Synthesis and properties of multi-walled carbon nanotubes coated with inorganic nanoparticles

Rare earth fluoride EuF3 and TbF3 were coated on the multi-walled carbon nanotubes (MWNTs) via the intermediate of noncovalent hydrophobic interactions of the MWNTs surface with sodium dodecyl sulfate (SDS).They were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The nanoparticle sizes of metal fluorides and sulfides on MWNTs are less than 20 nm. The photo physical properties of the composites were investigated, which indicated the composites exhibited the optical transitions within the 4f shell of the rare earth ions.     

Polypyrrole coated carbon nanotubes: Synthesis,characterization, and enhanced electrical properties

We describe a simple approach to the synthesis of MWNT/polypyrrole nanotubes by the in situ chemical polymerization of pyrrole on the carbon nanotubes using ferric chloride as an oxidant. The effects of pyrrole concentration on the coating and properties of the resulting complex nanotubes were studied by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and thermal gravimetric analysis. The coated PPy layers could be controlled easily by adjusting a feed ratio of pyrrole to MWNTs. FT-IR results suggested an existence of interaction between the –COOH groups of chemically modified MWNTs and NH groups of the PPy. SEM and TEM studies indicated that each individual MWNT could be coated with PPy. The resultant nanotubes enhanced electrical conductivity compared to PPy and MWNT which was strongly influenced by the feed ratio of pyrrole to MWNTs.     

Electrostatic interaction of multi-walled carbon nanotubes composites with CdTe and CdSe nanoparticles

Composites were prepared by the electrostatic interaction between carboxylated multi-walled carbon nanotubes (c-MWNTs) and either cadmium telluride (CdTe) or cadmium selenide (CdSe) nanoparticles. Multi-walled carbon nanotubes (MWNTs) were oxidized by an aqueous acid mixture, and both the CdTe and CdSe nanoparticles were stabilized by 2-(dimethylamino) ethanethiol hydrochloride in water to develop negatively and positively charged outer surfaces, respectively. Optical properties were investigated by UV/Vis and photoluminescence (PL) analyses. CdX (X = Te, or Se) nanoparticles showed emissions at the same position regardless of the existence of c-MWNTs. This result suggests that the interaction between CdX and c-MWNTs does not affect the photoluminescence of CdX nanoparticles in their composites. The binding energies and redox potential positions of the CdX nanoparticles in their c-MWNT-CdX composites shifted from those of the pure nanoparticles. These changes indicate that the electron densities on the interfaces of CdX nanoparticles and c-MWNTs were redistributed after the formation of composites due to the strong electrostatic interaction between the components.     

Enhanced thermal and electrical properties of poly (D,L-lactide)/multi-walled carbon nanotubes composites by in-situ polymerization

Biodegradable poly (D,L-lactide) (PLA)/carboxyl-functionalized multi-walled carbon nanotubes (c-MWCNTs) composites were achieved via in-situ polymerization. These as-prepared composite materials were characterized with FT-IR, XRD, TG, DSC, SEM, and high insulation resistance meter. The results demonstrate that the multi-walled carbon nanotube was carboxyl functionalized, which improved the collection between c-MWCNTs and PLA, and further realized the graft copolymerization of c-MWCNTs and PLA. There is a higher glass transition temperature and a lower pyrolysis temperature of PLA/c-MWCNTs composites than pure PLA. The c-MWCNTs gave a better dispersion than unmodified MWCNTs in the PLA matrix, and an even coating of PLA on the surface of c-MWCNTs was obtained, which increased the interfacial interaction. High insulation resistance analysis showed that the addition of c-MWCNTs increased the electric conductivity, and c-MWCNTs performed against the large dielectric coefficient and electrostatic state of PLA. These results demonstrated that c-MWCNTs modified PLA composites were beneficial for potential application in the development of heat-resisting and conductivity plastic engineering.     

