EP0347386A1 - Method to simultaneously pulverize and vaporize metals into particles of varied size distribution - Google Patents

Method to simultaneously pulverize and vaporize metals into particles of varied size distribution Download PDF

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Publication number
EP0347386A1
EP0347386A1 EP89810438A EP89810438A EP0347386A1 EP 0347386 A1 EP0347386 A1 EP 0347386A1 EP 89810438 A EP89810438 A EP 89810438A EP 89810438 A EP89810438 A EP 89810438A EP 0347386 A1 EP0347386 A1 EP 0347386A1
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EP
European Patent Office
Prior art keywords
metal
arc
gas
sample
particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89810438A
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German (de)
English (en)
French (fr)
Inventor
Peter C/O Dag Richter Boswell
Tatjana Berce
Guy Negaty-Hindi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Battelle Memorial Institute Inc
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Battelle Memorial Institute Inc
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Filing date
Publication date
Application filed by Battelle Memorial Institute Inc filed Critical Battelle Memorial Institute Inc
Publication of EP0347386A1 publication Critical patent/EP0347386A1/en
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge

Definitions

  • the present invention concerns a method to simultaneously pulverize and vaporize a metal or an alloy into particles of varied ranges of size distribution, this being by means of an electric arc (plasma) acting on said metal or alloy in a pulverization enclosure under an atmosphere of a gas which becomes activated, e.g. it dissociates, when subjected to the effect of said plasma of the electric arc.
  • a gas which becomes activated e.g. it dissociates, when subjected to the effect of said plasma of the electric arc.
  • the metal subjected to the electric arc melts at least partly (for instance the surface of the metal becomes fluid) and the activated gas dissolves in the molten metal, especial­ly in the hotter area therof.
  • the disso­ciated atoms of the activated gas bind again and the released energy causes the molten metal to boil and evaporate.
  • the arc power is narrow and concentrated on a relatively small portion of the sample surface, the vapor evolution is very dense and this vapor undergoes condensation to sub-micron particles (fumes or dust) which can be collected.
  • the molten metal is subject to convection displacements whereby the dissolved gas moves along to some­what cooler areas of the sample (cooler because they avoid the direct action of the arc).
  • the vapori­zation is little or nought and hence the external pressure dwindles and the dissolved gas can suddenly escape by building large bubbles which burst and sputter the metal into particles larger than the dust particles which result from metal vapor condensation.
  • the newly formed larger particles can be of the order of several ⁇ m to several hundreds of ⁇ m.
  • US-A-4,376,740 discloses a meth­od in which a hydrogen stream is activated by an electric arc or a plasma and discharged toward a molten metal or alloy mass which results into pulverization of this metal to particles of sizes below 10 ⁇ m.
  • activated hydrogen sources elemental hydrogen, NH3, CH4, C2H6, propane and ethylene are mentioned.
  • the activated hydrogen can be diluted in a noble gas such as He, Ne, Ar, etc.
  • the metal powder is wiped off by the hydrogen stream to a duct connected to a sedimentation enclosure in which it collects.
  • Document US-A-4,689,075 concerns a method for making ultra-fine powders from metals or ceramics, i.e. particles of size definitely below 1 ⁇ m.
  • this method at least two different materials are pulverized simultaneously using elec­tric arcs operating under gas pressures ranging from 50 Torr to 3 atmospheres, the selected gases being hydrogen, nitrogen, oxygen or mixtures thereof.
  • the newly formed particles from both or more materials are taken up in a gas stream whose turbulent motion ensures proper mixing of the different par­ticles as they are still suspended in the gas. From the opera­ting conditions disclosed in this document, it would appear that the particles generated result from an evaporation pro­cess rather than from the spattering of bubbles in the molten material.
  • document JA-59-190.302 des­cribes the manufacture of superfine particles by subjecting a metal, a semi-conductor material or an alloy to melting under the electric arc in the presence of hydrogen, or nitrogen, or a hydrogen generating gas.
  • the molten metal is held in a cylinder arranged coaxially with an arc generating electrode and provided with a piston which operates on the molten metal for keeping it at constant level with respect to the electrode; hence, the voltage, the length and the current of the electric arc are under constant control.
  • the metal vapor which emanates from the metal area directly under the arc will progressively bring about a screening effect thereto and prevent the activated gas from being in contact with the molten metal. Hence the rate of evaporation also decreases progressively.
