Nanostructured silicon production from quartzite ore by low-energy wet blending of the reagents, reduction in controlled atmosphere, and hydrometallurgy

High-purity porous nanostructured silicon particles were successfully produced from quartzite rock via the multi-step processing route including primary acid leaching of crashed quartzite feedstock, wet blending of quartzite and magnesium powder, reduction, and final multi-stage hydrometallurgical purification of the products. Laboratory-grade silica was also treated for comparison. The effect of silica purity, reactants’ molar ratios (Mg:SiO2), and hydrometallurgical refining on reaction products were investigated and discussed through the results of X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDS) and inductively coupled plasma-mass spectrometry (ICP-MS). The results indicated that the combination of primary acid treatment, combustion synthesis in controlled atmosphere, and final special acid leaching process is an efficient route for the production of porous nanostructured elemental silicon particles with a uniform structure that can be used in several applications in the energy sector with or without further processing. Keywords: Porous nanostructured silicon particles, Reduction by magnesium, Hydrometallurgical treatment, Quartzite rock

Fracture toughness of reactive bonded Co–Mn and Cu–Mn contact layers after long-term aging

Creating a tough bond for the electrical contact between metallic interconnects and ceramic solid oxide cells (SOC) in a stack is challenging due to restrictions on the assembly temperature. The reactive oxidation bonding in the formation of Co2MnO4 (CoMn) and Cu1.3Mn1.7O4 (CuMn) spinel oxides from metallic precursors could provide a potential solution for achieving tough and well-conducting contact layers. These contact layers are deposited from metallic precursors onto CoCe-coated AISI441 substrates to achieve high toughness even after aging for 3000 h at typical operating temperatures for SOCs. The interface fracture energy of CoMn and CuMn contact layers was measured for as-sintered and aged samples by using a modified four-point bending test. After the fracture test, X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy were used to determine phase evolution and possible reactions at the contact layer/interconnect interface. The results show that the interface fracture energy of sintered CoMn contact layer (6.1 J/m2) decreased to 2.9 J/m2 after aging at 850 ○C for 3000 h while the fracture energy for CuMn increased from 6.4 J/m2 to 19.7 J/m2

Fracture toughness of reactive bonded Co–Mn and Cu–Mn contact layers after long-term aging

Creating a tough bond for the electrical contact between metallic interconnects and ceramic solid oxide cells (SOC) in a stack is challenging due to restrictions on the assembly temperature. The reactive oxidation bonding in the formation of Co2MnO4 (CoMn) and Cu1.3Mn1.7O4 (CuMn) spinel oxides from metallic precursors could provide a potential solution for achieving tough and well-conducting contact layers. These contact layers are deposited from metallic precursors onto CoCe-coated AISI441 substrates to achieve high toughness even after aging for 3000 h at typical operating temperatures for SOCs. The interface fracture energy of CoMn and CuMn contact layers was measured for as-sintered and aged samples by using a modified four-point bending test. After the fracture test, X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy were used to determine phase evolution and possible reactions at the contact layer/interconnect interface. The results show that the interface fracture energy of sintered CoMn contact layer (6.1 J/m2) decreased to 2.9 J/m2 after aging at 850 ○C for 3000 h while the fracture energy for CuMn increased from 6.4 J/m2 to 19.7 J/m2.publishedVersio

Rapid Solid-State Gas Sensing Realized via Fast K⁺ Transport Kinetics in Earth Abundant Rock-Silicates

Here we report on the discovery of a novel fast potassium super stoichiometric silicate, with fully earth-abundant nominal chemical composition of K2+xMg1−x/2SiO4, which exhibits near superionic K+ conductivity, up to 5 × 10−5 S cm−1 at room temperature. Fast K+ conduction is attributed to a high Continuous Symmetry Measure value in K-polyhedrons, coupled with a low packing ratio of Corner-Sharing-framework. This is the first time that such a high conductivity is measured by a rock-silicate formed only by abundant metal ions. K2+xMg1−x/2SiO4 displays excellent stability under air and humidity, which renders it a very promising candidate for economical fabrication of electrochemical devices such as potentiometric gas sensors. We demonstrated this by fabricating a gas sensor for SO2 detection, as the first demonstration of type III potentiometric gas sensors using K+ conductors. At 500 °C and SO2 concentrations in the range of 0–10 ppm, the sensor exhibited high sensitivities (69–72 mV dec−1), robust signal output (220 mV for 2 ppm of SO2), fast response times (1–6 min), and excellent stability in ambient condition