106 results about "Tungsten acid" patented technology

The invention belongs to the technical field of scattered metal recovery, and particularly relates to a recycling method of tungsten-rhenium alloy waste. The tungsten-rhenium alloy is a solid solution strengthened alloy which takes tungsten element as a matrix and consists of the tungsten element and rhenium element, and has the characteristics of high melting point, high strength and high hardness. As the price is high, it is very necessary to comprehensively utilize the tungsten-rhenium alloy waste. The invention discloses a recycling method of tungsten-rhenium alloy waste. Firstly, tungsten-rhenium alloy waste is cleaned, dried and smashed, and waste powder is formed; then dispersing the waste material powder into water dissolved with ammonium metatungstate and a surfactant; then, carrying out spray drying to form mixed powder; and finally, the mixed powder is subjected to roasting and hydrogen reduction, and tungsten-rhenium alloy powder with the metal rhenium content lower than the metal rhenium content in the tungsten-rhenium alloy waste is formed. Compared with an existing tungsten-rhenium alloy waste recycling method, the recycling method has the advantages of being simple in process, low in energy consumption, small in loss and good in uniformity.

One or more embodiments of the invention relate to the field of industrial solid waste recycling, in particular to a method for preparing tungstic acid from a hard alloy waste tungsten grinding material, and the method comprises the following steps: S1, carrying out roasting pretreatment on the waste tungsten grinding material to obtain a roasted material; s2, mixing the roasted material obtained in S1 with an acidic solution, and stirring to obtain a solid-liquid mixture; s3, putting the solid-liquid mixture obtained in S2 into a high-pressure kettle; s3-1, oxidizing gas is introduced into the high-pressure kettle, and a stirring leaching reaction is carried out; s3-2, after the reaction is completed, carrying out liquid-solid separation; and S3-3, after liquid-solid separation, washing the leaching residues with hot water for 3-5 times to obtain the leaching residues which are tungstic acid solid phases and a leaching solution which is a cobalt salt solution. The problems that in the prior art, various hard alloy waste tungsten grinding material regeneration treatment technologies are tedious in technological process, large in tungsten loss, high in treatment cost and the like are solved.

The invention belongs to the technical field of functional materials, and particularly relates to ultra-thick tabular tungsten oxide and a preparation method thereof.The preparation method of the ultra-thick tabular tungsten oxide comprises the following steps that S1, ammonium tungstate is added into deionized water and stirred to be dissolved at the temperature of 70-90 DEG C, and a clarified ammonium tungstate solution is obtained; s2, cooling the clarified ammonium tungstate solution to normal temperature at a cooling rate of 0.5-2 DEG C / h, and then carrying out suction filtration to obtain plate-shaped ammonium tungstate crystals; s3, calcining the tabular ammonium tungstate crystal to obtain ultra-thick tabular tungsten oxide; ammonium tungstate is adopted as a raw material, controllability is high, tungsten oxide which is uniform in particle size and complete in plate shape is obtained through optimized crystallization and calcination, the purity is larger than or equal to 99%, the problems that traditional tungsten oxide is agglomerated and disordered in shape are solved, functional adaptability is high, the plate-shaped structure can be directionally oriented, the dielectric performance, the breakdown performance and other performance are improved, and the method is suitable for multiple high-end scenes; parameters are easy to control, and operation is simple, green and safe.

The invention belongs to the technical field of waste recovery, and discloses a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, which comprises the following steps: mixing the tungsten-containing waste, the scheelite smelting slag containing calcium phosphate and sodium salt, roasting to obtain a roasted material, leaching the roasted material with water to obtain a sodium phosphate solution and water leaching slag, and the water leaching residues are subjected to alkaline leaching, and then a sodium tungstate solution and alkaline leaching residues are obtained. The invention further comprises application of the sodium phosphate solution to scheelite decomposition. According to the method, phosphorus in the scheelite smelting slag and tungsten in the tungsten-containing waste can be efficiently recycled while the low cost, the minimum environmental pollution and the operation convenience are kept, and therefore cyclic utilization and sustainable development of resources are powerfully promoted.

