Polymer materials are widely used in daily life, but the flammability of most polymers has greatly restricted their applications. The addition of flame retardants into polymer matrix to form composites is the most eff...
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Polymer materials are widely used in daily life, but the flammability of most polymers has greatly restricted their applications. The addition of flame retardants into polymer matrix to form composites is the most effective method to improve the flame retarding properties. Here, a novel flame retarding composite is reported from polydopamine (PdA) and polystyrene (PS) through a latex technique. To maximize the potential of PdA in improving the properties of composites, PdA layers are first coated on PS microspheres and then the PdA coated PS microspheres are hot pressed to afford PdA/PS composites. Morphological characterizations of the cross sections of composites and the char after burning demonstrate the formation of three-dimensional continuous network of PdA layers inside PS matrix, while differential scanning calorimetry, thermogravimetric analysis, tensile test, and cone calorimeter test confirm the visibly enhanced thermal, mechanical, and flame retarding properties of composites as compared to neat PS. These improvements are attributed to the strong interfacial interactions between PdA and PS, physical barrier effect of continuous PdA layers, and good free-radical scavenging ability of PdA. This work demonstrates the great potential of PdA as additive for green and facile construction of flame retarding composites. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47740.
developing high-strength Al-(La,Ce)alloys for additive manufacturing(AM)would entail considerable economic *** this work,a novel near-eutectic Al-La alloy containing 5.50 wt.%Mg and 0.60 wt.%Mn was designed and fabric...
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developing high-strength Al-(La,Ce)alloys for additive manufacturing(AM)would entail considerable economic *** this work,a novel near-eutectic Al-La alloy containing 5.50 wt.%Mg and 0.60 wt.%Mn was designed and fabricated via selective laser melting(SLM).Submicron Al_(11)La_(3)intermetallics with 3dcontinuous cellular-dendritic and granular morphologies were observed at the interior and boundary of the melt pool,***,these intermetallics are hierarchical and contained numerous Al_(6)Mn and Mg_(2)Si secondary *** as-fabricated alloy exhibited a tensile yield strength(YS)of 334 MPa and ultimate tensile strength(UTS)of 588 MPa at room temperature,which is the high-est UTS reported for Al-(La,Ce)alloys with an appreciable failure strain of∼6.4%.The 3dcontinuous cellular dendritic intermetallic and high Mg content afford significant strengthening and work harden-ing *** addition,the hierarchical feature of the intermetallics generated additional microcracks to coordinate the deformation.
A new strategy for improving high-temperature compressive strength and tribological properties of Al2O3/Cr2O3 composites was proposed in this study. The three-dimensional (3d) continuous Al2O3 ceramic matrix containin...
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A new strategy for improving high-temperature compressive strength and tribological properties of Al2O3/Cr2O3 composites was proposed in this study. The three-dimensional (3d) continuous Al2O3 ceramic matrix containing Cr2O3 particles was fabricated, and the influencing mechanisms of compositions andstructures on the anti-wear and friction-reducing performance of composites at high temperature were revealed. Results show that the enrichment degree of Cr2O3 in the composites can be significantly improved based on the 3d continuous structuredesign compared with Al2O3/Cr2O3 composite containing uniform compositions. Under friction conditions, the Cr2O3 phase with large enrichment degree can preferentially contact with the micro-asperities on the friction pair surface under the action of grain refinement at high temperature, so that the softened Cr2O3 is easy to be sheared anddragged to the worn surfaces of the friction couples to form the friction film and transfer film. Meanwhile, under the favorable effect of the high load-carrying capacity of continuous Al2O3 matrix, Al2O3/Cr2O3 composites show excellent tribological properties at high temperature. The friction coefficient and wear rate of Al2O3/Cr2O3 composites with 3d continuous structure sliding against Al2O3 pin can be reduced to 0.35 and 2.2 x 10(-6)mm(3).N(-1)m(-1) at 800 degrees C, and it still presents excellent friction-reducing and anti-wear properties at 1000 degrees C. (C) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-Nd license (http://***/licenses/by-nc-nd/4.0/).
ZrO2(Y2O3)-graphite composites with a three-dimensional (3d) continuousstructure were prepared by using a core-shell design of graphite and ZrO2(Y2O3). The effect of structure on the friction-reducing and anti-wear m...
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ZrO2(Y2O3)-graphite composites with a three-dimensional (3d) continuousstructure were prepared by using a core-shell design of graphite and ZrO2(Y2O3). The effect of structure on the friction-reducing and anti-wear mechanisms from room temperature to 700 degrees C was investigated. during high-temperature friction, abrasive wear and brittle fracture are the main wear mechanisms for ZrO2(Y2O3)-graphite composites with homogeneous composition. For the composites with 3dstructure, the continuous ZrO2 matrix with high load-carrying capacity and the formation of a dense friction layer with self-lubricating and thermal oxidation resistance improve the tribological properties significantly, reducing the coefficient of friction by about 10% and the wear rate by nearly two orders of magnitude when coupled with GH4169 alloys at 600 degrees C.
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