Nano Quartz

1
Nano Quartz

• Cafer T. Yavuz
• 10/9/2006

2
Quartz in nature

• SiO2, Silicon dioxide (70)
• Macrocrystalline varieties
• Amethyst is the purple gemstone variety.
• Citrine is a yellow to orange gemstone variety
  that is rare in nature but is often created by
  heating Amethyst.
• Milky Quartz is the cloudy white variety.
• Rock crystal is the clear variety that is also
  used as a gemstone.
• Rose quartz is a pink to reddish pink variety.
• Smoky quartz is the brown to gray variety.

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Uses of quartz

• For quality glass
• Electrical components, fiber optics
• Optical lenses
• Ornamental stone and as gemstones
• Thermal Insulators, infrared ceramic materials
• Abrasives
• Crystal oscillators
• Healing crystals (!)
• Building stones

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Structure

• One of 8 other SiO2 structures but the most
  stable one.
• Isostructural with AlPO4 (berlinite) helix
  chains of silicon tetrahedrons

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Sources for Quartz

• Mining
• Industrial, synthetic production
• Charles Sawyers cultured quartz process
• Chemical synthesis

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Nano Quartz

• Enhanced physical, electronic and optical
  properties
• Nanoscale piezo-electric behaviour

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Methods for nano quartz

• Grinding, ball-milling
• Bottom-up synthesis from silicas
• CHALLENGE the amorphous state of silica is
  nearly equal in energy to that of a-quartz
• CHALLENGE extremely rapid growth rate in
  conditions required for its nucleation
• (80 nm/sec at 263 C in 0.5 M NaOH)

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Previous methods
Starting material Method Medium Final Size Author Year
Cristobalite (SiO2) hydrothermal hot-press Alkaline 58 µm Hosaka 1991
Amorphous silica Vapor Pressure 240 ºC 450 ºC Alkaline 1-10 µm Lee 1996
Silica Carbon nanotubes Alkaline 10 nm 100 µm Zhang 1999
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Hydrothermal Synthesis -1
200 - 300 ºC
Fumed silica NaOH
18 5 nm Nanoquartz
minireactor
Bertone et. al. 2003
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Hydrothermal Synthesis -1
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Hydrothermal Synthesis -2
Sodium silicate HCl
210 ºC
Silica gel NaOH
800 nm Nanoquartz
autoclaves
Lia et. al. 2003
2 µm
14 hours
22 hours
70 hours
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Hydrothermal Synthesis -2
Q Quartz C a-Cristobalite X SiO2-X2
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Hydrothermal Synthesis -3
1000 ºC
Amorphous Silica Nanoparticles
core-shell Nanoquartz
additives TiO2, CaO
Okabayashi et. al. 2005
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Hydrothermal Synthesis -3
1 Homo-3C 2 Shell-3C 3 Core-3C
All Shell-3C, numbers rep. hours
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Conclusions

• There are only 6 published synthesis of
  nano-quartz all of them starts from silica
• Quartz is challenging to synthesize.
• Size control lacks, further purification is
  needed
• New methods, especially non-aqueous, need to be
  explored