OAJ Materials and Devices

A A XRD Study of the CuAl Layered Double Hydroxide Synthesis Evolution

2024-08-19T13:55:09+00:00

It is a challenge to determine the active part of a solid phase in chemical process when the purity of the aforesaid is not sufficient and could jeopardize the solid real applications. CuAl LDH phase has been obtained with low percentage of impurities and the intention to use it as photoreduction or photoxidation catalyst and /or templating agent in the design of nanohybrid composites photocatalysts, for CO₂ storage that could facilitate its later abatement and/or highly efficient semiconductor material. A set of synthesis were implemented with a mixture of Cu(NO₃)₂2.5H₂O and Al(NO₃)₃.9H₂O with Na₂CO₃ and NaOH using coprecipitation at variable pH. Keeping constant a low CO₃^2-/Cu²⁺ + Al³⁺ fraction in all sets, constant basic pH and ageing time (96h) with slight variations in T, resulted in mixed phases of malachite, CuAl LDH and traces of Cu(OH)₂. At basic pH and T with different ageing time, similar XRD patterns were measured with noticeable differences, though. When the carbonate ratio, ageing time, and pH were constant (7.50, 96 h, 9.24), modest changes in T generated key dissimilitude in the diffractograms. The resulting band gap energy of this LDH coincided with the visible spectral region energy. A more precise tuning of variables has led to a high degree of optimization of the CuAl LDH and further contributes to comprehend how varied synthesis conditions influence this metastable hydrotalcite Obtention.

Thermal Annealing Impact on the Properties of CdSe/PbSe Superlattice Thin Films

2024-09-02T03:24:55+00:00

Superlattice thin films of CdSe/PbSe were successfully deposited on glass substrate using successive ionic layer adsorption reaction (SILAR) method to study their properties for possible semiconductor device applications. Cadmium (II) chloride hemi (pentahydrate), lead nitrate and sodium hydrogen selenide were the precursor for Cd²⁺, Pb²⁺ and Se^2- ions sources respectively. The SILAR process involved a total cycle time of 100 seconds for a complete SILAR cycle with a total of six cycles made as one layer of CdSe used as a substrate for PbSe to form CdSe/PbSe superlattice films. The deposited thin films were subjected to thermal annealing at different temperatures of 300 K, 373 K, 423 K 473 K and 523 K and characterized for their optical, structural elemental and morphological properties using UV-Vis spectroscopy, X-ray diffraction and SEM/EDS techniques. The results of the optical properties showed that absorbance is high in the VIS region while transmittance is low in the VIS region but increased to high values in the NIR region and was significantly influenced by thermal annealing. The bandgap energies of the films were found to be 1.8 eV, 1.75 eV, 1.65 eV,1.8 eV and 1.88 eV after thermal annealing at 300 K, 373 K, 423 K, 473 K and 523 K respectively. The XRD analysis showed that the deposited thin films are polycrystalline with diffraction spectra showing an increase in intensity at an annealing temperature of 523 K and preferential lattice planes of 101, 103, 203 attributed to CdSe and 100, 200, 220 attributed to PbSe films. The EDS results indicate that the films composed of Cd, Pb, Se and other elements traceable to the substrate used. The SEM results showed that the CdSe/PbSe superlattice films contained agglomeration of nanorods and rice grain-shaped nanoparticles of different sizes and shapes that were found to increase with an increase in annealing temperature. These observed properties position the films for photodetector, solar cells, light emitting diodes, photoconductors and many other electronic and optoelectronic device applications.

Optical characterization of reduced graphene Based composite thin films: Left- Handed Materials (Metamaterials)

2024-08-19T14:35:13+00:00

Negative index material is a type of metamaterial with negative refractive index; being an artificial material, its fabrication is quite difficult, scaling up the production to meet the commercial demand is a challenge and the strong energy dissipation by metals poses another difficulty. This study employed a low cost, scalable technique (Electrodeposition) to synthesis Al and Ca doped NiO-ZnO-rGO thin films on fluorine doped tin oxide (FTO) without any complexing agents. The thin films were optically characterized using double Spectrophotometer within 300-1000 nm wavelength. Results reveal low absorption for all films but high transmittance of max. 78 % for luminum doped thin films. The incorporation of Al³⁺ and Ca²⁺ indicate the optical band gap of NiO-ZnO-rGO shifted to low energy (2.0 eV) and high energy (2.20 eV) respectively. All the composite thin films have unique features; negative refractive indexes, negative imaginary dielectric constant, and negative optical conductivity. These optical results of the films show they are novel left handed materials suitable for wider applications such as telemedicine, internet of things, transmission lines, energy storage devices, bio sensing, wearable devices etc.