纤维素基气敏导电复合材料的制备及其性能的研究
发布时间：2018-11-08 11:31
【摘要】：气敏材料在工业、农业、医学及国防等领域均具有十分广泛的应用,与之相关的研究有着非常重要理论和实际意义。气敏材料主要分为无机气敏材料、有机气敏材料及无机/有机复合气敏材料三大类,应用比较多的是无机/有机复合气敏材料。本论文以棉纤维为基材,以离子液体为溶剂,石墨和碳纳米管(MWCNTs)为导电填料,分别制备了三种基于纤维素纤维的气敏导电复合材料:石墨/纤维素基气敏复合材料、MWCNTs/壳聚糖/纤维素基气敏复合材料以及MWCNTs/羟丙基甲基纤维素(HPMC)/纤维素基气敏复合材料。论文对三种气敏材料的结构和性能进行了表征,并且详细研究了其气敏导电行为和逾渗性质,得到以下主要结论:(1)以N,N-羰基二咪唑(CDI)为交联剂,对石墨和纤维素进行接枝交联,进而制备出石墨/纤维素基气敏导电复合材料。该材料的逾渗值约为5wt%,对多种极性气体,如甲醇、乙醇和丙酮等显示较好的敏感性和重复使用性能,对非极性气体的敏感性非常低。影响该材料的气敏性的因素包括所检测气体的极性和饱和蒸汽压。该复合材料对极性气体的响应行为具有明显的负蒸汽系数效应(NVC)。交联接枝之后的纤维素纤维的结晶度降低,结晶指数由0.46降到0.32。(2)以离子液体[BMIm]Cl为溶剂,通过涂覆方式制备了MWCNTs/壳聚糖/纤维素基气敏导电复合材料。壳聚糖的加入改善了碳纳米管在纤维素基体中的分散性能。当复合材料基体中壳聚糖和纤维素的质量比为1:7时,碳纳米管含量在逾渗阈值(2.8wt%)附近时,对极性有机溶剂蒸气,如甲醇、乙醇、丙酮、氯仿等表现出了良好的敏感性和重复使用性能,而对非极性有机溶剂蒸汽,如四氯化碳及苯等蒸汽则几乎没有敏感性。同时,该材料对无机气体,如氨气也具有良好的敏感性和重复使用性。纤维素基气敏导电复合材料具有气敏性的原因包括:所测气体的物理吸附和脱附、“相似相容”和气体饱和蒸汽压以及“NVC效应”。(3)以离子液体体[BMIm]Cl为溶剂,制备了MWCNTs/HPMC/纤维素基气敏导电复合材料。该材料对部分极性有机气体,如甲醇、乙醇、丙酮等表现出良好的气敏性和重复使用性。与添加壳聚糖相比,纤维素基体中加入HPMC,复合材料的杨氏模量由28.84 MPa提高到58.93 MPa,力学强度明显提高,其气敏性能得到改善。同时,该复合材料对所处环境的真空度也具有一定的敏感性,在真空度为0.02到0.12的范围内,当环境真空度逐渐降低时,复合材料电阻逐渐增大,呈现一定的线性相关性,环境真空度恢复到常压状态时,材料的电阻也逐渐恢复到初始值,并且表现出良好的可重复性。该材料对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.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
本文编号：2318372
[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.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
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