蜂窝陶瓷骨架微结构修饰调控制备Pd/CNTs@CHC催化剂用于PS加氢

通过高温焙烧和氢氟酸瞬间蚀刻修饰堇青石蜂窝陶瓷骨架和孔壁表面结构,采用XRD、SEM、TEM表征修饰前后结构和形貌变化,探究陶瓷结构对机械强度、碳纳米管形貌结构及复合载体性质的影响,考察Pd/CNTs@CHC-HFn催化剂催化聚苯乙烯（PS）加氢性能及催化剂用量与加氢度的关系。结果表明,高温焙烧消除了骨架内部孔道,陶瓷表面变得平整密实;瞬间蚀刻增大了表面粗糙度,易于CNTs在表面生长,但蚀刻次数增加,导致蚀刻由表面向骨架内部侵入、CNTs在骨架内部生长,降低载体的机械强度。CNTs@CHC-HFn载体表面的CNTs可显著提高复合催化剂的加氢性能,其中加氢活性位Pd分布均匀,平均粒径为3.6 nm,当催化剂用量为3.0 g cat·（g PS）^-1时,其中含0.378 g CNTs和0.054 g Pd,反应6 h加氢度可达100%。     

紫外光辐照ABS/碳纳米管的研究

丙烯腊—丁二烯—苯乙烯共聚物(ABS)在室温、氮气环境下，通过紫外光辐照，在其分子链上引入了碳纳米管(CNTs)。通过荧光光谱分析，ABS／CNTs在418nm处有强的荧光发射峰；透射电子显微镜观察发现，CNTs在端头处打开及转弯处打断，被ABS包覆，ABS/CNTs的体积电阻率随CNTs的加入量增多而降低；紫外光辐照ABS/CNTs的导电性显著优于熔融共混ABS/CNTs；扫描电子显微镜表明，CNTs在紫外光辐照ABS基体中均匀分布。     

Preparation and mechanical properties of waterborne polyurethane/carbon nanotube composites

Waterborne polyurethane (WBPU) and multiwalled carbon nanotubes (CNTs) composite films with 0–4.0 wt% CNTs were prepared by ultrasonic dispersion of carboxylic acid‐functionalized CNTs in WBPU followed by emulsion casting process. The elongations at break of the WBPU/CNTs composites increase with the incorporation of CNTs. The tensile strength and crystallinity of the nanocomposite films with lower CNTs contents (<2 wt%) increase obviously; while the tensile strengths of the composites with more CNTs (≥2 wt%) decrease, in contrast to the pure PU film. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicated that the CNTs are uniformly dispersed in the composites incorporated with lower CNTs contents (≤1.5 wt%). However, aggregation of CNTs increased with increasing CNTs content in the WBPU/CNTs composites, causing the macrophase separation. The dispersion state of the CNTs affects the crystallinity of the PU matrix and the phase separation of the composites, which are two key factors to influence the mechanical properties of the WBPU/CNTs composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effects of Al interlayer coating and thermal treatment on electron emission characteristics of carbon nanotubes deposited by electrophoretic method

The effects of aluminum (Al) interlayer coating and thermal post-treatment on the electron emission characteristics of carbon nanotubes (CNTs) were investigated. These CNTs were deposited on conical-shaped tungsten (W) substrates using an electrophoretic method. The Al interlayers were coated on the W substrates via magnetron sputtering prior to the deposition of CNTs. Compared with the as-deposited CNTs, the thermally treated CNTs revealed significantly improved electron emission characteristics, such as the decrease of turn-on electric fields and the increase of emission currents. The observations of Raman spectra confirmed that the improved emission characteristics of the thermally treated CNTs were ascribed to their enhanced crystal qualities. The coating of Al interlayers played a role in enhancing the long-term emission stabilities of the CNTs. The thermally treated CNTs with Al interlayers sustained stable emission currents without any significant degradation even after continuous operation of 20 h. The X-ray photoelectron spectroscopy (XPS) study suggested that the cohesive forces between the CNTs and the underlying substrates were strengthened by the coating of Al interlayers.     

以煤炭直接液化残渣为原料制备炭纳米管

以煤炭直接液化残渣为原料,采用直流电弧放电法成功制备出炭纳米管.采用扫描电子显微镜、透射电子显微镜、高分辨透射电镜以及X射线衍射等手段对炭纳米管的形貌和结构进行了表征.结果表明,所得直而长的多壁炭纳米管具有很好的石墨化程度;其长度达几微米,内径约80 nm,外径约120 nm;残留在液化残渣中的黄铁矿及液化过程中产生的磁黄铁矿对炭纳米管的形成有催化作用.     

