295 results about "Porous silicon carbide" patented technology

The invention discloses silicon carbide porous ceramic and a preparation method thereof. The silicon carbide porous ceramic is characterized by comprising the following components in percentage by weight: 30 to 45 percent of silicon carbide powder, 5 to 10 percent of carbon powder, 35 to 50 percent of silicon powder and 3 to 12 percent of adhesive phenol resin. The method comprises the following steps of: ball-milling the silicon carbide powder, the carbon powder and the silicon powder and wet-mixing to obtain mixed powder; adding the adhesive phenol resin for granulation; performing compression molding; drying a molded green body and then placing into an air furnace to remove adhesives; sintering the green body according to a reaction sintering process after the adhesives are removed; and recrystallizing a product obtained by the reaction sintering at the high temperature of over 2,000 DEG C and removing silicon to obtain a single-phase porous silicon carbide material. The porous silicon carbide material prepared by the invention has the characteristics of controllable porosity, high strength, high corrosion resistance and high thermal stability, can be widely used as a filteringmaterial in high temperature atmospheres and corrosive atmospheres and a carrier material for a chemical reaction and can be used for high-temperature heat insulation.

The invention discloses a method for preparing an aluminum silicon carbide composite material. Liquid metal aluminum is filled in a porous silicon carbide substrate which is prepared from spherical silicon carbide powder and spherical silicon powder which serve as raw materials and has a three-dimensional through hole structure through an injection molding process so as to form a bicontinuous phase, the density of the aluminum silicon carbide composite material and the product uniformity are improved, and a high-strength AlSiC substrate is obtained by changing molding pressure, adjusting ingredients of the spherical powder with different particle sizes, adding a pore-forming agent, and sintering at the temperature of between 1,400 and 2,400 DEG C. The porous substrate is fixed in a cavityof an injection machine, and the liquid metal aluminum enters the cavity from an injection port and is filled in through holes of the AlSiC substrate through a gas-liquid mixed injection process so as to form the aluminum silicon carbide composite material with a silicon carbide and metal aluminum bicontinuous phase structure. The aluminum silicon carbide composite material prepared by the process has the heat conductivity of 190 to 280 W / mK and the thermal expansion coefficient of 5.5 to 11.5*10(-6)K at room temperature of 200 DEG C, and has high rigidity, low density, high weldability and low machining amount.

The invention discloses a preparation method of a porous silicon-carbide ceramic provided with oriented pores. Firstly, according to weight percentage, 0 to 30 percent of carbon powder, 0 to 50 percent of silicon powder and 0 to 60 percent of silica are added into the 10 to 100 percent of the basic material of silicon-carbide; wherein, the granularity of the silicon-carbide is W3.5 to P220, and one granularity or two granularities are adopted for graduation; then the equally mixed materials are processed through powder accumulation or normal ceramic forming process to obtain a green compact which is put into a graphite crucible or a saggar; the graphite crucible or saggar is placed into a vacuum sintering furnace provided with a temperature field with a temperature grade from 15 to 30 DEG C / cm, and then the temperature is raised to 1900 to 2500 DEG C in an argon environment and with pressure of 0.2 to 1 multipliedby 10 <5>Pa, and the insulation work for the graphite crucible or saggar is preserved for 0.5 to 3 hours; finally the temperature naturally falls down under air protection and the sintered body is taken out, namely, the recrystallization porous silicon-carbide ceramic provided with oriented pores is obtained.

A method of producing a densified SiC article is provided. Near-net shape porous silicon carbide articles are produced and densified using the developed method. A substantial number of pores within the porous near-net shape silicon carbide article are filled (impregnated) with a carbon precursor, a silicon carbide precursor, or a mixture of both. The carbon precursor can be liquid or gas. The filled SiC preform is heated to convert the carbon or silicon carbide precursor to porous carbon or SiC preform inside the pores of the net-shape silicon carbide article. The impregnation / pyrolysis cycle is repeated until the desired amount of carbon and / or silicon carbide is achieved. In case of a carbon or a mixture of silicon carbide / carbon precursor is used, the pyrolyzed near-net shape silicon carbide article is then contacted with silicon in an inert atmosphere. The silicon diffuses through the pyrolyzed near-net shape silicon carbide article and reacts with the carbon contained within the pores of the porous SiC preform producing a new phase of silicon carbide within the pores of the near-net shape silicon carbide article. The produced silicon carbide is a near-net dense silicon carbide article.

The invention belongs to the field of catalysis of zeolite crystals, in particular to a porous zeolite molecular sieve coating material on a surface of silicon carbide ceramics and a preparation method thereof. The zeolite molecular sieve coating is uniformly loaded on the surface of a porous silicon carbide ceramics carrier, and the zeolite molecular sieve coating has a double-pore canal structure composed of micropores of zeolite molecular sieves and macropores formed by mutual overlapping of zeolite crystals. The preparation method comprises the following steps: coating a zeolite precursor sol layer on the surface of porous silicon carbide ceramics, wherein the mol ratio of ethyl orthosilicate, tetrapropyl ammonium hydroxide and de-ionized water is 1:0.1-1.0:29; and growing in a secondary growth solution, wherein the mol ratio of ethyl orthosilicate, tetrapropyl ammonium hydroxide and de-ionized water is 1:0.05-1.0:110. Micron-sized pore canals are formed among the zeolite crystals in the coating, thereby improving the utilization efficiency of the zeolite coating. At the same time, the method has the advantages of simple process and low energy consumption, and the prepared zeolite molecular sieve coating is uniformly loaded and stably combined.

