Wet chemical synthesis of ZnO nanocrystals: dependence of growth and morphology on the solvent composition

Zinc oxide (ZnO) nanocrystals were prepared using a wet chemical route starting from zinc acetate dihydrate dissolved in pure ethanol, pure water, and mixtures of ethanol and water. X-ray diffraction (XRD) studies along with thermogravimetric analyses results show that ZnO begins to crystallize at a temperature lower than 100 °C in a starting solution having 1:4 ethanol–water volume ratio. For other starting solutions, ZnO forms above 150 °C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies confirm the formation of nanoparticles of size ~15–20 nm and XRD analysis shows that the particles crystallize in the wurtzite structure. SEM and TEM studies show that ZnO particles grown in pure ethanol, pure water and in ethanol–water mixtures (other than the 1:4 mixture) have similar morphology, with the nanocrystals forming randomly grouped clusters. In the case of 1:4 solvent, however, the morphology is different, ZnO in this case growing in the form of chain like structures which appear like rods. Room temperature photoluminescence spectra exhibit a strong emission band in the red region probably caused by transitions between deep levels involving zinc interstitials.     

A study of electro-osmotic and magnetohybrid nanoliquid flow via radiative heat transfer past an exponentially accelerated plate

This paper explores the electro-osmotic flow with a uniform magnetic transverse field and thermal radiation. An investigation has been conducted on electromagnetohydrodynamics (EMHD) boundary layer past a moving upright accelerated plate in hybrid nanoliquids. Two specific water-based hybrid nanoliquids are taken into account, which include copper and aluminum oxide. To define the electrical potential distribution in the fluid medium, the Poisson–Boltzmann distribution is used and linearized by Debye–Huckel. The control equations are solved by the transformation technique of Laplace and results are obtained in a closed shape. The quantitative analysis of the nanoliquid temperature, axial velocity, and Nusselt number on the accelerated plate for several values of the related parameters is shown by a graph. Hybrid nanoliquids are known to create fluid flows significantly larger than nanoliquids, which are very helpful in cleaning the contaminated water in a nuclear plant.     

Tuning the oxygen reduction reactivity of interconnected porous carbon by incorporation of phosphorus and activity enhancement through blending with 2D metal dichalcogenides materials

Design and construction of strong oxygen reduction reaction (ORR) electrocatalysts with high activity and durability are the main concerns in proton exchange membrane fuel cells (PEMFCs). In this study, a unique interconnected porous carbon (ICPC) and phosphorus doped ICPC (P-ICPC) were synthesized and utilized as a support matrix for ORR in alkaline medium. The activity of P-ICPC further enhanced by compositing with 2D metal dichalcogenide MoS₂ materials through facile hydrothermal method. The structural characterization indicated that the addition of phosphorus created more defective site in the carbon structure. The MoS₂/P-ICPC catalyst exhibited enhanced ORR activity, and its performance is close to commercial Pt/C catalyst with regards to current density and onset potential. The synthesized MoS₂/P-ICPC catalyst shows better stability regarding activity even after the 2000 cycles of acceleration test. The electron transfer number (n) obtained for MoS₂/P-ICPC is ～3.8, indicating that the oxygen reduction reaction proceeds via 4e^? pathway with the similar kinetics of commercial Pt/C. The current results revealed that the synthesized MoS₂/P-ICPC material might be a better catalyst for oxygen reduction reaction.     

Inventory of aggregates in an expanding urban area

Faced with a potential shortage of aggregate, the Minnesota Department of Transportation funded a study to inventory the aggregates in four pilot areas of the state and compare it with the estimated requirements in these areas. Based on the results of the study, several methods were suggested to enhance the aggregate supply in these areas. The aggregate resources in the four pilot areas were determined by analyzing the geology of the deposits, both natural aggregate and crushed rock. In addition, reserves in permitted properties were determined using a questionnaire that was given to each quarry operator in these areas. Permitted properties were defined as those for which permits have been issued by the government unit having jurisdiction. Analysis of the questionnaire date was supplemented with interviews of county and state highway department personnel and local planning agencies. Aggregate demand in the four areas was determined from national and county models of demand. Computer-aided multiple regression models defined the relationships between aggregate demand and construction of public and private facilities, ratio of non-metal to metal construction products, and the price of aggregate. Four methods were suggested for enhancing the aggregate supply. These included the definition of quantity and quality of aggregate in the vicinity of urban areas, improvement in beneficiation techniques to maximize the utilization of mined material, development of end-use specifications to permit maximum use of lower grade reserves and of recycled pavements, and revision of land use regulations to prevent the loss of aggregate reserves to urban sprawl.