EP0161245B1 - Low density, electromagnetic radiation absorption composition - Google Patents

Low density, electromagnetic radiation absorption composition Download PDF

Info

Publication number
EP0161245B1
EP0161245B1 EP83903870A EP83903870A EP0161245B1 EP 0161245 B1 EP0161245 B1 EP 0161245B1 EP 83903870 A EP83903870 A EP 83903870A EP 83903870 A EP83903870 A EP 83903870A EP 0161245 B1 EP0161245 B1 EP 0161245B1
Authority
EP
European Patent Office
Prior art keywords
composition
absorber
elm
attenuator
magnetic
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.)
Expired - Lifetime
Application number
EP83903870A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0161245A4 (en
EP0161245A1 (en
Inventor
Jitka Solc
Robert Francis Harris
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.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Publication of EP0161245A1 publication Critical patent/EP0161245A1/en
Publication of EP0161245A4 publication Critical patent/EP0161245A4/en
Application granted granted Critical
Publication of EP0161245B1 publication Critical patent/EP0161245B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
    • H01Q17/004—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems using non-directional dissipative particles, e.g. ferrite powders

Definitions

  • This invention relates to a composition for suppressing electromagnetic radiation and, particularly, for reducing the reflection of microwave energy.
  • Artificial dielectrics are generally formed by dispersing a magnetic powder or other natural absorber in a dielectric material, such as plastics including thermoplastics and thermosets, ceramics, waxes and the like.
  • the artificial dielectrics which have been formed by loading the aforementioned dielectric binders with magnetic metals, semi-conductors, ferromagnetic oxides or ferrites have very desirable magnetic and dielectric properties.
  • solid ferrites i.e., ferromagnetic ferrites formed of ferric oxide and other bivalent metal oxides
  • ferromagnetic ferrites formed of ferric oxide and other bivalent metal oxides
  • ferrites in the form of solid coatings display the higher permeabilities which are required for broad band operation.
  • Such solid ferrite coatings are capable of higher permeabilities than those exhibited by the ferrite powders since the amgnetic properties of ferrite decline appreciably by grinding it into powder form.
  • ferrites that are both non-conductive and ferromagnetic provide within a single composition the potentially optimum dielectric and magnetic properties.
  • a filled plastic composition which is suitable for use as a radar shield.
  • the composite comprises a first layer of a thermosetting polymer filled with particles of aluminum, iridium, tin, lead, bismuth or elements from Group IIB to Group VIIB of the Table of Elements and a second layer of polymer filled with oxides of these metals.
  • the metal concentration is from 40-93% by weight and the metal oxide concentration is from 40-90 weight percent.
  • the particle size of the filler is from 0.1 to 30 pm. It is also possible to mix the metal and the metal oxide in the same polymer prior curing.
  • the polymer is nonpolar in character.
  • An electromagnetic absorption composition having a density less than 6 g/cm 3 comprising a dielectric matrix having dispersed therein magnetic additives characterized in that the magnetic additives comprise
  • the present invention is such a low density ELM absorption composition which exhibits high efficiency in the absorption of electromagnetic radiation, particularly at microwave frequencies.
  • ELM compositions comprises (1) a dielectric material (hereinafter called dielectric matrix) having dispersed therein (2) a colloidal-size particulate of a material capable of absorbing electromagnetic radiation (hereinafter called ELM absorber) and (3) a particulate of a metal-containing material capable of providing increased attenuation of electromagnetic radiation (hereinafter called ELM attenuator).
  • ELM absorber a colloidal-size particulate of a material capable of absorbing electromagnetic radiation
