Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.     

Mechanical and tribological properties of self-lubricating metal matrix nanocomposites reinforced by carbon nanotubes (CNTs) and graphene – A review

Rapid innovation in nanotechnology in recent years enabled development of advanced metal matrix nanocomposites for structural engineering and functional devices. Carbonous materials, such as graphite, carbon nanotubes (CNT's), and graphene possess unique electrical, mechanical, and thermal properties. Owe to their lubricious nature, these carbonous materials have attracted researchers to synthesize lightweight self-lubricating metal matrix nanocomposites with superior mechanical and tribological properties for several applications in automotive and aerospace industries. This review focuses on the recent development in mechanical and tribological behavior of self-lubricating metallic nanocomposites reinforced by carbonous nanomaterials such as CNT and graphene. The review includes development of self-lubricating nanocomposites, related issues in their processing, their characterization, and investigation of their tribological behavior. The results reveal that adding CNT and graphene to metals decreases both coefficient of friction and wear rate as well as increases the tensile strength. The mechanisms involved for the improved mechanical and tribological behavior is discussed.     

Mechanical properties and microstructure of SiC-reinforced Mg-(2,4)Al-1Si nanocomposites fabricated by ultrasonic cavitation based solidification processing

Nano-sized SiC enhanced magnesium matrix nanocomposites, Mg-2Al-1SiC with 2% SiC and Mg-4Al-1Si with 2% SiC, were successfully fabricated by ultrasonic cavitation based dispersion of SiC nanoparticles in Mg-(2,4)Al-1Si magnesium alloy melts. As compared to the magnesium alloy matrixes, the mechanical properties including tensile strength and yield strength of the Mg-2Al-1Si/2% SiC and Mg-4Al-1Si/2% SiC nanocomposites were improved significantly, while the ductility of magnesium alloy matrix castings was retained. While there were some SiC micro-clusters in the microstructure of nanocomposites, the SiC nanoparticles were dispersed well outside the areas of micro-clusters. Most micro-clusters were located along the grain boundaries while most separate SiC nanoparticles were embedded inside the grains. TEM study of the interface between SiC nanoparticles and Mg-(2,4)Al-1Si metal matrixes suggested that SiC bonds well with the metal matrixes without forming an intermediate phase.     

Synthesis and characterization of dual particle (MWCT+B4C) reinforced sintered hybrid aluminum matrix composites

ABSTRACT

Metal matrix nanocomposites (MMNCs) consist of a metal matrix reinforced with nanoparticles, featuring physical and mechanical properties very different from those of the matrix. Especially carbon nanotubes (CNTs) can improve the matrix material in terms of wear resistance, damping properties, and mechanical strength. The present investigation deals with the synthesis and characterization of aluminum matrix reinforced with micro-B₄C particles, and multiwall carbon nanotubes (MWCNTs) which have been prepared by powder metallurgy route. Powder mixture containing fixed weight (%) of B₄C and different wt% of MWCNT as reinforcement constituents that are uniaxial cold pressed and later green compacts are sintered in continues electric furnace. Microstructure and Mechanical properties such as microhardness and density are examined. Microstructure of samples has been investigated using scanning electron microscope (SEM). X-ray diffraction(XRD), energy dispersive x-ray (EDAX), atomic force microscope (AFM), and transmission electron microscope (TEM). TEM microstructure of the nanocomposite shows the homogeneous dispersion of MWCNT in the aluminum matrix. The results indicated that the increase in wt % of MWCNT improves the bonding and mechanical properties.     

Void formation in metal matrix composites by solidification and shrinkage of an AlSi7 matrix between densely packed particles

Particle reinforced metals are developed as heat sink materials for advanced thermal management applications. Metal matrix composites combine the high thermal conductivity of a metal with a low coefficient of thermal expansion of ceramic reinforcements. SiC and carbon diamond particle reinforced aluminum offer suitable thermal properties for heat sink applications. These composites are produced by liquid metal infiltration of a densely packed particle preform. Wettability, interface bonding strength and thermal mismatch are critical for void formation which leads to thermal fatigue damage under operation. The evolution of voids in AlSiC and AlCD has been studied by in-situ high resolution synchrotron tomography during matrix solidification. Large irregularly shaped matrix voids form during eutectic solidification. These voids help alleviate thermal expansion mismatch stresses by visco-plastic matrix deformation during cooling to RT after solidification, if sufficient interface bonding strength is assumed.     

