No description available.

It is projected that by 2020, there will be 138 million Americans over 45, the age at which the increased incidence of heart diseases is documented. Many will require stents. This multi-billion dollar industry, with over 2 million patients worldwide, 15% of whom use Nitinol stents have experienced a decline in sales recently, due in part to thrombosis. It is a sudden blood clot that forms inside stents. As a result, the Food and Drug Administration and American Heart Association are calling for a new generation of stents, new designs and different alloys that are more adaptable to the arteries. The future of Nitinol therefore depends on a better understanding of the mechanisms by which Nitinol surfaces can be rendered stable and inert. In this investigation, binary and ternary Nitinol alloys were prepared and subjected to various surface treatments such as electropolishing (EP), magnetoelectropolishing (MEP) and water boiling & passivation (W&P). In vitro corrosion tests were conducted on Nitinol alloys in accordance with ASTM F 2129-08. The metal ions released into the electrolyte during corrosion tests were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Biocompatibility was assessed by observing the growth of human umbilical vein endothelial cells (HUVEC) on the surface of Nitinol alloys. Static and dynamic immersion tests were performed by immersing the Nitinol alloys in cell culture media and measuring the amount of metal ions released in solution. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions on the growth of HUVEC cells. The surfaces of the alloys were studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Finally, wettability and surface energy were measured by Contact Angle Meter, whereas surface roughness was measured by Atomic Force Microscopy (AFM). All the surface treated alloys exhibited high resistance to corrosion when compared with untreated alloys. SRB assays revealed that Ni and Cu ions exhibited greater toxicity than Cr, Ta and Ti ions on HUVEC cells. EP and MEP alloys possessed relatively smooth surfaces and some were composed of nickel oxides instead of elemental nickel as determined by XPS. MEP exhibited lowest surface energy and lowest surface roughness.

No description available.

Niobium (Nb) has the highest superconducting transition temperature (9.2 K) of the pure metals, which makes it the most used material for the construction of superconducting radio frequency (SRF) accelerators. The performance of the accelerator is critically dependent upon the quality of Nb surface. Electropolishing (EP) in hydrofluoric acid (HF)-containing electrolytes is the currently accepted treatment process. The presence of HF is necessary for the removal of the passive oxide surface film formed in aqueous electrolytes. But HF is hazardous and must be contained without human exposure and eliminated in an environmentally appropriate manner. In the present dissertation project, HF-Free EP of Nb was performed in sulfuric acid-methanol electrolytes. Sulfuric concentrations of 0.1 M, 0.5 M, 1 M, 2 M, and 3 M were used. Cyclic voltammetry and potential hold experiments were performed in cells of both two-electrode and three-electrode setups to evaluate the electrochemical process. The influence of electrolyte concentration, temperature, and EP duration was investigated. At room temperature, both the corrosion rate and the surface quality obtained were comparable to those currently obtained with HF-based processing. With decreasing temperature, the mean current level decreased and the surface quality improved substantially. For a desired average material removal of 100 μM, nanometer scale surface roughness was obtained under multiple conditions. Mechanism of EP was also investigated by electrochemical impedance spectroscopy (EIS). The EIS diagram indicates the presence of a compact film during EP at mass transport controlled limiting current and a film-free surface during EP at ohmic controlled current. Transfer from a film-free surface to an anodic film precipitation with decreasing temperature was also observed. Microsmoothing is only achieved under mass transport control. Nb⁵⁺ ions are determined to be the mass transport limiting species. / Ph. D.

A novel mirror finishing method using a conductive polymer as the tool electrode is presented. It has been known that the conductive polymers have many advantages, such as to conduct a micro-current, to be easily processed into various shapes, to hold abrasives, and to have an excellent wear resistance. The effects of particle size, machining time, concentration of electrolyte, working current, and load on the surface roughness and the removal depth of SUS-304 stainless steel are investigated.When the operative parameters are set for the particle size of 3 £gm, the concentration of electrolyte of 10 wt%, the working current ranged from 10 to 20 mA, and the load of 10 N, the surface roughness Rmax, which originally is 1.4 £gm, can be reduced to 0.17~0.24 £gm after the machining time of 3 min. The surface roughness Ra can be achieved to 7.897 nm under the optimal condition. In addition, experimental results show that there is an optimal region of the working current at the concentration of electrolyte of 10 wt%. According to the surface profiles and SEM micrographs, three machining regions can be classified as (1) the mechanical polishing region, (2) the electro-chemical buffing (ECB) region, and (3) the excessive corrosion region. To achieve a high-quality mirror-like surface, the machining region must be operated at the ECB region.

