Structural Integrity Of Carbon Nanotubes Research Articles

Effect of Carbon Nanotubes on the Mechanical, Thermal, and Electrical Properties of Tin-Based Lead-Free Solders: A Review

Carbon nanotubes (CNTs) are being applied with increasing frequency for advanced soldering. They have excellent mechanical, electrical, and thermal properties and are primarily used to reinforce lead-free solders. This paper discusses the strengthening mechanism of CNTs, introduces the preparation methods of CNT composite solders, and focuses on the review of tin-based lead-free solders reinforced with unmodified CNTs and metal-modified CNTs. The addition of CNTs can effectively improve the ultimate tensile strength, microhardness, shear strength, and creep resistance of the solder. However, the practical application of CNT composite solders has been a challenge for researchers for decades. The most significant issue is uniform dispersion due to the large density and surface differences between CNTs and solders. Other concerns are the structural integrity of CNTs and their limited addition amount, solder wettability, and interfacial bonding. CNT composite solders can only be widely used in a real sense when these challenges are properly addressed and overcome. At present, there is a lack of comprehensive reviews covering the structure, the strengthening mechanism, the preparation method of CNT composite solders, and the influence of CNT types on their strengthening effects. Therefore, this paper aims to fill this gap and contribute to solving the problems faced by the application of CNTs in solder. Future work is expected to focus on improving the dispersion and bonding of CNTs and optimizing the preparation method.

Printability enhancement and mechanical property improvement via in situ synthesis of carbon nanotubes on aluminium powder

A strategy of powder surface functional modification involving in situ synthesis of carbon nanotubes (CNTs) on Al powder is described to address the poor forming ability and inferior mechanical properties of Al parts produced by laser powder bed fusion. The obtained CNTs-Al composite powder exhibited a combination of high sphericity and flowability of powder, as well as good dispersion uniformity, bonding force and structural integrity of CNTs. The presence of CNTs significantly reduced the laser reflectivity and enhanced the printability of Al powder. The in situ synthesized CNTs contributed to reinforcement after printing and enhanced the tensile properties of printed sample. The printing behavior of powder, the distribution of reinforcement, and the tensile properties of printed sample were optimized by tuning the content of CNTs. The CNT-content in the composite powder was optimized at 0.96 wt% to achieve the synergy of high forming quality, densification and good tensile properties. • High-quality carbon nanotubes (CNTs) were in situ synthesized on Al powder. • Coating CNTs effectively increased the laser absorptivity of Al powder. • The incompatible issue of Al powder with laser additive manufacturing was addressed. • High forming quality and good properties of were obtained in the printed composite.

Sintering-free fabrication of high-strength titanium matrix composites reinforced with carbon nanotubes

To keep high structural integrity of carbon nanotubes (CNTs) in titanium (Ti), sintering and sintering-based consolidation processes were widely applied to fabricate CNTs/Ti composites. However, sintering processes were faced with the dilemma between insufficient densification at low sintering temperatures and excessive CNTs-Ti reaction at high temperatures. In this study, a sintering-free process combining cold compaction and hot extrusion (CC-HE) was developed to fabricate CNTs/Ti composites. The CC-HE-processed CNTs/Ti composites achieved superior tensile strength of 1262 MPa, which registered the new record among the pure Ti matrix composites reinforced with CNTs and graphene in available literature. By comparison study on CC-HE and the referential sintered CNTs/Ti composites, it was revealed that the high strength of CC-HE composites was attributed to the improved effects of grain refinement and secondary-phase strengthening, as a result of enhanced CNT integrity. The results provide a facile and large-scale-production pathway to fabricate high-performance carbon/Ti composites, which can be also applicable to other metal matrix composites.

Enhanced Mechanical Properties of Novel Aluminum Foams Synergistically Reinforced by NiO Particles and In Situ Grown Carbon Nanotubes

Novel aluminum (Al) foams synergistically reinforced by NiO particles and in situ grown carbon nanotubes (CNTs) have been fabricated in this work via the combination of ball milling, chemical vapor deposition (CVD) and space-holder techniques. In the Al foams (CNT/NiO/Al), pores with controllable size and morphology were formed with carbamide particles as space-holders, and NiO particles were uniformly distributed in the Al matrix and played the role of dispersion strengthening. Meanwhile, NiO particles can also provide Ni catalysts to induce the formation of CNTs in situ in the pores of Al foams, and the CNTs were interwoven into a network, forming the strong bonding with Al matrix and providing the effective support and reinforcement to the pore wall. The results showed that, the compressive yield strength of the CNT/NiO/Al composite foams was approximately 79.5% and 21.1% higher than that of pure Al foams and NiO/Al composite foams, respectively. And the energy absorption capacity of the CNT/NiO/Al composite foams was also significantly enhanced. The improved mechanical properties were due to the good dispersion and structural-integrity of CNTs in the Al matrix, as well as the good dispersion strengthening of NiO particles.

Tailoring and characterization of carbon nanotube dispersity in CNT/6061Al composites

The dispersity of carbon nanotubes in CNT/6061Al composites was tailored by varying the pre-dispersion state of CNTs on Al spherical powders, which was controlled by the high-shear pre-dispersion process. The difference in the dispersity and structural integrity of carbon nanotubes and the degree of interfacial reaction in the composites were analyzed by Raman spectroscopy mapping. The results show that Raman spectroscopy mapping is sensitive and can be used as a mesoscopic tool to evaluation of the overall status of CNTs in the composite. It also show that the slight adjust of the pre-dispersion state of the CNTs can achieve an improvement of tensile strength up to about 50 MPa. Specifically, under appropriate pre-mixing speed which makes CNTs partially embedded in the surface of Al powders, uniform dispersion of CNTs and good interface bonding can be simultaneously achieved, resulting in higher strengthening effect and good ductility.