  • the pulverization operating conditions will vary and, as a consequence, the distribution of the production of the very fine particles (which result from fumes condensation) and that of larger particles (spattering) is progressively shifted from where it was at the beginning.
  • the methods of the prior art did not allow by only setting up appropriately the opera­ting conditions to selectively favour the production of either very fine dust issued from evaporation, or spattered parti­cles, or both.
  • the present inventors have attempted to remedy the aforementioned drawbacks and, as a consequence, they invented the method summarized in claim 1.
  • An electric arc is generated locally in the gas between a ring electrode in the nozzle and the metal to be pulverized by a magnetic field which acts on a portion of the gas curtain and which can be progressively rotated along the ring by conventional means.
  • the metal in the pot heats up and melts locally so that part of the arc activated gas dissolves therein.
  • the portions of molten metal no longer under the arc cool slightly, become oversaturated with dissolved gas and erupt with production of spattered particles which are wiped off by the annular gas stream.
  • the method disclosed in this document does not involve simultaneous controlled evapo­ration of the molten metal like in the present invention.
  • the stream of gas is blown permanently on the perimeter of the metal to be pulverized which, operationally, is not economical.
  • no gas stream is projected over the molten metal, but an alternation of "live” or active periods with “dormant” or quiescent ones is brought about, i.e. periods in which the metal is subjected to the electric arc and will progressively tend to dynamic thermal and chemical equilibrium successively alternate with "passive" periods in which the metallic dust of evaporation is elimi­nated and during which the metal cools off sufficiently for restoring the initial chemical and thermal conditions which promote effective pulverization at the beginning of the next period.
  • steps can also be taken to remove the metal­lic dust or fumes resulting from condensation of the vapors from the operating zone under the electric arc, this being possible, for instance by condensing the dust on a surface with particle attracting properties or by carrying away the particles and allowing them to settle into an appropriate receptacle.
  • the initial yield of the pulveri­zation operation is progressively perturbed and inhibited toward the end of a previous live period by the presence of metal vapor in the zone directly influenced by the electric arc, favorable operating conditions are renewed during the quiescent period and fully restored at the beginning of the next live period.
  • the duration of the live and dormant periods is quite variable and depends on many features, namely the kind of metal to be pulverized, the electric arc operating parameters, the size of the metal particles and the volume or weight distribution ratio between the particles of micronic or over­micronic size (produced by spattering) and the sub-micronic particles which result from metal vapor condensation.
  • the live periods will end before sputtering occurs, i.e. before the phenomena involving dissolved gas evolution become significant.
  • the arc parameters will be adjusted corresponding­ly, i.e. energy density, arc length, arc intensity and so on, so that the evaporation phenomena are minimized as much as possible and the duration of the live phase is determined in function to the evolution of the operation, e.g. the course of the pulverization progressive inhibition.
  • the live and dormant periods are in the order of a few seconds to a few minutes, e.g. 5 sec. to 5 min. and are set by experiment depending on the needs. Naturally the duration of the live and dormant phases can be identical or different.
  • the apparatus pictured in fig. 1 comprises a gas tight pulverization enclosure 1 housing a supporting structure 3 of a metal sample 3 to be pulverized.
  • a cathode 4 of zirconia/tungsten or thoriated tungsten (or any electrically conducting refractory material).
  • This cathode 4 is provided with a liquid cooling circuit 5, with a power line 6 connected to a power supply not represented and with an element 7 connected to a lever 8 rocked at position 9 for raising and lowering the cathode 4.
  • the enclosure 1 further comprises a receptacle 11 which surrounds holder 3, itself cooled by a liquid circuit 10, which receptacle 11 serves to collect the particles 12 of the pulverized metal that settle to the bottom thereof.
  • the recep­tacle is also cooled by a liquid circuit 10a, and the enclo­sure is also cooled by circuit 10b.
  • the enclosure 1 further comprises a gas input 12 and an output 13 connected to a decantation element not represented here (for instance a cyclone) to retain by deposition the ultra-fine dust resulting from direct evaporation.
  • a decantation element not represented here (for instance a cyclone) to retain by deposition the ultra-fine dust resulting from direct evaporation.
  • This gas can be hydrogen or a mixture of hydrogen and a noble gas such as argon, e.g. a 5-50 % (v/v) H2/Ar mixture.
  • the electrode 4 (cathode) is connected to a negative terminal of an electric generator while the enclosure is connected to the positive terminal.