The invention discloses a preparation method of low-oxygen-index surface needle-shaped high-specific-surface blue tungsten, which comprises the following steps: by taking ammonium paratungstate as a raw material, putting the raw material into a mechanically-sealed rotary calcining furnace with the furnace tube inner diameter of 400mm, and calcining at the calcining temperature of 580-620 DEG C in a first zone, 600-660 DEG C in a second zone and 600-640 DEG C in a third zone for 1-3 hours; the feeding frequency is 13-19 Hz, the furnace rotation frequency is 25-35 Hz, the negative pressure in the furnace is-400 + / -200 mm water column, the nitrogen flow is 0-4 M < 3 > / h, the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten is prepared, the oxygen index is 2.90-2.94, the surface of the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten is full of fine needle-shaped morphology, the specific surface area reaches 10-14 m < 2 > / g, and the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten can be used for preparing the high-specific-surface blue tungsten. The method is suitable for producing high-quality fine, superfine and nano-particle tungsten powder, tungsten carbide powder and corresponding hard alloy products.

The invention provides submicron high-purity tungsten powder and a preparation method thereof, and relates to the field of tungsten powder preparation. Ammonium paratungstate and ammonia water are mixed to obtain a mixture, the mixture is subjected to ammonia dissolving treatment, and a first ammonium tungstate solution is obtained through filtering; carrying out first ion exchange on the first ammonium tungstate solution by adopting strong acid cation exchange resin to obtain a first ion-exchanged solution; carrying out second ion exchange on the solution subjected to the first ion exchange by adopting chelating resin to obtain a high-purity ammonium tungstate solution; the high-purity ammonium tungstate solution is subjected to vacuum spraying and freeze drying, and a submicron tungsten precursor is obtained; and carrying out hydrogen reduction reaction on the submicron tungsten precursor to obtain the submicron high-purity tungsten powder. Insoluble particles and metal cation impurities in the solution can be effectively removed, and the high-purity tungsten precursor solution is obtained; raw materials are easy to obtain, and operation is simple.

The invention belongs to the technical field of tungsten and tungsten products, and particularly relates to a doped tungsten oxide composite material and a preparation method and application thereof. The invention provides a method for preparing doped tungsten oxide by a chemical precipitation method, which comprises the following steps: dispersing two aqueous solutions in the form of tiny liquid drops in an atomization manner, and carrying out chemical reaction at the moment of contact and mixing, so that rare earth element cations are rapidly combined with hydroxyl anions in an alkaline environment; the preparation method comprises the following steps: adding ammonium paratungstate into an ammonium paratungstate precursor, quickly drying at high temperature, nucleating to obtain the doped ammonium paratungstate precursor, realizing uniform distribution of rare earth elements, and calcining at high temperature to obtain the doped tungsten oxide composite material with uniform particle size. The invention aims to provide a preparation method of a short-process doped composite material powder which can be efficiently industrialized and is uniform in nanoscale particle size.

The invention belongs to the technical field of electrochromic films, and discloses a method for preparing a high-visible-light-transmittance tungsten oxide electrochromic film at low temperature based on a chemical bath method.The method comprises the steps that sodium tungstate is dissolved in water to obtain a sodium tungstate solution, the sodium tungstate solution and an oxalic acid solution are added into deionized water, stirring is conducted, and then the high-visible-light-transmittance tungsten oxide electrochromic film is obtained; adding hydrochloric acid to obtain a mixed solution, immersing FTO conductive glass into the mixed solution, and carrying out ultrasonic oscillation; and heating the reaction system at 60 DEG C for reaction, and washing, drying and annealing the FTO conductive glass on which the yellow film grows to obtain the tungsten oxide electrochromic layer. According to the method, the reaction conditions are mild, growth of the precursor film is completed through low temperature and raw material matching cooperation, and the tungsten oxide electrochromic film with high light transmittance and excellent electrochromic performance is finally prepared.

A modified lithium iron phosphate, a preparation method therefor and a use thereof. The preparation method comprises the following steps: (1) mixing a zirconium salt, a tungstate and a solvent, to obtain a mixed salt solution, adjusting the pH, then adding lithium iron phosphate and performing a heating reaction; (2) separating a slurry obtained by the heating reaction into a solid and a liquid, and subjecting the obtained solid to a one-step sintering treatment, to obtain a first sintered material; (3) mixing an organic carbon source, a lithium source and the first sintered material, and performing a second sintering treatment, to obtain a modified lithium iron phosphate. A material having a negative thermal expansion effect is used as a coating layer, which is then coated with an electrically conductive material, causing pores to appear during a second coating process due to the negative thermal expansion effect, which is conducive to the embedding of organic matter and improves bonding tightness between the two layers of coatings. The pores generated during the negative thermal expansion process are conducive to the entry of lithium ions, which can better generate lithium tungstate and lithium zirconate from the tungsten oxide and zirconium oxide generated by decomposition.

