Surface Treatment Of Carbon Nanotubes Research Articles

Progress on carbon nanotube filled polymer-based thermal conductive composites

<p indent="0mm">In the 5G era, the effective thermal management has become more demanding due to the ever-rising integration of electronic devices. High thermal conductivity materials play a crucial role in the field of thermal management, for example, thermal interface materials (TIMs) are used to fill the gap between the electronic chip and the heat sink to improve thermal transfer. In recent years, polymers have become a popular choice for thermal conductive materials because of their light, economical and excellent insulation and processability. To improve the thermal conductivity of materials, inorganic fillers with high thermal conductivity are generally composited with polymers. With the merits of high thermal conductivity, desirable chemical stability, carbon nanotubes (CNTs) are considered to have broad application potential in thermal conductive composites. Simple composition methods failed to increase thermal conductivity of composite materials to expected levels due to the large interfacial thermal resistance between CNTs and polymers and the disorderly distribution of CNTs in polymers. Therefore, reasonable design of polymer composites filled with CNTs is the key to achieving high thermal conductivity. This review mainly introduces the application of CNTs in thermal conductive polymer composites. Based on the existing theoretical research on thermal conductivity of composites and the application of molecular dynamics, more feasible strategies for improving the thermal conductivity of polymer composites filled with CNTs have been proposed. The approaches that improve the thermal conductivity of composites are mainly introduced from three aspects. (1) The intrinsic thermal conductivity of CNTs is an important factor affecting the thermal conductivity of polymer-based composites. CNTs and their macroscopic bulk materials both have excellent thermal conductivity. However, the thermal conductivity test results of the macroscopic materials of CNTs (such as CNTs fibers, arrays, and films) showed that the thermal conductivity of the macroscopic materials of CNTs was much smaller than that of single CNTs due to impurities, defects and inter-tube contact thermal resistance. Studies have shown that purification of CNTs and reduction of intertubular contact thermal resistance can improve the intrinsic thermal conductivity of CNTs. (2) From a microscopic perspective, phonons, the quantized energy of lattice vibration, are the main mechanism of heat conduction in most carbon fillers and polymers. Phonon scattering occurs in the process of phonon transfer, including the scattering between phonons and the scattering at the interface caused by defects and impurities, resulting in thermal resistance. The bonding strength of fillers and polymer interfaces are the crucial factors affecting the transmission of phonons. Hence, the thermal conductivity of composites could be effectively enhanced by surface treatment of CNTs, including covalent functionalization and non-covalent functionalization. Studies have shown that the functionalization can enhance the interfacial interaction between CNTs and polymers, while improving the dispersion of CNTs in polymers. (3) According to the thermal conduction network theory, the key to improving the thermal conductivity is whether the fillers can form a large number of continuous thermal conduction paths in the polymers and maintain a stable existence. However, high CNTs content usually affects the comprehensive properties of composites. To solve this problem, the arrangement and distribution of CNTs in the polymer should be improved to construct more heat conduction pathways, which can achieve high thermal conductivity at a low filling content. Here we introduce some effective methods, including the synergy effect, field orientation and the construction of 3D network structures. In this review, the characteristics and improvement effects of different technical approaches are summarized, which provides a reference for the research and application of CNT-filled polymer-based composites with high thermal conductivity. Finally, the future development prospects of carbon nanomaterial-filled polymer composites are discussed from perspectives of theoretical research, experimental design and engineering application.

Iron nanoparticle surface treatment of carbon nanotubes to increase fatigue strength of steel composites

A simple, scalable, and reproducible method is used to decorate carbon nanotubes (CNTs) with metal nanoparticles (NPs). Decorating CNTs with iron NPs prior to forming steel-based metal matrix composites (MMCs) improves the high-cycle fatigue (HCF) strength of the MMC by more than 350% vs. plain 1084 steel and more than 100% vs. an MMC with untreated CNTs. An inverse correlation between CNT loading and tensile strength was observed. The CNT surface treatment uses an organic microenvironment surrounding suspended CNTs and emulsion chemistry to treat individual CNTs or small bundles. This process can be adapted to work with other metal NPs or CNT types. This work demonstrates the potential for metal-treated CNTs to further improve the HCF strength of MMCs and paves a pathway toward additional CNT-reinforced composites.

