99results about How to "High ceramic yield" patented technology

The invention discloses novel liquid polycarbosilane which is low in viscosity and high in storage stability and is crosslinkable, a preparation method of novel liquid polycarbosilane, and an application of novel liquid polycarbosilane. Polycarbosilane is prepared by adopting chloromethyl alkoxy silane or mixtures of chloromethyl alkoxy silane as raw materials by virtue of Grignard coupling reaction and reduction reaction, and the structure of polycarbosilane is shown in a formula (I) in the specification. The structure simultaneously contains Si-H bonds and unsaturated bonds such as C=C bonds, can be subjected to self-crosslinking and curing under a certain condition, has relatively high ceramic yield, and can be used as a silicon carbide precursor of a polymer precursor impregnation pyrolysis (PIP) process. Polycarbosilane disclosed by the invention is adjustable in structural composition, good in storage stability, low in viscosity and relatively low in boiling point, and has the utilization potentiality of being used as a silicon carbide ceramic precursor for chemical vapor deposition/chemical vapor infiltration (CVD/CVI). In addition, polycarbosilane can also be used for replacing commonly-used divinyl benzene to serve as a crosslinking agent of solid-state polycarbosilane (PCS).

The invention relates to a photocuring material which comprises the following components in percentage by weight: 60-98% of hyperbranched polycarbosilane, 0-35% of active diluent, 0.1-8% of photoinitiator and 0-10% of additive, wherein the hyperbranched polycarbosilane contains an unsaturated double bond, and the number-average molecular weight of the hyperbranched polycarbosilane is 300-15,000; the unsaturated double bond is acryloyloxy, methylacryloyloxy, vinyl or allyl; and the content of the unsaturated double bond in the hyperbranched polycarbosilane is 1-30% by weight. The invention also relates to an application of the photocuring material in photocuring 3D printing and an application in preparation of a SiC component. The photocuring material provided by the invention has relatively low viscosity and is convenient to spray out of a nozzle of 3D printing equipment while the curing speed is high and the shrinkage rate in curing is little.

The invention relates to a pore gradient silicon carbide porous ceramic and a preparation method thereof, and belongs to the technical field of preparation of porous ceramic. The pore gradient silicon carbide porous ceramic comprises polycarbosilane and silicon carbide powder, wherein a total weight of the silicon carbide powder is calculated as 100 parts, and the polycarbosilane accounts for 2-10 parts; the pore gradient silicon carbide porous ceramic can also comprise 5-15 parts of powdered carbon; the silicon carbide powder comprises fine silicon carbide powder, crude silicon carbide powder or a mixture of fine silicon carbide powder and crude silicon carbide powder. According to the invention, the pore gradient silicon carbide porous ceramic can be prepared at a low temperature; porous ceramic of various shapes can be prepared; a ceramic precursor has high ceramic yield; the prepared pore gradient silicon carbide porous ceramic has controllable three dimensional communicating pores, and distribution of which can be designed; and pore gradient silicon carbide porous ceramic in large size can be prepared.

The invention relates to a preparation method for liquid polyborosilazane and belongs to the field of inorganic nonmetallic materials. The preparation method comprises the following steps: liquid polyborosilazane and 9-borabicyclo [3,3,1]-nonane are added in a solvent in inert atmosphere to obtain mixed solution, then the obtained mixed solution is hydroborated under the stirring condition, and then the solvent is removed after completion of hydroboration to obtain the liquid polyborosilazane. The preparation method solves the problems in the traditional polymer route that excessive cross-linking is easily caused in the hydroboration addition reaction, and solid polyborosilazane has poorer fluidity. The prepared liquid polyborosilazane has good fluidity and high ceramic yield and can be directly used for the high polymer infiltration and pyrolysis method for preparing SiBCN ceramic matrix composites.

