Effect of nano-sized calcium carbonate on cure kinetics and properties of polyester/epoxy blend powder coatings

Today's strict environmental laws pose significant challenges for coating's formulators to look for eco-friendly products. Powder coatings, particularly polyester/epoxy blends have demonstrated their ability as alternatives to traditional solvent-borne coatings. Recently, the use of nanoparticles such as nano-CaCO₃ (nCaCO₃) has been suggested as a beneficial strategy towards powder coating application with improved properties. Here, we study the effect of nCaCO₃ on morphology, cure behavior, adhesion and hardness of polyester/epoxy systems. The nanoparticles shape, size and dispersion state were investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. Furthermore, isothermal cure characterization of the neat and filled systems was performed using a torque rheometer. The most important finding based on the rheological studies was the catalytic effect of nCaCO₃ on cure reaction of polyester/epoxy, leading to the shorter curing time. Moreover, the kinetic analyses of rheograms revealed a marked decrease in the activation energy of the cure process upon raising nCaCO₃ content. Interestingly, pull-off adhesion and hardness tests showed that the hardness and adhesion strength were dramatically increased by the addition of nCaCO₃ into the polyester/epoxy system compared to pure blend resin. Therefore, considering the strong competition in powder coating market, the use of nCaCO₃ as a commercial and inexpensive nanofiller is necessary not only to reduce the dwell time which has benefits in terms of the energy consumption and economics, but also to improve the performance of final polyester/epoxy coating.     

Fabrication and characterization of robust hydrophobic lotus leaf-like surface on Si3N4 porous membrane via polymer-derived SiNCO inorganic nanoparticle modification

Robust hydrophobic surface was produced by modifying the surface of porous Si₃N₄ membrane, via aminolysis and pyrolysis process, with organosilane-derived inorganic SiNCO nanoparticles, which are tightly adhered to the Si₃N₄ grains. The resultant material had a high water contact angle of 142°, attributed to -Si-CH₃ surface terminal groups and a lotus leaf-like hierarchical structure of the nanoparticles, which had a frame structure with Si-N and Si-O covalent bonds in their bulk. The hydrophobic behavior remained practically unchanged after exposure of the produced membranes to aqueous solutions of humic acid, HCl and NaOH, to benzene, as well as to stirring abrasive slurry with SiC particles, and after exposure at high temperatures, up to 500?°C, to air. The inorganic membrane can be considered for use in a broad range of applications which require robust hydrophobic surfaces.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

Conductivity and anticorrosion performance of polyaniline/zinc composites: Investigation of zinc particle size and distribution effect

Polyaniline/zinc composites and nanocomposites were prepared using solution mixing method. Zinc (Zn) particles with an average particle size of 60 μm and zinc nanoparticles with an average particle size of 35 nm were used as fillers in polyaniline (PANI) matrix. Films and coatings of PANI/Zn composites and nanocomposites were prepared by the solution casting method. Electrical conductivity and anticorrosion properties of PANI/Zn composite and nanocomposite films and coatings with different zinc loadings were evaluated. According to the results, electrical conductivity and anticorrosion performances of both PANI/Zn composites and nanocomposites were increased by increasing the zinc loading. Also results showed that the PANI/Zn nanocomposite films and coatings have better electrical conductivity and corrosion protection effect on iron coupons compared to that of PANI/Zn composite.     

Recent Developments for Prediction of Power of Aromatic and Non‐Aromatic Energetic Materials along with a Novel Computer Code for Prediction of Their Power

The explosive power or strength of an energetic material shows its capacity for doing useful work. This work reviews recent developments for prediction of power of energetic compounds. A new user‐friendly computer code is also introduced to predict the relative power of a desired energetic compound as compared to 2,4,6‐trinitrotoluene (TNT). It is based on the best available methods, which can be used for different types of energetic compounds including nitroaromatics, nitroaliphatics, nitramines, and nitrate esters. The computed relative powers are consistent with the measured data for some new materials containing complex molecular structures.     

Suppression of phonon‐mediated hot carrier relaxation in type‐II InAs/AlAsxSb1 − x quantum wells: a practical route to hot carrier solar cells

InAs/AlAs_xSb_{1 − x} quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature‐dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon‐mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K, photoluminescence measurements are consistent with type‐I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At elevated temperatures, hole delocalization reveals the true type‐II band alignment, where it is observed that inhibited radiative recombination due to the spatial separation of the charge carriers dominates hot carrier relaxation. This decoupling of phonon‐mediated relaxation results in robust hot carriers at higher temperatures, even at lower excitation powers. These results indicate type‐II quantum wells offer potential as practical hot carrier systems. Copyright © 2016 John Wiley & Sons, Ltd.     

Steady-state and dynamic desorption of organic vapor from activated carbon with electrothermal swing adsorption

A new method to achieve steady-state and dynamic-tracking desorption of organic compounds from activated carbon was developed and tested with a bench-scale system. Activated carbon fiber cloth (ACFC) was used to adsorb methyl ethyl ketone (MEK) from air streams. Direct electrothermal heating was then used to desorb the vapor to generate select vapor concentrations at 500 ppmv and 5000 ppmv in air. Dynamic-tracking desorption was also achieved with carefully controlled yet variable vapor concentrations between 250 ppmv and 5000 ppmv, while also allowing the flow rate of the carrier gas to change by 100%. These results were also compared to conditions when recovering MEK as a liquid, and using microwaves as the source of energy to regenerate the adsorbent to provide MEK as a vapor or a liquid.     

A new and applicable method to calculate mass and heat transfer coefficients and efficiency of industrial distillation columns containing structured packings

Most of the methods developed for efficiency estimation of distillation columns were based on the empirical mass transfer and hydraulic relations correlated to laboratory data. Therefore, these methods cannot estimate efficiency of industrial columns with sufficient accuracy. In this paper, a new and applicable method was developed for calculation of efficiency (and mass and heat transfer coefficients) of distillation columns containing structured packings. This method has potential advantages; e.g., it can calculate efficiency without using any empirical mass transfer and hydraulic correlations and models, and without the need to estimate the operational and hydraulic parameters of column. Therefore, it will be free of errors, limitations, and complexities of such empirical items. In addition, precision of the method does not decrease with increasing complexity of operating conditions and design parameters of column. The method can be used for efficiency calculation of any structured packing, including new ones, in distillation columns.     

A practical eco-environmental distribution network planning model including fuel cells and non-renewable distributed energy resources

This paper presents a long-term dynamic multi-objective planning model for distribution network expansion along with distributed energy options. The proposed model optimizes two objectives, namely costs and emissions and determines the optimal schemes of sizing, placement and specially the dynamics (i.e., timing) of investments on distributed generation units and network reinforcements over the planning period. An efficient two-stage heuristic method is proposed to solve the formulated planning problem. The effectiveness of the proposed model is demonstrated by applying it to a distribution network and comparing the simulation results with other methods and models.