Surface roughness exists at many length scales-from atomic dimensions to meters. At sub-micron scale, the distribution of roughness is largely dependent on the process that generates the surface through the mechanisms of material removal/addition involved and the process parameters. The focus of the research is to quantitatively characterize the evolution of sub-micron scale surface roughness in the mechanical, chemical and electrochemical material removal techniques and study the influence of roughness on the mechanical behavior of surfaces. High purity aluminum surfaces are subjected to surface dissolution techniques such as electropolishing, chemical etching and anodization. Owing to the lack of sufficient lateral resolution in conventional roughness measurement techniques and appropriate scale independent roughness characterization techniques, the effect sub-micron scale electrochemical inhomogeneities present on the surfaces have on the roughness evolution at various length scales has not been understood. In this work, the power spectral density method of roughness characterization is used to quantitatively evaluate the roughness length scales affected in the surface generation processes as a function of time. Results indicate that in the case of electropolishing, roughness is not uniformly reduced at all length scales. Further, cut-off frequencies are suggested to optimize the electropolishing process. In chemical etching, the nature of roughness produced is found to be dependent on the nature of the starting surface. The nature of surface and sub-surface structures produced in the initial stage of the anodization process, and the transition from a disordered to an ordered structure are studied. In order to study the mechanical behavior of surfaces as a function of surface roughness, a single asperity indentation is modeled using nanoindentation of micropillar produced by focused ion beam machining of aluminum surfaces. Load-displacement curves are constructed to show the transition from a single asperity deformation to bulk deformation as function of indentation depth. Additionally, indentation responses of polymer coated surfaces with varying degree of roughness that were produced by the aforementioned surface generation processes are studied. it is shown how high interface roughness gives rise to high scatter both in loading and unloading portions of the load-displacement curves. Finally, porous alumina surface generated by the anodization process discussed above is indented to simulate a multi-asperity interaction.

This is predominantly a qualitative study on the manufacturing of micronozzles with an additive manufacturing (AM) technique, namely the laser-powered powder bed fusion (PBF-LB).  Manufacturing of micronozzles with standard microelectromechanical system technology often results in 2.5-D or close to 3-D structures and does not yield a fully rotationally symmetric nozzle. For this reason, AM can be a better solution. However, the structures obtained with PBF-LB exhibit very rough surfaces which will impair the performance of the micronozzle. To improve the surface finish electropolishing was performed on the interior walls.  Given the shape and the scale of the components, uniformity of the polishing is a challenge, calling for an inventive electrode configuration and electrolyte feed solution. The approach was to integrate an electrode on the inside of the converging part of the nozzle, to serve as a cathode for the electropolishing, already in the process, and to make the nozzle itself the vital part of the fluidic system.  With this, titanium micronozzles were manufactured with throat diameters varying between 300 and 800 μm. With the resolution of the used AM technique, it was possible to integrate the internal electrode in the micronozzles with a designed throat diameter down to 600 μm. Below this, the anode, and cathode, sometimes made contact short-circuiting the cell. Profilometry showed a decrease of the average surface roughness (𝑅𝑅𝑎𝑎) with 15-60 % for the electropolished micronozzles. The Schlieren imaging showed an exhaust that followed the throat’s axial direction and also demonstrated pressure disks and, hence, a supersonic jet exhaust. This study has shown that AM is a viable choice for manufacturing of rotationally symmetric micronozzles, and that electropolishing could be used to decrease the surface roughness on their inside uniformly with the integration of a cathode.

The use of ultracold neutrons (UCN) to study fundamental parameters such as the neutron lifetime and decay correlations in polarized neutron beta decay are poised to make significant contributions to our understand of the Standard Model and its extensions. To this end, the UCNA experiment is pursuing a precision measurement (0.2%) of the angular correlation between the neutron spin and the direction of emission of the electron in polarized neutron decay (the ``A'' asymmetry). The UCNA experiment makes use of the spallation-driven solid deuterium (SD2) UCN source at the Los Alamos Neutron Science Center (LANSCE). The UCN leave the source and are 100% polarized by passing through a strong magnetic field before their decay is observed by a very sensitive electron spectrometer. UCN guides facilitate the transfer of UCN from the source to the spectrometer. Common guide materials include stainless steel, copper, aluminum, and quartz. Often a thin film is applied to these components to increase their ability to transport/bottle and preserve the polarization of UCN. In the region of the SD2 UCN source, nickel-58 films are applied, whereas once the UCN are polarized, diamond-like carbon (DLC) films are employed. This dissertation covers the application, process developments, and characterization of these coatings. In addition a study concerning the surface finish resulting from the mechanical polishing and electropolishing of the guides that make up the UCNA beamline is presented. / Ph. D.

