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Search Results: 1 - 10 of 316801 matches for " K. N. Mohana "
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Corrosion Behavior and Adsorption Thermodynamics of Some Schiff Bases on Mild Steel Corrosion in Industrial Water Medium
S. S. Shivakumar,K. N. Mohana
International Journal of Corrosion , 2013, DOI: 10.1155/2013/543204
Abstract: The inhibition performance and adsorption behavior of (E)-2-(3-nitrobenzylidene) hydrazine carbothioamide (SB1) and (E)-2-(4-(dimethylamino) benzylidene) hydrazine carbothioamide (SB2) on mild steel corrosion in industrial water medium have been investigated by gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results revealed that inhibition efficiency depends on both the concentration of the inhibitors and temperature of the system. Increasing temperature reduces the inhibition efficiency of both inhibitors. Polarization studies indicated that these compounds behave as mixed type of inhibitors. The adsorption of both inhibitors was spontaneous and followed Langmuir adsorption isotherm. Thermodynamic parameters are calculated and discussed. The relation between inhibition efficiency and molecular structures of SB1 and SB2 was discussed by considering quantum chemical parameters. The surface adsorbed film was characterized by scanning electron microscopy (SEM). 1. Introduction Mild steel (MS) is the widely used material in the fabrication of heating and cooling water system in many industries. Therefore, study of corrosion inhibition of mild steel in industrial water medium is a subject of technological importance. Organic compounds which are extensively used in several industries as corrosion inhibitors in various environments [1–3]. The anticorrosive property of these inhibitors depends on the specific interaction between certain functional groups in the inhibitors with the active centers on the metal surface [4–7]. Hetero atoms such as nitrogen, oxygen, and sulphur present in the inhibitors play an important role in this interaction by donating lone pair of electrons [8–12]. Hence the organic compounds containing these hetero atoms and multiple bonds behave as efficient corrosion inhibitors due to the availability of π-electrons for interaction with the metal surface [13]. The compounds containing an azo methine group (–C=N–) in their skeleton (Schiff bases) are the best examples for this type of corrosion inhibitors. They can be synthesized by condensation of primary amines with carbonyl compounds [14]. Schiff bases were reported as effective corrosion inhibitors for mild steel, copper, and aluminum in various media [15–24]. Although most of the commercial corrosion inhibitors are synthesized by using aldehydes and amines as main components, usually these Schiff bases possess more inhibition efficiency than their constituent carbonyls and amines [25, 26]. The higher inhibition efficiencies of
Inhibition Behaviour of Some Isonicotinic Acid Hydrazides on the Corrosion of Mild Steel in Hydrochloric Acid Solution
M. P. Chakravarthy,K. N. Mohana
International Journal of Corrosion , 2013, DOI: 10.1155/2013/854781
Abstract: New corrosion inhibitors, namely, isonicotinic acid (1H-indol-3-yl-methylene)hydrazide (INIMH) and isonicotinic acid (1H-pyrrol-2-yl-methylene)hydrazide (INPMH), have been synthesized, and their inhibitive characteristics for the corrosion of mild steel in 0.5?M HCl were investigated by mass loss and electrochemical techniques. The structures of the synthesized compounds were confirmed using spectral studies. Potentiodynamic polarization studies revealed that the investigated inhibitors are of mixed type. Various thermodynamic parameters were evaluated. Langmuir adsorption isotherm was found to be the best description for both inhibitors. FTIR spectra, energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were performed to characterize the passive film on the metal surface. 1. Introduction Mild steel is the most important engineering material particularly for structural, instrumental, industrial, and automobile applications. Corrosion problem occurs in these industries and can cause disastrous damage to metal and alloy structures causing economic consequences in terms of repair, replacement, and product losses. Pickling is a treatment on metallic surfaces in order to remove tightly adherent oxide films, stains, rust, or scale resulting from hot forming, heat treating, welding, and other high temperature operations [1]. The two acids commonly used in pickling are hydrochloric acid or sulphuric acid or it may be a combination of acids and may also contain nitric or hydrofluoric acids. Once the acid is rinsed out, the freshly cleaned steel will be very prone to oxidation (corrode) unless we apply a corrosion inhibitor of some type [2]. Therefore, a wide variety of corrosion inhibitors ranging from rare earth elements [3, 4] to organic compounds [5–8] have been used. The use of inhibitors is one of the practical methods for preventing corrosion of mild steel especially in acid media [9]. Inhibitors protect the metal by adsorbing on the surface and retard metal corrosion in aggressive environment. Selection of an appropriate inhibitor for specific environment and metal is of great importance. Generally, the heterocyclic organic compounds having higher basicity and electron density on the heteroatoms like oxygen, nitrogen, and sulphur have a tendency to resist corrosion [10, 11]. It has been known that efficient inhibitors should possess plentiful pi-electrons and unshared electron pairs on either nitrogen atoms or sulfur atoms of the inhibitors to the d-orbital of iron. The adsorption characteristics of organic molecules are also
