多元功能化碳纳米管改性聚酰亚胺复合薄膜的分散性及电性能研究

用混酸、Fenton试剂和硅烷偶联剂KH-550对多壁碳纳米管(MWNTs)进行功能化改性,通过原位聚合法制备一系列聚酰亚胺(PI)/MWNTs复合薄膜。对MWNTs功能化前后官能团变化及在PI基体中的分散情况和复合薄膜的电性能进行测试和表征。结果表明:MWNTs经多元功能化修饰后在PI基体中的分散性相比单一功能化MWNTs有了显著提高;单一功能化MWNTs的引入使复合薄膜的介电常数和介电损耗增加,介电强度降低;引入多元功能化MWNTs使复合薄膜的介电常数进一步提高,但介电损耗增加及介电强度下降的幅度减小了。     

耐高温聚间苯二甲酰间苯二胺介电复合材料的制备及性能

采用水热法以二氧化钛(TiO2)纳米粒子为原料合成了高长径比钛酸钡纳米线((BaTiO3 nanowires(BTN));为了改善BTN与聚合物基体的相容性并保持BTN完整的化学结构,选择聚乙烯吡咯烷酮(PVP)作为改性剂,通过物理吸附作用将其包裹在BTN表面形成P-BTN纳米线;随后将P-BTN作为高介电常数填料加入到聚间苯二甲酰间苯二胺(PMIA)基体中制备出耐高温的PMIA介电复合材料.研究了P-BTN含量对PMIA复合材料介电性能、击穿强度的影响以及高温下P-BTN/PMIA复合材料介电性能的变化.结果表明:BTN经过PVP表面改性后,在P-BTN含量较高时依然可以均匀地分散在PMIA基体中,且与PMIA基体具有良好的相容性;随着P-BTN含量的增加,PMIA复合材料的介电常数提升明显;100 Hz时,含有15％(质量分数)P-BTN的PMIA复合材料的介电常数提升至18.5,相较于纯PMIA增加了7.4倍,同时介电损耗依然较低;在高温环境中(150～250℃),P-BTN/PMIA复合材料的介电性能稳定,没有出现明显波动,满足高温环境对材料介电性能的使用要求;此外,低含量P-BTN还可以改善PMIA介电复合材料的击穿强度,适用于更高电场强度环境中.     

载银多壁碳纳米管抗菌剂结构与性能的研究

以多壁碳纳米管(MWNTs)为载体,通过化学吸附的方法制备载银多壁碳纳米管(Ag/MWNTs)抗菌剂.用SEM、TEM、FT-IR、XRD对其表观形貌、结构进行了表征.结果表明,银离子(Ag+)被吸附到MWNTs的表面,通过抑菌环实验表明,Ag/MWNTs对大肠杆菌和金黄色葡萄球菌都有很好的抗菌效果.     

四嗪改性碳纳米管环氧摩擦材料的研究

利用Diles-Alder反应,采用3,6-二氨基-1,2,4,5-四嗪对碳纳米管(CNTs)改性处理,考察了改性处理对碳纳米管表面结构、分散程度以及对环氧复合材料性能的影响,通过扫描电镜(SEM)、红外光谱(FTIR)Raman)分析了材料表面磨损形貌、多壁碳纳米管(MWNTs)分散程度以及碳纳米管结构变化,并探讨复合材料摩擦磨损机理、四嗪与碳纳米管反应机理.结果表明,通过四嗪化合物处理碳纳米管后,碳管表面连接活性基团氨基,结构形态发生改变,提高碳纳米管在基体中分散性和复合材料摩擦性能,8h处理MWNTs/EP比未处理MWNTs/EP复合材料摩擦系数降低6.5%,磨耗率降低71.4%.     

碳纳米管的分散性研究及其对复合电纺纤维的影响

将多壁碳纳米管(MWNTs)在硝酸中回流纯化,使用不同类型的表面活性剂将纯化后的MWNTs功能化分散,再将其加入到聚乙烯醇(PVA)和聚氧化乙烯(PEO)物理共混纺丝溶液中进行静电纺丝。利用扫描电子显微镜(SEM)、红外光谱仪(IR)、X衍射射线仪(XRD)和分光光度计等对纯化和功能化分散的MWNTs以及得到的超细纤维进行表征。结果表明,通过硝酸回流纯化处理,MWNTs的杂质被去除,晶格结构变得更加完整。在超声波作用下,十二烷基硫酸钠使纯化后的MWNTs在水溶液中具有较好的分散稳定性。进行功能化分散的MWNTs的加入使静电纺超细纤维的平均直径减小。     

