characterizations of BNT ceramics synthesized by different techniques

Bismuth Sodium Titanate (Na0.5Bi0.5TiO3) was prepared by the conventional solid state route as well as the chemical route. Calcination of the sample prepared through the solid state route was done at 7500C for 8 hours and of the sample prepared through the chemical route at 6000C for 6 hours. XRD of the samples was done in which a single perovskite phase was confirmed. The samples were sintered using the conventional sintering method at 11500C for two hours and using the microwave sintering method at 11500C for 30 minutes with a heating rate of 400/min. SEM images of the samples were taken which showed dense microstructure and uniform grain size. Comparative study of dielectric properties of the samples was done. PE loop measurements were done to confirm the ferroelectric naturte of the sample

A Study on the Development of Refractories for Carbon Black Reactor

High alumina refractories are manufactured with high quality raw materials and normally possess good hot properties and can be lined in operation zones with critical conditions. However, certain application areas require very high specifications. An example is the carbon black reactor which operates beyond 2000°C. Here, conventional high alumina refractories do not give good performance and life. In the present study, an attempt has been made to study the development of refractories suitable for use in carbon black reactor. Zirconia is added to high alumina refractories to improve its thermo mechanical properties and spalling resistance. Transformation toughening due to tetragonal to monoclinic phase change in zirconia is utilized for the improvement of properties. Zirconia can be obtained from many sources. The raw materials selected have an important bearing on the properties of the final product. Three different sources of zirconia were used to optimize zirconia. This was followed by optimization of reactive alumina. Reactive alumina has very fine particle size which helps to achieve better sintering and reduces porosity. Hot properties were further improved by the addition of chrome oxide. Physical, thermal and thermo – mechanical properties, critical to operating conditions in the carbon black reactor, were studied and reported in this thesis

Multilayered and Chemiresistive Thin and Thick Film Gas Sensors for Air Quality Monitoring

Selective detection of gases such as nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), and various volatile organic components (VOCs) is necessary for air quality monitoring. Detection of hydrogen (H2) is equally important as it is a flammable gas and poses serious threat of explosion when exposed to oxygen gas. We have studied the sensing characteristics of these gases using thin film deposited by chemical solution deposition as well as relatively thicker films deposited by atmospheric plasma spray (APS) process. The chapter starts with the sensing mechanism of chemiresistive sensors followed by the definition of gas sensing parameters. Subsequently, we have demonstrated selective NO2 sensing characteristics of zinc oxide-graphene (ZnO-G) multilayered thin film followed by CO and H2 sensing characteristics of ZnO thin film and SnO2 thick film. Cross-sensitivity among CO and H2 gases has been addressed through the analysis of conductance transients with the determination of activation energy, Ea, and heat of adsorption, Q. The concepts of reversible and irreversible sensing have also been discussed in relation to CO and H2 gases. CO2 sensing characteristics of LaFe0.8Co0.2O3 (LFCO)-ZnO thin film have been elucidated. Interference from CO has been addressed with principal component analyses and the ascertaining of Ea and Q values. Additionally, the variation of response with temperature for each gas was simulated to determine distinct parameters for the individual gases. Further, VOC sensing characteristics of copper oxide (CuO) thin film and WO3-SnO2 thick film were investigated. Principal component analysis was performed to discriminate the gases in CuO thin film. The interaction of WO3-SnO2 thick film with various VOCs was found to obey the Freundlich adsorption isotherm based on which Ea and Q values were determined

Real-time, noise and drift resilient formaldehyde sensing at room temperature with aerogel filaments

Formaldehyde, a known human carcinogen, is a common indoor air pollutant. However, its real-time and selective recognition from interfering gases remains challenging, especially for low-power sensors suffering from noise and baseline drift. We report a fully 3D-printed quantum dot/graphene-based aerogel sensor for highly sensitive and real-time recognition of formaldehyde at room temperature. By optimising the morphology and doping of the printed structures, we achieve a record-high response of 15.23 percent for 1 parts-per-million formaldehyde and an ultralow detection limit of 8.02 parts-per-billion consuming only 130 uW power. Based on measured dynamic response snapshots, we also develop an intelligent computational algorithm for robust and accurate detection in real time despite simulated substantial noise and baseline drift, hitherto unachievable for room-temperature sensors. Our framework in combining materials engineering, structural design and computational algorithm to capture dynamic response offers unprecedented real-time identification capabilities of formaldehyde and other volatile organic compounds at room temperature.Comment: Main manuscript: 21 pages, 5 figure. Supplementary: 21 pages. 13 Figures, 2 tabl

Universal Murray's law for optimised fluid transport in synthetic structures

Materials following Murray's law are of significant interest due to their unique porous structure and optimal mass transfer ability. However, it is challenging to construct such biomimetic hierarchical channels with perfectly cylindrical pores in synthetic systems following the existing theory. Achieving superior mass transport capacity revealed by Murray's law in nanostructured materials has thus far remained out of reach. We propose a Universal Murray's law applicable to a wide range of hierarchical structures, shapes and generalised transfer processes. We experimentally demonstrate optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, we also show a significantly improved sensor response dynamic. Our work provides a solid framework for designing synthetic Murray materials with arbitrarily shaped channels for superior mass transfer capabilities, with future implications in catalysis, sensing and energy applications.Comment: 19 pages, 4 figure

Catalytic oxidation and selective sensing of carbon monoxide for sense and shoot device using ZnO–CuO hybrids

