37 results about "Barium ferrite" patented technology

The invention relates to an M-type barium ferrite single crystal material and a preparation method and application thereof.The preparation method comprises the steps that metal source mixed powder and a fluxing agent are evenly mixed and subjected to primary sintering, and the metal source mixed powder comprises a barium source and an iron source; and carrying out secondary sintering on the obtained intermediate powder to obtain the M-type barium ferrite single crystal material. Wherein the secondary sintering comprises a heating stage, a heat preservation stage and a cooling stage, and the cooling stage comprises first-stage cooling, second-stage cooling and third-stage cooling which are sequentially carried out. According to the invention, the fluxing agent and the raw materials are added to form a eutectic system, melting can be realized at a temperature far lower than the melting point of the raw materials, and the cooling process is accurately controlled to slowly separate out the target M-type barium ferrite single crystal from the supersaturated molten liquid and reduce thermal stress and defects, so that the M-type barium ferrite single crystal material with high integrity and high purity is obtained. And moreover, the preparation method disclosed by the invention is simple, low in cost and easy for large-scale industrial production.

The invention provides anti-burst and anti-impact sacrificial concrete and a preparation method thereof. The sacrificial concrete is prepared from the following components in parts by weight: 600 to 700 parts of cement, 250 to 350 parts of superfine fly ash, 100 to 150 parts of silica fume, 900 to 1100 parts of quartz sand, 70 to 120 parts of barium ferrite, 140 to 170 parts of steel fiber, 4 to 20 parts of sisal fiber, 193 to 213 parts of water and 15 to 20 parts of water reducing agent. The preparation method comprises the following steps: sequentially mixing and stirring the raw materials, pouring, forming and curing. The sacrificial concrete disclosed by the invention has good sacrificial property, and the water content of raw materials is lower than 5%, so that the hydrogen yield in the interaction process of a reactor core melt and a sacrificial material is reduced; and the sisal hemp is heated to form gaps and channels, so that the high-temperature bursting resistance is improved.

The invention relates to a preparation method of a YIG-M type barium ferrite mixed material for a microstrip line circulator. The preparation method comprises the following steps: firstly, preparing YIG precursor powder and barium ferrite powder; pressing the YIG precursor powder into a green body, and sintering to obtain phase-formed YIG ferrite; and crushing the YIG ferrite, mixing the crushed YIG ferrite with the barium ferrite precursor powder according to a mass ratio of 1: 2-2: 1, pressing the mixture into a green body, and carrying out sintering phase formation to obtain the YIG-M type barium ferrite mixed material. The external bias magnetic field of the prepared mixed material is far smaller than that of a traditional YIG material, a good circulation effect can be achieved only through a smaller permanent magnet, and a circulator can be further miniaturized and integrated.

The invention relates to a method for preparing nano barium ferrite powder, in particular to a method for preparing nano barium ferrite through cooperation of laser annealing and neodymium doping. The method comprises the following steps: S1, preparing a ferrite amorphous strip from raw materials including Fe2O3, BaO, Nd2O3 and B2O3 by utilizing a smelting melt-spinning method; s2, irradiating the ferrite amorphous strip in the step S1 by using laser, and carrying out laser annealing; and S3, carrying out pickling crushing and filtering washing treatment on the annealed strip, and drying to obtain the neodymium-doped nano barium ferrite. According to the preparation method disclosed by the invention, through the synergistic effect of laser annealing and strong absorption of neodymium ions, overgrowth of crystal grains is effectively inhibited, and the particle size distribution of the nano ferrite is narrowed, so that the problems of wide particle size distribution of powder, low production efficiency and the like in the existing preparation technology are solved.

The present invention relates to the field of refractory materials, and specifically to a method for preparing silicon nitride composite refractory materials. A method for preparing silicon nitride composite refractory materials, comprising the following steps: magnetization treatment of investment casting waste sand; preparation of refractory premix; nitrogen sintering of the refractory premix; and directional pressing and sintering of magnetized refractory blanks. The present invention adds nano-barium ferrite magnetic particles to investment casting waste sand, and subsequently nitrogen sinters the refractory premix so that the nano-barium ferrite magnetic particles are uniformly dispersed in the silicon nitride crystals. The obtained refractory blank is then magnetized and directionally pressed in a magnetic field, so that the silicon nitride crystals combined with the nano-barium ferrite magnetic particles are oriented, thereby reducing the internal stress of the silicon nitride composite refractory material during thermal expansion, lowering its thermal expansion coefficient, and effectively improving the thermal conductivity of the silicon nitride composite refractory material, thereby improving its refractory performance.

