Part of a series of articles on |
Nanotechnology |
---|
Nanomaterials |
Nanomedicine |
Molecular self-assembly |
Nanoelectronics |
Scanning probe microscopy |
Molecular nanotechnology |
Nanotechnology Portal |
Carbon nanotube metal matrix composites (CNT-MMC) are an emerging class of new materials that are being developed to take advantage of the high tensile strength and electrical conductivity of carbon nanotube materials. Critical to the realization of CNT-MMC possessing optimal properties in these areas are the development of synthetic techniques that are (a) economically producible, (b) provide for a homogeneous dispersion of nanotubes in the metallic matrix, and (c) lead to strong interfacial adhesion between the metallic matrix and the carbon nanotubes. Since the development of CNT-MMC is still in the research phase, the current focus is primarily on improving these latter two areas.
Contents |
According to the new production systems, Carbon nanotubes reinforced metal matrix composites (CNT-MMC) may produce several different methods. These production methods are: [1] [2]
Powder metallurgy Route Technics
Electrochemical Routes(for non-structural applications)
Melt Processing
Novel Techniques
Indigenous techniques
Sintering is one of the oldest method in production technics and used to produce density-controlled materials and components from metal or ceramic powders by applying thermal energy. [3] Synthesis and sintering of nanocrystalline ceramic powders have attracted much attention due to their promising properties.[4] The high active surface area of nanopowders results in lowering sintering temperature relative to coarser powders. Although low temperature sintering suppresses the grain growth, high density of interfaces and grain boundaries in nanocrystalline powders leads to accelerated grain growth during sintering. [5]
Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms.Multi-walled carbon nanotube was tested to have a tensile strength of 63 gigapascals (GPa).[9]Further studies, conducted in 2008, revealed that individual CNT shells have strengths of up to ~100 GPa, which is in good agreement with quantum/atomistic models.[10] Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3,[11] its specific strength of up to 48,000 kN·m·kg−1 is the best of known materials, compared to high-carbon steel's 154 kN·m·kg−1. CNTs are not nearly as strong under compression. Because of their hollow structure and high aspect ratio, they tend to undergo buckling when placed under compressive, torsional, or bending stress.[12]
Material | Young's modulus (TPa) | Tensile strength (GPa) | Elongation at break (%) |
---|---|---|---|
SWNTE | ~1 (from 1 to 5) | 13–53 | 16 |
Armchair SWNTT | 0.94 | 126.2 | 23.1 |
Zigzag SWNTT | 0.94 | 94.5 | 15.6–17.5 |
Chiral SWNT | 0.92 | ||
MWNTE | 0.2[9]–0.8[17]–0.95[9] | 11[9]–63[9]–150[17] | |
Stainless steelE | 0.186[18]–0.214[19] | 0.38[18]–1.55[19] | 15–50 |
Kevlar–29&149E | 0.06–0.18[20] | 3.6–3.8[20] | ~2 |
EExperimental observation; TTheoretical prediction
Nanonetworks are expected to expand the capabilities of single nanomachines both in terms of complexity and range of operation by allowing them to coordinate, share and fuse information. CNT metal matrix composites enable new applications of nanotechnology in the military technology and industrial and consumer goods applications.
Nanomachines are largely in the research-and-development phase,[21] but some primitive molecular machines have been tested. An example is a sensor having a switch approximately 1.5 nanometers across, capable of counting specific molecules in a chemical sample. The first useful applications of nanomachines might be in medical technology,[22] which could be used to identify and destroy cancer cells.[23][24] Another potential application is the detection of toxic chemicals, and the measurement of their concentrations, in the environment.In addition CNT-MM composite will be the main material for the military robots, especially to strentgh the robot soldier's armours.
