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In this research, upconversion nanocrystals incorporated with MOR zeolite composites were synthesized using the desilicated MOR zeolite as a host for the in situ growth of NaREF4 (RE = Y, Gd) Yb/Er nanocrystals. The structure and morphology of the composites were studied with XRD, XPS, and TEM measurements, and the spectral studies indicated that the subsequent thermal treatment can effectively improve the upconversion emission intensity of Er3+. By using the NaYF4:Yb/Er@DSi1.0MOR-HT composite that holds the strongest upconversion emission, a probe of UCNC@DSiMOR/BPEI was constructed with the modification of branched poly ethylenimine for the detection of Cu2+. It was indicated that the integrated emission intensity of Er3+ shows a linear dependence with the logarithm value of the Cu2+ concentration ranging from 0.1 to 10 μM. This study offered a feasible method for the construction of UCNC@zeolite composites with enhanced upconversion emission, which may have a potential application as fluorescent probes for the detection of various metal ions by adjusting the doping luminescent center. [ABSTRACT FROM AUTHOR]

The mechanical properties of quasi-brittle materials, which are widely used in engineering applications, are often affected by the thermal condition of their service environment. Moreover, the materials appear brittle when subjected to tensile loading and show plastic characteristics under high pressure. These two phenomena manifest under different circumstances as completely different mechanical behaviors in the material. To accurately describe the mechanical response, the material behavior, and the failure mechanism of quasi-brittle materials with the thermo-mechanical coupling effect, the influence of the thermal condition is considered in calculating bond forces in the stretching and compression stages, based on a new bond-based Peridynamic (BB-PD) model. In this study, a novel bond-based Peridynamic, fully coupled, thermo-mechanical model is proposed for quasi-brittle materials, with a heat conduction component to account for the effect of the thermo-mechanical coupling. Numerical simulations are carried out to demonstrate the validity and capability of the proposed model. The results reveal that agreement could be found between our model and the experimental data, which show good reliability and promise in the proposed approach. [ABSTRACT FROM AUTHOR]

To protect magnesium alloy surfaces from wear and corrosion, an Fe-based amorphous coating was prepared on WE43 through the Ni60 interlayer by high-velocity oxygen-fuel (HVOF) spraying. The porosity was ~1%, and the amorphous content exceeded 90%. The wear and corrosion resistance of the composite coating with WC particles wrapped in a Ni layer as the reinforcing phase were compared with that of the completely amorphous coating. The friction coefficient (COF) of the composite coating was 0.3, which is only half of that of the WE43 substrate, and the composite coating exhibited a more stable wear behavior than the completely amorphous coating. The corrosion tendency of the composite coating is lower than that of stainless steel, with a corrosion potential of −0.331 V, and the addition of WC particles did not deteriorate the corrosion resistance considerably. The bonding mechanism of the bonding interface between the amorphous structure and the particles of the reinforcing phase was investigated by transmission electron microscopy (TEM). Reinforcing particles were confirmed to form metallurgical bonding with the coating. It was found that the Ni layer showed excellent bonding performance in the form of a mixture that is amorphous and nanocrystalline. Therefore, the Fe-based amorphous composite coating on a magnesium alloy surface shows a potential protective effect. [ABSTRACT FROM AUTHOR]

The straight groove test of AZ31B magnesium alloy sheet by electric hot temperature-controlled incremental sheet forming (ISF) was conducted at different temperatures. The temperature influence on fracture depth, deformation force and strain distribution was investigated. It was found that the limit depth and major strain increased as the temperature rose and that the forming force decreased correspondingly. Furthermore, the fracture behavior changed from brittle fracture to ductile fracture. Considering the formability and surface wear comprehensively, the optimized forming temperature was determined to be 300 °C. The microstructure of the groove specimen was analyzed and the dynamic recrystallization (DRX) was considered to be the reason for the improved formability. The degree of DRX depended on the temperature and degree of deformation, which resulted in non-uniform distribution of hardness within the cross section of the groove specimen. [ABSTRACT FROM AUTHOR]

Nitrogen hybridization is an attractive way to enhance the wettability and electric conductivity of porous carbon, which increases the capacitance of carbon-based supercapacitor, however, there is lack of low-cost methods to prepare the nitrogen-doped porous carbon materials. Herein, a novel facile nitrogen-containing bio-phenolic resin was synthesized by polymerization of the carbamate bio-oil, Phenol and paraformaldehyde. As a precursor of nitrogen-doped porous carbon, the nitrogen-containing bio-phenol resin was activated by the one-step molten-salt method. The resultant nitrogen-doped porous carbon showed a high specific surface area up to 1401 m2·g−1. As a supercapacitor electrode, the nitrogen-doped porous carbons showed specific capacitance of 159 F·g−1 at 0.5 A·g−1. It also exhibited high cyclic stability with 94.8% retention of the initial specific capacitance over 1000 charge-discharge cycles at 1.0 A·g−1. The results suggest that these nitrogen-containing bio-phenol resin provide a new source of nitrogen-doped porous carbon for high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Titanates materials have attracted considerable interest due to their unusual functional and structural properties for many applications such as high-performance composites, devices, etc. Thus, the development of a large-scale synthesis method for preparing high-quality titanates at a low cost is desired. In this study, a series of quaternary titanates including K0.8Mg0.4Ti1.6O4, Na0.9Mg0.45Ti1.55O4, Na0.75Fe0.75Ti0.25O2, NaFeTiO4, and K2.3Fe2.3Ti5.7O16 are synthesized by a simple molten salt method using inexpensive salts of KCl and NaCl. The starting materials, intermediate products, final products, and their transformations were studied by using TG-DSC, XRD, SEM, and EDS. The results show that the grain size, morphology, and chemical composition of the synthesized quaternary titanates can be controlled simply by varying the experimental conditions. The molar ratio of mixed molten salts is critical to the morphology of products. When KCl:NaCl = 3:1, the morphology of K0.8Mg0.4Ti1.6O4 changes from platelet to board and then bar-like by increasing the molar ratio of molten salt (KCl–NaCl) to raw materials from 0.7 to 2.5. NaFeTiO4 needles and Na0.75Fe0.75Ti0.25O2 platelets are obtained when the molar ratio of molten salt (NaCl) to raw materials is 4. Pure phase of Na0.9Mg0.45Ti1.55O4 and K2.3Fe2.3Ti5.7O16 are also observed. The formation and growth mechanisms of both potassium magnesium titanates and sodium iron titanates are discussed based on the characterization results. [ABSTRACT FROM AUTHOR]