The invention provides a preparation method of a CeF3 doped M type barium ferrite single crystal. The preparation method comprises the following steps: S1, drying raw materials BaCO3, Fe2O3 and CeF3 and a fluxing agent LiF-NaF-B2O3; s2, raw materials BaCO3 and Fe2O3 are weighed, meanwhile, a proper amount of CeF3 powder is added, the raw materials and a fluxing agent LiF-NaF-B2O3 are mixed, and a mixed raw material is obtained; s3, putting the mixed raw material into a platinum crucible, sealing the platinum crucible, and filling protective gas; s4, the platinum crucible is heated, the temperature of the interior of the platinum crucible is increased to 1120-1200 DEG C, heat preservation is conducted, and the mixed raw materials are fully molten and homogenized; s5, cooling the interior of the platinum crucible to 990-1030 DEG C, lt; 001gt, 001gt; inserting the oriented seed crystal into a platinum crucible, and then cooling to 900-950 DEG C; s6, rotating the seed crystal, and meanwhile, adopting a lifting mode; and S7, annealing treatment is carried out, such that a complete single crystal is obtained. According to the invention, stable doping of Ce < 3 + > ions is realized, a pollution-free preparation process is adopted, large-size single crystals are prepared, and the performance of the prepared single crystals is optimized.

The invention belongs to the technical field of stealth coatings, and relates to a PI-based porous wave-absorbing coating based on flame spraying and a preparation method of the PI-based porous wave-absorbing coating. The PI-based porous wave-absorbing coating takes porous polyimide as a continuous matrix, and neodymium-doped barium ferrite and multi-walled carbon nanotubes are dispersed in the porous polyimide matrix; through a flame spraying method, spraying suspension liquid formed by 4, 4 '-diaminodiphenyl ether, pyromellitic dianhydride, neodymium-doped barium ferrite, multi-walled carbon nanotubes and an organic solvent is sprayed on the surface of a substrate. The PI-based porous wave-absorbing coating provided by the invention has excellent broadband strong absorption characteristic, can keep stable wave-absorbing performance in a wider thickness range, shows remarkable thickness insensitivity, and greatly reduces the precision requirement on thickness control of the coating.

The application belongs to the technical field of electronic information materials, and specifically provides a method for preparing M-type barium ferrite monocrystal thin film under low temperature conditions; the method is characterized by innovative design of liquid phase raw materials and strict design of liquid phase epitaxy process parameters, and can grow the M-type barium ferrite monocrystal thin film with excellent performance on SGGG (111) substrate by liquid phase epitaxy method under low temperature conditions of 830-850 DEG C, which is not only simple in process and low in cost, but also has high crystallization quality, no impurities and defects. The M-type barium ferrite monocrystal thin film prepared by the method is a single crystal material, the film thickness is up to 150 mu m, the saturation magnetization is about 4500 Oe, the remanence is about 1000 Oe, the easy magnetization axis (c axis) is perpendicular to the film surface, has high uniaxial magnetic crystal anisotropy field, and is very beneficial to realize self-bias design of the device.

This invention belongs to the field of magnetic nanomaterials technology, specifically relating to a method for chemically synthesizing fine M-type barium ferrite nanomaterials. This method involves co-precipitation of Fe and Ba salt solutions in a magnetic field to prepare small and uniform M-type barium ferrite nanomaterials. Applying a magnetic field increases the nucleation rate and refines the particles; adjusting the magnetic field strength controls the length of the M-type barium ferrite nanowires. Changing the type and amount of co-precipitating dispersant, the type of flux, and the mixing ratio of flux to precursor further controls the size of the nanomaterials and the length of the nanowires. Adjusting the sintering temperature and time controls the morphology and size of the product.

