Synthesis of polyethylene glycol-polystyrene core-shell structure particles in a plasma-fluidized bed reactor

Particles with core-shell structure with polystyrene (PS) core and polyethylene glycol (PEG) grafted on the surface were synthesized in a plasma-fluidized bed reactor. The virgin, plasma-treated, and grafted powders were characterized by the DPPH method, UV-vis spectrophotometer, NMR, FT-IR and SEM. The plasma-treated PS powders have well formed peroxide on the surface. By PEG grafting polymerization, PEG is well grafted and dispersed on the surface of the plasma-treated PS powders. The PEG-g-PS powder exhibits the core shell structure in the cross-sectional SEM image, and it can be claimed that well dispersed PEG grafting polymerization on PS surface can be achieved in the plasma fluidized bed reactor.     

The effect of rear surface polishing to the performance of thin crystalline silicon solar cells

As the thickness of crystalline silicon solar cells decreases, light loss cannot be avoided due to the absorption limit in long wavelength light. Internal rear side reflection can be enhanced by polishing the rear surface. The rear polishing processes are performed before the texturing and before and after doping the emitter layer to optimize the solar cell fabrication process sequences. All cells made by rear surface polishing showed improved light trapping in long wavelength region (900-1100 nm) compared to that in the conventional cells. However, silicon solar cells fabricated by rear polishing before and after doping have similar (35.5 mA/cm²) or lower (35.26 mA/cm²) short circuit current density compared to the cells produced by the conventional process (35.59 mA/cm²) due to pore damage to the anti-reflection layer and the surface of the emitter layer during rear polishing. This surface damage was effectively prevented adapting the rear surface polishing before the front surface texturing, which led to increasing the current density from 35.59 to 36.29 mA/cm².     

Regioselective Synthesis of 1,2‐ and 1,4‐Dihydroquinolines by Palladium‐Catalyzed Intramolecular N‐Arylation

A series of 1,2‐ and 1,4‐dihydroquinolines has been successfully prepared. The Pd‐catalyzed intramolecular N‐arylation of Z‐enamines, formally prepared by the Horner–Wadsworth–Emmons olefination, proceeded efficiently to furnish the cyclized products. Depending on the cyclization conditions, substituted 1,4‐dihydroquinolines and further isomerized 1,2‐dihydroquinolines were independently obtained in high yields with an excellent control of isomerization of the double bond.

     

Palladium‐Catalyzed Direct Arylations of 1,2‐Azolo[1,5‐a]pyridines using Copper(I) Chloride as a Lewis Acid Activator and the Synthesis of 2,6‐Disubstituted Pyridines

A direct method for the arylation of 1,2‐azolo[1,5‐a]pyridines has been developed. In the process, the fused pyridines react with aryl halides in the presence of the palladium complex Pd(OAc)₂(Phen) as a catalyst and copper(I) chloride (CuCl) as a Lewis acid to form arylated derivatives. While pyrazolo[1,5‐a]pyridines and [1,2,4]triazolo[1,5‐a]pyridines are arylated at ortho‐positions of their pyridine rings using this method, in situ ring‐opening of the formed C‐7 arylated [1,5‐a]pyridine takes place to generate the 2,6‐disubstituted pyridine. Also, upon treatment with lithium diisopropylamide (LDA), C‐7 arylated pyrazolo[1,5‐a]pyridine‐3‐carboxylates react to produce diversely substituted 2,6‐disubstituted pyridines. Finally, a sequential C‐3 arylation was accomplished through a two‐step sequence involving hydrolysis of pyrazolo[1,5‐a]pyridine‐3‐carboxylates followed by the bimetallic Pd/Cu‐catalyzed decarboxylative coupling reaction with aryl bromide.

     

Spin synthesis of monolayer of SiO2 thin films

The highly ordered monolayer of submicron size silica (SiO₂) particles (235 nm) is developed on p-silicon by using three-step spin-coating in colloidal suspension, which has significant potential in various applications. The influence of three-step spin speeds, spinning time, acceleration time between different steps, concentration of SiO₂ particles in the solution, solution quantity, and the ambient humidity (relative humidity) on the properties of monolayer SiO₂ are studied in order to achieve a large area monolayer film. A relatively high surface coverage and uniform monolayer film of SiO₂ particles in the range of 85%-90% are achieved by appropriate control of the preparative parameters. We conclude that this method can be useful in industrial applications, because of the fabrication speed, surface coverage and cost of the process.     

Oriented colloidal-crystal thin films of polystyrene spheres via spin coating

We developed a simple and inexpensive synthesis of a large-scale close-packed monolayer of polystyrene sphere arrays, which have a variety of applications. The influence of three step spin speeds, spinning time, solution quantity and relative humidity is studied in order to achieve a large area close-packed monolayer.A relatively high surface coverage and uniform monolayer of PS spheres in the range of 85%–90% are achieved by appropriate control of the preparative parameters. Also the effect of the oxygen plasma etching process on the reduction of PS spheres has been studied. We conclude that it can be useful in industrial applications, because of the fabrication speed, surface coverage, control over PS spheres and cost of the process.     

Incorporation of postconsumer polyurethane foam into a polymer/clay aerogel matrix

The feasibility of incorporating ground recycled polyurethane (PU) foam into clay/polymer aerogels was demonstrated, and a range of compositions were prepared and characterized to determine the effect of variation in the formulations on density and mechanical properties of the resulting materials. This study followed a modified combinatorial approach. Initially, experiments were performed in water using either sodium exchanged montmorillonite or laponite clay, poly(vinyl alcohol) (PVOH) solution as the polymer binder, and the recycled PU foam. Freezing and freeze‐drying the aqueous gels produced aerogels, which were characterized through density and mechanical testing, scanning electron microscopy, and thermal gravimetric analysis. The study was expanded by exploring alternative binder chemistries, including the use of an alginate polymer in place of the PVOH or adding a polyisocyanate as a crosslinking agent for PVOH. The effect of recycled PU foam content, clay type and level, and binder type and level on the mechanical properties of the aerogels were determined and will be discussed herein. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42586.     

Solid‐State Conversion of Single Crystals: The Principle and the State‐of‐the‐Art

Solid‐state conversion of single crystals from polycrystalline materials has the advantages of cost‐effectiveness, chemical homogeneity, and versatility over the conventional melt growth and solution growth methods, particularly for systems with high melting points, incongruent melting, high reactivity (volatility), and phase transformations at high temperature. Nevertheless, for commercial production, this technique has only been successful in a few limited systems, in particular ferroelectric systems. This is mostly because of the difficulty in controlling the microstructure, particularly suppressing grain growth in the polycrystal during its conversion. This article describes the principle and the current status of the solid‐state conversion of single crystals. We first introduce the recently developed principle of microstructural evolution to explain the basis of the microstructure control in polycrystals for solid‐state conversion. We then report recent technical developments in fabricating single crystals by the solid‐state single crystal growth (SSCG) method and their physical properties. The SSCG method is expected to be studied and utilized more widely in fabricating single crystals with complex compositions as a strong alternative to the melt growth and solution growth methods.