Baokang Dang

Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

Bio-Inspired nacre-like nanolignocellulose-poly (vinyl alcohol)-TiO 2 composite with superior mechanical and photocatalytic properties

Nacre, the gold standard for biomimicry, provides an excellent example and guideline for assembling high-performance composites. Inspired by the layered structure and extraordinary strength and toughness of natural nacre, nacre-like nanolignocellulose/poly (vinyl alcohol)/TiO2 composites possessed the similar layered structure of natural nacre were constructed through hot-pressing process. Poly (vinyl alcohol) and TiO2 nanoparticles have been used as nanofillers to improve the mechanical performance and synchronously endow the superior photocatalytic activity of the composites. This research would be provided a promising candidate for the photooxidation of volatile organic compounds also combined with outstanding mechanical property.

Cellulose Fibers Constructed Convenient Recyclable 3D Graphene-Formicary-like δ-Bi2O3 Aerogels for the Selective Capture of Iodide

Radioiodine is highly radioactive and acutely toxic, which can be a serious health threat, and requires effective control. To fully utilize an adsorbent and reduce the overall production cost, successive recycling applications become necessary. Here, 3D formicary-like δ-Bi2O3 (FL-δ-Bi2O3) aerogel adsorbents were synthesized using a one-pot hydrothermal method. In this hybrid structure, abundant flowerlike δ-Bi2O3 (MR-δ-Bi2O3) microspheres were inlaid into the interconnected ant nest channel, forming a 3D hierarchical structure, which is applied as an efficient adsorbent with easy recovery for radioiodine removal. Notably, the FL-δ-Bi2O3 aerogel adsorbent exhibited a very high uptake capacity of 2.04 mmol/g by forming an insoluble Bi4I2O5 phase. Moreover, the FL-δ-Bi2O3 worked in a wide pH range of 4-10 and displayed fast uptake kinetics and excellent selectivity due to the 3D porous interconnected network and larger specific surface area. Importantly, the recycling process is easy, using only tweezers to directly move the 3D aerogel adsorbents from one reaction system to another. Therefore, the FL-δ-Bi2O3 aerogel may be a promising practical adsorbent for the selective capture of radioactive iodide.

Fabrication of a Nano-ZnO/Polyethylene/Wood-Fiber Composite with Enhanced Microwave Absorption and Photocatalytic Activity via a Facile Hot-Press Method

A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were dispersed on the wood fibers’ surface through a viscous cationic polyacrylamide (CPAM) solution. The reflection loss (RL) value of the resulting composite was −21 dB, with a thickness of 3.5 mm in the frequency of 17.17 GHz. The PE/ZnO/wood-fiber (PZW) composite exhibited superior photocatalytic activity (84% methyl orange degradation within 300 min) under UV light irradiation. ZnO nanoparticels (NPs) increased the storage modulus of the PZW composite, and the damping factor was transferred to the higher temperature region. The PZW composite exhibited the maximum flexural strength of 58 MPa and a modulus of elasticity (MOE) of 9625 MPa. Meanwhile, it also displayed dimensional stability (thickness swelling value of 9%).

Effect of carbon fiber addition on the electromagnetic shielding properties of carbon fiber/polyacrylamide/wood based fiberboards

Carbon fiber (CF) reinforced polyacrylamide/wood fiber composite boards are fabricated by mechanical grind-assisted hot-pressing, and are used for electromagnetic interference (EMI) shielding. CF with an average diameter of 150 nm is distributed on wood fiber, which is then encased by polyacrylamide. The CF/polyacrylamide/wood fiber (CPW) composite exhibits an optimal EMI shielding effectiveness (SE) of 41.03 dB compared to that of polyacrylamide/wood fiber composite (0.41 dB), which meets the requirements of commercial merchandise. Meanwhile, the CPW composite also shows high mechanical strength. The maximum modulus of rupture (MOR) and modulus of elasticity (MOE) of CPW composites are 39.52 MPa and 5823.15 MPa, respectively. The MOR and MOE of CPW composites increased by 38% and 96%, respectively, compared to that of polyacrylamide/wood fiber composite (28.64 and 2967.35 MPa).

