Search

The crystallization behavior and mechanical properties of melt-spun (Al 90 Fe 5 Ce 5 ) 100−x Ti x (x = 0, 4, 8 and 12 at.%) alloys have been investigated. The amorphous phase seems to be stable up to x = 8. The crystallization products for the amorphous alloys with x = 0–8 mainly composed of fcc-Al and icosahedral phases in the glassy matrix. The load dependent hardness behavior of amorphous alloys with and without Ti addition has been studied. The hardness value of the amorphous alloys has been found to be 3.72 and 3.07 GPa for x = 0 and 8 at 100 g load respectively. The annealed ribbons have higher hardness and strength as compared to that of as-synthesized ribbons. The enhanced values of hardness of the (Al 90 Fe 5 Ce 5 ) 100−x Ti x (x = 0, 4 and 8) alloys are attributed to the combined effects of icosahedral nanoparticles and Al nanoparticles in amorphous matrix. The absence of cracks around the indentation area up to 500 g of load for amorphous alloys suggests better capability to resist crack propagation in comparison to the annealed alloys. The formation of shear bands around the indentation periphery has been observed. The number of visible shear bands for the as-synthesized ribbons is higher in comparison to those of annealed ribbons. The values of yield strength and Meyer exponent of these alloys are also compared.

This study deals with the effect of controlled crystallization of melt spun Ce 75 Al 25 − x Ga x (x = 0, 2, 4 and 6 at.%) and Ce 60 Cu 25 Al 15 − x Ga x (x = 0, 1, 2 and 4 at.%) metallic glasses on the formation of nano-composites. It has been found that the substitution of Ga significantly affects the devitrification behavior of these alloys. The Ce 75 Al 25 − x Ga x alloys with x = 0 shows the formation of hexagonal phase (AlCe 3 type) while the alloys with x ≥ 2 give rise to the formation of tetragonal phase (Al 2 CeGa 2 type). Contrary to this, for the Ce 60 Cu 25 Al 15 − x Ga x alloys, hexagonal phase of AlCeCu type for x = 0 transforms to hexagonal phase of Al 2 Cu 3 Ce type for x ≥ 1. The indentation behavior of nano-composites permitted us to understand the nature of microhardness, yield strength and strain hardening constant. They are compared for the above two alloy systems. The load dependent hardness values of annealed ribbons of Ce 75 Al 19 Ga 6 and Ce 60 Cu 25 Al 13 Ga 2 alloys have been found to be ~ 2.80 GPa and ~ 2.96 GPa, respectively. The absence of cracks around the indentation area up to 200 g of load for Ce 60 Cu 25 Al 15 − x Ga x alloys suggests better capability to resist crack propagation in comparison to Ce 75 Al 25 − x Ga x alloys. Latter display cracks at 200 g load. The formation of shear bands around the periphery of the indenter has been observed. The number of visible shear bands in a given area for the Ce 75 Al 25 − x Ga x alloys is higher in comparison to those of Ce 60 Cu 25 Al 15 − x Ga x alloys. The values of yield strength and Meyer exponent of these alloys are also compared.

The substitution of Ga in Ce 75 Al 25 − x Ga x (x = 0 and 4 at.%) metallic glasses (MGs) has led to phase separation giving rise to nano-amorphous domains in a glassy matrix. The CeL 3 -edge XAS spectra for x = 4 has shown appearance of 4f 0 delocalized states. The temperature coefficient of resistance (TCR) becomes higher with addition of Ga. The magnetic field tuned magnetoresistance (MR) transition from positive to negative values has been observed for the first time with Ga substitution. These changes in the transport properties have been discussed in terms of formation of nano-amorphous domains and its link with 4f electrons for Ce atoms.

The present report describes the catalytic activity of mechanically activated nano quasicrystalline Al65Cu20Fe15 and related nano crystalline Al50Cu28Fe22 for the synthesis of carbon nanotubes (CNTs). CNTs are synthesized by catalytic decomposition of ethanol through nano quasicrystalline Al65Cu20Fe15 and related crystalline Al50Cu28Fe22 alloys as a catalyst. The synthesized multi-walled CNTs exhibits tube diameter ranging from 5 to 25 nm. The synthesized CNTs are characterized by scanning and transmission electron microscopy. It is found that Al65Cu20Fe15 nanoquasicystal shows better catalytic behaviour as compared to nano-crystalline Al50Cu28Fe22 alloys for decomposition of ethanol during the synthesis of multi-walled CNTs.