  • the cathode is low­ered toward the sample 3 by means of the lever elements 7, 8 so as to trigger the development of an arc 14 between the electrode 4 and the sample 3 (see fig. 2).
  • the metal heats up, its melts and starts evaporating in the space directly subjec­ted to the arc as indicated by arrows 15.
  • the gas which fills the enclosure under reduced pressure e.g. 100-800 Torr gets activated by dissociation and starts dissolving into the mol­ten metal, more particularly in the space 14 which belongs to where the arc strikes the metal; then the dissolved gas is driven by the thermal displacement of the molten metal outside the hotter region 14 and there it starts forming bubbles 16 because of oversaturation.
  • a sreen can be interposed on the path of the fumes, for instance a removable wall capable of collec­ting the dust by electrostatic means wherefrom it can be gathered later.
  • the present apparatus is therefore capable of selecting metal powders depending on particle size. It should be noted that if, when the arc is disconnected, the tip of the cathode is dipped into the molten metal, a metal film adheres to the cathode. Then, when the arc is switched on again, one may transiently invert the direction of current (inverted polarity) which brings about instant pulverization of the metal film adhering to the cathode.
  • Fig. 3 represents a holder 22 of conductive refractory material comprising a rod 23 which can be rotated by some common mechanism (not shown here).
  • This holder comprises two recesses 24a, 24b each of which contains a sample of metal to be pulverized. Each recess can be put in turn in facing rela­tion with the electric arc 14 (exactly like the one sample 3 of Fig. 1), so that when one of the sample is the live phase, the second is quiescent. Transfer from one position to the other can be progressive (slow continuous rotation) or with substantially no or little transition (fast 180° step).
  • the number of recesses carrying metal samples can exceed 2 (it can be 4, 6 or more), or the sample can be a full ring (as in GB-A- 2.176.502) which rotates regularly, each portion of which enters repeatedly the active area of the arc and from there moves away for a next turn.
  • metals can be powderized in the present method including common and precious metals such as Al, Fe, Ni, Cu, Mn, Cr, W, Ni, Ag, Au, Pd, Pt, Rh, etc. and the alloys of two or more of these metals.
  • the actual pressure in the enclosure also has an influen­ce on the respective contribution of evaporation and spatter­ ing; lower pressures favor evaporation; high pressures, e.g. 730 - 750 Torr favor spattering.
  • the enclosure 1 is a Balzers sealed enclosure of 1 m3, water-cooled.
  • the crucible cooled by water, is of copper and has a diameter of 6,3 cm. It is connected to the enclosure by a vertical pillar.
  • the electrode is of thoriated-tungsten; it is water-cooled and its diameter is 6,4 mm.
  • the enclosure is evacuated by two pumps Balzers, a primary pump and a diffusion pump.
  • the gas is a 20 to 50 % (v/v) mixture of H2 and argon.
  • the generator can provide an arc of about 50 to 200 A.
  • a sample of metal flakes (about 5 to 30 g) was placed in the crucible; then, after flushing the enclosure with argon, it was filled with the above gas mixture under 740 Torr; the flow rate was very slow (about 5 - 10 l/hr removed by output 13 and replaced correspondingly by input 12).
  • the gases are provided from usual pressure cylinders equiped with pressure reducers and rotameters. After starting the arc by bringing the electrode near the crucible (5 mm), the electrode was withdrawn slightly (gap 10 mm) and the current was adjusted to a value below the priming value. The arc remained on for the duration of a live period.
  • a 50/50 by weight iron/nickel alloy was powderized under the following conditions.
  • Tungsten electrode (2% of thorium), diameter 6.3 mm, placed at 5 mm from the sample (active period).
  • Electrode as in Example 3 set at 3 mm from the sample metal contained in a copper crucible cooled with water cir­culation.
  • the gas used in the enclosure can also be of a kind that may react with the molten metal to be powderized, i.e. the operation provides a powder of a compound of the metal and the gas.
  • the operation provides a powder of a compound of the metal and the gas.
  • H2/Ar 30/70 (v/v), 740 Torr; 20 V, 150 A; tungsten electrode with 1% of Th, diameter 6.4 mm placed at a distance of 8 mm from the sample; graphite crucible; active periods 1 min; dead periods 1.5 min.
  • the yield was below 2 g/hr.
  • H2/Ar 20/20 (v/v), 740 Torr; 17 in, 120 A; tungsten electrode with 2% of Th, 6.3 mm of diameter, placed at 8 mm of the substrate; copper crucible. Live and dead periods, 1 min. each. By operating under a continuous regime, the production of powder was unsignificant.
  • the average size of the powder particles can be varied by modifying the various parameters that control pulverization, e.g. the gas pressure in the enclosure, the material of the electrode and its size as well as the distance between the electrode and the metal sample, and also the intensity of the electric arc.
  • the metal melts easily and the live period is long with a very strong arc all the available surface of the metal becomes melted and the production of fumes (very fine particles) predominates.

