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The magnesium hydride (MH)-doped carbon nanotubes (CNTs) are studied by density functional theory (DFT). MH is doped at three different sites of CNTs and the corresponding binding energies have been calculated. The hydrogen adsorption binding energies on these structures have been determined. The binding energy of adsorption for third and fourth H2molecule addition is exactly nearer to the applicable target, for achieving room temperature kinetics. The H site on CNT is the effective site for MH doping compared to other sites. The storage capacity of H2molecules, when five H2molecules are adsorbed on MH is 1.6wt%. It is shown that MH doped at various sites of CNT can be used as a good hydrogen storage medium at ambient temperatures. [ABSTRACT FROM PUBLISHER]

Al-decorated, single-walled carbon nanotube has been investigated for hydrogen storage applications by using Density Functional Theory (DFT) based calculations. Single Al atom-decorated on (8,0) CNT adsorbs upto six H2 molecules with a binding energy of 0.201 eV/H2. Uniform decoration of Al atom is considered for hydrogen adsorption. The first Al atom has a binding energy of 1.98 eV on (8,0) CNT and it decreases to 1.33 eV/Al and 0.922 eV/Al respectively, when the number of Al atoms is increased to four and eight. Each Al atom in (8,0) CNT-8Al adsorbs four H2 molecules, without clustering of Al atoms, and the storage capacity reaches to 6.15 wt%. This gravimetric storage capacity is higher than the revised 2015 target of U.S Department of Energy (DOE). The average adsorption binding energy of H2 in (8,0) CNT-8(Al+4H2), i.e. 0.214 eV/H2, lies between 0.20 and 0.60 eV/H2 which is required for adsorbing and desorbing H2 molecules at near ambient conditions. Thus, Al-decorated (8,0) CNT is proposed as a good hydrogen storage medium which could be useful for onboard automobile applications, at near ambient conditions. [ABSTRACT FROM AUTHOR]

Abstract: Lithium decoration is an effective strategy for improving the hydrogen adsorption binding energy and the storage capacity in carbon nanostructures. Here, it is shown that Li-decorated double carbon vacancy graphene (DVG) can be used as an efficient hydrogen storage medium by means of Density Functional Theory (DFT) based calculations. The Li binding energy in DVG is 4.04 eV, which is much higher than that of pristine graphene. A maximum of four hydrogen molecules adsorb on Li decorated on one side of DVG and this leads to a gravimetric storage capacity of 3.89 wt% with an average adsorption binding energy of 0.23 eV/H2. When Li is decorated on both sides of DVG, the gravimetric storage capacity reaches 7.26 wt% with a binding energy of 0.26 eV/H2 which shows that desorption would take place at ambient conditions. [Copyright &y& Elsevier]

Abstract: Adsorption binding energies have been calculated for Nickel-doped single-walled carbon nanotubes (CNTs). Density Functional Theory (DFT) with double numerical polarization (DNP) has been used for finding the total energies of the structures. It is found that the Nickel doped CNTs show fluctuation in the binding energies of hydrogen adsorption which is overcome by passivating the Nickel atom with two hydrogen atoms. The density of states (DOS) and Mullikan atomic charge analysis have been carried to confirm the charge transfer from Ni to the carbon atoms of the CNT. The smallest CNT (diameter ≈ 4 Å) with the chirality of (5,0) has been taken for hydrogen adsorption studies. Geometry optimization shows that Ni atom prefers bridge site rather than the centre of the hexagon. The H2 binding energies obtained in the present study reveal that desorption would take place above room temperature in Ni doped (5,0) CNTs. [Copyright &y& Elsevier]

