538 results about "Graphite crucible" patented technology

The invention relates to the technical field of silicon carbide single crystal growth, in particular to a high-purity semi-insulating silicon carbide single crystal for an optical element and a growth process thereof.The growth process includes the steps that S1, silicon carbide powder, a graphite crucible and the like are assembled to form a thermal field device, the thermal field device is placed in an induction furnace, room-temperature furnace washing treatment and low-temperature furnace washing treatment are sequentially carried out, and the silicon carbide powder is obtained; carrying out thermal field impurity removal treatment; s2, assembling the silicon carbide seed crystal and the impurity-removed thermal field device, raising the temperature in the induction furnace, conveying high-purity argon or mixed gas of high-purity argon and high-purity hydrogen into the induction furnace, and performing crystal growth; s3, after crystal growth is finished, high-temperature and high-pressure annealing treatment is carried out firstly, then furnace cooling treatment is carried out, and the high-purity semi-insulating silicon carbide crystal ingot for the optical element is obtained. The silicon carbide crystal ingot with excellent light transmission performance and high resistivity is obtained by selecting specific raw materials, reasonably designing an assembly mode and combining processes of thermal field impurity removal, high-temperature and high-pressure annealing and the like.

The invention discloses a graphite crucible silicon infiltration resistant coating based on a gradient boron nitride-silicon carbide composite structure and a preparation method thereof. The coating is composed of hexagonal boron nitride nanosheets, beta-type silicon carbide nanowires, yttrium aluminum garnet precursor sol and the like, and effective blocking of 1500-1600 DEG C silicon melt is achieved through gradient structural design and an in-situ self-repairing mechanism. The preparation process comprises the steps of h-BN activation, S C carbon layer deposition, slurry mixing and spraying and segmented heat treatment. The molten silicon contact angle of the coating reaches 158 + / -2 degrees at the temperature of 1550 DEG C, through cracks do not exist after 50 times of thermal shock circulation, the coating is effective after being continuously used for 48 batches under the industrial working condition, the problems of silicon infiltration interface adhesion and thermal shock failure of a traditional graphite crucible are solved, and the coating has remarkable industrial application value.

The utility model relates to the technical field of single crystal preparation by a liquid phase epitaxy method, in particular to a leading forced convection introducing device for single crystal growth by a resistance heating LPE method, which comprises a graphite crucible and a graphite heating component arranged on the outer side of the graphite crucible, one end of the graphite seed crystal rod extends into the graphite crucible and is connected with the graphite seed crystal support; the seed crystal is adhered to the bottom surface of the graphite seed crystal support; the graphite annular turbofan is arranged in the graphite crucible; the graphite annular turbofan is connected with the graphite seed rod through a jackscrew clamp; the other end of the graphite seed crystal rod is externally connected with a seed crystal lifting and rotating mechanism; and the graphite seed crystal rod drives the seed crystal and the graphite annular turbofan to do lifting and rotating motion. According to the device, the influence of adverse convection on the whole flow field is weakened, and the controllability of the whole flow field can be improved; and meanwhile, an ideal temperature field for growing high-quality silicon carbide crystals in the growth cavity is ensured.

A repairing agent and repairing method for a graphite crucible. The repairing agent is a two-component repairing agent and comprises an interface repairing agent and a surface layer repairing agent. The interface repairing agent is prepared by taking graphite powder, paraffin oil, asphalt powder, pyridine, and an SiC-Y2O3 slurry as raw materials, and the surface layer repairing agent is prepared by taking petroleum coke powder, graphite powder, asphalt powder, and a resin material as raw materials. The corresponding graphite crucible repairing method relates to using a repairing agent as a tool to repair a damaged area of a damaged graphite crucible; during repairing of the damaged graphite crucible, coating the damaged area of the damaged graphite crucible with an interface repairing agent; after the coating is completed, covering the coating area by an aluminum foil, wrapping with a glass fiber mesh, performing pre-curing treatment, and using a surface repairing paste to finally complete the repairing operation of the graphite crucible. The repairing agent and the repairing method have a good repairing effect on the damaged graphite crucible and can be used to prolong the service life of the damaged graphite crucible.

