Patent Publication Number: US-7708815-B2

Title: Composite hydrogen storage material and methods related thereto

Description:
PRIORITY OF INVENTION 
     This non-provisional application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/673,859, filed Apr. 22, 2005, which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention relate to a composite hydrogen storage material. Specifically, embodiments of the present invention relate to a composite hydrogen storage material for occluding and desorbing hydrogen. 
     BACKGROUND 
     Conventionally, hydrogen may be stored in the form of metal hydride powders. During the hydriding/dehydriding cycle, strain behavior causes the particle bed to become unstable, resulting in settling and compacting of the particle bed. Through repeated cycling, the three-dimensional relationship of the powder particles continues to change, causing strain to continue to increase. When using metal hydride powders, inefficient heat transfer can hamper the rate and effectiveness of the hydriding/dehydriding cycle. 
     When using traditional metal hydride powders, safety and handling issues arise as many materials are pyrophoric, or become pyrophoric once contacted with hydrogen. In addition, powders may be blown into the hydrogen stream, which requires complicating filtering and also introduces a pressure drop into the fuel system. 
     The hydriding/dehydriding process imparts strain on the storage medium causing it to expand during charging and contract during discharge. This strain, which can be quite significant, is conventionally dealt with by designing a hydride storage vessel with expansion room to accommodate the strain. However, the unstable nature of the particle bed causes the packing of hydride material, effectively filling up the expansion room and causing significant strain to be exerted on the walls of the storage vessel. Therefore, the storage vessel must be designed to deal with this internally induced mechanical strain, either by increasing wall thickness or developing a system of internal structures to cause the bed to ‘unpack’ itself when straining occurs. The need for these complicated designs of a storage vessel effectively reduces the volumetric hydrogen storage density of the metal hydride powders. 
     The hydriding/dehydriding process causes the powder particles to pack more tightly, thus increasing the compaction of the system. The three-dimensional relationship of the particles changes throughout the hydriding/dehydriding cycle, negatively affecting the hydrogen storage ability of the powder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIG. 1  illustrates a block flow diagram of a method of making a composite hydrogen storage material, according to some embodiments of the invention. 
         FIG. 2  illustrates a block flow diagram of a method to occlude and desorb hydrogen using a composite hydrogen storage material, according to some embodiments of the invention. 
         FIG. 3  illustrates a graphical view of the pressure-composition-temperature (PCT) profile of a hydriding/dehydriding cycle of an exemplary metal hydride hydrogen storage material, that may be used in some embodiments of the invention. 
         FIG. 4  illustrates a perspective view of a storage vessel utilizing a composite hydrogen storage material in communication with a device, according to some embodiments of the invention. 
         FIG. 5  illustrates a perspective view of a storage vessel utilizing a composite hydrogen storage material, according to some embodiments of the invention. 
         FIG. 6  illustrates a cross-sectional view of a storage vessel utilizing a composite hydrogen storage material disposed on an interior wall, according to some embodiments of the invention. 
         FIG. 7  illustrates a cross-sectional view of a storage vessel utilizing a composite hydrogen storage material as a matrix substantially filling the storage vessel, according to some embodiments of the invention. 
         FIG. 8  illustrates a cross-sectional view of a storage vessel a composite hydrogen storage material as a plurality of layers in a matrix within the storage vessel, according to some embodiments of the invention. 
         FIG. 9  illustrates a perspective view of a composite hydrogen storage material structure, according to some embodiments of the invention. 
     
    
    
     SUMMARY 
     Embodiments of the invention relate to a composite hydrogen storage material comprising active material particles and a binder, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles. Further, embodiments relate to a hydrogen storage system comprising a storage vessel, a composite hydrogen storage material disposed in the storage vessel, wherein the composite hydrogen storage material comprises active material particles and a binder, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles and at least one port for communicating with an external device. 
     Embodiments of the invention relate to a method for making a composite hydrogen storage material comprising forming a fine powder of active material particles, mixing a binder with the fine powder to provide a mixture and heating the mixture sufficient to form a composite hydrogen storage material, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles. Embodiments of the invention also relate to a method of using a composite hydrogen storage material, the method comprising occluding hydrogen onto or within a composite hydrogen storage material, wherein the composite hydrogen storage material comprises active material particles and a binder, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles and desorbing hydrogen from the composite hydrogen storage material. 