多壁碳纳米管/壳聚糖复合材料的制备及电催化性能

采用混酸法制备羧基化多壁碳纳米管以及采用超声凝聚法制备壳聚糖纳米粒子,再通过静电自组装的方法制备碳纳米管/壳聚糖(相对分子质量(Mr)不小于5万和不小于10万)、碳纳米管/高密度壳聚糖、碳纳米管/羧化壳聚糖、多壁碳纳米管/壳聚糖盐酸盐复合材料。通过SEM、HRTEM及XRD对产品进行微观结构分析,利用循环伏安法对H2O2在碳纳米管/壳聚糖修饰电极上的电化学行为进行研究。结果表明:壳聚糖盐酸盐对碳纳米管具有较好的包覆效果,包覆层厚度约为3.5nm,静置12h后具有良好的溶液分散性;碳纳米管/壳聚糖盐酸盐修饰玻碳电极改善了H2O2的氧化还原电流,同时还降低了H2O2的氧化还原的过电势,对其电化学催化性能具有良好的促进作用。     

Zinc oxide nanoparticle decorated multi-walled carbon nanotubes and their optical properties

A simple and efficient approach is developed for the synthesis of single crystal zinc oxide (ZnO) nanoparticles on multi-walled carbon nanotubes (MWNT). Moreover, the effect of heat treatment on ZnO-coated MWNT is investigated. The results reveal that the MWNT are decorated by ZnO particles. The MWNT are continuously coated by ZnO nanoparticles at 450 and 600 °C, and the average size of ZnO nanoparticles is about 11 and 48 nm, respectively. However, the coated layer of ZnO on the surface of MWNT becomes discontinuous when the temperature of heat treatment reaches 750 °C. The average size of ZnO particles at 750 °C is about 89 nm. Furthermore, the UV emission of MWNT is improved significantly through modification with ZnO.     

Synthesis and characterization of carbon nanotubes decorated with strontium ferrite nanoparticles

A uniform coated compound material was obtained by the in situ sol–gel reaction among modified carbon nanotubes, nitric acid strontium, and nitric acid iron. The results indicated that the carbon nanotubes were coated with M-type magnetoplumbite ferrite, and its size was at the nanometer level. Along with the increase in the content of carbon nanotubes, the tubular structures of the carbon nanotubes were clearer and the coating effect was better. The coercive force of the samples increased simultaneously with the increase in the content of carbon nanotubes.     

Conducting and magnetic behaviors of polyaniline coated multi-walled carbon nanotube composites containing monodispersed magnetite nanoparticles

High conductivity and supermagnetism of polyaniline (PANI)-coated multi-walled carbon nanotube (MWCNT) composites containing monodispersed 6 nm iron oxide (Fe₃O₄) nanoparticles has been successfully synthesized by in situ chemical oxidative polymerization using anionic surfactant dodecylbenzenesulfonic acid sodium salt. Hydrophilic 6 nm spherical Fe₃O₄ nanoparticles fabricated by the thermal decomposition process were chemically modified using 11-aminoundecanoic acid tetramethylammonium salt. The modified nanoparticles were further mixed with carboxylic acid containing multi-walled carbon nanotubes (c-MWCNTs) in an aqueous solution to form one-dimensional Fe₃O₄ coated c-MWCNT template and PANI/c-MWCNT nanocomposite were then synthesized via in situ chemical oxidative polymerization in HCl solution. Structural and morphological analysis using FESEM, HRTEM and XRD showed that the fabricated Fe₃O₄ coated c-MWCNT/PANI nanocomposites are one-dimensional core (Fe₃O₄ coated c-MWCNT)–shell (PANI) structures. The electrical conductivity of 1 wt% Fe₃O₄ coated c-MWCNT/PANI nanocomposites at room temperature is 37.7 S/cm, which is decreased to 28.6 S/cm with the loading of 5 wt% Fe₃O₄ nanoparticles. The magnetic properties of Fe₃O₄ coated c-MWCNT/PANI nanocomposites exhibit supermagnetism with saturation magnetization in the range of 0.04–0.15 emu/g, which increases as the amount of Fe₃O₄ nanoparticles increases.     

