Made available in DSpace on 2017-07-21T20:43:49Z (GMT). No. of bitstreams: 1 Dis_Ariel_final.pdf: 5083548 bytes, checksum: acac140ede5eeafdd769aa58a612e863 (MD5) Previous issue date: 2016-08-25 / This work aims to study the electrochemical steel ASTM A285 Grade C and the same welded with coated electrode AWS E 7018 in the solution of industrial white liquor used in pulp and paper industry by the Kraft method. Samples were withdrawn by electroerosion into three regions: the base metal (BM), the heat affected zone (HAZ) and at the weld metal (WM). Corrosion rates of the three metal regions were determined in 8°C, 16°C, 24°C, 35°C, 42°C, 50°C and 60°C temperature. The values of corrosion rates were compared with the BM, ZTA and WM corrosion rates in electrolytic solutions of the main chemical components of the industrial white liquor in the same temperature range. These solutions were 0,1 mol/L of Na2SO4; 2.276 mol/L of NaOH; 0.126 mol/L of Na2S; 0.128 mol/L of Na2CO3 and simulated white liquor composed of the above solutions with the same molar concentrations. The BM to 24°C, industrial white liquor aerated presented corrosion rate of 0.022 mm/year, 0.045 mm/year for the HAZ and 0.032 mm/year for the WM. It was observed that the HAZ corrosion rates were higher than BM and WM in all solutions studied. Lower corrosion rates were in Na2CO3, followed by NaOH, Na2S, simulated white liquor and finally with the highest corrosion rates in white liquor industry. All solutions are presented alkaline, except sodium sulfate, and it was observed that the three regions are passivated when compared to a reference solution of 0.1 mol/L Na2SO4, and aerated with a pH between 6.0 to 6.5. This passivation film are complex chemical composition due to the presence in solution of OH- HS- ion. From the corrosion potentials of BM in each solution and the pH values it was found that the BM region is passivated according iron Pourbaix diagram in water. Chronoamperometry and voltammetric studies showed that these passivation films that promote greater protection against corrosion, they are solubilized in NaOH solution, simulated white liquor and industrial white liquor when submitted to anodic polarization in potential near at +2.0 V versus saturated calomel electrode. In Na2S and Na2CO3 solution was observed the formation of thick deposits on the surface of BM and when analyzed by EDS was observed the presence of phases such as oxides, sulfides and possibly iron carbonate. / Este trabalho tem como objetivo o estudo eletroquímico do aço ASTM A285 Grau C soldados com eletrodo revestido AWS E 7018 em meio de licor branco industrial empregado na indústria de papel e celulose pelo método Kraft. As amostras foram retiradas por eletroerosão em três regiões: metal base (MB), região termicamente afetada pela soldagem (ZTA) e pelo metal de solda (MS). As taxas de corrosão das três regiões metálicas foram determinadas em temperaturas de 8°C a 60°C. Os valores das taxas de corrosão foram comparados com as taxas de corrosão do MB, ZTA e MS em soluções eletrolíticas dos principais componentes químicos do licor branco industrial, no mesmo intervalo de temperatura. Estas soluções foram de 0,1 mol/L de Na2SO4; 2,276 mol/L de NaOH; 0,126 mol/L de Na2S; 0,128 mol/L de Na2CO3 e em um licor branco simulado composto pelas soluções acima com as mesmas concentrações molares. O MB, a 24°C, em licor branco industrial, aerado, apresentou taxa de corrosão de 0,022 mm/ano, 0,045 mm/ano para a ZTA e 0,032 mm/ano par o MS. Observou-se que as taxas de corrosão da ZTA foram superior a do MB e MS em todas as soluções estudadas. As taxas de corrosão mais baixas foram em Na2CO3, seguido pela solução de NaOH, Na2S, licor branco simulado e finalmente, com as maiores taxas de corrosão, em licor branco industrial. Todas as soluções apresentaram-se alcalinas, exceto a de sulfato de sódio, e constatou-se que as três regiões encontravam-se passivadas quando comparada a uma solução de referência de 0,1 mol/L de Na2SO4,aerada e com pH entre 6,0 a 6,5. Estes filmes de passivação são de composição química complexa devido a presença em solução de íon OH- e HS-. A partir dos potenciais de corrosão do MB em cada solução e dos valores do pH foi verificado que a região do MB encontra-se passivado segundo o diagrama de Pourbaix de ferro em água. Estudos voltamétricos e de cronoamperometria mostraram que estes filmes de passivação, que promovem uma maior proteção contra a corrosão, são solubilizados em meio de NaOH, licor branco simulado e no licor branco industrial quando submetidos a polarizações anódicas em potenciais próximos de +2,0 V versus eletrodo de calomelano saturado. Em solução de Na2S e Na2CO3 foi observado à formação de depósitos espessos sobre a superfície do MB e quando analisados por EDS, observou-se a presença de fases como de óxidos, sulfetos e possivelmente carbonato de ferro.