The application belongs to the technical field of metallurgy, and particularly relates to medium-granularity tungsten carbide powder and a preparation method and application thereof. The preparation method comprises the following steps: S1, obtaining high-purity ammonium paratungstate, and calcining the high-purity ammonium paratungstate to obtain tungsten oxide, wherein K in the high-purity ammonium paratungstate is less than or equal to 1 ppm, Na in the high-purity ammonium paratungstate is less than or equal to 1 ppm, and the specific surface area of the tungsten oxide is 0.3-1.0 m 2 / g; S2, first hydrogen reduction, second hydrogen reduction and third hydrogen reduction are performed on the tungsten oxide to obtain tungsten powder; S3, the tungsten powder is sieved and carbon is added to obtain a tungsten-carbon mixture, carbonization, crushing and sieving are performed on the tungsten-carbon mixture to obtain medium-granularity tungsten carbide powder. The application selects high-purity ammonium paratungstate with less than 1 ppm of impurity elements such as potassium and sodium as raw material, which can effectively reduce abnormal growth of tungsten powder particles caused by impurity elements in the reduction process, tungsten powder particles are developed completely by adopting three-stage hydrogen reduction, the powder activity is low, and the particle size increase is small in the subsequent carbonization process.

The invention belongs to the technical field of tungsten and tungsten products, and particularly relates to a preparation method and application of a rare earth oxide doped tungsten composite material. A tungsten salt solution and a rare earth metal salt solution are dispersed and distributed in a high-temperature environment in a tiny suspension form in an atomization manner and are mixed with each other. Then, at a high temperature, liquid drops formed by mixing are rapidly dried and are subjected to pyrolytic reaction to form tungsten oxide and nano rare earth oxide. In the subsequent reduction reaction, tungsten oxide is reduced into tungsten powder, and the rare earth oxide retains the original components and structure and is uniformly distributed. The invention provides the method capable of efficiently and industrially preparing the uniform rare earth doped tungsten powder in a short process, ammonium paratungstate does not need to be produced, the influence of the genetic effect of ammonium paratungstate is reduced, the process steps are reduced, and the energy utilization rate is increased; the rare earth and the tungsten element are uniformly mixed in a liquid-liquid mixing mode, the tungsten powder uniformly doped with the rare earth is obtained through high-temperature rapid oxidation, and no waste liquid is generated in the production process.

The invention provides a tungsten-scandium-based impregnated cathode and a preparation method and application thereof, and belongs to the technical field of hot cathode materials. The preparation method of the tungsten-scandium-based impregnated cathode provided by the invention comprises the following steps: adding ammonium metatungstate and scandium nitrate into water to obtain a mixed solution; freeze-drying the mixed solution to obtain uniformly mixed precursor powder; performing heat treatment on the precursor powder to obtain a porous tungsten scandium rod; the porous tungsten-scandium rod is subjected to post-treatment, and the tungsten-scandium-based impregnated cathode is obtained; wherein the concentration of ammonium metatungstate in the mixed solution is 0.1-0.4 g / mL; the ratio of ammonium metatungstate to scandium nitrate in the mixed solution is that the content of tungsten in the porous tungsten-scandium rod is 95-99 wt%, and the content of scandium oxide is 1-5 wt%; the freeze-drying temperature is lower than-50 DEG C, the freeze-drying vacuum degree is lower than 20 Pa, and the freeze-drying time is 48-72 hours.

The invention discloses a dressing and smelting combined treatment method for tungsten-tin bulk concentrate, and belongs to the technical field of mineral processing. The method comprises the steps that tungsten-tin bulk concentrate obtained through flotation of a metal ion-hydroximic acid complex collecting agent from tungsten-tin polymetallic ore under the low-alkalinity condition is directly subjected to size mixing, flotation is conducted under the high-alkalinity condition, and bulk concentrate of wolframite and cassiterite and scheelite concentrate are obtained; leaching the scheelite concentrate by using mixed acid to obtain a tungstate-containing acid leaching solution and gypsum; bulk concentrate of wolframite and cassiterite is decomposed through alkaline process autoclaving to obtain tungsten-containing alkaline leaching liquid and tin-rich slag, and cassiterite is recycled from the tin-rich slag through centrifugation. According to the method, OH <-> is used for precisely regulating and controlling the coordination structures of the collecting agents, and efficient separation of scheelite, wolframite and cassiterite is achieved by means of the adsorption characteristic difference of the collecting agents of different coordination structures on the wolframite and the scheelite. And then wet metallurgy is combined to achieve clean and efficient utilization of tungsten resources in the tungsten-tin bulk concentrate and comprehensive recovery of tin resources, and huge economic and environmental benefits are achieved.