Ce travail de thèse s’inscrit dans lecadre du projet « MOMEQA » dont l’objectif est le soutien à l’innovation dans l’industrie horlogère en Franche-Comté. La première impression visuelle conditionne notre relation à l’objet, c’est pourquoi une finition soignée est primordiale. L’électropolissage est un procédéde dissolution électrochimique permettant der éduire la rugosité de surface d’un objet. La pièce traitée constitue l’anode dans une cellule d’électrolyse. La première partie de l’étude est consacrée aux laitons et à l’acier inoxydable 316 L. Une étude électrochimique préliminaire a permis de définir les conditions optimales d’électropolissage pour chaque matériau et milieu. La suite de l’étude a été dédiée à l’étude des comportements des aciers inoxydables 316L de fonderie comme de fabrication additive, afin de mettre en évidence l’influence du procédé de fabrication sur l’aptitude à l’électropolissage. Un dispositif spécialement conçu a également permis de faire varier les conditions hydrodynamiques et d’appliquer des ultrasons,en vue d’optimiser l’agitation. L’obtention d’une finition poli miroir sur des carrures de montres a validé la conception du pilote. Enfin, l’usage d’un électrolyte moins nocif que les mélanges d’acides, le Deep Eutectic Solvent constitué d’un mélange de chlorure de choline et d’éthylène glycol se montre prometteur. L’utilisation de ces olvant non-conventionnel permet d’utiliser des techniques d’analyses de surface impraticables in-situ en milieu très corrosif, tel que l’AFM. Finalement, un modèle décrivant les mécanismes d’électropolissage de l’acier inoxydable 316 L dans les deux milieux a été proposé, qui permet une bonne simulation des résultats de spectroscopie d’impédance électrochimique / This work is part of the project"MOMEQA" whose main purpose is to supportinnovation in watchmaking industry in Franche-Comté. For high-end pieces, the first visualimpression is crucial and that is why a neatfinishing is required. This is achieved byelectropolishing, which consists in anelectrochemical dissolution process that enablessurface roughness reduction. Although it ispresent in several applications, fundamentalmechanisms of electrochemical polishingremain poorly understood and tailoring theprocess to additive manufacturing parts is in itsearly stages. The first part of the study isdedicated to brass and 316L stainless steel.Basic electrolytic baths (H3PO4 for brasses anda H3PO4/ H2SO4 mixture for 316L stainlesssteel) are used as references. A preliminaryelectrochemical study allows the determinationof optimal electropolishing conditions for eachmaterial and medium. A special attention hasbeen paid to characterization methods, such asmicro-roughness, brightness, microstructure,texture and corrosion resistance. Subsequently,the study was restricted to both cast and additivemanufacturing 316L stainless steels, in order toidentify the influence of manufacturing processon the electropolishing ability. To meet theproject requirements, a pilot cell dedicated tolarge area parts was designed and built. The aimwas to study the scale-up as well as the effectsof workpieces shape. The outcome of this studywas the realization of a mirror finish on a watchdial, allowing validation of the pilot-cell design.The last part of our study consists in replicatingthe process in a less harmful electrolyte, a greensolvent (Deep Eutectic Solvent), made by amixture of choline chloride and ethylene glycol.This allows successful electropolishing,compatible with an industrial application.Moreover, it makes possible in-situ AFMmeasurements, impossible in highly corrosiveelectrolytes. Finally, a model forelectropolishing mechanism in the case of 316Lstainless steel was proposed for both media,allowing a good simulation of electrochemicalimpedance spectroscopy behaviour.