The present communication deals with the hydrogen storage performance of ambient pressure dried pristine as well as platinum doped carbon aerogel (CA-0.10 Pt). These carbon aerogels (CAs) have been prepared from resorcinol-formaldehyde (R–F) through sol–gel synthesis route with sodium carbonate as a catalyst (C). The synthesis parameters adapted led to the formation of CA having preponderance of submicropores. Structural and microstructural characteristics of these carbon aerogels have been investigated through XRD, SEM, TEM, nitrogen adsorption and Raman spectroscopic techniques. Nitrogen adsorption and TEM studies confirm the large density of micropores with the majority of pores having sizes between 0.30 and 1.46 nm (submicropores). The hydrogen storage characteristics of as synthesized carbon aerogels have been investigated by monitoring the hydrogen ad/desorption curves. At room temperature and at pressure upto 22 atm the CA and CA-0.1 Pt have hydrogen storage capacity of 0.40 wt.% and 0.33 wt.% respectively. However, under the same pressure but at liquid nitrogen temperature CA and CA-0.10 Pt have hydrogen storage capacity of 5.65 wt.% and 5.15 wt.%. Feasible reasons for the high hydrogen storage capacities at liquid nitrogen temperature for the present CAs have been put forward.

Graphene decorated with Fe clusters is proposed to be a possible alternative catalyst for the hydrogenation and dehydrogenation reactions of MgH2. In particular, graphene decorated with Fe clusters is effective for both hydrogenation and dehydrogenation processes of MgH2. The change in enthalpy and entropy values of hydrogen absorption determined for MgH2 with 5 wt% graphene decorated with Fe clusters is −50.4 ± 2.9 kJ per mole of H2 and 99.8 ± 5.2 J K−1 per mole of H2, respectively. This is significantly lower than those for well-established metal catalysts and nano-interfacial confined MgH2. Moreover, the graphene decorated with Fe clusters facilitates the fast rehydrogenation kinetics of MgH2, which reabsorbed 90% of the total reabsorption capacity in less than 4 minutes at 300 °C and 20 atm. In addition, TEM analysis reveals that MgH2 particles are covered by graphene with Fe clusters, resulting in the reduction of grain growth. Density functional theory shows that the defects in graphene act as the active sites for the dehydrogenation of MgH2, while the Fe clusters reduce the adsorption of dissociated H atoms, resulting in low-temperature dehydrogenation. Thus, graphene decorated with metal clusters could open up a new way of designing a new type of catalyst which could replace transition metal catalysts.

Herein, we demonstrated the synthesis of a hollow cylinder with a new architecture of up to several centimeters in diameter and several centimeters long and having ∼100 μm wall thickness. The hollow carbon cylinder was formed by radially aligned CNTs. These CNTs were grown on ferrocene derived Fe nanoparticles deposited throughout the inner wall of the quartz growth tube. This new ingenious carbon architecture was grown by a customized spray pyrolysis method. Furthermore, we also synthesized such carbon hollow cylinders using different precursor concentrations (ferrocene:benzene), different phases and microstructures to evaluate their EMI shielding effectiveness. The structural and microstructural characterizations of these hollow carbon cylinders comprising radially aligned CNTs were examined through various techniques, including XRD, Raman, FTIR, XPS, SEM, TEM, and HRTEM spectroscopy. Furthermore, the magnetic measurements (M–H) were performed for such structures to probe the magnetic properties of these carbon hollow cylinders for different concentrations. Furthermore, the EMI shielding through different concentrations of Fe bearing CNTs were explored in detail for tailoring the desired shielding effectiveness value for possible potential applications. Hence, our synthesis method provides a unique architecture for promising next generation building blocks in the form of carbon hollow cylinders made up of radially aligned CNTs over the conventional randomly oriented CNTs. This could be directly used to make it as a co-axial cover for electrical cables to protect them from EMI pollutants.

The present investigation describes the hydrogen sorption (de/absorption) behavior of MgH2 catalyzed by graphene sheet templated Fe3O4 nanoparticles (Fe3O4@GS). Hydrogen sorption studies reveal that MgH2 catalyzed by Fe3O4@GS (MgH2:Fe3O4@GS) offers improved hydrogen storage behavior as compared to stand-alone MgH2 catalyzed by graphene sheets (GS) (MgH2:GS) or Fe3O4 nanoparticles (MgH2:Fe3O4). The MgH2:Fe3O4@GS has an onset desorption temperature of ∼262 °C (∼142 °C lower than pristine MgH2), while MgH2:GS and MgH2:Fe3O4 have onset desorption temperatures of ∼275 °C and ∼298 °C respectively. In contrast to this, MgH2:GS absorbs 4.40 wt% and MgH2:Fe3O4 absorbs 5.50 wt% in 2.50 minutes at 290 °C under 15 atm hydrogen pressure. On the other hand, MgH2:Fe3O4@GS absorbs 6.20 wt% hydrogen in 2.50 minutes (which is considerably higher than recently studied catalyzed MgH2 systems) under identical temperature and pressure conditions. The MgH2 catalyzed with Fe3O4@GS shows negligible degradation of the storage capacity even after 25 cycles. Additionally, the desorption activation energy for MgH2:Fe3O4@GS has been found to be 90.53 kJ mol−1 (which is considerably lower as compared to metal/metal oxide catalyzed MgH2 and fluorographene catalyzed MgH2). The formation enthalpy for MgH2:Fe3O4@GS is 60.62 kJ per mole of H2 (13.44 kJ mol−1 lower than bulk MgH2). The catalytic effect of Fe3O4@GS has been described and discussed with the help of structural (X-ray diffraction (XRD)), micro structural (electron microscopy) and Raman spectroscopic studies.

