Showing papers on "Hydrogen storage published in 1996"
TL;DR: In this paper, reaction models for the formation and decomposition of metal hydrides with one rate determining partial reaction step are presented, based on reasonable physical assumptions for each of the partial steps.
236 citations
TL;DR: In this article, the effect of substitutions of Sn for Ni in LaNi5 on the performance of the metal hydride alloy anode in terms of cyclic lifetime, capacity, and kinetics was investigated.
Abstract: Electrochemical studies were performed on LaNi5–xSnx with 0 <= x <= 0.5. We measured the effect of the Sn substituent on the kinetics of charge-transfer and diffusion during hydrogen absorption and desorption, and the cyclic lifetimes of LaNi5–-xSnx electrodes in 250 mAh laboratory test cells. We report beneficial effects of making small substitutions of Sn for Ni in LaNi5 on the performance of the metal hydride alloy anode in terms of cyclic lifetime, capacity, and kinetics. The optimal concentration of Sn in LaNi5–xSnx alloys for negative electrodes in alkaline rechargeable secondary cells was found to lie in the range 0.25 <= x <= 0.3.
177 citations
TL;DR: In this article, the initial hydriding characteristics, as well as the compositional transformation of composites made of La2Mg17 + LaNi5 mechanically milled in a 2:1 weight ratio were investigated.
140 citations
Patent•
20 Sep 1996TL;DR: A hydrogen generator employs substantially adiabatic hydrolysis and thermal decomposition of chemical hydrides to provide a controllable generation of hydrogen from a small, lightweight container as mentioned in this paper.
Abstract: A hydrogen generator employs substantially adiabatic hydrolysis and thermal decomposition of chemical hydrides to provide a controllable generation of hydrogen from a small, lightweight container. The hydrogen generator includes a thermally isolated container for containing a chemical hydride, a preheater to heat the chemical hydride to a predetermined temperature before the chemical hydride is hydrolyzed, a water supply controlled to maintain substantially adiabatic and controlled generation of hydrogen from said chemical hydride, and a buffer to supply an initial flow of hydrogen during generator start-up, absorb excess hydrogen during generator shut-down, and to smooth the hydrogen flow due to changing loads.
140 citations
TL;DR: In this paper, the effects of substitution with foreign metals on the crystallographic, thermodynamic and electrochemical properties of AB5-type hydrogen storage alloys were investigated, and both the unit cell volume and the −ΔH value increased with increasing metallic bond radius of the foreign metal.
127 citations
TL;DR: In this paper, the desorption of hydrogen from a novel material, a Ti45Zr38Ni17•H quasicrystal, was observed using high-temperature powder x-ray diffraction, demonstrating the potential utility of Ti-based quasics in place of crystalline or amorphous hydrides for hydrogen storage applications.
Abstract: The desorption of hydrogen from a novel material, a Ti45Zr38Ni17‐H quasicrystal, was observed using high‐temperature powder x‐ray diffraction, demonstrating the potential utility of Ti‐based quasicrystals in place of crystalline or amorphous hydrides for hydrogen storage applications. The maximum observed change in hydrogen concentration was from 61 at. %, corresponding to a hydrogen‐to‐metal ratio (H/M) of 1.54, at 91 °C to less than 2.5 at. % (H/M=0.025) at 620 °C. The onset temperature of desorption is below 350 °C. Surface oxidation was found to promote the formation of crystalline hydride phases. Highly oxidized samples transformed to a mixture of the C14 Laves and C15 Laves crystalline hydrides, and the Ti2Ni phase. When the oxidation was less severe, a reversible transformation between the quasicrystal and crystalline hydride phases was clearly observed, demonstrating the stability of the Ti45Zr38Ni17 quasicrystal at very low hydrogen concentrations, and temperatures as high as 661 °C. This is the ...
102 citations
TL;DR: In this article, a reduction mechanism, partly based on heterolytic dissociation of H2, is proposed to reduce the amount of hydrogen stored in the host oxide and the reduction of Ce4+ to Ce3+.
