煤基碳泡沫综述

概述了煤基碳泡沫的发展概况。阐述了煤基碳泡沫的制备方法和应用，分析了RVC碳泡沫、中间相沥青基碳泡沫和煤基碳泡沫的结构和性能特点，并且展望了煤基碳泡沫的潜在应用和研究方向。     

水溶性煤基发光碳点的室温快速合成及其在Fe3+离子检测中的应用(英文)

碳量子点具有优异的光学性质，良好的水溶性、低毒性、原料来源广、成本低、生物相容性好等诸多优点，广泛应用于发光器件、生物检测、能源存储与转换领域，但在实际应用中还存在合成过程复杂、产率低等挑战。本文以煤为原料，以甲酸和双氧水为氧化剂，在室温下可大量合成煤基发光碳点，考查了氧化剂的添加量、反应时间对煤基发光碳点的产率及反光性质的影响，结果表明煤基发光碳点产率高达54%，且具有良好的水溶性、光稳定性、耐盐性和较高的发光量子效率。制备的煤基发光碳点可用于Fe³⁺离子的特异性检测，检测限低于600 n mol L^-1。该合成方法为煤的高附加值利用和设计开发煤基新材料提供了新途径。     

新型多孔碳泡沫材料的制备及其应用研究

碳泡沫材料不同于常规碳材料,是一种以碳原子相互连接成为骨架结构的轻质多孔固体材料,具有新颖的结构和形貌。空腔的结构包括五边形十二面体和球形等。由于具有独特的微观结构、较高的孔体积和较大的表面积以及优良的热导率和抗压性等特点,使其在众多领域里显示出潜在的应用价值,可应用于催化剂载体材料、复合材料和电化学等领域。因此,新型的碳泡沫材料及其应用研究迅速成为碳材料研究领域的热点之一。综述了新型碳泡沫材料的制备及其应用的研究进展,探讨了碳泡沫材料制备和应用方面所面临的实际问题以及今后在实际应用中的发展趋势和前景。     

基于分形理论的碳泡沫有效导热系数研究

以煤焦油基中间相沥青为原料，在一定的温度和压力条件下升温发泡，然后再经碳化、石墨化便可以制得一种高导热系数的多孔材料——碳泡沫。应用分形理论讨论了这种新型多孔材料的导热特性，推导出了碳泡沫的面积分形维数，并在此基础上建立了石墨化碳泡沫材料的导热模型，采用热阻法导出了石墨化碳泡沫材料的等效导热系数的关系式，计算出了碳泡沫的有效导热系数，计算结果与碳泡沫样品的实测值基本一致，这种方法为更好地利用其优良的导热性能提供了理论基础。     

煤基球形多孔碳用于锂离子电池负极材料的性能研

因具有较短的锂离子扩散路径、大的比表面积等优势, 球形碳材料在锂离子电池负极材料中展露出良好的应用前景。研究以新疆库车产煤为原料, 采用电弧放电法及化学活化法制备出了具有多孔结构的煤基球形碳。通过X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱(Raman)、氮气吸脱附法和恒电流充放电等测试手段对材料结构、形貌和电化学性能进行了表征。结果表明, 在100 mA/g的电流密度下, 煤基球形多孔碳的首次放电比容量可达到1188.9 mAh/g, 远高于商业石墨负极372 mAh/g的理论比容量。此外, 该材料还表现出了良好的循环稳定性, 经历200圈循环后的放电比容量为844.9 mAh/g。煤基球形多孔碳优异的电化学性能得益于活化过程所产生的分级孔道结构能为锂离子提供更多储存空间, 从而提高了电极的容量及循环稳定性。     