The present invention relates to the field of the preparation of silicon carbide crystals, and in particular to a device and method for the diameter expansion growth of a silicon carbide crystal. The device comprises a graphite diameter expansion device comprising a porous graphite diameter expansion ring. The porous graphite diameter expansion ring serves as a gas channel and is used for releasing an accumulated growth atmosphere during the diameter expansion growth of the silicon carbide crystal. The porous graphite diameter expansion ring not only ensures the smoothness of gas exhaust, but also solves the problem of polycrystalline silicon carbide growing on an edge of a silicon carbide seed crystal hindering the diameter expansion of the silicon carbide crystal. In addition, in the axial direction of the graphite diameter expansion device and in a direction away from the silicon carbide seed crystal, the porosity of the porous graphite diameter expansion ring gradually decreases, so that the growth atmosphere in a graphite crucible is controlled to ensure that the growth atmosphere can be discharged in time when the growth atmosphere is excessive in the early stage, and the discharge amount is reduced when the growth atmosphere in the later growth stage is insufficient, thus increasing the growth rate of the silicon carbide crystal. In addition, hard graphite felt is arranged around the diameter expansion device to serve as a heat insulation material, so that a rational temperature gradient of silicon carbide crystal growth is maintained.

The invention discloses a device and a method for preparing a single-walled carbon nanotube by a thermal plasma CVD (chemical vapor deposition) method, and relates to the technical field of nano carbon material preparation, the device structurally comprises a thermal plasma electric arc furnace, a CVD growth chamber, a cooling chamber and a collecting tank which are sequentially connected in series, the thermal plasma electric arc furnace structurally comprises hollow graphite serving as a cathode, a graphite crucible serving as an anode and a furnace body. The graphite crucible is located on the lower portion of the thermal plasma electric arc furnace, and the hollow graphite is located on the upper portion of the thermal plasma electric arc furnace and above the graphite crucible. According to the device and the method, a two-step continuous growth process is adopted, so that the yield and the quality of the single-walled carbon nanotube are remarkably improved; and meanwhile, the common problems of excessive catalyst, coking short circuit, arc breaking and the like in the process of preparing the single-walled carbon nanotube by a conventional plasma arc method can be effectively avoided through a shallow crucible and a bottom gas inlet mode, so that the continuous stability and the yield of the reaction are greatly improved, and the method is an effective route for large-scale preparation and has important commercial value.

The invention discloses an inner wall defect detection device for graphite crucible production based on vision, and relates to the technical field of vision detection. Through cooperation of the clamping assembly and the adjusting assembly, the device can automatically adjust and position according to the actual material volume and height; the surface conditions of the inner wall of the crucible at different angles can be simultaneously detected by the device through the detection assembly, so that the capability of accurately detecting fine defects by the device is realized; the analysis module is used for firstly eliminating the regional images with the abnormal count exceeding the preset threshold value, then calculating the mean value of the numbered gray blocks corresponding to the remaining regional images as gray value data, and comparing the gray value data with the gray image of the standard component, so that the interference of the abnormal region on the overall data analysis is effectively avoided, and the reliability of the detection result is ensured; meanwhile, the total abnormal area is obtained by calculating the product of the number of the abnormal gray blocks and the area of the pixel blocks, a quantitative basis is provided for defect judgment, and the detection result is more persuasive.

