154results about How to "Increase dielectric loss" patented technology

The invention relates to a method for preparing ferriferrous oxide microwave adsorbing material by utilizing copper-iron tailing pyrite cinder, comprising the following steps: the copper-iron tailing pyrite cinder is soaked by curing acid to obtain crude ferric sulphate solution; reduction reaction is carried out to obtain crude ferrous sulphate solution; purification and heating in water bath are carried out, NaOH solution is dropped to maintain reaction, air is blown in, reaction end point is recognized by measuring molar ratio Fe / Fe , magnetic adsorptive separation and drying are carried out for obtaining Fe3O4 magnetic particles; the obtained Fe3O4 magnetic particles is evenly stirred with melted ceresin wax, pressing and cooling are carried out for manufacturing the adsorbing material. The method has the beneficial effects that: 1) the iron recovery can reach about 80 percent by effectively extracting from the copper-iron tailing pyrite cinder; 2) the obtained Fe3O4 has high purity without impurities; 3) a new pathway for comprehensively utilizing the cinder is opened up, and a new raw material and a process are provided for the production of relative iron microwave adsorbing materials.

The invention discloses a carbonyl iron/graphene/polyvinylpyrrolidone compound wave-absorbing material, a preparation method thereof and the prepared wave-absorbing plate prepared by the method. The carbonyl iron/graphene/polyvinylpyrrolidone compound wave-absorbing material comprises a carbonyl iron powder core layer, a reduction-oxidation graphene layer which is coated on the periphery of the carbonyl iron powder core layer and a polyvinylpyrrolidone layer which is coated on the periphery of the reduction-oxidation graphene layer. The carbonyl iron/graphene/polyvinylpyrrolidone compound wave-absorbing material disclosed by the invention is characterized by simple preparation process, strong electromagnetic wave absorption capacity, wide frequency bandwidth, low cost and important application value in the fields of microwave absorption, electromagnetic leakage solution, electromagnetic shielding, and the like.

The invention discloses a zirconium and titanium-co-doped barium ferrite wave-absorbing powder material. The chemical formula is BaFe(12-x)ZrxTixO19, wherein x is equal to 0.2-0.4. The zirconium and titanium-co-doped barium ferrite is single-phase polycrystalline powder, and Fe<3+> and Fe<2+> exist in the barium ferrite at the same time. A preparation method comprises the following step of preparing the zirconium and titanium-co-doped barium ferrite wave-absorbing powder material by virtue of a self-propagating combustion method which is combined with ball-milling and a sequential secondary vacuum high-temperature thermal treatment process. The wave-absorbing material disclosed by the invention has the characteristics of being strong in absorption loss, wide in wave absorbing bandwidth, thin in match thickness and wide in modulated wave-absorbing frequency range. The effective wave absorbing bandwidth is controlled in a frequency range of 18-40GHz, double absorption peaks appear, the maximum absorbing bandwidth can reach 16GHz, the optimum match thickness is just about 1mm, and the optimum reflection loss RL value at the special frequency can reach about -48dB. The barium ferrite wave-absorbing powder material is simple in preparation process, can be used for a wave-absorbing coating, and can be widely applied to the fields of electromagnetic shielding and stealth.

The invention relates to a preparation method of a foam aluminium alloy wave-absorbing material, comprising surface pretreatment of foam aluminium alloy substrates, preparation of wave-absorbing coating and spraying of the wave-absorbing coating. The preparation method of the wave-absorbing material comprises the following steps of: (1) adding a coupling agent to polyaniline, adding a rare earth oxide after ball milling wet mixing, drying after ball milling wet mixing, and dry mixing to prepare a composite filler; (2) adding the coupling agent to the composite filler to prepare a coupling filler; (3) uniformly mixing a dispersing agent and a diluent, and adding the mixture to the coupling filler to prepare a dispersed filler; and (4) mixing epoxide resin with polyamide to prepare a film forming matter, grinding the film forming matter together with the dispersed filler, mixing, stirring, carrying out sonic oscillation, stirring and sieving, wherein the screenings are used as wave-absorbing coating. The wave-absorbing agent foam aluminium alloy-based wave-absorbing material doped with rare earth oxide has excellent wave-absorbing performance, and the bandwidth lower than -10dB can reach 13.5GHz in the frequency range of 26.5GHz to 40.0GHz.