The invention provides anti-corrosion sacrificial concrete and a preparation method thereof. The anti-corrosion sacrifice concrete is prepared from the following components in parts by weight: 300 to 400 parts of cement, 30 to 50 parts of barium ferrite, 100 to 150 parts of fly ash, 10 to 50 parts of silica fume, 350 to 900 parts of quartz sand, 700 to 900 parts of hematite iron ore, 300 to 1300 parts of steel grit, 3 to 8 parts of polypropylene fiber, 210 to 230 parts of water and 3 to 9 parts of a water reducing agent. The preparation method comprises the following steps: sequentially mixing and stirring the raw materials, pouring, forming and curing. The sacrificial concrete disclosed by the invention has the synergistic advantages of high crack resistance and impermeability, and the corrosion rate of the aluminoferrite cement-based sacrificial concrete under extreme thermochemical erosion is fundamentally reduced; the doping of the steel grit leads to the formation of a discontinuous metal ceramic barrier layer in the holes of the sacrificial concrete at high temperature, so that the corrosion permeation rate of the sacrificial concrete is obviously reduced.

The invention provides a preparation method of an M-type barium ferrite single crystal, which comprises the following steps: S1, weighing raw materials BaCO3 and Fe2O3, mixing the raw materials to obtain a primary mixture, and mixing the primary mixture with a fluxing agent LiF-NaF-B2O3 to obtain a mixed raw material, s2, the mixed raw materials are put into a platinum crucible, the temperature is increased to 1200-1270 DEG C, and then heat preservation is conducted; s3, the platinum crucible is cooled to 1100-1150 DEG C, and then a tilt part is inserted; 001gt, 001gt; an oriented seed crystal; s4, continuously cooling, and rotating the seed crystal; s5, after the platinum crucible is cooled to 970-1000 DEG C, crystal growth is finished; and S6, lifting the crystal away from the liquid level, and carrying out annealing treatment to obtain the M-type barium ferrite single crystal. The problems of small crystal size, toxic pollution and microwave performance degradation in the prior art are solved, and size bottleneck breakthrough, pollution-free process, component stability control and microwave performance optimization are realized.

The application discloses a rare earth neodymium / transition metal ion double-site substituted M-type barium ferrite wave-absorbing powder material and a preparation method thereof. 1‑x Nd x Fe 12‑x A x O 19 , wherein A is Zn, Co, Ni, Ti or Zr, and x=0.02-0.3. The preparation method comprises the following steps: substituting a rare earth element neodymium and transition metal ions A into Ba 2+ and Fe 3+ sites of M-type barium ferrite respectively to simultaneously substitute different element sites in the M-type barium ferrite, and obtain the M-type barium ferrite wave-absorbing powder material substituted by the rare earth element neodymium ion and the transition metal ion, wherein the transition metal ion A is Zn 2+ , Co 2+ , Ni 2+ , Ti 4+ or Zr 4+ . The application can improve electromagnetic parameters of the M-type barium ferrite, and obtain a high-efficiency wave-absorbing powder material capable of being applied in double frequency bands.

The present invention discloses a barium ferrite composite material, its preparation method, and its application, belonging to the field of battery technology. The barium ferrite composite material comprises a barium ferrite core and a conductive shell coating the barium ferrite core; the conductive shell is made of at least one of copper, silver, and gold. While retaining the advantages of barium ferrite, the conductive shell further enhances the conductivity and structural stability of the barium ferrite composite material, making it potentially suitable for use in lithium-ion batteries.

The invention provides anti-radiation concrete based on iron tailing waste and a preparation method thereof, and relates to the technical field of concrete preparation, the anti-radiation concrete is prepared from the following raw materials by weight: 200-240 parts of P.O42.5 cement, 100-130 parts of grade I fly ash, 90-100 parts of grade S95 mineral powder, 2000-2350 parts of composite aggregate, 150-165 parts of water, 10.5-12 parts of a water reducer and 1-3 parts of boron carbide powder, the composite aggregate comprises coarse aggregate and fine aggregate, and the fine aggregate is modified iron tailings and is prepared by ball-milling and coating iron tailings and barium ferrite powder. The anti-radiation concrete has the beneficial effects that the anti-radiation concrete is produced by using the tailing waste, solid waste is comprehensively utilized, and environmental pollution is reduced.