The invention discloses equipment and a method for preparing an aluminum silicon carbide (Al-SiC) composite material through a pressure infiltration process, and belongs to the technical field of metal matrix composite material preparation. The efficient pressure preparation equipment for the aluminum-silicon carbide composite material comprises a furnace body, a lower graphite crucible, an upper graphite crucible, a liftable graphite rod, an inflation connector and an exhaust connector, during specific use, an aluminum ingot and a silicon carbide preform are heated respectively and prevented from making contact with each other, so that the interface reaction strength is relieved, and combination of aluminum and silicon carbide is facilitated; after the target temperature is reached, the graphite rod is lifted to open the leak hole, so that the molten aluminum falls into the lower graphite crucible, and under the action of high-pressure gas, the molten aluminum is infiltrated into the silicon carbide prefabricated body, so that the aluminum-silicon carbide composite material is prepared; the problems of low density, poor process stability, violent interface reaction and low bonding strength in the prior art can be solved.

The invention discloses a composite crucible for large-size AlN single crystal growth and a preparation method thereof, and belongs to the technical field of PVT method crystal growth. A heat conduction device is arranged in a cavity of the composite crucible and is composed of a plurality of high-purity graphite plates, the high-purity graphite plates are distributed at equal included angles to form a wing-shaped structure, the inner surface of the high-purity graphite crucible and the surfaces of the high-purity graphite plates are covered with a metal tantalum Ta layer or a TaC coating, and the high-purity graphite plates and the high-purity graphite plates are subjected to heat conduction under the temperature environment of 1800-2600 DEG C, so that the heat conduction effect of the high-purity graphite plates is improved. And TaC / C material layers are formed on the inner surface of the high-purity graphite crucible and the high-purity graphite plate. The heat conduction efficiency of the large-size crucible can be greatly improved, the problem that heat transfer from the side wall of the crucible to the source powder center is insufficient in the powder burning process can be remarkably solved, the uniformity of large-size AlN crystals is improved, thermal stress in crystal growth is relieved, and favorable conditions are created for preparing large-size and high-quality AlN single crystals.

The invention provides aluminum-lithium-based multi-component alloy powder and a preparation method thereof. The aluminum-lithium-based multi-element alloy powder comprises aluminum, lithium and functional adding elements. The functional additive element is at least one of silicon, magnesium and rare earth elements; the total weight of the aluminum-lithium-based multi-component alloy powder is 100%, and the aluminum accounts for 50%-98.5%; 1%-10% of lithium; 0.5%-40% of functional additive elements; the preparation method comprises the following steps: under the protection of argon, weighing the raw materials containing the elements according to the raw materials, putting the raw materials into a silicon carbide graphite crucible smelting furnace for smelting, carrying out blowing stirring by adopting argon to obtain an aluminum-lithium-based multi-element alloy feed liquid, feeding the aluminum-lithium-based multi-element alloy feed liquid into a tight coupling gas atomization tank, atomizing the aluminum-lithium-based multi-element alloy feed liquid into liquid drops, and condensing the liquid drops in gravity drop to obtain the aluminum-lithium-based multi-element alloy powder. The phase composition of the alloy powder is changed by introducing functional adding elements, so that the oxidation resistance of the aluminum-lithium-based alloy powder is improved while it is guaranteed that the aluminum-lithium-based alloy powder has a high calorific value.

The invention relates to the technical field of silicon carbide materials, in particular to P-type silicon carbide powder and a preparation method and application thereof.The preparation method includes the steps that S1, dopant particles are subjected to plasma cleaning treatment, screening treatment and drying treatment; and S2, heating the reaction chamber, constructing a gradient temperature zone, conveying dopant particles into the reaction chamber from the top of the reaction chamber, conveying the preheated mixed gas into the reaction chamber from the bottom of the reaction chamber, regulating the pressure in the reaction chamber, and forming the P-type silicon carbide polycrystalline powder with a gradient structure, discharging from the bottom of the reaction chamber; and S3, collecting the P-type silicon carbide polycrystalline powder, placing the collected P-type silicon carbide polycrystalline powder in a graphite crucible, raising the temperature in the graphite crucible, carrying out heat preservation, and cooling to obtain the P-type silicon carbide powder. When the doping agent is used for crystal growth, the diffusion process of doping agent particles in a powder system can be limited, and the effect of sufficiently and stably supplying Al in the crystal growth process is achieved.

