83 results about "Maghemite" patented technology

The subject of the invention is superparamagnetic nanoparticle probes based on iron oxides, to advantage magnetite or maghemite, with modified surface, coated with mono-, di- or polysaccharides from the group including D-arabinose, D-glucose, D-galactose, D-mannose, lactose, maltose, dextrans and dextrins, or with amino acids or poly(amino acid)s from the group including alanine, glycine, glutamine, asparagine, histidine, arginine, L-lysine, aspartic and glutamic acid or with synthetic polymers based on (meth)acrylic acid and their derivatives selected from the group containing poly(N,N-dimethylacrylamide), poly(N,N-dimethylmethacrylamide), poly(N,N-diethylacrylamide), poly(N,N-diethylmethacrylamide), poly(N-isopropylacrylamide), poly(N-isopropylmethacrylamide), which form a colloid consisting of particles with narrow distribution with polydispersity index smaller than 1.3, the average size of which amounts to 0.5-30 nm, to advantage 1-10 nm, the iron content is 70-99.9 wt. %, to advantage 90 wt. %, the modification agent content 0.1-30 wt. %, to advantage 10 wt. %.

The particles of size smaller than 2 nm with polydispersity index smaller than 1.1 can be obtained by a modified method of preparation.

Superparamagnetic nanoparticle probes according to the invention are prepared by pre-precipitation of colloidal Fe(OH)₃ by the treatment of aqueous 0.1-0.2M solution of Fe(III) salt, to advantage FeCl₃, with less than an equimolar amount of NH₄OH, at 21° C., under sonication, to which a solution of a Fe(II) salt, to advantage FeCl₂, is added in the mole ratio Fe(III)/Fe(II)=2 under sonication and the mixture is poured into five- to tenfold, to advantage eightfold, molar excess of 0.5M NH₄OH. The mixture is left aging for 0-30 min, to advantage 15 min, and then the precipitate is repeatedly, to advantage 7-10 times, magnetically separated and washed with deionized water. Then 1-3 fold amount, to advantage 1.5 fold amount, relative to the amount of magnetite, of 0.1 M aqueous solution of sodium citrate is added and then, dropwise, 1-3 fold amount, to advantage 1.5 fold amount, relative to the amount of magnetite, of 0.7 M aqueous solution of sodium hypochlorite. The precipitate is repeatedly, to advantage 7-10 times, washed with deionized water under the formation of colloidal maghemite to which, after dilution, is added dropwise, to advantage under 5-min sonication, an aqueous solution of a modification agent, in the weight ratio modification agent/iron oxide=0.1-10, to advantage 0.2 for amino acids and poly(amino acid)s and 5 for saccharides.

The particles smaller than 2 nm with polydispersity index smaller than 1.1 are prepared by mixing at 21° C. 1 volume part of 10-60 wt. %, to advantage 50 wt. %, of an aqueous solution of a saccharide, disaccharide or polysaccharide, such as D-arabinose, D-glucose, D-galactose, D-mannose, lactose, maltose, dextran and dextrins, and 1 volume part of aqueous solution of a Fe(II) and Fe(III) salt, to advantage FeCl₂ and FeCl₃, where the molar ratio Fe(III)/Fe(II)=2. A 5-15%, to advantage 7.5%, solution of NH₄OH is added until pH 12 is attained and the mixture is heated at 60° C. for 15 min. The mixture is then sonicated at 350 W for 5 min and then washed for 24 h by dialysis in water using a membrane with molecular weight cut-off 14,000 until pH 7 is reached. The volume of solution is reduced by evaporation so that the final dry matter content is 50-100 mg/ml, to advantage 80 mg per 1 ml.

Superparamagnetic nanoparticle probes according to the invention can be used for labelling cells used in magnetic resonance imaging for monitoring their movement, localization, survival and differentiation especially in detection of pathologies with cell dysfunction and of tissue regeneration and also for labelling and monitoring cells administered for cell therapy purposes, in particular embryonal stem cells, fetal stem cells, stem cells of an adult human including bone marrow stem cells, olfactory glial cells, fat tissue cells, in the recipient organism by magnetic resonance.

The preparation of labelled cells proceeds by adding to the complete culture medium 5-20 μl, to advantage 10 μl, of a colloid containing 0.05-45 mg iron oxide per ml, to advantage 1-5 mg iron oxide per ml of the medium, and culturing the cells for a period of 1-7 days, to advantage for 1-3 days, at 37° C. and 5% of CO₂.