Adsorption and Corrosion Inhibition Characteristics of Some Nicotinamide Derivatives on Mild Steel in Hydrochloric Acid Solution
M. P. Chakravarthy,K. N. Mohana
ISRN Corrosion , 2014, DOI: 10.1155/2014/687276
Abstract: The present investigation includes the study of corrosion inhibition effect of N-(1H-Indol-3-ylmethylene)-nicotinamide (IMN) and N-(3,4,5-trimethoxy-benzylidene)-nicotinamide (TMN) on mild steel in 0.5?M HCl by mass loss and electrochemical measurements. The obtained results showed that inhibition efficiency increased with the increasing concentration of inhibitors and decreased with increase in temperature and immersion time. Potentiodynamic polarization curves indicate that both IMN and TMN were acting as mixed type of inhibitors. Langmuir adsorption isotherm model was employed to determine the equilibrium of adsorption for inhibiting process in both inhibitors. Nyquist plots revealed that, as the concentration of the inhibitors increases, double layer capacitance ( ) and corrosion current ( ) decreases, while polarization resistance ( ) increases. Various thermodynamic parameters for the adsorption of inhibitors on mild steel were computed and discussed. The passive film formed on the metal surface was characterized by FTIR, EDX, and SEM. 1. Introduction Mild steel (MS) is cheap, strong, stiff, and widely used engineering material because of its good mechanical properties. It is the most important structural material exposed to outdoor conditions especially in acidic media [1] where corrosion is considerably more severe. Because of the general aggressiveness of acid solutions, inhibitors are commonly used to reduce the corrosive attack on metallic materials [2, 3]. Therefore, selection of an appropriate inhibitor ranging from rare earth elements [4] to organic compounds [5–8] for specific environment and metal is of great importance. In other words, the efficiency of these compounds is attributed to their steric factors, functional groups, lone pairs of electrons present on the hetero atoms, and pi-orbital character of donating electrons which determine the type of interaction between organic molecules and the metallic surfaces. The presence of corrosion inhibitors in a little amount blocks the corrosion sites and enhances the adsorption process, thereby increasing the life time of the metallic materials [9, 10]. A review of the literature reveals that the applicability of organic compounds as corrosion inhibitors for MS in acidic media has been recognized for a long time. A large number of organic compounds, particularly those containing nitrogen, oxygen, or sulphur in a conjugated system, are known to be applied as inhibitors to control acid corrosion of iron and steel. The inhibition process has been shown to occur via inhibitor adsorption, and
Fabrication of Curcumin Encapsulated Chitosan-PVA Silver Nanocomposite Films for Improved Antimicrobial Activity  [PDF]
K. Vimala, Murali Mohan Yallapu, K. Varaprasad, N. Narayana Reddy, S. Ravindra, N. Sudhakar Naidu, K. Mohana Raju
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.21008
Abstract: The present study explores the in situ fabrication of chitosan-poly(vinyl alcohol)-silver nanocomposite films in view of their increasing applications as antimicrobial packaging, wound dressing and antibacterial materials. The reduction of silver ions into silver nanoparticles (AgNPs) is achieved in acidic solution of chitosan (C) and poly (vinyl alcohol) (PVA) using their functional groups (-OH, -COOH, -NH2 groups). The presence of silver nanoparticles in the chito-san-PVA film is confirmed by UV-Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and X-ray Dif-fraction (XRD) analysis. The Scanning Electron Microscopic (SEM) images illustrate the presence of embedded silver nanoparticles throughout the films. In addition, the formed silver nanoparticles have an average particle size of ~ 16.5 nm as observed by Transmission Electron Microscopy (TEM). The anti-microbial and anti-fungal activity of the chitosan-PVA silver nanoparticle films have demonstrated significant effects against Escherichia coli (E. coli), Pseudomonas, Staphylococcus, Micrococcus, Candida albicans, and Pseudomonas aeruginosa (P. aeruginosa). To improve further their therapeutic efficacy as anti-microbial agents, curcumin encapsulated chitosan-PVA silver nanocomposite films are developed which showed enormous growth inhibition of E. coli compared to curcumin and chitosan-PVA silver nanoparticles film alone. Therefore, the present study clearly provides novel antimicrobial films which are potentially useful in preventing/treating infections.
Determination of Quantum Yield for the Photochemical Decomposition of Dichloramine-B and Dibromamine-B in Aqueous Acetic Acid Medium
K. N. Mohana,N. Prasad,P. M. Ramadas Bhandarkar
Journal of Chemistry , 2007, DOI: 10.1155/2007/413836
Gabapentinium picrate
Hongqi Li,H. S. Yathirajan,L. Mallesha,K. N. Mohana
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809008952
Abstract: The title compound {systematic name: [1-(carboxymethyl)cyclohexyl]methanaminium 2,4,6-trinitrophenolate}, C9H18NO2+·C6H2N3O7 , was synthesized from picric acid and gabapentin. The crystal packing is stabilized by intramolecular N—H...O=N and N—H...O—Ph hydrogen bonds. An O—H...O interaction is also present.
