The aim of this article is to investigate the sensing performance of NO gas molecule on the graphene nanoribbon domain for the determination of structural and electronic properties. Effect of an ...alkali metal (lithium) and a transition metal (iron) on the armchair oriented graphene nanoribbon (ArGNR) surface for the sensing purpose of NO gas has been performed through the quantum mechanics based Density Functional Theory (DFT) calculations. Various configurations of ArGNR doped with Li and Fe atoms such as one-edge doped, center doped, both-edge doped Li-ArGNR and Fe-ArGNR have been simulated, and a detailed comparative study of lithium and iron doping on different configurations of ArGNRs for the adsorption energy, stability analysis, band gap analysis and density of states analysis has been quantitatively evaluated. By comparing the adsorption energy of NO, it is found that Li doping enhances the strength of NO adsorption on the different variants of ArGNR. Computational results predict that the undoped ArGNR is insensitive to the NO gas adsorption with adsorption energy of about −0.41 eV. Our results determine that substitutional doping of Li doping at one edge doped and both-edge doped position increases the adsorption abilities of ArGNRs in these configurations with adsorption energies of approximately −6.92 eV and −9.64 eV that is 16 and 23 times greater than the pristine ArGNR (Pr-ArGNR). Band nature for both type of doping estimates the changing behavior of ArGNRs from semiconductor to metallic transition after the adsorption of NO molecule. It is concluded that the Li doping at one edge and both edge position of ArGNR makes it an excellent potential sensing material for the sensing purpose of NO gas as compared to the Fe doped configurations.
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•ArGNR sensor materials doped with lithium and iron are investigated for NO adsorption using DFT calculation.•Sensitivity of materials was enhanced by doping of ArGNR with lithium and iron atoms.•Lithium doping provides more active sites for the adsorption phenomenon.•Lithium doped materials at one-edge and both-edge have higher adsorption energies and more charge transfer.•Adsorption energies for one-edge and both-edge doped lithium increased upto 16 and 23 times greater than pristine ArGNR.
Tensile tests were performed on specimens in normalised and tempered condition at temperatures ranging from 300 to 873K and at four strain rates in the range 6.33×10−5 to 6.33×10−3s−1 to examine ...serrated flow behaviour in 9Cr–1Mo ferritic steel. At all strain rates, the steel exhibited different types of serrations namely type A, B and C serrations at intermediate temperatures, and the nature and type of serrations were strongly dependent on temperature and applied strain rate. Serrations were observed only after a specimen was deformed beyond a critical plastic strain. Critical strain for type A and A+B serrations decreases with increase in temperature and decrease in strain rate. Inverse temperature dependence of critical strain for type C serrations was observed. The activation energy of 86kJmol−1 obtained for serrated flow suggested that diffusion of an interstitial solute such as carbon is responsible for dynamic strain ageing in 9Cr–1Mo steel.
Tertiary creep behaviour of 9Cr–1Mo ferritic steel Choudhary, B.K.
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
11/2013, Letnik:
585
Journal Article
Recenzirano
The paper presents tertiary creep behaviour of thick section 9Cr–1Mo ferritic steel forging at 793 and 873K. The stress dependence of rupture life obeyed power law. The steel exhibited distinct low ...and high stress regimes characterised by separate values of power law exponent and constant in the creep rate–rupture life relationships of Monkman–Grant type. Extensive tertiary creep in terms of both the large time spent and the large creep strain accumulation during tertiary creep has been observed. The prolonged tertiary creep was associated with the high and distinct values of creep damage tolerance factors in the low and high stress regimes indicating dominance of microstructural degradation in the steel. Separate master creep curves have been obtained for low and high stress regimes in the coupled relationship for creep deformation and damage that depends only on creep damage tolerance factor envisaged in the continuum damage mechanics approach.
This article covers the molecular structure optimization and spectroscopic studies, such as Raman, UV–Vis absorption and FTIR, carried out for novel, biodegradable and biocompatible chitosan-graphene ...oxide (CS-GO) polymer nanocomposites (PNCs), which were synthesized by using simple blending technique followed by ultrasonification treatment. In addition, the structural and electrical properties have also been investigated. Under molecular structure optimization, the structural geometry, electronic structure (HOMO and LUMO) and potential distribution have been computed. X-ray diffraction of PNCs reveals that the crystallized phase of GO dominates over the CS giving modification in crystallite size and presence of micro-strain. FTIR and Raman spectroscopic studies have been carried out to confirm the proper formation of PNCs and presence of functional group in the composites. The surface morphology has been studied with the help of FESEM to confirm proper dispersion of GO sheets. Optical absorption edge and band gap analyzed from UV–Vis analysis reveal the semiconducting nature of PNCs. In addition, the optical band gap is tuned by varying the content of GO in PNCs. This tuning in band gap has also been supported by XRD and computational results. The dielectric constant and dc conductivity are found increased with increasing content of GO in PNCs. Additionally, the I–V characteristics of PNCs shows Ohmic type conduction with rising in current due to incorporation of GO. In view of the results achieved, the usage of CS-GO PNC is suitable for future development of optical and Gas sensors and UV-detectors, and therefore, such composite may be proven as a potential and suitable candidate for the optoelectronic or electrical devices operating at high frequencies.
Tensile tests were performed at a wide range of strain rates (3.16×10−5−3.16×10−3s−1) and temperatures (300–1123K) to examine serrated flow behaviour, an important manifestation of dynamic strain ...ageing (DSA), in type 316L(N) austenitic stainless steel. The steel exhibited distinct low and high temperature serrated flow regimes separated by a retardation bay. Based on the activation energy value of 115kJmol−1, diffusion of interstitial carbon has been suggested to be responsible for serrated flow in the low temperature regime. In the high temperature regime, an average activation energy value of 206kJmol−1 obtained using different methods indicated that diffusion of substitutional chromium atom is responsible for DSA. Disappearance of serrations at high temperatures has been ascribed to the effects associated with precipitation reaction between chromium and carbon atoms. The influence of nitrogen retarding DSA in type 316L(N) stainless steel has been discussed.