Abstract: Interaction of hydrogen with a series of mixed oxides CeMx(M = Cu, Ni; 0 < x⩽ 5) precursors of catalysts for hydrogenation reactions has been studied in the 300–1073 K temperature range. In situ XRD, XPS, EPR and thermogravimetric techniques have been used to characterize the processes occurring during the hydrogen treatment, and the amounts of hydrogen occluded in the solids when treated at different temperatures under flowing H2 have also been determined. The most interesting phenomena have been found to occur in the activation temperature range. They involve a non-negligible expansion of the ceria-based lattice which has been attributed to the high amount of hydrogen stored in the host oxide and the reduction of Ce4+ to Ce3+. The M2+ reduction is slowed down, depending on the content of M2+ in the ceria lattice: redox processes between Ce4+, Ce3+, M and M+ or M2+ have been clearly demonstrated. Finally, a reduction mechanism, partly based on heterolytic dissociation of H2, is proposed. This may be extended to bulk mixed oxides with other transition metals, and to a certain extent to metals of Group VIII (Rh, Pd, Ir, Pt) deposited on ceria.
101 citations
TL;DR: In particular, the presence of tetrahydrofuran in the milling process strongly affected the hydriding and dehydriding kinetics of the resulting composites as discussed by the authors.
91 citations
TL;DR: In this paper, the substitution effects of other transition elements, such as Cr, V, Cu, Fe, Ni for Mn, were examined and it was found that Cr was suitable for decreasing the hysteresis, Cu could flatten the plateau with decreasing storage capacity, and V could effectively lower the plateau pressure without decreasing the storage capacity.
83 citations
01 Oct 1996
TL;DR: In this paper, a 3-step purification process was used to purify carbon single-wall nanotubes (SWNTs) and then cut them into shorter segments.
Abstract: Carbon single-wall nanotubes (SWNTs) are essentially elongated pores of molecular dimensions and are capable of adsorbing hydrogen at relatively high temperatures and low pressures. This behavior is unique to these materials and indicates that SWNTs are the ideal building block for constructing safe, efficient, and high energy density adsorbents for hydrogen storage applications. In past work we developed methods for preparing and opening SWNTs, discovered the unique adsorption properties of these new materials, confirmed that hydrogen is stabilized by physical rather than chemical interactions, measured the strength of interaction to be ~ 5 times higher than for adsorption on planar graphite, and performed infrared absorption spectroscopy to determine the chemical nature of the surface terminations before, during, and after oxidation. We also made significant advances in the synthesis of SWNT materials by turning to a laser-vaporization method rather than the arc-generation method employed previously. In addition, we began to develop methods to purify nanotubes and cut nanotubes into shorter segments. This year we have made further advances in the development of our laser synthesis technique, and we now generate crude material containing 20-30 wt% SWNTs at a rate of ~150 mg / hr or ~ 1.5 g / day. In addition we have perfected a very simple 3-step purification process which results in material that is > 98 wt% pure which is the purest reported to date. In conjunction with the purification method we pioneered a thermal gravimetric analysis (TGA) technique which enables accurate determination of SWNT wt% contents in carbon soot. Finally, we have simplified our previous nanotube cutting technique and have developed a process that allows for highly reproducible cutting of our purified laser-generated materials. The new cutting method enables the opening of laser-produced tubes which were unreactive to the oxidation methods that successfully opened our previously synthesized arc-generated tubes, and offers a path towards organizing nanotube segments to enable high volumetric hydrogen storage densities. Most importantly, this year we have demonstrated that purified cut SWNTs adsorb between 3.5 ‐ 4.5 wt% hydrogen under ambient conditions in several minutes and that the adsorbed hydrogen is effectively “capped” by CO 2 making it stable for weeks in atmospheric conditions.
81 citations
TL;DR: The potential of hydrogen in the emerging energy-environment scene as a promising alternative for simultaneously solving the two problems concerning the protection of the environment and optimum energy utilization, has by now, been very clearly understood as mentioned in this paper.
TL;DR: The hydrogen storage properties of a novel Mg{sub 2}Ni alloy powder prepared with a mechanical grinding method were investigated in this article, where the powder was transformed to an amorphous-like state by this treatment.
