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Zirconia‐toughened alumina (ZTA) ceramics with high mechanical properties were sintered by hot‐pressing method using SiC particles (SiCp) and SiC whiskers (SiCw) as the reinforcing agents simultaneously. The influences of sintering temperature, SiCp, and SiCw contents on the microstructure and mechanical properties of ZTA ceramics were investigated. It was found that both SiCp and SiCw could contribute to grain refinement significantly and promote the mechanical properties of the ceramics. However, the excess addition of SiCp or SiCw led to the formation of pores with large sizes and degraded the mechanical properties instead. When 13 wt% SiCp was introduced, the maximum flexural strength of 1180.0 MPa and fracture toughness of 15.9 MPa·m1/2 were obtained, whereas the maximum flexural strength of 1314.0 MPa and fracture toughness of 14.7 MPa·m1/2 were achieved at 20 wt% SiCw. Interestingly, the simultaneous addition of SiCp and SiCw could further improve the mechanical properties, and the highest flexural strength of 1334.0 MPa and fracture toughness of 16.0 MPa·m1/2 were achieved at a SiCw/SiCp ratio of 16/4. The reinforcement mechanisms in the ceramics mainly included the phase transformation toughening of ZrO2, the crack deflection and bridging of SiCp and SiCw, and the pull‐out of SiCw. [ABSTRACT FROM AUTHOR]

Rubber blends are widely used for combining the advantages of each rubber component. However, to date, how to determine and distinguish the vulcanization kinetics for each single rubber phase in rubber blends during the co‐vulcanization process is still a challenge. Herein, high‐resolution pyrolysis gas chromatography–mass spectrometry (HR PyGC‐MS) was employed for the first time to investigate the vulcanization kinetics of natural rubber (NR) and styrene–butadiene rubber (SBR) in NR/SBR blends filled with modified silica (SiO2). The reaction rates of crosslinking of each rubber phase in NR/SBR were calculated, which showed that the crosslinking rates of NR were much lower than those of SBR phase in the unfilled blends and blends filled with unmodified and silane modified silica. Interestingly, the vulcanization rates of NR and SBR phase were approximately same in the vulcanization accelerator modified silica filled blends, showing better co‐vulcanization. In addition, the vulcanization accelerator modified silica was uniformly dispersed and endowed rubber blends with higher mechanical strength compared to the untreated silica. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48838. [ABSTRACT FROM AUTHOR]

Recycling of waste printed circuit boards nonmetallic powders (WPCBPs), as one of the significant challenges for sustainable development of resources, has attracted tremendous attentions from scientific and industrial researchers. In this work, the feasibility of WPCBP as curing accelerator and reinforcing filler in styrene‐butadiene rubber (SBR) composites was first explored. Vulcanization parameters and kinetics of SBR compounds were systematically investigated by moving‐die rheometer and differential scanning calorimeter. The results suggested that the incorporation of WPCBP can effectively reduce vulcanization activation energy and shorten the manufacturing cycle of SBR/SiO2 composites, which may be attributed to the activation effect from metal oxide and accelerating effect from residual additives in WPCBP. On the other hand, the coupling interfacial interactions of rubber‐SiO2 and rubber‐WPCBP result in simultaneous enhancements of tensile strength, tensile modulus, and extensibility of SBR/SiO2/WPCBP composites. Moreover, the potential applications and challenges of SBR/SiO2/WPCBP composites were also briefly analyzed. This work offers a green and efficient reutilization approach of WPCBP in elastomer composites, which may be a valuable inspiration for the high‐valued utilization of WPCBP and the preparation of high‐performance and low‐cost elastomer composites. [ABSTRACT FROM AUTHOR]

In this study, mullite–zirconia (ZrO 2 ) composites were fabricated by hot pressing sintering method. The effects of sintering temperature and holding time on the microstructures, phase compositions and mechanical properties of the composites were investigated. The results indicated that the size of t-ZrO 2 grain varies with sintering temperature and holding time, and the maximum flexural strength of 674.05 MPa and fracture toughness of 12.08 MPa   m 1/2 are obtained when the sintering temperature is 1500 °C with holding times of 20 and 60 min, respectively. Finite element method was employed to analyze the relationship between grain size and mechanical properties of mullite–ZrO 2 composites for the first time. The results showed that the maximum stress on mullite–ZrO 2 interface increases with the growth of t-ZrO 2 grain size, which enhances the generation and propagation of cracks on grain boundaries significantly and degrades the flexural strength and fracture toughness of the mullite–ZrO 2 composite ceramics. [ABSTRACT FROM AUTHOR]