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  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Coating By Spraying Or Casting (AREA)
EP89810438A 1988-06-13 1989-06-09 Method to simultaneously pulverize and vaporize metals into particles of varied size distribution Withdrawn EP0347386A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH225388A CH676681A5 (enrdf_load_stackoverflow) 1988-06-13 1988-06-13
CH2253/88 1988-06-13

Publications (1)

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EP0347386A1 true EP0347386A1 (en) 1989-12-20

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EP (1) EP0347386A1 (enrdf_load_stackoverflow)
JP (1) JPH0234707A (enrdf_load_stackoverflow)
CH (1) CH676681A5 (enrdf_load_stackoverflow)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0718061A1 (en) * 1994-12-23 1996-06-26 Institute of Petroleum Chemistry, Russian Academy of Sciences Active metal powders
EP1109641A4 (en) * 1998-07-21 2004-10-06 Commw Scient Ind Res Org METHOD AND APPARATUS FOR PRODUCING VAPORS OF MATERIALS
US6972115B1 (en) 1999-09-03 2005-12-06 American Inter-Metallics, Inc. Apparatus and methods for the production of powders
US9023754B2 (en) 2005-04-19 2015-05-05 SDCmaterials, Inc. Nano-skeletal catalyst
US9089840B2 (en) 2007-10-15 2015-07-28 SDCmaterials, Inc. Method and system for forming plug and play oxide catalysts
US9149797B2 (en) 2009-12-15 2015-10-06 SDCmaterials, Inc. Catalyst production method and system
US9156025B2 (en) 2012-11-21 2015-10-13 SDCmaterials, Inc. Three-way catalytic converter using nanoparticles
US9216406B2 (en) 2011-02-23 2015-12-22 SDCmaterials, Inc. Wet chemical and plasma methods of forming stable PtPd catalysts
US9308524B2 (en) 2009-12-15 2016-04-12 SDCmaterials, Inc. Advanced catalysts for automotive applications
US9332636B2 (en) 2009-12-15 2016-05-03 SDCmaterials, Inc. Sandwich of impact resistant material
US9427732B2 (en) 2013-10-22 2016-08-30 SDCmaterials, Inc. Catalyst design for heavy-duty diesel combustion engines
US9498751B2 (en) 2011-08-19 2016-11-22 SDCmaterials, Inc. Coated substrates for use in catalysis and catalytic converters and methods of coating substrates with washcoat compositions
US9511352B2 (en) 2012-11-21 2016-12-06 SDCmaterials, Inc. Three-way catalytic converter using nanoparticles
US9517448B2 (en) 2013-10-22 2016-12-13 SDCmaterials, Inc. Compositions of lean NOx trap (LNT) systems and methods of making and using same
US9522388B2 (en) 2009-12-15 2016-12-20 SDCmaterials, Inc. Pinning and affixing nano-active material
US9586179B2 (en) 2013-07-25 2017-03-07 SDCmaterials, Inc. Washcoats and coated substrates for catalytic converters and methods of making and using same
US9687811B2 (en) 2014-03-21 2017-06-27 SDCmaterials, Inc. Compositions for passive NOx adsorption (PNA) systems and methods of making and using same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008069759A (ja) * 2006-09-15 2008-03-27 Hokuetsu Kogyo Co Ltd エンジン駆動型作業機

