Ni nanomateryelinin erime sürecinde ebad şekil ve boyuta bağlı fiziksel özelliklerinin incelenmesi
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Dosyalar
Tarih
2012
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Trakya Üniversitesi Fen Bilimleri Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu tezde, Nano boyutlu Ni (nikel) metalik sistemlerinin ergime sürecindeki bazı fiziksel özelliklerinin nanometaryelinin ebadına, geometrisine ve boyuta bağlılığı termodinamik modeller kullanılarak incelenmiştir. Ni nanomateryalinin (NM), (0) boyutlu nanoparçacık, (1) boyutlu nanotel ve (2) boyulu nanofilm halindeki ergime noktaları, kohesif enerjileri, erime entropisi ve entalpileri'nin ebad, şekil ve boyuta bağlılığı nanometaryellerin birim örgü yapılarına dayalı teorik modeller kullanılarak hesaplanmıştır. Bu amaçla Ikozahedral (ICO) ve kübo-oktahedral (CO), küresel, düzgün tetrahedral ve düzgün oktahedral geometrik yapılarına sahip 0.5-30nm çaplı Ni nanoparçacıkları; ile çalışılmıştır. Hegzagonal ve silindirik ince Ni nanotelleri ile ince Ni nanoflimleri ele alınarak; farklı boyutta benzer geometriye sahip nanomateryeller için geliştirilen teorik modeller kullanılmıştır. Elde edilen sonuçlar var olan deneysel sonuçlar ve simülasyon sonuçları ile karşılaştırılarak; Lu ve Shandiz-Safaei tarafından öne sürülen modellerin geçerliliği test edilmiştir. Kullanılan modellerde NM ebadının azalması ile birlikte erime sıcaklıklarının düştüğü, erime entalpisi ve entropisinin sıfıra gittiği tespit edilmiş, Lu ve Safaei-Shandiz modellerinin 3nm çapından küçük Nikel NM'in erime entropisi ve entalpileri için farklı negatif değerler verdiği ilk kez bu tezde gösterilmiştir. Ayrıca Shandiz-Safaei ve Lu modelleri ile hesaplanan erime entropisi ve entalpilerinin çapı 10nm'den büyük Ni NM için birbirleri ile örtüştüğü bulunmuştur.
Abstract
In this thesis, size, shape and dimensionality effect on the phsical properties of Nicel (Ni) nanomaterials(NM) during melting processes have been investigated using thermodynamics models. The size, shape and dimensionality dependent melting point, cohesive energy, melting entropy and enthalpy of zero (0) dimensional nanoparticles, one(1) dimensional nanowires, two (2) dimensional nanofilms of Ni nanomaterials are calculated using the therotical models based on the unit lattice structures of nanomaterials. For this purpose, 0,5 ? 30nm diameter of Ni Icosehedral (ICO) and cubo ? octahedral (CO), spherical, regular tetrahedral and regular octahedral nanoparticles have been studied. The theoretical models those obtained for the nanomaterials with different dimensionality as those same basal shapes are used for considering the hexagonal and cylindrical thin Ni nanowires and thin Ni nanofilms. The results are compared with those obtained by experiment and MD simulations for testing the validity of the models proposed by Lu and Shandiz-Safaei. It is mention that the models predict, the melting point depression, the melting entropy and enthalpy converge to zero when the NM size decreases. With considering the particles having a diameter lower than 3nm, the Lu and Shandiz-Safaei models predict different negative values of melting entropy and enthalpies of Ni NM that was found the first time in this thessis. Furthermore it was found that, the calculated values for melting entropy and enthalpies of Ni NM in the Lu and Shandiz-Safaei models are more appropriate for the particles having a diameter higher than 10nm.
Abstract
In this thesis, size, shape and dimensionality effect on the phsical properties of Nicel (Ni) nanomaterials(NM) during melting processes have been investigated using thermodynamics models. The size, shape and dimensionality dependent melting point, cohesive energy, melting entropy and enthalpy of zero (0) dimensional nanoparticles, one(1) dimensional nanowires, two (2) dimensional nanofilms of Ni nanomaterials are calculated using the therotical models based on the unit lattice structures of nanomaterials. For this purpose, 0,5 ? 30nm diameter of Ni Icosehedral (ICO) and cubo ? octahedral (CO), spherical, regular tetrahedral and regular octahedral nanoparticles have been studied. The theoretical models those obtained for the nanomaterials with different dimensionality as those same basal shapes are used for considering the hexagonal and cylindrical thin Ni nanowires and thin Ni nanofilms. The results are compared with those obtained by experiment and MD simulations for testing the validity of the models proposed by Lu and Shandiz-Safaei. It is mention that the models predict, the melting point depression, the melting entropy and enthalpy converge to zero when the NM size decreases. With considering the particles having a diameter lower than 3nm, the Lu and Shandiz-Safaei models predict different negative values of melting entropy and enthalpies of Ni NM that was found the first time in this thessis. Furthermore it was found that, the calculated values for melting entropy and enthalpies of Ni NM in the Lu and Shandiz-Safaei models are more appropriate for the particles having a diameter higher than 10nm.
Açıklama
Yüksek Lisans Tezi
Anahtar Kelimeler
Ni Nanotelleri, Entalpi, Entropi, Ni Nanparçacıkları, Erime Sıcaklığı, Melting Temperature, Enthalpy, Ni Nanoparticles, Ni Nanowires, Entropy