结晶驱动含氟组分向表面离析

我们通过原子转移自由基技术合成了一系列三嵌段聚合物聚甲基丙烯酸丁酯-b-聚甲基丙烯酸十八酯-b-聚甲基丙烯酸全氟辛基乙酯(PBMA-b-PODMA-b-PFMA。分析结果显示当聚甲基丙烯酸全氟辛基乙酯聚合度在1~2时,表面富积度随ODMA段长的增加而增加。这是由于PODMA在结晶过程中,驱动低表面含氟组分离析到表面所致。     

Influence of dispersion states of carbon nanotubes on physical properties of epoxy nanocomposites

Effects of different dispersion states of carbon nanotubes (CNTs) on rheological, mechanical, electrical, and thermal properties of the epoxy nanocomposites were studied. The dispersion states were altered depending upon whether a solvent was employed or not. To characterize dispersion of the CNTs, field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) were used. It was found that the nanocomposites containing poorly dispersed CNTs exhibited higher storage modulus, loss modulus, and complex viscosity than ones with well dispersed CNTs. It means that the poorly dispersed CNTs/epoxy composites have, from a rheological point of view, a more solid-like behavior. Tensile strength and elongation at break of the nanocomposites with different dispersion of CNTs were measured. Both of the well and the poorly dispersed CNTs composites showed a percolation threshold of electrical conductivity at less than 0.5 wt.% CNTs loading and the former had higher electrical and thermal conductivities than the latter. Effects of the CNTs content on the physical properties were also examined experimentally. As loading of the CNTs increased, improved results were obtained. From the morphological observation by FESEM and TEM, it was found that when the solvent was not used in the CNTs dispersion process, aggregates of pristine CNTs remained in the nanocomposites.     

Reinforcement of precursor-derived Si–C–N ceramics with carbon nanotubes

Nanocomposites consisting of precursor-derived Si–C–N ceramics incorporated with carbon nanotubes (CNTs) were successfully prepared by casting of a mixture of CNTs and a liquid precursor polymer followed by cross-linking and thermolysis. The effect of CNTs on the fracture toughness of these nanocomposites was investigated by a thermal loading technique. The results reveal a dependence of the fracture toughness on the type of the CNTs. One type shows a significant increase of the fracture toughness at CNT contents of only 1–2 mass%, whereas the other one exhibits no effect. The microstructural effects of CNTs observed at the fracture surfaces of the nanocomposites by scanning electron microscope (SEM) and transmission electron microscope (TEM) can be correlated with the observed fracture toughness behavior.     

Aligned carbon nanotubes by catalytic decomposition of C2H2 over Ni–Cr alloy

High density, well-aligned carbon nanotubes (CNTs) were prepared by thermally decomposing acetylene at 700 °C with the help of Ni–Cr alloy as catalyst in a thermal chemical vapor deposition system. The density and alignment of CNTs were characterized by scanning electron microscope (SEM). It was found that the density of the CNTs could be remarkably increased and the alignment could be improved with the decrease of the thickness ratio of Ni:Cr. Also found in our experiment was that the catalyst encapsulated in CNT was single crystal Ni, which was confirmed by high-resolution transmission electron microscopy (HRTEM) and electron dispersion X-ray spectrum (EDX). Finally, the growth mode of CNTs was discussed based on the Ni–Cr alloy catalysts under our experimental conditions. The results are helpful in providing a better understanding of the acting of catalyst and the controlling of the desirable density and alignment of CNTs for various applications.     

Fabrication of Nanocomposite Powders of Carbon Nanotubes and Montmorillonite

Nanocomposite powders of carbon nanotubes (CNTs) and montmorillonite (MMT) were successfully synthesized by heating the mixed composites of polypropylene, nickel (Ni) catalyst, and organic-modified montmorillonite in large quantities after the Ni catalysts were removed. Transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy show the co-presence of CNTs and MMT. The interlayer distance of MMT was enlarged because of the CNTs, which result in MMT being partly exfoliated and buried in the CNTs. These current nanocomposite powders of CNTs and MMT with superstructure are therefore expected to be ideal fillers for high-performance polymer nanocomposites.     

Decoration of multi-walled carbon nanotubes by polymer wrapping and its application in MWCNT/polyethylene composites

ABSTRACT: We dispersed the non-covalent functionalization of multi-walled carbon nanotubes (CNTs) with a polymer dispersant and obtained a powder of polymer-wrapped CNTs. The UV-vis absorption spectrum was used to investigate the optimal weight ratio of the CNTs and polymer dispersant. The powder of polymer-wrapped CNTs had improved the drawbacks of CNTs of being lightweight and difficult to process, and it can re-disperse in a solvent. Then, we blended the polymer-wrapped CNTs and polyethylene (PE) by melt-mixing and produced a conductive masterbatch and CNT/PE composites. The polymer-wrapped CNTs showed lower surface resistivity in composites than the raw CNTs. The scanning electron microscopy images also showed that the polymer-wrapped CNTs can disperse well in composites than the raw CNTs.     