Surface Treatment of Carbon Nanotubes Using Modified Tapioca Starch for Improved Force Detection Consistency in Smart Cementitious Materials.

The remarkable mechanical properties and piezo-responses of carbon nanotubes (CNT) makes this group of nanomaterials an ideal candidate for use in smart cementitious materials to monitor forces and the corresponding structural health conditions of civil structures. However, the inconsistency in measurements is the major challenge of CNT-enabled smart cementitious materials to be widely applied for force detection. In this study, the modified tapioca starch co-polymer is introduced to surface treat the CNTs for a better dispersion of CNTs; thus, to reduce the inconsistency of force measurements of the CNTs modified smart cementitious materials. Cement mortar with bare (unmodified) CNTs (direct mixing method) and surfactant surface treated CNTs using sodium dodecyl benzenesulfonate (NaDDBS) were used as the control. The experimental results showed that when compared with samples made from bare CNTs, the samples made by modified tapioca starch co-polymer coated CNTs (CCNTs) showed higher dynamic load induced piezo-responses with significantly improved consistency and less hysteresis in the cementitious materials. When compared with the samples prepared with the surfactant method, the samples made by the developed CCNTs showed slightly increased force detection sensitivity with significantly improved consistency in piezo-response and only minor hysteresis, indicating enhanced dispersion effectiveness. The new CNT surface coating method can be scaled up easily to cater the potential industry needs for future wide application of smart cementitious materials.

Preparation of CNTs / Aluminum Foam Composites

This article uses powder metallurgy to prepare aluminum foam and carbon nanotubes (CNTs) / foam aluminum composites. The effects of the surface treatment of carbon nanotubes, the amount of pore-forming agent, and the amount of carbon nanotubes on the microstructure of aluminum foam and its composites were studied by means of infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The results show that the mixed acid treatment of CNTs can effectively disperse CNTs and introduce new functional groups on their surfaces. Using NH4HCO3 as a pore-forming agent and using powder metallurgy, a porosity of 41% to 79%, Cellular pure foam aluminum material and CNTs / foam aluminum matrix composite with 60% porosity.

Conductive mechanism of CNTs enhanced conductive magnetic fluid

In this research, conductive magnetic fluid is prepared using carbon nanotubes (CNTs) as enhancing phase. The fluid is a superparamagnetic material. Experimental results show that CNTs form conductive networks. Meanwhile, surface treatment of CNTs is not conducive to enhance the conductivity, which has been confirmed by our calculations. More interestingly, when we apply an external magnetic field, the conductivity of the magnetic fluid increases along the magnetic field direction, showing anisotropy. These unique properties of the conductive magnetic fluid make it very promising in microwave absorbers and electromagnetic shields.

Effects of dispersion methods and surface treatment of carbon nano-tubes on defect detectability and static strengths of adhesive joints

Adhesive bonding and bolting are two typical joining methods of composites. Adhesive bonding does not require holes, and the load is distributed over a larger area than that in mechanical joints. However, such bonding is highly sensitive to the surface treatment, service temperature, humidity, and other environmental conditions. In particular, the formation of kissing bonds (due to surface defects or contamination) reduces the bonding strength significantly. The electrical-impedance method using carbon nano-tubes (CNTs) is a highly promising technology that helps in detecting different types of bonding defects. In this study, aluminum-to-aluminum adhesive joints with 1wt% CNTs were fabricated. The static strengths and defect detectabilities determined using the electrical-impedance method were then evaluated. To uniformly disperse the CNTs into the adhesive, a sonication process, a three-roll-mill process, and solvent were employed. The defect detectabilities and static strengths of the adhesive joints produced using five different types of dispersion methods were then evaluated. Moreover, the defect detectability and static strength of the adhesive joints with respect to the surface treatment of the CNTs were investigated.

