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7439-95-4Relevant academic research and scientific papers
The effect of H2 partial pressure on the reaction progression and reversibility of lithium-containing multicomponent destabilized hydrogen storage systems
Price, Tobias E. C.,Grant, David M.,Weston, David,Hansen, Thomas,Arnbjerg, Lene M.,Ravnsbaek, Dorthe B.,Jensen, Torben R.,Walker, Gavin S.
, p. 13534 - 13538 (2011)
It is known that the reaction path for the decomposition of LiBH 4:MgH2 systems is dependent on whether decomposition is performed under vacuum or under a hydrogen pressure (typically 1-5 bar). However, the sensitivity of this multicomponent hydride system to partial pressures of H2 has not been investigated previously. A combination of in situ powder neutron and X-ray diffraction (deuterides were used for the neutron experiments) have shed light on the effect of low partial pressures of hydrogen on the decomposition of these materials. Different partial pressures have been achieved through the use of different vacuum systems. It was found that all the samples decomposed to form Li-Mg alloys regardless of the vacuum system used or sample stoichiometry of the multicomponent system. However, upon cooling the reaction products, the alloys showed phase instability in all but the highest efficiency pumps (i.e., lowest base pressures), with the alloys reacting to form LiH and Mg. This work has significant impact on the investigation of Li-containing multicomponent systems and the reproducibility of results if different dynamic vacuum conditions are used, as this affects the apparent amount of hydrogen evolved (as determined by ex situ experiments). These results have also helped to explain differences in the reported reversibility of the systems, with Li-rich samples forming a passivating hydride layer, hindering further hydrogenation.
High hydrogen storage capacity of nanosized magnesium synthesized by high energy ball-milling
Imamura, Hayao,Masanari, Kazuo,Kusuhara, Mitsuya,Katsumoto, Hikaru,Sumi, Takeshi,Sakata, Yoshihisa
, p. 211 - 216 (2005)
To prepare nanosized magnesium which reversibly absorbs hydrogen with high capacity even under mild conditions, high energy ball-milling of Mg or MgH 2 with benzene or cyclohexane as additives have been studied. In ball-milling of Mg or MgH2, the use of the organic additives is very crucial in determining the characteristics of the resulting nanosized magnesium. Benzene and cyclohexane served to maintain the high-degree dispersion of nanostructured magnesium with small crystallite sizes (9-10 nm) and high surface areas (24-25 m2 g-1). The behavior of hydrogen absorption by the magnesium was extensively evaluated by differential scanning calorimetry (DSC) measurements and volumetric techniques. The nanosized magnesium prepared by ball-milling of MgH2 with benzene showed reversible DSC traces for hydriding/dehydriding under 0.1 MPa hydrogen pressure. Moreover, 1 at.% Al-doped or 2.9at.% Ni-doped nanosized samples obtained by milling of MgH2 with solutions of Al(C2H5) 3 or Ni(C5H5)2 in benzene showed satisfying hydrogen absorption rates, respectively. The reversible hydrogen absorption by the 1 at.% Al-doped sample approximately reached a maximal capacity of 7.3 wt.% even at a 0.1 MPa H2 atmosphere.
Formation of one-dimensional MgH2 nano-structures by hydrogen induced disproportionation
Zlotea, Claudia,Lu, Jun,Andersson, Yvonne
, p. 357 - 362 (2006)
Remarkable formation of one-dimensional single crystalline MgH2 structures in the nano- and micro-meters ranges is reported. These structures have been tailored by hydrogen absorption and subsequent disproportionation of bulk Mg24Y5. The MgH2 whiskers have been structurally and morphologically characterized by X-rays diffraction, scanning and transmission electron microcopies. A growth model is proposed for the early stage of the whiskers formation by combining surface chemical and morphological investigations. The formation of MgH2 whiskers opens new engineering explorations and challenges for further experimental and theoretical studies.
Structural Diversity and Trends in Properties of an Array of Hydrogen-Rich Ammonium Metal Borohydrides
Cerny, Radovan,Cho, Young Whan,Grinderslev, Jakob B.,Jensen, Torben R.,Jepsen, Lars H.,Lee, Young-Su,Mller, Kasper T.
, p. 12733 - 12747 (2020)
Metal borohydrides are a fascinating and continuously expanding class of materials, showing promising applications within many different fields of research. This study presents 17 derivatives of the hydrogen-rich ammonium borohydride, NH4BH4, which all exhibit high gravimetric hydrogen densities (>9.2 wt % of H2). A detailed insight into the crystal structures combining X-ray diffraction and density functional theory calculations exposes an intriguing structural variety ranging from three-dimensional (3D) frameworks, 2D-layered, and 1D-chainlike structures to structures built from isolated complex anions, in all cases containing NH4+ countercations. Dihydrogen interactions between complex NH4+ and BH4- ions contribute to the structural diversity and flexibility, while inducing an inherent instability facilitating hydrogen release. The thermal stability of the ammonium metal borohydrides, as a function of a range of structural properties, is analyzed in detail. The Pauling electronegativity of the metal, the structural dimensionality, the dihydrogen bond length, the relative amount of NH4+ to BH4-, and the nearest coordination sphere of NH4+ are among the most important factors. Hydrogen release usually occurs in three steps, involving new intermediate compounds, observed as crystalline, polymeric, and amorphous materials. This research provides new opportunities for the design and tailoring of novel functional materials with interesting properties.