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR550891A (fr) * 1922-05-02 1923-03-22 Procédé pour réduire les métaux en particules infiniment petites
FR937763A (fr) * 1946-11-18 1948-08-26 Procédé et dispositifs pour l'obtention de poudres métalliques
US4238427A (en) * 1979-04-05 1980-12-09 Chisholm Douglas S Atomization of molten metals
WO1984004065A1 (en) * 1983-04-13 1984-10-25 Nuclear Metals Inc Rotary electrode disk apparatus for producing metal powders
GB2176582A (en) * 1985-06-20 1986-12-31 Daido Steel Co Ltd Furnace for producing fine grains
US4689075A (en) * 1984-10-16 1987-08-25 National Research Institute For Metals Process for producing mixed ultrafine powder of metals or ceramics

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR550891A (fr) * 1922-05-02 1923-03-22 Procédé pour réduire les métaux en particules infiniment petites
FR937763A (fr) * 1946-11-18 1948-08-26 Procédé et dispositifs pour l'obtention de poudres métalliques
US4238427A (en) * 1979-04-05 1980-12-09 Chisholm Douglas S Atomization of molten metals
WO1984004065A1 (en) * 1983-04-13 1984-10-25 Nuclear Metals Inc Rotary electrode disk apparatus for producing metal powders
US4689075A (en) * 1984-10-16 1987-08-25 National Research Institute For Metals Process for producing mixed ultrafine powder of metals or ceramics
GB2176582A (en) * 1985-06-20 1986-12-31 Daido Steel Co Ltd Furnace for producing fine grains