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In this thesis, I explore model systems for planar atomic and molecular scale electronics on surfaces. The nanoscale systems are experimentally investigated by combining scanning tunneling microscopy (STM) with atomic and molecular manipulation. Furthermore, the on-surface chemical synthesis of molecules, as well as the construction of atomic wires on selected surfaces is applied. Polycyclic aromatic hydrocarbon (PAH) molecules play a key role in this work, as they can provide the functionality of the molecular scale devices. In the first part of this work, I investigate different PAH´s on the Au(111) surface. The precursor molecules form supramolecular assemblies and the on-surface synthesis approach to obtain the desired molecular products is used. In particular, bisanthene molecules via a cyclodehydrogenation reaction and the non-alternant polyaromatic hydrocarbon diindenopyrene after a thermally induced debromination followed by selective ring-closure to form a five-membered ring are obtained. An interesting surface for future applications is the passivated silicon Si(001)-(2x1):H. I prepare this surface and characterize the substrate. The surface has a band gap and molecules are electronically decoupled from the semiconducting substrate due to the passivation layer. Furthermore, atomic defects on this substrate, so called dangling bonds (DB´s), have defined electronic states. I show that it is possible to produce DB defects controllably by applying voltage pulses using the tip of the STM and achieve with this method atomic wires with DB´s. The third part of this thesis deals with the investigation of molecular structures on Si(001)-(2x1):H. I present the generation of hexacene by a surface assisted reduction. This result can be generalized for the generation of PAH´s after deoxygenation on passivated silicon and can open new routes to design functional molecules on this substrate. Secondly, one-dimensional chains of acetylbiphenyl (ABP) molecules are explored. They interact via its pi-stacked phenyl rings that are considered as conducting channel. Finally, I demonstrate that a single ABP molecule acts as a switch, as one can reversibly passivate and depassivate a single DB by a hydrogen transfer. In the last part of this work, I test the new low-temperature four-probe STM located at CEMES-CNRS in Toulouse. This machine is constructed for the development of molecular scale devices. For this purposes an atomic precision is needed for all the different tips at the same time and a high stability of this scanning probe microscope must be achieved. I perform a manipulation experiment of molecules to test the necessary submolecular precision. For that reason, supramolecular assemblies of ABP molecules on Au(111) are imaged and manipulated by any of the four tips using the lateral manipulation mode as well as by voltage pulses. The stability of the system is shown, as all tips of the four-probe STM work independently in parallel.:1 Introduction 2 Fundamentals of scanning tunneling microscopy 2.1 The working principle 2.2 Scanning tunneling spectroscopy 2.3 Manipulation modes 2.4 Modeling 3 Experimental setup, materials and methods 3.1 The scanning tunneling microscope 3.2 The Au(111) surface 3.3 Further experimental details 4 On-surface synthesis of molecules 4.1 Introduction 4.2 Generation of a periacene 4.3 Investigating a non-alternant PAH 4.4 Conclusion 5 The passivated silicon surface 5.1 Introduction 5.2 Preparation of passivated silicon 5.3 Characterization of Si(001)-(2x1):H 5.4 Tip-induced formation of dangling bonds 5.5 Conclusion 6 Organic molecules on passivated silicon 6.1 Introduction 6.2 Hexacene generated on passivated silicon 6.3 Acetylbiphenyl on passivated silicon 6.4 Conclusion 7 Testing a low temperature four-probe STM 7.1 Introduction 7.2 The four-probe STM 7.3 Performance test of the four-probe STM on Au(111) 7.4 Manipulation of ABP assemblies 7.5 Conclusion 8 Summary and outlook 9 Appendix 9.1 Dibromo-dimethyl-naphtalene on Au(111) 9.2 Epiminotetracene on Au(111) Bibliography Curriculum vitae Scientific contributions Acknowledgement Statement of authorship / In dieser Arbeit untersuche ich Modellsysteme für planare atomare und molekulare Elektronik auf Oberflächen. Die Systeme auf der Nanoskala werden