Sinterability of Forsterite Prepared via Solid‐State Reaction

Abstract

In this work, the sinterability of forsterite powder synthesized via solid‐state reaction was investigated. X‐ray diffraction (XRD) analyses indicate that the synthesized powder possessed peaks that correspond to stoichiometric forsterite. Scanning electron micrographs revealed that the powders were formed agglomerates, which were made up of loosely packed fine particles. Subsequently, the forsterite powders were cold isostatically pressed into a disk shape under 200 MPa and sintered in air at temperature ranging from 1200°C to 1500°C (interval of 50°C) with ramp rate of 10°C/min and dwelling time of 2 h. The sinterability of each sintered samples was examined in terms of phase stability, relative density, Vickers hardness, fracture toughness, and microstructural examination. XRD examination on all the sintered samples exhibited pure forsterite, in which the generated peaks were found to be in a good agreement with JCPDS card no. 34‐0189. The densification of forsterite progressed to reach a maximum relative density of ~91% at 1500°C. This study also revealed that high‐strength forsterite ceramic can be synthesized via solid‐state reaction as forsterite attained favorable mechanical properties, having fracture toughness of 4.88 MPam1/2 and hardness of 7.11 GPa at 1400°C.

Low‐temperature molten salt synthesis of forsterite powders with controllable morphology

“…Thus, the sinterability is higher for the powders calcined at lower temperatures. For the powders calcined at 700°C, the relative density of the corresponding ceramics is as high as 98.9% which is much higher than that for the ceramics prepared from powders made by the conventional solid‐state reaction process …”

“…Figure (b) shows the XRD patterns of powders prepared at various temperatures by keeping the initial MgO/SiO 2 molar ratio at 2:1.3. It can be seen that single‐phase forsterite powders can be synthesized at 700°C, which is at least 400°C lower than the synthesis temperature required in conventional solid‐state reaction . During the MSS process, when the temperature exceeds the eutectic point of NaCl–KCl salt mixture, a liquid phase forms, which provides a liquid medium for the reaction of MgO and SiO 2.…”

“…In addition, the sinterability of forsterite prepared via conventional solid‐state reaction is always poor. Some investigations showed that the relative density is only about 91% for the forsterite sintered at 1500°C . Therefore, it is necessary to explore methods to synthesize forsterite powders with better sinterability at low calcining temperatures.…”

“…Increasing synthetic temperature often leads to the formation of enstatite (MgSiO 3 ) and periclase (MgO) instead of forsterite. In recent years, many researchers have dedicated to synthesizing forsterite powders by various techniques, including conventional solid-state reaction method, sol-gel techniques, polymer precursor method, and high energy ball milling et al [5][6][7][8][9][10][11][12][13] With the conventional solid-state reaction method, high calcining temperature (about 1100-1400°C) and long reaction time are usually required, 5,6 but the powders obtained are relatively large in particle size and irregular in morphology. The formation of MgSiO 3 and MgO is difficult to avoid during the process of forsterite synthesis.…”

The synthesis and properties of high-quality forsterite ceramics using desert drift sands to replace traditional raw materials

“…8) It was found that the enstatite and MgO interphases are very stable in forsterite ceramic even though a sufficient solid-state reaction between magnesium oxide (MgO) and talc [Mg 3 Si 4 (OH) 2 ] occurs in a temperature range of 12001500°C for 2 h. 9) A high-strength forsterite ceramic can be prepared using magnesium oxide (MgO, 97 wt %) and talc [Mg 3 Si 4 O 10 (OH) 2 , 99 wt %] when sintered at 12001500°C, a maximum density of 91% and the highest mechanical properties were obtained respectively when sintered at 1500 and 1400°C. 10) A forsterite was prepared utilizing 57.62 wt % serpentine and 42.38 wt % magnesium chloride water solution when sintered at 1300°C for 2 h, a small amount of SiO 2 , MgSiO 3 and MgO still companied.…”