發(fā)布時(shí)間：2018-11-08 11:31

【摘要】：氣敏材料在工業(yè)、農(nóng)業(yè)、醫(yī)學(xué)及國(guó)防等領(lǐng)域均具有十分廣泛的應(yīng)用,與之相關(guān)的研究有著非常重要理論和實(shí)際意義。氣敏材料主要分為無(wú)機(jī)氣敏材料、有機(jī)氣敏材料及無(wú)機(jī)/有機(jī)復(fù)合氣敏材料三大類(lèi),應(yīng)用比較多的是無(wú)機(jī)/有機(jī)復(fù)合氣敏材料。本論文以棉纖維為基材,以離子液體為溶劑,石墨和碳納米管(MWCNTs)為導(dǎo)電填料,分別制備了三種基于纖維素纖維的氣敏導(dǎo)電復(fù)合材料:石墨/纖維素基氣敏復(fù)合材料、MWCNTs/殼聚糖/纖維素基氣敏復(fù)合材料以及MWCNTs/羥丙基甲基纖維素(HPMC)/纖維素基氣敏復(fù)合材料。論文對(duì)三種氣敏材料的結(jié)構(gòu)和性能進(jìn)行了表征,并且詳細(xì)研究了其氣敏導(dǎo)電行為和逾滲性質(zhì),得到以下主要結(jié)論:(1)以N,N-羰基二咪唑(CDI)為交聯(lián)劑,對(duì)石墨和纖維素進(jìn)行接枝交聯(lián),進(jìn)而制備出石墨/纖維素基氣敏導(dǎo)電復(fù)合材料。該材料的逾滲值約為5wt%,對(duì)多種極性氣體,如甲醇、乙醇和丙酮等顯示較好的敏感性和重復(fù)使用性能,對(duì)非極性氣體的敏感性非常低。影響該材料的氣敏性的因素包括所檢測(cè)氣體的極性和飽和蒸汽壓。該復(fù)合材料對(duì)極性氣體的響應(yīng)行為具有明顯的負(fù)蒸汽系數(shù)效應(yīng)(NVC)。交聯(lián)接枝之后的纖維素纖維的結(jié)晶度降低,結(jié)晶指數(shù)由0.46降到0.32。(2)以離子液體[BMIm]Cl為溶劑,通過(guò)涂覆方式制備了MWCNTs/殼聚糖/纖維素基氣敏導(dǎo)電復(fù)合材料。殼聚糖的加入改善了碳納米管在纖維素基體中的分散性能。當(dāng)復(fù)合材料基體中殼聚糖和纖維素的質(zhì)量比為1:7時(shí),碳納米管含量在逾滲閾值(2.8wt%)附近時(shí),對(duì)極性有機(jī)溶劑蒸氣,如甲醇、乙醇、丙酮、氯仿等表現(xiàn)出了良好的敏感性和重復(fù)使用性能,而對(duì)非極性有機(jī)溶劑蒸汽,如四氯化碳及苯等蒸汽則幾乎沒(méi)有敏感性。同時(shí),該材料對(duì)無(wú)機(jī)氣體,如氨氣也具有良好的敏感性和重復(fù)使用性。纖維素基氣敏導(dǎo)電復(fù)合材料具有氣敏性的原因包括:所測(cè)氣體的物理吸附和脫附、“相似相容”和氣體飽和蒸汽壓以及“NVC效應(yīng)”。(3)以離子液體體[BMIm]Cl為溶劑,制備了MWCNTs/HPMC/纖維素基氣敏導(dǎo)電復(fù)合材料。該材料對(duì)部分極性有機(jī)氣體,如甲醇、乙醇、丙酮等表現(xiàn)出良好的氣敏性和重復(fù)使用性。與添加殼聚糖相比,纖維素基體中加入HPMC,復(fù)合材料的楊氏模量由28.84 MPa提高到58.93 MPa,力學(xué)強(qiáng)度明顯提高,其氣敏性能得到改善。同時(shí),該復(fù)合材料對(duì)所處環(huán)境的真空度也具有一定的敏感性,在真空度為0.02到0.12的范圍內(nèi),當(dāng)環(huán)境真空度逐漸降低時(shí),復(fù)合材料電阻逐漸增大,呈現(xiàn)一定的線性相關(guān)性,環(huán)境真空度恢復(fù)到常壓狀態(tài)時(shí),材料的電阻也逐漸恢復(fù)到初始值,并且表現(xiàn)出良好的可重復(fù)性。該材料對(duì)甲醛也具有一定的敏感性。
[Abstract]:Gas sensing materials are widely used in industry, agriculture, medicine and national defense, and the related research is of great theoretical and practical significance. The gas sensing materials are mainly classified into inorganic gas sensing materials, organic gas sensing materials and inorganic / organic composite gas sensing materials. In this paper, using cotton fiber as substrate, ionic liquid as solvent, graphite and carbon nanotube (MWCNTs) as conductive filler, three kinds of gas-sensing conductive composites based on cellulose fiber: graphite / cellulose based gas sensing composite were prepared, respectively. MWCNTs/ chitosan / cellulose based gas sensing composites and MWCNTs/ hydroxypropyl methyl cellulose (HPMC) / cellulose based gas sensing composites. In this paper, the structure and properties of three kinds of gas-sensing materials were characterized, and their gas-sensitive conductive behavior and percolation properties were studied in detail. The main conclusions were as