Structural and electrical properties of donor-doped NBT system synthesized by microwave-assisted solid-state reaction route

Journal of Materials Science: Materials in Electronics - A-site donor-doped NBT systems (Na0.5Bi0.5)1-xMxTi(1-x/4)O3 (M?=?La and Sm) were synthesized by microwave-assisted solid-state...     

Multi-Fidelity High-Throughput Optimization of Electrical Conductivity in P3HT-CNT Composites

Combining high-throughput experiments with machine learning accelerates materials and process optimization toward user-specified target properties. In this study, a rapid machine learning-driven automated flow mixing setup with a high-throughput drop-casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a > 10 ×  improvement relative to quantified, manual-controlled baseline. Regio-regular poly-3-hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state-of-the-art 1000 S cm⁻¹. The results are subsequently verified and explained using offline high-fidelity experiments. Graph-based model selection strategies with classical regression that optimize among multi-fidelity noisy input-output measurements are introduced. These strategies present a robust machine-learning driven high-throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites.     

Composition-Dependent Photoluminescence Properties and Anti-Counterfeiting Applications of A2AgX3 (A = Rb,Cs; X = Cl,Br, I)

Copper(I) halides are emerging as attractive alternatives to lead halide perovskites for optical and electronic applications. However, blue-emitting all-inorganic copper(I) halides suffer from poor stability and lack of tunability of their photoluminescence (PL) properties. Here, the preparation of silver(I) halides A₂AgX₃ (A = Rb, Cs; X = Cl, Br, I) through solid-state synthesis is reported. In contrast to the Cu(I) analogs, A₂AgX₃ are broad-band emitters sensitive to A and X site substitutions. First-principle calculations show that defect-bound excitons are responsible for the observed main PL peaks in Rb₂AgX₃ and that self-trapped excitons (STEs) contribute to a minor PL peak in Rb₂AgBr₃. This is in sharp contrast to Rb₂CuX₃, in which the PL is dominated by the emission by STEs. Moreover, the replacement of Cu(I) with Ag(I) in A₂AgX₃ significantly improves photostability and stability in the air under ambient conditions, which enables their consideration for practical applications. Thus, luminescent inks based on A₂AgX₃ are prepared and successfully used in anti-counterfeiting applications. The excellent light emission properties, significantly improved stability, simple preparation method, and tunable light emission properties demonstrated by A₂AgX₃ suggest that silver(I) halides may be attractive alternatives to toxic lead halide perovskites and unstable copper(I) halides for optical applications.     

Phase‐dependent radiation‐resistant behavior of BaTiO3: An in situ X‐ray diffraction study

The radiation‐resistant response of BaTiO₃ in the tetragonal and rhombohedral phases on exposure to 100 MeV Ag⁷⁺ ion irradiation was investigated by in situ X‐ray diffraction (XRD) at room temperature (300 K) and low temperature (25 K), respectively. This study revealed that the BaTiO₃ in rhombohedral phase retained crystallinity up to an ion fluence of 1×10¹⁴ ions/cm², whereas tetragonal phase amorphized at much lower fluence viz. 1×10¹³ ions/cm². The in situ XRD along with Raman spectroscopy studies revealed that BaTiO₃ in rhombohedral phase is more radiation resistant than that of tetragonal phase. The density functional theory (DFT) calculations confirmed higher bond strength of rhombohedral phase as compared to tetragonal phase, which supported the experimental result of higher radiation stability of rhombohedral phase. The theoretical predictions on high‐temperature phase will be of relevance to the nuclear waste applications.     