experimentell durch die Kombination aus Rastertunnelmikroskopie (RTM) und atomarer sowie molekularer Manipulation untersucht. Moleküle werden durch die oberflächenchemische Synthese generiert und atomare Drähte auf ausgewählten Oberflächen hergestellt. Polyzyklisch aromatische Kohlenwasserstoff (PAK) Moleküle spielen bei dieser Arbeit eine Schlüsselrolle, da sie die passiven und aktiven Elemente auf molekularem Maßstab darstellen können. Im ersten Teil dieser Arbeit untersuche ich verschiedene PAK´s auf der Au(111)-Oberfläche. Die Präkursoren bilden dabei supramolekulare Anordnungen und ich nutze die Oberflächensynthese, um die gewünschten molekulare Produkte zu erhalten. Im Speziellen habe ich Bisanthen-Moleküle über eine Zyklodehydrogenationsreaktion und das nicht-alternierende PAK Diindenopyren erzeugt. Dieses entsteht nach einer thermisch-induzierten Debromierung gefolgt von selektivem Ringschluss, sodass ein fünfgliedriger Ring gebildet wird. Eine interessante Oberfläche für zukünftige Anwendungen ist das passivierte Silizium Si(001)-(2x1):H. Ich habe diese Oberfläche erfolgreich präpariert und das Substrat charakterisiert. Die Oberfläche hat eine Bandlücke und Moleküle sind elektronisch von dem halbleitenden Substrat durch die Passivierungsschicht entkoppelt. Desweiteren haben atomare Defekte dieser Oberfläche, sogenannte Dangling-Bond´s (DB’s), definierte elektronische Zustände innerhalb der Bandlücke. Ich habe DB´s kontrolliert durch Spannungspulse mithilfe der Spitze des RTM erzeugt und stelle so atomare Drähte mit DB Defekten her. Der dritte Teil dieser Arbeit befasst sich mit der Untersuchung molekularer Strukturen auf Si(001)-(2x1):H. Die Erzeugung von Hexacen auf passivierten Silizium durch eine oberflächenunterstützte Reduktion wird gezeigt. Dieses Ergebnis ist eine neue Strategie für die Herstellung von PAK´s nach der Deoxygenierung und eröffnet neue Wege um funktionelle Moleküle auf diesem Substrat zu entwerfen. Zweitens zeige ich, dass Acetylbiphenyl (ABP) Moleküle eindimensionale Ketten auf dieser Oberfläche bilden. Diese interagieren über ihre Phenylringe, welche als leitender Kanal gesehen werden können. Zudem kann ein einzelnes ABP Molekül wie ein Schalter genutzt werden, da es reversibel einzelne DB´s durch Wasserstoffübertragung passivieren und depassivieren kann. Im letzten Teil dieser Arbeit wird das neue Tieftemperatur Vier-Sonden RTM, welches sich in CEMES-CNRS in Toulouse befindet, getestet. Diese Maschine ist für die Herstellung und Untersuchung von Geräten im molekularem Maßstab konstruiert worden. Zu diesem Zweck ist eine atomare Präzision für die verschiedenen Spitzen zur gleichen Zeit erforderlich und eine hohe Stabilität des Rastersondenmikroskops muss gewährleistet sein. Ich führe ein Manipulationsversuch an Molekülen durch, um die notwendige submolekulare Präzision zu testen. Dafür werden supramolekulare Anordnungen von ABP-Molekülen auf Au(111) abgebildet und die Strukturen mit jeder der vier Spitzen im lateralen Manipulationsmodus und durch Spannungpulse bewegt. Damit habe ich die Stabilität des Systems getestet und konnte zeigen, dass alle Spitzen des Systems unabhängig voneinander parallel arbeiten.:1 Introduction 2 Fundamentals of scanning tunneling microscopy 2.1 The working principle 2.2 Scanning tunneling spectroscopy 2.3 Manipulation modes 2.4 Modeling 3 Experimental setup, materials and methods 3.1 The scanning tunneling microscope 3.2 The Au(111) surface 3.3 Further experimental details 4 On-surface synthesis of molecules 4.1 Introduction 4.2 Generation of a periacene 4.3 Investigating a non-alternant PAH 4.4 Conclusion 5 The passivated silicon surface 5.1 Introduction 5.2 Preparation of passivated silicon 5.3 Characterization of Si(001)-(2x1):H 5.4 Tip-induced formation of dangling bonds 5.5 Conclusion 6 Organic molecules on passivated silicon 6.1 Introduction 6.2 Hexacene generated on passivated silicon 6.3 Acetylbiphenyl on passivated silicon 6.4 Conclusion 7 Testing a low temperature four-probe STM 7.1 Introduction 7.2 The four-probe STM 7.3 Performance test of the four-probe STM on Au(111) 7.4 Manipulation of ABP assemblies 7.5 Conclusion 8 Summary and outlook 9 Appendix 9.1 Dibromo-dimethyl-naphtalene on Au(111) 9.2 Epiminotetracene on Au(111) Bibliography Curriculum vitae Scientific contributions Acknowledgement Statement of authorship