Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

Pyrolysis characteristics of Oriental white oak: Kinetic study and fast pyrolysis in a fluidized bed with an improved reaction system

The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol^− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil.     

MECHANISMS OF ICE CRYSTALLIZATION AND RECRYSTALLIZATION IN ICE CREAM: A REVIEW

This review article focuses on the mechanisms of ice crystallization and recrystallization and factors that influence them in ice creams. Ice crystallization is an important factor that determines ice cream's final quality. The smaller the ice crystal size is in the final product, the better the quality is. Large ice crystals cause a coarse, grainy, and icy texture in ice cream. The initial ice crystals are formed in the freezer barrel and then grow in size during hardening and storage. Recrystallization during storage is influenced by various factors, including total solids, initial freezing temperature, unfrozen water, stabilizer type, sweetener type, and storage temperature. The roles of these factors, especially stabilizers, are discussed.     

Improvement in CO2 absorption and reduction of absorbent loss in aqueous NH3/triethanolamine/2-amino-2-methyl-1-propanol blends

Changes in the CO₂ absorption rates and capacities of the absorbent 2-amino-2-methyl-1-propanol (AMP), blended with NH₃ and other additives, were investigated toward performance improvement. The NH₃-blended absorbent removed CO₂ more efficiently than the AMP absorbent alone. However, absorbent loss through NH₃ evaporation was observed under these conditions. A second absorbent, the tertiary amine triethanolamine (TEA), which has a low vapor pressure, was selected and blended with the NH₃/AMP system to reduce NH₃ evaporation. Its effects on NH₃ loss and the absorption rate and capacity of the NH₃/AMP system were investigated, and the optimum blending ratios were determined. In addition, the absorbent blend at the optimum blending ratio was compared to AMP alone and the commercially available absorbent monoethanolamine at the same weight ratio. The thermal stabilities of the absorbents, under conditions used in the CO₂ absorption process, were compared by thermogravimetric analysis.     

N-doped anodic titania nanotube arrays for hydrogen production

Titanium dioxide (TiO₂) nanotube arrays are grown in a mixed electrolyte by anodizing process. The anodic nanotubes for N-doping were calcinated at 773 K in a tube furnace with a mixture of NH₃ and Ar gas. The photocatalytic activity of N-doped TiO₂ nanotubes was carried out in a water-splitting reaction under UV and visible light irradiation. Various characterization techniques (Scanning electron microscopy, X-ray diffractometry, X-ray photo-electron spectroscopy, etc.) are used to study the surface morphology, phase of structure, and binding energy.