Abstract: We present a density functional theory (DFT) study on the hydrogen storage capacity of (5,5) arm-chair single walled carbon nanotubes (SWCNTs) functionalized with magnesium hydride (MgH2). Being lightweight and rich in hydrogen, MgH2 adsorbs H2 molecules in the vicinity of carbon nanotubes. The H2 molecules are adsorbed dissociatively on SWCNT + MgH2 complex. The H–H distance gets increased by more than ten times of the initial bond length 0.74 Å of the H2 molecule. The hydrogen storage capacity of three configurations namely C1MgH2, C5MgH2 and C10MgH2 is reported. The density of states is computed for all the systems. The average binding energies of C5MgH2 and C10MgH2 when H2 molecule is adsorbed are 1.86 eV/H2 and 1.96 eV/H2, which are approximately equal. Thus, increasing the number of MgH2 molecule does not vary the binding energy of H2 adsorption. The corresponding temperature, in which desorption will take place, is 2285 K and 2457 K for C5MgH2 and C10MgH2 systems respectively, which are much above the room temperature. [Copyright &y& Elsevier]

The phase structure and magnetic behavior of sputter deposited and annealed Ni–Mn–Ga thin films of varying thickness have been studied. The as-deposited films exhibited quasi-amorphous structure having paramagnetic nature at room temperature. After annealing at 873 K for 30 min ferromagnetic ordering is recovered and the quasi-amorphous structure has changed to nanocrystalline structure. At low film thickness (<300 nm), the annealed films exhibited a mixture of cubic austenite (L2 1 ) and martensite phases while at thickness greater than 1000 nm ordered L1 2 phase was observed. The magnetic properties were found to strongly depend on the structure of the constituent phases in the films. [ABSTRACT FROM AUTHOR]

Ferromagnetic shape memory alloy (FSMA) is one of the smart materials which finds increasing industrial applications. This paper deals with the effect of Mn substitution for Ga on martensitic and magnetic transformation temperature of polycrystalline Ni-Mn-Ga alloy prepared in argon atmosphere. The prepared alloy has been characterized by means of scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and superconducting quantum interference device (SQUID). Magnetic property of alloy has been analyzed with vibrating sample magnetometer (VSM). From the VSM measurement, it is studied that the saturation magnetization of polycrystalline ferromagnetic shape memory occurs at high magnetic field. The main finding of this article is the raise in transformation temperature by 28 K/atom. As the working temperature is above room temperature, it seems to be a promising candidate for practical applications. The result reported here may help for further research in the field of polycrystalline Ni-Mn-Ga alloy. [ABSTRACT FROM AUTHOR]

Abstract: Ni–Mn–Ga nanoparticles were prepared by ball milling technique. X-ray diffraction pattern of the milled powders has a broad peak near the location of the prominent peak for the Heusler phase of Ni2MnGa, indicating very disordered structures with small particle sizes. Structural properties of milled Ni–Mn–Ga particles recover to those of the bulk state after appropriate annealing temperature. It is worth noting that particles with size above 50nm exhibit martensitic transformation. The average internal stress was calculated to be 2.83–1.13MPa stored in the distorted lattice. Saturation magnetization of the milled sample increases with annealing temperature due to re-crystallization and grain growth. [ABSTRACT FROM AUTHOR]

Abstract: Aim of this paper is to study the transformation temperature of Ni–Mn–Ga single crystals by using differential scanning calorimetry. It shows that martensitic temperature abruptly increase with increasing Mn concentration whereas Curie transition to decrease. The calculated value of electron-to-atom ratio (e/a) reveal that it increases with increased doping of Mn in place of Ga at fixed Ni content. The crystal structures at room temperature were studied using XRD pattern. Thermo-magnetic behavior of the Ni–Mn–Ga alloy shows the ferromagnetic nature and its behaviour is slightly losing due to antiferromagnetic ordering of excess Mn atoms. Microstructure from SEM image confirm that the alloys are martensitic plates. The martensitic plates contain fewer stripes like magnetic domains. [Copyright &y& Elsevier]

