The cohesive fracture of thin films is a concern for the reliability of many devices in microelectronics, MEMS, photovoltaics, and other applications. In microelectronic packaging the cohesive fracture toughness has become a concern with new low-k dielectric materials currently being used. To obtain the low-k values needed to meet electrical performance goals, the mechanical strength of the material has decreased. This has resulted in cohesive cracks occurring in the Back End of Line (BEoL) dielectric layers of the microelectronic packages. These cracks lead to electronic failures and occur after thermal loading (due to CTE mismatch of materials) and mechanical loading. To prevent these cohesive cracks, it is necessary to measure the cohesive fracture resistance of these thin films to implement during the design and analysis process. Many of the current tests to measure the cohesive fracture resistance of thin films are based on methods developed for larger scale specimens. These methods can be difficult to apply to thin films due to their size and require mechanical fixturing, physical contact near the crack tip, and complicated stress fields. Therefore, a fixtureless cohesive fracture resistance measurement technique has been developed that utilizes photolithography fabrication processes. This technique uses a superlayer thin film with a high intrinsic stress deposited on top of the desired test material to drive cohesive fracture through the thickness of test material. In addition to developing a technique to measure the fracture resistance of dielectric thin films, the use of carbon nanotube (CNT) forests as off-chip interconnects is investigated as a potential method to mitigate the fracture of these materials. The compressive and tensile modulus of CNT forests is characterized, and it is seen that the modulus is several orders of magnitude less than that of a single straight CNT. The low-modulus CNT forest will help mechanically decouple the chip from the board and reduce stress occurring in the dielectric layers as compared to the current technology of solder ball interconnects and therefore improve reliability. The mechanical performance of these CNT interconnects is investigated by creating a finite-element model of a flip chip electronic package utilizing CNT interconnects and comparing the chip stresses to a traditional solder ball interconnect scenario. Additionally, flip chips are fabricated with CNT forest interconnects, assembled to an FR4 substrate, and subjected to accelerated thermomechanical testing to experimentally investigate their performance.

Measurement of all the mechanical properties of carbon nanotubes is extremely difficult because of its small size. In the present work, all the five transverse isotropic properties of single wall carbon nanotubes (SWCNTs) and double wall carbon nanotubes are estimated through molecular structural mechanics for different chirality, length and assumed thickness. Armchair, zigzag & chiral SWCNTs and polychiral DWCNTs are considered for the analysis. Longitudinal and lateral Young’s modulus; longitudinal and lateral Poisson’s ratio and shear modulus are estimated for 1080 SWCNTs and 1170 polychiral DWCNTs. Effect of temperature on all the properties of SWCNT are investigated. Modal characterization of SWCNT is carried out in base fixed condition and different mode shapes viz. axial, torsion and bending mode shapes are identified based on the effective mass. Once the transverse isotropic properties of SWCNTs are estimated, these are used to estimate the transverse isotropic properties of nanocomposites embedded with SWCNT agglomerates. During the manufacturing of nanocomposite, SWCNT agglomerates are formed due to sticking of number of SWCNTs. Parametric studies are carried out to see the effect of SWCNT length on the properties of nanocomposite. Empirical formulae for all the transverse isotropic properties of SWCNT at room temperature and elevated temperature; frequency of SWCNT are derived. Empirical formulae for polychiral DWCNT transverse isotropic properties are estimated. Input for these empirical formulae are the length, chirality and assumed thickness. Empirical formulae were also derived for nanocomposite embedded with different number of SWCNTs having different chirality. The derived empirical formulae were validated with available analytical and experimental results for some sample cases.

This dissertation describes the development of a processing route for fabricating conventional and doped multi-wall carbon nanotube (MWCNT)/polymer composite films for dielectric applications. Previous research has shown that such composites are promising dielectric materials, but their commercial development has been impeded by the nanotube agglomeration in the polymer matrix and the inefficiency in forming uniform films. Moreover, the harsh fabrication treatments often disrupt the structure of the nanotubes, hence damaging their inherent electrical properties. This work presents safer routes for forming non-aqueous, surfactant free dispersions of conventional and doped MWCNTs, which can be readily mixed with polymers and formed into films through aerosol spraying. Dispersibility behaviour of in-house synthesised conventional, nitrogen doped (N-MWCNTs), and boron doped (B-MWCNTs) MWCNTs was studied in 22 organic solvents. Based on thermodynamic theories it was suggested that doping, in particular nitrogen doping, significantly reduced the surface energy of the nanotubes. This aspect was crucial to understand the dispersibility of N-MWCNTs in low surface energy solvents and to achieve dispersions with high nanotube concentrations (0.82 mg/ml). Also, a "destruction reduced sonication protocol" involving mild sonication was suggested for forming MWCNT dispersions in organic solvents. Dispersions formed using this protocol were homogeneous and showed high stability of at least 2.5 years. Furthermore, the effect of ultrasonic probes on MWCNT lengths was studied and a decrease of 96–99% for MWCNTs and 85–95% for N-MWCNTs was observed. A numerical value for the nanotube length decrease during sonication has been reported for the first time. Preliminary studies to generate dielectric films of MWCNT/perfluoro alkoxy polymer were performed using aerosol spraying. An improvement in the dielectric constant (3.56) with a low dissipation factor (0.003) was observed in 0.3 wt.% B- MWCNT/PFA composite films. Consistency in the test results from various parts of the films confirmed the uniformity of the nanotube distribution within the composite. Future work should concentrate on the effects of B-MWCNTs and N-MWCNTs at the percolation threshold due to their inherent electric properties.