The invention relates to organosilane modified bisphenol A-typed cyanate ester resin and a preparation method thereof, which have the technical characteristics that the following steps are included: heating and fusing the bisphenol A-typed cyanate ester monomer; adding organosilane to be heated and stirred; carrying out pre-polymerization, pouring the pre-polymer into a preheated mold; vacuumizing to remove bubbles; putting into an oven to be solidified based on certain solidification technology to obtain the organosilane modified bisphenol A-typed cyanate ester resin. Compared with the traditional ethylene rhodanate modification method, the method of the invention ensures the ethylene rhodanate modification system to have excellent mechanical performance, heat performance and dielectric performance owing to the fact that the organosilane is characterized by low molecular weight and good compatibility with the ethylene rhodanate resin. Furthermore, the modification system has favorable impact strength, bending strength and excellent heat resistance and dielectric performance, which can be used as the resin matrix of electronic encapsulating materials and wave-transparent composite materials.

The invention discloses a dielectric-based broadband tunable metamaterial wave-absorbing body and relates to the field of wave-absorbing materials and metamaterials. An electromagnetic wave-absorbingunit is formed by combining a soil material with a dielectric substrate on which a conductive thin film is pasted; and impedance matching is achieved through the electromagnetic wave-absorbing unit and a free space to achieve a relatively good wave-absorbing effect. The metamaterial wave-absorbing body is formed by periodically arranged wave-absorbing units and comprises the dielectric substrate,the soil material and the conductive thin film clung to the dielectric substrate. Square holes which are circular in inside are firstly engraved into the dielectric substrate, and then the soil material is embedded into the holes of the dielectric substrate and is in contact with the conductive thin film. By using the characteristic that the soil material has a high dielectric loss along with thechange of the water content in a microwave frequency band, the wave-absorbing bandwidth can be significantly increased under the condition of a relatively small thickness; main raw materials are easyto obtain and the metamaterial wave-absorbing body is eco-friendly, simple in structure, mature in preparation process, low in cost and suitable for large-scale production; and the wave-absorbing effect of the metamaterial wave-absorbing body can be adjusted through changing the water content of the soil material, so that operation is more convenient and concise.

The invention relates to a polydopamine (PDA) modified fluororesin mixture, a prepreg prepared from the polydopamine modified fluororesin mixture and a copper-clad plate. The surface of an inorganic filler is modified with amino, and then PDA is connected to the surface of the inorganic filler through chemical bonds through a reaction of the amino and dopamine. By modifying glass fiber cloth withthe PDA, on one hand, the compatibility between the inorganic filler and fluororesin is improved, and the dispersity of the inorganic filler in the fluororesin matrix is promoted; on the other hand, the interaction between the inorganic filler, the fluororesin, the glass fiber cloth and copper foil is enhanced. Furthermore, the high-frequency copper-clad plate prepared from the prepreg, a film andcopper foil is good in thermal-mechanical property, dielectric property, combination property stability and uniformity, especially, the copper foil peel strength is very high, and the requirements ofthe high-frequency communication field for various combination properties of a substrate material can be met.

The invention relates to a fluorine-containing polymer/conductive fiber dielectric material and a preparation method thereof.The fluorine-containing polymer/conductive fiber dielectric material is formed by mixing conductive fiber and a fluorine-containing polymer cPVDF material.The conductive fiber is polymer fiber with the surface coated with silver.The preparation method of the conductive fiber comprises the steps that the polymer fiber is placed in a dopamine alkaline aqueous solution to be soaked for a period of time, then taken out to react in air for a period of time, subjected to the soaking-autopolymerization reaction repeatedly and repeatedly lifted and pulled, washed with deionized water and dried to obtain the polydopamine modified fiber; the surface of the polydopamine modified fiber is coated with a layer of silver through a chemical silvering method; finally, the obtained fiber is thoroughly washed with distilled water, and dried in a vacuum drying box to obtain the conductive fiber.The conductive fiber is used as a filler and mixed with fluorine-containing polymer cPVDF; due to the fact that the surface layer of the conductive fiber is the conductive material, the dielectric constant of the composite material can be improved, dielectric loss will not be greatly increased when the dielectric constant is increased, the dielectric property is excellent, and the using range is wide.

The invention relates to the technical field of manufacturing of microwave dielectric ceramic materials, and particularly relates to a BMN (bismuth magnesium niobate)-based microwave dielectric ceramic material and a preparation method thereof. By regulating the reasonable ratio of dielectric functional additive, the material provided by the invention comprises the following components in percentage by mol: 58-59% of Bi2O3, 6.8-6.9% of MgO, 24-33% of Nb2O5, 0.15-0.2% of Li2CO3 and 1.2-10.2% of SnO2, wherein Bi2O3, MgO and Nb2O5 are main materials; Li2CO3 is dielectric functional additive; and SnO2 is dielectric functional additive. For the BMN-based ceramic material prepared through the traditional solid-phase synthesis method, the dielectric constant is 143-175, the dielectric loss is 0.00038-0.00049, and the dielectric temperature coefficient is (-536)-(-432)ppm/DEG C. The BMN-based microwave dielectric ceramic material provided by the invention can be used for a dielectric voltage-controlled microwave device in an integrated circuit.