The invention relates to an organometallic polymer ceramic precursor, and a preparation method and application thereof. The organometallic polymer ceramic precursor is prepared by copolymerization of a double-bond-containing organometallic zirconium or titanium or hafnium monomer and a boron-containing monomer. By using the organometallic polymer ceramic precursor for preparing M(Zr,Ti,Hf)-B-C ceramic, the ceramic yield is up to 40-60%, and the content of the super-high-temperature-resistant component (ZrC/ZrB2,TiC/TiB2,HfC/HfB2) in the prepared ceramic material is higher than 70 wt%. When being treated at 2000 DEG C for 2 hours, the organometallic polymer ceramic precursor is not subjected to obvious weight loss, thereby having favorable high-temperature resistance.

This invention provides a method for preparing a polycarbosilane by decomposition and rearrangement a cyclic silane compound or chain polysilane under the catalysis of a boron-containing catalyst in a trace amount (less than 1 wt %). In the method, poly(dimethylsilane) (denoted as PDMS) or a thermal decomposition product thereof, i.e., a liquid silane-carbosilane compound (denoted as LPS), is used as the raw material, less than 1 wt % of the boron-containing catalyst (with respect to the amount of the raw material) is added, and then the temperature is gradually increased to the reaction temperature under atmospheric pressure or high pressure to perform the thermal decomposition/rearrangement reaction so as to obtain solid polycarbosilane (PCS) with a higher ceramic yield. This method has advantages, such as short reaction time, high synthetic yield, good product quality, simple equipment and safe operation; and the polycarbosilane prepared is a polymeric precursor for SiC, and can be used for the preparation of SiC fibres and SiC-based composite materials.

The invention relates to a graphite carbon sleeve gradient anti-oxidation coating and a preparation method thereof. The preparation method comprises the following steps: the surface of a graphite carbon sleeve is pretreated; polyaluminocarbosilane (PACS) serves as a precursor for preparing the graphite carbon sleeve gradient anti-oxidation coating; the PACS has the advantages of high ceramic production rate and good effects of anti-oxidation and high temperature resistance; the pre-treated graphite carbon sleeve is immersed in a xylene solution of the PACS under the vacuum condition, kept under the vacuum condition for 1-10 min, macerated under the condition of pressurizing 10 MPa, dried and placed in an electric furnace, raised to 1,100-1,600 DEG C, and is cracked for preparing the graphite carbon sleeve gradient anti-oxidation coating.

The invention discloses a Cf/MC-SiC composite material and a preparation method thereof. The Cf/MC-SiC composite material comprises a carbon fiber fabricated part, an MC substrate and an SiC substrate, wherein M is Zr or Hf, the MC substrate and the SiC substrate are uniformly filled in the holes of the carbon fiber fabricated part, in the Cf/MC-SiC composite material, the volume fraction of the MC substrate is 10%-20%, the volume fraction of the SiC substrate is 20%-30%, and the percentage of opening of 2%-10%. The preparation method comprises the following steps that (1) a precursor is soaked and split for preparing a Cf/MC blank; (2) a Cf/MC-C blank is prepared; (3) the Cf/MC-SiC composite material is prepared with a gas phase siliconizing method. The Cf/MC-SiC composite material has the advantages that the material is high in content of MC substrate, low in porosity, high in heat conductivity, excellent in oxidation resistance, ablation resistance and mechanical property and the like, and the preparation method is simple in technology and easy to implement.

The invention discloses a preparation method of polycarbosilane containing high-activity cross-linking groups. The method comprises the following steps that after polycarbosilane, halogenated reagentsand solvents are mixed, a halogenation reaction is performed, and partially-halogenated polycarbosilane is obtained; the obtained polycarbosilane, an acid absorbent and a compound containing high-activity cross-linking groups are mixed and then stirred, and the polycarbosilane containing high-activity cross-linking groups is obtained through separation. The invention further discloses the polycarbosilane containing high-activity cross-linking groups prepared through the preparation method. The preparation method is low in reaction temperature and short in time, and adopts few side reactions,and the product with high purity can be obtained through centrifuging, concentrating and purifying in the follow-up steps. The introducing amount of cross-linking groups can be controlled by controlling the halogenation degree, the thermosetting or photo setting speed of the obtained polycarbosilane is increased, and the product can have the high ceramic yield.

