Evaluation of recovery characteristic of acidic and alkaline solutions from NaNO3 using conventional electrodialysis and electrodialysis with bipolar membranes

We compared the electrodialysis performance for HNO₃ and NaOH recovery from NaNO₃ solution by conventional electrodialysis (ED) and electrodialysis with bipolar membranes (EDBM) at constant current and constant voltage. The individual resistances of the components of the electrodialysis systems were also evaluated. The electrodialysis extent for HNO₃ and NaOH recovery from NaNO₃ solution was almost proportional to the total amount of electricity supplied to the system, regardless of the operation mode and the electrodialysis systems. For the same volume of feed solution, the energy consumption and current efficiency differed depending on the operation mode and the electrodialysis system. In both the ED and EDBM systems, the conductivity of the feed solution strongly affected the overall cell resistance after approximately 50% of the ions in the feed solution had migrated.     

Synthesis and characterization of TiO2 nanoparticles chemically coated with zwitterionic polymer brushes

This study introduces a synthetic method to graft zwitterionic poly (2-methacryroyloxyethyl phosphoryl choline) brushes onto TiO₂ nanoparticles with thickness of a few nanometers. The grafting of zwitterionic polymer brushes was characterized by electron microscope measurements, zeta-potential analysis, and thermo-gravimetric analysis. The technique we employed to synthesize those hybrid nanoparticles was a modified seeded emulsion polymerization in which the polymerization loci were changed in the stage of radical initiation and chain propagation. We have found that the polymerization loci should be on the surface for achieving the effective grafting of polymer brushes. From the suspension rheology studies, we have observed that the suspension of our hybrid nanoparticles was dominated by the attractive force as well as by packing volume effect. This unique rheological behavior is expected to be useful for understanding the inter-particle interactions in complex formulations.     

Realizing the Potential of ZnO with Alternative Non‐Metallic Co‐Dopants as Electrode Materials for Small Molecule Optoelectronic Devices

High performance indium tin oxide (ITO)‐free small molecule organic solar cells and organic light‐emitting diodes (OLEDs) are demonstrated using optimized ZnO electrodes with alternative non‐metallic co‐dopants. The co‐doping of hydrogen and fluorine reduces the metal content of ZnO thin films, resulting in a low absorption coefficient, a high transmittance, and a low refractive index as well as the high conductivity, which are needed for the application in organic solar cells and OLEDs. While the established metal‐doped ZnO films have good electrical and optical properties, their application in organic devices is not as efficient as other alternative electrode approaches. The optimized ZnO electrodes presented here are employed in organic solar cells as well as OLEDs and allow not only the replacement of ITO, but also significantly improve the efficiency compared to lab‐standard ITO. The enhanced performance is attributed to outstanding optical properties and spontaneously nanostructured surfaces of the ZnO films with non‐metallic co‐dopants and their straightforward integration with molecular doping technology, which avoids several common drawbacks of ZnO electrodes. The observations show that optimized ZnO films with non‐metallic co‐dopants are a promising and competitive electrode for low‐cost and high performance organic solar cells and OLEDs.     

Hydrogen production via the aqueous phase reforming of polyols over three dimensionally mesoporous carbon supported catalysts

In order to investigate the relationship between the type of polyol feed and three-dimensionally mesoporous carbon supports with different mesopore structures and sizes, aqueous phase reforming (APR) reactions of xylitol and glycerol were carried out in a continuous fixed bed reactor. The effect of reaction conditions such as the reaction temperature and pressure on the APR performance were studied in the range of 215–250 °C and 28–45 bar. Three-dimensionally bimodal mesoporous carbon (3D-BMC) with the larger secondary mesopores showed the best catalytic performance in terms of carbon conversion to gas, hydrogen yield, selectivity, and hydrogen production rate due to its unique mesoporous structure, regardless of the kind of polyol feed. In addition, the reaction temperature and pressure significantly affected catalytic performance in the APR of polyols. The product selectivity was dependent on the reaction conditions and the type of polyol feed. The hydrogen selectivity of glycerol was higher than that of xylitol, whereas alkane selectivity was higher for xylitol, and the selectivity increased significantly by promoting the reactions favorable for alkane formation with increased reaction temperature and pressure.     