The invention discloses a compound maghemite ore dressing method. The compound maghemite ore dressing method comprises the following steps: feeding compound maghemite ore into an ore grinding-grading-low-intensity magnetic separation operation segment to obtain low intensity magnetic separation concentrate and low-intensity magnetic separation tailings; feeding the low-intensity magnetic separation concentrate into a fine sieving operation segment to obtain finely-sieved concentrate C1; feeding the low-intensity magnetic separation tailings into a high-intensity magnetic separation operation segment, and throwing out high-intensity magnetic separation tailings T1 to obtain high-intensity magnetic separation concentrate; combining coarse fraction low-intensity magnetic separation concentrate with the high-intensity magnetic separation concentrate, and feeding the mixture into a pre-grading-two-stage ore grinding-reverse flotation operation segment to obtain reverse flotation concentrate C2, and throwing out reverse flotation concentrate T2. In the method, staged ore grinding and high-intensity tailing throwing are adopted, so that discarding as soon as possible is realized; the low-intensity magnetic separation concentrate is obtained by fine sieving, so that collection as soon as possible is realized; oversize finely-sieved and high-intensity coarse concentrate is ground, so that the amount of ore ground at a second segment is lowered greatly, and energy-saving and consumption lowering are facilitated; an oversize finely-sieved product is reground and floated, so that the flotation grade is raised, and the adaptability of negative ion reverse floatation to ore characteristic fluctuation is improved.

The present invention provides a method for making modified jacobsite, Al-doped maghemite or modified maghemite nanoparticles that can be used to adsorb heavy metals, such as Cr(VI), found in wastewater. The magnetic nanoparticles can be separated using a magnetic field after adsorbing heavy metals from wastewater, and processed for reused.

The invention discloses a multi-stage suspension magnetizing roasting-magnetic separation system and method for refractory iron ore, which belongs to the field of mineral processing technology. This system comprises multistage suspension preheater, multistage suspension oxidizer, multistage suspension redactor, on-line grade analyzer, ore-like splitter, magnetic separator, dust remover, roots blower and other components and connection modes. The refractory iron ore treated by the present method can be produced to homogeneous magnetite or maghemite accurately, and through magnetic separation, on-line grade analyzer detection and ore-like splitter, the concentrate powder which reach the set grade can be obtained, and the unqualified ore powder enters the next stage of oxidation-reduction-magnetic separation-split treatment. Through the present system and method, products with different roasting quality can be obtained, and can avoid the phenomenon of over burning or under burning occurring in the past process and equipment.

The invention discloses a preparation method of Gamma-Fe2O3 magnetic nanometer particles. The invention adopts a two-step hydro-thermal method and synthesizes maghemite (Gamma-Fe2O3) nanometer particles. Step 1: with ferrous salt, sodium hydroxide and hydrazine hydrate as raw materials, black Fe3O4 nanometer particles are synthesized by a hydro-thermal method. Step 2: with oxyful as oxidant, the black Fe3O4 nanometer particles obtained at Step 1 is thermal oxidized into mahogany Gamma-Fe2O3 nanometer particles. The Gamma-Fe2O3 nanometer particles obtained by the invention with particle size being 50-100 nanometers has excellent crystallization and dispersion and is magnetic with saturated magnetization rate being 68emu/g.

The invention relates to a beneficiation process of maghemite. Raw ores are the maghemite. The iron grade is 41%-43%. The content of ferruginous clay is over 30%. The beneficiation process of the maghemite is characterized in that crushed products with the grain size being 12-0 mm are processed according to the following technological flow comprising that (1) pre-grading and closed-loop ore grinding are conducted during ore grinding, (2) weak intensity magnetic separation-medium intensity magnetic separation-high intensity magnetic separation-elutriation magnetic separation are conducted during magnetic separation, and (3) spiral chute roughing separation, concentration and scavenging are conducted during gravity separation; and the comprehensive concentrates composed of magnetic separation concentrates and gravity separation concentrates are obtained, wherein the grade of the comprehensive concentrates is 62% or over, and the recovery rate is 62.00-63.00%. The beneficiation process ofthe maghemite has the advantages that the crushed products are graded in advance, only one-stage closed loop ore grinding is adopted, and therefore investment and energy consumption are reduced; (2)magnetic separation concentrates are directly obtained from the products of the one-stage ore grinding through an elutriation magnetic separator; and (3) tailing discarding is conducted on coarse andfine classification overflow of cyclone to remove the ferruginous clay before gravity separation, so that the influence of the ferruginous clay on the quality of the gravity separation concentrates islowered.