The invention discloses a Ca / Co-Ni doped barium ferrite broadband wave-absorbing ceramic preparation method, which comprises: carrying out wet ball milling on each reaction raw material according to a certain ratio, drying, pre-sintering at a temperature of 950-1000 DEG C to obtain pre-sintered powder, carrying out mixing grinding on the pre-sintered powder and polyvinyl alcohol, carrying out granulation, placing in a mold, and carrying out pressure maintaining for 5 min under a pressure of 16 MPa to prepare a green body; and finally, carrying out heat preservation and glue discharging in a rapid heating furnace at the temperature of 550-650 DEG C, and then continuously heating to 1250-1350 DEG C and sintering to prepare the ceramic. The three-ion-doped ceramic prepared by the method has an M-type phase structure, the ceramic has a soft magnetic characteristic due to doping, the complex dielectric constant of the ceramic is increased, and a formant is generated. And the wave-absorbing bandwidth of the ceramic with the thickness of 1.5 mm, of which the RL is less than-5dB, is 13.5 GHz. The preparation method has the advantages of simple process, rapidness, high practicability and no need of microstructure control, and the prepared ceramic material has the advantages of high temperature resistance, high wave-absorbing property, wide absorption frequency band and the like.

The invention discloses a permanent magnetic ferrite magnetic tile and a manufacturing method thereof, the permanent magnetic ferrite magnetic tile comprises a main material and an additive, the main material and the additive comprise the following components by weight: 50-70% of strontium ferrite; 20%-35% of barium ferrite; an additive: 1.5%-3% of neodymium oxide; 0.5%-2% of praseodymium oxide; 1%-3% of zirconium oxide; 1%-2% of aluminum oxide; 0.5%-1% of titanium oxide; 0.2%-0.6% of boron oxide; the sum of all the components is 100%. Through ferrite proportion optimization and rare earth doping, the residual magnetism of the permanent magnetic ferrite magnetic shoe can reach 430 mT, the demagnetization capability is larger than or equal to 300 kA / m, the magnetism of the permanent magnetic ferrite magnetic shoe is improved compared with a traditional formula, the magnetic flux attenuation rate at the temperature of 200 DEG C is smaller than or equal to 8% and lower than the average level, the stability of the permanent magnetic ferrite magnetic shoe in the high-temperature environment is higher, and the service life of the permanent magnetic ferrite magnetic shoe is prolonged. The compressive strength of the permanent magnetic ferrite magnetic tile is greater than or equal to 3600N, the crack-free qualification rate is greater than or equal to 98%, the mechanical strength is effectively improved, the permanent magnetic ferrite magnetic tile is not easy to crack due to vibration or impact, the waste adding proportion is improved to 30% in the manufacturing process of the permanent magnetic ferrite magnetic tile, and the raw material cost is reduced by 25%.

The invention relates to the field of barium ferrite magnetic powder processing, and particularly discloses a sintering furnace for barium ferrite magnetic powder, which comprises a furnace body, the furnace body is provided with a furnace mouth, and the furnace mouth is communicated with a hearth; the furnace door is arranged at the furnace opening through a lifting device and used for closing or opening the furnace opening; a heat conduction part is formed at the top of the furnace body; the sintering furnace further comprises a blocking assembly and a heating roller, and the heating roller is rotationally arranged above the heat conduction part. Spiral blades are arranged on the inner wall of the heating roller; a driving assembly; at least two heating rollers are arranged in the horizontal direction, each heating roller is provided with an inlet and an outlet, the conveying component comprises a conveying track and a lifting assembly, the conveying track is provided with a feeding port and a discharging port, the feeding port is located in the outlet of the heating roller, the discharging port is located in the inlet of the adjacent heating roller, and the lifting assembly is located in the conveying track. The height of the conveying track is gradually reduced from the feeding hole to the discharging hole to form a discharging slide way; the lifting assembly is installed on the heating roller and synchronously rotates along with the heating roller.

