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Process for reducing the iron content in 356 secondary aluminum alloy is developed in the current study. The Fe-rich intermetallic compounds (or sludge) were removed by sedimentation of liquid aluminum through alloy addition. Effects of alloy additions were first surveyed by thermodynamic evaluation. The sedimentation temperature and time were designed according to the solidification curves of the secondary aluminum alloys. In this study, combinations of 0–2 wt% of manganese (Mn) and chromium (Cr) were added to the melts for isothermal sedimentation. Fe-rich sludges of Al(FeMn)Si, Al(FeCr)Si, and Al(FeMnCr)Si compounds were formed, and sedimented. Mn tends to increase the sludge particle size, while Cr addition has the effects of refining the precipitates and increasing aspect ratios of the precipitate morphology. Although chromium demonstrated higher iron removal capability than manganese, when more than 1 wt% Cr is added, the Al13Cr4Si4 phase forms without further removing Fe. When both Mn and Cr additions are excessive, Mn- and Cr-rich phases are formed at the center of the sludge phase. Therefore, excessive Mn and Cr cannot further increase iron removal rate. For optimum iron removal conditions, 1 wt% Mn- and 1 wt% Cr-added melts can remove 73.8% of Fe from the 356 secondary alloy and recover 77.3% secondary alloy by gravity separation method.

Combining low-dimensional layers of dissimilar metal oxide materials to form a heterojunction structure offers a potent strategy to improve the performance and stability of thin-film transistors (TFTs). Here, we study the impact of channel layer thicknesses on the operating characteristics of In2O3/ZnO heterojunction TFTs prepared via sputtering. The conduction band offset present at the In2O3/ZnO heterointerface affects the device's operating characteristics, as is the thickness of the individual oxide layers. The latter is investigated using a variety of experimental and computational modeling techniques. An average field-effect mobility ( μFE) of >50 cm2 V−1 s−1, accompanied by a low threshold voltage and a high on/off ratio (∼108), is achieved using an optimal channel configuration. The high μFE in these TFTs is found to correlate with the presence of a quasi-two-dimensional electron gas at the In2O3/ZnO interface. This work provides important insight into the operating principles of heterojunction metal oxide TFTs, which can aid further developments.

Solid‐state transistor sensors that can detect biomolecules in real time are highly attractive for emerging bioanalytical applications. However, combining upscalable manufacturing with the required performance remains challenging. Here, an alternative biosensor transistor concept is developed, which relies on a solution‐processed In2O3/ZnO semiconducting heterojunction featuring a geometrically engineered tri‐channel architecture for the rapid, real‐time detection of important biomolecules. The sensor combines a high electron mobility channel, attributed to the electronic properties of the In2O3/ZnO heterointerface, in close proximity to a sensing surface featuring tethered analyte receptors. The unusual tri‐channel design enables strong coupling between the buried electron channel and electrostatic perturbations occurring during receptor–analyte interactions allowing for robust, real‐time detection of biomolecules down to attomolar (am) concentrations. The experimental findings are corroborated by extensive device simulations, highlighting the unique advantages of the heterojunction tri‐channel design. By functionalizing the surface of the geometrically engineered channel with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) antibody receptors, real‐time detection of the SARS‐CoV‐2 spike S1 protein down to am concentrations is demonstrated in under 2 min in physiological relevant conditions., A solution‐processed metal oxide heterojunction channel with a geometrically engineered tri‐channel architecture several millimeters in size, is developed and used as a generic platform for robust, selective, and ultrasensitive detection of various biomolecules. As a proof‐of‐concept, selective sensing of the SARS‐CoV‐2 spike protein down to attomolar concentrations in under 2 min is demonstrated.

In the original version of this article, Annadurai Dhinakar’s first and last names were transposed. The original article has been corrected.