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- 2018
- Solar Photovoltaic (SPV)
- Fuzzy Logic Control (FLC)
- MATLAB/Simulink
- Simulation
- Variable Step Size Incremental Conductance (VSS InC)
- Maximum Power Point Tracking (MPPT)
- Electrical Engineering and Automation
- Cochin University College of Engineering
- T.K.M College of Engineering
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Effect of build geometry and orientation on microstructure and properties of additively manufactured 316L stainless steel by laser metal deposition
摘要： The effect of build geometry and orientation on the microstructure and mechanical properties of additively manufactured AISI 316L stainless steel was studied. For this an integrated laser metal deposition system was used to build two test blocks, Block 1 and Block 2, such that Block 1 had its longest dimension parallel to the build direction while Block 2 had its longest dimension perpendicular to the build direction. Samples with different orientations with respect to the build direction were extracted from the two blocks and characterized in detail. Block 1 was found to have a coarser defect-free microstructure, while Block 2 had a finer microstructure with extensive inter-track/layer defects. The yield strengths and tensile strengths of Block 2 samples were higher than Block 1 samples, but their strain hardening capacities and ductility values were lower. These differences in microstructure and mechanical properties were shown to be an outcome of the different build rates and consequent thermal histories of the two blocks. In order to explain the variation of yield strength with sample orientation, an alternate measure for grain size called “effective grain size” was introduced, which revealed the effect of grain orientation on the mean free path for dislocation motion and hence yield/flow stress. Variation of yield strength with the effective grain size was found to follow Hall-Petch behaviour.
关键词： Anisotropy,Additive Manufacturing,Grain Size,Tensile Behaviour,Orientation
更新于2025-11-28 14:24:20
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Grain size evolution under different cooling rate in laser additive manufacturing of superalloy
摘要： The processing parameters in laser additive manufacturing have a crucial impact on solidification microstructure especially grain size, thus influencing the properties of the final products. In this paper, experiments were conducted to investigate the effects of processing parameters including scanning speed, laser power and powder feeding rate on grain size of the solidified track during laser metal deposition. A three-dimensional model considering heat transfer, phase change and Marangoni convection flow had also been developed to simulate the solidification parameters especially cooling rate (G × R) to illustrate the underlying mechanisms. The experimental and simulated results indicated that cooling rate increased and grain size decreased from 8.7 μm to 4.7 μm with the increase of scanning speed from 2 mm/s to 10 mm/s. Contrarily, cooling rate decreased and grain size increased with the increase of laser power and powder feeding rate. The numerical and experimental results provide the additive manufacturing process with the potential of microstructure control and performance optimization.
关键词： Grain size,Laser additive manufacturing,Superalloy,Solidification,Cooling rate
更新于2025-11-21 11:18:25
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Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics
摘要： In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.
关键词： Dielectric properties,Grain size,X-ray diffraction,Optical properties,Sintering
更新于2025-11-21 11:18:25
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Rapid synthesis of AlON powders by low temperature solid-state reaction
摘要： High synthesis temperatures and long soaking times are generally required to fabricate AlON powders, which can cause coarsening and aggregation of the powder. Solid-state reaction methods form AlON powders by a direct reaction of Al2O3 and AlN, enabling rapid synthesis of AlON powder at low temperatures. In this work, single phase AlON powders were fabricated by a solid-state reaction method using Al2O3 and AlN powders as raw materials. To lower the synthesis temperature and shorten the soaking time, the raw materials particle sizes and the homogeneity of the Al2O3/AlN mixture were investigated. The effects of AlN content, synthesis temperature, and soaking time on the synthesis of AlON powders were examined. When the AlN content was 27 mol %, single phase AlON powders were synthesized by calcining Al2O3/AlN mixture at 1680 °C for 20 min. After ball-milling at 250 rpm for 24 h, the synthesized AlON powder was ground into a single phase fine AlON powder with an average particle diameter of 320 nm, a narrow size distribution, and good dispersibility. Transparent AlON ceramics with dimensions of Φ100 mm × 1 mm were fabricated by pressureless sintering the produced fine AlON powder.
