Dispersion analysis of carbon nanotubes, carbon onions, and nanodiamonds for their application as reinforcement phase in nickel metal matrix composites (original) (raw)
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Nickel-carbon nanocomposites: Synthesis, structural changes and strengthening mechanisms
Acta Materialia
The present work investigates Ni-nanodiamond and Ni-graphite composites produced by mechanical synthesis and subsequent heat treatments. Processing of nickel-carbon nanocomposites by this powder metallurgy route poses specific challenges, as carbon phases are prone to carbide conversion and amorphization. The processing window for carbide prevention has been established through X-ray diffraction by a systematic variation of the milling parameters. Transmission electron microscopy confirmed the absence of carbide and showed homogeneous particle distributions, as well as intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained largely unaffected by mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. The results on the annealed nanocomposites showed that milling with Ni accelerated graphitization of the carbon phases during heat treatments at 973 and 1073 K in both composites. At the finer scales, the nanocomposites exhibited a remarkable microhardness enhancement ($70%) compared with pure nanostructured nickel. The Hall-Petch relation and the Orowan-Ashby equation are used to discuss strengthening mechanisms and the load transfer ability to the reinforcing particles.
Strength versus ductility in carbon nanotube reinforced nickel matrix nanocomposites
Journal of Materials Research, 2014
Two types of carbon nanotube reinforced nickel (CNT/Ni) nanocomposites were processed, both involving spark plasma sintering (SPS) of precursor powders consisting of nickel and carbon nanotubes. The first type involved simple mechanical dry milling of nickel and CNT powders, followed by sintering using SPS, resulting in nanocomposites exhibiting a tensile yield strength of 350 MPa (about two times that of SPS processed monolithic nickel with a strength of 160 MPa) and about 30% elongation to failure. In contrast, the nanocomposites processed by SPS of powders prepared by molecular-level mixing (MLM) exhibited substantially higher tensile yield strength of 690 MPa but limited ductility with an 8% elongation to failure. While the former type of processing involving dry-milling is expected to be lower in cost as well as easy to scale-up, the latter type of processing technique involving MLM leads to a more homogeneous distribution of nanotubes, leading to extraordinarily high strength levels.
In-situ nanodiamond to carbon onion transformation in metal matrix composites
Carbon, 2018
In the present study, nickel matrix composites reinforced with a fine distribution of nanodiamonds (6.5 vol%) as reinforcement phase are annealed in vacuum at different temperatures ranging from 750 °C to 1300 °C. This is carried out to evaluate the in-situ transformation of nanodiamonds to carbon onions within a previously densified composite. The resulting materials are thoroughly analyzed by complementary analytical methods, including Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The proposed in-situ transformation method presents two main benefits. On one hand, since the particle distribution of a nanodiamond-reinforced composite is significantly more homogenous than in case of the carbon onions, it is expected that the transformed particles will preserve the initial distribution features of nanodiamonds. On the other hand, the proposed process allows for the tuning of the sp 3 /sp 2 carbon ratio by applying a single straightforward post-processing step.
Advanced Engineering Materials, 2017
Nickel matrix composites are produced with concentrations of 0.5-10 vol.% of carbon nanotubes (MWCNTs), onion-like carbon (OLC) or nanodiamonds (nDs) as reinforcements by hot pressing. After densification, a secondary annealing step is conducted to induce grain growth and thus to analyse the effect of the different carbon nanoparticles (CNP) and their concentrations on the microstructure. Grain sizes are measured by electron backscatter diffraction and a model based on the Zener equation is adapted to predict the observed grain refinement for all CNP. It is shown that the model is valid, as long as no saturation value of the refinement effect is reached. However, the individual concentration at which a saturation value is reached differs, which is correlated to the mean CNP agglomerate diameter distribution. For MWCNTs and OLCs, an increasing grain refinement is observed for up to 3 vol.% and 6.5 vol.%, respectively. However, for nDs the mean grain size is decreasing up to 10 vol.%. This difference is correlated to different hybridization states or different particle geometries for all CNP. As information regarding hybridization state and particle
Carbon nanotubes for integration into nanocomposite materials
2006
We have synthesised carbon nanotubes by thermal chemical vapour deposition using C 2 H 2 /N 2 . Multiwalled carbon nanotubes (MWNTs) have been produced uniformly with high yield on Si substrates using thin nickel layers as catalyst material. It is observed that surface modification of the Ni by annealing in N 2 and etching in an HF solution prior to the reaction of C 2 H 2 gas are crucial steps for MWNTs growth. This pretreatment, coupled with growth temperature, can be used to control the diameters of the carbon nanotubes grown. We have used such MWNTs as reinforcements within a polymer matrix to produce a composite material with improved properties.