We have investigated the structural and magnetic phase transitions in Sr doped polycrystalline Tb0.55Sr0.45MnO3, using temperature-dependent high-resolution neutron powder diffraction in the HRPT diffractometer at PSI to address the origin of magnetization reversal at low temperature. The solid solution Tb0.55Sr0.45MnO3 crystallizes in O′ type orthorhombic structure having the Pnma symmetry. The substitution of the divalent cation of Sr2+ at the site of Tb3+ dilutes the Mn–Tb interaction and affects the magnetic structure, which was observed by the field and temperature-dependent dc magnetization and neutron diffraction study. The temperature-dependent zero field-cooled and field cooled dc magnetization study reveals the indication of spin reversal phenomena, which is the nature of canted antiferromagnetic or ferrimagnetic transition at 100 Oe because of Mn–Mn sub-lattices interaction below 65 K. By increasing the applied magnetic field up to 20 kOe, a weak ferromagnetic type of behaviour is observed. The field-dependent magnetization shows weak coercivity due to the canted spin structure at low temperatures. The low-temperature neutron diffraction study of polycrystalline Tb0.55Sr0.45MnO3 reveals the non-collinear canted antiferromagnetic structure due to Tb ordering at 1.5 K, which turns into a non-collinear ferromagnetic structure along with spin canting followed by the spin reversal phenomena at 25 K.

To explore the practical feasibility of exotic carbon, various types of geometries of CNT configurations have been investigated such as CNT film, vertically aligned nanotubes, 3D pillared graphene-CNT network etc. High-performance and applicability of CNT derived electrodes in electrochemical energy storage depend on the structural design and high aspect ratio geometry. Here, we have strategically designed electrode derived from a special type of 3D geometry known as carbon hollow cylinders (CHCs) made up of CNTs arranged in the radial direction. The exceptional geometry provides a high areal capacity of 513.92 C/cm2 at an applied current density of 16 mA/cm2. Also, high specific energy of 41.13 mWh/cm2 at the specific power of 5694.92 mW/cm2 originated from supercapacitors and battery response of the electrode material was attained, which idealized the fundamental of theory of composite type electrode material. Hence, proposed geometry sets a stepping stone for a paradigm shift in light-weight electrode which is not only binder-free but also designed with a special geometry that provides an exceptional higher areal capacity with stable network.

In present investigation, the selective removal of Al from the quasi-lattice sites of quasicrystalline alloy surface was examined in order to produce the nano-particles of metal/metal oxides within the micro-porous network. Al was selectively etched from both the as-cast as well as annealed Al63Cu25Fe12 quasicrystalline alloys through the treatment with 10 mol NaOH solution at different time interval. In the as-cast sample, higher density of porosity was observed compared to that of annealed alloy. However, dealloying specifically for 4 and 8 h yielded nano-size particles on quasicrystalline surface (of both the alloys) in which very fine particles were detected at 8 h. The increase in density and decrease in size of the nano-particles was found with dealloying duration. X-ray diffraction analysis was performed to characterize the samples. Scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis were carried out to investigate the surface microstructure, internal morphology and chemical composition. The chemical dealloying treatments yielded nano-particles of Cu and Fe along with their oxides on the quasicrystalline surface. Furthermore, the catalytic activity of leached quasicrystalline materials was evaluated towards degradation of non-biodegradable and hazardous methylene blue (organic dye).

The present investigation reports the formation and stability of multi-component AB2-type Laves phase in Ti–Zr–Ni (V, Cr, Fe, Mn, Co)ternary to octonary alloys system. To probe the formation and stability of AB2-type Laves phase in high-entropy alloys, a series of multi-component alloys have been synthesized via melting under protective Ar atmosphere and subsequent annealing at 525 K for 40 h. Systematic investigation has been carried out to understand phase stability using both thermodynamic and parametric approaches. X-ray diffraction measurement and Rietveld analysis indicate the formation of C14 Laves phase in multi-component alloys. The enthalpy of mixing (ΔHmix), size difference (δ) and valence electron concentrations (VEC) have been found to play stellar role in controlling the formation of multi-component Laves phase in these alloys. The valence electron concentrations and electrons per atom ratio (e/a) dictate the choice of elements for the stabilization of Laves phase in these high-entropy alloys.

