基于从头计算法的三维碳同素异形体结构设计

由于独特的成键特性,在不同温度和压强下,碳具有丰富的结构特性。除了实验上已发现各种同素异形体,理论计算也预言了丰富的新结构。在本文中,我们对第一性原理计算预言的三维碳同素异形体做了综述,特别地,我们着重关注了泡沫状的碳结构。碳泡沫主要由石墨片断以各种碳键连接而成,具体多孔结构及较大的表面积。另外,针对由低维碳结构,如碳富勒烯、纳米芽、纳米管及石墨烯等组成的三维碳超结构以及其他三维碳晶体我们也做了概述。这些新型碳结构有的由混杂的sp-sp²碳或者纯sp²碳组成(H-6, bct-4, C-20, K₄等),有的质量密度比金刚石还大(C₈, hP3, tl12, tp12等),有的可以由石墨在室温高压下转化而成(M碳, bct-4碳, W碳, Z碳等)。在这些预言的碳同素异形体中,有些在将来可能在实验室合成。     

一维新型碳的同素异形体:碳链

碳链是一种完全一维的、具有电子轨道sp杂化结构的新型碳的同素异形体.正是由于碳链的独特的一维结构,使其拥有区别于富勒烯、石墨烯和碳纳米管的化学键,从而表现出更加优异的性能,如:理论预言碳链的机械强度是石墨烯的几倍;碳链的导热也类似于石墨烯和碳纳米管;碳链是具有直接带隙的半导体材料,且带隙的大小可以通过其长度来调控,其长...     

漫话碳的同素异形体

本文主要介绍了至今发现的碳的多种同素异形体,如已知结构的六方石墨和三方石墨、立方金刚石和六方金刚石尚在研究之中的富勒烯碳原子簇和一些结构尚未确定的碳晶。     

非金属元素的同素异形体(二)——再谈碳的同素异形体

以“同一元素的不同形态的纯单质互称同素异形体”来定义,对数目众多的碳的同素异形体进行了归纳,它们可分为石墨、金刚石、富勒烯碳原子簇和新型纳米材料等4类。简要叙述了各种同素异形体的存在、组成、结构、制备、性质,并强调了计算化学对同素异形体的预测和现代科学技术发展对制备的作用及其在材料中的应用。     

碳基介熵材料:理论与实验

富碳型材料,包括纯碳材料的各种同素异形体、碳基骨架的稠环芳香分子、聚合物、框架材料等,已成为当今材料领域最重要的研究领域之一.在这些研究当中,很大一部分工作都是研究材料本身的结构与性质,而忽略了这些材料之间的内在联系.课本中的很多概念,如同分异构体、同素异形体和拓扑缺陷,已经无法用于深入理解种类和数量繁多的富碳型材料之间的构效关系.这就使得通过改变已知材料的有限结构来调控材料的性质变得工作重复而繁重,且基础理解受限于研究个体上.作者将从材料"熵"的概念入手,尝试理解富碳型材料之间熵的相对高低,并建议基于"介熵"的认识开发新型富碳型材料、开发新型介熵富碳型材料的全新性质.基于对具体的不同的新型富碳型材料的讨论,将"介熵"这一概念引入到同素异形体、同分异构体以及广泛存在于碳材料中的拓扑缺陷的理解上.类似富碳型材料的关系不再模糊地停留在几何结构层面上,为今后介熵富碳型材料及其他介熵材料的开发提供参考.     

