阅读说明：本技术 一种碳纤维增强SiHfOC复合材料及其制备方法 (Carbon fiber reinforced SiHfOC composite material and preparation method thereof ) 是由 郭蕾 马青松 于 2020-07-10 设计创作，主要内容包括：本发明公开了一种碳纤维增强SiHfOC复合材料及其制备方法,以碳纤维预制件为增强体,以含Hf的聚硅氧烷做先驱体,利用先驱体浸渍裂解法(PIP)通过反复浸渍-固化-裂解获得C/SiHfOC复合材料,该过程中采用的含Hf的聚硅氧烷先驱体是由无机铪盐与硅树脂通过溶胶-凝胶过程获得,引入的Hf质量占硅树脂质量比的5-25％。本发明解决了SiOC基体耐高温性能有限的问题,利用引入异质元素Hf对SiOC基体进行结构改性,工艺流程简单,对设备要求低,引入Hf后的C/SiHfOC复合材料具有较好的热稳定性。(The invention discloses a carbon fiber reinforced SiHfOC composite material and a preparation method thereof, wherein a carbon fiber prefabricated member is taken as a reinforcement body, Hf-containing polysiloxane is taken as a precursor body, a precursor body impregnation pyrolysis method (PIP) is utilized to obtain the C/SiHfOC composite material through repeated impregnation-solidification-pyrolysis, the Hf-containing polysiloxane precursor adopted in the process is obtained by inorganic hafnium salt and silicon resin through a sol-gel process, and the introduced Hf accounts for 5-25% of the mass ratio of the silicon resin. The method solves the problem of limited high temperature resistance of the SiOC matrix, structurally modifies the SiOC matrix by introducing the heterogeneous element Hf, has simple process flow and low requirement on equipment, and the Hf-introduced C/SiHfOC composite material has better thermal stability.)

1. A preparation method of a carbon fiber reinforced SiHfOC composite material is characterized by comprising the following steps: the method comprises the following steps:

1) dipping: preparing a carbon fiber prefabricated part, placing the carbon fiber prefabricated part under the vacuum condition with the pressure of less than 500Pa, and soaking the carbon fiber prefabricated part by using a Hf-containing polysiloxane precursor solution;

the Hf-containing polysiloxane precursor solution is a mixed sol of hafnium sol and a silicon resin ethanol solution, Hf introduced into the Hf-containing polysiloxane accounts for 5-25% of the mass of the silicon resin, and the hafnium sol is prepared from HfOCl₂·8H₂Dissolving O in ethanol and adding chelatePrepared after the preparation, HfOCl₂·8H₂The mass ratio of O to ethanol is 1-4:4, and the chelating agent and HfOCl₂·8H₂The mass ratio of O is 1-4: 1;

the chelating agent is acetylacetone;

the mass concentration of the silicon resin ethanol solution is 20-60%, and the silicon resin is methyl silicon resin;

2) and (3) curing: standing the carbon fiber prefabricated part dipped in the step to form gel, and crosslinking and curing the gelled prefabricated part at the temperature of 150-250 ℃;

3) cracking: performing pyrolysis on the carbon fiber prefabricated part subjected to crosslinking and curing in the previous step in an inert atmosphere, wherein the pyrolysis temperature is 1000-1200 ℃, and the pyrolysis time is 30-120 min;

repeating the dipping-curing-cracking cycle for 10-16 times until the weight of the sample is increased by no more than 1% when the cycle is finished compared with the weight of the sample when the cycle is finished, and finishing the preparation to obtain the carbon fiber reinforced SiHfOC composite material.

2. The method of claim 1, wherein the step of forming the SiHfOC composite material comprises: the carbon fiber prefabricated part in the step 1) is one of a 2.5-dimensional braided fabric, a plain cloth laminated sewing prefabricated part, a three-dimensional needled felt, a three-dimensional four-way braided fabric, a three-dimensional five-way braided fabric or a three-dimensional six-way braided fabric.