Optimization of processing conditions to reduce oil uptake and enhance physico-chemical properties of deep fried rice crackers

Physico-chemical properties of fried rice crackers were studied as a function of fish powder content, processing conditions, frying temperature and frying time. The results showed that addition of fish powder content at 5, 10 and 15 g/100 g reduced the oil uptake by approximately 10, 14 and 22 g/100 g (db), respectively in comparison to the control without fish powder. The deep fried rice crackers mixed with fish powder tended to be lower in hardness, lower in expansion ratio and higher in bulk density in comparison to the control sample. The color parameter, L^∗ of fried rice crackers decreased with increase in fish powder content. In contrast, a^∗ and b^∗ values increased with increase in fish powder content. The moisture content of deep fried rice crackers decreased with increase in frying temperature and frying time. The oil uptake in fried rice crackers increased with increase in frying time but decreased with increase in frying temperature. With increase in frying temperature and time, the texture of rice crackers became harder, the bulk density increased, and the expansion ratio decreased. The optimum conditions resulting in desirable physico-chemical properties and minimum oil uptake were rice crackers with fish powder content of 9 g/100 g, fried at a temperature of 220 °C for 60 s.     

Synthesis and characterization of lanthanide(III) complexes with a mesogenic Schiff-base,N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine

A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine, H₂ddsdp (abbreviated as H₂L³) that exhibits nematic mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H₂L³, upon condensation with hydrated lanthanide(III) nitrates, yields Ln^III complexes of the general composition [Ln₂(L³H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. Among the metal complexes, only that of Ho^III is found to be mesogenic with smectic-X and nematic phases. The IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L³H₂) to the Ln^III ions through two phenolate oxygens, rendering the overall geometry of the complexes to seven-coordinated polyhedron, possibly distorted mono-capped octahedron.     

Experimental and first-principles studies of BiVO4/BiV1-xMnxO4-y n-n+ homojunction for efficient charge carrier separation in sunlight induced water splitting

Though bismuth vanadate (BiVO₄) is extensively used as a photoactive material, its performance in harnessing solar energy is limited by ineffective separation of photo-excited charge carriers. We demonstrate here a concept of n-n⁺ homojunction of BiVO₄/BiV_1-xMn_xO_4-y, which improves its charge separation efficiency. Using first-principles theoretical calculations, we determine the effect of Mn substitution on oxygen vacancy formation energies and associated changes in the electronic structure of BiVO₄. Showing that Mn substitution pushes the Fermi level of BiVO₄ towards its conduction band, we predict that the associated enhanced bending of bands at the homojunction (BiVO₄/BiV_1-xMn_xO_4-y) facilitates efficient separation of charge carriers. With Mott-Schottky experiments, we verify the increased band bending at the n-n⁺ homojunction, and show that the maximum photocurrent density measured in a sample with n-n⁺ homojunction is ten times higher than that obtained of the pristine sample. Secondly, Mn substitution in BiVO₄ also reduces the oxygen vacancy formation energy, promoting higher concentration of O-vacancies, further enhancing the photoelectrochemical response.     

Comparison of Microwave and Conventional Frying on Quality Attributes and Fat Content of Potatoes

A comparative analysis of quality attributes (moisture, fat, color, and relaxation modulus) of French fries was performed between conventional and microwave frying. Experiments were performed in triplicate for both frying operations at temperatures of 177, 185, and 193 °C for frying times of 60, 90, and 120 s. The real‐time pressure and temperature profiles at above conditions indicated that during microwave frying, gage pressure had greater magnitudes that lasted longer, and the temperature increased to boiling point of water faster in comparison to conventional frying. Lower magnitude of negative pressure during microwave frying is expected to have caused lower fat content in fries obtained using this method (0.08 g/g solids less at 185 °C and 0.07 g/g solids less at 193 °C) than conventional frying. The lightness parameter (L^*) decreased to a lesser extent in microwave frying than in conventional frying. The stress relaxation function of the French fries were significantly different between the 2 frying operations. Consumer test confirmed that reduced fat uptake during microwave frying did not compromise with desirable quality attributes of French fries. X‐ray micro‐computed tomography scanning provided complementary understanding about differences in microstructural properties of fries made using microwave and conventional frying.