  • ELM attenuator a particulate of a metal-containing material capable of providing increased attenuation of electromagnetic radiation
  • the concentration of ELM absorber in the ELM composition is advantageously sufficient to provide a magnetic loss tangent greater than 0.05 at a frequency of 2 Gigahertz (GHz) and a composition thickness of 2 centimeters (cm).
  • the concentration of ELM attenuator is sufficient to provide the ELM composition with an attenuation of greater than 0.5 decibels per centimeter (dB/cm) under the aforementioned conditions.
  • a low density ELM composition has a density less than 6 grams per cubic centimeter (g/cm 3 ).
  • the low density ELM composition of the present invention exhibits dissipative properties higher than would be expected at the concentrations of ELM absorber being employed.
  • composition according to this invention can be used as base for a stable fluid dispersion of the aforementioned ELM attenuator and colloidal-sized particles of the dielectric matrix containing colloidal or sub-colloidal particles of the ELM absorber.
  • a dispersion can be applied as a coating and dried to form a continuous film wherein the particles of the ELM absorber are maintained in an essentially discrete spaced apart relationship by the dielectric matrix.
  • particles of the ELM attenuator are also substantially maintained in an essentially discrete spaced apart relation by the dielectric matrix.
  • the ELM composition of this invention is particularly effective as an electromagnetic radiation absorber in such applications as paints and coatings to be used for reflection reduction for metal structures such as towers, bridges, ships, etc.; microwave camouflage and radar camouflage; coatings for appliances wherein microwave radiation absorption is desired, such as in microwave ovens and microwave browning devices: applications related to the transport of solar energy from space satellites; and the like.
  • This ELM composition is also well suited for molding shaped articles and for fabrication into foams and fibers.
  • the low density ELM composition of the present invention has a density, an attenuation and a magnetic loss tangent as defined hereinbefore.
  • Preferred compositions have (1) densities in the range from 1.2 to 5, most preferably from 1.5 to 3, g/cm 3 ; (2) magnetic loss tangent greater than 0.1, most preferably greater than 0.2 under the conditions specified hereinbefore; and (3) attenuation greater than 1 dB/cm, most preferably greater than 2 dB/cm.
  • the ELM compositions comprises three essential components: (1) a dielectric solid matrix acting as the continuous phase for the composition, (2) a particulate ELM absorber that is maintained in an essentially discrete, spaced apart relationship by the matrix and (3) a particulate ELM attenuator.
  • the ELM attenuator is also essentially totally dispersed in the dielectric matrix.
  • the dielectric matrix is suitably any normally solid material capable of serving as an insulating matrix (binder) for the ELM absorber. Preferably, it has an electrical resistivity greater than 106 ohms per centimeter (ohms/cm), more preferably greater than 10" ohms/cm, most preferably from 10 15 to 10 20 ohms/cm.
  • suitable dielectrics include glass, ceramics, waxes, plastics, including thermoplastics and thermosets, rubber polymers and the like, with the synthetic plastics being preferred.
  • polymers that are water-insoluble and are prepared from hydrophobic monomers that are essentially water-immiscible, i.e., the monomer forms a separate phase when 5 grams of the monomer is mixed with 100 grams of water.
  • Such water immiscible monomers will polymerize under emulsion polymerization conditions to form a water-insoluble polymer which will exist in the form of a stable aqueous colloidal dispersion, usually with the aid of suitable surface active. agents.
  • the ELM absorber is a material (1) which absorbs electromagnetic radiation having frequencies in the range from 0.3 to 20 GHz and (2) which is in .the form of a colloidal or sub-colloidal size particulate.
