电泳沉积CNTs掺杂C/C复合材料的微观组织与弯曲性能

采用电泳沉积(EPD)在1k碳布表面均匀加载了碳纳米管(CNTs), 借助化学气相沉积(CVD)致密化碳布叠层预制体, 制备了EPD CNTs掺杂的二维(2D)碳/碳(C/C)复合材料。研究了EPD CNTs对2D C/C复合材料致密化过程、微观组织和弯曲性能的影响。研究结果表明: EPD CNTs在碳纤维表面呈现平面内高密度、杂乱取向分布特征, 该形貌CNTs降低了热解炭在碳纤维预制体内的沉积速率, 诱导了高石墨微晶堆垛高度(L_c)、低(002)晶面面内方向上的沉积有序度(L_a)热解炭的形成; EPD CNTs的掺杂可提高C/C复合材料的弯曲强度和模量: 当CNTs含量为0.74wt%时, 复合材料弯曲强度和模量可达150.83 MPa和23.44 GPa, 比纯C/C复合材料提高了31.4%和13.9%; 继续提高CNTs含量, 复合材料弯曲强度降低, 这与过高含量EPD CNTs导致复合材料密度降低有关; 同时, EPD CNTs的掺杂使得C/C复合材料断裂模式由脆性断裂转变为假塑性断裂, 复合材料断裂塑性的提高是由于EPD CNTs造成的碳基体结构的变化以及碳纤维的大量拔出。     

机磨热加工法合成碳纳米管

机磨热加工法是批量制取碳纳米管(CNTs)的方法之一.在氩气氛中研磨鳞片石墨为无定形的纳米炭粉,而后在1350℃～1380℃下退火获得碳纳米管(CNTs).用XRD,SEM,FE-TEM,HRTEM和拉曼光谱对纳米炭粉及CNTs进行表征.发现:CNTs具有不同的形貌,长度约几毫米,直径为30nm～70nm.螺旋状多壁碳纳米管有高的长径比(～1000)和高的结晶度(ID/IG:～0.03).     

碳纳米管"种子"上生长碳纳米管和氮掺杂碳纳米管

以碳纳米管(CNTs)作"种子",液体石蜡和三聚氰胺分别作碳源和碳/氮源,利用爆炸辅助化学气相沉积法在CNTs"种子"上合成出新的CNTs和氮掺杂碳纳米管(CNx).透射电镜(TEM)和电子能量损失谱(EELS)测试表明:新合成的CNTs具有空心管状结构,而CNx呈竹节状且氮的原子分数高达17.3%.CNTs"种子"的作用归因于其端部的纳米级弯曲和开放性边缘具有吸附并外延Cn/CN物种的功能.     

碳纤维上原位生长碳纳米管对C/C复合材料弯曲性能的影响

以碳毡为基底原位生长了碳纳米管（CNTs）,借助化学气相渗透制备了CNTs-C/C复合材料。研究了催化剂含量对碳纳米管生长的影响以及不同含量碳纳米管对C/C复合材料弯曲性能的影响。结果表明：催化剂对CNTs产量影响较大,且含量越多,生成的CNTs量越大;原位生长CNTs引入的催化剂会导致CNTs-C/C复合材料弯曲性能变差;CNTs的加入改变了热解碳的沉积行为,诱导了球状和锥状小尺寸热解碳的形成,减少了微裂纹的出现。适量CNTs能提高C/C复合材料的弯曲强度和模量,并改善材料的断裂行为。     

纳米碳管增强炭/炭复合材料的研究进展

纳米碳管(CNTs)具有独特的结构、优异的力学性能、热稳定性与传导性能,是炭/炭(C/C)复合材料理想的增强体.综述了纳米碳管增强炭/炭(CNTs/C/C)复合材料的制备方法,讨论了该复合材料的微观结构、摩擦学性能和传导性能,并展望了CNTs/C/C复合材料的潜在应用和发展趋势.     

