溶膠凝膠法制備連續(xù)氧化鋁纖維的基礎(chǔ)研究
發(fā)布時(shí)間：2019-06-22 15:21
【摘要】：氧化鋁纖維是一種重要的無(wú)機(jī)氧化物陶瓷纖維,由于其優(yōu)異的化學(xué)穩(wěn)定性、結(jié)構(gòu)穩(wěn)定性和絕熱性,已經(jīng)被廣泛地應(yīng)用于高溫絕熱材料、高溫反應(yīng)中的催化劑擔(dān)體、耐火材料以及樹(shù)脂、金屬和陶瓷基復(fù)合材料的增強(qiáng)材料。溶膠凝膠法是常用的制備氧化鋁纖維的方法。本文采用溶膠凝膠法制備出有一定長(zhǎng)度的氧化鋁纖維,并對(duì)其基本過(guò)程開(kāi)展了基礎(chǔ)研究,為進(jìn)一步制備連續(xù)氧化鋁纖維奠定了基礎(chǔ)。 以異丙醇鋁(AIP)、硝酸鋁(AN)和蒸餾水(H_2O)為基本原料,采用溶膠凝膠法,通過(guò)加熱回流、蒸發(fā)濃縮得到可紡的氧化鋁前驅(qū)凝膠。采用人工挑絲得到連續(xù)的凝膠纖維,經(jīng)過(guò)后續(xù)的干燥和熱處理過(guò)程得到長(zhǎng)約20cm,直徑20-30μm的α-氧化鋁陶瓷纖維。 通過(guò)PH、粒度、FTIR、NMR等分析測(cè)試手段的跟蹤檢測(cè),對(duì)溶膠凝膠過(guò)程中發(fā)生的化學(xué)反應(yīng)及其相應(yīng)的粒子結(jié)構(gòu)的變化進(jìn)行了研究。在溶膠凝膠過(guò)程中水解反應(yīng)和聚合反應(yīng)是同時(shí)存在的,前期以水解反應(yīng)為主,后期則是聚合反應(yīng)占據(jù)主導(dǎo)地位。在反應(yīng)初期體系中粒子以八面體形式存在,隨著反應(yīng)的進(jìn)行,四面體粒子開(kāi)始出現(xiàn),八面體與四面體的量均在增加;結(jié)構(gòu)對(duì)稱的低分子量粒子逐漸向低對(duì)稱結(jié)構(gòu)的高分子量粒子轉(zhuǎn)變。隨著濃縮的進(jìn)行,溶膠粒子由線性大分子向網(wǎng)絡(luò)結(jié)構(gòu)轉(zhuǎn)變。 采用單因素輪換法對(duì)前驅(qū)凝膠的合成工藝進(jìn)行了優(yōu)化�？杉從z合成的優(yōu)化工藝參數(shù)為AIP/AN的摩爾比為3/1,O/AN摩爾比為100,乳酸用量為AIP與AN總量的4wt%,濃縮溫度為80℃。采用該工藝合成得到的前驅(qū)凝膠可紡性好,固體含量較高。 對(duì)得到凝膠的組成結(jié)構(gòu)研究表明:凝膠主要由Al、O、C、N和H元素組成,元素分布均勻。其中N主要以游離的NO3-的形式存在,C則以未完全水解的異丙醇基以及乳酸的形式存在,Al只與O相連接,以Al-O-Al的形式存在于凝膠結(jié)構(gòu)中。凝膠主要以Al-O-Al或Al-OH-Al橋鍵結(jié)構(gòu)為骨架,附帶有殘余的烷氧基,其中Al-O-Al在空間上以鋁氧四面體(AlO4)和鋁氧八面體(AlO6)結(jié)構(gòu)的形式存在。 對(duì)凝膠的可紡性研究表明:凝膠可紡的必要結(jié)構(gòu)條件是,凝膠由適度交聯(lián)的高聚合度的線性大分子組成,并且沒(méi)有因過(guò)分水解產(chǎn)生沉淀顆粒。得到可紡凝膠的溶膠PH范圍為3.05-3.45;凝膠可紡性與粘度密切相關(guān),其可紡的粘度范圍為30-60Pa·s,在此范圍內(nèi),凝膠纖維的直徑隨粘度的增大而增大。纖維成型受外界環(huán)境的溫度和濕度影響,其中濕度對(duì)其影響較大�？諝鉂穸仍�65%-75%的范圍內(nèi),溫度在25-30℃時(shí),凝膠較易成纖,得到的凝膠纖維無(wú)色透明有光澤,表面光滑無(wú)明顯缺陷,有一定的柔韌性,最長(zhǎng)可達(dá)2-3m,其直徑約為30-40μm。 凝膠纖維的干燥過(guò)程受到干燥環(huán)境的溫度、濕度和壓力的影響。水分的揮發(fā)速率隨溫度的增大、濕度的減小、壓力的減小而增加。實(shí)驗(yàn)表明,當(dāng)干燥溫度在25℃-40℃,濕度為45%-65%的范圍時(shí),凝膠纖維的干燥效果較好同時(shí)生成的缺陷較少。 通過(guò)TG、DSC、MS、FTIR和XRD等手段研究了凝膠纖維的熱處理過(guò)程。此過(guò)程可以分為三個(gè)階段:第一階段為室溫到120℃,主要是由干燥后凝膠纖維中殘余的自由水的揮發(fā)導(dǎo)致的。第二階段為120℃到600℃,這一階段失重呈直線下降的趨勢(shì),該階段內(nèi)體系發(fā)生比較劇烈的化學(xué)反應(yīng)包括羥基分解、有機(jī)物分解及硝酸根分解所致,此階段無(wú)機(jī)化過(guò)程基本完成。第三階段為600℃到1200℃,此階段失重幾乎為零,纖維由無(wú)定型態(tài)向結(jié)晶態(tài)轉(zhuǎn)變。 結(jié)晶動(dòng)力學(xué)研究表明,γ-Al_2O_3結(jié)晶活化能為253.31KJ/mol,α-Al_2O_3結(jié)晶活化能為301.60KJ/mol。γ-Al_2O_3的結(jié)晶活化能隨著結(jié)晶率的增大呈現(xiàn)逐步增加的趨勢(shì);α-Al_2O_3的結(jié)晶活化能隨結(jié)晶率的增加變化不大,α-Al_2O_3的結(jié)晶過(guò)程比γ-Al_2O_3結(jié)晶過(guò)程簡(jiǎn)單。 為了得到直徑細(xì)而均勻、表觀缺陷少、結(jié)構(gòu)致密、晶粒小而均勻且堆積緊密、孔洞率小的高性能氧化鋁纖維,對(duì)熱處理工藝進(jìn)行了優(yōu)化,確定以下熱處理制度:以1℃/min從室溫緩慢升溫至600℃后保溫2h,接著以10℃/min快速升溫至1300℃,保溫1h。另外加張燒成的纖維比未加張燒成的纖維更能維持纖維形狀,而且表面缺陷較少。
[Abstract]:The alumina fiber is an important inorganic oxide ceramic fiber, which has been widely used in high-temperature heat-insulating material, catalyst supporter, refractory material and resin in high-temperature reaction due to its excellent chemical stability, structural stability and heat-insulating property. Reinforced materials of metal and ceramic-based composites. The sol-gel method is a commonly used method for preparing the alumina fiber. In this paper, the sol-gel method was used to prepare the alumina fiber with a certain length, and the basic research was carried out on the basic process, which laid the foundation for the further preparation of continuous alumina fiber. The spinnable alumina precursor was obtained by the method of sol-gel, by heating, refluxing and evaporating to obtain the spinnable alumina precursor by using the method of sol-gel method, such as aluminum isopropoxide (AIP), aluminum nitrate (AN) and distilled water (H _ 2O) as the basic raw material. The continuous gel fiber is obtained by using the artificial thread, and the following drying and heat