This invention provides nano-tungsten carbide and its preparation method. The preparation method includes: providing ammonium paratungstate; calcining the ammonium paratungstate to form purple tungsten; oxidizing the purple tungsten in pure oxygen to form yellow tungsten; ball milling the yellow tungsten with carbon, then isostatically pressing it into a block, followed by carbon reduction to obtain a tungsten-carbon mixed block; carbonizing the tungsten-carbon mixed block, and then crushing it to obtain nano-tungsten carbide powder. This invention can reduce the manufacturing cost of nano-tungsten carbide and is beneficial for preparing finer tungsten carbide powder.

The application relates to the technical field of tungsten-rhenium alloy, and discloses a tungsten-rhenium alloy stir head material for friction stir welding, which is characterized in that the tungsten-rhenium alloy stir head material is prepared by reducing and sintering tungsten-rhenium precursors, the tungsten-rhenium precursors are prepared by using ammonium metatungstate, ammonium rhenate and oxalic acid as raw materials, and the application further discloses a preparation method of the tungsten-rhenium alloy stir head material, which comprises the following steps: S1, tungsten-rhenium precursor preparation: after ammonium metatungstate, ammonium rhenate and oxalic acid are dissolved, stirred and heated to react, spray drying is carried out to obtain tungsten-rhenium precursor powder; and S2, tungsten-rhenium precursor powder reduction: tungsten-rhenium precursor powder is heated and reduced in a hydrogen environment to obtain tungsten-rhenium alloy powder. The preparation process is simple, fast, low in cost and convenient for batch industrial production; the prepared single-phase tungsten-rhenium alloy is high in hardness and density and uniform in composition; the relative density of the tungsten-rhenium alloy after sintering reaches 99.6%, the microhardness value is 585+ / -5 Hv, and the grain size is 1-2 mu m.

The invention discloses an amorphous electrochromic film inlaid with Cs-doped tungsten trioxide quantum dots as well as a preparation method and application of the amorphous electrochromic film. The preparation method comprises the following steps: S1, adding hydrochloric acid into a sodium tungstate dihydrate aqueous solution to obtain a precipitate; washing the precipitate until the pH value of the supernate is greater than 3, and then drying the precipitate to obtain hydrated tungstic acid powder; dissolving hydrated tungstic acid powder in a hydrogen peroxide solution to obtain a peroxy tungstic acid solution, and then adding a substance containing a Cs element to obtain a Cs-peroxy tungstic acid solution; the molar ratio of Cs ions to W ions in the Cs-peroxotungstic acid solution is not less than 1: 100 and less than 5: 100; s2, heating, evaporating and concentrating the Cs-peroxy tungstic acid solution to obtain a precursor solution containing a bimetal oxygen cluster; and transferring the precursor solution containing the bimetal oxygen clusters to a substrate by adopting a film coating process, and annealing to obtain the amorphous tungsten trioxide electrochromic film inlaid with the Cs-doped tungsten trioxide quantum dots.

The invention belongs to the technical field of electrochemistry, and relates to a preparation method of a self-leaching / assembled nickel-tungsten alloy composite material, which comprises the following steps: preparing nickel nitrate hexahydrate, ammonium metatungstate and deionized water into a solution, transferring the solution and a pretreated base material into a stainless steel autoclave with a Teflon lining, carrying out hydrothermal reaction, and cleaning to obtain a nano precursor NiWO-Sub; carrying out reduction heat treatment under the protection of a hydrogen-containing atmosphere to obtain a tungsten composite precursor Ni-WO-Comp; and performing electrochemical activation treatment by adopting a cyclic voltammetry method. Through a self-leaching-assembling strategy, controllable leaching of a tungsten element and in-situ optimized assembling of a material structure are achieved in the electrochemical activation process, the formed amorphous WOx and W-doped NiW alloy composite structure is balanced under the high-concentration W leaching effect, continuous tungsten leaching in an industrial-grade electrolyzed water environment is effectively inhibited, and the yield of the tungsten-doped WOx and W-doped NiW alloy composite structure is improved. And the long-term catalytic stability of the nickel-tungsten alloy electrode is obviously improved. And the preparation process is simple and easy to implement, can be attached to various different substrates, and is easy to implement industrially.