  • Preferred ELM absorbers can be further characterized as paramagnetic or superparamagnetic due to their small size.
  • examples of such materials are compounds of magnetic metals such as ferromagnetic oxides of ferrities, e.g., Fe 3 0 4 , as well as ferromagnetic ferrites formed of ferric oxide and various bivalent metal oxides such as metal oxides of nickel, zinc and manganese; magnetic metals such as iron, cobalt and nickel and their alloys; and other known ELM absorbing materials such as carbon black, graphite and the like.
  • the ELM absorber generally contains particles having a maximum dimension less than about 1 pm, preferably in the range from about 0.01 to 0.7 pm. Of these materials, the magnetic metallic compounds are preferred, with Fe 3 0 4 being most preferred.
  • the ELM attenuator is preferably a ferromagnetic material which is capable of providing microwave attenuation as described hereinbefore.
  • the ELM attenuator is in the form of particles having a dimension greater than 1 pm, preferably in the range from 1.5 to 100 pm, most preferably from 2 to 75 um.
  • attenuating materials are iron, cobalt, nickel, and other ferromagnetic metals as well as alloys of such metals. Of these materials, metallic iron is preferred, with carbonyl iron being most preferred. It is understood, however, that in addition to carbonyl iron, metallic iron made by other procedures such as electrolytic iron, reduced iron and atomized iron are preferred.
  • ELM absorbing compositions of this invention it is advantageous to disperse the ELM absorber into the dielectric matrix such that dielectric matrix forms a continuous phase that maintains the particles of ELM absorber in an essentially discrete, spaced apart relationship.
  • Any of a variety of conventional blending procedures for incorporating a colloidal or sub-colloidal particulate into dielectric binders are suitably employed for this purpose.
  • the dielectric matrix having the ELM absorber dispersed therein is prepared by initially forming an aqueous dispersion of the ELM absorber by contacting colloidal or sub-colloidal particles of said absorber with an aqueous solution of a water-soluble surfactant or emulsifier, thereby forming the dispersion which contains from 5 to 70 weight percent of the absorber particles.
  • aqueous dispersions of ELM absorbers are the so-called ferrofluids such as disclosed in the US-A-3,981,844, preferably those having an average particle diameter in the range from 0.05 to 0.1 micrometer.
  • such fluids are aqueous dispersions of the magnetic metals which are stabilized by the presence of surfactants, emulsifiers and/or chemical dispersants as described hereinafter.
  • suitable surface active agents, dispersants or emulsifiers include salts of fatty acids such as potassium oleate, metal alkyl sulfates such as sodium lauryl sulfate, salts of alkyl aryl sulfonic acids such as sodium dodecylbenzene sulfonate, polysoaps such as sodium polyacrylate and alkali metal salts of methyl methacrylate/2-sulfoethyl methacrylate copolymers and other sulfoalkyl acrylate copolymers, and other anionic surfactants such as the dihexyl ester of sodium sulfosuccinic acid; nonionic surfactants such as the nonionic condensates of ethylene oxide with propylene oxide, ethylene glycol and/or propylene glycol; and cationic surfactants such as alkylamine-guanidine polyoxyethanols, as well as a wide variety of micelle generating substances described by
  • such surface active agents are employed in concentrations in the range from 0.2 to 10, most preferably from 1 to 6, weight percent based on the aqueous phase.
  • Particularly desirable processes for forming such aqueous colloidal dispersions of the ELM absorber are described in US-A-(s), 3,826,667; 3,981,844; 3,843,540 and Industrial Engineering Production and Research Development, Vol. 19, 147-151 (1980).
  • the aqueous dispersion of the ELM absorber is then combined with the water-immiscible monomer as described herein to form the desired emulsion by normal mixing procedures, for example, by passing both the dispersion and monomer through a high shear mixing device such as a Waring blender, homogenizer or ultrasonic mixer.