含碳纳米管导电剂改善Li_4Ti_5O_(12)电极电化学性能

采用一种较为实用的调浆方法,考察了碳纳米管与乙炔黑的复合物(CNTs/AB)导电剂、乙炔黑(AB)导电剂和碳纳米管(CNTs)导电剂对Li_4Ti_5O_(12)电化学性能的影响,并用恒流充放电、扫描电子显微镜(SEM)和交流阻抗(AC)对添加上述3种导电剂制备得到的电极片进行研究.结果表明,采用该调浆流程能够克服CNTs在使用时出现的团聚问题,CNTs/AB复合物在改善Li_4Ti_5O_(12)电化学性能尤其在容量发挥和倍率性能方面比单一AB和CNTs具有明显优势.CNTs/AB复合物中两者的质量百分比为1:2～1:1时,0.5C时,Li_4Ti_5O_(12)电极的首次放电容量可高达157.0mAh/g,10.0C时,其放电容量可达到128.3mAh/g.与单一导电剂AB和CNTs相比,CNTs与AB复合使用时,由于CNTs的高长径比和良好导电性能使之能够起到"桥梁"作用把部分没有与活性物质充分接触的颗粒状导电剂AB与活性物质连接起来,因此两者的有机结合提高了CNTs/AB与活性材料的接触面积,使电极片能够形成有效的导电网络,有利于Li_4Ti_5O_(12)导电性能的提高.     

电化学法聚吡咯/碳纳米管复合膜的制备与表征

以对甲苯磺酸(PTSA)为掺杂剂、碳纳米管(CNTs)为增强相通过电化学恒电位法在不锈钢电极表面合成聚吡咯/碳纳米管(PPy/CNTs)复合膜.采用扫描电镜(SEM)和四探针测试仪对PPy/CNTs膜的微现形貌和电导率进行表征.通过交流阻抗谱(EIS)、循环伏安法(CV)研究了PPy/CNTs膜的电化学行为.系统研究了...     

合成温度对Li2FeSiO4／C电化学性能的影响

采用球磨掺碳及固相法合成锂离子电池正极材料Li2FeSiO4/C,研究了合成温度对材料结构和电化学性能的影响.用X射线衍射(XRD)、扫描电镜(SEM)对材料的结构与形貌进行了表征;并对不同焙烧温度下合成的Li2FeSiO4/C材料的电化学性能进行了研究.结果表明,650℃合成的Li:FeSiO4/C电化学性能最佳,在C/16的倍率下首次放电容量达到144.8mAh/g,10次循环后容量仍保持有136.5mAh/g.     

T6热处理对1.0%CNTs@TiO2/2024复合材料腐蚀性能研究

目的 研究T6热处理对1.0％CNTs@TiO2/2024(CNTs质量分数为1.0％)微观组织和腐蚀性能的影响,以期提高2024复合材料的耐腐蚀性能.方法 通过熔铸法制备CNTs质量分数为1.0％的CNTs@TiO2/2024复合材料,并研究了T6热处理(495℃,2 h+180℃,4～16 h)对CNTs质量分数为1.0％的CNTs@TiO2/2024复合材料微观组织和腐蚀性能的影响.结果 经固溶处理(495℃,2 h),S相(Al2CuMg)和θ相(Al2Cu)基本融入基体中;在时效处理(180℃,12 h)后,S相和θ相均匀析出.当加入CNTs质量分数为1.0％的CNTs后,与2024合金相比,复合材料的腐蚀电流密度大幅度增加了77.4％.与2024合金相比,T6态复合材料的腐蚀电位增加了4.4％,腐蚀电流密度下降了80.9％.结论 CNTs的加入会降低2024合金耐腐蚀性能,但是合适的T6处理工艺能够很好地提升其耐腐蚀性能,有效拓宽该系复合材料的应用领域.     

SiC/CNTs纳米复合材料吸波性能的研究

采用聚碳硅烷前驱体转化法制备了SiC/CNTs纳米复合材料, 采用扫描电子显微镜、透射电子显微镜、高分辨电子显微镜对样品进行了微观结构分析, 并测试了材料在2～18GHz频率范围内的电磁参数. 结果表明, 当初始聚碳硅烷/二甲苯溶液浓度为10%～15%时, 聚碳硅烷前驱体转化法在CNTs表面可以制备SiC包覆层均匀致密的复合一维纳米材料. SiC包覆CNTs一维纳米材料的电磁参数测试表明, 其损耗机制以介电损耗为主, 当聚碳硅烷含量为15%时, SiC/CNTs纳米复合材料具有最高的介电常数和损耗角, 较好的电磁波吸收特性, 并表现出复合效应.     