Abstract: The hydrogen storage properties of a novel Mg{sub 2}Ni alloy powder prepared with a mechanical grinding method were investigated This alloy powder was transformed to an amorphous-like state by this treatment As a result, an electrode of this alloy shows a large discharge capacity (750 mAh/g) which is 25 times higher than that of AB{sub 5}-type alloys This significant improvement of hydrogen storage properties seems to be achieved by the increase in the crystal boundary and a heterogeneous strain in this alloy The hydrogen equilibrium pressure of this alloy increased markedly
Patent•
06 May 1996
TL;DR: In this paper, the authors defined non-uniform heterogeneous powder particles for electrochemical uses, and said powder particles comprising at least two separate and distinct hydrogen storage alloys selected from the group consisting of: Ovonic LaNi5 type alloys, Ovonic TiNi type alloy, and Ovonic MgNi based alloys.
Abstract: Non-uniform heterogeneous powder particles for electrochemical uses, and said powder particles comprising at least two separate and distinct hydrogen storage alloys selected from the group consisting of: Ovonic LaNi5 type alloys, Ovonic TiNi type alloys, and Ovonic MgNi based alloys.
TL;DR: In this article, the authors studied the pressure-composition isotherms and electrochemical characteristics of titanium-based hydrogen storage alloys for various compositions and found that they have high discharge capacity.
TL;DR: In this article, the effects of yttrium additions on the electrode performance of Mg1.9Al0.1Ni0.7Y0.3 alloys have been investigated.
TL;DR: In this article, heat-treatment at 973 and 1473 K was conducted on a V 3 TiNi 0.56 alloy, which consisted of a V-based solid solution main phase for hydrogen storage and a TiNi-based secondary phase for electrochemical reaction.
TL;DR: In this paper, the hydrogen diffusion coefficient, DH, in the Pd films was measured by the electrochemical stripping method in the pdH solid solution (α-phase) at the temperatures ranging from 280 to 330 K.
Patent•
19 Nov 1996
TL;DR: In this paper, the authors proposed the use of ordered multicomponent hydrogen storage material characterized by extraordinarily high storage capacity due to a high density of useable hydrogen storage sites (greater than 1023 defect sites/cc) and/or an extremely small crystallite size.
Abstract: Disordered Multicomponent hydrogen storage material characterized by extraordinarily high storage capacity due to a high density of useable hydrogen storage sites (greater than 1023 defect sites/cc) and/or an extremely small crystallite size, as shown on the graph in the figure. The hydrogen storage material can be employed for electrochemical, fuel cell and gas phase applications. The material may be selected from either of the modified LaNi?5? or modified TiNi families formulated to have a crystallite size of less than 200 Angstroms and most preferably less than 100 Angstroms.
TL;DR: The hydriding kinetics of hydrogen storage materials in the two-phase regions have been studied in this article, where it is believed that the process is best classified into three steps: dissolution of hydrogen into the alloy or its hydride, diffusion of hydrogen atoms through the alloy, and nucleation and growth of β-hydride (hydride depositing from supersaturated α-solid solution).
TL;DR: The role of renewable hydrogen in Global Energy-Environment-economic system is discussed in this paper. But, it is not yet clear whether renewable hydrogen can meet its full potential as a renewable energy source.
01 Oct 1996
TL;DR: In this paper, two new generations of materials, Generation III and Generation IV, were developed, which are synthesized directly from NaH, Al, Ti-dopant and Na-metal.
Abstract: Ti-doped Alanates offer an entirely new prospect for lightweight hydrogen storage. These materials have nearly ideal equilibrium thermodynamics, good packing densities, moderate volume expansion and useful sintering properties. However, there is much room for improving both absorption and desorption kinetics, and the less-than-theoretical reversible capacities. Our work has focused on finding solutions to these problems to achieve the performance requirements needed to supply onboard hydrogen for PEM fuel cell powered vehicles. Two new generations of materials have been developed. These are; Generation III and Generation IV Ti-doped sodium alanates that are synthesized directly from NaH, Al, Ti-dopant and Na-metal, Al, Ti-dopant respectively. These materials have demonstrated better kinetics than materials produced using earlier methods. In addition, the direct synthesis is performed without the use of solvents. The result is a hydrogen storage material that is less-expensive to produce and delivers hydrogen free of hydrocarbon impurities. To improve capacity we have investigated the use of Ti-halides other than TiCl3 to catalyze hydrogen absorption and desorption in NaAlH4. TiF3 and TiCl2 appear to work equally as well as TiCl3 and reduce the overall capacity loss due to the formation of NaCl or NaF. Scaled-up engineering properties studies and cycle-life measurements are also performed. Initial results from some of those measurements will also be presented.
