may find application in oil spill recovery but also can be used to remove toxic organic dyes and hazardous toxic metal ions from wastewater. Moreover, the gelator can be recycled several times without significant loss of activity, suggesting the sustainability of this new gelator. This holds future promise for environmental remediation by using peptide-based gelators

Optimisation of machining parameters for hard machining: grey relational theory approach and ANOVA

The present paper deals with experimental investigations carried out for machinability study of hardened steel and to obtain optimum process parameters by grey relational analysis. An orthogonal array, grey relations, grey relational coefficients and analysis of variance (ANOVA) are applied to study the performance characteristics of machining process parameters such as cutting speed, feed, depth of cut and width of cut with consideration of multiple responses, i.e. volume of material removed, surface finish, tool wear and tool life. Tool wear patterns are measured using optical microscope and analysed using scanning electron microscope and X-ray diffraction technique. Chipping and adhesion are main causes of wear. The optimum process parameters are calculated for rough machining and finish machining using grey theory and results are compared with ANOVA

Force Prediction Model of Zirconia Toughened Alumina (ZTA) Inserts in Hard Turning of AISI 4340 Steel Using Response Surface Methodology

In the present study, an attempt has been made to investigate the effect of cutting parameters (cutting speed, feed and depth of cut) on machining forces (feed force, thrust force and cutting force) in finish hard turning of AISI 4340 steel using developed Zirconia Toughened Alumina (ZTA) insert prepared by powder metallurgy process route. The machining experiments were performed based on standard Response Surface Methodology (RSM) called Central Composite Design (CCD). The mathematical model of each forces have been developed using second order regression analysis. The adequacy of the models and influence of each operating factors have been carried out based on Analysis of Variance (ANOVA) techniques. It can be concluded from the present study that cutting speed and depth of cut have predominant effect on feed force whereas feed and depth of cut are the two most influencing factors for thrust force determination. But, in case of cutting force modeling, all the three parameters (feed rate, depth of cut and cutting speed) have significant effect. Key parameters and their effects on forces have also been presented in graphical contours which may help for choosing operating parameter preciously. Optimized model indicates 76.51% desirability level for economy in conventional machining process

Potential use of polyphenol oxidases (PPO) in the bioremediation of phenolic contaminants containing industrial wastewater

The present review emphasizes on the use of Polyphenol oxidase (PPO) enzyme in the bioremediation of phenolic contaminants from industrial wastewater. PPO is a group of enzyme that mainly exists in two forms; tyrosinase (E.C. 1.14.18.1) and laccase (E.C. 1.10.3.1) which are widely distributed among microorganisms, plants and animals. These oxidoreductive enzymes remain effective in a wide range of pH and temperature, particularly if they are immobilized on some carrier or matrices, and they can degrade a wide variety of mono and/or diphenolic compounds. However, high production costs inhibit the widespread use of these enzymes for remediation in industrial scale. Nevertheless, bench studies and field studies have shown enzymatic wastewater treatment to be feasible options for biodegradation of phenols through biological route. Nanomaterials-PPO conjugates have been also applied for removal of phenols which has successfully lower down the drawbacks of enzymatic water treatment. Therefore in this article various approaches and current state of use of PPO in the bioremediation of wastewater, as well as the benefits and disadvantages associated with the use of such enzymes have been overviewed

Improved efficiency of ZnO hierarchical particle based dye sensitized solar cell by incorporating thin passivation layer in photo-anode

Present article describes the DSSC performances of photo-anodes prepared using hydrothermal route derived ZnO particles having dissimilar morphologies i.e. simple micro-rod and nano-tips decorated micro-rod. The surface of nano-tips decorated micro-rod is uneven and patterned which facilitate more dye adsorption and better scattering of the incident light resulting superior photo-conversion efficiency (PCE) (η ~ 1.09%) than micro-rod ZnO (η ~ 0.86%). To further improve the efficiency of nano-tips decorated micro-rod ZnO based DSSC, thin passivation layer of ZnO is introduced in the corresponding photo-anode and a higher PCE (η ~ 1.29%) is achieved. The compact thin passivation layer here expedites the transportation of photo-excited electrons, restricts the undesired recombination reactions and prevents the direct contact of electrolyte with conducting substrates. Attempt is made to understand the effect of passivation layer on the transportation kinetics of photo-excited electrons by analyzing the electrochemical impedance spectra of the developed cells

Kinetic Insight on Improved Chemi-Resistive Response of Hydrothermal Synthesized Pt Loaded TiO2 Nano-rods Toward Vapor Phase Isopropanol

Flower like microstructure composed of eccentrically grown vertically aligned titania nano-rods is prepared through spherical carbon template mediated hydrothermal route. Mechanistic pathways for the growth of said esthetic architecture is proposed by studying their phase formation behavior and morphological features. Chemi-resistive type sensing properties of prepared titania flowers for the detection of isopropanol are studied by varying the sensor operating temperature (225–300°C) and vapor concentration (10–200 ppm). Distinguishable sensitivity of titania flowers is identified for the detection of even 10 ppm isopropanol. Catalytic amount of Pt nano-particles (synthesized through chemical method) are introduced over prepared flower like titania to improve further their sensitivity. The plausible isopropanol sensing mechanism over TiO2 flowers as well as influence of operating temperature and role of Pt nanoparticles as chemical sensitizer in enhancing the response is explained. The current response transients of both the TiO2 flowers and their Pt modified counterpart for detecting low concentration (10–50 ppm) of isopropanol are modeled in accordance to Langmuir-Hinshelwood reaction mechanism and the rate constants for the respective surface reactions are estimated. The higher rate constant for the interaction of isopropanol over titania flowers than Pt modified counterparts is explained using the concept of decaying depleted layer during sensing

Simultaneous Adsorption–Desorption Processes in the Conductance Transient of Anatase Titania for Sensing Ethanol: A Distinctive Feature with Kinetic Perception

A distinctive feature in the operating temperature-dependent conductance transients of titania sensor is identified during chemi-resistive type detection of ethanol vapor. Precisely, simultaneous adsorption of ethanol and desorption of the corresponding oxidized product over anatase titania sensor are reflected systematically in the response transients measured with the rise in operating temperature. An attempt is made here to understand the origin of the said feature based on the reaction sequences of ethanol over sensor surface. For a fixed ethanol concentration (200 ppm), the conductance transients obtained for response process are modeled using Langmuir–Hinshelwood reaction mechanism and the characteristic time constants are estimated for adsorption and desorption of ethanol. From the temperature variations of these characteristic time constants, the activation energies for the adsorption and desorption of ethanol over sensor surface is estimated. In addition, the general ethanol sensing characteristics (response %, response time, etc.) of the anatase titania is also reported by varying the ethanol concentration (50–500 ppm) and sensor operating temperature (275–375 °C)

Taguchi method and ANOVA: An approach for process parameters optimization ofhard machining while machining hardened steel

686-695In this paper, Taguchi method is applied to find optimum process parameters for end milling while hard machining of hardened steel. A L18 array, signal-to-noise ratio and analysis of variance (ANOVA) are applied to study performance characteristics of machining parameters (cutting speed, feed, depth of cut and width of cut) with consideration of surface finish and tool life.Chipping and adhesion are observed to be main causes of wear. Results obtained by Taguchi method match closely with ANOVA and cutting speed is most influencing parameter. Multiple regression equations are formulated for estimating predicted values of surface roughness and tool wear