  • a high shear mixing device such as a Waring blender, homogenizer or ultrasonic mixer.
  • the monomer is added continuously to the aqueous dispersion of the ELM absorber during the polymerization.
  • the monomer is in the form of an aqueous emulsion of the monomer which emulsion is maintained by a water-soluble monomer and/or a water-soluble emulsifier such as described hereinbefore.
  • the aqueous emulsion of the ELM absorber and water-immiscible monomer can be prepared by adding colloidal or sub-colloidal particles of the ELM absorber to an existing aqueous emulsion of monomer.
  • the aqueous phase is present in a proportion sufficient to be the continuous phase of the emulsion.
  • the ELM absorber is present in proportions sufficient to provide the dielectric/absorber particulate with the desired dissipative properties.
  • the water-immiscible monomer is present in proportion sufficient to enclose or encapsulate the ELM absorber when polymerized.
  • the emulsifier and/or surface active agent is present to provide an aqueous colloidal emulsion which is sufficiently stable to be subjected to emulsion polymerization conditions.
  • the emulsion contains from 0.1 to 25 weight percent of ELM absorber, from 1 to 30 weight percent of monomer and a remaining amount of the aqueous phase including emulsifier (surfactant), catalyst and the like.
  • Suitable water-immiscible monomers that can be employed to prepare the aforementioned dielectric/absorber include monovinylidene aromatic monomers such as styrene, vinyl tolune, t-butyl styrene, chlorostyrene, vinyllbenzyl chloride and vinyl pyridine; alkyl esters of ⁇ ,8-ethylenically unsaturated acids such as ethyl acrylate, methyl methacrylate, butyl acrylate and 2-ethylhexyl acrylate; unsaturated esters of saturated carboxylic acids such as vinyl acetate, unsaturated halides such as vinyl chloride and vinylidene chloride; unsaturated nitriles such as acrylonitrile; dienes such as butadiene and isoprene; and the like.
  • monovinylidene aromatics such as styrene and the alkyl acrylates such as butyl acrylate are preferred
  • relatively minor portions e.g., less than 10, preferably less than 5, weight percent based on total monomer component, of a water-soluble monomer such as an ethylenically unsaturated carboxylic acid or its salt such as acrylic acid or sodium acrylate; methacrylic acid, itaconic acid and maleic acid; an ethylenically unsaturated carboxamide such as acrylamide; vinyl pyrrolidone; hydroxyalkl acrylates and methacrylates such as hyroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate; aminoalkyl esters of unsaturated acids such as 2.
  • a water-soluble monomer such as an ethylenically unsaturated carboxylic acid or its salt such as acrylic acid or sodium acrylate; methacrylic acid, itaconic acid and maleic acid; an ethylenically unsaturated carboxamide such as acrylamide; vinyl pyrrolidone;
  • aminoethyl methacrylate epoxy functional monomers such as glycidyl methacrylate; sulfoalkyl esters of unsaturated acids such as 2-sulfoethyl methacrylate; ethylenically unsaturated quaternary ammonium compounds such as vinylbenzyl trimethyl ammonium chloride may be employed. It is critical in the practice of this preferred embodiment,that such water-soluble monomers not be employed in amounts sufficient to render the resulting polymer soluble in water.
  • Particularly effective monomer recipes for the pracice of this invention are those containing from 20 to 90 weight percent of styrene, from 10 to 80 weight percent of alkyl acrylate such as butyl acrylate and from 0.01 to 2 weight percent of the unsaturated carboxylic acids such as acrylic acid, with said weight percentages being based on the weight of total monomers.
  • the emulsion polymerization conditions employed in the practice of this preferred embodiment of the invention are generally those of conventional free-radical type polymerizations carried out in the presence of a radical initiator such as a peroxygen compound, an azo catalyst, ultraviolet light and the like.