低温等离子体改性碳纳米管对再生沥青性能的影响

本研究工作利用低温等离子体处理多壁碳纳米管(MWNTs),设计开发了低温等离子体改性MWNTs复合再生剂,并以此对老化沥青进行再生处理。通过XPS和SEM对低温等离子体改性MWNTs的化学成分和分散性及其与基体的相容性进行分析,探讨了低温等离子体改性MWNTs的作用机制。利用FTIR和TG对再生沥青胶结料的组分、热稳定性和耐老化性进行研究。最后采用针入度、软化点、延度测试对沥青再生效果及综合性能进行了评估。结果表明:低温等离子体改性MWNTs能够在其表面引入大量的含氧官能团,有效解决了MWNTs与基质沥青存在的界面问题,提高了MWNTs的分散性及MWNTs与沥青基体的结合力,使再生沥青的力学性能大幅提高。同时,MWNTs能够吸附再生剂中的部分油分,起到缓释作用,较好地克服了传统再生剂由于油分快速流失所导致的胶结料迅速老化的问题。因此,该技术在提高再生胶结料综合性能的同时也有效地改善了其抗老化性能。     

多壁碳纳米管/聚亚苯基苯并二噁唑复合材料的微结构与性能

以甲基磺酸(MSA)为溶剂通过溶液共混法制备了不同多壁碳纳米管(MWNTs)含量的多壁碳纳米管/聚亚苯基苯并二噁唑(MWNTs/PBO)复合材料, 用扫描电镜(SEM)对热处理前后复合材料的微结构进行了分析, 并对其导电、力学和耐热性能进行了研究。结果表明: MWNTs能均匀地分散在聚合物基体中, 并能形成一定的网络结构, 热处理后的复合材料较热处理前的结构更致密, 导电性能和力学性能都有所改善, 其中MWNTs质量分数为10％的热处理后复合材料与纯PBO聚合物相比, 体积电阻率降低约9个数量级, 而拉伸强度和拉伸模量分别提高了95％和53％, 耐热性能也有一定的提高。      

利用笼形聚倍半硅氧烷增强多壁碳纳米管在水溶液中的分散性

以笼形聚倍半硅氧烷(POSS)为物理分散剂,利用POSS与多壁碳纳米管(MWNTs)间较强的相互作用,在水溶液中对MWNTs进行分散。借助紫外吸光度对POSS分散的MWNTs浓度和稳定性进行了表征,测定了分散液的Zeta电位和离心后上清液中固体物质的质量分数,并用透射电镜观察了POSS与MWNTs间的结合情况。结果表明,POSS可以显著提高MWNTs在水溶液中的分散性,且提高程度与其有机官能团R的结构有关。在所采用的五种POSS中,八异丁基笼形聚倍半硅氧烷(POSSC)的分散效果最好。在此基础上,优化得到POSSC分散MWNTs的最佳条件,即MWNTs浓度为30mg/L,POSSC和MWNTs的质量比为1。此时,POSSC可较好地吸附在MWNTs表面对其进行分散,得到具有良好稳定性的MWNTs水分散液。该分散方法简单高效且不破坏MWNTs的完整结构,所得分散液可用于复合材料的制备。     

多壁碳纳米管/聚苯乙烯-聚氯乙烯复合材料的导电特性

用溶液共混法制得了MWNTs/PS-PVC复合材料,进行了电导率的测试分析.通过对载流子浓度、迁 移率的测量以及电导活化能的计算等分析研究了影响MWNTs/PS-PVC复合材料电导率的因素和导电机制.结 果表明:当PS与PVC的质量比为1∶1时,MWNTs/PS-PVC复合材料的导电阈值最低;当MWNTs的质量分 数为1.5％,PS在PS-PVC基体中的质量分数为50％时,MWNTs/PS-PVC复合材料的电导率比MWNTs/PVC单一聚合物复合材料的提高了4个数量级.在导电网络的形成过程中,MWNTs/PS-PVC复合材料中形成的与无机化合物超晶格结构类似的n-i-p-i结构,降低了MWNTs/PS-PVC复合材料的电导活化能,增加了载流子浓度,使MWNTs/PS-PVC复合材料电导率显著提高.     

