Micro/nano-reinforcements in bimodal-grained matrix: A heterostructure strategy for toughening particulate reinforced metal matrix composites

The preparation of a soybean flour adhesive with good bonding and prepressing performance, toughness, mildew resistance, and fire retardancy to address the problem of formaldehyde pollution is crucial; however, it also presents a challenge. The core–shell structure can achieve various properties by tailoring-making the core–shell composition. In this study, a core–shell structure [email protected] with hyperbranched polyamide (HBPA) as the core and tannin (TA) as the shell was prepared and used to modify SF adhesives. The results showed that the pyrogallol group of the tannin shell endowed the adhesive with excellent prepressing performance (0.75 MPa of prepressing intension), toughness, and coating performance, rendering the adhesive more suitable for plywood fabrication. Owing to the dense tannins in [email protected], the resultant adhesive exhibited superior mildew resistance (12 d). After closed-mouth placement for 12 d, the prepressing intension was reduced by 17.3% to 0.62 MPa, which still met the usage requirement. The wet shear strength of the plywood prepared using the resultant adhesive was 1.05 MPa—that is, 133.3% higher than that of the unmodified SF adhesive. The synthesized adhesive also showed antibacterial properties (inhibition zone = 8 mm), flame retardancy (LOI = 32.3%), and volatile organic compound release (6.86*106 mg/m2·h) lower than those of commonly used urea–formaldehyde resins and epoxy resins. 

Preparation of a strong and multiple-function soybean flour adhesive via the construction of tannin microspheres with a core–shell structure

Synergy of RHA and silica sand on physico-mechanical and tribological properties of waste plastic–reinforced thermoplastic composites as floor tiles

This parper reports a simple extrusion pathway for fabricating Zn–1Mg alloy with a bimodal structure. The alloy was prepared by casting and extruding at 200 °C and an extrusion ratio of 25:1. Microstructure and mechanical properties of the Zn–1Mg alloys were systematically investigated using OM, XRD, SEM, EBSD, TEM, and tensile tests. The results show that the Zn–1Mg alloy consisted of primary α-Zn dendrites and a three-component eutectic structure of α-Zn + Mg2Zn11 + MgZn2. The yield strength, ultimate tensile strength and elongation of extruded alloy at room temperature reached ∼289 MPa, ∼320 MPa, and ∼32%; and the average size of fine grains and coarse grains were ∼1.65 and ∼6.84 μm, respectively. Besides, dynamic recrystallization occurred during hot deformation, and particles in the broken phase were effective sites for the nucleation of dynamic recrystallized grains nucleation via a particle-stimulated nucleation mechanism. 

Effective strengthening and toughening in Zn–1Mg alloy with bimodal grain structure achieved by conventional extrusion

Enhancing the proportional limit of Al matrix composites (AMCs) is critical to the reliability of precision electronic instruments. In this paper, SiC/Al composites containing stacking faults (SFs) were successfully fabricated using pressure infiltration method. The proportional limit (σp5 and σp100) of SiC/Al composites with SFs reached 65 MPa and 124 MPa, respectively, which was 8%–22% higher than theoretical prediction of the Brown-Lukens empirical formula. In-situ TEM tensile test was conducted to reveal the strengthening behavior of SFs during micro-plasticity. The results showed that the extra strengthening effect in SiC/Al composites with SFs includes elastic interactions of SF extension, sessile stair-rod partial dislocations and interactions of SF networks and dislocation arrays. This work reveals the influence of SFs on the micro-plasticity and strengthening behavior of AMCs and proposes a new strategy to endow AMCs with higher proportional limit for precision instrumentation applications. 

In-situ TEM study on the effect of stacking faults on micro-plasticity and proportional limit in SiC/Al composites

Designing heterogeneous structures is a promising pathway for overcoming the trade-off between strength and toughness in metal matrix composites (MMCs). Herein, we report an innovative strategy for fabricating graphene nanosheet-Cu reinforced Al matrix (GNS-Cu/Al) composites with heterogeneous structure. This strategy involves the consolidation of unique composite powders with core-shell grain structure, which are synthesized with the aid of in-situ GNS-Cu hybrids. Results reveal that the fabricated GNS-Cu/Al composite exhibits multiple microstructural heterogeneities, including both heterogeneous grain structure and reinforcement spatial distribution, which endow the composite with a prominent combination of tensile strength of ∼437 MPa, fracture elongation of ∼12.5% and toughness of ∼48.7 MJ m−3. It is confirmed that such microstructural heterogeneities in GNS-Cu/Al composite contribute significant hetero-deformation induced (HDI) stress strengthening and sustained strain hardening, making the key mechanical properties of GNS-Cu/Al considerably outperform the counterpart of Cu/Al composite. Moreover, the coordinated deformation and crack bridging/blunting behaviors are demonstrated to be responsible for the exceptional toughness of GNS-Cu/Al composite. This work offers a promising bottom-up tactic to fabricate Al matrix composites with heterogeneous structures and superior mechanical performances for structural applications. 

Exceptional mechanical properties of aluminum matrix composites with heterogeneous structure induced by in-situ graphene nanosheet-Cu hybrids

A novel lanthanum/modified fly ash (La/MFA) composite adsorbent prepared by simple solution reaction was used for the adsorption of Congo Red (CR) dye from aqueous solution. The morphology and particle size distribution of the composite were characterized, and the equilibrium adsorption was researched. The results show that the adsorption of CR onto La/MFA can reach equilibrium in 30 minutes. The entire adsorption process can be well described by pseudo-second-order kinetic equation at different temperatures. The value of apparent adsorption activation energy is 16.2kJ/mol. The isothermal data conform to the Langmuir model with the maximum adsorption capacity of 714 mg/g at 298K. According to the negative values of Gibbs free energy change (ΔG°) and enthalpy change (ΔH°), and reduction of Langmuir adsorption coefficient with the increase of temperature, the adsorption system from 298K to 328K is confirmed to be of spontaneous and exothermic nature. The results of SEM and particle size analysis indicate that the particle sizes and specific surface of La/MFA are smaller and coarser than those of FA. As a low-value composite adsorbent, La/MFA is especially effective for the removal of high concentration CR.

Xiao Hong Lin

Papers

Exceptional mechanical properties of aluminum matrix composites with heterogeneous structure induced by in-situ graphene nanosheet-Cu hybrids

Adsorption of Congo Red from Aqueous Solution Using La/MFA Composite as Adsorbent