The invention discloses a porous ceramic carrier for a high-temperature and high-pressure inorganic filtering membrane and a preparation method for the porous ceramic carrier. The porous silicon carbide ceramic carrier is prepared by silicon carbide, a binding agent and a pore-forming agent, wherein the mass ratio of the silicon carbide to the binding agent is 80-90:10-20, and the utilization quantity of the pore-forming agent is 35-45% of the sum of the volumes of the silicon carbide, the binding agent and the pore-forming agent. The preparation method includes adding the binding agent and the pore-forming agent in silicon carbide powder; performing ball milling, drying and vacuum heat casting forming; and performing pressureless sintering for a formed blank. Sintering temperature rangesfrom 1250 DEG C to 1350 DEG C, and heat insulation time ranges from 2 hours to 4 hours. As raw materials form main materials by means of fine size grading, the binding agent and the pore-forming agent are added by a special process, technologies such as unique vacuum heat casting forming and the like are adopted, and mechanical strength and porosity of the porous carrier can be improved effectively. The prepared silicon carbide porous ceramic carrier has excellent performances of fine thermal shock resistance, low coefficient of thermal expansion, fine mechanical and chemical stability at high temperature and under high pressure, and the like.

The invention relates to a preparation technique for a molecular sieve coating material, in particular to a preparation method for a molecular sieve coating material on a porous silicon carbide ceramic surface. Porous silicon carbide ceramic is used as a carrier, solid raw materials such as silicon blocks, quartz, silicon-aluminum composite oxide sintered powder with adjustable silicon-aluminum atomic ratio and the like are used as a silicon source or a silicon-aluminum source, and the raw materials are synthesized through in-situ hydrothermal reaction. The porous silicon carbide ceramic surface is provided with microporous structures. The use of the solid silicon source or silicon-aluminum source can enable the release speed of the silicon source or silicon-aluminum source for the growth of crystal nucleus to be controllable. Thereby, the prepared molecular sieve coating is evenly loaded on the surface of the silicon carbide ceramic carrier, the silicon-to-aluminum ratio can be accurately controlled, and the composite material formed by the molecular sieve and the porous silicon carbide ceramic has unique microporous / macroporous structures; and the chemical bonding between the molecular sieve and the porous silicon carbide ceramic is realized and the interfacial bonding strength is high. The invention has the advantages that the technology of the method is simple, the operation is convenient, the complex equipment is not required, the preparation cost is low and the method is more suitable for industrialized mass production.

The invention which belongs to the technical field of structured catalysts and application technologies thereof concretely relates to a high intercrystal poriness zeolite coating material on the surface of a porous silicon carbide carrier and a preparation method thereof. The porous silicon carbide carrier involved by the material has a macroscopic porous structure, for example a foamy structure,and a honeycomb structure. The zeolite coating has a high intercrystal poriness. According to the preparation method, the surface of the porous silicon carbide carrier is modified by a colloidal zeolite guiding agent to realize the preferred growth of zeolite crystal on the surface of the porous silicon carbide carrier; and the alkalinity of a secondary growth solution, the concentration of nutrients, and the addition of alkali metal ions are controlled to control the intercrystal poriness of zeolite. The coating material has the advantages of high intercrystal poriness, small zeolite crystaldimension, good molecular diffusion ability, large zeolite load capacity, adjustable silica-alumina ratio of the zeolite crystal and zeolite coating thickness, and good binding ability of the zeolitecrystal with the surface of the porous silicon carbide carrier. The structured catalyst which is in favor of mass and heat transfer reinforcement has wide application prospects in fields of catalysis, adsorption, separation and the like.

The invention belongs to the field of catalysts and an application of the catalysts, and in particular relates to a porous silicon-carbide carrier surface gradient pore molecular sieve coating and a preparation method thereof. The porous silicon-carbide carrier surface gradient pore molecular sieve coating has the intercrystal porosity with continuous gradient change, the porosity among molecular sieve crystals in an inner molecular sieve coating is low, and the porosity among molecular sieve crystals in an outer molecular sieve coating is high. The coating is realized through two-step coating combined with steam treatment: a colloidal state molecular sieve precursor is coated on the surface of a foamed silicon-carbide carrier; a mixer of the colloidal state molecular sieve precursor, the molecular sieve crystals and a pore forming agent is coated; and finally, the molecular sieve precursor is converted into the molecular sieve crystals through steam treatment so as to realize the firm bonding between the coating and the carrier. The proportion of the colloidal state molecular sieve precursor to the molecular sieve crystals is controlled, the pore forming agent is added, and the intercrystal porosity of the coating can be regulated. The gradient coating and the carrier are firmly bonded, and the coating is high in mass transfer capacity and suitable for large-scale preparation.