Tensile tests were performed at strain rates ranging from 3.16 × 10
−5
to 3.16 × 10
−3
s
−1
over the temperatures ranging from 300 K to 1123 K (27 °C to 850 °C) to examine the effects of temperature ...and strain rate on tensile deformation and fracture behavior of nitrogen-alloyed low carbon grade type 316L(N) austenitic stainless steel. The variations of flow stress/strength values, work hardening rate, and tensile ductility with respect to temperature exhibited distinct three temperature regimes. The steel exhibited distinct low- and high-temperature serrated flow regimes and anomalous variations in terms of plateaus/peaks in flow stress/strength values and work hardening rate, negative strain rate sensitivity, and ductility minima at intermediate temperatures. The fracture mode remained transgranular. At high temperatures, the dominance of dynamic recovery is reflected in the rapid decrease in flow stress/strength values, work hardening rate, and increase in ductility with the increasing temperature and the decreasing strain rate.
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Tensile deformation behaviour of body centred cubic (BCC) iron nanowires with initial orientation of 〈100〉/{100} has been investigated using molecular dynamics (MD) simulations. MD ...simulations were performed at 10K employing a strain rate of 1×108s−1 for the nanowires with cross section width (d) ranging from 1.42 to 24.27nm. BCC Fe nanowires exhibited two different behaviours as a function of size. Young’s modulus, and yield and flow stresses decreased rapidly with increase in nanowire size up to 11.42nm followed by gradual decrease approaching towards saturation at larger size. The〈100〉/{100} nanowires up to 11.42nm size deform by twinning at low strains and undergo twinning mediated reorientation to〈110〉/{112} configuration. The reoriented nanowires deform by slip mode at high strains resulting in high ductility and failure by necking. Beyond 11.42nm size, the reorientation mechanism ceases to operate and the nanowires deform only by twinning exhibiting low ductility and failure by cleavage. The size dependent deformation behaviour has been discussed in terms of the number of active slip systems operating during deformation in Fe nanowires.
In our experiments 30 hypoglycaemic medicinal plants (known and less known) have been selected for thorough studies from indigenous folk medicines, Ayurvedic, Unani and Siddha systems of medicines. ...In all the experiments with different herbal samples (vacuum dried 95% ethanolic extracts), definite blood glucose lowering effect within 2 weeks have been confirmed in alloxan diabetic albino rats. Blood glucose values are brought down close to normal fasting level using herbal samples at a dose of 250 mg/kg once, twice or thrice daily, as needed. While evaluating comparative hypoglycaemic activity of the experimental herbal samples, significant blood glucose lowering activities are observed in decreasing order in the following 24 samples—
Coccinia indica,
Tragia involucrata,
G. sylvestre,
Pterocarpus marsupium,
T. foenum-graecum,
Moringa oleifera,
Eugenia jambolana,
Tinospora cordifolia,
Swertia chirayita,
Momordica charantia,
Ficus glomerata,
Ficus benghalensis,
Vinca rosea,
Premna integrifolia,
Mucuna prurita,
Terminalia bellirica,
Sesbenia aegyptiaca,
Azadirachta indica,
Dendrocalamus hamiltonii,
Zingiber officinale,
Aegle marmelos,
Cinnamomum tamala,
Trichosanthes cucumerina and
Ocimum sanctum. Present studies besides confirming hypoglycaemic activities of the experimental herbal samples, help identify more potent indigenous hypoglycaemic herbs (in crude ethanolic extract) from the comparative study of the reported experimental results.
Creep deformation and fracture behaviour of indigenously developed modified 9Cr–1Mo steel for steam generator (SG) tube application has been examined at 823, 848 and 873
K. Creep tests were performed ...on flat creep specimens machined from normalised and tempered SG tubes at stresses ranging from 125 to 275
MPa. The stress dependence of minimum creep rate obeyed Norton’s power law. Similarly, the rupture life dependence on stress obeyed a power law. The fracture mode remained transgranular at all test conditions examined. The analysis of creep data indicated that the steel obey Monkman–Grant and modified Monkman–Grant relationships and display high creep damage tolerance factor. The tertiary creep was examined in terms of the variations of time to onset of tertiary creep with rupture life, and a recently proposed concept of time to reach Monkman–Grant ductility, and its relationship with rupture life that depends only on damage tolerance factor. SG tube steel exhibited creep-rupture strength comparable to those reported in literature and specified in the nuclear design code RCC-MR.
Tensile deformation behaviour of 〈110〉/{111} oriented body centred cubic (BCC) iron nanowires has been examined using molecular dynamics (MD) simulations at 10K. MD simulations were performed on ...nanowires with cross section width in the range 1.42–24.27nm. The results indicated that the deformation behaviour in BCC Fe nanowires is governed by full dislocation slip irrespective of nanowire size. The initiation of plastic deformation occurred by the collective emission of dislocation loops originating from the corner of the nanowires. Following yielding, accumulation of straight screw dislocations with increasing plastic deformation has been observed. Presence of curved slip steps observed in the surface morphology suggested the occurrence of cross slip in large size nanowires. Evidence of cross slip was not noticed in small size nanowires. The variations of Young’s modulus, yield strength and flow stress with nanowire size displaying strong size effects in BCC Fe nanowires have been presented.
