Shape-Memory and Anisotropic Carbon Aerogel from Biomass and Graphene Oxide

Biomass, as the most abundant and sustainable resource on the earth, has been regarded as an ideal carbon source to prepare various carbon materials. However, manufacturing shape-memory carbon aerogels with excellent compressibility and elasticity from biomass remains an open challenge. Herein, a cellulose-derived carbon aerogel with an anisotropic architecture is fabricated with the assistance of graphene oxide (GO) through a directional freeze-drying process and carbonization. The carbon aerogel displays excellent shape-memory performances, with high stress and height retentions of 93.6% and 95.5% after 1000 compression cycles, respectively. Moreover, the carbon aerogel can identify large ranges of compression strain (10–80%), and demonstrates excellent current stability during cyclic compression. The carbon aerogel can precisely capture a variety of biological signals in the human body, and thus can be used in wearable electronic devices.     

Preparation and characteristics of electrospun activated carbon materials having meso- and macropores

Mesoporous activated carbon samples were prepared from electrospun PAN-based carbon fibers using physical activation with silica. Textural characterization was performed using nitrogen adsorption at 77 K. The BET specific surface area and pore size distribution of silica activated carbon materials were investigated. According to the increment of silica, BET specific surface area was increased about thirty times and it was found that silica activated carbon materials were highly mesoporous by studying pore surface distribution and pore volume distribution. Surface morphology of silica activated carbon materials were observed by SEM images. The spherical typed carbon materials were investigated. The diameter of spherical typed carbon materials was increased in proportional of the increment of silica.     

一步法制备糖蜜基活性炭及其界面吸附行为

以糖厂废弃的糖蜜为原料,Na_2CO_3为活化剂,采用一步直接化学活化法制备了糖蜜基活性炭(AC).采用X射线衍射(XRD)、扫描电子显微镜(SEM)、N_2吸附-脱附及元素分析手段对产物进行了表征,证实其为多孔的石墨化碳材料,比表面积高达1023 m~2/g.研究了糖蜜基活性炭对溶液中的重金属离子Pb(Ⅱ)的脱除性能,结果表明:糖蜜基活性炭的吸附容量高于市售活性炭(CC),且所需吸附时间和投炭量均低于市售活性炭;其吸附动力学符合准二级动力学的Langmuir吸附,为单分子层的化学吸附;吸附Pb(Ⅱ)的糖蜜基活性炭可循环再生和重复使用.     

碳纳米管的化学修饰以及作为润滑油添加剂的摩擦学性能研究

采用硫酸和硝酸混合酸对催化裂解法(CVD法)制备的多壁碳纳米管(MWNNTs)进行纯化,然后运用硬脂酸对碳纳米管进行表面修饰,并研究了硬脂酸修饰后的碳纳米管的表面状况以及作为润滑油添加剂的摩擦学行为．实验结果表明,在硫酸催化剂作用下,通过酯化反应碳纳米管能够被硬脂酸包覆,并且硬脂酸修饰的碳纳米管作为润滑油添加剂能够显著提高基础油的减摩抗磨性能,当添加量为0．15％左右时,润滑油的减摩抗磨性能最佳,与基础油相比可以使摩擦系数下降10％左右,磨损量下降30％～60％．     

Characteristics of Nonafluorobutyl Methyl Ether (NFE) Adsorption onto Activated Carbon Fibers and Different-Size-Activated Carbon Particles

The characteristics of adsorption of 1,1,1,2,2,3,3,4,4-nonafluorobutyl methyl ether (NFE), a chlorofluorocarbon (CFC) replacement, onto six different activated carbon; preparations (three activated carbon fibers and three different-sized activated carbon particles) were investigated to evaluate the interaction between activated carbon surfaces and NFE. The amount of NFE adsorbed onto the three activated carbon fibers increased with increasing specific surface area and pore volume. The amount of NFE adsorbed onto the three different-sized-activated carbon particles increased with an increase in the particle diameter of the granular activated carbon. The differential heat of the NFE adsorption onto three activated carbon fibers depended on the porosity structure of the activated carbon fibers. The adsorption rate of NFE was also investigated in order to evaluate the efficiency of NFE recovery by the activated carbon surface. The Sameshima equation was used to obtain the isotherms of NFE adsorption onto the activated carbon fibers and different-sized-activated carbon particles. The rate constant k for NFE adsorption onto activated carbon fibers was larger for increased specific surface area and pore volume. The rate of NFE adsorption on activated carbons of three different particle sizes decreased with increasing particle diameter at a low initial pressure. The adsorption isotherms of NFE for the six activated carbons conformed to the Dubinin-Radushkevich equation; the constants BE(0) (the affinity between adsorbate and adsorbent) and W(0) (the adsorption capacity) were calculated. These results indicated that the interaction between the activated carbon and NFE was larger with the smaller specific surface area of the activated carbon fibers and with the smaller particle diameter of the different-sized-activated carbon particles. The degree of packing of NFE in the pores of the activated carbon fibers was greater than that in the pores of the granular activated carbons. Copyright 2000 Academic Press.     