The invention relates to the field of silicon carbide wafer preparation, in particular to a semi-insulating silicon carbide wafer annealing device and method, the annealing device comprises a crucible cover and a graphite crucible which are detachably connected, an annealing chamber is arranged in the graphite crucible, the annealing chamber comprises a wafer supporting area and a powder area, and the powder area is arranged in the crucible cover. The gas pressure control assembly is used for controlling gas components and pressure intensity in the annealing chamber; the heating device is used for heating the annealing chamber in a partitioned manner; and the heat preservation system is arranged outside the crucible cover and the graphite crucible in a sleeving manner. By means of the annealing device, the problems of silicon carbide wafer intrinsic point defect screening and concentration control can be effectively solved, the Fermi energy level is controlled at the EH6 / 7 energy level position, and the silicon carbide wafer obtained through annealing finally achieves control over the electrical resistivity larger than 1E12 ohm cm.

The invention discloses a ceramic component gradient modified C / C-SiC-ZrC composite material and a preparation method thereof, and belongs to the technical field of carbon / carbon composite material matrix modification preparation, a carbon fiber preform and a heating element are placed in chemical liquid phase vaporization deposition equipment, a precursor solution is added until the carbon fiber preform is fully soaked, and a ceramic component gradient modified C / C-SiC-ZrC composite material is obtained; and carrying out chemical liquid phase vaporization deposition reaction to obtain the low-density C / C composite material with porosity in unidirectional gradient distribution. And putting the mixture into a graphite crucible with a carbon-rich area facing downwards and a carbon-less area facing upwards, completely putting the graphite crucible into the ceramic powder for modification, reacting and infiltrating, and cooling to room temperature to obtain the C / C-SiC-ZrC composite material with the gradient modified ceramic components. The end with high ceramic content endows the material with a high-temperature thermal protection function, the end with high pyrolytic carbon content can effectively conduct heat generated in a ceramic-rich area, and the end with low ceramic content can effectively conduct heat generated in a ceramic-rich area. Due to the gradient design from the ceramic-rich area to the carbon-rich area, the material has high-temperature oxidation resistance and ablation resistance and is light, and lightweight design of an aerospace thermal protection structure is facilitated.

The invention discloses a silicon carbide single crystal growth apparatus and a silicon carbide single crystal growth method. The silicon carbide single crystal growth device comprises a growth system, the growth system comprises a graphite crucible, a seed crystal support and a crucible support, the crucible support is arranged on the lower side of the graphite crucible, the graphite crucible is used for containing a growth solution, and the seed crystal support is arranged above the growth solution; wherein one side, close to the growth solution, of the seed crystal support is provided with at least one seed crystal bonding area, the seed crystal bonding area is used for bonding off-axis seed crystals, and the center of the seed crystal bonding area does not coincide with the center of the seed crystal support. The off-axis seed crystal is eccentrically arranged on the seed crystal support, so that the step flow direction of single crystal growth can be effectively controlled to be opposite to the solution convection direction, complete reverse step growth of the solution in the single flow direction in the seed crystal range is realized, the crystal quality can be effectively improved, and the growth efficiency is improved. Meanwhile, the off-axis seed crystal is adopted, so that the cost is greatly reduced.

The invention discloses a method for analyzing the content of nitrogen in silicon-calcium-barium, which comprises the following steps of: filling a prepared powder sample into a graphite crucible filled with a tin sheet, heating by a pulse electrode furnace until the powder sample is molten, extracting nitrogen in a molecular form in helium flow, separating the nitrogen from other gas extracts, and measuring by using a thermal conductivity method. According to the method for analyzing the content of nitrogen in silicon-calcium-barium, the tin sheet is adopted as the fluxing agent, nitrogen release is greatly improved, and the accuracy of the determination method is improved. The method is simple, rapid and accurate in determination process.