In recent years, much progress has been made on the development of aerospace materials for structural and engine applications. Alloys, such as Al-based alloys, Mg-based alloys, Ti-based alloys, and Ni-based alloys, are developed for aerospace industry with outstanding advantages. Composite materials, the innovative materials, are taking more and more important roles in aircrafts. However, recent aerospace materials still face some major challenges, such as insufficient mechanical properties, fretting wear, stress corrosion cracking, and corrosion. Consequently, extensive studies have been conducted to develop the next generation aerospace materials with superior mechanical performance and corrosion resistance to achieve improvements in both performance and life cycle cost. This review focuses on the following topics: (1) materials requirements in design of aircraft structures and engines, (2) recent advances in the development of aerospace materials, (3) challenges faced by recent aerospace materials, and (4) future trends in aerospace materials. [ABSTRACT FROM AUTHOR]

ABSTRACT Epoxidized natural rubber (ENR)-silica hybrids without any other additives were prepared by an open-mill mixing method at room temperature. The curing characteristics, crosslinking density, mechanical properties, and dynamical mechanical properties were investigated. The results indicate that the ENR-silica hybrid materials could be cured with silica as a crosslinking and reinforcing agent. Attenuated total reflection-Fourier transform infrared spectroscopy and solid-state 13C-NMR spectroscopy exposed the characteristics of the interfacial interaction in the hybrids and confirmed the existence of chemical bonds and hydrogen bonds between the epoxy group and SiOH. Scanning electron microscopy illustrated a good dispersion of silica in the ENR matrix. Meanwhile, the modulus at 100% elongation of the hybrid reached 9.64 MPa when 100-phr silica was loaded; a similar trend was observed for the hardness. Finally, our findings might extend the concept of rubber curing and open a new space for making an environmentally friendly rubber composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44605. [ABSTRACT FROM AUTHOR]

In recent years, much progress has been made on the development of biodegradable magnesium alloys as “smart” implants in cardiovascular and orthopedic applications. Mg-based alloys as biodegradable implants have outstanding advantages over Fe-based and Zn-based ones. However, the extensive applications of Mg-based alloys are still inhibited mainly by their high degradation rates and consequent loss in mechanical integrity. Consequently, extensive studies have been conducted to develop Mg-based alloys with superior mechanical and corrosion performance. This review focuses on the following topics: (i) the design criteria of biodegradable materials; (ii) alloy development strategy; (iii) in vitro performances of currently developed Mg-based alloys; and (iv) in vivo performances of currently developed Mg-based implants, especially Mg-based alloys under clinical trials. [ABSTRACT FROM AUTHOR]

Mollusk shells have highly complex hierarchical structures and unique mechanical properties, which have been widely studied, especially in fresh shells. However, few studies have revealed differences in the structure-property correlations of shells during the permineralization process, which occurs after organism death. To better understand the effect of permineralization on the microstructure and mechanical properties of shells, this study investigated and compared the compositions, microstructures, and mechanical properties of Tridacna gigas and permineralized J- Tridacna gigas. The results showed that permineralized J- Tridacna gigas possessed coarsened aragonite minerals, less anisotropy and organic matter, and higher hardness and strength than Tridacna gigas. The toughening mechanisms of Tridacna gigas , including crack deflection, aragonite platelet pull-out, and mineral bridges, were discovered during Vickers hardness tests. Moreover, the permineralization mechanism comprised three main steps: organic matter dissolution, aragonite plate compaction, and recrystallization. This work further elaborates the permineralization mechanism, which can help increase the crystal size and improve the strength and hardness of materials. Moreover, this study provides valuable insights into the design of bioinspired advanced materials with outstanding hardness and strength. Image 1 • The microstructure-mechanical properties of J- Tridacna gigas and normal Tridacna gigas were comprehensively studied. • Crystals were coarsened through the fusion and recrystallization of aragonite platelets. • Less porosity and organic matter content of J- Tridacna gigas was found compared to Tridacna gigas. • Permineralization led to higher compressive strength and hardness of Tridacna gigas. [ABSTRACT FROM AUTHOR]

Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes–silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes–silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail. [ABSTRACT FROM AUTHOR]

Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle (silica-s-VA7). Functional nanoparticles can not only effectively crosslink rubber without sulfur as a novel vulcanizator, but are also evenly dispersed in the rubber matrix and improve the dispersion of the remaining pristine silica as an interfacial compatibilizer. In addition, the thicker immobilized polymer layer and prominent crosslinking density of SBR nanocomposites simultaneously demonstrate that the novel vulcanizing agent silica-s-VA7 gives rise to significant improvement on the rubber–filler interfacial adhesion on account of the covalent linkages of organic and inorganic interfaces between elastomer and nanofillers. We envisage that this strategy may provide a new avenue to implement high-efficiency design for a multifunctional rubber-vulcanizing agent through an organic and inorganic hybridization mechanism. [ABSTRACT FROM AUTHOR]

