纳米碳源制备低碳铝碳耐火材料微结构和力学性能研究

发布时间：2018-05-11 09:54

本文选题：铝碳耐火材料 + 复合纳米碳　；参考：《武汉科技大学》2016年博士论文

【摘要】：传统铝碳耐火材料(10-30 wt%C)兼具良好的耐高温、抗热震、抗渣侵蚀等性能而被广泛地用作水口、滑板和塞棒等关键部位的功能性耐火材料,但随着高效连铸、洁净钢冶炼等技术的发展,开发优质低碳铝碳耐火材料(5 wt%C)刻不容缓。但是,单纯地降低铝碳耐火材料中的微米级石墨含量将会导致材料韧性降低,抗热震性恶化。从耐火材料的发展趋势来看,基质结构纳米化将是实现耐火材料低碳化的重要途径。目前,人们已开始将纳米炭黑、碳纳米管、氧化石墨烯片和膨胀石墨(可以看作是大量石墨烯片和气孔的叠层组合)等纳米碳源和微米级鳞片石墨复合作为碳复合耐火材料的碳源,在降低材料中碳含量的同时,优化材料的性能。在高温下材料中纳米碳源可能会发生结构演变或蚀变,如何控制和减缓其结构蚀变,发挥纳米碳的本征性能;对于开发新一代低碳甚至超低碳耐火材料(5 wt%C,甚至低于3 wt%C)时,必须考虑如何发挥纳米碳源协同增强增韧作用,进一步降低材料中碳含量;如何通过表征碳复合耐火材料的力学性能参数来判别材料抗热震性的优劣?针对上述问题,本论文的研究工作主要有:首先研究纳米炭黑在铝碳耐火材料中的结构演变及其炭黑种类对铝碳耐火材料微结构与性能的影响;其次,研究铝碳耐火材料中多壁碳纳米管(MWCNTs)结构演变及机理,探讨控制和减缓MWCNTs结构蚀变的方法;进而以纳米炭黑为基础碳源,研究外加MWCNTs以及原位催化形成MWCNTs与纳米炭黑复合纳米碳对铝碳耐火材料性能的影响;再次,在研究膨胀石墨复合纳米炭黑对铝碳耐火材料性能影响的基础上,进一步以原位催化形成碳纳米管的方式制备纳米炭黑、MWCNTs与膨胀石墨复合铝碳耐火材料,探明多种纳米碳复合对铝碳耐火材料综合性能的影响;最后,利用楔形劈裂测试手段结合断口结构与形貌分析研究铝碳耐火材料受拉伸载荷时的断裂行为和抵抗裂纹破坏的能力,以揭示铝碳耐火材料的微结构与抗热震性的关联性。为炭质,外层为碳化硅质)。在铝碳耐火材料中炭黑与含硅气相物质基于气-固反应形成核壳结构,同时在颗粒间隙气-固反应原位形成碳化硅晶须,其长径比随着引入炭黑的粒径增加而增大,从而提高了材料的力学性能,但是材料的抗热震性却与此相反。复合添加纳米炭黑N220和亚微米炭黑N990能够提高材料的力学性能和抗热震性。2.高温下MWCNTs的结构演变主要受体系中的SiO(g)分压影响。铝碳耐火材料中MWCNTs在含单质Si添加剂时的结构演变分为以下几个步骤:1000℃处理后在MWCNTs表面缺陷处形成碳化硅层,部分MWCNTs蚀变为碳化硅晶须;1200℃及更高温度处理后大量MWCNTs蚀变成为碳化硅晶须。与仅添加单质Si相比,硅微粉引入可以促进SiO(g)分压升高,从而加速MWCNTs的蚀变进程;相反地,B4C的引入显著降低了SiO(g)分压,有效抑制MWCNTs的结构蚀变。3.碳化硼在铝碳耐火材料中具有催化作用,改变纳米碳的形貌并催化树脂裂解碳形成MWCNTs和准石墨烯结构,有助于提高抗热震性。相对于仅添加单质硅的铝碳耐火材料来说,硅微粉引入促进了高温下碳化硅晶须的形成,材料的强度得到了提高但同时也增加了材料的脆性,不利于材料抗热震性的提高;相反,碳化硼的引入保留了更多的MWCNTs以及其催化形成的一维和二维纳米碳结构有助于提高材料的韧性,从而改善了材料的抗热震性。4.纳米炭黑和碳纳米管复合铝碳耐火材料具有比纳米炭黑和微米鳞片石墨复合材料更优异的性能。含有0.9wt%纳米炭黑复合0.1wt%MWCNTs可媲美1wt%纳米炭黑与1wt%鳞片石墨复合铝碳耐火材料的抗热震性。而原位催化树脂形成MWCNTs解决了MWCNTs在基质中分散性问题,MWCNTs与树脂残炭形成交织结构,进一步提高了材料的结合强度和韧性。5.多种纳米碳(纳米炭黑、碳纳米管和膨胀石墨)在铝碳耐火材料中起到协同增强增韧作用。膨胀石墨复合纳米炭黑引入铝碳耐火材料中主要发挥纳米炭黑柔性颗粒以及膨胀石墨多孔蠕虫状结构对材料应力的吸收和缓冲作用,显著改善材料的抗热震性。在此基础上,原位催化树脂形成MWCNTs与纳米炭黑和膨胀石墨起到协同增强增韧作用,能够在不降低抗热震性的基础上,进一步提高低碳铝碳耐火材料的综合性能。通过上述研究工作,可以得到以下主要结论:1.高温下铝碳耐火材料中炭黑颗粒与含硅气相物质作用形成核-壳结构(内层6.基于楔形劈裂法实验建立了纳米碳源制备铝碳耐火材料断裂行为、抗热震性与材料微结构之间的关联。基于楔形劈裂法测试认为提高材料的强度有助于抵抗裂纹的形成,而增加材料的韧性则提高材料抵抗裂纹增殖的能力。因此,以纳米炭黑、原位催化形成碳纳米管和膨胀石墨为碳源的铝碳耐火材料由于纳米炭黑、原位催化形成纳米碳、膨胀石墨以及高温下生成的碳化硅晶须起到了协同强韧化作用,增加了材料断裂过程中的能量耗散机制,提高了材料抵抗应力破坏的能力,显示出了较好的抗热震性。
[Abstract]:The traditional aluminum carbon refractories (10-30 wt%C) have been widely used as functional refractories in the key parts of water ports, skateboards and stoppers. But with the development of high efficiency continuous casting, clean steel smelting and other technologies, the development of high quality and low carbon aluminum carbon refractories (5 wt%C) is urgent. The pure reduction of microscale graphite content in aluminum carbon refractories will lead to lower toughness and thermal shock resistance. From the development trend of refractory materials, matrix nanostructure will be an important way to realize low carbonization of refractory materials. At present, carbon black, carbon nanotubes, graphene oxide tablets and expanded graphite have been started. As a carbon source of carbon composite refractories, it can be considered as a carbon source of carbon composite refractories, such as a large number of graphene sheets and pores, as a carbon source of carbon composite refractories, to reduce the carbon content of the materials and to optimize the properties of the materials. The structure evolution or alteration of carbon nanometers in the materials at high temperature may be developed and how to