中间相沥青基泡沫炭的研究进展

中间相沥青基泡沫炭是一种具有低密度、高强度、高导热、高导电、耐火、耐高温、抗冲击、抗氧化等性能的新型炭材料,具有广泛的应用前景.不同的原料和方法所制备的沥青基泡沫炭的结构、性能和应用也有所不同,通过对以石油系、萘系和煤沥青或改性煤沥青为原料制备中间相沥青基泡沫炭,讨论了制备工艺对泡沫炭的影响,同时对泡沫炭的改性研究及应用进行了概述.     

泡沫炭的研究进展

介绍了泡沫炭的基本性质及制备方法:泡沫炭是一种性能优异,用途广泛的新型炭材料;不同的制备原料和方法所得泡沫炭的结构和性能也有所不同.通常用于制备泡沫炭的原料包括有机聚合物、中间相沥青以及煤和煤系物.重点阐述了以煤和煤系物作为前体制备泡沫炭的相关工作,综述了泡沫炭的结构、性能及近年来国内外的研究进展,并对其潜在的应用和发展趋势做了初步总结.     

自发泡法制备沥青基泡沫炭工艺对其结构性能的影响

在众多的炭材料中,泡沫炭以其优异的物理和化学性能被广泛地应用于化学工程、航天航空、生物工程等领域。沥青基泡沫炭更是成为了泡沫炭材料领域的研究热点。本文就近年来自发泡法制备沥青基泡沫炭的工艺进行综述,分析总结了原料、发泡温度等工艺条件对沥青基泡沫炭结构及性能的影响,简述其形成机理,对沥青基泡沫炭将来的发展进行了展望。     

不同前驱体泡沫炭的制备及形貌对比研究

泡沫炭具有低密度、高强度、高导热、抗冲击、耐高温、抗氧化等诸多特点,因而具有广泛的应用前景。本文分别以萘系中间相沥青、煤系中间相沥青及氧化沥青为原料,采用低温氧化法取代溶剂萃取法来调制原料的族组成,制备适宜发泡的前驱体,通过对比所制泡沫炭的形貌结构来提出以氧化沥青为原料制备泡沫炭的可行性。     

超临界流体制备中间相沥青泡沫炭

以萘系中间相沥青为原料,利用超临界流体(Supercritical Fluid)作为发泡剂制备中间相沥青泡沫,经氧化炭化处理获得泡沫炭材料.通过分析中间相沥青的流变性能以及比较不同溶剂对中间相沥青的溶解性能,选择合适的超临界溶剂,可以制备出泡孔均匀,开孔率高的泡沫炭材料.研究了中间相沥青-溶剂系统的超临界状态下的发泡过程.考察溶剂比例、发泡压力、系统温度、压力释放速率等发泡条件对超临界流体制备中间相沥青泡沫炭的影响.     

发泡条件对中间相沥青基泡沫炭形成的影响

以石油系中间相沥青为原料，在不同发泡时间和压力、温度为440℃时发泡制得生料泡沫炭，经过氧化、炭化等处理得到了具有均一孔结构的泡沫炭。利用SEM观察孔结构并测定体积密度和真密度的方法计算出不同制备条件下所得到的泡沫炭的孔隙率的数据，发现泡沫炭的孔隙率与孔径主要受发泡压力的影响，可利用改变发泡压力的方法控制泡沫炭的孔结构。通过对泡沫炭生料进行氧化、炭化等后处理可有效地提高产物泡沫炭的密度、孔隙率和强度等材料性能。     

泡沫炭的最新研究进展

泡沫炭是一种新型的炭材料,具有密度小、强度高、导电、导热、热稳定、化学稳定等良好的物理和化学性能。制备泡沫炭的前驱体主要包括有机聚合物和中间相沥青,不同前驱体所制备的泡沫炭结构和性能也有一定差异。本文从泡沫炭的制备、改性、性能及应用等方面综述了近年来泡沫炭的最新研究进展,重点阐述了中间相沥青基泡沫炭的制备和性能,并指出了泡沫炭的未来研究方向。     