  • a radical initiator such as a peroxygen compound, an azo catalyst, ultraviolet light and the like.
  • such polymerization is carried out in the presence of a water-soluble peroxygen compound at temperatures in the range from 50° to 90°C.
  • the emulsion is generally agitated during the polymerization period in order to maintain adequate feed transfer.
  • the concentration of catalyst is normally in the range from 0.005 to 8, preferably from 0.01 to 5, weight percent based on total monomer.
  • Suitable catalysts include inorganic persulfate compounds such as sodium persulfate, potassium persulfate, ammonium persulfate; peroxides such as hydrogen peroxide, t-butyl hydroperoxide, dibenzol peroxide and dilauroyl peroxide; azo catalysts such as azobisisobutyronitrile, and other common free-radial generating compounds.
  • peroxides such as hydrogen peroxide, t-butyl hydroperoxide, dibenzol peroxide and dilauroyl peroxide
  • azo catalysts such as azobisisobutyronitrile, and other common free-radial generating compounds.
  • free-radical generating radiation means such as ultraviolet radiation, electron beam radiation and gamma radiation.
  • a redox catalyst composition can be employed wherein the polymerization temperature ranges from 25° to 80°C.
  • Exemplary redox catalyst compositions include a peroxygen compound as described hereinbefore, preferably potassium persulfate or t-butyl hydroperoxide and a reducing component such as sodium metabisulfite and sodium formaldehyde hydrosulfite. It is also suitable to employ various chain transfer agents such as mercaptans, e.g., dodecyl mercaptan; dialkyl xanthogen disulfides; dialyl disulfides and others listed in Blackley, supra, Chapter 8 in concentrations as described therein.
  • mercaptans e.g., dodecyl mercaptan
  • dialkyl xanthogen disulfides dialyl disulfides and others listed in Blackley, supra, Chapter 8 in concentrations as described therein.
  • the resulting aqueous dispersion of the particles of dielectric/ELM absorber can be withdrawn from the polymerization vessel nd (1) the dispersion is employed as is or (2) the unreacted monomer and other volatiles are removed to form a concentrated dispersion and then used as a paint base for the ELM composition or (3) the dielectric/ELM absorber particulate can be separated from the aqueous continuous phase of the dispersion by conventional means such as spray drying or drying under vacuum. If dried, the dielectric/ELM absorber particulate preferably contains from 10 to 80, most preferably from 15 to 70, weight percent of the ELM absorber and from 90 to 20, most preferably from 85 to 30, weight percent of dielectric matrix polymer.
  • the dielectric/ELM absorber in the form of an aqueous dispersion or a dry colloidal-size particulate is then combined with the ELM attenuator to provide the desired low density, ELM absorbing composition.
  • the ELM attenuator (particulate) is dispersed as an aqueous dispersion of the dielectric/ELM absorber, thereby forming a coating composition which can be applied to any substrate as desired and dried to a continuous coating capable of absorbing ELM radiation.
  • the ELM attenuator may be encapsulated in a suitably dielectric material as defined hereinbefore prior to combination with the dielectric/ELM absorber.
  • the ELM attenuator and dielectric/ELM absorber may be in the form of aqueous dispersions and/or in the form of dry powders when combined.
  • the resulting low density, ELM compositions can be fabricated into an article of desired shape by conventional fabrication techniques such as injection or compression molding, extrusion and the like.
  • the ELM composition in the form of a dry powder is dispersed in a nonaqueous liquid and employed as desired, e.g., as a paint base for other coating formulations.
  • ELM absorbing compositions that employ colloidal-size Fe 3 0 4 as the ELM absorber and carbonyl iron as the ELM attenuator have an ELM absorber:ELM attenuator weight ratio from 90: 10 to 40:60, most preferably from 80:20 to 55:45. in the preferred ELM compositions, the weight ratio of the sum of ELM absorber and ELM attenuator to the dielectric matrix is from 85:15 to 10:90, most preferably from 70:30 to 55:45.