Today's militaries often use high-quality helmets made of ballistic materials such as Kevlar and Aramid, which offer improved protection. Some helmets also have good non-ballistic protective qualities, though many do not.[25] Non-ballistic injuries may be caused by many things, such as concussive shock waves from explosions, physical attacks, motor vehicle accidents, or falls.[26]Another application for the future soldier is powered exoskeleton system. Powered exoskeleton, also known as powered armor, or exoframe, is a powered mobile machine consisting primarily of an exoskeleton-like framework worn by a person and a power supply that supplies at least part of the activation-energy for limb movement.Powered exoskeletons are designed to assist and protect the soldiers and officers.Currently MIT is working on combat jackets that use CNT fibers to stop bullets and to monitor the condition of the wearer.[27]
Advanced Modular Armor Protection (AMAP) is modular composite armour concept, developed by the German company IBD Deisenroth Engineering. According to IBD AMAP is a 4th generation composite armour, making use of nano-ceramics and modern steel alloy technologies.[28] AMAP is making use of new advanced steel alloys, Aluminium-Titanium alloys, nanometric steels, ceramics and nano-ceramics. The new high-hardened steel needs 30% less thickness to offer the same protection level as ARMOX500Z High Hard Armour steel.[28] While Titanium requires only 58% as much weight as rolled homogeneous armour (RHA) for reaching the same level of protection, Mat 7720 new, a newly developed Aluminium-Titanium alloy, needs only 38% of the weight.[28] That means that this alloy is more than twice as protective as RHA of the same weight.
AMAP is also making use of new nano-ceramics, which are harder and lighter than current ceramics, while having multi-hit capability. Normal ceramic tiles and a liner backing have a mass-efficiency (EM) value of 3 compared to normal steel armour, while it fulfills STANAG 4569. The new nano-crystalline ceramic materials should increase the hardness compared to current ceramics by 70% and the weight reduction is 30%, therefore the EM value is larger than 4.[28] Furthermore the higher fracture toughness increases the general multi-hit capability. Some AMAP-modules might consist of this new ceramic tiles glued on a backing liner and overlaid by a cover, a concept which is also used by MEXAS.[29] Lightweight SLAT armour is also part of the AMAP family.
The TK-X (MBT-X) project, the new Type 10 main battle tank design use composition of modular components of nano-crystal steel (nor Triple Hardness Steel), Modular ceramic composite armor, partly reinforced MMC and Light weight upper armor.
Space elevator is a proposed non-rocket spacelaunch structure (a structure designed to transport material from a celestial body's surface into space).The required strength of the cable will vary along its length, since at various points it has to carry the weight of the cable below, or provide a centripetal force to retain the cable and counterweight above. While some variants of the space elevator concept are technologically feasible, current technology is not capable of manufacturing tether materials that are sufficiently strong and light to build an Earth-based space elevator of the geostationary orbital tether type. Recent concepts for a space elevator are notable for their plans to use carbon nanotube or boron nitride nanotube based materials as the tensile element in the tether design, since the measured strength of carbon nanotubes appears great enough to make this possible.[30]
Materiomics is defined as the study of the material properties of natural and synthetic materials by examining fundamental links between processes, structures and properties at multiple scales, from nano to macro, by using systematic experimental, theoretical or computational methods and refers to the study of the processes, structures and properties of materials from a fundamental, systematic perspective by incorporating all relevant scales, from nano to macro, in the synthesis and function of materials and structures. The integrated view of these interactions at all scales is referred to as a material's materiome.
Materiomics includes the study of a broad range of materials, which includes metals, ceramics and polymers as well as biological materials and tissues and their interaction with synthetic materials. Materiomics finds applications in elucidating the biological role of materials in biology, for instance in the progression and diagnosis or the treatment of diseases. Others have proposed to apply materiomics concepts to help identify new material platforms for tissue engineering applications, for instance for the de novo development of biomaterials. Materiomics might also hold promises for nanoscience and nanotechnology, where the understanding of material concepts at multiple scales could enable the bottom-up development of new structures and materials or devices, including biomimetic and bioinspired structures.
Nanotough is to obtain a deeper understanding of the interfacial structure of nanocomposites within a polyolefin matrix and thus use nanoparticles like nanoclay to turn upside down the construction of a number of well-known products, where today metals or plastics are used in for example cars or aircrafts. The project will enable realization of the great performance potential of these materials through development of novel multiphase and hybrid nanocomposites.
Nanotough project aims to improve the stiffness of polyolefin nanocomposites while not only maintaining but also improving the toughness of the matrix considerably. The technical objective is to optimize and, through novel interface design, to develop new cost effective hybrid (nanofiller-fibre) nanocomposites as an alternative to heavily filled polymers and expensive engineering polymers and fulfill industry requirements for high performance materials in high tech applications. [31]