Papers by Keyword: Absorption

Abstract: This paper presents an in-depth spectroscopic analysis of Al₂O₃-40%TiO₂ coatings deposited via HVOF thermal spraying on a 10CrMo9.10 heat-resistant steel substrate. The study aims to correlate the optoelectronic and structural properties of the coatings with their composition and microstructure. Spectroscopic investigations revealed intense absorption in the visible (VIS) region due to electronic transitions from the valence band to the conduction band of the ceramic materials and high reflectivity in the ultraviolet (UV) region. These properties make the coatings particularly useful for protective systems in solar thermal power plants. The detailed characterization of the optical properties of the Al₂O₃-40%TiO₂ coatings obtained through HVOF technology was made possible by corroborating spectroscopic results. These insights are essential for understanding the mechanisms that govern the performance of these coatings in protective applications under high temperatures and aggressive environments.

Abstract: A theoretical study of the effect of applying a lateral electric field on type I and type II GaAs/AlGaAs quantum ring with different Al concentration in the barrier is presented. The effect on the quantum states of the carriers was investigated using the approximation of the effective mass. It’s showed that the electric field has a great effect on the wavefunction and the energy of the carriers. The transition point of the quantum ring from type I to type II was found with increasing electric field strength. For electric fields less than 4.75 x 10^-4 V/cm, the quantum ring is of type II: the symmetry of electron ground state is X. Above this threshold, it transitions to type I : the symmetry of electron ground state is Γ. Also, the effects of electric field on the linear and non-linear optical properties of the studied structure illuminated with different incident optical intensity were studied. There is an increase in the radiative lifetime with a notable decrease in the absorption coefficient and the refractive index with the increase in the intensity of the electric field. It’s noted that the increase in the type II quantum ring lifetime (20%) is greater than that of type I quantum ring (10 %) due to the confinement of the G-electron in the quantum ring which is not the case with the X-electron. To the best of our knowledge, this article is the first theoretical study of the influence of lateral electric field on physical properties of type II GaAs/AlGaAs quantum ring structures.

Abstract: Water pollution poses a significant challenge to water consumption, particularly in relation to drinking purposes. Various factors such as industrial discharge, improper waste management, waste build-up, and natural activities contribute to the contamination of water bodies. Adequate water treatment plays a crucial role in the preservation of water quality and compliance with environmental regulations. The treatment process typically involves the application of physical, chemical, and biological techniques, with a common reliance on chemical substances and intricate systems. Recent studies have increasingly explored the utilization of cost-efficient natural materials for water treatment, highlighting benefits like affordability, user-friendliness, health advantages, and widespread availability. This particular investigation aimed to assess the suitability of selected natural substances for the treatment of wastewater, focusing primarily on methods like adsorption, absorption, and filtration. A number of earth materials, notably three distinct types of clays prevalent in Sri Lanka, were singled out for examination. The findings unveiled that these clays predominantly consist of over 75% iron in their mineral composition, with certain samples displaying finer particles to enhance porosity and permeability. These raw materials exhibit potential for the fabrication of wastewater treatment systems intended for the elimination of suspended particles, dissolved solids, heavy metals, pathogens, oils, and toxic compounds. Their distinct chemical properties render them appropriate for catalytic reactions and advanced chemical processes

Abstract: The article shows the process of preparing an oxide layer on the surface of titanium for use in industrial catalysis. Data from physical and chemical studies are presented, namely microhardness, porosity, thickness, specific surface area, adhesion and thermal stability of the active layer.To determine the physicochemical characteristics of the resulting oxide layer, the following analysis methods were used: X-ray diffraction analysis (XRD), X-ray diffraction phase analysis (XPA), X-ray absorption analysis (XRA), and X-ray fluorescence analysis. The thickness of the oxide layer depending on the duration of anodization was estimated by optical microscopy.

Abstract: Amino acid lanthanide complexes are a promising class of environmentally friendly and non-toxic optical organic materials that find extensive applications in biomedicine, molecular probes, and optical devices. In this study, three amino acid lanthanide complexes, octanoyl glycine gadolinium (Gd(oct-ala)₃×H₂O), octanoyl serine gadolinium (Gd(oct-ser)₃×H₂O), and octanoyl phenylalanine gadolinium (Gd(oct-phe)₃×H₂O), were synthesized by reacting octanoyl amino acid ligands with gadolinium chloride. The coordination structure of the gadolinium complexes was determined by elemental analysis and infrared spectroscopy. XRD and polarized light microscopy confirmed the amorphous structure of the complexes. DSC and TG-DTA were used to investigate the thermodynamic stability of the gadolinium complexes, and their solubility and UV-visible light absorption properties were also evaluated. Our results demonstrate that all three gadolinium complexes exhibit excellent UV-visible light absorption performance, with the Gd(oct-phe)₃×H₂O containing a phenyl ring showing the highest light absorption efficiency.

