Polyhedral boranes and carboranes have acquired their popularity for constructing meso and nano-size structures for an array of applications from pharmaceuticals to material science. These three-dimensional boranes range from 4 to 22 boron atom per molecules with delocalized bonding analogous to aromatic compounds. The unique vibrational spectroscopy of the BH function allows for possible application of these species to bioimaging. Silver nanoparticles functionalized with ortho-carboranes have been reported for bioimaging using Surface-enhanced Raman scattering (SERS). The silver nanoparticles were functionalized with antibodies specific to cancer cell receptors. Bonding thiol-substituted carboranes to these particles allowed for observation of enhanced Raman signals as the imaging mode. Here, attempts to synthesize second generation carborane molecules with additional Raman-active group such as nitrile were conducted. Hybrid diblock copolymers have the ability to self-assemble in different morphological patterns depending on the type and ratio of monomers and the compatibilities in various solvents. Linear hybrid diblock copolymers were synthesized by ring-opening metathesis polymerization (ROMP) reactions with norbornenyl-based decaborane and various amounts of norbornene and norbornenyl-ester derivative monomers. Their self-assembly behaviour in various solvents were characterized by NMR, TGA, DSC, and SEM. P(norbornene)60-b-p(norbornenyl-decaborane)40 polymers showed lamellar morphology patterns when slowly evaporated from chloroform. Based on results and the SEM images, a few of these diblock copolymers were used as ceramic precursors and pyrolyzed to elevated temperatures forming boron nitride and boron carbonitride nano-ordered ceramics

Cubic boron nitride (cBN) thin films offer attractive mechanical and electrical properties. The synthesis of cBN films have been deposited using both physical and chemical vapor deposition methods, which generate internal residual, stresses that result in delamination of the film from substrates. Boron nitride films were deposited using electron beam evaporation without bias voltage and nitrogen bombardment (to reduce stresses) were characterize using FTIR, XRD, SEM, EDS, TEM, and AFM techniques. In addition, a pin-on-disk tribological test was used to measure coefficient of friction. Results indicated that samples deposited at 400°C contained higher cubic phase of BN compared to those films deposited at room temperature. A BN film containing cubic phase deposited at 400°C for 2 hours showed 0.1 friction coefficient.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2014. / Boron nitride (BN) in its cubic form (cubic boron nitride (c-BN)) is one of the known superhard materials with superior mechanical, chemical and electronic properties. These properties have made it an excellent material in many modern industrial and electronic applications and as such, extensive research grounds have been developed for over half a decade now with the aim of finding alternative ways to synthesize it. The work presented in this thesis was inspired by the fact that defects introduced into the hexagonal form of boron nitride (h-BN) under certain conditions can lead to a change in its local structure and hence the formation of the cubic BN symmetry. The work focused on the introduction of different ions which included helium, lithium, boron, nitrogen and argon into h-BN, by the ion implantation process, in order to promote a defect-induced phase change to the cubic symmetry and possibly to other BN polymorphs. We introduced these ions at different fluences (number of ions per unit area) and energies so as to investigate the best conditions that will influence the lowest activation energy that will in turn favour the c-BN formation. The resulting thin hard layer could be an excellent sub-surface treatment. All the samples used were high quality polycrystalline and single crystal h-BN, obtained from various manufacturers. The fluence range used was from 1×1013 ions/cm2 to 5×1016 ions/cm2, with energy ranging from 40 keV to 150 keV. This energy and fluence choice was inspired by previous research that had been done at higher energies (MeV range) and recommended that low energy (keV range) and fluence could induce similar change. To investigate these effects, various analysis techniques were employed. The major techniques involved optical vibrational methods using Raman Spectroscopy ii iii (RS) and Fourier Transform Infrared Spectroscopy (FTIR) carried out on the samples before and after implantation. Other techniques used included Glancing Incidence X-ray Diffraction (GIXRD), Transmission Electron Microscopy (TEM), and Energy Dispersive X-ray Spectroscopy (EDS). Raman and FTIR measurements showed the introduction of new phonon and vibrational modes in the samples after implantation. The position, size and broadening suggested that they originated from a symmetry attributed to nano-structured cubic BN (nc-BN). The nature and extent of the nc-BN features was very dependent on the implantation parameters with different atomic mass ions each having an optimum fluence with regards to the intensities of the Raman and FTIR signal associated with them. Glancing incidence X-ray diffraction showed new diffraction patterns whose angles corresponded to the cubic and rhombohedral BN symmetries. The linewidths of these peaks were used to estimate the crystal size, which were in the nanoscale range, hence complementing the results obtained by optical spectroscopy. The High-Angle Annular Dark-field Scanning Transmission Electron microscopy (HAADF-STEM) analyses showed regions with low contrast within the implanted region, suggesting that there were regions within the implanted layer that contained dense structures which were attributed to the cubic BN symmetry. Computer simulations using the Stopping and Range of Ions in Matter (SRIM) programme were performed to understand the events that take place during the interaction of the ions with h-BN. Phonon confinement model calculations were also performed to understand the nature of peaks forming after implantation with an aim of support Raman measurements and to estimate the size of the nc-BN domains. With these complementary analyses, it was concluded that indeed implantation is an effective method of creating nanocrystalline c-BN under less extreme conditions of pressure and temperature.

Thesis (Ph.D.)--City University of Hong Kong, 2009. / "Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 127-136)

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The electrochemical properties of graphene were investigated using a novel and clean method to fabricate device structures with mechanically exfoliated graphene samples. Graphene is known as being particularly sensitive to both contaminating fabrication methods and the substrate it is placed on, with these effects being detrimental to accurate research into the fundamental properties and sensing applications of graphene. This thesis presents micron scale graphene electrodes that have not been subject to polymer contamination or micro-lithography methods. The effect of utilising atomically flat hexagonal boron nitride as a substrate material was investigated, believed to be the first example of this for graphene electrochemical measurements. Cyclic voltammetry demonstrated the expected steady-state behaviour for microelectrodes in the hemispherical diffusion regime. The reduction of IrCl62- in weak KCl electrolytes was studied to investigate the electron transfer characteristics of the graphene devices and the reproducibility of the measurements. Average values of the standard rate constant, k0 and the transfer coefficient, alpha were found to be 3.04 ± 0.78 ×10-3 cms-1 and 0.272 ± 0.024 respectively. These values differ significantly from previous similar studies, with the effect of reduced charge doping from the substrate and the potential dependence of the density of electronic states thought to account for the differences. Despite the clean fabrication methods, a relatively large variation between separate devices was found, highlighting an inherent variation in the properties of graphene samples.

The decomposition of Ammonium Perchlorate (AP), a strong oxidizer used in solid rocket propellant, is widely studied in an attempt to increase the burn characteristics of propellants. Many materials have been shown to catalyze its decomposition, but little is known about the mechanism by which AP decomposition becomes catalyzed. In this study, Boron Nitride (BN) nanostructures, a material previously unknown to act as a catalyst, is studied. The decomposition reaction is studied by thermo-gravimetric analysis / differential scanning calorimetry, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The goal of this study is to discover the activation energy of this catalyst reaction, intermediary products of the reaction, mechanism of reaction and end state of the boron nitride nanostructures (ie, if the BN acts as a true catalyst, or participates on the overall reaction and has some end state that*s different from the initial state). Four variations of BN have been synthesized using a hydrothermal process; BN nanoribbons, Boron Rich BN, Nitrogen-Rich BN, and high surface area BN. It is shown that the decomposition of AP is significantly altered when in the presence of BN and the mechanism through which BN catalyzes the decomposition is most likely the presence of oxidized nitrogen species on the BN material.

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