The Relationship Between Carbon Nanotube Surface Status and Electrocatalytic Performance Toward Oxygen Reduction Reaction of Cobalt Phthalocyanine /Carbon Nanotube

Recently, noble metals and their alloys nanoparticles supported on the carbon materials as carbon-based composite electrocatalysts are widely studied. However, on one hand, the high cost associated to these noble metals is still a drawback for full commercial application; on the other hand, their designing is limited by their characteristic. It is important to develop a new catalyst with low cost, high catalytic activity and wide designing for oxygen reduction reaction. Cobalt Phthalocyanine (CoPc) has high catalytic activity, and its special macrocyclic structure can perform well with the carbon materials toward Oxygen Reduction Reaction (ORR). Thus, the design of relationship between CoPc and its carbon-base is a necessary mission for this new catalyst for ORR. This abstract mainly focused on the different surface treatment of carbon nanotubes (CNTs) connect to CoPc and their electrocatalytic performance for the ORR process. Investigating raw CNTs, acidification CNTs (AF-CNTs) and activation CNTs gives us three different surface treatment CNTs coated by CoPc, which have higher electrocatalytic performance than CoPc itself. Here we find CoPc /AF-CNTs exhibit highest catalytic activity, and the Tafel Polarization curve test showed that CoPc/AF-MWCNTs perform the highest exchange current density (i0) in oxygen reduction reaction, and even its reaction rate is faster than commercial catalyst. The results indicated that the broken CNTs surface is beneficial for coating CoPc, as well as the charge transformation during the catalytic process. At the same time oxygen- containing groups on carbon-base can promote catalytic activity of CoPc for the ORR process. Figure 1

Noble metals supported on carbon nanotubes using supercritical fluids for the preparation of composite materials: A look at the interface

Carbon nanotubes (CNTs) have attracted great interest from scientific and industrial communities thanks to their remarkable properties. However, even if their mass production is nowadays well-known, the methods commonly used lead to bundles made of hundreds of single nanotubes with inert surface. Through the description of a simple, rapid and green procedure to uniformly decorate CNTs with metal nanoparticles (Ag, Pd), this paper presents a look at the CNTs-metal interface as a function of the functionalization technique.Three types of CNTs are considered for deposition: raw CNTs, CNTs functionalized with the reference HNO3/H2SO4 method and CNTs functionalized with our approach using CO2/EtOH/H2O/H2O2 under temperature and pressure. For functionalized CNTs the Pd atoms and CNTs are linked by oxygen atoms and the coating is made of metallic palladium nanoparticles while palladium oxide nanoparticles are formed on raw CNTs, the functionalization having an influence on the nucleation and growth phenomenon. Furthermore the surface treatment of CNTs in acidic solution has a major drawback with CNTs contamination that is why a functionalization with CO2/EtOH/H2O/H2O2 under temperature and pressure is preferred. In addition, electron tomography has shown that the use of supercritical fluids leads to a uniform deposition of metal inside the bundles of CNTs. The orientation relationship between palladium nanoparticles and CNTs has also been determined; the {111} planes of palladium nanoparticles are parallel to the CNTs graphite planes. The supercritical fluids chemical deposition method appears as an interesting alternative process for the uniform decoration of CNTs with strong interfaces for the preparation of composite materials.

Dispersion Enhancement of Multi-Walled Carbon Nanotube (MWCNT) in Nitrile Rubber (NBR)

Attempts to enhance dispersion degree of multi-walled carbon nanotubes (CNT) in nitrile rubber (NBR) matrix, and to improve the NBR-CNT interaction were carried out by different approaches, namely, sonication and chemical treatments of CNTs with nitric acid (HNO3), nitric-sulfuric acid mixture (HNO3/H2SO4) and potassium permanganate (KMnO4). Rheological behavior of NBR/CNT composites was monitored as an indication of filler dispersion degree using the Rubber Process Analyzer (RPA2000) via the alteration in Payne effect. Results gained reveal the magnitude of Payne effect in the following order: untreated system&gt; sonicated system&gt; HNO3 system&gt; HNO3/H2SO4 KMnO4 system, implying a significant improvement in the state-of-mix of NBR/CNT composites by sonication and/or chemical treatment of CNT prior to being mixed with NBR. The SEM results demonstrate the highest magnitude of CNT dispersion in the system with HNO3 followed by the sonicated system untreated system, HNO3/H2SO4 KMnO4. The SEM results suggest that the surface treatment of CNT with HNO3 yields highest magnitude of improvement in CNT dispersion. Poor CNT dispersion after treatment with HNO3/H2SO4 or KMnO4 is due probably to the re-agglomeration of CNT during the drying stage after the chemical treatment process.

