Phase appearance during polymerization of fluorinated polyimide monomers and deposition into the microscopic‐scale trenches in supercritical carbon dioxide

The phase appearance during the synthesis of fluorinated polyamic acid (PAA) from 2,2‐bis(3,4‐anhydrodicarboxyphenyl)‐hexafluoropropane (6FDA) and 2,2′‐bis(trifluoromethyl)?4,4′‐diaminobiphenyl (TFDB) in supercritical carbon dioxide (scCO₂) was investigated to obtain fundamental data for the deposition of fluorinate polyimides (PI) using scCO₂. All polymerizations were carried out at 30 MPa for 60 min. The experimental temperatures ranged from 50 to 70 °C, and each of the monomer concentrations ranged from 0.67 × 10^?5 to 3.3 × 10^?5 mol cm^?3. The holding time of the transparent phases, which was the time from the beginning of the polymerization to the appearance of a turbid phase, was increased with either a decrease in the polymerization temperature or a decrease in the initial monomer concentration. The holding time of the fluorinated PAA was longer than that of the monomers of Kapton‐type PAA. The deposition of PI into the microscopic‐scale trenches that had formed on the silicon wafer was successful in scCO₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43334.     

Effects of fast noises on long-range correlations

Improvement in time resolution sometimes introduces fast (short-range) random noises into temporal data sequences. These noises affect the results of power-spectrum analyses and the detrended fluctuation analysis (DFA). The DFA is one of useful methods for analyzing long-range correlations in non-stationary sequences. The effects of noises are discussed based on artificial temporal sequences. Short-range noises prevent power-spectrum analyses from detecting long-range correlations. The DFA can extract long-range correlations from noisy time sequences. The DFA also gives the threshold time length, under which the noises dominate.     

Natural Bio-additive Chlorophyll Derivative Enables 17.30% Efficiency Organic Solar Cells

Additive-assisted donor and acceptor domain regulation is regarded as an effective strategy to further release the potential photovoltaic performance of the existing organic solar cells (OSCs). Meanwhile, it is also critical to find high-efficient, stable, non-toxic, and low-cost biological materials as bio-additives to replace the traditional toxic halogen-based additives. In this study, bio-additives derived from a natural chlorophyll pigment named as ZnChl and H₂Chl are employed to optimize the morphology and molecular stack of the PM6:Y6 active layer. The eutectic molecular stack of the blends is more ordered and tighter after introducing the bio-additive chlorophyll derivatives to the system compared to the pristine PM6:Y6 blends. Owing to such a fine-tuned donor-acceptor microstructure network, the photovoltaic performance of the H₂Chl bio-additive-based OSC achieves a 17.30% PCE and ZnChl-based device obtains an efficiency of 16.61%, which is much higher than that of the control device with a 15.97% PCE. The result proves the feasibility of introducing environmental- and eco-friendly chlorophyll derivatives as bio-additives to further improve the photovoltaic performance of the OSCs.     

Detection of Failures around Main Cracks and Their Relation to the Fracture Toughness of Cement Pastes

Fluorescence microscopy examinations revealed the characteristics of crack path and the presence of local failures around the main cracks in hardened cement pastes. Reduction in the water: cement ratio and the addition of silica fume led to a decrease in locally damaged regions around the main cracks. However, the R - curve of the silica fume-free cement paste with the water: cement ratio of 0.55 was much different from that of the silica fume-bearing paste. The silica fume-bearing cement paste exhibited a relatively flat R -curve, whereas reduction in the water: cement ratio in the silica fume-free paste led to a rising R-curve. These results were related to the toughening mechanisms of cement pastes derived from the characteristics of the crack path and the areas of local failures around main cracks that were revealed by fluoresence microscopy. Presumably, these differences in fracture toughness resulted from the nature of hydration products and/or their inherent microstructure.     

Study on polystyrene thin film on glass substrate by scanning acoustic microscope

Acoustic micrograph and V(z) curves of polystyrene thin films on hydrophobic modified and unmodified alumino silicate glass substrates were studied in the frequency range from 170 to 450 MHz by a scanning acoustic microscope. The bright and dark parts in the acoustic micrograph of the unmodified glass samples appeared owing to permeation of water into the film. The blister was observed after about 20 s from dropping water. Sizes of the blister depended on the time and the thickness of thin films. On the other hand, the acoustic micrograph of the hydrophobic modified samples was a uniform image and the peeling of the thin film was not observed. V(z) curves of polystyrene thin film on the modified glass substrates had two oscillation periods in a certain frequency range that depended on the thickness of thin films. The short cycle and the long cycle components were assigned to a leaky surface acoustic wave (LSAW) and a leaky pseudo Sezawa wave, respectively. Velocities of the LSAW decreased linearly with an increase in film thickness.     

