Showing papers on "Hydrogen storage published in 1989"

Selection and preparation of activated carbon for fuel gas storage

Abstract: Increasing the surface acidity of active carbons can lead to an increase in capacity for hydrogen adsorption. Increasing the surface basicity can facilitate methane adsorption. The treatment of carbons is most effective when the carbon source material is selected to have a low ash content i.e., below about 3%, and where the ash consists predominantly of alkali metals alkali earth, with only minimal amounts of transition metals and silicon. The carbon is washed in water or acid and then oxidized, e.g. in a stream of oxygen and an inert gas at an elevated temperature.

Method for preparing materials for hydrogen storage and for hydride electrode applications

Abstract: A method for providing a multicomponent alloy for hydrogen storage and for a hydride electrode. The steps involved in the method include: providing a quantity of elements A, B, C, . . . , where said elements are selected from the group consisting of Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, Zr, Nb, Pd, Mo, Ca, Si, C, Cu, Ta, and rare earth elements, the quantity of the elements including nickel and at least two other elements from said group; apportioning the quantity of the elements in order to form a composition A a B b C c . . . such that the composition A a B b C c . . . contains 5 to 65 mole percent of nickel and further such that the composition A a B b C c . . . has, when in the form of a multicomponent alloy, a heat of hydride formation that is in a range of between -3.5 and -9.0 kcal/mold H; and, finally, melting the composition A a B b C c . . . in order to form the desired multicomponent alloy.

Current Problems in the Development and Application of Hydrogen Storage Materials

Abstract: The basic and useful features of HSA such as high H storage capacity, rapid and reversible mass, pressure and heat reactions, catalytic surface properties and isotopic and purificatory effects are well known. Actually, many interesting applications utilizing these features are undertaken/1-4/. However, the longterm and extensive uses of HSA by hydriding and dehydriding cycles induce property changes which are caused both by intrinsic factors such as the pulverization, alterations in the surface, structure and composition and the cycling induced defects generations in HSA, and by extrinsic factors such as the manufacturing conditions, pretreatments or prehistory, H2 purity and the cyclic conditions. These factors are overlapping and interlocking in the cyclic reactions, which makes it difficult or partly impossible to measure the inherent

Method for the continuous fabrication of comminuted hydrogen storage alloy material negative electrodes

Abstract: An improved method for the continuous fabrication of metal-hydride, electrochemical, hydrogen storage alloy, negative electrodes for use in rechargeable nickel metal hydride cells. The improved method comprises the steps of reducing the size of a high hardness, metal hydride, hydrogen storage alloy by shattering it along natural fracture line thereof. The process next includes providing measured amounts of powered metal hydride electrochemical hydrogen storage alloy material and disposing said material upon a continuous wire mesh screen substrate. Thereafter, the powdered metal hydride electrochemical hydrogen storage alloy and wire mesh screen are subjected to a compaction process wherein they are rolled and pressed so as to form a single integral electrode web which is subsequently exposed to a high temperature sintering process in a chemically inert environment. The sintering process is designed to drive off excess moisture in the material while discouraging oxidation of the electrode web and set the electrode web state of charge.

Preparation of vanadium rich hydrogen storage alloy materials

Abstract: Disclosed is a method of forming a vanadium-rich, multi-component reversible, electrochemical hydrogen storage alloy directly from a vanadium-reductant alloy without first obtaining pure vanadium. In one exemplification the vanadium-reductant alloy is a vanadium-aluminum alloy of low oxygen content, while in another exemplification the vanadium-reductant alloy is refined by electron beam evaporation, and in a third exemplification the vanadium-reductant alloy contains further reductants that reduce the oxygen content without adding impurities to the alloy. The vanadium-reductant alloy is directly used as a precursor in forming the electrochemical hydrogen storage alloy.