碳纳米管的活化处理及对其电化学容量影响的研究

采用KOH为活性剂,对碳纳米管进行活化处理,经透射电子显微镜和高分辨透射电子显微镜从不同角度观察,发现得到了两端开口,管长较短,管壁粗糙的活性碳纳米管．用氮气自动吸附仪测试了活化前后两种碳纳米管的比表面积,发现活性碳纳米管具有比活化前碳纳米管更高的有效比表面积,将这两种碳纳米管分别作为电极材料应用于电化学超级电容器,经测试,发现活化后的碳纳米管的电化学容量大大提高,在有机电解液中达到了50F／g．     

Microstructure and properties of polyacrylonitrile based carbon fibers

The microstructure of polyacrylonitrile (PAN)-based carbon fibers with different mechanical properties was investigated. It was found that the tensile strength of the PAN-based carbon fibers generally decrease with the increase in the modulus. The properties of PAN-based carbon fiber are mainly controlled by the microstructure and microvoids. The increase in size and orientation of graphite crystallites follows the decrease in interlayer space of graphite sheets, which accompanies the increase in modulus and decrease in tensile strength of the carbon fibers. Simultaneously, the increase in the modulus of the carbon fibers accompanies the merging of the elliptical microvoids along the fiber axis and the turbostratic graphite in the carbon fibers transforms into 3D ordered graphite lamellar structure. This work provides useful information on tailoring the mechanical properties of carbon fibers by adjusting the microstructure.     

The Cohesive Energy and Vibration Characteristics of Parallel Single-Walled Carbon Nanotubes

Based on the van der Waals (vdW) interaction between carbon atoms, the interface cohesive energy between parallel single-walled carbon nanotubes was studied using continuous mechanics theory, and the influence of the diameter of carbon nanotubes and the distance between them on the cohesive energy was analyzed. The results show that the size has little effect on the cohesive energy between carbon nanotubes when the length of carbon nanotubes is over 10 nm. At the same time, we analyzed the cohesive energy between parallel carbon nanotubes with the molecular dynamics simulation method. The results of the two methods were compared and found to be very consistent. Based on the vdW interaction between parallel carbon nanotubes, the vibration characteristics of the two parallel carbon nanotube system were analyzed based on the continuous mechanical Euler-beam model. The effects of the vdW force between carbon nanotubes, the diameter and length of carbon nanotubes on the vibration frequency of carbon nanotubes was studied. The obtained results are helpful in improving the understanding of the vibration characteristics of carbon nanotubes and provide an important theoretical basis for their application.     

扶手椅型单壁碳纳米管的结构和稳定性

用AM1和PM3两种方法对相同长度不同直径以及相同直径不同长度的扶手椅型单壁碳纳米管进行了优化, 并对AM1方法优化所得到的碳纳米管的几何结构进行了振动频率分析和p轨道轴矢量(POAV)分析, 发现了其热力学稳定性随碳纳米管直径和长度的变化规律, 讨论了各碳纳米管的张力、碳原子的杂化状态和共轭程度随碳纳米管直径的变化关系, 并与苯和C60做了比较。     

Syntheses and properties of fluorinated carbon materials

In this review, the more recent topics in the field of fluorinated carbon materials are given with the emphasis on the research work presented by our group. The direct fluorination and/or oxyfluorination of various carbon materials, especially of new carbon materials, i.e. nanotubes, carbon fibers, and activated carbon fibers have been described. It has been shown that fluorination can be one of the most effective methods to modify and control physico-chemical properties of carbon materials.     