Cited By (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0718061A1 (en) * 1994-12-23 1996-06-26 Institute of Petroleum Chemistry, Russian Academy of Sciences Active metal powders
EP1109641A4 (en) * 1998-07-21 2004-10-06 Commw Scient Ind Res Org METHOD AND APPARATUS FOR PRODUCING VAPORS OF MATERIALS
US6972115B1 (en) 1999-09-03 2005-12-06 American Inter-Metallics, Inc. Apparatus and methods for the production of powders
US9719727B2 (en) 2005-04-19 2017-08-01 SDCmaterials, Inc. Fluid recirculation system for use in vapor phase particle production system
US9023754B2 (en) 2005-04-19 2015-05-05 SDCmaterials, Inc. Nano-skeletal catalyst
US9132404B2 (en) 2005-04-19 2015-09-15 SDCmaterials, Inc. Gas delivery system with constant overpressure relative to ambient to system with varying vacuum suction
US9599405B2 (en) 2005-04-19 2017-03-21 SDCmaterials, Inc. Highly turbulent quench chamber
US9216398B2 (en) 2005-04-19 2015-12-22 SDCmaterials, Inc. Method and apparatus for making uniform and ultrasmall nanoparticles
US9180423B2 (en) 2005-04-19 2015-11-10 SDCmaterials, Inc. Highly turbulent quench chamber
US9186663B2 (en) 2007-10-15 2015-11-17 SDCmaterials, Inc. Method and system for forming plug and play metal compound catalysts
US9737878B2 (en) 2007-10-15 2017-08-22 SDCmaterials, Inc. Method and system for forming plug and play metal catalysts
US9302260B2 (en) 2007-10-15 2016-04-05 SDCmaterials, Inc. Method and system for forming plug and play metal catalysts
US9089840B2 (en) 2007-10-15 2015-07-28 SDCmaterials, Inc. Method and system for forming plug and play oxide catalysts
US9597662B2 (en) 2007-10-15 2017-03-21 SDCmaterials, Inc. Method and system for forming plug and play metal compound catalysts
US9592492B2 (en) 2007-10-15 2017-03-14 SDCmaterials, Inc. Method and system for forming plug and play oxide catalysts
US9522388B2 (en) 2009-12-15 2016-12-20 SDCmaterials, Inc. Pinning and affixing nano-active material
US9308524B2 (en) 2009-12-15 2016-04-12 SDCmaterials, Inc. Advanced catalysts for automotive applications
US9332636B2 (en) 2009-12-15 2016-05-03 SDCmaterials, Inc. Sandwich of impact resistant material
US9149797B2 (en) 2009-12-15 2015-10-06 SDCmaterials, Inc. Catalyst production method and system
US9533289B2 (en) 2009-12-15 2017-01-03 SDCmaterials, Inc. Advanced catalysts for automotive applications
US9433938B2 (en) 2011-02-23 2016-09-06 SDCmaterials, Inc. Wet chemical and plasma methods of forming stable PTPD catalysts
US9216406B2 (en) 2011-02-23 2015-12-22 SDCmaterials, Inc. Wet chemical and plasma methods of forming stable PtPd catalysts
US9498751B2 (en) 2011-08-19 2016-11-22 SDCmaterials, Inc. Coated substrates for use in catalysis and catalytic converters and methods of coating substrates with washcoat compositions
US9156025B2 (en) 2012-11-21 2015-10-13 SDCmaterials, Inc. Three-way catalytic converter using nanoparticles
US9533299B2 (en) 2012-11-21 2017-01-03 SDCmaterials, Inc. Three-way catalytic converter using nanoparticles
US9511352B2 (en) 2012-11-21 2016-12-06 SDCmaterials, Inc. Three-way catalytic converter using nanoparticles
US9586179B2 (en) 2013-07-25 2017-03-07 SDCmaterials, Inc. Washcoats and coated substrates for catalytic converters and methods of making and using same
US9427732B2 (en) 2013-10-22 2016-08-30 SDCmaterials, Inc. Catalyst design for heavy-duty diesel combustion engines
US9566568B2 (en) 2013-10-22 2017-02-14 SDCmaterials, Inc. Catalyst design for heavy-duty diesel combustion engines
US9517448B2 (en) 2013-10-22 2016-12-13 SDCmaterials, Inc. Compositions of lean NOx trap (LNT) systems and methods of making and using same
US9950316B2 (en) 2013-10-22 2018-04-24 Umicore Ag & Co. Kg Catalyst design for heavy-duty diesel combustion engines
US9687811B2 (en) 2014-03-21 2017-06-27 SDCmaterials, Inc. Compositions for passive NOx adsorption (PNA) systems and methods of making and using same
US10086356B2 (en) 2014-03-21 2018-10-02 Umicore Ag & Co. Kg Compositions for passive NOx adsorption (PNA) systems and methods of making and using same
US10413880B2 (en) 2014-03-21 2019-09-17 Umicore Ag & Co. Kg Compositions for passive NOx adsorption (PNA) systems and methods of making and using same

Also Published As

Publication number Publication date
CH676681A5 (enrdf_load_stackoverflow) 1991-02-28
JPH0234707A (ja) 1990-02-05

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