Synthesis of Vanadium Dioxide Synthesis of Vanadium Dioxide Nanowires with Varying Acid Nanowires with Varying Acid and Vanadium Sources and Vanadium Sources I ntern: Peter LaCorte I ntern: Peter LaCorte Mechanical Engineering Mechanical Engineering Santa Barbara City College Santa Barbara City College Mentor: Kinson Kam Mentor: Kinson Kam Faculty Advisor: Prof. Anthony K. Cheetham Faculty Advisor: Prof. Anthony K. Cheetham
Vanadium Dioxide: Vanadium Dioxide: Changing phases Changing phases Thermal phase change from a semiconductor to a metal Thermal phase change from a semiconductor to a metal • Occurs at 67˚ C Occurs at 67˚ C • Ultra fast switching(20 ns) • Ultra fast switching(20 ns) • Blocks infrared light as a metal • Blocks infrared light as a metal • and not as a semiconductor and not as a semiconductor • Possible Applications Possible Applications • Thermochromic coatings � Thermochromic coatings � (“Smart” Windows ) (“Smart” Windows ) � Fiber Optic Switching � Fiber Optic Switching Courtesy of www.balticsww.com Courtesy of www.balticsww.com
Bulk vs. nano, what is the Bulk vs. nano, what is the ? difference ? difference Dimension on the nanoscale Dimension on the nanoscale Electrical change: Conductivity Electrical change: Conductivity Optical change: Visible color Optical change: Visible color Thermal change: Temperature at which a phase change occurs Thermal change: Temperature at which a phase change occurs
Hydrothermal Synthesis Hydrothermal Synthesis The Autoclave The Autoclave � Procedure � Procedure Solution: Solution: � � Stainless Steal Stainless Steal Vanadium Source Vanadium Source Canister Lid Canister Lid + Carboxylic Acids + Carboxylic Acids Spring Spring + 10ml H + 10ml H 2 2 O O Rupture Rupture disk disk 1 mmol vanadium 1 mmol vanadium � � (NH 4 (NH 4 VO VO 3 3 , VOSO , VOSO 4 4 ·xH ·xH 2 2 O, V O, V 2 2 O O 5 5 ) ) Teflon Liner Teflon Liner Corrosion disk Corrosion disk Acids added drop wise to pH ~2.5 Acids added drop wise to pH ~2.5 � � 180˚C at 2 days 180˚C at 2 days � � Stainless Steal Stainless Steal Canister Canister Washed with Ethanol Washed with Ethanol � � Centrifuged Centrifuged � � Schem atic Diagram Schem atic Diagram Dried in vacuum 60˚C for 4hrs Dried in vacuum 60˚C for 4hrs � �
Powder X- -ray Diffraction: ray Diffraction: Powder X A way of identifying the crystal structure A way of identifying the crystal structure Bragg’s law Bragg’s law X- - ray Data ray Data X Counts Counts (a.u.) (a.u.) 90000 90000 40000 40000 10000 10000 EQUATION LEGEND EQUATION LEGEND 0 0 n= Integer value n= Integer value 10 10 20 20 50 50 60 60 70 70 30 40 30 40 θ ] Position [2 2 θ λ = Wavelength of X λ = Wavelength of X- - ray(1.54Å) ray(1.54Å) d= Spacing of atomic planes d= Spacing of atomic planes θ = Angle of diffraction θ = Angle of diffraction
Scanning Electron Scanning Electron Microscopy Microscopy Taking advantage of the wave nature of the electron Taking advantage of the wave nature of the electron � Wave length = ~ 1Å � Schem atic Diagram Schem atic Diagram Wave length = ~ 1Å Electron gun Electron gun � Details as small as 10nm � Details as small as 10nm Illuminating Illuminating lens system lens system can be distinguished can be distinguished Scan coil Scan coil Final lens Final lens Detector Detector Specimen Specimen To pumps To pumps Courtesy of Courtesy of www.geos.ed.ac.uk www.geos.ed.ac.uk
Ammonium Metavanadate Ammonium Metavanadate (NH 4 VO 3 ) (NH 4 VO 3 ) Acetic Acid Oxalic Acid Tartaric Acid Acetic Acid Oxalic Acid Tartaric Acid ~ 600nm ~ 200nm ~ 100 ~ 100- - 200nm 200nm ~ 600nm ~ 200nm Intensity (a.u.) VO VO 2 2 + C + C VO 2 VO 2 + C + C Unidentified Unidentified 10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70 Position [°2Theta]
Vanadyl Sulfate Hydrate Vanadyl Sulfate Hydrate (VOSO 4 ·H H 2 O) ) (VOSO 4 · 2 O Acetic Acid Oxalic Acid Tartaric Acid Acetic Acid Oxalic Acid Tartaric Acid ~ 150- - 200nm 200nm microns ~ 100 ~ 100- - 150nm 150nm ~ 150 microns Intensity (a.u.) V 3 V 3 O O 7 7 ·H ·H 2 2 O O V 3 V 3 O O 7 7 ·H ·H 2 2 O O Unidentified Unidentified 10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70 Position [°2Theta]
Vanadium Pentoxide Vanadium Pentoxide (V 2 O 5 ) (V 2 O 5 ) Acetic Acid Oxalic Acid Tartaric Acid Acetic Acid Oxalic Acid Tartaric Acid ~ 200nm ~ 100nm ~ 1 ~ 1µ µm m ~ 200nm ~ 100nm Intensity (a.u.) V 2 V 2 O O 5 V 3 V 3 O O 7 7 ·H ·H 2 2 O O VO 2 VO 2 5 10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70 Position [°2Theta]
Conclusions Conclusions Synthesis of nanowires Synthesis of nanowires explored using different vanadium explored using different vanadium sources and carboxylic acids sources and carboxylic acids Samples characterized by X- Samples characterized by X - ray diffraction and Scanning ray diffraction and Scanning Electron Microscopy Electron Microscopy Future Research Future Research Affects of changing length of carbon chains on the Affects of changing length of carbon chains on the � � morphology morphology Characterization of the different morphologies Characterization of the different morphologies � � • Photoluminescence • Photoluminescence • • Conductivity Conductivity The effective implementation of these materials in new The effective implementation of these materials in new � � technologies technologies
Acknowledgements Acknowledgements Mentor: Kinson Kam Mentor: Kinson Kam Faculty Advisor: Prof. Anthony K. Cheetham Cheetham Faculty Advisor: Prof. Anthony K. I NSET: Trevor Hirst, Liu- I NSET: Trevor Hirst, Liu - Yen Kram er, Nick Arnold, Mike Northern Yen Kram er, Nick Arnold, Mike Northern Materials Research Lab: Joe Doyle, The Cheetham group Materials Research Lab: Joe Doyle, The Cheetham group Funding: The I nterdisciplinary Research Group 2 , Funding: The I nterdisciplinary Research Group 2 , The California Nano System I nstitute, The California Nano System I nstitute, and The National Science Foundation and The National Science Foundation
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