發(fā)布時(shí)間：2018-05-07 22:10

  本文選題：堇青石 + 熱膨脹系數(shù)��； 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：堇青石(2MgO·2Al_2O_3·5SiO_2)具有低熱膨脹系數(shù)的優(yōu)良性能,還具有良好的高溫性能和吸附性能,較大的比表面積,穩(wěn)定的化學(xué)性能和良好的介電性能等。因此,堇青石陶瓷在汽車(chē)尾氣處理、臭氧抑制催化、有毒氣體凈化、作為渦輪發(fā)動(dòng)機(jī)的熱交換機(jī)等領(lǐng)域發(fā)揮著很大的作用。由于堇青石的應(yīng)用范圍仍在擴(kuò)大,對(duì)其性能,尤其是對(duì)熱膨脹性能提出更高的要求。如何有效地降低堇青石陶瓷的熱膨脹系數(shù)成為一個(gè)熱門(mén)的研究課題。本實(shí)驗(yàn)采用高溫固相反應(yīng)合成法,用“滑石-高嶺土-氧化鋁”系統(tǒng)進(jìn)行制備堇青石陶瓷。因此本實(shí)驗(yàn)所用的主要原料有滑石、高嶺土、煅燒高嶺土和氫氧化鋁等。重點(diǎn)研究了原料化學(xué)組成、添加劑和造孔劑等對(duì)堇青石性能的影響。通過(guò)XRD、FT-IR和SEM分別對(duì)陶瓷的物相組成、晶體結(jié)構(gòu)、表觀形貌、孔形、孔徑和孔分布等進(jìn)行觀察,通過(guò)比較堇青石陶瓷樣品的熱膨脹系數(shù),吸水率、氣孔率和抗壓強(qiáng)度等性能參數(shù),優(yōu)化配比和制備工藝條件。得到的主要結(jié)論如下:優(yōu)選制備堇青石陶瓷的最佳基礎(chǔ)配方是富含鋁的配方,其中鋁鎂比為1.05。該樣品的熱膨脹系數(shù)為1.619×10-6/℃;吸水率和氣孔率分別為14.66%和25.12%。SEM圖中可以看到分布有孔結(jié)構(gòu)和裂紋,且其大小和分布比較均勻。從XRD譜圖和FT-IR光譜圖分析,當(dāng)原料中含有較多的Al_2O_3,可以與MgO充分反應(yīng)生成鎂鋁比尖晶石,再與SiO_2反應(yīng)從而生成大量的堇青石,可以減少中間相的剩余,有利于堇青石的生成,減少其他雜相的生成。以五氧化二釩、熔融石英和二氧化鋯為添加劑制備陶瓷,發(fā)現(xiàn)添加4%V_2O_5效果最佳。樣品的熱膨脹系數(shù)降至最低為0.866×10-6 ℃-1;吸水率和氣孔率分別增至22.65%,33%。通過(guò)XRD和FT-IR分析,雖有少量的頑火輝石,但樣品中的堇青石純度依然較高;V_2O_5中V~(5+)離子具有較高的活性,在燒結(jié)過(guò)程中進(jìn)入到六元大通道中從而引起六元環(huán)一定程度的畸變;并形成新鍵V-O-Si和V-O,取代Al-O-Si鍵和Mg-O鍵。堇青石結(jié)構(gòu)便發(fā)生微小變形,這使得堇青石晶體結(jié)構(gòu)在a軸更緊湊,c軸結(jié)構(gòu)不受影響。使堇青石的熱膨脹系數(shù)降低,同時(shí),V_2O_5的分解可以在陶瓷樣品產(chǎn)生許多均勻分布的微孔,使陶瓷的氣孔率增大。以甲基纖維素、淀粉、碳粉和稻殼為造孔劑制備陶瓷,發(fā)現(xiàn)添加10%甲基纖維素效果最佳。可使陶瓷的吸水率和氣孔率大幅提升,分別為29.87%和40.53%,同時(shí)可使陶瓷的熱膨脹系數(shù)降低為1.029×10-6 ℃-1;XRD和FT-IR分析結(jié)果顯示,樣品中幾乎為堇青石純相,含少量頑火輝石;SEM測(cè)試顯示,堇青石晶粒尺寸大小分布均勻,形成的氣孔多,但形態(tài)不規(guī)則。
[Abstract]:Cordierite 2MgO 2Al_2O_3 5SiO2) has excellent properties of low thermal expansion coefficient, good high temperature properties and adsorption properties, large specific surface area, stable chemical properties and good dielectric properties. Therefore, cordierite ceramics play an important role in automobile exhaust treatment, ozone suppression catalysis, toxic gas purification, as a turbine engine heat exchanger and other fields. Because the application range of cordierite is still expanding, the performance of cordierite, especially the thermal expansion property, is required higher. How to effectively reduce the thermal expansion coefficient of cordierite ceramics has become a hot research topic. Cordierite ceramics were prepared by using "talc-kaolin-alumina" system. Therefore, the main materials used in this experiment are talc, kaolin, calcined kaolin and aluminum hydroxide. The effects of chemical composition of raw materials, additives and pore-making agents on the properties of cordierite were studied. The phase composition, crystal structure, apparent morphology, pore shape, pore size and pore distribution of cordierite ceramics were observed by XRDD-FT-IR and SEM, respectively. The thermal expansion coefficient, water absorption rate, porosity and compressive strength of cordierite ceramics were compared. Optimization of the ratio and preparation conditions. The main conclusions are as follows: the best base formula for the preparation of cordierite ceramics is the aluminum-rich formula, in which the ratio of aluminum to magnesium is 1.05. The thermal expansion coefficient of the sample is 1.619 脳 10 ~ (-6) / 鈩，

本文編號(hào)：1858665