A codoping route to realize low resistive and stable p-type conduction in (Li, Ni):ZnO thin films grown by pulsed laser deposition

We report on the growth of Li-Ni codoped p-type ZnO thin films using pulsed laser deposition. Two mole percent Li monodoped ZnO film shows highly insulating behavior. However, a spectacular decrease in electrical resistivity, from 3.6 × 10(3) to 0.15 Ω cm, is observed by incorporating 2 mol % of Ni in the Li-doped ZnO film. Moreover, the activation energy drops to 6 meV from 78 meV with Ni incorporation in Li:ZnO lattice. The codoped [ZnO:(Li, Ni)] thin film shows p-type conduction with room temperature hole concentration of 3.2 × 10(17) cm(-3). Photo-Hall measurements show that the Li-Ni codoped p-ZnO film is highly stable even with UV illumination. XPS measurements reveal that most favorable chemical state of Ni is Ni(3+) in (Li, Ni): ZnO. We argue that these Ni(3+) ions act as reactive donors and increase the Li solubility limit. Codoping of Li, with other transitional metal ions (Mn, Co, etc.) in place of Ni could be the key to realize hole-dominated conductivity in ZnO to envisage ZnO-based homoepitaxial devices.     

Design and development of a safer non-invasive transungual drug delivery system for topical treatment of onychomycosis

Objective: The main objective of this study is to develop a safer non-invasive treatment for nail infections since the current treatment regimen has drawbacks like, incidence of systemic side-effects and higher cost. Proposed topical treatment on the other hand can drastically improve the situation, hence highly desirable. This work was undertaken with a hypothesis to develop a transungual microemulsion gel for topical treatment of onychomycosis.

Methods: Benzyl alcohol and isopropyl myristate were used as oil, Pluronic F68 as surfactant and ethanol as co surfactant, in double-distilled water and loading itraconazole as the model antifungal drug. Pseudo-ternary phase diagram was developed by titrating different ratios of total oil and water with total surfactant, and K_m ratio was fixed at 1:1. Microemulsion formulations were prepared based on the phase diagram and incorporated in gels by adding Carbopol 934P. Nail permeation enhancers like urea and salicylic acid were used to increase drug permeation through the nail plate. Parameters like drug loading, clarity, particle size distribution, drug entrapment efficiency (DEE), drug release profile, release kinetics and nail uptake were checked for the evaluation of the formulations.

Results: Complete release of drug from the formulation varied from 60 to 120?min. The optimized formulation had DEE of 92.75%, complete drug release in 60?min and highest nail uptake of 0.386%/mm² (39?µg of drug) with 5% urea as nail permeation enhancer.

Conclusion: The formulation may prove beneficial in safer treatment of onychomycosis.     

A comparative study of microstructure and mechanical behavior of CO2 and diode laser deposited Cu–38Ni alloy

Cu–38Ni alloy was deposited on C71500 (Cu–30Ni) substrates by a laser-aided direct metal deposition technique using CO₂ and diode lasers. Structure–property relationships of deposited specimens were investigated by optical microscopy, electron microscopy, X-ray diffraction techniques, and microhardness and tensile measurements. Laser-deposited specimens’ microstructures were primarily dendritic, forming columnar grains growing epitaxially from the substrate and subsequent layers along the preferred crystallographic growth. The grain growth pattern and grain size distribution was significantly different in both specimens. The lattice parameter of the solid solution phase was relatively larger in diode laser-formed specimen; CO₂ laser-formed specimens showed relatively higher but non-uniform hardness distribution whereas a very uniform hardness distribution was observed in diode laser formed specimens. Diode laser formed specimens showed higher tensile properties compared to CO₂ laser formed specimens which were comparable to C71500 substrates. Microstructure and mechanical behavior were explained based on laser processing parameters.     