In the present work, we have demonstrated that ZnO–CuO based hetero-composites exhibit selective CO sensing with T 100 is in close proximity to T opt to yield simultaneous CO sensing together with its 100% catalytic oxidation for sense and shoot devices. When these heterocomposites are exposed to CO, reduction of Cu 2 + ions in CuO grains leads to a strong metal semiconductor interaction (SMSI) between Cu 2 + /Cu + /Cu 0 species (in CuO grains) and ZnO grains across the ZnO-CuO interface. The SMSI interaction promotes the generation of oxygen vacancies in neighboring ZnO lattice. Eventually activated oxygen (O ∗ ads ) and CO (CO ∗ ads ) are preferentially chemisorbed on zinc oxide (in its vacant oxygen sites) and CuO (on the surface of Cu 2 + /Cu + /Cu 0 ions) respectively. The activated oxygen reacts immediately with adsorbed CO to yield selective CO sensing together with 100% CO oxidation. For ZnO–CuO (1:1) composites, the measured T opt ( ∼175 °C) and T 100 ( ∼200 °C) temperatures are significantly lowered as compared to the respective temperatures measured for indium doped ZnO (T opt ∼300 °C, T 100 ∼550 °C) and CuO (T opt ∼200 °C,T 100 ∼300 °C) catalysts. Fine tuning of the mole fraction of ZnO and CuO are necessary for these hetero-composites to yield T 100 of catalytic activity close to T opt for maximum CO sensing

Real-time, noise and drift resilient formaldehyde sensing at room temperature with aerogel filaments

Formaldehyde, a known human carcinogen, is a common indoor air pollutant. However, its real-time and selective recognition from interfering gases remains challenging, especially for low-power sensors suffering from noise and baseline drift. We report a fully 3D-printed quantum dot/graphene-based aerogel sensor for highly sensitive and real-time recognition of formaldehyde at room temperature. By optimising the morphology and doping of printed structures, we achieve a record-high and stable response of 15.23 % for 1 part-per-million formaldehyde and an ultralow detection limit of 8.02 parts-per-billion consuming only ∼130 μW power. Based on measured dynamic response snapshots, we also develop intelligent computational algorithms for robust and accurate detection in real time despite simulated substantial noise and baseline drift, hitherto unachievable for room- temperature sensors. Our framework in combining materials engineering, structural design and computational algorithm to capture dynamic response offers unprecedented real-time identification capabilities of formaldehyde and other volatile organic compounds at room temperature.EP/W024284/1, EP/W023229/1, EP/T014601/1, EP/P024947/1, EP/R00661X/

Real-time, noise and drift resilient formaldehyde sensing at room temperature with aerogel filaments

Formaldehyde, a known human carcinogen, is a common indoor air pollutant. However, its real-time and selective recognition from interfering gases remains challenging, especially for low-power sensors suffering from noise and baseline drift. We report a fully 3D-printed quantum dot/graphene-based aerogel sensor for highly sensitive and real-time recognition of formaldehyde at room temperature. By optimizing the morphology and doping of printed structures, we achieve a record-high and stable response of 15.23% for 1 part per million formaldehyde and an ultralow detection limit of 8.02 parts per billion consuming only ∼130-microwatt power. On the basis of measured dynamic response snapshots, we also develop intelligent computational algorithms for robust and accurate detection in real time despite simulated substantial noise and baseline drift, hitherto unachievable for room temperature sensors. Our framework in combining materials engineering, structural design, and computational algorithm to capture dynamic response offers unprecedented real-time identification capabilities of formaldehyde and other volatile organic compounds at room temperature

Universal Murray’s law for optimised fluid transport in synthetic structures

Materials following Murray’s law are of significant interest due to their unique porous structure and optimal mass transfer ability. However, it is challenging to construct such biomimetic hierarchical channels with perfectly cylindrical pores in synthetic systems following the existing theory. Achieving superior mass transport capacity revealed by Murray’s law in nanostructured materials has thus far remained out of reach. We propose a Universal Murray’s law applicable to a wide range of hierarchical structures, shapes and generalised transfer processes. We experimentally demonstrate optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, we also show a significantly improved sensor response dynamic. In this work, we provide a solid framework for designing synthetic Murray materials with arbitrarily shaped channels for superior mass transfer capabilities, with future implications in catalysis, sensing and energy applications.EPSRC: EP/W024284/

Universal Murray’s law for optimised fluid transport in synthetic structures

Acknowledgements: This research was supported by EPSRC (EP/W024284/1), National Natural Science Foundation of China (22293020, 22293022), National Key R&D Program of China (2021YFE0115800), WBI-MOST (SUB/2021/IND493971/524448), and Royal Society Newton International Fellowship (Grant No. NIF\R1\211458). B. Z. would like to acknowledge CSC-Cambridge scholarship for financial support.AbstractMaterials following Murray’s law are of significant interest due to their unique porous structure and optimal mass transfer ability. However, it is challenging to construct such biomimetic hierarchical channels with perfectly cylindrical pores in synthetic systems following the existing theory. Achieving superior mass transport capacity revealed by Murray’s law in nanostructured materials has thus far remained out of reach. We propose a Universal Murray’s law applicable to a wide range of hierarchical structures, shapes and generalised transfer processes. We experimentally demonstrate optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, we also show a significantly improved sensor response dynamics. In this work, we provide a solid framework for designing synthetic Murray materials with arbitrarily shaped channels for superior mass transfer capabilities, with future implications in catalysis, sensing and energy applications.</jats:p