Dielectric Properties of Coronene Film Deposited onto Silicon Substrate by Spin Coating for Optoelectronic Applications

Silicon - To determine the electrical modulus, dielectric properties, and ac conductivity of Coronene semiconductor layer, we have produced Al/Coronene/n-Si structure by using the thermally...     

Synthesis of submicron AlN powder using dynamic/thermochemical method

Carbothermal reduction and nitridation (CRN) method, used for the synthesis of nitride-based ceramic powders, is an effective and economic technique that has been widely investigated. In this study, a CRN-based novel approach, denominated as dynamic/thermochemical method (DTM), has been used to synthesize submicron high-purity aluminum nitride (AlN) powders with equiaxed-sized particles. DTM is a modified CRN method in which the reaction takes place in a controlled atmosphere using a rotary tube furnace, allowing the synthesis of fine particle-size powders in a relatively short time. Following the DTM process, homogeneous submicron AlN powders were synthesized from a mixture of aluminum hydroxide (Al(OH)₃) and carbon black at 1450°C for 1.5 h. Furthermore, dynamic synthesis parameters, as well as the use of ammonia (NH₃) and propane (C₃H₈) gas mixtures instead of carbon black and nitrogen, were investigated.     

Conductive polyaniline–polythiophene/poly(ethylene terephthalate) composite fiber: Effects of pH and washing processes on surface resistivity

A conductive polyaniline (PAn)–polythiophene (PTh)/poly(ethylene terephthalate) (PET) composite fiber was prepared by polymerization of aniline and thiophene in the presence of PET fibers in an organic medium with FeCl₃. The effects of polymerization conditions, such as polymerization medium, mol ratios of aniline/thiophene and FeCl₃/aniline‐thiophene as well as polymerization temperature and time, were investigated on PAn–PTh content (%) and surface resistivity of the composite. The composite with the lowest surface resistivity (1.30 MΩ/cm²) was obtained by polymerization of aniline and thiophene (1/3 mol ratio) in acetonitrile/chloroform (1/5 volume ratio) at 20°C. The surface resistivity of the PAn–PTh/PET composite containing 4.8% PAn–PTh was increased from 1.9 MΩ/cm² to 270 MΩ/cm² at pH 11. The washing durability of the composites was determined with domestic and commercial laundering processes by monitoring the surface resistivity and morphology. The composite was also characterized with FTIR, TGA, elemental analysis, optic microscope and SEM techniques. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41979.     

Spray-Dried Mesoporous Hydroxyapatite–Chitosan Biocomposites

In this study, hydroxyapatite–chitosan composites with weight ratio of 1:0.1 were produced by spray-drying technique using two different inlet temperature. Besides, the effect of weight change of hydroxyapatite on composites was investigated on composites which were spray-dried in the selected temperature. Synthesized hydroxyapatite–chitosan samples were characterized using Fourier transform infrared microscopy, scanning electron microscopy, X-ray fluorescence spectroscopy, Brunauer–Emmet–Teller method, and X-ray diffraction. Particle size measurements were also performed in this content. Simulated body fluid studies were conducted on selected samples. According to results, hydroxyapatite–chitosan sample was successfully synthesized. Spray-dried mesoporous microspheres with high surface areas could be suitable for biomedical usage.     

Preparation and characterization of membranes obtained from blends of acrylonitrile copolymers with poly(vinyl alcohol)

New microfiltration and ultrafiltration membranes were obtained using acrylonitrile‐vinyl acetate copolymers in mixture with poly(vinyl alcohol) (PVA). Thus, a blend polymer solution was prepared in dimethylsulfoxide (DMSO) and used to obtain bicomponent polymer membranes by phase inversion. The rheological behavior of the DMSO polymer solutions was, mostly, dilatant at low shear gradients and pseudo plastic with quasi Newtonian tendency at higher gradients. Membranes were characterized by Fourier transform infrared spectrometry (FTIR), optical microscopy, atomic force microscopy, thermal gravimetric analysis‐differential thermal gravimetry, and pure water flux (PWF). FTIR spectra displayed the characteristic bands for acrylonitrile, vinyl acetate, and PVA. The morphology and the porosity can be tailored by the preparation conditions. PVA allows controlling the size of the pores and enables, in principle, to use the resulted membranes as supports for enzyme immobilization. PVA content influences the thermal stability. PWF values depend on the copolymer, on the content in PVA, but also on the coagulation bath composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41013.     