煤基球形多孔碳用于锂离子电池负极材料的性能研究

因具有较短的锂离子扩散路径、大的比表面积等优势,球形碳材料在锂离子电池负极材料中展露出良好的应用前景。研究以新疆库车产煤为原料,采用电弧放电法及化学活化法制备出了具有多孔结构的煤基球形碳。通过X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱(Raman)、氮气吸脱附法和恒电流充放电等测试手段对材料结构、形貌和电化学性能进行了表征。结果表明,在100 m A/g的电流密度下,煤基球形多孔碳的首次放电比容量可达到1188.9 mAh/g,远高于商业石墨负极372 mAh/g的理论比容量。此外,该材料还表现出了良好的循环稳定性,经历200圈循环后的放电比容量为844.9 mAh/g。煤基球形多孔碳优异的电化学性能得益于活化过程所产生的分级孔道结构能为锂离子提供更多储存空间,从而提高了电极的容量及循环稳定性。     

运用分形方法预测石墨化碳泡沫方向导热系数

石墨化碳泡沫是高导热系数材料,具有方向导热性能,垂直发泡方向(xy平面)和沿发泡方向(垂直xy平面)的导热系数有明显的差异.应用分形方法通过确定碳泡沫的泡孔结构的分形维数,结合泡孔热阻单元,分析了石墨化碳泡沫的导热特性,推导出了碳泡沫的方向导热模型.计算结果与文献中石墨化碳泡沫样品的实测值基本一致,该方法为更好地利用其优良的方向导热性能提供了理论基础.     

煤基石墨烯宏观体的制备及其在CO_2光催化还原过程中的应用

石墨烯是一种新型二维碳质材料,以石墨烯为基本结构单元构筑宏观石墨烯材料是石墨烯走向实际应用的重要途径。以煤基石墨为原料,综合采用Hummers法、化学还原及冷冻干燥过程制备出煤基石墨烯宏观体。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、拉曼光谱等对样品形貌结构进行了分析表征。此外,以煤基石墨烯宏观体为光催化剂填料搭建固定床反应器,应用于CO_2光催化还原过程。结果表明,煤基石墨烯宏观体对CO_2光催化还原反应具有较高的催化活性,目标产物甲醇的产率最高可达65.91μmol/g·cat。     

泡沫炭材料研究进展

泡沫炭是由孔泡和相互连接的孔泡壁组成的一种轻质多孔材料,在许多民用和军用领域有广泛的应用前景,是一种极具开发潜力的碳材料。主要介绍了泡沫炭的制备方法、结构、性能及应用,并结合泡沫炭的研究现状,展望了其今后发展方向。     

低密度TMPTA泡沫的制备及表征

低密度聚合物泡沫在惯性约束聚变靶及电磁内爆靶中应用十分广泛。以三羟甲基丙烷三丙烯酸酯(TMP-TA)为聚合单体,安息香甲基醚为引发剂,通过紫外光引发生成凝胶,经超临界干燥得到TMPTA泡沫材料。通过红外光谱仪和元素分析仪确定了TMPTA单体中官能团转化率及泡沫纯度的表征。实验结果表明,聚合反应过程中,在1636cm-1附近碳碳双键(C=C)的转化率为40.48%,泡沫为高纯度的低密度TMPTA泡沫,机械强度可满足核磁内爆靶(Z-pinch)靶装配的需求。     

Controlling bubble density in MWNT/polymer nanocomposite foams by MWNT surface modification

Polymer nanocomposite foams are promising substitutes for polymeric foams. Carbon nanotube/polymer nanocomposite foams possess high strength, low density, and can be made conductive. Creating polymer foams with controlled foam morphology is of great importance for controlling foam properties. The foam morphology is influenced by the foaming conditions and filler properties. For carbon nanotube/polymer composite foams, dispersion state and aspect ratio of the carbon nanotubes have been shown to influence the bubble density and bubble size. In the current study, the influence of carbon nanotube surface chemistry on the bubble density of multi-walled carbon nanotube/poly(methyl methacrylate), MWNT/PMMA, nanocomposite foams was investigated. The surface of the MWNTs with controlled aspect ratio was covalently modified with glycidyl phenyl ether (GPE). Surface modified MWNT/PMMA nanocomposite foams were produced using a supercritical carbon dioxide foaming process. At constant MWNT concentration, the bubble density of polymer nanocomposite foams filled with GPE surface modified MWNT was found to be several times higher than that of polymer nanocomposite foams filled with nitric acid treated MWNT. After the MWNTs were modified with GPE, the surface chemistry of the MWNT became the dominant factor in determining the bubble density while the MWNT aspect ratio became less influential.     