A carrier core material for an electrophotographic developer containing Li ferrite, maghemite, and Fe₃O₄, wherein a part thereof is substituted with Mn, a Li content is 1 to 2.5% by weight, a Mn content is 2 to 7.5% by weight, and a silicon content is 25 to 10,000 ppm, a compression breaking strength is 130 MPa or more, an SF-1 is 125 to 145, respective cumulative strengths of respective spinel crystal structure faces in X-ray diffraction satisfy a certain equation, a vacuum resistivity R₅₀₀ across a 2 mm gap when a measurement voltage of 500 V is applied is 1×10⁶ to 5×10⁹Ω, and a vacuum resistivity R₁₀₀₀ across a 6.5 mm gap when a measurement voltage of 1,000 V is applied is 5×10⁷ to 1×10¹⁰Ω.

A magnetic recording medium of the present invention comprises: a plastic substrate; and a cobalt-containing maghemite thin film formed on said substrate, containing cobalt at a molar ratio of cobalt to iron of not more than 0.06:1, and having either a spacing of a plane (311) of not more than 2.510 Å, a spacing of a plane (222) of not more than 2.415 Å or a spacing of a plane (220) of not more than 2.950 Å; and has a coercive force of not less than 2,000 Oe. Such magnetic recording medium suitably applicable to existent magnetic recording systems using a ring-type magnetic head and capable of using a plastic substrate for providing a magnetic recording medium for high-density recording.

A carrier core material for an electrophotographic developer including Li ferrite, maghemite, and Fe₃O₄, wherein a part thereof is substituted with Mn, Li content is 1 to 2.5% by weight, Mn content is 2 to 7.5% by weight, and silicon content is 25 to 10,000 ppm, the following equation (1) is satisfied when respective integrated strengths of spinel crystal structure (110), (210), (211), and (311) faces in X-ray diffraction are respectively I₁₁₀, I₂₁₀, I₂₁₁, and I₃₁₁, a resistivity R₅₀ of 50 V across a 6.5 mm gap is 5×10⁷ to 7×10⁸Ω, and a resistivity R₁₀₀₀ of V across a 6.5 mm gap is 1×10⁷ to 8×10⁸Ω.

2<100×(I₁₁₀+I₂₁₀+I₂₁₁)/I₃₁₁<14   (1)

The invention discloses a magnetically separable and recyclable iron oxide SCR denitration catalyst and an application method thereof. The catalyst is prepared through the following steps: with a limonite ore as a raw material, crushing and screening to form particles, calcining the particles in an atmosphere of hydrogen or carbon monoxide, so as to reduce goethite in the particles to be magnetite to obtain the catalyst, or further calcining in an air atmosphere, so that the magnetite is oxidized to be maghemite to obtain the catalyst, wherein the goethite content of the limonite ore is not less than 60%, the limonite ore has a nano-micro hierarchical porous structure, and the specific surface area of the limonite ore is not less than 10m<2>/g. When in use, the catalyst and ammonia are simultaneously fed into a flue gas flow at the temperature of 300-450 DEG C, and the catalyst and dust are together adsorbed onto the electrode plate of an electric dust collector or the surface of a filter bag and then are collected into a dust hopper through a dust cleaning method; the SCR denitration catalyst in the material discharged from the dust hopper is separated and recycled through a magnetic separation method; if inactivated, the SCR denitration catalyst can be washed and regenerated with water or weak aqua ammonia.

In a metal oxide nanoparticle and a synthetic method thereof, and in particular to maghemite (γ-Fe₂O₃) nanoparticles usable as a superhigh density magnetic recording substance by having good shape anisotropy and magnetic characteristics, hematite (α-Fe₂O₃) nanoparticles usable as a precursor to the maghemite or a catalyst, maghemite and hematite-mixed nanoparticles and a synthetic method thereof, the method for synthesizing metal oxide nanoparticles includes forming a reverse micelle solution by adding distilled water, a surfactant and a solvent to metallic salt not less than trivalent, precipitating and separating gel type amorphous metal oxide particles by adding proton scavenger to the reverse micelle solution; adjusting a molar ratio of metal oxide to the surfactant by washing the gel type amorphous metal oxide particles with a polar solvent; and crystallizing metal oxide nanoparticles through heating or reflux after dispersing the gel type amorphous metal oxide particles in a non-polar solvent having a high boiling point.