Thoughening of poly(lactic acid) with silicone rubber

In this study, poly(lactic acid) (PLA) was blended with silicone rubber (SR) to improve its impact strength and toughness by using dynamic crosslinking in the presence of peroxide during melt compounding. The SR to PLA ratio, peroxide and coagent concentrations were taken as experimental parameters. Blends were evaluated in terms of their thermal properties, tensile and impact strengths, dynamic mechanical properties, and micro‐structure. Results showed that PLA was successfully toughened with SR using dynamic crosslinking. Impact strength and energy of fracture in tensile test improved up to 4 and 10 times, respectively. On the other hand, yield strength and stiffness of blends deteriorated by the incorporation of SR. Thermal analysis pointed out that presence of SR decreased the cold crystallization temperature. It was observed from scanning electron microscopy (SEM) that the energy absorbing mechanism under impact loads in PLA/SR blends is tortuosity in the crack patterns. POLYM. ENG. SCI., 54:2029–2036, 2014. © 2013 Society of Plastics Engineers     

Process intensification for heavy oil upgrading using supercritical water

Demand for light hydrocarbons has been steadily increasing in the market with a corresponding decrease in heavy hydrocarbon demand. Therefore, there is a need to develop environmentally friendly and efficient technologies for conversion of heavy molecular weight hydrocarbons. Supercritical fluids (SCF) are attracting increased attention as solvents for green chemistry and among those supercritical water (SCH₂O) is promising for the upgrading of heavy hydrocarbons. Because of a sharp decrease in its dielectric constant, water loses its polarity when brought to the supercritical conditions and its properties starts to resemble the properties of hydrocarbons and becomes an excellent solvent for organic compounds. Moreover, increased ionic product of water leads to an increasing [H₃O⁺] concentration and thus promotes the reactions requiring the addition of an acid. Solvation power enables the extraction of lighter compounds while increased [H₃O⁺] concentration makes the reactive extractions of heavy hydrocarbons possible. As a result of its favorable properties, a wide variety of process intensification studies have been carried out using near critical or SCH₂O such as combined distillation-cracking-fractionation and in some cases even without the utilization of catalysts and/or hydrogen. In this review, recent advances on reactions of hydrocarbons occurring in a SCH₂O environment will be highlighted. Fundamental aspects of these reactions including their thermodynamics and kinetics will be discussed. Experimental and theoretical developments on phase equilibria of relevant water–hydrocarbons systems will be presented.     

Enhancement of hybrid sol–gel coating and industrial application on polished porcelain stoneware tiles and investigation of the performance

The aim of this study was to improve stain resistance and cleanability of polished porcelain tiles by sealing the micro-pores on the tile surface with hybrid sol–gel solution. For this purpose, solutions of a hybrid system based on sol–gel technology were prepared. The obtained solution were applied to polished unglazed tiles and subsequently spread with soft tissue thereon. To achieve complete sealing, both organic and inorganic particles of different sizes were mixed with obtained sol–gel hybrid systems. Coated surfaces were investigated by means of a scanning electron microscope. The stain resistance and the cleanability of the tile surface were tested according to ISO-10545-2014 standard. It has been shown that prepared sealing material permanently prevents formation of stains such as olive oil, green staining paste, iodine solution on the surface of polished porcelain tiles. The remains of stains on the surface can easily be removed from it with a cleaning agent.     

Inactivation of particle-associated microorganisms in wastewater disinfection: modeling of ozone and chlorine reactive diffusive transport in polydispersed suspensions

Occlusion of microorganisms in wastewater particles often governs the overall performance of a disinfection system, and the associated health risks of post-disinfected effluents. Little is currently known on the penetration of chemical oxidants into particles developed in wastewater treatment. In this work, a reactive transport model that incorporates intra- and extra-particle chemical decay, radial intra-particle diffusion, mass transfer resistance at particle surfaces, and non-linear reaction kinetics within a competitive multi-particle size aqueous environment, was used to analyze the penetration of ozone and chlorine into wastewater particles. Individual characteristics from two secondary wastewater treatment facilities were used in model calibration. Simulations revealed that significant ozone transport within particles greater than 6 microm required large initial concentrations to exhaust the preferential reaction with aqueous soluble matter. Chlorinated samples exhibited apparently slower reactions and thus deeper penetration (22-40 microm). Chlorine penetration was less sensitive to variations in the extra-particle reaction and disinfectant concentration than ozone. Model simulations that considered elevated initial concentrations of chemical disinfectants revealed that complete inactivation of all particle size domains was not possible with current disinfection practices (e.g., contact times). Reduction in the health risks associated with wastewater particles requires treatment that efficiently balances particle removal (filtration) and particle inactivation (disinfection).