线型碳的化学法合成研究进展

线型碳是碳的一种新的同素异形体,可望应用于生物医学和材料科学。线型碳的合成方法主要包括物理法和化学法。近年来,基于利用有机小分子或各种聚合物为原料的化学合成法发展迅速,本文主要综述其研究新进展。     

功能纳米碳点“照亮”应用征途

<正>近30余年来,世界各国的科学家致力于创制全新的不同维数碳同素异形体,纳米碳材料的家族成员得以持续不断增加,引领和开创了众多全新的科技领域。1985年,英国Harold Kroto和美国Robert Curl及Richard Smalley三位教授在莱斯大学制备出由60个碳原子组成的簇状分子C_(60)~1,开辟了零维纳米碳材料-富勒烯的新领域,荣获了1996年度诺贝尔化学奖。1991年,日本筑波NEC实验室的Iijima博士发现了一维纳米碳材料-碳纳米管~2;碳纳米管具有碳六边形组成的蜂窝状结构组     

Pc-carbon:一种可能的超硬碳材料

基于密度泛函理论计算预测了一种新型碳同素异形体（Pc-carbon）.声子色散谱和弹性常数计算证实了Pc-carbon的动力学和力学稳定性.计算结果显示，Pc-carbon是弹性各向异性的，其维氏硬度达到87.6 GPa.应力应变计算结果表明，Pc-carbon的理想拉伸强度和剪切强度分别为65.8 GPa和56.5 GPa，进一步证实了其超硬特性.电子结构计算结果表明，Pc-carbon是带宽为0.99 eV的半导体.     

诺贝尔奖宠儿——碳元素的前世今生

碳元素历史悠久,与现代人类社会联系紧密,对人类未来意义重大,多次斩获诺贝尔奖。在揭开碳元素的发现史之后,介绍了活性炭、碳纤维、玻璃碳等无定形碳以及热解炭等过渡碳的重要作用。此外,晶形碳的经典同素异形体--C60富勒烯、碳纳米管、石墨烯的独特结构造就了其在纳米材料领域的非凡用途;新型同素异形体的合成、发现与应用更是碳元素研究领域的热点。     

β型线型碳及其应用研究

聚炔碳即线型碳。它是指以sp杂化成键为特征的单质碳，碳分子以共轭三键-（-C≡C-）。一型（α-型）和累积双键=（C=C）n=型（β-型）存在，是碳的一种同素异形体。线型碳可能是一种超强纤维和常温超导材料。近来由于其在生物医学上的应用更引起了国际化学界和材料科学的关注。由于线型碳的高生物相溶性、完全的抗尿盐腐蚀性、高化学惰性，可用作外科缝线、器官替代物等，在一定条件下线型碳还可能向金刚石、纳米碳管、富勒烯转化，     

The Colloidal Stabilization of Carbon with Carbon: Carbon Nanobubbles as both Dispersant and Glue for Carbon Nanotubes

The superior physical properties of carbon nanotubes (CNTs) have led to their broad application. Intrinsically, CNTs tend to agglomerate from hydrophobic interactions, which is highly undesirable for solution processing and device fabrication. Commonly, a stabilizer consisting of organic surfactants or polymers is used to disperse CNTs. Recently, we synthesized nitrogen‐doped carbon hollow nanospheres (25–90 nm), termed carbon “nanobubbles”. They bear superior dispersability in water and distinctive graphitic order. Herein, we describe the nanobubble‐assisted dispersion of CNTs in aqueous solution upon sonication. This process relies on the π–π interaction between the two aromatic carbon nanostructures, which can process their carbon mixture in water into conductive filter membranes, ink, and discs. This stabilization can be extended to other aromatic carbons. In addition, the π–π interaction may create a new type of carbon p–n junction that can be used to improve charge separation.     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

Growth of Single-walled Carbon Nanotubes on Substrates Using Carbon Monoxide as Carbon Source

The growth of single-walled carbon nanotubes(SWCNTs) on substrates has attracted great interests because of the potential applications in various fields. Carbon monoxide(CO) was used as the carbon source for the growth of SWCNTs on silicon substrates. Random or oriented SWCNTs can be produced by varying the CO flow rate. When the flow rate of CO was as low as 20 sccm(sccm:standard cubic centimeter per minute), dense SWCNT networks with clean surface were produced. When the flow rate was above 50 sccm, vertically aligned SWCNT(VA-SWCNT) arrays were grown. Well-aligned VA-SWCNT arrays were obtained in the temperature range of 650-800℃ and the content of large-diameter(above 1.7 nm) tubes in the array increased with the temperature. The height of the array was affected by the growth temperature, the CO flow rate, and the growth time. These findings indicate CO can be used as an efficient carbon source for the growth of SWCNTs on substrates under low flow rates.     

