No description available.

Bottom-up self-assembly has the potential to fabricate nanostructures with advanced electrical features. DNA templates have been used to enable such self-assembling methods due to their versatility and compatibility with various nanomaterials. This dissertation describes research to advance several different steps of biotemplated nanofabrication, from DNA assembly to characterization. I assembled different nanomaterials including surfactant-coated Au nanorods, DNA-linked Au nanorods and Pd nanoparticles on DNA nanotubes ~10 micrometer long, and on ~400 nm long bar-shaped DNA origami templates. I optimized seeding by changing the surfactant and magnesium ion concentrations in the seeding solution. After successful seeding, I performed electroless plating on those nanostructures to fabricate continuous nanowires. Using the four-point probe technique, I performed resistivity measurements for Au nanowires on DNA nanotubes and obtained values between 9.3 x 10-6 and 1.2 x 10-3 ohm meter. Finally, I demonstrated the directed placement of DNA origami using block copolymer self-assembly. I created a gold nanodot array using block copolymer patterning and metal evaporation followed by lift-off. Then, I used different ligand groups and DNA hybridization to attach DNA origami to the nanodots. The DNA hybridization approach showed greater DNA attachment to Au nanodots than localization by electrostatic interaction. These results represent vital progress in understanding DNA-templated components, nanomaterials, and block copolymer nanolithography. The work in this dissertation shows potential for creating DNA-templated nanodevices and their placement in an ordered array in future nanoelectronics. Each of the described materials and techniques further has potential for addressing the need for increased complexity and integration for future applications.

No description available.

No description available.

No description available.

No description available.

The superior properties of carbon nanotubes (CNTs) are best manifest in bulk materials when the CNTs are organized in tandem and embedded in a continuous matrix. Decorating the CNTs with magnetic nanoparticles (MNPs) facilitates their expedient organization with a magnetic field. One of the most convenient methods for their decoration is to first treat the CNTs with oxidative acids, and then coprecipitated MNPs in situ. This method results magnetized CNTs that are covalently functionalized with the MNPs. The associated destruction in the CNTs required running a comparative study of this protocol to identify the influence of the acid treatment on the decoration of multiwalled CNTs (MWNTs). Further, we explore means to tune the physical properties of these magnetized CNTs (mMWNTs) by varying the (1) MNP material composition, and (2) MNP:MWNT (w/w) magnetization weight ratio (γ). The resulted composite materials (mMWNTs) are utilized to synthesize a novel and hitherto unreported class of colloidal suspensions (MCCs) for which the dispersed phase, which consists of MWNTs decorated with MNPs, is both magnetoresponsive and electrically conductive. Synthesis of the dispersed phase merges processes for producing ferrofluids and mMWNTs. Later, these MCCs are adapted and engineered to produce a biological ink containing MWNTs that are twice functionalized, first with MNPs and thereafter with the anti-c-Myc monoclonal antibodies (Abs). The ink is pipetted and dynamically self-organized by an external magnetic field into a dense electrically conducting sensor strip that measures the decrease in current when a sample containing c-Myc antigens (Ags) is deposited on it. On the other side, a nondestructive methods to magnetize MWNTs and provide a means to remotely manipulate them is through the electroless deposition of magnetic nickel nanoparticles on their surfaces. The noncovalent bonds between Ni nanoparticles and MWNTs produce a Ni-MWNT hybrid material (NiCH) that is electrically conductive and has an enhanced magnetic susceptibility and elastic modulus. Raising γ (Ni:MWNT weight ratios) increases the coating layer thickness, which influences the NiCH magnetic properties and tunes its elastic modulus. The NiCH was used to fabricate Ni-MWNT macrostructures and tune their morphologies by changing the direction of an applied magnetic field. Leveraging the hydrophilic Ni-MWNT outer surface, a water-based conductive ink was created and used to print a conductive path that had an electrical resistivity of 5.9 Ωm, illustrating the potential of this material for printing electronic circuits. Further, the NiCHs are introduced into an epoxy matrix at low 0.25-1% volume fractions and aligned along the direction of an applied magnetic field, which produces anisotropic bulk properties. However, nanoparticles aligned in perpendicular directions in sequential layers result in an effectively isotropic composite material. Furthermore, the subsequent annealing of the NiCH in the presence of air oxidizes nickel to nickel oxide whereas carbon is released as gaseous carbon dioxide, which leads to a novel approach for the fabrication of nickel oxide nanotubes (NiONTs) based on MWNTs as a sacrificial template. New chelating polyelectrolytes are used as dispersing agents to achieve high colloidal stability both for NiCH and NiONTs. A gravimetric specific capacitance of 245.3 F g-1 and areal capacitance of 3.28 F cm-2 at a scan rate of 2 mV s-1 is achieved with an electrode fabricated using nickel oxide nanotubes as the active element with a mass loading of 24.1 mg/cm2. / Thesis / Doctor of Philosophy (PhD) / The superior properties of carbon nanotubes (CNTs) are best manifested in bulk materials when the CNTs are organized axially and in tandem, and embedded in a continuous matrix. Decorating the CNTs with magnetic nanoparticles (MNPs) facilitates their organization through “action from a distance” with a magnetic field. The attachment of MNPs to the surfaces of CNTs can be realized through covalent or non-covalent (i.e. physical) bonding. This work develops both methodologies to investigate how the physical properties of magnetized CNT (mCNT) can be tuned and produce new CNT-based nanostructures for particular applications. First, mCNTs are utilized to synthesize a hitherto unreported class of colloidal suspensions based on which a magnetic bio-ink is fabricated to print a fast-response biological sensor. Next, nickel-coated CNTs prepared using electroless deposition are used in the form of a filler at low volume fractions in an epoxy matrix, where they are aligned along multiple-direction using a magnetic field, producing either anisotropic or isotropic bulk properties on demand. Finally, subsequent annealing of nickel-coated CNTs in air oxidizes nickel to nickel oxide while carbon is released in the form of gaseous carbon dioxide. This leads to another novel approach for the fabrication of nickel oxide nanotubes, which are demonstrated to be an alternate viable material to fabricate electrodes for use in supercapacitors.