The embodiment of the present application relates to a device and method for preparing high-purity germanium powder by hydrogen reduction of germanium dioxide, belonging to the technical fields of germanium metallurgy and preparation of high-purity germanium materials. The device for preparing high-purity germanium powder by hydrogen reduction of germanium dioxide in the embodiment of the present application includes a furnace body. A furnace tube is penetrated through the furnace body, and both ends of the furnace tube extend outside the furnace body and are fixed by a furnace tube support. The furnace tube support is fixedly arranged on the furnace body. Inside the furnace tube, a graphite crucible assembly and a furnace plug are sequentially arranged from bottom to top, and there is a gap between the graphite crucible assembly and the furnace plug. The present application greatly reduces the usage amount of hydrogen, significantly improves the hydrogen utilization rate, and shortens the production cycle.

The invention discloses a molybdenum-vanadium-aluminum intermediate alloy and a low-cost preparation method thereof. The molybdenum-vanadium-aluminum intermediate alloy comprises the following chemical components in percentage by mass: 39-41% of Mo, 39-41% of V and the balance of Al. The method comprises the following steps: uniformly mixing vanadium oxide (tablets replace powder), molybdenum trioxide, metal aluminum, calcium fluoride, calcium oxide and a cold material according to a mass ratio of (28-32): (24-26): (32-35): (10-13): (1.5-4): (5-10); then putting the mixture into a graphite crucible for tamping treatment; and finally, the metal powder is directly ignited for a reduction reaction, and the molybdenum-vanadium-aluminum intermediate alloy can be obtained. According to the method, the recovery rates of the molybdenum and the vanadium are increased by adjusting the components and the ratio of the raw materials and the auxiliary materials and adopting a one-step aluminothermic reduction method, and the recovery rates of the molybdenum and the vanadium can reach 95 wt% or above and 96 wt% or above respectively.

According to the method, a high-pressure induction heating furnace is adopted, and under the nitrogen atmosphere of 2-5 MPa, a graphite crucible with the inner wall coated with silicon carbide (SiC) and a porous SiC carbon source are utilized to control the nitrogen content in a silicon melt and stabilize components; by introducing 0.05-0.30 wt% of an aluminum or yttrium cosolvent, the nitrogen dissolving efficiency and wettability are improved, in the method, a 10-30 DEG C temperature gradient of a carbon source region and a seed crystal region is established, convection of a nitrogen-containing silicon melt is induced, epitaxial growth of the beta-SiN single crystal is promoted, and the growth of the beta-SiN single crystal is further improved by controlling the immersion depth and the cooling rate of the seed crystal. And finally, the (0001)-oriented high-quality beta-SiN single crystal substrate with the thickness larger than or equal to 500 m and the dislocation density smaller than or equal to 1 * 10 cm is prepared. Compared with the traditional PVT and CVD methods, the method provided by the invention can effectively reduce the growth temperature and thermal stress, inhibit Si evaporation and significantly improve the crystal size and quality, and is suitable for the field of high-frequency and high-power semiconductor device manufacturing.

The invention provides a graphite sagger and a preparation method and application thereof, and belongs to the technical field of graphite saggers. The preparation method comprises the following steps: crushing and shaping a graphite raw material to obtain raw materials with different particle sizes, granulating and spheroidizing to form graphite materials with different particle sizes, grading and mixing according to a ratio, isostatic pressing, carbonizing and sintering to prepare the graphite saggar. By adopting a high-temperature granulation process, light small molecules in the raw materials can be removed, asphalt carbon can be filled, and meanwhile, a layer of coating can be formed on the surface of a matrix, so that surface defects are improved, and the compactness of the matrix material is improved; the material can be spheroidized through mechanical acting force, the diameter-thickness ratio difference is reduced, the particle orientation is reduced, the surface energy is reduced, the filling property is improved, and the stacking efficiency is optimized, so that the purpose of improving the strength and density of the base material is achieved; in addition, the strength and the density of a finished product can be improved through excellent grain composition and isostatic pressing forming.