MgO载体化学气相沉积法制备碳纳米管的影响因素

用MgO载体化学气相沉积(CVD)技术制备了碳纳米管(CNTs).并用扫描电镜(SEM)、高分辨透射电镜(HRTEM)和微区拉曼光谱仪研究分析了各种沉积条件下CNTs的形貌结构.对CVD法制备CNTs的主要影响因素如碳源气体种类、沉积温度和Fe催化颗粒在MgO载体中的百分含量进行了分析讨论.     

乙酰丙酮铁为催化剂源在碳纤维表面生长碳纳米管的工艺研究

以乙酰丙酮铁为催化剂源,三甘醇为溶剂,通过溶剂热法在碳纤维表面负载催化剂前驱体,在H2与N2中一定温度下进行还原,采用化学气相沉积法在碳纤维表面生长碳纳米管。研究了催化剂的负载条件和碳纳米管的生长条件,采用XRD、FTIR、RAMAN对乙酰丙酮铁在三甘醇中反应在碳纤维表面负载催化剂前驱体产物进行分析,用SEM、TEM对催化剂前驱体粒子及碳纳米管的形貌进行表征。结果表明:催化剂前驱体为粒径30nm左右的Fe3O4颗粒,当催化剂的还原温度为415℃、还原时间为60min时,Fe3O4颗粒还原成纳米Fe颗粒;当碳纳米管的生长温度为750℃、生长时间为30min、气流体积比为V(N2)∶V(H2)∶V(C2H2)=50∶10∶10时能在碳纤维表面生长出形貌均一、管径为30~60nm的碳纳米管。     

Growth of metal-free carbon nanotubes on glass substrate with an amorphous carbon catalyst layer

We have investigated the direct growth of metal-free carbon nanotubes (CNTs) on glass substrates with microwave-plasma enhanced chemical vapor deposition (MPECVD). Amorphous carbon (a-C) films were used as a catalyst layer to grow metal-free CNTs. The a-C films were deposited on Corning glass substrates using RF magnetron sputtering with the use of a carbon target (99.99%) at room temperature. They were pretreated with hydrogen plasma using a microwave PECVD at 600 degrees C. Then, CNTs were prepared using microwave PECVD with a mixture of methane (CH4) and hydrogen (H2) gases. The CNTs were grown at different substrate temperatures (400 degrees C, 500 degrees C, and 600 degrees C) for 30 minutes. Other conditions were fixed. The growth trends of CNTs against substrate temperature were observed by field emission scanning electron microscopy (FE-SEM). The structure of a-C catalyst layer and grown CNTs were measured by Raman spectroscopy. High-resolution transmission electron microscopy (HR-TEM) images showed that the CNTs had bamboo-like multi-walled structures. Energy dispersive spectroscopy (EDS) measurements confirmed that the CNTs consisted of only carbon.     

沉积条件对碳纤维表面碳纳米管生长的影响

采用化学气相沉积(CVD)法在碳纤维(CF)表面原位生长碳纳米管(CNTs)。考察了不同催化剂、沉积温度、氢气流量以及样品距进气口距离等工艺参数对CNTs-CF生长的影响。利用SEM和高分辨透射电子显微镜(HRTEM)对CNTs-CF形貌和微结构进行了表征和分析。结果表明:在CF表面原位生长的CNTs为多壁结构,其中以Ni为催化剂得到的CNTs直径小、分布均匀;在600~750℃温度范围内,随着温度的升高,CNTs直径和长度减小,产量降低;随着氢气流量的增加,CNTs直径和长度均增加;距进气口30cm,在CF表面得到的CNTs覆盖率高、直径小且分布窄,有利于制备高质量CNTs。     

化学气相沉积法合成碳纳米管及其导电性能研究

以二甲硫醚为碳源前驱体,Co/MgO为催化剂,采用化学气相沉积法生长出碳纳米管及Y形碳纳米管,此法稳定性及重现性较好.通过扫描电子显微镜、透射电子显微镜、拉曼光谱及X射线衍射对产品形态和结构进行了分析和表征,结果表明,所制备的碳纳米管形态较规整、纯度较高,具有较好的石墨微晶结构;导电性能测试结果显示,Y形碳纳米管各分支均呈现出典型的金属性导电性能.     