Engineered components can gain desirable properties when coated with surface materials. Wear-resistant coatings can improve the performance of contacting surfaces and allow for an extended life of the parts. Hard chromium has been the plating material of choice for certain wear and corrosion- resistant coatings because of its desirable combination of chemical resistance, adhesion, and mechanical properties. However, hexavalent chromium, a component of the process for applying hard chromium coatings, has been recognized by the EPA as having hazardous health and environmental impacts. Existing and planned environmental regulations restricts the use of process chemicals containing hexavalent chromium ions. This substantiates a need to develop an environmental friendly process for alternative coatings. Praxair has reported that Cr-Ni-C particles have a better corrosion resistance than current chromium carbide and nickel chromium powders. Today, Cr-Ni-C provides great qualities for flame spray and does not contain the toxic compounds used to deposit hard chromium, but is not compatible with application by cold spray. The purpose of this thesis project is to compare two processes for plating metal powder, chromium nickel carbide (Cr-Ni-C, CRC-410-1 from Praxair), with nickel. The particles were encapsulated using three different methods: one electroplating method previously used on particles, and two electroless plating processes using different solutions. The Cr-Ni-C particles were successfully encapsulated with Ni by one of the electroless deposition methods. The electrolytic deposition experiments did not yield the uniformity of coating without agglomeration that is being attained in industrial practice today. Further research on this method is recommended, due to the material operational cost in an industrial setting that is projected to be over 200 times cheaper than electroless deposition method. In the meantime, it should be possible to produce enough coated powder by electroless deposition to validate the utility of this coated powder in depositing wear- and corrosion-resistant coatings of Cr-Ni-C by cold spray.