The present invention relates to the technical field of multiferroic materials, and in particular to a cold sintering auxiliary preparation method of bismuth ferrite-barium titanate / barium ferrite composite ceramic with excellent ferroelectric properties: (1) ingredients are prepared according to the correct stoichiometric ratio, ball milled and dried, and sieved to obtain powder; (2) the obtained powder is calcined at high temperature, ball milled and sieved to obtain powder; (3) the obtained powder is added with polyvinyl alcohol (PVA, concentration is 5wt%), and the powder is ground and mixed uniformly; (4) the obtained powder is cold sintered under 500MPa pressure and 180°C to obtain a preliminarily densified ceramic green body; (5) the obtained ceramic green body is heat treated at different temperatures. The sintering temperature of the material can be significantly reduced after the cold sintering treatment, thereby refining the grain size of the ceramic and improving the performance of the composite ceramic.

The invention relates to the technical field of preparation methods of high-strength ferrite plastic magnetic granules, in particular to high-strength ferrite plastic magnetic granules and a preparation method thereof.The high-strength ferrite plastic magnetic granules are prepared from, by weight, 84 wt%-90 wt% of ferrite magnetic powder, 8 wt%-13 wt% of binder, 1 wt%-3 wt% of flexibilizer, 0.3 wt%-0.8 wt% of coupling agent and 0.5 wt%-1.5 wt% of lubricant. 0.2 wt% to 0.5 wt% of an antioxidant; the ferrite magnetic powder is strontium ferrite or barium ferrite or combined magnetic powder of the strontium ferrite and the barium ferrite, and the average particle size is 0.8-2.0 microns; the binder is composed of nylon 6 powder modified by a fiber material, and the fiber material is selected from one of long glass fiber and carbon fiber. Tests prove that the ferrite injection molding granules provided by the invention have the maximum magnetic energy product (BH) max of more than or equal to 15.1 kJ / m < 3 >, the bending strength of not less than 150MPa and the crushing strength of more than or equal to 60MPa, have good magnetic properties and relatively high mechanical properties, and are suitable for extrusion of complex shapes.

The invention provides a preparation method of a CeO2 doped M type barium ferrite single crystal. The preparation method comprises the following steps: S1, carrying out vacuum drying on raw material BaCO3, Fe2O3 and CeO2 powder, a fluxing agent LiF-NaF-B2O3 and a reducing agent Zn powder; s2, weighing and mixing the raw materials, the fluxing agent and the reducing agent to obtain a mixed raw material; s3, filling the mixed raw materials into a platinum crucible; s4, the platinum crucible is subjected to programmed heating and heat preservation, so that the mixed raw materials are fully molten and react, and a melt with uniform chemical components is formed; s5, slowly cooling the platinum crucible, 001gt, 001gt; inserting the oriented seed crystal into the surface of the melt, and rotating; the programmed cooling of the platinum crucible is extremely slow, and meanwhile, the lifting operation is matched; s6, after crystal growth is completed, programmed cooling is conducted to the room temperature, then annealing treatment is conducted, and therefore the CeO2 doped M-type barium ferrite single crystal is obtained. Precise valence state regulation and control are achieved, size limitation is broken through, heavy metal pollution is thoroughly eliminated, and comprehensive performance is optimized.

The invention relates to an M-type barium ferrite polycrystalline material suitable for a Ka-band self-biased circulator and a preparation method of the M-type barium ferrite polycrystalline material, the molecular formula of the crystal is Ba0. 7La0. 3Fe (10.9-11.7)-xZn0. 3ScxO19, and x is more than 0 and less than 0.6. The preparation method comprises the following steps: calculating the element ratio, weighing the raw materials BaCO3, Fe2O3, La (OH) 3, ZnO and Sc2O3, mixing the raw materials, matching with a steel ball for wet grinding, standing after wet grinding, filtering water, drying a deposited material, grinding the dried material into powder, and pressing the powder into a cake blank; presintering the cake blank sample at high temperature to form an M phase; the method comprises the following steps: crushing an M-phase sample into powder, carrying out ball milling, controlling the particle size of the powder to be smaller than a single domain critical limit 0.9 mu m, standing ball-milled slurry on filter cloth for 8 hours, controlling the moisture content to be 30-40%, and then carrying out wet orientation to form a preferred orientation green body; and sintering the green body at high temperature. The magnetocrystalline anisotropic field has the advantages that the numerical value of the magnetocrystalline anisotropic field can meet about 8000 Oe, the magnetocrystalline anisotropic field can be adjusted according to the Sc content, and the service conditions of self-biased circulators with different center frequencies can be met.

