Nano-Materials Research Lab. (NMRL)
Carbon Nanotubes (CNT): Carbon nanotubes are a relatively new material system, only discovered in 1991, and of particular interest to many researchers is the nanotubes very interesting electronic structure. Theoretical work has shown that carbon nanotubes can exhibit metallic and semi-conducting behavior depending on the magnitude and direction of the chiral vector. Through utilization of this chirality, many novel nanoscale devices are possible including; field-effect transistors, field-emission electron sources, nano-coils, and other devices based on metal/semi-conductor and semi-conductor/semi-conductor heterojunctions.
The mechanical aspects of carbon nanotubes also show great promise in the development of high-strength lightweight reinforced composite materials for structural and biological applications. Both theory and experiment have estimated the Young’s modulus of single and multi-wall carbon nanotubes near 1 Tpa, approximately an order of magnitude higher than SiC and diamond.
Nanotube Growth
Deposition Systems: We have two CVD carbon nanotube deposition systems within NMRL. The first is a ‘simple’ high temperature CVD growth system with a methane feed gas and 4” capability. The second is a lower temperature plasma system with 1” capability and acetylene feed gas.
As the CVD process entails the catalytic decomposition of methane over a Ni or Fe based catalyst in a tube furnace, the influence parameters of reaction time and different carrier gases on the growth morphology of CNTs are being studied using SEM, in-situ TEM, AFM (Harris) and Raman analysis (Dines).
Nanotube Catalyst Systems: Formation and performance of the catalyst is key to optimal growth of CNTs. In addition to conventional sol-gel CNT catalyst growth methods, NMRL (in collaboration with Aktina) have developed a novel nanoscale catalyst particle system to provide non-lithographically dispersed catalyst down to 5 nm.
To achieve a controllable growth of the CNTs, understanding of their growth mechanism is important. The generally accepted growth processes of CNTs by CVD involve adsorption and decomposition of hydrocarbon gases containing carbon on metal surfaces, dissolution and diffusion of the released carbon atoms in the catalyst, and precipitation of the graphite-like layers. State-of-the-art modeling and simulation to aid in the understanding of the growth process is being employed.
Nanotube Functionalization – An Enabling Technology
To expand the use of CNTs, it is necessary for them to be functionalized. The combination of nanotubes with proteins and other natural products allows the compatibility of such materials with biological systems. Dispersibility of CNTs in aqueous media is a fundamental pre-requisite for biological and engineering applications. CNTs are practically insoluble in any type of solvent and only the development of strategies for linking chemical moieties on the tubes has facilitated their dispersion, allowing solubility to be modulated in different solvents.
Bio-Engineering
In the past, graphite has been associated with various toxological effects including dermatitis and inflammation. In defence of CNTs, studies so far have focused on the effects of pristine CNT. Significant efforts have been made to improve CNT solubility and a remarkable reduction in toxicity has resulted.
Medical and Dental Materials Engineering
Implant Technology: These studies are focused on stimulating bone cell migration and differentiation and nerve cell growth.
Nano-Materials for Optical Devices
The interaction of CNTs with light has many potential applications for ultra-compact tuneable emitters and detectors. The phonon-photon interaction cross-section can increase by up to 5 orders of magnitude and optical observation of single-nanotube phenomena becomes feasible. Such enhancement could lead to enhanced thresholdless lasers, single-photon sources, and absorbers with low saturation fluence.
Nano-Particle Enhanced Infrastructure Materials
NMRL is working with the Concrete Technology Unit at Dundee, on the development of CNT-concrete composites to give specific functional behaviour to structural materials. It has been shown that CNTs can provide enhanced energy absorbing and tensile strain capacity.
Nano Electro-Mechanical Systems (NEMS) Utilizing Nanotubes
NEMS takes advantage of the nanotube’s electro-mechanical and perfect structural properties. The high Young’s modulus of nanotubes (1TPa) and their defect-free nature could enable CNT oscillators with a resonance frequency of ~1GHz and very high Q.
Nano-Materials for Power Applications
The extraordinary conductivity of CNTs (electrical=104S/cm) coupled with their high aspect ratio has contributed to dramatic enhancement in composite conductivity. Improvements in the performance of power devices, such as thin-film polymeric solar cells, enhanced electrodes, fuel cells, lithium-ion batteries and thermionic power supplies has been shown.
Nano-Emissive Displays
This R&D project investigates recent technology developments that have shown potential to produce flat panel NEDs using either arrays of nano-crystalline silicon, or carbon nanotube emitters illuminating each pixel. This project has investigated the controlled stimulation of these emitters enabling them to emit electrons and act as a miniature electron gun. Theses NED technologies have the potential to deliver large screen (100”) CRT-level performance, with enhanced brightness, wide angle viewing, contrast, response time and wide colour gamut.
Materials Engineering for Environmental & Renewable Energy Applications
Hydrogen Storage, Carbon Sequestration and Water treatment
This page is maintained by the Nanoscale Materials Research Laboratory.
del.icio.us
digg
reddit
facebook
stumbleupon