  • these compositions optionally contain other ingredients such as stabilizers, pigments, fillers, blowing agents, corrosion inhibitors and other additives commonly employed in ELM absorbing compositions.
  • An aqueous dispersion of magnetic iron oxide (Fe 3 0 4 ) (ELM absorber) is prepared by mixing aqueous solutions of ferric and ferrous salts in amounts to maintain the Fe +3 /Fe +2 molar ratio at -2:1. Magnetic iron oxide is then precipitated at 0°-10°C by rapid addition of 1N NH 4 0H and vigorous agitation until a pH of 9-10 is reached. Immediately thereafter, the dispersant is introduced with agitation to the aqueous medium containing the precipitated iron oxide and the mixture is heated at 90°C for one hour. During this period, hydrochloric acid is added until the pH of the mixture reaches 7.5.
  • the particles of precipitated iron oxide are washed with deionized water and redispersed in deionized water containing -0.5 g of a potassium salt of a functionalized oligomer (Polywet ® KX-4 sold by Uniroyal Chemical) per gram of precipitated iron oxide, by using an ultrasonic probe. Magnetization of the dispersed iron oxide is measured by a Collpits oscillator circuit technique.
  • a potassium salt of a functionalized oligomer Polywet ® KX-4 sold by Uniroyal Chemical
  • the monomer stream consists of 64 g of styrene, 16 g of butyl acrylate and 3 g of t-butyl hydroperoxide.
  • the aqueous stream consists of 110 g of deionized water, 2.9 g of the potassium salt of a functionalized oligomer ("Polywet® KX-4") and 2 g of sodium formaldehyde hydrosulfite.
  • the resulting reaction mixture is stirred and maintained under nitrogen at 90°C for an additional half hour.
  • the resulting 25 percent solids latex is concentrated by distillation under vacuum to a 30.3 percent solids latex (dielectric/ELM absorber) having dispersed particles with a polymeric as well as magnetic characteristic.
  • the particles of this latex have a narrow particle size distribution and an average particle diameter of 0.11 pm as determined by hydrodynamic chromatography.
  • the latex remains stable in an applied magnetic field of 1800 gauss and exhibits properties common to magnetic colloids.
  • such magnetic colloids are magnetizable liquids that are instantly demagnitized upon removal of a magnetic field and levitate an object upon application of a magenetic field.
  • Magnetization of the latex by a Collpits oscillator circuit technique described by E. A. Paterson et al. in the Journal of Colloidal and Interfacial Science, 70, 3 (1977), is estimated to be 135 gauss.
  • the particles of the latex are recovered by freeze drying the latex at -80°C under vacuum at 0.5 mm Hg.
  • ELM composition (Sample No. 1) is prepared by dry blending 50.3 g of a dry powder of the aforementioned latex (55.4 percent dielectric/44.6 percent Fe 3 0 4 ) with 33.5 g of carbonyl iron (ELM attenuator) having an average particle size of 3-4 micrometers and sold by GAF Corporation under the trade name Super Fine Special.
  • the blending is carried out on a Brabender mixing apparatus and the resultang blend is then compression molded into flat plates (0.8 cm thicknessx2.6 cm diameter) at 2000 pounds of positive pressure and 230°C for 2 minutes.
  • the sample is cooled to room temperature and the pressure on the sample is released.
  • the resultant plate of the ELM composition is machined into two flat disks having a diameter of 2.54 cm and a thickness of 0.64 cm and 0.32 cm, respectively.
  • a second ELM composition (Sample No. 2) is prepared following the foregoing procedure using 56.5 g of the dry powder of the latex and 18.8 g of the carbonyl iron. The sample is similarly blended, molded and fabricated into disks. For purposes of comparison, a third sample (Sample No. C) of dry particles of the latex is molded and fabricated into disks by the foregoing procedure.
  • compositions of the present invention exhibit significantly better attenuation at a given frequency than does the composition of Sample No. C.