The invention relates to a silicon nitride crystal based on high static nitrogen pressure and active nitrogen regulation and a growth method thereof. The silicon nitride crystal is prepared by the growth method, and the method adopts a physical gas phase transmission process and specifically comprises the following steps: introducing high static pressure nitrogen (1-3 bar) and trace NH3 / N2 mixed gas into source powder formed by mixing high-purity beta-Si3N4 and polycrystalline silicon, and dynamically maintaining the gas phase N / Si molar ratio to be (1.33 + / -0.1): 1, thereby inhibiting the decomposition of the source powder and stabilizing the crystal growth; carrying out spray granulation on the source powder, carrying out compression molding, placing the obtained product in a graphite crucible with the inner wall coated with TaC, and carrying out ordered epitaxial growth by controlling the temperature difference of a temperature zone at 1800-2000 DEG C and the axial temperature gradient; according to the method, the dislocation density and the carbon impurity content of the silicon nitride crystal can be remarkably reduced, then the high-purity silicon nitride crystal with a complete structure and a smooth surface is obtained, and the method is suitable for the fields of high-temperature electronic devices and deep ultraviolet light electronics.

The present invention provides a graphite crucible arc-edge polishing device, which relates to the technical field of polishing and includes: a working station base, a driving motor is fixedly installed on the left side inside the working station base; feed screws are rotatably installed on the left and right sides of the top of the working station base; clamping guide grooves are formed on the left and right sides at the top end inside the working station base; force-bearing clamping blocks are slidably installed inside the clamping guide grooves; positioning clamping plates are fixedly installed on the inner sides of the force-bearing clamping blocks. When the polishing base and the replaceable grinding disc are in the stationary position of the non-working state, the locking of the replaceable grinding disc by the limiting block can be automatically released, so as to facilitate the easy replacement of the replaceable grinding disc when not in use, and solve the problem that although the fasteners can effectively ensure the stability of the polishing assembly during use, they also significantly increase the complexity and time consumption in the disassembly and replacement process and reduce the convenience of the polishing assembly in maintenance operations.

The invention provides a method for synchronously recovering iron and rare earth from iron separation tailings, which comprises the following steps of: roasting the pretreated iron separation tailings in a graphite crucible to obtain a roasted product; the roasted product is crushed and screened, oversize products and undersize products are obtained, and the oversize products are reduced iron products; the screen underflow and an acid solution are mixed for leaching, and leaching liquid containing rare earth elements and acid leaching residues are obtained; and adding a precipitant into the leachate to obtain a precipitate containing rare earth elements, and recovering fluorite concentrate from the acid leaching residues. According to the method, the traditional disjunction mode of pre-enrichment and then smelting is broken through, a roasting-acid leaching integrated process with deep beneficiation and smelting coupling is provided, the complex pre-enrichment link is abandoned, efficient and synchronous recovery of iron and rare earth is achieved, and the method has the advantages of being short in process, low in energy consumption, few in flotation reagent, high in rare earth recovery rate, high in resource comprehensive utilization rate and the like.

The invention discloses a method for preparing oxide eutectic ceramics in an ultrafast high-temperature furnace. Proportioning the raw material powder according to the eutectic components, and sequentially carrying out ball milling, drying, sieving and compression molding; putting the green body into a thin-wall graphite crucible, and putting the thin-wall graphite crucible into an interlayer hole of a heating carbon felt element; and heating to a set temperature in an ultrafast manner, keeping the temperature for an extremely short time, and cooling to obtain the oxide eutectic ceramic. According to the method, the eutectic structure of the oxide ceramic is rapidly formed by adopting ultrafast heating and Joule heat radiation heating at the furnace temperature far lower than the eutectic temperature, and the structure morphology of the eutectic ceramic can be regulated and controlled by adjusting temperature parameters. The obtained eutectic structure is fine in size and excellent in mechanical property; the problems that an existing oxide eutectic ceramic preparation method is long in consumed time, high in cost, complex in bulk material preparation process and the like are solved.