天然橡胶/炭黑/多壁碳纳米管复合材料的结构与性能研究

采用乳液混合共沉得到天然橡胶(NR)/多壁碳纳米管(MWNTs)母胶,母胶依次与硅烷偶联剂、天然橡胶、炭黑(CB)、硫磺等混炼、硫化得到NR/CB/MWNTs复合材料。MWNTs分散在十二烷基苯磺酸钠(SDBS)水溶液中,SDBS吸附在MWNTs表面使MWNTs稳定分散在水中。MWNTs悬浮液与NR乳液混合后,MWNTs随NR一起絮凝沉淀。为提高MWNTs与NR基体的界面粘结,母胶与偶联剂混炼后再与其他组分混炼。分散在母胶中的MWNTs与各混炼组分充分混合使MWNTs均匀分布于NR/CB/MWNTs复合材料中。MWNTs的均匀分散、MWNTs与NR的界面粘结以及MWNTs与CB的协同增强效应使NR/CB/MWNTs复合材料获得较高的力学性能、动态储能模量、玻璃化转变温度、导电性和导热性。     

Study on morphology and characterization of poly(mphenylene isophtalamide)/multi-walled carbon nanotubes composite nanofibers by electrospinning

Electrospinning technique is the main method of preparing polymer nanofiber simply, directly and continuously at present. In this work, electrospinning blend solution was prepared by in-situ polymerization using acid-modified multi-walled carbon nanotubes (MWNTs), m-phenylenediamine (MPD) and isophthaloyl chloride (IPC). And then composite nanofibers were prepared by electrospinning. MWNTs played an important role in nanofiber's properties. The effects of MWNTs on the morphology and characterization of the MWNTs/PMIA composite nanofibers were investigated. Scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), and X-ray diffraction (XRD) were utilized to characterize the MWNTs/PMIA nanofibers morphology and properties. The experimental results indicated that the nanofibers diameter decreased and solution dynamic viscosity increased with increasing MWNTs contents. XRD data demonstrated that PMIA composite nanofibers had the same crystal type as the pure PMIA nanofiber, and crystallinity was improved with increasing MWNTs loading. Transmission electron microscopy (TEM) was used to confirm MWNTs aligned along the axis of composite nanofibers.     

Biocompatibility and toxicological studies of carbon nanotubes doped with nitrogen

In this report, we compare the toxicological effects between pure carbon multiwalled nanotubes (MWNTs) and N-doped multiwalled carbon (CNx) nanotubes. Different doses of tubes were administered in various ways to mice: nasal, oral, intratracheal, and intraperitoneal. We have found that when MWNTs were injected into the mice's trachea, the mice could die by dyspnea depending on the MWNTs doses. However, CNx nanotubes never caused the death of any mouse. We always found that CNx nanotubes were far more tolerated by the mice when compared to MWNTs. Extremely high concentrations of CNx nanotubes administrated directly into the mice's trachea only induced granulomatous inflammatory responses. Importantly, all other routes of administration did not induce signs of distress or tissue changes on any treated mouse. We therefore believe that CNx nanotubes are less harmful than MWNTs or SWNTs and might be more advantageous for bioapplications.     

Synthesis and thermoelectric power of nitrogen-doped carbon nanotubes

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.     

酸处理碳纳米管/PBO复合材料的制备与表征

用原位聚合法成功地制备了碳纳米管/聚对苯撑苯并双口恶唑(PBO)复合材料。用FT-IR、XPS、SEM和AFM对碳纳米管和所制备的复合材料进行了表征,结果表明,碳纳米管的酸处理效果好,表面含有C-O、COOH等极性官能团;复合材料中碳纳米管在聚合物基体中分散均匀,两相界面间存在较强的作用力。     

Preparation, morphology and properties of acylchloride-grafted multiwall carbon nanotubes/fluorinated polyimide composites

A fluorinated polyimide (PI) was synthesized by a two-step reaction from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride and 2,2′-bis(trifluoromethyl)-4,4′diaminobiphenyl. A series of PI composites with various mass fractions of multi-walled carbon nanotubes (MWNTs) were prepared by either an in situ polymerization or blending process. To increase the chemical compatibility of carbon nanotubes with the PI matrix, MWNTs were treated with an acid mixture and sulfoxide chloride by turns. Results show that the dispersion of the MWNTs is highly improved in the PI by modification. The modified MWNTs are dispersed homogeneously in the matrix, while the structures of the PI and MWNTs are stable in the preparation process. The thermal stability of the nanocomposites is slightly lower than that of the pure PI. With incorporating MWNTs, the storage modulus and glass transition temperature of the composite films enhanced comparing to that of PI matrix. The dielectric constants of the composites increase sharply, which is favorable to their practical use in anti-static materials and embedded capacitors.     