碳糊电极和化学修饰碳糊电极的制备及性能综述

碳糊电极在电化学研究中起着非常重要的作用．从电极材料选用和修饰剂选择方面综述了碳糊电极和化学修饰碳糊电极制备的几种方法,分析了碳糊电极和化学修饰碳糊电极制备技术存在的主要问题及其原因,评价了碳糊电极和化学修饰碳糊电极的表征技术、性能以及影响电极性能的因素．概括了近年来本课题组在碳糊电极研究中的一些结果．     

Experimental and modeling study on hydrate formation in wet activated carbon

The formation of methane hydrate in wet activated carbon was studied. The experimental results demonstrated that the formation of methane hydrate could be enhanced by immersing activated carbon in water. A maximum actual storage capacity of 212 standard volumes of gas per volume of water was achieved. The apparent storage capacity of the activated carbon + hydrate bed increased with the increasing of mass ratio of water to carbon until reaching a maximum, then decreased drastically as the bulk water phase emerged above the wet carbon bed. The highest apparent storage capacity achieved was 140 v/v. A hydrate formation mechanism in the wet activated carbon was proposed and a mathematical model was developed. It has been shown that the proposed model is adequate for describing the hydrate formation kinetics in wet activated carbon. The kinetic model and the measured kinetic data were used to determine the formation conditions of methane hydrate in wet carbon, which are in good agreement with literature values and demonstrate that hydrate formation in wet carbon requires lower temperature or higher pressure than in the free water system.     

多壁碳纳米管的制备及改性处理

用自制的镍 硅二元气凝胶作催化剂,合成了多壁碳纳米管.甲烷在680℃催化裂解120min,再升温至800℃继续裂解20min,得到多壁碳纳米管.TEM、HRTEM和Raman光谱分析表明,所得多壁碳纳米管与高定向石墨具有相似的层状结构,其管径分布均匀,约15～30nm左右,长径比大,管端封闭,并含有金属催化剂粒子;采用不同方法改性处理,发现经过稀硝酸浸泡和空气氧化处理后,能去除碳管中金属催化剂,同时碳纳米管管长变短,端帽开口,能有效利用内表面,比表面积增大.     

Structure and properties relationships for aromatic polyimides and their derived carbon membranes: experimental and simulation approaches

The main objective of this study is to investigate the factors of the chemical structure and physical properties of rigid polyimides in determining the performance of derived carbon membranes through both the experimental and simulation methods. Four polyimides made of different dianhydrides were pyrolyzed at 550 and 800 degrees C under vacuum conditions. The resultant carbon membranes exhibit excellent gas separation performances beyond the traditional upper limit line for polymer membranes. The thermal stability and the fractional free volume (FFV) of polyimides were examined by a thermogravimetric analyzer and a density meter. The chain properties of polyimide, such as flatness, chain linearity, and mobility, were simulated using the Cerius(2) software. All above characterizations of polyimides were related to the microstructure and gas transport properties of the resultant carbon membranes. It was observed that the high FFV values and low thermal stability of polyimide produce carbon membranes with bigger pore and higher gas permeability at low pyrolysis temperatures. Therefore, polyimides with big thermally labile side groups should be preferred to prepare carbon membranes at low pyrolysis temperatures for high permeability applications. On the other side, since the flatness and in-plane orientation of precursors may lead carbon membranes to ordered structure, thus obtaining high gas selectivity, linear polyimides with more coplanar aromatic rings should be first choice to prepare carbon membranes at high pyrolysis temperatures for high selectivity applications. The location of the indan group also affects chain flatness and in-plane orientation. As a result, carbon membranes derived from the BTDA-DAI precursor have superior separation performance to those derived from Matrimid.     

KOH活化木屑生物炭制备活性炭及其表征

以木屑热裂解的生物质炭为原料,氢氧化钾为活化剂,采用化学活化法制备活性炭,探讨了碱炭比、活化温度和活化时间对活性炭吸附亚甲基蓝吸附值的影响。 利用N2吸附实验、XRD和FTIR等实验技术,对原料与制备活性炭的结构与性能进行了表征。 结果表明,在碱炭质量比为1.5、活化温度750 ℃、活化时间2 h的条件下,所制备的活性炭对亚甲基蓝吸附值为255 mg/g,BET总比表面积为1514 m2/g,中孔比表面积为110 m2/g,吸附总孔容为0.821 cm3/g,中孔孔容为0.117 cm3/g,吸附平均孔径为2.170 nm。     

流化床甲烷/丙烷临氧CO2重整制合成气反应研究

研究了流化床反应器中甲烷、丙烷临氧自热CO2重整制合成气反应中不同催化剂的性能及表面积碳行为，并用热重分析、激光拉曼及透射电镜研究了催化剂表面的积碳物种及积碳量。结果表明，贵金属Pd、Pt由于对烷烃有较强的裂解作用，镍基及贵金属修饰的镍基催化剂表面有大量的纤维状炭生成；碱土和稀土金属改性的镍基催化剂有较好的抗积碳性能，大量碱土金属CaO修饰微球硅胶后负载的镍基催化剂在同等的反应条件下没有发现积碳，碱土金属对催化剂表面碱性的增强是催化剂抗积碳性能提高的原因。     