Mine tailings-based geopolymers: Properties,applications and industrial prospects

The use of mine tailings (MTs) as aggregates or precursors of alkali-activated materials and geopolymers (GPs) seems to be a promising approach for their sustainable utilization since it allows not only reducing the dynamics of MTs accumulation in the environment and the environmental damage they cause but also it combines the advantages geopolymer technology that is associated with reducing the carbon footprint, the ability to utilize other technogenic aluminosilicate waste, the versatility of the properties of GPs as a general construction binder. Taking into account the complex material composition of mine tailings, and relatively little knowledge of the features of the geopolymerization of tailings and the influence of various factors on the properties of MTs-based geopolymers, there is now a need to generalize these aspects and assess the prospects for possible applications. This article is a generalization and a detailed analysis of the relationship between structural, mechanical, and thermal properties, durability, leaching behavior, and other important characteristics of MTs-based geopolymers. Here, in addition to the key fundamental aspects of the formation of properties of MTs based geopolymers, well-known examples of their applications in binder pastes, mortars, and concretes, as well as bricks, backfill materials, adsorbents, porous materials, and other promising applications are considered in detail. In addition, economic and production aspects are also discussed.     

Adhesion of charged powders to a metal surface in the powdercoating process

Substrate-particle adhesion of electrostatically charged, nonconducting particles deposited on electrically grounded substrates is discussed. Glass microspheres of diameters ranging from 25.5-74.1 μm, charged by corona and tribe-charging, were deposited in a monolayer on conducting stannic-oxide coated surfaces of glass plates (NESA). The total force of adhesion due to electrostatic, van der Waals, and gravitational forces was measured by observing the removal of particles by applying a known electric field between the particle coated surface and a clean surface of a second NESA glass, placed parallel to it at a distance of 0.013 m. The adhesive force was measured as a function of particle size and charge. The net average charge on the particles was measured using a Faraday cup. The experimental values agree well with the calculated force of adhesion for a single layer deposition. The charge decay of the particles was studied using a noncontact electrostatic voltmeter. The charge relaxation time of the deposited powder was found to increase with time. A physical model of the adhesion of charged powder paints deposited on a grounded metal substrate is presented. The role of the forces acting on a spherical polymer particle deposited on the surface of a uniform coating of powder paint is investigated as a function of particle diameter and charge. The particles are assumed to be unipolarly charged and deposited uniformly on the substrate. The relative magnitudes of the electrostatic attractive and repulsive forces are analyzed as functions of powder film thickness and particle size     

Longitudinal spatial variation in ecological conditions in an in‐channel floodplain river system during flow pulses

A field survey was conducted during flow pulses to investigate the longitudinal spatial patterns in water quality, dissolved inorganic and organic matter, phytoplankton, planktonic bacteria, zooplankton, gross primary productivity (GPP) of phytoplankton and planktonic respiration (PR) in channels of the large floodplain system (～124 km in length) of the Macquarie Marshes, south‐eastern Australia. Four river reaches (areas) with distinct hydrogeomorphological characteristics within the distributary zone of the lower Macquarie River were chosen for analysis of abiotic and biotic variables in their in‐stream environments. The results showed marked longitudinal spatial variation in the values within and among the measured environmental variables including such functional aspects as primary productivity and PR. The variables that tended to have increasing values in a downstream direction were conductivity, total nitrogen (TN), total phosphorus (TP), dissolved reactive phosphorus (DRP), dissolved silica, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP), ratio of DOC/DON and counts of planktonic bacteria. Conversely, the values that tended to decrease downstream were the ratios of TN/TP, DIN/DRP, DOC/DOP, DON/DOP and GPP/PR. Variables that had a localized peak(s) were dissolved oxygen, turbidity, dissolved inorganic nitrogen, GPP, PR and counts of cyanobacteria, diatoms, green algae, cryptomonads, protozoans, rotifers, copepods and cladocerans. Overall, two distinct ecological zones were identified within the broader distributary functional process zone (FPZ): these being the upstream zone with relatively high levels of DO, turbidity, diatoms and GPP/PR ratio, and the downstream zone with relatively high levels of nutrients, dissolved organic matter, cyanobacteria, planktonic bacteria, protozoans and cladocerans. The results of this study describe the spatial connectivity of ecological processes related to hydrogeomorphological factors within a FPZ of a riverine ecosystem, and support the predictions of the riverine ecosystem synthesis framework that ecological patterns and processes can be discontinuous on a longitudinal spatial scale. Copyright © 2010 John Wiley & Sons, Ltd.