Les microfils métalliques polycristallins produits par étirage à froid présentent une résistance mécanique significative en faisant des candidats idéaux pour les renforts de composites. Des études antérieures sur des fils de nickel polycristallin pur ont montré une dépendance importante par rapport à la taille de la limite d'élasticité et de la résistance à la traction, ainsi que de la ductilité.Le but de cette étude est de comprendre cet effet de la taille dans les microfils de nickel pur polycristallin par analyse de diffraction des rayons X in-situ (DRX) et simulations de la plasticité cristalline par éléments finis (CPFE). Des essais de traction monotone et cyclique in-situ sous rayonnement synchrotron ont été réalisés sur des microfils de diamètres allant de 100 à 40 μm. Les fils étirés à 100 micromètres obtenus dans le commerce présentent une architecture cœur-coquille avec une texture de fibre <111> dominante dans le cœur et une texture à double fibre hétérogène <111> et <100> dans la coquille. La réduction de la taille de l'échantillon par polissage électrolytique conduit à des fils ayant une microstructure homogène, tandis que la réduction de la taille de l'échantillon par un étirage à froid supplémentaire conduit à des fils avec une texture plus intense tout en conservant l'architecture cœur-coquille.La limite d'élasticité et la résistance à la traction des fils électropolis augmentent avec la diminution du diamètre, tandis que la ductilité diminue avec la réduction du diamètre. Dans le cas des fils étirés à froid, on observe que la limite d'élasticité et la résistance à la traction, ainsi que la ductilité, augmentent avec la diminution du diamètre. L'analyse DRX indique une plasticité successive des familles de grains sous iso-déformation. Nous avons observé que le gradient de la texture du microfil active des mécanismes de déformation qui ne sont pas observés pour les microfils à texture homogène. Pour comprendre l'influence de différents paramètres microstructuraux, notamment l'influence de la texture cristallographique, une microstructure représentative 3D a été générée et des simulations CPFE ont été réalisées. Le comportement simulé moyen des différentes familles de grains (<111>, <100>) concorde bien avec les résultats expérimentaux. La simulation CPFE indique une hétérogénéité du champ de contrainte à travers la microstructure en présence d'un gradient de texture cristallographique.Nous montrons que la micro-texture (texture simple ou double texture) et leur dispersion spatiale (homogène ou architecturée) peuvent être utilisées comme stratégie de conception pour obtenir une microstructure optimale en fonction de l’ensemble désiré de propriétés mécaniques. / Polycrystalline metallic microwires produced by cold-drawing exhibit significant mechanical strength that make them ideal candidates for reinforcement of composites. Previous studies on polycrystalline pure nickel wires have indicated a significant size dependence of their yield and tensile strength as well as their ductility. The aim of this study is to understand these size effects by in-situ X-ray diffraction (XRD) analysis and crystal plasticity finite element (CPFE) simulations. In-situ monotonous and cyclic tensile tests under synchrotron radiation were carried on microwires with diameters ranging from 100 to 40 µm. The commercially obtained 100µm as-drawn wires exhibit a core-shell architecture with <111> fiber texture dominant in core and heterogeneous dual fiber texture <111> and <100> in the shell. Reduction of specimen size by electropolishing leads to wires having a homogeneous microstructure, whereas reduction of specimen size by further cold drawing leads to wires with a sharper texture while retaining the core-shell architecture.The yield and tensile strength of the electropolished wires increase with decreasing diameter, whereas the ductility decrease with decreasing diameter. In the case of cold-drawn wires, the yield and tensile strength, and also the ductility was observed to increase with decreasing diameter. The XRD analysis indicates successive yielding of grain families under iso-strain condition. The gradient in the texture of the microwire was seen to activate deformation mechanisms which are not seen for microwires with homogeneous texture. To understand the influence of different microstructural parameters, and notably the influence of crystallographic texture, 3D representative microstructure was generated and CPFE simulations were carried out. The simulated average behavior of different grain families (<111>, <100>) agrees well with the experimental results. The CPFE simulations indicate heterogeneity in stress field across the microstructure in the presence of a gradient in crystallographic texture.We show that the microstructure engineering of micro-texture components (single- or dual-texture) and their spatial spread (homogenous or architectured) can be used as design guidelines for obtaining optimal microstructure in accordance with desired set of mechanical properties.