The invention belongs to the technical field of recycling of rare and noble metal secondary resources, and discloses a method for preparing a tungsten compound and chloroplatinate from a waste catalyst and application of the method. The method comprises the following steps: (1) firing and crushing the waste catalyst, (2) reacting the waste catalyst with acid, (3) filtering and discarding filtrate, (4) reacting the precipitate with ammonia water, filtering to obtain an ammonium tungstate solution, and retaining filter residues; (5) concentrating the ammonium tungstate solution, crystallizing, separating and drying to obtain an ammonium paratungstate finished product; and (6) reacting the filter residues retained in the step (4) with aqua regia to prepare chloroplatinate. And (7) firing the ammonium paratungstate at a high temperature to obtain tungsten trioxide. According to the method, tungsten and platinum can be effectively separated from the carrier, and the recovery rate of rare and precious metals is increased.

The present invention provides a method for preparing a fluorine adsorbent, which uses tungsten trioxide, ammonium metatungstate, and water glass as raw materials, obtains a granular substrate after granulation and sintering, then performs a primary modification with a phosphoric acid solution, and after drying, performs a secondary modification with an aluminum chloride aqueous solution, and obtains a fluorine adsorbent after washing and drying. The present invention also provides the use of the adsorbent obtained by the above preparation method in removing fluoride ions from water. The present invention utilizes Al4(PO4) x (OH) 12‑3x The material's rapid adsorption capacity for fluoride ions enables it to quickly capture fluoride ions in water, ensuring that the fluoride ion concentration in the produced water meets the standard. It has the ability to adsorb fluoride ions in large capacity, which can reduce the number of regenerations and increase the adsorption capacity and water treatment volume of the adsorbent per unit volume.

The invention relates to the technical field of high-grade alkylphenol preparation, in particular to a method for preparing high-grade alkylphenol from lignin oil. The method comprises the following steps: mixing lignin oil, a tungsten acid catalyst and a reaction solvent, and carrying out a catalytic reaction to obtain a reaction solution; and then separating the reaction liquid to obtain the higher alkylphenol, wherein the reaction solvent is selected from one or more of tetrahydrofuran, tetrahydropyran, dioxane and isopropyl alcohol. The method provided by the invention is carried out in the specific reaction solvent, the application of a noble metal catalyst can be avoided, the reaction condition is mild, the side reaction is less, the conversion rate of monomer phenolic substances in the lignin oil by the catalyst is more than 70%, the selectivity of higher alkylphenol is more than 25%, and the added value of the lignin oil can be obviously improved.

The invention discloses a high-efficiency comprehensive recovery and smelting method for low-grade tungsten-molybdenum ore, which belongs to the field of tungsten-molybdenum metallurgy technology, including: grinding the ore to 40-80% of -0.074mm, making a 30-50% concentration slurry; adding sodium carbonate to adjust the pH to 8-10, using dodecyl mercaptan and oleic acid mixed flotation to obtain a tungsten-molybdenum mixed concentrate; passing the concentrate slurry through oxygen pressure oxidation at 120-150°C and 0.5-2.0MPa for 1-5h; filtering the filtrate and extracting and separating it to obtain ammonium molybdate and ammonium tungstate products. This method effectively solves the technical problems of low flotation recovery of tungsten-molybdenum ore, difficulty in obtaining tungsten and molybdenum concentrate products by flotation, and large amounts of tungsten and molybdenum resources being wasted or unable to be effectively developed.

The present invention relates to the field of alloy preparation technology, and discloses a method for preparing a high-performance tungsten-rhenium alloy, comprising the following steps: Step 1: Preparation of tungsten-rhenium alloy powder, dissolving a certain proportion of ammonium metatungstate, ammonium rhenate, and oxalic acid in deionized water, and placing the solution in a magnetic stirrer for heating to 100-120°C. The solution is allowed to react for 3-5 hours, and the solid content of the precursor solution is 25%-32%. Precursor powder is then prepared using a spray drying device, and the spray drying parameters are set: inlet air temperature of 200-230°C, outlet air temperature of 100-120°C, atomizer speed of 300-350r / min, and feed rate of 1-2L / h. The tungsten-rhenium precursor is then hydrogen reduced, the tungsten-rhenium precursor is spread flat in a calcined boat, the calcined boat is then placed in a hydrogen reduction furnace, the hydrogen reduction furnace is vacuumed, and hydrogen is then introduced. The preparation method proposed in the present invention can prepare a single-phase tungsten-rhenium alloy with good solid solubility, high high-temperature strength, high hardness, high density and certain ductility.