The effect of CO impurity on the hydrogenation properties of LaNi5, LaNi4.7Al0.3 and MmNi4.5Al0.5 during hydriding-dehydriding cycling

Abstract: In an investigation of the extrinsic degradation behaviour of LaNi 5 , LaNi 4.7 Al 0.3 and MmNi 4.5 Al 0.5 alloys, the changes of the amount of the absorbed hydrogen on each cycle were measured during the pressure-induced hydriding-dehydriding cycling in hydrogen containing CO as an impurity. For all alloys, the amount of the absorbed hydrogen decreased continuously as the number of cycles was increased. LaNi 5 and LaNi 4.7 A1 0.3 are degraded completely within 20 cycles, MmNi 4.5 Al 0.5 within 80 cycles. The loss of hydrogen storage capacities is caused by the deactivation of the active sites for the dissociative chemisorption of hydrogen molecules by the preferential adsorption of the CO impurity. This is confirmed by the thermal desorption experiments for the fully degraded samples and the analysis of the composition of the gases evolved from the degraded specimens during the thermal desorption by the gas chromatography. Partial substitution of nickel by aluminium improves the resistance of the alloys to the CO impurity, which is due to the changes of the surface electronic structure induced by the partial substitution of aluminium for nickel. But the resistance of the LaNi 4.7 A1 0.3 alloy to the CO impurity is much poorer than that of MmNi 4.5 A1 0.5 alloy, which is caused by the successive accumulation of retained hydrogen in LaNi 4.7 A1 0.3 which is not desorbed completely during the dehydriding period of each cycle.

Activation and deactivation mechanisms for thin-film iron-titanium hydrides

Abstract: FeTi is an alloy capable of reversible hydrogen storage at reasonable temperatures and pressures; however, it requires an initial activation procedure and experiences losses in sorption capacity after a number of charge-discharge cycles. Previous investigations are unclear as to the mechanism involved so that a detailed investigation was warranted. Backscatter conversion electron Mossbauer spectroscopy (CEMS), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to probe the entire 10 nm, the top 2 nm and the top monolayer respectively of FeTi thin films after fabrication and various annealing, reduction and oxidation treatments. Data from these analyses support an initial ultrahigh-vacuum activation mechanism whereby iron oxides present on the surface are reduced by metallic titanium species in underlying FeTi layers to produce TiO2 and metallic iron domains. Metallic iron domains are exposed to the gas phase and are capable of dissociating molecular hydrogen. The mechanism responsible for the gradual loss in sorption capacity (i.e. cyclic deactivation) occurs when FeTi decomposes into metallic iron and TiO2 by reaction of titanium with ppm levels of O 2 H 2 O impurities in the H2 charging gas. Each of these products is relatively inactive toward reversible hydrogen storage in comparison with FeTi and they gradually accumulate over a number of charge-discharge cycles. Both initial activation and cyclic deactivation involve decomposition of FeTi in the surface region. Surface coatings may be helpful in eliminating the above noted phenomena.

Hydrogen Fuel for Motorcars

Abstract: Hydrogen is a potential secondary energy carrier that meets the requirements for an energy source of the future. Its combustion does not produce carbon monoxide, carbon dioxide or hydrocarbons. The present review describes the most important technical questions relating to the mobile use of hydrogen. Besides the discussion of the three suitable technologies for storing hydrogen in a vehicle – gaseous hydrogen in pressure vessels, liquefied hydrogen in vacuum-insulated tanks, and chemically compounded hydrogen in metal hydride stores – the properties of a hydrogen engine with external and internal mixture formation are described and compared. Furthermore, the design of the hydrogen-powered vehicles as developed at Daimler-Benz is shown. The review closes with the discussion of basic conditions for a future introduction of hydrogen as a fuel.

Method and apparatus for size reducing of metal hydride hydrogen storage material.

Abstract: Apparatus for the hydride-dehydride cycling comminution of metal hydride, hydrogen storage alloy materials, which comminuted hydrogen storage alloy material is adapted for use in the negative electrode of hydrogen storage, electrochemical cells.

