Nitinol based micro/nano structures and hybrid nanocomposites

• Κύριος συγγραφέας: Παππά, Ευανθία
• Άλλοι συγγραφείς: Παπανικολάου, Γεώργιος
• Μορφή: Thesis
• Γλώσσα: English
• Έκδοση: 2016
• Θέματα: Composites; Multilayeres; Smart materials; Nitinol; CNTs; Acrylic polymers; DSC; Thermal conductivity; BDS; Modeling; Σύνθετα; Πολύστρωτα; Έξυπνα υλικά; Θερμικές ιδιότητες,; Ηλεκτρικές ιδιότητες; 620.115

In recent years functional nanomaterials gain a significant role in global industrial and space applications. The current investigation focuses on new functional hybrid multilayered composites that are eco-friendly and biocompatible. The present study consists of two main parts; the first part is the state of the art while the second part consists of the manufacturing processes, and the thermo-electrical characterization of the composites manufactured. Regarding the state of the art, there is an extensive bibliographic study on smart materials and more precisely shape memory composites (SMCs). The term "shape memory" refers to the ability of certain materials to annihilate a shape deformation. A particular alloy, of the family of shape memory alloys (SMA), with increasing importance in many industrials applications, is Nitinol. It is an inter-metallic alloy with excellent physic-mechanical and thermo-electric properties. Along with Nitinol, additional materials used in the present study are carbon nanotubes (CNTs) and acrylic resin. CNTs are forms of graphite; they are excellent candidates in electrical and thermal conductivity as well as in many mechanical testes. Acrylic resin polymer is the third part of the manufactured hybrid composite. Acrylic resin belongs to the family of vinyl polymers; they possess high resistivity in environmental corrosion besides their transparency properties. All aforementioned materials have undergone a series of thermal and electric tests. The manufacturing processes and the thermo-electrical characterization of the composites manufactured are presented in the second part of this study. The tested materials were categorized into 2 types: the surface treated composites and the surface untreated. The acrylic resin was embedded via spraying; while CNTs were injected on substrates. Nitinol’s surface was treated via anodization; due to that process a thin oxide film occurred on the surface of the alloy and an increased roughness was observed. The effect of the anodization along with the influence of the stacking sequence were investigated by means of electro-thermal analysis. Thermal conductivity tests and Differential Scanning Calorimetry (DSC) were conducted while the electrical conductivity measurements were performed by means of Broadband Dielectric Spectroscopy (BDS). The Scanning Electron Microscopy (SEM) and Stereoscopy were the optical characterization techniques. Multilayered hybrid composites with shape memory effect are a new field of study with an ever-increasing industrial interest. Not only the specific manufactured hybrid composites can be used in space and automobile applications, but also they have many biomedical approaches due to their biocompatibility and bioactivity.