The realization of quasicrystals has attracted a considerable attention due to their unusual structures and properties. The concept of quasicrystals in the atomically thin materials is even more appealing due to the in‐plane covalent bonds and weak interlayer interactions. Here, it is demonstrated that 2D quasicrystals can be created/isolated from bulk phases because of long‐range interlayer ordered aperiodic arrangements. An ultrasonication‐assisted exfoliation of polygrained icosahedral Al–Pd–Mn quasicrystals at room temperature shows the formation of a large area of mono‐ and few layers in threefold quasicrystalline plane. The formation of these layers from random grain orientation consistently indicates that the threefold plane is most stable in comparison to the twofold and fivefold planes in icosahedral clusters. The above experimental observations are further supported with help of theoretical simulations. The mono‐ and few‐layered aperiodic planes render plentiful active sites for the catalysis of hydrogen evolution reaction. The threefold 2D quasicrystalline plane exhibits a hydrogen evolution reaction overpotential of ≈100 mV (160 times less than bulk counterpart) and long‐term durability. These systems constitute the first demonstration of quasicrystalline monolayer ordering in a free‐standing thin layer without requiring the support of periodic or aperiodic substrate., by Thakur Prasad Yadav, Cristiano F. Woellner, Shyam K. Sinha, Tiva Sharifi, Amey Apte, Nilay Krishna Mukhopadhyay, Onkar Nath Srivastava, Robert Vajtai, Douglas S. Galvao, Chandra Sekhar Tiwary and Pulickel M. Ajayan

The high-entropy Ti–Zr–V–Cr–Ni (20 at% each) alloy consisting of all five hydride-forming elements was successfully synthesised by the conventional melting and casting as well as by the melt-spinning technique. The as-cast alloy consists entirely of the micron size hexagonal Laves Phase of C14 type; whereas, the melt-spun ribbon exhibits the evolution of nanocrystalline Laves phase. There was no evidence of any amorphous or any other metastable phases in the present processing condition. This is the first report of synthesising a single phase of high-entropy complex intermetallic compound in the equiatomic quinary alloy system. The detailed characterisation by X-ray diffraction, scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the existence of a single-phase multi-component hexagonal C14-type Laves phase in all the as-cast, melt-spun and annealed alloys. The lattice parameter a = 5.08 Å and c = 8.41 Å was determined from the annealed material (annealing at 1173 K). The thermodynamic calculations following the Miedema’s approach support the stability of the high-entropy multi-component Laves phase compared to that of the solid solution or glassy phases. The high hardness value (8.92 GPa at 25 g load) has been observed in nanocrystalline high-entropy alloy ribbon without any cracking. It implies that high-yield strength (~3.00 GPa) and the reasonable fracture toughness can be achieved in this high-entropy material.

The formation of nano-amorphous domains in melt spun ribbons of Ce75Al25 − xGax alloys with x = 0, 0.01, 0.1, 0.5 and 1 is reported. For x = 0, a homogenous metallic glass feature is observed. Ga substitution has led to phase separation giving rise to nano-amorphous domains in a glassy matrix. The rationale of phase separation could not be explained in terms of enthalpy of mixing of the three possible binaries in this system. The Ce L3-edge XAS spectra of melt-spun ribbons for x = 0, 0.5 and 4 have shown appearance of 4f0 delocalized states in Ga substituted alloy. Such a substitution has led to shortening of Ce–Ce distance in the alloys owing to chemical pressure. This work, therefore, opens up new direction of research for delineating issues pertaining to phase separation in amorphous systems.

The effect of cooling rate on the mechanical behavior of Zr–Ga–Cu–Ni melt-spun glassy alloys has been studied using micro-indentation technique. The ribbons of alloy have been synthesized at three cooling rates corresponding to wheel speeds of 30, 40 and 50 m/s. The glass forming indicators and indentation characteristic have been investigated. The measurements by differential scanning calorimeters show that the ribbons synthesized at faster cooling rate contains larger amount of heats of relaxation, crystallization enthalpy and free volume. The indentation experiments demonstrate that with the same chemical composition, the ribbons synthesized at slow cooling rate exhibits higher hardness and yield strength than those synthesized at faster cooling rate. The ribbons synthesized at 50 m/s contains the large free volume and thus favors the formation of shear bands. The study is focused on investigations of these materials to understand the correlation between the cooling rate and the mechanical behavior of these alloys.

The present work describes the synthesis and characterization of Ni45Fe5Mn40Sn10 Heusler alloys. The constituent pure metals were melted in radio frequency induction furnace to form the alloy and then cooled it quickly. The as-cast alloy was annealed at 850 °C for 24 h in vacuum and cooled in two different conditions i.e. self-cooling at room temperature in air and sudden cooling at liquid nitrogen temperature (quenched). The X-ray diffraction, scanning and transmission electron microscopic techniques have been used for structural/microstructural characterization as well as chemical analysis of the material. The effect of annealing and subsequent cooling in two different conditions has been described and discussed in the context of evolution of B2 and orthorhombic martensite with lattice parameter a= 0.65 nm, b=0.59 nm and c=0.56 nm.

It is well-known that the evolution of society is guided by several environmental strains. One of the important strains existing at this point of time is climate change due to pollution. Other issue of paramount importance is ?energy?. One of the comparatively new energy vectors which is typically suited for India is ?hydrogen?. Hydrogen is an indigeneous fuel since it can be produced by dissociating water with a variety of input energies, out of which solar energy is of particular importance. India has both of these in plenty. Hydrogen produced from water burns back to water after use. It is thus climate-friendly, inexhaustible, clean and indigenous fuel. Hydrogen must first be produced, afterwards stored, and then

In the present investigation, the effect of Ga substitution at Al site on the phase formation and stabilization of decagonal quasicrystalline phase in the rapidly solidified Al70−xGaxPd13Mn17 alloys have been studied by employing X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. The as-cast and rapidly solidified alloys with x = 0, 2.5 and 5 have been investigated. The melt-spinning technique has been used for rapid solidification of the as-cast alloys. The alloys up to 5 at.% Ga exhibit the formation of small amount of icosahedral quasicrystalline phases along with major amount of decagonal phase in the rapidly solidied ribbons. The energy dispersive X-ray analysis investigations suggest the homogeneous presence of Ga in the quasicrystalline alloys.

