| Author | Kasi, Jafar Khan |
| Call Number | AIT Diss no.ISE-12-23 |
| Note | A dissertation submitted in partial fulfillment of the requirements for the
degree of Doctor of Philosophy in
Microelectronics, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-12-23 |
| Abstract | Anodic aluminum oxide (AAO) nano-porous membrane is popular for its self-organized nanostructure in the field of science and technology. It has hexagonal arrangement of pores which are parallel to each other and perpendicular to the surface. AAO can also be used for the fabrication of micro-nano combined structures, but it has some limitations. During fabrication of three dimensional (3D) structures sometimes they experience cracks. AAO has less mechanical strength which devalues their application in the field where high stress is involved. This research investigated the generation of cracks in various AAO based 3D structures; determine the optimum conditions where these cracks can be prevented. This research is divided in the following part
1) Characterization of cracks in AAO tubular, rectangular, triangular shapes.
2) Study the behavior of AAO nanochannels at the edge of rectangular shape where cracks are initiated.
3) Fabrication of cracks free micro-nano combined 3D structures.
AAO was fabricated at external surface of Al cylinder with different diameter and thickness. Cracks were observed in those cases where the membrane thickness was increased or the diameter was reduced to a certain limit. By changing anodization time, cracks free transparent AAO tubular membranes of different diameters were successfully fabricated. A relationship was developed on the basis of a statistical model for the anodization time, cracks per millimeter and diameter. In rectangular and triangular shapes cracks were observed at their edges.
The geometry of AAO nanochannels were studied in plane membranes and in rectangular membrane where cracks were generated. In plane membrane the AAO nanochannels were perpendicular to the surface and parallel to each other. However in rectangular shape where cracks were generated at their edges, it was observed that nanochannels bend when they come closer to each other from both sides. It is concluded that Al experiences volume expansion when it converts in AAO; this expansion is responsible for generation of cracks at the edges of rectangular block and bending of AAO nanochannels at that point.
Taking advantage of study on cracks, the micro-nano combined 3D structures were fabricated. For fabrication of AAO 3D structures a simple procedure has been introduced which does not require the assistance of scaffolding or molding process. Various shapes including micro conical tube, micro cone, and micro bowl have been fabricated. The fabricated 3D shapes have potential applications in drug delivery systems and in sensors.
iv
Using AAO template CNT has been grown in nanochannels. CNT is popular for excellent mechanical, thermal, electrical and optical properties. To get the composite membrane, CNT was synthesized inside AAO nanochannels by chemical vapor deposition method at atmospheric pressure. Ethanol was used as a hydrocarbon source and Co–Mo as catalyst. CNT was synthesized at different temperature. High graphitic multiwall carbon nanotube (MWCNT) was found at 750oC, while carbon nanofiber (CNF) was found at 800oC and above temperature. |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-12-23 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Microelectronics (ME) |
| Chairperson(s) | Afzulpurkar, Nitin V.; |
| Examination Committee(s) | Adisorn Tuantranont ;Amporn Poyai;Bohez, Erik L. J. : Sirapat Pratontep;Busnaina, Ahmed A. ; |
| Scholarship Donor(s) | University of Balochistan Quetta, Pakistan;
Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2012 |