Aluminum hypophosphite in combination with expandable graphite as a novel flame retardant system for rigid polyurethane foams

The main aim of this work was to investigate the synergistic effect of expandable graphite (EG) and aluminum hypophosphite (AHP) on the flame retardancy of rigid polyurethane foams (RPUFs). A series of flame retardant RPUF containing EG and AHP were prepared by one‐shot and free‐rise method. The flame retardant, thermal degradation, and combustion properties of RPUF hybrids were characterized through limiting oxygen index (LOI) test, vertical burning (UL‐94) test, thermogravimetric analysis and microscale combustion calorimeter. The LOI and UL‐94 results showed that the RPUF sample with 10 wt% EG and 5 wt% AHP passed UL‐94 V‐0 rating and reached a relatively high LOI value of 28.5%, which is superior over other EG/AHP ratios in RPUF at the equivalent filler loading. Microscale combustion calorimeter results revealed that the incorporation of EG and AHP into RPUF reduced the peak heat release rate and total heat release, thus decrease the fire risk of RPUF significantly. Incorporation of EG and AHP improved the thermal stability of RPUF as observed from the thermogravimetric analysis results and also enhanced the thermal resistance of char layer at high temperature from scanning electron microscopy and Raman spectroscopy. Moreover, it could be seen from thermogravimetric analysis/infrared spectrometry spectra that the addition of EG and AHP significantly decreased the combustible gaseous products such as hydrocarbons and ethers. Finally, the synergistic mechanism in flame retardancy was discussed and speculated. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and evaluation of PANI/PTT electromagnetic shielding fabric by in-situ chemical polymerization

To prepare the flexible and stretchable electromagnetic shielding (EMS) fabric with environmental stability, this paper uses polytrimethylene terephthalate (PTT) fabric as substrate, the aniline monomer as raw material, hydrochloric acid (HCl) as the doping agent, ammonium persulfate (APS) as the oxidant to produce polyaniline (PANI)/PTT electromagnetic shielding fabric by in-situ chemical polymerization. It studies the influence of APS and HCl concentration on the surface electrical resistance and the absorption loss of electromagnetic shielding fabric. It can be observed that an increasing APS and HCl facilitate the absorption and spread of PANI into PTT fabric to form a conductive network, and improve the absorption loss efficiency, while the excess APS and HCl will hinder the PANI polymerization. The high electrical conductivity and absorption loss of the PANI/PTT fabric are obtained at the concentration of An 0.4 M, APS 0.4 M, HCl 1.25 M, and polymerization reaction time 120 min. Meanwhile, in-situ polymerization of PANI does not introduce new impurities and destroy the molecular structure of PTT.     

TiO2/Fe2O3异质结薄膜的制备及其光电特性的研究

通过水热法成功在FTO上制得Ti O2/Fe2O3异质结薄膜,采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)、紫外-可见吸收光谱(UV-Vis)分析测试手段对样品的形貌和结构进行了表征。结果表明,Ti O2/Fe2O3异质结是由直径约200~300 nm的Ti O2纳米棒镶嵌着Fe2O3纳米颗粒组成。通过光电流测试,证明Ti O2/Fe2O3异质结的可见光光电转换效率相比Ti O2明显提高,并对Ti O2/Fe2O3异质结的光电转换机理进行了分析。     

Effect of ethyl cellulose microencapsulated ammonium polyphosphate on flame retardancy,mechanical and thermal properties of flame retardant poly(butylene succinate) composites

Ethyl cellulose, a widely used bio-degradable shell material, microencapsulated ammonium polyphosphate (MAPP) was added to the bio-degradable poly(butylene succinate) (PBS) to improve its flame retardancy, compatibility, and thermal stability. The MAPP was well characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), water contact angle, and thermogravimetric (TG) analysis. The SEM results indicate the improved dispersion of MAPP into PBS matrix and the formation of the strong interfacial adhesion between MAPP and PBS than APP. With the incorporation of MAPP and char-forming agent into PBS, the limiting oxygen index of the composite was increased to 35.5 %, and the sample can pass the UL-94 V-0 rating, while the un-microencapsulated counterpart cannot reach the rating. The cone calorimeter test showed that the peak heat release rate was decreased by 46.7 % and the burning time was also prolonged compared to the pure PBS. The increased melt flow index and rheology test indicated the increase of viscosity and the improvement of anti-dripping properties. Moreover, the mechanical properties and thermal stability of MAPP composite were also obviously enhanced after the microencapsulation by mechanical, dynamical mechanical thermal analysis, and TG analysis.     