Effects of the surface treatment on the properties of polyaniline coated carbon nanotubes/epoxy composites

Abstract The effects of a surface treatment of carbon nanotubes (CNTs) on the electrical conductivity and the hydrophilicity of a polyaniline (PAni) coated CNTs (PAni-CNTs)/epoxy (EP) composites were examined. The surface of the CNTs was treated with various chemicals, such as acid mixtures (HNO 3 :H 2 SO 4 ), potassium persulfate (KPS) and sodium dodecyl sulfate (SDS), to improve their dispersion and reactivity with PAni. The electrical conductivity and hydrophilicity of PAni-CNTs and their EP composites were strongly affected by the surface treatment of the CNTs. The surface-treating materials remained on the surface of the CNTs affected the reactivity of the CNTs surface to PAni, and thus resulted in different PAni amounts in the PAni-CNTs. The electrical conductivity of the PAni-CNTs/EP composites decreased, but the hydrophilicity increased, with increasing the amount of PAni coating on the CNTs surface.

Damage-free surface treatment of carbon nanotubes and self-assembled monolayer devices using a neutral beam process for fusing top–down and bottom–up processes

Plasma etching processes have been used for the past 30 years to shrink the pattern size of integrated devices. However, the inherent problems of plasma processes, such as ultraviolet photon radiation damage, limit the effectiveness of etching and surface treatments of nanoscale devices. To overcome these problems, we developed a neutral beam surface treatment process. The process uses neutral beams and a defect-free surface process to fabricate carbon nanotubes and self-assemble mono-layer devices. We found that neutral beams can be used to produce atomically defect-free surfaces in carbon nanotubes and organic molecules. This technique has potential for fabricating nanodevices.

Effect of surface treatment for carbon nanotubes on morphological and rheological properties of poly(ethylene oxide) nanocomposites

Poly(ethylene oxide) nanocomposites filled with functionalized multi-walled carbon nanotubes are prepared and characterized using rheological and morphological measurements. This study investigates how the surface treatment of carbon nanotubes (CNTs) affects the CNT dispersion state. It is found that the nanocomposites have a higher effective volume fraction than the real volume fraction of the CNTs. The dispersion state of the CNTs is identified by using field emission scanning electron spectroscope and transmission electron microscope. The rheological findings indicate that there exists a percolated network structure of the CNTs in the nanocomposites, which was confirmed by electrical conductivity measurements as well as morphological observation. POLYM. ENG. SCI., 46:1350–1357, 2006. © 2006 Society of Plastics Engineers

A study on the effect of surface treatment of carbon nanotubes for liquid crystalline epoxide–carbon nanotube composites

Chemical surface oxidation of carbon nanotubes was employed to modify the interfaces between liquid crystalline epoxide (LCE) molecules and carbon nanotubes (CNs). Polar functional groups are formed on the surfaces of the carbon nanotubes as a result of the treatment. The thermotropic behavior of the nematic liquid crystalline (LC) phase in liquid crystalline epoxide–carbon nanotube (LCE–CN) composites has been examined using polarized optical microscopy. The LC phase in the LCE–surface oxidized CN composite evolves at a lower temperature compared to that for LCE–CN, due to polar interactions. The mechanical properties of LCE–CN composites tend to increase with increasing CN content. The electrical conductivity of LCE–CN composites was found to increases dramatically compared to that of pristine LCE resin, up to 5 wt% CN loading, and then increase linearly with increasing CN content at high CN loadings. An investigation of the thermal properties of LCE–CNs in relation to the surface treatment of CNs was also undertaken. Surface oxidation of CNs was found to improve the mechanical durability and thermal stability of LCE–CN composites.