Electrodeposition of aluminum, aluminum/magnesium alloys, and magnesium from organometallic electrolytes
Mayer
, p. 2806 - 2809 (1990)
In a previous publication we reported the evaluation of the organometallic aluminum electrolytes for electroforming applications. The electroformed deposits were of high purity and therefore exhibited a relatively low ultimate tensile strength of 65.5 MPa
Decomposition and oxidation of magnesium diboride
Guo, Yang,Zhang, Wei,Yang, Dong,Yao, Ru-Liang
, p. 754 - 759 (2012)
The decomposition and oxidation behavior of magnesium diboride (MgB 2) have been studied using thermogravimetry (TG), XRD and SEM-EDS. The reactions were carried out by heating MgB2powder in a stream of argon or air at atmospheric pressure. In the temperature range explored (298-1673 K), four successive steps were observed in the decomposition process of MgB2. The rate-limiting steps of the decomposition process were found to be associated with the nucleation or formation of boron-rich phases. The oxidation process of MgB2comprised five successive phases in the temperature range explored (298-1673 K). There was close relationship between the decomposition and oxidation behavior of MgB2. Experimental results showed that the decomposition reactions occurred during the oxidation process. The acceleration shown in the weight gain curve can be ascribed to the rapid oxidation of Mg vapor released from the decomposition reactions. The microstructure and composition of the oxide scale formed in the oxidation process were investigated using XRD and SEM-EDS. The oxide layer structure was identified based on the experimental results in this study.
RETRACTED ARTICLE: Study on reaction mechanism of dehydrogenation of magnesium hydride by in situ transmission electron microscopy
Isobe, Shigehito,Ono, Akifumi,Yao, Hao,Wang, Yongming,Hashimoto, Naoyuki,Ohnuki, Somei
, (2010)
In situ observation on dehydrogenation of MgH2 was performed by using transmission electron microscope (TEM). The dehydrogenation of MgH 2 with 1 mol % Nb2 O5 and formation of nanosized Mg particles were observe
Thermoelectric properties and microstructure of Mg3Sb2
Condron, Cathie L.,Kauzlarich, Susan M.,Gascoin, Franck,Snyder, G. Jeffrey
, p. 2252 - 2257 (2006)
Mg3Sb2 has been prepared by direct reaction of the elements. Powder X-ray diffraction, thermal gravimetric, differential scanning calorimetery, and microprobe data were obtained on hot pressed samples. Single phase samples of Mg
Crystal structure of κ-Ag2Mg5
Castro, Facundo J.,Primo, Gastón A.,Urretavizcaya, Guillermina
, p. 243 - 246 (2018)
The structure of κ-Ag2Mg5 has been refined based on X-ray powder diffraction measurements (Rwp = 0.083). The compound has been prepared by combining mechanical alloying techniques and thermal treatments. The intermetallic presents the prototypical structure of Co2Al5, an hexagonal crystal with the symmetries of space group P63/mmc, and belongs to the family of kappa-phase structure compounds. The unit cell dimensions are a=8.630(1) ? and c=8.914(1) ?. Five crystallographically independent sites are occupied, Wyckoff positions 12k, 6h and 2a are filled with Mg, another 6h site is occupied with Ag, and the 2c site presents mixed Ag/Mg occupancy. The crystal chemistry of the structure and bonding are briefly discussed in the paper.
Hydrogenation Properties of Mg83.3Cu7.2Y9.5with Long Period Stacking Ordered Structure and Formation of Polymorphic γ-MgH2
Asano, Kohta,Charbonnier, Véronique,Kim, Hyunjeong,Sakaki, Kouji
, p. 14263 - 14274 (2020)
Nanosizing is known to affect the hydrogenation properties of magnesium. For this reason, the long period stacking ordered (LPSO) structures, made of the stacking of nanolayers of magnesium and nanolayers of Mg-A-B (with A = rare earth and B = transition metal), were herein considered. A Mg83.3Cu7.2Y9.5 LPSO compound with 18R structure was successfully synthesized. Its hydrogenation properties were investigated at temperatures between 150 and 400 °C. The X-ray diffraction (XRD) analysis indicates that the LPSO structure decomposes into magnesium hydride, yttrium hydride, and an intermetallic compound (Mg2Cu or MgCu2). The pressure composition (PC) isotherm for Mg83.3Cu7.2Y9.5 at 400 °C combined with XRD analysis allows one to understand the three-step hydrogenation pathway, detailed in this paper. At this hydrogenation temperature, the fully hydrogenated compound contains magnesium hydride exclusively crystallized in the most stable tetragonal structure (100% of α-MgH2 was formed). When the pristine LPSO was hydrogenated at lower temperature, the amount of α-MgH2 decreased, while its polymorphic structure, γ-MgH2, appeared. Finally, hydrogenation of Mg83.3Cu7.2Y9.5 at 150 °C led to the formation of γ-MgH2 with a high phase fraction (82% of γ-MgH2/MgH2). These results suggest that the crystallographic structure of the magnesium hydride can be controlled by the hydrogenation temperature of LPSO compounds.