The mechanical properties and the deformation mechanism of Cu single crystal metal and bi-crystal Cu metals are explored by the molecular statics simulations for the nanoindentation and nanoscratching process. In the simulation of nanoindentation, the relationship of load, influenced depth and displacement are obtained to investigate the deformation mechanism of Cu metals. The variations of averaged bond length are used to understand condition of atoms deformation. For the nanoindentation on two single crystal surfaces, our results indicate that the influenced depths can be affected by the tip indentation and the motion of dislocations. In the case of the bi-crystal system, because the interfaces between two crystal orientations can provide the resistance to the motions of dislocation, the influenced depths can be affected by the existence of the interface. Eventually, the variations of averaged bond length are also used to explore the structural deformation under the different nanoindentation depths and nanoscratching distances during the nanoscratching process. Moreover, the deformation mechanism during nanoindentation and nanoscratching process are also discussed in this article.

The deformation between interface, adhesion mechanism and the transparency of multi-layer flexible electronics composite were discussed. First, ITO (Indium Tin Oxide), Al (Aluminum) and ZnO (Zinc Oxide) were sputtered on a PET (Poly Ethylene Terephthalate) substrate by PVD (Physical Vapor Deposition) sequentially, to form ZnO/ITO/PET and ZnO/Al/PET which is the essential multi-layer structure in the transducer of flexible electronics. ITO/PET structure was widely applied to the touch panel. PET substrate possesses a good optical penetrability, low thermal expansion coefficient and lower price. However, the heat-resisting and chemical stability are poor. In this study, we explore the feasibility of the PDMS (Polydimethylsiloxane) substrate. It not only possesses good optical penetrability, but also exhibits higher PH selectivity than PET. In the analysis, the periodic external force was pressed on the flexible composite films to realize the difference between before and after experiment. Then the composite films were examined by nanoindentation and nanoscratch system (Berkovich and Conical probe with the radius of curvature of 20nm and 10um), four-point probe and spectrometer to measure the mechanical, electrical and optical properties, respectively. To investigate the effect of external force on these composite films, the interaction of films was discussed through external force testing by nanoscratch test.

Silicon nitride thin films are of interest in the biomedical engineering field due to their biocompatibility and favorable tribological properties. Evaluation and understanding of the properties of these films under diverse loading and failure conditions is a necessary prerequisite to their use in biomedical devices. Three wafers of silicon nitride-coated silicon were obtained from Lawrence Livermore National Laboratory and used to create 96 samples. Samples were subjected to nanoindentation testing to evaluate the mechanical properties of the film. Samples were subjected to nanoimpact testing to compare the damage resistance of the film to separate nanoimpact types. Samples were subjected to nanoscratch testing to evaluate the consistency of the critical load of the film. Results showed that there were no significant differences in the mechanical properties of the film across the tested groups. There was a significant difference observed in the rate of damage to the film between pendulum oscillation nanoimpact testing and sample oscillation nanoimpact testing, with the former causing more damage with all experiment variables controlled for. Results showed that the critical load measure for the film was significantly different between different nanoscratch test parameters. The conclusions from this study will support future work for in vitro and in vivo testing of ceramic thin films for biomedical applications.