In this work, the self-reinforced silicon nitride ceramics with crystal seed of β-Si3N4 particles were investigated. Firstly, the seeds were prepared by heating of α-Si3N4 powder with Yb2O3 and MgO, respectively. Then the self-reinforced silicon nitride ceramics were obtained by HP-sintering of α-Si3N4 powder, Yb2O3 and the as-prepared seeds which were not treated with acid and/or alkali solution. The results indicated that the introduction of seed with Yb2O3 could obviously increase the toughness and room temperature strength of the ceramics. Furthermore, its high temperature strength (1200 °C) could nearly keep higher value as the one of room temperature measured from unreinforced ceramic. However, the seed with MgO abruptly decrease the high temperature strength of the ceramics. The SEM and TEM characterization showed that the rod-like seed particle could favor the toughness and the presence of the Mg promote the formation of crystalline secondary phase. [Copyright &y& Elsevier]

The montmorillonite (MMT) functionalized by butadiene-styrene-vinylpyridine rubber (VPR) latex was prepared in aqueous solution. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the interactions between MMT layer and VPR to be hydrogen bond and electrovalent bond. Then, influences of VPR on the structure and properties of NR/MMT composites were investigated through swelling property representation, dynamical mechanic analysis (DMA), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results indicated the exfoliation or dispersion of MMT in NR matrix was improved significantly by adding VPR, as well as the enhanced constrained regions and rubber-filler interaction. Finally, the mechanical properties as tensile stress, tear strength of composites were promoted by 45.2%, 51.6% respectively at 8 wt% VPR loading compared to unfunctionalized composite, where the tanδ at 60 °C was decreased by 42.7% simultaneously that is beneficial to the development of low rolling resistance tyre. Fig. 11. Functionalized mechanism of VPR on montmorillonite (MMT) in NR/MMT composites. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Al 2 O 3 -ZrO 2 composite ceramics with different proportions were fabricated by isostatic compaction and sintered by the normal pressure sintering method. The effect of proportions on the microstructures, mechanical properties and sintering properties of Al 2 O 3 -ZrO 2 ceramics were investigated. The results show that as the volume fraction of ZrO 2 increases from 0% to 50%, the relative bulk density gradually decreases from 90% to 88.5% and the porosity increases from 0.182% to 0.197%, but the flexural strength increases from 291 to 423 MPa. In order to explain this "abnormal phenomenon", a finite element method was applied to calculate the maximum tensile stress on the Al 2 O 3 -ZrO 2 grain interface under tensile condition for the first time. The results indicate that the maximum grain interface tensile stress (MTS) of the Al 2 O 3 -ZrO 2 composite gradually decreases from 148.18 to 96.89 MPa as the volume fraction of ZrO 2 increases from 25% to 100%, which may be the main reason for their progressive flexural strength of Al 2 O 3 -ZrO 2 composite from 320 to 604 MPa. In addition, the pure Al 2 O 3 model has low MTS, and its ceramic material also has good sintering performance, but its flexural strength is worst compared to other Al 2 O 3 -ZrO 2 composite ceramics. This is due to the large sizes of defects generated by abnormal growth of Al 2 O 3 particles. [ABSTRACT FROM AUTHOR]

The CrWN glass molding coating was synthesized by plasma enhanced magnetron sputtering (PEMS). The effect of annealing environment (e.g., vacuum, N 2 and Air) on the microstructure and mechanical property of as-deposited coating was investigated by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM) and nanoindentation tests. Results showed that the as-deposited coating exhibited dense columnar structure consisting of multilayer CrN and W 2 N phases. The vacuum annealed coating showed similar thickness to that of as-deposited coating, but underwent visible surface coarsening because of slight oxygen erosion. The N 2 and air annealed coatings suffered from varying degree of oxidation damage accompanied by the formation of mixed WO 3 -CrWO 4 phases, which consequently resulted in severe thickness expansion and surface coarsening. The vacuum annealing induced a spinodal decomposition of supersaturated solid solution to form nm-sized CrN and W 2 N domains. Strain fields originating from the lattice mismatch eventually caused a pronounced age-hardening in the vacuum annealed coating. Whereas the N 2 and air annealed coatings showed significant mechanical degradation because these loose WO 3 -CrWO 4 oxides degraded the stable matrix structure. Our results clearly demonstrated that vacuum environment effectively suppressed the oxidation damage and mechanical degradation of glass molding coating. • The microstructure and mechanical property of the annealed coating are studied. • The vacuum annealing induces spinodal decomposition and light oxidation damage. • The N 2 and air annealing induce serious volume expansion and surface coarsening. • The vacuum annealed coating shows a pronounced age-hardening effect. • The N 2 and air annealed coatings suffer from remarkable mechanical degradation. [ABSTRACT FROM AUTHOR]