     DETAILED DESCRIPTION 
     The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the invention. The embodiments may be combined, other embodiments may be utilized, or structural, and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. 
     In this document, the terms “a” or “an” are used to include one or more than one and the term “or” is used to refer to a nonexclusive or unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. 
     Embodiments of the invention provide a composite hydrogen storage material and methods related thereto. The composite hydrogen storage material allows for the occlusion and desorption of hydrogen in which the particle bed packing traditionally caused by decrepitation during the hydriding/dehydriding cycle is reduced or eliminated. The composite hydrogen storage material comprises active material particles and a binder, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles. The composite hydrogen storage material may deform under hydriding, but substantially returns to its original shape and morphology, thus the three-dimensional relationships between the active material particles are essentially unchanged throughout multiple hydriding/dehydriding cycles. 
     The composite hydrogen storage material also may act as a load bearing member within a storage vessel, effectively increasing the volumetric energy storage of the vessel. By utilizing the composite hydrogen storage material of the embodiments of the invention, requirements for filtration of loose metal hydride particles in the desorbed hydrogen stream is eliminated and the traditional problems of powder compaction in metal hydride storage vessels are eliminated. The composite hydrogen storage material is more thermally conductive than traditional metal hydride powders and retains similar absorption/desorption rate and capacity limits. The use of a composite hydrogen storage material for hydrogen storage is safer than traditional metal hydride powders as there is much less risk of storage vessel rupture due to powder compaction. Further, the use of a composite hydrogen storage material for hydrogen storage may allow for better compliance with national and international regulatory laws and procedures regarding the transport of hydrogen and hydrogen storage vessels. 
     DEFINITIONS 
     As used herein, “composite hydrogen storage material” refers to active material particles mixed with a binder, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles. 
     As used herein, “relative spatial relationships” refers to three-dimensional relationships between particles. Such three-dimensional relationships between particles in the context of the present invention will remain substantially unchanged. For example, the distance between particles may change during the hydriding/dehydriding cycle, but the particles return to substantially the same position relative to the other particles over the course of one complete cycle. The particle structure may have, e.g., an elastic property, in that the particles may move, but maintain substantially the same three-dimensional positioning substantially relative to other particles as they move. An exemplary indicator of whether a material meets the above characteristics is a qualitative measurement based upon, e.g., the volume, packing density or porosity or a dimension (e.g. length) of the composite material over repeated cycles. As such, when length of the formed composite is used as the indicator, the length of the formed composite will be at least about 80% and not more than about 120% of the parent length measured. 
     As used herein, “occlude” or “occluding” or “occlusion” refers to absorbing or adsorbing and retaining a substance. Hydrogen may be the substance occluded, for example. A substance may be occluded chemically or physically, such as by chemisorption or physisorption, for example. 
     As used herein, “desorb” or “desorbing” or “desorption” refers to the removal of an absorbed or adsorbed substance. Hydrogen may be removed from active material particles, for example. The hydrogen may be bound physically or chemically, for example. 
     As used herein, “immobilize” refers to the holding of particles, such that relative spatial relationships are maintained. For example, active material particles may be immobilized, allowing them to move, but keeping the particles substantially in the same geometric relationship to one another throughout multiple hydriding/dehydriding cycles. 
     As used herein, “metal hydride particles” or “metal hydrides” refer to metal or metal alloy particles that are capable of forming metal hydrides when contacted with hydrogen. Examples of such metal or metal alloys are LaNi 5 , FeTi, Mg 2 Ni and ZrV 2 . Such compounds are representative examples of the more general description of metal hydride compounds: AB, AB 2 , A 2 B, AB 5  and BCC, respectively. When bound with hydrogen, these compounds form metal hydride complexes, such as MgH 2 , Mg 2 NiH 4 , FeTiH 2  and LaNi 5 H 6 , for example. Examples of metals used to form metal hydrides include vanadium, magnesium, lithium, aluminum, calcium, transition metals, lanthanides, and intermetallic compounds and solid solutions thereof. 