The present invention relates to a W-type barium ferrite doped with rare earth cerium element and nickel element and a preparation method thereof. The preparation method comprises the following steps: dissolving an iron salt, a barium salt, a nickel salt, a cerium salt and citric acid in water to obtain a precursor solution; then subjecting the solution to an oil bath to obtain a gel; and then calcining the dried gel at a high temperature to obtain a W-type barium ferrite doped with rare earth cerium element and nickel element. The W-type barium ferrite doped with rare earth cerium element and nickel element of the present invention has good impedance matching and strong loss ability, and has good wave absorption performance at a relatively thin thickness.

The invention discloses a lanthanum oxide and barium ferrite composite material, the composite material is prepared by doping lanthanum oxide La2O3 with barium ferrite BaFe12O19 as a matrix, the chemical component of the composite material is Ba (1-x) LaxFe12O19, and x is more than or equal to 0.2 and less than or equal to 0.8. The range of x is any one of 0.2, 0.4, 0.6 and 0.8. The preparation method has the beneficial effects that the magnetic performance stability is improved, the electromagnetic wave absorption performance is enhanced, the impedance matching characteristic is improved, the crystallinity and microstructure of the material are optimized, no impurity phase exists, the process controllability is high, the preparation process is simple and convenient, and the cost is low.

The invention discloses a preparation method of magnetic hollow glass beads, and belongs to the technical field of functional material preparation. Comprising the following steps: 1, mixing various glass forming raw materials, melting at 1400-1600 DEG C to obtain molten glass, and carrying out water quenching, crushing and grading to obtain magnetic glass powder; step 2, mixing magnetic glass powder with the paste according to a mass ratio of 1: (1-2.5), adding sodium dodecyl benzene sulfonate, and performing spray granulation to form magnetic precursor particles; 3, placing the precursor particles in a negative pressure spheroidizing furnace, and carrying out foaming and spheroidizing treatment; and then, carrying out hydrofluoric acid surface etching on the obtained microbeads to form a frosted layer, coating the frosted layer with a barium ferrite magnetized layer, and carrying out separation and collection by a specific gravity separation method to obtain the magnetic glass microbeads.

The application discloses a preparation method of a chiral ferromagnetic monodomain liquid crystal material, and synthesizes Sc-doped barium ferrite nanosheets through a hydrothermal method, modifies the nanosheets by using citric acid, obtains ferromagnetic barium ferrite nanosheets, and uniformly disperses the ferromagnetic barium ferrite nanosheets into a chiral liquid crystal matrix; under the action of a weak magnetic field (as low as 30 mT), the anisotropic nanosheet orientation is coupled with the chiral liquid crystal orientation, the nanosheets are oriented along the magnetic field direction, and the ordered arrangement of the chiral liquid crystal matrix is guided; the chiral cluster aggregates and liquid crystal domains in the chiral liquid crystal matrix are migrated and fused, and finally, a wireless, planar defect chiral ferromagnetic monodomain structure is formed. The chiral ferromagnetic monodomain liquid crystal material has magnetic response, and the magneto-optic effect under the action of a magnetic field provides a basis for the application of the chiral ferromagnetic monodomain liquid crystal material in the fields of optical equipment and flexible machines.

