Effects of CaCO₃ additive on properties and microstructure of corundum‐ And mullite‐based ceramic proppants

Abstract

Corundum-mullite ceramic proppants have been successfully synthesized using raw materials of natural bauxite and solid waste coal gangue, CaCO 3 , as additive. The influences of calcium carbonate additive on phase composition, microstructure, and mechanical performances were systematically investigated. The results indicate that the addition of CaCO 3 promotes the formation of liquid phase at lower temperature during sintering process, which is beneficial to the densification of the samples and the reduction of sintering temperature. Moreover, the mullite grains become finer and finer with the content of CaCO 3 additive increasing, which improves the toughness and strength of the samples via a grain refinement strengthening mechanism. The ceramic proppants exhibit optimal performances with additive of 5 wt.% at 1350°C, and the breakage ratio under 52 MPa closed pressure is the lowest. Additionally, the sintering temperature is dropped by 150°C compared with the samples without adding calcium carbonate.

Influence of zirconia on the sintering behaviour and mechanical properties of reaction-sintered mullite-based composite ceramics

“…The decomposition of kaolin to form mullite also yields cristobalite (Sainz et al , 2000; Sahnoune et al , 2013; Aswad et al , 2021), which transforms into an amorphous phase at high temperatures and impacts the mechanical properties of mullite composite ceramics negatively. To improve the mechanical strength and fracture resistance of mullite composite ceramics, some recent papers have focused on the modification of mullite through the introduction of secondary phases (Ji et al , 2013; Mahmood et al , 2017; Qian et al , 2020; Qin et al , 2020; Sarker et al , 2022). Some agents, such as Al 2 O 3 (Wu et al , 2016), ZrO 2 (Sistani et al , 2019) and SiC (Jing et al , 2014), have been employed as secondary phases to reinforce mullite ceramics.…”

Effects of sintering temperature on microstructure and properties of low‐grade bauxite‐based ceramic proppant

“…Due to the low content of Al 2 O 3 in the raw material, mullite is the main sintering product, only a small amount of corundum is distributed in the proppant, so it is difficult to observe the micromorphology of corundum. The corundum crystal develops completely under the action of sintering driving force when the temperature rises to 1340℃, and the crystal billet gradually develops into flat and layered corundum 41 . The flat corundum and rod‐shaped mullite are interlaced and woven to form a three‐dimensional network structure, which also corresponds to the raised platform structure in Figure 6C.…”

Mechanical properties of in situ synthesized mullite‐based composite ceramics with three‐dimensional network structure

“…Mullite possesses outstanding properties, such as high melting point, low thermal expansion coefficient, high‐temperature resistance, strong creep, and thermal shock resistance 12 . As a result, it is widely used to fabricate oxide/oxide ceramic composites 13–16 . Moreover, using cheap coal gangue instead of pure raw materials in the synthesis of mullite allows one to solve the problems associated with environmental pollution, reduce the costs, and realize its value‐added utilization.…”

“…obtained mullite whisker ceramic microfiltration membranes with a high degree of open porosity and high mechanical strength with coal gangue. Qin et al 16 . developed mullite‐based ceramic proppants with ultra‐low density and high strength.…”

“…12 As a result, it is widely used to fabricate oxide/oxide ceramic composites. [13][14][15][16] Moreover, using cheap coal gangue instead of pure raw materials in the synthesis of mullite allows one to solve the problems associated with environmental pollution, reduce the costs, and realize its value-added utilization. In this respect, resource utilization of coal gangue has attracted increased attention over the past years.…”