工业级原料制备碳纳米管的研究

为降低碳纳米管批量制备的原料成本,以焦化苯和二茂铁为主要原料(工业级),采用浮游催化热解法制备碳纳米管,用TEM、SEM、Raman、XRD等对产物的形貌和结构进行观察和表征,着重讨论了二茂铁的分解温度和苯的挥发温度对碳纳米管的制备及其形貌的影响,并对其影响机理进行了分析.研究表明:在噻吩体积分数为0.55 mL/100 mL苯、炉膛反应温度为1170℃的前提下,当二茂铁的分解温度为150℃、苯的挥发温度为50℃时,用工业级原料完全可以制备出碳纳米管,此时,碳纳米管的内径分布在0.88~1.15 nm.     

环己烷浮游催化法在碳纤维表面生长碳纳米管

以环己烷为碳源、二茂铁为催化剂前躯,采用浮游催化法成功的在碳纤维表面生长了碳纳米管(CNT),制备了多尺度杂化材料CNTs/CF。实验重点考察了反应温度、二茂铁浓度、载气等参数对CNT在纤维表面生长的影响,通过扫描电镜(SEM)、投射电镜(TEM)研究了CNTs/CF的形貌及产物CNT的微观结构。当固定反应温度为820℃、二茂铁-环己烷浓度为2g/100mL时,随着氢气在载气中含量在0～100%范围内变化,产物CNT直径亦有86nm降低至39nm。通过单丝拉伸测试发现,相比初始碳纤维,不同长度的CNTs/CF单纤维强度下降幅度均在10%以内。     

Low Temperature Growth of Vertically Aligned Carbon Nanotubes via Floating Catalyst Chemical Vapor Deposition Method

Synthesis of carbon nanotubes (CNTs) below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups.However,the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced.In this work,the effects of varying the preheating temperature on the synthesis of CNT were investigated.The reaction temperature was set at 570℃.The preheating set temperature was varied from 150 to 400℃ at 50℃ interval.Three O-ring shape heating mantels were used as heating source for the preheater.In situ monitoring device was used to observe the temperature profile in the reactor.Benzene and ferrocene were used as the carbon source and catalyst precursor,respectively.Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃.When the preheating temperature was increased up to 400℃,both the length and the alignment of CNTs produced were improved.     

Carbon dioxide as a carbon source for synthesis of carbon nanotubes by chemical vapor deposition

Carbon dioxide was successfully used as carbon source in the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) over Fe/CaO catalyst. The product was evaluated using both transmission electron microscopy (TEM) and Raman spectroscopy. Crooked and branching structures of multi-walled carbon nanotubes (MCNTs) with diameters of around 50 nm were observed on the TEM micrographs. Raman spectrum results show that the nanotubes have small defects, which is in agreement with the results of TEM. The influence of reaction variable such as furnace temperature and types of support media was also studied and the reaction mechanism was then discussed in this paper.     

Alternative Synthesis Method for Carbon Nanotubes

It is demonstrated that carbon nanotubes (CNTs) can be synthetized on the surface of an example carbon background, activated carbon, using the thermal conversion of poly(furfuryl alcohol) (PFA). This newly discovered CNTs synthesis method is an alternative solution to previously known methods, e.g., chemical vapor deposition, arc discharge, and laser ablation. Scanning electron microscopy and high‐resolution transmission electron microscopy images deliver direct evidence of CNT formation through the thermal degradation of PFA in a temperature range of 500–700 °C. The discovered process consists of the free growth of CNTs from PFA without any mechanical patterning, casting, or molding. CNTs obtained in this manner resemble MWCNTs in size, though according to microscopic investigation the tubes do not possess the well‐developed layered structure of MWCNTs. Nonetheless, X‐ray photoelectron spectroscopy and Raman spectroscopy studies fully confirm that carbon (C) is the main elemental constituent of the tubes (C atomic content above 85%) and C atoms are structured in a manner typical of defected CNTs (D, G, and G' intensity ratios).