control and reduce the structure of the materials In the development of a new generation of low carbon or ultra-low carbon refractories (5 wt%C, or even less than 3 wt%C), it is necessary to consider how to enhance the synergistic toughening effect of nano carbon source and further reduce the carbon content in the material, and how to distinguish the heat resistance by characterizing the mechanical properties of the carbon composite refractory. In view of the above problems, the main research work in this paper is as follows: firstly, the structure evolution of nano carbon black in aluminum carbon refractories and the influence of carbon black on the microstructure and properties of aluminum carbon refractories are studied. Secondly, the structure evolution and mechanism of multi wall carbon nanometers (MWCNTs) in aluminum carbon refractories are studied, and the control and reduction are discussed. In addition, the effect of MWCNTs and in situ catalytic formation of MWCNTs and nano carbon black carbon nano carbon on the properties of Al C refractories was studied with nano carbon black as the base carbon source, and on the basis of the study on the effect of the expanded graphite composite nano carbon black on the properties of Al C refractory material, further in situ catalysis was carried out. Carbon nanotubes were formed to prepare carbon black, MWCNTs and expanded graphite composite al carbon refractories, and the effects of a variety of carbon nanocomposites on the comprehensive properties of aluminum carbon refractories were explored. Finally, the fracture behavior and resistance of aluminum carbon fire resistant material under tensile load were studied by the fracture structure and morphology analysis by wedge splitting test. The ability of crack failure to reveal the correlation between microstructure and thermal shock resistance of Al carbon refractories. Carbon and silicon carbide in the outer layer. Carbon black and silicon gas phase material in Al C refractories form a shell structure based on gas solid reaction, and in situ formation of silicon carbide whiskers in the interstitial gas solid reaction, with the length diameter ratio introduced. The increase of the particle size of carbon black increases the mechanical properties of the material, but the thermal shock resistance of the material is the opposite. Adding nano carbon black N220 and submicron carbon black N990 can improve the mechanical properties and thermal shock resistance of the materials. The structural evolution of MWCNTs at.2. at high temperature is mainly influenced by the partial pressure of SiO (g) in the system. The structure evolution of MWCNTs in the material containing a single Si additive is divided into the following steps: the silicon carbide layer is formed at the surface defect of MWCNTs at 1000 C, and the partial MWCNTs alteration becomes silicon carbide whisker, and a large amount of MWCNTs alteration becomes SiC whisker after 1200 and higher temperature treatment. The SiO (g) partial pressure increases, thus accelerating the alteration process of MWCNTs; on the contrary, the introduction of B4C significantly reduces the partial pressure of SiO (g), effectively restraining the structural alteration of MWCNTs and the catalytic action of boron carbide in the aluminum carbon refractories, changing the morphology