     As used herein, “active material particles” refer to material particles capable of storing hydrogen or to material particles that may occlude and desorb hydrogen, such as metal hydrides, for example. The active material may be a metal, metal alloy or metal compound capable of forming a metal hydride when in contact with hydrogen. For example, the active material may be LaNi 5 , FeTi, a mischmetal, a mixture of metals or an ore, such as MmNi 5 , wherein Mm refers to a mixture of lanthanides. The active material particles may occlude hydrogen by chemisorption, physisorption or a combination thereof. Active material particles may also include silicas, aluminas, zeolites, graphite, activated carbons, nano-structured carbons, micro-ceramics, nano-ceramics, boron nitride nanotubes, palladium-containing materials or combinations thereof. 
     As used herein, “porosity” refers to the ratio of void space in a volume to the total volume (1-volume density). 
     As used herein, “packing density” refers to the efficiency with which the active material is packed. Packing density is the percentage of the total composite volume that is taken up by the active material. For example, a composite with a packing density of about 50% and a porosity of about 40% would consist of about 50% active material, about 10% inactive material, such as binders or additives, and about 40% void space by volume. 
     As used herein, “fine powder” refers to a powder comprising particles with a small size. For example, the fine powder may substantially be comprised of particles sized below about 100 microns. The fine powder may be substantially comprised of particles sized below about 50 microns, about 10 microns, about 1 micron or about 10 nanometers, for example. 
     Referring to  FIG. 1 , a block flow diagram of a method  100  of making a composite hydrogen storage material is shown, according to some embodiments of the invention. Active material particles may be formed  102  into a fine powder. A binder may be mixed  104  with the fine powder sufficient to create a mixture. The mixture may be heated  106  sufficient to form a composite hydrogen storage material, wherein the binder immobilizes the active material particles sufficient to maintain relative spatial relationships between the active material particles. 
     Active material particles may be comprised of material particles that are capable of storing hydrogen or of material particles that occlude and desorb hydrogen. Metal hydrides are examples. Examples may be LaNi 5 , FeTi, Mg 2 Ni and ZrV 2 . The active material particles may form  102  a fine powder. The fine powder may be formed  102  by milling, for example chemical milling, ball milling, high energy ball milling, or jet milling, or grinding, or by atomizing liquid metals to form small particles, or combinations thereof, for example. 
     The fine powder may be mixed  104  with a binder, such as a thermoplastic binder. Examples of suitable binders include polypropylene, polyethylene, polyvinylidene fluoride (PVDF), hexaflouropropylene vinylidene fluoride copolymer, cross-linked copolymers, polytetrafluoroethylene (PTFE), perfluoro alkoxy (PFA), thermoplastic polyesters (for example, Nylon™). If a thermoplastic binder is used, the binder may be readily melt-processable and may have an elongation to break of at least about 20%, for example. The amount of binder may be about 50% by weight or less of the mixture. The binder may be flexible enough to withstand the charging/discharging (hydriding/dehydriding) strain, while not melting or softening during the elevated temperatures of the charging phase. 
     The mixture may be heated  106  to form a composite hydrogen storage material. The composite hydrogen storage material produced may have a porosity from about 0.1% to about 50%, for example. The composite hydrogen storage material may have a porosity of about 5% to about 40% or from about 15% to about 25%, for example. The packing density of the active material into the metal hydride composite may be no less than about 40%, for example. The packing density may be from about 45% to about 90%, from about 60% to about 80% or greater than about 70%, for example. Optionally, the composite hydrogen storage material may undergo pressure treatment. The compression pressure may be from about 0.2 MPa to about 1000 MPa, or from about 100 MPa to about 400 MPa. In addition, the mixture may be vibrated as well. A further step may include molding of the composite hydrogen storage material. Examples of molding include compression molding, injection molding, extrusion or combinations thereof. The composite hydrogen storage material may be molded into a specific shape, such as a prismatic shape, a pellet, a wafer, a disc, a film, a sheet, a perforated sheet, a rod or combinations thereof. 
     The composite hydrogen storage material can have sufficient structural strength with a proper binder to withstand the strain induced by charging and discharging the active material particles without causing the composite to fracture. Structural strength of the composite hydrogen storage material allows it to be used as a load bearing member that can resist the force exerted by the hydrogen absorbing into the metal hydride particles. Due to this ability to resist the force produced by particle strain, the composite hydrogen storage material is able to retain its structural integrity and remain as a solid during multiple occlusion and desorption cycles. The composite hydrogen storage material may be shaped as pellets, discs, spheres, wafers, rectangular wafers or any porous or geometric shape. 