GPA INNOVATIVE S.L. (also known from now as GPA) was founded in Barcelona in 2013, legally constituted as STEROS GPA Innovative S.L., in order to provide solutions to various strategic challenges in the field of product design and the development of industrial applications. Among the eight different business lines, the main one is known as DLyte®. DLyte® is based on the patented DryLyte® Technology, the world's first dry-electropolishing process and it is suitable for the most common industrial metals, alloys and composite materials. It automates, simplifies and standardizes the post-processing of these set of materials, improving the surface finish obtained with traditional polishing processes. Within 918 machines on the market, 521 are used in the dental industry (representing the 56.75% of the total business). Therefore, to improve the polishing surface quality of dental alloys is a must for the company. Within this context, the very first aim of this Master thesis is to determine which DryLyte® electrolyte and/or electrical parameters are more suitable for polishing dental materials and in particular CoCr RPDs (chrome cobalt - Removable Partial Dentures). For that, an exhaustive electrolyte characterization and a surface analysis of the workpieces before and after being polished with this technology is realized. Also, another goal is to find a compromise between the electrical parameters and the better surface quality finish of RPDs and, last but not least, to ascertain if CoCr RPDs can be successfully polished under direct current (DC).

<p>Electropolishing is a commonly used method of mitigating surface roughness and yielding a polished appearance. One of the first described and most studied of electropolishing systems is the anodization of copper in phosphoric acid. Under normal conditions this reduces copper surface roughness substantially; however deviating from optimal electropolishing conditions can promote the development of semi-ordered surface roughness. Anodizing copper substrates in 98-100% H₃PO₄ solutions generated feature heights ranging from 0.5 - 2µm and surface area increases in excess of 30% were obtained. The samples demonstrated a macroscopic optical dullness characteristic of this type of surface roughening. Investigations as to their applicability in surface enhanced Raman spectroscopy and electron field emission were conducted. And while their formation mechanism is still speculated on, it is believed that oxygen evolution and subsequent bubble formation plays a key role. Electrochemical and microscopic imaging techniques were the primary methodologies used to probe the optical dulling phenomenon. With data obtained from experiments utilizing these techniques and others a qualitative mechanism is proposed.</p> / Master of Science (MSc)

This diploma thesis deals with the automation of the electropolishing process, which is per-former as the last step in the preparation of metallographic samples intended for observation in an electron microscope. A complete hardware design of a single-purpose machine has been developed, which provides the automatic preperation of up to six samples per insertion. There was the design of a manipulator for sample handling together with chemically re-sistant sample holder suitable for automatic operation as a part of solution. The design of the whole machine was developed with regard to the safety of the operator. The thesis includes detailed 3D model of the device and the desing of an application for measurement in the LabVIEW. It describes the future working process of the machine, including a description of a software for controlling the machine and sending process data of each sample to the to the database in accordance with the principles of industry 4.0. In the conclusion, the achieved results and the proposal of further steps necessary for the realization of the machine are for-mulated.