This invention belongs to the field of cathode materials, and provides a ternary cathode material, its preparation method, and a battery. The tungsten content of the ternary cathode material provided by this invention gradually decreases along a direction perpendicular to the surface of the ternary cathode material towards the interior, and the tungsten element in the ternary cathode material is mainly distributed within a depth range of 100 nm. The tungsten element material on the outer surface of the ternary active material includes tungsten oxide and lithium tungstate. The formed lithium tungstate consumes the residual lithium on the surface of the ternary active material, reducing the residual lithium content on the surface of the ternary cathode material. In the preparation method of the ternary cathode material provided by this invention, tungsten chloride with a low melting point is deposited on the surface of the ternary active material, and then the tungsten chloride is oxidized to tungsten oxide using an oxidation reaction to obtain the ternary cathode material. This reduces heat consumption while ensuring that the tungsten element is uniformly distributed on the surface of the ternary cathode material, thereby obtaining a ternary cathode material with high compressive strength, low surface residual lithium content, and good cycle performance.

The utility model relates to the technical field of tungsten smelting equipment, and provides an ammonia-free tungsten smelting drying device which comprises a first support, a drying cylinder is fixedly connected to the first support, an air inlet, a feeding port, a vacuumizing port and an air outlet are formed in the upper end of the drying cylinder, a discharging port is formed in the lower end of the drying cylinder, and a stirring shaft is arranged in the drying cylinder. The stirring shaft is used for stirring materials in the drying cylinder, and a driving mechanism is arranged on the left side of the drying cylinder and used for driving the stirring shaft to rotate. The middle parts of the connecting rods are fixedly connected with the stirring shaft, and the two ends of the connecting rods are fixedly connected with buckets. When the device is used for drying the tungstic acid, the tungstic acid can be greatly stirred, the heating is more uniform, the water vapor emission is more sufficient, and the drying quality and efficiency are improved; the hot air making contact with tungstic acid is conveyed to the dehumidifier, water vapor in the hot air is removed, then the dried hot air is conveyed into the drying cylinder again through the circulating fan, and energy waste is avoided.

This invention relates to a method for preparing and applying a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide, belonging to the field of gas sensor technology. The invention discloses a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide and its application as a sensing material in a highly selective and sensitive flexible NO2 gas sensor. The invention utilizes a liquid-phase growth method, using SnSe2 nanosheets, ammonium tungstate, and diphenyldiselenoether as raw materials, and varying reaction conditions such as temperature, reaction time, and raw material content to prepare the ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide. Subsequently, these nanosheets are sprayed onto interdigitated electrodes and dried to form a film, thus preparing a chemielectric resistive gas sensor capable of detecting low concentrations of nitrogen dioxide gas at room temperature. It not only possesses high sensitivity and selectivity but can also be applied to flexible NO2 gas sensing.

The invention belongs to the technical field of metallurgy, and particularly relates to medium-particle tungsten carbide powder and a preparation method and application thereof.The preparation method comprises the following steps that S1, high-purity ammonium paratungstate is obtained, the high-purity ammonium paratungstate is calcined to obtain tungsten oxide, K in the high-purity ammonium paratungstate is smaller than or equal to 1 ppm, Na in the high-purity ammonium paratungstate is smaller than or equal to 1 ppm, N is smaller than or equal to 1 ppm, and N is smaller than or equal to 1 ppm; the specific surface area of the tungsten oxide is 0.3-1.0 m < 2 > / g; s2, the tungsten oxide is subjected to first hydrogen reduction, second hydrogen reduction and third hydrogen reduction, and tungsten powder is obtained; and S3, the tungsten powder is sieved, a tungsten-carbon mixture is obtained after carbon is added, the tungsten-carbon mixture is carbonized, crushed and sieved, and the medium-particle tungsten carbide powder is obtained. According to the method, high-purity ammonium paratungstate with the content of impurity elements such as potassium and sodium smaller than 1 ppm is selected as the raw material, abnormal growth of tungsten powder particles caused by the impurity elements in the reduction process can be effectively reduced, three-section hydrogen reduction is adopted, the tungsten powder particles are developed completely, the powder activity is low, and the particle size increase in the subsequent carbonization process is small.