Fabrication of aluminum foam stabilized by copper-coated carbon fibers

Short copper-coated carbon fibers were used as novel stabilizer for aluminum foam. Aluminum foams containing 0.35, 1.0, 1.7 vol.% copper-coated carbon fibers were fabricated by a melt route. Foaming behavior and microstructure of these foams were observed. Results show that copper-coated carbon fibers can stabilize aluminum foam by preventing cell wall rupture and reducing coalescence. The fibers are mostly located inside cell wall and form a network structure, which can generate separating force and prevent cell wall from rupture. The volume fraction of copper-coated carbon fibers needed to stabilize aluminum foam is as low as 0.35 vol.%, and the foam is more stable when more fibers are used.     

Strength and ductility of as-plated and sintered CVD nickel foams

Low density, open cell nickel foams produced by chemical vapor deposition (CVD) are made for electrochemical applications. One process involves nickel carbonyl decomposition within a plater whereby nickel is deposited onto a reticulated polyurethane (PU) foam substrate. The as-plated nickel foams are then sintered in a partially reducing atmosphere at high temperature in order to enhance ductility. The high strength and brittleness of the as-plated foams presents a material handling challenge in manufacturing. As-plated foams are much stronger than sintered foams of the same density. Our analysis shows that the strengthening in the as-plated nickel foams is due to a combination of grain size, solid solution strengthening, dislocations and nano-porosity. Of these, the effects due to interstitial carbon are dominant. This is lost upon sintering. Foam ductility does not show the usual inverse trend with strength. Instead, foam ductility and bendability show little variation with carbon or sulfur level or with the level of nano-porosity, which are among the strongest strengthening sources in the foams.     

Preparation of polybenzoxazine foam and its transformation to carbon foam

An organic foam derived from a new type of phenolic resin, namely polybenzoxazine, was successfully prepared with a noncomplex and economical foaming method by using azodicarbonamide (AZD) as a foaming agent. The influence of foam density on the physical and mechanical properties of the foams was studied. All resulting polybenzoxazine foams and carbon foams exhibit a tailorable uniform microstructure. Polybenzoxazine foams showed a density in the range of 273–407 kg/m³, and a compressive strength and a compressive modulus in the range of 5.2–12.4 MPa and 268–681 MPa, respectively. The foam density not only affects the physical and mechanical properties, but also affects the deformation response of the foam. In addition, the polybenzoxazine foam was further transformed into carbon foam by carbonization at 800 °C under an inert atmosphere, and its properties were examined.     

MWNT reinforced polyurethane foam: Processing, characterization and modelling of mechanical properties

The mechanical properties of a foam material changes when the foam is reinforced with nanoparticles. In this paper it is investigated how the addition of multi-walled carbon nanotubes (MWNTs) influences the effective properties of polyurethane foam. Both pure and nano-reinforced foams containing different amounts of MWNT are produced and both pristine and functionalized MWNT are used as reinforcement. The MWNT are dispersed in the polyol using high-shear mixing with various mixing times to examine how that influences the properties of the produced foams. SEM is used to characterize the microstructure of the produced foams and these examinations reveals that the foam changes from a completely closed cell material for the pure PU foam to a partly open celled foam when adding MWNT. Compressive tests are performed in order to determine the strength and stiffness of the produced foams and the increase in these properties are very dependent on both the wt.% of MWNT and the mixing time used to disperse them in the polyol. Furthermore, the effective properties of the reinforced foams are determined using the Mori-Tanaka (MT) method and generally the correlation between the experimentally and numerically determined properties improves when the mixing time used increases for a constant wt.% of MWNT.     

Tailoring properties of reticulated vitreous carbon foams with tunable density

Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09–0.42 g/cm³ were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.     