Landscapes

  • Compositions Of Macromolecular Compounds (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Conductive Materials (AREA)
  • Aerials With Secondary Devices (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Hard Magnetic Materials (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Paints Or Removers (AREA)
EP83903870A 1983-11-07 1983-11-07 Low density, electromagnetic radiation absorption composition Expired - Lifetime EP0161245B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1983/001747 WO1985002265A1 (en) 1983-11-07 1983-11-07 Low density, electromagnetic radiation absorption composition

Publications (3)

Publication Number Publication Date
EP0161245A1 EP0161245A1 (en) 1985-11-21
EP0161245A4 EP0161245A4 (en) 1986-04-15
EP0161245B1 true EP0161245B1 (en) 1990-07-25

Family

ID=22175559

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83903870A Expired - Lifetime EP0161245B1 (en) 1983-11-07 1983-11-07 Low density, electromagnetic radiation absorption composition

Country Status (7)

Country Link
EP (1) EP0161245B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS61500338A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
AU (1) AU562564B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE3381770D1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DK (1) DK301185D0 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
NO (1) NO167170C (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
WO (1) WO1985002265A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Families Citing this family (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2671368B2 (ja) * 1988-04-13 1997-10-29 株式会社リケン 磁気シールドシート
DE3900856A1 (de) * 1989-01-13 1990-07-26 Messerschmitt Boelkow Blohm Fassadenaufbau von hochbauten
CA2005198A1 (en) * 1989-01-26 1990-07-26 Charles E. Boyer, Iii Microwave absorber employing acicular magnetic metallic filaments
GB2269594B (en) * 1992-08-11 1995-08-30 Siemens Plessey Electronic Load material for use in microwave lenses
GB2308127A (en) * 1995-12-15 1997-06-18 Ams Polymers Radiation absorbing materials
IT1303021B1 (it) * 1998-04-17 2000-10-20 M M T S R L Dispositivo assorbitore di onde elettromagnetiche
FR2818445B1 (fr) * 2000-12-18 2003-03-07 Marie Claude Bonnabaud Dispositif de decouplage de resonance pour la protection du corps humain
JP5259096B2 (ja) * 2007-02-13 2013-08-07 浜松ホトニクス株式会社 ファイバオプティック及びその製造方法
CN107069274B (zh) 2010-05-07 2020-08-18 安费诺有限公司 高性能线缆连接器
WO2012076764A2 (fr) * 2010-12-06 2012-06-14 Schultz, Christophe Technologie piezo gel - peinture pour eradiquer les pollutions electromagnetiques et les courants statiques
US9831588B2 (en) 2012-08-22 2017-11-28 Amphenol Corporation High-frequency electrical connector
WO2015112773A1 (en) 2014-01-22 2015-07-30 Amphenol Corporation Very high speed, high electrical interconnection system with edge to broadside transition
CN108701922B (zh) 2015-07-07 2020-02-14 Afci亚洲私人有限公司 电连接器
WO2018039164A1 (en) 2016-08-23 2018-03-01 Amphenol Corporation Connector configurable for high performance
CN208862209U (zh) 2018-09-26 2019-05-14 安费诺东亚电子科技(深圳)有限公司 一种连接器及其应用的pcb板
US12300936B2 (en) 2019-02-19 2025-05-13 Amphenol Corporation High speed connector
TW202135385A (zh) 2020-01-27 2021-09-16 美商Ｆｃｉ美國有限責任公司 高速連接器
WO2021154718A1 (en) 2020-01-27 2021-08-05 Fci Usa Llc High speed, high density direct mate orthogonal connector
CN111707895A (zh) * 2020-06-22 2020-09-25 合肥博雷电气有限公司 一种基于机器学习的电磁环境复杂度评估方法及系统
CN215816516U (zh) 2020-09-22 2022-02-11 安费诺商用电子产品(成都)有限公司 电连接器
CN213636403U (zh) 2020-09-25 2021-07-06 安费诺商用电子产品(成都)有限公司 电连接器
CN215266741U (zh) 2021-08-13 2021-12-21 安费诺商用电子产品(成都)有限公司 一种满足高带宽传输的高性能卡类连接器

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610250A (en) * 1946-11-05 1952-09-09 Hazeltine Research Inc Electromagnetic-wave energyabsorbing material
US2544391A (en) * 1948-12-30 1951-03-06 Monsanto Chemicals Coating composition
US4024318A (en) * 1966-02-17 1977-05-17 Exxon Research And Engineering Company Metal-filled plastic material
US3843593A (en) * 1972-06-05 1974-10-22 Du Pont Radar absorptive coating composition of an acrylic polymer,a polyester and an isocyanate cross-linking agent
US3981844A (en) * 1975-06-30 1976-09-21 Ibm Stable emulsion and method for preparation thereof
JPS51163498U (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1976-06-09 1976-12-27
JPS54121047A (en) * 1978-03-13 1979-09-19 Tdk Corp Electric wave absorbing material
JPS54121046A (en) * 1978-03-13 1979-09-19 Tdk Corp Electric wave absorbing material
JPS5639080A (en) * 1979-09-08 1981-04-14 Nippon Shinyaku Co Ltd Benzisothiazole derivative
DE3024888A1 (de) * 1980-07-01 1982-02-04 Bayer Ag, 5090 Leverkusen Verbundmaterial zur abschirmung elektromagnetischer strahlung
US4663288A (en) * 1985-05-22 1987-05-05 Nabisco Brands, Inc. Process for purification of enzymes

