Microstructure and Properties of Aluminum-Graphene-SiC Matrix Composites after Friction Stir Processing.

Enhancing the mechanical properties of conventional ceramic particles-reinforced aluminum (Al 1060) metal matrix composites (AMCs) with lower detrimental phases is difficult. In this research work, AMCs are reinforced with graphene nanosheet (GNS) and hybrid reinforcement (GNS combined with 20% SiC, synthesized by shift-speed ball milling (SSBM), and further fabricated by two-pass friction stir processing (FSP). The effect of GNS content and the addition of SiC on the microstructure and mechanical properties of AMCs are studied. The microstructure, elemental, and phase composition of the developed composite are examined using SEM, EDS, and XRD techniques, respectively. Mechanical properties such as hardness, wear, and tensile strength are analyzed. The experimental results show that the GNS and the SiC are fairly distributed in the Al matrix via SSBM, which is beneficial for the mechanical properties of the composites. The maximum tensile strength of the composites is approximately 171.3 MPa in AMCs reinforced by hybrid reinforcements. The tensile strength of the GNS/Al composites increases when the GNS content increases from 0 to 1%, but then reduces with the further increase in GNS content. The hardness increases by 2.3%, 24.9%, 28.9%, and 41.8% when the Al 1060 is reinforced with 0.5, 1, 2% GNS, and a hybrid of SiC and GNS, respectively. The SiC provides further enhancement of the hardness of AMCs reinforced by GNS. The coefficient of friction decreases by about 7%, 13%, and 17% with the reinforcement of 0.5, 1, and 2% GNS, respectively. Hybrid reinforcement has the lowest friction coefficient (0.41). The decreasing friction coefficient contributes to the self-lubrication of GNSs, the reduction in the contact area with the substrate, and the load-bearing ability of ceramic particles. According to this study, the strengthening mechanisms of the composites may be due to thermal mismatch, grain refinement, and Orowan looping. In summary, such hybrid reinforcements effectively improve the mechanical and tribological properties of the composites.

Improving the Mechanical Properties of a Lattice Structure Composed of Struts with a Tri-Directional Elliptical Cylindrical Section via Selective Laser Melting.

In recent years, lattice structures produced via additive manufacturing have been increasingly investigated for their unique mechanical properties and the flexible and diverse approaches available to design them. The design of a strut with variable cross-sections in a lattice structure is required to improve the mechanical properties. In this study, a lattice structure design method based on a strut cross-section composed of a mixture of three ellipses named a tri-directional elliptical cylindrical section (TEC) is proposed. The lattice structures were fabricated via the selective laser melting of 316L alloy. The finite element analysis results show that the TEC strut possessed the high mechanical properties of lattice structures. Compression experiments confirmed that the novel lattice structure with the TEC strut exhibited increases in the elastic modulus, compressive yield strength, and energy absorption capacity of 24.99%, 21.66%, and 20.50%, respectively, compared with the conventional lattice structure at an equal level of porosity.

Catalase-integrated metal-organic framework with synergetic catalytic activity for colorimetric sensing.

As a platform for enzyme immobilization, metal-organic frameworks (MOFs) can protect enzyme activity from the interference of external adverse environment. Although these strategies have been proven to produce good results, little consideration has been given to the functional similarity of MOFs to the encapsulated enzyme. Here, catalase (CAT) was encapsulated in Fe-BTC with peroxidase-like activity to obtain a stable composite (CAT@Fe-BTC) with synergistic catalytic activity. Depending on the superior selectivity and high catalytic activity of CAT@Fe-BTC, colorimetric sensing for the detection of hydrogen peroxide and phenol was developed. This work demonstrates that the integration of functional MOFs with natural enzyme can be well applied to the construction of efficient catalysts.

Fabrication of Pt doped TiO2-ZnO@ZIF-8 core@shell photocatalyst with enhanced activity for phenol degradation.