     Optionally, the composite hydrogen storage material may be comprised of additional ingredients, additives or structures that improve the thermal or mechanical properties of the composite. Examples include graphite flakes, carbon fibers, carbon nanofibers, carbon nanotubes, polymer fibers, thermal conductive materials, a metal honeycomb/lattice, metal fibers, wire, metal particles, glass fibers, and combinations thereof. Examples of thermally conductive materials are aluminum foil, aluminum honeycomb, aluminum powder, carbon fibers, carbon flakes and similar materials. Examples of structural additives include carbon flakes, carbon nanotubes, fibers of fiberglass, carbon fibers, carbon nanofibers and combinations thereof. A lubricant may be an example of an additive. A portion of the composite hydrogen storage material may optionally be removed during manufacture in order to expose such additional materials as thermally conductive materials and structural additives for example. 
     Additionally, an adsorbent or absorbent material can be added to the composite hydrogen storage material. The adsorbent or absorbent material may adsorb or absorb materials toxic to the active ingredient or that may interfere with the hydriding/dehydriding process. Some examples may include activated carbon, calcium oxide, other metals that readily oxidize, or ‘oxygen getters’. 
     Optionally, a fire retardant may be added to the composite hydrogen storage material. Suitable specific fire retardants include, e.g., phosphonium ammonium borate (i.e., phospho-ammonium boron); 3,4,5,6-dibemzo-1,2-oxaphosphane-2-oxide or 9,10-dihydro-9-oxa-10-phospaphenanthrene-10-oxide (OPC) [CAS Registry Number 35948-25-5]; sulfamic acid monoammonium salt (ammonium sulfamate) [CAS Registry Number 7773-06-0]; di-n-butyltin oxide (DBTO) [CAS Registry Number 818-08-6]; di-n-octyltin oxide (DOTO) [CAS Registry Number 780-08-6]; dibutyltin diacetate di-n-butyltin diacetate (NS-8) [CAS Registry Number 1067-33-0]; dibutyltin dilaurate di-n-butyltin dilaurate (Stann BL) [CAS Registry Number 77-58-7]; ferrocene; iron pentacarbonyl; ammonium sulfate; ammonium phosphate; zinc chloride; and combinations thereof, for example. 
     The following are examples of composite hydrogen storage materials and methods related thereto, according to some embodiments of the invention 
     Example 1 
     5 grams LaNi 5  powder with a particle size of about 1 micron or less is mixed with 0.2 grams of Atofina&#39;s 2851 kynarflex (Polyvinylidiene fluoride derivative) grade thermoplastic powder with a particle size of about 0.1 micron or less. The mixture is compression molded at about 100 MPa and 165° C. in a mold of the desired shape. The mold is then cooled to room temperature while maintaining the 100 MPa of compression pressure. The resulting part released from the mold is a porous solid composite with about 28% porosity, a mass of 5.2 grams, a specific gravity of about 5.2, and a LaNi 5  packing factor of about 60%. 
     Example 2 
     5 grams LaNi 5  powder with a particle size of about 1 micron or less is mixed with 0.2 grams of graphitic flakes with a particle size of about 1-10 microns and with 0.2 grams of Atofina&#39;s 2851 kynarflex (Polyvinylidiene fluoride derivative) grade thermoplastic powder with a particle size of about 0.1 micron or less. The mixture is compression molded at 100 MPa and 165° C. in a mold of the desired shape. The mold is then cooled to room temperature while maintaining the about 100 MPa of compression pressure. The resulting part released from the mold is a porous solid composite with about 28% porosity, a mass of 5.4 grams, a specific gravity of about 5.0, and a LaNi 5  packing factor of about 56%. The addition of the graphitic flakes increases the strength and thermal conductivity of the composite solid. These improved properties are beneficial to improve the rate of hydrogen charging and the structural integrity of the part. 
