Silicate ceramics are of considerable promise as high frequency dielectrics in emerging millimetre wave applications including high bandwidth wireless communication and sensing. In this review, we show how high quality factors and low, thermally stable permittivities arise in ordered silicate structures. On the basis of a large number of existing studies, the dielectric performance of silicate ceramics is comprehensively summarised and presented, showing how microstructure and SiO4 tetrahedral connectivity affect polarizability and dielectric losses. We critically examine the appropriateness of silicate materials in future applications as effective millimetre wave dielectrics with low losses and tuneable permittivities. The development of new soft chemistry based processing routes for silicate dielectric ceramics is identified as being instrumental towards the reduction of processing temperatures, thus enabling silicate ceramics to be co-fired in the production of components functioning in the mm wave regime.

Controlling the composition, size, and morphology of transition-metal carbides and metals is important for product selectivity in industrial catalytic processes, such as in the Fischer–Tropsch synthesis (FTS). The formation of iron–cobalt carbide nanocatalysts can enhance selectivity in the FTS process if the iron to cobalt ratios are controlled. Unfortunately, this is difficult to achieve in nanocrystals due to ion migration, differences in formation rates, and the requirement of perfect critical nuclei to form prior to the growth of the nanocrystal in colloidal synthesis. In this manuscript, a mixed metal iron–cobalt Prussian blue analogue (PBA) mesocrystal is shown to act as a template for isolating pure phase iron–cobalt carbide and iron–cobalt alloy nanocrystals. The formation of the individual nanocrystals from the heterometallic mesocrystal occurs through sequential decomposition and recrystallization events. The steps in the interconversion are observed by in situ and ex situ analytical techniques allowing a mechanism for carbide and metal formation to be proposed. The synthetic route is scalable and likely to be extendable to a wider range of bimetallic materials using the diverse range of Prussian blue analogues (PBAs) reported in the literature.

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The adaption of the sol-gel autocombustion method to the Cu/ZrO2 system opens new pathways for the specific optimisation of the activity, long-term stability and CO2 selectivity of methanol steam reforming...

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Here we demonstrate that by applying exclusively Martian resources a processing route involving suspensions of mineral particles called slurries or slips can be established for manufacturing ceramics on Mars. We developed water-based slurries without the use of additives that had a 51 wt. % solid load resembling commercial porcelain slurries in respect to the particle size distribution and rheological properties. These slurries were used to slip cast discs, rings and vases that were sintered at temperatures between 1000 and 1130 °C using different sintering schedules, the latter were set-up according the results of hot-stage microscopic characterization. The microstructure, porosity and the mechanical properties were characterized by SEM, X-ray computer tomography and Weibull analysis. Our wet processing of minerals yields ceramics with complex shapes that show similar mechanical properties to porcelain and could serve as a technology for future Mars colonization. The best quality parts with completely vitrificated matrix supporting a few idiomorphic crystals are obtained at 1130 °C with 10 h dwell time with volume and linear shrinkage as much as ~62% and ~17% and a characteristic compressive strength of 51 MPa.

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