Production of high strength Al-Al2O3 composite by accumulative roll bonding

Recently accumulative roll bonding has been used as a novel method to produce particle reinforced metal matrix composites. In this study, aluminum matrix composite reinforced by submicron particulate alumina was successfully produced and the effects of number of ARB cycles and the amount of alumina content on the microstructure and mechanical properties of composites were investigated. According to the results of tensile tests, it is shown that the yield and tensile strengths of the composite are increased with the number of ARB cycles. Scanning electron microscopy (SEM) reveals that particles have a random and uniform distribution in the matrix by the ARB cycles and a strong mechanical bonding takes place at the interface of particle-matrix. It is also found that the tensile strength of the composite, as a function of alumina content, has a maximum value at 2 vol.%, which is 5.1 times higher than that of the annealed aluminum.     

Carbon Nanotube Pullout,Interfacial Properties,and Toughening in Ceramic Nanocomposites: Mechanistic Insights from Single Fiber Pullout Analysis

While debonding and subsequent pullout at fiber‐matrix interfaces can improve fracture toughness in ceramic nanocomposites, the magnitudes of these contributions are currently the subject of ongoing debate. To provide quantitative insight into these mechanisms, ceramic matrix nanocomposites were fabricated with a polymer‐derived ceramic matrix, using multiwalled carbon nanotubes (MWCNTs) that exhibit relatively long pullout lengths. In situ micromechanical pullout tests on individual MWCNTs were used to directly measure the strength of the fiber‐matrix interface. Similar pullout lengths were also observed in bulk and thin film composites, where the fracture toughness of the composite films was measured and found to be higher than that of the matrix material. The interfacial properties from the micromechanical test and the pullout lengths from the composite films were then used to estimate the energy release rates for fiber debonding and pullout. Based on the observed MWCNT and composite failure mechanisms, these results are discussed in terms of their relation to previous estimates of toughening in MWCNT‐ceramic nanocomposites, and in terms of design possibilities for further fracture toughness improvements.     

金属基复合材料(MMCs)的原位制备

本文概述了几种原位法制备颗粒增强金属基复合材料 (MMCs)的基本原理和过程 ,包括原位凝固自生法、VLS法、自蔓延高温合成法 (SHS)、接触反应法、固 液反应法、混合盐反应法及直接氧化法 ,简述了原位复合材料的基本性能 ,并提出了今后的发展方向     

Microstructural Analysis of the Reinforced Al‐Cu5mgti/Tib2 5 wt % Alloy for Investment Casting Applications

The paper describes the influence of 5 wt % titanium diboride (TiB₂) particles on the microstructure of an Al‐Cu alloy produced by plaster casting process. The elaboration route leads to a composite material with 1% of in situ TiB₂ particles and 4% ex situ of TiB₂ particles. The comparison of the reinforced alloy with the corresponding non‐reinforced counterpart makes clear that the presence of TiB₂ particles has a large influence in the observed microstructure. The presence of TiB₂ particles decreases the grain sizes and the porosity level. It is also found that TiB₂ particles play an important role in the precipitation events of Al₂Cu precipitates that are formed during solidification at the TiB₂/aluminum matrix interfaces.     

Polymer Nanocomposites with Ultrahigh Energy Density and High Discharge Efficiency by Modulating their Nanostructures in Three Dimensions

Manipulating microstructures of composites in three dimensions has been a long standing challenge. An approach is proposed and demonstrated to fabricate artificial nanocomposites by controlling the 3D distribution and orientation of oxide nanoparticles in a polymer matrix. In addition to possessing much enhanced mechanical properties, these nanocomposites can sustain extremely high voltages up to ≈10 kV, exhibiting high dielectric breakdown strength and low leakage current. These nanocomposites show great promise in resolving the paradox between dielectric constant and breakdown strength, leading to ultrahigh electrical energy density (over 2000% higher than that of the bench‐mark polymer dielectrics) and discharge efficiency. This approach opens up a new avenue for the design and modulation of nanocomposites. It is adaptable to the roll‐to‐roll fabrication process and could be employed as a general technique for the mass production of composites with intricate nanostructures, which is otherwise not possible using conventional polymer processing techniques.     

Innovative light metals: metal matrix composites and foamed aluminium

Low weight is required especially for those means of transport, in which material properties have to be evaluated with respect to their specific mass. The possibility of increasing the specific properties of recyclable light metals are described: reinforcements by ceramic particulates, by continuous ceramic or carbon fibres, or by the reduction of weight by foaming the metal. Examples of castings, extrusions and forgings of particulate reinforced (<30 vol.%) aluminium alloys are given and their advantages including stiffness and wear resistance are presented. The technique of selective reinforcements by co-extrusion of particulate reinforced alloys together with conventional alloys is described. High volume fractions (>40 vol.%) of reinforcements can be produced by gas pressure infiltration of either particulate or fibre preforms. In the case of aluminium matrix, the specific strength can be increased by a factor of up to 15, and the specific stiffness by a factor of up to 7, whereas for carbon fibre reinforced magnesium the specific strength can be increased even more. The anisotropy of fibre reinforced metal matrix composites is discussed as well as the possibilities to use cross ply preforms. The technique of foaming aluminium alloys yields materials with a specific mass in the range of 0.3–1.0 g/cm³. Such structures with essentially closed pores exhibit higher specific stiffness for beams and membranes than massive metal. The measurement and definition of stiffness and strength values appropriate for aluminium foams are presented by referring to compression tests.     