     Example 3 
     5 grams LaNi 5  powder with a particle size of about 1 micron or less is mixed with 0.2 grams of Polyparaphenylene terephthalamide (Kevlar) fibers about 10-20 microns in diameter/about 1-2 mm long and with 0.2 grams of Atofina&#39;s 2851 kynarflex (Polyvinylidiene fluoride derivative) grade thermoplastic powder with a particle size of about 0.1 micron or less. The mixture is compression molded at about 100 MPa and 165° C. in a mold of the desired shape. The mold is then cooled to room temperature while maintaining the 100 MPa of compression pressure. The resulting part released from the mold is a porous solid composite with about 28% porosity, a mass of 5.4 grams, a specific gravity of about 4.9, and a LaNi 5  packing factor of about 53%. The addition of the Polyparaphenylene terephthalamide fibers increases the strength of the composite material 
     Example 4 
     5 grams LaNi 5  powder with a particle size of about 1 micron or less is mixed with 0.2 grams of activated carbon with a particle size of about 1-10 microns and with 0.2 grams of Atofina&#39;s 2851 kynarflex (Polyvinylidiene fluoride derivative) grade thermoplastic powder with a particle size of about 0.1 micron or less. The mixture is compression molded at 100 MPa and 165° C. in a mold of the desired shape. The mold is then cooled to room temperature while maintaining the about 100 MPa of compression pressure. The resulting part released from the mold is a porous solid composite with about 28% porosity, a mass of 5.4 grams, a specific gravity of about 4.8, and a LaNi5 packing factor of about 52%. The activated carbon serves to adsorb harmful compounds that may otherwise contaminate the metal hydride during charging. 
     Referring to  FIG. 2 , a block flow diagram of a method  200  to occlude and desorb hydrogen using a composite hydrogen storage material is shown, according to some embodiments of the invention. A composite hydrogen storage material  202  may be placed in a storage vessel  204  to create a composite hydrogen storage material-vessel structure  206 . Hydrogen may be occluded  208  onto or within a composite hydrogen storage material-vessel structure  206  sufficient to produce a composite hydrogen storage material-vessel structure storing hydrogen  210 . The hydrogen may be desorbed  212 , which readies the composite hydrogen storage material-vessel structure  206  for another cycle of hydrogen absorption/desorption. The absorption/desorption of hydrogen may be repeated numerous times, up to about 10,000, or up to about 100,000 for example, depending on the hydride material used. 
     A composite hydrogen storage material  202  may be placed in a storage vessel  204 , such as a tank or container. As an example, the composite hydrogen storage material  202  may be utilized in a cellular fuel tank such as discussed in Zimmermann, U.S. Provisional Patent Application Ser. No. 60/757,782, entitled “CELLULAR RESERVOIR AND METHODS RELATED THERETO,” filed Jan. 9, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
     Because of its structural strength in solid form, the composite hydrogen storage material  202  serves the dual function of storing hydrogen and also of holding the hydrogen storage particles in a fixed relative spatial relationship. Therefore, the function of resisting the strain induced by the charging of hydrogen onto the material is fulfilled entirely by the composite hydrogen storage material. As a result, the vessel for storing the hydrogen  210  need be designed to resist only the gas pressure of the system. 
     Referring to  FIG. 3 , a graphical display of the absorbing/desorbing characteristics of an exemplary hydrogen storage material within a storage vessel is shown.  FIG. 3  shows a graphical view of the pressure-composition-temperature (PCT) profile of a hydriding/dehydriding cycle of a metal hydride hydrogen storage material, such as one which may be used in some embodiments of the invention. 
     Referring to  FIG. 4 , a perspective view of a storage vessel utilizing a composite hydrogen storage material in communication with a device  400  is shown, according to some embodiments of the invention. The storage vessel  410  comprises an external wall  408 , an optional pressure relief functionality  406 , and port  404  in which to communicate with an external device  402 . The optional pressure relief functionality  406  may be a pressure relief mechanism, such as a valve, a spring loaded-valve, a fusible trigger, a rupture disk, a diaphragm, or a vent feature, which may be integral to a tank. The port  404  may be a sealable port, for example. The external device may be a fuel cell system, a hydrogen source, a heat pump, a hydrogen compressor, or air conditioning system, for example. External device  402  may also be a gas management device, such as a regulator, check valve, on/off valve or other interconnection, for example. Alternatively, a portion of one of the exterior walls  408  may comprise a fuel cell layer, fuel cell system, a hydrogen source, a heat pump or a hydrogen compressor, for example. 
     When used in conjunction with a fuel cell, it is possible to create a compact system for powering portable electronic devices. Some examples of portable electronics for use with the fuel cell include, but are not limited to, cellular phones, satellite phones, laptop computers, computer accessories, displays, personal audio or video players, medical devices, televisions, transmitters, receivers, lighting devices including outdoor lighting or flashlights, electronic toys, or any device conventionally used with batteries. 