The role of the attrition milling on the grain size and distribution of the carbon nanotubes in YSZ powders

The aim of present work was the examination of the role of the high efficient attrition milling on the structure and grain size of ZrO2 – 8mol.% Y2O3 (YSZ) and on the distribution of multiwall carbon nanotubes (MWCNTs) in these powder mixtures. The microstructure of YSZ/MWCNTs powder mixtures with 1, 5, 10wt.% MWCNTs was investigated. Detailed study confirmed the YSZ grain size decrease and simultaneously the non-destructive homogenization of MWCNTs in the ceramic powder mixtures. The best homogenization degree was achieved in the case of YSZ/1wt.% MWCNT powder. Raman scattering measurements were performed to investigate the atomic bonding and structural integrity of carbon nanotubes. The presence of the G and D bands in each samples at ∼1590 and ∼1355cm−1 confirmed the unaffected structural integrity of MWCNTs after the milling process. In addition to Raman measurements the high resolution transmission electron microscopy (HRTEM) studies have shown that the structure of MWCNTs remains intact after milling.

Structural integrity and dispersion characteristics of carbon nanotubes in titanium-based alloy

Over the years, carbon nanotubes have attracted much attention in engineering materials research due to their outstanding and superlative properties. Owing to the demands for lightweight materials with excellent mechanical and thermal properties for diverse industrial applications encouraged the incorporation of carbon nanotubes into titanium alloys. However, there are various challenges associated with the incorporation of carbon nanotubes into titanium alloys which includes; uniform dispersion and retaining the structural integrity of carbon nanotubes after dispersion. Past works have emphasized the importance of homogeneous dispersion with less structural damage to the carbon nanotubes in the various metal matrix. Therefore, this research focused on dispersion of 0.5 wt. % multiwalled carbon nanotubes in Ti6Al4V using low energy ball milling and evaluating the dispersion characteristics and structural integrity of MWCNTs in Ti6Al4V after dispersion. Various characterization techniques such as high-resolution transmission electron microscopy, scanning electron microscopy, X-Ray diffraction and Raman spectroscopy were adopted to ascertain the microstructural evolution, morphology, interfacial reaction and structural integrity of the carbon nanotubes in the Ti6Al4V powders before and after dispersion. The results indicated homogeneous dispersion of carbon nanotubes with less structural damages which are confirmed from the (ID/IG) ratio of the Raman spectra and the TEM images.

Functionalization of super-aligned carbon nanotube film using hydrogen peroxide solution and its application in copper electrodeposition

In order to make super-aligned carbon nanotubes (SACNT) homogeneously spread in electrolytes, a swift and effective method was devised for surface functionalization of SACNT film by ohmic heating using hydrogen peroxide solution. Controllable generation of defects and notable graft of oxygen functional groups on the sidewall of SACNTs were induced as proven by X-ray photoelectron spectroscopy and Raman spectroscopy. Differently from the harsh wet chemical oxidation, the super-aligned morphology and structural integrity of carbon nanotubes in the SACNT film were found to be well preserved by electron microscopy analysis. The functionalized treatment can remove extraneous material contaminating SACNT film and improve its conductivity. The grafting of polar ionizable groups has been proved to effectively eliminate the agglomeration of SACNTs. When the oxidized SACNT film was used as host material for electrodeposition of copper, the composite film of well-bonded SACNTs and Cu was successfully prepared.

Thermal conductivity of carbon nanotube–silver composite

The molecular level mixing method was extended to fabricate carbon nanotube reinforced silver composite. The influence of type of carbon nanotubes (single/multiwall) reinforcement and their mode of functionalization (covalent/non-covalent) on thermal conductivity of silver composite was investigated. X-ray diffraction and electron diffraction spectroscopy (EDS) confirm the presence of silver and carbon in the composite powder. High resolution scanning electron microscopy and transmission electron microscopy ascertain embedded, anchored and homogeneously implanted carbon nanotubes in silver matrix. Effect of covalent functionalization on multiwall carbon nanotubes was monitored by Raman and Fourier transform infrared spectroscopy. These investigations confirm the addition of functional groups and structural integrity of carbon nanotubes even after covalent functionalization. Thermal conductivity of composites was measured by a laser flash technique and theoretically analyzed using an effective medium approach. The experimental results reveal that thermal conductivity decreases after incorporation of covalently functionalized multiwall nanotubes and single wall carbon nanotubes. However, non-covalently functionalized multiwall nanotube reinforcement leads to the increase in effective thermal conductivity of the composite and is in agreement with theoretical predictions derived from effective medium theory, in absence of interfacial thermal resistance.

ChemInform Abstract: Pt‐Based Nanoparticles on Non‐Covalent Functionalized Carbon Nanotubes as Effective Electrocatalysts for Proton Exchange Membrane Fuel Cells

AbstractReview: 168 refs.

Controlled growth of nanostructured MnO2 on carbon nanotubes for high-performance electrochemical capacitors

The rational combination of transition metal oxides and carbon materials has been regarded as an efficient way of accessing the next-generation electrode materials for electrochemical capacitors. Here we demonstrate a facile synthesis of nanostructured MnO2 supported on carbon nanotubes (CNTs) via a direct redox route. By varying the reaction time, it can be convenient to control the growth density of MnO2 as well as the structural integrity of CNTs, which endow the novel hybrids with adjustable electrochemical performance. As a consequence, the resulting MnO2-CNT electrodes exhibit a maximum specific capacitance of 247.9Fg-1, with good rate capability and extraordinary cycling life stability (92.8% retention of initial capacitance after 5000 cycles), suggesting such materials have great potential in constructing high-performance energy-storage systems.