34results about How to "Good high temperature chemical stability" patented technology

The invention provides a method for manufacturing a corundum crucible for vacuum induction melting superalloys. The steps are as follows: 1) the alumina raw material is composed of tabular corundum with a particle size of 1-4mm, tabular corundum with a particle size of 0.1-1mm, and plate-shaped corundum with a particle size of 0.1mm or less. Shaped corundum, bimodal active α-alumina and nanocrystalline α-alumina are mixed in a mass percentage of 15-40: 15-40: 15-40: 3-8: 3-8, and then alumina raw materials, The dispersing agent and the binding agent are uniformly mixed at a mass ratio of 100:0.5-2:5-15 to obtain alumina slurry; 2) adding 0.1-0.3% of the total mass of alumina slurry to the initiator, Mix at 2-30°C for 3-10min; 3) After vacuum degassing the alumina slurry obtained in step 2) at 2-30°C for 5min, immediately pour it into the crucible forming mold; 4) heat it together with the mold to 45-55 After keeping at ℃ for 5-35 minutes, demoulding, and then drying at room temperature; 5) Place the dried crucible blank at 1500-1650 ℃ for more than 3 hours, and then cool to room temperature to obtain the target product. The content of impurity elements is low when the crucible of the present invention is used to smelt superalloys.

The invention discloses a method for preparing a 3D printing integrated silicon carbide heat shield. The prepared ceramic slurry is added to the barrel of a 3D printer, and the ceramic slurry is extruded into a filamentary unit body, which is piled up layer by layer and formed. Obtain an integral heat shield ceramic green body; the first layer is an inner layer, and the inner layer is an integral structural layer with a thickness of 5-15mm, and its inner wall is the main reflective surface; the second layer is initially an auxiliary reflective layer, and the auxiliary reflective layer The reflective layer and the thermal insulation layer have convective slots that create turbulent flow. The 3D printed integral silicon carbide heat shield prepared by this method; the heat shield that can be printed has a regular overall structure, the polished inner surface forms a reflective surface, and is subjected to high-temperature desiliconization treatment to remove high-temperature sintering pollution such as silicon vapor; The high temperature chemical stability is good, and the atmosphere in the furnace has a three-dimensional network outer layer with low thermal conductivity, the stability of the printing structure, the heat shield has a precise process installation position, and better controllability.

The invention belongs to the field of high-emissivity materials, in particular to a method for preparing perovskite-type high-emissivity spherical agglomerated powder. The method comprises steps: 1) La 2 o 3 、Cr 2 o 3 And the oxide of M is LaCr 1‑x m x o 3 After metering, put it into a ball mill tank, add absolute ethanol, and ball mill to mix evenly to obtain a slurry, then the ball mill slurry is first rotated and then dried to obtain a mixed powder; 2) Put the powder, dispersant and binder into The slurry is obtained by ball milling in a ball mill tank; 3) sending the slurry into a prilling tower for spray granulation to obtain a spherical agglomerated powder; 4) heat-treating the spherical agglomerated powder at high temperature to obtain the product. The powder prepared by this method has almost no miscellaneous items, good high temperature chemical stability, and high emissivity of the powder. The emissivity of the whole band can reach more than 0.90. It is an ideal high emissivity material with high sphericity and fluidity. Good, the particle size distribution is uniform, which meets the needs of surface modification technologies such as thermal spraying.

The invention discloses a boron nitride-boron carbide-graphite composite heating element used for high temperature electric heating, which is composed of a graphite matrix, a boron carbide intermediate layer coated on the outer surface of the graphite matrix and a boron nitride surface layer coated outside the boron carbide intermediate layer. The profile of the graphite matrix can be designed and treated according to the requirements of the electric heating equipments, the graphite matrix requires high temperature pretreatment; the boron carbide intermediate layer is coated on the surface of the graphite matrix, the thickness is 0.02-1mm, and the boron carbide intermediate layer can be prepared by chemical vapor deposition; the boron nitride surface layer is coated outside the boron carbide intermediate layer, and the thickness is 0.1-10mm, and the boron nitride surface layer is prepared by chemical vapor deposition. The boron nitride-boron carbide-graphite composite heating element can realize the electric heating requirements under the temperature of 2000-2800 DEG C, and has the advantages of stable electrical resistivity of the heating element, long usage life, accurate temperature control and less high temperature environmental pollution.

The invention discloses a method for melting and casting an alpha alumina product, which comprises the following steps: calculating the weight of the raw materials according to the following chemical components, as a percentage by weight based on the oxides, 98-99 of Al2O3, 0.1-0.5 of SiO2, 0.9-1.2 of Na2O, preparing a mixture, then adding into an electric arc furnace for melting and refining, then casting into a mold, removing the mold to obtain the alpha alumina product. The alpha alumina product provided in the invention has the advantages of no cracks, tight structure, high refractoriness and high strength of temperature structure, good chemical stability at high temperature, wherein the refractoriness temperature is above 1900 DEG C, the compressive strength at normal temperature is more than 200 Mpa, which can satisfy the use requirements of nonferrous metals furnaces and high temperature tunnel kilns, the service life is long and the production cost of users can be greatly reduced, so that the method of the invention can provide visible economic benefit to the users.

The invention relates to a ceramic composite material and a preparation method thereof. The material is an A2B2O7-C ceramic composite material, wherein A is Sc, Y, La, Nd, Eu, Gd, Dy, Er, Yb or Lu, B is Zr, Hf, Ce or Ti, C is SiO2, SiC, MoSi2 or PMMA, the volume fraction of C is greater than 0% and no more than 15% and the particle size of C is 1 to 35mu m; the material has low thermal conductivity of photons and stable chemical properties at high temperature. The method comprises the following steps: preparing A2B2O7 powder from ZrOCl2.8H2O with a purity of no less than 99% and rare earth oxide by using a chemical co-precipitation process; mixing C with a purity of no less than 99% with A2B2O7 powder so as to prepare A2B2O7-C composite powder; and sintering A2B2O7-C composite powder at a temperature of 1200 to 1600 DEG C in an inert gas atmosphere for 20 to 60 min so as to obtain the material. The method is simple and is suitable for industrial popularization.

A new type of blanking column for a hot-loading energy-saving sealed submerged arc furnace is characterized in that the new type of blanking column includes a non-metallic blanking column, and the top of the non-metallic blanking column is connected to a connecting flange of a support seat, and the non-metallic blanking column A reinforced grid of heat-resistant metal is embedded in the column body of the feeding column. The invention has the characteristics of anti-oxidation and high temperature resistance, long service life, non-conduction, non-magnetic conduction and the like. The invention has the advantages of small thermal expansion coefficient, high strength, high hardness, erosion resistance, good high temperature chemical stability, anti-oxidation, etc., and at the same time, the non-metallic material is non-conductive, non-magnetic, safe and reliable; heat-resistant metal reinforced grid and non-metallic The linear expansion coefficients of the materials in the feeding column cavity have certain differences, and the high-temperature-resistant insulating coating separates them to reduce the thermal stress caused by temperature changes; at the same time, the high-temperature-resistant insulating coating improves the insulation performance of the metal grid.