The invention relates to a preparation method of a SiC whisker reinforced mullite anti-oxidation coating and belongs to the technical field of preparation of high-temperature anti-oxidation/anti-corrosion coatings. A preparation route comprises steps as follows: firstly, high-performance mullite precursor sol is synthesized with a sol-gel method, then SiC whiskers are dispersed uniformly into the mullite precursor sol in a manner of ultrasound and later ball-milling, a SiC whisker reinforced mullite coating precursor suspension is obtained, then the coating precursor suspension is applied to the surface of a substrate with a high-precision dip-coating process, and finally, the SiC whisker reinforced mullite coating can be obtained after coating sintering. The preparation method breaks through a preparation technology of a whisker reinforced high-temperature anti-oxidation composite coating on the basis of the sol-gel process, has the advantages of simple process, low cost, high efficiency, high substrate shape adaptability and the like and has broad development prospect.

The invention discloses a method for preparing a spinnable polysiloxane ceramic precursor for SiC fibers, which comprises the following steps of: (1) adding chlorosilane, chlorinated siloxane and dimethylbenzene into a neck flask according to a certain mass ratio; (2) vacuumizing the neck flask, introducing N2 for protection, slowly raising the temperature to 70-90DEG C, keeping constant temperature, simultaneously performing mechanical stirring, dripping aqueous solution of an alkaline substance, and continuously stirring for reaction for 6 to 24 hours at constant temperature under the protection of the N2; (3) standing reaction liquid to separate out water and impurities of the lower layer, and taking polysiloxane dimethylbenzene solution of the upper layer out; and (4) distilling the polysiloxane dimethylbenzene solution of the upper layer under reduced pressure to remove a dimethylbenzene solvent. The compound raw materials are mature industrial materials, and are wide in sources; the reaction process is easy to control, the preparation yield is high, and the product purity is high; and the prepared polysiloxane ceramic precursor is low in cost, higher in ceramic yield and good spinnability.

The invention provides an organometallic polymer composite ceramic precursor and a preparation method and application thereof.The organometallic polymer composite ceramic precursor can be used to prepare Zr-Si-C-N ceramics, the yield of the ceramics is 40-60%, no evident weight loss is discovered when the ceramics are processed at 2000 DEG C for 2 hours, and the ceramics are good in high temperature resistance.The ceramics are promising in application prospect in fields such as aviation and supersonic aircrafts.

The invention relates to a manufacture method for polysilane with double bond. It adopts electrochemical synthesis method, uses magnesium block as anode and cathode. Methyl trichlorosilane and allyl chloride are taking polymerization in tetrahydrofuran solution to compound polysilane with double bond. It has the advantages of mild reacting condition, easy to control, easy to operate, safe, high yield, short producing cycle. And it is suitable to be used in industrial in large.

The invention provides a preparation method and application of an HfC ceramic precursor.The preparation method includes the steps of firstly, adding solvent into a reactor, adding organic hafnium compound and cyanamide organic matter, and vacuumizing and drying the reactor; secondly, rising the temperature, performing continuous stirring reaction under the protection of nitrogen atmosphere, and evaporating the reaction products to remove the solvent so as to obtain white solid.The HfC ceramic precursor prepared by the method is high in ceramic yield, good in high-temperature resistance and suitable for being used to prepare high-performance hafnium carbide ceramics and composite materials thereof, and the ultrahigh-temperature HfC component content of the ceramic materials prepared by the HfC ceramic precursor is higher than 79%.