31 Dec 1996
TL;DR: Ammonia (NH{sub 3}) is a high octane fuel (110) that can replace CO{sub 2} producing fuels in automobile transportation as mentioned in this paper, but it shares with hydrogen the virtue of yielding only water and nitrogen as combustion products when burned in internal combustion engines but avoids the packaging, safety and logistic problems of using hydrogen fuels in motor vehicles.
Abstract: Ammonia (NH{sub 3}) is a high octane fuel (110) that can replace CO{sub 2} producing fuels in automobile transportation. It shares with hydrogen the virtue of yielding only water and nitrogen as combustion products when burned in internal combustion engines but avoids the packaging, safety and logistic problems of using hydrogen fuels in motor vehicles. Ammonia can be stored under moderate pressure at ambient temperatures. (Its physical properties are closely similar to those of liquid propane.) It can be packaged in a volume compatible with present automobiles. It is used as a fertilizer in quantities of over 100 million tons per year so that facilitates for its storage, safe handling, transportation and distribution are available worldwide. It could be an economical replacement for gasoline if the foreseen costs of air pollution and global warming caused by fossil fuels are included in the economic evaluation.
TL;DR: In this paper, the vanadium-based alloys of V 3 TiNi 0.56 M 0.24 were investigated in order to clarify the influences of additives, except for zirconium and hafnium.
Patent•
04 Apr 1996
TL;DR: A disordered electrochemical hydrogen storage alloy comprising: (Base Alloy)a Co b Mn c Fe d Sn e where the Base Alloy comprises 0.1 to 60 atomic percent Ti, 0. 1 to 40 atomic percent Zr and 0. 56 atomic percent Cr as mentioned in this paper.
Abstract: A disordered electrochemical hydrogen storage alloy comprising: (Base Alloy)a Co b Mn c Fe d Sn e where the Base Alloy comprises 0.1 to 60 atomic percent Ti, 0.1 to 40 atomic percent Zr, 0 to 60 atomic percent V, 0.1 to 57 atomic percent Ni, and 0 to 56 atomic percent Cr; b is 0 to 7.5 atomic percent; c is 13 to 17 atomic percent; d is 0 to 3.5 atomic percent; e is 0 to 1.5 atomic percent; and a + b + c + d + e = 100 atomic percent.
TL;DR: In this article, the synthesis and characterisation of FeTi 1 + x + 4.5wt%Mm (x = 0.3, 0.4 and 0.5) was reported.
TL;DR: In this article, the results of the recovery, purification to a high purity and transport of the hydrogen abstracted from the purge gas of a synthetic ammonia plant and the application of hydrogen to the tin bath in a float glass factory 25 km away from the ammonia plant by means of mobile metal hydride hydrogen container are reported.
TL;DR: In this article, an experimental study has been carried out to investigate transient transport processes of hydrogen and heat between two coupled reactors in a metal hydride cooling system, where the authors measured the amount of hydrogen gas transferrable between the paired metal hydides and the optimum value of the charged hydrogen amount was found for the maximum hydrogen transfer.
TL;DR: In this article, the performance of composite alloys with general formula Mg-x wt.% CFMmNi 2, (10, 10, 30, 40 and 50) has been investigated and it has been found that the composite material has an optimum storage capacity of approximately 5.6 wt% at the optimum temperature of around 500°C.
TL;DR: In this paper, the effects of potassium-boron addition on the performance of titanium-based hydrogen storage alloy electrodes were studied for the first time in the present work, and a novel idea was also given by the present authors for the prevention of the capacity decay of hydrogen storage electrode.
TL;DR: In this paper, the effects of alloying on the hydrogen absorption and desorption characteristics of LaNi5 intermetallic compounds were investigated by the DV-Xα cluster method.