Preparation of High Mechanical Performance Nano-Fe3O4/Wood Fiber Binderless Composite Boards for Electromagnetic Absorption via a Facile and Green Method

Fe3O4/wood fiber composites are prepared with a green mechanical method using only distilled water as a solvent without any chemical agents, and then a binderless composite board with high mechanical properties is obtained via a hot-press for electromagnetic (EM) absorption. The fibers are connected by hydrogen bonds after being mechanically pretreated, and Fe3O4 nanoparticles (NPs) are attached to the fiber surface through physical adsorption. The composite board is bonded by an adhesive, which is provided by the reaction of fiber composition under high temperature and pressure. The Nano-Fe3O4/Fiber (NFF) binderless composite board shows remarkable microwave absorption properties and high mechanical strength. The optional reflection loss (RL) of the as-prepared binderless composite board is −31.90 dB. The bending strength of the NFF binderless composite board is 36.36 MPa with the addition of 6% nano-Fe3O4, the modulus of elasticity (MOE) is 6842.16 MPa, and the internal bond (IB) strength is 0.81 MPa. These results demonstrate that magnetic nanoparticles are deposited in binderless composite board by hot pressing, which is the easiest way to produce high mechanical strength and EM absorbers.

Ultrafine Mn ferrite by anchoring in a cellulose framework for efficient toxic ions capture and fast water/oil separation

The serious agglomeration phenomenon of ultrafine nanoparticles is widespread, resulting in low utilization and poor performance of adsorbents in the scavenging of toxic ions. Herein, ultrafine MnFe2O4 (8-13 nm) are uniformly anchored onto the cellulose framework by fast hydrothermal and freeze-drying processes. The as-prepared super-hydrophilic MnFe2O4/cellulose aerogel (MCA) had a three-dimensional (3D) network structure with interconnected and forked fibrils, developed porous structure and high surface area. Combined with the adsorption-aggregation effect of cellulose and high surface activity of the low agglomerated ultrafine MnFe2O4, the adsorption efficiency of MCA was strongly improved and thus achieved a higher utilization. To enable its further use in a hostile environment for the treatment of severe oil pollution, FAS-17 was used to modify the MnFe2O4/cellulose aerogel (F-MCA) for achieving full utilization of their intrinsic structural features. The lipophilic F-MCA exhibited a large bearing capacity on the water and fast adsorption performance for oils/organic solvents.

The properties of fibreboard based on nanolignocelluloses/CaCO 3 /PMMA composite synthesized through mechano-chemical method

The purpose of this study was to develop a rapid and green method for the synthesis of lignocelluloses-based materials with superior mechanical properties. Samples were produced by hot-pressed method using different concentrations of CaCO3 and poly (methyl methacrylate) particles-filled nanolignocelluloses composites which was synthesized through mechano-chemical method. Poly (methyl methacrylate) and CaCO3 nanoparticles have been used as nanofillers. Bending strength, elasticity modulus, and dimensional stability, thermal properties of the developed lignocelluloses-based composites were determined. In view of the experimental results, it is found that the composites materials have good mechanical, dimensional stability, and thermal properties which enhanced as the filler loading increased. Thus, herein described lignocelluloses-based materials showed important characteristics to be concluded that these composites are suitable to be used for the design of flooring and construction systems.

Author Correction: The properties of fibreboard based on nanolignocelluloses/CaCO 3 /PMMA composite synthesized through mechano-chemical method

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High Mechanical Property of Laminated Electromechanical Sensors by Carbonized Nanolignocellulose/Graphene Composites

Although widely used in nanocomposites, the effect of embedding graphene in carbonized nanolignocellulose substrates is less clear. We added graphene to a carbonized nanolignocellulose to change its mechanical and electromechanical properties. Here, the laminated carbonized nanolignocellulose/graphene composites were fabricated by carbonizing the nanolignocellulose/graphene composites prepared through mechanochemistry and flow-directed assembly process. The resulting composites exhibit excellent mechanical property with the ultimate bending strength of 25.6 ± 4.2 MPa. It is observed reversible electrical resistance change in these composites with strain, which is associated with the tunneling conduction model. This type of high-strength conductive composite has great potential applications in load-bearing electromechanical sensors.