Synthesis, Structure and Field Emission of Carbon Nanotubes

Multiwall and single-wall nanotubes were produced by carbon arc discharge in helium, and their structures were investigated by electron microscopy. Field emission from (1) as-grown multiwall nanotubes (MWNTs), (2) purified MWNTs and (3) purified single-wall nanotubes (SWNTs) was investigated by field emission microscopy. Of the three kinds of nanotubes studied, purified MWNTs whose tips are open provided the highest current at a fixed voltage. Although purified SWNTs provided the second highest current, SWNTs are not so robust as MWNTs against ion bombardment. As an application of nanotube field emitters, we manufactured cathode ray tube (CRT) lighting-elements by replacing conventional thermionic cathodes with nanotube field emitters. Stable electron emission, adequate luminance, and long life of the emitters were substantiated.     

NEXAFS study of multi-walled carbon nanotubes functionalization with sulfonated poly(ether ether ketone) chains

Functionalization of multi-walled carbon nanotubes (MWNTs) surface by sulfonated poly (ether ether ketone) SPEEK chains using a direct attachment reaction was investigated. A two step method was performed. MWNTs were oxidized by a nitric acid treatment to generate carboxyl groups on their surface. The grafting reaction of sulfonated groups of SPEEK with carboxyl groups present on the surface of oxidized MWNTs readily proceeds by using hexane diamine as an interlinking molecule. Transmission electron microscopy (TEM) shows that tubes are wrapped by polymer chains. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) at the C K-edge, O K-edge, and N K-edge and X-ray photoelectron spectroscopy (XPS) were used to give evidence of covalent functionalization of MWNTs by SPEEK macromolecules.     

Design of an Assembly of Poly(benzimidazole), Carbon Nanotubes,and Pt Nanoparticles for a Fuel‐Cell Electrocatalyst with an Ideal Interfacial Nanostructure

A newly designed and fabricated novel nanocomposite composed of multiwalled carbon nanotubes (MWNTs), poly(benzimidazole) (PBI), and Pt nanoparticles. This composite is fabricated by the preparation of PBI‐wrapped MWNTs (MWNT/PBI), followed by Pt loading onto the MWNT/PBI. As a result of the PBI wrapping, the loading efficiency of the Pt nanoparticles onto the MWNTs is dramatically improved up to 58.8% compared to that of the pristine MWNTs (41.0%). The process also allows homogeneous Pt immobilization onto the surface of MWNTs without any strong oxidation process for the MWNTs that is typically used for metal supporting on carbon nanotubes. Far‐IR spectroscopy of the composite shows a peak from the Pt? N bonding, indicating that these improvements are derived from the coordination of the Pt ion with the PBI molecules. Cyclic voltammogram measurements reveal that the Pt nanoparticles deposited on the MWNT/PBI shows higher utilization efficiency (74%) for electrocatalysts compared to that on the pristine MWNT (39%).     

Synthesis,Structure and Field Emission of Carbon Nanotubes

Abstract

Multiwall and single-wall nanotubes were produced by carbon arc discharge in helium, and their structures were investigated by electron microscopy. Field emission from (1) as-grown multiwall nanotubes (MWNTs), (2) purified MWNTs and (3) purified single-wall nanotubes (SWNTs) was investigated by field emission microscopy. Of the three kinds of nanotubes studied, purified MWNTs whose tips are open provided the highest current at a fixed voltage. Although purified SWNTs provided the second highest current, SWNTs are not so robust as MWNTs against ion bombardment. As an application of nanotube field emitters, we manufactured cathode ray tube (CRT) lighting-elements by replacing conventional thermionic cathodes with nanotube field emitters. Stable electron emission, adequate luminance, and long life of the emitters were substantiated.     

多壁碳纳米管填充丁苯橡胶复合材料的研究

采用浓硝酸(HNO3)氧化处理后的多壁碳纳米管(MWNTs)与丁苯橡胶(SBR)及其他配合剂在开炼机上进行混炼加工制备MWNTs／橡胶复合材料，并与炭黑补强橡胶体系进行对比，进而研究了MWNTs／橡胶复合材料的物理性能，并初步探讨了该材料微观结构与性能之间的关系。结果表明：随着MWNTs质量百分含量的增加，橡胶复合材料的力学性能也随之增高；MWNTs／橡胶复合材料的抗撕裂强度(25．9kN／m)、硬度(58)、磨耗(0．22mL/1．61km)性能较炭黑／橡胶体系要好。由MWNTs补强的橡胶对开发具有低滚动滞后性和抗疲劳损失的轮胎胎面胶将有很大的实用潜力。