Denna studie har utförts på Calamo AB som arbetar med elektropolering och betning av rostfritt stål. Efter ytbehandlingssteget krävs sköljning av godset för att avlägsna kemikalierester vilket medför att stora mängder surt sköljvatten uppstår. Idag används våtkemisk fällningsanläggning för att rena sköljvattnet. Det befintliga reningsverket kräver flertalet tillsatser samtidigt som mängden slam som går till deponi är stor. Företaget vill utreda miljönyttan med att installera en vakuumindunstare för att ersätta det befintliga reningsverket som reningsmetod samt se över möjligheten att minska sin vattenförbrukning i samband med sköljning av gods för att bland annat kunna reducera storleken på indunstaren, minska belastningen på reningsstegen samt reducera mängden avfall. Studiens mål var att kartlägga uppkomsten av förorenat sköljvatten, identifiera potentiella vattenbesparande åtgärder och hur dessa åtgärder påverkar effektiviteten hos reningsanläggningarna. Samt visa hur installation av en vakuumindunstare förändrar företagets miljöpåverkan och utreda om det finns möjligheter att återanvända eller återvinna kemikalier och metaller från processen. Kartläggning och flödesmätningar av sköljvattenbehovet utfördes med hjälp av information av personal på Calamo samt en ultraljudsmätare. Vattenbesparande åtgärder, påverkan på reningsanläggning samt möjligheter till återvinning av kemikalier undersöktes genom litteraturstudie samt modellering i Excel. Utredningen av miljönyttan genom att ersätta befintligt reningsverk med vakuumindunstare utfördes med hjälp av LCA-värden hämtade från databasen SimaPro 8.0.4. Flera olika förslag på vattenbesparande åtgärder studerades och dessa gav en total vattenreduktion till reningsverket på mellan 5 - 81 % beroende på hur många samt vilka åtgärder som vidtogs. Enligt miljöberäkningarna genererar vakuumindunstaren 3 gånger högre utsläpp av koldioxidekvivalenter och 7 gånger större behov av icke förnyelsebar energi jämfört med det befintliga reningsverket. Genom att installera sprutskölj med motströmsteknik i stycke, sammankoppla befintliga sköljkar i avdelningarna betning, AVFKA samt automaten och installera sparsköljstank i alla avdelningar uppnås en reduktion av förorenat vatten till reningsstegen på 81%, vilket ytterligare kan optimeras genom installation av jonbytare, återanvändning av varmt vatten från renrum. Dessutom ökar föroreningshalten med 61% då dessa åtgärder vidtas vilket gynnar reningseffektiviteten i reningsanläggningarna och därav rekommenderas detta alternativ. Även kemikalieanvändningen och förluster av metalljoner reduceras avsevärt i processen genom användningen av sparskölj. Att installera vakuumindunstare rekommenderas inte på grund av dess stora energianvändning, dock kan andra resultat uppstå då andra LCA-värden används samt genom andra antaganden och hänsyn till kemikalie- och metallåtervinning istället för deponi. / This study has been carried out at Calamo AB, which works with electropolishing and pickling of stainless steel. After the surface treatment step, rinsing of the material is required to remove chemical residues, which results in large amounts of acid rinse water. Today, wet chemical precipitation plant is used to clean the rinse water. The existing treatment plant requires most additives, while the amount of sludge that goes to landfill is large. The company wants to investigate the environmental benefits of installing a vacuum evaporator to replace the existing sewage treatment plant as a purification method and to review the possibility of reducing its water consumption in connection with rinsing of goods in order to reduce the size of the evaporator, reduce the load on the purification steps and reduce the amount of waste. The aim of the study was to map the emergence of polluted rinse water, identify potential water-saving measures and how these measures affect the efficiency of the treatment plants. And show how the installation of a vacuum evaporator changes the company's environmental impact and investigate whether there are opportunities to reuse or recycle chemicals and metals from the process. Mapping and flow measurements of the rinse water requirement were performed using information from staff at Calamo and an ultrasonic meter. Water-saving measures, impact on treatment plant and opportunities for recycling of chemicals were investigated through literature study and modeling in Excel. The study of the environmental benefits by replacing existing treatment plants with vacuum evaporators was carried out using LCA values obtained from the database SimaPro 8.0.4. Several different proposals for water-saving measures were studied and these gave a total water reduction to the treatment plant of between 5 - 81% depending on how many and what measures were taken. According to the environmental calculations, the vacuum evaporator generates 3 times higher emissions of carbon dioxide equivalents and 7 times the need for non-renewable energy compared to the existing treatment plant. By installing spray rinse with countercurrent technology in one piece, interconnecting existing rinses in the cuttings departments, AVFKA as well as the dispenser and installing sparse rinse tank in all departments, a reduction of contaminated water to the purification steps of 81% is achieved, which can be further optimized by installation of ion exchangers, reuse of hot water from clean room. In addition, the pollutant content increases by 61% as these measures are taken, which favors the purification efficiency of the treatment plants and hence this option is recommended. The use of chemicals and losses of metal ions are also considerably reduced in the process through the use of savings rinses. Installing vacuum evaporators is not recommended due to its large energy use, however, other results may arise when other LCA values are used, as well as through other assumptions and considerations for chemical and metal recycling instead of landfill.