Mesophase AR pitch derived carbon foam: Effect of temperature, pressure and pressure release time

For the carbon foam production, mesophase pitch pellets are heated up in a reactor in an aluminum mold to specified pressures and finally pressure released to obtain green carbon foam samples. The green foams were then stabilized and carbonized. The effects of various temperatures, pressures and pressure release times on production of carbons foams are investigated. The samples are subjected to SEM, mechanical testing, mercury porosimetry analysis and bulk density determination for characterization. For the processing temperatures of 553, 556, 566 and 573 K, the densities of the foams produced were 380, 390, 410 and 560 kg/m³ respectively. The compressive strengths of the respective samples were increased from 1.47, to 3.31 MPa for the lowest and highest temperatures. The processing pressures were 3.8, 5.8, 6.8 and 7.8 MPa. The bulk density and the compressive strength of the carbon foams produced were changed from 500 to 580 kg/m³, and 1.87 to 3.52 MPa for the lowest and highest pressures respectively. Pressure release times of 5 s, 80 s, 160 s and 600 s are used to produce different carbon foam samples. The densities and the comprehensive strengths measured for the highest and lowest pressure release times changed from 560 to 240 kg/m³ and 3.31 to 2.16 MPa respectively. The pore size distribution of all of the products changed between 0.052×10^-6m and 120×10^-6m. Increase in temperature and pressure increased the bulk density and compressive strength of the carbon foams. The mercury porosimetry results show % porosity increase with increasing temperature and pressure. On the other hand, increase in pressure release time decreased the bulk density, compressive strength of the carbon foam.     

中间相沥青基泡沫炭的制备与结构表征

将石油系中间相沥青利用限定尺寸法发泡后获得了泡沫炭,泡沫炭再经氧化、炭化和石墨化处理获得了具有良好孔结构的泡沫炭.利用SEM和XRD分析了泡沫炭的形态和结构.发现调整发泡模具中的自由空间可以控制泡沫炭的孔径;炭化和石墨化后泡沫炭的孔径减小,孔壁片层取向接近石墨;泡沫炭的孔壁由平直孔壁和“Y”形孔壁结构成,前者内部片层取向优于后者.大孔径泡沫炭的孔壁具有更紧密的内部分子排列,但其微晶尺寸较小.     

Piezoresistive and compression resistance relaxation behavior of water blown carbon nanotube/polyurethane composite foam

The in-situ bulk polycondensation process in combination with a ball milling dispersion process was used to prepare the water blown multiwall carbon nanotubes (CNT)/polyurethane (PU) composite foam. The mechanical properties, piezoresistive properties, strain sensitivity, stress and resistance relaxation behaviors of the composite foams were investigated. The results show that the CNT/PU composite foam has a better compression strength than the unfilled polyurethane foams and a negative pressure coefficient behavior under uniaxial compression. The resistance response of CNT/PU nanocomposites foam under cyclic compressive loading was quite stable. The nanocomposite foam containing a weight fraction of carbon nanotubes close to the percolation threshold presents the largest strain sensitivity for the resistance. The characteristic of resistance relaxation of CNT/PU composite foam is different from the stress relaxation due to the different relaxation mechanism. During compressive stress relaxation, the CNT/PU foam composites have excellent resistance recoverability while poor stress recoverability.     

无反射层泡沫夹层结构设计及吸波性能研究EI北大核心CSCD

针对无反射层的电磁隐身需求,本工作对透波层/吸波泡沫/透波层的夹层结构的吸波性能进行仿真计算,据此制备不同电磁参数的吸波泡沫,对其进行电磁特性表征,并研究吸波泡沫夹层结构的雷达散射截面(RCS)性能。结果表明:在吸波泡沫介电常数为2.3~2.7,介电损耗为0.24~0.26时,无反射层的夹层结构在宽频范围内具有最优的吸波性能。加入炭黑吸收剂泡沫的介电常数和介电损耗具有明显的变化规律,吸波PMI泡沫的电磁特性与仿真计算最优吸波泡沫较接近。炭黑质量分数为8%时吸波PMI泡沫夹层结构在2~18 GHz频率范围内具有最优的隐身性能,与仿真计算结果相对应,其通过低频透波、高频吸波实现电磁波隐身。