本文選題：一維陶瓷材料 + 熔鹽法��； 參考：《天津大學(xué)》2010年博士論文

【摘要】：在一定條件下,晶體沿著線性鏈方向生長(zhǎng)的陶瓷材料被稱為一維陶瓷材料。一維材料在其他維度方向上生長(zhǎng)受限,因此表現(xiàn)出不同于傳統(tǒng)材料的特殊性能。其中一維莫來(lái)石陶瓷由于其優(yōu)異的熱震性、抗蠕變性,以及高溫下室溫強(qiáng)度衰減小的特性,已經(jīng)應(yīng)用于晶須補(bǔ)強(qiáng)、涂層技術(shù)、過(guò)濾膜、高溫催化反應(yīng)器等方面。熔鹽法是一種濕法化學(xué)合成方法,其優(yōu)勢(shì)在于合成的粉體無(wú)團(tuán)聚、工藝簡(jiǎn)單;與其他液相法相比,其合成出的一維晶體質(zhì)量更高。本文中,對(duì)采用熔鹽法合成一維莫來(lái)石陶瓷進(jìn)行了研究。 對(duì)前驅(qū)體的研究表明,采用化學(xué)活性高、溶解能力強(qiáng)的前驅(qū)體,有助于獲得獨(dú)立分散的一維莫來(lái)石晶體。以Al_2(SO_4)_3、無(wú)定形SiO_2、Na_2SO_4為原料,其配比Al/Si/Na為2/1/8(原子比)時(shí),在1000℃保溫3h條件下,HF酸洗后最終產(chǎn)物全部為一維莫來(lái)石晶體。XRD、EDS、HR-TEM結(jié)果表明所得的莫來(lái)石晶體為富Al組成,光致發(fā)光性能反映出富Al組成產(chǎn)生的氧空位缺陷。對(duì)溫度制度的研究表明,快速升溫有助于莫來(lái)石相的生成;合成溫度過(guò)高,莫來(lái)石晶體會(huì)在1100℃左右發(fā)生分解形成NaAlSiO_4。 對(duì)莫來(lái)石晶體生長(zhǎng)機(jī)理的研究表明。熔鹽法合成過(guò)程中,當(dāng)液相中不斷生成的莫來(lái)石超過(guò)其過(guò)飽和度時(shí),莫來(lái)石開(kāi)始成核。在液固生長(zhǎng)界面處,莫來(lái)石單體的沉淀是可逆的,因此生長(zhǎng)能夠按照其能量最低的原則不斷進(jìn)行調(diào)整,從而最大限度的保證其在c軸方向的自由生長(zhǎng)。莫來(lái)石晶體在界面處的生長(zhǎng)位置是由二維平臺(tái)提供的,這個(gè)過(guò)程所需克服的能量壁壘大,當(dāng)二維平臺(tái)耗盡時(shí),晶體即停止生長(zhǎng)。莫來(lái)石晶體在熔鹽法中的生長(zhǎng)屬于LS生長(zhǎng)機(jī)理。 通過(guò)對(duì)B_2O_3外加劑的研究,發(fā)現(xiàn)莫來(lái)石晶體尺寸的減小,當(dāng)B_2O_3/SiO_2達(dá)到0.04(摩爾比)時(shí)形成了納米級(jí)別莫來(lái)石晶體,其歸因于B_2O_3的加入有助于成核速率加快。通過(guò)對(duì)莫來(lái)石晶種的研究,發(fā)現(xiàn)晶種的加入能夠在一定程度上提高熔鹽法制備莫來(lái)石晶體的產(chǎn)率,莫來(lái)石晶體的尺寸減小、尺寸更加均勻,這是由于晶種的加入能夠?yàn)槟獊?lái)石晶體提供生長(zhǎng)位點(diǎn),提高了莫來(lái)石晶體初期形核速率。
[Abstract]:Under certain conditions, ceramic materials grown along linear chains are called one-dimensional ceramic materials. One-dimensional materials exhibit special properties different from traditional materials due to their limited growth in other dimensions. One-dimensional mullite ceramics have been used in whisker reinforcement coating technology filtration membrane and high temperature catalytic reactor due to their excellent thermal shock resistance creep resistance and low strength attenuation at room temperature. Molten salt method is a wet chemical synthesis method, its advantage is that the synthesized powder has no agglomeration and the process is simple. Compared with other liquid phase method, the synthesized one-dimensional crystal has higher quality. In this paper, the synthesis of one-dimensional mullite ceramics by molten salt method was studied. The study of the precursor shows that the use of the precursor with high chemical activity and strong solubility is helpful to obtain the independent dispersed one-dimensional mullite crystal. When the Al/Si/Na ratio is 2 / 1 / 8 (atomic ratio), the final product after acid washing at 1000 鈩，

本文編號(hào)：1851703