Also Published As

Publication number Publication date
NO852701L (no) 1985-07-04
DE3381770D1 (de) 1990-08-30
DK301185A (da) 1985-07-02
NO167170C (no) 1991-10-09
EP0161245A4 (en) 1986-04-15
DK301185D0 (da) 1985-07-02
NO167170B (no) 1991-07-01
JPS61500338A (ja) 1986-02-27
WO1985002265A1 (en) 1985-05-23
EP0161245A1 (en) 1985-11-21
AU562564B2 (en) 1987-06-11
JPH0422325B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1992-04-16
AU2340784A (en) 1985-06-03

Similar Documents

Publication Publication Date Title
EP0161245B1 (en) Low density, electromagnetic radiation absorption composition
US4414339A (en) Low density, electromagnetic radiation absorption composition
US4824587A (en) Composites of coercive particles and superparamagnetic particles
US4116906A (en) Coatings for preventing reflection of electromagnetic wave and coating material for forming said coatings
US4609608A (en) Colloidal size hydrophobic polymer particulate having discrete particles of a metal dispersed therein
Bueno et al. Microwave-absorbing properties of Ni0. 50–xZn0. 50− xMe2xFe2O4 (Me= Cu, Mn, Mg) ferrite–wax composite in X-band frequencies
CA1188017A (en) Colloidal size hydrophobic polymer particulate having discrete particles of an inorganic material dispersed therein
KR920007431B1 (ko) 전파 흡수재
US5676877A (en) Process for producing a magnetic fluid and composition therefor
US4438179A (en) Resin particles with magnetic particles bonded to surface
CN116063846B (zh) 一种吸波材料的制备方法
CN113260242A (zh) 一种掺杂稀土元素的磁性粒子负载于层状MXene上的复合吸波材料
CN108822797A (zh) 一种钛硅碳复合吸波剂及其制备方法与应用
US4862174A (en) Electromagnetic wave absorber
CN109971300A (zh) 一种吸波涂层及其制备方法
US7175909B2 (en) Hydrophilic magnetic metal oxide nanoparticles and preparing method thereof
CN109796932A (zh) 一种复合吸波材料及其制备方法
CA1195488A (en) Low density, electromagnetic radiation absorption composition
CN111286225A (zh) 一种石墨烯吸波膜涂料及其制备方法和应用
Chakraborty et al. Electromagnetic interference reflectivity of nanostructured manganese ferrite reinforced polypyrrole composites
EP0380267B1 (en) Microwave absorber employing acicular magnetic metallic filaments
JPH03238895A (ja) マイクロ波―吸収素材
EP0392065A1 (en) Micro composite systems and processes for making same
CN117545264A (zh) 一种低频吸波材料及其制备方法
US4532153A (en) Method of bonding magnetic particles to a resin particle

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19850708

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE FR GB LI NL SE

A4 Supplementary search report drawn up and despatched

Effective date: 19860415

17Q First examination report despatched

Effective date: 19880830

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): CH DE FR GB LI NL SE

ET Fr: translation filed
REF Corresponds to:

Ref document number: 3381770

Country of ref document: DE

Date of ref document: 19900830

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19910829

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19910903

Year of fee payment: 9

Ref country code: SE

Payment date: 19910903

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19910907

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19911001

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19911130

Year of fee payment: 9

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19921107

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19921108

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19921130

Ref country code: CH

Effective date: 19921130

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19930601

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19921107

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930730

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930803

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

EUG Se: european patent has lapsed

Ref document number: 83903870.0

Effective date: 19930610