The present study deals with the use of ZrFe2 for the formation of pure phase of hydrogen storage material Mg(NH2)2/LiH. Since ZrFe2 is harder than the starting material LiNH2 and MgH2, pulverization effect produced by ZrFe2 assists in the synthesis of pure phase. The formation of pure Mg(NH2)2/LiH has been examined by XRD and confirmed by FTIR. The catalytic effect of ZrFe2 has been found to improve significantly the de/rehydrogenation characteristic of Mg(NH2)2/LiH. The ZrFe2 catalyzed Mg(NH2)2/LiH shows good recyclability. The activation energy of ZrFe2 catalyzed Mg(NH2)2/LiH was found to be 74.80 kJ/mol which is better than several other reported studies using different catalysts. Based on experimental results, a viable mechanism for dehydrogenation of Mg(NH2)2 in the presence of ZrFe2 has also been proposed.

The unfavorable de/re-hydrogenation aspects of high storage capacity material, Mg can be overcome by synthesis of composites with known intermetallic hydrogen storage alloys. In this work, a new additive, ZrFe2Hx intermetallic hydride, is used to synthesize MgH2–ZrFe2Hx nanocomposite by reactive mechanical milling technique. Also this report describes the comparison of hydrogen sorption behavior of MgH2–ZrFe2 and MgH2–ZrFe2Hx nanocomposites. It is found that the composite containing ZrFe2 and ZrFe2Hx leads to decrease in desorption temperature from 410 °C (for MgH2) to 350 and 290 °C respectively. The activation energy for rehydrogenation of composite is found to be ∼61 kJ/mol. This is lowered by 30 kJ/mol compared to the pristine milled MgH2 (92 kJ/mol). Thus, the results show significant improvement of hydrogenation behavior with the addition of ZrFe2Hx. Reasons for better catalytic activity achieved by using ZrFe2Hx have been put forwarded. Based on the present studies it can be suggest that the use of hydride version instead of the parent intermetallic phase for synthesizing the composite with MgH2 has a distinct advantage in improving the hydrogenation behavior of MgH2.

Single-walled carbon nanotubes (SWCNTs) have been synthesized by electric arc discharge method using annealed coal electrode in the presence of Fe as well as Ni–Y as catalysts. Multi-walled carbon nanotubes (MWCNTs) have been synthesized without using any catalysts. The efforts have also been made to synthesized graphene like nanosheets from bituminous coal. The as-synthesized samples have been characterized through scanning and transmission electron microscopy, Raman and Fourier transform infrared spectroscopy. The formation of SWCNTs which holds nearly perfect one dimensional structure is confirmed by the presence of radial breathing mode. A feasible mechanism of CNTs formation from coal described here with the help of Fourier transform infrared spectroscopy.

The present study suggests high pressure mechanochemical treatment is a better strategy for the synthesis of performance enhanced reversible alanates. The reactants NaH/KH + Al along with catalysts (TiCl3, TiF3 and TiO2) milled under 100 bar hydrogen pressure for 30 h effectively transforms to products (NaAlH4 and KAlH4) in a single step. The as-synthesized NaAlH4 and KAlH4 samples release hydrogen at the temperatures of ∼100 °C and 215 °C, respectively. The stability of the KAlH4 phase can be further reduced by extending the high pressure mechanochemical reaction time to 80 h. The XRD and TEM analysis of the residues observed after extracting the NaAlH4 from the TiCl3 catalyzed material confirms the presence of Ti–Al alloy and highly dispersed NaCl nanoparticles. Catalytic activity is therefore attributed to mechano-chemical activation which involves catalytically active species (for e.g. Ti–Al) and defects/vacancies/strain in the system.

Here we report the microwave shielding properties of a light weight three dimensional (3D) sponge like graphene aerogel (GA) derived from graphene oxide (GO). GA is a new exotic form of graphene nanosheet, which shows improved shielding features as compared to its pristine counterpart. The structural and microstructural characteristics of this new indigenous 3D sponge like graphene aerogel architecture have been probed by XRD, Raman, SEM and TEM/HRTEM. Furthermore, the porosity of this newly synthesized structure has been investigated by the Brunauer–Emmett–Teller (BET) method, which confirms the high surface area of ∼516 m2 g−1 with an average pore diameter of ∼2.5 nm. The high surface area and better porosity improve the EMI shielding effectiveness of GA. Simultaneously, the GA nanostructure also enhances the dielectric properties which provide a better alternative for EMI shielding materials as compared to GO. This engineered GA exhibits enhanced shielding effectiveness (∼20.0 dB at 0.20 g in a frequency region of 12.4 to 18.0 GHz) as compared to the conventional GO. Thus, the result of the EMI shielding of GA offers a new ingenious nanostructure which can be used as an EMI pollutant quencher for next-generation EMI shielding devices.

