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The processing map of Mo-Nb single crystals was established on the base of Prasad instability. The hot deformation behavior of Mo-Nb single crystals has been characterized through stress-strain curves and processing map in the temperature range of 1100∼1300 °C and strain rate range of 0.001∼10 s−1. The results indicate that the flow stress is affected significantly by deformation temperature and strain rate during the hot deformation of Mo-Nb single crystals. Based on the processing map, the optimum condition for hot deformation of Mo-Nb single crystals is in the region of high temperatures (>1190 °C) and high strain rates (>3.16 s−1). Microstructure observation of deformed specimens at different deforming conditions shows that lots of orthogonal cracks, which result from the movement of dislocations along with the glide planes, are observed in specimens deformed at 1100 °C/0.01 s−1 and 1150 °C/10 s−1. Less cracks can be observed in specimens deformed at 1250 °C/0.01 s−1, and few cracks are found in specimens deformed at 1300 °C/10 s−1. The XRD result shows that the specimen deformed at 1300 °C/10 s−1 retains single crystal structure, indicating that the specimen does not undergo instability of flow during hot deformation, which are in good agreement with the results of Mo-Nb single crystals predicted from processing map.

The load-displacement curves, elastic modulus, indent morphology, nanohardness and elastic recovery of high purity tungsten single crystal were investigated by nanoindentation and scanning probe microscopy. Results show that W (111) crystal plane undergoes elastic deformation and plastic deformation during the loading-unloading process, and the load-displacement curve does not show discontinuity, which demonstrates that cracks and brittle fracture are not formed in the indents. Moreover, the pile-up behavior around indents reveals that tungsten single crystal has a low work hardening tend. The nanohardness and elastic modulus of tungsten single crystal were measured by continuous stiffness measurement (CSM), and a size effect on the nanohardness and elastic modulus of tungsten single crystal was observed, which decrease with the increase of indentation depth. The Nix-Gao model was employed to analyze the nanoindentation mechanical characteristics of tungsten single crystals, and the characteristic length (h*), the intrinsic hardness in the limit of infinite depth (H0) and size effect index (m) were calculated to be 1490 nm, 6.79 GPa and 0.18, respectively, which indicates that tungsten single crystal has a significant size effect when the indentation depth is below 1490 nm, and the size effect becomes more insignificant when indentation depth is above 1490 nm. When the impression is deeper than 2450 nm, the nanoindentation size effect on the hardness will disappear.

Chemical grafting and pad-dry physical treatment with maleic anhydride (MA) and 2-hydroxyethyl methacrylate (HEMA) were employed to improve the fire resistance of polyamide 66 (PA 66) fabric, respectively. The flammability characterization demonstrated that chemical grafting could improve the antidripping property of the fabric by the elimination of the melting process which resulted from the so-called “scaffolding effect” during combustion. Pad-dry physical treatment improved the fire performance (including antidripping tendency) of PA 66 fabric through notable molten contraction which could keep the fabric away from the igniting source. It has been suggested that the premature decomposition of the monomers/graft chains can remove the heat from the fiber and delay the further decomposition of the substrate. The chemical grafting significantly improved the hydrophilicity of the samples, while the physical treatment decreased the hydrophilicity of PA 66 samples.

The novel phosphorus/nitrogen-containing flame retardant hexa(phosphaphenanthrene aminophenoxyl)cyclotriphosphazene (HPAPC), which contains phosphaphenanthrene [9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO)] and phosphazene (hexachlorocyclotriphosphazene) groups, was synthesized by the classic Atherton–Todd reaction, and its chemical structure was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. Poly(lactic acid) (PLA) composites containing HPAPC were prepared by melt blending, and their fire performance and thermal behaviors were investigated in terms of limiting oxygen index (LOI), vertical burning (UL-94), cone calorimeter tests, and thermogravimetric analysis (TGA). The LOI value could reach up to 34.7%, and UL-94 could pass V-0 for the PLA composite containing only 5 wt % HPAPC. TGA results showed that the char formation of PLA could be significantly improved by the presence of HPAPC. The evolved gas of the composite was analyzed by F...

Rutile-type TiO 2 (r-TiO 2 ) or anatase-type TiO 2 (a-TiO 2 ) in association with a conventional intumescent flame retardant system which contains ammonium polyphosphate/pentaerythritol/melamine (APP–PER–MEL) was introduced to silicone-acrylate coatings to improve the fire resistance. The effect of TiO 2 on the fire-resistance and thermal properties of APP–PER–MEL coating has been investigated by using big panel method and thermogravimetry (TG). The limit of fire-resistance of the sample containing 30 phr rutile-type TiO 2 (73 min) is much longer than that of the sample containing 30 phr anatase-type TiO 2 (34 min). The morphology and structure of charring layers were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The relationship between charring process and melt flow rate (MFR) of silicone-acrylate was also discussed. It is suggested that MFR value can significantly affect the formation of char, and a moderate silicone-acrylate MFR is required to form good quality char.

Kaolin clay was introduced into an intumescent flame retardant (IFR) system containing ammonium polyphosphate as an acid source and pentaerythritol as a carbonization agent in order to improve the thermal stability and flame retardancy of polypropylene (PP) composite. The flame retardancy and smoke suppression was evaluated by the limiting oxygen index, vertical burning UL-94, and cone calorimeter (CONE) tests. The limiting oxygen index value was increased from 30 to 33 at the presence of 2 phr kaolin. The peak heat release rate value decreased from 1002 kW/m2 of neat PP to 318 kW/m2 of PP/40 phr IFR and then to 222 kW/m2 of PP/38 phr IFR/2 phr kaolin. The time of the peak heat release rate was significantly prolonged after the introduction of kaolin. The morphology of char after combustion was characterized by a scanning electron microscope, and it revealed more compact char structure that was obtained at the presence of kaolin. The mechanism of kaolin on improving the retardancy and smoke suppression of PP/IFR composite was proposed on the basis of X-ray photoelectron spectroscopy analysis. Copyright © 2014 John Wiley & Sons, Ltd.

Microwave induced surface modification was used in grafting 2-hydroxyethyl methacrylate (HEMA) onto polyamide 66 (PA 66) fabric in order to improve its hydrophilicity and fire performance. Effects of reaction time, reaction temperature, initiator concentration and monomer concentration on the percentage of grafting (PG%) were investigated. It showed that the optimal reaction conditions were as follows: the reaction time was 60 min, the reaction temperature was 80°C, the initiator concentration was 0.5 wt.%, and the monomer concentration was 5 wt.%. The possible grafting mechanism was proposed and described. The chemical structure of grafted PA 66 fabric was characterized by attenuated total reflection infrared spectroscopy (ATR-FTIR), 13C nuclear magnetic resonance spectroscopy (13C NMR), and scanning electron microscopy (SEM). The results demonstrated that HEMA incorporated on the alkyl carbon site near amino-group of PA 66 chain through covalent bonds. Thermal behavior analysis indicated that the grafting treatment could decrease the decomposition temperature and increase the amount of char residue. The hydrophilicity of PA 66 fabric was also improved by the grafting treatment. The fire performance test showed that the limit oxygen index (LOI) values were decreased slightly, while the dripping tendency was reduced significantly. The mechanical property analysis showed that the elongation at break increased from 23.5% to 43.8%.