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Because of the superior optical and electrical properties, copper-impregnated size tuneable high-temperature stable manganese dioxide semiconductor quantum dots (SQDs) have been successfully synthesized by a modified chemical synthesis technique. Their size-dependent dielectric properties, semiconducting properties, and current–voltage (I–V) characteristics have been investigated. X-ray diffraction pattern and Raman spectra confirmed that the required phase is present. Because of the different sintering temperature tuneable size of SQDs has been found and confirmed by high-resolution transmission electron microscopy. The band gap energy of the material is found to be 1.25–1.67 eV, measured from Tauc plot using UV–vis absorbance spectrum and their semiconducting properties have been confirmed by the non linear current–voltage (I–V) behavior. Most intense green emission peak of photoluminescence (PL) spectroscopy confirms the oxygen vacancy defect state. The stoke shifting of Raman spectra, UV absorption, and PL emission are the footprint of quantum confinement effect. Incorporation of a little amount of Cu in tetragonal hollandite structure of α-MnO2 generates strain within that structure. This leads to create sufficient crystal defect state as well as rise in dielectric constant accompanied with low dielectric loss and higher ac conductivity. All these highly desirable properties make the SQDs a potential candidate for developing multifunctional photo-electronic devices. Owing to the tuneable band gap and electronic transport of the SQDs, we realized that the controllable size paves the way for designing SQDs possessing unique properties for optical and electronic device applications. Using this material as a high dielectric separator, a high-performance supercapacitor has been successfully fabricated which can light up 15 light-emitting diodes for 47 min 23 s after charging them only for 30 s.

α-MnO2 nanoparticles with increasing copper doping concentration have been synthesized through a modified hydrothermal technique. Doping-induced microstructural defects inside the host material lead to a giant dielectric constant 1.6 ×...

D rop size distribution is an important characterizing parameter of a spray. In the present work a theoretical model has been described, based on the maximum entropy formalism principle, for the determination of the drop size distribution in a spray issued from a pressure swirl atomizer. The atomization ef ciency is also derived from the model, assuming the velocities of all the drop sizes to be uniform. The results show that the drop size distribution, described from the present model, resembles the R osin-R ammler type distribution very well, with a dispersion parameter of 3.47. The atomization ef ciency is found to decrease with the increase in liquid mass owrates, when the pressure differential across the atomizer remains the same. On the other hand, an increase in the ori ce diameter increases the atomization ef ciency, when the liquid mass ow rate and pressure differential are the same. The ratio of the surface energy to the kinetic energy at the atomizer exit is seen to in uence the atomization ef ciency.

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The present work has attempted a unification of the empirical spray parameters for the pressure swirl atomizers with the maximum entropy formalism principle for the predictions of both size and velocity distributions in a spray. The information entropy is maximized under suitable constraint conditions to evaluate a number-based droplet size and velocity joint distribution parameter. The constraint equations have been defined to include the spray parameters, such as the Sauter mean diameter, spray cone angle and liquid film thickness, to consider their influence on the distribution. A comparison of the predicted results using the present theory is made with the experimental data available in the literature and good agreement is achieved. The effects of the atomizer input conditions, such as injection pressure, ambient pressure and the properties of atomizing liquids, on the size and velocity distributions are studied using the present model. A calculation of the efficiency of the atomization process using the size and velocity distribution functions is also made to study the effect of operating conditions on the performance of atomization.