Anodize Alüminyum Şablonlara Elektrolitik Kaplama Yöntemi İle Kendi Kendini Taşıyabilen Ni-w Nano Tellerin Kaplanması Ve Karakterizasyonu
Anodize Alüminyum Şablonlara Elektrolitik Kaplama Yöntemi İle Kendi Kendini Taşıyabilen Ni-w Nano Tellerin Kaplanması Ve Karakterizasyonu
Dosyalar
Tarih
2013-01-08
Yazarlar
Paşaoğlu, Doğan Işıhan
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Institute of Science and Technology
Özet
Ni-W alaşımlarının elektrokaplama yöntemiyle üretilmesi ilgi çekici bir konudur. Kaplama sonucu elde edilen ürünler, tribolojik, manyetik, elektriksel ve elektro-erozyon özellikleri açısından benzersiz bir bileşime sahiptir. Bu yöntemle üretilen Ni-W kaplamalar yüksek çekme mukavemeti ve sertlik özelliklerinin yanısıra, güçlü asitlere karşı yüksek direnci ve yüksek ergime sıcaklığıyla ön plana çıkmakta ve sert krom kaplamalara alternatif olarak görülmektedir. Bu özelliklerin yanısıra, Ni-W alaşımları, hidrojen çıkışı ve sülfürden arındırma gibi işlemler açısından elektrokatalitik özellikleriyle umut vaad etmektedir. Bu çalışmanın amacı, grubumuz tarafından daha önceden geliştirilen bir yöntem yardımıyla kendi kendini taşıyabilen Ni-W nanotel üretmek ve karakterizasyon çalışmalarını yürütmektir. Yapılan deneyler, şablon olarak anodize alüminyum oksit (AAO) şablonların, grubumuzca zinkatlama yöntemine dayanan bir metotla aktifleştirilmesi ve doğru akım elektrolitik kaplama yöntemi ile AAO şablonlara Ni-W nanotel kaplanmasına dayanmaktadır. Kaplama devam ettirildikçe porlar Ni-W nanoteller ile doldırılmakta ve ardından AAO ve Al katmanları çözülerek geriye kendi kendini taşıyabilen nanoteller kalmaktadır. Ni-W nanotellerin üretimi için öncelikle AAO şablonların üretimi optimize edilmiştir. Önceden tavlanan ve elektro parlatma işlemine tabi tutulan saf alüminyum numuneler, okzalik asit ile iki basamaklı anodizasyon basmaklarından geçirilmiş; yaklaşık100nm por çapı elde edilmiştir. Anodizasyon süresi ayarlanarak kalınlık 2 µm elde edilmiştir. Elde edilen porlu yapının tabanları elektrokimyasal ayrışma ve zinkatlama yöntemi ile doğru akım elektrolitik kaplama için hazır hale getirilmiştir. Elektrolitik kaplama deneyleri 1.25 A/dm2, 1.56 A/dm2, 1.87 A/dm2 ve 2.18 A/dm2 değerlerinde gerçekleştirilmiştir. Atomik %9 W içeren Ni-W alaşım eldesi için optimizasyonlar yapılmış; kullanılan çözeltinim kritik pH ve kaplama anındaki akım yoğunluk değerleri ortaya çıkarılmıştır. Deneylerin sonunda, uzunlukları 1.5-1.8 µm ve çapları ortalama 120 nm ile 140 nm arası değişen Ni-W nanoteller başarı ile üretilmiştir. Elde edilen numuneler Watts çözeltisi ile kalınlaştırılmış ve ardından AAO ve Al katmanları NaOH çözeltisinde çözülmüştür; kendi kendini taşıyan Ni-W nanoteller üretilmiştir. Ardından FEG-SEM ve XRD analizleri yapılmış, elektrokatalitik özellikleri polarizasyon eğileri üzerinden incelenmiş ve Ni-W nanotellerin düz elektrolitik Ni kaplamalara göre davranışı irdelenmiştir. Deney sonuçları, yapı içine oksit katılımı engellenebilirse Ni-W nanotellerin elektrokatalitik malzeme olarak kullanılabilme potansiyeline sahip oldukları göstermiştir. Bu üretim yöntemi sayesinde ilk defa kendi kendini taşıyabilen Ni-W nanotel yapılar üretilmiştır; ve yüksek yüzey alanları nedeniyle kullanım alanlarının genişleyeceği düşünülmektedir.
