摘要:
Leached nanocrystalline materials having a high specific surface are particularly useful for storing hydrogen or as catalysts or electrocatalysts in the manufacture electrodes, especially for fuel cells. Such materials can be manufactured by preparing a nanocrystalline material consisting of a metastable composite or alloy of at least two different chemical elements. To be nanocrystalline, this material must have a crystalline structure with the grain size lower than 100 nm. Then, the so prepared nanocrystalline material can be subjected to a leaching treatment in order to eliminate partially or totally one of the elements of the composite or alloy. This leaching results in nanocrystalline materials having a porous structure and, thereby, the requested high specific surface.
摘要:
The invention is concerned with a process for the preparation of a supported catalyst having a nanocrystalline structure and a surface area preferably higher than 2 m2/g. The process comprises preparing by mechanical grinding a nanocrystalline material consisting of a metastable composite or alloy of at least two different elements or compounds containing at least one catalytic species and subjecting the nanocrystalline material to leaching with a leaching solution in order to eliminate totally or partially at least of one of the two elements or compounds, other than the at least one catalytic species. At least one further element or compound that is non-leachable and that acts as a support for the at least one catalytic species is added to the material during the grinding step or to the leaching solution during the leaching step.
摘要:
The present invention relates to a hydrogen storage container containing at least an hydrogen storage composition and hydrogen, the hydrogen including solid state hydrogen and gaseous hydrogen, the hydrogen storage composition including at least a portion of the solid state hydrogen and having an high equilibrium plateau pressure, wherein the solid state hydrogen defines at least 5% by weight of the total weight of the contained hydrogen, and wherein the gaseous hydrogen has a pressure greater than the high equilibrium plateau pressure and defines at least 5% by weight of the total weight of the contained hydrogen.
摘要:
The invention concerns a method for preparing a nanocomposite based on magnesium and another element or compound known to absorb hydrogen and hardly miscible when ground with magnesium or its hydride, such as vanadium, titanium or niobium. The method is characterised in that it consists in submitting magnesium or a compound based on magnesium known to absorb hydrogen to hydrogenation to obtain the corresponding hydride in powder form. Said resulting powder hydride is then mixed with the other element or compound or a hydride of said other element or compound and the resulting mixture is subjected to intense mechanical grinding until the corresponding nanocomposite is obtained in the form of a hydride. Finally, if necessary, the resulting nanocomposite is subjected to hydrogen desorption. The invention also concerns the resulting nanocomposite based on Mg, which has the advantage of being inexpensive and highly efficient for storing hydrogen owing to its microstructure (that is owing to the nature of its interfaces and the spatial distribution of its constituents) which is extremely fine and provides an excellent synergistic effect between Mg and the other element or compound.
摘要:
An improved method is disclosed for producing gaseous hydrogen by subjecting a metal or a metal hydride to a chemical reaction. In this method, the metal or metal hydride subjected to the chemical reaction is nanocrystalline. Indeed, it has been found that when, instead of using conventional metal hydrides (Mg-based or others), use is made of a metal or metal hydride that is or has been subjected to intensive mechanical deformations, such as a metastable nanocrystalline metal hydride, then the chemical reaction, especially hydrolysis, will take place much more readily, at a much higher rate and, most of the time, up to completion.
摘要:
Disclosed is a method for rapidly carrying out a hydrogenation of a material capable of absorbing hydrogen. It was discovered that when a powder of a material capable of absorbing hydrogen is ground under a hydrogen pressure, not at room temperature but at a higher temperature (about 300° C. in the case of magnesium) and in the presence of a hydrogenation activator such as graphite and optionally a catalyst, it is possible to transform completely the powder of this material into a hydride. Such a transformation is achieved in a period of time less than 1 hour whereas the known methods call for periods of time as much as 10 times longer. This is an unexpected result which gives rise to a considerable reduction in the cost of manufacture of an hydride, particularly MgH2.
摘要:
An alloy of formula:Ti.sub.30+x Ru.sub.15+y Fe.sub.25+z O.sub.30+t M.sub.uwherein M represent at least one metal selected from the group consisting of chromium, manganese, vanadium, tungsten, antimony, platinum and lead; x is an integer ranging between -30 and +50; y is an integer ranging between -10 and +35; z is an integer ranging between -25 and +70; t is an integer ranging between -28 and +10; and u is an integer ranging between 0 and +50; x, y, z, t and u being selected so that: x+y+z+t+u=0. This alloy, especially when it has a nanocrystalline structure, is useful for the manufacture cathodes for the electro-chemical synthesis of sodium chlorate. These cathodes have an over-potential of hydrogen lower than the one of the soft-steel cathodes presently in use.
摘要翻译:合金:Ti30 + x Ru15 + yFe25 + zO30 + t Mu其中M代表选自铬,锰,钒,钨,锑,铂和铅中的至少一种金属; x是在-30和+50之间的整数; y为-10和+35之间的整数; z是在-25和+70之间的整数; t是-28和+10之间的整数; u是0到+50之间的整数; x,y,z,t和u被选择为:x + y + z + t + u = 0。 这种合金,特别是当其具有纳米晶体结构时,可用于制造电化学合成氯酸钠的阴极。 这些阴极具有比当前使用的软钢阴极之一低的氢的过电位。
摘要:
The invention concerns a piece based on one or several metal hydrides capable of reversibly absorbing hydrogen. Said piece is in the form of a thin and dense band, having a thickness preferably not more than 1 mm and porosity preferably less than 20%. The piece is obtained by rolling a powder of selected hydride(s), with or without additional component(s), such as binders or heat-transfer elements. Said piece can easily be produced on an industrial scale. By its very nature, it is particularly adapted for use as a base element in a tank for storing and transporting hydrogen. It can also be used in a Ni-MH typre battery for storing and transporting energy.
摘要:
The invention concerns an apparatus for the titration and circulation of gases to determine metal hydride storing properties, with improved response time, greater dynamic range in terms of the usable amount of powder and the maximum pressure accessible and increased sensitivity. The invention also concerns a circulating apparatus considerably reducing the time for analysing and determining the properties of absorbent and adsorbent materials during a large number of adsorption-desorption cycles. Both sets of apparatus are provided with a reference tube inside their oven, near the sample-holder. Said sample-holder tube and reference tube are connected on either side of the differential pressure sensor, thereby considerably enhancing the overall performance of the titration system.
摘要:
A process is described for preparing a nanocrystalline powder of an alloy of at least two metals by an intensive mechanical grinding step performed upon powders of the metals which make up the alloy. The grinding is performed at atmospheric pressure under an inert atmosphere, and is carried out at a temperature in the range of 100.degree.-400.degree. C. In this manner, one obtains crystallites of the alloy having a grain size lower than 100 nm by grinding for a period of time lower by about an order of magnitude than the time necessary to achieve this grain size by a similar grinding step carried out at ambient temperature.