TY - JOUR
T1 - Synthesis of large ETS-4 crystals in the Na and Na/K systems
T2 - The effects of alkali metal ion and synthesis mixture alkalinity
AU - Yilmaz, Bilge
AU - Warzywoda, Juliusz
AU - Sacco, Albert
N1 - Funding Information:
The authors would like to acknowledge NASA for financial support and Dr. Steven M. Kuznicki for an introduction into the ETS materials.
PY - 2004/10/15
Y1 - 2004/10/15
N2 - The effects of Si/Ti ratio, initial pH, type of pH modifier and alkali metal cation system on ETS-4 crystal size and morphology were investigated. In the Na system at lower initial pH values (11.50-12.80), polycrystalline ETS-4 was obtained from all synthesis mixtures investigated (Si/Ti = 3.0-3.6), using either base (sodium hydroxide) or acid (sulfuric acid) as a pH modifier. When the initial pH was adjusted to range from 12.90 to 13.50 using acid, base or a combination of both, monolithic ETS-4 crystals with rectangular prism morphology were obtained. The average length of these crystals increased from ~15 μm at pH = 12.90 to ~40 μm at pH= 13.50. These results indicate that in the Na system, morphology and size of ETS-4 are not directly related to the synthesis mixture Si/Ti ratio or the type of pH modifier used. The strong dependence of crystal characteristics on the initial pH suggests that alkalinity is a major factor affecting ETS-4 crystallization. When half of the Na ions were replaced by K ions in synthesis mixtures with initial pH = 12.90, the resulting Na/K system yielded large single ETS-4 crystals with average dimensions ~10 × 200 × 20 μm. These are the largest ETS-4 crystals reported to date. These results suggest a structure-breaking role for K ions in ETS-4 crystallization.
AB - The effects of Si/Ti ratio, initial pH, type of pH modifier and alkali metal cation system on ETS-4 crystal size and morphology were investigated. In the Na system at lower initial pH values (11.50-12.80), polycrystalline ETS-4 was obtained from all synthesis mixtures investigated (Si/Ti = 3.0-3.6), using either base (sodium hydroxide) or acid (sulfuric acid) as a pH modifier. When the initial pH was adjusted to range from 12.90 to 13.50 using acid, base or a combination of both, monolithic ETS-4 crystals with rectangular prism morphology were obtained. The average length of these crystals increased from ~15 μm at pH = 12.90 to ~40 μm at pH= 13.50. These results indicate that in the Na system, morphology and size of ETS-4 are not directly related to the synthesis mixture Si/Ti ratio or the type of pH modifier used. The strong dependence of crystal characteristics on the initial pH suggests that alkalinity is a major factor affecting ETS-4 crystallization. When half of the Na ions were replaced by K ions in synthesis mixtures with initial pH = 12.90, the resulting Na/K system yielded large single ETS-4 crystals with average dimensions ~10 × 200 × 20 μm. These are the largest ETS-4 crystals reported to date. These results suggest a structure-breaking role for K ions in ETS-4 crystallization.
KW - A1. Crystal morphology
KW - A2. Large crystal growth
KW - A2. Synthesis
KW - A3. Quantum wires
KW - B1. ETS-4
KW - B1. Titanosilicates
UR - http://www.scopus.com/inward/record.url?scp=4944250300&partnerID=8YFLogxK
U2 - 10.1016/j.jcrysgro.2004.07.050
DO - 10.1016/j.jcrysgro.2004.07.050
M3 - Article
AN - SCOPUS:4944250300
SN - 0022-0248
VL - 271
SP - 325
EP - 331
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
IS - 1-2
ER -