Hydrogen absorption-desorption kinetics of MmNi5 and related compounds

Abstract: A study was made to determine the effects of aluminum and iron substitution on the reaction kinetics of MmNi 5 ( Mm = mischmetal). Each sample used in this study i.e. MmNi 5 , MmNi 4.5 A1 0.5 and MmNi 4.85 Fe 0.15 , was mixed with a heat buffer so that nearly isothermal conditions could be maintained. Experiments were also designed so that the ratio of the equilibrium plateau pressure to the opposing pressure was the same for each sample. This was done to ensure that the thermodynamic driving force acting on each sample was the same. In addition, a sufficiently large number of absorption-desorption cycles were initially done on each sample for reproducible results to be obtained. The relative reaction rates among the various samples studied were found to change with the temperatures and pressure ratios that were chosen. Thus it is very important that any comparison of the reaction kinetics of metal hydrides should also include information about the temperature intervals used and the activation energies of each sample, as well as quantitative expressions showing how the reaction rates change with the imposed pressure ratio. At 25 °C and a pressure ratio of 2, reaction rates were found to be in the following order: MmNi 5 > MmNi 4.5 Al 0.5 ≈ LaNi 5 > MmNi 4.85 Fe 0.15 Thus it was concluded that aluminum and iron substitution has a deleterious effect on the reaction kinetics of MmNi 5 hydride. Of the materials studied, MmNi 4.5 Al 0.5 seems to be the most practical material for hydrogen storage. This is because it has thermodynamic and kinetic properties similar to those of LaNi 5 but at a cheaper price.

Fuel cell power source system

Abstract: PURPOSE:To obtain a thermally stable, compact power source system by using a heater to which electricity is supplied from a storage battery in starting, fuel waste heat from a cell, part of waste heat in steady load operation, and waste heat in a cell cooling line as a heat source for hydrogen dissociation. CONSTITUTION:A heater R1 to which electricity is supplied from a storage battery B in starting, fuel waste heat E2 of unreacted hydrogen and unreacted air exhausted from a cell, at least part of waste heat E2 in steady load operation, and waste heat E1 in a cell cooling line are used as the heat source for hydrogen dissociation of a hydrogen storage alloy incorporated in a hydrogen storage unit H. Waste heat exhausted to the outside of a system is decreased and that makes heat control of the system easy. A thermally stable, clean, compact portable power source system can be obtained.

Solar Energy Storage by Metal Hydride

Abstract: The utilization of solar energy has been being investigated intensively in the world because of the cleanliness and of the enormously large amount of energy transmitted from the sun to the earth/1-3/. However, when the low and intermittent energy density of the solar energy is taken into account, the storage of solar energy, namely increasing the energy density, is indespensable for practicl utilizations. Such an intermittent and fluctuating natural energy can be captured by conversion, in some cases via thermal or mechanical energy, to electric energy. The electric energy may be stored in rechargable batteries or converted to chemical energy as H2 and 02 production by water electrolysis. The produced H2 can be stored in metal hydrides(MH) with a very high H storage density/4-7/. The highly advantageous features in the natural energy storage by MH include

Fuel cell product liquid gas stripper

Abstract: Removal of gas from an oxidant containing liquid stream by chemically reacting hydrogen and the oxidant gas. The hydrogen is prevented from dissolving in the liquid by an electrochemical hydrogen pump that transports the hydrogen, as ions, back to the hydrogen side of the ion exchange membrane.

Development of New Mischmetal — Nickel Hydrogen Storage Alloys According to the Specific Requirements of Different Applications*

Abstract: The requirements of metal-hydride technology on the properties of metal hydrides in general and the specific requirements of different applications on metal hydrides are discussed. A brief review on the research and development of rareearth-nickel hydrogen storage alloys is made. Special emphasis is laid on the influence of substitutions with metallic elements on the thermodynamic properties of the al loys. Several new mischmetal-nieke 1 hydrogen storage alloys developed by the authors for hydrogen storage, for hydride hydrogen purification, for hydrogen separation and recovery, for hydrogen compression and for hydride electrodes are reported.

Hydrogen storage body

Abstract: PURPOSE:To prevent refining, to improve the thermal conductivity and mechanical strength, and to obtain the title hydrogen storage body with elevated applicable temp. by forming hydrogen storage alloy powder with thermosetting resin as a binder. CONSTITUTION:Hydrogen storage alloy powder is formed into a desired shape with thermosetting resin as a binder to obtain the hydrogen storage body. The powder of the metal or alloy having high thermal conductivity can be added to the hydrogen storage alloy powder to improve the thermal conductivity of the hydrogen storage body. The powder of the metal selected from Au, Ag, Pd, Pt, Al, Ni, Cu, Zn, Sn, and Pb is preferably added. Phenolic resin, epoxy resin, etc., are used as the thermosetting resin. The ratio of the alloy powder to thermosetting resin is determined so that requisite strength, especially durability, can be imparted to the storage body and hydrogen can be smoothly absorbed and released.

