Patent Application: US-201113335423-A

Abstract:
the invention discloses the incorporation of nanostructured additives into high - performance , hydrogen - rich polymeric materials to provide radiation shields for use against galactic cosmic radiation and solar energetic particles as well as secondary particulate and electromagnetic radiation resulting from nuclear reactions within the shield . nanostructured materials are defined as having at least one dimension in the nanometer range , and may include metallic and metal - oxide nanoparticles , nanotubes , nanoclays , coated polymeric nanoparticles and pairs of materials forming a nanostructured interface . functionalization of additives is performed to increase their compatability with polymeric materials . hydrogen - rich polymers refer to those having interstitial hydrogen or hydrogen - containing materials pendant to the polymer backbone . one embodiment of the invention comprises a radiation shield in which a nanostructured additive capable of shielding against electromagnetic radiation is incorporated with a hydrogen - rich polymer capable of slowing energetic particles . multifunctional structural shields may also protect against atomic oxygen degradation and control electrostatic discharge .

Description:
nanoparticle or nanostructured materials can be prepared by evaporation , sol - gel processing , directed self - assembly , oxidation or reduction of suitable precursors , electrochemical synthesis or other means . in one embodiment , a nanostructured material can be prepared by mixing hydrogen - rich , high - performance polymer with appropriate metal or metal oxide nanoparticles or metal - ligand cluster . each of these nanostructured materials can serve a function within a high - performance polymer with the net result that a multifunctional material is formed . for example , nanostructured boron , borohydrides or boron carbides and other additives can be mixed in a poly ( amic acid ) solution before imidization to form a polyimide . piperidine - modified boron nanoparticles can be used with hydrogen - rich polyimides . the poly ( amic acid ) is made from various combinations of dianhydrides and diamines displaying significant hydrogen content . bisphenols may also be used after they are converted to diamines . these combinations may include both dianhydrides and two of the diamines to prepare a copolymer that may have more - suitable solubility characteristics than either of the two corresponding homopolymers . combinations of metallic nanoparticle additives can be used to shield against various high - energy photon and particulate radiations . polyimide films are cast from the poly ( amic acid ) solutions using a doctor blade to set the thickness . imidization of poly ( amic acid ) is achieved by oven - processing of the resultant film or refluxing the polymerizing solution using a dean - stark trap to remove the water by product . in a second example , polyimides prepared with oxydianiline ( oda ) and 3 , 3 ′, 4 , 4 ′- benzophenone tetracarboxylic dianhydride ( btda ) monomers can be loaded with 10 and 15 wt % tungsten nanoparticles that are treated with benzyl mercaptan . the btda and oda monomers are reacted to form btda - oda polyimide films that are flexible to the point of being creaseable . the nanocomposite films are effective as an electromagnetic radiation shield . fig1 is a schematic representation of a single hydrogenous polymer specimen of the radiation shield 12 containing electromagnetic radiation - absorbing nanoparticle additive . the constituents of the hydrogenous polymer specimen may include any of a wide range of high - performance polymers , polymer functional - group - forming additives or combinations of low molecular weight nanoparticles , metallorganic materials or low molecular weight fibers . nanoparticles , including metals , metal oxides and metallic complexes , containing elements with high atomic number ( high - z ), which include tungsten , are added to the hydrogenous polymers . a radiation 101 may include galactic cosmic radiation , solar energetic particles , x - rays , gamma radiation , particle emitters and particle beams . the radiation 101 is incident on the radiation shield 12 . the shield 12 is a single specimen containing multiple components , such as hydrogenous polymers or high - performance polymer precursors , and nanoparticles containing elements having a high atomic number ( high - z ), which include tungsten , as shown in fig1 . the radiation is incident upon the hydrogenous polymer specimen that serves as a m oderator to slow or attenuate both the incoming high - energy gcr nuclei via coulombic interactions and energetic neutrons . t he hydrogen - rich polymer specimen may contain fibers , nanoparticles , high aspect ratio nanoparticles , low atomic number ( low - z ) nanoparticles , including aluminum and nickel , and high atomic number ( high - z ) electromagnetic radiation - absorbing materials to provide enhanced shielding . one advantage of the structure is the amenability of providing a structure serving multiple functions , such as radiation shielding , electrostatic discharge control , and protection against atomic oxygen degradation while not significantly affecting the thermo - mechanical characteristics of high - performance polymers . fig2 is a schematic representation of a single hydrogenous polymer specimen of the radiation shield 22 containing a neutron - absorbing nanoparticle additive . a radiation 101 may include galactic cosmic radiation , solar energetic particles , x - rays , gamma radiation , particle emitters and particle beams . the radiation 101 is incident on the radiation shield 22 . the shield 22 is a single specimen containing multiple components , such as hydrogenous polymers or high - performance polymer precursors , and nanoparticles containing elements having large neutron - capture cross sections , which include boron , as shown in fig2 . the radiation is incident upon the hydrogenous polymer specimen that serves as a moderator to slow or attenuate both the incoming high - energy gcr nuclei via coulombic interactions and energetic neutrons . the hydrogen - rich polymer specimen may contain fibers , nanoparticles , high aspect ratio nanoparticles , low atomic number ( low - z ) nanoparticles , including aluminum and nickel , and high atomic number ( high - z ) electromagnetic radiation - absorbing materials to provide enhanced shielding . one advantage of the structure is the amenability of providing a structure serving multiple functions , such as radiation shielding , electrostatic discharge control , and protection against atomic oxygen degradation while not significantly affecting the thermo - mechanical characteristics of high - performance polymers . fig3 is a s chematic representation of a single hydrogenous specimen component of the radiation shield 32 containing a nanoparticle additive that shields against both electromagnetic radiation and neutrons . a radiation 101 may include galactic cosmic radiation , solar energetic particles , x - rays , gamma radiation , particle emitters and particle beams . the radiation 101 is incident on the radiation shield 32 . the shield 32 is a single specimen containing multiple components , such as hydrogenous polymers or high - performance polymer precursors , and nanoparticles containing elements having both a high atomic number ( high - z ) and a large neutron - capture cross section , which include gadolinium and samarium , as shown in fig3 the radiation is incident upon the hydrogenous polymer specimen that serves as a moderator to slow or attenuate both the incoming high - energy gcr nuclei via coulombic interactions and energetic neutrons . the hydrogen - rich polymer specimen may contain fibers , nanoparticles , high aspect ratio nanoparticles , low atomic number ( low - z ) nanoparticles , including aluminum and nickel , and a high atomic number ( high - z ) electromagnetic radiation - absorbing materials to provide enhanced shielding . one advantage of the structure is the amenability of providing a structure serving multiple functions , such as radiation shielding , electrostatic discharge control , and protection against atomic oxygen degradation while not significantly affecting the thermo - mechanical characteristics of high - performance polymers . fig4 is a schematic representation of a multi - layered radiation shield 40 incorporating significant features of multiple shield compositions combined in a layered structure . a radiation 101 may include galactic cosmic radiation , solar energetic particles , x - rays , gamma radiation , particle emitters and particle beams . the radiation 101 is incident on the multilayered radiation shield 40 . each layer in the shield 40 may be composed of multiple components , such as hydrogenous polymers or high - performance polymer precursors , and nanoparticles containing elements having a high atomic number ( high - z ), which include tungsten , a large neutron - capture cross section , which include boron , or having both a high atomic number ( high - z ) and a large neutron - capture cross section , which include gadolinium and samarium , as shown in fig4 . the radiation is incident upon the outer hydrogenous polymer layer 42 that serves as a moderator to slow or attenuate both the incoming high - energy gcr nuclei via coulombic interactions and energetic neutrons . constituents of the structure may include middle shield layer 12 to moderate ionizing electromagnetic radiation as well as middle shield layer 22 to capture neutrons . the shield structure is built over a hydrogenous polymer inner layer 44 that serves further to reduce secondary emissions from