Study on the changing regularity of structure and properties of PC aged outdoor in western areas of China

As an important engineering material, polycarbonate (PC) has been used widely. When exposed to the environment, PC will have aging process, which will reduce its performance and efficiency. This article studies the changing regularities of PCs structure and properties of ageing in western areas of China by measuring the change of intrinsic viscosity (IV), thermal decomposition temperature, glass transition temperature, and the groups within PC. The analysis of its IV, DSC, and thermo gravimetric analysis exhibited the same changing regularity, i.e., the aged PC (in Lasa, Yuli, and Jiangjin) experienced degradation and crosslinking, while degradation occurred earlier in the process of ageing, crosslinking predominated in later period. In addition, the results of UV absorption spectra and infrared absorption spectra showed the evidence of decomposition of the ester groups, resulting in the production of alcohol and phenol. And the results of mechanical tests indicated that the ductility disappeared mainly in the first year of outdoor aging. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of nitrogen-doped porous graphitic carbons using nano-CaCO3 as template,graphitization catalyst,and activating agent

Nitrogen-doped porous graphitic carbons (NPGCs) with controlled structures were synthesized using cheap nano-CaCO₃ as template, melamine-formaldehyde resin as carbon precursor, and dilute HCl as template removing agent. In addition to its use as a template, the nano-CaCO₃ acted as an internal activating agent to produce micro- and mesopores, as an adsorbent to remove the released hazardous gases (i.e. HCN, NH₃), and as a mild graphitization catalyst. The obtained NPGCs with hierarchical nanopores contained as high as 20.9 wt% of nitrogen, had surface areas of up to 834 m² g^–1, and also exhibited high thermal stability with respect to oxidation. Using carbohydrate or phenolic resin as the carbon precursor, this simple approach was also capable of producing hierarchical porous graphitic carbons with high surface area (up to 1683 m² g^–1) and extremely large pore volumes (>6 cm³ g^–1). X-ray diffraction and infrared spectroscopy suggested that the intermediate CaCN₂ or CaC₂ generated during the carbonization plays a critical role in the formation of the graphitic structure.     

Preparation and characterization of electrospun polyurethane/inorganic‐particles nanofibers

To develop a novel functional fibrous scaffold, a blend‐electrospinning technique was applied to transfer polyurethane/inorganic‐particles solutions into nanofibers, in which titanium dioxide, copper, or/and silver nanoparticles were used. The resultant nanofibers were subsequently characterized by means of scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and tensile mechanical test. Furthermore, the structural change and the thermal properties of the electrospun fabrics were examined by X‐ray diffraction and differential scanning calorimetry, respectively. Antibacterial performance of the resulting nanofibrous mats on Escherichia coli and Staphylococcus aureus was also measured. Experimental results have shown that when the ratio of polyurethane solution and titanium dioxide sol was in 3.5:1, 89.55% of the Escherichia coli and 82.35% of the Staphylococcus aureus bacteria were killed under a UV‐light activation. However, the introduction of silver or/and cuprum nanoparticles into the polyurethane/TiO₂ (in the ratio of 3.5:1) nanofibers led to a significant improvement in their antibacterial ability without any photocatalysis.POLYM. COMPOS., 33:2045–2057, 2012. © 2012 Society of Plastics Engineers     

Bismuth-catalyzed synthesis of ZnO nanowires and their photoluminescence properties

By means of heating a mixture of Zn and Bi powders, we have successfully prepared ZnO nanowires. Since the produced nanowires correspond to the pure hexagonal ZnO phase with no catalytic nanoparticles being observed at the tips, the growth is dominated by the base-growth mechanism, in which Bi species at the bottom of the nanowires played a catalytic role. Photoluminescence (PL) analysis of indicated that the integrated intensity ratio of the 2.5 eV-band to the UV band increased with increased growth temperature. An increase of the Bi₂O₃ phase itself, Bi₂O₃ phase-induced oxygen vacancies, and an increase of oxygen vacancies in ZnO with increasing growth temperature were responsible for the intensification and the appearance of the 2.5 eV-band.     

Effect of electrode and substrate on the fatigue behavior of PZT thick films fabricated by aerosol deposition

10 μm-thick lead zirconate titanate (PZT) films with identical LaNiO₃ (LNO) top and bottom electrodes were fabricated on silicon and yttria-stabilized zirconia (YSZ) substrates by aerosol deposition (AD). A Pt electrode was also made for comparison. The dielectric, ferroelectric and fatigue behaviors at different fields were investigated. The PZT films on YSZ/LNO showed the highest dielectric and ferroelectric properties and good fatigue behavior under various fields. PZT films with a Pt electrode also showed good fatigue behavior up to 10⁸ cycles as thicker film can minimize the effect of defect entrapment near the interface.     

