Synthesis of Vanadium Dioxide Synthesis of Vanadium Dioxide - - PowerPoint PPT Presentation

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

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

Vanadium Dioxide: Vanadium Dioxide:

Changing phases Changing phases

Courtesy of www.balticsww.com Courtesy of www.balticsww.com

Bulk vs. nano, what is the Bulk vs. nano, what is the difference difference?

?

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

Dimension on the nanoscale Dimension on the nanoscale

Hydrothermal Synthesis Hydrothermal Synthesis

• Procedure

Procedure

• Solution:

Solution: Vanadium Source Vanadium Source + Carboxylic Acids + Carboxylic Acids + 10ml H + 10ml H2

2O

O

• 1 mmol vanadium

1 mmol vanadium (NH (NH4

4VO

VO3

3, VOSO

, VOSO4

4·xH

·xH2

2O, V

O, V2

2O

O5

5)

)

• 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

• Washed with Ethanol

Washed with Ethanol

• Centrifuged

Centrifuged

• Dried in vacuum 60˚C for 4hrs

Dried in vacuum 60˚C for 4hrs

Rupture Rupture disk disk Corrosion disk Corrosion disk Stainless Steal Stainless Steal Canister Lid Canister Lid Spring Spring Teflon Liner Teflon Liner Stainless Steal Stainless Steal Canister Canister

The Autoclave The Autoclave

Schem atic Diagram Schem atic Diagram

Powder X Powder X-

• ray Diffraction:

ray Diffraction:

A way of identifying the crystal structure A way of identifying the crystal structure Bragg’s law Bragg’s law

EQUATION LEGEND EQUATION LEGEND n= Integer value n= Integer value λ λ= Wavelength of X = Wavelength of X-

• ray(1.54Å)

ray(1.54Å) d= Spacing of atomic planes d= Spacing of atomic planes

θ θ = Angle of diffraction

= Angle of diffraction

Position [2 2θ θ]

10 10 20 20 30 30 40 40 50 50 60 60 70 70 10000 10000 40000 40000 90000 90000

Counts Counts

(a.u.) (a.u.)

X X-

• ray Data

ray Data

Scanning Electron Scanning Electron Microscopy Microscopy

To pumps To pumps

Electron gun Electron gun Illuminating Illuminating lens system lens system

Scan coil Scan coil

Final lens Final lens Specimen Specimen Detector Detector

Schem atic Diagram Schem atic Diagram

Taking advantage of the wave nature of the electron Taking advantage of the wave nature of the electron

• Wave length = ~ 1Å

Wave length = ~ 1Å

• Details as small as 10nm

Details as small as 10nm can be distinguished can be distinguished

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Intensity

(a.u.)

Ammonium Metavanadate Ammonium Metavanadate

(NH (NH4

4VO

VO3

3)

)

Oxalic Acid Oxalic Acid Acetic Acid Acetic Acid ~ 200nm ~ 200nm ~ 600nm ~ 600nm ~ 100 ~ 100-

• 200nm

200nm Tartaric Acid Tartaric Acid

Position [°2Theta] 10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70 VO VO2

2 + C

+ C VO VO2

2 + C

+ C Unidentified Unidentified

Position [°2Theta]

Intensity

(a.u.)

10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70

Vanadyl Sulfate Hydrate Vanadyl Sulfate Hydrate

(VOSO (VOSO4

4·

·H H2

2O

O) )

Oxalic Acid Oxalic Acid Acetic Acid Acetic Acid microns microns ~ 150 ~ 150-

• 200nm

200nm ~ 100 ~ 100-

• 150nm

150nm Tartaric Acid Tartaric Acid

V V3

3O

O7

7·H

·H2

2O

O V V3

3O

O7

7·H

·H2

2O

O Unidentified Unidentified

Position [°2Theta]

Intensity

(a.u.)

10 20 30 40 50 60 70 10 20 30 40 50 60 70 10 20 30 40 50 60 70

Vanadium Pentoxide Vanadium Pentoxide

(V (V2

2O

O5

5)

)

Oxalic Acid Oxalic Acid Acetic Acid Acetic Acid ~ 100nm ~ 100nm ~ 200nm ~ 200nm ~ 1 ~ 1µ µm m Tartaric Acid Tartaric Acid

V V2

2O

O5

5

V V3

3O

O7

7·H

·H2

2O

O VO VO2

2

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

Conclusions Conclusions

Synthesis of Synthesis of nanowires 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

Mentor: Kinson Kam Mentor: Kinson Kam Faculty Advisor: Prof. Anthony K. Faculty Advisor: Prof. Anthony K. Cheetham Cheetham 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

Acknowledgements Acknowledgements