follows: (1) N- (N-carbonyl) diimidazole (CDI) was used as crosslinking agent. Graphite / cellulose based gas-sensing conductive composites were prepared by graft crosslinking of graphite and cellulose. The percolation value of the material is about 5 wts. it shows good sensitivity and reusability to many polar gases such as methanol ethanol and acetone and its sensitivity to non-polar gases is very low. Factors affecting the gas sensitivity of the material include the polarity of the gas detected and the saturated vapor pressure. The response behavior of the composite to polar gas has obvious negative vapor coefficient effect (NVC). The crystallinity of cellulose fibers after crosslinking and grafting decreased from 0.46 to 0.32. (2) MWCNTs/ chitosan / cellulose based gas-sensing conductive composites were prepared by coating with ionic liquid [BMIm] Cl as solvent. The addition of chitosan improved the dispersion of carbon nanotubes in cellulose matrix. When the mass ratio of chitosan to cellulose in the matrix is 1:7 and the content of carbon nanotubes is near the percolation threshold (2.8 wt%), the polar organic solvent vapor, such as methanol, ethanol, acetone, is obtained. Chloroform shows good sensitivity and reusability, but it has little sensitivity to non-polar organic solvent vapor, such as carbon tetrachloride and benzene. At the same time, the material has good sensitivity and reusability to inorganic gases such as ammonia. The reasons for the gas sensitivity of cellulose based gas-sensing conductive composites include: physical adsorption and desorption of measured gases, "similarity compatibility" and gas saturated vapor pressure, and "NVC effect". (3) Ionic liquid [BMIm] Cl is used as solvent. MWCNTs/HPMC/ cellulose-based gas-sensing conductive composites were prepared. This material has good gas sensitivity and reusability to some polar organic gases such as methanol, ethanol and acetone. Compared with chitosan, the Young's modulus of HPMC, composites in cellulose matrix was increased from 28.84 MPa to 58.93 MPa, and its gas sensitivity was improved. At the same time, the composite has a certain sensitivity to the vacuum degree of the environment. In the range of 0.02 to 0.12, the resistance of the composite increases gradually when the vacuum degree decreases gradually. There is a certain linear correlation and the resistance of the material gradually recovers to the initial value when the ambient vacuum returns to the normal state and shows good reproducibility. The material is also sensitive to formaldehyde.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TB332

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