Direct synthesis of hydrogen storage alloys from their oxides

Tan, Serdar
The aim of this study is the synthesis of hydrogen storage compounds by electrodeoxidation technique which offers an inexpensive and rapid route to synthesize compounds from oxide mixtures. Within the scope of this study, two hydrogen storage compounds, FeTi and Mg2Ni, are aimed to be produced by this technique. In the first part, effect of sintering conditions on synthesis of FeTi was studied. For this purpose, oxide pellets made out of Fe2O3-TiO2 powders were sintered at temperatures between 900 °C – 1300 °C. Experiments showed that by sintering at 1100 °C, Fe2TiO5 forms and particle size remains comparatively small, which improve the reducibility of the oxide pellet. Experimental studies showed that the reduction of MgO rich MgO-NiO oxide pellet to synthesize Mg2Ni occurs only at extreme deoxidation conditions. Pure MgO remains intact after deoxidation. In contrast to these, pure NiO and NiO rich MgO-NiO mixtures were deoxidized successfully to Ni and MgNi2, respectively. Conductivity measurements address the low conductivity of MgO-rich systems as one of the reasons behind those difficulties in reduction. In the last part, a study was carried out to elucidate the low reducibility of oxides. It is considered that the oxygen permeability becomes important when the reduction-induced volumetric change does not yield fragmentation into solid-state. The approach successfully explains why MgO particles could not be reduced at ordinary deoxidation conditions. The study addresses that Mg layer formed at the surface of MgO particles blocks the oxygen transport between MgO and electrolyte as Mg has low oxygen permeability.


Hydrogen storage in magnesium based thin films
Akyıldız, Hasan; Öztürk, Tayfur; Özenbaş, Ahmet Macit; Department of Metallurgical and Materials Engineering (2010)
A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed; one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a t...
Hydrogen bonding in polyanilines
Bahçeci, S.; Toppare, Levent Kamil; Yurtsever, E. (Elsevier BV, 1994-12)
Hydrogen bonding between poly(bisphenol A carbonate) (PC) and polyaniline (PAn) is analyzed using semi-empirical quantum methodology. Fully optimized AM1 molecular orbital calculations are reported for various aniline structures (monomer, dimer and trimer), the monomer of the PC and the hydrogen-bonded model of PAn-PC oligomer.
Continuous synthesis of graphite with tunable interlayer distance
ÇAKMAK, GÜLHAN; Öztürk, Tayfur (2019-06-01)
A study was carried out to produce graphite with controlled interlayer distance synthesized from methane using hydrogen as modifying agent. The synthesis was carried out in radio frequency (r.f.) thermal plasma where the methane-to-hydrogen ratio varied systematically over a wide range. The synthesized materials were investigated in terms of structure, morphology and the interlayer distance. It is found that there is a critical fraction of hydrogen, around half of that of methane flow rate, up to which it i...
Chemical preparation of the binary compounds of CaO-Al2O3 system by combustion synthesis
Uysal, O; Tas, AC (1997-05-07)
The binary compounds (C(3)A: Ca3Al2O6, C(12)A(7): Ca12Al14O33, CA: CaAl2O4, CA(2): CaAl4O7 and CA(6): CaAl12O19) of CaO-Al2O3 system have been synthesized as high compound-purity ceramic powders by using the Combustion Synthesis (CS) method. Materials characterization of the above-mentioned phases were performed by powder XRD, FTIR, SEM and EDXS. It has hereby been shown that by using this synthesis procedure it would be possible to manufacture high-purity ceramic powders of CA, CA(2), and C(12)A(7) at 850 ...
Direct synthesis of Mg-Ni compounds from their oxides
Tan, Serdar; Aydınol, Mehmet Kadri; Öztürk, Tayfur; Karakaya, İshak (2010-08-13)
A study was carried out on the synthesis of Mg-Ni compounds as well as on the extraction of pure Ni and Mg from their oxides using the method of electro-deoxidation. The oxides sintered at 1200 degrees C were in the form of discrete phases NiO and MgO, suitably proportioned to yield Ni, MgNi2, Mg2Ni and Mg. The oxides were electrolyzed at 3.2 V in a eutectic mixture of CaCl2-NaCl solution maintained at a constant temperature (900-600 degrees C), using a graphite anode. The study has shown that NiO rich mixt...
Citation Formats
S. Tan, “Direct synthesis of hydrogen storage alloys from their oxides,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.