Laser chemical deposition of nanomaterials and their applications
Nanomaterials have the characteristics of small sizes, large surface to volume ratio and unique physical properties. Due to large surface to volume ratio, nanomaterials exhibit superior performances in applications of battery, catalyst, sensors and so on. The study of making nanomaterials at good quality and high productivity is of importance for nano products penetrating the market and benefiting the society. For bottom-up nanomanufacturing methods, the fundamental nucleation process greatly influences the quality and productivity of the method and the performance of the product. In this dissertation, laser chemical deposition is the subject of study. Both the nucleation process and its strong impacts are investigated. The nucleation pathway depends on the energy input. Observations from single pulse synthesis of iron oxide indicate when laser intensity is high enough, crystal is formed directly; When laser intensity is low, amorphous material nucleates initially and nanocrystals are obtained through a multi-step pathway. The nucleation pathway determines the morphology and microstructure (quality) of resulting materials. In multiple pulses experiment, the multi-step nucleation pathway results in nanosheet structure on a planar substrate and nanotube structure within a 3D template. It is shown that the relationship between quality and productivity of the method depends on the nucleation pathways. To correlate different nucleation pathways to temperature conditions, computer simulations are implemented to calculate the temperature distribution under different laser parameters. Factors governing the productivity or growth rate of the nanotube are shown. It is found that nanotube are formed through multi-step nucleation. Compared to state-of-art solution based methods, the growth rate of SnO 2 nanotube by laser chemical deposition is more than 1000 times faster. It is shown the productivity is influenced by the chemical concentration and laser intensity. This solution based method can produce materials for a wide range of applications. Synthesis of tin oxide, ferrihydrite, manganese oxide and zinc sulfide nanomaterials are demonstrated in this dissertation. They can be used in the applications of lithium ion battery, heavy metal absorbent, super-capacitor and solar cell respectively. The performance of nanomaterials by laser chemical deposition in lithium ion battery is shown in details. Coin cell lithium ion battery was assembled with the SnO2 nanotube made by the method. The SnO2 nanotube is mesoporous and composed of ultra-small crystals. Because of its large exposed surface area, the electrode exhibit large capacity density (>1000 mAh/g at first cycle) and fast charge/discharge capability. Part of the original methods and applications are patent pending.
Liu, Purdue University.
Inorganic chemistry|Industrial engineering|Nanotechnology
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