Improvement of mechanical properties of Sn-58Bi alloy with multi-walled carbon nanotubes

Carbon nanotubes (CNTs) reinforced Sn-58Bi composites were successfully fabricated through ball-milling method and low temperature melting process.The influence of multi-walled carbon nanotubes (MWCNTs) on the mechanical strength and ductility of Sn-58Bi lead-free alloy was studied.The mechanical test results show that the bending strength of Sn-58Bi-0.03CNTs (mass fraction,%) composite is increased by 10.5% than that of the Sn-58Bi alloy,which can be attributed to the reduction of Sn-rich segregation and the grain refinement.The toughness of Sn-58Bi-0.03CNTs composite is increased by 48.9% than that of the matrix materials.It is indicated that the influence of CNTs on the strength of Sn-58Bi-xCNTs composite is insignificant.In addition,the fracture mechanism of CNTs reinforced Sn Bi composite was analyzed.The corresponding fracture surface comparison between the Sn-58Bi-0.03CNTs composite and the monolithic Sn-58Bi alloy was made to identify the influence of CNTs on the fracture behavior and the reinforcing effect of CNTs.     

Gold nanoparticles–polyaniline composite material: Synthesis,structure and electrical properties

Gold nanoparticles–polyaniline composite materials were synthesised and their structure and electrical properties were analised. Different stabilizing agents were used resulting in the formation of nanoparticles with sizes within 5–10 nm. The best results were obtained when the composite material was obtained during the polymerization of the anilinium salt in the presence of the mixture composed by dodecyl benzene sulfonic acid and 2-mercaptoethanesulfonic acid stabilized gold nanoparticles. Electrical properties of this composite material demonstrated the formation of Schottky barriers between polyaniline and gold particles, an essential property for its use in bio-inspired complex information handling materials.     

Bent-shape effects of multi-walled carbon nanotube on the electrical conductivity and rheological properties of polycarbonate/multi-walled carbon nanotube nanocomposites

In this study, polycarbonate (PC)/multi-walled carbon nanotube (MWCNT) nancomposites have been prepared by pretreating MWCNT solutions with ultrasonication. We demonstrate that the electrical conductivity and rheological properties of PC/MWCNT nanocomposites strongly depend on the mesoscopic shape factor (l_sp/d), which is represented by the ratio between the static bending persistence length (l_sp) and outer diameter (d) of the MWCNT. The electrical conductivity of PC/MWCNT nanocomposites increases linearly with increasing (l_sp/d)² and the percolation threshold of PC/MWCNT nanocomposites decreases linearly with increasing (l_sp/d)² of MWCNTs. The storage modulus of PC/MWCNT nanocomposites increases linearly with increasing (l_sp/d)² of MWCNTs at all frequency ranges.     

In situ synthesis of palladium nanoparticles on multi-walled carbon nanotubes and their electroactivity for ethanol oxidation

Pd nanoparticles(Pd-NPs)were prepared and directly anchored on the surface of multi-walled carbon nanotubes(MWCNTs)in the absence of chemical reduction agent,where MWCNTs were used as both the chemical reduction agent and the support substrate of Pd-NPs.Effect of various surfactants on the in situ deposition of PdNPs on MWCNTs was investigated.When MWCNTs were modified with a cationic surfactant(hexadecyl trimethyl ammonium bromide,CTAB),the amount of the Pd-NPs(Pd-NP/CTAB-MWCNT)generated by such an in situ deposition method gets a notable increase,and the size of the as-synthesized Pd-NPs becomes smaller,compared with those in the absence of any surfactant(Pd-NP/MWCNT)or in the presence of an anionic surfactant SDS(Pd-NP/SDS-MWCNT)and a neutral surfactant OP(PdNP/OP-MWCNT).Results show that the MWCNTs modified with CTAB are propitious to the in situ reduction of Pd2?.Among the prepared catalysts,Pd-NP/CTABMWCNT displays the highest electroactivity for ethanol oxidation in alkaline media.     