Orientador: Cecilia A. C. Zavaglia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-25T02:10:22Z (GMT). No. of bitstreams: 1 Fernandes_BeatrizLuci_D.pdf: 8612737 bytes, checksum: 5b82e95884b98b376d5146b5ea2586e9 (MD5) Previous issue date: 1999 / Resumo: Apesar dos 30 anos de história, engenheiros e pesquisadores continuam procurando soluções para problemas que persistem até os dias de hoje, em relação à resistência ao desgaste de superfícies articuladas e à fixação aos tecidos ósseos de implantes ortopédicos de quadril. Esses problemas estão interligados, desde que a formação de grandes partículas nas articulações é o principal fator responsável pela perda da prótese e a qualidade da fixação do implante determina a produção dessas partículas. O material das amostras, analisadas neste trabalho, foi um dos empregados atualmente em próteses totais de quadril não cimentadas, ou seja, liga Ti6Al-7Nb revestida de hidroxiapatita (HA), aplicada através da técnica de aspersão por plasma. O principal objetivo deste trabalho foi apresentar uma alternativa para a avaliação da resistência da interface, utilizando-se uma nova técnica, rápida e confiável. As informações contidas estão relacionadas à técnica de deposição de materiais em forma de pó através de aspersão por plasma; ao estudo da resistência à adesão da HA sobre a liga de titânio através de ensaio de nanorisco e à caracterização superficial das amostras por determinação da rugosidade superficial, difração de raio-X e imagens do Microscópio Eletrônico de Varredura / Abstract: In spite of 30 years of history, engineers and researchers in general, are still trying to find solutions for the problems related to wear resistance of sliding surfaces and related to biological attachment of hip prostheses. These two questions are connected since the debris released in the joints are the main factor for loosing the prostheses and the fixation quality determines the production of those debris. The samples analyzed on this work were made of materials presently applied on hip prostheses like Ti-6Al-7Nb alloy with hydroxyapatite coating applied by plasma spray method. The main purpose of this work was to present an alternative to analyze the adhesion strength between the HA and the Ti-6Al-7Nb alloy using a new technique, fast and reliable. The information presented are related to the plasma spray' s deposition technique using powdered materials, to the evaluation of the interface between the two materials through the nanoscratch test and to the surface characterization using a mechanical profiler (profilometer), an X-Ray Diffract meter and a Scanning Electron Microscope / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Carbon nanotubes (CNT) could serve as potential reinforcement for metal matrix composites for improved mechanical properties. However dispersion of carbon nanotubes (CNT) in the matrix has been a longstanding problem, since they tend to form clusters to minimize their surface area. The aim of this study was to use plasma and cold spraying techniques to synthesize CNT reinforced aluminum composite with improved dispersion and to quantify the degree of CNT dispersion as it influences the mechanical properties. Novel method of spray drying was used to disperse CNTs in Al-12 wt.% Si pre-alloyed powder, which was used as feedstock for plasma and cold spraying. A new method for quantification of CNT distribution was developed. Two parameters for CNT dispersion quantification, namely Dispersion parameter (DP) and Clustering Parameter (CP) have been proposed based on the image analysis and distance between the centers of CNTs. Nanomechanical properties were correlated with the dispersion of CNTs in the microstructure. Coating microstructure evolution has been discussed in terms of splat formation, deformation and damage of CNTs and CNT/matrix interface. Effect of Si and CNT content on the reaction at CNT/matrix interface was thermodynamically and kinetically studied. A pseudo phase diagram was computed which predicts the interfacial carbide for reaction between CNT and Al-Si alloy at processing temperature. Kinetic aspects showed that Al4C3 forms with Al-12 wt.% Si alloy while SiC forms with Al-23wt.% Si alloy. Mechanical properties at nano, micro and macro-scale were evaluated using nanoindentation and nanoscratch, microindentation and bulk tensile testing respectively. Nano and micro-scale mechanical properties (elastic modulus, hardness and yield strength) displayed improvement whereas macro-scale mechanical properties were poor. The inversion of the mechanical properties at different scale length was attributed to the porosity, CNT clustering, CNT-splat adhesion and Al4C3 formation at the CNT/matrix interface. The Dispersion parameter (DP) was more sensitive than Clustering parameter (CP) in measuring degree of CNT distribution in the matrix.

One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org). Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut ( brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 X 10-8 atm-cc/ sec on a helium leak detector were measured. Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold, an adhesion layer must be used on the alumina surface. Niobium (Nb), Tantalum (Ta) and Tungsten (W) were chosen for evaluation since all are refractory (less dissolution into molten gold), all form stable oxides (necessary for adhesion to alumina) and all are readily thin film deposited as metals. Wetting studies are also performed to determine the wetting angle of pure gold to Ti, Ta, Nb and W substrates. Nano tribological scratch testing of thin film of Nb (which demonstrated the best wetting properties towards gold) on polished 96% alumina ceramic is performed to determine the adhesion strength of thin film to the substrate. The wetting studies also determined the thickness of the intermetallic compounds layers formed between Ti and gold, reaction microstructure and the dissolution of the metal into the molten gold.