The invention belongs to the technical field of tungsten material manufacturing, and particularly relates to a tungsten-cerium alloy wire and a preparation method thereof.The preparation method comprises the steps that a cerium-containing solution and ammonium paratungstate are mixed through a spray mixing method and dried, and a mixture is obtained; the mixture is calcined at the temperature lower than or equal to 900 DEG C and reduced in the hydrogen atmosphere at the temperature of 800-1050 DEG C, and cerium-containing tungsten powder is obtained; the cerium-containing tungsten powder is subjected to isostatic pressing forming, sintered for 1-1.5 h at the temperature of 1500-1600 DEG C in the hydrogen atmosphere and then sintered for 5-8 h at the temperature of 2300-2450 DEG C, and a tungsten rod is obtained; and the tungsten rod is subjected to rolling, electric pulse treatment, forging and wire drawing treatment, and the tungsten-cerium alloy wire with the diameter being 20-28 microns is obtained. The cerium element is uniformly distributed in the alloy wire through solid-liquid cerium doping; through the two-stage sintering process, the compactness and the mechanical property of the tungsten rod are improved; the prepared tungsten-cerium alloy wire has excellent tensile strength, high elongation and excellent fatigue resistance, and shows low edge breakage rate, low wire breakage rate and long service life in silicon nitride ceramic substrate cutting.

The application belongs to the technical field of nanometer material preparation, and particularly relates to a kind of spherical-like nanometer tungsten oxide and a preparation method thereof, wherein the preparation method of the spherical-like nanometer tungsten oxide comprises the following steps: S1, obtaining an ammonium tungstate solution; S2, adding liquid nitrogen dropwise into the ammonium tungstate solution to obtain spherical-like nanometer crystals; and S3, calcining the spherical-like nanometer crystals to obtain spherical-like nanometer tungsten oxide; the application has simple process, strong controllability, easy-to-adjust parameters, simple raw materials, is suitable for large-scale industrial production, introduces liquid nitrogen quenching process, uses ultra-low temperature environment to make solution reach high supersaturation instantaneously and generate a large number of fine crystal nuclei, at the same time, the tiny nitrogen bubbles formed by liquid nitrogen vaporization effectively inhibit the collision and agglomeration between the newly generated crystal nuclei, thereby ensuring good dispersity of the product.

The invention discloses a tungsten carbide silver contact material and a preparation method thereof, and the preparation method comprises the following steps: adding a silver nitrate solution into a sodium tungstate solution, stirring at a constant temperature, standing and aging to obtain an Ag2WO4.nH2O colloidal precipitate, carrying out suction filtration and washing, dispersing and dissolving, and carrying out ultrasonic oscillation to obtain an Ag2WO4.nH2O sol; wC powder is added into the Ag2WO4.nH2O sol, first-time ball milling is carried out, two-phase mixed slurry is obtained, silver powder and a dispersing agent are added into the two-phase mixed slurry, second-time ball milling is carried out, three-phase mixed slurry is obtained, granulation and vacuum drying treatment are carried out, and composite feed is obtained; pressing the composite feed to obtain a green body; the green body is placed in a sintering furnace to be subjected to three-section heating gradient sintering treatment, the tungsten carbide silver contact material is obtained, the tungsten carbide silver contact material is composed of, by mass, 35%-80% of WC, 15%-60% of Ag and 1%-5% of Ag4WOx, and the tungsten carbide silver contact material has high density, high hardness, high conductivity and good fusion welding resistance.

The invention belongs to the field of waste hard alloy recovery treatment, and particularly relates to a waste WC-Co hard alloy microwave oxidizing roasting method, the waste WC-Co hard alloy with the particle size below 150 mu m is subjected to oxidizing roasting under the assistance of microwaves, an oxidation product containing tungsten oxide and cobalt tungstate is obtained, the oxidizing roasting temperature is 400 DEG C or above, the oxidizing time is 30 min or above, and the oxidizing product containing tungsten oxide and cobalt tungstate is obtained. And the power of the microwave is more than 600W. According to the method, the waste WC-Co hard alloy is heated for oxidizing roasting by innovatively adopting microwave selective heating, so that the oxidation effect can be remarkably improved based on a brand new mechanism.