treatment process is carried out to obtain the 1-alumina ceramic fiber with the length of about 20 cm and the diameter of 20-30 & mu; m The chemical reaction and the corresponding particle structure in the sol-gel process are carried out by the trace detection of the analytical and analytical methods such as PH, particle size, FTIR, NMR and the like. In the process of sol-gel, the hydrolysis reaction and the polymerization reaction are the same, in the prophase, the hydrolysis reaction is the main and the latter is the main part of the polymerization reaction. In that initial system of the reaction, the particle are present in an octahedral form, and as the reaction proceeds, the amount of the octahedral and the tetrahedra is increase, and the structure-symmetric low-molecular-weight particles gradually move toward the high-molecular-weight particles of the low-symmetric structure. Subtransformation. As the concentration progresses, the sol particles are bound to the network by linear macromolecules. Method for synthesizing precursor gel by single factor rotation method the optimized process parameters of the spinnable gel synthesis are that the molar ratio of the AIP/ AN to the AIP/ AN is 3/1, the molar ratio of the O/ AN is 100, the amount of the lactic acid is 4 wt% of the total amount of AIP and the AN, the concentration temperature The obtained precursor gel prepared by the process has good spinnability, The composition structure of the obtained gel shows that the gel is mainly composed of Al, O, C, N and H elements. In which N is present mainly in the form of free NO3-, C is present in the form of non-fully hydrolyzed isopropyl alcohol and lactic acid, and Al is only connected to the O and deposited in the form of Al-O-Al. in that gel structure, the gel is mainly composed of an Al-O-Al or Al-OH-Al bridge bond structure as a framework, and a residual alkoxy group is attached, wherein Al-O-Al is in a space in an aluminum-oxygen tetrahedron (AlO4) and an aluminum-oxygen octahedron (AlO6), in the form of a structure, the spinnability of the gel shows that the gel can be spun by the necessary structural condition that the gel is composed of a moderately cross-linked linear macromolecule with a high degree of polymerization, The sol PH range of the spinnable gel is 3.05-3.45, the spinnability of the gel is closely related to the viscosity, the spinnability of the sol can be in the range of 30-60 Pa 路 s, and the diameter of the gel fiber in this range the fiber formation is influenced by the temperature and the humidity of the external environment, The air humidity is in the range of 65-75%, the temperature is 25-30 DEG C, the gel is more easily formed, the obtained gel fiber is colorless and transparent, and up to 2-3 m, the diameter of which can be up to 2-3 m, the drying process of the gel fibers is subjected to a drying environment, The effect of temperature, humidity, and pressure. The rate of evaporation of water increases with temperature and humidity. The experiment shows that when the drying temperature is in the range of 25 鈩，
本文編號(hào)：2504706
[Abstract]:The alumina fiber is an important inorganic oxide ceramic fiber, which has been widely used in high-temperature heat-insulating material, catalyst supporter, refractory material and resin in high-temperature reaction due to its excellent chemical stability, structural stability and heat-insulating property. Reinforced materials of metal and ceramic-based composites. The sol-gel method is a commonly used method for preparing the alumina fiber. In this paper, the sol-gel method was used to prepare the alumina fiber with a certain length, and the basic research was