Phenol's presence in aqueous solution due to the pollution from chemical and agricultural industries (e.g., coking tobacco leaves) causes severe environmental problems. As a result, many scientists and engineers search for catalysts to remove phenol from water by photodegradation. Thus, we synthesized Pt-doped TiO2-ZnO@ZIF-8 core@shell particles (Pt/TiO2-ZnO@ZIF-8) by a simple method involving crystallization, absorption, pyrolysis and growth steps. The resulting materials were analyzed by the powder X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM, respectively), surface area measurements and UV-vis absorption spectroscopy. The photocatalytic activities of our materials were evaluated by phenol degradation in aqueous solutions. Pt-doped TiO2-ZnO particles possessed a polyhedral structure and exhibited broad absorption above 400 nm. Coating with ZIF-8 increased the specific surface area of the Pt-doped TiO2-ZnO particles. Both Pt doping and ZIF-8 coating significantly enhanced the photocatalytic performance of TiO2-ZnO. Pt/TiO2-ZnO@ZIF-8 decomposed 99.7 % of phenol after the corresponding solution was exposed to UV light for 24 min. This performance was significantly better than the phenol decomposition ability of TiO2-ZnO, Pt/TiO2-ZnO and TiO2, which degraded 76.1 %, 95.2 % and 86.9 % of phenol, respectively. Pt/TiO2-ZnO@ZIF-8 also demonstrated excellent recycling stability. All these properties, including photostability, made our novel Pt/TiO2-ZnO@ZIF-8 catalyst a promising material for practical applications in environmental remediation.

Anterograde lag screw placement in the posterior column of the acetabulum: A case report and literature review.

Acetabular fractures are complex injuries with an annual incidence of approximately 4 per 100,000 (Laird and Keating, 2005 [1]. Although the open reduction is currently advocated for treating acetabular fractures, some acetabular fractures can be treated by minimally invasive surgery, with the advantages of minor trauma, less bleeding, reduced infection, and shorter operation time. Therefore, we report a case of a patient with a transverse fracture involving the acetabulum treated with a new method of cannulated screw fixation combined with a personalized 3D printed guide to achieving minimally invasive and precise treatment of acetabular fractures while we review the relevant papers.

Microstructure and Mechanical Properties of Friction Stir-Welded Dissimilar Joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn Alloys.

In order to clarify the microstructural evolution and the mechanical property of dissimilar friction stir-welded joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn magnesium alloys, two types of arrangement with ZK60 at advancing side (AS) or retreating side (RS) were adopted. The macrostructure and the microstructure of the dissimilar welded joints were discussed, and the microhardness and the transverse tensile properties of the joints were measured. There are three stirring sub-zones with different compositions and two clear interfaces within the joints. Due to the effect of both the original grain size of base materials and the growth of recrystallized grains, in the stir zone (SZ), the grain size of ZK60 increased slightly, while the grain size of Mg-4.6Al-1.2Sn-0.7Zn decreased significantly. The dissolution of precipitates was gradually significant from RS to AS within the SZ due to the gradual increase in strain and heat. The grain refinement led to an increase in hardness, while the dissolution of precipitates resulted in a decrease in hardness. The performance of the joints obtained with ZK60 placed on the RS is slightly better than that of that on the AS. The tensile fracture of both joints occurred at the interface between SZ and the thermos-mechanical affected zone at the AS, and showed a quasi-dissociative fracture.

The increase of osteopontin and ß-carboxy-terminal cross-linking telopeptide of type I collagen enhances the risk of hip fracture in the elderly.

BACKGROUND: Hip fracture in the elderly is a health burden worldwide due to its high mortality rate. This study was conducted to determine the possible mechanisms of osteopontin (OPN) and ß-carboxy-terminal cross-linking telopeptide of type I collagen (ß-CTX) in hip fracture in the elderly. MATERIALS AND METHODS: In the study, we recruited 108 elderly patients with hip fracture diagnosed from May 2012 to May 2015 at the Third Hospital of Xiamen and 86 healthy individuals without a history of hip fracture were taken as controls. Serum levels of OPN and ß-CTX were then determined. The T and Z values for bone mineral density (BMD) were also measured. Moreover, logistic regression analysis was performed to assess the risk and protective factors for hip fracture in the elderly. RESULTS: Serum levels of both OPN and ß-CTX were increased in elderly patients with hip fracture. OPN was positively correlated with ß-CTX. In addition, the levels of OPN and ß-CTX shared a positive association with the age, and a negative association with the BMD, in terms of T and Z values of the hip. In addition, increased BMD and outdoor sports might be protective factors for hip fracture, and an increase in levels of OPN and ß-CTX might be associated with a higher risk of hip fracture in the elderly population. DISCUSSION: Collectively, increased serum levels of OPN and ß-CTX might be correlated with a higher risk of a hip fracture and have predictive values in the occurrence of hip fracture in the elderly.