Optimal Power Flow Using Firefly Algorithm with Unified Power Flow Controller  [PDF]
T. Hariharan, K. Mohana Sundaram
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.78168
Abstract: Firefly algorithm is the new intelligent algorithm used for all complex engineering optimization problems. Power system has many complex optimization problems one of which is the optimal power flow (OPF). Basically, it is minimizing optimization problem and subjected to many complex objective functions and constraints. Hence, firefly algorithm is used to solve OPF in this paper. The aim of the firefly is to optimize the control variables, namely generated real power, voltage magnitude and tap setting of transformers. Flexible AC Transmission system (FACTS) devices may used in the power system to improve the quality of the power supply and to reduce the cost of the generation. FACTS devices are classified into series, shunt, shunt-series and series-series connected devices. Unified power flow controller (UPFC) is shunt-series type device that posses all capabilities to control real, reactive powers, voltage and reactance of the connected line in the power system. Hence, UPFC is included in the considered IEEE 30 bus for the OPF solution.
Voltammetric Behaviour and Analysis of Fluchloralin
K. Balaji,C. Sridevi,N. Ananda Kumar Reddy,K. Mohana Muni Sidda Reddy
Journal of Chemistry , 2010, DOI: 10.1155/2010/419705
Barrier Inhomogeneity and Electrical Properties of InN Nanodots/Si Heterojunction Diodes
Mahesh Kumar,Basanta Roul,Thirumaleshwara N. Bhat,Mohana K. Rajpalke,A. T. Kalghatgi,S. B. Krupanidhi
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/189731
Abstract: The electrical transport behavior of indium nitride nanodot-silicon (InN ND-Si) heterostructure Schottky diodes is reported here, which have been fabricated by plasma-assisted molecular beam epitaxy. InN ND structures were grown on a 20?nm InN buffer layer on Si substrates. These dots were found to be single crystalline and grown along [0 0 0 1] direction. Temperature-dependent current density-voltage plots ( ) reveal that the ideality factor ( ) and Schottky barrier height (SBH) ( ) are temperature dependent. The incorrect values of the Richardson constant ( ) produced suggest an inhomogeneous barrier. Descriptions of the experimental results were explained by using two models. First one is barrier height inhomogeneities (BHIs) model, in which considering an effective area of the inhomogeneous contact provided a procedure for a correct determination of . The Richardson constant is extracted ~110?A cm?2 K?2 using the BHI model and that is in very good agreement with the theoretical value of 112?A cm?2 K?2. The second model uses Gaussian statistics and by this, mean barrier height and were found to be 0.69?eV and 113?A cm?2 K?2, respectively. 1. Introduction Group III nitrides represent a material class with promising electronic and optical properties [1]. Among these, InN possesses the lowest effective mass, the highest mobility, narrow band gap of 0.7–0.9?eV and the highest saturation velocity [2, 3], which make this an attractive material for applications in solar cells, terahertz emitters, and detectors [4–6]. Good quality InN layers are difficult to grow because of the low dissociation temperature of InN and the lack of an appropriate substrate [7, 8]. The above constraints lead to the formation of dislocations and strain in the grown epitaxial layers resulting in the degradation of the device performance. Grandal et al. [9] reported that defect- and strain-free InN nanocolumns of very high crystal quality can be grown by molecular beam epitaxy (MBE) with and without buffer layer on silicon substrates. Since silicon is the most sought semiconductor material, it is very important to understand the transport mechanism of InN nanostructure-based devices and their behavior at different temperatures prior to their adoption in the fabrication of optoelectronic devices. In the present study, InN nanodot (ND) structures were grown on Si substrates using an InN buffer layer by plasma-assisted MBE. The interfaces of the semiconductor heterostructures are important part of semiconductor electronic and optoelectronic devices. One of the most interesting
Study of InN nanorods growth mechanism using ultrathin Au layer by plasma-assisted MBE on Si(111)
Mahesh Kumar,Mohana K. Rajpalke,Basanta Roul,Thirumaleshwara N. Bhat,S. B. Krupanidhi
Applied Nanoscience , 2013, DOI: 10.1007/s13204-012-0176-7
Abstract: InN nanorods (NRs) were grown on Si(111) substrate by plasma-assisted molecular beam epitaxy. The growth of InN NRs has been demonstrated using an electron-beam evaporated (~2 nm) Au layer prior to the initiation of growth. The structure and morphology of as deposited Au film, annealed at 600 °C, and InN NRs were investigated using X-ray photoelectron spectroscopy and scanning electron microscopy. Chemical characterization was performed with energy dispersive X-ray analysis. Single-crystalline wurtzite structure of InN NRs is verified by transmission electron microscopy. The formation process of NRs is investigated and a qualitative mechanism is proposed.
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