fragmentation reactions within the shield . the ordering of the various constituents is not restricted to that shown in fig4 . the hydrogen - rich polymer layer may contain fibers , nanoparticles , high aspect ratio nanoparticles , low atomic number ( low - z ) nanoparticles , including aluminum and nickel , and high atomic number ( high - z ) electromagnetic radiation - absorbing materials to provide enhanced shielding . one advantage of the structure is the amenability of providing a structure serving multiple functions , such as radiation shielding , electrostatic discharge control , and protection against atomic oxygen degradation while not significantly affecting the thermo - mechanical characteristics of high - performance polymers . nanoparticle functionalization ensuring interfacial compatibility between the additive material and the high - performance polymer nanoparticles , nanotubes or other nanostructured materials serve in particle capture and high - energy photon attenuation . t hese nanostructured materials are oriented to provide enhanced capture cross section . lead - free materials with high neutron - capture cross section include boron , rare earth metals and their oxides , which include gadolinium oxide and samarium oxide , and high atomic number ( high - z ) materials , such as tungsten . the nanostructured materials can be oriented via functional inorganic or organic groups linked to the surface of the material . these functional groups also delay or prohibit aggregation of the nanoparticles . for example , 3 - aminopropyltrimethoxysilane ( apsi ) are used to encapsulate hybrid gadolinium - oxide nanoparticles within a polysiloxane shell ( bridot et al ., 2007 ). phenyltrimethoxysilane ( phsi ) can serve to make the inorganic nanoparticles more compatible with aromatic organic polymers . unmodified samarium - oxide and gadolinium - oxide nanoparticles aggregate and settle within organic solvents , such as chloroform . apsi or phsi modifications make the gadolinium - oxide nanoparticles more compatible with an organic solvent or polymer . in the case where the nanostructured material is sol - gel derived , an organic material , which include apsi and phsi , may be added during the polycondensation reaction . in another example , thiol ( or mercaptan ) agents are used to modify the surface of the metallic nanoparticles , which include aluminum , nickel and tungsten , with an organic ligand , thus increasing the compatibility between the inorganic nanoparticle additive and the organic polymer . in a fourth example , amines are used to modify the surface of boron nanoparticles . nanoparticle - modifying agents include , but are not limited to phenyltrimethoxysilane , benzyl mercaptan , thiophenol , aniline , benzyl amine , pyridine and piperidine . the additive material incorporated into the polymer may be an organometallic salt . for example , gadolinium phenylacetate can be prepared by disso lying gadolinium nitrate in dilute ammonia with a weakly basic aqueous solution of sodium phenylacetate . the compatibility of the additive and the high - performance polymer is ensured by the organic nature of the salt . polymer modification and incorporation of polymer additives enhancing radiation shielding and protection against atomic oxygen high - performance polymers serve as a structural basis for the present invention . hydrogen - rich polyimides can be formed by the reaction of dianhydride and diamine monomers in dimethylacetamide ( dmac ) solvent . polyimide films are cast from poly ( amic acid ). the poly ( amic ) acid is able to be imidized . 2 , 2 - bis ( 4 - hydroxyphenyl ) propane ( bisphenol a or bpa ) is reacted with t - butyl methyl ether in the presence of sulfuric acid catalyst to prepare t - butyl substituted bpa monomer . hydrogen - rich polymers are synthesized using bisphenol , dimine or dianhydride core structures including 2 , 2 - bis ( 4 - hydroxyphenyl ) propane , 1 , 4 - bis [( 4 - hydroxyphenyl )- 2 - propyl ] benzene , 1 , 4 - bis [( 4 - hydroxy - 3 , 5 - dimethylphenyl )- 2 - propyl ] benzene , and 2 , 2 ′- bis ( 3 , 5 - di - t - butyl - 4 - hydroxyphenyl ) propane . poly ( arylene ether ) s can be fabricated as polymer - matrix composites , coatings , films and fibers for use in space applications . commercial examples of high - performance poly ( arylene ether ) s are poly ( ether ether ketone ) ( peek ) and poly ( ether imide ) ( ultem ®). poly ( arylene ether ) s are resistant to acids and alkalis , are resistant to hydrolysis , are flame retardant , maintain good mechanical properties at high temperatures , and have excellent thermal stability . high - performance poly ( arylene ether ) s can be modified by adding substituents that are rich in hydrogen atoms . this accomplishes multiple objectives : it renders the polymer a better shielding material against