The electrodeposition of Ni-W alloys is an interesting subject due to the unique properties of the final products such as the combination of tribological, magnetic, electrical and electro-erosion properties. They exhibit high tensile strength and hardness properties, high resistance to strong acids and have high melting temperature. They are also considered as alternative for hard chromium coatings. Besides these properties Ni-W alloys are promising materials for electrocatalytic applications such hydrogen evolution, desulphurization. The aim of this study was to produce free standing Ni-W alloy nanowires with a previously developed method in our group and to conduct characterization analyses. The method is based on using anodized alumium oxide (AAO) as templates. With a special method based on zincating that was developed within the group, the bottoms of the pores of the prepared AAO templates are activated. By this process the AAO templates become ready for filling the pores with metal using DC electroplating. By continuing the electrodeposition after filling of the pores, the wires within the pores are covered by a layer of the same metal. This layer supported the wires after dissolving away the AAO and aluminum creating an easily handled free standing structure. For the production of Ni-W nanowires the parameters of the AAO template formation was optimized. After two step anodization of annealed and electropolished pure aluminum in oxalic acid solutions well ordered pores around 100 nm in diameter was obtained. The length of the pores was adjusted to 2 µm by tuning the anodization time. This porous structure was pore bottom activated with a method based on electrochemical dissociation and zincating that allowed the DC electrodeposition starting from pore bottoms. The samples were electrodeposited in 1.25 A/dm2, 1.56 A/dm2, 1.87 A/dm2 and 2.18 A/dm2 . After optimization of Ni-W alloy deposition for obtaining 9 at% W in the deposit pore filling experiments were conducted revealing the need of futher optimization for achieving a succesfull electrodeposition within the pores. The critical role of solution pH and deposition current density was revealed. At the end of the experiments, Ni-W nanowires with the length of 1.5-1.8 µm and diameters ranging from 120nm to 140 nm were produced. After thickening the Ni-W coated layer with Watts solution and dissolving the AAO and Al layers of the samples in NaOH solution, free-standing Ni-W nanowires were obtained. FEG-SEM, XRD analyses were performed and polarization curves for electrocatalytic activity were investigated. It was demonstrated that Ni-W nanowires have a potential to be utilized as electrocatalysts if oxide formation in the structure is avoided. This method of production introduced is the first study that showed the possibility of the production of free standing Ni-W structures with the said method and believed to extend the high surface area related applications, such as catalysis, of these alloys.
The electrodeposition of Ni-W alloys is an interesting subject due to the unique properties of the final products such as the combination of tribological, magnetic, electrical and electro-erosion properties. They exhibit high tensile strength and hardness properties, high resistance to strong acids and have high melting temperature. They are also considered as alternative for hard chromium coatings. Besides these properties Ni-W alloys are promising materials for electrocatalytic applications such hydrogen evolution, desulphurization. The aim of this study was to produce free standing Ni-W alloy nanowires with a previously developed method in our group and to conduct characterization analyses. The method is based on using anodized alumium oxide (AAO) as templates. With a special method based on zincating that was developed within the group, the bottoms of the pores of the prepared AAO templates are activated. By this process the AAO templates become ready for filling the pores with metal using DC electroplating. By continuing the electrodeposition after filling of the pores, the wires within the pores are covered by a layer of the same metal. This layer supported the wires after dissolving away the AAO and aluminum creating an easily handled free standing structure. For the production of Ni-W nanowires the parameters of the AAO template formation was optimized. After two step anodization of annealed and electropolished pure aluminum in oxalic acid solutions well ordered pores around 100 nm in diameter was obtained. The length of the pores was adjusted to 2 µm by tuning the anodization time. This porous structure was pore bottom activated with a method based on electrochemical dissociation and zincating that allowed the DC electrodeposition starting from pore bottoms. The samples were electrodeposited in 1.25 A/dm2, 1.56 A/dm2, 1.87 A/dm2 and 2.18 A/dm2 . After optimization of Ni-W alloy deposition for obtaining 9 at% W in the deposit pore filling experiments were conducted revealing the need of futher optimization for achieving a succesfull electrodeposition within the pores. The critical role of solution pH and deposition current density was revealed. At the end of the experiments, Ni-W nanowires with the length of 1.5-1.8 µm and diameters ranging from 120nm to 140 nm were produced. After thickening the Ni-W coated layer with Watts solution and dissolving the AAO and Al layers of the samples in NaOH solution, free-standing Ni-W nanowires were obtained. FEG-SEM, XRD analyses were performed and polarization curves for electrocatalytic activity were investigated. It was demonstrated that Ni-W nanowires have a potential to be utilized as electrocatalysts if oxide formation in the structure is avoided. This method of production introduced is the first study that showed the possibility of the production of free standing Ni-W structures with the said method and believed to extend the high surface area related applications, such as catalysis, of these alloys.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2011
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2011
Anahtar kelimeler
nanotel,
elektrolitik kaplama,
Ni-W kaplamalar,
elektrokatalitik aktivite,
nanowires,
electrodeposition,
Ni-W coatings,
electrocatalytic activity