To achieve simultaneous improvement of both corrective force Hc and a magnetocrystalline anisotropy constant Ku in finely pulverized hexagonal barium ferrite magnetic powder.SOLUTION: Provided is a method for producing hexagonal barium ferrite magnetic powder, which includes a crystallization step of synthesizing hexagonal barium ferrite crystals by subjecting a precursor to a crystallization heat treatment, the precursor containing a constituent element of hexagonal barium ferrite magnetic powder. As the precursor, there is used a material having a mass increase rate of 0.08% or less at 700°C based on a mass at 300°C when subjected to thermogravimetry which includes heating with a heating rate of 10°C / min from room temperature to a temperature of 700°C or higher in an air atmosphere and also has a saturation magnetization σs of 5.0 Am2 / kg or less.SELECTED DRAWING: Figure 4

The invention belongs to the field of Raman detection, and relates to a flexible SERS (Surface Enhanced Raman Scattering) substrate based on a flexoelectric effect and a preparation method thereof. The flexible SERS substrate based on the flexoelectric effect comprises a polydimethylsiloxane substrate, and a barium titanate film, a barium ferrite film and a silver film which are sequentially arranged on the polydimethylsiloxane substrate from bottom to top. Barium titanate is sputtered onto a polydimethylsiloxane substrate through a magnetron sputtering film deposition system, barium ferrite and a silver film are sequentially sputtered after annealing, and the flexible SERS substrate based on the flexoelectric effect can be obtained through polarization. The flexible SERS substrate has the advantages of high SERS sensitivity, low cost, simple operation steps, long service life, good uniformity and repeatability and the like, and the structure can further promote application and popularization of SERS in practice. The preparation method of the flexible SERS substrate is simple, low in cost and easy for batch production.

The invention relates to the field of refractory materials, in particular to a preparation method of a silicon nitride multiphase refractory material. The invention relates to a preparation method of a silicon nitride multiphase refractory material. The preparation method comprises the following steps: magnetizing investment casting waste sand; preparing a refractory premix; performing nitrogen sintering on the refractory premix; and directionally pressing and sintering the magnetized refractory blank. Nanometer barium ferrite magnetic particles are added into investment casting waste sand, then nitrogen sintering is conducted on a refractory premix, the nanometer barium ferrite magnetic particles are evenly dispersed in silicon nitride crystals, and then magnetizing and magnetic field directional pressing are conducted on the obtained refractory blank. The silicon nitride crystals combined with the nano barium ferrite magnetic particles are directionally arranged, the internal stress of the silicon nitride complex-phase refractory material during thermal expansion is reduced, the thermal expansion coefficient of the silicon nitride complex-phase refractory material is reduced, meanwhile, the thermal conductivity of the silicon nitride complex-phase refractory material can be effectively improved, and the fire resistance of the silicon nitride complex-phase refractory material is improved.

The invention provides a preparation method of a barium ferrite loaded conductive MOF, and relates to the technical field of metal organic materials, and the preparation method comprises the following steps: placing barium ferrite in an MOF precursor solution, then carrying out a hydrothermal reaction, and enabling MOF to grow in situ on the surface of the barium ferrite and crystallize to obtain the barium ferrite loaded conductive MOF, wherein the MOF precursor solution contains metal ions and an MOF precursor solution of a conjugated organic ligand. The barium ferrite is a hard magnetic material and has strong magnetism, the barium ferrite is used as a substrate, the conductive MOF grows on the surface of the barium ferrite through hydrothermal reaction, and the obtained barium ferrite loaded conductive MOF inherits the strong magnetism of a barium ferrite core. After the barium ferrite loaded conductive MOF is applied, only one magnet is needed, the composite material can be rapidly and completely sucked out from a solution, rapid, efficient and nearly lossless recovery is achieved, and the problem that an MOF material powder material prepared through an existing method is difficult to recover is solved.

The application discloses a rare earth neodymium and pentavalent ion double-site substituted M-type barium ferrite double-band wave absorber and a preparation method thereof. 1‑x Nd x Fe 12‑y A y O 19 , wherein A is a pentavalent transition metal ion Nb or Ta, x=0.05-0.3, and y=0.05-0.3. The application realizes double-site substitution of the M-type barium ferrite by using the rare earth element Nd 3+ and the non-magnetic ion A (Nb 5+ , Ta 5+ ) to respectively replace part of Ba 2+ ions and part of Fe 3+ ions of the M-type barium ferrite, so that the obtained wave absorbing material has the characteristics of strong reflection loss, wide effective absorption bandwidth and thin matching thickness.