Chee Lip Gan

Hierarchically porous silicon carbide (SiC) is an important catalyst support widely used in various gas and liquid catalytic processes. Conventional approaches to fabricate such SiC have limited design flexibility and separated catalyst‐loading step is necessitated. Herein, a one‐step, direct vat‐photopolymerization 3D printing of hierarchically porous SiC loaded with Co/Ni based catalyst is demonstrated with Pickering emulsion as feedstock for the first time. Compared with normal ceramic slurries, Pickering emulsion dramatically increases the cure depth (by 50%) and emulsion stability, which allow continuous printing of complex SiC structures with uniform pore morphology. The resultant hierarchical porous SiC offered ≈40% better mechanical strength as compared with non‐hierarchical counterpart. By dissolving metal salts into aqueous phase in Pickering emulsions, complex architected structures with Co or Ni/Co in situ loaded in SiC matrix are printed. The metal salts are then thermally converted into oxides or silicates as catalysts anchored on SiC, exhibiting excellent catalytic activity and reusability. The emulsion templating strategy holds great facility to load various highly attractive materials such as high entropy oxides or functional fillers whilst reaping the benefits of vat photopolymerization for a myriad of applications in catalysis, batteries, and structural supports.

UV-based vat photopolymerisation (VP) of silicon carbide (SiC) ceramics has been challenging due to strong UV absorbance and high refractive index of SiC. Yet, strategies such as particle modification or use of coarser particles have led to low sample densities and/or impurities that diminish the final properties of printed SiC ceramics. Herein, a novel vat photopolymerization driven by near-infrared radiation (NIR) light to enable direct 3D printing of SiC ceramics using unmodified fine SiC particles was demonstrated. A type II photopolymerization resin system was first identified and optimized to allow 50-60 wt% SiC particles being loaded and printed with NIR light. The use of NIR light offered penetration depths of up to 4 times and cure depths up to 2 times higher than that of UV based photocuring for a slurry containing 50 wt% SiC particles, further along with much better printing fidelities, where deviation from designed dimensions is only ±7% (vs. 165.5% for UV light). The NIR-based printed SiC ceramics possessed excellent mechanical properties, with flexural strengths reaching 290 ± 20 MPa at a relative density of 86.29%, significantly higher than that of many other VP printed SiC ceramics (~100 – 220 MPa) at similar density. These properties were achieved without any additional particle modification or post-filtration steps, allowing the VP of SiC to be as practical as the VP of common oxide ceramics such as alumina and zirconia.

Small-scale shape memory ceramics exhibit superior shape memory or superelasticity properties, while their integration into a matrix material and the subsequent attainment of their reversible tetragonal-monoclinic phase transformations remains a challenge. Here, cerium-doped zirconia (CZ) reinforced aluminum (Al) matrix composite is fabricated, and both macroscopic and microscopic mechanical tests reveal more than doubled compressive strength and energy absorbance of the composites as compared with pure Al. Full austenitization in the CZ single-crystal clusters is achieved when they are constrained by the Al matrix, and reversible martensitic transformation triggered by thermal or stress stimuli is observed in the composite micro-pillars without causing fracture in the composite. These results are interpreted by the strong geometric confinement offered by the Al matrix, the robust CZ/Al interface and the local three-dimensional particle network/force-chain configuration that effectively transfer mechanical loads, and the decent flowability of the matrix that accommodates the volume change during phase transformation.

Floating gate-based flash memory is a widely used storage medium for sensitive data that may be relevant to forensic investigations. For various data extraction techniques, the accuracy of the recovered data is critical to ensuring the integrity of information as forensic evidence. In cases where the devices are physically or digitally damaged, invasive data extraction techniques serve as a last resort, and can directly extract binary from individual memory cells. Here we introduce a new invasive data extraction technique called selective chemical engraving. This electrochemical-based approach could systematically imprint the data of ‘0’ and ‘1’ as cavities on memory surfaces, which can subsequently be imaged with an optical microscope and SEM. This technique is capable of extracting data stored in embedded flash memory in microcontrollers of 40 nm technology node with a high accuracy of 99.66%. The error correction code (ECC) stored in the flash memory was also extracted together with the data. By analysing the extracted ECC, we were able to accurately derive the error correction algorithm of single error correction-double error detection (SEC-DED). The reconstructed SEC-DED code was then used to correct all 0.34% of errors. The high data retrieval accuracy (99.66%) together with the error correction capability led to a 100% accuracy of recovered data. This selective chemical engraving approach offers a comprehensive solution for the lowest-level data retrieval and correction from 40 nm technology flash memory, providing a new avenue for forensic data extraction.