Abstract: The effect of electrical and thermal treatment on silver nanowire (AgNW) network morphology and its impact on ultraviolet-visible (UV/Vis) and luminescence spectra is reported. The results exhibit that the conductivity enhancing welding of the single AgNWs at connection points changes the network morphology towards an increased proportion of spherical like structures. This inhomogeneity which is particularly noticeable for joule heated films not only gives rise to an inhomogeneous line broadening in absorption and luminescence spectra but also causes a red shift of the surface plasmon resonances in comparison to a non post-treated AgNW network. With increasing inhomogeneity either due to welding or beginning degradation the d-sp interband excitation pathway is especially efficient for the decay of surface plasmons and shows the strong coupling of the corresponding exciting and emitting photons to the surface plasmon excitation.

Abstract: The paper shows that the introduction of up to 6 wt % of ferromanganese dust enhances the process of granule porization and improves the structural-mechanical properties. This is achieved due to the formation of low-base calcium hydrosilicates in the mineral matrix, reinforced by crystals of fayalite, orientite and pyroximite, which contribute to an increase in the dielectric component in the scattering of electromagnetic waves in the millimeter range. Granules with a developed pore structure in the frequency range from 110² to 3.1510³ Hz can absorb and scatter electromagnetic waves in the range of 54-58 dB. Granules in the temperature range from 20 to 300 °C are flame retardant and not prone to brittle fracture (F ≤ 4). The introduction of a 5% porous filler into the polymer matrix contributes to the growth of the effective part of the dielectric permittivity (μ to 1.5) and stabilization of the coefficient of attenuation of electromagnetic waves (from 2 to 4) in the range 110¹⁰ - 610¹⁰ Hz. The developed porous material is recommended to was used as a filler in the first layers of gradient-absorbing composites

Abstract: The construction industry is really concerned with producing better and durable building materials. Hence, the high cost of conventional building materials have resulted into use of locally available materials. This study assess the effect of varying cement content on engineering properties of fired lateritic bricks. The lateritic soil samples were stabilized with cement at 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 and 7.5%, cast in moulds and later fired for 8 hours at a 1000°C. Index properties (natural moisture content, specific gravity, particle size distribution and atterberg limit tests) were determined on the natural lateritic soil. While compressive strength, water absorption, abrasion and impact value test were determined on the cement fired bricks. The lateritic soil in its natural form were classified as A-6 and clay of high compressibility in accordance to ASTM D-3282. The results of the index properties are within acceptable limits for lateritic soil. The effect of varying cement content on the mechanical properties showed that the compressive strength of the bricks increases from 4.0 N/mm² at control (un-stabilized brick) to 7.3 N/mm² at 5% soil stabilization with cement. However, significant reductions in value was witnessed in the water absorption, abrasion and impact value results between the un-stabilized brick (control) and 5% cement fired bricks. The study concluded that fired bricks stabilized with 5% cement was found to be the best and most suitable for load and non-load bearing walls.

Abstract: The article aims to investigate polymer inorganic composites for electromagnetic radiation absorption using potassium titanates. The selected polyamide 6 (durethane brand) and sodium polytitanate materials contain TiО₂, K₂СО_3, and KCl received by charge sintering. Results showed that modification of polyamide 6 with sintering products in the form of a fine powder of potassium polytitanate with particle size 1-5 microns that contain the primary phase K₂O × 2TiO₂ with an admixture of a phase K₂O × 4TiO₂, which increased their strength properties. The optimal content of potassium polytitanate was over 10 % by mass. To fully ensure the reinforcing effect due to the filling of potassium polytitanate polyamide 6, it is necessary to use whiskers K₂O × 6TiO_2, which can be collected by the additional crystallization of the amorphous charge sintering product.

Abstract: Microwave absorber is commonly used in defense, electromagnetic compatibility (EMC)/electromagnetic interference (EMI) reduction and anechoic chamber application. Conventional electromagnetic (EM) absorbers have some constraints in practical handling due to its heavy weight. In this paper, the research focuses on the development of high performance and lightweight microwave absorber. A lightweight and simple design configuration of different rectangular slot size array implemented on hollow pyramidal microwave absorber are carried out. There are two different designs of different slot size array calculated based on 3GHz, 6GHz and 9GHz frequency slot size. The two designs have an opposite slots size array arrangement namely different slot size 3GHz, 6GHz, 9GHz order design array and different slot size 9GHz, 6GHz, 3GHz order design array. The absorption is measured using the Naval Research Laboratory (NRL) arch free space method in the frequency range of 1GHz to 12GHz covering L, S, C and X band. In the measurement result, the maximum absorption performance is obtained by the different slot size 9GHz, 6GHz, 3GHz order design array which is up to -44.23dB at X-band. The measurement results for both designs array show good absorption performance which exhibit below than -20dB especially at high frequency band. The proposed designs have been identified as the new approach to increase absorption improvement over a broad frequency range application.