The study on the effective factors of hydrothermal synthesis in preparing high quality crystalline α-quartz powders

Modeling the Surface Structure and Stability of α-Quartz

“…In addition, the high-frequency stability of α-quartz results in its use in high-frequency devices , and in cellular and satellite network applications . The need for ever smaller devices demands increased quality of single crystals of high uniformity. − Therefore, it is important to investigate any factors affecting crystal growth, for example, how reaction variables such as degree of supersaturation, temperature, solvent composition, and concentration of seed crystals influence the development of different faces of the α-quartz crystals, how to minimize the number of defects and dislocations in the crystals, and how pressure affects crystal growth …”

“…Furthermore, α-quartz crystals are routinely grown in a solution of alkali hydroxides and halides such as KOH, NaOH, and NaF. ,, Thus, we have also included in our simulations the adsorption of NaOH at different concentrations onto the various surfaces of quartz, where we aim to study the effect of the adsorption of these species on the surface structure and stability of the different crystal faces.…”

“…6 The need for ever smaller devices demands increased quality of single crystals of high uniformity. [4][5][6] Therefore, it is important to investigate any factors affecting crystal growth, for example, how reaction variables such as degree of supersaturation, temperature, solvent composition, and concentration of seed crystals influence the development of different faces of the R-quartz crystals, 7 how to minimize the number of defects and dislocations in the crystals, 8 and how pressure affects crystal growth. 9 Water is inevitably present at crystal nucleation and growth, and when present in the bulk, it reduces the crystal strength (hydrolytic weakening), 10,11 allowing deformation of the crystal.…”

Aerosol-assisted synthesis of monodisperse single-crystalline α-cristobalite nanospheres

“…5 Many efforts have been made for synthesizing a-cristobalite, for example by annealing boiled rice husks at high temperature. 6 Hydrothermal methods [7][8][9][10][11] employing amorphous silica as a starting material have been used, and result in tetragonal or cubic phases of cristobalite, respectively, when KF or NaF are used as the mineralization agents. However, for all these methods, based on cristobalite phase behavior, it has proven difficult to control cristobalite nucleation and crystal growth and therefore its size and morphology.…”

Hydrothermal synthesis of monodisperse single-crystalline alpha-quartz nanospheres

“…9 Various crystalline silica varieties [10][11][12] can be generated depending on the alkaline concentration, temperature and duration. However it is difficult to control crystal growth, and the quartz particles are often large and strongly aggregated 13 as a consequence of the high pressure and temperatures needed for practical growth times. 3,14 Bertone et al 15 prepared sub-micrometre-sized quartz powders using hydrothermal methods in alloy Parr bombs and classified them to get nanrrower size fractions of nanocrystalline quartz.…”