One-step synthesis of acid carbon and its catalytic activities for the oxathioacetalization

The novel acid carbon has been synthesized successfully via one-step hydrothermal carbonization. The acid carbon owned the morphologies of the spheres with smooth surfaces and the acidity of 2.4 mmol/g. The catalytic activities of the novel acid carbon were investigated through oxathioacetalization. The results showed that the acid carbon owned high activity for the reactions with the average yields over 95%. The advantages of high activity, stability, reusability, low cost for the simple synthetic procedure and wide application to various carbonyl compounds made the acid carbon one of the best choices for the reactions.     

Thermodynamic and transport properties of argon/carbon and helium/carbon mixtures in fullerene synthesis

The equilibrium composition and thermodynamic and transport properties of argon; carbon and helium/carbon mixtures are calculated in the temperature range 300–20,000 K. The curves for the composition of mixtures of 50%, carbon in argon or helium are shown fir a pressure of 1.33 × 10⁴ Pa. The calculations for the heat capacity at constant pressure (C_p) and transport coefficients are validated with other studies, for the cases or pure argon and pure helium at a pressure of 10⁵ Pa. The properties of mixtures with various proportions of carbon in argon and helium are calculated. Results are presented at pressures of 105 and 1.33 × 10⁴ Pa, typical of reactors for the synthesis of fullerenes and nanotubes. It is observed that the properties of carbon and mixtures of carbon with a buffer gas (argon or helium) are very different from those of the buffer gas, thus the need to consider this effect in simulations. In general, the mixtures follow trends intermediate to those of the pure gases from which they are composed except for the thermal conductivity which shows a deviation from this tendency in the region between 11,500 and 19,000 K for argon/carbon mixtures and between 8,000 and 12,000 K for helium/carbon mixtures. Also, the electrical conductivity of mixtures of low carbon concentration is very close to that ofpure carbon. A datafile containing the transport properties of mixtures for pressures between 10⁴ and 10⁵ Pa is available free of charge from the authors.     

Interaction forces between waterborne bacteria and activated carbon particles

Activated carbons remove waterborne bacteria from potable water systems through attractive Lifshitz-van der Waals forces despite electrostatic repulsion between negatively charged cells and carbon surfaces. In this paper we quantify the interaction forces between bacteria with negatively and positively charged, mesoporous wood-based carbons, as well as with a microporous coconut carbon. To this end, we glued carbon particles to the cantilever of an atomic force microscope and measured the interaction forces upon approach and retraction of thus made tips. Waterborne Raoultella terrigena and Escherichia coli adhered weakly (1-2 nN) to different activated carbon particles, and the main difference between the activated carbons was the percentage of curves with attractive sites revealed upon traversing of a carbon particle through the bacterial EPS layer. The percentage of curves showing adhesion forces upon retraction varied between 21% and 69%, and was highest for R. terrigena with positively charged carbon (66%) and a coconut carbon (69%). Macroscopic bacterial removal by the mesoporous carbon particles increased with increasing percentages of attractive sites revealed upon traversing a carbon particle through the outer bacterial surface layer.     

Effect of surface area and heteroatom of porous carbon materials on electrochemical capacitance in aqueous and organic electrolytes

A series of porous carbon materials with wide range of specific surface areas and different heteroatom contents had been prepared using polyaniline as carbon precursor and KOH as an activating agent. Effect of surface area and heteroatom of porous carbon materials on specific capacitance was investigated thoroughly in two typical aqueous KOH and organic 1-butyl-3- methylimidazolium tetrafluoroborate/acetonitirle electrolytes. The different trends of capacitance performance were observed in these two electrolytes. Electrochemical analyses suggested that the presence of faradaic interactions on heteroatom-enriched carbon materials in organic environment is less significant than that observed in aqueous electrolytes. Thus, in aqueous electrolyte, a balance between surface area and heteroatom content of activated porous carbon would be found to develop a supercapacitor with high energy density. In organic electrolyte, the capacitance performance of porous carbon is strongly dependent on the surface area. The results may be useful for the design of porous carbon-based supercapacitor with the desired capacitive performance in aqueous and organic electrolytes.