of the carbon nanoscale and catalyzing the resin cracking carbon to form the MWCNTs and para graphene structure, which helps to improve the thermal shock resistance. Relative to the aluminum carbon refractories with single silicon only, the introduction of silicon micro powder promoted the formation of silicon carbide whisker at high temperature. The strength of the material was improved but the brittleness of the material was increased and the thermal shock resistance of the material was increased. On the contrary, the introduction of boron carbide retained more MWCNTs and its catalytic formation. The two dimensional carbon nanostructure helps to improve the toughness of the material, thus improving the thermal shock resistance of the material,.4. nano carbon black and carbon nanotube composite aluminum carbon refractories have better performance than nano carbon black and micron scale graphite composite. The composite 0.1wt%MWCNTs containing 0.9wt% nano carbon black is comparable to that of 1wt% nano carbon black and 1wt% scale. The thermal shock resistance of the flake graphite composite al C refractories, and the formation of MWCNTs by the in-situ catalytic resin solution to the dispersion of MWCNTs in the matrix, and the formation of the interwoven structure of the MWCNTs and the resin residual carbon, further improving the bonding strength and toughness of the material.5. (nano carbon black, carbon nanotube and expanded graphite) in the aluminum carbon refractories The expanded graphite composite nano carbon black introduces the nano carbon black flexible particles and the porous worm like structure of the expanded graphite to the material stress absorption and buffer effect, and improves the thermal shock resistance of the material. On this basis, the in-situ catalytic resin forms MWCNTs and nano carbon black. With the expanded graphite, it can enhance the toughening effect, and can further improve the comprehensive performance of low carbon aluminum carbon refractories without reducing the thermal shock resistance. The following main conclusions can be obtained through the above research work: 1. the carbon black particles in the aluminum carbon refractories at high temperature formed the core shell structure (inner layer 6.). Based on the wedge splitting method, the fracture behavior of aluminum carbon refractories prepared by carbon nanometers is established. The relationship between the thermal shock resistance and the microstructure of the material is found. Based on the wedge splitting test, it is suggested that the strength of the material can help to resist the formation of the crack, and the toughness of the material increases the ability of the material to resist the crack growth. Carbon black, in situ catalyzed formation of carbon nanotubes and expanded graphite as carbon source, due to nano carbon black, in situ catalytic formation of carbon nanoscale, expanded graphite and silicon carbide whiskers generated at high temperature played a synergistic toughening effect, increased the energy dissipation mechanism during the fracture process, and improved the material resistance to stress damage. The ability to show good thermal shock resistance.

【学位授予单位】：武汉科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ175.1;TB383.1

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