Treatment of hydrogen storage alloy for alkaline second battery

Abstract: PURPOSE: To improve the initial activation of an alloy and the electric conductivity thereof without causing any drop in productivity by treating a pulverized hydrogen storage alloy in an acid water solution, and further treating the alloy in an alkaline water solution after the treatment in the acid water solution. CONSTITUTION: A pulverized hydrogen alloy is treated in an acid water solution, and thereafter further treated in an alkaline water solution. As a result, a dense oxide film formed on the surface of the alloy at the time of pulverization, is well removed due to the chemical properties thereof. Also, the surface of the alloy is covered with a porous film mainly composed of a hydroxide. Even when the alloy is exposed to the atmosphere, therefore, the surface of the alloy is free from the generation of a dense oxide film. Also, as the porous film resembles very much a film generated within the battery, the film can also be applied to a negative electrode without impairing the electrochemical activity of the battery. COPYRIGHT: (C)1991,JPO&Japio

Production of high-purity gaseous hydrogen

Abstract: PURPOSE:To easily and efficiently obtain high-purity gaseous hydrogen by successively introducing the raw gas into an adsorption tower packed with the adsorbent adsorbing the components other than hydrogen and a hydrogen occlusion tower packed with a hydrogen storage alloy, and desorbing the hydrogen. CONSTITUTION:The raw gas 1 (e.g., the steam-reformed gas of methanol) is passed through the adsorption towers 2, 2a, and 2b packed with the adsorbent (e.g., activated alumina and zeolite) adsorbing the components other than hydrogen to adsorb the CO, CO2, etc., other than hydrogen, and gaseous hydrogen is produced. The gaseous hydrogen is then introduced into the hydrogen occlusion towers 6 and 6a packed with a hydrogen storage alloy, occluded in the alloy, and separated from the components other than gaseous hydrogen. The hydrogen occlusion towers 6 and 6a are heated by the hot water at about 50 deg.C from lines 10 and 10a, hence gaseous hydrogen is desorbed, and high-purity gaseous hydrogen is discharged from a delivery line 11.

Storage vessel for hydrogen storage alloy

Abstract: PURPOSE:To accelerate heat transfer and to rapidly occlude and discharge hydrogen by packing fine metallic pieces having high heat conductivity between a formed hydrogen storage alloy and the inner wall of a vessel, and sintering the pieces. CONSTITUTION:The formed hydrogen storage alloy consisting of an La-Ni based alloy, an Fe-Tl based alloy, etc., is stored in the storage vessel. In the vessel, the fine pieces of a metal having high heat conductivity such as Al, Cu, and Ni are packed in the gap (preferably having a volume of 50-98% of the expansion of the formed hydrogen storage alloy). The ratio of the fine pieces to the hydrogen storage alloy is preferably controlled to <=50wt.%. In this storage vessel thus fabricated, the formed hydrogen storage alloy is closely connected to the inner wall of the vessel, and the firmness of attachment is further increased by the cubical, expansion of the alloy due to activation.

Thin Film Preparation of Hydrogen Storage Alloys by RF-Sputtering and Electrochemical Measurements of Their Hydrogen Storage Properties*

Abstract: Thin films of hydrogen storage alloys (LaNi5, LaNi2.5C02.5) were prepared by rf-sputtering. The atomic configuration (amorphous or crystalline) and the hydrogen capacity of the prepared thin films depended on the kinds of targets and substrates and the sputtering conditions such as rf-power, temperature, and sputtering time. The crystalline films had the oriented-structure in which the c-axis is parallel to the substrate plane. The hydrogen storage properties, such as the pressure-composition isotherms and the durability, were examined electrochemically for the alloy films prepared on a nickel