Method for synthesizing supercritical fluid of ceramic precursor polycarbosilane

A supercritical fluid and ceramic precursor technology, which is applied in the production of bulk chemicals, can solve problems such as uneven molecular weight distribution, low synthesis yield, and inability to solve reaction uniformity well

Inactive Publication Date: 2008-08-13
NAT UNIV OF DEFENSE TECH
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  • Abstract
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  • Claims
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Problems solved by technology

However, this method has problems such as low synthesis yield (40-50%), long time (>48hrs), low synthesis efficiency and low product molecular weight and uneven molecular weight distribution.
Chinese patent [Application No. 200410023185.4] discloses a method for synthesizing polycarbosilane at high temperature and high pressure. The method is to directly put PDMS or LPS into an autoclave, replace it with nitrogen gas under vacuum and pre-fill nitrogen gas, and heat up and pressurize at 430- PCS is synthesized at 490°C under a certain pressure.

Method used

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  • Method for synthesizing supercritical fluid of ceramic precursor polycarbosilane
  • Method for synthesizing supercritical fluid of ceramic precursor polycarbosilane
  • Method for synthesizing supercritical fluid of ceramic precursor polycarbosilane

Examples

Experimental program
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Embodiment 1

[0027] Embodiment 1, take PDMS as raw material, xylene as supercritical fluid medium supercritical synthesis of PCS:

[0028] Put 150g of PDMS and 100ml of xylene in the autoclave, stir evenly, evacuate and replace the gas in the autoclave with high-purity nitrogen twice, and then pre-add 4.0MPa of N 2 Pressure, seal. Then the temperature was raised to 380° C., and the reaction was carried out for 20 hours. The maximum reaction pressure was 6.0 MPa. After cooling, the crude product of PCS was obtained. The crude product was dissolved in xylene, filtered, and the filtrate was distilled under reduced pressure at 380° C. for 30 minutes. After cooling, a pale yellow resinous PCS precursor (SCFs-PCS1) was obtained. The synthesis yield of the SCFs-PCS1 is 65.8%, the softening point is 210.9-232.9° C., the number average molecular weight is 1826, and the molecular weight distribution coefficient Mw / Mn=1.23. The infrared spectrum of the product was determined as figure 1 shown (see...

Embodiment 2

[0029] Embodiment 2, using PDMS as raw material, xylene as supercritical fluid medium supercritical synthesis of PCS:

[0030] Using the same method as in Example 1, 200 g of PDMS and 125 ml of xylene were placed in an autoclave, reacted at 550 ° C for 1 h, and were post-treated in the same way to obtain SCFs-PCS2. The synthesis yield of the SCFs-PCS2 is 60.2%, the softening point is 156.5-172.7°C, the number average molecular weight is 1097, the molecular weight distribution coefficient Mw / Mn=1.45, and the typical Si-H, Si- CH 3 Absorbance ratio of the absorption peak A Si-H / A Si-CH3 = 0.938.

Embodiment 3

[0031] Embodiment 3, using PDMS as raw material, xylene as supercritical fluid medium supercritical synthesis of PCS:

[0032] Using the same method as in Example 1, 200 g of PDMS and 125 ml of xylene were placed in an autoclave, reacted at 460° C. for 4 h, and were post-treated in the same way to obtain SCFs-PCS3. The synthesis yield of the SCFs-PCS3 is 61.8%, the softening point is 203.8-238.7°C, the number average molecular weight is 1560, the molecular weight distribution coefficient Mw / Mn=1.78, and the typical Si-H, Si- CH 3 Absorbance ratio of the absorption peak A Si-H / A Si-CH3 = 0.917.

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Abstract

The invention discloses a organic silicon compound containing silicon-silicon bond, silicon-carbon bond, silicon-halogen bond and ceramics precursor poly carbon silicon alky synthesized under high pressure and with medium in supercritical fluid status which uses mixture of the aforementioned compound as raw material, uses solvent soluble of poly carbon silicon alky as supercritical fluid medium. Ceramics precursor poly carbon silicon alky with different molecular weight and different softening point can be obtained by controlling reaction condition of synthesis. The inventive method effectively improves uniformity of heat transfer and reaction, with short reaction time, high synthesis efficiency, high synthesis yield. The produced poly carbon silicon has a high molecular weight, high content of bonds of silicon and hydrogen and uniform distribution of molecular weight. The inventive method can be widely used in preparation of SiC fibre, SiC composite, heat resistant alloy with high strength, ceramic binder, SiC membrane, nano-wire, nano-pipe and nano-powder and so on.

Description

technical field [0001] The invention belongs to the synthesis of organic polymers. Specifically, it relates to a supercritical fluid synthesis method of polycarbosilane, a precursor for preparing silicon carbide ceramics. Background technique [0002] Silicon carbide (Silicon Carbide, SiC) ceramics have high temperature strength, strong oxidation resistance, good wear resistance, good thermal stability, small thermal expansion coefficient, high thermal conductivity, high hardness, thermal shock resistance and chemical corrosion resistance. It is widely used in various high-temperature structural parts materials, such as aerospace high-temperature components, nuclear reactor inner wall components, new engine cylinders, catalyst heat exchanger components, high-temperature sensors, seals, steam turbine rotors, nozzles, etc. The preparation of SiC ceramics by the precursor conversion method is a new method that has been studied and adopted more in recent years. Polycarbonsilan...

Claims

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Application Information

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IPC IPC(8): C08G77/60C04B35/571
CPCY02P20/54
Inventor 宋永才杨大祥
Owner NAT UNIV OF DEFENSE TECH
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