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Thermochromic Doped Vanadium Dioxide Coatings
for Smart WindowsGhouwaa Philander
iThemba LABSSupervisor: Prof. M.
Maaza
Energy Postgraduate Conference 2013
![Page 2: Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Ghouwaa Philander iThemba LABS Supervisor: Prof. M. Maaza Energy Postgraduate Conference](https://reader035.vdocuments.mx/reader035/viewer/2022062309/56649e445503460f94b38ffa/html5/thumbnails/2.jpg)
Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows
• Breaking it down– Vanadium Dioxide– Thermochromism and Doping
• Bringing it together– Smart Windows– Need
• Material Synthesized
• Conclusions and Future Work
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Contents
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Energy Postgraduate Conference 2013
Vanadium Dioxide (VO2)
• VO2 undergoes a transition at 68°C from the semi-conducting monoclinic phase to the metallic rutile phase, the latter which is IR opaque.
• VO2 exists in a number of morphologies with varying properties, dependant largely on method synthesis and growth.Whittaker et al. J. Phys. Chem. Lett. 2011, 2, 745–758
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows
• A compound that displays a reversible change in colour as a result of a change in temperature is ‘thermochromic’.– change in geometry– variation in coordination number– change in lattice formation
• Doping is the process of introducing a ‘metal’, as an impurity, into the crystal structure which introduces additional energy levels.
• Doping of VO2 compounds with tungsten reduces the naturally occurring transition temperature to even closer to room temperature.
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Thermochromism and Doping
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Energy Postgraduate Conference 2013
Smart Windows
Parkin and Manning. J. Chem. Ed. 2006, 83, 393-400
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows
• Heating, ventilation and air-conditioning, contribute an estimated 15% to South Africa’s current peak demand consumption.
• 33% saving in energy consumption will be realised if inside and outside temperature difference is maintained. (Eskom Communication Fact Sheet, January 2013)
• Objective: To develop a cost effective chemical method to produce efficient and viable VO2
coatings with enhanced properties, for use in smart window applications.
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Need
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Energy Postgraduate Conference 2013
Material Synthesized
20 30 40 50 60
5k
6k
7k
8k
9k
10k
(220)
(200)
(011)
(100)
Intensit
y (
cps)
2 (deg)
• A chemical method was used to synthesize a range of W-doped VO2 films from 0.5-2.5 wt%.
• Polymer assisted deposition with annealing in an oxygen deficient environment.
• Crystalline particle sizes ranged from 30-62 nm along the (011) plane. Variability in the dhkl showed evidence of W integration into the crystal lattice structure.
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Energy Postgraduate Conference 2013
Material Synthesized cont.
200 400 600 800 1000
0
10
20
30
40
50
60
Tra
nsm
itta
nce
(%
)
Wavelength (nm)
0.5% W
1% W
1.5% W
2% W
2.5% W
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows Energy Postgraduate Conference 2013
Material Synthesized cont.
20 30 40 50 60 70 80
0
10M
20M
30M
40M
50M
60M
Resis
tance (
ohm
s)
Temperature (oC)
• The phase transition is represented with a steep slope and takes place at approximately 33°C during the heating and cooling cycle.
• Hysteresis gap of 8.8°C at 27 MΩ .
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Thermochromic Doped Vanadium Dioxide Coatings for Smart Windows
• The method has achieved its primary objective of producing thermochromic VO2 films with enhanced properties.
• The reduced transition temperature achieved renders this material suitable for smart window applications.
• Future work will include further optimization of this method, including IR modulation studies.
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Conclusions and Future Work
THANK YOU