AZ91D/TiB2 Nanocomposites Fabricated by Solidification Nanoprocessing

AZ91D, as one of the most widely used casting magnesium alloys, still suffers from inadequate mechanical performances for various applications. Nanoparticles could be used to form high‐performance magnesium matrix nanocomposites. Among all nanoparticles, TiB₂ has great potentials to enhance the mechanical property of AZ91D. This paper studies the microstructures and mechanical property of AZ91D‐TiB₂ nanocomposites fabricated through solidification nanoprocessing. TiB₂ nanoparticles with a diameter of 25 nm are effectively fed into the AZ91D melt through a newly developed automatic nanoparticle‐feeding system. Ultrasonic cavitation is used to disperse these nanoparticles in AZ91D melt for casting. With 2.7 wt% (about 1.0 vol%) of TiB₂ nanoparticles addition, the mechanical property of AZ91D is much enhanced (by 21, 16, and 48% for yield strength, tensile strength, and ductility, respectively). Microstructural analysis with optical microscope, SEM, and S/TEM show that α‐Mg grain and a network of massive brittle intermetallic phase (β‐Mg₁₇Al₁₂) are simultaneously refined and modified. Further study suggests that the enhancement of mechanical properties of AZ91D is attributed not only to primary phase grain refinement, but also to the modification of intermetallic β‐Mg₁₇Al₁₂ by TiB₂ nanoparticles.     

颗粒增强镁基复合材料的研究现状及发展趋势

综述了颗粒增强镁基复合材料的研究概况,着重介绍了颗粒增强镁基复合材料的制备技术,界面行为和制备热力学与动力学三大研究热点,另外,对颗粒增强镁基复合材料的增强机理及常温力学性能作了简单介绍,最后,对颗粒增强镁基复合材料的研究方向进行了一些看法和展望,指出原位颗粒增强镁基复合材料的制备技术交城为制备镁基复合材料的发展趋势,镁基复合材料由于具有高的比强度,比模量和良好的耐磨性、耐高温性能和减震性能,在航空航天,特别是汽车工业具有在的应用前景和广阔的市场。     

Investigations on the microstructures and properties of in‐situ synthesized (TiB2+Fe2B)/steel‐based composites

By adding titanium and boron elements in the molten steel whose compositions were 0.10–0.30 %C, 0.20–0.50 %Si, 0.60–1.20 %Mn and 0.50–1.50 %Cu, particulate‐reinforced metal matrix composites (MMCs) were obtained. The reinforced phase and matrix were studied by means of the optical microscopy (OM), the scanning electron microscopy (SEM) and the X‐ray diffraction (XRD). Moreover, the mechanical properties and abrasion resistance of steel‐based MMCs were measured. The results show that the in‐situ reinforced particulates of steel‐based MMCs are TiB₂ and Fe₂B. After heat treatment, the in‐situ reinforced particulates change into the nodular and granular forms from the broken networks. The mechanical properties and abrasion resistance of steel‐based MMCs are improved obviously. At last, the reason that in‐situ reinforced particulates improve the properties of steel‐based MMCs is particularly analyzed.     

Al/CNT nanocomposite fabrication on the different property of raw material using a planetary ball mill

In recent years, significant research has been focused on the development of carbon nanotube (CNT) reinforced aluminum nanocomposites, which are quickly emerging because of their lightweight, high strength and other mechanical properties. The potential applications of these composites include the automotive and aerospace industries. In this study, powder metallurgy techniques are employed to fabricate aluminum (Al)/CNT nanocomposites with different raw material properties with optimized conditions. We successfully fabricated three different samples, including un-milled Al, un-milled Al with CNT and milled Al with CNT nanocomposites, in the presence of additional CNTs with various experimental conditions using a planetary ball mill. Scanning electron microscopy and field emission scanning electron microscopy are used to evaluate the particle morphology and CNT dispersion. The CNTs are well dispersed on the surface of the fabricated milled Al with CNT nanocomposites than un-milled Al with CNT nanocomposites for milling. The fabricated Al/CNT nanocomposites are processed by a compacting, sintering and rolling process. Vickers hardness measurements are used to characterize the mechanical properties. The hardness of the Al/CNT nanocomposites are improved milled Al with CNT nanocomposite compared other fabricated composites.     