关键词： B.Grain size,Aluminum oxynitride,A. Powders: solid-state reaction
更新于2025-11-19 16:56:35
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Distinguishing the effects of altered morphology and size on visible-light-induced water oxidation activity and photoelectrochemical performance of BaTaO2N crystal structures
摘要： Factors, including crystallinity, morphology, size, preferential orientation, growth, composition, porosity, surface area, etc., can directly influence the optical, charge-separation, charge-transfer and water oxidation and reduction properties of particle-based photocatalysts. Therefore, these factors must be considered when designing high-performance particle-based photocatalysts for solar water splitting. Here, a flux growth method was applied to alter the morphology and size of the Ba5Ta4O15 precursor oxide crystals using BaCl2, KCl, RbCl, CsCl, KCl+BaCl2 and K2SO4 at different solute concentrations, and the impact of nitridation with and without KCl flux was studied. Specifically, the effects of altered morphology and size on the visible-light-induced water oxidation activity and photoelectrochemical performance of the BaTaO2N crystal structures were investigated. Upon nitridation, the samples became porous due to the lattice shrinkage caused by the replacement of 3 O2? with 2 N3? in the anionic network. The BaTaO2N crystal structures obtained by nitridation without KCl flux show higher surface areas than do their counterparts prepared by nitridation with KCl flux because of the formation of porous networks. All samples exhibited a high anodic photocurrent upon nitridation without KCl flux compared with that of the samples obtained by nitridation with KCl flux. The findings demonstrate that it is important to specifically engineer photocatalytic crystals to reach their maximum potential in solar water splitting.
关键词： Water splitting,Visible light,Flux growth,Crystal size,Morphology,BaTaO2N
更新于2025-11-19 16:51:07
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Extraction of High-Quality Quantum Dot Photocatalysts via Combination of Size Selection and Electrochemiluminescence
摘要： Quantum dots (QDs) represent one of the most promising photocatalytic systems for solar hydrogen production. Tremendous works have been devoted to the design of QDs photocatalysts, but their further development is limited by the unwanted mix of high- and low-quality QDs with different activities. With multinary Ag-In-Zn-S (AIZS) QDs as an example, here, we present a simple method for the extraction and screening of efficient photocatalysts by combination of gradient centrifugation and electrochemiluminescence (ECL). With controllable introduction of poor solvent, the crude QDs were separated into five individual samples by gradient centrifugation, from which ECL tests were performed to get the surface state information for photocatalyst screening. By the combination of size-selective centrifugation and ECL screening, we were able to get the high-activity component (AIZS-#4), which achieved 1.68 mmol·g?1 h?1, 6 times higher than that of the initial AIZS QDs. This work provides an alternative useful pathway for obtaining high-quality QD photocatalysts, beyond pursuing of perfect synthetic conditions.
关键词： size selection,electrochemiluminescence,quantum dots,photocatalysis,I-III-VI
更新于2025-11-14 15:32:45
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The influence of particle size on the intensity and reproducibility of Raman spectra of compacted samples
摘要： Given the growing interest in the application of Raman spectroscopy for quantitative purposes in solid pharmaceutical preparations, a revision of the effect of particle size on Raman spectra of compacted samples is presented. For this purpose, a set of tablets of potassium hydrogen phthalate (KHP) of different particle size were prepared. KHP was used because of its purity and stability, which allow to consider that samples will not be altered during measurements; but also because of its chemical structure (aromatic ring and carboxylic groups), that are present in many active pharmaceutical ingredients (API). The latter makes possible to consider KHP as a model pseudo-API. As KHP tablets only contain a pure compound, the mapping strategy that was considered for measuring our samples will not be affected by subsampling issues. The spectra variance can be attributed to the intrinsically reproducibility in recording the spectra (which mainly depends on the instrument set-up) and the site-to-site differences in elastic scattering properties. Two different instrumental optics have been studied: a macro-Raman system and a Raman microscope (500 μm and 50 μm laser spot size, respectively). The effect of the spectra preprocessing is also evaluated. The overall results demonstrate raw Raman intensity increases with particle size up to a value that depends on tablet width and that the applied spectral preprocessing (baseline correction and a unit vector normalization), reduces the differences in Raman intensities due to the particle size, but does not completely eliminate it for the lower particle sizes (< 20 μm). For tablets containing particles with predefined sizes, it corrects the mapping site-to-site differences in elastic scattering.