Herein, we demonstrate a facile one pot synthesis of graphene nanosheets by electrochemical exfoliation of graphite. In the present study, we report a significant increase in the yield of graphene by electrolyte heating assisted electrochemical exfoliation method. The obtained results of heating assisted electrochemically exfoliated graphene (utilizing H2SO4 + KOH + DW) synthesis clearly exhibit that the yield increases ∼4.5 times i.e. from ∼17% (room temperature) to ∼77% (at 80 °C). A plausible mechanism for the enhanced yield based on lattice expansion and vibration of intercalated ions has been put forward and discussed in details. The quality of graphene was examined by Raman, XPS, FTIR, AFM, SEM, TEM/HRTEM and TGA techniques. The Raman as well as morphogenesis results confirm the quality of the graphene nanosheets. We have used this graphene as electromagnetic interference shielding material where a comparatively large quantity of graphene is required. This graphene exhibits enhanced shielding effectiveness (46 dB at 1 mm thickness of stacked graphene sheets in frequency region 12.4 to 18 GHz) as compared to conventional electromagnetic interference shielding materials, which is greater than the recommended limit (∼30 dB) for techno-commercial applications. Thus the present work is suggestive for future studies on enhancement of yield of high quality graphene by proposed method and the use of synthesized graphene in electromagnetic interference shielding and other possible applications.

In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.

In 2008, one of the most costly materials on earth was graphene which was obtained by exfoliation method, having a model area of a human hair cross section costing more than $1000 as of April 2008 [2]. Since then, hunger for searching low-cost, non-hazardous alternative methods for scalable production of graphene continued. Graphene’s flexible chemistry with an atomic thickness makes it superlatives in material science, an ideal candidate for countless applications. Incredibly light weight and flexible, yet 200 times stronger than steel. Highly conductive but at the same time transparent, first 2D material existing but is one million times smaller than the diameter of a single human hair. Having all these amazing properties, graphene is creating an impact in wide range of industries including in fields of electronics, EMI shielding, composites, sensing devices as well as in energy storage, biomedical devices, and many more. Application of this wonder material is restricted to our imagination only. These engineering applications necessitate accessibility of graphene on the large scale, and methods used to synthesize this are facile, cost-effective, simple, quick, and single-step process, and thus appropriate processes are essential for synthesizing it down to a single-sheet level. The quality and quantity of graphene also plays an essential role, as the occurrence of defects, structural disorders, impurities, multiple domains, grain boundaries, and wrinkles in the graphene sheet can leave an unwanted effect on its electronic and optical properties. The present chapter will be aimed at the preparation of high quality few-layer graphene on a bulk scale from graphite in an affordable, nontoxic, and easy method. The methods which will be discussed in this chapter will be mostly on microwave-assisted synthesis of graphene and electrochemical exfoliation method used in our lab as well as reported by other workers, and how these methods are advantageous over conventional exfoliation methods. Last segment of this chapter will deal with applications of graphene particularly in EMI shielding.

The utilization of solar energy for the conversion of water to hydrogen and oxygen has been considered to be an efficient strategy to solve crisis of energy and environment. Here, we report the synthesis of reduced graphene oxide–TiO2 nanoparticle composite system through the photocatalytic reduction of graphite oxide using TiO2 nanoparticles. Photoelectrochemical characterizations and hydrogen evolution measurements of these nanocomposites reveal that the presence of graphene enhances the photocurrent density and hydrogen generation rate. The optimum photocurrent density and hydrogen generation rate has been found to be 3.4 mA cm−2 and 127.5 μmole cm−2h−1 in 0.5 M Na2SO4 electrolyte solution under 1.5AM solar irradiance of white light with illumination intensity of 100 mW cm−2. In graphene–TiO2 nanocomposite, photogenerated electrons in TiO2 are scavenged by graphene sheets and percolate to counter electrode to reduce H+ to molecular hydrogen thus increasing the performance of water-splitting reaction.

The present investigations are focused on the effect of different Ti-based catalysts (Ti, TiO 2 , TiCl 3 and TiF 3 ) on de/re-hydrogenation characteristics of nanocrystalline MgH 2 . Desorption temperature of milled MgH 2 lowers from 380 to 350, 340, 310 and 260 °C with the addition of Ti, TiO 2, TiCl 3 and TiF 3 respectively. The rehydrogenation characteristics are also improved through the deployment of Ti-based catalysts. Among all Ti based additives, TiF 3 is found to be the most effective catalyst for hydrogen sorption from nano MgH 2 . The better catalytic effect of TiF 3 over other Ti-based catalyst can be explained on the basis of temperature programmed reduction (TPR) studies. TPR experiments performed for different Ti additives, reveals that there is no oxidation/reduction reaction below 400 °C except for TiF 3 . The TPR profile of TiF 3 shows some oxidation/reduction reaction exhibits at 200 °C. In order to further improve the sorption characteristics and cyclability of TiF 3 catalyzed nano MgH 2 , we have investigated the effect of SWCNTs in MgH 2 +TiF 3 sample. De/rehydrogenation characteristics reveal the synergistic effect of SWCNTs and TiF 3 in MgH 2 +TiF 3 sample. The details of the improvement in sorption behavior of MgH 2 –TiF 3 in presence of SWCNTs are described and discussed.