3. The method of claim 1, wherein the step of forming the SiHfOC composite material comprises: impregnating the product obtained in the step 1) with a Hf-containing polysiloxane precursor solution for 1-5 h.

4. The method of claim 1, wherein the step of forming the SiHfOC composite material comprises: the curing in the step 2) refers to: standing the carbon fiber prefabricated part soaked in the step for 8-20h to form gel, and then crosslinking and curing the carbon fiber prefabricated part subjected to gel at the temperature of 150-250 ℃ for 4-8 h.

5. A carbon fiber reinforced SiHfOC composite material is characterized in that: the method for preparing a carbon fiber reinforced SiHfOC composite material according to any one of claims 1-4.

Technical Field

The invention belongs to the technical field of high-temperature-resistant ceramic matrix composite materials, and particularly relates to a carbon fiber reinforced SiHfOC composite material and a preparation method thereof.

Background

The thermal protection technology is one of key technologies for heavy and violent requirements of aerospace aircrafts, manned airships and the like, and light weight, obdurability, high temperature resistance and ablation resistance are the focus of the research on a thermal protection system. The Continuous Fiber Reinforced Ceramic Matrix Composite (CFRCMC) becomes the mainstream development direction of high-temperature structural materials of hot end parts of aircraft propulsion systems and thermal protection systems due to the characteristics of high specific strength and specific modulus, high damage tolerance, corrosion resistance, wear resistance and the like.

Polysiloxane (PSO) derived SiOC ceramics are a cost-effective, lightweight, high-temperature structural material, and carbon fiber reinforced composites based on it have received much attention and intensive research. At present, because the temperature resistance of the SiOC matrix is not matched with that of the C fiber, the C/SiOC composite material can only be in service at 1250 ℃ under the low-pressure condition.

The high temperature resistance of the SiOC ceramic matrix can be improved by carrying out structural modification on the SiOC ceramic matrix, and two approaches of adding filler and introducing heterogeneous elements are mainly adopted: (1) the filler is a method for macroscopically regulating and controlling the structure, has the problem of uneven dispersion and has poor applicability to the fiber reinforced ceramic matrix composite; (2) by introducing heterogeneous elements, the molecular level and even the atomic level of the molecules of the raw material Polysiloxane (PSO) can be finely regulated, so that the modification of the SiOC ceramic structure is realized, the carbothermic reduction reaction is further inhibited, and the aim of improving the thermal stability of the SiOC ceramic is fulfilled.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a carbon fiber reinforced SiHfOC composite material and a preparation method thereof, namely a C/SiHfOC composite material and a preparation method thereof, the preparation method of the C/SiHfOC composite material is simple in process method, convenient to operate and low in cost, the high temperature resistance of the C/SiOC composite material is obviously improved, Hf element is introduced into an SiOC ceramic matrix to form HfO₂SiO which can be produced at high temperatures by first phase separation with SiOC₂Reaction to produce HfSiO₄Thereby blocking SiO₂The carbon thermal reduction reaction improves the thermal stability of the SiOC ceramic matrix, thereby improving the high temperature resistance of the C/SiOC composite material

The preparation method of the carbon fiber reinforced SiHfOC composite material comprises the following steps:

1) dipping: preparing a carbon fiber prefabricated part, placing the carbon fiber prefabricated part under the vacuum condition with the pressure of less than 500Pa, and soaking the carbon fiber prefabricated part by using a Hf-containing polysiloxane precursor solution; the Hf-containing polysiloxane is firstlyThe precursor solution is mixed sol of hafnium sol and silicon resin ethanol solution, Hf introduced into Hf-containing polysiloxane accounts for 5-25% of the mass of the silicon resin, and the hafnium sol is prepared from HfOCl₂·8H₂Dissolving O in ethanol and adding chelating agent to obtain HfOCl₂·8H₂The mass ratio of O to ethanol is (1-4) to 4, and the chelating agent and HfOCl₂·8H₂The mass ratio of O is (1-4) to 1, and the mass concentration of the silicon resin ethanol solution is 20-60%; the chelating agent is selected from acetylacetone, and the silicone resin is selected from low molecular weight methyl silicone (MK);