Este trabalho traz a aplicação de alta pressão e alta pressão/temperatura (4.0 GPa e 400º C), em amostras de nanotubos de carbono de paredes múltiplas (NTCPM) comerciais para a obtenção de amostras compactas. Os NTCPM foram funcionalizados com ácido nítrico e ácido nítrico/ácido sulfúrico e, também foram usados nanotubos de carbono dopados com nitrogênio. Foram também processadas amostras contendo nanotubos de carbono de paredes múltiplas incorporados em matriz de zircônia obtida pelo método sol-gel. Para aplicação da alta pressão foi usado um sistema com câmaras do tipo toroidal, utilizando grafite como meio transmissor de pressão. Foram obtidas amostras macroscópicas autossuportadas e com resistência ao manuseio principalmente nas amostras de nanotubos de carbono funcionalizados com ácido nítrico/ácido sulfúrico incorporados em zircônia. Para a caracterização das amostras foram utilizadas as técnicas de Microscopia Eletrônica de Transmissão, Espectroscopia Raman, Difração de Raios X e isotermas de adsorção/dessorção de nitrogênio com as quais foi possível determinar que mesmo após a aplicação de alta pressão/temperatura os nanotubos de carbono não sofrem significativas modificações na sua estrutura e nas suas propriedades morfológicas e texturais, confirmando então que os NTCPM mantém suas características originais, apresentando condições para aplicações em dispositivos. As amostras macroscópicas contendo nanotubos de carbono de paredes múltiplas incorporados em zircônia apresentaram ainda resistência à carga de milhares de vezes o seu peso e comportamento de materiais semi-condutores. / This work presents the application of high pressure and/or high pressure/temperature (4.0 GPa and 400 ° C), on different samples of commercial multi-walled carbon nanotube (MWCNT) to obtain compacted samples. MWCNT were functionalized with nitric acid and nitric acid/sulfuric acid, and also carbon nanotubes doped with nitrogen. MWCNT incorporated in a zirconia matrix obtained by sol-gel method were also processed. For high pressure application it was used a system with the toroidal-type chamber, using graphite as a pressure transmitting medium. Self-supported macroscopic samples were obtained, easy to handle, especially in samples of functionalized carbon nanotubes with nitric and sulfuric acid and also incorporated in zirconia. To characterize the samples it was used Transmission Electron Microscopy, Raman Spectroscopy, X-ray diffraction and nitrogen adsoption/desorption isotherms and it was determined that even after application of high pressure/temperature carbon nanotubes do not suffer significant changes in their structure and in their morphological and textural properties, confirming that the CNT keeps its original characteristics and providing conditions for device applications. The macroscopic samples containing MWCNT incorporated in zirconia also exhibited resistance to load of thousands times its own weight and behavior like semiconductor materials.

Este trabalho traz a aplicação de alta pressão e alta pressão/temperatura (4.0 GPa e 400º C), em amostras de nanotubos de carbono de paredes múltiplas (NTCPM) comerciais para a obtenção de amostras compactas. Os NTCPM foram funcionalizados com ácido nítrico e ácido nítrico/ácido sulfúrico e, também foram usados nanotubos de carbono dopados com nitrogênio. Foram também processadas amostras contendo nanotubos de carbono de paredes múltiplas incorporados em matriz de zircônia obtida pelo método sol-gel. Para aplicação da alta pressão foi usado um sistema com câmaras do tipo toroidal, utilizando grafite como meio transmissor de pressão. Foram obtidas amostras macroscópicas autossuportadas e com resistência ao manuseio principalmente nas amostras de nanotubos de carbono funcionalizados com ácido nítrico/ácido sulfúrico incorporados em zircônia. Para a caracterização das amostras foram utilizadas as técnicas de Microscopia Eletrônica de Transmissão, Espectroscopia Raman, Difração de Raios X e isotermas de adsorção/dessorção de nitrogênio com as quais foi possível determinar que mesmo após a aplicação de alta pressão/temperatura os nanotubos de carbono não sofrem significativas modificações na sua estrutura e nas suas propriedades morfológicas e texturais, confirmando então que os NTCPM mantém suas características originais, apresentando condições para aplicações em dispositivos. As amostras macroscópicas contendo nanotubos de carbono de paredes múltiplas incorporados em zircônia apresentaram ainda resistência à carga de milhares de vezes o seu peso e comportamento de materiais semi-condutores. / This work presents the application of high pressure and/or high pressure/temperature (4.0 GPa and 400 ° C), on different samples of commercial multi-walled carbon nanotube (MWCNT) to obtain compacted samples. MWCNT were functionalized with nitric acid and nitric acid/sulfuric acid, and also carbon nanotubes doped with nitrogen. MWCNT incorporated in a zirconia matrix obtained by sol-gel method were also processed. For high pressure application it was used a system with the toroidal-type chamber, using graphite as a pressure transmitting medium. Self-supported macroscopic samples were obtained, easy to handle, especially in samples of functionalized carbon nanotubes with nitric and sulfuric acid and also incorporated in zirconia. To characterize the samples it was used Transmission Electron Microscopy, Raman Spectroscopy, X-ray diffraction and nitrogen adsoption/desorption isotherms and it was determined that even after application of high pressure/temperature carbon nanotubes do not suffer significant changes in their structure and in their morphological and textural properties, confirming that the CNT keeps its original characteristics and providing conditions for device applications. The macroscopic samples containing MWCNT incorporated in zirconia also exhibited resistance to load of thousands times its own weight and behavior like semiconductor materials.