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH 2 –NaAlH 4 composite. De/rehydrogenation study reveals that MgH 2 –NaAlH 4 composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH 4 and MgH 2 . To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH 2 –NaAlH 4 composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH 2 –NaAlH 4 catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH 2 –NaAlH 4 is diminished to 0.45 wt.%.

The present article deals with filtration of seawater to remove sodium chloride (NaCl) using filter made from organized structures of carbon nanotubes (CNTs). The filter consists of hollow carbon cylinder (length ~10 cm, diameter ~1 cm), which is composed of radially aligned CNTs. This carbon hollow cylinder has been synthesized by continuous spray pyrolysis of ferrocene–benzene solution in argon atmosphere. The hollow cylinder has been turned into a water filter by closing one end and keeping a small funnel at the other. Filtration of seawater (Marina Beach, Chennai, India) has been obtained both under the self pressure of seawater column in the hollow cylinder and under the difference of pressure created by enclosing the filter in a vacuum tight container. It has been found that the efficiency of filtration is about two times higher under partial vacuum (~10–2 torr) created on the filtrate (water) side. After filtration of seawater, a deposit in the inner surface of hollow cylinder has been found. This deposit has been characterized by X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis, and it has been found that the deposit was NaCl. The filtration leads to almost complete removal of NaCl from the seawater.

Extensive studies performed here showed that Tamoxifen Citrate nanosuspension primed with several rigorous steps including pre-milling, magnetic stirring, sonication, high pressure homogenization was highly stable in its nano-forms and thus has been successfully nanonized. Optimization of the surfactant i.e., Tween 80® (Polysorbate 80) and stabilizer i.e., Pluronic F-68® (polaxamer188) ratio has been performed, and after optimization by employing several analytical techniques, the suitable ratio of surfactant:stabilizer for calculated dose of Tamoxifen Citrate was found to be 15% Tween 80 and 5% Polaxamer188. This quotient has been arrived at after considering the outcome of all the evaluations performed on the tamoxifen citrate nanosuspension (TEMParticle size, diffraction studies, FTIR-stability of drug molecule in the nanoformultion, Zeta potential-surface charge on molecules). Any chemical interactions amid the excipients and/or changes in the active therapeutic moiety were absent. It has been verified by performing FT-IR on the nano-formulations and Zeta potential of the nanosuspension was found to be 8.06 mV which is in the required range of Zeta Potential of +30 to −30 mV for nanoparticles suspended in Nanosuspension. Particle size of nano-formulation has been found to be ∼70 nm.This is idyllic for intra venous administration of the said drug formulation.

The glass forming ability and indentation characteristics of melt-spun Ce 75 Al 25− x Ga x ( x = 0, 2, 4 and 6 at.%) metallic glasses have been investigated. The substitution of Ga decreases the glass transition temperature ( T g ), while increases the supercooled liquid region (Δ T x ). The small amount of Ga substitution has led to appearance of second diffuse halos in the X-ray diffraction (XRD) pattern. The observation of “bi-amorphous phases” is thus asserted. The transmission electron microscopic images led us to conclude the formation of nano-amorphous domains after Ga substitution. The load dependent hardness behavior of metallic glasses with and without Ga substitution has been studied. The substitution of Ga improves the microhardness property of Ce–Al alloy. The formation of shear bands around the indentation periphery has been observed. The value of yield strength and Meyer exponent of these alloys has been compared.

Cicer α-galactosidase was immobilized onto functionalized graphene with immobilization efficiency of 84% using response surface methodology (Box-Behnken design). The immobilized enzyme had higher thermal stability than the soluble one, attractive for industrial applications. Immobilization of the enzyme lowered the Km to 1/3rd compared to the soluble enzyme. Raffinose family oligosaccharides (RFOs) are mainly responsible for flatulence by taking soybean derived food products. The immobilized enzyme can be used effectively for the hydrolysis of RFOs. After ten successive runs, the immobilized enzyme still retained approximately 60% activity, with soybean RFOs. The easy availability of enzyme source, ease of its immobilization on matrices, non-toxicity, increased stability of immobilized enzyme and effective hydrolysis of RFOs increase the Cicer α-galactosidase application in food processing industries.