石油系中间相沥青基泡沫炭的制备与结构研究

分别以中间相含量为100％和30％的两种石油系中间相沥青为前驱体制备泡沫炭，利用SEM、偏光显微镜观察泡沫炭的孔和孔壁等微观形貌，利用XRD分析石墨化泡沫炭的微晶结构。考察不同中间相含量前驱体的发泡性能，同时探讨了焦化手段对泡沫炭结构和性能的影响。结果表明，两种前驱体均能制备得到孔结构均匀、开孔率高的泡沫炭；100％中间相含量的前驱体相对更适合发泡；通过延长焦化时间可以优化泡沫炭结构、提高石墨化度，进而提高泡沫炭产品性能。     

沥青基泡沫炭的工艺制备及应用概述

泡沫炭是一种具有大尺寸孔径的网状功能型新型炭材料,具有密度小、强度高、导电、导热、热稳定、化学稳定等良好的物理和化学性能,已引起人们的广泛关注。本文综述了泡沫炭的发展历史、沥青基泡沫炭的制备方法及工艺影响,以及在电磁、热性能、结构材料、生物医药、过滤材料等方面的应用研究,并展望了沥青基泡沫炭的研究前景。     

煤沥青族组成耦合发泡行为对泡沫炭形貌和结构的影响研究

以来源丰富、价廉易得的煤系沥青为原料,通过空气氧化法制备高软化点沥青,再进行溶剂萃取调制沥青族组成来制备适宜的发泡前驱体,采用自发泡法制备泡沫炭,利用偏光显微镜和扫描电镜观察其微观结构。结果表明,通过调制沥青的族组成可有效调控泡沫炭的孔貌结构,其中甲苯可溶物TS影响最为显著。     

中间相沥青基泡沫炭的研究及应用

中间相沥青基泡沫炭具有低密度、高强度、高导热、抗冲击、耐高温、抗氧化等诸多特点,因而具有广泛的应用前景.目前,中间相沥青基泡沫炭最常用的制备方法是自发泡法.本文详细综述了中间相沥青基泡沫炭制备过程中的影响因素,也概述了近几年来国内外对泡沫炭的改性研究及应用.     

Preparation of mesophase-pitch-based carbon foams at low pressures

A simple method for preparing the mesophase-pitch-based carbon foams at low pressures through prolonging the soaking time in the preparation process of the mesophase pitch was disclosed. The physical properties, morphologies and the crystal structure of the as-obtained foams were investigated. Bulk density of the resultant carbon foams cover a range 0.514-0.624 g/cm³, under the preparation pressure range 0.5-2 MPa. The SEM micrographs revealed that the thermal shrinkage of the graphitized foams derived from the higher softening point mesophase pitch was less than that of the foam from the lower softening point; Optical micrographs showed that higher softening point mesophase pitch derived carbon foams exhibited better orientation and less microcracks in both junctions and ligaments; The XRD results revealed that higher softening point pitch derived graphitized foams exhibited smaller interlayer spacing and larger crystallite size. The properties of the carbon foam can be severely affected by the properties of the precursor, so it is critical to tailor the properties of the pitch precursor so as to obtain high performance and low cost products.     

酚醛泡沫在高温热处理过程中结构与性能的变化

以甲阶酚醛树脂为原料制备了酚醛泡沫,经高温热处理进而得到酚醛树脂基碳泡沫。通过FTIR、TGA、SEM、压缩强度及热导率检测等手段,分析研究了酚醛泡沫在高温热处理后结构与性能的变化情况。结果表明:氮气保护下,酚醛泡沫经高温处理后形成了以碳元素为主的碳泡沫;与酚醛泡沫相比,碳泡沫的表观密度、泡孔孔径较小,泡孔虽仍以闭孔结构为主,但是开孔结构明显增多;酚醛泡沫及碳泡沫的压缩强度和热导率都随着泡沫密度的增加而增大,另外同酚醛泡沫相比,碳泡沫的压缩强度和热导率均相对较高。     

Thermal‐Insulation,Electrical, and Mechanical Properties of Highly‐Expanded PMMA/MWCNT Nanocomposite Foams Fabricated by Supercritical CO2 Foaming