abstract: Electrostatic Discharge (ESD) is a unique issue in the electronics industry that can cause failures of electrical components and complete electronic systems. There is an entire industry that is focused on developing ESD compliant tooling using traditional manufacturing methods. This research work evaluates the feasibility to fabricate a PEEK-Carbon Nanotube composite filament for Fused Filament Fabrication (FFF) Additive Manufacturing that is ESD compliant. In addition, it demonstrates that the FFF process can be used to print tools with the required accuracy, ESD compliance and mechanical properties necessary for the electronics industry at a low rate production level. Current Additive Manufacturing technology can print high temperature polymers, such as PEEK, with the required mechanical properties but they are not ESD compliant and require post processing to create a product that is. There has been some research conducted using mixed multi-wall and single wall carbon nanotubes in a PEEK polymers, which improves mechanical properties while reducing bulk resistance to the levels required to be ESD compliant. This previous research has been used to develop a PEEK-CNT polymer matrix for the Fused Filament Fabrication additive manufacturing process / Dissertation/Thesis / Masters Thesis Engineering 2020

Carbon-infiltrated carbon nanotube (CICNT) forests are carbon nanotube (CNT) forests infiltrated with pyrolytic carbon to increase durability by becoming a solid material. This material can be tuned to maintain the nanotube geometry of a CNT forest and can also be fabricated on a variety of materials and geometries. Additionally, the present work has indicated that CICNT forests may resist bacterial proliferation and biofilm formation. This phenomenon is not due to the CICNT chemistry; it is presumably due to the CICNT nanostructure morphology. Thus, both silicon and stainless steel substrates were used to investigate CICNT's structural resistance to Methicillin-resistant Staphylococcus aureus (MRSA) biofilm. From in vitro experimental testing, CICNT on both these substrates resisted MRSA cell attachment and biofilm proliferation. The discovery of this non-pharmaceutical biofilm resistance expands the potential applications of CICNT to include medical devices that are prone to infection and/or devices that contribute to infection. Two representative applications were investigated: external fixator pins and scalpel blades. CICNT-coated versions of these applications underwent additional MRSA biofilm resistance testing as well as mechanical testing. In particular, external fixator pins were identified as a high potential application of CICNT surface coating technology. Previous work on both CNT and CICNT forests has largely been performed on planar structures. However, any potential medical device applications involve curved substrates. In particular, concave curvatures are challenging due to the potential for stress-related CICNT forest defects. Thus, the present work also included a study of the incidence rates and determining factors of these defects. SEM images of the cross-sections revealed different types of microscale forest defects while the top surface showed morphologies that are largely consistent with flat substrates. CICNT forest height and substrate curvature were identified as contributing factors to CICNT forest defect incidence rates. Thus, the present work advances the understanding of bacterial resistance and microstructure-related properties of CICNT surface coatings, with applications in medical devices.

This diploma thesis focuses on the influence of carbon nanotubes (CNTs) on the mechanical properties of a composite material with polyurethane (PU) matrix. The material was supplied in the form of thin films with thickness from 0.2 mm to 1.2 mm. The theoretical part of this thesis describes the production technology, properties and applications of composite materials PU/CNTs, and also deals with preparation technology and properties of both components of this composite material separately. The theoretical part also describes the principle of tensile testing of polymer materials. The experimental part of the thesis was primarily focused on comparing the tensile properties of a composite material PU/CNTs with tensile properties of pure PU. At first, tensile properties of pure PU were investigated, while the influence of various factors like strain rate, specimen thickness, heat treatment and aging was examined. In adition, stress relaxation tests and tests with strain rate jumps were performed on pure PU specimens. Then composite PU/CNTs was tested in tension and the results were compared with the results of tensile tests of pure PU. Composite material PU/CNTs was prepared with various concentrations, so it was possible to determine the effect of CNTs content on the tensile properties of the composite. The last part of this thesis deals with tensile tests of PU composite material with functionalized carbon nanotubes (PU/FCNTs), where the influence of surface modification (functionalization) of CNTs on the tensile properties composites was investigated. It was shown that the effect of both CNT and FCNT on mechanical properties of the composite is not significant. This conclusion was discussed on basis of the works of other authors, which do not unambiguously proved the positive effect of CNT or FCNT on mechanical properties of composites with polymer matrix.

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