carried out on the basic process, which laid the foundation for the further preparation of continuous alumina fiber. The spinnable alumina precursor was obtained by the method of sol-gel, by heating, refluxing and evaporating to obtain the spinnable alumina precursor by using the method of sol-gel method, such as aluminum isopropoxide (AIP), aluminum nitrate (AN) and distilled water (H _ 2O) as the basic raw material. The continuous gel fiber is obtained by using the artificial thread, and the following drying and heat treatment process is carried out to obtain the 1-alumina ceramic fiber with the length of about 20 cm and the diameter of 20-30 & mu; m The chemical reaction and the corresponding particle structure in the sol-gel process are carried out by the trace detection of the analytical and analytical methods such as PH, particle size, FTIR, NMR and the like. In the process of sol-gel, the hydrolysis reaction and the polymerization reaction are the same, in the prophase, the hydrolysis reaction is the main and the latter is the main part of the polymerization reaction. In that initial system of the reaction, the particle are present in an octahedral form, and as the reaction proceeds, the amount of the octahedral and the tetrahedra is increase, and the structure-symmetric low-molecular-weight particles gradually move toward the high-molecular-weight particles of the low-symmetric structure. Subtransformation. As the concentration progresses, the sol particles are bound to the network by linear macromolecules. Method for synthesizing precursor gel by single factor rotation method the optimized process parameters of the spinnable gel synthesis are that the molar ratio of the AIP/ AN to the AIP/ AN is 3/1, the molar ratio of the O/ AN is 100, the amount of the lactic acid is 4 wt% of the total amount of AIP and the AN, the concentration temperature The obtained precursor gel prepared by the process has good spinnability, The composition structure of the obtained gel shows that the gel is mainly composed of Al, O, C, N and H elements. In which N is present mainly in the form of free NO3-, C is present in the form of non-fully hydrolyzed isopropyl alcohol and lactic acid, and Al is only connected to the O and deposited in the form of Al-O-Al. in that gel structure, the gel is mainly composed of an Al-O-Al or Al-OH-Al bridge bond structure as a framework, and a residual alkoxy group is attached, wherein Al-O-Al is in a space in an aluminum-oxygen tetrahedron (AlO4) and an aluminum-oxygen octahedron (AlO6), in the form of a structure, the spinnability of the gel shows that the gel can be spun by the necessary structural condition that the gel is composed of a moderately cross-linked linear macromolecule with a high degree of polymerization, The sol PH range of the spinnable gel is 3.05-3.45, the spinnability of the gel is closely related to the viscosity, the spinnability of the sol can be in the range of 30-60 Pa 路 s, and the diameter of the gel fiber in this range the fiber formation is influenced by the temperature and the humidity of the external environment, The air humidity is in the range of 65-75%, the temperature is 25-30 DEG C, the gel is more easily formed, the obtained gel fiber is colorless and transparent, and up to 2-3 m, the diameter of which can be up to 2-3 m, the drying process of the gel fibers is subjected to a drying environment, The effect of temperature, humidity, and pressure. The rate of evaporation of water increases with temperature and humidity. The experiment shows that when the drying temperature is in the range of 25 鈩，
本文編號(hào)：2504706
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