Conducting polymer embedded with nanoferrite and titanium dioxide nanoparticles for microwave absorption

The present paper deals with the synthesis of conducting ferrimagnetic polyaniline nanocomposite embedded with γ-Fe₂O₃ (9–12 nm) and titanium dioxide (70–90 nm) nanoparticles via a micro-emulsion polymerization. The microwave absorption properties of nanocomposite in 12.4–18 GHz (Ku-band) frequency range shows shielding effectiveness due to absorption (SE_A) value of ?45 dB, which is much higher than polyaniline composite with iron oxide and polyaniline–TiO₂ composites. The higher EMI shielding is mainly arising due to combined effect of γ-Fe₂O₃ and TiO₂ that leads to more dielectric and magnetic losses which consequently contributed to higher values of shielding effectiveness. XRD analysis of the nanocomposite reveals the incorporation of nanoparticles in the conducting polymer matrix while the thermal gravimetric analysis (TGA) demonstrates that the nanocomposite is stable up to 250 °C.     

The adhesion and inhibitor properties of organic coatings investigated with very thin polymer films on noble metal electrodes

The electrochemical impedance and the rate of faradaic reactions are measured on platinum electrodes coated with very thin (≈10⁻⁵ cm) acrylonitrile glow-discharge polymer films. The desorption of the organic matrix from the metal surface after immersion into the aqueous 1 M H₂SO₄ is determined quantitatively. The rate of electrocatalytic charge-transfer reactions is directly proportional to the number of unblocked metal surface atoms as determined from the hydrogen adsorption capacitance. The relevance of such measurements for technical protective coatings is pointed out.     

Experimental and computational study of morphological and electrical properties of tin/plasma polymer nanocomposites

Composite tin/n-hexane plasma polymer films were prepared by means of RF magnetron sputtering of tin target in Ar:n-hexane mixture and characterised by various analytical techniques. Their chemical composition was examined by XPS, current-voltage characteristics were measured, and their structure was investigated by conventional TEM and electron tomography. The acquired three-dimensional reconstructions were morphologically analysed by a self-made computer analytical tool, which estimated the mean form factor and the average effective radius of the reconstructed metal inclusions.     

Synthesis of metallic copper nanoparticles using copper oxide nanoparticles as precursor and their metal–metal bonding properties

Abstract

This work proposes a method for preparing metallic Cu nanoparticles using CuO nanoparticles as a precursor, and performs metal–metal bonding by using the metallic Cu nanoparticles. Colloid solution of CuO nanoparticles with a longitudinal particle size of 13·0±3·0, a lateral particle size of 8·4±2·2 and a crystal size of 7·8 nm was prepared with salt base reaction using Cu(NO₃)₂ aqueous solution and NaOH aqueous solution. Preparation of the metallic Cu particle colloid solution was performed in water using the CuO nanoparticles, hydrazine and cetyltrimethylammonium bromide, which resulted in production of the metallic Cu nanoparticles with a particle size of 50·6 nm and a crystal size of 30·5 nm. Metallic copper discs could be bonded using the metallic Cu nanoparticles under annealing at 400°C and pressurising at 1·2 MPa for 5 min in H₂ gas. A shear strength required for separating the bonded discs was recorded as high as 39·6 MPa.     

锆丝电爆炸法制备氧化锆纳米颗粒及其特征

在空气中采用锆丝点爆炸法合成了纳米二氧化锆颗粒,根据实测电流、电压和由此计算得到的能量沉积波形分析了电爆炸和纳米颗粒形成过程。发现锆丝气化后在锆丝蒸汽和空气中形成电击穿现象诱发电爆炸并截断锆丝中的能量沉积。通过扫描电镜和透射电镜对产物进行了分析,发现纳米二氧化锆颗粒形貌呈近球形,粒度分布在30.6-69.4纳米之间。X射线衍射分析表明产物由单斜晶型(m- ZrO2)和四方晶型(t- ZrO2)二氧化锆组成,随着充电电压的提高,四方晶型二氧化锆含量增加而单斜晶型含量变小,二者粒度都呈变大趋势。