洋葱碳的制备与应用研究进展

洋葱碳独特的结构, 使其具有优异的物理化学性能。本文首先介绍了洋葱碳的分类和结构, 对几种传统的制备方法(包括电弧放电法、等离子体、电子束辐射、化学气相沉积、纳米金刚石真空退火、热解法)的优缺点进行归纳、总结。其次, 介绍了近年来发展起来的制备方法。随后,对近年来洋葱碳在锂离子二次电池负极、染料敏化太阳能电池对电极、电化学储氢电极、超级电容器电极、摩擦和磨损、催化领域的应用做一概述。最后, 指出了目前洋葱碳在制备和应用方面的不足, 对今后的研究做了展望。     

重油残渣基新型碳功能材料的研究进展

综述了以重油残渣为原料,采用化学气相沉积法、共炭化法和微波等离子体法可控制备气相生长碳纤维、碳微球、内包铁洋葱状富勒烯、纳米碳管、内包金属碳微米颗粒及定向碳纳米薄膜等各种高附加值碳材料;采用等离子体氧化法、酸处理法、化学还原法等方法对气相生长碳纤维和碳微球进行表面修饰,在产物表面引入含氧官能团,解决了可溶性碳材料的制备问题;在碳微球表面引入Pt纳米颗粒,使重油残渣基新型碳材料在表面修饰和功能化后可望成为性能优异的吸附和催化材料.     

纳米洋葱碳的制备及其纯化研究

以甲烷为碳源,316号不锈钢网为催化剂,800℃下催化裂解甲烷,采用化学气相沉积法制备平均粒径为70~100nm纳米洋葱碳,通过酸洗-低温煅烧-磁选方法对洋葱碳进行纯化处理。X射线衍射、扫描电子显微镜、透射电子显微镜、红外吸收光谱、拉曼光谱和振动样品磁强计对样品的形貌结构、物相组成及磁性能进行表征分析。结果表明,酸洗-低温煅烧能有效去除初产物中裸露的催化剂颗粒及无定型碳,磁选则实现将内包有[Fe-Ni]磁性催化剂的洋葱碳与空心的洋葱碳分离,最终获得纯净的空心纳米洋葱碳。     

金属对炭黑转化为洋葱状中空结构纳米碳的影响

研究了炭黑分别在 Fe、Co、Ni 三种金属化合物作用下的催化转化行为, 以期使炭黑质点中不连续的无规则小石墨片层重新组装、构筑成洋葱状中空结构纳米碳. 采用透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)和Raman光谱分析表征了炭黑及其催化炭化产物的微观形貌和结构. 结果表明: 尽管三种金属催化剂均可通过溶碳-析出机制形成过渡态碳包覆纳米金属颗粒, 继而构筑成由准球形同心石墨壳层组合的洋葱状中空结构纳米碳, 但三种金属催化剂显示不同的催化效果, 终碳产物的形态和纯度差异较大, 其中以Fe 的催化效果最好.     

洋葱状炭纳米粒子的无催化剂合成(英文)

描述了基于NaN3-C6Cl6混合物热解一步合成洋葱状碳纳米粒子的方法。应用EMS,XRD,Ramans研究了缓冲气体(Ar或空气)对炭产物的得率、形貌和结构的影响。产物包含洋葱炭、非晶碳和NaCl,通过简单的纯化处理即可完全除去副产物。洋葱状炭纳米粒子的形成由热解过程中压力迅速增加产生的震动波诱导苯基活性分子合并所制。     

水中电弧法制备碳纳米葱

采用水介质中石墨电极直流电弧放电法大量制备了高质量碳纳米葱（又称洋葱状富勒稀），借助Raman光谱仪和高分辨透射电镜（HRTEM）对制备产物进行了结构表征和几何形貌分析。实验结果表明：水介质中石墨电弧法制备的碳纳米产物主要聚集在水面附近和容器底部，放电电流大小对水面附近和容器底部产物的组成和形貌有显著影响。在放电电流约为40A时，水面附近产物是直径为5nm～20nm的球形、洋葱状碳纳米葱。其产率约4．3mg／min。研究结果表明：采用水介质中石墨电弧法能大量制备高质量的碳纳米葱。     

碳纳米纤维的制备及其复合材料在军工领域的应用

碳纳米纤维作为一种新型的碳材料，具有优异的物理、力学性能和化学稳定性。详细介绍了碳纳米纤维的主要制备方法，包括基体法、喷淋法、气相流动催化法及静电纺丝法等，并比较了各种制备方法的优缺点，阐述了碳纳米纤维复合材料在军工领域的应用，展望了碳纳米纤维及其复合材料的制备工艺及应用领域。     