The invention discloses a 6N high-purity silver raw material for a target material and a preparation method thereof.The preparation method of the 6N high-purity silver raw material for the target material comprises the following steps that 4.5 N silver is placed in a vacuum intermediate frequency furnace to be smelted, and an anode plate is prepared; silver nitrate is purified through a crystallization method and a silver oxide purification method, and high-purity silver nitrate is obtained; the anode plate is loaded into a ceramic membrane, the high-purity silver nitrate is taken to be prepared into an electrolysis mother solution, then the anode plate loaded into the ceramic membrane serves as an anode, titanium-coated silver serves as a cathode, the electrolysis mother solution serves as an electrolyte, and electrolysis is conducted to prepare high-purity silver powder; and the high-purity silver powder is placed in a graphite crucible to be subjected to vacuum melting and then poured into a graphite mold, and the 6N high-purity silver raw material for the target material is prepared. According to the 6N high-purity silver raw material for the target material and the preparation method of the 6N high-purity silver raw material, the purity and stability of the 6N high-purity silver raw material are improved on the basis of guaranteeing the purity of the 6N high-purity silver raw material through combination of various modes such as raw material optimization, equipment optimization and process step improvement.

The invention provides a production method of a vanadium-aluminum alloy. The production method comprises the following steps: treating raw materials; the high-purity calcium fluoride is dried; lime and water are mixed according to the proportion of 1: 1, and the mixture is put into a drying box to be dried; the preparation method comprises the following steps: proportioning the following raw materials: vanadium pentoxide, aluminum powder and calcium fluoride according to the ratio of 1: (0.58-0.68): (0.02-0.13), proportioning the calcium fluoride according to the unit reaction heat of 3100-3150 KJ / kg, and uniformly mixing; filling the mixture into a reaction furnace body, compacting, and spreading an ignition agent on the material; ignition reaction; after the reaction is finished, standing the furnace body for 24 hours, moving out the furnace body, naturally cooling for 48 hours, and discharging from the furnace; the method mainly solves the problems of high alloy carbon content caused by graphite falling of the alloy graphite crucible and oxidation film and nitride film phenomena caused by metal solidification cracks.

The invention discloses a method for preparing an ultra-high-temperature carbide ceramic coating by a liquid phase method, which comprises the following steps: placing a base material in a graphite crucible, adding mixed powder to completely cover the base material, heating to melt the mixed powder to form an ultra-high-temperature alloy assistant solution, keeping the temperature to carry out liquid phase reaction, and finally pulling the base material away from the melt to obtain the ultra-high-temperature carbide ceramic coating. The mixed powder comprises ultrahigh-temperature metal powder and Si powder, and the molar ratio of the ultrahigh-temperature metal powder to the Si powder is (0.15-0.65): (0.2-0.6); the superhigh-temperature metal powder is selected from at least one of Ta, Hf and Zr. According to the preparation method, the thickness of the coating is controllable, the thick superhigh-temperature carbide ceramic coating with high binding force can be obtained on the surface of the base material, holes can be sealed when the coating is deposited on the surface of the porous base material, and the compactness of the material can be improved.