The invention discloses an ablation-resistant organosilicon composite, and a preparation method and application thereof. The composite is a co-cured system of vinyl polymethylphenylsiloxane and silicic hydrovinyl polysilazane, and a silicic hydrogen addition or peroxide vulcanization system is adopted for vulcanization to obtain vulcanized rubber. The invention also discloses a preparation method and application of the composite. The ablation-resistant organosilicon composite has the characteristics of high high-temperature ceramic yield and favorable ablation resistance, and can be used for preparing heat insulating layers and fire-resisting cables of engines and the like.

The invention provides a preparation method of polymer precursor ceramic aerogel, which comprises the following steps of: under the protection of inert atmosphere, uniformly dispersing polycarbosilaneas a polymer precursor in an organic solvent to prepare a precursor solution; placing the precursor solution in an inert atmosphere, selectively adding a platinum catalyst, and carrying out a hydrosilylation reaction to obtain precursor gel; drying the precursor gel to obtain precursor aerogel; and placing the precursor aerogel in an inert atmosphere for high-temperature cracking to obtain the ceramic aerogel. According to the method, the used raw materials are simple in composition, the precursor synthesis process is simple, additional vinyl substances are avoided, and the obtained silicon carbide ceramic aerogel is low in oxygen content, high in purity, adjustable in C/Si ratio and high in ceramic yield.

The invention discloses a silicon-boron-azane ceramic precursor polymer containing borazine and a preparation method and application of the polymer. The silicon-boron-azane ceramic precursor polymer containing borazine has the structural characteristics that a molecular chain of the polymer has structures of borazine and silazane. The preparation method of the ceramic precursor polymer comprises the step that with ammonium chloride, organic primary amine, boron trihalide, dichlorosilane and ammonia gas as main raw materials, the silicon-boron-azane ceramic precursor polymer is synthesized through a three-step reaction under the protection of inert gas, wherein firstly, ammonium chloride or organic primary amine reacts with boron trihalide to synthesize b-trichloroborazine, secondly, b-trichloroborazine and a hydrocarbyl magnesium bromide Grignard reagent react with each other to obtain hydrocarbyl-substituted chloroborazine, and then hydrocarbyl-substituted chloroborazine and dichlorosilane are subjected to co-ammonolysis to synthesize the silicon-boron-azane ceramic precursor polymer. The silicon-boron-azane ceramic precursor polymer containing borazine is colorless or light yellow viscous liquid and is soluble in a common solvent and excellent in process performance. A precursor polymer solidified product can be pyrolyzed and transformed into ceramic, the yield of the ceramicis high, and the precursor polymer solidified product can be used for preparing silicon-boron-nitrogen ceramic-based composite materials.

The invention discloses a ceramic-based composite material and a preparation method thereof. The density of the composite material is 1.60-1.80g/cm<3>, the porosity is 11.5-14.5%, the interlaminar shear strength is 55-56MPa, the tensile strength at 1500 DEG C reaches 100MPa, and the bending strength in the fiber sewing direction at 1500 DEG C reaches 130MPa. According to the preparation method, the ceramic-based composite material is prepared by adopting a precursor impregnation-mold pressing low-temperature crosslinking-high-temperature cracking method. The composite material provided by theinvention is low in density, high in interlaminar strength and high in tensile strength at 1500 DEG C, and can be applied to the field of aerospace. The preparation method provided by the invention isshort in preparation period and low in cost, the temperature of mold pressing low-temperature crosslinking-high-temperature cracking is lower than 1000 DEG C, and the influence on a fiber system is small.

The invention provides a method for synthesizing a soluble ZrC ceramic precursor polymer. According to the method, Cp2ZrCl2 or CpZrCl3 is taken as the zirconium source, a double-bond Grignard reagent such as the allyl Grignard reagent and 3-butene Grignard reagent is taken as the carbon source, and an activated monomer obtained through reaction of the zirconium source and the carbon source is polymerized through a proper initiator to obtain a soluble ZrC ceramic precursor. A ZrC superhigh temperature ceramic material can be obtained through high-temperature pyrolysis of the prepared ZrC ceramic precursor.