Tato Diplomová práce se zabývá povrchovou analýzou nanokompozitní folie polyetherimidu (PEI) vyztuženého exfoliovanými grafitickými nanodestičkami (xGnP). Analyzovány byly take vzorky nevyztužené PEI folie a samostatné nanodestičky. Vzorky nanokompozitu a PEI folie byly plazmaticky leptány s využitím argonového plazmatu po dobu 1, 3 a 10 hod. Skenovací elektronová mikroskopie (SEM) byla použita pro charakterizaci samostatných nanodestiček rozptýlených na křemíkovém substrátu, původních či leptaných vzorků PEI folie a nanokompozitu. Nanodestičky byly identifikovány při povrchu leptané nanokompozitní folie. Mikroskopie atomárních sil (AFM) byla použita pro zobrazení povrchové topografie separovaných nanodestiček a odkrytých destiček při povrchu leptaného kompozitu. Povrchová drsnost (střední kvadratická hodnota, vzdálenost nejnižšího a nejvyššího bodu) leptaného nanokompozitu narůstala s prodlužující se dobou leptání. Akustická mikroskopie atomárních sil (AFAM) byla použita pro charakterizaci elastické anizotropie leptaných kompozitních vzorků. Nanoindentační měření umožnila charakterizaci lokálních mechanických vlastností PEI a nanokompozitních folií.

Plasma pretreatments are environmentally benign and energy efficient processes for modifying the surface chemistry of materials. In an effort to improve the strength of the titanium alloy/FM-5 polyimide adhesive joint for aerospace applications, oxygen plasma pretreatments and novel thin plasma polymerized (PP) films were investigated as adhesion promoters. Plasma treatments were carried out using custom-built, low pressure, radio frequency, inductively coupled plasma reactors. Ti-6Al-4V coupons were plasma treated and used to prepare miniature single lap shear (SLS) joints. The effects of plasma pretreatments on surface chemistry were studied using x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared analysis (FTIR), and contact angle measurements. Relationships between composition, mechanical properties, and adhesion of PP films on Ti-6Al-4V and silicon wafers were investigated. The nanomechanical properties (modulus, hardness and adhesion) were studied using atomic force microscopy (AFM) nanoindentation and nanoscratch testing. A design of experiments (DOE) three factorial model was used to optimize the parameters for oxygen plasma treatments. Oxygen plasma pretreatments enhanced joint strength by cleaning the titanium surface and creating an extended oxide layer. Nanoindentation of oxygen plasma treated substrates showed no change in the surface mechanical properties due to the oxygen plasma treatment. This suggested that the improved SLS strength of the oxygen plasma pretreated substrates was due to the cleaning of the substrate and the removal of carbonaceous contaminants, rather than any changes in the morphology of the oxide layer. PP acetylene films were predominantly carbon, with oxygen as the other main constituent (incorporated mostly as C-O and C=O). For all SLS specimens tested, the adhesion between PP acetylene and FM-5 adhesive was adequate. However, the strength of SLS joints was limited by the adhesion of the PP acetylene to the Ti-6Al-4V substrate. The effects of a large number of plasma parameters, such as substrate pretreatment, carrier gas, input power, flow rate and film thickness were investigated. All samples failed at the PP film/Ti-6Al-4V interface or within the PP acetylene film, and thicker PP films yielded lower SLS strengths. PP films deposited at lower power exhibited higher hardness and reduced modulus than films deposited at higher power. Overall, thinner films exhibited higher hardness and reduced Young's modulus than thicker films. PP films of higher hardness yielded higher critical loads at debond (thickness normalized) during the nanoscratch test. Thin films were developed via the vapor plasma polymerization of titanium(IV) isobutoxide (TiiB). XPS results suggested that titanium was incorporated into the film as TiO2 clusters dispersed in an organic matrix. No evidence for Ti-C was obtained from the XPS spectra. PP films of TiiB were much more compliant than PP acetylene films. This behavior was attributed to decreased fragmentation and lower crosslinking that occurred during PP TiiB film deposition. These PP films did not exhibit sol-gel-like qualities, and because of the way titanium was incorporated into the films, a more appropriate name for these films might be "titanium dioxide-doped plasma polymerized films." / Ph. D.