Ferroelectric-reinforced metal matrix composites (FR-MMCs) offer the potential to improve damping characteristics of structural materials. Many structural materials are valued based on their stiffness and strength; however, stiff materials typically have limited inherent ability to dampen mechanical or acoustic vibrations. The addition of ferroelectric ceramic particles may also augment the strength of the matrix, creating a multifunctional composite. The damping behavior of two FR-MMC systems has been examined. One involved the incorporation of barium titanate (BaTiO3) particles into a Cu- 10w%Sn (bearing bronze) matrix and the other incorporating them into an electroformed Ni matrix. Here the damping properties of the resulting ferroelectric reinforced metal matrix composites (FR-MMCs) have been investigated versus frequency, temperature (above and below the Curie temperature of the reinforcement), and number of strain cycles. FR-MMCs currently represent a material system capable of exhibiting increased damping ability, as compared to the structural metal matrix alone. Dynamic mechanical analysis and neutron diffraction have shown that much of this added damping ability can be attributed to the ferroelectric/ferroelastic nature of the reinforcement. / Ph. D.

This dissertation work focuses on the processability improvement of B4C, especially the compaction and sintering improvement of B4C by applying a Ni-B nanolayer coating on individual B4C particles. A modified electroless coating procedure was proposed and employed to coat nanometer Ni-B layer onto micron-sized B4C particles. The thickness was able to be tuned and controlled below 100 nm. Key parameters, including the amount of nickel source, the amount of the surface activation agent (PdCl2), the amount of the complexing agent (C2H8N2), and the addition rate of the reducing agent (NaBH4) were studied. When the targeted thickness was 5 nm, a continuous and uniform nanolayer coating was obtained with the optimal condition of individual parameter combined. Reduction of the as-coated B4C powder in a H2-Ar atmosphere was studied between 400-900C to reduce the surface oxides' Ni2O3 and B2O3. Reduction at 800C in hydrogen atmosphere was found to be the most effective condition to remove oxygen in the coating layer, with Ni2B as the reduction product. Compaction of the as-received, separated and uncoated, and separated with Ni-B coating B4C powders using uniaxial die compaction and combustion driven compaction (CDC) techniques was studied. CDC technique showed the advantage over the traditional uniaxial die compaction by yielding much higher green density and green strength (73% vs. 53.8% green density for the Ni-B coated B4C). Among compacts obtained from the same technique, Ni-B coated B4C compact yielded the densest packing with crack-free compact surface and the highest strength, demonstrating more bonding between B4C particles provided by Ni-B surface coating. Sintering of the Ni-B coated B4C in an Ar atmosphere between 1150 - 1600C with soaking time of 2 hrs and 10 hrs was studied. Liquid phase was found to form during the sintering process. Density measurement showed that the liquid phase Ni-B formed greatly facilitated B4C densification. Considerable density increase and inter-granular connection was achieved when sintered at 1600C for 10 hrs. The density enhancement by Ni-B coating was supported by transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) examination which showed that there was B4C species diffusion into liquid Ni-B phase. This liquid phase enhanced the diffusion of B4C species and formed strong bonding between B4C grains by dissolving small B4C particles and sharp edge and corners of B4C particles. Strength test demonstrated that the Ni-B coating dramatically improved the strength of B4C compacts by yielding a much higher strength of the Ni-B coated samples than the uncoated samples (13.97 vs. 1.79 MPa for the uinaxial die compacted samples, 27.03 vs. 2.21 MPa for the CDC samples). Electrical conductivity Ni-B coated B4C samples was also shown to be improved with the electrical resistivity being reduced from infinite for pure B4C samples to 1.8Ã 10-3 Ω·m for the Ni-B coated samples. This research work has shown that with the Ni-B coating, B4C densification can start at a temperature as low as 1600C via a liquid phase sintering process. / Ph. D.