     The storage vessel  410  may be of a small size and the optional pressure relief functionality  406  may be integrated into the design of the storage vessel  410 . For larger storage vessels  410 , a pressure activated relief device or temperature activated relief device may be usable. The activation temperature range may be from about 150° C. to about 400° C. for a temperature activated relief device. For a pressure activated relief device, the activation pressure may be from about 200 to about 1000 psi, but will depend on the thickness and strength of the storage vessel  410  walls. 
     Referring to  FIG. 5 , a perspective view of a storage vessel  500  utilizing a composite hydrogen storage material is shown, according to some embodiments of the invention. The storage vessel  500  comprises an optional pressure relief functionality  504  and port  506 . Pressure relief functionality  504  is optional and may be eliminated from the design of the storage vessel, particularly when the vessel is very small, or has been designed with an integral feature to fail while allowing reasonably safe relief of internal pressure. The port  506  may be used to communicate with any number of external devices (not shown in figure). 
     Referring to  FIG. 6 , a cross-sectional view of a storage vessel  600  utilizing a composite hydrogen storage material disposed on an interior wall is shown, according to some embodiments of the invention. The storage vessel  600  comprises an interior wall  606  and exterior wall  602 . A composite hydrogen storage material  604  may be disposed within the interior wall  606 , creating a space  608  between the composite hydrogen storage material  604  and interior wall  606 . The composite hydrogen storage material  604  may be in the form of matrix which may utilize a melt processible polymer, for example polyvinylidene fluoride, polyethylene or polypropylene, as the binder. The matrix may partially or entirely fill the interior space of the storage vessel  600 . 
     The composite hydrogen storage material  604  may be optionally adhered to at least a portion of at least one of the interior walls  606  of the storage vessel  600 . The composite hydrogen storage material  604  may be adhered using a melt processible polymer, for example. Alternatively, adhering may be performed by gluing the composite hydrogen storage material  604  to at least a portion of at least one of the interior walls  606 . An example of glue that may be utilized is an epoxy adhesive or a silicone adhesive, for example. 
     Referring to  FIG. 7 , a cross-sectional view of a storage vessel  700  utilizing a composite hydrogen storage material as a matrix substantially filling the storage vessel is shown, according to some embodiments of the invention. The storage vessel  700  comprises an interior wall  706  and exterior wall  702 . A composite hydrogen storage material  704  may be disposed as a matrix within the interior wall  702 , substantially filling the storage vessel  700 . 
     Referring to  FIG. 8 , a cross-sectional view of a storage vessel  800  utilizing a composite hydrogen storage material as a plurality of layers in a matrix within the storage vessel is shown, according to some embodiments of the invention. The storage vessel  800  comprises an interior wall  810  and exterior wall  802 . A composite hydrogen storage material  804  can be disposed as a plurality of layers within the interior wall  802 , creating spaces  806 . Between each layer of the composite hydrogen storage material  804 , may be placed an optional conductive member  808 . During the manufacture of the composite hydrogen storage material  804 , portions of the structure may be removed in order to expose a conductive member  808 . 
     For example, a storage vessel  800  may be filled with composite hydrogen storage material  804  so that storage vessels  800  of differing sizes may be built up from the same basic element. This would allow for the placement of composite hydrogen storage material  804  with other materials inside the storage vessel  800 , i.e. placing heat conducting members around the composite hydrogen storage material  804 , as shown. Some of the material may then be removed to expose parts of the composite  804  that have particular characteristics, such as exposing heat conducting members  808  embedded within the material. 
     Referring to  FIG. 9 , a perspective view of a composite hydrogen storage material structure  900  is shown, according to some embodiments of the invention. A composite hydrogen storage material structure  900  can be formed in such shapes as a rectangular wafer  902 , for example. The cross-sectional cut out illustrates the interaction of active material  904 , such as a metal hydride, and binder  908 , which may create one or more interstitial spaces or voids  906 . The spaces  906  allow for hydrogen diffusion and flow through the active material, such as metal hydride particles so that hydrogen is able to reach the interior of the formed composite hydrogen storage material. 
     While the present invention has been particularly shown and described with reference to preferred embodiments, it will be readily appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is intended that the claims be interpreted to cover the disclosed embodiment, those alternatives which have been discussed above and all equivalents thereto. 
     The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.