关键词： Raman spectroscopy,Peak intensity,Reproducibility of a raman spectrum,Particle size
更新于2025-11-14 15:16:37
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Design and characterization of the double-layered defected ground structure transmission line with less radiation loss
摘要： A double-layered DGS transmission line is proposed with a smaller DGS size and less radiation loss. Changing the air boundary to a dielectric boundary reduces the effective electric length at the DGS aperture area. An equivalent circuit model is introduced to analyze the DGS transmission line and the resonator circuit designs. Due to the increase in the effective dielectric constant, the proposed structure can be realized with less sensitivity to metallic environments. From the experimental results, the proposed double-layered DGS can achieve a reduction of 90.1% in size and insensitivity at up to 5 mm of separation from the DGS aperture to the metallic plate.
关键词： equivalent circuit models,effective dielectric constants,radiation loss,size reduction,defected ground structures
更新于2025-09-23 15:23:52
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Photo-Optical <i>In-Situ</i> Measurement of Drop Size Distributions: Applications in Research and Industry
摘要： The exact knowledge of Drop Size Distributions (DSD) plays a major role in various fields of applications to control and optimise processes as well as reduce waste. In the microbial production of advanced biofuels, oil droplets are produced under turbulent conditions in an aqueous medium containing many surface active components, which might hinder the recovery of the product. Knowledge of DSD is thus essential for process optimisation. This study demonstrates the capability of a photo-optical measurement method for DSD measurement in fermentation broth and in plate separators aimed at cost reduction in the microbial production of advanced biofuels. Measurements were made with model mixtures in a bioreactor, and at the inlet and outlet of a plate separator. In the bioreactor, the method was effective in detecting a broad range of droplet sizes and in differentiating other disperse components (e.g. microbial cells and gas bubbles). In the plate separator, the method was effective in determining the influence of the varied parameters on the separation efficiency.
关键词： biofuels,in-situ measurement,fermentation broth,Drop Size Distributions,plate separator,photo-optical measurement
更新于2025-09-23 15:23:52
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Electron surface scattering and quantum finite-size effect on dielectric and optical properties of thin gold films
摘要： With the size of metal nanostructures entering into the nanoscale region, electron surface scattering and quantum finite-size effect gradually dominate the physical properties of surface plasmon resonances. In this context, we investigate both the quantum corrected dielectric functions and the absorption spectra of thin gold films for different thickness by excluding and including electron surface scattering. Our results show that when don't taking into account electron surface scattering, the multiple peaks appear for both the quantum-corrected dielectric functions and the absorption spectra of thin gold films, which features the discretization of electronic states in small quantum-sized system. When including electron surface scattering, however, the multipeak structures are masked and even disappear due to a large broadening of themselves. The transition from the quantum results to the classical ones for increasing thickness is also clearly demonstrated for the two cases. Although we only discuss the dielectric function and optical absorption of gold films with quantum sizes, the phenomena are expected to be exhibited in other metal nanostructures. Our findings enrich our understanding of both electron surface scattering and quantum finite-size effect in small metal nanostructures, and pave the way for the designs of quantum plasmonic devices.
关键词： Quantum finite-size effect,Electron surface scattering
更新于2025-09-23 15:23:52