Additive manufacturing (AM) has the potential to overtake the conventional production of pipe systems of stainless steel grade 316L intended for bioprocessing applications by utilising powder bed fusion laser beam (PBF-LB) technologies. However, challenges such as high surface roughness need to be overcome and corrosion properties improved to meet industry standards. This can be done by applying surface post-treatments to the printed parts. Therefore, the first aim of this thesis was to investigate the ability of different post-treatments of PBF-LB 316L samples, including tumbling, electropolishing, chemical milling, Hirtisation®, and DryLyte®, to reduce the surface roughness. One set of samples was left untreated, as-built set, and used as reference. The second aim was to try to correlate the surface roughness with the corrosion properties of the various post-treated samples. Analytical techniques used included needle profilometry, light optical microscopy (LOM), critical pitting temperature (CPT), cyclic potentiodynamic polarisation (CPDP) and immersion in 1M NaCl and 1M NaOH for two different durations for each solution. While some results were expected, others were surprising. Even though tumbled samples resulted in the lowest surface roughness, the results for immersion and CPDP curves tests indicated the lowest corrosion resistance compared to the other post-treatments. On the other hand, electropolishing resulted in the lowest surface roughness reduction among the post-treated samples. However, these samples had comparatively high corrosion resistance in the CPT and CPDP tests. The DryLyte® samples were tested using two DryLyte® medias where one of them resulted in the second lowest surface roughness and showed highest corrosion resistance in all three corrosion tests even though the process parameters are still to be developed. The results for samples post-treated by Hirtisation® and chemical milling were inconsistent and need further investigations. The reference as-built set showed high corrosion resistance in its untreated state, indicating post-treatments having minor impact on its performance from a corrosion perspective. / Additiv tillverkning (AM) har möjlighet att konkurrera ut konventionell produktion av rörsystem i rostfritt stål typ 316L avsett för bioprocessapplikationer genom att använda pulverbäddsinfusionslaserstråleteknik (PBF-LB). För tekniken kvarstår dock utmaningar för att uppfylla branschstandarder då tillverkningen medför material med hög ytråhet och sämre korrosionsegenskaper än traditionella metoder. Detta kan åstadkommas genom olika typer av efterbearbetning av de printade ytorna. Ett syfte med denna studie var att utvärdera hur olika typer av efterbehandling av PBF-LB 316L (trumling, elektropolering, kemisk etsning, Hirtisation® och DryLyte®) påverkar ytråheten. Som referensmaterial användes obearbetade printade ytor. Studiens andra huvudmål var att undersöka möjligheten för korrelation mellan ytråhet efter behandling och korrosionsegenskaperna. Analyser gjordes med hjälp av nålprofilometri, ljusoptisk mikroskopi (LOM), bestämning av kritisk gropfrätningstemperatur (CPT), framtagning av cykliska potentiodynamiska polarisationskurvor (CPDP) samt nedsänkning i 1M NaCl och 1M NaOH under två olika tidsperioder per lösning. Resultaten var delvis väntade och delvis överraskande. Trots att de trumlade proverna resulterade i lägst ytråhet, visade de elektrokemiska studierna (CPDP) i de olika lösningarna på att lägre korrosionsbeständighet jämfört med övriga efterbehandlingar. Å andra sidan resulterade elektropolering resulterade i den lägsta minskningen i ytråhet bland de efterbehandlade proverna. Dessa prover visade dock på en jämförelsevis hög korrosionsbeständighet i både CPT och CPDP testerna. DryLyte®-proverna studerades med två olika DryLyte®-medier, varav en av dem gav näst lägst ytråhet samt visade högst korrosionsbeständighet i samtliga korrosionstester trots att processparametrarna inte ännu är optimerade för denna nya teknik. Resultaten för prover som efterbehandlats med Hirtisation® och kemisk etsning var tvetydiga och behöver studeras vidare. De obehandlade referensproverna indikerade hög korrosionsbeständighet, vilket tyder på att efterbehandlingar hade minimal påverkan ur ett korrosionsperspektiv.