Direct evidence for the existence of multi-walled carbon nanotubes with hexagonal cross-sections

Carbon nanotubes (CNTs) with a polygonal cross-section have been paid increasing attention since their three-dimensional structure is related to specific physical properties, which are found to be different in comparison to CNTs with a circular cross-section. Here, we report the existence of novel multi-walled CNTs yielding walls with a rounded-hexagonal configuration. This structure was directly confirmed for the first time by both cross-sectional transmission electron microscopy and electron tomography. The morphology of the Fe catalytic particle also exhibits hexagonal characteristics, and is proposed as the origin of the formation of the rounded-hexagonal walls of the CNT. This observation is of great importance with respect to the design of polygonal (such as pentagonal or hexagonal) cross-sectional CNTs. By controlling the morphology of the catalytic nanoparticles it will be possible to grow CNTs with desired electronic and mechanical properties.     

Synthesis and thermal characterization of poly(ester-ether urethane)s based on PHB and PCL-PEG-PCL blocks

A series of block poly(ester-ether urethane)s, poly(PHB/PCL-PEG-PCL), based on poly(3-hydroxybutyrate) (PHB-diol), as hard segments, and poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone), (PCL-PEG-PCL) triblock copolydiol, as soft segments, were prepared using 1,6-hexamethylene diisocyanate (HDI), as non-toxic connecting agent. Polyurethanes block copolymer was synthesized from bacterial PHB and PCL-PEG-PCL blocks. The chemical structure and molecular weights of polymers prepared were characterized by FTIR, ¹H NMR and GPC. The effect of chemical structure on the thermal and mechanical properties was studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. The DSC results revealed that poly(PHB/PCL-PEG-PCL) urethanes are semi-crystalline with two crystallizable PHB and PCL-PEG-PCL blocks. The thermal stability of the urethanes is less than neat PHB. The results of tensile testing showed that the extensibility of PHB is largely enhanced by the incorporation of PCL-PEG-PCL soft segments. Activation energy E _a , as a kinetic parameter of thermal decomposition, was estimated by each of the Ozawa and Kissinger methods. Close values of activation energy were obtained by both methods. The swelling behaviour of the copolymers was also investigated.     

Preparation and Electron Beam Irradiation of PVC/ENR/CNTs Nanocomposites

Poly (vinyl chloride), PVC/epoxidized natural rubber blend, ENR/carbon nanotubes, CNTs nanocomposites were prepared using melt intercalation and solution blending methods. In both preparation methods PVC: ENR: CNTs ratios were fixed at 50:50:2, while the 50/50 PVC/ENR blend without the addition of CNTs was used as control. The PVC/ENR/CNTs nanocomposites were exposed to electron beam (EB) irradiation at doses ranging from 0–200 kGy. The effects of two different preparation methods on the tensile properties, gel fraction and morphology of the PVC/ENR/CNTs nanocomposites were studied. Prior to EB irradiation, the addition of 2 phr of CNTs caused a drop in the tensile strength (Ts) of the 50/50 PVC/ENR blend, implying poor distribution of CNTs in the PVC/ENR blend matrix. However upon EB irradiation, the nanocomposites prepared by the melt blending method exhibited higher values of Ts as compared to the neat PVC/ENR blend due to occurrence of radiation-induced cross-linking in the PVC/ENR blend matrix. Transmission electron microscopy (TEM) images proved that a better dispersion of CNTs in PVC/ENR blend matrix can be achieved by melt intercalation compared to solution blending and the dispersion of CNTs was improved by irradiation. Scanning electron microscopy (SEM) results showed a distinct failure surface with formation of rough structure for the irradiated nanocomposites, which explains the higher values of tensile properties compared to the non-irradiated nanocomposites.     

等离子体条件下煤基富勒烯的制备及生成机理

以淄博贫煤为原料,用射频等离子体法合成碳纳米管（carbon nanotubes,CNTs）和纳米洋葱状富勒烯（nano—structured onion—like fullerenes,NSOFs）,运用场发射扫描电子显微镜（FE—SEM）和高分辨透射电子显微镜（HRTEM）对产物进行了表征和分析．结果表明：以淄博贫煤为原料制备出CNTs和NSOFs,CNTs直径分布均匀,约为10nm左右,准球状的NSOFs直径分布在8nm-30nm之间,石墨化程度较高;并对不同变质程度的煤制备富勒烯的生成机理进行了比较与讨论．     

Comparative study of the thermal and mechanical properties of nanocomposites prepared by in situ polymerization of ε‐caprolactone and functionalized carbon nanotubes