Physical Review B, 2010
We report an atomistic simulation study of the behavior of nanocomposite materials that are formed by incorporating single-walled carbon nanotubes ͑SWCNTs͒, with three different diameters, and a multiwalled carbon nanotube ͑MWCNT͒ into a single-crystal nickel matrix. The interactions between carbon and nickel atoms are described by a modified embedded atom method potential. Mechanical properties of these nanocomposite materials are predicted by atomistic calculations and compared with that of fcc nickel and pristine CNTs. Our simulations predict that all Ni/CNT composites studied in this work are mechanically stable. Their elastic properties depend on the volume fraction and diameter of embedded CNTs. The single-crystal Young's modulus ͑E 11 ͒ of Ni/SWCNT composites exhibit a large increase in the direction of CNTs alignment compared to that of a single-crystal nickel. However, a moderate but gradual decrease is seen for E 22 and E 33 in the transverse directions with increase in CNT diameters. As a consequence, Ni/SWCNTs show a gradual decrease for the polycrystalline Young's, bulk and shear moduli with the increasing CNT diameters and volume fractions. These reductions, although moderate, suggest that enhancement of mechanical properties for polycrystalline Ni/SWCNT nanocomposites are not achievable at any CNT volume fraction. The Ni/MWCNT composite with high CNT volume fraction shows the highest increase in E 11. Unlike the E 22 and E 33 for Ni/ SWCNTs, there is a significant increase in the E 22 and the E 33 for Ni/MWCNT. As a result, polycrystalline Ni/MWCNT composites show slight increase in the elastic properties. This suggests that nickel nanocomposites with enhanced mechanical properties can be fabricated using large volume fractions of larger diameter MWCNTs. Depending on type, alignment and volume fraction, Ni/CNT composites show varying degrees of elastic anisotropy and Poisson's ratio compared to pure Ni. Simulation predicts strong adhesion at the Ni/CNT interface and a significant interfacial stress transfer between CNT and Ni matrix.
Journal of Alloys and Compounds, 2019
Spark plasma sintered NiAl-CNTs intermetallic composites were fabricated via two different ball milling processes. One comprising of an exclusive low energy ball milling (LEBM), and the other comprising of a two-stage milling, typically a prolonged LEBM with a short term high energy ball milling (HEBM). The differently milled powders were consolidated, and the resulting composites characterized. This was done to determine the individual effects of agglomerations visa -vis the structural integrity of the nanotubes. The composites were extensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy (RS), scanning electron microscopy (SEM) and nanoindentation techniques. The uniform dispersion of slightly impaired CNTs led to better mechanical properties as compared to the in-homogenous dispersion of higher structural integrity CNTs in the NiAl intermetallic matrices. Results showed that the sample with a two-stage milling exhibited superior mechanical properties in terms of hardness, elastic modulus and fracture toughness with 422.79 Hv, 50.5 GPa and 9 MPa√m respectively.
Critical Reviews in Solid State and Materials Sciences, 2016
This article reviews the available literature published to date on the reinforcement of metals with carbon-nanofillers (CNTs and graphene), and also offers a specific focus on issues related to the mechanical and tribological properties of nanocomposites. Carbon-nanofillers (later denoted by C-nanofillers) are known to have extraordinary mechanical properties and multifaceted characteristics and are ideal candidates for the reinforcement of metals for numerous applications. However, their incorporation for practical applications has been challenging researchers for decades. The most important issue is uniform dispersion due to sizeable surface differences between carbon-nanofillers and metals. Other concerns are structural integrity, wetting with metals, and interfacial connections. Nanocomposite applications can only be effective when these challenges are properly addressed and overcome. Section 1 assesses the importance of C-nanofillers and expressly highlights current research efforts to optimize dispersion in different metals along with processing techniques in section 2. The authors give special attention on C-nanofillers reinforcement contribution to enhanced mechanical strength of metals presented in section 3. C-nanofillers dispersion evaluation tools are highlighted in section 4. Authors also focuses on C-nanofillers role and factors directly associated with metal nanocomposite strength, as reported in the literature. Particular consideration is also given to knowledge sharing of attendant strengthening mechanisms along with contribution reported for empirically derived models used to predict strength. Section 6 solely dedicated to the tribological aspects of C-nanofillers reinforced metallic nanocomposites. Lastly, future recommendations and works need attention is summarized.
Tribological Behavior of Carbon-Based Nanomaterial-Reinforced Nickel Metal Matrix Composites
Materials, 2021
Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) with exceptional mechanical, thermal, chemical, and electrical properties are enticing reinforcements for fabricating lightweight, high-strength, and wear-resistant metal matrix composites with superior mechanical and tribological performance. Nickel–carbon nanotube composite (Ni-CNT) and nickel–graphene nanoplatelet composite (Ni-GNP) were fabricated via mechanical milling followed by the spark plasma sintering (SPS) technique. The Ni-CNT/GNP composites with varying reinforcement concentrations (0.5, 2, and 5 wt%) were ball milled for twelve hours to explore the effect of reinforcement concentration and its dispersion in the nickel microstructure. The effect of varying CNT/GNP concentration on the microhardness and the tribological behavior was investigated and compared with SPS processed monolithic nickel. Ball-on-disc tribological tests were performed to determine the effect of different structural morphologies of CNTs and...