Molten Salt Synthesis Process Research Articles

Topochemical reaction of SrTiO 3 platelet crystals based on Sr 3Ti 2O 7 platelet precursor in molten salt synthesis process

Molten salt synthesis (MSS) is an effective method to prepare anisotropic shaped single crystals. In this study strontium titanate (SrTiO 3) (ST) platelet crystals were successfully synthesized based on Sr 3Ti 2O 7 (S3T2) platelet precursor in MSS process. The objective is to identify the formation mechanism of SrTiO 3 platelet crystals based on Sr 3Ti 2O 7 platelet precursor. During the synthesis process of Sr 3Ti 2O 7 and SrTiO 3 crystals, the final sizes are strongly influenced by the sorts of alkali chloride medium. Sr 3Ti 2O 7 and SrTiO 3 crystals with 30–50 μm in edge length and ∼2 μm in thickness are obtained in KCl medium. The conversion of SrTiO 3 platelet crystals from Sr 3Ti 2O 7 platelet precursor is a topochemical process, including diffusion of Sr and O atoms, and reconstruction of SrTiO 3 blocks. In the topochemical process, TiO 2 is the driving force of diffusion of Sr and O atoms from Sr O layer in Sr 3Ti 2O 7, which reacts with dissociative Sr 2+ and O 2− to form SrTiO 3 in different positions: deposited at interior pores and surface of Sr 3Ti 2O 7, and dispersed in molten salt medium.

Whisker-Like Hydroxyapatite Synthesized by Molten Salt Synthesis (MSS) of Nano-Hydroxyapatite in a KCl/NaCl Flux

A lot of attention has been given to bone cements due to their lack of mechanical properties. The improvement of this property is essential, once it makes possible the usage of these biomaterials in sites that require a significant mechanical strength resistance. To do so, reinforcement agents, such as fibers, in particular biocompatible fibers, have been synthesized [1]. This study reports the synthesis of stequiometric Hydroxyapatite whisker-like fibers utilizing the Molten Salt Synthesis process of nanometric Hydroxyapatite with a salt flux mixture of KCl/NaCl. According to SEM images, EDS analysis and X-ray diffraction, the fibers obtained presented well defined and elongated (main length of about 70µm) hexagonal morphology with Ca/P ratio of 1.66.

Synthesis of ZnNb 2O 6 powder with rod-like particle morphologies

A ZnNb 2O 6 powder was synthesized through the molten salt method. The XRD and SEM results indicated that the crystal ZnNb 2O 6 powder with rod-like particle morphologies could be obtained via this method at temperature of 600 °C, which is significantly lower than that required by solid-state reaction, where a calcining temperature of 800 °C was needed and the obtained ZnNb 2O 6 particles were equiaxial. The heat treatment temperature scarcely affected the ZnNb 2O 6 particle morphologies in the molten salt synthesis process.

Effects of molten salt synthesis (MSS) parameters on the morphology of Sr3Ti2O7 and SrTiO3 seed crystals

A two-step molten salt synthesis process was utilized to fabricate Sr3Ti2O7 and SrTiO3. High aspect ratio SrTiO3 seed crystals were developed by optimizing processing conditions such as temperature, salt-to-oxide ratio, and flux type in a systematic fashion. Sr3Ti2O7 seeds were synthesized at temperatures ranging from 1050–1350°C, using salt-to-oxide ratios of 3:1, 1:1, and 1:3, and various salt types, including NaCl, KCl, and a 1:1 combination of NaCl and KCl. Sr3Ti2O7 seeds synthesized at 1250°C with a 1:1 salt-to-oxide ratio in 100% NaCl salt resulted in a majority of higher aspect ratio platelets and elongated platelets as opposed to lower aspect ratio cubic-like and tetragonal-like morphologies. The seeds were 10–40 μm in length with aspect ratios of highly elongated platelets as high as 25:1. A second MSS step was used to synthesize SrTiO3 seeds of the proper composition by TiO2 addition to the Sr3Ti2O7 seeds and heat treatment at 1100°C. These studies showed that highly anisotropic SrTiO3 seeds could be produced at 1250°C using a 1:1 salt-to-oxide ratio in 100% NaCl flux. XRD studies of the resulting SrTiO3 seeds revealed that the increase in aspect ratio for these particular seeds also resulted in the enhancement of (200) peaks, which are of major interest for texturing of PMN-PT.