2) and (3) curing: standing the carbon fiber prefabricated part dipped in the step to form gel, and crosslinking and curing the gelled prefabricated part at the temperature of 150-250 ℃;

3) cracking: performing pyrolysis on the carbon fiber prefabricated part subjected to crosslinking and curing in the previous step in an inert atmosphere, wherein the pyrolysis temperature is 1000-1200 ℃, and the pyrolysis time is 30-120 min;

repeating the dipping-curing-cracking cycle for 10-16 times until the weight of the sample is increased by no more than 1% when the cycle is finished compared with the weight of the sample when the cycle is finished, and finishing the preparation to obtain the carbon fiber reinforced SiHfOC composite material.

The carbon fiber prefabricated part in the step 1) is one of a 2.5-dimensional braided fabric, a plain cloth laminated sewing prefabricated part, a three-dimensional needled felt, a three-dimensional four-way braided fabric, a three-dimensional five-way braided fabric or a three-dimensional six-way braided fabric.

Impregnating the product obtained in the step 1) with a Hf-containing polysiloxane precursor solution for 1-5 h.

The low molecular weight methyl silicone resin (MK) of step 1), MK being methyl silicone resin dissolved in toluene and having a very high SiO content₂Content, after complete oxidation, 80% SiO₂Calculated as solid resin content.

The curing in the step 2) refers to: standing the carbon fiber prefabricated part soaked in the step for 8-20h to form gel, and then crosslinking and curing the carbon fiber prefabricated part subjected to gel at the temperature of 150-250 ℃ for 4-8 h.

The invention also relates to the carbon fiber reinforced SiHfOC composite material prepared by the preparation method of the carbon fiber reinforced SiHfOC composite material, and under the condition of the same preparation process, the C/SiHfOC composite material prepared by the preparation method can improve the heat-resistant temperature of the C/SiOC composite material in a low-pressure condition by 100-200 ℃. Therefore, the C/SiHfOC composite material prepared by the invention has better high temperature resistance.

Compared with the prior art, the invention has the following advantages:

1. the invention adopts silicon resin and inorganic hafnium salt as raw materials to synthesize a polysiloxane precursor containing Hf by a sol-gel technology to prepare the C/SiHfOC composite material, introduces Hf element into an SiOC ceramic matrix, and forms HfO during high-temperature treatment₂And HfSiO₄The phase can improve the high temperature resistance, and in addition, the use of the inorganic hafnium salt as the Hf source can not only improve the introduction amount of the Hf element, but also reduce the cost.

2. The invention introduces Hf element to form HfO₂SiO which can be produced at high temperatures by first phase separation with SiOC₂Reaction to produce HfSiO₄Thereby blocking SiO₂The carbon thermal reduction reaction improves the thermal stability of the SiOC ceramic matrix, and further improves the high temperature resistance of the C/SiOC composite material.

3. The preparation method is simple, convenient to operate and low in cost, and the prepared C/SiHfOC composite material can improve the service temperature of the C/SiOC composite material by 100-200 ℃ under the low-pressure condition.

Drawings

FIG. 1 is a graph of load-displacement curves of mechanical properties of the C/SiOC composite material prepared in example 1 of the present invention, which were tested by vacuum high-temperature heat treatment at different temperatures.

FIG. 2 is a graph of load-displacement curves of mechanical properties of carbon fiber reinforced SiHfOC (C/SiHOC) composite materials prepared in example 1 of the present invention tested by vacuum high temperature heat treatment at different temperatures.

Detailed Description

The present invention is described in further detail below by way of examples, which should not be construed as limiting the invention thereto.