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Ceramic proppants with excellent performance were successfully prepared by second grade bauxite. The phase structure and the microstructure were investigated via X‐Ray diffraction and scanning electron microscopy. The results suggested that bulk density and apparent density constantly increased, while the breakage ratio gradually decreased with the increasing in sintering temperature. When the sintering temperature reached to 1500°C, the breakage ratio obtained lowest value of 3.6% under 52 MPa closed pressure, which satisfied the requirement of Chinese Petroleum and Gas Industry standard. Furthermore, the mode of fracture for ceramic proppants was transformed from intergranular fracture into transgranular fracture and open pores had larger influence than closed pores for breakage ratio of ceramic proppants. [ABSTRACT FROM AUTHOR]

Ceramics with aluminum borate whiskers (ABWs) were prepared from H3BO3 and Al2O3 reagent, with and without 6 wt% MnO2 used as an addition. The microstructures, phase composition, and crystal structure of the ceramics were analyzed via scanning electron microscopy, energy dispersive spectroscopy, and X‐ray diffraction, respectively. The results show that MnO2 is an effective addition for enhancing the flexural strength of ceramics. The MnO2 could lead to the distortion of lattice, and improve the mechanical strength via a solid solution strengthening mechanism. Moreover, the content of H3BO3 and the sintering temperature were also key factors in the manufacture of optimal ceramics. The ceramic made from 6 wt% MnO2 addition, 25 wt% H3BO3, and sintered at 1200°C, showed the highest flexural strength of 88.5 (±1.9) MPa, and had a bulk density of 1.64 g/cm3 and porosity of 44.2%. [ABSTRACT FROM AUTHOR]

To develop a novel utilization avenue for fly ash (FA), the Co‐loaded FA (CoFA) was constructed utilizing FA as raw material to acquire the enhanced microwave absorption (MA) performance. In this study, the CoFA composites were fabricated by a two‐step method, including the construction of FA‐based ceramic matrix and a subsequent loading of magnetic components. The results of XRD, SEM, and elemental mapping images revealed that Co particles generated from the carbothermal reduction were well dispersed over the interior and surface of matrix. Compared with pure FA, the as‐prepared CoFA composites demonstrated the impressive MA performances, which were attributed to the good impedance matching, conduction loss, and interfacial polarization effect between the matrix and Co. When the annealing temperature kept at 700°C, the minimum reflection loss (RLmin) of as‐prepared CoFA700 reached up to −40.5 dB and the broad absorption band was measured to be 4.7 GHz with a thickness of 2.0 mm, which was superior to pure FA. Our strategy might provide a new direction to the fabrication of high‐efficient MA materials derived from FA. [ABSTRACT FROM AUTHOR]

Corundum‐mullite ceramic proppants have been successfully synthesized using raw materials of natural bauxite and solid waste coal gangue, CaCO3, 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 CaCO3 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 CaCO3 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. [ABSTRACT FROM AUTHOR]