埃洛石纳米管模板法一步法制备一维碳纳米管/碳纳米棒混合纳米碳材料

利用埃洛石纳米管(HNTs)特有的中空纳米结构,以及丰富的界面化学性质,以聚乙烯醇(PVA)为碳源,采用浸渍填充纳米孔方法实现了一步制备一维碳纳米管(CNTs)/碳纳米棒(CNRs)混合纳米碳材料。考察模板剂(HNTs)和碳源(PVA)之间的比例关系对混合纳米碳材料的结构影响,利用XRD、FTIR、Raman、N2吸附-脱附测试、TEM、SEM以及电阻率和分散性等表征手段分析混合纳米碳材料的结构变化。结果发现,PVA填充含量的增加将导致产物中CNRs的质量分数增加;当PVA和HNTs质量之比为1∶1时,所制备的CNTs/CNRs的孔体积达到最大值2.142 cm~3·g-1,比表面积达到583 m~2·g-1,并且表现出较好的电导率和分散性,表明低的PVA填充比例制备的混合碳材料中CNTs含量较高。     

二氧化碳与低碳经济发展

由于二氧化碳无色无味,又存在于大气中,因此它在植物生长中的重要性被人类忽略了。其实二氧化碳是光合作用的反应物,是植物生长的重要原料;又是一种新型绿色肥料。人类应该着力开发以二氧化碳为原料的新型肥料发展低碳经济。     

Ni/γ-Al2O3催化剂上CH4-CO2重整体系中积碳-消碳的研究

用动态热重技术和色谱技术联用以及XRD和TEM等表征手段,研究了Ni/γ-Al     

Carbon clusters

Some of the most significant discoveries and achievements concerning the mass spectra and gas phase ion chemistry of carbon clusters are reviewed. These include (1) nanosecond and femtosecond laser ionizations; (2) ion structures through ion/molecule reactions, ion chromatography, and computational methods; (3) carbon cluster cooling through radiative decay, dissociative decay, and thermionic emission; (4) mechanisms and energetics of fragmentation reactions; (5) endohedral fullerenes including recent data on ion beam implantation, and (6) ion chemistry as a function of the fullerene charge state.     

Palladium-Catalyzed Addition of Carbon Monoxide and Carbon Tetrachloride to 1-Octene in Supercritical Carbon Dioxide

The Pd-catalyzed addition of carbon monoxide and carbon tetrachloride to 1-octene gave coadduct [alkyl 2-( 2, 2, 2-trichloroethyl)octanoate] as the major product in supercritical carbon dioxide by using pyridine as the base. It was found that the selectivity and the yield of coadduct were greatly affected by the pressure of carbon dioxide, the reaction temperature and the amounts of alcohol and base used.     

碳纳米管含量对炭炭复合材料组织及力学性能的影响

炭纤维上原位合成了均匀生长且具有伸张形貌的碳纳米管,借助化学气相渗透制备了碳纳米管增强的炭炭复合材料,研究了不同含量的碳纳米管对炭炭复合材料组织和力学性能的影响。结果表明：炭纤维上生长碳纳米管改变了热解炭的沉积行为,诱导了各向同性热解炭的生成,且随着碳纳米管含量的增加,各向同性热解炭的厚度增加,但是复合材料的d002值却明显降低。微量的碳纳米管即可显著提高复合材料的力学强度,随着其含量的增加,复合材料的力学强度和模量迅速提高,但材料的断裂行为却急剧恶化,断裂模式由最初的假塑性断裂转变为脆性断裂。