ABSTRACT Alkali vapor corrosion is critical for refractories used in the kilns and furnaces of diverse high‐temperature processing and manufacturing sectors such as gasifiers, cement production, and glass making. Gahnite (ZnAl 2 O 4 ) is being investigated as a potential chrome‐free refractory because of its similarity with the structure and properties of magnesium aluminate (MgAl 2 O 4 ) spinel. The alkali vapor corrosion of ZnAl 2 O 4 , MgAl 2 O 4 , and Mg 0.5 Zn 0.5 Al 2 O 4 was studied, according to ASTM C987‐10, at 1371°C for 24 h using sodium carbonate (Na 2 CO 3 ). The surface and the polished cross‐sections of the corroded ZnAl 2 O 4 , MgAl 2 O 4 , and Mg 0.5 Zn 0.5 Al 2 O 4 specimens were analyzed using x‐ray diffraction (XRD), microscopy, and energy‐dispersive spectroscopy (EDS) techniques. MgO in MgAl 2 O 4 , ZnO in ZnAl 2 O 4 , Mg 0.77 Zn 0.23 O, and NaAlO 2 were detected as the corrosion products for these specimens. The extent of corrosion substantially varied among the specimens despite the similarity in the corrosion products. The corrosion resistance increased in the following order: Mg 0.5 Zn 0.5 Al 2 O 4 > MgAl 2 O 4 > ZnAl 2 O 4 . The formation of a dense MgO and Mg 0.77 Zn 0.23 O layer for MgAl 2 O 4 and Mg 0.5 Zn 0.5 Al 2 O 4 , respectively, contributed to their superior resistance to alkali vapor corrosion. The underlying corrosion mechanisms are discussed based on experimental observations supported by thermodynamic analysis. Additionally, the results suggest that a partial Zn 2+ substitution for Mg 2+ in MgAl 2 O 4 can enhance the resistance to alkali vapor corrosion.
ABSTRACT To improve the performance and lifetime of refractories used at the tuyere zone in copper anode fire refining (CAFR) furnace, Al 2 O 3 ‒Cr 2 O 3 castables bonded with reactive magnesia (R‒C), hydratable alumina (H‒C), and calcium aluminate cement (C‒C) were comparatively investigated in terms of resistance to corrosion and infiltration by CAFR slag. The thermal shock resistance of the prepared castables was also studied. Results indicate that the R‒C castable formed Mg(Al,Cr) 2 O 4 spinel in situ at elevated temperatures. The Mg(Al,Cr) 2 O 4 spinel could incorporate Cu 2+ and Fe 2+ /Fe 3+ from the CAFR slag to form (Mg,Cu,Fe)(Al,Cr,Fe) 2 O 4 spinel, which blocked pores in the castable matrix and thus hindered further slag infiltration. Consequently, R‒C castables exhibited superior resistance to slag corrosion and infiltration compared with H‒C and C‒C castables. In addition, R‒C castables showed the highest residual strength ratio after thermal shock testing.
ABSTRACT To investigate the strain‐rate‐dependent compressive behavior of TiB 2 –B 4 C composite ceramics, quasi‐static tests and dynamic compression experiments were conducted using a universal testing machine and a split Hopkinson pressure bar system. Scanning electron microscopy‐based fractography was employed to examine failure mechanisms, and a modified microcrack‐driven model was used to interpret the strain‐rate effect. The results show that the compressive strength increases from approximately 4.73 ± 0.16 GPa at 10 − 3 s − 1 to 6.12 ± 0.18 GPa at an average strain rate of 3093 s −1 , demonstrating a pronounced strain‐rate strengthening effect. Microstructural analysis reveals a transition in fracture mode: intergranular fracture along TiB 2 /B 4 C boundaries dominates at low strain rates, whereas transgranular fracture of TiB 2 grains is prevalent at higher strain rates. The modified model yields a strain‐rate exponent of ∼1, indicating a narrower and more abrupt intermediate strain‐rate regime compared with monolithic ceramics. These findings suggest that the activation of smaller defects and two‐phase microstructural interactions are key factors controlling dynamic strength. The study provides fundamental insight into the mechanisms governing strain‐rate sensitivity in TiB 2 –B 4 C composites and offers guidance for optimizing their microstructure for high‐rate and protective structural applications.
ABSTRACT Cesium lead iodide (CsPbI 3 ), an all‐inorganic perovskite, has shown great promise for next‐generation energy conversion technologies because of its excellent optoelectronic characteristics, thermal stability, and adjustable band structure. With a direct bandgap of around 1.73 eV in its cubic α‐phase, CsPbI 3 is well‐suited for effective perovskite solar conversions (PSC's) with power conversion efficiencies higher than 20% when paired with surface passivation and proper film engineering. Applications in single‐junction and tandem photovoltaic (PV) designs have been made easier by the addition of perovskite quantum dots (QDs), which have better photostability, charge transport, and quantum confinement effects, owing to its low thermal conductivity and adjustable electrical characteristics, CsPbI 3 has shown promise in thermoelectric (TE) applications in addition to PVs, providing a route for hybrid energy harvesting. However, CsPbI 3 ’s phase instability, specifically, the spontaneous conversion of the black cubic α‐phase to the yellow non‐perovskite δ‐phase at ambient conditions, remains a barrier to commercialization. Its structural and environmental stability has been greatly enhanced by recent techniques, such as strain modulation, ligand engineering, doping, and nanostructuring. This review examines the most recent achievements in CsPbI 3 research, spanning its performance in PVs, QD‐based systems, TEs, and attempts to improve its long‐term stability. The report outlines future research routes to address current problems and maximize the potential of CsPbI 3 in multifunctional energy systems.
ABSTRACT Vat photopolymerization (VPP) has recently been applied to fabricate silicon nitride (Si 3 N 4 ) ceramics. To overcome limitations in Si 3 N 4 slurry curing performance, a multi‐functional modification strategy utilizing the metal‐organic framework MIL‐53(Al) was proposed. The introduction of MIL‐53(Al) simultaneously affects slurry photocuring performance and ceramic microstructural regulation. MIL‐53(Al) serves as a fluorescent active filler acting as an in situ photon source under ultraviolet irradiation, thereby enhancing the curing depth by an average of 17.5 µm. During the debinding process, the decomposition of MIL‐53(Al) leaves a pore structure and aluminum oxide that can assist sintering, facilitating phase transformation and forming a well‐interlocked β‐Si 3 N 4 microstructure. The sintered Si 3 N 4 ceramic exhibited a flexural strength of 269.2 ± 12.6 MPa, and a fracture toughness of 3.54 ± 0.21 MPa·m 1/2 at a porosity of 23.9%. This study demonstrates the multi‐functional role of MOF‐based additives for both enhancing slurry printability and tailoring ceramic microstructure in fabrication of porous Si 3 N 4 ceramics via VPP.