As an effort to compare the influence of several types of functionalized carbon nanotubes (CNTs) upon the mechanical and thermal properties of nanocomposites prepared with a poly(ε‐caprolactone) (PCL) as matrix and functionalized CNTs as fillers; nanocomposites of PCL–CNTs were studied in this study. CNTs were synthesized by chemical vapor deposition using dry ethanol as the carbon source. High resolution scanning electron microscopy, high resolution transmission electron microscopy, and Raman and infrared spectroscopies were used to characterize the CNTs obtained. Four chemical synthesis routes were exploited to add different types of chemical groups onto the surface of purified CNTs. Specifically, the authors inserted: (i) N‐methylpyrrolidine, (ii) carboxyl and hydroxyl, (iii) urethane, and (iv) phenylmethanol groups onto CNTs surface. Nanocomposites were synthesized by in situ polymerization of ε‐caprolactone (ε‐CL) in presence of 1 wt% of each type of functionalized CNTs. Young's moduli of the nanocomposites prepared with N‐methylpyrrolidine or carboxyl and hydroxyl functionalized CNTs are higher than the one of pure PCL, whereas all the mechanical properties of the nanocomposites containing urethane or phenylmethanol groups evaluated at the break point were higher than those of pure PCL. Thermal stability of all the nanocomposites studied improved with respect to pure PCL. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers     

Synthesis and field emission properties of carbon nanotubes/nanofibers grown on pyrolyzed polyaniline–SiO2 substrates

Pyrolyzed polyaniline–SiO₂ substrates with the rough surface containing some holes were prepared by the pyrolysis of polyaniline–SiO₂ composites at temperature of 900 °C. Carbon nanotubes/nanofibers (CNTs/CNFs) were grown on the rough surface and inside the holes using a CVD method with a xylene–ferrocene mixture as a carbon and catalyst precursor source. The structural and morphological properties of CNTs were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the SiO₂ content of the substrates was responsible to the diameter and electron field emission properties of CNTs.     

Synthesis and characterization of multi-walled carbon nanotubes reinforced polyamide 6 via in situ polymerization

Polyamide 6 (PA6)/carbon nanotubes (PA6/CNTs) composites have been prepared by in situ polymerization of ε-caprolactam in the presence of pristine and carboxylated multi-walled carbon nanotubes (MWNT and MWNTCOOH). Viscosity measurements show that adding 0.5 wt% of carbon nanotubes (CNTs) does not affect the molecular weight of PA6. Compared with pure PA6, the yield strength of PA6/CNTs composites loaded with 0.5 wt% CNTs is almost unchanged, and the tensile strength is increased slightly. Dynamic mechanical analysis (DMA) demonstrates that both the storage modulus (E′) and glass transition temperature (T_g) of the PA6/CNTs composites increase, particularly for PA6/MWNTCOOH, indicating there is some chemical bonding between PA6 and MWNTCOOH. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra small-angle X-ray scattering (USAXS) show that MWNT and MWNTCOOH are well dispersed in PA6 matrix. Comparison of the USAXS data with a stiff-rod model and wormlike rod model reveals that the CNTs are quite flexible, regardless the degree of chemical modification. Due to the flexibility of CNTs, mechanical properties of the PA6/CNTs composites are marginally enhanced.     

Combination of hot extrusion and spark plasma sintering for producing carbon nanotube reinforced aluminum matrix composites

Aluminum (Al)/carbon nanotube (CNT) composites with nanoscale dispersion and regular orientation of the CNTs were fabricated by a combination of some advanced powder processes. The CNTs were well dispersed onto the Al particles by a nanoscale dispersion method. Moreover, the highly densified CNT composites were prepared by spark plasma sintering and subsequent hot extrusion. Microstructural observations by optical, field-emission scanning electron, and high-resolution transmission electron microscopies confirmed that the sintered Al/CNT compact and extruded bulk material had a good dispersion of oriented CNTs. Raman spectroscopy showed that the processing did little damage to the CNTs. As a result, the composites exhibited tensile strengths that were thrice larger than pure aluminum because of the CNT reinforcement.     

Carbon nanotube reinforced hydroxyapatite composite coatings produced through laser surface alloying

Carbon nanotube (CNT) reinforced hydroxyapatite composite coatings have been successfully fabricated by laser surface alloying. The phase compositions and the microstructure of the composite coatings were studied using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). TEM observation showed that a large amount of CNTs can be found with their original tubular morphology in the composite coatings, even though some CNTs react with titanium element in the substrate during laser irradiation. Additionally, measurement on the elastic modulus, hardness of the composite coatings by nanoindentation tests indicated that the mechanical properties are affected by the amount of CNTs in the starting precursor materials. Therefore, CNT reinforced hydroxyapatite composite coating is a promising coating material for high-load-bearing metal implants.