Foaming behavior of poly(methyl methacrylate) (PMMA)/multi‐walled carbon nanotubes (MWCNTs) nanocomposites and thermally‐insulating, electrical, and mechanical properties of the nanocomposite foams are investigated. PMMA/MWCNT nanocomposites containing various amounts of MWCNTs are first prepared by combining solution and melt blending methods, and then foamed using CO₂. The foaming temperature and MWCNT content are varied for regulating the structure of PMMA/MWCNT nanocomposite foams. The electrical conductivity measurement results show that MWCNTs have little effect on the electrical conductivity of foams with large expansion ratio. Thermal conductivities of both solid and foamed PMMA/MWCNT nanocomposites are measured to evaluate their thermally insulating properties. The gas conduction, solid conduction, and thermal radiation of the foams are calculated for clarifying the effects of cellular structure and MWCNT content on thermal insulation properties. The result demonstrates that MWCNTs endowed foams with enhanced thermal insulation performance by blocking thermal radiation. Moreover, the compressive testing shows that MWCNTs improve the compressive strength and rigidity of foams. This research is essential for optimizing environmentally friendly thermal insulation nanocomposite foams with enhanced thermal‐insulation and compressive mechanical properties.     

Thermal properties of copper-coated carbon foams

Carbon foams, with 97% porosity, were electroplated with copper for different periods of time to achieve desired copper thicknesses and foam porosity. A light flash diffusivity instrument was used to measure the thermal conductivity of the coated samples. An analytical model was developed to calculate the effective thermal conductivity of the coated foams. It was observed that the copper-coated carbon foam with 50% porosity can attain a thermal conductivity of 180 W/m K. The results from the analytical model were compared to the experimental results and they were in a very good agreement. The above analyses demonstrated the significance of copper coating in tailoring carbon foam thermal properties. The developed analytical model was adopted to predict the thermal conductivity of the copper-coated carbon foams.     

Radiative properties of tannin-based,glasslike, carbon foams

This work deals with the measurement of radiative properties of lightweight rigid foams derived from tannins. Such cellular solids derived from renewable resources were investigated before and after carbonisation, the latter leading to glasslike carbon foams. Spectral quantities such as transmittance and reflectance were measured within the range of infrared wavelengths 1.5–12 μm, from which optical thickness, albedo, scattering and absorption coefficients, and absorptance were deduced. Temperature dependence of emissivity of carbon foams was also derived from measurements and from calculated blackbody emissive power. Both organic and carbon foams were shown to be poor thermal conductors, whose radiative transfer properties increase when the porosity decreases, due to both bigger cells, and to thinner and to less pore walls and struts. The radiative conductivity of carbon foams was deduced from the measured overall conductivity and from a simple analytical model accounting for the conduction conductivity.     

Processing and characterization of syntactic carbon foams containing hollow carbon microspheres

The effects of heat-treatment on the properties of carbon foams were studied. The carbon foam was first prepared by adding hollow carbon microspheres to phenolic resin, followed by post-curing, pre-carbonization and carbonization. The mechanisms of failure behaviour and the increase of electrical and thermal conductivities showed that the properties of the foams were influenced by the heat-treatment temperature. Results showed that the introduction of more interval voids during carbonization resulting in a reduction of the mechanical properties. Carbon foams with electrical conductivity of 1.20 S/cm and thermal conductivity of 12.85 W/mK were obtained.     

The influence of carbon nanotube aspect ratio on the foam morphology of MWNT/PMMA nanocomposite foams

Polymer nanocomposite foams, products from the foaming of polymer nanocomposites, have received increasing attention in both the scientific and industrial communities. Nanocomposite foams filled with carbon nanofibers or carbon nanotubes with high electrical conductivity, enhanced mechanical properties, and low density are potential effective electromagnetic interference (EMI) shielding materials. The EMI shielding efficiency depends on the electrical conductivity and bubble density, which in turn, depend on the properties of the filler. In the current study, multi walled carbon nanotubes (MWNT) with controlled aspect ratio were used to alter the bubble density in MWNT/poly(methyl methacrylate) (PMMA) nanocomposites. It was found that the nanocomposite foams filled with shorter MWNT had higher bubble density under the same foaming conditions and MWNT concentration. Both the ends and sidewalls of carbon nanotubes can act as heterogeneous bubble nucleation sites, but the ends are more effective compared to the sidewalls. Shorter nanotubes provide more ends at constant MWNT concentration compared to long nanotubes. As a result, the difference in the foam morphology, particularly the bubble density, is due to the difference in the number of effective bubble nucleation sites.