The Effect of Particle Morphology on Unipolar Diffusion Charging of Silver Nanowires

We investigated the effect of particle morphology on unipolar charging of nanowires. The average diameters of silver nanowires were 32, 48, and 68 nm. Particle electrical capacitance is an important parameter that determines the mean charge per particle in a continuum regime. We predicted that a nanowire has larger electrical capacitance than a sphere, and for a nanowire, the electrical capacitance increases as its diameter decreases. The mean charge per nanowire particle was calculated with the electrical capacitance obtained from theoretical analysis as a function of electrical mobility diameter. The mean charge per particle was measured for polystyrene latex particles with an electrical mobility diameter of 100–300 nm, and silver nanowires with an electrical mobility diameter of 200–400 nm. For a given electrical mobility diameter, the mean charge per particle of a nanowire in theoretical analysis and experiments was larger than that of a sphere, and it increased as the diameter of the nanowire decreased. Our results indicate that the mean charge per particle of a nanowire is dependent on particle morphology such as the diameter and the length.

Copyright 2015 American Association for Aerosol Research     

TEM Observations on 0.65Pb(Zr0.42Ti0.58)O3‐0.35Pb(Ni0.33Nb0.67)O3 Ceramics with CuO Additive

The microstructural properties and the chemical compositions of a 0.65Pb(Zr_0.42Ti_0.58)O₃‐0.35Pb(Ni_1/3Nb_2/3)O₃ (0.65PZT58‐0.35PNN) ceramic system sintered at 900°C for 4 h with 10 mol% CuO additives were studied using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS). CuO pockets were found as new microstructural constituents. The liquid phase has formed by the partial melting of CuO additives at the sintering temperature by reacting with Pb element in the matrix. The reaction started at the interfaces and then proceeded into the pocket through the diffusion of the Pb element. The presence of the Pb‐rich precipitates during cooling was confirmed by EDS analyses. Cu‐rich crystals in the pocket were observed near the boundaries between the matrix grain and the pocket. Rather smaller Pb‐Cu‐O‐contained particle segments were detected around the center of the pocket, demonstrating that the reaction of melting of CuO has occurred with the Pb element which was diffused from the matrix. Due to the existence of the liquid phase, a dense microstructure was achieved during the sintering process and abnormal grain growth occurred in the process.     

Simulation of dynamics and control of a double-effect LiBr–H2O absorption chiller

A dynamic model has been developed to simulate dynamic operation of a real double-effect absorption chiller. Dynamic behavior of working fluids in main components was modeled in first-order nonlinear differential equations based on heat and mass balances. Mass transport mechanisms among the main components were modeled by valve throttling, ‘U’ tube overflow and solution sub-cooling. The nonlinear dynamic equations coupled with the subroutines to calculate thermodynamic properties of working fluids were solved by a numerical method. The dynamic performance of the model was compared with the test data of a commercial medium chiller. The model showed a good agreement with the test data except for the first 83 min during which different flow rates of the weak solution caused some discrepancy. It was found that the chiller dynamics is governed by the inlet temperatures of the cooling water and the chilled water when the heat input to the chiller is relatively constant. For a step change of load at constant inlet temperatures of the cooling water and the chilled water, the response time of the chilled water exit temperature was about 15 min and it was due to the thermal capacities of the chiller. The dilution cycle was found to be an essential means for improvement of control performance as well as anti-crystallization.     

Mixture fraction analysis of combustion products in the upper layer of reduced-scale compartment fires

A mixture fraction analysis is performed to investigate the characteristics of chemical species production in smoky compartment fires burning condensed-phase hydrocarbon fuels. A series of fire experiments were conducted in a 2/5 scale compartment based on the ISO-9705 room. Gas species and soot measurements were made at two locations in the upper layer of the compartment. The fuels considered, heptane, toluene, and polystyrene, generate highly smoky fires over a range of natural ventilation conditions. The mass fractions of measured chemical species, such as unburned hydrocarbons, carbon monoxide, carbon dioxide, oxygen, and soot are presented as a function of mixture fraction and compared with state relationships based on the idealized reactions of a hydrocarbon fuel. The results show that plotting the local composition as a function of the mixture fraction adequately collapses hundreds of species measurements from an assortment of compartment conditions with varying heat release rates and spatial locations into a few coherent lines or bands. It is also shown that about half (or more) of the fuel carbon may exist in the form of carbonaceous soot in the upper layer of smoky compartment fires. Inclusion of soot in the mixture fraction analysis allows identification of fuel-rich or under-ventilated conditions.