The invention discloses a coated carbon fiber reinforced ABS/PP electromagnetic shielding composite material and a preparation method thereof. The electromagnetic shielding composite material is obtained through melt extrusion molding of nickel base alloy coated carbon fiber, ABS/PP blended resin, a crosslinking agent and a coupling agent. The prepared composite material has a good electromagneticshielding effect in an extremely wide frequency range, and also has high strength, high modulus, corrosion resistance and excellent thermal stability, and the preparation method of the composite material is simple and low in cost, and meets industrial production.

The invention discloses Fe3C-containing hollow composite carbon fiber with carbon nanotubes growing on inner and outer surfaces and a preparation method of the Fe3C-containing hollow composite carbonfiber, relates to a hollow fiber shielding material and a preparation method thereof, and aims to solve the technical problem that the existing carbon fiber and carbon nanotube composite material arepoor in electromagnetic shielding efficiency. The Fe3C-containing hollow composite carbon fiber with the carbon nanotubes growing on the inner and outer surfaces adopts a structure as follows: a carbonized fiber hollow tube containing magnetic Fe3C nanoparticles is used as a carrier, and the carbon nanotubes grow on the inner and outer surfaces of the hollow tube. The preparation method comprisesthe following steps: 1, preparing Fe3O4-PAN/PMMA hollow fibers; 2, growing the carbon nanotubes on the inner and outer surfaces of the Fe3O4-PAN hollow fiber. The Fe3C-containing hollow composite carbon fiber with the carbon nanotubes growing on the inner and outer surfaces has the electromagnetic shielding efficiency capable of reaching 80dB, and can be applied to the field of electromagnetic shielding.

The invention relates to a ceramic modified PTFE composite dielectric material with low dielectric constant and low thermal expansion. The PTFE composite material comprises PTFE and non-solid ceramicparticles, wherein the use amount of the non-solid ceramic particles is 1-60% of the overall volume fraction of the composite material, the dielectric constant of the modified PTFE composite dielectric material is 2.0-2.5, and the thermal expansion coefficient is 40-120 ppm/DEG C. The modified PTFE composite dielectric material has a low dielectric constant and a low thermal expansion coefficient.

The invention discloses a crosslinking type polyether sulphone base dielectric composite material and a preparation method and application thereof. The method adopts polyether sulphone with the good thermal and mechanical properties and active functional groups (allyl lateral groups) as a base material of a polymer, meanwhile, inorganic nano ceramic particles are adopted as inorganic nanofiller, organic functionalization modification is performed on the surface of the nanofiller, benzocyclobutene is introduced, inorganic nano ceramic particles with reactable functional groups and core shell structures are formed and adopted as crosslinking points to be subjected to a crosslinking reaction with the polyether sulphone polymer with the active functional groups, a three-dimensional network structure is formed, and the crosslinking type polyether sulphone base dielectric composite material with good heat resistance and flexibility and high energy storage density is prepared. The prepared polyether sulphone base dielectric composite film has a high dielectric constant and the wide temperature application range, meanwhile, the breakdown field strength is obviously improved, and thereforethe high energy storage density under high temperature is obtained.

The invention discloses a high-temperature absorbent and a preparation method thereof, and an ultrathin high-temperature wave-absorbing material and a preparation method thereof. The preparation method of the high-temperature absorbent comprises the following steps of: weighing TiO2, SrCO3 and Gd2O3 according to a stoichiometric ratio, sequentially carrying out ball milling, drying, grinding and sieving after mixing, heating the materials to a temperature of 1200-1350 DEG C, performing heat preservation treatment for 2-3.5 hours, performing presintering, and carrying out furnace cooling to obtain the absorbent with the molecular formula of Sr1-xGdxTiO3; Al2O3 and the Sr1-xGdxTiO3 absorbent are weighed according to a mass ratio of (1:9)-(4:6), and are mixed to sequentially perform ball milling, drying, grinding and sieving, and the materials are heated to a temperature of 1250-1400 DEG C, high-temperature pressure maintaining treatment is performed for 1.5-3h for vacuum hot pressing sintering, and furnace cooling is performed to prepare the absorbent with the molecular formula of Sr1-xGdxTiO3/Al2O3, wherein, 0.05<=x<=0.3. The problem that an existing ceramic wave-absorbing materialis large in thickness is solved.