Crystal phases and electric properties of (Na0.5K0.5)1−xNb1+x/5O3:yCuO,zLiSbO3 piezoceramics

In this study the electric property and the formation of crystal phases are characterized along with the increase of the A-site alkali deficiency(x) in the non-stoichiometric (Na_0.5K_0.5)_1?xNb_1+x/5O₃:yCuO + zLiSbO₃ (x = ?0.01 to 0.1; y = 0, 0.01; z = 0, 0.05) ceramics. Quantitative crystal phase analysis has been carried out using Rietveld method. The crystal structure of tetragonal tungstenbronze phase is discussed in relation with the P–E hysteresis and dielectric properties. The stoichiometric and the slightly alkali deficient samples show very leaky P–E loop. With increasing the alkali deficiency the electrical leakage decreases and the P–E loop shows the saturation. CuO and LiSbO₃ doping in the alkali deficient sample (x = 0.05, y = 0.01, z = 0) leads to the slim and pinched P–E loop shape. By CuO doping the P_r and P_s decreases to 13.9 and 20.87 μC/cm² from 25.6 and 27.2 μC/cm², respectively.     

Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Carbon nanotube reinforced bioglass composites have been successfully synthesized by two comparative sintering techniques, i.e., spark plasma sintering (SPS) and conventional compaction and sinteirng. The composites show improved mechanical properties, with SPS technique substantially better than conventional compact and sintering approach. Using SPS, compared with the 45S5Bioglass matrix, the maximum flexural strength and fracture toughness increased by 159% and 105%, respectively. Enhanced strength and toughness are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and bioglass powders during crack propagations.     

Sugar recovery from rice straw by dilute acid pretreatment

Rice straw was pretreated with dilute sulfuric acid in order to decrease the amorphous portion and enhance enzyme accessibility. Dilute acid pretreatment process was optimized using a statistical method, and the relationships between each factor were investigated. Saccharification of pretreated rice straw was then performed, followed by fermentation of glucose, the hydrolysate of the saccharification process. The optimal dilute acid pretreatment process was as follows: temperature 110 °C, reaction time 14.02 min, and acid concentration 1.2%. Following dilute acid pretreatment, the solid weight was decreased by about 20% and 73.14% of the theoretical maximum content of xylose was solubilized. Glucose was recovered at a rate of about 90% at 24 h after rice straw was treated with dilute acid. Qualitative analysis such as SEM, XRD, and FT-IR were conducted after the pretreatment process, and the results supported the pretreatment process.     

Phase separation induced ordered patterns in thin polymer blend films

Strategies for the utilization of phase separation to generate ordered pattern in polymer thin film are reviewed. First, the fundamental theory and factors influencing phase separation in polymer thin film are discussed. That is followed by a discussion of the formation of ordered patterns induced by phase separation in polymer thin films under the influence of a chemical heterogeneous substrate, convection or breath figures. The mechanisms and the conditions for well-ordered structures generated by phase separation are then discussed to show that multi-scaled/multi-component patterns, stimuli-responsive patterns may be developed by controlling the preparation conditions or exposing the sample to different environments more complex structures. Finally, applications of fabricated patterns in pattern generation and reproduction, antireflecting coating, catalysis, bio-chips and optoelectronics are also discussed.     

Structural characterization and computer-aided optimization of a small-molecule inhibitor of the Arp2/3 complex, a key regulator of the actin cytoskeleton

CK-666 (1) is a recently discovered small-molecule inhibitor of the actin-related protein 2/3 (Arp2/3) complex, a key actin cytoskeleton regulator with roles in bacterial pathogenesis and cancer cell motility. Although 1 is commercially available, the crystal structure of Arp2/3 complex with 1 bound has not been reported, making its mechanism of action uncertain. Furthermore, its relatively low potency increases its potential for off-target effects in vivo, complicating interpretation of its influence in cell biological studies and precluding its clinical use. Herein we report the crystal structure of 1 bound to Arp2/3 complex, which reveals that 1 binds between the Arp2 and Arp3 subunits to stabilize the inactive conformation of the complex. Based on the crystal structure, we used computational docking and free-energy perturbation calculations of monosubstituted derivatives of 1 to guide optimization efforts. Biochemical assays of ten newly synthesized compounds led to the identification of compound 2, which exhibits a threefold increase in inhibitory activity in vitro relative to 1. In addition, our computational analyses unveiled a surface groove at the interface of the Arp2 and Arp3 subunits that can be exploited for additional structure-based optimization.