Ex situ integration of iron oxide nanoparticles onto exfoliated expanded graphite flakes in aqueous suspension

Hybrid structures composed of exfoliated expanded graphite (EG) and iron oxide nanocrystals were produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA), or poly(acrylic acid) (PAA) were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under the support of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinnimide (NHS). EG flakes both naked and functionalized with branched polyethylenimine (PEI) were employed. Complete integration of the two constituents was achieved and stability was maintained for more than 12 months. No preferential spatial distribution of anchoring sites for attachment of iron oxide nanoparticles was observed, regardless of whether the EG flakes were used naked or functionalized with PEI molecules. The structural and physicochemical characteristics of the exfoliated expanded graphite and its hybrid nano-structures were investigated by SEM, TEM, FTIR and Raman techniques

Application of hydrides in hydrogen storage and compression: Achievements, outlook and perspectives

Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications. With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus. In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized. In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles. In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications.Fil: Bellosta von Colbe, Jose. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Ares Fernández, José Ramón. Universidad Autónoma de Madrid; EspañaFil: Jussara, Barale. Università di Torino; ItaliaFil: Baricco, Marcello. Università di Torino; ItaliaFil: Buckley, Craig E.. Curtin University; AustraliaFil: Capurso, Giovanni. Helmholtz Zentrum Geesthacht; AlemaniaFil: Gallandat, Noris. GRZ Technologies Ltd; SuizaFil: Grant, David M.. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino Unido. University of Nottingham; Estados UnidosFil: Guzik, Matylda N.. University of Oslo; NoruegaFil: Jacob, Isaac. Ben Gurion University of the Negev; IsraelFil: Jensen, Emil H.. University of Oslo; NoruegaFil: Jensen, Torben. University Aarhus; DinamarcaFil: Jepsen, Julian. Helmholtz Zentrum Geesthacht; AlemaniaFil: Klassen, Thomas. Helmholtz Zentrum Geesthacht; AlemaniaFil: Lototskyy, Mykhaylol V.. University of Cape Town; SudáfricaFil: Manickam, Kandavel. University of Nottingham; Estados Unidos. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino UnidoFil: Montone, Amelia. Casaccia Research Centre; ItaliaFil: Puszkiel, Julián Atilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Helmholtz Zentrum Geesthacht; AlemaniaFil: Sartori, Sabrina. University of Oslo; NoruegaFil: Sheppard, Drew A.. Curtin University; AustraliaFil: Stuart, Alastair. University of Nottingham; Estados Unidos. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino UnidoFil: Walker, Gavin. University of Nottingham; Estados Unidos. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino UnidoFil: Webb, Colin J.. Griffith University; AustraliaFil: Yang, Heena. Empa Materials Science & Technology; Suiza. École Polytechnique Fédérale de Lausanne; SuizaFil: Yartys, Volodymyr. Institute for Energy Technology; NoruegaFil: Züttel, Andreas. Empa Materials Science & Technology; Suiza. École Polytechnique Fédérale de Lausanne; SuizaFil: Dornheim, Martin. Helmholtz Zentrum Geesthacht; Alemani

Microstructural and Kinetic Evolution of Fe Doped MgH2 during H2 Cycling

The effect of extended H2 sorption cycles on the structure and on the hydrogen storage performances of MgH2 powders with 5 wt% of Fe particle catalyst is reported. MgH2 powders with and without Fe have been ball milled under Argon, the doped MgH2 nanocomposite has been cycled under hydrogen pressure up to a maximum of 47 desorption and absorption cycles at 300 °C. After acceleration during the first 10 cycles, the kinetics behavior of doped MgH2 is constant after extended cycling, in terms of maximum storage capacity and rate of sorption. The major effect of cycling on particle morphology is the progressive extraction of Mg from the MgO shell surrounding the powder particles. The Mg extraction from the MgO shell leaves the catalyst particles inside the hydride particles. Many empty MgO shells are observed in the pure ball milled MgH2 upon cycling at higher temperature, suggesting that this enhancement of the extraction efficiency is related to the higher operating temperature which favors Mg diffusivity with respect to the H ion one

TiO2 doped with nitrogen: Synthesis and characterization

In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxicle (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6-20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples.International Workshop on Nanostructured Materials (ANAOMAT 2006), Jun 21-23, 2006, Antalya, Turke

Dielectric properties of epoxy/graphite flakes composites: Influence of loading and surface treatment

Epoxy-rich carbon-based composites are well recognized materials in industries owing to their good mechanical properties and thermal stability. Here, dielectric properties of composites based on bisphenol-A-epoxy resin loaded with 5, 6, 10, and 15 wt% of graphite flakes (GF) have been studied. The frequency and temperature dependence of the dielectric permittivity, dielectric loss, and ac conductivity have been examined in temperature (−103 to 97°C) and frequency (20 Hz–200 kHz) range. Influence of the filler surface chemistry have been studied for composites loaded with 5 wt% GF obtained: (i) under wet milling, without or with adding Triton-100x as a surfactant, or (ii) under dry milling in the presence of KOH. The composite made of epoxy loaded with 5 wt% exfoliated expanded graphite flakes (EEG), was also prepared. The surface treatment with KOH notably increased dielectric constant of the composite, keeping low dielectric loss, while treatment with Triton-100x significantly increased tanδ. The composite loaded with exfoliated expanded graphite shows higher ac conductivity than those obtained with flaky graphite, GF. Possibility to change dielectric properties of the composites without changing the loading content can be used as an approach in tailoring one with desired dielectric properties