The invention belongs to the technical field of polymer based nano composite materials and preparation methods thereof, and particularly relates to a polyarylether ketone/carbon nanotube composite material with a high dielectric property and a preparation method thereof. The composite material consists of functionalized polyarylether ketone and carbon nanotubes, wherein in terms of the summation (100 percent) of the volume fractions of the functionalized polyarylether ketone and the carbon nanotubes, the carbon nanotubes account for 0.5 to 20 percent and the balance of the functionalized polyarylether ketone. Specifically, the carbon nanotubes (unmodified carbon nanotubes and carboxylic acid modified carbon nanotubes) as modified filling materials, the functionalized polyarylether ketone (sulfonated polyarylether ketone, amino functionalized polyarylether ketone and cyano functionalized polyarylether ketone) as base materials, and a method for solution blending is adopted to prepare the functionalized polyarylether ketone/carbon nanotube composite material with the high dielectric property, and simultaneously solve the problems of high dielectric loss, over-high loading level, reduced processability and the like.

The invention discloses a millimeter-wave low temperature co-fired ceramic material. The ceramic material comprises 44-49 wt% of a glass composition and 51-56 wt% of alumina and the glass compositioncomprises 10-37 wt% of CaO, 5-32 wt% of La2O3, 12-40 wt% of B2O3, 5-32 wt% of SiO2, 0.2-5 wt% of CuO, 0.1-10 wt% of P2O5, 0-1 wt% of Na2O and 0-1 wt% of K2O. The millimeter-wave low temperature co-fired ceramic material is prepared by melting and sintering the glass composition and alumina, and the obtained millimeter-wave low temperature co-fired ceramic material has good comprehensive performances, and has a dielectric constant of 6.4-7.3; and the dielectric loss at 15 GHz is less than 0.002, and the dielectric loss at 40 GHz is less than 0.003.

The invention provides a two-component microwave ferrite material as well as a preparation method and application thereof. The two-component microwave ferrite material comprises a first microwave ferrite material and a second microwave ferrite material. The two-component microwave ferrite material can be applied to microwave communication devices. The preparation method comprises the following steps: (1) mixing a first microwave ferrite material and a second microwave ferrite material according to a formula ratio, and then carrying out wet ball milling to obtain a ball milling material; (2) drying the ball-milled material obtained in the step (1), conducting sieving, and conducting granulating; and (3) sequentially molding and sintering the granulated particles obtained in the step (2) to obtain the two-component microwave ferrite material. Tests show that the ferromagnetic resonance line width [delta]H of the obtained material is less than or equal to 18Oe, the saturation magnetic moment 4[pi]Ms is less than or equal to 1260Gs, the dielectric loss tg[delta]e is less than or equal to 2*10<-4>, and the Curie temperature Tc is more than or equal to 260 DEG C. The stability and reliability of the material are greatly improved, and the material is more beneficial to industrial production.

The invention discloses a method for preparing a composite dielectric film. According to the method, the film is prepared by mixing fluorine-containing polymer and mixed crystal nanometer TiO2 and casting, wherein the molar ratio of two crystal forms in the mixed crystal nanometer TiO2 can be controlled according to reaction time, anatase accounts for 36 to 45 percent, and rutile accounts for 55 to 64 percent; and the composite dielectric film consists of the following components in percentage by mass: 5 to 40 percent of mixed crystal nanometer TiO2 and 60 to 95 percent of fluorine-containingpolymer. The composite dielectric film is a novel dielectric material with a high dielectric constant and low dielectric loss; the composite dielectric film with the required dielectric constant can be prepared by controlling the addition amount of a filler and the ratio of the filler to the crystal forms; and the composite dielectric film is easy to prepare, low in composite temperature and environment-friendly and has a wide application prospect.

The invention provides a preparation method of a conductive polymer composite wave-absorbing material. The method comprises the following steps: step 1, preparing a nano material/conductive polymer composite wave absorbing agent; 2, preparing a nano material/conductive polymer/binder composite material; 3, preparing a composite material wave-absorbing coating; and 4, hot-pressing and rolling the composite wave-absorbing coating. Through the preparation method, the wave-absorbing agent can be more uniformly dispersed in a binder, so that the wave-absorbing effect of each part of the composite material is more uniform. Meanwhile, due to the unique three-dimensional space structure of silicon nitride and silicon carbide and the excellent wave-absorbing performance under the low frequency band, the toughness and tensile strength of the composite wave-absorbing material can be improved, and the absorption frequency range of the composite material is widened.

The invention relates to a composite flexible high-dielectric film. The composite flexible high-dielectric film comprises a polymer and an MXene nano material dispersed in the polymer, wherein based on the total mass of the polymer and the MXene nano material, the mass percent of the MXene nano material is 0.5%-20%. The MXene nano material with excellent conductivity can improve the dielectric constant of the polymer; and the specific mass of the MXene nano-material with excellent conductivity is dispersed in the polymer, so that the MXene nano-material does not form a conductive path, large dielectric loss is not generated, and the polymer can maintain low dielectric loss. Compared with an existing polymer composite film, the composite flexible high-dielectric film has the advantages of being high in dielectric constant, low in dielectric loss and the like, and further has the advantages of being high in tensile property, excellent in flexibility and the like.