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The aim of this study was to improve the mechanical properties of Al 2 O 3 ceramics by the addition of Y 2 O 3 -stabilized ZrO 2 whiskers (designated as Al 2 O 3 /YSZ W composite) through the flux method and hot-pressing technology. The effect of YSZ W content on their microstructure , phase composition and transformability, mechanical properties, and wear resistance was systematically investigated. The Al 2 O 3 /YSZ W composites containing 10 wt% YSZ W exhibited the best mechanical performance, including the highest content of YSZ W tetragonal phase and transformability as well as the largest values in their relative density (99.5%), hardness (1969 HV), fracture toughness (9.57 MPa m 1/2 ) and flexural strength (855 MPa). The strengthening and toughening of the Al 2 O 3 /YSZ W composites were attributed to the YSZ W tetragonal-monoclinic phase transformation as well as the whiskers reinforcing effect. Furthermore, the Al 2 O 3 /YSZ W composites also showed the highest friction and wearing properties.

Si3N4 ceramics with excellent mechanical properties and microstructure were fabricated by microwave sintering. The effects of sintering additives on the densification, phase transformation and grain growth of Si3N4 ceramics were investigated. The results showed that Y2O3 can promote the phase transformation, MgO can decrease the sintering temperature, Al2O3 can increase the Vickers hardness of the samples and the combination of Y2O3 and MgO was more effective in enhancing the densification and phase transformation in the microwave sintering. The samples with 5 wt%Y2O3, 5 wt%MgO and 2 wt%Al2O3 sintering additives had the optimum mechanical properties when sintered at 1700 ℃ for 10 min. Its relative density, fracture toughness and Vickers hardness were 98.52±0.13%, 6.44±0.02 MPa m1/2 and 14.92±0.20 GPa, respectively. Compared to other microwave sintered Si3N4, the hardness and fracture toughness were enhanced by 6.6–24.3% and 5.6–11%, respectively, while the sintering holding time was reduced by 33.3–83.3%.

Ediacaran phosphorites capture the dynamics of the ultimate biolimiting nutrient, phosphorus, during perhaps the most critical transition of Earth's climatic and ecological history. Concomitant with the Neoproterozoic Oxygenation Event was the deposition of the first extensive phosphorites across marine shelves, typically interpreted as a basinward shift in the locus of phosphogenesis facilitated by deep-ocean oxygenation. Petrographic and spectroscopic analyses of proximal phosphorites from the Ediacaran Doushantuo Formation near the Yangtze Gorges area of South China reveal the presence of interlaminated pristine, muddy, and granular phosphorites that were cemented by early diagenetic iron phosphate, an additional, previously undocumented seafloor P sink. Transmitted- and reflected-light microscopy, cathodoluminescence microscopy, and back-scattered electron scanning electron microscopy were used to reconstruct the paragenesis of phosphorites at the Wanjiagou section near Zhangcunping (Hubei Province) and demonstrate that pristine phosphorite precipitated authigenically as francolite via microbially-mediated phosphogenesis as evidenced by preserved microbial laminations along with filamentous and coccoidal microfossils. Subsequent tidal reworking of pristine hardgrounds and phosphatic mudstones produced minimally-coated intraclasts and peloidal phosphatic grains that were cemented by iron phosphate soon after deposition but before compaction. Raman spectroscopy, bulk-sample and micro-X-ray diffractometry indicate the iron phosphate cement is composed of phosphosiderite/strengite (Fe+3PO4•2H2O). The presence of phosphosiderite can be attributed to either syndepositional oxidation of phosphorites or thermal stabilization of vivianite (Fe2+3(PO4)2•8H2O). In both cases, the occurrence of phosphosiderite represents the first direct evidence for iron phosphate minerals as a P sink during the Ediacaran and suggests phosphogenesis may have partially proceeded in ferruginous porewaters in contrast to the redox-independent process of francolite precipitation. Integration of petrographic and geochemical techniques, such as those employed in this study, offers the ability to corroborate P speciation analyses and provides an independent determination of P phase partitioning. Ultimately, this approach is paramount in testing hypotheses that suggest ferrous iron phosphate minerals played a regulatory role in global Proterozoic oxygenation.

Naturally occurring porous minerals as adsorbents for the remediation of environmental pollution has been one of the hot topics in environmental science and material science. In this study, the adsorption of iodate (IO3−) on two nanosized tubular halloysite samples (HBHal and SCHal, from Hubei and Sichuan Province, China, respectively) were investigated for the first time. To evaluate the impact of nanopore of halloysite on the adsorption of IO3−, chemically similar platy kaolinite was used for comparative studies in the batch experiments. The adsorption of IO3− on HBHal reached equilibrium within 36 h, and the adsorption kinetics and isotherm fitted the pseudo-second-order and Langmuir equation well, respectively. Both HBHal and SCHal exhibited high adsorption capability to IO3−, with distribution coefficients (Kd's) of 131.6 ± 14.6 and 126.6 ± 3.1 mL/g, respectively, which were >30 times higher than that for kaolinite (4.2 ± 2.3 mL/g). The specific surface area normalized Kd values on halloysite samples were >13.5-fold higher than that on kaolinite. In addition, halloysite had high selectivity to IO3−, and the adsorption capacities on the two halloysite samples were slightly affected by the concurrent anions, such as SO42−, NO3−, or ClO3−. It was proposed that the curved octahedral sheet caused geometry match between three oxygen atoms in the iodate and three OH above the vacant site of the octahedral sheet. This work also gave insight into the potential application of halloysite on the adsorption of radioactive iodate in natural and engineering environments.

Al0.3CoCrFeNi high-entropy alloy (HEA) prepared by mechanical alloying was used as a metal binder for the Ti(C,N)-based cermets by hot-pressing sintering. Room-temperature microstructure and high-temperature oxidation resistance, mechanical and wear resistance properties of the Ti(C,N)-based cermets with HEA metal binder (cermets TA) were comprehensively investigated and compared with the Ti(C,N)-based cermets containing the conventional Ni–Co metal binder (cermets TN). Different from the Ni–Co binder, the HEA metal binder not only largely enhanced the hardness and fracture toughness of Ti(C,N)-based cermets at room temperature, but also retained notably higher hardness (Vickers hardness 1137 HV), fracture toughness (6.46 MPa m1/2) and flexural strength (761 MPa) at 1000 °C. The mechanism for such an excellent retention of mechanical properties at high-temperature by the cermets TA is attributed to the hindrance of their slip systems and the higher oxidation resistance of HEA metal binder. Furthermore, the hardened cermets TA exhibited better friction and wearing properties at high-temperature.