In this paper, we have shown that gold nanoparticles (Au (NPs)) embedded in Rubia cordifolia (RC) matrix (RC-Au (NPs)) exhibit a high therapeutic value relating to its anti-inflammatory characteristics. It was prepared by utilizing the reducing properties of RC to convert HAuCl4 into Au (NPs). In order to compare its effectiveness, with respect to Au (NPs), the latter was synthesized separately by reducing HAuCl4 with lemon extract. These Au (NPs) along with RC-Au (NPs) were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and UV-visible spectroscopy. The enhancement in anti-inflammatory characteristics was assessed as its inhibitory potential for lipopolysaccharide (LPS)-induced nitric oxide (NO) release, by rat peritoneal macrophages. The RC-Au (NPs) significantly enhanced its potential to inhibit NO release, which was reported in terms of inhibitory concentration for 50% inhibition (IC50=11.98 ng/ml), as compared to either RC extract (IC50=47 × 103 ng/ml) or to Au (NPs) (IC50=587.50 ng/ml).

The present study deals with the microstructural changes with respect to the addition of Ti and their correlation with hydrogen storage characteristics of (Zr69.5Al7.5Cu12Ni11)100 − xTix (x = 0, 4 and 12) quasicrystalline alloys. The grain size of quasicrystals decreases with addition of Ti. It has been found that the alloy with x = 0 absorbed 1.20 wt. %, whereas the alloys with x = 4 and 12 absorbed 1.38 wt. % and 1.56 wt. % of hydrogen respectively. Hydrogenation was found to exhibit a significant effect on the structure/microstructure and microhardness behavior of (Zr69.5Al7.5Cu12Ni11)100 − xTix quasicrystalline alloys. Variation in the microhardness behavior has been discussed based on a structure–property correlation.

The present paper explores the enhancement in hydrogen sorption behavior of MgH2 with TiO2 nanoparticles. The catalytic effect of TiO2 nanoparticles with different sizes (7, 25, 50, 100 and 250 nm) were used for improving the sorption characteristics of MgH2. The MgH2 catalyzed with 50 nm of TiO2 exhibited the optimum catalytic effect for hydrogen sorption behavior. The desorption temperature of MgH2 catalyzed through 50 nm TiO2 was found to be 310 degrees C. This is 80 degrees C lower as compared to MgH2 having a desorption temperature of 390 degrees C. It was noticed that the dehydrogenated MgH2 catalyzed with 50 nm TiO2 reabsorbed 5.1 wt% of H2 within 6 minutes at temperature and pressure of 250 degrees C and 50 atm, respectively. The 50 nm TiO2 catalyst lowered the absorption activation energy of MgH2 from - 92 to - 52.7 kJ mol(-1).

The aim of the present investigation is to synthesize mixed sodium potassium alanate (K2NaAlH6) and to explore its hydrogen sorption characteristics. K2NaAlH6 is synthesized through ball milling of KH and NaAlH4 in the molar ratio 2:1 under hydrogen pressure of 10 bar. The temperature programmed desorption experiment shows that the synthesized K2NaAlH6 has peak desorption temperature of ∼352°C and reveals appreciable rehydrogenation kinetics under 6 bar hydrogen pressure at 300°C. The investigations are also focused on the catalytic effect of carbon nanostructures (CNS) namely, the graphene sheet (GS) and single wall carbon nanotube (SWCNT) and titanium halides (TiCl3 and TiF3) on K2NaAlH6. In the case of graphene and SWCNT catalyzed K2NaAlH6, the peak desorption temperature gets reduced to ∼347°C and ∼341°C respectively. The catalytic effects of CNS and titanium halide on K2NaAlH6 are also compared in the investigation. Between the two types of catalysts, halides are found to be better than CNS and out of the two halides, TiF3 is found to be the best catalyst for hydrogen sorption in K2NaAlH6. The peak desorption temperature decreases significantly from 352°C to ∼324°C for TiF3 catalyzed K2NaAlH6. Thus, the desorption activation energy reduces drastically from 124.43 kJ/mol (synthesized K2NaAlH6) to 88.05 kJ/mol for TiF3 catalyzed K2NaAlH6.

The effect of different carbon nanostructures specifically carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on the improvement of the de/re-hydrogenation characteristics of a Mg(NH2)2/LiH mixture have been studied. Amongst CNTs and CNFs, the improvement in the hydrogenation properties for the Mg(NH2)2/LiH mixture is higher when CNFs are used as a catalyst. Investigations are also focused on the deployment of two different types of CNF (a) CNF1 (synthesized using a ZrFe2 catalyst) and (b) CNF2 (synthesized using a LaNi5 catalyst). The results show that CNF2 is better. The maximum decomposition temperature for the pristine Mg(NH2)2/LiH mixture is found to be ∼250 °C, which is reduced to ∼180 and ∼150 °C for the sample mixed with 4 wt% of multi-walled carbon nanotubes (MWCNTs) and CNF2 respectively. The activation energy for the dehydrogenation reaction is found to be 74 and 68 kJ mol−1 for the samples mixed with MWCNT and CNF2 respectively, whereas the activation energy for the dehydrogenation reaction of the pristine Mg(NH2)2/LiH mixture is 97 kJ mol−1. The catalytic activity and the de/re-hydrogenation characteristics of the Mg(NH2)2/LiH mixture mixed with different carbon nanostructures are described and discussed.