本文選題：化學(xué)液相沉積法 + C/Si化物復(fù)合材料��； 參考：《濟(jì)南大學(xué)》2011年碩士論文

【摘要】：碳材料具有優(yōu)良的耐化學(xué)腐蝕、耐熱、良好的導(dǎo)熱性、低電阻率、抗輻射、導(dǎo)熱、降噪、減震等一系列力學(xué)和電學(xué)性能,已成為目前國際上新型技術(shù)研究領(lǐng)域中重點(diǎn)開發(fā)和研究的一種新材料,被廣泛應(yīng)用于國防軍事、航空航天等尖端領(lǐng)域及醫(yī)療、交通以及器械等民用領(lǐng)域。但是碳材料在高溫下非常容易被氧化,導(dǎo)致其各項(xiàng)性能下降。因此,對碳材料的抗氧化研究具有重要的意義。 快速制備工藝與結(jié)構(gòu)性能的關(guān)系是決定C/Si化物復(fù)合材料研究及發(fā)展的關(guān)鍵因素。本研究采用煤油為碳源、正硅酸乙酯為硅原,根據(jù)快速化學(xué)液相沉積工藝在不同實(shí)驗(yàn)條件下制備C/Si化物復(fù)合材料。本文以理論分析與工藝試驗(yàn)為基礎(chǔ),結(jié)合材料的微觀表征、致密化機(jī)理、抗氧化性能,對制備C/Si化物復(fù)合材料的工藝參數(shù)進(jìn)行了系統(tǒng)研究。主要研究內(nèi)容和結(jié)果如下: (1)研究了預(yù)制體的表面處理、預(yù)制體的直徑、電壓電流、保溫時間等工藝參數(shù)對復(fù)合材料微觀結(jié)構(gòu)的影響。表面處理后制備的Si化物涂層與預(yù)制體之間結(jié)合緊密,形成良好的梯度過渡。直徑為7mm的預(yù)制體制備的Si化物層與基體結(jié)合良好,涂層內(nèi)無明顯缺陷。隨著電壓電流的增大,涂層表面的顆粒越大,在電壓、電流分別為54V、86A時得到的Si化物涂層顆粒排列致密,表面光滑。保溫時間為3h,制備的涂層厚度在120μm左右。制備的Si化物涂層經(jīng)XRD分析可知,涂層內(nèi)同時存在SiC及無定形態(tài)的SiO_2。 (2)探討了快速化學(xué)液相沉積工藝的機(jī)理,分析表明:置于在液態(tài)前軀體內(nèi)的預(yù)制體,在制備涂層過程中存在的由內(nèi)而外的溫度梯度及連續(xù)的濃度梯度,是快速制備復(fù)合材料的關(guān)鍵,同時,沉積過程是化學(xué)動力控制機(jī)制和擴(kuò)散相互轉(zhuǎn)變的過程,并通過作圖模擬了沉積界面。 (3)通過分析表明,氧氣分子在沉積層表面裂紋以及沉積缺陷內(nèi)的擴(kuò)散均屬于混合型擴(kuò)散。用質(zhì)量損失率表征C/Si化物復(fù)合材料的氧化行為。隨著溫度的升高,復(fù)合材料的氧化質(zhì)量損失逐漸升高。抗氧化性能測試表明,C/Si化物復(fù)合材料在900℃下靜態(tài)空氣中氧化10h后質(zhì)量損失率僅為15.4%。 (4)研究了C/Si化物復(fù)合材料的氧化行為、氧化模式和氧化機(jī)理。C/Si化物復(fù)合材料的氧化行為受涂層內(nèi)的裂紋和沉積缺陷控制。在400℃～700℃內(nèi),C/Si化物復(fù)合材料的氧化速度由C-O2的反應(yīng)控制。在700℃～900℃內(nèi),氧化速度由氧通過沉積缺陷和涂層內(nèi)的微裂紋控制。溫度在900℃～1200之間,氧化速度由氧通過沉積缺陷的擴(kuò)散控制。在1200℃以上,氧化速度由于涂層表面產(chǎn)生的氣泡急劇加快。
[Abstract]:Carbon materials have excellent chemical corrosion resistance, heat resistance, good thermal conductivity, low resistivity, radiation resistance, thermal conductivity, noise reduction, shock absorption and a series of mechanical and electrical properties. It has become a new material in the field of new technology research in the world. It is widely used in the fields of national defense, aviation and aerospace, medical treatment, transportation, equipment and other civil fields. However, carbon materials are easily oxidized at high temperature, which results in the degradation of their properties. Therefore, it is of great significance to study the oxidation resistance of carbon materials. The relationship between the rapid preparation process and the structure and properties is the key factor to determine the research and development of C / Si composites. Using kerosene as carbon source and ethyl orthosilicate as silicogen, C / Si composites were prepared by rapid chemical liquid deposition under different experimental conditions. On the basis of theoretical analysis and technological tests, the process parameters of C / Si composites were systematically studied in this paper, combining with the microscopic characterization, densification mechanism and oxidation resistance of C / Si composites. The main contents and results are as follows: 1) the effects of surface treatment, diameter, voltage and current, and holding time of the preform on the microstructure of the composite were studied. After surface treatment, the Si coating is bonded closely with the preform, and a good gradient transition is formed. The silicide layer prepared by the 7mm preform binds well to the substrate, and there is no obvious defect in the coating. With the increase of voltage and current, the particles on the surface of the coating become larger. When the voltage and current are 54V / 86A, the particles of the coating are compact and the surface is smooth. The coating thickness is about 120 渭 m when the holding time is 3 h. XRD analysis showed that sic and amorphous Sio _ 2 in the coating existed simultaneously. The mechanism of rapid chemical liquid deposition was discussed. The results showed that the preform was placed in the liquid front body. The temperature gradient from inside to outside and the continuous concentration gradient in the process of coating preparation are the key to the rapid preparation of composite materials. At the same time, the deposition process is the process of chemical dynamic control mechanism and diffusion mutual transformation. The results show that the diffusion of oxygen molecules in the surface cracks and defects is mixed diffusion. The oxidation behavior of C / Si composites was characterized by mass loss rate. With the increase of temperature, the mass loss of oxidation increases gradually. The oxidation resistance test showed that the mass loss rate of C / Si composites was only 15.4g after oxidation in static air at 900 鈩，

本文編號：2040663