Ex situ integration of iron oxide nanoparticles onto the exfoliated expanded graphite flakes in water suspension

Hybrid structures composed of exfoliated expanded graphite (EG) and iron oxide nanocrystals have been produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA), or poly(acrylic) acid (PAA) were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under support of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccin-nimide (NHS). EG flakes have been used both, naked and functionalized with branched polyethylenimine (PEI). Complete integration of two constituents has been achieved and mainteined stable for more than 12 months. No preferential spatial distribution of anchoring sites for attachement of iron oxide nanoparticles has been observed, regardless EG flakes have been used naked or functionalized with PEI molecules. The structural and physico-chemical characteristics of the exfoliated expanded graphite and its hybrids nanostructures has been investigated by SEM, TEM, FTIR and Raman techniques. [Projekat Ministarstva nauke Republike Srbije, br. 45015

Hydrogen Desorption from MgH2 Based Nano-Micro Composites

The microstructure and hydrogen sorption behaviour of MgH2 based nano-hydrides with different additives prepared by ball milling and inert gas condensation has been investigated by XRD, Differential Scanning Calorimetry and Mechanical Spectroscopy. Preliminary results on materials with similar composition and different nanostructures show that suitable mechanical processing and additive additions induce in the nanostructured composites tailored channels for improved ab/de-sorption kinetics at reduced temperature

Combustion Synthesis and Characterization of CeO2 Nanopowder

Modified combustion procedure, named as polymer complex solution method (PCS), was used for synthesis of CeO2 nanopowder. As fuel was employed polyethylene glycol (PEG) with average molecular weight 200. Post-synthesis thermal treatments were done at 800 degrees C for 2 hours. X-ray powder diffraction, electron microscopy (SEM and TEM), laser light scattering, infrared spectroscopy, UV-VIS diffuse reflectance spectroscopy and luminescence spectroscopy were used as characterization methods. The objectives were to investigate the structure and morphology of the synthesized powder, in particular the aggregation and particle size distribution, and its luminescence properties. Photoluminescent properties of CeO2 nanopowder were determined from its emission and excitation spectra. In the excitation spectra two lines were present: one at 322 nm and other at 356 nm. Two lines were also visible in the emission spectra, one at 427 nm and other at 492 nm. Violet emission placed at 427 nm and excitation at 356 nm corresponded to D-5(1) - GT F-4(1) transition of cerium trivalent ion. A UV-VIS diffuse reflectance spectrum shows the absorption edge at 375 nm. The observed spectral blue shift revealed the presence of fine crystallites which escape XRD detection. The presented results demonstrate that this simple preparation technique provides well crystallized nanoparticles of CeO2

Combustion Synthesis and Characterization of CeO2 Nanopowder

Modified combustion procedure, named as polymer complex solution method (PCS), was used for synthesis of CeO2 nanopowder. As fuel was employed polyethylene glycol (PEG) with average molecular weight 200. Post-synthesis thermal treatments were done at 800 degrees C for 2 hours. X-ray powder diffraction, electron microscopy (SEM and TEM), laser light scattering, infrared spectroscopy, UV-VIS diffuse reflectance spectroscopy and luminescence spectroscopy were used as characterization methods. The objectives were to investigate the structure and morphology of the synthesized powder, in particular the aggregation and particle size distribution, and its luminescence properties. Photoluminescent properties of CeO2 nanopowder were determined from its emission and excitation spectra. In the excitation spectra two lines were present: one at 322 nm and other at 356 nm. Two lines were also visible in the emission spectra, one at 427 nm and other at 492 nm. Violet emission placed at 427 nm and excitation at 356 nm corresponded to D-5(1) - GT F-4(1) transition of cerium trivalent ion. A UV-VIS diffuse reflectance spectrum shows the absorption edge at 375 nm. The observed spectral blue shift revealed the presence of fine crystallites which escape XRD detection. The presented results demonstrate that this simple preparation technique provides well crystallized nanoparticles of CeO2

Structural and Optical Characterization of Flower-Like Rutile Nanostructures Doped with Fe3+

Flower-like agglomerates with sizes of 200-400 nm of pure and Fe3+-doped TiO2 with rutile crystalline structure were synthesized by the coprecipitation method. The morphology of the agglomerates was determined by electron microscopy (TEM and HRTEM). TiO2 agglomerates consist of nanorods with clearly visible crystalline faces, parallel to the axis of elongation whose direction was along the [101] direction of pure TiO2 and the [111] direction of doped TiO2. Furthermore, nanorods consist of chains of spherical particles, most likely interconnected through the so-called oriented attachment or grain-rotation-induced grain coalescence (GRIGC) process. UV/Vis reflection measurements revealed that the absorption of pure TiO2 was significantly shifted from UV toward the visible spectral region upon the incorporation of Fe3+ into the TiO2 host