水或液氮中电弧放电制备炭纳米材料

利用特制的电弧放电装置，研究了水或液氮中碳电弧放电形成炭纳米材料的机理。借助高分辨率透射电子显微镜对电弧放电生成的产物进行了观察和分析。结果表明：在水或液氮中碳电弧放电可以生成多壁碳纳米管和碳纳米洋葱结构，液氮中碳电弧放电可以生成单壁碳纳米角，水中钴催化碳电弧放电可以生成碳包裹的纳米钴颗粒。横向低频交变磁场会影响碳纳米材料的形核过程，并且可以推测磁场交变的频率5Hz与纳米管、纳米洋葱等结构的生长周期存在某种拟合。根据实验现象，提出了一种解释液体中碳电弧放电过程纳米材料生成的理论模型。     

纳米碳颗粒在催化中的应用及前景

概述了多壁富勒烯和新型纳米碳结构(纳米碳球)的表面修饰方法以及在催化中的应用研究现状,结果表明,化学氧化法对纳米碳颗粒进行表面修饰是有效的方法,可以改善其惰性表面,使其功能化.由于结构的独特性,纳米碳颗粒作为载体材料在电催化和某些脱氢反应中已经显示了较好的催化性能.预测了纳米碳在合成低碳烯烃中的潜在应用前景并为其在能源、化工领域中的应用提供了新的思路.     

氮掺杂洋葱状纳米碳球的制备与表征

以碳化钙和谷氨酸为原料,通过反应釜一步法在300℃下制备氮掺杂洋葱状纳米碳球,并改变反应物量来调控碳球的尺寸和结晶度。采用扫描电子显微镜、透射电子显微镜、X射线衍射仪、拉曼光谱仪、比表面积测试仪、X射线光电子能谱仪和元素分析仪对所得产物进行表征。结果表明,采用反应釜法能够成功掺杂氮原子进入碳原子晶格中。改变反应物摩尔量能够得到不同形貌的碳球,当碳化钙与谷氨酸的反应物摩尔比为3∶1时,得到尺寸为30～50 nm的洋葱状碳球;增加谷氨酸的摩尔量易于得到直径为60～100 nm的实心无定形纳米碳球;而增加碳化钙的摩尔量,同样得到洋葱状碳球,但结晶程度提升。反应过程中,谷氨酸不仅能够作为反应的引发剂,还能作为氮源和碳源,其热解形成的五元环化合物在碳球形成的过程中起到重要作用,为弯曲石墨片层的形成提供曲率,有利于洋葱状结构的形成。     

Flame synthesis of carbon nano onions using liquefied petroleum gas without catalyst

Densely agglomerated, high specific surface area carbon nano onions with diameter of 30–40 nm have been synthesized. Liquefied petroleum gas and air mixtures produced carbon nano onions in diffusion flames without catalyst. The optimized oxidant to fuel ratio which produces carbon nano onions has been found to be 0.1 slpm/slpm. The experiment yielded 70% pure carbon nano onions with a rate of 5 g/h. X-ray diffraction, high-resolution electron microscopy and Raman spectrum reveal the densely packed sp² hybridized carbon with (002) semi-crystalline hexagonal graphite reflection. The carbon nano onions are thermally stable up to 600 °C.     

Functionalization of Carbon Nanoparticles Modulates Inflammatory Cell Recruitment and NLRP3 Inflammasome Activation

The inflammatory effects of carbon nanoparticles (NPs) are highly disputed. Here it is demonstrated that endotoxin‐free preparations of raw carbon nanotubes (CNTs) are very limited in their capacity to promote inflammatory responses in vitro, as well as in vivo. Upon purification and selective oxidation of raw CNTs, a higher dispersibility is achieved in physiological solutions, but this process also enhances their inflammatory activity. In synergy with toll‐like receptor (TLR) ligands, CNTs promote NLRP3 inflammasome activation and it is shown for the first time that this property extends to spherical carbon nano‐onions (CNOs) of 6 nm in size. In contrast, the benzoic acid functionalization of purified CNTs and CNOs leads to significantly attenuated inflammatory properties. This is evidenced by a reduced secretion of the inflammatory cytokine IL‐1β, and a pronounced decrease in the recruitment of neutrophils and monocytes following injection into mice. Collectively, these results reveal that the inflammatory properties of carbon NPs are highly dependent on their physicochemical characteristics and crucially, that chemical surface functionalization allows significant moderation of these properties.     

