Nano Quartz Cafer T. Yavuz 10/9/2006

2 Quartz in nature SiO 2, Silicon dioxide (70%) Macrocrystalline varieties –Amethyst is the purple gemstone variety.Amethyst –Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.Citrine –Milky Quartz is the cloudy white variety.Milky Quartz –Rock crystal is the clear variety that is also used as a gemstone.Rock crystal –Rose quartz is a pink to reddish pink variety.Rose quartz –Smoky quartz is the brown to gray variety.Smoky quartz

3 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

4 Structure One of 8 other SiO 2 structures but the most stable one. Isostructural with AlPO 4 (berlinite): helix chains of silicon tetrahedrons

5 Sources for Quartz Mining Industrial, synthetic production –Charles Sawyer’s cultured quartz process Chemical synthesis*

6 Nano Quartz Enhanced physical, electronic and optical properties Nanoscale piezo-electric behaviour

7 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 α-quartz –[CHALLENGE]: extremely rapid growth rate in conditions required for its nucleation (80 nm/sec at 263 °C in 0.5 M NaOH)

8 Previous methods Starting materialMethodMediumFinal SizeAuthorYear Cristobalite (SiO 2 ) hydrothermal hot-press Alkaline5~8 μmHosaka1991 Amorphous silicaVapor Pressure 240 ºC ~ 450 ºC Alkaline1-10 μmLee1996 SilicaCarbon nanotubes Alkaline10 nm – 100 μm Zhang1999

9 Hydrothermal Synthesis -1 Fumed silica + NaOH 18 ± 5 nm Nanoquartz ºC minireactor Bertone et. al. 2003

10 Hydrothermal Synthesis -1

11 Hydrothermal Synthesis -2 Silica gel + NaOH ~800 nm Nanoquartz 210 ºC autoclaves Sodium silicate + HCl 14 hours 22 hours70 hours 2 μm Lia et. al. 2003

12 Hydrothermal Synthesis -2 Q: Quartz C: α-Cristobalite X: SiO 2 -X 2

13 Hydrothermal Synthesis -3 Amorphous Silica Nanoparticles core-shell Nanoquartz 1000 ºC Okabayashi et. al additives TiO 2, CaO

14 Hydrothermal Synthesis -3 1: Homo-3C 2: Shell-3C 3: Core-3C All Shell-3C, numbers rep. hours

15 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