The structure and the magnetic transitions have been investigated as a function of Mn in stoichiometric Ni2MnGa heusler alloys. Particular attention is paid to examine the linear increase of martensite transformation temperature on substituting Mn for Ga. It is observed that the martensite temperature increases and Curie temperature decreases with the effect of Mn content. Room-temperature magnetic measurements show the composition-dependent characteristics with decreasing magnetic saturation values and increasing coercivity values due to decrease in the magnetic exchange interaction strength with increasing Mn in place of Ga. The scanning electron microscopy image confirms that the Mn-rich alloys have the martensitic plates. [ABSTRACT FROM AUTHOR]

A new experimental set up to measure acoustic attenuation in ferromagnetic shape memory alloy and composites was designed and built. Acoustic attenuation in polyurethane (PU) polymer composites with Ni-Mn-Ga particulate fillers have been reported which exhibits greater vibration absorption than polymer/magnetostrictive composites due to the rearrangement of twin variants in Ni-Mn-Ga particles. Amplitude stress wave has been analysed for three different test samples. Above the low frequency, the acoustic attenuation is gradually decreased from PU to Ni-Mn-Ga/PU. The Ni-Mn-Ga/PU polymer composite is shown to be ideal for applications that require absorption of mechanical energy. [ABSTRACT FROM AUTHOR]

A series of a tetradentate N 2 O 2 Schiff base ligands (1a-e), [N,N′-(X)bis(salicylidene)1,2-phenylenediamine], salphens {where X = H (1a), Cl (1b), Br (1c), CH 3 (1d), OCH 3 (1e)} were synthesized from condensation of substituted salicylaldehydes with 1,2-phenylenediamine and nickel(II) complexes(2a-e) from corresponding Schiff base ligands(1a-e). The stoichiometric ratios of the prepared ligands (1a-e) and their Ni(II)-salphen complexes (2a-e) were structurally characterized by various analytical and spectroscopic techniques such as 1H NMR, FT-IR, mass, UV‐–visible, PXRD, magnetic moments and molar conductivity measurements. These results suggest that Ni(II)-salphen complexes (2a-e) have square planar geometry. The molar conductivity measurements indicate that all complexes (2a-e) are non-electrolytes. Density Functional Theory (DFT) calculations have been used to investigate the optimized structure and chemical reactivity of these Ni(II) complexes(2a-e) from their Frontier Molecular Orbitals (FMO). The binding capabilities of the Ni(II) Schiff base complexes (2a-e) with Bovine Serum Albumin (BSA) have been studied through electronic absorption, fluorescence and cyclic voltammetric methods. Further the nature of interaction of Ni(II) complexes (2a-e) towards BSA were confirmed using molecular docking analyses. All these results demonstrated that the Ni(II) complexes 2d and 2e have better binding affinity towards BSA among all the Ni(II) complexes. The antimicrobial studies reveal that the Ni(II)-salphen complexes (2a-e) have higher inhibitory effect than ligands (1a-e) against the selected pathogenic microorganisms. Furthermore, in vitro cytotoxicity of ligands (1a-e) and Ni(II) complexes(2a-e) were evaluated by MTT assay against MCF-7. The observed IC 50 values against MCF-7 cell lines suggest that Ni(II) complexes(2a-e) show more significant anticancer activity than their corresponding ligands(1a-e). It is explored that complexes 2d and 2e bearing electron donating groups have greater anticancer potency. Comparison of our results with cisplatin, Zn(II)-salphen and V(IV)-salphen complexes indicated that Ni(II)-salphen complexes can be considered as the potential candidates for use as effective anticancer agent in future. Unlabelled Image • DFT calculations optimize the molecular structure of synthesized Ni(II) complexes. • Ni(II) complexes 2d and 2e have strongest BSA binding affinity than other complexes. • Ni(II)-salphen complexes (2a-e) have significant biological activity. • Ni(II) complexes with electron donating groups have greater cytotoxicity against MCF7. • Significant cytotoxicity of 2e may propose it as promising anticancer agent in future. [ABSTRACT FROM AUTHOR]