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Switching interactively between first (L1) and second (L2) languages has been recognized as one of the salient characteristics of L2 writing. However, it is not clear how switching between languages is related to L2 proficiency nor how switching to the L1 assists writers with differing L2 proficiency in their composing processes. The present study investigated these issues with eight adult Chinese-speaking English as a Second Language (ESL) learners with two differing levels of proficiency in English performing two writing tasks: an informal personal letter and an argument essay. Data were the students' think-aloud protocols, retrospective interviews, questionnaires, and written compositions. Quantitative and qualitative analyses of these data show that the participants' frequencies of language-switching varied slightly by their L2 proficiency, suggesting that L2 proficiency might determine writers' approaches and qualities of thinking while composing in their L2.

In this work, two cross‐linked Salen‐based polyphosphazenes (Salen‐PZNs: Salen‐PZN‐1 microspheres and layered Salen‐PZN‐2), which contains Salen‐Schiff base and phosphazene components, were synthesized. The results showed that the peak heat release rate and total smoke production of 3% Salen‐PZN‐1/epoxy resin (EP) (3 wt% addition) were reduced by 23.8% and 87.3%, respectively. Meanwhile, after introducing the layered Salen‐PZN‐2 into EP, efficient flame resistance was obtained. The results of thermogravimetric analysis/infrared spectrometry proved that the harmful gasses of 5% Salen‐PZN‐1/EP composites were reduced during the combustion. The possible flame retardancy mechanism was considered to be the synergy of phosphate group catalysis, release of nitrogen‐containing noncombustible gasses and gas phase quenching. Therefore, this work provides a method for preparing polymers with highly efficient flame‐retardant properties. [ABSTRACT FROM AUTHOR]

Two novel Salen‐DPCPs metal complexes (Salen‐DPCP‐1 and Salen‐DPCP‐2), containing both Salen‐Schiff base (Salen), phenyl phosphate structures (DPCP) and nickel component, were prepared to reduce fire hazards of epoxy resin (EP). The results showed that 5 wt % addition of Salen‐DPCP‐1 brought a higher flame‐retardant efficiency to the EP, where the V‐0 rating in UL‐94 burning test and 31.5% of limiting oxygen index (LOI) were achieved. Meanwhile, total heat release, total smoke production, and total CO yield dramatically decreased by 28.1, 23.6, and 21.4%. In addition, these results basically reappeared when Salen‐DPCP‐2 were introduced into EP to obtain Salen‐DPCP‐2/EP composites. Chemical structure and morphology characterization of the carbon residue confirmed that Salen‐DPCPs improved the catalytic charring ability and the noncombustible gas releasing ability by the Fourier transform infrared, X‐ray photoelectron spectroscopy, and Scanning electron microscopy technology. Therefore, it is an efficient strategy to develop novel Salen composites modified by flame‐retardant groups to improve the fire rating of polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48734. [ABSTRACT FROM AUTHOR]

A novel poly(methyl methacrylate) (PMMA)‐based copolymer (PMMA‐co‐BDPA) rich in aromatic rings was synthesized via radical copolymerization between a phosphorus‐containing acrylic monomer (BDPA) and methyl methacrylate (MMA). UV‐vis spectroscopy demonstrated that the copolymer had high transparency. Thermogravimetric analysis (TGA) and a differential scanning calorimeter (DSC) were used to test the thermal properties of the composites. Additionally, the PMMA‐co‐BDPA‐15 copolymer exhibited a 23% increase in the limited oxygen index (LOI) value. A cone calorimeter test indicated that the peak heat release rate (pk‐HRR) of PMMA‐co‐BDPA was reduced by 29.2% compared with that of pure PMMA, and the carbon yield of burning was obviously increased. The combined test results demonstrated that the prepared copolymer material had good transparency, thermal stability, and flame retardancy. [ABSTRACT FROM AUTHOR]