Dissimilar Friction Stir Welding Between 5083 and 6082 Al Alloys Reinforced With TiC Nanoparticles

Dissimilar friction stir welding between aluminum alloys thick plates reinforced with TiC nanoparticles was conducted. The defect-free welds are characterized by good mechanical mixing between the joined materials as well as by good nanoparticle distribution and further grain refinement in comparison with the unreinforced weld. The local mechanical behavior of the produced metal matrix composites was studied and compared with their bulk counterparts and parent materials. Specifically, the measured mechanical properties in microscale and nanoscale (namely hardness and elastic modulus) are correlated with microstructure and the presence of fillers. The hardness, elastic modulus, ultimate tensile strength, percentage of elongation, and yield values increase with the presence of TiC nanoparticles.     

Study on bulk aluminum matrix nano-composite fabricated by ultrasonic dispersion of nano-sized SiC particles in molten aluminum alloy

Lightweight metal matrix nano-composites (MMNCs) (metal matrix with nano-sized ceramic particles) can be of significance for automobile, aerospace and numerous other applications. It would be advantageous to produce low-cost as-cast bulk lightweight components of MMNCs. However, it is extremely difficult to disperse nano-sized ceramic particles uniformly in molten metal. This paper presents a new method for an inexpensive fabrication of bulk lightweight MMNCs with reproducible microstructures and superior properties by use of ultrasonic nonlinear effects, namely transient cavitation and acoustic streaming, to achieve uniform dispersion of nano-sized SiC particles in molten aluminum alloy A356. Microstructural study was carried out with an optical microscope, SEM, EDS mapping, and XPS. It validates a good dispersion of nano-sized SiC in metal matrix. It also indicates that partial oxidation of SiC nanopartilces results in the formation of SiO₂ in the matrix. Mechanical properties of the as-cast MMNCs have been improved significantly even with a low weight fraction of nano-sized SiC. The ultrasonic fabrication methodology is promising to produce a wide range of other MMNCs.     

Statistical analysis of mechanical properties of pressureless sintered multiwalled carbon nanotube/alumina nanocomposites

Mechanical properties of pressureless sintered 0.15–1.2 vol.% multiwalled carbon nanotube reinforced alumina matrix nanocomposites have been analyzed using the 2-parameter Weibull statistics. Electron microscopy and phase analysis of nanocomposites sintered at 1700 °C for 2 h in Argon revealed existence of interpenetrating network of nanotubes in alumina, formation of thin interface resembling stoichiometric aluminum monoxycarbide and matrix grain refinement by nanotubes. Statistical analyses indicated that with increasing Vickers hardness testing load (4.9–19.6 N) and flexural strength measurement temperature (room temperature to 1100 °C), Weibull modulus of nanocomposites increased significantly suggesting improved consistency at higher load and temperature. The highest Weibull moduli were obtained for nanocomposites containing either 0.15 or 0.3 vol.% nanotube which were ∼40% and ∼15% higher than single phase alumina for hardness and strength, respectively, supporting the specimen size effect on reliability of present brittle ceramic matrix nanocomposites. Superior mechanical reliability of nanocomposites over pure alumina was primarily attributed to the presence of structurally intact nanotubes forming effective interface region to ensure proper load sharing, matrix grain refinement, and especially, at higher testing load and temperature, overall averaging effect of flaws to yield higher Weibull moduli.     

Mechanical and functional properties of ultrafine grained Al wires reinforced by nano-Al2O3 particles

A powder metallurgy route based on high-energy ball milling, powder consolidation by hot extrusion and cold rolling was used to produce Al composite wires reinforced with Al₂O₃ nanoparticles. The process was capable of preparing fully dense nanocomposites characterized by well dispersed nanoparticles in a ultra-fine grained matrix. Ball milling led to the fragmentation of the passivation oxide layer that covers the aluminum particles and of the alumina particle clusters added ex-situ in addition to embedding these nano-sized particles in the Al matrix and thus producing optimal precursors for subsequent consolidation. The nanocomposites showed improved mechanical performances in term of hardness and tensile strength. They also exhibited excellent damping behavior at high temperatures.     

Study on tensile properties and microstructure of cast AZ91D/AlN nanocomposites

AZ91D is a widely used magnesium alloy, but its application is generally limited to below 150 °C because of its weak creep resistance and tensile properties at elevated temperatures. In this study, high temperature (200 °C) tensile properties including yield strength and tensile strength of AZ91D are much improved by adding only about 1.0 wt% AlN nanoparticles in the AZ91D matrix through an innovative ultrasonic cavitation based dispersion of nanoparticles. The good ductility of AZ91D is also retained in AZ91D/1%AlN nanocomposites. It is found that ultrasonic cavitation based solidification processing is very effective to disperse AlN nanoparticles in AZ91D melts, which is difficult to obtain by traditional mechanical stirring methods. With a good combination of high temperature yield strength, tensile strength and ductility, AZ91D/1%AlN nanocomposite is promising as a new class of structural materials to be used at temperatures up to 200 °C or higher.