Effect of pyrolysis characteristics on ignition mechanism and NO emission of pulverized coal during oxy-fuel combustion

The effect of pyrolysis behavior on the ignition mechanism was investigated by thermogravimetric technique. The pyrolysis tests show that Datong bituminous coal (DT) pyrolyzes earlier and releases volatiles faster than does Guohua bituminous coal (GH). During oxy-fuel combustion, more volatiles accumulated around DT particles can be ignited easily with increasing oxygen concentration which results in the heterogeneous ignition transforming to homogeneous ignition, while for GH, less volatile is released during devolatilization and the coal particles are more likely ignited heterogeneously. After the transformation of ignition mechanism, the ignition temperature of DT decreases significantly, but the combustibility index S is not appreciably affected. The effect of pyrolysis characteristics on NO emissions was studied by a fixed-bed reactor. It is found that compared to GH, DT released NO more quickly and intensively which leads to more fuel-N converting to NO. With the rise in oxygen concentration, the NO yields of both coals reach the peak values at 40 % oxygen concentration and then decline mainly due to the enhanced homogeneous NO reductions at higher oxygen concentration. With the rise in furnace temperature, the NO yields of coal samples increase first and then decrease with a maximum at 900 °C which is possibly a result of the competing reactions of volatile-N oxidation and reduction in the process of NO formation.     

Preparation and characterization of sulfonated polyimide/TiO2 composite membrane for vanadium redox flow battery

A sulfonated polyimide (SPI)/TiO₂ composite membrane was fabricated by a blend way to improve its performance in vanadium redox flow battery (VRB). Both EDS and XRD results verify the successful preparation of the SPI/TiO₂ composite membrane. The surface SEM image shows its homogeneous structure. TG analysis identifies its thermal stability. The SPI/TiO₂ composite membrane possesses much lower permeability of VO²⁺ ions (2.02?×?10^?7 cm² min^?1) and favorable proton conductivity (3.12?×?10^?2 S cm^?1). The VRB single cell with SPI/TiO₂ composite membrane shows higher coulombic efficiency (93.80–98.00 %) and energy efficiency (83.20–67.61 %) at the current density ranged from 20 to 80 mA cm^?2 compared with that with Nafion 117 membrane. And the operational stability of the as-prepared composite membrane is good after 50 times of cycling tests. Therefore, the low-cost SPI/TiO₂ composite membrane with excellent battery performance exhibits a great potential for application in VRB.     

Zinc‐Catalyzed Borylation of Primary,Secondary and Tertiary Alkyl Halides with Alkoxy Diboron Reagents at Room Temperature

A new catalytic system based on a Zn^II NHC precursor has been developed for the cross‐coupling reaction of alkyl halides with diboron reagents, which represents a novel use of a Group XII catalyst for C? X borylation. This approach gives borylations of unactivated primary, secondary, and tertiary alkyl halides at room temperature to furnish alkyl boronates, with good functional‐group compatibility, under mild conditions. Preliminary mechanistic investigations demonstrated that this borylation reaction seems to involve one‐electron processes.     

Palladium‐Catalyzed Oxidative Carbonylation of N‐Allylamines for the Synthesis of β‐Lactams

β‐Lactam scaffolds are considered to be ideal building blocks for the synthesis of nitrogen‐containing compounds. A new palladium‐catalyzed oxidative carbonylation of N‐allylamines for the synthesis of α‐methylene‐β‐lactams is reported. DFT calculations suggest that the formation of β‐lactams via a four‐membered‐ring transition state is favorable.     

Toehold‐initiated Rolling Circle Amplification for Visualizing Individual MicroRNAs In Situ in Single Cells

The ability to quantitate and visualize microRNAs (miRNAs) in situ in single cells would greatly facilitate the elucidation of miRNA‐mediated regulatory circuits and their disease associations. A toehold‐initiated strand‐displacement process was used to initiate rolling circle amplification of specific miRNAs, an approach that achieves both stringent recognition and in situ amplification of the target miRNA. This assay, termed toehold‐initiated rolling circle amplification (TIRCA), can be utilized to identify miRNAs at physiological temperature with high specificity and to visualize individual miRNAs in situ in single cells within 3 h. TIRCA is a competitive candidate technique for in situ miRNA imaging and may help us to understand the role of miRNAs in cellular processes and human diseases in more detail.     

Magnetic Titanium Dioxide Nanocomposites for Surface‐Enhanced Resonance Raman Spectroscopic Determination and Degradation of Toxic Anilines and Phenols

Mesoporous M‐TiO₂ NCs, functionalized by PATP, can capture toxic anilines and phenols by azo coupling. Loading these nanodevices with Ag NPs offers the possibility for a sensitive quantitative determination of target compounds by SERRS spectroscopy, which allows multiplex detection because of the specific vibrational fingerprints. Sensitivity and selectivity can be further enhanced by concentrating the hybrid particles by an external magnet and compound‐specific binding (anilines versus phenols). The bound toxic compounds can be degraded by TiO₂‐assisted photocatalysis after removal of the loaded hybrid particles from the sample solution with an external magnet. The degradation process can be enhanced in the presence of plasmonic Ag nanostructures.