The invention belongs to the technical field of preparation of high-temperature heat-insulating and electromagnetic wave-absorbing materials, and relates to a bamboo-like silicon carbide nanowire based on freeze-dried vegetables / fruits and a preparation method and application of the bamboo-like silicon carbide nanowire based on the freeze-dried vegetables / fruits, and the preparation method comprises the following steps: putting the vegetables / fruits in a freeze dryer to obtain the freeze-dried vegetables / fruits; putting the freeze-dried vegetables / fruits into a high-temperature tubular furnace for carbonization to obtain a carbon template; putting the carbon template and a silicon source into a graphite crucible, putting the graphite crucible into a high-temperature tubular furnace, and calcining to obtain the bamboo-like silicon carbide nanowire based on the freeze-dried vegetables / fruits. The bamboo-like silicon carbide nanowire prepared by the method has excellent high-temperature heat insulation property and remarkable broadband electromagnetic wave absorption property, so that the enhancement of double functions of heat insulation and wave absorption is synergistically realized on the basis of a single material. The preparation process is simple and stable in flow, good in repeatability, green in raw material and extremely low in cost, and the problems of collapse and atrophy of the material structure caused by high temperature are solved.

The invention discloses a continuous and stable preparation device and method for a single-walled carbon nanotube, and relates to the technical field of nanocarbon material preparation, the continuous and stable preparation device for the single-walled carbon nanotube structurally comprises hollow graphite, a graphite crucible, a plasma electric arc furnace body, an air inlet and a discharge port, the hollow graphite serves as a cathode of the plasma electric arc furnace, and the graphite crucible serves as an anode of the plasma electric arc furnace. The plasma arc is initiated between the graphite electrodes, so that the plasma high-temperature evaporation catalyst is fully utilized, the defect of arc striking of a graphite cathode and a liquid catalyst anode in a conventional method is avoided, the evaporation rate of the catalyst is reduced, and the problem of arc breaking caused by metal droplet sputtering and coking in the liquid electrodes is solved; a series of defects of a conventional scheme are avoided through the convex crucible anode, so that the continuous stability of the reaction is greatly improved, and stable and continuous preparation of the single-walled carbon nanotube is realized.

The invention discloses a low-melting-point metal vacuum distillation-zone melting impurity removal device, the interior of the device is divided into a vacuum distillation zone and a zone melting zone which are communicated, the vacuum distillation zone comprises a graphite crucible and a special-shaped condensation cover, the inner side wall of the special-shaped condensation cover is provided with a triangular airflow separator, and the inner bottom wall of the special-shaped condensation cover is provided with a plane airflow splitter plate; a bottom outlet is communicated with a flow guide pipe and is connected with a zone melting pipe of the zone melting zone through a flow guide branch pipe; the method comprises the steps that firstly, low-melting-point metal is added, and all parts are installed; 2, carrying out vacuum distillation on the low-melting-point metal; and 3, carrying out regional purification on the vacuum distillation material in the regional melting pipe. According to the device, the vacuum distillation zone and the zone melting zone which are communicated are arranged, so that zone melting impurity removal is directly carried out after low-melting-point metal is subjected to vacuum distillation impurity removal, and the defects of air oxidation, pollution introduction, long charging time and the like caused by segmented charging are overcome; the method enhances the impurity removal effect and is suitable for the field of metal purification.

The invention relates to the technical field of silicon carbide materials, in particular to silicon carbide powder for growing P-type silicon carbide through a PVT method and a preparation method thereof.The preparation method comprises the steps that S1, a silicon material, an aluminum material and a transition metal material are evenly mixed to form a mixed material; s2, heating the graphite crucible to melt the mixed material to form a P-type alloy melt; s3, establishing a temperature gradient in the P-type alloy melt, growing a P-type silicon carbide polycrystalline ingot, controlling the cooling rate through a program, and cooling to obtain the P-type silicon carbide polycrystalline ingot; and S4, crushing treatment, screening treatment, cleaning treatment and drying treatment are conducted, and silicon carbide powder is obtained. The solubility of carbon in an alloy melt is remarkably improved by introducing a transition metal material; the aluminum atoms, silicon, transition metal and the like form a P-type alloy melt in a liquid form, so that the aluminum atoms are efficiently and uniformly doped into a silicon carbide crystal structure; the doping concentration and the doping uniformity of the silicon carbide powder are improved.