The invention discloses a manganese-doped maghemite catalyst used for thermal catalytic oxidation of formaldehyde, and a preparation method thereof. According to the preparation method, a ferric salt and a manganese salt are taken as the main raw materials; a manganese-doped maghemite precursor is synthesized via sodium hydroxide coprecipitation; and the manganese-doped maghemite precursor is subjected to washing, freeze drying, screening, and roasting oxidation so as to obtain the manganese-doped maghemite catalyst used for thermal catalytic oxidation of formaldehyde. The manganese-doped maghemite catalyst is granular, possesses spinel structures, and weak magnetism. The manganese-doped maghemite catalyst can be used for effective thermal catalytic oxidation of high-concentration formaldehyde, and can be used for removing high-concentration formaldehyde (>1000mL/m3) at 300 DEG C; formaldehyde removing rate is 90% or higher; catalytic activity is high; initiation temperature is low; thermal stability is excellent; separation and recovery are convenient; no secondary pollution is caused; cost is low; and the manganese-doped maghemite catalyst is suitable for purifying treatment of high concentration formaldehyde in industrial exhaust gas.

The invention relates to an animal magnetic ferritin material comprising a complete animal ferritin shell and a magnetic nanoparticle core, the diameter of which ranges from 1 nanometer to 8 nanometers. With dispersibility and dissolvability in water and polar solvents, the core comprises magnetite or maghemite. The preparation method of the animal magnetic ferritin material consists of: 1) subjecting an animal offal to pulp refining, filtering and centrifugation to remove other proteins, then conducting nickel column and molecular sieve chromatography to separate monosomic natural ferritin; 2) in an acidic condition, carrying out reduction and denucleation to the natural ferritin so as to obtain denulceated ferritin; 3) taking hydrogen peroxide as an oxidizing agent, and adding it to a denulceated ferritin solution for reaction to synthesize animal magnetic ferritin, with the mole ratio of Fe(II)/H2O2 greater than or equal to 2:1, the pH controlled at 7.1-11, and the temperature maintained at 25-70DEG C; 4) separating the obtained animal magnetic ferritin so as to obtain monodispersed and nonmagnetic interacting animal magnetic ferritin particles. The invention also provides a preparation method.

The invention discloses a magnetic renewable adsorbent for adsorbing gaseous zero-valent mercury and a preparation method of the magnetic renewable adsorbent, and belongs to the technical field of mercury adsorption. The adsorbent is formed by performing phosphomolybdic acid (HPMo) grafting on magnetite (Fe3O4) in a preparation process to form HPMo@Fe3O4, then performing high-temperature calcination to obtain MoO3@gamma-Fe2O3, and finally performing vulcanization modification. The phase change of maghemite is inhibited by a means of phosphomolybdic acid grafting, so as to improve the thermal stability of maghemite, and the magnetic property of maghemite is improved; meanwhile, the zero-valent mercury adsorption capacity of the phosphomolybdic acid grafted maghemite is improved by controlling the vulcanization effect of the surface of the phosphomolybdic acid grafted maghemite, the magnetic adsorbent which has excellent low-temperature zero-valent mercury adsorption capacity and can berecycled is prepared, and the magnetic adsorbent can be suitable for being combined with a wet-type electric precipitator to control mercury pollution of a coal-fired power plant in a centralized mode.

The invention relates to a high-yield two-product mixed maghemite beneficiation process. The high-yield two-product mixed maghemite beneficiation process comprises three-section breakage including coarse breaking, medium breaking and fine breaking on mixed maghemite, and is characterized by further comprising the following steps: sieving operation, a one-section closed circuit grinding operation implemented by a one-section ball-milling-cyclone, primary beneficiation operation, coarse and fine classification operation, reselection operation, secondary magnetic separation operation and centrifuging operation; a primary magnetic separation operation sieve treats overflow products of one-section closed circuit grinding operation, sieving operation and undersizes, the coarse and fine classification operation treats bulk concentrate obtained by primary beneficiation, the reselection operation treats coarse grain products of the coarse and fine classification operation, the secondary beneficiation operation treats coarse particle products of the coarse and fine classification operation, and the centrifuging operation treats bulk concentrates of secondary weak magnetic separation. The high-yield two-product mixed maghemite beneficiation process has the advantages that iron ore concentrates I with grade being 62% for pelletizing raw materials and iron ore concentrates II with grade being 58% for sintered raw materials can be selected out.

Maghemite (γ-Fe₂O₃) is formed by oxidizing iron stearate with methylmorpholine N-oxide (MNO). A mixture comprising iron stearate, MNO, a surfactant, and a solvent may be heated to maintain the mixture at a temperature of about 280 to about 320° C. for a sufficient period to form magnetic nanoparticles comprise maghemite. After heating, the mixture may be cooled to limit growth in size of the nanoparticles. The mixture may be heated for a period of about 15 minutes to about 30 minutes, such as about 15 minutes. The process may be adapted to also form quantum dots, and to form magnetic quantum dot (MQD) nanoparticles in an integrated process.