gcr and it would also slow energetic neutrons for subsequent capture by atoms having large thermal neutron - capture cross sections . one benefit of using a single - specimen structure containing both low atomic number ( low - z ) elements , including hydrogen , lithium , boron or carbon , and high atomic number ( high - z ) elements , including tungsten , gadolinium and samarium , is the reduced distance for electron and ion transfer among the components of the system . this can be extremely important in reducing the energy of high atomic number , high atomic numbers and high energy ( hze ) particles where interaction with high - z materials can lead to formation of fragments and secondary emission . secondary radiation , as a result of fragmentation , can be effectively shielded by a low atomic number material in the vicinity of a high atomic number constituent such that there is a minimal distance between point - of - generation of the secondary emission and components enhancing moderation and capture of the radiation . for example , electromagnetic radiation can be attenuated [ using additives containing elements having high atomic number in close proximity to carbon -, boron - or lithium - containing materials . a material providing a stable oxide , such as silicon oxide , may be incorporated in surface layers of the high - performance polymer to provide protection against atomic oxygen degradation . metallic nanoparticles , including nickel , in a polymer may form a protective oxide layer after exposure to atomic oxygen , thus protecting against atomic oxygen . the incorporation of metallic nanoparticles into the polymer matrix imparts interesting electrical properties that can make the nanocomposite material less prone to accumulating static charge the present invention combines nanoparticle additives to modify the properties of high - performance polymers . a functionalized nanoparticle or nanostructured material is used in conjunction with one or more hydrogen - rich , high - performance polymers to prepare a nanocomposite as a lightweight effective radiation shield . the conditions set forth in the foregoing examples are illustrative of various embodiments of the composition and the process of this invention , employing the concept of combining a hydrogen - rich monomer with nanoparticles to develop a high - performance polymer exhibiting multifuctionality specifically including enhanced radiation shielding . other properties include protection against atomic oxygen degradation and electrostatic discharge . the illustrative conditions may be varied in many ways by one skilled in the art . substitutions , modifications and alterations are permissible without departing from the spirit and scope of the invention as defined in the following claims . bridot , j .- l ., faure , a .- c ., laurent , s ., rivière , c ., billotey , c ., hiba , b ., janier , m ., josserand , v ., coll , j .- l ., elst , l . v ., muller , r ., roux , s ., perriat , p . and tillement , o ., ( 2007 ), “ hybrid gadolinium oxide nanoparticles : multimodal contrast agents for in vivo imaging ,” j . am . chem . soc . ; vol . 129 . no . 16 , pp . 5076 - 5084 . churchill , r . j ., aquino , e . c ., orwoll , r . a . and kiefer , r . l ., ( 2006 ), “ multifunctional metal - polymer nanocomposites for space applications ,” nasa phase i final report , contract number nnl06aa55p . churchill , r . j ., aquino , e . c ., orwoll , r . a . and kiefer , r . l ., ( 2007a ), “ incorporation of metallic nanoparticles in lightweight composite materials for radiation shielding in space - based monitoring of nuclear explosions ,” doe sbir phase i , grant number de - fg02 - 06er8463 , in preparation . churchill , r . j ., aquino , e . c ., orwoll , r . a . and kiefer , r . l ., ( 2007b ), “ multifunctional polymers incorporating high - z neutron - capture nanoparticles ,” nasa sbir phase i final report , contract number nnl07ab01p . churchill , r . j ., aquino , e . c ., orwoll , r . a . and kiefer , r . l ., ( 2008 ), “ hydrogen - rich , multifunctional polymeric nanocomposites for radiation shielding ,” nasa sbir phase final report , contract no . nnx08cc75p . churchill , r . j ., aquino , e . c ., groger , h . p ., orwoll , r . a . and kiefer , r . l ., ( 2009 ), “ multifunctional polymers incorporating high - z neutron - capture nanoparticles ,” nasa sbir phase ii final report , contract number nnl08aa17c . churchill , r . j ., aquino , e . c ., groger , h . p ., orwoll , r . a . and kiefer , r . l ., ( 2010 ), “ multilayer polymeric shielding to protect humans from galactic cosmic radiation ,” nasa sbir phase i final report , contract number nnx10cf05p . churchill , r . j ., aquino , e . c ., groger , h . p ., bate , n . g ., orwoll , r . a . and kiefer , r . l ., ( 2011 ), “ hydrogen - 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