β-Si3N4 Microcrystals Prepared by Carbothermal Reduction-Nitridation of Quartz

Abstract

Single phase β-Si3N4 with microcrystals was synthesized via carbothermal reduction-nitridation (CRN) of quartz and carbon coke powder as starting materials. The effects of reaction parameters, i.e., heating temperature, holding time, C/SiO2 ratio, Fe2O3 additive and β-Si3N4 seeds on the phase transformation and morphology of products were investigated and discussed. Rather than receiving a mixture of both α- and β- phases of Si3N4 in the products, we synthesized powders of β-Si3N4 single polymorph in this work. The mechanism for the CRN synthesis of β-Si3N4 from quartz and the formation mechanism of Fe3Si droplets were discussed. We also firstly reported the formation of Fe3Si Archimedean solids from a CRN process where Fe2O3 was introduced as additive. Comparing to the gear-like short columnar morphology observed in samples without β-Si3N4 seeding, the addition of β-Si3N4 seeds led to an elongated morphology of final products and much finer widths. In addition, the β-Si3N4 microcrystals exhibited a violet‒blue spectral emission range, which could be highly valuable for their future potential optoelectronic applications.

Effect of Zr on the solid sintering process of SiBCN ceramics: Diffusion couple method experiment and DFT calculation

“…With the development of the aerospace and defense industries, traditional silicon‐based ceramics have been proven insufficient in meeting the demand for high‐temperature structural materials 1–6 . As a novel structural material, SiBCN ceramics have recently gained considerable concern for their superior high‐temperature, oxidation, and creep resistance, in comparison to other silicon‐based ceramics (e.g., Si 3 N 4 ).…”

Molten-salt assisted synthesis and characterization of Mg2B2O5 and Al18B4O33 whiskers

“…Thanks to their excellent mechanical properties, wear resistance, low density, and thermal expansion coefficient, borate whiskers have attracted much attention in recent years, especially as mechanically strengthening materials in ceramics, metals and polymer materials [1][2][3]. In contrast to the high cost of the preparation process of SiC and Si 3 N 4 whiskers, inexpensive raw materials and relatively moderate reaction conditions make boratebased whiskers an economical proposition [4,5]. Among these, aluminum borate (Al 18 B 4 O 33 ) and magnesium borate (Mg 2 B 2 O 5 ) whiskers in particular are attracting increasing attention due to their demonstrated unique chemical and physical properties as well as wide potential applications.…”