Using 4,4-diaminodiphenyl methane as a curing agent, three kinds of monomers, 4,4′-dihydroxybenzophenone, diphenyl chlorophosphite and 1,4-phenylene diisocyanate (NCO), were introduced into a thermosetting resin (DGEBA). The flame retardancy properties of the composites were studied, and the results were compared with those of 5 wt% bis(bis(4-((diphenoxyphosphoryl)oxy)phenyl)methyl) 1,4-phenylenedicarbamate (DHPP-OH-NCO), 10 wt% DHPP-OH-NCO and 15 wt% DHPP-OH-NCO curing agents. The results showed that 15 wt% DHPP-OH-NCO had an improved flame retardancy, the limited oxygen index reached 33.5% and the vertical burning test (UL94) achieved a V-0 level. A cone calorimeter experiment showed that the addition of the flame retardant significantly reduced the amount of generated smoke and heat. Macroscopic digital images, scanning electron microscopy images and thermogravimetric analysis results further revealed that the epoxy resin (EP) with DHPP-OH-NCO exhibited greater char yields. The flame retardancy mechanism of the flame retardant was preliminarily shown by pyrolysis–gas chromatography–mass spectrometry analysis. The combined test results demonstrate that a high-efficiency phosphorous-containing flame retardant for EPs was successfully developed. [ABSTRACT FROM AUTHOR]

This paper reviewed the recent research progresses in polymers/graphene, polymers/ modified graphene and polymers/graphene/flame retardant nanocomposites and also introduced their flame retardance mechanisms. The effect of graphene on the mechanical properties of polymers was discussion, and the future development direction in the flame retardancy of polymers with graphene was prospected. [ABSTRACT FROM AUTHOR]

Abstract: A BiFe0.95Mn0.03Zn0.02O3/Bi3.15Nd0.85Ti2.9Zr0.1O12 (BFMZ/BNTZ) heterostructure thin film was prepared on Pt/Ti/SiO2/Si (100) substrate by a chemical solution deposition (CSD) technique. The structural, magnetic, dielectric properties, and leakage current of the BFMZ/BNTZ heterostructure thin film were thoroughly investigated. The analysis of X-ray diffraction (XRD) demonstrated that the BFMZ/BNTZ heterostructure thin film was of a polycrystalline perovskite structure. A slim magnetic hysteresis (M-H) loop for the BFMZ/BNTZ heterostructure thin film was observed. The dielectric constant together with dielectric loss measurement indicates that the BFMZ/BNTZ thin film exhibit a lossy dielectric with an ε r of 60.5 and a tan δ of 0.392 at a frequency of 1MHz. In addition, the leakage current density of BFMZ/BNTZ thin film measured at an applied electric field of 50kV/cm is about 5.65×10−4 A/cm2. [Copyright &y& Elsevier]

Abstract: Bi3.15Nd0.85Ti2.8-xZr0.2MnxO12 (BNTZM) thin films with various Mn content (x=0, 0.005, 0.01, 0.03, and 0.05) have been prepared on Pt/Ti/SiO2/Si (100) substrates by a chemical solution deposition (CSD) technique. The crystal structures of BNTZM thin film have been analyzed by X-ray diffraction (XRD). The dependence of Mn contents on the ferroelectric, dielectric properties, and leakage current of these BNTZM films have been thoroughly investigated. The XRD analysis demonstrated that all the BNTZM thin films were of typical bismuth-layer-structured ferroelectrics (BLSF) polycrystalline structure and exhibited a highly preferred (117) orientation. Among these BNTZM films, the BNTZM thin film with Mn content equal to 0.01 exhibits the maximum remnant polarization (2Pr) of 48μC/cm2 and a low coercive field (2Ec) of 177kV/cm. In addition, the BNTZM thin film with x=0.01 (Mn) showed a fatigue-free behavior up to 1×1010 read/write cycles. [Copyright &y& Elsevier]

Abstract: The Bi3.15Nd0.85Ti3-xZrxO12 (BNTZ) thin films with Zr content (x = 0, 0.05, 0. 1, 0.15, and 0.2) were prepared on Pt/Ti/SiO2/Si (100) substrates by chemical solution deposition (CSD) technique. The crystal structures of BNTZ films were analyzed by X-ray diffraction (XRD). The effects of Zr contents on the ferroelectric, dielectric properties, and leakage current of BNTZ films were thoroughly investigated. The XRD results demonstrated that all the films possessed a single phase bismuth-layered structure and exhibited the highly preferred (117) orientation. Among these films, the film with Zr content x = 0.1 held the maximum remanent polarization (2Pr) of 50.21 μC/cm2 and a low coercive field (2Ec) of 210 kV/cm. [ABSTRACT FROM AUTHOR]