Alkali Magnesium/Zinc Silicate Glasses with Low Rayleigh Scattering

The Rayleigh scattering of silicate glasses (M₂O-RO-SiO₂, M: Na and K, R: Mg, Ca, and Zn) was measured. Soda magnesium silicate (NMS) glasses exhibited the smallest scattering intensity. It is comparable with that of soda aluminosilicate (NAS) glass, one of the candidates for use in fabricating ultralow-loss fibers. The scattering intensity decreased with decreasing SiO₂ content, and NMS glasses with 60 mol% of SiO₂ are still stable against crystallization. It is concluded that NMS is a new candidate for ultralowloss fiber use.     

Zero-suppressed BDDs and their applications

In many real-life problems, we are often faced with manipulating sets of combinations. In this article, we study a special type of ordered binary decision diagram (OBDD), called zero-suppressed BDDs (ZBDDs). This data structure represents sets of combinations more efficiently than using original OBDDs. We discuss the basic data structures and algorithms for manipulating ZBDDs in contrast with the original OBDDs. We also present some practical applications of ZBDDs, such as solving combinatorial problems with unate cube set algebra, logic synthesis methods, Petri net processing, etc. We show that a ZBDD is a useful option in OBDD techniques, suitable for a part of the practical applications. Published online: 15 May 2001     

Kinetic study of quenching reactions of singlet oxygen and scavenging reactions of free radicals by α-, β-, λ- and σ-tocopheramines in ethanol solution and micellar dispersion

Quenching reactions of singlet oxygen and scavenging reactions of free radicals by α-, β-, λ- and σ-tocopheramines (Toc-amines) were investigated spectrophotometrically in ethanol and Triton X-100 micellar dispersions. The rate constants of quenching of singlet oxygen (k _Q ) by α-, β-, λ- and σ-Toc-amines increased as the total electron donating capacity of the methyl groups at the aromatic ring increased. A plot of logk _Q vs. peak oxidation potential (E _p) was found to be linear and the slope was negative. Similar results were obtained for scavenging of a phenoxyl radical (PhO.). The results suggest that charge transfer plays an important role in these reactions. Thek _Q values were found to be 1.30–2.57 times as large ask _Q for α-tocopherol (α-Toc). Although α-Toc has the highest antioxidant activity among natural tocopherols and related phenols, Toc-amines also can serve as antioxidants.     

接枝量对等离子体接枝聚异丙基丙烯酰胺开关的多孔膜的温度感应透过性的影响

The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-respousive diffusional permeability through porous membranes with plasma-grafted poly(N-isopropylacrylamide) (PNIPAM)gates was investigated. Both thermo-respousive flat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM were prepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formed homogeneously throughout the entire thickness of both the fiat polyethylene membranes andthe microcapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeability were heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulic permeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size; however, the water flux at 40℃ increases firstly to a peak because of the increase of hydrophobicity of the pore surface, and then decreases and finally tends to zero because of the pore size becoming smaller and smaller. For the diffusional permeability, the temperature shows different effects on the diffusional permeability coefficients of solutes across the membranes. When the graft yield was low, the diffusional coefficient of solute across the membrane was higher at temperature above the lower critical solution temperature (LCST) than that below the LCST; however, when the graft yield was high, the diffusional coefficient was lower at temperature above the LCST than that below the LCST. It is very important to choose or design a proper graft yield of PNIPAM for obtaining a desired thermo-respousive “on/off“ hydraulic or ditfusional permeability.     

Ultraviolet Patterning of Alkoxy-Derived Lithium Niobate Film

Patterned lithium niobate (LN) films were synthesized successfully from a precursor film containing 1-phenyl-1,3-butanedione (PBD) by ultraviolet (UV) irradiation. A LN precursor solution composed of lithium ethoxide and niobium ethoxide was modified with PBD in ethanol to form LiNb(OEt)_{6- n} (PBD) _n , which was designed to have a specific UV absorption at 330 nm. The precursor film began to crystallize at 400°C on sapphire C substrates. The UV absorption band at 330 nm in the precursor film decreased in intensity with increased exposure time to UV light. The patterned LN films crystallized at 550°C on sapphire C substrates showed a (006) preferred orientation.