Detonation-assisted self-assembly synthesis of carbon onions using organics with long carbon chain

The detonation of mixtures of organics with long carbon chains and explosives has been found to yield carbon onions without use of any catalyst. Octadecanoic acid, hexadecylic acid, behenic acid and CTAB (cetyltrimethylammonium bromide) have been used as raw materials. The recovered products were characterized using various techniques such as scanning electron microscope, transmission electron microscope, Raman spectroscopy, infrared spectroscopy and X-ray diffraction. The prepared carbon onions consist of concentric-shell graphitic layers with a narrow size distribution of 60 to 70 nm, which aggregated to form a chain-like structure. Formation mechanism of the carbon onions was proposed as that the organics with long chains broke their functional groups and self-assembled into carbon onions due to low free energy.     

纳米吸波材料的研究进展

介绍了纳米吸波材料的吸波原理。叙述了碳纳米管、纳米金属与合金、纳米陶瓷、纳米氧化物、纳米导电高分子几类吸波材料的特点和应用情况。比较了各种吸波材料的优缺点,对吸波材料的研究前景进行了展望。     

The effect of catalyst evolution at various temperatures on carbon nanostructures formed by chemical vapor deposition

Solid carbon nanofibers (CNFs), hollow CNFs, metal-filled carbon nanotubes (CNTs), and carbon onions were synthesized by chemical vapor deposition (CVD) using a novel Ni/Y catalyst supported on Cu at different reaction temperatures. XRD, TEM, and EDS analyses reveal that the structure of the catalyst changes with increasing reaction temperature. The evolution of Y doped in Ni directly influences the morphologies of the products. At relatively low temperature, Y is doped in Ni and causes CNF formation, and when the temperature is increased to above 650 °C, Y separates from Ni as yttria nanoparticles and carbon onions are synthesized. The catalyst evolution and carbon nanostructure growth mechanism are discussed in detail.     

分枝碳纳米管的制备及生长机理

分枝碳纳米管在微纳电子器件等领域具有十分广阔的应用前景。介绍了分枝碳纳米管的各种制备方法,探讨了分枝碳纳米管的不同生长机理,重点分析了影响分枝碳纳米管的形成及分叉的因素,对分枝碳纳米管的制备具有重要的指导意义。     

In situ observation of quasimelting of diamond and reversible graphite-diamond phase transformations

Because of technique difficulties in achieving the extreme high-pressure and high-temperature (HPHT) simultaneously, direct observation of the structures of carbon at extreme HPHT conditions has not been possible. Banhart and Ajayan discovered remarkably that carbon onions can act as nanoscopic pressure cells to generate high pressures. By heating carbon onions to approximately 700 degrees C and under electron beam irradiation, the graphite-to-diamond transformation was observed in situ by transmission electron microscopy (TEM). However, the highest achievable temperature in a TEM heating holder is less than 1000 degrees C. Here we report that, by using carbon nanotubes as heaters and carbon onions as high-pressure cells, temperatures higher than 2000 degrees C and pressures higher than 40 GPa were achieved simultaneously in carbon onions. At such HPHT conditions and facilitated by electron beam irradiation, the diamond formed in the carbon onion cores frequently changed its shape, size, orientation, and internal structure and moved like a fluid, implying that it was in a quasimelting state. The fluctuation between the solid phase of diamond and the fluid/amorphous phase of diamond-like carbon, and the changes of the shape, size, and orientation of the solid diamond, were attributed to the dynamic crystallization of diamond crystal from the quasimolten state and the dynamic graphite-diamond phase transformations. Our discovery offers unprecedented opportunities to studying the nanostructures of carbon at extreme conditions in situ and at an atomic scale.     

Review of nanocarbon-engineered multifunctional cementitious composites

As structural materials, cementitious materials are quasi-brittle and susceptible to cracking, and have no functional properties. Nanotechnology is introduced into cementitious materials to address these issues. Nano materials, especially nano carbon materials (NCMs) were found to be able to improve/modify the mechanical property, durability and functional properties of cementitious materials due to their excellent intrinsic properties and composite effects. Here, this review focuses on the recent progress of fabrication, properties, and structural applications of high-performance and multifunctional cementitious composites with NCMs including carbon nanofibers, carbon nanotubes and nano graphite platelets. The improvement/modification mechanisms of these NCMs to composites are also discussed.     

A new technique for fullerene onion formation

We present an original technique for growing large fullerene onions: carbon-ion implantation at high temperature into copper substrates. Used for carbon film growth (diamond or turbostratic carbon), this method is based on the immiscibility of carbon into copper and can produce an important density of giant carbon onions with size up to some micrometres which is the largest size observed up to now. We characterize these giant fullerenes by TEM, HRTEM and for the first time with AFM. On the basis of both experimental and numerical results we propose a mechanism of formation of the carbon onions during the implantation process.