The present master thesis work is intended as the continuation of the research collaboration between Politecnico di Milano, Department of Chemistry, Materials and Chemical Engineering and the Fermi National Accelerator Laboratory (FNAL) in Chicago (USA). The collaboration’s research theme resides in the development of Nb_3 Sn superconducting thin films of anobtained by electrodeposition process from ionic liquids of Nb_3 Sn superconducting thin films on Cu substrates. The starting point of this thesis work are the results ofwas athe previous thesis carried out in the Politecnico di Milano laboratories by Luigia Glionna, where . Namely, the pulsed galvonostatic deposition process was shown showed better result in terms ofto result in higher thickness and Nb atomic content of the deposited films, with respect to direct current deposition. Thus, the focus of the actual work is the optimization of the pulsed deposition process, searching for the most suitable deposition parameters which result in the better quality of the deposited films. Various Nb-Sn films have been deposited in pulsed condition from a BMIC- SnCl_2- NbCl_5 electrolytic solution with in a single compartment electrochemical cell. The effects of agitationhydrodynamics, duty cycle, applied current densityies and duration of the impulsepulse period on superficial surface morphological features, crystalline structure and chemical alloying composition has been carefully studiedinvestigated. The deposited samples showed a A general layered structure characterizes each deposited sample. In direct contact with the copper substrate layer a Sn-rich layer was found, probably consisting in an interdiffused Cu_3 Sn phase formed by thermal interdiffusionlayer is found. A Nb-Sn alloy grows on top of it. Finally, the superficial layer is composed by Cu-Nb-Sn oxides and chlorides. Phases rich in Nb are found on the deposited sample thanks to SEM/EDS measurements. XRD analysis are carried out to see if the interest Nb_3 Sn phase actually forms on Cu substrate. Based on XRD analysis, Thean univocal attribution identification of Nb_3 Sn crystalline phase is not certainwas not possible since because of the superimposition of the characteristic peaks with its characteristic peaks superimpose withthose of the Cu_3 Sn phaseformed by interdiffusion at the working temperature of 130 ℃. To overcome this problem and further improve the growth of the desired phase, the electroFor this reason, deposition was also carried out onto alternative Ni substrates are carried out to settle the XRD phases’ peak attribution and using two-compartments electrochemical cells.. Finally, depositions with separated compartment cell are explored, to investigate about evident differences with respect to the single compartment cell architecture.
Il presente lavoro di tesi è inteso come la continuazione de, progetto di ricerca tra il Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica e il Fermi National Accelerator Laboratory (FNAL) a Chicago (USA). Il tema della collaborazione di ricerca risiede nello sviluppo di film sottili superconduttori a base di Nb_3 Sn, ottenuti attraverso elettrodeposizione da liquidi ionici. Il punto d’inizio di questo lavoro di tesi è stato un precedente lavoro di tesi svolto nei laboratori del Politecnico di Milano da Luigia Glionna, dove il processo di deposizione galvanostatica in corrente pulsata mostrò i migliori risultati in termine di contenuto atomico di Nb e spessore del film depositato, rispetto alla deposizione in corrente continua. Quindi lo scopo dell’attuale lavoro è l’ottimizzazione del processo di deposizione in corrente pulsata, alla ricerca dei più appropriati parametri di deposizione che risultano nella migliore qualità del rivestimento depositato. Films di Nb-Sn sono stati depositati grazie a una cella a compartimento singolo in condizioni pulsate da una soluzione elettrolitica a base di BMIC- SnCl_2- NbCl_5. Gli effetti dell’agitazione, del duty cycle, dell’intensità di corrente e del periodo d’impulso sono stati studiati rispetto agli aspetti morfologici, alla struttura cristallina e alla composizione chimica dei depositi. I campioni depositati mostrano un aspetto stratificato. In contatto diretto con il substrato di rame è stato trovato uno strato ricco in stagno, probabilmente formatosi a causa dell’interdiffusione termica. Una lega Nb-Sn cresce su di esso. Infine, lo strato superficiale è è composto da ossidi e cloruri a base Cu-Nb-Sn. Riguardo le analisi XRD, l’identificazione univoca della fase cristallina del Nb_3 Sn non è stata possibile, a causa della sovrapposizione dei picchi caratteristici con la fase Cu_3 Sn. Per risolvere questo problema e migliorare ulteriormente la crescita della fase desiderata, l’elettrodeposizione è stata anche provata su substrati alternativi e usando una cella a due comportamenti.
Pulse plating of Nb-Sn films from ionic liquids
MARCELLI, MATTEO GIUSEPPE
2017/2018
Abstract
The present master thesis work is intended as the continuation of the research collaboration between Politecnico di Milano, Department of Chemistry, Materials and Chemical Engineering and the Fermi National Accelerator Laboratory (FNAL) in Chicago (USA). The collaboration’s research theme resides in the development of Nb_3 Sn superconducting thin films of anobtained by electrodeposition process from ionic liquids of Nb_3 Sn superconducting thin films on Cu substrates. The starting point of this thesis work are the results ofwas athe previous thesis carried out in the Politecnico di Milano laboratories by Luigia Glionna, where . Namely, the pulsed galvonostatic deposition process was shown showed better result in terms ofto result in higher thickness and Nb atomic content of the deposited films, with respect to direct current deposition. Thus, the focus of the actual work is the optimization of the pulsed deposition process, searching for the most suitable deposition parameters which result in the better quality of the deposited films. Various Nb-Sn films have been deposited in pulsed condition from a BMIC- SnCl_2- NbCl_5 electrolytic solution with in a single compartment electrochemical cell. The effects of agitationhydrodynamics, duty cycle, applied current densityies and duration of the impulsepulse period on superficial surface morphological features, crystalline structure and chemical alloying composition has been carefully studiedinvestigated. The deposited samples showed a A general layered structure characterizes each deposited sample. In direct contact with the copper substrate layer a Sn-rich layer was found, probably consisting in an interdiffused Cu_3 Sn phase formed by thermal interdiffusionlayer is found. A Nb-Sn alloy grows on top of it. Finally, the superficial layer is composed by Cu-Nb-Sn oxides and chlorides. Phases rich in Nb are found on the deposited sample thanks to SEM/EDS measurements. XRD analysis are carried out to see if the interest Nb_3 Sn phase actually forms on Cu substrate. Based on XRD analysis, Thean univocal attribution identification of Nb_3 Sn crystalline phase is not certainwas not possible since because of the superimposition of the characteristic peaks with its characteristic peaks superimpose withthose of the Cu_3 Sn phaseformed by interdiffusion at the working temperature of 130 ℃. To overcome this problem and further improve the growth of the desired phase, the electroFor this reason, deposition was also carried out onto alternative Ni substrates are carried out to settle the XRD phases’ peak attribution and using two-compartments electrochemical cells.. Finally, depositions with separated compartment cell are explored, to investigate about evident differences with respect to the single compartment cell architecture.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/145299