The invention relates to an iron separating method for metamorphic iron tailings. According to magnetite, hematite, maghemite, goethite and limonite in the metamorphic iron tailings, the magnetic separation-flotation technology is adopted, and primary roughing, secondary scavenging and secondary concentration are carried out. By the adoption of the method, the problems that the iron separating recovery rate of the iron tailings is low and the recovery cost is high in all metamorphic iron tailing production countries for a long time are solved. Compared with the prior art, the method is free of pollution, capable of recovering soluble iron at a low cost, short in technological process, simple in technology, high in recovery rate, low in recovery cost and suitable for industrial production.

The invention discloses a high-heat-resistant nitride-based cermet mould and a preparation method thereof. The high-heat-resistant nitride-based cermet mould is prepared from, by weight, 70-80 parts of titanium nitride, 40-50 parts of aluminum nitride, 15-20 parts of nickel powder, 10-20 parts of realgar powder, 10-20 parts of dickite powder, 4-8 parts of maghemite, 6-8 parts of germanium dioxide, 3-6 parts of potassium oxide, 3-11 parts of stainless steel powder and 3-5 parts of oleic acid. The high-heat-resistant nitride-based cermet mould prepared according to the method has excellent heat stability, abrasion resistance, oxidation resistance and high temperature resistance. Compared with an existing cermet mould, the high-heat-resistant nitride-based cermet mould has advantages that the service life of the mould is remarkably prolonged, and the high-heat-resistant boride-based cermet mould can be better applied under severe conditions such as high temperature and high pressure and makes a prominent progress in reduction of processing cost, improvement of production efficiency and the like.

The invention discloses a preparation method of magnetic nanocrystals with adjustable morphology. The preparation method comprises following steps: step 1, preparation of ferrihydrite precursors, wherein hydrolysis reaction is promoted by adding CuO into a Fe(NO3)3 solution so as to obtain the ferrihydrite (Fe5O7OH.4H2O) precursors; and step 2, preparation of the magnetic nanocrystals, wherein a mixture of the ferrihydrite precursors, a FeCl2 solution and a NaOH solution is subjected to heating processing so as to obtain the maghemite (gamma-Fe2O3) nanocrystals. Technological conditions of the preparation method is mild, raw material cost is low, and it is possible to obtain ball-shaped, rod-shaped or sheet-shaped magnetic nanocrystals by controlling the synthesis conditions.

The present invention relates to a single-step simple and economical process for the preparation of nanosized acicular magnetic iron oxide particles of maghemite phase of size ranging between 300-350 nm in magnetic field at room temperature by biomimetic route, and a method of obtaining a magnetic memory storage device using the said particles.

A magnetic recording medium comprises a polymer film substrate having an elongated shape or a polymer flexible substrate; an underlayer having a thickness of less than 10 nm, which is formed on the substrate; and a magnetic recording layer comprising a spinel iron oxide thin film containing maghemite as a main component, which is formed on the underlayer and has a coercive force of not less than 159 kA/m (2000 Oe). The present invention provides the magnetic recording medium comprising a spinel iron oxide thin film containing maghemite as a main component, which exhibits an excellent recording resolution performance while maintaining a high coercive force and a high coercive force squareness.

The invention relates to a Chinese chestnut shaped ferric oxide shell structure magnetic absorbent particle as a water treatment agent for absorbing high-toxicity heavy metal ions and a preparation method thereof. The Chinese chestnut shaped ferric oxide shell structure magnetic absorbent particle is characterized in that the inside is of a porous structure formed by amorphous ferric oxide nano particles, and a shell is formed in a manner that a plurality of crystallized maghemite nano bars vertical grow on the amorphous ferric oxide nano particles. The preparation method comprises the steps of: mixing chloride, Fe(CO)5 and N,N-dimethylformamide according to the proportion of (0.01-1.6)mmol:0.50mL:(10-160)mL, and stirring to obtain a solution; and transferring the solution to an agitated reactor, heating at a temperature of 160-220 DEG C for 1-32h, and cooling to room temperature; collecting a brown settlement, cleaning and drying in vacuum to obtain the Chinese chestnut shaped ferric oxide shell structure magnetic absorbent particle. The invention has the advantages of simple synthesis method and mild reaction condition. The Chinese chestnut shaped ferric oxide shell structure magnetic absorbent particle has stronger absorbing capacity to heavy metal ions in water.

The invention relates to compositions containing Bacillus sp., optionally with magnetite, useful in methods for collecting algae. The invention also relates to methods for collecting algae by contacting algae and bare maghemite and compositions thereof.