The dissertation thesis deals with the preparation and characterisation of a-CSi:H and a CSiO:H thin films prepared using the process of plasma enhanced chemical vapour deposition (PECVD). Tetravinylsilane (TVS) and its mixtures with argon and oxygen were used to deposit films on both planar substrates and fibre bundles. Main characterisation techniques were employed to study the topography of films, namely atomic force microscopy (AFM). Their mechanical properties were studied through nanoindentation; the nanoscratch test was used to assess the film adhesion to the substrate. Other analysed properties were internal stress and friction coefficient. The particular attention was paid to the work of adhesion and its determination. This knowledge was further applied to the preparation of surface treatments of glass fibres and, subsequently, polymer composites. Those were tested using the push-out test and the short beam shear test. Based on the results, the effects of deposition conditions and the relationships between the studied properties and quantities were determined.

Ce mémoire de maîtrise vise à étudier les propriétés physico-chimiques de couches minces organosiliciées produites par une décharge à barrière diélectrique à la pression atmosphérique (AP-DBD). Dans un premier temps, nous avons comparé des revêtements SiOCH sur verre obtenus en AP-DBD avec ceux produits dans un plasma à couplage capacitif à basse pression (LP-CCP). Dans les deux cas, en ayant recours à l’hexamethyldisiloxane et l’oxygène comme précurseurs chimiques pour le dépôt, on mesure un désordre structurel plus important avec une augmentation de la teneur en carbone dans la couche mince de SiOCH. On trouve également que la présence de groupes carbonés réduit leur adhésion au substrat. En particulier, la contrainte devant être appliquée avant qu’il y ait délamination semble fortement liée à la teneur en carbone. En dépit des différences dans les dynamiques de dépôt en AP-PECVD versus en LP-CCP, les procédés offrant des compositions chimiques similaires révèlent des propriétés mécaniques comparables (dureté, module de Young et élasticité). Dans un deuxième temps, nous avons déposé des couches minces SiOCH par AP-PECVD sur divers substrats polymériques à partir d’un précurseur cyclique (tetramethylcyclotetrasiloxane) plutôt que linéaire (hexamethyldisiloxane) dans un environnement semi-industriel. Dans ces conditions, les mesures de nanorayures (nanoscratch) indiquent que le substrat cède sous la contrainte appliquée avant qu’il y ait délamination de la couche mince déposée. De plus, en raison des faibles épaisseurs des revêtements, elles n’influencent pas réellement les propriétés mécaniques des substrats (dureté et module de Young). On note également que la teneur en carbone et la mouillabilité à l’eau sont étroitement liées à l’énergie déposée dans le plasma par molécule du précurseur. / This master thesis aims to examine the physicochemical properties of organosilicon thin films produced by atmospheric pressure, dielectric barrier discharges (AP-DBD). First, we compare SiOCH coatings deposited on glass by AP-DBD with those prepared by low-pressure, capacitively coupled plasma (LP-CCP). In both cases, using hexamethyldisiloxane and oxygen as chemical precursors for plasma deposition, a more important structural disorder was observed in SiOCH films with higher carbon content. We also show that the presence of functional carbon groups weakens the adhesion of the coatings to the substrate. In particular, the load needed to induce delamination seems to be strongly linked with the carbon content in the plasma deposited SiOCH thin films. Despite the differences in deposition dynamics in AP-PECVD versus LP-CCP, samples with similar chemical compositions reveal comparable mechanical properties (hardness, Young’s modulus, and elasticity index). Subsequently, we deposited SiOCH thin films by AP-PECVD on various polymeric substrates from a cyclic precursor (tetramethylcyclotetrasiloxane) instead of a linear one (hexamethyldisiloxane) in a semi-industrial environment. In these conditions, nanoscratch measurements indicate that the substrate breaks under load before any delamination of the coating can be observed. Furthermore, due to the low thickness of the plasma-deposited coatings, it is found that they do not influence the mechanical properties of the substrate (hardness and Young’s modulus). We also find that the carbon content and wettability with water are tightly related to the energy injected into the plasma per precursor molecules.